morphology and environment of cold water coral carbonate mounds on the nw european margin cold water coral carbonate mounds owing their presence mainly to the framework building coral lophelia pertusa and the activity of associated organisms are common along the european margin with their spatial distribution allowing them to be divided into a number of mound provinces variation in mound attributes are explored via a series of case studies on mound provinces that have been the most intensely investigated belgica hovland pelagia logachev and norwegian mounds morphological variation between mound provinces is discussed under the premise that mound morphology is an expression of the environmental conditions under which mounds are initiated and grow cold water coral carbonate mounds can be divided into those exhibiting inherited morphologies where mound morphology reflects the morphology of the colonised features and developed morphology where the mounds assume their own gross morphology mainly reflecting dominant hydrodynamic controls finer scale surface morphological features mainly reflecting biological growth forms are also discussed

age constraints on the origin and growth history of a deep water coral mound in the northeast atlantic drilled during integrated ocean drilling program expedition 307 sr isotope stratigraphy provides a new age model for the first complete section drilled through a deep water coral mound the 155 m long section from challenger mound in the porcupine sea bight southwest of ireland is on miocene siliciclastics and consists entirely of sediments bearing well preserved cold water coral lophelia pertusa the 87sr 86sr values of 28 coral specimens from the mound show an upward increasing trend correspond to ages from 2 6 to 0 5 ma and identify a significant hiatus from ca 1 7 to 1 0 ma at 23 6 m below seafloor the age of the basal mound sediments coincides with the intensification of northern hemisphere glaciations that set up the modern stratification of the northeast atlantic and enabled coral growth mound growth persisted throughout glacial interglacial fluctuations reached a maximum rate 24 cm k y ca 2 0 ma and ceased at 1 7 ma unlike other buried mounds in porcupine seabight challenger mound was only partly covered during its growth interruption and growth restarted ca 1 0 ma

reefs of the deep the biology and geology of cold water coral ecosystems coral reefs are generally associated with shallow tropical seas however recent deep ocean exploration using advanced acoustics and submersibles has revealed unexpectedly widespread and diverse coral ecosystems in deep waters on continental shelves slopes seamounts and ridge systems around the world advances reviewed here include the use of corals as paleoclimatic archives and their biogeological functioning biodiversity and biogeography threats to these fragile long lived and rich ecosystems are mounting the impacts of deep water trawling are already widespread and effects of ocean acidification are potentially devastating

late pliocene to recent planktonic foraminifera from the north atlantic dsdp site 552a quantitative palaeotemperature analysis

middle miocene southern ocean cooling and antarctic cryosphere expansion magnesium calcium data from southern ocean planktonic foraminifera demonstrate that high latitude similar to55degreess southwest pacific sea surface temperatures ssts cooled 6degrees to 7degreesc during the middle miocene climate transition 14 2 to 13 8 million years ago stepwise surface cooling is paced by eccentricity forcing and precedes antarctic cryosphere expansion by similar to60 thousand years suggesting the involvement of additional feedbacks during this interval of inferred low atmospheric partial pressure of co2 pco 2 comparing ssts and global carbon cycling proxies challenges the notion that episodic pco2 drawdown drove this major cenozoic climate transition sst salinity and ice volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat vapor transport triggering ice growth and global cooling

paleoenvironmental reconstruction of challenger mound initiation in the porcupine seabight ne atlantic the understanding of the paleoenvironment during initiation and early development of deep cold water coral carbonate mounds in the ne atlantic is currently a focus of international research the integrated ocean drilling program iodp expedition 307 drilled the 155 m high challenger mound in the porcupine seabight sw off ireland in order to investigate for the first time sediments from the base of a giant carbonate mound in this study we focus in high resolution on 12 m of sediments from site 1317 encompassing the mound base the mound initiation and start up phase coincide with the intensification of the northern hemisphere glaciation inhg at around 2 7 ma further carbonate mound development seems to be strongly dependent on rapid changes in paleoceanographic and climatic conditions at the pliocene pleistocene boundary especially characterized and caused by the interaction of intermediate water masses the mediterranean outflow water mow the eastern north atlantic water enaw and the influence of southern component water scw this study is based on well established proxies such as 18o and 13c of planktonic globigerina bulloides and benthic foraminifera fontbotia wuellerstorfi discanomalina coronata lobatula lobatula lobatula antarctica and planulina ariminensis as well as grain size parameters to identify the paleoenvironmental and paleoecological setting favourable for the initial coral colonization on the mound stable oxygen and carbon isotope records of benthic foraminiferal species indicate that l lobatula provides a reliable isotopic signature for paleoenvironmental reconstructions in particular 18o values of l lobatula indicate that initial mound growth started in a glacial mode with moderate excursions in 18o values carbon isotope values of d coronata are significantly offset compared to other epibenthic species this offset may be related to vital effects bottom water temperatures calculated using standard equations based on 18o of foraminiferal tests range between 7 and 11 c consistent with the known temperature range conducive for cold water coral growth and development bottom currents transporting intermediate water masses of southern origin mediterranean and bay of biscay enhanced at 2 6 ma supporting first coral settlements with the inhg the benthic 13c and the sortable silt records indicate that the early pleistocene hydrodynamic regime was characterized by weaker current intensities associated with vertical movements of mow or its replacement by scw at intermediate depth after these sluggish phases enhanced mow flow dominated again and led to stronger current intensities and most probably sediment erosion on challenger mound erosion in combination with early diagenetic oxidation processes overprinted the sediment layers as indicated by dissolved coral skeletons the increase in ca content and sediment density minimum 13cplanktonic values as well as the occurrence of gypsum and pyrite implying a careful evaluation of original and overprinted geochemical signals we conclude that the challenger mound development was already influenced by short term variability of water masses from southern origin and possible erosional events comparable to the late pleistocene setting

review of recent developments in mineral magnetism of the chinese loess mineral magnetism of the chinese loess has been investigated for more than 20 years although there is a consensus that the neoformation of fine grained maghemite particles in the superparamagnetic sp and single domain sd grain size regions accounts for the magnetic enhancement in the chinese paleosols quantitative retrieval of paleoclimatic signals in terms of rock magnetic proxies is still a subject of debate the ambiguities arise from the inherent complexities of magnetic proxies as well as the multiple factors that control the pedogenic processes therefore a better description of the magnetic assemblage including its mineralogy grain size distribution and stoichiometry of two distinct origins pedogenic and eolian can help us better understand mechanisms behind variations in magnetic proxies at different timescales in order to link them to the paleoclimatic processes this review focuses on recent developments in loess magnetism and carefully evaluates merits and limitations of rock magnetic proxies furthermore several currently unsolved problems are addressed

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator

growth and erosion of a cold water coral covered carbonate mound in the northeast atlantic during the late pleistocene and holocene the first detailed stratigraphic record from a deep water carbonate mound in the northeast atlantic based on absolute datings u th and ams 14c and stable oxygen isotope records reveals that its top sediment sequences are condensed by numerous hiatuses according to stable isotope data mainly sediments with an intermediate signal are preserved on the mound while almost all fully glacial and interglacial sediments have either not been deposited or have been eroded later the resulting hiatuses reduce the late pleistocene sediment accumulation at propeller mound to amounts smaller than the background sedimentation the hiatuses most likely result due to the sweeping of the mound in turn with the re establishment of vigour interglacial circulation patterns after sluggish current regimes during glacials thus within the discussion if internal fluid driven or external environmentally driven processes control the evolution of such carbonate mounds our findings for propeller mound clearly point to environmental forcing as the dominant mechanism shaping deep water carbonate mounds in the ne atlantic during the late pleistocene and holocene

integrated stratigraphy and palaeoecology of the lower and middle miocene of the porcupine basin a high resolution palynological analysis and a detailed palaeomagnetic study of a marine sequence recovered during iodp expedition leg 307 in the porcupine basin southwest of ireland provide new insights into the regional depositional history and palaeoenvironmental evolution during early neogene times the hole 1318b studied was drilled on the upper slope of the continental margin in a water depth of 409 m upslope from a province of carbonate mounds the belgica mound province the diverse and well preserved dinoflagellate cyst associations consist typically of deep neritic and oceanic species mixed with a neritic component transported from the shelf reflecting the deep depositional setting at the continental margin the palaeomagnetic record together with the ranges of key dinoflagellate cyst species constrain the age of the studied sequence between 16 7 ma and 12 01 ma that is between the late burdigalian and late serravallian the distinct unconformity terminating the miocene sequence correlates to the global sequence boundary ser4 tor1 dated at 10 5 ma and represents according to previous extensive seismic studies a basin wide erosional event the overlying sediments are of middle pleistocene or younger age downslope from iodp site 1318 carbonate mounds root on the erosional surface the dinoflagellate cyst associations from the porcupine basin distinctly mirror the global cooling phase following the middle miocene climatic optimum cooling phase mi3 a short lived glaciation is particularly well expressed and here dated at 13 6 ma the palynomorph record furthermore indicates a reduction of the productivity and an increase of oceanic oligotrophic species after 14 ma suggesting a reduction or perhaps even a shutdown of the upwelling

a major and long term pliocene intensification of the mediterranean outflow 3 5 3 3 ma ago largely continuous millennial scale records of benthic delta o 18 mg ca based temperature and salinity variations in bottom waters were obtained from deep sea drilling project dsdp site 548 east atlantic continental margin near ireland 1250 m water depth for the period 3 7 3 0 ma ago high epsilon nd values of 10 7 to 9 show that this site monitored changes in mediterranean outflow water mow throughout the mid pliocene bottom water variability at ocean drilling progam odp site 978 alboran sea 1930 m water depth provides a complementary record of mow composition near its west mediterranean source both sites show a singular and persistent rise in bottom water salinities by 0 7 1 4 psu and in densities by similar to 1 kg m 3 from 3 5 to 3 3 ma ago which is matched by an similar to 3 degrees c increase in bottom water temperature at site 548 this event suggests the onset of strongly enhanced deep water convection in the mediterranean sea and a related increase in mow flow as a result of major aridification in the mediterranean source region in harmony with model suggestions the enhanced mow flow has possibly intensified upper north atlantic deep water formation

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

evidence for oligocene middle miocene abyssal circulation changes in the western north atlantic previous studies of benthic foraminiferal isotopic composition have demonstrated that a latest eocene earliest oligocene benthic foraminiferal 18o increase occurred in the pacific southern and atlantic oceans1 9 a middle miocene 18o increase has been noted in the pacific southern and south atlantic oceans1 3 7 10 11 and tentatively identified in the north atlantic12 13 due to the incomplete nature of the north atlantic stratigraphical record14 15 however the oligocene to middle miocene isotopic record of this ocean is poorly understood in the modern ocean the north atlantic and its marginal seas has a critical role in abyssal circulation influencing deep and bottom water hydrography as far away as the north pacific16 18 we now report oxygen isotope measurements on oligocene to middle miocene 12 36 myr bp benthic foraminifera in the western north atlantic which show two periods of enriched 18o values early oligocene and early middle miocene these enriched intervals are interpreted as resulting in part from the build up of continental ice sheets the oligocene to middle miocene 13c record shows three cycles of enrichment and depletion of large enough magnitude to be useful for time stratigraphical correlations within the biostratigraphical age resolution 18o and 13c records correlate with records from other oceans helping to establish a useful tertiary isotopic stratigraphy an atlantic pacific 13c contrast of 0 3 0 9 during the latest oligocene to middle miocene 12 26 myr bp indicates north atlantic deep and bottom water production analogous to modern north atlantic deep water nadw

the middle miocene climatic transition east antarctic ice sheet development deep ocean circulation and global carbon cycling abstract the middle miocene represents a major change in state in cenozoic climatic evolution following the climax of neogene warmth in the late early miocene at 16 ma the early stage of this climatic transition from 16 to 14 8 ma was marked by major short term variations in global climates east antarctic ice sheet eais volume sea level and deep ocean circulation in the later stage from 14 8 to 12 9 ma climatic developments included major growth of the eais and associated antarctic cooling a distinct increase in the meridional temperature gradient large fluctuations in sea level followed by a global sea level fall and important changes in deep water circulation including increased production of southern component water east antarctic ice sheet growth and polar cooling also had large effects on global carbon cycling and on the terrestrial biosphere including aridification of mid latitude continental regions increased stability of the eais after 14 8 ma represents a crucial step in the establishment of late neogene global climate systems what controlled these changes in polar climates and the east antarctic ice sheet deep ocean circulation changes probably played a major role in the evolution and variation in polar climates as they have throughout the cenozoic oxygen and carbon isotopic evidence for warm saline deep water production in the eastern tethyan northern indian ocean indicates that meridional heat transport to the antarctic inhibited cenozoic polar cooling and eais growth during the early middle miocene from 16 to 14 8 ma inferred competition between warm low latitude sources derived from the eastern tethyan northern indian ocean and a cold high latitude source southern component water from 16 to 14 8 ma may have been associated with instability in the antarctic climate and cryosphere reduction of warm saline deep water flow to the southern ocean at 14 8 ma may have decreased meridional heat transport to the antarctic cooling the region and leading to increased production of southern component water these middle miocene climatic and cryospheric changes in the antarctic had profound effects on marine and terrestrial climates as the meridional surface temperature gradient increased boundaries between climatic zones strengthened leading to increased aridification of mid latitude continental regions in australia africa and north and south america enhancing the development of grasslands and stimulating the evolution of grazing mammals

a geostrophic transport estimate for the florida current from the oxygen isotope composition of benthic foraminifera we present a new method for the quantitative reconstruction of upper ocean flows for during times in the past for the warm t 5 c surface ocean density can be accurately reconstructed from calcite precipitated in equilibrium with seawater as both of these properties increase with decreasing temperature and increasing salinity vertical density profiles can be reconstructed from the oxygen isotopic composition of benthic foraminifera the net volume transport between two vertical density profiles can be calculated using the geostrophic method using benthic foraminifera from surface sediment samples from either side of the florida straits florida keys and little bahama bank we reconstruct two vertical density profiles and calculate a volume transport of 32 sv using this method this agrees well with estimates from physical oceanographic methods of 30 32 sv for the mean annual volume transport we explore the sensitivity of this technique to various changes in the relationship between temperature and salinity as well as salinity and the oxygen isotopic composition of seawater

carbonate budget of a cold water coral mound challenger mound iodp exp 307 abstract cold water coral ecosystems represent a worldwide distributed carbonate factory which is so far not considered in global carbonate budget estimations the herein presented study evaluates the carbonate budget of a complete cold water coral mound sequence from challenger mound belgica mound province porcupine seabight sw offshore ireland drilled during iodp expedition 307 reaching back to the late pliocene versus background sediment derived calcite dominated carbonate cores from adjacent drift deposits were examined for comparison studies challenger mound which developed in a fast growth phase unit m1 2 7 to 1 6 ma and a slower growth phase or mound decline unit m2 0 8 ma until today separated by a so called mound crisis displays increased carbonate accumulation rates for both phases 17 3 g cm 2 ka for unit m1 and 5 7 g cm 2 ka for unit m2 compared to adjacent drift deposits but only about 33 to 40 wt of the carbonate is derived from corals bulk sedimentation rates of on and off mound deposits suggest a decline of challenger mound since the onset of drift deposition in the area about 1 2 ma ago yet total carbonate accumulation rates as well as hemipelagic background sediment derived carbonate accumulation rates from challenger mound unit m2 still exceed the carbonate accumulation rates of the adjacent drift deposits the selective enrichment of background sediment derived carbonate by a factor of 2 0 in a cwc mound is herein observed for the first time this might be caused by the different hydrodynamic behaviour and slower settlement of marine fluff rich in calcareous detritus compared to siliciclastic sediments and its effective baffling by the coral framework and or the active catch of the calcareous plankton by the corals the carbonate accumulation rates of challenger mound are about 4 to 12 of the carbonate accumulation rates of tropical shallow water reefs but exceeds the carbonate accumulation rates of continental slopes by a factor of 3 9 to 11 8 the carbonate production for the entire belgica mound province is estimated with 3 2 10 3 t a for unit m1 and 1 0 10 3 t a for unit m2

atypical δ13c signature in globigerina bulloides at the odp site 723a arabian sea implications of environmental changes caused by upwelling production of globigerina bulloides generally increases during upwelling in the tropical ocean and in particular during southwest monsoon season in the arabian sea we studied the 13 c signatures of g bulloides from ocean drilling program odp site 723a located in the intense upwelling area along the oman margin arabian sea the 13 c signature of g bulloides from the oman margin during the last 19 ka ranges from 2 65 to 1 13 strikingly the 13 c values of g bulloides are about 1 lower than that of benthic foraminifera uvigerina excellens at this site apparently the vital effects induced carbon isotopic fractionation in g bulloides results in abnormal 13 c values during upwelling seasons g bulloides calcifies faster perhaps because of high nutrient availability faster calcification rates in this species require higher respiration which involves more respired co 2 enriched with 12 c accounting for nearly 10 of shell carbon therefore the combination the foraminifera of faster calcification and involvement of respired co 2 would induce more negative 13 c in g bulloides compared to other foraminifera apart from vital effects the environmental changes caused by the variations of upwelling intensity during holocene and last glacial maximum also affected the down core 13 c record of g bulloides in the arabian sea significant ontogenic differences in both 18 o and 13 c occurred between large and small size classes of g bulloides

x ray imagery and physical core logging as a proxy of the content of sediment cores in cold water coral mound provinces a case study from porcupine seabight sw of ireland three provinces characterized by the presence of carbonate mounds interpreted as cold water coral banks have been reported in porcupine seabight sw of ireland and were recently subjected to many detailed studies this contribution discusses the use of x ray imagery and physical properties in deciphering palaeoceanographic sedimentological and biological processes physical property core logging and x ray imagery are used to identify and describe sedimentation regimes and so their respective palaeoceanographic and palaeoclimatological settings in two mound provinces respectively the belgica mound province and the magellan mound province both provinces show at present time clear differences in the hydrodynamic environment this study confirms that also during the past the oceanographic and sedimentological environment of both provinces differ clearly impacts of glacial interglacial variations and locally derived ice rafting events ire comparable with the north atlantic heinrich events he have been recognized in both provinces moreover the combination of x ray imagery magnetic susceptibility gamma density and p wave velocity makes it possible to estimate the coral content and coral distribution in unopened cores localized on top of carbonate mounds a comparison between on mound and off mound cores in both provinces allowed revealing some mechanisms of mound evolution and coral growth versus time

fault associated seabed mounds carbonate knolls off western ireland and north west australia abstract groups of seabed mounds suspected to be modern carbonate knolls or bioherms have been located on reflection seismic data in the porcupine basin off western ireland and in the vulcan sub basin off north west australia the size of these mounds is impressive often being over 1 km across and over 100 m high in the porcupine basin they occur in water depths of 650 1000 m whereas in the vulcan sub basin they occur in water depths of 200 350 m shallow seabed coring in the porcupine basin has provided data on the age lithological composition and hydrocarbon concentrations in the upper 3 m layer of sediment both on and off the mounds in both basins the mounds occur close to faults which may provide conduits for upward migrating hydrocarbons the seepage of hydrocarbons is suspected to have caused local eutrophication or fertilization by providing nutrients to bacteria which in turn are part of the food chain for higher organisms the dominant organism in the porcupine basin examples appears to be the deep water coral lophelia sp whereas in the vulcan sub basin the mounds appear to be halimeda dominated

thermohaline instability in the north atlantic during meltwater events stable isotope and ice rafted detritus records from core so75 26kl portuguese margin a benthic isotope record has been measured for core so75 26kl from the upper portuguese margin 1099 m water depth to monitor the response of thermohaline overturn in the north atlantic during heinrich events evaluating benthic 18o in ts diagrams in conjunction with equilibrium c fractionation implies that advection of mediterranean outflow water mow to the upper portuguese margin was significantly reduced during the last glacial 15 compared to 30 today the benthic isotope record along core so75 26kl therefore primarily monitors variability of glacial north atlantic conveyor circulation the 14c accelerator mass spectrometry ages of 13 54 07 and 20 46 12 ka for two ice rafted detritus ird layers in the upper core section and an interpolated age of 36 1 ka for a third ird layer deeper in the core are in the range of published 14c ages for heinrich events h1 h2 and h4 marked depletion of benthic 13c by 0 7 1 1 during the heinrich events suggests reduced thermohaline overturn in the north atlantic during these events close similarity between meltwater patterns inferred from planktonic 18o at site 609 and ventilation patterns inferred from benthic 13c in core so75 26kl implies coupling between thermohaline overturn and surface forcing as is also suggested by ocean circulation models benthic 13c starts to decrease 1 5 2 5 kyr before heinrich events hl and h4 fully increased values are reached 1 5 3 kyr after the events indicating a successive slowdown of thermohaline circulation well before the events and resumption of the conveyor s full strength well after the events benthic 13c changes in the course of the heinrich events show subtle maxima and minima suggesting oscillatory behavior of thermohaline circulation a distinct feature of thermohaline instability in numerical models inferrred gradual spin up of thermohaline circulation after hl and h4 is in contrast to abrupt wanning in the north atlantic region that is indicated by sudden increases in greenland ice core 18o and in marine faunal records from the northern north atlantic from this we infer that thermohaline circulation can explain only in part the rapid climatic oscillations seen in glacial sections of the greenland ice core record

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

the messinian early pliocene stratigraphic record in the southern bajo segura basin betic cordillera spain implications for the mediterranean salinity crisis financial aid was provided by research projects bte2003 05047 cgl2005 06224 bte cgl2007 65832 bte mec and gv04b 629 generalitat valenciana and the paleoenvironmental changes group ua

the 2 6 ma depositional sequence from the challenger cold water coral carbonate mound iodp exp 307 sediment contributors and hydrodynamic palaeo environments during iodp expedition 307 the first complete sequence through a cold water coral carbonate mound a bio geological seafloor feature created through successive stages of cold water coral mediated sediment accumulation was successfully acquired the full recovery of the challenger mound one of the large ca 155 m high coral carbonate mounds along the ne atlantic continental margin belgica mound province eastern porcupine seabight facilitates for the first time the study of the entire development of a coral carbonate mound and hence allows the identification of the environmental conditions driving and maintaining the entire build up of these remarkable seafloor habitats in this study the different sediment contributors to the challenger mound are identified and assessed throughout its entire 2 6 ma long development high resolution siliciclastic particle size end member modelling and its ground truthing xrd quartz sand surface microtextures indicate the influence of an all dominant contour current system operating in variable energetic modes for most of the sediment accumulation history of the challenger mound only local short distance current controlled sediment re dispersal is evidenced while iceberg rafting is identified as an important depositional mechanism throughout the whole mound development period furthermore evidence for icebergs repeatedly reaching the eastern porcupine seabight continental margin even in the early stages of northern hemisphere glacial expansion is preserved in the mound sequence supporting the existing coral stratigraphy the challenger mound depositional sequence reveals a two phase development separated by a significant hiatus the lower mound phase m1 2 6 1 7 ma indicates a semi continuous steadily changing fast accumulating current controlled depositional environment the condensed upper mound phase m2 998 1 5 ka bears witness of a distinct shift to a more glacially influenced low accumulation environment most likely resulting from a reduced capacity to deposit and or preserve sediments cold water coral density at the site of deposition is assumed to play an essential role in sediment deposition and preservation on challenger mound it enabled the preservation of a unique higher resolution record in the lower m1 sequence in the otherwise erosive non depositional early pleistocene environment along the nw european continental margin the potential of coral carbonate mounds as intermediate water depth continental margin plio pleistocene palaeo archives is thereby showcased

therese mound a case study of coral bank development in the belgica mound province porcupine seabight high resolution seismic profiles swath bathymetry side scan sonar data and video imageries are analysed in this detailed study of five carbonate mounds from the belgica mound province with special emphasis on the well surveyed therese mound the selected mounds are located in the deepest part of the belgica mound province at water depths of 950 m seismic data illustrate that the underlying geology is characterised by drift sedimentation in a general northerly flowing current regime sigmoidal sediment bodies create local slope breaks on the most recent local erosional surface which act as the mound base no preferential mound substratum is observed neither is there any indication for deep geological controls on coral bank development seismic evidence suggests that the start up of the coral bank development was shortly after a major erosional event of late pliocene quaternary age the coral bank geometry has been clearly affected by the local topography of this erosional base and the prevailing current regime the summits of the coral banks are relatively flat and the flanks are steepest on their upper slopes deposition of the encased drift sequence has been influenced by the coral bank topography sediment waves are formed besides the coral banks and are the most pronounced bedforms these seabed structures are probably induced by bottom current up to 1 m s large sediment waves are colonised by living corals and might represent the initial phase of coral bank development the biological facies distribution of the coral banks illustrate a living coral cap on the summit and upper slope and a decline of living coral populations toward the lower flanks the data suggest that the development of the coral banks in this area is clearly an interaction between biological growth processes and drift deposition both influenced by the local topography and current regime

hydrodynamics and cold water coral facies distribution related to recent sedimentary processes at galway mound west of ireland abstract cold water coral carbonate mound development is the result of complex and interactive hydrographical biological and geological processes that can result in morphostructures several hundred meters high the case study presented here investigates one of these large mounds galway mound in the eastern porcupine seabight to build an understanding of mound forming processes and the driving factors for the first time bottom current data have been recorded at six locations over a mound thus allowing an interpretation of the local flow field to be made in addition to the overall flow pattern in the porcupine seabight the recorded data display distinct diurnal tides comparison of the local flow field coral facies distributions current induced seabed features and grain size distributions over the galway mound highlights a correlation between the abundance of living corals with areas of enhanced bottom currents however the interplay of contour currents tidal currents and the local topography further influences the coral facies and results in a distinct asymmetry in the coral facies distribution at galway mound by baffling sediment the corals also affect sedimentation on the mound

early and middle miocene stable isotopes implications for deepwater circulation and climate the middle miocene 18o increase represents a fundamental change in the ocean atmosphere system which like late pleistocene climates may be related to deepwater circulation patterns there has been some debate concerning the early to early middle miocene deepwater circulation patterns specifically recent discussions have focused on the relative roles of northern component water ncw production and warm saline deep water originating in the eastern tethys our time series and time slice reconstructions indicate that ncw and tethyan outflow water two relatively warm deepwater masses were produced from 20 to 16 ma ncw was produced again from 12 5 to 10 5 ma another feature of the early and middle miocene oceans was the presence of a high 13c intermediate water mass in the southern hemisphere which apparently originated in the southern ocean miocene climates appear to be related directly to deepwater circulation changes deep waters warmed in the early miocene by 3 c 20 to 16 ma and cooled by a similar amount during the middle miocene 18o increase 14 8 to 12 6 ma corresponding to the increase 20 ma and subsequent decrease 16 ma in the production of ncw and tethyan outflow water large 0 6 relatively rapid 0 5 m y 18o increases in both benthic and planktonic foraminifera i e the mi zones of miller et al 1991a and wright and miller 1992a were superimposed in the long term deepwater temperature changes they are interpreted as reflecting continental ice growth events seven of these m y glacial interglacial cycles have been recognized in the early to middle miocene two of these glacial interglacial cycles mi3 and mi4 combined with a 2 to 3 c decrease in deepwater temperatures to produce the middle miocene 18o shift

large deep water coral banks in the porcupine basin southwest of ireland the porcupine basin southwest of ireland was one of the earliest sites from where the deep water corals lophelia sp and madrepora sp were recovered these deep water corals have since been found all along the atlantic margins of europe in water depths ranging from 50 to more than 2000 m recent geophysical studies have demonstrated the mound building potential of deep water corals available data indicate that three major provinces of coral bank occurrences can be identified in the porcupine basin 1 high relief surface mounds which have a dimension of 1 by 5 km and a height up to 200 m hovland mounds flanked to the north by 2 a swarm of buried mounds somewhat smaller up to 90 m and with more irregular shapes than those recognised in area 1 magellan mounds and 3 outcropping or buried conical mounds single or in elongated clusters up to 150 m high occurring on the southeastern slope of the basin belgica mounds as far as can be inferred from shallow cores the surface lithology predominantly consists of an upper layer rich in foraminiferal sand and terrigenous silty clay with intercalations of biogenic rubble the banks host a remarkable number of colonies of living and dead lophelia pertusa and madrepora oculata the living and dead assemblages are underlain by a significant layer of coral debris in a muddy matrix deep water coral debris together with a living association of the same species covers the surface of the belgica and hovland mounds which may suggest that these corals have played a significant role in the development of the mound structures the capacity for mound formation by scleractinian corals in the aphotic zone has been known for some time examples are found at different locations along the shelves and the continental margins of the north atlantic the role of the corals in these deep water build ups is still a point of debate though the genesis and initial control of mound settings in this basin might be related to hydrocarbon seeps it appears that the major development of the porcupine coral banks in recent geological times has most likely been controlled by oceanic circulation and dynamics in water masses and nutrient supply

carbonate budget of a cold water coral carbonate mound propeller mound porcupine seabight high resolution studies from the propeller mound a cold water coral carbonate mound in the ne atlantic show that this mound consists of 50 carbonate justifying the name carbonate mound through the last 300 000 years approximately one third of the carbonate has been contributed by cold water corals namely lophelia pertusa and madrepora oculata this coral bound contribution to the carbonate budget of propeller mound is probably accompanied by an unknown portion of sediments buffered from suspension by the corals however extended hiatuses in propeller mound sequences only allow the calculation of a net carbonate accumulation thus net carbonate accumulation for the last 175 kyr accounts for only 0 3 g cm2 kyr which is even less than for the off mound sediments these data imply that propeller mound faces burial by hemipelagic sediments as has happened to numerous buried carbonate mounds found slightly to the north of the investigated area

carbonate mound development at the sw rockall trough margin based on high resolution tobi and seismic recording abstract in 2002 high resolution sidescan sonar images of a mound area at the sw rockall trough margin were recorded with the tobi deep towed sidescan sonar processed tobi images with a pixel resolution of 6 m provide a unique overview of the carbonate mound distribution and related sedimentary features around the mounds three morphologically distinct areas can be recognised on the tobi mosaic in area i between 500 and 600 m water depth upslope of the mounds giant sediment waves are found with wavelengths up to 500 m with wave crests of more than 10 km long and with an amplitude of up to 30 m reflected with a high backscatter on the tobi image area ii between 600 and 1000 m water depth along the upper margin flank is characterised by clustered and isolated carbonate mounds forming elongated ridges with an orientation perpendicular to the slope sedimentary structures such as flow ridges sediment waves local scouring at the foot of some mounds and draping of sediment around mounds indicate the influence of strong near bed currents oriented in two main current directions parallel to the margin as well as in a similar direction as the mound clusters the mound clusters are several kilometres long can be over 380 m high and are dissected by downslope directed channels on the tobi image the mounds appear as regions of high backscatter caused by the presence of cold water coral colonies on the sediment and by distinct shadows all mounds have their tops at a specific depth level 500 600 m water depth area iii between 900 and 1200 m water depth below the mounds is characterised by disturbed sediments with distinct slump scars and flow ridges 2d high resolution seismic profiling perpendicular and parallel to the slope across the mounds does in general not reveal strong internal reflectors within the mounds in contrast three strong reflectors can be observed in the sedimentary sequence underneath the mounds the upper reflector c10 of early pliocene age is an erosional unconformity above which most of the mounds and sediment waves seem to have developed the second erosional unconformity c20 of middle miocene age is formed by an apparent irregular surface that locally is dissected by some small faults reflectors c10 and c20 have been found in two different mound clusters in the mound area indicating that mound development possibly started after formation of reflector c20 the third reflector forms the acoustic basement which is locally dissected by some small faults that are located below the mounds at least two stages of mound formation are recognised on the seismic profiles

progressive reduction in ne atlantic intermediate water ventilation prior to heinrich events response to nw european ice sheet instabilities we present high resolution benthic 13c records from intermediate water depth core site md01 2461 1153 m water depth from the porcupine seabight ne atlantic spanning 43 to 8 kyr b p at an average proxy time step of 160 56 years this core provides information on the linkage between records from the portuguese margin and high latitude north atlantic basin allowing additional insights into north atlantic thermohaline circulation thc variability during millennial scale climatic events of the last glacial together these records document both discrete and progressive reductions in glacial north atlantic intermediate water gnaiw formation preceding heinrich h events 1 2 and 4 recorded through the apparent interchange of glacial northern and southern sourced intermediate water signatures along the european margin close coupling of nw european ice sheet nweis instability and gnaiw formation is observed through transient advances of scw along the european margin concurrent with pulses of ice rafted debris and meltwater release into the ne atlantic between 27 and 16 kyr b p when the nweis was at maximum extent and proximal to last glacial maximum convection zones in the open north atlantic it is such nweis instability and meltwater forcing that may have triggered reduced north atlantic thc prior to collapse of the laurentide ice sheet at h1 and h2 precursory reduction in gnaiw formation prior to h4 may also be inferred however limited nweis ice volume prior to h4 and convection occurring in the norwegian greenland sea require that if a meltwater trigger is invoked as appears to be the case at h1 and h2 the source of meltwater prior to h4 is elsewhere likely higher latitude ice sheets clarification of the sequencing and likely mechanisms of precursory decrease of the north atlantic thc support theories of h event initiation relating to ice shelf growth during cold periods associated with reduced north atlantic thc and subsequent ablation through subsurface warming and sea level rise associated with further reductions in meridional overturning

sediment accumulation on a cold water carbonate mound at the southwest rockall trough margin abstract cold water corals build isolated and clustered carbonate mound ridges several kilometres long and wide and up to 380 m high at the southwest rockall trough margin photo and video observations as well as coring have shown that mainly the upper mound flanks and summits are covered with a thriving living coral cover and associated fauna box cores prove the presence of living coral colonies on top of a thick layer of coral debris which is to a large extent abraded and bio eroded before being buried the coral framework is filled with sediment from settling pelagic material and parts of the fauna living at the mounds resulting in a 120 cm thick layer of sediments since 10 800 yr component analysis of a piston core from the top of a carbonate mound shows a complete record of cold water coral mound facies comprising many different species living at the mounds an alternation of skeletal and cement dominated intervals was distinguished in the piston core stable isotope analysis of planktonic and benthic foraminifera indicates a continuous sedimentation pattern since the younger dryas the deeper and older part of the core showing mainly intermediate isotope values is dominated by the presence of large hiatuses spanning a total of up to 200 000 yr hiatuses in the core may reflect periods of non deposition or erosion which may be linked to glacial interglacial variability environmental conditions probably change at glacial interglacial timescales influencing the local hydrodynamic regime food supply and sedimentation rate around the carbonate mounds affecting coral growth and therefore carbonate mound development

benthic dynamics at the carbonate mound regions of the porcupine sea bight continental margin a brief review is given of some dynamical processes that influence the benthic dynamics within the carbonate mound provinces located at the porcupine bank sea bight margin ne atlantic the depth range of the mounds in this region 600 1 000 m marks the upper boundary of the mediterranean outflow water above which eastern north atlantic water dominates both water masses are carried northwards by the eastern boundary slope current in the benthic boundary layer both the action of internal waves and other tidal period baroclinic waves may enhance the bottom currents and add to both the residual and maximum flow strength both residual and maximum bottom currents vary at different mound locations with stronger currents found at belgica se porcupine sea bight mound and pelagia nw porcupine bank mound regions whilst weakest currents are found at the hovland and magellan mounds at the northern sea bight margin the differences may be attributed to the presence of internal waves pelagia or bottom intensified diurnal waves belgica these different dynamical regimes are likely to have implications for the distribution patterns of live coral at the different locations

vivaldi 1991 a study of the formation circulation and ventilation of eastern north atlantic central water abstract a synoptic hydrographic data set comprising 32 full depth ctd casts and 2500 ctd seasoar profiles to 500 m is used to describe the s properties and circulation of central water east of the mid atlantic ridge and between 39 n and 54 n eastward transport of 20 10 6 m 3 s 1 in the north atlantic current turns entirely northwards to the west of 54 n 20 w this transport consists in the upper layers of western north atlantic water freshened at temperatures below 10 c by mixing with subarctic intermediate water northern and southern branches of the north atlantic current are well defined and both turn northwards west of 20 w a further 10 10 6 m 3 s 1 of eastern north atlantic water forms and recirculates anticyclonically to the west of spain south of the north atlantic current and north of 40 n eastern north atlantic water is most weakly stratified east of 20 w and there is clear correlation between weakly stratified pycnostads and positive salinity anomalies relative to western north atlantic water thus eastern north atlantic water is a winter mode water in which strong winter cooling has increased the density and hence also the salinity anomaly at a given temperature near the southern entrance to the rockall trough there is evidence that salinities are also increased by mediterranean water influence circulation south of the north atlantic current is complex there is no evidence for direct ventilation southwards across 40 n where water properties s potential vorticity and cfc 113 and historical data all indicate westward ventilation east of 24 w with weak southward ventilation occurring further west in the vicinity of the azores the circulation pattern suggested is remarkably similar to that proposed by helland hansen and nansen in 1926 the eastern north atlantic geophysiske publicajoner 4 1 76 with anticyclonic circulation of colder eastern north atlantic water north of 40 n meeting warmer water from south of 40 n circulating cyclonically north of the azores current the distribution of pycnostads and s properties between 20 w and 35 w north of the azores indicates alternate bands of western and eastern north atlantic water moving eastward and westward respectively including evidence for westward motion immediately south of the southern branch of the north atlantic current possibly by westward propagation of anticyclonic eddies containing deep pycnostads

structure and development of giant carbonate mounds at the sw and se rockall trough margins ne atlantic ocean abstract high resolution seismic reflection profiling carried out in 1997 1999 showed that giant carbonate mounds occur between 500 and 1200 m water depth along both the se and sw margins of rockall trough the mounds rise 5 300 m above the surrounding seafloor and have diameters at their bases of up to 5 km buried mounds at relatively shallow depths below the seafloor are also found both individual and complex clusters of mounds can be recognized smaller and individual sometimes buried mounds are found at the upper slope on the sw rockall trough margin higher steeper and individual mounds are found deeper downslope 900 1100 m at the middle slope the mounds merge into a complex structure and form complex clusters with a very irregular upper surface and an apparent lack of internal reflectors 600 1000 m depth initial results of high resolution 3d seismic profiling at 30 m line spacing in august 2000 in two boxes of 750 m 14 5 km covering a small central part of the sw rockall trough mound area indicate two stages of mound development here the latest probably of pliocene holocene age this age based on the presence of a regionally recognizable unconformity below the mounds is also assumed for the mounds of the se rockall trough porcupine bank margin

eastern north atlantic deep sea corals tracing upper intermediate water δ14c during the holocene abstract paired 230th u and 14c dating were performed on deep sea corals lophelia pertusa and madrepora oculata from the northeastern north atlantic at 730 m bsl to investigate past changes of the thermohaline circulation these were estimated using the 14c value of the upper intermediate waters based on the 14c ages of the top and base of each coral where possible and the 230th u dating the reliability of these estimates was checked by dating two very young corals of the species l pertusa one of these corals collected alive in 1999 ad gave a 230th u age of 1995 4 ad after correction for non radiogenic 230th another coral the top of which dated to 1969 6 ad recorded the atmospheric 14c 12c increase due to the nuclear tests in the early 1960s the calculated 14c values from these two corals agree with those measured at geosecs station 23 in 1972 1973 ostlund et al earth planet sci lett 23 1974 69 86 and 1991 1992 nydal and gisfelos radiocarbon 38 1996 389 406 this together with the 100 aragonite content and the 234u and 230th 232th values of all the dated corals indicates that none of the corals behaved as open systems with respect to their u series nuclides and that they closely represent the water mass properties in which they lived the pre anthropogenic 14c value of the north atlantic intermediate waters was estimated at 69 4 the reservoir age varies from 400 years to 600 years and this variation is due to atmospheric 14c 12c changes a reservoir age of 610 80 years close to the pre anthropogenic value was determined from one coral dated at 10 430 120 cal yr bp when the global sea level was approximately at 35 m bard et al nature 382 1996 241 244 this suggests a modern like pattern of the oceanic circulation prevailed in the northeast atlantic ocean at this time although the deglaciation was not completely achieved

environmental changes and growth history of a cold water carbonate mound propeller mound porcupine seabight on and off mound sediment cores from propeller mound hovland mound province porcupine seabight were analysed to understand better the evolution of a carbonate mound the evaluation of benthic foraminiferal assemblages from the off mound position helps to determine the changes of the environmental controls on propeller mound in glacial and interglacial times two different assemblages describe the holocene and marine isotope stage mis 2 and late mis 3 31 kyr bp the different assemblages are related to changes in oceanographic conditions surface productivity and the waxing and waning of the british irish ice sheet biis during the last glacial stages the interglacial assemblage is related to a higher supply of organic material and stronger current intensities in water depth of recent coral growth during the last glaciation the benthic faunas showed high abundances of cassidulinid species implying cold bottom waters and a reduced availability of organic matter high sedimentation rates and the domination of elphidium excavatum point to shelf erosion related to sea level lowering 50 m and the progradation of the biis onto the shelf a different assemblage described for the on mound core is dominated by discanomalina coronata gavelinopsis translucens planulina ariminensis cibicides lobatulus and to a lower degree by hyrrokkin sarcophaga these species are only found or show significantly higher relative abundances in on mound samples and their maximum contribution in the lower part of the record indicates a higher coral growth density on propeller mound in an earlier period they are less abundant during the holocene however this dataset portrays the boundary conditions of the habitable range for the cold water coral lophelia pertusa which dominates the deep water reefal ecosystem on the upper flanks of propeller mound the growth of this ecosystem occurs during interglacial and interstadial periods whereas a retreat of corals is documented in the absence of glacial sediments on mound glacial conditions with cold intermediate waters a weak current regime and high sedimentation rates provide an unfavourable environmental setting for lophelia corals to grow a late pleistocene decrease is observed in the mound growth for propeller mound which might face its complete burial in the future as it already happened to the buried mounds of the magellan mound province further north

origin glacial interglacial responses and controlling factors of a cold water coral mound in ne atlantic 1 recent deep ocean exploration has revealed unexpectedly widespread and diverse coral ecosystems in deep water on continental shelves slopes seamounts and ridge systems around the world origin and growth history of these cold water coral mounds are poorly known owing to a lack of complete stratigraphic sections through them here we show high resolution oxygen isotope records of planktic foraminifers from the base to the top of challenger mound southwest of ireland which was drilled during integrated ocean drilling program expedition 307 challenger mound began to grow during isotope stage 92 2 24 million years ago ma immediately after the onset of northern hemisphere glaciation and the initiation of modern stratification in the northeast atlantic mound initiation was likely due to reintroduction of mediterranean outflow water mow and ensuing development of a density gradient with overlying northeastern atlantic water neaw where organic matter was prone to be stagnated and fueled the coral ecosystem coral growth continued for 11 glacial interglacial cycles until isotopic stage 72 1 82 ma with glacial siliciclastic input from the continental margin after a long hiatus that separates the lower mound and the upper mound coral growth restored for a short time in isotope stages 19 18 0 8 0 7 ma in which sediments were either eroded or not deposited during a full glacial stage the development pattern of the water mass interface between mow and neaw might have changed because of the fluctuations of the mow production which is responsible for the amplitude in ice volume oscillations from the low amplitude 41 ka cycles for the lower mound to the high amplitude 100 ka cycles for the upper mound the average sedimentation and caco3 production rates of the lower mound were evaluated 27 cm ka and 31 1 g cm2 ka respectively

diagenetic formation of gypsum and dolomite in a cold water coral mound in the porcupine seabight off ireland authigenic gypsum was found in a gravity core retrieved from the top of mound perseverance a giant cold water coral mound in the porcupine basin off ireland the occurrence of gypsum in such an environment is intriguing because gypsum a classic evaporitic mineral is undersaturated with respect to sea water sedimentological petrographic and isotopic evidence point to diagenetic formation of the gypsum tied to oxidation of sedimentary sulphide minerals i e pyrite this oxidation is attributed to a phase of increased bottom currents which caused erosion and enhanced inflow of oxidizing fluids into the mound sediments the oxidation of pyrite produced acidity causing carbonate dissolution and subsequently leading to pore water oversaturation with respect to gypsum and dolomite calculations based on the isotopic compositions of gypsum and pyrite reveal that between 21 6 and 28 6 of the sulphate incorporated into the gypsum derived from pyrite oxidation the dissolution of carbonate increased the porosity in the affected sediment layer but promoted lithification of the sediments at the sediment water interface thus authigenic gypsum can serve as a signature for diagenetic oxidation events in carbonate rich sediments these observations demonstrate that fluid flow steered by environmental factors has an important effect on the diagenesis of coral mounds

growth history of a cold water coral covered carbonate mound galway mound porcupine seabight ne atlantic abstract during the past decade knowledge about the ecology and the environment of giant carbonate mounds has been growing continuously however still little is known about their growth dynamics three gravity cores from galway mound belgica mound province in the porcupine seabight off ireland were investigated for their sedimentological geophysical and geochemical properties to get insight into the long term development of this cold water coral covered carbonate mound these data were supplemented by radiometric age determinations on planktonic foraminifera and coral skeletons the records from three different settings on galway mound reveal a coherent growth history that in general is similar to what is known from other carbonate mounds at the irish margin however whereas other cores are often disturbed by numerous and not correlateable hiatuses galway mound in contrast appears to be characterised by only one major hiatus representing a time gap of 250 kyr several mechanisms are discussed in this study as possible causes for the observed stratigraphic record at galway mound the most likely explanation is that the hiatus has its origin in a major mass wasting event on an instable possibly glacial unit that could have acted as a slip plane the overall late quaternary growth history of galway mound fits well into existing cyclical mound development models pointing to galway mound being an actively growing mound coral bank stage at present

paleoceanographic implications of miocene deep sea hiatuses miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages the subsequent changes in oceanic circulation and development of major antarctic glaciation the consequences and timing of these events can be observed in variations in the distribution of deep sea hiatuses sedimentation patterns and biogeographic distribution of planktic organisms the opening of the drake passage in the latest oligocene to early miocene 25 20 ma resulted in the establishment of the deep circumpolar current which led to thermal isolation of antarctica and increased global cooling this development was associated with a major turnover in planktic organisms resulting in the evolution of neogene assemblages and the eventual extinction of paleogene assemblages the erosive patterns of two widespread hiatuses ph 23 0 22 5 ma and nh 1 20 18 ma indicate that a deep circumequatorial circulation existed at this time characterized by a broad band of carbonate ooze deposition siliceous sedimentation was restricted to the north atlantic and a narrow band around antarctica a major reorganization in deep sea sedimentation and hiatus distribution patterns occurred near the early middle miocene boundary apparently resulting from changes in oceanic circulation beginning at this time deep sea erosion occurred throughout the caribbean hiatus nh 2 16 15 ma suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents and or intensification of the gulf stream sediment distribution patterns changed dramatically with the sudden appearance of siliceous ooze deposition in the marginal and east equatorial north pacific by 16 0 to 15 5 ma coincident with the decline of siliceous sedimentation in the north atlantic this silica switch may have been caused by the introduction of norwegian overflow water into the north atlantic acting as a barrier to outcropping of silica rich antarctic bottom water the main aspects of the present oceanic circulation system and sediment distribution pattern were established by 13 5 to 12 5 ma hiatus nh 3 coincident with the establishment of a major east antarctic ice cap antarctic glaciation resulted in a broadening belt of siliceous ooze deposition around antarctica increased siliceous sedimentation in the marginal and east equatorial north pacific and indian oceans and further northward restriction of siliceous sediments in the north atlantic periodic cool climatic events were accompanied by lower eustatic sea levels and widespread deep sea erosion at 12 to 11 ma nh 4 10 to 9 ma nh 5 7 5 to 6 2 ma nh 6 and 5 2 to 4 7 ma nh 7

the magellan mound province in the porcupine basin the magellan mound province is one of the three known provinces of carbonate mounds or cold water coral banks in the porcupine seabight west of ireland it has been studied in detail using a large and varied data set 2d and 3d seismic data sidescan sonar imagery and video data collected during rov deployment have been used to describe the mounds in terms of origin growth processes and burial the aim of this paper is to present the magellan mounds and their setting in an integrated holistic way

high frequency climate linkages between the north atlantic and the mediterranean during marine oxygen isotope stage 100 mis100 high resolution records of mediterranean and north atlantic deep sea sediments indicate that rapid changes in hydrology and climate occurred during marine oxygen isotope stage 100 mis100 at 2 52 ma which exhibits characteristics similar to late pleistocene dansgaard oeschger bond cycles and heinrich events as in the late pleistocene north atlantic oceanographic and atmospheric changes were probably transmitted into the mediterranean by some combination of surface water inflow and atlantic mediterranean atmospheric pressure gradients our data suggest that the mechanism s responsible for sub milankovitch and millennial scale climate oscillations were the same over at least the past 2 6 ma notwithstanding the transition from the 41 kyr dominated glacial cycles of the late pliocene to the 100 kyr cycles of the late pleistocene

cadmium calcium and carbon isotope reconstructions of the glacial northeast atlantic ocean the 13c and cd measurements from benthic foraminifera from biogeochemical ocean flux study bofs northeast atlantic ocean sediment cores are presented the 13c values in glacial foraminifera are consistent with those from elsewhere in the north atlantic ocean for intermediate water 1000 2000 m water depth 13c values were higher at the last glacial maximum than in present north atlantic deep water nadw whereas for deep water 2000 m they were lower during the glacial maximum the cd concentrations of glacial northeast atlantic intermediate water were lower than those of present nadw however deepwater cd concentrations increased to values between nadw and present pacific deep water pdw the 13c and cd data are consistent and show that the northeast atlantic ocean was strongly stratified with 13c enriched low cd intermediate water overlying 13c depleted high cd deep water the glacial water column comprised two different water masses deep water similar in character to present antarctic bottom water aabw and intermediate water different in character from both aabw and nadw and any present intermediate depth north atlantic water the characteristics of glacial intermediate water were however similar to present near surface waters in the north atlantic which suggests rapid ventilation of the glacial ocean to depths of up to 2000 m by cold nutrient depleted young surface waters

late glacial to holocene history of the mediterranean outflow evidence from benthic foraminiferal assemblages and stable isotopes at the portuguese margin records of benthic foraminiferal assemblage variations and benthic 13c along 12 sediment cores from the western iberian margin between 36 and 42 n at water depths from 820 to 3580 m are used to monitor fluctuations of the mediterranean outflow water mow during the past 30 ka the chronostratigraphy of the cores is based on planktonic 18o records 14c ams dating and the recognition of heinrich events h1 through h4 increased abundances of suspension feeding benthic foraminifers denoted as epibenthos group closely match areas where the recent mow core layers impinge on the continental slope at 800 and 1300 m water depth and near bottom current velocities are enhanced elevated epibenthos group abundances increased benthic 13c and sedimentological evidence for winnowing and erosion are found in glacial sections up to the earliest termination i in cores at water depths between 1600 and 2200 m off southern portugal the combined evidence reveals enhanced current activity at these depths due to a deep glacial mow the mow advection at the portuguese margin during the last glacial was about 700 m deeper than today conceivably forced by increased mow density due to higher salinity and colder temperatures of mediterranean waters the deep mow current gradually decreased in strength and shoaled to 1300 m water depth during the termination and early holocene a shallow mow core layer became active with the onset of termination i at depths between 600 and 1000 m both the shallow and deep mow current culminated during the younger dryas period the present flow pattern with two mow core layers centred at 800 and 1300 m water depth was established between 7 5 and 5 5 ka

changes in east atlantic deepwater circulation over the last 30 000 years eight time slice reconstructions using 95 epibenthic 13c records eight time slices were reconstructed to trace the distribution of east atlantic deepwater and intermediate water masses over the last 30 000 years our results show that there have been three distinct modes of deepwater circulation near the stage 3 2 boundary the origin of north atlantic deep water nadw was similar to today mode 1 however after late stage 3 the source region of the nadw end member shifted from the norwegian greenland sea to areas south of iceland mode 2 a reduced nadw flow persisted during the last glacial maximum with constant preformed 13c values the nutrient content of nadw increased markedly near the azores fracture zone from north to south probably because of the mixing of upwelled antarctic bottom water aabw from below which then advected with much higher flux rates into the northeast atlantic later the spread of glacial meltwater over the north atlantic led to a marked short term ventilation minimum below 1800 m about 13 500 14c years ago mode 3 the formation of nadw recommenced abruptly north of iceland 12 800 12 500 years ago and reached a volume approaching that of the holocene in the younger dryas 10 800 10 350 years b p another short term shutdown of deepwater formation followed between 10 200 and 9 600 years b p linked to a further major meltwater pulse into the atlantic each renewal of deepwater formation led to a marked release of fossil co2 from the ocean the likely cause of the contemporaneous 14c plateaus over the last 9000 years deepwater circulation varied little from today apart from a slight increase in aabw about 7000 14c years ago it is also shown that the oxygenated mediterranean outflow varied largely independent of the variations in deepwater circulation over the last 30 000 years

miocene evolution of atmospheric carbon dioxide changes in pco2 or ocean circulation are generally invoked to explain warm early miocene climates and a rapid east antarctic ice sheet eais expansion in the middle miocene this study reconstructs late oligocene to late miocene pco2 from ep values based on carbon isotopic analyses of diunsaturated alkenones and planktonic foraminifera from deep sea drilling project sites 588 and 608 and ocean drilling program site 730 our results indicate that highest pco2 occurred during the latest oligocene 350 ppmv but decreased rapidly at 25 ma the early and middle miocene was characterized by low pco2 260 190 ppmv lower intervals of pco2 correspond to inferred organic carbon burial events and glacial episodes with the lowest concentrations occurring during the middle miocene there is no evidence for either high pco2 during the late early miocene climatic optimum or a sharp pco2 decrease associated with eais growth paradoxically pco2 increased following eais growth and obtained preindustrial levels by 10 ma although we emphasize an oceanographic control on miocene climate low pco2 could have primed the climate system to respond sensitively to changes in heat and vapor transport

benthic isotope evidence for changes of the mediterranean outflow during the late quaternary a suit of sediment cores close to and south of the strait of gibraltar 12 36 n 500 2800 m water depth were analyzed for stable isotopes in epibenthic foraminifers cibicidoides wuellerstorfi and planulina ariminensis during peak glacial times the data exhibit higher 13c values of up to 1 6 at intermediate depths near the strait of gibraltar 36 n the values decrease to the south as evidenced by our data but also to the north as revealed by data of intermediate depth cores north of 38 n in duplessy et al 1987 thus the distribution pattern of 13c provides crucial evidence for an increased influence of nutrient depleted mediterranean outflow water mow on the glacial northeast atlantic hydrography during oxygen isotope terminations i and ii the meridional carbon isotope gradient indicates a significantly decreased but still active mow as deduced from the 18o fluctuations the temperatures of the mow in the atlantic were lower during glacial times by as much as 5 c during glacial times and during termination i the maximum 13c values of the mow correlate with minimum values of the north atlantic deep water nadw and vice versa this inverse response to climatic change of the carbon isotope signals of both water masses indicates that the supply of saline mow to the north atlantic may be less important for the formation of nadw than previously assumed

yanshanian late mesozoic ore deposits in china an introduction to the special issue abstract the late jurassic cretaceous yanshanian orogeny or yenshan movement one of the most important tectonothermal events is first recognized in china especially eastern china this late mesozoic orogeny which was initiated most likely by a mesozoic tectonic switch strongly reworked or destructed the older continental lithospheres or cratonic keels that are manifested by alternating compressive and extensional deformation voluminous igneous rocks and a variety of characteristic magmatic hydrothermal mineral systems despite its first discovery and definition in yenshan yinshan area of north china craton the yanshanian orogeny probably is of global tectonic magmatic and metallogenic significance however there have been hot debates on the precise starting time accurate duration or time interval detailed processes and evolution linked to deep lithospheres tectonic nature and geodynamic mechanism s of the yanshanian orogeny which inevitably have hindered the understanding of the genesis mineralizing processes and geodynamic mechanism of the late mesozoic magmatic hydrothermal mineral systems this special issue captures some of the latest research results on the yanshanian ore deposits that are involved into a few main mesozoic metallogenic belts or provinces from northeast to southwest china including 1 the jiaodong peninsula metallogenic province in the north china craton 2 the middle lower yangtze river valley metallogenic belt in the central eastern china 3 the jiangnan and 4 the nanling metallogenic belts in the south china block 5 the southeastern china coast metallogenic belt and 6 the sanjiang metallogenic belt in southwest china through a multidisciplinary study this special issue re investigated and re evaluated the relationship between the late mesozoic magmatic hydrothermal mineral systems and the yanshanian tectonothermal events in the studied metallogenic belts or provinces a few important contributions to the topic in this special issue yanshanian metallogeny are summarized as followings 1 a new ore deposit type i e the intracontinental reactivation type has been suggested to interpret the genesis of those au polymetallic deposits that are hosted within older metamorphic rocks and related to the late mesozoic basin and range extensional settings 2 late mesozoic re activation of the preexisting structures by the yanshanian tectono thermal event s might be an important mechanism controlling the yanshanian large scale mineralization 3 a type granites formed by partial melting of the mesoproterozoic crust but with inputs from mantle derived melt are also favorable for sn mineralization in addition to s type and i type granites as previously recognized 4 calculated oxygen fugacities o 2 of granitic magmas based on chemical compositions of primary biotite have been confirmed to be effective proxy for distinguishing cu au mo w sn pb zn mineralized granites from barren granites 5 a significant epoch of w sn magmatic hydrothermal ore system at ca 145 135 ma has been identified in the southeastern china coast metallogenic belt and 6 in addition to traditional structural geology mineralogy petrology geochemistry and geochronology new analytical techniques e g cu isotopes and data treatment method e g bi dimensional empirical mode decomposition can be used to provide more constraints for deep exploration

microhabitat preferences and stable carbon isotopes of endobenthic foraminifera clue to quantitative reconstruction of oceanic new production seventeen surface sediment samples from the north atlantic ocean off ne greenland between 76 and 81 n and nine samples from the south atlantic ocean close to bouvet island between 48 and 55 s were taken with the aid of a multiple corer and investigated for their live rose bengal stained benthic foraminiferal content within the upper 15 cm of sediment preferentially endobenthic melonis barleeanum m zaandami and bulimina aculeata as well as preferentially epibenthic lobatula lobatula were counted from 1 cm thick sediment slices each and analyzed for stable carbon and oxygen isotopic compositions of their calcareous tests live and dead specimens were counted and measured separately the carbon isotopic composition of the foraminifera was compared to that of the dissolved inorganic carbon dic of simultaneously sampled bottom water during a period of one month one station off ne greenland was replicately sampled once every week and samples were processed as above live specimens of lobatula lobatula are confined to the uppermost two centimeters of sediment live specimens of melonis spp are found down to eight centimeters within the sediment but with a distinct sub surface maximum between two and five centimeters the down core distribution of live bulimina aculeata shows a distinct surface maximum in the top centimeter and constant but low numbers down to 11 cm subbottom depth the average stable carbon isotopic composition d13c per mil vpdb of live l lobatula off ne greenland is by 0 4 0 1 per mil higher than the d13cdic of the ambient bottom water at the time of sampling there is evidence that this species calcify before the ice free season when bottom water d13cdic is supposed to be higher this would reconfirm the one to one relationship between d13c of ambient water dic and cibicids widely used by paleoceanographers live m barleeanum show a negative offset from bottom water dic of 1 7 0 6 per mil in the uppermost sediment and of 2 2 0 5 per mil in three to four centimeters subbottom depth all d13c values of live melonis spp decrease within the upper four centimeters regardless of the time of sampling and site investigated the offset of live b aculeata from bottom water d13cdic values of eight stations rather constantly amounts 0 6 0 1 per mil no matter what subbottom depth the specimens are from at one station however where is strong indication of elevated organic carbon flux the negative offset averaged over all sub bottom depths increases to 1 5 0 2 per mil buliminids actively move within the sediment and by this either record an average isotope signal of the pore water or the signal of one specific calcification depth the recorded signal however depends on the organic carbon flux and reflects general but site specific pore water d13cdic values if compared with epibenthic d13c values from the same site not influenced by pore water and related phytodetritus layer effects bulimina d13c values bear some potential as a paleoproductivity proxy specimens of melonis spp seem to prefer a more static way of life and calcify at different but individually fix depths within the sediment although live specimens thus record a stratified pore water d13c signal there is no means yet to correct for bioturbational and early diagenetic effects in fossil faunas