combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

the fugloy reef at 70 n acoustic signature geologic geomorphologic and oceanographic setting this is the first in depth study of a cluster of cold water coral reefs the fugloy reefs found at 70 n on the norwegian margin combining high resolution seismic reflection data side scan sonar video images and oceanographic measurements reveals the geologic geomorphologic and oceanographic setting in which the reefs occur the reefs consist mainly of the scleractinian ahermatypic lophelia pertusa and exist below the thermocline at water depths between 140 m and 190 m the reefs appear as cone shaped acoustically transparent features on seismic reflection data consistently located in places characterized by the availability of hard substrate high relief and periodical exposure to high tidal currents 30 cm s these currents transport water of the norwegian atlantic current to the reefs from an area with fluid expulsion related pockmarks the spatial relationship between reef pockmark locations and current directions suggests that seepage of biogenic gas might be a catalyst to reef growth with a height of more than 40 m some of the fugloy reefs are among the highest reported from the norwegian margin this indicates highly favourable growth conditions and conservative estimates indicate a net growth rate for the reefs of 5 mm year we expect that cold water reefs will be found further north along the barents sea margin as general awareness on the geophysical signature and appearance of the reefs increases because all known factors involved in reef establishment and growth are within the required intervals also further north

a simple model of fjord and coastal circulation interaction abstract the dynamical interaction of a narrow fjord with a wind driven coastal regime is investigated using a linear two layer numerical model the coriolis acceleration is important in the coastal regime but assumed to he unimportant in the fjord dynamical because v 0 for a wide variety of wind conditions bottom topography and model parameters the wind forced coastal circulation with its geostrophic alongshore currants has a strong effect on the circulation within the fjord these geostrophic currents control the free surface and pycnocline displacement at the fjord mouth thereby strongly affecting fjord circulation this mechanism is an alternative to the classical idea of hydraulic control at the mouth by sills or constrictions model simulators also show that the free surface slope is a baroclinic effect and that alongshore and across shore winds affect the fjord differently alongshore winds produce flooding while up and down fjord winds simply sat up the surface we find that offshore win

dynamics of mild strombolian activity on mt etna abstract here we report the first measurements of gas masses released during a rare period of strombolian activity at the bocca nuova crater mt etna sicily uv camera data acquired for 195 events over an 27 minute period 27th july 2012 indicate erupted so2 masses ranging from 0 1 to 14 kg per event with corresponding total gas masses of 0 1 to 74 kg thus the activity was characterised by more frequent and smaller events than typically associated with strombolian activity on volcanoes such as stromboli events releasing larger measured gas masses were followed by relatively long repose periods before the following burst a feature not previously reported on from gas measurement data if we assume that gas transport within the magma can be represented by a train of rising gas pockets or slugs then the high frequency of events indicates that these slugs must have been in close proximity in this case the longer repose durations associated with the larger slugs would be consistent with interactions between adjacent slugs leading to coalescence a process expedited close to the surface by rapid slug expansion we apply basic modelling considerations to the measured gas masses in order to investigate potential slug characteristics governing the observed activity we also cross correlated the acquired gas fluxes with contemporaneously obtained seismic data but found no relationship between the series in line with the mild form of manifest explosivity

a deglacial middle holocene record of biogenic sedimentation and paleoproductivity changes from the northern norwegian continental shelf 1 the relative proportions of marine organic carbon and biogenic carbonate in a high resolution record from a glacial trough on the northern norwegian continental shelf were used to decipher changes in biogenic sedimentation and paleoproductivity from the last deglaciation to the middle holocene decadal scale to century scale oscillations in biogenic sedimentation and surface ocean productivity recorded in the andfjorden sediments are synchronous with abrupt climate changes in open oceanic and atmospheric regimes of the high northern latitudes following several fluctuations during the bolling allerod interstadial the most dramatic drop in marine organic carbon and biogenic carbonate proportions occurred during the younger dryas however many short term and low amplitude events during the preboreal and the holocene have also affected biogenic sedimentation in the outer andfjorden apparently these abrupt changes in biogenic sedimentation were caused by the suppression of a potential upwelling center in the outer andfjorden by variable atlantic water inflow over the past 14 000 years the adjustment of decadal high productivity coastal systems to freshwater forced multiple cooling events during the late glacial to middle holocene highlights the impact of global climate changes on the climate sensitive local ecosystems off coastal norway

paleomagnetic constraints on eruption patterns at the pacaya composite volcano guatemala pacaya volcano is an active composite volcano located in the volcanic highlands of guatemala about 40 km south of guatemala city volcanism at pacaya alternates between strombolian and vulcanian and during the past five years there has been a marked increase in the violence of eruptions the volcano is composed principally of basalt flows interbedded with thin scoria fall units several pyroclastic surge beds and at least one welded tuff between 400 and 2000 years bp the w sw sector of the volcano collapsed producing a horseshoeshaped amphitheater 0 65 km3 and providing a window into the cone s infrastructure lava flows and tephra exposed in the amphitheater are more then 200 m thick and when combined with flows erupted recently represent between 30 and 40 of the cone s history pacaya is ideally suited for a paleomagnetic study into the timing and duration of eruption episodes at a large composite volcano we drilled 27 paleomagnetic sites 25 aa flows 1 dike and 1 welded tuff from four lava flow sequences with between 4 and 14 sites per sequence the four sequences represent initial through historic activity at pacaya we resolved what appear to be 22 time independent paleomagnetic sites by averaging together directions from successive sites where the sitemean directions were indistinguishable at the 95 level of confidence however mean sequence directions of individual lava flow sequences yielded unusually high fisher precision parameters k 44 224 and small circles of 63 confidence a63 1 6 6 1 suggesting as few as three or four time independent sites were collected this indicates that activity as pacaya is strongly episodic and that episodes are characterized by voluminous outpouring of lavas modelling the data using holocene psv rates confirms this and shows that differences in within sequence directions 6 11 5 are consistent with emplacement of lava flow sequences in less than 100 years to as many as 300 years relatively larger differences in directions 18 23 between subjacent lava flow sequences indicates that repose is at least 300 500 years and could be even longer

geochemical and physical constraints for the occurrence of living cold water corals cold water coral communities cover a wide range of possible habitats in terms of latitude ocean basins and depth with ongoing studies continually expanding occurrences in various regions of the global ocean a range of factors determines the formation of cold water coral reefs such as physical hydrochemical and biological e g food supply factors recently more and more modeling studies have emerged using a variety of mathematical approaches have emerged including environmental niche factor analysis enfa and predictive habitat suitability models however only few studies have attempted to characterize the underlying suite of hydro biogeochemical and physical constraints of cold water coral reefs and to differentiate between pristine reef growth vs sites with reduced or no coral occurrences this study concentrates on new data and a compilation of existing data sets on the physical and chemical properties in the ne atlantic and the mediterranean it explores the influence of ambient bottom waters and its characteristics on living cold water reefs and mounds formed by lophelia pertusa several questions are addressed 1 what are the physical and geochemical boundary conditions of living cold water corals 2 do these geochemical parameters correlate with proposed physical prerequisites 3 is there a general difference in the signature of living and dead coral sites

multiparameter quantification of gas release during weak strombolian eruptions at pacaya volcano guatemala 1 activity at pacaya volcano guatemala is characterized by persistent degassing coupled at times with lava effusion and or coincident strombolian style explosions we used 0 25 hz sample rate sulfur dioxide emission data from a uv camera and coincident infrasound recordings to investigate the link between varied emission rates and infrasound events degassing rates varied on two scales during this study smaller more rapid variations on the scale of 1 to 3 minutes are superimposed on larger slower changes over 30 minutes to 1 hour the acoustic record was dominated by repeated n shaped events characteristic of strombolian explosions because of the high resolution of the gas measurements we were able to calculate gas masses for individual explosions from both datasets and find the two estimates agree within an order of magnitude the infrasound explosion records correlate with small pulses in degassing but the longer term degassing trends may represent a deeper process

identification of contrasting seasonal sea ice conditions during the younger dryas abstract a palaeo sea ice reconstruction for northern norway for the interval ca 13 8 7 2 cal ka bp has been performed using a combined organic geochemical proxy based study of a marine sediment core jm99 1200 obtained from andfjorden 69 15 95 n 16 25 09 e and the outcomes compared with a series of other palaeoclimate studies carried out previously within this study particular emphasis has been placed on the identification of the sea ice conditions during the younger dryas and the application of different biomarker based proxies to both identify and quantify seasonal sea ice conditions firstly the appearance of the specific sea ice diatom proxy ip 25 at ca 12 9 cal ka bp in the sedimentary record has provided an unambiguous but qualitative measure of seasonal sea ice and thus the onset of the younger dryas stadial the near continuous occurrence of ip 25 for the next ca 1400 yr demonstrates seasonal sea ice during this interval although variable abundances suggest that the recurrent conditions in the early mid younger dryas ca 12 9 11 9 cal ka bp changed significantly from stable to highly variable sea ice conditions at ca 11 9 cal ka bp and this instability in sea ice prevailed for the subsequent ca 400 yr during which an extremely short interval of permanent or near permanent sea ice was observed at ca 11 75 cal ka bp at ca 11 5 cal ka bp ip 25 disappeared from the record indicating ice free conditions that signified the beginning of the holocene the ip 25 concentrations were also combined with those of the open water phytoplankton biomarker brassicasterol to generate p b ip 25 data from which more quantitative measurements of sea ice were determined p b ip 25 data were consistent with consecutively seasonal then infrequent sea ice cover for the early mid and late younger dryas while further comparisons of the p b ip 25 data with the outcomes of previous correlations with modelled sea ice concentrations suggested that these intervals were characterised by ca 60 90 and ca 0 60 sea ice cover respectively both qualitative and quantitative sea ice records were also consistent with sea surface temperature and other palaeoclimate estimates derived previously from various other proxy studies the contrasting seasonal sea ice conditions during the younger dryas were further verified through a comparison of the concentrations of ip 25 with those of another highly branched isoprenoid hbi alkene that is di unsaturated and believed to also be produced by sea ice diatoms the ratio of the hbi diene to ip 25 termed dip 25 is believed to provide a useful indicator of stability or variability in sea ice conditions and complements the outcomes from the ip 25 and p b ip 25 index data the identification of contrasting seasonal sea ice conditions during the younger dryas will likely contribute to the debate regarding the climatic impacts that took place during this intriguing interval

a continuous marine record 8000 1600 cal yr bp from the malangenfjord north norway foraminiferal and isotopic evidence holocene oceanography and climate were studied in the continuous marine sediment sequence in a piston core from the high latitude malangenfjord north norway using benthic foraminifera and stable isotopes radiocarbon dates indicate that the investigated sequence covers the period from c 8000 to 1600 cal bp and has a sedimentation rate of 0 3 12 7 m 1000 years bottom water temperatures reconstructed from benthic foraminiferal stable isotopes in the malangenfjord show a cooling of c 3 c ranging from 10 c and reaching c 7 c at 1600 cal yr bp which is similar to present bottom water temperature at the core location a planktic foraminiferal 18o record was established from c 6400 to 1600 cal yr bp generally following the same pattem as the benthic record this long term cooling correlates to the decreasing insolation at 70 n following the orbital forcing the long term cooling also corresponds well with atmospheric proxy records implying a close ocean atmosphere coupling it is also indicated both b

glacier fluctuations equilibrium line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene based on lacustrine and morpho stratigraphical evidence from lyngen in troms northern norway 13 marginal moraines have been mapped in front of lenangsbreene in strupskardet moraines m1 m13 are inferred to represent glacier halts or advance readvance taking place during the lateglacial and holocene the presence of collapse depressions suggests that some of them were ice cored m1 m3 a chronological framework taking into account a combination of former shorelines and related glacier meltwater channels lichenometry and ams radiocarbon dated lacustrine sediments spanning the last 20 000 cal yr bp has been established the distal glacier fed lake aspvatnet was isolated from the sea c 10 300 cal yr bp and the lacustrine sediments have been investigated by use of loss on ignition loi magnetic susceptibility water content wet and dry bulk density dbd and the magnetic parameters anhysteretic remanent magnetization arm and saturation remanent magnetization sirm there is in general good agr

so2 emissions to the atmosphere from active volcanoes in guatemala and el salvador 1999 2002 ground based and aircraft correlation spectrometer cospec measurements at the principal active volcanoes in guatemala pacaya santiaguito fuego and tacana and el salvador santa ana and san miguel were carried out at intervals during the period 1999 2002 as part of an attempt to measure baseline so2 emissions of potentially dangerous volcanoes and to better understand their eruption mechanisms we discuss some of the uncertainties involved in interpreting intermittent gas data together with possible improvements other problems pertaining to current monitoring of so2 and implications for future studies are also discussed santa ana volcano is proposed to be a venting hydrothermal system while santiaguito fuego pacaya and san miguel all exhibit open vent characteristics data for tacana volcano are presented but are not enough to make descriptions of its characteristics and activity pacaya is emitting high fluxes of so2 1000 tonnes day while the other vents are much lower emitters 20 300 tonnes day in general so2 emissions at pacaya suggest a large circulating and convecting high level chamber the most recent emission rates at fuego were measured during its current active phase since january 2002 average so2 emission rates during 1999 2002 are 1350 tonnes day for pacaya 340 tonnes day for fuego 120 tonnes day for santiaguito 260 tonnes day for san miguel 140 tonnes day for santa ana and 30 tonnes day for tacana these volcanoes account for about 6 to 12 of the estimated annual global volcanic output of so2

sedimentation patterns on a cold water coral mound off mauritania an unconformity bound glacial sequence 135 cm thick of a coral bearing sediment core collected from the flank of a cold water coral mound in the banda mound province off mauritania was analysed in order to study the relation between coral framework growth and its filling by hemipelagic sediments u series dates obtained from the cold water coral species lophelia pertusa were compared to c 14 dates of planktonic foraminifera of the surrounding matrix sediments the coral ages ranging from 45 1 to 32 3 ka bp exhibit no clear depositional trend while on the other hand the c 14 dates of the matrix sediment provide ages within a much narrower time window of 3000 yrs 34 6 31 8 cal ka bp corresponding to the latest phase of the coral growth period in addition high resolution computer tomography data revealed a subdivision of the investigated sediment package into three distinct parts defined by the portion and fragmentation of corals and associated macrofauna as well as in the density of the matrix sediments grain size spectra obtained on the matrix sediments show a homogeneous pattern throughout the core sediment package with minor variations these features are interpreted as indicators of redeposition based on the observed structures and the dating results the sediments were interpreted as deposits of a mass wasting event namely a debris flow during this event the sediment unit must have been entirely mixed resulting in averaging of the foraminifera ages from the whole unit and giving randomly distributed coral ages in this context for the first time mass wasting is proposed to be a substantial process of mound progradation by exporting material from the mound top to the flanks hence it may not only be an erosional feature but also widening the base of the mound thus allowing further vertical mound growth

production and accumulation of calcium carbonate in the ocean budget of a nonsteady state present day production of caco3 in tne world ocean is calculated to be about 5 billion tons bt per year of which about 3 bt accumulate in sediments the other 40 is dissolved nearly half of the carbonate sediment accumulates on reefs banks and tropical shelves and consists largely of metastable aragonite and magnesian calcite deep sea carbonates predominantly calcitic coccoliths and planktonic foraminifera have orders of magnitude lower productivity and accumulation rates than shallow water carbonates but they cover orders of magnitude larger basin area twice as much calcium is removed from the oceans by present day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity 1 6 bt suggesting that outputs have been overestimated or inputs underestimated that one or more other inputs have not been identified and or that the oceans are not presently in steady state one missing calcium source might be groundwater although its present day input is probably much smaller than that of rivers if as seems likely caco3 accumulation presently exceeds terrestial and hydrothermal input this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level shallow water accumulation decreases by an order of magnitude with a 100 m drop in sea level while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow water carbonates

the vestfjorden traenadjupet palaeo ice stream drainage system mid norwegian continental shelf abstract an ice stream in the vestfjorden traenadjupet depressions off northern norway transported glacial debris to the shelf edge and into the deep sea during the last glaciation our interpretation is based mainly on regional and detailed bathymetry and 2d and 3d seismic data this palaeo ice stream was approximately 400 km long and covered an area of 20 000 km 2 including a complex system of tributary fjords and valleys in nordland county the drainage basin had an area of ca 150 000 km 2 within the fennoscandian ice sheet fis during the last glacial maximum lgm the location of the palaeo ice stream prevented large ice masses from reaching the montainous areas of lofoten and vesteralen a local ice dome was established in these areas the palaeo ice stream eroded extensively into both mesozoic and cenozoic sedimentary rocks and quaternary sediments a pattern of well developed subglacial sedimentary bedforms was produced e g mega scale lineations drumlins ice stream shear margin moraines are located on both sides of traenadjupet defining the width of the palaeo ice stream 90 km at the shelf edge these moraines are commonly 10 20 m high a few kilometres wide and reach several tens of kilometres in length a large recessional moraine the tennholmen ridge has been mapped in vestfjorden it is 80 m high 20 km wide and 60 km long we have interpreted this ridge as a grounding line moraine formed during a halt or a readvance of the ice stream during the last deglaciation the large transport of glacial debris towards the grounding line occurred during this stage northeast of the tennholmen ridge several smaller moraine ridges were developed at still stands during deglaciation

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

paleo redox fronts and their formation in carbonate mound sediments from the rockall trough abstract piston cores from the summits of coral topped carbonate mounds at the south west rockall trough margin reveal that the sediments have undergone significant post depositional modifications affecting the original geochemical signature and mineralogical composition of the sediments this diagenetic imprint provides information about the geochemical processes within cold water coral mounds the most prominent result of diagenetic alteration of the primary sediment composition is the absence or poor preservation of aragonitic coral skeletons in certain depth intervals associated with lithification this study focuses on the enrichment of redox sensitive elements and the dissolution of primary magnetic ferric iron minerals in the depth interval below lithification levels by combining the magnetic susceptibility with the xrf signal of fe and ti specifically intervals with susceptibility variations related to the conversion of strongly magnetic into weakly magnetic iron species can be defined in all three studied cores a succession is recognised with a lithified interval with aragonite dissolution and low mg calcite precipitates that is underlain by an interval of magnetite dissolution and of iron and manganese enrichment for the most recent lithified interval it is demonstrated that initial lithification occurred before an erosional regime was in place most likely near the end of interglacial or at the start of glacial periods

the so2 camera a simple fast and cheap method for ground based imaging of so2 in volcanic plumes 1 so2 flux is widely monitored on active volcanoes as it gives a window into the hidden subsurface magma dynamics we present here a new approach to so2 flux monitoring using ultraviolet imaging of the volcanic plume through carefully chosen filters to produce images of so2 column amount the so2 camera heralds a breakthrough in both our ability to measure so2 flux at unprecedented frequencies 2 hz and at unprecedented accuracy thanks to the application of correlation techniques to determine wind speed directly from the images and the ability to measure the whole profile simultaneously in this paper we detail the commercially available pieces required to construct the so2 camera introduce a retrieval scheme to determine so2 amounts from the images and present results from a field campaign in november 2005 on sakurajima volcano japan

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

microspar development during early marine burial diagenesis a comparison of pliocene carbonates from the bahamas with silurian limestones from gotland sweden comparison of ultrastructures in pliocene periplatform carbonates from the bahamas with silurian limestones from gotland sweden reveals that despite the differences in primary sediment composition and age they reflect a similar mechanism of lithification in both sequences calcite microspar was formed as a primary cement at an early stage of marine burial diagenesis neither significant compression nor meteoric influence are necessary for the formation of calcite microspar a model is proposed for the process of microsparitic cementation of fine grained aragonite needle muds comprising four stages 1 unconsolidated aragonite dominated carbonate mud 2 precipitation of microspar that engulfs aragonite needles 3 dissolution of aragonite resulting in pitted surfaces of the microspar crystals and 4 slight recrystallization our results contradict the widespread opinion that microspar necessarily is a product of secondary recrystallization of a previously lithified micrite

changes in fossil assemblage in sediment cores from mingulay reef complex ne atlantic implications for coral reef build up ct scanning and descriptions of sedimentary sequences have been conducted to describe the internal structure and define the evolutionary sequence of events leading to the build up of cold water coral reef constructed by the azooxanthellate scleractinian lophelia pertusa two vibrocores containing coral clasts and associated fauna embedded in a matrix of marine sediment were taken at the mingulay reef complex an inshore 120 190 m water depth l pertusa reef off western scotland the cores were scanned using computed x ray tomography ct scan with the aim of 1 reconstructing and quantifying the relative abundance and preservation of coral fragments in the cores 2 identifying distinct reef facies and hence 3 providing data that could lead to a conceptual model of reef growth u series dates were obtained on l pertusa clasts from the two sediment cores to provide a temporal framework of the reef build up after exploring a range of methods for processing ct scans three simple parameters were used to classify different strata within the cores the overall density of the cores the number of fossil clasts and the sum of the area of clasts detected by the ct scan these parameters were validated by comparing with density measurements from a multi sensor core logger mscl and physical dissection and analysis of fossils in the cores from the ct scan analyses three distinct reef facies were evident coral rich sediment rich and shelly coral hash layers the succession and rapid cycle of reef framework forming l pertusa development disturbance and recovery allow us to provide a model of cold water coral reef build up including shifts in biodiversity physical chemical biological processes and the sedimentary regime

anatomy and dynamics of a floodplain powder river montana u s a abstract centimeter scale measurements on several powder river floodplains provide insights into the nature of overbank depositional processes that created the floodplains during a 20 year period after a major flood in 1978 rising stages initially entered across a sill at the downriver end of the floodplains later as stages continued to rise water entered the floodplains through distinct low saddles along natural levees the annual maximum depth of water over the levee crest averaged 0 19 m from 1983 through 1996 and the estimated flow velocities were approximately 0 15 m s 1 water ponded in the floodplain trough a topographic low between the natural levee and the pre flood riverbank and mud settled as thin layers of nearly constant thickness mud layers alternated with sand layers which were relatively thick near the channel together these beds created a distinctive natural levee in some locations individual flood deposits began as a thin mud layer that gradually coarsened upwards to medium grained sand coarsening upwards sequences form initially as mud because only the uppermost layers of water in the channel supply the first overbank flows which are rich in mud but starved of sand at successively higher stages fine sands and then medium sands increase in concentration in the floodwater and are deposited as fine and medium sand layers overlying the initial mud layer theoretical predictions from mathematical models of sediment transport by advection and diffusion indicate that these processes acting alone are unlikely to create the observed sand layers of nearly uniform thickness that extend across much of the floodplain we infer that other transport processes notably bedload transport must be important along powder river even with the centimeter scale measurements of floodplain deposits daily hydraulic data and precise annual surface topographic surveys we were unable to determine any clear correspondence between the gauged flow record of overbank floods and the depositional layers mapped in the floodplain these results provide a detailed example of floodplain deposits and depositional processes that should prove useful for interpreting natural levee deposits in a variety of geologic settings

coral mound development at the campeche cold water coral province southern gulf of mexico implications of antarctic intermediate water increased influence during interglacials abstract coral mounds formed by framework forming scleractinian cold water corals cwc mainly lophelia pertusa are a common seabed feature along the atlantic continental margins while coral mound areas in the ne atlantic reveal a climate dependent temporal pattern of cwc occurrence and mound aggradation that is related to distinct environmental conditions e g productivity water mass properties hydrodynamics the long term development of cwc and coral mounds at the western side of the atlantic is less well documented and understood here we present a 260 kyr coral record from the recently described campeche cwc province in the southern gulf of mexico combined with a reconstruction of the paleo environmental conditions for the last 140 kyr uranium series dating of 26 coral samples reveals that cwc growth predominantly coincided with interglacial periods highest vertical mound aggradation rates of 34 to 40 cm kyr 1 occurred during the holocene the reduced occurrence of cwc and the concurrent almost complete stagnation in mound aggradation during glacial periods could be linked to a diminished presence of antarctic intermediate water at those intermediate depths in which the coral mounds occur such setting would have caused a less dynamic bottom current regime resulting in a reduced food supply to the cwc along the campeche bank

large scale paleoceanographic variations in the western mediterranean sea during the last 34 000 years from enhanced cold water coral growth to declining mounds abstract quantitative and qualitative analyses of cold water coral cwc fragments from two sediment cores obtained from the melilla mounds field mmf in the alboran sea western mediterranean sea reveal an alternation of periods dominated by distinct cwc species the lower parts of the cores are dominated by the cwc species lophelia pertusa which is successively replaced in the upper parts by the species madrepora oculata and dendrophyllids the transition in the macrofauna coincides with a characteristic change in the benthic foraminiferal assemblage benthic foraminiferal assemblage bfaglacial in accordance with benthic cibicides lobatulus and planktic globigerina bulloides 13c and 18o values provide evidence for generally high surface productivity cold and well ventilated bottom waters lasting from the end of marine isotope stage 3 33 3 ka bp reaching a maximum at the transition allerod younger dryas together with 13c of the organic carbon and rock eval pyrolysis benthic foraminiferal assemblage bfainterglacial established since the early holocene indicates that the mmf experienced a decrease in bottom water energy that caused an organic carbon enrichment in the sediments and also depleted oxygen waters compared to the pre holocene interval dominated by the planktic foraminifera neogloboquadrina incompta and the benthic foraminiferal assemblage bfaglacial the organic carbon deposited during the holocene in the mmf contains more refractory components in relation to sea level rise and modern oceanographic configuration based on our data we suggest that l pertusa has a higher ecological requirement than m oculata and dendrophyllids especially with regard to oxygen and nutrient availability

volume flow rate estimation for small explosions at mt etna italy from acoustic waveform inversion this study was supported by nerc grant ne p00105x 1 and by european unions horizon 2020 research and innovation programme under the marie sklodowska curie grant agreement 798480

cold water coral mounds in the southern alboran sea western mediterranean sea internal waves as an important driver for mound formation since the last deglaciation abstract cold water corals cwcs are widely distributed in the entire alboran sea western mediterranean sea but only along the moroccan margin they have formed numerous coral mounds which are constrained to the west and the east melilla cwc mound provinces wmcp and emcp while information already exists about the most recent development of the coral mounds in the emcp the temporal evolution of the mounds in the wmcp was unknown up to the present in this study we present for the first time cwc ages obtained from four sediment cores collected from different mounds of the wmcp which allowed to decipher their development since the last deglaciation our results revealed two pronounced periods of coral mound formation the average mound aggradation rates were of 75 176 cm kyr 1 during the bolling allerod interstadial and the early holocene only temporarily interrupted during the younger dryas when aggradation rates decreased to

good neighbours shaped by vigorous currents cold water coral mounds and contourites in the north atlantic abstract over the recent years two research fields addressing continental slope sedimentary systems have gained significant momentum contourites and cold water coral mounds being both related to intense bottom currents and being both dependent on sediment supply they share some commonalities resulting in their widespread co occurrence however as cold water coral mounds predominantly occur in shallow to intermediate water depths this co occurrence is restricted to these depth levels for both systems the available knowledge is derived basically from north atlantic ocean settings indicating the potential to discover such systems hidden in the other ocean basins as well as still hidden in the atlantic contourites and cold water coral mounds have the capability of providing high resolution palaeo environmental records although with often differing temporal ranges and or temporal resolutions applying the concept of a joint exploitation of sedimentary records obtained from mounds and contourites offers the unique possibility of analysing contourite and mound development as well as the related palaeo environmental settings much more comprehensively than done when only considering one of these archives thus after two decades of intense research providing significant knowledge about contourites and cold water coral mounds from the north atlantic new ideas and concepts may arise from a close collaboration of scientists working in these two fields

holocene sea level changes and barrier reef formation on an oceanic island palau islands western pacific abstract internal facies and development of an oceanic island s barrier reef were revealed by the stratigraphical study of six drill cores in palau islands western pacific the holocene reef development is primarily constrained at its foundation by the antecedent topography of pleistocene substratum holocene barrier reef is an increment on the pleistocene barrier reef which had been subaerially exposed during glacial stages about 8300 cal year bp calibrated calendar years b p branching acropora facies initially formed a bank on the seaward side of a pleistocene limestone surface with a vertical accumulation rate as high as 30 m ka ka 1000 years after 7200 cal year bp when the sea level rise rate decreased reef crest facies caught up with the sea surface with an accumulation rate of less than 2 2 m ka corals found in the reef crest facies are similar to the present day reef crest corals dominated by acropora digitifera and a humilis after the reef crest was formed bioclastic sand and gravel facies prograded lagoonward of the reef crest and consisted mostly of reef derived materials the construction of patch reefs post dated the barrier reef formation the mature barrier reef provided calm conditions inside the lagoon which then led to the construction of patch reefs and fringing reefs sea level changes deduced from the accumulation curves show rapid rise before 7200 cal year bp followed by a slight rise of 4 m at its maximum this change in sea level rise rate inspired the change in reef facies from branching acropora to reef crest

the holocene occurrence of cold water corals in the ne atlantic implications for coral carbonate mound evolution abstract u series dating of constructional cold water corals is a powerful tool to reconstruct the evolution of corals on carbonate mounds here we have investigated the time framework of corals such as lophelia pertusa and madrepora oculata on five different mound settings of the eastern north atlantic on rockall bank and in porcupine seabight sampled at variable depth and location 610 880 m water depth we have found that the past 11 ka reflect a period generally favourable for coral development we further determined local mound growth rates and identified mound surface erosion framework collapse during times of active coral framework construction local vertical mound growth rates vary between less than 5 cm ka 1 and up to 220 cm ka 1 we interpret rates exceeding 15 cm ka 1 as representative of densely populated coral reefs during times of reduced or absent coral development mound evolution rates are by far smaller 0 to 1 the time resolution achieved here furthermore provides first evidence for reduced coral ecosystem activity at 1 8 2 0 ka 4 2 4 8 ka and between 6 and 8 2 ka within the holocene that may be related to climate driven changes of the coral growth environments during glacial periods coral growth in those areas seems apparently extremely reduced or is even absent on mounds

near surface velocity structure of pacaya volcano guatemala derived from small aperture array analysis of seismic tremor knowledge of the typically complicated near surface structure on volcanoes is critical for determining accurate seismic event locations and seismic source mechanisms associated with precursory and eruptive activity to generate a near surface velocity model for the active cone of pacaya volcano guatemala we recorded seismic tremor and ambient noise with a small aperture array of 11 short period seismometers in january 2011 the diffuse wavefield was investigated using the spatial autocorrelation spac method and we computed rayleigh and love dispersion curves at the array location the phase velocities for rayleigh waves range from 1000 m s at 2 hz to 230 m s at 10 hz those for love waves range from 600 to 250 m s over the same frequency band such low velocities are consistent with the presence of unconsolidated tephra on the surface of the volcano interspersed with lava flows assuming they represent the fundamental modes of rayleigh and love waves we inverted the dispersion curves to produce a shear wave velocity model of the upper 500 m beneath the array online material s wave velocity models obtained from inversion and love and rayleigh wave dispersion curves

a complete record of holocene glacier variability at austre okstindbreen northern norway an integrated approach arctic glaciers are currently undergoing major changes but accurate knowledge about how they varied during the entire holocene is still scarce here we present a new complete glacier record from austre okstindbreen in nordland northern norway this reconstruction is based on a number of short and long cores retrieved from several downstream basins which have been analyzed by a suite of methods including geochemical elements xrf rock magnetic properties dry bulk density dbd and loss on ignition loi lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar gpr independently lichen dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210pb dated lake sediment chronology this integrated approach reveals that austre okstindbreen is the first known glacier in scandinavia to possibly have survived the holocene thermal optimum it also brackets the four largest glacier advances to c 7400 7000 1400 1200 900 700 and 300 150 years before ad 2000 b2k in contrast to most reconstructed glaciers in scandinavia the largest glacier advance was not associated with the little ice age but rather to an earlier period centred at 1300 b2k both the moraine chronology and the lacustrine records document this neoglacial advance compared to other glacier reconstructions from the northern hemisphere we identify near synchronous glacier advances occurring roughly at 4000 b2k 2700 b2k 1300 b2k and during the little ice age these correlative advances across the northern hemisphere suggest that these observed centennial scale events are a shared feature regardless of the large geographical distances separating them some minor discrepancies between different geographical areas may be caused by lack of precise dating but local climatic conditions may play a role as well

high precision tims u series and ams c 14 dating of a coral reef lagoon sediment core from southern south china sea accurate dating of lagoon sediments has been a difficult problem although lagoon profiles usually with high deposition rates have a great potential for high resolution climate reconstruction we report 26 high precision tims u series dates on 25 coral branches and five ams c 14 dates on foraminifera for a 15 4 m long lagoon core from yongshu reef nansha area southern south china sea all the dates are in the correct stratigraphical sequence providing the best chronology so far reported for lagoon deposits the results reveal a similar to 4000 a continuous depositional history with sedimentation rates varying from 0 8 to 24 6 mm a 1 with an average of 3 85 mm a 1 which corresponds to an average net carbonate accumulation rate of similar to 2700 g caco3 m 2 a 1 significantly higher than the mean value 800 400 g caco3 m 2 a 1 used for lagoons in general in previous studies of global carbonate budget episodes of accelerated depositions within the last 1000 years correlate well with strong storm events identified by u series dates of storm transported coral blocks in the area however in the longer term the sedimentation rates during the past 1000 years were much higher than earlier on probably due to more vigorous wave reef interaction as a result of relative sea level fall since 500 ad and expansion of reef flat area supplying more sediments the coral tims u series ages and foraminifera ams 14c dates reveal intriguing apparent radiocarbon reservoir ages r from 572 to 1052 years which are much higher than global mean values of similar to 400 years c 2006 elsevier ltd all rights reserved

thousands of cold water coral mounds along the moroccan atlantic continental margin distribution and morphometry abstract coral mounds formed by framework forming cold water corals pierce the seabed along most continental margins of the atlantic ocean and new sites are continuously being discovered here we describe an extremely high accumulation of coral mounds at the nw moroccan atlantic margin between 35 n and 35 5 n within an area of only 1440 km2 3400 mounds were found exposed at the seabed the coral mounds are nowadays characterized by an almost complete lack of living cold water corals in addition numerous buried mounds were identified in hydroacoustic sub bottom profiles and are estimated to be 3 7 times more frequent than the exposed mounds consequently a total of 16 000 buried and exposed mounds is estimated for the entire study area the exposed mounds are rather small with a mean height of 18 m and show a conspicuous arrangement in two slope parallel belts that centre in water depths between 720 and 870 m and 890 980 m respectively putting them among the deepest mound occurrences discovered so far in the atlantic the mostly elongated mounds largely stretch downslope pointing to a significant influence of internal waves in the mound formation process moreover based on their average dimensions the entire coral mound volume can be estimated as 1 3 km3 which means the mounds store a considerable amount of coral carbonate highlighting their potentially important role as regional carbonate factories in combination with further occurrences of coral mounds along the moroccan margin both in the mediterranean and in the atlantic ocean these new findings underline morocco s role as a hotspot for the occurrence of cold water coral mounds

mid to late holocene oxygen isotopes from voldafjorden western norway basin water in deep silled norwegian fjords is primarily influenced by inflowing atlantic water originating from the norwegian atlantic current nwac previous studies suggest that benthic foraminiferal oxygen isotope records from such fjords are strongly influenced by variability in this current the present paper presents a mid to late holocene record 6 2 2 ka with 17 yr time resolution from a western norwegian deep silled fjord voldafjorden an age model based on ten ams radiocarbon dates on marine carbonates and on one plant macrofossil has been established the study focuses on the oxygen isotope results obtained from two species of benthic foraminifera cassidulina laevigata and uvigerina mediterranea the 18o c laevigata record has systematically larger amplitudes than the 18o u mediterranea record which most likely is related to different life cycles periods of calcification the oxygen isotope results show a clear shift towards higher values between 5 and 4 ka interpreted to reflect

late glacial to holocene environmental changes and climate variability evidence from voldafjorden western norway sedimentological micropalaeontological benthic foraminifers and dinoflagellate cysts stable isotope data and ams 14c datings on cores and surface samples in addition to acoustic data have been obtained from voldafjorden western norway based on these data the late glacial and holocene sedimentological processes and variability in circulation and fjord environments are outlined glacial marine sedimentation prevailed in the voldafjorden between 11 0 kyr and 9 2 kyr bp radiocarbon years in the later part of the allerod period and for the rest of the holocene there was deposition of fine grained normal marine sediments in the fjord basin turbidite layers recorded in core material and on acoustic profiles dated to ca 2 1 6 9 7 6 ca 9 6 and ca 11 0 kyr bp interrupted the marine sedimentation the event dated to between 6 9 and 7 6 kyr bp probably corresponds to a tsunami resulting from large scale sliding on the continental margin off norway the storegga tsunami during the later part of the allerod period voldafjorden had a strongly stratified water column with cold bottom water and warm surface water reaching interglacial temperatures during the summer seasons during the younger dryas cold event there was a return to arctic sea surface summer temperatures possibly with year round sea ice cover the entire benthic fauna being composed of arctic species the first strong holocene warming observed simultaneously in bottom and sea surface temperature proxies occurred at ca 10 1 kyr bp bottom water proxies indicate two cold periods possibly with 2 c lowering of temperatures at ca 10 0 pbo 1 and at 9 8 kyr bp pbo 2 these events may both result from catastrophic outbursts of baltic glacial lake water the remainder of the holocene experienced variability in basin water temperature indicated by oxygen isotope measurements with an amplitude of ca 2 c with cooler periods at ca 8 4 9 0 5 6 5 2 4 6 4 2 3 5 2 2 1 2 and 0 4 0 8 kyr bp changes in the fjord hydrology through the past 11 3 kyr show a close correspondence both in amplitude and timing of events recorded in cores from the norwegian sea region and the north atlantic these data suggest a close relationship between fjord environments and variability in large scale oceanic circulation copyright 2001 john wiley sons ltd

holocene mean july temperature and winter precipitation in western norway inferred from palynological and glaciological lake sediment proxies reconstructions of mean july temperature tjul and winter precipitation pw for the last 11 500 years on the folgefonna peninsula are presented tjul was reconstructed using pollen climate transfer functions and pw was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation season temperature at the equilibrium line altitude ela with a reconstructed former ela using tjul as the proxy for ablation season temperature the reconstructions from the folgefonna peninsula suggest that the early holocene was relatively cool and dry until c 8000 cal yr bp followed by a warm and humid mid holocene until c 4000 cal yr bp with inferred tjul above 128c and pw reaching as high as 225 of the present day subsequent to c 4000 cal yr bp a reduction is seen in both inferred tjul and pw with large fluctuations during the last 500 years in addition new calculations of pw from two glaciers hardangerjokulen and jostedalsbreen in southern norway are presented the results show that pw varied in phase at all glaciers probably as a response to the same climate forcing factor during the early holocene a major shift is suggested between winds from the west and the east

paleoceanographic development in the sw barents sea during the late weichselian early holocene transition abstract the late weichselian early holocene variability of the north atlantic current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions the investigated sediment core is from 409 m water depth in the sw barents sea eight accelerator mass spectrometry ams 14c dates show that the core covers the last 20 000 cal yr b p with a centennial scale resolution during late weichselian early holocene planktic foraminiferal assemblages were analyzed using the 100 m size fraction and foraminiferal planktic and benthic 13c and 18o isotopes were measured furthermore a range of physical and chemical analyses has been carried out on the bulk sediment samples four time periods have been identified which represent the varying oceanographic conditions in ingoydjupet a glacial trough located off the north coast of norway in the sw barents sea 1 the late glacial before ca 15 000 cal yr b p influenced by the nearby ice sheets with high amounts of sea ice or iceberg transported detritus 2 the late oldest dryas stadial and the bolling allerod interstadial ca 15 000 12 700 cal yr b p with cold surface water conditions influenced by the collapse of the nearby ice sheets high amounts of sea ice or iceberg transported detritus and melt water and weak subsurface inflow of atlantic water 3 the younger dryas cold stadial 12 700 11 650 cal yr b p with low primary productivity and extensive sea ice cover and 4 the preboreal and early holocene 11 650 6800 cal yr b p cal yr b p with strong influx of atlantic water into the area near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production

barite and barium in sediments and coral skeletons around the hydrocarbon exploration drilling site in the traena deep norwegian sea barite and barium concentrations in bottom sediments and coral skeletons from the vicinity of the hydrocarbon exploration well drilled in 1992 1993 in the traena deep norwegian sea have been studied to assess the spreading of the drilling mud and related ecological effects on lophelia petrusa coral reefs sand size barite crystals derived from the drilling mud and elevated ba concentrations in surface 0 2 cm sediments were found up to 4 km from the exploration drilling site 210pb dating results on sediment cores indicate that ba rich surface intervals 0 2 cm record ca 20 years of sedimentation history and connect ba enrichment with exploration drilling the geographic distribution of ba contents in sediments allowed the reconstruction of the drilling mud dispersal pattern showing transport eastward from the drilling site consistent with the prevailing current directions the presence of relatively coarse grained sediments and barite crystals trapped in coral polyps ca 500 m down current from the drilling site reflects the elevated turbulence and sediment supply during the drilling activity this elevated sediment dispersion likely placed a stress upon the coral reefs but due to strong currents that effectively dilute episodic drilling waste and sediment discharges the damage does not appear significant

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

lithoherms on the florida hatteras slope sections of the florida hatteras slope were investigated during dives of the johnson sea link i submersible and us navy s submarine nr 1 numerous calcareous coral capped lithoherms often exceeding 40 m in elevation were encountered in the subphotic depths below 440 m one huge lithoherm complex was explored that forms a long slope parallel ridge perched on the seaward edge of mid slope terrace this lithoherm belt is 400 m wide more than 4 4 km long and 150 m high on its down slope flank direct observations and side scan imaging indicate that the long axes of individual ridge crest mounds trend perpendicular to the regional current flow away from the ridge individual lithoherms trend more parallel with regional current flow and occur without obvious bedrock control all of these structures have very steeply sloping flanks frequently 30 60 where cemented crusts are exposed by erosion thickets of living ahermatypic coral coat the crest and up stream flanks of these topographic features living deep water coral have modern 14c ages 700 80 year bp and trap older 3250 100 year bp sediment rich in fine grained aragonite elsewhere older deep water coral rubble 20 230 230 year bp traps younger sediment 13 760 140 year bp the trapped sediments contain 50 aragonite fines 62 5 m the friable crusts exposed on these flanks are generally similar in composition to the sediments that accumulate on the crests of these structures they are older 14c ages of 17 770 330 and 32 710 570 year bp and contain less aragonite 20 and more high magnesium calcite apparently lithoherms grow upwards by trapping fine sediments within ahermatypic coral thickets on their crests and upstream flanks cemented crusts may be a consequence of earlier paleoceanographic conditions or a result of gradual and ongoing cementation and diagenesis the large size platform edge position and linear trend of this deep water lithoherm complex are strikingly similar to a shallow marginal reef system

discovery of a giant cold water coral mound province along the northern argentine margin and its link to the regional contourite depositional system and oceanographic setting abstract in the southern oceans only a few cold water coral mound sites have so far been reported compared to the extensively surveyed north atlantic here we document for the first time the widespread occurrence of exposed and buried coral mounds at the northern argentine margin named northern argentine mound province namp the integration of multibeam bathymetry sediment echosounder acoustic doppler current profiler adcp and ctd data allowed the characterisation of its morphosedimentary stratigraphic and hydrodynamic setting the namp covering at least 2000 km2 represents the largest coral mound province in terms of areal extent reported so far and a major site in the southern oceans the coral mound distribution is directly linked to morphosedimentary features of the regional contourite depositional system cds influenced by the antarctic intermediate water aaiw the upper circumpolar deep water ucdw and their interface forming a complex bottom current controlled environment here termed coral contourite system coral mounds are most abundant in the lower aaiw between 900 and 1050 m just above the ewing terrace moat which has been shaped by high velocity currents associated with the aaiw ucdw boundary this clustering appears to be the result of an increased concentration of suspended sediment and food particles transported along the aaiw ucdw density gradient and delivered upward by turbulent hydrodynamic processes which are enhanced by the irregular moat topography within the ewing terrace moat coral mounds are restricted to topographic obstacles modifying the otherwise highly erosive destructive hydrodynamic regime and thereby locally creating favourable conditions for coral growth the low velocity currents of the ucdw currently influencing the ewing terrace promote extensive contourite deposition which has led to a progressive demise and burial of pre existing mounds the presence of these buried mounds suggests past mound aggradation 100 to 150 m deeper likely due to a downward shift of the aaiw during glacials as a consequence of sea level lowering overall the mound formation in the namp seems to be mainly controlled by the availability of suspended particles in combination with a sufficient bottom current strength keeping material in suspension while preventing destructive erosion and excessive sedimentation our study highlights 1 the importance of high energy processes at water mass boundaries for the delivery of sediment and food particles to corals 2 the role of the aaiw as a crucial water mass for coral mound development 3 the variability of mounds in response to glacial interglacial cycles and 4 the potential of cdss in general and the argentine margin in particular as hotspots for coral mounds and thus ideal site for future studies

periodic volcanic degassing behavior the mount etna example 1 in contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes which have long been known to manifest episodes of highly periodic behavior the spectral properties of volcanic gas flux time series remain poorly constrained due to a previous lack of hightemporal resolution gas sensing techniques here we report on so2 flux measurements performed on mount etna with a novel uv imaging technique of unprecedented sampling frequency 0 5hz which reveal for the first time a rapid periodic structure in degassing from this target these gas flux modulations have considerable temporal variability in their characteristics and involve two period bands 40 250 and 500 1200s a notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root mean square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma air interface citation tamburello g a aiuppa a j s mcgonigle p allard a cannata g giudice e p kantzas and t d pering 2013 periodic volcanic degassing behavior the mount etna example geophys res lett 40 4818 4822 doi 10 1002 grl 50924

growth of north east atlantic cold water coral reefs and mounds during the holocene a high resolution u series and 14c chronology we investigated the holocene growth history of the mingulay reef complex a seascape of inshore cold water coral reefs off western scotland using u series and radiocarbon dating methods both chronologies revealed episodic occurrences of the reef framework forming scleractinian coral lophelia pertusa during the late holocene downcore u series dating revealed unprecedented reef growth rates of up to 12 mm a 1 with a mean rate of 3 4 mm a 1 our study highlighted a persistent hiatus in coral occurrence from 1 4 ka to modern times despite present day conditions being conducive for coral growth the growth history of the complex was punctuated at least twice by periods of reduced growth rates 1 75 2 8 ka 3 2 3 6 ka and to a lesser extent at 3 8 4 ka and at 4 2 ka timing of coral hiatuses and reduced reef growth rates at mingulay were synchronous with those occurring across the wider northern european region which suggests a close relationship between these ecosystems and large scale shifts in palaeoenvironmental regimes associated with changes to the north atlantic subpolar gyre

quantification of the gas mass emitted during single explosions on stromboli with the so2 imaging camera we performed measurements using an so2 imaging camera of the so2 gas mass emitted during five discrete explosive events on stromboli volcano on 3 october 2006 the so2 gas mass released during discrete explosions was 15 40 kg per explosion producing 3 8 of the total daily so2 gas emission demonstrating that in terms of gas flux strombolian explosions are a second order phenomenon compared with quiescent degassing using the typical gas composition measured with op ftir allows us to determine the total gas mass released during an explosion as 360 960 kg with a volume of 1500 4100 m 3 at 1 bar at the probable source pressure of gas slug formation of 75 mpa this gas amount would occupy a volume equivalent to a sphere with a radius of 0 8 1 m comparable with estimates of stromboli s conduit geometry c 2009 elsevier b v all rights reserved

an experimental study of the flow structure and acoustics of jets implications for volcano infrasound abstract aeroacoustic jet noise theory describes the relationship between acoustic signals and jet operating parameters based on empirical aeroacoustic relationships a link between peak frequency and amplitude and jet diameter and velocity has been used by volcano acousticians to return the operating parameters of column generating volcanic eruptions there are however significant differences between the nozzle geometries and structures of flows studied in the aeroacoustic literature and flows emitted from volcanic vents these differences raise questions as to the validity of applying engineering relationships to volcanic eruptions combining particle image velocimetry and acoustic data we investigated the flow structures acoustic signals and dominant source locations of jet flows emitted from three simple nozzle geometries convergent straight and divergent flows from the straight and divergent nozzles exited in a more developed flow regime than those emitted from convergent nozzles while for the convergent nozzles dominant sound sources were located within the jet flow the dominant signals from the straight and divergent nozzles were located in the region of the nozzle exit consequently for the straight and divergent nozzles it was not possible to differentiate between signals generated by the jet flow and those generated by internal sound sources without beamforming analysis in order to better replicate the volcanic case and in contrast to studies for industrial applications our experimental test section was not engineered to minimise internal noise without acoustic treatment such as screens choke plates and paddles jet noise signals were contaminated by signals generated within the test rig and so even for the convergent nozzles the aeroacoustic relationships derived from engineering studies could not be used to retrieve the jet operating parameters our results indicate that in the volcanic case the raw acoustic spectra will contain signals generated by both in conduit and above vent processes therefore inversions for volcanic jet parameters such as mass eruption rate from standard aeroacoustic relationships may be unreliable

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

postglacial carbonate production by cold water corals on the norwegian shelf and their role in the global carbonate budget cold water coral reefs have been neglected in calculations of global carbonate production we present the first calculations of the amount of caco 3 produced by cold water corals on the norwegian shelf in postglacial time showing that the reef building lophelia pertusa in norwegian waters contributes 54 188 g m 2 yr locally or 0 03 0 38 g m 2 yr averaged over the entire shelf these estimates indicate that cold water reef caco 3 flux is 4 12 of the tropical reefs a first tentative global estimate indicates that cold water coral caco 3 production could add 1 to the total marine caco 3 production the spatial and temporal evolution of cold water reefs and thus their influence on atmospheric co 2 is difficult to reconstruct but factors that dominantly influence the rate of coral growth include sea level and oceanographic changes submarine slides and anthropogenic activity the results show that other shelf and slope environments should be assessed in a similar manner to further constrain and evaluate the global caco 3 production by cold water corals and their possible contribution to the caco 3 budget

an adaptive sampling strategy developed for studies of diffuse volcanic soil gas emissions abstract the spatial distribution of diffuse soil degassing from a volcanic source and quantifying of the amount of gas release are key aspects for understanding the gas release pattern the measurement of the entirety of a particular area of interest cannot be possible due to obvious logistical and economic restrictions to reduce the logistic and economic impacts spatial interpolation techniques are generally used with limited observation which is always associated with a high level of uncertainty in the quantification of diffuse soil degassing here we are developing an adaptive sampling strategy and robust analytical tool that can be used to guide measurement strategies by optimizing the sampling locations and reducing the uncertainty for gas emission estimation our adaptive sampling strategy hybridized two well known algorithms kriging interpolation and genetic algorithm optimizer to optimize the locations of future sampling we have validated our tool using a synthetic data set and then applied it to two volcanic soil degassing data sets pacaya volcano and yellowstone volcano both the synthetic data results and case study applications demonstrated that the developed adaptive sampling tool significantly outperforms random and pseudo random approaches to reduce the uncertainty of gas quantification

applications of x ray computed tomography in the geosciences x ray computed tomography ct is a technique that allows non destructive imaging and quantification of internal features of objects it was originally developed as a medical imaging technique but it is now also becoming widely used for the study of materials in engineering and the geosciences x ray ct reveals differences in density and atomic composition and can therefore be used for the study of porosity the relative distribution of contrasting solid phases and the penetration of injected solutions as a non destructive technique it is ideally suited for monitoring of processes such as the movement of solutions and the behaviour of materials under compression because large numbers of parallel two dimensional cross sections can be obtained three dimensional representations of selected features can be created in this book various applications of x ray ct in the geosciences are illustrated by papers covering a wide range of disciplines including petrology soil science petroleum geology geomechanics and sedimentology

late weichselian deglaciation and early holocene development of a cold water coral reef along the lopphavet shelf northern norway recorded by benthic foraminifera and ostracoda cold water coral cwc settlement in northern norway is strongly related to the outlet glaciers of the fennoscandian ice sheet and dating of known cwc structures show clearly post glacial ages two gravity cores pos391 559 2 277 cm long and pos391 559 3 282 cm long were recovered on a cwc reef in the area of lopphavet northern norway detailed investigations on lithology sediment structures and composition micropaleontology foraminifera and ostracoda and ams 14c dating on the epibenthic foraminifera discanomalina coronata were performed on the two cores phosphorus analyses were performed only on core pos391 559 3 results indicate that the whole core pos391 559 2 is representative of a cwc reef environment the base of the core is dated at 10 600 120 cal yr bp thus representing one of the oldest ages of a norwegian coral reef core pos391 559 3 documents the passage from a proximal glacier environment characterized by fine silty sediments with intercalation of several dropstone layers to a cwc ecosystem the transition from the glacial to the interglacial stage is dated as old as 10 725 205 cal yr bp whereas the base of the core is dated to an age of 15 300 550 cal yr bp diversity of benthic foraminifera is higher within the cwc especially in the intervals containing coral framework five clusters are identified based on the bray curtis similarity term analyses and the interpretation of data shows that they are related to different ecological settings e g fluctuations of the sea ice cover influence of the warmer and more saline atlantic water masses transitional to a fully interglacial environment well oxygenated nutrient rich and high current setting being conducive to cwc ostracod assemblages show that these crustaceans may be also used to characterize sedimentary facies on cwc reefs

environmental constraints on holocene cold water coral reef growth off norway insights from a multiproxy approach high latitude cold water coral cwc reefs are particularly susceptible due to enhanced co2 uptake in these regions using precisely dated u th cwcs lophelia pertusa retrieved during research cruise pos 391 lopphavet 70 6 n oslofjord 59 n we applied boron isotopes 11b ba ca li mg and u ca ratios to reconstruct the environmental boundary conditions of cwc reef growth the sedimentary record from these cwc reefs reveals a lack of corals between 6 4 and 4 8 ka the question remains if this phenomenon is related to changes in the carbonate system or other causes the initial postglacial setting had elevated ba ca ratios indicative of meltwater fluxes showing a decreasing trend towards cessation at 6 4 ka with a oscillation pattern similar to continental glacier fluctuations downcore u ca ratios reveal an increasing trend which is outside the range of modern u ca variability in l pertusa suggesting changes of seawater ph near 6 4 ka the reconstructed bwt at lopphavet reveals a striking similarity to barent sea surface and sub sea surface temperature records we infer that meltwater pulses weakened the north atlantic current system resulting in southward advances of cold and co2 rich arctic waters a corresponding shift in the 11b record from 25 0 to 27 0 probably implies enhanced ph up regulation of the cwcs due to the higher pco2 concentrations of ambient seawater which hastened mid holocene cwc reef decline on the norwegian margin

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

seismic and acoustic observations at mount erebus volcano ross island antarctica 1994 1998 volcanic activity at mount erebus is dominated by eruptive activity within a phonolitic summit lava lake common eruption styles range from passive degassing to strombolian explosions which typically occur several times daily and occasionally in swarms of up to 900 per day shallow explosions although generally the result of steady exsolution of volatiles from depth can be triggered by surficial input of h 2o through mass wasting of rock snow and ice from the crater walls broadband observations of strombolian explosions document very long period vlp signals with strong spectral peaks near 20 12 and 7 s which are polarized in the vertical radial plane these signals precede lava lake surface explosions by 1 5 s are highly repeatable and persist for up to 200 s first motions indicate a deflationary source with any precursory inflation being below the 30 s passband of our instruments particle motions suggest a vlp source residing up to 800 m below the lava lake surface however this depth could be exaggerated by near field radial tilt seismic and acoustic signals associated with lava lake explosions commonly show evidence for multiple bubble bursts in corresponding complexity features resulting from varying time delays and relative sizes of superimposed bursts a systematic decrease in seismic acoustic ratio for smaller surface explosions suggests that either the seismic energy from the smallest shallowest bubble bursts experiences much greater seismic attenuation than energy arising from larger events which may involve a deeper less attenuative portion of the magma column and or that the shallowest layer is seismically isolated from deeper parts of a stratified magma column which are not excited by the smallest explosions due to sharp impedance contrasts across distinct layers tremor at erebus is uncommon with only a few isolated instances identified in five years of monitoring some tremor events are nearly monochromatic and some exhibit numerous gliding harmonic spectral lines q 2000 elsevier science b v all rights reserved

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

cold water corals are they hydrocarbon seep related numerous cold water ahermatypic coral reefs so called lophelia reefs up to 30m high 150m wide and 400m long occur at waterdepths from 100 to 350 m off mid norway after the discovery of relatively high interstitial methane concentrations 204 ppb in sediments collected at the base of one of these reef structures a causative link between the presence of the reefs and local micro seepage through seabed of light hydrocarbons is here suggested shallow seismic records gathered across this and other reef colonies off mid norway also indicate the existence of gas charged sediments below the reefs

preboreal onset of cold water coral growth beyond the arctic circle revealed by coupled radiocarbon and u series dating and neodymium isotopes cold water coral mounds of lophelia pertusa are widespread across the scandinavian shelf which was completely ice covered during the last glacial maximum between 22 to 18 ka bp rapid deglacial meltdown of the fennoscandian inland ice and the retreat of its ice streams freed most of the shelf of ice by 15 ka bp however cold water coral growth commenced only after the pleistocene holocene transition at 11 65 ka bp when modern like climatic patterns and oceanographic conditions were established a tight climatic coupling has been constrained with u series ages coupled 14c ages provide local reservoir ages from various gravity cores in a fjord setting in stjernsund at 70 n and on the open shelf in traenadjupet at 66 n reinvestigation of earlier 14c coral chronologies suggests that coral ecosystems widely established themselves across the entire 3000 km long scandinavian shelf prior to 10 ka bp the earliest occurrence of madrepora oculata at 2 4 ka bp suggests a late holocene colonization of the norwegian shelf which is linked to a prominent mound growth hiatus in traenadjupet 64 n mound growth rates near the northern biogeographic boundary of l pertusa with up to 614 cm ka 1 during certain growth periods are much higher than the previously reported fastest rates of 220 cm ka 1 from the irish margin contemporaneous rapid fjordbasin sedimentation is slower with 63 cm ka 1 matrix 14c ages overlap with coral 14c ages from the same horizon this indicates rapid framework construction and efficient trapping of background sediment hiatuses are frequent in on mound sediments and only short periods of coral growth are recorded coupled 14c and end values indicate a persistent holocene inflow of the north atlantic current in stjernsund but also deglacial meltwater mixing during the early holocene prior to 9 5 ka bp reservoir ages are overall close to the surface marine reservoir age but r is highly localized

three dimensional grain fabric measurements using high resolution x ray computed tomography abstract high resolution x ray computed tomography hrxct provides detailed imagery of the interiors of rocks up to hand sample size non destructively and in three dimensions new tools described here allow these data to be used for analysis of grain fabrics two separate sets of measurement techniques have been developed the first concentrates on quantifying individual crystals phenocrysts porphyroblasts or other discrete objects or void spaces within a sample quantifiable properties include location size shape orientation and contact relationships with adjacent objects the second set of techniques performs a more general fabric analysis on any distinguishable component in a sample a fabric tensor can be computed based on a number of metrics including the star volume distribution svd star length distribution sld and mean intercept length mil methods the fabric tensors provide principal component directions and magnitudes which in turn provide a measure of degree of anisotropy and shape indices because the svd and sld measure only the material of interest whereas the mil is also influenced by spatial distribution results can be divergent for sparse phases also introduced is a three dimensional rose diagram that can be viewed interactively and inspected to reveal further details about non orthogonal directional components these techniques are demonstrated through analysis of a garnet kyanite schist from mica dam british columbia

magmatic evolution of pacaya and cerro chiquito volcanological complex guatemala four major phases are distinguished during the building of the pacaya volcanological complex guatemala 1 the ancestral volcano now much eroded covered by younger deposits and battered by faulting and landslides 2 the initial cone made up of large lava flows and dated at about 0 5 ma 3 andesito dacitic domes cerro chiquito dome and others emplaced during an extrusive phase at about 0 16 ma and 4 the active pacaya volcano lavas of phases 2 and 4 are basalts and basaltic andesites with almost the same major and trace element compositions classical enrichment in lile and depletion in hfse are observed phase 3 domes show magma mingling features the dacitic host rock includes basaltic andestic enclaves 20 to 30 in volume according to geochemical and mineralogic data mg fe ratios of basic minerals higher in dacite groundmass glasses sodic in dacite and potassic in basaltic andesite the basaltic andesites and dacites of phase 3 cannot be related by a simple fractional crystallization process the existence of such differences suggests that magma mingling mixing processes were involved by a connection between the two magma chambers prior to the extrusion of the andesito dacitic domes however some trace element data clearly suggest that fractional crystallization played a significant role in the differentiation of these lavas remelting of amphibole bearing cumulates from the dacite may also have played a role in the basaltic andesitic liquid genesis thermodynamical parameters of each liquid are contrasted the basaltic andesitic magma at a high temperature 1037 c and in relatively small amounts is embayed in the cooler 905 c dacitic magma the former liquid denser 2 72 and less viscous 103 31 poises for free crystal liquid may crystallize while the latter lighter 2 60 and more viscous 104 46 poises remains still liquid isotopic data 0 70383 87sr 86sr 0 70400 0 512785 143nd 144nd 0 512908 18 61 206pb 204pb 18 66 15 56 207pb 204pb 15 58 38 30 208pb 204pb 38 40 indicate that all the lavas from pacaya as well as from cerro chiquito are cogenetic and derive from the same mantle source sr nd and pb isotope ratios are similar to those of oibs 230th 232th activity ratios on two historical lavas are respectively 1 2 and 1 3 the th excess is similar to that of other calcalkaline volcanoes emplaced on a continental crust these lavas evolved possibly in separate magma chambers through processes of fractional crystallization and magma mixing

the origin of deep water coral topped mounds in the northern rockall trough northeast atlantic mounds associated with the cold water coral lophelia pertusa are widespread in the north atlantic although the factors controlling their distribution are not well understood here we examine a group of small coral topped mounds the darwin mounds which occur at 1000 m water depth in the northern rockall trough northwest of the uk individual mounds are up to 75 m in diameter and 5 m high although some mound like targets seen on sidescan sonar have little or even negative relief some mounds are associated with tail like features imaged as elongate patches of moderate backscatter up to 500 m long elongated parallel to prevailing bottom currents high resolution sidescan images and seabed photographs show hundreds of coral colonies each a metre or so across on each individual mound many other organisms mainly suspension feeders occur in association with the coral piston cores from the mounds contain predominantly quartz sand with only scattered coral fragments showing that bioclastic material is not a major contributor to mound building a field of seabed pockmarks occurs immediately south of the darwin mounds on sidescan sonar data pockmarks are low relief circular depressions typically around 50 m in diameter the seafloor around the pockmarks consists of uniform heavily burrowed muddy sediments and no specific biological communities nor any sedimentological or photographic evidence for active seepage were observed the distribution of mounds and pockmarks suggests a gradual transition from mounds in the north to pockmarks in the south this combined with the lack of bioclastic material in the mound sediments suggests that both mounds and pockmarks are created by fluid escape from below the seafloor mounds occur where fluids carry subsurface sand to the surface where it forms mounds because bottom currents are not strong enough to disperse it pockmarks form where muddy material is eroded by fluid escape but dispersed by bottom currents despite the origin of mounds through fluid escape we suggest that it is the elevated mound topography rather than any fluid escape that is advantageous to the corals this is supported 1 by the wide variety of suspension feeding organisms that occur on the mounds since all of these are unlikely to have a specialised seepage related lifestyle and 2 because corals and their associated community do not occur around pockmarks where seepage has also occurred but elevated topography is absent

diagenetic processes in carbonate mound sediments at the south west rockall trough margin cold water coral covered carbonate mounds at the south west margin of the rockall trough form ridges several kilometres long and up to 380 m high piston cores obtained at three mound crests reveal the complex internal structure of the mound build up with alternating unlithified coral dominated intervals and lithified intervals the most recent lithified interval is covered by corals embedded in a fine grained matrix comprising ca 11 000 years of continuous mound evolution before this time 230th u dating shows the presence of several hiatuses in mound build up aragonitic coral material is absent or only present as mouldic porosity in the lithified intervals and coccoliths display widespread overgrowth downcore x ray fluorescence scanning computer tomography scan images and petrographic observations indicate different degrees of diagenetic alteration the upper boundary of the most recent lithified interval shows some erosional features but petrographic observations indicate that initial lithification of the sediments is not related to this erosive event or to long term non sedimentation but to earlier sub surface diagenesis organic matter oxidation and the subsequent lowering of the saturation state of the carbonate system drives dissolution of the unstable aragonitic coral skeletons depending on the openness of the system this can lead to precipitation of a more stable low magnesium carbonate a model is presented describing the sedimentary and diagenetic processes leading to the formation of lithified intervals

3d quantification of mineral components and porosity distribution in westphalian c sandstone by microfocus x ray computed tomography abstract microfocus x ray computed tomography ct measurements were performed on deltaic sandstone samples from the diagenetically altered westphalian c strata campine basin north east belgium in order to collect three dimensional data on mineral quartz kaolinite ankerite etc and porosity distribution the acquired ct data were compared with point counting results of stained impregnated thin sections to qualify the sensitivity of ct comparison between techniques shows positive results with regard to the quantification of main mineral phases such as quartz and ankerite and porosity distribution however major discrepancies exist when studying the clay minerals this can be explained by the influence of microporosity associated with these clay minerals resulting in partial volume effects

grounding pleistocene icebergs shape recent deep water coral reefs the widespread view that scleractinian corals in cold and deep waters of high latitudes are slow growing organisms that do not form reefs is challenged by the discovery of a huge coral reef over 13 km in length 10 to 35 m in height and up to 300 m in width formed by the coral lophelia pertusa in water depths of 270 to 310 m at 64 n on the sula ridge mid norwegian shelf cruises in 1994 1995 and manned submersible operations in may 1997 provide data and observations from which the structure and development of the sula ridge coral reef have been determined the fennoscandian icesheet retreated from the mid norwegian shelf prior to 12 000 years before present and modern oceanographic conditions were established at 8000 years before present coral growth since that time has resulted in a large deep water shelf reef for which recent stable isotopic studies have demonstrated high growth rates for these azooxanthellate cold water corals information on the geometry of deep water coral reefs and their environmental controls is still fragmentary controversial and raises issues of conservation in this area of active fishing and oil exploration this paper reports on the discovery of what is probably one of the largest deep water coral reefs existing in the northeast atlantic and indicates that its siting is due to post glacial structures iceberg plough marks events the second storegga slide and local conditions on the seafloor surprisingly reef accumulation rates on the sula ridge are comparable with those measured on tropical coral reefs

development of an ultra violet digital camera for volcanic so2 imaging abstract in an effort to improve monitoring of passive volcano degassing we have constructed and tested a digital camera for quantifying the sulfur dioxide so 2 content of volcanic plumes the camera utilizes a bandpass filter to collect photons in the ultra violet uv region where so 2 selectively absorbs uv light so 2 is quantified by imaging calibration cells of known so 2 concentrations images of volcanic so 2 plumes were collected at four active volcanoes with persistent passive degassing villarrica located in chile and santiaguito fuego and pacaya located in guatemala images were collected from distances ranging between 4 and 28 km away with acceptable detection up to approximately 16 km camera set up time in the field ranges from 5 10 min and temporal resolution of up to 6 images per minute is possible which combined with the camera s field of view makes a continuous so 2 dataset attainable variable in plume concentrations can be observed and accurate plume speeds or rise rates can readily be determined by tracing individual portions of the plume within sequential images initial fluxes computed from camera images require a correction for the effects of environmental light scattered into the field of view at fuego volcano simultaneous measurements of corrected so 2 fluxes with the camera and a correlation spectrometer cospec agreed within 25 experiments at the other sites were equally encouraging and demonstrated the camera s ability to detect so 2 under variable background meteorological and environmental conditions this early work has shown great success in imaging so 2 plumes and offers promise for volcano monitoring due to its rapid deployment and data processing capabilities relatively low cost and improved interpretation afforded by synoptic coverage from a range of distances

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around

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

variability in eruption style and associated very long period events at fuego volcano guatemala 1 repeated short term deployments of seismic infrasound video and gas emission instruments at fuego volcano guatemala have revealed three types of very long period vlp events associated with conduit sealing pressure accumulation and release in 2008 ash rich explosions issued from a vent on the western flank and produced one type of vlp type 1 impulsive bomb rich explosions from the summit vent in 2009 produced a shorter period vlp type 2 but also generated ash release type 3 vlp events occurred during ash free exhalations from the summit in 2008 and had waveform shapes similar to type 2 events weak infrasound records for type 1 explosions compared to type 2 suggest lower pressures and higher magma porosity for type 1 type 3 events correlate with spikes in so2 emission rate and are driven by partial sealing and rapid release of ash free gas at the summit vent variations in the vlp period may provide a new tool for monitoring conditions within the conduit

holocene climate variability of the norwegian atlantic current during high and low solar insolation forcing 1 a high resolution sediment core from the voring plateau has been studied to document the centennial to millennial variability of the surface water conditions during the holocene climate optimum hco and the late holocene period lhp in order to evaluate the effects of solar insolation on surface ocean climatology quantitative august summer sea surface temperatures sssts with a time resolution of 2 40 years are reconstructed by using three different diatom transfer function methods spectral and scale space methods are applied to the records to explore the variability present in the time series at different time scales the ssst development in core md95 2011 shows a delayed response to northern hemisphere maximum summer insolation at 11 000 years b p the record shows the maximum ssst of the hco to be from 7 3 to 8 9 kyr b p which implies that the site was located in the regional warm water pool removed from the oceanic fronts and arctic waters superimposed on the general cooling trend are higher frequency variabilities at time scales of 80 120 210 320 320 640 and 640 1280 years the climate variations at the time scale of 320 640 years are documented both for periods of high and low solar orbital insolation we found evidence that the submillennial scale mode of variability 640 900 years in ssst evident during the lhp is directly associated with varying solar forcing at the shorter scale of 260 450 years the ssst during the lhp displays a lagged response to solar forcing with a phase locked behavior indicating the existence of a feedback mechanism in the climate system triggered by variations in the solar constant as well as the role of the thermal inertia of the ocean the abruptness of the cooling events in the lhp especially pronounced during the onsets of the holocene cold period i approximately 2300 years b p and the little ice age approximately 550 years b p can be explained by a shutdown of deep convection in the nordic seas in response to negative solar insolation anomalies these cooling events are on the order of 1 5 c

aggradation and carbonate accumulation of holocene norwegian cold water coral reefs cold water coral ecosystems present common carbonate factories along the atlantic continental margins where they can form large reef structures there is increasing knowledge on their ecology molecular genetics environmental controls and threats available however information on their carbo nate production and accumulation is still very limited even though this information is essential for their evaluation as carbonate sinks the aim of this study is to provide high resolution reef aggradation and carbonate accumulation rates for norwegian cold water coral reefs from various settings sunds inner shelf and shelf margin furthermore it introduces a new approach for the evaluation of the cold water coral preservation within cold water coral deposits by computed tomography analysis this approach allows the differentiation of various kinds of cold water coral deposits by their macrofossil clast size and orientation signature the obtained results suggest that preservation of cold water coral frameworks in living position is favoured by high reef aggradation rates while preservation of coral rubble prevails by moderate aggradation rates a high degree of macrofossil fragmentation indicates condensed intervals or unconformities the observed aggradation rates with up to 1500 cm kyr 1 exhibit the highest rates from cold water coral reefs so far reef aggradation within the studied cores was restricted to the early and late holocene available datings of norwegian cold water corals support this age pattern for other fjords while on the shelf cold water coral ages are reported additionally from the early middle holocene the obtained mean carbonate accumulation rates of up to 103 g cm 2 kyr 1 exceed previous estimates of cold water coral reefs by a factor of two to three and by almost one order of magnitude to adjacent sedimentary environments shelf slope and deep sea only fjord basins locally exhibit carbonate accumulation rates in the range of the cold water coral reefs furthermore cold water coral reef carbonate accumulation rates are in the range of tropical reef carbonate accumulation rates these results clearly suggest the importance of cold water coral reefs as local maybe regional to global carbonate sinks

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

x ray computed tomography imaging of gas migration in water saturated sediments from capillary invasion to conduit opening 1 the strong coupling between multiphase flow and sediment mechanics determines the spatial distribution and migration dynamics of gas percolating through liquid filled soft granular media here we investigate by means of controlled experiments and computed tomography ct imaging the preferential mode of gas migration in three dimensional samples of water saturated silica sand and silica silt sediments our experimental system allowed us to independently control radial and axial confining stresses and pore pressure while performing continuous x ray ct scanning the ct image analysis of the three dimensional gas migration provides the first experimental confirmation that capillary invasion preferentially occurs in coarse grained sediments whereas grain displacement and conduit openings are dominant in fine grained sediments our findings allow us to rationalize prior field observations and pore scale modeling results and provide critical experimental evidence to explain the means by which conduits for the transit of methane gas may be established through the gas hydrate stability zone in oceanic sediments and cause large episodic releases of carbon into the deep ocean

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

millennial scale variability in atlantic water advection to the nordic seas derived from holocene coccolith concentration records abstract abundance patterns of coccolith species in two holocene marine cores retrieved off norway and northern iceland are indicative of millennial scale modulations in the flow of the main norwegian atlantic current and secondary north iceland irminger current branches of the north atlantic drift to the nordic seas long term trends in coccolith abundance changes reflect major holocene steps in atlantic water transfer to the nordic seas at orbital scale with important constraints on the convective activity of the nordic seas that leads to the formation of the precursor water mass of north atlantic deep water millennial scale holocene episodes of increased advection of atlantic waters off norway are associated with enhanced winter precipitation over scandinavia increased sea salt fluxes over greenland and strengthened wind over iceland thereby suggesting a common atmospheric forcing the location and intensity of the westerlies and the associated changes in mid to high latitude pressure gradients our biotic data indicate an opposite pattern of atlantic water inflow at suborbital scale between the western denmark and eastern iceland scotland straits of the northern atlantic throughout the holocene this as supported by present observational and simulated data further highlights the role of atmospheric oscillations in the recent history of the north atlantic nordic seas water mass exchanges across the greenland scotland ridge such atmospheric processes are thought to explain the observed coupling between periods of excess export of arctic sea ice to the nordic seas and intervals of maximum inflow of atlantic water to the norwegian sea throughout the last 11 000 years

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

water mass characteristics and sill dynamics in a subpolar cold water coral reef setting at stjernsund northern norway the stjernsund located in subpolar setting at 70 5 n off northern norway hosts a thriving cold water coral reef community on a morainic sill dives with manned submersible jago identified the different reef zones and sedimentary facies on top and on the slopes of the sill hydrographic investigations indicate different water mass distribution east and west of the sill winter mode water and norwegian coastal water variability depends on the runoff and freshwater discharge into the fjord atlantic water dynamics are almost entirely tidally driven high resolution ctd time series covering a full tidal cycle demonstrate mixing processes occurring east of the sill additionally the different bathymetric distribution of living corals on the western and eastern slope of the sill portrays the dependence on these tidal dynamics the living corals thrive just below the isopycnal of 27 5 kg m 3 which marks the boundary between norwegian coastal water and atlantic water

volcanic eruptions observed with infrasound 1 infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes here we present new results from erebus fuego and villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters such as eruption duration source mechanism and explosive gas flux

do norwegian deep water coral reefs rely on seeping fluids hundreds of large coral reefs up to 45 m high exist a on the continental shelf and b on morainic threshold ridges in fjords of northern mid and southwest norway they occur in water depths between 400 and 40 m and contain a large variety of megafauna the most common frame building coral is lophelia pertusa l the oldest reef found to date is 8600 calendar years old determined by radiocarbon dating of buried lophelia skeleton even though many of these reefs have been known to science for over 200 years there is as yet no viable and unifying hypothesis to explain their existence in deep cool waters other than perhaps the hydraulic theory presented by the author in 1990 it states that primary producers mainly bacteria are locally formed and concentrated at reef locations due to seepage of light hydrocarbons mainly methane on the continental shelf and nutrient rich groundwater in the fjords the hydraulic theory is supported by the following topographic reflection seismic and geochemical indicators for the continental shelf reefs a seaward dipping sedimentary permeable strata enhanced acoustic seismic reflectors adjacent pockmark craters locally elevated light hydrocarbon sediment content locally elevated seawater methane content for the fjord reefs b threshold morainic substratum rather than adjacent hardrock substratum sub surface dipping sedimentary layers h2s smell of near surface sediment samples these indicators or reef associated observations have been documented by german british and norwegian researchers over the last 10 15 years however all the listed indicators do not necessarily occur at each of the respective shelf and fjord reef locations simultaneously

the giant mauritanian cold water coral mound province oxygen control on coral mound formation abstract the largest coherent cold water coral cwc mound province in the atlantic ocean exists along the mauritanian margin where up to 100 m high mounds extend over a distance of 400 km arranged in two slope parallel chains in 400 550 m water depth additionally cwcs are present in the numerous submarine canyons with isolated coral mounds being developed on some canyon flanks seventy seven uranium series coral ages were assessed to elucidate the timing of cwc colonisation and coral mound development along the mauritanian margin for the last 120 000 years our results show that cwcs were present on the mounds during the last interglacial though in low numbers corresponding to coral mound aggradation rates of 16 cm kyr 1 most prolific periods for cwc growth are identified for the last glacial and deglaciation resulting in enhanced mound aggradation 1000 cm kyr 1 before mound formation stagnated along the entire margin with the onset of the holocene until today the mauritanian mounds are in a dormant state with only scarce cwc growth in the canyons live cwcs are abundant since the late holocene at least thus the canyons may serve as a refuge to cwcs potentially enabling the observed modest re colonisation pulse on the mounds along the open slope the timing and rate of the pre holocene coral mound aggradation and the cessation of mound formation varied between the individual mounds which was likely the consequence of vertical lateral changes in water mass structure that placed the mounds near or out of oxygen depleted waters respectively