geologic evolution of the iraqi zagros and its influence on the distribution of hydrocarbons in the kurdistan region whereas the vast majority of discovered hydrocarbon reserves in iraq reside in cretaceous and cenozoic reservoirs numerous oil and gas fields have been discovered recently in deeper jurassic and triassic reservoirs in the kurdistan region of iraq this study presents a middle upper jurassic thermal maturity map for the kurdistan region of iraq and demonstrates that regional first order trends in jurassic source rock maturity show a close correlation to the spatial distribution of oil gravities within the overlying jurassic and cretaceous reservoirs this distribution is consistent with compartmentalization of the active source rock kitchens due to zagros folding resulting in relatively short distance migration and charge of the anticlinal structures from the adjacent synclinal lows the thermal maturity map confirms relatively low maturity over the mosul high where the cretaceous and cenozoic section overlying the source rock interval is relatively thin and increasing maturity to the southeast as the thickness of the cenozoic foredeep sediments increases toward the depocenter located in the southeastern iraqi zagros and the adjacent iranian zagros the correlative trend in oil gravities is exemplified by the recent jurassic discoveries low to medium gravity oils 14 27 api in shaikan and atrush to the northwest light oil 39 47 api in mirawa and bina bawi and gas condensate 55 api in miran west to the southeast understanding thermal maturity patterns and hydrocarbon fluid type distributions will help to guide risk assessment for remaining prospectivity and future exploration drilling within the kurdistan region of iraq

volume change reconstruction of swiss glaciers from length change data 1 a novel method to reconstruct glacier volume changes from a measured length record is presented and tested for 13 glaciers in the swiss alps the response of a glacier to changes in climate is modeled with a two parameter dynamical system in the variables length and volume driven by a history of equilibrium line altitude ela the model yields variations of glacier length and volume a dynamically equivalent simple model desm is determined for each glacier by matching modeled and measured length changes the volume changes predicted with the desm agree well with measurements for 12 glaciers whereas agreement is poor for one glacier with topographic breaks in the terminus area for all glaciers which are located in different climate regions the length and volume changes are reproduced with the same ela history this agreement shows that the macroscopic glacier response to the climate history is well correlated over a whole mountain range modeling the future evolution of the glaciers under a constant present day climate reveals that fast reacting glaciers are close to equilibrium whereas length and volume of the large valley glaciers would be reduced during the next century by an amount similar to the volume lost during the last 150 years

the eastern termination of the zagros fold and thrust belt iran structures evolution and relationships between salt plugs folding and faulting 1 the zagros mountains result from the ongoing collision between the arabian and central iran plates the main features of the eastern zagros are 1 numerous emerged or buried salt diapirs made up of late precambrian hormuz salt and 2 the irregular along strike shape of the collision related detachment folds with frequent bending to understand this layout four geological cross sections have been constructed from the persian gulf foreland basin to the inner part of the zagros fold and thrust belt shortening in the deformed parts of the sections is less than 10 and is mainly accommodated by detachment folding we show that late cenozoic folding occurred in a region that was already punctuated by salt domes and diapirs in fact almost continuous halokinesis developed since the earlier paleozoic i e just short time after the deposition of the hormuz salt and continued up to the present these preexisting salt structures and their relevant local thickening strongly influenced both the localization and the direction of folds

historical glacier fluctuations of jostedalsbreen and folgefonna southern norway reassessed by new pictorial and written evidence glaciers are sensitive indicators of past climate and thus valuable sources of climate history unfortunately direct determinations of glacier changes variations in length and mass balance did not start with increasing accuracy before the end of the nineteenth century therefore historical and geomorphological evidence has to be used to reconstruct glacier variability for preceding time periods here we present new glacier length reconstructions for selected outlet glaciers of jostedalsbreen and folgefonna two ice caps in southern norway a wealth of different historical sources drawings paintings prints photographs maps written accounts about 400 documents allows reconstruction of glacier length variations for the last 300 jostedalsbreen and 200 years folgefonna respectively we present historical material newly collected for briksdalsbreen boyabreen store supphellebreen bergsetbreen nigardsbreen lodalsbreen all jostedalsbreen and bondhusbrea buerbreen both southern folgefon

a comparison of khuff and arab reservoir potential throughout the middle east a compilation of average porosity and permeability data for petroleum reservoirs in the permian triassic khuff formation and the jurassic arab formation shows that most khuff reservoirs have an average porosity of less than 12 whereas most arab reservoirs have an average porosity of 12 26 higher porosity correlates with shallower depth suggesting that burial diagenesis is the main cause of the overall porosity difference between these units deeper burial of khuff reservoirs is inferred to have resulted in greater porosity loss by chemical compaction and associated cementation a broad correlation also exists between average porosity and average permeability suggesting that deeper burial and the resulting porosity decrease are also a primary cause of the lower permeabilities of the khuff reservoirs in addition to greater burial depth however a combination of depositional and early diagenetic factors is also reflected in the lower average porosity and permeability values of the khuff reservoirs khuff strata were deposited on an extensive poorly circulated very low relief shelf and consist in large part of interbedded mudstones and grainstones having relatively fine grain size with major amounts of depositional calcium sulfate present arab reservoirs were deposited under better circulated conditions near platform margins facing deep intracratonic basins and thus have coarser more grain dominated fabrics and lesser overall content of chemically precipitated grains calcium sulfate and dolomite khuff deposits were likely composed of less stable mineralogy than arab sediments because the late permian was a time of aragonite seas whereas the late jurassic was a time of calcite seas the combined result of these factors is that arab reservoirs are characterized by greater preservation of primary depositional pore types more coarsely crystalline dolomite fabrics and lesser plugging by anhydrite finally a possible factor affecting the average porosity and permeability values is petroleum composition which is gas in most khuff reservoirs and oil in arab reservoirs lower economic cutoff values for gas production would favor inclusion of low permeability zones in khuff reservoirs thus reducing average reservoir values two main aspects of these results are innovative this is the first time that porosity and permeability values for either khuff or arab reservoirs have been examined regionally second the conclusion that thermal exposure is the primary control on average porosity and permeability in these units is consistent with previous work from other carbonates but is new for the middle east

interplay between detrital and diagenetic processes since the last glacial maximum on the northwest iberian continental shelf abstract integrated analyses of magnetic geochemical and textural data on six cores from the northwestern iberian continental shelf allowed the reconstruction of the paleoenvironmental evolution of this area since the last glacial maximum lgm four sedimentary units were identified representing a succession from fluvial and subaerial settings to high and finally low energy marine deposits subsequent to the post lgm sea level rise the uppermost unit was deposited during the holocene and its magnetic properties were controlled by the interplay between detrital input and early diagenetic reductive dissolution of magnetic minerals identification of a primary steady state early diagenetic signal allowed the recognition of periods of increased detrital input bounded by intervals of lower detrital input and intensified reductive diagenesis related to intensified upwelling in the area these paleoenvironmental alternations are consistent with the climatic evolution of the late holocene during the roman warm period and medieval warm period the combined effect of greater humidity and intense agricultural and mining activities led to a greater erosion and transport of detrital sediments to the shelf in contrast enhanced diagenetic reduction intervals caused by upwelling intensification were roughly coincident with the colder dark ages and the little ice age

radiometric sand mud characterisation in the rhine meuse estuary part b in situ mapping traditionally obtaining accurate spatial information about the textural composition of heterogeneous aquatic sediments requires extensive sediment sampling to avoid a costly and time consuming operation a new in situ technique has been investigated this technique characterises sediment components by the activity concentrations of natural radionuclides in situ activity concentrations are continuously measured with the multi detector system for underwater sediment activity medusa a detector trailed over the bottom by a towing vessel containing a highly sensitive gamma ray bgo detector a water depth sensor and a microphone from the collected gamma ray spectra the activity concentrations of k 40 u 238 and th 232 are derived during two separate field surveys of 5 days each medusa was applied to the hollandsch diep and haringvliet two fresh water basins each approximately 20 km long and 2 3 km wide in the rhine meuse estuary the netherlands in part a of this paper this issue it has been illustrated how the radiometric fingerprint of sand and mud in the area was determined this fingerprint was then used to calculate the sand mud ratio from the u 238 and th 232 activity concentrations of about 25 000 medusa data points the interpolated sand mud distribution of the top layer of the aquatic sediment shows a distinct correlation with bathymetry the deeper channels are mud rich whereas the shallow zones are predominantly sandy in general the mud content decreases in the seaward direction this corroborates well with the morphological development of the area in which the deposition of mud is highest near the rivers outflow in the cast the absolute total random error in the sand map varies between 6 and 18 where the largest errors are caused principally by spatial variability of the sediment composition at present the radiometric results underestimate the mud content by 10 30 due to a higher water content of sediment with high mud contents 60 the simultaneously recorded friction sound levels provide qualitative information with respect to the sediment composition sandy areas show a higher sound level than muddy areas with the sound and sand map showing a striking similarity c 2002 elsevier science b v all rights reserved

an oscillating trend in phanerozoic non skeletal carbonate mineralogy textural and compositional data on ancient ooids and cements suggest the existence of an oscillating phanerozoic temporal trend in non skeletal carbonate mineralogy the trend shows good correlation with eustatic climatic oscillations proposed by others the most likely mechanism appears to be plate tectonically influenced oscillations in pco2 the vapour pressure of co2 rather than change in oceanic mg ca ratio

sandstone vs carbonate petroleum reservoirs a global perspective on porosity depth and porosity permeability relationships plots are presented comparing average porosity vs depth for 30 122 siliciclastic petroleum reservoirs and 10 481 carbonate petroleum reservoirs covering all petroleum producing countries except canada however separate plots cover 5534 siliciclastic and 2830 carbonate reservoirs of the alberta basin in canada average permeability vs average porosity is shown for the non canadian reservoirs key similarities and differences between sandstones and carbonates are noted and implications are discussed regarding the dominant factors controlling reservoir quality in each lithology trends of steadily decreasing median and maximum porosity with increasing depth reflect burial diagenetic porosity loss in response to increasing thermal exposure with depth these trends seem inconsistent with the suggestions that both sandstones and carbonates commonly increase in porosity by dissolution during deeper burial carbonate reservoirs have lower values of median and maximum porosity for a given burial depth probably because of greater chemical reactivity of carbonate minerals relative to quartz and the resulting lower resistance to chemical compaction and associated cementation relative paucity of low porosity 0 8 siliciclastic reservoirs at all depths compared with carbonates may reflect the more common occurrence of fractures in carbonates and the effectiveness of these fractures for facilitating economic flow rates in low porosity rock overall carbonate reservoirs do not have lower permeability for a given porosity compared with sandstones but do have strikingly lower proportions of both high porosity and high permeability values the data presented can serve as a general guide for the distribution of reservoir quality that can reasonably be expected in exploration wells drilled to any given depth in the absence of detailed geologic information such as burial and thermal history

on the climate geometry imbalance response time and volume area scaling of an alpine glacier insights from a 3 d flow model applied to vadret da morteratsch switzerland a two dimensional surface mass balance model is coupled to a three dimensional higher order ice flow model to assess the imbalance between climate and glacier geometry for the morteratsch engadine switzerland glacier complex the climate geometry imbalance has never been larger than at present indicating that the temperature increase is faster than the geometry is able to adapt to we derive response times from transient and steady state geometries and find that the volume response time is correlated to the magnitude of the mass balance forcing it varies between 22 and 43 years while the length response time is between 47 and 55 years subsequently the modelled response times are compared with different analytical methods from the literature the effect of a climatic perturbation on the response time which produces a spatially distributed mass balance forcing is also examined we investigate the effect of glacier size on the response time and project that the response time will decrease in the future due to a surface steepening finally volume area scaling methods with different parameters are tested and an alternative method is proposed that takes into account the surface slope the effect of a transient state on the method is also evaluated

2d basin modeling study of the binak trough northwestern persian gulf iran abstract the northwestern part of the persian gulf is one of the most prominent hydrocarbon exploration and production areas oilfields are located in structural highs formed around the cenomanian depression known as binak trough to evaluate the highly variable source rock maturity timing of hydrocarbon generation as well as migration pattern and the remaining hydrocarbon potential of the early cretaceous source rocks burial and thermal histories were constructed for four production wells and one pseudo well in addition two cross sections covering the depression and the structural highs around the trough were investigated by 2d basin modeling to provide a better regional overview on basin evolution the modeling results indicate that whereas the cretaceous source rocks are immature or early mature at the location of oilfields they reached sufficient maturity to generate and expel considerable amounts of hydrocarbons in the binak depression the main phase of oil generation and expulsion from the cretaceous source rocks is relatively recent and thus highly favorable for the conservation of hydrocarbon accumulations trap charging occurred through the late miocene to pliocene after the zagros folding 2d models predict that the albian source rock still has significant hydrocarbon generation potential whereas the lower neocomian source rock has reached already a high transformation ratio within the deep kitchen area oil migration occurs in both lateral and vertical directions this migration pattern could explain the distribution of identified oil families in the northwestern part of the persian gulf

on the imbalance and response time of glaciers in the european alps glaciers in the european alps rapidly lose mass to adapt to changes in climate conditions here we investigate the relationship and lag between climate forcing and geometric glacier response with a regional glacier evolution model accounting for ice dynamics the volume loss occurring as a result of the glacier climate imbalance increased over the early 21st century from about 35 in 2001 to 44 in 2010 this committed loss reduced to 40 by 2018 indicating that temperature increase was outweighing glacier retreat in the early 2000s but that the fast retreat effectively somewhat diminished glacier imbalances we analyze the lag in glacier response for each individual glacier and find mean response times of 50 28 years our findings indicate that the response time is primarily controlled by glacier slope and secondarily by elevation range and mass balance gradient rather than by glacier size

estimating response times of vadret da morteratsch vadret da palu briksdalsbreen and nigardsbreen from their length records length records of two pairs of glaciers are used to reconstruct the equilibrium line altitude ela and to estimate glacier response times the method is based on the assumption that neighbouring glaciers should be subject to the same climatic forcing and that differences in the length records are thus caused by differences in response times and climate sensitivities by means of a control method in which the difference between the reconstructed histories of the ela is minimized realistic response times are found the pairs of glaciers studied are i vadret da morteratsch and vadret da paluin the swiss alps and ii briksdalsbreen and nigardsbreen in southern norway in both cases the reconstructed ela histories of the individual glaciers are very similar in spite of the large differences in the length records short e folding response times are found for the steep glaciers 4 4 years for vadret da palii 5 0 years for briksdalsbreen for the larger glaciers with a more gentle slope the response times are substantially larger 33 0 years for vadret da morteratsch 34 8 years for nigardsbreen

little ice age precipitation in jotunheimen southern norway recently published glaciological data from southern norway enable analysis of changes in glacier geometry since the little ice age lia and estimation of the magnitude of the lia precipitation anomaly glacier area extents in the jotunheimen region have been created for 2003 using glacier outlines derived from landsat and for the lia maximum about ad 1750 by using glacier outlines defined by moraines a 25 m digital terrain model from 1980 was used to derive inventory data for both times both inventories provide area and altitude range as well as length slope and aspect of the glaciers area altitude profiles a z for the lia maximum are calculated from the 1980 profiles by assuming that the area increase distribution a z was concentrated at low altitude and it integrates to the measured area difference between 1980 and the lia under this assumption the regionally averaged mean altitude change from 1980 to the lia z 68 m glacier mass balance measurements show that the mass balance gradie

particle size related mineral magnetic source sediment linkages in the rhode river catchment maryland usa characterization of both the source materials and the bottom sediments of an estuary by magnetic characters on a particle size basis allows the source of the bottom sediments to be determined and indicates a shift in sediment sources corresponding to changing land use patterns the major source of the sediments in the lower part of cores from the middle of the estuary is eroding shorelines soil derived particulates from the uplands dominate the upper part of the cores this change in source occurred in the early part of the 19th century the magnetic character of the most recent sediments suggests a progressive depletion through time of the upland soils in the finest fractions

time scale for adjustment of glaciers to changes in mass balance the length of time tm over which a glacier responds to a prior change in climate is investigated with reference to the linearized theory of kinematic waves and to results from numerical models we show the following tm may in general be estimated by a volume time scale describing the time required for a step change in mass balance to supply the volume difference between the initial and final steady states the factor f in the classical estimate of m l u where i is glacier length and u is terminus velocity has a simple geometrical interpretation ft is the ratio of thickness change averaged over the full length i to the change at the terminus although both u and f relate to dynamic processes local to the terminus zone the ratio f u and therefore tm are insensitive to details of the terminus dynamics in contrast to conclusions derived from some simplified kinematic wave models a more robust estimate of tm independent of terminus dynamics is given by tm h b where h is a thickness scale for the glacier and b is the mass balance rate negative at the terminus we suggest that tm for mountain glaciers can be substantially less than the 1o2 103 years commonly considered to be theoretically expected

temperature reconstruction from the length fluctuations of small glaciers in the eastern alps northeastern italy in this study a linear model computing the air temperature fluctuations from the measured glacier snout fluctuations has been applied for the first time to three small glaciers in the western tauern alps eastern alps in the period 1929 2011 the considered glaciers with areas between 0 2 and 1 3 hbox km 2 are characterized by relevant time variations of their morphology length and slope the model requires the knowledge of two parameters the glacier climate sensitivity c s and the glacier response time tau both depending on the glacier morphological characteristics and on the precipitation applied to the glaciers assuming c s and tau as in the original formulation it underestimates the temperature increase of approx 1 8 circ hbox c derived over the whole period from the in situ data given the characteristics of these small glaciers these parameters have been recalibrated by means of a non linear least square regression using an independent set of glaciers their mean value is of about 210 m k and 3 8 years respectively with the recalibrated values of the new glacier climate sensitivity c s and response time tau the temperature fluctuations derived by the model reproduce well those obtained from the observed temperatures computed over the hydrological year with linear correlations between 0 8 and 0 9 the increase of the modeled mean temperature over the whole period fits in with that derived from observed temperature considering that the length fluctuations of these small glaciers affect significantly their slope and length we tested the impact in the model of a time dependent formulation of c s and tau the results indicate slight improvements both in the values of the correlation between the reconstructed and the observed temperature fluctuations and in the global temperature increase given the above value of climate sensitivity the large retreat of the small alpine glaciers threatens their survival within a few decades but the morphological changes in progress may counteract the glacier disappearance

glacier fluctuations of jostedalsbreen western norway during the past 20 years the sensitive response of maritime mountain glaciers the steep outlet glaciers of jostedalsbreen western norway are good examples of sensitively reacting maritime mountain glaciers their changes in length frontal position and lower tongue s morphology during the past 20 years have been well documented at first they experienced a strong frontal advance after ad 2000 glacier behaviour was dominated by a strong frontal retreat in some cases causing a separation of the lowermost glacier tongue in this paper the glacier length changes are presented both visually and numerically supplemented by mass balance and meteorological data the glacier behaviour is interpreted and its causes are discussed whereas the factors controlling the advance during the 1990s seem clear the interpretation of the most recent retreat still leaves some uncertainties the actual glacier front behaviour cannot fully be related to the mass balance data terminus response times and relations between individual mass balance and meteorological parameters have changed some hypoth

chemostratigraphy of the jurassic system applications limitations and implications for palaeoceanography current chemostratigraphical studies of the jurassic system primarily involve the use of one sedimentary component marine organic carbon one divalent transition metal substituted in carbonate manganese and two isotopic tracers strontium isotope ratios 87 sr 86 sr and carbon isotope ratios 13 c carb and 13 c org in carbonate and in organic matter other parameters such as mg ca and sr ca ratios in calcite oxygen isotope ratios 18 o in carbonate sulphur isotope ratios 34 s in carbonate hosted sulphate nitrogen isotope ratios 15 n org in organic matter osmium isotope ratios 187 os 188 os in black shales and neodymium isotope ratios 143 nd 144 nd in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors stratigraphical patterns in total organic carbon toc can be of either local or regional significance depending on the lateral extent of the former nutrient rich and productive water mass divalent manganese follows a similar pattern being concentrated most probably as a very early diagenetic phase only in oxygen depleted waters that typically underlie zones of elevated organic productivity shifts in mg ca and sr ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes strontium isotope ratios from pristine skeletal calcite provide a global signal 13 c values from carbonates with minimal diagenetic overprint potentially do the same although small spatial differences in palaeo water mass composition may have been locally significant oxygen isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful because they reflect palaeotemperature the evaporation precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase nitrogen isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis neodymium isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems preliminary data on sulphur isotope ratios in carbonates and osmium isotope ratios in organic rich shales both potentially offering global correlation indicate that these tracers may be valuable although the records at present are not sufficiently well established to allow high resolution regional correlation in all cases biostratigraphically well dated reference sections against which the relevant geochemical data have been calibrated are required in the first instance to date studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern boreal and southern tethyan europe carbon isotope stratigraphy has been undertaken primarily but not exclusively on bulk pelagic sediments from the alpine mediterranean or tethyan domain and strontium isotope stratigraphy has been undertaken largely on calcitic skeletal material belemnites and oysters from northern and southern europe in many sections including those containing ammonites multi parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means strontium isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record

using csem techniques to map the shallow section of seafloor from the coastline to the edges of the continental slope many important processes occur within the shallow section of the seafloor on the continental shelf and slope yet conventional geophysical constraints on the physical properties within this critical boundary layer are limited some of the key constraints involve quantification of fluids within the seafloor which can be provided by electrical methods this paper reviews the application of a towed em system to map the uppermost 20 m of seafloor in a variety of settings ranging from nearshore regions in water depths of approximately 10 m on the continental shelf out to water depths of 1300 m the system is a mapping tool that provides areal maps of seafloor resistivity and has been used for a variety of purposes including sedimentary characterization and facies mapping evaluation of groundwater discharge and mapping seafloor mounds in the gulf of mexico thought to contain massive deposits of gas hydrate

sediment provenance in a tropical fluvial and marine context by magnetic fingerprinting of transportable sand fractions the sources and fluxes of sediment to the great barrier reef lagoon from northeastern australian rivers have been the subject of much concern and study with the large catchments of the burdekin and fitzroy rivers thought to be the key sources at present here the utility of newly developed magnetic fingerprinting methods for identifying sediment provenance both onshore and offshore and in association with individual large flood events is investigated within the burdekin catchment sediments are mobilized from different subcatchments by runoff generated by intense localized rainfall events magnetic measurements were made on untreated and acid treated samples of river channel sediments within the burdekin river subcatchments and from the estuarine and inner shelf depocentres of burdekin river sediments the acid treatment removes all discrete magnetic particles and coatings and leaves magnetic inclusions protected within host silicate grains as the basis of the measured magnetic signature of a sample the magnetic properties of the acid treated samples display statistically distinct sediment provenance groupings sand samples from the upper burdekin river appear magnetically distinct from samples from tributaries of the burdekin e g hann creek fanning river and also from nearby coastal rivers including the haughton suspended sand samples from a burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999 comparisons of the terrestrial acid treated sand fractions with the same acid treated sand size fractions from transects taken offshore suggest that the surface sediments in upstart bay and bowling green bay have different sources some of these sources are as yet unidentified but may represent the unsampled lower discharge south western burdekin subcatchments and or along shore drift of sand from the south perhaps even from the fitzroy river over millennial timescales of cyclone pumping the magnetic inclusion method precludes any obfuscation or confounding of sediment source which might arise from hydraulic sorting and or post depositional magnetic diagenesis or authigenesis

response of valley glaciers to climate change and kinematic waves a study with a numerical ice flow model a simple numerical flow model that couples mass divergence directly to basal shear stress as the only driving force is used to study kinematic waves cinematic waves that result from a perturbation of the ice thickness or mass balance are compared with the linear kinematic wave theory of nye weertman the wave velocity is calculated as a function of the wavelength and amplitude of a perturbation the modelled wave velocity is typically 6 8 times the vertically averaged velocity in the flow direction whereas linear theory predicts a factor of only 5 an experiment with the geometry of hintereisferner austria shows that the increase in the local ice velocity during a kinematic wave is about 10 but varies slightly depending on the position along the glacier and the amplitude of the kinematic wave cinematic waves are thus hard to detect from velocity measurements the dynamics of simple continuity models are rich enough to support a variety of kinematic wave phenomena such models are a useful tool to study the response of valley glaciers to climate change

recent sedimentation and sedimentary budgets on the western iberian shelf abstract thus study is based on 31 box core samples collected mainly from the mud patches of the galician and north portuguese shelf each of these cores some decimetres in length have been described radiographied and sampled each centimetre for grain size analysis and measurement of the particulate organic carbon corg content 210pb excess profiles have been measured using gamma spectrometry which combined with the analysis of the vertical variations of the sedimentary facies have allowed estimates of sedimentation rates these rates were found to vary between 0 05 and 0 40 cm yr 1 considering the latitudinal variation of sedimentation rates around the 100m contour we note that the maximum rates occurred off the douro estuary in the southern sector and also near the galician rias to the north the organic content corg of sediments varied between 0 4 and 2 latitudinally corg showed a decrease from the south to the north these results coupled with the sedimentary map see dias gonzalez garcia diaz del rio 2001 have permitted us to establish the detrital mass budget and an inventory of corg burial

modelling the evolution of vadret da morteratsch switzerland since the little ice age and into the future we use a 3 d higher order glacier flow model for vadret da morteratsch engadin switzerland to simulate its strong retreat since the end of the little ice age lia and to project its future disintegration under a warming climate the flow model coupled to a 2 d energy balance model is initialized with the known maximum glacier extent during the lia and subsequently forced with mean monthly precipitation and temperature records to correctly reproduce the observed retreat of the glacier front for the period 1864 2010 additional mass balance perturbations are required to account for uncertainties in the initial state the mass balance model and climate variations not captured by the ambient meteorological records changes in glacier volume and area are in good agreement with additional information from historical topographic maps under constant 2001 10 climate conditions a strong retreat and mass loss continue and vadret da morteratsch disconnects from its main tributary vadret pers before 2020 the future glacier evolution is analysed in detail to understand the timing and rate of retreat and to assess the role of ice dynamics assuming a linearly increasing warming of 3 c by 2100 only isolated and largely stagnant ice patches remain at high elevation

future fluctuations of mer de glace french alps assessed using a parameterized model calibrated with past thickness changes simulations of glacier evolution are needed to assess future changes in the runoff regime of mountain catchments a simplified parameterized model is applied here to simulate future thickness changes and glacier retreat of mer de glace french alps a normalized thickness change function describing the spatial distribution of surface elevation changes as a function of elevation has been determined the model reveals that under present climatic conditions mer de glace will continue to shrink dramatically in the coming decades retreating by 1200 m between now and 2040 the method has certain limitations related to the uncertainties of the normalized function based on thickness change data an error of 10 in the normalized function leads to uncertainties of 46 30 and 18 in mer de glace front surface area and glacier wide mass balance changes respectively in 2040 because the difference of the normalized function largely exceeds 10 from one glacier to another even within a given glacier size class and elevation range it would be very risky to extrapolate the normalized function to unmeasured glaciers consequently the method is applicable only on glaciers where past surface elevation changes are well constrained

on estimating length fluctuations of glaciers caused by changes in climatic forcing the reaction of alpine glaciers to shifts in the equilibrium line altitude ela is calculated by using a two dimensional numerical model to solve the full equations for the velocity and stress fields full system model in the absence of basal motion rates of advance and retreat of the snout of typically sized alpine glaciers are found to be insensitive to the details of the flow at the snout even when the glaciers are far from steady state a comparison of results obtained with a full system model and a shallow ice approximation sia model yields no significant differences in advance or retreat rates this assumption has been implicitly made in numerous previous climatic studies and is here shown to be well justified using a realistic mass balance altitude feedback only slight model dependent changes in steady state lengths are found the relative importance of mass balance and glacier dynamics for the transient response of alpine glaciers to changes in the ela is given a precise meaning by determining the model dependent additional shifts in ela needed for the sia and the full system models to produce identical changes in length for alpine glaciers these additional shifts in ela are on the order of 10 m which is within the error range of ela estimates it follows that at least in the absence of significant basal motion there is no need to include the effects of horizontal stresses when calculating the reaction of alpine glaciers to climatic changes attention should focus on accurate determination of the mass balance distribution and model tuning to give realistic ice thickness distributions

climate and glacier fluctuations at jostedalsbreen and folgefonna southwestern norway and in the western alps from the little ice age until the present the influence of the north atlantic oscillation glacier length though an indirect and delayed signal of climate conditions can be used to determine the relationship between climate and glacier response this study discusses glacier length change of eight outlet glaciers of jostedalsbreen and folgefonna southern norway from the little ice age lia until the present a climate index was calculated from meteorological data from bergen to determine the specific frontal time lags of the individual glaciers short and steep outlet glaciers such as briksdalsbreen react rapidly to changes in climatic conditions whereas long and gently descending glaciers such as nigardsbreen need longer time to adjust to changes in temperature and or precipitation the time lag of briksdalsbreen was about twice as long during the lia as today the correlations between north atlantic oscillation nao and climate conditions and glacier fluctuations in norway and the european western alps were analysed as the influence of the nao on glacier fluctuations is most pronounced during winter only the winter nao index was considered fluctuations of maritime norwegian glaciers are highly correlated with the nao whereas variations of more continental glaciers in the european western alps are only partly influenced by the nao and tend to be anti correlated however the anti correlation with the nao is not constant during the record and significantly weaker or even inversed during some periods a comparison of the lia glacier fluctuations in southern norway and the european western alps suggests that the asynchronous lia maxima in the two regions may partly be attributed to multidecadal trends in the nao

fingerprinting upland sediment sources particle size specific magnetic linkages between soils lake sediments and suspended sediments accelerated erosion of fine grained sediment is an environmental problem of international dimensions erosion control strategies and targeting of mitigation measures require robust and quantitative identification of sediment sources here we use magnetic fingerprinting to characterize soils and examine their affinity with and contribution to suspended sediments transported within two subcatchments feeding bassenthwaite lake northwest england a high resolution soil magnetic susceptibility survey was made using a field susceptometer zh instruments sm400 probe combining the spatial and vertical down profile soil magnetic data a subset of soil profiles was selected for detailed laboratory based magnetic remanence analyses the magnetic properties of the catchment soils are highly particle size dependent magnetic analyses were performed on the 31 63 m fraction for particle size specific comparison both with the suspended sediments and lake sediments fuzzy cluster analysis groups the soil magnetic data into six clusters apparently reflecting variations in parent material and horizon type with three magnetically hard soils as unclassified outliers examination of the cluster affinity of the soils suspended sediments and lake sediments indicates that topsoils of the upper newlands valley and subsoils around keskadale beck are a major source of the newlands beck suspended load and the recent post nineteenth century sediments in the deep lake basin older lake sediments show strong affinity with a small number of the derwent suspended sediments and one of the glenderamackin soils a large number of derwent suspended sediments show no affinity with any of the soils or lake sediments instead forming a coherent discrete and statistically unclassified group possibly resulting from mixing between the magnetically hard subsoils of the medium to high altitude glenderamackin and troutbeck areas and softer lower altitude glenderamackin soils the lack of any affinity of these suspended sediments with the lake sediments may indicate deposition along the derwent flood plain and or in the shallow delta of lake bassenthwaite particle size specific magnetic fingerprinting is thus shown to be both highly discriminatory and quantitatively robust even within the homogeneous geological units of this catchment area such a methodological approach has important implications for small large scale catchment management where sources of sediment arising from areas with uniform geology have been difficult to determine using other approaches such as geochemical or radionuclide analyses

structural evolution of harmaliyah oil field eastern saudi arabia the history of structural growth of the harmaliyah oil field in eastern saudi arabia was studied by means of a series of paleostructural maps to determine if early entrapment of hydrocarbons played an important role in preserving the high porosity of the kimmeridgian upper jurassic arab d reservoir the arab d has been affected by shallow or preburial diagenesis a common feature in arabian upper jurassic calcarenitic reservoirs closure forming the structural trap in the arab d at harmaliyah oil field developed principally during the late turonian late cretaceous during kimmeridgian late jurassic early turonian late cretaceous time shallow or preburial diagenesis of the calcarenitic arab d reservoir rocks seems to have played a major part in preservation of por sity before the porosity was filled with hydrocarbons

early diagenesis of magnetic minerals in marine transitional environments geochemical signatures of hydrodynamic forcing abstract the low field magnetic susceptibility of surficial sediments from the ria de pontevedra nw spain shows a characteristic hydrodynamically driven textural control where diamagnetic sandy bioclastic carbonates occur toward the coastline leaving the finer muddy sediments to be deposited in the central and deeper areas of the ria three gravity cores were collected from the inner core 1 middle core 2 and outer core 3 zones of the clayey rich central axis of the ria from which the magnetic properties geochemical characteristics and hydrodynamic regime of the uppermost 90 cm of the sediment record were reconstructed profiles have a distinctive pattern that is controlled by depth isothermal remanent magnetization irm acquisition curves facilitated the identification of three well defined zones with depth depending on their degree of magnetic saturation and thus of their dominant magnetic behaviour magnetite like goethite like and greigite like this zonation is interpreted as the result of mineralogical changes during early diagenesis the relative depths of each zone are mostly dependent on distance to the open sea with the magnetite like zones being thicker in the outermost part of the ria toward the inner part of the ria the three zones become shallower and thinner in the innermost areas only greigite like coercivities are observed good correlation between magnetic and geochemical parameters such as vs 2fe s or h cr vs c s demonstrates that magnetic property variations with depth are diagenetically controlled and that these parameters can be used as magnetic proxies for early diagenesis similar significant positive correlations were found between of the clay fraction and modelled wave heights and between other magnetic and hydrodynamic parameters providing magnetic evidence of cryptic wave climate forcing of the diagenetic pathway the combined analysis of the magnetic geochemical and hydrodynamic data ultimately indicates that the sediment distribution and subsequent diagenetic pathway in this type of transitional environment mostly depend on the local distribution of wave energy and water depth rather than on estuarine like circulation processes

on mapping seafloor mineral deposits with central loop transient electromagnetics electromagnetic methods are commonly employed in exploration for land based mineral deposits a suite of airborne land and borehole electromagnetic techniques consisting of different coil and dipole configurations have been developed over the last few decades for this purpose in contrast although the commercial value of marine mineral deposits has been recognized for decades the development of suitable marine electromagnetic methods for mineral exploration at sea is still in its infancy one particularly interesting electromagnetic method which could be used to image a mineral deposit on the ocean floor is the central loop configuration central loop systems consist of concentric transmitting and receiving loops of wire while these types of systems are frequently used in land based or airborne surveys to our knowledge neither system has been used for marine mineral exploration the advantages of using central loop systems at sea are twofold 1 simplified navigation because the transmitter and receiver are concentric and 2 simplified operation because only one compact unit must be deployed we produced layered seafloor type curves for two particular types of central loop methods the in loop and coincident loop configurations in particular we consider models inspired by real marine mineral exploration scenarios consisting of overburdens 0 to 5 m thick overlying a conductive ore body 5 to 30 m thick modeling and resolution analyses showed that using a 50 m 2 transmitting loop with 20 a of current these two configurations are useful tools to determine the overburden depth to a conductive ore deposit and its thickness in the most extreme case absolute voltage errors on the order of 10 nv are required to resolve the base of a 30 m thick ore deposit whether such noise floors can be achieved in real marine environments remains to be seen

tidal induced large scale regular bed form patterns in a three dimensional shallow water model the three dimensional model presented in this paper is used to study how tidal currents form wave like bottom patterns inclusion of vertical flow structure turns out to be necessary to describe the formation or absence of all known large scale regular bottom features the tide and topography are treated as a coupled system and the potential free instabilities in this system are investigated a linear stability analysis is used to study the dynamics of bed forms this yields information on the role of physical mechanisms such information cannot be obtained by direct numerical nonlinear simulation the basic state represents a horizontal elliptical flow veering in vertical direction over a flat bottom it is shown that in such a system modes can grow which have characteristics of both tidal sand banks and sand waves the model predictions are compared with observations and show good agreement

hydrothermal dolomitization of the bekhme formation upper cretaceous zagros basin kurdistan region of iraq record of oil migration and degradation abstract the common presence of oil seepages in dolostones is widespread in cretaceous carbonate successions of the kurdistan region of iraq this integrated field petrographic chemical stable c o and sr isotopes and fluid inclusion study aims to link dolomitization to the origin and geochemical evolution of fluids and oil migration in the upper cretaceous bekhme carbonates flux of hot basinal hydrothermal brines which is suggested to have occurred during the zagros orogeny resulted in dolomitization and cementation of vugs and fractures by coarse crystalline saddle dolomite equant calcite and anhydrite the saddle dolomite and host dolostones have similar stable isotopic composition and formed prior to oil migration from hot 81 115 c basinal nacl mgcl2 h2o brines with salinities of 18 22 wt nacl eq the equant calcite cement which surrounds and hence postdates saddle dolomite has precipitated during oil migration from cooler 60 110 c nacl cacl2 h2o brines 14 18 wt nacl eq the yellowish fluorescence color of oil inclusions in the equant calcite indicates that the oil had api gravity of 15 25 composition which is lighter than present day oil in the reservoirs api of 10 17 this difference in oil composition is attributed to oil degradation by the flux of meteoric water which is evidenced by the low 13c values 8 5 to 3 9 vpdb as well as by nil salinity and low temperature in fluid inclusions of late columnar calcite cement this study demonstrates that linking fluid flux history and related diagenesis to the tectonic evolution of the basin provides important clues to the timing of oil migration degradation and reservoir evolution

a new glacier inventory for the jostedalsbreen region norway from landsat tm scenes of 2006 and changes since 1966 pronounced changes in glacier mass and length were observed for the monitored glaciers in the jostedalsbreen region norway since the last glacier inventories were compiled in the 1960s and 1980s however the current overall extent of the glaciers in the region is not well known to obtain this information we have compiled a new inventory from two mosaicked landsat thematic mapper tm scenes acquired in 2006 that have excellent snow conditions for glacier mapping the first suitable scenes for this purpose after 22 years of imaging with tm drainage divides and topographic inventory parameters were derived from a 25 m national digital elevation model for 1450 glaciers by digitizing glacier outlines from 1 50 000 scale topographic maps of 1966 we calculated changes in glacier area for 300 glaciers cumulative length changes for the 1997 2006 period were derived from an additional tm scene and compared with field measurements for nine glaciers overall we find a 9 area loss since 1966 with a clear dependence on glacier size however seasonal snow in 1966 in some regions made area determination challenging the satellite derived length changes confirmed the observed high spatial variability and were in good agreement with field data 1 pixel apart from glacier tongues in cast shadow the new inventory will be freely available from the global land ice measurements from space glims glacier database

sediment distribution patterns on the galicia minho continental shelf abstract a sedimentological and bathymetric study of the minho galicia shelf shows a strong contrast between a southern shelf region with a thin partially relict cover of sands and gravel and a northern region where fine grained sediments predominate this contrast is explained through differences in the sediment supply the oceanographic environment storms and ocean currents and the morphology of the shelf which results from its underlying tectonic framework most sediment is supplied to the galicia minho shelf by river discharges onto the minho shelf particularly that from the douro river in the northern part of the shelf the galician rias act as sediment traps rather than sediment suppliers the bulk of the sediment washes out of the rivers during episodic storm events while most of the coarse sediments remain deposited close to the coast the fine grained material is exported to the outer areas of the shelf subsequently coarse sediments close to the coast are transported southwards by the littoral drift whereas the fine grained material is frequently resuspended through the action of the large swells who influence reaches deep into the water this frequent resuspension has a long term sorting effect on the sediments furthermore resuspended sediments on the middle and outer regions of the shelf are transported northwards by a poleward flowing bottom current as a consequence of the differential transport of coarse sediments to the south and of the fine grained sediments to the north the outer reaches of the minho shelf are relatively poor in recent sediments in many areas relict sediments as well as features associated with ancient coastlines and river mouths still appear as seabed features in contrast the northern regions of the shelf are covered by a thin veneer of fine grained material that smooth other most of these fossil features the fine grained sediment fractions mostly very fine sands to coarse silts are deposited in two large mud patches the douro and the galicia mud patches which are situated at water depths of around 100 120 m these two mud patches are both controlled by the local hydrodynamics and morphology the beiral de viana to the west of the douro mud patch is a plateau up to 20 m high lying parallel to the shelf break and is a morphological expression of an underlying horst system this plateau acts as a barrier that prevents the drift of some of the fine grained material to the west out over the shelf break and the continental slope the galicia mud patch is situated on the eastern part of the galician shelf to the north of the douro mud patch it is situated near the extension of the porto tomar fault which results in the shelf being usually steep in this region down to a depth of about 100 m west of this area the slope is much more gentle northward transport of the sediment is strongly reduced by the e w trending outcrops of plutonic and metamorphic rocks

a macroscopic approach to glacier dynamics a simple approach to glacier dynamics is explored in which there is postulated to be a relationship between area and volume with three parameters the time for area to respond to changes in volume a thickness scale and an area characterizing the condition of the initial stale this approach gives a good fit to the measurements of cumulative balance and area on south cascade glacier from 1970 97 the area time scale is roughly 8 years the thickness scale about 123 m and the 1970 area roughly 4 larger than required for adjustment with volume combining this relationship with a version of mass continuity expressed in terms of area and volume produces a theory of glacier area and volume response to climate in which another time constant the volume time scale appears area and volume both respond like a damped spring and mass system the damping of the south cascade response is approximately critical and the volume time scale is roughly 48 vexes six times the area time scale the critically damped spring and mass analogy reproduces the time dependence predicted by the more complicated traditional theory of nyc

surface expressions of the ghawar structure saudi arabia abstract the ghawar anticline is approximately 225 km long and 25 km wide in the subsurface but the surface structural expression is not obvious identifying subtle structural imprints in the young mio pliocene sedimentary cover is therefore of great importance in developing a structural growth model for the ghawar field the ghawar area between the jafurah sand desert to the east and the rubayda dahna sand deserts to the west is characterized by a rougher topography when compared to the surrounding rather smooth flat areas this rough geomorphology of the structure can also be noticed on the satellite images a geomorphologic elevation map of the area and a subsurface structural contour map of the top arab d upper jurassic reservoir reveal very similar geometric shapes calcareous sandstone deposits of the youngest hofuf formation mio pliocene cap the structural highs along the axis of the anticline and spectacular fractures caves mesas and monumental geomorphologic features have developed in the escarpments fractures in the dam formation middle miocene are not as conspicuous as in the hofuf formation but indigenous fractures are clearly recognized in this formation a match between the directions of some topographic lineaments and projected surface traces of subsurface faults from seismic cross sections can be observed however at the field locations faults have yet to be defined on the surface surface indications suggest that the structure has been active until the present day elevations of a bedding plane on the shedgum plateau reveal a 0 25 dip angle which cannot be distinguished on the surface by the human eye the movements that occurred during the 4 million years since the pliocene period reveal an average tilting of 0 06 per one million years

measuring the shallow porosity structure of sediments on the continental shelf a comparison of an electromagnetic approach with cores and acoustic backscatter we validate estimates of shallow sedimentary porosities made on the continental shelf by electromagnetic methods through a comparison with those measured directly in cores specifically we show that an electromagnetic surveying system we have used to measure sediment resistivity in a number of seafloor locations returns porosity depth profiles that are related to those measured in cores and that our data have good sensitivity to the structure within the uppermost few tens of centimeters of seafloor we then consider inferences of sediment type made by observations of acoustic backscatter in the light of our porosity measurements our results suggest that electromagnetic methods provide complementary information that can be used to improve grain type estimates at and just below the seafloor especially when combined with acoustic backscatter data because the system is pulled along the seafloor data can be quickly collected from a large area of seafloor and can be used to interpolate facies conditions between core locations

lithostratigraphy and depositional environments of the upper jurassic arab c carbonate and associated evaporites in the abqaiq field eastern saudi arabia lithostratigraphy and depositional environment of the arab c carbonate in eastern saudi arabia were studied using cores and well logs from the abqaiq oil field a 275 m upper jurassic evaporite sequence occurs between the sulaiy yamama thamama group and the tuwaiq hanifa arab d tuwaiq group carbonate sequences dolomite and limestone interbeds of 1 30 m in thickness within the evaporite sequence are continuous over long distances and have uniform thicknesses and log characteristics indicating an aggradational type of deposition the lithologically heterogeneous arab c carbonate is the thickest interbed reaching 26 30 m in thickness lithology types recognized in the arab c carbonate are 1 ooid bioclast grainstone 2 oolite grainstone 3 pellet grainstone 4 p llet packstone 5 skeletal wackestone 6 mudstone 7 anhydritic limestone and 8 dolomite the arab c carbonate has been divided into seven layers based on lithology and porosity variations four layers 1 3 5 7 are porous calcarenitic carbonates and the other three layers are nonporous a basinal subaqueous rather than a sabkha type deposition is interpreted for the evaporite sequence lithological and sedimentological successions in the arab c carbonate indicate abrupt storm type deposition and an open marine connection with the restricted evaporite basin this sequence was followed by a subtidal carbonate deposition and then a gradual upward return to an evaporitic environment as a consequence of depositional environments a massive very porous interval developed in the lower arab c carbonate sequence and alternating porous and nonporous layers developed in the upper arab c

lithofacies distribution and sediment dynamics on a storm dominated shelf from combined photographic acoustic and sedimentological profiling methods bay of plenty new zealand abstract sediment dynamics on a storm dominated shelf western bay of plenty new zealand were mapped and analyzed using the newly developed multi sensor benthic profiler marum neridis iii an area of 60 km 7 km between 2 and 35 m water depth was surveyed with this bottom towed sled equipped with a high resolution camera for continuous close up seafloor photography and a ctd with connected turbidity sensor here we introduce our approach of using this multi parameter dataset combined with sidescan sonography and sedimentological analyses to create detailed lithofacies and bedform distribution maps and to derive regional sediment transport patterns for the assessment of sediment distribution photographs were classified and their spatial distribution mapped out according to associated acoustic backscatter from a sidescan sonar this provisional map was used to choose target locations for surficial sediment sampling and subsequent laboratory analysis of grain size distribution and mineralogical composition finally photographic granulometric and mineralogical facies were combined into a unified lithofacies map and corresponding stratigraphic model eight distinct types of lithofacies with seawards increasing grain size were discriminated and interpreted as reworked relict deposits overlain by post transgressional fluvial sediments the dominant transport processes in different water depths were identified based on type and orientation of bedforms as well as bottom water turbidity and lithofacies distribution observed bedforms include subaquatic dunes coarse sand ribbons and sorted bedforms of varying dimensions which were interpreted as being initially formed by erosion under fair weather conditions sediment is transported from the northwest towards the southeast by littoral drift during storm events a current from the southeast to the northweast is induced which is transporting sediment along the shore in up to 35 m water depth shorewards oriented cross shore transport is taking place in up to 60 m water depth and is likewise initiated by storm events our study demonstrates how benthic photographic profiling delivers comprehensive compositional structural and environmental information which compares well with results obtained by traditional probing methods but offers much higher spatial resolution while covering larger areas multi sensor benthic profiling enhances the interpretability of acoustic seafloor mapping techniques and is a rapid and economic approach to seabed and habitat mapping especially in muddy to sandy facies

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

inversion of marine multifrequency electromagnetic profiling data a new approach to resolve surficial sediment stratification s u m m a r y electromagnetic induction emi methods are widely used on land tomap electric conductivity and or magnetic susceptibility distributions of surficial sediments in contrast the application of these methods in marine environments is relatively novel based on the recently developed electromagnetic benthic profiler marum neridis iii we investigate the potential of concentric loop emi methods to recover conductivity and susceptibility of layered marine sediments sensitivity analyses based on a data and model normalized jacobian matrix were performed to compare the influence of conductivity and susceptibility to in phase and quadrature components at different frequencies both parameters substantially affect the em response however the influence of susceptibility decreases more with depth and offers lower depth resolution than that of conductivity a 1 d inversion algorithm to reconstruct vertical conductivity distributions was developed from existing non linear inversion methods using apparent conductivity and apparent susceptibility recovered from simultaneous half space inversion as a priori information this algorithmwas tested on synthetic and real marine emdata from a commercial multifrequency concentric loop emi system gem 3 the results indicate that our inversion algorithm yields meaningful results down to approximately 3 m depth under typical shallowmarine conditions the comparison of inversion results recovered with 1 d and 2 d constraints showed that combining lateral with vertical constraints substantially improves the resolution of the inversion outputs field data from the nw iberian shelf was calibrated according to a processing flow specifically designed for underwater conditions and analysed inversion outputs are in good agreement with ground truthing stratigraphic investigations and deliver relevant clues on past and present sediment dynamics

projected effects of temperature changes on the italian western tauri glaciers eastern alps a linear model was used to investigate the behaviour of the italian western tauri glaciers as a result of temperature changes projected for the 21st century the model estimates the temperature variations once the glacier snout length variations are known and vice versa it estimates the glacier snout length variations once the air temperature variations are known or predicted the 46 glaciers of the italian western tauri 35 76 of which have areas smaller than 0 5 km 2 and only 7 15 larger than 1 km 2 are mostly mountain type glaciers and only three are presently valley glaciers the model has been forced by the air temperature projections of the a1b emission scenario which indicates an increase in temperature of 2 7 c from 2015 to 2100 the results show a shortening of more than 35 for mountain glaciers by 2100 with a surface loss of more than 60 and smaller reductions for valley glaciers the consequent fragmentation into smaller units would lead to the extinction of 95 of the existing glaciers by the end of the century possibly leaving only the valley glaciers surviving

log derived reservoir properties and porosity preservation of upper jurassic arab formation in saudi arabia abstract various types of wireline log analysis were conducted for the arab reservoirs of upper jurassic age in eastern saudi arabia after evaluating the values of the cementation factor m in the archie equation and the formation water resistivity r w values such as total primary and secondary porosities lithological composition water or hydrocarbon saturation and permeability were estimated using combinations of various logs some of the results such as the estimated porosity and permeability were then compared with the available core analysis results the estimated percentage of dolomite was also plotted against the percentage porosity in an attempt to show a possible effect of dolomitization on porosity dolomitization seems to increase the porosity in the early and intermediate stages but tends to reduce porosity in the later or near completion stages of dolomitization this finding coincides with the earlier work of power based on petrographical and petrophysical studies the calculated average porosity of the arab reservoirs is up to 30 which is exceptionally high if the effects of depth of burial between 4000 and 9000 ft and the geological age of about 160 million years upper jurassic are taken into consideration to explain such high porosity values for the arab reservoirs probable geological physical chemical factors such as acidic formation fluids reduced fluid mobility and ion exchange capacity tectonic forces and dolomitization are suggested

evaluation of gas hydrate deposits in an active seep area using marine controlled source electromagnetics results from opouawe bank hikurangi margin new zealand several known gas seep sites along the hikurangi margin off the east coast of new zealand were surveyed by marine controlled source electromagnetic csem experiments a bottom towed electric dipole dipole system was used to reveal the occurrence of gas hydrate and methane related to the seeps the experiments were part of the international multidisciplinary research program new vents carried out on german r v sonne in 2007 cruise so191 to study key parameters controlling the release and transformation of methane from marine cold vents and shallow gas hydrate deposits two csem lines have been surveyed over known seep sites on opouawe bank in the wairarapa region off the se corner of the north island the data have been inverted to sub seafloor apparent resistivity profiles and one dimensional layered models clearly anomalous resistivities are coincident with the location of two gas seep sites north tower and south tower on opouawe bank a layer of concentrated gas hydrate within the uppermost 100 m below the seafloor is likely to cause the anomalous resistivities but free gas and thick carbonate crusts may also play a role seismic data show evidence of fault related venting which may also indicate the distribution of gas hydrates and or authigenic carbonate geochemical profiles indicate an increase of methane flux and the formation of gas hydrate in the shallow sediment section around the seep sites takahe is another seep site in the area where active venting higher heat flow shallow gas hydrate recovered from cores and seismic fault planes but only moderately elevated resistivities have been observed the reasons could be a the gas hydrate concentration is too low even though methane venting is evident b strong temporal or spatial variation of the seep activity and c the thermal anomaly indicates rather temperature driven fluid expulsion that hampers the formation of gas hydrate beneath the vent

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

what do glaciers tell us about climate variability and climate change glaciers respond to long term climate changes and also to the year to year fluctuations inherent in a constant climate differentiating between these factors is critical for the correct interpretation of past glacier fluctuations and for the correct attribution of current changes previous work has established that century scale kilometre scale fluctuations can occur in a constant climate this study asks two further questions of practical significance how likely is an excursion of a given magnitude in a given amount of time and how large a trend in length is statistically significant a linear model permits analytical answers wherein the dependencies on glacier geometry and climate setting can be clearly understood the expressions are validated with a flowline glacier model the likelihood of glacier excursions is well characterized by extreme value statistics although probabilities are acutely sensitive to some poorly known glacier properties conventional statistical tests can be used for establishing the significance of an observed glacier trend however it is important to determine the independent information in the observations which can be effectively estimated from the glacier geometry finally the retreat of glaciers around mount baker washington state usa is consistent with but not independent proof of the regional climate warming that is established from the instrumental record

two dimensional mapping of sea ice keels with airborne electromagnetics airborne electromagnetic aem equipment can be used to sense sea ice thickness by interpreting the aem data to obtain the distance from the towed bird that holds the em system to the ice seawater interface the ice thickness itself is obtained by subtracting from that quantity the distance from the bird to the upper ice surface as determined by a laser altimeter to interpret aem data acquired over sea ice keels we first solve the forward problem using an integral equation approach to the neumann boundary value problem in this approach we assume that sea ice is an insulator and that seawater is a perfect conductor when the ice keel is two dimensional the pertinent equations can be transformed into the wavenumber domain along the strike direction resulting in the rapid numerical computation of the aem response by compiling numerical model results we constructed an interpretation chart that relates the parameters of the observed aem response anomaly to the geometric variables of the ice keel the

formation of magnetite enriched zones in and offshore of a mesotidal estuarine lagoon an environmental magnetic study of tauranga harbour and bay of plenty new zealand 1 magnetic iron minerals are widespread and indicative sediment constituents in estuarine coastal and shelf systems we combine environmental magnetic sedimentological and numerical methods to identify magnetite enriched placer like zones in a complex coastal system and delineate their formation mechanisms magnetic susceptibility and remanence measurements on 245 surficial sediment samples collected in and around tauranga harbour the largest barrier enclosed tidal estuary of new zealand reveal several discrete enrichment zones controlled by local hydrodynamic conditions active magnetite enrichment takes place in tidal channels which feed into two coast parallel nearshore magnetite enriched belts centered at water depths of 6 10 m and 10 20 m a close correlation between magnetite content and magnetic grain size was found where higher susceptibility values are associated within coarser magnetic crystal sizes two key mechanisms for magnetite enrichment are identified first tide induced residual currents primarily enable magnetite enrichment within the estuarine channel network a coast parallel fine sand magnetite enrichment belt in water depths of less than 10 m along the barrier island has a strong decrease in magnetite content away from the southern tidal inlet and is apparently related to active coast parallel transport combined with mobilizing surf zone processes a second less pronounced but more uniform magnetite enrichment belt at 10 20 m water depth is composed of non mobile medium coarse grained relict sands which have been reworked during post glacial sea level transgression we demonstrate the potential of magnetic methods to reveal and differentiate coastal magnetite enrichment patterns and investigate their formative mechanisms

vulcan a deep towed csem receiver we have developed a three axis electric field receiver designed to be towed behind a marine electromagnetic transmitter for the purpose of mapping the electrical resistivity in the upper 1000 m of seafloor geology by careful adjustment of buoyancy and the use of real time monitoring of depth and altitude we are able to deep tow multiple receivers on arrays up to 1200 m long within 50 m of the seafloor thereby obtaining good coupling to geology the rigid body of the receiver is designed to reduce noise associated with lateral motion of flexible antennas during towing and allows the measurement of the vertical electric field component which modeling shows to be particularly sensitive to near seafloor resistivity variations the positions and orientations of the receivers are continuously measured and realistic estimates of positioning errors can be used to build an error model for the data during a test in the san diego trough offshore california inversions of the data were able to fit amplitude and phase of horizontal electric fields at three frequencies on three receivers to about 1 in amplitude and 1 in phase and vertical fields to about 5 in amplitude and 5 in phase the geological target of the tests was a known cold seep and methane vent in 1000 m water depth which inversions show to be associated with a 1 km wide resistor at a depth between 50 and 150 m below seafloor given the high resistivity 30 m and position within the gas hydrate stability field we interpret this to be massive methane hydrate

empirical relation between carbonate porosity and thermal maturity an approach to regional porosity prediction data indicate that porosity loss in subsurface carbonate rocks can be empirically represented by the power function thgr a tti b where thgr is regional porosity tti is lopatin s time temperature index of thermal maturity the exponent b equals approximately 0 372 and the multiplier a is constant for a given data population but varies by an order of magnitude overall implications include the following 1 the decrease of carbonate porosity by burial diagenesis is a maturation process depending exponentially on temperature and linearly on time 2 the exponent b is essentially independent of the rock matrix and may reflect rate limiting processes of diffusive transport 3 the multiplying coefficient a incorporates the net effect on porosity of all depositional and diagenetic parameters within constraints carbonate porosity prediction appears possible on a regional measurement scale as a function of thermal maturity estimation of carbonate porosity at the time of hydrocarbon generation migration or trapping also appears possible

response of the himalayan glacial cycles to multiple equilibrium of climate system a review abstract the astronomical theory of milankovitch supports the waxing and waning of ice sheets and polar glaciers by orbital forcing excluding the fact that small changes in solar radiation flux are difficult to reconcile with the amplitude of glacial cycles the numerical model explaining the 100 kyr problem has now revealed that the phase locking mechanism of orbital forcing has started to modulate the climatic transitions since 1 2 myr back and remained locked till present climatic state rial et al 2013 however the true evidence to confirm it is not present the present study is an attempt to comprehend the concept of synchronization of summer insolation modulation and internal climate forcing responsible for glacial interglacial termination present in and around the himalaya tibet and worldwide we present geographical evidences of glaciations from the himalayan tibet region pointing out that responses i e 18 24 kyr and 60 70 kyr bp glaciation events are similar to the progression in climatic data and glaciations cycles for the last 100 kyr the compelling evidence presents a possible explanation towards synchronized modulation of 100 kyr orbital cycles with 41 kyr obliquity cycles coincidently resulting in unprecedentedly large glaciation around the last glacial cycle 60 70 kyr bp and the last glacial maxima 18 24 kys bp by considering the influence of internal and external factors on glacier mechanism we underline the most probable cause of 41 kyr cycle obliquity as the foremost driver of glaciations in the himalaya and tibet on longer timescales we provide several lines of evidence to establish the possible connection of glaciation events and orbital cycles with the help of geographical and geological records consistent with the fact that resonance might be faded through time but the effect of frequency modulation still persists in the system

gulf of mexico sediment sources and sediment transport trends from magnetic susceptibility measurements of surface samples abstract the magnetic properties from 200 trigger core top and van veen grab sediment samples recovered from throughout the gulf of mexico have been analyzed and used to characterize sediment source and flow pattern distributions magnetic parameters included are anhysteretic remanent magnetism arm and magnetic susceptibility ms measurements results from these measurements are compared to previously determined calcium carbonate percentages and clay and hematite influx trajectories into the gulf of mexico for the same samples reported by balsam and beeson balsam w l and beeson j p 2003 sea floor sediment distribution in the gulf of mexico deep sea res i 50 1421 1444 the arm results give an estimate of magnetic grain size distributions and by analogy grain size distributions in general whereas ms patterns show high detrital sediment accumulation zones within the gulf the dominant influx of modern high susceptibility sediment into the gulf of mexico appears to originate from the red river flow into atchafalaya river basin and out into the gulf from atchafalaya bay with significant additional contributions from the mississippi river through the southwest pass of the mississippi river delta this material then moves across the continental shelf and down through the mississippi canyon into the deep gulf where it is redistributed at depths 3600 m the eastern shelf margins in the gulf offshore from alabama and florida are accumulating calcite or quartz rich medium to fine grained sediment that has a very low or diamagnetic ms signature from the louisiana to texas gulf coast margins ms is moderate to high suggesting a river influx of magnetic constituents from the volcanic fields in new mexico and from igneous and metamorphic sources in the mississippi basin offshore from western mexico the ms is high to moderate but the yucatan shelf margin is characterized by low to diamagnetic ms values due to sediment dominated by calcite sands and oozes a trend that continues to the east onto the west florida shelf additional measurements of samples collected in association with sites characterized by hydrocarbon seepage exhibit anomalously low ms values the samples from the lower shelf and slope areas are typified by iron reduction by bacterial organisms in these samples these results produce anomalous localized lows in the ms trends observed

magnetic mineral and sediment porosity distribution on a storm dominated shelf investigated by benthic electromagnetic profiling bay of plenty new zealand abstract magnetic susceptibility and electric conductivity within the uppermost meter of the seafloor were measured with high resolution along 33 coast normal profiles in the bay of plenty new zealand using the recently developed electromagnetic benthic profiler marum neridis iii these parameters are used to determine magnetic mineral concentration and porosity of mostly volcanoclastic sediments between 2 and 35 m water depth to investigate distribution and formation of magnetic mineral enrichments on a storm dominated shelf in general magnetic mineral concentration susceptibility is inversely correlated to porosity conductivity along profiles susceptibility maxima and conductivity minima were commonly found on bathymetrical elevations such as dune and ripple crests cores and grab samples show the highest degree of enrichment in the uppermost 20 cm of the seafloor complementing petromagnetic analysis indicates a spectrum of feti oxides in the sediment ranging from magnetite and hematite over titanomagnetite tm40 and tm60 to titanohematite likely th80 and th95 three distinct zones of magnetic mineral enrichment could be identified a coast parallel structure with low porosity in recent fine sand between 5 and 20 m water depth a widespread structure with low porosity in older transgressionally reworked coarse sand in up to 30 m water depth and third structure coarse sand with high porosity located mostly below 30 m while the fine sand structure is interpreted as the result of an active process the other two appear to be relics sorting by grain size selective entrainment appears to be the major formation mechanism this study demonstrates how electromagnetic benthic profiling in combination with environmental magnetic laboratory analysis provides reliable highly interpretable data that allow insight into sorting processes within the boundaries of established lithofacies that are difficult to detect using a classical sedimentological approach

glacier thickening and decay analysis from 50 years of glaciological observations performed on glacier d argentiere mont blanc area france numerous glaciological data have been obtained from measurements carried out on glacier d argentiere mont blanc area france since the beginning of the 20th century moreover data on annual mass balance ice flow velocity thickness variation and length fluctuation have been obtained from yearly measurements performed since 1975 this dataset provides an excellent opportunity to analyze the relationships between surface mass balance and dynamic response over time periods during which net mass balance changed from positive to negative following a positive specific net balance period between 1960 and 1981 the ablation zone experienced a large increase in thickness and ice flow velocities conversely the highly negative specific net balance period since 1982 has led to strong thinning deceleration and retreat of the tongue the response of these observed dynamics to surface mass balance is analyzed from ice flux calculations performed on three transverse cross sections our results reveal that the ice fluxes are largely accommodated by ice flow velocities velocity fluctuations are synchronous over the entire area studied in the largest part of the glacier no compressing extending flow change has been observed over the last 30 years and thickness changes are solely driven by surface mass balance changes however on the tongue of the glacier thickness changes do not depend on surface mass balance but are mainly driven by changes in the longitudinal strain rate

mapping the magnetic susceptibility and electric conductivity of marine surficial sediments by benthic em profiling distribution accumulation and diagenesis of surficial sediments in coastal and continental shelf systems follow complex chains of localized processes and form deposits of great spatial variability given the environmental and economic relevance of ocean margins there is growing need for innovative geophysical exploration methods to characterize seafloor sediments by more than acoustic properties a newly conceptualized benthic profiling and data processing approach based on controlled source electromagnetic csem imaging permits to coevally quantify the magnetic susceptibility and the electric conductivity of shallow marine deposits the two physical properties differ fundamentally insofar as magnetic susceptibility mostly assesses solid particle characteristics such as terrigenous or iron mineral content redox state and contamination level while electric conductivity primarily relates to the fluid filled pore space and detects salinity porosity and grain size variations we develop and validate a layered half space inversion algorithm for submarine multifrequency csem with concentric sensor configuration guided by results of modeling we modified a commercial land csem sensor for submarine application which was mounted into a nonconductive and nonmagnetic bottom towed sled this benthic em profiler neridis ii achieves 25 soundings second at 3 4 knots over continuous profiles of up to a hundred kilometers magnetic susceptibility is determined from the 75 hz in phase response 90 signal originates from the top 50 cm while electric conductivity is derived from the 5 khz out of phase quadrature component 90 signal from the top 92 cm exemplary survey data from the north west iberian margin underline the excellent sensitivity functionality and robustness of the system in littoral 0 50 m and neritic 50 300 m environments susceptibility versus porosity crossplots successfully identify known lithofacies units and their transitions all presently available data indicate an eminent potential of csem profiling for assessing the complex distribution of shallow marine surficial sediments and for revealing climatic hydrodynamic diagenetic and anthropogenic factors governing their formation

the briksdalsbre event a winter precipitation induced decadal scale glacial advance in southern norway in the ad 1990s and its implications in the ad 1990s maritime glaciers in scandinavia started to advance as a response to positive net mass balance in the preceding years invoking annual advance rates in the order of 50 60 m and a total frontal advance of 285 m at briksdalsbreen in less than a decade records from six south norwegian glaciers with continuous annual front measurements are used to evaluate the magnitude duration climatic causes and frontal time lags involved in this mass balance perturbation and the following frontal response of glaciers in southern norway a climate index based on meteorological data from bergen unequivocally demonstrates that the main cause for the large glacier advances in scandinavia in the 1990s was high winter precipitation linked to positive nao index in the winters of 1988 1989 1989 1990 1992 1993 1994 1995 1997 1998 and 1999 2000 less positive or negative glacier mass balance years were 1990 1991 1993 1994 1995 1997 and 1998 1999 between 1996 1997 and 2009 briksdalsbreen retreated

occurrence of organic matter rich deposits middle jurassic to lower cretaceous from qalikuh locality zagros basin south west of iran a possible oil shale resource abstract organic rich deposits of qalikuh locality zagros basin southwest of iran are unconventional hydrocarbon resources considered as an oil shale which is hosted within a carbonate succession with the age range of middle jurassic to lower cretaceous leco carbon rock eval vi and modified fischer assay analysis were performed on some outcrop samples of these resources to investigate the occurrence of oil shale in the studied samples mean total organic carbon toc is 17 3 wt and the average of petroleum genetic potential s1 s2 is 98 kg hc t rock furthermore toc has direct relationship with petroleum genetic potential hydrogen index hi tmax diagram indicates that the organic matter corresponds to type ii kerogen of probable marine origin with high quality of oil generation according to rock eval data and bitumen reflectance brr the samples are thermally early mature based on the studied samples oil yield of the qalikuh oil shales ranges from 6 1 to 7 9 wt mean oil gas ratio is 2 7 and mean oil yield is 56 7 l t rock according to the observations the production value of qalikuh oil shale is more or less similar in the entire studied regions whereas the total production is below the expected values the produced oil is considerably lighter higher api than that of most other known oil shales

petroleum system analysis of the northwestern part of the persian gulf iranian sector abstract geochemical geological and geophysical data were used to identify and update genetic oil families potential source rocks and hydrocarbon generation kitchen as well as probable migration pathways in the northwestern part of the persian gulf rock eval analysis was performed on 52 cutting samples of prospective cretaceous tertiary source rocks according to the results most of the samples have poor to fair potential for hydrocarbon generation except for the albian formation which possesses good to excellent source rock characteristics in the study area two genetic oil families were identified based on source and age related biomarkers as well as stable carbon isotope ratios for 23 crude oil samples family i occurs in upper jurassic lower cretaceous reservoirs mainly in the surmeh hith basin whereas family ii occurs in lower cretaceous tertiary reservoirs mainly in the garau gotnia basin all attempts to correlate the identified families to prospective source rocks failed due to substantial maturity differences between the oils and rock samples inversion correlation based on detailed isotopic and biomarker analyses however confirms that the carbonates and marls of the neocomian and albian formations are the main oil generating facies for families i and ii respectively the geographical extension and composition of the identified oil families are highly affected by source rock facies distribution and migration pathways 2d cross sections provided in the region indicate the dominance of lateral and vertical migration pathways from the binak depression as the main hydrocarbon generation kitchen toward the structural highs in the study area

factors controlling porosity in upper carboniferous lower permian carbonate strata of the barents sea a 300 m 1000 ft thick succession of shallow and warm water carbonates has been studied in well cores from the southernmost barents sea offshore north norway these upper paleozoic strata contain numerous zones of moderate to high porosity including a wide range of depositional facies despite moderately high burial temperatures and the absence of petroleum charge most porosity appears to be either primary or created during early eogenetic diagenesis negative correlation between porosity and both bulk rock alumina content and stylolite frequency reflects the influence of phyllosilicate minerals in localizing stylolitic dissolution this provides part of the explanation for the overall correlation between porosity and the platform s stratigraphic evolution the early stage of mixed siliciclastic carbonate deposition has low porosity because of extensive chemical compaction in aluminous beds the following siliciclastic poor stage shows upward increasing porosity associated with aggradation of muddy buildups and wackestones followed by the progradation of a more proximal facies belt of thinly bedded dolomitic mudstones maximum porosity development occurs in the overlying little dolomitized grain shoal facies belt which shows upward decrease in porosity because of a transgressive trend that developed progressively lower energy depositional conditions favoring the occurrence of stylolite prone shaly laminations a general porosity favorable factor is the presence of a stratified column of high salinity brine enforcing a closed diagenetic system during burial limestones and dolostones comprising this platform have very different proportions of low and high porosity values limestones have positively skewed frequency distribution many samples 5 porosity whereas dolostones have higher average porosity with symmetric distribution few samples 5 porosity the low limestone porosities result from cementation by coarse calcite spar in grain dominated samples and matrix compaction and cementation in muddy facies features that are less common in dolostones possibly because of lesser propensity for stylolite development and the resistance of early dolomitized matrix to compaction steve received a ph d from the university of california at los angeles in 1978 he works on sandstone and carbonate petrology sedimentology and stratigraphy

review paper instrumentation for marine magnetotelluric and controlled source electromagnetic sounding we review and describe the electromagnetic transmitters and receivers used to carry out magnetotelluric and controlled source soundings in the marine environment academic studies using marine electromagnetic methods started in the 1970s but during the last decade these methods have been used extensively by the offshore hydrocarbon exploration industry the principal sensors magnetometers and nonpolarizing electrodes are similar to those used on land but magnetotelluric field strengths are not only much smaller on the deep sea floor but also fall off more rapidly with increasing frequency as a result magnetotelluric signals approach the noise floor of electric field and induction coil sensors 0 1 nv m and 0 1 pt at around 1 hz in typical continental shelf environments fluxgate magnetometers have higher noise than induction coils at periods shorter than 500 s but can still be used to collect seafloor magnetotelluric data down to 40 100 s controlled source transmitters using electric dipoles can be towed continuously through the seawater or on the sea bed achieving output currents of 1000 a or more limited by the conductivity of seawater and the power that can be transmitted down the cables used to tow the devices behind a ship the maximum source receiver separation achieved in controlled source soundings depends on both the transmitter dipole moment and on the receiver noise floor and is typically around 10 km in continental shelf exploration environments the position of both receivers and transmitters needs to be navigated using either long baseline or short baseline acoustic ranging while sea floor receivers need additional measurements of orientations from compasses and tiltmeters all equipment has to be packaged to accommodate the high pressure up to 40 mpa and corrosive properties of seawater usually receiver instruments are self contained battery powered and have highly accurate clocks for timekeeping even when towed on the sea floor or in the water column behind a transmitter

origin of dolomite in the arab d reservoir from the ghawar field saudi arabia evidence from petrographic and geochemical constraints a significant proportion of oil production from the kim meridgian arab d strata in the ghawar field saudi arabia originates from dolomitized rocks stratigraphic petrographic and geochemical data suggest that at least four episodes of dolomitization affected these sediments the lower portion of the arab d zone 3 is only partially dolomitized with the dolomite frequently being associated with firm grounds we propose that these dolomites were formed on an outer ramp setting with a maximum water depth of 50 m during a period of nondeposition with the dolomitization process being promoted by the oxidation of organic material and the diffusion of mg 21 from the overlying seawater the dolomites in zone 2b are geochemically dis tinct compared to those in zone 3 in that they have relatively positive oxygen isotope compositions 2 1t o22 compared to 26 5 the relatively positive oxygen isotope composition and the geochemical sim ilarity of zone 2b to the dolomites in zone 1 which are intimately associated with the overlying evaporites has led us to conclude that the zone 2 dolomites probably formed by the reflux of hypersaline fluids through the sediments these hypersaline fluids bypassed zone 2a by moving through the grain dominated sediments early cemen tation and dolomite formation made these units more susceptible to later fracturing that affected the entire arab d formation this frac turing allowed higher temperature fluids to leach the dolostones there by removing any remaining calcite and partially resetting the oxygen isotope composition of some of the dolomites as a result of this later dolomitization event rocks that were only partially dolomitized were leached creating units with extremely high permeability and porosity super k intervals dolomites in the lower zone 3 were recrystallized during burial by the normal geothermal gradient leading to the pre sent negative oxygen isotope values zone 1 dolomites are petrograph ically distinct from zone 2 dolomite in that they are mimetic and fabric preserving although they are geochemically similar this mimetic style of dolomitization occurs immediately adjacent to the overlying anhy drite and is interpreted to have formed very shortly after deposition from hypersaline brines recovery and their presence is inferred from a combination of production data and the diameter of the bore hole as measured using the caliper log as a result of the importance of dolomite in the formation of the super k intervals within the arab d an understanding of the paragenesis of these zones is important not only in predicting super k formation within the arab d but also as an analogue for understanding other dolomitized res ervoirs with high permeability and porosity previous characterization work of dolostones from the arab d in the ghawar field cantrell et al 2004 has identified three types of dolomite with distinctive petrographic stratigraphic and geochemical characteristics fabric preserving non fabric preserving and baroque dolomite fabric pre serving dolomite is very finely crystalline in which petrographic details of the original limestone fabric are usually well preserved fabric preserving dolomite contains low concentrations of fe average 247 ppm fe and relatively positive oxygen isotope values average

the geology of the kuh e dalneshin area of southern iran and its bearing on the evolution of southern tethys the kuh e dalneshin area lay close to the northern margin of the arabian continent during mesozoic and palaeogene times recent mapping has shown that except perhaps in the late cretaceous it was inactive until it collided with central iran in the miocene the collision represented by a neogene melange zone in the ne resulted in the zagros orogeny and is expressed in the shelf sediments by folding parallel faulting and a possible arcuate sinistral shear in the late cretaceous a localized deepening of the shelf dates from the cenomanian a narrow trough in the w subsided to abyssal depths in the turonian following a period of faulting a more wide spread subsidence affected the shelf in the coniacian and santonian autochthonous cherts and associated sediments accumulated basaltic volcanics were erupted in the ne part of this basin and permian to cenomanian neritic exotic blocks were derived presumably from an uplift at the shelf edge the rocks from the outer edge of this basin slid westwards over their autochthonous counterparts probably in the campanian accompanied by further gliding of masses of earlier mesozoic cherts which had previously been emplaced on the continental margin a sheet of mantle peridotite partly serpentinized and enclosing neritic and metamorphic exotics in turn slid into the basin shelf sedimentation was renewed in the late campanian or maestrichtian but the transgression did not reach the area until the eocene the derivation and emplacement of the allochthonous rocks in the late cretaceous are still imperfectly understood alternative models are discussed one involving gliding from an aborted spreading ridge along the continental margin the other more conventionally based on subduction processes a preference is expressed for the former

the impact of climate change on future frontal variations of briksdalsbreen western norway a flowline model coupled with a surface mass balance model forced by climate data from bergen was used to simulate future frontal changes of briksdalsbreen a western outlet glacier from jostedalsbreen western norway under various future climate scenarios the model was used to calculate the time lag of frontal response to a sudden and short change in the mass balance according to the model the front has a time lag for maximum advance rate of 4 5 years in close agreement with previous studies the response time for briksdalsbreen was calculated by running the model for 200 years with different mass balance perturbations for mass balance perturbations of 0 3 and 0 6 m w e the model yields response times of 52 and 60 years respectively we ran the model from 1963 to 2007 with measured mass balance data and from 2007 to 2085 using calculated mass balances from 12 different climate scenarios the model predicts retreat up the steep valley from the lake inlet with a total frontal retreat of 2 5 5 0 km by 2085 a spectacular icefall one of the main tourist attractions in western norway may thus disappear and the glacier may become a plateau glacier that will gradually melt down

committed retreat controls on glacier disequilibrium in a warming climate the widespread retreat of mountain glaciers is a striking emblem of recent climate change yet mass balance observations indicate that many glaciers are out of equilibrium with current climate meaning that observed retreats do not show the full response to warming this is a fundamental consequence of glacier dynamics mountain glaciers typically have multidecadal response timescales and so their response lags centennial scale climate trends a substantial difference between transient and equilibrium glacier length persists throughout the warming period we refer to this length difference as disequilibrium forcing idealized glacier geometries with gradual warming shows that the glacier response timescale fundamentally governs the evolution of disequilibrium comparing a hierarchy of different glacier models suggests that accurate estimates of ice thickness and climatology which control the timescale are more important than higher order ice dynamics for capturing disequilibrium current glacier disequilibrium has previously been estimated for a selection of individual glaciers our idealized modeling shows that sustained disequilibrium is a fundamental response of glacier dynamics and is robust across a range of glacier geometries this implies that many mountain glaciers are committed to additional kilometer scale retreats even without further warming disequilibrium must also be addressed when calibrating glacier models used for climate reconstructions and projections of retreat in response to future warming

global and hemispheric temperature reconstruction from glacier length fluctuations temperature reconstructions for recent centuries provide a historical context for the warming over the twentieth century we reconstruct annual averaged surface temperatures of the past 400 years on hemispherical and global scale from glacier length fluctuations we use the glacier length records of 308 glaciers the reconstruction is a temperature proxy with decadal resolution that is completely independent of other temperature records temperatures are derived from glacier length changes using a linear response equation and an analytical glacier model that is calibrated on numerical model results the global and hemispherical temperatures reconstructed from glacier length fluctuations are in good agreement with the instrumental record of the last century furthermore our results agree with existing multi proxy reconstructions of temperature in the pre instrumental period the temperature record obtained from glacier fluctuations confirms the pronounced warming of the twentieth century giving a global cumulative warming of 0 94 0 31 k over the period 1830 2000 and a cumulative warming of 0 84 0 35 k over the period 1600 2000

facies and sedimentary environment of the permian carbonates khuff formation in the united arab emirates abstract the late permian to early triassic khuff formation of the united arab emirates is a 625 970 m thick sequence of shallow water carbonates dolomites limestones and dolomitic limestones with subordinate anhydrite it can be subdivided into ten facies units distinguished on the basis of their depositional textures that represent an overall regressive carbonate evaporite sequence based on the paleoecology sedimentary structures and lithology four distinct depositional settings can be recognized supratidal sabkha lagoon shoal and shallow shelf the khuff formation has both primary interparticle and secondary dissolution vugs and intercrystalline porosities

dissolution and pyritization of magnetite in anoxie marine sediments concentrations of magnetite were determined with depth in sediments of varying h2s content taken from long island sound foam nwc and sachem sites and from a site in the rapidly depositing subaqueous portion of the mississippi delta for the three long island sound sites dissolution of magnetite during burial is clearly demonstrated and for all four sites the rate of magnetite dissolution is proportional to the concentration of dissolved pore water sulfide by combining magnetite depth distributions with sedimentation rate data and measurements of dissolved sulfide we find that magnetite dissolution is well described by the following rate law dcmagdt 1 1 10 5c0 5bcmagamag where cmag is the concentration of magnetite grams per gram of sediment cs is the concentration of dissolved sulfide mm and amag is the specific surface area of magnetite in the sediment cm2 per gram of magnetite this equation means that for a typical range of magnetite surface areas and dissolved sulfide concentrations the half life of magnetite in anoxic marine sediments ranges from about 50 to 1000 years sem observations of magnetite grains from the different sediment sites reveal that magnetite dissolution may be accompanied by extensive replacement by pyrite this only occurs if magnetite is in contact with high concentrations of h2s 1 mm for relatively long periods of time several hundred years with low concentrations of h2s 1 mm magnetite dissolution occurs without identifiable pyrite replacement we suggest that this feature of magnetite diagenesis may prove to be a useful paleosulfide indicator

conventional versus reference surface mass balance glacier surface mass balance evaluated over the actual glacier geometry depends not only on climatic variations but also on the dynamic adjustment of glacier geometry therefore it has been proposed that reference surface balances calculated over a constant glacier hypsometry are better suited for climatic interpretation here we present a comparison of 82 year modelled time series 1926 2008 of conventional and reference surface balance for 36 swiss glaciers over this time period the investigated glaciers have lost 22 of their area and ice surface elevation close to the current glacier terminus has decreased by 78 m on average conventional balance in the last decade at 0 91 m w e a 1 is 0 14 m w e a 1 less negative than the reference surface balance about half of the negative stabilizing feedback on mass balance due to glacier terminus retreat is compensated by more negative mass balances due to surface lowering short term climatic variability is clearly reflected in the conventional mass balance series however the magnitude of the long term negative trend is underestimated compared to that found in the reference surface balance series both conventional and reference surface specific balances show large spatial variability among the 36 glaciers

holocene evolution of mud depocentres on a high energy low accumulation shelf nw iberia the high energy low accumulation nw iberian shelf features three confined holocene mud depocentres here we show that the evolution of such depocentres follows successive steps the flooding of inner shelf zones and river catchment areas by the late deglacial sea level rise provided the precondition for shelf mud deposition following this the holocene deceleration of the sea level rise caused a rapid refill of the accommodation space within river valleys subsequently the export of major amounts of fines was initiated the initial onset and loci of shelf mud deposition were related to deposition favouring conditions in mid shelf position or to the presence of morphological highs which act as sediment traps by providing protection against stronger hydrodynamic energy the detailed reconstruction of the holocene depocentre evolution shows for the first time that the expansion of such shelf mud deposits cannot only occur by linear growth off the associated sediment source rather they might develop around centres that are fully disconnected from the source of original sediment supply and expand later into specific directions based on these differences and on the connection of the individual mud depocentres to the material source we propose a conceptual subdivision of the group mid shelf mud depocentres

present day sedimentary processes on the northern iberian shelf abstract the galicia minho shelf features two large mud patches the douro and the galicia mud patches these are recent sediment bodies that have accumulated under a combination of conditions including 1 abundant supplies of sediment 2 morphological barriers that act as sediment traps and 3 hydrographic conditions that favour the accumulation of fine sediment in these sinks this paper describes the mechanisms controlling the deposition of the fine grained sediment depositions and the processes that result in resuspension processes on the galicia minho shelf fine grained sediments are provided from discharges from the river basins on the southern sector of the shelf mainly the douro and minho rivers sediments are exported from river estuaries onto the shelf during episodic flood events in contrast most of the sediments originating from the galician hinterland fail to contribute significantly to sedimentation on the shelf because they are retained in the galician rias which function as sediment traps sediments deposited on the shelf are frequently remobilized particularly during southwesterly storms that coincide with downwelling conditions once in suspension the fine grained sediments are transported northwards by the poleward flowing bottom currents and are eventually deposited on the douro and galicia mud patches after a series of resuspension events the locations of the two mud patches are strongly influenced by the shelf morphology fines already deposited on the mud patches are occasionally reintroduced into the system by large storm events some material from the douro mud patch and adjacent areas is re deposited in the galicia mud patch it is probable that sediments re suspended from the galicia mud patch are carried off the shelf when storm events coincide with downwelling conditions

on the theory of sea floor conductivity mapping using transient electromagnetic systems the electrical conductivity of the sea floor is usually much less than that of the seawater above it a theoretical study of the transient step on responses of some common controlled source electromagnetic systems to adjoining conductive half spaces shows that two systems the horizontal in line electric dipole dipole and horizontal coaxial magnetic dipole dipole are capable of accurately measuring the relatively low conductivity of the sea floor in the presence of seawater for these systems the position in time of the initial transient is indicative of the conductivity of the sea floor while at distinctly later times a second characteristic of the transient is a measure of the seawater conductivity the diagnostic separation in time between the two parts of the transient response does not occur for many other systems including several systems commonly used for exploration on land a change in the conductivity of the sea floor produces a minor perturbation in what is essentially a seawater response some transient responses which could be observed with a practical deep towed coaxial magnetic dipole dipole system located near the sea floor are those for the half space the layer over a conductive or resistive basement and the half space with an intermediate resistive zone the system response to two adjoining half spaces representing seawater and sea floor respectively is derived analytically the solution is valid for all time provided the conductivity ratio is greater than about ten or less than about one tenth the analytic theory confirms the validity of numerical evaluations of closed form solutions to these layered earth models a lateral conductor such as a vertical infinite conductive dike outcropping at the sea floor delays the arrival of the initial crustal transient response the delay varies linearly with the conductance of the dike this suggests that time delay could be inverted directly to give a measure of the anomalous integrated conductance of the sea floor both between and in the vicinity of the transmitter and the receiver dipoles

the relationship between petroleum emplacement and carbonate reservoir quality examples from abu dhabi and the amu darya basin abstract the relative importance of petroleum emplacement in inhibiting diagenetic processes and preserving porosity and permeability in lower cretaceous thamama group kharaib formation carbonate reservoirs of abu dhabi uae and in callovian kimmeridgian carbonate reservoirs of the amu darya basin in uzbekistan and turkmenistan has been evaluated by combining geologic petrophysical and geochemical data when petroleum emplacement is synchronous with and prior to significant burial cementation in carbonates primary petroleum inclusions are trapped in the cements the process appears to be characterised by steep intra field porosity depth trends within a more gradual regional decline in porosity with depth this has profound implications for the prediction of porosity in carbonate reservoirs reservoir quality is better in grainstones and packstones compared to adjacent wackestones and lime mudstones in the kharaib formation because of preserved macroporosity intergranular vuggy mouldic the pore system in the finer units is dominated by micropores these features indicate a primary textural control on porosity and permeability within the grainstones and packstones macroporosity is variably filled by late equant sparry calcite cements porosity and permeability variations in grainstones and packstones at a reservoir scale are therefore controlled by the variation in amount of equant sparry calcite cement this in turn depends on the timing of the precipitation of this cement relative to petroleum emplacement as shown by fluid inclusion data where petroleum emplacement has occurred relatively early at migration foci prior to significant burial cementation by equant sparry calcite reservoir quality is preserved where it has occurred after significant burial cementation reservoir quality has been destroyed in the amu darya sequences primary macroporosity is commonly preserved down to depths of 11 000 ft 3 5 km with differences in the porosity and permeability characteristics of grainstones being controlled by variations in the amount of early probably freshwater cement and the extent of associated dissolution small volumes of burial cements do occur but they do not contain petroleum inclusions consequently there is no firm evidence that petroleum emplacement has inhibited diagenesis in this area this part of the study has shown that it is not always possible to obtain conclusive evidence from the diagenesis to pin down the processes responsible for the preservation of reservoir quality and that petroleum filling may not always be the primary cause the relationships documented here show that the race for space between diagenetic waters and petroleum is a major control on reservoir quality in the thamama group carbonate reservoirs but is not so important for the jurassic carbonates in the amu darya basin