applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

strong climate coupling of terrestrial and marine environments in the miocene of northwest europe a palynological and organic geochemical record from a shallow marine paleoenvironmental setting in se netherlands documents the coupled marine and terrestrial climate evolution from the late burdigalian 17 ma through the early zanclean 4 5 ma proxy climate records show several coeval variations in both relative sea surface deduced from percent cool dinocysts and terrestrial subtropical vs cool temperate pollen temperature indices the terrestrial climatic trend is confirmed by a quantitative reconstruction of annual mean air temperature based on the distribution of fossil branched glycerol dialkyl glycerol tetraethers showing a cooling from 27 c to 14 c between 17 and 5 ma punctuated by short term variations decreases in sea surface temperature broadly correlate to inferred third order sea level variations and correspond to isotope glacial events mi 3 through mi 7 an additional strong sst decrease occurs around 8 4 ma coincident with a strong reduction and regional disappearance of subtropical pollen types this cooling phase seems associated with lowered sea levels but it has not yet been described from the deep sea 18o record 2009 elsevier b v

southern african topography and erosion history plumes or plate tectonics the physiography of southern africa comprises a narrow coastal plain separated from an inland plateau by a horseshoe shaped escarpment the interior of the inland plateau is a sedimentary basin the drainage network of southern africa is characterized by three river divides broadly parallel to the coastline these features contrast strongly with the broad dome and radial drainage patterns predicted by models which ascribe the physiography of southern africa to uplift over a deep mantle plume the drainage divides are interpreted as axes of epeirogenic uplift the ages of these axes which young from the margin to the interior correlate closely with major reorganizations of spreading regimes in the oceanic ridges surrounding southern africa suggesting an origin from stresses related to plate motion successive epeirogenic uplifts of southern africa on the axes forming the major river divides initiated cyclic episodes of denudation which are coeval with erosion surfaces recognized elsewhere across africa

the tectonic evolution of the fennoscandian border zone in denmark abstract the fennoscandian border zone is a complex tectonic zone defining the border between the stable fennoscandian baltic shield and the metastable danish basin and polish trough it forms the northwestern part of the tornquist teisseyre lineament one of the major european tectonic sutures intricate tectonic movements took place within the fennoscandian border zone from early paleozoic to recent time it is postulated that its evolution was dominated during the early palaeozoic by tensional tectonics and during the late paleozoic by dextral wrench movements the latter led to the development of curvilinear faults and the subsidence of pull apart basins transtensional stresses governing the triassic to early cretaceous evolution of the fennoscandian border zone induced the differential subsidence of rift basins during the late cretaceous and early cenozoic dextral transpressional stresses induced the partial inversion of mesozoic basins associated with the fennoscandian border zone this is reflected by the uplift of a major anticlinorium over which cretaceous strata became progressively truncated whilst adjacent areas developed into late cretaceous early tertiary depocentres basin inversion diminishes to the northwest along the fennoscandian border zone and disappears in the skagerrak area

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

quantifying the role of geographic change in cenozoic ocean heat transport using uncoupled atmosphere and ocean models abstract a series of five cenozoic atmospheric general circulation model agcm experiments has been performed using a new set of paleogeographic reconstructions for 55 40 33 20 and 14 ma the five continental reconstructions incorporate the tectonic evolution of early eocene to middle miocene continental positions and topography with all other model boundary conditions and forcings held constant the series of agcm experiments captures a

tertiary sea level movements around southern africa sedimentological micropaleontological and seismic profiling data elucidate the history of tertiary sea level movements around southern africa these new data show that landward movement of the sea began in early paleocene time and continued into the early eocene the sea probably reached its maximum paleocene height during the early eocene and is today represented by outcrops up to at least 204 m and probably as high as 360 m above modern sea level a brief regressive pulse occurred during the middle eocene with renewed transgression in the late eocene a major regression followed probably spanning all of oligocene and early miocene times this regression exposed much of the continental shelf and is clearly represented on seismic reflection profiles by a widespread unconformity the major neogene transgression began in the middle miocene and probably reached its greatest extent in the late miocene or early pliocene the overall middle miocene to early pliocene transgression was interrupted by a brie

coupled thermal and hydrological evolution of tropical africa over the last deglaciation we analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the congo river outflow and the results enabled us to reconstruct large scale continental temperature changes in tropical africa that span the past 25 000 years tropical african temperatures gradually increased from 21 to 25 c over the last deglaciation which is a larger warming than estimated for the tropical atlantic ocean a direct comparison with sea surface temperature estimates from the same core revealed that the land sea temperature difference was through the thermal pressure gradient an important control on central african precipitation patterns

middle to late miocene oxygen isotope stratigraphy of odp site 1085 se atlantic new constrains on miocene climate variability and sea level fluctuations abstract the middle miocene 18o increase represents a fundamental change in earth s climate system due to a major expansion and permanent establishment of the east antarctic ice sheet accompanied by some effect of deepwater cooling the long term cooling trend in the middle to late miocene was superimposed by several punctuated periods of glaciations mi events characterized by oxygen isotopic shifts that have been related to the waxing and waning of the antarctic ice sheet and bottom water cooling here we present a high resolution benthic stable oxygen isotope record from odp site 1085 located at the southwestern african continental margin that provides a detailed chronology for the middle to late miocene 13 9 7 3 ma climate transition in the eastern south atlantic a composite fe intensity record obtained by xrf core scanning odp sites 1085 and 1087 was used to construct an astronomically calibrated chronology based on orbital tuning the oxygen isotope data exhibit four distinct 18o excursions which have astronomical ages of 13 8 13 2 11 7 and 10 4 ma and correspond to the mi3 mi4 mi5 and mi6 events a global climate record was extracted from the oxygen isotopic composition both long and short term variabilities in the climate record are discussed in terms of sea level and deep water temperature changes the oxygen isotope data support a causal link between sequence boundaries traced from the shelf and glacioeustatic changes due to ice sheet growth spectral analysis of the benthic 18o record shows strong power in the 400 kyr and 100 kyr bands documenting a paleoceanographic response to eccentricity modulated variations in precession a spectral peak around 180 kyr might be related to the asymmetry of the obliquity cycle indicating that the response of the dominantly unipolar antarctic ice sheet to obliquity induced variations probably controlled the middle to late miocene climate system maxima in the 18o record interpreted as glacial periods correspond to minima in 100 kyr eccentricity cycle and minima in the 174 kyr obliquity modulation strong middle to late miocene glacial events are associated with 400 kyr eccentricity minima and obliquity modulation minima thus fluctuations in the amplitude of obliquity and eccentricity seem to be the driving force for the middle to late miocene climate variability

geochemistry of campanian maastrichtian brachiopods from the rordal 1 core denmark differential responses to environmental change and diagenesis abstract past marine environmental conditions can be reconstructed from geochemical signatures of both benthic and planktic organisms and particularly brachiopods have been extensively used for this purpose however it is seldom possible to investigate the links between environmental conditions and shell geochemistry in monospecific records over extended periods of time here we present geochemical data from the 100 m thick brachiopod rich upper campanian upper maastrichtian chalk 73 8 68 6 ma of the rordal 1 drill core northern denmark two species that lived attached to small substrate argyrotheca bronnii roemer and gisilina jasmundi steinich and one secondarily free living species magas chitoniformis schlotheim have been studied for element concentrations as well as c and o isotope signatures each species has a unique chemical signature with m chitoniformis showing lowest mg and mn concentrations a bronnii the highest mn concentrations and g jasmundi the highest sr concentrations all three species display decreasing mg ca ratios throughout the studied interval and distinct mn enrichments in the campanian maastrichtian boundary cmb interval in the campanian part of the succession the three species are slightly enriched in 13 c median 13 c values of 0 0 to 0 5 and 18 o median 18 o values of 0 3 to 0 6 with respect to coeval chalk in the course of the maastrichtian the two attached species acquire progressively lighter isotopic compositions with a bronnii reaching 13 c and 18 o values 1 0 lower than coeval chalk the secondarily free living species m chitoniformis on the other hand becomes isotopically heavier and reaches 13 c and 18 o enrichments of 1 0 at the top of the core the observed differences between the species illustrate species specific signatures of biomineralisation diagenesis and response to environmental change this geochemical complexity illustrates that a comprehensive geochemistry based picture of the late cretaceous chalk sea can only be painted using detailed multi species and multi proxy datasets

miocene fluvial systems and palynofloras at the southwestern tip of africa implications for regional and global fluctuations in climate and ecosystems abstract high amplitude climate fluctuations have been inferred from marine isotope data in the early neogene but few well documented terrestrial records exist from this era to gauge the effects of these high latitude events on continental climates and ecosystems the extensive three dimensional exposures of miocene fluvial and fluvio lacustrine sediments in the rondeberg clay pit near cape town provide a unique window on this era palaeomagnetic data suggests that the deposits accumulated over a period of ilex type euphorb type rhamnaceae and mesothermic podocarpus type palynofloras suggests a humid subtropical tropical climate however abundant charcoal charred in situ tree stumps overall poor preservation of organics evidence for upward drying lacustrine successions and an appreciable fynbos presence point to cyclical periods of drought we suggest that these climate fluctuations may have been influenced by the orbital pacing seen in the marine isotope record of the earlier miocene pointing to a high latitude link with mid latitude terrestrial climate patterns earlier studies of pollen spectra from the nearby slightly older noordhoek deposits show cyclical alternations from tropical to cooler climates and more recent biogeochemical work has shown dramatic coincident fluctuations in depositional temperature these vegetation changes were previously correlated with major global events embracing the entire neogene from the oligo miocene late oligocene to early miocene to the pliocene we offer a different interpretation suggesting that the deposits represent a much shorter time interval in the earlier miocene and that these climate fluctuations may have been influenced by orbital forcing evinced in the marine isotope record along the northern west coast the arrisdrift vertebrate fossil assemblage in early middle miocene terrace deposits of the orange river indicate a tropical climate but possibly less humid than in the south with more open vegetation patterns the presence of pedogenic calcretes and gypcretes in the deposits suggests periodic extremes of aridity not seen in south the current pronounced north aridity gradient from humid temperate to hyper arid may have had its inception in the earlier miocene

warm arctic continents during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum petm 55 5 ma is a geologically relatively brief episode of extreme warmth both deep and surface ocean temperatures increased by up to 5 c in equatorial waters and up to 8 c in mid and high latitude waters from the continents the annual mean air temperature response during the petm is still largely unknown mainly due to a lack of quantitative temperature proxies and sufficient suitable continuous high resolution records recently a new proxy for continental temperature reconstructions has been proposed based on the distribution of membrane lipids of bacteria in present day soils j w h weijers s schouten j c van den donker e c hopmans j s sinninghe damste 2007 environmental controls on bacterial tetraether membrane lipid distribution in soils geochimica et cosmochimica acta 71 703 713 and shown to reconstruct annual mean air temperature in this study we applied this new proxy in an attempt to reconstruct the air temperature in high latitude continental areas during the petm by analysis of a marine sedimentary sequence obtained from the lomonosov ridge in the central arctic ocean integrated ocean drilling program expedition 302 site 004 hole a the results indicate a warming of 8 c above background values of 17 c this warming is coincident with a similar rise in sea surface temperatures documented earlier our results thus further confirm the warm conditions in the arctic and point to a strongly reduced latitudinal temperature gradient during the petm 2007 elsevier b v all rights reserved

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

age and implications of the forest bed falkland islands southwest atlantic ocean evidence from fossil pollen and spores diverse pollen and spore assemblages microfloras are preserved in organic clays and lignites associated with fossil tree remains in the forest bed at present these microfloras provide the only reliable basis for determining the age composition structure and affinity of the forest bed community the bed is suggested to be middle miocene to early pliocene age range oligocene early pliocene based on the time distribution of a number of rare pollen types and the present day ecology of their nearest living relatives in central southern america and the southwest pacific the wet forest community whose remains form the forest bed was a form of broadleaf gymnosperm temperate rainforest in which dacrydium lagarostrobos and podocarpus are likely to have formed an overstorey above a closed canopy dominated by nothofagus nothofagus spp the latter subgenus is now endemic to uniformly wet regions in southern south america whilst two of the tall gymnosperms dacrydium lagarostrobos are now endemic to the southwest pacific region an extinct probable shrub sized conifer podosporites microsaccatus appears to have formed the ground cover ferns and fern allies were very rare in contrast to most living nothofagus gymnosperm communities fossil pollen and spore types produced by uncommon subcanopy tree shrub and fern species potentially provide a means for more accurately dating the deposit once their time of first occurrence and extinction at subantarctic latitudes in the southwest atlantic region is established nearest living equivalents given in parentheses clavatipollenites cf glarius hedyosmum thymelaepollis sp ovidia type and cyatheacidites annulatus lophosoria this will require palynostratigraphic analysis of late palaeogene neogene sediments recovered from basins surrounding the falkland islands for example from dsdp site 329 drilled on the maurice ewing bank at the eastern margin of the falkland plateau

the effects of geothermal heating on the ocean overturning circulation 1 we examine the response of an overturning circulation driven by differential thermal forcing along the top horizontal boundary to a small additional heat flux applied at the bottom horizontal boundary the system forms a simple thermally driven flow that provides insight into the ocean s meridional overturning circulation we conclude that the additional destabilising geothermal heat flux tends to promote a more vigorous full depth overturning having approximately 10 greater volume flux than with no bottom heating no significant change is observed in the vertical density structure in contrast the addition of a stabilising heat flux at the base leads to a shallow partial depth circulation the key diagnostic for the significance of the geothermal flux appears to be the ratio of the buoyancy flux supplied at the bottom to the residual buoyancy flux driving the downwelling plume through the base of the thermocline

climatic and sea level controls on late quaternary eolian activity on the agulhas plain south africa abstract located at the interface between the temperate westerly and sub tropical climate systems south africa s winter rainfall zone wrz is a key location in understanding late quaternary atmospheric circulation dynamics inactive eolian deposits in the wrz comprising pan fringing lunette and coastal dunes were investigated to establish their depositional ages and utility as paleoenvironmental indicators the resulting optical luminescence chronology reveals episodic lunette accretion at 60 000 45 000 yr 12 000 13 000 yr 2800 2600 yr 1200 yr and episodes of lunette and coastal dune accretion on the agulhas plain are temporally distinct reflecting differing fundamental controls on their activity comparisons to previously published data also reveal that the lunettes differ in age from more ancient coastal eolianites lunette deposition is asynchronous between locations reflecting the topographic and hydrological setting of the individual pans in near coastal settings with limited surface recharge lunette accretion appears to be at least partially controlled by sea level induced changes in groundwater levels those pans with more significant surface recharge particularly from fluvial systems may produce less ambiguous paleoenvironmental records with pan status more strongly reflecting regional hydrological conditions lunette orientation is indicative of strong westerly winds during both the pleistocene and holocene lunette accretion would have been promoted by reduced on shore moisture transport during the summer months enhancing rainfall seasonality such conditions would have been promoted by increased continentality as the agulhas bank was exposed during low sea level stands

the last interglacial sea level high stand on the southern cape coastline of south africa abstract the continental margin of southern south africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long term eustatic sea level changes we report a suite of optical luminescence ages and supplementary amino acid racemization data which provide paleosea level index points for three sites on this coastline deposits in the swartvlei and groot brak estuaries display tidal inlet facies overlain by shoreface or eolian facies contemporary facies relations suggest a probable high stand 6 0 8 5 m above modern sea level amsl at cape agulhas evidence of a past sea level high stand comprises a gravel beach ca 3 8 m amsl and an overlying sandy shoreface facies up to 7 5 m amsl osl ages between 138 7 ka and 118 7 ka confirm a last interglacial age for all marginal marine facies the high stand was followed by a sea level regression that was associated with the accumulation of eolian dunes dating to between 122 7 ka and 113 6 ka these data provide the first rigorous numerical age constraints for last interglacial sea level fluctuations in this region revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far field locations

constraints on the application of the mbt cbt palaeothermometer at high latitude environments svalbard norway abstract branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids of unknown bacteria that are ubiquitous in soil and peat two indices based on the distribution of these lipids in soils the cyclization of branched tetraethers cbt and the methylation of branched tetraethers mbt indices have been shown to correlate with soil ph and mean annual air temperature mat and soil ph respectively and can be used to reconstruct mat in palaeoenvironments to verify the extent to which branched gdgts in marine sediments reflect the distribution pattern on land and whether these proxies are applicable for palaeoclimate reconstruction in high latitude environments with a mat of

west coast dune plumes climate driven contrasts in dunefield morphogenesis along the western and southern south african coasts abstract this study examines two major late quaternary coastal dune systems situated in the southwestern most extremity of africa the false bay and duinefontyn dune plumes formed in close proximity but under contrasting oceanographic regimes warm agulhas and cold benguela oceanic current systems respectively the false bay and duinefontyn dune plumes have hitherto lacked the objective numerical chronology required to realize their full potential in unraveling the complex palaeo oceanographic and palaeoclimatic history of the region here we present a dual amino acid racemizationn aar and optically stimulated luminescence osl chronological framework from the extensive three dimensional exposures in sea cliffs at false bay three generations of dune deposition corresponding with orbitally forced climatic sea level cycles mis 7 mis 5 and holocene were resolved whereas the duinefontyn plume is dominated by mis 5 and holocene sedimentation at false bay and duinefontyn glacial periods are marked by the development of mature palaeosols confirming the link between glacio eustacy and dune deposition determined previously on the west and southern coasts of south africa along the west coast dune plumes typify dunefield morphology whereas shoreline parallel dune cordons are commonly developed on the southern coast these regional variations in dune system morphogenesis are largely controlled by contrasting wind and rainfall patterns the attenuated dimensions of the mis 5 plumes at false bay and duinefontyn may indicate a weakening of the south atlantic anticyclone during the last interglacial at false bay stone artifacts illustrate a human presence in the region during mis 7

late quaternary peat accumulation in southern africa abstract it is suggested that the accumulation of peat deposits and other organic sediment may be a clue to the timing of moister periods in the late quaternary climatic history of southern africa data presented from 26 sites across the sub continent point to two periods during which organic sedimentation commenced suggesting a moister late pleistocene and a period during the mid late holocene when conditions also became more conducive to peat formation owing to the confusing and conflicting nature of other palaeoenvironmental information organic sediment accumulation chronologies seem to provide additional insight into the environmental history of southern africa and the implications of this are discussed

global miocene tectonics and the modern world abstract an amazing congruence of seemingly unrelated diverse global events began in the middle and upper miocene and established our modern world two global orogenic belts were active mostly in the middle and upper miocene while backarc basins formed along the eastern margin of asia coincident with these events global temperatures cooled in both the ocean and atmosphere desertification occurred from central asia into and across most of northern africa and also in australia and in southern south america coincident with the expansion of the antarctic ice cap at 14 ma there was initial widespread deep sea erosion and changes in patterns of deep sea sedimentation muddy pelagic sedimentation increased six fold in the north and central atlantic and pacific oceans and global changes in circulation lead to more diatomites in the pacific and fewer in the atlantic by the end of the miocene most of the mediterranean sea had evaporated broadly coincident with these events many old large river systems were destroyed and new ones formed as much of the world s landscape changed collectively these global on shore tectonic and ocean atmospheric events provide the foundation for our modern world a mixture of new and rejuvenated orogenic belts and their far field effects distant epiorogenic uplift rain shadow deserts large alluvial aprons and distant deltas as inherited gondwanan landscapes persisted remote from plate boundaries thus at the end of the miocene much of the world s landscape except for that changed by pleistocene continental glaciation would be recognizable to us today we argue that all of these events had the same ultimate common cause an internal earth engine that drove plate motions in two broad ways first the opening and closing of seven key gateways to deep water oceanic currents radically altered global heat transfer and changed a lingering greenhouse to an icehouse world secondly these events were in part coincident with renewed heat flow in the african and pacific superplumes that energized global plate motions in the middle and upper miocene we hope this global synthesis will stimulate more research on the many global events of the miocene to understand better both our modern world and earlier global orogenies

laboratory simulation of the geothermal heating effects on ocean overturning circulation motivated by a desire to understand the geothermal heating effects on ocean circulation a large scale circulation generated and sustained by thermal forcing at the surface subject to a small amount of heating from the bottom boundary is investigated through laboratory experiments motivated by understanding the geothermal heating effects on ocean circulation despite its idealization our experiments demonstrate that the leading order effect of geothermal heating is to significantly enhance the abyssal overturning in agreement with the findings in ocean circulation models our experiments also demonstrate that geothermal heating cannot influence the poleward heat transport due to the strong stratification in the thermocline our study further reveals that the ratio of geothermal flux induced turbulent dissipation to the dissipation due to other energies is the key parameter determining the dynamical importance of geothermal heating this quantity explains why the impact of geothermal heating is sensitive to the deep stratification the diapycnal mixing and the amount of geothermal flux moreover it is found that this dissipation ratio may be used to understand results from different studies in a consistent way this article is protected by copyright all rights reserved

stratal geometries facies and sea floor erosion in upper cretaceous chalk normandy france unusual lenticular stratal geometries and facies of the upper cretaceous chalk of coastal haute normandie france are described and interpreted thirteen facies within these chalks are described and illustrated on the basis of field thin section and sem investigations nannofossil mudstones nannofossil hardgrounds echinoderm wackestones and packstones echinoderm hardgrounds bryozoan mudstones and wackestones bryozoan hardgrounds bryozoan packstones and wackestones inoceramid wackestones inoceramid hardgrounds sponge hardgrounds marly chalks conglomeratic chalks and debris flow chalks these facies occur within lenticular bedded structures with both concave up and concave down geometries which have been previously interpreted as megaripples mud mounds or tectonic structures detailed examination of the structures and the associated facies indicates that the concave up geometries were formed from submarine erosion and redeposition in nw se longitudinal channels the concave down geometries developed between adjacent channels assessment of the regional and temporal setting indicates that the erosion occurred in the armorican cornubian straits of the anglo paris basin during sea level lowstands within these straits channelling is preferentially developed on the positive south western block to the lillebonne fecamp cotentin fault

seismic stratigraphy and geological evolution of the cenozoic cool water eucla platform great australian bight seismic images of the continental margin in the western great australian bight reveal the internal anatomy of a long lived cenozoic cool water carbonate shelf the cenozoic succession is divisible into seven seismic sequences that reflect four depositional phases phase a paleocene middle eocene is a progradational siliciclastic wedge deposited in a depositional sag and represents lowstand and transgressive sedimentation phase b middle eocene earliest middle miocene contains cool water ramp carbonates with biogenic mounds eocene oligocene overlain by a warm water flat topped platform rimmed by the early middle miocene little barrier reef coeval deep water carbonate deposition formed a multi lobed sediment apron this phase was terminated by gentle uplift and tilting throughout southern australia in the late middle miocene phase c late miocene early pliocene represents cool water lowstand wedge and ramp deposition and contains numerous biogenic mounds in the youngest sequence this phase is terminated by an unconformity attributed to marine erosion phase d pliocene quaternary is a thick succession of cool water carbonates with spectacular clinoform ramp geometry that forms most of the modern outer shelf and contains large deep water biogenic mounds this platform the first large cool water carbonate shelf imaged by high quality seismic reflection data demonstrates the interaction between regional tectonic and local and global paleo oceanographic processes as australia drifted northward during the cenozoic the great australian bight moved from high to middle latitudes and the regional oceanographic regime remained cool water largely because of coeval development of the antarctic circumpolar current in the evolving southern ocean short episodes of warm water deposition probably reflect incursions of a proto leeuwin current from the indian ocean whereas growth of the miocene coral algal little barrier reef resulted from a short term global increase in sea surface temperatures this platform dominated by stacked carbonate ramps is most similar to the west florida shelf but contains many more biogenic mounds the western great australian bight carbonate platform is an excellent modern analog for the mesoscale structure of cool water platforms in the older geologic record

last interglacial fossil elephant trackways dated by osl aar in coastal aeolianites still bay south africa abstract the impressive pleistocene coastal aeolianite exposures in sea cliffs east of still bay on the west southern coast of south africa host a rich archive of fossil mammalian trackways including the african elephant loxodonta africana neither the ichnofossils nor their host sediments have been described in any detail and chronologies remained uncertain this paper presents a new optically stimulated luminescence osl and amino acid racemisation aar chronology the first joint application of osl aar dating in south africa this provides a temporal framework for assessing the palaeoenvironmental significance of dune sedimentation patterns pedogenesis and ichnology the pleistocene aeolianite exposures at still bay represent the recently eroded remnants of a dune cordon mainly built by coalesced parabolic dune systems sedimentary facies are dominated by large scale planar cross stratification formed by foreset progradation in the nose and trailing arms of the dunes and low angle bedding chiefly representing sedimentation in low relief interdune terrain the main dune building wind regime was westerly associated with cyclonic polar frontal systems as at the present time the osl and aar dating demonstrate ages ranging from mis 5e to 5b and termination of pleistocene aeolian sedimentation at 90 ka the pleistocene aeolianite is separated from the overlying holocene dunes dated to 8 ka by a major hiatus recorded by a horizon of intense pedogenesis elephant footprints were seen in profile as casts on the underside of beds and as natural impressions the taphonomic processes controlling the morphology and preservation of these unique ichnofossils were found to be complex the presence of loxodonta africana at still bay represents the southernmost occurrence of this species recorded to date and possibly a closer proximity of woodland during mis 5 this and other observations may indicate a higher moisture regime than at present there is no available evidence that the elephants were predated by contemporary middle stone age people

convection driven by differential heating at a horizontal boundary we report laboratory and numerical experiments with the convective circulation that develops in a long channel driven by heating and cooling through opposite halves of the horizontal base the problem is similar to that posed by stommel proc natl acad sci vol 48 1962 p 766 and rossby deep sea res vol 12 1965 p 9 tellus vol 50 1998 p 242 where flow forced by a linear temperature variation along the ocean surface or the base of a tank presented a demonstration of the smallness of sinking regions in the meridional overturning circulation of the oceans in contrast to the previous experiments we use small aspect ratio larger rayleigh numbers piecewise uniform boundary conditions and an imposed input heat flux the flow is characterized by a vigorous overturning circulation cell filling the box length and depth a stable thermocline forms above the cooled base and is advected over the heated part of the base where it is eroded from below by small scale three dimensional convection forming a convective mixed layer at the endwall the convective mixing is overshadowed by a narrow but turbulent plume rising through the full depth of the box the return flow along the top of the box is turbulent with large slowly migrating eddies and occupies approximately a third of the total depth theoretical scaling laws give temperature differences thermocline thickness and velocities that are in good agreement with the experimental data and two dimensional numerical solutions the measured and computed density structure is largely similar to the thermocline and abyssal stratification in the oceans

the zambezi delta mozambique channel east africa high resolution dating combining bio orbital and seismic stratigraphies to determine climate palaeoprecipitation and tectonic controls on a passive margin abstract the zambezi delta draining the southern african plateau and the southern part of the east african rift is one of a the largest delta of africa with a long lasting history starting during early cretaceous with more than 12 km of sediments deposited the zambezi delta is therefore a unique archive of the past topographic evolution of southern and eastern africa and their related deformations but also of the climate changes global and regional consequences of local topographic growths understanding this archive supposes to get a high resolution dating of the sediments our two objectives are here 1 to construct an age model of the zambezi cenozoic delta using a combination of biostratigraphy orbital stratigraphy and sequence stratigraphy and 2 to determine the palaeoprecipitation variations of the zambezi catchment from the oligocene to present day in a known tectonic framework the neogene sequences were dated at high resolution assuming that the third order sequences are of eustatic origin and record long term eccentricity cycles the sequences were correlated in ages on the calculated earth orbital solutions of laskar for the time intervals provided by the biostratigraphy nannofossils planktonic foraminifers the palaeoprecipitation record was based on the definition of a humidity index based on pollen analysis and associated botanical associations the late oligocene was a quite wet period getting dryer in the uppermost chattian the base tortonian 11 ma was a humid period the messinian was a dry period with a slight increase of the humidity during the zanclean and a sharp increase around the zanclean piacenzian boundary the zambezi delta has recorded the uplifts of the southern african plateau around 85 ma and around 25 ma and those of the southward migration of the east african rift since 5 5 ma

the late miocene onset of high productivity in the benguela current upwelling system as part of a global pattern abstract we have examined the history of the elevated primary productivity associated with the benguela current upwelling system off southwest africa using sediments from 7 5 to 4 8 ma at ocean drilling program site 1085 in the middle cape basin sedimentation rates are low until 6 9 ma low accumulation rates of benthic foraminifers and organic carbon indicate that biological productivity was also low paleoproductivity dramatically increased at 6 7 6 5 ma and was highly variable until 4 8 ma with productivity maxima during cooler periods the presence of radiolarian opal only between 5 8 and 5 2 ma suggests an interlude of silica rich intermediate water in the cape basin the onset of heightened productivity under the benguela current is mirrored by similar increases reported between 6 9 and 6 7 ma in the tropical eastern pacific the western and northern pacific and the indian ocean the similarity between the patterns at site 1085 and in the pacific and indian oceans suggests that the dramatic productivity increase off southwest africa is part of a global response to paleoceanographic changes

massive volcanism at the permian triassic boundary and its impact on the isotopic composition of the ocean and atmosphere abstract bulk carbonate and conodonts from three permian triassic p t boundary sections at guryul ravine kashmir abadeh central iran and pufels bula bulla italy were investigated for 13 c and 18 o carbon isotope data highlight environmental changes across the p t boundary and show the following features 1 a gradual decrease of 4 to more than 7 starting in the late permian changhsingian c bachmanni zone with two superimposed transient positive excursions in the c meishanensis h praeparvus and the m ultima s mostleri zones 2 two 13 c minima the first at the p t boundary and a higher occasionally double minimum in the lower i isarcica zone it is unlikely that the short lived phenomena such as a breakdown in biological productivity due to catastrophic mass extinction a sudden release of oceanic methane hydrates or meteorite impact s could have been the main control on the latest permian carbon isotope curve because of its prolonged 0 5 ma duration gradual decrease and the existence of a 1 positive shift at the main extinction horizon the p t boundary 13 c trend matches in time and magnitude the eruption of the siberian traps and other contemporaneous volcanism suggesting that volcanogenic effects such as outgassed co 2 from volcanism and even more thermal metamorphism of organic rich sediments as the likely cause of the negative trend

palynological and lithological evidence for the miocene palaeoenvironment in the saldanha region south africa abstract palynological and lithological studies were carried out on a section of clays of the elandsfontyn formation in the langebaanweg area the pollen assemblages suggest a middle miocene age for these clays which is supported by fossil faunal evidence in the overlying gravel member of the late miocene saldanha formation the pollen sequence indicates the retrogressive succession of subtropical tropical gallery forest to dominant palm vegetation and finally to marsh these changes are clearly related to the lithological evidence for the progressive lateral northward migration of the palaeo berg river it is possible that the middle miocene global high sea level cycle may have influenced these palaeoenvironmental changes

regional velocity depth anomalies north sea chalk a record of overpressure and neogene uplift and erosion a normal velocity depth trend for the upper cretaceous danian chalk group is determined by identifying interval velocity data that represent maximum burial in areas unaffected by overpressuring these data are derived from 845 wells throughout the north sea basin data from pelagic carbonate deposits on a stable plateau constrain the trend for shallow depths positive velocity anomalies relative to the trend are mapped along the western and eastern margins of the north sea basin and reflect regional neogene uplift and erosion of up to 1 km along the present day limit of the chalk a hiatus at the base of the quaternary increases in magnitude away from the basin center where a complete cenozoic succession is found this hiatus is consistent in size with the missing section estimated from chalk velocities when allowance is made for the quaternary reburial of the chalk negative velocity anomalies in the central and southern parts of the basin outline an area within which overpressures in the chalk exceed 10 mpa equivalent to a burial anomaly greater than 1 km relative to the normal trend the chalk pressure system is primarily dependent on overburden properties because retention of overpressure generated by the load of the upper overburden depends on the thickness and sealing quality of the lower overburden therefore the chalk is considered to represent a regional aquitard and the hydrodynamic model of long distance migration within the chalk is rejected the neogene uplift and erosion of the margins of the north sea basin and the rapid late cenozoic subsidence of its center fit into a pattern of late cenozoic vertical movements around the north atlantic

contourite drift types and their distribution in the north and south atlantic ocean basins abstract patterns of sediment accumulation under the control of deep bottom currents depend on interacting factors intensity of the regional deep circulation morphology of the sea floor coriolis effects abundance of terrigenous and biogenic supplies subsequent turbidity of deep nepheloid layers and depth of the ccd based on many examples of bottom current deposits from the atlantic and from other oceans we recognise three major types of contourite accumulation 1 giant elongate drifts 2 contourite sheets and 3 channel related drifts they generally occur in distinct topographic settings and show different geometries facies and rates of deposition in the north atlantic strong bottom circulation an open basin system and high sediment supply have led to the construction of large elongate contourite drifts which have striking relief 200 1000 m above the surrounding sea floor and are composed of muddy contourites rich in calcareous pelagic material in the south atlantic strong bottom currents are often trapped in gyre like circulation patterns around topographically closed basins or are accelerated through deep narrow connecting passages the resulting deposits are mainly extensive contourite sheets covered by fields of large sediment waves and channel related drifts including contourite fans constructed at the downstream exit of deep passages

the cretaceous palaeogene boundary at stevns klint denmark inversion tectonics or sea floor topography the cretaceous palaeogene boundary interval is exposed over 12 km in the coastal cliff stevns klint denmark an important lowermost danian hardground has been interpreted as an originally horizontal marine abrasion surface its present elevation varies from a few metres below to about 35 m above sea level this relief has traditionally been considered as resulting from late or post danian laramide folding new seismic profiles offshore stevns klint show however that the base chalk reflector is not folded is remarkably planar and has a gentle northward dip thus the folding hypothesis cannot be upheld seismic stratigraphic analysis of the chalk group necessitates a fundamental revision of general ideas of chalk deposition a highly irregular sea floor topography was formed at many levels and includes broad valleys ridges channels drifts and mounds a system of major wnw ese oriented valleys and ridges can be traced into the succession exposed in stevns klint and further inland where it corresponds to the relief of the cretaceous palaeogene boundary the marked topographic elements of the chalk sea floor are elongate with a wnw orientation roughly parallel to the axis of the danish basin and to the sorgenfrei tornquist zone forming the ne border of the basin the sea floor relief undoubtedly reflects the influence of strong contour parallel bottom currents the cretaceous palaeogene boundary succession at stevns klint was thus developed on an underlying sea floor topographic relief of about 40 m recognition of the highly irregular current influenced topography of the late cretaceous sea floor stands in marked contrast to the conventional picture of quiet pelagic deposition of the chalk

the development and seismic expression of synsedimentary features within the chalk of southern england seismic reflection data acquired onshore to the north of bournemouth southern england image clearly a series of prominent concave up troughs or depressions and concave down mounded structures within the white chalk subgroup the chalk lithostratigraphy in the area of study is established from borehole geophysical log correlations these correlations then provide calibration of the seismic reflection data indicating that the structures are concentrated at levels between the lewes nodular chalk formation and tarrant chalk member and towards the base of the portsdown chalk formation onlap downlap and truncation of reflectors are observed with the most dramatic features forming a stacked series directly overlying faulting of jurassic strata similar stratal geometries have been described from comparable levels in the chalk of the north sea and in outcrop in britain and france to many they represent channels formed by submarine erosion and redeposition of the chalk during relative sea level falls linked to tectonics we also interpret a number of apparently incisive structures and slumped infill sequences described here as being of primary syndepositional origin the slumping and the close association of these features with underlying faults and proximity to nearby major crustal faults may be indicative of submarine erosion of the chalk caused by sea level changes linked to syndepositional fault movements however evidence of toplap downlap pairs is also suggestive of more aggradational mounding or laterally migrating surfaces or facies belts the presence of any such structures implies rapid lateral variations in the chalk that would have implications not only for aquifer management and future storage schemes but also during the processing of seismic reflection data and general studies and correlations of the chalk across southern britain

late quaternary palaeoenvironments of the winter rainfall zone of southern africa palynological and sedimentological evidence from the agulhas plain abstract south africa s winter rainfall zone is a climatically sensitive region lying at the interface of the earth s temperate and sub tropical climatic systems its seasonally arid climate has generally prevented the preservation of long and organic rich sedimentary deposits producing a spatially limited and temporally biased quaternary record this paper seeks to address this issue further and develop a fuller understanding of the wider climatic changes in this region during the late quaternary modern climatic data does not support the definitions of the winter rainfall zone presented in previous syntheses and this factor amongst others may explain difficulties in resolving the palaeoenvironmental record in this region we present palaeoenvironmental evidence from the agulhas plain an area marginal to the modern winter rainfall zone cored sedimentological and palynological records from two pans are integrated with previously reported records of aeolian activity providing evidence for phases of enhanced aridity and humidity during the late quaternary the record is fragmentary which may reflect the cycling of sediment between the pans and their accompanying lunette dunes lacustrine sedimentary sequences dating to c 33 ka 47 ka provide evidence for enhanced humidity consistent with evidence in the winter and year round rainfall zones increased humidity is also recorded from c 2 ka following drier conditions than the present c 2 7 2 5 ka palynological evidence supports the sedimentological interpretations of pan water status and offers rare insights into the nature of the region s unique fynbos vegetation during the late pleistocene

miocene climate and vegetation changes in the cape peninsula south africa evidence from biogeochemistry and palynology organic material from the noordhoek area on the western margin of the cape peninsula south africa was obtained from a 50 m long drill core dominated by fluvio lacustrine siliciclastic sediments the aim of this study is to constrain fluctuations in climate and the decline of tropical vegetation elements along the southwestern coast and the cape peninsula of south africa during the late cenozoic phase when the benguela upwelling system was established the approach was to combine palynological biogeochemical tetraether lipids and stable isotope c n studies of the organic bearing record from the noordhoek area on the western margin of the cape peninsula bulk c and n isotope data of sediment organic matter point to a predominantly c3 higher plant source vegetation mean annual air temperature mat from the analyses of tetraether lipids mbt cbt index was compared with palynomorphs from partly unpublished data of a previously drilled core adjacent to the study site the palynomorphs are of subtropical affinities and suggest that an open riparian forest would have existed in the early to middle miocene of the southwestern coast of south africa together these data sources allow vegetation and climate reconstructions of subtropical conditions during the early to middle miocene which comprised fluctuating open riparian forest and swamp vegetation temperatures rose in the middle miocene and were higher than those of the present day

upwelling intensification as part of the pliocene pleistocene climate transition a deep sea sediment core underlying the benguela upwelling system off southwest africa provides a continuous time series of sea surface temperature sst for the past 4 5 million years our results indicate that temperatures in the region have declined by about 10 c since 3 2 million years ago records of paleoproductivity suggest that this cooling was associated with an increase in wind driven upwelling tied to a shift from relatively stable global warmth during the mid pliocene to the high amplitude glacial interglacial cycles of the late quaternary these observations imply that atlantic ocean surface water circulation was radically different during the mid pliocene

regional and global context of the late cenozoic langebaanweg lbw palaeontological site west coast of south africa the palaeontological site of langebaanweg lbw is internationally renowned for its prolific diverse and exceptionally well preserved mio pliocene vertebrate faunas the site is located on the southern west coast of south africa which represents a passive intraplate trailing edge setting the southern african subcontinent is also removed from glacial influence and has experienced no cenozoic volcanic activity rates of vertical crustal motion are consequently low and late cenozoic shoreline datums at lbw chiefly reflect glacio eustatic sea level history the primary aim of this study is to clarify the chronology as well as the regional and global context of lbw and to review previous work on these aspects lbw is ideally situated to document the complex interactions of ocean atmosphere and land and their respective influence on climate evolution given its location near the coast and mix of marine estuarine and terrestrial faunas and depositional settings this paper also provides a background to the study of the vast existing faunal collections and a guide to undiscovered fossil deposits towards these ends the first detailed geological topographic maps of the site and surrounds accompanied by a summary stratigraphic column are provided virtual geological modelling using a subsurface database has clarified the spatial and temporal relationships of sedimentary facies as well as their depositional settings the geological and palaeontological record at lbw tracks and documents the major regional and global climatic oceanographic events of the late cenozoic during the oligocene drawdown in sea levels the landscape was etched by river incision fluctuating sea levels of the neogene periodically reversed the trend from erosion to deposition preserving contemporary faunas and floras in the oligocene palaeovalleys earlier miocene pollen from fluvial facies indicates a humid sub tropical climate reflecting a warm southern atlantic ocean the abrupt late middle miocene global cooling monterey excursion coincided with intensified cold upwelling in the benguela current and extensive phosphate authigenesis a globally documented early pliocene highstand possibly related to the shoaling of the isthmus of panama reached 90 m above sea level asl implying extensive melting of the cryosphere palaeomagnetic data in tandem with global sea level reconstructions suggested an age of 5 15 0 1 ma for the faunas and a correlation with the earlier part of this transgression a subtropical c3 vegetation is indicated by the faunas and floras but with a significant contribution by sclerophytic fynbos pointing to a cooler and more seasonal climate than in the miocene a mid pliocene highstand to 50 m asl truncated the early pliocene succession at lbw and the globally documented late pliocene highstand to 30 m asl saw the atlantic shoreline approaching lbw for the last time with the progressive climatic cooling and instability of the terminal pliocene culminating in the growth of the arctic ice cap strengthening southerly winds driven by a tighter coiled south atlantic anticyclone deposited extensive coastal dune fields over the region

vegetation history inferred from pollen in late quaternary faecal deposits hyraceum in the cape winter rain region and its bearing on past climates in south africa abstract pollen analysis shed light on vegetation community structure over the last 23 000 year in the western cape the pollen from dated hyrax faecal accumulations hyraceum relates to the evolution of climate and contributes to proxy records in southern africa principal components analyses of the pollen data and 13c values of the hyrax dung samples show millennial and shorter scale temperature moisture and seasonality variations in the winter rain region the moisture availability at times do not parallel that in previously studied proxy records in the summer rain region showing an asynchronous moist event in the early holocene and drier conditions in the middle holocene anomalies in climate between the two regions may depend on the degree of northward or southward shifting of winter and summer rain circulation systems scenarios with winter rain or cool growing seasons mostly typify the dung sequence but do not exclude the possibility of southward displacement of the westerly belt under precessional strength with slight summer rain increases during the last glacial maximum limited southward displacement is also possible during the mid holocene

geothermal heating and its influence on the meridional overturning circulation the effect of geothermal heating on the meridional overturning circulation is examined using an idealized coarse resolution ocean general circulation model this heating is parameterized as a spatially uniform heat flux of 50 mw m 2 through the flat ocean floor in contrast with previous studies that have considered an isolated hotspot or a series of plumes along the mid atlantic ridge the equilibrated response is largely advective a deep perturbation of the meridional overturning cell on the order of several sv is produced connecting with an upper level circulation at high latitudes allowing the additional heat to be released to the atmosphere rising motion in the perturbation deep cell is concentrated near the equator the upward penetration of this cell is limited by the thermocline analogous to the role of the stratosphere in limiting the upward penetration of convective plumes in the atmosphere the magnitude of the advective response is inversely proportional to the deep stratification with a weaker background meridional overturning circulation and a less stratified abyss the overturning maximum of the perturbation deep cell is increased this advective response also cools the low latitude thermocline the qualitative behavior is similar in both a single hemisphere and double hemisphere configuration the anomalous circulation driven by geothermal fluxes is more substantial than previously thought we are able to understand the structure and strength of the response in the idealized geometry and further extend these ideas to explain the results of adcroft et al 2001 where the impact of geothermal heating was examined using a global configuration

high resolution shear wave seismics across the carlsberg fault zone south of copenhagen implications for linking mesozoic and late pleistocene structures abstract the carlsberg fault zone cfz is a nnw sse striking structure close to the transition zone between the danish basin and the baltic shield we examine the fault evolution by combining very high resolution onshore shear wave seismic data one conventional onshore seismic profile and marine reflection seismic profiles the faulting geometry indicates a strong influence of triassic subsidence and rifting in the central european basin system growth strata within the cfz surrounding hollviken graben reveal syntectonic sedimentation in the lower triassic indicating the opening to be a result of triassic rifting in the upper cretaceous growth faulting documents continued rifting these findings contrast the late cretaceous to paleogene inversion tectonics in neighboring structures such as the tornquist zone the high resolution shear wave seismic method was used to image faulting in quaternary and danian layers in the cfz the portable compact vibrator source elvis iii s8 was used to acquire a 1150 m long seismic section on the island amager south of copenhagen the shallow subsurface in the investigation area is dominated by quaternary glacial till deposits in the upper 5 11 m and danian limestone below in the shear wave profile we imaged the uppermost 30 m of the western part of cfz the complex fault zone comprises normal block faults and one reverse block fault the observed faults cut through the danian as well as the quaternary overburden hence there are strong indicators for ongoing faulting like mapped faulting in quaternary sediments and ongoing subsidence of the eastern block of the cfz as interpreted by other authors the lack of earthquakes localized in the fault zone implies that either the frequency of occurring earthquakes is too small to be recorded in the observation time span or that the movement of the shallow sub surface layers may be due to other sources than purely tectonic processes

the cenozoic history of the coastal landscape of the southern cape province south africa a review abstract we discuss the latest viewpoints and the problems involved in reconstructing the cenozoic history of the southern cape coastal landscape based on planation levels evidence of sea level fluctuations plateau clays and fluvial deposits silcretes and coastal sequences limestones lignites and cover sands we propose a tentative chronology of the cenozoic history of the southern cape controversy still surrounds the development of the coastal platform there being two schools of thought the upper erosion surface is an early to mid tertiary peneplain preserved by a ferricrete and silcrete cuirasse surficial boulder beds gravels sands and clays attest to extensive fluvial action on the proto coastal forelands a combination of residual and transported material seems the best explanation of the origins of the weathered clays on the coastal platform the recent pleistocene to holocene sand cordons onshore and offshore in the wilderness embayment exhibit a regular spatial and temporal pattern together with the older sands covering the coastal plateau six phases of development have been identified the interpretation of the knysna formation of sands clays and lignites is still uncertain the lignite beds are probably the key to understanding the stratigraphy of the whole region

characterization of double diffusive convection steps and heat budget in the deep arctic ocean 1 in this paper we explore the hydrographic structure and heat budget in the deep canada basin by using data measured with mclane moored profilers mmp bottom pressure recorders bpr and conductivity temperature depth ctd profilers upward from the bottom a homogeneous bottom layer and its overlaying double diffusive convection ddc steps are well identified at mooring a 75 n 150 w we find that the deep water is in weak diapycnal mixing because the effective diffusivity of the bottom layer is 1 8 10 5 m2s 1 while that of the other steps is 10 6 m2s 1 the vertical heat flux through the ddc steps is evaluated by using different methods we find that the heat flux 0 1 11 mwm 2 is much smaller than geothermal heating 50 mwm 2 this suggests that the stack of ddc steps acts as a thermal barrier in the deep basin moreover the temporal distributions of temperature and salinity differences across the interface are exponential whereas those of heat flux and effective diffusivity are found to be approximately lognormal both are the result of strong intermittency between 2003 and 2011 temperature fluctuations close to the sea floor were distributed asymmetrically and skewed toward positive values which provide a direct observation that geothermal heating was transferred into the ocean both bpr and ctd data suggest that geothermal heating and not the warming of the upper ocean is the dominant mechanism responsible for the warming of deep water as the ddc steps prevent vertical heat transfer geothermal heating is unlikely to have a significant effect on the middle and upper arctic ocean

coupling of co2 and ice sheet stability over major climate transitions of the last 20 million years the co2 content of the atmosphere has varied cyclically between 180 and 280 ppmv over the last 800 000 years closely coupled with temperature and sea level for earlier periods in earth s history pco2 is much less certain and the relationship between pco2 and climate remains poorly constrained we use boron calcium ratios in foraminifera to estimate pco2 during major climate transitions of the last 20 million years myr during the middle miocene when temperatures were 3 to 6 c

significantly warmer arctic surface temperatures during the pliocene indicated by multiple independent proxies temperatures in the arctic have increased by an astounding 1 c in response to anthropogenic forcing over the past 20 years and are expected to rise further in the coming decades the pliocene 2 6 5 3 ma is of particular interest as an analog for future warming because global temperatures were signifi cantly warmer than today for a sustained period of time with continental confi gurations similar to present here we estimate mean annual temperature mat based upon three independent proxies from an early pliocene peat deposit in the canadian high arctic our proxies including oxygen isotopes and annual ring widths mat 0 5 1 9 c coexistence of paleovegetation mat 0 4 4 1 c and bacterial tetraether composition in paleosols mat 0 6 5 0 c yield estimates that are statistically indistinguishable the consensus among these proxies suggests that arctic temperatures were 19 c warmer during the pliocene than at present while atmospheric co 2 concentrations were 390 ppmv these elevated arctic pliocene temperatures result in a greatly reduced and asymmetrical latitudinal temperature gradient that is probably the result of increased poleward heat transport and decreased albedo these results indicate that arctic temperatures may be exceedingly sensitive to anthropogenic co 2 emissions

bottom current controlled sedimentation a synthesis of the contourite problem abstract an overview of the main items concerning deep bottom current controlled deposits is presented these include the definition of contourites their processes of deposition and facies characteristics contourite drift types and seismic patterns the interplay of turbidity and bottom current processes and the correlation between bottom current processes and global changes in climate sea level from this discussion several of the more significant problems are highlighted which we believe should be priority targets for future research 1 identification of contourites especially in ancient series where they are interbedded with turbidites and other facies 2 refinement of the numerous parameters used as tracers of palaeocirculation patterns 3 understanding the interaction between the different types of bottom currents and also between bottom current and other deep water processes 4 distinction in the sedimentary record between the effects of short time scale bottom current variations due to regional causes like benthic storms and geological scale current fluctuations related to climatic or astronomic control 5 understanding the control of glacial interglacial climatic cycles on the nature and rate of contourite deposition