mixing processes in modern estuarine sediments from the gulf of khambhat western india abstract sandy and muddy detritus from two distinctive end member provenance terrains basaltic and granitic are transported to the estuaries of the gulf of khambhat by fluvial discharge and opposing tidal currents making this embayment ideal for investigating the effects of mineralogical and geochemical mixing on sediment composition in estuarine depositional systems rivers flowing predominantly from the north over precambrian metasediments and granites supply a felsic plutoniclastic sand to the gulf whilst a mafic volcaniclastic sand sourced by deccan basalts is transported by rivers draining the western ghats and from the local coastal erosion in the southern part of the gulf sediments from the tapti estuary are rich in basaltic rock fragments 50 and are characterised by a distinctly basaltic source composition la sc 0 25 0 86 th sc 0 12 0 40 cr th 13 121 eu eu 0 93 1 68 and lree hree 2 96 6 57 by contrast the sediments of the sabarmati inner estuary are rich in quartz grains 80 as evident from the major and trace element compositions la sc 1 38 6 63 th sc 0 58 2 98 cr th 0 58 19 39 eu eu 0 46 0 86 and lree hree 2 90 11 40 the detrital compositions of the remaining major estuaries the narmada dhadhar and mahi scatter across a broad range in a qfr diagram and contain varying amounts of quartz feldspar and rock fragments in the narmada estuary the mixed signature characterised by ree values including eu eu 0 42 2 28 and lree hree 4 37 14 80 is caused by the presence of diverse rock types that crop out in the source area in the mahi estuary which largely flows across felsic source terrains the compositional signature is controlled by mixing of felsic detritus from riverine input with mafic sediments from seaward side in the estuary the two end member detrital compositions plutoniclastic and volcaniclastic are mixed in the macro tidal estuaries mixing of sediment takes place where fluvial currents and tidal flows interact and the proportion of mixing varies systematically from outer to central to inner estuary a high degree of mixing of felsic sediments with deccan basalt derived sediments takes place in the outer estuary resulting in felsic mafic ratios of 40 60 sediments in the central estuaries 65 35 and in the fluvial dominated inner estuaries 90 10 are characterised by moderate to minor degrees of mixing the mixing in estuaries is systematic and is reflected in both the mineralogy and geochemistry of the sediments provenances of ancient estuarine successions should therefore be interpreted with great care incorporating awareness of the mixing processes which influence sediment compositions to different degrees in estuaries especially those characterised by strong tidal currents

chromium and nickel as indicators of source to sink sediment transfer in a holocene alluvial and coastal system po plain italy abstract a reliable quantitative estimate of changes in source to sink sediment transfer requires that high resolution stratigraphic studies be coupled with accurate reconstructions of spatial and temporal variability of the sediment routing system through time source to sink patterns from the contributing upland river catchments to the deltaic and coastal system are reconstructed from the holocene succession of the po plain on the basis of selected geochemical indicators sediment supplied to the delta area by the major trunk river the po exhibits naturally high cr and ni values which invariably exceed the maximum permissible concentrations for unpolluted sites this anomaly reflects remarkable sediment contribution from ultramafic ophiolitic parent rocks cropping out in the po drainage basin western alps and nw apennines in contrast alluvial and coastal plain deposits supplied by ophiolite free apenninic catchments invariably display lower cr and ni contents for constant sediment provenance domain cr and ni distribution is observed to be controlled primarily by hydraulic sorting clay silt deposits floodplain swamp and lagoon bay facies associations invariably show higher metal concentrations than their sandy counterparts fluvial channel distributary channel and beach ridge facies associations from a stratigraphic perspective in sedimentary basins characterized by strong differences in sediment composition geochemical fingerprinting of individual facies associations framed by surfaces of chronostratigraphic significance is proposed as an invaluable approach towards an accurate quantitative assessment of sediment storage in alluvial and coastal depositional systems as opposed to volumetric reconstructions based on lithologic or geometric criteria alone

mechanisms of formation of deep basins on continental crust in the verkhoyansk fold belt miogeosynclines and cratonic basins abstract the verkhoyansk fold belt is a wide folded area in northeastern asia a large sedimentary basin 10 15 km deep was formed there by a slow subsidence of continental crust during 1000 ma in the late proterozoic middle paleozoic there are no deformations in the sedimentary cover that could indicate significant lithospheric stretching or shortening during this slow subsidence a number of deep basins 5 15 km of the same type exist or existed in other areas they can be called cratonic basins a slow gabbro eclogite transformation in the lowermost crust that occurred in a thick cratonic lithosphere can be suggested as a mechanism for their formation several deep water basins were formed in the verkhoyansk fold belt by rapid subsidence of continental crust during 1 5 ma in the late paleozoic and early mesozoic the subsidence occurred without significant stretching or thrust loading the basins formed were strongly folded in the late mesozoic under the convergent plate motions there were many basins of the same type in the other fold belts among deep basins on continental crust only those produced by rapid subsidence were intensely folded they can be called miogeosynclines rapid gabbro eclogite transformation with the destruction of the basaltic layer may be suggested as the mechanism of their formation this probably occurred under upwelling of hydrous anomalous mantle to the base of the crust

role of crustal stretching on subsidence of the continental crust abstract the principal areas of subsidence of the continental crust are wide intracontinental basins and passive continental margins in many intracontinental basins crustal extension amounts to only a few percent and is unable to explain their subsidence as shown for the timan pechora pre caspian and west texas basins the deep black sea and south caspian basins are underlain by highly attenuated continental crust having velocities in the 7 km s range that shows no evidence for significant extension in passive margins upper crustal extension ranges between 10 and 40 whereas the lower crust is attenuated by 2 3 times e g campos basin north biscay margin large discrepancy between upper crustal stretching and lower crustal attenuation is seen in the crustal configuration of many intracontinental grabens e g baikal and dniepr prypyat basins only in highly extended areas such as the basin and range province and the east china rift system does crustal stretching account for the observed crustal thinning the observed discrepancy between upper extension and crustal thinning across intracontinental rifts and passive margins and particularly in some wide intracontinental basins suggests that crustal stretching alone cannot account for the subsidence of these basins phase transformations in the lower crust probably facilitated by the presence of hydrous fluids can cause rapid 1 ma as well as long term 200 1500 ma upward displacement of the moho discontinuity resulting in high amplitude subsidence of the crust in areas of crustal extension this mechanism can overprint subsidence induced by thermal relaxation of the lithosphere the case of the black sea and south caspian basins shows that density increase of the lithosphere can also occur independently of crustal stretching

geochemical and mineralogical variations as indicators of provenance changes in late quaternary deposits of se po plain combined geochemical and mineralogical characterisation of mudstone prone successions can provide suitable indicators of sediment provenance a case study from the late quaternary depositional sequence of southeastern po plain shows that major changes in geochemical and mineralogical composition can be ascribed to changes in sediment dispersal patterns occurring during the last 30 ka in response to fluctuating sea level the po river with a mixed contribution from the alpine and apenninic chains and its southern tributaries flowing from the apennines acted as the major feeders for the study area during the late quaternary chromium and nickel among trace elements and serpentine and dolomite among minerals appear as the major provenance indicators for the study succession allowing distinction of an apenninic chromium and serpentine poor province from a mixed alpine apenninic po related chromium and serpentine rich province the relatively low cr al2o3 and serpentine silicate ratios recorded in sediments of late pleistocene age 30 ka bp which accumulated at the last glacial maximum suggest that during lowstand times and early stages of transgression the southeastern po plain was beyond the po river influence being fed uniquely by rivers of apenninic provenance increasing cr al2o3 and serpentine silicate ratios recorded within back barrier transgressive deposits 8 10 ka bp in the comacchio and ravenna sectors reflect a major change in sediment supply taking place during the holocene when partially barred environments largely connected with the open sea became established in the study area and po derived detritus was delivered to estuaries and lagoons by littoral drift maximum chromium and serpentine values are recorded at peak transgression and during the following sea level highstand 6 ka bp present when sediment supply exceeded the rate at which new accommodation space was created leading to extensive po delta progradation the drop in cr al2o3 and serpentine silicate ratios recorded in some cores at top of the holocene succession reflects the local reestablishment behind the prograding po delta complexes of an alluvial plain drained by rivers of apenninic provenance as a result of distributary channel switching and delta lobe abandonment geochemical and mineralogical analyses show negligible compositional variations between pleistocene and holocene deposits landward of the line of maximum marine incursion especially close to the basin margin in these instances sample composition throughout the entire stratigraphic succession clearly suggests an ongoing supply from the adjacent apenninic chain comparison with sand compositional analyses from major sand bodies of the same stratigraphic succession highlights the complementary but fundamental role of geochemical and mineralogical characterisation of clays for provenance research

new evidence on the evolution of the po delta coastal plain during the holocene abstract the po coastal plain dominated by the po and adige rivers deltaic systems is characterized by beach ridges which mark successive positions of the coastline during the holocene the most evident of these ridges are the most recent ones their dating is mainly based on archaeological and historical data the complex formed by some of the most prominent beach ridges was previously considered by experts to be the first post glacial shoreline this shoreline enclosed a single lagoonal system comprising the lagoon of venice and the delta of the main rivers more recent studies have instead allowed us to recognize other beach ridges older than this one these beach ridges are partially or totally buried by alluvial sediments belonging we believe to active subboreal shorelines additionally other studies we are now carrying out such as the geomorphologic map of the po plain and the venetian lagoonal system project have allowed the identification of older buried intertidal facies this work proposes a progradational model mainly developed by the building of the marine deltas including episodic or discontinuous lagoonal environments in opposition to the continuous lagoonal system model described up to now

isotopic and geochemical studies of nodules in kimberlite have implications for the lower continental crust lower crustal xenoliths from the calcutteroo kimberlitic pipes in south australia show a surprisingly diverse range in nd and sr isotopic compositions and rare earth element ree abundances mafic granulite and garnet clinopyroxenite xenoliths have measured end 0 values between 6 1 and 7 9 both light l ree enrichments and depletions low rb sr ratios 0 005 0 040 and relatively high 87sr 86sr ratios of from 0 70675 to 0 70919 a felsic xenolith has compositions more typical of upper crustal rocks with end 0 21 4 lree enrichments rb sr 1 47 and 87sr 86sr 0 85987 an approximate correlation also exists between sm nd versus 143nd 144nd and rb sr versus 87sr 86sr indicating major intracrustal differentiation in the lower crust at 2 400 myr this produced extremely low rb sr ratios and both relative lree enrichments low sm nd and depletions high sm nd if these results are typical then they indicate that the lower crust has higher 87sr 86sr and more positive end 0 values than previous estimates1 5 this may require revision of total crustal compositions and crust mantle evolutionary models1 5

petrography and temporal changes in petrofacies of deep marine ainsa jaca basin sandstone systems early and middle eocene spanish pyrenees a petrographic study of 157 samples from the early to middle eocene deep marine sandy systems ainsa jaca basin spanish pyrenees shows that each system has a characteristic petrofacies three main petrofacies are recognized petrofacies 1 sandstones comprise mainly siliciclastic grains 80 subordinate terrigenous carbonate grains and negligible intrabasinal grains petrofacies 2 hybrid arenites are characterized by significant amounts 10 of intrabasinal carbonate grains petrofacies 3 calcilithites contain relatively abundant 10 extrabasinal carbonate grains on the basis of these petrofacies a revised correlation of the sandy systems is proposed between the more proximal ainsa basin and the more distal jaca basin sediments now separated by the boltana anticline across which it is impossible to actually trace out individual beds or sandstone packages between both basins the arenite composition in the ainsa and jaca basins is interpreted as being controlled mainly by synsedimentary tectonic processes that led to changes in sediment sources during basin evolution

on the mechanism of graben formation abstract the structure of the crust and mantle and the subsidence history of the baikal and dneprovsko prypyatsky basins are analyzed considerable thinning of the crust from several ten percents to two hundred percent takes place under both basins the extension of the upper crust is much smaller 4 6 under these conditions both basins should be considered as grabens and not as rifts produced by stretching artyushkov 1987 in the baikal and prypyatsky basins and in some places in the dneprovsko basin the moho is underlain by a layer of rocks with v p 7 2 7 8 km s in the absence of volcanism in the baikal and under stable tectonic conditions in the dneprovsko prypyatsky basin these should be garnet granulites with rather high density very rapid water loaded subsidence at a rate 1 km ma took place in the baikal in the pleistocene and in the dneprovsko prypyatsky basin in the late devonian the subsidence of such short duration without intense stretching at the surface can be produced only by contraction of rocks in the lithosphere this most probably took place due to gabbro garnet granulite eclogite transformation in the lower crust under migration of fluid from the asthenospheric layer fluid migration through these zones was a cause of gabbro eclogite transformation in long narrow zones which produced deep grabens at the earth s surface

silicic magma petrogenesis in iceland by remelting of hydrothermally altered crust based on oxygen isotope diversity and disequilibria between zircon and magma with implications for morb terra nova 24 227 232 2012 abstract petrogenesis of silicic magmas in iceland has fundamental significance for understanding the relative importance of fractional crystallization of mantle derived basalt and partial melting of hydrothermally altered basaltic crust in formation of the earliest continental crust first results of in situ oxygen isotope investigation of zircons in large volume silicic eruptive products of three volcanoes in iceland askja torfajokull and hekla demonstrate isotope diversity and disequilibria and long u th zircon pre eruptive residence of 103 104 year this suggests that zircons did not grow from their host melts but instead were inherited from older magma batches and leftover cumulates with generally low and variable 18o values this study demonstrates that segregation of cubic kilometres of silicic magma is faster than mineral diffusive or recrystallization time scales estimated at 103 years and it suggests that partial melting of hydrothermally altered and oxidized oceanic crust is the mechanism that best explains silicic rocks in iceland and early earth environments

global sea level control on local parasequence architecture from the holocene record of the po plain italy abstract holocene deposits exhibit distinct predictable and chronologically constrained facies patterns that are quite useful as appropriate modern analogs for interpreting the ancient record in this study we examined the sedimentary response of the po plain coastal system to short term millennial scale relative fluctuations of sea level through high resolution sequence stratigraphic analysis of the holocene succession meters thick parasequences form the building blocks of stratigraphic architecture above the younger dryas paleosol a prominent stratigraphic marker that demarcates the transgressive surface early holocene parasequences s 1 3 record alternating periods of rapid flooding and gradual shoaling and are stacked in a retrogradational pattern that mostly reflects stepped post glacial eustatic rise conversely middle to late holocene parasequences s 4 8 record a complex pattern of coastal progradation and delta upbuilding that took place following sea level stabilization at highstand starting at about 7 cal ky bp the prominent transgressive surface at the base of parasequence 1 correlates with the period of rapid global sea level rise at the onset of the holocene mwp 1b whereas flooding surfaces associated with parasequences 2 and 3 apparently reflect minor early holocene eustatic jumps reported in the literature changes in shoreline trajectory parasequence architecture and lithofacies distribution during the following eustatic highstand had instead an overwhelming autogenic component mostly driven by river avulsions delta lobe switching local subsidence and sediment compaction we document a 1000 year delayed response of the coastal depositional system to marine incursion farther inland from the maximum landward position of the shoreline a dramatic reduction in sediment flux due to fluvial avulsion resulted in marine inundation in back barrier position whereas coastal progradation was simultaneously taking place basinwards we demonstrate that the landward equivalents of marine flooding surfaces parasequence boundaries may be defined by brackish and freshwater fossil assemblages and traced for tens of kilometers into the non marine realm this makes millennial scale parasequences whether auto or allogenic in origin much more powerful than systems tracts for mapping detailed extents and volumes of sediment bodies the holocene parasequences of the po coastal plain with strong age control and a detailed understanding of sea level variation may provide insight into the driving mechanisms and predictability of successions characterized by similar depositional styles but with poor age constraint resulting in more robust interpretations of the ancient record

sedimentary response to late quaternary sea level changes in the romagna coastal plain northern italy data from 17 continuously cored boreholes 40 170 m deep reveal the subsurface stratigraphy of the romagna coastal plain sedimentological and microfaunal data allow the distinction of eight facies associations of late pleistocene holocene age including 18 lithofacies and 16 faunal associations ten 14c dates provide the basis to establish a sequence stratigraphic framework for the succession corresponding to the upper part 35 ky bp of the last glacio eustatic cycle the eight facies associations can be grouped into lowstand transgressive and highstand systems tracts the upper part of the lowstand systems tract consists of alluvial plain deposits these accumulated during the late pleistocene when the shoreline was 250 km south of its present day position a pronounced stratigraphic hiatus between 25 and 8 8 ky bp is invariably recorded at the upper boundary transgressive surface of these pleistocene indurated and locally pedogenized alluvial deposits the succeeding postglacial history is represented by a well developed transgressive regressive cycle transgressive deposits interpreted to reflect the rapid landward migration of a barrier lagoon system include two wedge shaped paralic and marine units these thicken in opposite directions and are separated by a ravinement surface above the transgressive deposits the maximum flooding surface mfs marks the change from a transgressive barrier lagoon complex to a prograding wave dominated delta system early po delta the mfs can be traced landwards where it constitutes the base of lagoonal deposits an aggradational to progradational stacking pattern of upper delta plain marsh lower delta plain lagoon bay and delta front beach ridge deposits reflects the progressive increase in the sediment supply accommodation ratio during the following highstand the alluvial deposits capping the sequence accumulated by the 13th century ad in response to an avulsion event that caused abandonment of the former po delta lobe and the northward migration of the po river towards its present position

the east carpathians indications of phase transitions lithospheric failure and decoupled evolution of thrust belt and its foreland abstract an analysis is presented of the tectonic development of the east carpathians since the late oligocene the geological and geomorphological data show that five epochs of convergence and nappe emplacement took place with the last one occurring 11 12 m y b p after these compressional events the nappe surface remained near sea level the crustal uplift which formed the present mountains began 3 m y b p and after 99 of the shortening of the carpathians had been completed the pre carpathian foreland basin up to 3 5 km deep formed on the margin of the east european platform in the middle miocene analysis of the evolution of the basin shows that it deepened away from the nappe stack and most of the subsidence occurred when there was no convergence this precludes lithospheric flexure due to convergence as a mechanism for basin formation at 11 12 m y b p the inner part of the basin 50 km wide was overridden by the carpathian nappe up to 12 14 km thick at that time a slight crustal uplift took place rather than subsidence in the shallow remnant outer basin part the present foredeep which emerged above sea level an additional 7 8 km of subsidence then occurred in the foredeep of the southeastern carpathians in the late miocene early pleistocene when very little convergence took place the evolution of the carpathian foredeep shows that lithospheric flexure of 2 5 km occurred in regions 20 40 km wide similar amounts of flexure and large basement faults exist under the nappe this style of deformation indicates flexural rigidity of the lithosphere that is several orders of magnitude smaller than in stable cratonic regions under a low flexural rigidity the crust should be close to local isostasy then the isostatic response to superposition of a 10 13 km thick nappe on the platform margin which was near sea level would form high mountains the crustal surface however remained at a low altitude we interpret this to be the result of contraction of gabbro in the lower crust with the formation of dense garnet granulites during nappe emplacement a layer of these dense rocks 20 km thick with p wave velocities 7 5 7 6 km s exists in the lower crust of the east carpathians according to the geophysical data there is no cool high velocity slab now subducting towards the intra carpathian area an increase in the mean height of the carpathians by only 1 km since the termination of convergence precludes a recent slab detachment rapid metamorphism of mafic rocks in the lower crust requires the infiltration of volatiles from the asthenosphere infiltration of volatiles into mantle lithosphere and the upper crust could strongly reduce their viscosity these phenomena might be the cause of an abrupt loss of lithospheric rigidity on the margin of the east european platform in the neogene lithospheric failure allowed the incorporation of this region into the carpathian fold belt after a long period of cratonic development

sand composition and sedimentary evolution of a late quaternary depositional sequence northwestern adriatic coast italy abstract in order to detect temporal and spatial variations in detrital supply in the upper part of the last depositional sequence of late pleistocene holocene age we conducted a combined petrographic and stratigraphic study in the romagna coastal plain south of the po delta northern italy we analyzed heavy minerals and the bulk composition of sands from cores and surface samples by using petrographic and stratigraphic data on composition of modern beach and major river deposits new aspects of detrital dispersal mechanisms and the depositional history of the study area are documented the heavy mineral distribution coupled with the dolostone and volcanic rock fragment contents of bulk sands allow identification of three different petrofacies petrofacies a petrofacies b and petrofacies c which have been interpreted as of apenninic mixed eastern alps po river basin and po river catchment basin provenance respectively distribution of the three petrofacies changed through time in response to landward and seaward shifting of the coastline during the late pleistocene lowstand a pure apenninic provenance characterized the romagna coastal plain petrofacies a during the holocene transgression when the shoreline migrated tens of kilometers west of its present position eastern alpine sediment sources fed littoral facies petrofacies b probably as a result of southward transport by littoral drift this sediment supply continued during the early regressive phases and was cut off by a change in coastal morphology related to the development of the early po delta this led to the establishment of a sediment supply entirely related to the po river catchment basin petrofacies c changes in the compositional signature of sand in the youngest beach ridges mark the abandonment of the early po delta due to an avulsion event and testify to the establishment of a coastal system fed by rivers draining the apennines petrofacies a we emphasize sand petrography as an important tool in studying the internal architecture of sandy clastic depositional units on detailed spatial scales and its use in deciphering the depositional history of complex sedimentary successions fig 1 location of the study area end page 829

mechanism of formation of hydrocarbon basins the west siberia volga urals timan pechora basins and the permian basin of texas abstract many authors suggest that a large role in the formation of hydrocarbon basins is played by stretching or thrust loading our previous analysis artyushkov and baer 1983 1984a b 1986 has revealed a large number of deep basins on continental crust in fold belts that were formed by rapid subsidence without significant stretching or thrust loading this paper shows that the hydrocarbon basins of west siberia volga urals timan pechora and the permian basin in texas pertain to the same basin type water loaded basins 0 3 0 5 km deep were produced in these regions by rapid subsidence in 1 ma shallow water and deeper water strata cover the same area in the basins which precludes significant stretching during the subsidence there was no folding in the adjacent regions ai the epochs of the subsidence which precludes thrust loading a short duration of the subsidence precludes a significant role of thermal relaxation rapid subsidence was commonly preceded by slight crustal uplift in the volga urals and timan pechora it was also preceded by slight volcanism we suggest destruction of the lower crust under asthenospheric upwelling to the base of the crust as a cause of rapid subsidence the asthenospheric upwelling strongly increases the heat flow which ensures hydrocarbon maturation at shallow depth activization of local tectonic movements from crustal heating occurs after rapid subsidence which produces numerous traps for hydrocarbons deposition of highly organic rocks good source rocks and the formation of reefs and or clinoforms good reservoirs commonly occur after rapid subsidence deposition of shales and evaporites good seals takes place in deeper water basins formed by rapid subsidence diapirism of the latter rocks produces additional hydrocarbon traps the combination of all the above effects associated with rapid subsidence produces very favourable conditions for the generation and preservation of hydrocarbons almost all large hydrocarbon fields in the basins considered are located in regions of rapid subsidence there are no large fields in the adjacent sedimentary basins formed by slow subsidence although the sediment thickness is commonly high

dynamics of rare earth elements in water soil systems the case study of the pineta san vitale ravenna italy abstract the european union site of community importance pineta san vitale ravenna italy is located in a complex lagoon system nearby the adriatic sea this area is affected by relevant environmental pressures related to subsidence groundwater salinization and industrial contamination the occurrence of rare earth elements ree and the characterization of processes that control their migration in the water soil system were performed for implementing the knowledge of the present environmental status in the area nine soil profiles were opened in the pineta san vitale and each horizon was characterized in the parent material dominant quartz followed by plagioclase mica chlorite and calcite were recognized by xrd topsoil samples were characterized by neutral or sub acid ph relatively high organic carbon content loi up to 43 wt toc 38 61 g kg and low carbonate 11 20 g kg caco 3 subsoil horizons were sub alkaline or moderately alkaline rich in carbonate up to 114 g kg caco 3 and depleted in organic matter the electrical conductivity ec 0 2 4 2 ms cm values along the soil profiles did depend on the water table fluctuations and the salinity of groundwater sequential extraction tests on two soil profiles showed the highest y and ree occurrence in the residual fraction of soils with values generally increasing at depth and total amounts similar to values estimated in the upper continental crust ucc poor fractionation of ree was observed when the bulk soil horizon was considered but different ree patterns occurred in the organic oxide and carbonate soil fractions suggesting ree fractionation during weathering and pedogenic processes physical chemical parameters and concentrations of total and dissolved elements were determined in 44 water samples waters showed near neutral or slightly alkaline ph 6 8 8 0 and total dissolved solids mostly in the range of 2 to 24 g l with values increasing with increasing seawater influence concentrations of ree determined in waters filtered through 0 4 m pore size filters varied from 0 1 to 189 g l 0 7 10 9 1 3 10 6 mol l ree with the highest values observed in soil waters ree values were not related to salinity nor to major ions while were positively correlated to al concentrations further filtration through 0 015 m pore size filters removed about 90 of ree compared to the 0 4 m filtered samples i e the studied waters showed a small quantity of truly dissolved ree species speciation modeling results by visual minteq indicated that truly dissolved ree species are dominated by bi dentate organic complexes in the soil waters rich in dissolved organic carbon up to 74 mg l doc aqueous complex with the carbonate and bicarbonate ligands increased in waters having low doc ucc normalized patterns of ree in the colloidal fraction of soil waters showed slight enrichments in the middle ree mree likely due to preferential adsorption of the mree onto truly dissolved in soil waters showed slight enrichments in the heavy ree hree probably due to dominant low molecular weight doc in the truly dissolved fraction for evaluating the potential ree contribution from the atmosphere 12 vegetation samples ivy leaves were submitted to leaching tests using acidulated water as a proxy of rain water the ree leached from leaves were in the range of 0 5 to 10 g kg ree suggesting a significant atmospheric contribution to the water soil system ucc normalized patterns of ree leached from leaves were nearly flat possibly indicating a dominant geogenic source of atmospheric ree

barometric pressure influence on water table fluctuations in coastal aquifers of partially enclosed seas an example from the adriatic coast italy summary the water table level fluctuations in a coastal phreatic aquifer of the adriatic coast southern po plain italy were recorded to characterize groundwater level response to sea level fluctuations tide induced fluctuations atmospheric pressure loading and recharge from rainfall have all been recognized in the measured water table changes we also identified additional water table fluctuations that are not related to rain atmospheric pressure or tides we propose that these additional fluctuations are related to interaction of groundwater seiche events and inverted barometric effects their amplitude is important because at a distance of 70 m from the coast they have a magnitude of 0 07 m whereas the local tide has a 1 m amplitude seiches are standing waves that create sea water fluxes which affect groundwater below the first row of dunes in the study area we propose that this inverted barometric effect is an important process in creating water fluxes in the coastal zone that may strongly affect the position and width of the mixing zone between salt and fresh water

mechanism of formation of fold belts and associated seismic anisotropy summary fold belts form due to shortening of deep basins on oceaic and continental crust basins on the oceanic crust should be characterized by a pronounced seismic anisotropy in the mantle lithosphere deep basins on the continental crust may develop from the stretching or the destruction of the lower crust under asthenospheric upwelling these processes can produce seismic anisotropy in both the crust and mantle lithosphere the character of the anisotropy is different for different basin forming processes considerable anisotropy should also arise from compression of the crust and mantle in fold belts the formation of fold belts produces the original seismic anisotropy in continental lithosphere

mechanism of continental crust subsidence in fold belts the urals appalachians and scandinavian caledonides abstract formation of deep basins on continental crust is usually explained by lithospheric stretching stretching produces the large deformations in the upper brittle part of the crust that have been found in many rift valleys the sedimentary cover of deep basins on continental crust is exposed at the surface in fold belts in many places some undeformed basins have been covered by detailed seismic profiling and drilling the sedimentary cover structure in the urals appalachians and in the scandinavian caledonides has been analysed no deformations typical of stretching were found in the greater part of the basins on continental crust high magnitude subsidence without stretching can be produced by thrust loading or by a large density increase in the crust or mantle paleotectonic conditions exclude thrust loading as a cause of formation of the major basins in the above fold belts most of them were formed in cool cratonic areas by rapid subsidence in a few m y their initial depth was 1 3 km subsidence of this type cannot be produced by thermal relaxation without significant stretching gabbro eclogite transformation in the lower crust is proposed as a possible mechanism intense shortening of continental crust is observed only where rapid subsidence of a large magnitude took place before the folding not one cratonic block was strongly compressed in the fold belts considered

the evolution of the north german basin and the metamorphism of the lower crust in an integrated analysis metamorphic processes in the accreted crust potential field anomalies temperature field and subsidence history are summarized into a model for the development of the north german basin the model integrates observed phenomena such as the high nitrogen content in natural gases in permian sandstone reservoirs and the structure of the crust with model calculations rock density increase subsequent volume reduction and loss of volatiles during metamorphism lead to a depression at the surface of the earth the load of the sediments which will be deposited in the depression enhances the subsidence and the ongoing metamorphism the model provides an alternative to the application of existing tectonic stretching models for the explanation of the subsidence of sedimentary basins

mechanism of continental crust subsidence in the alpine belt abstract formation of deep basins on continental crust in fold belts is often explained by stretching this mechanism inevitably produces large deformations in the upper crust no deformations typical of significant stretching were revealed in the predominant part of deep basins on continental crust in the alpine belt this means that these basins were not produced by stretching most basins were formed during a short period of time of a few million years the short duration of the subsidences eliminates thermal relaxation as the mechanism the space and time relationships between the subsidence and orogeny and the profile of the basin floor exclude thrust loading as a cause of formation for practically all large basins gabbro to eclogite transformation is suggested as a mechanism of rapid subsidence this occurs under the upwelling of hydrous asthenosphere at moderate temperature to the base of the crust eclogite sinking into the mantle results in a strong attenuation of the crust and lithosphere which permits intense subsequent folding the major part of deep basins in continental crust that formed by rapid subsidence was intensely shortened in the alpine belt significant crustal shortening did not spread over the cratonic lithosphere

arenite petrography in sequence stratigraphy stratigraphic boundary surfaces and internal anatomy of unconformity bounded units may be deciphered by using properly conceived petrography that identifies compositional spatial and temporal characteristics of sand grains discussion of two case studies of synorogenic deep marine successions indicates the potential of this method when intrabasinal source areas are present relative sea level changes can exert direct influence on the intrabasinal extrabasinal grain budget in this case genetically significant unconformity bounded units are not only characterized by their internal facies architecture but also by internal organization in petrosomes as it is for biozones in biostratigraphy when intrabasinal source areas are narrow or absent relative sea level changes only control the timing of the record in deep sea sands of tectonic modifications in hinterland sources in this case unconformity bounded sequences may be fingerprinted with distinctive detrital compositions these results emphasiz

facies and stacking patterns of shelf deltas within the palaeogene battfjellet formation nordenskiold land svalbard implications for subsurface reservoir prediction textural and mineralogical properties of the sediment facies characteristics both derived from well data stacking patterns derived from well and seismic data and plan view shapes derived from seismic data are all essential components when reconstructing reservoir geometries from subsurface data sets without the availability of all these sources of information reservoir predictions can potentially deviate significantly from the true geometries in particular inferences about internal sandbody geometry from plan view considerations isopach maps and seismic attribute maps may lead to erroneous conclusions without knowledge of facies and textural properties of the sediment analysis of well exposed sedimentary systems has the potential to establish links between internal facies characteristics and large scale geometry and to improve models coupling information at these variable scales the palaeogene battfjellet formation svalbard has been studied with the aim to unravel internal characteristics and external form by investigating sediment properties facies and stacking patterns the formation shows a combination of texturally and mineralogically very immature sediments a predominance of wave generated or wave induced sedimentary structures and a stacking pattern of highly variable numbers of parasequences at localities few kilometres apart that best can be explained in terms of small shifting deltaic lobes that produced a complex pattern of overlapping sandbodies the strong evidence of wave action in the receiving basin could in itself indicate strike extensive sandstone bodies however the complex sandbody arrangement and the immaturity of the sediments preclude such an interpretation traditional facies models coupling plan view geometries with internal facies characteristics such as the coupling of strike extensive barrier systems with wave dominated sedimentary structures or the coupling of elongated fluvial dominated deltas with offshore directed current generated structures are much too simple and may lead to erroneous interpretations if the complexity revealed by all sources of data is not appreciated

onshore to offshore anatomy of a late quaternary source to sink system po plain adriatic sea italy abstract in understanding the evolution of siliciclastic systems late quaternary analogs may enable reliable predictive models of facies tract architecture the po plain adriatic sea system where a wealth of research has been conducted during the last 20 years represents one of the most intensively investigated late quaternary successions with the aid of a chronologically well constrained stratigraphy paleoenvironmental evolution is tracked for the first time from fluvial to deep marine realms over 1000 km in length vertical stacking trends onshore and stratal terminations offshore are the key observations that allow identification of surfaces with sequence stratigraphic significance systems tract boundaries in the distinct segments of the system recurring motifs in stratigraphic architecture showing tight coupling of sedimentary responses among source area catchment basin and coastal and marine depocenters reveal a cyclicity driven by glacio eustatic fluctuations in the milankovitch band due to high rates of subsidence middle pleistocene forced regressive systems tracts are exceptionally expanded and the mis5e mis2 interval late pleistocene preserves a nearly continuous record of fourth order 100 kyr stepwise sea level fall the stratigraphic architecture of last glacial maximum deposits highlights the genetic relations between channel belt development pedogenesis and sediment delivery to the lowstand delta through narrow incised valley conduits the late glacial holocene succession records the last episode of sea level rise and stabilization through well developed patterns of shoreline transgression regression tst hst that can be readily traced updip from offshore to onshore locations architectural styles across the whole system reflect a dominance of allogenic forcing in the tst as opposed to a predominantly autogenic control on stratigraphic development in the hst external drivers of facies architecture were also effective on millennial timescales the younger dryas cold reversal which marks the transgressive surface on land records a short lived episode of subaqueous progradation that is correlative onshore with widespread immature paleosol development and small sized channel belt formation quantitative assessment of sediment budgets over different time intervals requires precise positioning of the key bounding surfaces based on this approach we outline for the first time over the entire po adriatic basin an estimate of the sediment volumes stored in each systems tract

stratigraphic paleoecology bathymetric signatures and sequence overprint of mollusk associations from upper quaternary sequences of the po plain italy upper quaternary sequences of the po plain italy were used to assess the informative strength and sequence stratigraphic overprint of quantitative paleoecological patterns three densely sampled cores 89 samples 98 genera 23 280 specimens dominated by extant mollusk species with known environmental distributions were analyzed with detrended correspondence analysis dca the dca scores calibrated using extant genera provided outstanding estimates of bathymetry 3 m and related environmental parameters depth related successions of mollusk associations delineated by using dca were consistent with independent sequence stratigraphic interpretations and yielded insights inaccessible via routine techniques e g depth estimates for maximum flooding surfaces the dca ordination demonstrates the severity of the sequence stratigraphic overprint samples are highly uniform taxonomically during late transgressive systems tracts and highly variable during the following highstand systems tracts when analyzed across comparable systems tracts similar species associations repeat during the last and current interglacial cycles suggesting that po plain mollusk associations have remained remarkably stable over the past 125 k y the results are consistent with the bathymetric interpretation of the dc axis 1 postulated previously for the paleozoic fossil record demonstrate the sequence stratigraphic overprint of paleoecological patterns predicted by computer modeling and illustrate the utility of quantitative paleoecological patterns in augmenting sequence stratigraphic interpretations

saltwater intrusion in the unconfined coastal aquifer of ravenna italy a numerical model summary the ravenna pine forests represent an historical landmark in the po river plain they have great environmental historical and tourist value the san vitale pine forest is located 10 km north of the town it is surrounded by an urban area the city industrial infrastructure and the waterworks of the agricultural drainage system most land in this area is below mean sea level as a result no natural freshwater hydraulic gradient contrasts the density gradient of saltwater in the last century many events land subsidence land reclamation and drainage urban and industrial development and gas and deep groundwater extractions coastal dune destruction led to the intrusion of large volumes of brackish and saline groundwater today the freshwater in this coastal aquifer consists of low salinity water lenses floating on the saltwater wedge this study is aimed at understanding how past and present human activities have affected the saltwater intrusion process in the phreatic aquifer and how the predicted future sea level rise will affect the salinisation process we used a numerical model to quantify these effects on the density dependent groundwater flow hydraulic head and salinity distribution seepage and salt load fluxes to the surface water system the simulations show that over the last century artificial subsidence and heavy drainage started the salinisation process in the study area and a relative sea level rise will accelerate the increase in salt load in the coming decades affecting the entire aquifer climatic conditions in the area result in limited precipitations throughout the year and preclude efficient aquifer recharge especially in spring and summer when saltwater seepage is extensive the lack of a continuous coastal dune system favors salt wedge intrusion

facies architecture and latest pleistocene holocene depositional history of the po delta comacchio area italy abstract integrated sedimentological and micropaleontological study of 16 cores and 137 piezocone penetration tests approximately 40 m deep in the comacchio area enables the documentation of the depositional history of southeastern po plain in the last 30 ka in response to fluctuating sea level sedimentation within an alluvial plain was the dominant feature across the entire study area during the pronounced sea level fall that culminated in the last glacial maximum thin lowstand fluvial sediments form the lower part of a shallow incised valley above the last glacial maximum unconformity whereas a characteristic paleosol separates the last glacial alluvial plain deposits from the overlying postglacial deposits in the interfluves transgressive and highstand deposits show a well developed stacking pattern of retrogradational coastal plain and estuarine and progradational deltaic facies detailed reconstruction of transgressive paleogeography shows evolutionary features that can be useful for refin

late quaternary depositional architecture of po and tevere river deltas italy and worldwide comparison with coeval deltaic successions abstract po and tevere rivers form two of the most important deltas of the whole mediterranean area detailed investigations have been carried out in the last decade beneath the present delta plains of these two river systems using borehole data correlation with the aid of radiocarbon dates and other dating methods pollens archaeology a detailed sequence stratigraphic framework has been constructed in both areas especially for the last glacial interglacial cycle regional subsidence combined with short term sea level fluctuations of relatively high amplitude played a fundamental role in creating subtracting accommodation during the long phase of falling sea level which followed the tyrrhenian substage 5e transgressive event a discontinuous record of this phase is present in the subsurface of the po plain whereas poor or no preservation has been detected in the tevere area progradational lowstand wedges accumulated during the last glacial maximum mostly in the central part of the basins far from the present deltas and are lacking in the study areas where a hiatal surface is invariably recorded below the transgressive deposits glacioeustasy exerted a major control on sedimentation in both areas during the latest pleistocene holocene sea level rise infilling of fluvial valleys and rapid landward migration of barrier lagoon systems in the context of wave dominated estuaries characterized the transgressive phase in both po and tevere systems in place drowning and transgressive submergence mechanisms of barrier migration were effective predominantly between 13 5 and 9 ka bp in contrast shoreface retreat was dominant in the late transgressive phase the maximum flooding surface mfs can be traced physically from continental to marine deposits and has similar characteristics in the po and tevere river systems being marked by peat layers or lagoonal deposits at landward locations and by distinctive lithological characteristics and micro and macrofossils assemblages basinwards above the mfs the early highstand systems tract records initially the filling of the lagoons followed by the rapid progradation of wave dominate delta systems and flanking strandplains autocyclic processes such as distributary channel avulsion delta lobe abandonment and local subsidence due to sediment compaction were the fundamental controlling factors on sedimentation during deposition of the hst the stratigraphic architecture of the post glacial po and tevere delta complexes closely resembles the basic facies successions documented from coeval deposits of wave dominated and wave influenced clastic coasts both locally within the mediterranean area and in other parts of the world our study emphasizes however some additional features and major differences with previously published depositional models including i the development of backstepping wave dominated estuaries during transgression ii consistent changes through time in the mechanism of barrier migration iii a later construction of the delta systems with respect to what traditionally considered

rifts and grabens abstract deep basins on continental crust can be divided into two main types basins with normal faults and the basement both tilted in the same direction s type and in opposite directions a type a high intensity of stretching occurs in the basins of the a type under a large angle of block tilting this can also be typical of the s type basins of a very small width l that does not exceed the thickness of the prestretched crust h c 0 l h c 0 only in basins of these two k is extension sufficient to explain the subsidence by stretching they can be called rifts extended basins in the basin and range province are a typical example deep basins of a type with a small angle of block tilting and deep basins of s type with a width l h c 0 cannot be produced by stretching under a width h c 0 l 100 km they can be call grabens the fen wei graben in central china and the viking graben in the north sea belong to this structural type

hydrochemical and physical processes influencing salinization and freshening in mediterranean low lying coastal environments abstract ground and surface water chemistry and stable isotope data from the coastal zone near ravenna italy have been examined to determine the geochemical conditions and processes that occur and their implications for fresh water availability in the various brackish saline coastal environments fresh water in shallow coastal aquifers is often not enough to provide drinking water but it may sustain agriculture and natural environments such as pine forests dunes and lagoons the hydrochemistry and stable o and h isotopes of the ground and surface water near ravenna were investigated in relation to these particular environments rivers drainage channels lagoons coastal dunes paleo dunes agricultural fields and gravel pit lakes emphasis was put on the spatial distribution of ground water bodies with similar hydrochemistry most water samples are of the brackish to saline nacl type nacl concentration 300 20 000 mg l with a negative base exchange index bex that is indicative of cation exchange reactions caused by water rock interactions during the infiltration of saline water in a fresh water aquifer calcium dominated fresh water is found only in the rivers in the irrigation and drainage channels and in a few ground water samples the analysis of stable isotopes and so 4 2 cl and 18o cl ratios shows that the major chemical and physical processes determining the salinity in the area are evaporation mixing with saline water cation exchange oxidation of organic matter migration and seepage of hyper saline water the migration and upward seepage of hyper saline water driven by the hydraulic gradients induced by the drainage system causes the aquifer to become more saline over time the areas where natural recharge occurs have always been small and this in combination with the mediterranean climate results in very little natural recharge therefore unless drastic changes to the hydraulic infrastructure are made the coastal aquifer near ravenna will become more saline and will threaten the ecology of current natural areas as well as the farmland

geodynamics of rift plume interaction in iceland as constrained by new 40ar 39ar and in situ u pb zircon ages abstract the interaction between a rift zone and a mantle plume leads to exceptional situations in iceland where the island is 1 5 wider than expected given the north atlantic spreading rate in order to give a better idea of the timeframe of this evolution we present 32 new 40 ar 39 ar and in situ u pb dating on zircon from 16 volcanic systems located from the west to east coasts of iceland the north iceland rift zone nirz was initiated at least 12 ma ago furthermore during these last 12 ma the nirz half spreading rate was between 0 7 and 1 2 cm yr and it propagated to the south at a rate of 1 0 1 2 cm yr the excess width of iceland can thus not be explained by faster spreading rate in the past here we discuss a model that explains the 200 km excess of crust taking into account the eastward relocation of the rift zone and corresponding older crustal capture over the course of iceland s geological history the most recent rift relocation is dated at approximately 6 ma at snaefellsnes peninsula in the west whereas the oldest volcanic systems 15 13 ma from the extreme north east of iceland were most likely generated at the kolbeinsey ridge north of iceland rather than in the nirz itself the need for rift relocations and crustal capture to explain the width of iceland strongly suggests that during rift plume interaction the mantle plume plays an active role it forces the active rift zone to be frequently relocated by rift jumps above its center leaving inactive rift zones as older synclines in the geological record this result in an eastward position of the rift zone in iceland relative to the north atlantic ridge and it can be predicted that in a few tens of millions of years the mid atlantic ridge and the icelandic plume may become decoupled

sand compositional changes as a support for sequence stratigraphic interpretation the middle upper pleistocene to holocene deposits of the roman basin rome italy abstract sand composition is one of the factors of a stratigraphic succession that best records the interaction between allogenic and autogenic processes this is particularly true for the quaternary successions where the effects of this processes are better recognized and differentiated the quaternary succession of the roman basin and in particular the one developed during the late early pleistocene to holocene records a close interaction among tectonic uplift volcanism climate and glacio eustasy such interaction is reflected in a complex stratal pattern and stratigraphic architecture where high rank and low rank depositional sequences are developed and where qualitative and quantitative changes in sand composition are recorded in the same systems tracts the analyzed succession corresponding to the high rank ponte galeria sequence pgs was supplied by the tiber river and its tributaries which developed along the latium tyrrhenian margin such deposits include sediment derived from carbonate to siliciclastic meso cenozoic rocks and from pleistocene volcanic complexes of the roman magmatic province we defined three main sand petrofacies a b c that have a good correspondence with lowstand lst transgressive tst and highstand hst systems tracts of pgs which reflect changes in sand composition and sand provenance under the effects of tectonism volcaniclastic input sedimentary processes and relative sea level variations petrofacies a is feldspatho litho quartzose to feldspatho quartzo lithic in composition it records the erosion and influx of siliciclastic and carbonate rock detritus without volcanic input into the lst fluvial and coastal sands of the pgs petrofacies b is characterized by a modal composition varying from feldspathic to litho feldspathic and feldspatho quartzo lithic it characterizes the tst of the pgs and reflects the abrupt and rapid introduction of volcaniclastic sediment into the system petrofacies c is feldspatho quartzo lithic in composition this petrofacies characterizes the hst of pgs and with respect to the other two petrofacies better records the effects of downstream transport and river mouth sedimentary processes sand samples collected from ancient deposits are similar in composition to the modern tiber river suggesting provenance from a similar river system results show that tectonism during middle upper pleistocene volcanic activity in the sabatini cimini and vulsini volcanic complexes played a major role controlling stream network reorganization in the tiber drainage basin and resulted in enhanced volcaniclastic input from ash fall and recycling of pyroclastic flows volcanic input volcanic lithics and associated phenocrysts and postdepositional alteration during paleosol development define pre syn and post volcanic compositions in the high rank ponte galeria depositional sequence in low rank depositional sequences several processes produced variable quartz feldspar and quartz lithic ratios as well as textural changes these include hydraulic sorting during fluvial and coastal transport and postdepositional in situ weathering processes weathering and pedogenic processes in the source area catchment potentially remove provenance information reducing correlation potential of petrographic signatures of proximal successions in the tiber river sedimentary basin this work tests the effectiveness of using variation in sand composition as a tool in sequence stratigraphy

the southern urals decoupled evolution of the thrust belt and its foreland a consequence of metamorphism and lithospheric weakening an analysis is presented of the mechanisms of tectonic evolution of the southern part of the urals between 48n and 60n in the carboniferous triassic a low tectonic activity was typical of the area in the early carboniferous after closure of the uralian ocean in the late devonian a nappe 10 15 km thick overrode a shallow water shelf on the margin of the east european platform in the early late carboniferous it is commonly supposed that strong shortening and thickening of continental crust result in mountain building however no high mountains were formed and the nappe surface reached the altitude of only 0 5 km no high topography was formed after another collisional events at the end of the late carboniferous in the second half of the early permian and at the start of the middle triassic a low magnitude of the crustal uplift in the regions of collision indicates a synchronous density increase from rapid metamorphism in mafic rocks in the lower crust this required infiltration of volatiles from the asthenosphere as a catalyst a layer of dense mafic rocks 20 km thick still exists at the base of the uralian crust it maintains the crust up to 60 km thick at a mean altitude 0 5 km the mountains 1 5 km high were formed in the late permian and early triassic when there was no collision their moderate height precluded asthenospheric upwelling to the base of the crust which at that time was 65 70 km thick the mountains could be formed due to delamination of the lower part of mantle root with blocks of dense eclogite and or retrogression in a presence of fluids of eclogites in the lower crust into less dense facies the formation of foreland basins is commonly attributed to deflection of the elastic lithosphere under surface and subsurface loads in thrust belts most of tectonic subsidence on the uralian foreland occurred in a form of short impulses a few million years long each they took place at the beginning and at the end of the late carboniferous and in the late permian rapid crustal subsidence occurred when there was no collision in the urals furthermore the basin deepened away from thrust belt these features preclude deflection of the elastic lithosphere as a subsidence mechanism to ensure the subsidence a rapid density increase was necessary it took place due to metamorphism in the lower crust under infiltration of volatiles the absence of flexural reaction on the uralian foreland on collision in thrust belt together with narrow wavelength basement deformations under the nappe indicate a high degree of weakening of the lithosphere such deformations took also place on the uralian foreland at the epochs of rapid subsidences when there was no collision in thrust belt

geochemistry and stable isotope composition of surface waters from the ravenna plain italy implications for the management of water resources in agricultural lands this paper examines the issues related to salinization and water quality in the complex drainage system of the historical land reclamation of lamone basin ravenna coastal plain northern italy with the aim of guiding ongoing agricultural related decisions major and trace element concentration and o h b sr isotope ratios were measured on surface water from a network of canals and ditches sampling was carried out during the winter period and in summer to assess the effects of agricultural water management on the aquatic system results show widespread salinization of waters over the entire crop due to both the direct saltwater inland flushing through the canals in proximity of the mouths and sea salt leaching from soils during winter salinization is partly mitigated by rainfalls while in summer dilution processes are due to freshwater input from outside the watershed planned to assist the agricultural water demand in the winter season the concentration of some elements such as fe mn al and cu in waters exceeds the maximum permissible limits imposed by the italian regulations while during summer the concentration of these elements is significantly reduced a seasonal cycling is established where the bottom sediments of canals and ditches act as sinks of harmful elements mostly through adsorption by fe mn al oxy hydroxide solid phases the irrigation practice although improving the water quality increases water turbidity by re mobilization of sediments which act as transport agents of contaminants with detrimental effects that may become significant over the years

mantle plumes and the metamorphism of the lower crust and their influence on basin evolution abstract since the stretching model appears to be not applicable to the subsidence of accretionary crust basins located on this crust type may have an alternative origin examples of such basins are the west siberia basin and the north german basin both basins showed intensive volcanism and magmatism during the initial phase of their development remarkably the west siberia basin is closely located to the hotspot related siberian flood basalts with a similar permo triassic age and the location of the north german basin in permian times is identical with the present day position of the tibesti hotspot in northern africa these two basins may have specific relations to hotspot heat sources of the earth s underlying mantle due to these heat sources thermal metamorphism within the lower layers of the accretionary crust may occur resulting in rock density increase and subsequent shrinkage of the affected rock volumes these shrinkage processes will lead to the development of topographic lows their filling with sediments and the subsequent start of an exponentially declining isostatic metamorphic basin subsidence in addition to the analyses of metamorphic processes potential field anomalies temperature fields and histories of subsidence have been integrated into one single model that can explain the development of the north german basin similarly the east african rift and eifel hotspots affected parts of the overriding continental plates the east african rift hotspot can be traced back to the afar flood basalts and the dniepr donets basin whereas the eifel hotspot can be linked to the north sea basin continental drift templates present day hotspot locations flood basalt areas metamorphic facies as function of temperature and crust categories are taken as published in recent literature

sand composition changes across key boundaries of siliciclastic and hybrid depositional sequences abstract sand composition of arenite successions is sensitive to a suite of factors operating between initial grain production and final diagenesis on a variety of spatial and temporal scales seven allogenic factors the relative importance of which relies upon the complex interaction between tectonics eustasy and climate play a decisive role in dictating petrofacies distribution within siliciclastic to hybrid depositional sequences these factors include i tectonic exhumation ii physical and chemical rock breakdown iii change in sediment flux iv change in source basin physiography v shelf colonization by organisms vi generation of chemical grains and vii volcanism autogenic processes may locally have a considerable influence on the type and amount of sediment supplied to the basin thus interfering with the external control based upon literature data a conceptual framework of expected compositional changes across the key surfaces for sequence stratigraphic interpretation is outlined two case histories from the miocene shelf to turbidite deposits of the northern apennines and the quaternary alluvial to nearshore succession of the adriatic coast respectively are used as references to illustrate how arenite petrofacies changes can be framed into a sequence stratigraphic scheme on multiple timescales

soluble ions dynamics in mediterranean coastal pinewood forest soils interested by saline groundwater abstract the aim of the study was to evaluate the dynamics of soluble ions in the soils of a pinewood forest of the mediterranean coastal area in the province of ravenna italy a one year monitoring was carried out in four entisols of the san vitale pinewood forest a vulnerable natural area due to subsidence and salt water intrusion ionic soluble forms were examined in saturated paste extracts spes and compared to groundwater soluble forms due to the local thermo pluviometric conditions both the water table depth and groundwater electrical conductivity ecw varied widely ranging respectively from 0 to 162 cm in depth and from 2 to 28 ds m 1 in salinity content as expected this greatly influenced soluble ions concentrations in soil horizons leading to variations in salt s speciation in soils with a deep water table typic ustipsamments superficial horizons showed a prevalence of ca 2 and hco 3 ion forms during the whole year while in the deep horizons na and cl were the dominant ions during summertime in soils with a shallow water table sodic psammaquents superficial ions enrichment was detected with na and cl ions being prevalent autumn and winter rainfall provoked the leaching of both na and especially of cl ions leaving hco 3 as the main anion in the soils with intermediate water table depth and moderate salinity aquic ustipsamments less relevant variations were observed during winter the ca 2 ion was the most present at the soil surface together with hco 3 during summer ca 2 and cl were the most present ions at the soil surface at deeper horizons na and cl ions always prevailed the sodium adsorption ratio sar reached the greatest values 40 during summertime in sodic psammaquents superficial horizons and in typic ustipsamments deep horizons on the basis of mixing curves na and cl displayed a conservative behavior and a likely sea origin both the ca 2 and so 4 2 ions appeared to be partially released from the solid soil fraction while the mg 2 ion seemed to be partially absorbed by the solid matrix on the basis of the hydrochemical characterization of both groundwater and soil spes it was possible to identify different refreshing and salinization processes along the soil profiles the one year monitoring of both the whole soil profile and groundwater never performed before allows a better understanding of the presence of distinct plant species and disease symptoms

influence of sediment provenance on background values of potentially toxic metals from near surface sediments of po coastal plain italy systematic variability in metal concentrations is recorded in near surface 1 m deep late quaternary sediments of po coastal plain across the boundary between alluvial deposits of apenninic provenance and a formerly active now abandoned delta lobe of the po river in the latter area high cr and ni concentrations exceeding the national standard limits are attributed to sediment provenance from ultramafic source rocks of po catchment basin and not to anthropogenic impact spatial distribution of carbonate related elements such as ca and sr displays consistent differences between the two areas confirming a primary control of provenance domains on sediment composition accurate facies characterization of near surface sediments coupled with detailed information on sediment dispersal patterns enable a reliable interpretation of the spatial variability of major elements and trace metals in the study area particularly detailed reconstructions of source area composition and changes in flow directions through historical times allow precise correlation of apparently anomalous geochemical patterns with distinctive depositional events such as shifts in channel course crevasse splay formation and beach ridge evolution the findings of unusually high natural provenance controlled heavy metal concentrations in pre industrial near surface levels highlight the contribution of a sedimentological approach to a reliable interpretation of geochemical data this should be taken into account when determining background values versus anthropogenic impact

tracing provenance and pathways of late holocene fluvio deltaic sediments by heavy metal spatial distribution po plain northern apennines system italy

composition and longshore dispersal of sands from the po and adige rivers since the pre etruscan age abstract the sands presently carried by the po river differ from those of the adige river mainly in the content of dolomite and of fragments of acidic volcanic rocks and to a lesser degree in the content of some heavy mineral species such differences individuate two petrographic provinces compositional data of samples from paleoriver beds and bars reveal that the same differences were present during past times complex admixtures of sands from the two petrographic provinces are often observed in sands from beach ridges whose shape also depends on eolian activity and on the consequent formation of dunes the beach ridges are the product of an evolution from protruding deltaic bodies to a marked regularity of the coastline such modifications are mainly due to marine erosional processes which are of greatest relative importance during periods of decreased fluvial discharge under these conditions the river supplied sands are redistributed with resultant admixture of sands from the two petrographic provinces the sands from deltaic channel mouth bars have compositions that become increasingly uniprovincial from early to late depositional stages these bars form at times of increased fluvial deposition when the rivers build prominent deltas that modify a previously straight coastline under such conditions longshore transport of sands gradually become less important so that mixing of sediments derived from the different provenances gradually becomes negligible since pre etruscan times the sands carried by the adige river were transported longshore towards the south and were mixed with sands from the po river moving north the convergence zone between the two provinces was usually controlled by whichever distributary of the po had the higher discharge among northern po branches that distributary would produce a marked deltaic body that modified the coastline until the southward drift of the adige sands ceased by comparing compositional data with the historical geomorphic evolution of the system the most active mouths of the po in terms of discharge have been identified from the etruscan age to the present