return of the coral reef hypothesis basin to shelf partitioning of caco3 and its effect on atmospheric co2 differences in the rate of coral reef carbonate deposition from the pleistocene to the holocene may account for the quaternary variation of atmospheric co sub 2 volumes of carbonate associated with holocene reefs require an average deposition rate of 2 0 times 10 sup 13 mol yr for the past 5 ka in light of combined riverine mid ocean ridge and ground water fluxes of calcium to the oceans of 2 3 times 10 sub 13 mol yr the current flux of calcium carbonate to pelagic sediments must be far below the pleistocene average of 1 2 times 10 sub 13 mol yr the authors suggest that sea level change shifts the locus of carbonate deposition from the deep sea to the shelves as the normal glacial interglacial pattern of deposition of quaternary global carbonates to assess the impact of these changes on atmospheric co sub 2 a simple numerical simulation of the global carbon cycle was developed atmospheric co sub 2 as well as calcite saturation depth and sediment responses to these carbonate deposition changes are examined atmospheric co sub 2 changes close to those observed in the vostok ice core approximately 80 ppm co sub 2 for the quaternary are observed as well as the approximate depth changes in percent carbonate of sediments measured in themore pacific ocean over the same time interval less

nominally hydrous magmatism on the moon for the past 40 years the moon has been described as nearly devoid of indigenous water however evidence for water both on the lunar surface and within the lunar interior have recently emerged calling into question this long standing lunar dogma in the present study hydroxyl as well as fluoride and chloride was analyzed by secondary ion mass spectrometry in apatite ca5 po4 3 f cl oh from three different lunar samples in order to obtain quantitative constraints on the abundance of water in the lunar interior this work confirms that hundreds to thousands of ppm water of the structural form hydroxyl is present in apatite from the moon moreover two of the studied samples likely had water preserved from magmatic processes which would qualify the water as being indigenous to the moon the presence of hydroxyl in apatite from a number of different types of lunar rocks indicates that water may be ubiquitous within the lunar interior potentially as early as the time of lunar formation the water contents analyzed for the lunar apatite indicate minimum water contents of their lunar source region to range from 64 ppb to 5 ppm h2o this lower limit range of water contents is at least two orders of magnitude greater than the previously reported value for the bulk moon and the actual source region water contents could be significantly higher

neritic and pelagic carbonate sedimentation in the marine environment ignorance is not bliss synthesis of available data allows us to define general patterns of late quaternary carbonate production and sedimentation in the global ocean during high stands of sea level the neritic and pelagic environments appear to sequester approximately similar amounts of carbonate whereas during low stands of sea level the decreased neritic zone produces and accumulates approximately an order of magnitude less carbonate assuming that global accumulation of deep sea carbonates remains more or less constant during glacially induced changes in sea level the ocean becomes depleted with respect to calcium carbonate during high stands and recharges during low stands before we can achieve a better understanding of the global carbonate system however we need a better understanding of key environments and processes a production and accumulation on continental shelves both as potential sinks accumulation and as sources export to the deep sea b a better measure of pelagic carbonate production and c late quaternary late pleistocene and holocene mass accumulation rates in the deep sea

high resolution characterization of vadose zone dynamics using cross borehole radar characterization of the dynamics of moisture migration in the unsaturated zone of aquifers is essential if reliable estimates of the transport of pollutants threatening such aquifers are to be made electrical geophysical investigation techniques such as ground penetrating radar offer suitable methods for monitoring moisture content changes in the vadose zone moreover these tools permit relatively large measurement scales appropriate for hydrological models of unsaturated processes and thus they offer a distinct advantage over conventional measurement approaches ground penetrating radar when applied in transmission mode between boreholes can provide high resolution information on lithological and hydrological features the technique may be applied in tomographic mode and in a much simpler vertical profile mode both modes of measurement have been utilized using two boreholes 5 m apart located at a field site in the uk sherwood sandstone aquifer radar transmission measurements have been used to characterize the change in moisture content in unsaturated sandstone due to controlled water tracer injection continual monitoring of cross borehole radar measurements over an 18 month period has also permitted determination of travel times of natural loading to the system and has revealed the impact of subtle contrasts in lithology on changes in moisture content over time the time series of inferred moisture contents show clearly wetting and drying fronts migrating at a rate of approximately 2 m month 1 throughout the sandstone

hydrous melting of the martian mantle produced both depleted and enriched shergottites the search for water in our solar system is one of the primary driving forces for planetary science and exploration because water plays an important role in many geologic processes and is required for biologic processes as we currently understand them excluding earth mars is the most promising destination in the inner solar system to find water as it is undoubtedly responsible for shaping many geomorphologic features observed on the present day martian surface however the water content of the martian interior is currently unresolved much of our information about the martian interior comes from studies of the basaltic martian meteorites shergottites in this study we examined the water contents of magmatic apatites from a geochemically enriched shergottite the shergotty meteorite and a geochemically depleted shergottite the queen alexandria range 94201 meteorite from these data we determined that there was little difference in water contents between the geochemically depleted and enriched shergottite magmas the water contents of the apatite imply that shergottite parent magmas contained 730 2870 ppm h 2 o prior to degassing furthermore the martian mantle contains 73 290 ppm h 2 o and underwent hydrous melting as recently as 327 ma in the absence of plate tectonics the presence of water in the interior of mars requires planetary differentiation under hydrous conditions this is the first evidence of significant hydrogen storage in a planetary interior at the time of core formation and this process could support elevated h abundances in the interiors of other terrestrial bodies like the moon mercury venus large differentiated asteroids and earth

a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

deep pacific caco 3 compensation and glacial interglacial atmospheric co 2 abstract benthic foraminiferal 13c suggests that there was a net shift of isotopically light metabolic co2 from the upper ocean into the deep ocean during the last glacial period according to the caco3 compensation hypothesis this should have caused a transient drop in deep ocean co32 that was eventually reversed by seafloor dissolution of caco3 the resulting increase in whole ocean ph may have had a significant impact on atmospheric co2 compounding any decrease that was due to the initial vertical co2 shift the opposite hypothetically occurred during deglaciation when co2 was returned to the upper ocean and atmosphere and deep ocean co32 temporarily increased followed by excess burial of caco3 and a drop in whole ocean ph the deep sea record of caco3 preservation appears to reflect these processes with the largest excursion during deglaciation as expected but various factors make quantification of deep sea paleo co32 difficult here we reconstruct deep equatorial pacific co32 over the last glacial interglacial cycle using benthic foraminiferal zn ca which is strongly affected by saturation state during calcite precipitation our data are in agreement with the caco3 compensation theory including glacial co32 concentrations similar to or slightly lower than today and a termination i co32 peak of 25 30 mol kg 1 the deglacial co32 rise precedes ice sheet melting consistent with the timing of the atmospheric co2 rise a later portion of the peak could reflect removal of co2 from the atmosphere ocean system due to boreal forest regrowth caco3 compensation alone may explain more than one third of the atmospheric co2 lowering during glacial times

ground penetrating radar and its use in sedimentology principles problems and progress abstract ground penetrating radar gpr also referred to as ground probing radar surface penetrating radar subsurface radar georadar or impulse radar is a noninvasive geophysical technique that detects electrical discontinuities in the shallow subsurface

the influence of pore water advection benthic photosynthesis and respiration on calcium carbonate dynamics in reef sands to investigate diel calcium carbonate caco3 dynamics in permeable coral reef sands we measured porewater profiles and fluxes of oxygen o2 nutrients ph calcium ca2 and alkalinity ta across the sediment water interface in sands of different permeability at heron reef australia background flushing rates were high most likely as a result of infaunal burrow irrigation but flux chamber stirring enhanced pore water exchange light and pore water advection fueled high rates of benthic primary production and calcification in sunlit surface sediments in the light benthic photosynthesis and calcification induced surface minima in ca2 and ta and peaks in ph and o2 oxygen penetration depth in coarse sands decreased from 1 2 cm during the day to 0 6 cm at night total oxygen uptake tou in dark chambers was three to fourteen times greater than diffusive uptake and showed a direct effect of pore water advection greater sediment oxygen consumption rates were observed in higher permeability sands in the dark ta release was not stimulated by increasing tou because of a damping effect of pore water advection on metabolic caco3 dissolution efficiency on a daily basis caco3 undergoes net dissolution in heron reef sands however pore water advection can reverse the caco3 budget and promote caco3 preservation under the most energetic conditions

the chlorine isotopic composition of martian meteorites 1 chlorine isotope composition of martian mantle and crustal reservoirs and their interactions the martian meteorites record a wide diversity of environments processes and ages much work has been done to decipher potential mantle sources for martian magmas and their interactions with crustal and surface environments chlorine isotopes provide a unique opportunity to assess interactions between martian mantle derived magmas and the crust we have measured the cl isotopic composition of 17 samples that span the range of known ages martian environments and mantle reservoirs the 37cl of the martian mantle as represented by the olivine phyric shergottites nwa 2737 chassignite and shergotty basaltic shergottite has a low value of approximately 3 8 this value is lower than that of all other planetary bodies measured thus far the martian crust as represented by regolith breccia nwa 7034 is variably enriched in the heavy isotope of cl this enrichment is reflective of preferential loss of 35cl to space most basaltic shergottites less shergotty nakhlites chassigny and allan hills 84001 lie on a continuum between the martian mantle and crust this intermediate range is explained by mechanical mixing through impact fluid interaction and assimilation fractional crystallization

prominence of ichnologically influenced macroporosity in the karst biscayne aquifer stratiform super k zones a combination of cyclostratigraphic ichnologic and borehole geophysical analyses of continuous core holes tracer test analyses and lattice boltzmann fl ow simulations was used to quantify biogenic macroporosity and permeability of the biscayne aquifer southeastern florida biogenic macroporosity largely manifests as 1 ichnogenic macroporosity primarily related to postdepositional burrowing activity by callianassid shrimp and fossilization of components of their complex burrow systems ophiomorpha and 2 biomoldic macroporosity originating from dissolution of fossil hard parts principally mollusk shells ophiomorpha dominated ichnofabric provides the greatest contribution to hydrologic characteristics in the biscayne aquifer in a 345 km 2 study area stratiform tabular shaped units of thalassinidean associated macroporosity are commonly confi ned to the lower part of upward shallowing highfrequency cycles throughout aggradational cycles and in one case they stack vertically within the lower part of a high frequency cycle set broad continuity of many of the macroporous units concentrates groundwater fl ow in extremely permeable passageways thus making the aquifer vulnerable to long distance transport of contaminants ichnogenic macroporosity represents an alternative pathway for concentrated groundwater fl ow that differs considerably from standard karst fl ow system paradigms which describe groundwater movement through fractures and cavernous dissolution features permeabilities were calculated using lattice boltzmann methods lbms applied to computer renderings assembled from x ray computed tomography scans of various biogenic macroporous limestone samples the highest simulated lbm permeabilities were about fi ve orders of magnitude greater than standard laboratory measurements using air permeability methods which are limited in their application to extremely permeable macroporous rock samples based on their close conformance to analytical solutions for pipe fl ow lbms offer a new means of obtaining accurate permeability values for such materials we suggest that the stratiform ichnogenic groundwater fl ow zones have permeabilities even more extreme 2 5 orders of magnitude higher than the jurassic super k zones of the giant ghawar oil fi eld the fl ow zones of the pleistocene biscayne aquifer provide examples of ichnogenic macroporosity for comparative analysis of origin and evolution in other carbonate aquifers as well as petroleum reservoirs

carbonate production on isolated banks since 20 k a bp climatic implications abstract a new database on the distribution of isolated low latitude banks is evaluated to assess their carbonate production and climatic impact since the last glacial maximum lgm most bank summits are 70 m deep or shallower the few substrates and the high rates of sea level rise suggest that neritic carbonate production from the lgm to ca 14 k a bp when sea level reached 70 m was generally low flooding of banks at 70 m depth below sea level after 14 k a bp caused carbonate production to rise episodically although these banks drowned fast carbonate production peaked during the holocene when maximum flooding of the bank summits occurred the emission of co 2 to the atmosphere resulting from carbonate production would have risen in line with the steps in production a crude estimate of this emission is presented

radar frequency dielectric dispersion in sandstone implications for determination of moisture and clay content 1 the relationship between dielectric permittivity water saturation and clay content for the sherwood sandstone from ne england was characterized as part of a wider study of the vadose zone moisture dynamics and pollution vulnerability of this aquifer dielectric permittivity was measured over the full range of saturation levels for various lithologies ranging from clean medium grained sandstone to fine grained sandstone containing up to 5 clay using a specially constructed dielectric cell dielectric constant kr is largely independent of frequency between 350 mhz and 1000 mhz below 350 mhz kr of fine grained clay rich sandstone shows frequency dispersion tests on physical models of the sandstone consisting of a fine fraction of ottawa sand and montmorillonite clay indicate that the clay minerals within the sandstone are responsible for its frequency dispersive behavior these tests also show that increasing pore fluid salinity increases dielectric dispersion at the lower end of the frequency range which indicates that this arises from the interfacial maxwell wagner mechanism associated with platy clay particles water saturated sand clay mixtures show very low dielectric constants at high frequencies over 650 mhz this effect is independent of salinity and probably results from the layered geometric arrangement of solids bound and free water within the swelling clay the complex refractive index method crim with a mineral dielectric constant of about 5 provides a good match to the water saturation versus dielectric constant data for all sherwood sandstone lithologies at frequencies between 350 and 1000 mhz and for clay poor sandstone at lower frequencies below 350 mhz the presence of a few percent of clay in some sherwood sandstone lithologies raises their crim best fit mineral dielectric constant substantially

neritic carbonate for six submerged coral reefs from northern australia implications for holocene global carbon dioxide abstract total contribution of six recently discovered submerged coral reefs in northern australia to holocene neritic caco3 and co2 is assessed to address a gap in global budgets caco3 production for the reef framework and inter reefal deposits is 0 26 0 28 mt holocene co2 production is 0 14 0 16 mt coral and coralline algae are the dominant sources of holocene caco3 although foraminifers and molluscs are the dominant constituents of inter reefal deposits the total amount of holocene neritic caco3 produced by the six submerged coral reefs is several orders of magnitude smaller than that calculated using accepted caco3 production values because of very low production a give up growth history and presumed significant dissolution and exports the contribution of submerged coral reefs to global holocene neritic caco3 is estimated to be 0 26 0 62 gt which yields 0 15 0 37 gt of co2 this amount of co2 is 0 02 0 05 of the 780 gt added to the atmosphere since 18 kyr bp contributions from australian submerged coral reefs are estimated to be 0 05 gt caco3 and 0 03 gt co2 for an emergent reef area of 47 9 103 km2 based on the growth history of the submerged coral reefs in the gulf of carpentaria maximum global holocene caco3 fluxes could have attained 0 3 gt yr 1 between 11 and 7 ka bp this additional caco3 would have culminated in a maximum caco3 production from all emergent and submerged coral reefs of 1 2 gt yr 1 and neritic caco3 production of 2 75 gt yr 1 the dilemma remains that the global area and caco3 mass of submerged coral reefs are currently unknown it is inevitable that many more submerged coral reefs will be found our findings imply that submerged coral reefs are a small but fundamental source of holocene neritic caco3 and co2

exploring the interplay between infiltration dynamics and critical zone structures with multiscale geophysical imaging a review abstract infiltration is the process of water entering into and routings through the subsurface it has a profound impact on water flux in the earth s critical zone cz influencing phenomena such as overland flow stream generation plant available water and groundwater recharge as well as the associated cz processes and functions of weathering erosion slope stability and food production however reliable measurement of infiltration in structured geomedia soils and regolith with hidden subsurface features remain challenging the increasing availability of geophysical techniques has helped them emerge as viable options for minimally invasive determination of infiltration at the pedon to hillslope or catchment scales geophysical methods replace the educated guesswork of interpreting field data from traditional infiltrometers with direct visualization and quantification this paper provides a comprehensive literature review of various applications of geophysical techniques used to 1 visualize infiltration relevant structures 2 monitor non uniform or preferential infiltration patterns and 3 map soil moisture distribution after infiltration it then proposes a new conceptualization form and function dualism for subsurface hydrology to link preferential infiltration to cz structures with the goal of formulating more realistic infiltration theories related to subsurface structural heterogeneity the characterization of both subsurface structures form and infiltration dynamics function via geophysical imaging should help infiltration models currently emphasizing macroscale behaviors rooted in the continuum concept expand to accommodate the microscale nature of preferential flow integrating multiple geophysical approaches and developments into the new generation of geophysical techniques will further enhance our ability to see into the fabric of the subsurface and capture the dynamics of non uniform infiltration through the hidden half of the cz this approach offers exciting opportunities for understanding the complex interactions between cz structures and cz processes

early loss fractionation and redistribution of chlorine in the moon as revealed by the low ti lunar mare basalt suite abstract the relative abundances of chlorine isotopes measured in low ti basalts from the moon appear to reflect mixing between two reservoirs one component representing the urkreep the final product of the crystallization of the lunar magma ocean with 37 cl 25 relative to standard mean ocean chlorine the other representing either a mare basalt reservoir or meteoritic materials with 37 cl 0 using the abundances of other kreep enriched elements as proxies for the abundance of cl in low ti mare basalts which is difficult to constrain due to magmatic processes such as fractional crystallization and degassing we find that the urkreep contains 28 times higher cl abundance 25 170 ppm cl as compared to the low 37 cl end member in the observed mixing relationship chlorine with an urkreep c i ratio of 0 2 to 1 5 is 500 to 3400 times less enriched than refractory incompatibles such as u and th and is consistent with incomplete loss of cl species taking place during or prior to the magma ocean phase the preservation of multiple isotopically distinct reservoirs of cl can be explained by 1 incomplete degassing pre or syn giant impact with preservation of undegassed chondritic cl and subsequent formation of an enriched and isotopically fractionated reservoir or 2 development of both high concentration high 37 cl and low concentration low 37 cl reservoirs during the degassing and crystallization of the lunar magma ocean a range of model bulk lunar cl abundances from 0 3 0 6 ppm allows us to place cl in the context of the rest of the elements of the periodic table and suggests that cl behaves as only a moderately volatile element during degassing chlorine isotope fractionation resulting from loss syn or pre magma ocean is characterized by 1000 ln 3 96 to 4 04 abundance and isotopic constraints are consistent with the loss of cl being limited by vaporization of mixtures of cl salts such as hcl zncl2 fecl2 and nacl these new constraints on the chlorine abundance and isotopic values of urkreep make it a well constrained target for dynamic models aiming to test plausible conditions for the formation of the earth moon system

chlorine isotopic compositions of apatite in apollo 14 rocks evidence for widespread vapor phase metasomatism on the lunar nearside 4 billion years ago abstract compared to most other planetary materials in the solar system some lunar rocks display high 37cl signatures loss of cl in a h cl environment has been invoked to explain the heavy signatures observed in lunar samples either during volcanic eruptions onto the lunar surface or during large scale degassing of the lunar magma ocean to explore the conditions under which cl isotope fractionation occurred in lunar basaltic melts five apollo 14 crystalline samples were selected 14053 19 14072 13 14073 9 14310 171 along with basaltic clast 14321 1482 for in situ analysis of cl isotopes using secondary ion mass spectrometry cl isotopes were measured within the mineral apatite with 37cl values ranging from 14 6 1 6 to 40 0 2 9 these values expand the range previously reported for apatite in lunar rocks and include some of the heaviest cl isotope compositions measured in lunar samples to date the data here do not display a trend between increasing rare earth elements contents and 37cl values reported in previous studies other processes that can explain the wide inter and intra sample variability of 37cl values are explored magmatic degassing is suggested to have potentially played a role in fractionating cl isotope in these samples degassing alone however could not create the wide variability in isotopic signatures our favored hypothesis to explain small scale heterogeneity is late stage interaction with a volatile rich gas phase originating from devolatilization of lunar surface regolith rocks 4 billion years ago this period coincides with vapor induced metasomastism recorded in other lunar samples collected at the apollo 16 and 17 landing sites pointing to the possibility of widespread volatile induced metasomatism on the lunar nearside at that time potentially attributed to the imbrium formation event

geophysical evidence for the lateral distribution of free phase gas at the peat basin scale in a large northern peatland 1 northern peatlands contribute to the global carbon cycle by way of gas emissions in the form of biogenic carbon dioxide and methane originating in the subsurface determining how much gas is present and where it is trapped is essential to understanding the role of northern peatlands on the global carbon cycle particularly in regard to methane cycling in this study spatial variability in free phase gas content was estimated using ground penetrating radar gpr along a 1 4 km transect crossing distinct peat landforms including a bog crest midslope lawn and fen variations in gas content and distribution were observed in landforms crossed by this transect estimated gas content up to 25 by volume was observed in landforms dominated by woody surface vegetation in areas of the midslope lawn the estimated gas content was greater than 15 while estimated gas contents between 0 and 7 were found in the fen changes in estimated gas content of up to 20 were observed over distances of 100 m across a transition between a stand of 10 m tall trees and an adjacent fen the mean of the estimated errors in gas content is 1 3 suggesting that these large changes in estimated gas content between landforms can be clearly determined using geophysical methods a geophysical image of the distribution of free phase across this transect reveals evidence for gas storage in deep peat in intervals as thin as 0 35 m these data support conceptual models based on accumulation and storage of free phase gas in deep peat

characterization of the porosity distribution in the upper part of the karst biscayne aquifer using common offset ground penetrating radar everglades national park florida summary the karst biscayne aquifer is characterized by a heterogeneous spatial arrangement of porosity and hydraulic conductivity making conceptualization difficult the biscayne aquifer is the primary source of drinking water for millions of people in south florida thus information concerning the distribution of karst features that concentrate the groundwater flow and affect contaminant transport is critical the principal purpose of the study was to investigate the ability of two dimensional ground penetrating radar gpr to rapidly characterize porosity variability in the karst biscayne aquifer in south florida an 800 m long gpr transect of a previously investigated area at the long pine key nature trail in everglades national park collected in fast acquisition common offset mode shows hundreds of diffraction hyperbolae the distribution of diffraction hyperbolae was used to estimate electromagnetic em wave velocity at each diffraction location and to assess both horizontal and vertical changes in velocity within the transect a petrophysical model complex refractive index model or crim was used to estimate total bulk porosity a set of common midpoint surveys at selected locations distributed along the common offset transect also were collected for comparison with the common offsets and were used to constrain one dimensional 1 d distributions of porosity with depth porosity values for the saturated miami limestone ranged between 25 and 41 for common offset gpr surveys and between 23 and 39 for common midpoint gpr surveys laboratory measurements of porosity in five whole core samples from the saturated part of the aquifer in the study area ranged between 7 1 and 41 8 gpr estimates of porosity were found to be valid only under saturated conditions other limitations are related to the vertical resolution of the gpr signal and the volume of the material considered by the measurement methodology overall good correspondence between gpr estimates and the direct porosity values from the whole core samples confirms the ability of gpr common offset surveys to provide rapid characterization of porosity variability in the biscayne aquifer the common offset survey method has several advantages 1 improved time efficiency in comparison to other gpr acquisition modes such as common midpoints and 2 enhanced lateral continuity of porosity estimates particularly when compared to porosity measurements on 1 d samples such as rock cores the results also support the presence of areas of low em wave velocity or high porosity under saturated conditions causing velocity pull down areas and apparent sag features in the reflection record this study shows that gpr can be a useful tool for improving understanding of the petrophysical properties of highly heterogeneous systems such as karst aquifers and thus may assist with the development of more accurate groundwater flow models such as those used for restoration efforts in the everglades

coral reef geomorphology as a function of seasonal prevailing currents and larval dispersal abstract recent ecological and oceanographic evidence has demonstrated that coral recruitment can be highly localised and very successful in areas of high water residence time eddy areas on coral reefs these areas occur in the lee of time averaged and depth averaged far field currents in this study several reefs in the central region of the great barrier reef australia were examined to determine the relationship between asymmetry in reef geomorphology wind direction time and depth averaged currents particularly during the coral spawning season detailed fine scale bathymetric data were plotted in three dimensions for four reefs helix reef wheeler reef myrmidon reef and rib reef the perspective from which each reef was viewed was rotated until maximum asymmetry steep vs gentle slope from the floor of the continental shelf to the ocean s surface was achieved the compass orientation of the reef s asymmetry was then compared with known directions of tradewinds and time and depth averaged currents asymmetry in overall reef geomorphology was found generally not to be related to tradewinds or resultant surface driven currents it was however found to be more closely associated with time and depth averaged seasonal currents often prevailing at the time of coral spawning we propose that far field currents near field currents and coral recruitment processes prevailing during the time of coral spawning have differentially enhanced lateral extension of the reef in a direction down current far field currents through geological time we also propose that this relationship may be of assistance in hind casting seasonal low velocity depth and time averaged palaeo currents surrounding fossil reefs in addition to tools already available for hind casting wind forced surface currents and waves

influence of variable rates of neritic carbonate deposition on atmospheric carbon dioxide and pelagic sediments short term imbalances in the global cycle of shallow water calcium carbonate deposition and dissolution may be responsible for much of the observed pleistocene change in atmospheric carbon dioxide content however any proposed changes in the alkalinity balance of the ocean must be reconciled with the sedimentary record of deep sea carbonates the possible magnitude of the effect of shallow water carbonate deposition on the dissolution of pelagic carbonate can be tested using numerical simulations of the global carbon cycle boundary conditions can be defined by using extant shallow water carbonate accumulation data and pelagic carbonate deposition dissolution data on timescales of thousands of years carbonate deposition versus dissolution is rarely out of equilibrium by more than 1 5 x 10 13 mole yr 1 results indicate that the carbonate chemistry of the ocean is rarely at equilibrium on timescales less than 10 ka this disequilibrium is probably due to sea level induced changes in shallow water calcium carbonate deposition dissolution an interpretation that does not conflict with pelagic sedimentary data from the central pacific

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

the moon a taylor perspective we address several current lunar problems the data suggest that the moon likely possesses an fe rich metallic core a few percent of lunar volume although definitive proof is lacking refractory elements appear to be enriched relative both to the composition of the primordial solar nebula ci and the earth very volatile elements appear to be depleted uniformly at high levels we adopt the single impact hypothesis for lunar origin which formed a high temperature silicate vapor disk mostly of metal poor silicate material from an impactor theia that was already depleted in volatiles we speculate that the curious lunar bulk composition resulted from condensation from high temperature vapor at around a few earth radii this could produce an enriched refractory element composition that cut off below 1000 k producing a uniform depletion in very volatile elements

coral reef sedimentation on rodrigues and the western indian ocean and its impact on the carbon cycle coral reefs in the southwest indian ocean cover an area of ca 18530 km2 compared with a global reef area of nearly 300000 km2 these regions are important as fishing grounds tourist attractions and as a significant component of the global carbon cycle the mass of calcium carbonate stored within holocene neritic sediments is a number that we are only now beginning to quantify with any confidence in stark contrast to the mass and sedimentation rates associated with pelagic calcium carbonate which have been relatively well defined for decades we report new data that demonstrate that the reefs at rodrigues like those at reunion and mauritius only reached a mature state reached sea level by 2 3 ka thousands of years later than most of the reefs in the australasian region yet field observations show that the large lagoon at rodrigues is already completely full of carbonate detritus typical lagoon depth less than 1 m at low spring tide the presence of aeolian dunes at rodrigues indicates periodic exposure of past lagoons throughout the pleistocene the absence of elevated pleistocene reef deposits on the island indicates that the island has not been uplifted most holocene reefs are between 15 and 20 m in thickness and those in the southwest indian ocean appear to be consistent with this observation we support the view that the co2 flux associated with coral reef growth acts as a climate change amplifier during deglaciation adding co2 to a warming world southwest indian ocean reefs could have added 7 10 to this global flux during the holocene

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

phosphate halogen metasomatism of lunar granulite 79215 impact induced fractionation of volatiles and incompatible elements in the last decade it has been recognized that the moon contains significant proportions of volatile elements h f cl and that they are transported through the lunar crust and across its surface here we document a significant segment of that volatile cycle in lunar granulite breccia 79215 impact induced remobilization of volatiles and vapor phase transport with extreme elemental fractionation 79215 contains 1 volume of fluorapatite ca 5 po 4 3 f cl oh in crystals to 1 mm long which is reflected in its analyzed abundances of f cl and p the apatite has a molar f cl ratio of 10 and contains only 25 ppm oh and low abundances of the rare earth elements ree the chlorine in the apatite is isotopically heavy at 37 cl 32 7 1 6 hydrogen in the apatite is heavy at d 1060 180 much of that d came from spallogenic nuclear reactions and the original d was lower between 350 and 700 unlike other p rich lunar rocks e g 65015 79215 lacks abundant k and ree and other igneous incompatible elements characteristic of the lunar kreep component here we show that the p and halogens in 79215 were added to an otherwise normal granulite by vapor phase metasomatism similar to rock alteration by fumarolic exhalations as observed on earth the ultimate source of the p and halogens was most likely kreep it being the richest reservoir of p on the moon and 79215 having h and cl isotopic compositions consistent with kreep a kreep rich rock was heated and devolatilized by an impact event this vapor was fractionated by interaction with solid phases including merrillite a volatile free phosphate mineral a fe ti oxide and a zr bearing phase these solids removed ree th zr hf etc from the vapor and allowed the vapor to transport primarily p f and cl with lesser proportions of ba and u into 79215 vapor deposited crystals of apatite to 30 m are known in some lunar regolith samples but lunar vapor has not before this been implicated in significant mass transfer it seems unlikely however that phosphate halogen metasomatism is related to the high th sm abundance ratios of this and other lunar magnesian granulites the metasomatism of 79215 emphasizes the importance of impact heating in the lunar volatile cycle both in mobilizing volatile components into vapor and in generating strong elemental fractionations

the global distribution of earth s critical zone and its controlling factors the near surface layer of earth which provides essential elements for supporting life is now recognized as the critical zone cz this study provides the first global assessment of the cz thickness czt and its controlling factors by combining data sets of climate vegetation height vh water table depth wtd groundwater thickness gwt topography and lithologic data the analysis shows that czt ranges from 0 7 to 223 5 m with an average value of 36 8 m across continental areas czt is thickest in midlatitudes subtropical to temperate zones the proportion of aboveground part vh to czt is 19 9 16 7 mean one standard deviation while it is 80 1 16 7 for the underground part wtd gwt a generalized linear model shows that compound topographic index ln a tan b where a is the upslope contributing area and b is the slope degree of the landscape and potential evapotranspiration are the first two major controlling factors on the variations in czt this study opens opportunities for further advancing cz science by providing one of its most important properties its thickness

comparison of differential diagenesis of two oolites on the lower triassic platform margin ne sichuan basin implications for the co evolution of rock structure and porosity abstract two oolites of the lower triassic feixianguan formation on the margins of the kaijiang liangping k l trough in the ne sichuan basin were deposited in the upper parts of similar shallowing upward sequences and are capped by a subaerial exposure surface however they have contrasting diagenetic histories and reservoir qualities the sour oolitic dolostone reservoirs on the eastern side of the k l trough have significantly higher porosities than the sweet oolitic limestone reservoirs on the western side a petrologic and geochemical comparison of the two oolites was carried out so as to investigate the role of diagenetic processes on the co evolution of oolite structure and pore network on both sides of the k l trough eogenetic meteoric digenesis led to an inversion of texture with ooid dissolution and interparticle cementation in the oolite layers close to the exposure surface the layers relatively far from the exposure surface mostly underwent recrystallization in association with connate seawater resulting in neomorphic fabrics in the ooid cortices and less interparticle calcite cement during the subsequent dolomitization the early formed oolite structure were mostly inherited by the dolostones on the eastern side with fabric retentive textures in the layers close to the exposure surface and fabric destructive textures in the layers far from the exposure surface during deeper burial the oolitic limestones were subjected to extensive calcite cementation and porosity loss whereas the dolostones generally retained more porosity and have better connectivity of the micropore network the higher porosity of the dolostones is ascribed to lesser chemical compaction and associated cement precipitation rather than the creation of new pores porosity enhancement is closely dependent on the absence of the calcite cement related to pressure solution the heterogeneity of the dolostone fabrics and the porosity was further enhanced by the subsequent recrystallization and the dissolution reprecipitation process induced by thermochemical sulfate reduction during which small amounts of net porosity are calculated to have been created the oolitic limestones are the best reservoirs close to the exposure surface whereas the most porous dolostones with the highest degree of fabric destruction are commonly some distance from the exposure surface these results provide some insights into the diagenetic controls on oolite structure and porosity and have implications for predicting the porosity of deeply buried oolitic reservoirs so have global theoretical and practical significance

morphological characterisation of reef types in torres strait and an assessment of their carbonate production coral reefs represent major accumulations of calcium carbonate caco3 the particularly labyrinthine network of reefs in torres strait north of the great barrier reef gbr has been examined in order to estimate their gross caco3 productivity the approach involved a two step procedure first characterising and classifying the morphology of reefs based on a classification scheme widely employed on the gbr and then estimating gross caco3 productivity rates across the region using a regional census based approach this was undertaken by independently verifying published rates of coral reef community gross production for use in torres strait based on site specific ecological and morphological data a total of 606 reef platforms were mapped and classified using classification trees despite the complexity of the maze of reefs in torres strait there are broad morphological similarities with reefs in the gbr the spatial distribution and dimensions of reef types across both regions are underpinned by similar geological processes sea level history in the holocene and exposure to the same wind wave energetic regime resulting in comparable geomorphic zonation however the presence of strong tidal currents flowing through torres strait and the relatively shallow and narrow dimensions of the shelf exert a control on local morphology and spatial distribution of the reef platforms a total amount of 8 7million tonnes of caco3 per year at an average rate of 3 7kg caco3m 2yr 1 g were estimated for the studied area extrapolated production rates based on detailed and regional census based approaches for geomorphic zones across torres strait were comparable to those reported elsewhere particularly values for the gbr based on alkalinity reduction methods however differences in mapping methodologies and the impact of reduced calcification due to global trends in coral reef ecological decline and changing oceanic physical conditions warrant further research the novel method proposed in this study to characterise the geomorphology of reef types based on classification trees provides an objective and repeatable data driven approach that combined with regional census based approaches has the potential to be adapted and transferred to different coral reef regions depicting a more accurate picture of interactions between reef ecology and geomorphology

an evaluation of models of apatite compositional variability using apatite from the middle banded series of the stillwater complex montana apatite is a relatively common accessory mineral in the olivine bearing zones ob iii and ob iv of the middle banded series of the stillwater complex occurring interstitial to cumulus grains as monomineralic inclusions in cumulus grains and in polymineralic clusters which may or may not be included in the cumulus grains eighty nine of 185 samples examined were found to contain some apatite the f cl oh content of the apatite show distinct stratigraphic variations xclap mole fraction cl in apatite of interstitial apatite increases upsection in both ob iii and ob iv with average values ranging from 0 15 to 0 85 in ob iii and from 0 03 to 0 60 in ob iv xfap varies inversely with xclapwith average values ranging from 0 00 to 0 70 while xohap remains relatively constant near 0 40 or decreases slightly with height these variations are remarkable given that no appreciable stratigraphic variations in either the major or trace element compositions of any of the cumulus minerals are found in the 800 m of section that comprise ob iii and ob iv within sample variation of xclap for samples containing cl rich apatite is substantially larger up to 0 65 xclap than for samples with more f rich apatite xclap varies by approximately 0 15 although interstitial apatite is found throughout ob iii and ob iv apatite occurring as monomineralic inclusion in cumulus grains or in polymineralic clusters is almost exclusively found in samples with cl rich apatite the data are best explained by a model involving the degassing of a cl rich volatile phase from the crystallizing interstitial liquid the up section migration of this fluid resulted in the crystallization of f rich apatite in the lower portion and progressive cl enrichment in the apatite with height the presence of hornblende bearing dikes veins and pegmatoids at the level of maximum cl enrichment is consistent with a fluid migration model

imaging rainfall drainage within the miami oolitic limestone using high resolution time lapse ground penetrating radar 1 the vadose zone of the miami limestone is capable of draining several centimeters of rainfall within a fraction of an hour once the water enters the ground little is known about the flow paths in the oolitic rock a new rotary laser positioned ground penetrating radar gpr system enables centimeter precise and rapid acquisition of time lapse surveys in the field two dimensional 2 d gpr time lapse surveying at a 3 min interval before during and after rainfall shows how buried sand filled dissolution sinks efficiently drain the bulk of the rainwater hourly repeated 3 d imaging of a dissolution sink in response to surface infiltration shows how the wetting front propagates at a rate of 0 6 1 2 m h traversing the 5 m thick vadose zone within hours at the same time some of the water migrates laterally into the host rock guided by stratigraphic unit boundaries average lateral propagation measured over a 28 hour period was of the order of 0 1 m h on a seasonal time frame redistribution involves the entire rock volume comparing 3 d surveys acquired after wet summer and dry winter conditions shows good gpr event correspondence but also time shifts up to 20 ns caused by the change of overall water content within the vadose zone high precision time lapse gpr imaging can therefore be used to noninvasively characterize natural drainage inside the vadose zone ranging from transient loading to seasonal variation

the role of the global carbonate cycle in the regulation and evolution of the earth system we review one of the most ancient of all the global biogeochemical cycles and one which reflects the profound geochemical and biological changes that have occurred as the earth system has evolved through time that of calcium carbonate caco3 in particular we highlight a mid mesozoic revolution in the nature and location of carbonate deposition in the marine environment driven by the ecological success of calcareous plankton this drove the creation of a responsive deep sea sedimentary sink of caco3 the result is that biologically driven carbonate deposition provides a significant buffering of ocean chemistry and of atmospheric co2 in the modern system however the same calcifying organisms that under pin the deep sea carbonate sink are now threatened by the continued atmospheric release of fossil fuel co2 and increasing acidity of the surface ocean we are not yet in a position to predict what the impact on caco3 production will be or how the uptake of fossil fuel co2 by the ocean will be affected this uncertainty in the future trajectory of atmospheric co2 that comes from incomplete understanding of the marine carbonate cycle is cause for concern

lunar magma ocean crystallization revisited bulk composition early cumulate mineralogy and the source regions of the highlands mg suite abstract crystallization of the lunar magma ocean lmo has been numerically modeled and its products inferred from sample observations but it has never been fully tested experimentally this study is a reexamination of the lmo hypothesis by means of the first experimental simulation of lunar differentiation two end member bulk moon compositions are considered one enriched in refractory lithophile elements relative to earth and one with no such enrichment a two stage model of magma ocean crystallization based on geophysical constraints is simulated and features early crystal suspension and equilibrium crystallization followed by fractional crystallization of the residual magma ocean an initially entirely molten moon is assumed part 1 of this study presented here focuses on stage 1 of this model and considers the early cumulates formed by equilibrium crystallization differences in mantle mineralogy resulting from different bulk moon compositions and implications for the source regions of the highlands mg suite refractory element enriched bulk moon compositions produce a deep mantle that contains garnet and trace cr spinel in addition to low ca pyroxene and olivine in contrast compositions without refractory element enrichment produce a deep dunitic mantle with low ca pyroxene but without an aluminous phase the differences in bulk composition are magnified in the residual melt the residual lmo from the refractory element enriched composition will likely produce plagioclase and ilmenite earlier and in greater quantities both compositions produce mg rich early cumulate piles that extend from the core mantle boundary to 355 km depth if 50 equilibrium crystallization and whole moon melting are assumed these early lmo cumulates provide good fits for the source regions for a component of the high mg ni and co poor parental magmas of the mg suite cumulates if certain conditions are called upon the olivine in early lmo cumulates produced by either bulk moon composition is far too rich in cr to be reasonable for the source regions of the mg suite meaning either core formation in the presence of s and or c must be invoked to deplete the lmo and the crystallizing olivine in cr or that current estimates of the bulk lunar cr content are too high we infer that melts meeting the criteria of the mg suite parents could be produced from early lmo cumulates by solid state kreep and plagioclase hybridization near the base of the crust and subsequent partial melting additionally we propose a revised model for mg suite petrogenesis

carbonate and terrigenous sediment budgets for two inshore turbid reefs on the central great barrier reef abstract inshore turbid zone reefs on the great barrier reef gbr occur within 20 km of the mainland coast under marine environmental conditions with respect to sedimentation rates turbidity and water quality that are generally considered marginal for reef growth despite this data from various benthic habitat assessments report high 30 coral cover in these environments and reef core records show them to be characterised by relatively rapid rates of vertical accretion 2 8 mm year a long term trend indicative of high net carbonate productivity and in situ carbonate framework accumulation however the lack of quantitative data on terrigenous sediment input and flux rates and on carbonate production rates has inhibited understanding of both ecological timescale rates of carbonate production and the aggregated long term net impacts of sediments on reef growth to address this knowledge gap a modern carbonate budget and terrigenous sediment model that quantified allochthonous sediment inputs onto within and off reef was developed at two inshore reefs middle reef and paluma shoals both are located within the central region of the gbr and are subjected to high terrigenous sediment load 11 000 tonnes year and fluctuating turbidity 5 to 100 mg l regimes based on sediment dynamic modelling over 81 of sediments delivered were transported off reef with net sediment accumulation limited to sheltered reef habitats net carbonate production was high 6 9 kg m2 year due to high coral cover 30 high coral calcification rates acropora average 6 3 g cm2 year and low bioerosion rates 0 3 to 5 kg m2 year but varied spatially with highest net carbonate production 10 kg m2 year within deep 2 m at lat windward reef zones high carbonate framework production has enabled middle reef and paluma shoals to vertically accrete rapidly middle reef establishing at depths of 4 m paluma shoals at 3 m depth and both reaching sea level in

early degassing of lunar urkreep by crust breaching impact s current models for the moon s formation have yet to fully account for the thermal evolution of the moon in the presence of h2o and other volatiles of particular importance is chlorine since most lunar samples are characterised by unique heavy 37cl values significantly deviating from those of other planetary materials including earth for which 37cl values cluster around 0 in order to unravel the cause s of the moon s unique chlorine isotope signature we performed a comprehensive study of high precision in situ cl isotope measurements of apatite from a suite of apollo samples with a range of geochemical characteristics and petrologic types the cl isotopic compositions measured in lunar apatite in the studied samples display a wide range of 37cl values reaching a maximum value of 36 which are positively correlated with the amount of potassium k rare earth element ree and phosphorous p kreep component in each sample using these new data integrated with existing h isotope data obtained for the same samples we are able to place these findings in the context of the canonical lunar magma ocean lmo model the results are consistent with the urkreep reservoir being characterised by a 37cl 30 such a heavy cl isotope signature requires metal chloride degassing from a cl enriched urkreep lmo residue a process likely to have been triggered by at least one large crust breaching impact event that facilitated the transport and exposure of urkreep liquid to the lunar surface

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

application of high frequency ground penetrating radar to the reconstruction of 3d sedimentary architecture in a flume model of a fluvial system abstract ground penetrating radar gpr offers a fast and efficient method for visualizing three dimensional 3d images of shallow subsurface structures we investigated the application of gpr to nondestructive imaging of deposits formed in a small experimental flume using a high frequency gpr antenna the gpr measurements made with a 1 6 ghz antenna were conducted on flume models of sandy fluvial systems we conducted two experiments one to reveal the penetration depth and resolution of the gpr antenna and to reconstruct the 3d architecture of fluvial deposits created in a flume and the other to examine the characteristics of reflection boundaries the experimental materials were mainly loamy soil the first experiment showed that a 1 6 ghz antenna was suited to laboratory use offering a depth resolution of 2 3 cm in full penetration of a bed 15 24 cm thick gpr scanning yielded an accurate reconstruction of the 3d architecture of a fluvial channel using magnetite marker beds the second experiment also successfully imaged a 3d architecture using quartz sand instead of magnetite and loamy soil which have different relative permittivities this research shows that gpr is a feasible technique for 3d analysis of experimental flume deposits

a review of lunar chronology revealing a preponderance of 4 34 4 37 ga ages in this study data obtained from sm nd and rb sr isotopic measurements of lunar highlands samples are renormalized to common standard values and then used to define ages with a common isochron regression algorithm the reliability of these ages is evaluated using five criteria that include whether 1 the ages are defined by multiple isotopic systems 2 the data demonstrate limited scatter outside uncertainty 3 initial isotopic compositions are consistent with the petrogenesis of the samples 4 the ages are defined by an isotopic system that is resistant to disturbance by impact metamorphism and 5 the rare earth element abundances determined by isotope dilution of bulk of mineral fractions match those measured by in situ analyses from this analysis it is apparent that the oldest highlands rock ages are some of the least reliable and that there is little support for crustal ages older than 4 40 ga a model age for ur kreep formation calculated using the most reliable mg suite sm nd isotopic systematics in conjunction with sm nd analyses of kreep basalts is 4389 45 ma this age is a good match to the lu hf model age of 4353 37 ma determined using a subset of this sample suite the average modelmore age of 4353 25 ma determined on mare basalts with the 146sm 142nd isotopic system with a peak in pb pb ages observed in lunar zircons of 4340 20 ma and the oldest terrestrial zircon age of 4374 6 ma the preponderance of ages between 4 34 and 4 37 ga reflect either primordial solidification of a lunar magma ocean or a widespread secondary magmatic event on the lunar nearside the first scenario is not consistent with the oldest ages reported for lunar zircons whereas the second scenario does not account for concordance between ages of crustal rocks and mantle reservoirs less

sundaland peat carbon dynamics and its contribution to the holocene atmospheric co2 concentration the sunda shelf is a large submerged extension of the continental shelf of mainland asia joining the islands of borneo java and sumatra and forming the shallow seabed of the south china sea recent studies identified present day peatlands in southeast asia as a globally important carbon reservoir however little is known about sundaland paleo peatlands and their role in the global carbon cycle since the last glacial maximum using a topography based sea level driven model we estimate the potential spatial extent of peatlands during the late pleistocene and early holocene across the low lying sundaland plains we then use the estimated peatland area together with data on carbon accumulation rates to calculate the total peat carbon pool on the sunda shelf finally using a global biogeochemical model we analyze the relative influence of the predicted sundaland peat dynamics and other carbon change mechanisms specifically high latitude forest growth and peat formation shallow sea carbonate deposition ocean warming and combinations of them on the global carbon cycle of the holocene we identify a feedback mechanism between sea level and peatland carbon sequestration in sundaland that reduced atmospheric co2 concentration by about 4 5 ppm and increased 13c by 0 05 during the holocene we also show that a concurrence of mechanisms that includes sundaland peat dynamics produces model results that are consistent with proxy records especially with respect to 13c

toward explaining the holocene carbon dioxide and carbon isotope records results from transient ocean carbon cycle climate simulations records of atmospheric co2 and d 13 c as well as the spatiotemporal evolution of d 13 c and carbonate ion concentration in the deep sea deposition of shallow water carbonate carbonate compensation of land uptake during the glacial termination land carbon uptake and release during the holocene and the response of the ocean sediment system to marine changes during the termination contribute roughly equally to the reconstructed late holocene pco2 rise of 20 ppmv the 5 ppmv early holocene pco2 decrease reflects terrestrial uptake largely compensated by carbonate deposition and ocean sediment responses additional small contributions arise from holocene changes in sea surface temperature ocean circulation and export productivity the holocene pco2 variations result from the subtle balance of forcings and processes acting on different timescales and partly in opposite direction as well as from memory effects associated with changes occurring during the termination different interglacial periods with different forcing histories are thus expected to yield different pco2 evolutions as documented by ice cores

full resolution 3d radar stratigraphy of complex oolitic sedimentary architecture miami limestone florida u s a abstract at the field scale m s to 100 s m it is often difficult to define the true three dimensional form of depositional units or facies within sediments or sedimentary rocks due to inherent spatial bias in traditional data sources such as outcrops and cores full resolution 3d ground penetrating radar gpr surveying has the potential to overcome this problem southwest of miami paleotopography on the upper pleistocene miami limestone formation indicates the former presence of a large oolitic barrier bar backed by extensive ooid shoals data from three closely spaced cores and two large outcrops on the barrier bar allow initial subdivision of the miami limestone in to a lower mottled oolitic facies and an upper bedded oolitic facies however detailed correlation between the cores and outcrops is problematic due to spatial aliasing a 250 mhz full resolution 3d gpr data set was collected over an area of 45 m 24 m that encompassed the location of the three cores depth of radar wave penetration was around 6 m and both horizontal and vertical resolution was approximately 0 1 m for the 6500 m3 rock volume such that the upper bedded oolitic facies was imaged without spatial aliasing radar surfaces and intervening radar facies define two main radar package types low angle sheet and sigmoidal the low angle sheet radar packages are interpreted as oolitic shoal deposits consisting of tidal bars covered by ebb orientated straight crested sand waves the overlying sigmoidal radar packages record barrier bar formation through alongshore progradation comparable sedimentary successions from both pleistocene and modern deposits in the bahamas suggest that the three evolutionary stages recorded for the miami limestone are typical of many transgressive ooid shoal complexes

h and cl isotope systematics of apatite in brecciated lunar meteorites northwest africa 4472 northwest africa 773 sayh al uhaymir 169 and kalahari 009 we have investigated the h and cl systematics in apatite from four brecciated lunar meteorites in northwest africa nwa 4472 most of the apatites contain 2000 6000 ppm h2o with d between 200 and 0 except for one grain isolated in the matrix which contains 6000 ppm h2o with d of 500 900 this low d apatite contains 2500 7500 ppm cl associated with 37cl of 15 20 while the high d grain contains 2500 ppm cl with 37cl of 7 15 in nwa 773 apatites in a first group contain 700 2500 ppm h2o with d values averaging around 0 100 while apatites in a second group contain 5500 16500 ppm h2o with d 250 50 in sayh al uhaymir sau 169 and kalahari kal 009 apatites are similar in terms of their h2o contents 600 3000 ppm and d values 100 to 200 in sau 169 apatites contain 6000 10 000 ppm cl characterized by 37cl of 5 12 overall most of the analyzed apatite grains have d within the range reported for carbonaceous chondrites similar to apatite analyzed in ancient 3 9 ga lunar magmatic one grain in nwa 4472 has h and cl isotope compositions similar to apatite from mare basalts with an age of 4 35 ga this grain could be a representative of the oldest known lunar volcanic activity finally since numerous evolved clasts in nwa 773 formed through silicate liquid immiscibility the apatite grains with extremely high h2o contents reaching pure hydroxylapatite composition could provide insights into the effects of such process on the evolution of volatiles in lunar magmas

chlorine distribution and its isotopic composition in rusty rock 66095 implications for volatile element enrichments of rusty rock and lunar soils origin of rusty alteration and volatile element behavior on the moon abstract an interesting characteristic of the pyroclastic glass bead deposits select impact produced lithologies such as the rusty rock 66095 and unique lunar soils from the apollo 16 landing site is their unusual enrichments in 204 pb cd bi br i ge sb tl zn and cl which indicates that portions of these sample contain a substantial volatile component sample 66095 a fine grained subophitic to ophitic polymict melt breccia also hosts a pervasive low temperature volatile rich oxyhydrated mineral assemblage the volatile element enrichments in these assorted lunar lithologies have been attributed to a variety of extra lunar and lunar processes whereas the oxyhydration in 66095 has long been thought to represent either terrestrial alteration of lunar chlorides and fe ni metal to feo oh cl or indigenous lunar processes in 66095 cl is accommodated in feo oh cl phosphates and chlorides and is heterogeneously distributed the low temperature alteration occurs as rims around fe ni metal and sulfide grains and as dispersed grains in the adjacent matrix micro raman and transmission electron microscope tem imaging indicate that akaganeite feo oh cl is the dominant feo oh polymorph and is intergrown with goethite feo oh and hematite fe 2 o 3 tem observations indicate a well defined nanometer scale stratigraphy to the alteration for example kamacite body centered cubic face centered cubic fcc fe ni alloy lawrencite fecl 2 akaganeite the lunar lawrencite fe ni cl 2 in 66095 does not react directly to akaganeite on earth rather lawrencite exposed to terrestrial conditions reacts to form an amorphous fe and cl bearing phase nano crystalline goethite and hematite the morphology of these terrestrial alteration products is significantly different than that of the akaganeite occurring in 66095 the chlorine isotopic compositions of these volatile rich samples are enriched in heavy cl for 66095 the 37 cl ranges from 14 0 to 15 6 whereas the 37 cl for the volatile rich a16 soils ranges from 5 6 to 15 7 based on these data it appears likely that the volatile element enrichments and the cl isotopic fractionation observed in 66095 and the apollo 16 soils did not result from extra lunar additions but are most likely indigenous to the moon lawrencite was deposited on mineral surfaces at approximately 650 c to 570 c from a metal chloride bearing h poor gas phase this gas phase was also responsible for the transport of other metals e g zn cu pb fe the fractionation of cl isotopes in the rusty rock can be attributed to fumarole processes in a low h system the origin and formation of the akaganeite is more enigmatic the cl isotopes are consistent with it replacing lawrencite however numerous nanometer scale observations are not consistent with a terrestrial origin and indicate multiple episodes of oxyhydration

reef sedimentary accretion model reefsam understanding coral reef evolution on holocene time scales using 3d stratigraphic forward modelling abstract a detailed understanding of the development of coral reefs and their internal structure has important applications for predicting future reef trajectories in light of climate changes petroleum exploration and reconstructing past environmental changes such as sea level numerical computer modelling provides a quantitative means of testing and understanding reef processes and better predicting past and future reef development however most existing carbonate stratigraphic forward models sfms focus on the platform scale and several limitations in their simulation of important reef processes and reef scale features e g patch reefs sand aprons have been previously identified we present the reef sedimentary accretion model reefsam a new carbonate sfm designed to test new approaches to modelling processes important at the reef scale with the goal of better simulating reef features and evolution at higher temporal and spatial resolutions specific developments include a sediment transport model which calculates deposition based on a range of grain sizes additional controls on coralgal growth including wave energy and surface substrate specificity and model outputs showing categorized paleo conditions composition paleo depth and paleo energy along with numerous quantitative measures for objective comparison of model results to real world observational data which is often more abundant for modern holocene reefs than buried ancient reefs simulations of the well studied holocene one tree reef otr in the southern great barrier reef gbr showed improvements upon previous modelling attempts in both quantitative measures e g lagoon size or reef sea level catch up time and the ability to produce more realistic reef scale morphological features e g lagoonal patch reefs mostly sand filled lagoon and reef development characteristics e g transition from mostly vertical aggradation during sea level catch up to horizontal progradation afterwards controls on reef maturity lagoonal filling identified in previous modelling experiments were corroborated sensitivity testing also revealed a very high sensitivity to reef drowning these results indicate the new modelling approaches are viable and provide a way forward for future holocene reef evolution model development

apatites in lunar kreep basalts the missing link to understanding the h isotope systematics of the moon recent re analyses of lunar samples have undoubtedly measured indigenous water challenging the paradigm of a dry moon and arguing that some portions of the lunar interior are as wet as some regions of the earth s mantle and that water in both planetary bodies likely share a common origin mare basalts indirectly sample the lunar mantle and are affected by petrogenetic processes such as crystallization and degassing that can modify characteristics of indigenous water in primary mantle melts analyses of apatite in phosphorus rich kreep k ree rare earth elements p basalts may provide more reliable estimates for the water content of lunar magmas as some apatites likely crystallized before substantial degassing occurred in lunar kreep basalt sample 15386 apatite h 2 o content and h isotopic composition suggest that degassing occurred during apatite crystallization the lowest d value of 90 100 representing an upper limit for the isotopic composition of water in the parental magma interpretation of the data for kreep basalt 15386 suggests that this basalt is characterized by relatively elevated h 2 o contents and ci chondrite type d values similar to those proposed for other mare basalts and pyroclastic glasses on the other hand most of the apatites in lunar kreep basalt 72275 and lunar meteorite nwa 773 crystallized before degassing and h isotope fractionation and their d h ratios thus directly refl ect those of their source regions these apatites have an average d value of 130 50 suggesting the presence of a water reservoir in the moon characterized by moderate h 2 o contents and h isotopic composition similar to that of earth s interior these fi ndings imply that signifi cant amounts of water in the moon were inherited from the proto earth surviving the purported moon forming impact event

estimating porosity and solid dielectric permittivity in the miami limestone using high frequency ground penetrating radar gpr measurements at the laboratory scale subsurface water flow in south florida is largely controlled by the heterogeneous nature of the karst limestone in the biscayne aquifer and its upper formation the miami limestone these heterogeneities are amplified by dissolution structures that induce changes in the aquifer s material and physical properties i e porosity and dielectric permittivity and create preferential flow paths understanding such patterns are critical for the development of realistic groundwater flow models particularly in the everglades where restoration of hydrological conditions is intended in this work we used noninvasive ground penetrating radar gpr to estimate the spatial variability in porosity and the dielectric permittivity of the solid phase of the limestone at centimeter scale resolution to evaluate the potential for field based gpr studies a laboratory setup that included high frequency gpr measurements under completely unsaturated and saturated conditions was used to estimate changes in electromagnetic wave velocity through miami limestone samples the complex refractive index model was used to derive estimates of porosity and dielectric permittivity of the solid phase of the limestone porosity estimates of the samples ranged between 45 2 and 66 0 and showed good correspondence with estimates of porosity using analytical and digital image techniques solid dielectric permittivity values ranged between 7 0 and 13 0 this study shows the ability of gpr to image the spatial variability of porosity and dielectric permittivity in the miami limestone and shows potential for expanding these results to larger scales and other karst aquifers

sediment transport and mixing depth on a coral reef sand apron this paper investigates the mechanics of sediment transport on a subtidal sand apron located on a coral reef environment in this environment 100 of the sediment is carbonate bioclasts generated in situ the sand apron is located on the back reef and only affected by waves during high tides it is commonly accepted in the literature that sand aprons are features that prograde lagoonwards and that most of the progradation occurs during high energy events measurements of water depths waves currents and near bed suspended sediment concentrations all at 10 hz on the sand apron were undertaken over a nine day intensive field campaign over both spring and neap tides waves and tides were also measured in the lagoon the topography and bathymetry of the sand apron were measured and mixing depth was obtained on three transects using depth of disturbance rods we found that sediment transport on sand aprons is not solely restricted to high energy events but occurs on a daily basis during spring tides the main factor controlling the sediment transport was the water depth above the bed with depths of 2 2 3 m allowing waves to promote the most sediment transport this corresponds to a depth over the reef crest of 1 6 1 9 m the second most important control was waves transport was observed when h on the apron was 0 1 m or greater in contrast current magnitude was not a controlling mechanism for sediment entrainment but did affect sediment transport the morphology of the sand apron was shown to affect the direction of currents with the currents also expected to influence the morphology of the sand apron the currents measured during this field campaign were aligned with a shallow channel in the sand apron mixing depths were small 2 5 cm yet they were larger than the values predicted by empirical formulae for gentle siliciclastic ocean beaches

water hydrogen in the lunar mantle results from petrology and magma ocean modeling abstract measurements of hydroxyl or water in lunar materials are being used to suggest that melting source regions within the moon contained tens to hundreds of ppm water the compositions of magmatic source regions in the moon can be calculated using magma ocean fractional solidification models given an initial bulk composition our magma ocean models demonstrate that to make a source region with 10 to 200 ppm water the bulk magma ocean must contain 100 to 1000 ppm water or more and in a 1000 km deep lunar magma ocean 1000 ppm water is equivalent to 5 of an earth ocean by weight as solidification of the magma ocean continues water and other incompatible elements are progressively enriched in the evolving liquids the final kreep like liquids would contain the greatest fraction of water we suggest that a bulk magma ocean with over 100 ppm water is prohibited by constraints on these kreep like final magma ocean liquids and by the thermodynamic equilibrium requirement with metallic iron in mare basalts we conclude that bulk lunar interior water contents must be at the low end of the range posited by recent observations

chromite symplectites in mg suite troctolite 76535 as evidence for infiltration metasomatism of a lunar layered intrusion abstract despite the very low chromium concentrations in its cumulus olivine 140 ppm lunar troctolite 76535 contains large amounts of cr sporadically but highly concentrated in symplectite assemblages consisting of mg al chromite and two pyroxenes previously proposed symplectite formation mechanisms include crystallization of trapped interstitial melt diffusion of cr from cumulus olivine and or remobilization of cumulus chromite grains these mechanisms would imply that the highly cr depleted nature of mg suite parental magmas and their source materials inferred from cumulus olivine may be illusory we have conducted a detailed petrologic and textural study of symplectites as well as chromite veins intercumulus assemblages olivine hosted melt inclusions and clinopyroxene troilite veins in 76535 with the goals of constraining the origin of the symplectites and the degree of cr depletion in mg suite magmas relative to other lunar basalts orthopyroxene and clinopyroxene in melt inclusions are depleted in cr relative to their symplectite counterparts averaging 900 and 1200 ppm vs 7400 and 8100 ppm cr 2 o 3 respectively olivine in contact with symplectite assemblages may exhibit a diffusion profile of cr going into olivine whereas olivine boundaries away from symplectites show no diffusion profile there is also a distinct lack of primary chromite as inclusions in cumulus phases and melt inclusions multiple textural observations melt inclusion chemistry and modeling of chromite olivine equilibrium rule out previously proposed symplectite formation mechanisms and strongly suggest that chromite was not a primary crystallization product of the 76535 parental magma accordingly the post cumulus addition of cr and fe is required to produce the symplectites after considering multiple models the addition of cr and fe to 76535 via infiltration metasomatism by an exogenous chromite saturated melt is the model most consistent with multiple textural and geochemical observations failure of models that call upon cr diffusion out of olivine grains imply that the observed cr depleted nature of olivine observed in many mg suite lithologies is a primary feature of the cr depleted nature of the mg suite parental magmas and their source materials this substantial depletion of cr in the magma relative to mare basalt magmas still requires a satisfactory explanation in order to be consistent with mg suite petrogenetic models and currently accepted bulk moon compositions additionally if the intimate interaction of migrating melts with early lunar crustal lithologies was a widespread phenomenon after lmo solidification it provides another mechanism by which to reset or delay closure of radiogenic isotopic systems and explain the mg suite ferroan anorthosite age overlap

implications of coral reef buildup for the controls on atmospheric co2 since the last glacial maximum we examine the effect on atmospheric co2 of the occurrence of increased shallow water carbonate deposition and regrowth of the terrestrial biosphere following the last glacial we find that contrary to recent speculations that changes in terrestrial carbon storage were primarily responsible for the observed similar to20 ppmv late holocene co2 rise a more likely explanation is coral reef buildup and other forms of shallow water carbonate deposition during this time the importance of a responsive terrestrial carbon reservoir may instead be as a negative feedback restricting the rate of co2 rise possible in the early stages of the deglacial transition this separation in time of the primary impacts of regrowth of the terrestrial biosphere and increased shallow water carbonate deposition explains the occurrence of an early holocene carbonate preservation event observed in deep sea sediments we demonstrate that their combined influence is also consistent with available proxy estimates of deep ocean carbonate ion concentration changes over the last 21 kyr accounting for the processes that act on the carbonate chemistry of the ocean as a whole then allows us to place strong constraints on the nature of the remaining processes that must be operating at the deglacial transition by subtracting the net co2 effect of coral reef buildup and terrestrial biosphere regrowth from recent high resolution ice core data we highlight two periods from 17 0 to 13 8 kyr and 12 3 to 11 2 kyr bp characterized by sustained rapid rates of co2 increase 12 ppmv kyr 1 because these periods are coincident with southern hemisphere deglaciation we argue that changes in the biogeochemical properties of the southern ocean surface are the most likely cause

delineation of macroporous zones in the unsaturated portion of the miami limestone using ground penetrating radar miami dade county florida summary the atlantic coastal ridge in dade county is an ooid shoal formed during the late pleistocene the ridge is composed of the eogenetic karst miami limestone characterized by a heterogeneous distribution of porosity that can manifest as large touching vug macroporous features with sizes in the meters and tens of meters direct evidence for the presence of such large dissolution features is only visible when exposed to the surface which may be problematic in urbanized areas for that reason it is critical to detect any potential precursors for such dissolution features at the subsurface level the purpose of this study was to investigate the ability of ground penetrating radar to detect areas of macroporosity by quantifying changes in electromagnetic wave velocity and relate them to changes in porosity after application of the complex refractive index model crim in order to constrain volumetric water content vwc in the crim an experiment using miami limestone samples was designed to understand 1 the range of typical vwcs and 2 the effect of capillary fringe on water table elevation the results show several areas where increases in em wave travel time associated with contrasts in porosity exceeding 40 cannot be explained by changes in vwcs typically shown in the miami limestone this study may help understand porosity variability in the unsaturated part of the miami limestone and if expanded to larger scales may aid groundwater flow models by better capturing distributions of macroporous areas that may contribute to direct recharge of the biscayne aquifer

new evidence for episodic post glacial sea level rise central great barrier reef australia abstract we present an extensive database of 364 radiocarbon dates from coastal and marine sediments of the central great barrier reef gbr shelf of which 110 are previously unpublished the elevation data have been reduced to a common datum australian height datum ahd and the various sources of error have been assessed using modern lithological and biological relationships with sea level the elements of the radiocarbon database have been converted into sea level indicators the upper bound of the assembled dataset corresponds to a best estimate sea level curve and the full dataset provides a narrow envelope for sea level rise on the gbr shelf for the last 11 12 kyr not including hydro isostatic crustal flexing the envelope is consistent with episodic rise in post glacial sea levels the rising post glacial sea level probably included stillstands or minor falls at ca 45 m ahd at ca 10 5 kyr b p 5 m 7 8 kyr b p 2 m ca 6 kyr b p and 1 7 m 5 5 kyr b p there is evidence for a significant fall in sea level between stillstands at 11 m 8 5 kyr b p and 17 m 8 2 kyr b p stillstand durations apparently ranged between the vertical spread in the derived sea level data is very wide the use of shell material for dating seems unreliable and prone to large and unpredictable errors data from bulk mangrove muds appear reliable for determination of ancient sea level but may at times result in sea level being placed up to 4 m below the true level in situ biogenic carbonates such as preserved oyster beds and coral micro atolls are the most reliable indicators of sea level position while deposits of mangrove mud give a useful first order approximation of ancient sea levels caution should be used in drawing sea level curves from few data points we conclude that the post 11 12 kyr b p relative rise in sea level was episodic on the central gbr continental margin more data are required to define clearly sea level change up to ca 20 m at 9 kyr b p

lunar mg suite thermobarometry and petrogenesis of parental magmas using compilations of internally consistent thermodynamic data on minerals and advances in quantifying the energetics of crystalline solid solutions we have recalculated the pressures and temperatures of equilibration of troctolite sample 76535 and a number of spinel cataclasites the five phase assemblage olivine orthopyroxene clinopyroxene cr spinel plagioclase which occurs in symplectite assemblages in 76535 gives equilibration temperatures from 800 900 c and pressures from 200 to 250 mpa indicating a deep 40 50 km crustal source spinel cataclasite assemblages give minimum pressures of 100 mpa mg suite magmas were apparently intruded throughout the lunar crust early in lunar history the textures and equilibration temperatures in many mg suite samples are consistent with sub solidus recrystallization and the mg rich minerals of some refractory troctolites and dunites may be residues of a crustal melting process or products of subsolidus elemental redistribution the sm nd age of 4 26 0 06 ga of troctolite 76535 most likely represents the time of sub solidus recrystallization and or partial melting in an attempt to identify the primary source material for the mg suite magmas a variety of models were tested using the melts and magfox codes a good fit between mineral compositions and crystallization sequences is obtained by 20 batch melting at 0 5 gpa of an average whole moon composition with an mg of 0 85 melts formed by batch melting at higher pressures and melts formed by poly baric partial fusion over the pressure range from 2 0 to 0 3 gpa were either too poor in mg and or crystallized clinopyroxene before orthopyroxene mixing with 10 20 urkreep which is required to satisfy the ree constraints of the mg suite reduces the mg of the parental magmas and requires a whole moon mg closer to that of the terrestrial mantle

significance of shallow core transects for reef models and sea level curves heron reef great barrier reef a sequence of shallow reef cores from heron reef great barrier reef provides new insights into holocene reef growth models isochron analysis of a leeward core transect suggests that the north western end of heron reef reached current sea level by ca 6 5 kyr bp and then prograded leeward at a rate of ca 19 6 m kyr between 5 1 kyr and 4 1 kyr bp pre 1950 to the present reef margin a single short core on the opposing margin of the reef is consistent with greater and more recent progradation there further to the east one windward core reached modern sea level by ca 6 3 kyr bp suggesting near keep up behaviour at that location but the opposing leeward margin behind the lagoon reached sea level much more recently hence heron reef exhibited significantly different reef growth behaviour on different parts of the same margin mean reef accretion rates calculated from within 20 m of one another in the leeward core transect varied between ca 2 9 m and 4 7 m kyr depending on relative position in the prograding wedge these cores serve as a warning regarding the use of isolated cores to inform reef growth rates because apparent aggradation at any given location on a reef varies depending on its location relative to a prograding margin only transects of closely spaced cores can document reef behaviour adequately so as to inform reef growth models and sea level curves the cores also emphasize potential problems in u series dates for corals within a shallow ca 1 5 m zone beneath the reef flat apparent age inversions restricted to that active diagenetic zone may reflect remobilization and concentration of th in irregularly distributed microbialites or biofilms that were missed during sample vetting importantly the th containing contaminant causes ages to appear too old rather than too young as would be expected from younger cement

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

evidence for metasomatism of the lunar highlands and the origin of whitlockite abstract the presence of rare earth element rich ree rich whitlockite in the relatively primitive ree poor lunar highlands presents a paragenetic problem to the petrologist comparison with occurrences in mare basalt mesostasis assemblages demonstrates that whitlockite in the lunar highlands has not resulted from the crystallization of the residual interstitial melt furthermore by the nature of ree partition coefficients for whitlockite it is demonstrated that they cannot have crystallized from kreepy melts rather we suggest that the only lunar melt which contains high enough ree abundances is the basic immiscible melt derived from a kreepy liquid we envisage that whitlockite found in the lunar highlands is a post cumulus metasomatic phase precipitated from a melt formed when urkreep underwent silicate liquid immiscibility the basic immiscible melt thus produced was able to percolate through the lunar highlands due to its low viscosity and act as a metasomatizing agent apatite is occasionally found as either epitactic overgrowths on the whitlockites mantled by whitlockite or in composite grains with whitlockite in all cases these apatites contain much lower ree contents than the corresponding whitlockite experimental results suggest either 1 1 apatite and whitlockite have essentially the same ree kd s 2 2 apatite has lower ree kd s than whitlockite both scenarios can be used to explain certain apatite whitlockite associations for example apatite and whitlockite having the same ree kd s can explain the situation where apatite appears to have crystallized after whitlockite this is because apatite crystallization requires a certain level of halogens in the melt these levels are only realized after whitlockite crystallization which enriches the residual melt in f and cl but depletes it in the rees therefore when apatite crystallizes it will contain lower ree abundances than whitlockite however relationships where apatite and whitlockite appear to have co crystallized or apatite crystallized before whitlockite require apatite to have lower ree kd s even if both experimental results are correct the whitlockite parental melt still requires ree abundances greater than in kreep urkreep the parental melt has similar ree abundances to a calculated reepy immiscible melt from kreep urkreep

modeled estimates of global reef habitat and carbonate production since the last glacial maximum estimated changes in reef area and caco3 production since the last glacial maximum lgm are presented for the first time based on a model reefhab which uses measured environmental data to predict global distribution of reef habitat suitable reef habitat is defined by temperature salinity nutrients and the depth attenuated level of photosynthetically available radiation par caco3 production is calculated as a function of par when minimum par levels were chosen to restrict reef growth to 30 m depth and less modern reef area totaled 584 746 10 km global carbonate production which takes into account topographic relief as a control on carbonate accumulation was 1 00 gt yr 1 these values are close to the most widely accepted estimates of reef area and carbonate production and demonstrate that basic environmental data can be used to define reef habitat and calcification to simulate reef habitat changes since the lgm the model was run at 1 kyr intervals using appropriate sea level and temperature values these runs show that at the lgm reef area was restricted to 20 of that today and carbonate production to 27 due primarily to a reduction in available space at the lower sea level and secondarily to lower sea surface temperatures nonetheless these values suggest that reef growth prior to shelf flooding was more extensive than previously thought a crude estimate of reef released co2 to the atmosphere since the lgm is of the same order of magnitude as the atmospheric co2 change recorded in the vostok ice core which emphasizes the role of neritic carbonates within the global carbon cycle this model currently addresses only the major physical and chemical controls on reef carbonate production but it provides a template for estimating shallow tropical carbonate production both in the present and in the past as such the model highlights several long standing issues regarding reef carbonates particularly in terms of better defining the roles of light temperature aragonite saturation state and topography on reef calcification

a concise compilation of petrologic information on possibly pristine nonmare moon rocks ansrn q cr to facilitate systematic study of the surviving compositionally pristine endogenously igneous rocks of the ancient lunar crust a compilation has been generated of all likely samples along with key information on the petrologic characteristics and chemistry of each sample the compilation includes 260 samples besides information related to the likelihood of each sample being truly pristine i e mainly its texture and siderophile element abundances information is compiled on mineral content listing major phases present as well as basic information on mineral compositions on size expressed as mass and on whether a reasonably comprehensive chemical analysis has been published the compilation also classifies the samples into seven categories of confidence in the pristine composition of the samples reflecting an estimation of the relative likelihood that each arguably pristine sample is in fact pristine for many purposes it is crucial to avoid inclusion of polymict rocks in a data base on petrologic diagrams such as a plot of average mg mg 100 x molar mg mg fe in a low ca mafic silicate vs average an content in plagioclase rocks in the top three categories of the confidence in pristine character appear distinctly bimodal in composition with roughly half belonging to a ferroan suite characterized by high an despite relatively low mg when samples of low to moderate pristine character are included the bimodality appears less distinct sample mass can also be important with a data base restricted to samples more massive than i g there is a clear distinction in feldspar content and bulk density between ferroan and nonferroan mgsuite rocks such that only the ferroan suite rocks are likely to have formed as flotation cumulates with a data base including smaller samples the same basic pattern is seen but only in a blurred form as the two rock types show considerable overlap in their modal feldspar contents

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

fabric selective diagenesis in the late pleistocene miami limestone abstract the miami limestone is a late pleistocene ooid sand body which has undergone 130 000 years of meteoric diagenesis the resultant limestone has a generally high but variable 15 60 porosity which is indirectly related to the amount of primary aragonite remaining in the limestone 0 45 the predominant textural theme in porosity development is the role of the primary sediment fabric which controls early cementation and porosity development on the scale of individual grains and sedimentary structures and is still influential during late development of channel and cavernous porosity the porosity development within the miami limestone reflects a change from an early system wherein fabric selective diagenesis occurred primarily as a function of the ability of the sediment to retain pore water to a system wherein the cemented sediments channelize water flow and effectively isolate portions of metastable aragonitic limestone from meteoric waters

effects of magnetite on high frequency ground penetrating radar large concentrations of magnetite in sedimentary deposits and soils with igneous parent material have been reported to affect geophysical sensor performance we have undertaken the first systematic experimental effort to understand the effects of magnetite for ground penetrating radar gpr characterization of the shallow subsurface laboratory experiments were conducted to study how homogeneous magnetite sand mixtures and magnetite concentrated in layers affect the propagation behavior velocity attenuation of high frequency gpr waves and the reflection characteristics of a buried target important observations were that magnetite had a strong effect on signal velocity and reflection at magnitudes comparable to what has been observed in small scale laboratory experiments that measured electromagnetic properties of magnetite silica mixtures magnetite also altered signal attenuation and affected the reflection characteristics of buried targets our results indicated important implications for several fields including land mine detection martian exploration engineering and moisture mapping using satellite remote sensing and radiometers

interplay of late cenozoic siliciclastic supply and carbonate response on the southeast florida platform abstract high resolution seismic reflection data collected along the length of the caloosahatchee river in southwestern florida have been correlated to nannofossil biostratigraphy and strontium isotope chemostratigraphy at six continuously cored boreholes these data are interpreted to show a major late miocene to early pliocene fluvial deltaic depositional system that prograded southward across the carbonate florida platform interrupting nearly continuous carbonate deposition since early in the cretaceous connection of the platform top to a continental source of siliciclastics and significant paleotopography combined to focus accumulation of an immense supply of siliciclastics on the southeastern part of the florida platform the remarkably thick 100 m sand rich depositional system which is characterized by clinoformal progradation filled in deep accommodation while antecedent paleotopography directed deltaic progradation southward within the middle of the present day florida peninsula the deltaic depositional system may have prograded about 200 km southward to the middle and upper florida keys where late miocene to pliocene siliciclastics form the foundation of the quaternary carbonate shelf and shelf margin of the florida keys these far traveled siliciclastic deposits filled accommodation on the southeastern part of the florida platform so that paleobathymetry was sufficiently shallow to allow quaternary recovery of carbonate sedimentation in the area of southern peninsular florida and the florida keys

evolution of biogenic gases in peat blocks inferred from noninvasive dielectric permittivity measurements 1 peatlands contain methanogenic archea responsible for generating significant amounts of free phase biogenic gases for example methane and carbon dioxide but considerable uncertainty still exists regarding the mechanisms of formation and spatial distribution of these gases within the soil matrix we demonstrate the effectiveness of a new method to record noninvasively the evolution spatial distribution and emission patterns of biogenic gases in a peat soil a peat block 0 022 m3 was extracted from a large freshwater peatland in maine the bulk dielectric permittivity at 1 2 ghz for multiple slices of the block was measured noninvasively 1 as temperature was increased 2 c d 1 from 5 c to 21 c and 2 for a subsequent 2 month period during which temperature was held constant at 21 1 c methane emissions at the surface and peat surface deformation were monitored concurrently using a portable methane detector and a grid of surface elevation rods respectively our results demonstrate that 1 the measurement of electromagnetic wave traveltimes across a peat block offers a unique and more accurate when compared to surface deformation measurements way to monitor gasdynamics and spatial gas distribution within a peat block without any disturbance to the natural gas regime 2 the ebullition under our experimental conditions seems to preferentially occur from the near surface peat and shows some correspondence with changes in atmospheric pressure and 3 the ebullition flux exhibits periodicity suggesting that it may be predictable and quantifiable which could assist climate modeling efforts our findings are consistent with previous studies based on gasdynamics in peat soils including gas volumes and fluxes associated with biogenic gas ebullition

petrogenesis of lunar troctolites models of petrogenesis for lunar troctolites are severely constrained by the high mg 88 values of the most primitive members of the mg rich suite melts derived by partial melting of olivine cumulates to the lunar magma ocean have high mg but are strongly undersaturated with respect to plagioclase assimilation of lunar crust cannot bring these melts to the plagioclase liquidus without unduly reducing the mg values of olivine partial melts derived by melting a iherzolite primitive interior have higher normative plagioclase contents but require sources with mg 90 more terrestrial like mg 88 values are permitted if rising thermal plumes are capable of entraining the most mg rich cumulates of the magma ocean the mg values of lunar troctolites may therefore reflect a hybrid source composed of primitive mantle and mg rich cumulates of the magma ocean higher mg values may also arise from the reduction of small amounts of feo to fe alternatively the parent magmas to lunar troctolites may be impact melts of the anorthositic crust and the mg rich dunite cumulates of the magma ocean the latter were brought to the upper mantle during the overturn of the unstable cumulate pile of the magma ocean

early diagenesis driven by widespread meteoric infiltration of a central european carbonate ramp a reinterpretation of the upper muschelkalk abstract meteoric diagenesis of carbonate ramps is often difficult to interpret and can commonly be confused with other coinciding diagenetic processes the middle triassic upper muschelkalk of switzerland provides an insightful case in which the effects of several overprinting diagenetic environments including matrix dolomitization can be clearly unravelled previous studies suggested that diagenesis took place in connate marine waters with later meteoric waters being invoked to explain recrystallization of dolomite in this study diagenetic analyses c o stable isotope ratios thin section point counting cathodoluminescence and uv fluorescence microscopy of calcitic bioclastic samples have revealed that early diagenesis pre stylolitization and the accompanying porosity evolution did not occur exclusively in the presence of marine fluids five sequential stages of diagenesis have been identified marine shallow burial mixing zone meteoric and dolomitization marine diagenesis induced precipitation of bladed and inclusion rich syntaxial cements that fluoresce strongly under uv light both cements account for a mean 7 5 vol reduction in the porosity of bioclastic beds shallow burial diagenesis likely induced mouldic porosity and associated fluorescent dog tooth cementation based on light oxygen isotope and elevated strontium isotope ratios matrix aragonite calcite neomorphism is interpreted to have occurred in a mixture of marine and meteoric fluids the combination of shallow burial and mixing zone processes reduced porosity on average by 4 8 vol evidence for subsequent meteoric diagenesis is found in abundant dog tooth and blocky calcite cements that have mean 18 o vpdb of 9 36 and no signs of recrystallization these meteoric cements reduced porosity by a further 13 4 vol percolation of meteoric water through the ramp was driven by hydraulic gradients on an adjacent basement high which was exposed by a cycle of early ladinian regressions following meteoric diagenesis the upper muschelkalk was dolomitized by refluxing brines this complex history of diagenesis resulted in moderate porosities in dolomitized rocks up to 20 and low porosities

permeable coral reef sediment dissolution driven by elevated pco2 and pore water advection 1 ocean acidification oa is expected to drive the transition of coral reef ecosystems from net calcium carbonate caco3 precipitating to net dissolving within the next century although permeable sediments represent the largest reservoir of caco3 in coral reefs the dissolution of shallow caco3 sands under future pco2 levels has not been measured under natural conditions in situ advective chamber incubations under elevated pco2 800 atm shifted the sediments from net precipitating to net dissolving pore water advection more than doubled dissolution rates 1 10 g caco3 m 2 d 1 when compared to diffusive conditions 0 42 g caco3 m 2 d 1 sediment dissolution could reduce net ecosystem calcification rates of the heron island lagoon by 8 within the next century which is equivalent to a 25 reduction in the global average calcification rate of coral lagoons the dissolution of caco3 sediments needs to be taken into account in order to address how oa will impact the net accretion of coral reefs under future predicted increases in co2

bathymetric expression of the fitzroy river palaeochannel northeast australia response of a major river to sea level change on a semi rimmed mixed siliciclastic carbonate shelf abstract palaeo river channels record the response of alluvial and estuarine depositional environments to sea level change and are also important geological indicators of former subaerial unconformities earlier studies have characterised lowstand palaeochannels on the central great barrier reef gbr shelf of northeastern australia reporting channel entrenchment shelf aggradation and topographic control of rivers by the outer shelf reef barrier we report the bathymetric expression of a palaeochannel corresponding to the last glacial lowstand path of the fitzroy river a high sediment yield river in the southern gbr during regression and lowstand the fitzroy river palaeochannel entrenched into the low gradient middle shelf and may have begun to incise the steeper outer shelf between the exposed reef platforms the wide spacing of outer shelf reefs and the continuous seabed slope may have enabled the palaeo fitzroy to maintain connection with the lowstand shoreline without becoming trapped behind shelf edge reefs the palaeochannel now forms a prominent depression across the middle and outer shelf evidently the sloping inter reefal seabed of the southern gbr coupled with tidal processes and wave exposure has limited shelf aggradation since the transgression this finding provides evidence that modern bathymetry can reflect palaeochannel location on the gbr shelf our results offer new insights into the evolution of the southern gbr shelf and show that no single existing model is able to adequately explain the behaviour of lowstand palaeochannels on rimmed siliciclastic carbonate shelves

heterogeneous distribution of h2o in the martian interior implications for the abundance of h2o in depleted and enriched mantle sources we conducted a petrologic study of apatite within 12 martian meteorites including 11 shergottites and one basaltic regolith breccia these data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the martian interior apatites in individual martian meteorites span a wide range of compositions indicating they did not form by equilibrium crystallization in fact the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a cl rich crustal component we determined that most martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the martian mantle using the subset of samples that did not exhibit crustal contamination we determined that the enriched shergottite source has 36 73 ppm h2o and the depleted source has 14 23 ppm h2o this result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle we also estimated the h2o cl and f content of the martian crust using known crust mantle distributions for incompatible lithophile elements we determined that the bulk martian crust has 1410 ppm h2o 450 ppm cl and 106 ppm f and cl and h2o are preferentially distributed toward the martian surface the estimate of crustal h2o results in a global equivalent surface layer gel of 229 m which can account for at least some of the surface features on mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on mars surface

porosity of the miami limestone late pleistocene lower florida keys abstract this study investigates the amount and variability of porosity in the approximately 130 000 year old politic grainstones of the miami limestone in the lower florida keys porosity is derived from porosimeter measurements of 326 plugs and core pieces representing 11 locations spanning about 65 km because larger voids in our samples result primarily from scouring by circulating water used in coring and plugging measurements of matrix porosity rather than of bulk porosity represent the formation better in situ x ray diffraction analyses show that the rocks have undergone substantial inversion of aragonite to calcite mean aragonite content of the matrix is 40 percent but are not yet approaching mineralogical stabilization porosity of these partially stabilized rocks averages 36 percent a decrease of 5 10 percent from that of the initial sediments a qualitative interpretation suggests that the reduction in pore volume correlates with the degree of inversion of aragonite to calcite and that the porosity decrease associated with complete mineralogical stabilization could be on the order of 15 20 percent porosity is narrowly distributed the standard deviation of porosity for the entire data set is only 4 percent and much of this variability is on the relatively small scale of primary sedimentary fabric although the pre burial near surface meteoric environment may set the stage for subsequent porosity evolution results imply that significant porosity loss and porosity diversity in similar but much older rocks develop during burial diagenesis

holocene sediments of wistari reef towards a global quantification of coral reef related neritic sedimentation in the holocene wistari reef within the southern great barrier reef is a shallow coral reef platform featuring a very clearly defined leeward accretionary wedge of carbonate sediments the total global area of shallowly submerged coral reef has been quantified as 255 000 km 2 the question then becomes what additional area of sediment of significant thickness is associated with the measured shallow reef areas t at wistari reef the leeward sedimentary wedge has an area and a thickness that are roughly equal to the holocene sediments that have accumulated on the platform several important observations can be made from these data firstly the area of significant neritic carbonate sedimentation 1 m ka associated with coral reefs is near 500000 km 2 secondly the production rate of neritic carbonates at wistari reef is almost 50 less than the accumulation rate needed to obtain the volume of holocene reef sediments observed this implies that both production and accumulation neritic carbonate must have been more than a factor of two higher in the early to mid holocene c 2001 elsevier science b v all rights reserved

the chlorine isotopic composition of the moon insights from melt inclusions abstract the moon exhibits a heavier chlorine cl isotopic composition compared to the earth several hypotheses have been put forward to explain this difference based mostly on analyses of apatite in lunar samples complemented by bulk rock data the earliest hypothesis argued for cl isotope fractionation during the degassing of anhydrous basaltic magmas on the moon subsequently other hypotheses emerged linking cl isotope fractionation on the moon with the degassing during the crystallization of the lunar magma ocean lmo currently a variant of the lmo degassing model involving mixing between two end member components defined by early formed cumulates from which mare magmas were subsequently derived and a kreep component which formed towards the end of the lmo crystallization seems to reconcile some existing cl isotope data on lunar samples to further ascertain the history of cl in the moon and to investigate any evolution of cl during magma crystallization and emplacement events which could help resolve the chlorine isotopic variation between the earth and the moon we analysed the cl abundance and its isotopic composition in 36 olivine and pyroxene hosted melt inclusions mi in five apollo basalts 10020 12004 12040 14072 and 15016 olivine hosted mi have an average of 3 3 1 4 ppm cl higher cl abundances 11 9 ppm on average are measured for pyroxene hosted mi consistent with their formation at later stages in the crystallization of their parental melt compared to olivines chlorine isotopic composition 37 cl of mi in the five apollo basalts have weighted averages of 12 8 2 4 and 10 1 3 2 for olivine and pyroxene hosted mi respectively which are statistically indistinguishable these isotopic compositions are also similar to those measured in apatite in these lunar basalts with the exception of sample 14072 which is known to have a distinct petrogenetic history compared to other mare basalts based on our dataset we conclude that post mi entrapment no significant cl isotopic fractionation occurred during the crystallization and subsequent eruption of the parent magma and that cl isotopic composition of mi and apatite primarily reflect the signature of the source region of these lunar basalts our findings are compatible with the hypothesis that in the majority of the cases the heavy cl isotopic signature of the moon was acquired during the earliest stages of lmo evolution interestingly mi data from 14072 suggests that apollo 14 lunar basalts might be an exception and may have experienced post crystallization processes possibly metasomatism resulting in additional cl isotopic fractionation recorded by apatite but not melt inclusions

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

distinct chlorine isotopic reservoirs on mars implications for character extent and relative timing of crustal interactions with mantle derived magmas evolution of the martian atmosphere and the building blocks of an early mars the style magnitude timing and mixing components involved in the interaction between mantle derived martian magmas and martian crust have long been a point of debate understanding this process is fundamental to deciphering the composition of the martian crust and its interaction with the atmosphere the compositional diversity and oxygen fugacity variations in the martian mantle the bulk composition of mars and the materials from which it accreted and the noble gas composition of mars and the sun recent studies of the chlorine isotopic composition of martian meteorites imply that although the variation in delta sup 37 cl is limited total range of approximately14 per mille there appears to be distinct signatures for the martian crust and mantle however there are potential issues with this interpretation new cl isotope data from the sam sample analysis at mars instrument on the mars science lab indicate a very wide range of cl isotopic compositions on the martian surface recent measurements by 10 duplicated the results of 7 8 but placed them within the context of sam surface data in addition martian meteorite chassigny contains trapped noble gases with isotopic ratios similar to solar abundance and has long been considered a pristine mantle derived sample however previous studies of apatite in chassigny indicate that crustal fluids have interacted with regions interstitial to the cumulus olivine the initial cl isotope measurements of apatite in chassigny suggest an addition of crustal component to this lithology apparently contradicting the rare gas data here we examine the cl isotopic composition of multiple generations and textures of apatite in chassigny to extricate the crustal and mantle components in this meteorite and to reveal the style and timing of the addition of crustal components to mantle derived magmas these data reveal distinct martian cl sources whose signatures have their origins linked to both the early solar system and the evolving martian atmosphere

increase of atmospheric co2 during deglaciation constraints on the coral reef hypothesis from patterns of deposition 1 the coral reef hypothesis asserts that carbonate production on newly flooded shelves contributes importantly to the rise of atmospheric carbon dioxide during deglaciation we seek to constrain the timing and strength of such carbon dioxide flux by re assessing reef and platform distribution in the world ocean the pattern of reef growth that emerges suggests that emission of co 2 resulting from carbonate production was important particularly during the late stages of deglaciation the effect peaked during the early holocene and presumably contributed to the warming in the climatic optimum

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold