carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

elastic flexure and distributed deformation along australia s north west shelf neogene tectonics of the bonaparte and browse basins neogene collision between australia and the banda arc modified the adjacent bonaparte and browse basins of the north west shelf of australia modification comprised both continuous long wavelength amplification of permo carboniferous basement topography and flexure and normal faulting of triassic recent sedimentary cover deformation was continu ous across the browse and bonaparte basins despite the basins beings separated by a rupture barrier style accommodation zone the browse bonaparte transition the degree of basement control and mechanisms of fault linkage vary significantly across this transition and reflect differences in the structural relief amplitude and depth of rifted basement either side of the transition neogene collision amplified the architectural divide amplification of basement topography over wavelengths of several hundred kilometres was associated with negligible horizontal length change the transcurrent component of neogene deformation was partitioned outboard of any continuous flexural amplification

structure and composition of organic reefs and carbonate mud mounds concepts and categories defined here as essentially in place calcareous deposits created by sessile organisms organic reefs are diverse and complex structures with a long geological history their classification has been the subject of fierce debate often characterized by reliance on subjective features such as wave resistance and qualitative attempts to discriminate between first and second class reefs in contrast emphasis is here placed on the objective characteristic of the type of sedimentary support which largely determines the sedimentary composition of the deposit constructional and depositional processes result in three principal sedimentary components matrix m essentially in place skeletons s and cavity cement c whose proportions can be represented on msc triangular plots separately or together these components also provide the structural support for the reef on these compositional and structural bases three main categories of organic reef are recognized 1 matrix supported reefs agglutinated microbial reefs cluster reefs segment reefs 2 skeleton supported reefs frame reefs 3 cement supported reefs cement reefs agglutinated microbial reefs possess laminated clotted or aphanitic fabrics created by microbial trapping of particulate sediment in place skeletons and large primary cavities are rare early cementation may provide added support topographic relief is limited by the need for currents to provide sediment to accreting surfaces cluster reefs skeletal reefs in which essentially in place skeletons are adjacent but not in contact resulting in matrix support characterized by relatively high matrix skeleton ratios and low volumes of extra skeletal early cement sediment trapping is an important corollary of skeletal growth and cluster reef organisms are tolerant of loose sediment absence of framework limits the topographic relief that cluster reefs can attain relative to spatial extent and may permit bedding to develop within the reef close cluster reefs have skeletons up to 1 unit distance apart spaced cluster reefs have skeletons more than 1 and up to 2 unit distances apart with increasing separation of skeletons they grade to level bottom communities segment reefs matrix supported reefs in which skeletons are adjacent and may be in contact but are mostly disarticulated and mainly parauthochtonous matrix abundance is high and early cement relatively low moderate relief can develop in response to intense on reef sediment production frame reefs skeletal reefs in which essentially in place skeletons including calcified microbes are in contact characterized by relatively high skeleton matrix ratio skeletal support enables them to raise themselves above the substrate independently of cementation and particulate sedimentation simultaneously by creating partly open shelter cavities skeletal support may facilitate early cementation both relief and early lithification promote marginal talus formation skeletal shape and orientation distinguish conical stick like dendritic domical and laminar frames each of these may be open or filled open frame reefs

plate convergence foreland development and fault reactivation primary controls on brine migration thermal histories and trap breach in the timor sea australia during the latest miocene and early pliocene 5 5 mabp the collision of the australian and eurasian plates resulted in proto foreland development and significant structural reactivation in the timor sea north western australia flexural extension resulting from the down warping of the australian plate into the developing timor trough resulted in the dilatation of the major jurassic and older extensional faults and the formation of shallow mio pliocene fault arrays an integrated multidisciplinary study of hydrocarbon traps from this region using 2 d and 3 d seismic data stable isotope geochemistry fluid inclusion measurements and apatite fission track data has revealed that this fault reactivation produced three categories of traps high hit moderate mit and low lit integrity traps these have characteristic hydrocarbon fill spill fluid flow and thermal histories in mits and lits the dilatation was moderate to intense respectively and allowed hot 90 130 c highly saline 200 000 ppm salinity brines from deep palaeozoic evaporites to migrate up the reactivated faults and chemically and thermally affect the reservoir and shallower intervals apatite fission track data suggest that fluid migration lasted for between 100 000 and one million years in the case of the mits but for only 10 000 100 000 years in the lits this major fluid flow event resulted in the development of a prominent localised late tertiary heating spike in the mits which can significantly affect the accuracy of modelled thermal histories in the lits the thermal effect is less marked due to the more transient nature of the fluid flow event hits were largely unreactivated and hence conduits for brine migration from depth were absent consequently these traps are the most representative of the thermal histories of the source rock depocentres where mits or lits were charged the associated loss of fault seal integrity facilitated hydrocarbon loss from the mesozoic reservoirs which co migrated with the brines up through the mio pliocene fault network upon entering a shallow clastic aquifer system the eocene grebe formation bacterial oxidation of the hydrocarbons liberated co2 which in turn resulted in significant and very isotopically light carbonate cementation this cementation produces sufficient acoustic impedance with the surrounding uncemented sands that it allows these hydrocarbon related diagenetic zones hrdzs to be mapped seismically since both the size and acoustic response of the hrdzs are directly proportional to the amount of hydrocarbons that have leaked from the traps their presence or absence provides a powerful indicator predrill of both trap integrity and the likely thermal regime that that traps have experienced an important observation is that the leaky fault segments over partially breached traps typically only extended for 200 1000 m whereas over the breached traps leaky segments extended for 3000 5000 m consequently exploration programs acquiring remote sensing geochemical data such as geochemical sniffer and airborne laser fluorosensor alf techniques should have closely spaced line spacings if leaky potentially commercial fields are to be detected reliably potential analogues exist between the processes documented during hrdz formation namely the mixing at shallow depths of basinal brines hydrocarbons and connate waters and processes occurring during the formation of pb zn and other low temperature ore deposits

fluid flow through carbonate platforms as evidence for deep seated reservoirs in northwest australia fluid flow features in carbonate platforms of the outer browse basin northwest australia are investigated using 3d seismic and borehole data during the cenozoic the study area evolved from a carbonate ramp to a rimmed platform with isolated carbonate build ups as such it played a key role in focusing fluid on their buoyant flow to the surface statistical analyses of direct hydrocarbon indicators show fluid flow to be focused in elevated areas i e the greater is the focusing of fluid the larger is the carbonate platform or isolated build up locally karst systems created regions of enhanced permeability through the evolving carbonate stratigraphy karstified horizons are located on the top of carbonate build ups and platform clinoforms as fluid buoyantly concentrates and diffuses up into topographic highs in turn the putative migration of gas and fluid generated hypogenic karst systems enhancing permeability in otherwise lower permeability rock based on the interpreted data we suggest a pivotal relationship between the presence of carbonate build ups and karsts in the browse basin and hydrocarbon accumulations at depth areas of elevated topography focus sub surface fluid enhancing the permeability of carbonate successions in turn focused fluid flow can lead to the generation of methanogenic carbonates promoting the growth of isolated build ups and leading to further generation of elevated features this grants the identification of similar features on seismic data from northwest australia and other equatorial margins in the world as a valid proxy for the recognition of hydrocarbon accumulations below thick carbonate successions

the importance of changing oceanography in controlling late quaternary carbonate sedimentation on a high energy tropical oceanic ramp north western australia the north west shelf is an ocean facing carbonate ramp that lies in a warm water setting adjacent to an arid hinterland of moderate to low relief the sea floor is strongly affected by cyclonic storms long period swells and large internal tides resulting in preferentially accumulating coarse grained sediments circulation is dominated by the south flowing low salinity leeuwin current upwelling associated with the indian ocean gyre seaward flowing saline bottom waters generated by seasonal evaporation and flashy fluvial discharge sediments are palimpsest a variable mixture of relict stranded and holocene grains relict intraclasts both skeletal and lithic interpreted as having formed during sea level highstands of marine isotope stages mis 3 and 4 are now localized to the mid ramp the most conspicuous stranded particles are ooids and peloids which 14c dating shows formed at 15 4 12 7 ka in somewhat saline waters during initial stages of post last glacial maximum lgm sea level rise it appears that initiation of leeuwin current flow with its relatively less saline but oceanic waters arrested ooid formation such that subsequent benthic holocene sediment is principally biofragmental with sedimentation localized to the inner ramp and a ridge of planktic foraminifera offshore inner ramp deposits are a mixture of heterozoan and photozoan elements depositional facies reflect episodic environmental perturbation by riverine derived sediments and nutrients resulting in a mixed habitat of oligotrophic coral reefs and large benthic foraminifera and mesotrophic macroalgae and bryozoans indicators holocene mid ramp sediment is heterozoan in character but sparse most probably because of the periodic seaward flow of saline bottom waters generated by coastal evaporation holocene outer ramp sediment is mainly pelagic veneering shallow water sediments of marine isotope stage 2 including lgm deposits phosphate accumulations at 200 m water depth suggest periodic upwelling or fe redox pumping whereas enhanced near surface productivity probably associated with the interaction between the leeuwin current and indian ocean surface water results in a linear ridge of pelagic sediment at 140 m water depth this ramp depositional system in an arid climate has important applications for the geological record inner ramp sediments can contain important heterozoan elements mid ramp sediments with bedforms created by internal tides can form in water depths exceeding 50 m saline outflow can arrest or dramatically slow mid ramp sedimentation mimicking maximum flooding intervals and outer ramp planktic productivity can generate locally important fine grained carbonate sediment bodies changing oceanography during sea level rise can profoundly affect sediment composition sedimentation rate and packaging

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

u pb dating of a terminal pliocene coral from the indonesian seaway abstract pristine detrital platygyra corals were discovered in an exhumed package of syn orogenic marine sediments on the island of timor in the eastern indonesian region and dated using u pb techniques a single coral from the upper part of the sequence yields a 238 u 206 pb 207 pb 206 pb concordia age of 2 66 0 14 2 ma that is supported by coral 87 sr 86 sr chemostratigraphy and foraminiferal biostratigraphy from bounding strata minor u series disequilibrium is best explained by u mobility within the last 150 ka as pore water chemistry was altered during exhumation and is unlikely to have affected 238 u 206 pb and the apparent sample age by more than 1 2 the ability to date corals beyond the limits of 14 c and u th techniques provides the opportunity to improve the temporal resolution of associated marine chronostratigraphic records in this instance we refine the timing of timor s emergence from beneath the waters of the indonesian seaway is and the initiation of turbiditic deposition at the study site to between ca 3 35 and 2 66 ma these results have implications for the evolution of topography and is oceanic pathways in the active orogenic belts along the northern fringes of the australian plate

plate boundary reorganization in the active banda arc continent collision insights from new gps measurements abstract new gps measurements reveal that large sections of the se asian plate are progressively accreting to the edge of the australian continent by distribution of strain away from the deformation front to forearc and backarc plate boundary segments the study was designed to investigate relative motions across suspected plate boundary segments in the transition from subduction to collision the oblique nature of the collision provides a way to quantify the spatial and temporal distribution of strain from the deformation front to the back arc the 12 sites we measured from bali to timor included some from an earlier study and 7 additional stations which extended the epoch of observation to ten years at many sites the resulting gps velocity field delineates at least three sunda arc forearc regions around 500 km in strike length that shows different amounts of coupling to the australian plate movement of these regions relative to se asia increases from 21 to 41 to 63 eastward toward the most advanced stages of collision the regions are bounded by the deformation front to the south the flores wetar backarc thrust system to the north and poorly defined structures on the sides the suture zone between the nw australian continental margin and the sunda banda arcs is still evolving with more than 20 mm yr of movement measured across the timor trough deformation front between timor and australia

overview of the mars science laboratory mission bradbury landing to yellowknife bay and beyond the mars science laboratory mission reached bradbury landing in august 2012 in its first 500 sols the rover curiosity was commissioned and began its investigation of the habitability of past and present environments within gale crater curiosity traversed eastward toward glenelg investigating a boulder with a highly alkaline basaltic composition encountering numerous exposures of outcropping pebble conglomerate and sampling aeolian sediment at rocknest and lacustrine mudstones at yellowknife bay on sol 324 the mission turned its focus southwest beginning a year long journey to the lower reaches of mt sharp with brief stops at the darwin and cooperstown waypoints the unprecedented complexity of the rover and payload systems posed challenges to science operations as did a number of anomalies operational processes were revised to include additional opportunities for advance planning by the science and engineering teams

neogene evolution of the mixed carbonate siliciclastic system in the gulf of papua papua new guinea this paper outlines the evolution of the late cenozoic mixed carbonate siliciclastic depositional system in the gulf of papua gop using seismic gravity multibeam bathymetry well data sets and landsat imagery the deposition of the mixed sedimentary sequences was influenced by dynamic interplay of tectonics eustasy in situ carbonate production and siliciclastic sediment supply the roles of these major factors are estimated during different periods of the gop margin evolution the cenozoic mixed system in the gop formed in distinct phases the first phase late cretaceous paleocene was mostly driven by tectonics rifting created grabens and uplifted structural blocks which served later as pedestals for carbonate edifices active neritic carbonate accumulation characterized the second phase eocene middle miocene during this phase mostly eustatic fluctuations controlled the large scale sedimentary geometries of the carbonate system the third phase late miocene early pliocene was characterized by extensive demise of the carbonate platforms in the central part of the study area which can be triggered by one or combination of several factors such as eustatic sea level fluctuations increased tectonic subsidence uplift sudden influx of siliciclastics or dramatic changes in environmental conditions and climate the fourth phase late pliocene holocene was dominated by siliciclastics which resulted in the burial of drowned and or active carbonate platforms although some platforms still remain alive until present day

the precambrian terranes of yemen and their correlation with those of saudi arabia and somalia implications for the accretion of gondwana

evolution of late oligocene early miocene attached and isolated carbonate platforms in a volcanic ridge context maldives type yadana field offshore myanmar this study investigates the stratigraphic evolution of the late oligocene early miocene carbonate platforms of the yadana area offshore myanmar well data regional 2d and local 3d seismic surveys allow the identification of three shallow water carbonate platforms yadana 3df and 3de showing various morphologic and stratigraphic patterns influenced by the presence of a paleohigh the identification of seven seismic sequences in the yadana area constrains the stratigraphic evolution in three stages 1 development of aggrading attached and isolated platforms during the chattian 2 a period of platform emersion during the oligocene miocene transition 3 drowning of the smaller buildup 3de associated with km scale backstepping on the large platforms 3df and yadana during the aquitanian the aquitanian marks the onset of renewed volcanic activity associated with the development of fringing carbonate reefs during the burdigalian the rapid similar to 6 my development of these wide similar to 5 70 km and thick similar to 300 850 m carbonate platforms has been mainly controlled by the subsidence however the results highlight a strong overprint of eustatic fluctuations on the rates of change in accommodation and hence on the stratigraphic architecture of the carbonate platforms based on an alternative model for the cenozoic geodynamic evolution of the yadana area our results suggest that the platforms developed on a volcanic ridge of hotspot origin located in the indian ocean and not on a volcanic arc subduction jump processes are interpreted to have played a key role in the demise of all platforms by drastically changing the paleoenvironmental conditions during the early miocene and led to the present day location of the yadana ridge in a back arc setting the carbonate platforms from the yadana area are thus a representative example of the interplay between global mechanisms and local paleoenvironmental parameters on carbonate platform initiation growth and demise c 2017 elsevier ltd all rights reserved

rapid pliocene uplift of timor palynology of exhumed pliocene marine turbidites and marl beds on the island of timor provide insights into crustal deformation in the indonesian region between ca 4 5 and ca 3 ma palynomorphs were sourced primarily from australia and new guinea with increasing swamp and mangrove elements sourced from an emerging proto timor following ca 3 1 ma pollen and charcoal evidence track the rapid uplift of timor to a high island with the progressive appearance of montane and dry lee side floristic elements early to mid pliocene uplift rates of 0 5 0 6 mm yr 1 increased to 2 5 mm yr 1 in the latest pliocene the rapid topographic development of timor leste initiated earlier but followed a pattern similar to that of more westerly localities in the timor sector of the banda arc timor s emergence from the marine environment is closely correlated with the timing of closure of the indonesian seaway to deep dwelling foraminfera

sea level at the last glacial maximum evidence from northwestern australia to constrain ice volumes for oxygen isotope stage 2 new sea level information from the bonaparte gulf in northwestern australia is used to constrain the magnitude and rates of change of ice volumes during the last glacial maximum lgm the region is tectonically stable and far from the former ice covered regions the glacio hydro isostatic adjustment of the coast is therefore relatively small and the corrections for this evect are not sensitive to details of the rebound model microfossil analysis and ams radiocarbon dating of 11 gravity cores taken across the shelf and bonaparte gulf demonstrate that 1 the lgm sea levels were locally at 125 4 m 2 the lgm terminated abruptly at 19 000 cal yr bp with a rapid rise in sea level of about 15 m over the next 500 years and 3 the onset of the minimum sea levels occurred before 22 000 cal yr bp when corrected for the glacio hydro isostatic evects the increase of lgm ice volumes over the present day ice volume is 52 5 106 km3 the termination of the lgm is marked by a rapid ice discharge of 5 2 106 km3 2001 elsevier science b v all rights reserved

surface deformation and slab mantle interaction during banda arc subduction rollback the reason for the spectacular curvature of the banda subduction zone is debated tomographic images and plate reconstructions reveal subduction of a single slab the ancient geometry of the australian plate as well as the interaction between the slab and the mantle caused the deformation of the slab the spectacularly curved banda arc comprises young oceanic crust1 2 enclosed by a volcanic inner arc outer arc islands and a trough parallel to the australian continental margin3 4 5 strong seismic activity in the upper mantle defines a folded surface6 7 for which there are two contrasting explanations deformation of a single slab5 8 or two separate slabs subducting from the north and south6 9 here we combine seismic tomography with the plate tectonic evolution of the region to infer that the banda arc results from subduction of a single slab our palaeogeographic reconstruction shows that a jurassic embayment which consisted of dense oceanic lithosphere enclosed by continental crust once existed within the australian plate banda subduction began about 15 million years ago when active java subduction tore eastwards into the embayment the present morphology of the subducting slab is only partially controlled by the shape of the embayment as the australian plate moved northward at a high speed of about 7 cm yr 1 the banda oceanic slab rolled back towards the south southeast accompanied by active delamination separating the crust from the denser mantle increasing resistance of the mantle to plate motion progressively folded the slab and caused strong deformation of the crust the banda arc represents an outstanding example of large scale deformation of the earth s crust in response to coupling between the crust slab and surrounding mantle

role of deep sourced fluids on the initiation and growth of isolated carbonate build ups abstract the relative role of the various mechanisms responsible for the formation of isolated carbonate build ups occurring on the seafloor along continental margins is still uncertain the interpretation of an extensive seismic dataset in the central vulcan sub basin nw australia allowed to evaluate the possible role of migration and seepage of deep sourced fluids during the initial growth of isolated carbonate build ups the neogene tectonic activity along the margin generated extensional fault systems that commonly displaced the seafloor thus apparently creating a substratum to the initiation of various carbonate build ups during the pleistocene the seismic data show reflections with enhanced amplitude respect to background values which are associated with both isolated carbonate build ups and normal faults the seismic character of these reflections supports the presence of fluids that migrated within the sedimentary pile throughout the investigated area the interpreted occurrence of methane derived authigenic carbonates mdac on the seismic surface upon which the carbonate build ups lay suggests that seepage of hydrocarbons likely occurred at the time of their initial formation the fluid migration appears focused in the areas above extensional faults which breached the seals of the mesozoic reservoirs combined tectonic activity and seepage are suggested to support the initial growth of the carbonate build ups various smaller buried carbonate build ups developed contemporaneously to those on the present day seafloor in sites that lack evidence of past hydrocarbon seepage their shorter life compared to those on the present day seafloor suggests their inability to keep up with the frequent relative sea level variations during the quaternary and the importance of deep sourced fluids for the carbonate build ups growth in the central vulcan sub basin the initiation of the numerous carbonate build ups documented along continental margins worldwide must be explained considering the complex and dynamic interplay of all factors potentially involved such as geological and oceanographic settings and an active petroleum system in particular the migration and seepage of deep sourced fluid can have an important role in controlling the genesis and growth of isolated carbonate build ups

recent terrigenous sedimentation in joseph bonaparte gulf northwestern australia abstract the southern part of the sahul shelf is an excellent example of a macro tidal carbonate clastic transition a distinct lobe of recent seaward fining sand sized material has prograded onto the shelf from the shallow southern part of joseph bonaparte gulf defining the path of bed load transport on the inner shelf while this is a dominantly calcareous shelf parts of the inner shelf are characterised by deep erosion in which relict sediments are excavated from the bed the mechanical destruction of both relict and contemporary biogenic material takes place feeding fine carbonate detrius into the transport stream and there is significant bypassing of recent terrigenous material the lobe of transported sediments in the joseph bonaparte gulf is carbonate rich and masks the significant input of recent terrigenous material

fault associated seabed mounds carbonate knolls off western ireland and north west australia abstract groups of seabed mounds suspected to be modern carbonate knolls or bioherms have been located on reflection seismic data in the porcupine basin off western ireland and in the vulcan sub basin off north west australia the size of these mounds is impressive often being over 1 km across and over 100 m high in the porcupine basin they occur in water depths of 650 1000 m whereas in the vulcan sub basin they occur in water depths of 200 350 m shallow seabed coring in the porcupine basin has provided data on the age lithological composition and hydrocarbon concentrations in the upper 3 m layer of sediment both on and off the mounds in both basins the mounds occur close to faults which may provide conduits for upward migrating hydrocarbons the seepage of hydrocarbons is suspected to have caused local eutrophication or fertilization by providing nutrients to bacteria which in turn are part of the food chain for higher organisms the dominant organism in the porcupine basin examples appears to be the deep water coral lophelia sp whereas in the vulcan sub basin the mounds appear to be halimeda dominated

ocean trench blocked and obliterated by banda forearc collision with australian proximal continental slope abstract the bathymetry and abrupt changes in earthquake seismicity around the eastern end of the java trench suggest it is now blocked south east of sumba by the australian jurassic rifted continental margin forming the largely submarine roti savu ridge plate reconstructions have demonstrated that from at least 45 ma the java trench continued far to the east of sumba from about 12 ma the eastern part of the java trench called banda trench continued as the active plate boundary located between what was to become timor island then part of the australian proximal continental slope and the banda volcanic arc this banda trench began to be obliterated by continental margin arc collision between about 3 5 and 2 ma the present position of the defunct banda trench can be located by use of plate reconstructions earthquake seismology deep reflection seismology dsdp 262 results and geological mapping as being buried under the para autochthon below the foothills of southern timor locating the former trench guides the location of the apparently missing large southern part of the banda forearc that was carried over the australian continental margin during the final stage of the period of subduction of that continental margin that lasted from about 12 ma to about 3 5 ma tectonic collision is defined and distinguished from subduction and rollback collision in the southern part of the banda arc was initiated when the overriding forearc basement of the upper plate reached the proximal part of the australian continental slope of the lower plate and subduction stopped collision is characterised by fold and thrust deformation associated with the development of structurally high decollements this collision deformed the basement and cover of the forearc accretionary prism of the upper plate with part of the unsubducted australian cover rock sequences from the lower plate together with parts of the forearc basement they now form the exposed banda orogen the conversion of the northern flank of the timor trough from being the distal part of the banda forearc accretionary prism carried over the australian continental margin into a foreland basin was initiated by the cessation of subduction and simultaneous onset of collisional tectonics this reinterpretation of the locked eastern end of the java trench proposes that from its termination south of sumba to at least as far east as timor and probably far beyond the java banda trench and forearc overrode the subducting australian proximal continental slope locally to within 60 km of the shelf break part of the proximal forearc s accretionary prism together with part of the proximal continental slope cover sequence were detached and thrust northwards over the java banda trench and forearc by up to 80 km along the southwards dipping savu thrust and wetar suture these reinterpretations explain the present absence of any discernible subduction ocean trench in the southern banda arc and the narrowness of the forearc reduced to 30 km at atauro north of east timor

a review of the milankovitch climatic beat template for plio pleistocene sea level changes and sequence stratigraphy the milankovitch theory of climate change predicts that global ice volume and hence sea level changes were controlled by long term quasi periodic variations in the earth s orbital parameters obliquity precession and eccentricity d 18 o records from deep sea cores are a proxy for sea level changes and have an orbitally tuned chronology covering the last 5 ma the sea level signal in d 18 o data from east equatorial pacific core v19 30 is well calibrated with sea level data from coral terraces on huon peninsula new guinea over the last 140 ka and with less certainty back to 340 ka over the last 140 ka the sea level contribution to benthic glacial interglacial isotopic variation is about 1 2 1 3 or 0 011 m 1 and for core v19 30 the glacial age temperature contribution from deep ocean cooling of 1 7oc is 0 4 independent constraints on late pliocene sea level changes interpreted from shallow marine continental margin records indicate that the sea level d 18 o calibration may not have been the same over the last 2 6 ma and the temperature correction is unlikely to have been the same in all glacial periods and all ocean settings nevertheless the astronomically tuned isotopic records from deep sea cores provide an accurate chronology and approximate the magnitudes of sea level changes over the last 2 6 ma against which the facies architecture of stratigraphic sequences can be analysed and the concepts of sequence stratigraphy properly evaluated 1998 elsevier science b v all rights reserved

methods for identification of isolated carbonate buildups from seismic reflection data isolated carbonate buildups icbs are commonly attractive exploration targets however identifying icbs based only on seismic data can be difficult for a variety of reasons these include poor quality two dimensional data and a basic similarity between icbs and other features such as volcanoes erosional remnants and tilted fault blocks to address these difficulties and develop reliable methods to identify icbs 234 seismic images were analyzed the images included proven icbs and other features such as folds volcanoes and basement highs which may appear similar to icbs when imaged in seismic data from this analysis 18 identification criteria were derived to distinguish icbs from non icb features these criteria can be grouped into four categories regional constraints analysis of basic seismic geometries analysis of geophysical details and finer scale seismic geometries systematically assessing the criteria is useful because it requires critical evaluation of the evidence present in the available data working from the large scale regional geology to the fine details of seismic response it is also useful to summarize the criteria as a numerical score to facilitate comparison between different examples and different classes of icbs and non icbs our analysis of scores of different classes of features suggests that the criteria do have some discriminatory power but significant challenges remain

carbonate platform facies models various types of carbonate platforms are characterized by distinctive profiles facies and evolutionary sequences ramps may be homoclinal or distally steepened and may have fringing or barrier shoal water complexes of ooid pellet sands or skeletal banks homoclinal ramps pass seaward into deeper water without major break in slope and lack deep water breccias distally steepened ramps may be low energy and characterized by widespread shallow subwave base mud blankets or high energy with coastal beach dune complexes and widespread skeletal sand blankets slope facies may contain abundant breccias of slope derived clasts rimmed shelves have relatively flat tops and marked break in slopes at the high energy shallow shelf edge where they pass into deep water such shelves may be aggraded with peritidal facies extending over much of the shelf or incipiently drowned depending on magnitude of sea level fluctuations they may be accretionary or bypass types that include gullied slope escarpment and high relief erosional forms intrashelf basins occur on some shelves controlling distribution of reservoir and source beds isolated platforms are surrounded by deeper water and may be located on rifted continental margins or on submarine volcanoes most have high relief rimmed margins platforms that have been subjected to rapid sea level rise may be incipiently drowned and characterized by raised rims elevated patch or pinnacle reefs and widespread subwave base carbonate or fine clastic blankets completely drowned shelves develop where the shelf is submerged to subphotic depths terminating shallow water deposition and commonly resulting in blanketing of the shelf by deeper water facies some margins show extensive down to basin faulting that is contemporaneous with carbonate deposition or associated with thick prograding clastic sequences the various types of platforms change in response to variations in sedimentation subsidence or sea level rise and may form distinctive evolutionary sequences the relatively few models presented appear to accommodate most geological examples some of which contain major reservoir facies

deformation and exhumation in timor distinct stages of a young orogeny abstract timor island in the outer banda arc bordering the timor sea preserves the orogenic product of an arc continent collision between the australian plate and the banda arc that commenced after 10 9 9 8 ma gts2004 but emerged above sea level only 3 1 ma ago the orogenic pile includes large tracts of material from the australian margin including the permian to middle jurassic gondwana megasequence and the late jurassic to early late miocene australian margin megasequence which occur in thrust slices in addition material from the banda arc side of the plate margin referred to as the banda terrane occurs throughout the island and includes both seafloor metamorphosed igneous material and cover sediments also in thrust sheets however the distribution of thrust slices is unclear in many areas perhaps because only the uppermost nappes of the thrust pile are currently emergent and also because the thrust piles have been disrupted by later high angle faulting evidence from east timor suggests that the major break between deformed pre collisional strata and the relatively undeformed overlying deposits was during the late miocene 9 8 5 5 ma we present evidence for the timing of three distinct phases of orogenic development as determined from east timor including initial collision and emplacement of the early nappes creating loading and diapirism within the 9 8 5 5 ma interval a tectonic quiet interval 5 5 ma 4 5 ma that extended for about a million years during the middle of the collision and may represent the time of locking of the subduction system and a post 4 5 ma phase of uplift unroofing and further diapirism in response to isostatic rebound our conclusions offer an alternative model for the evolution of this part of the banda arc

geometric and depositional responses of carbonate build ups to miocene sea level and regional tectonics offshore northwest australia abstract the geometric and depositional responses of isolated carbonate build ups to miocene sea level change and regional tectonics are investigated using 3d seismic and borehole data from the browse basin north west australia combined with outcrop information from the cariatiz reef southeast spain the interpreted seismic volume documents five 5 miocene sequence boundaries and five 5 main seismic facies seismic attribute analyses proved to be a highly effective tool for interpreting carbonate facies but when compared with outcrop information from southeast spain attribute data are limited to features larger than 16 4 m vertically and 18 75 m horizontally estimations of reservoir potential are thus significantly underestimated when only based on the interpretation of seismic data as a corollary of the structural analysis in this work growth patterns suggest messinian structural partitioning across the browse basin with deformation associated with plate collision focused on preferentially oriented faults i e only influencing carbonate build up evolution at a local scale

controls on the distribution and growth of isolated carbonate build ups in the timor sea nw australia during the quaternary abstract isolated carbonate build ups icbs represent attractive hydrocarbon exploration targets they are often seen as long term transgressive features but their distribution within basins and growth history can be difficult to predict as they respond to the interplay between various tectonic eustatic and oceanographic parameters here we use a 3d seismic megasurvey 18 000 km2 combined with well data to understand the timing and mechanisms of formation of tropical quaternary icbs in nw australia at present the icbs are typically 1 30 km wide and form clusters of 150 build ups developing 2 85 km from the edge of a 650 km wide continental shelf our results demonstrate that the structural evolution of the margin had a major impact on the distribution of the icbs main period of fault activity commenced during the latest miocene early pliocene corresponding to the initial collision of the australian plate with banda arc fault activity increased from late pliocene and peaked during the early pleistocene it was associated with flexural reactivation of structural highs uplift and lows subsidence along the shelf margin seismic evidence of moat channel and drift deposits suggest that contour current activity intensified during the late early pleistocene ca 1 ma bp despite potentially good conditions for carbonate production basement highs and warm water ocean currents icbs did not form until the mid pleistocene ca 0 582 0 8 ma bp this age corresponds to the onset of major sea level fluctuations associated with repeated high amplitude 120 m rapid deglacial rises and slow falls thus we infer that the nw australia icbs formed due to 1 structural shaping of the margin 2 oceanographic changes and most importantly 3 onset of repeated high amplitude transgressions reactivating the carbonate production along isolated highs following 4th 5th order lowstand exposures and allowing catching up carbonate morphologies to develop

indian ocean climate and an absolute chronology over dansgaard oeschger events 9 to 13 oxygen isotope ratios of a stalagmite from socotra island in the indian ocean provide a record of changes in monsoon precipitation and climate for the time period from 42 to 55 thousand years before the present the pattern of precipitation bears a striking resemblance to the oxygen isotope record from greenland ice cores with increased tropical precipitation associated with warm periods in the high northern latitudes the largest change at the onset of interstadial 12 occurred very rapidly in about 25 years the chronology of the events found in our record requires a reevaluation of previously published time scales for climate events during this period

halimeda bioherms of the eastern java sea indonesia extensive areas of coalescing bioherms composed primarily of disarticulated halimeda plates occur on a large carbonate bank kalukalukuang bank located 50 to 70 km east of the central sunda shelf margin eastern java sea indonesia high resolution seismic profiles suggest that these features attain maximum thicknesses of up to 52 m above an acoustically reflective surface interpreted as the top of the pleistocene piston cores and vibracores from the bioherms indicate a composition of halimeda packstone containing varying amounts of foraminifera rich carbonate mud a shell lag occurs at their base above the pleistocene surface seismic stratigraphy of the bioherms suggests that they generally developed as individual mounds that accreted both vertically and laterally until they coalesced to form composite features discordant reflectors are common and probably represent morphological modifications associated with high energy events current scour or local mass movement halimeda bioherms occur in water depths 20 m on both exposed and reef protected bank margins unlike the only other recorded modern examples which occur in the lagoonal facies behind the northern great barrier ribbon reefs of australia their presence and rapid growth rates to 5 9 m 1000 yr as determined from carbon 14 dating of piston core subsamples are possibly related to upwelling of deep nutrient rich south moving water from makassar strait

paleo oceanographic and tectonic settings of early miocene reefs and associated carbonates of offshore southeast asia the late oligocene to early middle miocene was a period of widespread reef and associated carbonate deposition over a wide latitudinal range in the offshore region of southeast asia a generally rising eustatic sea level during this period allowed the accumulation of thick reefal units an expansion of the coral algal regional facies belt north to japan and south to new zealand occurred during the early miocene as the result of a reduced oceanic latitudinal temperature gradient an episode of enhanced organic carbon burial is reflected in a positive dgr13c excursion from 17 5 to 13 5 ma increasing paleo oceanographic equability may have resulted in reduced ocean circulation with the resultant development of an expanded oxygen minimum zone marine oil prone or anic carbon was deposited in silled anoxic basins both bounded by and within island arc systems a combination of tectonic and paleo oceanographic factors therefore created conditions that favored contemporaneous deposition of organic carbon rich source beds and reef reservoirs during the latest early to early middle miocene paleogeographic and facies reconstructions for an 18 m y interval indicate that deposition occurred in three tectonic settings 1 passive continental margins 2 convergent plate boundaries and 3 obliquely convergent plate boundaries in all these settings the vertical motion histories of fault bounded blocks and of larger tectonic elements within which they are contained directly controlled the geographical distribution of carbonate buildups their scal and morphology duration diagenesis and relationship to siliciclastics

new constraints on the origin of the australian great barrier reef results from an international project of deep coring two new boreholes provide the first direct evidence of the age of the australian great barrier reef an inner shelf sequence total depth 86 m basal age 210 40 ka comprises a dominantly siliciclastic unit thickness 52 86 m overlain by four carbonate units total thickness 0 34 m a shelf edge and slope sequence total depth 210 m reveals three major sections 1 a lower section of resedimented flows deposited on a lower slope 2 a mid section including intervals of corals rhodoliths and calcarenites with low angle graded laminae and 3 an upper section of four shelf margin coral reef units separated by karst surfaces bearing paleosols sr isotope and magnetostratigraphic data indicate that the central great barrier reef is relatively young post bruhnes matuyama boundary time and our best estimate for the onset of reef growth on the outer barrier system is ca 600 280 ka this date suggests that reef initiation may have been related to the onset of full eccentricity dominated glacio eustatic sea level oscillation as inferred from large amplitude saw tooth 100 k y 18o cycles after marine isotope stage 17 rather than to some regional environmental parameter a major question raised by our study is whether reef margins globally display a similar growth history the possibility of a global reef initiation event has important implications for basin to shelf partitioning of caco3 atmospheric carbon dioxide levels and global temperature change during quaternary time

sea level in the late quaternary patterns of variation and implications studies of oxygen isotopes in foraminifers from deepsea sediments yield information about rates of change of sea level for hundreds of thousands of years with a resolution of roughly 1 000 years the statistics regarding fluctuations for the late quaternary the last 900 000 years suggest that a rise of 10 m per 1 000 years 1 m per century is not unusual even when the system resides within a warm stage as now values near 2 m per century while rare are well within the range of a warm system beyond the 5 percentile of the overall range once sea level is near 10 m further rise becomes highly unlikely within the conditions of the late quaternary suggesting the presence of some kind of natural barrier that is lack of vulnerable ice the present volume of ice generally considered vulnerable greenland and west antarctic ice sheet adds up roughly to the observed limit

neogene history of the west pacific warm pool kuroshio and leeuwin currents 1 foraminiferal analysis of miocene to recent strata of the northwest shelf of australia is used to chart west pacific warm pool wpwp influence the assemblage is typified by larger foraminifera with ingressions of the indo pacific smaller taxa asterorotalia and pseudorotalia at around 4 ma and from 1 6 to 0 8 ma a review of recent and fossil biogeography of these taxa suggests their stratigraphic distribution can be used to document wpwp evolution from 10 to 4 4 ma a lack of biogeographic connectivity between the pacific and indian ocean suggests indonesian throughflow itf restriction during this period the collision of australia and asia trapped warmer waters in the pacific creating a central wpwp biogeographic province from the equator to 26 n by 3 ma indo pacific species migrated to japan with the initiation of the modern kuroshio current coinciding with the intensification of the north pacific gyre and northern hemisphere ice sheet expansion indo pacific taxa migrated to the northwest australia from 4 4 to 4 ma possibly because of limited itf the absence of indo pacific taxa in northwest australia indicates possible itf restriction from 4 to 1 6 ma full northwest australian biogeographic connectivity with the wpwp from 1 6 to 0 8 ma suggests an unrestricted stronger itf compared to today and the initiation of the modern leeuwin current the extinction of some indo pacific species in northwest australia after 0 8 ma may be related to the effects of large glacial interglacial oscillations and uplift of the indonesian archipelago causing indonesian seaway restriction

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

geodynamics of continental plate collision during late tertiary foreland basin evolution in the timor sea constraints from foreland sequences elastic flexure and normal faulting abstract tectonic subsidence of the australian lithosphere during the late tertiary propagates from the southwest to the northeast in the timor sea as a consequence of the oblique collision between the eurasian and australian plates we reconstruct the asynchronous nature of deflection of the australian plate created during the plate convergence by best matching the geometry of de compacted foreland strata against the predictions of simple bending elastic beam models we infer a maximum subsidence of 3500 m and a maximum width for the basin of 470 km the effective elastic thickness of the australian lithosphere 80 to 100 km does not change significantly during basin evolution the low curvature imposed on the plate 5 1 10 8 m 1 during bending is too small to weaken the plate yet abundant but small slip normal faulting related to bending implies some degree of inelastic yielding the polarity of fault propagation supports the oblique nature of the collision flexural models indicate that at least 570 km of australian plate mostly areas of stretched continental crust was flexed primarily by the tectonic loading of the timor island and that the total amount of subducted plate was at least 100 km during basin evolution

integrated 3 d reservoir modeling based on 3 d seismic the tertiary malampaya and camago buildups offshore palawan philippines three dimensional 3 d seismic interpretation and drilling results indicate complex sedimentary geometries of the malampaya and camago build ups offshore palawan philippines with localized progradation due to unidirectional offbank transport alternating with vertical aggradation successive reduction of size during buildup growth and backstepping of the protected landward margin in response to transgression ultimately appear to have triggered the demise of carbonate production and platform drowning the shallow water platform top sediments repeatedly show signs of subaerial exposure before reflooding a modeling functionality was developed to allow development of multiple scenario 3 d reservoir models in an exploration or appraisal stage the model enables merging of seismic scale observations based on 3 d volume and horizon analyses with subseismic scale information from well data however inherent noise within the seismic data introduced by the complex buildup morphology has resulted in inconsistent attribute distribution and fault dimming these difficulties are compounded by erratic velocity distribution within the limestone nonhyperbolic move out and a narrow relatively low frequency spectrum all of which prevent the use of the 3 d seismic volume as hard data but rather allow its use as a soft constraint for guiding the geological interpretation and ultimately the modeling process seismic data quality in such complex morphologic settings and scarcity of well data hamper greatly the use of geostatistically driven modeling approaches therefore a new functionality was developed within shell s proprietary integrated 3 d modeling suite geocap which allows deterministic model reservoirs using seismic horizon and volume interpretation sequence and cyclo stratigraphic architecture and the concept of reservoir rock type seismic velocity in clean carbonate formations is predominantly a function of porosity distribution to assess time to depth conversion uncertainty the reservoir rock type based models were first produced in the time domain only after differential 3 d depth conversion of these models could the scenarios be reconstructed in the depth domain the depth models subsequently were used to derive permeability and saturation 3 d distortions and thus hydrocarbon volumes for each deterministic scenario the models were then used for simulation purposes

impact of lithospheric flexure on the evolution of shallow faults in the timor foreland system abstract re evaluation of structural evolution on the laminaria high timor sea australia shows that lithosphere flexure associated with the tertiary collision between the australian north west margin and the banda volcanic arc is an important mechanism for neogene fault development and the reactivation of jurassic structures 2d elastic models of the lithosphere flexure show that increasing flexural extension is likely to affect the laminaria high from the late miocene onwards the evaluation of the neogene fault slip history based on instantaneous throw estimates suggests an initiation of faulting during the late miocene when the laminaria high entered the flexed area forebulge increasing fault growth is recorded during the pliocene and correlates with the laminaria high reaching the hinge of the forebulge structure maximum episodes of fault growth are recorded between the late pliocene and early pleistocene when the laminaria high was located near the forebulge hinge or in the slope where curvature and flexural stress are likely to be maximal nnw extension associated with plate flexure allowed the oblique extensional reactivation of buried reservoir bounding jurassic structures the orientation of the jurassic structures relative to the flexural extensional front appears as a key factor controlling the type of segment linkage between the reactivated jurassic faults and the newly developed neogene faults observations from the laminaria high suggest that with an angle 20 between hmax and strike orientation of the jurassic faults soft linkage is likely to occur between jurassic and neogene segments an angle

early stage orogenesis in the timor sea region nw australia neogene collision between the australian eurasia and pacific plates was coeval with the growth of major depocentres in the timor sea seismic cross sections across these troughs identify a characteristic architecture all three lie inboard of diffuse horst like structural highs and all mimic older depressions in the top permian and upper jurassic surfaces distortion of pre tectonic aptian oligo miocene sequences indicates apparent trough subsidence was coupled to uplift of outboard highs rudimentary cross section restoration identifies negligible strike normal length change we interpret apparent neogene subsidence to reflect amplification of basement topography this was not accommodated by discrete structural inversion rather landward propagation of contractional strain caused continuous vertical amplification of basement topography at shallow levels normal faulting accommodated flexure and thin skinned collapse of detached sedimentary cover permitting it to shed away from structural highs and pond in adjacent troughs we infer that shortening of the north west shelf accommodated oblique convergence between australia and the eurasia pacific arc and speculate that the transcurrent component of this deformation was partitioned well outboard neogene modification is interpreted to reflect the earliest stages of collisional orogenesis

palaeobathymetric gradients across timor during 5 7 3 3ma latest miocene pliocene and implications for collision uplift abstract palaeobathymetry is interpreted for the oldest post collision deposits present in timor the distributions of planktonic and benthic foraminifera in chalk marl and mudstone successions that accumulated during 5 7 3 3 ma form the bases for age zonation and water depth interpretation data from 77 samples collected from 11 stratigraphic sections in east timor are combined with information previously published from several sections in west timor to provide control points for palaeobathymetric contouring the bathymetric reconstruction is based on interpreted water depths at the control points in combination with aspects of the spatial geology of timor speculative bathymetric contours are illustrated for time slices represented by three planktonic foraminiferal zones n18 5 5 5 7 ma n19r 4 3 5 5 ma and n20r 3 3 4 3 ma studied samples provide evidence for three bathymetric zones 500 1000 m 1000 1500 m and 1500 2500 m and suggestions are made for the positions of the 500 m 1000 m and 1500 m contours during each time slice the contours show only very gradual variation from 5 7 ma to 3 3 ma and suggest a deepening bathymetric gradient from the northern region where the structurally deepest part of the orogenic pile the aileu metamorphic complex is now exposed to the south east and west the contour maps provide a suggestion for visualizing the topography of the evolving orogenic pile that forms timor from about 5 7 ma through to 3 3 ma the relatively undeformed friable chalk and marl deposits of zone 18 5 7 5 5 ma overlie highly deformed and diagenetically more altered strata this indicates that the initial phase of collision between the australian continent and the banda arc took place prior to 5 7 5 5 ma rather than later during the pliocene or pleistocene as some authors have suggested because of lack of substantiated stratigraphic evidence from anywhere in timor for the 9 8 5 7 ma interval covering much of the late miocene the antecedent topography cannot be determined the bathymetric reconstructions for 5 7 3 3 ma suggest that a deep foreland basin precursor of the present timor sea had developed by 5 7 ma with uplifted areas to the north in an emerging island

microearthquake seismicity and fault plane solutions related to arc continent collision in the eastern sunda arc indonesia the collision of australia with the eastern sunda and banda arcs of indonesia represents a modern example of the early stages of arc continent collision in order to obtain a more detailed view of the tectonics of the collision zone a microearthquake survey was conducted around the savu sea the region that encompasses the transition from subduction of indian ocean lithosphere on the west to collision or subduction of australian continental litho sphere on the east intermediate depth earth quakes were concentrated near pantar island the easternmost active volcano of the sunda arc and outline a northwest dipping zone that strikes n65oe from 70 to 150 km depth the seismic zone probably marks the western edge of the collision zone and its more northerly strike and the orientations of nodal planes from fault plane solutions indicate a 25 o bend in the subducted slab to a depth of at least 150 km because the convergence rate and the timing of collision from geologic observations on timor suggest that the oart of the slab now at 150 km depth was at the trench when australia first collided with timor we infer that continental crust or at least rifted continental margin crust caused the bend in the convergent margin and has been subducted to 150 km depth fault plane solutions of several events show nearly vertical nodal planes that trend parallel to the strike of the seismic zone along which a northwest side down sense of dis placement is indicated these events are concentrated at the southern top side of the seismic zone and suggest that the subducted lithosphere is presently detaching in the 50 100 km depth range beneath the eastern savu sea fault plane solutions for earthquakes within the upper part of the detaching slab 70 100 km depth have p and t axes whose trends lie parallel to the strike of the seismic zone and horizontal southeast trending b axes these earthquakes are interpreted as due to stresses caused by the bend in the subducting plate

african climate change and faunal evolution during the pliocene pleistocene abstract environmental theories of african faunal evolution state that important evolutionary changes during the pliocene pleistocene interval the last ca 5 3 million years were mediated by changes in african climate or shifts in climate variability marine sediment sequences demonstrate that subtropical african climate periodically oscillated between markedly wetter and drier conditions paced by earth orbital variations with evidence for step like 0 2 ma increases in african climate variability and aridity near 2 8 ma 1 7 ma and 1 0 ma coincident with the onset and intensification of high latitude glacial cycles analysis of the best dated and most complete african mammal fossil databases indicates african faunal assemblage and perhaps speciation changes during the pliocene pleistocene suggesting more varied and open habitats at 2 9 2 4 ma and after 1 8 ma these intervals correspond to key junctures in early hominid evolution including the emergence of our genus homo pliocene pleistocene shifts in african climate vegetation and faunal assemblages thus appear to be roughly contemporary although detailed comparisons are hampered by sampling gaps dating uncertainties and preservational biases in the fossil record further study of possible relations between african faunal and climatic change will benefit from the accelerating pace of important new fossil discoveries emerging molecular biomarker methods for reconstructing african paleovegetation changes tephra correlations between terrestrial and marine sequences as well as continuing collaborations between the paleoclimatic and paleoanthropological communities

evaluating hydrocarbon trap integrity during fault reactivation using geomechanical three dimensional modeling an example from the timor sea australia three dimensional 3 d coupled deformation and fluid flow numerical modeling are used to simulate the response of a relatively complex set of trap bounding faults to extensional reactivation and to investigate hydrocarbon preservation risk for structural traps in the offshore bonaparte basin laminaria high the timor sea australian north west shelf the model results show that the distributions of shear strain and dilation as well as fluid flux are heterogeneous along fault planes inferring lateral variability of fault seal effectiveness the distribution of high shear strain is seen as the main control on structural permeability and is primarily influenced by the structural architecture prereactivation fault size and distribution within the modeled fault population as well as fault corrugations driven by growth processes represent key elements driving the partitioning of strain and up fault fluid flow these factors are critical in determining oil preservation during the late reactivation phase on the laminaria high testing of the model against leakage indicators defined on 3 d seismic data correlates with the numerical prediction of fault seal effectiveness and explains the complex distribution of paleo and preserved oil columns in the study area