active and break phases in the south american monsoon system the south american monsoon system sams refers to the austral summer season features of deep convective activity and large scale circulation this study examines intraseasonal variations in the low level wind circulation in the amazon and their modulating effects on active and break phases in sams daily averages of outgoing longwave radiation olr ncep ncar reanalysis and gridded rainfall station data in brazil are used from 1 november to 28 february 1980 99 the direction of wind anomalies 10 70 days in the rondonia state brazil is used to classify periods of westerly w and easterly e low level wind regimes composites of w regime show low level wind anomalies crossing the equator southward and closing in a cyclonic anomalous circulation off the coast of argentina and uruguay broad areas of enhanced convection and rainfall are observed in central and southeast brazil suppressed convection is observed over the bolivian altiplano and in northern south america in contrast in the e regime opposite patterns are observed in the low level circulation con vection and rainfall anomalies the duration of active w regimes and break e regimes periods are quite similar with median values of 4 and 5 days respectively further investigation showed that the region of convection and rainfall anomalies over venezuela and northwest brazil is observed only in the 10 30 day band comparison of the results shown here with previous studies indicates the importance of intraseasonal variations in the activity of sams

late highstand patterns of shifting and stepping coastal barriers and washover fans late messinian sorbas basin se spain abstract the late messinian sorbas member up to 75 m thick consists in its type area of a parasequence set of three prograding coastal barriers sequences i iii associated with lagoon and washover sediments around the town of sorbas these strata can be studied exceptionally well due to absence of burrowing by raised messinian salinities and exposure along a network of up to 30 m deep canyons fifteen vertical sections were logged and carefully correlated this permits to reconstruct and discuss patterns of relative sea level movements between decimetres up to 15 m within a parasequence excellent examples of non tidal transgressive facies are characterized by lagoon and washover sediments instead of the usual combination of washover and tidal deposits channel and flood tidal delta implications for the sandstone connectivity are given the lower two sequences are deposited in a relatively large tectonically enhanced wedge shaped accommodation space they show both fining up deepening sequences followed by prograding coarsening up shoaling sequences and can be compared to the classical parasequences of the western interior basin usa progradation of sequence ii was interrupted by a major slide event most likely triggered by an earthquake which caused more than 400 m seaward slumping of a stretch of 1 km of coastal sands the architecture of sequence iii is more complex due to limited accommodation space characteristic for the late highstand so that this setting was very sensitive to sea level fluctuations this resulted in an intricate pattern of juxtaposed and superposed lagoonal muds washover fans and swash zones so called stranded coastal barriers occur which were left behind after seaward jump of the coastline over more than 1 5 km during forced regression the pattern of reconstructed sea level positions is well comparable to the sequential pattern shown by the correlated equivalents along the northern basin margin which belong to the so called terminal carbonate complex the problem of ranking the complex sequence iii as one or more parasequences and its consequences for cyclostratigraphy are shortly discussed two models of washover formation are given respectively during more rapid and more slow sea level rise the influence of synsedimentary folding on the location of barriers is discussed and also the source area of extra and intraclasts supplied to barriers and washovers after deposition of the sorbas member the sea withdrew from the sorbas basin probably as a result of the major downdrop in the mediterranean at the maximum isolation during the salinity crisis it is suggested that the semi enclosed setting of the basin resulted only in limited localized erosion in contrast to the deeper adjacent vera basin which was more open to the mediterranean

eustatic implications of late miocene depositional sequences in the melilla basin northeastern morocco abstract the age 5 78 ma or lower chron c3r of the major drawdown of the paleo mediterranean sea during the messinian salinity crisis has been established by combining results from stratigraphy paleontology magnetostratigraphy and argon dating for a late miocene sedimentary succession in the melilla basin ne morocco this event is inferred from a marine to continental series of carbonate and siliciclastic rocks that record the end of messinian marine deposition in the melilla basin and presumably marks the final isolation of the paleo mediterranean sea the evidence from the melilla basin is approximately coeval with an increase in benthic foraminiferal 18 o values from a deep marine section in the bou regreg valley nw morocco hodell et al 1994 this increase suggests that a glacio eustatic lowering of sea level at least contributed to the final closure of the mediterranean during the messinian salinity crisis the marine to continental succession onlaps a carbonate complex that contains evidence for multiple relative sea level changes leading up to the main drawdown from bottom to top the carbonate complex is composed of 1 an onlapping ramp 2 a prograding bioclastic platform 3 a prograding and locally downstepping porites reef complex and 4 a topography draping sequence composed of grainstones porites reefs and stromatolites terminal carbonate complex of esteban 1979 the transgressive ramp correlates to relatively low values of benthic foraminiferal 18 o values from a tortonian to lower messinian section at bou regreg hodell et al 1994 this correlation indicates at least in part a link between rising sea level and a reduction in global ice volume during deposition of the ramp a major fall in relative sea level 60 m occurred near the demise of the reef complex during chron c3n 1n at 5 95 0 10 ma this signals the initiation of drawdown and changing environmental conditions in the melilla basin a marginal basin and perhaps the entire paleo mediterranean sea a megabreccia interpreted as forming by solution collapse of evaporites on the basin margin of the reef complex occurs at the base of the terminal carbonate complex updip a major subaerial unconformity separates the reef complex and terminal carbonate complex evaporite deposition likely occurred during this exposure event and has been dated at 5 82 0 02 ma near the base of chron c3r we contend that these evaporites restricted to the shallow melilla basin are related to the continuation of the initial stage of the major drawdown of the paleo mediterranean sea

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

the 2012 august 11 mw 6 5 6 4 ahar varzghan earthquakes nw iran aftershock sequence analysis and evidence for activity migration

pinning points a method providing quantitative constraints on relative sea level history abstract quantitative constraints on the history of relative sea level allow for a better understanding of the controls on depositional sequence development the constraints are provided by pinning point curves plots of ancient relative sea level elevations pinning points versus time constructing a pinning point curve requires identification of ancient stratigraphic positions of sea level through interpretation of facies and surfaces formed at sea level then their ancient relative elevations are determined through reconstructing aspects of ancient paleotopography upper miocene strata from las negras southeastern spain preserve paleotopography contain ancient surfaces of subaerial exposure and contain facies deposited near sea level the pinning point curve illustrates a complex relative sea level history with large and small scale relative sea level fluctuations defined by 31 pinning points

nearshore temperate carbonate depositional systems lower tortonian agua amarga basin southern spain implications for carbonate sequence stratigraphy abstract the bryozoan rich lower tortonian carbonates of the agua amarga basin in southern spain province of almeria provide an example of sediments formed in a nearshore non tropical depositional setting based on data derived from logging of sections and from field mapping these lower tortonian carbonates form a depositional sequence which is subdivided into several depositional systems a lowstand systems tract which consists of volcaniclastic fan deltas and washover deposits formed on the leeward side of a basement shoal which delimited the basin towards the south a transgressive systems tract which is characterised by a landward encroachment of deposits is represented by submarine bars and dune deposits a highstand systems tract consists of progradational beach deposits owing to strong reworking and re distribution of the particles by currents and waves microfacies differentiation of the deposits in poor these tortonian non tropical carbonates display a style of deposition similar to siliciclastics suggesting that sequence stratigraphic concepts derived from tropical carbonates do not apply to non tropical carbonates

seismic characterization of switching platform geometries and dominant carbonate producers miocene las negras spain the primary goals of seismic interpretation and quantification are to understand and define reservoir architecture and the distribution of petrophysical properties since seismic interpretation is associated with major uncertainties outcrop analogues are used to support and improve the resulting conceptual models in this study the miocene carbonates of cerro de la molata las negras south east spain have been selected as an outcrop analogue the heterogeneous carbonate rocks of the cerro de la molata platform formed by a variety of carbonate producing factories resulting in various platform morphologies and a wide range of physical properties based on textural thin sections and petrophysical porosity density carbonate content and acoustic properties analyses of the sediment s eleven individual facies types were determined the data were used to produce synthetic seismic profiles of the outcrop the profiles demonstrate that the spatial distribution of the facies and the linked petrophysical properties are of key importance in the appearance of the synthetic seismic sections they reveal that carbonate factory and facies specific reflection patterns are determined by porosity contrasts diagenetic modifications and the input of non carbonate sediment the reflectors of the seismograms created with high frequency wavelets are coherent with the spatial distribution of the predefined facies within the depositional sequences the synthetic seismograms resulting from convolution with lower frequency wavelets do not show these details the major reflectors coincide with i the boundary between the volcanic basement and the overlying carbonates ii the platform geometries related to changes in carbonate factories thus sequence boundaries and iii diagenetic zones changes in seismic response related to diagenesis switching carbonate producers and linked platform geometries are an important finding that needs to be considered when interpreting seismic datasets this article is protected by copyright all rights reserved

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

climatic signatures in shallow water carbonates high resolution stratigraphic markers in structurally controlled carbonate buildups late miocene southern spain abstract neogene intramontane basins of the betic cordillera se spain have a complex tectonic and sedimentary history in the eastern almeria province movements along the carboneras strike slip fault system n50 e and its conjugated faults n140 e controlled the distributions of depocenters and stratigraphic architectures of late miocene sediments we have chosen the agua amarga area 1 to exemplify the potential of climatic signatures of biogenic associations in shallow water carbonates for high resolution chronostratigraphic correlations and 2 to describe stratigraphic architectures and facies distributions in a setting subject to synsedimentary tectonics the southwestern margin la higuera is formed by a gentle ramp dipping in a n50 e direction late tortonian and messinian deep and shallow water carbonates divide into eight depositional units neptunian autoclastic breccias neptunian dikes and submarine biogenic pavements unit h 1 document rapid flooding of the basin during a phase of intense tectonic dilatation late tortonian units h 2 7 late tortonian early messinian form wedges which dip and thicken in a basinward direction little lateral facies change and internal stratifications parallel with the basal surfaces imply deposition on a subhorizontal substratum the upper bounding surfaces are erosional and formed by truncation of tilted strata from wedge to wedge the angle of dip decreases upsection and is near zero in between the last units which have parallel bounding surfaces and rest subhorizontally unit h 7 8 this pattern results from cumulative rotational uplift which decreased upward but does not necessarily exclude vertical displacements of the youngest units the southeastern margin of the basin is mostly eroded but may have trended n50 e as indicated by the distribution of slumped reef blocks a relict of the margin is preserved at mesa de roldan and exhibits steep clinoforms dipping towards the nw n300 e and w n250 e synsedimentary tectonics are documented by nine shallow marine depositional units unit r 1 conglomerates associated with neptunian dikes units r 2 9 skeletal carbonates and reefs bounded by deep erosion surfaces and or truncation of individual units along a miocene fault at both flanks the shallow water biofacies record an identical trend of climatic warming and therefore bracket a similar amount of time temperate conditions prevailed during the latest tortonian and earliest messinian whereas tropical temperatures existed during the early and late messinian and perhaps during the tortonian messinian transition the number of depositional units reflecting these climatic periods of time and the stratal geometries however differ at both sites and within the basin which implies spatial variations in the generation of accomodation space on independent fault blocks these data also suggest that there cannot be any universal sequence stratigraphic model for late miocene shallow water carbonates of se spain and that the downstepping geometries observed in many other early messinian reefs of the betic cordillera reflect tectonic uplift

reef geometries erosion surfaces and high frequency sea level changes upper miocene reef complex mallorca spain the upper miocene reef complex of mallorca is a 20 km prograding unit which crops out in sea cliffs along the southern side of the island these vertical and exceptionally clean outcrops permit i identification of different facies lagoon reef front reef slope and open platform and their geometries and boundaries at different scales ranging from metre to kilometre and ii construction of a 6 km long high resolution cross section in the direction of reef progradation this cross section shows vertical shifts of the reefal facies and erosion surfaces linked to a general progradational pattern that defines the accretional units four hierarchical orders of magnitude 1 m to 4 m of accretional units are identified by consideration of the vertical facies shifts and by which erosion surfaces are truncated by other erosion surfaces all these orders show similar patterns horizontal beds of lagoonal facies in the upper part landward reefal and slope facies with sigmoidal bedding in the central part and open platform facies with subhorizontal bedding in the lower part basinwards the boundaries are erosion surfaces horizontal over the lagoon facies dipping basinwards over the reef front facies and connecting basinwards with their correlative conformities over the reef slope and open platform facies the four orders of accretional units are interpreted in terms of four 1 m to 4 m hierarchies of sea level cycles because i there is a close relation between the coral growth and the sea surface ii there are vertical shifts in the reefal facies and their relation to the erosion surfaces and iii there was very little tectonic subsidence in the study area during the late miocene additionally all these units can be described in terms of their position relative to the sea level cycle i the reefs prograde on the open platform sediments during low stands of sea level ii aggradation of the lagoon reef and open platform facies dominates during sea level rises and the lagoonal beds onlap landwards upon the previous erosion surface iii reefal progradation occurs during high stands of sea level and iv the 2 m sea level fall produces an off lapping reef and there is progradation with downward shifts of the reefal facies and erosion landward on the emerged older reefal units a erosion surfaces the 3 m and 4 m sea level falls produce only erosion b and c erosion surfaces although precise age data do not exist at present some speculations upon the frequency of these miocene relative sea level cycles can be made by comparisons with pleistocene cyclicity there is a good correlation between the miocene 2 m cycles and the 100 ka pleistocene cycles consequently the 1 m cycles can be assigned to a fourth order in relation to previously proposed global cycles and the 2 m to fifth order cycles all these accretional units could be defined as sequences according to the definition as commonly used in sequence stratigraphy however they represent higher than third order sea level cycles but are not parasequences the term subsequence therefore is suggested to define a part of a sequence bounded by erosion surfaces mostly subaerial and their correlative conformities basinwards a hierarchy of subsequences can be established

depositional sequences and correlation of middle to late miocene carbonate complexes las negras and nijar areas southeastern spain during serravallian through messinian time marine carbonates flanked topographic highs that rimmed neogene basins in the western mediterranean middle to upper miocene carbonate strata in the las negras and nijar areas southeastern spain are 50 150 m thick and display 50 200 m of shelf to basin relief over 1 2 km detailed studies in those areas document the effects of relative sea level change on sedimentation biotic composition and reef development we identify three previously unrecognized regionally correlatable depositional sequences ds1 ds2 ds3 that occur between the underlying basement and the overlying terminal carbonate complex the lower depositional sequences ds1 ds2 are mostly normal marine shelf ramp carbonates deposited on the flanks of basement highs the basal part of ds2 locally contains some megabreccia reef blocks composed of tarbellastraea and porites these blocks are the first evidence of reef growth in the area and represent a previously unrecognized period of reef development prior to the fringing reef development the reef blocks probably formed as upslope patch reefs that were eroded and transported to distal slope locations the upper sequence ds3 is characterized by clinoform strata of a porites dominated fringing reef complex that prograded basinward in a downstepping style with successively younger reefs forming in a topographically lower and more basinward position as a result of a net sea level drop regional correlation of miocene shallow marine strata between basins in spain and elsewhere in the western mediterranean is complicated because basins were semi isolated from adjacent basins making physical correlation impossible in addition age definitive biostratigraphic markers are poorly preserved in most of the miocene shallow water strata basinal sediments that are more easily dated by microfossils do not typically interfinger with the shallow marine strata in outcrop even where datable microfossils are found resolution of dating is poor our studies in the las negras and nijar areas illustrate the usefulness of integrating sedimentological geometric and biotic data with locally derived relative sea level accommodation space curves for correlation the relative sea level curves for each area show remarkable similarities in shape and magnitude of sea level changes these curves indicate several relative sea level fluctuations during miocene carbonate deposition prior to the major sea level drop at the end of ds3 deposition that culminated in the exposure of the basin margin deposits and the deposition of evaporites in basinal areas during the messinian the depositional sequences in the las negras and nijar areas may correlate with depositional sequences of similar age throughout the southern cabo de gata area in mallorca some 600 km to the northeast and possibly in other mediterranean locations the widespread occurrence and possible correlation of the depositional sequences suggest regional processes such as eustacy or tectonism for their formation the integration of sedimentological palaeontological and sequence stratigraphic studies and the construction of relative sea level accommodation space curves may help in the interpretation of depositional histories of shallow marine carbonate complexes and correlation of these strata between isolated areas other dating methods in addition to microfossil dating may allow for better age determination of the sequences and aid in identifying the importance of eustacy and tectonism in sequence development

late neogene recent uplift of the cabo de gata volcanic province almeria se spain abstract cabo de gata is a miocene volcanic province in the betic cordillera in southeastern spain the distribution of coastal deposits in the successive marine sedimentary units overlying the last volcanic episode about 7 5 ma old has been used to reconstruct the post volcanic palaeogeographic evolution of the region during the late neogene the current elevation of well dated shoreline marker rocks has been used to estimate uplift amount and rates since the late tortonian a n45 e aligned the strike of the carboneras fault system topographic relief was emergent in the cabo de gata region the extension and height of this island increased throughout the late neogene smaller independent islands were emergent and finally became connected to the main island during the messinian the carboneras and agua amarga pliocene sub basins were the last two marine basins prior to the final emergence of the region since the last volcanic eruption ca 7 5 ma maximum uplift of sedimentary rocks in cabo de gata has taken place on the western margin of the n45 e aligned palaeorelief the altitude of the shoreline marker rocks in the successive sedimentary units decreases eastwards to the present day coast and northwards of the rambla del plomo uplift rates since deposition remain nearly constant for the successive messinian rocks and decrease slightly for the lower pliocene outcrops most of the uplift took place before the pliocene while the main island enlarged uplift amounts and rates since deposition of the upper neogene sedimentary units in the cabo de gata area are similar to the ones estimated for laterally equivalent units in the eastern betic basins approximately 50 m ma despite its volcanic nature and the occurrence of the carboneras fault system the cabo de gata probably became elevated as a consequence of regional uplift in connection with the rest of the betic cordillera

field and modelling studies of cambrian carbonate cycles virginia appalachians reply abstract field studies coupled with computer modelling of carbonate cycles in the elbrook conococheague formations middle to upper cambrian in the appalachians have helped define the mechanisms of formation the sequence is up to 1 6 km thick and composed of cyclic peritidal carbonates these formed on an aggraded rimmed shelf on a mature passive continental margin the cycles 1 7 m thick have lower parts of subtidal intertidal carbonate and caps of dolomitic laminite containing minor quartz arenite shale and breccia sedimentation rates for these peritidal carbonate environments exceeded long term subsidence of the platform 0 01 to 0 1 m 1 000 yr thus the shelf stayed near to sea level i e was aggraded milankovitch 20 000 to 100 000 yr low amplitude sea level fluctuations few meters superimposed on 3rd order sea level fluctuation of 1 to 3 m y duration and less than 20 m amplitude caused periodic submergence of the gently sloping platform less than 0 02 m km slopes resulting in deposition of over 400 peritidal cycles in about 26 m y cycles that formed during 3rd order sea level rise are thick and limestone rich whereas those formed during 3rd order fall are thin quartzose and highly dolomitized the modelling suggests that fewer and thinner cycles formed during the long term falls compared to the rises reflecting decreased accommodation cycle frequency decreases into areas of lower subsidence rate open marine cycles typical of the outer shelf and cycles formed during 3rd order sea level rise contain digitate bioherms grainstone and ribbon carbonates in lower parts they reflect high subsidence rate and an open marine setting inner shelf cycles and cycles that formed during 3rd order sea level fall commonly are thrombolitic or have thin subtidal parts grainstone conglomerate or stromatolite and reflec the low subsidence rates interior areas of quaternary carbonate shelves are characterized by incipiently drowned facies and pinnacle reefs and are punctuated by soil caliche horizons and karst surface that reflect 100 m glacio eustatic sea level fluctuations in contrast many ancient shelves like the cambro ordovician shelf of the appalachians were flat topped and dominated by cyclic peritidal sequences lacking evidence of high amplitude sea level fluctuations such aggraded shelves may represent the typical state of mature carbonate shelves that formed in response to low amplitude milankovitch sea level fluctuations as opposed to the large scale fluctuations that typified the quaternary

rocky shores and development of the pliocene pleistocene arroyo blanco basin on isla carmen in the gulf of california mexico arroyo blanco basin on isla carmen preserves a 157 m thick nearly complete record of pliocene pleistocene history in the gulf of california examples of rocky shore geomorphology occur on all margins of this trapezoidal shaped 3 3 km2 basin a shoreline is developed in low relief on miocene andesite from the comondu group at the rear of the basin parallel to the long axis of the island two end walls trace normal faults that stayed active during the life of the basin and maintained steep rocky shores the basin is 64 filled by calcarudite and calcarenite derived from crushed rhodolith debris other facies include shell beds and stringers of andesite conglomerate that define a 4 6 ramp the ramp expanded onshore through pliocene time based on a succession of overlapping range zones for 22 macrofossils typical of lower through upper pliocene strata in the gulf of california the unconformity exposed 1 km inland at the rear of the basin is between miocene volcanics and pleistocene cap rock at an elevat

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

diagenesis associated with subaerial exposure of miocene strata southeastern spain implications for sea level change and preservation of low temperature fluid inclusions in calcite cement abstract many ancient carbonate rocks contain calcite cements that precipitated from shallow fresh groundwater that entered strata during events of subaerial exposure such low temperature cementation may be difficult to interpret from fluid inclusion studies because some of the inclusions may reequilibrate during later thermal events miocene rocks of southeast spain provide an example of the utility of fluid inclusion studies in rocks that have not been subjected to significant heating in the mesa roldan area one type of calcite cement occurs exclusively below a regional stratigraphic surface of enigmatic origin the cement has petrographic characteristics indicative of cementation in the vadose zone generally thought to be a zone of oxidation but has cathodoluminescent bands containing reduced manganese and iron primary fluid inclusions contain mostly fresh water have variable ratios of vapor to liquid and are at one atmosphere of pressure our observations indicate that calcite precipitated from a freshwater vadose zone which was subjected to local or repetitive saturation and minor brackish water the fluid inclusion data indicate that low temperature fluid inclusions can be preserved in ancient sequences despite a later history of different pore fluids this indication of subaerial diagenesis of distal slope deposits suggests a relative sea level drop of at least 50 55 m during the late miocene similar petrographic and fluid inclusion observations can be used to interpret sea level changes in other areas

seismic stratigraphic evidence for a submerged middle wisconsin barrier implications for sea level history high resolution seismic reflection data from the inner shelf and coastal zones of central new jersey document the presence of two depositional sequences seismic facies analysis of the lower sequence indicates the presence of a submerged barrier island complex 20 m below present sea level and 0 2 to 1 7 km seaward of the modern coastline vibracore data from within the study area and correlation to an extensive seismic data set that extends farther offshore identify this submerged barrier as the maximum highstand shoreface associated with the middle wisconsin oxygen isotope stage 3 interstade the results indicate that sea level was well below its present day level during the middle wisconsin and not at or above the present level as has been frequently proposed

use of fischer plots to define third order sea level curves in ordovician peritidal cyclic carbonates appalachians fischer plots in which cumulative cycle thickness corrected for linear subsidence is plotted against time were originally used in the study of triassic peritidal sequences to define short duration departures in relative sea level in the milankovitch range 104 to 105 yr however they also provide a means of assessing magnitude of third order 1 to 10 m y fluctuations in sea level which on the basis of their regional correlatability we ascribe to eustatic events

integrating outcrop data and forward computer modelling to unravel the development of a messinian carbonate platform in se spain sorbas basin geological mapping definition of facies distributions and reconstruction of platform interior growth geometries of the messinian cariatiz carbonate platform sorbas basin south spain were performed to evaluate the controlling factors in platform growth and to test a 3 d computer simulation program for the simulation with the program repro five platform related facies were modelled 1 the reef crest facies by the numerical solution of a fisher equation 2 the lagoonal facies by a function of water depth dependent carbonate production 3 the proximal and middle slope facies breccia and block facies calcarenite facies by a subroutine simulating gravity driven particle export from the reef crest 4 a distal slope and 5 a basinal facies by a pelagic rain function development of a fan delta conglomeratic system is simulated by using a siliciclastic point source and gravity driven particle redistribution a best fit between the observed platform growth geometries and modelling results is achieved by assuming that high frequency sea level changes superimposed onto a longer term sea level fall controlled platform growth for the modelling a relative sea level curve was reconstructed which is based on a deep sea benthic foraminiferal stable oxygen isotope record at odp site 926 with a 45 m eustatic sea level fall and a tectonic uplift component of 20 m the consistency of 3 d simulation results is corroborated by the coral growth rates provided by the fisher equation subroutine these rates of 28 mm year1 compare well to the coral growth rates in recent fringing reefs we propose that during the early stage of platform evolution the high frequency fluctuations were obliquity modulated precessional cycles whereas precessional cycles control later stages of platform growth repro provides a separate visualization of the different facies bodies as a function of time and space showing the intrinsic pattern of facies distribution in the platform this is the result of a combination of platform growth and syndepositional subaerial erosion for example only the youngest stages of reef framework facies in the development of the cariatiz carbonate platform are preserved

magmatic evolution of the alboran region the role of subduction in forming the western mediterranean and causing the messinian salinity crisis the magmatic evolution of the alboran region westernmost mediterranean contains important clues for improving our understanding of the origin of mediterranean style back arc basins and the desiccation of the mediterranean sea in the messinian we use new laser 40ar 39ar age and geochemical major and trace element and o sr nd pb isotope data from igneous rocks from southern spain the alboran sea and northern morocco to reconstruct the magmatic evolution of the westernmost mediterranean since the eocene lower oligocene dikes near malaga 33 6 0 6 ma and middle to upper miocene volcanic rocks from the alboran sea area 6 57 0 04 to 11 8 0 4 ma can be subdivided into two groups 1 lree depleted relative to n morb primarily tholeiitic series and 2 lree enriched primarily calc alkaline series volcanic rocks both groups are generally enriched in fluid mobile elements e g rb th u k and pb relative to fluid immobile elements e g nb ta lree the lree depleted group has 143nd 144nd 0 5128 0 5130 isotope ratios similar to atlantic morb but higher 87sr 86sr 0 7046 0 7100 in contrast the lree enriched group has less radiogenic nd 0 5121 0 5126 and tend to more radiogenic sr 0 7066 0 7205 isotopic composition pb isotope ratios are surprisingly uniform and have compositions similar to marine sediments analyses of mineral separates show that mafic melts with relatively low 18o 5 6 7 2 had high 87sr 86sr 0 7048 0 7088 7 4 10 6 14 1 and 8 4 40 0 49 3 modeling of the trace elements and sr nd pb o isotopic compositions provides compelling evidence for the contamination of the mantle source with hydrous fluids melts which can be explained through subduction of oceanic lithosphere beneath the alboran basin but not through detachment delamination of lithospheric mantle we present a geodynamic model that reconstructs the late eocene to quaternary evolution of the western mediterranean through westward roll back of subducted tethys oceanic lithosphere slab roll back resulted in a large scale reorganization of the western mediterranean paleogeography causing the closure of marine gateways linking the atlantic ocean to the mediterranean sea isolation of the mediterranean sea led to its desiccation causing the messinian salinity crisis

on the labeling length and objective basis of fischer plots abstract fischer plots of the accumulation of shallow marine carbonate cycles track the cumulative departure from mean cycle thickness through a vertical sequence of contiguous upward shallowing units this is a simple objective treatment of residuals in a time series and is applicable to other stratigraphic phenomena to reflect the noninterpretive construction of fischer plots the vertical axis should be labeled cumulative departure from mean cycle thickness and the horizontal axis cycle number the typical fischer plot is an erratic bridge that begins and ends at the same elevation but has the form of an irregular train of asymmetric waves which rise steeply and fall gradually the asymmetry of the individual waves arises because thinner than average cycles typically outnumber thick r cycles two to one the overall form of the wave train is sensitive to mean cycle thickness but can guide correlation and may have considerable interpretive potential provided that enough cycles are included to ensure a robust estimate of mean thickness runs tests demonstrate that fischer bridges for peritidal carbonates are unlikely to be the result of random stacking processes since this anticipated result does not emerge unequivocally for fischer plots of less than 50 cycles however we recommend against plotting such short sections

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

deposition and compaction of carbonate clinothems the silurian pipe creek junior complex of east central indiana many of the larger silurian mounds throughout the midwestern united states consist predominantly of thinly bedded carbonate units inclined at angles as great as 45 because these values exceed those for reasonable estimates of angles of repose two opposing end member models for their origin have been suggested the ramifications of which affect evaluation of carbonate sources and modes of deposition one implies that steeply sloping units exhibit primary inclinations are composed largely of autochthonous carbonate debris held in place by benthic organisms and or synsedimentary cement and that deposition took place in relatively deep low energy marine settings the other holds that present steep slopes are the result of differential compaction that most carbonate is allochthonous and that deposition took place in relatively shallow high energy marine environments the pipe creek junior quarry in east central indiana exposes as much as 45 m of such clinothems paleomagnetic signatures inclinations of geopetal cavity fillings and the density and geometry of vertical extension fractures which transect inclined units record 13 of postdepositional steepening restoration of inclined units to their initial slopes requires initial depositional inclinations of no more than 32 postdepositional compaction at pipe creek junior was increasingly important in finer grained downslope lithofacies grainstone units shortened 3 grainstone mudstone units shortened 30 and mudstone units shortened 58 compaction mechanisms however varied in different lithofacies dewatering resulted in 50 compaction of mudstone and 13 compaction of grainstone mudstone units pressure solution although less important than dewatering was most intense in grainstone mudstone lithofacies where shortening was at least 17 dissolution thinned mudstone and grainstone units 8 and 3 respectively data on unit rotation and unit shortening require that axes of flank bed rotation correspond approximately to the position of the present quarry rim suggesting that only minor amounts of silurian section have been removed during devonian and pleistocene erosion these relations in conjunction with data on over all complex geometry and flank bed lithologic features indicate that the pipe creek junior complex is not truly reefal in that it consists almost entirely of allochthonous biotic debris derived from horizontal wave swept bench surfaces and deposited on laterally prograding bench margin slopes at angles of repose other large midwestern silurian carbonate buildups may have formed in similar settings

repeated subaerial exposure of subtidal carbonate platforms triassic northern italy evidence for high frequency sea level oscillations on a 104 year scale triassic carbonate platforms in northern italy ladinian latemar carnian durrenstein norian dolomia principale consist of hundreds of stacked meter scale cycles each made of a subtidal unit with a cap rock that carries vadose cements pisoids and tepee structures these diagenetic caps are interpreted to be due to subaerial exposure of the subtidal sediments the absence of peritidal deposits rules out progradation as the cause of the exposure i e these are not ginsburg autocycles thus the repeated exposure must be the result of relative sea level oscillations which based on the number of cycles and time intervals involved occurred with an average frequency in the 104 year range we postulate a combination of small scale high frequency eustasy and local tectonic movements e g differential subsidence in the norian and infrequent pulses of uplift in the ladinian to explain the cyclicity and its internal variations