structurally controlled hydrothermal dolomites in albian carbonates of the ason valley basque cantabrian basin northern spain abstract shallow marine carbonate sedimentation dominated during the albian in the western part of the basque cantabrian basin in northern spain forming the large ramales platform this platform originated on a less subsiding tectonic block facing deeper and more subsiding areas to the south and east which were created by tectonic activity in the basin fracture related hydrothermal dolomites hosted in these albian carbonates are well exposed in the ason valley area mapping in the studied area revealed several dolomite bodies related to main faults that cut the stratification almost at right angles the bodies show a vertical development along fault strike up to 900 m thick from which kilometre scale branches expand following the stratification dolomitization is pervasive and independent of the limestone facies main dolomite facies are fine replacive sucrosic and saddle petrography c o and sr isotopes and fluid inclusion analysis support a polyphase hydrothermal dolomitization at fluid temperatures between 75 c and 240 c and highly variable salinity of up to 22 wt nacl fine dolomite replaced limestone first and then sucrosic and saddle dolomites replaced part of the first dolomite and cemented newly created fracture porosity together with different calcite cements zebra dolomites and hydroclastic breccias are products of this later stage burial analysis of the host rock supports maximum burial temperatures of 80 c and intense tectonic activity from the albian to turonian with a latest albian peak subsidence albian stretching of the crust and subsequent ascent of the isotherms in the area is suggested to have produced sufficient heat to the dolomitizing fluids the structural analysis indicates a strong transtensional tectonic activity in the studied area during albian to turonian time with the creation of an overstep between w e trending and n s trending faults fluids moved from subsiding areas to fractured uplifted parts of the ramales platform enhanced by diapiric activity

calibrating the end permian mass extinction the end permian mass extinction was the most severe biodiversity crisis in earth history to better constrain the timing and ultimately the causes of this event we collected a suite of geochronologic isotopic and biostratigraphic data on several well preserved sedimentary sections in south china high precision u pb dating reveals that the extinction peak occurred just before 252 28 0 08 million years ago after a decline of 2 per mil in 13c over 90 000 years and coincided with a 13c excursion of 5 that is estimated to have lasted 20 000 years the extinction interval was less than 200 000 years and synchronous in marine and terrestrial realms associated charcoal rich and soot bearing layers indicate widespread wildfires on land a massive release of thermogenic carbon dioxide and or methane may have caused the catastrophic extinction

diagenetic cycling of arsenic in amazon shelf sediments in order to help elucidate major natural controls on the diagenetic behavior of as vertical profiles of total dissolved and solid phase as were measured in amazon shelf deposits a deltaic region little influenced by human activity arsenic distributions are typically characterized by subsurface porewater maxima and surficial solid phase enrichment maximum porewater as concentrations 2 4 m are an order of magnitude greater than levels reported in most other coastal marine environments and elevated concentrations extend several meters below the sediment surface dissolved as varies inversely with easily leachable as 40 140 nmol g 1 in the solid phase and directly with increases in solid phase fe ii these patterns reflect a strong redox coupling with fe whereby oxidized as is associated with fe oxyhydroxides in surface sediments then subsequently reduced and released upon burial in the extensive suboxic zone upward diffusion and intense physical reworking of sediments presumably releases the dissolved arsenic fraction to the water column or allows for re adsorption in surface sediments arsenic porewater concentrations generally increase away from the river in some cases regular seasonal variations are evident apparently corresponding to nonsteady state ingrowth of diagenetic profiles following extensive sediment reworking during rising river flow the massive cycling of as in amazon shelf sediments is likely due to the combined effects of intense chemical weathering in regions of the drainage basin production of oxides and a turbulent physical regime present on the shelf both of which promote sedimentary cycling of fe and coupled elements during early diagenesis

geogenic arsenic anomalies in soils and stream waters of neogene emet basin kutahya western turkey arsenic is one of the most deleterious trace elements due essentially to its carcinogenicity resulting in the development of internal malignancies and skin cancer in this study arsenic concentrations of soils and stream waters in an area where the world class borate deposits of turkey occur are presented soil and stream water samples were collected from the emet basin of neogene age where intense borate mining activities have been practiced for about 60 years inductively coupled plasma mass spectrometry icp ms was employed to analyze arsenic concentrations in soils and gutzeit method for water samples as concentration levels in soils and waters ranged from 0 4 up to 2488 4 mg kg 1 mean 111 8 200 1 sd and from 8 to 243 g l mean 96 63 66 83 sd respectively while soil ph measurements varied between 5 97 and 7 75 avg 7 06 0 56 water ph values ranged from 6 44 to 8 32 avg 7 734 0 59 as contents of both soils and surface waters were significantly few tens to thousands times high exceeding the maximum contaminant levels of current us epa s maximum contaminant level of 0 01 mg as l western anatolian young down to about 1 my volcanic activities and shallow intrusive emplacements resulted in the formation of considerable number of geothermal and hydrothermal systems and kept them active for long enough that gave rise not only to the formation of numerous epithermal mineralizations rich in as sb hg bearing sulfide minerals but also to the formation of as enriched sedimentary and magmatic rocks their dissolution and redistribution within the rocks and resultant soils consequently made them geogenically as rich

formation and deformation of hyperextended rift systems insights from rift domain mapping in the bay of biscay pyrenees the bay of biscay and the pyrenees correspond to a lower cretaceous rift system including both oceanic and hyperextended rift domains the transition from preserved oceanic and rift domains in the west to their complete inversion in the east enables us to study the progressive reactivation of a hyperextended rift system we use seismic interpretation gravity inversion and field mapping to identify and map former rift domains and their subsequent reactivation we propose a new map and sections across the system illustrating the progressive integration of the rift domains into the orogen this study aims to provide insights on the formation of hyperextended rift systems and discuss their role during reactivation two spatially and temporally distinct rift systems can be distinguished the bay of biscay parentis and the pyrenean basque cantabrian rifts while the offshore bay of biscay represent a former mature oceanic domain the fossil remnants of hyperextended domains preserved onshore in the pyrenean cantabrian orogen record distributed extensional deformation partitioned between strongly segmented rift basins reactivation initiated in the exhumed mantle domain before it affected the hyperthinned domain both domains accommodated most of the shortening the final architecture of the orogen is acquired once the conjugate necking domains became involved in collisional processes the complex 3 d architecture of the initial rift system may partly explain the heterogeneous reactivation of the overall system these results have important implications for the formation and reactivation of hyperextended rift systems and for the restoration of the bay of biscay and pyrenean domains

an example of alternative correlation techniques in a low accommodation setting nonmarine hydrocarbon system the lower cretaceous mannville basal quartz succession of southern alberta chemostratigraphy and heavy mineral techniques have been applied to the lower cretaceous basal quartz in the western canada sedimentary basin the aim of the study is to demonstrate that these two techniques can be used to help understand the complex stratigraphy of reservoirs deposited in low accommodation fluvial settings the basal quartz is an ideal unit to demonstrate their applicability in stratigraphic studies of hydrocarbon reservoirs because extensive mapping and petrographic studies have enabled the establishment of a rigorous stratigraphic framework despite its complexity resulting from deposition in a low accommodation fluvial setting the three component units analyzed in the basal quartz horsefly unit bantry alderson taber bat unit and ellerslie unit each have unique geochemical and heavy mineral characteristics chemostratigraphic analysis shows that silty claystones from the horsefly bat and ellerslie units have distinctly different geochemistry from one another with the variations being caused by changes in clay mineralogy and other components such as feldspar apatite and zircon the geochemistry also suggests periodic volcanogenic input influenced the silty claystones of the basal quartz heavy mineral analysis shows that sandstones from the three units can be distinguished on the basis of ratio parameters such as apatite tourmaline rutile zircon and zircon tourmaline which are controlled by differences in provenance and intensity of weathering during transport

the permian triassic boundary lung cam expanded section vietnam as a high resolution proxy for the gssp at meishan china the lung cam expanded stratigraphic succession in vietnam is correlated herein to the meishan d section in china the gssp for the permian triassic boundary the first appearance datum of the conodont hindeodus parvus at meishan defines the permian triassic boundary and using published graphic correlation the permian triassic boundary level has been projected into the lung cam section using time series analysis of magnetic susceptibility data it is determined that h parvus arrived at lung cam 18 kyr before the permian triassic boundary data indicate that the lung cam section is expanded by 90 relative to the gssp section at meishan given the expanded lung cam section it is possible to resolve the timing of significant events during the permian triassic transition with high precision these events include major stepped extinctions beginning at 135 kyr and ending at 110 kyr below the permian triassic boundary with a duration of 25 kyr followed by deposition of lung cam ash bed 13 which is equivalent to siberian traps volcanism is graphically correlated to a precession time series model placing onset of this major volcanic event at 242 kyr before the ptb the meishan beds 25 and 26 at 100 kyr before the permian triassic boundary in addition the elemental geochemical carbon and oxygen isotope stratigraphy and magnetostratigraphy susceptibility datasets from lung cam allow good correlation to other permian triassic boundary succession these datasets are helpful when the conodont biostratigraphy is poorly known in sections with problems such as lithofacies variability or is undefined owing possibly to lithofacies exclusions anoxia or for other reasons the lung pu permian triassic boundary section 45 km from lung cam is used to test these problems

chemostratigraphy a method to improve interwell correlation in barren sequences a case study using onshore duckmantian stephanian sequences west midlands u k abstract chemostratigraphy has been applied to onshore duckmantian stephanian successions encountered in outcrop and penetrated by two boreholes from the west midlands u k these successions represent the onshore equivalents of the barren red measures which are important hydrocarbon bearing sequences in the southern north sea much is known about the onshore successions in terms of sedimentology mineralogy and provenance and thus they provide the ideal test for the validity of chemostratigraphy as a stratigraphic tool reliable inorganic geochemical data have been acquired from geochemical analyses of core sidewall core and cuttings samples with 19 elements being determined stratigraphic variations in elemental concentrations are compared with known variations in the mineralogical data the established lithostratigraphic units of the duckmantian stephanian intervals can also be recognized from the geochemical data and by using these data can be subdivided further this results in an independent chemostratigraphic correlation being established for the two boreholes which has been assessed statistically by discriminant function analysis from the geochemical and mineralogical data distinct changes in provenance are identified within the upper carboniferous successions the sediments of the coal measures were derived from a north westerly and westerly source caledonian whereas the etruria formation sediments came from the wales brabant massif the sediments having mixed caledonian and cadomian characteristics eventually these sediments were replaced by sediments from a southern hercynian source halesowen and salop formations

mobility of arsenic and trace element inventories in sediment cores from masuda city southwestern japan the vertical distribution of arsenic and other trace and major elements has been studied in four sediment cores from masuda city nagashima and okite in the shimane prefecture of southwestern japan the sediment cores were also subjected to leaching techniques and 14c dating the stratigraphic sequences in the cores consist of silt and sandy silt at top passing downward into gray to black clays elevated values of as pb zn cu ni cr and v are present in several horizons while abundances of these elements tend to be higher in the black and gray clays probably due to adsorption onto clay sediments higher concentrations of fe and total sulfur ts occur in black clays the correlations of the trace metals with iron suggest their adsorption onto fe oxy hydroxides whereas correlations with sulfur in some cores indicate that they were precipitated as fe sulfides age determinations suggest that clay horizons at 5 m depth were deposited at around 5 000 and 6 000 years bp 14c ages during the transgressive phase of sea level change the results of the leaching techniques in the core samples show that higher amounts of as were extracted with deionized water even at neutral ph as can be released from sediments to groundwater and therefore groundwater pollution is a concern in masuda city and the surrounding area

vertical geochemical variations and arsenic mobilization in the shallow alluvial aquifers of the chapai nawabganj district northwestern bangladesh implication of siderite precipitation core sediments from three disturbed boreholes jor ghat and raj and two undisturbed boreholes dw1 and dw2 were collected in the study area of the chapai nawabganj district of northwestern bangladesh for geochemical analyses in the study area groundwater samples from fourteen as contained private wells and five nested piezometers at both the dw1 and dw2 boreholes were also collected and analyzed the groundwater arsenic concentrations in the uppermost aquifer 10 40 m of depth range from 3 to 315 g l mean 47 73 73 41 g l while the arsenic content in sediments range from 2 to 14 mg kg mean 4 36 3 34 mg kg an environmental scanning electron microscope esem with an energy dispersive x ray spectrometer was used to investigate the presence of major and trace elements in the sediments groundwaters in the study area are generally the ca hco3 type with high concentrations of as but low levels of fe mn no3 and so 4 2 the concentrations of as fe mn decrease with depth in the groundwater showing vertical geochemical variations in the study area statistical analysis clearly shows that as is closely associated with fe and mn in the sediments of the jor core r 0 87 p 0 05 for fe and r 0 78 p 0 05 for mn and ghat core r 0 95 p 0 05 for fe and r 0 93 p 0 05 for mn while as is not correlated with fe and mn in groundwater the comparatively low fe and mn concentrations in some groundwater and the esem image revealed that siderite precipitated as a secondary mineral on the surface of the sediment particles the correlations along with results of sequential extraction experiments indicated that reductive dissolution of feooh and mnooh represents a mechanism for releasing arsenic into the groundwater

magnetostratigraphy susceptibility of the přidolian lochkovian silurian devonian gssp klonk czech republic and a coeval sequence in anti atlas morocco abstract the magnetosusceptibility event and cyclostratigraphy msec record for the p idolian lochkovian silurian devonian global boundary stratotype section and point gssp klonk prague basin czech republic is described and used to establish a magnetostratigraphy susceptibility profile for the gssp gssp msec data are summarized into three magnetozones msz the tma msz late p idolian with 13 msszs mssz the klonk msz latest p idolian and earliest lochkovian with 17 msszs and the voskop msz early lochkovian with 7 msszs the base of klonk mssz 2 is coincident with the base of lochkovian and the devonian the proposed magnetostratotype for the p idolian lochkovian boundary is supported by ms data from a nearby core through the gssp sequence and into the upper ludlow three additional mszs are recognized for the portion of the core sequence older than the gssp boundary sequence the extension of the mszs and msszs away from the proposed magnetostratotype is tested by comparison with a lochkovian sequence in the western sahara of southeastern morocco mszs are the result of global sea level fluctuations that alter base level and the pattern of erosion and influx of detrital paramagnetic mineral components into the marine environment large scale transgressive and regressive patterns interpreted from the msec data establish that the silurian devonian boundary in the barrandian region falls between a short lived transgressive pulse in the latest p idolian and an equally short lived regressive pulse in the earliest lochkovian msszs identified in the gssp and core sequences are the result of variation in climate cycles and the resulting periodicity can explained by either the 38 9 ka silurian and devonian equivalent of the modern 54 ka obliquity cycle or the eccentricity cycle of 106 ka periodicity use of the obliquity periodicity gives a duration for the barrandian lochkovian of 4 46 ma which agrees with the most recent geochronometric estimate of 4 5 ma for the lochkovian use of the eccentricity periodicity gives a duration for the barrandian lochkovian of 12 16 ma which agrees with the previous geochronometric estimates of 12 2 and 12 5 ma for the lochkovian in any case the cyclic nature of the msec data established by the msszs can be explained by variations in the rate of supply of weathered terrigenous paramagnetic grains to the marine system these variations in supply occurred due to climate changes resulting from the either the obliquity or eccentricity of the earth s orbit knowledge of the periodicity of lochkovian cycles in the barrandian area allows estimation of the rates of sediment accumulation the duration of fossil ranges and the rates of evolution depending on the choice of obliquity or eccentricity to explain the cyclicity in the barrandian lochkovian the estimated rate of sediment accumulation in the gssp outcrop averaged either 51 or 140 ka m the range of the graptoloid monograptus uniformis angustidens wholly contained within the lochkovian sequence at the gssp is also estimated at either 51 or 140 ka

facies discrimination in a mixed fluvio eolian setting using elemental whole rock geochemistry applications for reservoir characterization abstract fluvio eolian successions are generally characterized by a high degree of complexity and internal heterogeneity quantifying the rapid facies changes in time and space is a major challenge to characterization of hydrocarbon reservoirs we present a method for facies discrimination in fluvio eolian successions the method presented here is developed on the modern fluvio eolian sediments from the skeleton coast dune field namibia the examined sediments comprise eight different facies types eolian dune sands interdune fluvial channel sands intraerg mass flow deposits intraerg hyperconcentrated flow deposits fluvial channel sands fluvial mud lacustrine heterolithic sand and lacustrine heterolithic mud the contrasting provenance of the fluvial and eolian sediments results in a distinct source fingerprint which can be discriminated using elemental whole rock geochemistry a multivariate statistical technique performed on the geochemical data has enabled discrimination of seven of the eight facies types furthermore the facies discrimination method allowed a quantitative estimate of the degree of fluvial reworking of eolian sand the skeleton coast dune field was chosen as a test area for geochemical facies discrimination because of its remarkable difference between the immature fluvial source and the mature quartz rich eolian source we hope that the method presented here can be applied to subsurface data from geological settings with the same difference in fluvial and eolian sources it is furthermore hoped that the method can be used in more complex sedimentological settings

temporal and spatial correlations between changes in plate motions and the evolution of rifted basins in africa we present the results of a backstripping study incorporating over 200 wells in 14 different basins or groups of basins located on the african interior or continental margins these results presented as mean tectonic subsidence rates averaged over appropriate periods are compared with the opening histories and changes in plate motions of the atlantic and indian oceans and the tethys mediterranean area for seven time steps from the late jurassic until present the results indicate a temporal and spatial correlation between phases of rapid subsidence in african basins and changes in plate motions and therefore are promising in terms of applicability of large scale plate motions in the studies of paleo stresses in sedimentary basins especially at times of initial rifting and formation of subduction zones reactivation of the basins appears to be primarily controlled by the orientation of the basin and underlying basement structures with respect to the stress direction the basins are preferably formed within weaker zones mostly pan african shear zones and the distance from the active plate boundary to the weak zone plays a minor role in whether or not it will be reactivated the presence of three important hot spots which were active during the early stages of break up of gondwana may have been important in preweakening the lithosphere at their sites this may have played an additional role in the localization of the basin deformation

pulsating subsidence during a rift episode stratigraphic and tectonic consequences aptian albian northern spain backstripping analysis has been carried out on nine outcrop sections of the basque cantabrian aptian and albian of northern spain which consist of shallow water marine deposits up to 7000 m thick it reveals four main pulses of common accelerated subsidence i early aptian ii early albian iii lower late albian and iv uppermost late albian separated by tectonic quiescent intervals tectonic subsidence rates of 70 m myr 1 for the aptian and 101 m myr 1 for the albian were recorded sopuerta section the calculated stretching factor referred to a pre rift continental crust of 35 km is bs 1 32 and represents approximately 8 5 km of crustal thinning points of change towards lesser subsidence rate in the curves are correlated with major unconformities in the sections in the basque cantabrian basin and in boreal europe suggesting geodynamic changes related with the opening of bay of biscay minor variations of spreading direction and intensity are proposed to explain the subsidence pulses

multiple dolomitization events along the pozalagua fault pozalagua quarry basque cantabrian basin northern spain the pozalagua quarry in the basque cantabrian basin of northern spain exposes a unique set of fault associated dolomites that can be studied on a decametre scale the dolomites developed along the pozalagua fault system in slope deposited limestones of albian age following marine phreatic diagenesis the limestones were subject to meteoric karst formation the resulting cavities were filled either by angular limestone fragments in a black clay rich matrix or by cave floor pond now dolomitized sediments the subsequent diagenetic history reflects repeated periods of fracturing fluid expulsion dissolution and cementation contrasting fluid pulses resulted in the formation of a network of hydrothermal karst and the subsequent development of coarse crystalline calcite cement zebra dolomite recrystallized coarse crystalline dolomite elongated blue grey coarse crystalline dolomite cement in the open fault and finally coarse crystalline saddle dolomite decimetre size reworked host rock fragments present in the latter two dolomite phases probably reflect roof collapse fragments of a cave system that developed along the pozalagua fault system however there are also metre scale host rock fragments that apparently float in the coarse crystalline saddle dolomites implying that either fragment assimilation was a widespread process or violent expulsion of fluids occurred along the pozalagua fault system the presence of pre dolomite and post dolomite stylolites parallel to bedding supports a linkage between the diagenetic events and the late albian tectonism that affected the region

biostratigraphy and sedimentology of upper permian and lower triassic strata at masore western slovenia abstract upper permian and lowermost triassic strata of the masore section in western slovenia have been restudied by means of bio and lithostratigraphy this section is mainly characterized by a carbonate succession of the bellerophon formation deposited in a shallow marine ramp environment that was located in the western part of the paleotethys the permian triassic boundary ptb transition is marked by laminated microbialites stromatolites interpreted to reflect a deeper ramp environment the conodont elements recovered enabled the recognition of the hindeodus praeparvus zone of the uppermost permian upper changhsingian in the bellerophon formation gondolellids are documented in the ptb transitional interval with microbial microfacies whereas the isarcicella isarcica zone lower griesbachian lower triassic is recognized in the tectonically separated werfen formation just above the microbial microfacies part of the section the lowermost part of the microbialites is characterized by late permian species of foraminifers indicating that at least this part of the section is still upper permian

earliest oligocene increase in south atlantic productivity as interpreted from rock magnetics at deep sea drilling project site 522 the magnetic properties of the sediments rock magnetics at dsdp site 522 in the south atlantic exhibit clear differences between the latest eocene and earliest oligocene based on low temperature behavior of saturation remanence and hysteresis loops we attribute the difference to a slightly greater proportion of the finest grained so called superparamagnetic magnetite in the eocene sediments we believe that the lower proportion of very fine grained magnetite in the oligocene sediments is a result of incipient reduction diagenesis caused by increased productivity and hence increased labile organic carbon transport to the sediments due to an early oligocene increase in thermohaline circulation the eocene to oligocene transition at site 522 is also expressed by changes in microfossil assemblages increased carbonate content decreased insoluble residue and decreased foraminiferal shell fragmentation the increase in carbonate is synchronous with and parallels a change in the ratio of two of the rock magnetic parameters a ratio that tracks the decrease in the very fine grained magnetite component also parallel to these is a trend toward heavier 13c values in foraminiferal tests the increase in organic carbon transport to the sediments led to chemical dissolution of the finest grain size fraction of magnetite in the oligocene sediments hence a reduction in the superparamagnetic component and the change in the rock magnetic ratio in this way rock magnetics can be sensitive indicators of environmental changes such as fluctuations in organic carbon transport which may leave little other trace in the sedimentary record

magnetosusceptibility event and cyclostratigraphy method applied to marine rocks detrital input versus carbonate productivity magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion we show here that the magnetic susceptibility signature found in two forms resides mainly in paramagnetic and other detrital constituents in most marine rocks the first form is a short term low magnitude high frequency cyclic climate signature that is often useful for regional correlation the second form is a longer term higher magnitude low frequency signature resulting from transgressive and regressive events that can be used for global correlation fluctuations in detrital input due to eustatic based erosion are the primary cause of events these fluctuations are driven by large scale processes such as global orogenic cycles however variations in carbonate productivity cannot be ruled out when explaining the low magnitude climate driven cyclicity also observed in magnetic susceptibility data sets

diagenetic cycling of arsenic in the sediments of eutrophic baldeggersee switzerland sedimentation and benthic release of as was determined in baldeggersee a eutrophic lake in central switzerland sediment traps recorded as sedimentation during 1994 including a flood event in spring diagenetic processes were studied using porewater profiles at the sediment water interface and in deeper sediment strata deposited in the mesotrophic lake before 1885 sediment cores were used to calculate the accumulation and to construct the balance of sedimentation and remobilisation the results showed that the lake sediment acts as an efficient sink for as only 22 of the particulate as flux reaching the sediment surface was remobilised at the sediment water interface the as accumulation in the recent varved section of the eutrophic lake was 40 mg as m 2 a 1 iron reduction in older sediment caused a remobilisation of 1 2 mg as m 2 a 1 this upward flux from the deeper sediment was quantitatively immobilised in the recent sulfidic sediments the flood event in spring contributed about 34 of the yearly sediment load and led to distinct peak profiles of dissolved as in the porewater this evidence for rapid remobilisation disappeared within months

closing the mid palaeocene gap toward a complete astronomically tuned palaeocene epoch and selandian and thanetian gssps at zumaia basque basin w pyrenees abstract an integrated magneto bio and cyclostratigraphic framework is presented for the mid palaeocene interval from the hemi pelagic sea cliff section of zumaia in the basque basin the new 55 m long studied section expands about 3 5 myr and closes the gap between previously published integrated studies in the section the occurrence of magnetochron c26n is now documented and its duration complemented also by data from the ibaeta section and that for chrons c26r and c25r is estimated by counting precession related lithologic couplets assigned to have 21 kyr duration c25r 1449 kyr c26n 231 kyr c26r 2877 kyr consequently the zumaia section now provides the first complete palaeocene astronomically derived chronology rendering this section a master reference section due to limitations in the orbital calculations and uncertainties in the radiometric dating method no robust tuning and absolute ages can be given for the moment however the fos first occurrences of key calcareous plankton species and the mid palaeocene biotic event mpbe are placed within the magnetostratigraphic and cyclostratigraphic template along the studied mid palaeocene interval in addition the dataset provides the key elements for a proper settling of the thanetian and selandian global stratotype section and point gssps which is one of the primary objectives of the ics international commission of stratigraphy we consider the base of chron c26n and the criteria associated to the lithostratigraphic change between the danian limestone fm and the itzurun marl fm at zumaia as the respective delimiting points for the thanetian and selandian bases as recently agreed by the paleocene working group of the international subcommission of the paleogene stratigraphy of the ics consequently the duration of the thanetian selandian and danian component stages can be estimated at zumaia to be about 3129 kyr 2163 kyr and 4324 kyr respectively see text for error considerations however the mpbe located 8 precession cycles below the base of c26n in correspondence to a short eccentricity maxima at zumaia could also serve as a guiding criteria to approximate or redefine the thanetian base if this level demonstrated synchronous

changes in the global carbon cycle occurred as two episodes during the permian triassic crisis coeval records of ocean atmosphere and terrestrial change are crucial to understanding the pattern and causes of global mass extinction across the permian triassic boundary ptb however relationships among changes in different settings remain largely unclear primarily due to the challenges associated with the correlation among disparate records here we compare marine carbon isotopic records with marine and terrestrial environmental and biotic events recorded in sediments from the meishan ptb section of south china time scaled carbonate carbon isotopes exhibit two gradual major shifts across the ptb at meishan and these are duplicable elsewhere around the tethys ocean the two shifts are associated with two episodes of enhanced terrestrial weathering indicated by an increased abundance of 13 c enriched moretanes relative to hopanes and an elevated abundance of black carbon fragments key marine events previously reported for the ptb including photic zone euxinia faunal mass extinction and cyanobacterial expansion also occur as two episodes coinciding with both of the progressive shifts to negative 13 c values and enhanced weathering the temporal sequence of the duplicable events suggests that the biotic crisis was a consequence of prolonged and episodic changes in the marine and continental systems and argues against an extraterrestrial impact as the main cause

expression of the late aptian cold snaps and the oae1b in a highly subsiding carbonate platform aralar northern spain abstract cretaceous climate records provide evidence that major volcanic pulses with duration of 103 to several 105 yr triggered changes in climate and oceanography black shales of oceanic anoxic event 1b ca 113 109 ma are regarded as signatures of late aptian greenhouse pulses associated with volcanic episodes new tex86 paleotemperature record indicates that warm aptian climate was interrupted by repeated cold snaps alternating with described greenhouse pulses an extraordinary thick shallow water carbonate succession of the aralar platform from the southeastern basque cantabrian basin in spain provides a unique opportunity to test the hypothesis that cold phases interrupted warm climate in the aptian platform evolution is traced through time of the proposed aptian cold snaps alternating with greenhouse episodes new high resolution c isotope records established in the studied upper aptian platform carbonates serve as chemostratigraphic tool providing a link between carbonate platform evolution basinal black shale formation and associated changes in open ocean palaeotemperatures the late aptian cold snaps find their expression in a remarkably reduced neritic succession punctuated by several emersion horizons formed during sea level lowstands the studied section bears evidence for several episodes of choked carbonate production related to increased runoff at times of sea level rise during which orbitolinids bloomed in a sediment loaden lagoonal setting these intervals coincide with the deposition time of organic rich kilian and leenhardt levels belonging to oae1b

oligocene paleoceanography of the south atlantic paleoclimatic implications of sediment accumulation rates and magnetic susceptibility measurements paleoceanographic changes during the oligocene in the south atlantic have been examined using paleomagnetic rock magnetic carbonate content and sediment accumulation rate sar data we show that magnetic susceptibility ms is largely controlled by carbonate content at deep sea drilling project site 522 which in turn is the primary control on sar at the site over 5000 ms measurements were averaged over magnetostratigraphic polarity intervals for use as indicators of carbonate content and sar proxies the study produced three primary results 1 a spectral analysis of the ms data from one upper oligocene core reveals two dominant periodicities 44 7 10 4 kyr and 26 4 3 6 kyr which approximate milankovitch obliquity 41 kyr and precession 23 kyr periods 2 four pulses of increased sar lasting 1 to 2 m y punctuate the section implying longer term climatic changes these events are also seen in the contessa quarry section of the italian tethyan oligocene and 3 two of the sar maxima correspond to times of global cooling and possible ice volume increases at 31 and 36 ma

trace metal deposition and mobility in the sediments of two lakes near sudbury ontario the accumulation and mobility of fe mn al cu ni and pb in the sediments of two lakes clearwater ph 4 5 and mcfarlane ph 7 5 near sudbury ontario have been investigated the al cu and ni concentrations are expectedly relatively high in the overlying waters of clearwater lake and much lower for al and cu in mcfarlane lake the low trace metal concentrations found in the anoxic porewaters of clearwater lake could be explained by a sharp increase in porewater ph concomitant with so42 reduction and h2s production within the first 1 2 cm of the sediments which has conceivably led to the precipitation of mineral phases such as al oh 3 nis and cus in both lakes fe concentrations in anoxic porewaters appear to be controlled by fes and or feco3 formation solubility calculations also indicate mnco3 precipitation in mcfarlane lake in clearwater lake however both porewater and total mn were relatively low a possible result of the continuous loss of mn ii through the acidic interface it is suggested that upwardly decreasing total mn profiles resulting from the removal of mn from the top sediment layers under acidic conditions may constitute a reliable symptom of recent lake acidification the downward diffusion of ai cu and ni from the overlying water to the sediments has been estimated from their concentration gradients at the interface and compared to their total accumulation rates in the sediments in both lakes the diffusion of al is negligible compared to its accumulation rate however diffusion accounts for 24 52 of the accumulation of cu in the sediments of clearwater lake but appears negligible in mcfarlane lake the downward diffusive flux of ni is important and may explain 76 161 of the estimated ni accumulation rate in clearwater lake and 59 in mcfarlane lake the porewater cu and ni profiles suggest that the subsurface sedimentary trace metal peaks observed in clearwater lake as in other acid lakes may not be caused by sediment leaching or by a recent reduction in sedimentation but may have a diagenetic origin instead diffusion to the sediments thus appears to be an important and previously overlooked trace metal deposition mechanism particularly in acid lakes

arsenic distributions in porewaters and sediments of puget sound lake washington the washington coast and saanich inlet b c solid phase as mn al and excess 210pb and dissolved total as as 3 as 5 mn 2 fe 2 po 34 nh 4 and h2s profiles in 12 cores from puget sound lake washington the washington coast and saanich inlet b c are presented typically strong correlations between solid phase as and mn concentration maxima in surficial sediments are a result of intense as scavenging in the overlying waters by mn or ferich phases or solid phase as dissolution at depth followed by upward diffusion and co precipitation with mn or fe oxides at or near the sediment water interface atypically anthropogenic inputs cause high sedimentary as concentrations without accompanying high mn levels sedimentary as fluxes are an order of magnitude greater in puget sound and lake washington than off the washington coast and in saanich inlet porewater total as concentration profiles exhibit sub surface maxima with magnitudes 10 60 times greater than in overlying bottom waters porewater maxima in marine environments are proportional to associated solid phase as concentrations these maxima consistently occur within 1 0 cm of the bottom of the 210pb derived surface mixed layer suggesting solid phase as release to porewater in response to a redox gradient across this mixing boundary dissolved as behavior beneath these maxima indicates as removal to solid phases in marine but not lacustrine porewaters porewater as 3as 5 ratios are 1 0 for washington coastal environments and usually between 1 0 4 0 for puget sound and lake washington as 5 is below the detection limit in porewaters of saanich inlet when the overlying bottom water is anoxic but as 3as 5 ratios as low as 2 8 exist in near surface porewater under oxic bottom water conditions

subsidence of the atlantic moroccan margin during the mesozoic this paper presents a combined study based on seismic interpretation sequence stratigraphy and the evaluation of subsidence that aims to characterize the structure and development of the essaouira basin in morocco located in the coastal meseta adjoining the continental margin this basin records an initial carnian hettangian deformation phase during rifting in the central part of the north atlantic region the geometry of the basin as a function of time shows a succession of half grabens and horsts that developed westwards from reactivated hercynian structures the postrift stage is characterized by an aggrading sedimentary sequence as shown by concordant seismic sequences stacking over the onshore part of the basin the upper cretaceous coincides with a sequence showing a transition towards a prograding regime that leads to the topography of the present day margin using the high resolution analysis provided by sequence stratigraphy it is possible to recognize fine scale stratigraphic variations in

interplay between fracturing and hydrothermal fluid flow in the ason valley hydrothermal dolomites basque cantabrian basin spain in ason valley hydrothermal dolomite area basque cantabrian basin northern spain an overlapping stepover area between two major basement faults the cabuerniga and ruahermosa transtensional faults was the location for different scales and types of extensive frac tures this fracture mesh affected the albian ranero limestone and was formed in a dilational jog a regional fluid throughflow area it acted as pathway for overpressured fluids that controlled the dolomite mineralization in the ranero massif area the study of synchronous structural features fluid flow channelling and dolomitization processes indicated their tectonic control the fluid cir culated and concentrated preferentially in more fractured areas with increased permeability such as extensional chimneys creating dolomite bodies repeated extensive tectonic activity enhanced fracture porosity promoting overpressured fluid migration and cyclical dolomitization events the studied fracture pattern suggests the presence of sinistral transtension during the formation of extensional joint sets that channellized the mineralizing fluid flow a gradation in structural fea tures and dolomite facies and textures is visible from the main pozalagua fault dolomite body to peripheral dolomite bodies as the breccia body and ranero megajoints these differences could reflect a proximal distal trend from the main fluid flow area along the pozalagua fault to the ranero megajoints

high frequency moderate to high amplitude sea level oscillations during the late early aptian insights into the mid aptian event galve sub basin spain abstract this paper presents a field based stratigraphic architecture research from the aptian of spain in which high frequency 7 cycles ma moderate to high amplitude 8 127 m sea level oscillations are evidenced by the repeated incision of palaeovalleys in a carbonate platform developed during the late early aptian in a rift setting global eustacy tectonic uplift and mantle dynamic topography are considered as potential mechanisms to explain the observed relative sea level record glacioeustacy is interpreted as the most reliable mechanism to drive the observed sea level oscillations however other mechanisms as oscillations of the groundwater capacity of sedimentary basins and sudden flooding of major a basin as the south atlantic rift are also considered a major cooling event is proposed to occur during the late early aptian as a response to a large scale episode of ignimbritic volcanism increased burial of organic carbon during the aptian oae 1a and a significant demise of carbonate platforms this cooling event is interpreted as the origin for glacioeustatic sea level oscillations during the mid aptian

evidence for a change in the periodicity of tropical climate cycles at 2 4 myr from whole core magnetic susceptibility measurements the earth s orbit about the sun is influenced by gravitational interactions with the moon and other planets the resulting orbital perturbations give rise to cyclical variations in orbital eccentricity obliquity and precession with periods of 100 41 19 and 23 kyr respectively1 these variations are climatically important because they affect the seasonal and latitudinal distribution of solar radiation magnetic susceptibility measurements in deep sea sediment cores can be used as a sensitive indicator of temporal variations in the concentration of terrigenous material supplied to the sea bed here we use this approach to study the evolution of cycles of terrigenous sedimentation at ocean drilling program sites in the arabian sea and the eastern tropical atlantic we show from spectral analyses of the two susceptibility time series spanning the past 3 2 3 5 myr that the records are driven strongly by orbital forcing before 2 4 myr before present bp both records are strongly influenced by the 23 and 19 kyr periodicities but after 2 4 myr they are both significantly influenced by the 41 kyr periodicity this shift coincides with the beginning of major northern hemisphere glaciation which indicates for the indian ocean site that the supply of terrigenous sediment carried by monsoonal winds has responded to the rapid increase in ice cover at this time we cannot however exclude possible effects of changes in bottom water circulation on the susceptibility record of the atlantic site

a global scale plate reorganization event at 105 100 ma abstract a major plate reorganization is postulated to have occurred at approximately 100 ma however this reorganization has received limited attention despite being associated with the most prominent suite of fracture zone bends on the planet and many other geological events we investigate tectonic events from the period 110 to 90 ma and show that the reorganization occurred between 105 and 100 ma was global in scale and affected all major plates seafloor evidence for plate motion changes is abundant during this period with either fracture zone bends or terminations preserved in all ocean basins long lived eastern gondwanaland subduction ended along a 7000 km long section of the margin while elsewhere around the proto pacific rim subduction continued and there is evidence that compressional stresses increased in the overriding plates thrusting in western north america transpression and basin inversion in eastern asia and development of the present day andean style margin along western south america occurred contemporaneous with the development of an extensional regime in eastern gondwanaland basin instability in africa and western europe further demonstrates that lithospheric stress regime changes were widespread at this time considering the timing of the reorganization and the nature of associated plate boundary changes we suggest that eastern gondwanaland subduction cessation is the most likely driving mechanism for the reorganization subduction is the dominant driver of plate motion and therefore this event had the potential to strongly modify the balance of driving forces acting on the plates in the southwestern proto pacific and neighboring plates whereby producing widespread changes in plate motion and continental lithospheric stress patterns we propose that major changes in ridge trench interaction triggered the cessation of subduction the progressive subduction of two closely spaced perpendicular mid ocean ridges at the eastern gondwanaland subduction zone to the east of australia and new zealand respectively resulted in very young crust entering the trench and we suggest that by 105 100 ma there was insufficient negative buoyancy to drive subduction finally we propose that the plume push force of the bouvet plume that erupted near the african antarctic south american triple junction contributed to plate motion changes in the southern atlantic region

the madotz urgonian platform aralar northern spain paleoecological changes in response to early aptian global environmental events abstract sudden addition of carbon dioxide to the atmosphere can reduce the caco3 saturation and weaken the biocalcification potential of marine organisms in shallow water and in open marine settings in this study the response of an aptian neritic carbonate environment to sudden addition of carbon dioxide at the beginning of oceanic anoxic event 1a is investigated the beginning of the oae1a was coupled with a major perturbation on the carbon cycle as indicated by a negative carbon isotope excursion in the sedimentary record this isotope anomaly is regarded as a proxy for massive addition of volcanic or methane derived co2 to the atmosphere within only a few 104 years the impact of a rapid change in atmospheric pco2 on biocalcifiers in low latitude shallow water settings can be studied in a well preserved aptian carbonate shelf succession cropping out today in the aralar mountains ne spain the madotz section n spain preserves a continuous shallow water record that was deposited on a mid latitude atlantic oriented mixed siliciclastic carbonate ramp lower aptian sediments consist of two neritic limestone successions separated by orbitolinid rich marlstone enriched in organic matter the lower neritic limestone succession ends with a submarine hardground and the transition from the lower neritic limestone to the orbitolinid marlstone coincides with a negative spike in the organic carbon isotope record this negative spike can be correlated with the negative carbon isotope anomaly marking the base of oae1a the paleoecological change coinciding with the base of oae1a occurred at a time of sea level rise and it coincided with a demise of heavily calcified nannoconids in the tethys and pacific oceans the paleoecological change observed in the madotz section corresponds to a comparable change seen in the more distal and more expanded carbonate ramp section igaratza at the aralar mountains ocean acidification caused by sudden increase in pco2 may explain reduced calcification potential of some shallow water calcifiers calcification crisis was amplified by rising sea level increasing temperatures and increased flux of detrital material and nutrients from continents into coastal seas

the cretaceous peri atlantic alkaline pulse paap deep mantle plume origin or shallow lithospheric break up abstract although the early jurassic initial phases of atlantic rifting were marked by the tholeiitic basalt flows and dikes of the central atlantic magmatic province camp the cretaceous era was characterised by widespread alkaline igneous activity on widely separated peri atlantic continental margins nearly half the peri atlantic alkaline rocks dated between 250 to 50 ma fall within the 125 80 ma range this period of intense alkaline activity during the mid cretaceous formed the peri atlantic alkaline pulse paap the mechanisms for the opening of the atlantic ocean as well as for the camp and later paap magmatic events have been attributed either to deep mantle plumes or to a combination of tensional forces lithospheric rifting and structural controls we describe the paap event for the first time and test the plume and structural models the paap displays evidence of strong structural control and appears to be related to reactivation of pre existing lithospheric structures throughout the peri atlantic zone early stages of continental separation and abrupt changes in plate motion were the most likely mechanisms for the reactivation of favourably oriented pre existing structures mid cretaceous pulses in alkaline magmatic activity were closely associated with major atlantic tectonic events the opening of the south atlantic the change in intensity and direction of both seafloor spreading and plate motion and the consequent fluctuation in intra plate stresses were responsible for two spikes in peri atlantic alkaline magmatism at 125 ma and 85 80 ma the general lack of evidence for a deep hotspot associated with the peri atlantic zone seems incompatible with a mantle plume origin on the other hand the spatial distribution of the paap along passive continental margins suggests an ideal setting for the development of edge driven convection we propose that the periodic reactivation of deep seated pre existing zones of weakness during the major stages of atlantic tectonic evolution combined with coeval asthenospheric upwelling due to edge driven convection and continental insulation flow enhanced the ascent of alkaline magmas this mechanism of shallow small scale upwelling during periodic structural reactivation provides a more likely explanation for the paap than the commonly proposed deep mantle plume scenario

early diagenesis of arsenic in sediments of the kalix river estuary northern sweden solid phase as fe mn s and al and pore water total as fe mn and s have been determined for two cores from the kalix river estuary at the same station the depositional flux of arsenic was measured sediment traps fe iii oxides persist in the anoxic zone of the sediment and act as a carrier for arsenic down to depths of 10 15 cm the release of arsenic into the pore water is controlled by the reduction dissolution of these oxides as a result internal cycling of arsenic i e upward diffusion in pore water re adsorption onto fe iii oxides in the oxidized surface layer and reburial occurs in the uppermost 10 15 cm at the base of the arsenic cycling zone solid phase arsenic maxima 160 170 g g 1 of probable diagenetic origin occur the quantity of arsenic diffusing back towards the oxidized surface layer 2 2 g cm 2 yr 1 as is close to 75 of the quantity of arsenic being deposited due to sedimentation 2 9 g cm 2 yr 1 as however a mass balance for the surface layer indicates that re adsorption of arsenic onto fe iii oxides may effectively prevent diffusion of dissolved arsenic back into the overlying water column it is concluded that the interpretation of sedimentary arsenic profiles may be severely complicated due to post depositional migration of arsenic

thermo mechanical modelling of black sea basin de formation abstract we present the results of a thermo mechanical modelling study carried out to investigate the effect of pre rift rheology on subsequent basin de formation in the black sea area important differences are inferred for the bulk lithosphere structure and mechanical properties expressed in terms of different estimates for levels of necking in the western and eastern black sea respectively gravity data provide constraints on the mode of flexure in the black sea pointing to significant lateral variations in pre rift lithospheric strength these features strongly affect predictions for mesozoic cenozoic basin stratigraphy and have implications for the presence and development of rift shoulder topography on the margins of the black sea basins differences in lithosphere strength affect the mode of stress propagation from the basin margins into the central parts of the black sea basins during the post rift phase these post rift compressional stresses could be of key importance for long wavelength late neogene differential motions within the basins superimposed on vertical motions induced by rifting and subsequent sediment loading thermo mechanical modelling of integrated lithospheric strength points to a rapid increase of strength during the later stages of post rift evolution and the presence of relatively strong lithosphere in the centre of the basin these features predict preferential shortening induced by compressional activity of surrounding orogens to be primarily accommodated at the basins margins

natural enrichment of arsenic in loch lomond sediments abstract concentrations of arsenic in surface or near surface sediment in 12 of 13 cores from the three major basins of loch lomond are substantially enhanced up to 675 mg kg compared with background values of 15 50 mg kg sedimentary as profiles are attributed to post depositional enrichment processes since there are no recent significant sources of environmental as contamination anthropogenic or natural in the loch lomond area the enrichments can be interpreted in terms of post depositional diagenetic remobilization processes in sediment reducing zones followed by upward migration of as through interstitial waters and oxidation adsorption precipitation reactions in near surface oxidizing layers confirmation of the diagenetic adsorption hypothesis is provided directly by the analysis of as species 1 5 81 g l in pore water and indirectly via comparison with sedimentary phosphorus

early triassic disaster and opportunistic foraminifers in south china survival and recovery are important dynamic processes of biotic evolution during major geological transitions disaster and opportunistic taxa are two significant groups that dominate the ecosystem in the aftermath of mass extinction events disaster taxa appear immediately after such crises whilst opportunists pre date the crisis but also bloom in the aftermath this paper documents three disaster foraminiferal species and seven opportunistic foraminiferal species from lower triassic successions of south china they are characterized by extreme high abundance and low diversity and occurred occasionally in griesbachian smithian and spathian strata the characteristics small size simple morphology and stratigraphic ranges of these groups suggest that r selection is a commonly used strategy for survivors to cope with either harsh post extinction conditions and or environments lacking incumbents

comparison between the galicia and aquitaine margins abstract there is a great similarity between the galicia margin and the aquitaine margin i e the aquitaine basin and the north pyrenean zone in particular the timing of the rifting as well as the resulting structures exposure of perodotite tilted fault blocks normal and transverse faults half grabens are practically the same this comparison leads to the interpretation that the northern side of the pyrenean fold belt is inherited from the mesozoic deep passive margin of europe the cenozoic thrust sheets and reverse faults of the northern pyrenees zone are tentatively interpreted as former rift structures tilted blocks and listric faults which were removed during the convergence of the iberian and european plates during the paleocene and eocene

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

halokinetic sequences in carbonate systems an example from the middle albian bakio breccias formation basque country spain in diapir flanks unconformity bounded sedimentary packages associated with gravity driven deposits controlled by the ratio between the rates of sediment accumulation and diapir growth can be interpreted in the context of halokinetic sequences the bakio breccias formation basque country spain corresponds to redeposited carbonate deposit that developed in response to the bakio diapir growth during the middle albian these deposits provide on of the rare documented example of carbonate dominated halokinetic sequences the bakio breccias formation consists of an alternation of clast and matrix supported breccias calcirudite calcarenite and marl deposited along the flanks of the diapir the description and the analysis of the bakio breccias formation lead to a new model for carbonate dominated halokinetic sequences these sequences differ from their siliciclastic counterpart because sediment accumulation rate is controlled by carbonate platform growth on the topographic relief top of the diapirs while sediments are preferentially deposited in the mini basins adjacent of the diapirs in siliciclastic settings during transgressive system tract carbonate platform are able to keep up with the sea level rise and to aggrade on top of the diapirs forming thick and resistant roof which is assumed to limit the diapir growth and thus to favour the development of halokinetic sequences with low angle unconformities wedge halokinetic sequences during late highstand system tract deposition and lowstand system tract if present platform progradation results in high sediment accumulation in the adjacent depocenters loading the autochthonous salt layer and promote diapir growth and creation of topographic relief in addition if the diapir roof reaches emersion karstification of the carbonate platform top may also favour roof destruction and diapir growth depending on the thickness of the roof developed previously and the amplitude of the sea level fall the halokinetic sequences with the emersion and the karstification of the carbonate platform may display high angle unconformities hook halokinetic sequences furthermore gravity driven deposits are assumed to be more common in carbonate dominated halokinetic sequences compared to their siliciclastic counterparts since carbonate platform aggradation creates steep slopes on the diapir margins leading to the partial collapse of the margin even when limited diapir growth occurs the carbonate dominated halokinetic sequence model proposed here is an important tool for the prediction of potential reservoir distribution seal and hydrocarbon migration in flanks of salt diapirs where carbonate platform developed

low temperature exhumation history of variscan age rocks in the western cantabrian mountains nw spain recorded by apatite fission track data abstract this paper presents the first regional study of apatite fission track aft thermochronology to be undertaken in the western termination of the cantabrian mountains nw spain the mountains reach elevations of over 2600 m along the northern coast of spain and are comprised of a variscan crustal section uplifted due to cenozoic shortening along the northern iberian plate the study constrains the pattern and history of exhumation within the paleozoic bedrock over the past c 240 ma twenty one apatite fission track samples range in age from 246 7 26 9 ma to 78 1 3 7 ma with mean track lengths between 10 4 1 8 m and 12 4 1 4 m time temperature path modelling of the data indicates that different rates of continuous cooling took place during the three main tectonic events that affected the area a rapid cooling event that ended by the late jurassic corresponds to topographic decay during unroofing of the variscan orogen and the break up of pangea and is responsible for the largest amount of exhumation westernmost samples cooled coinciding with rifting in the north atlantic and bay of biscay during the late jurassic to early cretaceous by about 100 80 ma most samples had reached or passed through the upper boundary of the apatite partial annealing zone which indicate that regional denudation has not exceeded c 1 7 km since then for geothermal gradients 27 c km and a surface temperature of 15 c only three samples next to fault escarpments in the west cooled below 70 c since 80 ma reaching below 65 c before initiation of incipient subduction along the northern iberian margin by 46 ma an average cooling rate of 1 c ma reflects latest denudation as the new mountainous relief developed since then due to shortening and incipient subduction associated with convergence along the northern iberian plate the cantabrian mountains are one of the few natural examples of a coastal orogen in a juvenile stage of evolution

geochemical study of arsenic and other trace elements in groundwater and sediments of the old brahmaputra river plain bangladesh the geochemical study of groundwaters and core sediments from the old brahmaputra plain of bangladesh was conducted to investigate the distribution of arsenic and related trace elements groundwaters from tube wells are characterized by ph of 6 4 7 4 dissolved oxygen do of 0 8 1 8 mg l ca contents of 5 50 mg l and fe contents of 0 2 12 9 mg l arsenic concentrations ranged from 8 to 251 g l with an average value of 63 g l a strong positive correlation exists between as and fe r2 0 802 p 0 001 concentrations in groundwater the stratigraphic sequences in the cores consist of yellowish silty clays at top passing downward into grayish to yellowish clays and sands the uppermost 3 m and lower parts from 13 to 31 m of the core sediments are oxidized average oxidation reduction potential orp 170 and 220 mv respectively and the orp values gradually become negative from 3 to 13 m depths 35 to 180 mv indicating that anoxic conditions prevail in the shallow aquifers of the brahmaputra plain age determinations suggest that clay horizons at 10 m depth were deposited at around 2 000 and 5 000 years bp 14c ages during the transgressive phase of sea level change elevated concentrations of as pb zn cu ni cr and v are present in the silts and clays probably due to adsorption onto clay particles significant concentrations of as occur in black peat and peaty sediments at depths between 9 and 13 m a strong positive correlation between as and fe was found in the sediments indicating as may be adsorbed onto fe oxides in aquifer sediments

time series analysis of magnetic susceptibility variations in deep marine sedimentary rocks a test using the upper danian lower selandian proposed gssp spain abstract it has been clearly demonstrated that past climate fluctuations are recorded in marine sedimentary rocks however for many reasons extracting the climate signature is difficult initial low field mass specific magnetic susceptibility ms data can potentially provide a measure of climate variability and thus become a proxy characterizing climate cyclicity in a wide range of marine sediments this is due to the fact that climate change warm wet versus cold dry drives cyclic weathering and erosional variations that are recorded as the detrital components of marine sediment that dominates the ms to test the utility of ms to yield climate proxies in marine sediments showing major changes in lithology we have sampled the well studied danian selandian boundary interval lower paleocene at zumaia zumaya spain this interval represents a dramatic rapid lithologic change from danian carbonate dominated limestone marl couplets to a detrital dominated marl shale sequence in the selandian indicating onset of a major regression erosional event beginning in the lowest selandian sampling included a continuous sequence from the uppermost danian stage 3 71 m into the lowermost selandian stage 5 2 m a suite of 175 samples collected at 5 cm intervals our results indicate that ms measurements reflect changes in detrital sediment at the site first by closely tracking high frequency limestone marl couplets second with a large rapid shift toward higher ms values beginning at the danian selandian boundary resulting from a major regression and third by tracking low frequency climate controlled variations known to have occurred during deposition of these sediments ms zones developed from the cyclicity observed throughout the sequence supported by time series analysis using fourier transform ft methods applied to the ms results exhibit milankovitch cyclicities in the precessional 19 24 kyr obliquity 41 54 kyr and eccentricity bands 100 kyr this is in excellent agreement with previous ft work on the section using measured variations in cyclic bed thicknesses with the new ms data set and ft results we then developed a floating point time scale fpts for the sequence sampled covering 550 kyr through the danian selandian boundary interval yielding a time scale resolution for the uppermost danian to 10 000 years however only the 100 000 year eccentricity band for the selandian is sufficiently well developed for an fpts estimate and yields a time scale resolution of 50 000 years our test of the utility of ms data sets in this varying depositional setting demonstrated that these data can provide a climate proxy that is not disrupted by large lithologic changes

present environment of dam lake sambe southwestern japan a geochemical study of bottom sediments geochemical analyses of lakebed and core sediments from lake sambe on the outskirts of oda city in shimane prefecture in southwestern japan were carried out in order to assess the water quality and the concentration and distribution patterns of sixteen elements the lake water showed a stratified condition with respect to dissolved o2 and as fe and mn concentrations in the bottom layers which increased in the summer the chemical composition of the sediments as measured by x ray fluorescence included major and trace elements p ca sc ti v cr fe ni cu zn as sr zr pb and th and total sulfur ts elevated values of as zn v fe p and ts were present in several layers of the upper cores from 0 to 5 cm and other surface sediments increases in the abundances of these metals in lake sediments are probably related to the reducing condition of the sediments fine grained organic rich sediments and post depositional diagenetic remobilization moreover correlations between the concentrations of trace metals and iron in the sediments suggest their adsorption onto fe oxy hydroxides whereas correlations with sulfur indicate that they were precipitated as fe sulfides the average abundances of as pb zn and cu exceeded the lowest effect level and interim sediment quality guideline values that the new york state department of environmental conservation and the canadian council of ministers of the environment determined to have moderate impact on aquatic organisms in addition concentrations of as and zn exceeded the coastal ocean sediment database threshold value indicating potentially toxic levels therefore the presence of trace metals in the lake sediments may result in adverse effects on biota health

characteristics genesis and parameters controlling the development of a large stratabound htd body at matienzo ramales platform basque cantabrian basin northern spain abstract at matienzo basque cantabrian basin northern spain a large stratabound htd body 4 by 2 km 2 and 80 400 m thick delimited by two parallel sinistral strike slip faults is exposed in aptian carbonates the margins of the htd body are characterised by dolomite tongues indicating that some limestone beds were more prone to dolomitisation however no clear relationship between htd occurrence and precursor limestone facies can be established massive limestone beds as found at the top of the htd body act as barriers to hydrothermal processes since no dolomite is present in or above these beds three types of dolomites have been differentiated i e 1 matrix 2 coarse crystalline and 3 zebra dolomite the distribution of the dolomite types is attributed to ascending fluid flow and changing degree of dolomite oversaturation the dolomite body was formed by two dolomitisation phases under burial conditions no indications for a synsedimentary early diagenetic dolomitisation have been observed the first dolomitisation phase is characterized by ferroan dolomite and the second by non ferroan dolomite the two htd phases are characterised by depleted 18 o values ranging between 10 and 16 v pdb 13 c values similar to the aptian albian marine signature and homogenisation temperatures of primary fluid inclusions between 120 c and 150 c the dolomitising fluid was enriched in 87 sr compared to aptian seawater excluding the latter as an unmodified fluid source for dolomitisation microthermometry of primary fluid inclusions indicates that the dolomitising fluid evolved from a moderate saline 9 7 14 0 wt nacl to a more saline 10 9 21 0 wt nacl h 2 o nacl brine the dolomitising fluid likely originated from evaporated seawater fluid circulation through the dolomitised strata is inferred to have taken place during the tectonically active period of the late albian throughout which important sinistral strike slip movements along basement faults occurred

identifying globally synchronous permian triassic boundary levels in successions in china and vietnam using graphic correlation abstract understanding the timing and correlation of significant global events in earth history is facilitated by the global boundary stratotype section and point gssp concept along with multi proxy correlation techniques as an example the permian triassic boundary ptb gssp is used herein to correlate three ptb successions in east and southeast asia the ptb is defined using the first appearance datum fad of the conodont hindeodus parvus at the meishan d section in china by definition then meishan d is the only section on earth where the fad of h parvus represents the beginning of the triassic at 251 88 ma and thus the end of the permian therefore when correlating strata in any other section back to the ptb using biostratigraphic data the local lowest observed occurrence point loop of h parvus will probably not equate precisely to the defined fad gssp level the ptb for the beginning of the triassic at meishan d the graphic correlation method applied to ptb sites in china and vietnam is used herein to demonstrate that loops of h parvus in other successions are not equivalent in time to the ptb fad the loop and highest observed occurrence point hoop for conodont data at two other successions studied huangzhishan in china and lung cam in vietnam are used to determine the approximate level where the triassic begins in these successions resulting in high resolution correlation among the sections and correlation back to the ptb gssp level it is demonstrated that when critical biostratigraphic data are missing multiple proxy correlation techniques geochemical geophysical and in some regional instances unique lithostratigraphic information such as coeval ash beds can be used to aid in locating the boundary in successions that are not the defining gssp loop and hoop data are used to establish a line of correlation to differentiate between a defining ptb h parvus fad versus the h parvus loop in secondary successions and to project the ptb fad into secondary sections to define the ptb at these localities in addition the timing of h parvus arrivals at these sections is used to establish rough dispersal rates and patterns in the region

magnetostratigraphy susceptibility of the upper ordovician kope formation northern kentucky abstract as a test of the utility of magnetic susceptibility ms measurements for correlation among lithified marine sequences samples were collected from well studied shale and limestone outcrops of the upper ordovician kope formation northern kentucky the bulk initial low field ms of these samples is compared among two litho and biostratigraphically correlated sections containing the same beds the results of this comparison demonstrated an excellent correlation among equivalent beds thermomagnetic susceptibility analysis supports previous xrd work indicating that illite is primary and is the main paramagnetic mineral responsible for the ms variations observed in this study a composite of ms results for a sequence of 31 named shale limestone couplets is used to build a composite section of kope sequences for the area these ms variations permit division of the various sections into a set of 28 ms cycles within the kope formation covering 50 m of section these cycles suggest a systematic control by climate on the influx of detrital material that formed these sedimentary sequences and support other work indicating kope climate cyclicity

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

quantitative subsidence analysis of the mesozoic evolution of the lusitanian basin western iberian margin abstract quantitative subsidence analysis of 26 wells in the lusitanian basin provides new constraints on the western iberian mesozoic passive margin development backstripped tectonic subsidence curves show a three fold subdivision of vertical motions from late triassic onward continental rifting was initiated during the late triassic and early jurassic from middle jurassic onward a distinct different behaviour is expressed in the subsidence curves for the north and the south lusitanian basin during the middle jurassic the south lusitanian basin records a stretching episode with stretching factors of about 1 08 while the north lusitanian basin typically has a middle jurassic hiatus this different development is also expressed in the late jurassic and early cretaceous sedimentary sequence when both the north and south lusitanian basin are subjected to another stretching episode with a more pronounced development of the southern than of the northern part of the basin the stretching factors for this last phase are about 1 03 for the northern part and 1 08 for the southern part of the area this north south difference during the middle jurassic to early cretaceous for which the transition roughly coincides with the location of the nazare fault zone is probably a result of differences in pre rift crustal composition or thickness late cretaceous sediments are mostly absent in the analysed wells in the southern part of the basin the absence of the cretaceous record is a consequence of erosion due to cenozoic inversion of the basin the generally low estimates for stretching factors suggest that the analysed eastern part of the lusitanian basin forms the distal part of the mid cretaceous continental breakup a comparison with subsidence curves of neighbouring basins of iberia reflects general patterns in mesozoic basin development and confirms the generally held view that the extension leading to continental breakup migrated from south to north during the middle jurassic to early cretaceous in west iberia

early diagenetic influences on iron transformations in a freshwater lake sediment abstract iron transformations in a calcium carbonate rich fresh water sediment were studied by analyzing the relevant constituents of both interstitial water and solid matter analysis of interstitial water shows that the observed redox sequence no 3 nh 4 mno 2 mn ii feooh fe ii so 2 4 s ii is roughly in agreement with that predicted by the gibbs free energy for the corresponding reactions in contrast to marine sediments these redox transitions occur in the uppermost sediments i e at depths of 0 4 cm deeper in the sedimentary sequence the depth profile for dissolved iron exhibits a steady non linear increase up to 400 mol dm 3 in this anoxic zone according to thermodynamic predictions iron ii minerals such as iron sulfide siderite and vivianite should precipitate while fe iii oxides should be completely dissolved however microscopic analysis showed that fe iii oxides were present throughout the studied sediment furthermore scanning electron microscope energy dispersive spectroscopy analysis suggests the presence of iron sulfide could be verified but not that of siderite or vivianite these observations indicate kinetic control of iron transformations we have investigated the importance of kinetic control of iron distribution in anoxic sediments using a diagenetic model for dissolved iron ii a rough estimate of time scales for dissolution and precipitation rates was made by imposing limiting boundary conditions using the calculated rate constant we established that more than 1000 years would be required for the complete dissolution of fe iii oxides which is agreement with our observations and experimental data from the literature calculated precipitation rates of fe ii for a given mineral phase such as siderite yield a maximum value of 3 g feco3 g 1 dry sediment yr 1 such low rates would explain the absence of siderite and vivianite finally it can be inferred from the mn t fe t ratio in the sediments that this ratio depends on the redox conditions of the sediment water interface at the time of deposition thus this ratio can be used as paleo redox indicator in lacustrine sediments

a coarse grained turbidite system with morphotectonic control middle albian ondarroa northern iberia the middle albian ondarroa turbidite system is a coarse grained deep water unit which outcrops in the north eastern part of the basque cantabrian region west of the pyrenees it is about 18 km long and 7 km wide and shows an unusual l shape resulting from both a direct morphotectonic confinement and the presence of nearby shallow water carbonate buildups eight main facies have been distinguished within this turbidite system 1 clast supported conglomerates 2 mud supported conglomerates 3 slump deposits 4 normally graded pebbly sandstones 5 cross stratified sandstones 6 interbedded graded sandstones and mudstones 7 interbedded non graded sandstones and mudstones and 8 mudstones inner system middle system outer system and basin plain divisions have been distinguished the inner turbidite system is characterized by stacked channel fill conglomerates and lesser sandy turbidites and mudstones the middle system consists of sandy and conglomeratic fining upwards sequences normally several metres thick the outer system has alternating non channellized sandstones and mudstones without any predictable vertical arrangement the basin plain is characterized by mudstone siltstone laminations and lesser randomly occurring thin bedded sandy turbidites three main channel fills make up the inner turbidite system although all of them can be compared with the valley channel fills of the modern mississippi fan and thus their bases can be interpreted as sequence boundaries only the lowermost and the uppermost channel bases are documented as allocyclic boundaries the ondarroa turbidite system was deposited in an immature passive margin subjected to transtensional movements it filled a composite pull apart depression with coarse clastics derived from a narrow platform to the north of the present outcrops which was invaded by fan deltas a major pattern of sinistral strike slip faulting linked to the opening of the bay of biscay is invoked to explain the ondarroa turbidite system appearance and its tectonic confinement

syntectonic deposits and punctuated limb rotation in an albian submarine transpressional fold mutriku village basque cantabrian basin northern spain deep water syntectonic deposits and angular unconformities record the denudation and deformation history of the middle cretaceous aitzeta structure interpreted here as a monoclinal syncline associated with the high angle reverse mutriku fault basque cantabrian basin northern spain sedimentological and structural analyses combined with a precise chronostratigraphy based on ammonites permit us to document in detail the history of this syncline during 0 53 m y late albian callihoplites auritus subzone tectonism occurred during two major and two minor short lived pulses the sedimentary signatures of these pulses include unconformities and resedimented deposits derived from the uplifted rocks showing inverted clast stratigraphy in contrast intervening phases of tectonic calm were characterized by gentle hemipelagic sedimentation the major tectonic pulses were characterized by strong rotation and uplift of the syncline limb the two major pulses coincided with the lower and upper limits of the auritus subzone respectively and resulted in the following limb rotation and uplift values 42 and 250 m in the first pulse and 66 and 100 140 m in the second pulse a maximum duration of 0 12 m y for each major pulse has been calculated from which limb rotation and uplift rates of 0 35 k y and 2 08 m k y first pulse and 0 55 k y and 0 83 1 16 m k y second pulse are estimated growth strata and angular unconformity geometries temporal variation of deformation rates and bedding parallel faulting indicate folding by progressive limb rotation and associated flexural slip local northwest southeast compression is deduced in formation of the aitzeta syncline the presence of bedding parallel oblique faulting and minor drag folds suggests a component of right oblique movement along the mutriku fault

impact of early aptian carbon cycle perturbations on evolution of a marine shelf system in the basque cantabrian basin aralar n spain abstract the aptian oceanic anoxic event 1a oae1a ca 120 ma ago is one of the most prominent of a series of geologically brief intervals in the cretaceous reflecting a major perturbation in the global carbon cycle this carbon cycle perturbation is recorded in the c isotope stratigraphy in this study we present a new carbonate and organic carbon isotope record across oae1a from expanded shallow marine sections igaratza and iribas in the basque cantabrian basin n spain the sediments studied were accumulated on a mixed carbonate siliciclastic and carbonate shelf the 13 c carb and 13 c org curves obtained show a pronounced negative spike in the deshayesites weissi zone and a subsequent positive excursion within the newly described d deshayesi d furcata transition zone approximately equivalent to the upper d deshayesi zone of other sections specific changes in facies patterns and a reduction in neritic carbonate production predate the negative c isotope perturbation these changes coincide with global carbonate crises in neritic and pelagic environments corresponding with the beginning of oae1a selli level a condensed interval rich in ammonites is observed this horizon is linked to a major transgression with high biodiversity the ammonite bloom suggests enhanced primary productivity in the surface waters of the basque cantabrian basin at improving environmental conditions for selected biocalcifiers the ultimate recovery of shelf carbonate deposition occurred after oae1a and it coincided in time with the most positive values of the carbon isotope excursion based on carbon isotope stratigraphy it has been deduced that black shales corresponding to selli level are missing in aralar so that anoxia is not recorded in the studied sections of the marine shelf environment an organic rich interval aparein level postdates the early aptian major positive excursion the aparein event should be considered in the future research of oaes

wavelet transform mapping of effective elastic thickness and plate loading validation using synthetic data and application to the study of southern african tectonics 1 we present a new wavelet transform method to map spatial variations in effective elastic thickness te and plate loading ratio f the method assumes a model of thin plate flexural isostasy to describe the mechanical response of the lithosphere to vertical loading in this model the rheological properties of the lithosphere are aggregated into the effective elastic thickness te of an equivalent thin plate overlying an inviscid fluid a number of methods have been developed to map spatial variations in te in an attempt to assess regional patterns of flexural strength our new method first obtains local coherence and local admittance through wavelet cross spectral analysis of surface topography and bouguer gravity anomaly wavelet coherence is used to obtain the local characteristic wavelength which is a function of both te and the degree of relative loading f of the plate by subsurface loads and surface loads loading is the combined effect of erosion sedimentation intrusion faulting and metamorphism wavelet admittance in a normalized form is used to resolve this f te ambiguity and maps are made of the spatial variations in te and f we carry out extensive tests of the wavelet method on simulated topography and bouguer gravity anomaly data that we generate through finite difference simulations of flexural isostasy with spectrally realistic loads and simple spatial variations in te these tests demonstrate that the wavelet inversion method is reasonably robust to uncertainties in loading and in crustal thickness and is able to recover te to within 25 50 of its correct value we apply the wavelet method to southern africa and recover estimates of te principally in the range 25 50 km in good agreement with existing estimates from forward modeling and fourier coherence analyses we find that our te estimates often exceed estimates of crustal thickness pointing to a strong upper mantle in parts of southern africa

testing high resolution magnetic susceptibility and gamma radiation methods in the cenomanian turonian upper cretaceous gssp and near by coeval section abstract low field mass specific magnetic susceptibility and gamma radiation spectra grs field and laboratory data sets for two upper cretaceous marine sedimentary sequences representing the cenomanian turonian c t boundary in the western interior seaway in central colorado have been measured sections including the c t global boundary stratotype section and point gssp and a one kilometer distant co eval sequence the s section it has previously been established that both and grs data sets are controlled by detrital eolian fluxes into the marine environment although the effect of weathering if any on these parameters when exposed in outcrop is not well documented in addition these parameters are controlled by differing detrital eolian components that may be derived from different sources or be differentially concentrated within the marine system of great interest is 1 how well these data sets record climate cycles 2 how the and grs data are affected by weathering and 3 how well the two methods support each other reported here are the results of a number of field and laboratory experiments designed to evaluate instruments and how and grs data sets co vary and to test their usefulness as correlation tools in stratigraphy results show that both and 40k data sets from laboratory measurement on samples collected in the field where rocks are relatively fresh are generally well correlated respond closely to climate and the corresponding detrital eolian flux into the marine environment and can be used for a rough proxy for each other however weathering appears to affect the 40k data by removing 40k thus reducing correlation potential although does not appear to suffer as badly in more weathered sections and good correlations between sections remain field grs measurements produce a broadly smoothed data set that regionally can be very useful for correlation although potential global correlations are not tested here using data reported here and comparing these data to a 100 kyr cyclic eccentricity e1 climate model for the upper cretaceous at 93 9 ma shows that and 40k data measured in the laboratory can be used to build floating point time scales that produce essentially equivalent results as do other studies using absolute dates

structural controls on sedimentary basin evolution introduction this volume contains a collection of papers on structural controls on sedimentary basin evolution presented at the sixth annual workshop of the international lithosphere program task force origin of sedimentary basins in sitges at the rim of the ebro basin september 1995 previous workshops of the ilp task force had been in rueil malmaison france 1990 in matrahaza hungary 1991 on the rim of the pannonian basin in sundvollen norway 1992 in the oslo graben in benevento italy 1993 in the southern apennines fold andthrust belt and in the dead sea rift of israel 1994 the task force also organized a number of sessions during the 1992 and 1996 european geophysical society and the 1993 and 1995 european union of geosciences conferences reports of these meetings have been published in a number of special volumes and papers cloetingh et al 1993a b 1994 1995a b 1996 stephenson 1993 stephenson et al 1996 a position paper cloetingh sassi and task force team 1994 published in m a r i n e a n d p e t r o l e u m geo logy has outlined the task force strategy to pursue the development of a new generation of basin models using natural laboratories with high quality data sets obtained through close partnership with industry the 7th task force workshop was held on the faroe islands northern atlantic in 1996 with the aim of examining the dynamics of rifting

modern and last glacial maximum eolian sedimentation patterns in the atlantic ocean interpreted from sediment iron oxide content eolian dust derived from the desert regions of north africa is blown far into the tropical atlantic ocean by persistent easterly and northeasterly winds in this paper we demonstrate that the iron oxides hematite and goethite are a worthwhile addition to proxy monitors of eolian sedimentation in the tropical atlantic iron oxides are identified by diffuse reflectance spectrophotometry a technique capable of identifying these minerals in concentrations as low as 0 01 by weight we analyze samples from both the modern and last glacial maximum lgm synoptic levels from 178 sample locations yielding a total of 356 samples distributed throughout the atlantic ocean to determine the relative contribution of the iron oxides we factor analyzed the modern and lgm levels as a single data set the iron oxide factor explains about 25 of the variance in the combined core top and lgm data set mapped factor scores for the lgm and modern ocean indicate high iron oxide values are present in just two regions one off eastern north america and the other off northwest africa in the region off eastern north america iron oxide occurs primarily during the lgm as the previously noted brick red lutite a unique sediment type derived from the erosion of permo carboniferous red beds in atlantic canada a larger lobe shaped area of iron oxide rich sediment is present off northwest africa in both the modern and lgm levels the modern iron oxide lobe is coincident with the distribution of eolian dust as determined by observations from ships satellites and analysis of air samples during the lgm iron oxides exhibit a similar distribution except the southern margin of the region shifts equatorward and iron oxide concentration increases

high resolution sims oxygen isotope analysis on conodont apatite from south china and implications for the end permian mass extinction abstract understanding the interplay of climatic and biological events in deep time requires resolving the precise timing and pattern of paleotemperature changes and their temporal relationship with carbon cycle variations and biodiversity fluctuations in situ oxygen isotope analyses of conodont apatite from south china enables us to reconstruct high resolution seawater temperature records across the permian triassic boundary ptb intervals in the upper slope meishan lower slope shangsi and carbonate platform daijiagou and liangfengya settings constrained by the latest high precision geochronological dates and high resolution conodont biozones we can establish the temporal and spatial patterns of seawater temperature changes and assess their potential connections with the carbon cycle disruption and biodiversity decline we find a rapid warming of 10 c during the latest permian earliest triassic that postdated the onset of the negative shift in 13ccarb by 81 kyr thousand years the abrupt decline in 13ccarb by 32 kyr and the onset of mass extinction by 23 kyr which contradicts previous claims that the extreme temperature rise started immediately before or coincided with the onset of mass extinction our new evidence indicates that climate warming was most likely not a direct cause for the main pulse of the end permian mass extinction epme but rather a later participant or a catalyst that increased the pace of the biodiversity decline in addition a prominent cooling is recorded in the earliest changhsingian with the main phase a drop of 8 c in 0 2 ma confined to the lower part of the clarkina wangi zone and synchronous with the positive limb of the carbon isotope excursion cie around the wuchiapingian changhsingian boundary wcb in meishan and shangsi further long term and high resolution studies from other sections are needed to confirm the full contexts and underlying dynamics of the wcb cooling event

stable isotope response to lake eutrophication calibration of a high resolution lacustrine sequence from baldeggersee switzerland stable isotope analyses of discrete seasonal layers from a 108 yr annually laminated freeze core from baldeg gersee a small eutrophic lake in central switzerland provide information on the climatological and environmental factors including lake eutrophication that control oxygen and carbon isotopic composition of epilimnic biologically induced calcite precipitate during the last 100 yr baldeggersee has undergone major increases in productivity and eutrophication in response to nutrient loading from agriculture and industrialization in the lake s watershed calibration of the isotopic signal in baldeggersee to historical limnological data quantitatively links evidence of isotopic depletion in the sedimented calcite to trophic state of the lake 18o values from the spring summer light sediment layers steadily diverged to more depleted values in response to historical eutrophication measured 18o values were up to 21 5 more negative than calculated equilibrium 18o values evidence for 13c depletion in the calcite relative to equilibrium values is more difficult to ascertain because of an overall dominance of isotopic enrichment in the dissolved inorganic pool as productivity in baldeggersee increases a positive association exists between the degree of oxygen 18 depletion and the calcite crystal size thus large amorphous calcite grains can be used as a proxy for recognizing apparent isotopic nonequilibrium in sediment sequences from highly productive lacustrine environments from all geologic time scales in contrast to the light layers the oxygen isotopic composition of the calcite in the late summer fall dark sediment layers is unaffected by the apparent isotope nonequilibrium oxygen and carbon isotope values from the dark laminae in the baldeggersee sediment therefore provide environmental and climatological proxies that can be calibrated with known environmental and regional climate data for the last century

the permian triassic boundary at nhi tao vietnam evidence for recurrent influx of sulfidic watermasses to a shallow marine carbonate platform the permian triassic boundary at nhi tao cao bang province vietnam was sampled in a 7 5 m thick outcrop section at high resolution 5 cm intervals for chemostratigraphic and magnetic susceptibility analysis the section consists entirely of slightly argillaceous limestone representing shallow marine facies of the jinxi platform one of several large carbonate platforms within the nanpanjiang basin located on the southern margin of the south china craton upper permian strata beds 1 7 are mainly dark gray cherty fossiliferous wackestones and packstones containing a diverse open marine fauna whereas uppermost permian and lower triassic strata beds 9 and higher are medium gray calcimicrobial framestones containing rare macrofossils these facies are separated by a 12 cm thick oolitic pisolitic grainstone bed 8 that coincides with the disappearance of most late permian faunal elements as well as with the first appearance of various geochemical anomalies that continue into the lower triassic part of the section this late permian event horizon is characterized by 1 an abrupt decline in total organic carbon to near zero values 2 the onset of a sustained decline in carbonate 13c and 3 the first of eight concentration peaks in pyrite sulfur significantly each sulfide peak is associated with lower pyrite 34s values as well as with the onset of a negative carbonate 13c excursion or the acceleration of an excursion already in progress these chemostratigraphic relationships are consistent with multiple episodes of upwelling of sulfidic 34s and 13c depleted deep ocean waters onto the jinxi platform the first upwelling event was the most intense and caused a drastic reduction in primary productivity and the demise of the late permian fauna subsequent episodes were less intense but may have contributed to a delay in recovery of early triassic marine ecosystems a ten fold increase in magnetic susceptibility in bed 9 may record the influx of fine detrital particles following destruction of terrestrial ecosystems and massive soil erosion the terrestrial signal of the end permian catastrophe thus follows the marine signal with a 12 cm lag which may reflect the time of transit of soil derived particles across the nanpanjiang basin suggesting that the marine and terrestrial crises in the nhi tao region occurred more or less synchronously these observations suggest a model in which renewal of global ocean overturn followed a prolonged interval of deep ocean stagnation during the late permian with upwelling intensity modulated by short term 20 kyr climate cyclicity

upper devonian carbonate platform correlations and sea level variations recorded in magnetic susceptibility abstract this paper concerns the analysis of four outcrops in the frasnian upper devonian of belgium we compare the results of a precise sedimentological analysis with magnetic susceptibility ms data this comparison allows us to improve stratigraphic correlations and to test the relationship between magnetic susceptibility and sea level changes considering the sedimentological study different microfacies have been identified from the external belt dominated by relatively argillaceous open marine facies with crinoids to the biostromal and the lagoonal belt dominated by algae rich muddy facies fourth and third order sequences have also been identified and are probably related to sea level variations magnetic susceptibility data provides us very good fourth order correlations and the link between magnetic susceptibility and different sedimentological parameters is obvious more precisely ms appears to be related to fourth and third order sequences and to microfacies

role of structural inheritance and salt tectonics in the formation of pseudosymmetric continental rifts on the european margin of the hyperextended mauleon basin early cretaceous arzacq and tartas basins abstract arzacq and tartas were two cretaceous basins developing in the bay of biscay as secondary depocentres in the larger aquitaine basin they belong to an albian rift system where recent studies have stressed the role of simple shear thinning on the genesis of regional asymmetric basins however the two basins differ from recent models in having a pseudo symmetric morphology here we address the early cretaceous tectono sedimentary evolution of the arzacq and tartas rift basins and the lithospheric processes associated with their genesis these basins did not suffer major brittle deformation during rifting stage but nevertheless record a major change in their configuration between the aptian and the albian the arzacq basin shifted from a symmetric to a slightly asymmetric configuration this change was controlled by gravity sliding of the pre rift sedimentary cover in the eastern arzacq basin moving its depocenter south and by salt diapirism in the western arzacq basin moving its depocenter north several inherited paleozoic structures were reactivated as transfer zones and appear to be responsible for this depocenter shift the emplacement of salt diapirs at same time regionally limiting gravity sliding the tartas basin maintained a symmetric regime throughout the early cretaceous except along the barlanes transfer zone where the lussagnet salt diapir originated two drivers of subsidence are thus envisaged in the arzacq basin a neocomian aptian crustal thinning stage followed by reactivation of paleozoic faults in albian time accompanied by salt diapirism and gravity cover sliding the mauleon north pyrenean basin and its north adjacent tartas and arzacq basins thus formed part of a series of rift basins that progressed in maturity southward from a simple sag basin tartas to a slightly asymmetric basin aborted detachment arzacq to a hyperthinned basin mauleon our results offer new insights on the role of 1 structural inheritance in partitioning extensional strain 2 transfer zones as able to influence the sedimentary record of basins during crustal thinning and 3 pre rift salt decollements as able to separate the structural styles of sub and supra salt successions

widespread cretaceous inversion event in northern spain evidence from subsurface and palaeomagnetic data abstract in this paper we present geological evidence of a mid cretaceous inversion event in the polientes basin northern iberian plate based on geological data analysis of seismic profiles across the basin indicates that this tectonic event resulted in the uplift of the basin depocentre and the formation of an upright gentle anticline before cenomanian times the presence of a pre alpine syntectonic remagnetization in the jurassic and lower cretaceous rocks of the polientes basin allows us to define the geometry of the basin at the time between this early inversion event and the main alpine compressional period the early inversion in the polientes basin is consistent with a transpressional tectonic setting contemporaneous with the left lateral strike slip movement of iberia with respect to europe this study shows the successful use of two approaches to unravel the geodynamic scenario of the northern iberian plate during the cretaceous which was later obliterated during the tertiary pyrenean orogeny

hyperspectral image analysis of different carbonate lithologies limestone karst and hydrothermal dolomites the pozalagua quarry case study cantabria north west spain ground based hyperspectral imaging combined with terrestrial lidar scanning is a novel technique for outcrop analysis which has been applied to early and late albian carbonates of the pozalagua quarry cantabrian mountains spain an image processing workflow has been developed for differentiating limestone from dolomite providing additional sedimentary and diagenetic information and the possibility to quantitatively delineate diagenetic phases in an accurate way spectral absorption signatures can be linked to specific sedimentary or diagenetic products such as recent and palaeokarst hydrothermal karst solution enlarged fractures and different dolomite types some of the spectral signatures are related to iron manganese organic matter clay and or water content ground truthing accessible parts of the quarry showed that the classification based on hyperspectral image interpretation was very accurate this technique opens the possibility for quantitative data evaluation on sedimentary and diagenetic features in inaccessible outcrops this study demonstrates the potential of ground based imaging spectroscopy to provide information about the chemical mineralogical distribution in outcrops which could otherwise not be established using conventional field methods

carbon isotope and iridium event markers near the permian triassic boundary in the meishan section zhejiang province china abstract systematic investigations for carbon isotopes and iridium of the meishan section were carried out using very narrow sampling intervals the high resolution results demonstrate the following characteristics 1 a large drop in 13c 7 cm above the base of the triassic with a magnitude of about 6 2 a sharp ir peak of 2 02 ppb 10 cm above the base of the triassic whereas the ir mean of six samples equals 0 4 ppb the large negative carbon isotope shift the ir anomaly within a thin sublayer and microspherules all occur within a 20 cm thick section above the base of the triassic which has been defined to coincide with an abrupt facies change from carbonate to clay the geochemical results and the microspherules suggest that the permian triassic boundary event was catastrophic and probably caused by an extraterrestrial impact

stratigraphy of the middle devonian boundary formal definition of the susceptibility magnetostratotype in germany with comparisons to sections in the czech republic morocco and spain abstract one major difficulty in geology is high resolution correlation among widely separated sections especially in the paleozoic where magnetostratigraphy polarity is not well established because rocks are often remagnetized where critical biostratigraphic zonation may be poor or lacking or where structural complexities make correlations very difficult to address this problem we have been using magnetostratigraphy susceptibility measurements here we report our work from the middle devonian in europe and north africa the middle devonian emsian eifelian global boundary stratotype section and point gssp located in the eifel hills western germany was ratified by the international subcommission on stratigraphy in 1985 after careful evaluation of the biostratigraphy for this and many other sections the boundary interval has been characterized using biostratigraphy and the beginning of the eifelian stage has been specifically defined by the first occurrence of the conodont polygnathus costatus partitus we have collected the eifel hills section for magnetic susceptibility ms measurement and here we establish it as the magnetostratotype for the emsian eifelian stage boundary by formally defining the magnetostratigraphy susceptibility for the section we then collected measured and compared the magnetostratotype to four other sections for which conodont biostratigraphy has been studied and where p costatus partitus is present two emsian eifelian sections in morocco and two sections in the czech republic including the emsian eifelian parastratotype finally we have measured the ms for the el puerto creek section in the cantabrian mountains of spain and identified the location of the emsian eifelian boundary within the section based on ms comparison to the gssp in conjunction with excellent biostratigraphic indicators primarily brachiopods while the conodont zonation in the el puerto creek section is poorly defined we believe that the correspondence between the ms and biostratigraphy in the section allows the identification of the emsian eifelian boundary these results indicate that this method can be successfully applied to marine sequences where ambiguities in correlation exist

ground truthing chemostratigraphic correlations in fluvial systems changes in elemental chemistry have been used to define stratigraphic correlations between wellbores in petroleum basins few publications however relate defined chemical stratigraphy to physical correlations and none have been found that do so in fluvial systems here chemostratigraphy is applied to permian fluvial sediments within the beaufort group of the karoo basin in south africa and a correlation between three logged sections is defined this correlation is tested against physically determined chronostratigraphic correlations achieved using heli lidar data to provide a high resolution correlation between two sections 7 km 4 4 mi apart and mapping of strata using google earth to produce a correlation between sections 25 5 km 15 8 mi apart the chemostratigraphic characterization that is defined using data from fine grained lithologies resulted in the recognition of eight chemostratigraphic packages with thicknesses between 50 and 250 m 164 and 820 ft over a stratigraphic interval of approximately 900 m 2953 ft two distinctive changes in geochemical composition of the coarser lithologies fluvial channel belts were seen over this interval in the two sections that are 7 km 4 4 mi apart higher resolution subdivision of chemostratigraphic packages was achieved to produce four correlative geochemical units 30 60 m 98 197 ft in thickness that provide a high resolution correlation the chemostratigraphic and chronostratigraphic correlations are in close agreement in both the 7 km 4 4 mi and the 25 5 km 15 8 mi spaced sections the thickness of the study interval and spacing of sections is analogous to published chemostratigraphy studies on subsurface sequences thereby ground truthing the use of chemostratigraphy for correlation in subsurface fluvial systems that are to some degree analogous to the beaufort group sediments of this paper

the nappe des marbres unit of the basque cantabrian basin the tectono thermal evolution of a fossil hyperextended rift basin the architecture of the pyrenean cantabrian belt results from the inversion of a series of former cretaceous rift basins a ht lp metamorphic event dated at 105 to 85 ma ago is commonly associated with an albo cenomanian episode of hyperextension of the continental crust this metamorphism is well known in the eastern basque cantabrian basin within the nappe des marbres unit nmu that is preserved from intense compressional deformation during the pyrenean orogeny based on a structural study at the scale of the eastern basque cantabrian basin bcb and on a dense sampling for trscm estimates with the rscm method raman spectrometry on carbonaceous material we show following results 1 the nmu has recorded two major phases of deformation related to a localized extensional ductile foliation s1 during the cretaceous rifting and later by the regional n s shortening recorded by a regional cleavage s2 observed only in shale sediments 2 the nmu is affected by early salt tectonics related to several diapirs and salt walls fed by the upper triassic evaporitic layer 3 the nmu recorded maximum temperatures exceeding 550 c which represent some of the highest temperatures along the pyrenees these new data demonstrate that there is no e w lateral metamorphic gradient across the belt and that hyperextension rifting occurred consistently within a high thermal regime 4 metamorphic isograds are oblique in respect of the main structures suggesting that the metamorphic event postdates most of the early salt related deformations prior to or coeval with early stages of rifting as it represents one of the best preserved example of pre orogenic hyperextended basin the eastern bcb record may be used regionally to better understand the rift to orogen evolution of the pyrenean internal metamorphic zone but also more generally as an analog of salt bearing hyper extended rift record

intraplate deformation and 3d rheological structure of the rhine rift system and adjacent areas of the northern alpine foreland the lithosphere of the northern alpine foreland has undergone a polyphase evolution during which interacting stress induced intraplate deformation and upper mantle thermal perturbations controlled folding of the thermally weakened lithosphere in this paper we address relationships among deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography we focus on lithosphere memory and neotectonics paying special attention to the thermo mechanical structure of the rhine graben system and adjacent areas of the northern alpine foreland lithosphere we discuss implications for mechanisms of large scale intraplate deformation and links with surface processes and topography evolution

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

sequence stratigraphy and systems tracts of a mixed carbonate and siliciclastic platform basin setting the albian of lunada and soba northern spain in the lunada soba carbonate platform basin setting albian of basque cantabrian region northern spain nine type 1 depositional sequences have been identified their boundaries represent times of complete exposure of the platform with accompanying karstification and fluvial erosion relative sea level falls of 15 50 m have been estimated from depths of erosion or from diagenetic effects on platform materials and facies analysis during lowstands deposits of the corresponding systems tract onlapped the platform foreslope or filled incised valleys on the platform top these deposits comprise a variety of facies limestone megabreccias derived from the platform margin allodapic grainstones hemipelagic marls fine grained turbiditic sandstones basinal lutites fine gra ned estuarine sandstones bank bafflestones and grainstones fluvio deltaic pebbly conglomerates and sandstones and shallow water orbitolinid grainstones relative sea level rises were characterized by deposition of monotonous marls in the basin and by the growth of coral rudist mud mounds and accumulations of skeletal grainstones and marls sometimes with back stepping stacking on the platform during highstands hemipelagic marls and prodeltaic and talus delta lutites and sandstones dominated in the basin whereas coral wackestones and orbitolinid grainstones sometimes with prograding clinoforms dominated on the platform transgressive surfaces have erosion or simply omission features such as pebble lags or numerous burrows respectively no well developed condensed sections exis and they are represented by thin beds of marls rich in orbitolinids transgressive and highstand systems tracts are normally difficult to differentiate both in the basin and on the platform but in sequences with an accused wedge shape the presence of back stepping and prograding stacking patterns makes it easier four main types of sequences are documented based on geometrical characteristics three of them are continuous from the platform to the basin tabular wedge shaped with tilted base and wedge shaped with incised base the fourth type scalloped is discontinuous from the platform to the basin it results from the collapse of the platform margin whose debris contributed to form the following sequence and the unveiling of the underlying sequence at the site of collapse most of the sequence boundaries suggest a tectonic influence and three of them show angular unconformities in the basin margin and or the inner platform these angular unconformities show major erosional vacuities at the cores of anticlines on the inner platform they are attributed to phases of accentuated transpression in a major strike slip tectonosedimentary environment related to the opening of bay of biscay a local curve of albian relative sea level changes correlates in part with the eustatic curve of the vail charts

pyrenean orogeny and plate kinematics 1 the evolution of the pyrenees a mountain range between iberia and eurasia has remained the subject of many debates between geologists and geophysicists for a long time by combining the identification of seafloor spreading anomalies a33o to m0 in the bay of biscay with those in the north atlantic we have derived a position of a mean pole of rotation for the entire opening of the bay of biscay four hundred kilometers of shortening took place between the iberian and eurasian plates in the pyrenean domain during the opening of the bay of biscay from chrons m0 to a33o time 118 to 80 ma the deep seismic etude continentale et oceanique par reflexion et refraction sismique ecors profile shot across the pyrenees and teleseismic data show the presence of two distinct slabs which dip to the north the southern slab is linked to the subduction of the neo tethys ocean which was created from late jurassic to early aptian simultaneously elongated back arc basins formed along the future pyrenean domain this slab was active from at least 118 ma early aptian to 100 ma late albian the northern slab active since 85 ma is linked to the subduction of the lower continental crust located south of the pyrenean domain in the upper crust normal faults as well as the north pyrenean fault became reverse faults and former back arc basins were inverted giving rise to the uplift of the pyrenees as a double asymmetrical wedge