rapid analysis of 13c in plant wax n alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments long chain odd carbon numbered c25 to c35 n alkanes are characteristic components of epicuticular waxes produced by terrestrial higher plants they are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments the isotopic compositions of these products can serve as records of past vegetation we have developed a rapid method for stable carbon isotopic analyses of total plant wax n alkanes using a novel moving wire system coupled to an isotope ratio mass spectrometer mw irms the n alkane fractions are prepared from sediment samples by 1 saponification and extraction with organic solvents 2 chromatographic separation using silica gel 3 isolation of straight chain carbon skeletons using a zeolite molecular sieve and 4 oxidation and removal of unsaturated hydrocarbons with ruo4 short chain n alkanes of nonvascular plant origin c25 are removed by evaporation on the moving wire test samples processed using this procedure yielded n alkane fractions essentially free of interfering components the 13c values obtained by mw irms did not differ significantly from weighted averages of individual n alkane 13c values obtained by irmgc ms isotopic variations in compound class n alkane fractions from a latitudinal transect of core top sediments from the southwest african margin 3 n 28 s were congruent with those measured by compound specific isotopic analyses of plant wax n alkanes the amplitude of the variations was smaller indicating contributions from non plant wax hydrocarbons but the measurements revealed variations in carbon isotopic composition that are consistent with vegetation zones on the adjacent continent

vegetation change in equatorial west africa time slices for the last 150 ka abstract drawing on marine and terrestrial palynological data vegetation maps of equatorial west africa are presented for eleven time slices over the last 150 000 years long marine records are used as a basis for the regional picture and provide a chronology for the last glacial cycle much shorter terrestrial records help fill in the picture for the most recent periods and facilitate interpretation of regional patterns for the longer timescale temporal and spatial variation is revealed in relation to global patterns of climate change rain forest was widespread during oxygen isotope stages 1 and 5 but strongly reduced during stages 3 and 4 and especially during stages 2 and 6 when open grass rich vegetation prevailed glacial rain forest refuges are found in the southwest of the guinean mountains and along the eastern coast of the gulf of guinea miombo woodland of the zambezian vegetation zone expanded during stage 5 especially during the first half podocarpus forest had its largest expansion during substages 5d 115 to 105 ka and 5b 95 to 85 ka the last occurrence of podocarpus in the guinean mountains is during stage 5a the distribution of mangrove swamps was extremely reduced during glacial times during stage 6 savanna and open dry forest covered large areas along the northern coast of the gulf of guinea the southern saharan desert reached far to the south and the namib desert far to the north the area of rain forest was restricted mangrove swamps were strongly reduced and the area of podocarpus forest fluctuated during stage 5 large changes in the area of afromontane forest rain forest dry open forest and savanna occurred rain forest was widespread and mangroves were extensive along the coast during the last interglacial substage 5e podocarpus forest area strongly extended during substages 5d and 5b in substages 5c and 5a rain forest reclaimed areas it had lost in the previous substages 5d and 5b respectively mangrove swamps were less widespread in the later substages of stage 5 than during substage 5e during stage 4 the rain forest area was again strongly reduced and recovered only slightly during the following stage 3 also the mangrove swamp area was reduced except along the ivory coast and along the northwestern coast of the gulf of guinea podocarpus forest only occurred in angola and may be in congo during stage 4 again forest was much reduced during stage 2 and open vegetation types covered large parts of equatorial west africa mangrove swamps must have been rare at the beginning of the holocene mangrove swamps had recovered and reached their largest extension also the rain forests area increased in the early holocene and guinean and congolian rain forests were probably not separated by a savanna corridor now existing in togo and benin

mapping of c4 plant input from north west africa into north east atlantic sediments abstract mapping the abundance of 13c in leaf wax components in surface sediments recovered from the seafloor off northwest africa 0 35 n reveals a clear pattern of 13c distribution indicating systematic changes in the proportions of terrestrial c3 and c4 plant input at 20 n latitude we find that isotopically enriched products characteristic of c4 plants account for more than 50 of the terrigenous inputs this signal extends westward beneath the path of the dust laden sahara air layer sal high c4 contributions apparently carried by january trade winds also extend far into the gulf of guinea similar distributions are obtained if summed pollen counts for the chenopodiaceae amaranthaceae and the poaceae are used as an independent c4 proxy we conclude that the specificity of the latitudinal distribution of vegetation in north west africa and the pathways of the wind systems trade winds and sal are responsible for the observed isotopic patterns observed in the surface sediments molecular isotopic maps on the marine sedimentary time horizons e g during the last glacial maximum are thus a robust tool for assessing the phytogeographic changes on the tropical and sub tropical continents which have important implications for the changes in climatic and atmospheric conditions

volcanic components in pelitic sediments the origin of the clay minerals present in pelitic sediments has been widely debated weaver1 suggests that illite and interstratified illite smectite i s dominate the association of illite with marine sediments2 and the proposal3 4 that illite forms from smectite an expandable clay mineral sometimes referred to as montmorillonite in the marine environment has also been discussed weaver5 argues for a continental origin of illite produced by weathering of k feldspar others6 9 have shown that smectite and i s 20 50 illite are converted to i s of higher illite content 60 80 in pelitic sediments by low grade metamorphism per cent illite will always refer to the per cent illite in i s the designation should not be confused with the content of discrete illite or mica commonly present in these sediments here we present clay mineral and k ar data for cretaceous marine shales from the western interior of north america demonstrating a volcanic origin for much of these sediments this observation is correlated with eustatic sea level rise increased volcanic activity sedimentary preservation of organic matter and incorporated into a petrogenetic tectonic model for pelitic sediments

mineralogy of the upper albian sediments from the kirchrode i borehole with special emphasis on the clay mineralogy abstract the mineralogy of a 245 m thick section of upper albian marly clay stones to clayey marlstones from the kirchrode i borehole lower saxony basin of nw germany has been studied by x ray diffractometry infrared spectrometry chemical analysis and microscopy the investigations were carried out on bulk samples and grain size fractions the mineralogy of the sediments is characterised by biogenous carbonates mainly calcite by terrigenous detrital components and diagenetic minerals often enriched in concretions the calcite content fluctuates considerably between 20 and 50 most probably because of changes in the marine palaeoenvironment illite montmorillonite and kaolinite are the predominant clay minerals but in changing portions chlorite and alkali feldspars were detected only in traces mixed layer minerals such as illite smectites i s are also present in higher amounts in the lower part and less in the upper part of the core reworked upper carboniferous mudstones and siltstones are interpreted to have delivered part of the well crystallised illite kaolinite chlorite and quartz montmorillonites and mixed layer minerals together with kaolinite and illite may be inherited from weakly consolidated jurassic sediments aptian and albian claystones and marlstones and from palaeosols the increase in the proportion of montmorillonite among the clay minerals in the upper part of the upper albian may be due to redistribution of volcanic sediments after either terrestrial or submarine alteration of volcanic ash volcanic activity is known in this area e g the middle to upper albian flammenmergel at the southern margin of the lower saxony basin and around the north atlantic throughout aptian albian time but in the kirchrode i core ash fall was identified as a source for montmorillonite in only one layer namely at 87 25 m where high zr and nb concentrations were also found the mineralogical composition of the concretionary material is generally a mixture of biogenous calcite siliciclastic debris quartz and clay minerals and microcrystalline diagenetically formed fe mn carbonates rhodochrosite siderite and carbonate fluorapatite francolite rhodochrosite is more abundant in the lower part mn siderite in the upper part of the core concretions with fluorapatite francolite occur sporadically

mid pleistocene environmental change in tropical africa began as early as 1 05 ma palynological records from the congo fan reveal environmental change in equatorial africa occurring 1 05 ma ago 100 k y before the mid pleistocene climatic shift at 0 9 ma prior to 1 05 ma a glacial interglacial rhythm is not obvious in the african vegetation variation afterwards podocarpus spread in the mountains of central africa mainly during glacials and congo river discharge decreased the sequence of vegetation variation associated with the mid pleistocene glacials and interglacials differed from that observed during the late pleistocene between 0 9 and 0 6 ma interglacials were characterized by warm dry conditions and glacials were characterized by cool humid conditions while during the past 0 2 ma glacials were cold and dry and interglacials warm and humid our data indicate that before the northern hemisphere ice caps dramatically increased in size 0 9 0 6 ma low latitude climate forcing and response in the tropics played an important role in the initiation of 100 k y ice age cycles during the mid to late pleistocene however the climate conditions in the tropics were increasingly influenced by the glacialinterglacial variations of continental ice sheets

cryptic biostalactites in a submerged karst cave of the belize barrier reef revisited pendant bioconstructions cemented by microbial micrite abstract microbial carbonates are important components of postglacial tropical coral reef frameworks curious calcium carbonate protrusions in a submarine karst cave in the belize barrier reef platform were initially interpreted as being largely the product of physicochemical precipitation around a meshwork of serpulid tubes new petrographical mineralogical geochronological and inorganic and organic geochemical data suggest that sulfate reducing bacteria played a substantial role in carbonate formation just as in cryptic settings of other modern tropical coralgal reefs the bacterial involvement in carbonate authigenesis is indicated by the content and isotopic composition of carbonate associated sulfate the presence of non isoprenoidal sn 1 mono o alkyl glycerol monoethers mages and terminally branched fatty acids and the observation that the majority of molecular fossils assigned to sulfate reducing bacteria are tightly associated with the carbonate mineral lattice the carbonate protrusions that were formerly named pseudostalactites are termed biostalactites here to underline the significance of biological activity during carbonate formation the belize biostalactites are composed of four carbonate phases including serpulid tubes lithified sediment and microbial carbonate as well as unconsolidated sediment usually found in macroborings of bivalve molluscs lithified sediment and microbial carbonate are fine grained with clotted mottled and peloidal textures while serpulid tubes are aragonitic lithified sediment and microbial carbonates are mixtures of high magnesium calcite and aragonite magnesium calcite content increases with increasing consolidation lithified sediment and microbial carbonate are interpreted as fine biodetrital sediment that was subsequently cemented by authigenic micrite scalenohedral high magnesium calcite and acicular aragonite cements played a subordinate role in cementation carbon and oxygen stable isotope ratios of lithified sediment and microbial carbonate exhibit similar ranges as modern reefal microbialites our study exemplifies that heterotrophic bacteria can be a crucial agent that contributes to the formation of carbonate build ups by cementing skeletal frameworks in cryptic environments

reconstruction of se trade wind intensity based on sea surface temperature gradients in the southeast atlantic over the last 25 kyr 1 a prominent feature in the southeast atlantic is the angola benguela front abf the convergence between warm tropical and cold subtropical upwelled waters at present the sea surface temperature sst gradient across the abf and its position are influenced by the strength of southeasterly se trade winds here we present a record of changes in the abf sst gradient over the last 25 kyr variations in this sst contrast indicate that periods of strengthened se trade wind intensity occurred during the last glacial maximum the younger dryas and the mid to late holocene while heinrich event 1 the early part of the bolling allerod and the early holocene were periods of weakened se trade winds

molecular and isotopic records of c4 grassland expansion in the late miocene abstract siwalik paleosol and bengal fan sediment samples were analyzed for the abundance and isotopic composition ofn alkanes in order to test for molecular evidence of the expansion of c4 grasslands on the indian subcontinent the carbon isotopic compositions of high molecular weight alkanes in both the ancient soils and sediments record a shift from low 13c values ca 30 to higher values ca 22 prior to 6 ma this shift is similar in magnitude to that recorded by paleosol carbonate and fossil teeth and is consistent with a relatively rapid transition from dominantly c3 vegetation to an ecosystem dominated by c4 plants typical of semi arid grasslands the n alkane values from our paleosol samples indicate that the isotopic change began as early as 9 ma reflecting either a growing contribution of c4 plants to a dominantly c3 biomass or a decrease in water availability to c3 plants molecular and isotopic analyses of other compounds including n alcohols and low molecular weightn alkanes indicate paleosol organic matter contains contributions from a mixture of sources including vascular plants algae and or cyanobacteria and microorganisms a range of inputs is likewise reflected in the isotopic composition of the total organic carbon from these samples in addition then alkanes from two samples show little evidence for pedegenic inputs and we suggest the compounds were derived instead from the paleosol s parent materials we suggest the record of vegetation in ancient terrestrial ecosystems is better reconstructed using isotopic signatures of molecular markers rather than bulk organic carbon this approach provides a means of expanding the spatial and temporal records of c4 plant biomass which will help to resolve possible tectonic climatic or biological controls on the rise of this important component of the terrestrial biosphere

glacial interglacial changes in southern africa compound specific δ13c land plant biomarker and pollen records from southeast atlantic continental margin sediments this is part 2 of a study examining southwest african continental margin sediments from nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s representing two glacial mis 2 and 6a and two interglacial stages mis 1 and 5e contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 as indicators of land plant vegetation of different biosynthetic types were correlated with concentrations and distributions of pollen taxa in sediments of the same time horizons selected single pollen type data reveal details of vegetation changes but the overall picture is best illustrated by summing pollen known to predominantly derive from c4 plants or c4 plus cam plants the c4 plant signals in the biomarkers are recorded in the 13c data and in the abundances of c31 and c33n alkanes and the c32n alkanol calculated clusters of wind trajectories for austral summer and winter situations for the holocene and the last glacial maximum afford information on the source areas for the lipids and pollen and their transport pathways to the ocean this multidisciplinary approach provides clear evidence of latitudinal differences in leaf wax lipid and pollen composition with the holocene sedimentary data paralleling the current major phytogeographic zonations the northern sites congo fan area and northern angola basin get most of their terrestrial material from the congo basin and the angolan highlands dominated by c3 plants airborne particulates derived from the western and central south african hinterland dominated by deserts semideserts and savannah regions are rich in organic matter from c4 plants as can be expected from the present and glacial positions of the phytogeographic zones the carbon isotopic signatures of n alkanes and n alkanols both become isotopically more enriched in 13c from north to south in the northern part of the transect the relative importance of c4 plant indicators is higher during the glacials than in the interglacials indicating a northward extension of arid zones favoring grass vegetation in the south where grass rich vegetation merges into semidesert and desert the difference in c4 plant indicators is small

a north to south transect of holocene southeast atlantic continental margin sediments relationship between aerosol transport and compound specific δ13c land plant biomarker and pollen records 1 we examined near surface late holocene deep sea sediments at nine sites on a north south transect from the congo fan 4 s to the cape basin 30 s along the southwest african continental margin contents distribution patterns and molecular stable carbon isotope signatures of long chain n alkanes c27 c33 and n alkanols c22 c32 are indicators of land plant vegetation of different biosynthetic types which can be correlated with concentrations and distributions of pollen taxa in the same sediments calculated clusters of wind trajectories and satellite aerosol index imagery afford information on the source areas for the lipids and pollen on land and their transport pathways to the ocean sites this multidisciplinary approach on an almost continental scale provides clear evidence of latitudinal differences in lipid and pollen composition paralleling the major phytogeographic zonations on the adjacent continent dust and smoke aerosols are mainly derived from the western and central south african hinterland dominated by deserts semi deserts and savannah regions rich in c4 and cam plants the northern sites congo fan area and northern angola basin which get most of their terrestrial material from the congo basin and the angolan highlands may also receive some material from the chad region very little aerosol from the african continent is transported to the most southerly sites in the cape basin as can be expected from the present position of the phytogeographic zones the carbon isotopic signatures of the n alkanes and n alkanols both become isotopically more enriched in 13c from north to south the results of the study suggest that this combination of pollen data and compound specific isotope geochemical proxies can be effectively applied in the reconstruction of past continental phytogeographic developments

fossil hyrax dung and evidence of late pleistocene and holocene vegetation types in the namib desert abstract pollen was derived from fossil dung of herbivorous hyraxes deposited in a rock shelteron the highest mountain in namibia da ures or brandberg situated on the namib desert margin radiocarbon dating ranging in age between modern times and 30000yrbp showed it representsthe rst empirical pollen evidence of continental palaeovegetation during the late pleistocene alongthe western escarpment of southern africa the initial results indicate last glacial maximum vegeta tion differed totally from the current pattern as vegetation types were dominated by small asteraceaeshrubs in contrast to those of the holocene and modern times which show more succulents grassandwoody elements arboreal pollen the resultssuggest that cape oral communities didnot reachinto thetropics along thewestern escarpment ofafrica despite such pollentypes occurring inmarinecores copyright 2004 john wiley sons ltd keywords palynology namibia restionaceae late pleistocene last glacial maximum

precession driven changes in terrestrial organic matter input to the eastern mediterranean leading up to the messinian salinity crisis abstract eastern mediterranean sediments over the past 12 myr commonly show strongly developed precessional cyclicity thought to be a biogeochemical response to insolation driven freshwater input from run off the mediterranean s dominant freshwater source today and in the past is the nile which is fed by north african monsoon rain other smaller circum mediterranean rivers also contribute to mediterranean hydrology crucially run off through all of these systems appears to vary with precession but there is no direct evidence linking individual water sources to the biogeochemical response recorded in mediterranean sediments consequently it is not clear whether the north african monsoon is entirely responsible for the mediterranean s sedimentary cyclicity or whether other precessional signals such as atlantic storm precipitation drive it organic matter in sediments derives from both marine and terrestrial sources and biomarker analysis can be used to discriminate between the two thereby providing insight into sedimentary and ecological processes we analysed a wide range of lipids from the late miocene 6 6 5 9 ma pissouri section southern cyprus and reconstructed the vegetation supplied to this region by measuring the carbon isotopes of the terrestrial component to identify its geographic source bit branched isoprenoidal tetraether indices reflect changes in the relative abundance of marine vs terrestrial soil organic matter inputs and with the exception of records from the last deglaciation this work is the first application of the bit approach to the reconstruction of orbital impacts on sedimentological processes bit indices show that the organic matter supplied to cyprus changed over the course of each precession cycle and was dominantly terrestrial during insolation maxima when north african run off was enhanced the 13 c values from these intervals are compatible with tropical north african vegetation however the 13 c record indicates that during insolation minima organic material supplied to southern cyprus derives from a more arid source region this is likely to have been aeolian transported organic matter from the anatolian plateau demonstrating that even in mediterranean sedimentary systems influenced by nile run off there is more than one independent precessional organic matter contribution to the sedimentary cyclicity pissouri s organic geochemistry also illustrates a long term trend towards more saline mediterranean conditions during the 600 kyr leading up to the messinian salinity crisis

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

reconstructing pathways of aeolian pollen transport to the marine sediments along the coastline of sw africa the distribution of pollen in marine sediments is used to reconstruct pathways of terrigenous input to the oceans and provides a record of vegetation change on adjacent continents the wind transport routes of aeolian pollen is comprehensively illustrated by clusters of trajectories isobaric 4 day backward trajectories are calculated using the modelled wind field of echam3 and are clustered on a seasonal basis to estimate the main pathways of aeolian particles to sites of marine cores in the south eastern atlantic trajectories and clusters based on the modelled wind field of the last glacial maximum hardly differ from those of the present day trajectory clusters show three regional and two seasonal patterns determining the pathways of aeolian pollen transport into the south eastern atlantic ocean mainly transport out of the continent occurs during austral fall and winter when easterly and south easterly winds prevail south of 25 s winds blow mostly from the west and southwest and aeolian terrestrial input is very low generally a good latitudinal correspondence exists between the distribution patterns of pollen in marine surface sediments and the occurrence of the source plants on the adjacent continent the northern angola basin receives pollen and spores from the congolian and zambezian forests mainly through river discharge the zambezian vegetation zone is the main source area for wind blown pollen in sediments of the angola basin while the semi desert and desert areas are the main sources for pollen in sediments of the walvis basin and on the walvis ridge a transect of six marine pollen records along the south western african coast indicates considerable changes in the vegetation of southern africa between glacial and interglacial periods important changes in the vegetation are the decline of forests in equatorial africa and the north of southern africa and a northward shift of winter rain vegetation along the western escarpment

sources transport and deposition of terrestrial organic material a case study from southwestern africa abstract southwestern africa s coastal marine mudbelt a prominent holocene sediment package provides a valuable archive for reconstructing terrestrial palaeoclimates on the adjacent continent while the origin of terrestrial inorganic material has been intensively studied the sources of terrigenous organic material deposited in the mudbelt are yet unclear in this study plant wax derived n alkanes and their compound specific 13c in soils flood deposits and suspension loads from regional fluvial systems and marine sediments are analysed to characterize the origin of terrestrial organic material in the southwest african mudbelt soils from different biomes in the catchments of the orange river and small west coast rivers show on average distinct n alkane distributions and compound specific 13c values reflecting biome specific vegetation types most notably the winter rainfall associated fynbos biome of the southwestern cape in the fluvial sediment samples from the orange river changes in the n alkane distributions and compound specific 13c compositions reveal an overprint by local vegetation along the river s course the smaller west coast rivers show distinct signals reflecting their small catchment areas and particular vegetation communities marine surface sediments spanning a transect from the northern mudbelt 29 s to st helena bay 33 s reveal subtle but spatially coherent changes in n alkane distributions and compound specific 13c indicating the influence of orange river sediments in the northern mudbelt the increasing importance of terrigenous input from the adjacent western coastal biomes in the central mudbelt and contributions from the fynbos biome to the southern mudbelt these findings indicate the different sources of terrestrial organic material deposited in the mudbelt and highlight the potential the mudbelt has to preserve evidence of environmental change from the adjacent continent

synthetic reconstructions of southern african environments during the last glacial maximum 21 18kyr and the holocene altithermal 8 6kyr abstract the pash database has been assembling palaeoclimatic data from the southern hemisphere for a number of years the southern african sector now contains more than 100 records spanning the last 200 000 years a number of these relate to the last glacial maximum and holocene altithermal which represent the two most recent extremes in global temperatures syntheses of these records have permitted the preparation of preliminary palaeoenvironmental maps for the two intervals the results provide insights into probable changes in atmospheric circulation as temperatures across the subcontinent rose by 6 7 c these changes are in agreement with a present day model which has been developed to explain short term variations in southern african climate the results presented here should assist in calibrating models developed to predict future climate change

middle to late pleistocene vegetation and climate change in subtropical southern east africa in this study we investigate pleistocene vegetation and climate change in southern east africa by examining plant leaf waxes in a marine sediment core that receives terrestrial runoff from the limpopo river the plant leaf wax records are compared to a multi proxy sea surface temperature sst record and pollen assemblage data from the same site we find that indian ocean sst variability driven by high latitude obliquity exerted a strong control on the vegetation of southern east africa during the past 800 000 yr interglacial periods were characterized by relatively wetter and warmer conditions increased contributions of c3 vegetation and higher sst whereas glacial periods were marked by cooler and arid conditions increased contributions of c4 vegetation and lower sst we find that marine isotope stages mis 5e 11c 15e and 7a 7c are strongly expressed in the plant leaf wax records but mis 7e is absent while mis 9 is rather weak our plant leaf wax records also record the climate transition associated with the mid brunhes event mbe suggesting that the pre mbe interval 430 800 ka was characterized by higher inputs from grasses in comparison to relatively higher inputs from trees in the post mbe interval 430 to 0 ka differences in vegetation and sst of southern east africa between the pre and post mbe intervals appear to be related to shifts in the location of the subtropical front comparison with vegetation records from tropical east africa indicates that the vegetation of southern east africa while exhibiting glacial interglacial variability and notable differences between the pre and post mbe portions of the record likely did not experience such dramatic extremes as occurred to the north at lake malawi

lithic geochemistry of the claggett marine cyclothem in south central saskatchewan sediments of the lea park formation in south central saskatchewan were deposited in the claggett sea during the late cretaceous campanian claggett marine cycle rocks of the lea park formation have remained virtually unaffected by diagenetic alteration hence variations in mineralogical and chemical compositions result primarily from changes in the source of detritus quartz feldspar discrete illite kaolinite and chlorite were derived from weathering of the western highlands whereas illite smectite i s the dominant clay phase originated from volcanic ash changes in the proportions of these minerals suggest a large scale volcanic episode during deposition of the lea park sediments an episode that affected not only the detritus delivered to the seaway but also the chemical and isotopic compositions of the sea water itself 13c values of organic matter increase with little change in the quantity of organic carbon preserved through both the transgressive and regressive phases of the claggett cy

the cretaceous tertiary transition the fossil sequences from cores across the cretaceous tertiary boundary show a range of transition times and transition time intervals depending on the fossil indicators and the location of the site these variations together with the pattern of iridium distribution with depth at some sites differences in total amounts of iridium variations in noble metal abundances normalized to extraterrestrial concentrations the depositional effects that might be expected in a reducing environment and the clay mineralogy of the boundary layer clays put into question the interpretation that an extraterrestrial event was the cause of the faunal changes and the iridium anomaly in the vicinity of the cretaceous tertiary transition it seems more likely that an explanation for the changes during the transition will come from continued examination of the great variety of terrestrial events that took place at that time including extensive volcanism major regression of the sea from the land geochemical changes and paleoclimatic and paleoceanographic changes

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

relationship between antarctic sea ice and southwest african climate during the late quaternary here we compare late quaternary southwest african climate records from the west coast of southern africa published winter rainfall and trade wind intensity records from a core off the coast of namibia to records of antarctic sea ice extent this comparison reveals coherent changes between antarctic sea ice extent and the southwest african winter rain region since 45 k y b p with enhanced winter rainfall and trade wind vigor during periods of increased sea ice presence we propose an oceanic and atmospheric coupling between antarctic sea ice and the winter rainfall zone of southwest africa that may lead to increased desertification in the region if global warming persists

pendant bioconstructions cemented by microbial carbonate in submerged marine caves holocene se sicily abstract unusual pendant bioconstructions occur within two submerged caves in the plemmirio marine protected area south of syracuse se sicily these cm to dm sized bioconstructions project downward from the cave roofs the main framework builders are serpulids belonging to the genera protula semivermilia and josephella encrusting bryozoans corals hydrozoans and sponges are subordinately present whereas bivalves and brachiopods are overall rare these faunal associations are characteristic of the studied caves but only in some places they form small bioconstructions that are cemented by microbial carbonates made up by autochthonous peloidal to clotted peloidal and aphanitic micrite the autochthonous micrite stabilizes the pendant bioconstructions herein referred to as biostalactites the microbial carbonate reveals high contents of bacterial lipid biomarkers among the most abundant compounds are mono o alkyl glycerol ethers mages and branched fatty acids 10 me c16 0 iso and anteiso c15 0 and c17 0 interpreted as biomarkers of sulfate reducing bacteria other compounds preserved in the autochthonous carbonates include lipids derived from marine zoo and phytoplankton brassicasterol dinosterol and monounsaturated short chain fatty acids unspecified marine bacteria saturated and monounsaturated short chain fatty acids and land plants long chain fatty acids long chain alcohols stigmasterol sitosterol and campesterol the observed lipid biomarker signatures are remarkably similar to those of post glacial reefal microbialites where microbialite formation in cavities of the coral framework was also mediated by sulfate reducing bacteria in the submerged caves of plemmirio marine protected area serpulid colonies apparently occur preferentially where freshwater is seeping through crevices in the limestone the consequent nutrification is believed to favor serpulid aggregation and the growth of other skeletal i e bryozoans and corals and soft bodied organisms i e sponges and ascidiae the resultant accumulation of biomass and its taphonomy provide niches for sulfate reducing bacteria which induce carbonate precipitation cementing and stabilizing the biostalactites the finding of pendant cemented bioconstructions in the mazzere and granchi caves of the plemmirio marine protected area reveals that sulfate reducing bacteria are involved in microbialite formation in various cryptic environments the formation of such peloidal to clotted peloidal microcrystalline carbonates in cryptic ecosystems is a significant factor for the stabilization of different kinds of bioconstructions spanning from small biostalactites to large reefs

glacial interglacial environmental changes inferred from molecular and compound specific δ13c analyses of sediments from sacred lake mt kenya abstract molecular stratigraphic analyses including lipid distributions and compound specific 13c measurements have been performed at 15 levels in a sediment core from sacred lake mt kenya a high altitude 2350 m a s l freshwater lake with a record extending from the last glacial 40 000 cal yr bp through the present interglacial terrestrial and aquatic organic matter sources were independently assessed using source specific biomarkers 13c values of long chain n alkyl lipids from terrestrial higher plants exhibit large glacial to interglacial shifts those from the last glacial maximum lgm 20 to 18 indicate a terrestrial vegetation dominated by c4 grasses or sedges whereas those from the early holocene 34 to 27 reflect recolonization of the catchment area by c3 plants consistent with a rapid rise in the upper treeline specific algal biomarkers including five unsaturated hydrocarbons of novel structure ascribed to the microalga botryococcus braunii were abundant as confirmed by scanning electronic microscopy sem an extreme 13c shift of over 25 is displayed by the algal biomarkers an elevated value of 5 1 at the last glacial maximum lgm contrasting with a minimum value of 30 3 at the beginning of the holocene a major change in the molecular distributions of the algal biomarkers parallels this large 13c shift with acyclic isoprenoid hydrocarbons dominating the last glacial and cyclic isoprenoid hydrocarbons the holocene the low atmospheric partial pressure of co2 pco2 at the lgm would favour photosynthetic organisms possessing co2 concentrating mechanisms including terrestrial c4 grasses and freshwater green algae hence glacial interglacial changes in pco2 and in the co2 o2 ratio in particular had a significant impact on both terrestrial and aquatic ecosystems on mt kenya in addition to the effects of climate and local environmental factors

variability of the western mediterranean sea surface temperature during the last 25 000 years and its connection with the northern hemisphere climatic changes sea surface temperature sst profiles over the last 25 kyr derived from alkenone measurements are studied in four cores from a w e latitudinal transect encompassing the gulf of cadiz atlantic ocean the alboran sea and the southern tyrrhenian sea western mediterranean the results document the sensitivity of the mediterranean region to the short climatic changes of the north atlantic ocean particularly those involving the latitudinal position of the polar front the amplitude of the sst oscillations increases toward the tyrrhenian sea indicating an amplification effect of the atlantic signal by the climatic regime of the mediterranean region all studied cores show a shorter cooling phase 700 years for the younger dryas yd than that observed in the north atlantic region 1200 years this time diachroneity is related to an intra yd climatic change documented in the european continent minor oscillations in the southward displacement of the north atlantic polar front may also have driven this early warming in the studied area during the holocene a regional diachroneity propagating west to east is observed for the sst maxima 11 5 10 2 kyr b p in the gulf of cadiz 10 9 kyr b p in the alboran sea and 8 9 8 4 kyr b p in the thyrrenian sea a general cooling trend from these sst maxima to present day is observed during this stage which is marked by short cooling oscillations with a periodicity of 730 40 years and its harmonics

patterns of damage in igneous and sedimentary rocks under conditions simulating sea salt weathering a saline spray artificial ageing test was used to simulate the effects produced in granites and sedimentary rocks calcarenites micrites and breccia under conditions in coastal environments three main points were addressed in this study the durability of the different kinds of rock to salt decay the resulting weathering forms and the rock properties involved in the weathering processes for this mineralogical and textural characterization of each of the different rocks was carried out before and after the test the soluble salt content at different depths from the exposed surfaces was also determined two different weathering mechanisms were observed in the granite and calcareous rocks physical processes were involved in the weathering of granite samples whereas dissolution of calcite was also involved in the deterioration of the calcareous rocks we also showed that microstructural characteristics e g pore size distribution play a key role in salt damage because of their influence on saline solution transport and on the pressures developed within rocks during crystallization copyright 2003 john wiley sons ltd

climatic conditions in southern africa since the last glacial maximum inferred from pollen analysis abstract a review of late quaternary palaeoclimatic data derived from several pollen sequences between ca 22 and 34 s in southern africa shows a degree of similarity in temperature and moisture variations between the various site pollen data from sites such as wonderkrater and rietvlei transvaal tate vondo venda elim orange free state equus cave southern kalahari and boomplaas cape province suggest relative dryness during the last glacial maximum wet conditions during the late glacial and dry conditions during the early holocene ca 8000 yr b p followed by progressively moister conditions peaking soon after the development of a temperature optimum ca 6500 yr b p problems with radiocarbon dating of polleniferous spring deposits however prevent precise correlations of especially late pleistocene sequences different seasonal patterns in the late glacial and early holocene may explain palaeobotanical data and are partly compatible with simulations of past climates of kutzbach and guetter 1986

clay mineralogy of the cretaceous tertiary boundary clay analyses of the clay mineralogy of samples from the cretaceous tertiary boundary layer at four localities show that the boundary clay is neither mineralogically exotic nor distinct from locally derived clays above and below the boundary the significant ejecta component in the clay that is predicted by the asteroid impact scenario was not detected

sedimentary k ar signatures in clay fractions from mesozoic marine shelf environments in israel the k ar system in clay fractions from shallow marine carbonate shelf environments was investigated on silicate fractions clay minerals feldspar separated from 20 lower jurassic to upper cretaceous sedimentary rocks deposited in the southern tethys ocean the range of lithologies investigated included dolomite and chalk ir insoluble residue 90 the results show that k bearing clay fractions often have k ar ages similar to the suggested age of deposition which means either supply of land derived authigenic k bearing clays or synsedimentary diagenetic authigenesis or both this k ar synsedimentary signal is recorded in clay fractions from the whole range of studied lithologies and stratigraphic units among the clay minerals the synsedimentary k ar signature was recorded and retained in illite smectite of the 10 um fractions the k ar ages reflect the contribution of detrital mica and feldspar which accompanies the kaolinite dominated samples the overall results differ considerably from k ar age patterns observed in deep sea sediments a difference which may be connected with the occurrence of brines in these shelf deposits the findings indicate the potential in the k ar dating of fine ir fractions of marine shelf sediments in terms of geochronological stratigraphic and palaeogeographical aspects as well as in the petrology of clay minerals themselves

a 300 kyr record of aridity and wind strength in southwestern africa inferences from grain size distributions of sediments on walvis ridge se atlantic abstract the terrigenous fraction of sediments recovered from walvis ridge se atlantic ocean reveals a history of southwestern african climate of the last 300 kyr end member modelling of a data set of grain size distributions n 428 results in three end members the two coarsest end members are interpreted as eolian dust the third end member as hemipelagic mud the ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the se trade winds trade winds were intensified during glacials compared to interglacials changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern african aridity late quaternary southwestern african climate was relatively arid during the interglacial stages and relatively humid during the glacial stages owing to meridional shifts in the atmospheric circulation system during glacials the polar front shifted equatorward resulting in a northward displacement of the zone of westerlies causing increased rainfall in southwestern africa the equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient leading to enhanced atmospheric circulation and increased trade wind intensity

oxygen and hydrogen isotope geochemistry of cretaceous bentonites and shales from the disturbed belt montana the mineralogy o18 and d of the 0 1 m fraction of 22 cretaceous bentonites and the mineralogy and o18 of the 0 1 m fraction of 14 adjacent shales collected from outcrops in the sweetgrass arch and disturbed belt montana have been determined mixed layer illite smectite i s is the dominant mineral in the bulk bentonite and usually the only mineral in the 0 1 m fraction i s is also the major clay mineral in the shales the diagenetic grade in bentonite is qualitatively given by the percentage of illite layers in i s which varies from 2 to 25 sweetgrass arch to as high as 95 disturbed belt o18 of 0 1 m bentonite generally decreases from about 20 to about 13 with increasing diagenetic grade on a plot of d versus o18 data for the 0 1 m bentonite define a field that generally parallels but falls on the meteoric water line side of the smectite water line savin and epstein 1970 o18 of bulk bentonite is 1 to 3 more negative than the o18 of the 0 1 m fraction due to the presence of volcanic quartz and feldspar o18 of several size fractions of clay sized quartz separated from the bentonite varies from 11 to 24 and in a given bentonite generally increases with decreasing grain size among the different bentonites the o18 range of the different grain sizes decreases as the percentage of illite layers in the coexisting i s increases the o18 of 0 1 0 5 m shale quartz is generally 1 to 4 more positive than clay sized quartz from an adjacent bentonite and the o18 of 0 1 m i s concentrate of shales is generally 1 to 4 more negative than the 0 1 m i s from an adjacent bentonite isotopic temperatures interpreted to be maximum burial temperatures range between about 160 c shale to about 250 c bentonite the isotopic data can be interpreted using the stages 1 1 deposition of volcanic glassy ash containing some quartz and feldspar 2 2 devitrification into mostly 100 expandable smectite with a o18 of about 20 and d of 60 to 80 3 3 tectonic burial beneath thrust sheets in the disturbed belt region which induced elevated temperatures that allowed oxygen and hydrogen isotope reequilibration as the percentage of illite layers in i s increased and diagenetic quartz formed and 4 4 exhumation of the strata with preservation of o18o16 and d h attained during burial

intracrystalline boron isotope partitioning in illite smectite testing the geothermometer intracrystalline b isotope differences of 40 are observed between the interlayer and tetrahedral crystallographic sites of interstratified illite smectite i s we tested the hypothesis that partitioning of b isotopes between these sites could provide a low temperature single mineral geothermometer samples studied include a metabentonite transected by a dike in the cretaceous pierre shale 200 500 c buried mudstones from the eocene wilcox formation 60 125 c and i s products from hydrothermal experiments 300 350 c different reaction kinetics are represented by these different sample sets therefore results test the equilibrium partitioning of b in the interlayer vs tetrahedral sites in all samples interlayer 11 b values are isotopically heavier than the tetrahedral 11 b because 11 b prefers trigonal coordination we infer that b oh 3 dominates the interlayer sites within each sample set the intracrystalline differences are greatest 20 40 in the most expanded i s i e smectite rich and approach 0 as illitization increases there is good correlation r 0 84 between the interlayer 11 b calculated by mass balance and water 11 b indicated by the established maximum temperature of each sample these results suggest that the interlayer sites of i s preserve the b isotopic composition of water at the temperature that produced the authigenic illite direct measurements of interlayer 11 b equilibrated with water of known 11 b are needed to refine the relationship with temperature but the existing data indicate the following temperature dependent relationship t c 11 b tetrahedral 11 b interlayer 30 0 05