seismic stratigraphic reconstruction of plio quaternary depositional sequences on the continental shelf of korea strait abstract the korea strait is a seaway connecting the east sea with the east china sea the plio quaternary stratigraphy and sedimentation on the korea strait shelf was studied using a dense network of high resolution single channel seismic reflection profiles the shelf sequences above the acoustic basement consist of seven depositional sequences separated by erosional unconformities corresponding to falls in sea level individual sequences are characterized by well stratified and complex sigmoid oblique prograding reflection configurations reflecting a history of upbuilding and outbuilding in response to repetitive transgressive and regressive events driven by sea level changes during the regression to lowstand of sea level lowstand prograding wedges were formed seaward along the present shelf margin whereas during the highstand of sea level as in the present condition highstand deposits were deposited in the inner shelf along the coast however as the subsequent regression began the inner shelf highstand deposits were severely eroded out and or formed a condensed section volumetrically the forced regressive and lowstand systems tracts are the most important components of the korea strait consequently the plio quaternary sequence in this area consists of a succession of stacked progradational lowstand wedges mainly formed during the regression and lowstand of sea level

seismic stratigraphy of the southeastern black sea shelf from high resolution seismic records abstract high resolution seismic reflection profiles obtained from the shelves off the samsun and trabzon coasts southeastern black sea have revealed the existence of two distinct reflectors r and t reflector r forms the boundary between the upper depositional sequence a and the lower depositional sequence b seismo stratigraphically upper sequence a is characterized by stratified simple complex and lenticular seismic reflection configurations which imply changing depositional systems and or conditions changes of source and supply of sediments due to the relative change of sea level additionally the observed onlapping pattern within this sequence denotes rising of sea level during the last post glacial transgression the mounded seismic facies beyond the steep gradients on the shelf area of trabzon imply slump masses the lower depositional sequence b on the samsun and trabzon shelves is commonly characterized by chaotic reflection configurations which are interpreted either as strata deposited in a variable relatively high energy setting or as initially continous strata that have been deformed additionally the presence of some parallel subparallel reflections within this sequence denotes its stratified character the upper boundary of sequence b reflector r reflects a pre holocene unconformity probably caused by falling sea level at the time of the last glacial maximum additionally toplap termination at the upper boundary of sequence b indicates a stillstand of sea level at 91 m depth during the last glacial maximum based on borehole data sequence b is composed of consolidated sand and gravel admixtures in the samsun area and basalt agglomerate tuff series in the trabzon area reflector t forms the boundary of a zone of anomalous reflections acoustic turbidity at that are interpreted to represent gas in the sediments of the upper depositional sequence a the gas accumulations tend to occur in blanket and curtain forms depending on their appearances on seismic records

depositional history of quaternary sediments on the continental shelf off the southeastern coast of korea korea strait abstract the depositional history of quaternary sediments on the continental shelf off the southeastern coast of korea korea strait was investigated by means of analysing high resolution seismic profiles and sediment samples quaternary sediments up to 50 m thick overlie the irregular surface of the acoustic basement in the inner shelf the sedimentary column is comprised of two main sequences separated by a mid reflector which is interpreted as the pre holocene surface the holocene sequence reaching up to 30 m in thickness with a depocenter near the present river mouth is characterized by deposition in a prodelta environment while the upper pleistocene sequence represents deposition in deltaic or shallow water environments during the late glacial period most of the shelf was subaerially eroded and deposition took place only in the trough region the present location of marine built terraces indicates that the lowest position of sea level was about 130 m below its present level the subsequent postglacial transgression reworked pleistocene sediments to form a thin veneer of transgressive facies sea level rose rapidly in the early stages of the postglacial transgression and approached the present level at approximately 7000 5000 yrs b p recent sedimentation the holocene sequence probably began at that time

progradation of the late quaternary gediz delta turkey abstract detailed 3 5 khz seismic reflection profiling and coring have shown that the continental shelf break and slope off izmir bay turkey are formed by prograding deltaic silty mud sequences the muds contain shallow brackish water benthic and cold water planktonic foraminifera they were deposited when sea level was about 110 m below its present position during the last pleistocene glaciation slumping took place on the prodelta slope leaving rotational slump scars and imbricate slump blocks downslope delta top truncation took place in shallow water by erosive coastline retreat after distributary abandonment there has been little or no sedimentation since that time outer izmir bay is thus floored by relict sands following rapid post glacial transgression the gediz delta was reestablished in izmir bay archaeological evidence shows it has prograded during the last 3000 yrs at least six shifts in the position of the gediz mouth are distinguished during this time and abandoned delta top channels can be correlated with submarine delta lobe sequences

the tasmanides phanerozoic tectonic evolution of eastern australia the tasmanides occupy the eastern third of australia and provide an extensive record of the evolution of the eastern gondwanan convergent plate boundary from the cambrian to the triassic this article presents a summary of the primary building blocks igneous provinces and sedimentary basins within the tasmanides followed by a discussion of the timing and extent of deformation events relatively short episodes of contractional deformation alternated with longer periods of crustal extension accompanied by voluminous magmatism this behavior was likely controlled by plate boundary migration trench retreat and advance that was also responsible for bending and segmentation of the convergent plate margin as a result the tasmanides were subjected to at least three major phases of oroclinal bending in the silurian devonian and permian the most significant segmentation likely occurred at 420 400 ma along a lithospheric scale boundary that separated the northern and southern parts of the tasmanides exp

comparison between high resolution seismic and sequence stratigraphic approaches applied to the upper jurassic deposits of the dover strait area northern france abstract this study is an attempt to interpret very high resolution seismic data usually devoted to shallow marine surveys in terms of very high resolution seismic and sequence stratigraphy at the scale of the reservoir seismic data are compared with outcrop based observations in order to discuss the geometrical relationships between rock bodies and the nature of the seismic reflections in terms of seismic facies related to type lithologies two high resolution seismic surveys using a sparker were performed in the dover strait area some 100s of metres away from the boulonnais coastal cliffs the aim was to look to the 130 m thick mixed siliciclastic carbonate deposits of upper jurassic age kimmeridgian tithonian cropping out at the sea floor and to compare them to the coastal cliffs exposures the 100 m apart seismic profiles exhibit a 100 m deep penetration and 1 m in vertical resolution upper 30 ms part of the profiles four seismic facies are recognised on the seismic profiles they comprise ten seismic units which can be grouped into three broad families group 1 has a parallel aggradational reflection configuration and conformable boundaries which may correspond to the transgressive and highstand systems tracts the seismic facies exhibit either a high continuity high amplitude corresponding to clayey mudstone lithologies of the mid ramp environment or a high continuity low amplitude corresponding to shaly lithologies of the outer ramp environment group 2 has a sigmoid progradational reflection configuration bounded at the base by a downlap surface and at the top by a toplap surface these boundaries correspond respectively in the field to a marine regressive surface of erosion and a marine transgressive surface of erosion the seismic facies is cross layered and exhibits a moderate continuity low to moderate amplitude and moderate frequency group 2 corresponds to the bioclastic sand prone facies of the inner ramp environment it is interpreted as lowstand sharp based shorefaces group 3 exhibits a progradational complex to chaotic configuration it lies on an erosional unconformity with paleogullies the seismic facies shows discontinuous reflections with moderate amplitude and high to moderate frequency it corresponds in the field to cross bedded sandstones in channel fill arrangements of fluvial origin wealdian deposits marking the top of the section the different systems tracts sequence boundaries and depositional sequences identified onshore can be recognised as well on the seismic profiles but the comparison demonstrates that seismic data complement the onshore sequence stratigraphic analysis by providing the geometrical relationships between systems tracts onlap downlap toplap that cannot be observed onshore the maximum flooding surfaces however present no specific seismic signature on such a low angle ramp profile it can only be identified precisely in the field which also help to relate lithologies to seismic facies this study represents one of the first attempts to interpret very high resolution seismic data at the outcrop scale it will be improved again in the future by the collection of impedance logs and synthetic seismic traces from cored sections on the coastal cliffs for comparison with the seismic data

late quaternary deltaic lowstand wedges on the rhone continental shelf france abstract shallow seismic profiles on the rhone continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late quaternary glacioeustatic lowstands the wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf the thickness of individual wedges attains 50 meters at the shelf edge where they are sheared by slumping the wedges exhibit well developed progradational clinoforms episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms these represent small scale in the order of a few meters falls in sea level during the quaternary eustatic cycles the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf therefore the shelf edge builds up entirely with lowstand wedges

flow pattern within a permian submarine slump recorded by oblique folds and deformed fossils ulladulla south eastern australia the flow pattern within a slump in permian marine rocks of the southern sydney basin australia is recorded by folds and deformed fossils abundant brachiopod and bryzoan fossils in the slumped rocks are relatively undeformed but fossil crinoid stems have been deformed by relative rotation of individual ossicles measurement of the strain indicates that the deformation of the crinoids is consistent with flexural flow folding within the slump previous models assume that curved slump fold axes remain parallel to the enveloping bedding surface of a slump sheet detailed measurements of the orientation of slump folds in this study found fold axes to be oblique to bedding which is interpreted as a result of folds plunging downward towards the flanks of the slump or slump lobes in the present model fold axes are not generally parallel to the strike of the fold axial surface and this can explain differences between the orientations of slump fold axes and axial surfaces when these are used as directional indicators of slump movement

seismic stratigraphy and late quaternary sediments in inner and mid shelf areas of eastern mersin bay northeastern mediterranean sea abstract high resolution shallow seismic reflection uniboom profiles obtained in inner and mid shelf areas of eastern mersin bay turkey northeastern mediterranean show that the sedimentary column comprises two major and distinct lithological sequences c and b separated by a reflector r which is interpreted as the pre holocene surface the upper sedimentary sequence c is thought to represent roughtly the holocene and is characterized by parallel divergent to sigmoidal reflection patterns above unit 1 and sigmoidal obolique to disrupted wavy and hummocky reflection configurations below unit 2 this may reflect changes in relative sea level and or depositional conditions during the earlier and later stages of holocene the holocene sequence c reaches a maximum thickness of approximately 35 m about 500 600 m seaward of the mouth of seyhan river and thins in all directions away from this point adjacent shelf areas are characterized by thinner 10 15 m thick depositional sequences holocene sediment accumulation rates range from 1 to 3 5 m ka the lower sedimentary sequence b is marked by chaotic reflection configurations and is interpreted as having formed largely during the plio pleistocene the top of this sequence displays various channel onlap fills with parallel to oblique reflectors this record may represent the pre holocene surfaces produced by subaerial fluvial erosion of the pre existing shelf at least two or three orders of strong continuous reflectors similar to late pleistocene holocene unconformities are observed within sequence b and the repetitive pattern of the interfaces indicates cyclic sedimentation due to climatic fluctuations and oscillating sea level changes mostly in the pleistocene lithological logs from numerous soil borings on the adjacent coast suggest a significant increase in the thickness of the plio quaternary sequences from a few metres on the alluvial fan delta systems west of mersin to a few hundred metres on the fluvial plain delta system east of mersin climatic and sediment discharge fluctuations and coastal morphology controlled the temporal and spatial distributions of late pleistocene and holocene sediments in eastern mersin bay

late quaternary stratigraphy and paleogeography of the eastern nile delta egypt abstract a petrological study of numerous sediment borings identifies the late pleistocene and holocene lithofacies in the northeastern nile delta of egypt a coarsening upward sequence characterizes the major holocene depocenters located along the northern margin of the present delta stratigraphic correlation of radiocarbon dated sections and mapping of key facies such as delta front mud reveal the locations of four major holocene delta lobes related to former distributary branches of the nile river mendesian pelusiac tanitic and pre modern damietta these lobes formed primarily of marine prodelta and delta front deposits interfinger geographically but radiocarbon dating indicates that their bases are not synchronous lobes developed for the most part since 8000 years b p i e as the rate of eustatic sea level rise began to decrease climatic and sediment discharge fluctuations lateral migrations of distributaries and isostatic subsidence of land are additional factors that affected the temporal and spatial distributions of the lobes paleogeographic maps reveal the changes with time in the distributions of different lobes and deltaic plain environments marsh lagoons and concomitant displacement of the coastline holocene sediment accumulation rates to 500 cm per 1000 years are calculated this is 10 times greater than that on the nile cone and 50 times greater than on the egyptian continental shelf the delta coastal margin in the study area migrated northward by as much as 50 km during the past 5000 years an average progradational rate of up to 10 m per year the general configuration of the present delta developed during the past millennium the major changes recently induced by man in this region coupled with a series of continuing natural phenomena slow rise in sea level coastal erosion subsidence have markedly affected the evolution of the delta petrological study of the nile delta sediments provides baseline reference information to help recognize changes in the recent geological past to help identify those taking place at present and possibly to help predict those likely to occur in this region in the future

internal structure and evolution of the late quaternary sequence in a shallow embayment the amvrakikos gulf nw greece abstract the late quaternary stratigraphic pattern of the amvrakikos gulf in the eastern mediterranean has been studied on the basis of the analysis of high resolution seismic profiles and short sediment cores lowstand transgressive and highstand systems tracts have been identified that are configured in a major depositional sequence of a fifth order sea level cycle during the last glaciation when the sea level was lowered by 55 m relative to its present position ca 50 ka bp the amvrakikos gulf was probably emerged giving rise to a subaerial erosion and fluvial incision in the western shallow part of the gulf and b development of a paleo lake in the eastern deepest domain until the early phase of the post glacial transgression ca 11 50 ka bp a paleo river characterized by a dense network of v shaped valleys was draining the western part of the gulf and flowing into the ionian sea in the isolated eastern part lowstand lacustrine deposits deltaic and prodeltaic units accumulated within the paleo lake at the latter stage of the last post glacial transgression ca 11 ka bp seawater entered the gulf and the transgressive systems tract was deposited consisting of incised channel fills beach shoreface deposits and delta prodelta wedges buried terraces have been identified also within this transgressive tract that reveal a step like sea level rise since ca 6 ka bp when the sea level reached its present day position a distal prodeltaic unit has been deposited and overlain by prograding deltaic wedges the spatial distribution of these wedges provides evidence of a continuous shifting of the river mouths during holocene the recent sedimentation patterns are related to the terrigenous inputs primarily from the arachthos river located in the northeastern part of the gulf and secondarily from the louros river located in the northwestern part

late quaternary seismic stratigraphy in response to postglacial sea level rise at the mid eastern yellow sea late quaternary seismic stratigraphy and depositional history at the mid eastern yellow sea were investigated using high resolution seismic profiles and core sediments the results show that the shelf sequence consists of five sedimentary units formed since the lgm incised channel fill su1 estuarine deposit su2 thin sand veneer su3 tidal sand ridge su4 and central deltaic mud su5 the lowermost unit su1 above the sequence boundary is interpreted as channel fill deposits mainly formed during the lgm which belongs to the lowstand systems tract three units su2 su3 and su4 regarded as transgressive systems tract can be grouped into paralic and marine components separated by a ravinement surface su2 lying below the ravinement surface represents a paralic unit that consists of estuarine sediments left behind from shoreface erosion the top surface of su2 is truncated by an erosional surface and is overlain by two marine units su3 and su4 which were produced by shoreface erosion that shifted landward during the transgression su3 mainly distributed over a wide area of the central part is very thin whereas su4 on the eastern part off the korean peninsula forms serial sand ridges partly modified by modern tidal currents the uppermost unit su5 above the maximum flooding surface regarded as the highstand systems tract formed the thin deltaic mud patch derived from the huanghe river developed after the highstand sea level approximately 7 ka bp

seismic and geochemical evidence for shallow gas in sediment on navarin continental margin bering sea marine seismic studies coupled with geochemical investigations demonstrate that hydrocarbon gases are ubiquitous in the near surface 250 m or 820 ft depth sediment of the navarin continental margin in the northern bering sea three types of acoustic anomalies appear to be related to the presence of gas in the sediment these anomalies are most prevalent in the northern half of the navarin basin acoustic anomalies attributed to gas hydrates and to diagenetic boundaries are present on seismic records of the lower slope between navarinsky and zhemchug canyons hydrocarbon gases methane through butanes are common in the surface 5 m or 17 ft depth sediment of the navarin continental margin methane the most abundant hydrocarbon gas is present in amounts ranging from 84 000 to 1 l l of wet sediment these concentrations are two to three orders of magnitude greater than the other hydrocarbon gases the highest concentrations of methane greater than 1 000 l l were measured in sediment of navarinsky canyon and over the central part of the navarin basin the source of methane is mainly biogenic but the hydrocarbon gas compositions in 17 of 141 cores suggest the presence of thermogenic gas most of these 17 cores are from the continental slope at water depths greater than 150 m 490 ft no direct correlation could be found between acoustic anomalies and gas concentrations in the sediment this lack of correlation is probably due to the limited penetration of the gravity corer and the spotty distribution of hydrocarbon concentrations

constraining south atlantic growth with seafloor spreading data recent models of south atlantic opening history focus on early plate divergence by incorporating intracontinental deformation which is poorly constrained aiming to avoid the uncertainties in this approach we model the entire divergence history with a joint inversion for seafloor spreading data for this history the pre campanian motion parameters are the first to feature formal uncertainty estimates we date the onset of spreading at 138 ma with movement along intracontinental accommodation zones leading to the assembly of south america by 123 ma and africa by 106 ma part of the ridge in the agulhas basin jumped westward soon afterward toward the bouvet plume initiating the motion of a short lived malvinas plate the ne georgia and maud rises and agulhas plateau formed as a large igneous province over the plume farther north part of the ridge jumped eastward toward the tristan plume around 94 93 ma but seems not to have resulted in independent plate motion our results show that the south atlantic grew by diachronous breakup of continents on just two plates cretaceous intracontinental deformation in south america and africa can be interpreted in terms of the accommodation of stress associated with northward propagation of this process the pattern of accommodation is usually envisaged as focusing all of the strain in narrow belts with our rotations a commonly used set of such belts accounts instead for just 42 67 of the implied total strain we suggest that the remainder was accommodated at all scales within the continental interiors and the extended continental margins

is the abrupt drowning of the black sea shelf at 7150yrbp a myth abstract sedimentological and chronostratigraphic studies of the coastal plain sediments of the black sea near the sakarya river turkey and seismic stratigraphic survey of the shelf sediments off this river s mouth were carried out the results indicate that just prior to its flooding by the mediterranean waters at about 7200 yr bp the black sea was a fresh water lake emptying its waters into the sea of marmara the water level of this lake was about 18 m lower than the present sea level but above the 35 m sill depth of the bosphorus this finding contradicts with ryan et al 1997a ryan et al 1997b hypothesis that the black sea lake water level was more than 100 m below the sill depth of the bosphorus and that the drowning of the black sea shelf at 7150 yr bp was abrupt

plate tectonic evolution of the mediterranean middle east region abstract an interpretive model for the mesozoic cenozoic plate tectonic evolution of the mediterranean and adjacent areas is illustrated by a series of paleoposition maps at selected intervals between the late triassic and recent this interval witnessed an important period of tensional development during the triassic and jurassic that fragmented pangea after its late paleozoic consolidation a number of oceanic areas evolved through jurassic time all of which have since been consumed during the alpine orogeny during the cretaceous and tertiary sea floor spreading geometry in the north and south atlantic resulted in convergence between africa and eurasia that controlled the evolution of the mediterranean and adjacent middle east areas from the late mesozoic to recent the interpretation departs from several previous ones in the following respects 1 1 the eastern mediterranean and adjacent middle east area are interpreted to have developed as two seaways with an intervening continental sliver derived from africa that now comprises central turkey and west iran these seaways persisted from the late triassic to late cretaceous by which time they were largely consumed by northward subduction 2 2 spreading that produced the present eastern mediterranean sea developed during the late cretaceous driving the tripolitza eratosthenes iskenderun continental fragments northward from africa to collision with central turkey as the preceding southern arm of the mesozoic tethys sea floor was entirely consumed initial block faulting in this zone occurred during the jurassic and early cretaceous but without subsidence reaching clearly bathyal depths until the cenomanian turonian this differs from the timing of events in the ionian sequence of the pindic nappe of crete which shows a change from shallow carbonate shelf in the triassic to deep basin in the liassic to the north of equivalent platform facies of the tripolitza nappe 3 3 moesia and rhodope are concluded to have been a single plate until a rifting event that started during the late jurassic the balkan mountains are interpreted to represent an alpine inversion of this mesozoic rift system that extended west from the black sea basin 4 4 the eastern carpathian microcontinental sliver is concluded as continuing southward as the serbo macedonian massif that separates rhodope from the vardar zone rather than as rhodope itself 5 5 the scutari pec lineament is considered as representing a major discontinuity between the apulia pannonian plate and adjacent greece and turkey ophiolites to the northwest of this lineament originated in a single oceanic area the vardar zone ophiolites to the southeast of this lineament evolved from two oceanic areas those of interior greece and northern anatolia and the associated ankara melange relating to the vardar zone the former north arm of tethys and the pindos southern anatolia zagros oman ophiolites relating to a former south arm of mesozoic tethys 6 6 based on the history of development of various elements of the alpine system there is a strong suggestion that important dextral movement took place along a major strike slip fault system reaching from the middle east to the central alps between late cretaceous and middle eocene times

morphologic and seismic evidence of rapid submergence offshore cide sinop in the southern black sea shelf abstract multi beam bathymetric and multi channel seismic reflection data obtained offshore cide sinop have revealed important records on the latest transgression of the black sea for the first time a relatively large shelf plain within the narrow southern continental shelf characterized by a flat seafloor morphology at 100 water depth followed by a steep continental slope leading to 500 m depth this area is widely covered by submerged morphological features such as dunes lagoons possible aeolianites an eroded anticline and small channels that developed by aeolian and fluvial processes these morphological features sit upon an erosional surface that truncates the top of all seismic units and constitutes the seafloor over the whole shelf the recent prograded delta deposits around the shelf break are also truncated by the similar erosional surface these results indicate that offshore cide sinop was once a terrestrial landscape that was then submerged the interpreted paleoshoreline varies from 100 to 120 m this variation can be explained by not only sea level changes but also the active faults observed on the seismic section the effective protection of morphological features on the seafloor is the evidence of abrupt submergence rather than gradual in addition the absence of coastal onlaps suggests that these morphological features should have developed at low sea level before the latest sea level rise in the black sea

high resolution seismic study as a tool for sequence stratigraphic evidence of high frequency sea level changes latest pleistocene holocene example from the korea strait abstract sequence stratigraphic analysis of high resolution seismic reflection profiles and sediment data reveals that the latest pleistocene holocene deposits in the korea strait shelf off the southeastern korean peninsula form a high frequency sequence consisting of a set of lowstand transgressive and highstand systems tracts that corresponds to a fifth order 20 kyr sea level cycle eight depositional systems each with different seismic facies constitute the systems tracts the lowstand systems tract consisting of sandy mud forms a deltaic wedge that pinches out updip near or at the relict shelf edge the transgressive systems tract consisting mainly of sands includes six depositional systems 1 inner shelf transgressive layer 2 transgressive estuarine deltaic complex 3 transgressive sand ridge 4 mid shelf transgressive layer 5 incised channel fill and 6 beach shoreface complex although the transgressive systems tract is widely distributed it is much thinner than the lowstand and highstand systems tracts the highstand systems tract is composed of a prodelta shelf complex consisting almost exclusively of holocene muds the distribution and geometry of the systems tracts in the latest pleistocene holocene sequence in the korea strait shelf is different from that of vail s model in that 1 the lowstand systems tract consists only of the lowstand deltaic wedge which forms an elongated sediment body along the paleoshelf edge and 2 the highstand systems tract is completely confined to the inner shelf and forms a nearshore belt parallel to the coastline high frequency 20 kyr high amplitude magnitude of about 130 m sea level change together with strong currents flowing northeastward along the southeastern coast of the korean peninsula and varying sediment supply have resulted in this rather unusual stratigraphic architecture

ferromagnetic resonance characterization of greigite fe3s4 monoclinic pyrrhotite fe7s8 and non interacting titanomagnetite fe3 xtixo4 ferromagnetic resonance fmr spectroscopy has become an increasingly useful tool for studying the magnetic properties of natural samples magnetite fe3o4 is the only magnetic mineral that has been well characterized using fmr this limits the wider use of fmr in rock magnetism and paleomagnetism in this study we applied fmr analysis to a range of magnetic minerals including greigite fe3s4 monoclinic pyrrhotite fe7s8 magnetically non interacting titanomagnetite fe3 xtixo4 and synthetic magnetite chains to constrain interpretation of fmr analysis of natural samples and to explore applications of fmr spectroscopy we measured the fmr signatures of a wide range of well characterized samples at the x and q bands fmr spectra were also simulated numerically to compare with experimental results the effects of magnetic anisotropy mineralogy domain state and magnetostatic interactions on the fmr spectra are discussed for all studied minerals our experimental and theoretical analyses of magnetically non interacting tuff samples and magnetically interacting chains enable quantitative assessment of contributions of magnetostatic interactions and magnetic anisotropy to the fmr spectra our results also indicate that intact magnetosomes are a unique system with distinct fmr signatures while fmr analysis is useful for characterizing magnetic properties of natural samples care is needed when making interpretations because of overlaps in a range of fmr signatures of different magnetic minerals with different magnetic properties our analyses will help to constrain such interpretations in rock magnetic studies

seismic stratigraphy and quaternary sedimentation in the skagerrak northeastern north sea abstract ice movement sea level fluctuations and currents are the controlling factors of the late pleistocene and holocene sedimentation processes in the skagerrak the erosional truncation at the top of a mesozoic depositional sequence defines the extent of the norwegian channel and functions as the initial depositional surface for quaternary sedimentation on this surface in shallow waters off the danish coast weichselian glacial sediments are deposited an end morain ridge marks a temporary stillstand of the retreating ice front at the beginning of ice free conditions some 15 000 yrs ago when the sea was about 70 m below the present level the skagerrak was a fjord like forebasin of the northern atlantic and constituted a favorable outlet for rivers draining the subaerial glacial deposits of the southern skagerrak and the present southern north sea fluvial erosion released large amounts of detrital material which was laid down in the form of a progradational delta prodelta complex slumping and mass flow processes led to high sedimentation rates and a rapid infilling of the norwegian channel in front of the delta complex with the rapid transgression of the southern north sea at the beginning of the holocene a dramatic change in the depoenvironment of the skagerrak took place the modern current pattern became established whereby sediment transport and redeposition became the rule along the danish coast sandwaves and megaripples with an apparent northeasterly migration direction were formed as a result of the wind forced jutland current fine suspended particles bypass the coastal zones to settle out in the deep norwegian channel

geophysical and hydrological evaluation of two bog complexes in a northern peatland implications for the distribution of biogenic gases at the basin scale 1 ground penetrating radar gpr was used to determine peat basin geometry and the spatial distribution of free phase biogenic gasses in two separate units of a northern peatland central and southern unit of caribou bog maine the central unit is characterized by a deep basin structure 15 m maximum depth and a raised eccentric bog topographic profile up to 2 m topographic variation here numerous regions of electromagnetic em wave scattering are considered diagnostic of the presence of extensive free phase biogenic gas in contrast the southern unit is shallower 8 m maximum depth and has a slightly convex upwards bog profile less than 1 m topographic variation and areas of em wave scattering are notably absent the biogenic gas zones interpreted from gpr in the central unit are associated with 1 wooded heath vegetation at the surface 2 open pools at the surface 3 high water table elevations near the center of the basin and 4 a region of overpressure at approximately 5 m depth immediately below the zone of free phase gas accumulation the latter suggests 1 a transient pressure head associated with low hydraulic conductivity resulting from the biogenic gasses themselves or confining layers in the peat that restrict both gas release and groundwater flow and or 2 overpressure in the peat column as a result of the gas buildup itself in contrast the southern unit where zones of em scattering are absent is characterized by 1 predominantly shrub vegetation 2 a lack of open pools 3 only minor variations less than 1 m in water table elevation throughout the entire unit and 4 generally upward groundwater flow throughout the basin the results illustrate the nonuniformity of free phase biogenic gas distribution at the peat basin scale and provide insights into the processes and controls associated with ch4 and co2 accumulation in peatlands

late quaternary inner shelf deposits in response to late pleistocene holocene sea level changes nakdong river se korea abstract the high resolution seismic profiles from the inner shelf off the nakdong river in se korea can be directly correlated with the lithologic characteristics in the borehole data these correlations offer an opportunity to document the evolution of the inner shelf deposits with sediment supplies in response to the late quaternary sea level changes the inner shelf sequence in this area consists of four sedimentary units which comprise a set of lowstand transgressive and highstand systems tracts deposited since the last glacial maximum incised channel fill su1 estuary su2 sand veneer su3 and subaqueous delta su4 the lowermost unit su1 which overlies the sequence boundary is interpreted as fluvial deposits formed during the last glacial period and the early stage of transgression and belongs to the lowstand to transgressive systems tract the lower middle unit su2 lying below the ravinement surface represents a paralic component that consists of estuarine sandy mud or muddy sand developed between approximately 13 and 8 cal ka bp whereas the upper middle unit su3 above the ravinement surface corresponds to a marine component that consists of sand veneer produced by the shelf erosion during the ensuing sea level rise these two units su2 and su3 belong to the transgressive deposits the uppermost unit su4 regarded as the highstand systems tract formed the nakdong subaqueous delta including the proximal and distal systems developed after the highstand sea level at approximately 6 cal ka bp the lateral transition from the proximal to distal facies suggests a prograding delta system in the nakdong river

anomalous bathymetry and palaeobathymetric models of the mozambique basin and riiser larsen sea abstract in this study we introduce a palaeobathymetric model for the conjugate mozambique basin and riiser larsen sea built by employing backstripping techniques compensating for dynamic topography and plate motions the model is presented at 0 2 0 2 grid resolution making it suitable for future oceanographic and climate simulation model experiments aimed at a better understanding of the climatic and oceanographic relevance of oceanic gateways in the southern ocean at the present day the seafloor next to the mozambican continental margin is around 300 m shallower and that in the central mozambique channel is almost 1300 m shallower than their conjugate areas or the predictions of oceanic thermal subsidence models the cause of this anomalous depth is difficult to determine confidently because of sparse data in particular concerning sediment thickness and because of the wide range of amplitudes in modelled present day dynamic topography the distribution of shallow seafloor suggests that it might be attributed to the presence of thicker than usual oceanic crust which in turn can be attributed to the paleogene passage of the quathlamba plume beneath the basin we portray these effects in our palaeobathymetric models in contrast the riiser larsen sea has experienced fairly stable subsidence since its formation in jurassic times with only slight observable changes attributable to the onset of antarctic glaciation and during the middle miocene climate transition both basins display flexure over half wavelengths of 60 80 km with amplitudes of 1500 m towards their continental margins this plays an important role in models of palaeobathymetry for times older than 100 ma near the margins isolated areas of transitional or debatable crustal composition including beira high and gunnerus ridge are depicted to subside in a similar fashion to oceanic crust further into the indian ocean oceanic lithosphere younger than 100 ma on both plates has subsided to depths that are typical of thermal subsidence models finally the new palaeobathymetry had distinct consequences for the current systems in the young southern ocean during the time periods the onset of coast parallel bottom currents and associated contourite deposition in the mozambique channel at palaeo water depths of 3500 4000 m may be a consequence of either an opening of a deep water passage into the south atlantic between southwest indian ridge and agulhas plateau or into the tethys ocean in the late cretaceous

catastrophic flooding of the black sea abstract decades of seabed mapping reflection profiling and seabed sampling reveal that throughout the past two million years the black sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand when the exterior ocean lay below the relatively shallow sill of the bosporus outlet the black sea operated in two modes as in the neighboring caspian sea a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake thus during much of the cold glacial quaternary the expanded black sea s lake spilled into to the marmara sea and from there to the mediterranean however in the warm climate mode after receiving a vast volume of ice sheet meltwater the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge if the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across

heavy metal geochemistry of surface sediments from the southern black sea shelf and upper slope abstract a wide variety of sediment types mud to sandy gravel was obtained at fourty seven stations on the southern black sea shelf and upper slope and analyzed for their heavy metal geochemistry distribution of grain size carbonates organic carbon and heavy metals show marked changes in the topography biological activity and land geology of the region studied sediments constitued up to 39 caco3 mainly of biogenic origin from the shell remains of benthic organisms organic carbon contents of the sediments 0 13 3 09 usually reflect the prevailing primary productivities in the black sea although significant terrigenous influences are also inferred the heavy metal concentrations largely indicate the influences from the geochemical weathering of terrigenous sources on land in comparison with the average sedimentary rocks and other modern sediments from the adjacent regions the concentrations of cr ni cu zn and pb are somehow higher in the surface sediments from the southern black sea in particular cr ni and cu are found in high abundances in the eastern parts of the study area this is thought to reflect not only the well mixed fine grained nature of the sediments but also the possible contribution from metal rich rocks mafic and ultramafic sources and associated economic mineral deposits in the catchment areas of rivers which drain this part of the coast the presence of significant positive correlations between the concentrations of cr and ni and zn and pb strongly suggest common sources and or similar enrichment mechanisms for these metals the relationships among the geochemical variables revealed that fe and mn oxides hydrates and sulfides and organic phases together with the clay and silt sized grain fractions are the important associations of the studied heavy metals