integrated stratigraphy and paleoceanography of the messinian latest miocene across the north atlantic ocean the messinian was a time of major climatic and paleoceanographic change during the late cenozoic it is well known around the mediterranean region because of the giant anhydrite gypsum sequence and the suggested desiccation of the mediterranean sea however this interval is less constrained outside the mediterranean region where several paleoceanographic changes could have taken place because of the desiccation hence we present an integrated stratigraphic framework for future messinian paleoceanographic studies determination of the effect of the mediterranean desiccation on deep water paleoceanography and comparison of intra mediterranean paleoceanographic changes with those in the open oceans during the messinian stage four dsdp odp holes 552a 646b 608 and 547a from the north atlantic ocean and one land borehole from morocco have been studied to integrate bio magneto and stable isotope messinian stratigraphy with high resolution sampling our results produce the best assessment of the tortonian messinian boundaries in all holes because they do not rely on any one signal in paleomagnetic subchronozone csan lr in the sale borehole and dsdp site 609 a s d coiling direction change of neogloboquadrina pachyderma acostaensis appears to indicate pmow entering the northeastern atlantic ocean at least reaching 50 n diachrony and synchrony of some important messinian planktic foraminifera from these atlantic dsdp odp holes and the sale borehole such as the lo of gq dehiscens the lo of gt lenguaensis the fo and lo of gt conomiozea the fo of gt margaritae s s the fo of gt puncticulata and the fo of gt crassaformis are discussed for understanding some of the paleoceanographic changes this integrated stratigraphie framework presented here allows much better north atlantic correlations at this critical point in messinian geologic history

a comparison of three methods of mass balance determination in the tuyuksu glacier region tien shan central asia a photogrammetric survey in 1998 formed the basis for compiling a map of the tuyuksu glacier region in the northern tien shan central asia comparison with a map from 1958 enables calculation of the change in glacier volume over 40 years the results are compared with direct annual measurements carried out continuously since 1956 central tuyuksu glacier shows a mass balance of 12 6 m w e for the geodetic method and 16 8 m for glaciological measurements in view of the high accuracy of the maps the discrepancy can be explained mainly by deficiencies in the glaciological measurements application of the precipitation runoff model hbv eth represents the hydrological method of mass balance determination and delivers specific mass balance losses almost twice those indicated by the geodetic observations this discrepancy is suspected to be caused by erroneous runoff measurements the volume balance derived by the geodetic method is used to calibrate both the glaciological and the hydrological method

miocene stable isotopic stratigraphy and magnetostratigraphy of buff bay jamaica previously reported biostratigraphic relationships from middle upper miocene sections exposed near buff bay jamaica 18 n tropical bioprovince differ from the subtropical north atlantic sites 563 and 558 time scales for this interval rely on correlations established at these subtropical sites and the differences with the tropical section have implications to global correlations planktonic foraminiferal zones n13 and n15 are thick at buff bay but are virtually absent at sites 563 and 558 nannofossil zone nn9 is associated with zone n15 and uppermost zone n14 at buff bay but is associated with zone n16 at the other sites magnetostratigraphic data presented here further complicate the interpretation zone nn9 is associated with a thick normal magnetozone at sites 563 and 558 at buff bay it is associated with a thick reversed magnetozone although a secondary magnetization at buff bay makes it difficult to identify confidently miocene normal magnetozones the thick reversed magnetozone most likely represents the paleomagnetic field and correlates with chron c5r the magnetobiostratigraphic relationships require either diachrony of taxa or two mutually exclusive hiatuses in jamaica and the north atlantic we address this problem by analyzing benthic foraminiferal 18 o and 13 c from the buff bay section these isotopic data allow us to evaluate three hypotheses that reconcile the magneto bio and isotopic stratigraphic data and conclude that the first and last occurrences of five taxa were diachronous by 0 3 0 5 m y between tropical and subtropical locations this requires revised age estimates for late middle to early late miocene biostratigraphic datum levels we suggest that the ranges of several taxa are useful for endemic tropical or subtropical zonations but correlations between the low and midlatitudes were affected by an increase in latitudinal thermal gradients during the late middle miocene however we admit that further studies are needed before this issue is resolved

calcareous nannofossil biostratigraphy of the m del casino section northern apennines italy and paleoceanographic conditions at times of late miocene sapropel formation a detailed quantitative calcareous nannofossil analysis has been performed on 138 samples from the astronomically dated monte del casino section with the aim to identify and precisely date the most important calcareous nannofossil events across the tortonian messinian boundary in the mediterranean and to unravel paleoceanographic conditions at times of sapropel formation during the late miocene from the biostratigraphic perspective the genus amaurolithus provides three successive first occurrences fos a primus a c f amplificusand a delicatus dated at 7 446 7 434 and 7 226 ma respectively other bioevents include the base and top of the small reticulofenestrids acme dated at 7 644 and 6 697 ma and the fo fco and lo of r rotaria dated at 7 405 7 226 and 6 771 ma these events appear to be useful in improving biostratigraphic resolution in the tortonian messinian boundary interval at least for the mediterranean quantitative analysis revealed changes in the calcareous nannofossil assemblage associated with the sapropels the observed fluctuations suggest a single mechanism for sapropel formation in the mediterranean during the late neogene sapropels are characterized by a decrease in the total number of coccoliths interpreted mainly as a reduction in calcareous nannofossil production due to increased siliceous plankton production during spring blooms and an increase in reworked specimens interpreted to reflect enhanced continental input via river run off an increase in abundance of the genus rhabdosphaeracan be explained by opportunistic behavior at the end of the spring bloom when nutrient levels start to become impoverished as far as sea surface water temperature indicators are concerned warm water d pentaradiatus shows positive fluctuations in sapropels while cooler water d intercalaris and c pelagicus show negative fluctuations 1999 elsevier science b v all rights reserved

stratigraphic numerical modelling of a carbonate platform on the romanche transverse ridge equatorial atlantic abstract the romanche transverse ridge equatorial atlantic is located in the northern flank of the fracture zone opposite the eastern ridge transform intersection rti it constitutes a major positive topographic anomaly that reaches a height of over 4 km above the level predicted by the thermal subsidence curve a series of e w aligned peaks located on the crest of the transverse ridge were at sea level during early and middle miocene times they are presently capped by a 300 m thick shallow water carbonate platform that grew on a subsiding oceanic crust basement surface flattened by erosion at sea level these structures are now about 1 km below sea level high resolution seismic reflection surveys and multibeam morphobathymetry as well as study of samples recovered from the carbonate platform allowed a reconstruction of the paleoenvironment and of the vertical movements of the peaks starting from the lower miocene ages derived from microfossils suggest that the base of the carbonate platform dates from 17 25 m y ago and the sinking of the platform started between 18 and 13 m y ago these data were included in a numerical simulation model that takes into account thermal and tectonic subsidence growth potential of the carbonates subaerial and submarine erosion rates and mio pliocene absolute sea level fluctuations the results outline the subsidence history of the romanche transverse ridge and suggest post miocene subsidence faster than that predicted by the thermal cooling model

evidence for eutrophication in the northwestern pacific and eastern indian oceans during the miocene to pleistocene based on the nannofossil accumulation rate discoaster abundance and coccolith size distribution of reticulofenestra abstract to reconstruct the cenozoic paleoceanographic evolution in particular temporal changes in nutrient levels we studied calcareous nannofossil assemblages from ocean drilling program holes 1210a located in the northwestern pacific ocean and 762b situated in the eastern indian ocean at each site we focused on the relationships among the nannofossil accumulation rate nar relative abundance of discoaster and coccolith size of the genus reticulofenestra the co occurrence of a low nar high discoaster abundance and presence of large reticulofenestra suggest a deep thermocline and nutricline typical of oligotrophic conditions conversely the co occurrence of a high nar low discoaster abundance and presence of small reticulofenestra indicate a shallow thermocline and nutricline typical of eutrophic conditions the combination of these three parameters suggests that the gradual eutrophication and collapse of sea surface stratification occurred in the northwestern pacific ocean at 7 9 6 4 and 5 0 ma in contrast abrupt eutrophication is indicated at 8 8 ma in the eastern indian ocean although the timing of eutrophication differs between the pacific and indian ocean sites it roughly coincides with tectonic and or climatic events around the two oceans this finding suggests that tectonic and climatic events are capable of causing an increase in the terrestrial input and or coastal upwelling of nutrients that subsequently leads to the eutrophication of sea surface waters

palaeontological evidence of communication between the central paratethys and the mediterranean in the late badenian early serravalian abstract in the middle miocene the area of present day eastern slovenia was situated at the eastern mouth of the slovenian corridor a hypothetical seaway connecting the central paratethys and the mediterranean the exact location and time of closure of a seaway between the two neighbouring marine realms are still a matter of debate we studied badenian late langhian and early serravallian calcareous nannoplankton assemblages from eastern slovenia for their palaeogeographical significance by comparing them to contemporaneous central paratethyan and mediterranean assemblages and the assemblages described in selected odp and iodp reports assemblage composition and the sequence of biostratigraphic events observed in slovenia were very similar to that in several mediterranean sites comparison with the world ocean suggests that this similarity reflects communication between the mediterranean and paratethyan populations rather than a universal trend of nannoplankton evolution late badenian assemblages from different localities within the central paratethys exhibit considerable variation with respect to the presence of discoasters considered as typical of the mediterranean and the presence of rhabdosphaera poculi and hayella challengeri considered as typical of the eastern paratethys our results suggest the mixing of mediterranean and eastern paratethyan influences throughout the entire central paratethys during the late badenian the observed variability explains how opposing views on the status of the marine connection between the central paratethys and the mediterranean in the late badenian can arise from palaeontological studies of fossil assemblages considering only a single site or a small area the gastropod species pereiraea gervaisi migrated from the mediterranean to the central paratethys where it is only known from the immediate proximity of the hypothesised slovenian corridor this supports the thesis that the communication between the two seas took place via the slovenian corridor and not some other marine connection like the hypothetical axios vardar trench

snowline depression in the tropics during the last glaciation five primary methods have been used to reconstruct pleistocene snowlines or equilibrium line altitudes elas in the tropics 23 53n 23 53s during the last glaciation but each has inherent errors that limit the accuracy of the results additional potential errorsin determiningela depression involveestimates of modernsnowline altitude datingresolution topographicreconstructionof former glaciers orographic e ects the presence of rockfall debris on glaciers and calculation of regional ela gradients eustatic sea level lowering during the last glaciation is an additional factor in uencing estimates of ela depression ela in cases where modern snowline lies above a mountain summit only a minimum value for ela can be obtained at 12 tropical sites in africa the americas to 103s latitude and paci c islands estimates of average ela range from 440 to 1400m but most fall in the range of 800 1000m mean 1 900 135m in a regional study of ela depression in the southern tropical andes 8 223s an average ela of ca 920 250m has been reported based on the assumption that glacier mass balance was controlled solely by ablation season temperature and assuming a full glacial temperature lapse rate of 63c km depression of mean annual temperature in glaciated alpine areas was ca 5 4 0 83c if adjusted for a sea level fall of 120m at the glacial maximum this value is reduced to 4 7 0 83c the gure is based on the unlikely assumption that accumulation on alpine glaciers has been invariant nevertheless it is similar to values of temperaturedepresson 5 6 43c for the last glaciationobtainedfrom variousterrestrial sites but contrasts with tropical sea surface temperature estimates that are only 1 33c cooler than present 2001 elsevier science ltd all rights reserved

variations in the strontium isotopic ratio of seawater during the miocene stratigraphic and geochemical implications a composite strontium isotopic seawater curve was constructed for the miocene between 24 and 6 ma by combining 87sr 86sr measurements of planktonic foraminifera from deep sea drilling project sites 289 and 588 site 289 with its virtually continuous sedimentary record and high sedimentation rates 26 m m y was used for constructing the oligocene to mid miocene part of the record which included the calibration of 63 biostratigraphic datums to the sr seawater curve using the timescale of cande and kent 1992 across the oligocene miocene boundary a brief plateau occurred in the sr seawater curve 87sr 86sr values averaged 0 70824 which is coincident with a carbon isotopic maximum cm o m from 24 3 to 22 6 ma during the early miocene the strontium isotopic curve was marked by a steep rise in 87sr 86sr that included a break in slope near 19 ma the rate of growth was about 60 ppm m y between 22 5 and 19 0 ma and increased to over 80 ppm m y between 19 0 and 16 ma beginning at 16 ma between carbon isotopic maxima cm3 and cm4 of woodruff and savin 1991 the rate of 87sr 86sr growth slowed and 87sr 86sr values were near constant from 15 to 13 ma after 13 ma growth in 87sr 86sr resumed and continued until 9 ma when the rate of 87sr 86sr growth decreased to zero once again the entire miocene seawater curve can be described by a high order function and the first derivative d87sr 86sr dt of this function reveals two periods of increased slope the greatest rate of 87sr 86sr change occurred during the early miocene between 20 and 16 ma and a smaller but distinct period of increased slope also occurred during the late miocene between 12 and 9 ma these periods of steepened slope coincide with major phases of uplift and denudation of the himalayan tibetan plateau region supporting previous interpretations that the primary control on seawater 87sr 86sr during the miocene was related to the collision of india and asia the rapid increase in 87sr 86sr values during the early miocene from 20 to 16 ma imply high rates of chemical weathering and dissolved riverine fluxes to the oceans in the absence of another source of co2 these high rates of chemical weathering should have quickly resulted in a drawdown of atmospheric co2 and climatic cooling through a reversed greenhouse effect the paleoclimatic record however indicates a warming trend during the early miocene culminating in a climatic optimum between 17 and 14 5 ma we suggest that the high rates of chemical erosion and warm temperatures during the climatic optimum were caused by an increase in the contribution of volcanic co2 from the eruption of the columbia river flood basalts crfb between 17 and 15 ma the decrease in the rate of crfb eruptions at 15 ma and the removal of atmospheric carbon dioxide by increased organic carbon burial in monterey deposits eventually led to cooling and increased glaciation between 14 5 and 13 ma the crfb hypothesis helps to explain the significant time lag between the onset of increased rates of organic carbon burial in the monterey at 17 5 ma as marked by increased 13c values and the climatic cooling and glaciation during the middle miocene as marked by the increase in 18o values which did not begin until 14 5 ma

radiolarian stratigraphy across the oligocene miocene transition abstract recently the international union of geological sciences commission on stratigraphy working group on the paleogene neogene boundary proposed that the oligocene miocene boundary be placed at the base of chron c6cn2n at 23 8 ma on the cande and kent 1992 magnetic time scale where it is approximated by planktic foraminifera at the first occurrence of globorotalia kugleri and by calcareous nannofossils at the last occurrence of sphenolithus ciperoensis and the first and last occurrences of sphenolithus delphix and s capricornutus herein we show that in terms of radiolarians the base of chron c6cn2n can be correlated with the upper part of the lychnocanoma elongata zone between the last occurrence of artophormis gracilis 23 94 ma and the first occurrence of cyrtocapsella tetrapera 23 69 ma since the proposed stratotype at lemme carrosio italy does not contain radiolarians at the boundary we re examined 13 dsdp sites and established the stratigraphic sequence of 29 first and last radiolarian occurrences and one evolutionary transition across the boundary nine of these sites contain both calcareous and siliceous microfossils and thus allow for an integrated biostratigraphy paleomagnetic stratigraphy is not available for any of the dsdp cores examined however use of hodell and woodruff s 1994 strontium isotope curve from dsdp site 289 has permitted calibration of several low latitude microfossil datum levels against the geomagnetic polarity scale two new species lychnocanoma apodora and eucyrtidium plesiodiaphanes are described

mass balance of himalayan glaciers using aar and ela methods the accumulation area ratio aar for himalayan glaciers representing zero mass balance is substantially lower than for north america and europe regression analysis suggests 0 44 for the aar representing zero mass balance in the western himalaya a good correlation was observed when this method was applied to individual glaciers such as gara and gor garang in himachal pradesh india the correlation coefficients r using 6 and 7 years of data respectively were 0 88 and 0 96 for gara and gor garang glaciers respectively however when data from six western himalayan glaciers were correlated the correlation was 0 74 the aar was also estimated by using landsat images which can be useful in obtaining a trend in mass balance for a large number of himalayan glaciers for which very little information exists a higher correlation was observed between equilibrium line altitude ela and mass balance the field data from gara and gor garang glaciers shows a high correlation coefficient i e 0 92 and 0 94 respectively the ela values obtained from the landsat satellite images combined with topographic maps suggest positive mass balance for the year 1986 87 and negative for 1987 88

glaciological conditions in seven contrasting regions estimated with the degree day model we apply the degree day model to seven glacial regions that offer contrasting conditions and are well documented in the world glacier inventory the regions are axel heiberg island in arctic canada svalbard northern scandinavia southern norway the alps the caucasus and new zealand we estimate the average equilibrium line altitude ela for each half degree latitude longitude grid square from the median elevations of glaciers within the square and we extrapolate temperature from the uea cru climate research unit of the university of east anglia gridded climatology using the degree day model we calculate annual accumulation at the ela equal to ablation at the ela and other quantities like summer mean temperature length of melt season balance gradients and the sensitivity of mass balance to temperature and or precipitation changes glaciers can be characterized on a scale from cold dry axel heiberg island to warm wet new zealand corresponding to the contrast between maritime and continental climates mass balance sensitivities to temperature and or precipitation changes are relatively small for dry cold climate and relatively high for warm wet climate we could extend the approach to other glacier regions but we note that there are large areas for which ela data are not available as they are still not covered by the world glacier inventory

palaeoglaciation of parque natural lago de sanabria northwest spain abstract detailed geomorphological mapping provides evidence for at least three phases of glaciation in the parque natural lago de sanabria in northwest spain the most extensive glaciation was characterised by a large plateau ice cap a combination of geomorphological evidence and glacier modelling indicates that this ice cap covered an area of more than 440 km 2 with a maximum ice thickness of c 300 m and outlet glaciers reaching as low as 1000 m this represents the largest ice mass in iberia outside the pyrenees and one of the largest in the mountains of southern europe and the mediterranean region radiocarbon dates from the base of lacustrine sequences appear to suggest that the most extensive phase of ice cap glaciation occurred during the last cold stage weichselian with deglaciation occurring before 14 15 ka 14 c bp a second phase of glaciation is recorded by the moraines of valley glaciers which may have drained small plateau ice caps whilst a final phase of glaciation is recorded by moraines in the highest cirques

a review of calcareous nannofossil astrobiochronology encompassing the past 25 million years this paper presents a review of astrobiochronological calibration of recent to late oligocene calcareous nannofossil datum events biohorizons included in the paper are those of the widely used standard nannofossil zonations of martini e 1971 standard tertiary and quaternary calcareous nannoplankton zonation in farinacci a ed proceedings of the second international conference on planktonic microfossils roma rome ed tecnosci vol 2 pp 739 785 and okada h and bukry d 1980 supplementary modification and introduction of code numbers to the low latitude coccolith biostratigraphy zonation bukry 1973 1975 marine micropaleontology 51 321 325 as well as supplementary biohorizons proposed in the literature the biohorizons have been selected on the basis of the unambiguous taxonomy of the index taxa and their biostratigraphic usefulness we emphasise the application of rigorous methodology in nannofossil studies which permits an evaluation of biohorizons in terms of reliability and calibrates their potential correlatability astrochronological age estimates rely on the geologic timescale developed by the ics in 2004 with some new calibrations included we provide an overview of the relative position of biohorizons versus the astronomically calibrated ages of magnetic reversals and reference isotope stratigraphies surprisingly there are still few high resolution quantitative biostratigraphic studies of astrochronologically tuned sections in spite of the central role of such studies in addressing fundamental problems such as the tempo and mode of plankton evolution

mid mis3 climate inferred from reconstructing the dalijia shan ice cap north eastern tibetan plateau the local last glacial maximum lgml on dalijia shan occurred during mid marine isotope stage 3 mis3 which is consistent with some tibetan plateau records but asynchronous with the mis2 global last glacial maximum lgmg paleoclimatic reconstructions are key to advancing understanding such spatial and temporal patterns of paleoglaciation using multiple methods we reconstructed mid mis3 equilibrium line altitude ela on dalijia shan and inferred temperature depressions geomorphic ela reconstructions combined with empirical data on current ela temperature and precipitation yield a mid mis3 ela of 4000 78 m a s l 618 851 m lower than current and a temperature depression of 3 3 6 8 c independent glacial modeling using the degree day approach suggests a mid mis3 ela between 3971 and 4024 m a s l and a temperature depression of 4 2 5 6 c the consistency of these results indicate that mid mis3 temperature depressions in the dalijia shan region were 3 3 6 8 c which is less than the lgmg temperature depression inferred from regional climatic proxy data combined with other proxy data this suggests that the lgml glacial advance in dalijia shan resulted from lower temperatures and slightly reduced precipitation compared with present whereas the lgmg advance was more restricted because much colder conditions were combined with much lower precipitation

defining modern day area altitude balance ratios aabrs and their use in glacier climate reconstructions abstract with the increasing use of digital elevation models in palaeo glacier reconstructions and the availability of freeware spreadsheets the area altitude balance ratio aabr and balance ratio br methods are becoming increasingly used in palaeo glacier reconstruction for estimating equilibrium line altitudes ela and subsequently deriving quantitative estimates of palaeo climate while there are many data detailing contemporary accumulation area ratios there are still only a few studies that have established from contemporary environments aabr br ratios publicly available glacier mass balance world glacier monitoring service us geological survey and norwegian water directorate and spatial extent datasets provided the basis for this research from a time series of mass balance regressing specific net balance against ela allows the zero net balance ela to be identified once the zero balance ela is established the glacier hypsometry above and below the ela is defined the aabr br is calculated by using the right hand side the following aabr b n a b b n a c z a c a a c z a b a a b where b nab and b nac are the net mass balance gradients in the ablation and accumulation zones respectively z a c and z a b are the area weighted mean altitudes of the accumulation and ablation areas respectively and a ac and a ab are the areas of the accumulation and ablation areas respectively aabrs are calculated for a suite of glaciers located across a range of climatic zones and glacier types with antarctica being excluded the following representative aabrs are found a global aabr 1 75 0 71 mid latitude maritime 1 9 0 81 high latitude 2 24 0 85 north america west coast 2 09 0 93 north america eastern rockies 1 11 0 1 canadian arctic 2 91 0 35 svalbard 2 13 0 52 western norway 1 5 0 4 european alps 1 59 0 6 central asia 1 75 0 56 kamchatka 3 18 0 16 this study provides an empirically derived dataset characterising aabr ratios which may be used for ela estimation in palaeo glacier reconstructions and for palaeo climate quantification

paleoceanography of the mid pleistocene the fossil record of the pleistocene calcareous nannoplankton indicates that during the mid pleistocene 0 93 1 25 my occurred an episode of overwhelming dominance of smallgephyrocapsa during this episode normally abundant large size specimens of this genus mainlygephyrocapsa oceanica were virtually excluded from the phytoplankton of tropical and subtropical oceans the best modern analog of this dominantly smallgephyrocapsa assemblage is the subpolaremiliania huxleyi assemblage which implies that nutrient content was significantly greater and water temperature was lower in the photic water column of the tropical oceans than they are today increased equatorial upwelling in the oceans on a scale much greater than today may explain the above pattern to achieve such broad equatorial upwelling there must be a source and a drive for cold dense water the arctic ocean which was probably seasonally free of ice during this interval of the mid pleistocene is capable of providing the requisite source as well as a drive for the inferred equatorial upwelling the energy balance of a predominantly ice free arctic ocean requires an approximately three to seven fold increase of hydrospheric heat transport from the north atlantic to the arctic ocean which dictates a corresponding or even greater increase in the volume of warm water entering the arctic ocean at the surface and cold dense water exiting at depth to the north atlantic such enhanced dense water formation in the arctic ocean could drive the intensified equatorial upwelling implied by the smallgephyrocapsa dominance interval if the above scenario is correct then the climate of the earth s northern hemisphere during the mid pleistocene may have been very different from the younger pleistocene climate one manifestation of this difference may be the mid pleistocene shift in climatic cycle periodicity from 40 ky to 100 ky another important aspect is that the enhanced greenhouse effect expected during the next century because of an increase of atmospheric co2 is thought to lead directly to melting of the arctic ocean ice cover and of the greenland ice sheet thus the greenhouse arctic ocean and its attendant ocean circulation would resemble the inferred mid pleistocene conditions

using 10be exposure dating to constrain glacial advances during the late glacial and holocene on mount xuebaoding eastern tibetan plateau moraines preserved around mount xuebaoding 5588 m above sea level on the eastern margin of the tibetan plateau represent past glacial activity in this area the chronology of these moraines was established using 10be exposure dating the dating results revealed multiple glacial events prior to the late glacial 14 1 2 2 ka the late glacial 15 6 1 6 to 11 2 3 0 ka the early middle holocene 9 1 0 9 to 6 7 0 7 ka and the neoglacial periods 2 5 0 5 to 1 5 0 1 ka these glacial stages are consistent with the recalculated ages from surrounding areas throughout the indian and east asian monsoon influenced region on the eastern tibetan plateau comparing with other paleoclimate indexes we suggest that the late glacial event was mainly driven by low temperature the early middle holocene event by high precipitation and the late holocene neoglacial event by low temperature

integrated stratigraphy and 40ar 39ar chronology of early middle miocene sediments from dsdp leg 42a site 372 western mediterranean abstract an integrated magneto biostratigraphic framework is presented for middle miocene sediments of dsdp site 372 located in the western mediterranean detailed biostratigraphic analysis shows a nearly complete sequence of early middle miocene calcareous plankton bioevents in the mediterranean including the lco last common occurrence of the nannofossil sphenolithus heteromorphus which has been astronomically dated in the ras il pellegrin rip section on malta island abels h a hilgen f j krijgsman w kruk r w raffi i turco e zachariasse w j 2005 long period orbital control on middle miocene global cooling integrated stratigraphy and astronomical tuning of the blue clay formation on malta paleoceanography 20 pa4012 doi 10 1029 2004pa001129 11 pp thermal demagnetization of discrete samples revealed a characteristic low temperature component with dual polarities despite a weak paleomagnetic signal the resultant magnetostratigraphic record combined with the calcareous plankton biostratigraphy is straightforwardly correlated to the geomagnetic polarity time scale ck95 of cande and kent cande s c kent d v 1995 revised calibration of the geomagnetic polarity time scale for the late cretaceous and cenozoic j geophys res 100 6093 6095 and the astronomical tuned neogene time scale atnts04 of lourens et al lourens l j hilgen f j laskar j shackleton n j wilson d 2004 the neogene period in gradstein f m ogg j g smith a g eds a geologic time scale cambridge univ press pp 409 440 the subchrons recorded in site 372 succession range from c5br up to c5aar to confirm the magnetostratigraphic calibration 40ar 39ar dating was performed on feldspar of two volcanic ash layers the radio isotopic dating indicates a younger age for these two ash layers compared to the magnetostratigraphic calibrated ages according to the ck95 and atnts04 age models however if the astronomically calibrated age of 28 21 0 04 ma is used for the fish canyon standard fcs the age for the older ash layer exactly matches its atnts04 age ages for bioevents were calculated assuming constant sedimentation rates between magnetostratigraphic age tie points the s heteromorphus lco has an age of 13 54 ma and 13 63 ma according to ck95 and atnts04 respectively which is consistent with the astronomical tuned age of 13 65 ma determined at rip section abels h a hilgen f j krijgsman w kruk r w raffi i turco e zachariasse w j 2005 long period orbital control on middle miocene global cooling integrated stratigraphy and astronomical tuning of the blue clay formation on malta paleoceanography 20 pa4012 doi 10 1029 2004pa001129 11 pp we therefore conclude that the magnetostratigraphic calibration of dsdp site 372 is correct and that for the time being this site can be considered as a reference section for the early middle miocene of the mediterranean region

little ice age glaciers in the balkans low altitude glaciation enabled by cooler temperatures and local topoclimatic controls moraine ridges are present in the highest cirques of the durmitor massif in montenegro and post date the widespread pleistocene moraines of this area lichenometry suggests that at least eight glaciers were present in the 19th century and correlate with the culmination of the little ice age in the european alps cooler temperatures combined with local topoclimatic controls including windblown and avalanching snow as well as shading were crucial for the formation and survival of these glaciers below the regional equilibrium line altitude the resultant regional equilibrium line altitude ela was positioned close to the highest peaks between 2400 and 2500 m with local controls such as avalanche windblown snow and shading depressing the ela in the northern cirques to 2130 2210 m this ela position was very low for this latitude and lower than for most glaciers in the european alps at any time during the holocene and even equivalent to many alpine glaciers during the younger dryas today one glacier still survives in montenegro in a deep northeast facing cirque characterized by the largest combined areas of potential avalanche and windblown snow copyright 2009 john wiley sons ltd

controls on spatial variations of glacial erosion in the qilian shan northeastern tibetan plateau abstract understanding interactions between topography and glacial erosion is a key to advancing knowledge of mountain landscape evolution and is often hampered by the lack of quantitative data for glacial erosion here we examine spatial variations in glacial erosion in the qilian shan using a power law model y axb fit to cross profiles of glacial valleys we further analyze the impacts of glacial dynamics topography and lithology on the degree of glacial erosion using qualitative and quantitative methods although the distribution of glacial erosion is controlled by the combined effects of glacial dynamics topography and lithology average glacier size or ice flux and mean slope above the equilibrium line altitude are dominant controls in addition the topographic data analyzed through a b fr diagram suggests two opposite types of glacial valley cross profile development temperate maritime glacier valleys are mainly dominated by overdeepening while continental glacier valleys are mainly dominated by a widening process although this varies with lithology

size specific steady state accumulation area ratio an improvement for equilibrium line estimation of small palaeoglaciers abstract characteristic distribution of the steady state accumulation area ratio aar0 of valley and corrie glaciers was investigated in a global dataset comprised of 46 glaciers there is a positive relationship between aar0 and glacier area with smaller glaciers having lower values of aar0 compared with larger glaciers the relationship between glacier area s and steady state aar of studied glaciers can be optimally described by a logarithmic regression equation this relationship is thought to be a globally valid approximation if the size of the glacier is not smaller than 10 1 km2 in the case of palaeoglaciers an aar0 value of 0 44 0 07 is best applied on glaciers with areas in the range 0 1 1 km2 0 54 0 07 for glaciers covering areas between 1 and 4 km2 and 0 64 0 04 for glaciers larger than 4 km2 this assumes insignificant debris cover for the investigated palaeoglaciers the proposed size specific aar0 values take into account the geometric hypsometric properties of palaeo glaciers the results have major importance for palaeoglaciological reconstructions in many regions of former marginal niche glaciation characterized by small former glaciers

geomorphological evidence and 10be exposure ages for the last glacial maximum and deglaciation of the velka and mala studena dolina valleys in the high tatra mountains central europe abstract 10be exposure age chronology of the last glaciation was established in a key area at the southern slopes of the high tatra mts western carpathians in situ produced 10be in moraine boulders glacially transformed bedrock surfaces and rockfall accumulations constrains the timing of the last glacial maximum lgm glacier expansion and provides chronological evidence for the post lgm decay of one of the largest paleoglaciers in the range the uncertainty weighted mean age of 22 0 0 8 ka obtained for the terminal moraine in the forefield of the velka studena dolina valley indicates that the oldest moraine was deposited close to the global lgm this finding confirms that well preserved moraines in the range were formed during the last glacial cycle and that glaciation on the southern flank of the range was more extensive than earlier in the last glacial cycle the maximum glacier extent correlates with late wurmian weichselian glacier phases in the alps the bavarian bohemian forest and the krkonose mts but probably postdates the period of maximum glaciation in the southern carpathians re advance moraines at the mouth of the velka studena dolina valley and in the middle part of the mala studena dolina valley were deposited no later than around 20 5 ka and 15 5 ka respectively the timing of these advances is broadly synchronous within the high tatra mts as well as with glacier advances in the alps bavarian bohemian forest and krkonose mts 10be exposure ages obtained from glacially transformed bedrock surfaces range between 20 5 1 7 ka and 10 7 0 3 ka constraining the onset and the final phase of the deglaciation surface exposure dating of four rockfall accumulations produced uncertainty weighted mean ages of 20 2 1 2 ka 17 0 0 7 ka 16 5 0 4 ka and 15 6 0 7 ka these ages indicate that activation of rock slope failures occurred under paraglacial conditions within a few centuries up to 1400 years after the formation of re advance moraines

miocene nannofossil chronology in the north atlantic dsdp site 608 abstract dsdp north atlantic site 608 yielded an excellent miocene pelagic section which affords a further opportunity for elucidating the chronology of the calcareous nannofossil succession in the framework of magnetostratigraphic control most of the conventional zonal markers have been documented for this site and some of the earlier results are confirmed and refined in addition several unconventional and less known markers have been added the first two are the highest last occurrence of sphenolithus delphix and sphenolithus capricornutus at 23 6 ma which is immediately above the oligocene miocene boundary as identified by the last occurrence of reticulofenestra bisecta at 23 7 ma the next unconventional datum is the highest last occurrence of ilselithina fusa at 22 8 ma which is also the highest last occurrence of helicosphaera recta calcidiscus tropicus lowest first occurrence is at 19 5 ma which is also the lowest occurrence of sphenolithus belemnos and calcidiscus leptoporus lowest first occurrence coincides with that of sphenolithus heteromorphus at 18 5 ma sphenolithus dissimilis highest last occurrence is at 18 2 ma and the calcidiscus premacintyrei lowest first and highest last occurrences are respectively at 17 7 and 11 7 ma discoaster braarudii occurs from 11 6 to 11 3 ma and its highest last occurrence corresponds to that of cyclicargolithus floridanus minylitha convallis occurs from 9 0 to 6 9 ma within the range of minylitha at 8 0 ma a major shift occurs in reticulofenestrid placoliths from dominantly large reticulofenestra pseudoumbilicus and medium size reticulofenestra minutula species below to significant numbers of very small species dictyococcites productus and gephyrocapsa above this is interpreted to be a major though perhaps seasonal change of productivity of the north atlantic at site 608 a new genus and species cryptococcolithus takayamae is described and a variety reticulofenestra pseudoumbilicus var amplus is identified

sedimentation rates from calcareous nannofossil and planktonic foraminifera biostratigraphy in the andaman sea northern bay of bengal and eastern arabian sea abstract in this study we determined calcareous nannofossil and planktonic foraminifera events in sediments recovered during the 2006 indian national gas hydrate program nghp expedition 01 selected bioevents permitted the assignment of orbitally calibrated ages derivative sedimentation rate estimates and identification of sedimentary discontinuities in the andaman sea at hole nghp 01 17a a late miocene to recent record was recovered but with a significant hiatus during the latest miocene and pliocene sedimentation rates here vary from 50 m myr during the pleistocene to 130 m myr for the late miocene in the northern bay of bengal at hole nghp 01 19a the base of the cored record also reaches the late miocene and extends to recent but the same hiatus missing the pliocene is present at this hole a the early pleistocene at hole nghp 1 19a shows sensible variation in sedimentation rates ranging between 130 m myr and 10 m myr during the last 0 5 ma for the late miocene the sedimentation rate was ca 50 m myr in the western bay of bengal at hole nghp 01 10b d calcareous nannofossils were sparse and only foraminifera datums are available the base of the section is latest early pliocene to late pliocene and the majority of the record is considered younger than late pliocene due to the scarcity of calcareous nannofossils and the few foraminifera datums sedimentation rates were not determined here however hole nghp 01 16a in the same region recorded the highest occurrence of pseudoemiliania lacunosa an event that confirms a pleistocene age allowing us to estimate a sedimentation rate between 110 m myr and 450 m myr along the western peninsular indian margin at hole nghp 01 01a a continuous record from the holocene to the early oligocene indicates sedimentation rates of ca 25 m myr until the middle miocene and a sensible reduction downward reaching 4 m myr in the early miocene to the early oligocene no hiatuses were observed the large changes in sedimentation rates observed in these cores reflect long timescale changes in the environment likely induced by changes in the strength of the indian monsoon system

coccoliths in sediment traps from the norwegian sea abstract the fine fraction of surface sediment samples in the norwegian sea shows an unexpectedly high amount of calcareous nannoplankton investigations using time series sediment traps in the lofoten basin 69 n 1983 84 near bear island 75 n 1984 85 and in the fram strait 78 n 1984 85 provided information about the accumulation of this material in relation to the strong seasonality of biological production coccolith identification and counting by means of a scanning electron microscope indicated that the coccolith assemblages in the traps consist almost entirely of the two speciesemiliania huxleyi andcoccolithus pelagicus these species dominated the flux rate of the nannoplankton carbonate a further eight species only made minor contributions to the flux in the lofoten basin a distinct seasonality could be recognized in both standing crop and carbonate flux also the relationship between the two main species and the proportion of intact coccospheres showed an annual cycle in the sample series of the two northerly traps the seasonality was less distinct in general the coccolith flux decreases towards the north this was particularly evident for the smaller speciese huxleyi while the number of massivec pelagicus coccoliths and so the coccolith carbonate flux diminished only slightly additional investigations on water samples from the norwegian sea revealed species compositions that differed greatly from those in the sediment traps this suggests that selective processes change the relative species proportions during sedimentation

punctuated evolution of global climate cooling during the late middle to early late miocene high resolution planktonic foraminiferal and oxygen isotope records from the mediterranean high resolution planktonic foraminiferal and oxygen isotope records are presented from a mediterranean deep marine succession dated astronomically between 12 12 and 9 78 ma planktonic and benthic oxygen isotope records are punctuated by two episodes of 18o increase which have astronomical ages of 11 4 and 10 4 ma and correspond to the mi5 and mi6 events of miller et al 1991a these ice growth events coincide with low amplitude variations in the 1 2 myr obliquity cycle and are accompanied by significant faunal changes in the mediterranean such as the arrival of neogloboquadrinids the increase in abundance of the g apertura g obliquus group and the areal differentiation between n atlantica and n acostaensis short term variations in the planktonic foraminiferal and oxygen isotope records correspond to dominantly precession controlled sedimentary cycles features of the sapropel grey marl layers indicate that the short term astronomically controlled circum mediterranean climate changes remained basically the same over the last 12 myr

determining steady state accumulation area ratios of outlet glaciers for application of outlets in climate reconstructions abstract a steady state glacier equilibrium line altitude ela can be determined by the accumulation area ratio aar method aar varies with climate balance ratio and glacier type glacier geometry the method involves calculating steady state accumulation area ratios aar0 from mass balance characteristics of glaciers by statistical methods in order to confirm the application of linear regression to calculate aar0 in the case of outlet glaciers a method to reveal the mathematical relationship between annual net balance bn and aar was developed analyses carried out on bn aar data sets for 14 outlet glaciers showed that the best approximation for the bn aar relationship is linear with an average squared correlation coefficient of 0 786 but relatively strong non linearity was detected for several glaciers a possible explanation lies in the hypsometry of the observed glaciers results confirm the application of linear regression to calculation of aar0s for outlet glaciers an average aar0 of 0 58 was estimated as the type specific aar0 for outlet glaciers

relationship between surface water temperature and ice sheet expansion during the middle miocene abstract a three fold expansion of the antarctic ice sheet at 13 60 12 82 and 11 60 ma has been inferred from 18o maxima analyzed in planktonic and benthic foraminiferal tests although accompanying changes in sea surface temperature have not been detailed we present estimated changes in middle miocene surface water temperatures based on analysis of 18o in planktonic foraminifera collected at mid latitude deep sea drilling project sites in the north atlantic and south pacific oceans we also identify periods of ice sheet growth based on comparisons of benthic and planktonic foraminiferal 18o values our results indicate 1 a distinct cooling of the sea surface from 13 6 to 13 5 ma immediately following a peak in ice volume at 13 6 ma 2 a cooling of the sea surface during a period of increasing ice volume from 13 2 to 13 0 ma and 3 a development of the antarctic ice sheet during a period of cooling of the sea surface centered at 11 6 ma

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

the rif chain northern morocco in the late tortonian early messinian tectonics of the western mediterranean orogenic belt evidence from the tanger al manzla wedge top basin

reconstruction of equilibrium line altitudes for tropical and sub tropical glaciers past fluctuations of tropical and sub tropical glaciers provide important palaeoclimate proxies for regions where other forms of evidence are rare however published equilibrium line altitude ela estimates for tropical and sub tropical glaciers at the lgm vary widely reflecting the diversity of methods and approaches employed by different research groups this complicates regional and global comparisons of ela estimates and emphasises the need for standardised methods the distinctive character of tropical and sub tropical glaciers however means that standard methods for reconstructing former glacier limits elas and palaeoclimate need to be adapted for local conditions many methods of ela reconstruction explicitly or implicitly make assumptions about glacier mass balance gradients and care needs to be taken that the choice of accumulation area ratios aars balance ratios brs and terminus to head ratios thars is appropriate as such indices are influenced by climatic regime debris cover and other factors ela reconstructions should employ multiple methods and should be cross checked and fully reported to allow assessment of the accuracy of ela estimates reliable glacier chronologies are equally important dating should be based on multiple radiometric techniques wherever possible and method of dating the type of material dated and the context of the date must all be reported

former plateau ice fields in the godeanu mountains southern carpathians first evidence of glaciated peneplains in the carpathians abstract the existence of plateau ice fields in the southern carpathians has long been suggested due to the widespread presence of the bor scu surface in the region the bor scu surface is a peneplain consisting of flat plateaus in the elevation range of 1800 2200 m a s l it is present throughout the southern carpathians with the most typical appearance in the godeanu mountains these plateaus could have served as ice accumulation sites during the pleistocene glaciations as they were well above the steady state equilibrium line altitude ela 0 direct geomorphological evidence on the existence of plateau ice fields and thus well founded reconstructions are absent due to the lack of glacial landforms on the plateaus in order to test the existence of plateau ice fields a previous geomorphological survey and theoretical ice surface profiles based on a steady state perfectly plastic ice flow model were used based on these methods maps and three dimensional surface models of the former glaciers were created the ela 0 s of the paleoglaciers were estimated by the accumulation area ratio aar method according to our results three major ice fields on the central plateaus and several smaller ice fields on wide saddles were present in the godeanu mountains during the maximal glaciation the ice fields fed numerous surrounding valley glaciers several independent valley and cirque glaciers completely separated from the ice fields were also present further from the central mass of the mountain range the average ela 0 of the northern 1855 2 m a s l and the southern 1700 2 m a s l glaciers differed greatly we suggest that the surprisingly high average ela 0 of the northern glaciers was mostly caused by the missing lower sections of these paleoglaciers from our reconstructions due to the destroyed terminal glacial landforms however the terminal glacial landforms are quite well preserved in the southern valleys thus the average ela 0 of the southern paleoglaciers was suitable to correlate the maximal glaciation of the godeanu mountains with the maximal glaciation of the neighbouring retezat mountains

timing of glacial retreat in the wicklow mountains ireland conditioned by glacier size and topography this paper presents 170 schmidt hammer exposure ages from moraine boulders and glacially sculpted bedrock to reveal the post last glacial maximum lgm history of the wicklow mountains ireland these data suggest that large ice masses survived for 4 7 ka after retreat of the irish sea ice stream and were sustained by summit ice fields until 16 6 ka post lgm retreat was dynamic with re advance moraines deposited in response to heinrich stadial 1 however these events reflect short term ice front oscillations 1 ka during the long term retreat phase retreat from re advance positions was synchronous across the range and paced by climate with time progressive deglaciation from low to high elevation in contrast marked asynchroneity in the timing of younger dryas deglaciation is closely linked to snow redistribution and indicates that for small cirque glaciers 1 km2 topography can exert the primary control on glacier survival this result has important implications for palaeoclimate econstructions as cirque glacier dynamics may be unrelated to climate this is further complicated by post depositional processes which can result in moraine ages e g 10be which post date retreat future palaeoclimate studies should prioritise cirque glaciers where snow contributing areas are small and where postdepositional disturbance is limited matrix poor boulder rich moraines

fine fraction carbonate stable isotopes as indicators of seasonal shallow mixed layer paleohydrography we have measured stable isotopic compositions of miocene pelagic fine fraction 6 63 wm carbonates from oligotrophic deep sea sites in the pacific and atlantic oceans and compared them with those of coexisting foraminifers to test their utility as near sea surface indicators fine fraction carbonates primarily polyspecific nannofossils and surface dwelling planktic foraminiferal globigerinoides stable isotopes both have been considered to reflect surfacewater hydrographic conditions however our results indicate that fine fraction stable isotopes are offset from and do not correlate well with those of globigerinoides in contrast stable isotopic records of the deep dwelling planktic foraminifer globoquadrina are in good correspondence with the fine fraction records in terms of long term ca s 1 m y trends and temporal variability on the basis of a time series hydrography and flux study site in the oligotrophic subtropical north atlantic we interpret the isotopic discrepancies between fine fraction and globigerinoides as resulting primarily from season of calcification as well as possible vital effects we suggest that fine fraction stable isotope values from oligotrophic waters reflect late winter early spring relatively cool nutrient rich shallow mixedlayer conditions during the time of deep mixing i e spring bloom whereas globigerinoides stable isotope values record conditions that prevailed in the stratified surface waters in the warmer late spring fall this implies that paired analyses of fine fraction and surface dwelling planktic foraminiferal n 18 o could be applied to reconstruct paleoseasonality of the open oceans however because the fine fraction n 13 c values are not representative of the annual mean surface water n 13 c we recommend use of near surface dwelling planktic foraminiferal n 13 c as a proxy for n 13 c of stratified surface waters that are more or less in equilibrium with the atmosphere with respect to pco2

topographic control of asynchronous glacial advances a case study from annapurna nepal 1 differences in the timing of glacial advances which are commonly attributed to climatic changes can be due to variations in valley topography cosmogenic 10be dates from 24 glacial moraine boulders in 5 valleys define two age populations late glacial and early holocene moraine ages correlate with paleoglacier valley hypsometries moraines in valleys with lower maximum altitudes date to the late glacial whereas those in valleys with higher maximum altitudes are early holocene two valleys with similar equilibrium line altitudes elas but contrasting ages are 5 km apart and share the same aspect such that spatial differences in climate can be excluded a glacial mass balance cellular automata model of these two neighboring valleys predicts that change from a cooler drier to warmer wetter climate as at the holocene onset would lead to the glacier in the higher altitude catchment advancing while the lower one retreats or disappears even though the ela only shifted by 120 m

oligocene miocene biostratigraphy magnetostratigraphy and isotopic stratigraphy of the western north atlantic magnetostratigraphic records from western north atlantic deep sea drilling project dsdp sites 563 and 558 are correlated with the geomagnetic polarity time scale gpts berggren et ai 1984a 1984b using marine magnetic anomalies and selected biostratigraphic datum levels the magnetochronology established is used to make direct magnetobiostratigraphic correlations that agree with previous oligocene early miocene studies however we show that zones nn8 partim and nn9 and associated epoch 11 correlate with magnetic anomaly 5 chron csn this contrasts with previous indirect correlations of epoch 11 with anomaly sa and requires an upward adjustment of 1 5 2 0 m y for middle late miocene calcareous nannofossil zones we correlate the middle late miocene boundary with zone nn8 and earliest chron csn 10 4 ma

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

integrated stratigraphy of the st thomas section malta island a reference section for the lower burdigalian of the mediterranean region abstract the 91 15 m thick st thomas section belongs to the middle globigerina limestone which is the intermediate member of the globigerina limestone formation and crops out along the eastern cliff of the delimara peninsula the south eastern part of malta island the sedimentary record is composed of alternating calcareous marls and marly limestones with subordinated prominent bioturbated indurated limestones that are deposited in a pelagic environment for the first time paleomagnetic analyses of a burdigalian succession have provided reliable data that allow the identification of five magnetozones that have been correlated to the astronomically tuned neogene time scale spanning the early miocene c6n c5dn interval calcareous plankton quantitative analyses integrated with paleomagnetic analyses allowed us to identify and date several bioevents that have great potential for mediterranean and extra mediterranean correlations in the interval between 19 7 and 17 2 ma in particular the complete distributional range of the calcareous nannofossil sphenolithus belemnos has been recorded as follows the first occurrence fo at 19 12 ma the first common occurrence fco at 19 05 ma the last common occurrence lco at 18 44 ma and the last occurrence lo at 18 02 ma in addition the fo and the fco of sphenolithus heteromorphus have been documented at 18 29 ma and at 17 99 ma respectively a new paracme interval in the lower part of the range of this species is described between 17 56 and 17 31 ma concerning the planktonic foraminifera the main bioevents are the common interval top of paragloborotalia siakensis at 19 55 ma a common interval of globoquadrina dehiscens between 19 34 and 18 48 ma the globigerinoides subquadratus fo at 18 43 ma and the onset of an acme interval of paragloborotalia acrostoma that changes its coiling from random to prevalently sinistral at the same time at 18 40 ma these new biostratigraphic data allowed us to place the succession in the standard mediterranean calcareous plankton zonal schemes and to make some amendments to these schemes the fco of s belemnos was revealed a more reliable marker than its fo for the base of the mnn3a zone with regard to the planktonic foraminifera the p acrostoma ab r s has been used as a subzonal marker of the g dehiscens catapsydrax dissimilis zone which now comprises three subzones instead of two the deep marine paleoenvironmental setting the excellent outcrops and the recognition of a continuous succession of bio magnetostratigraphic events suggest that the st thomas section should be considered as a reference section for the lower burdigalian of the mediterranean area and for future studies in the definition of the burdigalian gssp

geomorphic influence on small glacier response to post little ice age climate warming julian alps europe the evolution of glaciers and ice patches as well as the equilibrium line altitude ela since the little ice age lia maximum were investigated in the julian alps south eastern european alps including ice masses that were previously unreported twenty three permanent firn and ice bodies have been recognized in the 1853 km2 of this alpine sector covering a total area in 2012 of 0 385 km2 about one fifth of the area covered during the lia 2 350 km2 these features were classified as very small glaciers glacierets or ice patches with major contribution to the mass balance from avalanches and wind blown snow localized snow accumulation is also enhanced in the area due to the irregular karst topography the ice masses in the region are at the lowest elevations of any glaciers in the alpine chain and are characterized by low dynamics the elas of the two major lia glaciers canin and triglav have been established at 2275 10 m and 2486 10 m respectively by considering the reconstructed area and digital elevation model dem and using an accumulation area ratio aar of 0 44 0 07 typical of small cirque glaciers changes in the ela and glaciers extension indicate a decoupling from climate this is most evident in the smallest avalanche dominated ice bodies which are currently controlled mainly by precipitation the damming effect of moraine ridges and pronival ramparts at the snout of small ice bodies in the julian alps represents a further geomorphological control on the evolution of such ice masses which seem to be resilient to recent climate warming instead of rapidly disappearing as should be expected copyright 2016 john wiley sons ltd

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

nannofossil evolutionary events in the mid pliocene an assessment of the degree of synchrony in the extinctions of reticulofenestra pseudoumbilicus and sphenolithus abies abstract the mid pliocene was an interval of subtle reorganisation within the nannoplankton community including the prominent and biostratigraphically important last occurrences of sphenolithus abies and reticulofenestra pseudoumbilicus the transition is part of the pliocene to recent attrition of nannofossil species that resulted from changes in the distribution of trophic resources and deep water and surface water current systems likely associated with the initiation of northern hemisphere glaciation the extinctions of sphenolithus abies and reticulofenestra pseudoumbilicus were analysed in detail at odp sites 659 662 and 926 in the equatorial and subequatorial atlantic these taxa show significantly different patterns of duration and timing of decline based on high resolution abundance records and calibration with oxygen isotope stratigraphy the initiation of abundance decline between 3 71 and 3 67 ma and the extinction of s abies between 3 56 and 3 52 ma are diachronous this extinction may have been a response to the intensification of glacial intervals at this time in contrast the last occurrence of r pseudoumbilicus at 3 81 3 82 ma appears to be a valid example of biostratigraphic although not necessarily biological synchrony in the fossil record direct environmental forcing is not attributable for the extinction of r pseudoumbilicus however indirect physical and or biological environmental stress may explain the observed patterns

miocene to pliocene calcareous nannofossil biostratigraphy at odp leg 177 sites 1088 and 1090 the calcareous nannofossil biostratigraphy of odp leg 177 sites 1088 and 1090 subantarctic sector from the atlantic ocean is discussed most nannofossil zonal boundaries of martini 1971 and okada and bukry 1980 were recognized for the studied mid high latitude sediments conventional low latitude marker species such as amaurolithus spp discoaster spp triquetrorhabdulus spp ceratolithus spp were recorded as rare and scattered which impeded the development of a detailed nannofossil biostratigraphic zonation of some miocene and pliocene intervals because of the absence of some primary biostratigraphic marker species additional second order bioevents such as the first occurrence of calcidiscus macintyrei and the last occurrence of coccolithus miopelagicus have been used to approximate the base of zones nn7 and nn8 respectively several disconformities disturbing the pliocene and miocene intervals of site 1090 could be determined based on nannofossil distribution although the occurrence of intervals with dissolved nannofloras and low species diversity prevented a reliable age assignment an acme of small gephyrocapsa was recognized near the lower middle pliocene boundary close to the nn15 nn16 zonal boundary presenting an event for further improvement of the calcareous nannofossil biostratigraphy of this interval time the first occurrence of pseudoemiliania lacunosa 4 m occurs close to this interval representing a fairly reliable event to approximate the base of nn15 zone when other biozonal events are absent a paracme of r pseudoumbilicus 7 m was detected in the lower pliocene nn12 and in the upper miocene nn11 these temporary absences of the species seem to be isochronous between high latitude and low middle latitude areas

modelling topoclimatic controls on palaeoglaciers implications for inferring palaeoclimate from geomorphic evidence abstract evidence of small glaciers is often used to infer past atmospheric climate through calculation of steady state elas however if topographic niches such as shading or windblown snow augmented mass balance then elas cannot reflect regional climate and determining the significance of these topoclimates is therefore important the brecon beacons south wales contains upland glacial landforms dating to the younger dryas 11 000 10 000 yr bp when local climate was at the threshold for glaciation this case study categorises topoclimate using three dimensional modelling of topography and reconstructed palaeoglaciers from two sites containing mapped moraines whose orientation suggest complex patterns of deglaciation ablation season solar radiation is modelled over multiple ice surfaces as shade from surrounding topography and intensity from ice surface incidence angle snowblow and avalanching potential models are also used and the significance of all topoclimate variables assessed against a mass balance deficit calculated for each glacier given palaeoclimate models for the region results demonstrate that both glaciers were likely to be heavily reliant on topoclimate and that previous studies underestimate the significance of solar radiation modelled over multiple ice surfaces reflecting patterns of recession results indicate that the distribution of topoclimate variables predicts the style of deglaciation at both sites possibly explaining the complexity of glacial evidence in this environment

granulometric characterization of paleosols in loess series by automated static image analysis abstract an automated image analysis method is proposed here to study the size and shape of siliciclastic sedimentary particles of paleosols of central european loess sequences several direct and indirect measurement techniques are available for grain size measurements of sedimentary mineral particles indirect techniques involve the use of some kind of physical laws however all requirements for calculations are in many cases not known even so the direct manual microscopic observation and measurement of large representative number of grains is time consuming and sometimes rather subjective therefore automated image analyses techniques provide a new and perspective way to analyse grain size and shape sedimentary particles here we test these indirect laser diffraction and direct automated static image analysis techniques and provide new granulometric size and shape data of paleosols our results demonstrate that grain size data of the mineral dust samples are strongly dependent on shape parameters of particles and shape heterogeneity was different between different size classes due to the irregular grain shape parameters uncertainties have arisen also for determination of grain sizes in this paper we present a possible correction procedure to reduce the differences among the results of the laser diffraction and image analysis methods by applying new correction factors results of the two approaches could become closer but the unknown thickness of particles remains a problem to solve the other presented correction procedure to assess the uncertain 3rd dimension of particles by their intensity size relationships makes us able to reduce further the deviations of the two sizing methods

revised correlations of early and middle miocene calcareous nannofossil events and magnetostratigraphy from dsdp site 563 north atlantic ocean abstract deep sea drilling project site 563 located on the west flank of the northern mid atlantic ridge recovered a long miocene section from which magnetostratigraphic and isotopic stratigraphy are available quantitative analyses of calcareous nannofossil assemblages have been performed in the lower and middle miocene sediments from site 563 the abundance patterns of the identified species allow us to determine several bioevents for this time interval the recognized biohorizons related to the available magnetostratigraphy provide new data on the biostratigraphic value of many species and on the synchroneity of the events over a wide geographic area relations with the oxygen isotope stratigraphy are also reported sphenolith distribution is examined in particular detail due to their biostratigraphic importance in the early miocene in particular the recently described species sphenolithus procerus sphenolithus tintinnabulum and sphenolithus multispinatus can be useful to subdivide the lower miocene zones nn2 and nn3 a large variety of reticulofenestra pseudoumbilicus has been identified within zones nn6 and nn7

glacial chronology and palaeoclimate in the bystra catchment western tatra mountains poland during the late pleistocene abstract deglaciation chronology of the bystra catchment western tatra mountains has been reconstructed based on 10be exposure age dating fourteen rock samples were collected from boulders located on three moraines that limit the horizontal extent of the lgm maximum advance and the lateglacial recessional stage the oldest preserved maximum moraine was dated at 15 5 0 8 ka an age that could be explained more likely by post depositional erosion of the moraine such scenario is supported by geomorphologic and palaeoclimatological evidence the younger cold stage is represented by well preserved termino lateral moraine systems in the kondratowa and sucha kasprowa valleys the distribution of the moraine ridges in both valleys suggest a complex history of deglaciation of the area the first late glacial re advance lg1 was followed by a cold oscillation lg2 that occurred at around 14 0 0 7 13 7 1 2 ka glaciers during both stages had nearly the same horizontal extent however their thickness and geometry changed significantly mainly due to local climatic conditions triggered by topography controlling the exposition to solar radiation the lg1 stage occurred probably during the pre bolling cold stage greenland stadial 2 1a however the lg2 stage can be correlated with the cooling at around 14 ka during the greenland interstadial 1 gi 1d older dryas this is the first chronological evidence of the older dryas in the tatra mountains the ela of the maximum bystra glacier was located at 1480 m a s l in accordance with the ela in the high tatra mountains during the lgm during the lg1 and lg2 stages the ela in the catchment rose up to 1520 1530 m a s l and was located approximately 100 150 m lower than in the eastern part of the massif climate modelling results show that the bystra glacier maximum advance could have advanced in the catchment when mean annual temperature was lower than today by 11 12 c and precipitation was reduced by 40 60 this is in accordance with lgm conditions previously reported for the high tatras during the lg1 and lg2 stages the temperature decrease in the study area reached 10 c and precipitation was lower by 30 compare to modern conditions this resulted in slightly higher accumulation 20 30 in the western tatra mountains compare to the high tatra mountains

paleoclimatic implications based on equilibrium line altitude depressions of reconstructed younger dryas and holocene cirque glaciers in inner nordfjord western norway abstract relative to a present cirque glacier in innner nordfjord western norway equilibrium line altitude ela depressions for reconstructed cirque glaciers formed during the younger dryas 11 000 10 000 yr b p the erdalen event 9100 200 yr b p and the little ice age mid 18th century are calculated by the use of accumulation area ratio aar and compared to the corresponding values for plateau glaciers the temperature precipitation ela tp ela as reflected by plateau glaciers gives considerably larger ela depressions than use of the temperature precipitation wind ela tpw ela for cirque glaciers ela depressions during the younger dryas erdalen event and the little ice age thus strongly indicate that cirque glaciers are much more sensitive to changes in winter precipitation than plateau glaciers the difference in ela depressions of contemporaneous plateau and cirque glaciers during the younger dryas erdalen event and the little ice age suggests that winter precipitation was reduced to 59 7 71 6 and 88 7 compared to present values taken into account the reduced winter precipitation the corresponding mean ablation season temperature depressions were probably 4 3 0 3 3 0 0 2 0 3 and 1 4 0 3 0 2 c respectively

integrated stratigraphy and astronomical calibration of the serravallian tortonian boundary section at monte gibliscemi sicily italy results are presented of an integrated stratigraphic calcareous plankton biostratigraphy cyclostratigraphy and magnetostratigraphy study of the serravallian tortonian s t boundary section of monte gibliscemi sicily italy astronomical calibration of the sedimentary cycles provides absolute ages for calcareous plankton bio events in the interval between 9 8 and 12 1 ma the first occurrence fo ofneogloboquadrina acostaensis usually taken to delimit the s t boundary is dated astronomically at 11 781 ma pre dating the migratory arrival of the species at low latitudes in the atlantic by almost 2 million years in contrast to delayed low latitude arrival of n acostaensis paragloborotalia mayeri shows a delayed low latitude extinction of slightly more than 0 7 million years with respect to the mediterranean last occurrence lo at 10 49 ma at ceara rise lo at 11 205 ma in the mediterranean the discoaster hamatus fo dated at 10 150 ma is clearly delayed with respect to the open ocean the ages of d kugleri first and last common occurrence fco and lco catinaster coalitus fo coccolithus miopelagicus last regular occurrence l r o and the d hamatus neohamatus cross over however are in good to excellent agreement with astronomically tuned ages for the same events at ceara rise tropical atlantic suggesting that both independently established timescales are consistent with one another the lack of a reliable magnetostratigraphy hampers a direct comparison with the geomagnetic polarity timescale of cande and kent 1995 ck95 but ages of calcareous nannofossil events suggests that ck95 is significantly younger over the studied time interval approximate astronomical ages for the polarity reversals were obtained by exporting astronomical ages of selected nannofossil events from ceara rise and the mediterranean to eastern equatorial pacific odp leg 138 site 845 which has a reliable magnetostratigraphy our data from the rio mazzapiedi castellania section reveal that the base of the tortonian stratotype corresponds almost exactly with the first regular occurrence fro of n acostaensis s s as defined in the present study dated at 10 554 ma an extrapolated age of 11 8 ma calculated for the top of the serravallian stratotype indicates that there is a gap between the top of the serravallian and the base of the tortonian stratotype potentially rendering all bio events in the interval between 11 8 and 10 554 ma suitable for delimiting the s t boundary despite the tectonic deformation and the lack of a magnetostratigraphy gibliscemi remains a candidate to define the s t boundary by means of the tortonian global boundary stratotype section and point gssp 2000 elsevier science b v all rights reserved

calcareous nannofossil biostratigraphy in the pearl river mouth basin south china sea and neogene reticulofenestrid coccoliths size distribution pattern abstract the calcareous nannofossil biostratigraphy of the pearl river mouth basin includes 26 bioevents and twenty zones combined zones from oligocene to early pleistocene and a middle eocene zone most zonal boundaries of other workers in other regions of the world are recognized especially those defined by last occurrences the nannofossil zones are placed within the lithostratigraphic units of the offshore basin the size distribution pattern of reticulofenestrids from middle miocene to pliocene can be used to further subdivide the neogene biostratigraphically bioevents can be used to recognize the neogene epoch boundaries in the area

loch lomond stadial glaciers in north harris outer hebrides north west scotland glacier reconstruction and palaeoclimatic implications abstract geomorphological mapping of north harris provides evidence for the former existence of 10 glaciers with a total area of ca 35 km2 a loch lomond younger dryas stadial age ca 12 9 11 5 kyr bp for this glacial episode is inferred from glacier configuration landsystems dominated by hummocky recessional moraines and relationships with lateglacial periglacial phenomena equilibrium line altitudes elas of 150 289 m were calculated for individual glaciers ela variability mainly reflects differences in snow contributing area the area weighted mean ela 204 m is consistent with a northwards decline in elas along the western seaboard of the british isles of 69 5 m 100 km 1 equivalent to a northwards ablation season temperature decrease of 0 42 c 100 km 1 this latitudinal temperature gradient implies a mean july sea level temperature of ca 7 2 c for the coldest part of the stade roughly 6 c lower than at present sea level precipitation at the time of the lls glacial maximum is inferred to have been between ca 1970 200 and 2350 200 mm yr 1 implying that lls precipitation was up to 25 greater than now patterns of recessional moraines indicate that the glaciers remained close to climatic equilibrium as they retreated to their sources though moraine belts implying near stationary or readvancing ice margins on flat valley floors are separated by moraine free zones indicating uninterrupted retreat calculation of elas for residual glaciers in former source areas suggests that summer warming of 1 0 c would have resulted in shrinkage of the glaciers to their sources

first 36cl cosmogenic moraine geochronology of the dinaric mountain karst velež and crvanj mountains of bosnia and herzegovina abstract this article presents the first attempt to date moraines in the dinaric mountain karst using cosmogenic 36cl surface exposure dating technique twenty samples were collected from moraine boulders from two sets of the lowest and largest lateral moraines on the vele 1965 m asl and crvanj mountains 1920 m asl in bosnia and herzegovina the dated lateral terminal moraine complexes spanning elevations from 980 to 1350 m asl are up to 2 7 km long and rise more than 100 m above the valley floor the moraine boulders yielded 36cl ages spanning from oldest dryas for vele 14 9 1 1 ka to younger dryas for crvanj 11 9 0 9 ka considering the average age of the two oldest samples from each lateral moraine as the most representative time of moraine emplacement the dated moraines mark the largest extent of glaciers in both study areas which have been reconstructed to 28 km2 for vele and 24 km2 for crvanj having a mean equilibrium line altitude at 1388 m and 1541 m respectively under modern precipitation values which account for 2000 mm the temperature depression between 8 and 10 c is required to sustain the palaeoglaciers with reconstructed equilibrium line altitudes glaciers of similar size with such low equilibrium line altitudes during the lateglacial have not been reported until now for the balkan peninsula it is very likely that the boulder ages reflect complex exhumation and denudation histories which at this point do not allow obtaining more precise moraine chronologies for the study areas nevertheless this article delivers new data on the extent and timing of quaternary glaciations in the mediterranean mountains where records of glacier fluctuations seem to be asynchronous amongst different areas it is clear that dating moraines with cosmogenic 36cl surface exposure dating in carbonate lithologies in areas of high precipitation like the dinaric karst remains challenging

miocene evolution of atmospheric carbon dioxide changes in pco2 or ocean circulation are generally invoked to explain warm early miocene climates and a rapid east antarctic ice sheet eais expansion in the middle miocene this study reconstructs late oligocene to late miocene pco2 from ep values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from deep sea drilling project sites 588 and 608 and ocean drilling program site 730 our results indicate that highest pco2 occurred during the latest oligocene 350 ppmv but decreased rapidly at 25 ma the early and middle miocene was characterized by low pco2 260 190 ppmv lower intervals of pco2 correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle miocene there is no evidence for either high pco2 during the late early miocene climatic optimum or a sharp pco2 decrease associated with eais growth paradoxically pco2 increased following eais growth and obtained preindustrial levels by 10 ma although we emphasize an oceanographic control on miocene climate low pco2 could have primed the climate system to respond sensitively to changes in heat and vapor transport

mid neogene mediterranean marine continental correlations an alternative interpretation recent revised magnetostratigraphic and astrochronologic calibrations of several calcareous planktonic microfossil datum events in particular coccolithus miopelagicus and neogloboquadrina acostaensis combined with our magnetobiostratigraphic investigation of a 10 m thick section at ecotet near lyon france in which terrestrial micromammals vallesian zone mn9 are intercalated with calcareous nannoplankton and planktonic foraminifera belonging to zones nn6 nn8 and n14 15 m11 and m12 respectively lead us to question the recent recalibration by krijgsman et al 1996 eart planet sci lett 142 367 380 of the aragonian vallesian mn7 8 mn9 boundary with chron c5r 1r v11 1 ma and the lower upper vallesian mn9 10 boundary with chron c4ar 2n v9 6 9 7 ma ecotet with a uniform reverse polarity is shown to be assignable uniquely to chron c5r interregional correlation of ecotet with mediterranean terrestrial stratigraphies indicates that progonomys whose first occurrence fo has been traditionally placed in mediterranean mammal zone mn10 was already present in mediterranean zone mn9 at v11 4 ma and did not experience a 2 million year delay in its putative prochoresis from asia

carbonaceous and phosphate rich sediments of the miocene monterey formation at el capitan state beach california u s a abstract the organic and phosphate rich interval of the monterey formation at el capitan state beach west of santa barbara california u s a late early to early late miocene in age is composed of a carbonaceous marl toc contents between 1 2 and 23 2 wt with intercalated phosphate rich laminae lenses and layers subordinate lithologies include ash layers dolomitized horizons and siliceous beds we distinguished five lithological units 1 a gray marl unit lacking major phosphate accumulations 16 3 ma average toc content 2 by weight average sedimentation rate 75 m my average toc accumulation rate 0 19 mg cm2 yr 2 a black marl unit including light colored phosphatic laminae lenses and discrete particles 16 3 14 5 ma average toc content 7 5 by weight average sedimentation rate 20 m my average toc accumulation rate 0 19 mg cm2 yr 3 a red marl unit including light colored phosphatic laminae lenses and commonly reworked particles 14 5 12 7 ma average toc content 15 by weight average sedimentation rate 20 m my 14 5 13 3 ma and 2 m my 13 3 12 7 ma respectively average toc accumulation rate 0 39 mg cm2 yr 14 5 13 3 ma and 0 04 mg cm2 yr 13 3 12 7 ma respectively 4 a unit of complex and condensed phosphatic beds interbedded with red marl 12 7 10 8 ma average sedimentation rate 3 m my and 5 a black marl unit with intercalated phosphatic laminae and lenses 10 8 ma average sedimentation rate 9 m my average toc accumulation rate 0 09 mg cm2 yr phosphogenesis and accumulation of phosphate were dynamic processes which started with local phosphogenesis leading to the formation of phosphatized particles as well as stratigraphically bound phosphogenesis leading to the formation of phosphate laminae and lenses phases of subsequent sediment reworking resulted in the concentration of phosphate particles in phosphate rich layers and repeated phases of sediment reworking and phosphogenesis ultimately resulted in the formation of the complex phosphate condensed horizons preservation of organic matter was favored by high productivity rates and by the development of dysaerobic bottom water conditions the dynamic sedimentary environment likely led to the formation of early diagenetic phosphatic lids which may have sealed off subjacent organic rich layers as well as to the rapid deposition of entire layers in the form of mud flows thereby eventually enhancing the potential of organic matter preservation our new age data suggest that at the el capitan state beach section the intervals characterized by high toc values and maximum toc accumulation rates red marl as well as significant quantities of in situ phosphates appeared in the late middle miocene i e during and after the major cooling phase at around 14 5 ma this implies that deposition of phosphate and organic carbon continued well after this cooling phase thereby underlining the observation that preservation of organic carbon in the monterey formation is not only dependent on climate change during the mid miocene but also on regional conditions

recognition and palaeoclimatic implications of late quaternary niche glaciation in eastern lesotho geomorphic evidence of former glaciation in the high drakensberg of southern africa has proven controversial with conflicting glacial and non glacial interpretations suggested for many landforms this paper presents new geomorphological sedimentological and micromorphological data and glacier mass balance modelling for a site in the leqooa valley eastern lesotho preserving what are considered to be moraines of a former niche glacier that existed during the last glacial maximum lgm the geomorphology and macro sedimentology of the deposits display characteristics of both active and passive transport by glacial processes however micromorphological analyses indicate a more complex history of glacial deposition and subsequent reworking by mass movement processes the application of a glacier reconstruction technique to determine whether this site could have supported a glacier indicates a reconstructed glacier equilibrium line altitude ela of 3136 m a s l and palaeoglacier mass balance characteristics comparable with modern analogues reflecting viable if marginal glaciation radiocarbon dates obtained from organic sediment within the moraines indicate that these are of lgm age the reconstructed palaeoclimatic conditions during the lgm suggest that snow accumulation in the drakensberg was significantly higher than considered by other studies and has substantial relevance for tuning regional climate models for southern africa during the last glacial cycle copyright 2009 john wiley sons ltd

nutricline variation in the equatorial atlantic coincident with the younger dryas variations in nutricline depth during the last deglaciation are recorded by the phytoplankton species florisphaera profunda a stacked record of six deep sea cores shows that across the entire equatorial atlantic there was a brief shallowing of the nutricline centered on 11 ka coincident with the younger dryas this shallowing is linked with high latitude north atlantic deglacial events we invoke high albedo and cool sea surface temperatures in the northern latitudes during 11 ka which steepened an already higher than expected winter insolation and hence temperature gradient for a time of june perihelion we postulate that the resultant increased pressure gradient caused an intensification of the northern hemisphere winter tropical easterlies which in turn caused equatorial divergence to occur in boreal winter