paravani a puzzling lake in the south caucasus abstract sediments of lake paravani the largest natural lake in the south caucasus were analysed to reconstruct the millennial history of the environment pollen analysis previously undertaken on the first core retrieved in the middle of the lake revealed a vegetation history for the last 12 millennia as part of the present study a new core was taken from the north western part of the lake pollen analysis was performed on this new core with the same methodology as for the previous one a sedimentological and geochemical analysis was also conducted on both cores in order to gain an understanding of the dynamics of erosion in the catchment area in response to landscape modifications the results show that the sediment deposits within lake paravani yield rather complex and puzzle like palaeoecological records despite the differences between the two records correlations have been made that are supported by the 14c dates by combining all of the data from both cores it was finally possible to reconstruct the puzzle of the environmental history recounted by the lake paravani sediments this reconstructed history is composed of four main phases 1 a steppic environment marked by pronounced erosion processes from 12 000 to 10 000 cal bp 2 a transition phase characterized by the expansion of grasses poaceae from 10 000 to 9 8 000 cal bp 3 a more forested phase from 9 8 000 to 2 000 cal bp during which the erosion fluxes decreased and 4 a decline in tree cover probably due to human activities over the last 2 millennia

climate and human environment relationships on the edge of the tenaghi philippon marsh northern greece during the neolithization process abstract palynological and sedimentological investigations carried out around the tell of dikili tash eastern macedonia greece one of the oldest neolithic sites in europe improve our understanding of the evolution of the paleoenvironment from the late pleistocene to the neolithic period 6500 3200 cal bc in this region while global climate reconstructions researches based on the study of the tenaghi philippon pollen record located 5 8 km from the tell have focused on forces that drive the environment at regional or global scales we attempt to use the sediment archives on the edge of the marsh to describe the context of the neolithization process and related environmental changes our aim is to provide new data on environmental change during the early holocene by combining pollen non pollen palynomorphs npps and sedimentological analyses to be compared with archaeological information the data give an overview of the original environment prior to the neolithic and thereafter a comprehensive view of the first human impacts on the vegetation cover in local lowland areas two new pollen records located respectively 1 75 km dik4 and 150 m dik12 from the archaeological site provide the first evidence of human agropastoral activities on the landscape associated with the early neolithic communitiessince at least 6400 cal bc largely earlier than observed in the reference pollen diagram in the tenaghi philippon marsh which shows a first human impact from the second millennium cal bc admittedly such impact on the local area around the site cannot be extrapolated to a regional scale raising question of the spatial representativeness of the previous records it also shows the need to develop multi scalar investigations to assess the impact of climatic change and human activities on the landscape during the earliest phase of the neolithic settlement in southeastern balkans

global cooling accelerated by early late eocene impacts at ocean drilling program site 689 maud rise southern ocean 18o records of fine fraction bulk carbonate and benthic foraminifers indicate that accelerated climate cooling took place following at least two closely spaced early late eocene extraterrestrial impact events a simultaneous surface water productivity increase as interpreted from 13c data is explained by enhanced water column mixing due to increased latitudinal temperature gradients these isotope data appear to be in concert with organic walled dinoflagellate cyst records across the same microkrystite bearing impact ejecta layer in the mid latitude massignano section central italy in particular the strong abundance increase of thalassiphora pelagica is interpreted to indicate cooling or increased productivity at massignano because impact induced cooling processes are active on time scales of a few years at most the estimated 100 k y duration of the cooling event appears to be too long to be explained by impact scenarios alone this implies that a feedback mechanism such as a global albedo increase due to extended snow and ice cover may have sustained impact induced cooling for a longer time after the impacts

europe s southernmost glaciers response and adaptation to climate change the southernmost glaciers in europe are located on the iberian apennine and balkan peninsulas in mid latitudes between 41 n and 44 n at altitudes ranging from 2000 to 3000 m a s l all these glaciers are a legacy of the little ice age lia they survive in a relatively warm environment mean annual temperature 0 ct o 1 c due to local topographic controls and high levels of accumulation as a result of avalanche and wind blown snow in the pirin mountains bulgaria snezhnika glacieret has been cored providing an archive of recent climate change small glaciers such as this respond quickly to climatic extremes since the lia maximum during the 19th century all southern european glaciers have retreated losing 30 100 of their volume however despite the trend towards warmer years since the late 1970s some glaciers still survive even after some of the hottest summers on record predicted future warming especially in summer and drier conditions in the mediterranean basin may result in the disappearance of all glacier features at these latitudes in europe within the next few decades

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

extended cretaceous tertiary boundary extinctions and delayed population change in planktonic foraminifera from brazos river texas high resolution planktonic foraminiferal analysis of three brazos river sections indicates a nearly continuous cretaceous tertiary k t boundary sedimentary record second only to the world s most complete record at el kef tunisia species extinctions occur over an extended period of time and with two major extinction episodes the first extinction episode with 46 of the species extinct occurs at and just below 10 15 cm a short hiatus at the base of a sandy shell hash and clay sand unit which was interpreted by bourgeois et al 1988 to represent a tsunami bed generated by the k t boundary bolide impact the top of this tsunami bed is about 17 20 cm below the k t boundary as defined by the first appearance of tertiary planktonic foraminifera the second extinction phase with 45 of the species extinct occurs 25 cm above the k t boundary zone p0 p1a boundary of the remaining seven surviving cretaceous species six gradually disappear during planktonic foraminiferal subzones p1a and basal p1b no species extinctions or major faunal assemblage changes are directly associated with the k t boundary iridium distribution is ambiguous with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined k t boundary relative abundances of dominant species are stable through the late maastrichtian and only minor abundance changes coincide with the first extinction episode or the k t boundary the first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in subzone p1a species disappearing at the two extinction episodes 46 and 45 constitute only a small percentage 8 and 5 of the individuals of the total planktonic foraminiferal population this suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes magnetostratigraphy indicates that the first extinction phase began about 310 000 years before the k t boundary and the second extinction phase occurred 50 000 years after the k t boundary this stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling the hypothesis of a global catastrophic mass extinction at the k t boundary caused by a large extraterrestrial impact is not supported by the brazos river planktonic foraminiferal data

oxygen isotope ranking of late eocene and oligocene planktonic foraminifers implications for oligocene sea surface temperatures and global ice volume abstract oxygen isotope analyses of late eocene and oligocene planktonic foraminifers from low and middle latitude sites in the atlantic basin show that different species from the same samples can yield significantly different isotopic values the range of isotopic values observed between species is greatest at low latitudes and declines poleward many planktonic foraminifers exhibit a systematic isotopic ranking with respect to each other and can therefore be grouped on the basis of their isotopic ranking the isotopic ranking of some taxa however appears to vary geographically and or through time isotopic and paleontologic data from dsdp site 522 indicate that commonly used isotopic temperature scales underestimate oligocene sea surface temperatures we suggest these temperature scales require revision to reflect the presence of oligocene glaciation comparison of isotopic and paleontologic data from sites 522 511 and 277 suggests cold low salinity surface waters were present in high southern latitudes during the early oligocene lowsalinity high latitude surface waters could be caused by eocene oligocene paleogeography or by the production of warm saline bottom water

calcareous plankton stratigraphy around the pliocene eltanin asteroid impact area se pacific documentation and application for geological and paleoceanographic reconstruction abstract conventional qualitative and semi quantitative analyses of calcareous nannofossils and planktic foraminifers from four cores ps2704 1 ps2708 1 ps2709 1 e13 4 documenting the area of the eltanin impact into the bellingshausen sea were done to a identify sediment disturbances and reworking b constrain the stratigraphic framework of the impact related sediment sequences and c evaluate probable environmental consequences of the impact the calcareous microfossil stratigraphy from the autochthonous sediments above and below the impact related sediments places the impact event into the late pliocene at around 2 15 ma and indicates that sediments as old as middle eocene were disturbed by the impact the qualitative and quantitative determination of displaced calcareous microfossils allows the reconstruction of sediment disturbances displacement and resettlement related to the impact event no signs for significant changes in the assemblages produced and sedimented after the impact could be observed indicating that the impact had no major influence on regional or global climate conditions that can be detected in the geological record

biochronology and paleoclimatic implications of middle eocene to oligocene planktic foraminiferal faunas abstract planktic foraminiferal assemblages have been analyzed quantitatively in six dsdp sites in the atlantic site 363 pacific sites 292 77b 277 and indian ocean sites 219 253 in order to determine the nature of the faunal turnover during middle eocene to oligocene time biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the atlantic pacific and indian oceans a high resolution biochronology based on dominant faunal characteristics and 55 datum events permits correlation between all three oceans with a high degree of precision population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during middle eocene to oligocene time planktic foraminiferal assemblage changes indicate a general cooling trend between middle eocene to oligocene time consistent with previously published oxygen isotope data major faunal changes indicating cooling episodes occur however at discrete intervals in the middle eocene 44 43 ma p13 the middle late eocene boundary 41 40 ma p14 p15 the late eocene 39 38 ma p15 p16 the eocene oligocene boundary 37 36 ma p18 and the late oligocene 31 29 ma p20 p21 with the exception of the e 0 boundary faunal changes occur abruptly during short stratigraphic intervals and are characterized by major species extinctions and first appearances the eocene oligocene boundary cooling is marked primarily by increasing abundances of cool water species this suggests that the e 0 boundary cooling which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes planktic foraminiferal faunas indicate that the e 0 boundary event is part of a continued cooling trend which began during the middle eocene two hiatus intervals are recognized in low and high latitude sections at the middle late eocene boundary and in the late eocene p15 p16 these hiatuses suggest that vigorous bottom water circulation began developing in the middle eocene consistent with the onset of the faunal cooling trend and well before the development of the psychrosphere at the e 0 boundary

age of eocene oligocene boundary based on extrapolation from north american microtektite layer microtektites believed to belong to the north american tektite strewn field have been found in upper eocene sediments in cores from nine deep sea drilling project sites in the caribbean sea gulf of mexico equatorial pacific and eastern equatorial indian ocean the microtektite layer has an age of 34 2 0 6 m y based on fission track dating of the microtektites and k ar and fission track dating of the north american tektites extrapolation from the microtektite layer to the overlying eocene oligocene boundary indicates an age of 32 3 0 9 m y for the eocene oligocene boundary as defined at each site in the initial reports of the deep sea drilling project this age is approximately 5 m y younger than the age of 37 5 m y that is generally assigned to the b undary based on recently published cenozoic time scales

the eocene oligocene boundary event in the deep sea analysis of middle eocene to early oligocene calcareous and siliceous microfossils shows gradual biotic changes with no massive extinction event across the eocene oligocene boundary biotic changes in the late paleogene appear to reflect changing paleoclimatic and paleoceanographic conditions and do not support suggestions of a catastrophic biotic event caused by a bolide impact at the eocenel oligocene boundary

chronological framework for the lateglacial pollen and macrofossil sequence in the pirin mountains bulgaria lake besbog and lake kremensko 5 the sediments of numerous cirque lakes in the pirin mountains have yielded several generalized pollen diagrams but low stratigraphic and temporal resolution has hampered detailed reconstruction of the vegetational history especially for the lateglacial new pollen and macrofossil analyses of high stratigraphic resolution combined with well controlled timedepth curves for lake besbog and lake kremensko 5 now permit the firm identification of the lateglacial interstadial interval bollingallerod dated at 13 8 12 6 ka cal bp at besbog and 14 1 12 8 ka cal bp at kremensko 5 and correlated with the greenland interstadial gi 1 14 5 12 6 ka cal bp macrofossil analyses indicate that during the bolling allerod period betula and juniperus occurred around the lakes at 2124 2250 m a s l following the younger dryas a betula woodland covered the mountains between 1900 and 2250 m in the early holocene because of higher summer insolation at this time the temperate deciduous forest reached up to 1900 m or 800 m above their present limit producing a regional pollen rain that dominated pollen deposition in the cirque lakes after about 7000 cal yr bp conifer forests replaced the birch woodland at middle and high elevations

oligocene glacio eustasy and erosion on the margins of the north atlantic oligocene foraminiferal 18 o records suggest the development of ice caps inferred glacio eustatic falls at ca 36 31 and 25 ma biostratigraphic analyses of wells from the united states east coast and irish continental margins consistently show that upper oligocene sediments overlie a diachronous erosional surface underlain by lower oligocene to eocene strata at the minimum the hiatus extends between ca 34 and 30 ma we speculate that erosion during a glacio eustatic fall near the early late oligocene boundary ca 32 31 ma developed 1 an unconformity on the margins 2 numerous canyons noted in seismic profiles from the margins of the north atlantic and 3 a coastal offlap event using 18 o data we apply a model for eustatic changes and margin response that explains the relationships of sea level unconformities and coastal onlap offlap events

lateglacial and holocene vegetation history at nisi fen and the boras mountains northern greece new pollen data from three contrasting sites in northern greece allow an analysis of spatial and temporal patterns of vegetation change during the holocene and lateglacial in northern greece at the principal site nisi fen six cores from the thickest surficial peat deposits have yielded a detailed composite ams 14c dated pollen record covering the period from 20000 cal bp almost to the present day cores kp 4 and bor 3 were taken from small mires at high elevations in the boras mountains a few kilometres to the north of nisi in which peat has been accumulating since the mid holocene our results show that only pinus expanded significantly during the lateglacial interstadial although small thermophilous tree populations were present in the region the younger dryas chronozone is at best marked by subtle vegetational change in favour of steppe taxa tree cover increased rapidly at the beginning of the holocene with deciduous woodland probably expanding above its present day altitudinal limits ther

large scale fluid infiltration metasomatism and re equilibration of archaean basement granulites during palaeoproterozoic thrust belt construction ungava orogen canada abstract the metamorphic history of the archaean superior province crystalline basement in the palaeoproterozoic ungava orogen attests to the importance of structural and geohydrological controls on a retrograde amphibolite granulite transition two distinct metamorphic suites separated in age by nearly one billion years are recognized in extensively exposed tonalitic to dioritic metaplutonic gneisses the older suite comprises c 2 7 ga granulite facies assemblages orthopyroxene clinopyroxene hornblende plagioclase ilmenite biotite quartz that record moderate pressures 5 kbar and high temperatures 800 c a younger c 1 8 ga suite resulted from amphibolitization of the granulites and is characterized by regionally extensive amphibolite facies mineral zones that broadly parallel the basal decollement of the overlying proterozoic cape smith thrust belt deformation mineral growth relationships in the amphibolitized basement indicate that extensive hydration and re equilibration of the archaean granulites occurred during thrust belt deformation the transition from granulite facies to amphibolite facies assemblages is characterized by the growth of garnet hornblende quartz cummingtonite coronas between plagioclase and orthopyroxene clinopyroxene as well as titanite coronas on ilmenite multi equilibrium thermobarometry on the coronitic assemblages documents re equilibration of the granulitic gneiss to 7 7 kbar at 644 c in the south and 9 8 kbar at 700 c in the north the variably deformed amphibolite facies domain sandwiched between the coronitic garnet zone and the basal decollement is marked by significant metasomatic changes in major element concentrations within tonalite these changes are compatible with equilibrium flow of an aqueous chloride fluid down a temperature gradient the source of fluids for basement hydration metasomatism is interpreted to be dehydrating clastic rocks in the overlying thrust belt with fluid flow probably focused along the basal decollement

lateglacial and holocene vegetation belts in the pirin mountains southwestern bulgaria pollen stratigraphy of a core 270 cm long from lake dalgoto at 2310 m in the northern pirin mountains southern bulgaria was treated by optimal partitioning and compared to a broken stick model to reveal statistically significant pollen zones the vegetational reconstructions presented here are based on pollen percentages and pollen influx on comparisons of modern and fossil pollen spectra and on macrofossil dates from other sites in the mountains during the younger dryas 11000 10200 14c yr bp an open xerophytic herb vegetation with artemisia and chenopodiaceae was widely developed around the lake deciduous trees growing at lower elevations contributed to the pollen rain deposited at the higher elevation sampling sites specifically from 10200 to 8500 yr bp quercus ulmus tilia and betula expanded rapidly at low and intermediate elevations and between 8500 and 6500 yr bp they extended to higher elevations close to the upper forest limit which was formed by betula pendula at about 1900 m coniferous species were limited in the region at this time after 6500 yr bp the expansion of conifers pinus peuce p sylvestris p mugo abies alba at high elevations forced the deciduous trees downward between 6500 and 3000 yr bp the forest limit at 2200 m was formed by p peuce and a alba had its maximum vertical range up to 1900 m later the abundance and vertical range of p peuce and a alba were reduced after 3000 yr bp picea expanded

miocene biochronology and paleoceanography of the north pacific abstract biostratigraphic correlation based on microfossil datum levels directly or indirectly tied to the paleomagnetic time scale provides a high resolution time control for the miocene in the equatorial and middle latitude north pacific faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen pacific faunal changes and abundance fluctuations of planktic foraminiferal species combined with the oxygen isotope record of foraminifers reveal the paleoclimatic and paleoceanographic history the planktic foraminiferal assemblage change in the early miocene extinction of oligocene fauna and rise of a highly diverse neogene fauna appears to be related to increased water mass stratification in the world oceans presumably resulting from the establishment of circum antarctic circulation an increase in the siliceous productivity in the eastern equatorial pacific region between 20 and 18 ma suggests that the vertical and horizontal circulation was intensified at that time climates cooled rapidly during the middle miocene between 14 and 13 ma suggesting the growth of a major east antarctic ice sheet paleoclimatic conditions remained generally cool although oscillating during the late miocene in the late early to middle miocene faunal provincialism developed between low and middle latitudes and by late miocene time a distinct provincialism similar to the present was established

holocene vegetation history in the upper forest belt of the eastern romanian carpathians abstract pollen analysis supported by nine ams 14 c dates from the poiana tiol peat sequence 1540 m in the rodnei mountains eastern romanian carpathians romania is used to reconstruct the holocene vegetation history in this mountain region the results are then compared with other sequences from romania and eastern europe in order to better understand the past dynamics of the main forest constituents the vegetation record at poiana tiol starts at ca 11 000 cal yr bp with the occurrence of rather closed woodlands composed of betula pinus picea abies alnus a viridis and ulmus picea abies was the dominant tree species for almost the entire period however during the last 3000 years p abies forests were largely replaced by pinus in the area temperate tree taxa fraxinus quercus acer tilia and corylus avellana were also common but likely at lower elevation c avellana expanded around 10 300 cal yr bp and reached maximum values after 9000 cal yr bp pollen of carpinus betulus and fagus sylvatica was already recorded around 7000 cal yr bp however the spread of c betulus occurred at ca 6000 cal yr bp with maximum values between 4800 cal yr bp and 3000 cal yr bp while f sylvatica spread from ca 3200 cal yr bp and attained maximum values between 2000 and 200 cal yr bp the first indications of human activities appeared around 3200 cal yr bp and intensified within the last 200 years comparison with other sequences from romania and surrounding countries reveals both similarity and great differences related to the location of glacial refugia climate change and human impact

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

relationship between an iridium anomaly and the north american microtektite layer in core rc9 58 from the caribbean sea in a previous publication an iridium anomaly was reported in core rc9 58 from the caribbean sea about 30 cm below the peak abundance of north american microtektites in order to determine more precisely the relationship between the iridium anomaly and the north american microtektite layer we searched for microtektites in the samples that were used for the iridium studies we found that the north american microtektite layer is actually two layers with the peak abundances separated by 25 cm the upper layer consists of normal north american microtektites and the lower layer consists of previously described clinopyroxene bearing spherules the iridium anomaly was found to correlate with the lower layer although the two layers appear to be the result of two separate events several lines of evidence suggest that they were produced by a single event the separation into two layers may have been produced by differential settling in the sediment due to density variations the correlation between the iridium anomaly and the north american microtektite layer supports the terrestrial impact origin for tektites

reconstruction of late glacial and early holocene near surface temperature anomalies in europe and their statistical interpretation abstract this paper presents the results of a variational analysis study based on the recently developed method by gebhardt et al to reconstruct paleo temperature fields on the typical scale of climate model output providing the necessary basis for quantitative comparison of reconstructions and model results additionally an extension of the approach takes into account the full statistics of the analysis error of the variational analysis to study the inherent uncertainties of the proxy data representing the imperfect paleo climate information and their impact on the field reconstruction the method is applied to reconstruct realizations of monthly mean temperature anomaly fields in europe for january and july in europe as averages for several time slices in the late glacial and holocene single realizations can differ substantially from the field of expectation values in terms of spatial patterns due to the inherent correlation of the spatial uncertainties of the paleo proxy data additionally the fields of expectation values generally are much smoother than the realizations this indicates that it is misleading to only consider expectation values further the ensembles of realization are used to calculate robust error measures for area mean values which is valuable for the quantitative comparison of the results of different time slices

stable isotopes in late middle eocene to oligocene foraminifera oxygen and carbon isotope ratios in eocene and oligocene planktonic and benthic foraminifera have been investigated from atlantic indian and pacific ocean locations the major changes in eocene oligocene benthic foraminiferal oxygen isotopes were enrichment of up to l in 18o associated with the middle late eocene boundary and the eocene oligocene boundary at locations which range from 1 to 4 km paleodepth although the synchronous eocene oligocene 18o enrichment began in the latest eocene most of the change occurred in the earliest oligocene the earliest oligocene enrichment in 18o is always larger in benthic foraminifera than in surface dwelling planktonic foraminifera a condition that indicates a combination of deep water cooling and increased ice volume planktonic foraminiferal 18o does not increase across the middle late eocene boundary at our one site with the most complete record deep sea drilling project site 363 walvis ridge this pattern suggests that benthic foraminiferal 18o increased 40 m y ago because of increased density of deep waters probably as a result of cooling although glaciation cannot be ruled out without more data stable isotope data are averaged for late eocene and earliest oligocene time intervals to evaluate paleoceanographic change average 18o of benthic foraminifera increased by 0 64 from the late eocene to the early oligocene 18o maximum whereas the average increase for planktonic foraminifera was 0 52 this similarity suggests that the eocene oligocene boundary 18o increase was caused primarily by increased continental glaciation coupled with deep sea cooling by as much as 2 c at some sites average 18o of surface dwelling planktonic foraminifera from 14 upper eocene and 17 lower oligocene locations when plotted versus paleo latitude reveals no change in the latitudinal 18o gradient the oligocene data are offset by 0 45 also believed to reflect increased continental glaciation at present there are too few deep sea sequences from high latitude locations to resolve an increase in the oceanic temperature gradient from eocene to oligocene time using oxygen isotopes

eocene paleoceanographic evolution at 20 30 s in the atlantic ocean abstract oceanographic changes in eocene bottom water have been traced with oxygen and carbon isotope values and gradients and benthic foraminiferal assemblages the south atlantic sections chosen for this study are located on an east west traverse depositional depths range from middle bathyal through abyssal the dsdp sites are located on the walvis ridge site 363 in the angola basin sites 522 523 the brazil basin site 19 hole 20c and on the rio grande rise site 357 in abyssal sites of the south atlantic the eocene bottom water environment can be divided into two distinct regimes the early eocene and the late eocene the middle eocene is transitional faunal distribution pattern indicate that source areas where bottom water formed were probably different between the two regimes during the early eocene warm saline water formed possibly in the tethyan ocean east of gibraltar there is good evidence that the late eocene bottom water of the south atlantic recorded at lower bathyal down to middle abyssal environments was formed in southern high latitude regions first invasion of cooler bottom water is recorded at upper abyssal depths around 46 ma earliest zone p12 site 19 from 40 ma late zone p15 onwards this signal is recorded at all sites except middle bathyal depth site 357 selected faunal parameters allow reconstruction of bottom water oxygenation episodically increased abundance of epifaunal species indicate a renewal of the bottom water accompanying these faunal changes 13 c values of benthic foraminefera increase whereas vertical 13 c benthic planktonic foraminifera gradients decrease

new pollen evidence from nariani georgia for delayed postglacial forest expansion in the south caucasus the nature and timing of environmental changes throughout the last glacial interglacial transition in the south caucasus and more widely in eastern europe are still not fully understood according to certain pollen records forest expansion occurred in many areas several millennia after what is considered worldwide as the onset of the holocene the current problem we face is that the time lag in forest expansion varies from one sequence to another sometimes with no delay at all moreover the potential forcing controlling factors behind this complex pattern contrary to the almost synchronous global holocene warming are still a matter for debate accordingly we revisit the issue of forest expansion through vegetation history obtained in the south caucasus using a new pollen record retrieved from the nariani paleolake south georgia these data attest to a steppic phase initially dominated by amaranthaceae chenopodiaceae 12 700 10 500 cal yr bp then by poaceae 10 500 9000 cal yr bp culminating with a more forested phase 9000 5000 calyrbp although some palaeoclimatic regional reconstructions show a wet early holocene we interpret the delay in forest expansion recorded in nariani 2500 years as the result of reduced spring precipitation which would have limited forest development at that time

stepwise mass extinctions and impact events late eocene to early oligocene abstract species ranges and relative abundances of dominant planktonic foraminifers of eight late eocene to early oligocene deep sea sections are discussed to determine the nature and magnitude of extinctions and to investigate a possible cause effect relationship between impact events and mass extinctions late eocene extinctions are neither catastrophic nor mass extinctions but occur stepwise over a period of about 1 2 million years four stepwise extinctions are identified at the middle late eocene boundary the upperglobigerapsis semiinvoluta zone theg semiinvoluta globorotalia cerroazulensis zone boundary and at the eocene oligocene boundary each stepwise extinction event represents a time of accelerated faunal turnover characterized by generally less than 15 species extinct and in itself is not a significant extinction event relative species abundance changes at each stepwise extinction event however indicate a turnover involving 60 of the population implying major environmental changes there microtektite horizons are present in late eocene sediments one in the upperg semiinvoluta zone 38 2 ma and two closely spaced layers only a few thousand years apart in the lower part of thegloborotalia cerroazulensis zone 37 2 ma each of the three impact events appears to have had some effect on microplankton communities however the overriding factor that led to the stepwise mass extinctions may have been the result of multiple causes as there is no evidence of impacts associated with the step preceding or the step following the deposition of the presently known microtektite horizons

planktonic and benthic foraminiferal extinction events during the last 100 m y abstract five major planktonic and benthic foraminiferal extinction events occurred during the past 100 m y at the cenomanian turonian c t boundary at the cretaceous tertiary k t boundary in the latest paleocene in the late eocene and in the early middle miocene to clarify the character of the five events i estimated 1 paleo waterdepths and paleoenvironments where foraminifera were affected 2 the duration of each extinction event and 3 evaluated possible causes for each extinction event on the basis of recent literature these extinction events can be classified into three fundamentally different types 1 the mass extinction event at the k t boundary was abrupt and concentrated among surface dwelling species 2 extinctions at the c t boundary and during the latest paleocene were abrupt and mainly affected intermediate and deep water taxa over short periods 3 the late eocene and early middle miocene events affected surface and deep water species and involved stepwise or gradual extinctions over a long period 4 m y i attributed the extinction events to 1 a bolide impact for the k t event 2 a decrease in dissolved oxygen in intermediate and deep waters due to climatic warming for the c t and latest paleocene events and 3 long term global cooling for the late eocene and early middle miocene events the following relationships exist between the causes and types of extinction events 1 large extraterrestrial impacts strongly affected surface dwelling organisms in short term extinction events 2 intermediate and deep water low oxygen conditions induced by climatic warming have severely affected intermediate and deep water organisms over medium and short terms

late eocene microkrystites and microtektites at maud rise ocean drilling project hole 689b southern ocean suggest a global extension of the approximately 35 5 ma pacific impact ejecta strewn field late eocene microtektites and microkrystites recovered from ocean drilling project hole 689b at maud rise southern ocean are stratigraphically and geochemically compared to spherules from the north american and pacific strewn fields and to devitrified spherules fiom the eocene oligocene global stratotype section and point section in massignano italy the odp 689b microkrystites compare well to the pacific strewn field microkrystites which suggests that the geographic extent of the pacific strewn field was much larger than previously documented the elemental composition of microtektites of odp hole 689b is comparable to tektites of the north american strewn field their 87sr 86sr ratio however is different we tentatively interpret this to reflect geochemical heterogeneity within the north american strewn field but can not exclude the option that the chemical discrepancies result from the existence of a third late eocene impact site

late eocene north american microtektites and clinopyroxene bearing spherules approximately 35 m y ago two events separated by only 10 000 20 000 years each spread roughly 1 billion metric tons of silicate spherules over large areas of the earth s surface the older event produced mostly clinopyroxene bearing spherules cpx spherules the cpx spherules have been found in the caribbean sea gulf of mexico equatorial pacific and eastern equatorial indian ocean the cpx spherule layer is associated with an iridium anomaly and appears to coincide with the extinction of several species of radiolaria the composition and widespread distribution of the cpx spherules indicate that they were formed by an impact event the younger layer of spherules consists of microtektites belonging to the north american tektite strewn field based on age and elemental and isotopic composition the north american microtektites have been found in the western equatorial atlantic on barbados in the caribbean sea and in the gulf of mexico the north american microtektite layer is not synchronous with an iridium anomaly nor does it appear to be associated with any major changes in the microfossils neither the cpx spherule event nor the north american tektite event appears to be associated with a climatic change but no detailed studies have been made across either layer excluding the cpx layer which contains mostly crystal bearing spherules the evidence at the present time indicates that there is only one late eocene microtektite layer and it is part of the north american strewn field

middle holocene rapid environmental changes and human adaptation in greece numerous researchers discuss of the collapse of civilizations in response to abrupt climate change in the mediterranean region the period between 6500 and 5000 cal yr bp is one of the least studied episodes of rapid climate change at the end of the late neolithic this period is characterized by a dramatic decline in settlement and a cultural break in the balkans high resolution paleoenvironmental proxy data obtained in the lower angitis valley enables an examination of the societal responses to rapid climatic change in greece development of a lasting fluvio lacustrine environment followed by enhanced fluvial activity is evident from 6000 cal yr bp paleoecological data show a succession of dry events at 5800 5700 5450 and 5000 4900 cal yr bp these events correspond to incursion of cold air masses to the eastern mediterranean confirming the climatic instability of the middle holocene climate transition two periods with farming and pastural activities 6300 5600 and 5100 4700 cal bp are evident the intervening period is marked by environmental changes but the continuous occurrence of anthropogenic taxa suggests the persistence of human activities despite the absence of archaeological evidence the environmental factors alone were not sufficient to trigger the observed societal changes

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

stable isotope evidence for gradual environmental changes and species survivorship across the cretaceous tertiary boundary high resolution 13c and 18o records have been generated from analyses of the planktonic foraminiferal species heterohelix globulosa and the benthonic foraminiferal taxon lenticulina spp from 3 m of a cored section spanning the cretaceous tertiary k t boundary at brazos river texas these are the first stable isotope records across the k t boundary based on monospecific and monogeneric foraminiferal samples they show a gradual decrease in 13c values of about 2 5 permil beginning at the k t boundary as defined by the first appearance of tertiary planktonic foraminifera and continuing 17 20 cm above the boundary approximately 40 000 years later gradual 13c depletion contrasts with the sudden 13c drop at the k t boundary observed in many deep sea sections the surface to bottom 13c gradient decreased to less than zero approximately 25 000 30 000 years after the k t boundary and remained negative for at least the next 140 000 years concomitant with change in 13c values is a gradual decrease of about 2 5 permil in 18c values which has not been observed at other localities this 18o depletion suggests changes in temperature and or salinity in the earliest paleocene gulf of mexico no extinction of foraminiferal species is associated with the k t boundary or the onset of 18o and 13c depletions instead two phases of cretaceous species extinctions occur one extinction phase is below the k t boundary and below the tsunami bed of bourgeois et al 1988 and may be linked to sea level regression and environmental perturbations the second extinction phase coincides with the minimum in 13c and 18o values in the early danian zone p0 pla and appears directly related to environmental changes reflected in the isotopic record h globulosa which is commonly present in maastrichtian and danian sediments exhibits significantly lower 18o 16o and 13c 12c ratios in tertiary sediments relative to specimens from maastrichtian sediments demonstrating the survival of this important cretaceous taxon after the k t boundary event

lateglacial to holocene vegetation development in the central rila mountains bulgaria the vegetation history of the central rila mountains for the last 14 000 years was reconstructed by means of pollen analysis and radiocarbon chronology of a core retrieved from lake manastirsko 2

late quaternary record of the vegetation and catchment related changes from lake paravani javakheti south caucasus abstract here we present a palynological and sedimentological record from a 96 cm sediment core covering the last 13 ka aiming to document palaeoecological changes in the central south caucasus driven by climate and or human impact the core was retrieved from lake paravani 2073 m asl 41 27 n 43 48 e located in the steppic grasslands of south caucasus in the samsari javakheti volcanic plateau the geomorphological features observed on the plateau including moraine deposits suggest the presence of local glaciers reaching the lake level during the last glacial periods based on sediment and pollen data three palaeoecological phases have been identified the first phase spanning the younger dryas and the early holocene corresponds to a steppic environment with a limited lake productivity driven by a cold and particularly dry climate according to the age depth model this phase ends near 8500 cal bp with the decline of chenopodiaceae the second phase starts with an important expansion of trees at 8300 cal years bp the delayed afforestation recorded in lake paravani is a pattern that has now been recognised widely through the black sea region s more continental areas as soon as the climatic and edaphic conditions were favourable the main deciduous and coniferous trees expanded concurrently due to the proximity of glacial forest refugia located in western caucasus this second phase marked by a climatic optimum is also characterized by an increase in lake productivity the third phase starts at 2000 3000 cal bp and corresponds to the decline of forests on the plateau and the expansion of herbaceous formations leading to the present day steppic environment this deforestation phase is driven by the deterioration of the climate conditions and human impact

middle oligocene cooling from equatorial pacific dsdp site 77b an apparently complete 150 m oligocene sequence of pelagic sediment at equatorial pacific deep sea drilling project site 77b has been analyzed for stable isotope and quantitative planktonic foraminiferal studies lower abundance of inferred warm water species and enrichment of 18 o and 12 c in foraminiferal tests during the interval 29 to 32 m y ago suggest cooler climate lowered sea level and significant volume of continental ice compared to earlier and later times in the oligocene

late eocene microtektites and radiolarian extinctions on barbados a late eocene microtektite layer has been found in three exposed sections on barbados west indies these microtektites and associated tektite fragments are compositionally similar to the north american tektites and thus like the caribbean and gulf of mexico microtektites may belong to the strewn field of north american microtektites which have been found in deep sea deposits from the caribbean sea across the pacific and into the northeastern indian ocean1 2 the north american layer has been reported to be approximately synchronous with several radiolarian extinctions3 4 and with an anomaly in iridium concentrations5 7 and it has been hypothesized that the microtektites the extinctions and the iridium anomaly are all related to an asteroid impact we report here that the radiolarian extinctions predate the microtektite layer and that the highest ir concentrations apparently coincide with the extinctions thus although the extinctions may be causally related to the ir anomaly the microtektites appear not to be

deep sea benthonic foraminiferal faunal turnover near the eocene oligocene boundary abstract eocene oligocene deep sea benthonic foraminifera in d s d p site 277 in the southwest pacific have been analyzed to determine the benthonic foraminiferal response to the development of the psychrosphere near the eocene oligocene boundary biostratigraphic ranges of 41 taxa show that 23 taxa are found throughout the late eocene to early oligocene sequence while 18 taxa exhibit first or last occurrences comparison of the faunal changes in site 277 with a benthonic foraminiferal oxygen isotope record shows that the development of the psychrosphere did not have a profound effect upon the benthonic foraminifera and the overall faunal change preceding and subsequent to the bottom water circulation event occurred gradually the inferred water mass event affected the relative abundance of one species epistominella umbonifera the lack of major faunal changes at the eocene oligocene boundary in site 277 probably reflects either wide environmental tolerances of the benthonic foraminifera or a bottom water temperature change less than 3 c examination of previously published benthonic foraminiferal biostratigraphic data from d s d p sites 167 171 357 360 363 and 400a and deep sea ostracode data from d s d p leg 3 show faunal changes occurred during discrete intervals in the middle eocene early oligocene the faunal patterns from these data and from site 277 show that the eocene oligocene cooling event did not cause rapid catastrophic changes of the benthonic faunas of the open ocean although significant faunal changes are associated with the water mass event in sites 167 171 and 400a the benthonic faunal changes in middle eocene early oligocene time are consistent with the gradual decrease of inferred bottom water temperatures based on previously published oxygen isotopic data the 18 o eocene oligocene enrichment of 0 76 is a major event in the southern ocean oxygen isotopic record but is considerably less in magnitude than the 1 75 2 00 change that occurred gradually from mid early eocene to the eocene oligocene boundary the benthonic foraminiferal and isotopic data indicate that bottom water circulation may have developed during the middle eocene to early oligocene interval with the 3 c bottom water cooling near the eocene oligocene boundary representing part of this development

indications of geomorphological activity in peat bog deposits in the pirin mountains sw bulgaria abstract peat bog deposits are reliable archives of climate and environment change but their sediment origin was underestimated in the bulgarian studies up to now the aim of this study is to enhance the understanding of lake sedimentation in order to improve the knowledge of lake dynamics under climate change during the holocene in the pirin mountains most of the cirques in pirin now are occupied by lakes or peat bogs and their deposits are most informative for the post glacial environment dynamics we used representative boreholes at 2250 m okadensko lake peaty area and 2240 m bezbog lake peaty area and one lower borehole at 1600 m a peat bog near gotse delchev hut to characterize the lateglacial and postglacial geomorphological processes previously published paleo paleobotanical studies of peat deposits at these different altitudes now are supplemented by sedimentological analyses grain size grain morphology mineralogical and textural analysis of mineral grains in order to distinguish indications for climate and environment changes are traced parallels between the palynological and sediment facies sequencing our data showed that after the active weathering and mass wasting processes in the alpine zone which was spreading to lower altitudes 1800 1900 m just after the glaciers retreat in general geomorphological processes dynamics constantly decreases current processes activity in the mountains remains mainly due to human impact especially constructions and deforestation

soil creep the driving factors evidence and significance for biogeomorphic and pedogenic domains and systems a critical literature review abstract soil and regolith creep have been analyzed for at least the last 140 years using many methodological configurations and temporal and spatial scales the general concept of creeping soil and its mechanism first proposed by w m davis and g k gilbert at the end of the 19th century evolved since the 1940s towards theoretical models and precise short and long term field measurements this fruitful epoch continued with results enhanced at the turn of the 20th century by the application of new research methods e g radiometry and a redefinition of the term soil creep to encompass the sum of stochastic shallow subsurface and near surface processes causing net downslope movement of soil or regolith simultaneously another possibility of creep detection was noticed in dendrochronology and since the 1970s in the formally defined discipline of dendrogeomorphology indirect evaluations of creep activity were performed based on tree ring analyses of bent trees this method found many followers but was also heavily criticized as imprecise and lacking in evidence of which kind of tree trunk curvature e g pistol butt like deformation s shape curvature could be ascribed to creep movement from the beginning soil creep was associated with the activity of living organisms on hillslopes however this aspect of creep studies has never been fully developed in spite of the solid foundations and directions of potential studies pointed out by charles darwin at the end of the 19th century in this paper we focus on the historical context of soil creep studies and highlight forest ecosystems as probably the most active environment of biogenic creep mainly due to tree uprooting and other biomechanical effects of living and dead trees root channel infilling tree root mounding etc that are a factors in biotransport in the final sections the position of biogenic creep in the structure of biogeomorphic systems is discussed in relation to such important conceptual frameworks as the biogeomorphic ecosystem biogeomorphic feedback window and ecosystem engineering we also describe several hypotheses that should be carefully tested in the future and propose several research methods that have the ability to further our knowledge about soil creep radiometry laser scanning and soil micromorphology

multiple microtektite horizons in upper eocene marine sediments no evidence for mass extinctions microtektites have been recovered from three horizons in eight middle eocene to middle oligocene marine sediment sequences five of these occurrences are coeval and of latest eocene age 37 5 to 38 0 million years ago three are coeval and of early late eocene age 38 5 to 39 5 million years ago and three are of middle oligocene age 31 to 32 million years ago in addition rare probable microtektites have been found in sediments with ages of about 36 0 to 36 5 million years the microtektite horizon at 37 5 to 38 0 million years can be correlated with the north american tektite strewn field which has a fission track age minimum of 34 to 35 million years and a paleomagnetic age of 37 5 to 38 0 million years there is no evidence for mass faunal extinctions at any of the microtektite horizons many of the distinct faunal changes that occurred in the middle eocene to middle oligocene can be related to the formation of the antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large scale dissolution of calcium carbonate and erosion which created areally extensive hiatuses in the deep sea sediment records the occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle eocene to middle oligocene time

holocene forest dynamics in northwestern romnania pollen analyses and ams radiocarbon measurements were carried out on peat deposits from the former crater lake preluca tiganului located in a mid altitude area of the gutaiului mountains nw romania in order to reconstruct the postglacial vegetation history at the lateglacial holocene transition the open vegetation was replaced by forest suggesting a fast response to climatic warming the rapid expansion of pinus betula and later picea may be due to their existence in the area during the lateglacial at approximately 11 250 cal yr bp the dense forest was composed primarily of ulmus and some picea betula and pinus a small population of ulmus might also have survived in the area during the lateglacial at 10750 cal yr bp quercus tilia and fraxinus followed by corylus at c 10200 cal yr bp expanded significantly in the forest the delay of approximately 550 years in their establishment as compared to the expansion of ulmus was probably due to their immigration from more distant localities

the eocene oligocene planktic foraminiferal transition extinctions impacts and hiatuses biostratigraphic study and re examination of 22 late eocene to early oligocene sections provides data in support of three and possibly a fourth late eocene impact events in the g index zone during a period of about 1 ma of the middle priabonian between 34 7 and 35 7 ma no major species extinctions or significant species abundance changes directly coincide with these impact events species extinctions are gradual and selective affecting primarily cool temperature intolerant surface dwellers these extinctions began with the onset of global cooling during the early middle eocene and culminated near the eocene oligocene boundary the global cooling was associated with the isolation of antarctica as australia moved northward the development of a circum antarctic circulation growth of antarctic ice sheet beginning by late middle eocene time and a change from a thermospheric to thermohaline circulation we find no evidence that the multiple late eocene impact events directly contributed to the climatic deterioration already in progress

estimating phytolith influx in lake sediments abstract so far no phytolith extraction protocols have been tested for accuracy and repeatability here we aim to display a phytolith extraction method combining the strengths of two widely used protocols supplemented with silica microspheres as exogenous markers for quantifying phytolith concentrations phytolith concentrations were estimated for samples from two sedimentary sequences in which numerical age depth models make it possible to calculate phytolith influxes phytolith numbers per cm2 per yr analysis of replicates confirmed the statistical robustness the repeatability and the very few biases of our extraction technique for small phytoliths since the relationship between grass silica short cells and microspheres was kept stable furthermore we demonstrated that silica microspheres are robust exogenous markers for estimating phytolith concentrations the minimum number of items i e phytoliths plus silica microspheres that must be counted to estimate phytolith concentrations and thus influxes depends on the ratio of phytoliths to microspheres r and is minimized when r 1 nevertheless we recommend using ratios r 1 in order to avoid having the counting process become excessively time consuming because microspheres are easier to identify and count than phytoliths

paleoclimatic analyses of middle eocene through oligocene planktic foraminiferal faunas quantitative faunal analyses and oxygen isotope ranking of individual planktic foraminiferal species from deep sea sequences of three oceans are used to make paleoceanographic and paleoclimatic inferences species grouped into surface intermediate and deep water categories based on 18o values provide evidence of major changes in water mass stratification and individual species abundances indicate low frequency cool warm oscillations these data suggest that relatively stable climatic phases with minor cool warm oscillations of 0 5 m y frequency are separated by rapid cooling events during middle eocene to early oligocene time five major climatic phases are evident in the water mass stratification between middle eocene through oligocene time phase changes occur at p14 p15 p15 p16 p20 p21 and p21 p22 zone boundaries and are marked by major faunal turnovers rapid cooling in the isotope record hiatuses and changes in the eustatic sea level a general cooling trend between middle eocene to early late oligocene is indicated by the successive replacement of warm middle eocene surface water species by cooler late eocene intermediate water species and still cooler oligocene intermediate and deep water species increased water mass stratification in the latest eocene p17 indicated by the coexistence of surface intermediate and deep dwelling species groups suggest that increased thermal gradients developed between the equator and poles nearly coincident with the development of the psychrosphere this pattern may be related to significant ice accumulation between late eocene and early late oligocene time

glaciations and paleoclimate of mount erciyes central turkey since the last glacial maximum inferred from 36cl cosmogenic dating and glacier modeling abstract forty four boulders from moraines in two glacial valleys of mount erciyes 38 53 n 35 45 e 3917 m central turkey dated with cosmogenic chlorine 36 36cl indicate four periods of glacial activity in the past 22 ka 1 ka 1000 calendar years last glacial maximum lgm glaciers were the most extensive reaching 6 km in length and descending to an altitude of 2150 m above sea level these glaciers started retreating 21 3 0 9 ka 1 ago they readvanced and retreated by 14 6 1 2 ka ago lateglacial and again by 9 3 0 5 ka ago early holocene the latest advance took place 3 8 0 4 ka ago late holocene using glacier modeling together with paleoclimate proxy data from the region we reconstructed the paleoclimate at these four discrete times the results show that lgm climate was 8 11 c colder than today and moisture levels were somewhat similar to modern values with a range between 20 more and 25 less than today the analysis of lateglacial advance suggests that the climate was colder by 4 5 6 4 c based on up to 1 5 times wetter conditions the early holocene was 2 1 4 9 c colder and up to twice as wet as today while the late holocene was 2 4 3 c colder and its precipitation amounts approached to similar conditions as today our paleoclimate reconstructions show a general trend of warming for the last 22 ka and an increase of moisture until early holocene and a decrease after that time the recent glacier terminates at 3450 m on the northwest side of the mountain it is a remnant from the last advance possibly during the little ice age repeated measurements of glacier length between 1902 and 2008 reveal a retreat rate of 4 2 m per year which corresponds to a warming rate of 0 9 1 2 c per century