ichnological characteristics of late cretaceous hemipelagic and pelagic sediments in a submarine high around the oae 2 event a case from the rybie section polish carpathians abstract the trace fossils alcyonidiopsis isp chondrites isp small and large palaeophycus isp planolites isp taenidium isp thalassinoides isp zoophycos isp and unnamed small spreite burrow structures have been found in the cenomanian turonian sediments in the rybie section they show significant stratigraphic variations in respect to the bonarelli level in the cenomanian from the base of the section up to just below the bonarelli level the fucoid marl in local lithostratigraphy a decrease in diversity and abundance of trace fossils and benthic foraminifers is present and related mainly to decreasing benthic food levels oxygenation changes have comparatively minor incidence but at least three thin anoxic layers occur about 2 m below the bonarelli level the bonarelli level shows the at least episodically anoxic sedimentation in the turonian part only small chondrites isp and planolites isp rarely occur the burial of organic matter and probably benthic food content was extremely low as revealed by red marls a gradual recovery of environmental conditions is marked by an increase in the diversity and abundance of trace fossils and benthic foraminifers by the turonian when grey marls egocina marl accumulated above the red marls the trends in ichnological record are confirmed by data on benthic foraminifers

trace fossils after the k t boundary event from the agost section se spain palaeogene trace fossils penetrate the uppermost cretaceous sediments in the agost section betic cordillera se spain chondrites targionii zoophycos isp planolites isp a planolites isp b thalassinoides isp a thalassinoides isp b thalassinoides isp c alcyonidiopsis longobardiae and diplocraterion parallelum have been identified a well developed endobenthic tiering pattern is interpreted the uppermost tier a represents major benthic activity in the shallowest sediments at or just below the seafloor recorded as bioturbated background only discrete rare planolites the next upper tier b displays the highest trace fossil diversity with planolites in the shallow levels and thalassinoides and alcyonidiopsis at slightly deeper ones the intermediate tier c contains randomly distributed thalassinoides and alcyonidiopsis cross cut by zoophycos and large and medium sized chondrites the deepest tier d contains zoophycos cross cut by medium and mainly small sized chondrites two interpretations are proposed 1 vertical partitioning of a singled multi tiered community under steady stable conditions in well oxygenated water bottom reflecting gradual changes deep into the sediment with decreasing oxygen pore water and benthic food and increasing substrate consistency and 2 sequential colonization and community replacement reflecting the work of two successive communities the first community mainly represented by planolites alcyonidiopsis and thalassinoides was produced in a shallow oxygenated soft substrate probably related to decreasing oxygen content and benthic food availability this community was replaced by deeply burrowing organisms that produced zoophycos and chondrites this sequential colonization can be determined by changes in environmental parameters related to the cretaceous palaeogene k t event or may have resulted from normal ecological and early diagenetic processes

reconstruction of the upper cretaceous chalks removed by dissolution during the cenozoic in the western paris basin during the cenozoic in the western paris basin atmospheric weathering of the chalks with flints of the upper cretaceous led to the creation of clay with flints a reconstitution of the chalks lost to dissolution is proposed and is based on the determination of the age of the parent chalks of the clay with flints and the quantification of the thickness of dissolved chalk the chalks affected by weathering range in age from turonian to maastrichtian thus confirming the deposition of calcareous sediments in the western paris basin up to the maastrichtian chalk weathering took place in situ as indicated by the preservation of the stratigraphic succession of the chalk in the clay with flints profiles weathering led to the dissolution of 20 200 m of chalk with regional variations the weathering rate varies between 2 1 and 14 5 m ma

ichnological record of deep sea palaeoenvironmental changes around the oceanic anoxic event 2 cenomanian turonian boundary an example from the barnasiowka section polish outer carpathians abstract trace fossil assemblages including planolites thalassinoides palaeophycus taenidium chondrites and trichichnus have been determined in the upper cenomanian turbiditic deep water succession corresponding to the pre oae 2 interval in the barnasiowka ostra gora section the skole nappe polish outer carpathians these assemblages indicate that oxygenation within sediment fluctuated from oxic to dysoxic zone the overlying uppermost cenomanian organic rich facies bonarelli equivalent horizon corresponding to the main interval of the oae 2 contains black shale layers devoid of trace fossils representing anoxic euxinic events and green shales that include chondrites planolites and thalassinoides recording dysoxic intervals three subintervals phases within the oae 2 sediments have been distinguished in the barnasiowka section based on trace fossil diversity ichnofabrics and chemical redox indices these phases correspond to intervals with various intensity of sea floor oxygenation ichnofabrics within the oae 2 succession was also controlled by consistency of sediment post oae 2 interval recorded by the earliest turonian red and green siliceous manganiferous shales and two fe mn layers represent sediments deposited in well oxygenated conditions under extremely low sedimentation rate most of the shales are parallel laminated and they do not include any benthic microfossils and trace fossils however some of the red and green layers display cryptic bioturbation these features are related to food scarcity cessation of gravity flows unfavorable characteristics of bottom water and a low consistency of substrate

impact of the paleocene eocene thermal maximum on the macrobenthic community ichnological record from the zumaia section northern spain article i nfo trace fossil assemblages from the latest paleocene to the earliest eocene were significantly affected by the environmental perturbation of the paleocene eocene thermal maximum petm high resolution ichnolo gical analysis shows well marked different ichnological features pre syn and post event a well developed normal tiered burrowing community is present in the sediments below the petm indicating oxic conditions and normal benthic food availability during the petm the record of trace fossil producers disappeared gradually but rapidly reflecting the global increase in temperature and the concentration of benthic food in the very shallow surface layer and probably the local depletion of oxygen within the sediments although probably not true anoxia the environmental perturbation significantly affected the whole benthic habitat as shown by the correspondence with the main phase of the benthic foraminiferal extinction after the petm the normal tiered burrowing community recovered gradually and slowly in a delayed return to pre petm environmental conditions the changes in the trace fossil assemblage thus document the impact of the petm on the macrobenthic community a decline in oxygen levels during the petm in a globally perturbed habitat due to global warming and the similarities and differences in the response of micro and macrobenthic communities to global phenomena thus ichnological analysis reveals as a very useful additional tool to understanding atmosphere ocean dynamic during petm and a potential way in future climate research 2011 elsevier b v all rights reserved

the last millennia history of detrital sedimentation in the lower seine valley normandy nw france review post glacial climate changes and sea level fluctuations have strongly influenced n w european environments and sedimentation to these natural events increasing anthropogenic pressure has to be added forest clearance and agricultural development are the main factors responsible for the erosional processes in northwest europe this article analyses holocene sequences of the lower seine valley lsv paris basin to understand better the origin of detrital and terrigenous input and how much humans have contributed to it three main sectors of the lsv are analysed estuarine fluvial and tributaries since neolithic times there are seven erosional phases that can be identified and essentially linked to human pressure terra nova 00 000 000 2010

boundary lines within petrologic diagrams which use oxides of major and minor elements use of some petrologic diagrams applied to analyses of volcanic rocks is unnecessarily difficult due to lack of data for construction of discriminant lines between rock series coordinates are provided for sufficient points to enable accurate plotting of the boundary lines within seven diagrams viz 1 tas total alkalies na2o k2o vs sio2 2 k2o vs sio2 3 afm 4 jensen 5 ktp k2o tio2 p2o5 6 fms feo mgo vs sio2 and 7 taktip k2o na2o k2o vs tio2p2o5 different versions of these boundaries are collated to indicate their variable position and it is demonstrated that inter laboratory analytical precision suffices to account for almost all of their spread on the tas and k2o vs sio2 diagrams

use of high resolution ichnological and stable isotope data for assessing completeness of a k p boundary section agost spain high resolution ichnological analysis has been performed at the agost section betic cordillera southeast spain in order to assess the completeness of the k p boundary transition below the biostratigraphic resolution intrasubzone high resolution planktonic foraminifera biozonation revealed that the first appearance of the palaeogene index species does not coincide with the k p boundary but is located a few centimetres above and calibrated 65 7 6 7 ky later the k p boundary to establish the continuity of this first interval of the lowermost danian hedbergella holmdelensis subzone and the existence of any hiatus below biostratigraphic resolution trace fossil analysis was revealed to be a useful tool planolites thalassinoides and alcyonidiopsis structures belonging to the upper tiers colonizing at or immediately after the k p boundary event were studied focusing on the isotopic composition of the filling materials and the genesis of thalassinoides rapid firmground generation and thalassinoides tracemaker colonization is mainly attributed to cessation of precipitation and or deposition of calcium carbonate but an incipient lithification is not disregarded the d 13 c data obtained from trace fossils fit well with those corresponding to a the k p boundary layer from 1 00x to 1 30x b the stratigraphic interval between 2 5 and 5 0 cm above the k p boundary between 0 32x and 0 47x and c the interval between 7 0 and 11 0 cm above the k p boundary between 0 69x and 0 79x revealing continuity in the colonization from the k p boundary event to the dark clay deposition above this macrobenthic colonization occurred continuously during the dark layer deposition from the k p boundary layer including the first centimetres evidencing completeness and the absence of hiatuses below biostratigraphic resolution intrasubzone at the agost section d 2005 elsevier b v all rights reserved

the early toarcian oceanic anoxic event in the external subbetic southiberian palaeomargin westernmost tethys geochemistry nannofossils and ichnology abstract the analysis of macroinvertebrates trace fossils calcareous nannofossils and geochemistry from pliensbachian to lower toarcian deposits of the subbetic southern spain allows us to interpret the incidence of the toarcian oceanic anoxic event t oae in the boundary between the tethys and the hispanic corridor trace fossils from the marl limestone rhythmite upper pliensbachian to lower toarcian indicate an oxygenated bottom a dark marly interval occurs above a fossil rich condensed surface with a negative excursion of 18o interpreted as evidence of the early toarcian transgression and a climate warming the carbon cycle perturbation is recorded by decreasing caco3 content and the negative excursion of 13c at the base of the serpentinum zone njt 6 nannofossil zone the barren interval for nektonic and benthic organisms at the beginning of the serpentinum zone confirms the oxygen restricted conditions in the sea floor environmental conditions were unfavourable for the development of calcareous nannoplankton as attested by the drop in absolute abundances the deep photic zone seemed to be particularly hostile to phytoplankton as shown by the decrease in relative abundance of the deep dweller mitrolithus jansae related to shoaling of the oxygen minimum zone in the water column increasing values of redox sensitive elements and total organic carbon as well as the record of pyrite framboids

nutrient spatial variation during intrabasinal upwelling at the cenomanian turonian oceanic anoxic event in the westernmost tethys an ichnological and facies approach abstract facies and ichnofabrics of two sections of the cenomanian turonian boundary interval are correlated and compared to evaluate changes in palaeoceanographic conditions controlled by palaeogeography in the distal zone of the westernmost tethys southern iberian continental palaeomargin the oceanic anoxic event oae 2 was interrupted by short aerobic or dysaerobic sub events with slight differences in facies and ichnofabrics these sub events display a tendency to expansion from the more distal section hedionda towards the proximal one el chorro the anoxia spread out from the open sea probably from slope upwellings higher diversity and abundance of trace fossils in comparatively distal position during the pre and post event intervals can be caused by a higher abundance of food available for tracemakers shape of the correlation bands of the oae 2 event suggests that the event started earlier by about a few tens of thousands years in the most distal areas than in proximal slightly higher bottom settings

stream water geochemistry from mine wastes in pena de hierro riotinto area sw spain a case of extreme acid mine drainage in this work we have studied the geochemistry of stream waters arising from waste dumps at the pena de hierro mine iberian pyrite belt sw spain and we have correlated them with the mineralogical and geochemical characteristics of the wastes to asses the source and factors affecting the release of trace elements the mineralogical composition and geochemistry of 58 borehole samples of waste dumps were studied in the 2 mm fraction twenty eight water samples collected in winter and summer from streams emerging from the waste dumps were analysed for ph eh conductivity temperature sulphates and major and trace elements the leachates from pyrite rich volcanic tuffs produced very acidic waters usually with phs below 2 and reaching values as low as 0 7 the partial dissolution of gossan which is mainly composed of fe oxy hydroxides and is rich in trace elements released high concentrations of fetot up to 33 g l as up to 72 mo up to 11 mg l on the other hand cd zn and pb reached up to 0 85 142 and 0 42 mg l respectively in the stream arising from roasted pyrite ashes and other pyritic wastes several elements such as al fe as co cu and mo were strongly correlated with the ph but cd and zn were not correlated under such acidic conditions the precipitation of jarosite seems to be an important factor in the retention of pb the mobility sequence of trace elements shows that co zn and cd were among the most mobile elements cu as and mo had intermediate mobility and pb was the most immobile this work shows that uncontrolled waste dumping increases the pollution potential and a selective management could reduce the release of trace elements into stream waters and mitigate the contamination

ichnological analysis of the bidart and sopelana cretaceous paleogene k pg boundary sections basque basin w pyrenees refining eco sedimentary environment abstract ichnological analysis of two cretaceous paleogene boundary sections at bidart se france and sopelana n spain has been conducted in order to refining eco sedimentary environment and to a make comparison with previous interpretations based on microfossils in both sections trace fossil assemblage is low diverse consisting of chondrites planolites thalassinoides trichichnus zoophycos and phycosiphon ascribed to the zoophycos ichnofacies however with distinct differences in the bidart section early danian dark filled trace fossil assemblage is more abundant in large thalassinoides zoophycos and larger chondrites and less abundant in trichichnus and small chondrites in comparison to the sopelana section sopelana is thus interpreted as a more offshore deeper section than bidart although both were located in the upper bathyal zone of the basin oxygenation below the sediment water interface was enough to favour a generalized total bioturbation of sediments the presence of chemichnia and trace fossils which tracemakers sequestered sediments from the sea floor in deep burrows zoophycos suggests at least periodical food deficiency the distribution and content of trace fossils across the k pg boundary do not change significantly revealing minor incidence of the k pg boundary event on the macrobenthic environment the k pg boundary transition including the boundary layer is nearly totally bioturbated hence a redistribution of microbiotic and abiotic components by tracemakers is possible

rio tinto estuary spain 5000 years of pollution mining of massive sulfide deposits in southwestern spain extending back to the copper and bronze ages has resulted in the pollution of the rio tinto fluvial estuarine complex the site of columbus departure for the new world in 1492 additional sources of potential pollution include the large industrial complex at huelva near the lower portion of the estuary extensive analysis of surface sediment samples and cores has established that there are no geographic trends in the distribution of the pollutants which include cu fe pb zn ti ba cr v and co these data have however demonstrated that tidal flux within the estuary carries phosphorus and perhaps other elements from the industrial complex at huelva to the tidal limit of the system several kilometers upstream from the discharge site radiometric analysis of short cores shows that sedimentation rates over at least the past couple of centuries have been about 0 3 cm year these data and that from a single deep core demonstrate that the estuary was polluted from mining activity long before the large scale operations began in the late nineteenth century

magmatic relationships and ages between adakites magnesian andesites and nb enriched basalt andesites from hispaniola record of a major change in the caribbean island arc magma sources abstract located in the cordillera central of the dominican republic the late cretaceous tireo fm tf records a major change of the magma sources in the caribbean island arc it comprises a 3 km thick sequence of arc related volcanic and volcano sedimentary rocks with variable geochemical characteristics combined detailed mapping stratigraphy geochemistry and u pb ar ar geochronology show that the volcanic rocks of the tireo fm include two main volcanic sequences the lower volcanic sequence is dominated by monotonous submarine vitric lithic tuffs and volcanic breccias of andesite to basaltic andesite with minor interbedded flows of basalts and andesites fossil and u pb and 40ar 39ar geochronological data show that arc magmatism in the lower sequence began to accumulate before 90 ma from the aptian to turonian these rocks constitute an island arc tholeiitic suite derived from melting by fluxing of a mantle wedge with subduction related hydrous fluids the upper volcanic sequence is characterized by a spatial and temporal association of adakites high mg andesites and nb enriched basalts which collectivelly define a shift in the composition of the subduction related erupted lavas a dacitic to rhyolitic explosive volcanism with subaerial and episodic aerial eruptions and sub volcanic emplacements of domes characterize mainly this stratigraphic interval the onset of this volcanism took place at turonian coniacian boundary and continued in the santonian to lower campanian with minor events in the late campanian adakites represent melts of the subducting slab magnesian andesites the product of hybridization of adakite liquids with mantle peridotite and nb enriched basalts melts of the residue from hybridization we propose a model of oblique ridge subduction at 90 ma and possibly subsequent slab window formation as principal cause of magmatic variations recorded in the caribbean island arc above a southwestern dipping subduction zone

petrochemistry and tectonic significance of cretaceous island arc rocks cordillera oriental dominican republic abstract cretaceous island arc rocks of the caribbean island arc system have been exposed by cenozoic faulting in the cordillera oriental in eastern hispaniola high k 2 o intermediate to felsic volcanic rocks loma la vega volcanics are interbedded with marine epiclastic sedimentary rocks and tuffs las guajabas tuffs and unconformably overlie pre aptian sedimentary rocks low k 2 o volcanic rocks guamira volcanics and a granodioritic to tonalitic intrusion el valle pluton the petrology and geochemistry of these units in conjunction with regional stratigraphic data are used to speculate on the tectonics of the newly developing caribbean island arc system during early and late cretaceous time the loma la vega volcanics are characterized by the presence of large phenocrysts of sanidine and minor amounts of clinopyroxene opaque oxides and rare leucite in a devitrified matrix of chlorite and clay although the volcanic rocks have undergone some low temperature alteration metamorphism which redistributed some major elements and large ion litho phile trace elements the high field strength elements rare earth elements and radiogenic isotopes appear to have been minimally affected based on abundances of the relatively immobile elements trace element enrichment patterns and isotopic compositions the loma la vega volcanics are considered part of the high k calc alkaline ca or shoshonitic island arc volcanic series in contrast pre aptian early cretaceous volcanic and plutonic rocks of the underlying los ranchos formation have chemical characteristics similar to rocks in the island arc tholeiitic or primitive island arc pia series that form coeval and along strike sections of the early cretaceous caribbean island arc in other parts of present day hispaniola cuba puerto rico and the virgin islands an abrupt and regional change in composition from island arc tholeiites to high k calc alkaline rocks is coincident with a hypothesized reversal in subduction polarity in pre aptian time as inferred from previously published tectonic models polarity reversal may have been triggered by attempted subduction of the caribbean oceanic plateau beneath this segment of the caribbean island arc the observed magmatic and tectonic effects of the proposed cretaceous caribbean arc reversal are similar to the better documented neogene subduction reversal event in the solomon islands arc in the southwest pacific

holocene evolution of a wetland in the lower seine valley marais vernier france estuaries like that of the seine river in nw europe developed in incised fluvial valleys after the last glacial maximum since the 1940s several authors have studied the largest wetland of the seine estuary the marais vernier to understand depositional environments during holocene infilling we reinterpret previous research based on new and published data for example fill thickness and material source to 1 describe facies and depositional environments 2 reconstruct palaeoenvironmental evolution 3 show the influence of local and global forcing on depositional environments before 7000 6000 cal bc terrestrial material was deposited because of catchment erosion related to changes in climate just before 7000 6000 cal bc estuarine material began to be deposited in low lying areas in response to sea level rise while terrestrial material still settled at higher elevations after this but before 5850 5710 cal bc estuarine material areas began to accumulate at both high and low elevations this marked a general flooding of the marais vernier synchronous with that at the seine estuary mouth soon after peat accumulated over a wide area as a response to a local change in accommodation and a worldwide drop in sea level a tidal channel developed to the west of the marais vernier providing minerogenic material after 1130 900 cal bc human influence becomes increasingly clear in the record this record of regional change during the holocene can serve as a reference for further studies in the area

fe oxide spherules infilling thalassinoides burrows at the cretaceous paleogene k p boundary evidence of a near contemporaneous macrobenthic colonization during the k p event a detailed ichnological analysis focused on thalassinoides structures recorded just below the cretaceous paleogene k p boundary layer of the agost section southeast spain aimed to evaluate macrobenthic colonization during the k p boundary event stereomicroscopy and field emission scanning electron microscopy analyses conducted on material filling in thalassinoides trace fossils reveal the presence of dark infill material that includes spherule like elements similar to those previously differentiated in the k p boundary layer energy dispersive x ray spectrometry indicates a ferruginous composition goethite spherules this represents the first record of spherules related to the k p boundary event within trace fossil infilling material the passive filling of this material into the thalassinoides bioturbation allows interpretation of the gravitational deposition just after thalassinoides trace maker colonization the absence of erosive sedimentary structures or other material deposited between the thalassinoides trace maker colonization and the spherule deposition is interpreted as evidence of rapid colonization during the k p boundary event nearly contemporary with the spherule layer deposition

carbon isotope evidence for the timing of the cretaceous palaeogene macrobenthic colonisation at the agost section southeast spain abstract the cretaceous palaeogene k t boundary section of agost southeast spain one of the most complete sections existing contains a well developed trace fossil assemblage composed of dark and light filled trace fossils registered in the uppermost cretaceous maastrichtian plummerita hantkeninoides biozone sediments the trace fossil assemblage reveals that significant macrobenthic colonisation occurred around the k t boundary interval however difficulties in recognising trace fossils affecting the k t boundary layer as well as in biostratigraphically characterising these trace fossils hindered a conclusive interpretation on the timing of this macrobenthic colonisation with the aim of this characterisation we determined the 13c of the carbonate fraction of dark and light filling materials from the trace fossils since the carbon isotope compositions of uppermost cretaceous and lowermost palaeogene materials are clearly different the data compiled provide evidence for a significant distinction between light filled trace fossils with 13c values higher than 1 6 peedee belemnite pdb and dark filled trace fossils with 13c values between 0 21 and 1 2 pdb most of these being lower than 0 7 pdb the comparison of these values with those from the uppermost maastrichtian to the lowermost danian sediments reveals that the macrobenthic colonisation occurred in different phases across the k t boundary interval

the neogene and quaternary clay with flints north and south of the english channel comparisons of distribution age genetic processes and geodynamics weathered residual accumulations termed clay with flints argiles a silex overlying cretaceous deposits are widespread in southern england and northwestern france geological and pedological studies and some field surveys indicate their distribution nature age and origin in france the microfaunas preserved in the hollow flints of the clay with flints demonstrate the preservation of the parent chalk stratigraphy in the sections studied i e the clay with flints corresponds to in situ weathering profiles however in england and in france an important part of the clay component is derived from a thin veneer of basal tertiary sediment overlying sub tertiary marine erosion surfaces of various palaeogene transgressions in england as in france the youngest generation of clay with flints can be dated from late pliocene to quaternary it formed after removal of different cenozoic deposits on many plateaus and during the downcutting of pleistocene rivers the most visible effect of subsequent weathering profile development is irregular dissolution of the underlying chalk to produce deep karstic pipes into which the clay with flints has slumped other pedological processes include rubification clay illuviation and cryoturbation clay with flints also provides evidence of quaternary palaeoenvironments cenozoic continental palaeosurfaces and their vertical deformation copyright 2003 john wiley sons ltd

the clay with flints of the western paris basin a potential aggregate resource with future increasing restrictions on extraction of alluvial materials for aggregate production the paris basin in particular is faced with the problem of substituting up to 62 more than 50 mt year of its requirements from other sources the clay with flints formation to the north west west and south east of paris has been the subject of intense studies aimed at determining its suitability as a potential source of substitute aggregate material the formation is located much closer to paris than alternative resources and because the cost of transport constitutes a major factor in the price of aggregates proximity to consumption centres is of prime importance two potential resources targets have been identified within the clay with flints the slope located clay with flints named bief a silex in france despite being rich in flint form deposits that are too small for industrial scale exploitation in addition the biefs a silex tend to be located in forested areas and subjected to environmental constraints where the plateau located clay with flints attains a thickness in excess of 30 m notably in northern eure et loir and southern eure departments an increase in the proportion of flint from 10 m downwards opens up the possibility of dry processing separation of the fine grained clayey matrix either direct from the quarry or after open air drying wet processing has been shown to be unrealistic because of the vast amounts of water that would be required the plateau deposits show far fewer environmental constraints and the resource potential for substituting a significant part of alluvial material consumption in the paris basin is excellent

use and abuse of the terms calcalkaline and calcalkalic the terms calcalkaline and calcalkalic are currently defined and used in multiple and non equivalent ways generally the variation of total fe as feo mgo within evolving subalkaline rock suites is regarded as the most distinctive character of calcalkaline compared with tholeiitic suites reflecting the relative timing of phase saturation with fe ti oxides plagioclase and ferromagnesian silicates other classification schemes are widely used including a minority of adherents to the original formalized definition of calcalkalic by peacock 1931 journal of geology 39 54 67 given the prevailing contradictory and confusing usage of these terms which leads to miscommunication it is proposed that the spectrum of subalkaline rocks be divided into high medium and low fe suites complementing divisions made on the basis of k contents the terms calcalkaline and calcalkalic should be restricted to rock suites that conform to peacock s definition

geological record of an acidic environment driven by iron hydrochemistry the tinto river system 1 the existence of possible hematitic strata on the surface of mars demands a search for terrestrial analogues formed in unusual environments this will help us to recognize and interpret environmental and perhaps biological signatures preserved in mars hematites such an analogue would allow us to establish valid reference systems based on geomicrobial and biogeochemical signatures two different aspects place the tinto river inside the boundaries of a natural extreme system its high level of biological diversity and the presence of fluvial rocks formed in the same acidic conditions as in the modern system which could predate the tertiary study of both the modern system and the ancient system is necessary to understand the formation of biosignatures a chemolithotrophic community that biooxidizes the iberian pyritic belt acidifying water ph between 0 9 and 3 0 and favoring high concentrations of ferric iron in solution up to 20 g l 1 maintains this iron driven system in spite of these extreme conditions high microbial diversity was found its acidic bacteria archaea and eukarya constitute a complex community supported by algal biomass in highly stable hydrochemical conditions which are achieved through iron buffering the ph is maintained at constant low levels even at very high water dilution in these conditions iron minerals as oxyhydroxides hydroxides and sulfates are formed the modern and recent parageneses contrast with the ancient tinto river terrace mineral associations which show dehydrated and desulfated iron oxides if this dehydration process is considered these tinto river ironstones may be a key for knowing some aquatic habitats which may have hosted a part of the early mars biosphere

age of the los ranchos formation dominican republic timing and tectonic setting of primitive island arc volcanism in the caribbean region this study reports u pb ages for zircons from the los ranchos formation which is part of the primitive island arc sequence the oldest volcanic rocks in the greater antilles zircons were analyzed from three samples quartz porphyry quartz keratophyre from the lower part of the formation quita sueno member fragmental quartz porphyry from the upper part of the formation pueblo viejo member and the cotui quartz diorite stock that intrudes the lower part of the formation the lower part of the los ranchos formation represented by the quita sueno sample formed at either 113 9 0 8 or 118 6 0 5 ma depending on interpretation of the data whereas the upper part represented by the pueblo viejo sample formed ca 110 9 0 8 ma the cotui stock rd 73 601 was emplaced ca 111 8 0 6 ma or 112 9 0 9 ma depending on whether eight grains reflect subtle inheritance these results show that the los ranchos formation was emplaced during the aptian albian transition that the cotui stock could have supplied magma to the volcanic sequence and fluids to the pueblo viejo gold silver deposit in the upper part of the formation and that carbonaceous sediments in the upper part of the formation formed at the same time as ocean anoxic event 1b paquier caribbean plate tectonic models involving invasion of anomalous pacific crust into the caribbean region appear to agree best with this age because they provide a mechanism for the change from primitive island arc pia to calcalkaline magmatism and account for the restricted ocean circulation necessary to generate regional anoxic conditions

petrogenesis of plagiogranite and associated diorites and mafic rocks in the habana matanzas ophiolites northwestern half of central cuba structural field relationships petrography and geochemical features of plagiogranites and associated intermediate diorite to mafic rocks basalt and gabbro of the habana matanzas ophiolites in northern cuba suggest that these felsic and mafic rock units represent a boundary case between forearc and volcanic arc ophiolite types subduction related basalts can be subdivided into back arc back arc to forearc forearc and volcanic arc types the majority of the basalts plot in the oceanic arc as well as joint oceanic arc continental arc field of the th yb nb yb diagram the samples that classify as volcanic arc basalts plot in the continental arc field of the th yb nb yb diagram and within the island arc tholeiite and boninite fields in the v ti diagram the habana matanzas plagiogranites and associated basalts diabases and gabbros display significantly negative ta nb anomalies and are depleted in heavy rare earth elements 40ar 39ar whole rock plateau ages of these plagiogranites reveal minimum crystallization ages of 98 11 0 50 ma providing the first important time constraint for suprasubduction zone oceanic crust formation on the island of cuba based on our petrogenetic modelling and geochemical characterization we conclude that magmas of the plagiogranites and associated intermediate rocks of the habana matanzas ophiolites were derived from partial melting of highly depleted pre existing crustal rocks basalt and or gabbro thematic collection this article is part of the tethyan ophiolites and tethyan seaways collection available at https www lyellcollection org cc tethyan ophiolites and tethyan seaways

is the cretaceous primitive island arc series in the circum caribbean region geochemically analogous to the modern island arc tholeiite series the early cretaceous island arc lavas in the caribbean region are frequently assigned to the primitive island arc pia series and not to the island arc tholeiite iat series however this review demonstrates that the caribbean pia rocks have immobile trace element abundances trace element ratios and nd hf isotope systematics which are indistinguishable from modern iat lavas thus it is proposed that the term pia series be discarded and that the early cretaceous island arc rocks in the caribbean be classified as iat rocks

slope clay with flints biefs a silex as indicators of quaternary periglacial dynamics in the western part of the paris basin france the lithology and distribution of the clay with flints occurring on slopes called biefs a silex in french suggests a twofold classification of these deposits according to slope angle biefs a silex formed as a solifluction deposit under quaternary periglacial conditions during valley development two biefs a silex facies suggest two phases of development between 800 000 and 20 000 yr bp copyright 2003 john wiley sons ltd

methodological issues raised by laser particle size analysis of deposits mapped as clay with flints from the palaeolithic site of dickett s field yarnhams farm hampshire uk abstract lower and middle palaeolithic stone tools evidence of the earliest occupation of britain are frequently to be found in association with deposits mapped as clay with flints which cap the highest chalk downland hilltops and plateaux of southern england these superficial deposits exhibit great lithological variability i e clay with flints sensu lato including plateau drift clay with flints sensu stricto loess and waterlain brickearths on both a local and regional geographical scale field observations suggest that particular facies of the clay with flints deposits in addition to the presence of solution features may be implicated in the retention of palaeolithic artefacts on these high levels detailed interpretation of sedimentological analyses is therefore required to identify a preservation potential correlation for palaeolithic sites on deposits mapped as clay with flints much of what is generally known about the sedimentology of these deposits is found in literature where the classic sieve and sedimentation methods pipette or hydrometer have been adopted to determine quantitatively particle size distribution of soils refinement in particle size methodologies of the fine fraction through the introduction of laser diffraction granulometry makes it difficult to compare laser research results with published data based on the use of the sieve sedimentation methods this presents problems when attempting to use the available data for both intra and inter palaeolithic site analysis our objective was to find suitable limits for the clay silt and sand fractions to enable calibration between the sieve sedimentation methods and laser diffraction granulometry which underestimates the clay fraction the resultant methodologies described here allow such calibrations to be made with confidence by applying these methodologies geologists soil scientists geomorphologists archaeologists and other workers can access important comparative sedimentological data that would otherwise not be available for interpretation of the depositional context of the sediments soils and any artefacts they may contain samples from the palaeolithic site of dickett s field yarnhams farm holybourne hampshire provided the focus of this work

the rio tinto basin spain mineralogy sedimentary geobiology and implications for interpretation of outcrop rocks at meridiani planum mars abstract exploration by the nasa rover opportunity has revealed sulfate and hematite rich sedimentary rocks exposed in craters and other surface features of meridiani planum mars modern holocene and plio pleistocene deposits of the rio tinto southwestern spain provide at least a partial environmental analog to meridiani planum rocks facilitating our understanding of meridiani mineral precipitation and diagenesis while informing considerations of martian astrobiology oxidation thought to be biologically mediated of pyritic ore bodies by groundwaters in the source area of the rio tinto generates headwaters enriched in sulfuric acid and ferric iron seasonal evaporation of river water drives precipitation of hydronium jarosite and schwertmannite while mg al fe3 copiapite coquimbite gypsum and other sulfate minerals precipitate nearby as efflorescences where locally variable source waters are brought to the surface by capillary action during the wet season hydrolysis of sulfate salts results in the precipitation of nanophase goethite holocene and plio pleistocene terraces show increasing goethite crystallinity and then replacement of goethite with hematite through time hematite in meridiani spherules also formed during diagenesis although whether these replaced precursor goethite or precipitated directly from groundwaters is not known the retention of jarosite and other soluble sulfate salts suggests that water limited the diagenesis of meridiani rocks diverse prokaryotic and eukaryotic microorganisms inhabit acidic and seasonally dry rio tinto environments organic matter does not persist in rio tinto sediments but biosignatures imparted to sedimentary rocks as macroscopic textures of coated microbial streamers surface blisters formed by biogenic gas and microfossils preserved as casts and molds in iron oxides help to shape strategies for astrobiological investigation of meridiani outcrops

ichnological analysis of the cretaceous palaeogene boundary interval at the caravaca section se spain abstract ichnological analysis of the cretaceous palaeogene k pg boundary at caravaca betic cordillera southeast spain reveals significant data for the interpretation of the k pg boundary event the uppermost maastrichtian marls below the cretaceous palaeogene k pg boundary at caravaca contains the dark coloured trace fossils chondrites targionii planolites thalassinoides zoophycos and alcyonidiopsis the composition of trace fossil associations in the upper maastrichtian and lower danian marls is generally the same yet much more poorly preserved in the latter showing in general no ichnological evidence of a severe macroinfaunal crisis at the k pg boundary the dark coloured trace fossils penetrate from two bioturbated horizons in the dark boundary layer separated by two horizons with primary lamination the ichnofauna rapidly recovered after the k pg event following deposition of the lower parallel laminated bed 14 mm thick that occurs in the dark boundary layer above the k pg boundary zoophycos is the deepest trace fossil penetrating as far as 90 cm below the k pg boundary probably in stiff or partly firm substrate which was dewatered to some extent during the slow accumulation of the danian dark boundary layer the firmness probably prevented the chondrites trace maker from deeper burrowing the maastrichtian sediments may be contaminated with danian microfossils due to bioturbation

modification of an oceanic plateau aruba dutch caribbean implications for the generation of continental crust the generation of the continental crust may be connected to mantle plume activity however the nature of this link and the processes involved are not well constrained an obstacle to understanding relationships between plume related mafic material and associated silicic rocks is that later tectonic movements are liable to obscure the original relationships particularly in ancient greenstone belts studies of younger analogous regions may help to clarify these relationships on the island of aruba in the southern caribbean a sequence of partly deformed mafic volcanic rocks intruded by a predominantly tonalitic batholith is exposed the mafic lavas show geochemical and isotopic affinities with other basaltic picritic and komatiitic rocks that crop out elsewhere in the caribbean these are well documented as belonging to an 88 91 ma plume related oceanic plateau which is allochthonous with respect to the americas and is thought to have been formed in the pacific region the 85 to 82 ma tonalitic rocks share some geochemical characteristics high sr and ba low nb and y with archaean tonalite trondhjemite granodiorite ttg suites field relationships suggest that deformation of the plateau sequence possibly related to collision with a subduction zone was synchronous with intrusion of the aruba batholith new incremental heating 40ar 39ar dates combined with existing palaeontological evidence show that cooling of the batholith occurred shortly after eruption of the plateau basalt sequence sr nd isotopic data for both rock suites are uniform 87sr 86sri 0 7035 endi 7 whereas pb isotopes are more variable plateau sequence 206pb 204pb 18 6 19 1 207pb 204pb 15 54 15 60 208pb 204pb 38 3 38 75 aruba batholith 206pb 204pb 18 4 18 9 207pb 204pb 15 51 15 56 208pb 204pb 38 0 38 5 this suggests that there has been a minor sedimentary input into the source region of the batholith however the limited time interval between basaltic and tonalitic magmatism makes a normal subduction related origin for the tonalites improbable instead models involving derivation of tonalite from partial melting of the plateau sequence or alternatively genesis in an unusual subduction zone environment are investigated

palaeoenvironmental turnover across the ypresian lutetian transition at the agost section southastern spain in search of a marker event to define the stratotype for the base of the lutetian stage marker events to define the stratotype for the base of the lutetian stage are poorly defined to elucidate such markers and characterize palaeoenvironmental turnovers we conducted an integrated study of the ypresian lutetian y l early middle eocene transition at the continuous agost section southeastern spain this 115 m thick section which consists of hemipelagic marls intercalated with hemipelagic limestones and turbidity sandstones spans from planktic foraminiferal zones p9 to p12 e7 to e10 and calcareous nannofossil zones cp11 to cp14a np13 to np16 we report quantitative analyses of planktic and benthic foraminifera and characterization of trace fossil assemblages that are integrated with mineralogical analyses relative to benthic forms planktic foraminifera constitute more than 80 of the foraminiferal assemblage we found that the most abundant planktic species belong to the genera acarinina morozovella subbotina and psudohastigerina benthic foraminiferal assemblages are strongly dominated by calcareous taxa with bolivinids being the most abundant group trace fossils showed the succession nereites zoophycos cruziana ichnofacies throughout the agost section in addition to changes in palaeobathymetry we deduced that quantity and quality of organic matter flux influenced by turbidity currents are the main factors controlling benthic assemblages we distinguished several mineralogical boundaries at the agost section each associated with lithological facies changes suggesting a change in provenance rather than changes in weathering conditions we made three observations that indicate an increase in sea water temperatures or a possible hyperthermal event related to the first occurrence fo of hantkeninids i e the p9 p10 boundary 1 a distinct peak in abundance of the benthic foraminifera aragonia aragonensis 2 the low diversity of benthic foraminiferal assemblages and 3 the occurrence of the planktic foraminifera clavigerinella eocenica and clavigerinella jarvisi benthic foraminiferal and trace fossil assemblages also suggest an associated relative fall of sea level from upper middle bathyal to sublittoral depths these characteristic indicators point to this boundary as a promising feature for defining the global stratotype section and point gssp for the base of the lutetian stage however complementary magnetobiostratigraphic studies carried out at the agost section point to the fo of calcareous nannofossil blackites inflatus base of cp12b which occurred 3 5 myr before the p9 p10 boundary as the most suitable primary marker event whatever the marker event chosen all the successive events recognized at the agost section allow a complete characterization of the y l transition and thus this section may be a suitable candidate to locate the gssp for the ypresian lutetian boundary c 2008 elsevier b v all rights reserved

palaeoenvironmental changes during the danian selandian boundary interval the ichnological record at the sopelana section basque basin w pyrenees abstract ichnological analysis was conducted in the danian selandian d s boundary interval from the sopelana section basque basin northern spain to improve characterization of the recently defined global stratotype section and point of the base of the selandian stage middle paleocene in the nearby zumaia section and to interpret the danian selandian boundary event with its associated palaeoenvironmental changes the trace fossil assemblage of the boundary interval is relatively scarce and shows low diversity consisting of chondrites planolites thalassinoides trichichnus and zoophycos which cross cut a diffuse burrow mottled background typical of a normal burrowing tiered community distribution of trace fossils shows local drops in abundance and diversity just above the d s boundary and about half a metre upwards into the succeeding selandian generally the selandian part of the section has slightly lower trace fossil diversity and abundance this is interpreted as due to a higher detrital food supply corresponding to a sea level fall in contrast to a decreased food supply during the selandian sea level rise smaller scale fluctuations of trace fossil diversity and abundance are also interpreted as due more to food content fluctuations in the sediment than to oxygenation of pore waters results reveal the minor influence of an extreme warming event hyperthermal conditions at the d s boundary which affected the whole benthic habitat contrarily a probable major effect of sea level fluctuations can be envisaged which determined variations in siliciclastic input and food content

stratigraphic and petrochemical data support subduction polarity reversal of the cretaceous caribbean island arc stratigraphic and petrochemical data from island arc rocks in the ne caribbean support previously proposed tectonic models of attempted subduction of the caribbean oceanic plateau beneath the caribbean island arc during pre aptian time 119 ma and consequent reversal of arc polarity from sw facing to ne facing by the early late cretaceous 97 ma we propose that reversal in subduction polarity is marked by an abrupt change from relatively depleted and non radiogenic tholeiites of the primitive island arc series to more enriched and radiogenic volcanic rocks of the calc alkaline series the stratigraphic contact between the primitive island arc series and the overlying calc alkaline series in central and eastern hispaniola dominican republic and puerto rico is a major unconformity overlain by a shallow marine limestone of aptian albian age we compare the characteristics of the proposed pre aptian caribbean subduction reversal event to the better documented neogene subduction reversal event in the so

the timing and pattern of biotic recovery following the end permian mass extinction the aftermath of the great end permian period mass extinction 252 myr ago shows how life can recover from the loss of 90 species globally the crisis was triggered by a number of physical environmental shocks global warming acid rain ocean acidification and ocean anoxia and some of these were repeated over the next 5 6 myr ammonoids and some other groups diversified rapidly within 1 3 myr but extinctions continued through the early triassic period triassic ecosystems were rebuilt stepwise from low to high trophic levels through the early to middle triassic and a stable complex ecosystem did not re emerge until the beginning of the middle triassic 8 9 myr after the crisis a positive aspect of the recovery was the emergence of entirely new groups such as marine reptiles and decapod crustaceans as well as new tetrapods on land including eventually dinosaurs the stepwise recovery of life in the triassic could have been delayed either by biotic drivers complex multispecies interactions or physical perturbations or a combination of both this is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large scale evolution from a much more devastated planet and biota than the others with only some 10 of species surviving the epme was much harsher than the other mass extinctions during which global species diversity reduced to only about 50 of the pre extinction total 1 2 24 26 this means that the triassic recovery has two profound implications first it may show qualitative as well as quantitative differences from the other post extinction recoveries and second it can act as an exemplar of what to expect at its most extreme when global biodiversity is pushed to the brink there are obvious implications for current concerns about biodiversity loss and recovery resulting from human impacts 27 28 in the past ten years attention has focused on the sedimentary successions in south china these are enormously laterally extensive with some formations extending more than 2 000 km from the zhejiang to yunnan provinces the huge exposures length of the sections and improving dating open up the opportunity to explore physical environmental and biotic changes through the extinction and recovery times in varied marine habitats and compare these with patterns elsewhere in the world fig 1 a fine scale forensic analysis of this extraordinary time in earth s history now becomes possible the end permian mass extinction the epme killed 80 96 of marine animal species and 70 of terrestrial vertebrate species

tectonic evolution of the caribbean the development of the caribbean is discussed in terms of modern tectonic theory the nature of the site on which the caribbean formed is examined and the development of the rifted margins of the caribbean is described constraints on caribbean evolution from the relative motions of north and south america are briefly examined and the caribbean oceanic plateau is discussed the great island arc system of the caribbean is addressed in detail emphasizing the way the great arc of the caribbean was segmented the role of central america in caribbean history is briefly considered

earthworm activity and archaeological stratigraphy a review of products and processes the activity of earthworms has long been understood to have significant effects on archaeological stratigraphy but many of the details have not been fully grasped by stratigraphers or by the specialists who advise them although worms are widely known to cause the burial of finds due to surface casting some of their other activities are less commonly recorded amongst these their active burial of stones and seeds their building of cairns and their production of calcium carbonate granules have mostly not been studied in any detail and have been little exploited from an interpretative point of view this paper reviews the existing knowledge as well as presenting some recent research carried out into various aspects of worm actions and their relationship to taphonomy

microgranulometric approach to a chalk karst western paris basin france abstract by definition karst is the result of dissolution and if the rock is not completely soluble residues will remain acquired particles these insoluble residues provide a history of karstic activity and can be found in the outflows after a possible storage period in the endokarst a direct connection even if temporary between the endokarst and the surface is reflected by the contribution of particles which are referred to as inherited we have studied the chalk karsts of haut normandie by comparing microgranulometric spectra of suspended matter sm in subterranean waters and in solutions of the main surface formations clay with flints complex cfc and loess and the chalk dissolution products of all local stratigraphic levels based on these microgranulometric spectra we propose a conceptual model for processes occurring in chalk karsts and a classification scheme for karstified systems according to how such systems deal with particles in a closed karst the suspended matter tends to come from the chalk itself while in the case of an open karst the majority of suspended particles comes from surface formations this notion of openness differs from the currently used categorization into allogenic and autogenic systems which depends upon an impermeable cover concentrating the infiltration

lateral and vertical variations in contaminated sediments from the tinto river area huelva sw spain incidence on tracemaker activity and implications of the palaeontological approach abstract geochemical and ichnological analyses of the tinto river area sw spain reveal the presence of macro tracemakers colonizing highly contaminated soils we found high concentrations of heavy metals and related elements mainly accumulated in the upper parts biofilms and thin salty crusts some concentrations including those of cu zn and as exceed the intervention levels for natural areas and indicate potentially toxic conditions ichnological analysis reveals the presence of biogenic structures produced by the activity of the earthworm lumbricus terrestris and the coleoptera platystethus both alternatives for colonization can be correlated with those used by fossil tracemakers and they serve to better understand biotic recovery after bio events in the past

geochemistry of quaternary sediments in terraces of the tinto river sw spain paleoenvironmental implications abstract the tinto river shows very high concentrations of toxic elements and acidity from its source in the mining area to its mouth in this paper we studied the evolution of the levels of toxic elements during part of the quaternary from the analysis of fluvial deposits that forming terraces were originated by the dynamics of the tinto river using a detailed geomorphological cartography up to nine terrace levels were differentiated in the lower sector of the basin whose ages range from the pleistocene to the holocene sampling and geochemical analyses major elements and trace were carried out in six of these levels in addition to sediments of the current flood plain the results of these analyses do not show any bias from the mid pleistocene t8 terrace 8 to the early holocene t1 moreover these geochemical contents are similar to the average values obtained by other authors for the entire south portuguese zone of the iberian massif however the current sediments of the tinto river t0 show a sharp increase in the levels of as cu pb and zn compared to the rest which indicates a serious increment of contamination by toxic elements although there are evidences on the existence of a natural process of oxidation of sulfides since the miocene the amounts of toxic elements released should be very small compared to those generated since the beginning of the mining activities in the iberian pyrite belt