holocene tidal levels and sedimentation rates using a diatom based palaeoenvironmental reconstruction the tees estuary northeastern england an established diatom based tidal level transfer function is used in combination with the present day relationship between sedimentation rate and altitude to reconstruct holocene tidal sediment accretion for the tees estuary northeastern england the results from five cores reveal two periods of enhanced sedimen tation the earlier of which 8000 6000 cal bp is related to relatively rapid sea level rise and increasing tidal range the later phase of increased tidal sedimentation also reflects an enhanced marine influence after c 3000 cal bp but may also be attributed to climate and human induced changes in terrestrial sediment flux to the coastal zone comparison of the reconstructed sediment accretion rates with actual rates calculated from radi ocarbon and luminescence dated sedimentary horizons reveals that this diatom based approach overestimates sediment accretion by a factor of three this overestimation is considered to be due to the contemporary sediment flux being an inappropriate analogue for the mid to late holocene rather than to any significant methodological flaws in the approach

the relationship between sedimentary facies and faunal associations in the llandovery siliciclastic ross brook formation arisaig nova scotia the llandovery siliciclastic ross brook formation of arisaig nova scotia comprises three broadly defined sedimentary facies these are a mottled silty mudstone facies facies a a laminated shale facies facies b and a laminated siltstone facies facies c facies a consists of variably bioturbated silty mudstones muddy siltstones and fissile shales it developed in relatively shallow water conditions mudstones were presumably deposited from suspension and siltstone laminae and thin layers were formed by increased wave and current activity mottling resulted from bioturbation by epifaunal and particularly infaunal benthic organisms within facies a two subfacies are recognized a i is mudstone dominated and a ii is fine grained siltstone dominated facies b consists of alternating laminae of undisturbed mudstone and fine grained siltstone probably produced as a result of deposition from suspension during a temporary upward expansion of the oxygen minimum layer facies c consists of 0 5 30 c

evidence for basin restriction during syn collisional basin formation in the silurian arisaig group nova scotia the arisaig basin in nova scotia canada provides a regional sedimentary record of an early silurian basin subsidence on the microcontinent of avalon the lower members of the arisaig group beechill cove and lower ross brook formations are likely to be deposited in a basin formed during syn to post collisional rifting subsidence driven by the collision of avalon and baltica the evolution of this constricted basin can be tracked by examining the geochemistry of the sedimentary rocks deposited within the basin here we report on the chemostratigraphy of the arisaig group a series of siliciclastics with a focus on understanding the redox chemistry during sedimentation the trace and major element geochemistry of this group provides insight into the oceanographic and geological processes that were influencing its depositional environment in particular concentrations of u v mo ni cd and pb indicate regional shifts in ocean redox state which serve as a proxy for changes in ocean circulation and regional tectonic activity we find evidence for anoxic conditions near the base of ross brook formation and attribute this anomaly in redox status to a significant change in physical mixing in the region trace element concentrations indicate that this anoxic event was associated with poor circulation rather than elevated productivity and organic matter burial based on these data we confirm that these sediments are deposited in a tectonically formed basin during a period of limited ocean circulation

hummocky cross stratification tropical hurricanes and intense winter storms most previous workers have inferred a storm origin for hummocky cross stratification which typically occurs in shallow marine deposits on the modern earth the only storms capable of profoundly affecting shallow marine depositional environments are severe tropical cyclones hurricanes and mid latitude winter wave cyclones intense winter storms this paper examines the palaeogeographic distribution including palaeolatitude and palaeogeographic setting of 107 occurrences of hummocky cross stratification ranging in age from the proterozoic to recent in each of these stratigraphic units both palaeolatitude and palaeogeography are consistent with a direct storm influence associated with the passage of hurricanes or winter storms directly over the site of deposition this palaeogeographic evidence lends support to the inferred storm origin for hummocky cross stratification further the distribution of the structure suggests that most occurrences 73 were generated by tropical hurricanes the remaining 27 being generated by intense mid latitude winter storms the preferential generation of hummocky cross stratification by hurricanes is consistent with 1 the known differences in the nature of the bottom flows generated by the two major storm types and 2 the inferred nature of the flows which form hummocky cross stratification hurricanes couple less effectively with the water column than do intense winter storms due to this ineffective coupling hurricane generated bottom flows tend to be oscillatory or multidirectional dominant with only minor unidirectional components of motion in contrast intense winter storms generally do couple effectively with the water column generating bottom flows which possess a dominant or significant unidirectional component most previous workers have suggested that hummocky cross stratification forms under oscillatory or multidirectional dominant flow thus it is conceptually reasonable that the vast majority of ancient occurrences of hummocky cross stratification were probably hurricane generated as suggested by the aforementioned palaeogeographic distribution the proterozoic palaeozoic neogene and quaternary were times when global climate was similar to that of today the distribution of hummocky cross stratification deposited during these times suggests that both hurricanes and intense winter storms occupied latitudinal belts during these times which were essentially identical to those occupied by their modern counterparts the mesozoic and palaeogene were non glacial times when global climate was much warmer than that of today the distribution of hummocky cross stratification deposited during this interval suggests that hurricanes occurred more frequently at higher latitudes during non glacial times than they do at present the possibility of a broadened hurricane belt during the mesozoic and palaeogene is consistent with climatic considerations a limited number of mesozoic and palaeogene rock units containing hummocky cross stratification were deposited in palaeogeographic settings that preclude a direct hurricane influence these examples were deposited in the middle latitudes suggesting that intense winter storms continued to form hummocky cross stratification in the middle latitudes during these much warmer times some previous workers have suggested that tsunamis may be capable of generating hummocky cross stratification the palaeogeographic distribution of the structure does not support an origin due to tsunamis lacustrine examples of hummocky cross stratification reported herein are the first known non marine occurrences they suggest that storm effects strongly influence the sedimentary record of some lakes

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

microfossil analysis of sediments representing the 1964 earthquake exposed at girdwood flats alaska usa abstract diatom pollen foraminifera and thecamoebian assemblages from an outcrop of peat and silt at girdwood flats in the upper turnagain arm of the cook inlet alaska record four phases of relative land and sea level changes the first phase is the development of freshwater swamp above high marsh sediments during relative land uplift caused by strain accumulation along the locked portion of the alaska aleutian subduction zone in second phase the top 2 cm of the peat all microfossil groups record pre seismic relative sea level rise relative land subsidence the third phase is rapid land subsidence 1 7 m during the earthquake of march 1964 that initiated intertidal silt accumulation above the peat the final phase is the colonisation of mudflat by salt marsh communities during post seismic land uplift the microfossil data compare favourably with sequences from washington oregon and british columbia that record late holocene submergence events caused by earthquakes the comparable changes in microfossil assemblages record the different phases of relative land and sea level changes and the magnitude of land subsidence caused by each earthquake expressed relative to the tidal range at the site these results raise the question whether preseismic sea level rise represents any kind of warning of large earthquakes

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

a holocene tsunami deposit in eastern scotland a thin regionally extensive laterally persistent sand layer identified within the holocene coastal sequences of eastern scotland dated to 7000 years bp is suggested to be a tsunami deposit the likely source of the tsunami wave is the earthquake induced second storegga slide on the norwegian continental slope at least 750 km northeast of the deposit

tidal marsh stratigraphy sea level change and large earthquakes i a 5000 year record in washington u s a abstract many of the estuaries of the pacific northwest of the u s a and canada contain stratigraphic sequences typified by alternating peat mud couplets recent studies in this region interpret such couplets as the product of repeated large magnitude s or 9 earthquakes on the cascadia subduction zone the resultant pattern of land level movements is described by a model the earthquake deformation cycle of coseismic land subsidence followed by land uplift during interseismic strain accumulation however peat mud couplets similar to those recorded in the pacific northwest are found on other less tectonically active temperate latitude coasts such as northwest europe and the atlantic coast of the u s a where they have been interpreted as the product of non seismic coastal processes in this paper we apply the methods and scientific framework common to sea level investigations in northwest europe to a sequence of peat mud couplets recorded in the lower johns river an estuary in southern washington to provide a test of the earthquake deformation cycle stratigraphic investigations of the intertidal sediments along the lower johns river using lithological pollen diatom and foraminiferal data show evidence for eight coastal submergence events during the last 5000 years to evaluate the earthquake deformation cycle we assess the lateral extent of peat mud couplets the synchroneity of submergence the presence of tsunami deposits accompanying submergence and the suddenness and amount of submergence each submergence is shown to be accompanied by changes in coastal sedimentation broadly commensurate with those predicted by the earthquake deformation cycle demonstrating the continued intermittent seismic activity of the cascadia subduction zone throughout the mid and late holocene quantitative analyses of contemporary and fossil biostratigraphic data using twinspan and detrended correspondence analysis enable us to estimate the magnitude of submergence accompanying each peat mud couplet one event was accompanied by submergence of about 1 5 m or more four events by intermediate submergence of about 1 0 5 m and a further three events by submergence of

late devensian and holocene relative sealevel changes at loch nan eala near arisaig northwest scotland pollen diatom radiocarbon and lithostratigraphical data from isolation basins in northwest scotland are used to quantify the reference water tide level indicative range and age of differenty types of isolation and connection contacts tendencies of sea level movement and relative sea level changes from the mid lateglacial interstadial 11 8 ka bp to the late holocene are constructed from these data relative sea level fell continuously from 17 8 m od at 11 8 ka bp to ca 5 2 m od at 10 1 ka bp from an unkown minimum between 10 ka and 9 ka bp relative sea level then rose to 6 3 m od at 8 3 ka bp the maximum holocene sea level occurred within the range 6 6 m od to 9 3 m od between 6 6 ka bp and 4 0 ka bp before falling to present isobase age altitude and quantitative rebound models for northwest scotland are tested using these sealevel data but none of the published models shows close agreement with the new results

tidal wetland record of holocene sea level movements and climate history abstract paleontological geochemical and lithological indicators of former marine and nonmarine influence are correlated between 13 cores from a tidal wetland wolfe glade on the southeast coast of delaware bay twenty new radiocarbon dates are used to establish the chronostratigraphy of marsh facies sediment iron content weight loss on ignition and remains of plants diatoms and foraminifera known to tolerate specific tidal inundation cycles are used to describe cored facies originating from supratidal intertidal and subtidal salt marsh subenvironments pollen assemblages are used to infer local holocene climate fluctuations and to reconstruct paleoenvironments during marsh evolution the record of paleoclimatology suggests the atlantic chron was warm with variable humidity in the region whereas the subboreal was dominated by cool and humid conditions the subatlantic was warmer and initially dryer with a cool humid phase prior to about 1 ka returning to warmer humid conditions in the last several centuries local relative sea level movements are characterized by five rapid short term episodes when the rate of sea level rise accelerated relative to the rate of marsh aggradation these episodes are recorded by transgressive facies contacts at 5 3 0 2 ka 4 4 0 2 ka 3 25 0 2 ka and 1 8 0 2 ka sidereal years an earlier transgressive facies contact dated 6 9 0 2 ka is probably not the product of a true sea level movement sea level movements are recorded throughout the marsh as palustrine or high marsh peats or peaty overlain by lower intertidal or subtidal marine deposits several features suggest that these episodes are local relative transgressions produced by short term accelerations in the rate of sea level rise relative to marsh aggradation the contemporaneity and apparent suddenness of marine inundations the sequence of facies indicating marine drowning the presence of similar events in marshes elsewhere in delaware bay and the marsh wide extent of indicative facies transitions we propose that the rapid and frequent sea level movements observed in wolfe glade are the result of surges and relaxations in the gulf stream and associated spin up and partial collapse of the north atlantic gyre in response to winds generated by changes in the north atlantic atmospheric thermal gradient associated with holocene climate fluctuations

sea level changes in the holocene over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly the search for a eustatic sea level curve having global relevance has ended studies into the rheology of the earth s crust and recognition that the geoid has not remained stable over time have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation as a part of this re appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro isostatic response particularly in the areas of the shelf seas in the later part of the post war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the holocene including not only errors in dating but also a large number of possible sources of errors in heighting as a result of this an increasing number of scientists are withholding judgement on the nature of sea level rise and more particularly on the problem of higher than present late holocene eustatic sea levels the problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed

cyclic deposits and hummocky cross stratification of probable storm origin in upper cretaceous rocks of the cape sebastian area southwestern oregon abstract cyclic deposits containing hummocky cross stratification occur in the upper part of the cape sebastian sandstone of bourgeois 1980 a shallow marine transgressive sandstone of late cetaceous age on the southern oregon coast the cycles average 1 6 m in thickness and consist where complete of a lower hummocky cross stratified sandstone a middle planar and ripple bedded sandstone with a shale bed in its middle part and an upper bioturbated sandstone noteworthy features of the hummocky cross stratification include the presence of depositional domes in addition to scoured depressions the absence of significant bedform migration and the presence of a small proportion of dip angles greater than the angle of repose 34 in addition to the large proportion of low 15 deg dip angles the lower stratified fining upward part of the cycle up to the top of the shale bed is interpreted as having accumulated under conditions of initially great but gradually decreasing current velocity and deposition rate the currents probably had a strong oscillatory component and the depositional event is inferred to have been a storm the part of the planar and ripple bedded sandstone above the shale bed was probably deposited during relatively fair weather after the storm but before re establishment of a normal benthic fauna the bioturbated sandstone is interpreted to have been deposited during fair weather or during minor storms separated by long intervals of fair weather

sedimentary fades depositional environments and faunal associations of the lower llandovery silurian beechill cove formation arisaig nova scotia six facies are recognised in the beechill cove formation these are 1 conglomerate facies deposited as a transgressive beach lag 2 red shale facies deposited in shoreface environments 3 mottled mudstone facies extensively bioturbated sediments indicative of shallow subtidal areas influenced by low sedimentation rates 4 regular layered facies shelf turbidites generated by storm activity and superimposed on quiescent subtidal environments 5 lenticular facies including a thinner bedded more persistent and a thicker bedded lenticular subfacies induced by storm activity and deposited in shallow subtidal environments and 6 laminated shale facies produced by sediment fallout from suspension in a low energy environment where the oxygen minimum layer intersected the sediment water interface three faunal associations occur which have distinct distributional patterns the lingula clintoni association which is characterized by l clintoni in life position and a moderately diverse but abundan

models of rapid relative sea level change in washington and oregon usa much geological evidence points to repeated plate boundary earthquakes on the cas cadia subduction zone pacific northwest usa current land motions calculated using shortterm 100 yr tide gauge repeat levelling and other geodetic data record deformation during the present interseismic period these short term data form the basis of efforts to model longer term plate boundary deformation and assess seismic hazard in this region in this paper we use relative sea level rsl data from the last 4000 cal yr bp to examine four aspects of these plate boundary deformation models over several earthquake cycles rates of isostatic rebound the spatial pattern and magnitude of coseismic deformation and rates of interseismic strain accumulation age altitude plots of rsl data from a 300 km long string of sites stretching from copalis river central washington to alsea bay central oregon reveal a systematic northsouth decline in the rate of isostatic rebound equal to c 0 25 0 02 mm yr 1 100 krn high

holocene sea level change and coastal evolution in the humber estuary eastern england an assessment of rapid coastal change new stratigraphic data collected from six sites in the humber estuary establish a record of holocene relative sea level rsl change and enable testing of four possible causes of rapid coastal change sea level rise changes in sedimentation storm surge history and human impact mean high water of spring tides mhwst in the humber rose from c 9 m od at 7500 cal yrs bp to 0 m od by 4000 cal yrs bp at an average long term rate of c 3 9 mm yr 1 after this the rate of rise gradually decreased to c 1 mm yr discrete episodes of rapid rsl rise are not identified although their absence may reflect limited data availability however we do observe two episodes of rapid coastal change in the humber estuary the first occurs between c 3200 and 1900 cal yrs bp as marine conditions expand to their holocene maximum and then contract this pattern of coastal development differs from that in the east anglian fenlands suggesting local processes control sedimentation at one or both of these sites the sec

correlation of lower silurian strata from the michigan upper peninsula to manitoulin island the same approach in using sea level curves to refine time rock correlations between widely separated regions also has an important application in resolving the tangle of dual stratigraphic nomenclature that often develops in neighboring regions divided by political boundaries a good example is the lower silurian of the michigan upper peninsula and manitoulin island ontario four peaks in sea level fluctuation are recorded in both areas by coeval pentamerid communities stratigraphically intermixed with coral algal and ostracode vermiform communities indicative of shallower water conditions despite many similarities between the rock units containing these fossil communities most are identified by different formation names on opposite sides of the u s canadian border this study details the eastward thinning of strata across the boundary area the cordell dolomite of michigan is extended to manitoulin island but not the underlying schoolcraft dolomite due to the pinching out of beds that define its u

great earthquakes and tsunamis of the past 2000 years at the salmon river estuary central oregon coast usa four buried tidal marsh soils at a protected inlet near the mouth of the salmon river yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami deposited sand during great earthquakes at the cascadia subduction zone an extensive landward tapering sheet of sand overlies a peaty tidal marsh soil over much of the lower estuary limited pollen and macrofossil data suggest that the soil suddenly subsided 0 3 1 0 m shortly before burial regional correlation of similar soils at tens of estuaries to the north and south and precise 14c ages from one salmon river site imply that the youngest soil subsided during the great earthquake of 26 january a d 1700 evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older soil stratigraphy can be explained by local hydrographic changes in the estuary regional 14c correlation of two of the three older soils with soils at sites that better meet criteria for a great earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes pollen evidence of sudden coseismic subsidence from the older soils is inconclusive probably because the amount of subsidence was small 0 5 m the shallow depths of the older soils yield rates of relative sea level rise substantially less than rates previously calculated for oregon estuaries manuscript received 10 october 2003

holocene sedimentation on the north norfolk barrier coast in relation to relative sea level change fourteen distinct sedimentary environments have been recognised in the surface sediments of the intertidal zone of the north norfolk coast nine of these can be distinguished in borehole samples on the basis of sedimentological and micro palaeontological characteristics they comprise gravel channel sand intertidal sand intertidal silty sand intertidal mud and marsh creek lower salt marsh upper salt marsh dune sand and peat sediment accumulations have been penetrated to a depth of 8 m od and basal peats dated by 14c back to 8410 50 years bp an overall rate of sediment accumulation and subsidence of about 1 m per thousand years is indicated there is considerable persistence of sedimentary environments in the same areas during up building but some erosion and roll over of the coastal barrier system has occurred evidence of positive and negative sea level tendencies are present in the record but the main development of the tract is determined by sediment supply to the beach and marshes positive sea level tendencies occur at c 6610 5970 4630 and 2790 bp negative sea level tendencies occur at 4520 to 4450 and possibly 3470 bp

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

chondrites a trace fossil indicator of anoxia in sediments the trace fossil chondrites a highly branched burrow system of unknown endobenthic deposit feeders occurs in all types of sediment including those deposited under anaerobic conditions in some cases such as the jurassic posidonienschiefer formation of germany chondrites occurs in black laminated carbonaceous sediment that was deposited in chemically reducing conditions in other cases such as numerous oxic clastic and carbonate units throughout the geologic column chondrites typically represents the last trace fossil in a biotutbation sequence this indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters

late quaternary sea level changes and crustal movements in eastern england and eastern scotland an assessment of models of coastal evolution abstract the most comprehensive records of late quaternary coastal environmental change in eastern england and eastern scotland are obtained from the intercalated semi terrestrial peats and intertidal silts clays and sands that have accumulated in estuaries and coastal lowlands radiocarbon dated sea level index points from sites in north east england are evaluated with reference to first a conceptual model of coastal sedimentary environments and second a model of pollen assemblages in holocene coastal environments analysis of these new data indicates differential crustal uplift within north east england of ca 0 2 mm yr for the last 4000 to 5000 radiocarbon years this pattern of uplift is consistent with models of holocene crustal deformation in scotland and england the uplift is attributable to the combined effects of ice unloading and water loading

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

flandrian sea level changes in the fenland i the geographical setting and evidence of relative sea level changes the flandrian sediments of the fenland record the infilling of the wash embayment on the east coast of england uk since at least 6500 bp changes in sea level have been a major control on the rate and pattern of sediment accumulation new data are presented from the area which together with published information allow the reconstruction of palaeoenvironments from 6500 to 2500 bp the major environmental changes involved alternations between freshwater fen and intertidal marine sedimentation each episode was characterised by transitional changes as vegetation and sediment zones shifted over large areas marine brackish sediments are found up to 45 km inland of the present coast radiocarbon dated sea level index points with relevant stratigraphic and micropalaeontological data ranging from 6415 bp at 8 17m od to 2595 bp at 1 45m od are described

storm effects on siliciclastic and carbonate shelf sediments in the medial silurian succession of pennsylvania abstract upper llandoverian through wenlockian strata in the pennsylvania part of the northern appalachian basin formed on a gentle epeiric ramp that extended from marginal tidal flats through coarser grained mid shelf shoals to a muddy basin center over approximately 10 million years the composition of the accumulating sediment evolved from siliciclastic to carbonate while the ramp maintained a relatively similar configuration and position below sea level and while storm generated processes continued as the major producers of sediment characteristics in both siliciclastic and carbonate parts of the succession sedimentary structures and their sequences are generally similar with only a small number of dissimilar features resulting from the differences in composition small scale coarsening and shallowing upward sequences are present in both mid shelf bar and basin transition deposits although specific sequence characteristics are different in siliciclastic and carbonate parts such sequences record cyclic fluctuations of relative sea level while the composition of the sediment evolved over this extended period the gentle ramp gradient was maintained largely by the processes generated by storms such processes were more effective because of the fluctuations of relative sea level

on the postglacial isostatic adjustment of the british isles and the shallow viscoelastic structure of the earth summary observations of postglacial relative sea level rsl history at sites beyond the margins of the main accumulations of wu rm wisconsin devensian ice may be invoked to test the accuracy of global models of the glacial isostatic adjustment process the existing database of rsl time series for the british isles forms a continuous network of sites that sample the coasts of scotland england and wales fairly uniformly and which may be especially important in this regard not only are these 14c data for the holocene epoch of very high quality in terms of our knowledge of the coastal environment and relationship to palaeo sea level of each age measurement but they are especially numerous and relate to an island that was itself partly glaciated in the north essentially ice free in the south and located well outboard of the massive ice sheet that covered fennoscandia at the last glacial maximum lgm taken together the time series from 55 distinct locations allow us to perform a fairly stringent test of the recently formulated ice 4g vm2 global model of the isostatic adjustment process even without modification this model has been shown to fit most of the time series in the uk data set rather well in order to satisfy very recently published a priori constraints on the maximum thickness of the scottish ice sheet however we find that the lithospheric thickness the feature of the radial viscoelastic structure to which the rebound data from scotland are most sensitive must be somewhat reduced whereas the assumed thickness of the lithosphere in ice 4g vm2 was near to 120 km best fits to the scottish data require a lithospheric thickness near to 90 km this reduced value for lithospheric thickness agrees exceedingly well with the latest estimates of this earth property based on the inversion of oceanic geoid and topography data as the asymptotic thickness characteristic of the oldest ocean floor this would appear to be the best possible a priori estimate for the thickness of the cratonic lithospheres upon which the largest ice sheets of the late pleistocene are known to have rested we also demonstrate explicitly that inferences of the shallow viscoelastic structure beneath the british isles are strongly influenced by the details of the history of deglaciation at remote locations at antarctica in particular

analysis and interpretation of holocene sea level data the geography of the geoid1 and the lack of an acceptable methodology and definition of terms for sea level studies have impeded the realization of the objectives of the international geological correlation programme project 61 on holocene sea level changes2 these were to establish a graph of the trend of mean sea level over the globe and the relationship between sea level climate change and the global ice budget2 a solution to the problems of correlation is proposed here the use of terms transgression and regression has been a major cause of misinterpretation2 and the terms transgressive overlap and regressive overlap have been proposed as descriptive lithostratigraphic terms in which no process is implied3 5 the processes involved in the development of coastal stratigraphical sequences are dependent on the position and rate of change of sea level and these sequences contain evidence of tendencies of sea level6 8 the application of the concept of sea level tendency permits meaningful correlations between rising and subsiding areas and introduces an objectivity to correlation schemes showing transgression sequences 9 10

variations in the pattern and rate of isostatic uplift indicated by a comparison of holocene sea level curves from scotland differences in the timing of maxima and minima and shape between sea level curves from the western forth valley lower strathearn inner moray firth and eastern solway firth areas of scotland are interpreted as being due to differences in isostatic uplift and different methodologies used to interpret the basic data possible changes in the relative rates of uplift between areas suggest that the practice of applying the western forth model of relative sea level change to other parts of scotland must be questioned

upper mantle structure in the southeastern canadian cordillera a seismic broadside wide angle experiment in canada s southeastern cordillera has revealed an anomalous and unexpected seismic arrival analysis of the data shows that the arrival is unlikely to be a crustal or shallow mantle phase or multiple or converted waves the kinematic characteristics of this arrival dictate that it is a reflection from within or from the base of a low velocity zone 7 8 8 0 km s 1 situated at a depth of 59 to 62 km that we identify as the top of the asthenosphere this leads to the conclusion that the base of the lithosphere is at a depth of 50 2 km in the region the interpreted shallow asthenosphere bolsters earlier conclusions of a heat source at depth in the southeastern canadian cordillera the interpretation also shows that stratification in the upper mantle is resolvable by current wide angle seismic experiments

holocene coastal change and geoarchaeology at howick northumberland uk the recent discovery of one of the earliest mesolithic occupation sites in northern britain at howick on the northumberland coast in association with multiperiod archaeological evidence nearby highlights the importance of uk coastal settings as focii of human occupation through the holocene environmental evidence from a nearby river valley 8 15 m of sediment ranging in age from about 12 000 cal bp to the present records local and regional environmental change twenty four radiocarbon dates based on plant macrofossils provide a strong chronological framework calcareous microfossil assemblages foraminifera ostracods have been recovered from the fine grained sediments recording a change from marine through to brackish and eventually freshwater conditions between about 8200 and 6500 cal bp a preliminary pollen study of the core has permitted a reconstruction of the regional vegetation as it responded to climatic amelioration and human influence upon the landscape radiocarbon dating and sedimentological evidence indicates a major hiatus between approximately 11 000 and 8000 years bp including the period of mesolithic occupation represented by a 30 cm layer of coarse sands and sandstone pebbles probably the result of a significant high energy event dated to about 8300 cal bp although not a typical tsunami deposit the age and context suggests that this may be associated with the storegga slide event already well documented along the eastern coast of scotland the sedimentary and biological remains at howick record environmental change over much of the holocene and are compared with other environmental change records from the region to provide an environmental framework for the archaeology of this coastline

late devensian and holocene relative sea level changes in northwestern scotland new data to test existing models abstract pollen diatom lithostratigraphic and radiocarbon data from five sites in northwestern scotland provide new data from an area previously devoid of reliable and precise information on late devensian and holocene sea level changes the sites cover a range of palaeoenvironments indicative of diversity in coastal evolution since deglaciation for each site and palaeoenvironment the reference water tide level indicative range age and tendency of sea level movement of all sea level index points are quantified to enable correlation of the diverse coastal environments the data record patterns of relative sea level change and tendencies of sea level movement from 12 ka bp to 1 ka bp this is the longest and most comprehensive published record of relative sea level change from the area the information is used to test the accuracy of existing models of relative sea level change the results are only broadly consistent with a quantitative rebound model and there is significant disagreement with empirical models during the late devensian and the early holocene

holocene glacial rebound and sea level change in nw europe summary observations of late pleistocene and holocene sea level change relative to the crust exhibit very considerable variations across nw europe in consequence of the response of the earth s crust to the deglaciation of fennoscandia and of the water added to the oceans from the melting of all late pleistocene ice sheets inversion of sea level observations from a site near the centre of the fennoscandian ice sheet and from three sites located beyond the margin of the ice sheet at the time of maximum glaciation yield a range of plausible models for the earth s response and for the ice models further constraints on this range of models is placed by a comparison of observed sea levels with predicted values at other sites near the former ice sheet margins the resulting mantle parameters are upper mantle viscosity 3 5 x 10 pa s lower mantle viscosity 2 7 x loz1 pa s lithospheric thickness 100150 km these values represent effective parameters that describe the response of the earth to surface loading of short to intermediate wavelengths on a time scale of 104yr the lower mantle viscosity is poorly constrained but the marked increase from upper to lower mantle is a characteristic of all plausible solutions the inversion places a constraint on the total volume of ice in the fennoscandian ice sheet such that the equivalent sea level rise from this contribution is about 13 14 m a less well determined constraint of about 10 m equivalent sea level rise is suggested for the barents kara ice sheet the inversion also indicates that a small amount of melt water from ice sheets far away from europe continued to be added into the oceans during late holocene time so as to raise the equivalent sea level by about 3 m during the past 6000 yr consistent with similar inversions of data from sites in the australian and pacific regions

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

flandrian sea level changes in the fenland ii tendencies of sea level movement altitudinal changes and local and regional factors stratigraphic micropalaeontologic and radiocarbon data show that since c 6500 bp the fenland has been influenced by 7 periods of positive sea level tendencies and by 6 periods of negative sea level tendencies despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea level tendencies were clearly characterised by a rise in sea level the development of transgressive overlaps and a landward movement of the coastline the periods of negative sea level tendencies were characterised by the development of regressive overlaps a seaward movement of the coastline and a reduced or negative rate of sea level rise the various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels all changes within the fenland were not synchronous and local factors influenced the exact nature of each sea level indicator dominant regional and local factors have been identified for different areas and different time periods the chronological and spatial characteristics of the sequences within the fenland are best explained by a palaeocoastline without supratidal barriers controlling sedimentation the data indicate an average crustal subsidence in the fenland of 0 9m 1000 years since c 6500 bp and the pattern of positive and negative tendencies of sea level movement is also seen in the chronologies for north west england and north east scotland