the cretaceous tertiary boundary stratotype section at el kef tunisia how catastrophic was the mass extinction abstract the cretaceous tertiary k t boundary stratotype section at el kef tunisia represents the most complete and expanded sedimentary record across this important mass extinction horizon presently known high resolution analysis of planktic foraminifera in two outcrops el kef i stratotype and el kef ii along with comparisons between planktic and benthic foraminifera calcareous nannofossils ostracods pollen and spores and dinoflagellates indicate that major changes across the k t boundary are registered only in benthic and planktic foraminifera and calcareous nannofossils biotic changes in benthic foraminifera are unique to el kef and similarly shallow continental shelf sections and appear to be the result of a sea level regression in the latest maastrichtian followed by a sea level rise across the k t boundary that was accompanied by expansion of the local oxygen minimum zone omz biotic changes in planktic foraminifera appear partly related to these conditions also but in general reflect more global oceanographic changes for instance species extinctions are gradual and selective as observed in k t sections worldwide rather than random and abrupt although there is a 69 decline in species richness between 25 cm below and 10 cm above the k t boundary only rare species disappeared their combined relative abundance constitute less than 20 of the total population about 52 of these extinct taxa 8 of the population are large ornate morphologically complex tropical subtropical forms that lived at or below the thermocline no planktic foraminifera from this depth range survived the k t boundary event all survivor taxa were surface dwellers living within the photic zone their relative abundance 80 dominates both cretaceous and early tertiary populations these data indicate that the k t biotic record in the shallow continental shelf section at el kef was significantly influenced by local conditions which combined with the latest maastrichtian sea level regression and subsequent sea level rise resulted in shallowing of the local omz relative to the sea surface shallowing of the local omz lead to the selective disappearance of benthic faunas and may have adversely affected the surviving photic zone dwellers the selective nature of species extinctions however appear to be related partly to long term global oceanographic changes which were accelerated at the k t boundary possibly by a bolide impact

nature and timing of extinctions in cretaceous tertiary planktic foraminifera preserved in deccan intertrappean sediments of the krishna godavari basin india in c29r below the cretaceous tertiary boundary ktb massive deccan trap eruptions in india covered an area the size of france or texas and produced the world s largest and longest lava megaflows 1500 km across india through the krishna godavari k g basin into the bay of bengal investigation of ten deep wells from the k g basin revealed four lava megaflows separated by sand silt and shale with the last megaflow ending at or near the ktb the biologic response in india was swift and devastating during deccan eruptions prior to the first megaflow planktic foraminifera suffered 50 species extinctions survivors suffered another 50 extinctions after the first megaflow leaving just 7 8 species no recovery occurred between the next three megaflows and the mass extinction was complete with the last mega flow at or near the ktb the last phase of deccan volcanism occurred in the early danian c29n with deposition of another four megaflows accompanied by delayed biotic recovery of marine plankton correlative with these intense volcanic phases climate changed from humid tropical to arid conditions and returned to normal tropical humidity after the last phase of volcanism the global climatic and biotic effects attributable to deccan volcanism have yet to be fully investigated however preliminary studies from india to texas reveal extreme climate changes associated with highstress environmental conditions among planktic foraminifera leading to blooms of the disaster opportunist guembelitria cretacea during the late maastrichtian

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

epicontinental permian cretaceous seaways in central india the debate for the narmada versus godavari rifts for the cretaceous tertiary incursion abstract this study presents an overview of mesozoic transgressions that influenced the palaeogeography of central india and offers an analysis of the existing evidence for the interpretation of the depositional record of infra and inter trappean sequences these data are then used to understand the respective palaeogeographic settings of the narmada and the godavari master valleys leading to a reappraisal of the paths suggested thus far for a cretaceous tertiary k t seaway major rift related discontinuities have been subjected to reactivation episodes during the mesozoic these tectonic events caused the initiation of several pericratonic basins the riftogenic valley systems have been affected by transgressions from the western margin of india through the narmada valley and or from the eastern margin through the godavari valley however for the most part these continent scale valley systems have hosted mainly mesozoic fluviatile and lacustrine sediment successions besides a marine incursion from the west in the lower reaches of narmada valley is widely recognised on the basis of the late cretaceous bagh beds additionally the maastrichtian palaeogeography of these valley systems of central india have been strongly influenced by the uplift resulting from the thermo magmatic flux associated with the deccan volcanism this resulted in major topographic readjustments within the godavari and narmada tapti palaeovalleys resulting in turn in major basinal depressions as revealed from the reconstruction of the palaeo digital elevation model significantly removed from the eastern and western coastal margins of india isolated occurrences of marine biota such as foraminifera marine algae and palm fossils have been found in infra and inter trappean maastrichtian and danian sequences of central india their presence in these inland basins is enigmatic and three hypotheses have been proposed to explain the presence of marine environments in these basins a trans deccan strait connecting both the margins of india through pre existing rift systems b an 800 km long seaway through the narmada valley and c a marine incursion through the godavari valley this palaeogeographic analysis supports a marine incursion through the godavari rift and presents arguments against the other two

stratigraphy structure and volcanology of the se deccan continental flood basalt province implications for eruptive extent and volumes the deccan volcanic province is one of the world9s largest continental flood basalt provinces and derives additional importance because its eruptions 64 67 ma straddle the cretaceous tertiary boundary to better assess the environmental impact of deccan volcanism and its possible effect upon cretaceous tertiary boundary biota it is necessary to document the stratigraphy chronology and volume of the eruptions new chemostratigraphical data permit mapping of the se deccan these data strengthen the likelihood that the rajahmundry traps of eastern india were originally fed by long distance flows and are an extension of the main deccan volcanic province an east west cross section reveals a depression or moat around the se periphery of the deccan volcanic province this provided a site in which shallow lakes initially formed and along which later lava eruptions became channelled and confined published palaeomagnetic data indicate that the lavas of the se deccan were erupted during chron 29r coeval with the cretaceous tertiary boundary and the chemostratigraphic data place the associated lake sediments i e lameta group beneath and within lavas of the wai subgroup finally these new map data are combined with previous work to provide a quantitative estimate for the original deccan volcanic province eruptive volume of c 1 3 10 6 km 3

chicxulub impact predates k t boundary new evidence from brazos texas abstract multidisciplinary studies including stratigraphy sedimentology mineralogy and geochemistry of the new core mullinax 1 and outcrops along the brazos river and cottonmouth creek falls county texas reveal the complex history of the chicxulub impact the event deposit and the k t boundary event the k t boundary as identified by the negative 13c shift first occurrence of danian planktic foraminifera and palynomorphs occurs 80 cm above the event deposit in core mullinax 1 the underlying 80 cm interval was deposited in a shallow low oxygen environment during the latest maastrichtian as indicated by high stress microfossil assemblages small shells and burrows infilled with framboidal pyrite the underlying event deposit commonly interpreted as k t impact tsunami consists of a basal conglomerate with clasts containing chicxulub impact spherules repeated upward fining units of spherule rich sands followed by hummocky cross bedded and laminated sands which are burrowed by thalassinoides planolites and ophiomorpha and truncated by erosion this suggests a series of temporally separated storm events with re colonization of the ocean floor by invertebrates between storms rather than a series of waning tsunami generated waves the lithified clasts with impact spherules at the base of the event deposit provide strong evidence that the chicxulub impact ejecta layer predates the event deposit but was eroded and re deposited during the latest maastrichtian sea level lowstand the original chicxulub ejecta layer was discovered in a 3 cm thick yellow clay layer interbedded in undisturbed late maastrichtian clay and mudstones 40 cm below the base of the event deposit and near the base of planktic foraminiferal zone cf1 which spans the last 300 kyr of the maastrichtian the yellow clay consists of cheto smectite derived from alteration of impact glass as indicated by rare altered glass spherules with similar chemical compositions as reworked spherules from the event deposit and chicxulub impact spherules from ne mexico and haiti the brazos sections thus provide strong evidence that the chicxulub impact predates the k t boundary by about 300 kyr consistent with earlier observations in ne mexico and the chicxulub crater core yaxcopoil 1

does δ13ccarb of the chinese loess indicate past c3 c4 abundance a review of research on stable carbon isotopes of the chinese loess current research on stable carbon isotopes of the chinese loess is reviewed the stable carbon isotopic composition of soil organic matter som 13corg of paleosols formed during interglacials is more positive than that within loess accumulated during glacials spatially it becomes progressively more negative from the eastern chinese loess plateau clp to the western however stable carbon isotopic composition of pedogenic carbonates 13ccarb from the same sequence produces an opposing trend both temporally and spatially and variation differs from expectations under conditions of equilibrium this indicates that 13ccarb in the chinese loess cannot be used to reconstruct the relative proportion of c3 c4 plants in past ecological communities furthermore use of 13ccarb to reconstruct the expansion of c4 plants in older tertiary red clay deposits is considered unreliable we believe 13ccarb may act as an indirect indicator of vegetation density following on changes in moisture supply controlled by the intensity of the asian summer monsoon but conclude that full understanding of the paleoclimatic significance of 13ccarb in the chinese loess and underlying tertiary red clay requires better understanding of modern isotopic processes

biotic effects of the chicxulub impact k t catastrophe and sea level change in texas abstract biotic effects of the chicxulub impact the k t event and sea level change upon planktic foraminifera were evaluated in a new core and outcrops along the brazos river texas about 1000 km from the chicxulub impact crater on yucatan mexico sediment deposition occurred in a middle neritic environment that shallowed to inner neritic depths near the end of the maastrichtian the sea level fall scoured submarine channels which were infilled by a sandstone complex with reworked chicxulub impact spherules and clasts with spherules near the base the original chicxulub impact ejecta layer was discovered 45 60 cm below the sandstone complex and predates the k t mass extinction by about 300 000 years results show that the chicxulub impact caused no species extinctions or any other significant biotic effects the subsequent sea level fall to inner neritic depth resulted in the disappearance of all larger 150 m deeper dwelling species creating a pseudo mass extinction and a survivor assemblage of small surface dwellers and low oxygen tolerant taxa the k t boundary and mass extinction was identified 40 80 cm above the sandstone complex where all but some heterohelicids hedbergellids and the disaster opportunistic guembelitrids went extinct coincident with the evolution of first danian species and the global 13c shift these data reveal that sea level changes profoundly influenced marine assemblages in near shore environments that the chicxulub impact and k t mass extinction are two separate and unrelated events and that the biotic effects of this impact have been vastly overestimated

calcareous nannoplankton assemblage changes linked to paleoenvironmental deterioration and recovery across the cretaceous paleogene boundary in the betic cordillera agost spain abstract investigations of calcareous nannoplankton assemblages including species richness and abundance data were performed across the k pg boundary interval at agost se spain between 100 cm and 100 cm below and respectively above the boundary at a considerable high resolution averaging 2 cm from a total of 98 species of the upper maastrichtian only 13 survived mass extinction while the rest of the 86 vanished in the k pg fallout layer a slight progressive decline in species richness and abundance was observed toward the top of the maastrichtian where mixed assemblages consisting of both cold water taxa and typical tethyan ones are present four successive acme events were observed i e markalius inversus and the calcareous dinoflagellate genus thoracosphaera starting from the base of the paleocene followed by those of braarudosphaera bigelowii and neobiscutum parvulum the most prominent acme intervals belong to thoracosphaera spp and b bigelowii opportunistic taxa for which the survival strategy may be linked to their capability to encyst and survive severe environmental deterioration at the upper part of the studied succession calcareous nannoplankton assemblages are already dominated by survivor species as well as incoming ones showing an early pioneer calcareous nannoplankton ecosystems about 35 40 kyr after the k pg boundary correlation between the calcareous nannoplankton assemblage fluctuation including species richness and abundance and the paleoenvironmental changes such as the eustatic and climatic modifications are also discussed

palaeoenvironmental changes at the frasnian famennian boundary in key european sections chemostratigraphic constraints abstract the study aims to put constraints on global environmental changes which took place during the frasnian famennian f f transition by using a geochemical multiproxy approach for this several key european f f boundary sections deposited in different palaeogeographic settings were selected including in addition to the stratotype and parastratotype sections of coumiac montagne noire france and steinbruch schmidt branau germany respectively also some other sections thoroughly characterized by other authors the drilling budesheimer bach prumer mulde germany kowala section holy cross mountains poland la serre france changes in the detrital flux along the sections were evaluated on the basis of both variations in mineral composition and in some diagnostic element ratios like ti al the biogenic flux was assessed as a function of the corg content the input of nutrients or the palaeoproductivity was determined by the p2o5 and ba in excess the degree of anoxia during deposition was constrained by determining the concentration of redox sensitive metals e g fe mn in the bulk sediment of specific element ratios e g v cr as well as the size of pyrite grains together with the degree of pyritization dop in the budesheimer bach core the hydrothermal and volcanic influence in the sedimentary record was detected using e g the al al fe mn and zr al2o3 ratios the kellwasser horizons are characterized by a general decrease in the detrital input together with the increase of al normalized concentration of some of the transition metals these changes are interpreted as reflecting a relative sea level rise and a higher hydrothermal influence in contrast to these the establishment of dysoxic anoxic conditions in the depositional environment as well as the increase of organic matter burial are not always restricted to the kellwasser horizons kwh moreover the hydrothermal influence can lead to misinterpretation with respect to redox conditions and productivity due to the additional input of some specific elements our results indicate the coincidence of sea level rise with hydrothermalism and volcanism during the deposition of the kwh in the area of south laurussia and north gondwana the resulting enrichment in metals and nutrients is coupled in several f f boundary sections with a higher microbial activity as already observed by some authors these effects coupled with a general lowering of the degree of oxygenation of the water bodies could have played a significant role in the demise of the biota

abrupt deep sea warming at the end of the cretaceous climatic and oceanographic variations during the last 2 m y of the maastrichtian inferred from high resolution 10 k y stable isotope analysis of the mid latitude south atlantic deep sea drilling project site 525 reveal a major warm pulse followed by rapid cooling prior to the cretaceous tertiary boundary between 66 85 and 65 52 ma cool but fluctuating temperatures average 9 9 and 15 4 c in intermediate and surface waters respectively this interval is followed by an abrupt short term warming between 65 45 and 65 11 ma which increased temperatures by 2 3 c in intermediate waters and decreased the vertical thermal gradient to an average of 2 7 c this warm pulse may be linked to increased atmospheric pco 2 increased poleward heat transport and the switch of an intermediate water source from high to lowmiddle latitudes during the last 100 k y of the maastrichtian intermediate and surface temperatures decreased by an average of 2 1 and 1 4 c respectively compared to the maximum temperature between 65 32 and 65 24 ma

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

main deccan volcanism phase ends near the k t boundary evidence from the krishna godavari basin se india abstract recent studies indicate that the bulk 80 of the deccan trap eruptions occurred over less than 0 8 m y in magnetic polarity c29r spanning the cretaceous tertiary k t boundary determining where within this major eruptive phase the k t mass extinction occurred has remained problematic for this reason models estimating the biotic and environmental consequences have generally underestimated the rate and quantity of deccan gas emissions by orders of magnitude leading to conclusions that volcanism could not have been one of the major causes for the k t mass extinction in this study we report that the most massive deccan trap eruption occurred near the k t mass extinction these results are based on sedimentologic microfacies and biostratigraphic data of 4 9 m thick intertrappean sediments in four quarry outcrops in the rajahmundry area of the krishna godavari basin of southeastern india in this area two deccan basalt flows known as the rajahmundry traps mark the longest lava flows extending 1500 km across the indian continent and into the bay of bengal the sediments directly overlying the lower rajahmundry trap contain early danian planktic foraminiferal assemblages of zone p1a which mark the evolution in the aftermath of the k t mass extinction the upper rajahmundry trap was deposited in magnetic polarity c29n preceding full biotic recovery these results suggest that volcanism may have played critical roles in both the k t mass extinction and the delayed biotic recovery

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

mock aridity and the paleoecology of volcanically influenced ecosystems the effects of volcanicity often mimic those of aridity and can lead to paleoenvironmental misinterpretations the occurrence of volcanically induced barrenness xeric conditions and extreme geochemical alkalinity or salinity in the context of a regionally more humid climate is dubbed here mock aridity biotic recovery at mount st helens washington and oldoinyo lengai kenya points to potential long term effects of volcanicity on the overall ecosystem contraindicating sedimentary rocks and fossils from kenya miocene rocks and contraindicating sites in u s pacific northwest miocene rocks both suggest interpretive problems due to mock aridity this calls for a reevaluation of volcanogenic sites derived from supposed climax ecosystems in the light of mock aridity

comments on deccan flood basalts at the cretaceous tertiary boundary by v courtillot j besse d vandamme r montigny j j jaeger and h cappetta the age of the flood basalts of the deccan area and the length of the interval during which the outpourings took place are not known precisely the authors have tried to date those basalts and estimate how long the volcanic activity lasted on the basis of new paleomagnetic paleontological and geochronological data of the deccan effusives they came to the preliminary conclusion that the volcanic activity may have lasted less than 1 ma and that the majority of the lavas poured out during chron 29r unfortunately the authors were not familiar with our paper on paleomagnetism and radiomettic age determinations of deccan trap lavas 2 in our paper we presented the paleomagnetic data derived from 223 individual lava flows from 16 sections all over the deccan area and gave the k ar age determinations for 13 selected unaltered lava flows we agree that the enormous volume of deccan extrusives poured out in a relatively short interval and that the volcanic activity was probably concerned with the spreading in the central indian ocean in late cretaceous and early tertiary time

intracanyon flows in the deccan province india case history of the rajahmundry traps the rajahmundry traps form small exposures of basaltic flows on either side of the godavari river near the east coast of india and they are thought to be late cretaceous early paleocene in age because they lie 400 km from the nearest surface exposures of the deccan traps their mode of formation remains unknown furthermore the rajahmundry traps show normal magnetic polarity indicating that they cannot be exact time equivalents of the large volumes of the deccan traps which show reversed magnetic polarity geochemical analyses reveal that the rajahmundry traps are of very uniform composition geochronological studies suggest an age of 64 ma marginally younger than the main sections western ghats of the deccan traps the only section of the main deccan province that may be stratigraphically equivalent on the basis of age geochemical signatures and magnetic polarity is the kolhapur formation at the southern end of the deccan province near the west coast 800 km from the rajahmundry traps we suggest that the rajahmundry traps and other basaltic material found near the mouth of the godavari river represent remnants of intracanyon flows that flowed eastward down the ancestral river systems of peninsular india away from the domed structure caused by the plume that led to the formation of the deccan traps similar intracanyon flows that have traveled 600 km from their source to the pacific coastline are well documented in association with the columbia river basalt province united states in the case of the rajahmundry traps the distance traveled would appear to be 1000 km

40k 40ar dating of the main deccan large igneous province further evidence of ktb age and short duration most mass extinctions coincide in time with outpourings of continental flood basalts cfb some 20 years ago it was shown courtillot v besse j vandamme d montigny r jaeger j j cappetta h 1986 deccan flood basalts at the cretaceous tertiary boundary earth planet sci lett 80 361 374 courtillot v feraud g maluski h vandamme d moreau m g besse j 1988 deccan flood basalts and the cretaceous tertiary boundary nature 333 843 846 duncan r a pyle d g 1988 rapid eruption of the deccan flood basalts at the cretaceous tertiary boundary nature 333 841 843 that the age of the deccan traps was close to the cretaceous tertiary kt boundary and its duration under 1 myr we have undertaken a new geochronological study using the unconventional 40k 40ar cassignol gillot technique which is particularly well suited to the potassium poor deccan lavas the mean of 4 determinations from the topmost ambenali and mahabaleshwar formations is 64 5 0 6 ma they straddle the c29r c29n reversal boundary for which they provide a new constraint the mean age of 3 determinations from the oldest jawhar formation is 64 8 0 6 ma the difference in age between top and bottom of a 3500 m composite section probably comprising 80 of the total deccan volume is statistically insignificant with the overall mean age being 64 7 0 6 ma n 7 our results are consistent with the most recent 40ar 39ar determinations knight k b renne p r halkett a white n 2003 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps earth planet sci lett 208 85 99 knight k b renne p r baker j waight t white n 2005 reply to 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps discussion by a k baksi earth planet sci lett 239 374 382 confirming that there should be no systematic difference between the two methods when they are used in an optimal way an earlier smaller but significant pulse of volcanism between 68 and 67 ma extending over at least 500 km in latitude in the northern part of the deccan cfb has also been identified after 2 to 3 ma of quiescence the second major phase of volcanism occurred near 65 ma expanding over most of the area covered by the first pulse and another 500 km to the south consistent with drift of india by 300 to 450 km at not vert similar 150 mm yr during the quiescence period new paleontological data from the remote rajahmundry section keller g adatte t gardin s bartolini a bajpai s humler e in prep the cretaceous tertiary boundary in deccan traps of the krishna godavari basin of southeastern india epsl to be submitted suggest that this second pulse can itself be divided into two major pulses one starting in c29r and ending at the kt boundary the second starting in the upper part of c29r and ending within c29n

correlation of the deccan and rajahmundry trap lavas are these the longest and largest lava flows on earth abstract we propose that the rajahmundry trap lavas found near the east coast of peninsular india are remnants of the longest lava flows yet recognized on earth 1000 km long these outlying deccan like lavas are shown to belong to the main deccan traps several previous studies have already suggested this correlation but have not demonstrated it categorically the exposed rajahmundry lavas are interpreted to be the distal parts of two very large volume p hoehoe flow fields one each from the ambenali and mahabaleshwar formations of the wai sub group in the deccan basalt group eruptive conditions required to emplace such long flows are met by plausible values for cooling and eruption rates and this is shown by applying a model for the formation of inflated p hoehoe sheet flow lobes the model predicts flow lobe thicknesses similar to those observed in the rajahmundry lavas for the last 400 km of flow the lava flows were confined to the pre existing krishna valley drainage system that existed in the basement beyond the edge of the gradually expanding deccan lava field allowing the flows to extend across the subcontinent to the eastern margin where they were emplaced into a littoral and or shallow marine environment these lavas and other individual flow fields in the wai sub group may exceed eruptive volumes of 5000 km3 which would place them amongst the largest magnitude effusive eruptive units yet known we suggest that the length of flood basalt lava flows on earth is restricted mainly by the size of land masses and topography in the case of the rajahmundry lavas the flows reached estuaries and the sea where their advance was perhaps effectively terminated by cooling and or disruption however it is only during large igneous province basaltic volcanism that such huge volumes of lava are erupted in single events and when the magma supply rate is sufficiently high and maintained to allow the formation of very long lava flows the rajahmundry lava fields were emplaced around 65 ma during the later times of deccan volcanism probably just after the k t environmental crisis however many lava forming eruptions of similar magnitude and style straddled the k t boundary

extinction dissolution and possible ocean acidification prior to the cretaceous paleogene k pg boundary in the tropical pacific abstract biotic perturbations and changes in ocean circulation during the maastrichtian stage of the latest cretaceous raise questions about whether the biosphere was preconditioned for the end cretaceous mass extinction of calcareous plankton a brief acme of inoceramid clams at 71 ma on shatsky rise in the tropical north pacific was followed by their extinction during the mid maastrichtian event at 70 1 ma associated with an abrupt warming of deep waters this was later followed by an interval of intense dissolution beginning 67 8 ma at odp site 1209 2387 m the late maastrichtian dissolution interval was initially gradual and is characterized by a low planktic benthic p b ratio highly fragmented planktic foraminifera mostly an absence of larger taxa low abundances of smaller taxa extremely low planktic foraminiferal numbers and low planktic foraminiferal and nannofossil species richness a partial recovery in carbonate preservation and calcareous plankton simple diversity began 250 kyr prior to the k pg boundary associated with the incursion of a younger more enriched 13c deep water mass although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier maastrichtian values a second brief dissolution event occurred 200 kyr before the boundary evidenced by renewed increase in planktic fragmentation but without a decrease in p b ratio our data show that changing deep water masses coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first 1 6 myr dissolution interval while deccan traps volcanism may have caused surface ocean acidification 200 kyr prior to the k pg mass extinction event

maastrichtian climate productivity and faunal turnovers in planktic foraminifera in south atlantic dsdp sites 525a and 21 abstract stratigraphic faunal and isotopic analyses of the maastrichtian at dsdp sites 525a and 21 in the south atlantic reveal a planktic foraminiferal fauna characterized by two major events an early late maastrichtian diversification and end maastrichtian mass extinction both events are accompanied by major changes in climate and productivity the diversification event which occurred in two steps between 70 5 and 69 1 ma increased species richness by a total of 43 and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity the onset of the terminal decline in maastrichtian species richness began at 67 5 ma and the first significant decline in surface productivity occurred at 66 2 ma coincident maximum cooling to 13 c in surface waters and the reduction of the surface to deep temperature gradient to less than 5 c major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the maastrichtian between 200 and 400 kyr before the k t boundary surface and deep waters warmed rapidly by 3 4 c and cooled again during the last 100 kyr of the maastrichtian surface productivity decreased only moderately across the k t boundary species richness began to decline during the late maastrichtian cooling and by k t boundary time the mass extinction had claimed 66 of the species viewed within the context of maastrichtian climate and productivity changes the k t mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact

environmental effects of deccan volcanism across the cretaceous tertiary transition in meghalaya india the um sohryngkew section of meghalaya ne india located 800 1000 km from the deccan volcanic province is one of the most complete cretaceous tertiary boundary ktb transitions worldwide with all defining and supporting criteria present mass extinction of planktic foraminifera first appearance of danian species 13c shift ir anomaly 12 ppb and ktb red layer the geochemical signature of the ktb layer indicates not only an extraterrestrial signal ni and all platinum group elements pges of a second impact that postdates chicxulub but also a significant component resulting from condensed sedimentation p redox fluctuations as co fe pb zn and to a lesser extent ni and cu and volcanism from the late maastrichtian c29r into the early danian a humid climate prevailed kaolinite 40 60 detrital minerals 50 80 during the latest maastrichtian periodic acid rains carbonate dissolution cia index 70 80 associated with pulsed deccan eruptions and strong continental weathering resulted in mesotrophic waters the resulting super stressed environmental conditions led to the demise of nearly all planktic foraminiferal species and blooms 95 of the disaster opportunist guembelitria cretacea these data reveal that detrimental marine conditions prevailed surrounding the deccan volcanic province during the main phase of eruptions in c29r below the ktb ultimately these environmental conditions led to regionally early extinctions followed by global extinctions at the ktb

calcareous nannofossil biostratigraphy and paleoecology of the cretaceous tertiary transition in the central eastern desert of egypt abstract the gebel qreiya and nearby wadi hamama sections of the central eastern desert are among the most complete k t boundary sequences known from egypt the two sections were analyzed spanning an interval from l 83 myr below to about 3 myr above the k t boundary a 1 cm thick red clay layer at the k t boundary at gebel qreiya contains an ir anomaly of 5 4 ppb the high resolution study and well preserved nannoflora provide good age control and the first quantitative records of calcareous nannofossil assemblages for paleoecological interpretations across the k t transition in egypt four zones micula murus micula prinsii np1 and np2 were distinguished and correlated with other nannofossil and planktonic foraminiferal zonations that are broadly applicable for the eastern tethys region latest maastrichtian assemblages are abundant and diverse though cretaceous species richness progressively decreased across the k t boundary dominant species include arkhangelskiella cymbiformis micula decussata and watznaueria barnesae with high abundance of dissolution resistant m decussata reflecting periods of high environmental stress thoracosphaera blooms mark the k t boundary and are followed by an acme of the opportunistic survivor braarudosphaera bigelowii the first appearance of the new tertiary species cruciplacolithus primus and an acme of coccolithus cavus pelagicus these successive abundance peaks provide the basis for subdivision of the early danian zones np1 and np2 into five subzones correlation of selected nannofossil taxa from the egyptian sections with those from various onshore marine and deep sea sections provides insights into their paleoenvironmental and paleoecological affinities

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

the 800 year long ion record from the lomonosovfonna svalbard ice core we present a high resolution record of water soluble ion chemistry from a 121 m ice core spanning about 800 years the core is well dated to 2 3 depth using cycle counting and reference horizons and a simple but close fitting model for the lower 1 3 of the core this core suffers from modest seasonal melt and so we present concentration data in decadal running means to minimize percolation effects sea salt ions na cl mg2 and k account for more than 70 of all ions in general sea salt ion concentrations are rather variable and have no clear association with climatic variations sulfate with 74 being from non sea salt sources has higher concentrations than seen on vestfonna ice cap but lower than in ny alesund aerosols suggesting central spitsbergen receives more marine westerly air masses than ny alesund but more sulfate enriched easterly air masses than nordaustlandet clear anthropogenic impacts are found for sulfate nitrate and ammonium and probably excess chloride after the mid twentieth century with sulfate showing a significant rise by the end of the nineteenth century sulfate and methanesulfonate concentrations correlate well during the twentieth century and it is clear that most of the preindustrial sulfate is of biogenic origin terrestrial component ca2 has the highest concentrations in the coldest part of the little ice age suggesting more windy conditions transporting local terrestrial dust to the ice cap all ion concentrations decrease at the end of the twentieth century which reflects loss of ions by runoff with non sea salt magnesium being particularly sensitive to melting

assessing eruption column height in ancient flood basalt eruptions a buoyant plume model is used to explore the ability of flood basalt eruptions to inject climate relevant gases into the stratosphere an example from the 1986 izu oshima basaltic fissure eruption validates the model s ability to reproduce the observed maximum plume heights of 12 16 km above sea level sustained above fire fountains the model predicts maximum plume heights of 13 17 km for source widths of between 4 16 m when 32 by mass of the erupted magma is fragmented and involved in the buoyant plume effective volatile content of 6 wt assuming that the miocene age roza eruption part of the columbia river basalt group sustained fire fountains of similar height to izu oshima 1 6 km above the vent we show that the roza eruption could have sustained buoyant ash and gas plumes that extended into the stratosphere at 45 n assuming 5 km long active fissure segments and 9000 mt of so2 released during explosive phases over a 10 15 year duration the 180km of known roza fissure length could have supported 36 explosive events phases each with a duration of 3 4 days each 5 km fissure segment could have emitted 62 mt of so2 per day into the stratosphere while actively fountaining the equivalent of about three 1991 mount pinatubo eruptions per day each fissure segment could have had one to several vents which subsequently produced lava without significant fountaining for a longer period within the decades long eruption sensitivity of plume rise height to ancient atmospheric conditions is explored although eruptions in the deccan traps 66ma may have generated buoyant plumes that rose to altitudes in excess of 18 km they may not have reached the stratosphere because the tropopause was substantially higher in the late cretaceous our results indicate that some flood basalt eruptions such as roza were capable of repeatedly injecting large masses of so2 into the stratosphere thus sustained flood basalt eruptions could have influenced climate on time scales of decades to centuries but the location i e latitude of the province and relevant paleoclimate is important and must be considered

k t transition in deccan traps of central india marks major marine seaway across india deccan intertrappean sediments in central india are generally considered as terrestrial deposits of maastrichtian age but the cretaceous tertiary k t position is still unknown here we report the discovery of the k t transition a marine incursion and environmental changes preserved within the intertrappean sediments at jhilmili chhindwara district madhya pradesh integrative biostratigraphic sedimentologic mineralogic and chemostratigraphic analyses reveal the basal danian in the intertrappean sediments between lower and upper trap basalts that regionally correspond to c29r and the c29r c29n transition respectively intertrappean deposition occurred in predominantly terrestrial semi humid to arid environments but a short aquatic interval of fresh water ponds and lakes followed by shallow coastal marine conditions with brackish marine ostracods and early danian zone p1a planktic foraminifera mark this interval very close to the k t boundary this marine incursion marks the existence of a nearby seaway probably extending inland from the west through the narmada and tapti rift valleys the jhilmili results thus identify the k t boundary near the end of the main phase of deccan eruptions and indicate that a major seaway extended at least 800 km across india

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

deposition and age of chicxulub impact spherules on gorgonilla island colombia the end cretaceous mass extinction 66 ma has long been associated with the chicxulub impact on the yucatan peninsula however consensus on the age of this impact has remained controversial because of differing interpretations on the stratigraphic position of chicxulub impact spherules relative to the mass extinction horizon one side argues that the impact occurred precisely at the cretaceous paleogene boundary thus coinciding with the mass extinction the other side argues that the impact predated the cretaceous paleogene boundary based on the discovery of primary impact spherules deposits in ne mexico and texas near the base of planktic foraminiferal zone cf1 dated at 170 k y before the cretaceous paleogene boundary a recent study of the most pristine chicxulub impact spherules discovered on gorgonilla island colombia suggested that they represent a primary impact deposit with an absolute age indistinguishable from the cretaceous paleogene boundary here we report on the gorgonilla section with the main objective of evaluating the nature of deposition and age of the spherule rich layer relative to the cretaceous paleogene boundary the gorgonilla section consists of light gray yellow calcareous siliceous mudstones pelagic deposits alternating with dark olive brown litharenites turbidites a 3 cm thick dark olive green spherule rich layer overlies an erosional surface separating maastrichtian and danian sediments this layer consists of a clast supported normally graded litharenite with abundant chicxulub impact glass spherules lithics mostly volcanic and maastrichtian as well as danian microfossils which transitions to a calcareous mudstone as particle size decreases mineralogical analysis shows that this layer is dominated by phyllosilicates similar to the litharenites turbidites that characterize the section based on these results the spherule rich layer is interpreted as a reworked early danian deposit associated with turbiditic currents a major hiatus 250 k y spanning the cretaceous paleogene boundary and the earliest danian is recorded at the base of the spherule rich layer based on planktic foraminiferal and radiolarian biostratigraphy and carbon stable isotopes erosion across the cretaceous paleogene boundary has been recorded worldwide and is generally attributed to rapid climate changes enhanced bottom water circulation during global cooling sea level fluctuations and or intensified tectonic activity chicxulub impact spherules are commonly reworked and redeposited into younger sediments overlying a cretaceous paleogene boundary hiatus of variable extent in the caribbean central america and north atlantic while primary deposits are rare and only known from ne mexico and texas because of their reworked nature gorgonilla spherules provide no stratigraphic evidence from which the timing of the impact can be inferred

deccan volcanism induced high stress environment during the cretaceous paleogene transition at zumaia spain evidence from magnetic mineralogical and biostratigraphic records abstract we conducted detailed rock magnetic mineralogical and geochemical mercury analyses spanning the cretaceous paleogene boundary kpb at zumaia spain to unravel the signature of deccan induced climate and environmental changes in the marine sedimentary record our biostratigraphic results show that zumaia is not complete and lacks the typical boundary clay zone p0 and the base of zone p1a 1 in the basal danian presence of an unusual 1m thick interval spanning the kpb is characterized by very low detrital magnetite and magnetosome biogenic magnetite contents and by the occurrence of akaganeite a very rare mineral on earth in oxidizing acidic and hyper chlorinated environments compatible with volcanic settings these benchmarks correlate with higher abundance of the opportunist guembelitria cretacea species detrital magnetite depletion is not linked to significant lithological changes suggesting that iron oxide dissolution by acidification is the most probable explanation the concomitant decrease in magnetosomes produced by magnetotactic bacteria at the anoxic oxic boundary is interpreted as the result of changes in seawater chemistry induced by surficial ocean acidification mercury peaks up to 20 50 ppb are common during the last 100 kyr of the maastrichtian zone cf1 but only one significant anomaly is present in the early danian which is likely due to the missing interval absence of correlation between mercury content r2 0 009 and total organic carbon r2 0 006 suggest that the former originated from the deccan traps eruptions no clear relation between the stratigraphic position of the mercury peaks and the magnetite depleted interval is observed although the frequency of the mercury peaks tends to increase close to the kpg boundary in contrast to bidart france and gubbio italy where magnetite depletion and akaganeite feature within a 50cm thick interval located 5 cm below the kpg boundary the same benchmarks are observed in a 1m thick interval encompassing the kpg boundary at zumaia results reinforce the synchronism of the major eruptions of the deccan traps magmatic province with the cretaceous paleogene kpg mass extinction and provide new clues to better correlate the deccan imprint of the global sedimentary record

new palaeomagnetic data from the mahabaleshwar plateau deccan flood basalt province india implications for the volcanostratigraphic architecture of continental flood basalt provinces abstract new magnetostratigraphic data from seven western ghats sections in the deccan volcanic province are presented these are combined with an established geochemically defined stratigraphy and volcanological logs to provide a correlated chronological eruptive framework we identify two magnetic polarities in five of the sections and these are assigned to chrons 29r and 29n importantly the reversal boundary represents an identifiable isochronous surface within the volcanic pile this surface occurs at different elevations as does the altitude of the geochemically defined formation boundary i e ambenali mahabaleshwar fms which defines a second isochronous surface inspection reveals significant differences in the number and thickness of lava units preserved between these two surfaces this indicates that there was significant local topography c 80 m across deccan volcanic province lava fields during their development an interpretation consistent with topographies observed across modern and historical examples e g hawaii iceland these data also indicate that the geochemical stratigraphies of continental flood basalt provinces can mask local and sub regional detail in lava stacking patterns when applied at smaller spatial scales 2 10 4 m finally transitional r n directions preserved in some eruptive units place constraints upon the rates of eruption and indicate c 2 ka periods of volcanic repose

the influence of deccan volcanism on climate insights from lacustrine intertrappean deposits anjar western india abstract a sedimentary succession from anjar sandwiched between basaltic flows records what transpired as continental india passed from cretaceous to tertiary times in the immediate vicinity of the deccan trap province the deposits consist of interlayered peloidal cherty limestones and shales the shales are dominated by the mineral sepiolite chert occurs as three varieties these include an amorphous cement microcrystalline quartz and chalcedony the last two usually fill gastropodal chambers and peloids these sediments are interpreted as being deposited in an alkaline closed basin lake that periodically received silica saturated hydrothermal solutions the lake in spite of having fluctuating shorelines was perennial this wave dominated lake was highly productive biogenically which is evident in the abundance of molluscan shell debris based on the sedimentological characteristics the site appears to be located proximal to the palaeo shoreline the palaeolatitude position of india during the maastrichtian would suggest a sub humid to humid seasonal climate in kachchh a semi arid climate is inferred on the basis of the lake deposits for anjar this apparent contradiction is believed to be due to mock aridity this term is used to explain volcanically influenced climates that mimic characters of xeric semi arid climates similar signatures of semi aridity in the indian peninsula are observed in calcic palaeosols of the contemporaneous lameta formation sediments around jabalpur

mass wasting and hiatuses during the cretaceous tertiary transition in the north atlantic relationship to the chicxulub impact deep sea sections in the north atlantic are claimed to contain the most complete sedimentary records and ultimate proof that the chicxulub impact is cretaceous tertiary boundary ktb in age and caused the mass extinction a multi disciplinary study of north atlantic dsdp sites 384 386 and 398 based on high resolution planktonic foraminiferal biostratigraphy carbon and oxygen stable isotopes clay and whole rock mineralogy and granulometry reveals the age stratigraphic completeness and nature of sedimentary disturbances results show a major hiatus across the ktb at site 384 with zones cf1 p0 and p1a missing spanning at least 540 ky similar to other north atlantic and caribbean localities associated with tectonic activity and gulf stream erosion at sites 386 and 398 discrete intervals of disturbed sediments with mm to cm thick spherule layers have previously been interpreted as the result of impact generated earthquakes at the ktb destabilizing continental margins prior to settling of impact spherules however improved age control based on planktonic foraminifera indicates spherule deposition in the early danian zone p1a 2 upper parvularugoglobigerina eugubina zone more than 100 ky after the ktb at site 386 two intervals of white chalk contain very small 63 m early danian zone p1a 2 assemblages 65 and common reworked cretaceous 35 species in contrast the in situ red brown and green abyssal clays of this core are devoid of carbonate in addition high calcite mica and kaolinite and upward fining are observed in the chalks indicating downslope transport from shallow waters and sediment winnowing via distal turbidites at site 398 convoluted red to tan sediments with early danian and reworked cretaceous species represent slumping of shallow water sediments as suggested by dominance of mica and low smectite compared to in situ deposition we conclude that mass wasting was likely the result of earthquakes associated with increased tectonic activity in the caribbean and the iberian peninsula during the early danian well after the chicxulub impact

weathering characteristics of interflow volcanic boles from mandla lobe eastern deccan volcanic province abstract the deccan volcanism straddling the cretaceous paleogene boundary resulted into one of the most extensive continental flood basalts in the western and central peninsular india the interflow sedimentary units boles often cited as paleosols are the rare archives of paleoenvironmental conditions existed during successive lava flows a debate on the origin of boles as true paleosols exists therefore in order to trace out regional extent of such conditions pedogenic non pedogenic in the context of their paleoenvironmental significance during the deccan volcanism we studied here mineral magnetic characteristics of 36 color differentiated bole beds from the mandla lobe in the eastern deccan volcanic province edvp classified into four types gray yellow brown and red based on their munsell notations the gray yellow and brown boles show dominantly ferrimagnetic composition chiefly magnetite and titanomagnetite while red boles characterize mixed ferri and antiferromagnetic mainly hematite mineralogy the granulometric domain parameters suggest larger single domain sd and the multidomain md ferrimagnets in the majority of cases whereas superparamagnetic sp particles with frequency dependent susceptibility fd 2 6 to 20 3 10 8 m 3 kg 1 are limited to the few red and brown boles only the significant presence of primary parent magnetic minerals i e coarse sd md titanomagnetite and magnetite in the majority of boles depict incipient to moderate weathering owing to limited time intervals during successive eruptions the combination of hematite and sp particles present only in the few red and brown boles depicts baking effect rather than pedogenesis the comparison of magnetic properties of boles from edvp and western deccan volcanic province wdvp shows significant differences in the concentration of sp ferrimagnetic particles and hematite attributed to variable weathering intensity duration and heating related alterations from the upper flows both edvp and wdvp boles indicate similar first order paleoenvironmental conditions without any major pedogenesis that can be regionally correlated

mid latitude terrestrial climate of east asia linked to global climate in the late cretaceous reply the late cretaceous late campanian to maastrichtian was characterized by a variable greenhouse climate with evidence for cooling and or glaciation and warming events most of these climatic signals are derived from marine records and knowledge of the terrestrial climate especially in the mid latitudes is limited due to fragmentary geological records on continents here we report mid latitude terrestrial stable oxygen and carbon isotope data from pedogenic carbonates in the nearly continuous late cretaceous age sk 1 core drilled in the songliao basin northeastern china our data indicate a punctuated mid latitude terrestrial climate in the late cretaceous we interpret the negative excursion of pedogenic carbonate 18o in the early maastrichtian to be the result of decreasing temperature and or strengthened westerlies during global cooling and possible glaciation providing valuable mid latitude terrestrial evidence for this event the negative 13c isotopic excursion ca 66 ma is modeled as higher primary productivity caused by increasing temperature and precipitation in response to a warming climate in the latest cretaceous our continuous stable isotopic records in the songliao basin are in accordance with previously published global late cretaceous records of climate variability from marine and terrestrial regions and demonstrate the sensitivity of mid latitude terrestrial climate in a greenhouse world

global climate change and planktic foraminiferal response in the maastrichtian 1 the lengthy warm stable climate of the cretaceous terminated in the campanian with a cooling trend interrupted in the early and latest maastrichtian by two events of global warming at 70 68 ma and at 65 78 65 57 ma these climatic oscillations had a profound effect on pelagic ecosystems especially on planktic foraminiferal populations here we compare biotic responses in the tropical subtropical tethyan open ocean and mesotrophic zin valley israel and oligotrophic tunisia slopes which correlate directly with global warming and cooling the two warming events coincide with blooms of guembelitria an extreme opportunist genus best known as the main survivor of the cretaceous paleogene k pg catastrophe in the maastrichtian guembelitria bloomed in the uppermost surface water above shelf and slope environments but failed to reach the open ocean as it did at k pg the coldest interval of the late maastrichtian 68 65 78 ma is marked by an acme of the otherwise rare species gansserina gansseri a deep dwelling keeled globotruncanid the g gansseri acme event can be traced from the deep ocean even onto the tethyan slope marking copious production and circulation of cold intermediate water this acme is abruptly terminated by extinction of the species a dramatic reversal attributed to a short term global warming episode this extinction corresponds precisely with the second bloom of guembelitria that began 300 kyr prior to the k pg event the antithetical relationship between blooming of guembelitria and the g gansseri acme reflects planktic foraminiferal sensitivity to warm cool warm cool climatic oscillations marking the end of the cretaceous

a high resolution marine 187os 188os record for the late maastrichtian distinguishing the chemical fingerprints of deccan volcanism and the kp impact event abstract a composite late maastrichtian 65 5 to 68 5 ma marine osmium os isotope record based on samples from the southern ocean odp site 690 the tropical pacific ocean dsdp site 577 the south atlantic dsdp site 525 and the paleo tethys ocean demonstrates that subaerially exposed pelagic carbonates can record seawater os isotope variations with a fidelity comparable to sediments recovered from the seafloor new results provide robust evidence of a 20 decline in seawater 187os 188os over a period of about 200 kyr early in magnetochron c29r well below the cretaceous paleogene boundary kpb confirming previously reported low resolution data from the south atlantic ocean new results also confirm a second more rapid decline in 187os 188os associated with the kpb that is accompanied by a significant increase in os concentrations complementary platinum pt and iridium ir concentration data indicate that the length scale of diagenetic remobilization of platinum group elements from the kpb is less than 1 m and does not obscure the pre kpb decline in 187os 188os increases in bulk sediment ir concentrations and decreases in bulk carbonate content that coincide with the os isotope shift suggest that carbonate burial flux may have been lower during the initial decline in 187os 188os we speculate that diminished carbonate burial rate may have been the result of ocean acidification caused by deccan volcanism

large scale climatic fluctuations in the latest ordovician on the yangtze block south china likely under warm and humid conditions low cia values however indicate the near absence of chemical weathering thereby refl ecting cool and or arid conditions in this paper the paleo climatic changes during the ordovician silurian transition were reconstructed in the light of cia values derived from the chemical composition of fi ne grained siliciclastic rocks in the mid upper yangtze river region china the infl u ences of paleoclimatic changes on biota are also discussed abstract the ordovician silurian transition was a critical interval in earth s history marked by dramatic climatic oceanic and biological turnovers here we present the chemical index of alteration cia as a proxy of changes in intensity of chemical weathering and its varia tions across the ordovician silurian boundaries wufeng through guanyinqiao to longmaxi formations from wangjiawan and nanbazi on the yangtze block south china in order to explore the climatic changes our data show that the cia values of sediments commonly range from 75 to 90 in the wufeng and longmaxi formations indicating a high degree of chemical weathering and thus a hot and humid climate during deposition in contrast a sharp drop in cia values most 60 70 in the guanyinqiao formation or hirnantian suggests an overall cold and arid climate interrupted by several intervals of warm climate when deposited the temporal coincidence of two phases of massive biotic extinctions with the beginning and end of the cold climate epoch respectively suggests that the large climatic changes could be one of the main controls on the mass extinctions although other factors may also have played a role

paleoecology of the cretaceous tertiary mass extinction in planktonic foraminifera abstract paleobiogeographic patterns of the cretaceous tertiary k t mass extinction in planktonic foraminifera in tunisia spanning environments from open marine upper bathyal to shelf and shallow marginal settings indicate a surprisingly selective and environmentally mediated mass extinction this selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction including species richness ecological generalists ecological specialists surface and subsurface dwellers whether based on the number of species or the relative percent abundances of species the following conclusions can be reached for shallow to deep environments about three quarters of the species disappeared at or near the k t boundary and only ecological generalists able to tolerate wide variations in temperature nutrients salinity and oxygen survived among the ecological generalists heterohelicids guembelitrids hedbergellids and globigerinellids only surface dwellers survived ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively biserials thrived during the latest maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early danian triserials thrived only in shallow marginal marine environments or similarly stressed ecosystems during the latest maastrichtian but dominated both open marine and restricted marginal settings in the early danian this highly selective mass extinction pattern reflects dramatic changes in temperature salinity oxygen and nutrients across the k t boundary in the low latitude tethys ocean which appear to be the result of both long term environmental changes e g climate sea level volcanism and short term effects bolide impact

chicxulub impact spherules in the north atlantic and caribbean age constraints and cretaceous tertiary boundary hiatus the chicxulub impact is commonly believed to have caused the cretaceous tertiary boundary mass extinction and a thin impact spherule layer in the north atlantic and caribbean is frequently cited as proof we evaluated this claim in the seven best north atlantic and caribbean cretaceous tertiary boundary sequences based on high resolution biostratigraphy quantitative faunal analyses and stable isotopes results reveal a major cretaceous tertiary boundary unconformity spanning most of danian subzone p1a 1 and maastrichtian zones cf1 cf2 400 ka in the nw atlantic bass river core odp sites 1049a 1049c and 1050c in the caribbean odp sites 999b and 1001b the unconformity spans from the early danian zone p1a 1 through to zones cf1 cf4 3 ma only in the demerara rise odp site 1259b is erosion relatively minor and restricted to the earliest danian zone p0 and most of subzone p1a 1 150 ka in all sites examined chicxulub impact spherules are reworked into the early danian subzone p1a 1 about 150 200 ka after the mass extinction a similar pattern of erosion and redeposition of impact spherules in danian sediments has previously been documented from cuba haiti belize guatemala south and central mexico this pattern can be explained by intensified gulf stream circulation at times of climate cooling and sea level changes the age of the chicxulub impact cannot be determined from these reworked impact spherule layers but can be evaluated based on the stratigraphically oldest spherule layer in ne mexico and texas which indicates that this impact predates the cretaceous tertiary boundary by about 130 150 ka