present day climatic equivalents of european cenozoic climates abstract recently continental climate evolution in central europe over the last 45 ma has been reconstructed from the palaeobotanical record using a nearest living relative methodology coexistence approach ca the reconstructed climate curves document in detail the transition from almost tropical conditions in the mid eocene to a temperate climate at the pliocene pleistocene transition the observed climatic shifts are primarily expressed as non proportional changes of the different variables taken into account in the present study a published palaeoclimate data set for a total of 42 macrofloras complemented by new calculations is used as base to analyse the climatic space in which a fossil flora existed to define these spaces ca intervals calculated for 3 temperature mean annual temperature cold and warm month mean and 3 precipitation variables mean annual precipitation mean monthly precipitation of the driest and of the wettest month are combined using a global gridded climatology 10 resolution this climate space is then utilized to identify recent climate analogues with respect to the variables regarded for 18 macrofloras climatic analogue regions with respect to 6 variables are identified on the globe for 16 macrofloras analogues exist when three temperature parameters and mean annual precipitation are regarded no recent equivalents are found in 8 cases this corroborates the assumption of the temporary existence of non analogue climates in the cenozoic as shown by multivariate statistics the observed anomalies with respect to present day conditions basically refer to high winter temperatures deploying a gis the recent climate analogues can be presented as sets of grid cells for each flora that can be mapped on a globe once identified these regions can be merged with adequate thematic layers to assess additional proxy data for the palaeofloras to exemplify the procedure koeppen climate type numbers of days with ground frost as well as matthews biome classes are reconstructed the resulting koeppen types ranging from a to c are largely consistent with data previously published the ground frost record shows almost frost free conditions for the mid eocene greenhouse and for the mid miocene climatic optimum for the chattian up to 7 days with ground frost result during the late miocene cooling the number of days with ground frost significantly increased the inferred matthews biomes reveal changing patterns of evergreen and deciduous forest cover when recent climate analogues are found for a fossil flora present climate can be used to calibrate the original ca data it is shown that calibration considerably improves the resolution of the continental climate records

geology of the fushun coalfield liaoning province people s republic of china abstract the fushun coalfield is located in liaoning province 45 km east of shenyang in a relatively small east west trending exposure of mesozoic and cenozoic rocks surrounded by precambrian terrane the coal is included in a sequence of early tertiary rocks consisting of paleocene basalt and tuff and eocene coal oil shale and mudstone these units have been folded into a syncline that plunges gently to the east the overturned north limb of this fold has been partly removed by a thrust fault the principal coal beds are low sulfur subbituminous and bituminous in rank are of limnic origin and are contained in the 55 m thick eocene guchengzi formation the field which has been active since the turn of the century has both open pit and underground mines the largest operation is the west open pit mine which measures 2 0 km wide 6 6 km long and 300 m deep coal is mined by means of power shovels trucks and an electric rail system oil shale from the eocene jijuntun formation is also mined

high resolution deep sea carbon and oxygen isotope records of eocene thermal maximum 2 and h2 eocene thermal maximum 2 etm2 and h2 were two short lived global warming events that occurred 2 m y after the paleocene eocene thermal maximum petm ca 56 ma we have generated benthic foraminiferal stable carbon and oxygen isotope records of four sites along a depth transect on walvis ridge 3 5 1 5 km paleodepth southeast atlantic ocean and one site on maud rise weddell sea to constrain the pattern and magnitude of their carbon isotope excursions cies and deep sea warming at all sites etm2 is characterized by 3 c warming and a 1 4 cie the h2 event that occurred 100 k y later is associated with 2 c warming and a 0 8 cie the magnitudes of the 13 c and 18 o excursions of both events are signifi cantly smaller than those during the petm but their coherent relation indicates that the 13 c change of the exogenic carbon pool was similarly related to warming during these events despite the much more gradual and transitioned onset of etm2 and h2

biogeographic gradients of middle eocene oligocene calcareous nannoplankton in the south atlantic ocean middle eocene oligocene calcareous nannoplankton have been analyzed quantitatively for eight dsdp and odp sites ranging from the equatorial zone to 65 s latitude in the south atlantic ocean there is a general decrease in calcareous nannoplankton species diversity from the middle eocene through the oligocene and species diversity also decreases towards the higher latitudes similar to findings of other studies the drop of the species diversity of calcareous nannoplankton across the eocene oligocene boundary is not drastic delineation of latitudinal distribution patterns of individual species or groups and r mode cluser analysis permit the classification of warm water taxa coccolithus formosus discoasters helicosphaerids and sphenoliths temperate water taxa coccoliths pelagicus cyclicargoliths floridanus group reticulofenestra bisecta reticulofenestra samodurovii reticulofenestra umbilica and cool water taxa chiasmoliths isthmolithus recurvus and reticulofenestra daviesii the abundance of warm water taxa plummets whereas the abundance of cool water taxa sharply increases across the eocene oligocene boundary at the middle and high latitude sites reflecting a profound cooling event in these areas polar ordination and similarity analyses reveal that steep latitudinal biogeographic gradients had been established at least by the middle eocene the gradient greatly increases near the eocene oligocene boundary indicating more severe and permanent cooling at the high latitudes the biogeographic gradient data of this study conflict with the widely accepted inference from the oxygen isotopic data that the thermal gradients between mid latitudes and high latitudes are low or nearly flat for the paleogene oceans lower surface water salinities in the high latitudes may have lowered the 18o values of the planktonic microfossils but apparently did not have significant effect on latitudinal distribution patterns of calcareous nannoplankton which offers an independent means for estimating latitudinal thermal gradients

stable warm tropical climate through the eocene epoch earth s climate cooled from a period of extreme warmth in the early eocene epoch ca 50 ma to the early oligocene ca 33 ma when a large ice cap first appeared on antarctica evidence from the planktonic foraminifer oxygen isotope record in deep sea cores has suggested that tropical sea surface temperatures declined by 5 10 degrees over this interval eventually becoming much cooler than modern temperatures here we present paleotemperature estimates from foraminifer isotopes and the membrane lipids of marine crenarcheota from new drill cores in tanzania that indicate a warm and generally stable tropical climate over this period we reinterpret the previously published isotope records in the light of comparative textural analysis of the deep sea foraminifer shells which shows that in contrast to the tanzanian material they have been diagenetically recrystallized we suggest that increasingly severe alteration of the deep sea plankton shells through the eocene produced a diagenetic overprint on their oxygen isotope ratios that imparts the false appearance of a tropical sea surface cooling trend this implies that the long term eocene climatic cooling trend occurred mainly at the poles and had little effect at lower latitudes

organic matter oxidation in deep sea sediments distribution in the sediment column and implications for calcite dissolution abstract this study uses pore water profiles of no3 and o2 from 34 deep sea study sites from five oceanic regions encompassing broad ranges of sediment composition and organic matter oxidation rate to analyze the depth distribution of organic matter oxidation within the sediment column while the results are consistent with those of hammond et al 1996 and hales 2003 the broader range of environmental variables considered in this study allows us to show that the depth of oxidation varies systematically with the integrated sedimentary organic matter oxidation rate the scale length for oxidation varies from large values of about 4 cm when the organic matter oxidation rate is 5 mol cm2 y to about 0 35 cm at oxidation rates above 20 mol cm2 y we have included this variability of organic matter oxidation depth in models of calcite dissolution our results show that variations in oxidation depth at a constant degree of supersaturation may result in changes in metabolic dissolution efficiency that are similar in magnitude to those resulting from basin wide variations in the degree of supersaturation with respect to calcite the model shows that when the ratio of sedimentary organic matter oxidation rate to calcite rain rate is held fixed at 0 8 mol mol metabolic dissolution is likely to be significant at all bottom water saturation levels and may result in dissolution of up to 50 of the calcite rain at the calcite saturation horizon

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

eocene continental climates and latitudinal temperature gradients global climate during the mesozoic and early cenozoic is thought to have been warmer than at present but there is debate about winter temperatures paleontological data indicate mild temperatures even at high latitudes and in mid latitude continental interiors whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels foliar physiognomy and floristic composition of 23 eocene floras from the interior of north america and australia indicate cold month means generally 2 c even where the mean annual temperature mat was

precipitation patterns in the miocene of central europe and the development of continentality abstract understanding climate patterns with their decisive influence on plant distribution and development is crucial to understanding the history of vegetation patterns in europe during the miocene this paper presents the detailed analyses of several precipitation parameters including monthly precipitation of the wettest driest and warmest months for five miocene stages in conjunction with seasonality of temperature those parameters provide a meaningful measure of continentality and can help to document miocene climate changes and patterns and their possible influence on vegetation climate reconstructions provided here are entirely based on palaeobotanical material in total 169 miocene floras were selected including 14 burdigalian 41 langhian 40 serravallian 36 tortonian and 38 messinian localities all floras were analysed using the coexistence approach the analysis of several precipitation parameters the statistical inter correlation of results and the comparison with modern patterns provides a comprehensive account on miocene precipitation miocene climatic changes after the mid miocene climatic optimum mmco are evidenced in our data set by three major factors i e 1 increasing seasonality of temperature 2 changes in the annual distribution of precipitation towards a precipitation peak in summer and 3 a late increase of longitudinal gradients of precipitation parameters evidence of continental climate in eastern europe first appears during the messinian in addition to changes in temperature shifts in the annual distribution of precipitation may have played a major role in post langhian climate changes however the most significant climatic transformations occurred later from the end of miocene through to the present several authors have described patterns of vegetation development in europe that are in good agreement with our finding of the first evidence for continental climate in eastern europe during the messinian our data do not support an onset of opening of vegetation during the tortonian or even earlier as has been described for some parts of eastern and southern europe possibly either non climatic parameters influenced such an early development or our data lack the required resolution and or spatial coverage to fully decipher the influence of continentality on vegetation and to correlate climate and vegetation statistically nevertheless climatic data that quantify continentality can provide a sound basis for explaining the expansion of grassland in eurasia

palaeoclimate and vegetation change in serbia during the last 30 ma abstract in the present study 14 published megafloras from the serbian cenozoic are analyzed with respect to vegetation type palaeoclimate and palaeogeographic settings the floras cover a time span from the oligocene to the late miocene the results obtained are compared with continental climate records from other parts of europe and discussed in the context of global climate change to obtain a quantitative palaeoclimate record a total of seven different climate variables is calculated for each of the floras using the coexistence approach it is shown that basic patterns of vegetation change such as the immigration of arcto tertiary deciduous floristic elements during the early miocene and the decreasing diversity of laurophyllous taxa during the late miocene are ruled by climate change and a changing palaeogeography the serbian cenozoic climate record shows a steep cooling gradient during the oligocene that is most probably is connected to a northward movement of tectonic plates the globally observed middle miocene climate optimum and the late miocene cooling are well reflected according to the palaeotemperatures calculated a warm temperate climate existed in serbia throughout the time span examined the late miocene cooling is most pronounced in winter temperatures and is connected to increasing seasonality precipitation rates obtained for the serbian cenozoic especially those of the warmest and wettest months tend to be lower when compared to the central european cenozoic according to climate analysis and the interpretation of vegetational data there is evidence for regionally drier conditions and increased seasonality of precipitation in the time span from the late badenian to the early sarmatian

early palaeocene palaeoclimatic inferences from fossil floras of the western interior usa abstract twenty one early palaeocene floral assemblages were collected from a variety of alluvial depositional environments from sites in the williston powder river and raton basins of the western interior of the usa leaf fossils were assigned to morphotypes and their physiognomy was quantified for palaeoclimatic analysis two methods were used climate leaf analysis multi variate program clamp and leaf margin analysis lma temperature estimates and trends derived from clamp and lma indicate that early palaeocene palaeotemperatures decreased from the latest cretaceous particularly in northern areas of north america climatic zones shifted southwards from their latest cretaceous positions resulting in a steepened north south temperature gradient and decreased equability in the early palaeocene sub tropical conditions prevailed as far north as the raton basin with the 20 c mean annual temperature isotherm megathermal mesothermal boundary located at approximately 45 n palaeolatitude the 13 c mean annual temperature isotherm mesothermal microthermal boundary was located at approximately 55 n palaeolatitude to the south of the williston basin clamp estimates indicate that precipitation increased significantly in all areas sampled directly after the k t boundary event especially in the southern rockies precipitation levels decreased somewhat after this initial peak but remained high throughout the early palaeocene evidence from this and other studies suggests that seasonality increased from the latest cretaceous into the palaeocene and was most pronounced in central and northerly areas of the north american continent

why do foliar physiognomic climate estimates sometimes differ from those observed insights from taphonomic information loss and a clamp case study from the ganges delta abstract palaeoclimate estimates derived from plant based proxies are potentially subject to uncertainties arising from taphonomic filtering in any given fossil assemblage it is possible to identify the kinds of likely taphonomic influences but virtually impossible to quantify the uncertainties they introduce because filtering removes information because that information is missing it cannot be measured an alternative approach is to measure the maximum uncertainty possible due to specific information loss within recognised analytical protocols in respect of the multivariate foliar physiognomic technique known as clamp climate leaf analysis multivariate program we have attempted to do this by experimentally degrading both the character state scores and the number and composition of taxa as subsets of the full range of character states and taxonomic diversity in the source vegetation in this study a stand of protected vegetation on green island 23 08 58 n 88 26 59 19 e within the ganges delta was sampled following standard clamp protocols the island is subject to annual flooding during the monsoon season and is typical of the kinds of naturally disturbed vegetation likely to be represented in ancient delta floodplain assemblages a total of 56 woody dicot taxa were scored in the living vegetation from this complete sample leaf character states for lobing margin size apex base length to width ratio and shape were removed in turn from all 56 taxa to give 7 analyses simulating worst case taphonomic loss of physiognomic data ten subsets of 20 randomly selected taxa were also analysed to simulate taphonomic diversity loss of almost two thirds of the potentially available taxa in the source vegetation in all cases the completeness statistic remained above the clamp recommended minimum of 0 66 the results show that in all cases the uncertainties arising from taphonomic processes either through taphonomic diversity or character state filtering were not significantly different from the statistical clamp uncertainties associated with the most commonly used calibration dataset physg3brc and gave similar climatic estimates as the source vegetation in its entirety this suggests that stratigraphically well constrained museum collections lacking detailed sedimentary or taphonomic context can still be used with confidence for clamp analyses leaf margin analysis displayed a greater sensitivity to diversity loss the green island estimates suggested a cooler moister climate than that indicated by the observed regional climate as derived from a 0 5 0 5 gridded data set used in climate modelling evaluation the likely cause for this disparity is the prevalence of a sub canopy microclimate signal developed by the vegetation itself and this is strongly dependant on the temperature and humidity characteristics of the regional climate as well as the proximity to water bodies within the sample size limitations of this study this disparity is larger than that introduced by taphonomic processes but potentially can be corrected for

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

cenozoic climate gradients in eurasia a palaeo perspective on future climate change abstract recent studies in the frame of the neclime neogene climate evolution in eurasia network provide a comprehensive inventory of continental palaeoclimate data for various time slices reconstructed from the palaeobotanical record the integrative analysis of spatial gradients and patterns observed from the proxy data together with data obtained from numeric modelling studies considerably improved our knowledge about the functioning of the climate system in the cenozoic when compared to the present an overall warmer more humid climate existed cenozoic climates are characterized by warm high latitudes shallow latitudinal and longitudinal gradients and wet continental interiors while concentration of greenhouse gases was about at the present day level or considerably higher thus these past climates potentially are valuable to better understand future climate change because they allow empirical access to climate situations that do not or not yet exist today in the present study continental climate data calculated from micro and macrofloras using the coexistence approach are analysed in order to compare past gradients and patterns and their anomalies relative to present day conditions with future climate change scenarios for the case study three time intervals are selected the mid eocene represents a very warm period of the cenozoic exemplifying greenhouse conditions with high atmospheric co 2 of over 1 100 ppmv the mid miocene is known as outstanding warm time interval as well the concentration of greenhouse gases is still controversially discussed but was certainly below the eocene level a third interval selected the tortonian represents a time span of subsequent cooling with the beginning of arctic glaciation for this period a pre industrial co 2 level is assumed it is shown that the study of past climate patterns provides important clues when evaluating modelling results for future scenarios anomalies predicted under global warming partly coincide with the palaeoclimate data sets as an example for greenhouse conditions the mid eocene data also show a strong warming of the high latitudes and a significant positive anomaly of winter temperatures in the continental interior as in the model study for the future scenario however for the tortonian where a pre industrial co 2 can be assumed data show the best agreement with predicted patterns

increased seasonality through the eocene to oligocene transition in northern high latitudes a profound global climate shift took place at the eocene oligocene transition approximately 33 5 million years ago when cretaceous early palaeogene greenhouse conditions gave way to icehouse conditions during this interval changes in the earth s orbit and a long term drop in atmospheric carbon dioxide concentrations resulted in both the growth of antarctic ice sheets to approximately their modern size and the appearance of northern hemisphere glacial ice however palaeoclimatic studies of this interval are contradictory although some analyses indicate no major climatic changes others imply cooler temperatures increased seasonality and or aridity climatic conditions in high northern latitudes over this interval are particularly poorly known here we present northern high latitude terrestrial climate estimates for the eocene to oligocene interval based on bioclimatic analysis of terrestrially derived spore and pollen assemblages preserved in marine sediments from the norwegian greenland sea our data indicate a cooling of approximately 5 degrees c in cold month winter mean temperatures to 0 2 degrees c and a concomitant increased seasonality before the oi 1 glaciation event these data indicate that a cooling component is indeed incorporated in the delta 18 o isotope shift across the eocene oligocene transition however the relatively warm summer temperatures at that time mean that continental ice on east greenland was probably restricted to alpine outlet glaciers

did paleogene north atlantic rift related eruptions drive early eocene climate cooling abstract the delivery of volcanogenic sulphur into the upper atmosphere by explosive eruptions is known to cause significant temporary climate cooling therefore phreatomagmatic and phreatoplinian eruptions occurring during the final rifting stages of active flood basalt provinces provide a potent mechanism for triggering climate change during the early eocene the northeast atlantic margin was subjected to repeated ashfall for 0 5 m y this was the result of extensive phreatomagmatic activity along 3000 km of the opening northeast atlantic rift these widespread predominantly basaltic ashes are now preserved in marine sediments of the balder formation and its equivalents and occur over an area extending from the faroe islands to denmark and southern england these ash bearing sediments also contain pollen and spore floras derived from low diversity forests that grew in cooler drier climates than were experienced either before or after these highly explosive eruptions in addition coeval plant macrofossil evidence from the bighorn basin wyoming usa also shows a comparable pattern of vegetation change the coincidence of the ashes and cooler climate pollen and spore floras in northwest europe identifies volcanism as the primary cause of climate cooling estimates show that whilst relatively few phreatomagmatic eruptive centres along the 3000 km opening rift system could readily generate 0 5 1 c cooling on an annual basis only persistent or repeated volcanic phases would have been able to achieve the long term cooling effect observed in the floral record we propose that the cumulative effect of repeated balder formation eruptions initiated a biodiversity crisis in the northeast atlantic margin forests only the decline of this persistent volcanic activity and the subsequent climatic warming at the start of the eocene thermal maximum allowed the growth of subtropical forests to develop across the region

paleogene temperature gradient seasonal variation and climate evolution of northeast china abstract continental paleogene climates have been well studied in europe and north america but very little is known from asia because paleoclimatic results have only been reported from particular geological intervals here based on 29 plant assemblages from 8 well age controlled fossiliferous sites we quantitatively reconstruct the climates through most of the paleogene of northeast china and discuss related seasonal variations our results demonstrate that the mean annual temperature mat gradient was fairly shallow 0 27 c 1 latitude during the paleocene throughout this region in the eocene seasonality was high in the region indicated by marked differences in both temperature and precipitation between winters and summers of the sites the paleo east asian monsoon must have had intensified at least in the late mid eocene shown by apparent differences in annual precipitation distribution at all the sites regarding the paleogene climatic evolution of northeast china our quantitative results suggest that mat overall declined from warm in the paleocene and eocene to moderate in the oligocene generally consistent with the trend of marine records but with some distinctions two significant cooling events are recognized in the early and mid eocene with mat 3 4 c and 3 8 c lower and winter temperature 5 8 c and 4 7 c lower respectively in similar magnitudes to corresponding variations in europe and north america furthermore the present results show that mat rebounded in the late mid eocene and then decreased until the oligocene a similar pattern demonstrated in europe during the mid eocene to oligocene interval

late paleocene early eocene climate changes in southwestern wyoming paleobotanical analysis the warmest global temperatures of the cenozoic era occurred in early eocene time following a warming trend that started in late paleocene time the greater green river basin of southwestern wyoming is one of the best areas in the rocky mountains for paleobotanical investigation of the paleocene eocene climatic transition intensive sampling has resulted in the recovery of an estimated 189 species of plant macrofossils from the tiffanian clarkforkian wasatchian and bridgerian land mammal ages the leaf morphologies and taxonomic affinities of these fossils were used in combination with other indicators to evaluate paleocene eocene climates following cool humid conditions in the tiffanian the clarkforkian was humid and subtropical and several plant families with modern tropical affinities appeared however as in the tiffanian clarkforkian floras had low diversity and were dominated by a single species in the birch family mean annual temperature mat rose from an estimated 12 c in the tiffanian to 19 c in the clarkforkian while mean annual precipitation map for the tiffanian and clarkforkian is estimated to have been 130 150 cm little fossil plant material is preserved from the latest clarkforkian or the earliest wasatchian which is thought to have contained an interval of cooling and drying followed by renewed warming by the middle wasatchian the time of the cenozoic thermal maximum the inferred mat was about 21 c and the map was near 140 cm a second influx of plant families with tropical affinities appeared in the area and diversity increased significantly but most plant families known from the clarkforkian persisted species turnover from the clarkforkian to the wasatchian was greater than 80 a second turnover of more than 80 of species but not families from the wasatchian to the early bridgerian accompanied drying and increased seasonality of precipitation the early bridgerian mat is inferred to have been near 20 c and the map to have been about 80 cm except for the tiffanian and possibly portions of the early wasatchian paleoclimates during the study interval were predominantly frost free although the moderating influence of the green river lake system has been suggested as a possible explanation for mild eocene winters in wyoming this study shows that virtually frostfree climates existed in the area prior to and independent of significant lake development