the sedimentary expression of oceanic anoxic event 1b in the north atlantic abstract the aptian albian oceanic anoxic event 1b contains the record of severalperturbations in the global carbon cycle and multiple black shale levels particularly in the western tethys the local lithological expression of anoceanic anoxic event depends on palaeogeographical and depositional settingas well as on regional palaeoclimate marine sediments at a particular locationmay therefore be more or less organic rich or not at all and they may consistof different lithologies in most studies however much of the lithologicalvariability associated with oceanic anoxic events is left unaccounted for and thus the exact processes leading to the enrichment of organic matter in thesemarine sediments and their subsequent preservation in the geological recordare unknown this study focuses on the local sedimentary processes behindthe deposition of organic rich sediments at deep sea drilling project site 545and ocean drilling program sites 1049 and 1276 in the north atlantic duringoceanic anoxic event 1b although speci cally dealing with the sedimentsdeposited during this particular event at these localities it is expected that thesame processes were responsible for determining the exact sedimentaryproducts at localities in similar settings as well as during other similar eventsin the mesozoic here it is shown that the deposition of organic richsediments during oceanic anoxic event 1b was a consequence of theenhanced productivity favoured by upwelling and by riverine nutrientinput or aeolian fertilization of the euphotic zone depending ongeographical location slope instability processes resulted in the transfer ofpart of these organic rich sediments from the shelf to deep sea depocentres asmud laden organic rich turbidites especially in the northern north atlantic the so called black shales are much more varied than their name implies the end product of sedimentation during an oceanic anoxic event at aparticular location is commonly the result of several equi nal processes actingon a local scale rather than the direct result of basinal or even globalmechanisms keywords aptian albian kilian event north atlantic oae 1b oceandrilling program oceanic anoxic event paquier event

the lilliput effect in the aftermath of the end permian extinction event early triassic animal body fossils and trace fossils are small relative to those in older and younger intervals size decreases sharply through the end permian extinction event and permian triassic boundary and the smallest sizes are encountered in the parvus and isarcica zones of the earliest induan animals appearing within these two zones are also exceedingly small compared to younger congenerics and conspecifics temporary dramatic size decrease of surviving taxa in the immediate aftermath of the extinction event is an example of the lilliput effect coined by urbanek a 1993 biotic crises in the history of upper silurian graptoloids a palaeobiological model historical biology 7 29 50 body size increases somewhat from the carinata zone mid induan but remains depressed for the duration of the early triassic and pre extinction sizes are not commonly recorded until at least the middle triassic marine and terrestrial faunas appear to be similarly affected the lilliput effect and longer term size reduction could be the result of several factors environmental parameters such as marine anoxia due to low atmospheric concentrations of oxygen at this time coupled with sluggish ocean circulation in a greenhouse world and food shortage are the likely proximal causes for the early triassic lilliput effect no single cause can explain all the observations and a combination of factors are likely to be involved

geochemistry of peruvian near surface sediments sixteen short sediment cores were recovered from the upper edge ueo within wo and below bo the oxygen minimum zone omz off peru during cruise 147 of r v sonne solids were analyzed for major trace elements total organic carbon total inorganic carbon total sulfur the stable sulfur isotope composition 34 s of pyrite and sulfate reduction rates srr pore waters were analyzed for dissolved sulfate sulfide and 34 s of sulfate in all cores highest srr were observed in the top 5 cm where pore water sulfate concentrations varied little due to resupply of sulfate by sulfide oxidation and or diffusion of sulfate from bottom water 34 s of dissolved sulfate showed only minor downcore increases strong 32 s enrichments in sedimentary pyrite to 48 vs v cdt are due to processes in the oxidative part of the sulfur cycle in addition to sulfate reduction manganese and co are significantly depleted in peruvian upwelling sediments most likely due to mobilization from particles settling through the omz whereas release of both elements from reducing sediments only seems to occur in near coastal sites cadmium mo and re are exceptionally enriched in wo sediments 600 m water depth high re and moderate cd and mo enrichments are seen in bo sediments 600 m water depth re mo ratios indicate anoxic and suboxic conditions for wo and bo sediments respectively cadmium and mo downcore profiles suggest considerable contribution to ueo wo sediments by a biodetrital phase whereas re presumably accumulates via diffusion across the sediment water interface to precipitation depth uranium is distinctly enriched in wo sediments due to sulfidic conditions and in some bo sediments due to phosphorites silver transfer to suboxic bo sediments is likely governed by diatomaceous matter input whereas in anoxic wo sediments ag is presumably trapped due to sulfide precipitation cadmium cu zn ni cr ag and t1 predominantly accumulate via biogenic pre concentration in plankton remains rhenium sb as v u and mo are enriched in accordance with seawater te availability lead and bi enrichment in ueo surface sediments is likely contributed by anthropogenic activity mining accumulation rates of toc cd mo u and v from peruvian and namibian sediments exceed those from the oman margin and gulf of california due to enhanced preservation off peru and namibia copyright 2004 elsevier ltd

pollen and lignin records of late quaternary vegetation lake washington analyses of lignin oxidation products and pollen for an 11 meter core from lake washington provide independent but similar reconstructions of the late quaternary vegetation in the puget lowland an exception is in sediments of the late pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region this dissimilarity appears to result from different major provenances eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the lake washington drainage basin

macroevolutionary history of the planktic foraminifera planktic foraminifera are an abundant component of deep sea sediment and are critical to geohistorical research primarily because as a biological and geochemical system they are sensitive to coupled bio hydro lithosphere interactions they are also well sampled and studied throughout their evolutionary history here we combine a synoptic global compilation of planktic foraminifera with a stochastic null model of taxonomic turnover to identify statistically significant increases in macroevolutionary rates there are three taxonomic diversifications and two distinct extinctions in the history of the group the well known cretaceous paleogene extinction is of unprecedented magnitude and abruptness and is linked to rapid environmental perturbations associated with bolide impact the eocene oligocene boundary extinction occurs due to a combination of factors related to a major reorganization of the global climate system changes in ocean stratification seawater chemistry and global climate recur as primary

anoxic vs dysoxic events reflected in sediment geochemistry during the cenomanian turonian boundary event cretaceous in the umbria marche basin of central italy abstract one of the most spectacular expressions of global oceanic anoxic events oaes of the cretaceous is the livello bonarelli of central italy deposited during the cenomanian turonian boundary event ctbe or oae2 at around 93 5 ma at furlo in the umbria marche basin in italy the bonarelli consists of approximately 1 m of c org rich shales interbedded with radiolarian rich layers and contrasts sharply with the extensive over and underlying siliceous limestones several minor c org rich intervals herein termed black levels average thickness 4 5 cm are interbedded within the scaglia bianca beneath the bonarelli x ray fluorescence and icp ms analyses show that these sediments consist of different mixing systems with three end members 1 sio 2 caco 3 scaglia bianca 2 average shale caco 3 black levels and 3 average shale sio 2 bonarelli given the sharp lithologic contacts and the little geochemical mixing between the groups these are thought to represent rapid switching events between sedimentary modes major element concentrations are generally low except for si and p owing to dilution by silica up to 96 and carbonates as al normalised ratios for elements such as ti or zr taken as proxies for higher energy environments are close to average shale values excess sio 2 is most likely linked to biogenic processes rather than quartz element al ratios of ti mg k rb and zr are fairly constant pointing to a mostly homogeneous source area the black levels and bonarelli are characterised by lower mg al ratios compared to the scaglia bianca sediments suggesting variability in chlorite input which could be linked with short term sea level drops indicated by ti al ratios the bonarelli sediments are severely depleted in mn which is indicative of oxygen depleted bottom water conditions and an open marine environment while the black levels appear to have been deposited in a much more restricted setting a model involving partial physical isolation of the furlo site by a sill coupled to omz variations by extra basinal forcing mechanisms is proposed to account for these conflicting data based on re mo ratios the bonarelli sediments were deposited under varying oxygen depletion levels from suboxic to anoxic while re mo ratios in the black levels show deposition under less oxygen deficient conditions most minor elements many of them redox sensitive or sulphide residing are strongly enriched in the c org rich sediments further documenting the absence of oxygen and potential availability of hydrogen sulphide in the water column at times while high zn concentrations suggest elevated submarine hydrothermal activity during this time interval ba is also present in very high concentrations up to 1 4 with an average weighed concentration of 0 6 for the entire bonarelli and is probably indicative of high paleoproductivity in this area this is further supported by high p concentrations hinting at nutrient availability at this site

coquitlam drift a pre vashon fraser glacial formation in the fraser lowland british columbia coquitlam drift is formally defined and stratotypes established for it in the coquitlam port moody area b c it is a pleistocene formation consisting of till glaciofluvial ice contact and glaciomarine sediments deposited between 21 700 and 18 700 years bp during the fraser glaciation late wisconsin and prior to the main vashon glacial maximum at about 14 500 years bp the drift was deposited in short pulses by valley and piedmont glaciers fluctuating into the fraser lowland from the coast mountains to the north and cascade mountains to the east

high resolution carbon isotope records of the aptian to lower albian from se france and the mazagan plateau dsdp site 545 a stratigraphic tool for paleoceanographic and paleobiologic reconstruction high resolution carbon isotope stratigraphy is established for the aptian to lower albian of the vocontian basin se france and correlated to the carbon isotope record of the mazagan plateau dsdp site 545 the carbon isotope stratigraphy of the vocontian basin is proposed as a standard reference curve for the aptian to lower albian due to the completeness and high temporal resolution of the stratigraphic succession the good biostratigraphical time control and the frequent occurrence of regional to global black shale horizons including oceanic anoxic events 1a oae 1a of the lower aptian and oae 1b of the lower albian the carbon isotope record appears better suited for long distance short term correlation of different marine and terrestrial environments than biostratigraphy because of the synchroneity of carbon isotope signals in a range of sediment types however the combination of both biostratigraphy and carbon isotope stratigraphy provides an effective tool to reconstruct biotic change and paleoceanography and to correlate regional to global black shale horizons in different marine environments this combined approach allows us to ascertain the synchroneities or diachroneities of first and last appearances of biostratigraphic marker species based on the demonstrated diachroneity of important biostratigraphic markers of the aptian albian boundary the globally observed break point between the end of the uppermost aptian positive carbon isotope excursion and the onset of the pronounced negative shift of 13c values is an alternative criterion the distinctive structure and amplitudes of the carbon isotope record are observed in both the inorganic and organic carbon and can therefore be recognized in all marine and terrestrial environments of the aptian to lower albian

high resolution geochemical and biotic records of the tethyan bonarelli level oae2 latest cenomanian from the calabianca guidaloca composite section northwestern sicily italy abstract high resolution micropalaeontological and chemostratigraphic records for the upper cenomanian portion of the calabianca guidaloca composite section nw sicily provide new insight into the palaeoclimatic and palaeoceanographic evolution of the tethys ocean the bonarelli level equivalent was identified on the basis of lithology and well constrained by calcareous plankton biostratigraphy and radiolarian assemblages as well as by the 13 c curve showing a marked positive excursion up to 4 7 the bonarelli level equivalent deposition is characterized by highly eutrophic conditions as testified by radiolarian proliferation black shale samples from the calabianca guidaloca composite section contain very high toc up to 26 and moderate to high amounts of caco 3 on average 20 among the planktonic foraminifera hedbergellids and globigerinelloids tolerated the environmental stress induced by the oceanic anoxic event 2 oae2 the occurrence of some benthic foraminifera testifies to dysoxic rather than completely anoxic conditions at the sea floor during the deposition of some portions of the bonarelli level equivalent based on micropalaeontological results and geochemical proxies 13 c d rb ti v ni ba si cr the bonarelli level equivalent is interpreted as a high productivity event driven by increasingly warm and humid climatic conditions promoting an accelerated hydrological cycle we propose that periodically increased riverine influxes triggered by enhanced humidity resulted in a sluggish circulation mode and consequent anoxic euxinic conditions favouring the preservation of organic matter at the sea floor spectral analyses performed on selected geochemical signals reveal within the main high productivity event a strong orbital climatic forcing represented by a long term eccentricity steered humidity cyclicity that amplifies a short term precession controlled productivity fluctuation

tephrochronology of late wisconsin deglaciation and holocene glacier fluctuations near glacier peak north cascade range washington abstract tephra layers near glacier peak in the north cascade range provide limiting dates for four periods of alpine glacier advance field relations suggest that late wisconsin alpine glaciers last advanced prior to the eruption of tephra layers from glacier peak about 11 250 yr b p late wisconsin deglaciation in the central north cascades was complete prior to the glacier peak tephra eruptions glaciers again expanded in the early holocene about 8400 8300 yr b p soil formed in alpine meadows during an episode of mild climate in the middle holocene prior to at least two intervals of glacier expansion an older episode between 5100 and 3400 yr b p and a younger episode within the last 1000 yr

rhenium and molybdenum enrichments in sediments as indicators of oxic suboxic and sulfidic conditions of deposition abstract the trace elements re and mo both behave conservatively in seawater yet are strongly enriched in reducing sediments their potential for authigenic enrichment above crustal concentrations is greater than for many other elements due to the high ratio of metal sw metal crust we present sedimentary re and mo data from box and multi cores spanning a range of redox conditions from well oxygenated sites to locations with substantial sulfide concentrations at the oxic sites re and mo as expected accumulate at concentrations close to their crustal abundances re shows substantial enrichment in suboxic absence of o 2 and h 2 s sediments of the sea of japan in sediments within the oxygen minimum of the pakistan margin as well as in sediments underlying the sulfide bearing waters of the black sea and saanich inlet re enrichment occurs in these cores just below the depths of fe and u reduction only in the sediments underlying the sulfidic waters of the black sea and saanich inlet is there substantial authigenic mo accumulation absence of re and mo enrichments in sediment trap samples from the sulfide bearing basins suggests that the addition of both metals occurs at or below the sediment water interface the re and mo concentration profiles are modeled to hindcast the removal depth of re and mo in the sediments which along with the re mo ratio determine whether oxic suboxic or sulfidic conditions were present in the water column or in the sediments in the past using this approach historical redox conditions can be inferred even in environments such as continental margins where a substantial lithogenic component can obscure authigenic enrichments of other metals

investigation of pre extinction dwarfing in cenozoic planktonic foraminifera abstract we propose a phenomenon termed pre extinction dwarfing in cenozoic planktonic foraminifera high resolution morphometric analysis shows a reduction in maximum or mean test size in the 2 20 kyr interval preceding the extinction of pliocene globorotalia exilis and globorotalia miocenica from the caribbean sea and middle eocene morozovelloides crassatus from the western north atlantic through a series of case studies and review of qualitative observations from the literature we suggest that dwarfing occurs in a number of species of planktonic foraminifera foreshadowing their demise and that such size changes are not just a phenomenon associated with mass extinction events we propose that this is a common stress induced pattern that results in diminutive size in the pre extinction interval

ecological and evolutionary response of tethyan planktonic foraminifera to the middle eocene climatic optimum meco from the alano section ne italy abstract the enigmatic middle eocene climatic optimum meco is a transient 500 kyr warming event that significantly interrupted at 40 ma the long term cooling through the middle and late eocene eventually resulting in establishment of permanent antarctic ice sheet this event is still poorly known and data on the biotic response are so far scarce here we present a detailed planktonic foraminiferal analysis of the meco interval from a marginal basin of the central western tethys alano section northeastern italy the expanded and continuous alano section provides an excellent record of this event and offers an appealing opportunity to better understand the role of climate upon calcareous plankton evolution a sapropel like interval characterized by excursions in both the carbon and oxygen bulk carbonate isotope records represents the lithological expression of the post meco event in the study area and follows the 18 o negative shift interpreted as representing the meco warming high resolution quantitative analysis performed on both 38 m and 63 m fractions reveals pronounced and complex changes in planktonic foraminiferal assemblages indicating a strong environmental perturbation that parallels the variations of the stable isotope curves corresponding to the meco and post meco intervals these changes consist primarily in a marked increase in abundance of the relatively eutrophic subbotinids and of the small low oxygen tolerant streptochilus chiloguembelina and pseudohastigerina at the same time the arrival of the abundant opportunist eutrophic jenkinsina and pseudoglobigerinella bolivariana typical species of very high productivity areas also occurs the pronounced shift from oligotrophic to more eutrophic opportunist low oxygen tolerant planktonic foraminiferal assemblages suggests increased nutrient input and surface ocean productivity in response to the environmental perturbation associated with the meco particularly critical environmental conditions have been reached during the deposition of the sapropel like beds as testified by the presence of common giant and or odd morphotypes this is interpreted as evidence of transient alteration in the ocean chemistry the enhanced surface water productivity inferred by planktonic foraminiferal assemblages at the onset of the event should have resulted in heavier 13 c values the recorded lightening of the carbon stable isotope preceding the maximum warmth therefore represents a robust indication that it derives principally by a conspicuous increase of p co 2 the increased productivity of surface waters also supported by geochemical data may have acted as mechanism for p co 2 reduction and returned the climate system to the general eocene cooling trend the oxygen depleted deep waters and the organic carbon burial following the peak of the meco event represent the local response to the meco warming and suggest that high sequestration of organic matter if representing a widespread response to this event might have contributed to the decrease of p co 2 as well though the true mechanisms are still obscure several lines of evidence indicate a potential pressure on planktonic foraminiferal evolution during the meco event including permanent changes besides transient and ecologically controlled variations

extended cretaceous tertiary boundary extinctions and delayed population change in planktonic foraminifera from brazos river texas high resolution planktonic foraminiferal analysis of three brazos river sections indicates a nearly continuous cretaceous tertiary k t boundary sedimentary record second only to the world s most complete record at el kef tunisia species extinctions occur over an extended period of time and with two major extinction episodes the first extinction episode with 46 of the species extinct occurs at and just below 10 15 cm a short hiatus at the base of a sandy shell hash and clay sand unit which was interpreted by bourgeois et al 1988 to represent a tsunami bed generated by the k t boundary bolide impact the top of this tsunami bed is about 17 20 cm below the k t boundary as defined by the first appearance of tertiary planktonic foraminifera the second extinction phase with 45 of the species extinct occurs 25 cm above the k t boundary zone p0 p1a boundary of the remaining seven surviving cretaceous species six gradually disappear during planktonic foraminiferal subzones p1a and basal p1b no species extinctions or major faunal assemblage changes are directly associated with the k t boundary iridium distribution is ambiguous with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined k t boundary relative abundances of dominant species are stable through the late maastrichtian and only minor abundance changes coincide with the first extinction episode or the k t boundary the first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in subzone p1a species disappearing at the two extinction episodes 46 and 45 constitute only a small percentage 8 and 5 of the individuals of the total planktonic foraminiferal population this suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes magnetostratigraphy indicates that the first extinction phase began about 310 000 years before the k t boundary and the second extinction phase occurred 50 000 years after the k t boundary this stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling the hypothesis of a global catastrophic mass extinction at the k t boundary caused by a large extraterrestrial impact is not supported by the brazos river planktonic foraminiferal data

cretaceous oceanic anoxic events and radially elongated chambered planktonic foraminifera paleoecological and paleoceanographic implications chamber elongation is a recurring morphological character in cretaceous and cenozoic planktonic foraminiferal evolution suggesting that the clavate body plan takes advantage through particular environmental conditions cretaceous planktonic foraminifera bearing radially elongated chambers become repeatedly a consistent component of assemblages in correspondence with the deposition of remarkable organic layers that record the effects of oceanic anoxic events oaes due to this apparent correspondence chamber elongation has been recently interpreted as an adaptation to low oxygen levels in the upper water column the paleoceanographic significance of planktonic foraminifera with radially elongated chambers remains however unclear we investigated in great detail the distribution and abundance of elongated chambered planktonic foraminifera in an interval of about 40 myr across the cretaceous oaes in different well dated sections the increased abundance of planktonic foraminifera with elongated chambers can be a markedly evident feature across the faraoni the selli and the bonarelli oaes however each event shows its own peculiarities remarkably the first radiation of the cretaceous elongated chambered morphotypes just predates the latest hauterivian faraoni event the selli event records the greatest diversification number of species of the group bearing elongated chambers however this was a period of great diversification in the planktonic foraminifera this evidence may suggest that radiation of these forms was driven by more than upper water column anoxia per se e g increased upper water column stratification greater productivity and or greater seasonality the albian oae1b oae1c and oae1d display the lowest abundance and diversity of this group conversely according to the available data the first appearances of the species muricohedbergella simplex and of the genus schackoina occur close to the oae1b and oae1d respectively in the italian record the relative abundance of radially elongated chambered forms appears to be larger before the onset of the bonarelli event with respect to the selli event the pattern involving this group across the bonarelli event appears more regular thus indicating that the onset and the end of the oae2 depend on very powerful global factors and are less influenced by local aspects we speculate that the relative abundance of planktonic foraminifera with radially elongated chambers may be proportional to the strength of the environmental perturbation related to the oaes thus reinforcing the idea that the ecological perturbation related to the oae2 was more severe for the former several lines of evidence suggest that water oxygenation could not have been the single controlling factor governing the development of elongate chambers the role of availability of food and the nature of food has been so far probably underestimated it is most likely that an interplay of several influential physical chemical and ecological factors i e dissolved oxygen concentration temperature salinity nutrients type of food trace elements was responsible for such a morphological adaptation we document linkages between the distribution abundance morphometric changes and evolution of the cretaceous radially elongated chambered planktonic foraminifera and the major igneous geological geochemical climate nutrification and biotic events and biocalcification trends

morphometric response of late aptian planktonic foraminiferal communities to environmental changes a case study of paraticinella rohri at poggio le guaine central italy abstract the aptian albian boundary interval represents a pivotal time of pronounced climate ocean changes associated with oceanic anoxic event 1b oae 1b that seriously influenced marine pelagic ecosystems the sedimentary successions record the first and most significant species turnover in the evolutionary history of planktonic foraminifera consisting of the selective extinction disappearance of large aptian species and resulting in inter specific size reduction the post extinction dwarfing as in the lilliput effect in the earliest albian assemblages in this study we investigate how the planktonic foraminifera respond to crucial environmental stress and if any intra specific decrease in test size predate the extinction pre extinction dwarfing paraticinella rohri was chosen as the most representative of the aptian planktonic foraminiferal taxa and its test size evolution was compared with the high resolution record of redox and productivity geochemical proxies through the uppermost aptian lowermost albian pelagic succession of poggio le guaine central italy our geochemical data document long term fluctuations characteristic of a system with transitions among different states oligotrophic mesotrophic eutrophic and oxic dysoxic anoxic the strong correlation of the large test size changes of pa rohri during its total range with higher productivity increased baexcess concentrations suggests that the trophic regime was the key factor controlling robust abundance and size variability in this taxon the progressive increase in surface water fertility during the late aptian offered optimum ecological conditions for planktonic foraminifera that increased in abundance size and specific diversity after the transient anoxic 113 jacob sub event smaller to dwarfed specimens of pa rohri and depauperate planktonic foraminifera assemblages faced high selective pressures due to more oligotrophic conditions transition to a more eutrophic ocean in the latest aptian irreversibly eroded their resilience and aptian dwarfed k strategist taxa became extinct the planktonic foraminifera turnover has been therefore the result of an irreversible and drastic regime shift toward a more eutrophic ecosystem that promoted the thriving of small sized opportunistic disaster planktonic foraminiferal species and the siliceous radiolaria

the cretaceous paleogene transition at galanderud northern alborz iran a multidisciplinary approach abstract we investigated the cretaceous paleogene k pg transition at the galanderud section northern alborz iran to identify the pattern of mass extinction of planktic foraminifera and to unravel the associated paleoenvironmental changes in a little studied area of the eastern tethys we applied a high resolution quantitative and multidisciplinary study based upon benthic and planktic foraminiferal assemblages clay mineralogy rock magnetic properties stable isotopes and geochemistry in this section the k pg boundary is marked by an abrupt change in lithology from marl to a clay boundary layer a marked decrease in magnetic susceptibility a negative 2 2 13c excursion and a peak in iridium in the uppermost maastrichtian foraminifera are well preserved and diversified suggesting a stable mesotrophic environment by contrast the k pg boundary and basal danian is marked by high values of epifaunal benthic morphogroups low planktic diversity and high percentages of opportunistic species guembelitria cretacea and cervisiella operculata suggesting highly stressed and variable conditions partly due to the dramatic collapse of calcareous primary producers benthic foraminiferal assemblages indicate outer neritic uppermost bathyal depths with slight bathymetric variations the most peculiar and unique aspect of the galanderud section is the occurrence of the three thin chalk layers interbedded within clays above the k pg boundary each marked by positive shifts in 13c and 18o values and consisting of 80 carbonate we propose that the chalk clay deposits in the basal danian reflect changes in seawater chemistry and dynamic changes in circulation upwelling alternating with episodes of enhanced weathering and runoff this section on the northern margin of eastern tethys provides new clues about the pattern of the k pg mass extinction and the paleoenvironmental changes occurring during the biotic recovery phase

atlantic cooling associated with a marine biotic crisis during the mid cretaceous period most of the marine biotic crises that occurred during the hot mesozoic era have been linked to episodes of extreme warmth 1 2 others however may have occurred during cooler intervals that interrupted cretaceous greenhouse warmth 3 5 there are some indications of cooling in the late aptian 6 8 116 114 myr ago but it has not been definitively linked to biotic crisis here we assess the timing and magnitude of late aptian cooling and its association with biotic crises using a suite of geochemical and micropalaeontological assessments from a marine sediment core from the north atlantic ocean as well as global biogeochemical modelling sea surface temperatures derived from the tex86 proxy suggest that surface waters cooled by about 5 degrees c during the two million years coincident with a positive delta c 13 excursion of approximately 2 parts per thousand in carbonates and organic carbon surface productivity was enhanced during this period but the abundance of planktonic foraminifera and nannoconid phytoplankton declined our simulations with a biogeochemical model indicate that the delta c 13 excursion associated with the cooling could be explained by the burial of about 812 000 gigatons of carbon over 2 5 million years about 50 of the this carbon burial occurred in the atlantic southern and tethys ocean basins we conclude that global cooling during greenhouse conditions can cause perturbations to marine ecosystems and biogeochemical cycles at scales comparable to those associated with global warming

a paleoceanographic model for the early evolutionary history of planktonic foraminifera the first major radiations of planktonic foraminifera occurred during the mid cretaceous however this period of great diversification was interrupted by two intervals of pronounced paleoceanographic paleoecologic change one during the latest aptian early albian and a second associated with the cenomanian turonian boudary both of these times corresponded with widespread organic carbon burial during intervals commonly referred to as oceanic anoxic events oae 1 and 2 respectively this synthesis focuses on the evolutionary history of aptian early cenomanian planktonic foraminifera and the relationship with oae 1 dynamic paleoceanographic changes controlled the course of planktonic foraminiferal evolution during the mid cretaceous heightened plate tectonic activity a major long term rise of global sea level and an overall increase of global temperatures characterized aptian albian time as proposed here the evolutionary history of aptian early cenomanian planktonic foraminifera was influenced most strongly by changes in the density structure and stability of the upper water column via changes in the sites and rates of water mass production through time and perhaps by subtle changes in oceanic productivity including trophic structure and shifts in productivity centers with rising sea level the creation and growth of epicontinental seas played a major role in regional climate change water mass production and water column structure epicontinental seas were also an important factor in creating vast new niche space and increased biotic diversity for many marine organisms the amplified seasonality and instability of epicontinental seas resulted in habitation of the upper water column by morphologically simple eurytopic planktonic foraminifera several new species of epicontinental sea dwelling planktonic foraminifera appeared during the mid cretaceous however much of the diversification of morphologic form took place in oceanic areas during times of oceanic stability and upper water column stratification during mid to late aptian and late albian time a decline in diversity and return to simple morphotypes occurred when oceanic stability was disrupted and the upper water column was poorly stratified during latest aptian early albian time

late glacial vegetation and climate at the manis mastodon site olympic peninsula washington abstract as the late wisconsin cordilleran ice sheet retreated sediment accumulated in shallow depressions at the manis mastodon archaeological site on the olympic peninsula near sequim washington pollen plant macrofossils and bones of mastodon caribou and bison occur within the lower 47 cm of these deposits the fossil pollen and seed assemblages indicate persistence for 1000 yr 11 000 12 000 yr b p of an herb and shrub dominated landscape at a time when forest species appear elsewhere in washington and in adjacent british columbia at present sequim is near the northern coastal limits of both cactaceae and ceratophyllum mean annual precipitation is 42 7 cm and summer temperatures average 15 16 c in july the absence of coniferous trees and the presence of cactus and ceratophyllum in late glacial sediments are explained by a regional climate that was drier and at least as warm as today these conditions persisted in the rain shadow of the olympic mountains until at least 11 000 yr b p

mercury anomalies in upper aptian lower albian sediments from the tethys realm abstract the upper aptian lower albian stratigraphic interval documents important perturbations in the carbon cycle associated with the oceanic anoxic event 1b oae 1b tentatively connected with pulses in volcanic activity and the formation of the southern kerguelen plateau however uncertainties in existing age models for this interval preclude a robust and definitely convincing cause effect connection between these two events a sedimentary record from the poggio le guaine section umbria marche basin shows anomalously high levels of mercury during the upper aptian lower albian interval the persistence of the anomalies of hg after normalization against toc al and fe suggests that chemical and physical processes related to organic matter scavenging adsorption onto clay minerals hydrous iron oxides and sulphur only played a secondary role as mechanisms for hg accumulation in the sediments in agreement with previous studies in which anomalous enrichments of hg in sedimentary records were interpreted as monitors of enhanced volcanic activity we speculate that the hg enrichments documented in the poggio le guaine section reflect a rapid increase in atmospheric hg content associated with a massive release of volcanic hg and possibly suggest a multi phase emplacement of the southern kerguelen plateau skp as a realistic source nonetheless comparison of hg profiles and micropalaeontological data from the poggio le guaine section reasonably excludes the possibility that the global biotic turnover horizon documented in the upper aptian could be directly attributed to the volcanic pulses of the skp emplacement

vashon drift definition of the formation in the georgia depression southwest british columbia vashon drift was deposited during the fraser glaciation late wisconsinan at the time of maximum expansion of the southwestern part of the cordilleran ice sheet when it filled the georgia depression about 14 500 years ago the drift is present throughout the depression and comprises till and glaciofluvial and glaciolacustrine sediments derived from source areas surrounding the coastal trough it is overlain by capilano sediments and underlain by quadra sand also of fraser age drift deposition was diachronous and complex probably caused by alpine glaciers coalescing in the trough with the ice margin repeatedly grounding and floating in seawater studies of bedrock striae till fabrics and clast provenance reveal that vashon ice movement was generally southward although locally controlled by topography a time space diagram is presented that confirms the long held hypothesis that advance and decay of vashon ice were rapid

planktonic foraminifers across the bonarelli event oae2 latest cenomanian the italian record abstract a high resolution quantitative study of the planktonic foraminiferal assemblages across the bonarelli level oae2 latest cenomanian of italy from different areas and geological settings has allowed the recognition of several events and biotic changes including acmes and crises of different genera it provides evidence of a progressive and rapid change of palaeoenvironmental conditions reaching a climax coincident with the bonarelli event and of the subsequent gradual although not complete resumption of previous conditions the observed pattern is illustrated by marked changes in the assemblages that indicate five discrete phases of environmental perturbation within the marine ecosystem though there are several similarities our analyses highlight that each section has its own peculiarities clearly indicating more or less extreme environmental conditions

10be and ba concentrations in west african sediments trace productivity in the past particle reactive elements are scavenged to a higher degree at ocean margins than in the open ocean due to higher fluxes of biogenic and terrigenous particles in order to determine the influence of these processes on the depositional fluxes of10be and barium we have performed high resolution measurements on sediment core geob 1008 3 from the congo fan because the core is dominated by terrigenous matter supplied by the congo river it has a high average mass accumulation rate of 6 5 cm kyr biogenic10be and ba concentrations were calculated from total concentrations by subtracting the terrigenous components of10be and ba which are assumed to be proportional to the flux of al2o3 the meanba al weight ratio of the terrigenous component was determined to be 0 0045 the unusualy high terrigenous10be concentrations of 9 1 109 atoms g al2o3 are either due to input of particles with high10be content by the congo river or due to scavenging of oceanic10be by riverine particles the maxima of biogenic10be and ba concentrations coincide with maxima of the paleoproductivity rates time series analysis of the10be and of ba concentration profiles reveals a strong dominance of the precessional period of 24 kyr which also controls the rates of paleoproductivity in this core during the maxima of productivity the flux of biogenic ba is enhanced to a larger extent than that of biogenic10be applying a model for coastal scavenging we ascribe the observed higher sensitivity of ba to biogenic particle fluxes to the fact that the ocean residence time of ba is approximately 10 times longer than that of10be

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

barium peaks at glacial terminations in sediments of the equatorial atlantic ocean relicts of deglacial productivity pulses in sediment cores recovered from oligotrophic settings of the western and eastern north equatorial atlantic ocean ceara rise and sierra leone rise distinct peaks of excess barium were detected at glacial interglacial transitions these ba maxima are unrelated to any other potential productivity proxy e g organic carbon carbonate or opal moreover they coincide with minima in organic carbon contents despite the lack of correlation between excess barium and organic carbon we ascribe these ba spikes to pulses of productivity that occurred during glacial interglacial transitions the discrepancy between barium and organic carbon in these transitional sediment intervals is attributed to the action of downward progressing oxidation fronts during deglacial nonsteady state depositional conditions the oxidation fronts were initiated due to the overall low sedimentation rates prevailing in the study areas and an increase in bottom water oxygen concentrations at the onset of enhanced nadw production during interglacial periods the fronts led to a very efficient oxidation of the organic carbon initially present leaving peaks in solid phase barium as relicts of these short time productivity events this assumption is supported by the depth arrangement of the solid phase peaks of ba fe and mn along the 6 5 oxygen isotope stage boundary in sediments of the ceara rise which show striking similarities to the distribution of these elements in oxidized sapropel intervals in eastern mediterranean sediments it remains unclear whether productivity was proportional to the magnitude of the baexcess maxima possibly higher dissolved ba concentrations in intermediate and deep waters during glacial interglacial transitions caused the precipitation of barite to increase out of proportion of the postulated deglacial productivity pulses

guembelitria dominated late maastrichtian planktic foraminiferal assemblages mimic early danian in central egypt abstract during the late maastrichtian 66 8 65 5 ma the asyut basin in central egypt experienced a breakdown of the surface to bottom gradient of the 13c 12c ratio with planktic 13c values 0 2 0 8 lighter than benthic values planktic foraminiferal species diversity was reduced by more than 50 with assemblages dominated 60 90 by the opportunistic blooms of the disaster species guembelitria cretacea which mimic the early danian the prolonged breakdown in productivity occurred during a time of tectonic activity and increased terrestrial runoff that may have resulted in highly eutrophic waters coupled with a sea level regression 65 5 ma that led to restricted circulation increased productivity during the short climate warming between 65 4 and 65 2 ma is associated with increased species diversity abundant rugoglobigerinids and common heterohelicids at the end of the maastrichtian decreased productivity coincided with the k t impact and mass extinction followed by characteristically early danian low diversity assemblages the similarity of the late maastrichtian and post k t impact guembelitria dominated assemblages reveals that the planktic foraminiferal response to the k t catastrophe was not unique but followed a predictable pattern of response to severe environmental perturbations

formation of the late aptian niveau fallot black shales in the vocontian basin se france evidence from foraminifera palynomorphs and stable isotopes abstract we present paleoceanographic models for the formation of the marlstone facies and the most prominent black shale intervals of the late aptian niveau fallot black shale succession from the vocontian basin se france in the lower part of the succession the composition of benthic foraminiferal assemblages of the niveau fallot 2 and 2 black shales suggests an enhanced burial of organic matter due to more eutrophic conditions and resulting low oxygen conditions at the seafloor in the upper part of the succession including niveau fallot 3 and 4 a third order sea level fall indicated by a decrease in the stable carbon isotope values may have resulted in a reduced water mass exchange between the vocontian basin and the western tethyan ocean this may have led to dysoxic conditions at the seafloor of the vocontian basin and may have favored the formation of organic rich sediments as shown by benthic foraminiferal assemblages decreased evaporation however is proposed as the most important mechanism causing a restriction of deep water formation within the basin which finally led to the formation of the niveau fallot 3 and 4 black shales based on our investigations the formation of the niveau fallot black shales was caused by different factors the most prominent ones include sea level fluctuations increasing productivity and changes in precipitation and evaporation rates furthermore niveau fallot 3 can probably be correlated with the thalmann black shale event in california and a dark horizon at the mazagan plateau dsdp site 545

regional significance of an early holocene moraine in enchantment lakes basin north cascade range washington abstract the upper enchantment lakes basin in the north cascade range of washington displays two moraine belts each recording an episode of glacier advance after the end of the last glaciation the inner belt the brynhild 0 1 to 0 5 km beyond existing glaciers postdates mount st helens wn tephra 450 yr old which lies only beyond the moraines the morainal surface is only slightly weathered is almost barren of lichens and is devoid of soil evidence suggesting that the brynhild moraines are no more than a century old the outer moraine the brisingamen 0 3 to 0 7 km beyond existing glaciers is weathered and is covered with large lichens on and behind the brisingamen moraine the mazama ash 6900 yr old is present beneath the mount st helens yn and wn tephras despite more than 7 millennia of weathering the rock surface behind the brisingamen moraine is measurably less weathered than the surface beyond which was last glaciated during the rat creek advance about 13 000 yr ago the age of the brisingamen moraine therefore is probably early holocene the brisingamen moraine evidently correlates with moraines near glacier peak near mount rainier in northeastern and central oregon in the southern canadian rockies and in the northern u s rocky mountains these regional effects suggest that a climatic episode of cooling or increased snowfall affected the entire region some time during the early holocene

lag of the fraser glacial maximum in the pacific northwest pollen and macrofossil evidence from western fraser lowland british columbia pollen and macrofossil evidence from two sites in northwestern fraser lowland reveals that abies lasiocarpa picea cf engelmannii forest and parkland grew there about 18 000 years ago under cold humid continental conditions taxus brevifolia was also a significant constituent of this forest this plant assemblage resembles the essf biogeoclimatic zone of subalpine elevations in the northern interior of british columbia 900 2250 m climate was probably cold with low to moderate rainfall and characterized by long cold wet winters and very short probably dry frost free summers mean annual temperature was depressed about 8 c and the tree line was probably 1200 1500 m lower than today fraser lowland was probably removed from pacific oceanic influence because the land sea interface was located on the continental shelf to the west of vancouver island and washington about the time of the last global glacial maximum global depression of sea level and quadra sand aggradation in the pacific northwest lo

evolution patterns of radiolaria and organic matter variations a new approach to identify sea level changes in mid cretaceous pelagic environments the relation between sea level changes plankton productivity and evolution as well as the occurrence of anoxic sediments provides an interesting avenue of paleooceanographic research in this context we examined mid cretaceous radiolarian faunas carbonate isotopic and organic matter type data of deep sea drilling project and ocean drilling program cores from the north atlantic and samples from outcrops of the western tethys from central and northern italy former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the cenomanian turonian boundary an expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera causing the extinction of deeper dwelling forms although this model is well established for the cenomanian turonian boundary not much is known about the causes of extinctions and radiations during the entire mid cretaceous aptian turonian we demonstrate that the dimension of the oxygen minimum zone which depends on the relative sea level and the corresponding nutrient supply causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid cretaceous this new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework

calcareous nannoplankton response to late albian oceanic anoxic event 1d in the western north atlantic well preserved nannofossil and stable isotope records from the mid cretaceous of ocean drilling project leg 171b western north atlantic indicate cyclical productivity based variations in surface water characteristics suggesting orbitally paced changes in upwelling intensity and the strength of deep mixing associated with oceanic anoxic event oae 1d paleontologic and isotopic evidence suggest that collapse of upper water column stratification associated with oae1d was preceded by approximately 1 m y of progressively decreasing water column stability and increasing surface water fertility thirteen species went extinct during a short ca 200 k y interval associated with oae1d nine of these have morphological characters suggesting adaptation to specific depths in the photic zone simultaneous extinction of these depth zoned species suggests that stratification collapse disrupted the habitat space for these specialized forms resulting in extinction a cyclostratigraphic model provides age estimates of several important nannofossil datums including the first appearances of eiffellithus turriseiffelii 100 95 ma and corollithion kennedyi 99 55 ma

litho bio and chemostratigraphy across the cenomanian turonian boundary oae 2 in the vocontian basin of southeastern france the oceanic anoxic event 2 oae 2 was one of at least two large oceanic anoxic events during the cretaceous period and it is characterized in the stratigraphic record by double positive peaks in the 13c curves of carbonate and organic carbon since the positive 13c shift is believed to have resulted from massive burial of isotopically depleted organic carbon generated globally in anoxic oceanic environments the positive 13c shift tend to coincide with widespread deposition of organic rich sediments in the case of oae 2 however the organic rich horizons do not accord exactly with the two intervals with positive 13c shifts at many sites such as pueblo tarfaya eastbourne and gubbio e g tsikos h jenkyns h c walsworth bell b petrizzo m r forster a kolonic s erba e premoli silva i baas m wagner t sinninghe dameste j s 2004 carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities journal of the geological society london 161 711 719 the thomel level of the cenomanian turonian c t boundary in the vocontian basin southeastern france accumulated during the oae 2 and it is marked by frequent intercalations of black shale and organic rich marl detailed litho bio and chemostratigraphy analyses across the c t boundary in the vocontian basin indicate that the 13ccarbonate profile fluctuation across the thomel level corresponds well with changes in lithofacies total organic carbon toc and calcium carbonate caco3 abundance positive 13c excursions within the oae 2 correlate with basal and middle parts of the thomel level that are characterized by high toc low caco3 and predominantly contain organic rich sediments such as black shale and dark gray marl on the other hand negative 13c intervals within the oae 2 correspond with lower and upper parts of the thomel level that consist of marly limestone and limy marl with low toc and high caco3 values since the fluctuation of redox conditions during thomel level deposition in the vocontian basin coincides well with the global carbon burial rate indicated by its 13c profile the thomel level could be an ideal candidate for the reference section of the oae 2

high resolution stable isotope records from the upper cretaceous rocks of italy and spain glacial episodes in a greenhouse planet high resolution 13c and 18o records from upper albian to lower santonian pelagic carbonates of the contessa quarry section in italy exhibit large positive oxygen isotopic excursions of 1 in the lower cenomanian and upper turonian coniacian strata within the uncertainties of biostratigraphic correlation these positive excursions appear to correspond to times of large sea level regressions in global sequence stratigraphic sea level curves several lines of evidence suggest that the major 18o excursions in contessa reflect episodes of global cooling and not differential diagenesis numerical models of oxygen isotope exchange during diagenesis show that a high contrast in the degree of alteration would be required to produce these signals as artifacts of diagenesis and lithological data provide no evidence for such large contrasts in the degree of alteration furthermore although precise correlation with a section in the south of spain is hampered by stratigraphic complexities the general sequence of major positive 18o excursions is reproduced it is unlikely that differential diagenesis would produce similar artifacts in multiple sites one explanation for the link between episodes of global cooling and sea level falls is that global cooling events led to polar ice sheet accumulation lowering sea level although ice free conditions have been inferred from evidence for a much warmer climate in late cretaceous time our results suggest that the relationship between continental high latitude ice sheets and overall climatic warmth warrants further examination

stratigraphy and chronology of quaternary deposits of the puget lowland and olympic mountains of washington and the cascade mountains of washington and oregon in the southern puget lowland probably are correlative with salmon springs drift but farther north drift directly beneath vashon till is most likely correlative with much younger drifts such as the double bluff or possession drifts thus virtually all previouslymapped salmon springs drift needs to be re examined to determine if it is indeed correlative with salmon springs drift or is younger

contrasting molybdenum cycling and isotopic properties in euxinic versus non euxinic sediments and sedimentary rocks refining the paleoproxies abstract the redox sensitive transition element molybdenum is present in the earth s crust at trace concentrations but is abundant in seawater marine sediments and ancient sedimentary rocks these occurrences have led to the development of a suite of paleoredox proxies based on the bulk concentration of mo its isotopic composition and the covariation of mo with total organic carbon toc in ancient black shales however these proxies have almost exclusively targeted the identification and interpretation of euxinic environments where bottom waters are both anoxic and sulfidic here we present a discussion of the mo geochemistry of non euxinic sediments where hydrogen sulfide is sometimes present yet always restricted to pore waters we propose a new paleoredox application that uses mo concentrations to help distinguish between environments where sulfide was present in the bottom waters and environments where sulfide was restricted to pore waters under ideal conditions it is also possible to infer the presence of mn oxides recycling in non euxinic paleoenvironments based on the mo isotope composition of ancient black shales providing a critical constraint on bottom water oxygenation

cenomanian turonian carbonate and organic carbon isotope records biostratigraphy and provenance of a key section in ne sicily italy palaeoceanographic and palaeogeographic implications abstract in eastern sicily a series of highly organic rich black shales occur as exotic blocks 100 m across floating in tectonized sediments argille varicolori unit containing olistoliths of cretaceous palaeogene age a 19 metre section through one of these blocks near the town of novara di sicilia includes cyclically bedded black shales marlstones and claystones which have been dated using planktonic foraminiferal and nannofossil biostratigraphy on this basis the section is assigned to the latest cenomanian and clearly represents a manifestation of the oceanic anoxic event characteristic of that interval total organic carbon values range up to 23 and the relatively high hydrogen indices record the presence of marine organic matter of low thermal maturity high resolution carbonate and organic carbon isotope curves are comparable with those recorded elsewhere in indicating a significant positive excursion and confirm that in the novara di sicilia section the black shales are latest cenomanian in age by comparison with cenomanian turonian black shales exposed elsewhere in italy calabianca section western sicily livello bonarelli bottaccione gorge gubbio marche umbria the section of novara di sicilia is different in being more stratigraphically expanded however this section from eastern sicily does resemble extremely closely coeval sediments cropping out in tunisia and morocco this association is taken as evidence that the argille varicolori unit includes elements that were initially deposited on the north african shelf during cretaceous time

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

palaeoceanographic differences of early late aptian black shale events in the vocontian basin se france abstract a high resolution study focussing on the distribution of calcareous nannofossils and carbon isotopes was carried out to improve the understanding of mid cretaceous black shale formation the studied interval of the early late aptian is characterized by two major black shale couplets the niveau noire 4 nn4 and niveau noire calcaire 2 nnc2 of the serre chaitieu section in the vocontian basin se france breheret 1997 this interval occurs within a long term negative carbon isotope excursion of 1 5 following the early aptian oceanic anoxic event 1a oae1a in contrast to the local nn4 black shales the black shales of nnc2 are of regional significance and occur at the end of the major negative carbon isotope excursion of the early late aptian time equivalent black shales are suggested to be coeval with black shales found in the western tethys and atlantic ocean herrle et al 2004 calcareous nannofossil analyses and carbon isotopes indicate higher surface water productivity mesotrophic warmer surface water and higher sea level during the formation of the nn4 black shales in contrast the formation of the nnc2 black shales took place during a cooler phase lower surface water productivity and lower sea level a sea level fall may cause a restriction of water mass exchange between the open marine western tethys and the vocontian basin this resulted in a longer residence time of the bottom water decreased ventilation and less mixing of surface waters and thus enhanced preservation of organic matter at the sea floor our results indicate that the black shale formation of nn4 and nnc2 was caused by different processes such as increased surface water productivity and enhanced preservation of organic matter at the sea floor thus we emphasize the role of different forcing factors which control the formation of local and regional black shales the most important factors are sea level fluctuations increasing productivity and changes in precipitation and evaporation rates

a comparison between excess barium and barite as indicators of carbon export 1 since dymond et al 1992 proposed the paleoproductivity algorithm based on bio ba which relies on a strong correlation between ba and organic carbon fluxes in sediment traps this proxy has been applied in many paleoproductivity studies barite the main carrier of particulate barium in the water column and the phase associated with carbon export has also been suggested as a reliable paleoproductivity proxy in some locations we demonstrate that baexcess total barium minus the fraction associated with terrigenous material frequently overestimates babarite barium associated with the mineral barite most likely due to the inclusion of barium from phases other than barite and terrigenous silicates e g carbonate organic matter opal fe mn oxides and hydroxides a comparison between overlying oceanic carbon export and carbon export derived from baexcess shows that the dymond et al 1992 algorithm frequently underestimates carbon export but is still a useful carbon export indicator if all caveats are considered before the algorithm is applied babarite accumulation rates from a wide range of core top sediments from different oceanic settings are highly correlated to surface ocean 14 c and chlorophyll a measurements of primary production this relationship varies by ocean basin but with the application of the appropriate f ratio to 14 c and chlorophyll a primary production estimates the plot of babarite accumulation and carbon export for the equatorial pacific atlantic and southern ocean converges to a global relationship that can be used to reconstruct paleo carbon export index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 4825 oceanography biological and chemical geochemistry keywords paleoproductivity barite export production excess barium marine sediments citation eagle m a paytan k r arrigo g van dijken and r w murray a comparison between excess barium and barite as indicators of carbon export paleoceanography 18 1 1021 doi 10 1029 2002pa000793 2003

the evolutionary history of size variation of planktic foraminiferal assemblages in the cenozoic abstract the iterative evolutionary radiation of planktic foraminifers is a well documented macroevolutionary process here we document the accompanying size changes in entire planktic foraminiferal assemblages for the past 70 my and their relationship to paleoenvironmental changes after the size decrease at the cretaceous paleogene k p boundary high latitude assemblages remained consistently small size evolution in low latitudes can be divided into three major phases the first is characterized by dwarfs 65 42 ma the second shows moderate size fluctuations 42 14 ma and in the third phase planktic foraminifers have grown to the unprecedented sizes observed today our analyses of size variability with paleoproxy records indicate that periods of size increase coincided with phases of global cooling eocene and neogene these periods were characterized by enhanced latitudinal and vertical temperature gradients in the oceans and high diversity polytaxy in the paleocene and during the oligocene the observed minor size changes of the largely low diversity oligotaxic assemblages seem to correlate with productivity changes however polytaxy per se was not responsible for larger test sizes

influence of oceanic anoxic events on the evolution of mid cretaceous radiolaria in the north atlantic and western tethys abstract mid cretaceous aptian turonian extinction radiation events of radiolaria from the north atlantic and western tethys are summarized in relation to oceanic anoxic events oae from investigations of radiolarian faunas black shales and stable carbon isotopes extinction and radiation events of radiolaria can be observed from the late early aptian the earliest albian the latest albian and the cenomanian turonian boundary these events correlate well with organic carbon rich sediments that contain type ii kerogen and show positive 13c excursions they correspond to the oceanic anoxic events oae in the early aptian oae 1a selli level early albian oae 1b late albian oae 1d and latest cenomanian oae 2 bonarelli level detailed investigations of the two most significant events the selli and the bonarelli level in the umbria marche basin of central italy show that extinctions coincide with the first occurrence of marine black shales type ii kerogen and the most prominent rise of 13corg values stepwise extinctions and continuous radiations precede and follow the events similar patterns are evident for the oae 1b and 1d black shales dominated by terrestrial organic matter type iii kerogen e g oae 1c are not characterized by isotopic excursions or by radiolarian extinction radiation events contemporaneous drowning events documented from carbonate platforms around the investigated basins provide a link to a model where flooding of lowlands and leaching of nutrients during a relative rise of sea level lead to an increased productivity and an expansion of the oxygen minimum zone omz because of the loss of deep habitats deeper dwelling forms become extinct shallower dwelling radiolarians survive a narrowing of the omz during highstands and relative sea level falls together with a coupled decrease of the nutrient supply leads to the development of new niches and therefore to radiation

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

response of planktic foraminiferal size to late quaternary climate change 1 geographical size distribution within entire holocene foraminiferal assemblages is related to global environmental gradients such as temperature primary productivity and environmental variability this study demonstrates that these correlations are also recognizable in late quaternary assemblages from three locations in the south atlantic on temporal and latitudinal scales the size response to temporal paleoenvironmental changes during glacial interglacial cycles mimics the geographic holocene size variability the amplitude of size variability is directly related to the amplitude of the climatic fluctuations as shown by the stable size temperature relationship over time the documented changes in the assemblage size are caused by species replacement and intraspecific size variability the relative importance of these processes depends on the environmental setting species have been shown to reach their maximum size and abundance under certain optimum conditions and decrease in size if environmental conditions differ from these optima we confirm that late quaternary species sizes were largest at paleotemperatures identical to holocene ones

the cenomanian turonian oceanic anoxic event ii palaeoceanographic controls on organic matter production and preservation correlation of the 13c spike with the well dated occurrences of strata rich in organic carbon detailed in schlanger et al this volume indicates that a global episode of intense organic carbon orgc burial took place during the latest cenomanian earliest turonian oceanic anoxic event oae a plenus through i labiatus macrofossil zones and upper r cushmani trz through w archecretacea prz foraminiferal zones over a period of no more than 1 million years m y the shape of the 13c curve indicates that rates of orgc burial gradually increased in the early part of the late cenomanian increased more rapidly in the later cenomanian and levelled off at peak values in latest cenomanian early turonian time during the maximum rate of orgc burial the 13c values decreased nearly to pre late cenomanian levels in the early to middle turonian the decrease in 13c reflects decreasing rates of orgc burial following the cenomanian turonian oceanic anoxic event as well as the probable oxidation and return of significant amounts of orgc to the oceans following regression and re oxygenation of much of the deeper water masses in contact with the seafloor

decline of the maastrichtian pelagic ecosystem based on planktic foraminifera assemblage change implication for the terminal cretaceous faunal crisis an outer shelf upper slope tropical tethyan pelagic environment existed over southern israel during maastrichtian time planktic foraminifera in the 63 and 149 m size fractions from four sections in this area were studied quantitatively for a high resolution ecostratigraphic analysis of the pre cretaceous tertiary k t paleoenvironment during the maastrichtian 41 of the planktic foraminifera species became extinct mostly keeled globotruncanidae which also became quantitatively reduced near the end of the maastrichtian from as much as 35 to only 5 of the planktic foraminifera population evolutionary replacement of extinct species by new forms nearly ceased in that interval two major opportunistic blooms of guembelitria took place associated with reduced abundances of keeled forms and the dominant species heterohelix globulosa the first bloom occurred within the upper gansserina gansseri to lower abathomphalus mayaroensis zones and the second within the plummerita hantkeninoides zone the extinctions concomitant changes in faunal dominance and opportunist blooms indicate that the pelagic ecosystem in the negev area experienced multiple stresses during the maastrichtian the planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the k t boundary crisis

early holocene glacier advance in the north cascade range washington moraines and glacial drift of the white chuck advance were deposited in early holocene time in cirques near glacier peak washington these sediments overlie glacier peak tephra including layers g n f c m t and b which were erupted between about 12 500 and 11 250 yr b p white chuck drift is overlain by mazama tephra layer o deposited about 6 700 yr b p charcoal collected from till deposited during the white chuck advance is about 8 300 to 8 400 radiocarbon years old indicating that the glacial advance that deposited the till occurred about this time and that a previously unrecognized period of cooling and or increased precipitation of sufficient intensity to produce glacial advances comparable to or greater than those of the recent little ice age occurred in early holocene time in the north cascade range other pre altithermal moraines from the cascades the rocky mountains laurentide canada and baffin island may have been produced during this cool period

water depth and diagenetic constraints on the use of barium as a palaeoproductivity indicator sediments underneath the high productivity areas of the coastal upwclling and equatorial divergence zones in the pacific and indian oceans are enriched in barium and on this basis the barium content of the sediments has long been suggested as a potential palaeoproductivity indicator analyses of sediments from the peru margin corroborate the pattern of enhanced barium accumulation in areas of high primary productivity in the deep ocean but also show that this pattern cannot be extended to shallow water deposits sediments from the peru shelf lack any barium enrichment whereas this element is significantly enriched in slope and basinal deposits in water columns deeper than 2000 m this depth effect is further illustrated at site 682 located in the rapidly subsiding lima basin the quaternary sequence deposited at water depths 3000 m is enriched in organic carbon opal and biogenic barium the miocene sediments although deposited under highly productive waters associated with a coastal upwclling centre do not show an enrichment in the barium record corresponding to the very high organic carbon and opal levels a pattern that is consistent with deposition in shallow basins in addition to the effect of water depth on the barium distribution overprinting of primary signals can be observed in sediments from upwclling areas undergoing strong anoxic diagenesis microcrystalline barite is partly dissolved in intervals depleted in interstitial sulphate as shown for sediments from the peru margin dissolution of barite in sulphate depleted intervals of deep water sections leads to high barium concentrations near the termination of the sulphate reducing zone where downward sulphate and upward barium diffusion foster local barite precipitation in diagenetic fronts the barium distribution in sedimentary oxic and suboxic environments at deep water depositional sites has a high potential as a palaeoproductivity indicator however barium accumulation as a proxy for ocean fertility should be used with caution in areas of varying water depths and in anoxic diagenetic environments where sulphate depletion undcrsatur ates the interstitial waters with respect to barite

high resolution chemostratigraphy of the late aptian early albian oceanic anoxic event oae 1b from the poggio le guaine section umbria marche basin central italy an integrated study of multiple geochemical proxies 13ccarb 13corg toc hi caco3 trace elements al ratios of the late aptian early albian oceanic anoxic event oae 1b has been performed on the pelagic sedimentary sequence of poggio le guaine umbria marche basin central italy a comparison of the newly collected stable isotope carbon curve with the records from the vocontian basin se france dsdp site 545 and hole 1049c provided a reliable and precise identification of the four main prominent black shale levels 113 jacob kilian urbino paquier and leenhardt that characterize the oae 1b the studied record shows an increase in the marine organic carbon accumulation rate in particular in the 113 jacob and urbino paquier levels in the other black shales toc values are 1 with evidence of degraded marine organic matter completely anoxic conditions were never established during the sediment deposition although evidence of oxygen depletion at the bottom of the basin is clearly documented by the distribution pattern of redox sensitive trace metals the results suggest an increase in organic carbon burial rates during the oae 1b due to the effect of enhanced surface productivity as supported by a major increase in ba al and reduced bottom water ventilation notably the kilian and urbino paquier levels from the plg section are characterized by the absence of correlative shifts in 13ccarb and 13corg the increase in the 13corg values in these levels is explained by an increase in the relative contribution of 13c enriched marine planktonic archaeal biomass while the concomitant negative excursions recorded in the 13ccarb could reflect a major contribution of isotopically light terrestrial carbonate ions from increased continental runoff during documented more humid conditions

contrasting origins of early cretaceous black shales in the vocontian basin evidence from palynological and calcareous nannofossil records abstract detailed records of spore pollen assemblages particulate organic matter om dinoflagellate cysts and calcareous nannofossils provide new insights into the palaeoclimatic and palaeoceanographic conditions during formation of early cretaceous black shales in the vocontian basin southeastern france the early aptian niveau goguel which corresponds to the oae1a and the regionally distributed late aptian niveau jacob have been studied with regard to changes in terrestrial vegetation patterns terrigenous inputs and palaeofertility conditions palynological results from both black shale intervals exhibit a rich and stable floral pattern dominated by various ferns different types of cycads bennettites as well as by several conifer families dinoflagellate cyst assemblages and the calcareous nannofossil based nutrient index show no prominent changes in surface water productivity across the two studied intervals in the vocontian basin significant variations are observed in terrestrial detrital input indicated by changes in absolute abundances of marine and terrestrial palynomorphs according to our results the laminated om rich horizons of the niveau goguel interval reflect deposition during times of reduced siliciclastic input episodes of pronounced condensation were accompanied by anoxic conditions preventing degradation of the predominantly marine derived om in contrast the niveau jacob is characterised by a strong increase in terrestrial palynomorphs most probably reflecting an abrupt increase in riverine runoff the enhanced terrestrial om input may have triggered oxygen depletion in bottom waters resulting in turn in increased om preservation our results highlight the variety of processes that controlled the accumulation of om in the vocontian basin and they illustrate that enhanced surface water productivity is not an indispensable prerequisite for the formation of mid cretaceous black shales

biogenic barium and the detrital ba al ratio a comparison of their direct and indirect determination biogenic barium concentrations obtained from direct determination by a three step sequential extraction procedure are compared to those obtained from the widely used indirect normative calculation based on total digestion a comparison of the biogenic barium from the direct sequential extraction and the indirect normative calculation clearly shows that the detrital ba al ratio is the critical factor in the normative approach and that erroneous assumptions based on this ratio may introduce significant errors to the calculated biogenic barium overall the crustal average ba al ratio of 0 005 0 01 is much higher than our directly determined global average of 0 0037 this would result in an underestimation of the biogenic barium and thus of the primary productivity calculated using the ba flux obtained from the normatively calculated ba record using our ba al det ratio of 0 0037 leads to normatively calculated biogenic barium results that are in reasonable agreement with the biogenic barium from sequential extraction for samples of the atlantic pacific and indian ocean our directly determined regional ba al det ratios deviate from those calculated or assumed from hinterland ratios and our global average ba al det is lower than the one commonly reported therefore in sediments with a significant terrigenous fraction the sequential extraction technique is always required

lake tapps tephra an early pleistocene stratigraphic marker in the puget lowland washington abstract the rhyolitic lake tapps tephra was deposited about 1 0 myr ago shortly after culmination of the early phase of the salmon springs glaciation in the puget lowland it is contained within sediments that were deposited in ponds or lakes in front of the reteating glacier an herb dominated tundra existed in the southern puget lowland at that time lake tapps tephra is most likely the product of an eruption that in part was phreatomagmatic it forms an early pleistocene stratigraphic marker across the southern sector of the puget lowland and provides a link between puget lobe sediments of the cordilleran ice sheet and sediments deposited by olympic alpine glaciers

lilliput effect in late maastrichtian planktic foraminifera response to environmental stress the lilliput effect marks morphologic and intraspecies size reductions in response to environmental stresses commonly associated with the aftermath of mass extinctions this study shows that the lilliput effect is a universal biotic response associated with greenhouse warming mesotrophic or restricted basins shallow marginal settings and volcanically active regions during the late maastrichtian sedimentary sequences analyzed from tunisia egypt texas argentina the south atlantic and indian ocean reveal that the biotic stress response appears uniform regardless of the cause varying only with the degree of biotic stress overall late maastrichtian environments span a continuum from optimum conditions to the catastrophic mass extinctions with a predictable set of biotic responses relative to the degree of stress induced by oxygen salinity temperature and nutrient variations as a result of climate and sea level changes and volcanism early stages of biotic stress result in diversity reduction and the elimination of large specialized species k strategists leading to morphologic size reduction via selective extinction disappearances and intraspecies dwarfing of survivors later stages of biotic stress result in the complete disappearance of k strategists intraspecies dwarfing of r strategists and dominance by low oxygen tolerant small heterohelicids at the extreme end of the biotic response are volcanically influenced environments which cause the same detrimental biotic effects as observed in the aftermath of the k t mass extinction including the disappearance of most species and blooms of the disaster opportunist guembelitria

biogeography and evolution of body size in marine plankton body size is a central feature of any organism reflecting its physiology ecology and evolutionary history marine microplankton are major contributors to the particulate inorganic carbonate foraminifers and coccolithophorids and opal flux radiolaria and diatoms in the ocean and hence size changes in these organisms can influence global biogeochemical cycles this paper is discussing abiotic influences on micro and macroecological size changes among major marine plankton groups linking these to evolutionary size changes during the neogene we review the patterns and outline the causes of size changes geographically and through time in coccolithophorids foraminifers and radiolarians the main feature of the neogene size record is a dramatic size increase in foraminifers a similarly dramatic reduction in the size range of coccolithophorids and highly variable size patterns in radiolarians we argue that the observed pattern is too complex to be explained by a simple common forcing and propose that speculations on the response of oceanic biomineralisation to global warming have to consider the scales at which marine plankton evolve

late pleistocene and early holocene environmental history of southwestern washington state u s a a comparison of pollen records and associated plant remains from sites along a major precipitation gradient in southwestern washington enables reconstruction of the late quaternary environment during glacial and early holocene time during the evans creek stade 25 000 17 000 years bp little moisture reached lowlands east of the olympic mountains and as a result both the puget trough and the columbia basin featured a cold dry climate and parkland tundra vegetation in glacial time greatest aridity seems to have occurred between 19 000 and 17 000 years bp after 17 000 years bp the development of mesophytic subalpine parkland suggests that maritime conditions extended farther east into the puget trough and the cascade range became an important precipitation divide conditions warmer and or drier than today developed throughout western washington between 10 000 and 8000 6000 years bp vegetation on opposite sides of the cascade range became dissimilar as early as 17 000 years bp but this trend was ac

3d imaging challenges in steeply dipping mining structures new lights on acquisition geometry and processing from the brunswick no 6 seismic data canada we have analyzed and processed a 38 km 2 nonorthogonal 3d surface reflection seismic data in the brunswick no 6 area to better understand the effect of acquisition geometry on the resultant image

trace element behavior and redox facies in core shales of upper pennsylvanian kansas type cyclothems the black shale submember of core shales of pennsylvanian kansas type cyclothems is highly enriched in redox sensitive trace elements tes relative to the overlying gray shale submember as well as to many other modern and ancient organic rich deposits controls on trace element behavior in the black shale can be inferred from trace element enrichment factors efs relative to gray shale and the relationship of tes to total organic carbon toc most tes conformed to one of two patterns 1 mo u v zn and pb exhibited moderate efs and strong covariation with toc in samples having 10 wt toc and 2 cu ni cr and co exhibited low efs and moderate to strong covariation with toc in all samples these patterns are inferred to represent different responses to benthic redox conditions the first pattern is characteristic of tes of strong euxinic affinity i e those taken up in solid solution by fe sulfide or involved in other reactions catalyzed by free h2s and resident mainly in authigenic phases whereas the second pattern is characteristic of tes of weak euxinic affinity i e those not strongly influenced by the presence of free h2s and resident mainly in the organic carbon or detrital fractions of the sediment these inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples euxinic conditions were considered to have existed if at least two of four redox indicator trace elements mo u v zn showed euxinic levels of enrichment and nonsulfidic anoxic conditions were inferred otherwise the validity of the procedure is indicated by 1 agreement among all four redox indicators for a large majority of samples 69 of 185 2 among samples yielding a mixed redox signal a systematic sequence of te enrichment v zn mo u and 3 for tes of weak euxinic affinity reduced variance among samples representing each redox facies sequential enrichment may be a response to differential redox thresholds for accumulation e g v or postdepositional remobilization of trace elements e g u and may provide a basis for finer assessment of redox conditions in low oxygen paleoenvironments than permitted by simple classification schemes the multiproxy procedure for redox facies analysis developed in this study is likely to be more reliable than widely used single proxy indicators based on trace elements e g mo authigenic u or v v ni or c s fe systematics e g s toc or dop d 2004 elsevier b v all rights reserved

elevated primary productivity of calcareous nannoplankton associated with ocean anoxic event 1b during the aptian albian transition early cretaceous 1 previous isotopic investigations of aptian albian oceanic anoxic event oae 1b from the western north atlantic blake nose posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column resulting in lowered dissolved oxygen and enhanced organic matter preservation we examined calcareous nannofossils from the same site in the western north atlantic blake nose to evaluate changes in surface water conditions prior to during and after the aptian albian oae1b the results of our analysis conflict somewhat with the previous interpretation that oae1b at blake nose was linked to water column stratification the signal from calcareous nannofossils indicates that in the late aptian prior to oae1b oligotrophic conditions in the surface waters were replaced by mesotrophic conditions that persisted throughout the oae event and into the early albian we speculate that increased surface water productivity facilitated to some degree the development of oae1b at blake nose

biotic effects of late maastrichtian mantle plume volcanism implications for impacts and mass extinctions abstract during the late maastrichtian dsdp site 216 on ninetyeast ridge indian ocean passed over a mantle plume leading to volcanic eruptions islands built to sea level and catastrophic environmental conditions for planktic and benthic foraminifera the biotic effects were severe including dwarfing of all benthic and planktic species a 90 reduction in species diversity exclusion of all ecological specialists near absence of ecological generalists and dominance of the disaster opportunist guembelitria alternating with low o2 tolerant species these faunal characteristics are identical to those of the k t boundary mass extinction except that the fauna recovered after site 216 passed beyond the influence of mantle plume volcanism about 500 kyr before the k t boundary similar biotic effects have been observed in madagascar israel and egypt the direct correlation between mantle plume volcanism and biotic effects on ninetyeast ridge and the similarity to the k t mass extinction which is generally attributed to a large impact reveal that impacts and volcanism can cause similar environmental catastrophes this raises the inevitable question are mass extinctions caused by impacts or mantle plume volcanism the unequivocal correlation between intense volcanism and high stress assemblages necessitates a review of current impact and mass extinction theories

marine productivity changes during the end permian crisis and early triassic recovery abstract the latest permian mass extinction lpme coincided with major changes in the composition of marine plankton communities yet little is known about concurrent changes in primary productivity earlier studies have inferred both decreased and increased productivity in marine ecosystems immediately following the end permian crisis here we assess secular and regional patterns of productivity variation during the crisis through an analysis of the burial fluxes of three elemental proxies total organic carbon toc phosphorus p and biogenic barium babio primary productivity rates appear to have increased from the pre crisis late permian through the early triassic in many parts of the world although the south china craton is unusual in exhibiting a pronounced decline at that time most of the 14 permian triassic study sections show concurrent increases in sediment bulk accumulation rates suggesting two possible influences linked to subaerial weathering rate changes 1 intensified chemical weathering resulting in an increased riverine flux of nutrients that stimulated marine productivity and 2 intensified physical weathering leading to higher fluxes of particulate detrital sediment to continental shelves thus enhancing the preservation of organic matter in marine sediments an additional factor especially in the south china region may have been the intensified recycling of bacterioplankton derived organic matter in the ocean surface layer reducing the export flux rather than primary productivity per se the ecosystem stresses imposed by elevated fluxes of nutrients and particulate sediment as well as by locally reduced export fluxes of organic matter may have been important factors in the 2 to 5 million year long delay in the recovery of early triassic marine ecosystems

the effect of sea surface properties on shell morphology and size of the planktonic foraminifer neogloboquadrina pachyderma in the north atlantic abstract the variability in size and shape of shells of the polar planktonic foraminifer neogloboquadrina pachyderma have been quantified in 33 recent surface sediment samples throughout the northern atlantic ocean and correlated with the properties of the ambient surface waters the aim of the study was to determine whether any of the morphological features could be used to reconstruct sea surface properties in the polar realm of the north atlantic where most paleotemperature proxies appear to fail the analyses revealed that shell morphology is only weakly controlled by habitat properties whereas shell size showed a strong correlation with sea surface temperature the regression of mean shell size on sea surface temperature revealed the presence of two trends among the sinistrally coiled shells a continuous increase in shell size with decreasing sst in sediments deposited under polar water masses and a continuous increase in shell size with increasing sst in samples from transitional waters the second trend mirrors the trend observed for dextrally coiled shells which are frequent in the same samples and signal the presence of n incompta the identical mean shell size trends among the sinistral and dextral specimens in the temperate samples confirms the results of earlier genetic studies which indicated the existence of a small but distinct proportion of opposite coiling in n incompta to which the sinistral shells in the temperate samples could be attributed the linear correlation between mean shell size and sea surface temperature in the polar domain summer sst

a record of late quaternary vegetation from davis lake southern puget lowland washington abstract pollen and macrofossil analyses of a core spanning 26 000 yr from davis lake reveal late pleistocene and holocene vegetational patterns in the puget lowland the core ranges lithologically from a basal inorganic clay to a detritus gyttja to an upper fibrous peat and includes eight tephra units the late pleistocene pollen sequence records two intervals of tundra parkland vegetation the earlier of these has high percentages of picea gramineae and artemisia pollen and represents the vegetation during the evans creek stade fraser glaciation ca 25 000 17 000 yr b p the later parkland interval is dominated by picea tsuga mertensiana and gramineae it corresponds to the maximum ice advance in the puget lowland during the vashon stade fraser glaciation ca 14 000 yr b p an increase in pinus ontorta pollen between the two tundra parkland intervals suggests a temporary rise in treeline during an unnamed interstade after 13 500 yr b p a mixed woodland of subalpine and lowland conifers grew at davis lake during a period of rapid climatic amelioration in the early holocene the prolonged expansion of pseudotsuga and alnus woodland suggests dry temperate conditions similar to those of present rainshadow sites in the puget lowland more mesic forests of tsuga eterophylla thuja plicata and pseudotsuga similar to present lowland vegetation appeared in the late holocene ca 5500 yr b p

the geochemistry of redox sensitive trace metals in sediments abstract we analyzed the redox sensitive elements v mo u re and cd in surface sediments from the northwest african margin the u s northwest margin and the arabian sea to determine their response under a range of redox conditions where oxygen penetrates 1 cm or less into the sediments mo and v diffuse to the overlying water as mn is reduced and remobilized authigenic enrichments of u re and cd are evident under these redox conditions with the onset of sulfate reduction all of the metals accumulate authigenically with re being by far the most enriched general trends in authigenic metal accumulation are described by calculating authigenic fluxes for the 3 main redox regimes oxic reducing where oxygen penetrates 1 cm and anoxic conditions using a simple diagenesis model and global estimates of organic carbon rain rate and bottom water oxygen concentrations we calculate the area of sediments below 1000 m water depth in which oxygen penetration is 1 cm to be 4 of the ocean floor we conclude that sediments where oxygen penetrates 1 cm release mn v and mo to seawater at rates of 140 260 60 150 and 5 10 of their respective riverine fluxes using the authigenic metal concentrations and accumulation rates from this work and other literature these sediments are sinks for re cd and u with burial fluxes of 70 140 30 80 and 20 40 respectively of their dissolved riverine inputs we modeled the sensitivity of the response of seawater re cd and v concentrations to changes in the area of reducing sediments where oxygen penetrates 1 cm our analysis suggests a negligible change in seawater re concentration whereas seawater concentrations of cd and v could have decreased and increased respectively by 5 10 over 20 kyr if the area of reducing sediments increased by a factor of 2 and by 10 20 if the area increased by a factor of 3 the concentration variations for a factor of 2 increase in the area of reducing sediments are at about the level of uncertainty of cd ca and v ca ratios observed in foraminifera shells over the last 40 kyr this implies that the area of reducing sediments in the ocean deeper than 1000 m 4 has not been greater than twice the present value in the recent past

fluctuations of the oxygen minimum zone at the end of oceanic anoxic event 2 reflected by benthic and planktic fossils the latest cenomanian to early turonian late cretaceous section at vallecillo mexico contains a continuous and highly fossiliferous sedimentary record across the late oceanic anoxic event oae 2 and shows similar distributions of benthic inoceramids and planktic foraminifers during this period of an expanded oxygen minimum zone omz we suggest that these synchronous abundance changes result from similar environmental vulnerability of planktotrophic larval stages of inoceramids and deeper dwelling planktic foraminifers and that these synchronous changes reflect the expansion of the omz the abundances of ammonites and fishes used as independent control groups do not correlate and rule out a preservational bias ammonites fishes and their hatchlings thus populated shallower water depths than inoceramid gametes and planktic foramininifers the improving conditions at the end of oae 2 resulted in the dispersal of new inoceramid and foraminiferal morphotypes

paleoenvironmental and paleoceanographic changes across the cenomanian turonian boundary event oceanic anoxic event 2 as indicated by foraminiferal assemblages from the eastern margin of the cretaceous western interior sea abstract two sites near the eastern margin of the cretaceous western interior sea wis were investigated the section at cuba kansas ck is 630 km east of the gssp for the cenomanian turonian boundary at rock canyon colorado rc and the section near sioux city iowa sci is 315 km northeast of the cuba site surprisingly planktic foraminifera dominate all the studied samples despite the relative proximity of the sites to the paleo shoreline and presumed neritic water depths such dominance suggests inhospitable benthic environments and benthic foraminiferal assemblages indicate that seafloor oxygen in the wis decreased eastward therefore the hypothesis of an influx of freshwater into the wis from the western margin forming a fresh water cap that diminished eastward is not supported benthic foraminifera are scarce in most studied samples and species diversity is low in the ck section diversity and abundance increase abruptly in the uppermost cenomanian benthonic zone at the initiation of the 13corg positive excursion marking the onset of oceanic anoxic event oae 2 in the sci section however the benthonic zone is recognized only by presence of nodosaria bighornensis that has a stratigraphic range restricted to this interval other benthic taxa are very rare or absent the favorable conditions of the benthonic zone were short lived while relatively diverse planktic foraminiferal assemblages including keeled species characterize the initial 13c excursion at the ck site dwarfed specimens of heterohelix and hedbergella dominate the assemblages at the more proximal sioux city site furthermore most of the biostratigraphic events recognized in the basin center rc section can be traced into the ck section but not into the sci section including the rotalipora spp and globigerinelloides bentonensis extinctions the heterohelix shift event and the brief benthic recovery event correlation between eastern wis sites shows that the sci section is thicker suggesting a major sediment source to the east this may explain the inhospitable benthic conditions and development of a dead zone seasonal hypoxia analogous to the modern shelf of the northern gulf of mexico proximal to active discharge of the mississippi river development of estuarine circulation in the wis provided the eastern part of the basin with input of calcareous plankton from the south including planktic foraminifera foraminiferal assemblages total organic carbon toc and 13c data of the studied sections suggest a two fold history of greenhorn transgression and oae 2 development the initial phase is a global signal characterized by a positive 13c excursion low toc values and high foraminiferal species diversity the second phase is characterized by overprinting by local conditions in the wis including high fluvial input relatively high toc values and low foraminiferal species diversity these findings suggest that the eastern margin records unique depositional and biotic environments further revealing the dynamic and complex nature of the wis and its sedimentary cycles

age of the salmon springs glaciation in washington a tephra bed within the salmon springs drift at its type locality near sumner washington has a zircon fission track age of 0 84 0 21 m y and the immediately overlying silts are reversely magnetized the same distinctive tephra at auburn washington has a glass fission track age of 0 66 0 04 m y and a zircon age of 0 87 0 27 m y the bracketing silts are likewise reversely magnetized therefore the salmon springs drift as defined at its type section is of middle quaternary age and is much older than the currently accepted age of about 70 000 yr

reconstruction of short term palaeoceanographic changes during the formation of the late albian niveau breistroffer black shales oceanic anoxic event 1d se france the niveau breistroffer black shale succession in the vocontian basin se france is the regional equivalent of the widely distributed late albian oceanic anoxic event 1d the studied black shale rich interval at the col de palluel section is 6 28 m thick and comprises four black shale units with up to 2 5 wt total organic carbon toc intercalated with marlstones calcareous nannofossil palynomorph planktic foraminifera and stable isotopic data from the niveau breistroffer succession suggest that short term climate changes influenced its deposition with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition an increase in the terrigenous marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation a nutrient index based on calcareous nannofossils and the abundance pattern of small 63 125 m hedbergellid foraminifera show short term changes in the productivity of the surface water surface water productivity was reduced during black shale formation and increased during marlstone deposition a calcareous nannofossil temperature index and bulk rock oxygen isotope data indicate relative temperature changes with warmer surface waters for black shale samples at these times warm humid climate and reduced surface water productivity were accompanied by greater abundances of subsurface dwelling calcareous nannofossils nannoconids and planktic foraminifera rotaliporids these taxa presumably indicate more stratified surface water conditions we suggest that the formation of the niveau breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation this in turn caused a decrease in low latitude deep water formation and probably an increase in surface water stratification the combination of these two mechanisms caused depleted o 2 concentrations in the bottom water that increased the preservation potential of organic matter

correlating environmental changes during early albian oceanic anoxic event 1b using benthic foraminiferal paleoecology abstract the nature and consequences of mid cretaceous oceanic anoxic events oaes are the subject of ongoing debate and recent studies have shown that different scenarios are needed to explain each of these events nevertheless similarities between the different oaes can be observed here we have reconstructed paleoenvironmental changes during the early albian oae 1b using benthic foraminiferal distributions and lithologies in three sections from different basins and paleowater depths eutrophic conditions as indicated by the presence of infaunal as well as opportunistic genera such as gyroidinoides pseudobolivina pleurostomella and bolivinitids prevailed before and during the oae and led to dysoxic to anoxic conditions dysoxia was most intense in the bathyal sections but also occurred in the outer shelf where more heterogeneous patterns of foraminiferal distributions are believed to reflect fluctuations of the upper boundary of an oxygen minimum zone a change from eutrophic to mesotrophic conditions caused the termination of oae 1b and opportunistic benthic foraminifera e g pseudobolivina pleurostomella were the first to subsequently repopulate the bathyal sea floor repopulation occurred rapidly in the shallow settings and gradually in the deeper sites where a normal diverse pre event fauna was established a few tens of thousands of years after oae 1b

disaster opportunists guembelitrinidae index for environmental catastrophes blooms of the disaster opportunist guembelitria species are proxies for environmental catastrophes whether impact or volcanism leading to severe biotic stress crises that may range from temporary exclusion of ecological specialists and generalists to mass extinctions during the late maastrichtian and early danian zones p0 and pla guembelitria blooms show global distributions but with the largest blooms 40 80 guembelitria in low and middle latitudes and only minor blooms 10 20 in high latitudes late maastrichtian guembelitria blooms are so far known from the indian ocean and eastern tethys the most intense guembelitria blooms 60 guembelitria occurred in shallow continental shelf areas slope shelf margins and volcanic provinces of the indian ocean what these environments have in common is high nutrient influx eutrophication either from continental runoff upwelling along continental margins or volcanic input at times of biotic crises guembelitria blooms may have spread rapidly to the exclusion of most or all other species much like today s red tides but with near global distributions a simple model can explain the ecological succession and recovery phases that follow major biotic perturbations caused by impacts or volcanism that lead to exclusion of specialist and most generalist species within such highly stressed environments guembelitria is the only genus to thrive and without competition rapidly reproduce and exponentially increase their populations when nutrients are depleted populations rapidly decrease leading to ecologic niches for other generalists and ecosystem recovery small low o2 tolerant heterohelicid populations mark this second stage followed by small trochospiral and planispiral species with further environmental recovery increasing competition niche development and restoration of a well stratified water mass oligotrophic conditions are restored opening habitats for the highly specialized and diverse species and a return to normal diverse assemblages this ecological succession is observed in association with mantle plume volcanism in the indian ocean and eastern tethys during the late maastrichtian and in association with the k t impact and volcanism during the early tertiary d 2004 elsevier b v all rights reserved

biotic effects of impacts and volcanism the biotic effects of late maastrichtian mantle plume volcanism on ninetyeast ridge and deccan volcanism mirror those of the cretaceous tertiary kt mass extinction and impact event planktonic foraminifera responded to high stress conditions with the same impoverished and small sized species assemblages dominated by the disaster opportunists guembelitria cretacea which characterize the kt mass extinction worldwide similar high stress late maastrichtian assemblages have recently been documented from madagascar israel and egypt biotic effects of volcanism cannot be differentiated from those of impacts though every period of intense volcanism is associated with high stress assemblages this is not the case with every impact the most catastrophic biotic effects occurred at the kt boundary 65 0 ma when intense deccan volcanism coincided with a major impact and caused the mass extinction of all tropical and subtropical species the chicxulub impact which now appears to have predated the kt boundary by about 300 kyr coincided with intense deccan volcanism that resulted in high biotic stress and greenhouse warming but no major extinctions the unequivocal connection between intense volcanism and high stress assemblages during the late maastrichtian to early danian and the evidence of multiple impacts necessitates revision of current impact and mass extinction theories

origin of rhythmic albian black shales piobbico core central italy calcareous nannofossil quantitative and statistical analyses and paleoceanographic reconstructions 1 the mid cretaceous 120 90 ma was a time of excess atmospheric co2 greenhouse climate and widespread o2 deficiency in the ocean the albian is punctuated by brief intermittent episodes of anoxia dysoxia recorded as cyclic black shales in the western tethys and atlantic oceans the albian section of the piobbico core central italy contains 30 m 10 ma of rhythmic black shales that were sampled at a high resolution and examined for calcareous nannofossil assemblages and c and o stable isotopes unlike oceanic anoxic events productivity was not the primary factor controlling the deposition of albian rhythmic black shales it is suggested that during warm humid climatic cycles higher temperatures and or increased precipitation and runoff produced density stratification at a regional scale recurrent lowered salinity in the early albian and warming in the late albian are credited with causing development of a pycnocline resulting in slower rates of deep water renewal and consequent anoxia

palynology and paleotemperature analysis of the whidbey formation puget lowland washington a series of pollen assemblages and the environments of deposition are shown by samples from 143 levels of interbedded sand silt clay and peaty and woody sediments in sections from the pleistocene whidbey formation at useless bay the type locality west beach point wilson and foulweather bluff deposition of the formation is interpreted to have taken place over a broad floodplain under fluvial conditions where drainage shifted between and into tracts of paludified ground of the four sections studied only useless bay and point wilson contain assemblages with analogs found in the modern pollen rain on the floodplains of the nisqually skokomish and chehalis rivers in western washington q mode factor analysis of pollen percentages in the whidbey samples extracted douglas fir pine alder grass and sedge as the principals for 93 of the data stepwise regression relating modern pollen rain and temperature resulted in a transfer function that when applied to the principals for the whidbey produced mean july temperatures for the intervals represented by the sections temperature curves for useless bay and point wilson show maxima comparable with the modern average of 15 8 c maximum values at west beach and foulweather bluff are approximately 2 lower these curves when compared with curves from late quaternary deposits and the interglacial puyallup and alderton formations indicate that sediments belonging to the whidbey are largely from an interglacial age comparable to the holocene or present interglaciation but also from cooler episodes similar to the late fraser glaciation

late pleistocene proboscideans and early fraser glacial sedimentation in eastern fraser lowland british columbia three recently radiocarbon dated tusk segments from eastern fraser lowland indicate pleistocene proboscideans probably mammoths lived there between 22 700 and 21 400 years ago during early fraser for the fraser lowland ice advance into the area palynomorphs from silty sand adhering to a tusk indicate the animals grazed on open grassy floodplain sedimentologic and altimeter studies of tusk bearing gravel indicate an early fraser sandur at least 10 km long and deposited at the same time as coquitlam drift formed in chilliwack valley at the same time that a sandur or kame terrace was deposited against the north side of promontory ridge probably about 21 000 years ago the time of coquitlam glacial maximum in western fraser lowland ice blocked chilliwack valley creating a glacial lake whose freshwater pediastrum bearing laminated silt has been observed up to 200 m asl stratigraphy and history of the area following deposition of the above gravels and silt are still uncertain without more chronolo

the cenomanian turonian boundary event on the moroccan atlantic margin agadir basin stable isotope and sequence stratigraphy abstract correlations of four sections constrained by stable isotope stratigraphy and micropalaeontology along a 80 km long e w oriented transect from the western high atlas to the present day coast taghazoute show that the cenomanian turonian boundary event ctbe occurred within shallow water oyster bearing limestones and marls and not in the overlying black shale the age of the laminated shale is early turonian as the planktonic marker helvetoglobotruncana helvetica is found from its first centimetres upward the underlying deposits hosting the ctbe event are bounded by two unconformities interpreted as emersion surfaces and represent the strongest seawardshifts of facies in the local cenomanian sedimentary wedge the 13 c anomaly is only recorded in the coastal taghazoute section not in other sections landward meaning that the ctbe occurred here during a short transgressive phase within an overall regressive trend the lower turonian black shale of the taghazoute section is transgressive onto the second unconformity and pass landward to white evenly laminated chert bearing mudstones then to bioturbated mudstones in the easternmost sections of the transect western high atlas