sediment dispersal and quantitative stratigraphic architecture across an ancient shelf two large 200 to 300 km near continuous outcrop transects and extensive well log data ca 2800 wells allow analysis of sedimentological characteristics and stratigraphic architecture across a large area ca 60 000 km2 of the latest santonian to middle campanian shelf along the western margin of the western interior seaway in eastern utah and western colorado usa genetically linked depositional systems are mapped at high chronostratigraphic resolution ca 0 1 to 0 5 ma within their sequence stratigraphic context in the lower part of the studied interval sediment was dispersed via wave dominated deltaic systems with a compound clinoform geomorphology in which an inner wave dominated shoreface clinoform was separated by a muddy subaqueous topset from an outer clinoform containing sand poor gravity flow deposits these strata are characterized by relatively steep net regressive shoreline trajectories 0 1 with concave landward geometries narrow nearshore belts of storm reworked sandstones 2 to 22 km wide offshore mudstone belts 250 km and relatively high sediment accumulation rates ca 0 27 mm year 1 the middle and upper parts of the studied interval also contain wave dominated shorefaces but coeval offshore mudstones enclose abundant isolated tide influenced sandstones that were transported sub parallel to the regional palaeoshoreline by basinal hydrodynamic tidal circulation these strata are characterized by relatively shallow net regressive shoreline trajectories 190 km and relatively low sediment accumulation rates ca 0 11 mm year 1 the change in shelfal sediment dispersal and stratigraphic architecture from i compound clinoform deltas characterized by across shelf sediment transport to ii wave dominated shorelines with isolated tide influenced sandbodies characterized by along shelf sediment transport is interpreted as reflecting increased interaction with the hydrodynamic regime in the seaway as successive shelfal depositional systems advanced out of a sheltered embayment utah bight this advance was driven by a decreasing tectonic subsidence rate which also suppressed autogenic controls on stratigraphic architecture

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

the response of a simple antarctic ice flow model to temperature and sea level fluctuations over the cenozoic era an ice flow model is used to simulate the antarctic ice sheet volume and deep sea temperature record during cenozoic times we used a vertically integrated axisymmetric ice sheet model including bedrock adjustment in order to overcome strong numerical hysteresis effects during climate change the model is solved on a stretching grid the cenozoic reconstruction of the antarctic ice sheet is accomplished by splitting the global oxygen isotope record derived from benthic foraminifera into an ice volume and a deep sea temperature component the model is tuned to reconstruct the initiation of a large ice sheet of continental size at 34 ma the resulting ice volume curve shows that small ice caps

latest cretaceous earliest paleogene vegetation and climate change at the high southern latitudes palynological evidence from seymour island antarctic peninsula abstract fluctuations in late cretaceous climate were already influencing biotic change prior to the environmental upheaval at the cretaceous paleogene k pg boundary but their general nature magnitude and timing remain controversial a high resolution dataset on terrestrially derived palynomorphs is presented from the high southern palaeolatitudes that unlocks details of small scale climate variability throughout this period of significant global change specifically this is a quantitative spore and pollen analysis of an expanded uppermost cretaceous to lowermost paleogene maastrichtian earliest danian shallow marine sedimentary succession from seymour island off the northeastern tip of the antarctic peninsula then as now located at 65 s using nearest living relatives the first detailed vegetation habitat and climate reconstruction is presented for the emergent volcanic arc at this time on the coastal lowlands a cool to warm temperate rainforest is envisaged growing in a riverine landscape with both wet river margin pond and relatively dry interfluve canopy gap habitats diverse podocarps and southern beech trees grew alongside angiosperm herbs and shrubs in mean annual temperatures of 10 15 c higher altitude araucarian forests gave way to open ericaceous heathland beyond the tree line in subalpine to alpine conditions with mean annual temperatures of a cold 5 8 c there is no exact modern botanical equivalent but the closest modern flora is that of the andes of southern chile and argentina maastrichtian climate is shown to have fluctuated from cool humid conditions through a rapid warming 2 million years prior to the k pg transition followed by cooling during the earliest danian a trend supported by previous work on this interval

the magnitude and cause of short term eustatic cretaceous sea level change a synthesis abstract no consensus currently exists regarding the magnitude of cretaceous short term less than 3 ma in duration eustatic sea level change the lack of a consensus limits the ability to predict sedimentary facies and architecture and to assess the potential drivers of eustasy during a period of earth history considered as significantly warmer than today consequently this review documents weighs synthesises and summarises records of short term relative sea level change and evaluates the observed trends in magnitude within the context of potential climatic drivers and their eustatic expression although cretaceous sea level change is addressed in many publications estimates of absolute values are relatively limited often cover short time intervals and use different methods based upon integrated geological and statistical analyses four broad episodes of magnitude change have been identified three of these episodes reflect trends of increasing magnitudes of sea level change from the berriasian to early hauterivian late hauterivian to aptian and santonian to maastrichtian the fourth episode reflects a decreasing magnitude trend from the albian to coniacian in addition the maximum magnitude of sea level change at an approximate stage level has been identified and categorised as slight less than 10 m modest 10 to 40 m or significant 41 to 65 m significant magnitudes are inferred for the valanginian aptian albian and maastrichtian exclusively slight magnitudes are restricted to the berriasian such an assessment casts doubt on the repeated and stratigraphically widespread episodes of very large magnitudes more than 75 m advocated by some workers and instead defines distinct periods and magnitudes of sea level change that should be globally reflected in sedimentary facies patterns for example intervals of sea level fall of significant magnitude are commonly associated with the increased delivery of sediment into basinal settings including the marked progradation of shallow marine sediments whilst up systems tract there can be enhanced development of karst and erosional features because climatically driven eustasy is the likely cause of short term sea level change an assessment of the characteristic maximum magnitude limits of the principal climatic drivers thermo aquifer and glacio eustasy has been made such a comparison argues for glacio eustasy as the driver of significant short term sea level change in addition climate proxy data demonstrates that the valanginian aptian albian and maastrichtian are intervals of cooling within the cretaceous thereby supporting the link between significant magnitudes and glacio eustasy

paleoatmospheric pco2 fluctuations across the cretaceous tertiary boundary recorded from paleosol carbonates in ne china abstract a dramatic change in atmospheric composition has been postulated because of global carbon cycle disruption during the cretaceous k tertiary t transition following the chicxulub impact and deccan trap eruptions here pedogenic carbonates were collected from drill core of a borehole sk 1 n straddling the late cretaceous and early paleocene strata in the songliao basin northeast china to reconstruct atmospheric co 2 concentrations using a paleosol paleobarometer our estimates for atmospheric pco 2 from paleosol carbonates range between 277 115 ppmv and 837 164 ppmv between 67 8 ma and 63 1 ma one large 66 65 5 ma and several small co 2 spikes 64 7 64 2 ma during the latest maastrichtian to earliest danian are reported here and incorporated with previously published pco 2 estimates also estimated from paleosol carbonates these co 2 spikes are attributed to one million year long emplacement of the large deccan flood basalts along with the extraterrestrial impact at the k t boundary

a far field record of the end ordovician glaciation the ellis bay formation anticosti island eastern canada abstract the end ordovician was a critical period in earth history it was a time of global climatic change with large scale continental glaciations a wealth of recent work has documented the stratigraphical records from the near field areas i e from various gondwanan continental relics where glaciation was more severely felt there is an urgent need to re examine the stratigraphic record from the far field areas at greater levels of resolution than it has been hitherto possible in order to understand the timing duration and character at the glaciation centred around the ordovician silurian o s boundary one of the best exposed and most complete stratigraphic records from paleotropical areas near the boundary is on anticosti island in eastern canada the east west trending 200 km long ellis bay hirnantian outcrop belt with superb coastal exposures at both ends of anticosti island is slightly oblique to the paleoshoreline with near shore siliciclastic dominated facies restricted to the eastern part of the island and more offshore carbonate dominated facies present along the central and western parts these mixed carbonate siliciclastic facies accumulated along a storm dominated beach to offshore profile they are organized into a stacked set of shallowing upward offshore to shoreline facies successions typically coarsening upward separated by deepening upward facies successions typically fining upward formed during intervening transgressions high frequency glacio eustatic fluctuations were the dominant control on the development of tr sequences observed in the ellis bay succession of anticosti island although tectonic subsidence had a substantial secondary effect on thickness five tr sequences are recognized allowing for precise correlation along the ellis bay outcrop belt in the eastern sections relatively thin tr sequences are locally bounded by unconformities a typical sequence begins with thin transgressive limestone overlain by a maximum flooding calcareous shale grading up into regressive storm influenced proximal to transitional zone fine sandstone grainstone and shale which are sharply overlain by shoreface to foreshore sandstone grainstone in the central and western sections the thicker tr sequences have more symmetrical transgressive regressive components reflecting greater subsidence compensated by a higher carbonate sediment supply two discrete glacial periods are recognized during the deposition of the hirnantian ellis bay succession with the younger one recording large sea level changes 50 m in magnitude caused by the development of very large ice sheets over western gondwana abundant ice conditions on the globe during the end ordovician and the resulting high amplitude eustasy appear to have left distinctive stratigraphical imprints on mixed paleotropical siliciclastic carbonate ramps

upper cretaceous sequences and sea level history new jersey coastal plain we developed a late cretaceous sea level estimate from upper cretaceous sequences at bass river and ancora new jersey odp ocean drilling program leg 174ax we dated 11 14 sequences by integrating sr isotope and biostratigraphy age resolution 0 5 m y and then estimated paleoenvironmental changes within the sequences from lithofacies and biofacies analyses sequences generally shallow up section from middle neritic to inner neritic paleodepths as shown by the transition from thin basal glauconite shelf sands transgressive systems tracts tst to medial prodelta silty clays highstand systems tracts hst and finally to upper delta front quartz sands hst sea level estimates obtained by backstripping accounting for paleodepth variations sediment loading compaction and basin subsidence indicate that large 25 m and rapid 1 m y sea level variations occurred during the late cretaceous greenhouse world the fact that the timing of upper cretaceous sequence boundaries in new jersey is similar to the sea level lowering records of exxon production research company epr northwest european sections and russian platform outcrops points to a global cause because backstripping seismicity seismic stratigraphic data and sediment distribution patterns all indicate minimal tectonic effects on the new jersey coastal plain we interpret that we have isolated a eustatic signature the only known mechanism that can explain such global changes glacio eustasy is consistent with foraminiferal 18 o data either continental ice sheets paced sea level changes during the late cretaceous or our understanding of causal mechanisms for global sea level change is fundamentally flawed comparison of our eustatic history with published ice sheet models and milankovitch predictions suggests that small 5 10 10 6 km 3 ephemeral and areally restricted antarctic ice sheets paced the late cretaceous global sea level change new jersey and russian eustatic estimates are typically one half of the epr amplitudes though this difference varies through time yielding markedly different eustatic curves we conclude that new jersey provides the best available estimate for late cretaceous sea level variations

geologic controls on transgressive regressive cycles in the upper pictured cliffs sandstone and coal geometry in the lower fruitland formation northern san juan basin new mexico and colorado three upper pictured cliffs sandstone tongues in the northern part of the san juan basin record high frequency transgressive episodes during the late cretaceous and are inferred to have been caused by eustatic sea level rise coincident with differential subsidence outcrop and subsurface studies show that each tongue is an amalgamated barrier strand plain unit up to 100 ft 30 m thick successive upper pictured cliffs tongues display an imbricate relation and are offset basinward reflecting net shoreline progradation northeastward upper pictured cliffs barrier strand plain sandstones underlie and bound thickest fruitland coal seams on the seaward side controls on fruitland coal seam thickness and continuity are a function of local facies distribution in a coastal plain setting shoreline positions related to transgressive regressive cycles and basin subsidence during periods of relative sea level rise the pictured cliffs shoreline was temporarily stabilized allowing thick coastal plain peats to accumulate although some coal seams in the lower fruitland tongue override abandoned pictured cliffs shoreline deposits many pinch out against them differences in the degree of continuity of these coal seams relative to coeval shoreline sandstones are attributed to either differential subsidence in the northern part of the basin multiple episodes of sea level rise local variations in accommodation and progradation stabilization of the shoreline by aggrading peat deposits or a combination of these factors fruitland coalbed methane resources and productivity are partly controlled by coal seam thickness other important factors include thermal maturity fracturing and overpressuring the dominant production trend occurs in the northern part of the basin and is oriented northwestward coinciding with the greatest fruitland net coal thickness similar relationships between trends of thick coal seams of coeval origin with stacked shoreface sandstones exist in other western interior basins in the united states and serve as models for coalbed methane exploration in other basins of the world

geochemical and palynological sea level proxies in hemipelagic sediments a critical assessment from the upper cretaceous of the czech republic geochemical and palynological records are presented for an expanded turonian coniacian hemipelagic succession in the central bohemian cretaceous basin a high resolution stratigraphic framework is provided by biostratigraphy and organic carbon stable isotope 13corg chemostratigraphy a short term 100 kyr sea level curve has been derived from high resolution transgressive regressive maxima shore proximity data established from basin wide sediment geometries the viability of geochemical and palynological parameters as potential sea level proxies is tested against this independently derived sea level record elemental chemostratigraphy is demonstrated to offer a reliable means of identifying medium to long term 0 4 2 4 myr sea level trends manganese maxima are associated with periods of high sea level and troughs with intervals of low sea level falling mn contents accompany regression and rising values transgression major transgressive events associated with medium term sea level change are marked by sharp increases in ti al ratios but short term 100 kyr sea level cycles are not consistently identified long term 13corg variation and dinoflagellate cyst species richness are positively correlated and show similarities to the sea level curve baseline trends have a cycle duration close to the 2 4 myr long eccentricity cycle dinocyst species richness closely follows short term changes in sea level with marked increases in dinocyst diversity coincident with most short term flooding events periods of rapid sea level rise caused an influx of a more diverse outer shelf assemblage into the study area together with the addition of shallower water species some of which may have been transported into the central basin by hypopycnal flows changes in the proportion and abundance of peridinioid dinoflagellate cysts principally palaeohystrichophora infusorioides were controlled principally by changing nutrient levels proximity proxies derived from geochemical and palynological data are not always consistent with the independent sea level model this exemplifies the need to understand all factors influencing elemental geochemical and palynological proxies before making simplistic sea level interpretations

correlation of eocene oligocene marine and continental records orbital cyclicity magnetostratigraphy and sequence stratigraphy of the solent group isle of wight uk the magnetostratigraphy clay mineralogy cyclostratigraphy and sequence stratigraphy of the estuarine and continental solent group isle of wight hampshire basin uk which is of late eocene early oligocene age were investigated a new magnetostratigraphy for the solent group is correlated to the chronostratigraphic standard using limited biostratigraphical data and it is concluded that the base of the oligocene falls close to the base of the bembridge limestone formation a long time series of clay mineral xrd data was generated which shows striking variation in illitic clay abundance illite is interpreted to have formed in gley palaeosols through repeated wetting and drying in response to high seasonality high illitic clay values are tuned to c 400 ka eccentricity maxima to develop an age model in addition to a very strong c 400 ka signal in the data spectral analysis of the clay data also confirms the influence of short eccentricity c 100 ka and obliquity c 40 ka cycles the succession displays seven conspicuous 10 20 m thick sequences which represent transitions from transgressive estuarine environments through highstand floodplains to freshwater lakes the sequences correspond exactly to the long eccentricity c 400 ka cycles a sea level curve is derived using the amount of incision as a minimum measure of eustatic fall but there is no evidence of a major eustatic drop of 30 90 m corresponding to the early oligocene glaciation of antarctica it is likely that incision was suppressed by rapid rates of subsidence

application of sequence stratigraphic concepts to the upper cretaceous tununk shale member of the mancos shale formation south central utah parasequence styles in shelfal mudstone strata

palaeoceanography broken greenhouse windows large and rapid global sea level changes indicate that polar ice sheets may have ephemerally existed during the cretaceous greenhouse climate two oxygen isotopic studies provide evidence for and against this conclusion

organic rich and manganese sedimentation during the cenomanian turonian boundary event in the outer carpathian basins a new record from the skole nappe poland abstract upper cenomanian lower turonian strata in the splawa section of the skole nappe outer carpathians poland provide a detailed palaeoenvironmental record of the oceanic anoxic event oae 2 from a deep water basin below the ccd at the northern margin of the western tethys the oae 2 succession consists of black parallel laminated radiolarian shales enriched in organic matter of mainly marine origin toc up to 8 organic carbon isotope variations together with microfossil datum events allowed to correlate the studied organic rich facies with other black shale successions along the outer carpathians and other areas of the western tethys the mean values of sedimentation rate 3 5 5 5 mm kyr and organic matter accumulation rate 0 5 g m2 year calculated for the oae 2 interval in the outer carpathian basins are comparable to the values from other deep water marginal basins in the western tethys the average redox sensitive trace metal contents and their enrichment factors indicate water column anoxia in the outer carpathian basins intensified during the interval of the largest shift in 13c values the periods of bottom anoxia were interrupted by intervals of variable eh conditions with sedimentation of hemipelagic green shales including poor agglutinated foraminiferal assemblages an increase in productivity of organic and siliceous plankton during the oae 2 is documented based on increased values of silica and barium enrichments this closely corresponds to an interval of the largest positive stable carbon isotope excursion related to the beginning of the largest sea level rise linked with intensive coastal upwelling extremely low sedimentation rate or even hiatuses and the increase in deep water circulation causing basin oxygenation resulted in precipitation of two ferromanganese layers their formation was related to changes in hydrodynamic conditions at the basin floor expressed by precipitation of fe mn carbonates some chemical indices seem to suggest that the primary metal enrichments could be related to hydrothermal activity however the concentrations of some elements show also on hydrogenic to diagenetic influences in these metalliferous sediments the precipitation of these fe mn sediments was probably synchronous with the manganese enrichment across the c t transition recorded in other western tethyan basins and in the adjacent epicontinental seas

18o 16o and d h ratios of pedogenic kaolinite in a north american cenomanian laterite paleoclimatic implications abstract kaolinite gibbsite and quartz are the dominant minerals in samples collected from two outcrops of a cenomanian 95 ma laterite in southwestern minnesota a combination of measured yields and isotope ratios permitted mass balance calculations of the d and 18 o values of the kaolinite in these samples these calculations yielded kaolinite d values of about 73 and 18 o values of about 18 7 the d and 18 o values appear to preserve information on the ancient weathering system if formed in hydrogen and oxygen isotope equilibrium with water characterized by the global meteoric water line gmwl the kaolinite d and 18 o values indicate a crystallization temperature of 22 5 c a nominal paleotemperature of 22 c implies a 18 o value for the corresponding water of 6 3 the combination of temperature and meteoric water 18 o values is consistent with relatively intense rainfall at that mid paleolatitude location 40 n on the eastern shore of the north american western interior seaway the inferred cenomanian paleosol temperature of 22 c is in general accord with published mid cretaceous continental mean annual temperatures mat estimated from leaf margin analyses of fossil plants when compared with results from a published gcm based cenomanian climate simulation which specifies a latitudinal sea surface temperature sst gradient that was either near modern or smaller than modern the kaolinite paleotemperature of 22 c is closer to the gcm predicted mat for a smaller equator to pole temperature difference in the mid cretaceous moreover the warm kaolinite derived mid paleolatitude temperature of 22 c is associated with proxy estimates of high concentrations of atmospheric co 2 in the cenomanian the overall similarity of proxy and model results suggests that the general features of cenomanian continental climate in that north american locale are probably being revealed

cool episodes in the cretaceous exploring the effects of physical forcings on antarctic snow accumulation the question whether large scale glaciations on antarctica were possible in a late mesozoic greenhouse climate such as the late cretaceous is an intriguing one the most recent years have provided an increasing number of studies investigating the growth and decay of paleo continental ice sheets on antarctica possibly large enough to affect sea level since the outcome of these studies doesn t provide a basis for a conclusive decision we have performed a number of model runs using an atmospheric general circulation model agcm to test whether large volumes of snow might have accumulated even under late cretaceous greenhouse conditions by varying orbital parameters as well as topography and atmospheric co2 concentrations our models indicate the possibility of an antarctic ice shield build up large enough to drive sea level fluctuations on the order of tens of meters within 20 000 years this is supported under the assumption of pco2 levels 800 ppm low insolation and elevated topography the growth of a major antarctic ice sheet would be possible on reasonable time scales to accumulate about half the present day snow ice volume which is required to explain the documented shifts in oxygen isotopes our model results suggest a time span between 20 000 and 80 000 years for these ice volumes to accumulate

blake nose stable isotopic evidence against the mid cenomanian glaciation hypothesis detailed multitaxon stable isotope 18 o and 13 c data from blake nose western north atlantic argue against a mid cenomanian glaciation event during the mid cretaceous greenhouse results generated are precisely correlated to sea level changes inferred from european sequence stratigraphy using the twin 13 c excursions mid cenomanian event mce ia and mce ib microfossils analyzed surface dwelling to deep dwelling planktonic foraminifera benthic foraminifera coccoliths show remarkably consistent intertaxon 18 o and 13 c offsets comparative scanning electron microscope and sr ca analyses allow some 18 o data to be eliminated because of selective diagenesis across mce ia the proposed interval of major glacioeustatic regression the planktonic 18 o values are constant for each taxon the absence of a mean seawater 18 o shift contradicts predictions for the mid cenomanian glaciation episode the benthic 18 o records show significant fluctuations during mce i implying short term variability in north atlantic intermediate water and deep water circulation patterns and or sources at that time

oligocene eustasy from two dimensional sequence stratigraphic backstripping estimates of the magnitudes of changes in third order 0 522 m y eustasy were obtained for oligocene sequences defined by a suite of largely onshore boreholes of the new jersey coastal plain benthic foraminiferal biofacies and multiple age constraints in a sequence stratigraphic framework formed the database for this study the geometry of the margin through time was determined using two dimensional backstripping the depth ranges of benthic foraminiferal biofacies were determined from a combination of standard factor analysis techniques and the backstripped geometries benthic foraminiferal biofacies were then used to determine the depths of the oligocene margin profiles obtained from backstripping the water depths of 16 of these horizons were confirmed by independent benthic biofacies determinations from at least two wells this internal consistency indicates that the data and the twodimensional backstripping approach were robust where benthic biofacies require a vertical shift of the horizons generated by two dimensional backstripping eustatic changes were required and were readily calculated results indicate a major eustatic fall from the end of the eocene to the first record of oligocene deposition subsequent long term shoaling of sea level through the oligocene was 30 m in 10 m y superimposed on this long term trend were higher frequency third order variations in eustasy with amplitudes of 40 m or less

a pulse in the planet regional control of high frequency changes in relative sea level by mantle convection abstract an explanation for high frequency cycles of sea level in non glacial times has remained elusive despite more than two centuries of research since lavoisier9s seminal observations were published in 1789 in the development of seismic stratigraphy in the 1970s putatively global high frequency changes in relative sea level vail third order cycles were attributed to an unknown eustatic mechanism prompting a search for mesozoic ice ages over the last decade a regional mechanism of sea level control has been developed from studies of the sedimentary record in high quality oil industry data these geological studies have supported the geophysical prediction that significant regional control of sea level is exercised by mantle induced vertical motions of the earth9s surface these vertical motions can occur over time intervals from several tens of million years to less than a million years with amplitudes of tens of metres or more even at the shorter intervals the vertical motions are not confined to regions with major hotspots there are two related controls of surface vertical motion evolution of mantle convection cells and pulsing flow within each cell the effects are evident in the sedimentary record of north atlantic basins mantle convection provides an alternative regional mechanism to eustatic control for explaining medium frequency to high frequency sea level cycles

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

does ice drive early maastrichtian eustasy a large 30 40 m rapid 1 m y earliest maastrichtian sea level drop inferred from new jersey sequence stratigraphic records correlates with synchronous 18o increases in deep water benthic and low latitude surface dwelling planktonic foraminifera the coincidence of these events argues for the development of a moderate sized ice sheet during the early maastrichtian

the cretaceous paleogene boundary foraminifera sea grasses sea level change and sequence stratigraphy abstract the tsunami generated by the chicxulub impact eroded the uppermost cretaceous surface of the gulf coast region u s a forming a distinctive topography that was previously interpreted as a sequence boundary at more distal sites such as stevns klint denmark there appears to be no sequence boundary at the cretaceous paleogene boundary but there is one within the uppermost maastrichtian between the sigerslev and hojerup members and another in the lowermost paleocene top of zone p1a both of these surfaces are identified by distinctive phosphatized and incipient hardgrounds the changes in sea level involved in the generation of uppermost cretaceous sequences are thought to have been minimal as in the gulpen and maastricht formations of the maastricht area netherlands the presence of sea grasses and their associated foraminifera would indicate that the chalk sea floor remained within the range of water depth that would allow photosynthesis

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

late maastrichtian warming in the boreal realm calcareous nannofossil evidence from denmark abstract the climate of the mid to late cretaceous was probably one of the warmest of the phanerozoic but by the late maastrichtian distinctly cool high latitude regions had developed studies from low latitude sites have demonstrated that the late maastrichtian cooling was punctuated by two pulses of warming but the response of nannoplankton to climatic fluctuation in the mid to high northern latitudes is not well documented a high resolution nannofossil study was undertaken on subsurface chalk sections of denmark which provide a stratigraphically complete record of late maastrichtian sedimentation of nannofossil ooze in an extensive mid to high latitude carbonate province the quantitative nannofossil data from cored sections through the upper maastrichtian chalk reveal subtle but significant shifts in taxa interpreted as having been sensitive to temperature fluctuations arkhangelskiella cymbiformis kamptnerius magnificus lucianorhabdus cayeuxii nephrolithus frequens and watznaueria barnesiae and indicate two late maastrichtian warming events correlatable with those of low latitude records and a decrease in surface water temperatures in the latest maastrichtian

can humans force a return to a cretaceous climate abstract the modern pole to equator sea level temperature difference is about 50 c that of the mid cretaceous ranged from 30 c to as little as 24 c implying a much more equable climate this may have been caused by 1 reduction of the ice forced albedo of the polar regions 2 more efficient meridional energy transport by the atmosphere and ocean and 3 increased atmospheric greenhouse gas concentrations earth s icy polar regions stabilize its present inequable climate through the ice albedo feedback effect the polar ice results in permanent atmospheric highs that stabilize earth s wind systems in turn the stable winds drive the ocean currents and determine the location of the frontal systems that separate the low and high latitude oceanic gyre systems and bound the region where water sinks into the ocean interior as thermocline and intermediate water masses increased ocean heat transport can assist in making a more equable climate but unrealistic volume transports would be required to warm the polar regions to cretaceous levels the major factor forcing the equable climate of the cretaceous is now thought to be increased greenhouse gas concentrations dominated by co2 the modern rate of change in atmospheric concentration is greater than 200 ppmv per century and increasing this compares with 1 ppmv per century during the last deglaciation at current rates of fossil fuel burning atmospheric co2 levels will reach cretaceous levels of 2 times the pre industrial level about 2070 and 8 times the pre industrial level shortly after 2300 it is likely that cretaceous atmospheric co2 concentrations will last for many thousands to tens of thousands of years in addition to increased atmospheric greenhouse gas concentrations a return to climatic conditions resembling those of the cretaceous would require ice free poles and large changes in atmospheric and oceanic circulation arctic sea ice is melting much more rapidly than had been expected and the arctic ocean will soon be free of sea ice in summer the greenland ice sheet is melting more rapidly than expected because of greenhouse warming surface meltwater forms lakes and then flows down through crevasses and holes in the ice to lubricate the base allowing ice steams to flow much more rapidly the lifetime of the greenland ice sheet may be only a few hundred years the west antarctic ice sheet is inherently unstable being grounded on rock well below sea level the ice shelves blocking ice streams off west antarctica have begun to melt from beneath and break up as the southern ocean warms the east antarctic ice sheet has been regarded as highly stable but discovery of lakes beneath the ice and fast flowing ice streams raises questions about whether the ice sheet will ultimately succumb to global warming and disintegrate i conclude that a return to climatic conditions resembling those of the mid cretaceous is not only possible but also likely unless humanity can organize an effective campaign to stop co2 emissions to the atmosphere and remove some of the excess co2 already introduced

variations of olivine fo ni contents and highly chalcophile element abundances in arc ultramafic cumulates southern alaska abstract recent drilling in the duke island complex shows that some olivine clinopyroxenites from hall cove contain low s but high pt pd in contrast dunites from the duke island complex and the yellow hill intrusion on nearby annette island are low in pt pd as well as s new data from this study show that the low s ultramafic rocks from duke and annette islands are extreme cumulates of olivine and or clinopyroxene and all contain trace to minor amounts of cumulus sulfide as a result the ratios of the least mobile highly chalcophile elements in these rocks mainly reflect those of original sulfide liquids which in turn reflect those of their parental magmas our data also show that all dunite samples from annette island contain ni depleted primitive olivine with fo contents 90 mol and ni contents

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

eustatic curve for the middle jurassic cretaceous based on russian platform and siberian stratigraphy zonal resolution we have used the stratigraphy of the central part of the russian platform and surrounding regions to construct a calibrated eustatic curve for the bajocian through the santonian the study area is centrally located in the large eurasian continental craton and was covered by shallow seas during much of the jurassic and cretaceous the geographic setting was a very low gradient ramp that was repeatedly flooded and exposed analysis of stratal geometry of the region suggests tectonic stability throughout most of mesozoic marine deposition the paleogeography of the region led to extremely low rates of sediment influx as a result accommodation potential was limited and is interpreted to have been determined primarily by eustatic variations the central part of the russian latform thus provides a useful frame of reference for the quantification of eustatic variations throughout the jurassic and cretaceous the biostratigraphy of the russian platform provides the basis for reliably determining age and eustatic events the mesozoic section of the central part of the russian platform is characterized by numerous hiatuses in this study we filled the sediment gaps left by unconformities in the central part of the russian platform with data from stratigraphic information from the more continuous stratigraphy of the neighboring subsiding regions such as northern siberia although these sections reflect subsidence the time scale of variations in subsidence rate is probably long relative to the duration of the stratigraphic gaps to be filled so the subsidence rate can be calculated and filtered from the stratigraphic data we thus have compiled a more complete eustatic curve than would be p ssible on the basis of russian platform stratigraphy alone relative sea level curves were generated by backstripping stratigraphic data from well and outcrop sections distributed throughout the central part of the russian platform for determining paleowater depth we developed a model specifically designed for this region based on paleoecology sedimentology geochemistry and paleogeography the curve describes a series of high frequency eustatic events superimposed on longer term trends many of the events identified from our study can be correlated to those found by haq et al 1988 and other sea level studies from other parts of the world but there are significant differences in the relative magnitudes of events because the eustatic curve resulting from this study is based on a stable reference frame the curve can be used in sedimentary basin modeling and as a tool for quantifying subsidence history from the stratigraphy of passive margins basins and other active regions

cenomanian to coniacian sea level changes in the lower benue trough nkalagu area nigeria and the eastern dahomey basin palaeontological and sedimentological evidence for eustasy and tectonism

the cenomanian turonian boundary event oae2 and palaeoenvironmental change in epicontinental seas new insights from the dinocyst and geochemical records abstract organic walled dinoflagellate cyst dinocyst and geochemical records across the cenomanian turonian boundary ctb are presented for the nw european reference section at eastbourne england dinocyst and nannofossil fertility indexes indicate that an upwelling driven productivity pulse accompanied a eustatic sea level fall that preceded by at least 40 kyr the global rise in 13 c values that marks the onset of oceanic anoxic event 2 oae2 and the deposition of black shales in the deep ocean a marine productivity collapse in the latest cenomanian is evidenced by the falling absolute and relative abundance of peridinioid dinocysts believed to be the product of heterotrophic dinoflagellates this biotic change accompanied transgression and sharply rising sea surface temperatures following an atlantic wide episode of short lived cooling geochemical tracers provide evidence of caribbean colombian plateau volcanism the increase in water depth caused by the latest cenomanian transgression resulted in less eutrophic waters in epicontinental seas where ctb biotic turnover was driven largely by water mass changes rather than oxygen depletion the species richness absolute abundance ratio of dinocysts is proposed as a water mass stability proxy

on the origin of cenozoic and mesozoic third order eustatic sequences abstract the origin of third order eustatic sequences is reviewed by comparing recent sequence stratigraphic data to the latest best constrained astronomical model middle eocene to holocene icehouse sequences correspond to 1 2 myr obliquity cycles constraints from oxygen isotope records highlight the link between icehouse sea level lowerings sequence boundaries and 1 2 myr obliquity nodes mesozoic greenhouse sequences show some relation with the 2 4 myr eccentricity cycles suggesting that orbital forcing contribute to sea level change we suggest that during the icehouse large ice sheets associated with significant glacioeustatic changes 25 m up to 120 m changes were mainly governed by obliquity forcing during icehouse worlds obliquity forcing was the stongest control on global sea level and depositional sequences additionally during the middle eocene third order sequences were glacioeustatically driven in tune with 1 2 myr obliquity cycle suggesting that the presence of significant ice sheets is earlier than previously supposed i e early eocene in contrast during greenhouse worlds e g ephemeral small to medium sized or no ice sheets 0 25 m glacioeustatic changes the expression of obliquity in the sedimentary record is weak and intermittent instead the eccentricity signature which is the modulator of climatic precession is documented moreover we presume that greenhouse sequences on the myr scale are global and hence cannot be caused by regional tectonism e g intraplate stress or mantle hot blobs instead the eccentricity link implies a weaker glacioeustatic control because thermoeustasy is too small to explain the sea level changes stratigraphically well documented fourth order sequences may be linked to the astronomically stable strongest amplitude 405 kyr eccentricity cycle and possibly to 160 200 kyr obliquity modulation cycles fifth order sequences to the short 100 kyr eccentricity cycles and finally sixth order sequences to the fundamental obliquity 40 kyr and climatic precession 20 kyr cycles these astronomical cycles could be preserved in the sedimentary record and have been demonstrated to control sea level changes accordingly by placing depositional sequence orders into a high resolution temporal framework i e orbital periodicities standardization of eustatic sequence hierarchy may be possible

strontium isotope stratigraphy of upper cretaceous rudist bivalves biozones evolutionary patterns and sea level change calibrated to numerical ages abstract numerical ages derived from strontium isotope stratigraphy of 81 late turonian maastrichtian rudist localities from the caribbean to oman are used to establish stratigraphical ranges of readily identifiable taxa of rudist bivalves hippuritida based on these ranges seven biozones for the turonian maastrichtian of the central eastern mediterranean tethys and three biozones for the mid campanian maastrichtian of the arabian plate are established most of these are interval zones each based on the first stratigraphical appearance of the nominal taxon micro evolutionary patterns such as phyletic size increase have been demonstrated for some of the nominal species as well as a trend of stratigraphical range expansion from the turonian to the maastrichtian implications of the geochronology of late cretaceous carbonate platforms for the biostratigraphy of other benthic fossils are briefly discussed three significant gaps in the stratigraphical distribution of rudist localities in the lower middle and uppermost campanian respectively correlate with other records of sea level change indicating that they correspond to major eustatic sea level falls only a limited number of rudist taxa is evaluated here but the early and latest campanian sea level falls correspond to faunal turnover and extinction of characteristic associations of late cretaceous hippuritida the final extinction of the hippuritida at the cretaceous paleogene boundary is evaluated based on the available numerical ages of eighteen late maastrichtian localities eighteen genera are recorded at the six youngest localities which thus have a species richness similar to older late cretaceous localities while the ultimate cause for extinction of the hippuritida must be evaluated on time scales beyond the resolution of strontium isotope stratigraphy the data set evaluated provides some insight into the pattern of their demise which is considered to be the result of a high degree of endemism indicating limited exchange between increasingly isolated populations this isolation was possibly related to the gradual decrease in the areal extent of maastrichtian carbonate platforms due to a long term cooling trend and local tectonics that affected carbonate platform growth in the regions studied

phanerozoic large igneous provinces lips heatt haline euxinic acidic thermal transgression episodes and mass extinctions abstract the phanerozoic consists of three mutually exclusive climate states icehouse greenhouse and hothouse the greenhouse is the default state representing 70 of the phanerozoic it is characterized by a weak thermal mode pole driven deep water formation with little or no continental sea ice and weakly oxic cool water sinking near the poles nitrogen limitation characterizes greenhouse oceans in which ammonium may be the dominant bioavailable form of nitrogen the steady state greenhouse default must be forced to produce either of the other two states continent continent collision produces the intense chemical weathering that draws down atmospheric co2 and results in the icehouse state that comprises 20 25 of the phanerozoic icehouses have ice caps in contact with the ocean that produce icebergs and foster sea ice formation sea ice formation fills the ocean with highly oxic phosphorus limited icewater except for a thin layer of warm surface water in the tropics of the 23 most conspicuous mass extinctions of the phanerozoic including the late ediacaran 4 are associated with ice volume related regressions and 3 are problematic we suggest that the other 16 mass extinctions occurred when greenhouse climate was forced to hothouse climate large igneous provinces lips can trigger the heatt haline euxinic acidic thermal transgression mechanism which can force greenhouse climate to a hothouse climate state the rapid voluminous co2 emissions of lips cause a series of events that result in very slow but pronounced haline mode circulation mid latitude driven deep water formation that produces warm saline bottom water at very dry hot subtropical and middle latitudes this water upwells at the poles causing warm and moist equable climate hothouse development promotes deep sea anoxia that is generated in concert with co2 buildup and warming the spread of anoxia favors reduced nitrogen over nitrate and limited iron dust curtails nitrogen fixation this leads to dominance of primary productivity by primitive green algae and or cyanobacteria progression to euxinia that reaches the photic zone severely curtails primary productivity via poisoning even as availability of usable nitrogen plummets the result is eukaryotic mass extinction we suggest that the 16 phanerozoic mass extinctions referred to above resulted at least in part from the heatt process evidence for this relationship at 11 of the most severe extinctions is convincing data sets for the other 5 are strongly suggestive of heatt related mass extinction but do not yet have enough documentation to reliably characterize them as heatt episodes

a new high resolution carbon isotope stratigraphy for the campanian bottaccione section its implications for global correlation ocean circulation and astrochronology abstract a high resolution carbon isotope record is presented for campanian strata of the bottaccione section umbria marche basin through an interval that constitutes the standard reference section for the geomagnetic polarity time scale the identification of prominent 13 c excursions and high frequency variations allows the establishment of robust stratigraphic markers to link this new tethyan 13 c record with the boreal realm lagerdorf kronsmoor section northwest germany and the trunch borehole norfolk uk a decoupling of baseline 13 c values between the boreal and the tethyan realm is observed during the mid campanian reflecting a plausible change in intermediate deep water mass exchange due to a more restricted tethyan gateway this is hypothesized to be a consequence of northward movements of africa associated with opening of the south atlantic ocean statistical evaluation of a segment of the 13 c dataset with the timeopt method for astrochronologic testing provides strong evidence of astronomical forcing and underscores the potential for development of a complete astronomically tuned campanian stage at bottaccione allowing astronomical calibration of key geomagnetic and paleobiologic datums

stable isotope records across the cretaceous paleogene transition stevns klint denmark new insights from the chromium isotope system abstract late cretaceous to early paleogene time represents a critical transitional period in earth history global events include short term instability in climate and ocean circulation large igneous province emplacement and catastrophic extinction of marine and terrestrial fauna due at least in part to a bolide impact event the response of the ocean system to cretaceous paleogene k pg global events has been the subject of much research yet fundamental questions remain regarding carbon cycling climate ocean mixing and redox conditions to help elucidate paleoceanographic changes across the k pg transition we revisit the classic maastrichtian to danian chalk limestone succession at stevns klint denmark with a suite of new geochemical data including insights from the redox sensitive chromium isotope system we use carbon and oxygen isotope trends to form a well constrained framework for the succession before presenting strontium isotope chromium isotope and rare earth element data for the units deposited both before and after the k pg event carbon isotopes show only minor perturbation across the k pg boundary and oxygen isotopes record a prominent positive excursion with both of these trends standing in contrast to many k pg boundary sections worldwide strontium isotopes record a spike towards more radiogenic values which is consistent with a globally observed short term weathering pulse the chromium isotope profile of maastrichtian chalk begins with strongly positive values followed by a sharp negative excursion associated with a facies shift and initiation of bottom currents in the chalk sea 53 cr values then recover before falling steadily across the k pg boundary and into the danian limestone chromium isotope trends do not correspond to changes in hydrothermal input or basin redox conditions instead we propose that mixing of water masses with distinct chromium isotope signatures controlled temporal chromium isotope variability the local mixing event inferred from our maastrichtian chromium isotope data could be related to a temporary inflow of tethyan bottom waters or the shift from end maastrichtian greenhouse warming associated with deccan volcanism to the worldwide cooling phase that immediately preceded the k pg boundary no immediate change in chromium isotopes is recorded across the k pg boundary indicating that the bolide impactor did not substantially perturb the marine chromium cycle at least at the scale resolvable by our data instead chromium isotope trends continued to be controlled by local oceanographic processes highlighting the potential of the chromium isotope system to record isotopic heterogeneity and mixing events in ancient oceans

integrated stratigraphic studies of paleocene lowermost eocene sequences new jersey coastal plain evidence for glacioeustatic control 1 we describe seven paleocene to lowermost eocene sequences in core holes at island beach bass river ancora millville and sea girt nj ocean drilling program leg 150x 174ax and analyze benthic foraminiferal assemblages to assess paleodepth changes within sequences these sequences are referred to as pa0 pa1a pa1b pa2a pa2b pa3a and pa3b paleocene sequence boundaries are identified by unconformities and variations in benthic foraminiferal biofacies we used q mode factor analysis and paleoslope modeling to identify three distinct middle outer neritic benthic foraminiferal assemblages and their associated water depths paleodepths during the early paleocene and deposition of pa0 pa1a and pa2b were 80 m with 20 m changes across sequence boundaries a long term shallowing occurred through the late paleocene where paleodepths were 50 70 m in pa3a this trend drastically changes in the earliest eocene where the paleodepths of sequence pa3b were 120 150 m new jersey paleocene sequence boundaries correlate with those in other regions and with 18o increases in the deep sea suggesting paleocene eustatic lowerings were associated with ice growth events

stable isotopes and geochemistry of a campanian maastrichtian pelagic succession mudurnu goynuk basin nw turkey implications for palaeoceanography palaeoclimate and sea level fluctuations this study focuses on the palaeoclimatic evolution and relative sea level fluctuations of the northern branch of neotethys during the late campanian early danian the studied succession ismailler section is located in the mudurnu goynuk basin nw turkey and dominated by apparently continuous pelagic muddy deposits stable isotopic and elemental compositions of the mudrocks are investigated in order to evaluate the palaeoceanographic conditions as well as broad tectonic reconstruction of the basin the mudrock geochemistry suggests a tectonic reorganization during late campanian as reflected by a distinct shift from felsic to mafic sediment provenance in the ismailler section five 13c events are identified four or which are well correlatable with major events in other records around the world such as the late campanian event lce campanian maastrictian boundary cmb and the late maastrichtian event lme the relative sea level variations in the basin typically match both short and long term global sea level fluctuations the remaining globally uncorrelatable 13c event does coincide with tectonic uplift and the abrupt negative 13c shift and is inferred to be the result of regional factors the dominance of worldwide events in the records of the relatively restricted ocean branch reflects the strength of global factors

comment on sea level control on facies architecture in the cenomanian coniacian apulian margin western tethys a record of glacio eustatic fluctuations during the cretaceous greenhouse by s galeotti g rusciadelli m sprovieri l lanci a gaudio and s pekar palaeogeography palaeoclimatology palaeoecology 276 2009 196 205 abstract galeotti et al 2009 galeotti s rusciadelli g sprovieri m lanci l gaudio a pekar s a record of glacio eustatic fluctuations during the cretaceous greenhouse palaeogeogr palaeoclimatol palaeoecol 276 196 205 hereafter getal09 use the sequence stratigraphic record of a cenomanian coniacian base of slope succession exposed in the morrone mountain of central italy to calibrate the sea level history inferred from the adjacent lazio abruzzi carbonate platform the episodes of sea level fall recorded by this carbonate platform and slope in the western tethys are said to coincide with episodes of global cooling and sea level fall recorded in the new jersey margin miller k g sugarman p j browning j v kominz m a hernandez j c olsson r k wright j d feigenson m d van sickel w 2003 late cretaceous chronology of large rapid sea level changes glacioeustasy during the greenhouse world geology 31 585 588 on the basis of this correlation getal09 claim that the late cretaceous sea level history of the lazio abruzzi carbonate platform was controlled by glacio eustatic fluctuations this conclusion conflicts with a wealth of published data supporting the view that the major unconformities in the cretaceous carbonate platforms of central southern italy were controlled by regional tectonics we will show how the sea level history of the lazio abruzzi carbonate platform proposed by getal09 and its correlation with the base of slope section hinge on a misrepresentation of the chronostratigraphic resolution attainable with biostratigraphy in shallow water carbonate facies we will also show how contrary to what claimed by getal09 the age model for their base of slope section does not support the correlation with the new jersey margin sequences finally we will argue that in upper cretaceous carbonate platforms the integration of bio and chemostratigraphy can greatly improve stratigraphic resolution and chronostratigraphic correlation this is a prerequisite for using the shallow water record to test the hypothesis of global glacio eustatic fluctuations in the cretaceous greenhouse

the evidence and implications of polar ice during the mesozoic abstract the mesozoic perhaps representing the longest period of warmth during phanerozoic earth history contains in general sparse and frequently equivocal evidence for polar ice although this time is undoubtedly punctuated by oscillations in climate whether sufficient to lead to polar cooling and the formation of polar ice an inviting mechanism to account for faunal and floral distribution patterns and large scale sea level change has been widely debated mesozoic evidence for glacial conditions includes abraded rock surfaces generally unsorted stone rich beds and the presence of dropstones rafted by ice within a finer grained host sediment faunal and floral evidence has also been utilised to determine the presence or absence of cold or sub freezing polar conditions together with more indirect evidence for glacial conditions derived from general circulation model gcm simulations of climate the analysis of clay mineral distributions glendonite abundance and palaeontological and sedimentological evidence for globally synchronous sea level change the extent of possible glacial environments during the mesozoic has been established by plotting published reports of glacial sediments on palaeogeographic reconstructions the general clustering of evidence at high palaeolatitudes suggests that the extent of polar ice during the mesozoic is likely to have been approximately one third the size of the present day based on such evidence a number of episodes of cold or sub freezing polar climates during the bajocian bathonian tithonian volgian valanginian and aptian are recognised evidence exists possibly also for a cold episode during the early jurassic pliensbachian although poorly constrained owing to limited biostratigraphical control the longevity of these events may be represented by a cold snap within a stage although undoubtedly the possible smearing of ages may have had the effect of lengthening and hence promoting the importance of these proposed events the climate regime of the earth during these times may be hypothesised to be characterised by a relatively steep pole to equator temperature gradient where low latitude regions are as warm or warmer than today the evidence to support such reasoning includes sharp increases in the areal distribution of both glendonites and deposits with affinities to glacial tillites and dropstones for these times coincidental falls of sea level arid events and an increased bipolarity of faunas at these times imparts further confidence that these events were of a magnitude to effect the earth as a whole

campanian maastrichtian intermediate to deep water changes in the high latitudes benthic foraminiferal evidence 1 during the latest cretaceous cooling phase a positive shift in benthic foraminiferal 18o values lasting about 1 5 myr 71 5 70 ma can be observed at a global scale campanian maastrichtian boundary event cmbe this 18o excursion is interpreted as being influenced by a change in intermediate to deep water circulation or by temporal build up of antarctic ice sheets here we test whether benthic foraminiferal assemblages from a southern high latitudinal site near antarctica odp site 690 are influenced by the cmbe if the 18o transition reflects a change in intermediate to deep water circulation from low latitude to high latitude water masses then this change would result in cooler temperatures higher oxygen concentration and possibly lower organic matter flux at the seafloor resulting in a major benthic foraminiferal assemblage change if however the 18o transition was mainly triggered by ice formation no considerable compositional difference in benthic foraminiferal assemblages would be expected our data show a separation of the studied succession into two parts with distinctly different benthic foraminiferal assemblages species dominating the older part 73 0 70 5 ma tolerate less bottom water oxygenation and are typical components of low latitude assemblages in contrast the younger part 70 0 68 0 ma is characterized by species that indicate well oxygenated bottom waters and species common in high latitude assemblages we interpret the observed change in benthic foraminiferal assemblages toward a well oxygenated environment to reflect the onset of a shift from low latitude toward high latitude dominated intermediate to deep water sources this implies that a change in oceanic circulation was at least a major component of the cmbe

cenozoic global sea level sequences and the new jersey transect results from coastal plain and continental slope drilling the new jersey sea level transect was designed to evaluate the relationships among global sea level eustatic change unconformity bounded sequences and variations in subsidence sediment supply and climate on a passive continental margin by sampling and dating cenozoic strata from coastal plain and continental slope locations we show that sequence boundaries correlate within 0 5 myr regionally onshore offshore and interregionally new jersey alabama bahamas implicating a global cause sequence boundaries correlate with 18o increases for at least the past 42 myr consistent with an ice volume glacioeustatic control although a causal relationship is not required because of uncertainties in ages and correlations evidence for a causal connection is provided by preliminary miocene data from slope site 904 that directly link 18o increases with sequence boundaries we conclude that variation in the size of ice sheets has been a primary control on the formation of sequence boundaries since 42 ma we speculate that prior to this the growth and decay of small ice sheets caused small amplitude sea level changes 20 m in this supposedly ice free world because eocene sequence boundaries also appear to correlate with minor 18o increases subsidence estimates backstripping indicate amplitudes of short term million year scale lowerings that are consistent with estimates derived from 18o studies 25 50 m in the oligocene middle miocene and 10 20 m in the eocene and a long term lowering of 150 200 m over the past 65 myr consistent with estimates derived from volume changes on mid ocean ridges although our results are consistent with the general number and timing of paleocene to middle miocene sequences published by workers at exxon production research company our estimates of sea level amplitudes are substantially lower than theirs lithofacies patterns within sequences follow repetitive predictable patterns 1 coastal plain sequences consist of basal transgressive sands overlain by regressive highstand silts and quartz sands and 2 although slope lithofacies variations are subdued reworked sediments constitute lowstand deposits causing the strongest most extensive seismic reflections despite a primary eustatic control on sequence boundaries new jersey sequences were also influenced by changes in tectonics sediment supply and climate during the early to middle eocene low siliciclastic and high pelagic input associated with warm climates resulted in widespread carbonate deposition and thin sequences late middle eocene and earliest oligocene cooling events curtailed carbonate deposition in the coastal plain and slope respectively resulting in a switch to siliciclastic sedimentation in onshore areas oligocene sequences are thin owing to low siliciclastic and pelagic input and their distribution is patchy reflecting migration or progradation of depocenters in contrast miocene onshore sequences are thicker reflecting increased sediment supply and they are more complete downdip owing to simple tectonics we conclude that the new jersey margin provides a natural laboratory for unraveling complex interactions of eustasy tectonics changes in sediment supply and climate change

testing for ice sheets during the mid cretaceous greenhouse using glassy foraminiferal calcite from the mid cenomanian tropics on demerara rise the mid cretaceous is widely considered the archetypal ice free greenhouse interval in earth history with a thermal maximum around cenomanian turonian boundary time ca 90 ma however contemporaneous glaciations have been hypothesized based on sequence stratigraphic evidence for rapid sea level oscillation and oxygen isotope excursions in records generated from carbonates of questionable preservation and or of low resolution we present new oxygen isotope records for the mid cenomanian demerara rise that are of much higher resolution than previously available taken from both planktic and benthic foraminifers and utilizing only extremely well preserved glassy foraminifers our records show no evidence of glaciation calling into question the hypothesized ice sheets and rendering the origin of inferred rapid sea level oscillations enigmatic simple mass balance calculations demonstrate that this cretaceous sea level paradox is unlikely to be explained by hidden ice sheets existing below the limit of 18 o detection

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

late cretaceous transgression on a cimmerian high neka valley eastern alborz iran a geodynamic event recorded by glauconitic sands abstract in the neka valley eastern alborz iran glaucony bearing marine sediments of early middle santonian age directly overlie palaeozoic to triassic units deformed during the eo cimmerian orogenic event late triassic the upper cretaceous open marine sediments were deposited on a flat surface lacking any evidence of pedogenesis the geochemical and morphological features of glaucony grains which characterize the base 1 to 1 5 m of the upper cretaceous succession indicate an autochthonous origin of the highly evolved glaucony denoting a long lasting period of low sedimentation rate the development of glaucony in the observed stratigraphic position is indicative of a rapid drowning of the former cimmerian relief that cannot be explained by a eustatic rise alone the palaeo depth needed for the development of glaucony and for the presence of the observed bathyal foraminifera assemblages is greater than the maximum eustatic excursion documented in the cretaceous the occurrence of glaucony in this stratigraphic position reflects thus an important episode of increased subsidence rates related to a geodynamic event framed in a time interval of major plate reorganization in the complex puzzle of the iranian plates the subsidence event that caused the development of the glauconitic horizon in the neka valley could likely represent the effect of a santonian stage of the complex and long lasting story of the opening of the caspian sea

cretaceous oceanic red beds as possible consequence of oceanic anoxic events article i nfo oceanic anoxic events oaes represent brief periods of burial of large amounts of organic carbon in the oceans during cretaceous time burial of organic carbon which preferentially sequestered isotopically lighter carbon during oaes resulted in positive 13 c excursions of 2 3 recognizable in global ocean these deposits are typically dark grey to black shales considered to be the result of interaction between extreme warm climate ocean circulation high bioproductivity and organic carbon preservation less interest has been given to periods between oaes when oxic deep sea deposits such as red marls and red shales were deposited during mid and late cretaceous the latter deposits are associated with very low content of organic carbon and oxic depositional environments which dominated western tethys in post turonian time up to the early eocene feedbacks among geochemical cycles in response to decreasing global temperatures increasing deep ocean circulation forced by high latitude deep water formation along the antarctic margin and widening and deepening of the interconnections between the oceanic basins may have been responsible for the major paleoceanographic change from deposition of organic carbon rich black shales during mid cretaceous to world wide deposition of cretaceous oceanic red beds corbs in the late cretaceous the presence of corbs sandwiched between mid cretaceous oaes may reflect major climate and paleoceanographic changes in a contrast to extremely warm climates during the oaes the corbs suggest cold periods and therefore oscillating climate shifts that have seldom been considered during modeling of cretaceous

stable isotope composition of late cretaceous benthic foraminifera from the southern south atlantic biological and environmental effects abstract the stable carbon and oxygen isotope composition of different benthic foraminiferal species of the latest campanian and earliest maastrichtian from ocean drilling project hole 690c weddell sea southern south atlantic 1800 m paleowater depth have been investigated the total range of measured isotope values of all samples exceeds 4 for 13c and 1 1 for 18o carbon isotope values of proposed deep infaunal species are generally similar or only slightly lower when compared to proposed epifaunal to shallow infaunal species interspecific differences vary between samples probably reflecting temporal changes in organic carbon fluxes to the sea floor constantly lower 13c values for pullenia marssoni and pullenia reussi suggest the deepest habitat for these species the strong depletion of 13c values by up to 3 within lenticulinids may be attributed to a deep infaunal microhabitat strong vital effects or different feeding strategy when compared to other species or modern lenticulinids the mean 18o values reveal a strong separation of epifaunal to shallow infaunal and deep infaunal species epifaunal to shallow infaunal species are characterized by low 18o values deep infaunal species by higher values this result possibly reflects lower metabolic rates and longer life cycles of deep infaunal species or the operating of a pore water co32 effect on the benthic foraminiferal stable isotopes pyramidina szajnochae shows an enrichment of oxygen isotopes with test size comprising a total of 0 6 between 250 and 1250 m shell size although 13c lacks a corresponding trend these data likely represent the presence of changes in metabolic rates during ontogenesis these results demonstrate the general applicability of multi species stable isotope measurements of pristine cretaceous benthic foraminifera to reconstruct past microhabitats and to evaluate biological and environmental effects on the stable isotope composition

transatlantic correlations in the campanian maastrichtian stages by eustatic changes of sea level abstract there is good evidence that high sea levels peaked simultaneously during the late albian to turonian in the usa and northwest europe therefore it is to be expected that the principal peaks during the campanian maastrichtian now well dated in northwest europe should be detectable in the usa of the four main peaks in europe no 3 low in the zone of belemnitella langei is the most prominent and can be recognized with confidence in the western interior new jersey alabama mississippi and probably in texas the other peaks can be identified with various degrees of confidence but the sea did not persist long enough in the western interior for the last peak early in the late maastrichtian to be developed there the results change the generally assumed position of the campanian maastrichtian boundary on the foraminiferal scale the base of the maastrichtian on the belemnite scale is a considerable distance above the top of the zone of globotruncanita calcarata possibly as high as the base of the zone of gansserina gansseri in north temperate regions on the ammonite scale in the western interior of the usa the boundary is probably at the base of the zone of baculites baculus at 70 7 ma but could be at the base of the zone of b eliasi

long term and short term global cenozoic sea level estimates backstripping analysis of three continuously cored well dated boreholes from the new jersey coastal plain ocean drilling program odp leg 150x indicates a long term 10 8 n10 7 yr eustatic fall of 100 m since 55 ma early eocene and suggests short term 0 5n3 m y eustatic falls of less than 70 m eustatic estimates are calculated from residuals between the decompacted unloaded and paleodepth corrected records and tectonic subsidence assuming a cooling lithospheric plate because the residuals are similar among the three sites we interpret them as an approximation of the eustatic signal

climate induced fluctuations in sea level during non glacial times during periods of time when the earth supports ice caps sea level fluctuates periodically at intervals of 104 105 yr with amplitudes of tens to more than 100 metres these fluctuations result from expansions and contractions of continental ice sheets that occur in phase with the milankovitch periodicities of the earth s orbit1 2 smaller amplitude sea level fluctuations associated with milankovitch periodicities are also evident during warm periods such as the late triassic3 5 which lack strong evidence for continental glaciation6 we argue here that in times of limited ice volume periodic climate induced changes in lake and groundwater storage have the potential to produce small fluctuations in sea level this mechanism could contribute a small component of the sea level change observed in the quaternary period and may dominate the milankovitch eustatic sea level signal during earlier periods with limited ice volume6 we present evidence of contemporaneous milankovitch periodicities in late triassic lake sediments7 and sea level fluctuation3 5 which support the causal link between lake water storage and eustasy

a guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

astrochronology of the late turonian implications for the behavior of the carbon cycle at the demise of peak greenhouse abstract a series of prominent carbon cycle perturbations indicated by carbon isotope excursions of up to 2 marked climatic and oceanographic changes that followed the peak mid cretaceous greenhouse the nature and forcing mechanisms of these changes remain poorly understood partly due to the lack of a detailed temporal control in this interval here we present an orbitally calibrated time scale which is based on hemipelagic rhythmites in the bohemian cretaceous basin and which can be linked to the established chronostratigraphic framework using inoceramid biostratigraphy and carbon isotope signature in the new age model the late turonian defined by the first occurrence of i perplexus below and the first occurrence of c deformis erectus above spans 1 56 0 07 myr when anchored to the newly refined age of the turonian coniacian boundary sageman et al in press the onset of the late turonian is 91 31 0 45 ma inoceramid zones i perplexus and m scupini span 0 76 0 05 myr and 0 80 0 05 myr respectively a time domain record of carbon isotope variations was obtained by pinning published 13ccarb data to the orbital time scale using 9 biostratigraphic and carbon isotope markers the timing of major carbon isotope excursions suggests a link to 405 kyr eccentricity changes and in the early late turonian to 100 kyr eccentricity variations however over 80 of the variance in the late turonian 13 c occurs at longer million year scales the key features of the 13ccarb signature including the amplified long term variance can be reproduced with simple models of orbitally driven isotopic mass balance at a constant carbon isotope fractionation the best fit to the 13ccarb signature is obtained with enhanced organic burial at high eccentricity in accordance with monsoonal forcing of organic accumulation in the low latitude atlantic and or buildup of low latitude terrestrial carbon reservoirs alternative solutions should consider changing carbon isotope fractionation due to pco2 and or nutrient flux changes

quantitative analysis of the dimensions and distribution of channelized fluvial sandbodies within a large outcrop dataset upper cretaceous blackhawk formation wasatch plateau central utah u s a abstract conceptual and quantitative models of fluvial stratigraphy typically argue that alluvial architecture is driven by a combination of allogenic processes e g tectonic subsidence sea level sediment supply and autogenic behaviors e g avulsion we test these models via analysis of a large c 200 m thick by 100 km depositional strike extent alluvial to coastal plain succession that records shoreline progradation in response to decreasing tectonic subsidence late cretaceous blackhawk formation wasatch plateau central utah u s a oblique aerial photographs and architectural panels of six nearly linear nearly vertical cliff face windows were used to characterize the dimensions apparent widths thicknesses and spatial distributions of channelized fluvial sandbodies two statistical measures raster based lacunarity and point based l function are used to investigate whether the distribution of channelized sandbodies show significant regularity randomness or clustering over 490 channelized fluvial sandbodies are identified in the six cliff face windows from base to top of the blackhawk formation sandbodies broadly increase in width and decrease in overall abundance per unit area clustering of sandbodies occurs relatively frequently in lower coastal plain strata 50 km from the coeval shoreline a strong negative correlation between lacunarity and stratigraphic position is also observed such that a wider range and greater variety of spatial gaps occurs between sandbodies in lower coastal plain strata relative to upper coastal plain and alluvial strata comparison with numerical modeling studies of fluvial stratigraphic architecture implies the predominance of an avulsion generated pattern of sandbody distribution that includes an element of compensational stacking on the upper coastal plain and alluvial plain for a range of distances from the coeval shoreline c 40 130 km and tectonic subsidence rates c 40 700 m myr on the lower coastal plain 50 km from the coeval shoreline localized clustering of channelized sandbodies is interpreted to have formed by avulsion of deltaic distributary channels downstream of delta apex avulsion nodes possibly modulated by low amplitude 30 m sea level fluctuations

impacts of palaeogeography and sea level changes on mid cretaceous climate climate is often depicted as globally warm during the middle part of the cretaceous however major tectonic events such as the break up of gondwana or sea level changes inducing the flooding of vast continental areas occurred from 120 to 95 ma resulting in drastic climatic re organisations in order to investigate the impact of plate tectonics and sea level change on climate we performed climatic simulations during the cenomanian 95 ma and aptian 120 ma using an atmospheric general circulation model problems with models lie in our knowledge of a few key factors for examples the middle cretaceous sea surface temperature gradient from equator to pole remains an open question and it is not clear yet how flat it was two sensitivity experiments for each period prescribing a flatter sst gradient based on oxygen isotopic data have been done in order to test its climatic consequences we discuss separately the effect of palaeogeography and meridional sst gradient impacts in the northern hemisphere the flooding of large continental areas due to sea level rise leads to a more equable climate in the mid latitudes however the impact of epicontinental seas varies seasonally from site to site due to local feedbacks in the southern hemisphere the breakup of gondwana deeply affects the climate of this region moderating the seasonal thermal variations in addition we test the impact of a flatter sst gradient on climate and we show that simulations with flat sst gradients compare well with field data we analyse the remaining model data discrepancies in terms of missing feedbacks co2 vegetation but also of new measurements that enable to infer a better meridional variation of sea surface temperature

sea level fall carbonate production rainy days how do they relate insight from triassic carbonate platforms western tethys southern alps italy the interplay of sea level fall climate and sedimentological changes is recorded across two sequence boundaries at the top of two triassic carbonate platform systems in the western tethys earliest carnian and norian rhaetian boundary in age paleolatitude 18 25 n the sea level falls caused subaerial exposure of the platform top and decreased carbonate production leading to starvation in the intraplatform basins followed by deposition of shale evidence of freshwater input indicates that the change in sedimentation was driven by increased rainfall on the previously arid european hinterland and tethys coast a uniformitarian approach holocene sea level changes and global warming are coupled with changes in the distribution of precipitation implicates global cooling as the probable cause of the observed sea level climate and sedimentological changes global cooling likely triggered the sea level fall by increased storage of fresh water in continental settings and change in seawater density probably coupled with ephemeral ice sheet development possible even during greenhouse intervals such as the triassic furthermore global cooling caused a shift toward the equator of the poleward boundary of the arid belt this model is supported by the traceability of the sequence boundaries and climate sensitive facies from the tethys shelf up to the european continent the observed association of global climate changes sea level fall sedimentological changes and shift toward humid climate documents how climate sensitive facies record the control exerted by global changes on local sedimentation

extensive thin sequences spanning cretaceous foredeep suggest high frequency eustatic control late cenomanian western canada foreland basin early late cenomanian rocks of the doe creek unit are near the base of the kaskapau formation and were deposited in a broad very shallow embayment that occupied the foredeep of the western canada foreland basin the doe creek unit consists of 13 upward shoaling sequences typically 3 10 m thick subsurface correlation shows that sequences can be traced for 100 350 km from the fore deep toward the forebulge on the proximal and distal margins of the embayment each sequence is capped by a flooding surface commonly underlain by a paleosol developed in marine mudstone in the center of the embayment most sequences are capped by one or more isolated sharp based sandstone bodies interpreted as lowstand delta front deposits flooding surfaces on top of each sequence are continuously traceable in well logs from the foredeep to the vicinity of the forebulge implying simultaneous transgression across the basin every sequence shows an abrupt upward shallowing usually to emergence that was caused by accommodation loss not sediment accumulation a vertical relative sea level excursion of 10 m on a time scale spanning a maximum range of 9 74 k y is estimated for each sequence because transgressions and regressions appear to be in phase across the basin sequences are better explained by eustasy rather than by flexural reciprocal sedimentation a glacioeustatic mechanism provides the most likely explanation

midlatitude shelf seas in the cenomanian turonian greenhouse world temperature evolution and north atlantic circulation 1 an 8 million year record of subtropical and midlatitude shelf sea temperatures derived from oxygen isotopes of well preserved brachiopods from a variety of european sections demonstrates a long term cenomanian temperature rise 16 20 c midlatitudes that reached its maximum early in the late turonian 23 c midlatitudes superimposed on the long term trend shelf sea temperatures vary at shorter timescales in relation to global carbon cycle perturbations in the mid cenomanian and the late turonian two minor shelf sea cooling events 2 3 c coincide with carbon cycle perturbations and times of high amplitude sea level falls although this evidence supports the hypothesis of potential glacioeustatic effects on cretaceous sea level the occurrence of minimum shelf sea temperatures within transgressive beds argues for regional changes in shelf sea circulation as the most plausible mechanism the major carbon cycle event in the latest cenomanian oceanic anoxic event 2 is accompanied by a substantial increase in shelf sea temperatures 4 5 c that occurred 150 kyr after the commencement of the 13c excursion and is related to the spread of oceanic conditions in western european shelf sea basins our oxygen isotope record and published 18o data of pristinely preserved foraminifera allow the consideration of north atlantic surface water properties in the cenomanian along a transect from the tropics to the midlatitudes on the basis of fossil derived 18o estimated w ranges and modeled salinities temperature salinity density ranges were estimated for tropical subtropical and midlatitude surface waters accordingly the cenomanian temperate shelf seas waters have potentially the highest surface water density and could have contributed to north atlantic intermediate to deep waters in the preopening stage of the equatorial atlantic gateway

early maastrichtian carbon cycle perturbation and cooling event implications from the south atlantic ocean published stable isotope records in marine carbonate are characterized by a positive 18o excursion associated with a negative 13c shift during the early maastrichtian however the cause and even the precise timing of these excursions remain uncertain we have generated high resolution foraminiferal stable isotope and grey scale records for the latest campanian to early maastrichtian 73 68 ma at two ocean drilling program sites 525 walvis ridge and 690 weddell sea we demonstrate that the negative 13c excursion is decoupled from the 18o increase with a lag of about 600 kyr our 13c records both planktic and benthic show an amplitude for the negative excursion of 0 7 that falls between about 72 1 and 70 7 ma our planktic 18o records indicate an overall increase of 1 2 from 73 to 68 ma at site 690 whereas at site 525 they record a slightly smaller increase 1 that peaks around 70 1 ma with decreasing values thereafter our benthic 18o data indicate an increase of 1 5 at site 525 and 0 7 at site 690 between about 71 4 and 69 9 ma benthic 18o values show different baseline values at the two sites before and after the excursion but the larger increase at site 525 means that the values attained at the peak of the excursion are similar at the two sites we interpret this observation in terms of water mass changes the excursion is interpreted to reflect a cooling of bottom waters in response to the strengthening contribution of intermediate to deep water production in the high southern latitudes rather than increased ice volume the associated carbon cycle perturbations that we observe are interpreted to reflect a weakening of surface water stratification and increased productivity as supported by our grey value data

possible solutions to several enigmas of cretaceous climate the nature of the warm climates of the cretaceous has been enigmatic since the first numerical climate models were run in the late 1970s quantitative simulations of the paleoclimate have consistently failed to agree with information from plant and animal fossils and climate sensitive sediments the cold continental interior paradox first described by deconto et al in barrera e johnson c eds evolution of the cretaceous ocean climate system vol 332 geological society of america special paper boulder pp 391 406 1999 has been an enigma with extensive continental interiors especially in northeast asia modeled as below freezing in spite of plant and other evidence to the contrary we reconsider the paleoelevations of specific areas particularly along the northeastern siberian continental margin where paleofloras indeed indicate higher temperatures than suggested by current climate models evidence for significant masses of ice on land during even the otherwise warmest times of the cretaceous is solved by reinterpretation of the 18o record of fossil plankton the signal interpreted as an increase in ice volume on land is the same as the signal for an increase in the volume of groundwater reservoirs on land the problem of a warm arctic where fossil floras indicate that they never experienced freezing conditions in winter could not be solved by numerical simulations using higher co2 equivalent greenhouse gas concentrations we propose a solution by assuming that paleoelevations were less than today and that there were much more extensive wetlands lakes meandering rivers swamps bogs on the continents than previously assumed using 8 co2 equivalent greenhouse gas concentrations and assuming 50 75 water surfaces providing water vapor as a supplementary greenhouse gas on the continents reduces the meridional temperature gradients under these conditions the equatorial to polar region temperature gradients produce conditions compatible with fossil and sedimentological evidence

late cretaceous climatic trends and a positive carbon isotope excursion at the santonian campanian boundary in british columbia northeastern pacific abstract this study presents oxygen and carbon isotope data obtained from well preserved ammonite and bivalve fossils of the upper cretaceous nanaimo group of southwestern british columbia canada palaeotemperatures for the late santonian campanian of british columbia determined on the basis of oxygen isotopic analysis suggest a odirect relationship with basic late cretaceous climatic trends e g temperature fall toward the cool climates of the maastrichtian the coolest campanian palaeotemperatures were calculated from the ammonite pachydiscus cf ootacodensis stoliczka 11 3 26 4 c and the bivalve inoceramus vancouverensis shumard about 19 7 c from the late campanian occidentalis zone northumberland formation in contrast the highest palaeotemperatures were obtained from the shells of presumed earliest campanian bivalves and varied between 25 1 and 33 7 c which we assume to represent the regional expression of the early campanian warming event the santonian campanian boundary in british columbia is associated with a positive 13c excursion to 4 2 which appears to be contemporaneous with the santonian campanian boundary event reported recently from other regions i e europe tunisia japan and tibet the lack of organic rich laminated black shales indicating strong oxygen depletion in the marine realm through the santonian campanian of the nanaimo group including the santonian campanian boundary interval seems to be in agreement with the suggestion that most of the world s oceans were characterised by oxygen rich deep waters during coniacian campanian time

from bars to valleys the sedimentology and seismic geomorphology of fluvial to estuarine incised valley fills of the grand rapids formation lower cretaceous iron river field alberta canada abstract a high resolution 3d seismic data set from alberta canada has revealed great detail in the morphology and architecture of a series of incised valley fills from the grand rapids formation albian lower cretaceous a large scale well log study was used to place the seismic stratigraphic architecture in regional context seismic facies were calibrated with numerous cores and wells the data reveal that the grand rapids formation was composed of shoreface parasequences cut by many incisions filled with fluvial to estuarine facies the incisions contain one to several channel fills with a range of bar architectures but dominated by lateral accretion incised valleys are here defined as any fluvial incision that is bounded below by a sequence boundary incised valleys form in response to a relative fall in sea level and unlike distributary channels are not in facies relationship with the surrounding sediments into which they are incised a range of direct and indirect evidence indicates that all of the studied incisions into the shoreface parasequences are incised valleys thirty two incised valleys were identified in the grand rapids formation in the 3d seismic they range in width from a few tens of meters to a few kilometers and in depth from 5 to 60 m there is no relationship between the size of a valley and its stratigraphic position composite sequence boundaries have many intersecting incised valleys of a range of size high frequency sequence boundaries have only a few incised valleys none of the incised valleys have a dendritic drainage network they mostly have straight to gently sinuous edges they were interpreted to have formed from fluvial entrenchment rather than knickpoint migration valleys also exhibit large variations in depth of the thalweg over short distances this is interpreted to result from local processes based on the application of an engineering model that predicts scour depth of modern channels

middle eocene lower miocene calcareous nannofossil magnetobiochronology of odp holes 699a and 703a in the subantarctic south atlantic abstract the distribution of calcareous nannofossils is documented for the middle eocene through lowermost miocene cores from ocean drilling program holes 699a and 703a in the subantarctic south atlantic the detailed nannofossil biostratigraphies established in combination with published magnetostratigraphic data have provided a fairly detailed age model for each hole this study suggests that the middle eocene through lowermost miocene section from hole 699a is virtually complete a major hiatus has been identified in hole 703a in the earliest oligocene coincident with an abrupt cooling in the southern ocean comparison of the nannofossil datum ages calibrated with magnetostratigraphy in the two holes with those from mid and southern high latitudes demonstrates synchroneity or diachroneity for the following nannofossil datums 1 the last occurrence lo of reticulofenestra bisecta is a consistent and reliable biostratigraphic marker for the oligocene miocene boundary from mid to high latitudes but not in extreme high latitudes 2 similarly the lo of chiasmolithus altus has a consistent age of about 26 8 ma in the southern ocean except in the extreme high latitudes where the datum appears to be substantially younger 3 the lo of reticulofenestra umbilica is about 32 9 ma in the southern ocean 4 the lo of isthmolithus recurvus is reliable and consistent from mid through high latitudes and correlates with the lower part of subchron c12r 34 4 ma 5 the lo of reticulofenestra oamaruensis has a consistent age of 36 0 ma at all four southern ocean sites that have yielded a lower oligocene magnetostratigraphy 6 the first occurrence fo of r oamaruensis is at 38 4 ma in the southern ocean and 7 the fo of i recurvus shows some age variations from mid to high latitudes and the age range is 38 5 39 0 ma at the five southern ocean sites

shelf margin architecture variability and its role in sediment budget partitioning into deep water areas abstract a review of 127 shelf margin accretion segments from 24 margins worldwide suggests that sediment flux can be low or high that shelf accommodation can be low medium or high and that climatic conditions can be icehouse or greenhouse the interplay of these three variables yields four main greenhouse margins and six main icehouse margins and thus has a fundamental control on shelf margin architectural styles providing new tools for predicting internal architecture of deep water systems in greenhouse settings there is commonly a strong supply drive because of higher temperatures more variable precipitation and higher sediment discharge but only modest shelf accommodation because of low frequency and low amplitude eustatic sea level changes low shelf accommodation is able to deliver significant volumes of sand sourced from either low or high sediment supply areas to deep water environments and residence time for deltas at greenhouse margins is likely to be relatively long because of the low amplitude of greenhouse sea level changes medium accommodation in contrast may overwhelm any low sediment supply but could be partly overwhelmed by high sediment supply which in turn can inhibit fans or encourage highstand fans in icehouse settings there is a strong cross shelf accommodation drive created by high frequency and high amplitude eustatic sea level changes thus causing significant and frequently repeated transits of river mouths and deltas across the shelf sandy basin floor fans created by low accommodation are predicted with either high or low sediment flux both medium and high accommodation can be volumetrically overwhelmed by high sediment supply which in turn cause greater volumes of sediment storage on the shelf resulting in volumetrically less significant highstand or transgressive submarine fans however a low supply may barely allow deltas to reach the shelf edge causing the deep water areas to be dominantly muddy

evidence for glacial control of rapid sea level changes in the early cretaceous lower cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves strontium data from an interval spanning 7 million years in the berriasian valanginian imply that global sea level fluctuated about 50 meters over time scales of 200 000 to 500 000 years which is in agreement with the exxon sea level curve oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes if glaciation caused all the rapid sea level changes in the cretaceous that are indicated by the exxon curve then an antarctic ice sheet may have existed despite overall climatic warmth

towards a sequence stratigraphic solution set for autogenic processes and allogenic controls upper cretaceous strata book cliffs utah usa upper cretaceous strata exposed in the book cliffs of east central utah are widely used as an archetype for the sequence stratigraphy of marginal marine and shallow marine deposits their stratal architectures are classically interpreted in terms of accommodation controls that were external to the sediment routing system allogenic and that forced the formation of flooding surfaces sequence boundaries and parasequence and parasequence set stacking patterns processes internal to the sediment routing system autogenic and allogenic sediment supply controls provide alternatives that can plausibly explain aspects of the stratal architecture including the following 1 switching of wave dominated delta lobes expressed by the internal architecture of parasequences 2 river avulsion expressed by the internal architecture of multistorey fluvial sandbodies and related deposits 3 avulsion generated clustering of fluvial sandbodies in delta plain strata 4 autoretreat owing to increasing sediment storage on the delta plain as it lengthened during progradation expressed by progradational to aggradational stacking of parasequences 5 sediment supply control on the stacking of and sediment grain size fractionation within parasequence sets the various potential allogenic controls and autogenic processes are combined to form a sequence stratigraphic solution set this approach avoids anchoring of sequence stratigraphic interpretations on a specific control and acknowledges the non unique origin of stratal architectures

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

late cretaceous chronology of large rapid sea level changes glacioeustasy during the greenhouse world we provide a record of global sea level eustatic variations of the late cretaceous 99 65 ma greenhouse world ocean drilling program leg 174ax provided a record of 11 14 upper cretaceous sequences in the new jersey coastal plain that were dated by in tegrating sr isotopic stratigraphy and biostratigraphy backstripping yielded a late cre taceous eustatic estimate for these sequences taking into account sediment loading com paction paleowater depth and basin subsidence we show that late cretaceous sea level changes were large 25 m and rapid k1 m y suggesting a glacioeustatic control three large d 18 o increases are linked to sequence boundaries others lack sufficient d 18 o data consistent with a glacioeustatic cause and with the development of small 10 6 km 3 ephemeral ice sheets in antarctica our sequence boundaries correlate with sea level falls recorded by exxon production research and sections from northwest europe and russia indicating a global cause although the exxon record differs from backstripped estimates in amplitude and shape

global correlation of cenomanian upper cretaceous sequences evidence for milankovitch control on sea level we have investigated the sequence stratigraphy of two widely separated marine cenomanian successions in southeast india and northwest europe and used high resolution ammonite biostratigraphy to demonstrate that sea level changes are globally synchronous and therefore must be eustatically controlled sequence scale sea level changes in the cenomanian were driven by the long eccentricity cycle 400 k y in the milankovitch band we hypothesize that during pre quaternary time the third order sequences of vail and haq are essentially a sediment response to sea level changes driven by the 400 k y cycle construction of a relative sea level curve for the marginal marine succession in india demonstrates that the short term sea level changes are rapid 10 100 m m y and have a magnitude of 2 20 m glacioeustasy is a possible but unproven driving mechanism

secular variation in late cretaceous carbon isotopes a new δ13c carbonate reference curve for the cenomanian campanian 99 6 70 6 ma carbon stable isotope variation through the cenomanian santonian stages is characterized using data for 1769 bulk pelagic carbonate samples collected from seven chalk successions in england the sections show consistent stratigraphic trends and 13c values that provide a basis for highresolution correlation positive and negative 13cexcursions and inflection points on the isotope profiles are used to define 72 isotope events key markers are provided by positive 13c excursions of up to 2 the albian cenomanianboundary event mid cenomanian event i thecenomanian turonian boundary event the bridgewick hitch wood and navigation events of late turonian age and the santonian campanian boundary event isotope events are isochronous within a framework provided by macrofossil datum levels and bentonite horizons an age calibrated composite 13c reference curve and an isotope event stratigraphy are constructed using data from the english chalk the isotope stratigraphy is applied to successions in germany france spain and italy correlation with pelagic sections at gubbio central italy demonstrates general agreement between biostratigraphic and chemostratigraphic criteria in the cenomanian turonian stages confirming established relationships between tethyan planktonic foraminiferal and boreal macrofossil biozonations correlation of the coniacian santonian stages is less clear cut magnetostratigraphic evidence for placing the base of chron 33r near the base of the upper santonian is in good agreement with the carbon isotope correlation but generates significant anomalies regarding the placement of the santonian and campanian stage boundaries with respect to tethyan planktonic foraminiferal and nannofossil zones isotope stratigraphy offers a more reliable criterion for detailed correlation of cenomanian santonian strata than biostratigraphy with the addition of campanian 13c data from one of the english sections a composite cenomanian campanian age calibrated reference curve is presented that can be utilized in future chemostratigraphic studies the cenomanian campanian carbon isotope curve is remarkably similar in shape to supposedly eustatic sea level curves increasing 13c values accompanying sea level rise associated with transgression and falling 13c values characterizing sea level fall and regression the correlation between carbon isotopes and sea level is explained by variations in epicontinental sea area affecting organic matter burial fluxes increasing shallow sea floor area and increased accommodation space accompanying sea level rise allowedmore efficient burial ofmarine organic matter with the preferential removal of 12c from the marine carbon reservoir during sea level fall reduced seafloor area marine erosion of previously deposited sediments and exposure of basin margins led to reduced organiccarbon burial fluxes and oxidation of previously deposited organic matter causing falling 13c values additionally drowning of carbonate platforms during periods of rapid sea level rise may have reduced the global inorganic relative to the organic carbon flux further enhancing 13c values while renewed platform growth during late transgressions and highstands prompted increased carbonate deposition variations in nutrient supply changing rates of oceanic turnover and the sequestration or liberation of methane from gas hydrates may also have played a role in controlling carbon isotope ratios

detection of late cretaceous eustatic signatures using quantitative biostratigraphy this study tested the potential for high resolution quantitative biostratigraphic methods to distinguish tectonic from supposedly eustatic sequences the study employed automated multidimensional graphic correlation using constrained optimization program conop our analysis was based on 15 onshore sections in eastern new zealand spanning the coniacian to maastrichtian stages upper cretaceous and 398 well constrained lowest or highest occurrence records derived from 245 dinoflagellate species the age of the resulting composite section was calibrated using six dated bioevents two of these events were tied to geochemical or paleomagnetic datums following calibration the composite section had an average relative temporal resolution of less than 130 k y through the study interval although the succession of events was not dated to this level of precision in an absolute sense although the conop composite will not resolve unconformities or condensed intervals that occur across all studied sections such global unconformities can be identified using clusters of events that are placed at a single composite level fifteen major event clusters were identified 10 of which coincided closely with sequence boundaries identified in the northern hemisphere the probability of this coincidence arising by chance alone is 8 although these results must be regarded as provisional they suggest that high resolution quantitative stratigraphy can provide a potent tool for the identification and correlation of stratigraphic sequences furthermore our findings add significant support for recent studies that have argued for the presence of late cretaceous eustasy

the maastrichtian record from shatsky rise northwest pacific a tropical perspective on global ecological and oceanographic changes we present new isotopic and micropaleontological data from a depth transect on shatsky rise that record the response of the tropical pacific to global biotic and oceanographic shifts during the mid maastrichtian results reveal a coupling between the upper ocean characterized by a weak thermocline and low to intermediate productivity and intermediate waters during the earliest maastrichtian oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the north pacific isotopic shifts through the early maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the southern ocean although the cooler water mass remained dominant through the remainder of the maastrichtian it was displaced intermittently at shallow intermediate depths by north pacific intermediate water the globally recognized mid maastrichtian event similar to 69 ma manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of shatsky rise is characterized by an abrupt increase similar to 2degrees 3degrees c in sea surface temperatures a greater flux of organic matter out of the surface ocean and warmer similar to 4degrees c intermediate waters results implicate simultaneous changes in surface waters and the sources distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid maastrichtian time