impact of the late glacial eruption of the laacher see volcano central rhineland germany abstract within a period of a few weeks toward the end of the allerod interstadial the major plinian eruption of the laacher see volcano produced some 20 km3 of eruptiva covering and preserving the late glacial landscape in the german central rhineland over an area of more than 1000 km2 correlation of terrestrial archives with the greenland ice core records and improved calibration of the radiocarbon timescale permit a precise accurate age determination of the laacher see event some 200 yr before the onset of the younger dryas cold episode carbonized trees and botanical macrofossils preserved by laacher see tephra permit detailed regional paleoenvironmental reconstruction and show that open woodland were typical for the cool and humid hemiboreal climatic conditions during the late allerod this woodland provided the habitat for a large variety of animal species documented at both paleontological and final paleolithic archeological sites preserved below laacher see deposits of special interest are numerous animal tracks intercalated in middle laacher see deposits at the south of the neuwied basin this knowledge may help to evaluate possible supraregional impacts of this volcanic event on northern hemispheric environment and climate during the late allerod

distribution and genesis of soils of the northeastern united states abstract the soils of the northeastern united states central and northern appalachians north of the glacial border are spodosols inceptisols alfisols and some entisols and histosols these soils are relatively young 12 18 ka climate frigid soil temperatures parent material acidic sandy and vegetation conifers are the major soil forming factors affecting the genesis of the spodosols while parent material calcareous material is a determining factor affecting the genesis of the alfisols the inceptisols of southern new england are slightly different better developed cambic horizon than those of the appalachian plateau the genesis of the alfisols of the unglaciated appalachian plateau and triassic lowlands are also significantly influenced by carbonates and basic minerals in their parent material ultisols are found only south of the glacial border ultisols on the appalachian plateau and in the northern ridge and valley are young soils and should be identified as parent material ultisols while those of the southern ridge and valley piedmont and coastal plain show significant soil development and should be identified as genetic ultisols the soils south of the glacial border on steep slopes have been affected significantly by erosion during the cold cycles of the pleistocene while soils on gentle slopes have been affected to a lesser degree much of the material eroded during the late pleistocene has accumulated on lower sideslopes as colluvium the erosional and depositional processes have resulted in a complex mosaic of moderate to well developed soils on the more stable landscape surfaces and moderate to weakly developed soils on the erosional and depositional surfaces

geological factors and evolution of southwestern gondwana triassic plants abstract a synergistic model based on reciprocal influences between biotic and abiotic factors is developed for the triassic of southwestern gondwana changes in physical environment exerted a strong influence on the characteristics and evolution of plant assemblages the permian triassic extinction and the change from palaeophytic to mesophytic floras is one of the most striking examples of direct influence of physical environment upon plant communities pangea coalescence the distribution of land masses and seas the spreading of continental climates megamonsoonal conditions and the waning polar glaciation determined the expansion of xeromorphic morphotypes that became dominant during the whole mesozoic in southwestern gondwana the introduction or invasion of immigrant lineages suggests a strong asymmetrical interchange from the euroamerican realm to the gondwana realm in addition generalised extensional volcanism development of intracratonic rifts and the palaeolatitudinal location of climatic zones during the early middle triassic favoured extinction of the glossopteris flora and explosive diversification of endemic groups from the chronological viewpoint the barrealian cortaderitian and florian stages are recognised in the triassic of southwestern gondwana these stages are respectively characterised by a appearance of mesophytic elements and coexistence of palaeozoic and mesozoic groups b maximum diversification of the dicroidium flora and c dicroidium flora decline and replacement by morphotypes with strong jurassic affinity these palaeofloristic changes seem to be strongly influenced by tectonic evolution of sedimentary basins temporal and regional distribution of sedimentary environments and intra triassic palaeoclimatic change

global coal gap between permian triassic extinction and middle triassic recovery of peat forming plants early triassic coals are unknown and middle triassic coals are rare and thin the early triassic coal gap began with extinction of peat forming plants at the end of the permian ca 250 ma with no coal known anywhere until middle triassic 243 ma permian levels of plant diversity and peat thickness were not recovered until late triassic 230 ma tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal bearing sequences are present also in early triassic rocks nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers insects or tetrapod herbivores which became cosmopolitan and much reduced in diversity across the permian triassic boundary instead we favor explanations involving extinction of peat forming plants at the permian triassic boundary followed by a hiatus of some 10 m y until newly evolved peat forming plants developed tolerance to the acidic dysaerobic conditions of wetlands this view is compatible not only with the paleobotanical record of extinction of swamp plants but also with indications of a terminal permian productivity crash from delta sup 13 c sub org and total organic carbon of both nonmarine and shallow marine shales 205 refs 3 figs more 3 tabs less

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

evolution and environmental impacts of the eruption of laacher see volcano germany 12 900 a bp abstract laacher see volcano lsv 40 km south of bonn explosively erupted ca 6 3 km 3 of chemically strongly zoned phonolite magma probably during spring 12 900 years ago the resulting eruption column having reached at least 20 km in height the bulk of the laacher see tephra lst was deposited east of the volcano within the neuwied basin lst ashes form the most important stratigraphic marker in lateglacial deposits over much of central europe a minimum of 2 mt total s was calculated to have been released during the eruption by comparing pre and posteruptive volatile concentrations in glass inclusions and pumice matrix glasses because a separate s bearing vapor phase was probably present in the magma prior to eruption as indicated by the high melt h 2 o contents close to saturation level the actual amount of s released during the eruption could have significantly exceeded 2 mt the sulfuric acid aerosol layer resulting from the massive stratospheric s input probably resided in the stratosphere for years and most likely had a significant impact on climate and thus the environment increased precipitation in central europe and or impairment of the vegetation cover for several years is suggested by several proxies especially increased sediment supply into lakes proximal to the eruptive center major environmental impacts include an initial blast that felled trees up to 4 km away from vent fast deposition of huge tephra volumes led to the complete disruption of rhine river within the lower neuwied basin and the damming up of a lake ca 140 km 2 in areal extent sudden collapse of the temporary tephra dam caused a catastrophic flood wave downstream whose deposits are recognized as far north as bonn reworking of unconsolidated tephra deposits over several 100 km 2 was widespread and extensive generating abundant lahars and flood plain deposits a braided river system established in neuwied basin probably persisted up to several years recent reports for a second eruption of lsv are not confirmed

precambrian permafrost horizons as indicators of palaeoclimate abstract periglacial phenomena such as polygonal wedge structures and microrelief features commonly preserved in fossil permafrost horizons can provide valuable information on palaeoclimate including indications of mean annual air temperature seasonal temperature range relative precipitation and evidence for long term 104 years oscillations of climate such features are known from early and late proterozoic rocks and indicate mean annual air temperatures as low as 12 to 20 c or lower and strongly seasonal periglacial climates these palaeoclimatic data together with information on palaeolatitude and proximity to palaeo sea level may impose strong constraints on palaeoclimate models for proterozoic glaciation

middle late triassic 230 5 ma singularity in the stratigraphic and magmatic history of the pangean heat anomaly the phanerozoic history of continental dispersal and coalescence contains an epoch of radical change at about the middle late triassic boundary 230 5 ma marked by 1 the final coalescence of pangea by the contact of south china and cimmeria with laurasia and terminal compressive deformation in australia and southern africa and 2 the incipient dispersal of pangea by the onset of continental rifting in eastern north america and northwest africa argentina east africa and western australia this epoch of coalescence and incipient dispersal correlates with a change from 1 an icehouse state to a greenhouse state and 2 changes from a fall to a rise in the sea level curve in the emplacement of north american granite and in the cumulative curve of reversed to normal magnetic polarity these changes are interpreted as indicating the first major loss from the heat accumulated beneath pangea now represented by the atlantic african geoid high

climatic significance of natric horizons in permian asselian palaeosols of north central kansas usa columnar structured horizons have been recognized in ancient coastal palaeosols of several lower permian asselian stratigraphic units of north central kansas these strongly developed columnar polygonal shaped peds are characteristic of sodium influenced natric argillic horizons and are commonly indicative of semi arid to arid environments evaporite features above and below these palaeosols support the conclusion for a dry palaeoclimate the columnar peds are typically 3 15 cm in diameter and exhibit domed tops fine clay fills the cracks between the columnar peds and is generally of a darker colour than the peds each natric horizon has a low value and chroma colour apparently the result of carbonate accumulation the natric horizons in these permian palaeosols appear to have been partially influenced by sodium rich groundwaters root traces and root moulds are found between peds in all natric horizons indicating plant succession after columnar ped formation these sodium influenced palaeosol profiles occur as part of a spectrum of palaeosol types that indicate cyclical climate change associated with glacioeustatic sea level fluctuations

equability continentality and tertiary climate the crocodilian perspective the distributions of fossil crocodilians are used to examine north american continental paleoclimates for four time periods in the cenozoic control groups provide a qualitative means of examining the completeness of the record and thus the validity of crocodilian patterns by analogy with the range of the extant american alligator alligator mississippiensis the patterns imply that mid to high latitude continental interiors during the eocene and miocene did not undergo seasonal temperature extremes as great as those observed in such areas today this is compatible with the paleobotanical data during both the late oligocene and the pleistocene times of major glaciation crocodilians were restricted to more maritime localities

high frequency controls on alluvial successions an integrated sedimentological and palaeopedological approach to the plio pleistocene of argentina abstract plio pleistocene palaeosol bearing alluvial strata are continuously exposed along the marine cliffs of southeastern buenos aires province argentina the study interval was deposited by a mixed predominantly suspended load fluvial system outcrops are dominated by floodplain siltstones and mudstones that exhibit a cyclic alternation between calcic and vertic palaeosols this cyclicity is represented by meter scale alluvial cycles that show as a general trend a gradual increase in the proportion of channel fill deposits up section cyclic variations in palaeosols facies and architectural elements can be related to allogenic drivers such as climate and eustasy for the lower punta san andres alloformation the stratigraphic arrangement of the recognised palaeosols and the clay mineral distribution indicate that the palaeoclimate was subhumid average mean annual precipitation map 840 mm seasonal and temperate average mean annual temperature mat 7 85 c for at least 1 ma from ca 2 9 ma to ca 1 8 ma late pliocene early pleistocene with several intervals in which conditions became drier and probably colder even though climate was a major control on palaeosol development it is suggested here that it was not the main control on high frequency cycles variations in the orbital parameters more specifically in insolation were interpreted as having controlled the sedimentation and architectural evolution of the lower punta san andres alloformation depositional systems

depositional setting and paleobotany of permian and triassic permineralized peat from the central transantarctic mountains antarctica abstract silicified peat is known from two sites in the central transantarctic mountains both are within a 2 km thick permo triassic sandstone shale sequence that was deposited by braided streams in a rapidly subsiding foreland basin along the paleo pacific margin of antarctica upper permian permineralized peat occurs as scattered boulders just above a channel form sandstone in the upper part of the buckley formation on skaar ridge overlooking the beardmore glacier these boulders are erosional remnants of fine grained deposits that accumulated in shallow lakes or swamps on a flood plain at fremouw peak the peat occurs near the top of the fremouw formation in strata that are probably middle to late triassic in age the peat consists of large blocks that were rafted into a sandy braided stream channel during a flood and then stranded and buried as flood waters receded both sites are characterized by exceptionally well preserved plant material although the composition and diversity of the two floras are very different permineralization apparently took place rapidly and was enhanced by the dissolution of siliceous volcanic detritus that is abundant in both formations

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

volatile composition of the phonolitic laacher see magma 12 900 yr bp implications for syn eruptive degassing of s f cl and h 2 o a volatile rich and chemically zoned phonolitic magma reservoir was tapped successively during the eruption of laacher see volcano ca 12 900 years bp and produced a tephra sequence consisting of phenocryst poor highly evolved phonolite at the base and phenocryst rich more mafic phonolite at the top the stratospheric volatile loading was estimated by comparing pre and post eruptive s f cl and h2o contents of undegassed glass inclusions and partially degassed matrix glasses glass inclusions 150 1490 ppm s and host matrix glasses 150 820 ppm s both document a strong s decrease during progressive magmatic differentiation which is interpreted to be partially caused by crystallization of hauyne the s6 stotal ratio of the pre eruptive melt increased with differentiation from 8 to 71 as indicated by s k wavelength shift measurements in glass inclusions sulfate rich highly evolved phonolitic magma was erupted during plinian and sulfide rich more mafic phonolitic magma during late phreatomagmatic phases f and cl became enriched during late stages of differentiation glass inclusions 690 4060 ppm f 1770 4400 ppm cl matrix glasses 680 3660 ppm f 2130 4330 ppm cl the most differentiated melts maximum 13 wt na2o occur only as matrix glass and are extremely f enriched 5080 8780 ppm but cl depleted 460 2820 ppm suggesting that f was retained in the melt whereas some cl was lost during pre and or syn eruptive degassing the h2o contents of glass inclusions increase irregularly with differentiation 2 5 5 7 wt matrix glasses are h2o depleted 0 2 2 8 wt compared to most glass inclusions showing that most h2o was released to the atmosphere by explosive degassing a mass balance calculation yields a syn eruptive volatile release of 1 9 tg stotal 6 6 tg cl and 403 tg h2o from the melt this is a minimum estimate since s and cl could have accumulated in a separate fluid phase as indicated by fluid inclusions in hauyne and pre eruption h2o contents close to saturation level at the likely pressure temperature conditions in the laacher see magma reservoir we estimate that at least ca 20 tg so2 were injected into the stratosphere causing a significant negative climate forcing as reflected by several paleoclimate proxies and as shown by recent modeling

high resolution lacustrine record of the late glacial holocene transition in central europe abstract in this paper we present the high resolution record of proxy climatic data in central europe during the final stages of the last deglaciation derived from the annually laminated sediments of lake go ciaz central poland the isotopic palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the younger dryas completed within 150 and 70 years respectively in close agreement with the previous estimates derived from the polar ice cores and marine sediments in the upper yd some amelioration of climate took place already about 600 years before the main yd preboreal transition counting of annual varves in the lake sediments allows a direct estimate of the duration of the younger sdryas in central europe it lasted approximately 1640 years substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves but agreeing with the radiocarbon calibration data obtained for barbados corals the calendar ages of the boundaries of the yd 12 920 and 11 280 cal bp are tentatively set

a younger dryas varve chronology from the rehwiese palaeolake record in ne germany abstract the first 1400 year floating varve chronology for north eastern germany covering the late allerod to the early holocene has been established by microscopic varve counts from the rehwiese palaeolake sediment record the laacher see tephra lst at the base of the studied interval forms the tephrochronological anchor point the fine laminations were examined using a combination of micro facies and xrf analyses and are typical of calcite varves which in this case provide mainly a warm season signal two varve types with different sub layer structures have been distinguished i complex varves consisting of up to four seasonal sub layers formed during the allerod and early holocene periods and ii simple two sub layer type varves only occurring during the younger dryas the precision of the chronology has been improved by varve to varve comparison of two independently analyzed sediment profiles based on well defined micro marker layers this has enabled both 1 the precise location of single missing varves in one of the sediment profiles and 2 the verification of varve interpolation in disturbed varve intervals in the parallel core inter annual and decadal scale variability in sediment deposition processes were traced by multi proxy data series including seasonal layer thickness high resolution element scans and total organic and inorganic carbon data at a five varve resolution these data support the idea of a two phase younger dryas with the first interval 12 675 12 275 varve years bp characterised by a still significant but gradually decreasing warm season calcite precipitation and a second phase 12 275 11 690 varve years bp with only weak calcite precipitation detailed correlation of these two phases with the meerfelder maar record based on the lst isochrone and independent varve counts provides clues about regional differences and seasonal aspects of yd climate change along a transect from a location proximal to the north atlantic in the west to a more continental site in the east

varve chronology and palynology of the lateglacial in northwest germany from lacustrine sediments of hamelsee in lower saxony abstract the hamelsee is a dolina from a collapse over permian salt that occurred at the end of the pleniglacial it is more than 21 m deep and contains 18 m of lacustrine sediments the lateglacial sediments in the central part of the lake consist of 2 7 m from 15 to 17 7 m of sapropelic and silty muds which are mostly laminated and partly bioturbated minor slumps occur mainly during colder phases the subdivision of the lateglacial is based on pollen zones multidisciplinary studies of the microfacies from thin sections geochemistry pollen analysis and rotifer analysis allow environmental and palaeoclimatological interpretations to be made the biozones of the lateglacial and their boundaries are marked by rapid climatic changes though covering comparatively short periods of time they are not monotonous but characterized by minor internal climatic fluctuations the sediments of the meiendorf and oldest dryas are not laminated the allerod sediment is seasonally varved without interruption and encompasses 625 yr the eruption of the laacher see volcano 12 900 cal bp had an impact on the climate during the following 10 yr the transition from the allerod to the younger dryas took some 50 yr and it occurred 200 yr after the eruption of the laacher see volcano the abrupt change at the end of the lateglacial 11 560 cal bp occurred within less than 10 yr however many proxies reacted with a time lapse of 15 to 30 yr

the carnian humid episode of the late triassic a review from 1989 to 1994 a series of papers outlined evidence for a brief episode of climate change from arid to humid and then back to arid during the carnian stage of the late triassic epoch this time of climate change was compared to marine and terrestrial biotic changes mainly extinction and then radiation of flora and fauna subsequently termed albeit incorrectly the carnian pluvial event cpe by successive authors interest in this episode of climatic change has increased steadily with new evidence being published as well as several challenges to the theory the exact nature of this humid episode whether reflecting widespread precipitation or more local effects as well as its ultimate cause remains equivocal bed by bed sampling of the carnian in the southern alps dolomites shows the episode began with a negative carbon isotope excursion that lasted for only part of one ammonoid zone a austriacum however that the carnian humid episode represents a significantly longer period both environmentally and biotically is irrefutable the evidence is strongest in the european middle eastern himalayan north american and japanese successions but not always so clear in south america antarctica and australia the eruption of the wrangellia large igneous province and global warming causing increased evaporation in the tethyan and panthalassic oceans are suggested as causes for the humid episode

micromorphological studies of the complex early oligocene himalayan foreland palaeosols in relation to asian monsoon climate abstract the cenozoic himalayan orogeny not only modified asia s climate but also affected global climate one of its significant outcomes is the inception of asian monsoon climate though researchers have shown that changes in himalaya and tibetan plateau elevations control its evolution however reached no consensus on pre miocene timing of monsoon climate inception perhaps due only limited studies in pre miocene himalayan sediments another possibility is that we have restricted our studies in deducing a relationship between himalayan tectonic upheavals and monsoon climate however priority should be to first explore any palaeomonsoon signatures since deposition of himalayan foreland basin hfb sediments because some researchers have reported palaeomonsoon signatures during eocene oligocene time here we report another such study from early oligocene dagshai palaeosols of subathu sub basin india detailed morphological and micromorphological studies revealed abundant presence of matrix and intrusive pedofeatures in mature palaeosol profiles most striking evidence is the presence of fe mn oxide and carbonate pedofeatures together the concretions present in the thick bk horizons having diffuse boundaries show intermixing and or alternation of calcite and iron oxides also occurrence of pedogenic carbonate nodules is not restricted in bk horizon as is observed in present monsoon dominant regions and nodules are impure dense and largely micritic similar to those documented in indo gangetic holocene soils further most common fe mn oxide nodules are typical impregnative and associated with granostriated fabric which is indicative of soils formed under seasonal wet and dry cycles furthermore occurrence of illuvial coatings and carbonate together in the b horizon indicate prevalence of sufficient wet and dry cycles respectively all these features indicate presence of seasonal climatic conditions and therefore monsoon conditions prevailed during early oligocene time which is contrary to the most common known late miocene age of indian monsoon inception

towards a late quaternary tephrochronological framework for the southernmost part of south america the laguna potrok aike tephra record abstract a total of 18 tephra samples have been analysed from the composite sediment sequence from site 2 of the laguna potrok aike icdp expedition 5022 from southern patagonia argentina which extends back to ca 51 ka cal bp analyses of the volcanic glass show that all layers but one are rhyolitic in composition with sio2 contents ranging between ca 74 5 and 78 wt and suggest an origin in the austral andean volcanic zone avz 49 55 s nonetheless two main data clusters occur one group with k2o contents between ca 1 5 and 2 0 wt indicating an origin in the mt burney volcanic area and one group with k2o contents between ca 2 7 and 3 9 wt tentatively correlated with viedma lautaro and the aguilera volcanoes in the northern part of the avz the early holocene tephra mb1 and the late pleistocene reclus r1 tephra occur in the upper part of the sequence periods with significant tephra deposition occurred between ca 51 44 ka cal bp and ca 31 25 ka cal bp with a decrease in tephra layer frequency between these two periods

climate related variations in the composition of the late glacial and early holocene sediments of lake perespilno eastern poland abstract this paper presents an array of analyses of the laminated sediments of lake perespilno eastern poland covering the period between older dryas and preboreal using the varve chronologies pollen and 14 c data the laminated sequence of lake perespilno has been synchronised with that of lake go ciaz the length of the allerod and younger dryas periods derived from lake perespilno sediments agrees well with the previous estimates according to our data the climate in the allerod was relatively mild with some increase of precipitation and humidity after ca 13 2 kyr cal bp the beginning of the younger dryas is marked by drastic changes in temperature as well as humidity thinning of forests facilitated input of allochtonous material to the lake it seems that the groundwater level as well as lake level dropped significantly and the period of lowest water table was prolonged for ca 300 years surprisingly the abrupt warming at the beginning of the holocene is only slightly reflected in the sediments changes in sediment composition at that time seem to be controlled more by the development of surrounding vegetation than by the climate itself

the evidence and implications of polar ice during the mesozoic abstract the mesozoic perhaps representing the longest period of warmth during phanerozoic earth history contains in general sparse and frequently equivocal evidence for polar ice although this time is undoubtedly punctuated by oscillations in climate whether sufficient to lead to polar cooling and the formation of polar ice an inviting mechanism to account for faunal and floral distribution patterns and large scale sea level change has been widely debated mesozoic evidence for glacial conditions includes abraded rock surfaces generally unsorted stone rich beds and the presence of dropstones rafted by ice within a finer grained host sediment faunal and floral evidence has also been utilised to determine the presence or absence of cold or sub freezing polar conditions together with more indirect evidence for glacial conditions derived from general circulation model gcm simulations of climate the analysis of clay mineral distributions glendonite abundance and palaeontological and sedimentological evidence for globally synchronous sea level change the extent of possible glacial environments during the mesozoic has been established by plotting published reports of glacial sediments on palaeogeographic reconstructions the general clustering of evidence at high palaeolatitudes suggests that the extent of polar ice during the mesozoic is likely to have been approximately one third the size of the present day based on such evidence a number of episodes of cold or sub freezing polar climates during the bajocian bathonian tithonian volgian valanginian and aptian are recognised evidence exists possibly also for a cold episode during the early jurassic pliensbachian although poorly constrained owing to limited biostratigraphical control the longevity of these events may be represented by a cold snap within a stage although undoubtedly the possible smearing of ages may have had the effect of lengthening and hence promoting the importance of these proposed events the climate regime of the earth during these times may be hypothesised to be characterised by a relatively steep pole to equator temperature gradient where low latitude regions are as warm or warmer than today the evidence to support such reasoning includes sharp increases in the areal distribution of both glendonites and deposits with affinities to glacial tillites and dropstones for these times coincidental falls of sea level arid events and an increased bipolarity of faunas at these times imparts further confidence that these events were of a magnitude to effect the earth as a whole

palaeoenvironmental significance of late permian palaeosols in the south eastern iberian ranges spain the late permian wuchiapingian alcotas formation in the se iberian ranges consists of one red alluvial succession where abundant soil profiles developed detailed petrographical and sedimentological studies in seven sections of the alcotas formation allow six different types of palaeosols with distinctive characteristics and different palaeogeographical distribution to be distinguished throughout the south eastern iberian basin these characteristics are in turn related to topographic climatic and tectonic controls the vertical distribution of the palaeosols is used to differentiate the formation in three parts from bottom to top showing both drastic and gradual vertical upwards palaeoenvironmental changes in the sections reconstruction of palaeoenvironmental conditions based on palaeosols provides evidence for understanding the events that occurred during the late permian some few millions of years before the well known permian triassic global crisis

δ13c depth profiles from paleosols across the permian triassic boundary evidence for methane release stable carbon isotopic analyses of organic carbon 13 c in individual paleosol profiles from permian triassic sequences of antarctica reveal systematic isotopic variations with profile depth these variations are in many cases analogous to those in modern soils which are functions of redox conditions soil development and degree and type of microbial decay in modern soils these isotopic depth functions develop independently from vegetation changes c 3 versus c 4 vegetation and can be diagnostic of soil orders this study shows that soil intrinsic functions can be preserved in the 13 c values of paleosols as old as 260 ma and constitute valuable data for paleoecological interpretations a large carbon isotopic offset of as much as 10 in whole paleosol profiles across the permian triassic boundary indicates significant changes in the soil biogeochemistry and the soil atmosphere system early triassic paleosols are distinctive in their extremely low 13 c values to 42 and often show an anomalous 13 c depth distribution compared to both permian paleosols and modern soils highly depleted 13 c values as the ones in early triassic paleosols are suggested to be associated with microbial methane oxidation methanotrophy this hypothesis implies increased methane concentrations in the early triassic soil atmosphere system increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the permian triassic boundary

north european last glacial interglacial transition lgit 15 9 ka tephrochronology extended limits and new events high precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change although radiocarbon is the traditional method for dating late quaternary sedimentary sequences particularly during the last glacial interglacial transition lgit 15 9 ka there are inherent problems with the method particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content an alternative method is the use of tephras that act as time parallel marker horizons within europe numerous volcanic centres are known to have erupted during the lgit providing considerable potential for high precision correlation independent of past radiocarbon fluctuations here we report the first identification of the vedde ash and askja tephra in ireland significantly extending the known provenance of these events we have also identified two new horizons the roddans port tephras a and b and tentatively recognise an additional horizon from vallensgard mose denmark that provide crucial additional chronological control for the lgit two phases of the laacher see tephra lst are reported the lower laacher see tephra llst and probably the c2 phase of the middle laacher see tephra mlst c2 indicating a more northeasterly distribution of this fan than reported previously copyright 2006 john wiley sons ltd

a tephrochronology for the lateglacial palynological record of the endinger bruch vorpommern north east germany the tephrostratigraphy of lake sediments in the endinger bruch provides the first robust age model for the lateglacial palynological records of vorpommern north east germany cryptotephra investigations revealed six tephra layers within sediments spanning from open vegetation phase i bolling 15 ka to the early holocene betula pinus forest phase pre boreal 10 5 ka four of these layers have been correlated with previously described tephra layers found in sites across europe the laacher see tephra eifel volcanic field is present in very high concentrations within sediments of the lateglacial betula pinus forest phase allerod the vedde ash iceland lies midway through open vegetation phase iii younger dryas the hasseldalen and the askja tephras iceland lie in the early holocene betula pinus forest phase preboreal these tephra layers have independently derived age estimates which have been imported into the endinger bruch record furthermore the layers facilitate direct correlation of the regional vegetation record with other palaeoenvironmental archives which contain one or more of the same tephra layers from greenland to southern europe in doing this localized variations are confirmed in some aspects of the pollen stratigraphy however transitions between the main vegetation phases appear to occur synchronously within centennial errors with the equivalent environmental transitions observed in sites across the european continent copyright 2011 john wiley sons ltd

the eruptive center of the late quaternary laacher see tephra about 5 km3 of phonolite magma were erupted 11 000 years ago in the laacher see area in plinian and vulcanian eruptions the eruptive vents for all tephra in dispute for over 200 years must have been located entirely within the laacher see basin because 1 all deposits are thickest in the tuffring surrounding the basin with one exception pyroclastic flow deposits are thickest 2 to 6 km away from the rim of the basin having ponded in radial valleys three plinian fallout layers show minor secondary thickness maxima 12 to 16 km east of laacher see 2 axes of all depositional fans and single tephra sheets converge in the laacher see basin 3 diameters of both lithic and pumice clasts reach their maxima in outcrops close to laacher see volcano 4 directions of asymmetric ballistic impact sags indicate the laacher see basin as source area 5 the dimension of laacher see crater roughly corresponds to the erupted volume of phonolitic tephra 5 3 km3 magma dre and lithic clasts 0 7 km3 6 xenolith types are consistent with an eruptive center within the laacher see basin 7 the systematic chemical and mineralogical zonation of the tephra deposits from highly differentiated aphyric phonolite at the base to highly phyric mafic phonolite at the top strongly suggests eruption from a single compositionally zoned magma column 8 several lines of evidence indicate migration of the main eruptive focus from the south to the north during the later part of the eruption both vents however being confined within the laacher see basin

tephrostratigraphy of a lateglacial lake sediment sequence at wegliny southwest poland abstract this paper presents the first late quaternary locality in the present day territories of poland where multiple cryptotephra layers have been identified located near wegliny in southwest poland study of the lateglacial gyttja deposits reveals the presence of at least four non visible tephra horizons electron microprobe and laser ablation icpms analysis of glass shards suggests products from at least two icelandic volcanic centres katla and snaesfellsness of particular importance is the discovery of two eruptions believed to originate from the east eifel volcanic field within the allerod chronozone one correlates with the well documented laacher see tephra lst but the second horizon herein designated t642 t655 would appear to represent an earlier precursor eruption the chemical composition of the lst and the precursor tephra both appear to match to the upper laacher see tephra ulst phase which previously was thought to have dispersed not to the northeast but in a southerly direction towards the alpine foreland this indicates the eruption dynamics of the laacher see are more complex than hitherto recognised

large phreatomagmatic vent complex at coombs hills antarctica wet explosive initiation of flood basalt volcanism in the ferrar karoo lip the mawson formation and correlatives in the transantarctic mountains and south africa record an early eruption episode related to the onset of ferrar karoo flood basalt volcanism mawson formation rocks at coombs hills comprise mainly 80 vol structureless tuff breccia and coarse lapilli tuff cut by irregular dikes and sills within a large vent complex 30 km2 quenched juvenile fragments of generally low but variable vesicularity accretionary lapilli and country rock clasts within vent fill and pyroclastic density current deposits point to explosive interaction of basalt with groundwater in porous country rock and wet vent filling debris metre scale dikes and pods of coherent basalt in places merge imperceptibly into peperite and then into surrounding breccia steeply dipping to sub vertical depositional contacts juxtapose volcaniclastic rocks of contrasting componentry and grainsize these sub vertical tuff breccia zones are inferred to have formed when jets of debris steam water passed through unconsolidated vent filling deposits these jets of debris may have sometimes breached the surface to form subaerial tephra jets which fed subaerial pyroclastic density currents and fall deposits others however probably died out within vent fill before reaching the surface allowing mixing and recycling of clasts which never reached the atmosphere most of the ejecta that did escape the debris filled vents was rapidly recycled as vents broadened via lateral quarrying of country rock and bedded pyroclastic vent rim deposits which collapsed along the margins into individual vents the unstratified poorly sorted deposits comprising most of the complex are capped by tuff lapilli tuff and tuff breccia beds inferred to have been deposited on the floor of the vent complex by pyroclastic density currents development of the extensive coombs hills vent complex involved interaction of large volumes of magma and water we infer that recycling of water as well as recycling of pyroclasts was important in maintaining water supply for phreatomagmatic interactions even when aquifer rock in the vent walls lay far from eruption sites as a consequence of vent complex widening the proportion of recycled water increased with vent complex size in the same way that the proportion of recycled tephra did though water recycling leaves no direct rock record the volcaniclastic deposits within the vent complex show through their lithofacies structural architecture lithofacies characteristics and particle properties clear evidence for extensive and varied recycling of material as the complex evolved

granulation of weak rock as a precursor to peperite formation coal peperite coombs hills antarctica abstract peperite formed by mingling of magma with coal and with fragmented coal plus other country rock is exposed at coombs hills antarctica in rocks of the mawson formation where ferrar supergroup basalt encountered the beacon supergroup continental sedimentary succession an internally laminated 0 5 m thick coal bed passes gradationally through a coal fragment dominated peperite into a glass rich basalt dominated coal fragment matrix peperite and then into coherent basalt initial interaction of magma with water saturated coal and host sediments locally brecciated the coal subsequent mingling of basalt with a slurry of coal fragments and water driven by viscosity and density contrasts between the basalt and the slurry and by flow inhomogeneities in intruding magma led to increasingly complex mingling of the two fluids via bifurcation of fingering viscous flows this mingling was complicated by the participation of phases with time and space dependent thermal properties and viscosity coal fragments coal water slurry and basaltic magma and the generation of multiple gas phases through devolatilisation of heated coal the initial elastic response of the coal fragments to stress resulted in a fluidal mingling of coal and basalt facilitated by softening of coal during heating associated with intrusion and b localised formation of blocky coal clasts during high stress events associated with passage of a liquid and or a gas phase s through the coal the presence of fluidal and blocky shaped coal fragments in the coal peperite with both curved and planar surfaces bounding single coal clasts suggests that clast morphology in the magma sediment dispersion was controlled at very small scales by the time temperature and stress dependent qualities of the coal fluidal and blocky clast shapes in the coal peperite coupled with vesicles in the coal clasts suggest that transient properties of either the host or intrusion during non explosive magma sediment interaction may exert a strong control on clast morphology and mingling characteristics

point counting pores and illuvial clay in thin section abstract six soil thin sections containing various amounts of illuvial clay previously estimated by ten operators were point counted four times by an additional experienced operator the results indicate that a count of 6000 points over a section area of 25 25 mm is sufficient to quantify satisfactorily the pore space of the section replicated results for illuvial clay however differed widely for some sections these differences are attributed both to difficulties in recognising illuvial clay and to orientation and variability of soil components variability of results for illuvial clay in this study was less than that reported for ten operators but nonetheless it is evident that for most sections the amount of illuvial clay cannot be estimated precisely by a single count of 6000 points suggestions are made for improving the reliability of estimates of illuvial clay in soil thin sections and an improved basis for reporting results is proposed

a pedotype approach to latest cretaceous and earliest tertiary paleosols in eastern montana a pedotype approach to the study of paleosols emphasizes individual profiles it is an alternative approach to the study of geosols which are laterally extensive suites of paleosols or pedofacies which are pedogenically distinctive sedimentary facies this is the first pedotype study of paleosols across the cretaceous tertiary boundary in eastern montana pedotypes allow assessment of sedimentation and fossilization the sequence of paleosols across the cretaceous tertiary boundary at bug creek is one of high temporal resolution because most available geological time can be accounted for by differing degree of development inferred for each pedotype paleosols at bug creek include pedotypes that preserve plant fossils well but were unfavorable for preservation of fossil vertebrates pedotypes also allow reassessment of ecosystem change despite indications of catastrophe at the cretaceous tertiary boundary the array of paleocene and cretaceous pedotypes are not strikingly different the upper cretaceous hell creek formation includes pedotypes interpreted as gleyed alfisols inceptisols and entisols probably formed under seasonally water logged forest and mean annual rainfall of the order of 900 1200 mm most paleosols of the lower paleocene tullock formation were histosols but some can be interpreted as gleyed inceptisols and entisols probably formed under bald cypress swamps in a humid climate with 1200 mm mean annual rainfall broadly comparable pedotypes were present before and after the cretaceous tertiary boundary although paleocene flood plain forest lived in paleosols chemically a little more oligotrophic than cretaceous paleosols this modest difference supports the idea that change to coaly facies in the earliest paleocene was a local shift in sedimentary environment such local changes do not begin to account for profound disruption in specific composition of plant and animal communities at the cretaceous tertiary boundary in eastern montana

pangaean climates megamonsoons of the megacontinent the climate for a highly idealized geographic representation of the megacontinent of pangaea corresponding to the period 250 200 m y ago is explored using a low resolution atmospheric general circulation model that is coupled to a static mixed layer ocean of constant depth with a provision for sea ice formation and decay soil moisture is included as a predicted variable on the continent because there are large uncertainties about key factors that might influence the pangaean climate sensitivity experiments are used to examine the climate for two different mean elevations 0 and 1000 m two different snowcover prescriptions and two different levels of implied greenhouse heating and solar luminosity modern co2 concentration and modern solar luminosity fivefold increase in modern co2 concentration and a 1 decrease in modern solar luminosity in all of the experiments the large bipolar land masses of laurasia and gondwanaland joined near the equator in the west and separated by the tethys sea in the east exhibit extreme continentality with hot summers cold winters and large scale summer and winter monsoon circulations year round or seasonal aridity is simulated for all but the eastern coastal regions the tropical western coast and the regions poleward of 40 latitude the simulated climate of the idealized pangaean continent has many features that correspond qualitatively with geologic evidence for tropical warmth and aridity in the late permian and triassic however the model results serve mainly to indicate the importance of various climate forming factors geography topography heating detailed comparisons will require new experiments with better models and more accurate geologic boundary conditions

a regional tephrostratigraphic framework for central and southern european climate archives during the last glacial to interglacial transition comparisons north and south of the alps abstract this paper summarises the results of tephrochronological investigations into a suite of central and southern european records which include rotmeer southern germany soppensee and rotsee central swiss plateau lago di lavarone and lago piccolo di avigliana italian southern alpine foreland these sites provide records of palaeoenvironmental changes for the last glacial to interglacial transition lgit at the boundary between north atlantic and mediterranean climatic influences chemical characterisation of glass shards in volcanic ash layers indicates that multiple volcanic sources have contributed to the central european tephra record amongst other volcanic markers the laacher see tephra originating from the eifel region of germany c 12 9 0 1 ka and the vedde ash from iceland c 12 1 0 1 ka are found co located within the sediments of rotmeer soppensee rotsee and lago piccolo di avigliana these key horizons which bracket the onset of the younger dryas stadial provide precise calendrically dated tie points around which a detailed picture of the timing of local and regional environmental transitions can be constructed using the co located tephra layers the re colonisation of northern italian catchment areas by quercus is shown to occur just prior to the deposition of the laacher see tephra layer whereas to the north of the alps quercus and other thermophilous trees do not reappear until several centuries after the deposition of the vedde ash furthermore the discovery of the vedde ash in lago piccolo di avigliana and lago di lavarone is indicative of atmospheric transport of polar air into southern europe during the younger dryas stadial matching evidence proposed for such transport of polar air during the last glacial maximum lgm

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

middle triassic paleosols and paleoclimate of antarctica abstract the lashly formation in the allan hills of southern victoria land antarctica is now at a latitude of 76 s and during the middle triassic was at least 70 s the combined evidence of fossil roots and soils indicates a paleoclimate unusual for such a high latitude temperate paleotemperature is indicated by roots logs and leaves of woody plants and the degree of chemical weathering and clay formation within the paleosols paleosols of the lashly formation are more like soils of southern sweden than those of either finland or southern europe silt infiltration structures around root traces and in cracks within the paleosols are evidence for a seasonally snowy climate but there is no evidence of ice wedges or other permafrost features in the paleosols other evidence of climatic seasonality includes well defined growth rings in fossil wood and abscission scars at the base of fossil leaves diverse broadleaf plants and noncalcareous paleosols indicate a humid climate with mean annual precipitation of about 1200 mm such a wet climate is anomalous for the interior of the supercontinent of pangea and such a warm and mildly seasonal climate is anomalous for such high latitudes this paleoclimatic anomaly may be a lingering effect of global greenhouse initiated at the permian triassic boundary paleoclimatic variables calculated here may be useful for recalibrating global paleoclimatic models for the middle triassic

late oligocene bunch grassland and early miocene sod grassland paleosols from central oregon usa abstract fossil soils burrows and mammals of the upper john day formation in central oregon are evidence of bunch grasses and open semiarid vegetation as old as late oligocene earliest arikareean 30 ma root traces in these paleosols include both stout tapering tubes like roots of trees as well as sinuous filamentous tubes similar to roots of grasses paleosol structure is fine subangular blocky with patchy distribution of grass like roots as in wooded grassland and sagebrush steppe with bunch grasses cursoriality in horses mesohippus miohippus and hypsodonty in rhinos diceratherium is also evidence for open grassy vegetation trace fossils of pallichnus dung beetle boli and edaphichnium earthworm chimneys are characteristic of wooded grassland paleosols whereas taenidium cicada burrows dominates desert shrubland paleosols as has also been found in quaternary paleosols and soils of eastern washington in both oligocene and quaternary paleosol sequences arid shrubland and semiarid grassland paleosols alternate on milankovitch frequencies 23 41 100 ka the oldest known paleosols in oregon with crumb structure and abundant fine fossil root traces characteristic of sod grasslands are dated by mammalian biostratigraphy as hemingfordian early miocene ca 19 ma wooded grassland habitats are indicated by scattered chalcedony calcite rhizoconcretions from large woody plants and by fossil chalicotheres moropus camels gentilicamelus paratylopus and horses parahippus silty texture and silcrete horizons are evidence of semiarid to arid paleoclimate and are in striking contrast to highly calcareous and clayey underlying paleosols of the john day formation these silcrete paleosols may represent the miocene onset of summer dry mediterranean seasonality as opposed to a summer wet monsoonal pattern of seasonality found in this region during the oligocene oregon s early rangelands can be compared with those in the north american great plains granular structured calcareous paleosols of the brule formation of south dakota are evidence of dry bunch grasslands as old as 33 ma early orellan early oligocene and crumb structured paleosols of the anderson ranch formation of nebraska are evidence of sod grasslands as old as 19 ma late arikareean early miocene although grasses were a conspicuous part of dry rangelands well back into the oligocene early and middle miocene sod grasslands in north america were restricted to regions estimated to have had less than 400 mm mean annual precipitation

an inter laboratory comparison of the electron probe microanalysis of glass geochemistry abstract tephrochronology commonly relies upon grain discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions the use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists it is widely recognised that both precision and accuracy must be maximised and that rigorous standardisation procedures must be followed in this paper the performances of seven northern european electron microprobe centres are compared using a geochemically homogeneous obsidian secondary standard the results reveal that a number of tephra oriented probe centres could benefit from exercises similar to the programme outlined within in particular it is evident that a number of these centres undertaking tephrochronological investigations have generated geochemical data that may be inadequate in terms of distinguishing between tephras inaccuracy in the determination of sodium is seen to be the main difficulty in recent years the application of distal tephrochronology to stratigraphical problems in the northern european quaternary record has become increasingly common geochemical standardisation is essential at an early stage in the development of a regional tephrochronological framework and we hope exercises such as presented here will encourage the production of reliable tephra geochemical data

permian triassic boundary in the central transantarctic mountains antarctica the permian triassic boundary occurs within a relatively complete terrestrial sequence in the shackleton glacier area of the central transantarctic mountains the boundary is within a 7 to 10 m thick interval between the permian glossopteris flora and the lower triassic lystrosaurus fauna this interval representing on the order of 200 k y records some of the events that occurred in the transition from the permian to triassic in the best documented section at graphite peak in the beardmore glacier region protohaploxypinus microcorpus zone palynomorphs which we assign to the latest permian record the declining glossopteris flora and occur near the top of the buckley coal measures just below a previously reported major negative 13c excursion in the shackleton glacier area the permian glossopteris flora including fossil wood roots and leaves occurs within the lower part of the fremouw formation the antarctic lystrosaurus assemblage of early triassic age has several species in common with the south african fauna that lived 20 to 35 closer to the equator the migration of vertebrates from southern africa into antarctica in the early triassic supports hypotheses of runaway greenhouse warming possibly related to co2 emissions from siberian flood basalts and large methane gas releases changes in flora bracketing the first of the major negative 13c anomalies near the boundary in antarctica and in east greenland support the hypothesis that a global event perhaps through mutations caused by enhanced ultraviolet radiation may have played a role in the destruction of floras

soil formation in the transantarctic mountains from the middle paleozoic to the anthropocene abstract in the transantarctic mountains tams soils from the middle paleozoic and from the oligocene to the present have been examined soils representing other sections of the geologic column are missing probably because of the low proportion of ice free areas 0 35 in antarctica the evolution of soils in antarctica reflects changes in climate and geologic conditions as the continent became separated and increasingly isolated from gondwana a greenhouse climate existed during the middle paleozoic and an icehouse climate began in the early oligocene the climate of the tams has become increasingly hyper arid since the middle miocene humans have had a dramatic effect on the climate of the tams during the anthropocene the first forest soils under callixylon archaeopteris forest on earth identified as alfisols were discovered in antarctica and assigned to the middle devonian during the permian dicroidium forests covered entisols and inceptisols in the oligocene nothofagus podocarpaceae forests contained gelisols miocene aged soils enriched in silt are common in the tams but they tend to be poorly developed because they have been eroded a soil evolutionary sequence exists in the tams from the holocene through the pliocene that includes glacic haploturbels on ice cored holocene drift typic haploturbels on late pleistocene surfaces typic anhyorthels on middle pleistocene surfaces salic anhyorthels on early pleistocene surfaces and petrosalic anhyorthels on pliocene surfaces these changes reflect gradual sublimation of ice in ice cored drift and ice wedge polygons a recovery of the surface from cryoturbation accumulation of salts and eventual development of a salt pan soils of the tams are undergoing rapid change as the climate warms including loss of semi permanent snowbanks an expansion of the hyporheic zone flushing of salts from soils along valley walls and the development of thermokarst

timing of the late vistulian weichselian glacial phases in poland abstract the lower vistula region in northern poland is a stratotype area for the vistulian weichselian glaciation and during last glacial maximum lgm the southernmost extension of the scandinavian ice sheet occurred in western poland and in eastern germany reinterpretation of the available geochronological data radiocarbon 36 cl and 10 be ages supplied with new field geological evidence mostly for the late vistulian ice sheet limits and movement directions was focused in three key regions in poland during the late middle vistulian there was one or two ice sheet advances in the lower vistula region the late vistulian maximum ice sheet limit in poland was time transgressive and occurred at 24 19 kyrs bp generally the younger to the east ice sheet limits during the leszno phase occurred at 24 cal 10 be 36 cl kyrs the poznan phase ice sheet limit was dated to 19 10 be 36 cl kyrs and the pomeranian phase ice sheet limit about 16 17 10 be 36 cl kyrs every late vistulian glacial phase in poland was preceded by an ice sheet retreat

contribution of late permian palaeogeography in maintaining a temperate climate in gondwana numerical simulations based on general circulation and energy balance models consistently indicate that the high latitudes of gondwana experienced seasonal extremes in climate during the late permian period1 3 but palaeogeographic maps based on the distribution of climate sensitive rocks4 palynological and palaeobotanical data5 6 and dicynodont fossil records7 all imply a temperate climate the reason for this discrepancy has not been clear recently it has emerged from studies of upper permian fluviolacustrine deposits throughout southern africa that the geography was dominated by a series of giant lakes perhaps interconnected within major fluvial frameworks8 here i review these data and their implications for a temperate climate i suggest that the discrepancy between the climate modelling results which indicate seasonal temperature extremes and the increasing body of geological information documenting a temperate climate may be explained by the fact that the palaeogeography used in the models does not take into account the existence of these lakes and rivers which would have had a major influence on the regional climate the results demonstrate the importance of incorporating accurate palaeogeographies into numerical modelling studies when attempting to reconstruct past climates

the role of seasonality in abrupt climate change abstract a case is made that seasonality switches dominated by wintertime were instrumental in abrupt climate changes in the north atlantic region during the last glaciation and into the holocene the primary evidence comes from mismatches between mean annual temperatures from greenland ice cores in comparison with snowline changes in east greenland northern europe and north america the most likely explanation is a shutdown or reduction in strength of the conveyor this allows the spread of winter sea ice across the north atlantic thus causing the northern region to experience much colder winters because they mimic the greenland temperature rather than the snowline signal changes in the atlantic intertropical convergence zone and the asian monsoon may also share a winter linkage with greenland thus the paleoclimate record is consistent with the notion that a huge continental sector of the northern hemisphere stretching from greenland to asia was close to an extreme winter threshold during much of the last glaciation winter climate crossed this threshold repeatedly with marked changes in seasonality that may well have amplified and propagated a signal of abrupt change throughout the hemisphere and into the tropics

late miocene advent of tall grassland paleosols in oregon abstract paleosols in the late miocene rattlesnake formation reveal three successive paleoclimatic regimens that can be dated using cumulative paleosol development prior to the radiometrically dated rattlesnake ash flow tuff 7 05 ma the basal rattlesnake formation ca 7 5 7 3 ma has a suite of weakly calcareous paleosols indicating subhumid paleoclimate 800 1000 mm mean annual precipitation or map and seasonal waterlogging a shift at ca 7 3 ma to semi arid paleoclimate map 500 850 is indicated by paleosols with calcic horizons at depths of 105 85 cm a second shift at ca 7 2 ma ushered in an assemblage of soils with shallow 36 53 cm calcic horizons indicating semi arid conditions map 200 600 mm not much different from today along with the climatic shifts documented by the paleosols there also are substantial changes in alluvial architecture and paleotopography the lower rattlesnake formation ca 7 5 7 2 ma was deposited by a stream flowing northeast in an ancestral john day valley the upper part of the formation ca 7 2 7 1 ma was deposited within large alluvial fans shed from the growing anticline of picture gorge basalt to the north stepwise changes in former vegetation can also be interpreted from paleosols the basal rattlesnake formation 7 5 7 3 ma has a suite of paleosols with root traces clay skins and manganese nodules like those of riparian woodland and seasonally waterlogged riparian meadow the succeeding paleoclimatic sequence 7 3 7 2 ma includes the earliest known mollic paleosols with deep 50 cm calcareous nodules interpreted as former soils of tall grassland also found are manganese stained paleosols of seasonally waterlogged meadows and weakly developed paleosols of early successional riparian vegetation a later paleoclimatic sequence 7 2 7 1 ma includes desert shrubland paleosols as well as paleosols of early successional riparian vegetation fossil bones and teeth found in many paleosols indicate coeval changes in mammalian faunas the major shift from woodland to grassland at ca 7 3 ma introduced into this area tall grassland ecosystems including large cursorial horses and pronghorns aridification continued with the shift to shrubland ca 7 2 ma early hemphillian which corresponds to continent wide mass extinction of most remaining browsing mammals from the clarendonian chronofauna

high resolution sequence stratigraphy and continental environmental evolution an example from east central argentina abstract the aims of this contribution is to establish a high resolution sequence stratigraphic scheme for the continental deposits that constitute the punta san andres alloformation plio pleistocene in east central argentina to analyze the basin fill evolution and to identify and assess the role that extrinsic factors such as climate and sea level oscillations played during evolution of the unit for the high resolution sequence stratigraphical study of the punta san andres alloformation high and low accommodation system tracts were defined mainly on the basis of the architectural elements present in the succession also taking into account the relative degree of channel and floodplain deposits discontinuities and the nature of depositional systems generated during variations in accommodation helped identify two fourth order high accommodation system tracts and two fourth order low accommodation system tracts at a third order scale the punta san andres alloformation may be interpreted as the progradation of continental depositional systems characterized by a braided system in the proximal areas and a low sinuosity single channel system in the distal areas defined by a high rate of sediment supply and discharge peaks which periodically flooded the plains and generated high aggradation rates during the late pliocene and lower pleistocene

tracing the laacher see tephra in the varved sediment record of the trzechowskie palaeolake in central northern poland abstract tephrochronological studies of partly varved sediments of trzechowskie palaeolake in central northern poland led to the finding of the late allerod laacher see tephra lst from the eifel volcanic field for the first time in a very distal site ca 840 km ene from its volcanic source the detection of glass shards of the lst involved a comprehensive combination of techniques i e biostratigraphical constrains high resolution xrf core scanning and areal xrf mapping of impregnated sediment slabs as well as detailed visual inspection of sediments the major element chemistry of volcanic glass confirmed the laacher see tephra composition in trzechowskie palaeolake sediments suggesting a deposition from the middle laacher see tephra mlst c or upper laacher see tephra ulst dispersal fans the finding of the lst in this palaeolake enables direct synchronisation with other high resolution archives in north central europe i e lake meerfelder maar rehwiese palaeolake to investigate regional variations of environmental responses at the onset of the younger dryas along a west east transect through north central europe