development of a chenier plain firth of thames new zealand abstract a chenier plain is a prograded coastal plain in which ridges composed of coarse material moved by longshore drift are stranded overlying finer grained marine or littoral sediments subsurface data from the miranda coastal plain firth of thames new zealand confirm that shell ridges between kaiaua and miranda are true cheniers surveys of a modern chenier indicate that coarse sediment and shell form sand bars on the foreshore and that these migrate landwards through swash action subsequently a shell ridge is built on the sand bar from shell derived from offshore and reworked from the north and storm events form a storm crest above high spring tide level deposition of fine grained sediment occurs in an embayed tidal flat behind the chenier and within this environment the bivalve mactra ovata is found these sediments can accrete to an elevation at which mangrove and salt marsh are able to colonise the chenier may continue to transgress landwards though at a slower rate retreating over the embayed tidal flat mangrove or marsh and compressing these sediments erosion of these compressed muds on the face of the beach leaves specimens of mactra in their growth position exposed on the modern chenier at an elevation of 0 62 0 80 m above msl stratigraphical observations along a west east profile across the coastal plain reveal that sandy muddy sediments are underlain by peat clayey tephra and older marine sediments and 4 radiometric dates of 30 000 yrs b p have been determined on these shell ridges on the plain are underlain by blue muds within which occurs a band of mactra ovata tristis in growth position these sediments are considered analogous to the embayed tidal flat sediments behind the modern chenier the continuity of the shell layer radiometrically dated to 3650 60 yrs b p to landward and 1260 50 yrs b p to seaward implies that there have not been oscillations of sea level during this regressive coastal phase while the shell ridges have developed mactra were also found in situ at the north and south of the coastal plain dated to 4510 70 and 200 60 yrs b p respectively from elevations on sub fossil mactra it is implied that sea level was 0 70 0 90 m above present 3600 years ago and that it fell gradually until 1200 years ago when it was close to present erosion deposition and migration of a chenier can occur simultaneously and long term variations in sea level or in sediment supply do not appear necessary to explain the episodic formation of chenier ridges

island ecosystem and biodiversity dynamics in northeastern australia during the holocene unravelling short term impacts and long term drivers vegetation changes of tropical lizard island great barrier reef world heritage area australia over the last 8000 years are derived from palaeoenvironmental analysis of a 475 cm long sediment core during early holocene sea level rise flooding of the continental shelf and thus isolation of lizard island the pollen record shows the gradual establishment of a mangrove forest paralleled by contraction of the near coastal palm and grass dominated vegetation subsequently mid holocene relative environmental stability supported a diverse rhizophora dominated mangrove and open mixed sclerophyll vegetation inland around 6000 years ago a profound disturbance of the mangrove is recorded by a siliciclastic layer and we hypothesise that this deposit documents the impact of a storm or cyclone postevent environmental conditions were strongly altered with enhanced estuarine conditions supporting a sonneratia and bruguiera dominated mangrove forest during late holocene sea level fall and stabilisation prograd

the development of a chenier sequence on the victoria delta joseph bonaparte gulf northern australia abstract a chenier sequence on the victoria delta northwestern australia has been dated five chenier ridges formed rapidly over a 1000 yr period from 2020 yrs b p to 1210 yrs b p these were associated with the progradation of a fine sandy shoreline during periods of reduced mud input to the southeastern part of the joseph bonaparte gulf the cheniers formed during an arid phase in the late holocene and the reduced mud input to the shelf is believed to have been directly related to the associated reduction in fluvial discharge shell from a more recent ridge which formed within the last 1000 yrs gave dates of between 4050 yrs b p and 5970 yrs b p the progressive winnowing of fines from the inner shelf muddy sand zone during the periods of low mud input may have resulted in the release during the last of these periods of this older shell material the possibility that the cheniers formed as the result of delta channel switching by the ord river has not been entirely ruled out

structure and development of shell cheniers in essex southeast england investigated using high frequency ground penetrating radar abstract the stratigraphy and internal structure of contemporary shell cheniers on the southern essex coast england were investigated using a high frequency 900 mhz ground penetrating radar gpr system the cheniers lie on the seaward edge of laterally eroding saltmarshes at the junction with the tidal flats four main types of chenier are recognised each with a characteristic morphology and dynamic status migrated radar reflection profiles obtained from each of the chenier types achieved a sub decimetre vertical resolution ground truthing data demonstrate that the radar profiles accurately delineate the subsurface stratigraphy and sedimentary structure of the cheniers interpretation of the radar stratigraphy derived from the radar reflection profiles allows various deposits to be identified these have resulted from overwashing overtopping sedimentation across the whole of a seaward dipping beachface or berm ridge welding onto the upper beachface each chenier is characterised by a different spatial arrangement of these four basic depositional units the results from the gpr surveys support the hypothesis that each of the chenier types represents a distinct phase in the development of these contemporary coastal landforms however a simple model involving a linear progression through chenier types 1 4 with time appears inappropriate instead two main evolutionary pathways are proposed with the sequence of development being principally controlled by the nature of the cheniers longer term sediment budgets

the geomorphology of the mississippi river chenier plain abstract the chenier plain of the mississippi river is a shore parallel zone of alternating transgressive clastic ridges separated by progradational mudflats the term chenier is derived from the cajun term chene for oak the tree species that colonizes the crests of the higher ridges the mississippi river chenier plain stretches 200 km from sabine pass texas to southwest point louisiana and ranges between 20 and 30 km wide with elevations of 2 6 m the timing and the process of formation could be re evaluated in the light of new chronostratigraphic findings in the mississippi river delta plain the stratigraphic relationship between the teche and lafourche delta complexes and ship shoal offshore indicates that these delta complexes belong to different delta plains that developed at different sealevels it appears that the teche delta complex is associated with the late holocene delta plain which developed 7000 to 3000 yrs b p when sealevel stood 5 6 m lower than present a regional transgression occurred between approximately 3000 bp and 2500 yrs b p leading to the transgressive submergence of the late holocene delta plain producing the regional teche shoreline the timing of this transgression conforms to the age of the most landward ridge in the chenier plain the little chenier little pecan island trend which dates at about 2500 yrs b p this ridge trend was originally interpreted as representing the teche delta complex switching event with the landward holocene pleistocene contact representing the high stand shoreline the implication of this new interpretation is that the little chenier little pecan island trend represents the high stand shoreline a continuation of the teche shoreline separating the late holocene and recent delta plains and that the holocene pleistocene contact represents the leading edge of the marshes transgressing onto the prairie terrace significant mudflat progradation seems to require a westerly position of the mississippi river but the numerous different forms and ages of cheniers do not correspond well to the timing of major delta complex switching progradation of the chenier plain appears to be associated with building of the recent delta plain and not the teche complex of the late holocene delta plain the occurrence of individual ridges appears to be primarily tied to delta lobe switching within the lafourche complex and variations in sediment supply from local rivers the recent development of the atchafalaya delta complex to the west is the closest position of an active distributary to the chenier plain since sealevel stabilization a new episode of rapid mudflat progradation is thus taking place

chenier research on the australian coast abstract cheniers occur in numerous locations across northern australia principally in association with river mouths and adjacent riverine and tidal mudflats this region is characterised by hot wet summers warm dry winters meso macro tidal ranges low waves tropical cyclones hurricanes and mangrove forests all of which play a role in chenier evolution a few chenier sites exist in arid regions of southern australia where all sediments are of in situ biogenic and marine origin studies of australian cheniers commenced in the 1970 s and now encompass all regions although many specific sites remain uninvestigated

the chenier coast of suriname modern and geological development abstract the holocene coastal plain of suriname is part of the extensive chenier plain between the amazon river and the orinoco river the development began approximately 6000 yrs b p and was interrupted twice by periods of erosion or non deposition along the present coastline large shoreface attached mudbanks migrate continually to the west cheniers are formed in the interbank areas the geological development and stratigraphy of the suriname chenier plain and the morphodynamic development of the modern coastline are discussed some hypothetical explanations of the geological development from the actual morphodynamics are briefly discussed a new approach has been developed involving the analysis of aerial photographs using a geographical information system this was used to analyse the geomorphological changes of the suriname coastline

storm cycles in the last millennium recorded in yongshu reef southern south china sea large storm relocated porites coral blocks are widespread on the reef flats of nansha area southern south china sea detailed investigations of coral reef ecology geomorphology and sedimentation on yongshu reef indicate that such storm relocated blocks originated from large porites lutea corals growing on the spurs within the reef front living coral zone because the coral reef has experienced sustained subsidence and reef development during the holocene dead corals were continuously covered by newly growing coral colonies for this reason the coral blocks must have been relocated by storms from the living sites and therefore the ages of these storm relocated corals should approximate the times when the storms occurred rapid emplacement of these blocks is also evidenced by the lack of coral overgrowth encrustation or subtidal alteration u series dating of the storm relocated blocks as well as of in situ reef flat corals suggests that during the last 1000 years at least six strong storms occurred in 1064 30 1210 5 1201 4 1336 9 1443 9 1685 8 1680 6 1872 15 ad respectively with an average 160 year cycle 110 240 years the last storm which occurred in 1872 15 ad also led to mortality of the reef flat corals dated at similar to 130 years ago thus the storm had significant impacts on coral reef ecology and morphology c 2004 elsevier b v all rights reserved

the chenier plain coastal system of guyana abstract the low chenier coast of northeastern of south america bears holocene cheniers which are considered as useful features because they protect the coast against marine erosion as sites for human settlement and the transportation network the relationship between chenier formation and the morphology of the coast is striking most cheniers in guyana are old features it is believed that clusters of cheniers were formed when large quantities of sand were available during periods of dry climatic conditions when fine particles were transported by the streams towards the sea during pluvial climates chenier formation naturally decreased a similar cycle of shorter duration based on the movements of mud shoals in the nearshore area of the continental shelf affects the coastal process resulting in the formation or destruction of cheniers on the guyana coast chenier formation is not as active as on the suriname coast much research is necessary to survey and protect these important features

chenier plain development in northern sierra leone west africa abstract the coast of northern sierra leone between the scarcies and mellacoree estuaries forms a prograding muddy holocene plain comprising two separate as yet undated clusters of sand cheniers the general coastal morpho stratigraphy and available data on regional climatic and sealevel history suggest that alternations between muddy progradation and chenier cluster formation have been controlled by a probable conjunction of several factors including the local geomorphic framework a climatically induced change in mud supply and relative sealevel oscillations since the middle holocene the inner chenier cluster was apparently elaborated under conditions of efficient wave action over a deep largely unfilled mellacoree estuary and at a time of reduced mud availability it peters out seaward probably in response to several factors including an increase in mud supply from the upland a negative sealevel pulse resulting in higher rates of mud export from accreted inner tidal flats increased muddy sedimentation over a shallower nearshore zone and attenuated wave action as a result of energy capture by accreted estuarine shoals the outer cluster which partly fringes the coast was formed in a mayor embayment representing the terminus of longshore sand drift it is suggested that its formation may have been favoured by a higher sealevel resulting in efficient winnowing of sands from subtidal muds a greater propensity for accretion of tidal flats landwards and consequently a lower mud supply to the foreshore although the timing of muddy progradation and chenier formation has not been determined the foregoing interpretation suggests a complex sequence of events reflecting as much the influence of local morphodynamic factors as external factors

palaeogeography and dynamics of the deltaic wetland of save river mozambique abstract many mangrove wetland systems in deltaic environments are negatively affected by massive sedimentation from river inflows in this paper we use the example of the save river delta to assess the palaeogeographic distribution of mangrove wetlands and to analyze their dynamics to track past occurrences of mangrove wetlands in the study area we have integrated sedimentological data with siliceous microfossil analysis combined with ams radiocarbon and osl dating the results show a fine grained deposit with an approximate thickness of 2 m present at different sampling sites in the upper deltaic plain the deposit is interbedded between sand layers while in the lower deltaic plain the deposit occupies the uppermost stratigraphic position in most of the sampling sites the deposit shows a succession with brackish marine diatoms at the bottom of the sequence while the upper part shows only scattered occurrences based on sedimentological and microfossil characteristics we have interpreted the layer to represent a mangrove wetland deposit the development of the deposit in the study area is suggested to have been initiated around 3100 cal yr bp induced by sea level rise thereafter the development followed the combined effect of a sea level fall and delta progradation processes in some areas particularly in the proximal part of the delta the mangrove deposit has developed progressively on top of the delta front from around 1300 years ago osl onwards massive alluvial sedimentation impacted the mangrove ecosystem however the retreat of mangrove wetland coincided with a regional fall of sea level at the edges of the alluvial deposit the current mangrove ecosystem has reclaimed the habitat in some sectors where gully erosion has exposed the once extinct mangrove habitat

aspects of the emplacement evolution and 14c chronology of ridges on a coastal spit groote eylandt northern australia a coastal spit on groote eylandt in the western gulf of carpentaria northern australia began to form between 3000 and 2000 yr b p in response to the migration of a large parabolic dune across the coastline systematic discrepancies in the 14c chronology and the remarkable preservation of fragile shelly material indicated a complex origin for a series of concentric beach ridges one of the shell species deposited in the beach ridges clypeomorus bifasciata sowerby was being continuously incorporated through normal wave action while a second species fragum whitleyi iredale was introduced only under storm conditions the importance of selecting a single shell species for 14c dating and understanding the environmental tolerance of the species is highlighted a conceptual model for the emplacement of surficial ridge material under bedload flow during storm set up is proposed it is argued that these ridges act as offshore bars rather than storm beaches during storm events this would have significant implications for the environmental interpretation of some types of spits and beach ridges in particular sea level estimates based on the assumption that these types of ridges are formed as beaches are open to question

depositional model for a chenier plain gulf of carpentaria australia the southern coast of the gulf of carpentaria northern australia consists of a broad chenier plain which is comparable in size and morphology to those reported on the coasts of surinam and south western louisiana the carpentaria chenier plain has at some locations prograded over 30 km since the middle holocene by deposition of low tide muds over subtidal muds during periods of increased sediment input by the rivers chenier ridges are formed during periods of reduced sediment flux by wave induced sorting and redistribution processes an alternation of increased and decreased sediment flux from fluvial sources has occurred several times during the upper holocene such variation in sediment supply is believed to be related to temporal fluctuations in rainfall over the drainage basin which surrounds the southern and eastern gulf

a new mechanism for chenier development and a facies model of the saltes island chenier plain sw spain abstract the scientific literature describes two types of cheniers these two types differ in the origin of the coarse sediments that constitute the ridge and the relative significance of the transversal and longitudinal wave transport in both cases storm waves are described as the main factor responsible of the origin and development and both final facies are characterized by ridges of coarse sediments above the finer sediments of a tidal flat the odiel tinto estuary is one of the most significant estuarine systems of the mesotidal huelva coast on the northwestern portion of the gulf of cadiz and saltes island is a part of the closure history of the estuarine system previous works on saltes island described the surficial disposition of sandy landforms as a classic ridge chain or a barrier island succession nevertheless an architectural scheme based on a vibracore study shows a disposition that accord to the typical chenier plain facies model this disagreement was the basis for a controversy about the origin of the ridges in this study historical nautical charts and aerial photographs document the evolution of the last of these cheniers during the past 200 years in contrast to the accepted models of chenier evolution the cheniers of saltes island migrated on the tidal flat but did not evolve only during storms indeed their development occurred mainly during high spring tides the data presented in this paper are used as the basis for a new conceptual model of chenier generation and evolution the model consists of a migration of sand bars in a similar way to the classic beach ridges with the difference that in our case the bars migrate over a tidal flat from a local point of view this paper removes the controversy about the origin of the island s geomorphology but from a global point of view this mechanism can explain certain chenier plains in estuarine mouths located in other coasts of the world

mangrove dynamics in the southwestern caribbean since the little ice age a history of human and natural disturbances relatively little is known about the long term response of caribbean mangroves to human and natural disturbances during the little ice age lia we present new palynological information on the dynamics of the bahia honda mangrove from the eastern coast of san andres island in the southwestern caribbean for the late holocene major changes in the bahia honda pollen record show the combined effects of natural events strong storms and sea level rise and human disturbances these changes are supported by 14c dates sedimentological and palynological information a storm most probably a hurricane was recorded around ad 1600 caused sediment reworking and the subsequent loss of about 2000 years of the vegetation record the devastation of tree vegetation by this event allowed the expansion of heliophytic vegetation e g grasses and vines mangroves and coastal vegetation started to recover at ad 1700 reaching their maximum extent within a few decades when microforaminifera shells became abundant at

from platform top to adjacent deep sea new source to sink insights into carbonate sediment production and transfer in the sw indian ocean glorieuses archipelago abstract over the past ten years a huge amount of source to sink studies have aimed to unravel the tectonic climatic and other processes that shape the landscape from mountains to the deep ocean interestingly these studies have been mainly dedicated to siliciclastic or mixed systems for which the connection between drainage basins continental shelves slope and basin environments are often well constrained here we present a study focusing on a source to sink study dedicated to a pure carbonate system located in the sw indian ocean glorieuses archipelago extensive field sampling and geophysical acquisition across the carbonate platform have allowed us to estimate the composition the lateral variability and volumes of neritic sands deposited on the platform top additional seismic and bathymetric surveys across the platform interior illustrate the presence of plurimetric sandy bodies deposited along the leeward platform edge corresponding to the export of carbonate sediments from the platform top toward the platform edge under the influence of dominant currents and wind driven processes high resolution seismic bathymetric data and sediment cores acquired along the leeward slope and basin adjacent to the carbonate platform highlight the presence of channel levee complexes and turbiditic lobes which have accumulated on the seafloor on top of a 250 m thick sedimentary basin at 2000 3400 m water depth our study points out that carbonate sands and aragonitic mud produced on the platform top during the holocene have been shed to the adjacent basin we also demonstrate that this routing system was active at least throughout the last three glacial interglacial cycles this study has important consequences for our understanding of carbonate sedimentation processes occurring in the vicinity of isolated carbonate platforms 1 it highlights the role of oceanographic conditions in the distribution of sediment on a platform top and its export along the platform edge and the adjacent basin 2 it contributes to quantify the productivity of a carbonate platform as well as its sediment storage capacity 3 a first estimate of a carbonate source to sink system is proposed demonstrating that 0 57 km3 of sediments have been produced during the holocene 0 3 km3 being presently stored on the platform and the remaining having been exported to the deep basin

cheniers and chenier plains a general introduction abstract cheniers and chenier plains have been studied in many coastal regions throughout the world an inventory of the investigations currently being carried out is presented in this and accompanying papers cheniers and chenier plains are azonal features their distribution ranges from tropical to the subarctic regions and they show a variety of features progradational shorelines where mud accretion is temporarily interrupted favour the development of these features in addition to the concept of otvos and price who define cheniers and chenier plains as being formed exclusively in relation to littoral progradational environments it is suggested here that chenier formation in deltaic progradational environments should also be included genetically two types of cheniers can be distinguished depending on the origin of the related sediments cheniers developing due to wave winnowing of the muddy sediments and the subsequent concentration of the coarser particles to form a longshore bar or ridge which is driven shoreward and cheniers built by littoral drift in both cases they can be recognised by their sedimentary structures when cheniers arrive onshore they will migrate further landward due to washover processes under extreme hydrodynamical conditions e g spring tides storm surges etc to summarise the information concerning the episodic development of chenier plains in order to produce a or a few universal model s appears to be very difficult owing to the numerous factors that influence their formation these include river mouth shifting sealevel changes climatic changes storm frequency mortality of shellfish and bay geometry owing to this sensitivity to environmental changes during their formation cheniers are considered to be very important geomorphological features they provide a relatively accurate record of sealevel and environmental changes which can be dated with high resolution

carbide metal assemblages in a sample returned from asteroid 25143 itokawa evidence for methane rich fluids during metamorphism abstract we found that the particle ra qd02 0115 returned by the hayabusa spacecraft from near earth asteroid 25143 itokawa contains the iron carbide haxonite fe 21 9 22 7 co 0 2 0 3 ni 0 2 0 8 c 6 and several fe ni alloys including multi domain tetrataenite and spinodally decomposed taenite ellipsoidal to nearly spherical voids occur throughout the particle and suggest the presence of a fluid phase during textural and chemical equilibration of the host rock within the parent asteroid of 25143 itokawa the calculated solubility of carbon in fe ni metal indicates that the carbide formed at temperatures larger than 600 c during thermal metamorphism of the ll chondritic mineral assemblage haxonite formed metastably with respect to graphite and cohenite probably due to its high degree of lattice match with neighboring taenite a low cooling rate at peak metamorphic temperatures and the hindered nucleation of graphite thermodynamic equilibrium calculations indicate that the fluid present was dry h 2 o poor and dominated by methane the reactive fluid most plausibly had an atomic h c ratio of 4 5 and was derived from the reduction of macromolecular insoluble organic matter iom that initially co accreted with water ice the initial presence of water is a necessary assumption to provide sufficient hydrogen for the formation of methane from hydrolyzed iom metallic iron was in turn partially oxidized and incorporated into the ferromagnesian silicates during the high temperature stage of metamorphism an exemplary bulk reaction from unequilibrated material on the left to an equilibrated assemblage on the right may be written as 330 ch 0 8 o 0 2 iom 500 h 2 o ice g 681 fe in alloy 566 fesio 3 in opx 300 ch 4 g 32 h 2 g 5 fe 23 c 6 in hx 566 fe 2 sio 4 in ol opx orthopyroxene hx haxonite ol olivine g fluid species the best estimate of the fluid rock ratio in the region of the ll parent body where ra qd02 0115 formed is about 3 10 3 and corresponds to an initial ice rock ratio of about 7 10 3 both by mass

estuarine infill and coastal progradation southern van diemen gulf northern australia abstract there are several estuaries associated with the pronouncedly seasonal rivers which drain northwards from the middle proterozoic sandstone arnhem land plateau and the tertiary koolpinyah land surface into the macrotidal van diemen gulf in the northern territory of australia the holocene development of these investigated in greatest detail for the south alligator river with an upland catchment of 10 000 km2 through drilling palynology and radiocarbon dating comprises both estuarine infill and coastal progradation three phases of estuarine infill can be recognised i a transgressive phase 8000 6800 years b p of marine incursion ii a big swamp phase 6800 5300 years b p of widespread mangrove forest development and iii a sinuous cuspate phase of floodplain development since 5300 years b p during which the tidal river has meandered and reworked earlier estuarine sediments since 6000 years b p the south alligator coastal plain has prograded at a decelerating rate with two phases of chenier ridge formation a similar pattern of estuarine infill and decelerating coastal plain progradation is demonstrated for the adelaide and mary rivers both with catchments of 6000 km2 the southern shore of van diemem gulf appears to have changed its overall position little during the last 2000 years the major source for the clay silt and fine sands which have infilled the estuary and coastal plain has been from seaward dispite the similarity of development coastal sediment build up has had different effects on the morphology of each tidal river the adelaide has undergone a major diversion and no longer flows directly into van diemen gulf but occupies a former fluvial course and the mary has been blocked entirely and its former estuarine palaeochannels have been infilled with tide transported sediment

storm impact and evolution of a mangrove fringed chenier plain shoal bay darwin australia abstract storms are considered to have significant impacts on the development of chenier plains particularly through the devastation of mangrove vegetation but also in terms of winnowing sand and shell from mudflats and forming chenier ridges shoal bay in the beagle gulf northern australia contains a small chenier plain which was struck by a severe tropical cyclone cyclone tracy on christmas day 1974 as it devastated the city of darwin the morphology vegetation and stratigraphy of the plain are described the plain is underlain by lower intertidal sand with shell hash a radiocarbon age of 6130 years bp indicates mangrove colonisation of this flat at the time that sea level stabilised around its present level after the postglacial transgression subsequently progradation of mudflats has occurred especially around 2300 years ago and shells of this age are found both in growth position from within the mudflats and incorporated into the shelly chenier ridges a further phase of build out and subsequent erosion is reflected by stumps and in situ bivalves being excavated presently on the foreshore radiocarbon dating about 900 1100 years bp within this context of evolution cyclone tracy can be seen to have had severe consequences upon the patterning of mangroves with extensive windthrow of ceriops and defoliation of rhizophora at the western end of the plain recovery of the mangrove vegetation has been gradual and is still incomplete however the storm had little influence on the pattern of landform development indeed the aerial photographic sequence indicates a trend by which sand shoals are gradually reworked landwards in places moving through mangrove vegetation the study suggests that rather than pronounced regional episodes of alternative mudflat buildout and erosion both processes occur simultaneously at different points along this foreshore

oligocene to pliocene palaeogeographic evolution of the cankiri corum basin central anatolia turkey abstract the cankiri corum basin is one of the largest basins of central anatolia to have developed oligocene to quaternary terrestrial environments the basin contains significant raw materials for industry and energy but the determination of their distribution patterns requires a good knowledge of the stratigraphic and spatial distribution of deposits besides evolving tectonic regimes in the basin and the sedimentary sequences controlled by them can play key roles in revealing the regional paleogeography on the basis of a new chronological framework provided by mammalian fossils and sedimentological data ten sedimentary formations have been identified for the oligocene pleistocene time interval from the oldest to the youngest these are the incik guvendik kizilirmak kilcak kumartas hancili bayindir akkasdagi bozkir and degim formations during early oligocene times an alluvial fan and braided and meandering rivers deposits developed at the northern and eastern rims of the basin whereas lacustrine products dominated by evaporitic deposits occurred in vast areas at the center in late oligocene the lake area contracted and dominant floodplains and braided rivers took place in the central area of the basin during early middle miocene large lacustrine areas dominated by organic clastic deposits developed in the northern and middle parts of the basin lake shore facies were formed in northern parts of the basin and on some paleohighs surrounding the lake in the orta and abanozu regions volcanic activity started during the middle miocene and lasted until the beginning of late miocene during late miocene there were different types of lacustrine environments in the northern and southern parts of the basin a hypersaline lake characterized by evaporitic deposits in the north and carbonate rich shallow lakes and swamps in the south a younger evaporitic lake formed in early pliocene in the northern part of the basin and covered vast areas its deposits are as thick as 400 m from late pliocene the thick sedimentary sequences deposited during the oligocene early pliocene interval become fragmented and deformed by a tectonic wedge bounded by a normal fault in the west and a thrust in the east sedimentary products of this tectonic regime are represented by thick alluvial fan sequences of the degim formation

holocene cheniers in the yangtze delta china abstract nineteen cheniers formed in the middle and late holocene have been distinguished and studied in fair weather the wave action along the yangtze delta is weak with a wave height of 0 5 1 0 m and average wave energy of 0 127 erg s however in late summer and early autumn the coastal area is usually swept by typhoons which sometimes are extremely violent the development of cheniers is mainly controlled by these strong typhoons as a result a number of the sedimentary characteristics of the cheniers are related to the typhoon generated high energy environment moreover the study shows that the top elevation of a fully developed chenier indicates the spring high water level during a violent typhoon 11 12 on the beaufort scale