deep sea carbonates reading the carbon isotope signal the carbon isotope signal in deep sea sediments reflects a mix of 1 global changes in the rates of exchange of the ocean s carbon reservoir with biosphere soil and sediments 2 global and regional changes in surface water productivity 3 internal shifts in water mass structure and circulation basin basin fractionation oxygen minimum development and 4 organism specific fractionation effects due to changes in micro habitat and or ontogenic fractionation vital effects additional complications arise from differential preservation it is impossible to entirely isolate these various factors as a rule of thumb long period signals that are parallel for planktonic and benthic data reflect external global fractionation patterns whilst short period signals are more likely tied to internal patterns water mass fractionation the various approaches to interpretation are illustrated with three case studies the glacial holocene transition the messinian carbon shift and the miocene monterey excursion

sedimentological characteristics and facies of the evaporite bearing kirmir formation neogene beypazari basin central anatolia turkey a thick sedimentary sequence comprising fluvial lacustrine and volcano sedimentary rocks is present in the neogene beypazari basin central anatolia these units display considerable lateral facies variation and interfinger with alkaline volcanic rocks along the north eastern margin of the basin the uppermost miocene kirmir formation contains rlumerous evaporite horizons the evaporite sequence is up to 250 m thick and may be divided into four lithofacies in ascending stratigraphical order these are 1 gypsiferous claystotie facies 2 thenardite glauberite facies 3 laminar gypsum facies and 4 crystalline gypsum facies these facies interfinger with one another laterally along a section from the margins to central parts of the basin the lithological and sedimentological features of the kirmir formation indicate fluvial saline playa mudflat hypersaline ephemeral playa lake and very shallow subaqueous playa lake depositional environments which probably were influenced by alternating semi arid and evaporative conditions

miocene transgression in the central and eastern parts of the sivas basin central anatolia turkey and the cenozoic palaeogeographical evolution we present here a reappraisal of the tectonic setting stratigraphy and palaeogeography of the central part of the sivas basin from palaeocene to late miocene the sivas basin is located in the collision zone between the pontides southern eurasia and anatolia a continental block rifted from gondwana the basin overlies ophiolites that were obducted onto anatolia from tethys to the north the central anatolian crystalline complex cacc experienced similar ophiolite obduction during campanian time followed by exhumation and thrusting onto previously emplaced units during maastrichtian time to the east crustal extension related to exhumation of the cacc created grabens during the early tertiary including the sivas basin the sivas basin underwent several tectonic events during paleogene neogene the basin fill varies with several sub basins each being characterised by a distinctive sequence especially during oligocene and miocene evaporite deposition in the central part of the basin during early oligocene was followed by mid late oligocene fluvio lacustrine deposition the weight of overlying fluvial sediments triggered salt tectonics and salt diapir formation lacustrine layers that are interbedded within the fluviatile sediments have locally yielded charophytes of late oligocene age emergent areas including the pre existing sivas basin and neighbouring areas were then flooded from the east by a shallow sea giving rise to a range of open marine sub basins coralgal reef barriers and subsiding restricted marine sub basins utilising new data from foraminifera molluscs corals and nannoplankton the age of the marine transgression is reassessed as aquitanian specifically age diagnostic nannoplankton assemblages of classical type occur at the base of the transgressive sequence however classical stratigraphic markers have not been found within the planktic foraminiferal assemblages even in the open marine settings in the restricted marine sediments there are rich planktic foraminiferal assemblages of classical type but these are of little use in stratigraphy in contrast the gastropod fauna indicate a burdigalian age sediment reworking in the restricted marine environments precludes stratigraphic determination in such environments micro and nano organisms experienced atypical developmental conditions the small benthic foraminifera and associated ostracod assemblages are good indicators of salinity which varied considerably within the restricted marine sub basins some of the corals within the coralgal reefs barriers are also dated as aquitanian a combination of the salt tectonics and the late miocene north westward verging thrusting created the present basin complexity

tertiary evolution of the sivas basin central turkey abstract the sivas basin is one of several basins in turkey formed during closure of the northern branch of neotethys in early tertiary times cretaceous ophiolitic fragments and eocene platform carbonates and volcaniclastics transported northwards into the basin as olistoliths and grain flow aprons were incorporated into autochthonous eocene turbidites and bioclastic limestones the sequence as a whole was thrust northwards in late eocene times a southward sloping terrestial foreland basin related to northward directed thrusting developed during oligocene times a piggy back basin developed on top of this thrust system during the late oligocene the eocene thrusts were reactivated probably resulting in northward propagation of thrusts in the subsurface in early and mid miocene times the basin was floored by a thrust sheet which had been cut by n s trending tear faults or oblique culminations as a result of non uniform thrust advance in pre miocene times these n s faults were subsequently reactivated as extensional faults radial to the thrust front during early to mid miocene alluvial and shallow marine sedimentation later strike slip displacement along the n s faults was associated with the development of the northern boundary fault of the sivas basin in late miocene times which is regarded as a left lateral transpressive fault related to the north anatolian fault zone

clastic petrofacies provenance and organic facies of the bozbel formation lutetian in the eastern sivas basin turkey abstract the bozbel formation lutetian of the eastern part of the sivas basin central anatolia turkey displays a range of lithofacies which vary greatly in thickness the formation consists of conglomerates sandstones mudstones and shales marls limestones and sandy limestones clayey limestones tuffites and volcanic breccias the aim of this study is to determine the clastic petrofacies of the sandstones and to describe the characteristics of the organic facies and source rocks present in the bozbel formation the sandstones can be classified essentially as arkoses lithic arkoses and feldspathic litharenites cement rich and containing minor amounts of olivine pyroxene chlorite biotite muscovite and opaque minerals these sands were derived from magmatic arc and mixed provenances the source rock characters of the finer grained bozbel rocks and their organic facies have been determined by means of total organic carbon t o c analyses rock eval pyrolysis vitrinite reflectance data and clay mineral paragenesis together with illite crystallinity values the organic matter content is dominated by type 3 kerogen illite crystallinity indices and vitrinite reflectance data run parallel with each other and are consistent with the catagenetic stage of organic matter evolution the bozbel formation in the south hafik region is appropriately mature to yield hydrocarbons but because of the generally low content of organic matter it is unlikely to have generated petroleum but is known to be gas prone

the hunghae formation se korea miocene debris aprons in a back arc intraslope basin during early to middle miocene times a sudden opening of the ulleung tsushima back arc basin in the east sea sea of japan led to the development of intraslope basins along the rifted southwestern margin southeast korea abrupt subsidence resulted in the deposition of the 200 m thick hunghae formation middle miocene a sand mudstone sequence that can be divided into five facies facies i sand and mudstone couplet and ii coarse sand are turbiditic in origin as evidenced by massive graded crudely layered and parallel laminated sand beds facies iii homogeneous mudstone is characterized by various lignite and plant fragments clastic and biogenic grains that are randomly oriented suggestive of hemipelagic deposition facies iv chaotic deposit is characterized by the disruption of beds the presence of isolated siltstone blocks or balls and large clasts in the muddy matrix indicative of retrogressive rockfall and slide slump facies v conglomerate is of debris flow origin as evidenced by clast and matrix supported features floating large clasts and absence of traction structures individual facies are organized into two types of facies association 1 homogeneous mudstone facies iii associated randomly with the rest facies i ii iv and v indicative of hemipelagic and episodic sediment gravity flow processes respectively 2 conglomerate facies v coarse sand facies ii and sand mudstone couplet facies i representing the flow transformation from debris flow to high and low concentration turbidity currents these facies associations are similar in many respects to modern and ancient debris or slope aprons found elsewhere numerous isolated slide slump blocks wedged conglomerates with armoured mudstone balls discontinuous lignite containing sand mudstone beds chaotic structure and growth faults suggest that the deposition occurred on a steep slope intraslope basin off coalescing fan deltas mainly by unchannellized sediment gravity flows ancient deposits with irregular facies sequences can be viewed as debris apron systems which provide alternatives to submarine fan models in many clastic basins with a line rather than point source

regional setting and role of meteoric water in dolomite formation and diagenesis in an evaporite basin studies in the zechstein permian deposits of poland the zechstein basin of poland was an area of widespread cyclical deposition of carbonates and evaporites during late permian time the zechstein shelves along both the northern and the southern margins of the basin were sites of shallow water sedimentation during the formation of the main dolomite and platy dolomite two widespread carbonate units these units consist of oolitic peloidal skeletal micritic and evaporitic carbonates formed in depositional settings ranging from open marine to coastal lagoonal sabkha and salina although originally deposited as limestones the main dolomite and platy dolomite are inferred to have been completely replaced by dolomite through very early stage essentially penecontemporaneous reflux of hypersaline brines the dolomites of the two basin margins however have very different petrographic and isotopic characteristics many northern shelf dolomites show early stage calcitization dedolomitization and even in some cases evidence of a subsequent redolomitization event these northern shelf samples also have a broad range of carbon and oxygen isotopic ratios up to 12 0 for oxygen samples from the southern shelf on the other hand are petrographically much simpler they do not show complex calcitization and redolomitization patterns likewise their isotopic values are much more tightly clustered with only about a 5 0 range of oxygen isotopic ratios the differences between dolomites of the same age from the northern and southern margins are best explained by regional variations in river water influx during episodic exposure events associated with regional or global sea level fluctuations the distribution of clastic terrigenous materials and palaeokarstic features indicate that areas of the northern shelf had extensive river input an influx largely lacking on the southern shelf early formed dolomites appear to have been calcitized during sea level lowstands through the infiltration of meteoric fluids into the evaporitic dolomites created during the previous highstand in some cases redolomitization occurred when meteoric fluids were again replaced by hypersaline brines during subsequent sea level highstands although repeated sea level fluctuations are clearly evident in these strata it is likely that associated climatic changes rainfall variations also played a role in forming these complex diagenetic patterns age equivalent strata from texas and new mexico from sites at much lower palaeolatitudes show no such alteration patterns samples from greenland slightly higher palaeolatitudes show even more intense diagenetic alteration during depositional cycles thus the examination of patterns of diagenesis may be useful in interpreting ancient palaeolatitudinally sensitive climate patterns

dynamic stratigraphy of an evaporite to red bed sequence gipskeuper triassic southwest german basin abstract the dynamics of evaporite accumulation are studied in the gipskeuper triassic of the southwest german epicontinental basin based on a hierarchical three level stratigraphic analysis 1 among the various stratification types the following are most important a thin carbonate intervals with marine faunas b massive sulfates with selenite indicating very shallow subaqueous gypsum precipitation c thin bedded gypsarenites with a variety of sedimentary structures suggesting clastic evaporite accumulation during high energy events gypsum tempestites d laminated gypsum with spectacular tepee structures testifying inter to supratidal settings e green grey and reddish claystones with nodular gypsum indicating evaporitic playa mudflats 2 facies sequences occur in several varieties and commonly form 1 4 m thick transgressive regressive cycles with shallowing upwards trends the long recognized carbonate marker beds represent short term trans or ingressions into the almost flat keuper basin highly disturbed tepee horizons form widely correlatable regressive peaks these sequences form evaporite equivalents to the ubiquitous shallowing upward cycles known from carbonate systems 3 the basin fill consists of a small scale cycles being vertically stacked upon each other to form the basic building block of the layer cake architecture of the gipskeuper succession the stacking of small scale cycles is superimposed onto a larger scale regressive cycle which records a general shift from restricted marginal marine to hypersaline marine to the more continental red bed deposition of the overlying keuper this hierarchy of cycles probably reflects various orders of eustatic sealevel fluctuations the gipskeuper thus exemplifies dynamics of evaporite accumulation and allows us to understand some of the processes that produce a layer cake stratigraphy its cycle hierarchy is a common motif in the entire southwest german basin fill and appears typical for epicontinental basins

neogene planktonic foraminifera and events in japan abstract the warm water constituents of successive neogene planktonic foraminiferal assemblages in japan are identified and expressed as percentages of the total planktonic fauna by this means five major events have been recognized 1 a marine temperature optimum in the earliest middle miocene zone n8b 2 an abrupt cooling since early middel miocene time 3 a rise in temperature culminating in latest miocene to earliest pliocene time zones n17b and n18 4 an accelerated evolutionary event during the early pliocene zone n19b n21a 5 a short warm episode in the early pliocene zone n21a

depositional processes paleoflow patterns and evolution of a miocene gravelly fan delta system in se korea constrained by anisotropy of magnetic susceptibility analysis of interbedded mudrocks abstract anisotropy of magnetic susceptibility ams has been used as a proxy of grain fabrics and as a basis of interpretation of depositional processes and paleocurrent directions in sedimentary successions in this paper we present the results of the ams analysis of over 900 core specimens from the sandy to muddy deposits intercalated between the gravelly deposits of a miocene fan delta system in se korea analyses of the mean magnetic susceptibility thermomagnetic property and hysteresis show that paramagnetic minerals are the main contributors to the ams of the deposits the ams analysis shows that the deposits have four types of magnetic fabrics including 1 horizontal and type a imbricated fabrics characterized by girdle distributed to weakly clustered k 1 and k 2 axes on the bedding plane and subvertical to variably tilted k 3 axes 2 type b imbricated fabric characterized by well clustered k 1 and k 2 axes and subvertical to tilted k 3 axes and 3 rolling fabric characterized by streak distributed k 2 and k 3 axes along a plane perpendicular to the k 1 axes these fabric types are interpreted to have resulted from suspension settling horizontal and type a imbricated fabrics turbidity currents type b imbricated fabric and debris flows rolling fabric modification of the primary fabrics during sediment compaction on a slope resulted in a wide range of imbrication angles in all fabric types paleocurrent directions inferred from the ams data are generally consistent with those obtained by previous field studies of the gravelly sequences and provide additional information of the temporal change of the paleoflow pattern which is related to the growth exhumation and dissection of the fan delta system this study thus suggests that much information can be drawn from the ams analysis of mudrocks regarding not only the depositional processes and paleoflow pattern but also the evolution of a depositional system

timing of rotational motion of southwest japan inferred from paleomagnetism abstract paleomagnetic field directions for the period younger than 35 ma are obtained from igneous rocks distributed in the san in district inner zone of southwest japan the remanent magnetization of samples between 30 and 35 ma old are fairly well grouped with a mean direction of d 65 9 i 48 6 and 95 6 5 this result establishes that southwest japan rotated clockwise 56 12 during the past 30 m y a declination value of about 60 is observed in the rocks of 28 ma d 52 2 i 33 5 and 21 ma d 69 9 i 49 5 comparing this with results from dacitic rocks with an age of 15 ma in other areas of southwest japan suggests that rotational motion did not occur possibly until 15 ma these results require that the rotation of southwest japan occurred just after the shikoku basin had been created

distinct sedimentary processes reflected in the isotopic signatures of dolomitic concretions in the miocene pohang basin southwestern east sea abstract dolomitic concretions in diatomaceous hemipelagic sediments of the miocene pohang basin in the southwestern east sea sea of japan preserve distinct signals of two independent sedimentary processes which controlled the extents of isotopic compositions variable 18o 9 1 to 0 7 and high 13c 3 1 to 17 9 values suggest that the concretions formed in the methanogenic zone with alteration of the residual mid miocene seawater by volcanogenic sediments remarkable 18o and 13c values show a strong linear relationship indicating that distinctly independent depositional processes operated during the formation of the concretions the degree of methanogenesis was enhanced during rapid hemipelagic sedimentation of organic rich particles resulting in higher 13c values and the effect of volcaniclastics was diluted maintaining the original properties of ambient mid miocene seawater in contrast lower 18o and 87sr 86sr values characterize the effect of volcaniclastic sediments that were transported by intermittent gravity flows and interacted with mid miocene seawater the input of volcaniclastic sediment probably degraded the role of methanogenesis by lowering the contents of organic matter and thereby decreased the 13c values within the concretions isotopic signals recorded within the concretions highlight understanding of the depositional environment and evolution of the pore water chemistry

present day stress field modelling of southern italy constrained by stress and gps data abstract the present day tectonic setting of the italian peninsula is very complex and involves competing geodynamic processes in this context southern peninsular italy is characterised by extension along the apenninic belt and in the tyrrhenian margin and by transpression in the apulia gargano region the extension is well defined by means of geological seismological and contemporary stress data for the latter only few data are available in the apulia gargano region leaving the state of stress in that area unresolved here we develop a finite element model of the southern italian region in order to predict the contemporary stress field our model predictions are constrained by model independent observations of the orientation of maximum horizontal stress s hmax the tectonic regime and the horizontal velocities derived from gps observations we performed a blind test with 31 newly acquired s h max orientations in the southern apennines these new data come from the analysis of orehole breakouts performed in 46 deep oil exploration wells ranging in depth from 1300 to 5500 m the model results agree with the stress data that define a prevailing nw se s h max orientation along the apenninic belt and foredeep and thus are capable to predict the stress field where no stress information is available we first analyse how much model predictions based on older data deviate from present day stress data and then recalibrate the models based on our new stress data giving insight into the resolution of both models and data in the studied region which is affected by low deformation rates we find that geodetic data alone cannot resolve such low levels of deformation due to the high relative measurement errors we conclude that both gps and stress data are required to constrain model results

messinian pre evaporite sapropels and precession induced oscillations in western mediterranean climate abstract cyclical fluctuations in planktic foraminiferal assemblages have been recognized in the pre evaporitic messinian in a marginal basin of the western mediterranean the fluctuations coincide with a dominantly precession controlled sedimentary cyclicity sapropels during sapropel deposition high planktic foraminiferal diversities are indicative of relatively stable marine conditions while during homogeneous marl deposition low diversities seem to indicate the presence of unfavourable more saline surface water conditions the dominance of a precession related signal indicates that regional climate oscillations rather than obliquity related glacio eustatically controlled influxes of atlantic and or mediterranean waters are responsible for the faunal fluctuations and sedimentary cyclicity our scenario links the persistence of normal marine conditions during sapropel formation with increased rainfall and run off along the western mediterranean at times that perihelion occurred in northern hemisphere summer less favourable highly saline surface water conditions prevailed during periods of drier climate induced by opposite precessional extremes the cyclical oceanographic fluctuations could also have governed periodic reef growth along the margins

paleoenvironmental changes associated with the holocene marine transgression yellow sea hwanghae benthic foraminiferal and stable isotopic data from two radiocarbon dated cores from the yellow sea record paleoenvironmental changes largely associated with the holocene marine transgression the holocene marine transgression began significantly earlier 12 9 ka in the central part of the yellow sea as recorded in 278 cm long core cc 02 water depth 77 5 m compared with 7 9 ka in a tidal flat on west coast of korea as recorded in 350 cm long vibra core dh4 1 water depth 1 8 m the benthic foraminiferal assemblages in the lower part of cc 02 and the entire marine sequence of dh4 1 are dominated by assemblages characteristic of shallow 50 m waters ammonia ketienziensis ishizaki astrononion italicum cushman and edwards and hanzawaia nipponica asano after 7 5 ka in the central yellow sea much higher 18o 1 6 to 1 8 and 13c 0 1 to 0 7 values of a ketienziensis reflect a change to more open ocean higher salinity environments with deeper waters dominated by the hwanghae cold water as in the present day

fluvial aeolian interactions part i modern systems two modern fluvial aeolian depositional systems great sand dunes national monument colorado and the mojave river wash california are remarkably similar in spite of different climates sizes fluvial sediment textures and relative directions of aeolian and fluvial transport dune growth and migration and deflation of blowouts create 8 10 m of local relief in unflooded aeolian landscapes there are six prominent fluvial aeolian interactions 1 fluvial flow extends into the aeolian system until it is dammed by aeolian landforms 2 interdune areas overbank interdunes upstream of aeolian dams and alongside channels are flooded 3 water erodes dunes alongside channels and interdunes 4 flood waters deposit sediment in interdune areas 5 fluvially derived groundwater floods interdunes interdune playas 6 wind erodes fluvial sediment and redeposits it in the aeolian system unique and characteristic sediments are deposited in overbank interdunes and in interdune playas reflecting alternate fluvial and aeolian processes and rapidly changing flow and salinity conditions these fluvial aeolian interdune deposits are characterized by irregular concave up bases and flat upper surfaces containing mudcracks or evaporite cement characteristic low relief surfaces form in aeolian systems as an effect of flooding fluvial deposits are resistant to aeolian deflation aeolian sand is preserved when flood sediments are deposited around the bases of the dunes thus repetitive fluvial and aeolian aggradation tends to be stepwise as interdune floors are suddenly raised during floods the effects of flooding should be easy to recognize in ancient aeolianites even beyond the area covered with overbank muds

neogene events in japan and the pacific abstract based on a refined distribution chart of marine molluscan faunas of japan in time and space some key neogene events in japan are discussed with reference to those in the pacific region the mid neogene climatic optimum around 16 ma and a cooling of seawater temperature since 15 ma are considered to be of pan pacific scale the opening of the sea of japan began around 16 ma simultaneously with the climatic optimum two tectonic events the closing of the indonesian seaway and of the central american seaway possibly caused episodes of warm seawater temperatures on the pacific side of japan at 6 ma and 3 ma respectively the izu peninsula on the pacific side of central japan was a volcanic island in the tropical pacific in early miocene time during the northward drift of the island relict species of lepidocyclina manifested an evolutionary change and lasted until 5 ma biotic evolutionary accelerations found in some endemic mollusca of japan since 3 ma are most likely due to phased drops of seawater temperature

evolution of the miocene waup basin se korea in response to dextral shear along the southwestern margin of the east sea sea of japan abstract the waup basin se korea is a nonmarine basin created coevally with the back arc opening of the east sea sea of japan during the miocene the basin is bounded by normal faults in the northwestern and southeastern margins and by dextral strike slip faults in the northeastern and southwestern margins a number of intrabasinal faults with dextral strike slip and normal senses of slip are also present delineating three structural domains of the basin i e the ne central and sw blocks the basin fills composed of alluvial to lacustrine deposits and dacitic to basaltic volcanogenic rocks have the geometry of a half graben in the ne and central blocks and a graben in the sw block they are younging from the ne to the sw blocks suggestive of propagating rifting of the basin and associated depocenter migration structural and stratigraphic data suggest that the ne and central blocks were produced by nw se extension during the early miocene 22 17 ma involving northwestward block tilting and subsequent clockwise horizontal block rotation on the other hand the sw block formed at about 17 ma by nw se extension and experienced neither block tilting nor block rotation the reconstructed configuration of the waup basin is that of a pull apart basin produced by nnw directed dextral strike slip stress and associated nw se extensional stress the ages of the basin fills ca 22 to

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

the middle miocene climatic transition east antarctic ice sheet development deep ocean circulation and global carbon cycling abstract the middle miocene represents a major change in state in cenozoic climatic evolution following the climax of neogene warmth in the late early miocene at 16 ma the early stage of this climatic transition from 16 to 14 8 ma was marked by major short term variations in global climates east antarctic ice sheet eais volume sea level and deep ocean circulation in the later stage from 14 8 to 12 9 ma climatic developments included major growth of the eais and associated antarctic cooling a distinct increase in the meridional temperature gradient large fluctuations in sea level followed by a global sea level fall and important changes in deep water circulation including increased production of southern component water east antarctic ice sheet growth and polar cooling also had large effects on global carbon cycling and on the terrestrial biosphere including aridification of mid latitude continental regions increased stability of the eais after 14 8 ma represents a crucial step in the establishment of late neogene global climate systems what controlled these changes in polar climates and the east antarctic ice sheet deep ocean circulation changes probably played a major role in the evolution and variation in polar climates as they have throughout the cenozoic oxygen and carbon isotopic evidence for warm saline deep water production in the eastern tethyan northern indian ocean indicates that meridional heat transport to the antarctic inhibited cenozoic polar cooling and eais growth during the early middle miocene from 16 to 14 8 ma inferred competition between warm low latitude sources derived from the eastern tethyan northern indian ocean and a cold high latitude source southern component water from 16 to 14 8 ma may have been associated with instability in the antarctic climate and cryosphere reduction of warm saline deep water flow to the southern ocean at 14 8 ma may have decreased meridional heat transport to the antarctic cooling the region and leading to increased production of southern component water these middle miocene climatic and cryospheric changes in the antarctic had profound effects on marine and terrestrial climates as the meridional surface temperature gradient increased boundaries between climatic zones strengthened leading to increased aridification of mid latitude continental regions in australia africa and north and south america enhancing the development of grasslands and stimulating the evolution of grazing mammals

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

sandy high energy flood sedimentation some criteria for recognition with an example from the devonian of s w england abstract many modern sand deposits resulting from episodic floods in semi arid zones are dominated by parallel laminations but parallel laminated sands are not a major feature in perennial streams single flood events may deposit over 1 5 m of parallel laminated sand hence ancient parallel laminated sand dominated alluvial deposits may be the product of ephemeral flows the trentishoe formation hangman sandstone group middle devonian of north devon consists in part of laterally extensive beds of parallel laminated fine grained red sandstones that build multistorey sand bodies individual beds are little more than 1 m thick but may extend laterally for hundreds of metres a vertical sequence of erosion surface sparse silt clasts parallel laminations silt drape is often found suggesting high flow stage deposition of plane bedded sand followed by a very rapid waning of flow with silt fallout in the final stages of the flood this sequence bears marked similarity to certain modern ephemeral flow sands

fluvial processes and cyclicity in terminal fan deposits an example from the late devonian of southwest ireland abstract the gun point formation is a sandstone dominated sequence approximately 1 5 2 5 km thick which forms part of a major 6 km late devonian alluvial basin fill succession in southwest ireland it is interpreted as the deposits of a southerly flowing terminal fan system which operated under a semi arid climate the proximal zone was characterized by low sinuosity gravelly feeder channels which passed downstream into a medial zone dominated by a sandy braidplain further south in the distal zone phases of high energy flood activity were centred on transient low sinuosity ephemeral channels and were separated by more quiescent periods of shallow sheetflooding subaerial exposure and non deposition sedimentary parameters such as set thickness coset thickness channel sand body density and maximum sand body thickness all exhibit regular cyclic fluctuations with a periodicity of 160 180 m the cycles are interpreted as evidence of regular discharge variations which may have been a response to the 412 ka orbital eccentricity cycle a second periodicity of approximately 700 m has also been detected and is thought to reflect long term variations in basin subsidence

early neogene biochemostratigraphy of pohang basin a paleoceanographic response to the early opening of the sea of japan east sea abstract the location of the pohang basin near the korea strait in the southwest of the sea of japan east sea makes this area appropriate for providing a record of paleoenvironmental biotic changes associated with the early neogene 16 5 ma opening of this gateway to the pacific ocean stable isotopic and planktonic foraminiferal records are presented that assist with the understanding of paleoenvironmental changes in the sea of japan resulting from the opening of the korea strait the oldest sediments of early neogene age of the pohang basin overlie cretaceous basement and are early miocene 16 5 ma shallow estuarine facies containing a benthic foraminiferal assemblage dominated by ammonia beccarii l the oldest early neogene planktonic foraminiferal assemblages in the basin are 16 5 ma in age latest early miocene foraminiferal zone n8 the migration of these planktonic assemblages to the sea of japan at that time appears to have resulted from the initial opening of the korea strait the overlying early neogene marine sequence of the pohang basin extends from 16 5 ma zone n8 through 14 ma zone n10 change in the oxygen isotopic record of the pohang basin sequence suggests strong local paleoenvironmental control related to the early opening of the korea strait early middle miocene isotopic temperatures of planktonic foraminifera are relatively cool at 15 ma at a time when global temperatures were high in the middle low latitude regions it was not until 14 8 ma that isotopic temperatures of planktonic foraminifera increased markedly this distinct warming is inferred to reflect the major intrusion of the kuroshio current into the sea of japan probably as a result of further critical opening and deepening of the korea strait at this time planktonic foraminifera increased in abundance reflecting expanding oceanic influence a cooling that followed at 14 5 ma when the strait was well open is unlikely to reflect local tectonic control on the paleoceanography but global cooling during the early middle miocene associated with the expansion of the east antarctic ice sheet

the hydrological setting occurrence and significance of gypsum in late quaternary salt lakes in south australia well exposed often laminated gypsum sequences occur in many quarternary salt lakes in southern south australia the gypsum in the salt lakes is classified by increasing grain size into gypsite gypsarenite and selenite the salt lakes are classified by age and hydrological setting into coastal salinas which are holocene sea water fed groundwater lakes and continental playas which are late pleistocene endorheic basins a study of the relationships between coastal salina hydrology and the associated gypsum deposition has shown the different types of gypsum form under distinct hydrological regimes as the hydrology above a coastal salina depositional surface changes through time so does the type of gypsum deposited application of a gypsum depositional model derived from a study of the coastal salina gypsum to those portions of a continental playa gypsum unit where deposition is no longer occurring confirms the applicability of the model to non salina gypsum deposits

sedimentary and diagenetic markers of the restriction in a marine basin the lorca basin se spain during the messinian abstract the lorca basin southeastern spain is part of a chain of small marginal neogene basins located in the structurally active betic area the upper miocene messinian sequence is composed of a thick diatomite bearing series tripoli unit overlain by the main evaporites analogous to the classical succession that records the main events during the salinity crisis in the mediterranean region the shallow restricted conditions of this region amplified the sedimentary responses to local and global forcings an integrated approach using sedimentology micropalaeontology stable isotope geochemistry and organic geochemistry has been applied to the tortonian messinian succession of the lorca basin in order to obtain a continuous record of the environmental changes the sediments record two major events which affected the whole mediterranean 1 high levels of productivity that led to the formation of the diatomite bearing deposits in the early messinian tripoli and 2 the messinian salinity crisis with its two major stages represented by the halite and gypsum units both mainly precipitated from marine derived brines the rapid reflooding of the mediterranean by normal marine waters at the base of the pliocene did not reach the lorca basin nor other basins of this part of the betic area instead continental sediments were deposited as a consequence of the regional uplift of se iberia which started close to the messinian pliocene boundary the most prominent feature of this basin concerns the record of its restriction by the time of the deposition of the tripoli unit which led to intercalations of precursor evaporitic layers consisting of ca sulphate deposited in sub aqueous and sabkha conditions interbedded with diatomites this alternation of evaporites and diatomites proves that the lorca basin was periodically restricted and reflooded by marine waters a possible cause for this being relative sea level fluctuations in the mediterranean this strengthens evidence of diachronism that suggests that the onset of the first messinian evaporitic deposition was not synchronous but was dependent on bathymetry and local tectonics high productivity during the early messinian in this basin is demonstrated by the thick deposits of diatomites however stagnation episodes may have occurred during this interval as suggested by the preservation of high amounts of organic matter organic rich shales and the extent of bacterial sulphate reduction which apparently occurred during early diagenesis the formation of organo sulphur compounds replacement of sulphates by carbonates and the high levels of elemental sulphur are by products of diagenetic processes occurring in a restricted hypersaline environment

synrift stratigraphic geometry in a transfer zone coarse grained delta complex miocene pohang basin se korea the gojusan fan delta is a coarse grained delta complex on the western margin of the miocene pohang basin se korea the deposits consist of five facies associations fa alluvial fan conglomerates fa i shallow marine mouthbar sandstones fa ii fluvial and mouth bar conglomerates fa iii gilberttype foreset conglomerates fa iv and hemipelagic mudstones fa v different facies associations characterize the northern central and southern parts of the delta complex to the north fa iv is laterally juxtaposed with fa i or the basement with scarp derived breccias along the contact centrally and to the south fa i is laterally juxtaposed with fa ii with an abrupt facies change and local inliers of basement rocks along the contact early alluvial fan and mouth bar deposits are overlain by the topset fa iii and truncated by the foreset fa iv of a gilbert type delta in the central part of the fan delta complex whereas fa ii passes transitionally upward into fa iii in the south with the latter extending basinward into a gently inclined shoal water delta front gilbert type and shoal water geometries are therefore developed in the same delta complex the composite delta geometry is interpreted as reflecting 1 its development near an extensional transfer zone where the hangingwall relief was variable over short distances along strike and 2 the operation of intrabasinal faults this interpretation contrasts with previous studies that viewed the delta complex as having formed along a pull apart basin margin

sedimentology and evaporite genesis in a holocene continental sabkha playa basin bristol dry lake california bristol dry lake a 155 km2 continental sabkha playa basin in the mojave desert of south eastern california is filled with at least 300 m of interbedded terrigenous clastics gypsum anhydrite and halite evaporite facies conform approximately to a bull s eye pattern with gypsum and anhydrite surrounding a basin centre accumulation of halite transects through bristol dry lake from the alluvial fan to the centre of the playa reveal 1 crudely bedded alluvial fan clastics interfingering with 2 playa margin sand flat and wadi sand and silt followed by 3 gypsum anhydrite chaotic mud halite and clay of the saline mud flat and 4 salt pan halite beds terrigenous clastics were deposited in bristol dry lake by sheetflow and by suspension settling from ponded floodwater some sediment has been reworked by aeolian processes to form barchan dunes around the playa margin thin nodular like beds of anhydrite and several types of gypsum occur across most of the playa giant hopper shaped halite cubes are suspended in saline mud flat facies suggesting that they grew displacively in brine soaked sediment just below the surface thick beds 4 m of halite in the playa centre may have formed through a complex alternating history of subaqueous and intrasedimentary precipitation under the influence of periodic floods intense evaporation and brine level lowering and capillary discharge of brines the stratigraphy in the playa centre is cyclic an ideal cycle consists of 1 chaotic mud halite at the base overlain by 2 green to red clay with abundant giant hoppers and at the top 3 red clay gypsum and anhydrite with flaser to wavy bedded sand and silt this type of cycle probably records a gradual progradation of mud flat facies over salt pans bristol dry lake sediments are nearly identical to some of the permian evaporites of the permian basin region u s a and they can serve as modern analogues for ancient sabkha facies analysis

diagenetic study on the neogene sedimentary basin as paleoenvironmental proxy data for an offshore co2 storage project in pohang basin south korea abstract as the importance of reducing greenhouse gas emissions has attracted much attention pohang basin has been identified as a co2 geological sequestration test site in korea this study aims to provide a better understanding of the diagenetic history of pohang basin through mineralogical and microstructural analyses with a focus on tectonic evolution in the reservoirs offshore of the pohang basin during the east sea sea of japan opening in the miocene we focused on two sections in the core that are considered to be target layers for co2 storage samples were analyzed for texture observation and chemical analysis the major mineral components include quartz feldspar illite chlorite kaolinite and calcite and the minor mineral components include pyrite siderite iron oxide and titanium oxide the detrital grains are composed of quartz and feldspar and the primary pore is cemented with kaolinite i calcite pyrite and chlorite the analyzed chlorites are differentiated into five types by their textural characteristics such as pore filling pf pore filling with kaolinite pf k pore lining pl replaced rd and detrital da chlorites and they were all categorized as either brunsvigite diabantite or ripidolite generally the dissolution of feldspar is observed for all samples the diagenetic temperature is estimated by chlorite geothermometry to be 170 c on average which is higher than the present temperature of pohang basin 55 60 c considering all results together the target layers have undergone diagenetic processes from early diagenesis eogenesis to late diagenesis mesogenesis and uplift related diagenesis telogenesis after sedimentation of the pohang basin kaolinite i calcite and pyrite were cemented in the pore and detrital mica was replaced with chlorite as the burial depth increased the dissolution of feldspar advanced the high temperature resulting from the chlorite geothermometry could be influenced by the burial heat as source also the neogene volcanism and related tectonics known as eoil orogeny could become a heat source capable of high temperatures and a high geothermal gradient and tectonically compressional environment may have influenced fluid flow after the uplift kaolinite ii was precipitated in both an intergranular pore and intragranular pore as a result of dissolution the effects of diagenesis such as cementation and dissolution in co2 reservoir rocks could be an important factor in assessing the appropriacy of predicting potential charge after injection in carbon capture and storage project

storm generated sedimentary structures in subtidal marine facies with examples from the middle and upper ordovician of southwestern virginia abstract the role of storms is of major importance in forming stratification in open shelf facies though storm processes on modern shelves are not fully understood enough is known to see how sediments are influenced storms transport sand away from coastal areas and suspend and transport sand and mud on the open shelf when wave base is lowered storms generate winnowed lag deposits of shells or gravel but coarser sediment and shells of megafauna are little transported except in very near shore environments the martinsburg formation middle and upper ordovician of southwestern virginia was deposited on a storm influenced open marine platform in contrast to the classic turbidite flysch basin of the martinsburg in the great valley of virginia to the northeast deposition of most martinsburg sediments was due to storms sediments deposited during single storm events occur in characteristic fining upward sequences 1 to 80 cm thick in both carbonate and terrigenous clastic dominated areas of the platform individual storm deposits consist of a sharp erosional base overlain by a couplet of whole fossil packstone and laminated calcarenite siltite or quartzose siltstone to very fine sandstone which is gradational to shale packstones are typically intraclastic have shells aligned parallel o bedding and convex up often with adhering or contained mud and have abundant infiltration textures such as cement filled shelter voids packstones grade abruptly to a laminated bed with horizontal plane lamination large and small scale in phase undulatory lamination and wave ripple cross lamination commonly occurring in ordered vertical sequences laminated beds contain escape burrows are weekly graded and have irregularly mounded upper bed surfaces laminated beds grade upward to shale containing horizontal branching burrows and marine fossils the faunal content of the fining upward sequences matches that of the interbedded shale storm generated beds vary greatly in thickness laterally and frequently pinch out completely fining upward sequences formed by scouring winnowing and suspension of the sand and mud during the height of the storm to form the erosional base and autochthonous lag of whole fossils storms preferentially preserve whole fossils rather than fragmenting them infiltration of finer sediment into the lag deposit and deposition of the laminated bed occurred as the storm waned laminated beds are molded into a distinctive suite of sedimentary structures by wave generated currents the shale represents deposition of finest storm suspended material and continued hemipelagic sedimentation similar sequences are widely distributed in the geologic record variability of storm generated sequences can be related to changing water depth thus storm deposits may be useful in basin analysis to estimate relative water depths and trace transgressive and regressive events

mid miocene isotope stratigraphy in the deep sea high resolution correlations paleoclimatic cycles and sediment preservation mid miocene pelagic sedimentary sections can be correlated using intermediate and high resolution oxygen and carbon isotopic records of benthic foraminifera precision of a few tens of thousands of years is readily achievable at sites with high sedimentation rates for example deep sea drilling project sites 289 and 574 the mid miocene carbon isotope records are characterized by an interval of high 13c values between 17 and 13 5 ma the monterey excursion of vincent and berger 1985 upon which are superimposed a series of periodic or quasi periodic fluctuations in 13c values these fluctuations have a period of approximately 440 kyr suggestive of the 413 kyr cycle predicted by milankovitch theory vincent and berger proposed that the monterey excursion was the result of increased organic carbon burial in continental margins sediments the increased 13c values called 13c maxima superimposed on the generally high mid miocene signal coincide with increases in 18o values suggesting that periods of cooling and or ice buildup were associated with exceptionally rapid burial of organic carbon and lowered atmospheric co2 levels it is likely that during the monterey excursion the ocean atmosphere system became progressively more sensitive to small changes in insolation ultimately leading to major cooling of deep water and expansion of continental ice we have assigned an absolute chronology based on biostratigraphic and magneto biostratigraphic datum levels to the isotope stratigraphy and have used that chronology to correlate unconformities seismic reflectors carbonate minima and dissolution intervals intervals of sediment containing 13c maxima are usually better preserved than the overlying and underlying sediments indicating that the 13c values of tco2 in deep water and the corrosiveness of seawater are inversely correlated this again suggests that the 13c maxima were associated with rapid burial of organic carbon and reduced levels of atmospheric co2 the absolute chronology we have assigned to the isotopic record indicates that the major mid miocene deepwater cooling ice volume expansion took 2 m y and was not abrupt as had been reported previously the cooling appears abrupt at many sites because the interval is characterized by a number of dissolution intervals the cooling was not monotonic and the 2 m y interval included an episode of especially rapid cooling as well as a brief return to warmer conditions before the final phase of the cooling period the increase in 18o values of benthic foraminifera between 14 9 and 12 9 ma was greatest at deeper water sites and at sites closest to antarctica the data suggest that the 18o value of seawater increased by no more than about 1 1 per mil during this interval and that the remainder of the change in benthic 18o values resulted from cooling in antarctic regions of deepwater formation equatorial planktonic foraminifera from sites 237 and 289 exhibit a series of 0 4 per mil steplike increases in 13c values only one of these increases in planktonic 13c is correlated with any of the features in the mid miocene benthic carbon isotope record

relations between monterey formation deposition and middle miocene global cooling naples beach section california an oxygen and carbon isotopic stratigraphy has been established for the miocene monterey formation 18 to 8 ma at naples beach santa barbara county california correlation to the deep sea climatic record provides a test of the monterey hypothesis which suggests that organic carbon rich deposition in the monterey formation fostered middle miocene global cooling through drawdown of atmospheric partial co 2 oxygen isotopic correlation of the naples beach section to the deep sea record suggests that increased organic carbon rich deposition coincided closely with deep water cooling and major east antarctic ice sheet growth from 14 5 to 14 1 ma and with a 13 c maximum in deep sea records these results support a corollary of the monterey hypothesis that episodic organic carbon rich deposition within the monterey formation contributed to deep sea 13 c maxima and to synchronous global cooling

revised stratigraphy and reinterpretation of the miocene pohang basinfill se korea sequence development in response to tectonism and eustasy in a back arc basin margin abstract the miocene pohang basin is a pull apart basin formed along the eastern continental margin of korea ecmk during the back arc opening of the east sea sea of japan the basin is filled by more than 1 km thick nonmarine to deep marine strata these strata show extreme vertical and lateral lithofacies changes and have caused decades long controversies on their nature and stratigraphy previous sedimentological studies suggest that the basinfill was deposited by a series of contemporaneously developed depositional systems including fan delta prodelta slope apron and basin plain detailed mapping and magnetotelluric surveying show however that the basinfill is composed of several packages of strata sequences that are bounded by distinct and laterally persistent stratigraphic discontinuities sequence boundaries this suggests that the depositional systems in the pohang basin developed sequentially rather than contemporaneously six packages of strata are identified in the basin a nonmarine to shallow marine transgressive sequence sequence 1 a gilbert type delta conglomerate sequence 2 and alternations of submarine conglomerates and hemipelagic mudstones sequences 3 6 the conglomerates and hemipelagic mudstones of the latter four sequences are interpreted to represent lowstand depositional systems slope apron submarine fan and high gradient delta and condensed intervals respectively compilation of geochronologic paleomagnetic and biostratigraphic data suggests that sequence 1 formed during the gradual subsidence of the ecmk prior to 17 ma whereas sequence 2 formed in response to abrupt downfaulting of the pohang basin at about 17 ma both sequences are interpreted to have developed in response to the early miocene back arc opening tectonism of the east sea on the other hand sequences 3 6 formed between 17 and about 10 5 ma the pohang basin was subject to only minor tectonism during this period and could record global sea level fluctuations we suggest that the four alternations of conglomerates lowstand systems and hemipelagic mudstones condensed intervals resulted most probably from the 3rd order glacioeustatic cycles during the middle miocene this finding implies that the signatures of global sea level fluctuations can be deciphered from a tectonically active sedimentary basin if the timing of regional tectonic development is well constrained and the global sea level chart of haq et al haq b w hardenbol j vail p r 1987 chronology of fluctuating sea levels since the triassic science 235 1156 1167 haq b u hardenbol j vail p r 1988 mesozoic and cenozoic chronostratigraphy and eustatic cycles in wilgus c k hastings b s posamentier h van wagoner j ross c a kendall c g s c eds sea level changes an integrated approach soc econ paleont mineral spec publ 42 pp 71 108 may serve as a guide to basinfill interpretation even in tectonically active sedimentary basins

stable oxygen and carbon isotopes of carbonate concretions of the miocene yeonil group in the pohang basin korea types of concretions and formation condition abstract carbonate concretions in the miocene sedimentary rocks of the yeonil group in the pohang basin korea were investigated in terms of stable oxygen and carbon isotope composition to delineate the origin and associated diagenetic environment for their formation carbonate concretions are widely distributed in all the sedimentary rocks in the pohang basin showing that the calcitic concretions are preserved within the mass flow deposits and the dolomitic ones mostly in the hemipelagic siliceous rocks diatomites concretions can be classified into four different types on the basis of the stable isotopic signatures each of which represents its own geochemical range type i concretions are calcitic and are composed of micrite to microspar they occur in the conglomerates and sandstones which were deposited by mass flows debris flow to turbidity current it shows relatively lower 18 o 14 0 to 9 3 and 13 c 19 6 to 8 4 values these concretions grew in a sulfate reducing zone under the influence of residual ambient seawater which had been significantly modified by volcanogenic sediments type ii concretions are also calcitic composed mostly of micrite with minor microspar and found in the sandstones these concretions are characterized by relatively high 18 o 1 8 to 2 4 and variable 13 c 17 3 to 0 4 values these isotopic signatures reflect that type ii concretions formed from just beneath the sediment water interface down to the sulfate reducing zone through the early stage of methanogenesis type iii concretions are also calcitic and composed largely of micrite with a minor contribution of microspar they are observed in hemipelagic mudrocks which were deposited under the influence of mass flows they are characterized by intermediate to high 18 o 4 6 to 1 6 and high 13 c 1 3 to 8 8 values these concretions grew in a methanogenic zone by residual ambient seawater and or seawater slightly modified by reaction with volcanogenic sediments type iv concretions are dolomite with calcite inclusion and occur in hemipelagic siliceous rocks these concretions are mostly composed of micrite and characterized by variable 18 o 9 1 to 0 7 and high 13 c 3 1 to 17 9 values suggesting formation in the methanogenic zone although the residual ambient seawater is slightly modified by volcanogenic sediments the same type of the concretions is widely distributed throughout the basin and always shows its own distinctive stable isotopic signature this means that the formation of the given type depends upon the lithology and composition of host sediments that are closely related to the depositional process of the fan delta systems regardless of their localities further the different types of concretions are also found at the different but closely spaced stratigraphic levels in the same locality displaying the distinctive diagenetic conditions for each type such preservation of the unique diagenetic signatures in individual type of concretion suggests that the concretions formed in a completely closed diagenetic system therefore caution should be made to simplify and generalize the diagenetic condition for the formation of any concretions in a large sedimentary basin

miocene tectonic evolution of the basins and fault systems se korea dextral simple shear during the east sea sea of japan opening crustal deformation of se korea caused by back arc opening of the east sea sea of japan commenced locally in the late oligocene intense deformation occurred during the early miocene accompanying extension of parallelogram shaped pull apart basins between nnw striking principal displacement zones clockwise rotation and northwestward tilting of blocks and southwestward propagating rifting at about 17 ma the crustal deformation suddenly expanded westward and northward owing to activation of the yeonil tectonic line resulting in a dramatic change of depositional environment and the subsidence of wedge shaped pull apart basins the yeonil tectonic line and western border faults of the pohang basin are the westernmost limit of the miocene crustal deformation all the features of crustal deformation in se korea support the pull apart model for the east sea opening however they indicate that the nnw striking faults such as the yeonil tectonic line acted as the principal displacement zones rather than the nne striking yangsan fault under a consistent dextral simple shear at about 16 ma the collision of the philippine sea plate with the japanese islands caused a tectonic inversion this inversion resulted in a compositional change of basaltic magma at about 15 ma and crustal uplift in se korea which caused the cessation of sedimentation at about 10 ma

oligocene deposits of the zara hafik region sivas central turkey evolution from storm influenced shelf to evaporitic basin new stratigraphical and micropalaeontological data supplemented by detailed sedimentological and petrographical observations have been obtained from an almost completely exposed oligocene miocene succession near celalli in the zara hafik basin which forms part of a long lived zone of subsidence associated with the north anatolian fault system four laterally extensive lithostratigraphical units have been distinguished and ostracod microfaunas indicate that the lower two units are of middle oligocene age while bivalve brachiopod faunas from the third unit are also oligocene the status of the uppermost unit of redbeds remains equivocal but microfaunas from the capping marls are of lowermost miocene age

tectonic history of ulleung basin margin east sea sea of japan a geologic history analysis of an exploratory well drilled on the southern margin of the ulleung back arc basin east sea western part of the sea of japan reveals that tectonic force and sedimentary loading played a major role in the subsidence of the paleo ulleung basin where a thick clastic sequence was deposited during the neogene initial subsidence was most likely caused by a tectonic force related to the back arc rifting and spreading associated with convergent processes the southern margin underwent regional deformation uplift faulting and folding toward the late miocene this event was probably due to back arc deformation caused by changes both in plate motions and in subduction mode at the convergent zones

fluvial evaporitic and shallow marine facies architecture depositional evolution and cyclicity in the sivas basin lower to middle miocene central turkey abstract lower to middle miocene rocks in the karayun region of the sivas basin are represented by the agilkaya and egribucak formations forming a 4 km thick continuous section each formation is subdivided into three members representing similar lithofacies the lower members are made up of fluvial sheet sandstone and red mudstone that migrated laterally on a flood basin within a semi arid fan system the middle members are composed of bedded to massive gypsum and red green mudstone of a coastal and or continental sabkha environment they are intercalated with lagoonal dolomitic limestone and bituminous shale in the agilkaya formation and fluvial red pink sandstone red mudstone in the egribucak formation the upper members are made up of shallow marine fossiliferous mudstone and sandy limestone rapid vertical and horizontal facies changes in both formations reflect the locally subsiding nature of this molassic basin the overall section can be also subdivided into three orders of fining upward cycles type i cycles correspond to the agilkaya and egribucak formations each around 2 km thick and indicate two long term transgressive phases controlled by tectono eustatic factors type ii cycles 140 m thick on average are formed by alternations of fluvial sheet sandstone and red mudstone capped by up to 50 m thick red flood basin mudstone a 400 ka period milankovitch cyclicity related to astronomical climatic fluctuations is suggested as a governing mechanism although subsidence cannot be excluded the existence of laterally persistent fluvial sheet sandstone overlain by red mudstone that forms fining upward type iii cycles 10 m thick on average is attributed to changes in subsidence rate rhythmic alternations between gypsum beds and red green mudstone and or dolomitic limestone and bituminous shale observed in the middle members might be related to minor periodical climatic changes rather than to tectonics

a palaeomagnetic study of the sivas basin central turkey crustal deformation during lateral extrusion of the anatolian block abstract the sivas basin is a complex collage of eocene and younger rocks located within the wedge shaped eastern margin of the anatolian block between the dextral north anatolian fault zone and the sinistral eastern anatolian fault zone it has been subject to ongoing deformation by movement of the arabian block into eurasia and concomittant sideways expulsion of the anatolian block post collisional deformation since mid miocene times has been dominated by n s to nw se compression expressed by thrusting and strike slip faulting cretaceous and eocene rocks were magnetically overprinted to variable degrees during the collisional phase although these overprints have since been rotated mostly anticlockwise rocks emplaced during the neotectonic history are high fidelity palaeomagnetic recorders of subsequent block movements regional anticlockwise rotation is recognised across the basin with differential rotation of fault and thrust bounded blocks an absence of perceptible differences between group mean rotations identified from miocene pliocene and quaternary units shows that most regional rotation has been concentrated within the latest phase of the neotectonic history during quaternary times at an average rate of 10 ma commencement of this rotation postdates initiation of the north anatolian fault zone implying that compression following collision was accomodated initially by crustal thickening during late miocene and pliocene times subsequent anticlockwise rotations have resulted from sideways expulsion of blocks to the south of the central anatolian thrust along major ne sw sinistral faults to achieve the crustal shortening resulting from n s compression these fault orientations and their sense of motion are explained by a prandtl model involving deformation of a triangular plastic terrane the anatolian block between two rigid plates eurasia and afro arabia the variations in regional rotation identified by palaeomagnetism show that average contemporary anticlockwise rotation of anatolia revealed by gps data 1 2 ma is achieved by variable and locally large block rotations between major thrusts and strike slip faults

alluvial sedimentation patterns in the munster basin ireland post caledonian southern ireland witnessed the development of a ne sw orientated half graben known as the munster basin more than 7 km of non marine sediments accumulated in the basin during the late middle and late devonian marine conditions became established in the southern part of the basin at the end of the devonian in this paper a model for the evolving style of sedimentation in the basin and its periphery is constructed with the aim of identifying the major factors which controlled sedimentation patterns and the architecture of the basin fill the depositional history of the basin is considered in terms of four successive episodes during episode i gravelly alluvial fans flanked upland areas around the northeastern and northern basin perimeter these graded southwestwards to a floodplain dominated by sheet floods in the western part of the basin the first of three major fluvial influxes into the basin commenced during episode ii the first influx developed into a large sandy braided complex the sediment was derived from a distant source area located to the north and west of the basin and was transported diagonally across the basin towards the southeast episode iii witnessed a second influx which drained into the basin from the northeast and north river channels were of low sinuosity and graded distally to an ephemeral playa lake episode iv was marked by a third fluvial influx from the west and northwest this was confined to the southern half of the basin and drainage was directed towards the east the fluvial distributaries were flanked by permanently flooded overbank areas this influx coincided with the first marine transgression which advanced westwards the end of episode iv coincided with the beginning of the carboniferous and was marked by a major marine transgression sediment input to the basin was influenced by stable areas occupied by granitic plutons on either side of the basin and a southward downthrowing fault along its northern margin the drainage direction was principally controlled by e w trending within basin faults and an e w trending stable area located to the south the basin was fundamentally of the axial transport type the main drainage having been directed towards the east though there was also a strong lateral influx from the north northwest and northeast stable areas around the basin periphery resulted in either no sediment preservation or sequences of multistorey channel deposits while thick sequences dominated by fine grained floodplain or overbank deposits characterized areas of higher subsidence rate within the basin movement on the northern basin margin fault was probably the major cause of the first fluvial influx while regional subsidence of the basin and its northern periphery resulted in the second influx the third influx was a response to local subsidence in the southern part of the munster basin this also contributed to the simultaneous westward marine transgression in this area towards the end of the devonian source area denudation and retreat in association with a sea level rise were ultimately responsible for terminating the alluvial regime in the munster basin

paleoceanographic evolution of the japan sea abstract multidisciplinary studies on nearly continuous hemipelagic sequences recovered from the deeper parts of the japan sea during odp leg 127 128 in 1989 yielded new information on the paleoceanographic conditions of the sea since its establishment as a deep marginal basin of significant size approximately at 20 ma by synthesizing these new information on surface and bottom water conditions ccd biogenic silica accumulation and paleogeog raphy it is possible to reconstruct changes in paleo ocean circulation within the sea it is also possible to specify the ultimate cause of such changes by comparing their timing and nature with those of global paleoceanographic as well as local tectonic events the result of our synthesis suggests that the japan sea has been responding to the high frequency changes of global surface conditions in very sensitive manner throughout its history however the mode of its response changed from time to time the changes in response mode have been strongly influenced by such factors as sill depth position of channels and the degree of closure of the sea which were controlled either by local tectonism or global eustatic sea level changes

coarse grained debris flow deposits in the miocene fan deltas se korea a scaling analysis abstract the viscoplastic and inertial grain flow models have been widely used as tools for description and interpretation of ancient debris flow deposits providing a basis to estimate yield strength viscosity cohesion and internal friction angle recent studies suggest however that a debris flow is an intimate mixture of solid and fluid in which a number of momentum transfer mechanisms operate it is therefore necessary to evaluate the relative importance of different momentum transport processes to properly describe a debris flow scaling analysis may be useful to this end using the bagnold number the ratio of inertial grain stress to viscous shear stress savage number the ratio of inertial grain stress to shear stress borne by sustained grain contacts friction number the ratio of frictional shear stress to viscous shear stress and darcy number the ratio of grain fluid interaction stress to inertial grain stress scaling analyses of miocene gravelly debris flow deposits in korea suggest that different types of debris flows can be better distinguished by the analyses providing some implications for debris flow processes

facies partitioning and stratal pattern in salt controlled marine to continental mini basins examples from the late oligocene to early miocene of the sivas basin turkey the sivas basin turkey records a complex interaction between sedimentation salt tectonics and regional shortening leading to the formation of numerous mini basins the segmentation into mini basins was initiated during the oligocene by the deposition of the fluvio lacustrine karayun fm this continental succession is overlain abruptly by an oligo miocene shallow marine succession karacaoren fm which comprises two main sub environments i mixed deltaic and carbonate ramp ii coastal plain and lagoon the karacaoren fm forms a marine succession more than 1500 m thick that passes vertically upwards into a continental succession the fluvial dominated benlikaya fm these two formations are the focus of the present study during the period of marine sedimentation the competing accumulation of carbonates and clastics is related not only to the topography inherited from salt tectonics but also to relative sea level variations expressed by two large scale transgressive regressive cycles we analyse these complex facies and stratal relationships to illustrate the modifications induced by salt tectonics this study is based on extensive fieldwork and mapping making use of numerous measured stratigraphic sections and aerial photos over a large area comprising more than fifteen adjacent outcropping mini basins the aim of this study is to provide a detailed description of the stratigraphic relationships correlations and sedimentary systems distribution in mini basins during deposition of the oligo miocene shallow marine and continental successions we first clarify the vertical stratigraphic succession of the oligo miocene marine and continental deposits and establish correlations between the studied mini basins these correlations then allow us to characterize and assess the local effects of salt withdrawal in relation to the regional forcings associated with flexural subsidence tectonic shortening and relative sea level changes an improved understanding of the complex interactions of these variables provides a framework to distinguish the mechanisms that control facies distribution and stratal geometry in salt basins

deposition and early alteration of evaporites summary the depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories marginal mixed shallow subaqueous and subaerial shallow and deep subaqueous these three environmental groupings hold for both marine and nonmarine settings although the details of continental evaporites may be far more complex than in most marine fed water bodies the primary evaporite morphologies from many continental playa hypersaline marine and marine marginal depositional settings are reasonably well understood because of the numerous detailed studies of recent holocene and cenozoic deposits that serve as models for sedimentary interpretation the sedimentological features that develop in deeper water settings are inferred based on examination of unaltered cenozoic deposits each environmental setting develops characteristic depositional features and patterns and one facies grades into the next because there may be significant physiochemical changes in water composition during deposition as well as sudden change s in both water depth and basinal circulation description and interpretation of evaporative rocks should not be based on mineralogy alone but on the distinct sedimentary characteristics of each part of a deposit in cases where sediments still reflect their primary mineralogy and morphology most of the environments can now be recognized however geochemical studies are commonly required to determine the source s of the original water the determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions bromine content of chloride salts and the stable isotopes of strontium sulphur carbon and oxygen only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled

palaeogeographic and burial controls on anhydrite genesis the badenian basin in the carpathian foredeep southern poland western ukraine the badenian middle miocene ca sulphate deposits of the fore carpathian basin including the shelf and adjacent salt depocentre have undergone varying degrees of diagenetic change they are preserved mainly as primary gypsum in the peripheral part of the platform whereas toward the centre of the basin where great subsidence occurred during the miocene they have been totally transformed into anhydrite the facies variation and sequence of badenian anhydrites reflect different genetic patterns of two members of the ca sulphate formation in the lower member restricted to the platform anhydrite formed mainly by synsedimentary anhydritization via nodule formation whereas in the upper member distributed throughout the platform and depocentre the various gypsum anhydrite lithofacies display a continuum of distinctive anhydrite type fabrics these fabrics are based on petrographic features and show from the centre to the margin 1 syndepositional interstitial growth of displacive anhydrite 2 early diagenetic displacive to replacive by replacement of former gypsum anhydrite formation near the depositional surface 3 early diagenetic displacive to replacive anhydrite formation during shallow burial and 4 late diagenetic and only partial replacement of gypsum at deeper burial the cross shelf lateral relations of anhydrite lithofacies and fabrics suggest that the diagenesis developed as a diachronous process these fabrics of the upper member reflect both palaeogeographic linked to different parts of the basin and burial controls anhydrite growth started very early in the basin centre presumably related to high salinity pore fluids anhydritization prograded updip toward the shelf landward in a generalized cross section through the basin the intensity of gypsum replacement by anhydrite was progressively attenuated landward by a decrease in the salinity of the pore fluids in each part of the basin the anhydrite fabric was also controlled by the texture and degree of lithification of the fine grained primary gypsum lithofacies recrystallization of these anhydrite fabrics during late diagenesis linked to deeper burial conditions is insignificant allowing reconstruction of the original anhydritization pattern