archean paleoproterozoic transition the indian perspective abstract india has perhaps the richest paleoarchean to paleoproterozoic crustal components on earth miller et al 2018 notwithstanding this much of the indian subcontinent remains unexplored compared to other ancient cratons in north america australia brazil and africa there are five archean cratonic nuclei in india the aravalli bundelkhand singhbhum bastar and the dharwar with well preserved proterozoic supracrustal sequences this paper critically reviews the paleoarchean to paleoproterozoic supracrustal record of the indian subcontinent with special emphasis on the archean paleoproterozoic transition which is generally placed at 2 5 ga based on the emplacement age of the great dyke of zimbabwe in general the archean paleoproterozoic transition in indian cratonic blocks is associated with high continental freeboard condition unlike north america south africa and western australia the indian cratonic blocks except bastar are devoid of paleoproterozoic glacial diamictite mazumder et al 2015 however similar to the pongola supergroup of south africa there are evidences of neoarchean glaciation in dharwar ojakangas et al 2014 in contrast to the global scenario of extensive development of bif across the archean paleoproterozoic transition the indian paleoproterozoic successions are devoid of banded iron formation bif except the 1 85 ga old bif in bundelkhand in contrast the majority of the indian bifs are of paleoarchean or neoarchean age thus the geodynamic and supracrustal data collected from five indian archean cratonic blocks do not correspond uniquely and precisely to a global change in tectonic style onset of neoarchean global magmatism and rifting or lithostratigraphic and environmental changes suggested across the archean paleoproterozoic transition van kranendonk et al 2012 therefore a revision and redefinition of the archean proterozoic boundary is outstanding this article is part of a special issue entitled archean earth processes edited by rajat mazumder and patrick eriksson

distinguishing climatic and tectonic signals in the sedimentary successions of marginal basins using sr isotopes an example from the messinian salinity crisis eastern mediterranean the evolution of oceanic 87 sr 86 sr through the tertiary has been sufficiently well documented to provide a useful stratigraphic tool for carbonate rich marine sediments which were deposited in basins connected to the global oceans in isolated basins sea water 87 sr 86 sr will diverge from coeval oceanic values thus if independent age information exists the geochemical signature can constrain the timing of isolation in marginal basins formed in tectonically active settings the timing of isolation is critical to the assessment of the relative importance of climate or tectonic controls on that event previously isolation has been assumed to coincide with the last occurrence of open marine fauna however in an example from the eastern mediterranean 87 sr 86 sr data challenge that assumption and can be interpreted as indicating a protracted period of isolation c 3 ma during which time marine conditions prevailed prior to the messinian salinity crisis at the end of the miocene this allows tectonic and climatic signals to be distinguished since although convergence of africa with eurasia was responsible for isolation of this part of the mediterranean it is more likely that later climatic change triggered desiccation

modelling the effect of evaporation on the salinity 87 sr 86 sr relationship in modern and ancient marginal marine systems the mediterranean messinian salinity crisis abstract palaeosalinity reconstructions in marginal marine environments based on sr isotope data assume simple two end member mixing of river and ocean water an improved model that incorporates the effect of evaporation is used to demonstrate that this approach is not valid in evaporation dominated systems however sr isotope records combined with faunal and lithological constraints on salinity can be used to assess the palaeohydrological conditions of ancient marginal marine systems this new method is used to interpret deviations from the global seawater sr isotope curve observed in mediterranean successions during and up to 3 myr prior to messinian evaporite deposition results suggest that no absolute change in the net evaporation flux is required to explain the three to four fold rise in salinity of mediterranean water at the carbonate evaporite transition modelled sr isotope records indicate that this increase in salinity was synchronous with an increase in the dominance of atlantic water inflow in the hydrological budget of the mediterranean the messinian salinity crisis may therefore have been the response to a marine transgression

messinian lago mare deposits near the strait of gibraltar malaga basin s spain a new stratigraphic unit named lm unit located at the base of the pliocene marine succession in the eastern sector of the malaga basin has been distinguished this unit is composed of two fining upward sequences bounded by a discontinuity related to synsedimentary tectonic activity both sequences are made up of basal alluvial deposits overlain by subaquatic deposits the lower sequence contains rich mollusc faunas characterized by bivalves lymnocardiinae and dreissenidae of paratethyan origin and non marine gastropods typical of oligo low mesohaline shallow waters and low diversified ostracod faunas of paratethyan origin loxocorniculina djafarovi tyrrhenocythere pontica euxinocythere maeotocythere praebaquana and amnicythere propinqua typical of low mesohaline waters alternances of monospecific ostracod assemblages made of cyprideis agrigentina or oligotypic assemblages made of c agrigentina and loxoconcha spp and richer assemblages made of l djafarovi accompanied by several amnicythere spp and camptocypria sp 1 characterize the upper sequence pointing to more unstable environment affected by salinity and depth changes some samples collected from this upper sequence yielded rare planktonic and benthic foraminifera which could suggest the sporadic establishment of quasi normal marine conditions in the westernmost mediterranean during the deposition of this sequence the palaeontological data and the palaeomagnetic results obtained in both the lm unit and the overlying pliocene marine sediments restrict the age of the former to the post evaporitic late messinian the age and the environmental conditions correlate these deposits with the lago mare event occurring throughout the mediterranean before the quick and widespread marine flooding of the mediterranean at the beginning of the pliocene

geochemistry and petrogenesis of mafic magmatic rocks of the jharol belt india geodynamic implication abstract the belt consisting of deep water meta sediments of the aravalli supergroup hosts numerous mafic and ultramafic rocks occurring at two different structural levels these are the basal bagdunda volcanics and the gopir magmatic rocks represented by gopir dikes and flows associated with the ultramafic rocks along the kaliguman lineament the bagdunda and gopir mafic volcanic rocks are sub alkaline varying in composition from high mg tholeiite to basaltic komatiite they are predominantly lree depleted but some flat ree patterns are also observed bulk geochemical data especially the incompatible trace elements discount the possibility of crustal contamination gopir dikes are highly enriched in terms of their ree ce sm n and ce yb n and other incompatible trace elements and closely resemble the basal aravalli volcanics their ratio rock ratio pm and normalized multi element abundance patterns depict their overall enriched nature compared to n morb and primitive mantle the gopir and bagdunda volcanics reflect trace element characteristics transitional between e morb and oib gopir dikes show remarkable similarity with continental tholeiite and continental flood basalts cfbs with negative nb p and ti anomalies and low nb ce ratio unlike the volcanics of both the suites petrogenetic modeling based on the compositionally corrected mg and fe abundances for gopir dikes gopir and bagdunda volcanics indicates a their derivation from non pyrolitic sources b their derivation from sources that were variably enriched in fe mg ratios with large variation in their fe contents and c olivine was a major phase to fractionate followed by a lesser amount of clinopyroxene in the case of gopir volcanics whereas in bagdunda volcanics a combination of olivine and clinopyroxene fractionation is suggested based on the geochemical data supported by field evidence we propose a geodynamic model for the development of the jharol belt in which we suggest that the basement rock i e the banded gneissic complex bgc started rifting probably under influence of a mantle plume during the late archaean early proterozoic period during the opening of the basin magma derived from asthenospheric mantle reached the surface contemporaneously with sedimentation the first phase of volcanism is represented by bagdunda volcanics with continuous rifting the crust became highly attenuated and facilitated asthenospheric upwelling causing high degrees of melting indicated by a large volume of mafic and ultramafic rocks during the second phase of magmatism gopir volcanics that occurred at later stages of jharol sedimentation coeval melting of the sub continental lithosphere under the adjoining bgc craton probably caused the emplacement of dikes along with the gopir volcanics at this stage of progressive rifting an oceanic crust very similar to that in marginal basins developed in the jharol belt

petrology geochemistry and na metasomatism of triassic jurassic non marine clastic sediments in the newark hartford and deerfield rift basins northeastern usa many sandstones and associated siltstones and shales of the triassic jurassic newark supergroup in the newark hartford and deerfield rift basins are immature feldspathic alluvial and lacustrine closed basin deposits they were derived from felsic igneous and metamorphic continental blocks on the flanks of their depositional basins the provenance was dominantly calc alkaline basement rocks similar to the sierra nevada of california the physical and chemical environments of erosion and deposition were probably similar to those in moist pleistocene holocene alluvial basins and playas in the great basin of california and nevada new petrographic and geochemical data for 113 samples indicate that albite rich sandstones and shales of the stockton lockatong and passaic formations in the newark basin and in the portland and east berlin formations of the hartford basin and analcime rich shales up to 52 normative analcime of the lockatong formation have unusually high na2o contents 4 7 textural evidence indicates both sodium replacement in feldspars and formation of authigenic albite and analcime in these rocks by comparison with modem sediments derived from similar provenance using mixing models it is estimated that up to 4 na2o was diagenetically added to the detrital clastics trace metals co cr cu ni zn abundances were apparently enhanced by deposition from brines in the lockatong formation analcime deposition occurred in shales with al2o3 na2o sio2 0 46 this ratio is found only in sediments to which na has been added from salts brines source rocks and the weathering products derived from them may be considered as a closed system in which sodium was retained partly in solids as feldspar and part went into solution during weathering the dilute solution migrated into the depositional basin where evaporation yielded concentrated brine during semi arid to arid climate in the drier parts of 21 000 yr milankovitch cycles reaction of brine during diagenesis at near surface and or shallow depths 2 km with ca plagioclase k feldspar and layer silicates at estimated temperatures 50 c to 100 c and ph 7 9 yielded thermodynamically stable authigenic albite and analcime in the sodium metasomatised clastic sediments low activity of k precluded development of authigenic k feldspar however k from solution incorporated into muds and silts as smectites were transformed to illite some lockatong beds contain anomalously high p2o5 ce la y th and u in authigenic apatite or monazite suggestive of mobilization of these elements in diagenesis

the northern apennines palynological record as a contribute for the reconstruction of the messinian palaeoenvironments abstract the messinian stage has long been associated with an overall warm and dry climate whereas recent researches indicate either a warm and humid or a cool and dry climate the integrated stratigraphic record of vegetation and climatic changes from northern apennines sites provides the solution to this apparent contradiction its integration with the updated geological and sedimentological studies provides additional data for the reconstruction of the depositional palaeoenvironments in both marginal and deeper sub basins of the apennines foredeep the onset of the mediterranean salinity crisis msc is recorded in the gessoso solfifera of the vena del gesso marginal sub basin cyclical humid conditions corresponding to precession minima developed during the deposition of the shales interbedded with the gypsum 5 9 to 5 6 ma some cooler events took also place under the effects of global glacial stadials and regional factors apennines uplift at present no major changes from moist to dry conditions are attested to just before the salinity crisis as well as in sicily so climate did not play a major role in the onset of the msc despite the favourable context provided by inferred thermo xeric conditions in southern italy a drier episode indicated by the expansion of the open vegetation including the northward migration of lygeum postdates the onset of the salinity crisis of about 400 kyr in the lower post evaporitic deposits of maccarone deeper sub basin it falls within a period of global warming whereas at a regional scale it could correlate p p to the evaporite deposition in deeper basins and to hiatuses in the marginal basins of sicily and of the western sector of northern apennines its sudden end about 100 kyr later in coincidence with a significant increase of pinaceae indicates a turnover in the terrestrial setting not linked to major climate changes but possibly to a complex interaction between other palaeoenvironmental factors e g tectonics and eustatism in contrast organic walled dinoflagellate cysts exclude significant modifications in aquatic settings insaturation of either open marine or brackish conditions in the latter a later change is marked by the arrival of impagidinium sp 1 a species here referred instead to caspidinium rugosum about 7 m below the first colombaccio this occurrence together with the spread of pediastrum indicates a freshwater dilution i e the lago mare event during wetter climatic conditions on the adjacent landmass increase of tsuga and cedrus the successive arrival and or dominance of other paratethyan taxa such as i sp 2 i sp 3 and galeacysta etrusca indicate highly variable water environments marine vs continental water inputs during the deposition of the uppermost post evaporitic deposits the lago mare is stratigraphically sandwiched between an ash layer 130 m below dated at 5 5 ma and the beginning of the pliocene where a peak of impagidinium patulum marks the onset of open marine conditions the dominant humid subtropical to warm temperate climate indicates differences in both temperature and moisture values with respect to the coeval southern sections revealing climatic gradients within the mediterranean at least from the messinian no dramatic vegetation and climate changes have been recorded during the msc major changes occurred later as indicated by the palynological record from 2 6 ma this palynostratigraphic record is a good reference for more recent models of the development of the msc and for establishing time relationships between the apennine and sicilian successions

easternmost mediterranean evidence of the zanclean flooding event and subsequent surface uplift adana basin southern turkey according to the literature the adana basin at the easternmost part of the mediterranean basin in southern turkey records the pliocene stage with shallow marine to fluvial deposits our micropalaeontological analysis of samples from the adana basin reveal late lago mare biofacies with paratethyan ostracod assemblages pertaining to the loxocorniculina djafarovi zone grey clays rich in planktonic foraminifera lie above the lago mare deposits within the grey clays the continuous occurrence of the calcareous nannofossil reticulofenestra zancleana and the base of the reticulofenestra pseudoumbilicus paracme points to an early zanclean age 5 332 5 199 ma both ostracod and benthic foraminifera indicate epibathyal and bathyal environments 87 sr 86 sr measurements on planktonic and benthic foraminifera fall below the mean global ocean value for the early zanclean indicating potentially insufficient mixing of low 87 sr 86 sr mediterranean brackish lago mare water with the global ocean in the earliest pliocene we utilize the ages and palaeodepths of the marine sediments together with their modern elevations to determine uplift rates of the adana basin of 0 06 to 0 13 mm a 1 since 5 2 5 3 ma total uplift of 350 650 m from surface data and 0 02 0 13 mm a 1 since c 1 8 ma total uplift of 30 230 m from subsurface data

thrust top lacustrine lagoonal basin development in accretionary wedges late messinian lago mare episode in the central apennines italy abstract we analysed in detail the geometry sedimentology and palaeontology both mollusc and ostracod assemblages of a small lacustrine lagoonal basin located at about 1100 m a s l in the marsica region of the apennines at le vicenne locality l aquila abruzzo central italy the structure of the basin infill deposits outlines an open syncline with an e w axis polygenic conglomerates interbedded with clay levels and sandy marls which constitute roughly coarsening upward progradational sequences are the dominant lithologies these sequences are interpreted as lacustrine to coastal lagoon deposits with episodic fan delta supplies this sedimentological interpretation is also supported by mollusc and ostracod assemblages which suggest that the sedimentary environment was characterized by a mesohaline closed water body with salinity probably ranging from 10 to 13 both mollusc and ostracod assemblages show a clear paratethyan influence in the ostracod assemblage ten species out of the fourteen collected forms belong to the loxoconcha djaffarovi zone as defined by carbonnel 1978 thus it is possible to refer the siltitic clayey intercalations of le vicenne to the top of the messinian post salinity crisis the presence of a strong angular unconformity at the base of the basin together with the structural setting of its deposits suggesting a light compressive deformation are common features in all the thrust top basins recognized in the central apennines taking into account the regional data the age of the youngest deposit involved in the substratum siliciclastic turbidites which recorded the messinian salinity crisis and the palaeobiological indications given by the mollusc and ostracod assemblages it is possible to constrain the origin of the le vicenne basin to the messinian lago mare early pliocene tectono sedimentary event of the apennines the recognition in the marsica range of this thrust top basin allows us to attempt a palinspastic reconstruction locating the marsica region in the latest miocene early pliocene active thrust zone of the apennine accretionary wedge

stratigraphic record of the early mesozoic breakup of pangea in the laurasia gondwana rift system rift basins of the central atlantic margins cam of north america and morocco preserve largely continental sequences of sedimentary strata and less important minor basalt flows spanning much of the early mesozoic the best known is the newark basin of new jersey new york and pennsylvania where an astronomically calibrated magnetic polarity time scale is developed lacustrine cycles of milankovitch origin are commonly present in cam basins with the period changing from 10 ky paleoequator with coals to 20 ky 4 10n to perhaps 40 ky northward with evaporites cycles of100 ky 413 ky and2 my are also important four mostly unconformity bounded tectonostratigraphic sequences are present the anisian ts i is fluvial and eolian ts ii ts iv late triassic to early jurassic consist of tripartite lacustrine sequences caused by extension pulses the newark basin accumulation rate history allows comparison with quantitative rift basin models the north american plate s slow northward drift resulted in a relative shift of climate although the rapid humidification during the latest triassic and early jurassic is associated with a sea level rise the triassic jurassic mass extinction is of independent origin plausibly impact related

remote sensing of geological structure in temperate agricultural terrains agricultural patterns dominate most remotely sensed images of lowland north europe and camouflage shadow patterns related to topography and hence to underlying geological structure images of those parts of the near infrared spectrum close to absorption features controlled by h o h bond stretching in plant cells and soil moisture largely remove this hindrance to interpretation if they are acquired at an early stage in the growing season the most easily available and most useful images of this type are those of band 5 from the landsat thematic mapper spatial filtering techniques applied to digital images can enhance them for structural interpretation if filter matrices and viewing scales are chosen to match the dimensions of the most common elements of the landscape and the peak of visual acuity filters to enhance directional attributes of an agricultural scene give appealing results but contain spurious linear features that masquerade as faults

trace elements in shale as indicators of crustal provenance and terrane accretion in the southern canadian cordillera in this study the trace element geochemistry of shale is used to infer the nature of adjacent crustal blocks during terrane amalgamation and accretion in southern british columbia the geochemistry of about fifty shale samples from one of the best dated stratigraphic sections in the north america cordillera is used to 1 infer proximity to source regions characterized by juvenile ocean arcs continental arcs and ophiolites and 2 address a controversy concerning the timing of terrane amalgamation and accretion this study includes analyses of shale from the entire mesozoic stratigraphic section of the cadwallader terrane and overlying tyaughton basin as well as argillites from the structurally adjacent bridge river complex the mid cretaceous albian strata of the upper taylor creek group show light rare earth lree enrichment la n sm n of 3 0 and anomalously high cr and ni older units upper triassic lower cretaceous that stratigraphically underlie the upper taylor creek group have less lree enrichment high ba n la n ratios and no cr or ni anomaly the mid cretaceous strata were probably derived from a continental arc during a period of uplift and erosion of ultramafic rocks probably ophiolites and the co extensive nature of these sediments suggests accretion of many basement terranes to the edge of a continent the trace element geochemistry of the older strata is similar to that of sediment derived from an oceanic arc however lower cretaceous strata of the relay mountain group may record the incipient collision and progressive closure of this ocean basin the bridge river complex which is dominated by oceanic rocks and is interpreted to be an accretionary complex contains two suites of argillites one of which shows significant lree enrichment and isotopic data suggest a jurassic cretaceous age for these argillites that compose the matrix in this complex leitch et al 1991 we suggest that the bridge river complex was a jurassic cretaceous accretionary complex that formed outboard of the methow section of rocks and was not juxtaposed with the cadwallader terrane and tyaughton basin until the albian when these terranes were accreted to north america paleomagnetic data from these rocks maxson et al 1993 indicate that accretion took place at the latitude of central mexico and that subsequent strike slip faulting brought these terranes to their present position by eocene time

decoding the mediterranean salinity crisis this historical narrative traces the steps to unravel over a span of 40 years an extraordinary event in which 5 of the dissolved salt of the oceans of the world was extracted in a fraction of a million years to form a deposit more than 1 million km 3 in volume a buried abyssal salt layer was identified with reflection profiling and sampled during the deep sea drilling project leg 13 the dolomite gypsum anhydrite and halite in the drill cores paint a surprising picture of a mediterranean desert lying more than 3 km below the atlantic ocean with brine pools that shrank and expanded by the evaporative power of the sun the desert drowned suddenly when the gibraltar barrier gave way the explanation of deep basin shallow water desiccation and the notion of a catastrophic zanclean flood had a mixed reception however the hypothesis became broadly accepted following subsequent drilling expeditions nevertheless as experts examined the evaporate facies and sequences of equivalent age in the terrestrial outcrops weaknesses appeared in the concept of repeated flooding and drying to account for the magnitude of the deposits the rosetta stone used to decipher conflicting interpretations turns out not to be the deposits but the erosion surfaces that enclose them these surfaces and their detritus formed in response to the drop in base level during evaporative drawdown extend to the basin floor evaporative drawdown began halfway through the salinity crisis when influx from the atlantic no longer kept up with evaporation prior to that time a million years passed as a sea of brine concentrated towards halite precipitation during the later part of this interval more than 14 cyclic beds of gypsum accumulated along shallow margins modulated by orbital forcing the thick salt on the deep seabed precipitated in just the next few cycles when drawdown commenced and the brine volume shrank upon closure of the atlantic spillway the remnants of the briny sea transformed into salt pans and endorheic lakes fed from watersheds of eurasia and africa the revised model of evaporative concentration now has shallow margin shallow water and deep basin deep water precursors to desiccation

trace and rare earth element ree characteristics of mudstones from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin implications for provenance depositional conditions and paleoclimate abstract the interpretation of depositional conditions provenance and paleoclimate provide important information to understand hydrocarbon source rock formation and distribution the concentrations of trace elements and rare earth elements rees of fifty mudstone samples from eocene pinghu formation and oligocene huagang formation in xihu sag east china sea basin were determined by inductively coupled plasma mass spectrometry icp ms to test the depositional conditions provenance and paleoclimate evidences from the visual comparisons of the simple bivariate plots diagrams and statistical comparisons of the mann whitney rank sum test suggest that there may be a common source for the pinghu formation and huagang formation mudstones sedimentary provenance from bivariate plots diagrams of hf versus la th and la sc versus co th shows that pinghu formation mudstones are mainly composed of mixed felsic basic source and acidic source whereas huagang formation is mainly acidic source additionally the ree vs la yb discrimination diagram shows that the property of the provenance for the pinghu formation mudstones consists sedimentary rock alkaline basalt and a small amount of continent tholeiitic basalts whereas that of the huagang formation is mainly alkaline basalt and sedimentary rock discriminant diagrams consisting of la th sc and th co zr 10 suggest that the mudstones of two formations were deposited in continental island arc and active continental margin tectonic setting redox proxies v ni v v ni and ce indicate that most of the mudstones of two formations were deposited in a relatively dysoxic anoxic condition the cool and humid climate represented by sr cu and rb sr ratios were prevailing in xihu sag during the eocene and oligocene period and the oligocene was cooler than eocene moreover five long term base level cycles siii1 siii5 and four sequence boundaries sb2 sb5 were recognized in the pinghu formation and huagang formation based on the previous research we find that the abnormal surfaces of geochemical parameters such as v ni sr ba u ti v ti ti and ree to some extent agree with sequence boundaries sb2 sb3 sb4 and sb5 in mudstones additionally the increment of ti and ree concentrations and the decrease of sr ba v ni u ti and v ti ratios above the sb4 indicates that terrigenous clast grew significantly and the sea level dropped after late eocene which is related with the late eocene tectonic movement

new biostratigraphic information from the western part of the hamburg klippe pennsylvania and its significance for interpreting the depositional and tectonic history of the klippe biostratigraphic investigation of the graptolite and conodont faunas of the western part of the hamburg klippe of eastern pennsylvania permits a revised stratigraphic framework and new conclusions regarding its likely tectonic setting graptolite and conodont data reveal an almost complete lower to lower upper ordovician zonal section no cambrian strata appear to be present with the possible exception of the uppermost part during early to early middle ordovician time medium to fine grained siliciclastics and minor carbonate sediments were deposited in a lower slope and rise setting these sediments were consolidated and incorporated as olistoliths in an olistostrome possibly as a trench fill complex during the middle ordovician darriwilian 3 4 this olistostrome which contains large lower and lower middle ordovician fragments within a matrix of shales siltstones and sandstones of da 3 4 age is herein named the shellsville member of the dauphin formation turbidites here assigned to the nyes road member of the dauphin formation were also deposited during da 3 4 time these rocks interfinger with red beds of the here named manada hill member of the dauphin formation the red shales cherts and associated rocks of the manada hill member are pelagic deposits that range in age from at least early arenig through middle llanvirn time these allochthonous rocks were emplaced as a gravity generated klippe into the martinsburg foreland basin during late climacograptus bicornis or early dicranograptus clingani time these three members compose the dauphin formation new in the western part of the klippe area prior to emplacement of the allochthon syntectonic flysch and scattered wildflysch of the martinsburg formation were deposited some graptolite faunas from the martinsburg formation where contiguous with the klippe may be slightly older than those known from areas farther from the klippe this could indicate an earlier start of deposition in the martinsburg foreland basin in advance of the allochthon the klippe occupied a large space in the martinsburg foreland basin and it diverted deposition in this area until it was finally covered by late martinsburg age sediment the dauphin formation is now structurally interleaved and folded with the martinsburg formation as a result of late taconian and later alleghenian tectonism

sedimentary and tectonic evolution of the vena del gesso basin northern apennines italy implications for the onset of the messinian salinity crisis the integration of field and subsurface data permits a substantial revision of the sedimentary evolution of the vena del gesso basin a thrust top basin in the northern apennines where shallow water primary gypsum deposits related to the messinian salinity crisis were well developed and preserved as inferred from lateral and vertical facies changes within the underlying deep marine turbidites of the marnoso arenacea formation evaporite precipitation occurred in a basin bounded to the north and to the east by a thrust related anticline actively growing since the late tortonian both gypsum deposition and subsequent deformation were strongly controlled by evolving paleobathymetry driven by tectonics primary gypsum precipitated in a shallow silled basin while in the adjacent deeper and larger foredeep basin organic rich shales were deposited gypsum deposits underwent severe postdepositional deformation related to large scale gravitational collapse as a result of a regional uplift event also coincident with the end of the evaporitic phase along the inner shallower dipping limb of the anticline bounding the basin large scale poorly deformed gypsum slabs moved downslope along a detachment surface developed at the contact with the underlying euxinic shales forming both extensional and compressional features and showing an overall southwestern vergence the identification of a south southwest dipping paleoslope here pointed out for the first time suggests that the deformational features affecting the gypsum unit were probably driven by gravity and not by active thrusting as thought up to now the steeper frontal limb of the anticline promoted the transformation of gypsum slides into debris flows and turbidite currents that deposited their load in the adjacent deeper basin this gravitational deformation was sealed by postevaporitic upper messinian lagomare deposits the sedimentary history of the vena del gesso basin suggests that the messinian salinity crisis in the apennine foredeep as well as in the balearic tyrrhenian sicily and eastern mediterranean basins was tightly linked to tectonic processes the large scale postdepositional collapse of primary evaporitic deposits is a widespread feature in the mediterranean basins and it may have altered the original stratigraphic relationships in some places this finding has potentially important implications for a correct paleoenvironmental reconstruction of the onset of the messinian salinity crisis

structural relationships and srnd isotope systematics of polymetamorphic granitic gneisses and granitic rocks from central rajasthan india implications for the evolution of the aravalli craton this paper reviews the state of structural and geochronological knowledge of precambrian cratonic rocks in part of central rajasthan india and contributes new observations and isotopic data on the structural features and age of granitic rocks in the area the granitic rocks comprise plutons of two suites bgc and sendra suites which intrude ortho and paragneisses the archean banded gneiss complex bgc and its inliers as well as the proterozoic delhi supergroup nearly all the plutons show a foliation and a lineation which are mostly the result of solid state deformation although a magmatic component of strain is apparent in some of them the intensity of these structural fabrics varies from weak to extremely strong samples of granitic rocks from the bgc suite yield ages from sm nd isotopic data which scatter around a 2 83 ga reference isochron nd t of 4 1 with depleted mantle model ages ranging from 2 6 to 3 0 ga scatter of the data suggests that the bgc is a composite group of gneisses and confirms the antiquity of the bgc within this part of the aravalli delhi orogenic belt rb sr isotopic data of the bgc suite lie on a 1 7 ga reference isochron indicating a thermal event at that time data from plutons of the sendra suite on the other hand show some scatter but define a model ii isochron with slope equivalent to an age of 0 966 250 ga initial 87sr86sr of 0 70390 0 01889 mswd 311 the scatter of data could reflect open system behavior during a subsequent thermal event malani volcanics although independent evidence for such is lacking in the study area ages calculated from our rb sr data are within the error of published results from previous workers structural observations on granitic rocks within the bgc inlier at ajmer suggest that the inlier could represent a remobilized diapiric ridge emplaced into the delhi supergroup during the 1 7 ga thermotectonic event contemporaneously with formation of d1 structures in the wall rock although the radiometric age of the latter structures is not well constrained microtexture mineralogy and field relations of granitic rocks of the sendra suite point to those plutons being emplaced into the delhi supergroup during the 0 966 ga thermotectonic event late syntectonic relative to d2 indicating that d2 is 0 96 1 0 ga d3 represents retrograde deformation synchronous with cooling of the regional thermal framework and local pluton cooling probably between 0 96 and 0 90 ga further geochronological geochemical and structural work on the plutons and wall rock of both suites is necessary to establish a rigorous thermotectonic chronology by which to accurately model the crustal evolution of this part of central rajasthan

sedimentary facies depositional environments and palaeogeographic evolution of the neogene denizli basin sw anatolia turkey abstract the denizli basin southwestern anatolia turkey contains a record of environmental changes dating since the early miocene detailed facies analysis of the neogene formations in this half graben enables us to document successive depositional regimes and palaeogeographic settings sedimentation commenced in the early miocene with the deposition of alluvial fan and fluvial facies kizilburun formation at this stage alluvial fans sourced from elevated areas to the south prograded towards the basin centre the middle miocene time saw the establishment of marginal lacustrine and wetland environments followed by the development of a shallow lake sazak formation the uppermost part of this unit consists of evaporitic saline lake and saline mudflat facies that grade upward into brackish lacustrine deposits of late miocene pliocene age kolankaya formation the lake became shallower at the end of the pliocene time as is indicated by expansion shoreface foreshore facies in the early quaternary the denizli basin was transformed into a graben by the activation of ese trending normal faults alluvial fans were active at the basin margins whereas a meandering river system occupied the basin central part oxygen isotope data from carbonates in the successive formations show an alternation of wetter climatic periods when fresh water settings predominated and very arid periods when the basin hosted brackish to hypersaline lakes the neogene sedimentation was controlled by an active ese trending major normal fault along the basin s southern margin and by climatically induced lake level changes the deposition was more or less continuous from the early miocene to late pliocene time with local unconformities developed only in the uppermost part of the basin fill succession the unconformable base of the overlying quaternary deposits reflects the basin s transformation from a half graben into a graben system

microfacies analysis and paleoenvironmental significance of palustrine carbonates in the thakkhola mustang graben nepal himalaya abstract the thakkhola mustang graben represents the extensional tectonic phase of the tibetan plateau uplift and whole himalayan orogeny it is situated at the northern side of the dhaulagiri and annapurna ranges and south of the yarlang tsangpo suture zone stratigraphically the oldest sedimentary units are the tetang and thakkhola formations miocene while the sammargaon marpha and kaligandaki formations lying disconformably above these formations represent plio pleistocene units in this study different lacustrine carbonates and calcretes were investigated within different lithological units and depositional environments to interpret the palaeoenvironmental and palaeoclimatological evolution of the area geological mapping construction of columnar sections and carbonate sampling were carried out in the field and stable oxygen and carbon isotope analyses and thin section analyses were done in the laboratory lacustrine facies contained abundant pelletal charophytic algae oncolitic algal micritic palustrine limestones with ostracods and micritic mudstones with root traces stable carbon and oxygen isotope analysis from the carbonates show a range of 13 c values from 0 6 to 11 1 v pdb and 18 o values from 13 5 to 25 v pdb discontinuous growth of oncolites and spherical pellets 25 40 m in diameter in micritic limestone algal mats and charophyte algae indicate the presence of both shallow and deep water carbonates ostracods in dark micritic carbonates indicate quiet and calm water conditions microfabrics of the carbonates suggest that they were deposited in a flat and shallow lacustrine environment the 18 o values of the investigated limestones of the thakkhola mustang graben suggest that it attained the current elevation level prior to the east west extension of the himalaya

spot image data as an aid to structural mapping in the southern aravalli hills of rajasthan india the 10 to 20 m resolution of spot image data together with their potential for stereoscopic viewing provides an excellent base for geological mapping inremote and rugged terrain that is akin to high level aerial photographs their large format 60 60 km also gives the advantage of synoptic coverage that ranks with images from the landsat series of satellites use of stereo pairs of single band spot images has enabled some revision of existing geological maps of the southern aravalli hills in rajasthan at a scale of 1 100000 and has added significantly to knowledge of their complex mid proterozoic structure in particular many possibly early low angled faults have been discovered together with the tectonic nature of a major terrain boundary and much detail of intricate structures has been added in the more remote areas the potentialfor lithological discrimination of multispectral spot data is severely limited by its restricted coverage of geologically important spectral features and it is far surpassed by that of landsat thematic mapper data which would have been capable of more comprehensive lithofacies reconnaissance had they been available

the 2 7 2 0 ga volcano sedimentary record of africa india and australia evidence for global and local changes in sea level and continental freeboard abstract the 2 7 2 0 ga volcano sedimentary records of the african indian and australian cratons indicate two broadly defined periods of extensive drowning of the emergent continental areas concomitant with lowered freeboard carbonate banded iron formation bif platforms characterised the first such event at ca 2 6 2 4 ga africa and australia to 2 7 ga india these earlier globally enhanced sea levels are ascribed to increased mid ocean ridge activity possibly related to breakup of a postulated late archaean southern supercontinent alternatively a transition from global scale catastrophic mantle overturn events to the onset of plate tectonics may have occurred in the late archaean nelson 1998 earth planet sci lett 158 109 119 both explanations of increased mid ocean ridge activity are compatible with significant early to middle archaean crustal growth armstrong 1981 phil trans r soc london a 301 443 472 with the emergent high freeboard cratons being subjected to aggressive weathering and erosion enhanced continental crustal growth near the archaean proterozoic boundary mclennan and taylor 1982 j geol 90 347 361 related to the development of significant island arc complexes would have resulted in common lowered freeboard enhanced sea level conditions at the passive margins of the southern cratons the diachronous nature of these earlier transgressions in the various cratons may reflect the effect of local tectonic movements and or the thermal state of the cratons from ca 2 4 2 2 ga cratons that make up the present day continents of india africa and australia had relatively high continental freeboard and lowered sea levels glacigenic deposits are preserved on the kaapvaal africa singhbhum india and pilbara australia cratons the second broadly defined drowning event at ca 2 15 ga was probably due to post glacial climatic amelioration freeboard was reduced by the combination of eustatic rise and the reestablishment of aggressive weathering as warmer palaeoclimates returned in india carbonates were more prominent than the siliciclastic sediments including prominent black shales seen in africa and australia

astrochronology for the messinian sorbas basin se spain and orbital precessional forcing for evaporite cyclicity the sorbas basin of se spain contains one of the most complete sedimentary successions of the mediterranean reflecting the increasing salinity during the messinian salinity crisis a detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves here we present an astrochronological framework for the messinian of the central part of the sorbas basin this framework will form a solid basis for high resolution correlations to the marginal carbonate facies and to the central mediterranean area the early messinian abad member contains 55 precession induced sedimentary cycles marked by homogeneous marl opalrich bed alternations in the lower abad and by homogeneous marl sapropel alternations in the upper abad astronomical tuning results in an age of 5 96 ma for the transition to the yesares evaporites and thus for the onset of the messinian salinity crisis the marl sapropel cycles of the upper abad are replaced by gypsum sapropel cycles 14 in the yesares member indicating that the evaporite cyclicity is related to precession controlled oscillations in circum mediterranean climate as well as a consequence gypsum beds correspond to precession maxima insolation minima and relatively dry climate sapropelitic marls to precession minima insolation maxima and relatively wet climate an alternative glacio eustatic obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high sedimentation during the abad yesares and the overlying coastal sequences of the sorbas member took place in a continuously marine environment indicating that marine conditions in the sorbas basin prevailed at least until 5 60 5 54 ma according to our scenario deposition of the yesares and sorbas member took place synchronously with deposition of the lower evaporites in the central mediterranean finally the continental zorreras member consists of 8 sedimentary cycles of alternating reddish silts dry climate and yellowish sands wet climate which correlates very well with the upper evaporites and lago mare facies of the mediterranean q 2001 elsevier science b v all rights reserved

the late messinian salinity crisis and late miocene tectonism interaction and consequences on the physiography and post rift evolution of the gulf of lions margin the interpretation of rhone maritime seismic profiles and the accurate mapping of all the structural features affecting the miocene cover made it possible for us to develop herein a new structural model for the top of the eroded miocene of the gulf of lions platform late miocene extensional faults exerted a considerable structural control on the messinian erosion in particular mapping of transfer zones has shown that these structures controlled retrogressive erosion of the platform this late miocene extension could have been caused by gravity driven destabilization of the platform associated with base level lowering at the onset of the messinian salinity crisis

geochemical controls on arsenic and rare earth elements approximately along a groundwater flow path in the shallow aquifer of the hetao basin inner mongolia article i nfo groundwaters and sediments were sampled approximately along a groundwater flow path in the shallow aquifer of the hetao basin inner mongolia along a flow path with a length of about 9 km groundwater evolves from ca hco3 so4 through mg ca hco3 cl to na cl hco3 from the recharge zone to the discharge

testing models for the messinian salinity crisis the messinian record in almeria se spain abstract neogene intermontane basins in almeria province se spain display excellent exposures of messinian late miocene sequences the sorbas almeria nijar and vera basins maintained connection with the mediterranean throughout the messinian except during the major desiccation phase leading to the formation of salt in the deep centre of the western mediterranean these basins were part of the western mediterranean with no separate link to the atlantic ocean the presence of normal marine sediments in these basins reflects the western mediterranean watermass messinian pre evaporitic sediments in the basins of southeastern almeria do not show gradual change towards evaporite deposits instead they contain stenohaline invertebrates right up to a major erosion surface that separates them from overlying gypsum deposits this contradicts suggestion of progressive salinity increase in this part of the western mediterranean prior to the messinian salinity crisis msc it also indicates that initiation of evaporite precipitation was not synchronous throughout the mediterranean basin there is no major erosion surface within or at the top of the evaporites in these almeria basins and the gypsum beds exhibit upward transition to siliciclastic and carbonate deposits this is inconsistent with a model of messinian mediterranean evaporite formation whereby deposition of marginal evaporites was followed by their erosion during drawdown that resulted in formation of evaporites in the centre of the western mediterranean the presence of stenohaline biotas in siliciclastic deposits interbedded with the gypsum and in the messinian post evaporitic sediments challenges the view that a long standing large body of brackish water the lago mare filled the western mediterranean following the msc and prior to early pliocene flooding it also contradicts the concept of many relatively small brackish basins spread across an otherwise desiccated western mediterranean basin the basins of southeastern almeria record normal marine early messinian sedimentation that was abruptly interrupted by sealevel fall this drawdown most likely resulted in precipitation of evaporites in the central deep western mediterranean basin following this episode final marine reflooding of the western mediterranean took place during the late messinian and the mediterranean sea rose to a level similar to or higher than that preceding the salinity crisis

orbitally forced paleoenvironmental and paleoclimate changes in the late postevaporitic messinian of the central mediterranean basin paleoenvironmental and paleoclimate changes that occurred during the late postevaporitic stage of the mediterranean basin in the messinian foreland domain of the adriatic region offer a new perspective on the relationship between orbital forcing and climate response the magnetic susceptibility record of the fonte dei pulcini a section maiella mountains italy allows us to orbitally tune the record between 5 394 and 5 336 ma and to temporally constrain the paleoenvironmental and paleoclimate changes evidenced by quantitative paleontological palynomorphs ostracods and calcareous nannofossils stable isotope 18 o and 13 c and x ray diffraction xrd analyses the base of the fonte dei pulcini a section is characterized by paratethyan ostracods and dinocysts which point to the late messinian lago mare biofacies loxocorniculina djafarovi zone of the mediterranean messinian stratigraphy from paleontological and geochemical 18 o analyses there is no evidence of a marine incursion in the fonte dei pulcini a section the major changes in terms of paleodepth paleosalinity evaporation versus precipitation aridity versus humidity and reworking processes occurred in the upper part of the fonte dei pulcini a section during the last messinian insolation cycle i cycle 511 512 which is characterized by high amplitude oscillations in contrast the lower part of the fonte dei pulcini a section which was deposited during relatively low amplitude insolation cycles is characterized by more stable environmental conditions comparing summer insolation with the paleoenvironmental changes at the fonte dei pulcini a section we identify delays of several thousands of years between orbital forcing and climate response

the late messinian lago mare event and the zanclean reflooding in the mediterranean sea new insights from the cuevas del almanzora section vera basin south eastern spain abstract the return to normal marine conditions in the mediterranean sea after the end of the messinian salinity crisis msc that led to the deposition of thick evaporitic succession followed by settlement of brackish to freshwater conditions of the lago mare is still subject to extensive debate between two opposite scenarios one scenario implies an abrupt reflooding through the gibraltar gateway of the mediterranean sea previously disconnected from the world ocean and partly desiccated the second scenario postulates that the mediterranean sea kept a high water level throughout the messinian salinity crisis and was connected continuously to the atlantic ocean and to the paratethys the stratigraphic record of the classical cuevas del almanzora section vera basin is of a crucial importance as the vera basin is located on the eastern margin of the alboran sea close to the gibraltar gateway where atlantic waters reflooded the mediterranean sea after the msc the present new study completes previous investigations pierre et al 2006 and is mostly focused on detailed sedimentological observations analysis of ostracod and foraminifer assemblages and on stable isotopes study of three species of planktonic foraminifers globigerina bulloides globigerinoides obliquus s l and sphaeroidinellopsis spp from the lower pliocene deposits biostratigraphical correlations with the reference deep sea section from odp site 975 balearic basin and the onshore succession of eraclea minoa sicily provide an accurate chronostratigraphy and paleoclimatic reconstruction during the zanclean during the late messinian the vera basin was characterized by very unstable lacustrine to brackish environments with significant water depth variations and the deposits display evidences of subaerial exposure the ostracod content is dominated by loxocorniculina djafarovi and cyprideis gr agrigentina associated to reworked planktonic foraminifera from older sediments the messinian zanclean contact is well marked by a clear erosional surface that grades laterally into a megabreccia with reworked gypsum blocks and to the large incision of the palomares canyon in the offshore domain the marine reflooding occurred abruptly with a sea level rise by more than 250 m an important value for a marginal basin in this western part of the mediterranean sea the marine invasion began with the onset of the lowermost biozone mpl 1 at the base of the zanclean the fluctuations of the planktonic foraminifer assemblages and of their stable isotopes allowed to identify five lithological cycles forced by milankovitch precession periodicity as well as paleoclimatic variations through the lower part of the zanclean thus these new data allow us to reaffirm that the messinian zanclean boundary corresponds to a major change characterized by an instantaneous restoration of marine conditions at the onset of the pliocene related to the abrupt re flooding of the mediterranean sea from the atlantic ocean

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

the monte carrubba formation messinian sicily and its correlatives new light on basin wide processes controlling sediment and biota distributions during the palaeomediterranean mediterranean transition abstract a little known marine miocene messinian succession in the hyblean region of south eastern sicily preserves a carbonate ramp sequence which developed on the tectonically stable foreland margins of the african plate pelagian block the ramp monte carrubba formation was distally steepened and contained a shoalwater barrier and lagoonal inner ramp complex the outer ramp is poorly preserved though distal deep water ramp facies tellaro formation in the south hyblean region preserve a full globorotalia mediterranea subzone and major part of the globigerina multiloba subzone succession this ramp sequence faithfully records the subtle interplay between the global eustatic curve and internal palaeomediterranean base level signatures for the late miocene the earliest second order palaeomediterranean lowstand occurred in the late tortonian at about 7 3 ma and a second occurred at about 6 75 ma within the early messinian g mediterranea subzone both were in the order of 40 m and global sea level was probably restored to the palaeomediterranean after the lowstands although the overriding control at the time was the global eustatic curve harmonic discrepencies between it and the palaeomediterranean curve resulted from constriction of the atlantic connection during the latest tortonian from about 6 4 ma until about 5 96 ma increasingly restricted conditions developed across the monte carrubba inner ramp these faithfully reflect many second order constriction driven palaeomediterranean sea level oscillations which were superimposed on to the falling global signal as the connecting atlantic seaways became constricted these oscillations resulted in major reductions in planktonic faunal diversity within the outer ramp followed by total emergence of the inner ramp by about 6 05 ma marine deposition continued until about 5 96 ma in the southern part of the hyblean region however between 6 05 ma and about 5 6 ma the amplitude of successive palaeomediterranean sea level oscillations increased to over 100 m causing prolonged periods of total palaeomediterranean isolation the hyblean carbonate suite also contains post messinian salinity crisis post msc lago mare highstand deposits which are developed unconformably above the monte carrubba formation the widespread distribution of hyposaline to near marine congeria faunas within the lago mare episode argues for high post msc mediterranean water levels in the central mediterranean late messinian in this article we draw together disparate regional evidence from this stable foreland setting and assimilate it with published data from regions lying on the european plate in order to demonstrate that the tectonically stable monte carrubba succession provides an unambiguous record of central palaeomediterranean base level change during the messinian furthermore the post msc sequence demonstrates a prolonged mediterranean base level rise throughout the late messinian leaving little readjustment necessary in order to restore mediterranean base level to global water levels in basal pliocene times

dalradian slides and basin development a radical interpretation of stratigraphy and structure in the sw and central highlands of scotland movements on syndepositional listric faults are responsible for many of the lateral variations in dalradian stratigraphy sedimentary facies and thickness variations show that the surface traces of these faults correspond in many cases to what have previously been interpreted as tectonic slides although normal faults thrusts and sedimentary contacts may also mark their position three main episodes of faulting are described in the islay to lochaber area appin group sedimentation was controlled by a fault now represented by the loch skerrols thrust fort william slide ossian steep belt in the islay jura area an anomalously thick islay subgroup succession accumulated in a half graben bounded by a listric normal fault to the nw and terminated by transfer faults at each end the deposition of a thick easdale subgroup section was controlled by movements on what is now the benderloch ballachulish slide this listric fault terminates southwards in the scarba fault and probably extends north into the ossian steep belt the thinness of the appin and lower argyll group succession between the ericht laidon and bridge of balgie faults is an original feature the stratigraphic gap represented by the boundary slide here is reinterpreted as a disconformity however further east the boundary slide may well be a listric fault movement on which accommodated the thick succession around schiehallion the development of the major structure was influenced by the geometry of the sedimentary basins the schiehallion tummel area is reinterpreted as lying on the lower limb of the ben lui fold this resolves the problem of the emplacement of the tay nappe which is likely to be a gravity structure derived from above the ossian steep belt

another look at rare earth elements in shales linear correlation and mass balance considerations indicate that clays are more important than zircon or other heavy minerals in hosting both light and heavy ree in cratonic shales considering the uniformity of the eu anomaly and ree distributions in cratonic shales it seems likely that detritus is thoroughly mixed during weathering and sediment transport and that the ree patterns in shales reflect the average ree pattern of the sources regardless of the ratio of clays to heavy minerals in the shales shales suspended river loads and near shore marine sediments all have broadly similar ree patterns and reported hree depletions in the latter two groups may reflect incomplete dissolution of heavy minerals during sample preparation ree distributions in shales and suspended river loads determined by inna are similar to those in average upper continent crust and ree distributions in shale averages nasc and paas seem to be reasonably representative of the average composition of post archean upper continental crust

tectonics of the southern and central appalachian internides the appalachian orogen was constructed along the ancient precambrian continental margin of eastern north america by a series of compressional events that began in the ordovician and episodically spanned much of the paleozoic era the processes of accretion of suspect and exotic terranes together with terrane collision and ultimately completion of the wilson cycle by continent continent collision resulted in construction of the appalachian orogen figure 1 these paleogeographic elements are rep resented by the various lithotectonic units visible today in the southern and central appalachians figure 2 these subdivisions represent the late precambrian rifted margin and early paleozoic platform that were formed directly upon north american grenvillian basement cumberland allegheny plateau valley and ridge and western blue ridge the offshore north american slope rise assemblage hamburg klippe southern appalachian eastern blue ridge and inner piedmont and higher thrust sheets of the maryland northern virginia piedmont and the exotic carolina or avalon and wilmington terranes the carolina ter rane contains the alleghanian high grade metamorphic core these elements form the basis for this analysis and review of the present state of knowledge of the tectonic history of the southern and central appalachian internides the appalachian orogen has been the subject of study by geologists at least since the early nineteenth century early fundamental concepts such as the geosynclinal theory of mountain building dana 1873 hall 1883

the occurrence and geochemistry of arsenic in groundwaters of the newark basin of pennsylvania abstract elevated as concentrations in groundwater in the eastern united states have been recognized predominantly in the accretionary geologic terranes of northern new england a retrospective examination of more than 18 000 existing groundwater samples from the pennsylvania department of environmental protection pa dep drinking water and sampling information system database indicates that elevated groundwater as concentrations occur throughout the northern half of the piedmont province of pennsylvania chemical analyses of 53 samples collected in 2005 from drinking water wells in this area all had detectable as and 23 of these samples contained elevated 133 nmol l or 10 g l concentrations of as elevated concentrations of as in the groundwater samples were most common in the mesozoic sedimentary strata composed of sandstone and red mudstone with interbedded gray shale and gray to black siltstone and shale arsenic was typically not elevated in groundwater of diabase intrusions of the newark basin or in crystalline and calcareous aquifers to the north of the newark basin geochemical parameters such as ph and oxidation reduction potential can indicate mobility mechanisms of as in some regions in this area measured groundwater conditions were predominantly oxidizing eh 50 mv and more than 85 of samples contained arsenate as the dominant as species variations in ph were strongly correlated to the as concentration with highest as concentrations observed at ph values greater than 6 4 the original source of as is most likely the black and gray shales that contain some arsenian pyrite with groundwater concentrations likely to be controlled by adsorption desorption reactions with fe oxides in the red mudstone aquifer materials

origin and age of the mediterranean messinian evaporites implications from sr isotopes strontium isotope ratios from the messinian late miocene 6 4 to 4 85 ma evaporites of the mediterranean basin 1 2 support a subdivision into stratigraphically lower predominantly marine deposits lower evaporites lev lower gypsum and main salt characterized by sr isotopic ratios generally equivalent to those of messinian seawater and stratigraphically higher deposits upper evaporites uev with 87sr 86sr ratios lower than messinian seawater the range of 87sr 86sr ratios of the lev unit from the eastern mediterranean overlap with values obtained from essentially coeval red sea evaporites 3 strontium isotopic ratios measured from the upper evaporites however are lower and a high proportion of this sr was probably derived from low 87sr 86sr continental runoff that characterizes much of this basin 4 these results therefore strongly support depositional models utilizing a deep desiccated basin 1 with a constant marine inflow during the early stages including salt formation followed by a series of long lasting and sometimes isolated desiccation events that produced a strong but variable continental influence on the sr isotopic compositions of the uev strontium isotopic measurements can also be used to asses the actual timing of the deposition of the lev ratios obtained from oyster fragments and foraminifers from pre evaporitic units at odp site 654 tyrrhenian sea suggest that the major rifting phase in this region occurred between 8 and 6 5 ma ratios obtained from the early lev from the mediterranean sea suggest that initiation of evaporite deposition began about 5 65 ma ago results from units immediately overlying the uev in sicily suggest termination of evaporite deposition about 4 9 ma ago errors associated with these age estimates are about 0 5 ma 2

high frequency cyclicity in the latest messinian adriatic foreland basin insight into palaeoclimate and palaeoenvironments of the mediterranean lago mare episode abstract late messinian lago mare deposits show high frequency cyclicity in the whole mediterranean basin both millimeter and centimeter scale cyclicities have been observed in several odp sites as well as in stratigraphic sections from the mediterranean borderland we have analyzed a well exposed late messinian lago mare section from the adriatic side of the central apennines italy at the fonte dei pulcini section se majella mts millimeter and centimeter scale white and dark couplets have been observed in the field a 50 cm regular spaced sampling has been performed in the uppermost 53 m of the late messinian lago mare clays on the 107 collected samples geochemical caco 3 content mineralogical xrd analyses and micropalaeontological investigations have been performed in addition sem and microprobe investigations as well as mineralogical and micropalaeontological analyses have been carried out on single lamina from a 34 cm thick interval of millimeter scale laminites besides the 10 3 cycles m and 10 2 cycles m frequencies observed in the field spectral analyses performed on the caco 3 data set indicated other high frequency cyclicities 0 47 cycles m 0 35 cycles m and 0 17 cycles m taking into account the estimated sedimentation rate these frequencies correspond respectively to periodicities of 1 year 10 years 2 1 kyr 2 8 kyr and 5 6 kyr these sub milankovitch cyclicities have been related to annual and sunspot solar activity the millimeter scale couplets are interpreted as varves sedimented in an ephemeral water environment marginal to a perennial brackish water lagoonal basin these varved sediments reflect a marked seasonality characterized by the alternation of arid and more humid climatic phases the presence of high values of smectite 60 80 in the clay minerals of the analyzed samples could be a consequence of these climatic oscillations from drier to moister conditions the climatic scenario suggested in this paper for the late messinian lago mare episode is in agreement with the monsoon system that according to some authors starting from 5 8 ma developed in the mediterranean area

distribution of arsenic and other trace elements in the holocene sediments of the meghna river delta bangladesh geochemical study of the holocene sediments of the meghna river delta chandpur bangladesh was conducted to investigate the distribution of arsenic and related trace and major elements the work carried out includes analyses of core sediments and provenance study by rare earth element ree analysis results showed that the cores pass downward from silty clays and clays into fine to medium sands the uppermost 3 m of the core sediments are oxidized average oxidation reduction potential orp 230 mv and the orp values gradually become negative with depths 45 to 170 mv indicating anoxic conditions prevail in the meghna sediments the ree patterns of all lithotypes in the study areas are similar and are comparable to the average upper continental crust arsenic and other trace elements pb zn cu ni and cr have greater concentrations in the silts and clays compared to those in the sands positive correlation between as and fe was found in the sediments indicating as may be adsorbed on fe oxides in aquifer sediments

the mediterranean messinian salinity crisis an apennine foredeep perspective abstract owing to its expanded stratigraphic sections the apennine thrust belt offers the opportunity to better understand the evaporitic and post evaporitic messinian events a physical stratigraphic framework of messinian deposits based on facies analysis and basin wide correlation of key surfaces and sedimentary cycles is presented it is shown that the messinian apennine foredeep had marginal basins with shallow water primary evaporites and deeper basins where resedimented evaporites accumulated under relatively deep water conditions like many other mediterranean examples primary shallow water evaporites of apenninic marginal basins show evidence for subaerial exposure and erosion however the development of such an erosional surface does not correspond to the deposition of primary evaporites in the deepest part of the basin s here the unconformity can be traced towards the base of resedimented evaporites or to a level within them implying that the deeper basins of the apennine foredeep never underwent desiccation during the messinian salinity crisis but rather received the eroded marginal evaporites this fact usually overlooked raises important questions about the deep desiccation model of the mediterranean

late proterozoic rift control on the shape of the appalachians the pennsylvania reentrant the pennsylvania reentrant the most prominent deviation in the trend of the appalachians is the product of late proterozoic rifting the peters creek formation pennsylvania maryland piedmont contains rift gene rated deep water turbidite deposits of late proterozoic cambrian age these rocks are an extension of the westminster terrane and lie well to the northeast of the southern appalachian late proterozoic cambrian rift basin lynchburg chilhowee group basin the basin into which the peters creek formation was deposited may have connected the southern rift basin with one to the north the preservation of the peters creek formation and other age equivalent units within the pennsylvania reentrant indicates that the new york promontory acted as a buttress to paleozoic orogenic activity

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

carbonates associated with alluvial fans an example from the messinian colombacci formation of the pietrarubbia basin northern marche italy abstract the carbonates known as colombacci of a terrestrial series deposited within an upper messinian basin in marche italy have been examined by means of stable isotope analyses aas analyses study of thin sections and sem observations the results of the analyses attest to the in situ production of the carbonates in shallow ponds induced by biological activity as well as to the considerable influence of meteoric waters on late messinian sedimentation the carbonates were compared to coeval limestones from neighbouring basins the composition of the latter is indicative of precipitation out of meteoric water as well minor differences reflect the distinct settings of the separate marginal basins of the messinian mediterranean

the mediterranean water body in the late messinian interpreting the record from marginal basins on sicily the stratigraphic record of climatic and palaeoceanographic changes in the mediterranean during the late messinian is controversial on sicily sedimentary facies show a steady transgression suggesting that sub basins were hydrodynamically linked to a larger water body here we test this hypothesis using strontium isotope studies from messinian materials collected from a range of sites in the caltanissetta basin of central sicily the strata include a regionally regressive first cycle of early mid messinian age and a younger transgressive second cycle these cycles are separated by an inter regional unconformity which may be correlated with base level low stand in the mediterranean 87 sr 86 sr ratios for all first cycle gypsum fall within the expected global marine composition 0 70891 0 70897 all second cycle analyses fall within a grouping of significantly lower values 0 70868 0 70878 a surprisingly tight but discrepant grouping for data collected from shells of a brackish water fauna and from gypsum analyses from these different second cycle materials are statistically indistinguishable these results indicate that the strontium isotopic composition of waters from different sub basins on sicily are indistinguishable regardless of salinity during the late messinian therefore these basins must have mixed with a larger homogenized reservoir which we infer was the ancestral mediterranean thus circum mediterranean basins may indeed chart regional palaeoceanographic and climatic events by the end of messinian times the base level of the mediterranean was within the range of the world9s oceans but the water body probably had a distinctly different but internally homogeneous strontium isotopic composition

evolution of lower proterozoic epicontinental deposits stromatolite bearing aravalli rocks of udaipur rajasthan india abstract the aravalli rocks 2060 ma old which crop out around udaipur western india comprise a thick sequence of metasediments with stromatolites and basal volcanics resting unconformably over a peneplained basement known as the banded gneissic complex ca 2585 ma old the rocks have undergone a very low grade of metamorphism and display a complex structure resulting from two major and several minor episodes of folding there are two distinctly different facies sequences in the aravalli rocks indicating deep sea and nearshore shelf environments the stratigraphic sequence of the rocks deposited under the shelf environment starts with basic volcanics and tuffs altered to greenschists and quartizites with arkosic conglomerate in the next sequence carbonates predominate in association with orthoquartzites carbonaceous phyllites phyllites and stromatolitic rock phosphate the carbonate sequence passes upward into greywacke phyllite lithic arenite in the distal parts and conglomerate arkose orthoquartzite in proximal areas the youngest sequence comprises orthoquartzite with silty arenite the distribution of different facies particularly that of dolomite with stromatolitic rock phosphate is controlled by sea floor topography suggesting the presence of an epicontinental sea bounded by a landmass to the west and a series of islands and shoals sedimentation in the shelf and epicontinental sea was presumably triggered by development of fault controlled troughs along craton margins terrigenous debris was deposited in newly developed troughs with contemporaneous volcanicity along trough margins with the erasing of the ephemeral relief in the provenance carbonate deposition was initiated the environment encouraged algal growth and formation of stromatolitic rock phosphate carbonaceous phyllites developed in areas of restricted circulation rapid influx of terrigenous detritus with renewed tectonism in the next phase resulted in the deposition of a turbidite sequence of greywacke phyllite and lithic arenite in the deeper parts of the epicontinental sea and conglomerate arkose orthoquartizite in the marginal areas the final phase of sedimentation was presumably under fluvial conditions which marked the completion of epicontinental trough filling the nature of the terrigenous clasts indicates a predominantly granitic source of sediments supply of sediment was mainly from the continent to the east and partly from a landmass to the west the cycle of sedimentation noted in the epicontinental aravalli sea is broadly similar to the model of tectonic stages suggested by krynine 1942

quantitative filling model for continental extensional basins with applications to early mesozoic rifts of eastern north america in many half graben strata progressively onlap the hanging wall block of the basins indicating that both the basins and their depositional surface areas were growing in size through time based on these constraints we have constructed a quantitative model for the stratigraphic evolution of extensional basins with the simplifying assumptions of constant volume input of sediments and water per unit time as well as a uniform subsidence rate and a fixed outlet level the model predicts 1 a transition from fluvial to lacustrine deposition 2 systematically decreasing accumulation rates in lacustrine strata and 3 a rapid increase in lake depth after the onset of lacustrine deposition followed by a systematic decrease when parameterized for the early mesozoic basins of eastern north america the model s predictions match trends observed in late triassic age rocks significant deviations from the model s predictions occur in early jurassic age strata in which markedly higher accumulation rates and greater lake depths point to an increased extension rate that led to increased asymmetry in these half graben the model makes it possible to extract from the sedimentary record those events in the history of an extensional basin that are due solely to the filling of a basin growing in size through time and those that are due to changes in tectonics climate or sediment and water budgets

geological and geochemical examination of arsenic contamination in groundwater in the holocene terai basin nepal geological and geochemical study has been carried out to investigate arsenic contamination in groundwater in nawalparasi the western terai district of nepal the work carried out includes analyses of core sediments provenance study by rare earth elements analyses 14c dating and water analyses results showed that distribution of the major and trace elements are not homogeneous in different grain size sediments geochemical characteristics and sediment assemblages of the arsenic contaminated nawalparasi and uncontaminated bhairahawa area have been compared geochemical compositions of sediments from both the areas are similar however water chemistry and sedimentary facies vary significantly extraction test of sediment samples showed significant leaching of arsenic and iron chemical reduction and contribution from organic matter could be a plausible explanation for the arsenic release in groundwater from the terai sediments

integrated analyses constraining the provenance of sandstones mudstones and conglomerates a case study the laojunshan conglomerate qilian orogen northwest china the qilian orogenic belt in the northern tibetan plateau connects the altaids to the north with the tethyan orogenic system to the south and occupies a key tectonic position in the evolution and assembly of asia the belt con tains a wide range of subduction accretion related petrotectonic units the early middle devonian laojunshan con glomerate deposited unconformably upon cambrian silurian strata along the northern margin of the north qilian terrane contains a record of the late paleozoic tectonism of the qilian orogen its provenance and tectonic setting are critical in understanding not only the tectonic evolution of tibetan plateau but paleozoic global reconstructions as well the composition of clastic conglomerates and heavy mineral assemblages of sandstones suggests that coeval mafic felsic metamorphic and sedimentary rocks were the main sources the geochemistry of volcanic clasts and paleocurrent and paleogeographic data suggest derivation from subduction accretion complexes in the north qilian terrane the geochemistry of siltstones and mudstones indicates that the laojunshan conglomerate was derived from an arc and accumulated in an active continental margin geochemical data of granitoid clasts suggest that they were de rived from ordovician silurian subduction related magmatic rocks mafic and ultramafic clasts chromite and magne tite decrease upwards in the stratigraphy whereas metamorphic sedimentary and granitoid clasts and garnet increase these data imply that mafic rocks were the predominant source during initial deposition regional studies suggest that the north china plate subducted southwards and produced subduction related arc magmatism along the southern margin of the north qilian terrane during the early middle devonian therefore we interpret the laojunshan conglomerate as a fore arc basin fill

a box model of the late miocene mediterranean sea implications from combined 87sr 86sr and salinity data 1 under certain conditions the strontium isotope ratio in the water of a semi enclosed basin is known to be sensitive to the relative size of ocean water inflow and river input combining sr isotope ratios measured in mediterranean late miocene successions with data on past salinity one can derive quantitative information on the mediterranean hydrological budget at times before and during the messinian salinity crisis msc previous studies obtained this hydrological budget by inverting the salinity and strontium data with steady state solutions to the conservation equations of salt strontium and water here we develop a box model with a time dependent set of equations to investigate the coeval evolution of salinity and sr ratios under different water budgets gateway restrictions and riverine sr characteristics model results are compared with the salinity and strontium ratio data from the mediterranean with a present day water budget strontium ratios in the mediterranean never reach the observed messinian values regardless of gateway restriction and water budget however a model with tripled river input as inferred for the late miocene is able to reproduce the sr ratios observed the onset of the msc can be explained with a simple restriction of the gateway s between the mediterranean and atlantic lower evaporite gypsum formed in a basin with less outflow to the atlantic than modeled in previous studies because of the large late miocene river input evaporite thicknesses predicted by our model and consistent with the messinian sr ratios are on the low end of the thickness range inferred from seismics

application of ree geochemical signatures for mesozoic sediment provenance to the gettysburg basin pennsylvania rift basins adjacent to accreted terranes provide accommodation space for sediments eroded from these terranes despite similar depositional environments and geologic age rocks of the triassic gettysburg basin have approximately half the arsenic concentrations of the adjacent newark basin quartz feldspar lithics qfl diagrams and rare earth element ree geochemical signatures can inform sediment provenance here we investigate ree geochemical signatures of the sedimentary rocks in the triassic gettysburg rift basin with the goal of distinguishing the main sources of siliciclastic sediment among the appalachian foreland in the rift footwall from piedmont arc and iapetan continental margin rocks exposed in the hanging wall and ultimately understanding the geochemical cycling of arsenic to the gettysburg basin shale normalized ree spider diagrams and mann whitney tests on trace element ratios suggest that the gettysburg basin samples show patterns that most closely resemble those of the iapetus continental slope rise iapetus rift volcanic and accretionary complex deposits mann whitney rank sum analysis suggest that the iapetus continental slope rise terrane is the main source of sediments to the basin which confirms results from prior qfl analysis and shows the utility of ree fingerprinting in provenance analysis the main sources of sediment have smaller minimum and maximum arsenic concentrations than other terranes and the newark basin sediments additionally suggesting the source of arsenic to the gettysburg basin is based upon specific terranes

paleoenvironmental changes at the messinian pliocene boundary in the eastern mediterranean southern cyprus basins significance of the messinian lago mare abstract the study of the late messinian early pliocene sediments in south cyprus pissouri and polemi basins and the comparison with the offshore coeval deposits drilled in the odp leg 160 boreholes provide new data illustrating the environmental changes which occurred in the eastern mediterranean at the end of the salinity crisis the messinian pliocene transition is marked by a very rapid environmental change indicated by sharp variations in lithology sedimentology microfaunal assemblages and stable isotope composition the latest messinian interval is dominated by the lago mare oligo mesohaline environments the most striking feature in the pissouri basin is the intercalation between the uppermost gypsum bed and the base of the zanclean deposits of four main horizons of paleosols interbedded with carbonates and conglomerates paleosols indicate periods of subaerial exposure long enough to permit pedogenesis to develop conglomerates indicate intense erosion of the troodos massif and its sedimentary cover as a result of the water level drop tectonic activity and more humid climatic conditions thus several subaerial exposure phases occurred in the marginal areas like the pissouri basin whereas shallow oligohaline conditions persisted in the deeper parts of the basin as indicated at odp site 968 both in the pissouri basin and on the flank of the erathostenes seamount the late messinian paleosols are directly overlain by the lowermost pliocene sediments deposited in well oxygenated deep marine conditions this drastic change of water depth shows that the water level of the late messinian saline to brackish lakes dropped far below that of the world ocean at least more than several hundred meters both these base level fluctuations and the oligohaline conditions caused intensive erosion karstification of the upper gypsum beds as also reported from many other mediterranean regions moreover the study of the polemi sections shows that oligohaline conditions had already started during the deposition of the upper gypsum sub unit typical brackish and fresh water assemblages are present in the last two gypsum layers and intergypsum beds this indicates that freshwater dilution i e the lago mare conditions resulted from a progressive change of the hydrological budget which started during deposition of the upper evaporites and climaxed after the deposition of the uppermost gypsum layer classical lago mare facies during this time periods of increased evaporation over precipitation led to deposition of the uppermost gypsum layers this evolution is interpreted as being due both to the severance from the open ocean and to the increasing contribution of the runoff precipitation versus marine inputs in the hydrological budget of the mediterranean

offshore evidence of polyphase erosion in the valencia basin northwestern mediterranean scenario for the messinian salinity crisis the messinian salinity crisis at the end of the miocene strongly affected the physiography of the mediterranean margins and in particular that of the valencia basin and its margins the valencia basin which is an aborted tertiary rift related to the opening of the oceanic provencal basin shows evidence of two major messinian erosion surfaces a basal erosion surface bes and a top erosion surface tes bracketing the messinian evaporite succession the basin s margins show only a single erosion surface here termed the margins erosion surface mes in examining the geometrical relationships of these erosion surfaces with the deep basin facies deposited in the abyssal provencal basin during the messinian salinity crisis we have been able to establish a chronology for the messinian in the valencia basin briefly the basal erosion surface extends the margins erosion surface into the central valencia basin and records an early and important sea level fall at the beginning of the messinian salinity crisis the miocene basin series were incised by canyons while the exposed margins underwent substantial subaerial erosion the basin s detrital products linked to this basal erosion grade laterally into the massive messinian salt layer of the provencal basin the overlying upper evaporites unit appears to be widely transgressive beyond the edge of the messinian salt and onlaps the basal erosion surface in the valencia basin this disposition suggests a progressive sea level rise during the deposition of the upper evaporites possibly due to the rapid accumulation of thousands of metres of shallow water evaporite facies in the provencal basin the top erosion surface at the top of the upper evaporites shows a network of incisions and we suggest that this final erosion was

sr isotope constraints on the mediterranean environment at the end of the messinian salinity crisis probably the most profound event that has affected the mediter ranean is the desiccation which occurred at the end of the miocene1 8 during this period there was a very rapid change from deep open marine conditions to environments of shallow water carbonate and massive evaporite deposition1 10 here we show that ostracod valves found in messinian lago mare lake sea sediments have a uniform but generally lower sr isotopic composition than contemporary sea water thus providing evidence that some of the major mediterranean basins for example balearic and levantine basins formed large lacustrine systems that were probably interconnected towards the end of the messinian salinity crisis1 3 after the major evaporites were deposited the most likely source of fresh water is from continental rivers flowing from the eastern european inland paratethys sea or perhaps the nile river in the lower part of the lago mare some ostracods have sr isotopic compositions identical to contemporary sea water indicating a transient influence of marine derived water sr compo sitions greater than that in contemporary sea water are only found in ostracods from onshore sediments in the sorbas basin4 5 of southeastern spain suggesting that this small basin adjacent to the straits of gibraltar became isolated after the deposition of the major evaporite sequences

geochemical indicators in western mediterranean messinian evaporites implications for the salinity crisis abstract the messinian salinity crisis msc led to deposition of one of the youngest saline giant on earth the increasing restriction of the connections between the mediterranean the atlantic ocean and the freshwater paratethyan basins resulted in the deposition of massive amounts of evaporites gypsum anhydrite halite and potash salts in shallow marginal basins as well as in deep mediterranean basins here we show that each gypsum unit in the circum mediterranean marginal basins in sicily and spain is characterized by a narrow range of sulfate isotopic values 34s 23 and 18o 14 in the lower gypsum 34s 23 and 18o 17 in the upper gypsum sulfate isotope compositions found in msc evaporites from a variety of circum mediterranean basins are homogenously high relative to expected late miocene marine evaporites 34s 22 and 18o 12 this points to a stratified mediterranean sea with a high salinity dense and anoxic bottom water mass an intermediate depth gypsum saturated brine flooded marginal basins from which selenite deposits formed during the msc stage 1 primary lower gypsum and msc stage 3 upper gypsum messinian brines were gradually affected by biogenic redox processes and isotopically differentiated from global seawater values the homogeneity of isotopic signatures between distant synchronous gypsum deposits further supports the deep basin deep water model for the mediterranean during the entire msc event

late neogene erosion of the alps a climate driver as with many mountain belts globally the alps have seen a large increase in sediment yield in the late neogene the hypothesis that this increase results from climate change impacts on erosion rate over the past 5 ma is testable given the extensive work completed in the alps sediment budgets thermochronology based cooling rates and estimates of modern rock uplift and erosion in the western alps are reviewed to search for correlation in space and time that might fingerprint climatic events major increases in sediment yield are apparent starting in the late messinian 5 5 mya and accelerating toward the present day this suggests the occurrence of a series of climatic changes that increased erosion rates even as tectonic processes appear to have slowed or stopped at present tight correlations in time are difficult to establish and there remain open questions about the role of tectonics in the coupled system

paleoenvironmental significance of messinian post evaporitic lacustrine carbonates in the northern apennines italy the post evaporitic messinian in the northern sector of the adriatic foredeep is characterized by the occurrence of abundant terrigenous deposits which have been subdivided into two allostratigraphic units p ev1 p ev2 separated by an erosional unconformity of regional importance the p ev1 consists of basal complex of resedimented evaporites overlain by monotonous succession of mudstone siltstone alternations thin bedded turbidites with an overall coarsening and shallowing upwards trend it is possibly related to the rapid basin infill after the end of the salinity crisis the upper unit p ev2 shows in the most marginal areas a clear cyclical stacking pattern made up of three fining up sequences with fan delta conglomerates at the base of each cycle here a peculiar feature of the p ev2 deposits is the occurrence of three distinct laminated limestone horizons termed colombacci interbedded with fine grained varved mudstones these limestones are abiotic despite the occurrence of abundant ostracod assemblages lago mare fauna in the interbedding pelites and are interpreted as inorganically precipitated deposited in a relatively deep water environment possibly anoxic and related to permanent stratification of water mass events during periods of lake level maxima the combination of petrographical and geochemical observations on carbonate layers reveals that they correspond to events characterized by significant variations of environmental conditions however 18o 5 30 0 2 and 13c 9 28 1 68 signatures suggest that the precipitation of low mg calcite often occurred in a non marine environment and that meteoric water input had a considerable influence on late messinian sedimentation moreover the limestones have a uniform 87sr 86sr composition 0 70864 0 70875 in the range of other lago mare sediments from elsewhere in the mediterranean suggesting that some of the major mediterranean basins were likely interconnected during the lago mare phase a strongly reduced rate of hydrological exchange with the ocean is also possible but the possibility of marine influence during this stage is not completely excluded

the messinian of the nijar basin se spain sedimentation depositional environments and paleogeographic evolution abstract the reconstruction of the depositional events related to the messinian salinity crisis msc of the mediterranean is generally hampered by an incomplete stratal record in the circum mediterranean basins the sediments of the northern part of the nijar basin however provide an excellent and continuous record of late messinian sediments because features of severe erosion are lacking especially the successions of the deeper part of the basin had sufficient accommodation space to warrant ongoing deposition and may thus serve as a testing ground for existing hypotheses regarding the msc conformable contacts with the overlying pliocene and good correlation possibilities with the adjacent astronomically dated messinian of the sorbas basin provide the necessary age constraints the main body of evaporites in the nijar basin yesares formation has been affected by local dissolution and erosion prior to deposition of the latest messinian lago mare facies pelitic float breccias show textures indicating flowage and or mass transport and include slumped and slided stratal packets due to foundering of the mixed evaporitic clastic margin increased runoff of meteoric waters probably played an important role as these packet slides are perfectly sealed by the hyposaline lago mare strata field observations show that marginal sediments commonly classified as the terminal carbonate complex tcc are a lateral equivalent of the basinal yesares evaporites the latest messinian deposits feos formation are characterized by a sedimentary cyclicity related to fluctuating base levels consisting of chalky marly laminitic strata alternating with continental coarser clastic intervals despite considerable w e facies changes and indications for discrete tectonic events a persistent sequential pattern of eight lago mare cycles is present which are interpreted as precession controlled variations in regional climate instead of one major desiccation event in the latest messinian the repeatedly fluctuating water levels of the lago mare episode may have been the cause of the widespread vigorous erosion and canyon cutting in the lower evaporites abrupt non erosional contacts with the normal marine pliocene take place above the continental interval of the last lago mare cycle indicating that flooding took place during a period of lowered water levels the paleogeographic configuration of the nijar sorbas and vera basins has changed considerably during the messinian separation of the formerly interconnected basins is thought to have started in the late yesares times by tectonic uplift of the basement complexes in the latest messinian of the nijar basin two different coarse clastic supply areas can be distinguished which point to the partial emergence of the sierra cabrera and the cabo de gata block and activity of the sierra alhamilla and carboneras faults concerning the overall regional tectonic activity tectonics were probably also instrumental for the restoration of the atlantic gateway in the basal pliocene

rare earth element distributions among minerals in a granodiorite and their petrogenetic implications a study of the distribution of lanthanide rare earths in a granodiorite from the eastern peninsular ranges batholith southern california reveals that a large fraction of the ree in this rock resides in the accessory phases sphene and allanite the minerals plagioclase alkali feldspar biotite epidote and apatite each contribute approximately 1 or less of each ree to the whole rock with the exception of eu for which plagioclase contributes 7 sphene and allanite together contain 80 to 95 of each ree each of these phases is zoned in ree concentration with substantial decreases from core to margin textural observations argue for relatively early saturation and precipitation of sphene and allanite in the magma ree zoning trends in sphene and allanite and unexpectedly low ree concentrations in largely later crystallizing minerals such as feldspar indicate that the precipitation of sphene and allanite significantly reduced ree concentrations in residual melts these results illustrate the potential that sphene and allanite have for controlling the behavior of ree in granitic magmas available information collectively suggest that the sampled granodiorite existed as a complete melt that the ree contained in the assemblage of phases were derived by direct crystallization from the melt and that the melt behaved essentially as a closed system once crystallization of the phases now present began close correspondences between the major and trace element chemistries of the granodiorite and phenocryst poor lavas from similar tectonic settings support these conclusions the ree pattern of the granodiorite melt appears to have originated at depth and is characteristic of its source regions and derivation mechanism the high liquidus temperature of a granodiorite melt 1000 c indicates the importance of mantle derived components within the sources of batholithic magmas in the peninsular ranges

regional sediment sources versus the indus river system the plio pleistocene of the peshawar basin nw pakistan abstract sedimentary archives within the peshawar basin in northwest pakistan preserve a record of siliciclastic supply patterns during the plio pleistocene epoch the basin fill consists of fluvial floodplain clays overlain by thick lacustrine glaciofluvial rhythmites with deposits of multiple alluvial fans in the southern parts of the basin and topped by loess deposits in ideal vertical successions framework mineralogical composition and bulk sediment geochemical proxies of these sediments indicate detritus derivation from dominantly acidic igneous sources with contribution from medium grade metamorphic rocks there appears to be no significant contribution from ultramafic mafic or very high grade metamorphic sources in addition sediments from the southern part of the basin support supply from low grade metamorphic rocks and carbonate sediments overall sedimentation occurred in an active continental margin setting under conditions of insignificant chemical weathering the uplift of the attock cherat range during the late pliocene 2 8 ma restricted the indus river from shedding its detritus into the basin therefore the sediments of the peshawar basin do not reflect signatures of the indus river siliciclastics and thus lack the basic igneous geochemical signal which is otherwise typical for the himalayas hinterland on the contrary the geochemical signatures of these sediments favour predominant detritus flux from the acidic rocks of the peshawar plain alkaline igneous complex ppaic and associated metasediments therefore the kabul swat river and other local tributaries of this smaller river system that originated within the ppaic and associated mountains are considered the major transporting agents which contributed siliciclastics into the peshawar basin during the plio pleistocene additionally in the southern part of the basin the uplifting attock cherat range appeared to have contributed detritus in the form of alluvial fluvial fan deposits

did the mediterranean marine reflooding precede the mio pliocene boundary paleontological and geochemical evidence from upper messinian sequences of tuscany italy abstract the events related to the messinian salinity crisis are among the most deeply investigated of earth s history according to the current hypothesis of neogene paleogeographic evolution approximately 5 5 ma ago after evaporitic sedimentation and before the mio pliocene boundary the mediterranean was characterized by the widespread development of non marine environments inhabited by molluscs and ostracods of brackish affinity the messinian post evaporitic deposits that testify such a dramatic environmental change are commonly referred to as lago mare and have been reported from several outcrops and boreholes throughout the entire mediterranean basin the origin of lago mare conditions is commonly interpreted as the result of the synergistic effect of both the humid climatic conditions and change of the drainage patterns at the mediterranean scale with the capture of paratethyan brackish waters a few recent studies however suggest that such a scenario probably represents an oversimplification of the original context from both a paleogeographical and paleoenvironmental point of view unfortunately the results of these studies have never been commonly accepted and the proposed evidences have been considered questionable in this paper we describe the fish assemblages from the lago mare deposits of two localities cava serredi and podere torricella located in the neogene hinterland basins of tuscany central italy these assemblages consists of a mixture of marine euryhaline and stenohaline taxa suggesting that the depositional environments were characterized by permanently open connections with a marine basin filled with normal marine waters in order to better define the paleontological significance of these upper messinian fish assemblages the oxygen carbon and strontium isotopic composition of fish otoliths and other fossils has been measured these isotopic compositions are strongly indicative of the presence of normal marine conditions close to the depositional environments testified by the sedimentary sequences thereby implying that the interpretation of the geochemical results are consistent with those derived from the paleoecological analyses of the fish assemblages based on the integrated paleoichthyological geochemical approach discussed in this paper it is possible to unambiguously demonstrate that normal marine rather than fresh or brackish waters were present in the mediterranean at least during the upper part of the lago mare event providing an unquestionable evidence that the marine refilling of the basin preceded the mio pliocene boundary

the miocene pliocene boundary and the messinian salinity crisis in the easternmost mediterranean insights from the hatay graben southern turkey accepted manuscript version published version at http dx doi org 10 1016 j sedgeo 2015 11 012 license in accordance with the journal s policy cc by nc nd

tectonic environment of the devonian gramscatho basin south cornwall framework mode and geochemical evidence from turbiditic sandstones the portscatho formation within the allochthonous unit of the middle and upper devonian gramscatho group is a thick sequence of deep water sandstones and interbedded slates deposited by southerly derived turbidity currents into the gramscatho basin of south cornwall throughout an approximately 3 5 km thick sequence the portscatho formation is petrographically and chemically coherent except that the upper section shows a higher proportion of metamorphic clasts high but variable cr and low uniform zr abundances complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition similar to average upper continental crust but with an admixture of minor intermediate basic material flysch deposition took place in a fore arc setting the presence of an arc to the south of cornwall during the devonian implies that there was subduction at the margin of the gramscatho basin whose ultimate closure was accommodated by the northward stacking of flysch ophiolite nappes

sedimentary facies and depositional environments of early mesozoic newark supergroup basins eastern north america abstract the early mesozoic newark supergroup consists of continental sedimentary rocks and basalt flows that occupy a ne trending belt of elongate basins exposed in eastern north america the basins were filled over a period of 30 40 m y spanning the late triassic to early jurassic prior to the opening of the north atlantic ocean the sedimentary rocks are here divided into four principal lithofacies the alluvial fan facies includes deposits dominated by 1 debris flows 2 shallow braided streams 3 deeper braided streams with trough crossbeds or 4 intense bioturbation or hyperconcentrated flows tabular unstratified muddy sandstone the fluvial facies include deposits of 1 shallow ephemeral braided streams 2 deeper flashflooding braided streams with poor sorting and crossbeds 3 perennial braided rivers 4 meandering rivers 5 meandering streams with high suspended loads 6 overbank areas or local flood plain lakes or 7 local streams and or colluvium the lacustrine facies includes deposits of 1 deep perennial lakes 2 shallow perennial lakes 3 shallow ephemeral lakes 4 playa dry mudflats 5 salt encrusted saline mudflats or 6 vegetated mudflats the lake margin clastic facies includes deposits of 1 birdfoot deltas 2 stacked gilbert type deltas 3 sheet deltas 4 wave reworked alluvial fans or 5 wave sorted sand sheets coal deposits are present in the lake margin clastic and the lacustrine facies of carnian age late triassic only in basins of south central virginia and north and south carolina eolian deposits are known only from the basins in nova scotia and connecticut evaporites and their pseudomorphs occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes and some evaporite and alkaline minerals present in the mesozoic rocks may be a result of later diagenesis these relationships suggest climatic variations across paleolatitudes more humid to the south where coal beds are preserved and more arid in the north where evaporites and eolian deposits are common fluctuations in paleoclimate that caused lake levels to rise and fall in hydrologically closed basins are preserved as lacustrine cycles of various scales including major shifts in the late triassic from a wet carnian to an arid norian in contrast fluvial deposits were mainly formed in response to the tectonic evolution of the basins but to some extent also reflect climatic changes the newark supergroup illustrates the complexity of rift basin sedimentation and the problems that may arise from using a single modern analog for sedimentary deposition spanning millions of years it also shows that a tremendous wealth of depositional climatic and tectonic information is preserved in ancient rift basin deposits which can be recovered if the depositional processes of modern rift basin deposits are understood

the enigmatic messinian pliocene section of cuevas del almanzora vera basin se spain revisited erosional features and strontium isotope ages abstract the cuevas del almanzora section was in the late seventies the focus of a discussion because of alleged continuous marine messinian to pliocene sedimentation however a discontinuity has been shown to exist in the shape of laminated strata including the late messinian brackish lacustrine lago mare biofacies more recently benson and rakic el bied 1991 concluded that the section is still one of the best biostratigraphic successions for the western mediterranean in which to document terminal miocene events but that it entirely has an early messinian age i e it antedates deposition of the main evaporites this paper presents strontium isotope ages indicating that the classic threefold division in an earlier marine messinian a lago mare and a pliocene interval sensu geerlings et al 1980 cita et al 1980 should be maintained moreover the sr isotopic composition of the euryhaline cyprideis ostracodes from the lago mare laminites is similar to those from central mediterranean basins this stresses the importance of late messinian water exchange between the vera basin and the then enclosed mediterranean it thus refutes the opinion of benson and rakic el bied 1991 that this interval is a local facies of no particular stratigraphic importance a time gap of up to 0 8 ma between the youngest marine strata of the messinian and the overlying pliocene provides a maximum timing for the duration of the messinian salinity crisis during which very little net sedimentation occurred compared to coeval deposits in for example the nearby nijar and sorbas basins in the cuevas section an inconspicuous and hitherto overlooked erosional gap has been observed this separates the lago mare marls from the pliocene marls more field observations have been made and are discussed in the light of existing interpretations in order to demonstrate the importance of more widespread erosion in the vera basin gypsum containing mass flow deposits filling up a late messinian palaeorelief in the garrucha area are shown to be derived from the basin these probably continue offshore as feeder channels related to a late messinian sea level fall a holistic approach of a key section thereby not overlooking the regional geology is a necessary step to be made before far reaching claims can be made about its interregional significance

late messinian lago mare ostracod palaeoecology a correspondence analysis approach abstract in this paper two different italian late messinian lago mare ostracod assemblages dominated mainly by extinct paratethyan species have been analysed by means of detrended correspondence analysis dca the obtained plots have been compared and with the help of the limited autoecological data on similar living species and geochemical data on the sediments in which they were included the autoecology and synecology of the lago mare assemblages have been inferred in particular it seems reasonable to suppose that 1 assemblages made only by pointed candonids are typical of rather deep possibly less than one hundred meters of depth and freshwater oligohaline environments 2 assemblages mainly composed of leptocytheridae point to shallow probably few tens of meters of depth and mesohaline waters 3 diversified and even assemblages made both by pointed candonids and leptocytheridae are common in rather deep less than one hundred meters of depth but oligo low mesohaline environments 4 caspiocypris seems rather tolerant of brackish salinities but prefers shallow environments 5 tyrrhenocythere could be an indicator of shallow and fresh oligohaline waters 6 cyprideis is an indicator of shallow waters but can withstand a very wide salinity range

transport of rare earth elements by hydrocarbon bearing brines implications for ore deposition and the use of rees as fluid source tracers abstract low temperature 100 160 c hydrocarbon bearing brines mobilize ree at concentrations up to several thousand ppm total rare earth elements ree at el hammam morocco the major element chemistry na ca mg and temperature of the fluids in this system are consistent with those of oil field brines in contrast ree concentrations in the fluid suggest a significant element input from a magmatic source spatially related lamprophyres predating the formation of el hammam share a similar trace element signature therefore hydrocarbon bearing basinal brines seem to have leached some of these elements through fluid rock interaction from the lamprophyres supporting the ability of oil field brines to mobilize not only base metals as in mississippi valley type mvt deposits but also rare earth elements the stability constants of ree aqueous complex at temperatures of 100 160 c the chemistry of oil field brines worldwide and the partitioning behavior of ree between fluorite and water at el hammam indicate that acetate carbonate and fluoride are likely to be major contributors to ree mobilization in these settings the direct implications of the low temperature transport of ree by oil bearing brines is that in systems where these kind of fluids occur the ree signature observed may not reflect the source of the fluid as much as a combination of fluid source and fluid rock interaction in addition oil field brines can efficiently scavenge transport and deposit ree leading to anomalously high accumulations such as the el hammam fluorite deposit and may also contribute to ree mobilization and concentration in other systems

arsenic iron and organic matter in sediments and groundwater in the pannonian basin hungary in the central part of the pannonian basin factors controlling the distribution of as in sediments and groundwater of the upper 500 m were studied in core samples the amounts of as fe and mn extractable with hydroxylamine hydrochloride nh2oh hcl in 25 acetic acid the proportion of the 0 063 mm size fraction and the sediment organic c corg contents were measured in the groundwaters concentrations of as humic substances and selected major chemical components were determined in most core samples extractable fe as feooh and corg are correlated but some samples have excess fe or organic matter in cases where either excess fe or excess organic matter is found the amount of as is also elevated the spatial distribution of as in the groundwater and the lack of a consistent correlation of as with a single component indicate that there is no single factor controlling the concentration of dissolved as over the entire study area the only consistent feature is enrichment of as relative to fe in the groundwater compared to the sediments this suggests that the dissolution of fe minerals which primarily adsorb as is not congruent in reducing conditions fe iii oxyhydroxides together with adsorbed as dissolve and siderite with little or no as precipitates when sub regions are separated and studied individually it can be shown that hydrogeological features of the sediments the proportions of fe minerals and sedimentary organic matter and the concentration of dissolved humic materials all influence the accumulation and mobilization of as the significance of the different mobilizing processes however and the mean concentration of as is different in the recharge through flow and discharge areas

the early mesozoic birdsboro central atlantic margin basin in the mid atlantic region eastern united states the early mesozoic birdsboro basin new name was a single elongate depositional trough in the present mid atlantic area of the eastern united states extending northeastward from central virginia across maryland pennsylvania and new jersey into southern new york what now remains after erosion comprises the barboursville culpeper gettysburg and newark remnants some 7 km of late triassic and early jurassic continental sediments of varying provenances entered and spread across in the birdsboro basin in several depositional environments the five resulting sedimentary lithosomes include feldspathic sandstone quartzose sandstone red silty mudstone gray shale and fanglomerate the extensive interbedding intertonguing and lateral gradation among these lithosomes suggest that they were contemporary and closely interrelated the feldspathic sandstone lithosome contains sediment with a southeastern provenance that accumulated in a bajada environment extending the length of the southeastern side of the basin sediment in the quartzose sandstone lithosome had a northwestern provenance the coarse grained fraction formed regional alluvial fans at the mouths of four major input centers the finer grained fraction was deposited in the distal reaches of these fans and in the playa environments in the interfan areas this fraction formed the red silty mudstone lithosome gray black shales and argillites of the gray shale lithosome accumulated in lacustrine environments in the interfan areas the fanglomerate lithosome comprises numerous small lobate deposits of poorly sorted sediment along both basin margins the location and time of activity of the northwest input centers largely determined the distribution and areal extent of the various depositional environments and consequent lithosomes along the length and across the width of the basin the birdsboro basin was deformed tilted faulted and folded sometime after the deposition of the youngest preserved rocks early sinemurian the deformation varied along the length of the basin producing differences in the amount of tilting structural elevation and subsequent erosion the present erosional remnants create the illusion of four originally separate depositional basins

evolution of the miocene sedimentary fill of the gediz graben sw turkey abstract the gediz graben is a continental extensional basin filled with miocene to recent sediments the evolution of the graben can be expressed in terms of two phases i miocene half graben phase and ii post miocene graben phase the miocene half graben phase was governed by the southern margin structure evolution of which significantly controlled the stratigraphic variability in the basin alluvial fluvial and lacustrine systems developed in the graben as a function of distance to the southern margin thus alluvial deposits with coarse grained facies dominate the southern margin and grade into finer fractions of fluvial and or lacustrine deposits to the north this depositional architecture repeated three times during the miocene and deposited alasehir caltilik and gediz formations these formations depict distinct thickness and grain size decrease from south to north to emphasize the half graben configuration for the favour of the southern margin the post miocene graben phase started with the faulting of the northern margin this resulted in relatively balanced partitioning of the subsidence between the two margins although the preceding asymmetry was inherited by the graben sediment influx became bipolar and alluvial fan systems developed along the both margins

ostracod faunas and brackish water environments of the late messinian sapigno section northern apennines italy abstract the sediments and ostracod assemblages from a small lacustrine basin located in the montefeltro area sapigno syncline romagna marche apennine central italy have been studied in detail from a section covering a broad interval spanning the late messinian post evaporitic sequence the latter consists of a non marine mainly terrigenous succession with molluscs and brackish water ostracods it represents the lago mare phase s s and is interpreted as shallow to relatively deep water lacustrine deposits characterized by a low salinity with occasional interactions with fluvial and littoral processes rich and diverse ostracod assemblages occur throughout the studied succession thirty species were recognized which characterize a loxocorniculina djafarovi fossil assemblage widespread in the western mediterranean during the latest part of the messinian it is a residual assemblage of a non marine fauna inhabiting hypohaline environments and testifies to the presence of large interconnected brackish water bodies lago mare along the margins and in the depths of a mediterranean basin isolated from the world ocean the ostracod faunas have paratethyan affinities but only a few species are common to both the western mediterranean and the eastern basins of paratethys