testing the reliability of discrimination diagrams for determining the tectonic depositional environment of ancient sedimentary basins the lower palaeozoic rocks of the west of ireland caledonides provide a novel way to test the reliability of discrimination diagrams in sedimentary rocks a comparison between the geochemical signature of the tuff bands and the signature from the adjacent sedimentary rocks reveals that a combination of multi element diagrams and discrimination diagrams is best suited to identify the tectonic environment of deposition the tuff bands from the ordovician and silurian formations all carry an active continental margin signature only three of the sedimentary discrimination diagrams assigned more than 50 of the samples to this setting the results from the discrimination diagrams indicate an active margin setting for the ordovician mweelrea and rosroe formations and the silurian formations whilst the derrylea and sheeffry sedimentary samples have a passive margin signature overall the results show that in the case where felsic volcanism occurred on a quartz rich source region the active continental margin field on many established discrimination diagrams is not reliable in identifying this setting however the study highlights one of the key strengths of discrimination diagrams in their ability to be used as a lever to reveal significant information about the sediment source as in this case to identify sediment that has been transported from different tectonic settings and deposited in one sedimentary basin

sedimentological features of sabellaria spinulosa biocontructions abstract sedentary polychaete sabellaria spinulosa leukhart 1849 is a suspension feeder that builds tubes by cementing together terrigenous particles under a set of environmental conditions s spinulosa can form reefs consisting of hundreds or thousands of worm tubes that can vary greatly in thickness size and patchiness the more developed reefs form in areas with a large and continuous supply of sand turbulent water nutrient availability and rocky seafloor recently for the first time in the mediterranean area a large reef of s spinulosa has been discovered along the northern gargano coast at torre mileto adriatic sea southern italy in this paper we will detail the main sedimentological data of this worm reef in order to evaluate the kind of terrigenous particles involved in the worm tube constructions detailed grain size and petrographic analyses were carried out on both reef and soft sediment substrate samples it is demonstrated that s spinulosa selects sands on the basis of their grain size and shape and not their composition it is also shown that some seasonal variations of these parameters are the result of the interplay between reef growth and degradation periods mainly related to physical processes in particular the degradation stages seem to be induced mainly by storm wave action while the reef growth is the result of the complex interaction between ecological and physical processes

a geomorphological investigation of the formation and evolution of the kaiafas sand dune field kyparissiakos gulf ionian sea eastern mediterranean in the late holocene the present investigation concerns the formation and evolution of the dune field of the central part of the kyparissiakos gulf western coast of peloponnesos greece this dune field is associated with the kaiafas lagoon and consists of four dune lines that lie at distances of 600 200 100 and 70 m from the coastline the dune field has developed on top of a barrier beach that formed subsequently to the completion of the last phase of rapid sea level rise i e after 6 000 bp consisting mostly of medium sand with good sorting due to its aeolian formation assuming a steady wind regime and adequate sediment availability during the late holocene a period of approximately 1 350 years has been estimated to be the minimum time required for the formation of the dune field this formation period may also include intervals when the development processes were more or less intensive on the basis of radio carbon dating secondary fluctuations of air temperature and published information it is proposed that the 4th oldest dune line started forming between the years 400 ad and 1 000 ad whilst the 1st youngest dune line started forming after 1 520 ad the dune field especially its youngest line seems to be in equilibrium with its adjacent beach zone and the nearshore hydrodynamics being beyond the reach of wave run up on the other hand the dune field over the past decades has been subjected to intense human intervention agriculture construction forest fires etc that has locally destroyed and or destabilised part of the dunes finally the expected sea level rise due to global warming is undoubtedly a threat to the existence of the dune field

geomorphology and preservation potential of coastal and submerged aeolianite examples from kwazulu natal south africa abstract the distribution and geomorphology of aeolianite outcrop on the coast of kwazulu natal south africa are described in the context of its preservation potential in the geological record aeolianite on the contemporary coast comprises discontinuous widely spaced outcrops less than 100 m in longshore extent and typically 50 60 m wide that reflects the combined action of subaerial weathering and physical abrasion in the coastal zone since the mid holocene approximately 7000 yrs the dominant morphological component is an intertidal erosional platform that slopes gently landward it is fronted by a notch in the mid intertidal zone 0 m msl and contains active erosional potholes on its seaward margin the platform surface is encrusted by a variety of marine organisms landward of and contiguous with the intertidal surface are small elevated outcrops of aeolianite in the supratidal zone these comprise a 3 m high seaward scarp with a basal notch in the high intertidal zone 1 m msl gullies in the scarp trap coarse clasts of eroded aeolianite as well as bedrock the upper surface of the supratidal aeolianite is planar with large potholes within which accumulations of coarse clasts and oyster shells have been cemented the upper surface is interpreted as a remnant of an intertidal platform formed at a higher mid holocene sea level the supratidal outcrop is subject to weathering and disintegration major joints divide the outcrop into cuboid blocks with axes of 3 4 m eroded blocks on the seaward face that exceed 1 m diameter remain in situ and become locked in place by repeated shaking smaller blocks that collapse from the seaward face accumulate in small gullies or are dispersed the facet most likely to be preserved in the geological record is the planar intertidal platform the morphology of aeolianite on the contemporary coast is markedly different from submerged aeolianite ridges on the adjacent shelf which are of higher relief wider and more laterally extensive preservation potential of aeolianite under subaerial conditions is low and the widespread high relief aeolianite on the shelf is attributed to rapid inundation or burial during transgression

pore fluid effects on seismic velocity in anisotropic rocks a simple new technique predicts the high and low frequency saturated velocities in anisotropic rocks entirely in terms of measurable dry rock properties without the need for idealized crack geometries measurements of dry velocity versus pressure and porosity versus pressure contain all of the necessary information for predicting the frequency dependent effects of fluid saturation furthermore these measurements automatically incorporate all pore interaction so there is no limitation to low crack density the velocities are found to depend on five key interrelated variables frequency the distribution of compliant crack like porosity the intrinsic or noncrack anisotropy fluid viscosity and compressibility and effective pressure the sensitivity of velocities to saturation is generally greater at high frequencies than low frequencies the magnitude of the differences from dry to saturated and from low frequency to high frequency is determined by the compliant or crack like porosity predictions of s

laboratory measurements of elastic properties of carbonate rocks during injection of reactive co2 saturated water 1 to investigate the coupled physical and chemical effects of injecting co2 rich water into carbonate rock samples we monitor the elastic and transport properties of six carbonate rocks along with the calcium content and ph of the pore fluid under constant confining pressure carbonate samples range from calcite limestones containing dolomite to pure calcite mudstones which allow us to study how mineral composition and microstructure affect the magnitude of the observed changes the elastic properties of both the saturated and dry rock i e rock frame show a gradual loss of sstrength upon injection as testified by the continuous decrease in the dry p and s wave velocity and by proxy the bulk and shear moduli the magnitude of the observed changes in the elastic properties varies among the samples with a maximum relative change of 24 7 871 m s and 21 2 443 m s in p and s wave velocities respectively the decrease is also accompanied by a relative increase in permeability up to 495 and porosity up to 19 the observed changes likely derive from a change in microstructure which is monitored over time via scanning electron microscopy the variation in porosity results from two competing and interdependent processes the chemical dissolution of calcite and the resulting mechanical compaction under pressure the results of this study show that upon injection of fluids that are in chemical disequilibrium with the hosting rock the variation of the elastic properties cannot be described by existing rock physics models

adjustment of a drainage network to capture induced base level change an example from the sorbas basin se spain abstract quaternary catchments in the south of the sorbas basin se spain have been affected by two regionally significant river captures the river captures were triggered by changes in regional gradients associated with sustained quaternary uplift in the region of 160 m ma 1 the first capture occurred in the early pleistocene and re routed 15 of the original sorbas basin drainage into the carboneras basin to the south the second occurred in the late pleistocene and re routed 73 of the original sorbas basin drainage to the east this latter capture had dramatic consequences for base level in the sorbas basin master drainage local base level was lowered by 90 m at the capture site 50 m at 7 km upstream and 25 m at 13 km upstream of the site the base level change instigated a complex re organisation of the drainage networks in systems tributary to the master drainage over the ensuing period some 100 ka after the capture drainage systems closer to the capture site experienced a tenfold increase in incision rates over most of their network those located some 13 km upstream of the capture site experienced a fivefold increase in incision although in this instance the changes do not appear to have propagated to the headwater regions of the drainage nets the sensitivity of individual catchments was largely governed by geological controls structure and lithology the detailed network evolution in the most sensitive areas can be traced by reconstructing former drainage pathways using abandoned drainage cols and the alignment and degree of incision of the drainage networks three main stages of evolution can be identified which record the progressive spread of base level changes from the master drainage these are stage 1 pre capture original south to north consequent drainage stage 2 early stage post capture aggressive subsequent southwest to northeast and east west drainage developed along structural lineaments first in the east of the area stage 2a and later in the west of the area stage 2b and stage 3 late stage post capture obsequent drainage developing on the topography of the stage 2 drainage all stages of the network evolution are associated with drainage re routing as a function of river capture at a variety of scales the results highlight the complex response of the fluvial system and the very different geomorphological histories of adjacent catchments emphasising the need for regional approaches for examining long term changes in fluvial systems

geochemical evolution of oligocene middle miocene sediments in the deep water area of the pearl river mouth basin northern south china sea abstract the deep water area of the pearl river mouth basin in the south china sea has received much scientific attention since the ocean drilling program odp leg 184 in 1999 due to its potential economic prospects and distinct tectono sedimentary evolutionary processes in this study we present the composition of major and trace elements from two newly sampled deep water boreholes by6 and lw3 in the baiyun sag of the southern pearl river mouth basin the geochemical evolution in the oligocene middle miocene as well as potential controlling factors are investigated based on a comparative study with previous data from odp site 1148 and borehole py33 the chemical index of alteration cia and a cn k plot reveal that the observed weathering trends are not compatible for the four discussed boreholes sedimentary sorting is primarily observed in borehole py33 where data trend away from the a apex to the feldspar join in the a cn k plot and show a spread of al 2 o 3 sio 2 and nb zr ratios compared to chemical weathering and hydrodynamic sorting provenance has a greater impact on sediment composition of the deep water area from the north the pearl river was the primary sediment supply however a positive eu anomaly and the provenance discrimination diagrams i e la th versus th yb and zr co versus th co reveal the mafic nature of borehole by6 sediments in the zhuhai lower zhujiang 32 0 18 5 ma and upper hanjiang 13 8 10 5 ma formations these compositions are unusual and differ from the well defined felsic sources in the majority of the baiyun sag these discrepancies are likely related to multistage magmatism the sediments at site 1148 are characterized by slightly enriched heavy rare earth elements and relatively high zr co ratios which could possibly be caused by zircon enrichment from local sources

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

holocene evolution and sea level changes in the battaglia basin area eastern gargano coast apulia italy abstract the battaglia basin east gargano southern italy is a former waterbody represented as a lake on historical maps the detailed study of two cores bat1 and bat2 and additional information obtained from several other drill holes allowed reconstruction of the holocene evolution of the basin the earlier phases date back to before 7000 cal bp when a high energy beach developed around 6900 cal bp a shallow freshwater body was established before 5950 cal bp sea water flooded the area initially creating a sheltered bay followed by the hydrobiidae and abra segmentum lagoon around 2700 cal bp freshwater conditions were re established the battaglia basin phase lasted until recent times paleoenvironmental information in combination with 14c dating made possible the reconstruction of a local holocene relative sea level curve showing a continuous rise interrupted around 2730 yr bp by an abrupt drop after that sea level started again to rise this evolutionary pattern rise fast drop rise matches results obtained in other apulian areas although it has not been ascertained that the holocene battaglia evolution has been driven by tectonic movements considering the historical gargano activity the tectonic hypothesis looks reasonable

geochemical signature of provenance tectonics and chemical weathering in the quaternary flood plain sediments of the hindon river gangetic plain india abstract the ganga basin in the himalayan foreland is a part of the world s largest area of modern alluvial sedimentation flood plain sediments of the hindon river of the gangetic plain have been analyzed for sediment texture major and trace elements including rare earth elements rees the results have been used to characterize the source rock composition and to understand the intensity of chemical weathering tectonics and their interplay in the hindon flood plain the sediments of the hindon flood plain dominantly consist of sand sized particles with little silt and clay the geochemistry of the hindon sediments has been compared to the siwalik mudstone of the siwalik group siwaliks the siwalik sedimentary rocks like sandstones mudstones and conglomerates are the known source rocks for the hindon flood plain sediments mudstone geochemistry has been considered best to represent the source rock characteristics the ucc upper continental crust normalized major and trace elements of the hindon flood plain sediments are very similar to the siwalik mudstone except for th and cr furthermore the average chondrite normalized ree pattern of the hindon flood plain sediments is similar to the siwalik mudstone textural immaturity k rb ratios and the average cia chemical index of alteration and pia plagioclase index of alteration values of the hindon flood plain sediments indicate that the sediments have not been affected by chemical weathering our study suggests that the active tectonics of the himalayas and monsoon climate enhances only physical erosion of the source rocks siwaliks rather than the chemical alteration these factors help the hindon sediments to retain their parental and tectonic signature even after recycling

geochemistry of archean shales from the pilbara supergroup western australia archean clastic sedimentary rocks are well exposed in the pilbara block of western australia shales from turbidites in the gorge creek group ca 3 4 ae and shales from the whim creek group ca 2 7 ae have been examined the gorge creek group samples characterized by muscovite quartzchlorite mineralogy are enriched in incompatible elements k th u lree by factors of about two when compared to younger archean shales from the yilgarn block alkali and alkaline earth elements are depleted in a systematic fashion according to size when compared with an estimate of archean upper crust abundances this depletion is less notable in the whim creek group such a pattern indicates the source of these rocks underwent a rather severe episode of weathering the gorge creek group also has fairly high b content 85 29 ppm which may indicate normal marine conditions during deposition rare earth element ree patterns for the pilbara samples are characterized by light ree enrichment lanybn 7 5 and no or very slight eu depletion eueu 0 82 0 99 a source comprised of about 80 felsic igneous rocks without large negative eu anomalies felsic volcanics tonalites trondhjemites and 20 mafic ultramafic volcanics is indicated by the trace element data very high abundances of cr and ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for

onshore geologic storage of co2 the possibility that substantial quantities of co2 can be injected into subsurface porous rock formations has been investigated sufficiently to show that pore space available to contain the co2 is abundant multiple rock types and physical mechanisms can be used to trap the co2 indefinitely with careful site selection and operations leakage to the near surface region can be avoided the next step is to test these injection processes at the scale of a large power plant

geomorphology of soft clastic rock coasts in the mid western adriatic sea abruzzo italy abstract we present the first detailed overall study on the rock coasts in the central adriatic sea abruzzo italy which is one of the few cases of a coast with clastic soft rocks in the entire mediterranean area the coast is composed of cliffs with small beaches coastal slopes with or without a contiguous coastal plain and intervening low lying coasts it is developed on the eastern seaward side of a wide plateau and mesa landscape shaped on an early middle pleistocene clay sand sandstone conglomerate marine sequence covered by late pleistocene holocene continental deposits the study focuses on the overall coast and on eight specific sites combining i dem 2 m cell lidar derived analysis and geological geomorphological surveys of the emerged and submerged areas for the cliff coastal slope characterization ii the results of u th 14c sediment dating and archaeological and palaeontological attributions for constraining the coastal evolution and iii aerial photo time series 1954 2013 time span analysis for the recent cliff retreat assessment the overall features of the cliffs and coastal slopes were defined in terms of their morphology lithology tectonic setting landforms and geomorphological processes whereas the analysis of late pleistocene holocene continental deposits and landform distribution defined and constrained the evolution of the coastal system this enabled us to define eight different types of coastal cliffs slopes meaningful for clastic soft rock coasts the coastal types were defined in terms of i lithology 15 cliffs on marine sandstone 15 cliffs on marine conglomerate 3 cliffs on continental deposits 43 coastal slopes on clay sand sandstone conglomerate sequences ii morphostructural setting i e clay sandstone conglomerate interface elevation and iii of state of activity 3 8 active cliffs 13 8 inactive cliffs 15 9 palaeocliffs 43 of inactive and locally reactivated landslides on coastal slopes variable retreat rates were also defined from retreat measurements over a 60 year time span ranging from 0 15 m yr to 1 m yr and were found to be induced by episodic and localized cliff recession processes and connected to combined wave cut and gravity induced slope processes the assessment of coastal and gravity induced geomorphological processes combined with the analysis and dating of the continental deposits allowed us to define the late pleistocene to present evolution and timing and the evolutionary mechanisms of the main coastal types of soft rock coasts they are connected to wave cut and gravity induced erosion cycles on cliffs and to large rotational ancient landsliding with local recent reactivations on coastal slopes for the different coastal types the expected hazard conditions were outlined

frequency dependent anisotropy due to meso scale fractures in the presence of equant porosity fractured rock is often modelled under the assumption of perfect fluid pressure equalization between the fractures and equant porosity this is consistent with laboratory estimates of the characteristic squirt flow frequency however these laboratory measurements are carried out on rock samples which do not contain large fractures we consider coupled fluid motion on two scales the grain scale which controls behaviour in laboratory experiments and the fracture scale our approach reproduces generally accepted results in the low and high frequency limits even under the assumption of a high squirt flow frequency we find that frequency dependent anisotropy can occur in the seismic frequency band when larger fractures are present shear wave splitting becomes dependent on frequency with the size of the fractures playing a controlling role in the relationship strong anisotropic attenuation can occur in the seismic frequency band the magnitude of the frequency dependence is influenced strongly by the extent of equant porosity with these results it becomes possible in principle to distinguish between fracture and microcrack induced anisotropy or more ambitiously to measure a characteristic fracture length from seismic data

effective medium modeling of gas hydrate filled fractures using the sonic log in the krishna godavari basin offshore eastern india 1 indian national gas hydrate program expedition 01 has established that clay rich marine sediment from the krishna godavari kg basin in the eastern indian margin hosts one of the richest gas hydrate deposits in the world resistivity at bit images and pressure cores reveal that the gas hydrate morphology in clay rich sediment varies from complex vein structures grain displacing to invisible pore filling existing rock physics models which relate acoustic data to in situ gas hydrate concentrations generally assume isotropic pore filling gas hydrate which yields misleading concentration estimates for fractured fine grained sediments the anisotropic kg basin sediment presents additional complications here we apply differential effective medium theory to incorporate grain displacing morphologies by which gas hydrate is included as vertical ellipsoids with aspect ratios ranging from those of thin veins up to those of nodules in an elastic anisotropic background we have estimated gas hydrate concentrations from sonic velocities at hole 10d in the kg basin considering three basic gas hydrate morphologies i pore filling ii grain displacing and iii a combination of grain displacing and pore filling average gas hydrate saturations for these three cases are 35 42 27 30 and 33 41 of the total porosity respectively in the depth range 60 140 m below seafloor mbsf saturation is highest at 67 mbsf for any morphology but the values differ between morphologies for the pore filling morphology the maximum gas hydrate saturation of 56 is 18 22 higher than the grain displacing morphology and 2 9 higher than the combined morphology estimates differ by 6 of the sediment volume with rotations of gas hydrate veins from vertical to horizontal

the coastal archives of the last 15 ka in the atlantic mediterranean spanish linkage area sea level and climate changes sea level and climate changes archived in various coastal environments during the last part of the last glacial and present interglacial periods are investigated by interpolating available geomorphology sedimentology palaeontology and geochronology data the coastal response to these changes depended on the environment and geographic location changes of sea level during the rising transgressive phase are well recorded in the sedimentary filling of the estuaries whereas during the phase of highstand they are best recorded in beach barrier environments the postglacial rise of sea level took place in two phases a rapid rise until 6500 cal bp and a second phase of near stability with minor oscillations of metric magnitude regarding climate changes there is no record of changing temperatures in the coastal zones of southern spain although there is in precipitation and wind intensity velocity after 7 5 cal ka bp the general climatic trend towards aridity was punctuated by several short lived centennial episodes of increased aridity that occurred with a millennial cycle often coincident with bond cool events and in some cases with decreases of sea surface temperatures the absence of human intervention in vegetation composition until 2000 bp suggests that most environmental coastal shifts were climatically driven

ree geochemistry of recent clastic sediments from the kaveri floodplains southern india implication to source area weathering and sedimentary processes abstract the kaveri river drains through archean gneissic and charnockitic terranes in south india the rare earth element ree chemistry of the floodplain sediments along with their major and trace element composition in different size fractions are discussed we observe a strong coherence between ree and tio2 contents in the sediments which is suggestive of strong control by titanite or its weathered products on the ree chemistry ree concentrations also show a general increase with decreasing size of bulk sediments different size fractions and of light and heavy mineral fractions this suggests the presence of ree in the fe oxy hydroxide surface coatings on clastic grains formed by the weathering of hornblende and titanite in the granodioritic to dioritic protoliths we also interpret the data as showing that ree patterns of clastic sediments notably eu anomaly are affected by the degree of source rock weathering as well as by the fluvial processes of sorting and mineral differentiation therefore for provenance study sediments having all granulometric grades such as the floodplain sediments are preferable because they most closely represent the source particularly when the source region suffered little chemical weathering in the present case the sediments were derived from the high standing hills of archean charnockites because of their recent uplift and physical denudation

an effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate bearing sediments the presence of gas hydrate in marine sediments alters their physical properties in some circumstances gas hydrate may cement sediment grains together and dramatically increase the seismic p and s wave velocities of the composite medium hydrate may also form a load bearing structure within the sediment microstructure but with different seismic wave attenuation characteristics changing the attenuation behaviour of the composite here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate bearing sediments the velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure the attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures we relate velocity and attenuation increases in hydrate bearing sediments to their hydrate content using an effective medium inversion algorithm based on the self consistent approximation sca differential effective medium dem theory and biot and squirt flow mechanisms of fluid flow the inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space we applied our algorithm to a data set from the mallik 2l 38 well mackenzie delta canada and to data from laboratory measurements on gas rich and water saturated sand samples predictions using our algorithm match the borehole data and water saturated laboratory data if the proportion of hydrate contributing to the load bearing structure increases with hydrate saturation the predictions match the gas rich laboratory data if that proportion decreases with hydrate saturation we attribute this difference to differences in hydrate formation mechanisms between the two environments

fluid substitution effects on seismic anisotropy we derive equations for hti and orthorhombic symmetries to analyze fluid substitution effects in porous fractured media the derivations are based on the anisotropic gassmann equation and linear slip theory we assess the influence of fluid substitution gas brine and oil on elastic moduli velocities anisotropy and azimuthal amplitude variations we find that in the direction normal to fractures p wave moduli increase as much as 56 and p wave velocity increases up to 19 for gas to brine substitution for the direction parallel to fractures p wave velocity remains almost constant when porosity is low 5 but can increase up to 4 if porosity is high 25 since p waves in two different directions have different sensitivities to fluids and fractures the thomsen s parameters defined for hti and orthorhombic symmetries and are sensitive to fluid types and fractures we also found that is sensitive to porosity for liquid saturation but insensitive to porosity for the case of gas saturation gassmann assumes and as has been observed that shear modulus does not depend on fluids and we observe no changes in shear wave splitting for different fluids the azimuthal amplitude variation is dependent on fluid types fractures and porosity we observe up to 12 increase in azimuthal amplitude variation for low porosity gas sands after brine saturation and 6 decrease for high porosity gas sands we find that the percentage changes in gas to oil substitution are about half that of the gas to brine case the equations we have derived provide a useful tool to quantitatively evaluate the effects of fluid substitution on seismic anisotropy

2d multifractal analysis and porosity scaling estimation in lower cretaceous carbonates abstractthe study of scaling porosity in carbonate rocks has great importance because 1 porosity measurements are usually made at scales that are different from the one of interest and 2 carbonate formations contain most of the hydrocarbon reservoirs and aquifers in the world despite these facts scaling porosity in heterogeneous media such as carbonate rocks is still an open problem the heterogeneity of carbonate rocks mainly resides in their complex texture we have extended previous studies on carbonate multifractal behavior in pore space morphology at different scales and we have developed a new equation based in fractal geometry that could be used to scale the porosity in our methodology we 1 perform a multifractal analysis in thin section images of a set of complex carbonate rocks from the lower cretaceous 2 review the effect of magnification in scanning electronic microscope and thin section images 3 deduce a new scaling equation for porosity and finally 4 evaluate this equati

anisotropic effective medium modeling of the elastic properties of shales shales are complex porous materials normally consisting of percolating and interpenetrating fluid and solid phases the solid phase is generally comprised of several mineral components and forms an intricate and anisotropic microstructure the shape orientation and connection of the two phases control the anisotropic elastic properties of the composite solid we develop a theoretical framework that allows us to predict the effective elastic properties of shales its usefulness is demonstrated with numerical modeling and by comparison with established ultrasonic laboratory experiments the theory is based on a combination of anisotropic formulations of the self consistent sca and differential effective medium dem approximations this combination guarantees that both the fluid and solid phases percolate at all porosities our modeling of the elastic properties of shales proceeds in four steps first we consider the case of an aligned biconnected clay fluid composite composed of ellipsoidal inclusion

holocene aeolian morphogenetic phases in southern italy problems in 14c age determinations using terrestrial gastropods abstract radiocarbon age determination is one of the most important methods for dating holocene events in particular it has been used to reconstruct the sequence of aeolian morphogenetic phases along the apulia and basilicata coasts southern italy in these areas three main holocene morphogenetic phases have been recognized using radiocarbon data obtained from sub fossil terrestrial gastropods archaeological data and osl analyses those of the middle holocene period of the greek roman time and of the middle ages sub fossil terrestrial gastropods have been considered suitable indicators in the detecting holocene climate environmental changes however it is well known that they could show problems as chronological indicators mainly due to aging effects induced by i micro particles of calcite aragonite in the shell structure derived from the local substratum and ii a variation of co 2 content in the plants eaten in order to verify these hypotheses living terrestrial gastropods were collected from coastal areas and analysed using ams the results indicate that many living gastropods gave ages of 1500 years older than those expected thus confirming the aging effect as 14 c ages of middle and late holocene aeolian morphogenetic phases obtained from terrestrial gastropods seem to be confirmed by archaeological data and osl analyses the aim of this work is to verify if the age anomalies obtained from modern gastropods could be extended to the entire holocene period

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

the palaeoenvironmental study of the alimini piccolo lake enables a reconstruction of holocene sea level changes in southeast italy based on multiproxy investigations of a 250 cm long sediment core ali1 a reconstruction of palaeoenvironmental dynamics for the alimini piccolo lake south adriatic coast of apulia italy is proposed our results indicate that shortly before 5500 cal yr bp a marsh environment established from 5400 cal bp the marsh progressively became a lagoon and did not change until 3320 cal bp when alimini piccolo evolved into a shallow sheltered freshwater basin around 1400 cal yr bp the basin became again a lagoon changes of the deposition environments and the chronological framework defined in the ali1 sequence allowed speculation about local relative sea level motions through the mid late holocene using proxy data molluscs foraminifers ostracods and plant macro remains as environment and bathymetry indicators we reconstruct the elevation of the basin bottom above or below sea level through time plant macro fossils have proved to be an especially reliable source of data for sea level reconstr

active intraplate deformation in south india abstract two characteristics of the indian plate are the intraplate deformation of the oceanic crust to the south of bay of bengal and the ongoing uplift of the continental crust in the southern indian peninsula an irregular line connecting mulki on the west coast and pulicat lake on the east coast close to 13 n constitutes a major drainage divide several large rivers of south india diverge from this line this nearly east west trending ridge is characterised by gravity high relatively thinner crust and microseismicity the shoreline at either ends is convex towards sea the coastal region particularly in the west is highly dissected the coastal zone consists of series of beach ridges and swales indicating uplift of land a close scrutiny of the river channels indicates that the rivers south of the major water divide have successively shifted southward leaving behind paleochannels on the quaternary terrain there is similar migration of streams to the north shifting northward even in areas where the gradient is low the rivers have elevated terraces resulting from valley deepending the tide gauge records for mangalore and madras show a relative fall in sea level occurrence of a dead oyster colony above the intertidal zone substantiates the tide gauge data these observations indicate that the continental crust close to mulki pulicat lake axis is undergoing compression and uplift related to the north south oriented regional stress field

holocene coastal dune development and environmental changes in apulia southern italy abstract the coastal area of southern apulia is characterised by marine deposits of pleistocene and holocene ages it shows the effects of different phases of coastal morphology evolution during the middle and upper pleistocene a number of marine terraces were shaped in some places they are characterised by thin beach deposits along with a dune belt and relative back dune deposits two important morphogenetic phases occurred during the holocene the former was characterised by deposition of beach deposits placed slightly above present mean sea level and by formation of dune belts which were radiometrically aged about 6000 years bp this event marks the end of the rapid postglacial transgression that occurred during the holocene climatic optimum during the younger phase dated at about 2500 years bp deposition of aeolian sands occurred archaeological and morphological evidences suggest that this phase should be related to a low sea level stand followed by a slow sea level rise up to the present position and by humid temperate climatic conditions the collected data about the holocene dune belts occurring along the apulian coastline suggest that main phases of dune development could be related to the effects of sea level changes climatic conditions and in a subordinate way to human activity

t matrix approach to shale acoustics summary the t matrix approach of quantum scattering theory is used here to place many long wavelength equivalent medium approximations for porous composites polycrystals and cracked media on a common footing and to indicate their limitations but also to derive some new results based on two point statistics in this way we have obtained an insight into the difficult problem of elastic inclusions at finite concentrations which is of foremost relevance when estimating the effective material parameters of porous cracked shales involving stacks of more or less horizontally aligned clay platelets mixed together with more rounded silt minerals and with fluid filling the spaces a rather involved perturbative analysis of the effects of interactions between or structural correlations among the various inclusions minerals and cavities making up a real shale of hexagonal symmetry was performed in an attempt to obtain a better match between theoretical predictions based on a combination of coherent and optical potential approximations and experimental results recovered from ultrasonic wave speeds for the effective elastic stiffness tensor for the particular data set considered in this study the t matrix approach was able to match the data better than the approach of hornby et al but the match was not completely satisfactory further progress in theoretical shale modelling may come from a better knowledge of the elastic properties of pure clay minerals a more detailed knowledge of the microstructure of shales the incorporation of constraints obtained from comparisons between theoretical predictions and experimental results as well as a continuing development of the t matrix approach numerical results also for the effect of bedding parallel microcracks on the elasticity of such a real shale have value in illustrating the importance of taking into account the effects of spatial distribution when trying to deal with non dilute mixtures of highly contrasting material properties

geochemical evolution of archean shales from south africa i the swaziland and pongola supergroups abstract the fig tree group and moodies group part of the swaziland supergroup are exposed in the barberton mountain land and are 3 3 3 5 ga old shales from the fig tree group are characterized by variable rare earth element ree patterns with lan ybn 5 5 1 8 95 confidence and eu eu 0 97 0 18 shales from the moodies group have more fractionated ree patterns lan ybn 8 7 2 0 and less variable eu anomalies eu eu 0 92 0 02 both groups are characterized by very high abundances of cr and ni modelling of those trace elements which are relatively unfractionated during sedimentary processes ree th sc is consistent with the derivation of these sedimentary rocks from a mixture of the archean bimodal igneous suite mafic volcanics tonalites trondhjemites felsic volcanics with the moodies group requiring a larger percentage of the felsic end member the data for shales from the swaziland supergroup support models suggesting that the archean exposed crust was of more mafic composition than the post archean upper crust and that intracrustal melting was relatively unimportant in differentiating the archean crust the pongola supergroup is younger than the swaziland supergroup but older than 2 9 ga shales and mudstones from the nsuze and mozaan groups show ree characteristics intermediate between the older shales of the swaziland supergroup and typical post archean shales one quartzite sample from the witwatersrand supergroup ca 2 6 ga has a ree pattern virtually parallel to average post archean shales but with much lower abundances the change from typical archean to post archean sedimentary trace element patterns has been documented in early proterozoic successions from canada and australia this change has been related to a short interval of intense growth and chemical differentiation of the continental crust during the late archean 2 7 2 5 ga in southern africa this change appears to have taken place much earlier 3 2 2 9 ga but can be related to similar processes thus the period of crustal evolution related to the archean proterozoic boundary while virtually episodic regionally occurred over a protracted period world wide during the period ca 3 2 2 5 ga

pore scale simulation of density driven convection in fractured porous media during geological co2 sequestration 1 global warming is attributed to the excessive emission of greenhouse gases one of whose main components is carbon dioxide co2 a promising long term solution for mitigating global warming is geological co2 sequestration which is the capture and storage of enormous amounts of co2 in underground reservoirs in order to reduce co2 build up in the atmosphere in this study a pore scale lattice boltzmann method was used to simulate density driven convection in a porous medium with a fracture to study geological co2 sequestration in deep saline aquifers the co2 brine interface was located at the top of the domain both fracture width and body force were varied to generate different ra numbers in order to investigate the effect of ra on the convection all simulated data can be fitted by the same trend implying that the characteristic length of the system was dominated by the fracture width when ra was high enough increasing ra did not reduce the critical time for the onset of instability apparently also it did not increase the maximum peak vertical velocity noticeably therefore there existed asymptotic values for the critical time and maximum peak vertical velocity with high ra numbers the high frequency oscillation of turbulence greatly enhanced the dissolution of co2 into brine after the onset of convective instability the brine with a high co2 concentration intruded into the underlying unaffected brine which increased the interfacial area between the co2 rich brine and unaffected brine and consequently favored the migration of co2 into the fracture and porous medium this study is the first pore scale one investigating density driven convection during geological co2 sequestration in deep saline aquifers whereas most existing research is focused on the field scale and the dissolved co2 concentration at the top boundary is usually assumed to be saturated

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

decoupling of erosion and precipitation in the himalayas the hypothesis that abrupt spatial gradients in erosion can cause high strain rates in active orogens has been supported by numerical models that couple erosional processes with lithospheric deformation via gravitational feedbacks1 2 3 most such models invoke a stream power rule in which either increased discharge or steeper channel slopes cause higher erosion rates spatial variations in precipitation and slopes are therefore predicted to correlate with gradients in both erosion rates and crustal strain here we combine observations from a meteorological network across the greater himalaya nepal along with estimates of erosion rates at geologic timescales greater than 100 000 yr from low temperature thermochronometry across a zone of about 20 km length spanning the himalayan crest and encompassing a more than fivefold difference in monsoon precipitation significant spatial variations in geologic erosion rates are not detectable decreased rainfall is not balanced by steeper channels instead additional factors that influence river incision rates such as channel width and sediment concentrations must compensate for decreasing precipitation overall spatially constant erosion is a response to uniform upward tectonic transport of greater himalayan rock above a crustal ramp

geochemistry of loess paleosol sediments of kashmir valley india provenance and weathering abstract middle to late pleistocene loess paleosol sediments of kashmir valley india were analyzed for major trace and ree elements in order to determine their chemical composition provenance and intensity of palaeo weathering of the source rocks these sediments are generally enriched with fe 2 o 3 mgo mno tio 2 y ni cu zn th u sc v and co while contents of sio 2 k 2 o na 2 o p 2 o 5 sr nb and hf are lower than the ucc chondrite normalized ree patterns are characterized by moderate enrichment of lrees relatively flat hree pattern gd cn yb cn 1 93 2 31 and lack of prominent negative eu anomaly eu eu 0 73 1 01 average 0 81 paas normalized ree are characterized by slightly higher lree depleted hree and positive eu anomaly various provenance discrimination diagrams reveal that the kashmir loess paleosol sediments are derived from the mixed source rocks suggesting large provenance with variable geological settings which apparently have undergone weak to moderate recycling processes weathering indices such as cia ciw and pia values 71 87 83 83 and 80 57 respectively and a cn k diagram imply weak to moderate weathering of the source material

some seismological and geometric features of intraplate earthquakes to understand the nature and cause of intraplate earthquakes we carried out a systematic search for common features associated with them various geological geophysical and seismic data were analyzed and geometric and seismic parameters were compared for 29 intraplate events m 4 5 occurring worldwide the results suggest that intraplate earthquakes occur by the reactivation of pre existing zones of weakness in a compressional stress regime which is generally oriented parallel to the absolute direction of plate motion two styles of faulting were observed for type a earthquakes observed in the eastern united states eastern china western europe and west africa deformation occurs by strike slip motion on steeply dipping faults type b events are usually associated with thrust or normal faulting and were observed in eastern canada fennoscandia australia and peninsular india focal depths did not explain the differences between type a and type b earthquakes rather the differences are due to the perturbation of a regional stress field by a local stress field the regional stress field for type a events is primarily due to ridge push forces the method of stress perturbation varied from region to region the earthquakes in the type b category were further divided into three subcategories type b1 occurring in eastern canada and fennoscandia type b2 occurring in australia peninsular india and central brazil and type b3 occurring in the gulf coast of the u s the inferred causes of the perturbing stresses are deglaciation intracontinental resistive forces resulting from the collision of plates and the deposition of a large thickness of sediments respectively type a events were found to be associated with intersecting faults and generally supported the intersection model of talwani 1988 and had analogs in plate boundary events

geochemistry of archean shales from the witwatersrand supergroup south africa source area weathering and provenance with a few exceptions shales from the archean witwatersrand supergroup 2800 ma in south africa are depleted in na ca lile ree and hfse compared to phanerozoic shales cr co and ni are enriched in all witwatersrand shales and fe and mg are high in shales from the west rand groups wrg and lower central rand group crg shales from the crg and uppermost wrg are enriched in na al lile ree hfse and transition metals relative to shales from the lower wrg chondrite normalized ree patterns for all witwatersrand shales are enriched in light ree and exhibit small to moderate negative eu anomalies a positive correlation of ree and al2o3 contents in the shales suggests that ree are contained principally in clay minerals relative to shales from the crg shales from the wrg exhibit depletions of na ca and sr a feature probably reflecting intense chemical weathering of their source rocks cia indices in witwatersrand shales are variable chiefly 70 98 even within the same shale unit such variations reflect chiefly variable climatic zones or rates of tectonic uplift in source areas with perhaps some contribution from provenance and element remobilization during metamorphism compared to present day upper continental crust all but the orange grove roodepoort and k8 shales appear to have been derived from continental sources depleted in lile ree and hfse and enriched in transition metals computer mixing models based on six relatively immobile elements th hf yb la sc co and four source rocks indicate that the relative proportions of granite basalt and komatiite increased with time in sediment source areas at the expense of tonalite the contributions of basalt and komatiite appear to reach a maximum during deposition of the booysens shale and granite during deposition of the k8 shales and possibly during deposition of the orange grove shales

weathering of lower crustal rocks in the kaveri river catchment southern india implications to sediment geochemistry in the upper catchment of the kaveri river in the sahyadri mountains of southern india middle to lower crustal archean granulite grade mafic and felsic rocks with similar structures and textures are exposed under the conditions of active tectonics high rainfall and thick tropical vegetation occurrence of the two major rock types in close association under identical geological geographical and biological conditions provides an uncommon situation for the study of weathering elemental mobilization and sediment generation processes field observations mineralogical and geochemical data including major trace and rare earth elements ree of fresh rocks and variably weathered saprolite samples suggest that close association of mafic and felsic rocks accelerates the denudational processes by early weathering of mafic minerals in felsic rocks and mafic rocks in the terrain due to differential weathering of rocks unweathered to less weathered felsic grains are likely transferred to the coarser fraction of fluvial sediments deposited on the floodplains of the river imposing an upper continental crust ucc geochemical signature it is found that during chemical weathering in addition to other factors weatherability of host minerals of ree control the mobility of ree in the weathering profile it is suggested from the observations on the weathering process and on the geochemistry of derivative sediments that in a tectonically active system with a climate maximum as in sahyadris an equilibrium could be dynamically maintained between weathering and erosional regimes also we infer from our study that there exist certain commonalities between surface denudational and mantle magmatic geochemical differentiation processes similarity of these processes therefore may have implication to common ucc like geochemistry of post archean sediments

utilizing the onset of time lapse changes a robust basis for reservoir monitoring and characterization time lapse monitoring is useful for imaging changes in geophysical attributes due to fluid flow in trying to use time lapse data for reservoir characterization difficulties often arise when relating changes in geophysical observations to changes in fluid saturation and pressure as an alternative approach for reservoir monitoring and characterization we introduce the idea of an onset time the time at which a measured quantity such as a seismic traveltime or a reflection amplitude begins to deviate from its background value we illustrate the idea and demonstrate its utility through the consideration of traveltimes recorded by the continuous active source seismic monitoring system at the frio pilot site near houston texas the system which transmits an elastic wave every 15 min is used to monitor the movement of carbon dioxide injected into a permeable sand formation from these data we can estimate the onset of changes in seismic traveltimes to six receivers in an adjacent borehole numerical simulation and synthetic tests indicate that the onset times are not very sensitive to the method used to compute the effective fluid bulk modulus and correspondingly the seismic compressional velocity rather the onset times are strongly influenced by saturation changes within the formation specifically by the break through time of the injected fluid phase by means of an iterative inversion algorithm we use the onset times to estimate permeability variations between the boreholes at the frio pilot site the authors 2014 published by oxford university press on behalf of the royal astronomical society

holocene sea level fluctuations and coastal evolution in the central algarve southern portugal in armacao de pera bay southern portugal environmental changes during the holocene can be interpreted based on the morphological and sedimentological similarities between older geomorphic features cemented beach and dune rocks and present coastal features using knowledge of the present beach and dune processes we propose a two step model for the evolution of armacao de pera bay first during the rapid sea level rise between about 8 800 and 6 600 yr cal bp the bay changed from a positive to a negative budget littoral cell and transgressive dunes formed favoured by drought conditions at about 5 000 yr cal bp during a sea level maximum beach width was less than the critical fetch and dunes stabilized and underwent cementation during the wetter atlantic climatic event the second phase of dune accumulation started at about 3 200 yr cal bp due to a regression of sea level during which the bay changed back to a positive budget littoral cell in which beach width was greater than the critical fetch currently the beach width is less than the critical fetch dunes are inactive and the sedimentary budget is negative due to sediment storage in local river systems

geological controls on the formation of alluvial meanders and floodplain wetlands the example of the klip river eastern free state south africa tooth s mccarthy t s brandt t hancox p j morris r 2002 geological controls on the formation of alluvial meanders and floodplain wetlands the example of the klip river eastern free state south africa earth surface processes and landforms 27 8 797 815

elastic properties of hydrate bearing sediments using effective medium theory accurate and detailed models of the seismic velocity structure of gas hydrate bearing sediments may be determined by careful analysis of controlled source seismic data however interpretation of these velocities in terms of hydrate saturation of the pore space has hitherto relied on semiempirical formulas and or simple effective medium theory we develop a rigorous theoretical scheme to relate the seismic properties of a clay rich hydrate bearing sediment to its porosity mineralogy microstructural features and hydrate saturation we consider separately the two possible end members for the distribution of hydrate in the pore space 1 hydrates are unconnected and located in the pore voids without appreciable grain contact and 2 connected hydrates are forming cement binding around the grains the scheme is transversely isotropic to allow for anisotropy due to alignment of clay platelets and is based on a combination of a self consistent approximation a differential effective medium theory and a method of smoothing for crystalline aggregates we have applied the scheme to lithological and seismic velocity data from ocean drilling program site 995 on the blake ridge southeastern u s continental margin to make estimates of the hydrate saturation it was found that the hydrates are probably unconnected and their volume concentration varies between approx 0 at 100 m below the seabed and approx 9 at 400 m depth just above the bottom simulating reflector if the clay platelet orientation distribution resembles the function we have used

seismic characterization of thin beds containing patchy carbon dioxide brine distributions a study based on numerical simulations we studied the seismic attenuation and velocity dispersion effects produced by wave induced fluid flow in weakly consolidated sandstones containing patchy carbon dioxide co2 brine distributions the analysis also focuses on the velocity pushdown because of the presence of this gas as well as on the role of the wave induced fluid flow mesoscopic effects on the amplitude variation with angle ava seismic response of thin layers containing co2 such as those found at the utsira sand sleipner field offshore norway we found that this loss mechanism may play a key role on conventional surface seismic data suggesting that further data analysis may provide useful information on the characteristics of the fluid distributions in these environments numerical experiments let us observe that although mesoscopic effects can be very significant in this kind of media the seismic response of a given isolated thin layer computed considering such effects is very similar to that of a homogeneous elastic thin layer with a compressional velocity equal to that of the original porous rock averaged in the effective data bandwidth this suggests that the thin bed prestack spectral inversion method published by the authors could be used to estimate representative compressional velocities and layer thicknesses in these environments in effect results using realistic synthetic prestack seismic data show that isolated co2bearing thin beds can be characterized in terms of their thicknesses and representative compressional velocities this information can be qualitatively related to co2 saturations and volumes thus the prestack spectral inversion method could find application in the monitoring of the evolution of co2 plumes at injection sites similar to that at the sleipner field

vegetation dynamics and climate during the deglaciation in the south adriatic basin from a marine record the pollen record of a marine core in the south adriatic basin that is radiometrically dated and correlated to the global climate variation by the oxygen isotope curve documents the vegetation changes which occurred around that basin since 17 ka thousands year bp during the end of the last glacial maximum at 16 7 15 ka the altitudinal range is occupied at low and high elevations by a desert and a semi desert dominated by the shrubby sage brush artemisia and at middle elevation by a grass steppe with stands of pine trees where soil conditions are favourable during the deglaciation between 15 and 10 ka a steppe forest with a succession of deciduous trees appears at middle elevation within the grass steppe but its development is interrupted by a set back a re expansion of the semi desert which is coeval with the younger dryas of higher european latitude the holocene is identified by the spread of the mixed deciduous and mediterranean forests which culminates between 8 6 and 6 ka during the end of the boreal and the atlantic chronozones while the most recent sapropel is formed in the deep marine basins of the eastern mediterranean including the south adriatic one between the cold and arid glacial maximum and the warmest and wettest climate optimum during the atlantic chronozone this vegetation dynamics is constrained by the availability of moisture at low elevation by temperature at high elevation and by a combination of both at middle elevation

coastal towers and historical sea level change along the salento coast southern apulia italy abstract the perimeter of salento peninsula southern apulia italy is studded by numerous coastal towers built in the xvi century aiming to create an early warning system against pirates attacks at present two of them fiumicelli tower on the adriatic coast and pali tower on the ionian one have bases a few decimeters below mean sea level the unusual position of both coastal towers can be explained by taking into account geomorphological features of the coastal area and the relative sea level change during the last 500 years geomorphological analysis reveals the occurrence directly in front of the two coastal towers of a wide rocky shore platform to about 1 m depth if a mean sea level about 0 6 1 0 m below present position is supposed at the time of coastal tower construction the wide shore platform would be slightly above sea level and would be able to protect the towers from sea storms furthermore by comparing these data with the results of available glacio hydro isostatic models for southern apulia during the late holocene it is possible to postulate tectonic subsidence of the salento coastal area during the last five centuries the collated data establish the quaternary tectonic history of salento peninsula it experienced a period of general subsidence during the lower pleistocene that was interrupted by rapid uplift during the middle pleistocene uplift stopped at mis 9 3 about 330 ka replaced by a phase of substantial stability which lasted until the late pleistocene holocene finally active tectonic subsidence has affected the coast of salento peninsula during the last four millennia probably in response to the recent doming of the region

major element ree and other trace element behavior in amphibolite weathering under semiarid conditions in southern india abstract a body of komatiitic amphibolite an enclave within the archean high grade orthogneisses in southern india shows mild chemical weathering under semiarid conditions along fractures chemical weathering has advanced chemical index of alteration documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape mathrm cia 53 end document cia of fresh documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage

human induced hydrogeological changes and sinkholes in the coastal gypsum karst of lesina marina area foggia province italy abstract in 1930 a canal was excavated to connect the lesina lagoon with the adriatic sea modifying the track of the previous existing acquarotta canal the 1100 m long stretch of the canal situated next to the coast exposed unknown highly cavernous gypsum bedrock underlying a loose sandy cover during the last two decades a large number of cover collapse and cover suffosion sinkholes have formed along two bands situated next to the canal impinging the adjacent lesina marina residential area the area affected by subsidence has increased exponentially from 1999 to 2009 the tight spatial correlation between the sinkholes and the canal reveals that the subsidence phenomenon has been induced by the local hydrogeological changes caused by the canal in the coastal evaporite aquifer 1 local lowering of the average water table 2 deflection of the groundwater flow lines towards the canal and increase in flow velocity 3 amplification of the groundwater level oscillations largely controlled by the tidal regime 4 local reversals in the groundwater flow changing the canal temporarily from effluent to influent these changes in the hydrogeological functioning of the system have favoured both internal erosion and karstification processes hydrochemical evidence reveals that gypsum dissolution is a currently active process favoured by fresh water and sea water mixing and cation exchange processes most likely the partial replacement of a concrete lining in the canal by pervious gabions in 1993 provided more adequate conditions for the evacuation of the sediments filling the karst conduits accelerating internal erosion and sinkhole development

remote sensing revealed drainage anomalies and related tectonics of south india abstract drainages have characteristic pattern and life histories with youthful stage in hilly areas mature stage in plains and old stage in the coastal zones the deviations from their normal life histories especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the eustatic and isostatic changes this especially after the advent of earth observing satellites has attracted the geoscientists from all over the world for studying such drainage anomalies in this connection a study has been undertaken in parts of south india falling south of 14 south latitude to comprehensively map some drainage anomalies like deflected drainages eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom the mapping of such mega drainage anomalies and the related lineaments faults from the satellite digital data and the integration of such lineaments faults with the overall lineament map of south india showed that the study area is marked by active n s block faults and ne sw sinistral and nw se dextral strike slip faults such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the indian plate towards northerly is still active and deforming the indian plate

a rb sr record of the weathering response to environmental changes in westerly winds across the tarim basin in the late miocene to the early pleistocene the long term record of lacustrine deposits in the tarim basin seems to provide a record of climate influenced by westerly winds to characterize the evolution of westerly winds we analyzed concentrations of rb v zn sc and sr for the drill core ls2 from lop nor in the eastern tarim basin the rb sr ratio in lacustrine deposits depends primarily on the sr element activity during weathering after the influence of source provenance has been removed we assume that with such a correction the rb sr ratio is controlled by precipitation which depends on moisture transport by westerly winds to the tarim basin the rb sr ratio displays a large amplitude oscillation that generally follows a pattern similar to that of pollen and ostracod assemblages which support the inference that rainfall amount affects the rb sr ratio and in turn suggests that it may serve as an index of precipitation that was transported by westerly wind all these climatic proxies obviously changed since the late miocene suggesting stronger aridification that may be attributed to a latitudinal shift in westerly winds since the late miocene a southward migration of westerly winds which then transported more moisture to the southern and eastern parts of the tibetan plateau agrees with modeling results and the geological record during that time this event may be causally related to the expansion of the northern hemisphere ice and or regional tectonic uplift of high mountains around the tarim basin

fluvial geomorphology and neotectonic activity based on field and gpr data katrol hill range kachchh western india abstract the largely rocky and rugged landscape of the katrol hill range composed of mesozoic rocks and structurally controlled occurrences of quaternary sediments is delimited to the north by north facing range front scarps of the seismically active e w trending katrol hill fault khf the landscape and drainage characteristics of the katrol hill range are documented together with ground penetrating radar gpr investigations along the khf to delineate its nature for understanding neotectonic activity in the contemporary tectonic setting the overall geomorphology is controlled by the south oriented tilt block structure of the range indicated by its pronounced influence on the morphology and drainage network the drainage comprises north flowing and south flowing rivers with the drainage divide located close to the northern edge of the range which also marks the highest topographic elevations the narrow zone between the crest line and the drainage divide has been identified as the zone of gorges where gorges and deeply incised fluvial valleys have been formed within quaternary sediments by the various north flowing streams the quaternary sediments consist of bouldery colluvial deposits in front of the range front scarps valley fill miliolites and alluvial deposits of late pleistocene age within the back valleys and scarp derived colluvium forming the youngest deposit based on the geomorphic and stratigraphic evidence three major phases of quaternary tectonic uplift in the katrol hill range are inferred the oldest pre miliolite phase middle pleistocene was followed by a prominent phase of fluvial incision with formation of gorges during early holocene and then by the last one during late holocene continuing at present uplift of the range occurred in well marked phases during the quaternary in response to differential uplift along the khf under an overall compressive stress regime gpr investigations at selected sites show that the khf is a steep south dipping reverse fault near the surface which becomes vertical at depth this suggests neotectonic reactivation of the khf under a compressive stress regime responsible for active southward tilting of the katrol hill range

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

middle to late holocene paleochannels and migration of the palar river tamil nadu implications of neotectonic activity abstract geomorphic tectonic and sedimentary investigations have been carried out to understand the landscape evolution of the palar river basin southern peninsular india for this purpose satellite data interpretations coupled with field investigations fluvial architecture and optically stimulated luminescence osl dating methods were adopted to infer climatic variations and neotectonic deformation that took place during the mid to late holocene period several paleochannels have been identified in the northern part of the present day palar river the distribution pattern of the palar paleochannels and its present course indicate its migration towards the south leaving behind the old palar river streams as paleochannels significant changes in the morphological characteristics channel width and river pattern in the successive paleochannels reveal evidences of channel movement by avulsion largely controlled by reactivation of pre existing lineaments and intensified ne monsoon based on osl ages two major phases of migration have been identified that occurred between 4 83 ka to 1 88 ka first phase occurred between 3 59 ka to 3 26 ka due to intensified monsoon accompanied with small scale neotectonic activity the second phase took place between 2 42 ka to 1 88 ka which occurred probably due to the rapid upstream avulsion this rapid avulsion is due to the close proximity of mpa and the reactivation of the pre existing lineaments moreover the present palar river basin exhibits evidences of neotectonic activity such as soft sediment deformation structures anomalous drainage deflections and reactivation of lineaments and faults further indicating that the palar river is still draining a tectonically active region thus neotctonics and fluctuations in the intensity of monsoon are largely responsible for sculpting the present landscape

elastic wave velocity in marine sediments with gas hydrates effective medium modeling we offer a first principle based effective medium model for elastic wave velocity in unconsolidated high porosity ocean bottom sediments containing gas hydrate the dry sediment frame elastic constants depend on porosity elastic moduli of the solid phase and effective pressure elastic moduli of saturated sediment are calculated from those of the dry frame using gassmann s equation to model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions a hydrate modifies the pore fluid elastic properties without affecting the frame b hydrate becomes a component of the solid phase modifying the elasticity of the frame the goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data we apply the model to sonic and vsp data from odp hole 995 and obtain hydrate concentration estimates from assumption b consistent with estimates obtained from resistivity chlorinity and evolved gas data

geochemistry of buried river sediments from ghaggar plains nw india multi proxy records of variations in provenance paleoclimate and paleovegetation patterns in the late quaternary abstract we report the first geochemical record in two drill sediment cores from a buried channel in the ghaggar plains of nw india which are used to infer variations in provenance paleoclimate and paleovegetation in the locality during the late quaternary aeolian sediments 150 ka in both the cores are overlain by fluvial sediments 75 ka recent major oxide compositions of the core sediments n 35 generally vary between that observed for the modern day ghaggar sutlej and yamuna river sand the isotopic composition 87sr 86sr 0 7365 to 0 7783 and end 14 6 to 19 0 of core sediments n 18 suggest binary mixing of sediments from compositionally distinct higher himalaya hh and lesser himalaya lh endmembers in the catchment and support involvement of a river system originating in the himalayan hinterland distinctly higher 87sr 86sr and lower end in the core sediments during glacial periods can be explained by increasing sediment contribution from lh high 87sr 86sr and low end due to an increase in glacial cover over hh whereas relatively less glacial cover over hh during interglacial periods resulted in more erosion and sediment contribution from hh the down core sr nd isotopic variability clearly reflects climate controlled sediment erosion in the himalayan catchment temporal variations in 18o and 13c of carbonate nodules n 27 are consistent with that reported from the ganga interfluves the 13c variability 4 1 to 1 2 in carbonates is mainly controlled by the extent of silicate hh versus carbonate lh source weathering due to significant climatic shifts the 13c of sediment organic matter 27 4 to 23 2 n 24 suggests dominantly c3 plants in the catchment during the last 75 ka more negative 13c values in sediments during glacial periods relative to those during interglacial periods can be explained by increasing c4 abundance during interglacial periods characterized with both higher summer rainfall and mean annual temperature

tectonics sedimentation and surface processes from the erosional engine to basin deposition this special issue collects a number of papers mainly reflecting discussions during the tectonics sedimentation and surface processes sessions tssp organized at recent egu conferences 2012 2013 2014 as well as related studies that have appeared in earth surface processes and landforms over the last two years the sedimentary record has long been used to invert for deformation at all scales and in all tectonics settings growth strata sediment provenance sequence stratigraphy and changing depositional environments have all provided first order constraints on quantifying deformation at a range of spatial and temporal scales at the same time these studies have motivated much work on the influence of tectonics on both sedimentation patterns and basin fill successions however relatively few studies have considered the whole integrated system of catchment erosion fluvial transport and sediment deposition together often concentrating on either the basin or the catchment separately recently however methodological progress in quantifying rates of surface processes in the upstream erosion and transfer zones as well as revived interest in the couplings between surface processes tectonics and climate have made it possible to renew our understanding of the interactions between sedimentation and tectonics within the framework of the whole integrated sediment routing system although the studies within this special issue are only a fraction of the work presented over the last five years of the tssp sessions the manuscripts presented here reflect a selection of the broad content and diversity of studies that integrate both sedimentation and surface processes to understand deformation in the context of sedimentary systems they highlight and are organized into three active challenges of the field 1 tectonics and climate into landscapes 2 signal propagation within sediment routing systems and 3 modeling of tectonic and surface processes

dynamic poroelasticity a unified model with the squirt and the biot mechanisms the velocities and attenuation of seismic and acoustic waves in rocks with fluids are affected by the two most important modes of fluid solid interaction 1 the biot mechanism where the fluid is forced to participate in the solid s motion by viscous friction and inertial coupling and 2 the squirt flow mechanism where the fluid is squeezed out of thin pores deformed by a passing wave traditionally both modes have been modeled separately with the biot mechanism treated in a macroscopic framework and the squirt flow examined at the individual pore level we offer a model which treats both mechanisms as coupled processes and relates p velocity and attenuation to macroscopic parameters the biot poroelastic constants porosity permeability fluid com pressibility and viscosity and a newly introduced microscale parameter a characteristic squirt flow length the latter is referred to as a fundamental rock property that can be determined experimentally we show that the squirt flow mechanism dominates the biot mechanism and is responsible for measured large velocity dispersion and attenuation values the model directly relates p velocity and attenuation to measurable rock and fluid properties therefore it allows one to realistically interpret velocity dispersion and or attenuation in terms of fluid properties changes e g viscosity during thermal enhanced oil recovery eor or to link seismic measurements to reservoir properties as an example of the latter transformation we relate permeability to attenuation and achieve good qualitative correlation with experimental data

squirt flow in fully saturated rocks we estimate velocity frequency dispersion and attenuation in fully saturated rocks by employing the squirt flow mechanism of solid fluid interaction in this model pore fluid is squeezed from thin soft cracks into the surrounding large pores information about the compliance of these soft cracks at low confining pressures is extracted from high pressure velocity data the frequency dependence of squirt induced pressure in the soft cracks is linked with the porosity and permeability of the soft pore space and the characteristic squirt flow length these unknown parameters are combined into one expression that is assumed to be a fundamental rock property that does not depend on frequency the appropriate value of this expression for a given rock can be found by matching our theoretical predictions with the experimental measurements of attenuation or velocity the low frequency velocity limits as given by our model are identical to those predicted by gassmann s formula the high frequency limits may sign

the last 140 ka in the afro asian arid semi arid transitional zone abstract during the last ten years a great number of geological or other proxy records provided radiocarbon u th or tl dated information on the past climatic oscillations in the arid semi arid zones extending between the atlantic and the pacific comparisons and a synthetic view of these results can now be attempted for the last 140 ka and compared with global changes as registered in oceanic or ice cores and with palaeomonsson models for this purpose wide spatial and time scales have to be used on the whole arid humid alternations roughly fit global changes cold phases corresponding to an extension of the arid areas to the south warm phases corresponding to the shrinking of the same to the north the last interglacial is associated with an increase of precipitation throughout the area considered isotopic stage 4 brings no evidence whatsoever of humid conditions two wetter episodes are registrated during stage 3 a major rainfall decrease is everywhere associated with the last glacial maximum 21 15 ka in most regions the arid or semi arid zones extending several hundred kilometers southwards relative to the present day pattern the two abrupt deglaciation steps and the younger dryas are recorded in all of the most sensitive regions at the margins of the present day monsoonal range during the holocene the precipitation increases everywhere by 100 400 mn relative to the present day values the optimum being at 8 5 6 5 ka a climatic deterioration follows with an irregular pattern of dry wet episodes according to the different geographic conditions the humid phase terminates at 3 5 3 ka in the whole transitional zone the major southward shift of the monsoonal precipitation range since its optimum some 8000 years ago fits the astronomical neoglacial trend and may possibly be correlated with past stage 5d although its rapidity and spatial importance may just reflect one of the sharp successive cold warm variations registered by grip during the whole stage 5

holocene evolution of the palar river southern india tracking history of migration provenance weathering and tectonics abstract this study examines the catchment and source morphodynamics of the palar river southern peninsular india here we applied a multidisciplinary approach remote sensing techniques lineament analysis geochemistry and ground penetration radar for a better understanding of its evolution during holocene times the major lineaments present in the palar river basin are showing the ne sw trend there are five major faults identified in the palar river basin with a transition zone where frequent smaller magnitude earthquakes have occurred the major fault f1 a strike slip fault occurs in the upper part of the palar river following the ne sw trend other major faults present are f2 and f3 with a transition zone where frequent minor and major tremors are documented fault f4 traverses in parallel to the cheyyar river a rapid change in the river course has resulted due to the movement along these strike slip faults f 5 nearer to the east coast indicates a passive tectonic activity regime the after effects of tectonic activity in the basin is further implicit from the gpr profile the sediments of active palar river are dominantly litharenite arkose wacke while the paleochannels are shale in composition weathering proxies such as cia pia elemental ratios along with a cn k plot indicate that a post depositional intense weathering due to climatic variability for all paleochannel sediments due to ongoing tectonic activity in the sources region along with subsequent aggradation and degradation in fluvial regimes the sediments of active palar river shows low to moderate weathering moreover the geochemical data also reveals that the sediments from the palar river and paleochannels are predominately from active continental and passive continental margins respectively moreover the major oxide trace elements and ree elements data indicate that palar river sediments are from a felsic source while paleochannels are from mafic source hence our study suggests that the catchment area of the palar river has been shifted to the south during the holocene period due to tectonic uplift subsequently the sediments of the paleochannels have undergone post depositional weathering due to ongoing tectonic activity and monsoonal changes in the region enhances rapid erosion in the catchment area results in the deposition of the huge thickness of sediments from the middle to lower reaches of active palar river

arrested charnockite formation at kottavattam southern india at kottavattam southern kerala india late proterozoic homogeneous leptynitic garnet biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation charnockitization post dates the polyphase deformation regional high grade metamorphism and anatexis and evidently occurred at a late stage of the pan african tectonothermal history geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar p lith t conditions 650 700 degrees c 5 6kbar in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases x co2 0 7 0 6 x h2o 0 2 0 3 x n2 0 1 logf o2 l7 5 mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow outward migrating transition zones adjacent to the gneiss followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone compared to the host gneiss the charnockite shows higher concentrations of k na sr ba and zn and lower concentrations of mg fe ti v y zr and the hree with a complementary pattern in the narrow transition zones of biotite breakdown the p lith t x h2o data and chemical zonation patterns indicate charnockitization through subsolidus dehydration reaction in an open system subsequent residence of the carbonic fluids in the charnockite resulted in low grade alteration causing modification of the syn charnockitic elemental distribution patterns and the properties of entrapped fluids we favour an internally controlled process of arrested charnockitization in which during near isothermal uplift the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from fluid absent in the gneiss to fluid present in the fracture zones and to the development of an initial fluid pressure gradient triggering the dehydration reaction

the effect of chemical and physical processes on the acoustic properties of carbonate rocks carbonate rocks have major economic significance 60 of the world s oil reserves lie in carbonate reservoirs and the potential for additional gas reserves is huge however the relationship in carbonates between measured geophysical data and rock properties is complex due to the large variety of textures that arise during postdepositional diagenesis and to the chemical processes i e dissolution and replacement by newly formed phases that characterize carbonate forming minerals most experimental and theoretical rock physics research has focused on siliciclastic and shaly rocks however applying insights gained from clastics to carbonates is rarely straightforward and thus is questioned in the literature

predicting subsurface co2 movement from laboratory to field scale abstractfinding an appropriate model for time lapse seismic monitoring of co2 sequestered carbonate reservoir poses a great challenge because carbonate rocks have varying textures and highly reactive rock fluid system we introduced a frequency dependent model based on eshelby s inclusion and differential effective medium dem theory that can account for heterogeneity in microstructure of rocks and squirt flow we showed that the estimated velocities from the modified dem theory match well with the laboratory measurements ultrasonic of velocities of carbonate rocks saturated with co2 rich water the theory predicts significant decrease in saturated p and s wave velocities in the seismic frequency band as a consequence of porosity and permeability enhancement by the process of chemical dissolution of carbonates with the saturating fluid the study also showed the combined effect of chemical reaction and free co2 saturation on the elastic properties of rock we observed that the velocity dispersion and