stratigraphic and provenance evolution of the southern apennines foreland basin system during the middle miocene to pliocene irpinia sannio successions italy abstract the paper deals with original stratigraphic petrographic and structural data concerning the evolution of the southern apennines chain italy the main langhian to pliocene deposits cropping out in the northern sector of the southern apennines foreland basin system sannio irpinia area have been studied and correlated in order to document the effects of tectonic changes on the evolution of sandstone detrital modes and stratigraphic architecture the studied sandstone units can be grouped in five key intervals a numidian flysch mostly formed by langhian mature quartzarenitic deposits and conformable serravallian post numidian successions formed by arkosic and calciclastic arenaceous pelitic beds foreland depozones b langhian to tortonian san giorgio fm mostly composed of quartzofeldspatic sandstones foredeep depozone c tortonian to early messinian quartz feldspatic and partly sedimentary carbonatoclastic petrofacies thrust top successions vallone ponticello villanova del battista and san bartolomeo fms d late messinian quartzolithic to quartzofeldspatic sandstones torrente fiumarella anzano molasse and tufo altavilla unit which can be referred to infilled thrust top basins e unconformity bounded pliocene quartzofeldspatic sandstone strata wedge top depozones characterized by synsedimentary tectonic activity detrital modes of the serravallian through middle pliocene sandstones of the southern apennines foreland basin system testify clear provenance relations from the accreted terranes forming the southern apennine thrust belt the studied clastics show almost the same blended quartz feldspatic composition this condition could be related to the tectonic transport over thrust ramp of source rocks as suggested by the tectonic evolutionary model this study dealing with sedimentary provenance analysis and tectonostratigraphic evolution provides an example of the close relations between clastic compositions and foreland basin system development in southern apennines

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

the recycled orogenic sand provenance from an uplifted thrust belt betic cordillera southern spain the betic cordillera of southern spain represents an uplifted foreland fold thrust belt source rock types of the betic cordillera include metamorphic mainly phyllite schist quartzite and gneiss sedimentary siliciclastic and carbonate volcanic felsic to intermediate pyroclasts and mantle derived peridotite gabbro serpentinite and serpentine schist rocks the fluvial systems range that transect the betic cordillera are the major detrital source of sediment along the southern spanish coast supplying sand to beaches and offshore depositional systems in the alboran sea basin three key sand petrofacies derived from the betic mountain belt reflect the main clastic contribution of known source rocks all the sands are quartzolithic ranging from quartz rich to lithic rich fluvial systems draining the sierra de los filabres the sierra nevada the sierra de gador and the ma laga mountains and their related beaches constitute a metamorphic sedimenticlastic quartzolithic sand petrofacies qm34610 f463 lt6269 lm72614 lv264 ls26613 derived dominantly from the nevado fila bride alpuja rride and mala guide complexes this quartzolithic petrofacies extends from northeast of almeria to torremolinos southwest of ma laga and northeast of algeciras only one beach sand sample east of cabo de gata is volcanolithic volcanic detritus mainly having felsitic textures is derived from miocene 15 7 ma pyroclastic sequences cropping out in the southeast of the chain this metamorphic sedimenticlastic quartzolithic petrofacies changes in the coastal stretch from torremolinos to marbella where drainage systems cut across the serrania de ronda here source rock types include peridotite gabbro and serpentinite of the ronda peridotite massif and metamorphic rocks of the ma laguide and alpuja rride units the fluvial and beach sands of this area are quartzolithic qm32612 f1063 lt58611 and include abundant peridotite and serpentinite grains the latter quartzolithic petrofacies changes abruptly from algeciras to ca diz where the sand becomes quartz rich qm7765 f462 lt1964 this sand petrofacies is derived predominantly from recycling of sedimentary sequences mainly the quartzarenite turbidite units of the gibraltar arc the algeciras flysch this petrofacies is characterized by higher proportion of quartz grains and abundant sedimentary lithic fragments lm163 lv161 ls9863 the three onshore petrofacies plot in the recycled orogen provenance compositional field and the lithic to transitional to quartzose recycled subfields of dickinson 1985 they vary from lithic to transitional and quartzose depending on their source lithologies in the betic foreland fold thrust belt these actualistic petrofacies best describe the nature and distribution of sand petrofacies derived from a collisional fold thrust belt where primary and recycled source rocks are interfingered deep marine turbidites of the alboran basin have basinwide quartzolithic sands having close compositional relations with betic cordillera onshore sand petrofacies comparison of detrital modes from mainland to deep marine environments provides a suitable basis for interpreting the miocene to pleistocene sand dispersal history in the alboran basin these modern quartzolithic petrofacies are used to interpret analogous ancient collisional sandstone petrofacies of the alpine orogenic belt of the western central mediterranean region and of other collisional orogenic systems as a broader point of view

evidence for interaction of a spreading ridge with the outer california borderland abstract the southward passage of the rivera triple junction and its effect on the north american plate are primary controls on the miocene tectonic evolution of the outer borderland of california detrital modes of sand shed off the patton ridge and cored by the deep sea drilling project provide evidence of progressive tectonic erosion of the patton accretionary prism and near trench volcanism volcanic glass in the sediment is predominantly calcalkaline rhyolite and andesite typical of subduction related volcanism but also includes minor low k2o tholeiitic basalt we attribute these compositional features to interaction with a spreading ridge associated with a possible trench ridge trench triple junction along the patton escarpment from 18 to 16 ma this study suggests that evidence of ridge trench interaction may be commonly preserved along submerged plate margins in contrast to its more limited recognition and discussion in the literature based on exposed examples in chile japan and alaska

south america and a few grains of sand part 1 beach sands to study correlations between petrography and provenance of modern sands and thus contribute to improved interpretation of ancient sandstones this study reports on the petrography of 218 modern south american beach sands obtained from a shoreline of 25 300 km judged by quartz feldspar rock fragment ratios there are five major associations pacific 24 16 60 argentina 28 14 58 brazil 91 4 5 caribbean east 59 8 23 and caribbean west 54 17 29 study of potash feldspar volcanic rock fragments and the sio 2 al 2 o 3 ratio supplement q f rf ratios tectonics are the dominant control on the mineralogy both the pacific and brazilian associations which form 75 of south america s coastline identify correctly tectonic setting that is active margin composition for the pacific and passive margin for the brazilian however the argentine association would yield a serious error because sand with active margin composition overprints a passive margin variation of total quartz and feld

discriminating depositional environments of sands from modern source terranes using modal analysis abstract composition of modern beach dune and fluvial sands from the gulf of mexico coast and the kapiti and foxton coasts new zealand were compared in order to establish petrological criteria that discriminate between depositional environments and subenvironments the three areas were chosen because of their different sand compositions sand from the gulf of mexico is quartzofeldspathic to feldspatholithic sand from the kapiti coast sands is feldspatholithic and sand from the foxton is lithofeldspathic using a confidence level of 95 petrographic data were plotted as bar charts for each environment beach dune river and for each subenvironment inshore foreshore backshore of the beaches stoss crest lee face of eolian dunes upstream and mouths of the river the best discrimination of beach dune and river environments was achieved for the gulf of mexico sands using q f l and qm k p plots terranes with multiple source rock types such as the gulf of mexico enhance petrological discrimination between sands from beach dune and river subenvironments and environments in terranes with few rock source types such as the kapiti coast only the river sands can be discriminated from those of other environments the single rock source of the foxton coast allows little petrological discrimination between the beach dune and river sands this study examines compositional differences between beach dune and river subenvironments and environments and the degree to which these differences are dependent on the variation of rock types in the source terrane the study also shows the usefulness of q f l qm k p and lv lm ls bar charts the discrimination among beach dune and river sands is partly due to grain size variation

tracing the sources fate and recycling of fine sediments across a river delta interface abstract deltaic floodplains are thought to be long term depositional environments however there remains a limited understanding regarding timescales of depositional and erosional events sediment delivery pathways and sediment storage this study uses sediment concentration and sediment fingerprinting to examine the contribution of surface and subsurface sources to suspended sediment transiting the lower roanoke river north carolina united states the lower roanoke is disconnected from its high gradient uplands in the piedmont and appalachian mountains by a series of dams which effectively restricts suspended sediment delivery from the headwaters accordingly sediments from the lower roanoke river basin are the primary source of suspended sediment downstream of the dams the fingerprinting method utilized fallout radionuclide tracers 210pbxs and 137cs to examine the spatial variation of sediment source contributions to suspended sediment samples n 79 three end member sources were sampled 1 surface sources floodplains and topsoils n 60 2 subsurface sources channel bed and banks n 66 and 3 deltaic sources delta front and prodelta n 11 the results demonstrate that with decreasing river slope and increasing influence of estuarine driven flow dynamics the relative contribution of surface sediments to the suspended sediment load increases from 20 2 in the upper reach to 67 1 in the roanoke bayhead delta bhd at the river mouth the surface sediment contribution decreases and the delta front and prodelta sediments contribute 74 1 to the suspended load these results indicate that during the delta transgression erosion of the lower delta provides an additional source of sediment to the upper delta at the same time the lower deltaic plain considered a sediment sink and long term sediment storage site becomes erosional the lower river and distributary network of the delta plain which were thought to only disperse sediments in a seaward direction may also have an important landward directed sediment dispersal component that provides nourishment and fortification to the upper bhd at the cost of the eroding lower delta recognition of these contrasting sediment pathways in the roanoke river highlights that these complex bidirectional processes may exist in other eroding deltas understanding these bidirectional processes will be necessary for the ongoing management of deltaic environments under increasing anthropogenic stress such as land use change and accelerating sea level rise

petrology chemistry and texture of modern river sands amazon river system key idea following the spirit of p d krynine the sands of the world s largest tropical river system are studied to reveal much about the general origin of sand and sandstone thin section and chemical study of 95 sand samples from the amazon river system in brazil peru ecuador and colombia a river system with great contrasts in climate and rock types reveals that sands derived from the andes are lithic arenites whereas sands derived from precambrian terrains are much richer in quartz as are sands in rivers draining tertiary molasse sand becomes more mature downstream along the main stem of the amazon solimoes maranon so that a sample analyzed at the mouth does not accurately reflect headwater composition dilution by quartz rich tributaries and quartz rich tertiary outcrops possible differential elimination of rock fragments and even possible weathering on the modern flood plain of the amazon contribute to enhanced maturity downstream we speculate that although data on modern large subarti

cycling of dissolved rare earth elements in chesapeake bay the measurement of dissolved rare earth elements ree in the surface waters water column of anoxic basins and pore waters in chesapeake bay has provided new insights to the biogeochemistry and estuarine chemistry of ree all dissolved ree from the riverine source show large scale removal in the lower salinity zone 0 10 the shale normalized pattern of dissolved susquehanna river water is opposite in form to that of surface sediments in the bay the former is enriched in heavy ree hree while the latter are enriched in light ree lree neither component has a flat pattern normally assumed for river transported ree to the ocean the dissolved lree i e la ce nd sm and eu are enriched 3 to 9 times in the oxygen depleted deep waters over their concentrations in the oxic surface waters in contrast hree er yb and lu are slightly depleted all ree concentrations in the two surface 0 2 cm pore waters are greatly enriched 8 17 times 43 times for ce relative to oxygen depleted bottom waters and have relative abundances opposite to those of their sediments while ce has a positive anomaly in the pore waters negative anomalies exist in the oxygen depleted bottom waters the ree are participating in a set of complex biogeochemical cycles within the water column and surface sediments fractionation of ree during these cycles leads to the preferential enrichment of lree in the seasonally oxygen depleted bottom waters it is proposed that this fractionation is coupled to redox cycles of mn and fe and the interaction of dissolved ree with suspended particles and surficial sediments

the estuarine chemistry of rare earth elements comparison of the amazon fly sepik and the gulf of papua systems abstract a comparison of the amazon fly gulf of papua and sepik river systems has shown that there are two distinct processes operating on dissolved rare earth elements ree in estuaries large scale salt induced coagulation in the low salinity region and small to extensive release in the mid to high salinity region fractionation of the ree occurs during both removal and release the order of removal follows lree mree hree and the order of release follows hree mree lree where l m and h refer to light middle and heavy ree respectively hence estuarine reactions can modify the relative abundance of dissolved ree reaching the oceans operating in tandem the removal and release lead to the preferential removal of the lree and the preferential release of hree during estuarine mixing this combination in turn results in an effective river water flux river flux after modifications by estuarine chemistry which is evolved toward the ree composition of seawater which has a heavy ree enriched composition when normalized against the ree composition of rivers or the earth s continental crust the increase of dissolved ree in the mid to high salinity waters of the amazon and fly estuaries suggests a sediment and or suspended sediment source the lack of ree increases in the sepik river estuary strengthens this explanation as the mixing zone of this estuary is located over a deep shelf where there is little physical contact between bottom sediment and estuarine waters in marked contrast the amazon and fly estuaries are dominated by the active resuspension and deposition of bottom sediments the resupply of ree accompanied by fractionation may result from ree carbonate complexation during the reaction of seawater with suspended particles and or bottom sediment estuarine and shelf sediments may be important sources of dissolved nd to the oceans thereby helping to maintain the inter ocean differences in the nd isotopic composition of seawater by reducing the residence time of nd in the oceans

composition of the lower cretaceous source rock from the austral basin rio mayer formation patagonia argentina regional implication for unconventional reservoirs in the southern andes abstract the importance of the rio mayer formation lower cretaceous prodelta to marine outer shelf in the hydrocarbon development of the austral basin patagonia argentina has been recognized by several authors this unit plays a key role as source rock and caprock in the inoceramus inferior springhill petroleum system the most important in the basin in this work we demonstrate that the composition of the rio mayer formation highly matches with the requirements to be considered for shale oil gas exploitation the unit studied mainly consists of laminated black siliciclastic mudtones and shales with interbedded marlstones and sandstone levels and in subsurface shows toc values up to 3 and kerogen types between ii and iii compositional studies from outcrops of this unit are almost absent and constitute the main focus of this contribution a total of ten detailed sedimentological logs were measured from the field and x ray diffraction analysis xrd standard petrography scanning electron microscopy sem and determination of major elements in clay minerals by edax were carried out in order to characterize the composition of the rio mayer formation xrd analyses in fine grained sediments indicate a composition dominated by quartz and calcite with minor proportions of feldspars and clays marine sediments are dominated by illite and chlorite and commonly accompanied by mixed layered illite smectite is while the prodelta is smectite dominated with more than 90 of this clay both authigenic and detrital clays were identified using sem edax sandstones of the rio mayer formation are generally lithic and feldspar graywackes provenance analyses in sandstones make possible the discrimination of four groups of samples differentiated by their ages and palaeoenvironments in comparison with other important shale reservoirs from north america barnett marcellus woodford haynesville and doig the composition of the unit studied have more quartzitic composition reflecting in a high brittleness index bi that result in a clear brittle pattern

the effects of source lithology transport deposition and sampling scale on the composition of southern california sand the transverse ranges of southern california represent an uplifted and variably dissected mesozoic magmatic arc and mesozoic to holocene sedimentary and volcanic strata deposited in convergent and transform tectonic settings modern sand within part of the western transverse ranges represents first order sampling scale of the santa monica and the san gabriel mountains second order sampling scale of the santa clara river draining both mountain ranges and third order sampling scale of the beach system between the mouth of the santa clara river and the eastern santa monica mountains and turbidite sand of the hueneme mugu submarine fan source lithology includes plutonic and metamorphic rocks of the san gabriel mountains and sedimentary and volcanic rocks of the santa monica mountains first order sands have large compositional variability sand from local coastal drainage of the santa monica mountains ranges from basaltic feldspatholithic to quartzofeldspathic sand of the san gabriel mountains local drainages has three distinct petrofacies ranging from metamorphiclastic feldspatholithic to mixed metamorphi plutoniclastic and plutoniclastic quartzofeldspathic second order sand is represented by the main channel of the santa clara river the sand has an abrupt downstream compositional change from feldspathic to quartzofeldspathic third order sand beaches and deep sea turbidite samples of the santa monica basin is quartzofeldspathic beach sand is more quartz rich than is santa clara river sand whereas turbidite sand is more feldspar rich than is beach sand deep sea sand has intermediate composition with respect to second order samples of the santa clara river and third order samples of the beach system suggesting that 1 the santa clara river is the main source of sediments to the marine environment and 2 local entry points from canyons located near local drainages may generate turbidity currents during exceptional flood conditions petrologic data of modern sand of the study area are highly variable at first and second order scale whereas third order sand is homogenized the homogenized composition of deep marine sand is similar to the composition of most ancient sandstone derived primarily from the mesozoic dissected magmatic arc of southern california this study of the western transverse ranges illustrates the effects of source lithology transport depositional environment and sampling scale on sand composition of a complex system which provides insights regarding actualistic petrofacies models

geochemical and sedimentologic variations in inter annually laminated sediments from santa monica basin abstract laminated sediments were recently discovered in the center of santa monica basin california continental borderland and extend from the present day to at least the little ice age ca 1600 a d unlike the annual varves observed in santa barbara basin the light dark lamination couplets observed in 210 pb dated cores from the center of santa monica basin occur at 3 to 6 year intervals very similar in length to the el nino southern oscillation enso phenomena the mechanisms that control the temporal patterns of laminations in this basin are unknown potential causal mechanisms of lamination formation in santa monica basin include 1 changes in the flux of terrigenous vs marine organic carbon and detritus 2 surface water processes which affect marine productivity and organic carbon flux to the sediments and 3 deep water processes which affect oxygen renewal and preservation of organic matter within the basin a box core from the central portion of santa monica basin was analyzed using a suite of geochemical sedimentary and micropaleontologic techniques in order to a investigate which if any of these mechanisms has contributed to the occurrence of laminations and b reconstruct proxy records of climate change samples were extracted from this core at 1 mm increments and provide a temporal resolution of 1 3 years per sample a resolution which is comparable in length to the thickness of individual laminae within the core geochemical and micropaleontologic analyses of core samples provide paleoclimatic and paleoceanographic records which are comparable to and extend beyond historical regional and global climate records in addition to direct comparisons between these records spectral analysis was used to investigate whether there were similar patterns of variability that would implicate dominant forcing functions in the historic and proxy records herein we present preliminary results of records from ca 1860 to the present our results suggest that organic carbon fluxes are the dominant factors that affect lamination variability input of organic carbon is primarily a function of primary productivity and to a lesser extent a function of percentage of terrestrial input thus 1 and 2 are both mechanisms of lamination formation stability of 3 only allows preservation of the record of these variations variations in southern california rainfall appear to be linked to decadal scale variations in downcore density profiles and thus cause variations in the thickness and character of the laminations in the deepest portions of this basin thus filtered density records can be used to reconstruct general paleo rainfall trends which compare well with historic rainfall records variations in the isotopic composition of total organic carbon toc are compared to historic enso and climate records and primarily reflect changes in the relative contribution of marine organic carbon to the basin variations in the carbon isotopic composition of n pachyderma mirror changes in the sedimentary 13 c toc record from santa monica basin and suggest that primary productivity is the primary control on the flux of organic carbon to the sediments and exerts a strong influence on the interannual variability in lamination composition variations in paleo sea surface temperatures generated from the oxygen isotopic composition of n pachyderma correlate well with historical sst records and suggest potential usage as a proxy for general paleosst patterns oxygen sensitive assemblages of benthic foraminifera bolivina argentea and b spissa have been used to identify potential large scale flushing events and construct a historical record of variations in deep water oxygen levels spectral analysis of regional historic records indicate dominance of short term enso length and long term decadal patterns of climate variability the short term enso signal is not dominant in the santa monica proxy records however strong decadal length signals are identified in all of the proxy records and suggest that the dominant forcing mechanisms in santa monica basin may be decadal in length

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

the rare earth element chemistry of estuarine surface sediments in the chesapeake bay abstract concentrations of rare earth elements ree were measured in the fine fraction of shallow surface sediments from the lower chesapeake bay as studies suggest that coagulation of colloids dominates the removal of ree from the dissolved load in low salinity regions of estuaries ree in sediments showed spatial heterogeneity both laterally and longitudinally we observed the influence of salinity on the spatial and temporal variability in total ree content and on eu anomalies lower total ree was found in sediments deposited along the eastern shore the chemistry of the mid bay islands was distinct with higher overall ree content and slightly more positive ce anomaly values positive ce ce in the mid bay are attributed to coriolis acceleration restricting freshwater flow towards the west away from the islands leading to oxidative removal of ce from the pore waters to the sediments the presence of positive eu eu in sediments deposited along the eastern shore is linked to salinity we suggest that unique local conditions along the eastern shore possibly including submarine groundwater discharge of nutrient rich reducing waters combined with organic matter decay and the predominance of oceanic water flow toward this region leads to the development of a strong localized salinity gradient this study demonstrates the utility of ree sediment chemistry in identifying and resolving local and estuarine wide geochemical processes

geochemistry and deposition of 7be in river estuarine and coastal waters the atmospheric flux of cosmogenic 7be 53 3 day half life and the mode of 7be deposition in river estuarine and coastal environments have been examined the atmospheric flux of 7be commonly supports inventories ranging from 1 0 to 2 0 pci cm2 1 pci 0 037 bq beryllium 7 concentrations in water phase samples collected across salinity gradients in several estuaries along the eastern coastline of the united states range from 0 03 to 0 53 pci l and primarily reflect variations in 7be supply and sorption kinetics the major process controlling the concentration of 7be on estuarine suspended particles appears to be the length of time that these particles remain in the water column field particle to water distribution coefficients for 7be have a median value of about 4 104 but range over an order of magnitude reflecting short term variations in 7be input particle dynamics and particulate iron content rather than equilibrium sorption desorption responses to changes in water salinity or particle type residence times of 7be in the water column range from a few days in estuarine areas of rapid fine particle deposition to several weeks in high energy environments where pronounced sediment resuspension reintroduces deposited 7be back into the water column inventories of 7be in sediments range from nondetectable to 3 3 pci cm2 with the highest inventories in areas where fine particles are accumulating rapidly such sites are also major repositories for other particle reactive substances a 7be budget for the james estuary indicates that less than 5 of the expected 7be input is in the water column and that the short term estuarine trapping efficiency for atmospherically derived 7be is somewhere between 50 and 100

downstream changes in sand composition roundness and gravel size in a short headed high gradient stream northwestern italy abstract we assessed changes in grain composition and roundness of the 1 2 and 2 3 size fractions of sand along a 16 km length of the graveglia river liguria italy to its mouth at the tyrrhenian sea and then for 1 km along the beach rocks exposed in the drainage area include ophiolites ribbon chert limestone shale sandstone and quaternary sands the erosion of shale and limestone bedrock yields large amounts of sand but sand grains of these rock types decrease rapidly in abundance downstream chiefly through dilution rather than abrasion carbonate rock fragments that reach the beach survive wave abrasion but most shale grains do not predictably monocrystalline and polycry talline quartz and chert are the most durable grain types but serpentine basalt and unidentified rock fragments also show significant resistance to both stream and wave abrasion polycrystalline quartz feldspar basalt serpentine sandstone and shale grains are more abundant in the coarser sand size fraction monocrystalline quartz carbonate rock fragments and unidentified rock fragments are more abundant in the finer sand size fraction and chert and plutonic rock fragments have no size preference a comparison of the outcrop areas of the different rock types with the corresponding percentages of different grain types present in each of three drainage areas indicates that shale which breaks down readily to silt and clay size particles and chert which does not readily break down into sand size fragments are underrepresented in the sands limestone and serpentine however are overrepresented in comparison to outcrop area in certain drainage areas the overrepresentation of limestone reflects in part a sampling bias sand was sampled adjacent to limestone outcrops but the overrepresentation of serpentine reflects its resistance to weathering compared to other aluminosilicates and its durability shale limestone and serpentine increase in roundness downstream and along the beach to a maximum limiting value of 5 rho units medium grained shale clasts attain high rounding in only a few kilometers of transport downstream decrease in gravel size follows an exponential formula that can be expressed in linear form using phi size size 0 1167 distance km 10 29

provenance of the upper miocene modelo formation and subsidence analysis of the los angeles basin southern california implications for paleotectonic and paleogeographic reconstructions the los angeles basin has undergone three stages of development related to complex plate interactions within the evolving san andreas transform system transrotation 16 12 ma transtension 12 6 ma and transpression 6 0 ma timing of these stages correlates with microplate capture events along the continental margin and is expressed in changes in subsidence rates and provenance within the los angeles basin the modelo formation and related units were deposited in the northern part of the los angeles basin at bathyal depths during late miocene time the northern los angeles basin was segmented into three subbasins in each of which coarse sediment was deposited as submarine fans puente tarzana and simi a fourth fan system piru formed in the ventura basin just north of the los angeles basin the puente tarzana and piru fans were derived from the san gabriel block which consists primarily of crystalline basement and lesser volcanic and sedimentary components sandstone within the puente fan reflects unroofing of the central and eastern san gabriel block the tarzana fan was derived primarily from the central san gabriel block and the piru fan was derived primarily from the western san gabriel block which is distinctly characterized by ca rich plagioclase derived from proterozoic anorthosite and related bodies the lack of ca rich plagioclase in the other fans eliminates the western san gabriel block as a possible source area and confirms differentiation of the ventura basin from the los angeles basin by late miocene time the simi fan was derived from locally uplifted cretaceous and paleogene strata sandstone composition reflects the recycling of these sediments subsidence and provenance analyses are consistent with the following paleogeographic and paleotectonic reconstruction beginning at approximately 16 ma transrotation of the western transverse ranges induced extension and thermal subsidence of the los angeles basin area a second pulse of extension and thermal subsidence occurred when motion began along the san gabriel fault at 12 ma right slip of 60 70 km occurred along the san gabriel fault which produced transtension in the los angeles basin area and deposition of the puente tarzana simi and piru fan systems at 6 ma transform motion was transferred to the san andreas fault transpression has dominated the los angeles basin since 6 ma including rapid uplift flexural subsidence due to tectonic loading and rapid sedimentary filling the rapid subsidence and filling and the sudden switch between transtension and transpression in the los angeles basin are typical of strike slip basins in general however initiation of the los angeles basin by transrotation reflects the uncommon process of microplate capture along the rapidly evolving california margin

unraveling magmatic and orogenic provenance in modern sand the back arc side of the apennine thrust belt italy modern river and beach sands carried to and deposited along the coasts of the tyrrhenian sea are derived from multiple mag matic arc and orogenic sources including ophiolitic sequences and tur bidites issued from the ligurian ocean carbonate platform to pelagic sedimentary and metasedimentary successions originally deposited onto the adria continental margin and overlying foredeep clastic wedges undissected arc feldspatholithic signatures characterize limited areas capraia island tarquinia and napoli gulfs contrasting fea tures with respect to circum pacific suites low to very low p f ratio include sanidine as the most abundant detrital feldspar and common leucite and leucite bearing lithic fragments reflecting the potassic to ultrapotassic character of neogene quaternary magmatism green au gite associated with oxyhornblende and either abundant hypersthene tuscan magmatic province or minor olivine and spinel roman mag matic province is the dominant dense mineral dissected arc ar kosic signatures reflect unroofing of miocene monzogranitic stocks in the tuscan archipelago sands from ophiolitic sequences and remnant ocean sediments subduction complex provenance are characterized by common cel lular serpentinite with few chert grains basaltic to diabase and gab broic grains and by abundant shale to slate lithic grains respectively dense mineral suites are dominated by either diallage or chrome spinel sedimentaclastic sands ranging in composition from lithic to quartz ofelspathic are widespread thrust belt provenance richest in lith ic grains is detritus from mesozoic platform dominant carbonates with abundant dolostone to pelagic dominant limestone with abundant chert sedimentary successions metamorphiclastic sands with poly crystalline quartz phyllite and quartz mica or marble lithic grains from denuded core complexes are found locally apuane alps rela tively quartzose sands with abundant feldspars and garnet rich dense mineral assemblages are recycled from foredeep turbidites derived di rectly or indirectly chiefly from the alps this signature is foreign to the apennine accretionary wedge where continental basement is not structurally involved we calculate that one third of the sand grains deposited along tyrrhenian shores today are ultimately derived through long distance multistage transport and repeated recycling from the alps

drowning of the mississippi delta due to insufficient sediment supply and global sea level rise global sea level rise reduced sediment supply and subsidence threaten the stability of the mississippi delta calculations of riverine sediment load and storage indicate that 10 000 13 500 km2 of the delta could be submerged by ad 2100

the mesozoic successions of western sierra de zacatecas central mexico provenance and tectonic implications central mexico was subject to active tectonics related to subduction processes while it occupied a position in western equatorial pangea during early mesozoic time the subduction of the palaeo pacific plate along the western north american and south american active continental margins produced volcanic arc successions which were subsequently rifted and re incorporated to the continental margin in this context the fringing arcs are important in unravelling the continental accretionary record using petrographic analysis detrital zircon geochronology and structural geology this paper demonstrates that the guerrero arc guerrero terrane formed on top of a felsic volcaniclastic unit middle jurassic la pimienta formation and siliciclastic strata upper triassic zacatecas formation and arteaga complex of continental mexican provenance deposited across the continental margin and oceanic substrate this assemblage was rifted away from continental mexico to form an intervening oceanic assemblage upper jurassic lower cretaceous las pilas volcanosedimentary complex of the arperos basin then accreted back more or less at the same place all above the same east dipping subduction zone the accretion of the guerrero arc to the mexican continental mainland sierra madre terrane caused the deposition of a siliciclastic unit la escondida phyllite which recycled detritus from the volcaniclastic and siliciclastic underlying strata

sourceland controls on the composition of beach and fluvial sand of the northern tyrrhenian coast of calabria italy implications for actualistic petrofacies abstract the northern tyrrhenian margin of calabria in southern italy provides a natural laboratory for sampling sand at different scales small drainages first order rivers draining mountain ranges second order and marine environments beach to deep marine third order calabrian mountain ranges represent an uplifted and variable dissected thrust belt constituted by palaeozoic through pleistocene plutonic metamorphic ophiolitic carbonate and siliciclastic rocks the modern setting includes a mountainous coast having high rates of fluvial discharge and the deep marine paola basin the composition of modern fluvial and beach sands is useful for the interpretation of sediment transported into deeper water environments modern beach and fluvial sands of the northern tyrrhenian margin of calabria define three distinct petrologic provinces from north to the south 1 the lao littoral province has calclithite sand derived from erosion of dominantly carbonates of the southern apennines 2 the coastal range littoral province has quartzolithic sand derived from dominantly metamorphic schist and phyllite coastal range and 3 the santa eufemia littoral province has quarzofeldspathic sand derived from dominantly metamorphic coastal range and sila massif and plutono metamorphic mount poro provenances deep marine turbidites of the paola basin have basinwide quartzolithic turbidite sands having close compositional relations with coastal range littoral petrofacies only at the northern boundary of the paola basin calclithite turbidite sand record deep water dispersal of the lao littoral sands comparison of detrital modes from mainland to deep marine environments contribute to the models of dispersal pathways and geographical extension of actualistic sand petrofacies

rare earth elements as provenance indicators in north australian estuarine and coastal marine sediments rare earth elements ree in three grain size fractions of clay dominated estuarine and coastal sediments from the north australian coastline have been investigated for use as potential provenance indicators comparisons of data based on instrumental neutron activation analysis and inductively coupled plasma mass spectrometry revealed that hf digestions of zircon bearing samples resulted in unsatisfactory recovery of ree instead a relatively simple fast and safe partial digestion using hclo4 hno3 was used to extract ree mainly from clay minerals while excluding extraction of ree from zircons a comparison with published data for primary rock units within river catchments showed that the main ree systematics has been preserved in downstream clay rich sediments analysis of variance of la gd paas la yb paas and eu eu paas ratios in five areas showed that the 63 m fraction possessed the greatest discriminating power all five areas could be distinguished from each other at highly significant levels based on one or more of these ratios

spatial and temporal patterns of sedimentation in an infilling reservoir abstract river dams are ubiquitous globally altering the connection of up and downstream environments in particular they store vast amounts of sediment in their upstream reservoirs many of which are approaching storage capacity there is much interest in sediment management for these systems even though quantifying sedimentation rates remains somewhat challenging this study focuses on one such system conowingo reservoir upstream of the last and largest dam conowingo dam on the susquehanna river before it enters chesapeake bay the trapping capacity of conowingo reservoir has decreased since its creation in 1928 potentially increasing fluvial loading to the bay in addition large flood events can scour much more than the average annual sediment load from the reservoir bottom delivering exceptionally large sediment loads to the bay within days predicting the downstream impacts of both reservoir infill and scour events is essential for management however these predictions are limited by understanding of the complex spatial and temporal variability of sedimentation to evaluate this variability sedimentation rates are determined throughout the reservoir over seasonal to decadal time scales with the naturally occurring radioisotopes 7be and 210pb half lives 53 3 days and 22 3 years respectively as well as anthropogenically produced 137cs half life 30 7 y as an independent geochronometer these rates are placed within the context of sediment character mud content and fluvial sediment supply to the reservoir as well as its geomorphology in general seasonal sedimentation rates scale with fluvial loads and reflect deposition of watershed derived sediment spatial patterns of seasonal sedimentation follow those of river deltas incised by channels while decadal scale sedimentation rates increase downstream episodic event sedimentation in channels is suggested by the character of 210pb profiles which indicate non steady state sedimentation that makes application of sediment age dating models challenging in this system although sediment mud content has clearly decreased as the reservoir has filled observed changes in sedimentation rates may reflect biases of these models rather than physical changes

contrasting soils and landscapes of the piedmont and coastal plain eastern united states abstract the piedmont and coastal plain physiographic provinces comprise 80 percent of the atlantic coastal states from new jersey to georgia the provinces are climatically similar the soil moisture regime is udic the soil temperature regime is typically thermic from virginia through georgia although it is mesic at altitudes above 400 m in georgia and above 320 m in virginia the soil temperature regime is mesic for the piedmont and coastal plain from maryland through new jersey the tightly folded structurally complex crystalline rocks of the piedmont and the gently dipping layer cake clastic sedimentary rocks and sediments of the coastal plain respond differently to weathering pedogenesis and erosion the different responses result in two physiographically contrasting terrains each has distinctive near surface hydrology regolith drainage morphology and morphometry the piedmont is predominantly an erosional terrain interfluves are as narrow as 0 5 to 2 km and are convex upward valleys are as narrow as 0 1 to 0 5 km and generally v shaped in cross section alluvial terraces are rare and discontinuous soils in the piedmont are typically less than 1 m thick have less sand and more clay than coastal plain soils and generally have not developed sandy epipedons infiltration rates for piedmont soils are low at 6 15 cm h the soil saprolite soil rock and saprolite rock boundaries are distinct can be placed within 10 cm and are characterized by ponding and or lateral movement of water water movement through soil into saprolite and from saprolite into rock is along joints foliation bedding planes and faults soils and isotopic data indicate residence times consistent with a pleistocene age for most piedmont soils the coastal plain is both an erosional and a constructional terrain interfluves commonly are broader than 2 km and are flat valleys are commonly as wide as 1 km to greater than 10 km and contain numerous alluvial and estuarine terrace sequences that can be correlated along valleys for tens of kilometers coastal plain soils are typically as thick as 2 to 8 m have high sand content throughout and have sandy epipedons these epipedons consist of both a and e horizons and are 1 to 4 m thick in coastal plain soils the boundaries are transitional between the solum and the underlying parent material and between weathered and unweathered parent material infiltration rates for coastal plain soils are typically higher at 13 28 cm h than are those for piedmont soils indeed for unconsolidated quartz sand rates may exceed 50 cm h water moves directly from the soil into the parent material through intergranularpores with only minor channelization along macropores joints and fractures the comparatively high infiltration capacity results in relatively low surface runoff and correspondingly less erosion than on the piedmont uplands due to differences in piedmont and coastal plain erosion rates topographic inversion is common along the fall zone surfaces on cenozoic sedimentary deposits of the coastal plain are higher than erosional surfaces on regolith weathered from late precambrian to early paleozoic crystalline rocks of the piedmont isotopic paleontologic and soil data indicate that coastal plain surficial deposits are post middle miocene to holocene in age but most are from 5 to 2 ma thus the relatively uneroded surfaces comprise a pliocene landscape in the eastern third of the coastal plain deposits that are less than 3 5 ma include alluvial terraces marine terraces and barrier back barrier complexes as morphostratigraphic units that cover thousands of square kilometers isotopic and soil data indicate that eastern piedmont soils range from late pliocene to pleistocene in age but are predominantly less than 2 ma old thus the eroded uplands of the piedmont peneplain comprise a pleistocene landscape

physiographic controls on the composition of sediments derived from volcanic and sedimentary terrains on barro colorado island panama abstract the phenomena that control sand composition are complex dynamic and interlinked although source rock lithology is of critical importance in determining the allowable range of sand compositions chemical weathering may overprint the source rock signal substantially in the humid tropical environment of barro colorado island panama source rocks of similar lithological character produce sediments of differing compositions in different physiographic environments moreover sediments derived from source rocks of dissimilar mineralogical composition but produced on similar physiographic terrains may be nearly indistinguishable physiography influences the composition of sediments released from the source areas by controlling the duration of chemical weathering on relatively flat terrains rates at which loose solids are generated by weathering may exceed rates at which slope processes can remove this material soils are exposed to the weathering environment for long periods of time and are strongly leached consequently weathering products are cation poor and contain relatively immobile elements incompletely weathered detritus is not abundant and is greatly enriched in chemically resistant phases on steeper slopes potential solid erosion rates exceed weathering rates residence times of minerals within soils are short resulting in weathering products that are cation rich and contain an abundance of uns able phases on barro colorado island fluvial sediments are dominated by authigenic particles composed of secondary weathering products although the stability of many such particles in larger transportational and depositional systems and in the diagenetic environment has yet to be assessed they may be more important constituents of fluvial sediments in tropical environments than has been previously recognized

rates and processes of soil development on quaternary terraces in cajon pass california field and laboratory analyses of soils on 11 well dated fluvial terraces spanning the past 0 5 m y demonstrate that a threshold governs changes in several morphological and chemical characteristics of increasingly older soils correlations with respect to time among iron species soil morphology and soil silt and clay demonstrate that the chronosequence at cajon pass reflects primarily an evolutionary largely time dependent trend and does not reflect differences in external factors such as climate most of the soil development on holocene terraces of the cajon pass area is due to physical incorporation of eolian dust and organic material into initially very permeable gravels this process decreases soil permeability and is conducive for an increase in the magnitude of chemical weathering latest pleistocene and older pleistocene soils have developed clay and authigenic iron oxide rich b horizons at the expense of organic matter rich a horizons and color b horizons as the extent of chemical weathering has increased this conversion of the soil from a noncolloidal system to a much more colloidal system takes place over a relatively short period of time 4 000 yr and is herein defined as a type of pedologic threshold in the cajon pass area the attainment of the threshold and subsequent development of the argillic b horizon of soils on latest pleistocene terraces occurred during the holocene thus the absence of argillic horizons in soils on holocene terraces is attributable to simply their younger age rather than to the pleistocene to holocene climatic change the threshold is a function of several variables including influx rate of eolian dust and initial soil permeability therefore the time required to attain the threshold will vary in chronose quences characterized by geomorphic or geographic settings that are different from conditions found in cajon pass

provenance environmental and paleogeographic controls on sandstone composition in an incised valley system the eocene la meseta formation seymour island antarctica abstract the eocene la meseta formation is the youngest exposed unit of the back arc james ross basin antarctic peninsula cropping out in seymour marambio island the formation comprises 720 m of clastic sedimentary rocks of deltaic estuarine and shallow marine origin it was subdivided into six unconformity based units valle de las focas acantilados campamento cucullaea i cucullaea ii and submeseta allomembers grouped into three main facies associations facies association i represents valley confined deposition in a progradational aggradational tide dominated and wave influenced delta front delta plain environment facies association ii includes tidal channels mixed tidal flats tidal inlets and deltas washover and beach environments facies association iii represents nonconfined tide and storm influenced nearshore environments la meseta formation sandstones are quartzofeldspathic with some hybrid arenites glauconite and carbonate bioclasts rich sandstone detrital modes are subdivided into two distinctive petrofacies the low quartz petrofacies petrofacies i q 12 interpreted to retain the original provenance signal and the high quartz petrofacies petrofacies ii q 55 and l 1 4 is clearly dominated by volcanic derived clasts it developed at times of high sea level and or during later stages of the valley fill when an energy fence at the shoreline prevented delivery of sediment from the antarctic peninsula thus enhancing the relative participation of local volcanic sources

tectonic versus chemical weathering controls on the composition of fluvial sands in tropical environments the compositions of fluvial sands collected in mountainous regions along the volcanic front in central america and along the andean front in venezuela and colombia correlate with the tectonic setting of their source terrains the sands derived from the central american volcanic arc are compositionally distinct from those derived from the andean terrains and minor variations in tectonic style can also be discriminated subtle differences in tectonic setting and source rock composition are recognizable only when modification by chemical weathering is slight they are strongest in sands from low order streams draining mountainous areas with modest alluvial plain development sands that have been exposed to weathering for extended periods during alluvial storage are progressively enriched in chemically stable phases with increased weathering sands from continental terrains converge toward a supermature quartz arenite end member and the imprint left by source rock composition and tectonic setting is obscured in intraoceanic terrains a similar but much less pronounced enrichment in stable phases relative to less stable phases is observed similarly overprinting the tectonic signal although detailed tectonic information is easily lost sands derived from intraoceanic terrains are distinguishable from those derived from continental terrains even after long exposure to intense chemical weathering conditions

a model for neogene crustal rotations transtension and transpression in southern california two episodes of crustal rotation have occurred in the regions of southern california and the mojave desert since the beginning of miocene time an early miocene episode of clockwise crustal rotation is associated with widespread north south to north northeast south southwest crustal extension throughout southeast california and western arizona this episode is apparently related to changing subduction parameters of the farallon plate a middle miocene and later episode of clockwise rotation in the transverse ranges and bordering areas is related to shear between the pacific and north american plates in both episodes clockwise crustal rotations first occur in a deforming zone which has a component of extension across its trend and shear along its trend the effects of extension are most pronounced in the earlier episode but clear in the later one also the pacific north american deforming zone began contracting in width during pliocene time but clockwise rotations continued and are probably in progress today

experimental study of the influence of oil wet calcite cements on oil migration and implications for clastic reservoirs abstract the influence of oil wet calcite cements on oil migration in clastic reservoirs is of significant interest in the field of petroleum exploration however the microscopic migration of oil in microscopic pore spaces with oil wet calcite cements has not been directly observed microscopic observations of oil migration were conducted in a glass micromodel at normal temperature and pressure to investigate the influence mechanism of oil wet calcite cements on oil migration in pore spaces the calcites were precipitated as cements prior to the oil migration a two dimensional glass micromodel with two interconnected spaces with the same pore throat structures was used in the experimental study a new method to create firmly adhering calcites was used to precipitate equal amounts of calcites in the two interconnected spaces the oil migration was recorded in real time under a microscope throughout the experiment the experimental results show that oil migration occurs faster in spaces with than without oil wet calcites during the oil migration in the pore throat spaces the oil migrates towards the surfaces of the oil wet calcites when the oil is in contact with the calcites the presence of oil wet calcites significantly reduces the oil breakthrough pressure the electrostatic attraction between the carboxylic groups and calcites and the intermolecular forces between the carboxylic groups and organic molecules in the oil cause the oil migration towards the surfaces of the oil wet calcites the experimental results indicate that oil preferentially migrates into clastic reservoirs that possess appropriate amounts of oil wet calcite cements precipitated prior to oil emplacement

changes in phosphorus biogeochemistry along an estuarine salinity gradient the iron conveyer belt we used sequential extractions to quantify different forms of particulate phosphorus pp in sediments along the salinity gradient of the patuxent river estuary about 50 90 of the pp was phosphate bound to iron oxides fe p and 8 30 was organic p org p loosely sorbed phosphate sorb p detrital apatite and authigenic plus biogenic apatite each made up 10 of the pp suspended sediments from the watershed and deposited sediments in tidal freshwater had the highest concentrations of fe p ranging about 30 55 mmol g21 sediment as pore water salinity increased to 7 along the estuarine gradient fe p declined to 15 25 mmol g21 org p increased from 4 to 10 mmol g21 sorb p increased from 0 5 to 2 5 mmol g21 and total sediment pp declined from 60 to 40 mmol g21 concentrations of pore water solutes also changed with salinity as salinity increased dissolved fe and ammonium decreased while dissolved phosphate increased near the freshwater end of the gradient the molar ratio of pore water ammonium phosphate was generally 16 the redfield ratio and ranged up to 700 while at the saline end of the gradient the ratio was generally 16 and ranged down to 1 5 our observations are consistent with the hypothesis that phosphate is released from terrigenous sediments when they are deposited in saline portions of the estuary where sulfide may enhance dissolution of fe p and form fe sulfide precipitates such phosphate release may contribute to the generally observed switch from phosphorus limitation in freshwater to nitrogen limitation in coastal marine water

the influence of climate and topography on rock fragment abundance in modern fluival sands of the southern blue ridge mountains north carolina chemical weathering influences the detrital composition of sand size sediment derived from source areas subject to different amounts of precipitation in the coweeta basin north carolina of the grain types studied rock fragments are most sensitive to chemical degradation therefore their abundance is the best indicator of cumulative weathering effects destruction of sand size rock fragments by chemical weathering is a function of both the intensity and duration of chemical weathering experienced by grains in regoliths of the source area in the coweeta basin the intensity of chemical weathering is directly related to the climate via effective precipitation in individual subbasins whereas the duration of chemical weathering is inversely related to the relief ratio of the watershed therefore soils in watersheds with low relief ratios and high discharge per unit area experience the most extensive chemical weathering and sediments derived from these watersheds contain the lowest percentage of rock fragments the effects of climate alone cannot explain the systematic variation of rock fragment abundance in sediments from the coweeta basin the compositional imprint left on these sediments by chemical weathering is a function of both climate and topographic slope in the sediment source area

petrology and diagenesis of the eocene butano sandstone la honda basin california the lower and middle eocene butano sandstone at least 1500 m and possibly as much as 3000 m thick was deposited as a submarine fan in a narrow restricted continental borderland setting its quartzofeldspathic composition suggests a local provenance from plutonic and metamorphic rocks of the salinian terrane it crops out in three belts of which the middle belt in the central part of the basin was buried the deepest and underwent the most significant diagenetic changes the central belt made up of middle fan deposits contains higher amounts of quartz and lower amounts of feldspar than the more proximal southern inner fan deposits and more distal northern outer fan deposits the presence of authigenic albite laumontite and pore filling kaolinite and chlorite suggests that decreases of feldspars mainly plagioclasej are related mainly to dissolution of plagioclase it is possible that at least 20 25 of the plagioclase with respect to total feldspar has been diagenetically dissolved in the butano sand

provenance of volcaniclastic beach sand in a magmatic arc setting an example from lipari island aeolian archipelago tyrrhenian sea lipari an active volcanic island in the aeolian magmatic arc is an excellent area to determine the effects of multiple source lithology climate weathering transport and depositional environment on epiclastic sand composition volcaniclastic sand samples from 12 modern beaches were petrographically characterized using the gazzi dickinson method and the proportions of source rocks in combination with topography in associated coastal drainage basins were quantified using gis several types of bedrock in the 12 drainage basins that are the likely prominent sources for sand at each sampled beach were recognized and divided into two categories of provenance lithotypes lavas and pyroclastic rocks ranging in composition from basaltic andesitic to andesitic to rhyolitic volcanic lithic fragments from lipari beach sand consist of colourless and black glassy volcanic fragments with lathwork felsitic vitric and microlitic textures moreover high amounts of detrital less durable minerals such as pyroxene olivine and fe oxides illustrate how the analysed sands preserve the source rock s provenance signals applying the concept of sand generation index we see that these lithotypes have different propensities to create detritus in terms of both grain size and composition clastic contribution from pyroclastic rock outcrops such as pumice is not found in the size ranges studied suggesting that these pumiceous source rocks probably only produce gravel or very fine sand and silt this finding has implications for the stratigraphic record because pumice clasts ranging from medium to fine grain size could be underrepresented in older volcaniclastic deposits and overrepresented in other size fractions

interpretation of neovolcanic versus palaeovolcanic sand grains an example from miocene deep marine sandstone of the topanga group southern california despite abundant data on volcaniclastic sand stone the compositional spatial and temporal distribution of volcanic detritus within the sedimentary record is poorly documented one of the most intricate tasks in optical analysis of sand stone containing volcanic particles is to distinguish grains derived by erosion of ancient volcanic rocks i e palaeovolcanic noncoeval grains from grains generated by active volcanism subaqueous and or subaerial during sedimentation neovolcanic coeval grains deep marine volcaniclastic sandstones of the middle topanga group of southern california are interstratified with 3000 m thick volcanic deposits both subaqueous and subaerial lava and pyroclastic rocks ranging from basalt andesite to dacite these rocks overlie quartzofeldspathic sandstones petrofacies 1 of the lower topanga group derived from deep erosion of a mesozoic magmatic arc changes in sandstone composition in the middle topanga group provide an example of the influence of coeval volcanism on deep marine sedimentation volcaniclastic strata were deposited in deep marine portions of a turbidite complex volcaniclastic apron built onto a succession of intrabasinal lava flows and on the steep flanks of subaerially emplaced lava flows and pyroclastic rocks distinctive petrofacies 2 5 directly overlying basalt and basaltic andesite lava flows petrofacies 2 is a pure volcanolithic sandstone including vitric microlitic and lathwork volcanic grains and neovolcanic crystals plagioclase pyroxene and olivine the abundance of quenched glass palagonite fragments suggests a subaqueous neovolcanic provenance whereas sandstones including andesite and minor basalt grains suggest subaerial neovolcanic provenance this petrofacies probably was deposited during syneruptive periods testifying to provenance from both intrabasinal and extrabasinal volcanic events deposited during intereruptive periods impure volcanolithic petrofacies 3 includes both neovolcanic 85 and older detritus derived from plutonic metamorphic and palaeovolcanic rocks during post eruptive periods the overlying quartzofeldspathic petrofacies 4 and 5 testify to progressive decrease of neovolcanic detritus 48 14 and increase of plutonic metamorphic and palaeovolcanic detritus the upper topanga group calabasas formation conformably overlying the middle unit has dominantly plutoniclastic sandstone petrofacies 6 neovolcanic detritus is drastically reduced 4 whereas palaeovolcanic detritus is similar to percentages of the lower topanga group petrofacies 1 the middle topanga group sandstones are vertically organized into four

textural and compositional controls on modern beach and dune sands new zealand textural compositional physical and geophysical determinations were carried out on 111 beach and dune sand samples from two areas in new zealand the kapiti foxton coast sourced by terranes of andesite and greywackes and the farewell spit wharariki coast sourced by a wide variety of paleozoic terranes our aim is to understand how long shore drift beach width and source rock control the sedimentological and petrographic characteristics of beach and dune sands furthermore this study shows the usefulness of specific minerals quartz plagioclase with magnetite inclusions monomineralic opaque grains to interpret the physical processes fluvial discharges long shore currents winds that distribute beach and dune sands in narrow and wide coastal plains this was done by means of direct grain size and modal analyses and indirect specific gravity magnetic non magnetic separations m nm magnetic susceptibility measurements hysteresis loops methods results are compared with beach sands from hawaii oregon the spanish mediterranean elba island and southern california compositionally the kapiti foxton sands are similar to first order immature sands which retain their fluvial signature this results from the high discharge of rivers and the narrow beaches that control the composition of the kapiti foxton sands the abundance of feldspar with magnetite inclusions controls the specific gravity of the kapiti foxton sands due to their low content of opaque minerals and coarse grain size magnetic susceptibility of the sands is related mainly to the abundance of feldspars with fe oxides volcanic lithics and free opaque minerals the farewell spit wharariki sands are slightly more mature than the kapiti foxton sands the composition of the farewell spit wharariki sands does not reflect accurately their provenance due to the prevalence of long shore drift waves little river input and a wide beach low abundance of feldspar with magnetite inclusions and free opaque grains produces poor correlations between specific gravity sg and fe oxide bearing minerals the small correlation between opaque grains and m nm may be related to grain size the magnetic susceptibility of farewell spit wharariki sands is low due to the low content of grains with magnetite inclusions hysteresis and isothermal remnant magnetization irm agree with the magnetic susceptibility values copyright 2006 john wiley sons ltd

chemical weathering response to tectonic forcing a soils perspective from the san gabriel mountains california abstract what controls the chemical weathering of soils in tectonically active landscapes recent field and modeling studies suggest that tectonic forcing and associated increases in erosion rates may either promote or hinder soil chemical weathering these competing trajectories are dependent on two primary controls the availability of fresh minerals and their residence time on the landsurface here we explore rates and extents of soil weathering in the san gabriel mountains of california where previous work has measured clear tectonic fingerprints on rates of long term exhumation hillslope erosion and landscape morphology we quantify chemical weathering across this landscape by elemental analysis of soils saprolites and bedrock on six sites that bracket the low gradient hillslopes of the relict upland plateau and the high gradient hillslopes at the margins of the tectonically driven incising landscape average chemical depletion fractions which measure weathering losses from soil relative to unweathered parent material decrease with increasing elevation and decreasing temperature reflecting a combination of climate influence and potential dust inputs from the mojave desert weathering fluxes from non dust affected sites with similar elevations climates and lithology correlate with both erosion rates and hillslope gradient on low gradient hillslopes 25 weathering intensities and rates both decrease as erosion rates increase and soils thin at the highest denudation rates 300 t km 2 y 1 saprolite production is outpaced and soils are produced directly from fractured rock these patterns are consistent with those predicted by a previously published model for denudation weathering relationships based on mineral weathering kinetics variable weathering extents in soils indicate that weathering in the sgm is largely kinetically limited this study is the first to quantify decreases in both rates and extents of soil chemical weathering with increasing erosion rates and suggests tectonic uplift in rapidly eroding and incising landscapes may not stimulate increased silicate weathering

petrofacies and provenance of the puente formation middle to upper miocene los angeles basin southern california implications for rapid uplift and accumulation rates abstract the puente formation is a middle upper miocene clastic unit lying unconformably on the lower middle miocene el modeno volcanics and topanga group in the los angeles basin the puente formation about 3900 m thick is composed of conglomerate sandstone and mudrock deposited as a submarine fan at bathyal depths several intrabasinal discordances suggest tectonic activity during deposition the succession consists of two main upward thickening and coarsening megacycles reflecting submarine fan progradation the puente formation is characterized up section by 1 thin bedded sandstone and shale la vida member grading to thick bedded sandstone and conglomerate soquel member 2 thin bedded mudrock and sandstone yorba member grading to thick to very thick bedded sandstone and conglomerate sycamore canyon member sandstones of the puente formation are quartzofeldspathic qm35f54lt11 their compositions suggest local provenance from the plutonic volcanic and metamorphic rocks of the san gabriel mountains and surrounding areas petrologic parameters however suggest variable contribution of these source rocks through time four petrofacies with distinctive parameters coincide with the lithostratigraphic subdivisions coarse grained plutonic rock fragments are abundant throughout the succession and consist of plagioclase rich plutonic rocks probably sourced in part from the lowe granodiorite lathwork microlitic to felsitic volcanic lithic grains are also present in the lower and middle part in the la vida petrofacies there is also an intrabasinal cont ibution intraclasts and bioclasts from shelfal areas in the yorba petrofacies there is a local increase of volcanic detritus lv l 0 81 represented by coarser volcanic lithics and abundant volcaniclastic matrix metamorphic detritus is not very abundant the sycamore canyon petrofacies is dominantly plutoniclastic rg r 0 90 hornblende bearing plutonic rock fragments including very abundant hornblende grains the plutonic detritus is dominantly plagioclase orthoclase biotite bearing in the lower part and hornblende bearing in the upper part suggesting unroofing of the lowe granodiorite complex as a key element of uplift of the san gabriel mountains other neogene sandstones deposited in the los angeles basin also consist dominantly of plutoniclastic detritus related to the unroofing of arc related plutonic rocks dissected magmatic arc for example the up section increase in plutonic detritus is consistent with the composition of the upper miocene lower pliocene capistrano formation qm50f47lt3 which has a composition identical to the sycamore canyon petrofacies there is consistent provenance signal in spite of complex transrotational tectonics responsible for opening of the los angeles basin and later transpressional processes which are still active detailed provenance study of the puente formation and related units provides important constraints on paleogeographic and paleotectonic reco structions of southern california basins and uplifts

evaluating estuarine sediment provenance from geochemical patterns in upper chesapeake bay abstract geochemical patterns in upper chesapeake bay sediments can reflect a variety of important processes spatial and down core geochemical patterns are useful for understanding the underlying conservative sediment provenance and non conservative salinity redox anthropogenic influences processes driving these patterns distinguishing conservative and non conservative processes to quantify sediment sources will help develop management strategies to limit excess sedimentation in estuaries in this study elemental concentrations were measured via inductively coupled plasma mass spectroscopy icp ms and analyzed using principal component analysis the sediment geochemistry data were then analyzed to evaluate contributions of susquehanna river and shoreline erosion to bottom sediments in the upper bay using a sediment provenance analysis elements associated with aluminosilicate minerals which were sensitive to grain size changes and rare earth elements which were sensitive to salinity changes explained the most variability in the dataset variability in heavy metal concentrations demonstrated decadal changes in anthropogenic inputs the results from the sediment provenance analysis indicated that the susquehanna river is the dominant source of fine sediment in the upper bay

detrital modes and provenance of miocene sandstones and modern sands to the southern apennines thrust top basins italy abstract the cilento group lower middle miocene the monte sacro conglomerate upper miocene the gorgoglione formation upper miocene and the crati submarine fan holocene are four turbidite sequences deposited in northwest southeast trending thrust top basins of the southern apennines italy foreland region the corigliano basin is a part of the modern taranto gulf foredeep basin that developed since the late pleistocene sandstone detrital modes of the miocene turbidite units are quartzofeldspathic petrofacies 1 2a 4 5 8 q62f25l13 quartzolithic petrofacies 2b q60f16l24 and arkosic petrofacies 7 q50f45l5 reflecting a collisional orogenic provenance volcanolithic sandstones petrofacies 3 q23f11l66 suggest an important contribution also from a volcanic source area related to the convergent continental margin volcanism connected with the collisional tectonic regime that affected the western mediterranean e g sardinia volcanic arc individual carbonatoclastic beds hybrid arenite biocalcarenite and mudstone are interbedded with sandstone units of the ilento group they have siliciclastic content of about 35 and are quartzofeldspathic petrofacies 6 q53f23l24 these beds 0 10 65 m thick record impulsive gravitational collapses of the carbonate platform passive margin to the east and southeast the petrologic parameters show a temporal evolution from metasedimentary to granitic gneissic provenance ascribed to different tectonostratigraphic units of the calabrian arc nine miocene petrofacies suggest dynamic evolution of the source terranes from laughian to tortonian time facies dispersal patterns and petrologic parameters of the miocene sandstones suggest a provenance from the northern and western margins of the basins comparison between the holocene crati fan petrofacies 9 q54f24l22 and miocene detrital modes suggests that the sandstones of the cilento group the monte sacro conglomerate and the gorgoglione formation were derived from unroofing of the thrusted basement block transported by torrential type fluvio deltaic systems and then funneled into a major turbidite dispersal system analogous to the modern crati submarine fan of the corigliano thrust top basin

mid quaternary decoupling of sediment routing in the nankai forearc revealed by provenance analysis of turbiditic sands coring during integrated ocean drilling program expeditions 315 316 and 333 recovered turbiditic sands from the forearc kumano basin site c0002 a quaternary slope basin site c0018 and uplifted trench wedge site c0006 along the kumano transect of the nankai trough accretionary wedge offshore of southwest japan the compositions of the submarine turbiditic sands here are investigated in terms of bulk and heavy mineral modal compositions to identify their provenance and dispersal mechanisms as they may reflect changes in regional tectonics during the past ca 1 5 myrs the results show a marked change in the detrital signature and heavy mineral composition in the forearc and slope basin facies around 1 ma this sudden change is interpreted to reflect a major change in the sand provenance rather than heavy mineral dissolution and or diagenetic effects in response to changing tectonics and sedimentation patterns in the trench slope basin the sands older than 1 ma were probably eroded from the exposed cretaceous tertiary accretionary complex of the shimanto belt and transported via the former course of the tenryu submarine canyon system which today enters the nankai trough northeast of the study area in contrast the high abundance of volcanic lithics and volcanic heavy mineral suites of the sands younger than 1 ma points to a strong volcanic component of sediment derived from the izu honshu collision zones and probably funnelled to this site through the suruga canyon however sands in the forearc basin show persistent presence of blue sodic amphiboles across the 1 ma boundary indicating continuous flux of sediments from the kumano kinokawa river this implies that the sands in the older turbidites were transported by transverse flow down the slope the slope basin facies then switched to reflect longitudinal flow around 1 ma when the turbiditic sand tapped a volcanic provenance in the izu honshu collision zone while the sediments transported transversely became confined in the kumano basin therefore the change in the depositional systems around 1 ma is a manifestation of the decoupling of the sediment routing pattern from transverse to long distance axial flow in response to forearc high uplift along the megasplay fault

a source to sink compositional model of a present highstand an example in the low rank tiber depositional sequence latium tyrrhenian margin italy abstract our source to sink compositional model of sediment distribution in the present highstand of the tiber depositional sequence has important implications for sediment source lithology generation transport and deposition in the tiber river system sand compositional trends reflect provenance mixing anthropic intervention and the effects of local autogenic factors in continental to marine depositional environments fluvial feldspatho quartzo lithic sand results from the contribution of the major tributaries of the tiber drainage basin which can be divided into two sub basins separated by the corbara dam built in the 1950s upstream drainage basin sand has a siliciclastic sedimentary lithic signature whereas carbonate and volcanic lithic fragments dominate downstream drainage basin sand downstream sand is further modified in the coastal environment by hydraulic sorting and mixed with detritus derived from the recycling of coastal dune sand and altered volcaniclastic paleosols the latter are associated with lower course floodplain and channel deposits which produce a quartzo feldspatho lithic sand sediment grain size zonation in the marine environment is influenced by coastal hydrodynamics which in turn produce two detrital populations with distinct compositional signatures and hydraulic behavior coarser minerals essentially pyroxene phenocrysts and finer feldspar grains are progressively concentrated in higher energy and lower energy environments respectively biogenic continental shelf and slope deposits off the tiber river mouth show very little riverine influence this study of the last highstand system tract in the tiber depositional sequence clarifies the effects of hydraulic sorting grain size dependence and sediment reworking in controlling the final composition of modern sand this knowledge can be used to better understand detrital modes of ancient sedimentary successions

geochemical signature of provenance in sand size material in soils and stream sediments near the tobacco root batholith montana u s a abstract trace element geochemistry of sandstones are being used to determine provenance we have conducted preliminary and limited experiments to determine to what extent daughter sands retain the geochemical signature of parent rocks six sets of first order stream sediments soils from adjacent slopes and a variety of parent rocks were collected from southwestern montana u s a sampling in a low relief area ensured that climate and residence time of soils on slopes could be eliminated as variables sand size fractions of stream sediments and soils and the corresponding parent rocks granodiorite quartz monzonite granite gneiss biotite tonalite gneiss and amphibolite were analyzed for most major elements and selected trace elements petrologic modal analysis of the parent rocks and the 0 25 0 50 mm fraction of each sand was done to monitor major mineralogic control if any on chemical compositions of the samples our data show that the abundances of the si and al in sediments do not discriminate provenance abundances of ca mg fe and ti may broadly distinguish between sands derived from metamorphic and igneous source rocks at least in the area studied differences in abundances of the ba and th and the ratio of la lu between granitic tonalitic and amphibolitic parent rocks are preserved in the daughter sediments that we studied however the size of the eu anomaly in the ree patterns of different daughter sediments is not diagnostic of parent rocks abundances of co and sc distinguish between sediments derived from felsic and mafic rocks a better provenance discrimination is obtained if the ratios la sc th sc la co ba sc and ba co are used petrologic modal data show that mineral contents and chemical compositions of parent rocks are compatible with each other the chemical composition of the sands may be roughly correlated to the petrological modal data but the abundances of some minor and trace elements of sediments cannot be inferred from modal mineralogy this is expected because these elements may concentrate in accessory minerals and or may weather out into aqueous or clay mineral fractions it is also compatible with conclusions of previous studies that some of these elements do not reside in sand size fractions of siliciclastic sediments

petrology of holocene sand peninsular ranges california and baja norte mexico implications for provenance discrimination models abstract the peninsular ranges of southern california and baja california norte mexico represent an uplifted and variably dissected mesozoic magmatic arc they are composed mostly of cretaceous plutonic rocks and mesozoic greenschist to amphibolite facies metasedimentary and metavolcanic rocks in order to evaluate the reliability of the diamond shaped qnuquqp provenance discrimination diagram developed by basu et al 1975 and the qfl provenance discrimination diagram developed by dickinson et al 1983 we collected 62 samples of holocene sand from four drainage basins along the west side of the peninsular ranges the qfl composition of each specimen was determined by the gazzi dickinson point counting method the relative percentages of med um grained fragments of qnu qu and qp were determined by counting 100 grains in each specimen the results of our study indicate that holocene sands derived from the peninsular ranges have the following average petrological characteristics 1 sands derived mostly or exclusively from plutonic rocks are composed of 16 46 percent q 54 83 percent f and 0 2 0 5 percent l the medium grained quartz population produced by erosion of mostly or exclusively plutonic rocks consists of 61 77 percent qnu 4 17 percent qu and 13 27 percent qp 2 sands originating from the erosion of metasedimentary rocks are composed of 63 percent q 13 percent f and 24 percent l the medium grained quartz population derived from a metasedimentary source is made up of 25 percent qnu 9 percent qu and 66 percent qp 3 sands produced by the erosion of mostly or exclusively metavolcanic rocks are composed of 19 percent q 39 44 percent f and 38 43 percent l the medium grained quartz population originating from a mostly or exclusively metavolcanic source consists of 48 74 percent qnu 6 percent qu and 20 46 percent qp petrological data obtained during this study indicate that the qfl provenance discrimination model generally yields a correct interpretation of tectonic setting when applied to holocene sand from the peninsular ranges data however also show that local source areas produce sands that when interpreted on the basis of their position on the qfl provenance discrimination diagram yield an erroneous interpretation of tectonic setting data obtained from counting varieties of medium grained quartz show that detrital quartz populations produced by plutonic rocks are discriminated from those derived from metasedimentary rocks by the qnuquqp provenance discrimination diagram in contrast quartz populations originating from a mostly or exclusively metavolcanic source are difficult to interpret on the qnuquqp diagram therefore we recommend that the qfl provenance discrimination model be used with caution when sand or sandstone samples are from a limited geographic area and that the qnuquqp provenance discrimination diagram be used with prudence when metavolcanics are suspected in the provenance

particle borne radionuclides as tracers for sediment in the susquehanna river and chesapeake bay abstract the chesapeake bay receives nearly 1 000 000 tonnes of sediment annually from its major tributary the susquehanna river the pattern of deposition of this sediment affects the lifetime of the estuarine resource and the fate of any sediment borne contaminants previous estimates of the extent to which susquehanna river sediment is transported down the chesapeake have differed considerably by use of reactor generated radionuclides adsorbed on the river sediment a sediment budget has been compiled for the upper chesapeake bay and the reservoirs on the lower susquehanna reservoirs impound nearly 1 400 000 tonnes of sediment annually behind the power dams on the lower susquehanna river without the dams sediment delivery to the upper bay would more than double the uppermost chesapeake bay within and above the turbidity maximum retains virtually all of the fluvial sediment delivered to it the result is an annual sedimentation rate of approximately 3 mm yr 1 in the upper bay an infilling rate that is nearly equal to the regional rate of sea level rise

regional geochemistry of trace elements in chesapeake bay sediments the concentrations of cr mn fe co ni cu zn cd and pb in 177 surface sediment samples from throughout chesapeake bay are reported analyses were made of both unfractionated samples and the 63 m fractions analytical uncertainty always less than 10 controlled reproducibility in analyses of the 63 m fractions but sampling variance controlled reproducibility in the unfractionated samples especially when coarse grained sediments were being analyzed sediments in the northernmost part of the bay are enriched relative to average continental crust in all elements except cr this reflects the composition of dissolved and suspended material being delivered to that region by the susquehanna river the enriched sediments appear not to be transported south of baltimore in significant quantily zinc cadmium and lead are enriched relative to average crust throughout the bay and in most other estuaries in the eastern united states

tectonic climatic and lithologic influences on landscape fractal dimension and hypsometry implications for landscape evolution in the san gabriel mountains california east west variation in tectonic activity and strong north south climatic gradients provide a unique opportunity to study tectonic climatic and lithologic influences on landscape evolution in the san gabriel mountains california the competing tendencies of constructive tectonic and degradational climatic effects act against lithologic resistance to influence fluvial systems and thus the nature of adjacent and nested drainage basins landscape fractal dimension d a measure of surface roughness over a variety of scales and the hypsometric integral i a measure of the distribution of landmass volume above a reference plane are useful measures of altitudinal variation with scale as such they may provide clues as to the relative influences of tectonism climate and rock type topographic analyses of the san gabriel mountains clearly indicate that tectonism strongly influences d at range wavelength scales while rock type variation apparently influences d and i at smaller scales tectonism is also shown to influence i across the mountain piedmont junction at all scales investigated tectonic activity shows strong negative correlation with both i and d because tectonically active portions of the mountain front do not allow time for much landscape dissection by lower order streams three dimensional topographic modeling suggests climatic parameters exert a stronger influence on d than does tectonism this modeling also suggests an inverse correlation between range scale d and i with varying climate and uplift rate a positive correlation is observed in the san gabriel mountains we suggest this difference results from 1 differences in uplift style between the san gabriel mountains and the models and or 2 variation in rock type erodibility present in the san gabriel mountains but which was not modeled we postulate that the interaction of tectonic climatic and lithologic parameters influences the stable i and d to which a landscape evolves key questions remaining include 1 the time required to reach a stable i or d after a climatic or tectonic change 2 what does the fractal nature of topography tell us about the scaling characteristics of major landforming processes 3 how does climate influence range scale i and both range and small scale d and 4 what are the effects on i and d of range scale lithologic variation both in the models and in real landscapes

the impact of hydroclimate and dam construction on terrigenous detrital sediment composition in a 250 year santa barbara basin record off southern california abstract the recurrence and magnitude of southern california hydroclimate extremes are poorly resolved due to the relatively short duration

processes controlling fe mn and zn in sediments of northern chesapeake bay the dominant physical and chemical processes that control fe mn and zn are explored by comparing the compositions of sediments and their sources the mnfe and znfe ratios in sediment are found to be largely unaffected by local hydraulic sorting unlike the actual concentrations of fe mn and zn and thus are useful indicators of origin the sediments in northern chesapeake bay have markedly lower mnfe and znfe ratios than those found in the susquehanna river dissolved plus suspended under ordinary flow but not under high flow conditions since high flow conditions dominate sediment transport seaward loss of a major fraction of the river derived mn and zn need not be invoked to reconcile sediment and river compositions sediments in the seaward end of the northern bay have higher mnfe and znfe ratios than their principal external source the eroding shore deposits the excess zn appears to be derived from the atmosphere the required depositional flux of zn is consistent with measurements of the total atmospheric flux the excess mn can be explained by remobilization of roughly 5 of the river borne mn from sediments in the landward part of the northern bay because rare floods influence sediment composition markedly comparing suspended particles in the river at ordinary stages with resuspended sediment in the estuary would lead to the false interpretation that mn and zn were being desorbed in the saltwater

distribution provenance and early diagenesis of major and trace metals in sediment cores from the mandovi estuary western india major elements and trace metals were analyzed in four sediment cores recovered along a transect in the mandovi estuary for their distribution provenance and early diagenesis the sediments were clayey silts in cores from the upper lower estuary and sand dominated in cores from the middle estuary bay organic carbon oc content varied from 0 5 to 4 with higher values in fine grained sediments the mean fe and mn contents of sediments from the upper middle estuary were 3 5 times and 8 13 times respectively higher than the reference sediment rs from the same estuary the mean fe and mn contents of sediments from the lower estuary bay were close to the rs strong inter metal correlation among ti v cr and zr in all the cores indicated their contribution from a common source probably the laterites from hinterland trace metals were more enriched in fine grained sediments than in sand dominated sediments early diagenetic control on the redistribution of metal is evident in core sediments from the middle estuary to bay the distribution of mo u and pb followed that of fe and mn in the upper estuary and oc in the lower estuary bay our results indicated strong anthropogenic contribution of metals from ore deposits in the upper middle estuary the mn and cr contents of sediment in the upper middle estuary and fe in the middle estuary were highly enriched suggestive of significant pollution signal more trace metals from the middle estuary were moderately enriched speciation studies showed mn and pb occurred abundantly in non residual phases high mn content and its high percentage in exchangeable and reductive phases indicate that it was susceptible to be mobilized however fe cu and ni occurred abundantly in residual phases and less percentage of them were expected to be bio available

spectral gamma ray logging of the gres d annot se france an outcrop analogue to geophysical facies mapping and well log correlation of sand rich turbidite reservoirs abstract spectral gamma ray grs logging is a powerful tool in cyclo and sequence stratigraphy of carbonate depositional systems in siliciclastic systems with low chemical maturity the multi component character of sediment complicates the interpretation of such logs this work focuses on understand better the relationships between grs logs and siliciclastic facies stacking patterns using grs measurements combined with lithology modal composition and geochemistry this study is focused on outcrops in the st antonin annot grand coyer chalufy areas of the oligocene gres d annot formation se france the studied siliciclastics reveal moderately high total radioactivity and mean concentrations of k 3 8 u 4 5 ppm and th 13 ppm u and th are predominantly contained within heavy minerals and so tend to be concentrated in mudstones and heterolithic sand mud facies whereas sandstone and conglomerate facies have slightly higher levels of k due to higher contents of k feldspars and micas the abundance of minerals containing radioactive elements and the relatively low compositional contrast between different facies are considered the main reasons why the standard gamma ray measurements provide only a limited proxy for lithology in this case two complete regressive to transgressive cycles were identified based on combined th and th k logs and facies stacking patterns the cycle boundaries are marked by shifts towards coarse grained facies abrupt increase of u and th concentrations and th k ratio within the proximal deposits at the st antonin section in the distal chalufy section the response of the gamma ray proxies to facies shifts is reversed these boundaries interpreted as basal surfaces of forced regression can be correlated with prominent erosional surfaces at the annot section grs logging is a sensitive method capable of indicating changes of genetic depositional units in sand rich turbidite systems however detailed facies analysis mineralogy and geochemistry producing the radioactive signal are necessary to correctly interpret such logs

the geological setting of santa monica and san pedro basins california continental borderland the california continental borderland s present configuration dates from about 4 to 5 106 years before present bp and is the most recent of several configuration of the southern california margin that have evolved after the north america plate over rode the east pacific rise about 30 106 years ago the present morphology is a series of two to three northwest southeast trending rows of depressions separated by banks and insular ridges two inner basins santa monica and san pedro have been the site for the california basin study cabs funded by the us department of energy the santa monica and san pedro basins contain post miocene sediment thicknesses of about 2 5 and 1 5 km respectively during the holocene past 10 000 years about 10 12m have accumulated the sediment entered the basin by one or a combination of processes including particle infall mainly as bioaggregates from surface waters from nepheloid plumes surface mid depth and near bottom from turbidity currents mass movements and to a very minor degree direct precipitation in santa monica basin during the last century particle infall nepheloid plume transport have been the most common processes the former process has been dominant in thecentral basin at water depths from 900 945m where characteristic silt clay is found with a typical mean particle diameter of about 0 0006mm standard deviation 2 skewness near zero kurtosis is typically 2 platykurtic these values indicate broad near log normal particle size distributions the calcium carbonate content averages about 10 and organic carbon about 4 surficial sediment bulk densities are 1 1 1 2 and accumulation rates range from 16 30mg cm 2yr1 in this central fine deposit bottom water oxygen contents are at or below 0 1 ml 1 1 so that bioturbation is inhibited thus preserving the primary sedimentary stratification there appear to be annual varves but the laminae couplets are not simple wet dry season pairs their formation is related to longer period climatic events el nino cycle of 3 to 4 years is dominant and is also affected by aperiodic bottom water flushing events the anoxic zone of bottom water has expanded over the past 300 to 350 years from a samll area in the northeastern basin floor ca 120km2 at 300 years bp and now covers most of the basin floor below depths of about 850m 1290km2 this expansion may have been primarily relaed to ocean circulation rate changes following the little ice age but is also likely to have been strongly affected by subsequent major changes in the natural drainages post european colonization the bottom water oxygen contents must also reflect the introduction of oxidizable pollutants coincident with the shift to agricultural mission era and then to urban use late 19th century to present of the adjacent mainland such localized effects are also suggested by the contrasting very large increases in the area of low oxygen bottom water in santa monica basin relative to the minimal changes in the area of anoxia in santa barbara basin over the same period and the lack of such zone in san pedro basin in the san pedro basin the bottom waters have remained dysaerobic so its sediments are bioturbated and preserve little or no evidence of primary stratification dumping of oil drilling muds and cuttings during the couple of decades prior to 1970 has left a surficial deposit ranging from 1 to 15cm in thickness forming a bull s eye isopach pattern as seen in radiographs bottom water oxygen content is usually 0 2ml o21 1 bottom infauna and epifauna are sparse central basin floor sediments water depths 800m of san pedro basin have textural characteristics similar to those of santa monica basin with distal basin floor surficial sediments being deposited primarily by particle infall and nepheloid flow at the present time mean diameters 0 006mm standard deviation 2 skewness 0 and kurtosis 2 platykurtic calcium carbonate content averages 8 10 and organic carbon is about 4 an estimate of the contemporary sedimentation rate was determined for a single box core of 25 29mg cm 2 yr1 from the central basin near the present distributary margin it cannot be considered necessarily to be representative mixing is indicated by the data an important climatic factor is the alternation of multi year wet and dry periods the california basin study was conducted during an extended dry period of low river discharge this undoubtedly will have affected the conclusions of the study related to sediment water interactions and pollutant transport by suspended clays