bryozoans as carbonate sediment producers on the cool water lacepede shelf southern australia abstract modern sediments on the lacepede shelf and adjacent slope are typical mid latitude cool water palimpsest deposits dominated by bryozoan mollusc and quartz particles bryozoan bioclasts form autochthonous and to a lesser extent allochthonous accumulations across the grain size spectrum from mud to boulder size the bryozoan skeletons are grouped on the basis of architecture and style of disarticulation fragmentation into nine morphotypes erect rigid forms comprise 1 fenestrate 2 foliose 3 flat robust branching and 4 delicate branching morphotypes large adeona sp skeletons are recognised as a separate type of fenestrate form because of their distinctive shape mineralogy and restricted environment erect flexible forms are either 5 articulated branching or 6 articulated zooidal other important morphotypes are 7 encrusting 8 nodular arborescent and 9 vagrant differences in skeletal architecture result in distinct particle types encrusting morphotypes on soft organic substrates and the wide variety of erect rigid forms are broken into fragments erect flexible forms disintegrate upon death into definitive sand and silt size grains encrusting morphotypes on hard substrates nodular arborescent and vagrant forms remain whole and when large accumulate in place morphotypes are mineralogically distinct and so bryozoan sediment composition is environmentally controlled shallow water

paleolatitude distribution of phanerozoic marine ooids and cements opdyke b n and wilkinson b h 1990 paleolatitude distribution of phanerozoic marine ooids and cements palaeogeogr palaeoclimatol palaeoecol 78 135 148 data on 493 phanerozoic marine ooid and cement occurrences indicate that the dominance of calcite versus aragonite in tropical marine settings has changed in response to variation in atmospheric co2 and or oceanic temperature gradient holocene ooid and cement precipitation occurs over similar latitudes with means centered around 24 and 28 respectively aragonite and calcite also display roughly comparable distributions with average occurrences between 25 and 28 surface seawater saturation values requisite for ooid cement carbonate precipitation are at least 3 8 rs for aragonite and 3 4 a s for calcite ancient ooid cement occurrences vary in space and time with depositional zones generally closer to the equator during continental emergence greatest extent correlates with periods of maximum transgression aragonite formation is favored in more equatorial localities than calcite when cement ooid distributions are narrow and continents are emergent similarity of latitude distribution of marine ooids cement and biogenic carbonate suggests that physicochemical processes that control levels of carbonate saturation were more important in predicating sites of limestone accumulation in phanerozoic seas than biological processes related to net productivity of various carbonate platform communities continental position and tropical shelf area available for carbonate accumulation dictates the relative abundance of shallow water inorganic carbonate precipitates in space and time

meteoric like fabrics forming in marine waters implications for the use of petrography to identify diagenetic environments petrographic fabrics have long been used to identify meteoric diagenesis of carbonate sediments however on the basis of oxygen isotopic data we document similar fabrics forming in marine pore fluids in the shallow subsurface of great bahama bank therefore petrographic fabrics alone are not reliable indicators of diagenetic environments even for shallow water sediments in our study skeletal grainstones show two distinct diagenetic assemblages either dissolution of aragonitic grains and minimal cementation high permeability intervals or abundant blocky spar cement and neomorphism of aragonitic skeletal grains low permeability intervals these marine burial fabrics are present as shallow as 110 m below sea level well above the aragonite compensation depth a feature that must be considered for models of diagenesis in ancient carbonate sediments marine burial diagenesis may be important in ancient carbonate sediments deposited in moderate water depths or in shallow water during rising sea level where meteoric diagenesis is suppressed

shallow water transmission loss prediction using the biot sediment model experimental data and predicted propagation loss from three shallow water test sites with highly varied sediments are compared for frequencies from 25 to 800 hz the predicted loss was obtained using normal mode and adiabatic normal mode models with the sediment absorption calculated using the theory of biot the theory predicted a linear variation of absorption with frequency for a site off corpus christi texas having a mud bottom the mean grain size was 6 37 phi the absorption was predicted to vary as frequency raised to the 1 76 power for a site off daytona beach florida having a medium to coarse sand bottom the mean grain size was 0 85 phi range independent propagation was assumed for the sites just noted and the agreement between measured and predicted loss was good for frequencies from 100 to 600 hz range dependent conditions existed for the third site off the coast of nova scotia where the sound speed profile bottom sediments and depth varied with range good agreement was obtained be

missing aragonitic biota and the diagenetic evolution of heterozoan carbonates a case study from the oligo miocene of the central mediterranean abstract several previous studies have addressed the diagenetic evolution of heterozoan carbonate assemblages generally it is assumed that early diagenetic processes in heterozoan settings are mainly destructive including abrasion and dissolution on the sea floor constructive diagenesis cementation is delayed to later stages in the burial environment with pressure solution of calcitic grains acting as a cement source this paper presents a study of oligo miocene inner to outer ramp heterozoan carbonates from the central mediterranean maltese islands and sicily indicating that early diagenetic processes are more important than previously assumed four to five different cement types including fibrous two types of epitaxial bladed and blocky cement are distinguished based on transmitted light microscopy cathodoluminescence microscopy allowed a differentiation between primary high mg calcitic fibrous and epitaxial cement i and primary low mg calcitic epitaxial cement ii bladed and blocky cements stable isotope data indicate cement precipitation from marine marine derived and meteoric waters trace element analyses point to cementation in an open system maltese islands and a closed system sicily our investigations show that the majority of constructive diagenetic processes in these rocks occurs rather early in the shallow marine burial environment which is transitional between the marine seafloor and the deep burial diagenetic environment the main cement source in this environment is assumed to be aragonite we suggest careful consideration of the importance of aragonitic components in fossil heterozoan settings which seem to be more abundant than previously assumed and can act as a major early cement source due to the low preservation potential of these components detailed geochemical studies are necessary to detect aragonite as the cement source our findings also have implications when considering the reservoir qualities of these rocks because primary porosity can be occluded early and secondary porosity is not preserved

radar imaging mechanism of the seabed results of the c star experiment in 1996 with special emphasis on the relaxation rate of short waves due to current variations abstract during the field experiment of the coastal sediment transport assessment using sar imagery project of the marine science and technology program of the european commission an air sea interaction drift buoy asib system was equipped with special sensors and instruments to measure the position the water depth the surface current velocity and direction the modulation characteristics of short wave energies and relevant air sea interaction parameters due to undulations in the seabed the asib system was operated from on board a research vessel and the data were measured while the buoy drifted in the tidal currents across sand waves of the study area all buoy measurements were analyzed by computing frequency spectra of low and high frequency waves scalar spectra between 0 1 and 50 hz the whole range of short water waves was recorded by these in situ measurements on board the buoy which is responsible for the backscattering of commonly used air and spaceborne imaging radars a comprehensive da

marine cements in mid tertiary cool water shelf limestones of new zealand and southern australia large areas of southern australia and new zealand are covered by mid tertiary limestones formed in cool water shelf environments the generally destructive character of sea floor diagenesis in such settings precludes ubiquitous inorganic precipitation of carbonates yet these limestones include occasional units with marine cements 1 within rare in situ biomounds 2 within some stacked cross bedded sand bodies 3 at the top of metre scale subtidal carbonate cycles and 4 most commonly associated with certain unconformities the marine cements are dominated by isopachous rinds of fibrous to bladed spar interstitial homogeneous micrite and interstitial micropeloidal micrite often precipitated sequentially in that order internal sedimentation of microbioclastic micrite may occur at any stage the paradox of marine cemented limestone units in an overall destructive cool water diagenetic regime may be explained by the precipitation of cement as intermediate mg calcite from marine waters undersaturated with respect to aragonite in some of the marine cemented limestones aragonite biomoulds may include marine cement sediment internally suggesting that dissolution of aragonite can at times be wholly marine and not always involve meteoric influences we suggest that marine cementation occurred preferentially but not exclusively during periods of relatively lowered sea level probably glacio eustatically driven in the mid tertiary at times of reduced sea level there was a relative increase in both the temperature and the carbonate saturation state of the shelf waters and the locus of carbonate sedimentation shifted towards formerly deeper shelf sites which now experienced increased swell wave and or tidal energy levels fostering sediment abrasion and reworking reduced sedimentation rates and freer exchange of sediment pore waters energy levels were probably also enhanced by increased upwelling of cold deep waters onto the southern ocean margins of the australasian carbonate platforms where water mass mixing warming and loss of co2 locally maintained critical levels of carbonate saturation for sea floor cement precipitation and promoted the phosphate glauconite mineralization associated with some of the marine cemented limestone units

triassic latemar cycle tops subaerial exposure of platform carbonates under tropical arid climate the triassic latemar platform in the dolomites italy is the site of several ongoing controversies perhaps the most interesting debate focuses on apparent cyclic deposition within the latemar platform whose nature and duration are still open to debate further disagreement concerns the lack of meteoric diagenesis related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence here an evaluation of the nature of latemar cycle tops is presented combining evidence from previous work and new field petrographic and geochemical data cycle tops are ranked according to increasing exposure duration and spatial extent type i surfaces lacking unequivocal evidence of prolonged supratidal conditions type ii dolomite caps formed in warm evaporitic intertidal lagoonal waters followed by exposure of perhaps intermediate duration type iii clastic rich red calcareous horizons with some showing platform wide extent representing prolonged supratidal conditions and type iv discontinuities in tepee belts genetically related to type ii and iii surfaces but likely representing shorter lived exposure stages petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking this is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that where present are here interpreted as marine vadose in origin the scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid triassic climate the low latitude tropical but arid setting of the latemar situated in the western extension of the tethys ocean its isolation from nearby continental areas and overall short term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops high amounts of aeolian clastic material beneath some cycle tops along with high fe and mn elemental abundances argue for intermittent subaerial conditions this study proposes an enhancement of the classical allan and matthews 1982 isotope model for subaerial exposure under strongly arid climates as the subaerial exposure nature of latemar cycle tops and therefore eustasy as the cause for cyclicity have been previously challenged due to the lack of meteoric induced isotopic signatures the outcome of this study is of significance for the ongoing latemar stratigraphic controversy

the distribution and palaeoenvironment of early miocene phosphorites of southeast sicily and their relationships with the maltese phosphorites abstract several phosphatic limestone localites occur within the irminio member ragusa formation of the western hyblean of southeast sicily in areas of maximum development such as around sampieri and modica the phosphatized intraslcast dominated deposits attain a thickness of up to 0 6m and are associated with a phosphatized underlying hardground thin and possibly discontinous spreads of phosphatized intraclast form a broader zone beyond the central semi autochthonous zone microfossil analysis of associated strata demonstrates that all occurences of phosphatized strata within the irminio member are restricted to a single level of probable late burdigalian early miocene age the bed correlates well both biostratigraphically and lithologically with the upper main phosphorite conglomerate bed of the maltese islands which lie c 95 km south of the sicilian province five more distinct phosphorite beds occur in the maltese islands being best developed in the western and northern parts of the islands they range in age from aquitanian to late burdigalian these are principally francolite replaced micrate conglomerates which may be associated with phosphatized underlying hardgrounds in places a major central mediterranean phosphatogenic province of early miocene age is postulated inorder to account for the simultaneous occurrence of phosphorites in sicily and malta

subtidal carbonate cycles implications for allocyclic vs autocyclic controls thick successions of repetitive metre scale subtidal carbonate cycles require that short term sedimentation rates approximate long term accumulation rates in order to maintain submergence below peritidal depths intrinsic processes such as storm and wave reworking and redistribution may act to inhibit aggradation into the zone of optimal carbonate production the presence of subtidal vs peritidal carbonate cycles may be a function of energy regime that in turn may relate to platform morphology the ultimate control on stacked subtidal cycles appears to be eustasy acting in concert with intrinsic processes such as storm and wave reworking

diagenetic comparisons between non tropical cenozoic limestones of new zealand and tropical mississippian limestones from indiana usa is the non tropical model better than the tropical model abstract mississippian limestones exposed in indiana u s a were deposited in a shallow tropical ocean however many properties of these limestones are more like those of modern and cenozoic non tropical limestones such as those found in new zealand the dominant skeletal grains in the indiana limestones are calcitic echinoderms bryozoans and brachiopods the dominant skeletal grains in most cenozoic limestones of new zealand are calcitic bryozoans echinoderms bivalve molluscs and foraminifera in contrast modern and cenozoic tropical limestones contain an abundance of aragonitic green algae corals and molluscs early in diagenesis the metastable aragonite dissolves and reprecipitates as calcite causing early cementation of the sediments originally aragonitic fossils that have dissolved can be identified as molds that are commonly filled with secondary calcite because they contained little aragonite most of the indiana and new zealand limestones did not have an abundant source of early cement except for local cases in which grains were cemented in contact with carbonate supersaturated seawater grainstones were relatively deeply buried with little cement between the grains this resulted in mechanical and chemical compaction of skeletal grains producing a fitted fabric with greatly reduced pore space either open or filled with cement between the grains cement in these aragonite poor grainstones comes largely from pressure dissolution between grains and along stylolitic seams in the rock features that are common only after burial beyond a few hundred meters the final product of deeply buried up to 2000 m cenozoic new zealand grainstones is similar to the mississippian grainstones of indiana in the indiana limestones we have only the final product of this extensive burial diagenesis however the new zealand sediments and rocks reveal all steps of formation of the final deeply buried limestone the reason for the scarcity of originally aragonitic fossil grains in paleozoic rocks worldwide is unknown organisms with aragonitic skeletons such as some molluscan groups and calcareous green algae were present but seldom in much abundance the aragonitic scleractinian corals had not yet evolved previous researchers have noted that non skeletal precipitates such as ooids and cements have at times during the paleozoic been predominantly aragonite and at other times calcite they have attributed this difference to secular variation in seawater chemistry icehouse vs greenhouse seas abundance of aragonitic and calcitic skeletal grains does not follow this pattern

stratigraphy and sedimentology of phosphate rich sediments in malta and south eastern sicily latest oligocene to early late miocene the maltese archipelago and south eastern sicily include an uppermost oligocene to upper miocene hemipelagic sedimentary succession representing the malta hyblean plateau which limits the eastern mediterranean to the west this succession hosts a unique and well exposed series of condensed and allochthonous phosphate rich beds which were formed in a sedimentary regime of erosion sediment reworking and frequent gravity flow deposition the combination of nannofossil biostratigraphy and 87sr 86sr isotope stratigraphy allows for the precise attribution of ages to the phosphate deposits and for the distinction of three periods of major phosphogenesis the first phase occurred between 24 5 and 21 ma and 25 and 18 9 ma clustering of ages between 25 and 22 5 ma on malta and sicily respectively the second and third phases of phosphogenesis are documented from the maltese islands and are dated as 17 2 to 13 1 ma and 10 9 to 9 8 ma respectively the phosphate rich beds are associated with hiatuses and phases of important condensation which for the oldest phosphogenic period envelop the time period of 23 2 to 22 ma for the fomm ir rhi bay section malta and from 19 1 to 16 3 ma for the sections of sampieri and modica sicily for the second phase of phosphogenesis on the maltese islands a consistent hiatus was found which embraces the time period of approximately 17 to 15 ma also the third phase of phosphogenesis appears to be associated with a major hiatus which probably envelops the time period between 12 5 and 10 9 ma but a better age control is needed here the correspondence in timing of the maltese sicilian phases of phosphogenesis with major phases of phosphogenesis outside the mediterranean realm to maxima in oceanic phosphorus burial rates and maxima in the 13c benthic foraminiferal record suggests that the palaeoceanographic evolution of the eastern mediterranean was well in phase with that of other ocean basins until at least the early late miocene despite its increasing isolation due to the gradual closure of the eurasian arabian strait and progressive sea level fall

burial dominated cementation in non tropical carbonates of the oligocene te kuiti group new zealand abstract cementation of bryozoan echinoid benthic foraminiferal temperate shelf carbonates of the oligocene te kuiti group north island new zealand occurred mainly during subsurface burial the calcite cements in the limestones are dominated by equant and syntaxial rim spar which typically becomes ferroan given an iron supply and compared to the skeletal material with normal marine 18o values from 2 to 1 more depleted in 18o with depth of burial the 18o composition of bulk cement samples ranging from 1 to 7 these trends reflect the establishment in pore waters during sediment burial of reducing conditions and gradually increasing temperatures 20 50 c respectively the 13c values 0 to 3 of the cements remain the same as the host marine shells suggesting the source of carbon in the cements was simply redistributed marine carbonate derived from shell dissolution two gradational burial diagenetic environments influenced by marine derived porewaters are arbitrarily distinguished shallow burial phase and moderate burial phase during the shallow burial phase down to 500 600 m sub bottom depth the carbonates lost at least 25 of their original porosity by mechanical compaction and were selectively cemented by non ferroan or usually ferroan variably luminescent slightly 18o depleted sparry calcite cement 18o 2 to 4 mainly as syntaxial rims about echinoid grains these shallow burial cements form less than about 10 of total cement in the majority of the limestones and their source was probably mainly mild intergranular dissolution of calcitic skeletal fragments accompanying the onset of chemical compaction during the moderate burial phase between about 600 and 1100 m sub bottom depth porosity loss continued typically to about 70 of its original value as a result of pressure solution of calcitic bioclasts associated with more advanced stages of chemical compaction this involved development of a wide variety of non sutured and microstylolitic solution seams including both single and composite wispy or continuous bedding parallel types and non parallel reticulate forms the released carbonate was precipitated as ferroan or non ferroan where iron supply was negligible dull luminescent strongly 18o depleted 18o 4 to 7 mainly equant calcite spar cement occluding available pore space in the limestones

mixed carbonate siliciclastic record on the north african margin malta coupling of weathering processes and mid miocene climate we investigated rock outcrops spanning the middle miocene global climate cooling step on the maltese islands in order to reconstruct continental weathering rates and terrigenous fluxes as well as to explore the coupling between these later regional climate and carbonate accumulations sedimentation at this location was dominated during the oligocene and early miocene by a transitional platform to slope carbonates but progressively switched to a clay rich carbonate slope system in the middle miocene around 13 ma an abrupt change toward clay dominated marls occurred and marl deposition persisted until the tortonian ca 12 ma when a shallow water carbonate ramp was reestablished clay mineralogy and bulk rock oxygen isotope analyses suggest that the deposition of the blue clay formation was mainly caused by global climate change and related change in the rate of continental weathering a significant negative correlation r 2 0 65 exists between the carbonate content and the 1 8 o record this combined with the variation of mass accumulation rate of terrigenous material suggests that shorter term periods of globally cooler climate mi events were associated with higher rates of accumulation in continental derived material since during the miocene malta was attached to the north african margin we propose that the observed trends were due to a regional increase in rainfall during cooler periods which consequently increased continental weathering and runoff we further suggest that this pattern was linked to the perturbation of atmospheric fronts due to an increased thermal gradient during the miocene thus regional increase in rainfall might have been linked to the northward migration of the intertropical convergence zone itcz

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

deep water bathymetric features imaged by spaceborne sar in the gulf stream region current 2 ms 1 and favorable ocean stratification sar image analysis shows the basic characteristics of these bathymetric features a coincident sea surface temperature image shows that the bathymetric feature is only visible by sar within the gs pathway the dominant wavelength of the wave like feature is about 2 3 km and their crests are perpendicular to the gs axis shipboard sounding measurements confirm the sar observation a theoretical consideration of the ocean current and corrugated bathymetry interaction in a 3 layer ocean is presented using representative ocean density profile data and the gs current data we analyze the requirements for the generation and upward propagation of the disturbance induced by the current bathymetry interaction citation li x x yang q zheng l j pietrafesa w g pichel z li and x li 2010 deep water bathymetric features imaged by spaceborne sar in the gulf stream region geophys res lett 37 l19603

the complex diagenetic history of discontinuities in shallow marine carbonate rocks new insights from high resolution ion microprobe investigation of δ18o and δ13c of early cements sedimentary gaps are a major obstacle in the reconstruction of a carbonate platform s history in order to improve the understanding of the early diagenesis and the succession of events occurring during the formation of discontinuity surfaces in limestones secondary ion mass spectrometry was used for the first time to measure the 18o and 13c signatures of 12 early cement and fabric stages in several discontinuity surfaces from the jurassic carbonate platform of the paris basin pendant cements show a high variability in 18o which was impossible to detect by the less precise microdrilling method the morphology of a given cement can be produced in various environments and dogtooth cements especially can precipitate in marine phreatic and meteoric phreatic to vadose environments marine dogtooth cements and micritic microbially induced fabrics precipitated directly as low magnesium calcite in marine waters as attested by the preservation of their initial 18o and 13c signals five discontinuity types are recognized based on high resolution geochemical analyses and their palaeoenvironmental history can be reconstructed two exposure surfaces with non ferroan pendant or meniscus cements formed in the oxidizing vadose zone a hardground displays marine fibrous cements and non ferroan dogtooth cements that formed in a subtidal environment in oxidizing water two composite surfaces have undergone both marine and subaerial lithification composite surface 1 displays non luminescent ferroan dogtooth cements that precipitated in reduced conditions in seawater followed by brown luminescent dogtooth cements characteristic of a meteoric phreatic environment composite surface 2 exhibits microbially induced fabrics that formed in marine water with abundant organic matter the latter discontinuity initially formed in a subtidal environment was subsequently exposed to meteoric conditions as evidenced by ferroan geopetal cements a high resolution ion microprobe study is essential to precisely document the successive diagenetic environments that have affected carbonate rocks and discontinuities with a polygenic and intricate history this article is protected by copyright all rights reserved

early diagenesis of carbonates on a cool water carbonate shelf southern australia abstract the southern australian continental margin is an immense cool water carbonate factory the high energy open shelf is blanketed by heterozoan carbonates of both holocene and late pleistocene age three distinct grain types have been identified and radiocarbon dated these include 1 relict grains highly abraded iron stained intraclasts formed during the intermediate sea level stands of marine isotope stages 3 and 4 2 stranded grains gray and buff colored abraded biofragments and intraclasts marooned during the sea level rise associated with marine isotope stage 2 and 3 holocene grains unaltered biofragments formed during marine isotope stage 1 optical mineralogical and chemical characterization of grains of each age has revealed pathways of early diagenesis in this realm both calcitic and aragonite biogenic grains undergo dissolution while dissolution of calcitic components is minor and incomplete relict sediments are predominantly mg calcite aragonitic skeletons undergo significant dissolution within 30 000 years in contrast to early dissolution of aragonite micritic calcite cement with 12 mol mgco3 is a significant diagenetic phase in these sediments infilling many stranded and most relict skeletons similar cement precipitates between grains forming small numbers of cemented grain aggregates in most samples microprobe and icp ms analysis demonstrates fe oxides mn oxides and associated clay minerals discolor stranded and relict grains by coating grain surfaces and infesting micropores such coatings begin to form on holocene grains during or soon after formation the oxides scavenge trace elements including v ti cr and ree altering the elemental compositions of biogenic carbonate

controls of facies and sediment composition on the diagenetic pathway of shallow water heterozoan carbonates the oligocene of the maltese islands relatively few studies have so far addressed diagenetic processes in heterozoan carbonates and the role that sediment composition and depositional facies exert over diagenetic pathways this paper presents a study of oligocene shallow water heterozoan carbonates from the maltese islands we investigate stratigraphic distribution abundance and timing of diagenetic features and their relationship to sediment composition and depositional facies the studied carbonate rocks comprise rud to packstones of the heterozoan association predominantly containing coralline red algae bryozoans echinoids and benthic foraminifers xrd analyses show that all high mg calcite has been transformed to low mg calcite and that no aragonite is preserved diagenetic processes include dissolution of aragonitic biota neomorphism of high mg calcitic biota to low mg calcite and cementation by fibrous bladed epitaxial and blocky cements stable isotopes on bulk rock integrated with petrographic data suggest that the study interval was not exposed to significant meteoric diagenesis we interpret early cementation to have taken place in the marine and marine burial environment the distribution and abundance of early diagenetic features determining the diagenetic pathway can be related to the primary sediment composition and depositional texture sorting and micrite content are important controls over the abundance of diagenetic features

submarine cementation and subaerial exposure in oligo miocene temperate carbonates torquay basin australia abstract at least four hardgrounds are present throughout the 27 m thick exposed oligo miocene cool water point addis limestone of the torquay basin in southeastern australia they range from thin a few centimeters thick incipient layers that have a nodular fabric to thick up to 1 m thick continuous hardgrounds the hardgrounds tend to be at the top of coarsening upward cycles and are typically overlain by low relief erosion surfaces the uppermost hardground is the best developed and most widespread in the point addis limestone and can be observed in all exposures of the succession at some localities it shows evidence of karstification such as dissolution pits clints and grikes and dissolution pinnacles whether karstified or not well developed hardgrounds are overlain by a lag c nglomerate that consists of hardground intraclasts with marine fe oxide crusts the hardgrounds are cemented by a first generation isopachous inclusion rich columnar and fibrous radiaxial calcite of marine origin with trace element compositions mg2 0 68 1 74 mole mgco3 fe2 800 4690 ppm sr2 0 260 ppm mn2 0 230 ppm and cathodoluminescence dull blotchy indicative of stabilized mg calcite the isopachous cements are invariably overlain by homogeneous peloidal or microbioclastic micrite having trace element compositions mg2 0 77 1 54 mole mgco3 fe2 760 10 030 ppm sr2 0 240 ppm mn2 60 340 ppm and cathodoluminescence dull blotchy again indicative of stabilized mg calcite this micrite is always closely associated wi h the isopachous cements and appears to be of marine origin perhaps being analogous to the micritic precipitates described from reefal settings clear calcite is the last cement generation in the hardgrounds and has attributes of meteoric cements nonluminescent mg2 0 12 0 87 mole mgco3 fe2 0 230 ppm sr2 and mn2 below detection limits the whole rock stable isotope compositions of the hardgrounds and host limestone indicate that the whole unit has been subjected to pervasive alteration by meteoric fluids the least altered carbonates analyzed from the point addis limestone are brachiopods d13c 1 5 to 2 2 pdb d18o 1 7 to 0 9 pdb and the unkarstified hardgrounds d13c 3 8 to 1 0 pdb d18o 0 6 to 0 6 pdb these hardground occurrences help promote the validity of a unique sea level driven model for the formation of hardgrounds in cool water settings we propose that the development of these hardgrounds was an entirely marine process produced by relative sea level drop and entry of the sea floor into the zone of wave reworking marine cementation may begin in the form of nodules at and below the seawater sediment interface and involves both slow sedimentation and shallowing of the cool waters the nodules can later merge to form continuous hardgrounds in such a high energy environment nondeposition and erosion are the dominant processes and marine cementation can occur further sea level drop would lead to subaerial exposure of the previously formed hardgrounds as found in one inst nce in the point addis limestone at coastal exposures

application of bryozoan zoarial growth form studies in facies analysis of non tropical carbonate deposits in new zealand abstract the fragmental remains of bryozoan colonies are the dominant skeletal contributor in many modern and ancient occurrences of non tropical shelf carbonate deposits the taxonomic complexity of the bryozoa the difficulties of systematic classification except by specialists the wide range of particle sizes and of preservation state in the carbonate deposits and the often well cemented nature of host limestones all limit the sedimentological interpretation of the commonly diverse bryozoan component however following the pioneer work of stach in the 1930 s the potential exists for sedimentologists to obtain useful paleo environmental information about the deposits by recording simply the nature and relative abundances of the various growth shapes of the bryozoan material known as their zoarial colonial growth forms here we propose a simple descriptive terminology covering both cheilostome and cyclostome bryozoans that involves four main growth forms encrusting erect rigid erect flexible and free living and a selection of subcategories based on shape identification of these habitat related growth form types is aided by reference to line drawings specimen photographs and photomicrographs of thin section slices the scheme is illustrated by examining briefly some possible environmental controls on the spatial and or time variations in the nature and distribution of colonial growth forms in several examples of modern and tertiary bryozoan dominated carbonate deposits in new zealand we anticipate that the routine description and quantification of bryozoan colonial growth types in non tropical carbonates generally will facilitate the recognition and interpretation of contrasting sub facies within the global foramol bryomol group of carbonate deposits

subsurface and deeper ocean remote sensing from satellites an overview and new results satellite remote sensors cannot see far beneath the surface layers of the ocean yet many important ocean processes and features are located well below the surface and at considerable depths examples include mediterranean eddies meddies mixed layer depth internal waves and bottom topography deeper ocean remote sensing is becoming even more important because recent data seem to indicate that the deeper ocean is responding to climate variability and change many of these subsurface phenomena have surface manifestations which can be interpreted with the help of models to derive key parameters of deeper ocean processes the objective of this paper is to provide an overview of satellite remote sensing and modeling techniques which enable scientists to characterize subsurface and deeper ocean processes and features and to present some new results

characterization and origin of permeability porosity heterogeneity in shallow marine carbonates from core scale to 3d reservoir dimension middle jurassic paris basin france abstract nuclear magnetic resonance nmr stable isotope geochemistry of micro sampled cores nmr well logs and 3d modeling are used to investigate the carbonate permeability porosity heterogeneity along 230 m thick limestones of the paris basin despite the global low porosity and permeability of the limestones two aquifers units with porosity greater than 15 were identified these two aquifers are very different in terms of pore through radii and nmr signal the first one a1 aquifer 1 is a 7 m thick mudstone unit dominated by extended microporosity with pore throat radii of 0 25 m to 0 3 m the second one a2 aquifer 2 is a 15 m thick oolitic grainstone units showing macropores reaching 100 m and pore throat radii of 32 m from core descriptions and wireline logs on 26 wells a 3d static geological model is build the fine tuning of permeability calculations from nmr logs realized along 12 of the wells allows porosity and permeability heterogeneity to be distributed within a 3d model at the reservoir scale area of about 2000 km2 which match the flow behavior illustrated by well tests associated with early meteoric calcite cements and poorly developed burial blocky calcite cements the porous and permeable intervals may be predicted in two stratigraphic and diagenetic considerations firstly the syn sedimentary meteoric dissolution or neomorphism of the initial high magnesium calcite and aragonite particles or clasts into low magnesium calcite particles or cements prevented most mechanical and chemical compaction during the first steps of burial secondly the regional stratigraphic architecture reveals the presence of local permeability barriers which prevented early cretaceous lateral meteoric water circulation and the associated burial calcite cementation

non tropical carbonates related to rocky submarine cliffs miocene almeria southern spain abstract upper miocene deposits in the cabo de gata region se spain provide a unique opportunity to study cliff related temperate carbonates a poorly known type of fossil non tropical carbonates the studied submarine cliffs lie on the western flank of the monte ricardillo volcanic dome two main biocenoses colonised the cliff walls vertical and subvertical walls were either overgrown by vermetid gastropods forming a vermetid framestone or colonised by robust branching bryozoans which were reworked post mortem and accumulated as aprons at the foot of the submarine cliffs coralline algae in the vermetid build up indicate palaeodepths below 15 20 m depressions in front of the cliffs were occupied by nodular bryozoans and bivalves within these depressions barnacles settled on secondary hard substrates with progressive flooding of the depositional area substrate relief was filled in and a carbonate ramp with facies belts following the palaeobathymetric gradient evolved a delicate branching bryozoan facies occurs in the proximal part of the ramp and a nodular bryozoan bivalve facies in its middle part distally these deposits give way to a coralline algal facies these results provide a first insight into temperate water carbonates related to rocky submarine cliffs this work also reveals a major control of substrate relief on temperate carbonate facies and biofacies

ocean sand ridge signatures in the bohai sea observed by satellite ocean color and synthetic aperture radar measurements abstract satellite measurements from synthetic aperture radar sar and the moderate resolution imaging spectroradiometer modis onboard the aqua platform are used to study the ocean sand ridges in the eastern bohai sea in china even though the imaging mechanisms for sar and modis aqua remote sensing are different the sand ridges are shown to have exactly the same patterns in images from both sensors therefore the location extension and coverage of the ocean sand ridges can be detected and cross examined by both sar and modis aqua observations satellite images show quite different sand ridge distribution pattern from the published bathymetry map based on in situ data that shows six sand ridges in the area 10 finger shaped sand ridges are identified from satellite observations the tidal current sand ridge interaction driven physical and optical changes are assessed and evaluated the existence of sand ridges causes enhanced water diffuse attenuation coefficient k d 490 and elevated normalized water leaving radiance at the red and near infrared nir wavelengths the sea surface over the sand ridges experiences significant seasonal variability of water turbidity and shows remarkable differences from nearby ocean regions during winter k d 490 values are about 2 3 m 1 over the ridges while the maximum k d 490 in the neighboring oceans is approximately 1 5 m 1 in summer the enhancement of the sea surface turbidity is less significant than that which occurs in winter

record of a tectonically controlled regression captured by changes in carbonate skeletal associations on a structured island shelf mid pleistocene rhodes greece the plio pleistocene warm temperate carbonate deposits along the se coast of rhodes greece formed on a highly structured island shelf during a major transgression regression cycle which reached bathyal depth during maximal transgression the complex palaeobathymetry exhibits many characteristics of submarine canyons especially of so called blind or headless canyons a canyon type which is especially common in the modern mediterranean this study presents the palaeoenvironmental evolution of one of these canyons which is today represented by the lardos valley eastern central rhodes the studied section comprises the middle pleistocene 900 300 ka and describes a shallowing upward trend from bathyal to circalitoral depth thin fossiliferous debris flow layers document turnovers and abundance changes in fauna and floral of hard bottom communities which developed on the adjacent basement slopes and highs the comparison of the obtained results with other studies from the southeastern coast of rhodes suggests a high degree of diachroneity of lithological boundaries of these plio pleistocene deposits which can be best explained by progressive infill of small depocentres located at different altitude levels hence lithological changes are interpreted to be time transgressive from distal low altitude to proximal high altitude during transgression while time transgressive from proximal to distal during regression consequently the best chronostratigraphic correlation horizon is the surface of maximal transgression the most probable age for this surface could be estimated at 1 1 to 0 8 ma 0 2 0 5 ma younger than previous estimates furthermore the current lithostratigraphic schemes for the plio pleistocene deposits of southeastern rhodes are reviewed and revised highlights the studied outcrop documents the uplift of rhodes during the middle pleistocene the plio pleistocene stratigraphy of rhodes is reviewed and revised the studied sedimentary unit is interpreted as submarine canyon deposit diachroneity of canyon deposits is most likely due to different altitudes of small depocentres

synsedimentary cemented calcarenite layers in oligo miocene cool water shelf limestones eucla platform southern australia abstract the abrakurrie limestone is a bryozoan rich cool water open shelf unit of oligocene middle miocene age beneath the nullarbor plain the sediments have been in the meteoric diagenetic environment never buried more than a few hundred meters since middle miocene time the unit is composed of meter scale subtidal cycles each of which is capped by an erosion surface the upper several centimeters of most cycles are well lithified forming distinctive hard layers in otherwise friable carbonates intergranular cements in these layers are now isopachous rinds of low magnesium calcite crystals are inclusion rich generally fibrous and have a speckled cathodoluminescence signature cements in intergranular pores at the tops of cycles are overlain by interstitial marine sediment the cem nts are interpreted to have been marine precipitates in the form of magnesium calcite originally containing from 8 12 mole mgco3 and having a 18o value of 1 0 0 5 versus pdb stable carbon and oxygen isotope values in these interpreted marine hardgrounds are distinctly more positive than values from underlying soft sediments reflecting alteration under lower water rock ratio conditions due to reduced permeabilities covariance in stable isotope values from different localities suggests diagenesis in groundwaters of mixed composition fluid inclusions indicate neomorphism in fluids with salinities equal to or slightly greater than seawater alteration is envisaged to have taken place in a paleogroundwater system of variably mixed saline continental waters and seawater occurrence of similar to identical cemented layers and cements in coeval cool water new zealand shelf carbonates suggests that such cementation was a sporadic but widespread phenomenon on mid cenozoic platforms in this area by inference cool water carbonates of all ages may contain units lithified on the seafloor by cements containing low to intermediate amounts of magnesium cool water is not an inhibitor to synsedimentary cementation

whitecap features induced by submarine sand waves in stereo optical imagery under high wind speed conditions waves break on the sea surface producing whitecaps which can be recorded in optical satellite images however the breaking of waves is also influenced by submarine topography in this study we investigate the whitecap features induced by submarine sand waves using optical stereo images we determine the whitecap coverage in images and estimate the probabilities of wave breaking the observed and estimated results are in agreement with some previous investigation results a physical model is used to discuss the mechanisms of wave breaking along sand wave crests the physical model is able to qualitatively explain the differences between the observed whitecap coverage and the estimated probability of wave breaking between the sand wave area swa and the background area bga further analysis shows that the periodic sand wave system may play the role of a frequency control device and may result in more broken waves in the swa than in the bga this study demonstrates that it is possible to observe submarine topography under high wind conditions by using whitecap features

determination of water depth with high resolution satellite imagery over variable bottom types a standard algorithm for determining depth in clear water from passive sensors exists but it requires tuning of five parameters and does not retrieve depths where the bottom has an extremely low albedo to address these issues we developed an empirical solution using a ratio of reflectances that has only two tunable parameters and can be applied to low albedo features the two algorithms the standard linear transform and the new ratio transform were compared through analysis of ikonos satellite imagery against lidar bathymetry the coefficients for the ratio algorithm were tuned manually to a few depths from a nautical chart yet performed as well as the linear algorithm tuned using multiple linear regression against the lidar both algorithms compensate for variable bottom type and albedo sand pavement algae coral and retrieve bathymetry in water depths of less than 10 15 m however the linear transform does not distinguish depths 15 m and is more subject to variability across the studied atolls the ratio transform can in clear water retrieve depths in 25 m of water and shows greater stability between different areas it also performs slightly better in scattering turbidity than the linear transform the ratio algorithm is somewhat noisier and cannot always adequately resolve fine morphology structures smaller than 4 5 pixels in water depths 15 20 m in general the ratio transform is more robust than the linear transform

spring neap tidal effects on satellite ocean color observations in the bohai sea yellow sea and east china sea 1 eight year ocean color observations between 2002 and 2009 from the moderate resolution imaging spectroradiometer modis onboard the aqua satellite are used to quantitatively assess the spring neap tidal effects on variability of ocean optical and biogeochemical properties in the bohai sea yellow sea and east china sea we demonstrate that spring neap tidal variation is one of important ocean processes that drive both the synoptic scale and mesoscale changes of the ocean optical biological and biogeochemical properties in the coastal region normalized water leaving radiance spectra nlw water diffuse attenuation coefficient at the wavelength of 490 nm kd 490 and total suspended matter tsm concentration show significant spring neap variations in the coastal region within a lunar cycle of 29 53 days in the open ocean however spring neap tidal effects on ocean color data are negligible the entire areal coverage of the turbid waters kd 490 0 3 m 1 showing significant spring neap tidal variations is 4 5 105 km2 similar coverage of moderately turbid waters 0 1 kd 490 0 3 m 1 is also impacted by the spring neap tides the magnitude of the spring neap tidal effects on the variations of the satellite ocean color properties e g kd 490 and tsm is in the same order as the seasonal variations in the coastal region highest kd 490 and largest turbid water coverage lag the new moon or full moon about 2 3 days while the lowest kd 490 and smallest turbid water coverage are also 2 3 days behind the one quarter or three quarter moon this is attributed to the seawater inertia and the friction against the seabed as well as the sediment resuspension process

paleotemperatures and ice volume of the past 27 myr revisited with paired mg ca and 18o 16o measurements on benthic foraminifera 1 we explore the applicability of paired mg ca and 18o 16o measurements on benthic foraminifera from southern ocean site 747 to paleoceanographic reconstructions on pre pleistocene timescales we focus on the late oligocene through pleistocene 27 0 ma history of paleotemperatures and the evolution of the 18o values of seawater 18osw at a temporal resolution of 100 200 kyr absolute paleotemperature estimates depend on assumptions of how mg ca ratios of seawater have changed over the past 27 myr but relative changes that occur on geologically brief timescales are robust results indicate that at the oligocene to miocene boundary 23 8 ma temperatures lag the increase in global ice volume deduced from benthic foraminiferal 18o values but the smaller scale miocene glaciations are accompanied by ocean cooling of 1 c during the mid miocene phase of antarctic ice sheet growth 15 13 ma water temperatures cool by 3 c unlike the benthic foraminiferal 18o values which remain relatively constant thereafter temperatures vary by 3 c and reach maxima at 12 and 8 5 ma the onset of significant northern hemisphere glaciation during the late pliocene is synchronous with an 4 c cooling at site 747 a comparison of our 18osw curve to the haq et al 1987 sea level curve yields excellent agreement between sequence boundaries and times of increasing seawater 18o 16o ratios at 12 11 ma in particular when benthic foraminiferal 18o values do not support a further increase in ice volume the 18osw curve comes to a maximum that corresponds to a major mid miocene sea level regression the agreement between the character of our mg ca based 18osw curve and sequence stratigraphy demonstrates that benthic foramaniferal mg ca ratios can be used to trace the 18osw on pre pleistocene timescales despite a number of uncertainties related to poorly constrained temperature calibrations and paleoseawater mg ca ratios the mg ca record also highlights that deep ocean temperatures can vary independently and unexpectedly from ice volume changes which can lead to misinterpretations of the 18o record

sediment supply to the continental shelf by the major rivers of china the yalu luan the yellow changjiang and pearl rivers discharge 90 of china s total annual input of 20 14 10 8 t of sediment to the sea this huge volume of sediment is deposited in the river mouths and in the vicinity of the inner shelves in the form of deltas or submarine sandy ridges depending upon the dominant processes or dynamics of the area even though the continental shelves of the china seas were coastal plains during the late pleistocene modern river sediments rarely extend to the outer shelves except in response to changes in sea level

suspended sediment signatures induced by shallow water undulating bottom topography near surface signatures of suspended sediment concentration ssc related to submerged bed forms displayed in visible band data gathered by space borne imaging sensors are described detailed acoustic doppler current profiler adcp data of vertical current velocity component echo intensity modulation of ssc and related oceanographic and meteorological observations in a tidal inlet of the north sea have been analyzed to understand the associated hydrodynamics of the optical imaging mechanism theoretical considerations based on the navier stokes and sediment continuity equations have been carried out as a first approximation these theoretical results explain signatures of enhanced ssc of in situ measurements and analyzed space borne images strong currents flowing over steep bottom topography are able to stir up the sediments to form both a general continuum of ssc and localized pulses of higher ssc in the vicinity of the causative bed feature itself the strain rate equivalent to the current gradient is an important parameter describing near water surface oceanographic and meteorological phenomena in the visible and microwave part of the electromagnetic spectrum observed by shore and ship based as well as air and space borne remote sensing systems significant disagreements between theoretical results of the strain rate generated by the surface current and in situ observations at the crests of submerged ridges and sand waves were identified possible explanations could be first the current velocity may not be barotropic near the crests of such bed forms and second mass conservation may not only be maintained through an acceleration or deceleration of the flow this implies that active up and downwelling effects of the three dimensional current field can also play a significant role for hydrodynamic interaction between current and underwater bed forms

microstratigraphy of calcite cements in pliocene cool water limestones new zealand relationship to sea level burial and exhumation events

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

linking early diagenesis and sedimentary facies to sequence stratigraphy on a prograding oolitic wedge the bathonian of western france aquitaine basin to improve the understanding of the distribution of reservoir properties along carbonate platform margins the connection between facies sequence stratigraphy and early diagenesis of discontinuities along the bathonian prograding oolitic wedge of the northeastern aquitaine platform was investigated eight facies are distributed along a 50 km outcropping transect in 1 toe of slope 2 infralittoral prograding oolitic wedge 3 platform margin shoal 4 open marine platform interior 5 foreshore and 6 terrestrial settings the transition from shallow platform to toe of slope facies is marked in the field by clinoforms hundred of meters long carbonate production was confined to the shallow platform but carbonates were exported basinward toward the breakpoint where they cascaded down a 20 25 slope ooid to intraclast grainstones to rudstones pass into alternating marl limestone deposits at an estimated paleodepth of 40 75 m three sea level falls of about 10 m caused the formation of discontinuities corresponding to sequence boundaries along these discontinuities erosional marine hardgrounds formed in a high hydrodynamic environment at a water depth of less than 10 m displaying isopachous fibrous cements and meniscus type cements the cements pass landward into meniscus and microstalactitic forms along the same discontinuities which are characteristic of subaerial exposure during the deposition of transgressive systems tracts carbonate accumulation remained located mostly on the shallow platform energy level increased and carbonates were exported during the deposition of highstand systems tracts forming the infralittoral prograding oolitic wedge during the deposition of lowstand systems tracts carbonate production fell to near zero and intraclast strata derived from the erosion of hardgrounds on the shallow platform prograded basinward early diagenetic cements are related exclusively to discontinuities that are not found within the prograding wedge because of the continuous high sedimentation rate under lower hydrodynamic conditions this absence of early cementation within the infralittoral prograding oolitic wedge was conducive to porosity conservation making such features good targets for carbonate reservoir exploration this study proposes a novel sequence stratigraphy model for oolitic platform wedges including facies and early diagenesis features

petrogenesis of cenozoic temperate water calcarenites south australia a model for meteoric shallow burial diagenesis of shallow water calcite sediments abstract the gambler limestone is one of several extensive shallow water shelf carbonates of eocene to miocene age exposed along the southern margin of australia it is a muddy to grainy bryozoan calcarenite with accessory benthonic foraminifers and echinoids the sediments originally composed almost entirely of calcite or mg calcite have been in vadose and phreatic environments for over 10 ma yet are virtually unlithified the only cements of any consequence are epitaxial on echinoids numerous karst features dolines caves speleothems and surface karren attest to prolonged residence in the meteoric zone the gambler limestone is presently one of the best fresh water aquuifers in australia most flow occurs through intergranular pores in sediments with over 30 porosity cementation is by minor intergranular pressure solution which has developed under overburden of less than 100 m the overlying naracoorte limestone miocene a calcarenite of warmer water aspect contains numerous aragonite molds and is well cemented we propose that such cool water limestones are a better model for the meteoric diagenesis of calcite sediments of all ages than are aragonite rich tropical sediments it is probable that many similar early and middle paleozoic calcite limestones may have been in the meteoric zone for prolonged periods yet contain little or no petrographic or geochemical record of such exposure

detection of natural oil slicks in the nw gulf of mexico using modis imagery i we demonstrate the unique capability of the modis instruments in detecting oil slicks in an open ocean environment on 13 may 2006 in the nw gulf of mexico where water depth ranges from 50 to 2500 m one 250 m resolution modis image showed at least 164 surface slicks under sun glint glint reflectance l g ranged between 0 0001 and 0 06 sr 1 after discounting other possible causes we believe these are the result of natural seeps our analysis showed total coverage of 1900 km 2 with individual slicks varying in surface area 1 1 7 14 8 km 2 and length 19 2 12 4 km concurrent sar imagery showed similar area estimates to within 30 this estimate based on a single image is higher than earlier estimates from a database of multi date sar images for the same region inspection of 200 images for the month of may between 2000 and 2008 revealed similar slicks on at least 50 images on 2 june 2005 slicks were detected under sun glint with both negative contrast l g 0 05 sr 1 these slicks could not be detected in glint free modis images collected on the same day because of the near daily revisit and wide sun glint coverage e g 800 km e w between march and october at 25 n systematic and global application of the modis 250 m imagery can help locate natural seeps and improve estimates of seepage rates in the world s ocean

palaeoenvironment and palaeogeography of miocene marls from southeast sicily and the maltese islands abstract tortonian marls and clays are extensively developed in southeast sicily macrofaunas are sparsely distributed in these strata except for a new section at musenna hill in the vittoria scoglitti area this section together with two other coastal sequences of about the same age are described for the first time their abundant faunas are recorded ecological requirements for these faunas are considered and some attempt is made to place them into the known sicilian miocene stratigraphy the musenna hill section shows a particularly close relationship to the upper part of the miocene blue clay formation of the maltese islands both from the viewpoint of sediment and macrofauna the maltese faunas are recorded in detail for the first time and ecological and palaeogeographical information is considered an attempt at an overall regional palaeoenvironmental reconstruction is made for the maltese and southeast sicilian parts of the central mediterranean for tortonian times

a skeletal assemblage classification system for non tropical carbonate deposits based on new zealand cenozoic limestones abstract cenozoic limestones in new zealand are mainly skeletal grainstones and packstones formed under non tropical climatic conditions in open marine shelf or ramp environments following petrographic analysis of the nature and abundance of the skeletal components in nearly 500 samples of these limestones a complete linkage cluster analysis identified seven major skeletal assemblages that may be regarded as subdivisions of the single foramol skeletal association defined by lees and buller 1972 for temperate region carbonate deposits the seven assemblages are given contracted names as follows a barnamol barnacle bivalve dominated b bimol bivalve dominated c bryomol bryozoan bivalve dominated d echinofor echinoderm benthic foraminiferal dominated e nannofor nannofossil planktonic foraminiferal dominated f rhodalgal calcareous red algal dominated and g rhodechfor calcareous red algal echinoderm benthic foraminiferal dominated a composite triangular classification diagram has been devised for naming the skeletal assemblage of an unknown sample on the basis of its three main skeletal components the diagram successfully characterises more than 85 of the new zealand cenozoic limestone samples and also appears to be applicable for the skeletal assemblage designation of many overseas examples of non tropical carbonate deposits limitations relate mainly to locally common skeletal types e g serpulids brachiopods that are presently not incorporated into the new zealand based scheme the general ecological preferences of the main skeletal contributors in each of the seven skeletal assemblages form a basis for relating the assemblages to broad shelf habitats consequently as well as the benefits of providing a more consistent skeletal assemblage terminology for comparative studies between different workers the scheme can assist with the paleoenvironmental interpretation of non tropical skeletal carbonate facies

diagenesis and compositional partitioning of quaternary cool water carbonate aeolianites southeastern australia abstract middle to late pleistocene stranded carbonate sea beaches adjacent aeolian dunes and pleistocene aeolianites together with holocene marginal marine calcareous sediments across southeastern australia contain the longest record of such deposition in the modern world stretching back to at least 900 ky mis 23 the grains are were derived from a suite of cool water heterozoan carbonate sediments produced on the adjacent offshore shelf most modern shelf carbonate sediments in the region today are aragonite rich but the aragonite is presently slowly being dissolved on or just below the seafloor before the deposits enter the rock record beach dune sediments are derived mainly from the shallow 30 meters deep adjacent seafloor they are mollusk rich but with most bryozoan particles having been destroyed in the surf zone the mollusks are dominantly aragonite these nearshore sediments are swept onshore before any significant seafloor diagenesis can take place and so are compositionally different from the eventual aragonite poor open shelf sediments aragonite skeletal fragments in the dunes progressively dissolve with time under a semi arid climate and produce diagenetic low magnesium calcite meteoric cements a well known process common in tropical aragonitic pleistocene aeolianites the loss of metastable minerals with time is matched by a progressive and well understood change in stable isotopes such alteration in this environment however seems to take longer than in tropical carbonates with lithification herein not beginning until 200 ka and complete cementation being achieved in 450 ky thus neither aeolianites nor offshore marine carbonates record the composition of the original sediment aeolianites lack the important bryozoan constituents whereas neritic deposits lack the prolific mollusks this partitioning revealed for the first time answers the conundrum as to why some cool water neritic shelf and coastal sediments in the rock record are compositionally different

tidal deposition systems of china s continental shelf with special reference to the eastern bohai sea abstract the continental shelf of china has undergone a large scale marine transgression tidal currents have become the main active agent and have had a profound influence on the deposition and geomorphology of the shelf the continental shelf of china has five modern tidal deposition systems 1 the eastern part of the yellow sea 2 the eastern part of the bohai sea 3 off the mouth of yangtze river 4 to the west of taiwan and 5 the strait of qiongzhou when the tidal current speed is above 150 cm s erosion dominates and reciprocating currents form deep scour furrows when the tidal current speed is 50 to 150 cm s deposition is dominant and tidal currents form tidal shoals i e tidal sand ridges and tidal sand sheets whose margins are near an absolute ellipticity value for the m2 tidal component of 0 4 when the absolute m2 value is less than 0 4 a reciprocating current is strong enough to form tidal sand ridges when the absolute value is above 0 4 a rotating current increases so as to form a tidal sand sheet tidal deposition material came mainly from tidal erosion and locally redeposition of late pleistocene sediments and from the neighbouring sea bottom the tidal deposition system in the eastern bohai sea is a typical example it consists of the laotieshan channel scour furrow the liaodong shoal sand ridges and the bozhong shoal sand sheet the maximum tidal current speed in the laotieshan channel where strong erosion occurs is up to 250 cm s in the liaodong shoal the maximum tidal current speed is 64 115 cm s and the absolute ellipticity value of the m2 tidal component is less than 0 4 in the bozhong shoal the maximum tidal speed is 58 79 cm s and the absolute ellipticity value of the m2 tidal component is above 0 4 the small scale bedforms surveyed in detail in the area show that the sand ridges and sand sheet are still under the action of tidal current processes at the present time based on the interpretation of tidal currents bedforms and sediment thickness it is inferred that the general direction of sediment transport within the study area is nnw from the laotieshan channel to the liaodong and bozhong shoals the small scale bedforms in the detailed survey area indicate a local net sediment transport from south to north

sea surface manifestation of along tidal channel underwater ridges imaged by sar a group of submerged ocean bottom sand ridges in the bohai sea china are shown in radarsat 1 and envisat synthetic aperture radar sar images the sand ridges appear as fingerlike quasi linear features in the sar images examining the detailed local bathymetry chart we find that these features coincide with the satellite images the heights of the sand ridges are less than 10 m and the water depth is between 10 and 30 m the spacing of the sand ridges is about 10 km and the length of the sand ridges is about 20 km the same sand ridges are also visible on a moderate resolution imaging spectroradiometer modis true color image the semidiurnal and diurnal tidal currents in this area are almost parallel to the major axis of these sand ridges these observations cannot be explained using the existing 1 d sar imaging model which is not applicable to sand ridges parallel to the tidal current in this paper we consider the shallow water current bathymetry in a 2 d space an analytical ocean model was applied to demonstrate the temporal variations of the current divergence and convergence that are induced by the along sand ridge direction current and ridge interaction a radar simulation model is used to simulate the variation of normalized radar cross section nrcs induced by the ocean surface current the simulated nrcs variation is similar to that extracted from the calibrated sar image simulation results also show that the nrcs variation becomes negligible when the ocean current is set to about half of the maximum tidal current

crystal habit geochemistry and cathodoluminescence of magnesian calcite marine cements from the lower slope of little bahama bank the petrography and geochemistry of marine magnesian calcite cements recovered from the sea floor on the lower thermocline lower slope of little bahama bank address three issues concerning inorganic carbonates 1 crystal habit of marine magnesian calcite cements 2 cation composition of marine precipitates and 3 origins of cathodoluminescence in calcite bladed and blocky limpid spar cements formed contemporaneously within the same intraparticle pore as shown by banded cathodoluminescence traced without interruption through both cement habits bladed and blocky cements exhibit a positively covariant linear relationship for mg and sr having low proximal early formed compositions and high distal late formed compositions linear covariance of mg and sr is interpreted to indicate that the concentrations of these cations were controlled by kinetic effects as they formed with early precipitation occurring more rapidly than later precipitation precipitation rates apparently did not affect cement habit limpid isopachous bladed spar cements the distal third of which are brightly cathodoluminescent have a wide range of mg and sr compositions which is almost completely spanned by both distal cathodoluminescent and proximal noncathodoluminescent parts of cements occurring within the same pore mg and sr do not have a linear relationship these cements are interpreted to have recrystallized in deep cool sea water during recrystallization magnesium was lost and in some cases manganese the principal cathodoluminescence excitor was presumably gained

compositional changes in sigmoidal carbonate clinoforms late tithonian eastern sardinia italy insights from quantitative microfacies analyses quantitative analysis of sediment composition was performed on a kilometre wide section of upper tithonian low relief up to 70 m gently inclined 3 to 15 sigmoidal carbonate clinoforms eastern sardinia to identify changes in sediment composition along the slope and across the studied succession these changes may reflect modifications of the carbonate factory and of processes responsible for sediment transport point count analysis of carbonate microfacies q mode r mode cluster analysis and spearman s rank provided a composition based classification of microfacies and highlighted relationships among sediment components the studied clinoforms are mainly composed of non skeletal grains 70 such as peloids and lithoclasts together with micrite and cements and only a limited contribution from coated grains 2 among skeletal grains 28 the greatest contribution derives from a coral stromatoporoid encruster reef that provided 15 of the components crinoids brachiopods and other along slope thriving biota provided nearly 5 of the allochems whilst fragments of molluscs gastropods bivalves and diceratids from the backreef sourced another 2 the contribution of platform interior biota is negligible 1 the association of composition based facies varies along the slope the upper slope beds consist of coral stromatoporoid grainstone to rudstone the middle slope deposits are dominated by encruster lithoclast grainstone and packstone at the lower slope peloidal lithoclastic packstone as well as brachiopod crinoidal wackestone prevail also the association of skeletal grains changes along the slope the encruster frame builder association typifies the upper slope whilst encrusters characterize the middle slope sediments in the lower slope encrusters are equally represented as the brachiopod crinoid association along slope compositional changes evidence a scarce downslope transport of frame builders and a progressive enrichment in along slope thriving biota quantitative analysis of microfacies allowed the sigmoidal clinoforms to be grouped into six sets each set gathers sigmoids with a similar sediment composition coated grains are dominant in the first set whilst they are lacking in the overlying sets reflecting a change in the carbonate factory other major compositional changes among the sets concern the relative amounts of peloids micrite frame builders corals and stromatoporoids and encrusters the contribution of peloids varies inversely to that of cements and micrite as evidenced in the third and fifth sets which respectively record the highest occurrence of peloids or cement and micrite variations in the amount of frame builders and encrusters are instead non linear high percentages of both frame builders and encrusters as recorded in the second and fifth sets are related to low amounts of peloids and lithoclasts that probably reflect episodes of reduced background sedimentation this study demonstrates that quantitative analysis of carbonate microfacies represents a powerful tool that can improve the reconstruction of the stacking pattern in carbonate slope successions both in outcrop and in subsurface settings

cool water carbonates in an eocene palaeoestuary norseman formation western australia abstract numerous palaeovalleys formed extensive drowned estuaries during eocene transgressions along the southwestern part of the southern margin of australia the tertiary sediments of the cowan palaeovalley have been extensively drilled revealing deposition of the norseman formation during the middle eocene tortachilla transgression initial deposition occurred during transgression of the valley to form a drowned estuary sediments consisted of coarse grained muddy lithic iron and glauconite rich sands and gravels of mixed carbonate and quartz pure carbonates accumulated during the highstand produced by a typical shallow temperate water assemblage of bryozoans coralline algae echinoids and molluscs and were swept into shoals by strong tidal currents minor tropical components in the form of large benthic foraminifers and dasycladacean algae are present coarse bryozoan and trough cross bedded carbonate sands accumulated in the margins of the estuary and fine bryozoan sands in the deeper parts rhodoliths accumulated to form shoals in sheltered localities the spencer gulf and gulf st vincent of south australia provide close modern analogues to the cowan palaeovalley and the norseman formation modern carbonate sediments off esperance on the south coast of western australia contain tropical faunal elements within an otherwise temperate skeletal assemblage and also provide a modern analogue the norseman formation thus provides an excellent example of cool water carbonate deposition in near shore tide dominated environments this study complements and contrasts existing cool water shelf facies models based on tertiary carbonates deposited on deep shelves elsewhere in southern australia

mesozoic syn and postrifting evolution of the central apennines italy the role of triassic evaporites abstractjurassic cretaceous syn and postrift successions from the central apennines were backstripped to gain information on the mesozoic evolution of the passive margin of the adriatic plate early jurassic rifting led to the development of a horst and graben paleogeography the latium abruzzi carbonate platform and the sabina umbria marche pelagic basin subsidence curves were built for both carbonate platform and pelagic basin domains from original and literature stratigraphic data the paleodepositional depths of the deepwater sediments were reconstructed from field geology data including new paleontological data it is proposed that after the deposition of lower hettangian shallow water carbonates an abrupt increase in paleowater depth to 600 1000 m occurred during the late hettangian sinemurian synrift stage the postrift stage was characterized by basin filling with decreasing paleowater depths during the jurassic and by a new deepening during the cretaceous our backstripping curves show

rare earth elements in the sedimentary cycle a pilot study of the first leg the effects of source rock composition and climate on the natural abundances of rare elements ree in the first leg of the sedimentary cycle are evaluated using a study with holocene fluvia sands the medium grained sand fraction of samples collected from first order streams exclusively draining granitic plutons in montana semi arid georgia humid and south carolina humid are analyzed it is found that the ree distribution patterns but not the total absolute abundances of the daughter sands are very similar despite compositional differences between parent plutons averages of the three areas are determined to have a la lu ratio of about 103 showing a depletion of heavy ree with respect to an average granite la lu 79 or the composition of north american shales la lu 55 however the eu sm ratio in sands from these areas is about 0 22 which is very close to this ratio in north american shales 0 21 although the overall ree distribution of these sands is not similar to that of the north american shales in any way it is concluded that the major rock type but neither its minor subdivisions nor the climate controls the ree distribution patterns in first cycle daughter sands although the total and the parent rock normalized abundances of ree in sands from humid areas are much lower than those in sands from arid areas

documentation and characterization of the lower cretaceous valanginian calvin and winn carbonate shelves and shelf margins onshore northcentral gulf of mexico the lower cretaceous stratigraphic section in the northern gulf of mexico gom comprises several well documented carbonate systems that have prominent shelf margin buildups including the berriasian knowles limestone ramp and shelf system barremian sligo formation shelf system aptian pearsall formation ramp system and albian glen rose edwards and stuart city formations shelf systems two lesser known but large scale lower cretaceous valanginian carbonate shelf to shelf margin systems are documented in this investigation using core wireline log and regional 2d seismic data the platform margin succession of the older calvin section comprises a shelf margin buildup back reef reef and fore reef facies that may be as thick as 2000 ft 610 m the seaward margin of the shelf as displayed by seismic data suggests shelf to basin relief of as much as 1000 ft 305 m and margin to lagoon relief of 200 to 500 ft 60 to 140 m relief estimates are not decompacted major reef building organisms are lithocodium stromatoporoids and corals the winn limestone is younger than the calvin limestone and at the shelf margin it may have been 600 to 800 ft 180 to 245 m thick it is composed of organisms similar to those of the calvin reef complex considering the vertical position of the calvin platform succeeding the major bypass of calvin lowstand siliciclastic sands the platform probably records a transgression which is consistent with its highly aggradational depositional style the winn shelf margin was initiated landward of the calvin shelf margin and did not prograde as far seaward as the calvin shelf margin the recognition of these two lower cretaceous carbonate systems is important because they further detail the stratigraphic history and architecture of this deeply buried lowermost lower cretaceous section in the gom these formations are also potential deep gas tight carbonate low porosity plays

water and sediment movement in the vicinity of linear sandbanks the norfolk banks southern north sea geophysical surveys current meter measurements and fluorescent sand tracer experiments were undertaken in the vicinity of the broken bank the data are used to establish localised and regional patterns of water and sediment movement the results obtained confirm mechanisms proposed previously for sandbank growth with particular reference to the north sea these include the clockwise circulation of water and sand with convergence at the crestline secondary helical water circulations do not appear to be a dominant process influencing sandbank maintenance however such circulation may still be important in the initial formation of linear sandbanks and or at some stages in the bank development on a regional basis residual currents bedform asymmetries and tracer dispersion indicate an offshore sediment transport component this observation supports the hypothesis of other investigators formed on the basis of geomorphological observations and numerical model predictions concerning the movement of sand under extreme conditions moreover these transport pathways may persist under low wave and tidally dominated conditions as opposed to being restricted to storm activity

an improved composite surface model for the radar backscattering cross section of the ocean surface 2 model response to surface roughness variations and the radar imaging of underwater bottom topography in the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections nrcs of the ocean surface the proposed model accounts for the impact of the full two dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute nrcs values for a variety of radar configurations and wind speeds satisfactorily after some reasonable tuning of the input ocean wave spectrum this paper focuses on the modulation of the nrcs in the presence of spatially varying surface currents first the sensitivity of the nrcs to intensity variations of different ocean wave spectral components is investigated then the hydrodynamic modulation of the wave spectrum over underwater bottom topography in tidal waters is computed in different ways and the resulting radar signatures are discussed the composite surface model yields comparable radar signatures at high 10 ghz x band and low 1 ghz l band radar frequencies which is in much better agreement with experimental results than the predictions of a first order bragg scattering model on the other hand measured variations of the nrcs at high radar frequencies appear to be still underestimated in some cases which may be due to shortcomings of our description of the wave current interaction by conventional weak hydrodynamic interaction theory possible improvements of the theory are discussed and requirements for future experiments are formulated

sedimentologic and diagenetic controls on pore network characteristics of oligocene miocene ramp carbonates majella mountain central italy this article addresses the controls exerted by sedimentologic and diagenetic factors on the preservation and modification of pore network characteristics porosity pore types sizes shapes and distribution of carbonates belonging to the bolognano formation this formation exposed at the majella mountain italy is composed of oligocene miocene carbonates deposited in middle to outer ramp settings the carbonates consist of 1 grainstones predominantly composed of either larger benthic foraminifera especially lepidocyclina or bryozoans 2 grainstones to packstones with abundant echinoid plates and spines and 3 marly wackestones to mudstones with planktonic foraminifera the results of this field and laboratory based study are consistent with skeletal grain assemblages grain sizes sorting and shapes all representing the sedimentologic factors responsible for high values of connected primary macroporosity in grainstones deposited on the high energy middle to proximal outer ramp cementation responsible for porosity reduction and overall macropore shape and distribution in grainstones to packstones deposited on the intermediate outer ramp was mainly dependent on the following factors 1 amount of echinoid plates and spines 2 grain size 3 grain sorting and shapes and 4 clay amount differently in the wackestones to mudstones laid down on the low energy distal outer ramp matrix is the key sedimentologic factor responsible for low values of scattered macroporosity and dominance of microporosity the aforementioned results may be useful to improve the prediction of reservoir quality by means of mapping simulating and assessing individual carbonate facies with peculiar pore network characteristics

quaternary bryozoan reef mounds in cool water upper slope environments great australian bight bryozoan reef mounds are common features in the geological record occurring within mid ramp slope paleoenvironments especially in paleozoic carbonate successions but until now have not been recorded from the modern ocean recent scientific drilling in the great australian bight ocean drilling program leg 182 has confirmed the existence of shallow subsurface bryozoan reef mounds in modern water depths of 200 350 m these structures have as much as 65 m of synoptic relief and occur both as single mounds and as mound complexes they are unlithified have a floatstone texture and are rich in delicate branching encrusting and or nodular arborescent flat robust branching fenestrate and articulated zooidal bryozoan growth forms the muddy matrix is composed of foraminifers serpulids fecal pellets irregular bioclasts sponge spicules and calcareous nannofossils the 14c accelerator mass spectrometry dates of 26 6 35 1 ka indicate that the most recent mounds the tops of which are 7 10 m below the modern seafloor flourished during the last glacial lowstand but perished during transgressive sea level rise this history reflects changing oceanographic current patterns strong upwelling during lowstands and reduced upwelling and lowered trophic resources during highstands large specimens of benthic foraminifers restricted to the mounds confirm overall mesotrophic growth conditions the mounds are similar in geometry scale general composition and paleoenvironments to older structures but lack obvious microbial influence and extensive synsedimentary cementation such differences reflect either short term local conditions or long term temporal changes in ocean chemistry and biology

oxygen and carbon stable isotope records of the lochkovian pragian boundary interval from the prague basin lower devonian czech republic abstract climate changes close to the lochkovian pragian event are still widely discussed carbonate 18o and 13c and conodont apatite 18o from medial to distal carbonate ramp sediments were analysed to provide further stable isotope data from the stratotype area in the prague basin the uppermost silurian to lower emsian 18o trends are put into an updated conodont biostratigraphy framework carbonate 18o and 13c are discussed in the context of facies dependent diagenesis the 13c pattern measured from different sections enables the correlation of intervals with development of different facies inside the prague basin positive 13c shifts are often coupled with trends of decreasing computed gamma ray cgr values interpreted as regressions whereas negative 13c shifts commonly coincide with opposite trends in cgr the lochkovian pragian boundary interval coincided with an increase in carbonate 13c and an increase in the 18o of conodont apatite and carbonate which we interpret as consequence of climate cooling generally the lochkovian was warmer than the pragian and earliest emsian