recruitment variation during a pilot colonization study of hydrothermal vents 9 50 n east pacific rise abstract colonization of basalt plates deployed by submersible was measured in a three year pilot study at hydrothermal vents near 9 50 n on the east pacific rise most species and speciesgroups were capable of colonizing plates in both warm diffuse vent flows of up to 25 c and cool no detectable temperature anomaly zones the discovery of numerous protoconch stage recruits of the limpet lepetodrilus elevatus on basalt plates in both warm and cool zones and in two study sites separated by 1 km indicated that a very recent regional settlement event had taken place size distributions of the l elevatus colonists suggest a previous distinct recruitment event also may have taken place during the three year interval of the prominent vent taxa whose adult distributions were known a few colonized only the zones inhabited by adults the scallop bathypecten the polychaete paralvinella and vestimentiferan tubeworms but two others colonized outside the adult ranges the bivalve bathymodiolus and the polychaete laminatubus taxonomic uncertainties have been denoted by the results suggest that both temporal variation in recruitment and post settlement biological interactions are important in structuring communities at hydrothermal vents

recent macroids on the kikai jima shelf central ryukyu islands japan sandy and gravelly carbonate sediments found off kikai jima southern japan a coral reef related island shelf represent the northernmost sub tropical carbonate deposits in the central ryukyu islands ryukyus on the kikai jima shelf at water depths of 61 to 105 m these sediments are characterized by macroid pavements since the abundance of very small and of exceptionally large macroids may indicate specific hydrodynamic controls regarding constraints on growth and taphonomy the detailed analysis of recent and fossil macroid pavements is meaningful ecologically and environmentally macroids ranging in size from ca 25 to 130 mm in diameter are spheroidal and sub spheroidal in shape and consist mainly of the encrusting foraminifer acervulina inhaerens and subordinate thin encrusting and lumpy coralline algae accessory components include bryozoans serpulids and to a lesser extent encrusting arborescent foraminifera homotrema and miniacina low sedimentation rates and occasional movement due to current action are indicated by sizes shapes and growth forms of the studied macroids the entobia gastrochaenolites trypanites maeandropolydora ichnocoenosis and the bioerosion index for coated grains introduced herein the deep water tidally induced current energy was sufficient to maintain multi directional growth spheroidal shapes of the larger macroids and to initiate macroid growth using the diverse biogenic remnants as nuclei the asymmetrical inner arrangement suggests possible periods of stability for the macroids the residence time of the coated grain in its original environment determines the size and morphology of the macroid and the selection of coating organisms the composition of the coating community is mainly a consequence of component growth rates in relation to turnover time and residence time long term studies are needed to assess the spatial and temporal resolution of present day encrusting communities across biogeographic provinces and shelf to slope regions

alpha and beta diversity of encrusting foraminifera that recruit to long term experiments along a carbonate platform to slope gradient paleoecological and paleoenvironmental implications abstract the spatial and temporal distribution and diversity of sediment dwelling foraminifera are reasonably well known but encrusting hard substrate dwelling foraminifera are little studied encrusting foraminifera are common in the world s oceans attached to floating debris or marine animals in the water column to living on rocks sand grains and organisms in benthic environments from shallow to deep marine regions with projected ocean acidification and warming conditions these important calcifying protists that comprise beaches buffer sediments and contribute to complex food webs are potentially in peril results indicate that calcifying foraminifera were the first to colonize experimental molluscan substrates within the first year in shallow habitats with colonization offshore in subsequent years agglutinated foraminifera become more common after one year species richness diversity remained relatively similar throughout the study but species turnover diversity was greatest within the first year and between the shelf slope break and deeper water following the thermocline and photic zone regions the equivalent of the shannon entropy index provided important information on diversity and community structure paleobathymetric distributions can be resolved after six years into four distinct foraminiferal distributional zones shallow shelf 15 m outer shelf 33 m shelf slope break 73 88 m and slope depths 213 m to 267 m some encrusting foraminifera are invasive settling in high numbers within the first year and increasing their abundance through the duration of the experiment a foraminiferan discorbis bertheloti was discovered to bioerode carbonate and is a potentially excellent paleobathymetric indicator for 15 33 m depths results differ from previously reported pioneer and climax foraminiferal communities documented for caribbean coral reefs because long term experiments reveal the spatial and temporal development and distribution of carbonate producing encrusting foraminifera in these climatically sensitive regions

multikilometer sized reefs built by foraminifera solenomeris from the early eocene of the pyrenean domain s france n spain palaeoecologic relations with coral reefs abstract solenomeris foraminifera reefs of the early ypresian pyrenean gulf were previously mistaken for red algal or incertae sedis algal reefs solenomeris has recently been referred to the acervulinid foraminifera these foraminifera buildups are described in detail and their palaeoecology is discussed the distribution of these reefs within the languedoc basin demonstrates their preference for bathymetric highs of external platforms in common with coral reefs to which they locally succeed during the early ypresian transgression all solenomeris reefs examined are located either at the outer periphery of a lagoon with small operculina or on the external margin of a carbonate platform characterized by various miliolida they extend into deeper waters than the associated coral reefs even in turbid environments unfavourable for encrusting coralline algae the reconstruction of the palaeoecology of solenomeris shows many similarities with corals however corals probably require higher light and oxygen levels especially when present near their northern limit the global distribution of solenomeris reefs can not be established until their correct identifications have been made instead of algal reefs

determining the strength of the deep western boundary current using the chlorofluoromethane ratio abstract the dilution of a passive tracer during deep water formation and the subsequent advection mixing in a deep boundary current is modeled with application to chlorofluoromethanes cfms in the north atlantic two different types of boundary currents are considered a uniform flow and a simple shear flow in each case the core of the flow mixes with surrounding water which continually accumulates cfms in an extreme case the coupled systems predicts that the cfm ratio in the current is unaltered from the ratio of its source water save for a time lag more realistic cases however suggests that the ratio is not a conserved quantity but is substantially altered in both the overflow basin and boundary current matching the model results to cfm data collected near the grand banks gives a predicted average core speed of 5 10 cm s 1 for the deep western boundary current and provides a constraint on the transport and diffusivity of the flow as well

deformation of kilauea volcano during 1982 and 1983 a transition period a major transition in the style of deformation of kilauea volcano occurred during the period january 1982 through november 1983 prior to 1983 the deformation was dominated by magma intrusions rapid extension of the summit and seaward movement of the south flank the pattern of activity changed to magma eruption and slowed deformation of the volcanic edifice in january 1983 an earthquake swarm in the southwest rift zone in june 1982 and an intrusion of a large dike in the east rift zone in january 1983 prepared the volcano for the eruptive sequences that continue today we estimate the sources of surface displacements associated with these events using a least squares nonlinear inversion technique and planar dislocations the models are constrained with measurements of line length changes and of surface height changes from tide gauges water wells and spirit level tilt data deformation associated with the 1982 earthquake swarm is best modeled as the emplacement of a steeply dipping dike in the upper and middle southwest rift zone extending from 2 3 km to 10 11 km depth with a width of 1 2 m tilt measurements gathered at the time of the earthquake swarm record a small deflation of kilauea s summit however trilateration data indicate the summit was rapidly extending in 1982 the extension and our models are consistent with seaward slip of the south flank on a low angle basal thrust fault dislocation models of the january 1983 dike intrusion yield a 14 to l5 km long dike along the zone of observed ground rupture the dike extends from just below the surface to the region of the most intense rift zone seismicity at 4 5 km depth a strong nonlinear relationship among height dip and width results in a suite of models that explain the data equally well tests of parameter sensitivity indicate that the dike width and height are the least constrained parameters the best fit average width ranges from 1 7 to 2 8 m our models also include a source of contraction at 5 km depth that produces 40 cm of ground subsidence near makaopuhi the point of initiation of the intrusion this location is consistent with geochemical and seismic evidence that indicate magma is stored in the rift zone residual errors for all models indicate that substantial line length changes are unexplained seaward motions of the south flank during 1982 and 1983 are not well modeled by simple dikes and summit deflations however attempts to constrain low angle faults in the south flank were only partly successful due to the limited extent of the geodetic networks

syn depositional alteration of coral reef framework through bioerosion encrustation and cementation taphonomic signatures of reef accretion and reef depositional events the development of coral reef framework and the preservational character of both in situ and rubble coral is strongly influenced by a range of physical chemical and biologically mediated taphonomic processes these operate at or just below the reef framework water interface and can be defined as having either a constructive or destructive effect upon primary reef framework i e coral constituents constructional activities add additional calcium carbonate to the primary framework structure via secondary framework growth and early cementation destructive processes which remove or degrade primary and secondary framework carbonate are associated with the effects of either physical mainly storm disturbance or biological erosion termed bioerosion key bioeroding groups include the grazing fish and echinoid groups as well as the activities of an array of infaunal borers these include specific groups of sponges bivalves and worms termed macroborers as well as cyanobacteria chlorophytes rhodophytes and fungi termed microborers the relative importance of each process and the rates at which they operate vary spatially across individual reef systems in addition many of these processes leave distinctive signatures on or in the coral framework in some cases e g calcareous encrusters these are the skeletons of the organisms themselves whilst in other cases the organism may leave behind a trace of their activity e g macro and microborers these represent useful palaeoenvironmental tools firstly because they often have good preservation potential and secondly because the range and extent of many of the individual species groups and processes involved exhibit reasonably well constrained environment and or depth related distributions as a result these taphonomically important organisms or processes can be used to delineate between reef environments in core or outcrop and to aid the interpretation of reef depositional processes and events this review summarises current understanding regarding the distribution of these species processes within contemporary reef settings and considers the suites of taphonomic signatures that may aid in the recognition and interpretation of depositional environments and events

diversity taphonomy and behavior of encrusting foraminifera on experimental shells deployed along a shelf to slope bathymetric gradient lee stocking island bahamas abstract encrusting foraminifera that settled on experimental arrays deployed for 2 years in shelf 15 m 30 m shelf edge 70 m and slope 183 253 m environments off the carbonate platform of lee stocking island bahamas were found to occur in four environmental indicator guilds each with common and unique encrusting species these guilds can be used as paleobathymetric and temporal guides indicating how long a substrate was exposed on the sea floor prior to burial taphonomic signatures of encrusting foraminifera also changed with depth resulting in four foraminiferal taphofacies that varied from corrasion dissolution and abrasion at shallow sites to pristine tests at the deepest sites the taphonomic processes for encrusting foraminifera were found to be decoupled from those reported for invertebrate hardparts in this region perhaps related to their ability to nestle within sutures or other depressions deemed taphonomic refugia on the shell substrates the shelf edge site had the highest foraminiferal diversity associated with the highest physical damage to the tests which is counter intuitive to the intermediate disturbance hypothesis idh which posits that high physical disturbance leads to low species diversity while the idh appeared true for the shallowest sites it does not completely explain the high foraminiferal diversity at the shelf edge where physical taphonomic factors were high behavioral interactions such as overgrowth interactions also varied with depth and these can be used to examine depth related paleobehavioral patterns in the past thus the often overlooked encrusting foraminifera are excellent candidates for paleocommunity and paleoenvironmental analyses

paleomagnetism and geochronology of the ecstall pluton in the coast mountains of british columbia evidence for local deformation rather than large scale transport 1 samples for geochronologic geobarometric and paleomagnetic analyses were collected across the northern portion of the ecstall pluton southeast of prince rupert british columbia al in hornblende geobarometry indicates pressures from 740 10 to 840 30 mpa corresponding to crystallization depths of 25 to 30 km u pb analyses of zircons from western central and eastern localities within the pluton yield crystallization ages of 91 5 1 0 ma 90 8 1 0 ma and 90 5 1 0 ma respectively rock magnetic experiments reflected light microscopy and thermal demagnetization behavior suggest that natural remanent magnetism is carried by low ti titanohematite unblocking temperatures of the characteristic remanent magnetization chrm are dominantly in the 560 c to 630 c range with age of magnetization approximated by the 40ar 39ar hornblende ages of 84 2 0 10 ma on the western margin and 76 4 0 6 ma in the center of the pluton site mean chrm directions were isolated for paleomagnetic samples from 23 sites and are distributed along a small circle with subhorizontal axis at 340 azimuth chrm directions from the central portion of the pluton are concordant with the expected cretaceous magnetic field direction while chrm directions from the western margin are discordant by 70 folding of the ecstall pluton either during late cretaceous west directed thrust transport above the convex upward prince rupert shear zone or during younger deformation of the pluton and underlying shear zone can account for the paleomagnetic data and is consistent with the geochronologic geobarometric and structural geologic observations

preferential dissolution of carbonate shells driven by petroleum seep activity in the gulf of mexico abstract authigenic carbonates are common at deep sea petroleum seeps as a result of excess bicarbonate production during microbial degradation of hydrocarbons coupled to sulfate reduction consequently these seep environments are supersaturated with respect to carbonates this finding conflicts with taphonomic data that dissolution is the most pervasive mode of shell alteration at seeps we provide here the first study linking the preservational process with the chemical characterization of the taphonomically active zone at petroleum seep sites this characterization is made possible using fine scale porewater carbonate chemistry data and skeletal material deployed for 8 years at petroleum seep sites in the northwestern gulf of mexico microelectrode measurements of ph and pco2 identify a very restricted zone of caco3 undersaturation immediately below the sediment water interface in otherwise supersaturated environments i e sandwiched between supersaturated bottom seawater and sediment porewater this zonation characterizes the taphonomically active zone and is a result of a highly compressed redox front between acid generating aerobic oxidation of reduced chemical species including hydrocarbons h2s and planktonic and terrestrial organic carbon and base generating sulfate reduction coupled to ch4 oxidation porewater geochemistry is spatially variable at seep sites and produces variable shell dissolution signatures shells deployed at seep sites have moderate to severe dissolution that is consistent with a much higher flux of total dissolved inorganic carbon dic from the porewater to the bottom water therefore a mosaic of preservational conditions is directly related to the spatially and chemically varying taphonomically active zones found at seep sites these findings support the variability of carbonate preservation reported for globally distributed phanerozoic fossil seeps and the view that data from field taphonomy can significantly upgrade and validate carbonate destruction rates used in geochemical and climatic models carbon mass balance analyses also lead to an important conclusion that carbonate dissolution forms a very important mechanism for benthic carbon recycling possibly accounting for 50 of the benthic dic flux to the bottom water in northern gulf of mexico petroleum seep sediments

the importance of symbiont bearing benthic foraminifera for west pacific carbonate beach environments abstract in the tropical central and west pacific as well as in the east indian ocean symbiont bearing benthic foraminifera often are the main producers of calcium carbonate grains deposited at beaches the proportion of foraminiferal tests in medium sized to coarse sand grains may range from 20 to 95 this depends on two factors productivity and transport because foraminifers do not live on or in the sandy bottom near the beaches but prefer firm substrate in high energy environments close to the front of coral reefs foraminiferal tests are produced in extreme numbers on the reef crest of sesoko island okinawa japan 0 6 kg m 2 year 1 which is covered by macroalgae or in the transition zone between the crest and the reef moat 1 3 kg m 2 year 1 empty tests released by reproduction or death are entrained at the reef crest by waves and transported by currents this transport depends on the direction and intensity of currents connecting the habitat reef crest and transition to moat with the deposition area central moat lagoon beach habitat destruction and or the interruption or diversion of water flow hinders the accumulation of foraminiferal tests at the beach where deepening the moat intensifies beach parallel currents supply to and deposition at the beach are reduced while the remaining sand is eroded by tropical cyclones understanding the ecology especially population dynamics of larger foraminifera in combination with factors influencing the transport of empty tests is essential to preserve the balance between deposition and removal of sand at carbonate beaches in the west pacific and east indian ocean

paleoenvironmental evidence for latest pleistocene sea level fluctuations on the new jersey outer continental shelf combining high resolution sequence stratigraphy and foraminiferal analysis foraminiferal assemblages in vibracored sediments within 5 m of the seafloor document high resolution sea level fluctuations and confirm the complex quaternary depositional history of the new jersey margin biostratigraphic data have been integrated with ongoing 2 d 3 d high resolution seismic analyses to interpret paleoenvironments of surficial stratigraphy beneath the modern middle to outer shelf cluster analysis of foraminiferal assemblages sampled every 20 cm average define four sample groups a d dominated by benthic species group a characterized by cibicides lobatulus is a middle to outer shelf assemblage 60 100 m water depths group b is composed of middle shelf species 30 60 m water depths and is characterized by low abundances and a fairly uniform distribution of foraminifera which suggests reworking and or a high rate of sediment accumulation group c dominated by elphidium excavatum is an inner to middle shelf assemblage 10 40 m water depths group d present in only one core and dominated by ammonia beccarii represents marginal marine environments 0 10 m water depths with fluctuations in salinity in general the modern sedimentary veneer i e the upper 20 cm is characterized by the deeper water fauna of group a sediments below these modern deposits are characterized by groups b and c reflecting shallower water depths and variable sediment accumulation rates on the inner and middle shelf taken together the group succession in the cores suggests an overall se to nw landward transgression in these latest pleistocene holocene deposits seismic analysis indicates that one core 27 penetrates the flank of a buried channel including its fill and the pre channel section within the channel three alternations of groups c and d suggest fluctuations between marginal marine and middle shelf paleoenvironments high frequency perhaps very small 10 m changes in base level are indicated using previously published ams 14c dates these fluctuations can be constrained as having occurred between 45 000 yr b p channel incision and 12 500 yr b p channel filling suggesting the non uniform nature of the last wisconsinan deglaciation

quantification of the intrusion process at kīlauea volcano hawai i abstract the characteristic size of two types of intrusions identified beneath k lauea s east rift zone are uniquely estimated by combining time constraints from fractional crystallization and the rates of magma solidification during cooling some intrusions were rapidly emplaced as dikes but stalled before reaching the surface and cooled and crystallized to feed later fractionated eruptions more specifically using the observed time interval between initial emplacement and eruption of fractionated lava whose degree of fractionation is estimated from petrologic mixing calculations the extent of solidification or cooling needed to produce this amount of fractionation can be directly inferred and from the known erupted volumes the spatial extent or size of this fractionated volume can be analytically related to the full size of the source body itself two examples yield dike widths of 82 and 68 m other intrusions remain close to the east rift magma transport path and are observed to last for decades or longer as viable magma bodies that may participate in feeding later eruptions the thickness of semi permanent reservoirs near the east rift zone magma transport path can be estimated by assuming a resupply rate that is sufficiently frequent to restrict cooling to these calculations show that long term heating of the wallrock of the magma transport paths serves to slow conduit cooling which may be partly responsible for sustaining long east rift zone eruptions adjacent to the vertical transport path beneath k lauea s summit the combined effects of heating and ever increasing magma supply rate may have forced a commensurate enlarging of the conduit perhaps explaining the occurrence of a temporary burst of deep 5 15 km long period earthquake swarms between 1987 and 1992

palaeoenvironmental paleontologic and stratigraphic significance of vertebrate remains in pleistocene limnic and alluvial deposits from southeastern sicily abstract in southeastern sicily on the hyblean plateau limnic deposits overlie early pleistocene marine sediments and are covered by early middle pleistocene marine sands in the limnic deposits fossil remains of large mammals have been collected and these represent the oldest found in a well established pleistocene stratigraphic succession in sicily the faunal association includes elephas falconeri busk the smallest sicilian elephant an elephant less reduced in size than e falconeri a canid vulpes sp rodents leithia melitensis adams chiroptera insectivora fishes birds amphibians bufo sp discoglossus sp and reptiles lacerta sp testudo sp emys orbicularis linnaeus alluvial fan deposits overlying the limnic deposits contain elephas mnaidriensis adams hippopotamus pentlandi meyer cervus siciliae pohlig and bovidae these new findings provide the stratigraphic evidence to definitively discredit previous chronological schemes for the pleistocene dwarf elephants which assumed a progressive decrease of the size with time a hypothesis recently questioned by isoleucine epimerization age determination which however were object of discussion these findings also represent a new step toward a better knowledge of the taphonomic conditions of the pleistocene mammal bearing deposits in mediterranean islands traditionally linked to karstic environment distribution of mammal faunas in the hyblean plateau proves fundamental in recognizing and dating pleistocene mammal faunas in sicily the new findings fully confirm the assumption that sicily experienced two elephant immigrations in pleistocene times

foraminiferal record of environmental changes messinian of the los yesos area sorbas basin se spain the late messinian of the sorbas basin betic cordillera se spain has been sampled to estimate 1 the paleoenvironmental changes recorded by the benthic foraminifers in pre evaporitic and evaporitic units and 2 the impact of the messinian salinity crisis on the foraminiferal biodiversity in the pre evaporitic unit foraminifers indicate a circalittoral to bathyal environments and show significant changes in bottom water oxygenation simultaneously the occurrences of epiphytic damaged foraminifers and the blocks of porites point out the presence of plant substrates and coral reefs on the infralittoral zone the overlying evaporitic unit is characterized by four subaqeous selenitic gypsum layers and three marine fossiliferous intercalations each episode of gypsum deposition ends with a desiccation event each fossiliferous intercalations traduce a rapid reflooding of the basin by marine waters corresponding to infralittoral to upper bathyal environments with normal marine conditions during the evaporitic period the ecological conditions in the water column were intermittently favorable to the development of marine organisms and moreover the marginal basins of the betic cordillera were not continuously desiccated during the messinian the low percentage of extinct species 5 at the messinian pliocene boundary and the occurrences of benthic foraminifers in the evaporitic unit indicate that the infralittoral to upper bathyal environments have not been completely modified and or barren during the messinian salinity crisis i e the messinian salinity crisis is not associated with a biological crisis

the temporal resolution of epibiont assemblages are they ecological snapshots or overexposures abstract the effects of time averaging on the fossil record of soft substrate marine faunas have been investigated in great detail but the temporal resolution of epibiont assemblages has been inferred only from limited duration deployment experiments individually dated shells provide insight into the temporal resolution of epibiont assemblages and the taphonomic history of their hosts over decades to centuries epibiont abundance and richness were evaluated for 86 dated valves of the rhynchonelliform brachiopod bouchardia rosea collected from the inner shelf maximum abundance occurred on shells less than 400 yr old and maximum diversity was attained within a century taphonomic evidence does not support models of live host colonization net accumulation or erasure of epibionts over time encrustation appears to have occurred during a brief interval between host death and burial with no evidence of significant recolonization of exhumed shells epibiont assemblages of individually dated shells preserv

taphonomy of holocene cryptic biotas from st croix virgin islands information loss and preservational biases surveys of submarine caves and overhanging ledges from st croix virgin islands provide new insights into the preservational processes active therein and into the taphonomy of ancient counterparts comparisons of preservable skeletonized versus nonpreservable unskeletonized components of these modern cryptic communities indicate that there is significant information loss in areals coverage taxonomic richness and diversity of fossilized examples quantitative estimates of such losses have been made in addition skeletal differences between early and late stage successional groups suggest biased representation of the former in the geologic record nonpreservable later colonizers may further erase the record of skeletonized forms through destructive life processes such forms of taphonomic information loss are probable in ancient counterparts and must be considered in accurate reconstruction of cryptic paleocommunities

taphonomic losses become taphonomic gains an experimental approach using the rocky shore gastropod tegula funebralis abstract the gaps in the fossil record are not liabilities for paleontologists but rather assets for evolutionary and paleoecological studies the fossil record of rocky shore invertebrates is deemed poor resulting from the bias of a high energy physical environment the poor fossil record of the pleistocene rocky shore gastropod tegula funebralis appears to be no exception to this rule however field studies including experimentally deployed shells in two habitats reveal five important taphonomic processes that affect the resultant fossil resource for these gastropods 1 the predilection for tegula shells by the intertidal hermit crab pagurus samuelis affects the longevity of the shells 2 hermit crab occupied shells of tegula have a distinct array of bionts distinguishable from the living snail and empty experimentally tethered shells 3 biont types on tethered shells differ between two habitats mudflat and rocky intertidal and are thus useful for paleoenvironmental determinations 4 physical processes greatly affected intact shell longevity of experimental shells at the rocky intertidal site whereas at the mudflat site mistaken predation by durophagous crabs was the most important agent of shell destruction and 5 despite these taphonomic losses the pleistocene fossil record of tegula retains a good record of the biological factors that affect its preservation that of pagurid crustaceans and their gastropod shell associated bionts taphonomic losses when viewed from a hierarchy of shell users then are gains in biological information that indicate the level of complexity within the shell using community and this record is not completely lost in high energy regimes

percentage carrying capacity in fossil successions a new ecostratigraphic tool with potential for detecting palaeoenvironmental change illustrated using bathyal benthic foraminifera in the late quaternary of odp hole 1006a santaren channel abstract the percent carrying capacity kp is the equilibrium population in percentage terms of a species that an area can support while adequately meeting the needs of every individual it is readily determined from a time series of percentage abundances for a species in which pit is the percentage abundance of the ith species at time t the percentage point change in abundance of a species pi between two samples is given by pi pit 1 pit where pit 1 is the percentage abundance at a subsequent time t 1 the rate of population change in percentage points for each percent at a given time or point t here termed rt is given by rt pi pit linear regression of rt against pit gives rt rm s pit in which the constant rm is the rate of increase in rt where pit approaches zero and the negative slope s represents the combined strength of intraspecific interspecific and abiotic interactions for the species investigated setting rt 0 so that pit kp and rm s kp 0 gives kp rm s the upper quaternary of odp 1006a contains two subsections with rich bathyal benthic foraminiferal assemblages separated by samples yielding few specimens values of rm s and kp were calculated for five species globocassidulina subglobosa planulina ariminensis cibicidoides pachyderma cassidulina laevigata uvigerina laevis within these subsections and 95 confidence intervals were computed for rm and s the rate of change of the percentage abundance for each percent rt as indicated by the slope s differs between species p ariminensis and c pachyderma vs c laevigata and can also vary within a single species over time g subglobosa likewise values of rm differ between species p ariminensis vs c pachyderma and can also change within a single species over time g subglobosa points of change from one value of kp to another in a stratigraphic section mark regime shifts and have potential for ecostratigraphic correlation within the upper quaternary of odp hole 1006a they apparently reflect an increase in the organic matter flux in the uppermost part of the section the method described here can be applied to any species in any taxon for which percentage data are available for those in the hydrocarbon industry it should prove especially useful for detailed studies of intervals of economic interest

gradients and patterns of sclerobionts on experimentally deployed bivalve shells synopsis of bathymetric and temporal trends on a decadal time scale bivalve shells deployed experimentally in a variety of environments of deposition eods and over a wide range of depths from 15 to 570 m in the bahamas and gulf of mexico were assessed for encrusting and endolithic bionts sclerobionts sensu taylor and wilson 2002 that accumulated over 1 2 8 and 12 13 year intervals data include percent coverage and when possible identification to generic or species level taxonomic categories data were binned into two further categories based on guilds and whether or not sclerobionts were judged to be preservable each study site shows substantial variability in both percent coverage and species richness composition which we attribute to partial burial of different individuals or parts of arrays average values of taxonomic richness guild number and percent coverage for a given eod represent a combination of exposed and buried shells as would be typical of a time averaged fossil assemblage maximally covered shells give the potential coverage for each site in both study areas there are characteristic patterns in terms of overall percentage of shells covered by sclerobionts numbers and extent of coverage by different guilds as well as by different taxa for most eods there is a progressive though non linear increase in both species richness and areal coverage through the twelve years exceptions are in the 30 m site in the bahamas and parker bank and flower garden sites in the gulf of mexico which show a significant decline in areal coverage though not in richness this effect may result from differences in sediment cover over time these sites showed a tendency to have many or all experimental bags completely sediment covered in the later sampling cluster analysis and non metric multidimensional scaling nmds of various shell substrate species at all eods from the bahamas and gulf of mexico reveal discrete groupings that are related to both depth light gradient and other factors such as variations in sedimentation and salinity similar numbers of guilds are found at various eods although the specific guild types represented differ in general highest average richness values are recorded for carbonate 70 90 m wall and deep reef sites 69 to 70 taxa and lowest are for the efg brine pool no sclerobionts other than bacterial films after 12 13 years and deeper dysphotic to subphotic sites max values 25 taxa surprisingly shallow water sites 30 m yield only moderate diversities of 40 50 taxa this results in part from the fact that certain encrusters especially the foraminifer gypsina and coralline algae tend to overgrow others and dominate space in addition to burial effects certain taxa notably the serpulid pseudovermilia are ubiquitous while other taxa e g larger foraminifera vermetid gastropods and many bryozoans are largely restricted to shallower depths a combination of species richness average coverage and key taxa permits discrimination of groups of eods and potentially in tandem with other evidence of depth gradients

dense saline plumes in exuma sound bahamas cold dense plumes have been associated with coral killoff on tropical shelves as well as with sediment movement from banks to the deep basins adjacent to shallow banks this paper presents evidence that plumes of dense salty water generated over shallow banks entrain ambient water rather than descending intact to a density compensation level as has sometimes been assumed and that plumes can spread laterally distances of tens of kilometers from their source in exuma sound dense salty water appears to be formed year round by cooling or by evaporation over shallow banks the water is forced by tidal currents through the channels between islands onto the narrow shelves of exuma sound where it likely moves as gravity currents the gravity currents entrain basin water as they cross the shelf and cascade over the steep shelf edge into exuma sound after which they are advected by ambient currents around the sound a numerical streamtube model was used to explore early details of plume evolution the model predicts that the plumes entrain 2 6 5 0 parts ambient water particularly as they traverse the gently sloping shelf the resulting loss of density contrast means that the model plumes reach their density level in exuma sound at relatively shallow depths 50 95 m just below the base of the mixed layer the final depth of modeled plumes is relatively consistent with observed plume depths which vary seasonally 75 m in early winter to 45 m in summer depending on the depth and density characteristics of the seasonal mixed layer over the sound observed plume thickness ranges from 40 m in winter to 20 30 m in summer final salinity values exceed 36 8 practical salinity units final density ranges from sigmat 23 75 to 24 5 plume depth vertical structure and longevity are shown to depend on upper ocean mixing processes such as convection and wind mixing

calciturbidites and calcidebrites sea level variations or tectonic processes abstract the compositional variation of pleistocene carbonate gravity deposits from the exuma sound basin bahamas and of turonian conacian deposits from the southern provence basin france was determined the bahamian carbonate platform is located in a tectonically stable passive margin setting and the gravity deposits were deposited in an environment controlled by eustatic sea level fluctuations in contrast the southern provence basin sediments were deposited in a tectonic active regime two types of gravity deposits were present in the cores of odp leg 101 site 632a i e calciturbidites and calcidebrites in analogy with earlier studies haak and schlager 1989 the compositional variations in the calciturbidites could be linked to different sources on the carbonate margin i e platform interior platform edge platform slope interglacial sea level highstands calciturbidites show a dominance of non skeletal grains derived from the platform interior while glacial sea level lowstands calciturbidites show a dominance of skeletal platform edge to platform slope derived grains hence the calciturbidite composition can be used to reconstruct the position in relative sea level in contrast the composition of the calcidebrites remained unaltered through time and showed a clear dominance of platform edge derived sediments in addition it was shown that the calcidebrites were deposited during regressions in the southern provence basin spb the gravity deposits were deposited during episodes of sea level rise coinciding with a series of earthquakes associated with the opening of the spb the spb megabreccias show a mix of sediment grains derived from the platform interior the platform edge and the upper slope thus in contrast to the exuma sound calcidebrites with their platform margin domain specific composition the spb megabreccias have a composition that could not be assigned to a single domain on the platform margin and comprise a total mix of platform margin domains in conclusion this study shows that the composition of calciturbidites calcidebrites and megabreccias can be used to determine which processes eustatic variations or tectonic events triggered the redeposition of these gravity deposits

the mechanics of sill inception propagation and growth experimental evidence for rapid reduction in magmatic overpressure abstract a model of magma propagation in the crust is presented using a series of analogue experiments where dyed water is injected at a constant flux into layers of solidified gelatine the gelatine layers are transparent and when intruded deform in an almost ideal elastic manner under the experimental conditions low gelatine concentration 2 5 or 3 wt and low temperature 5 10 c the upper gelatine layer was 1 0 to 1 5 times stiffer than the lower layer with either a weak or strong interface strength between the gelatine layers the gelatine is seeded with 20 50 m diameter pmma rhb neutrally buoyant particles that are fluoresced by a pulsed vertical laser sheet centred on the injection point digital image correlation dic is used to calculate incremental strain and finite strain in the deforming host material as it is intruded this is mapped in 2d for the developing experimental volcanic plumbing system that comprises a feeder dyke and sill since the gelatine deforms elastically strain measurements correlate with stress our results indicate that for constant magma flux the moment of sill inception is characterised by a significant magmatic pressure decrease of up to 60 this is evidenced by the rapid contraction of the feeder dyke at the moment the sill forms sill propagation is then controlled by the fracture properties of the weak interface with fluid from the feeder dyke extracted to help grow the sill pressure drops during sill inception and growth are likely to be important in volcanic systems where destabilisation of the magmatic plumbing system could trigger an eruption

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

tracking labrador sea water property signals along the deep western boundary current observations of the deep western boundary current dwbc at line w on the western north atlantic continental slope southeast of cape cod from 1995 to 2014 reveal water mass changes that are consistent with changes in source water properties upstream in the labrador sea this is most evident in the cold dense and deep class of labrador sea water dlsw that was created and progressively replenished and deepened by recurring winter convection during the severe winters of 1987 1994 the arrival of this record cold fresh and low potential vorticity anomaly at line w lags its formation in the labrador sea by 3 7 years complementary observations along the path of the dwbc provide further evidence that this anomaly is advected along the boundary and indicate that stirring between the boundary and the interior intensifies south of the flemish cap finally the consistency of the data with realistic advective and mixing time scales is assessed using the waugh and hall 2005 model framework the data are found to be best represented by a mean transit time of 5 years from the labrador sea to line w with a leading order role for both advection by the dwbc and mixing between the boundary flow and interior waters

differentiation and magma mixing on kilauea s east rift zone a further look at the eruptions of 1955 and 1960 part ii the 1960 lavas new and detailed petrographic observations mineral compositional data and whole rock vs glass compositional trends document magma mixing in lavas erupted from kilauea s lower east rift zone in 1960 evidence includes the occurrence of heterogeneous phenocryst assemblages including resorbed and reversely zoned minerals in the lavas inferred to be hybrids calculations suggest that this mixing which is shown to have taken place within magma reservoirs recharged at the end of the 1955 eruption involved introduction of four different magmas these magmas originated beneath kilauea s summit and moved into the rift reservoirs beginning 10 days after the eruption began we used microprobe analyses of glass to calculate temperatures of liquids erupted in 1955 and 1960 we then used the calculated proportions of stored and recharge components to estimate the temperature of the recharge components and found those temperatures to be consistent with the temperature of the same magmas as they appeared at kilauea s summit our studies reinforce conclusions reached in previous studies of kilauea s magmatic plumbing we infer that magma enters shallow storage beneath kilauea s summit and also moves laterally into the fluid core of the east rift zone during this process if magmas of distinctive chemistry are present they retain their chemical identity and the amount of cooling is comparable for magma transported either upward or laterally to eruption sites intrusions within a few kilometers of the surface cool and crystallize to produce fractionated magma magma mixing occurs both within bodies of previously fractionated magma and when new magma intersects a preexisting reservoir magma is otherwise prevented from mixing either by wall rock septa or by differing thermal and density characteristics of the successive magma batches

a generalized transport theory water mass composition and age abstract a general theory to describe and understand advective and diffusive ocean transport is reported it allows any passive tracer field with an atmospheric source to be constructed by superposing sea surface contributions with a generalized green s function called the boundary propagator of the passive tracer equation the boundary propagator has the interpretation of the joint water mass and transit time distribution from the sea surface the theory thus includes the classical oceanographic idea of water mass analysis and extends it to allow for a distribution of transit times from the sea surface the joint water mass and transit time distribution contains complete information about the transport processes in the flow it captures this information in a more accessible way than using velocity and diffusivity fields however at least for the case of sequestration and transport of dissolved material by the ocean circulation the boundary propagator is thus the natural quantity to consider when discus

aeromagnetic study of the island of hawaii an aeromagnetic study of the island of hawaii provides new insight on magnetic properties of subsurface rock and geologic structure on a regional scale spectral depth analysis delineates two shallow magnetic zones each roughly 1 5 km thick lying at a depth of 1 km one zone of unknown origin lies in the center of the island and correlates with a regional magnetic high the other zone coincides with pronounced magnetic lows paralleling kilauea s active east rift zone these magnetic lows probably depict rocks chemically altered by hydrothermal fluids in which titanomagnetite has been destroyed analysis of magnetic terrain effects indicates that magnetization also decreases with depth within mauna kea and mauna loa we estimate that magnetization is reduced by about half at a depth of 1 km the magnetic method is particularly useful in delineating the lateral extent of local shield structures such as rifts summit calderas pit craters and vent fissures rifts possess characteristic magnetic patterns primarily long wavelength linear magnetic low zones we propose alteration processes reduce magnetizations along the flanks of rifts on the other hand along young rifts e g kilauea s east rift zone short wavelength magnetic anomalies probably reflect slowly cooled unaltered intrusions altered rock may also produce magnetic lows that help define buried summit calderas

differentiation and magma mixing on kilauea s east rift zone the lavas of the 1955 east rift eruption of kilauea volcano have been the object of considerable petrologic interest for two reasons first the early 1955 lavas are among the most differentiated ever erupted at kilauea and second the petrographic character and chemical composition of the lava being erupted changed significantly during the eruption this shift from more differentiated mgo 5 0 5 7 to more magnesian mgo 6 2 6 8 lava has been variously interpreted as either due to systematic excavation of a zoned differentiated magma body or to invasion of the differentiated magma by more primitive magma followed by rapid mixing and eruption of the resulting hybrid magmas petrologic examination of several nearvent spatter samples of the late 1955 lavas shows abundant evidence for magma mixing including resorbed and or reversely zoned crystals of olivine augite and plagioclase in addition the compositional ranges of olivine plagioclase and groundmass sulfide are very large implying that the assemblages are hybrid core compositions of olivine phenocrysts range from fo85 to fo77 the most magnesian olivines in these samples must have originally crystallized from a melt containing 8 0 8 5 mgo which is distinctly more magnesian than the bulk composition of the late 1955 lavas the majorelement and trace element data are either permissive or supportive of a hybrid origin for the late 1955 lavas in particular the compositional trends of the 1955 lavas on plots of cao vs mgo and the virtual invariance of al2o3 and sr in these plagioclase phyric lavas are more easily explained by magma mixing than by fractionation the pattern of internal disequilibrium re equilibration in the late 1955 spatter samples is consistent with reintrusion and mixing having occurred at least twice during the latter part of the 1955 eruption plagioclase zonation preserves possible evidence for additional earlier reintrusion events least squares modelling the mixing of early 1955 bulk compositions with various summit lavas olivine pick the 1952 summit lava as most like the primitive component the results also indicate the primitive component had mgo 7 5 8 0 corresponding to liquidus temperatures of 1165 1175 c the absence of fe ti oxide phenocrysts in the late 1955 lavas implies that the cooler component of the hybrid had t 1110 c thus the thermal contrast between the two components may have been as much as 55 65 c sufficient to produce the conspicuous disequilibrium effects visible in the spatter samples

the impact of the mediterranean outflow water mow on benthic foraminiferal assemblages and surface sediments at the southern portuguese continental margin benthic foraminifera and surface sediments were analyzed from 23 box core and core top samples from 250 to 3600 m depth at the southern portuguese continental margin between 37 and 38 n this area is affected by the mow which flows northwards along the slope between 600 and 1500 m waterdepth sediment structures grain size distribution and clay mineral assemblages of surface sediments indicate active winnowing in the upper part of the mow and deposition of the fine fraction near its lower boundary r mode cluster analyses of foraminiferal census data from the 250 m fraction revealed four associations the shelf edge association occurs on glauconitic shelf and upper slope sands down to 268 m the upper slope association is recognized between 498 and 1300 m where sand silt clays to clayey silts are encountered the lower slope association is found between 1405 and 2985 m and differs markedly from assemblages below 3000 m deep water association where the near surface sediments are soft hemipelagic clays the boundary layer association shows no significant depth limits but abundance maxima both in the density interface above the mow and in the interval of decreasing turbulence below it the boundaries of the shelf edge and upper slope association correspond to these hydrographic boundary layers whereas the boundary between lower slope and deep water assemblage is related to threshold values of nutrient flux to the benthic community examination of hard substrates reveals 27 different species of epibenthic foraminifera six of these the epibenthos group were found attached to elevated substrates only within the mow above the mow elevated substrates were inhabited by different species whilst below the mow they were not used by any epibenthic foraminifers evidently the hydrodynamic environment of the mow current provides an ecological niche which is efficiently used by opportunistic suspension feeders the epibenthos group is more abundant in the middle part of the study area between 37 20 and 37 40 n where the sand content of surface sediments is also higher both indicate an enhanced sediment water interaction in this area which results from an obstruction of the mow flow by the principes d avis basement spur

january 30 1997 eruptive event on kilauea volcano hawaii as monitored by continuous gps a continuous global positioning system gps network on kilauea volcano captured the most recent fissure eruption in kilauea s east rift zone erz in unprecedented spatial and temporal detail the short eruption drained the lava pond at pueu oeo leading to a two month long pause in its on going eruption models of the gps data indicate that the intrusion s bottom edge extended to only 2 4 km continuous gps data reveal rift opening 8 hours prior to the eruption absence of precursory summit inflation rules out magma storage overpressurization as the eruption s cause we infer that stresses in the shallow rift created by the continued deep rift dilation and slip on the south flank decollement caused the rift intrusion

mid holocene relative sea level changes along atlantic patagonia new data from camarones chubut argentina this paper concerns the relative sea level changes associated with the atlantic patagonian coast derived from sea level index points whose elevation was determined by a differential global position system dgps bioencrustations from outcrops located near camarones chubut argentina consist of autochthonous deposits characterized by austromegabalanus psittacus molina 1782 encrusting acervulinid foraminifera coralline red algae and bryozoans the association of the different organisms is interpreted as being associated with an intertidal environment and they have been used as index points to establish the relative sea level position the main conclusion is that the relative sea level between c 7000 and 5300 cal yr bp was in the range of c 2 4 m a s l with a mean value of c 3 5 m a s l our data seem to support the existence of different rates of relative sea level fall in different sectors of atlantic patagonia during the holocene and highlight the importance of a more precise and accurate r

spatiotemporal evolution of dike opening and decollement slip at kīlauea volcano hawai i 1 rapid changes in ground tilt and gps positions on k lauea volcano hawai i are interpreted as resulting from a shallow two segment dike intrusion into the east rift zone that began at 1217 utc 0217 hst on 17 june 2007 and lasted almost 3 days as a result of the intrusion a very small volume of basalt about 1500 m3 erupted on 19 june northward tilt at a coastal tiltmeter subsidence of south flank gps sites southeastward displacements at southwestern flank gps sites and a swarm of flank earthquakes suggest that a slow slip event occurred on the decollement beneath k lauea s south flank concurrent with the rift intrusion we use 4 min gps positions that include estimates of time dependent tropospheric gradients and ground tilt data to study the spatial and temporal relationships between the two inferred shallow steeply dipping dike segments extending from the surface to about 2 km depth and decollement slip at 8 km depth we invert for the temporal evolution of distributed dike opening and decollement slip in independent inversions at each time step using a nonnegative least squares algorithm on the basis of these inversions the intrusion occurred in two stages that correspond spatially and temporally with concentrated rift zone seismicity the dike opening began on the western of the two segments before jumping to the eastern segment where the majority of opening accumulated dike opening preceded the start of decollement slip at an 84 confidence level the latter is indicated by the onset of northward tilt of a coastal tiltmeter displacements at southwest flank gps sites began about 18 h later and are interpreted as resulting from slow slip on the southwestern flank additional constraints on the evolution of the intrusion and decollement slip come from inversion of an envisat interferogram that spans the intrusion until 0822 utc on 18 june 2007 combined with gps and tilt data this inversion shows that up to 0822 utc on 18 june decollement slip is only required in a limited region offshore of ka ena point a similar inversion of the complete event which includes gps and tilt data up to 21 june and a second envisat interferogram spanning the complete intrusion until 21 june shows decollement slip spread westward across the south flank this may suggest westward migration of the decollement slip as the event progressed

propagation of tracer signals in boundary currents abstract the propagation of a range of tracer signals in a simple model of the deep western boundary current is examined analytical expressions are derived in certain limits for the transit time distributions and the propagation times tracer ages of tracers with exponentially growing or periodic concentration histories at the boundary current s origin if mixing between the boundary current and the surrounding ocean is either very slow or very rapid then all tracer signals propagate at the same rate in contrast for intermediate mixing rates tracer ages generally depend on the history of the tracer variations at the origin and range from the advective time along the current to the much larger mean age close agreement of the model with chlorofluorocarbon cfc and tritium observations in the north atlantic deep western boundary current dwbc is obtained when the model is in the intermediate mixing regime with current speed around 5 cm s 1 and mixing time scale around 1 yr in this regime anomalies