late pleistocene holocene climatic and vegetational history of the brazilian caatinga the fossil dunes of the middle sao francisco river palynological studies of a peat bog sequence with a basal date of 10 990 80 yr b p provide a history of vegetational and climatic changes in the icatu river valley located inside a large system of stabilized sand dunes at the middle sao francisco river at 10o24 0 s 43o13 0 w in northeastern brazil the present day vegetation of the valley is vereda a mauritia vinifera palm swamp forest bordered by a narrow strip of semi deciduous tropical forest the adjacent dunes are stabilized by arboreal caatinga and cerrado vegetation in some areas the palynological profile of the saquinho locality within this valley was divided into five pollen zones zone sa1 10 990 10 540 yr b p contains pollen of taxa found in present amazonian and atlantic forests as well as from montane taxa thus suggesting very humid climatic conditions synchronous with more reduced temperatures zone sa2 10 540 6790 yr b p has pollen spectra from a vegetation type dominated by mauritia suggesting progressive warming and high humidity levels the period between 8920 and 8910 yr b p has rapid sedimentation rate few thermoluminescence tl dates pronounced increase of mauritia and ilex pollen suggesting a very moist climate from 8910 to 6790 yr b p there is a progressive decline in forest taxa and a gradual increase of caatinga and cerrado taxa on the landscape zone sa3 6790 ca 6230 yr b p does not contain palynomorphs possibly indicating semi arid conditions zone sa4 ca 6230 ca 4535 yr b p marks the return of mosaic vegetation composed of gallery forest cerrado and caatinga taxa indicating moister climatic conditions a marked decline in moisture levels characterizes the period between 4240 yr b p and present as suggested by an increase in caatinga and cerrado species and a decline in gallery forest taxa zone sa5 ca 4535 yr b p present establishes the present vegetational and climatic pattern of the icatu river valley 1999 elsevier science b v all rights reserved

stable organic carbon isotope stratigraphy across oceanic anoxic event 2 of demerara rise western tropical atlantic ocean drilling program odp leg 207 recovered expanded sections of organic carbon rich laminated shales on demerara rise western tropical atlantic high resolution organic carbon isotope and total organic carbon toc records are presented which span the cenomanian turonian boundary interval ctbi including the oceanic anoxic event oae 2 from four sites oriented along a nw striking depth transect these records represent the first high resolution carbon isotope records across oae 2 from the south american margin of the tropical atlantic due to the scarcity of age significant fossils the main purpose of this study was to develop a detailed carbon isotope stratigraphy in order to correlate the ctbi across the depth transect and to tie this to biostratigraphically well defined sections in the western interior basin pueblo usa boreal shelf seas eastbourne england and western tethys oued mellegue tunisia all four sections studied document a 6 increase of 13corg values at the base of the ctbi which is followed by an interval of elevated 13corg values and a subsequent decrease our results supply an important stratigraphic base for subsequent paleoceanographic studies on late cenomanian to early turonian sediments from demerara rise and elsewhere

cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

sediment transport during recent cave flooding events and characterization of speleothem archives of past flooding abstract extreme precipitation events have a disproportionate impact on landscape evolution and on human constructions and the frequency and intensity of extreme events may vary with changes in mean climate in the past and in the future we document the potential for cave sediment archives to record past changes in the frequency of flooding events by characterizing the modern processes responsible for sediment deposition and mobilization during floods and linking these to their incorporation in speleothem deposits we focus on the cueva fria cave system in nw spain which like other caves in the region features abundant sandy sediments sourced from dominant sandstone lithologies in the catchment area in this case delineated by our dye trace study in this system the extreme flood conditions in june 2010 caused overflow of the cave stream and deposition of nearly 1 m of sand in sectors near the cave stream and resulted in burial of some stalagmites in 30 cm of sand in more distal sectors all sectioned stalagmites growing

two million years of river and cave aggradation in ne brazil implications for speleogenesis and landscape evolution abstract this study characterizes and provides ages for an extensive sedimentary record occurring in lapa doce and torrinha caves ne brazil with 40 km of surveyed passages these caves integrate a distributary cave system fed by allogenic recharge from the surrounding sandstone plateaus sediment petrography together with descriptions of depositional facies and architectural elements shows four depositional units related to fluvial and standing water environments these include from bottom to top 1 a channel unit including lateral bars deposited during an ordinary flood regime 2 a sandy flood unit including minor channel and scour fills derived from bank full equivalent flood events 3 mud caps deposited in standing water that often reach the ceiling and 4 intraclast breccias associated with collapse of the mud caps under saturated conditions the deposits were dated using a combination of cosmogenic nuclide burial dating and u series dating of flowstone cosmogenic nuclide data point to fluvial aggradation being active since 1 91 0 12 my and extending until 0 36 0 08 my with intensive cave and valley aggradation events between 0 78 0 10 my and 0 44 0 12 my long term alluviation of the cave system seems to be important in forming passages determining their configuration and setting up a general distributary pattern evident in passage morphology and sedimentary sequences mud caps overlapping the fluvial deposits are interpreted as the products of successive rising and lowering of the water table static level radiometric ages of interstratified flowstones and speleothems show that these oscillations were active at least since 115 ky ago and finally ceased around 12 ky ago indicated by the recurrent age obtained from uneroded capping flowstones these long term water table oscillations may drive paragenetic expansion of the whole cave system valleys caves and other landforms in our study area are part of an ancient landscape with multiple episodes of burial and exhumation despite the possibility of much older sediment being preserved somewhere in the cave system our data indicate a younger quaternary age for the bulk of the sediment filling the study caves

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

late cretaceous carbon isotope stratigraphy in europe correlation and relations with sea level and sediment stability abstract upper cretaceous upper cenomanian to lower coniacian stable carbon isotope stratigraphy of german hemipelagic marls borehole dresden blasewitz pelagic carbonates quarries salzgitter salder and sohlde and of two turonian to santonian pelagic sections in the northern alpine helvetic zone supplemented by published carbon isotope data kent southern england gubbio italy are used for correlations of northern temperate boreal and tethyan sections general carbon isotopic trends are different in pelagic and hemipelagic carbonates probably in response to the input of terrestrial organic carbon to the inner shelf carbon reservoir including sediments the global component in the carbon isotope stratigraphy is best recorded in pelagic carbonates sufficient biostratigraphic control is present to correlate all sections across facies boundaries and between the two biogeographic provinces hiatuses produce breaks in the gradual carbon isotopic trends and their duration can be estimated relative to complete sections a broad 13c minimum straddles the turonian coniacian boundary at the proposed boundary stratotype salzgitter salder with its center about 0 5 1 m below the biostratigraphic reference level first occurrence of c rotundatus fiege sensu troger non fiege increases and maxima of pelagic 13c values occur during phases of sediment accumulation decreasing pelagic 13c values and minima characterise phases of sediment erosion the amplitudes of these stratigraphic fluctuations may indicate the intensity of sediment reworking changes in the sediment accumulation erosion ratio and accompanied carbon isotopic variation may be related to short term sea level fluctuations and their effect on fine grained sediment stability

karst landscape evolution in the littoral area of the bay of biscay north iberian peninsula the western pyrenean area contains extensive karst areas however their genesis and development are still mostly unknown in this work we make a general description of the karst landscape in different karst areas 1 rasa type 2 cone type karst and 3 alpine type karst the first two types are present in the littoral area where geomorphological evolution mostly depends on sea level and climatic changes we focused our study in two karst areas of the littoral cone type karst we correlate different caves created from different stable water table levels three representative caves are studied in detail studying their stratigraphic record based on allostratigraphy finally we dated the different phases of speleothem formation in the three caves using all this information we defined four stable paleowater table levels at 50 150 220 and 350 m asl controlled by sea level changes and isostatic uplift events the lowest level is the youngest with an age of c 1 ma we discovered that the interior of the three caves display very similar endokarst allostratigraphic sequences characterized firstly by an erosion phase a fluvio karst input flowstone speleothem formation and finally dripping speleothem formation the chronological data shows a correlation between these phases and pleistocene climatic phases the erosion phase is related to the falling sea level fluviokarst detrital input is related to cold glacial stages and the formation of speleothems is related to the warmest interglacial moments and high sea level periods

the quaternary vertebrate fauna of the limestone cave gruta do ioio northeastern brazil o quaternary pleistocene bahia brazil cave deposits abstract the present study reports the quaternary vertebrate fauna of gruta do ioi a partially submerged limestone cave located in central bahia northeastern brazil a semi arid weather prevails nowadays in the area which is mostly covered by a xeric low arboreal scrubland known as caatinga the identified taxa include rhamdia osteichtyes siluriformes caiman crocodyliformes caimaninae myocastor cf myocastor coypus rodentia myocastoridae holochilus sciureus rodentia sigmodontinae natalus cf natalus macrourus chiroptera natalidae tonatia bidens trachops cirrhosus chiroptera phyllostomi dae and eira cf eira barbara carnivora mustelidae whereas rhamdia and caiman have scarce fossil records the recovered mammals have already been reported from quaternary localities of northeastern brazil although only two of them are present in the current local fauna taphonomic signatures and the nature of the fossiliferous site indicate that the vertebrates lived inside or nearby the cave including the swamp by its main entrance radiocarbon dating of dental bioapatite yielded calibrated ages between 19 980 and 22 040 bp this indicates that the accumulation started at least during the late pleistocene within the last glacial maximum in agreement with the mode of life of most taxa recognized here previous studies indicated that this was a wetter period in the region

multiple dolomitization events along the pozalagua fault pozalagua quarry basque cantabrian basin northern spain the pozalagua quarry in the basque cantabrian basin of northern spain exposes a unique set of fault associated dolomites that can be studied on a decametre scale the dolomites developed along the pozalagua fault system in slope deposited limestones of albian age following marine phreatic diagenesis the limestones were subject to meteoric karst formation the resulting cavities were filled either by angular limestone fragments in a black clay rich matrix or by cave floor pond now dolomitized sediments the subsequent diagenetic history reflects repeated periods of fracturing fluid expulsion dissolution and cementation contrasting fluid pulses resulted in the formation of a network of hydrothermal karst and the subsequent development of coarse crystalline calcite cement zebra dolomite recrystallized coarse crystalline dolomite elongated blue grey coarse crystalline dolomite cement in the open fault and finally coarse crystalline saddle dolomite decimetre size reworked host rock fragments present in the latter two dolomite phases probably reflect roof collapse fragments of a cave system that developed along the pozalagua fault system however there are also metre scale host rock fragments that apparently float in the coarse crystalline saddle dolomites implying that either fragment assimilation was a widespread process or violent expulsion of fluids occurred along the pozalagua fault system the presence of pre dolomite and post dolomite stylolites parallel to bedding supports a linkage between the diagenetic events and the late albian tectonism that affected the region

late cretaceous upwelling system along the southern tethys margin israel interrelationship between productivity bottom water environments and organic matter preservation organic rich upper cretaceous sequences in israel were deposited in an extensive highly productive upwelling linked system which prevailed along the southern tethys margin and lasted for 19 m y santonian to late maastrichtian an understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in israel representing an outer shefela and an inner zin facies belt the nature of the upwelling system and its effect on the sedimentary record is related to two basic environmental parameters namely paleoproductivity intensity and oxygen levels at the bottom the assessment of these parameters and their interrelationship has been performed through the development of paleontological foraminiferal criteria which are independent of the organic matter content following the establishment of these criteria it is concluded that the productivity reached its maximum intensity during the late campanian which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin this distribution is expressed in varied lithology organic rich carbonates phosphorites and siliceous rocks at the core of upwelling and a uniform lithology organic rich carbonates at the margin of this system the uniform lithology of the maastrichtian in both basins composed of organic rich carbonates is ascribed to a gradual weakening of productivity the bottom conditions in the inner belt during the late campanian the time of maximum surface productivity were near anoxic changing to more aerated dysaerobic conditions during the early maastrichtian in the outer belt a more aerated bottom dysaerobic prevailed throughout the late campanian to late maastrichtian the elevated organic matter content in both basins reflects the overall environment of high productivity its actual variations however seem to be unrelated to changes in surface productivity and bottom oxygen levels

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

cyclic sedimentation in brazilian caves mechanisms and palaeoenvironmental significance abstract caves associated with doline slopes in the tectonically stable area of eastern brazil display remarkable sequences of clastic sediment intercalated with calcite layers sediment erosion has also occurred allowing access to formerly sediment filled passages the palaeoenvironmental meaning and chronology of these three processes i e clastic sediment input clastic sediment erosion and speleothem precipitation were studied in both semi arid campo formoso and sub humid lagoa santa areas through 230 th dating and stratigraphical analyses the dry climate of the campo formoso area prevents speleothem deposition at present but soil erosion results in valley aggradation and cave infilling growth periods of speleothems and travertines in this area have allowed the recognition of recurrent past phases of increased humidity correlated with wet conditions recorded in southeastern brazil speleothem calcite at the lagoa santa area there is limited speleothem precipitation and sediment input at present however sediment entrainment is actively exhuming speleothems and exposing cave passages sediment erosion inside caves in the area is interpreted as being due to intermediate climatic conditions not wet enough to favour speleothem deposition and not too dry to allow doline slope erosion and sediment transport into caves due to the low rates of denudation and isostatic rebound inherent to tectonically stable areas cave passages will remain within the range of sediment infill and erosion for a much longer time than in tectonically active areas spanning in average at least three full glacial interglacial cycles as uplift proceeds cave passages will be decoupled from the doline bottom and no longer will be affected by erosion or infilling episodes sediment filled passages in many caves in the lagoa santa region are relict features that display ancient clastic and chemical precipitation the three processes described above have occurred throughout the life history of the caves resulting in complex sediment assemblages that can however show significant intra and inter site variations

role of sediment in speleogenesis sedimentation and paragenesis although the effects of sedimentation in caves have been recognised for many years its role in speleogenesis is frequently overlooked influxes of sediment into a cave system fundamentally alter the way cave passages develop either by alluviation in a vadose environment forcing lateral corrosion and the development of notches or by upwards dissolution in a phreatic environment through a process known as paragenesis sediment influxes affect the hydrological functioning of a karst aquifer by changing the way conduits behave and subsequently develop both in plan and long section here we give an overview of the mechanisms of cave sedimentation and describe how the process of alluviation and paragenesis affect speleogenesis a characteristic suite of meso and micro scale dissolutional features can be used to recognise paragenetic development which is reviewed here in a vadose environment these include alluvial notches whilst in a phreatic environment half tubes anastomoses and pendants bedrock fins and paragenetic dissolution ramps result using these to identify phases of sedimentation and paragenesis is crucial for reconstructing denudation chronologies from cave deposits we suggest that sedimentation and paragenesis are most likely to occur in certain geomorphological situations such as ice marginal and periglacial environments beneath thick residual soils and where rivers can transport fluvial sediment into a cave either via stream sinks or back flooding

interhemispheric anti phasing of rainfall during the last glacial period abstract we have obtained a high resolution oxygen isotopic record of cave calcite from caverna botuvera 27 13 s 49 09 w southern brazil which covers most of the last 36 thousand years ka with an average resolution of a few to several decades the chronology was determined with 46 u th ages from two stalagmites tests for equilibrium conditions show that oxygen isotopic variations are primarily caused by climate change we interpret our record in terms of meteoric precipitation changes hence the variability of south american monsoon sam intensity the oxygen isotopic profile broadly follows local insolation changes and shows clear millennial scale variations during the last glacial period with amplitudes as large as 3 but with smaller centennial scale shifts 1 during the holocene the overall record is strikingly similar to but strongly anti correlated with a number of records from the northern hemisphere we compared our record to other precisely dated contemporaneous records from hulu cave eastern china minima in 18o wet periods intense sam at our site are synchronous with maxima in 18o dry periods weak east asian monsoon eam in eastern china within precise dating errors and vice versa this anti phased precipitation relationship between two low latitude locations may be interhemispheric in extent based on comparison with records from other sites precipitation anti phasing may be related to north south shifts in the mean position of the intertropical convergence zone itcz and asymmetry in hadley circulation in two hemispheres associated not with seasonal changes as observed today but with millennial scale climate shifts the millennial scale atmospheric see saw patterns that we observe could have important controls and feedbacks on climate within hemispheres because of water vapor s greenhouse properties

identification and importance of critical depositional gaps in pitfall cave environments the fossiliferous deposit of cuvieri cave eastern brazil abstract the majority of extinct brazilian late quaternary mammal i e megafauna remains comes from cave deposits and was retrieved through excavations lacking detailed stratigraphical context this poses a major problem since these deposits present multifaceted processes of formation based on the meticulous excavation of a pitfall site within cuvieri cave minas gerais eastern brazil this article describes a critical albeit subtle temporal discontinuity between different fossiliferous sedimentary facies and discusses its significance to the contextualization of the paleontological remains recovered from the site the discontinuity was described based on sedimentary analyses bone deposition processes taxonomy and ams radiocarbon chronology two facies were distinguished and named according to their color and texture an upper dark brown silt loam bsl and a lower dark reddish brown silt loam rbsl besides color differences they present differences in grain size distribution and chemical composition these analyses show that the rbsl has in its composition only half the sand and one third more the silt than bsl it also shows that mean percent values for the rbsl in comparison to the bsl are higher for silica 42 35 versus 15 80 aluminum 18 63 versus 7 58 and iron 8 45 versus 3 79 and lower for calcium 10 07 versus 36 14 and volatiles 13 86 versus 30 10 these differences are attributed to changes in sediment source and entrance route differences were also observed in the faunal remain analyses rbsl has abundant megafauna remains originally deposited within this facies while the scarce megafauna material found in bsl is the result of mixing processes despite these differences animal entrapment is considered the best scenario to explain bone accumulation in both facies ams radiocarbon dates indicate that the bsl was deposited during the holocene with dates ranging from 8580 cal yr bp to the present while the rbsl deposition dates to the holocene pleistocene transition 13 600 10 660 cal yr bp radiocarbon dating also indicates that the subtle erosional surface that limits both facies represents a temporal gap between a minimum age of 8 4 cal kyr bp and a maximum age of 11 0 cal kyr bp the recognition of this discontinuity allows for a more accurate interpretation of bone accumulation enabling the differentiation of faunal assemblages that might otherwise be considered part of a continuum

provenance study of endokarst fine sediments through mineralogical and geochemical data lezetxiki ii cave northern iberia abstract the characteristics and provenance of the fine sediment forming the matrix of detrital endokarst fill can vary greatly and their study provides valuable information about the paleoenvironment and the different sedimentary and diagenetic processes in which it was formed and deposited this paper applies this study to the case of lezetxiki ii cave arrasate gipuzkoa using x ray diffraction xrd x ray fluorescence xrf and scanning electron microscopy sem eds analysis with samples of endokarst sediment rocks and soils in the surroundings of the cave the following source areas and sedimentary processes have been identified 1 allochthonous sedimentation through the fluviokarst processes which eroded soils formed on siliciclastic formations it is characterised by a high percentage of illite in the sediment and predominated in relatively cold periods in mis 6 and mis 2 4 2 sedimentation through infiltration from karst fissures of the autochthonous soils formed on the limestone substrate terra rossa it is characterised by a higher vermiculite content and prevailed in the warm mis 5 period and the holocene 3 chemical sedimentation where calcite precipitated in the form of speleothems in warmer and more humid periods and 4 deposition of microfauna bones in owl pellets

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

the respective role of atmospheric carbon dioxide and orbital parameters on ice sheet evolution at the eocene oligocene transition the continental scale initiation of the antarctic ice sheet at the eocene oligocene boundary eocene oligocene transition eot 34 ma is associated with a global reorganization of the climate if data studies have assessed the precise timing and magnitudes of the ice steps modeling studies have been unable to reproduce a transient ice evolution during the eocene oligocene transition in agreement with the data here we simulate this transition using general circulation models coupled to an ice sheet model our simulations reveal a threshold for continental scale glaciation of 900 ppm 100 to 150 ppm higher than previous studies this result supports the existence of ephemeral ice sheets during the middle eocene as similar co 2 levels 900 1000 ppm have been reached episodically during this period transient runs show that the ice growth is accurately timed with eot 1 and oi 1 the two 18 o excursions occurring during the transition we show that co 2 and orbital variations are crucial in initiating these steps with eot 1 corresponding to the occurrence of low summer insolation whereas oi 1 is controlled by a major co 2 drop the two 18 o steps record both ice growth and temperature representing some 10 30 m eustatic sea level fall and 2 4 c cooling at eot 1 and 70 20 m and 0 2 c for oi 1 the simulated magnitude of the ice steps 10 m for eot 1 and 63 m for oi 1 and the overall cooling at various locations show a good agreement with the data which supports our results concerning this critical transition

karst pocket valleys and their implications on pliocene quaternary hydrology and climate examples from the nullarbor plain southern australia abstract karst on the nullarbor plain has been studied and described in detail in the past but it lacked the determination of the karst discharge and palaeo watertable levels that would explain the palaeohydrological regime in this area this study explores the existence of previously unrecognised features in this area karst pocket valleys and gives a review on pocket valleys worldwide initial gis analyses were followed up by detailed field work sampling mapping and measuring of morphological geological and hydrological characteristics of representative valleys on the wylie and hampton scarps of the nullarbor plain rock and sand samples were examined for mineralogy texture and grain size and a u pb dating of a speleothem from a cave within a pocket valley enabled the establishment of a time frame of the pocket valleys formation and its palaeoenvironmental implications the pocket valleys document the hydrological evolution of the nullarbor karst system and the neogene pleistocene palaeoclimatic evolution of the southern hemisphere a review of pocket valleys in different climatic and geological settings suggests that their basic characteristics remain the same and their often overlooked utility as environmental indicators can be used for further palaeoenvironmental studies the main period of intensive karstification and widening of hydrologically active underground conduits is placed into the wetter climates of the pliocene epoch subsequent drier climates and lowering of the watertable that followed sea level retreat in the quaternary resulted in formation of the pocket valleys gravitational undermining slumping exudation and collapse which combined with periodic heavy rainfall events and discharge due to impeded drainage caused the retreat of the pocket valleys from the edge of escarpments

holocene dryness and human occupation in brazil during the archaic gap an overview of the archaeological data produced over the last decades for brazil coupled with a background of recent paleoenvironmental studies suggests that during the mid holocene vast areas of central brazil ceased to be occupied by human groups independent data from dated human skeletons rock shelter stratigraphy and chronology of open air sites converge to support the inference that these areas were depopulated or altogether abandoned paleoenvironmental data suggest that dryness events constitute the major cause behind the observed trends this phenomenon expands the already perceived notion that climatic stresses had a major role in the shaping of human settlement patterns in marginal environments such as deserts and high altitude settings

cave sedimentation in the new guinea highlands this paper investigates the nature and processes of sedimentation of allogenic cave deposits in the high relief everwet karsts of montane new guinea under the high intensity rainfall regime episodic mass movements in small karst catchments provide a wide range of sediment textures from clayey gravels to fine clays these allogenic sediments are deposited into pools of water within the caves giving sedimentary structures analogous to turbidites diamictons within the cave relate to episodic mudflows in the catchment these deposits move as fluidized masses in a manner similar to some esker deposits cross stratified sediments are formed by dumping of pulses of sediment laden water into deep pools extremely fine grained clays and muds accrete parallel to underlying surfaces following flood pulses these deposits represent the last phase of catchment instability when a small amount of slopewash occurs catchment processes are dominated by solution and episodic mass movements when the thick root mat which masks the ground is disrupted some slopewash occurs but it is not a major component in catchment processes

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

euxinia and primary production in late cretaceous eastern equatorial atlantic surface waters fostered orbitally driven formation of marine black shales 1 oceanic anoxic events oae in the cretaceous represent major perturbations in the global climate and ocean system characterized by widespread deposition of organic carbon in the ocean the causes and effects of these events are poorly constrained mainly because of the lack of high resolution marine records here we report the distribution of molecular markers from a millennial scale record of coniacian santonian black shale oae 3 from ocean drilling program site 959 in the deep ivorian basin in the eastern equatorial atlantic highly branched isoprenoids and alkenone derived organic compounds indicate that diatoms and calcareous nanoplankton were important primary producers changes in redox sensitive trace metal accumulation and biomarkers of green sulfur bacteria provide evidence for extreme variations in redox conditions with intervals of lower photic zone euxinia pze accordingly oxygen in the coniacian santonian tropical atlantic was absent as during the cenomanian turonian boundary oae 2 but over more restricted geographic area and more limited time intervals we hypothesize that pze was a common phenomenon typical in large areas of tropical continental margins these conditions fostered sequestration of atmospheric co2 and thus helped cause the positive excursion in 13c of carbonate documented in higher latitude marine records

stratigraphy and geochronology of pitfall accumulations in caves and fissures bermuda abstract deep fractures fissures and avens skylights in limestone cave roofs create natural traps for sediments and biota fissures fill quickly with surface sediment and organisms soon after opening debris cones are formed as materials fall wash or drift on air through openings in cave skylights such deposits in admiral s and grand canyon cave bermuda contain distinct beds and are composed of mixtures of sediment and charcoal together with fossils of land snails crabs birds reptiles and bats the pitfall accumulations were periodically sealed over by calcite flowstone a stratigraphic record of surface activity and fauna through both glacial and interglacial periods has been preserved the succession also provides an ideal setting in which to compare several geochronological methods calibrated 14 c ages on charcoal and shells provide dated horizons at 1600 12 800 and about 35 000 14 c yr bp thermal ionization mass spectrometric tims ages on several flowstone layers constrain the entire sequence in the admiral s cave sequence between 126 300 900 yr termination ii and historical times a continuous relative age record generated by amino acid epimerization aae geochronology d alloisoleucine l isoleucine or aile ile on the pulmonate land gastropod poecilozonites verifies the biostratigraphy reveals a minimal degree of mixing between stratigraphic units and establishes an independent temporal link between the subterranean and subaerial deposits of bermuda this convergence between stratigraphy and geochronology yields a precisely dated succession from the oceanic island of bermuda and thus presents a unique opportunity to assess the rates and processes of evolutionary and climate change during that interval

the influence of bedrock derived acidity in the development of surface and underground karst evidence from the precambrian carbonates of semi arid northeastern brazil very extensive cave systems are developed in precambrian una group carbonates in the campo formoso area eastern brazil in contrast the area is largely devoid of significant surface karst landforms as would be expected given its semi arid climate the caves in the area display many morphological features characteristic of deep seated hypogenic caves such as lack of relationship with the surface ramiform network pattern abrupt variations of passage cross sections and absence of fluvial sediments but do not show evidence of vertical passages marking the ascending path of acidic water nor present extensive gypsum or acid clay mineral deposits hydrochemical analyses of present day ground water indicate that oxidation of bedrock sulphide is an active process and sulphuric acid may be the main agent driving carbonate dissolution in the area a shallow mode of speleogenesis is thus proposed in which sulphuric acid produced through the oxidation of sulphide beds within the carbonates controls cave initiation and development moreover the geological situation of the area in an ancient stable passive margin precludes the possibility of deep seated sources of acidity under dry climate due to the absence of recharge solutional landforms will be largely subdued in the surface hypogenic processes if present are likely to predominate producing a landscape characterized by a marked disparity in the comparative degree of development between surface and underground landforms rates of karst landform development have traditionally been analysed through a climatic perspective runoff being the main controlling factor in promoting karst development this view needs to be reassessed in the light of the growing awareness of the importance of climate independent processes related to hypogenic sources of acidity copyright 2003 john wiley sons ltd

u series dating and taphonomy of quaternary vertebrates from brazilian caves abstract the geochronology and taphonomy of internationally important fossil bearing cave deposits were studied both in the semi arid northern bahia area and the subtropical southeastern lagoa santa area of brazil taphonomic analysis suggests that the processes responsible for bone accumulation in the brazilian caves vary between sites and taphonomic bias can therefore be significant in causing differences in faunal composition in the toca da boa vista caves the presence of single articulated skeletons and the entrance related distribution indicate that random penetration of animals is the main mechanism of fossil accumulation a process that biases the assemblage to smaller species and takes place over extended time periods in nearby toca dos ossos cave transport by runoff in the cave river is predominant and biases the fauna remains to larger more robust bones and species deposition probably also occurred only at times of enhanced runoff giving a more contemporaneous assemblage similar processes were responsible for emplacement of the copious fossil remains in the more humid lagoa santa area where terrigenous fossil deposits are found intercalated by massive speleothem calcite layers in this area runoff under a drier climate probably accounts for the sediment emplacement inside caves in both areas the mode of emplacement implies bias in the fossil record resulting in fossil assemblages that do not mirror surface faunas limiting palaeoenvironmental reconstruction mass spectrometric u series analysis of speleothem calcite overlaying fossil remains gives minimum ages for fossil deposition these ages confirm the previous view that many of the deposits derive from the late glacial but also show that much older material some 350 000 yr is also present the habitat requirements of critical fossil species such as bats and monkeys strongly suggest that they derive from much wetter periods when forest cover was present in the currently semi arid northern bahia area taphonomy exerts a major control on the diversity and mode of emplacement of cave fossil deposits in eastern brazil and thus detailed sedimentological and hydrological studies coupled with a sound geochronological approach are essential in quantifying the relative importance of each taphonomic processes before faunal and palaeoecological interpretations can be attempted

diagenetic changes on bone histology of quaternary mammals from a tropical cave deposit in southeastern brazil abstract karst caves are suitable environments for the accumulation and preservation of fossils cave deposits are often complex and the environmental conditions within cave sites result from intricate interactions between various biological physical and chemical factors however it is not fully understood how the complexity of the environmental conditions of caves influences bone diagenesis the study of the initial stages of bone diagenesis depends to a large extent on understanding the changes in the bone histology to contribute to this issue we examine a set of postmortem changes affecting the bone histology of quaternary mammals that accumulated naturally in locus 2 a pitfall site in cuvieri cave located in the tropical region of brazil our analyses show that bones deposited in caves may be subject to a peculiar set of environmental conditions that in tropical regions may prevent the preservation of bone histological structure the effect of diagenetic processes on the bones differs depending on the taphonomic stage of the bone and the diagenetic alterations appear to have influenced each other the deposition of bioclasts following the entrapment of individuals in locus 2 favours the proliferation of bacteria on bones and appears to be important in directing the diagenetic alteration the hydrological regime of the cave that is recharge with potential phases of higher humidity also is important in directing the diagenetic alteration and further decreased the preservation potential of the bone microstructure the formation of macroscopic and microscopic cracks related to bone weathering in caves shows that the taphonomic processes peculiar to these environments are poorly understood highlighting the need for more research to be conducted on cave taphonomy

upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 abstract time stratigraphic patterns of stable carbon isotopic ratios recorded in terrestrial organic matter from cenomanian maastrichtian successions for the russian far east can be correlated to those of carbonate carbon from well studied successions for other parts of the world age indicative biostratigraphy based on regional ammonoids and inoceramid bivalves are well established in japan and can be applied to the whole cretaceous succession except for the upper cenomanian lower turonian and the upper part of the maastrichtian zones lacking macrofossils globally correlative carbon isotopic events previously documented with carbonate carbon from europe and with carbonate carbon and marine organic matter from the u s western interior are recognized with similar magnitude through uppermost cenomanian lower campanian in ascending order these events are positive spike across the cenomanian turonian boundary step like leveled segment followed by negative shift lower middle turonian trough like negative excursion middle upper turonian positive rebound coupled with following broad peak coniacian and positive peak basal campanian followed by modest negative excursion the parallel fluctuation of the 13 c value between the terrestrial organic matter and carbonate suggests carbon isotopic equilibrium between surface seawater and atmospheric co 2 and demonstrates that the isotopic curve of terrestrial organic carbon can be used to monitor carbon isotopic fluctuations of co 2 in the ocean atmosphere system in the upper campanian and maastrichtian a negative 13 c excursion within chron 33r and a following rapid rebound can be correlated with the same distinctive carbon isotopic feature of carbonate observed in the deep sea cores from south and north atlantic the indian and the pacific oceans within this interval the 13 c value of terrestrial organic matter also reflects carbon isotopic fluctuation of the global co 2 reservoir with relatively minor regional local noise

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

paleoceanographic significance of high resolution carbon isotope records across the cenomanian turonian boundary in the western interior and new jersey coastal plain usa carbon isotope measurements have been made on bulk carbonate and organic matter in three sections across the cenomanian turonian boundary the stratigraphy records the positive carbon isotopic excursion that is associated with the major oceanic anoxic event oae2 comparison of toc and isotopic data in sections from a range of different environments suggests that the positive excursion is a response to increased burial of organic matter in the deep ocean the lack of coupled negative shifts in 13corg and 13ccarb records at the onset of oae2 does not support a causal role for volcanism or methane hydrate dissociation

the brazilian megamastofauna of the pleistocene holocene transition and its relationship with the early human settlement of the continent abstract one of the most intriguing questions regarding the brazilian late quaternary extinct megafauna and homo sapiens is to what extent they coexisted and how humans could have contributed to the former s extinction the aim of this article is to review the chronological and archaeological evidences of their coexistence in brazil and to evaluate the degree of direct interaction between them critical assessment of the brazilian megafauna chronological data shows that several of the late pleistoscene early holocene dates available so far cannot be considered reliable but the few that do suggest that at least two species catonyx cuvieri ground sloth smilodon populator saber toothed cat survived until the beginning of the holocene in southeast brazil archaeological data indicates that the first human groups arrived in brazil and were inhabiting this region during the last millennia of the pleistocene and consequently they coexisted with the extinct fauna in some parts of brazil for at least one thousand years there is no robust evidence favoring any kind of direct interaction between humans and megafauna prior to their extinction to date it is not possible to properly judge the indirect influence of humans landscape transformation introduction of predators among others in this extinction event intense and to some extent unique climate changes between the last glacial maximum and the holocene favors the interpretation that they had a major contribution to the megafauna extinction although the scarcity of data impedes the proper testing of this hypothesis

integrated depositional model for the cenomanian turonian organic rich strata in north africa abstract during the late cenomanian early turonian c t oceanic anoxic event oae2 organic rich strata was deposited in rift shelf basins and slopes across north africa and in deep sea basins of the adjacent oceans based on a review of published and unpublished information this paper documents the distribution and organic richness of c t strata across the whole region within a palaeogeographic framework and systematically analyses the conditions and processes which controlled their deposition previously the c t in north africa has been most intensively studied in southern morocco tarfaya and tunisia only little data is availabe for other parts of north africa namely algeria libya and egypt because distribution of c t corg strata there becomes more patchy a general decrease in peak organic richness and black shale thickness occurs from west to east partly as a result of upwelling along the moroccan atlantic coast and the absence of upwelling in the eastern mediterranean area furthermore in the confined central atlantic the oxygen minimum zone omz in many places reached down to the deep sea floor 3 4 km while the lower limit of the omz along the north african tethys was much shallower and underlain by oxic water masses as documented by high resolution biostratigraphic and chemostratigraphic data c t black shale deposition in most areas outside the upwelling zone are restricted to a strong eustatic latest cenomanian transgressive phase triggered by this sea level rise the omz impinged onto the north african continental shelf and the margins of intrashelf basins which mostly formed during the early cretaceous as halfgrabens important units containing c t organic rich strata in the region are the atlantic tarfaya black shales morocco western sahara black shales and phtanites in the moroccan and algerian atlas the bahloul fm in the se constantine basin and in northern and central tunisia the etel fm in the sirte basin the al hilal fm in cyrenaica libya the abu roash fm in the abu gharadig and fayium basins western desert egypt the daliyya fm along the ne sinai palestine isreal coast and the shueib fm in west central jordan

missing records and depositional breaks in french late pleistocene cave sediments abstract cave entrance and rock shelter infillings are positioned within the pleistocene chronology for three areas of france northern alps franche comte and perigord despite minor local variations it is possible to identify regional types with a consistent depositional record over long intervals of time the interregional variability relates to the frequency and position of the gaps within the infillings sites in the northern alps have not yielded any artifacts older than the upper paleolithic magdalenian and dated sedimentary sequences do not go back beyond the older dryas more complete sequences in franche comte contain mousterian industries two major gaps occur here one lasting about 50 000 yr during the lower glacial and lower pleniglacial periods and the other lasting some 10 000 yr during the upper pleniglacial the sequences are more complete in the perigord where all major climatic phases have been identified with no significant sedimentary gaps differences in sedimentary records can be explained by variations in regional conditions during the last interglacial glacial cycle and especially by the distance from the maximum advance of ice daring glaciation

the cenomanian turonian extinction and oceanic anoxic event evidence from southern tibet deep shelf locations on the perigondwanan margin of southern tibet record a major extinction of foraminifera and calcareous nannoplankton in the latest cenomanian top of the rotalipora cushmani zone this is followed by a low diversity survival interval that straddles the cenomanian turonian boundary whiteinella archaeocretacea zone during which only low diversity surface water dwelling foraminifera and nannoplankton and microfilaments are present rapid recovery in the early turonian saw the appearance of new species the reappearance of many lazarus species and the reestablishment of a diverse community of planktonic foraminifera that included a range of shallow to deep water column dwellers the extinction and survival intervals coincide with the development of dysaerobic facies characterised by small sized burrows and moderately large sized framboid pyrite populations at no time does the water column appear to have become sulfidic this study indicates that the end cenomanian oceanic anoxic and extinction events were also manifested in moderately high southerly palaeolatitudes on the southern margin of the tethyan ocean thereby increasing the known extent of this global event albeit with the proviso that the anoxic event was a dysoxic one

cave clastic sediments and implications for speleogenesis new insights from the mugnano cave montagnola senese northern apennines italy abstract the study of cave clastic sediments has been considered one of the hottest topics during the last years because of their importance in paleoclimatic reconstructions and archaeological surveys this paper focuses on clastic deposits of the mugnano cave a small cave located in the siena district northern apennines italy showing unique features regarding the sedimentary fill mostly made of grey blue dolomitic silts the sedimentary succession was investigated through a detailed sedimentological analysis aimed at a better understanding of sedimentary processes active during the deposition the entire succession was subsequently reinterpreted through an allostratigraphic approach the recognition of an important erosional surface associated with a significant change in sedimentation allowed the distinguishing of two main allounits labelled mg1 and mg2 furthermore the different kinds of sediments collected in the cave were analysed using the xrf and xrd techniques in order to establish their chemical and mineralogical compositions the integration of lithological sedimentological allostratigraphic and mineralogical data permits formulation of an interesting hypothesis about speleogenetic processes that influenced the cave with particular reference to the processes capable of generating the underground space in this context most of the current available space results from a complex interplay between different processes disintegration of a particular lithofacies of the bedrock consequent production of sediments and deposition into a subterranean lake these sediments were removed from the cave during some non depositional and erosive phases which led to a positive balance in the available space

upper cretaceous carbon and oxygen isotope stratigraphy of hemipelagic carbonate facies from southern tibet china a high resolution carbon isotope curve derived from upper cretaceous hemipelagic sediments cropping out at tingri southern tibet shows similarities to patterns established on other continents notably in the presence of a well defined positive excursion across the cenomanian turonian boundary where 13 c values exceed 3 5 from the upper turonian to the lower campanian 13 c values generally decline apart from a minor positive excursion in the middle coniacian a trend that departs from that recorded from europe relatively low 13 c values c 1 at the santonian campanian and campanian maastrichtian boundaries in tibet define a prominent broad positive excursion centred in the middle campanian and terminated by an abrupt fall towards the close of the stage when compared with data from europe and north africa the 13 c values of the tibetan section are generally lower by c 1 5 except for the middle campanian positive excursion where values 13 c c 2 are comparable with those documented from europe and north africa these differences are interpreted as reflecting variable mixing of water masses carrying different carbon isotope signatures such that areas close to the major sinks of marine organic carbon recorded higher 13 c values than those located in more distal regions oxygen isotope ratios albeit affected by diagenesis may record a palaeotemperature signal

the cenomanian turonian oceanic anoxic event i stratigraphy and distribution of organic carbon rich beds and the marine δ13c excursion marine strata deposited during late cenomanian and early turonian time display lithological faunal and geochemical characteristics which indicate that significant parts of the world ocean were periodically oxygen deficient at or very close to the cenomanian turonian boundary between 90 5 and 91 5ma ago oxygen deficiencies were particularly marked over a period of 1ma this short lived episode of oceanic oxygen deficiency has been termed the cenomanian turonian oceanic anoxic event oae the widespread distribution of anoxic sediments deposited synchronously during such a short lived event indicates that such sediments are not simply the product of coincidental local climatic or basinal water mass characteristics but are the result of a global expansion and intensification of the cenomanian turonian oxygen minimum zone related to feedback between sea level rise and regional palaeoceanography the palaeoceanography of the cenomanian turonian oae is discussed in detail in a companion paper by arthur et al 1987 from authors

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

quaternary ecological and geomorphic changes associated with rainfall events in presently semi arid northeastern brazil several geomorphic features and palaeobiotic remains in now semi arid northeastern brazil indicate major palaeoenvironmental changes during past periods of increased rainfall 230th mass spectrometric ages of speleothems and travertines have allowed the determination of the timing and duration of wetter than present conditions the data demonstrate that wet events have occurred throughout much of the pleistocene present dry conditions having been established at the end of the younger dryas a markedly different fauna comprising megafaunal elements not adapted to the present low arboreal scrubland caatinga vegetation existed in the area palaeobotanical remains embedded in travertine indicate forested vegetation at these wetter intervals suggesting that the caatinga was then replaced or mixed with a semi deciduous forest due to the abundance of travertine sites containing fossil botanical remains in northeastern brazil it is believed that forest expansion occurred over large areas of the now semi arid zone showing that the long hypothesised forested links between biodiversity rich amazon and atlantic rainforests may indeed have existed during these moister phases copyright 2004 john wiley sons ltd

cave fills in miocene pliocene strata on cayman brac british west indies implications for the geological evolution of an isolated oceanic island abstract an 8 m high wall in a quarry on the west end of cayman brac exposes the upper part of the cayman formation miocene the lower part of the overlying pedro castle formation pliocene and the cayman unconformity which is a karstic unconformity that separates these formations the modern day karst surface caps the pedro castle formation this exposure also includes cross sections through two filled caves the lower cave 8 m long up to 2 5 m high and upper cave 23 m long up to 2 m high that are housed in the cayman formation and pedro castle formation respectively the lower cave is filled with caymanite which is formed of laminated varicolored dolomitized mudstones and grainstones that contain scattered marine fossils e g foraminifera red algae this cave connected to the cayman unconformity by a small diameter tunnel evolved as part of the karst system that developed during the messinian lowstand 7 3 5 3 ma the cave was filled and dolomitized prior to deposition of the pedro castle formation the upper cave is filled with a wide spectrum of lithotypes including dolostones calcareous mudstones terra rossa gastropod coquina coated grains and speleothems u th dating indicates that some of the flowstones are 500 000 years old whereas others are only 21 000 years old dolostones and mudstones in the basal part of the upper cave contain marine fossils foraminifera red algae whereas the younger deposits are devoid of such fossils the upper cave and its deposits developed after the sediments of the pedro castle formation had been deposited and lithified development of the cave filling deposits which includes a clear transition from marine to non marine influences was controlled by eustatic sea level changes and or westward tectonic tilting of cayman brac that occurred after the pedro castle formation became exposed probably during the late pliocene

chemostratigraphy versus biostratigraphy data from around the cenomanian turonian boundary a detailed isotopic profile is presented for a stratigraphically expanded cenomanian turonian boundary section in chalk facies exposed at eastbourne sussex and compared with data from pueblo colorado in both sections macro and micropalaeontological markers first appearances and disappearances are well constrained and their relative positions and relationship to the structure of the carbon isotope curve are identical this consistent relationship between two independent phenomena one geochemical the other biostratigraphical is taken as evidence for the likely synchroneity of both the biostratigraphical markers and the carbon isotope excursion in these two areas this interpretation contrasts with suggestions made recently by other authors whose data have been taken to imply a lack of correlation between the carbon isotope excursion in europe and north america

late cretaceous campanian carbon isotope events sea level change and correlation of the tethyan and boreal realms abstract carbon stable isotope stratigraphy provides unique insights into environmental change during the campanian the longest 83 5 71 3 ma but least well understood stage of the late cretaceous a new carbon isotope 13c profile for a 500 m thick campanian basal maastrichtian tethyan pelagic hemipelagic section near el kef northern tunisia is calibrated using data from a biostratigraphically well constrained succession at kalaat senan the general shapes of the tunisian 13c reference curve and published tethyan 13c profiles from elles tunisia and bidart sw france and a boreal curve for the trunch borehole eastern england are remarkably similar in all three areas a positive carbon isotope event of 0 2 13c in the mid campanian dated at 78 7 ma and a negative excursion of 0 4 in the upper campanian at 74 8 ma can be correlated between tunisia and england a positive excursion of 0 3 at 83 7 ma spans the santonian campanian boundary these isotope events enable precise inter regional correlations that are consistent with published nannofossil data review of campanian sea level data from north africa the middle east and northern europe indicates that major shifts in 13c profiles coincide with changes in eustatic sea level relatively stable 13c values in the lower campanian and their long term fall through the upper campanian reflect high and then falling eustatic sea levels and increased carbonate production short term 600 kyr positive excursions record greater organic productivity and or organic matter preservation and decreased carbonate fluxes during periods of rapid sea level rise and the drowning of carbonate platforms excursions were terminated by falling nutrient supply and increased carbonate deposition associated with epicontinental sea expansion and renewed carbonate platform growth during the late transgression and highstand negative excursions are linked principally to reworking of marine and terrestrial organic matter during rapid sea level fall carbon isotope stratigraphy is a powerful tool for correlation which can be used to test the validity of campanian global biostratigraphic frameworks and improve our understanding of the nature and timing of late cretaceous sea level change

δ13c values from the cenomanian turonian passage beds of southern tibet a group of bituminous sediments of mid cretaceous late cenomanian early turonian age are well exposed in the tingri gamba basin of southern tibet the characteristics of microfossils and geochemistry in the strata show that paleoceanographic environmental changes took place in the tethys himalayan sea the 13c profiles of southern tibet are characterized by a low high low cycle the maximum positive excursion of 2 0 occurs at the position just above the cenomanian and turonian boundary in tingri and 2 74 occurs underneath the cenomanian and turonian boundary in gamba the mid cretaceous in southern tibet is a short period of expansion of the tethys himalayan sea which brought about local sea level rise the positive excursion of 13c coincides with both global and local sea level rises the correlation of the 13c spike and well dated occurrence of layers rich in organic carbon indicate that intense orgc burial took place during the latest cenomanian to earliest turonian the positive 13c excursion reflects the burial of total dissolved carbon the positive excursion and excess carbon burial in southern tibet are coincident with the oceanic anoxic event during the time

quaternary depositional facies in cave entrances and their relation to landscape evolution the example of cuvieri cave eastern brazil abstract the correct determination of sedimentation processes in caves is often complicated by the unique characteristics of cave environments and their relationship to surface soil a study at cuvieri cave has allowed new insights into the dynamics and evolution of these types of sedimentary facies and their relation to the nearby landscape the cave is located in the lagoa santa karst eastern brazil and contains fossiliferous deposits of pleistocene holocene age at the base of three vertical pits near the cave entrance facies analysis was applied to sediments to understand sedimentation process and sediments were described according to their morphology grain size micromorphology chemical composition paleontological content and age results indicate that all deposits present a soil like aspect and although they record several depositional conditions sedimentary structures and textures are similar among different facies as such facies were defined by a combination of matrix color degree of cementation and sedimentological characteristics additionally abundance of fauna remains their taxonomic composition extant vs extinct completeness and degree of individuals articulation was evaluated differences between facies were produced by two main factors i change in source area and transport route from the epikarst to doline colluviation and back to epikarst and ii change in type of sediment cover injected from doline fed soils followed by talus debris and finally soils from modern epikarst the change in both factors is related to the landscape evolution mainly with the development and progressive enlargement and deepening of the nearby doline additionally the change in the type of sediment cover injected could also be related to climatic evolution the complex evolution of cuvieri cave sediments occurred over at least the last 300 kyr and is marked by periods in which entrance opening allowed the incorporation of vertebrate both extinct and extant remains into the sediment detailed multidisciplinary field and laboratory analyses are essential in unraveling the long history of sedimentation in caves providing a framework in which multiple events of sediment input and erosion can be correctly interpreted and related to the evolution of the landscape