sea level changes in a back arc foreland transition the late carboniferous permian karoo basin of south africa abstract the late carboniferous to early permian succession in the karoo basin consists in ascending stratigraphic order of diamictites mudrocks greywackes and immature sandstones the diamictites are interpreted as glacigene deposits laid down by a marine ice sheet on a shelf post glacial suspension settling of predominantly mud occurred on the basin floor during open marine and later brackish conditions basin floor fan deposits accumulated in the foredeep whereas deltaic mud silt and sand finally infilled the basin glacigene sedimentation occurred in a back arc basin during the late carboniferous and early permian the post glacial succession accumulated in a foreland basin in which the rising orogenic belt was the predominant sediment source relative sea levels following the major namurian regression apparently remained low during the extensive gondwana glaciation marine ice sheets are highly sensitive to sea level fluctuations and minor sea level rises probably climatically controlled were recorded as interglacials when parts of the marine ice sheet collapsed final collapse of the marine ice sheet was associated with a major transgression post glacial mudrock deposition was characterised by relatively high sea levels except for the period of basin floor fan deposition when there was a sea level lowstand final infilling of the basin by prograding deltas was accompanied by a major regression the late carboniferous to early permian sea level fluctuations in the karoo basin show correspondence with global eustatic cycles reflecting low tectonic interference with sea level patterns however late permian sea levels were predominantly tectonically controlled as a result of foreland basin evolution possible global eustatic events complemented apparent sea level changes within the basin during this period

stable isotope composition of late pleistocene holocene eobania vermiculata muller 1774 pulmonata stylommatophora shells from the central mediterranean basin data from grotta d oriente favignana sicily abstract this paper presents stable isotopic results oxygen and carbon from both modern and late pleistocene holocene shells of the land snail eobania vermiculata muller 1774 from favignana island sicily it aims to contribute to the understanding of climate and vegetation history of this region during formation of upper palaeolithic mesolithic and meso neolithic deposits of grotta d oriente ort results from both an evaporative model fbm and an empirical regional isotopic model i e linear relation between oxygen isotopic composition of shells 18 os and those of local precipitation 18 op indicate that the 18 os values of modern specimens are mainly controlled by local temperature relative humidity and 18 op at the time of snail activity data also suggest that the modern snails are nocturnally active almost all year round in the study area the carbon isotopic compositions of shells 13 cs of the same specimens indicate a diet prevalently or exclusively composed of c3 vegetation the 18 os values of late pleistocene specimens suggest that climate conditions at 14 2 ka cal bp were similar to the present day in agreement with additional 18 os records from southern italy by contrast early middle holocene shells are notably 18 o depleted and suggest wetter conditions possibly combined with a decrease in isotopic composition of precipitation source compared to the present day when compared with regional palaeoclimatic records a large scale isotopic response to millennial scale changes in atmospheric and hydrological conditions e g enhanced rainfall in the central eastern mediterranean is observed during the early middle holocene the 13 cs of late pleistocene and holocene specimens are consistently higher than those of modern ones for the late pleistocene this could be reasonably explained in terms of water stressed vegetation on the other hand this seems to be less valid for holocene counterparts when the climate was wetter probably 13 cs values result from the combination of distinct competing factors involving atmospheric co 2 concentration seasonal water budget vegetation type cover and other carbon sources results reveal coherent relationships between regional 18 os and 13 cs demonstrating that late pleistocene holocene land snail shell remains from archaeological sites may provide useful snapshots of past seasonal climate conditions

late quaternary soil erosion and landscape development in the apennine region central italy abstract this study on past soil erosion processes focuses on a catchment located in a mountainous sector of the central apennines 60 km northeast of rome humans are known to have interacted with the landscape in this region at least since the early iron age the area is highly sensitive to climatic changes and human intervention and thus is susceptible to soil erosion the environmental impact of past human activities has been examined by geomorphological and sedimentological investigations and supported by modelling operations percussion drillings in the floodplains reveal up to 10 m thick alluvial deposits combined sedimentological and geomorphological analysis suggests that the total sediment volume of the valley infill totals about 300 000 m3 of sediments radiocarbon dating documents that this alluvial sedimentation started during the sub atlantic period between the 1st and 2nd centuries bc and coincides with a shift from a flood quiescent to a flood prone phase according to historical sources the flood phase correlates chronologically with the roman occupation of the area when they practiced extensive logging in their territories gis modelling operations show a loss of soil surface of about 71 cm on average for the entire catchment 1 600 000 m3 loss of soil if long term land exploitation for wood supply is assumed the modeling showed that approximately 80 of the eroded soil has been fluvially transported out of the catchment so the present alluvial plains may represent only about 20 of the overall lost soil mass

holocene hydrological changes in south western mediterranean as recorded by lake level fluctuations at lago preola a coastal lake in southern sicily italy abstract this paper presents a high resolution lake level record for the holocene at lago preola sicily southern italy based on a specific sedimentological approach with a chronology derived from ams radiocarbon dates it gives evidence of three major successive palaeohydrological periods with 1 a pronounced dryness during the early holocene until ca 10300 cal bp 2 a highstand from ca 10300 to 4500 cal bp and 3 a marked lowstand from 4500 cal bp to present large amplitude lake level fluctuations characterise two transition phases at ca 10300 9000 and 6400 4500 cal bp period 2 was interrupted between 8300 and 7000 cal bp by a dry phase that was punctuated to ca 7300 cal bp by the deposition of a tephra from neighbouring pantelleria island comparisons of the preola record with other palaeohydrological records along north south and west east transects in the mediterranean show contrasting patterns of hydrological changes north south of around 40 n latitude the records highlight a mid holocene period characterised by lake level minima maxima humid mid holocene conditions over the mediterranean south of 40 n were probably linked to a strong weakening of the hadley cell circulation and of monsoon winds we suggest that the maximum of humidity in the mediterranean during the mid holocene was characterised by humid winters to the north of 40 n and humid summers to the south on a multi centennial scale the high resolution palaeohydrological reconstructions in the central mediterranean area reveal a strong climate reversal around 4500 4000 cal bp with contrasting changes in the hydrological cycle in addition to seasonal and inter hemispherical changes related to orbital forcing this major oscillation might be related to non linear responses of the climatic system to the gradual decrease in summer insolation at northern latitudes another major climate oscillation around 7500 7000 cal bp may have resulted from the combined effects of 1 a strong rate of change in insolation and 2 variations in solar activity finally comparisons of the preola lake level record with sicilian pollen records suggest a strong influence of moisture availability on vegetation development in sicily very dry early holocene conditions probably prevented the expansion of coastal evergreen forests while decreasing moisture availability since the onset of the late holocene may have exacerbated effects of intensive land use

glacial geomorphic features in the northern barents sea direct evidence for grounded ice and implications for the pattern of deglaciation and late glacial sedimentation

climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

a soil chronosequence study of the reno valley italy insights into the relative role of climate versus anthropogenic forcing on hillslope processes during the mid holocene abstract relatively few soil chronosequences with good age control exist for late pleistocene and holocene deposits in the mediterranean region of europe yet surface soils and their young buried counterparts can provide meaningful information about the timing and processes of landscape response to external forcing such as climate or anthropogenic change here we present the results of a study that examines a well dated chronosequence of nineteen soil exposures in surficial deposits ranging in age from hundreds of years to hundreds of thousands of years located in the reno river valley near bologna italy the soil forming climate of the reno valley sits on a threshold between that which facilitates the accumulation of caco 3 and that which facilitates the translocation and formation of clay minerals and iron oxides once formed secondary iron oxides are relatively immobile in oxidizing conditions in the soil profile and therefore consistently record age trends with feo fed ratios decreasing predictably with soil age for all soils in the chronosequence the morphology of secondary carbonate accumulation and its depth of leaching also vary predictably with soil age but only for soils younger than about 12 000 years in these young soils horizons that contain secondary carbonate progress from relatively shallow stage i bk horizons in late holocene aged soils to deeper stage iii bk horizons in latest pleistocene aged soils in soils older than approximately 12 000 cal ybp however carbonate dissolution during wetter climates and the addition of colluvium and or dust to terrace surfaces become important factors in the preservation of carbonate in the profile and carbonate content is not predictable by age alone without significant depositional additions these older soils become decalcified pedogenic carbonate precipitated during drier climates is susceptible to dissolution during wetter periods as evidenced by discontinuous carbonate coatings on grains in some soils therefore overall measurable pedogenic carbonate content is spatially and temporally variable as a function of input of fresh carbonate and locally controlled soil moisture conditions particle size does not decrease predictably with soil age for reno valley soils and appears to be strongly influenced by parent material variability in younger soils and by dust additions in older soils our detailed examination of soil stratigraphy in the reno valley revealed evidence of significant aggradation of colluvium and tributary fans in the middle holocene between 6000 and 4000 ybp this aggradation pre dates bronze age agricultural expansion and appears to be instead attributable to the climate conditions of the middle holocene that have been documented elsewhere in italy for this time period this study demonstrates that late pleistocene and holocene surface soils in the mediterranean region of europe can effectively help elucidate rates and processes of landscape evolution

preboreal climatic oscillations recorded by pollen and foraminifera in the southern adriatic sea abstract core sa03 1 from the southern adriatic sea ec eurostrataform project provides new information about climate changes and palaeocirculation in the adriatic region during the last deglaciation the results of an integrated study based on pollen and foraminifera records of the part of the core spanning the late pleistocene early holocene transition including the late younger dryas the preboreal and the beginning of the boreal are presented the major vegetation changes and the short term oscillations occurred during the early holocene warming in the southern adriatic basin on the basis of a high resolution pollen record are documented vegetation changes are correlated to short term oscillations detected in the foraminifera record during the same interval the two independent terrestrial and marine proxies indicate at least three short term cold and dry oscillations occurring at 11 2 11 10 8 10 4 and 10 cal ka bp according to the age depth model adopted in this study finally adopting an event stratigraphy approach the comparison of these results with two western mediterranean records of preboreal short term oscillations suggest the occurrence of synchronous bio events in the mediterranean basin

durations of soil formation and soil development indices in a holocene mediterranean floodplain abstract holocene and late pleistocene alluvial sequences of the mid medjerda floodplain northern tunisia reveal three types of soils with gradual transitions fluvisols calcaric cambisols calcaric and calcic luvisols chromic stratigraphic cross correlations palaeomagnetic secular variation and 14 c and irsl dating enable detailed information about ages and durations of soil formation in the floodplain weakly developed fluvisols calcaric commonly reveal late holocene ages with soil formation durations lasting between 100 and 300 years hence holocene soil formation is detectable in the exposures from durations of around 100 years onwards cambisols show predominantly mid holocene ages the durations of soil formation are between 800 and 5000 years calcic luvisols chromic feature late pleistocene ages with durations of soil formation between 10 000 and 40 000 years profile development indices were computed from simple field parameters like soil structure soil colour horizon thickness and leaching features the derived development indices show good correlation r 2 0 804 with the calculated durations of soil formation field parameters are well suited for a quantitative development index of holocene soil formation even if very weak developed soils are predominant the study shows that maturity stages of holocene alluvial soils in a homogeneous mediterranean environment are predominantly driven by soil formation duration

rbsr glauconite ages sabinian claibornian and jacksonian units southeastern atlantic coastal plain u s a abstract hand picked disordered to ordered authigenic glauconite from the nanjemoy formation virginia the santee limestone restricted and cross formation south carolina and the castle hayne limestone north carolina yield rb sr isochron ages 87rb 1 42 10 11 yr 1 for eocene units in the southeastern atlantic coastal plain the units zonal assignment of their contained nannofossil floras and radiometric age are 3 unit nannofossil zone age m y castle hayne limestone np 19 20 34 9 1 1 cross formation np 18 np 19 np 20 34 1 1 5 santee limestone upper part np 16 17 36 7 0 6 nanjemoy formation np 13 46 7 3 0 these ages and their nannofossil assemblages provide means of correlating southeastern atlantic coastal plain units with gulf coastal plain and european stratoypes correlation to gulf coast stratotypes based on nannofossil zones indicates that the nanjemoy formation in part is equivalent to the hatchetigbee formation the upper part of the santee limestone restricted is equivalent to the upper lisbon formation the gosport sand and the moodys branch formation upper claibornian lower jacksonian and the cross formation and the castle hayne limestone are equivalent to the yazoo group jacksonian previously reported k ar glauconite ages for the gulf coast units are different from the rb sr ages determined in this study as the rb sr age determinations show internal consistency when compared to their contained nannofossil zones whereas the k ar ages do not it is suggested that the previously reported k ar ages for the gulf coast claibornian and jacksonian are in error correlation of the southeastern atlantic coastal plain units to european stratoypes based on nannofossil zones indicates that the nanjemoy formation in part is equivalent to the type lutetian the upper part of the santee limestone restricted is equivalent to the upper bracklesham and barton beds and the cross formation and castle hayne limestone are equivalent to the lower and middle headon beds previously determined k ar and rb sr radiometric ages for the type lutetian the bracklesham and barton beds are identical to the ages determined in this study as a result it is suggested that rb sr glauconite isochron ages can be used for regional and inter regional correlation and that the eocene oligocene boundary is younger than 34 m y

contrasting patterns of hydrological changes in europe in response to holocene climate cooling phases the quantitative reconstruction of climatic parameters from pollen and lake level data obtained at saint jorioz lake annecy eastern france gives evidence for cooler and wetter conditions during the 8 2 ka cold event a comparison of these regional data with other hydrological records reconstructed in europe for the same period suggests as a working hypothesis that mid latitudes between ca 50 and 43 underwent wetter conditions in response to the cooling whereas northern and southern europe were marked by drier climate in the latter case leading to an interruption of the sapropel 1 formation in the mediterranean a similar hydrological tri partition of europe can be observed during other holocene cooling phases associated with north atlantic ird events data indicate that the middle zone characterised by wetter climate conditions could have had a more extended latitudinal amplitude during phases of climate cooling weaker than the 8 2 ka event the differences in expansion of the wet mid european zone depending on holocene climate cooling phases could reflect variations in the strength of the atlantic westerly jet in relation with the thermal gradient between high and low latitudes

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

discussion on the eocene oligocene boundary in the uk journal vol 163 2006 pp 401 415 jerry hooker margaret collinson stephen grimes nick sille david mattey write recognition of the eocene oligocene boundary in the hampshire basin uk has been debated since naming of the oligocene epoch in 1854 previously this was because the boundary itself had not been stabilized and because the strata concerned are largely non marine a global boundary stratotype and stratigraphic point gssp was established at massignano italy in 1993 in marine strata recognition of the boundary on extinction of the planktonic foraminiferan family hantkeninidae made boundary identification difficult in the continental realm correlation to marginal marine and non marine strata is nevertheless possible via magnetostratigraphic and sequence stratigraphic studies and importantly biostratigraphically via dinocyst zones at massignano brinkhuis biffi 1993 brinkhuis visscher 1995 therefore recent publication of the magnetostratigraphy sequence stratigraphy and orbital cyclicity of much of the hampshire basin solent group gale et al 2006 is welcomed and substantially increases the number of correlation tools available in this area such cyclical phenomena however rely on absolute dating or biostratigraphy for calibration no radiometric dates exist for the solent group so biostratigraphy remains the best means of dating the succession there are however problems with the way gale et al 2006 have interpreted biostratigraphic markers and therefore with their placement of the eocene oligocene boundary and associated events the organisms concerned are calcareous nannoplankton np zones and mammals mp reference levels thus the record by aubry 1985 of np22 in the argiles vertes de romainville paris basin was subsequently qualified by her aubry 1986 p 307 as zone np22 not younger possibly older np21 this dating was based solely on the presence of rare isthmolithus recurvus which ranges from np19 20 to np22 aubry 1992 this being the real level of dating for the argiles vertes de romainville

palynological evidence for climatic change and human activity during the holocene on minorca balearic islands four pollen diagrams from minorca balearic islands have been correlated with other previously studied sequences from majorca and minorca to define a holocene landscape sequence for the region from 8000 yr b p to the present the lower part of the pollen diagrams reflects a climatic phase with more rain and less marked seasonality than today significant quantities ofcorylus buxus and mesophilous taxa are found in the middle part between 5000 and 4000 yr b p a strong change is recorded in composition and structure of the vegetational landscape with vegetation appearing that was adapted to mediterranean conditions this episode coincided with the first human colonization of the island and also with a widespread climatic change in the western mediterranean region the change in taxa was complex and some sclerophyllous taxa sucholeaplayed an important role in the transformation of the landscape physiognomy from the mid holocene until the present although human activities have removed much of the mediterranean vegetation on the balearic islands it seems clear that the changes have been brought about in part by increasing dryness

controls on early permian shelf deglaciation in the karoo basin of south africa abstract the late carboniferous to early permian glacigene dwyka group has at its top three types of transitions from diamictite to postglacial mudrock in the southern karoo the type 1 transition sequence consists of clast poor carbonate rich diamictite having a sharp contact with the overlying mudrocks this diamicton accumulated slowly by rain out and sediment gravity flow processes during sedimentation the polar ice front was stabilised by a possible ice shelf collapse of the ice shelf caused rapid ice margin retreat the type 2 transition sequence consists of clast poor diamictite with sandstone bodies overlain by mudrock with ice rafted debris or thin interbedded debris flow diamictites deposition of the diamictite facies occurred during oscillations of a subpolar ice front with short stable periods of surface melting of the ice resulting in the formation of small subaqueous outwash fans the type 3 transition sequence consists of bouldery diamictite interbedded with massive or sandstone bearing diamictite overlain by mudrock with ice rafted debris or thin interbedded debris flow diamictites the sequence represents highly unstable ice front conditions and fluctuating sea levels with periods of rapid deposition probably by collapsing ice streams climatic conditions may have alternated between polar and subpolar the type 1 transition sequence is predominant in the western part and the type 3 sequence in the eastern part of the karoo basin long term controls on deglaciation was climatic warming as gondwana drifted over the pole as well as changes in land sea configuration superimposed on these were local controls such as relative sea level changes presence of deformable substrate and meltwater production

holocene environmental variability the record from lago grande di monticchio italy abstract the holocene pollen record from lago grande di monticchio reveals environmental changes throughout the holocene comparison of this record with other records of holocene environmental variability indicates that there is a temporal correlation between these changes and north atlantic events however the nature of this relationship and the underlying mechanism s is yet to be determined it is evidently complex with the apparent coincidence of sea surface temperature cooling events with both species expansions and disappearances the picture is further complicated by the interaction between human activity and natural environmental changes

paleogene geochronology an integrated approach geochronology is the conceptual division of continuous time as measured geochronometry by the progression in an ordinal series of events this is best achieved by an approach which integrates four independent data sets magnetostratigraphy seafloor spreading magnetic lineation patterns biostratigraphy and isotopic ages this integrated approach results in an ordinal framework which can measure time with greater resolution though perhaps less accuracy than a radiometric approach alone a comparative analysis of two recently proposed paleogene geochronologic time scales is presented

mid and late holocene fluvial chronology of tunisia abstract regarding fluvial response to recent climate change it is important to identify and understand previous changes of fluvial dynamics related to past climatic shifts in this paper periods of increased flood activity in central tunisian river systems are presented changes in holocene flood dynamics are reconstructed through a comprehensive analysis of 195 radiocarbon dates from alluvial archives holocene floodplain deposits in central tunisia normally consists of cohesive overbank fines which exhibit excellent preservation conditions against lateral erosion and therefore permit chronostratigraphic records of the entire holocene at most based on published radiocarbon dates two 14 c cumulative probability density plots are created for central tunisia the former represents activity dates indicating phases of increased fluvial dynamics the latter documents stability dates showing periods of soil formation and enhanced landscape stability within the floodplain and the catchment due to geomorphological considerations activity dates and stability dates should be mutually exclusive there is a good match for the mid holocene with increased periods of flooding from 6 2 to 6 0 4 8 to 4 5 4 1 to 3 7 and 3 3 to 3 0 ka these flood periods coincide with low soil formation signals on the other hand periods of increased alluvial soil formation from 6 8 to 6 6 5 9 to 4 8 4 5 to 4 1 3 7 to 3 3 3 0 to 2 8 and 1 8 to 1 6 ka coincide with periods of low flood plain aggradation the data reveal a coupling with north atlantic cooling short term periods of enhanced fluvial dynamics in central tunisia match well with north atlantic cooling the findings indicate a strong climatic link from 4 7 ka until today compared to the holocene floodplain dynamics in tunisian drylands the temperate mid latitudes show mid holocene switches in fluvial dynamics with opposite signs especially after 5 ka north atlantic driven flooding in the temperate central european river systems contrast sharply to flood dynamics in arid to semiarid mediterranean tunisia while under temperate climate conditions floodplain sedimentation decreases it increases under more arid conditions this may indicate that fluvial archives of dissimilar climatic zones reveal different threshold values and sedimentation patterns and therefore different responses to climatic shifts

the permo carboniferous dwyka formation of southern africa deposition by a predominantly subpolar marine ice sheet abstract the 800 m thick glacigene dwyka formation was deposited along the northern margin of the permo carboniferous dwyka basin which covered an area of approximately 2 10 6 km 2 in southwestern gondwana the palaeogeographic setting geochemical data of the mudrocks and diamictites and the palaeontology indicate marine conditions during sedimentation ice lobes from spreading centres in the north east and south coalesced in the basin to form an extensive ice cover from the westphalian to the late sakmarian lodgement rain out and subaqueous debris flow diamictons subaqueous and subglacial melt water sands suspended mud and turbidity current sands and silts accumulated in the dwyka basin sedimentation started on the continental shelf during a grounded ice sheet stage predominantly lodgement processes then a floating ice stage predominantly debris rain out and finally an ice sheet disintegration stage debris rain out sand fall out and suspension settling of mud the palaeogeographic setting presence of marine conditions in the basin and the scale of glaciation indicate deposition from a predominantly mid latitudinal marine ice sheet the overall characteristics of the glacial sequence are neither typical of a polar nor a temperate setting and for such ancient glaciations a subpolar setting with the presence of unstable ice shelves is suggested

model data comparison for the 8 2 ka bp event confirmation of a forcing mechanism by catastrophic drainage of laurentide lakes abstract to improve our understanding of the mechanism behind the 8 2 ka bp cooling event we compare proxy evidence with climate model simulations in which the thermohaline ocean circulation is perturbed by a freshwater pulse into the labrador sea both the proxy data and model results show a cooling that is mainly concentrated in the north atlantic region ranging from more than 5 c cooling in the nordic seas to about 0 5 1 c over europe and less than 0 5 c over the subtropical north atlantic data and model also indicate a weakening of the summer monsoon and generally a drier circum north atlantic over the south atlantic ocean the model simulates a slight warming mostly less than 0 5 c which falls within the uncertainty of proxy data and thus could not be confirmed to examine in detail the structure of the 8 2 ka bp event we also compare the modeled climatological evolution at two locations with high quality records revealing a generally consistent picture the good model data agreement confirms the hypothesis that the 8 2 ka bp event was forced by a freshwater induced weakening of the thermohaline circulation other forcings are unlikely since they would result in an alternative geographical distribution and expression of the climate response

holocene palaeohydrological changes in the northern mediterranean borderlands as reflected by the lake level record of lake ledro northeastern italy a lake level record of lake ledro northern italy spans the entire holocenewith a chronology derived from51 radiocarbon dates it is based on a specific sedimentological approach that combines data fromfive sediment profiles sampled in distinct locations in the littoral zone on a millennial scale the lake level record shows two successive periods from 11 700 to 4500 cal yr bp and from 4500 cal yr bp to the present characterized by lower and higher average lake levels respectively in addition to key seasonal and inter hemispherical changes in insolation the major hydrological change around 4500 cal yr bp may be related to a non linear response of the climate system to orbitally driven gradual decrease in insolation the ledro record questions the notion of an accentuated summer rain regime in the northern mediterranean borderlands during the boreal insolation maximum moreover the ledro record highlights that the holocenewas punctuated by successive centennial scale highstands correlations with the preboreal oscillation and the 8 2 ka event and comparisonwith the atmospheric 14c residual record suggest that short lived lake level fluctuations developed at ledro in response to 1 final steps of the deglaciation in the north atlantic area and 2 variations in solar activity

diatom and geochemical evidence of mid to late holocene climatic changes at lake holzmaar west eifel germany abstract changes in diatom assemblages geochemistry and stable carbon isotope composition of bulk organic matter in a varved sediment section from lake holzmaar west eifel germany were used to infer mid to late holocene climatic changes and human impact from 6340 to 1470 cal yr bp shifts in total lacustrine primary production were derived from 13 c org values changes in non siliceous algae biomass productivity were deduced from accumulation rates of organic matter diatom valve accumulation rates and biogenic opal accumulation rates were used as proxies for diatom productivity and for siliceous phytoplankton abundance respectively based on weighted averaging of relative diatom abundance in subsamples qualitative changes in past trophic status were inferred accumulation rates of minerogenic material and the toc tn molar ratio permitted the deduction of past changes in allochthonous matter influx diatom assemblage composition showed statistically significant changes around 5130 3660 and 2900 cal yr bp whereas planktonic diatom productivity was subject to distinct shifts around 5900 5130 4500 3600 2660 and approximately 1630 cal yr bp and siliceous phytoplankton biomass changed ca 6100 4500 2660 1900 and 1700 cal yr bp causally determined changes in diatom assemblage composition and productivity for example due to shifts in nutrient ratios and or concentrations invoked by changes in lake circulation patterns precipitation rates and or erosion rates are discussed glacier fluctuations and lake level changes reported from other study sites in western europe support the finding that reconstructed lacustrine processes are at least indirectly linked to climate palynological and archaeological evidence however has shown a strong superimposition of lacustrine processes with local regional anthropogenic activity since the iron age

the dwyka group in the northern part of kwazulu natal south africa sedimentation during late palaeozoic deglaciation abstract multiple sedimentary sequences up to and over 300 m thick and comprising the late palaeozoic dwyka group in the southeastern part of the african subcontinent were deposited during deglaciation of the gondwana ice sheet attention is focused on the northern part of kwazulu natal in south africa where the dwyka group represented by glaciogenic deposits rests on an uneven surface of archaean basement rocks these deposits occur on the northwestern flank of an elongate pre dwyka crustal downwarp which had a significant influence on the mode of sedimentation as it progressively subsided stratigraphic sections from selected localities in northern kwazulu natal display the thickness variations and marked vertical and lateral lithofacies changes that characterise the dwyka group of this region diamictite consistently occurs at the base of the dwyka sequences but is also interstratified with mainly arenaceous and conglomeratic lithotypes which predominate in the upper 60 160 m these heterolithic sequences reflect sedimentation from a retreating marine ice sheet during a rise in relative sea level which commenced towards the close of the carboniferous period in southwestern gondwana as the margin of the ice sheet receded towards an archaean upland region in the northwest this ice mass was locally grounded and stabilised on bathymetric highs of the irregular basement topography release of glacial debris produced diachronous sedimentary sequences as the ice sheet was temporarily pinned on successive basement highs during its episodic retreat matrix and clast supported conglomerates and associated sandstones testify to a plexus of sediment gravity flow and subaqueous outwash processes that occurred near the grounding line thick homogeneous blanket like diamictite facies in the southeastern and southern part of the region suggest an unimpeded retreat of the sediment laden marine sheet in the deeper parts of the basin rapid dissipation of the ice in the closing stages of deglaciation was followed by accumulation of postglacial muds which mantled the glaciogenic sediments in the northernmost part of the study area proximal products of deglaciation represented by conglomeratic deposits and associated sandstones are preserved in deep partly exhumed glaciated valleys and depressions along the southern periphery of the archaean upland the distinctive character of the dwyka group in northern kwazulu natal is partly attributable to the complex tectonic setting in which it occurs and reflects an interplay of various factors that controlled the styles of sedimentation during deglaciation

sediments from lago di mezzano central italy a record of lateglacial holocene climatic variations and anthropogenic impact microscopic geochemical and pollen analysis of sediment samples of a lateglacial holocene profile from lago di mezzano a maar lake in central italy reveals evidence of significant climatic and human induced environmental changes time control is provided by a combination of varve chronology and radiocarbon dating the well known lateglacial climatic variations a warmer interstadial and the younger dryas cold phase are clearly represented in all the parameters during the interval between 9200 and 5600 cal bp of the holocene climatic optimum annually laminated organic rich diatom gyttja was deposited two periods of diminished total organic carbon are identified within this interval the first one p1 ranges from 8200 to 7800 cal bp while the second p2 is centred around 6500 cal bp during p1 a predominance of diatoms stephanodiscus parvus and s minutulus over other algae represented by the total organic carbon content is observed the timing of this period coincides with the early to mid holocene climatic transition reported from ice cores and lake sediments stager and mayewski 1997 p2 is characterized by a decrease in all biogenic parameters including biogenic opal organic carbon as well as arboreal pollen from 5000 cal bp to date the sediment pattern changes coincide with the mid holocene climatic deterioration in addition to these natural variations human impact has been recorded and recognized from sedimentological features such as turbidites and charcoal as well as from reduced arboreal pollen content two middle bronze age 3700 cal bp and 3300 cal bp etruscan early roman 2500 cal bp longobardic ad 900 and modern settlements since ad 1700 have been distinguished on the basis of these data

palaeomagnetism of holocene and late pleistocene sediments from lago di mezzano and lago grande di monticchio italy initial results abstract palaeomagnetic records of the geomagnetic secular variation reaching back to 31 and 102 kyr cal bp respectively were obtained from two sediment cores from lago di mezzano central italy and two cores from lago grande di monticchio southern italy intra lake correlation was based on continuous high resolution susceptibility measurements and discrete dry density samples characteristic remanent magnetization chrm of all 4800 samples was determined by analysis of the results of progressive alternating field af demagnetization intra lake comparison of the resulting chrm directions confirms that the inclination and declination records reflect the palaeosecular variation of the local geomagnetic field composite curves of geomagnetic palaeosecular variations psv were created for each lake in order to compare the reconstructed psv records with those from lac du bouchet massif central france and lac de joux switzerland the good agreement in the general patterns of the inclination and declination records of all lakes mentioned above confirms the reconstructed psv records of the italian lakes investigated

hydrological changes in the european midlatitudes associated with freshwater outbursts from lake agassiz during the younger dryas event and the early holocene abstract recent studies of lake level fluctuations during the last deglaciation in eastern france jura mountains and pre alps and on the swiss plateau show distinct phases of higher water level developing at the beginning and during the latter part of greenland stade 1 i e younger dryas event and punctuating the early holocene period at 11 250 11 050 10 300 10 000 9550 9150 8300 8050 and 7550 7250 cal yr b p the phases at 11 250 11 050 and 8300 8050 cal yr b p appear to be related to the cool preboreal oscillation and the 8200 yr event assumed to be associated with deglaciation events a comparison of this mid european lake level record with the outbursts from proglacial lake agassiz in north america suggests that between 13 000 and 8000 cal yr b p phases of positive water balance were the response in west central europe to climate cooling episodes which were induced by perturbation of the thermohaline circulation due to sudden freshwater releases to oceans this probably was in response to a southward migration of the atlantic westerly jet and its associated cyclonic track moreover it is hypothesized that during the early holocene varying solar activity could have been a crucial factor by amplifying or reducing the possible effects of lake agassiz outbursts on the climate

climate vegetation and land use as drivers of holocene sedimentation a case study from lake saint point jura mountains eastern france a multiproxy approach to a sediment sequence at lake saint point in the french jura mountains gives evidence of a strong coupling between changes in terrestrial and lacustrine ecosystems throughout the holocene the early holocene 11 700 10 200 cal bp is characterised by the recovery of terrestrial and lake ecosystems favoured by climatic warming during the middle holocene 10 600 6200 cal bp the climatic optimum coincided with an extension of deciduous forests into the catchment area while lake sedimentation is dominated by authigenic carbonates and low detrital inputs after 6200 cal bp the neoglacial favoured expansion of abies fagus forests and increasing detrital inputs to the lake where ostracod fauna declined and changed in composition after 1200 cal bp human impact was responsible for extensive forest clearings in the catchment area while the lake basin shows contrasting pictures with increasing detrital input resuming sedimentation of authigenic carbonates and changes in dominant o

a late dwyka early permian varvite sequence near isandlwana zululand south africa abstract a 7 5 m thick varvite association is exposed in a shallow roadside pit near isandlwana the beds lie close to the top of the dwyka formation an important glacial and fluvioglacial association of late carboniferous to early permian age they have been bleached and indurated by igneous intrusion so that even fine sedimentary structures are well preserved and the strata rendered particularly suitable for detailed study a total of 624 varves and associated beds fall into three stratigraphic divisions each showing fining upward tendencies in respect of grain size and varve thickness remarkable similarities with pleistocene recent lacustrine varves permit reasoned deductions concerning the depositional environment recurrent thin low density turbidity currents actively supplemented suspension fall out as an agent of sedimentation

abrupt changes in early holocene tropical sea surface temperature derived from coral records for many high latitude regions of the globe it is now clear that the transition to modern climate following the last glacial maximum was punctuated by a number of rapid and substantial climate oscillations1 2 in contrast relatively little is known about how the tropics responded to the deglaciation because few high resolution records are available from lower latitudes corals have recently been shown to provide an important source of tropical climate records because they can be easily and accurately dated using either 14c or 230th and because past sea surface temperatures can be recovered from the sr ca ratios in coral skeletons here we use this technique to derive several early holocene sea surface temperature records from a coral drill core recovered from espiritu santo vanuatu in the tropical southwest pacific ocean these records indicate that sea surface temperatures in this region were depressed by as much as 6 5 c below modern values at 10 350 calendar years bp but rose very abruptly during the following 1 500 years this temperature increase lags the post younger dryas increase observed in a coral record from the tropical atlantic ocean3by about 3 000 years an unexpected phase shift that may ultimately shed light on the mechanisms of deglacial climate change

the lateglacial and holocene environmental history of the ioannina basin north west greece this study centres on palaeoenvironmental analysis of the upper part of a long core from the partially drained tectonic ioannina basin north west greece the data span the lateglacial and holocene and comprise pollen mollusc magnetic susceptibility loss on ignition and particle size analyses these augment previously published ostracod and stable isotope data from the same sediment sequence the age model for the sequence is based on 19 ams dates five of which were obtained using a novel procedure for the separation of microcharcoal from sediment the pollen data suggest that although temperate woodland expanded at the beginning of the lateglacial only limited woodland contraction occurred during the younger dryas chronozone despite strong evidence for a sharp drop in sea surface temperature in the neighbouring adriatic at this time in contrast large scale vegetational and sedimentological changes occur in concert during the holocene some of which may be ascribed to human impact comparison with other records from the ioannina basin suggests that previous more littoral pollen sequences did not constitute a wholly representative record of lateglacial and holocene vegetational change

abrupt early to mid holocene climatic transition registered at the equator and the poles paleoclimatic records from equatorial east africa antarctica and greenland reveal that atmospheric circulation changed abruptly at the early to mid holocene transition to full postglacial conditions a climatic reorganization occurred at all three sites between 8200 and 7800 years ago that lasted 200 years or less and appears to have been related to abrupt transitions in both marine and terrestrial records around the world

sedimentology dating and palaeoclimatic interpretation of a 76 3 ka record from lago grande di monticchio southern italy abstract detailed sedimentological and microstratigraphical investigations of lacustrine sediments from lago grande di monticchio southern italy provide a time scale based on rates of sedimentation obtained from annual laminations although not annually laminated throughout a time scale covering the last 76 3 ka is available by interpolation of sedimentation rates results of this chronology agree with radiocarbon dates and with ar ar dates on tephra layers from the same lacustrine sediment sequence occurrence of varves in combination with physical and geochemical properties are related to variations in the trophic state of the lake and to changing runoff both controlled by palaeoclimatic conditions water depth was relatively shallow with dominating bioturbation and only few varves preserved for most of the pleniglacial a marked increase in precipitation and related runoff characterises the early last glacial maximum when water depth reached a maximum and clastic varves were deposited subsequently water depth was shallower again a drastic change towards nutrient rich conditions occurred at the pleistocene holocene transition during the holocene organic varves were deposited two periods with higher organic productivity were recognised prior to the last glacial maximum around 50 ka and 73 ka these intervals are interpreted as the result of interstadial conditions the oldes of the two events shows laminations comparable to those at the glacial holocene transition the periods with increased minerogenic influx may be characterised as stadial conditions lasting from 14 40 ka and from 50 73 ka

holocene environmental change in eastern spain reconstructed through the multiproxy study of a pedo sedimentary sequence from les alcusses valencia spain abstract we present a multiproxy characterization of a complex polycyclic soil sequence from les alcusses moixent valencia se spain the area has abundant settlements dating from early neolithic to roman times the sequence comprises six main units dating back to 8 7 8 5 ka cal bp we integrated mineralogy inorganic ph grain size elemental composition and organic chemistry pyrolysis gas chromatography mass spectrometry pyrolysis gc ms micro charcoal pollen and non pollen palynomorph npp data all data is contextualized within a framework of archaeological information and radiocarbon dating with the aim of deciphering the holocene environmental changes we infer a shift from wetter and warmer in the early mid holocene to drier and cooler climatic conditions with increased fire occurrence in the mid late holocene particularly after 5 3 ka cal bp although the pollen record indicates a rapid forest retreat and expansion of grasslands for the neolithic period local proxies molecular soil om indicators and npp point to the presence of pine forest in the studied location well after the regional decline started the same proxies suggest a sharp forest decline after about 7 0 ka cal bp strong soil erosion likely linked both to climatic instability and the intensification of human exploitation resulted in a hiatus from the late neolithic to the roman period a certain climate amelioration wetter conditions and land abandonment or at least lower human pressure are suggested for the late roman period early middle ages direct evidence of changes in soil properties due to agriculture was not detected in the sequence except for the upper soil unit studied which reflects intense agricultural management with the possible use of agrochemicals

high resolution palaeohydrological reconstruction of central italy during the holocene the endorheic nature of lake trasimeno in combination with its position in central italy makes it a relevant site to better constrain spatial differences in holocene climatic variability in the med

lago grande di monticchio southern italy a long record of environmental change illustrated by sediment geochemistry abstract bulk geochemical analysis has been carried out on a 51 m sediment core from lago grande di monticchio in southern italy the record which may extend from the present back through more than one glacial cycle displays major variations in indicators of palaeoproductivity such as organic carbon and biogenic silica the most prominent change occurs at the holocene boundary lower in the sequence zones of moderately enhanced productivity highlight either interstadial or interglacial periods c n ratios and hydrogen indices provide possible indications of the sources and diagenetic state of the bulk organic matter but must be interpreted carefully as it is difficult to isolate the effects of these two factors changes in the clastic fraction e g na al ratio suggest that tephra deposition in the lake and its catchment has significantly altered the sedimentation this may also have influenced the biological productivity of the system

a high resolution late holocene palaeo environmental record from the central adriatic sea a multi proxy study of a holocene sediment core rf 93 30 from the western flank of the central adriatic in 77 m of water reveals a sequence of changes in terrestrial vegetation terrigenous sediment input and benthic fauna as well as evidence for variations in sea surface temperature spanning most of the last 7000 yr the chronology of sedimentation is based on several lines of evidence including ams 14c dates of foraminifera extracted from the core palaeomagnetic secular variation pollen indicators and dated tephra the temporal resolution increases towards the surface and for some of the properties measured is sub decadal for the last few centuries the main changes recorded in vegetation sedimentation and benthic foraminiferal assemblages appear to be directly related to human activity in the sediment source area which includes the po valley and the eastern flanks of the central and northern appenines the most striking episodes of deforestation and expanding human impact begin around 3600 bp late bronze age and 700 bp medieval and each leads to an acceleration in mass sedimentation and an increase in the proportion of terrigenous material reflecting the response of surface processes to widespread forest clearance and cultivation although human impact appears to be the proximal cause of these changes climatic effects may also have been important during these periods signs of stress are detectable in the benthic foram morphotype assemblages between these two periods of increased terrigeneous sedimentation there is smaller peak in sedimentation rate around 2400bp which is not associated with evidence for deforestation shifts in the balance between terrigenous and authigenic sedimentation or changes in benthic foraminifera the mineral magnetic record provides a sensitive indicator of changing sediment sources during forested periods of reduced terrigenous input it is dominated by authigenic bacterial magnetite whereas during periods of increased erosion anti ferromagetic minerals haematite and or goethite become more important as well as both paramagnetic minerals and super paramagnetic magnetite analysis of the alkenone u37k record provides an indication of possible changes in sea surface temperature during the period but it is premature to place too much reliance on these inferred changes until the indirect effects of past changes in the depth of the halocline and in circulation have been more fully evaluated the combination of methods used and the results obtained illustrate the potential value of such high resolution near shore marine sedimentary sequences for recording wide scale human impact documenting the effects of this on marine sedimentation and fauna and potentially disentangling evidence for human activities from that for past changes in climate

late pleistocene climatic variations as recorded in two italian maar lakes lago di mezzano lago grande di monticchio abstract sediment profiles from two maar lakes lago di mezzano central italy and lago grande di monticchio southern italy were investigated with respect to their minerogenic and biogenic sediment accumulation rates for a time window spanning the final 20 000 yr of the last glaciation the chronological framework is provided by calibrated radiocarbon ages varve counting calculation of sedimentation rates and tephrochronology in the time slice between 34 000 and 14 000 cal bp periods of increased minerogenic input are observed in both lacustrine records interrupted by periods of low minerogenic input these cyclic variations have an average recurrence time of 1785 yr for lago di mezzano and 2875 yr for lago grande di monticchio comparing well with marine and ice core data explanations for these pulses of increased minerogenic sedimentation include enhanced erosion and runoff the higher precipitation evaporation ratio required for this interpretation was possibly restricted to winter months as earlier published pollen analyses on sediments from lago grande di monticchio show a contemporary development of steppe vegetation an indicator for cool dry climatic conditions this may be connected with a southward shift of the westerlies and a reinforced jet stream agreement of lacustrine data from italy with late pleistocene glacial events in central italy with events recorded in marine archives from the north atlantic heinrich events and with oxygen isotope data from greenland ice cores is interpreted as evidence for the late pleistocene climate in europe being influenced by north atlantic climatic forcing which may be related to dansgaard oeschger cycles

the loess deposits of buca dei corvi section central italy revisited loess deposits have been described in the past for the upper section of buca dei corvi succession central italy in this paper the deposits were re analysed to clarify the depositional environment and to attempt a paleoclimate reconstruction two radiocarbon dates on pedogenic carbonate constrain the ages to the late glacial and are consistent with previous osl dating of the top of the succession the non marine mollusc assemblage shows typical character of cold and dry climatic conditions testified by strong oligotypical composition mineralogy and geochemistry of the sediments indicate the abundant presence of exotic quartz mineral which can be explained only by wind transport probably wind transport was also responsible of deposition of carbonate which then dissolved and re precipitated producing pedogenic concretions stable isotopes 13c 12c and 18o 16o ratios of the concretions are consistent with a climate drier than present conditions with an environment characterized by sparse vegetation

interpreting drivers of change in fluvial archives of the western mediterranean a critical view abstract fluvial archives in particular late glacial to holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution in view of the high significance of floodplain dynamics for the development of entire landscapes the number of studies that have been performed on floodplain sediments remains comparatively low especially regarding the western mediterranean region however one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics therefore a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation as a starting point for discussion this paper aims to give an overview of fluvial dynamic patterns in the western mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions the basis for this is provided by previous investigations on four different river systems in spain and northern africa the results of which are herein synthesized in order to propose a regional late pleistocene and holocene fluvial history for the western mediterranean realm basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils incision marks and aggradation phenomena since fluvial systems are open systems we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions a more comprehensive interpretation focuses on signals that are common to each of the studied river systems in this respect we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy supported approach for characterizing regional floodplain dynamics finally three alluvial soil formation periods were found in all settings a first phase after 15 ka ending with the younger dryas event a second one from 7 to 5 ka with a break between 6 5 and 5 5 ka and a third phase between 3 and 2 ka these soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation floodplain deposition floodplain erosion and or river incision in particular after 5 ka around 1 6 and at 1 ka and during the little ice age lia floodplain aggradation affected river systems in iberia and northern africa as well a cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra regional aridification that effected large areas of the western mediterranean in contrast the three mentioned soil formation periods can be linked with landscape stability most probably triggered by favorable climate conditions in the western mediterranean apart from these large scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self organization regarding future work we want to emphasize the great potential of yet rarely applied system oriented approaches that also attach importance to sub catchment dynamics as a link between catchment slopes and the main river floodplain

a weichselian deglaciation model applied to the early permian glaciation in the northeast karoo basin south africa it generally is assumed that the early permian gondwana deglaciation in south africa started with a collapse of the marine ice sheet the northeast part of the karoo basin became ice free as a result of this collapse the deglaciation here probably took place under temperate glacial conditions three glacial phases have been identified phase 1 the marine ice retreat of 400 km over the northeast karoo basin which may have been completed over a few thousand years the glaciers grounded in the shallower areas around the shore of the basin phase 2 the smaller now mainly continental ice sheet here re stabilised and remained more or less stationary for several tens of thousand years during this phase between 50 and 200 m of massive glaciomarine mud with dropstones accumulated in the open marine basin that became ice free during phase 1 isostatic uplift as a response to the first rapid deglaciation phase can be traced in the inland part of the region phase 3 the final deglaciation may have taken 10 to 20 kyr after this time no new ice sheet was built up over southern africa the entire early permian deglaciation of the northeast karoo basin was completed within thousands rather than millions of years phases 1 and 3 had lengths similar to typical quaternary deglaciations whereas phase 2 was a long stable phase more similar to a full quaternary glaciation copyright 2001 john wiley sons ltd

knickpoint recession rate and catchment area the case of uplifted rivers in eastern scotland knickpoint behaviour is a key to understanding both the landscape responses to a base level fall and the corresponding sediment fluxes from rejuvenated catchments and must be accommodated in numerical models of large scale landscape evolution knickpoint recession in streams draining to glacio isostatically uplifted shorelines in eastern scotland is used to assess whether knickpoint recession is a function of discharge here represented by its surrogate catchment area knickpoints are identified using ds plots log slope versus log downstream distance a statistically significant power relationship is found between distance of headward recession and catchment area such knickpoint recession data may be used to determine the values of m and n in the stream power law e kamsn the data have too many uncertainties however to judge definitively whether they are consistent with m n 1 bedrock erosion is proportional to stream power and kps should be maintained and propagate headwards or m 0 3 n 0 7 bedrock incision is proportional to shear stress and kps do not propagate but degrade in place by rotation or replacement nonetheless the e scotland m and n values point to the dominance of catchment area discharge in determining knickpoint retreat rates and are therefore more consistent with the stream power law formulation in which bedrock erosion is proportional to stream power copyright 2005 john wiley sons ltd

petrophysical and geochemical characterization of potential unconventional gas shale reservoirs in the southern karoo basin south africa abstract ten permian black shale samples from the southern karoo basin south africa were investigated regarding their shale gas generation potential storage capacity and transport properties samples originate from a 671 m deep borehole kzf 1 comprising the collingham whitehill and prince albert formations of the lower ecca group karoo supergroup based on organic geochemical analyses toc ts rock eval pyrolysis and vitrinite reflectance the whitehill formation was deposited under anoxic marine depositional conditions and has reached high thermal maturity the collingham and prince albert formation were deposited under suboxic to oxic conditions the amount of total organic carbon toc across all formations ranges between 0 5 and 6 1 wt and was highest for the whitehill formation samples the organic matter in the different lithologies are highly overmature with vitrinite reflectance values around 4 0 vrr and almost absent rock eval s1 and s2 peaks peak gas generation probably occurred due to tectono metamorphic overprinting during the cape orogeny 240 270 ma permeability ranges from 10 22 to 10 19 m2 1 100 ndarcy and is lowest for the whitehill and prince albert formation porosity at ambient stress ranges from 4 1 to 6 3 and is highest within the whitehill formation neither permeability nor porosity show significant dependence upon induced stress excess sorption capacity is highest for the whitehill formation nexcess10mpa ranging from 0 079 to 0 172 mmol g for the depth interval investigated here 671 m the estimated total gas storage capacity sum of free and adsorbed gas phase of the whitehill formation is approximately 400 to 465 mol ch4 per m3 rock using a simple one dimensional diffusion model we calculated the potentially remaining stored amount of gas in a modelled best case scenario it is assumed that dissipation of the gas only occurs through the side boundaries fractured dykes system whereas top and bottom are assumed to act as perfect seals assuming a fracture distance of 1000 m the model predicts complete gas dissipation to take place within a period of 10 2 to 102 ma regarding the peak gas generation at 240 270 ma the remaining shale gas potential is therefore considered extremely low

pollen plant macrofossil and charcoal records for palaeovegetation reconstruction in the mediterranean black sea corridor since the last glacial maximum new reconstructions of changing vegetation patterns in the mediterranean black sea corridor since the last glacial maximum are being produced by an improved biomisation scheme that uses both pollen and plant macrofossil data in conjunction changes in fire regimes over the same interval will also be reconstructed using both microscopic and macroscopic charcoal remains these reconstructions will allow a diagnosis of the interactions between climate fire and vegetation on millennial timescales and will also help to clarify the role of coastline and other geomorphic changes salinity and impacts of human activities in this region these new data sets are being produced as a result of collaboration between the palynology working group wg 2 within the igcp 521 project and the international palaeovegetation mapping project biome 6000 the main objective of this paper is to present the goals of this cooperation methodology including limitations and planned improvements and to show the initial results of some applications

compositional variations in sedimentary lacustrine organic matter and their implications for high alpine holocene environmental changes lake st moritz switzerland abstract organic matter accumulation and preservation in lakes with different geomorphological and climatic regimes is directly influenced not only by local but also by regional and more global climatic conditions thus compositional variations in lacustrine organic matter can be used as good indicators of paleoenvironmental conditions of deposition relatively high average toc 1 0 6 5 wt and good lamination characterize most of the holocene sequence of lake st moritz an alphine lake located in se switzerland however variations in the type and quality of the organic matter at discrete intervals have been distinguished using bulk parameters and biomarker distributions the most prominent change occurs at the late glacial holocene boundary where 13 c om hydrogen index and lipid concentrations indicate a substantial increase in primary productivity organic matter production and preservation appear to dominate from the early holocene until approximately 3 8 ka bp although variations in sterol contents and fatty acid distributions indicate superimposed fluctuations such as between 8 3 and 8 1 ka bp and 5 1 to 4 8 ka bp these variations in the lake trophic state can be correlated with other proglacial lakes in the region as well as with similar lacustrine records on both sides of the alps the result of this comparison indicates a synchronous character of major to medium amplitude climatic shifts on a european scale

the significance of maar volcanoes for palaeoclimatic studies in china abstract the sediments of maar lakes often provide paleoenvironmental records which are highly suitable for palaeoclimatic studies the main advantages of the records from maar lakes compared with other lacustrine records are as follows first the presence of varves annually laminated layers and tephra layers as well as other materials like terrestrial plant macrofossils charcoals organic carbon organic shells suitable for isotopic dating like ams 14c 210pb 137cs 238u 230th 40ar 39ar provides the possibility of developing several independent chronologies enabling the development of robust high resolution chronologies second maars and maar lakes can provide continuous sedimentary records spanning tens of thousands of years tianyang maar in china is hosted the longest known record spanning at least 400 kyr bp that are ideal for the investigation of climate change on different timescales including orbital millennial centennial and annual decadal third recent studies of biomarkers based on long chain alkenones lcas and glycerol dialkyl glycerol tetraethers gdgts have demonstrated the potential of maar lakes for quantitative paleotemperature reconstruction in this study we review some of the more significant achievements of palaeoclimatic research based on maar lake sediment sequences from china with the focus on chronology multiple timescales and quantitative paleoclimatic reconstruction

vegetation reconstruction on the basis of pollen in late pleistocene hyena coprolites from san teodoro cave sicily italy vegetation reconstruction based on pollen from coprolites of extinct spotted hyena crocuta crocuta spelaea goldfuss 1832 recovered from excavations carried out in 1998 at san teodoro cave sicily italy supports previous indications of pre late glacial conditions eight of the twelve coprolites analysed contained well preserved pollen grains there is a general similarity between the pollen contents from the coprolites but they show variability they suggest a main vegetation type dominated by steppic taxa poaceae artemisia ephedra chenopodiaceae and asteraceae but also including arboreal taxa pinus and cupressaceae low percentages of pollen of mesophilous woody taxa quercus betula abies alnus pistacia among others are noticeable suggesting the existence of nearby refugia for temperate and mediterranean vegetation a reconstruction of the landscape using the coprolite pollen record and other pollen records from sicily and south italy shows the predominance during the pre late glacial of a wooded steppe biome with elements representing a variety of local environmental conditions

paleogene calcareous nannoplankton biostratigraphy of northwestern europe abstract the classic paleogene stages thanetian cuisian lutetian bartonian ludian and stampian defined in the epicontinental deposits of the anglo paris basin s are placed within a standard biostratigraphic framework based on an analysis of their calcareous nannoplankton floras relatively precise biostratigraphic correlations can be made with some chronostratigraphic units e g lutetian while biostratigraphic resolution of others e g ludian is limited important hiatuses are recognized between certain chronostratigraphic units only the base of the lutetian late np14 and bartonian mid np16 stages can be precisely determined in terms of calcareous nannoplankton zones with the recent study of the magnetic polarity history of the paleogene of southern england and recent advances in magnetobiostratigraphic correlations in deep sea cores it is possible to interpret the paleogene history of the anglo paris basin s in a synoptic global framework in which paleomagnetic stratigraphy provides the chronologic and eustatic variations the graphic units of northwestern europe within rather than at the boundaries of i e at dynamic element redefinition of the boundaries of the standard paleogene chronostratigraphic unconformities eustatically controlled depositional cycles would result in more precise correlations in terms of standard calcareous nannoplankton biostratigraphy

marine flooding surfaces recorded in permian black shales and coal deposits of the main karoo basin south africa implications for basin dynamics and cross basin correlation abstract the marine origin of black shales in the context of the permian postglacial development of the karoo basin south africa is subject of an ongoing controversial discussion here we present and discuss palynological and sedimentological data providing evidence of a transgressive event during the early guadalupian palynofacies assemblages of the black shales of the southern basin include marine phytoplankton that exhibit peak abundance within the whitehill shales and which also occur within siltstones and glauconitic sandstones on top of the no 5 coal seam of the north eastern basin palynostratigraphic control makes this marine signal a powerful tool for cross basin correlation moreover palynofacies analysis demonstrates a facies transition from terrestrial lacustrine and fluvio deltaic in the northeast to deep marine in the south western parts of the basin

debris in icebergs and rates of glaci marine sedimentation observations from spitsbergen and a simple model debris distribution and content in spitsbergen icebergs varies but basal debris rich layers often 1 m thick are the most important sources of iceberg rafted material angular iceberg rafted clasts in the glaci marine record imply the presence of nunataks or valley walls rather than unbroken ice sheet surfaces indicating paleo ice mass configuration calculated iceberg melt rates imply that most iceberg rafted debris is released within spitsbergen fjords sedimentation from icebergs is calculated as 1 mm a 1 for inner mollerfjorden and 8 mm a 1 for inner kongsfjorden an order of magnitude lower than total sediment inputs turbid subglacial meltwater is a more important debris source a simple model is proposed to calculate the flux of basal debris in icebergs and iceberg sedimentation rates

late pleistocene and holocene alluvial archives in the southwestern mediterranean changes in fluvial dynamics and past human response abstract cohesive floodplains from the semiarid southwestern mediterranean morocco tunisia exhibit excellent preservation toward lateral erosion and present a continuous record of late pleistocene and holocene flood dynamics holocene mean sedimentation rates and 14 c cumulative probability plots from cohesive tunisian floodplain sequences reveal a coupling with north atlantic bond events short term periods of fluvial activity match well with north atlantic coolings the findings indicate a strong climatic link from 4 8 ka until today unlike fluvial archives from the humid mid latitudes semiarid southwest mediterranean alluvial archives exhibit phases of increased fluvial dynamics under generally drier conditions the 14 c cumulative probability plot of archeological sites in mediterranean north africa indicates correlations with alluvial records therefore prehistoric societies seemed to be very sensitive to past shifts in landscape dynamics

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

sedimentation and soil formation phases in the ghardimaou basin northern tunisia during the holocene chronological and stratigraphical interpretations as well as 14c dates and geoarchaeological investigations of detailed profiles from the mid medjerda valley northern tunisia allow us to reconstruct one late pleistocene and four holocene sedimentation cycles within the floodplain area initial results from pedological examinations including thin sections indicate a latest pleistocene and three holocene soil formation periods our observations from the medjerda valley are discussed in relation to current research in the southwestern mediterranean region the crise romaine shown in the headwaters of the medjerda river system by thick cobble accumulations is exhibited in the basin region by a clear accentuation of the water level amplitude catastrophic flooding can be observed for the first time in the late roman period after soil formation during middle ages ending at about 450 bp flooding again increased

deglaciation sequences in the permo carboniferous karoo and kalahari basins of southern africa a tool in the analysis of cyclic glaciomarine basin fills the late westphalian to artinskian glaciomarine deposits of the karoo and kalahari basins of southern africa consist of massive and stratified diamictite mudrock with ice rafted material sandstone silty rhythmite shale and subordinate conglomerate forming a cyclic succession recognizable across both basins a complete cycle comprises a resistant basal unit of apparently massive diamictite overlain by softer bedded stratified diamictite sandstone and mudrock with a total thickness of as much as 350 m four major cycles are observed each separated by bounding surfaces lateral facies changes are present in some cycles the massive diamictites formed as aprons and fans in front of the ice grounding line whereas the stratified diamictites represent more distal debris flow fans the sandstones originated in different environments as turbidite sands small subaqueous outwash channel sands and delta front sands the rhythmites and mudrock represent blanket deposits derived from turbid meltwater plumes cycles represent deglaciation sequences which formed during ice retreat phases caused by eustatic changes in the karoo and kalahari basins evidence for shorter term fluctuation of the ice margin is present within the major advance retreat cycles hardly any sediment was deposited during lowstand ice sheet expansion whereas a deglaciation sequence was laid down during a sea level rise and ice margin retreat with the volume of meltwater and sediment input depending on temporary stillstands of the ice margin during the retreat phase the duration of the cycles is between 9 and 11 ma suggesting major global tectono eustatic events smaller cycles probably linked to orbital forcing were superimposed on the longer term events a sequence stratigraphic approach using the stacking of deglaciation sequences with the ice margin advance phases forming bounding surfaces can be a tool in the framework analysis of ancient glaciomarine basin fills

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

major element geochemistry and paleoclimatology of the permo carboniferous glacigene dwyka formation and postglacial mudrocks in southern africa abstract a chemical index of alteration cia is used to quantify the degree of weathering of fine grained materials in the glacigenic permo carboniferous dwyka formation and succeeding stratigraphic units of southern africa diamictites in the dwyka formation have low cia values compatible with their glacigenic origin interbedded mudrocks show a wide scatter of values suggesting that at least some of them were deposited during periods when ice had retreated from the source areas samples from the prince albert shale which immediately overlies the dwyka formation show high cia values suggesting a rapid transition to a much more intensive weathering regime warmer climatic conditions samples from the succeeding whitehill shale have a low average value so that weathering was once more inhibited perhaps by a temporary return to a colder climate the highest stratigraphic units sampled the upper shales have an average cia value comparable to that of average shales and suggesting normal weathering conditions major element geochemical data can supplement sedimentological and paleontological information and provide a valuable contribution to the detailed paleoclimatic interpretation of such glacigenic successions

tephrostratigraphy chronology and climatic events of the mediterranean basin during the holocene an overview the identification and characterisation of high frequency climatic changes during the holocene requires natural archives with precise and accurate chronological control which is usually difficult to achieve using only 14c chronologies the presence of time spaced tephra beds in quaternary mediterranean successions represents an additional independent tool for dating and correlating different sedimentary archives these tephra layers are potentially useful for resolving long standing issues in paleoclimatology and can help towards correlating terrestrial and marine paleoclimate archives known major tephras of regional extent derive from central and southern italy the hellenic arc and from anatolia a striking feature of major holocene tephra deposition events in the mediterranean is that they are clustered rather than randomly distributed in time several tephra layers occurred at the time of the s1 sapropel formation between c 8 4 and 9 0 ka bp mercato gabellotto fiumebianco e1 cappadocia and ot

the potential of lake ohrid for long term palaeoenvironmental reconstructions abstract lake ohrid at the macedonian albanian border was likely tectonically formed during the tertiary and therefore is one of the oldest lakes in europe however only a few studies exist concerning the potential of lake ohrid sediments for long term palaeoenvironmental reconstructions within the scope of future potential deep drilling campaigns therefore as a first step a transect of short surface sediment cores was investigated for chronology physical properties grain size and biogeochemistry the results were compared with information derived from a shallow hydro acoustic seismic survey the investigations indicate a rather uniform and bioturbated sedimentation in the central part of the lake basin with mean sedimentation rates of ca 0 5 1 mm year the sediment composition is dominated by authigenetic carbonates diatom frustules or fragments form the major part of biogenic matter deposits as indicated by the relatively high contents of biogenic opal and low contents of total organic carbon and total nitrogen the shallow hydro acoustic seismic survey indicates that horizons of sediment redeposition occur sporadically towards the shore of the lake the sedimentation rate increases and sedimentation is increasingly influenced by local inflows or mass movement processes triggered by tectonic activities thus lake ohrid has a high potential for palaeoenvironmental reconstructions on a multi decadal scale and provides additional information concerning tectonic activity in the region

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

centennial scale late pleistocene to mid holocene synthetic profile of the medjerda valley northern tunisia during the late pleistocene to mid holocene the medjerda river system in mediterranean tunisia shows events of increased flooding and aggradation of relatively coarse overbank deposits geomorphic activity in river systems within this region correlate with aridification of the climate but not with temperature the late pleistocene to mid holocene synthetic profile of the ghardimaou floodplain mid medjerda river indicates fluvial activity from 12 4 to 11 8 6 6 to 6 0 and after 4 8 ka cal bp external correlations imply global and regional causes of the late pleistocene to mid holocene climatic development such as north atlantic deep water formation fluctuations in saharan humidity and impacts of local mediterranean weather phenomena palaeomagnetic records offer additional opportunities to interpret fluvial activity in river systems especially for detecting chronological hiatuses in apparently homogeneous sediment sequences

marine ice sheet decoupling as a mechanism for rapid episodic sea level change the record of such events and their influence on sedimentation abstract unlike terrestrial ice sheets marine ice sheets display more sensitivity to sea level than to climate and they are capable of rapid mass wasting this mass wasting involves ice shelf decoupling from the sea floor and rapid collapse followed by drawdown of the ice sheet glaciologists argue that the marine ice sheet decoupling mechanism could cause sea level rises of a few meters within several hundred years information regarding late wisconsinan holocene glacial history suggests that ice sheet deterioration did not occur at a steady rate studies of the antarctic continental shelf indicate ice sheets grounded over large portions of the shelf during the late wisconsinan glacial maximum and that their retreat from the continental shelf was rapid a study of the trinity sabine incised valley of the texas continental shelf yields a continuous record of holocene sedimentation and sea level change paired upper bay and tidal inlet estuarine systems reflect periods when relative sea level was either at a still stand or slowly rising the flooding surfaces of back stepping parasequences reflect periods of rapid sea level rise large sand bodies on the adjacent shelf used to derive previous sea level curves for the region may represent former shoreline deposits but they also show extensive reworking therefore the curves generated from studies of these sand bodies are inaccurate marine ice sheets have existed in antarctica since at least the late eocene so this mechanism for rapid sea level rise has been active throughout much of cenozoic time as well as during older glacial episodes

geoarchaeological and historical implications of late holocene landscape development in the carseolani mountains central apennines italy abstract this study investigates the relationship between late holocene landscape development and early human interaction by means of geomorphological and sedimentological analyses supported by gis modeling operations the selected geoarchives are sedimentary valley fills of two subwatersheds located in the upper turano river drainage basin 60 km northeast of rome italy where humans settled at least since the earliest classic period first the alluvial plains were identified and mapped through multiple gis operations thereafter 12 cores were taken from the alluvial plains collecting in total 68 m of alluvial profiles by sedimentological analyses i e grain size carbon determination together with 36 ams radiocarbon dates we identified phases when changes in the geomorphological evolution of the study area occurred starting around 4200 cal bp eight distinct clusters of increased cumulated probability density functions of the 14 c dates were observed representing enhanced alluvial deposition and or fluvial activity the shift from a phase of prevailing biostasy to a period of anthropic rhexistasy occurred after 4200 cal bp in the rio di riccetto and around 2200 cal bp in the more remote ovito watersheds dividing the alluvial sediment volumes by the potential erosion areas and assuming a sediment delivery ratio sdr between 0 21 and 0 46 we obtained an average late holocene surface lowering of 370 to 540 mm in the rio di riccetto and 400 to 510 mm in the ovito watersheds our results show that notable land reshaping occurred in the vicinity of the city of rome which can be attributed to human induced land cover changes

modelling net erosion responses to enviroclimatic changes recorded upon multisecular timescales land use change has been recognized throughout the earth as one of the most important factors influencing the occurrence of rainfall driven geomorphological processes however relating the occurrence of historical soil erosion rates is difficult because of the lack of long term research projects in river basins also complex models are not adequate to reconstruct erosion rate changes because they require significant input data not always available on long timescales given the problems with assessing sediment yield using complex erosion models the objective of this study is to explore a parsimonious scale adapted erosion model adt from the original thornes and douglas algorithms which aims at reconstruction of annual net erosion ane upon multisecular timescales as a test site the calore river basin 3015 km 2 in southern italy provides a peculiar and unique opportunity for modelling erosion responses to climate and land cover changes where input data generation and interpretation results were also supported by documented hydrogeomorphological events that occurred before and after land deforestation in this way aneadt values were reconstructed for the period 1675 2004 by using precipitation indexes complemented by recent instrumental records and by using land cover statistics from documented agrarian sources pulses of natural sedimentation in the predeforestation period have been related to vesuvius volcanic activity and changes in rainstorm frequency after deforestation the basin system became unstable with sudden fluctuations in the hydrogeomorphological regime contributing significantly to increased erosion and in turn sediment transport sequences via river drainage towards the tyrrhenian coast

the palaeogeography of part of southwestern gondwana during the permo carboniferous glaciation abstract the elevation of the base of the glacial deposits areas where glaciated bedrock is overlapped by post glacial sediments palaeoice flow directions thickness of the glacial sequence and the lithology lithofacies and clast composition were used as integrated parameters to reconstruct the permo carboniferous glaciated land surface over southern africa the palaeography is depicted by pre glaciation westphalian maximum glaciation end of carboniferous and post glaciation sakmarian maps the pre glaciation palaeogeography was dominated by a fluvially dissected highland surrounded in the south and southwest by flat lying lower palaeozoic marine sediments this surrounding platform in part covered by shallow seas and in the south and southwest bounded by a possible island arc system was the main depocentre for the glacial debris the palaeogeography during maximum glaciation consisted of a platform region karoo basin overdeepened troughs e g kalahari basin highlands windhoek cargonian and southern with extensive glacial valleys incised into these highlands and a shallow palaeo pacific sea arm reaching into the interior the alpine type southern highlands formed by late subduction from the south the post glaciation palaeogeography was controlled by isostatic crustal movements ratio of crustal depression by the weight of the ice and sediments to post glacial rebound and sea level rises large areas including major valleys were inundated by shallow seas irati and whitehill seas and fjords so that the land surfaces represent remnants including islands of the former highlands local high rebound rates caused erosion of the glacial sediments and the deposition of fluvial and deltaic beds in fjord heads and embayments favourable conditions for the formation of fossil fuels and base mineral and metal deposits occured in parts of the inundatedbasins

palaeoproductivity and environmental changes during the holocene in central italy as recorded in two crater lakes albano and nemi abstract three cores from two crater lakes in central italy albano and nemi spanning the last ca 11 kyr bp are discussed here they were analysed for organic matter dry density algal and photosynthetic bacteria pigments diatoms and cladocera these palaeolimnological records show great internal consistency in their response to distinct but inter related aspects of the lake catchment system and reflect major changes in these systems particularly in lake productivity the early holocene was characterised by very high productivity at both sites trends in productivity are similar for many proxies in the holocene records of lake albano and lake nemi trophic levels throughout much of the period of human activity ca 4000 yr bp onward are lower but have remained relatively high and stable at both lakes it is only in the last few decades that inferred productivity levels have exceeded those of the early holocene statistical analysis constrained incremental sum of square cluster analysis coniss showed five distinct periods during the holocene characterised by major variations in the abundance and community structure of biological remains and geochemistry a comparison of results from the different taxonomic groups has enabled the reconstruction of phases of increased productivity and the recognition of signals of anthropogenic impact on the lakes and their catchments from published pollen diagrams nine major deforestation events are recognised during the holocene these events in particular the one which occurred in both lakes at 1800 yr bp and identifies the roman period plus another at 3000 3500 yr bp related to agricultural activity during the bronze age produced profound changes in the pelagic community structure of diatoms and cladocera which in some cases were even more marked than the accelerated eutrophication seen in recent times the mid holocene climatic transition is also clearly evident and is characterised by a strong decrease in the concentrations of the biological proxies most of the observed lacustrine environmental changes are almost synchronous in the two lakes indicating the importance of regional rather than local changes

submarine debris flow deposits from the upper carboniferous dwyka tillite formation in the kalahari basin south africa four types of sediment gravity flow deposits occur interbedded with rhythmite shale siltsone mudstone and minor diamictite in a 230 m thick carboniferous glacial sequence shear and plug zones are present in the cohesive debris flow deposits which have a diamictic texture the high density turbidity flow deposits which consist of coarse to medium grained clastics are characterized by both normal and reverse grading the medium to fine grained low density turbidity flow deposits show normal grading and consist of bouma units a b d and e deposition occurred by gravity flow suspension settling and minor basal melt out during ice retreat along the southern margin of the kalahari basin immediately basinwards of the ice grounding line a proximal diamictite facies consisting predominantly of cohesive and high density turbidity flow deposits and minor melt out tills formed a distal sedimentary facies of graded sandstone and siltstone units deposited by low density turbidity flows and suspension settling of muds with ice rafted debris is located basinwards

mollusca stable isotope record of a core from lake frassino northern italy hydrological and climatic changes during the last 14 ka a core retrieved from lake frassino northern italy provided evidence of palaeohydrological change in this area during the last 14 ka lithological malacological and in particular stable isotope composition of freshwater shells allowed the delineation of the main phases of lake evolution between the lateglacial and holocene lateglacial conditions were drier than the holocene although a wetter period was inferred before c 14 ka according to the oxygen isotope composition of freshwater shells the holocene showed a clear bipartition the first part which lasted from 9100 to 7000 yr bp was drier and was followed by a rapid increase in humidity at 7000 6800 yr bp between 6800 and 5000 yr bp there were wetter and more stable conditions as indicated by smaller 18 o oscillations of pisidium and valvata shells from c 5000 to 2600 yr bp the record is characterized by larger fluctuations which may indicate that short term and particularly pronounced alternation of wet and dry periods occurred

high resolution sediment and vegetation responses to younger dryas climate change in varved lake sediments from meerfelder maar germany abstract this work focuses on a 1900 year section of varved sediments from lake meerfelder maar mfm extending from the late allerod to the preboreal varve counting provides the chronological framework and determines the length of younger dryas to 1025 1090 years a strong relation between climate change environment response and depositional processes has been found in consequence varve microfacies variations are a sensitive proxy for environment changes these are reflected for example in erosion processes within the lake s catchment minerogenic input and lake productivity diatom blooms the observed varve changes have been quantified by multiproxy analyses of physical and chemical sediment parameters with a resolution of between 8 and 40 years depending on sedimentation rate in addition high resolution palynological investigations provide the biostratigraphical subdivision based on changes in the vegetation occurring during the same time interval varve observations reveal that environment changes at the beginning and the end of the younger dryas occurred within 20 50 years furthermore sediment and vegetation changes were synchronous within the actual precision of the mfm and grip chronologies divergence of only a few decades terrestrial responses in western europe occurred quasi synchronous to temperature changes in greenland

the holocene climatic evolution of mediterranean italy a review of the continental geological data we present a synthesis of geological stratigraphic geomorphological and stable isotope data collected from continental archives to highlight the environmental and climatic differences between the first and second half of the holocene of central and southern italy the beginning of the holocene is marked by rapid environmental change in mediterranean italy between c 9500 cal bp and c 6000 5500 cal bp average temperatures were probably higher and environmental conditions were generally stable between c 9000 and 7000 cal bp meteoric precipitation was at its highest the end of the wetter period seems to occur later at c 6000 5000 cal bp since c 6000 5000 cal bp rapid climatic excursions are apparent in different palaeoclimate proxies with both variability in meteoric precipitation and temperature evident of particular relevance is the event occurring at c 4200 cal bp this event heralds a period of significant environmental change in the apennines and more generally in central italy

sediment and pollen evidence for an early to mid holocene humid period in the eastern sahara a major problem in the study of holocene palaeoenvironments of the arid and wind deflated sahara is the low preservation potential of sediments from which a record of past climatic change can be established several indirect and imprecisely dated pieces of evidence have suggested humid episodes in the holocene that may have supported more productive ecosystems and denser human populations than today searches for reliable proxy data on past climates however have failed to yield satisfactory results we report here the discovery of buried lake muds in north west sudan in the hyperarid core of the eastern sahara which yield sedimentological and palynological data clearly interpretable as recording an early to mid holocene humid episode that supported a relatively deep stratified lake surrounded by tropical savanna woodland vegetation

holocene seasonality changes in the central mediterranean region reconstructed from the pollen sequences of lake accesa italy and tenaghi philippon greece this study presents pollen based climate reconstructions of holocene temperature and precipitation seasonality for two high resolution pollen sequences from the central lake accesa central italy and eastern mediterranean tenaghi philippon greece regions the quantitative climate reconstruction uses multiple methods to provide an improved assessment of the uncertainties involved in palaeoclimate reconstructions the multimethod approach comprises partial least squares regression weighted average partial least squares regression the modern analogues technique and the non metric multidimensional scaling generalized additive model method we find two distinct climate intervals during the holocene the first is a moist period from 9500 to 7800 cal bp characterised by wet winters and dry summers resulting in a strongly seasonal hydrological contrast stronger than today that is interrupted by a short lived event around 8200 cal bp this event is characterised by wet winters and summers at accesa wh

northwestern european paleogene magnetostratigraphy biostratigraphy and paleogeography calcareous nannofossil evidence global calcareous nannofossil biostratigraphy is used to correlate the paleogene chronostratigraphic units of northwestern europe and standard nannofossil biozones such biostratigraphic correlations show that the lithostratigraphic sequence is discontinuous and allows interpretation of the paleogeography of northwestern europe during the paleogene and evaluation of the influence of global sea level eustatic changes on northwestern european stratigraphy a well documented unconformity occurs near the lower middle eocene boundary in the paris basin this unconformity which also can be traced in the london hampshire basin and in belgium correlates with a coastal offlap event presumed sea level of vail et al on the basis of magnetostratigraphic biostratigraphic correlations the duration of the hiatus associated with this unconformity can be estimated to be 0 6 to 1 5 m y in the hampshire basin and 2 to 4 m y in the paris basin

reworked hantkenina specimens at little stave creek alabama abstract abstract the eocene oligocene boundary in mississippi and alabama has been traditionally placed between the shubuta member of the yazoo formation and the overlying red bluff formation or its carbonate facies equivalent the bumpnose formation consequently the presence of eocene planktonic foraminifers in the red bluff and bumpnose has long been attributed to reworking to test the validity of this hypothesis samples were collected on both sides of the boundary from the upper shubuta and bumpnose units at little stave creek alabama and were examined for both calcareous nannofossil and planktonic foraminiferal content the calcereous nannofossil assemblage preserved in the matrix from inside handpicked specimens of hantkenina from both units was demonstrably older than the calcareous nannofossil assemblage from the surrounding sediment thus at least some of the hantkenina specimens in both the shubuta and bumpnose are indeed reworked which not only confirms the original hypothesis regarding reworking within the red bluff and bumpnose but also indicates that the last occurrence of hantkenina the shubuta bumpnose contact and the eocene oligocene boundary in the u s gulf coast may not be equivalent

palaeoclimatological reconstruction using stable isotope data on continental molluscs from valle di castiglione roma italy thirty molluscan shells from twenty levels from the first 4 5 m of a long core drilled in the crater lake of valle di castiglione near rome have been analysed for their oxygen and carbon stable isotope compositions the investigated portion of the core covers the last 14 2 ka bp the large range in 18o 11 suggests that hydrological conditions exercise the main control on the isotopic composition of the biogenic carbonate in the valle di castiglione palaeolake samples younger than about 5 ka show a marked 18o depletion which we attribute to the onset of a temperate wet climate corresponding to the maximum of humidity isotopic results are in good agreement with pollen analyses and prove to be a sensitive tool for reconstructing quaternary climatic evolution from the continental lacustrine sediments of central italy

human impact at lago di mezzano central italy during the bronze age a multidisciplinary approach abstract the purpose of this contribution is to disentangle climate forcing and human influence in the catchment of lago di mezzano through the interfingering of data obtained by means of archaeological geomorphological sedimentological and palynological approaches a systematic archaeological survey has been undertaken and three submerged settlement areas with piles pottery and metal tools have so far been found the artifacts indicate that the site was inhabited although not continuously during the bronze age geomorphological investigations and observations in some trenches dug out on the lake shore indicate that great variations in the lake s size and strong changes in the catchment lake surface area ratio occurred during the second half of the holocene palynological micro charcoal sedimentological and geochemical analyses carried out on long cores taken from the lake centre have indicated environmental changes due to either climatic influence or human impact even if human presence in the area has been detected during the whole bronze age period the human populations caused a strong impact only in two periods centred around 3600 and 3200 cal years bp when they settled along the lake shore and around 3400 cal years bp when they caused an increase in erosion leading to the beginning of the deposition of turbidites