morphometric analyses of aptian assipetra infracretacea and rucinolithus terebrodentarius nannoliths implications for taxonomy biostratigraphy and paleoceanography abstract morphometric analyses of aptian calcareous nannofossils revealed the occurrence of differently sized specimens of assipetra infracretacea and rucinolithus terebrodentarius the study was conducted on the cismon core in the tethys and dsdp site 463 in the pacific ocean with good bio magneto and chemostratigraphic control investigation was extended to selected samples from other low latitude sections cores to constrain the spatial and temporal distribution of the differently sized morphotypes normal and large sized specimens display the same ultrastructure but are clearly separated when maximum diameter is measured no transitional forms were observed the large sized specimens of assipetra infracretacea and rucinolithus terebrodentarius are here defined as new subspecies a infracretacea larsonii and r terebrodentarius youngii respectively both taxa have fo close to the barremian aptian boundary and lo close to the aptian albian boundary in all investigated sections they increase in abundance during the early aptian with maximum values during oae 1a and then gradually decrease during the late aptian the distribution and abundance of a infracretacea larsonii and r terebrodentarius youngii are coeval with major aptian igneous geological geochemical and biotic changes these nannoliths might therefore result from nutrification events and or physico chemical reorganization of the mid cretaceous ocean

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

a newly discovered norisoprenoid 2 6 15 19 tetramethylicosane in cretaceous black shales a novel c24 acyclic isoprenoid 2 6 15 19 tetramethylicosane tme has been unambiguously identified using a synthesised standard in the saturated hydrocarbon fractions and in the kerogen pyrolysates of samples from a lower albian black shale from southeastern france in addition a novel c26 acyclic isoprenoid 10 ethyl 2 6 15 19 tetramethylicosane etme was tentatively identified these compounds appear to be structurally strongly related to the relatively well known c25 isoprenoid 2 6 10 15 19 pentamethylicosane pme and their co occurrence in these sediments and similar 13c contents indicates a common origin this suggests an alternative biosynthetic pathway for the biosynthesis of pme via the methylation of tme rather than the tail to tail coupling of farnesyl and geranyl these irregular isoprenoids are likely to have originated as parts of ether lipids in some unknown archaea but exactly which organisms biosynthesised these compounds remains uncertain

fluctuation of organic carbon isotopes of the lower cretaceous in coastal southeastern china terrestrial response to the oceanic anoxic events oae1b abstract whether there are terrestrial responses to the oceanic anoxic events oaes remain enigmatic in this paper we report a case study in the lower cretaceous continental and transitional sequences of coastal southeastern china it may represent the first late aptian to albian terrestrial carbon isotope record from china several organic rich black shale and grayish black mudstone horizons were found to develop widely in the coastal southeastern china during the period from 113 3 ma to 99 3 ma when the cretaceous oaes were recorded primarily in marine sequences organic carbon isotope 13 c org total organic carbon toc and total nitrogen tn were analyzed for the black shales from two sections i e the shipu transitional and chong an continental sections five negative 13 c org excursions can be recognized for both the sections termed as si sv and ci cv events for the shipu s and chong an c sections respectively correlations between 13 c org toc and n c ratio suggest that the si siii and ci ciii events might have been caused by global factors i e the oae1b event based on analogs to typical oae1b reported in the tethyan and pacific basins they archived the terrestrial carbon isotope response to the oae1b accompanied with a disturbance of carbon isotope in carbon reservoir of the global ocean atmosphere system under a warm and humid climate

an association of benthic foraminifera and gypsum in holocene sediments of estuarine chesapeake bay usa two cores of holocene sediments recovered from the cape charles channel of chesapeake bay yielded radiocarbon ages of about 6 8 to 5 8 ka for the lower intervals fossil foraminifera preserved in these lower sediments are dominated by species of elphidium which make up about 90 of the assemblage throughout and probably signify deposition in hypersaline waters buccella frigida and ammonia beccarii are the only other species commonly present hypersalinity of bottom waters seems to have been main tained by water density stratification in a basin like section of the channel in core ptxt 4 p 1 transition to modern chesapeake conditions in which numbers of ammonia beccarii exceed those of elphidium com menced about 400 years ago in core ptxt 3 p 2 hypersalinity is further signified by the presence of abun dant euhedral crystals of gypsum in association with the fossil elphidium this occurrence of gypsum is not attributed to palaeoclimatic aridity but rather to inflow of groundwater from adjacent gypsiferous mio cene strata the study shows that in palaeoclimatic investigations the significance of the presence of gyp sum should be evaluated with cautionit does not necessarily signify an evaporative regime

chemostratigraphy of the jurassic system applications limitations and implications for palaeoceanography current chemostratigraphical studies of the jurassic system primarily involve the use of one sedimentary component marine organic carbon one divalent transition metal substituted in carbonate manganese and two isotopic tracers strontium isotope ratios 87 sr 86 sr and carbon isotope ratios 13 c carb and 13 c org in carbonate and in organic matter other parameters such as mg ca and sr ca ratios in calcite oxygen isotope ratios 18 o in carbonate sulphur isotope ratios 34 s in carbonate hosted sulphate nitrogen isotope ratios 15 n org in organic matter osmium isotope ratios 187 os 188 os in black shales and neodymium isotope ratios 143 nd 144 nd in various mineral phases are also useful but at present give poor resolution because the database is incomplete or compromised by various factors stratigraphical patterns in total organic carbon toc can be of either local or regional significance depending on the lateral extent of the former nutrient rich and productive water mass divalent manganese follows a similar pattern being concentrated most probably as a very early diagenetic phase only in oxygen depleted waters that typically underlie zones of elevated organic productivity shifts in mg ca and sr ca ratios on the time scale of ammonite subzones seem largely to reflect temperature changes strontium isotope ratios from pristine skeletal calcite provide a global signal 13 c values from carbonates with minimal diagenetic overprint potentially do the same although small spatial differences in palaeo water mass composition may have been locally significant oxygen isotope determinations on carbonate rocks and fossils generally yield values that are too scattered to be stratigraphically useful because they reflect palaeotemperature the evaporation precipitation balance in sea water and the impact of any diagenesis involving an aqueous phase nitrogen isotope ratios in organic matter reflect the chemistry of ancient water masses as affected by nitrate utilization and denitrification and the stratigraphical pattern of this parameter is more likely to correlate only on a regional basis neodymium isotope ratios in sea water are also water mass dependent and greatly affected by regional sources and oceanic current systems preliminary data on sulphur isotope ratios in carbonates and osmium isotope ratios in organic rich shales both potentially offering global correlation indicate that these tracers may be valuable although the records at present are not sufficiently well established to allow high resolution regional correlation in all cases biostratigraphically well dated reference sections against which the relevant geochemical data have been calibrated are required in the first instance to date studies on the stratigraphical distribution of organic carbon have been principally carried out in both northern boreal and southern tethyan europe carbon isotope stratigraphy has been undertaken primarily but not exclusively on bulk pelagic sediments from the alpine mediterranean or tethyan domain and strontium isotope stratigraphy has been undertaken largely on calcitic skeletal material belemnites and oysters from northern and southern europe in many sections including those containing ammonites multi parameter chemostratigraphy can give resolution that exceeds that attainable by classic biostratigraphical means strontium isotope ratios in skeletal calcite are a particularly powerful tool for illustrating changes in sedimentary rate and revealing gaps in the stratigraphical record

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

the cretaceous sedimentary history of the pindos basin greece the cretaceous sedimentary rocks of the pindos zone in western greece document the evolution of a tethyan deep water basin new sedimentological and micropalaeontological studies reveal a complex basin history siliceous sediments with abundant radiolaria and organic rich facies prevailed up to the early late cretaceous within the sediment starved pre middle cenomanian marked black shale levels appear that are probably linked to oceanic anoxic events at the change from the late early to the early middle cenomanian the sedimentary regime altered abruptly the early late cretaceous is characterized by major calcareous redepositional events orbitoline horizons and often associated siliciclastic turbidite deposition submarine fan environments in the late late cretaceous carbonate supply increased rapidly resulting in the evolution of a carbonate slope and basin plain setting pelagic and allodapic limestones recorded basinwide blooms in planktonic foraminifera elevata event and a polyphase redepositional history that is interpreted to reflect the sensitivity of the basin to the tectonic evolution of apulia

a euxinic southern north atlantic ocean during the cenomanian turonian oceanic anoxic event abstract during mid cretaceous times large amounts of organic carbon corg became sequestered in black shales possibly due to oceanic anoxic events characterized by the development of an extended oxygen minimum zone omz here we provide the first direct evidence for an open ocean omz in the cenomanian turonian c t southern north atlantic and in fact show that the base of the photic zone was euxinic as revealed by molecular fossils from photosynthetic green sulfur bacteria in c t black shales this together with evidence for bottom water anoxia and accumulation of redox sensitive trace metals and hydrogen rich organic matter indicates a continuously euxinic water column concurrent with the high corg accumulation rates which are 15 150 times greater in the southern than in the northern north atlantic and the low biological productivity this suggests that preservation controlled the accumulation of corg in c t black shales

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

obliquity pacing of the hydrological cycle during the oceanic anoxic event 2 abstract the oceanic anoxic event 2 oae2 ca 93 5 ma represents a major phase of environmental change during the mesozoic and is associated with a pronounced positive excursion in the carbon isotope record short term climate oscillations within the oae2 are recorded as milankovitch cycles which have been used to establish a precise temporal framework for the oae2 however few studies discuss the sedimentary expression of milankovitch cycles during the oae2 and its paleoenvironmental implications here we present carbonate and organic carbon isotope data from a biostratigraphically well dated organic rich oae2 interval in a sedimentary succession outcropping in the brianconnais domain at roter sattel fribourg prealps switzerland we sampled the oae2 interval 4 28 m for proxies of detrital sediment quantification al ti magnetic susceptibility at ultra high resolution 1 cm time series analysis of multiple detrital proxies permits the construction of an orbital timescale for the oae2 based for the first time on the stable 173 kyr s3 s6 obliquity modulation cycle the resulting oae2 orbital timescale at roter sattel is consistent with previous timescales obtained in the western interior basin and in southern tibet china our cyclostratigraphic results show an unusually strong obliquity signal during the initiation of oae2 previous studies have demonstrated that the onset of oae2 was associated with magmatic pulses coupled with increases in atmospheric pco2 followed by an overall gradual drawdown of co2 accordingly we suggest that detrital input during the oae2 was the result of intensified continental weathering related to magmatic activity the substantially release of greenhouse gases and an accelerated hydrological cycle modulated by obliquity cycles

organic carbon deposition in the cretaceous of the ionian basin nw greece the paquier event oae 1b revisited we present new stable c o isotopic biostratigraphic and organic geochemical data for the vigla shale member of the ionian zone in nw greece in order to characterize organic carbon rich strata that potentially record the impact of cretaceous oceanic anoxic events oaes in a section exposed near gotzikas nw epirus we sampled a number of decimetre thick organic carbon rich units enclosed within marly locally silicified vigla limestone berriasian turonian all these units are characterized by largely comparable bulk geochemical characteristics indicating a common marine origin and low thermal maturity however the stratigraphically highest of these black shales is further distinguished by its much higher total organic carbon toc content 28 9 wt and hydrogen index hi 529 and much enriched delta 13corg value minus sign 22 1 planktonic foraminiferal and calcareous nannofossil biostratigraphy indicate a lower to middle albian age for the strata immediately above and a lower aptian age for the strata below the uppermost black shale in terms of molecular organic geochemistry the latter black shale is also relatively enriched in specific isoprenoidal compounds especially monocyclic isoprenoids whose isotopic values are as high as minus sign 15 indicating a substantial archaeal contribution to the organic matter the striking similarities between the molecular signatures of the uppermost vigla black shale and coeval organic rich strata from se france and the north atlantic odp site 1049c indicate that this level constitutes a record of the paquier event oae 1b

the influence of preexisting structure and halokinesis on organic matter preservation and thrust system evolution in the ionian basin northwest greece the opening of the ionian basin and its internal differentiation is attested to by lateral facies and thickness variations of the formations deposited during the pliensbachian and tithonian synrift formations the beginning of the synrift sequence is represented by the siniais limestones pliensbachian and their lateral equivalent the louros limestones the geometric characteristics of the extensional basin depend on both extension related to the latest opening of the tethys ocean and halokinesis of the ionian zone evaporitic substratum the orientation of the extensional regime is deduced from the direction of stratigraphic pinch outs of the synrift formations directions of transport of slump features and direction of movement on synsedimentary faults observed in t e base of these formations in the half grabens the postrift period is marked by an unconformity at the base of the vigla limestones which represents the early berriasian breakup during which sedimentation was synchronous in the entire ionian basin the accumulation of organic matter in the lower and upper posidonia beds of the ionian zone during the toarcian and tithonian is directly related to the geometry of the synrift period of the ionian basin restricted subbasins were formed where the geometry of the basin favored stagnation and consequently the locally euxinic conditions of bottom waters anoxic conditions persisted locally to the postrift period in areas where the upper siliceous zone albian cenomanian of the vigla limestones is well developed these areas probably represent subbasins that were preserved by the continuation of halokinetic movements during the postrift period during the early miocene alpine orogeny collision related compressive stresses on the margin induced the reactivation of preexisting fractures which were responsible for the inversion tectonics that affected the mesozoic basin the geometric characteristics of the inverted basin were dependent on lithology evaporites geometry of the extensional structures and direction of the compressional phase the observed geometries do not always correspond to the classical scheme of inversion tectonics the geological evolution in the ionian basin is an example of inversion tectonics of a basin with an evaporitic substratum the opening of the ionian basin and the inversion tectonics influence both the source rocks and the probable hydrocarbon traps of the ionian zone

archaeal remains dominate marine organic matter from the early albian oceanic anoxic event 1b abstract the sources for both soluble and insoluble organic matter of the early albian 112 myr oceanic anoxic event oae 1b black shales of the ocean drilling program odp site 1049c north atlantic ocean off the coast of florida and the ravel section of the southeast france basin sefb were determined using optical chemical stable carbon and nitrogen isotopic analyses archaea derived isoprenoidal tetraether membrane lipids and free and macromolecularly bound isoprenoid alkanes are abundant in these black shales more specifically the presence of certain ether lipids bi tricyclic biphytane tetraethers indicates an important contribution of representatives of marine planktonic archaea the large difference up to 12 in 13c 12c ratios between algal biomarkers and the much more abundant planktonic archaea derived biomarkers indicates that the latter were living chemoautotrophically this offset in 13c 12c ratios was used to estimate that up to 40 of the organic matter of the sefb and up to 80 of the organic matter of odp site 1049c preserved in the black shales is derived from archaea furthermore it is shown that even though there are apparent similarities high organic carbon oc content distinct lamination 13c enrichment of oc between the black shales of oae1b and the cenomanian turonian 94 myr oae the origin of the organic matter archaeal versus phytoplanktonic and causes for 13c enrichment of oc are completely different

astronomical pacing of late cretaceous third and second order sea level sequences in the foz do amazonas basin abstract because of their relatively reduced tectonic influence post rift sedimentary successions have a propensity to preserve climatically driven cyclicity over long durations here we present an integrated cyclostratigraphic and sequence stratigraphic study of the post rift limoeiro sedimentary formation fm of the foz do amazonas basin offshore brazil which spans the entire late cretaceous epoch almost 35 myr long the principal goal of the present study is to decipher very long multi myr sedimentary cyclicities and their potential origin s in order to delineate the main controlling factors of post rift sediment sequences and packages we used gamma ray gr well log data for cyclostratigarphy and seismic data for sequence stratigraphy time series analysis of gr data shows a rich series of milankovitch frequency bands in particular long period cyclicities 405 kyr 2 4 myr 4 7 myr and 9 5 myr are detected with high fidelity seismic and sequence stratigraphic interpretation shows a striking sea level sl depositional sequence order matching the 4 7 myr orbital cyclicity inferred from cyclostratigraphy longer sl sequences interpreted in previous studies from the limoeiro fm closely match the 9 5 myr gr related orbital cycles thus we infer that the post rift limoeiro fm was deposited continuously under astronomical forcing over the late cretaceous epoch resulting in an extraordinary record of direct base and sea level responses to milankovitch climatic forcing including longer multi myr periodicities the 4 7 myr orbital component is recorded for the first time in sl sedimentary proxies thus allowing here to update sl hierarchical orders we suggest that third order and second order and suborders sl sequences were most likely paced by long period astronomical cycles 2 4 myr eccentricity and 4 7 and 9 5 myr orbital cycles respectively

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

biomarker evidence for intermittent photic zone euxinia in the aptian albian organic sedimentary record from the ionian zone epirus greece new biomarker evidence is presented that constrains the conditions of deposition and preservation of sediments rich in extractable organic matter from the aptian albian sedimentary record of the ionian zone in nw greece analyses were specifically carried out on total lipid extracts from 12 organic rich samples from the vigla shale member two of which represent the regional record for the early albian paquier event of oae1b in the aliphatic fractions compound groups such as n alkanes isoprenoid alkanes steroids hopanoids and terpenoids were recognized pointing to a mixed origin from algae and prokaryotes with an additional measurable contribution from terrigenous plant matter these compounds suggest deposition of the primary organic sediments under conditions of decreased bottom water oxygen concentrations mass spectral evidence from the aromatic fractions of most samples reveal the variable presence of diagenetic and catagenetic derivatives of carotenoid pigments including some with bound sulfur that are characteristic of photoautotrophic sulfur bacteria the presence of specific biomarkers originating from photosynthetic anaerobic microorganisms similar to those in ancient and contemporary euxinic basins such as the black sea suggest that photic zone euxinic conditions were intermittently operative in the aptian albian stages of the ionian basin but were not exclusively characteristic of the black shale representing the paquier event itself

first evidence for the cenomanian turonian oceanic anoxic event oae2 bonarelli event from the ionian zone western continental greece integrated biostratigraphic planktonic foraminifera calcareous nannofossils chemostratigraphic bulk c and o isotopes and compound specific organic geochemical studies of a mid cretaceous pelagic carbonate black shale succession of the ionian zone western greece provide the first evidence for the cenomanian turonian oceanic anoxic event oae2 bonarelli event in mainland greece the event is manifested by the occurrence of a relatively thin 35 cm yet exceptionally organic carbon rich 44 5 wt toc carbonate free black shale near the cenomanian turonian boundary within the vigla limestone formation berriasian turonian compared to the bonarelli black shale interval from the type locality of oae2 in marche umbria italy this black shale exhibits greatly reduced stratigraphic thickness coupled with a considerable relative enrichment in toc isotopically enriched 13c values for both bulk organic matter 22 2 and specific organic compounds are up to 5 higher than those of underlying organic rich strata of the aptian lower albian vigla shale member and thus compare very well with similar values of cenomanian turonian black shale occurrences elsewhere the relative predominance of bacterial hopanoids in the saturated apolar lipid fraction of the oae2 black shale of the ionian zone supports recent findings suggesting the abundance of n2 fixing cyanobacteria in cretaceous oceans during the cenomanian turonian and early aptian oceanic anoxic events

onset of the mid cretaceous greenhouse in the barremian aptian igneous events and the biological sedimentary and geochemical responses basalts and biostratigraphy dated at 125 120 ma from the ontong java and manihiki plateaus in the western pacific evidence the largest volcanic event in earth history in at least the past 160 m y the intervening nova canton trough rifted at about 121 118 ma and a number of guyots and seamounts formed concurrently or slightly later geological events that probably were responses to these volcanic tectonic events occurred in the following chronostratigraphic order biotic fluctuations began at about 122 5 ma at about 122 0 ma 87sr 86sr began to decline slowly metal concentrations of co mn pb yb and cu in sediments peaked at about 121 5 121 2 ma changes in planktonic communities and sedimentation culminated in a nannoconid crisis just prior to 120 5 ma and in the selli black shale oae la at about 120 5 119 5 ma a sharp drop in 13c occurred at the beginning of the selli event and rebounded into a longer positive excursion that reached a peak after the selli event at about 119 5 118 5 ma at 120 5 ma 87sr 86sr declined rapidly and reached a minimum at about 116 113 ma we speculate that the intensity of these latter responses suggests a corresponding peak in volcanic tectonic activity at about 121 119 ma

massive expansion of marine archaea during a mid cretaceous oceanic anoxic event biogeochemical and stable carbon isotopic analysis of black shale sequences deposited during an albian oceanic anoxic event 112 million years ago indicate that up to 80 weight percent of sedimentary organic carbon is derived from marine nonthermophilic archaea the carbon 13 content of archaeal molecular fossils indicates that these archaea were living chemoautotrophically their massive expansion may have been a response to the strong stratification of the ocean during this anoxic event indeed the sedimentary record of archaeal membrane lipids suggests that this anoxic event marks a time in earth history at which certain hyperthermophilic archaea adapted to low temperature environments

the source rock horizons of the ionian basin nw greece abstract the organic geochemical study of six geological sections and two wells in the ionian zone nw greece allows us to distinguish five horizons of possible source rocks the vigla shales cenomanian turonian the upper posidonia beds callovian tithonian the lower posidonia beds toarcian aalenian the marls at the base of the ammonitico rosso early toarcian and shale fragments incorporated within the triassic breccias these horizons have good hydrocarbon potential and an organic matter type i to ii in the deeper parts of the botsara sub basin the oil window is located in the interval between 3700 5800 m depth consequently the triassic shales have already entered the gas window the lower and upper posidonia beds and the marls at the base of the ammonitico rosso are mature in terms of oil generation the vigla shales maturity corresponds to the early maturation stage the timing of the principal oil source horizons maturation is the late jurassic for the triassic shale beds and the serravalian for the lower posidonia beds the preservation of the organic matter in the lower and upper posidonia beds through toarcian to tithonian and in the marls at the base of the ammonitico rosso during early toarcian are directly related to the geometry of the syn rift period of the ionian basin the organic matter preservation in the vigla shales is related to the sub basins that were preserved by the continuation of halokinetic movements during the post rift period the geometry of the restricted sub basins that were formed during the syn rift and post rift period of the ionian basin evolution favored water stagnation and the development of local euxinic conditions in the bottom waters these conditions were accentuated during the anoxic events that are known to have affected the tethys ocean during the early toarcian and late cenomanian the organic rich shale fragments within the triassic breccias were initially deposited as stratigraphic layers in sub basins of the evaporitic basin the establishment of evaporitic sedimentation in the entire basin favored the preservation of the organic matter the processes that resulted in the formation of the evaporite dissolution collapse breccias caused also the fragmentation of the organic rich layers which are present actually as organic rich shale fragments within the triassic breccias

camelus from the upper pleistocene of mount carmel israel a camelus metapodial found among the animal bones excavated by garrod from the levalloiso mousterian of the tabun cave mount carmel israel adds to the relatively small number of camelus finds reported from the pleistocene of the near east the mammal faunas associated with these finds suggest relatively dry open conditions but not desert conditions the tabun specimen is of moderate size in contrast to the very large camelus from far ah ii two species of camel may thus have been present in the near east during the upper pleistocene

short term environmental changes in the cretaceous tethyan ocean micropalaeontological evidence from the early albian oceanic anoxic event 1b to better understand the linkage between climate and ocean circulation under greenhouse conditions we have studied calcareous nannofossils palynomorphs and benthic foraminifera from the early albian oceanic anoxic event 1b black shale oae 1b in the vocontian basin se france we propose that monsoonal activity resulting from precessional forcing and modulated by eccentricity driven temperature changes represents the driving factor of oae 1b formation in low latitudes with the onset of oae 1b increasingly warm and humid conditions stronger winds and enhanced terrestrial input led to higher surface water productivity therefore increased productivity is an important factor for oae 1b formation in the vocontian basin however monsoonally forced productivity changes are a regional climate signal only the supraregional occurrence of the oae 1b is probably due to a reduction of deep water formation in the low latitudes under extremely warm and humid conditions leading to enhanced preservation of organic matter

further evidence for the development of photic zone euxinic conditions during mesozoic oceanic anoxic events periods in earth history characterized by extensive organic carbon deposition so called oceanic anoxic events oaes are the subject of considerable scrutiny insight into the extent of anoxic conditions in the water column has been provided by the reported occurrence of derivatives of isorenieratene a carotenoid found only in green sulphur bacteria and thus indicative of photic zone euxinia i e a water column containing free h 2 s in north atlantic deep sea sediments deposited during the cenomanian turonian boundary oae2 bonarelli event in this study we have used the distributions of chlorophyll and bacteriochlorophyll degradation products maleimides 1 h pyrrole 2 5 diones and high molecular weight porphyrins to examine further the cenomanian turonian boundary oae2 as well as other oaes of the early toarcian posidonienschiefer event and early aptian selli event in particular methyl isobutyl me i bu maleimide on structural grounds appears to be diagnostic of green sulphur bacteria this compound occurs in five of seven examined marls that record the early toarcian oae marche umbria italy further expanding the geographical range of toarcian sediments where evidence for photic zone euxinic conditions has been found me i bu maleimide occurs in three of six black shales spanning the livello selli marche umbria italy the type locality for the aptian oae1a providing the first evidence for photic zone euxinic conditions during this event with respect to the cenomanian turonian oae maleimide evidence for photic zone euxinic conditions was found in all the north atlantic sites investigated including those characterized by relatively organic lean sediments several tethyan sites and one site off western australia these data indicate that euxinic conditions were common in the water column during mesozoic oceanic anoxic events

the early toarcian jurassic anoxic event stratigraphic sedimentary and geochemical evidence detailed paleogeographic studies in the southern alps suggest that an oxygen minimum model is appropriate for interpreting conditions on tethyan continental margins advection of manganese in this low oxygen layer may explain the local occurrence of carbonate ores of this element carbon sulfur and iron sulfur ratios although showing considerable scatter suggest that bottom waters at this time were locally euxinic containing free hydrogen sulfide this oceanic anoxic event was preceded by significant faunal turnover of ammonites in tethys and accompanied by widespread extinction of benthos in northern europe in response to the lateral spread of anoxic bottom waters during transgression similar changes may be recognized in other parts of the world other anoxic events may have taken place during the jurassic but documentation is as yet meagre furthermore models for such phenomena remain largely speculative although upwelling and increased planktonic productivity commencing in pre toarcian time are favored for the falciferum zone event documented here from author

global and regional palaeoceanographic changes as recorded in the mid cretaceous aptian albian sequence of the ionian zone nw greece micropalaeontological and chemostratigraphic results from the mid cretaceous upper siliceous zone of the ionian zone studied in two localities of nw greece paliambela and panaya provide new insights into the palaeoceanographic evolution of tethys and better correlation with well studied italian successions 13 c carbonate and organic carbon isotope stratigraphy allows an improved correlation of the early aptian fourcade level with oceanic anoxic event 1a calcareous nannofossils point to intervals of reduced sedimentation within the late aptian part of the limestones overlying the fourcade level combined calcareous nannofossil radiolarian and planktonic foraminiferal biostratigraphy suggests that the overlying radiolarites named herein the dercourt member are essentially mid albian in age radiolarites of this age and thickness have not been identified in the well explored italian sections or in southern albania it is therefore likely that the dercourt radiolarites reflect a high productivity event localized in the greek area of the ionian zone possibly caused by a bathymetrically induced upwelling of intermediate to deep waters that entered the ionian trough following the opening of new oceanic gateways in the eastern mediterranean tethys

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities we present new detailed carbon isotope records for bulk carbonate total organic carbon toc and phytane from three key sections spanning the cenomanian turonian boundary interval eastbourne england gubbio italy tarfaya morocco with the purpose of establishing a common chemostratigraphic framework for oceanic anoxic event oae 2 isotope curves from all localities are characterized by a positive carbon isotope excursion of c 4 for toc and phytane and c 2 5 for carbonate although diagenetic overprinting appears to have obliterated the primary carbonate carbon isotope signal in at least part of the tarfaya section stratigraphically peak 13 c values for all components are followed by intervals of high near constant 13 c in the form of an isotopic plateau recognition of an unambiguous return to background 13 c values above the plateau is however contentious in all sections hence no firm chemostratigraphic marker for the end point of the positive isotopic excursion can be established the stratigraphically consistent first appearance of the calcareous nannofossil quadrum gartneri at or near the cenomanian turonian boundary as established by ammonite stratigraphy in conjunction with the end of the 13 c maximum characteristic of the isotopic plateau provides a potentially powerful tool for delimiting the stratigraphic extent and duration of oae 2 this oceanic anoxic event is demonstrated to be largely if not wholly confined to the latest part of the cenomanian stage

rapid warming and salinity changes of cretaceous surface waters in the subtropical north atlantic paleomarine carbon isotopic records reveal occasional and rapid release of greenhouse gases into the atmosphere the regional consequences on surface ocean properties and time relationships between the atmosphere and the ocean however are still far from understood we observe a sudden 1 5 shift in leaf wax n alkane 13c values at the onset of oceanic anoxic event oae 1b from early albian sediments off northwest africa deep sea drilling project site 545 that is best explained by the rapid release of isotopically light carbon into the cretaceous atmosphere this 1 5 shift in the n alkanes precedes a negative isotope excursion of similar magnitude observed in marine carbonate organic matter and algal steranes a tex86 based record of sea surface temperature sst confirms almost instantaneous warming by 3 5 c along with the marine isotope shifts at site 545 paralleled by an 2 c tex86 sst increase and a freshening of surface water salinity from 43 to 41 at blake nose ocean drilling program site 1049 multiproxy evidence indicates that once established these warm ssts prevailed and were stable during oae 1b suggesting that the emission of 13c depleted carbon started abruptly but then continued over tens of thousands of years the sst cooled by 1 2 c at the end of the event not reaching pre excursion levels the new records provide evidence for a time lag best estimate 1 3 k y between atmospheric and oceanic processes that we interpret as a direct response to changes in the atmospheric greenhouse gas concentrations followed by propagation into the ocean and subsequent heating of surface waters

consequences of moderate 25 000 yr lasting emission of light co 2 into the mid cretaceous ocean future warming is predicted to shift the earth system into a mode with progressive increase and vigour of extreme climate events possibly stimulating other mechanisms that invigorate global warming this study provides new data and modelling investigating climatic consequences and biogeochemical feedbacks that happened in a warmer world not vert similar 112 myr ago our study focuses on the cretaceous oceanic anoxic event oae 1b and explores how the earth system responded to a moderate not vert similar 25 000 yr lasting climate perturbation that is modelled to be less than 1 c in global average temperature using a new chronological model for oae 1b we present high resolution elemental and bulk carbon isotope records from dsdp site 545 from mazagan plateau off nw africa and combine this information with a coupled atmosphere land ocean model the simulations suggest that a perturbation at the onset of oae 1b caused almost instantaneous warming of the atmosphere on the order of 0 3 c followed by a longer not vert similar 45 000 yr period of not vert similar 0 8 c cooling the marine records from dsdp site 545 support that these moderate swings in global climate had immediate consequences for african continental supply of mineral matter and nutrients phosphorous subsequent oxygen availability and organic carbon burial in the eastern subtropical atlantic however without turning the ocean anoxic the match between modelling results and stratigraphic isotopic data support previous studies summarized in jenkyns h c 2003 evidence for rapid climate change in the mesozoic palaeogene greenhouse world the royal society 361 1885 1916 in that methane emission from marine hydrates albeit moderate in dimension may have been the trigger for oae 1b though we can not finally rule out alternative mechanisms following the hydrate mechanism a total of 1 15 1018 g methane carbon 13c 60 equivalent to about 10 to the total modern gas hydrate inventory generated the 13ccarb profile recorded in the section modelling suggests a combination of moderate scale methane pulses supplemented by continuous methane emission at elevated levels over not vert similar 25 000 yr the proposed mechanism though difficult to finally confirm in the geological past is arguably more likely to occur in a warmer world and apparently perturbs global climate and ocean chemistry almost instantaneously this study shows that once set off this mechanism can maintain earth s climate in a perturbed mode over geological time leading to pronounced changes in regional climate