high frequency cycles within pleistocene forced regressive conglomerate wedges bradanic area southern italy filling collapse scars middle pleistocene sedimentation in the bradanic area foreland basin of the southern apennines took place in a setting in which tectonic tilting created anomalous shelf gradients and where slope failures repeatedly occurred at the front of quickly prograding sedimentary wedges a coarse grained wave dominated coastal deltaic complex consisting of two downstepping forced regressive wedges prograded during the falling stage of a middle pleistocene glacio eustatic fluctuation p lacunosa zone conglomerate clinoforms show a dramatic increase in relief and steepness as a result of the infill of collapse scars compaction of prodelta mudstones due to the load of the scar filling conglomerates resulted in a slight deformation of the fills into broad synformal structures with gentle anticlinal closures at their distal ends accommodation space was created resulting in splitting of the prograding bodies into high frequency cycles which are thought to reflect the interaction of localized compactional subsidence with autocyclic shifting of river mouths and or climatically induced variations in sediment supply available chronologic constraints suggest average durations of small scale cycles on time scales shorter than those of milankovitch orbital frequencies this case history highlights the importance of some factors which are often neglected in sequence stratigraphic models e g physiography of the sea floor and localized sediment loading on one hand the bulk of falling stage wedges can be preserved as they prograde into intraplatform depressions represented by collapse scars on the other significant accommodation space is created by compactional subsidence leading to the splitting of a simple progradational unit into multiple small scale cycles

discontinuity surfaces clinoforms and facies architecture in a wave dominated shoreface shelf parasequence abstract detailed outcrop analysis of a wave dominated shoreface shelf parasequence exposed in the book cliffs utah reveals minor stratigraphic discontinuities which define clinoforms two types of discontinuity are recognized each with a distinctive lithologic character and geometry nondepositional discontinuities are marked by an abrupt decrease in the thickness and amalgamation of storm generated event beds and are interpreted to record hiatuses in sedimentation these discontinuities define clinoforms with a concave upward geometry that dip gently 0 02 0 58 over distances of 800 6000 m down depositional dip erosional discontinuities are marked by an abrupt increase in event bed amalgamation grain size and sand content and are interpreted as enhanced storm wave scours these discontinuities define more steeply dipping 0 22 0 95 concave upward clinoforms that extend over 100 1600 m down depositional dip and 500 1500 m along depositional strike the distribution and amalgamation of minor stratigraphic discontinuities defines linear zones of distinctive facies architecture that are oriented parallel to the paleoshoreline trend using the simple assumption that the shoreface shelf equilibrium profile remained approximately constant for each type of discontinuity throughout shoreface migration the bruun rule intra parasequence facies architecture can be speculatively interpreted in terms of shoreline trajectory which reflects the balance between sediment supply and accommodation the resulting interpretations support the notion that shoreline trajectory exerts a strong control on intra parasequence facies architecture and preservation of the shoreface shelf profile

the calcarenite di gravina formation in matera southern italy new insights for coarse grained large scale cross bedded bodies encased in offshore deposits excellent outcrops of the upper pliocene lower pleistocene calcarenite di gravina around matera southern italy provide continuous exposure of coarse grained clastic basin margin shoreline to offshore facies among these facies the most conspicuous and volumetrically important are the transition slope deposits that form large scale high angle cross bedded lithosomes these are laterally extensive parallel with the paleoshoreline and show seaward progradation we interpret them to represent avalanches of sediment swept out onto a depositional slope below wave base from the shoreface zone by storm waves and wind driven currents three types of building blocks are recognized based on bedding patterns and facies architecture embryonic parasequences mature parasequences and simple sequences parasequences formed during stillstands of sea level and simple sequences during high frequency cycles of relative change of sea level these building blocks are stacked in a backstepping configuration and onlap onto cretaceous limestone substrate backstepping is believed to be due to a tectonically forced transgression that is punctuated by high frequency cycles of sea level modern analogs for these building blocks are the holocene prograding prisms detected in high resolution seismic lines of the mediterranean shelves the reflection patterns of these seismic units resemble the bedding architecture of the matera simple sequences and parasequences and show similarities of shape size position and orientation of coastal setting and direction of progradation comparison of the holocene prisms and the pliocene pleistocene accretional units in matera indicates that they may represent the same begin page 662 genetic process progradation of clastic prisms below the wave base level the matera accretional units also show similarities with other examples of laterally extensive large scale cross bedded sand bodies encased in offshore deposits such as some sandbanks differentiating between these laterally extensive and seaward prograding cross bedded sand bodies and some coarse grained gilbert type deltas is difficult however if interpretations are based only on two dimensional 2 d outcrops in dip section without high resolution data it is also difficult to distinguish between transition slope and prograding shoreface lithosomes this difficulty may be acute where only seismic or well log data are available however certain other architectural characteristics such as stacking and preservation of facies belts and position of bounding surfaces as well as differences in associated sedimentary structures and fossil content may be used for interpretation the matera example provides a mechanism for emplacement in offshore settings of elongate and strandline parallel sand and gravel deposits that prograde seaward and that preserve a coarsening upward internal succession this article offers an interpretation for other ancient examples of large scale cross bedded lithosomes encased in offshore deposits

sedimentology of a marine intermontane pleistocene gilbert type fan delta complex in the crati basin calabria southern italy the crati basin is a pliocene holocene extensional basin filled by the progradation of different types of marine fan delta systems coarse grained gilbert type fan deltas developed during the pleistocene they represent the sedimentary response to a strong differential uplift involving the basin margins and the basin itself the differential uplift was responsible for the fragmentation of the basin into several sub basins into which these fan deltas prograded the protection and lateral confinement by structural highs steep coastlines and the absence of strong tidal action in the adjacent ionian sea allowed the regular progradation of these fan deltas in the restricted gulfs and narrow embayments of the crati basin for the classical gilbert type fan deltas in lacustrine settings homopycnal inflow favours a rapid mixing of water masses and deposition of sediment close to the river mouth in the case of the example described here the density contrast between the sea water and the inflowing river water caused the separation of the muddy fraction from the coarse sandy and conglomeratic part of the sediment this allowed the development of steep mud poor coarse grained delta foresets slope instability features slump scars conglomeratic flow slides are fairly scarce in the proximal parts of the san lorenzo del vallo system towards the north where protection from the ionian sea was less they increase in importance

sequence stratigraphy of the upper oligocene lower miocene of eastern jylland denmark role of structural relief and variable sediment supply in controlling sequence development the upper oligocene lower miocene succession in eastern jylland can be subdivided into three sequences a c from older to younger deposited on and around the ringkobing fyn high the development of the sequences reflects a complex interaction between eustatic sea level changes physiography and variable sediment supply superimposed on this frequent storms promoted longshore sediment transport and the development of spit systems adjacent to structural highs as a consequence sequence boundaries and flooding surfaces are not always expressed as portrayed in conventional sequence models sequence boundaries or flooding surfaces may only be marked by subtle changes in depositional environment that can only be revealed by careful integration of sedimentological observations with palynological data the influence of the topography resulted in the development of brackish water basins that were sufficiently large to permit the deposition of hummocky cross stratified sands with muds these deposits are overlain by clean hummocky and swaley cross stratified sands that were deposited in a fully marine high energy environment this evolution from mud rich storm influenced sediments to sand dominated shoreface sediments resulted from a rise in sea level and was not the result of shoreface progradation and downstepping during a sea level fall in addition to the topographic control on sequence development sediment supply to the study area changed significantly during the deposition of the three sequences initially the basin was sediment starved favouring the formation of glaucony rich sediments the sediment input gradually increased and the influence of structural highs and lows became less significant with time consequently both sequence boundaries and flooding surfaces are characterized by more conventional features in the younger part of the succession where a basinward displacement of the shoreline resulted in thick lowstand delta deposits

progradational gravel beach sequences in a moderate to high energy microtidal marine environment the anatomy of progradational gravel beaches was analysed in two different tectonic settings the strongly subsiding messinian foreland basin of the eastern southern alps and the rising pleistocene marine terraces of the outer margin of the apenninic chain progradation took place near the mouths of fan delta or braid delta distributaries debouching in microtidal landlocked basins palaeo adriatic and palaeo ionian seas a wind wave climate comparable to that of the present day was characterized by periodic intense storm activity most of the beachface progradation is thought to have taken place during the post storm recovery and fair weather stages whereas the impact of storms is mostly recorded by the cutting of erosional surfaces on the beachface and by emplacement of poorly sorted and coarse grained gravels on the shoreface by storm intensified seaward trending flows and behind the highest berms by washover processes analysis of the sequences led to the identification of a number of typical divisions which are differently developed in the two settings compared here the characteristics of the apenninic sequences suggest a strongly variable wind wave climate with periodic changes from a relatively dissipative barred morphology during storms accompanied by strong longshore currents and rip development to a more reflective state typical of recovery and fair weather stages the southern alpine sequences on the other hand are characterized by poor evidence of barred morphology and of longshore currents and widespread effects of shear and gravity sorting in the lower beachface gravels these features indicate a comparatively more reflective average state due to location of beaches along the deeply embayed head of the palaeo adriatic and the very narrow directional width of the incoming wave spectrum which was almost shore normal most of the time in addition to well developed shape zonation of gravels the common presence of wave generated gravel megaripples in the southern alpine sequences indicates the greater influence of long period waves due to the greater available fetch distances in both settings the cyclicity is thought to be genetically related to minor changes of sea level

the architectural variability of small scale cycles in shelf and ramp clastic systems the controlling factors many sedimentary successions are composed of metre to decametre scale cycles exhibiting various stratal architectures that depend on the complex interplay among several syndepositional controlling factors these controlling factors may produce extremely different stratal and facies architectures along relatively brief distances in the same basin but in contrast they also may form similar architectures in basins that experience a radically different tectonic setting the recognition of factors that controlled the architecture of small scale cycles therefore is very important to reconstruct the depositional history of sedimentary successions these factors include 1 the interplay between the rate of accommodation development and the rate of sediment supply a s 2 the amplitude and shape of the relative sea level curve 3 the position in the shoreface shelf system 4 the basin physiography 5 the shoreline trajectory 6 the climate driven environmental energy 7 the siliciclastic input vs carbonate production shoreface to shelf small scale cycles can be grouped into three main categories r cycles showing a dominant regressive interval t r cycles with transgressive and regressive intervals of similar thickness t cycles showing a dominant transgressive interval although some depositional settings may favour the deposition of a particular type of cycle these cycle motifs appear to be mainly controlled by the interaction of local and wider scale controlling factors for example t cycles may be present in both subsiding and uplifting settings depending on the interplay between the a s and the other factors cited above as a result r t r and t cycles may be recognized within the same depositional system these evidences suggest that care must be taken to apply general models that predict the stratal architecture of cycles mainly in function of the long term a s the correct prediction of the cycle architecture is important also for hydrocarbon researches as the thickness of potential reservoir deposits is the result of the interplay among factors discussed here

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

early holocene regressive spit platform and nearshore sedimentation on a glaciofluvial complex during the yoldia sea and the ancylus lake phases of the baltic basin sw finland abstract the depositional history of the virttaankangas plain a fan like enlargement of the large sakylanharju glaciofluvial ridge in sw finland is examined the sakylanharju ridge has been interpreted as having formed as an interlobate esker and the morphology of the virttaankangas plain as representing predominantly subaqueous glaciofluvial to glaciolacustrine deposition this investigation uses new sedimentologic outcrop data with extensive subsurface drilling gpr surveys seismic soundings and gravimetric measurement data provided by groundwater investigations to describe the stratigraphy morphology and depositional history of the plain in contrast to earlier interpretations the results emphasise the role of littoral processes in the origin of the virttaankangas plain the plain is interpreted as having originated during the development of a progradational sequence of spit platform and superimposed nearshore sediments deposited during the glacio isostatic forced regression of the yoldia sea and ancylus lake phases of the baltic basin 9900 9000 14 c bp documented depositional history supports an interval of retarded regression at the beginning of the ancylus lake phase i 9500 9200 14 c bp in the sakylanharju area

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

coralline algal reef frameworks published and unpublished accounts of coralline algal reef frameworks are reviewed the descriptions are divided into frameworks constructed from crustose coralline algae and those constructed from branching corallines crustose frameworks are briefly described and illustrated from the miocene of malta recent coralligene from the mediterranean eocene reefs from spain recent algal reefs of st croix u s virgin is and algal reefs from bermuda branching frameworks are briefly described and illustrated from the recent maerl of the ne atlantic recent mud mounds from florida recent algal reefs from st croix and recent algal ridges on pacific reefs crustose and branching frameworks show an increase in strength of construction early submarine cements and macro borers and a decrease in erodibility from low to high energy environments the occurrence of genera in coralline frameworks is primarily controlled by their geographic and water depth ranges the construction of coralline frameworks is seen as the result of competition for living space on shallow marine hard substrates

superimposed cycles of composite marine terraces the example of cutro terrace calabria southern italy abstract marine terraces are a valuable archive of information in the reconstruction of uplift and sea level history of coastal areas especially when they can be correlated with specific highstands of the eustatic curve usually the correlation is based on the assumption that any morphological terrace is the result of a single sea level fluctuation however if the surface of a terrace is reoccupied during successive transgressions the result may be a single morphological terrace which has in fact been generated by several superimposed sea level fluctuations this study illustrates what type of stratigraphic architecture may be recorded in the deposits of such composite marine terraces focusing on identification and interpretation of discontinuity surfaces and facies analysis the examined example is the marine terrace of cutro the highest and most extensive of five terraces preserved in a step like sequence along the coast of the crotone peninsula calabria southern italy the sedimentary cover of the cutro marine terrace had generally been regarded as the result of a single sea level oscillation but stratigraphic analysis and correlation of several sections has enabled the recognition of three distinct transgressive regressive sequences these cycles display an overall shallowing trend from shelf deposits represented in the first cycle by algal carbonate buildups to shoreface and alluvial deposits in the younger cycles the succession is now interpreted as a response to high frequency sea level fluctuations occurring during a long term interglacial such as those documented during marine isotope stage mis 7

progradational sequences in miocene shoreline deposits southeastern caliente range california abstract an exceptionally well exposed marine nonmarine transition in middle miocene strata exists in the southeastern caliente range california about 50 individual progradational sequences form a succession that ranges in thickness from approximately 1000 m where predominantly nonmarine to more than 2500 m where predominantly marine paleogeographic evidence in basalt flows near the top of the succession and in overlying fluvial deposits indicates that these middle miocene strata were deposited across a north northwest trending shoreline a complete progradational sequence typically is several meters to a few tens of meters thick and includes strata that represent three intertonguing stratigraphic units individual sequences generally rest on a thin gravel deposit interpreted as a transgressive lag on an erosional surface the gravel is overlain by structureless siltstone or fine grained sandstone deposited at water depths where the rate of faunal mixing exceeded that of production of structures by physical processes these rocks grade upward into bedded fine sandstone deposited closer to shore where physical processes exceeded bioturbation crossbedded lenses of coarse sand or fine gravel in the upper part of this facies suggest the presence of fairly long period surface waves the bedded fine sandstone is sharply ove lain by a cross bedded coarse sandstone facies that is interpreted as a combined offshore bar rip channel surf zone assemblage cross strata dip dominantly offshore suggesting substantial deposition from rip currents a secondary shoreparallel mode of cross strata direction suggests longshore currents produced by surface waves from the northwest the crossbedded coarse grained sandstone grades upward into planar bedded medium grained sandstone that is interpreted as a beach foreshore this facies grades upward through structureless medium grained sandstone into nonmarine or lagoonal red and green mudstone of the caliente formation the middle miocene succession was deposited in a subsiding basin that was otherwise remarkably stable tectonically the position of the strand line differed no more than a few kilometers through a period of 1 to 3 m y the average duration of the transgressive regressive cycles a few tens of thousands of years together with their distribution in groups of three or four in the lower two thirds of the succession is consistent with the pattern of long term climatic cycles produced by periodicity of the earth s solar orbit and may be related to eustatic sea level changes attendant to the development of the antarctic ice cap changes in the pattern of progradation in the upper part of the succession and nearby basaltic eruptions may have been precursors to the onset of movement along th san andreas fault in this area 12 14 m y ago

architectural complexity of a carbonate transgressive systems tract induced by basement physiography three dimensional exposure of the plio pleistocene calcarenite di gravina formation around matera horst italy permits analysis of the architecture and internal complexities of carbonate sedimentary bodies around a palaeoisland spatial organization of the different lithosomes along with their skeletal composition sedimentary structures and bedding patterns helps decipher the key factors that controlled platform architecture and distribution of heterogeneities basement physiography type and loci of carbonate production bottom currents and changes in accommodation relative sea level changes resulted from high frequency glacioeustatic cycles that punctuated an overall tectonically induced transgression topographic relief fragmentation of the limestone basement and wave energy controlled lithoclastic supply basement physiography and relative sea level changes determined the area available for carbonate producing biotas and thus the amount and type of skeletal sediments on the moderately dipping south western margin waves and associated currents re distributed the lithoclasts derived from coastal abrasion bioclasts mostly derived from epiphytic seaweed production in the shoreface infralittoral prisms resulted from downdip transport progradation and longshore transport which controlled along strike continuity of the prisms where basement continuity was interrupted at the margin of the palaeoisland a lithoclastic fan was deposited from dumping sediments carried by shore parallel currents fan shaped skeletal bodies coalesced to form an apron on the steeper northern side of the palaeoisland when a structural platform was flooded and epiphytic carbonates were shed red algae contribution depended on the available oligophotic area which in turn was controlled by high frequency sea level cycles basement physiography and apron aggradation the internal architecture of this apron resembles a low stand wedge but it accumulated during transgression deeper water contour parallel currents formed a lithosome at the foot of the structural relief interpreted as drift deposits it is composed of shallow water benthonic skeletal components planktonic foraminifera and some limeclasts

stratigraphy and sedimentology of fault controlled backstepping shorefaces middle pliocene of crotone basin southern italy abstract the middle pliocene sedimentary succession of the crotone basin in the calabria peloritani terrane southern italy was deposited during extensional tectonism dominated by a system of horst and half grabens the studied succession spartizzo lagoonal clays and scandale shallow marine deposits is up to 250 m thick and represents a barrier lagoon system that spans a tectonically controlled transgressive phase the succession is internally organised into six higher frequency cycles 20 80 m thick most of these cycles are formed by transgressive lagoonal deposits separated from the overlying regressive shoreface units by a wave ravinement surface lowstand fluvial deposits were recognized locally at the base of the last cycle the shoreface units are up to 50 m thick and typically consist of a coarsening upward succession of isolated to amalgamated hummocky cross strata that merge upwards into swaley and trough cross strata ne trending synsedimentary normal faults strongly controlled the deposition and enhanced subsidence and thickness expansion within the half graben basins

brittle deformations in the upper pleistocene deposits of the crotone peninsula calabria southern italy abstract the structural setting of the crotone peninsula calabria southern italy is discussed in this paper structural analyses were carried out both on a regional and an outcrop scale to detect the main structural systems and the stress field which affected the area during the late pleistocene the tectonic features observed in the area are represented by normal faults and extensional joints the regional scale faults are arranged in five main systems striking ene wsw nne ssw e w nw se and nnw sse they are responsible for the dislocation of four marine depositional units cutro terrace correlatable with the isotopic stage 7 s leonardo campolongo isola di capo rizzuto terrace correlatable with the isotopic substage 5e le castella capo rizzuto terrace correlatable with the isotopic substage 5c and capo colonne terrace correlatable with the isotopic substage 5a in several distinct terraces from the studies carried out on a mesostructural scale it is possible to conclude that for the last 200 000 yrs the crotone peninsula was affected by an extensional stress field the comparison between the average uplift rates calculated for the crotone peninsula terraces and those computed for several upper pleistocene deposits located in sicily calabria and campania suggests that the intense tectonics which affected the crotone peninsula can be related to the geodynamic activity of the calabrian arc

submerged late pleistocene reefs on the tectonically stable s e florida margin high precision geochronology stratigraphy resolution of substage 5a sea level elevation and orbital forcing abstract a well preserved submerged in situ fossil reef tract lies offshore of the southeast florida carbonate margin in the florida keys cores in two transects enabled reconstruction of reef stratigraphy and paleoenvironments paleo water depths and paleo sea levels because florida is tectonically stable the elevation data required correction only for the known minor subsidence rate twenty eight pristine aragonitic corals were dated via high precision tims u series methods to produce a comprehensive late pleistocene and early holocene geochronology the pleistocene section of the fossil reef includes a thick section of substage 5a reef growth recorded from 15 to 11 m msl spanning an age range of 86 2 80 9 ka paleoenvironmental reconstruction local water quality constraints and elevations of concurrent bahamian speleothem growth combine to limit sea level to 9 0 m msl at 83 ka this coincides unlagged with the 82 ka 65 n july insolation peak the absence of any lag suggests that the earlier peak in obliquity at 92 ka also controls paleoclimate and sea level a below present sea level estimate for substage 5a from the florida fossil reef data coincides more closely with uplift corrected reef data estimates of 15 to 13 m msl from tectonic margins such as barbados and haiti than with higher than present sea levels derived from detrital corals from bermuda and the u s atlantic coastal plain the best tims dates on corals and speleothem constraining sea level combine to produce a new regional sea level curve for the atlantic caribbean region for late isotope stage 5 and early stage 4

depositional systems and sequence stratigraphy of coarse grained deltas in a shallow marine strike slip setting the bohemian cretaceous basin czech republic deposits of coarse grained gilbert type deltas showing varying degrees of reworking of foresets by basinal currents were identified in middle turonian to early coniacian sandstones of the bohemian cretaceous basin the progradation of the deltaic packages earlier interpreted as large scale subaqueous dunes shelf ridges or subaqueous fault scarp accumulation terraces was controlled by high and low frequency relative sea level changes in a relatively slowly subsiding intracontinental strike slip basin end member types of the bohemian cretaceous coarse grained deltas are deep water deltas characterized by thick 50 80 m foreset packages with steep 10 30 foresets and shallow water deltas which deposited thin 15 m packages with foresets typically between 4 and 10 the differences in thickness and foreset slope angle were controlled predominantly by the accommodation available during progradation the depositional regime of the deltas was governed by i the fluvial input of abundant sand bedload with a minor proportion of gravel ii gravity flows most probably caused by liquefaction of the upper part of the unstable foreset slope and iii migration of sandy bedforms on the foreset slopes the bedform migration was driven by unidirectional currents of possible tidal origin individual foreset packages represent systems tracts or parts of systems tracts of depositional sequences a variety of stacking patterns of high frequency sequences exists in the basin caused by low frequency relative sea level changes as well as by local changes in sediment input because of generally low subsidence rates fluvial or beach topset strata were not preserved in the cases studied the absence of preserved fluvial facies which has been one of the main arguments against the fluvio deltaic origin of the sandstone bodies is explained by erosion of the topsets during transgression and their reworking into coarse grained lags of regional extent covering ravinement surfaces

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

protactinium 231 dating of carbonates by thermal ionization mass spectrometry implications for quaternary climate change measurement of protactinium 231 231pa in carbonates by thermal ionization mass spectroscopy yields 231pa ages that are more than 10 times more precise than those determined by decay counting carbonates between 10 and 250 000 years old can now be dated with 231pa methods barbados corals that have identical 231pa and thorium 230 230th ages indicate that the timing of sea level change over parts of the last glacial cycle is consistent with the predictions of the astronomical theory two devils hole calcite subsamples record identical 231pa and 230th ages suggesting that the chronology of this climate record is accurate

storm and tide dominated shorelines in cretaceous moosebar lower gates interval outcrop equivalents of deep basin gas trap in western canada the moosebar and gates formations crop out in the deformed foothills belt south of fort st john british columbia they permit examination of the depositional environments of sandstones and conglomerates that are gas bearing in the equivalent wilrich falher interval of the deep basin of alberta and british columbia the moosebar gates interval consists of several upward coarsening and marine to nonmarine sequences moosebar bioturbated shales pass upward into turbidites and offshore storm deposits flow directions indicate a north dipping paleoslope a second coarsening upward sequence at the top of the moosebar and base of the gates terminates in a lenticular fluvial conglomerate up to 30 m thick which is overlain by coals carbonaceous mudstones and sandstones above the carbonaceous zone a major lateral facies change is observed fluvial conglomerates in the south grade into beach conglomerates northward the upper part of the beach conglomerate consists of exposed three dimensional storm berms at least 500 m long up to 1 5 m high with wavelengths of 12 to 24 m the berms trend east west seaward of the conglomerate beach are herringbone cross bedded tidal sandstones with a marine trace fauna graded sharp based conglomerates also are present probably washed out to sea by storms farther north at the same stratigraphic level is a series of partly overlapping conglomerate bars up to 5 m thick and 40 to 50 m across the tops of these bars are covered with storm formed symmetric conglomeratic dunes details of the orientation and geometry of these conglomerate bodies along with their internal structure and pebble fabrics suggest that four major environments fluvial beach offshore conglomerate bars and offshore graded storm conglomerates should be identifiable and predictable in the subsurface

sequence stratigraphy and architectural variability in growth fault bounded basin fills a review of plio pleistocene stratal units of the crotone basin southern italy field examples from the pliocene to pleistocene succession of the crotone basin document the variability of stratal architecture in syntectonic units deposited in normal fault bounded basins relatively thick trangressive intervals are common within these successions as shown in the zinga 2 zinga 3 and strongoli stratal units transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones aggradational highstand shallow marine packages are typical of the lower pliocene succession in half graben basins these deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation relatively thick forced regressive deposits are common within basins during phases where the accommodation supply ratio is low e g the middle pleistocene san mauro sandstone these deposits influenced by growth faulting and folding recorded base level lowering linked to glacio eustasy a complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift e g the serra piani stratal unit such variations are thought to be related to the onset of an earliest mid pliocene transpressional tectonic phase the studied deposits therefore show a marked tectonic control that strongly influenced their stratal architecture these examples represent interesting cases of sequence stratigraphic analysis in growth faulted contexts

geochemical and petrographic studies of ta mineralization in the nuweibi albite granite complex eastern desert egypt the nuweibi albite granite is one of 14 known sn ta nb bearing granitoids in the eastern desert region of egypt the granite is a highly leucocratic albite rich rock with accessory columbite tantalite cassiterite microlite and ixiolite as well as topaz garnet and white mica ages of 450 600 ma were obtained from zircons by the 207pb 206pb evaporation method great uncertainty is caused by the small size and poor quality of the grains but the precision is sufficient to indicate that the granite is late or postorogenic with respect to the panafrican orogeny the nuweibi granite is divided into a western and an eastern part by a regional fault both parts of the granite are compositionally similar but there are important differences and a clear compositional gap between them so they are considered separate facies of an intrusive complex the eastern part of the granite is more highly mineralized has higher modal albite contents and higher ta nb ratios both in the whole rock and in the ore minerals it is suggested that the two parts of the granite evolved from a common source and were emplaced sequentially the eastern part representing a later more fractionated magma textural evidence strongly suggests that the granite has a magmatic origin overall but disturbance of geochemical trends at the whole rock scale and at the scale of zoning profiles in individual grains of columbite tantalite indicate post magmatic overprinting by analogy with other ta bearing albite granites the sodic bulk composition of the nuweibi granite can be explained by fluorine enrichment in the magma fluorine contents in the magma were high enough to stabilize topaz and muscovites contain 2 4 wt f however whole rock f contents are low we speculate that the low ca al and p contents of the magma prevented abundant f bearing minerals to form and led to loss of fluorine to now eroded roof rocks

raised pleistocene marine terraces of the crotone peninsula calabria southern italy facies analysis and organization of their deposits abstract wide marine terraces well known in the italian literature are present in the crotone peninsula ionian calabria they are related to the interplay between pleistocene sea level changes and the progressive uplift of the calabrian arc from the middle pleistocene onwards we present a description of facies organization and stratigraphical characteristics of the terrace deposits along with a new geological map of the area all the marine terraces unconformably overlie a plio pleistocene slope succession known as cutro clay the oldest and highest terrace named cutro terrace is placed between 90 and 200 m of elevation and is gently inclined south eastwards four younger terraces placed at progressively lower elevations and dipping seawards at low angles have been recognized the sedimentary deposits of the terraces are represented by mixed carbonate and siliciclastic bodies up to 10 m thick algal reefs and grainstone to rudstone deposits are common in the south eastern part of the study area whereas mostly siliciclastic sandstone units of shoreface environments are more abundant northwards and westwards the deposits of some terraces are made up of minor cycles bounded by subaerial transgressive and flooding surfaces referred to minor sea level fluctuations nne ene e and wnw trending normal fault systems are present within the study area and dissect the marine terraces specifically the activation of ene trending faults took place after the formation of the oldest terrace but prior to the formation of the younger terraces

mechanisms for forming discontinuity surfaces within shoreface shelf parasequences sea level sediment supply or wave regime abstract a 2d process response model was used to evaluate potential mechanisms involved in the formation of small scale stratigraphic variability that is observed within progradational wave dominated shoreface shelf parasequences model experiments which are based on scenarios that consist of a 25 ky progradational phase suggest that discontinuity surfaces form when either sediment supply or sea level fall rapidly or when wave height regime increases over relatively short time periods 102 104 y during coastal progradation in these cases mean deposition rate near the lower shoreface drops which combined with coastal progradation results in a discontinuity surface both observed and simulated discontinuity surfaces form predominantly in lower shoreface deposits and bound meter scale stratigraphic cycles simulations show that wave regime variability affects the shoreface shelf to a much greater depth than minor sea level change therefore facies shifts along wave climate induced bounding surfaces occur over wider reaches of the shoreface shelf system than sea level induced facies shifts high frequency variability in sediment supply rate results in the formation of discontinuity surfaces across which there are no distinct facies shifts

experiments on oscillatory flow and combined flow bed forms implications for interpreting parts of the shallow marine sedimentary record abstract analog laboratory experiments were conducted to investigate subaqueous bed forms generated under storm like oscillatory and combined flow experiments were carried out in a large wave tunnel and used a range of sand sizes fine and very fine wave periods 10 5 and 8 s oscillatory velocities 0 to 125 cm s and unidirectional velocities 0 to 25 cm s at low unidirectional velocities 10 cm s addition of an increasing collinear oscillatory flow caused the bed to evolve from small scale wavelength 100 cm symmetric orbital ripples to plane bed at higher unidirectional velocities 10 cm s a similar trend was noted but ripples were more asymmetric three phase diagrams are presented to summarize the observed relationships of bed configurations to flow conditions these diagrams are intended to assist in the interpretation of shallow marine sedimentary environments where oscillatory and combined flow are thought to be omnipresent distinctive features of small scale asymmetric combined flow ripples generated are a 3d planform round crest and convex up sigmoidal profile with local pronounced scour at the toe of the stoss side giving the ripple profile a boxy appearance similarly large scale asymmetric combined flow ripples had broad and round crests convex up stoss sides and compressed profiles due to scouring at the toe of the stoss side hummocky bed forms were generated under moderate to high oscillatory velocities and low unidirectional velocities hummocks were not observed as a distinct bed state but rather appeared to mark transitions in bed form scale and symmetry hummocks were more prevalent at longer oscillatory periods and in finer grained sediment stratification produced by synthetically aggrading hummocky bed profiles closely resembles hummocky cross stratification with the introduction of only a small unidirectional flow component hummocks evolve into downstream migrating large scale asymmetric ripples and the resultant cross stratification becomes similar to that produced by unidirectional flow dunes accordingly these experiments suggest that much of the hummocky cross stratification observed in the stratigraphic record is produced by storm generated long period oscillatory dominant combined flows inasmuch as long period high energy waves require deep wide basins to form hummocky cross stratification may therefore serve as a useful indicator of deposition in unrestricted open water conditions

periodicity of mesoscale phanerozoic sedimentary cycles and the role of milankovitch orbital modulation data on more than 200 mesoscale sedimentary cycles indicate that phanerozoic cycle periods are randomly distributed with respect to the four major milankovitch orbital parameters except late mississippian through late pennsylvanian cycles which show positive clustering about the 413 000 yr eccentricity period cycle periods calculated from average thicknesses and accumulation rates are strongly dependent on the former correlation coefficient 0 802 but relatively independent of the latter correlation coefficient 0 360 hence calculated period is largely a function of average cycle thickness and milankovitch range periods will be preferentially calculated for cycles with average thicknesses between 1 m and 20 m regardless of actual causes of cyclicity for individual cyclic sequences arguments for milankovitch control based solely on average period are unfounded comparison of short term holocene sedimentation rates and long term phanerozoic accumulation rates for cyclic peritidal and delta

residual topography lithospheric structure and sunken slabs in the central mediterranean abstract the central mediterranean comprises subduction collision and backarc extension all in a relatively small area in this paper we analyze the topography of this region examining the influence of subducting slabs on overriding plates we take the observed surface elevation remove the contribution of the crust to it and use the residual topography to identify regions that are unusually low unusually high or normal then we calculate lithospheric thickness where local isostasy applies the results provide information about the structure of the lithosphere in this complex region and about the vertical tectonics in particular we found a difference between the south tyrrhenian subduction zone and the apennines consistent with the processes of slab rollback and slab break off respectively in the south tyrrhenian the edge of the oceanic plate is strongly pulled down whereas the edge of the overriding plate the calabrian peninsula is uplifted this opposite trend indicates weak plate coupling that is the subducting slab which is rapidly rolling back hangs almost entirely on the oceanic plate and the overriding plate is free in contrast in the apennines high residual topography and uplifting are detected on both sides of the mountain belt consistent with complete break off of the subducted lithosphere

gravelly spit deposits in a transgressive systems tract the pleistocene higashikanbe gravel central japan the pleistocene higashikanbe gravel which crops out along the pacific coast of the atsumi peninsula central japan consists of well sorted pebble to cobble size gravel beds with minor sand beds the gravel includes large scale foreset beds 5 10 m high and overlying subhorizontal beds 0 5 3 m thick showing foreset and topset structure from which the gravel has previously been interpreted as deposits of a gilbert type delta however 1 the gravel beds lack evidence of fluvial activity such as channels in the subhorizontal beds 2 the foresets incline palaeolandwards 3 the gravels fill a fluvially incised valley and 4 the gravels overlie low energy deposits of a restricted environment such as a bay or an estuary the foresets generally dip towards the inferred palaeoshoreline indicating landward accretion of gravel reconstruction of the palaeogeography of the peninsula indicates that the higashikanbe gravel was deposited as a spit similar to that developed at the western tip of the present atsumi peninsula rather than as a delta according to the new interpretation the large scale foreset beds are deposits on the slopes of spit platforms and accreted in part to the sides of small islets that are fragments of the submerging spit during relative sea level rise the subhorizontal beds include nearshore deposits on the spit platform topsets and deposits of gravel shoals or bars which are reworked sediments of the spit beach gravels during a transgression the lack of spit beach facies in the subhorizontal beds results from truncation by shoreface erosion dome structure which is a cross sectional profile of a recurved gravel spit at its extreme point and sandy tidal channel deposits deposited between the small islets were also identified in the higashikanbe gravel the higashikanbe gravel fills a fluvially incised valley and occupies a significant part of a transgressive systems tract suggesting that gravelly spits are likely to be well developed during transgressions the large scale foreset beds and subhorizontal beds of gravelly spits in transgressive systems tracts contrast with the foreset and topset beds of deltas characteristic of highstand lowstand and shelf margin systems tracts

luminescence chronology of late pleistocene raised beaches in southern italy new data of relative sea level changes abstract littoral sediments forming terraces along the crotone peninsula coast southern italian have been investigated using sedimentological analysis and luminescence dating techniques and adopting assessments from previous work on fossil assemblages all sediment layers analysed were deposited in the nearshore environment between 20 m below and few metres above sea level during the falling sea level of a temperate warm climate interval the restoration of almost identical environmental conditions occurred in oxygen isotope substages 5e and 5a and in oxygen isotope stage 3 limits given by luminescence physics prevented accurate dating of the uppermost lying terrace former crotonian stage terrace and the presence of a substage 5c terrace is masked by the lack of suitable material for dating constraints on the positions of relative sea level from the reliable data set show that the sea level fell from 2 m during substage 5e to 29 m during substage 5a and then rose to 15 m during stage 3 observations for oxygen isotope stage 3 sea level at the crotone peninsula coast are inconsistent with those at the huon peninsula new guinea and in the western pacific the disagreement highlights the lack of knowledge concerning mediterranean thermohaline circulations and sea water exchanges between the atlantic and mediterranean seas during glacial cycles

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

sedimentology seismic facies and stratigraphy of a holocene spit platform complex interpreted from high resolution shallow seismics lysegrund southern kattegat denmark abstract eighty kilometres of high resolution seismic profile data 8 km km 2 were collected in the lysegrund area southern kattegat denmark to reconstruct the seismic stratigraphy of a holocene spit platform complex comparison of two sets of seismic data shows a significant difference in reflection pattern by using lap style analyses four holocene units were recognised in boomer profiles 0 8 2 0 khz they are closely examined in this paper and their geometry is illustrated in a series of isopach maps drawn to understand the development of the deposit in time and space three vibra cores provide the stratigraphic control and demonstrate the presence of three lithofacies with gradational boundaries in the interval that correlates with the three upper boomer units the three lithofacies are part of a single lithofacies succession in contrast to the boomer profiles the subbottom profiles 3 5 khz demonstrate continuous accretion surfaces within the lithofacies succession comparisons of the boomer and subbottom profile data therefore indicate that the three boomer units are genetically coupled and that there are no significant time gaps between units the three boomer units are interpreted to represent a spit platform complex that developed in three phases during a general rapid rise of relative sea level 10 mm a under conditions of excess sediment supply the source materials were mobilised from glacial fluvial sediments in a headland west of and close to the spit platform during phase 1 spit development occurred in shallow water this acted as a core to the development of a spit platform during phase 2 that consisted of three seismic facies identifiable on 3 5 khz subbottom profiles during phase 3 true foresets and bottomsets developed growth of the platform surface kept pace with sea level rise and the entire spit platform complex formed in less than a thousand years focusing on differences in the seismic data helps avoid pitfalls in choosing methods to interpret data the closely spaced seismic line net forms the basis of a 3d dynamic model of the spit platform that resembles the model of meistrell meistrell f j 1972 the split platform concept laboratory observations of spit development in schwartz m l ed spits and bars dowden hutchinson and ross stroudsberg pp 225 283

fault control of channel sandstones in dakota formation southwest powder river basin wyoming abstract the dakota formation is an important oil reservoir in the southwestern powder river basin and adjoining casper arch two fields burke ranch and south cole creek are used as examples to show the depositional environments of the dakota and to indicate the influence of tectonic control on the distribution of the environments burke ranch field is a stratigraphic trap which produces oil from the upper bench of the dakota the environment of deposition of the reservoir determined by subsurface analysis is a channel sandstone south cole creek field is a structural stratigraphic trap which produces from the lower bench of the dakota two distinct facies a channel and channel margin sandstone exist at south cole creek at both burke ranch and south cole creek it can be shown that the dakota channels were deposited on the downthrown side of faults which were present during dakota time and which now are reflected on the surface by drainage patterns an understanding of the environments of deposition of the dakota and control of the environments by paleotectonics is necessary for exploration for these prolific reservoirs end of article last page 1350

late pleistocene holocene sediments on the spanish continental shelves model for very high resolution sequence stratigraphy abstract sequence stratigraphy analysis of high resolution seismic profiles geopulse uniboom and 3 5 khz of late pleistocene holocene sediments has been carried out on five sectors of the spanish continental margin four types of depositional settings are distinguished in these sectors 1 low subsident ramps alboran margin cadiz gulf 2 high subsident 2m kyr ramps alicante valencia 3 ria type morphology on the atlantic passive margin ria de muros and 4 fault scarp morphology systems with subsidence balearic margin a type 1 sequence is interpreted in all these sectors being composed of lowstand systems tract transgressive systems tract and highstand systems tract this conforms to the basic concepts of sequence stratigraphy and each systems tract correlates with a particular part of the last eustatic hemicycle characteristic shelf features such as terraces terraces with beach deposits and progradational sediment wedges evidence a complex stacking of lesser sub sequences in all the systems tracts which must be related to very short period sea level stillstands and fall we propose a very high resolution sequence stratigraphy model in which the last sea level hemicycle is punctuated by p cycles 4500 years which give rise to the neo glacial events h cycles 2200 950 years and c cycles 500 50 years these cycles interact with each other thus establishing the placing of the high and low sea levels this attention to detail 1 explains sedimentary evolution on both the shelf and upper slope during late pleistocene holocene time 2 illustrates some departures from the classical sequence stratigraphy model and 3 also demonstrates that the late pleistocene holocene eustatic curve is not one simple transgression but is modulated by three differing period cycle groups below the milankovitch band our model is delimited by fluctuating sea level during pleistocene holocene times such features should be identifiable on any continental margin however localized features occur due to subsidence and continental shelf morphology which determ ine the location and depth of sedimentary bodies generated in each eustatic cycle

facies and cycle architecture of a pleistocene marine terrace crotone southern italy a sedimentary response to late quaternary high frequency glacio eustatic changes abstract cyclic late pleistocene shallow marine deposits such as those forming the sedimentary cover of some marine terraces allow a detailed study of the architecture of nearshore to offshore cycles deposited under the influence of high amplitude glacio eustatic changes the capo colonna marine terrace located near crotone southern italy is composed of two cycles recording a low frequency retrogradational trend which is thought to be the result of a generalized base level rise during a late pleistocene interglacial stage superimposed on regional uplift cycles of the capo colonna marine terrace are composed of coarse grained lags siliciclastic shoreface deposits and mostly carbonate shelf deposits and their general stratigraphic architecture evidences relatively thin transgressive and thick regressive intervals the latter can be top truncated due to wave ravinement during a subsequent erosional transgression the architectural style of the capo colonna marine terrace cycles is thought to be linked to very rapid base level rises related to the late pleistocene high amplitude glacio eustatic changes climatic variations controlling the sediment supply rate are considered less effective in the present context present results allow a comparison with other cyclic successions developed under icehouse climatic regimes showing a discrete variability in their stratal architecture

a late pleistocene coarse grained spit platform sequence in northern jylland denmark several well preserved late pleistocene spit systems occur uplifted in northern jylland denmark their present day morphological expression allows detailed study of spit growth patterns while the internal sedimentological organisation can be examined in a series of pits distributed along the length of the spits two characteristic vertical sequences are recognized in the systems the first sequence i consists of a giant scale cross bedded foreset unit overlain by topset and beach units while the second sequence ii consists of the foreset unit overlain by bar trough and beach units the two sequence types pass laterally into each other with a short overlap zone they can be interpreted in terms of meistrell s 1966 1972 model for spit platform growth based on scaled wave tank experiments the giant scale cross bedded unit corresponds to prograding of a coarse grained subaqueous spit platform while the topset bar trough and beach units reflect the growth of the subaerial spit the alternation between sequence i and ii reflects the inversely related growth of the spit and platform structures when the rate of subaqueous platform progradation declines the subaerial spit grows uniformly and when the platform progrades uniformly spit growth declines the model is probably only valid for relatively coarse grained systems because only these deposits would have a relatively steep front the water depth in which the spit system progrades and thus bottom topography determines the thickness of the giant scale cross bedded foreset unit because the water depth over the top of the platform is relatively constant if the water is less than a few metres deep the spit platform is not developed as seen where the late pleistocene spit systems prograded over elevations of the sea bottom conversely the correct recognition of spit platform sequences allows precise determination of sea level and water depth at the time of formation finally the model adds one further mode of formation of giant scale cross bedding to those already known from fluvial transverse lateral and point bars subtidal sand waves and gilbert deltas

facies and stratigraphic anatomy of a temperate carbonate sequence capo colonna terrace late pleistocene southern italy abstract accurate interpretation of ancient non tropical carbonate systems requires the development of appropriate facies and sequence stratigraphic models these models should account for the marked differences in sedimentation style among non tropical carbonates formed under different energy settings this paper presents data and a conceptual model of the sequence architecture of non tropical carbonates of moderate energy environments based on the late pleistocene deposits of capo colonna marine terrace calabria southern italy these deposits have the advantage of being continuously exposed along a proximal distal transect across the paleo shelf and their geometry has not been disturbed by later tectonic activity they consist of a transgressive regressive t r cycle whose genesis can confidently be related to one of the interstadial glacio eustatic fluctuations of marine isotope stage mis 5 eight different mixed carbonate siliciclastic and carbonate facies are present in the studied sequence of these biogenic dominated facies are invariably made up of skeletal remains of light independent organisms plus or minus red calcareous algae the heterozoan association the relatively young age of the deposits allows calibration of the paleoecological significance of observed facies by direct comparison with modern analogues from the mediterranean sea four laterally persistent discontinuity surfaces were identified along the transect and interpreted from bottom to top as 1 a basal ravinement surface 2 a submarine hardground locally acting as a substrate for algal boundstones 3 a regressive surface of marine erosion and 4 a surface of subaerial exposure sequence stratigraphic analysis indicates that the preserved t r cycle is asymmetric with a thicker regressive portion highstand deposits can be subdivided into a shore connected sandy prism and more distal autochthonous and parautochthonous skeletal accumulations and algal boundstones during forced regression a thin sharp based strongly progradational unit of calcarenites was deposited above the regressive surface of marine erosion the deposits of capo colonna terrace document the response of non tropical moderate energy carbonate ramps to sea level fluctuations during icehouse conditions their architecture can facilitate the interpretation of other successions from similar settings and provide an end member to be compared and contrasted with high wave energy cool water carbonates

sequence concepts at seismic and outcrop scale the distinction between physical and conceptual stratigraphic surfaces abstract the sequence stratigraphic terms maximum flooding surface and downlap surface as currently applied are ambiguous examples of these intra sequence surfaces are summarised from high frequency mid pleistocene sequences and from a cretaceous recent seismic megasequence both from new zealand at any one locality a mid pleistocene sequence contains up to four stratal discontinuities in ascending order the sequence boundary ravinement surface local flooding surface and downlap surface these physical surfaces which occur in outcrop are regionally diachronous and should be differentiated from theoretical isochronous horizons such as the time of maximum flooding horizon corresponding to maximum shoreline transgression and the time of peak eustatic or local relative sea level horizons corresponding to the highpoint of the eustatic and relative sea level cycles respectively in seismic studies the boundary between the transgressive and highstand systems tracts is usually located at the downlap surface on the basis of a major thermo tectonic sea level cycle in the canterbury basin it is shown that the downlap surface is not a single regional surface and that the change in slope associated with toes of successive prograding clinoforms rises in stratigraphic height basinwards the downlap surface therefore does not usually coincide with the maximum flooding horizon in plio pleistocene cyclothems a discrete unit the mid cycle shellbed straddles the contact between the transgressive and highstand systems tracts this unit might be classified within its own systems tract the condensed section systems tract csst alternatively the position of the boundary between the transgressive and highstand systems tracts can remain unspecified or unknowable

sand waves echinocardium traces and their bathyal depositional setting monte torre palaeostrait plio pleistocene southern italy stacked cross sets up to 2 5 m thick produced by sand wave migration and meniscate trace fossils produced by echinocardium cordatum both considered in the literature as typical of shallow water marine depositional settings commonly occur in the bathyal plio pleistocene deposits of monte torre calabria southern italy the plio pleistocene sediments form two coarsening upward depositional sequences separated by an unconformity and by a palaeobathymetric gap of at least 300 m the lower sequence passes upwards from hemipelagic marls and thin bedded turbidites to thick bedded sandy turbidites then to sand wave deposits alternated with sandy turbidites and finally to base of slope megabreccias facies characteristics and relationships and the occurrence of deep sea faunal associations indicate deposition in the bathyal zone the facies of the upper sequence reflect a fan delta environment no deeper than a few tens of metres the depositional setting of the lower sequence where the sand wave deposits and meniscate trace fossils occur appears to have been a tectonically controlled seaway connecting the tyrrhenian and ionian seas this seaway became progressively narrower with time evolving into a strait the overall coarsening upward trend reflects the upward transition from a low to a high energy environment possibly caused by the tectonic narrowing of the seaway deposition and erosion from high concentration turbidity currents and from tidal bottom currents were important processes periods of tectonic activity producing first the uplift of the seaway margins and culminating with the uplift of the strait sequence itself are marked by scattered rockfall deposits the strait setting causing the development of powerful oxygenated bottom currents produced optimal conditions in the bathyal zone for the colonization of sandy bottoms by a single infaunal r selected species echinocardium sp

anatomy of a late pleistocene clinoformal sedimentary body le castella calabria southern italy a case of prograding spit system abstract the le castella marine terrace is the smallest and youngest terrace of the crotone area southern italy and formed after a rapid marine ingression due to a glacio eustatic rise outpacing the regional uplift of the area the most prominent feature of the terrace deposits is a seaward accreting clinoform about 10 m thick inferred to be formed during forced regressive conditions this prograding body is mostly composed of bioclastic material and shows an internal complexity consisting of alternating oblique and sigmoid elementary units inferred to be produced mainly by changes of accommodation development foreset avalancing was due to sediment accumulation by gravity flow processes while topsets were characterized by the migration of medium to large scale dunes showing a unimodal palaeocurrent pattern oblique with respect to the dip direction of the large scale clinoform foresets the le castella clinoform starts to develop from a topographic step on the basement due to tectonics which also controlled the palaeoshoreline trend the recognized stratigraphic and facies architectures the palaeocurrent pattern and the inferred palaeogeographic setting during deposition all suggest that the le castella clinoform is an example of spit system attached to the mainland and accreted due to longshore transport the present example contributes to establish criteria allowing the recognition of ancient spit systems which still are poorly known and rarely documented in the pre quaternary geological record

rip currents as a geological tool this paper considers the nature and sedimentary significance of rip currents rip currents are the main factor responsible for the transport of coarse sediments from the littoral zone to greater depths such sediments deposited outside the zone of wave deformation may be identified as storm rip current increments within sediments deposited during fair weather composite beds deposited during a given wave cycle by storm rip currents are closely similar to turbidites and many so called fluxo turbidites described from flysch deposits using data gathered in studies conducted on the modern baltic coast supplemented by experimental work and theoretical considerations a sedimentary model is proposed the model may be used to interpret possible rip current deposits among shallow water turbidites and both modern storm sediments and ancient tempestites language en