cyclostratigraphic and δ13c record of the lower cretaceous adriatic platform croatia assessment of milankovitch forcing abstract the 700 m thick hauterivian to albian section from the interior of the large adriatic platform is exposed on mljet and korcula islands croatia the cyclic platform consists of meter scale parasequences bundled into parasequence sets superbundles and then into breccia bounded depositional sequences spectral analysis of time series cycle number vs cycle thickness shows peaks in the short term eccentricity 95 to 130 kyr bands and 160 to 200 kyr bands isotope samples from micrite matrix of mudstone and wackestone have 13c values generally from 1 5 to 2 vpdb and 18o from 1 to 3 5 vpdb adriatic platform 13c values are shifted 2 vpdb more negative than marine pelagic values a 13c and 18o meteoric signal is limited to just beneath sequence boundaries suggesting that the isotopic shift is due mainly to marine phreatic and synorogenic burial diagenesis major excursions on the 5 point smoothed 13c profile of the adriatic platform tied biostratigraphically to 13c curves from pelagic sections include the oceanic anoxic events oae1a 1b and 1c time series constructed from 13c values unsmoothed data vs stratigraphic position show peaks in the milankovitch band especially short term eccentricity most positive peaks are near parasequence set boundaries 50 to 60 and regressive parts of parasequences 20 although diagenetically shifted the 13c record retains a highly clipped memory of astronomically driven global 13c fluctuations albeit modified by platform water restriction during cyclic deposition

oceanographic and eustatic control of carbonate platform evolution and sequence stratigraphy on the cretaceous valanginian campanian passive margin northern gulf of mexico an integrated sequence stratigraphic study based on outcrop core and wireline log data documents the combined impact of cretaceous eustacy and oceanic anoxic events on carbonate shelf morphology and facies distributions in the northern gulf of mexico the diverse facies and abundant data of the comanche platform serve as a nearly complete global reference section and provide a sensitive record of external processes affecting cretaceous platform development regional cross sections across the shoreline to shelf margin profile provide a detailed record of mixed carbonate siliciclastic strata for the hauterivian to lower campanian stages ca 136 to 80 ma the study window on the slowly subsiding passive margin allows the stratigraphic response to external forcing mechanisms to be isolated from regional structural processes three second order supersequences comprised of eight composite sequences are recognized in the valanginian barremian the aptian albian and the cenomanian campanian the valanginian barremian supersequence transitioned from a siliciclastic ramp to carbonate rimmed shelf and is a product of glacial ice accumulation and melting as well as variable rates of mid ocean ridge volcanism the aptian albian supersequence chronicles the drowning and recovery of the platform surrounding oceanic anoxic events 1a and 1b the cenomanian campanian supersequence similarly documents shelf drowning following oceanic anoxic event 1d after which the platform evolved to a deep subtidal system consisting of anoxic dysoxic shale and chalk in the time surrounding oceanic anoxic event 2 each period of oceanic anoxia is associated with composite sequence maximum flooding termination of carbonate shelf sedimentation and deposition of condensed shale units in distally steepened ramp profiles composite sequences unaffected by oceanic anoxic events consist of aggradational to progradational shelves with an abundance of grain dominated facies and shallow subtidal to intertidal environments because they are products of eustacy and global oceanographic processes the three supersequences and most composite sequences defined in the south texas passive margin are recognizable in other carbonate platforms and published eustatic sea level curves

orbital control on carbon cycle and oceanography in the mid cretaceous greenhouse we established a new high resolution carbonate carbon isotope record of the albian interval of the marne a fucoidi formation central apennines italy which was deposited on the southern margin of the western tethys ocean bulk carbonate sampled with 10 15 cm spacing was used for the construction of a continuous carbon isotope curve through the albian stage spectral analyses reveal prominent 400 kyr cyclicity in the 13c curve which correlates with milankovitch long eccentricity changes cycles occurring in our record resemble those observed in several cenozoic 13c records suggesting that a link between orbital forcing and carbon cycling existed also under mid cretaceous greenhouse conditions based on comparisons with cenozoic eccentricity carbon cycle links we hypothesize that 400 kyr cycles in the mid cretaceous were related to a fluctuating monsoonal regime coupled with an unstable oceanic structure which made the oceanic carbon reservoir sensitive to orbital variations in the tethys these oceanographic conditions lasted until the late albian and then were replaced by a more stable circulation mode less sensitive to orbital forcing

carbon and oxygen isotope stratigraphy of the lower mississippian kinderhookian lower osagean western united states implications for seawater chemistry and glaciation a positive carbon isotope 1 3 c excursion has been recognized in upper kinderhookian and early osagean carbonates in three sections in southeast idaho and nevada the oldest 1 3 c peak 7 is dated to the isostichaconodont zone and a younger peak occurs in the typicus zone the shifts are recorded in a range of carbonate lithofacies representing various water depths along the shelf lithofacies sampled for 1 3 c and 1 8 o at the samaria mountain section in southeast idaho record the shallowest water conditions indicated by cross bedded skeletal and peloidal grainstones the deepest water conditions are present in the pahranagat range section in eastern nevada which consists mainly of bioturbated lime mudstone and skeletal wackestone the 1 3 c values from these widely separated sedimentary basins show a consistent trend that correlates with early mississippian curves generated from brachiopod calcite in western europe and the midcontinent of north america as well as dolomites in utah and wyoming 1 8 o values become more positive up section generally paralleling the positive trend in 1 3 c during the late kinderhookian no subaerial exposure surfaces are recognized in the sections examined in southeast idaho and nevada and at least the 1 3 c trends are interpreted as primary seawater fluctuations sea level changes occurred near the beginning of the late kinderhookian 1 3 c shift early to middle parts of the isosticha zone and within the peak of the 1 3 c excursion kinderhookian osagean boundary although tectonic changes associated with the antler orogeny have likely modified the eustatic signature

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

orbital forcing in a boreal cretaceous epeiric sea high resolution analysis of core and logging data upper albian of the kirchrode i drill core lower saxony basin nw germany abstract a 245 m 0 245 m subsurface core of upper albian marine sediments from north germany research well kirchrode i was studied to identify sequences and cycles of sedimentation and related forcing mechanisms on sedimentation in an epeiric sea of the sub boreal realm the core consists of monotonous gray marls with an exceptionally high sedimentation rate of 8 12 cm ka 1 in total it represents a period of approximately 2 5 4 ma a silty glauconite rich condensed layer marks a change in the succession at 132 m and is paralleled by the first occurrence of e turriseiffelii and g bentonensis the lower part of the core shows lenticular bedding siderite nodules average caco 3 content of ca 40 and an abundance of inoceramids inoceramus anglicus birostrina lissa actinoceramus sulcatus the upper part is characterised by plane bedding common siderite layers an average caco 3 content of ca 35 and an abundance of aucellinas aucellina gryphaeoides according to lithology and ichnofacies the succession represents a transgressive regressive cycle with distinct bimodality of lithology fossil and trace fossil content together with reworking and redeposition at the base and top we studied well log data sediment composition sediment color and carbonate content and applied various mathematical analysis techniques to these data principal component analysis spectral analysis fourier transform autocorrelation spectral analysis revealed well pronounced periodic cyclicity in the upper part of the upper albian 12 8 4 5 3 4 1 7 m the 12 m eccentricity cycles are the most intense cycles reflecting periodic changes in the terrigenous clastic supply chaotic transitional intervals occur around the middle upper albian upper albian and topmost albian parts of the core they are characterised by non cyclic changes in litho and biofacies mathematically these changes correspond to singularity points they are preceded by non orbital high frequency variations in carbonate content and in ray

carbon isotope stratigraphy in shallow water carbonates implications for cretaceous black shale deposition a barremian to albian succession on mount kanala part of a tethyan isolated carbonate platform was investigated for its 13c variations the limestone sequence is composed of a series of peritidal shallowing upward cycles with clear petrographic evidence for strong early diagenetic overprinting related to repeated subaerial exposure despite significant impact of diagenesis the observed changes in 13c can be very well correlated with deep water sections from different ocean basins and shallow water carbonate platforms in the middle east this lends further support to the applicability of 13c variations for stratigraphic purposes in shallow water limestones using the 13c signal time resolution in lower cretaceous platform carbonates can be significantly increased independent of bio zonations often hampered by ecological variability cyclostratigraphic analysis of the aptian part of the section shows that strong positive excursions of the cumulative departure from mean cycle thickness of the peritidal shallowing upward cycles coincide with global positive 13c excursions this and the fact that positive shifts in the 13c record are preserved within shallow water limestones provide evidence that black shale accumulation in the ocean basins occurred during sea level rise and flooding of platform tops integration of carbon isotope cyclo and sequence stratigraphic results from different carbonate platforms indicate that strong positive global 13c shifts and concurrent organic carbon burial during black shale deposition are ultimately caused by rapid rises of eustatic sea level hence the rate of change of eustatic sea level is considered to play a crucial role in black shale accumulation in the global ocean basins during the cretaceous

the uncertainties involved in extracting amplitude and frequency of orbitally driven sea level fluctuations from shallow water carbonate cycles in outcrops shallow water carbonates often form thick vertically stacked metre scale exposure bounded depositional packages here called carbonate cycles because the facies within carbonate cycles can be tied precisely to water depths they are considered ideal for reconstructing past sea level changes there is however increasing evidence that these depositional cycles are unreliable recorders of both the frequency and the amplitude of orbitally driven sea level fluctuations carbonate cycles record only a fraction of the amplitude of a sea level cycle a portion of the rise and nothing of the fall cores through the pleistocene cycles on great bahama bank illustrate this shortcoming although the amplitudes of the last nine sea level changes are each a hundred metres or more the thickness of the cycles varies from a few metres to ca 15 m the lack of correlation between sea level amplitude and cycle thickness is not eliminated for cycles deposited during times of lower sea level amplitudes for example the cretaceous upper cretaceous cycles on the maiella platform margin document the irregularly filled accommodation space and the resultant variability in cycle thickness and frequency uncertainties in assessing the frequencies of sea level changes from shallow water carbonate cycles are caused by missed beats and metre scale oscillations of sea level within highstands that potentially produce cycles of very short duration the random amplitude variability during the last 57 glacio eustatic sea level changes illustrates the difficulty of assessing missed beats where a sea level fluctuation is not recorded because the sea level rise does not reach the platform top missed beats are also produced by the depositional topography that is created by irregularly filled accommodation space as a result variable numbers of cycles are deposited across the platform further complicating orbital frequency analyses are decametre scale oscillations of the sea level during highstands the amplitude of these sub orbital sea level oscillations up to 17 m within the last interglacial marine isotope stage 5e are sufficient to expose shallow platforms like great bahama bank and subsequently produce an additional depositional cycle with similar facies successions the combined effects of missed beats and oscillations within highstands are likely to produce cycles and hiatuses of variable duration that are difficult to extract from the rock record consequently estimates of the orbital forcing mechanisms and frequencies from ancient shallow water carbonate cycles carry large uncertainties

the ombrina rospo plateau apulian platform evolution of a carbonate platform and its margins during the jurassic and cretaceous abstract in this paper we analyze the jurassic and cretaceous evolution of the buried northwards stretch of the apulia platform southern italy ombrina rospo plateau orp and adjacent adriatic basin exploration wells indicate that inner platform carbonate facies across the orp in the jurassic and lower cretaceous are capped along a subaerial exposure surface by oligocene miocene carbonates a nw trending intra platform basin casalbordino corridor was infilled with shallow to deeper water sediments in the late early to late cretaceous interval while platform margins were experiencing tectonic reactivation the orp to basin transitional belt formed a corner defining a nw and a ne margin the nw margin was essentially stationary a syn and early post rift platform toe bypass wedge formed when late hettangian sinemurian extension produced the platform basin relief export of platform material coupled with a halt of faulting made the platform slope profile continuous in the late early or early middle jurassic possibly across an ooidal rim late jurassic ellipsactinia coral reefs passed downdip into bioclastics the maiolica fm displays two cycles m1 m2 where m2 onlaps the slope built by m1 in the aptian with lithospheric arching a high angle fault rejuvenated the margin off this margin a narrow basin locked between the orp and a pelagic carbonate platform was largely infilled with turbidites sourced by the orp but the high hampered the dispersal of the sand fraction the ne margin displays prograding ooidal to bioclastic clinoforms middle and upper jurassic downlapping onto the rift basin in the lower cretaceous the platform recovered after a slow down of carbonate productivity m1 2 boundary the marne a fucoidi fm thickens at the toe of and seals a fault backstepping the margin further backstepping occurred 5 km platformwards along a cenomanian normal fault producing room for a rudist factory a retreating rocky shoreline sourced breccias while downdip the shallow water facies graded into the scaglia fm basin along a ramp like profile with low angle clinoforms merging with turbidites

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

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

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

shallow water records of astronomical forcing and the eccentricity paradox the translation of climate signals into sediments is a complex and poorly understood process and one that is likely to be inherently nonlinear a great deal of debate concerns the mismatch between the amplitude spectrum of astronomical insolation forcing and the amplitude spectrum of climatic signals derived from geological archives many ancient shallow water successions such as peritidal carbonates are widely suggested to show evidence for eccentricity band forcing despite eccentricity having a negligible affect on insolation instead eccentricity manifests itself primarily as the amplitude modulator of precession which dominates the insolation signal at low to mid latitudes the appearance and dominance of eccentricity band frequencies in stratigraphic data can arise however without the need to appeal to complex nonlinearities in the climate system or depositional environment instead eccentricity frequencies will appear as a consequence of signal driven nondeposition that results in a rectification of the precession dominated insolation signal furthermore it can be shown that this rectification effect is capable of inducing a signal driven modulation of cycle thickness i e a frequency modulation that can lead to a similar range of cycle bundling patterns documented from ancient shallow water successions numerical experiments using an astronomical insolation solution as an input signal emphasize how eccentricity can dominate climate records that have undergone only partial rectification and that are stratigraphically complete at astronomical time scales of resolution these experiments supported by geological observations thus describe a viable mechanism capable of explaining the eccentricity paradox in ancient shallow water successions and also emphasize how measures of stratigraphic completeness at astronomical time scales furnish no clue as to the likely fidelity of the actual climate forcing records or their spectra

the stable carbon isotopic composition of organic material in platform derived sediments implications for reconstructing the global carbon cycle in pelagic carbonate sediments the degree to which the 13c values of inorganic and organic fractions co vary has been used to interpret rates of production burial and decomposition of organic carbon this relationship is relatively consistent through time permitting estimates of organic carbon production and preservation however as the majority of pelagic sediments older than 200 myr have been subducted carbonate sediments deposited in epeiric seas and platforms are often substituted for pelagic carbonates in analyses of ancient global carbon cycling there are well known pitfalls to using shallow marine carbonate materials including diagenesis semi isolation of depositional environments and input of different types of sediments with varying inorganic 13c 13cinorganic values which can obscure any global signatures one method used to assess whether global changes in 13c are accurately represented by 13cinorganic records is to examine variations in the 13c of co occurring organic material 13corganic if a 13corganic record co varies with a co occurring 13cinorganic record it is argued that the signals must be related to variations in the global carbon cycle this assumption has been investigated by analysing the isotopic composition of the organic carbon preserved in the uppermost 150 m of periplatform sediments recovered during odp leg 166 from the western margin of great bahama bank the 13corganic values measured in this study were compared to previously published 13cinorganic records measured on identical samples thus allowing a study of the correlation between the two records through time these analyses showed that the correlation coefficient between 13cinorganic and 13corganic increased from the proximal location site 1005 r2 0 1 to the distal site site 1006 r2 0 63 the importance of platform derived carbonate and organic material at the proximal location site 1005 is reflected in the absence of a co variation between inorganic and organic 13c records which exhibit no correlation on the platform itself in contrast the co variance in 13c values at the basinal location site 1006 is explained by a two point mixing model which demonstrates the importance of both pelagic and platform derived carbonate and organic carbon in generating the positive correlation between the organic and inorganic 13c values this results in a correlation between 13cinorganic and 13corganic records at site 1006 that is unrelated to global carbon cycling such data question the applicability of using 13corganic values to support the ability of 13cinorganic values to record global carbon cycling in carbonates recovered from environments where multiple sources of carbonate and organic carbon contribute to the bulk 13c signal

cyclostratigraphy and high frequency carbon isotope fluctuations in upper cretaceous shallow water carbonates southern italy a detailed carbon isotope study has been carried out on a santonian upper cretaceous carbonate platform succession that crops out at monte sant erasmo southern italy previous centimetre scale studies on this succession have shown that high frequency eustatic changes resulting from the earth s orbital fluctuations controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles bundles groups of three to five elementary cycles and superbundles groups of three or four bundles the elementary cycles which correspond to single beds suggest a control caused by earth s precession the bundles and superbundles record the short 100 kyr and long 400 kyr eccentricity periodicity respectively the 1 3 c signal of the monte sant erasmo succession is cyclic in nature and may be considered to be a reliable proxy for the sedimentary evolution and related sea level history of the analysed sequence the carbon isotope cyclicity is recorded at bundle and superbundle level but it is not evident at the scale of the elementary cycles at least with the sampling interval used in this study spectral analysis of the 1 3 c record shows two main peaks corresponding to the short and long eccentricity periodicity whereas the precession signal is not evident in the power spectrum in addition lithofacies analysis shows that in each bundle and superbundle higher c isotope values occur in sediments characterized by marine cements whereas lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis early diagenesis driven by periodic sea level fluctuations developed in either shallow subtidal marine diagenesis or subaerial exposed meteoric overprint sedimentary environments and directly influenced the carbon isotope signature as a consequence the 1 3 c record at monte sant erasmo reflects high frequency climatic oscillations controlling both environmental and early diagenetic changes the long term isotopic record is similar to that of contemporaneous pelagic sections in england and elsewhere in italy it is concluded that the 1 3 c signature of shallow water carbonates such as those of monte sant erasmo offers great potential for correlation with coeval sections including those of the pelagic realm

orogenic evolution of the external dinarides in the ne adriatic region a model constrained by tectonostratigraphy of upper cretaceous to paleogene carbonates abstract mesozoic to cenozoic evolution of the central part of the adriatic plate external dinarides and adriatic foreland is still a matter of debate this is expressed by opposing paleogeographic models single carbonate platform adriatic or adriatic dinaridic versus two carbonate platforms adriatic and dinaridic separated by the inter platform budva cukali basin estimates of shortening during adria ne subduction that resulted in the development of the dinaric alps differ substantially the single platform model involves minor shortening achieved by folding and faulting along steep reverse faults the two platform model involves significant shortening achieved mainly by thrust stacking which resulted in almost complete underthrusting of the intervening basinal deposits analysis of upper cretaceous to paleogene stratigraphical data from both outcrops and boreholes allows regional correlation and the interpretation of major lithostratigraphic units as a result a few tectonostratigraphic units are recognized the tectonostratigraphy is used as a basis for a new model on the late mesozoic to cenozoic evolution of the region generally adriatic and dinaridic segments acted as major regional crustal entities of adria the upper portions of the sedimentary cover were differentially affected by progressive southwestward verging thin skinned deformations during the paleocene to eocene miocene the adriatic foreland stayed out of the deformations and is characterized predominantly by wrench and salt tectonics the regional tectonic map shows arcuate thrust fronts of the external dinarides they could be a consequence of both differential propagation of early orogenic thin skinned deformations over crustal fragments separated by transversal faults and or differential isostatic movements of the fragments the collision zone of the adriatic and dinaridic segments is characterized by late orogenic oligocene to miocene thick skinned compressional uplift exhumation related gravity gliding and still active escape tectonics wrenching these processes masked primary thin skinned deformations a significant amount of shortening within and between the thin skinned sedimentary covers is proposed therefore the question of the general paleogeography of the region and the original nw extent of the budva cukali basin ne adriatic trough remains open

the response of the north pacific ocean to decadal variability in atmospheric forcing wind versus buoyancy forcing abstract both wind and buoyancy forcing result in variability in the north pacific ocean thermocline a vertical modal analysis of the density deviations in a 30 yr run of an ocean general circulation model of the north pacific forced by atmospheric variability is used to identify the spatial and temporal patterns of the different baroclinic modes the different dynamic vertical modes show distinct propagation characteristics with the first baroclinic mode exhibiting consistent westward propagation at all latitudes the higher baroclinic modes show westward phase propagation at low latitudes but propagate eastward at higher latitudes the propagation characteristics of each mode can be understood by the inclusion of the zonal mean flow in the vertical structure equation evaluation of the ekman pumping and diapycnal fluxes in the quasigeostrophic potential vorticity equation for each dynamic vertical mode distinguishes their effects on the thermocline variability wind variability dominantly forces the f

climate response to orbital forcing across the oligocene miocene boundary spectral analyses of an uninterrupted 5 5 million year my long chronology of late oligocene early miocene climate and ocean carbon chemistry from two deep sea cores recovered in the western equatorial atlantic reveal variance concentrated at all milankovitch frequencies exceptional spectral power in climate is recorded at the 406 thousand year ky period eccentricity band over a 3 4 million year period 20 to 23 4 my ago ma as well as in the 125 and 95 ky bands over a 1 3 million year period 21 7 to 23 0 ma of suspected low greenhouse gas levels moreover a major transient glaciation at the epoch boundary approximately 23 ma mi 1 corresponds with a rare orbital congruence involving obliquity and eccentricity the anomaly which consists of low amplitude variance in obliquity a node and a minimum in eccentricity results in an extended period approximately 200 ky of low seasonality orbits favorable to ice sheet expansion on antarctica

the geochemistry of carbonate diagenesis the past present and future stable carbon and oxygen isotopes 18o and 13c values and trace elements have been applied to the study of diagenesis of carbonate rocks for over 50 years as valuable as these insights have been many problems regarding the interpretation of geochemical signals within mature rocks remain for example while the 18o values of carbonate rocks are dependent both upon the temperature and the 18o value of the fluid and additional information including trace element composition aids in interpreting such signals direct evidence of either the temperature or the composition of the fluids is required such information can be obtained by analysing the 18o value of any fluid inclusions or by measuring the temperature using a method such as the clumped isotope technique such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well known tendency for 18o values of carbonate rocks to decrease with increasing age unlike the 18o 13c values of carbonates are considered to be less influenced by diagenesis and more a reflection of primary changes in the global carbon cycle through time however many studies have not sufficiently emphasized the effects of diagenesis and other post depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored finally many additional proxies are poised to contribute to the interpretation of carbonate diagenesis although the study of carbonate diagenesis is at an exciting point with an explosion of new proxies and methods care should be taken to understand both old and new proxies before applying them to the ancient record

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

transgressive oversized radial ooid facies in the late jurassic adriatic platform interior low energy precipitates from highly supersaturated hypersaline waters dark gray oolitic units characterized by oversized ooids with primary radial calcite fabrics occur in the interior of the late jurassic late tithonian adriatic platform a large mesozoic tethyan isolated platform in croatia they differ from open marine platform margin ooid grainstones in their dark color cerebroid outlines broken and recoated grains abundant inclusions highly restricted biota and lack of cross stratifithey have been interpreted as being of vadose origin vadoids at tops of upward shallowing parasequences however detailed sections show that most oolitic units occur at bases of precessional parasequences overlying erosional surfaces on fenestral carbonates the oolitic units are similar to quiet water ooids that form today in low energy settings they developed in an arid climate during initial transgression of supratidal fl ats along lowenergy shores seaward of tidal fl ats and along the margins of restricted lagoons and intertidal ponds superimposed fenestral fabrics meniscus micrite cements and grain breakage occurred as they aggraded to high tide level and were subjected to wetting and drying thermal expansion and contraction and wind transport they migrated landward with transgression forming extensive sheets and were overlain by subtidal lagoonal facies that shallow up into fenestral carbonates these distinctive facies may have been overlooked in the geological record or their geological distribution requires juxtaposition of calcite seas high calcite supersaturation states arid climate and presence of fl at topped carbonate platforms in a greenhouse world

microbial laminite versus rooted and burrowed caps on peritidal cycles salinity control on parasequence development early cretaceous isolated carbonate platform croatia some parasequences in the interior of the early cretaceous isolated carbonate platform croatia which formed under a greenhouse climate lack the typical regressive tidal flat laminites instead these bioturbated emergent parasequences have burrowed and rooted upper parts capped with thin greenish paleo sols and are reminiscent of triassic lofer cycles we propose that the bioturbated cycle tops reflect coastal salinities that are normal marine brackish or metahaline whereas the transgressive rare and abundant regressive tidal flat laminites formed under hypersaline coastal waters thus these features may be used to track gross salinity changes of coastal waters on the platform through time in addi tion we suggest ways to evaluate whether the salinity changes relate to hypersaline embay ments on the platform or changes in the cli mate at the parasequence scale we propose that the bioturbated emer gent parasequences could have formed under semiarid conditions seaward of subtle shallow embayments on the platform con temporaneously in the bayheads micro bial laminites developed these would require time equivalent updip and downdip laminate capped and bioturbated emer gence capped parasequences however the para sequences could also have been con trolled by climate changes the laminite capped parasequences could have resulted from salinity increase with shallowing of the platform interior under semiarid condi tions stable climate in contrast the bio turbated emergence capped parasequences could have formed during times of more humid climate punctuating the overall semi arid climate the humid phase would have favored brackish to normal marine salinities in the coastal zone along with macrophytes and intense animal and plant bioturbation which would suppress development of lami nite caps thus these parasequences provide a means of tracking gross salinity of coastal waters and if climate induced then they have implications for fluctuating climates in greenhouse worlds

evolution of the adriatic carbonate platform palaeogeography main events and depositional dynamics abstract the adriatic carbonate platform adcp is one of the largest mesozoic carbonate platforms of the perimediterranean region its deposits comprise a major part of the entire carbonate succession of the croatian karst external or outer dinarides which is very thick in places more than 8000 m and ranges in age from the middle permian or even upper carboniferous to the eocene however only deposits ranging from the top of the lower jurassic toarcian to the top of the cretaceous can be attributed to the adcp defined as an isolated palaeogeographical entity although the entire carbonate succession of the karst dinarides was deposited within carbonate platform environments there were different types of carbonate platforms located in different palaeogeographical settings carboniferous to middle triassic mixed siliciclastic carbonate deposits were accumulated along the gondwanian margin on a spacious epeiric carbonate platform after tectonic activity culminating by regional middle triassic volcanism recorded throughout adria the african promontory a huge isolated carbonate southern tethyan megaplatform abbreviated as stm was formed with the area of the future adcp located in its inner part tectonic disintegration of the megaplatform during the middle to late early jurassic resulted in the establishment of several carbonate platforms including the adriatic apenninic and apulian separated by newly drowned deeper marine areas including the adriatic basin as a connection between the ionian and belluno basins lagonero basin and the area of the slovenian and bosnian troughs the adcp was characterised by predominantly shallow marine deposition although short or long periods of emergence were numerous as a consequence of the interaction of synsedimentary tectonics and eustatic changes also several events of temporary platform drowning were recorded especially in the late cretaceous when synsedimentary tectonics became stronger leading up to the final disintegration of the adcp the thickness of deposits formed during the 125 my of the adcp s existence is variable between 3500 and 5000 m the end of adcp deposition was marked by regional emergence between the cretaceous and the palaeogene deposition during the palaeogene was mainly controlled by intense synsedimentary tectonic deformation of the former platform area some carbonates mostly eocene in age were deposited on irregular ramp type carbonate platforms surrounding newly formed flysch basins and the final uplift of the dinarides reached its maximum in the oligocene miocene the adriatic carbonate platform represents a part although a relatively large and well preserved one of the broader shallow water carbonate platform that extended from ne italy to turkey although its continuity is somewhat debatable in the area near albanian greece boundary this large carbonate body which was deformed mostly in the cenozoic including a significant reduction of its width needs a specific name and the central mediterranean carbonate platform is proposed abbreviated to cmcp although the local names such as adcp for its nw part should be kept to enable easier communication and to facilitate description of local differences in platform evolution

orbitally modulated black shale deposition in the upper albian amadeus segment central italy a multi proxy reconstruction abstract the upper albian amadeus segment which falls within oceanic anoxic event 1c exhibits cyclical alternations of marls black shales and carbonate rich beds that record evidence of orbital climate and sedimentary dynamics a combined micropalaeontological planktic and benthic foraminifera and palynomorphs and geochemical stable isotopes clay mineralogy and major element distribution investigation allowed recognition of a remarkable influence of continental material within the black shales moreover the palaeoproductivity record is characterised by a non linear response to the orbital forcing the micropalaeontological and geochemical record suggests that upper albian bedded cycles in the marne a fucoidi formation resulted from interplay of changes in atmospheric and hydrological parameters of the western tethys and its drainage basin in particular deposition of the black shales occurred during precession minima in times of increased precipitation enhanced continental runoff and stratification of the upper water column in this respect the black shales of the amadeus segment share similarities with the neogene eastern mediterranean sapropels

fault slip rates for the active external dinarides thrust and fold belt 1 we present estimates of slip rates for active faults in the external dinarides this thrust and fold belt formed in the adria eurasia collision zone by the progressive formation of ne dipping thrusts in the footwalls of older structures we calculated the long term horizontal velocity field slip rates and related uncertainties for active faults using a thin shell finite element method we incorporated active faults with different effective fault frictions rheological properties appropriate geodynamic boundary conditions laterally varying heat flow and topography the results were obtained by comparing the modeled maximum compressive horizontal stress orientations with the world stress map database the calculated horizontal velocities decrease from the southeastern external dinarides to the northwestern parts of the thrust and fold belt this spatial pattern is also evident in the long term slip rates of active faults the highest slip rate was obtained for the montenegro active fault while the lowest rates were obtained for active faults in northwestern slovenia low slip rates influenced by local active diapirism are also characteristic for active faults in the offshore central external dinarides these findings are contradictory to the concept of adria as an internally rigid aseismic lithospheric block because the faults located in its interior release a part of the regional compressive stress we merged the modeling results and available slip rate estimates to obtain a composite solution for slip rates

paleoceanographic changes during the early cretaceous valanginian hauterivian evidence from oxygen and carbon stable isotopes we investigated valanginian hauterivian bulk rock and belemnite samples from vocontian basin sections in southeastern france for their stable carbon and oxygen isotope signature firstly because these sections permit calibration with high resolution biostratigraphy based on ammonites and secondly because detailed isotope studies for the hauterivian are lacking the results show that 13c values for bulk rock decrease during the late valanginian early hauterivian with 1 and increase again during the late hauterivian with 1 the 18o signal for bulk rock samples is mostly disturbed by diagenesis the belemnites show carbon and oxygen isotope values that are lower and higher than bulk rock samples respectively we explain this as the result of the belemnites recording a deeper water signal with lighter 13c values and heavier 18o values implicating colder water at greater depth the overall preservation of the belemnites is very good and permits the construction of a paleo temperature trend this trend shows warm deeper water temperatures during the late early valanginian 15 c and progressively cooler temperatures during the late valanginian and early hauterivian 11 c during the late hauterivian temperatures increase again 13 c we relate this cooling trend for deeper water to a second order sea level rise which allowed for the exchange of cold boreal and warm tethyan water masses the influx of cold nutrient rich water had a profound effect on carbonate producing biota along the northern margin of the tethys during the hauterivian leading to prolonged phases of condensation and platform destruction during the early hauterivian the carbonate system along the northern tethyan margin shifted into a green water mode of carbonate production high rates of carbonate production under mesotrophic conditions also observed in other parts of the world meant that the global carbon cycle became buffered shown by the stable trends in carbon isotopes

carbon isotope stratigraphy of early cretaceous urgonian shoal water deposits diachronous changes in carbonate platform production in the north western tethys abstract carbonate platforms are highly sensitive ecological systems that typically show rapid and characteristic response modes to environmental and climatic changes acting both on a regional scale and global scale a widely accepted hypothesis proposes that the late barremian stepwise establishment of the urgonian carbonate platform on the northern tethyan shelf was related to a gradual change from predominantly humid towards more arid greenhouse conditions this climate change resulted in the reorganisation of the carbonate platform ecosystem from heterozoan towards photozoan dominated assemblages and a decrease of organic matter burial in tethyan and boreal basins in order to decipher the palaeoenvironmental and climatic boundary conditions of these major changes in neritic and pelagic settings a precise chronostratigraphy of urgonian carbonate platform evolution is needed here we provide an integrated stratigraphic framework of lower barremian to lower aptian urgonian carbonate platform sections cluses forclaz located at the northern rim of the tethys subalpine chains ese france with special focus on sedimentological analyses and high resolution carbon isotope stratigraphy a characteristic barremian aptian carbon isotope pattern permits precise platform to basin correlation with cyclostratigraphic and ammonite dated pelagic and hemipelagic tethyan sections in the vocontian trough angles combe lambert glaise and umbria marche basin gorgo a cerbara similar to helvetic shoal water settings the carbonate platform in the subalpine chains experienced a gradual transition from heterozoan to photozoan dominated ecosystems this biogenic pattern points to a gradual change of the carbonate platform after the so called early barremian crisis towards an oligotrophic rimmed platform system urgonian limestone formation according to the chronostratigraphy of urgonian carbonate platform evolution in the subalpine chains established here the installation of a photozoan dominated rudist rich platform ecosystem referred to as urgonian limestones sensu stricto occurred at the early late barremian transition the onset of changes in the carbonate production mode heterozoan versus mixed heterozoan photozoan versus photozoan clearly predates the onset of similar lithological changes in the helvetic realm by about 1 0 to 1 2 myr the established chronostratigraphic framework points to a link between the change towards photozoan dominated limestones and fading palaeoenvironmental perturbations related to the mid barremian event which is associated with major faunal turnovers and the onset of cyclic black shale deposition in the central tethyan realm judging from palaeoenvironmental proxies including kaolinite phosphorus and black marl limestone ratios oscillating predominantly humid and relatively arid greenhouse conditions modulated the observed pattern in urgonian carbonate platform production mode and the varying frequencies of black shale deposits in the tethyan and boreal realms transient blooms of the orbitolinid foraminifera palorbitolina lenticularis at the onset of a marked upper barremian positive carbon isotope shift are interpreted to reflect increasing nutrient influx most probably related to accelerated hydrological cycling and or sea level rise these strata do not represent an over regional correlatable lithostratigraphic unit but likely an expression of progressive northern tethyan environmental and oceanographic change possibly related to ontong java large igneous province volcanism in the prelude of oceanic anoxic event 1a oae

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

a 9 myr cycle in cenozoic δ13c record and long term orbital eccentricity modulation is there a link abstract the 65 myr long cenozoic carbon isotope record 13 c of zachos et al 2001 2008 documents a strong long term cycle with a mean pseudoperiodicity close to 9 myr this cyclicity modulates the 2 4 myr eccentricity cycle amplitude hinting at a possible link between long term astronomical and geological variations some phase shifts between 9 myr 13 c and astronomical cycles suggest that additional processes e g tectonics contribute to these long term carbon cycle variations the strong response of 13 c to long term eccentricity periods 9 myr 2 4 myr 400 kyr supports the hypothesis that the long time residence of carbon in the oceans amplifies lower frequency or dampens higher frequency orbital variations additionally the strong expression of low amplitude 9 myr eccentricity cycle in the 13 c record could be explained by energy transfer process from higher to lower frequency cycles and all eccentricity components modulate the carrier climatic precession cycles finally the paleocene eocene thermal maximum petm 55 9 ma event which corresponds to a pronounced 13 c negative excursion is situated within a strong decrease in the most prominent 9 myr 13 c cycle hinting at a link between accelerated rates in 13 c variations and the petm this specific 9 myr 13 c cycle seems to be amplified by non orbital mechanisms in atmosphere continent ocean system such as previously suggested methane release from gas hydrate and volcanism

reconstructing nutricline dynamics of mid cretaceous oceans evidence from calcareous nannofossils from the niveau paquier black shale se france abstract a high resolution calcareous nannofossil record is presented from the lower albian niveau paquier black shale from the vocontian basin se france the niveau paquier black shale represents the regional equivalent of the supraregionally distributed oceanic anoxic event 1b oae 1b to reconstruct surface water fertility a nutrient index based on zeugrhabdotus erectus discorhabdus rotatorius high fertility indicators and watznaueria barnesae low fertility indicator was established using principal component analysis in addition the distribution of nannoconus spp and absolute abundances of coccoliths coccoliths per gram were used for reconstructing nutricline dynamics of the surface waters high surface water fertility coincides with low percentages of nannoconids and vice versa moreover high percentages of nannoconids correlate with low absolute abundances of all other coccoliths based on the observed nannoplankton distribution pattern and a suggested similarity in ecological requirements between nannoconids and the modern taxon florisphaera profunda a model is proposed that couples nannoconid abundances with dynamics of the nutricline time series analyses of the nutrient index show fluctuations within the precessional band the precession controlled fluctuations of the surface water fertility may represent a monsoonal signal with the nutrient supply in the surface waters depending on the strength of monsoonal activity during periods of enhanced monsoonal activity which were characterized by humid conditions and stronger winds mixing of the upper water column was enhanced during that time the abundance of nannoconids decreased as a consequence of enhanced wind stress that improved vertical mixing and led to an entrainment of nutrients into the surface waters this resulted in an increase of primary production during periods of reduced monsoonal activity marked by drier conditions and reduced wind stress the surface waters were depleted in nutrients as a result of a deep nutricline and a reduced nutrient supply to the upper photic zone in a stratified water column percentages of nannoconids increased according to the mechanisms outlined above fluctuations of the nutrient index and nannoconid percentages have been used as a proxy for reconstructing the physical structure of mid cretaceous oceans steered by precession forced monsoonal activity the results of the study show that the formation of the lower albian oae 1b from the vocontian basin occurred under strongly fluctuating surface waters fertility

simulation of long eccentricity 400 kyr cycle in ocean carbon reservoir during miocene climate optimum weathering and nutrient response to orbital change 1 deep sea foraminiferal 13c records contain abundant 400 kyr cycles indicating a link between eccentricity forcing and ocean carbon reservoir change here we simulate the oceanic 13c maxima events forced by the earth s orbital geometry during the miocene climate optimum mco 17 14 ma using a box model the simulated results of both surface and deep water 13c display co varying 400 kyr cycle modulated by orbital parameters weathering induced carbon input will change the burial ratio of carbonates to organic carbon and further result in periodic changes in the oceanic 13c the increase of riverine nutrient input which is synchronous with riverine carbon input often stimulates primary productivity and burial of organic carbon our results support that eccentricity maxima minima enhance reduce weathering intensity and nutrient supply which lead to minima maxima of 13c the prominent 400 kyr cycle of ocean carbon reservoir is interpreted as likely caused by a long memory of carbon in the ocean

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

bed configurations in steady unidirectional water flows part 1 scale model study using fine sands abstract reynolds froude scale modeling using hot water flows to model cold water flows was applied to the study of unidirectional flow bed configurations in a large thermally insulated laboratory flume three different water temperatures ranging from 14 to 75 c provided three different scale ratios from 1 1 to 2 3 effective sand sizes scaled to 10 c water were about 0 12 mm 0 18 mm and 0 28 mm relative to 10 c water use of hot water multiplied the effective flow depth and all flume dimensions by factors of up to 2 3 the flow velocity by factors of up to 1 5 and the water discharge by factors of up to 8 the effective dimensions of the flume scaled to 10 c water temperature ranged up to over 26 m long and 2 m wide with a flow depth of up to 0 5 m in the coarser sand sizes 0 17 0 26 mm three bed phases were observed ripples dunes and upper regime plane bed dunes tended to be two dimensional crests straight and continuous at low flow velocities and three dimensional crests sinuous and discontinuous at relatively high flow velocities except that at flow velocities transitional between ripples and dunes the bed showed a complex intermingling of irregular larger dunelike bed forms and smaller irregular ripples in the dune range ripples were prominently superimposed at relatively low flow velocities but nearly absent at relatively high flow velocities

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago