stratigraphy amino acid geochronology and correlation of quaternary sea level and glacial events broughton island arctic canada raised marine and glaciomarine terraces on broughton island record regional isostatic adjustments and eustatic sea level changes previous workers proposed three alternative glacial and sea level chronologies of the region these conflicts are resolved by the stratigraphic control provided by amino acid ratios d allo isoleucine l isoleucine in marine molluscs collected form cliff exposures amino acid ratios radiometric dates and relative weathering measurements on geomorphological features provide a basis for regional correlations based upon amino acid ratios the coastal sedimentary sequences all part of the broughton island formation can be subdivided into six units to which informal member names have been assigned these units delimit at least four glacial episodes during which local ice advanced around broughton island to the outer coast the youngest advance is correlative with deposits that are dated 54 000 bp and the absolute ages of older events have been estimated from minimum uranium s

late quaternary marine sediment accumulation in fiord shelf deep sea transects baffin island to baffin bay abstract piston cores from fiords shelf troughs and the deep sea off eastern baffin island n w t canada have been sampled for texture and detrital carbonate in the 2 ka over the last ca 10 ka three sets of two cores each lie on a fiord shelf transect and thus define variations in sediment accumulation gradients these continental margin data are compared with cruder estimates of holocene sediment accumulation at three sites farther offshore in baffin bay davis strait and the northern labrador sea minimum accumulation in a 2 ka interval was 200 kg m 2 with a maximum estimate of 8 800 kg m 2 detrital carbonate accumulation varies between 0 and 1 300 kg m 2 median accumulation for a typical fiord shelf deep sea transect over the last 10 ka have been 10 340 3493 and 820 kg m 2 at dsdp leg site 645 in central baffin bay the sedimentation rate ranged between 40 and 130 m ma ca 400 and 1200 kg m 2 2ka that is comparable with the late quaternary input into baffin bay

cyclic changes in the sedimentary environment during the last interglacial glacial cycle coastal jameson land east greenland abstract raised successions of sediments from the last interglacial glacial period along coastal jameson land east greenland comprise a variety of sedimentary facies that reflect cyclic changes of the sedimentary environment these changes are controlled by the fluctuations of relative sea level and glacier advances each of the sedimentary cycles starts with till deposition succeeded by marine mud sedimentation subaerial erosion deltaic and coastal sedimentation sea level changes alters from falling to rising during each sedimentary cycle and indicates that local east greenland glacier fluctuations generally lead the global eustatic cycles most of the deposits cover isotope stage 5 and successive higher sea level stands during each sedimentary cycle indicate a net growth of the greenland ice sheet during the early weichselian

holocene and pleistocene dissolution cycles in deep sea cores of baffin bay and davis strait palaeoceano graphic implications abstract calcium carbonate dissolution has been studied in several grab samples and piston cores from baffin bay and davis strait ranging in water depth from 200 to 2300 m the intensity of dissolution was determined from examining 1 the ratio of arenaceous to calcareous benthonic foraminifera 2 the ratio of benthonic to planktonic foraminifera 3 the relationships between the dissolution susceptible and dissolution resistant foraminifera 4 the degree of foraminiferal test fragmentation and 5 the relationships between plankton tows and the fauna in the surface sediments all core tops and grab samples from baffin bay surface sediments below 600 900 m water depth demonstrated intense dissolution of calcium carbonate sediments below 900 m were biogenic carbonate free indicating 100 foraminiferal loss due to dissolution possible causes of substantial undersaturation in calcium carbonate of baffin bay bottom water are very low temperatures and higher concentrations of carbon dioxide all cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1 3 5 7 and 9 similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom water masses during these periods the preservation state of biogenic carbonate debris in glacial isotope stages 2 4 6 8 and 10 is similar to the assemblage found in the water at present

asynchronous instability of the north american arctic and greenland ice sheets during the last deglaciation abstract the chronology of deglacial meltwater pulses from the laurentide ice sheet is well documented however the deglacial history of the north american arctic north eastern laurentide and innuitian and western greenland ice sheets draining into the labrador sea via baffin bay is less well constrained here we present new high resolution radiocarbon dated records from the central baffin bay spanning 17 to 10 kyr bp and documenting the full deglacial history of baffin bay sedimentological and geochemical data confirm the presence of two periods of enhanced detrital carbonate delivery termed baffin bay detrital carbonate events bbdcs these events are dated to 14 2 13 7 kyr bp and 12 7 11 kyr bp they are synchronous across baffin bay and their mineralogical signature indicates a common source of detrital carbonate from northern baffin bay the first event bbdc 1 postdates heinrich event 1 and the second event bbdc 0 predates the recently revised timing of heinrich event 0 the onset of the bbdc events appears not to be systematically linked to greenland temperature change as they occur during both interstadial and stadial periods this indicates that deglaciation of north american arctic and western greenland ice sheets with the associated iceberg and meltwater discharge were decoupled from the dominant north atlantic climate mode where iceberg discharge events from the laurentide ice sheet occurred during stadial periods

a new greenland deep ice core the polar ice sheets are rich sources of information on past atmospheric conditions including paleoclimates a new deep ice core has been drilled in south greenland comparison of the oxygen isotopic profile with that from camp century and with a deep sea foraminifera record indicates that the new core reaches back to about 90 000 years before present in a continuous sequence the details in the wisconsin part of the ice core records seem to be climatically significant and the general trends reveal all of the relevant emiliani stages recorded in deep sea cores the redated camp century record suggests a dramatic termination of the eem sangamon interglacial

atmospheric circulation patterns during glacial inception a possible candidate abstract models of atmospheric circulation in the north atlantic sector during glacial inception can be expanded to a hemispheric scale with the aid of diagnostic studies of the present climate the present greenland above ga atmospheric circulation type may be a candidate for the atmospheric circulation type required during glacial inception the pattern is an amplification with only minor phase shifts of the present average winter circulation pattern in the extratropical northern hemisphere southerly flow in the northwest atlantic is associated with warm ocean temperatures low sea ice in the davis strait and increased precipitation over northeast canada evidence from modeling of the present climate indicates that the ga pattern could be maintained by increased snow cover over eastern north america enhanced snow cover due to decreased northern hemisphere summer insolation could cause a similar response on an ice age time scale

changes in the heterogeneity of mesoscale distribution patterns of larval fish associated with a shallow coastal haline front abstract in june 1983 there was a large outflow of inland fresh waters from the rhone river that covered a broad area off the northern coast of catalonia northwestern mediterranean giving rise to a surface plume of fresh water with a distinct haline front at its southern edge this hydrodynamic event brought about substantial changes in the structure of the larval fish community in the area which was in turn reflected in an increase in spatial heterogeneity large numbers of species and individuals were found along the southern edge of the plume in association with the haline front whereas with the exception of certain species larval fish concentrations in the area covered by the plume tended to be considerably lower than in the rest of the area species predominantly located in the surface water layers were probably transported by the plume out to the plume s edge other species which apparently enjoy a broader vertical distribution range were less affected by the surface advection processes

milankovitch theory of ice ages hypothesis of ice sheet linkage between regional insolation and global climate abstract j d hays j imbrie and n j shackleton 1976 science 194 1121 1132 showed that the astronomical theory explained many features of late quaternary ice age climates but they did not specify the physical mechanisms involved here it is proposed that interlocked variations of ice sheet heat sinks in both polar hemispheres amplified and transmitted milankovitch summer half year insolation changes a version of the astronomical theory between 45 and 75 n into the globally synchronous climate changes recorded in geologic records it is suggested that late quaternary ice sheets had terrestrial components grounded above sea level melting margins fluctuations controlled by climate and marine components grounded below sea level drained largely by ice streams limited melting margins fluctuations controlled primarily by sea level and secondarily by climate interior surface elevations coupled to downdraw through ice streams northern hemisphere ice sheets were largely marine with minor melting margins in the arctic and terrestrial with major melting margins in the midlatitudes west antarctic and peripheral east antarctic ice was marine based and lacked melting margins because of their geographic array these terrestrial and marine components formed an ice sheet system whose variations were coupled on a global scale milankovitch summer isolation changes near midlatitude northern hemisphere melting margins controlled most variations of this system because advance or retreat of melting margins initiated concurrent eustatic sea level change such sea level change afforded the critical interlocking mechanism between terrestrial and marine components because it forced simultaneous expansion or contraction of marine margins in both polar hemispheres this initiated an amplifying feedback loop among all marine components and influenced interior downdraw through ice streams arctic summer insolation change was less important because northern melting margins were relatively minor its greatest influence was on surface ablation of ice streams that controlled interior downdraw this affected eustatic sea level and activated global linkage of marine sectors by analogy with present day antarctica late quaternary ice sheets were enormous planetary heat sinks due to their reflective and radiative surface characteristics it is suggested that the effectiveness of these ice sheet heat sinks varied with their areal extent and interior surface elevation thus it is postulated that concurrent growth or decay of these interlocked ice sheet heat sinks in both polar hemispheres served as the global amplifier of regional milankovitch summer insolation

structural architecture of the hydrothermal system from geophysical data in hammam bouhadjar area northwest of algeria we determine the structural architecture of the hydrothermal system of hammam bouhadjar area northwest of algeria by the use of geophysical data new gravity and electrical surveys covered an area of about 48 km2 in 2009 there were 350 gravity measurements made with a sampling of 500 m and 45 electrical soundings schlumberger type ab 1000 m the bouguer anomaly map shows a regression of gravity field towards the nw and se all of the observed anomalies are elongated in ne sw direction the results obtained from different processing methods gradients upward continuation euler deconvolution wavelet transform and modelling of gravity data were used to generate structural map of the studied area the vertical and horizontal variations of resistivity confirm the presence of superficial and deeper faults system following the geophysical gravity and electrical analysis and modelling we propose a model to explain the origin of the hammam bouhadjar thermal waters we suggest that the hot spring water comes from an aquifer located in sandstones lenses in the senono oligocene tellian unit following the gravity modelling the aquifer is identified at about 800 m the same depth where the geothermal gradient is insufficient to heat the water in these circumstances the aquifer is probably heated by volcanic processes connected with a hot compartment by faults and contacts affecting structures identified in depth the presence of a conductor along of the horseshoe area suggests that the water percolates into this area and then is drained by the different accidents to invade the whole area

a 17 ma onset for the post collisional k rich calc alkaline magmatism in the maghrebides evidence from bougaroun northeastern algeria and geodynamic implications bougaroun is the largest pluton 200 km2 in the 1200 km long neogene magmatic belt located along the mediterranean coast of maghreb new u pb dating on zircons and k ar ages on whole rocks and separated minerals document its emplacement at 17 ma within the lesser kabylian basement a continental block that collided with the african margin during the neogene this upper burdigalian intrusion is therefore the oldest presently identified k rich calc alkaline massif in the whole maghrebides magmatic lineament and marks the onset of its activity the bougaroun peraluminous felsic rocks display a very strong crustal imprint associated mafic rocks lree enriched gabbros have preserved the orogenic subduction related geochemical signature of their mantle source older depleted gabbros cropping out at cap bougaroun are devoid of clear subduction related imprint and yielded ar ar hornblende ages of 27 0 3 0 ma and 23 3 3 2 ma we suggest that they are related to the upper oligocene back arc rifted margin and early miocene oceanic crust formation of the nearby jijel basin an extension of the algerian basin developed during the african tethyan slab rollback the fact that the bougaroun pluton intrudes exhumed kabylian lower crustal units mantle slices and flysch nappes indicates that the kabylian margin was already stretched and in a post collisional setting at 17 ma we propose a tectono magmatic model involving an early miocene tethyan slab breakoff combined with delamination of the edges of the african and kabylian continental lithospheres at 17 ma the asthenospheric thermal flux upwelling through the slab tear induced the thermal erosion of the kabylian lithospheric mantle metasomatized during the previous subduction event and triggered its partial melting we attribute the strong trace element and isotopic crustal signature of bougaroun felsic rocks to extensive interactions between ascending mafic melts and the african crust underthrust beneath the kabylie de collo basement

interranual variability in horizontal patterns of larval fish assemblages in the northeastern aegean sea eastern mediterranean during early summer abstract larval fish community structure was studied in the northeastern aegean sea nea over an area influenced by the advection of black sea water bsw sampling was carried out in early summer during a period of 4 years 2003 2006 taxonomic composition and abundance presented high variability in space that remained relatively constant among years tow depth and indicators of trophic conditions in the upper water column i e zooplankton displacement volume fluorescence explained significantly the structure of larval assemblages during all surveys the northern continental shelf thracian and strymonikos shelf where a large amount of enriched low salinity bsw is retained was dominated by larvae of epipelagic species mainly anchovy engraulis encrasicolus interannual changes in horizontal extension of the bsw seemed to match closely observed changes in the distribution of anchovy larvae mesopelagic fish larvae were particularly abundant beyond the continental shelf over the north aegean trough where a strong frontal structure is created between the low salinity waters of bsw origin and the high salinity waters of the aegean sea larvae of certain mesopelagic species e g ceratoscopelus maderensis may occasionally be transported inshore when the prevailing current meanders towards the coast or feeds anticyclonic gyres over the continental shelf

late quaternary chronostratigraphic framework of deep baffin bay glaciomarine sediments from high resolution paleomagnetic data 1 the late quaternary baffin bay sediments provide exclusive records of greenland innuitian and laurentide ice sheet margin activities as well as information about the arctic and northern atlantic ocean linkages through the canadian arctic archipelago because of specific oceanographic conditions foraminiferal 18o stratigraphies and radiocarbon ages fail to provide reliable chronologies here we propose an original chronostratigraphy spanning the last glacial cycle based on high resolution paleomagnetic investigations on a 741 cm long core hu2008 029 016pc raised from the deep central baffin bay near odp site 645 two major difficulties were encountered 1 the high frequency occurrence of rapidly deposited layers related to short ice sheet margin events e g ice surges and 2 the magnetic grain size variability physical and magnetic mineralogical properties were used to screen out unreliable magnetic sediment layers the obtained relative paleointensity rpi proxy matches reference paleomagnetic stacks and regional records moreover the resulting record depicts two major excursions which were assigned to the laschamp and the norwegian greenland sea events it has thus been possible to derive a robust 115 ka chronology for the cored sequence we concluded that even under such a dynamic sedimentary regime magnetic properties of the sediments can provide a reliable chronostratigraphy together with information on sedimentary processes

effects of coastal transport on larval patches models and observations abstract we used a combination of field observations and numerical modeling to examine the physical mechanisms responsible for the evolution and transport of patches of blue crab larvae in the mouth of delaware bay the observations consisted of larval collections and surface salinity measurements taken along a moving spatial grid whose origin was determined by a satellite tracked drifter examination of field observations revealed a slender larval patch that was aligned with salinity contours measurement of the salting rate of the larval patch indicated that the patch moved through the offshore edge of a buoyant plume due to wind driven upwelling circulation a numerical model that provided realistic simulations of the flow field at the mouth of delaware bay and the adjoining coastal ocean was used to examine the physical mechanisms responsible for the movement and evolution of the patch we conducted a series of simulations in which we separately examined the effects of tides buoyancy driven flow and wind driven transport results showed that both tides and buoyancy driven flow tend to elongate an initially square fluid element although winds alone have little effect on the shape of a patch wind driven flow can effectively move a patch through a complex flow field in which the deformation by tides and buoyancy driven circulation can have significant effects this study represents the first observation and analysis of a larval patch that remains intact while moving through the edge of a buoyant plume it provides new insight into the shape of larval patches in delaware bay and any region with strong buoyancy and tidally driven flow suggesting that typical larval patches may not be characterized by equal across and alongshelf dimensions but instead tend to be slender shapes that are aligned with the flow field

late quaternary stratigraphy and paleoecology of northwest labrador sea abstract sedimentological study of 20 piston cores from the northwestern labrador sea shows that thin bedded distal turbidites are important constituents of the quaternary strata on the continental slope and rise sedimentation on the outer shelf ca 500 900 m is dominated by ice rafting and hemipelagic deposition detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9 studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern labrador sea during the early middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time microfossil data indicate that late glacial stages were characterized by year around sea ice cover and arctic surface water and by the dominance of cold dry arctic air masses transitions from glacial to interglacial stages are marked by the presence of low salinity melt water these data support models which postulate that open water in the labrador sea played an important role in supplying moisture to laurentide and greenland ice sheets

post eemian glacial inception part i the impact of summer seasonal temperature bias abstract post eemian glacial inception the transition between marine oxygen isotopic stage mois 5e and mois 5d began approximately 117 000 years before present 117 kyr bp and led to significant northern hemisphere glaciation within the ensuing 5000 yr previous sensitivity studies with atmospheric general circulation models agcms have had difficulty producing glacial nucleation in high northern latitude regions of the globe a base simulation of this process has been conducted using the canadian centre for climate modelling and analysis cccma gcmii with mixed layer slab ocean model constrained so as to ensure that the model reproduces the set of atmospheric model intercomparison project 2 amip2 modern sea surface temperatures ssts under conditions of modern radiative forcing this simulation demonstrates that entry into glacial conditions at 116 kyr bp requires only the introduction of post eemian orbital insolation and standard preindustrial co2 concentrations two additional sensitivity ex

sediments sedimentation rates and environments southeast baffin shelf and northwest labrador sea 8 26 ka ten 14c dated cores are described from the labrador sea continental slope and hatton and resolution basins on the southeast baffin shelf based on sharply defined detrital carbonate layers in the labrador sea cores we propose that the laurentide ice sheet reached the shelf break at both 20 and 15 14c ka 24 3 and 18 2 sidereal ka and contributed significant sediment to the northwest labrador sea both times the flux was 720 kg m2 ka during these periods of maximum ice extent the laurentide ice sheet retreated from its 15 ka position at the shelf break to the inner shelf between 14 and 12 14c ka ice proximal conditions recognized by relatively light 18o on near surface planktonic foraminifera high detrital carbonate and benthic foraminiferal faunas dominated by elphidium excavatum forma clavata cassidulina reniforme prevailed until at least 10 14c ka the ice readvanced toward resolution basin and across part of hatton basin at 11 14c ka accelerator mass spectrometry dates on core tops i

initiation and development of the laurentide and cordilleran ice sheets following the last interglaciation abstract fossil records from sites overridden by or adjacent to the laurentide ice sheet indicate that the climate of the last interglaciation oxygen isotope substage 5e ca 130 116 ka was warmer than today following the last interglaciation the laurentide ice sheet first developed during stage 5 over keewatin quebec and baffin island along its northern margin the ice sheet reached its maximum extent of the last glaciation during stage 5 the ice sheet advanced across baffin island onto the continental shelf early during stage 5 5d whereas the advance into the western canadian arctic occurred late during stage 5 5b the ice sheet also may have advanced into the st lawrence lowland during substage 5b although this event may be younger stage 4 the hudson bay lowland became ice free during substage 5a retreat of the ice sheet on baffin island occurred during late stage 5 probably substage 5a the exact timing of retreat from the western canadian arctic is unknown but it occurred before 48 ka the southern sector including the st lawrence lowland was ice free during late stage 5 the hudson bay lowland may have remained ice free through stage 4 and much of stage 3 because of conflicting chronologies however it is more likely that this area was glaciated throughout stage 3 and perhaps stage 4 nevertheless the data demonstrate that the lowland was ice free during part of the last glaciation an independent ice cap developed over the appalachian uplands and advanced across nova scotia during stage 4 perhaps as far as the edge of the continental shelf the ice cap remained active over nova scotia as a setellite to the laurentide ice sheet throughout the remainder of the last glaciation the ice sheet advanced into the st lawrence lowland during stage 4 and subsequently overwhelmed the local ice cap in the appalachian uplands advancing perhaps into northern new england but not farther south the lowland remained covered by the ice sheet until late stage 2 the ice sheet may also have advanced into the lake ontario basin during stage 4 the position of the northern margin of the laurentide ice sheet during stage 4 is not known but it remained an unknown distance behind its maximum position reached during stage 5 cores from baffin bay indicate a substantial decrease in high latitude glaciation during stage 4 following retreat the keewatin sector of the ice sheet may have remained over much of northwestern canada as a quasi stable ice mass until it readvanced during stage 2 similarly the baffin island sector of the ice sheet may have remained largely intact the southern margin of the ice sheet may have advanced into the lake ontario basin and upper mississippi valley during the middle of stage 3 ca 50 ka reaching its maximum extent of the last glaciation during stage 2 ca 18 21 ka advance of the northern margin was younger ca 8 13 ka than that of the southern margin this advance was less extensive than the penultimate advance stage 5 paleoenvironmental records indicate that the last interglaciation in areas covered by and near the cordilleran ice sheet was as warm as or warmer than present the cordilleran ice sheet appears to have developed during stage 5 or 4 at that time it advanced over southern british columbia and into the northern puget lowland there is no record of this event in northern areas that were later covered by the ice sheet the ice sheet disappeared before 59 ka at the beginning of a lengthy nonglacial interval paleoenvironmental records indicate that climate was similar to the present during part of this interval the ice sheet was absent and glaciers probably were confined to mountain areas throughout stage 3 climatic deterioration marking the end of this nonglacial interval may have begun as early as 29 ka by 14 15 ka the ice sheet had achieved its maximum extent of the last glaciation because there are few suitable dating methods capable of resolving events beyond the radiocarbon limit and because sites that preserve a record of events from the last glaciation are spatially restricted we consider this synthesis as tentative and subject to significant revision as dating methods improve nevertheless this perspective of the north american ice sheets through the last glaciation demonstrates their complex and dynamic behavior and attendant rapid fluctuations in ice volume

abrupt changes in marine conditions sunneshine fiord eastern baffin island nwt during the last deglacial transition younger dryas and h 0 events

comparison of uranium series radiocarbon and amino acid data from marine molluscs baffin island arctic canada uranium series and sup 14 c dates and the extent of amino acid racemization are reported for 24 marine shell samples from three areas of baffin island arctic canada when the radiometric dates are plotted against the ratio of d alloisoleucene l isoleucene in the shells five broad age groups are recognized the uranium series data indicate that sup 231 pa is incompletely retained in most fossil shells and that sup 230 th is lost from some of the samples therefore their apparent ages are minimum however a few dated samples in each group have yielded useful age results and the minimum ages of the five groups of samples are estimated as 7 000 to 11 000 greater than or equal to70 000 greater than or equal to136 000 greater than or equal to190 000 and 300 000 yr calculated integrated thermal histories based on the epimerization reaction in the mollusc hiatella arctica linne give paleotemperature estimates of around 5 sup o c compared to the present mean annual air temperature of about 11 sup o c

the last interglacial ocean the final effort of the climap project was a study of the last interglaciation a time of minimum ice volume some 122 000 yr ago coincident with the substage 5e oxygen isotopic minimum based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean last interglacial sea surface temperatures sst were compared with those today there are small sst departures in the mid latitude north atlantic warmer and the gulf of mexico cooler the eastern boundary currents of the south atlantic and pacific oceans are marked by large sst anomalies in individual cores but their interpretations are precluded by no analog problems and by discordancies among estimates from different biotic groups in general the last interglacial ocean was not significantly different from the modern ocean the relative sequencing of ice decay versus oceanic warming on the stage 6 5 oxygen isotopic transition and of ice growth versus oceanic cooling on the stage 5e 5d transition was also studied in most of the southern hemisphere the oceanic response marked by the biotic census counts preceded led the global ice volume response marked by the oxygen isotope signal by several thousand years the reverse pattern is evident in the north atlantic ocean and the gulf of mexico where the oceanic response lagged that of global ice volume by several thousand years as a result the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years these regional lead lag relationships agree with those observed on other transitions and in long term phase relationships they cannot be explained simply as artifacts of bioturbational translations of the original signals

quaternary glacial and marine stratigraphy of the qivitu peninsula northern cumberland peninsula baffin island canada summary sediments exposed along the outer coast of the qivitu peninsula record the advances and retreats of glaciers in the fiords bordering the peninsula and accompanying sea level fluctuations during the quaternary seven main lithofacies and 21 subfacies are recognized based on texture color bed thickness and lateral extent internal structures and abundance of macrofossils in contrast to earlier work in the area the interpretation of lithofacies genesis using a model of fiord glaciomarine sedimentation suggests that all lithofacies are of marine or glaciomarine origin with no evidence of grounded ice extending seaward of the peninsula the abundance and diversity of benthic foraminifera in selected samples and in situ subarctic molluscs shows that relatively warm water was present along the east baffin island coast during several periods of extensive fiord glaciers analysis of upward facies transitions in 54 stratigraphic sections suggests that facies sequences are cyclical these sedimentation cycles are interpreted in terms of glacier sea level responses during glacial interglacial cycles detailed relative time control for the lithofacies sequence is provided by time dependent amino acid ratios on the common shell fragments in many stratigraphic units because the stratigraphic sequence is marked by significant unconformities due to relative sea level regressions near the end of each glacial sedimentation cycle amino acid ratios on molluscs contemporaneous with particular cycles are statistically similar and distinct from ratios for older and younger cycles thus although few stratigraphic units can be physically traced for more than 0 5 km aminozones based on groups of animo acid ratios allow chronocorrelation and relative dating of units in each sedimentation cycle the qivitu stratigraphic sequence is divided into two formations consisting of a total of seven members for which formal names are proposed sediments predating the two most recent interglacials are lithologically similar to later beds suggesting that events during these earlier periods were of the same character as those of later glacial interglacial cycles biostratigraphic evidence suggests that a relatively mild climate prevailed in this region during the clyde and ayr lake glaciations and intervening cape broughton aquatherm the quajon interstade is correlative with the marine sediments deposited near the end of the ayr lake glaciation rather than the cape broughton aquatherm soil horizons indicate regressions at the end of the cape broughton aquatherm and ayr lake glaciation and pollen assemblages suggest that the terrestrial climate may have been warmer than the present climate a reinterpretation of u series dates and amino acid ratios on shells suggests that the cape broughton aquatherm and earlier events predate marine oxygen isotope substage 5e the ayr lake glaciation may have occurred well before the major interglacial glacial transition in more temperate latitudes but evidence from ocean cores in the north atlantic and ice cores from greenland and devon island supports the interpretation of warm water incursions into baffin bay during this ice advance following substage 5e by inference relative sea level during the period following the ary lake glaciation was lower than present sea level and glacier extent was restricted no evidence of an exceptionally cold dry climate has been found however distal glaciomarine sediments in the upper coastal cliffs suggest a limited readvance of fiord glaciers prior to the holocene near the beginning of the holocene 10 000 yr b p warmer water extended into the area as relative sea level fell and subsequently rose again to 15 m about 8 200 yr b p pollen assemblages in peat horizons suggest that during the earliest holocene a climate milder than that of the present day existed local deposition of eolian and soliflucted sediment may indicat deteriorating climate in late holocene time

practical techniques for 3d resistivity surveys and data inversion1 techniques to reduce the time needed to carry out 3d resistivity surveys with a moderate number 25 to 100 of electrodes and the computing time required to interpret the data have been developed the electrodes in a 3d survey are normally arranged in a square grid and the pole pole array is used to make the potential measurements the number of measurements required can be reduced to about one third of the maximum possible number without seriously degrading the resolution of the resulting inversion model by making measurements along the horizontal vertical and 45 diagonal rows of electrodes passing through the current electrode the smoothness constrained least squares inversion method is used for the data interpretation the computing time required by this technique can be greatly reduced by using a homogeneous half space as the starting model so that the jacobian matrix of partial derivatives can be calculated analytically a quasi newton updating method is then used to estimate the partial derivatives for subsequent iterations this inversion technique has been tested on synthetic and field data where a satisfactory model is obtained using a modest amount of computer time on an 80486dx2 66 microcomputer it takes about 20 minutes to invert the data from a 7 by 7 electrode survey grid using the techniques described below 3d resistivity surveys and data inversion can be carried out using commercially available field equipment and an inexpensive microcomputer

isotope stage 5 130 74 ka in greenland a review abstract marine and glacigene deposits dated with varying degrees of certainty to isotope stage 5 130 74 ka are exposed in coastal cliffs in 18 areas and localities in northern and eastern greenland dating methods include thermoluminescence tl u th methods and correlation with the deep sea record amino acid parameters are used for correlation between localities deposits from the last interglaciation isotope substage 5e are rare and have been found only at three localities in both west and east greenland their mollusc and foraminifer faunas indicate more vigorous sea surface circulation and sea surface temperatures some degrees higher than known from the holocene during this warm period ice sheet growth began in northwest greenland the ice sheet reached its maximum for the last ice age during the succeeding phase provisionally correlated with isotope substage 5d this was followed by a new warm period with increased influx of warm subarctic water and high summer temperatures on land provisionally correlated with isotope substage 5a in east greenland the observations indicate a more complex ice sheet history the record from greenland is very similar to that obtained in adjacent coastal areas of the high arctic implying that the rapid shifts from warm to cold during isotope stage 5 were especially conducive to the formation of the embryonic north american and scandinavian ice sheets at high northern latitudes probably because the pulses of warm water were required to advect sufficient moisture into these areas to allow the growth of continental ice sheets

the origin of intraplate deformation in the atlas system of western and central algeria from jurassic rifting to cenozoic quaternary inversion abstract analysis of petroleum exploration data supplemented by paleostress data enabled discussion of the origin of the deformation in the western and central saharan atlas algeria this intraplate area has recorded the breakup of pangea late triassic the opening of the maghrebian tethys since the dogger and subsequently its closure oligocene to present however the two periods of strong coupling between europe and africa late lutetian and pleistocene which correspond to rapid uplifts of the atlas system and important deformations are not collision related they can be correlated to the beginning and the end of the development of the western mediterranean sea

abrupt changes heinrich events in late quaternary north atlantic marine environments a history and review of data and concepts in the last several years evidence has mounted that a series of abrupt changes in sediment delivery and palaeoceanography effected the north atlantic they are recorded in a variety of proxy records but most dramatically in changes of grain size and mineralogy associated with postulated iceberg rafting events specifically heinrich h events this review paper examines the evidence for such evidence prior to the development of the heinrich event concept 1988 1992 and then examines the explosion of data and correlations that stemmed from the acceptance and use of this paradigm specific attention is focused on ideas pertaining to the cause s of glaciological mechanisms sediment delivery and sediment source and major gaps in our understanding of the underlying glaciological glacial geological and glacial marine processes are stressed abrupt changes across boundaries associated with h 2 in the labrador sea are illustrated from core hu87033 009lcf the case is made that correlations between records need to be more rigorous especially within the range of radiocarbon dating but it appears that abrupt changes in the delivery of iceberg rafted debris which characterize these intervals are multisourced it is unclear how global climate can simultaneously influence the abrupt behaviour of ice margins in different parts of the world for marine based margins changes in relative sea level are one possibility a qualitative model is presented for triggering h events which includes global changes in mass balance changes in relative sea level at ice margins due to glacial isostasy and changes in the basal thermal regime of tidewater ice streams 1998 john wiley sons ltd

earthquake induced flooding and paleoseismicity of the el asnam algeria fault related fold late quaternary activity of the el asnam thrust fault responsible for the october 10 1980 ms 7 3 earthquake and 36 km coseismic faulting is explored through diverse paleoseismological field methods we trenched through the main and secondary 1980 coseismic scarps made an analysis of earthquake induced flood deposits conducted a geomorphic study of leveling profiles and offset geological units across thrust and normal scarps and considered the geomorphology of the active fold twenty five radiocarbon ages from colluvial and alluvial deposits along with conventional fossils and artefacts dating of geological units show the timing of successive net vertical displacements on the thrust related fold and bending moment faults previous work showed that eight pre 1980 earthquakes occurred in clusters during the late holocene cumulative net vertical slip that amounts to 3 times the 1980 displacement is observed on multiple thrust fault scarps and offsets of geological units on bending moment faults maximum cumulative vertical displacements which are visible in different zones along the fault segments can reach 10 to 25 times the 1980 coseismic displacements the late quaternary uplift rate on the el asnam fault is 0 6 mm yr and taking into account slip variation along the fault this rate may range between 0 25 1 6 mm yr from which we obtain a shortening rate of 0 17 1 2 mm yr because the tell atlas mountains exhibit comparable seismogenic fault related folds with parallel and sequential structures of active faults a total average shortening rate of 2 05 mm yr during the late quaternary represents part of the convergence accommodated along the africa eurasia plate boundary

equilibrium line altitudes and paleoenvironment in the merchants bay area baffin island n w t canada the fiordlands south of merchants bay contain an extensive well preserved moraine record of a late foxe advance of local valley glaciers this has allowed accurate reconstruction of former glacier margins and computation of former equilibrium line altitudes elas by a variety of methods statistical comparison of three methods maximum lateral moraine elevation median elevation and accumulation area ratio aar shows that different techniques can give different results for the same glaciers lateral moraines gave estimates that were too low probably due to post glacial erosion or to non deposition median elevations and the aar method produced statistically similar results but only for glaciers of simple geometry the median elevation method fails to take into account variations in valley morphology and glaciological parameters and so is not reliable in all situations the aar method is supported by empirical evidence and is the best of the three methods for estimating former elas analysis of trend surfaces of present and late foxe elas shows changes in elevation and orientation through time due to changing environmental factors present elas are strongly influenced by local factors southerly storm tracks and warm maritime conditions paleo elas do not show this influence suggesting that davis strait may have been ice covered during the late foxe stade and that storm tracks were from the north

the influence of mesoscale physical processes on the larval fish community in the canaries ctz in summer abstract we have studied the relation between the hydrography the composition and horizontal structure of the larval fish community and the horizontal distribution patterns of larval fish abundances in an area characterised by strong mesoscale oceanographic activity located between the canary islands and the african coast the canaries coastal transition zone during august 1999 upwelling upwelling filaments cyclonic and anticyclonic eddies and island wakes are typical mesoscale features of the northwest african coast in summer a single upwelling filament off cabo juby was joined in mid august by a second that originated about 100 km to the north the two filaments flowed together and merged 100 km offshore the merged filament was partially entrained around a cyclonic eddy trapped between the canary islands and the african coast and interacted with cyclonic and anticyclonic eddies shed from gran canaria mesoscale oceanographic features strongly influenced the horizontal distributions of fish larvae eddies acted as a mechanism of concentration while upwelling filaments were dispersive transporting larvae from the african neritic zone into oceanic areas and towards the canary archipelago this transport was the major cause of the predominance of neritic larvae in the composition of the larval fish community of the area the results also suggest 1 that anchovy larvae are good indicators of the offshore displacement of upwelled water 2 that the alternation between anchovy and sardine as species dominant in the larval fish community of the area during summer depends upon the water temperature in the african upwelling region anchovy dominating at higher temperature 3 that a coupling of anchovy and sardine spawning with the mesoscale oceanographic structure formed by the upwelling filaments and trapped eddy overcomes the negative effect that ekman transport has on their populations

paleoenvironments of the last interglacial in northwest north atlantic region and adjacent mainland canada abstract the paleoenvironmental conditions that prevailed in the northwest north atlantic regions and adjacent mainland canada during the last interglacial are documented through lithostratigraphical and paleontological data in terrestrial sections and marine cores with special reference to the deep sea records that allow global correlations based on their isotopic stratigraphy the onshore paleovegetational data and the offshore planktonic faunal and algal records demonstrate much warmer than present terrestrial and marine environments during the climate optimum of the last interglacial sensu stricto isotopic substage 5e optimal conditions persisted in surface water of the labrador sea during the early glacial inception isotopic substage 5e 5d transition when extensive ice masses developed over arctic canada a deterioration of sea surface temperature in labrador sea followed the maximum 18 o peak of isotopic substage 5d during the later part of stage 5 climatic conditions similar to the present prevailed over southeastern canada and a recurrent warming is recorded in south central labrador sea fluctuating ice volumes in the canadian arctic led to episodic dilution of surface water masses in baffin bay and the eastern labrador sea and subarctic conditions apparently prevailed in nearshore environments of baffin island despite an ice marginal context

active coastal thrusting and folding and uplift rate of the sahel anticline and zemmouri earthquake area tell atlas algeria abstract major uplifts of late quaternary marine terraces are visible along the coastline of the tell atlas of algeria located along the africa eurasia convergent plate boundary the active tectonics of this region is associated with large shallow earthquakes m 6 5 numerous thrust mechanisms and surface fault related fold we conducted a detailed levelling survey of late pleistocene and holocene marine notches in the algiers region that experienced 0 50 m coastal uplift during the 2003 zemmouri earthquake mw 6 8 east of algiers holocene marine indicators show three pre 2003 main notch levels formed in the last 21 9 ka west of algiers on the sahel anticline the levelling of uplifted marine terraces shows a distinct staircase morphology with successive notches that document the incremental folding uplift during the late pleistocene and holocene the timing of successive uplifts related to past coseismic movements along this coastal region indicates episodic activity during the late holocene modelling of surface deformation in the zemmouri earthquake area implies a 50 km long 20 km wide ne sw trending se dipping fault rupture and an average 1 3 m coseismic slip at depth further west the 70 km long sahel fold is subdivided in 3 sub segments and shows 0 84 1 2 mm yr uplift rate in the last 120 140 ka the homogeneous holocene uplift of marine terraces and the anticline dimensions imply the possible occurrence of large earthquakes with mw 7 in the past the surface deformation and related successive uplifts are modelled to infer the size and characteristics of probable future earthquakes and their seismic hazard implications for the algiers region

paleoclimatic significance of subpolar foraminifera in high latitude marine sediments census data of subpolar planktonic foraminifera in high latitude sediment cores obtained using a 149 m mesh can be directly related to past surface water conditions in contrast analyses performed using material sieved with a 62 m mesh produce results that must be interpreted with regard to past dissolution conditions of the local deep or bottom waters this conclusion bears directly on the validity of several recent papers purporting to relate baffin bay and labrador sea paleo oceanography with wisconsinan glacial events in northeastern canada

bio and aminostratigraphy of some quaternary marine deposits in west greenland 14c dates and the geological setting of quaternary marine deposits from three sites in west greenland indicate a pre holocene age the mollusc faunas at the sites are distinctly different although

pollen analysis of the 1973 ice core from devon island glacier canada abstract meltwater from a 299 m long ice core was filtered and analyzed for fossil pollen and spores pollen concentration was higher in the late holocene and interglacial intervals ca 7 liter 1 than in the early holocene and wisconsinan ca 1 2 liter 1 ones the late holocene and interglacial assemblages were dominated by alnus alder whereas the early holocene and wisconsinan ones were dominated by betula birch and artemisia sage during the holocene and probably the last interglaciation most of the pollen and spores were blown a minimum of 1000 km from low arctic shrub tundra and adjacent subarctic picea spruce forest these areas were dominated by the arctic air mass during the summer pollinating season during the wisconsinan early holocene glacier ice and arctic air were more widespread and pollen sources were more distant thus at this time relatively little pollen was incorporated into the ice the devon ice core data suggest that there should have been pollen in the continental ice sheet of wisconsin time when the ice sheet retreated this pollen would be carried by meltwater and redeposited with silt and clay together with contemporary pollen producing an ecologically anomalous assemblage

palaeoclimate of baffin bay from 300 000 year record of foraminifera dinoflagellates and pollen several different models1 5 have attempted to relate quaternary marine and terrestrial records of ice sheet growth in the north atlantic region the models are derived from either discontinuous terrestrial records including marine fossils in raised shorelines1 2 or from deep sea calcareous microfossils3 4 this study correlates arctic marine and terrestrial data directly by comparing 18o foraminiferal dinoflagellate and pollen records from a core taken in baffin bay the core contains an almost continuous sequence of sediments deposited during isotope stages 1 10 subarctic foraminifera and atlantic dinoflagellates in early isotope stages 2 4 6 and 8 show that subarctic water entered southern baffin bay before the glacial maxima boreal subarctic pollen suggest that atlantic air flowed into baffin bay during the ice sheet growth phases these data support models which postulate that open water in the labrador sea had an important role in supplying moisture to laurentide and greenland ice sheets

land ocean correlations during the last interglacial glacial transition baffin bay northwestern north atlantic a review abstract evidence from terrestrial sections ice cores and marine cores are reviewed and used to develop a scenario for environmental change in the area of the extreme northwest north atlantic during marine isotope stages 5 and 4 the critical physical link between the landbased glacial chronology and marine events in baffin bay is the presence of carbonate rich drift along the baffin bay coast of bylot island and a detrital carbonate facies facies b in baffin bay sediments cores from baffin bay labrador sea can be dated by means of oxygen isotope variations and by peaks in the abundance of volcanic glass shards one occurrence of facies b is dated between late stage 5 and stage 4 and we correlate this event with the eclipse glaciation of bylot island and the ayr lake stade of the foxe glaciation of baffin island kogalu aminozone in contrast on west greenland amino acid racemization evidence suggests that the greenland ice sheet developed throughout stage 4 and reached a maximum in stage 3 svartenhuk advance 40 ka the oxygen isotope record in the devon island ice cap northwest baffin bay indicates that baffin bay was largely open during marine isotope stage 5 analyses of shallow water molluscan and foraminiferal assemblages deep water foraminifera pollen from iand sections and deep sea cores and dinoflagellates from marine cores indicate that interglacial conditions prevailed during much of the stage 5 4 glaciation

aminostratigraphy of quaternary marine and glaciomarine sediments qivitu peninsula baffin island a complex sequence of cyclical marine and glaciomarine lithofacies exposed along the coastal lowlands of the qivitu peninsula was deposited during the marine transgressions and regressions that affected this area during repeated glaciation of the region multivariate analysis of amino acid ratios measured on shell fragments of the pelecypods hiatella arctica and myatruncata in the lithostratigraphic units provides a basis for their chronocorrelation through the use of informal regional aminostratigraphic units termed aminozones all but the oldest aminozones correspond with particular lithostratigraphic units deposited during transgressive regressive periods when relative sea level was higher than present sea level discriminant analysis shows total amino acid fraction allo iso ratios from either species are the best overall criteria for assigning a shell sample to a particular aminozone but free fraction allo iso ratios are more useful in the younger zones the distribution of ratios in lithostratigraph