giant middle eocene bryozoan reef mounds in the great australian bight this paper reports the discovery of extensive middle eocene bryozoan reef complexes along the paleoshelf edge of the great australian bight gab the complexes form the earliest carbonate deposit in the gab which is the largest cenozoic cool water carbonate province on earth the bryozoan reef mounds previously misidentifi ed as volcanic bodies were deposited parallel to the shelf margin for more than 500 km along strike individual reef mound complexes are 60 150 km long as wide as 15 km and as thick as 200 m and dwarf all previously described examples superimposed on the distal margin of an underlying paleocene to mid eocene siliciclastic delta complex the reef mounds provide a critical insight into changing paleoenvironments of the australo antarctic gulf ca 43 ma coinciding with global and continent wide climatic and tectonic events the rapid growth and demise of reef mound building bryozoans raises new questions regarding the interplay of southern ocean opening ocean currents and biosphere interactions

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

middle and late quaternary glacial lake outburst floods drainage diversions and reorganization of fluvial systems in northwestern eurasia abstract the middle and late pleistocene glaciations of northern eurasia had a great impact on the evolution of the modern drainage system this paper presents a review and synthesis on the palaeogeography of glacial lakes their drainage and impact on the re organization of the drainage systems during the last two glacial interglacial cycles we will focus on four regions 1 northern central europe and fennoscandia 2 the central part of the east european plain 3 the west siberian plain and 4 the aral caspian black sea area the main findings of the last decade s include the improved chronology of some major river system formation and of meltwater overflows across the continental drainage divides major drainage systems of the north central and west central part of the east european plain upper volga upper dnieper formed due to overspill of glacial lakes in late mis 6 with a partial re organization upper dnieper in mis 2 the aral caspian black sea cascade acted as a sink for glacial meltwater from the north the major meltwater yield to the aral and caspian seas occurred in mis 6 and late mis 5 in mis 2 the meltwater delivery via the volga valley into the caspian sea was low and therefore had only a minor influence on the sea level considerable meltwater discharge to the black sea through the dnieper river system occurred around the maximal stage of the mis 2 glaciation and ceased very quickly after the onset of deglaciation

seismic and stratigraphic evidence for reef expansion and onset of aridity on the northwest shelf of australia during the pleistocene abstract modern reef the great barrier reef and ryukyu reef distribution in the indo pacific region is strongly controlled by warm currents east australian and kuroshio currents that radiate from the indo pacific warm pool the modern distribution of reefs south of 15 s on the western australian shelf is related to the presence of the warm leeuwin current however the age of the reefs south of 15 s and hence their temporal relationship to the leeuwin current has been largely unknown seismic and subsurface stratigraphic data show that reef growth and expansion on the northwest shelf of australia began in the middle pleistocene 0 5 ma the oldest ooids in the region are approximately synchronous with reef growth we suggest a two stage process for the spread of reefs to higher latitudes on the western australian coast first an increase in leeuwin current activity at approximately 1 ma brought warm waters and a tropical biota to the region and second increased aridity after 0 6 ma led to a decline in clastic input and increased alkalinity triggering ooid formation and reef expansion to higher latitudes associated with the switch to higher amplitude glacio eustatic cycles at the end of the middle pleistocene transition the timing and mechanisms for reef expansion south along the western australian coast has implications for the origin of the eastern australian middle pleistocene great barrier reef the new caledonia barrier reef and japanese ryukyu reef systems

coral growth bands a new and easy to use paleothermometer in paleoenvironment analysis and paleoceanography late miocene greece 1 modern scleractinian corals are classical components of marine shallow warm water ecosystems their occurrence and diversity patterns in the geological record have been widely used to infer past climates and environmental conditions coral skeletal composition data reflecting the nature of the coral environment are often affected by diagenetic alteration ghost structures of annual growth rhythms are however often well preserved in the transformed skeleton we show that these relicts represent a valuable source of information on growth conditions of fossil corals annual growth bands were measured in massive hemispherical porites of late miocene age from the island of crete greece that were found in patch reefs and level bottom associations of attached mixed clastic environments as well as isolated carbonate environments the miocene corals grew slowly about 2 4 mm yr 1 compatible with present day porites from high latitude reefs slow annual growth of the miocene corals is in good agreement with the position of crete at the margin of the miocene reef belt within a given time slice extension rates were lowest in level bottom environments and highest in attached inshore reef systems because sea surface temperatures ssts can be expected to be uniform within a time slice spatial variations in extension rates must reflect local variations in light levels low in the level bottom communities and nutrients high in the attached reef systems during the late miocene tortonian early messinian maximum linear extension rates remained remarkably constant within seven chronostratigraphic units and if the relationship of ssts and annual growth rates observed for modern massive indo pacific porites spp applies to the neogene minimum winter ssts were 20 21 c although our paleoclimatic record has a low resolution it fits the trends revealed by global data sets in the near future we expect this new and easy to use porites thermometer to add important new information to our understanding of neogene climate

browse basin northwest australia the evolution palaeogeography and petroleum potential of a passive continental margin abstract the browse basin located offshore on australia s northwest shelf is a passive margin basin formed by gondwana breakup and is also a known hydrocarbon province the basin was initiated in the late palaeozoic and developed through phases of triassic back rift subsidence jurassic continental breakup and cretaceous to cainozoic drift phase sedimentation this paper presents our interpretation of the detailed palaeoenvironments present in this western australian basin from the middle triassic to the oligocene we have constructed using available well and seismic data palaeogeographic maps of ten time slices covering this period the complex interplay of tectonics sediment supply eustasy and subsidence is documented and the maps produced are then utilised to suggest new hydrocarbon plays in the browse basin our interpretation of data from the browse basin gives only partial support to the global eustasy hypothesis of haq et al 1988 data from the late valangianian hauterivian and oligocene support the published eustatic curves to varying extents but those from the norian rhaetian kimmeridgian portlandian and berriasian are inconsistent with the same curves data from other times are inconclusive

the palaeolimnology of the aral sea a review abstract formerly the fourth largest inland water body in the world the volume and area of the aral sea have decreased dramatically over the past 30 yr largely as a result of human actions throughout its approximately 2 million year history the fate of this water body has been intimately linked with that of its two main in flowing rivers the amu darya and the syr darya we present a review of the hydrological palaeontological and sedimentological evidence for the evolution of the aral sea based largely on russian literature although the structure of the aral basin can be traced back to the late neogene the sea has only existed in its present form for the past 8 10 ka and the holocene history has been shaped by regional climatic variations the development of the associated drainage system and anthropogenic forces past hydrological changes in the aral basin have led to systematic shifts in the level of the aral sea which are reflected sedimentologically through the deposition of transgressive and regressive sedimentary units and geomorphologically through the development of terraces all the above data are integrated to produced a late quaternary history of this important water body

structural style in a young flexure induced oblique extensional system north western bonaparte basin australia abstract in the north western bonaparte basin north west shelf of australia neogene to recent flexure induced extension superimposed obliquely over the mesozoic rift structures thus the area offers a good opportunity to investigate the dynamics and architecture of oblique extension fault systems analysis of basin scale 2d and 3d seismic data along the vulcan sub basin shows that neogene deformation produced a new set of extensional en echelon faults at places accompanied by the reactivation of the mesozoic faults the pre existing mesozoic structures strongly control the distribution of the neogene recent deformation both at regional and local scales main controls on the neogene recent fault style density and segmentation linkage include 1 the orientation of the underlying mesozoic structures 2 the obliqueness of the younger extension relative to the rift inherited faults and 3 the proximity to the timor trough three types of vertical relationships have been observed between mesozoic and neogene recent faults hard linkages seems to develop when both fault systems trend parallel therefore increasing risks for trap integrity it is suggested that the orientation of maximum horizontal stress s hmax relative to the mesozoic faults forming hydrocarbon traps is critical for their potential seal leak behaviour stratigraphic growth across the faults indicates that main fault activity occurred during the plio pleistocene which corresponds to the timing of tectonic loading on timor island and the development of lithospheric flexure synchronism of normal faulting with flexural bending suggests that extensional deformation on the descending australian margin accompanied the formation of the timor trough

monsoon induced partial carbonate platform drowning maldives indian ocean multibeam maps and high resolution seismic images from the maldives reveal that a late miocene to early pliocene partial drowning of the platform was linked to strong sea bottom currents in the upper miocene to holocene currents shaped the drowned banks the current moats along the bank edges and the submarine dune fields bottom currents in the maldives are driven by the monsoon it is proposed that the onset and the intensification of the monsoon during the neogene provoked platform drowning through injection of nutrients into surface waters since the late miocene topographically triggered nutrient upwelling and vigorous currents switched the maldives atolls into an aggradational to backstepping mode which is a growth pattern usually attributed to episodes of rising sea level

accumulation rates from well dated late neogene carbonate platforms and margins abstract margins of large carbonate platforms isolated platforms and atolls are dynamic settings that both generate and accumulate sediments with the exceptions of modern platforms the rates of accumulation are often poorly constrained due to inadequate or unreliable subsurface age data a compilation is here presented of well dated late neogene ice house platform and margin accumulation for the interval from 7 to 2 ma the rates are grouped according to platform type and setting sea level effects and subsidence bathymetry control are the significant influences the six settings are 1 slow aggraded platform 2 partially drowned platform 3 fast aggraded platform 4 atolls 5 prograded margin and 6 periplatform mean rates are 10 to 20 m my for slow aggraded and partially drowned platforms 20 40 m my for atolls and a fast aggraded platform 40 m my for a current dominated prograded margin and 40 110 m my for most prograded and periplatform systems the maximum rates measured from the age depth plot are generally two to three times as high the mean accumulation rates and maximum rates are primarily related to the influence of sea level and to a lesser extent regional subsidence the shallow platforms and atolls are directly sea level controlled whereas the deeper margins are sea level influenced the platform top deposits have the lowest rates of accumulation 10 26 m my due to subaerial exposure and only intermittent flooding the deeper platform margins below lowstand base level are influenced by events on the shallow platform mainly to sediment production and offbank transport slope erosion and redeposition are also important prograded margins and periplatforms accept large volumes of allochthonous sediment and can have periods of extremely high 200 m my vertical accumulation separated by intervals of non deposition erosion or sediment bypass these data despite limitations provide some basic values for ice house carbonate accumulation and the relevant extrinsic controls the late neogene rates can help constrain the sediment dynamics of the carbonate platform and flank system data especially important for calibration of computer models and for the resultant reservoir attributes

climatic and eustatic signals in a global compilation of shallow marine carbonate accumulation rates two of the most important factors that control the accumulation rate of material in carbonate platform environments on geological time scales are climate and eustasy accurately assessing the importance of these interrelated factors through the study of both modern and ancient carbonate facies however is problematic these difficulties arise from both the complexities inherent in carbonate depositional systems and the demonstrable incompleteness of the stratigraphic record here a new compilation of more than 19 000 global phanerozoic shallow marine carbonate accumulation rates derived from nearly 300 individual stratigraphic sections is presented these data provide the first global holistic view of changes in shallow marine carbonate production in response to climate and eustasy on geological time scales notably a clear latitudinal dependence on carbonate accumulation rates is recognized in the data moreover it can also be demonstrated that rates calculated across the last glacial maximum and holocene track changes in sea level in detail the data show that globally averaged changes in carbonate accumulation rates lagged changes in sea level by ca 3 kyr reflecting the commonly observed delay in the response of individual carbonate successions to sea level rise differences between the rates of carbonate accumulation and sea level change over the past 25 kyr ostensibly reflect changing accumulation mode with platform drowning give up mode pervasive during peak early holocene sea level rise followed by a switch to catch up mode accumulation from ca 9 ka to the present carbonate accumulation rates older than the quaternary are typically calculated over time spans much greater than 100 kyr and at these time spans rates primarily reflect long term tectonically mediated accommodation space changes rather than shorter term changes in climate eustasy this finding coupled with issues of stratigraphic incompleteness and data abundance tempers the utility of this and other compilations for assessing accurately the role of climate and eustasy in mediating carbonate accumulation rates through geological time

late quaternary lake level and climate changes in arid central asia inferred from sediments of ebinur lake xinjiang northwestern china arid central asia plays an important role in global climate dynamics but large uncertainties remain in our understanding of the region s hydroclimate variability during the late quaternary here we present a new high resolution record of lacustrine sediment grain size and element chemistry from ebinur lake which was used to infer lake conditions and related climate changes in the study region between ca 39 2 and 3 6 ka end member modeling analysis of grain size data and pca of elemental data show that lake level fluctuated dramatically from 39 2 to 34 0 ka subsequently ebinur lake experienced a high stand from 34 0 to 28 0 ka under humid climate conditions the subsequent period from 28 0 to 12 0 ka was characterized by lake regression under dry climate conditions whereas afterward 12 0 3 6 ka considerably higher lake levels and humid conditions again prevailed millennial scale abrupt climate changes such as heinrich events h3 and h1 and the younger dryas which are documented in the north atlantic region are also detected in the sediment record from ebinur lake comparisons with other sediment records from arid central asia generally support the claim that climate change in this region was influenced mainly by variations in north atlantic sea surface temperatures through the westerlies

the role of sea surface temperature as a control on carbonate platform development in the western coral sea the derivation of a detailed sea surface paleotemperature curve for the middle miocene holocene 10 0 ma from odp site 811 on the queensland plateau northeast australia has clarified the role of sea surface temperature fluctuations as a control on the initiation and development of the extensive carbonate platforms of this region this curve was derived from isotopic analyses of the planktonic foraminifer globigerinoides ruber and converted to temperature using the surface water paleotemperature equation accounting for variations in global ice volume the accuracy of these data were confirmed by derivation of paleotemperatures using the water column isotopic gradient 13o corrected for salinity and variations in seafloor water mass temperature results indicate that during this period surface water temperatures were on average greater than the minimum required for tropical reef growth 20 c veron 1986 with the exception of the late miocene and earliest early pliocene 10 4 9 ma when there were repeated intervals of temperatures between 18 20 c tropical reef growth on the queensland plateau was extensive from the early to early middle miocene 21 13 ma after which reef development began to decline a lowstand near 11 ma probably exposed shallower portions of the plateau after re immersion near 7 ma the areal extent of reef development was greatly reduced 50 paleotemperature data from site 811 indicate that decreased sea surface temperatures were likely to have been instrumental in reducing the area of active reef growth on the queensland plateau reduced reefal growth rates continued until the late pliocene or quaternary despite the increase of average sea surface paleotemperatures to 22 23 c studies on modern corals show that when sea surface temperatures are below 24 c as they were from the late miocene to the pleistocene off northeast australia corals are stressed and growth rates are greatly reduced consequently when temperatures are in this range corals have difficulty keeping pace with subsidence and changing environmental factors in the late pliocene sedimentation rates increased due to increases in non reefal carbonate production and falling sea levels it was not until the mid quaternary 0 6 0 7 ma that sea surface paleotemperatures increased above 24 c as a result of the formation of a western coral sea warm water pool because of age discrepancies it is unclear exactly when an effective barrier developed on the central great barrier reef the formation of the warm water pool was likely to have either assisted the formation of this barrier and or permitted increased coral growth rates fluctuations in sea surface temperature can account for much of the observed spatial and temporal variations of reef growth and carbonate platform distribution off northeast australia and therefore we conclude that paleotemperature variations are a critical control on the development of carbonate platforms and must be considered an important cause of ancient platform drowning

seismic stratigraphy and geological evolution of the cenozoic cool water eucla platform great australian bight seismic images of the continental margin in the western great australian bight reveal the internal anatomy of a long lived cenozoic cool water carbonate shelf the cenozoic succession is divisible into seven seismic sequences that reflect four depositional phases phase a paleocene middle eocene is a progradational siliciclastic wedge deposited in a depositional sag and represents lowstand and transgressive sedimentation phase b middle eocene earliest middle miocene contains cool water ramp carbonates with biogenic mounds eocene oligocene overlain by a warm water flat topped platform rimmed by the early middle miocene little barrier reef coeval deep water carbonate deposition formed a multi lobed sediment apron this phase was terminated by gentle uplift and tilting throughout southern australia in the late middle miocene phase c late miocene early pliocene represents cool water lowstand wedge and ramp deposition and contains numerous biogenic mounds in the youngest sequence this phase is terminated by an unconformity attributed to marine erosion phase d pliocene quaternary is a thick succession of cool water carbonates with spectacular clinoform ramp geometry that forms most of the modern outer shelf and contains large deep water biogenic mounds this platform the first large cool water carbonate shelf imaged by high quality seismic reflection data demonstrates the interaction between regional tectonic and local and global paleo oceanographic processes as australia drifted northward during the cenozoic the great australian bight moved from high to middle latitudes and the regional oceanographic regime remained cool water largely because of coeval development of the antarctic circumpolar current in the evolving southern ocean short episodes of warm water deposition probably reflect incursions of a proto leeuwin current from the indian ocean whereas growth of the miocene coral algal little barrier reef resulted from a short term global increase in sea surface temperatures this platform dominated by stacked carbonate ramps is most similar to the west florida shelf but contains many more biogenic mounds the western great australian bight carbonate platform is an excellent modern analog for the mesoscale structure of cool water platforms in the older geologic record

a dynamic process for drowning carbonate reefs on the northeastern australian margin drowned carbonate reefs on passive margins are puzzling because of their enormous growth potential compared to typical rates of passive margin subsidence and moderate sea level fluctuations a possible solution to this paradox is that slow processes acting over geologic time weaken reefs and contribute to their ultimate demise the australian northeastern marginal plateaus known for their drowned reefs underwent a period of accelerated tectonic subsidence during the late miocene to pliocene that combined with a sequence of second order global sea level rises outpaced reef growth and drowned the once thriving miocene carbonate platforms however the mechanism for the observed anomalous subsidence of this relatively mature passive margin 1000 km from the nearest plate boundary is uncertain we use a coupled plate kinematic mantle flow model to show that in the late miocene northeastern australia overrode subducted slabs from eocene melanesian subduction north of papua new guinea we find that the rate of surface subsidence induced by the sinking slabs increases the likelihood that relative sea level rises outpaced late miocene reef growth in addition to the well known effects of long term plate processes and short term global sea level and climate change our results demonstrate that deep earth processes can play a substantial role in driving the evolution of passive margins and coral reefs

three dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves browse basin region australia this study analyses the three dimensional geometry of sedimentary features recorded on the modern sea floor and in the shallow subsurface of a shelf to upper slope region offshore australia that is characterized by a pronounced internal wave regime the data interpreted comprise an extensive 12 500 km2 industrial three dimensional seismic reflection survey that images the northern part of the browse basin australian north west shelf the most prominent seismic morphological features on the modern sea floor are submarine terrace escarpments fault scarps and incised channels as well as restricted areas of seismic distortion interpreted as mass wasting deposits besides these kilometre scale sea floor irregularities smaller bedforms were discovered also including a multitude of sediment waves with a lateral extent of several kilometres and heights up to 10 m these sedimentological features generally occur in extensive fields in water depths below 250 m mostly at the foot of submerged terraces along the scarps of modern faults and along the shelf break between the outer shelf and the upper continental rise additional bedforms that characterize the more planar regions of the outer shelf are elongate north west south east oriented furrows and ridges the formation of both sediment waves and furrow ridge systems requires flow velocities between 0 3 m sec 1 and 1 5 m sec 1 which could be generated by oceanic currents gravity currents or internal waves in the studied setting these velocities can be best explained as being generated by bottom currents induced by internal waves an interpretation that is discussed against oceanographic background data and modelling results in addition to the documentation of three dimensional seismic geomorphological features of the modern sea floor it was also possible to map kilometre scale buried sediment wave fields in the seismic volume down to ca 500 ms two way time below the present sea floor indicating the general potential for the preservation of such bedforms in the sedimentary record

genesis and dispersal of carbonate mud relative to late quaternary sea level change along a distally steepened carbonate ramp northwestern shelf western australia abstract accumulation of carbonate mud is minor on the northwest shelf western australia a broad 200 300 km wide distally steepened tropical carbonate ramp it is negligible along most of the inner ramp 0 to 50 m water depth owing to siliciclastic riverine input it is also negligible along the mid from 50 to 120 m ramp and where the entire ramp narrows to 100 km owing to constant reworking by storm waves and ocean swell in these areas carbonate mud is derived mostly from mechanical degradation of skeletal fragments but this does not include calcified remains of calcareous green algae e g halimeda although these plants grow locally only along the outer 120 to 200 m water depth ramp and slope is there any relatively abundant accumulation of carbonate mud here the sediment consists of modern pelagic foraminifer pteropod and nannoplantkon ooze and aragonitic needle rich 2 m micrite the latter having an age based on ams 14c of 19 ka distribution of aragonite micrite defines an extensive 5 0 104 km2 yet relatively narrow 40 km tract running 600 km along the platform margin crystal morphology mineralogy and isotope c o composition identify the micrite to be a seawater precipitate its production and seaward export having occurred during the last glacial maximum when lowered sea level transformed the otherwise broad platform into a narrow epicontinental shelf margin now the modern distal slope today this sediment body lies stranded in deep water about 200 300 km seaward of the shallow inner ramp the volume of micrite produced appears equal to the present day production potential of the great bahama bank rapid postglacial rise in sea level and change in platform geometry climate and oceanography were very influential factors in addition to water depth and area of submergence in the production and distribution of aragonite micrite along the northwest shelf in general 1 epicontinental carbonate platforms can lack substantial micrite accumulation when oceanic current and wave energies sweep unimpeded across a platform and coastal clastics and absence of shoal barriers prevent development of protective lagoons and carbonate tidal flats 2 not all highstand carbonate systems are associated with significant amounts of micrite in shallow water environments nor do they necessarily export large volumes of micrite to the periplatform realm and 3 some lowstand systems can produce and export volumes of carbonate mud that rival highstand systems

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

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

uranium series dating uranium decays through a number of radioactive daughter isotopes some of which have half lives comparable to the time scale of prehistoric archaeology the growth of these isotopes in naturally occurring materials at archaeological sites can be used to determine the age of sites the growth of 230th from its parent 234u can be used over a time range from a few hundred to half a million years calcite precipitated from running or dripping water in springs and caves as well as marls and soil deposited calcretes may be spatio temporally associated with archaeological materials they can be dated by 230th 234u and 234u 238u measurements with a precision of 5 10 of the age by alpha counting or 1 by mass spectrometry bones teeth mollusk and egg shells are also datable but present problems due to migration of parent u in and out of the samples during their burial history

palaeoenvironmental indicators from late holocene and contemporary ostracoda of the aral sea abstract the aral sea is a large terminal lake i e having no outflow in south western asia it is diminishing in size and the salinity of the water is increasing due to excessive withdrawal of water for irrigation from the two main rivers flowing into it the biota of the lake has been decimated and the chemical composition changed dramatically since 1960 three short sediment profiles two cores and one section are examined with a view to reconstructing the most recent history of the sea from microfossil assemblages historical and geological records indicate that since its formation aral sea levels have changed such variation may have been accompanied by changes in the chemistry of the sea through increased evaporation or precipitation in the present work analyses of the mg ca and sr ca molar ratios particularly the latter of benthonic ostracoda from the aforementioned cores indicate that although present salinity levels were never attained during the period of deposition of the sections studied past saalinity variation can be inferred oxygen and carbon isotope analyses of ostracoda and mollusca from one of the sections however indicates two possible periods of relative salinity increase

quantification of architectural variability and controls in an upper oligocene to lower miocene carbonate ramp browse basin australia abstract integration of seismic geomorphology and trajectory analysis of the oligocene through lower miocene distally steepened carbonate ramp system in the subsurface browse basin of the northwest shelf of australia introduces a new way to parameterize carbonate slope channel systems and their stability and sheds light on how basinward sediment transport is influenced by allogenic and autogenic controls seismic geomorphologic analysis identified large scale prograding clinoforms with an extensive slope channel system and slope angles of up to 12 clinoforms have an average slope angle of 8 a height of 500 m and prograded 9 km during the upper oligocene through the lower miocene relative sea level changes overprinted the effect of intermediate scale and small scale antecedent topography and determined progradation aggradation and slope angles of the system we introduce cumulative channel cross sectional area cccsa as the product of number of slope channels slope channel depth and slope channel width cccsa quantifies the capability of the slope channel system to transport sediment basinward and highlights phases of autogenic slope system re organization in response to changes in relative sea level abruptly increasing values of cccsa correlate with slope sediment bypass through the incision of new slope channels during system re organization phases at slope angles of 10 thus we propose that cccsa can be used as a proxy for slope system stability incision of new slope channels into the ramp margin created strike parallel variability of the ramp margin trajectory our seismically derived relative sea level curve and subsidence rates of 9 30 m myr indicate a good preservation of the subsidence and sea level signal in the data

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

seismic geomorphology and growth architecture of a miocene barrier reef browse basin nw australia abstract the cenozoic succession of browse basin is characterized by a carbonate system that developed from a non tropical ramp in eocene lower miocene times to a tropical rimmed platform in the middle miocene the evolution of the platform was unraveled through the interpretation of the seismic geomorphology and borehole data of the middle miocene tropical reef system the first reef structures developed during the early middle miocene as narrow linear reef belts with an oblique orientation with respect to shelf strike direction subsequently they prograded toward the platform margin to form a barrier reef with a minimum length of 40 km the barrier reef itself comprises three distinct ridges separated by progradational steps the second and third step are separated by a karstified horizon which is interpreted to represent the global sea level fall shortly before the serravallian tortonian boundary the following third ridge formed in a slightly downstepped position during the sea level lowstand and initial transgressive phase further sea level rise during the early tortonian first drowned the barrier reef system and subsequently also the patch reefs and relic atolls that had established in a backstepped position in the platform interior the similar evolution of the browse basin reef system and other contemporaneous carbonate systems indicates a strong impact of eustatic sea level changes relatively large subsidence rates in the study area possibly augmented the eustatic sea level rise in the tortonian and hence contributed to the drowning of the reef system however the initiation and final demise of the reef system was also governed by global and regional climate variations the first seismically defined reefs developed simultaneous to a maximum in the transport capacity of the indonesian throughflow which brings warm low salinity waters to the north west shelf reef drowning followed the restriction of this seaway close to the middle to early miocene boundary this near closure of the indonesian seaway possibly led to a regional amplification of the global middle to late miocene cooling trend and hampered the potential of the reef system to keep up with the rising sea level

the leaking bucket of a maldives atoll implications for the understanding of carbonate platform drowning abstract seismic and multibeam data as well as sediment samples were acquired in the south male atoll in the maldives archipelago in 2011 to unravel the stratigraphy and facies of the lagoonal deposits multichannel seismic lines show that the sedimentary succession locally reaches a maximum thickness of 15 20 m above an unconformity interpreted as the emersion surface which developed during the last glacial sea level lowstand such depocenters are located in current protected areas flanking the reef rim of the atoll or in infillings of karst dolinas much of the 50 m deep sea floor in the lagoon interior is current swept and has no or very minor sediment cover erosive current moats line drowned patch reefs whereas other areas are characterized by nondeposition karst sink holes blue holes and karst valleys occur throughout the lagoon from its rim to its center lagoonal sediments are mostly carbonate rubble and coarse grained carbonate sands with frequent large benthic foraminifers halimeda flakes red algal nodules mollusks bioclasts and intraclasts some of them glauconitic as well as very minor ooids finer grained deposits locally are deposited in current protected areas behind elongated faros i e small atolls which are part of the rim of south male atoll the south male atoll is a current flushed atoll where water and sediment export with the open sea is facilitated by the multiple passes dissecting the atoll rim with an elevated reef rim and tower like reefs in the atoll interior it is an example of a leaky bucket atoll which shares characteristics of incipiently drowned carbonate banks or drowning sequences as known from the geological record

seismic geomorphology and evolution of early mid miocene isolated carbonate build ups in the timor sea north west shelf of australia abstract analysis of extensive 2d and 3d seismic data reveals the presence of about sixty isolated carbonate build ups icbs of early mid miocene age spreading over a wide area of the northwestern bonaparte basin individual build ups are 100 m thick with an average diameter of 3 km integration of full volume 3d seismic attribute analysis with extensive biostratigraphic and lithological data from exploration wells allows examining the evolution of icbs and their associated morphologies at high resolution the development of icbs took place above a seismically flat surface the stratigraphic architecture of the build ups typically consists of 1 mid burdigalian initiation tf1 cn2 2 lateral expansion during the late burdigalian cn3 and 3 backstepping and drowning during the langhian tf2 cn4 this is followed by sub aerial exposure that probably corresponds to a major sea level fall during the serravallian only small patch reefs pinnacles developed afterwards during the late miocene the observed growth phases of the icbs correlate with global sea level fluctuations and major changes in global climate and oceanography the role of local tectonics in the initiation and demise of these build ups appears as minimal growth of the northwestern bonaparte basin icbs is synchronous with the establishment of tropical carbonate factories elsewhere along the australia s north west shelf that suggest an acme of reef development during the early to middle miocene

oligocene and miocene carbonate platform development in the browse basin australian northwest shelf abstract extensive 2d and 3d seismic reflection data calibrated by wells provide new insights into the lateral extent morphology internal architecture and age of carbonate platforms in the subsurface of the browse basin australian northwest shelf nws the oldest carbonate build ups are interpreted as a giant bryozoan build up complex of oligocene age 34 03 27 8 ma in the late burdigalian tropical reef growth began and numerous reef rimmed carbonate platforms progressively coalesced into an extensive barrier reef from the mid langhian to the early tortonian the browse basin contained an elongate along margin barrier reef system over 500 km long this barrier reef possibly extended in the southwest into the northern carnarvon basin after the early tortonian reefs on top or landward of this major barrier reef system were smaller and less connected this significant reduction in area covered by reef rimmed platforms likely resulted from cooling following the mid miocene climate optimum and relatively high subsidence rates the reef rimmed carbonate platforms that formed between the late burdigalian and the early tortonian are very similar throughout the browse basin platform development after the early tortonian was regionally diverse high subsidence rates in the northern browse basin are interpreted to have promoted the development of thick aggrading platforms lower subsidence in the south led to thinner more widespread platforms recurrently shifting location in response to eustatic change the final phase of reef decline around 6 ma coincides with an increase in current driven drift sedimentation current related winnowing of sediments from the lagoons and slopes of the remaining carbonate platforms likely contributed to their final drowning

geomorphological evidence of carbonate build up demise on equatorial margins a case study from offshore northwest australia abstract the demise of miocene carbonate build ups in the browse basin northwest australia has been explained as relating to geological and oceanographic processes these include accelerated tectonic subsidence driven by subduction ocean cooling following the mid miocene climate optimum nutrient excess poisoning by sediment drifts and local erosion driven by current winnowing occurring discretely or simultaneously here we critically assess the evidence for these different mechanisms using a combination of high resolution 3 d seismic data regional 2 d seismic profiles and numerical stratigraphic forward modelling seismic interpretation and numerical modelling found that the proposed uniform subsidence rate of 125 m ma between 16 5 ma and 5 33 ma for the northern browse basin belde et al 2017 when combined with the published estimate of eustatic sea level in miller et al 2005 was insufficient to drown the miocene carbonate sequence and generate the geomorphological changes barrier reef to isolated carbonate build ups observed on seismic data instead a subsidence profile comprising pulses of rapid and slow subsidence is required significantly our results suggest that subsidence rates exceeded 400 m ma in the northern browse basin and that parts of the basin record the accumulation of sediment drifts these sediment drifts are interpreted to have buried some carbonate build ups while suspended sediment reduced light transmissivity inhibiting carbonate production thus we postulate that current activity and excess nutrient supply are key but often overlooked oceanographic processes that lead to the demise of carbonate build ups

pinnacle features at the base of isolated carbonate buildups marking point sources of fluid offshore northwest australia we investigated pinnacle features at the base of late oligocene miocene isolated carbonate buildups using three dimensional seismic and borehole data from the browse basin northwest australia brightened seismic reflections dim spots and other evidence of fluid accumulation occur below most pinnacle features an important observation is that all pinnacles generated topography on successive late oligocene miocene paleoseafloors therefore forming preferential zones for the settlement of reef building organisms by raising the paleo seafloor into the photic zone their height ranges from 31 m to 174 m for a volume varying from 33 km3 to 11 105 km3 most of the pinnacles however are less than 2000 km3 in volume and present heights of 61 80 m as a result of this work pinnacles are explained as the first patch reefs formed in association with mud volcanoes or methanogenic carbonates and they are considered as precluding the growth of the larger isolated carbonate buildups we postulate that pinnacle features above fluidflow conduits demonstrate a valid seep reef relationship and we propose them to be refined diagnostic features for understanding fluid flow through geological time

active deformation in eastern indonesia and the philippines from gps and seismicity data in this study we combine global positioning system gps velocities with information on the style of regional seismicity to obtain a self consistent model velocity and strain rate field for the entire eastern indonesia and philippines region in the process of interpolating 93 previously published gps velocities the style and direction of the seismic strain rate field inferred from earthquakes with m0 1 1020 n m from the harvard centroid moment tensor catalog are used as constraints on the style and direction of model strain rates within the plate boundary zones the style and direction of the seismic strain rate field are found to be self similar for earthquakes up to m0 1 1020 n m equivalent to mw 7 3 our inversion result shows the following the java trench which lacks any significant historic seismicity delineates the australian plate au sunda block sunda plate boundary west of the island of sumba east of sumba convergence is distributed over the back arc and banda sea and there is no subduction at the timor trough suggesting that the northern boundary of the au plate runs north of this part of the banda arc through the banda sea in new guinea most motion is taken up as strike slip deformation in the northern part of the island delineating the pacific plate pa au boundary however some trench normal convergence is occurring at the new guinea trench evidence that the strain is partitioned in order to accommodate oblique pa au motion pa au motion is consistent with nuvel 1a direction but 8 mm yr 1 slower than the nuvel 1a estimate for pa au motion the sulawesi trench and molucca sea delineate zones of high strain rates consistent with high levels of active seismicity the sulawesi trench may take up some of the au sunda motion philippine sea plate motion is in a direction slightly northward of the nuvel ia estimate and is partitioned in some strike slip strain rates along the philippine fault and relatively larger trench normal convergence along the philippine trench and on the philippine mainland in the southern philippines and along the manila trench in the northern philippine islands the high level of strain rate along the manila trench is not released by any significant historic seismic activity for the entire eastern indonesia philippines region seismicity since 1963 has taken up 40 of the total moment rate inferred from our model

syn sedimentary deformation as a mechanism for the initiation of submarine gullies on a carbonate platform to slope transition browse basin australian north west shelf abstract syn sedimentary deformation and submarine channel initiation are both important processes influencing the stratigraphic development and reservoir properties of carbonate platforms based on a high resolution 3d seismic dataset our study shows that platform margin parallel syn sedimentary faulting in the vicinity of the clinoform breakpoint can lead to the indention of channel heads that subsequently grow and expand in headward and downslope direction the carbonate dominated miocene succession of the browse basin on the australian north west shelf reveals a distinct submarine channel system during a time of overall platform progradation the progradation occurs over a drowned eocene to lower miocene carbonate ramp which formed a large scale inflection previous studies investigated the architecture of the carbonate platform containing a large neogene barrier reef system we present a high resolution 3d seismic study of the contemporaneous platform to slope transition landward of first significant gullies a distinct network of margin parallel small scale arcuate faults is observed active faulting during appearance of the first gullies is exhibited by growth strata which are located directly basinward of the faults these steep 65 85 small scale faults are characterized by throws of 5 25 ms twt and show a tendency to merge laterally and vertically with adjacent faults syn sedimentary deformation associated with these faults likely triggered slope failure and the generation of turbidity currents finally leading to the growth of the gullies by headward and downslope erosion

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

early pliocene closing of the indonesian seaway evidence from north east indian ocean and tropical pacific deep sea cores abstract deep sea cores from sites 214 and 758 a ninetyeast ridge north east indian ocean 761 b wombat plateau north east indian ocean and 586 b ontong java plateau tropical pacific are ideally located for comparison of late neogene planktic foraminiferal biogeography and paleoceanographic records of tropical indian and pacific oceans to infer the timing of closing of the indonesian seaway a consistent stratigraphy was developed between sites 214 and 586 b using graphic correlation and was integrated with the paleomagnetic time scale of berggren et al 1985 to provide an accurate chronology to compare interocean stratigraphic ranges of late neogene planktic foraminifera tropical planktic foraminifera occur throughout each sequence at all sites at each site the miocene pliocene boundary is defined by the first appearance of globorotalia tumida 5 2 ma the early late pliocene boundary by the first appearance of globigerinoides fistulosus 3 2 ma and the pliocene pleistocene boundary by the last appearance of g fistulosus 1 6 ma neogene planktic foraminiferal assemblages at sites 214 758a 761 b and 586b are generally similar until the beginning of the pliocene 5 2 ma when the faunal record indicates divergence a notable difference is complete absence of early pliocene taxon pulleniatina spectabilis from all the indian ocean sites this difference suggests that the indonesian seaway became an effective biogeographic barrier to planktic foraminifera at the beginning of the pliocene however there is still exchange of surface waters through this seaway earlier studies suggested a middle to late miocene occurrence for this biogeographic barrier p spectabilis evolved from p primalis in the equatorial pacific at about 5 2 ma it is a short ranging early pliocene species spanning about 1 3 my and occurred only in pacific unlike earlier suggestions of a broader distribution into the indian ocean

spatial and temporal patterns of cenozoic dynamic topography around australia 1 despite its importance the spatial and temporal pattern of dynamic topography generated by mantle convective circulation is poorly known we present accurate estimates of dynamic topography from oceanic basins and continental margins surrounding australia our starting point is measurement of residual depth anomalies on the oldest oceanic floor adjacent to the continental shelf these anomalies were determined from a combined dataset of 200 seismic reflection and wide angle images of well sedimented oceanic crust they have amplitudes of between 1 km and 0 5 km and their spatial variation is broadly consistent with long wavelength free air gravity and shallow seismic tomographic anomalies along the northwest shelf a regional depth anomaly of 300 to 700 m intersects the adjacent continental shelf the temporal evolution of this anomaly was determined by analyzing the stratigraphic architecture of an extensive carbonate platform which fringes the shelf and records a dramatic switch from progradation to aggradation during neogene times three dimensional seismic mapping calibrated by boreholes was used to calculate water loaded subsidence histories at rollover points of clinoforms along the shelf at 9 3 ma the rate of subsidence increases from 5 to up 75 m myr 1 generating a subsidence anomaly of 300 to 700 m the amplitude of this anomaly varies along the shelf and cannot be generated by glacio eustatic sea level variation instead we propose that a regional subsidence episode which affects both the proximal shelf and the distal oceanic basin was generated by convective drawdown by combining our results with other published estimates of uplift and subsidence a map of australia which shows the spatial and temporal pattern of dynamic topography is presented most but not all of australia s epeirogeny can be attributed to rapid northward motion of the australian plate over a pre existing pattern of convective circulation

styles of eruptive activity on intraplate volcanoes in the society and austral hot spot regions bathymetry petrology and submersible observations submersible observations carried out in the society and austral hot spot regions south pacific during the teahitia ii cruise 1988 1989 enable us to propose a model relating the style of volcanism to the depth of eruption on large intraplate seamounts 1 the bases of volcanic edifices are characterized by broad flat flows formed during a high rate of discharge of a very fluid magma on the sea floor 2 the edifices flanks deeper than 500 m are mainly made up of bulbous tubular pillows and large drained lava tunnels occurring on slopes steeper than 60 70 these lava flows occur on lateral volcanic vents about 200 300 m high along linear rift zones which are formed on the flank of the major edifices 3 volcanic ejecta due to hydromagmatic eruptions occur at shallow depths 500 m in height are individual conical features built at a high rate of volcanic discharge localized along radial linear eruptive fissures called rift zones the slopes located between the rift zones are covered by talus material are limited and unimportant mass wasting sector collapse features were observed on the edifices the conical shaped features are the primary morphology of the intraplate volcanoes formed during edifice growth which is closely linked to the hydrostatic pressure of the magmatic column the mean values of the slopes 11 17 of intraplate seamounts are the same as those of subaerial intraplate shield volcanoes when the seawater hydrostatic pressure is taken into account

tectonically driven changes in the indian ocean circulation over the last 25 ma neodymium isotope evidence abstract changes in ancient oceanic current patterns have been strongly influenced by plate tectonics particularly by the opening or closing of gateways between different oceans such modifications of oceanic circulation have important consequences on climate we studied the nd seawater isotopic composition of indian and pacific ocean cores using nd isotopes which are good paleo oceanographic tracers we focused on the past 25 ma which are marked by the closure of the indonesian gateway as well as the mediterranean connection we show that a strong westerly oceanic surface current which we refer to the miocene indian ocean equatorial jet miojet linked the eastern and western indian ocean from 14 ma to 3 ma and infer that this major change in oceanic circulation probably induced important variations of global climate