the present day formation of apatite in mexican continental margin sediments abstract results of pore water and sediment analyses from the western mexican continental margin strongly suggest the present day formation of apatite the interstitial water phosphate and fluoride profiles indicate chemical removal at a depth which corresponds to a large maximum in the phosphorus content of the sediments apatite is identified within this maximum via x ray diffraction but is elsewhere undetectable in the core radioisotopic thorium uranium and radium data support the conclusion that this deposit is modern the present day depositional environment is consistent with those reported by other workers for phosphorite formation with the exception that pore water magnesium is not depleted below its seawater value

stratigraphic and sedimentological evidence for late wisconsinan sub glacial outburst floods to laurentian fan abstract sub glacial meltwater produces a distinctive stratigraphic and sedimentological response on the continental margin seismo stratigraphy of laurentian channel reveals thick till deposits at its seaward end that pass laterally into stratified sediment in deeper basins that may record periods of water build up beneath the ice two scales of meltwater discharge are recognised large scale that caused catastrophic erosion and transported large volumes of coarse sediment to the abyssal plain and smaller scale yielding principally muddy sediment sub glacial outburst floods from the laurentian channel ice stream delivered distinctive red sediment derived from permian carboniferous strata of the gulf of st lawrence directly to laurentian fan between ca 17 and 14 14 c ka separate from north atlantic heinrich events on levees of laurentian fan three major pulses of meltwater plume muds are separated by intervals dominated by hemipelagic sediments these meltwater intervals are recognised distally as periods of plume sedimentation on the scotian slope and ice rafting of hematite stained quartz to the north atlantic ocean in channels of laurentian fan at least one major sediment transport event is recognised that eroded the upper slope and the major fan valleys depositing a bed of gravel at least 3 m thick in the characteristically wide fan valleys and thick sand on the sohm abyssal plain the same event was probably responsible for giant flute like scours the age of the gravel bed is directly constrained only by the presence of local overlying holocene sediment much of the surface of the gravel bed was re worked by the 1929 grand banks turbidity current an erosional event on the upper slope likely correlative with the flood generated gravel bed has been dated at 16 5 14 c ka such large scale erosional flood events can be recognised back through several glacial cycles and have played an important role in the architectural evolution of laurentian fan

the quaternary lancaster sound trough mouth fan nw baffin bay the development of the lancaster sound trough mouth fan tmf and glacial history in arctic canada were studied using a high resolution seismic profile across the entire fan and two piston cores stacked tills separated by erosion surfaces on the shelf pass seaward through till deltas into thick transparent glacigenic debris flow gdf deposits on the slope separated by thin well stratified glaciomarine layers an age model was built by ties to the ocean drilling program site 645 the deepest gdf on the seismic profile was indicative of the onset of shelf crossing glaciation in the early pleistocene the transition of the growth of lancaster sound tmf from an aggradational sequence unit m to an aggradational progradational sequence unit f occurred at the middle pleistocene transition in glacial cyclicity in the most recent glacial cycle gdf sheets were deposited during heinrich events 4 and 2 according to the correlation of the main detrital carbonate beds in two piston cores the outmost till wedge reflects the maximum advance of the grounding glacier far seaward of previously proposed last glacial maximum ice extent copyright 2011 john wiley sons ltd

the 2002 2003 el nino equatorial waves sequence and their impact on sea surface temperature the recent decades have experienced changes in the characteristics of the el nino phenomenon with in particular an increased occurrence of so called modoki or central pacific el ninos here the 2002 2003 el nino characterized as a central pacific el nino is studied from an ocean general circulation model simulation the focus is on the sequence of equatorial waves and their impact on zonal and vertical advection the wave amplitude according to the most energetic baroclinic modes are first estimated which allows inferring the sequence of the intraseasonal equatorial kelvin ikw and rossby irw waves it is shown that energetic downwelling ikws forced in the western central pacific crossed the equatorial pacific reflections of ikws into irws onto the zonally varying thermocline and eastern boundary are also observed a simplified heat budget of the surface layer is then carried out to infer the dominant processes at work during the evolution of this event focusing on the wave induced advection terms the results indicate that the warming phase april november 2002 is mainly controlled by zonal advection of mean temperature accounted for by ikws and locally wind driven current and by vertical advection in the eastern pacific the cooling phase december 2002 to april 2003 is dominated by a reduction in solar radiation and the irw induced zonal advection of mean temperature respectively in the central and eastern equatorial pacific the recharge discharge process is also showed to be at work with the recharge discharge process operating mainly through the second first baroclinic mode

origin of unusually thick heinrich layers in ice proximal regions of the northwest labrador sea ten piston cores and a 25 m long giant piston core from the ice proximal region off hudson strait contain heinrich layers 1 and 2 identified by their sedimentary structure and high detrital carbonate content both layers are unusually thick on the upper labrador slope 3 8 2 1 m and on the lower slope and rise 1 5 1 0 m heinrich layers 1 and 2 can be subdivided into three units unit a is restricted to the upper slope and overlies hemipelagic sediment with a gradational boundary it is 6 1 m thick dark black to dark gray in color and made up of coarse ice rafted sand and granules dispersed in hemipelagic mud with a few faint laminations towards the top the overlying unit b is up to 3 35 m thick and consists of two facies i centimeter thick graded carbonate rich mud layers containing dispersed coarser grains in the mud interpreted as nepheloid flow deposits with coarse ice rafted debris and ii carbonate rich finely laminated mud layers which alternate with millimeter thick laminae of ice rafted debris unit c up to 0 90 m thick is devoid of sedimentary structures and consists of hemipelagic sediment with dispersed dropstones that increase in abundance towards the top of the unit data suggest the following sequence of processes could have occurred during the deposition of heinrich layers in ice proximal sites as the laurentide ice sheet grew it extended through the hudson strait ice stream outlet to a floating ice margin near the shelf edge and perhaps beyond to the upper slope and deposited unit a by releasing dropstones from the basal debris rich layer unit b is interpreted to be the deposits of the combined processes of nepheloid layer flow low density turbidity currents and massive ice rafting maximum carbonate content s 50 the lightest n 18 o values in very sparse planktonic foraminifera and low magnetic susceptibility are characteristic of unit b unit c is inferred to represent the time of waning supply of fines as nepheloid flow deposition ceased while the relative concentration of dropstones increased as a result of continuing intense ice rafting due to the reduction of fine grained sediment supply the carbonate concentration decreased to the labrador sea background level this finding was further supported by the appearance of darker colored sediments and heavier n 18 o values in neogloboquadrina pachyderma s which indicates the reduction of meltwater discharge

a re evaluation of the pleistocene behavior of the scoresby sund sector of the greenland ice sheet limited data on the past dynamics of the greenland ice sheet exceeding the ice core records have led to partly contradictory reconstructions whereas the scoresby sund sector of the greenland ice sheet has been suggested to be stable and not much larger than at present during the peak pleistocene glaciations the southeastern sector of the ice sheet has been inferred to be much more dynamic here we present seismic data showing that glacigenic debris flow deposits dominate the younger than ca 2 58 ma succession of the scoresby sund trough mouth fan on the east greenland continental margin suggesting much more frequent expansions of the greenland ice sheet to the shelf break than found previously from our new observations of the pleistocene stratigraphy we revise previous findings and conclude that the scoresby sund sector of the greenland ice sheet during the pleistocene 1 developed in line with other parts of the east greenland ice sheet and 2 was more dynamic and sensitive to past climatic changes than hitherto realized this rapid response of the glacier to climate forcing indicates how dynamic is the glacier ice front and what one might expect of the glacier as the influences of climate warming become more pronounced

quaternary sedimentary processes and budgets in orphan basin southwestern labrador sea abstract the continental slope in orphan basin northeast of newfoundland is underlain by several seaward thinning debris flow wedges alternating with acoustically stratified regionally extensive mainly hemipelagic sediments 18o stratigraphy and volcanic ash layers in a 11 67 m core indicate that the uppermost debris flow wedge formed during the last of several sea level lowstands in isotopic stages 2 4 similarly seismic reflection correlation of dated levels at dsdp site 111 with the orphan basin succession suggests that two deeper debris flow wedges were deposited during oxygen isotopic stages 6 and 8 the oldest of the debris flow deposits in at least three of the wedges formed well into the corresponding glacial cycle after ice sheets had reached the edge of the continental shelf slower deposition by hemipelagic processes and ice rafting formed the acoustically stratified units including heinrich layers the youngest three debris flow wedges each have volumes of 1300 1650 km3 approximately two thirds of this material is attributed to glacial erosion of mesozoic and tertiary strata beneath the northeast newfoundland shelf the remainder is believed to have been derived by glacial erosion of older bedrock that now forms the island of newfoundland the observed sediment volumes and the inferred basal and upper ages of the debris flow wedges imply an average glacial denudation rate of about 0 13 mm yr for this older bedrock and an average of about 60 m of glacial bedrock erosion since oxygen isotope stage 22 this denudation rate is similar to estimates from the barents sea region off norway

the physical properties of peru chile continental margin sediments the influence of coastal upwelling on sediment properties physical properties sediment texture water content wet bulk density grain specific gravity porosity shear strength and atterberg limits were determined for near surface sediments 0 to 4 m from the peru chile continental slope and eastern nazca plate these properties are strongly affected by organic matter which is concentrated in the slope deposits as a result of the high productivity in coastal upwelling areas off peru sediments with unique properties occur in a lens of organic rich mud on a portion of the upper slope 10 5 degrees to 13 6 degrees s which coincides with an area of intense upwelling the mud lens sediments are anomalously fine grained and have the highest water content and plasticity and lowest wet bulk density and grain specific gravity found along the margin variation of these properties on the mud lens and on the remainder of the slope and nazca plate correlates well with changes in organic content the undrained shear strength of the mud lens sediments is higher than might be expected for their high water content possibly resulting from the development of clay organic aggregates a distinctive feature of the upper slope mud lens is a surface layer 0 to 15 cm characterized by organic carbon concentrations of up to 20 percent dry weight extremely high water content maximum 853 dry weight and very low wet bulk density minimum 1 09 mg m 3 outside the mud lens organic matter is less abundant and the amount of clay size material in the sediment exerts a greater influence on the physical properties progressive fining of the sediments from south to north along the margin and with increasing distance from shore is accompanied by an increase in water content and plasticity and a decrease in wet bulk density and shear strength these sediments typically show less change in physical properties with depth of burial than those of the upper slope mud lens differences in sediment mineralogy and sedimentation rate also affect the physical properties but to a lesser extent than the variation of organic content or amount of clay

ocean chemistry during glacial time abstract measurements of co2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the co2 content of the atmosphere was considerably lower during peak glacial time than during holocene time the purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water two possible scenarios are presented one involves alternate storage and erosion of phosphorous leaving residues from shelf sediments the other involves changes in the c p ratio in the organic debris falling to the deep sea means of verifying the nutrient cycle hypothesis are also given it is shown that the 13c record as we know it in planktonic and benthic foraminifera the oxygen record as inferred from benthic foraminifera species distributions and the early post glacial caco3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented only if an early post glacial spike in the 13c record for planktonic shells could be found would it be possible to eliminate one of these hypotheses i e that involving shelf storage the implications of these nutrient hypotheses to climate theory are as follows if shelf storage is responsible for the glacial to interglacial co2 increase then the co2 change must be considered an amplifier of some primary cause the reason is that sea level changes are needed to drive deposition on and erosion from the shelves on the other hand if changes in the c p ratio for falling debris are responsible then the co2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle the latter is possible as self sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry

late quaternary stratigraphy and sedimentology of orphan basin implications for meltwater dispersal in the southern labrador sea abstract orphan basin is a deep water basin on the continental margin off newfoundland which throughout the late quaternary received proglacial sediment from local ice that crossed the continental shelf sediment from more distant sources was transported southward in the labrador current as proglacial plumes and in icebergs five sedimentary facies related to glacial processes are distinguished in cores recovered from orphan basin hemipelagic sediment nepheloid layer deposits layered mud beds rich in ice rafted detritus ird sand and mud turbidites and glaciogenic debris flow deposits ird rich beds correspond to periods of intensified iceberg calving and layered mud turbidites and glaciogenic debris flow deposits with glacial meltwater discharge in the late wisconsinan eight periods of meltwater discharge and iceberg calving from the newfoundland ice sheet are interpreted from the sediment facies in orphan basin these discharges coincide with the terminations of the colder periods of the d o cycles recorded in greenland ice cores the oldest minor meltwater event 27 5 28 5 cal ka corresponds to the first late wisconsinan ice advance across the grand banks and ne newfoundland shelf the following three meltwater discharges 23 23 5 23 8 24 5 and 25 27 cal ka deposited sand turbidites and glaciogenic debris flow deposits seaward of trinity trough which was occupied by an ice stream at this time and mud turbidites in the southern part of the basin derived from a mid shelf ice margin on the grand banks four periods of meltwater discharge occurred during the deglaciation and are centered at 15 18 5 19 75 and 20 75 cal ka the youngest is correlated to heinrich event 1 in the literature the 18 5 and 20 75 cal ka events have been recorded in multiple glacial settings in the north atlantic and therefore are interpreted as large scale events of meltwater discharge and iceberg calving but in orphan basin the 19 75 cal ka event is also of similar scale

jellyfish lake palau early diagenesis of organic matter in sediments of an anoxic marine lake jellyfish lake a meromictic marine lake in the palau islands western pacific ocean is accumulating organic matter rich sediments 46 wt wt below anoxic highly sulfidic bottom water elemental and stable isotope 13c data indicate that the sedimentary organic matter is primarily derived from vascular plant remains 65 90 and would form a type 2 kerogen a bacterial layer at the oxic anoxic interface in the water column may play an important role in the rapid recycling of algal derived organic matter from the highly productive surface waters the major postdepositional change in the sedimentary organic matter is carbohydrate biodegradation as shown by 13c nmr lignin and aliphatic substances are preserved in the sediments dissolved organic matter in pore waters is primarily composed of carbohydrates reflecting the degradation of sedimentary carbohydrates rate constants for organic carbon degradation and sulfate reduction in sediments of the lake are about 10 lower than in other anoxic sediments this may reflect the vascular plant source and partly degraded nature of the organic matter reaching the sediments of the lake elemental results from sediment cores and stable isotope 18o 13c studies of shells from the sediments indicate probable climatic or ecological fluctuations affecting the depositional environment of the lake between 80 and 110 yr ago the high sedimentation rate and stable environment of jellyfish lake make it a possible environment for studies of climatic fluctuations during the holocene

the norwegian greenland sea continental margins morphology and late quaternary sedimentary processes and environment the continental margins surrounding the norwegian greenland sea are to a large degree shaped by processes during the late quaternary the paper gives an overview of the morphology and the processes responsible for the formation of three main groups of morphological features slides trough mouth fans and channels several large late quaternary slides have been identified on the eastern norwegian greenland sea continental margin the origin of the slides may be due to high sedimentation rates leading to a build up of excess pore water pressure perhaps with additional pressure caused by gas bubbles triggering might have been prompted by earthquakes or by decomposition of gas hydrates trough mouth fans tmf are fans at the mouths of transverse troughs on presently or formerly glaciated continental shelves in the norwegian greenland sea seven tmfs have been identified varying in area from 2700 km2 to 215 000 km2 the trough mouth fans are depocentres of sediments which have accumulated in front of ice streams draining the large northwest european ice sheets the sediments deposited at the shelf break upper slope by the ice stream were remobilized and transported downslope mostly as debris flows the trough mouth fans hold the potential for giving information about the various ice streams feeding them with regard to velocity and ice discharge two large deep sea channel systems have been observed along the norwegian continental margin the lofoten basin channel and the inbis channel along the east greenland margin several channel systems have been identified the deep sea channels may have been formed by dense water originating from cooling sea ice formation and brine rejection close to the glacier margin or they may originate from small slides on the upper slope transforming into debris flows and turbidity currents

the physiography of high arctic cross shelf troughs abstract a comprehensive inventory of high arctic cross shelf troughs is compiled from international bathymetric chart of the arctic ocean ibcao bathymetric data v 3 0 the location of 75 cross shelf troughs is presented alongside a synthesis of their key physiographic characteristics and available glacial geological evidence the troughs are interpreted to have been occupied intermittently and eroded by marine terminating ice streams that traversed the shelf during at least one and often many quaternary full glacial periods considerable variation in cross shelf trough physiography exists in the high arctic trough lengths range between 35 and 1400 km widths from 12 to 260 km and maximum depths from 200 to 1000 m the longest cross shelf troughs extend through inter island channels on the beaufort sea queen elizabeth islands and barents kara sea margins the gradient of the upper slope beyond high arctic glacial troughs which ranges between 0 3 and 13 is shown to have a negative relationship with palaeo ice stream drainage basin area and trough length glacial sedimentary depocentres or trough mouth fans tmfs are inferred on the basis of bathymetric and where available seismic evidence to exist beyond the majority of high arctic cross shelf troughs evidence of shelf progradation or tmf development is absent from the slope beyond several high arctic troughs probably as a result of limited sediment supply to the margin and or sediment by passing of the upper slope on the south greenland continental margin it is likely that steep slopes prevented the development of significant glacial sedimentary depocentres beyond cross shelf troughs or that glacigenic debris has been removed from the upper slope by submarine slope failure

seabed morphology and shallow sedimentary structure of the storfjorden and kveithola trough mouth fans north west barents sea abstract this study aims to present an overview of the seafloor morphology and shallow sedimentary structure of the storfjorden and kveithola trough mouth fans tmfs on the northwestern barents sea continental margin data have been compiled from two international polar year ipy cruises svais of the bio hesperides and eglacom of the r v ogs explora that yielded 15 340 km2 of multi beam bathymetry and 9500 km of sub bottom seismic profiles in this area the continental shelf edge defines three wide and subdued sedimentary lobes forming storfjorden tmf one single lobe on kveithola tmf and three inter tmf areas on the continental slope the two northernmost lobes of storfjorden tmf lobes i and ii are composed by thick up to 50 m sequences of glacially derived debris flow deposits interbedded with thin a few metres de glacial and interglacial deposits a network of upper slope gullies incises these debris flow deposits as a consequence of subglacial meltwater release at or near the shelf break gullies evolve into channels whose morphologic evidence disappears midslope leaving place to a subdued chevron like morphological pattern inherited by the preceeding glacial maximum debris flow deposits a drastic change occurs on the continental slope of storfjorden tmf lobe iii and kveithola tmf where are several translational submarine landslides mostly originated in the upper slope the majority of which detach at the contact between middle weishelian glacigenic debris flows and the overlying acoustically laminated plumites dendritic canyon systems only develop in inter tmf areas the data suggest that tmf continental slope progradation depends on short lived episodes of extreme sedimentation during glacial maxima and during the early deglaciation phase and that an important controlling factor is the mechanism of ice stream retreat from the continental shelf edge we suggest that the two northern storfjorden sub ice streams were composed of thicker and perhaps faster ice progressively draining a distal and larger ice source mainly located on svalbard conversely the southernmost storfjorden sub ice stream and the kveithola ice stream were fed by a local smaller marine based ice dome grounded on spitsbergenbanken the ice dome persisted after the lgm maintaining a local ice drainage system close to the shelf edge whose sedimentary evidence can be found on the continental slope of the southern lobe of storfjorden tmf and kveithola tmf the high degree of lateral variability in the style of sedimentation on tmf slopes suggests that ice stream dynamics may vary considerably within the same glacial trough and that such variability affects the long term development of the architecture of tmfs

anatomy of labrador sea heinrich layers abstract heinrich layers h layers are distinct decimetre to centimetre thick layers of ice rafted debris ird that were deposited in the north atlantic during the late and middle pleistocene h layers h layers are characterized by high detrital carbonate and low foraminifera contents in the labrador sea h layers reach metre thickness in some proximal core sites near the iceberg source of the hudson strait ice stream and show five distinct depositional facies involving sediment lofting and low density turbidity currents as sediment delivery processes besides ice rafting thick massive ice rafted layers type i h layers occur in the most proximal parts of h layer 3 and older h layers within 300 km distance from the assumed hudson strait ice stream terminus h layers somewhat more distal than type i h layers consist predominantly of stacked thin layers of graded muds containing ird type ii h layers the graded muds that are spiked with ird resulted from the deposition of fine grained lofted sediment that collected dropstones and grains under the iceberg route at greater distance from the hudson strait outlet on the slope and rise south of the strait h layers on the levees of tributary canyons to the northwest atlantic mid ocean channel namoc consist of alternations of thin mud turbidites with intercalated laminae of ird type iii h layers on the levees of namoc type iv h layers consist of layers of ird alternating with fewer fine grained spill over turbidites because the spill over frequency from the deep channel was less than that from the less deep canyons on the slope type v is made up of bioturbated hemipelagic muds with coarser ird and occurs in regions between canyons not reached by spill over turbidity currents and in distal regions of the open ocean or on seamounts transport of significant portions of the sediment in h layers by suspended sediment columns lofted from sand carrying fresh water turbidity currents type ii and by low density turbidity currents types iii and iv explains the high percentage of detrital carbonate in the fine 80 of the total detrital carbonate of the bulk sediment which cannot be derived from icebergs alone it also explains the low magnetic susceptibility and low grey levels on the colour scale compared to h layers in the north atlantic east of greenland the anomalously great thickness of individual h layers on the slope and rise off the hudson strait as documented in isopach maps reflects the combined effect of the various processes involved in their deposition four hypotheses for the origin of h events are discussed i the binge purge model ii the subglacial outburst flow model iii the external forcing model and iv the catastrophic ice shelf break up model

accumulation and biological mixing of peru margin sediments abstract rates of sediment accumulation and biological particle mixing in eight cores from the peru shelf have been estimated by application of uranium series disequilibrium techniques and radiocarbon dating activities of 210pb 226ra 234th and 238u have been determined in closely spaced intervals in each sediment core biological particle mixing coefficients were determined via a two box advection diffusion steady state mixing model based on the distribution profiles of excess 210pb and in some cases excess 234th activities the sedimentation rates estimated were in the order of a few millimeters yr except for cores enriched in phosphatic components which displayed rates a few orders of magnitude slower bioturbation was significant in most cores studied with the exception of one core collected from within the middle of the oxygen minimum zone estimated biological mixing coefficients were in the order of 100 101 cm2 yr 1 for the surface mixed layer and 10 1 100 cm2 yr 1 for the layer below sediment slumping appears to have affected the 210pb distribution of two or three of our cores

down canyon evolution of turbidity currents at a late glacial ice margin halibut canyon offshore southeastern canada abstract submarine canyons are the principal conduit for turbidity currents transporting sediment to the deep sea this study examines the interplay between ice margin conditions and the style of turbidity currents during deglaciation from 19 to 11 ka we investigated 7 cores from halibut canyon located seaward of a small ice stream draining the newfoundland ice dome cores were x radiographed for sedimentary structures sediment provenance was assessed from x ray fluorescence geochemistry and age was determined by ams c 14 dating high resolution seismic profiles and cores show three phases of canyon evolution 1 canyon erosion by plunging hyperpycnal meltwater from shelf edge ice at maximum ice extent 2 during deglaciation active deposition of an inner levee by turbidity currents adjacent to an erosional talweg system recorded in cores from the younger dryas 12 ka to before h1 16 5 ka 3 passive canyon fill during the holocene by the alongslope labrador current with only minor down canyon sediment supply in the active canyon depositional phase turbidity currents were of variable size reaching thicknesses 390 m at 40 km down canyon numbers of sand beds and mean grain size decrease down canyon which is inferred to result from rapid entrainment of ambient seawater on the steep gradient and a downflow thinning of the lower part of the current with fine sand in suspension silt becomes increasingly segregated from muds downcanyon as a result of floc break up and re formation the processes inferred from halibut canyon are representative of other canyons on formerly glaciated margins

groundwater inflow and associated transport of phosphorus to a hypereutrophic lake hydrogeochemical data from lake sediment pore and well waters were used to quantify groundwater seepage and the associated transport of phosphorus to lake persimmon florida usa the data show that lake chloride concentrations vary as a function of lake elevations that are controlled by groundwater inflow a whole lake average seepage rate estimated using a simple one dimensional advection diffusion model fitted to the lake chloride profile currently averages 2 3 0 3 cm yr 1 and is in reasonable agreement with the rate of advective flow obtained from the pore water chloride profile the ratios of nutrient regeneration versus sulfate consumption indicate that the phosphorus enrichment in deeper portions of sediment pore water is most likely a result of groundwater phosphorus transport through sediment thus the net inputs of groundwater phosphorus to the lake calculated using the deep pore water phosphorus concentration are about 7 4 4 3 mg p m 2 yr 1 and comparable with recent in situ estimates from seepage meters this study provides a simple hydrogeochemical method for estimating hydrologic and phosphorus inputs via groundwater to the lake thereby supporting current efforts for lake management

petrology and major element geochemistry of peru margin phosphorites and associated diagenetic minerals authigenesis in modern organic rich sediments abstract new petrographic and major element geochemical data from modern peru margin upper slope outer shelf phosphorites are presented which provide insight into their origin and paragenetic relationship with other authigenic minerals glauconite pyrite and dolomite occurring in organic rich sediments glauconites are precipitated relatively early following the partial reduction of ferric iron and following this process phosphate pyrite and then dolomite precipitation take place at progressively deeper levels in the sediment in association with microbial reduction of sulfate as in many ancient economic phosphorite deposits the phosphatic facies here consist of nodules crusts coatings and strata composed of phosphatic pelletal grains ooids structureless grains intraclasts clumps and biogenic grains in association with organic rich biosiliceous sediments all are considered to have formed within a few centimeters or within a few tens of centimeters below the sediment water interface important factors that influence which morphology will tend to develop include the amount of available pore space the presence of suitable nucleation sites the amount and size of siliciclastic detritus incorporated as inclusions and the relative solution chemistries of the precipitating solutions bacterial mediation may play an important but as yet unspecified role in the precipitation process textural data and factor analysis of chemical data suggest that structureless pellets are relatively inclusion free na f mg co3 substituted pore water precipitates whereas ooids are inclusion rich pore water precipitates poor in lattice substituted components variations in nodular cement birefringence and crystallinity are suggested to have been produced by similar lattice substitutions that directly reflect pore water carbonate ion concentrations and thus relative degrees of organic matter degradation phosphate and dolomite are intimately mixed yet mineralogically distinct phases in phosphatized dolomicrites depth stratified threshold carbonate ion concentrations may control the lower limit at which phosphatic minerals may precipitate below depths of a few centimeters excessive carbonate ion concentrations and diminished reactive iron and sulfate concentrations favor the development of dolomite while precluding further development of phosphatic minerals and pyrite periodic sediment reorganization bioturbation current winnowing and erosion mass wasting etc plays an important role in both concentrating pelletal grains and maintaining nodules and crusts at critical depth levels in the sediment as well as mixing ordered mineral parageneses into complicated sequences

late weichselian submarine debris flow deposits on the bear island trough mouth fan sedimentary processes on the bear island trough mouth fan during the last glacial were studied using high resolution reflection seismics and gravity cores the fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km2 the large debris flows were generated when the barents sea ice sheet reached the shelf break glacigenic sediments transported to the grounding line were temporarily stored on the upper slope due to the high sedimentation rate the sediments were unstable and earthquakes oversteepening and or build up of excess pore pressure triggered sediment release generating large debris flows sediments were also eroded and incorporated during the downslope flow debris flows were the most important sediment distributing process due to the relatively high shear strength low flow mobility of the glacigenic diamicton and the low fan gradient the weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the early and mid weichselian the barents sea ice sheet might have reached the shelf break twice during the late weichselian on average one large debris flow comprising 18 km3 of sediments was released between every 35 to 75 years during the last glacial maximum

halide systematics in interstitial waters of ocean drilling sediment cores abstract the distribution of dissolved halides cl br i in interstitial waters of deep drill holes in the ocean is discussed for a number of environments hemi pelagic sediments hydrate containing sediments sediments affected by halide brines and also in hydrothermal environments the importance of the diagenesis of organic c in the production of i and br is discussed with reference to the observations of dissolved so 4 2 and nh 4 in the pore fluids more importantly in the zone of methano genesis below the so 4 2 reduction zone and usually associated with high organic c accumulation rates increases in i and br are of importance and usually are much higher than the increases observed in the so 4 2 reduction zone in pore fluids affected by dissolution of evaporites the br cl is often a strong indicator of the degree of evaporation of seawater demonstrated from results obtained in the mediterranean sea dissolution of halites on the other hand leads to br cl much lower than those of sea water in hydrothermal sediments there is no doubt that i and br contents of the fluids are influenced by hydrothermal alteration of the sediments and their organic c but signals are not clear the present study provides an overview of previous dsdp and odp studies of halide distributions in sedimentary pore waters in addition to other contributions on halide distributions in sedimentary pore waters in this symposium volume

late quaternary architecture of trough mouth fans debris flows and suspended sediments on the norwegian margin abstract trough mouth fans are the main marine depocentres for glacier derived sediments in the polar north atlantic but their growth through the late quaternary is complex glacigenic debris flows gdfs are sourced from a common and homogeneous part of the upper fan and only develop as coherent individual flows after downslope transport their genesis and mode of deposition mean that gdfs are confined to particular areas of trough mouth fans accumulation of these subglacial sediments is controlled by a combination of margin glaciology and fan morphology although most of the fan sediment is deposited as gdfs during glacials considerable areas of trough mouth fans are dominated by sedimentation of suspension deposits associated with extensive meltwater release from a warm based ice sheet and probable contour current activity the depositional sequence of these two sediment types may be important in generating the long run out distances of gdfs which are initiated and sustained over low gradients furthermore emplacement of gdfs is interpreted to be a relatively low frequency event and temporally at least fans are not dominated by this mode of sediment emplacement whilst ice sheets are at the shelf break large scale trough mouth fan development is therefore asynchronous and non uniform a result of the interaction between glaciology morphology and oceanography

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

interbedded late quaternary turbidites and contourites in flemish pass off southeast canada their recognition origin and temporal variation abstract the recognition of contourite and turbidite deposits in deep marine sequences can be challenging as deposits may show similar sedimentary characteristics in flemish pass a small 1100 m deep perched basin along the southeast canadian continental margin both types of deposits occur late quaternary sediments include thin sand layers interbedded with hemipelagic muds the distribution age sedimentary structures and petrology of these sands were used to distinguish between turbidite and contourite deposits which were then characterized by detailed grain size distribution for understanding the conditions leading to deposition of each type seven sediment facies each with a distinctive grain size distribution were recognized they are 1 transported contourites 2 winnowed beds 3 possible jokulhlaup deposits 4 sandy turbidites 5 muddy turbidites 6 hemipelagic sediment and 7 turbidites from well sorted materials sand packets comprised of several stacked turbidite sand beds some with erosive contacts were correlated from the margin to the basin floor showing clear distal fining and creating a small lobe the temporal distribution of the sand beds indicates that most turbidites and contourites were deposited at stadial to interstadial transitions this linkage may be related to variations in the oceanic circulation in flemish pass which winnowed turbidites and may have triggered turbidity currents by moving sands into canyon heads

the supply and accumulation of silica in the marine environment rivers and submarine hydrothermal emanations supply 6 1 1014g sio2 yr to the marine environment approximately two thirds of the silica supplied to the marine environment can be accounted for in continental margin and deep sea deposits siliceous deep sea sediments located beneath the antarctic polar front convergence account for over a fourth 1 6 1014g sio2 yr of the silica supplied to the oceans deep sea sediment accumulation rates beneath the polar front are highest in the south atlantic with values as large as 53cm kyr during the last 18 000 yr siliceous sediments in the bering sea sea of okhotsk and subarctic north pacific accumulate 0 6 1014g sio2 yr or 10 of the dissolved silica input to the oceans the accumulation of biogenic silica in estuarine deposits removes a maximum of 0 8 1014g sio2 yr although estuarine silica versus salinity plots indicate extensive removal of riverine silica from surface waters the removal rates must be considered as maximum values because of dissolution of siliceous material in estuarine sediments and bottom waters siliceous sediments from continental margin upwelling areas e g gulf of california walvis bay or peru chile coast have the highest biogenic silica accumulation rates in the marine environment 69 g sio2 cm2 kyr despite the rapid accumulation of biogenic silica upwelling areas account for less than 5 of the silica supplied to the marine environment because they are confined laterally to such small areas

jellyfish lake palau regeneration of c n si and p in anoxic marine lake sediments sediment cores from jellyfish lake were processed under an inert atmos phcre and the pore waters extracted and analyzed for the following parameters ph titration alkalinity ta cl h4si04 pod3 nh4 ca2 mg2 sod2 and h2s additionally in one set of pore water samples core lo the 613c of the x0 was also determined the ta h4si04 pod3 nh and h s increased with depth in the pore waters above anoxic bottom water values h s values increased to 3 8 pm in one case both h sio and pod3 concentrations increased to a maximum value and then decreased with depth suggesting removal into solid phases the h sio concentrations are equal to or greater than pore water values observed in sediments underlying upwelling areas pod3 concentrations are in general lower than pore water values from terrigenous nearshore areas but higher than nearshore carbonate pore water values from florida bay or bermuda the ca2 cl and mg2 cl ratios show slight decreases in the top 15 20 cm suggesting that authigenic carbonate may be forming this suggestion is supported by the fact that the pore waters are saturated with respect to caco due to the very high tas the 613c measurements of the pore water x0 are from a shorter core these measurements reach their most negative concentration at 72 cm and tilen become slightly heavier this change is accompanied by a decrease in ta suggesting the onset of methanogenesis at this location in this core

pleistocene glacial history of the nw european continental margin abstract in this paper new and previously published data on the pleistocene glacial impact on the nw european margin from ireland to svalbard between c 48 n 80 n are compiled the morphology of the glaciated part of the european margin strongly reflects repeated occurrence of fast moving ice streams creating numerous glacial troughs channels that are separated by shallow bank areas end moraines have been identified at several locations on the shelf suggesting shelf edge glaciation along the major part of the margin during the last glacial maximum deposition of stacked units of glacigenic debris flows on the continental slope form fans at a number of locations from 55 n and northwards whereas the margin to the south of this is characterised by the presence of submarine canyons glaciation curves based primarily on information from the glacial fed fan systems that depict the pleistocene trends in extent of glaciations along the margin have been compiled these curves suggest that extensive shelf glaciations started around svalbard at 1 6 1 3 ma while repeated periods of shelf edge glaciations on the uk margin started with mis 12 c 0 45 ma the available evidence for mis 2 suggest that shelf edge glaciation for the whole margin was reached between c 28 and 22 14 c ka bp and maximum positions after this were more limited in some regions north sea and lofoten the last glacial advance on the margin has been dated to 15 13 5 14 c ka bp and by c 13 14 c ka bp the shelf areas were completely deglaciated the younger dryas loch lomond advance reached the coastal areas in only a few regions

phosphate regeneration from sediments of the peru continental margin by dissolution of fish debris generally oxidative regeneration of phosphate from anoxic sediments is by microbially mediated sulfate reduction processes stoichiometric modelling of such reactions takes into consideration varying proportions of decomposable organically bound p to account for the ratios among nutrients in depth concentration profiles of near surface sediments new results of interstitial water composition from sediments underlying the water masses influenced by coastal upwelling of the eastern boundary current system off peru indicate that dissolution of phosphatic fish debris represents a mechanism for remineralization of phosphate comparable to or larger in magnitude than that by oxidative regeneration of organically bound p dissolved interstitial phosphate from fish debris is revealed by an excess amount of phosphate over that predicted from a simple stoichiometric oxidative regeneration model and by anomalously high dissolved interstitial fluoride concentrations phosphate flux estimates based on diffusion from the sediment suggest that this mechanism may generate up to 10 of the nutrient pool in the waters of the peru undercurrent partitioning of p among the two sources reveals further that fish debris phosphate is about four times more important than organically bound p in nutrient generation from sediments of the peru continental margin not only does this mechanism of regeneration affect the nutrient cycling but may also control widespread phosphorite formation in this area

carbon isotopic composition and lattice bound carbonate of peru chile margin phosphorites new light stable carbonate carbon isotope and lattice bound co2 data from quaternary peru chile margin phosphatic nodules crusts and pelletal grains and from associated dolomicritic concretions are presented which provide constraints on the timing and mechanisms of growth of these phases in organic carbon rich sediments comparison of 13c values from carbonate fluorapatite cfa nodules and pelletal grains 4 8 to 0 0 and 2 9 to 1 0 pdb respectively with pore water total dissolved 13c values from these sediments suggests early authigenic cfa precipitation from pore waters within a few centimeters of the sediment water interface in association with suboxic to perhaps anoxic microbial degradation of organic matter in contrast the dolomicritic cores of nodules recovered from about 12 s display both strongly negative to positive 13c values 10 8 to 6 1 characteristic of formation deeper in the sediments in association with methanogenic and perhaps sulfate reduction microbial processes the amount of structural carbonate in cfa suggests that carbonate substitution generally increases as 13c in cfa decreases a probable consequence of increasing carbonate and accompanying charge balancing substitutions in the cfa lattice in response to increasing pore water carbonate ion concentrations with depth below the sediment water interface in one buried upward growing nodule decreasing cfa 13c and increasing structural co2 also correspond to decreasing cfa growth rates these data suggest that in addition to other constraints such as pore water phosphorus and fluoride availability the lower limit of cfa precipitation in suboxic to anoxic sediments may be controlled by lattice poisoning due to excessive dissolved carbonate ion concentrations in organic rich peru chile margin sediments this depth threshold appears to be at approximately 5 10 cm below the sediment water interface where maximum cfa co2 contents of about 6 wt occur in less organic rich settings greater depths of precipitation of cfa may be anticipated below this relatively shallow depth of cfa precipitation on the peru shelf high pore water alkalinity and associated elevated total dissolved carbon and carbonate ion concentration apparently favor the precipitation of authigenic carbonates

reprint of anatomy of labrador sea heinrich layers abstract heinrich layers h layers are distinct decimetre to centimetre thick layers of ice rafted debris ird that were deposited in the north atlantic during the late and middle pleistocene h layers h layers are characterized by high detrital carbonate and low foraminifera contents in the labrador sea h layers reach metre thickness in some proximal core sites near the iceberg source of the hudson strait ice stream and show five distinct depositional facies involving sediment lofting and low density turbidity currents as sediment delivery processes besides ice rafting thick massive ice rafted layers type i h layers occur in the most proximal parts of h layer 3 and older h layers within 300 km distance from the assumed hudson strait ice stream terminus h layers somewhat more distal than type i h layers consist predominantly of stacked thin layers of graded muds containing ird type ii h layers the graded muds that are spiked with ird resulted from the deposition of fine grained lofted sediment that collected dropstones and grains under the iceberg route at greater distance from the hudson strait outlet on the slope and rise south of the strait h layers on the levees of tributary canyons to the northwest atlantic mid ocean channel namoc consist of alternations of thin mud turbidites with intercalated laminae of ird type iii h layers on the levees of namoc type iv h layers consist of layers of ird alternating with fewer fine grained spill over turbidites because the spill over frequency from the deep channel was less than that from the less deep canyons on the slope type v is made up of bioturbated hemipelagic muds with coarser ird and occurs in regions between canyons not reached by spill over turbidity currents and in distal regions of the open ocean or on seamounts transport of significant portions of the sediment in h layers by suspended sediment columns lofted from sand carrying fresh water turbidity currents type ii and by low density turbidity currents types iii and iv explains the high percentage of detrital carbonate in the fine 80 of the total detrital carbonate of the bulk sediment which cannot be derived from icebergs alone it also explains the low magnetic susceptibility and low grey levels on the colour scale compared to h layers in the north atlantic east of greenland the anomalously great thickness of individual h layers on the slope and rise off the hudson strait as documented in isopach maps reflects the combined effect of the various processes involved in their deposition four hypotheses for the origin of h events are discussed i the binge purge model ii the subglacial outburst flow model iii the external forcing model and iv the catastrophic ice shelf break up model

a study of the organic matter in tunisian phosphates series relevance to phosphorite genesis in the gafsa basin tunisia abstract in the gafsa basin tunisia peloidal fracolite is interbedded with shales limestones and rocks of intermediate lithology the rocks were deposited in an epicontinental sea and have been buried no more than 500 m the organic matter they contain is therefore thermally immature and in all units derived mainly from marine plankton particularly dinoflagellates the organic matter in the phosphorite units is composed predominantly of humic acids ha which are essentially located within the pellets these pellets are surrounded by an outer matrix in which the organic matter is similar to the kerogen comprised in the shally strata alternating with the phosphorite and limestone beds during weathering the content of the organic matter assocciated with the matrix decreases more rapidly than that of the organic matter entrapped within the pellets geochemical and palynological study of the organic matter in interbedded rocks of different lithology shale limestone phosphorite suggest that the shales were deposited in a reducing environment the limestones in one that was oxic whilst the phosphorites were formed in a redox environment inermediate between the two the interpretation of the data presented in this paper is that the genesis of shales phosphate and some carbonate beds excluding coquinas did not result from the deposition of initially sharply differentiated sediments but resulted from differences in diagenesis of sediments initially containing planktonic organic matter associated with clay and carbonate minerals

sedimentology and history of sediment sources to the nw labrador sea during the past glacial cycle abstract the paleoceanography and sediment dynamics of the northernmost labrador sea provides critical records of glacial history glacially dominated sedimentation and paleocirculation a reference core at 938 m on the se baffin slope was investigated with new oxygen isotope stratigraphy x ray fluorescence geochemistry and 18 14c ams dates and correlated to 14 regional deep water cores the reference core provides a paleoceanographic and sediment source record over the last 40 ka overlying a 3 m thick blocky mass transport deposit over mis 5 autochthonous sediment detrital carbonate rich sediment layers h0 h4 based on bulk geochemistry were derived principally from hudson strait shortly after h2 and h3 the shelf crossing cumberland sound ice stream supplied dark brown ice proximal stratified sediments minor supply of carbonate rich sediment from baffin bay allows chronologic integration of the baffin bay and labrador sea detrital carbonate records and implies an open seaway through davis strait the counterparts of h3 h4 and h5 events in the deep labrador basin are 4 10 m thick units of thin bedded carbonate rich mud turbidites from glacigenic debris flows on the hudson strait slope the behavior of the hudson strait ice stream changed through the last glacial cycle in h1 and h2 the ice stream retreated back across the shelf but did not deglaciate hudson bay in h3 h5 it remained at the shelf break long enough to supply thick turbidites and subsequent retreat after h4 and h5 deglaciated hudson bay the maximum extent of ice streams in hudson strait cumberland sound and lancaster sound was not synchronous

226ra in phosphate nodules from the peru chile seafloor abstract 226ra and other uranium series radionuclides have been measured in a suite of marine phosphorite samples from the upwelling area off peru chile by gamma ray spectrometry and radiochemical techniques our results lead to the following conclusions 1 phosphorite nodules typically show unidirectional growth at rates of 1 to 10 mm kyr 2 very young samples less than a few thousand years contain slight excess amounts of 226ra probably derived from pore fluids and 3 slow but persistent leakage of 226ra out of phosphate nodules occurs resulting in systematically lower 226ra ages compared to 230th ages for samples older than about twenty thousand years radium fluxes from these phosphate nodules appear to be 1 to 3 orders of magnitude less than those calculated for deep sea sediments and ferromanganese nodules

glacigenic debris flows on the north sea trough mouth fan during ice stream maxima abstract numerous short sediment cores which penetrate through the glacimarine section and into glacigenic debris flow debrites gdfs on the north sea fan are investigated the sampled gdfs represent the uppermost of several sequences of these stacked bodies many hundreds of metres thick the gdfs occurred over slopes from 0 3 to 0 7 and examples are found from the shelf break at the mouth of the norwegian channel to the norway basin floor 300 km distant the gdf diamicts are structureless and homogeneous in terms of grain size magnetic susceptibility nrm bulk density water carbonate foraminiferal and rock fragment content this applies both from gdf to gdf across the fan and in a proximal distal sense comparison of the investigated lithologic parameters with weichselian till from a borehole in the norwegian channel 200 km up ice shows striking similarity to the gdf debrites ams 14c dates at the gdf glacimarine contact and stratigraphic relationships indicate voluminous deposition before 18 ka continuing possibly uninterrupted until ca 16 ka and a final phase halting just before 15 ka when the norwegian channel became ice free this chronology the comparable lithologic character between till and gdf debrites and a seismic continuity confirms inferences that the gdfs are directly associated with glacial ice at the shelf break the glacial efflux has not been subject to subsequent sorting and the homogeneity of the gdf is thought to reflect thorough mixing in a deforming till layer beneath a fast flowing ice stream the glacimarine section subsequent to gdfs shows no indications of turbidity flow observations are compatible with a slow non disintegrating cohesive plug flow transport mechanism with little sediment water interaction on the upper surface minor distal differentiation might reflect a change in flow process deposition on the fan margins from water borne glacimarine processes simultaneous with gdf deposition is limited

sedimentary characteristics and depositional models of two types of homogenites in an eocene continental lake basin shulu sag eastern china abstract homogenites are homogeneous and structureless fine grained rocks they have been studied extensively in marine settings and are typically interpreted as being related to catastrophic events such as earthquakes however studies on lacustrine homogenite like rocks are limited new core data from the shulu sag in china reveal that thick massive calcilutites exist in the lower shahejie 3 formation which formed during the middle eocene rifting stage based on petrographic geochemical and mineralogical data these massive calcilutites are interpreted as homogenites and grouped into two types type a homogenite is composed of intrabasinal materials characterized by high calcite total organic carbon toc content and 13c value type a homogenite has two facies successions the first of which is characterized by homogeneous appearance capped by an erosional interface and the second is characterized by repeated massive laminated calcilutite successions type b homogenite contains abundant allochthonous materials displaying relatively high dolomite content and low calcite toc and 13c content type b homogenite represents the topmost finer portion of a graded megabed which includes from base to top grain supported carbonate conglomerates slumped deformed portions and debrites the whole unit can be considered as a megaturbidite earthquakes are the most reasonable triggers of homogenite formation in the shulu sag type a homogenites are thought to be derived by fluidification resuspension and decantation of lacustrine fines due to shock waves generated by an earthquake type b homogenites might be deposits of distal turbidity currents and turbid clouds transformed from other gravity flows the results of this study provide a better understanding of the formation of homogenites caused by earthquakes in a confined lacustrine basin

vertical structure variability and equatorial waves during central pacific and eastern pacific el ninos in a coupled general circulation model recent studies report that two types of el nino events have been observed one is the cold tongue el nino or eastern pacific el nino ep el nino which is characterized by relatively large sea surface temperature sst anomalies in the eastern pacific and the other is the warm pool el nino a k a central pacific el nino cp el nino or el nino modoki in which sst anomalies are confined to the central pacific here the vertical structure variability of the periods during ep and cp is investigated based on the gfdl cm2 1 model in order to explain the difference in equatorial wave dynamics and associated negative feedback mechanisms it is shown that the mean stratification in the vicinity of the thermocline of the central pacific is reduced during cp el nino which favours the contribution of the gravest baroclinic mode relatively to the higher order slower baroclinic mode energetic kelvin and first meridional rossby wave are evidenced during the cp el nino with distinctive amplitude and propagating characteristics according to their vertical structure mostly first and second baroclinic modes in particular the first baroclinic mode during cp el nino is associated to the ocean basin mode and participates to the recharge process during the whole el nino cycle whereas the second baroclinic mode is mostly driving the discharge process through the delayed oscillator mechanism this may explain that the phase transition from warm to neutral cold conditions during the cp el nino is delayed and or disrupted compared to the ep el nino our results have implications for the interpretation of the variability during periods of high cp el nino occurrence like the last decade

pore water fluoride in peru continental margin sediments uptake from seawater abstract fluoride analyses display downward decreasing pore water gradients in peru shelf phosphatic muds that require diffusion from the overlying seawater into the sediment column and removal by reaction within the upper few tens of centimeters presumably by incorporation into carbonate fluorapatite the profiles can be modeled as first order f removal with rate constants of 3 yr 1 and asymptotic f concentrations deep in the cores of 35 45 m almost one half the seawater value the integrated flux of fluoride from seawater into organic rich shelf sediments in coastal upwelling zones phosphatic muds yields a contemporaneous global f burial of 0 54 10 10 mol f yr 1 about one fifth the burial in other sinks mostly carbonates and opal the associated burial flux of phosphorus in shelf phosphorites is about 1 6 10 10 mol p yr 1 comparable to p burial in the deep sea with organic matter 1 4 10 10 mol yr 1 and biogenic carbonates 1 4 10 10 mol yr 1 thus phosphorite formation on the peru shelf is a significant contemporaneous process

microbial infestation a pathway of fluorine enrichment in bone apatite fragments negev phosphorites israel backscattered electron bse imaging and electron probe coupled analysis of bone debris in the negev phosphorites israel show that f concentrations vary considerably in these components and that these variations are driven by microbial activity the bone debris are microbially tunneled commonly with a micritic carbonate fluorapatite cfa phase filling the tunnels and gradually replacing the bone matrix as a rule the micritic cfa within the microbial tunnels is significantly much more fenriched f p2o5 0 106 0 125 than the bone matrix f p 2o5 0 083 0 104 similar results are obtained in bones at final stages of microbial infestation and micrite phosphate replacement the infested replacing envelope invading the bone debris is much f enriched enrichment factor of about 1 27 on average than the surviving bone that escaped boring these results are explained by redeposition as cfa of the microbially bored and dissolved hydroxyapatite presumably fostered by microbial f transfer from porewaters to the sites of cfa precipitation in bone microborings this pathway of f enrichment driven by microbial activity may also explain the enigmatic differential u enrichment previously observed in negev phosphorite bones q 2000 elsevier science b v all rights reserved

the glacial north sea fan southern norwegian margin architecture and evolution from the upper continental slope to the deep sea basin abstract high resolution seismic data have been used to study the ice stream fed north sea fan deposited from approximately marine isotope stage mis 12 and onwards located at the outlet of the norwegian channel on the se nordic seas continental slope the 110 000 km2 fan is dominated by glacigenic debris flows and slide debrites the fan is divided in two provinces by the volcanic more marginal high the proximal province has been characterised by alternation between deposition and erosion while the distal province has been dominated by deposition from mis 12 until the present the fan has received 32 000 km3 of sediments age constraints on fan stratigraphy provided by core investigations indicate that the fennoscandian ice sheet advanced to the shelf edge during mis 2 6 8 10 and probably 12 the fan experienced megaslides in late mis 6 9 and during mis 11 12

interannual long equatorial waves in the tropical atlantic from a high resolution ocean general circulation model experiment in 1981 2000 we investigate the tropical atlantic vertical structure variability 1981 2000 based on the clipper ocean general circulation model ogcm we aim at determining to what extent the observed interannual variability can be explained by the low frequency wave dynamics the linear vertical modes of the ogcm climatological stratification are estimated along the equator the baroclinic mode contributions to surface zonal current and sea level anomalies are calculated and analyzed at interannual timescales the second baroclinic mode is the most energetic the first third mode exhibits a variability peak in the west east the summed up contribution of the high order baroclinic modes 4 6 is as energetic as the gravest modes and is largest in the east wave components are then derived by projection onto the associated meridional structures the effect of longitudinal boundaries near the equator is taken into consideration equatorial kelvin and rossby waves propagations with phases speed close to the theory are identified for the first three baroclinic modes the comparison with a multimode linear simulation corroborates the propagating properties of the ogcm waves coefficients an estimation of the meridional boundary reflection efficiency indicates that wave reflections take place at both boundaries a 65 reflection efficiency is found at the eastern boundary our study suggests that low frequency wave dynamics is to a large extent at work in the tropical atlantic on the basis of what is known on the pacific el nino southern oscillation mode this may provide a guidance for investigating ocean atmosphere mechanisms that can lead to the atlantic zonal equatorial mode

submarine slope stability on high latitude glaciated svalbard barents sea margin abstract slope stability is evaluated at two locations on high latitude deep sea fans along the svalbard barents sea margin based on available samples and using an infinite slope analysis the stability evaluation uses the mohr coulomb failure criterion and a semi analytical approach based on gibson s formulation for determining the excess pore pressure build up due to sedimentation the main results are presented in the form of contour plots of slope safety factors in a diagram with axes of time and thickness of deposit the results show that during rapid sedimentation which mostly takes place during periods of maximum glaciation with the ice front located along the shelf edge slope failure will occur with a frequency varying between 95 and 170 years only part of the upper sedimented layer will be mobilised 10 30 m while the remaining thickness 40 70 m will remain at the initial sedimentation site these results may explain why the continental slope is characterised by relatively uniform sediment thickness from upper to lower slope

sensitivity of an intermediate ocean atmosphere coupled model of the tropical pacific to its oceanic vertical structure an intermediate ocean atmosphere coupled model icm of the tropical pacific is used to investigate the sensitivity of the coupled system to the oceanic vertical structure the model consists of a three baroclinicmode tropical pacific ocean and a gill tropical atmosphere the mixed layer is similar to the zebiak and cane zc coupled atmosphere ocean model but uses a different parameterization for subsurface temperature derived from xbt data a 100 yr simulation is made and the long term variability of the icm is briefly discussed and compared with the the observations and the zc model the icm reproduces regular enso events with a spectrum peak centered at the period 3 5 yr the presence of higher order vertical modes in the oceanic component of the model allows for reduced off equatorial variability of zonal current and thermocline anomalies and for finer meridional scale for sst anomaly variability in comparison with a simulation with one baroclinic mode only the nature of the processes sustaining the oscillations in the icm is then investigated based on the coupled instabilities and delayed oscillator theories it

constraining the efficiency of turbidity current generation from submarine debris flows and slides using laboratory experiments abstract results from a small set of laboratory experiments are presented here that help further constrain the processes governing the production of turbidity currents from impulsive failures of continental shelf and slope deposits three mechanisms by which sediment can be transferred from a parent debris flow to a less dense turbidity current were observed and quantified these mechanisms are grain by grain erosion of sediment from the leading edge of the parent flow detachment of thin layers of shearing material from the head of the parent flow and turbulent mixing at the head of the parent flow which transfer process dominates an experimental run depends on whether the large dynamic stresses focused on the head of the debris flow are sufficient to overcome a effective yield strength for the parent sediment water mixture and on whether the dynamic stresses are sufficient to induce the turbulent flow of the parent mixture analysis of data from marr et al geol soc am bull 113 2001 1377 and mohrig et al geol soc am bull 110 1998 387 support the use of a shear strength to dynamic stress ratio in constraining necessary critical values for occurrence of the different production mechanisms direct sampling of turbidity currents using racks of vertically stacked siphons was used to measure both the quantity of sediment eroded from the heads of non mixing parent flows and the distribution of particle sizes transported by the developing turbidity currents acoustic backscatter imaging was used to better resolve the internal boundary separating any turbulent mixing zone near the front of a flow from unmodified parent material

sediment characteristics in iceberg dominated fjords kangerlussuaq region east greenland abstract sediment cores from three east greenland fjords contain sediment lithofacies and depositional processes in an iceberg dominated glacial marine setting three major lithofacies diamicton fine grained mud and sand are deposited by two processes sediment rain out and sediment gravity flows the sediments in kangerlussuaq fjord are predominately fine grained muds deposited by rain out from icebergs and glacier meltwater with sediment gravity flows acting as secondary agents of deposition miki fjord records rain out of fine grained muds from a river plume emanating from a proglacial delta at the fjord head alternating units of diamicton and fine grained mud in nansen fjord are deposited by sediment rain out from icebergs particle size is governed by the oceanographic conditions in the fjord at the time of deposition despite their proximity to each other each fjord is distinguished by a distinct sedimentological signature kangerlussuaq fjord has low total organic carbon contact miki fjord has high mass magnetic susceptibility and nansen fjord has high amounts of ice rafted debris comparison of the east greenland iceberg dominated and alaska glacial meltwater dominated environments indicates few major differences between sediments deposited in these two settings this similarity raises doubt as to how well glacial marine sedimentary sequences can be used to interpret and reconstruct differences between glacial marine environments in the past without knowledge of sediment accumulation rates environmental conditions at the time of sediment deposition and comparable sedimentological data between studies

nutrient cycling and the biogeochemistry of manganese iron and zinc in jellyfish lake palau the oxic waters in jellyfish lake a stagnant marine lake in palau are depleted in n03 pod3 dissolved si mn fe and zn while the underlying anoxic waters are significantly enriched in these species and nh nh and pod3 regeneration and dissolved sulfide production in the anoxic zone yield a stoichiometry of c n p for organic matter undergoing recycling in the anoxic waters in the anoxic zone dissolved mn fe and zn reach maximum concentrations of 30 22 and 2 5 nm the fe concentrations are consistent with mackinawite or greigite solubility control mn approaches saturation with respect to haurite zn may be controlled by the solubility of zns coprecipitate the sediments are enriched in fe and depleted in zn relative to asian dust at enewetak a twobox model is used to calculate an eddy diffusion coefficient of 0 00 15 cm2 s l across the chemocline the upward diffusive loss of nh added to the sedimentation rate of n and multiplied by the stoichiometric c n ratio yields an organic carbon flux into the anoxic waters of 1 200 pmol c cm 2 yr i which is 13 of the total primary productivity

geometry and genesis of glacigenic debris flows on the north sea fan tobi imagery and deep tow boomer evidence abstract acoustic data have been used to study the upper sequence of glacigenic debris flows gdfs deposited during the last glacial maximum on the north sea fan the presumed gdf release area at the shelf break 450 m water depth exhibits a sequence up to 90 m thick thinning to less than 45 m basinward at approx 750 800 m depth on a low slope 0 6 0 8 a seismically featureless sequence at the shelf break changes distinctly the first kilometers basinward showing a significant occurrence of features interpreted as infilled transport chutes the straight or sinuous chutes feed into well defined relief building gdf lobes 10 40 km from the shelf break a lack of failure scarps at the shelf break suggests that the gdfs have been sourced by a relatively continuous release of material flow lines concentrated along the chutes and center of the gdfs suggest a laminar movement pattern in the gdf core supported by passive flanks based on the flow morphology high pore pressure and low sediment strength within a central core of the flow is assumed to have contributed to the mobility of the gdfs dissipation of pore pressure along the margins of the flow may have caused the margins freeze while the sediment in the core remained mobile

origin of shallow submarine mass movements and their glide planes sedimentological and geotechnical analyses from the continental slope off northern norway submarine landslides are often characterized by a basal surface of rupture parallel to the stratigraphy in which downslope movement is initiated however little is known about the sedimentology and physical properties of the sediments within these surfaces in this study we present a multiproxy analysis of the sediments collected from a giant piston core penetrating a shallow submarine mass transport deposit in combination with high resolution seismoacoustic data to identify and characterize the basal glide plane and the weaker sediments in which movement was initiated the initial phase of instability consists of a single fracture that formed due to the downslope movement of a mostly intact slab of sediments the 16 m long core comprising mostly undisturbed massive and laminated ice rafted debris rich clay penetrated this slab the base of the slab is characterized by a high amplitude semicontinuous reflection visible on the subbottom profiler data at about 12 5 m depth interpreted to originate from the glide plane on top of a plumite deposit this plumite has dilative behavior with pore pressure decrease with increasing shear strain and high undrained shear strength movement probably started within contouritic sediments immediately above the glide plane characterized by higher sensitivities and higher water contents the occurrence of the mass movements documented in this study are likely affected by the presence of a submarine landslide complex directly downslope the slide scar of this landslide complex promoted retrogressive movement farther upslope and progressive spreading of strain softening along the slide base and in the slide mass numerical models infinite slope bing and retrogressive slope models illustrate that the present day continental slope is essentially stable and allow reconstruction of the failure processes when initiated by an external trigger

late quaternary glacial history and meltwater discharges along the northeastern newfoundland shelf the geomorphology of the eastern canadian margin has been shaped by glacial processes during the quaternary many studies have focused on the ice sediment pathway through hudson strait to reconstruct the dynamics of the laurentide ice sheet and as a consequence little is known on its marginal ice domes here we reconstruct the dynamics of two trough mouth fans tmfs offshore ne newfoundland using sediment cores and radiocarbon ages supported by very high resolution seismic reflection profiles these two tmfs namely notre dame and hawke are fed by two glacial troughs incised in the bedrock the tmfs show a complete sedimentary sequence from 30 ka bp to the beginning of the holocene the sampled sedimentary record on the upper slope extends back to a thick heinrich event 3 h3 deposit that corresponds to the end of the maximum extent of the newfoundland ice dome above h3 a thick succession of turbidite deposits 10 m observed in both tmfs is correlated with periods of major meltwater supply from 2

an interglacial on snowball earth dynamic ice behaviour revealed in the chuos formation namibia the sturtian is the oldest ca 716 ma of three pan global glaciations in the cryogenian at omutirapo in northern namibia a 2 km wide 400 m deep palaeovalley is filled by glaciogenic strata of the chuos formation which represents the sturtian glacial record sedimentary logging of an exceptionally high quality exposure permits detailed stratigraphic descriptions and interpretations allowing two glacial cycles to be identified at the base of the exposed succession strong evidence supporting glaciation includes diamictites ice rafted dropstones and intensely sheared zones of interpreted subglacial origin these facies collectively represent ice proximal to ice rafted deposits upsection dropstone free mudstones in the middle of the succession and the absence of diamictites imply sedimentation free from glacial influence however the reappearance of glacial deposits above indicates a phase of sturtian glacial re advance comparison with age equivalent strata in south australia where evidence for sea ice free sedimentation has been established previously suggests that a sturtian interglacial may have been extensive implying global scale waxing and waning of ice sheets during a cryogenian glacial event

the influence of meltwater on the labrador current in heinrich event 1 and the younger dryas abstract the labrador current transports freshwater from the arctic regions to the northern atlantic and the freshwater flux can influence the meridional overturning circulation the response of the labrador current to meltwater processes is unclear during the deglaciation of the ice sheets around the northwest atlantic this study utilized cores from flemish pass to monitor variations in the strength of the labrador current by using the sortable silt proxy the carbonate content the amount of ice rafted detritus and xrf chemical data were measured to identify the main meltwater events during the last deglaciation this study observed a clear enhancement of the flow strength of the labrador current in heinrich event 1 and the younger dryas with the greatest flow strength during the younger dryas event the onset of the current enhancement was dated at ca 13 cal ka bp which preceded the enhanced ice rafted deposition in hudson strait by about one thousand years the current enhancement in flemish pass during the younger dryas event corresponds to the freshening of the surface water thus meltwater preceding significant iceberg supply has an important effect on the labrador current in heinrich events on the laurentide ice sheet margin

recognition classification and mechanical description of debris flows abstract various types of flow or mass movement involving water and sediments occur on steep slopes in mountainous areas among them debris flows are peculiar events during which a large volume of a highly concentrated viscous water debris mixture flows through a stream channel throughout the world these phenomena cause considerable damage but remain poorly understood although a basic knowledge is already available concerning their recognition and propagation firstly a synthesis of the useful practical criteria of recognition is proposed debris flows must be seen as intermediate phenomena between hyperconcentrated flows intense bed load transport and landslides separated from them by sharp transitions of some characteristics celerity deposit nature and flow type two parameters solid fraction and material type thought to be appropriate for a sound and practical classification are brought out and the corresponding complete classification of flow and mass movements in mountain areas is presented two extreme debris flow types are thus distinguished muddy debris flows and granular debris flows a critical review of recent advances in debris flow dynamic is then proposed it is pointed out that adequate work must be carried out in the field of non newtonian fluid mechanics in particular one fundamental rheological property of debris flow materials is the yield stress which explains thick deposits on steep slopes and can be inferred from field measurements furthermore it can be used to estimate viscous dissipation within the bulk during flow relevant models predicting muddy debris flow dynamics are already available whereas further progress is needed concerning granular flows

accounting for parameter uncertainties in model verification an illustration with tropical sea surface temperature abstract a simplified model originally developed to simulate sea surface temperature sst in the tropical pacific is extended in two directions first the model is formulated and run for the tropical atlantic second optimal values are determined for a number of model parameters especially those determining surface heat flux in the pacific the difference between model sst and data sst is the size of the probable error due to uncertainties in the heat flux 0 35 w m 2 in the equatorial atlantic the discrepancies may also be attributed to heat flux errors but model data differences in the atlantic near coastal regions north of 10 n and south of 10 s are too large to be explained by heat flux errors model problems involving other physical processes must be involved by giving the best result possible in the face of our uncertain knowledge of the parameters and observations the optimal fit procedure unambiguously indicates which oceanic features require model changes in order to be adequately chara

along slope variations in sediment lithofacies and depositional processes since the last glacial maximum on the northeast baffin margin canada abstract twelve piston cores were used to characterize late quaternary lithofacies depositional processes and deglacial history along the baffin bay slope between lancaster sound and home bay core investigations show four distinct laterally correlatable lithofacies along the slope basal and upper diamicton laminated red brown mud tan carbonate gravelly sandy mud and bioturbated brown mud basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from baffin island at 25 cal ka the distribution and character of laminated red brown mud suggests a lateral supply to baffin bay slope from ice proximal meltwater plumes and turbidity currents sourced in glacial ice from both baffin bay shelf and home bay between 41 5 cal ka to 14 2 cal ka an upper diamicton records a lesser localized glacial advance that ended at about 14 2 cal ka tan carbonate mud events represent ice rafted enhanced detrital carbonate delivery to the slope between 25 cal ka and 11 cal ka a gradual thinning of these events from northern to southern baffin bay corroborates a northern baffin bay lancaster sound or nares strait iceberg source proglacial facies seaward of home bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice rafted from lancaster sound baffin bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater as a result axial supply from the large ice streams north of baffin bay particularly lancaster sound is dominant in the baffin bay basin and lateral supply from smaller ice streams on baffin island predominates on the ne baffin slope

holocene glacimarine sedimentation inner scoresby sund east greenland the influence of fast flowing ice sheet outlet glaciers abstract holocene glacimarine sedimentation associated with fast flowing outlet glaciers draining the greenland ice sheet is investigated using sedimentary and acoustic data from inner scoresby sund east greenland sedimentation in inner scoresby sund is dominated by three processes which are influenced by differences in proximity to fast flowing outlet glaciers extent of glacier ice cover and fjord bathymetry 1 sediment gravity flow principally in the form of turbidity currents and debris flows 2 suspension sedimentation from turbid meltwater plumes and 3 iceberg rafting these processes result in texturally and sedimentologically heterogeneous lithofacies proportionally fine grained muds laminated stratified and massive facies dominate cores recovered from inner scoresby sund accounting for 80 of the total whereas diamict facies account for only 15 abundant fine grained muds demonstrate that meltwater flux and sedimentation is significant in this high arctic glacimarine environment in settings proximal to fast flowing outlet glaciers with increasing distance from these glacier termini muds are replaced progressively by iceberg rafted coarse grained sediment the dominance of this iceberg rafted sediment in outer scoresby sund reflects both its more distal location from fast flowing glacier termini and the high calving flux associated with these ice masses laminated muds deposited by turbidity currents and suspension settling from overflow plumes in inner scoresby sund are similar to lithofacies produced in temperate and subpolar glacimarine systems this implies a similarity in sedimentation processes and resulting facies across a wide spectrum of climatically glaciologically fast flowing and non fast flowing ice masses and oceanographically variable glacimarine settings recognition of laminated fine grained facies in the geological record therefore does not necessarily indicate a temperate palaeo glacial setting however the predominance of iceberg rafted diamict facies in ice distal sedimentary records suggests the former presence of relatively cold environmental conditions in which iceberg sedimentation played a dominant role

a meltwater origin for antarctic shelf bedforms with special attention to megalineations the geomorphology of troughs crossing the antarctic shelf is described and interpreted in terms of ice stream hydrology the scale of tunnel channels on the inner shelf and the absence of sediment at their mouths are taken to infer catastrophic drainage drumlins on the inner and outer shelves with pronounced crescentic and hairpin scours are also interpreted as products of catastrophic flow gullies and channels on the continental slope and turbidites on the rise and abyssal plain point to abundant meltwater discharge across the shelf attempts to explain this morphology and sedimentology in terms of release or discharge of meltwater by pressure melting strain heating darcian flow or advection in deforming till are shown to be unrealistic we suggest that meltwater flow across the middle and outer shelves might have been in broad turbulent floods which raises the possibility that megascale glacial lineations msgl on the shelf might originate by erosion in turbulent flow this possibility is explored by use of analogs for msgl from flood and eolian landscapes and marine environments an extended discussion reflects on objections that stand in the way of the flood hypothesis

trace elements at the intersection of marine biological and geochemical evolution life requires a wide variety of bioessential trace elements to act as structural components and reactive centers in metalloenzymes these requirements differ between organisms and have evolved over geological time likely guided in some part by environmental conditions until recently most of what was understood regarding trace element concentrations in the precambrian oceans was inferred by extrapolation geochemical modeling and or genomic studies however in the past decade the increasing availability of trace element and isotopic data for sedimentary rocks of all ages has yielded new and potentially more direct insights into secular changes in seawater composition and ultimately the evolution of the marine biosphere compiled records of many bioessential trace elements including ni mo p zn co cr se and i provide new insight into how trace element abundance in earth s ancient oceans may have been linked to biological evolution several of these trace elements display redox sensitive behavior while others are redox sensitive but not bioessential e g cr u their temporal trends in sedimentary archives provide useful constraints on changes in atmosphere ocean redox conditions that are linked to biological evolution for example the activity of oxygen producing photosynthetic cyanobacteria in this review we summarize available precambrian trace element proxy data and discuss how temporal trends in the seawater concentrations of specific trace elements may be linked to the evolution of both simple and complex life we also examine several biologically relevant and or redox sensitive trace elements that have yet to be fully examined in the sedimentary rock record e g cu cd w and suggest several directions for future studies

dynamics of sediments on a glacially influenced sediment starved current swept continental margin the se grand banks slope off newfoundland abstract the se grand banks slope is unusual on the glaciated eastern canadian margin in that it was remote from ice stream and glacial ice of the laurentide ice sheet lis it thus allows an analysis of the role of contour currents and landslides in sculpting the continental margin processes that are largely masked where downslope proglacial sediment supply dominated detailed oxygen isotope geotechnical pxrf and bulk sediment geochemical analyses were made on seven piston cores and were placed in context using multi beam bathymetry and high resolution seismic reflection profiles cores have a record of sedimentation back to mis6 preserved in autochthonous sediment and slide blocks contourites and mass transport deposits mtds detrital carbonate rich heinrich layers h are present throughout the succession but red mud layers of glacial meltwater origin from ice streams in the se sector of the lis are identified only during mis2 and late mis3 both layers allowed high resolution correlation between cores sediments on the upper slope above h2 are condensed and the section above h1 is five horizons with mtds with headscarps generally up to 25 m high are recognized in the upper 50 70 m thick mtds are blocky in cores and in their seismic and bathymetric expression resemble spreads with local thin mud clast conglomerates that ran out as debris flows over the contemporaneous seabed geotechnical data suggest that the seabed is stable under static conditions although there is geological evidence for fluid escape and geotechnical evidence for underconsolidation weak layers along which failure took place are found somewhere around h3 h4 and at or near the top of h5 and mis6 the low plasticity and liquid limit of the h layers make these layers susceptible to failure during cyclic loading episodic earthquakes are the most likely cause of failure

radiocarbon calibration curve spanning 0 to 50 000 years bp based on paired 230 th 234 u 238 u and 14 c dates on pristine corals abstract radiocarbon dating is the most widely used dating technique in the world recent advances in accelerator mass spectrometry ams and sample preparation techniques have reduced the sample size requirements by a factor of 1000 and decreased the measurement time from weeks to minutes today it is estimated that more than 90 percent of all measurements made on accelerator mass spectrometers are for radiocarbon age dates the production of 14 c in the atmosphere varies through time due to changes in the earth s geomagnetic field intensity and in its concentration which is regulated by the carbon cycle as a result of these two variables a radiocarbon age is not equivalent to a calendar age four decades of joint research by the dendrochronology and radiocarbon communities have produced a radiocarbon calibration data set of remarkable precision and accuracy extending from the present to approximately 12 000 calendar years before present this paper presents high precision paired 230 th 234 u 238 u and 14 c age determinations on pristine coral samples that enable us to extend the radiocarbon calibration curve from 12 000 to 50 000 years before present we developed a statistical model to properly estimate sample age conversion from radiocarbon years to calendar years taking full account of combined errors in input ages and calibration uncertainties our radiocarbon calibration program is publicly accessible at http www radiocarbon ldeo columbia edu along with full documentation of the samples data and our statistical calibration model

onset and growth of trough mouth fans on the north western barents sea margin implications for the evolution of the barents sea svalbard ice sheet abstract the aim of this study is to discuss the onset and growth of the bellsund hornsund and storfjorden trough mouth fans tmfs on the north western barents sea margin this is done on the basis of a seismo stratigraphic analysis of new 2d seismic reflection profiles and a new correlation between odp site 986 west of spitsbergen and the seismo stratigraphic network in the central part of the western barents sea margin we infer that reflector r4a marks the onset of both the development of the tmfs and the contourite deposition which dominate this part of the margin from this time onward we conclude that these deposits were frequently affected by episodes of small scale mass wasting focused at the mouth of the glacially eroded cross shelf troughs with a new interpolation between the few available constraints we propose an age of about 1 3 ma for the onset of both the development of the tmfs and the contourite deposition thus we hypothesize from our results and from previous studies that the barents sea svalbard ice sheet expanded first beyond the coast north of svalbard later reaching the shelf edge at the mouth of bjornoyrenna and then to storfjorden southern spitsbergen

experimental study of igneous and sedimentary apatite dissolution control of ph distance from equilibrium and temperature on dissolution rates apatite dissolution experiments were conducted using both a fluidized bed and stirred tank reactor over a range of ph temperature solution saturation state and on non carbonated and carbonated apatite compositions igneous fluorapatite fap and sedimentary carbonate fluorapatite cfa respectively from 2 8 5 were not possible due to detection limits of the analytical techniques used in this study and the high insolubility of fap for the cfa compositions studied the dissolution rate decreased with increasing ph from 4 ph 7 during early stages of the dissolution reaction for both fap and cfa mineral components were released in non stoichiometric ratios with reacted solution ratios of dissolved ca p and ca f being greater than mineral stoichiometric ratios suggesting that ca was preferentially released compared to p and f from the mineral structure during the early stages of dissolution an increase in reacted solution ph accompanies this early elevated release of ca as the dissolution reaction proceeded to steady state dissolution became congruent when normalized to bet measured surface area fap dissolved faster from 4 ph 7 compared to cfa the apparent arrhenius activation energy ea of fap dissolution over the temperature range of 25 55 c at ph 3 0 i 0 1 and pco2 0 is 8 3 0 2 kcal mol 1 both the apparent exchange of solution h for solid bound ca at low ph in the early stage of dissolution and the ea of dissolution suggest a surface and not a diffusion controlled dissolution reaction for fap and cfa the degree of undersaturation of the solution gr with respect to fap was important in determining the dissolution rate at ph 3 0 i 0 1 and pco2 0 the dissolution rate of fap was 5 greater in the far from equilibrium region compared to the near equilibrium slope region a simple apatite weathering model incorporating the experimental results from this study was constructed and numerical calculations suggest that during the phanerozoic both the surface area of igneous rock available for weathering and the average global temperature were important factors in determining the p weathering flux from apatite dissolution it is possible that elevated global temperatures coupled with relatively high surface area of igneous rock during the early to mid paleozoic resulted in elevated p weathering fluxes which along with climatic evolutionary pressures of the neoproterozoic facilitated the radiation of multicellular organisms large scale phosphorite deposition and abundance of calcium phosphate shelled organisms during the early cambrian

sediment properties flow characteristics and depositional environment of submarine mudflows bear island fan abstract recent gravity flows on the bear island fan consist of fine grained sediments that presently exhibit high densities 1 8 2 0 g cm 3 low water contents 30 40 dry weight and high estimated yield strengths 1100 1350 pa rheological analyses however reveal exceptionally low yield strengths 3 5 pa and lower for laboratory slurries 3 made with the mudflow sediments the low yield strengths are inconsistent with previous interpretations that the mudflows were spawned from glacial sediments that were rapidly deposited as till deltas on the upper slope of the fan or that they were emplaced as low density low cohesion fluidized mud abundant glacial flour in the mudflow samples is indicative of subglacial meltwater discharge this in turn suggests that the sediment originated from turbid plumes that settled into a low density high water content mud deposit in an open marine tidewater glacier environment such an environment may have existed during the mid late weichselian when an embayment in the barents shelf ice sheet left much of the inner shelf ice free subsequent advance of the ice front closed the embayment compressing the mud loss of water during compression increased the bulk density and yield strength of the mud the modified embayment mud was gradually pushed off the shelf generating mudflows on the fan morphologic evidence suggests that some mudflows may have hydroplaned indicating that flow speeds varied above and below a critical speed ca 5 m s marking the onset of hydroplaning

a conceptual model of the deglaciation of atlantic canada abstract we present a conceptual model for the deglaciation of atlantic canada in which a role is played by ice streams the ice margin lay close to the edge of the continental shelf at the last glacial maximum ice streams occupying shelf troughs comprised 1 a major ice stream in the laurentian channel 2 secondary streams in the bay of fundy gulf of maine trinity trough and notre dame channel and 3 lesser ice streams elsewhere early retreat in the northeast notre dame bay and in the southwest bay of fundy gulf of maine was mainly by calving along embayments by 18 ka radiocarbon years a calving embayment had opened on emerald basin scotian shelf retreat along channels marooned ice on intervening banks a major calving episode beginning just before 14 ka removed ice from the gulf of st lawrence triggering re advances down secondary troughs isolation of a newfoundland ice cap produced radial drainage via fiords and more extensive flow into the st george s bay lowlands on the west coast by 13 ka most ice was on land and was ablating by melting rather than calving shelf ice caps persisted until 11 ka

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

glaciogenic debris flow deposits of orphan basin offshore eastern canada sedimentological and rheological properties origin and relationship to meltwater discharge abstract glaciogenic debris flow deposits gdfs have been recognized in the last decade seaward of many shelf crossing ice streams the rheology of gdfs remains poorly understood ultra high resolution sparker seismic profiles and 25 long piston cores were used to define the architecture age and sediment properties of the gdf deposits in trinity trough mouth fan tmf offshore northeast newfoundland and hence understand their origin and emplacement the gdf deposits comprise poorly sorted gravelly mud individual gdf lenses are 5 30 m thick 2 10 km wide and up to 250 km long shear strength measurements and grain size analysis indicate that gdfs have a different more fluid rheology at their margins and tops exhibiting a surging flow behavior on the upper slope the transition from hard over consolidated till to thin proximal gdf deposits is exposed in a mid holocene landslide scar the transition between the two lithotypes appears gradual and no pre holocene failure scarps were detected a process involving the continuous release of subglacial flowing material with high pore pressure and low shear strength is invoked for the production of gdfs five stacked gdf units a e were deposited during the last glacial maximum 20 5 28 cal ka and can be correlated into a regional lithostratigraphy based on the presence of heinrich beds and 8 local meltwater events r1 8 represented by red plumite deposits south of the trinity tmf this correlation indicates that the timing of major gdf pulses corresponds to the early part of five meltwater discharge events 20 5 21 23 23 5 23 8 24 5 25 27 and 27 5 28 5 cal ka so that gdf deposits represent only a small period of time during a major glacial advance three meltwater events 19 2 20 23 23 5 and 25 27 cal ka produced hyperpycnal flows that resulted in the formation of channel systems and distal sand turbidites the presence of such erosional features in tmfs on the continental margins of the norwegian greenland sea suggests that this novel relationship between gdfs and hyperpycnal turbidites may be widespread and thus important for understanding the glaciological processes involved

depositional processes on the distal scoresby trough mouth fan odp site 987 implications for the pleistocene evolution of the scoresby sund sector of the greenland ice sheet accepted manuscript version licensed cc by nc nd 4 0 published version available at https doi org 10 1016 j margeo 2017 11 018

quaternary seismic stratigraphy of the north sea fan glacially fed gravity flow aprons hemipelagic sediments and large submarine slides abstract approximately 1000 km of high resolution sleeve gun array transects on the north sea fan located at the mouth of the norwegian channel reveal three dominant styles of sedimentation within a thick 900 m quaternary sediment wedge comprising numerous sequences these are interpreted as terrigenous hemipelagic sedimentation large scale translational slides and aprons of glaciogenic debris flow deposits contributing to considerable fan construction four large buried translational slides involved sediment volumes upwards of 3000 km 3 each and preceded the similarly dimensioned first storegga slide on the ne fan flank several thick 100 m terrigenous hemipelagic deposits apparently represent long lived 150 200 kyr periods of sedimentation whose distribution indicates fan input via the norwegian channel the upper sequences are each made upper sequences are each made up of one or several thick 100 m aprons comprising stacked lensoid and or lobate forms which range from 2 to 40 km in width and 15 to 60 m in thickness they characterize debris flows attributed to periodic input from several phases of a norwegian channel ice stream reaching the shelf edge subsidence in the outer norwegian channel allowed preservation of several glaciation cycles represented by sheet erosion bounded tills and progradational units much of the shelf slope transition has been preserved allowing a preliminary chronology of the fan sequences through correlation with borehole sediments in the norwegian channel debris flows which signal the initial shelf edge glaciation are not recognized from the initial glaciation in the channel 1 1 myr but are associated with a middle pleistocene and all following glacial erosion surfaces ges in the outer norwegian channel this was followed by six further sequences probably totalling over 13 000 km 3 of sediment at least four of these were shelf edge ice maximum events the last of which was late weichselian age 14 c ams considering earlier glaciation related hemipelagic sedimentation material since removed by the large slides and extensive unmapped areas total quaternary fan sedimentation was in the vicinity of 20 000 km 3

upper cretaceous campanian phosphorites in jordan implications for the formation of a south tethyan phosphorite giant a record of sedimentary authigenic and biological processes are preserved within the upper cretaceous campanian alhisa phosphorite formation ap in central and northern jordan the ap formed near the eastern extremity of the south tethyan phosphorite province stpp a carbonate dominated upper cretaceous to eocene phosphorite giant that extends from colombia north africa to the middle east multidisciplinary research of the ap and associated cherts chalks and oyster buildups indicate that phosphatic strata formed on a highly productive storm dominated east west trending epeiric platform along the south tethyan margin the onset of phosphogenesis and the accumulation of economic phosphorite coincided with a rise in relative sea level that onlapped peritidal carbonates of the ajlun group pristine phosphates are associated with well developed micrite concretionary horizons and contain abundant non keeled spiral planktic foraminifera and a low diversity benthic assemblage of buliminacean foraminifera suggesting that pristine phosphates are a condensed facies and phosphogenesis was stimulated by the effects of a highly productive surface ocean and the suboxic diagenesis of sedimentary organic matter the bulk sediment composition and absence of fe bearing authigenic phases such as glauconite pyrite including pyrite molds siderite and goethite within pristine phosphates suggests that deposition and authigenesis occurred under conditions of detrital starvation and that iron pumping played a minimal role in phosphogenesis authigenic precipitation of phosphate occurred in a broad array of sedimentary environments herein termed a phosphorite nursery that spanned the entire platform this is a non uniformitarian phenomenon reflecting precipitation of sedimentary apatite across a wide depositional spectrum in a variety of depositional settings wherever the conditions were suitable for phosphogenesis sedimentologic data indicate that pristine phosphates were concentrated into phosphatic grainstones through storm wave winnowing and storm generated shelf parallel geostrophic currents economic phosphorites formed through the amalgamation of storm induced event beds stratigraphic packaging of phosphatic strata indicates that temporal variations in storm frequency were a prerequisite for the formation of economic phosphorite syndepositional phosphogenesis reworking and amalgamation to form phosphorites contrasts sharply with the principles of baturin cycling a transgressive systems tract coupled with high surface productivity created detritally starved settings favourable for phosphogenesis storm reworking of pristine

diagenetic trends of fluorine concentration in negev phosphorites israel implications for carbonate fluorapatite composition during phosphogenesis an electron probe and chemical study of bulk phosphorite samples and separated constituents from various negev deposits was carried out together with xrd ftir spectroscopy and textural analysis the results allow a better understanding of the distribution of fluorine in these upper cretaceous phosphorite sequences and shed light on variations in the composition of the carbonate fluorapatite cfa phase during phosphogenesis two facies are recognized 1 a pristine microbially generated phosphorite facies 2 a recycled peloidal and biodetrital facies fluorine distribution in the negev phosphorites is facies controlled f p2o5 is much lower in the pristine facies 0 090 0 107 than in the recycled facies 0 107 0 120 in addition f p2o5 varies considerably between the various constituents of the phosphate fraction f poor francolites f p2o5 as low as 0 080 co exist with f rich francolites f p2o5 as high as 0 135 in the same phosphorite bulk sample a lower f p2o5 in francolite is associated with higher cd and zn concentrations in the phosphorite an increase in fe rich smectites in the clay fraction and the presence of structural oh in the francolite the lower f p2o5 ratios in the pristine facies are attributed to high organic deposition rates during the formation of these matted sediments leading to rapid burial of the in situ forming cfa this is possibly coupled with diffusion of f from sea water into bottom sediments being hampered by microbial mat coatings these conditions resulted in o2 depleted porefluids inducing the precipitation of cd rich zn sulphides and the formation of fe rich smectites f enrichment probably takes place when the earlier formed f poor primary cfa is relocated close to the sea floor and bathed with interstitial sea water solutions of higher f concentrations oxidation and removal of the sulphide bound cd and zn apparently occurred together with enrichment in f of the francolite combining chemical data with xrd and ftir results suggests a multistage growth for the negev phosphate constituents in shifting formational sites and porefluids of varying f concentrations this multiphase growth is reflected in the patchy distribution of f in the negev constituents and might explain the inverse correlation between mean co2 f and f p2o5 ratios of the analysed phosphorites in the two facies it also suggests that cfa or an amorphous precursor initially formed with some oh groups in the apatite structure which were subsequently substituted by f ions in recycled francolite through re equilibration with porefluids of higher f concentrations

shingled quaternary debris flow lenses on the north east newfoundland slope debris flow deposits are the principal component of quaternary continental slope sediments between the north east newfoundland shelf and central orphan basin in seismic profiles these deposits occur as shingled elongate acoustically transparent lenses with their long axes orientated downslope deposits of individual flows form positive mounds on the sea floor subsequent flows were diverted by the pre existing topography into bathymetric lows between older debris flow deposits these deposits show a large variation in the area of sea floor covered by individual flows about 60 1000 km2 average thickness of deposits 9 37 m and volume of sediment displaced 1 27 km3 the ratio of average thickness to a measure of deposit diameter termed the aspect ratio has a threefold variation from 0 0006 to 0 0021 very low depositional slopes and low aspect ratios suggest relatively low viscosities probably due to inmixing of water during downslope transport stratified sediments form three distinct horizons and are locally interbedded with the debris flow deposits these are mainly hemipelagic deposits the slope and rise to the west of the orphan basin are constructional in character the apparent absence of upper slope erosional features and the abundance of debris flow deposits on the slope suggest that the supply of sediment to the continental slope occurred predominantly during times of maximum extent of quaternary glacial ice the ice sheet grounding line during several glacial maxima must have been situated at or near the present shelf break supplying vast amounts of sediment directly to the upper slope oversteepening and subsequent slope failures fed material into deeper water

the role of deep water sedimentary processes in shaping a continental margin the northwest atlantic abstract the tectonic history of a margin dictates its general shape however its geomorphology is generally transformed by deep sea sedimentary processes the objective of this study is to show the influences of turbidity currents contour currents and sediment mass failures on the geomorphology of the deep water northwestern atlantic margin nwam between blake ridge and hudson trough spanning about 32 of latitude and the shelf edge to the abyssal plain this assessment is based on new multibeam echosounder data global bathymetric models and sub surface geophysical information the deep water nwam is divided into four broad geomorphologic classifications based on their bathymetric shape graded above grade stepped and out of grade these shapes were created as a function of the balance between sediment accumulation and removal that in turn were related to sedimentary processes and slope accommodation this descriptive method of classifying continental margins while being non interpretative is more informative than the conventional continental shelf slope and rise classification and better facilitates interpretation concerning dominant sedimentary processes areas of the margin dominated by turbidity currents and slope by pass developed graded slopes if sediments did not by pass the slope due to accommodation then an above grade or stepped slope resulted geostrophic currents created sedimentary bodies of a variety of forms and positions along the nwam detached drifts form linear above grade slopes along their crests from the shelf edge to the deep basin plastered drifts formed stepped slope profiles sediment mass failure has had a variety of consequences on the margin morphology large mass failures created out of grade profiles whereas smaller mass failures tended to remain on the slope and formed above grade profiles at trough mouth fans or nearly graded profiles such as offshore cape fear