u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

open system coral ages reveal persistent suborbital sea level cycles sea level is a sensitive index of global climate that has been linked to earth s orbital variations with a minimum periodicity of about 21 000 years although there is ample evidence for climate oscillations that are too frequent to be explained by orbital forcing suborbital frequency sea level change has been difficult to resolve primarily because of problems with uranium thorium coral dating here we use a new approach that corrects coral ages for the frequently observed open system behavior of uranium series nuclides substantially improving the resolution of sea level reconstruction this curve reveals persistent sea level oscillations that are too frequent to be explained exclusively by orbital forcing

aminostratigraphy and faunal correlations of late quaternary marine terraces pacific coast usa recent studies using the extent of racemization of amino acids to date fossil mollusc shells in the arctic1 the british isles2 and on the atlantic3 4 and pacific5 13 coasts of north america have relied mainly on theoretical kinetic models of racemization ages generated in this fashion are highly model dependent and require estimates of integrated long term diagenetic temperatures we present here an alternative empirical approach to aminostratigraphy in which we plot amino acid enantiomeric ratios versus latitude for localities along the pacific coast of the united states and generate isochronal correlations by connecting data points of geographically proximal localities that have similar d l ratios and zoogeographic aspect isochrons are calibrated at a few localities by independent radiometric dates the diagenetic temperature effect on racemization is reflected in the slope of the isochrons but the need to quantify temperature is eliminated

is xrf core scanning a viable method for coral palaeoclimate temperature reconstructions abstract the use of x ray fluorescence xrf core scanning for continuous high resolution analysis of sr ca in corals is investigated here as a new method for analyzing coral material corals are valuable archives for generating high resolution palaeoclimate records of sea surface temperatures of the tropical oceans but traditional methods of analyzing coral geochemistry involve extensive subsampling and wet chemistry techniques to obtain high precision elemental records more recent developments of micro beam techniques have limitations in the length of core that can be scanned at any one time xrf core scanning provides a fast non destructive method of analyzing long sections of coral cores whilst maintaining a high sampling resolution here we apply this method to two modern corals from the sunda strait indonesia and one tree island great barrier reef australia we find that results show that xrf core scanning of corals produce sr ca records that capture the annual cycle particularly from reef sites with a large sea surface temperature range coupled density measurements of the coral skeleton also aid in increasing the utility of xrf measurements obtained from coral material although difficulties remain in reliably reconstructing interannual temperature variability using xrf sr ca determinations we recommend that xrf can provide a valuable method of quick and non destructive screening of coral material prior to more targeted analysis using traditional destructive geochemical analysis

late quaternary slip on the santa cruz island fault california the style timing and pattern of slip on the santa cruz island fault were investigated by trenching the fault and by analysis of offset late quaternary landforms a trench excavated across the fault at christi beach on the western coast of the island exposed deformation of latest pleistocene to holocene sediments and pre quaternary rocks recording repeated large magnitude rupture events the most recent earthquake at this site occurred ca 5 ka coastal terraces preserved on western santa cruz island have been dated using the uranium series technique and by extrapolation using terrace elevations and the eustatic record offset of terraces and other landforms indicates that the santa cruz island fault is predominantly left lateral having a horizontal slip rate of not more than 1 1 mm yr and probably about 0 8 mm yr the fault also has a smaller reverse component slipping at a rate of between 0 1 and 0 2 mm yr combined with measurements of slip per event this information suggests a long term average recurrence interval of at least 2 7 k y and probably 4 5 k y and average earthquake magnitudes of mw 7 2 7 5 sense of slip recurrence interval and earthquake magnitudes calculated here for the santa cruz island fault are very similar to recent results for other faults along the southern margin of the western transverse range including the malibu coast fault the santa monica fault the hollywood fault and the raymond fault supporting the contention that these faults constitute a continuous and linked fault system which is characterized by large but relatively infrequent earthquakes

temperature and precipitation variability in eastern anatolia results from independent component analysis of lake van sediment data spanning the last 250 kyr bp abstract in this study we present the results of independent component analysis ica of previously published lake van data covering the last 250 kyr bp to shed light on the precipitation and temperature regime in eastern anatolia the data processed were the element intensities of ca fe k mn and si analyzed by xrf core scanner concentrations of toc and caco 3 content and b color reflectance from the ahlat ridge sediment record our analysis is based on application of ica on the data by changing the initial random unit vector several times and clustering possible independent components through average link agglomeration as components extracted by ica do not have a hierarchy mutual information which is a measure of information content between two random variables is used as a measure of similarity by which to select candidate components as a result we argue the independent component van ic8 which shows the highest similarity to the greenland 18 o record and visually similar to other regional temperature indicating data can be read as a proxy for temperature variability we also assert that the independent component van ic7 which has the highest similarity to b and visually similar to other regional precipitation proxies and with the lake level reconstruction from another sediment profile from lake van is a proxy of precipitation variability across the region our results show that the region s temperature approximately maps onto global records i e warm during interglacials and cold during stadials however the precipitation proxy reveals that the region was not dry or at least as wet as it is today during the end of the mis 6 and the lgm the mis 5e c and holocene were characterized by a wet period followed by dry intervals and dansgaard oeschger events are characterized as being warm and wet

coastal uplift associated with the 1992 cape mendocino earthquake northern california the april 25 1992 cape mendocino earthquake ms 7 1 uplifted 24 km of the northern california coast at the southern end of the cascadia subduction zone uplift which resulted in coastal emergence that caused extensive mortality of intertidal organisms between cape men docino and punta gorda we estimated the amount of uplift by measuring the vertical extent of mortality of 14 sessile intertidal species on rocky sections of shore the uplift profile along the coast is generally parallel to the strike of the earthquake focal mechanism and forms a broad flat topped arch 24 km long with a gentle south limb and a steeper north limb the maximum uplift of 1 4 0 2 m is near the center of the profile the profile is a manifestation of the more widespread domal upwarp produced by slip on an east dipping buried thrust fault along or near the cascadia megathrust small new emergent terraces have formed where wave cut intertidal platforms have been elevated the new terraces resemble raised late holocene benches that probably record paleoearthquakes similar to the 1992 event however several of the late holocene terraces are broader and more continuous these terraces which extend several tens of kilometres north and south of the 1992 uplift suggest that some paleoearthquakes were much larger than magnitude 7

relations among subduction parameters clues to the dynamics of the subduction process are found in the many measurable parameters of modern subduction zones based on a critical appraisal of the geophysical and geological literature 26 parameters are estimated for each of 39 modern subduction zones to isolate causal relationships among these parameters multivariate analysis is applied to this data set this analysis yields empirical quantitative relations that predict strain regime and strike slip faulting in the overriding plate maximum earthquake magnitude benioff zone length slab dip arc trench gap and maximum trench depth excellent correlation is found between length of the benioff zone and the product of convergence rate and age of the downgoing slab this relationship is consistent with the conductive heating model of molnar et al 1979 if the model is modified in one respect the rate of heating of the slab is not constant it is substantially slower during passage of the slab beneath the accretionary prism and overriding plate the structural style in the overriding plate is determined by its stress state though the stress state of overriding plates cannot be quantified one can classify each individual subduction zone into one of seven semiquantitative strain classes that form a continuum from strongly extensional class 1 back arc spreading to strongly compressional class 7 active folding and thrusting this analysis indicates that strain class is probably determined by a linear combination of convergence rate slab age and shallow slab dip interplate coupling controlled by convergence rate and slab age is an important control on strain regime and the primary control on earthquake magnitude arc parallel strike slip faulting is a common feature of convergent margins forming a forearc sliver between the strike slip fault and trench optimum conditions for the development of forearc slivers are oblique convergence a compressional environment and a continental overriding plate the primary factor controlling presence of strike slip faulting is coupling strongly oblique convergence is not required the rate of strike slip faulting is affected by both convergence obliquity and convergence rate maximum trench depth is a response to flexure of the underthrusting plate the amount of flexural deflection at the trench depends on the vertical component of slab pull force which is very sensitive to slab age and shallow slab dip shallow slab dip conforms to the cross sectional shape of the overriding plate which is controlled by width of the accretionary prism and duration of subduction deep slab dip is affected by the mantle trajectory established at shallow depth but may be modified by mantle flow much of the structural complexity of convergent margins is probably attributable to terrane juxtaposition associated with temporal changes in both forearc strike slip faulting and strain regime empirical equations relating subduction parameters can provide both a focus for future theoretical studies and a conceptual and kinematic link between plate tectonics and the geology of subduction zones

low uplift rates and terrace reoccupation inferred from mollusk aminostratigraphy coquimbo bay area chile abstract mollusk aminostratigraphy of quaternary marine terrace sediments at coquimbo bay chile combined with recently available electron spin resonance esr ages necessitates revision of the northern chilean relative sea level and terrace chronology protothaca and mulinia d alloisoleucine l isoleucine values define four aminozones which are consistent with available esr ages terrace reoccupation during successive high sea level stands is inferred on the basis of litho and aminostratigraphically defined unconformities in terrace sediments esr data and a nonlinear kinetic racemization model give approximate numerical ages for the aminozones and thus yield estimates of net uplift rates these rates averaged over intervals of one to several hundred thousand years have ranged from less than 0 1 m 1000 yr to no more than 0 2 m 1000 yr such slow uplift is the cause of terrace reoccupation as the amount of uplift between successive glacioeustatic high sea level stands is frequently not sufficient to isolate an earlier formed abrasion platform from rising sea level during a subsequent high stand

late quaternary uplift and earthquake potential of the san joaquin hills southern los angeles basin california analysis of emergent marine terraces in the san joaquin hills california and 230 th dating of solitary corals from the lowest terraces reveal that the san joaquin hills have risen at a rate of 0 21 0 27 m k y during the past 122 k y movement on a blind thrust fault in the southern los angeles basin has uplifted the san joaquin hills and has the potential to generate an m w 7 3 earthquake within this densely populated area our structural modeling suggests that the fault dips to the southwest and slips at 0 42 0 79 m k y yielding an estimated minimum average recurrence interval of 1650 3100 yr for moderate sized earthquakes recognition of this blind thrust extends the known area of active blind thrusts and fault related folding southward from los angeles into coastal orange county

geotechnical behaviour of saline sabkha soils the behaviour of salt cemented sabkha soil was investigated by considering the effect of brine and distilled water on its properties laboratory and field testing programmes were conducted to examine the effect of soaking and leaching on the structure compressibility collapse permeability load carrying capacity and settlement of sabkha soil results indicate that the percolation of distilled water through the sabkha causes destruction of the natural cementation leading to collapse increase in permeability reduction in strength and increase in settlement dissolution and leaching of halite gypsiferous and calcarenite cements occur leaving the quartz particles covered by a thin loose mat of illitic clay with large voids the collapse deformation of sabkha is inclusively linked to the ambient salt complex which determines the structural properties of the soil and promotes the development of collapse on wetting the soaking of sabkha produces practically negligible collapse leaching causes a signif

development of low background vacuum extraction and graphitization systems for 14c dating of old 40 60 ka samples abstract at the university of arizona s desert laboratory we recently constructed new low background vacuum extraction and graphitization systems that are dedicated to preparing old 40 60 ka samples for 14 c dating these systems are designed to minimize the amount of contaminant carbon specifically atmospheric carbon that is introduced to a sample during laboratory processing excluding contaminants is particularly important for 14 c dating of old samples because the impact of contamination increases with sample age in this study we processed 20 pretreated and 4 untreated aliquots of ceylon graphite a naturally occurring geological graphite to determine the total procedural background level and hence the practical limit of our systems samples were heated under vacuum at 240 c for 1 h to drive off water vapor and other atmospheric gases and then combusted in ultra high purity uhp o 2 at 500 and 850 c to monitor the removal of contaminants and to ensure complete combustion after so x no x and halide species were removed sample co 2 was converted to graphite via catalytic reduction of co fe and zn powders used in the graphitization process were oxidized scrubbed and reduced with uhp o 2 he and h 2 respectively to remove sorbed atmospheric c species graphite targets were stored in uhp ar until measurement by accelerator mass spectrometry ams to avoid potential interaction with atmospheric gases based on the ams results the background level of our system is characterized by a nonlinear inverse relationship with sample mass adjusted r 2 0 75 n 24 for a 1 mg graphite target the total procedural blank including chemical pretreatment combustion cleanup graphitization storage and ams measurement is 0 05 0 01 pmc 2 equivalent to a 14 c age of 61 1 1 8 ka this should not be taken as the upper limit of our system however because if the 14 c activity of a sample is statistically indistinguishable from the appropriate mass dependent blank value at the 95 confidence level 2 then its age is considered to be infinite thus for a 1 mg target the practical limit of our system is actually 55 ka for a 0 5 mg target the practical limit is 50 ka although our extraction system can accommodate inorganic samples e g calcite aragonite the above limits are only applicable to geological graphite charcoal and organic samples that are processed via combustion future work will be directed toward determining the appropriate background levels for inorganic materials

quaternary sea level events on northern san clemente island california abstract global sea level changes are expressed in the coastal landforms and deposits of northern san clemente island stratigraphic radiometric amino acid and pedologic dating techniques have allowed the development of a chronology of sea level changes for about the last 500 000 yr a uranium series date on coral of about 127 000 yr for the 2nd terrace serves as a calibration point for amino acid age estimates of four other mapped terraces two of these terraces have age estimates of about 80 000 105 000 yr another has an age estimate of about 127 000 yr and the 5th terrace on the west side of the island is estimated to be about 415 000 575 000 yr old these dates correlate reasonably well with marine terraces dated elsewhere and with stages of the oxygen isotope record that are thought to represent high stands of the sea weakly cemented calcareous dune sands eolianites are moderately extensive on northern san clemente island and appear to represent low stands of the sea since calcareous shelf sands were the most likely source a radiocarbon date of about 22 000 yr suggests that the youngest eolianite was deposited during the last glacial maximum an older eolianite is estimated to be about 140 000 195 000 yr old based on stratigraphic relations and degree of soil development the suggested ages for the eolianites also correlate well with oxygen isotope estimates of low sea levels

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

application of multivariate statistical analyses to itraxtm core scanner data for the identification of deep marine sedimentary facies a case study in the galician continental margin abstract the validity and usefulness of multivariate statistical tools for the facies characterization in deep marine environments have been applied on the geochemical sedimentological and magnetic data from a piston core extracted from the transitional zone in the galician continental margin the combination of geochemical profiles of fe mn ti ba and ca and magnetic susceptibility ms obtained using the itraxtm core scanner at the university of vigo together with the grain size grey level and r red g green b blue colour analyses have allowed characterizing and classifying the sediments of the core pc13 3 using spss package v 23 cluster analysis ca displays in the first level of the hierarchy two major groups that correspond with clay silt and sand facies in a second level it is possible to observe six subfacies that match de visu preliminary classification and allowed us to complete and improve the characterization and the facies limits in the whole core discriminant analysis da confirmed the validity of the cluster analyses and enhanced the results of the classification the principal component analysis pca shows four principal components coarse lithogenic fraction pc1 fine lithogenic fraction pc2 high density fraction pc3 and biogenic fraction pc4 these results are in concordance with the pearson correlation coefficient and the sem observations in general terms the results confirm the utility of the multivariate statistical methods applied on high resolution geochemical and magnetic data acquired with itraxtm corer scanner as a quick and complementary tool in sedimentary facies analysis and description in deep marine environments

a review of amino acid racemization studies in quaternary mollusks stratigraphic and chronologic applications in coastal and interglacial sites pacific and atlantic coasts united states united kingdom baffin island and tropical islands abstract amino acid racemization aar studies of quaternary mollusks mostly marine mollusks from coastal deposits are reviewed data obtained in regional studies from the u s atlantic and pacific coasts baffin island the united kingdom and tropical islands are discussed as they relate to method evaluation kinetic model development and aminostratigraphic applications u s pacific coast studies have been employed for estimating tectonic deformation rates study of molluscan zonation patterns in the late pleistocene and in kinetic model evaluation u s atlantic coast studies have identified multiple aminostratigraphic zones in areas with complex morphostratigraphic relationships and have also revealed some important conflicts between aminostratigraphic temperature concepts and radiometric data studies in the united kingdom involving coastal sites and non marine interglacial sites identify some stratigraphic and kinetic conflicts but provide a preliminary chronostratigraphic model for the classical interglacial terminology of the u k middle to late pleistocene baffin island studies involving aar data and u th dating of shells have resulted in some significant revisions of previous chronologic models the arctic environment has also stimulated some novel approaches in the collection and interpretation of aar results tropical island studies though few in number aid in calibration of observed racemization and also aid in correlation of coastal deposits with late pleistocene isotopic ice volume records

late quaternary deformation of marine terraces on the cascadia subduction zone near cape blanco oregon the cape blanco region of south coastal oregon sits on the upper plate of the cascadia subduction zone about 60 70 km east of the base of the continental slope though the region has no historic coseismic deformation late quaternary deposits and landforms show abundant evidence of uplift folding and faulting a set of five late quaternary marine terraces and one uplifted holocene beach berm are preserved in the cape blanco region stratigraphic and altitudinal surveys of these physiographic features combined with several numerical and correlation age determinations permit a reconstruction of tectonic deformation near cape blanco in approximately the last 200 000 years the most cogent aspects of the neotectonics in this part of the cascadia subduction zone are that an east west trending anticline deforms the lower three terraces 80 125 ka as well as accounting for uplift of the holocene storm berm latest movement on the anticline was no more than 2 000 years ago but the anticline also deforms sediments as old as middle miocene the anticline is consistent with a north south principal contraction axis at cape blanco in about the last 100 000 years an older terrace at cape blanco approximately 200 ka is offset by two reactivated faults whose movements prior to the eocene served to suture several terranes to the north american continent tectonic tilting in the older terrace is not consistent with a north south principle axis of contraction but the axis of tilt is parallel to north northwest striking structures developed in the quaternary fold belt offshore on the continental shelf the observed deformation indicates that regional stress in the vicinity of cape blanco in the late quaternary has been accommodated by a variable pattern of strain

late quaternary folding of coral reef terraces barbados uplifted late ouaternary coral reefs on the island of barbados record folding of the emergent crest of the lesser antilles accretionary prism barbados ridge complex since ca 1 ma three northeast striking folds are defined by systematic changes in altitudes in the crest of first high cliff a mostly constructional reef terrace about 125 ka and second high cliff a partially erosional reef terrace about 500 ka the folds have wavelengths of 6 to 8 km and fold axes extend about 10 km the largest anticline rises to the northeast where it has been breached by erosion exposing highly deformed eocene to lower miocene rocks of the scotland district uplift rates based on heights of the last interglacial first high cliff range from 0 07 to 0 44 mm yr quaternary folding on barbados indicates that the crest of the accretionary prism continues to be an active fold belt undergoing northwestsoutheast shortening

u series ages of solitary corals from the california coast by mass spectrometry the purpose of this study is to evaluate the feasibility of dating fossil solitary corals from pleistocene marine strandlines outside tropical latitudes using the recently developed high sensitivity high precision u series technique based on thermal ionization mass spectrometry tims the tims technique is much more efficient than conventional a spectrometry and as a result multiple samples of an individual coral skeleton or different specimens from the same bed can be analyzed detached and well rounded fossil specimens of the solitary coral balanophyllia elegans were collected from relict littoral deposits on emergent marine terraces along the california coast at cayucos terrace elevation 8 m previously dated at 124 and 117 ky by counting shell beach terrace elevation about 25 m previously undated nestor terrace san diego elevation 23 m previously dated at 131 to 109 ky bird rock terrace san diego elevation 8 m previously dated at 81 ky attached living specimens were collected from the intertidal zone on the modern terrace at moss beach concentrations of 232 th in both living and fossil specimens are much higher than in reef building corals 12 to 624 pmol g vs 0 1 to 1 6 pmol g respectively however because 230 th 232 th in balanophyllia elegans are very low 2 22 10 3 to 4 33 10 4 the high 232 th concentrations have negligible effect on the 230 th 234 u dates the high 232 th concentration in the living specimen 33 1 pmol g indicates that a significant amount of 232 th is incorporated in the aragonitic skeleton during growth or attached to clay sized silicates trapped in the skeletal material the calculated initial 234 u activities in the fossil specimens of balanophyllia elegans are higher than the 234 u activity in modern seawater or in the modern specimen the higher initial activities could possibly reflect the influx of 234 u enriched continental water into pleistocene coastal waters or it could reflect minor diagenetic alteration a persistent and fundamental problem in dating all corals samples from a compound specimen from the cayucos terrace were subjected to different preparation procedures samples prepared by a standard acid washing procedure yielded 230 th 234 u ages of 125 123 and 122 ky whereas samples prepared by an abbreviated procedure without acid washing yield significantly lower ages of 113 and 112 ky two other specimens from the same bed yielded 230 th 234 u ages of 118 and 115 ky also two specimens from a stratigraphically higher bed yielded ages of 120 and 117 ky and three specimens from a lower bed yield ages of 115 113 and 101 ky nine of the twelve ages of the treated samples from the cayucos terrace range from 125 to 113 ky however the ages do not follow the stratigraphie order two possible interpretations are 1 the age of the terrace deposit is 125 ky and all younger ages reflect variable diagenetic alteration or 2 the age of the terrace is 125 to 113 ky and the ages reflect sediment reworking over a period of 12 ky three specimens from a single bed on the shell beach terrace yield ages of 126 122 and 121 ky similar to the older ages from cayucos the ages of solitary corals from the cayucos and shell beach terraces are similar to ages of reef building corals from terraces at numerous tropical localities these are correlated with the last interglacial sea level highstand which probably stood 2 to 10 m above present sea level the youngest ages and present elevations of the cayucos and shell beach terraces yield tectonic uplift rates of 0 01 and 0 15 m ky respectively assuming the original elevation of each terrace was 7 m four specimens from the basal gravel on the nestor terrace yielded ages of 145 143 137 and 133 ky the three oldest ages however are older than that associated with the last interglacial the possible explanations for these older ages are 1 diagenic alteration or 2 the nestor terrace deposits reflect in some way a poorly documented early phase of the last interglacial sea level high stand

mass spectrometric 230th 234u 238u dating of the devils hole calcite vein the devils hole calcite vein contains a long term climatic record but requires accurate chronologic control for its interpretation mass spectrometric u series ages for samples from core dh 11 yielded 230 th ages with precisions ranging from less than 1 000 years 2 for samples younger than 140 ka thousands of years ago to less than 50 000 years for the oldest samples 566 ka the 234 u 238 u ages could be determined to a precision of 20 000 years for all ages calcite accumulated continuously from 566 ka until 60 ka at an average rate of 0 7 millimeter per 10 3 years the precise agreement between replicte analyses and the concordance of the 230 th 238 u 234 u 238 u ages for the oldest samples indicate that the dh 11 samples were closed systems and validate the dating technique in general

active tectonics of the loreto area baja california sur mexico abstract quaternary faulting and coastal uplift characterize the rifted margin of baja california near loreto the process by which strain between the north american and pacific plates became partitioned across the baja peninsula and the gulf of california is partially recorded in the tectonics of the loreto region the loreto fault which consists of a north south trending northern segment and a northwest southeast southern segment records part of this process as do other faults offshore during the pliocene the southern loreto fault was actively providing accommodation space for rapid sedimentation in the loreto basin basin subsidence which abruptly slowed at the end of the pliocene was replaced by uplift which occurred throughout the quaternary the quaternary history of the northern loreto fault is recorded in fault scarps cutting quaternary deposits fault studies indicate that cumulative normal slip on the northern loreto fault over the quaternary was only about 30 m latest pleistocene deposits are offset by about 5 m uplifted marine terraces which may record either isostatic uplift of the coastal region or faulting events offshore suggest rates of coastal uplift between 0 08 m ka to 0 16 m ka for the last 120 ka these results strongly suggest that since the end of the pliocene strain was transferred from the loreto fault to other faults probably offshore strain between the pacific and north american plates may therefore largely occur in the gulf of california rather than onshore in the loreto region despite the low quaternary strain rates recorded the offshore faults and the loreto fault may both represent significant seismic hazards albeit with long recurrence intervals

aridification of the egyptian sahara 5000 4000 cal bp revealed from x ray fluorescence analysis of nile delta sediments at kom al ahmer kom wasit abstract elemental xrf analysis carried out on an 8 m long core from the nile delta reveals a gradual increase in the ca ti ratio between 5000 and 4000 cal bp which is linked to the progressive development of hyper aridity in this region the increase results from elevated flux of aeolian material entering the nile river system from calcareous source rock geologies in the dryer egyptian sahara the most major increase in hyper aridity occurs around 4000 cal bp such a perspective suggests a locally abrupt regionally time transgressive inception of hyper aridity in this region at the end of the african humid period after this time reorganisation of wind circulation meant that less saharan derived aeolian material entered the nile valley and the contribution of aeolian material in the nile s sedimentary signal was also dwarfed by an increase in blue nile sedimentary flux chronological control is provided by two radiocarbon dates and the top and bottom of a well constrained pottery horizon that dates from the period of occupation of two nearby archaeological sites kom al ahmer and kom wasit

coastal tectonics on the eastern margin of the pacific rim late quaternary sea level history and uplift rates channel islands national park california usa abstract the pacific rim is a region where tectonic processes play a significant role in coastal landscape evolution coastal california on the eastern margin of the pacific rim is very active tectonically and geomorphic expressions of this include uplifted marine terraces there have been however conflicting estimates of the rate of late quaternary uplift of marine terraces in coastal california particularly for the northern channel islands in the present study the terraces on san miguel island and santa rosa island were mapped and new age estimates were generated using uranium series dating of fossil corals and amino acid geochronology of fossil mollusks results indicate that the 2nd terrace on both islands is 120 ka and the 1st terrace on santa rosa island is 80 ka these ages correspond to two global high sea stands of the last interglacial complex marine isotope stages mis 5 5 and 5 1 respectively the age estimates indicate that san miguel island and santa rosa island have been tectonically uplifted at rates of 0 12 0 20 m ka in the late quaternary similar to uplift rates inferred from previous studies on neighboring santa cruz island the newly estimated uplift rates for the northern channel islands are however an order of magnitude lower than a recent study that generated uplift rates from an offshore terrace dating to the last glacial period the differences between the estimated uplift rates in the present study and the offshore study are explained by the magnitude of glacial isostatic adjustment gia effects that were not known at the time of the earlier study set in the larger context of northeastern pacific rim tectonics channel islands uplift rates are higher than those coastal localities on the margin of the east pacific rise spreading center but slightly lower than those of most localities adjacent to the cascadia subduction zone the uplift rates reported here for the northern channel islands are similar to those reported for most other localities where strike slip tectonics are dominant but lower than localities where restraining bends such as the big bend of the san andreas fault result in crustal shortening

towards characterising rhyolitic tephra layers from new zealand with rapid non destructive μ xrf core scanning abstract tephra layers are of importance for the construction of reliable age control in late quaternary paleoenvironmental and volcanic hazard studies especially in volcanically active settings such as the north island of new zealand however their identification involves time consuming and destructive processing steps making the application of non destructive xrf core scanners potentially advantageous for tephra identification here we investigate the potential of the itrax xrf core scanner to differentiate between rhyolitic tephra layers sourced from various northern new zealand rhyolitic volcanic centres deposited in maar lakes of the auckland volcanic field in their macroscopic form these tephra layers are usually visibly distinct when surrounded by a dark organic rich sediment matrix although their attribution to source volcanic centre and eruption typically requires examination of their mineral assemblages combined with chemical fingerprinting of the rhyolite glass shards we demonstrate that xrf core scanning of rhyolitic tephra layers from the taupo volcanic zone and tuhua volcanic centre can also allow identification and sometimes differentiation of the tephra using xrf derived elemental counts especially high si k ca and very low br and ti different rhyolite tephra layers vary in their relative abundances of major minor and trace elements as is evident from electron microprobe and la icp ms analyses of their glass shards mo tube based xrf cannot detect na nor mg and is of lower reliability for the lighter elements ca al which play an important role in traditional tephra fingerprinting nevertheless we are able to demonstrate that xrf core scanning data can distinguish between previously identified tephra layers using multivariate statistics furthermore the study emphasises the need for a standard protocol for xrf core scanning of tephra layers for this approach to be more widely applicable especially to aid or be a substitute for conventional geochemical approaches used for tephra fingerprinting

application of the global positioning system to crustal deformation measurements 3 result from the southern california borderlands five years of measurements from the global positioning system gps satellites collected between 1986 and 1991 are used to investigate deformation in the offshore regions of southern california gps provides the first practical technique to make precise geodetic measurements in the region the geodetic network is situated along the california coastline from vandenberg 120 6 w 34 6 n to san diego with additional sites on santa cruz san nicolas santa catalina santa rosa and san clemente islands the precision of horizontal interstation vectors is subcentimeter and the interstation vector rate between ovro and vandenberg agrees with the very long baseline interferometry derived rate to within one standard deviation no significant motion is observed in the western santa barbara channel between vandenberg and santa rosa island 0 5 1 6 mm yr where the quoted uncertainties are one standard deviation motions in the eastern santa barbara channel are consistent with compressional deformation of 6 1 mm yr at n16 3 e this motion is in agreement with seismicity and an independent geodetic analysis for the period 1971 1987 larsen 1991 san clemente island is moving relative to san diego at the rate of 5 9 1 8 mm yr at a direction of n38 20 w the motion between san nicolas island and san clemente island 0 8 1 5 mm yr is insignificant

amino acid age estimates of marine terraces and sea levels on san nicolas island california fourteen marine terraces rising to an elevation of 274 m have been mapped on san nicolas island california the lowest terrace is 105 000 yr old on the basis of amino acid ratios in fossil mollusks slightly lower than those from the 120 000 yr old uranium series dated second terrace the age estimate and present elevation of the lowest terrace along with an assumption of constant uplift rate indicate a paleo sea level estimate of 10 to 12 m at about 105 000 b p supporting the general barbados model of sea level history the fourth and fifth terraces probably represent separate high sea level stands during the same interglacial complex 400 000 b p the eight and tenth terraces have amino acid ratios near equilibrium and imply ages of 600 000 yr collectively the data suggest long term average quaternary uplift rates of 0 2 0 3 m 1000 yr

turbidite emplacement on the southern balearic abyssal plain western mediterranean sea during marine isotope stages 1 3 an application of itrax xrf scanning of sediment cores to lithostratigraphic analysis the upper part 0 20 m of a long piston core from the se balearic abyssal plain spanning the past 50 ka has been studied using the itrax micro xrf core scanner to obtain downcore elemental profiles the ca fe ratio was found to be an effective parameter to distinguish between turbidites and pelagites because turbidites generally have higher fe contents and lower ca contents compared with pelagic intervals beds that were obscure when visually logged could be identified as turbidites or pelagites on their geochemical characteristics allowing more complete subdivision of the sequence into genetic units the itrax xrf data also provide useful information on textural grading bioturbative mixing identification of geochemically distinctive marker beds indications of differences in provenance and confirm or query the presence of early arrivals during turbidite emplacement a chronostratigraphic framework for the core based on accelerator mass spectrometry ams radiocarbon dating and correlation with oxygen isotope stages of pelagic intervals in other cores using calcium carbonate stratigraphy was also established this shows that turbidite emplacement on this part of the balearic abyssal plain has been modulated strongly by climate and sea level change with turbidite emplacement most frequent during the early holocene when the rate of post glacial sea level rise was greatest deposition of the coarsest i e sand and silt based turbidites at the core site was restricted to the full and late glacial 11 25 ka turbidite emplacement during oxygen isotope stage 3 was rare most of the turbidites at the site are distal but some coarse grained based turbidites are characterized by higher sr ca ratios possibly indicating a higher aragonite content higher ca and lower fe contents compared to other turbidites and are interpreted as having a more proximal shelf source such turbidites are generally rare however and restricted to full glacial and younger dryas time there is little evidence for large scale seismogenic turbidites expected to be seen as randomly timed emplacement seemingly independent of eustatic control at the core site despite proximity to the seismically active algerian margin 100 km to the south this suggests that seismogenic turbidites must largely bypass this part of the plain although the itrax core scanner provides a rapid and non destructive means of characterizing downcore geochemical distributions in great detail interpretation of the data requires caution and assessment from an informed standpoint analytical artefacts such as those caused by water or organic content degree of compaction grain size and mineral effects unevenness of the cut core surface and poor discrimination of closely spaced element xrf peaks need identification and elimination

age estimates and uplift rates for late pleistocene marine terraces southern oregon portion of the cascadia forearc marine terraces are prominent landforms along the southern oregon coast which forms part of the forearc region of the cascadia subduction zone interest in the cascadia subduction zone has increased because recent investigations have suggested that slip along plates at certain types of convergent margins is characteristically accompanied by large earthquakes in addition other investigations have suggested that convergent margins can be broadly classified by the magnitude of their uplift rates with these hypotheses in mind we generated new uranium series amino acid and stable isotope data for southern oregon marine terrace fossils these data along with terrace elevations and two alternative estimates of sea level at the time of terrace formation allow us to determine terrace ages and uplift rates uranium series analysis of fossil coral yields an age of 83 5 ka for the whisky run terrace at coquille point in bandon oregon a combination of amino acid and oxygen isotope data suggest ages of about 80 and 105 ka for the lowest two terraces at cape blanco these ages indicate uplift rates of 0 45 1 05 and 0 81 1 49 m kyr for coquille point and cape blanco respectively late quaternary uplift rates of marine terraces yield information about deformation in the overriding plate but it is unclear if such data vary systematically with convergent margin type in order to assess the utility of the southern oregon uplift rates for predicting the behavior of the cascadia subduction zone we compared late quaternary uplift rates derived from terrace data from subduction zones around the world on the basis of this comparison the southern oregon rates of vertical deformation are not unusually high or low furthermore late quaternary uplift rates show little relationship to the type of convergent margin these observations suggest that local structures may play a large role in uplift rate variability in addition while the type of convergent margin may place an upper limit on possible uplift rate greater upper limits serve to increase the range of possible uplift rates in the case of the southern oregon coast variability in uplift rate probably reflects local structures in the overriding plate and the rate of uplift cannot be used as a simple index of the potential for great earthquakes along the southern cascadia subduction zone

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

a revised morpho and chronostratigraphy of the late and middle pleistocene coral reef terraces on southern barbados west indies the barbados coral reef terraces are one of the few type localities worldwide that provide insights into interglacial sea level change during the late and middle pleistocene several sea level estimates have been established since the late 1960s and each has contributed to the barbados model of sea level change this paper presents new morpho and chonostratigraphic data from the barbados coral reef terraces developed over the last 12 years the work is based on significant advances in electron spin resonance esr dating of fossil coral air photo interpretation and a greatly improved geomorphic map of preserved fossil beach formations and reef terraces above present sea level the need for a revision of past published morpho and chronostratigraphies is best demonstrated on the southern part of the island the morpho and chronostratigraphic sequence in this region is both more complex and diverse than has been assumed so far the revised morphostratigraphy presented here includes a differentiation of coral reef terraces wave cut platforms and other erosive features such as notches and cliffs our study of these geomorphic features combined with new numeric dating results esr u th enable a revised estimate of the spatial and temporal variation in tectonic uplift rate within south barbados these new rates are an essential requirement for more precise glacio eustatic sea level reconstructions during the late and middle pleistocene from this region

sea level history of the past two interglacial periods new evidence from u series dating of reef corals from south florida abstract as a future warm climate analog much attention has been directed to studies of the last interglacial period or marine isotope substage mis 5 5 which occurred 120 000 years ago nevertheless there are still uncertainties with respect to its duration warmth and magnitude of sea level rise here we present new data from tectonically stable peninsular florida and the florida keys that provide estimates of the timing and magnitude of sea level rise during the last interglacial period the last interglacial high sea stand in south florida is recorded by the key largo limestone a fossil reef complex and the miami limestone an oolitic marine sediment thirty five new high precision uranium series ages of fossil corals from the key largo limestone indicate that sea level was significantly above present for at least 9000 years during the last interglacial period and possibly longer ooids from the miami limestone show open system histories with respect to u series dating but show a clear linear trend toward an age of 120 ka correlating this unit with the last interglacial corals of the key largo limestone older fossil reefs at three localities in the florida keys have ages of 200 ka and probably correlate to mis 7 these reefs imply sea level near or slightly above present during the penultimate interglacial period elevation measurements of both the key largo limestone and the miami limestone indicate that local relative sea level was at least 6 6 m and possibly as much as 8 3 m higher than present during the last interglacial period

a cool eastern pacific ocean at the close of the last interglacial complex abstract new high precision thermal ionization mass spectrometric tims u series ages of solitary corals balanophyllia elegans from several marine terrace localities along the california and southern oregon coasts date to the 80 000 yr bp high stand of sea correlative with marine isotope substage 5a late in the last interglacial complex ages of multiple corals from localities north of point ano nuevo central california and san nicolas island southern california suggest that this high sea stand could have lasted at least 8000 yr from 84 000 to 76 000 yr bp these ages overlap with those from marine deposits on tectonically stable bermuda and tectonically emergent barbados higher elevation terraces at two california localities in the palos verdes hills and on san nicolas island have corals with ages that range mostly from 121 000 to 116 000 yr bp correlative with marine isotope substage 5e these ages are similar to those reported for other terraces in southern california but are younger than some ages reported from hawaii barbados and the bahamas marine terrace faunas are excellent proxies for nearshore marine paleotemperatures during past high sea stands terraces on the palos verdes hills and san nicolas island dated to the 120 000 yr bp high sea stand have dominantly zoogeographically neutral species in exposed coastal localities indicating nearshore waters similar to those of today in contrast 80 000 yr bp exposed coastal localities typically have molluscan faunas characterized by numerous extralimital northern species and a lack of extralimital southern species these fossil assemblages are indicative of nearshore water temperatures that were cooler than modern temperatures at 80 000 yr bp waters at least as warm as today s at 120 000 yr bp and cooler than present at 80 000 yr bp are in excellent agreement with marine alkenone records and coastal vegetation records derived from pollen data from both southern and northern california decreased insolation or increased upwelling seem inadequate to explain the cool waters off the pacific coast from southern oregon to southern california at 80 000 yr bp we propose that a stronger california current or at least one with a greater component of subarctic waters may explain cooler than modern coastal waters during the 80 000 yr bp high sea stand

calibration of xrf core scanners for quantitative geochemical logging of sediment cores theory and application abstract on line analysis of split sediment cores by xrf core scanners has become increasingly popular in the past decade because it allows nondestructive extraction of near continuous records of element intensities from sediment cores with a minimum of analytical effort a disadvantage of xrf core scanning relative to conventional geochemical analysis is the problematic conversion of core scanner output to element concentrations the main reason for this long standing problem is the poorly constrained measurement geometry attributable to inhomogeneity of the specimens e g variable water content and grain size distribution irregularities of the split core surface and in some setups spatial variations in thickness of an adhesive pore water film which forms directly below a protective foil covering the core surface we propose a log ratio calibration model for xrf core scanners derived from a combination of xrf spectrometry theory principles of compositional data analysis and empirical evidence the log ratio calibration model provides accurate and precise predictions of sediment composition element concentrations from xrf core scanner output with a limited number of parameters namely 2 d 1 where d equals the number of chemical elements whose concentrations are to be estimated the model can accommodate the inherent non linearity of the relation between relative intensities and concentrations which is apparent from the fact that it provides unbiased estimates an immediate corollary of our results is that log ratios of element intensities which are related to log ratios of element abundances by a simple linear transformation provide the most easily interpretable signals of relative changes in chemical composition consistent use of log ratios of element intensities or concentrations should minimise the risk of drawing erroneous conclusions from geochemical proxies the relative standard deviation precision of predicted element concentrations in core geob7920 is less than 2 stochastic simulations indicate that this level of precision can be attained with 40 randomly selected calibration specimens improved control over input errors and development of robust goodness of fit statistics allows xrf core scanning to be developed into a rigorous quantitative measurement technology the log ratio calibration equation derived in this study may be adapted to inter laboratory and inter instrument calibration as well

late quaternary tectonic deformation in the cape arago bandon region of coastal oregon as deduced from wave cut platforms the cape arago region of south central oregon sits on the upper plate of the cascadia subduction zone about 80 km east of the base of the continental slope the style of late pleistocene deformation along the cascadia forearc near cape arago is well expressed by the altitudinal variation of a set of five uplifted wave cut platforms these platforms record open folding with a half wavelength of about 6 7 km as well as late quaternary offset on flexural slip reverse faults that parallel bedding in the underlying bedrock the folds have produced both landward and seaward tilts to the uplifted wave cut platforms because the folds cut obliquely across the coastline the magnitude of coastal uplift is variable in the case of the lowest 80 ka wave cut platform this variable uplift has resulted in coastal deformation ranging from subsidence to a maximum uplift of 0 8 m kyr quantitative analysis of the mechanism of flexural slip folding for the south slough syncline near cape arago indicates that the late quaternary strain rate has decreased in the last 200 kyr evidence of past great subduction style earthquakes such as regional uplift and regional landward tilting of wave cut platforms or regional submergence of coastlands is lacking inmore the cape arago region instead the deformational style is controlled by folding though localized folding is dominant the occurrence of great subduction style earthquakes is not precluded because localized folding could occur concurrently with regional coseismic deformation less

deformation in the santa barbara channel from gps measurements 1987 1991 geodesy is one of the few techniques that can be used to estimate strain rates across the submerged structures in the santa barbara channel by resolving relative surface velocities the global positioning system gps can be used to infer crustal deformation rates independent of geologic models gps measurements from the period 1987 1991 have been used to derive velocities for a 8 station network bounding the channel these estimates are based on 10 gps experiments each of several days in length over this 4 5 year period precision of individual determinations of intersite vectors range from 3 to 7 mm for the horizontal components and average 20 mm in the vertical the gps data indicate high rates of shortening in the eastern channel 6 1 mm yr at n16 3e and low rates of deformation in the western channel comparisons with previous geodetic studies suggest that deformation in the region has not been uniform over the last 100 years

uranium series coral ages from the us atlantic coastal plain the 80 ka problem revisited abstract uranium series coral ages for emergent units from the passive continental margin us atlantic coastal plain acp suggest sea level above present levels at the end of marine oxygen isotope stage mis 5 contradicting age elevation relations based on marine isotopic or coral reef models of ice equivalent sea level we have reexamined this problem by obtaining high precision 230th 238u and 231pa 235u thermal ionization mass spectrometric ages for recently collected and carefully cleaned acp corals many in situ we recognize samples that show no evidence for diagenesis on the basis of uranium isotopic composition and age concordance combining new and earlier data among those ages close to or within the age range of mis 5 over 85 cluster between 65 and 85 ka bp of the corals that we have analyzed those that show the least evidence for diagenesis on the basis of uranium isotopic composition and age concordance have ages between 80 and 85 ka bp consistent with a mis 5a correlation the units from which these samples have been collected are all emergent and have elevations within 3 5 m of those few units where early stage 5 125 000 ka bp coral ages have been obtained the acp appears to record an unusual history of relative sea level throughout mis 5 a history that is also apparent in the dated coral record for bermuda we speculate that this history is related to the regional near to intermediate field effects of ancestral laurentide ice sheets on last interglacial shorelines of the western north atlantic

current perspectives on the capabilities of high resolution xrf core scanners abstract the introduction and application of high resolution xrf core scanners has made an enormous contribution to palaeoclimate science over the last two decades these core scanners have become essential analytical tools for the investigation of sedimentary and other natural cumulative records of environmental change their widespread adoption by the environmental and geoscience communities has had a significant impact on the ability to systematically record high resolution chemical profiles in marine and lake sediments and soils the range of applications has broadened beyond sedimentology and palaeoclimatology and now extends into scanning samples of speleothems corals mumiyo mounds rocks sedimentary nodules archaeological artefacts tree sections and melt segregations other areas exploiting the capability of xrf core scanners are mineral exploration geotechnical characterisation soil remediation studies and carbon capture and storage research as a consequence of their ability to efficiently determine detailed non destructive elemental records in sediments and soils scientific papers published since the year 2000 now number more than 1000

interpreting quaternary uplift rates at the mendocino triple junction northern california from uplifted marine terraces analysis of the altitudinal spacing of 14 flights of marine terraces indicates a spatial pattern of varying uplift rates that agrees with that determined from previously dated terraces for the past 3 81 ka and temporal changes in uplift rates from 1 m ka to 3 5 m ka that may reflect response to changes in tectonic regime during passage of the mendocino triple junction mtj a possible mechanism for regional uplift is growth of a slab window south of the mtj the region of most rapid uplift is 25 43 km south of the mtj immediately south of the northern boundary of the slab window the coastline is tilted upward to the south in the region directly above the southern edge of the subducted gorda plate at point delgada 55 km south of the present mtj where the northern edge of the slab window passes approximately 300 ka uplift rates have been 1 2 m ka for at least 330 ka more than 1 4 m y after passage of the southern edge of the subducted slab at the mendocino coast uplift rates have been less than 0 4 m ka for at least 330 ka

ice volume and sea level during the last interglacial during the last interglacial period 125 000 years ago sea level was at least several meters higher than at present with substantial variability observed for peak sea level at geographically diverse sites speculation that the west antarctic ice sheet collapsed during the last interglacial period has drawn particular interest to understanding climate and ice sheet dynamics during this time interval we provide an internally consistent database of coral u th ages to assess last interglacial sea level observations in the context of isostatic modeling and stratigraphic evidence these data indicate that global eustatic sea level peaked 5 5 to 9 meters above present sea level requiring smaller ice sheets in both greenland and antarctica relative to today and indicating strong sea level sensitivity to small changes in radiative forcing

cortex a shipboard xrf scanner for element analyses in split sediment cores abstract the cortex corescanner texel is a non destructive xrf system for the logging of split sediment cores it is a seaworthy instrument that remains active during heavy weather conditions the scanner produces reliable counts for k to sr highly correlated with concentrations measured with atomic absorption spectrometry aas the option to scan al si and elements heavier than sr is in preparation a core section of 1 m can be scanned at 2 cm intervals within an hour a maximum resolution of 1 mm can be achieved at present each region and sedimentary environment requires separate calibration in the nearby future the generator settings will be standardized which may result in the development of a standard calibration procedure because of the high resolution of its semi quantitative records the cortex is a useful tool for detailed time series analysis inter core correlation and shipboard analysis

contrasting styles and rates of tectonic uplift of coral reef terraces in the ryukyu and daito islands southwestern japan abstract coral reef terraces on kikai hateruma and yonaguni in the ryukyu islands on the eurasian lithospheric plate and those of kita daito and minami daito islands on the philippine sea plate indicate three distinct patterns of coral reef terrace formation and preservation primarily reflecting different uplift rates the kikai type which includes many terraces from oxygen isotope stages 5e to 1 is a result of high uplift rate of ca 1 8 m kyr on the fore arc rise of a chilean type subduction zone arcward westward tilting and faulting are also characteristic of the kikai type the hateruma type is characterized by two coral reef terraces younger than the stage 5e terrace and they are arranged in a concentric annular pattern slow uplift rate of ca 0 3 m kyr adjacent to a mariana type subduction margin is typical of the hateruma type the emergence of kikai and hateruma islands is recent younger than isotope stage 5e and 7 respectively reflecting the active deformations of the leading edge at the overriding eurasian plate in the daito type atolls surrounded by fringing reefs have been uplifted very slowly less than 0 05 m kyr but over a time period of at least several million years slow uplift and long history of daito type islands is the result of up bulging of the philippine sea plate as it migrates toward the ryukyu trench

varved sediment responses to early holocene climate and environmental changes in lake meerfelder maar germany obtained from multivariate analyses of micro x ray fluorescence core scanning data

tectonic uplift of a middle wisconsin marine platform near the mendocino triple junction california an uplifted wave cut marine platform eroded across bedrock of the franciscan complex at point delgada northern california is overlain by 0 5 to 5 m of wave worked pea gravel which is in turn directly overlain by fluvial gravel and silt deposited as alluvial fans woody plant debris at the base of the fluvial deposits includes cones of brewer spruce picea breweriana which today are found only at higher elevations and latitudes fossil wood debris from this horizon yields a 14c date of 44 800 1 300 yr the 44 800 yr radiocarbon age for the base of the fluvial deposits establishes an approximate age for the immediately underlying marine gravels and wave cut platform we tentatively correlate this terrace with the middle wisconsin high sea level stand at 37 m dated at about 45 000 yr b p if this age is correct the tectonic uplift since middle wisconsin time has been 44 m and the average rate of uplift has been at least 1 0 m 1 000 yr this relatively high rate is probably related to interaction among the pacific gorda and north american plates at the mendocino triple junction

fault related fold growth and isostatic subsidence california channel islands in the northern channel islands of california preservation of paleo shoreline features both as uplifted landforms onshore and subsided depositional features offshore has allowed precise measurement of late quaternary fold growth relative to sea level and has helped to disentangle the relative contributions of tectonic forcing and isostatic response we precisely measured several hundred points on uplifted pleistocene coastal terraces of santa cruz and anacapa islands the elevations of which document anticlinal growth of the islands since at least 400 ka we also interpreted a dense grid of seismic reflection profiles that image a complex of eustatic lowstand deltas that record regional subsidence surrounding the uplifting structure we combined onshore uplift with offshore subsidence measurements to produce a quantitative mass balance of structural growth since 400 ka the data outlined above were then used to test the hypothesis that subsidence around the northern channel islands represents the flexural isostatic response to tectonic loading of the islands calculations of cumulative uplifted mass and cumulative subsided mass across the structure closely match the values predicted for density driven isostatic compensation and local flexural support although the wavelength of flexure predicted for the study area suggests that an additional component of flexural support may extend distally 10s of kilometers into the surrounding offshore basins in the northern channel islands isostatic subsidence is explicitly manifested because erosional mass removal is small because the crust here is relatively thin and weak and most importantly because sea level provides an absolute datum against which to measure vertical deformation an explicit treatment of the interplay between crustal thickening erosional denudation surface uplift and isostatic response helps to illustrate the conditions under which isostatic subsidence may or may not be a significant process where surface denudation rates approach the rate of rock uplift for example isostatic subsidence will approach zero in contrast failure to recognize isostatic subsidence in earthquake hazard studies can lead to order of magnitude errors in slip rate and hazard estimates

geochemical methods to infer landscape response to quaternary climate change and land use in depositional archives a review abstract understanding and quantifying the processes and geochemical cycles associated with catchment erosion the development of soils and weathering horizons and terrestrial habitat change beyond the scales of modern observations remain challenging such research however has become increasingly important to help predict future landscape change in light of increasing land use and rapid global warming we herein review organic and inorganic geochemical tools applied to depositional archives to better understand various aspects of landscape evolution on geological time scales we highlight the potentials and limitations of inorganic geochemical analytical methods such as major element geochemistry metal and radiogenic isotopes and in situ cosmogenic nuclides as qualitative semi quantitative and quantitative proxies for the transformation of bedrock material via regolith and soils to sediments we also show how stable isotope geochemistry applied to lacustrine endogenic carbonates can be used to infer rock water interactions vegetation change and soil development in limestone rich catchments proxies focusing on the silicilastic element of sediment formation transport and deposition are ideally combined with organic geochemical proxies for vegetation change and soil organic matter evolution in a catchment to gain a comprehensive picture of the critical zone s evolution over time multi proxy and multidisciplinary research combining organic and inorganic geochemical techniques from several sedimentary archives in the same catchment have high potential to provide comprehensive information on quaternary landscape evolution and thus improve the robustness of associated forecasting models

a geochemical application of the itrax scanner to a sediment core containing eastern mediterranean sapropel units the itrax micro x ray fluoresence xrf core scanner has been applied in a sediment geochemistry investigation the core sections selected contain examples of the organic rich sedimentary units sapropels that form periodically in the eastern mediterranean basin sapropels are visually obvious from their dark coloration but the itrax x radiograph also reveals physical property changes that result mainly from the high pore water content of sapropels a consideration of wavelength dispersive xrf data from discrete samples of the most recent sapropel s1 was made along with the set of elements reported by the itrax instrument s energy dispersive xrf system over core sections containing s1 this allowed selection of a suite of eight inter element ratios or element integrals through which characteristic features of sapropel development and geochemistry were revealed while recognizing that the measured xrf element integrals from the itrax do not have an exact constant relationship with element concentration over changing sediment types this combination of ratios provides significant information for geochemical interpretation these include evidence for i the presence of high corg contents in the visual sapropel from ba ti and br cl ratios ii a thinning of the original sapropel thickness by post depositional oxidation from mn ti and cu ti ratios iii pyrite authigenesis in the residual visual sapropel from fe ti and s cl ratios and the as integral and iv aragonite formation in and around the sapropel from the sr ca ratio these same ratios were then used to interpret itrax data from a deeper section of the same core containing the older sapropel s3 where the same characteristics including the relict post depositional oxidative thinning of the original unit could be identified with only minor differences of detail directions of supply of fe as and cu into the sapropels could be inferred from profile shapes

200 year industrial archaeological record preserved in an isle of man saltmarsh sediment sequence geochemical and radiochronological evidence abstract the isle of man situated in the central irish sea was a significant centre for pb and zn mineral extraction during the industrial revolution comminuted mining debris from the east snaefell and north laxey mining areas was transported through hydrological action from upland catchments to the coast this study focuses on an eastern coastal sediment sink and a salt marsh sediment sequence from port cornaa a sediment monolith was excavated sub sampled and geochemically investigated using itrax scanning wd xrf analysis and radionuclide methods since the island is only 55 km from one of the world s major nuclear reprocessing sites sellafield it was anticipated that a record of these radionuclide discharges 1951 present would be identifiable and contribute clear chronological markers the 137cs profile shows a sellafield discharge component and also a larger component that is attributed to the 1986 chernobyl airborne plume this contribution in the salt marsh sediment would be derived from the erosion and transport of chernobyl labelled upland soils into the marsh sediment depth was converted to age using natural 210pb and anthropogenic radionuclides 137cs and 239 240pu and a compelling age vs depth relationship was obtained the ability to reliably date the overall sediment section shows that sediment accumulation is uniform for the top 25 cm 5 mm y and from 25 to 70 cm 3 2 mm y the robust age depth model allows features in the geochemical profiles for s as pb zn and cu to be dated and used to infer events at the east snaefell and north laxey mines these include start up of mining introduction of more efficient mining practises i e water wheel technology change in the intensity of mining and final mine closure the study provides a 200 year industrial archaeological record for the east coast of the isle of man it demonstrates the benefits offered by a combined study involving non destructive high resolution itrax scanning conventional wdxrf and radionuclide dating

comparison of esr and tims u th dating of marine isotope stage mis 5e 5c and 5a coral from barbados implications for palaeo sea level changes in the caribbean abstract electron spin resonance esr dating of coral has become an efficient geochronological tool in supporting morphostratigraphic studies carried out on barbados during the last 10 years the newly developed approach for de determination de dmax plot procedure improves the precision of esr dating of pleistocene coral and therefore permits differentiation between the main marine isotope stages mis 5 7 9 and 11 and also between sub stages 5e c and a this study compares results of esr and tims uranium series dating u th of emergent last interglacial coral reef terraces from barbados and presents some implications for the timing and extent of sea level changes during marine isotope stages mis 5e c and a both dating methods indicate a distinct formation of up to three coral reef terraces during mis 5e at approximately 132 ka esr to 128 ka u th at c 128 ka esr and at c 120 ka u th to 118 ka esr it is also highly probable that three reef terraces were developed during mis 5c between c 103 ka u th and 105 ka esr the formation of two separate coral reefs during mis 5a is recognized for the first time on barbados with an age estimate for the older mis 5a 2 reef of 85 ka esr or 84 ka u th and an age estimate for the younger mis 5a 1 reef terraces of 74 ka esr or 77 ka u th assuming a constant uplift rate of 0 276 m ka at the south coast of barbados sea level reached its maximum during mis 5e 3 and mis 5e 2 between 132 and 128 ka ago after this sea level declined reaching a level of c 11 m below present sea level approx 118 120 ka ago mis 5e 1 during the substage 5c sea level was generally lower than in substage 5e it reached relative maxima at c 13 20 and 25 m during mis 5c approx 105 ka and formed three distinct coral reef terraces probably in relative short time intervals for the first time a double sea level oscillation is recognized on barbados during mis 5a an early mis 5a 2 c 85 ka with a sea level places at approx 21 m and a late mis 5a 1 sub stage c 74 or 77 ka with a sea level at approx 19 m below present sea level