end cretaceous marine mass extinction not caused by productivity collapse an asteroid impact at the end of the cretaceous caused mass extinction but extinction mechanisms are not well understood the collapse of sea surface to sea floor carbon isotope gradients has been interpreted as reflecting a global collapse of primary productivity strangelove ocean or export productivity living ocean which caused mass extinction higher in the marine food chain phytoplankton dependent benthic foraminifera on the deep sea floor however did not suffer significant extinction suggesting that export productivity persisted at a level sufficient to support their populations we compare benthic foraminiferal records with benthic and bulk stable carbon isotope records from the pacific southeast atlantic and southern oceans we conclude that end cretaceous decrease in export productivity was moderate regional and insufficient to explain marine mass extinction a transient episode of surface ocean acidification may have been the main cause of extinction of calcifying plankton and ammonites and recovery of productivity may have been as fast in the oceans as on land

the preservation potential of coastal coseismic and tsunami evidence observed following the 2012 mw 7 8 haida gwaii thrust earthquake abstract we describe near field coseismic and tsunami evidence collected following the 28 october 2012 m w 7 8 thrust earthquake that occurred offshore western haida gwaii british columbia and discuss factors that influence its extent and preservation potential observations indicate minor geomorphic and sedimentological impacts on the rugged and unpopulated west coast of the islands despite widespread coastal coseismic subsidence 0 5 m triggered landslides and tsunami waves exceeding 3 m in runup maximum 13 m along 230 km of coastline evidence left by the tsunami was minimal likely because it occurred during a low tide that restricted its onshore reach its flow depth and its capacity to entrain and transport significant amounts of clastic sediment sources of which are minimal or absent on the dominantly steep rocky coastline it is unlikely that subaerial evidence of coseismic subsidence and tsunami inundation will be recognizably recorded in the coastal stratigraphy of western haida gwaii due to the relatively small magnitude of subsidence a lack of suitable coastal environments such as tidal marshes to record paleoelevation differences sedimentation rates that are too low to bury a paleoseismic or paleotsunami record and long term relative sea level fall leading to erosion and bioturbation a higher preservation potential is likely for tsunami deposits in coastal lakes ponds and bogs as well as coseismic slope failure deposits offshore in lakes and in sheltered fjords our findings imply that large tsunamigenic earthquakes are likely undersampled in the paleoseismic record of haida gwaii and of other plate margins with similar characteristics

deep water agglutinated foraminiferal changes and stable isotope profiles across the cretaceous paleogene boundary in the rotwandgraben section eastern alps austria abstract the studied interval extends from 2 5 m below to 1 m above the cretaceous paleogene k p boundary and encompasses the uppermost abathomphalus mayaroensis po subzones poa guembelitria cretacea and pob globoconusa conusa p or parvularugoglobigerina eugubina and lowermost p1 subzone p1a or subbotina pseudobulloides planktonic foraminiferal zones the agglutinated benthic foraminiferal assemblages of the uppermost abathomphalus mayaroensis zone are moderately diversified and composed of mixed epifaunal and infaunal morphogroups in the lower part of the guembelitria cretacea subzone benthic foraminifers are extremely rare and represented only by a few epifaunal species in the upper part of this subzone they are still not abundant but assemblages are again moderately diversified in the globoconusa conusa subzone deep water agglutinated foraminifers are abundant highly diversified and represented by mixed epifaunal and infaunal morphogroups bulk rock stable isotope analysis shows a significant drop of both 13 c and 18 o values at the k p boundary it appears that a drastic decrease in abundance and diversity of deep water agglutinated foraminifers as well as a change of the community structure from mixed epifaunal and infaunal to one dominated by epifaunal morphogroups are related to a reduction in marine primary productivity the instantaneous environmental stress and the collapse of primary productivity are compatible with a large bolide impact

paleoceanography of the cretaceous tertiary boundary event inferences from stable isotopic and other data we report the results of new stable oxygen and carbon isotope analyses on carbonate fine fraction whole rock and benthic foraminifers caco3 and coarse fraction percentage determinations and trace element sr analyses on carbonate constituents across the cretaceous tertiary k t boundary in deep sea drilling project dsdp sites 47 2 356 384 and 577 and compare them with published results from k t boundary sections in other dsdp sites we used the trace element data and scanning electron microscope examination to evaluate possible diagenetic alteration and relative preservation of the samples analyzed in this study the 18o data when interpreted as isotopic paleotemperatures indicate relative stable surface water and deepwater temperatures in the late maestrichtian followed by somewhat fluctuating temperatures in the early paleocene however there is no indication of either a significant warming or cooling at or following the k t boundary several sites do exhibit somewhat heavier 18o values by about 0 5 across the boundary which might suggest a 2 3 c cooling at most however we interpret these somewhat heavier 18o values as reflecting slightly better preservation of 18o of carbonate constitutents in relatively clay rich intervals e g lower diagentic potential characteristic of the k t boundary the 13c values of carbonate fine fraction and planktonic foraminifers indicate a major negative excursion in surface water total dissolved carbon across the boundary the surface water and deepwater 13c values from benthic foraminifers combined with calculated decreases in carbonate accumulation rates at all sites in the earliest paleocene are consistent with a major decrease in productivity across the k t boundary the decrease in caco3 accumulation rates is due not to increased rates of dissolution but to decreased production in surface waters the low productivity episode lasted at least 1 m y beyond the k t boundary crisis suggesting that hypothesized catastrophic events alone such as impact of an apollo object are not the only explanation for the observed long term decrease in productivity there is also an indication in the 13c curves from several sites that the surface water 13c decrease began in the latest maestrichtian suggesting that the decrease in productivity may have been independent of a hypothesized impact event

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

benthic foraminiferal turnover across the cretaceous paleogene boundary at agost southeastern spain paleoenvironmental inferences abstract we studied upper cretaceous and lower paleogene benthic foraminifera from the agost section southeastern spain to infer paleobathymetrical changes and paleoenvironmental turnover across the cretaceous paleogene k p transition benthic foraminifera indicate uppermost bathyal depths at agost during the abathomphalus mayaroensis biochron from about 400 kyr before the k p boundary through the early plummerita hantkeninoides biochron about 120 150 kyr before that boundary the depth increased to middle bathyal for the remainder of the cretaceous and remained so for the danian part of the studied section parasubbotina pseudobulloides biochron at least 200 kyr after the k p boundary there were no perceivable bathymetrical changes at the k p boundary where 5 of the species became extinct and the species composition of the benthic foraminiferal fauna changed considerably below the boundary infaunal morphogroups constitute up to 65 73 of the faunas directly above the boundary in the black clays of the lower guembelitria cretacea biozone benthic foraminifera are rare several opportunistic taxa e g the agglutinant haplophragmoides sp have short peaks in relative abundance possibly reflecting low oxygen conditions as well as environmental instability with benthos receiving food from short lived local blooms of primary producers above the clays through the end of the studied interval epifaunal morphogroups dominate up to 70 of the assemblages or there is an even mixture or epifaunal and infaunal morphogroups infaunal groups do not recover to pre extinction relative abundances indicating that the food supply to the benthos did not recover fully over the studied interval about 200 kyr after the k p boundary the benthic foraminiferal faunal changes are compatible with the direct and indirect effects of an asteroid impact which severely destabilized primary producers and the oceanic food web that was dependent upon them

stable isotope toc and caco3 record across the cretaceous tertiary boundary at el kef tunisia we report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers caco3 and toc determinations of sediments across the cretaceous tertiary k t boundary at el kef tunisia we used grain size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation the data suggests the following sequence of events upper maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity a sharp cooling appears to begin just below the k t boundary the k t boundary is characterized by a sudden 2 negative shift in fine fraction 13c a slight 0 6 enrichment in benthic 13c and a reduction of about 40 in caco3 sedimentation these data imply strongly reduced surface water productivity as also observed in numerous deep sea sequences worldwide the lower danian planktic foraminiferal zones p0 p1a is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction 13c values and low 5 15 carbonate deposition at the base of subzone p1b caco3 benthic and fine fraction 13c values increase gradually and reach near pre k t boundary levels in subzone p1c indicating initial recovery after the k t boundary event about 300 000 400 000 years after the k t boundary the prolonged low productivity episode after the k t crisis and the pre k t boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single k t boundary bolide impact

the response of benthic foraminifera to the k pg boundary biotic crisis at elles northwestern tunisia abstract the high resolution quantitative study of benthic foraminifera from the elles section nw tunisia that contains one of the most complete cretaceous paleogene k pg boundary transition and spans about 357 kyr provides detailed data on the palaeoenvironmental turnover across the k pg boundary benthic foraminifera indicate outer neritic uppermost bathyal depths without perceivable bathymetrical changes throughout uppermost maastrichtian assemblages are well preserved and highly diversified indicating stable environment and mesotrophic to weakly eutrophic conditions during the latest cretaceous benthic foraminifera underwent a major faunal turnover in coincidence with the k pg boundary where a dramatic and sudden decrease in the percentage of both infaunal morphogroups and buliminids as well as in diversity heterogeneity and genus and species richness of the assemblages are recorded indicating overall oligotrophic conditions benthic foraminifera do not show significant extinction at the end of the cretaceous with only about 3 of the species clearly becoming extinct together with the temporary disappearance of some taxa a stepped pattern of faunal recovery and restructuring is recognizable during the lowermost danian reflecting the gradual restabilization of the environmental conditions after the k pg boundary event the nature and the abundance of food supply to the sea floor conditioned the faunal turnover in the earliest paleogene which reflects not only a sudden collapse of the food web due to the extinction of calcareous primary producers but also a major rapid change in composition and abundance of food supply just after the k pg boundary short term blooms of some opportunistic species within the g cretacea zone and the lowermost part of the ps pseudobulloides zone would reflect instability in the benthic assemblages that might be related to the transfer to the sea floor of food supply not easily used by the benthos through short term large blooms or changes in abundance of opportunistic various phytoplankton groups the major environmental instability at the sea floor that just follows the k pg boundary event may have been thus related to changes in the phytoplankton composition and abundance and would have taken place over a period of about 25 kyr benthic foraminiferal assemblages appear to stabilize in the lowermost part of zone ps pseudobulloides 65 kyr after the k pg boundary event the sea floor ecosystem at least at outer neritic uppermost bathyal depths may have recovered over a considerably shorter period than commonly suggested even if the food delivery to the sea floor had not fully recovered the pre k pg levels as indicated by the lower percentages of infaunal morphogroups and buliminids this would be also in agreement with the rapid recovery of terrestrial ecosystems following the biotic crisis at the k pg boundary the drastic change of benthic foraminiferal assemblages coincident with the k pg boundary at elles and their staggered reorganization during the lowermost paleogene are largely compatible with the catastrophic effects of a huge asteroid impact on earth at the k pg boundary that severely destabilized the oceanic phytoplankton based food web

changes in southern ocean bottom water environments associated with the middle eocene climatic optimum meco abstract the middle eocene climatic optimum meco was a 650 kyr long interval of pronounced warmth superimposed on the long term eocene cooling trend we investigate benthic foraminiferal assemblage and fossil fish tooth cerium anomaly variability from ocean drilling program odp site 738 in the indian sector of the southern ocean southern kerguelen plateau to assess changes in bottom water chemistry and effects on benthic foraminiferal ecosystems the studied section spans 41 9 to 38 4 ma encompassing the meco as well as extensive pre meco and post meco intervals we report a marked faunal turnover at 40 4 ma 200 kyrs after the onset of the meco at 40 6 ma from an assemblage dominated by epifaunal benthic foraminifera to an infaunal dominated assemblage the infaunal domination persisted until the termination of the meco at 39 95 ma thereafter the pre meco assemblage returned this change is attributed to an increase in export productivity associated with the warming possibly caused by an increase in continental runoff or the influence of a more eutrophic surface water mass superimposed on the change in tropic state the ce ce record shows a positive excursion during the 100 kyrs long meco peak warming at around 40 05 ma indicative of a decrease in bottom water oxygen content synchronously infaunal benthic foraminifera drop briefly in abundance hence we suggest that the peak warming is associated with bottom water oxygen depletion potentially caused by elevated productivity and or a transient influence of an older oxygen depleted water mass

k t boundary extinction geologically instantaneous or gradual event evidence from deep sea benthic foraminifera a stepped pattern of benthic foraminiferal decimation survival and recovery identified across the cretaceous tertiary k t boundary at caravaca southeast spain suggests that an exceptionally large influx of nutrients reached the sea floor suddenly at the time of the k t extinction event rapid reestablishment of pre k t boundary environmental conditions followed our data demonstrate a close coupling between the collapse of the ecologic system in the upper water column at caravaca and a correspondent decimation of bottom dwellers on the sea floor the dramatic environmental collapse of deep water benthic foraminiferal communities at the end of the cretaceous at caravaca suggests that the k t boundary event was geologically instantaneous and catastrophic

benthic foraminifera and environmental turnover across the cretaceous paleogene boundary at blake nose odp hole 1049c northwestern atlantic sediments recovered at lower bathyal odp site 1049 on blake nose northwestern atlantic offer an opportunity to study environmental changes at the cretaceous paleogene k p boundary relatively close to the chicxulub impact structure on the yucatan peninsula mexico in hole 1049c the boundary is located at the base of a 9 cm thick layer with abundant spherules considered to be impact ejecta uppermost maastrichtian oozes below and lowermost danian pelagic oozes above the spherulebed contain well preserved bathyal benthic foraminifera the spherule bed itself in contrast contains a mixture of shallow neritic and deeper bathyal species and specimens vary strongly in preservation this assemblage was probably formed by reworking and down slope transport triggered by the k p impact across the spherule bed i e the k p boundary only f7 of benthic foraminiferal species became extinct similar to the low extinction rates of benthic foraminifera worldwide quantitative analysis of benthic foraminiferal assemblages and morphogroups in the 63 am size fraction indicates a relatively eutrophic stable environment during the latest maastrichtian interrupted by a sudden decrease in the food supply to the benthos at the k p boundary and a decrease in diversity of the faunas followed by a stepped recovery during the earliest danian the recovery was probably linked to the gradual recovery of surface dwelling primary producers d 2004 elsevier b v all rights reserved

evidence and causes of the main extinction events in the paleogene based on extinction and survival patterns of foraminifera abstract we review the four main extinction events in the paleogene from the cretaceous paleogene boundary to the eocene oligocene boundary integrating the results obtained from a study of foraminiferal assemblages with other paleontological and geological data different survival strategies followed by the species are described and the duration of the phases of extinction survival and recovery is estimated the models and patterns of extinction of the foraminifera are highlighted we present a range of evidence and paleo environmental factors and analyze the possible causes of extinction a new terminology for mass extinction events is proposed sudden mass extinction would have happened virtually instantaneously and the process would have taken a few years or decades cretaceous paleogene boundary rapid mass extinction is defined as that which occurred in relatively short events around 100 kyr paleocene eocene and eocene oligocene boundaries slow mass extinctions are suggested to have lasted around 1 myr bartonian priabonian transition and may even have lasted for several million years

how bioturbation obscured the cretaceous palaeogene boundary record the cretaceous palaeogene k pg boundary interval is often penetrated by burrows which may obscure stratigraphic and micropalaeontological records leading to misinterpretations of the sequence of events spanning the k pg boundary here we assess the role of burrowing organisms in the redistribution of benthic foraminifera across the boundary at bidart france and report a strong relationship between the behaviour represented by pre and post k pg trace fossils and their benthic foraminiferal content we further infer a brief interval of eutrophic conditions at the seafloor as reported from other locations which disappeared from the lowermost danian stratigraphic record and is represented only inside post k pg trace fossils hosted in cretaceous strata the combined study of trace fossils and microfossils is a powerful tool in eco stratigraphy and event stratigraphy and can yield important insights into the completeness of the k pg record especially at locations such as bidart where this interval has traditionally been assumed to be complete

diverse patterns of ocean export productivity change across the cretaceous paleogene boundary new insights from biogenic barium 1 one of the best studied aspects of the k pg mass extinction is the decline and subsequent recovery of open ocean export productivity e g the flux of organic matter from the surface to deep ocean some export proxies including surface to deep water 13c gradients and carbonate sedimentation rates indicate a global decline in export productivity triggered by the extinction in contrast benthic foraminiferal and other geochemical productivity proxies suggest spatially and temporally heterogeneous k pg boundary effects here we address these conflicting export productivity patterns using new and compiled measurements of biogenic barium unlike a previous synthesis we find that the boundary effect on export productivity and the timing of recovery varied considerably between different oceanic sites the northeast and southwest atlantic southern ocean and indian ocean records saw export production plummet and remain depressed for 350 thousand to 2 million years biogenic barium and other proxies in the central pacific and some upwelling or neritic atlantic sites indicate the opposite with proxies recording either no change or increased export production in the early paleocene our results suggest that widespread declines in surface to deep ocean 13c do not record a global decrease in export productivity rather independent proxies including barium and other geochemical proxies and benthic community structure indicate that some regions were characterized by maintained or rapidly recovered organic flux from the surface ocean to the deep seafloor while other regions had profound reductions in export productivity that persisted long into the paleocene

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

dinoflagellate based sea surface temperature reconstructions across the cretaceous tertiary boundary abstract quantitative analysis of organic walled dinoflagellate cyst dinocyst assemblages from closely spaced samples across the cretaceous tertiary boundary ktb at el kef nw tunisia caravaca se spain and stevns klint e denmark allows for reconstructions of sea surface temperature sst trends the combined dinocyst based sst curves indicate relatively stable warm conditions during the latest maastrichtian in contrast to strongly fluctuating and on average cooler conditions during the earliest danian in detail the results indicate cooling across the ktb immediately followed by an interval of pronounced warming the latter recorded in all studied sections two more cooling pulses may be recognized in the overlying interval followed by a gradual return to stable relatively warm conditions our data furthermore show that these ktb related climatic changes invoked distinct migration among organic walled cyst producing dinoflagellates a group not pushed to extinction at the ktb recordable in both hemispheres recent models predict periods varying between several months to 8 13 yr of global cooling impact winter and reduced solar transmission as a direct result of the chicxulub ktb impact followed by relatively long term excess co 2 related global warming our results are in line with such models but suggest that the impact related cooling phase may have lasted longer and that marked climatic instability continued to some 100 000 yrs following the ktb event s

food supply to the seafloor in the pacific ocean after the cretaceous paleogene boundary event article i nfo deep sea benthic foraminifera show important but transient assemblage changes at the cretaceous paleogene k pg boundary when many biota suffered severe extinction we quantitatively analyzed benthic foraminiferal assemblages from lower bathyal upper abyssal 1500 2000 m northwest pacific odp site 1210 shatsky rise and compared the results with published data on assemblages at lower bathyal 1500 m pacific dsdp site 465 hess rise to gain insight in paleoecological and paleoenvironmental changes at that time at both sites diversity and heterogeneity rapidly decreased across the k pg boundary then recovered species assemblages at both sites show a similar pattern of turnover from the uppermost maastrichtian into the lowermost danian 1 the relative abundance of buliminids indicative of a generally high food supply increases towards the uppermost cretaceous and peaks rapidly just above the k pg boundary coeval with a peak in benthic foraminiferal accumulation rate bfar a proxy for food supply 2 a peak in relative abundance of stensioeina beccariiformis a cosmopolitan form generally more common at the middle than at the lower bathyal sites occurs just above the buliminid peak 3 the relative abundance of nuttallides truempyi a more oligotrophic form decreases at the boundary then increases above the peak in stensioeina beccariiformis the food supply to the deep sea in the pacific ocean thus apparently increased rather than decreased in the earliest danian the low benthic diversity during a time of high food supply indicates a stressed environment this stress might have been caused by reorganization of the planktic ecosystem primary producer niches vacated by the mass extinction of calcifying nannoplankton may have been rapidly b10 kyr filled by other possibly opportunistic primary producers leading to delivery of another type of food and or irregular food delivery through a succession of opportunistic blooms the deep sea benthic foraminiferal data thus are in strong disagreement with the widely accepted hypothesis that the global deep sea floor became severely food depleted following the k pg extinction due to the mass extinction of primary producers strangelove ocean model or to the collapse of the biotic pump living ocean model

the cretaceous palaeogene k p boundary at ain settara tunisia restructuring of benthic foraminiferal assemblages benthic foraminiferal assemblages in contrast to planktic foraminifera generally did not suffer mass extinctions at the cretaceous palaeogene k p boundary extinctions were fewer in deeper water however the outer shelf upper bathyal section at ain settara tunisia records a dramatic change in the structure of benthic foraminiferal assemblages across the k p boundary at the level of extinction of planktic assemblages and enrichment in ir and other geochemical anomalies highly diversified low dominance upper maastrichtian assemblages with infaunal and epifaunal morphogroups were suddenly replaced by taxonomically impoverished assemblages strongly dominated by epifaunal morphogroups this extinction or temporary emigration of most infaunal morphogroups is interpreted to be the result of a sudden breakdown in food supply this in turn is the consequence of a sudden collapse in primary productivity probably resulting from the impact of the k p asteroid

morphological mineral and geochemical characterization of soil profiles in meiganga as tools for rock weathering intensity and trend evaluation and residual ore deposit prospection in the mineralized domain of central cameroon

benthic foraminifera at the cretaceous tertiary boundary around the gulf of mexico cretaceous tertiary k t boundary sections in northeastern mexico contain marly formations separated by a controversial clastic unit benthic foraminifera in seven sections indicate middle and lower bathyal depths of deposition for the marls with the exception of the upper bathyal northernmost section mixed neritic bathyal faunas were present in the clastic unit indicating redeposition in the deep basin by mass wasting processes resulting from the k t bolide impact in the gulf of mexico benthic foraminifera in the mexican sections and at other deep sea locations were not subject to major extinction at the time of impact but there were temporary changes in assemblage composition benthic faunas indicate welloxygenated bottom waters and mesotrophic conditions during the late maastrichtian and increased food supply during the latest maastrichtian the food supply decreased drastically just after the k t boundary possibly because of the collapse of surface productivity cretaceous and early paleogene benthic foraminifera however did not exhibit the benthic pelagic coupling of present day faunas as documented by the lack of significant extinction at the k t collapse of surface productivity much of the food supplied to the benthic faunas along this continental margin might have been refractory material transported from land or shallow coastal regions the decrease in food supply at the k t boundary might be associated with the processes of mass wasting which removed surface food rich sediment benthic faunas show a staggered pattern of faunal recovery in the lowermost paleogene consistent with a staged recovery of the vertical organic flux but also with a gradual buildup of organic matter in the sediment

sudden death at the end of the mesozoic abstract a paleoecological analysis of the fossil record before and after the cretaceous tertiary boundary indicates that the widespread extinctions and biological stresses around the boundary are best explained in terms of a sudden significant but short temperature rise l alvarez and co authors having found an enrichment in iridium at the same boundary postulated that it was associated with the impact of an extraterrestrial body if this body struck the ocean the water injected into the atmosphere may have led to a transient increase in the global surface temperature this temperature pulse may have been primarily responsible for the effects observed in the biosphere the pattern of extinction of higher plant species suggests that splash down occurred in the northern pacific bering sea area

episodes of intensified biological productivity in the subtropical atlantic ocean during the termination of the middle eocene climatic optimum meco the middle eocene climatic optimum meco is an 500 kyr interval of pronounced global warming from which the climate system recovered in 50 kyr the deep sea sedimentary record can provide valuable insight on the marine ecosystem response to this protracted global warming event and consequently on the ecological changes during this time here we present new benthic foraminiferal assemblage data from ocean drilling program site 1051 in the subtropical north atlantic spanning the meco and post meco interval 41 1 to 39 5 ma we find little change in the species composition of benthic foraminiferal assemblages during the studied interval suggesting that the rate of environmental change was gradual enough that these organisms were able to adapt however we identify two transient intervals associated with peak warming higher productivity interval hpi 1 40 07 39 96 ma and shortly after the meco hpi 2 39 68 39 55 ma where benthic foraminiferal accumulation rates increase by an order of magnitude these hpis at site 1051 appear to coincide with intervals of strengthened productivity in the tethys southern ocean and south atlantic and we suggest that an intensified hydrological cycle during the climatic warmth of the meco was responsible for eutrophication of marine shelf and slope environments

recovery of the deep sea floor after the cretaceous paleogene boundary event the benthic foraminiferal record in the basque cantabrian basin and in south eastern spain abstract a detailed analysis of the upper cretaceous and lower paleogene benthic foraminiferal assemblages 63 m from the middle bathyal loya section basque cantabrian basin southwestern france has been carried out the benthic foraminiferal and palaeoenvironmental turnover across the k pg boundary at loya has been compared to that observed in the nearby bidart section both sections exhibit mesotrophic conditions in the uppermost maastrichtian and a drastic decrease in the nutrient supply to the sea floor in coincidence with the k pg boundary moreover a faunal recovery of the assemblages is observed through the lowermost danian the pattern of faunal and palaeoenvironmental recovery in the basque cantabrian basin has been compared to that observed in the middle bathyal agost and caravaca sections south eastern spain where a similar decrease in the food supply to the sea floor is observed in coincidence with the k pg boundary however whereas low oxygen conditions have been recorded in the lowermost danian in these two sections no evidence for oxygen deficiency has been found in the basque cantabrian basin thus pointing to the regional and not global nature of low oxygen conditions following the k pg boundary event benthic foraminifera from the g cretacea biozone suggest environmental instability in the basque cantabrian basin and in southeastern spain such environmental stress has been related not only to the collapse of the food web due to the extinction of calcareous primary producers but also to a rapidly changing food supply driven by phytoplankton blooms although stabilization of the ecosystems in surface waters probably occurred towards the upper part of the g cretacea biozone data available from the ps pseudobulloides biozone at bidart and agost indicate that food supply to the benthos had not completely recovered at least 200 kyr after the k pg boundary

biotic turnover in benthic foraminifera across the cretaceous tertiary boundary at el kef tunisia abstract the cretaceous tertiary boundary section exposed near el kef tunisia is the most complete boundary sequence known to date it contains nearly 1 m of black and gray boundary clay containing planktic foraminiferal zone poa b 2 m of clayey shales of p1a globigerina eugubina zone and 4 m of shales and marls of p1b g taurica zone quantitative analysis of the benthic foraminiferal fauna suggests that deposition during the latest cretaceous occurred in an upper slope to outer shelf environment which shallowed at the k t boundary to an outer to middle shelf depth and shallowed further by p1b time to mid shelf depth a major reduction in benthic diversity occurred near the k t boundary with about 50 of the fauna disappearing diversity remained an average of 37 lower during deposition of the first 3 m of sediment above the boundary poa b p1a and productivity was very low surviving and thriving foraminifers during this interval were primarily low oxygen tolerant epifaunal and infaunal species a sharp decrease in the low oxygen tolerant fauna and appearance of a shallow mid shelf fauna at about 4 m above the boundary p1b zone signals a second regression return to higher oxygen levels and higher productivity although the environmental effects of the k t boundary event can be inferred from benthic faunas the ultimate cause remains elusive faunal changes prior to and the long recovery period after the k t boundary are difficult to explain by a single impact hypothesis