late cenomanian to middle turonian high resolution carbon isotope stratigraphy new data from the munsterland cretaceous basin germany abstract new high resolution carbon isotope stratigraphies from two basinal pelagic carbonate successions in northern germany halle and oerlinghausen munsterland cretaceous basin resolve late cenomanian to early mid turonian carbon cycle variations at timescales of less than 100 kyr beside the major carbon isotope excursion of the late cenomanian oceanic anoxic event oae 2 11 small scale distinct features are precisely resolved in the 13c carbonate curve and related to boreal macrofossil zonations the small scale carbon isotope events correspond to secular 13c carbonate variations identified previously in the english chalk the boreal high resolution 13c carbonate curve shows a detailed coincidence with two tethyan 13c curves from italy what demonstrates the interregional significance of the 13c dates and allows their correlation within error limits of 40 kyr furthermore the new 13c curve enables the calibration of boreal and tethyan macro and microfossil zonations accordingly the tethyan calcareous nannoplankton boundary nc13 nc14 corresponds to the boreal fo of c woollgari the index taxon for the lower middle turonian boundary the cyclic appearance and the temporal spacing of the small scale carbon isotope events suggest that orbital forcing exerted control on surface water productivity and organic matter preservation at the sea floor

oceanic anoxic cycles orbital prelude to the bonarelli level oae 2 abstract the prelude to the second global oceanic anoxic event of the cretaceous oae 2 as recorded in the classic sections of the scaglia bianca formation in the umbria marches region of italy is characterized by an oscillation between black to gray organic rich cherts and white pelagic limestones spectral analysis of these lithologic alternations reveals a robust set of cycles whose periods are remarkably similar to the orbital cycles calculated by laskar et al laskar j robutel p joutel f gastineau m correia a c m levrard b 2004 a long term numerical solution for the insolation quantities of the earth astronomy and astrophysics 428 261 285 bandpass filtering shows that the 140 80 kyr signal approximates the envelope of the 26 16 kyr signal just as expected if these components represent responses to orbital eccentricity and precession matching the presumed eccentricity signal to the theoretical eccentricity of laskar et al yields an age for the base of the bonarelli level onset of oae 2 in italy of 94 21 ma 93 72 ma provides an alternative consistent with radiometric constraints from a correlative section in the western united states given the strong orbital control on the cyclic deposition of the organic rich precursors of oae 2 within the scaglia bianca formation we hypothesize that the timing of oae 2 itself is similarly controlled by astronomical variations indeed the occurrence of oae 2 coincides with a protracted period of unusually low insolation variation owing to simultaneous nodes in all orbital parameters we speculate that other oaes similarly coincided with insolation nodes and dampened seasonality from this perspective some but perhaps not all of the oaes may be periodic events reflecting cycles of oceanic anoxia that predictably punctuated a 50 myr period of cretaceous climate

a ductile thrust in the himalaya abstract although the nature and deformation pattern of basement rocks largely determine the structural behaviour of the continental crust in orogenic belts relatively little is known about the deformational processes at deep crustal levels this paper describes a large scale zone of intense ductile deformation from the himalayan region representing a major geotectonic element the main central thrust mct along which the homoclinal block of crystalline rocks of the greater himalaya is thrust over the younger sedimentary belt of the lesser himalaya it has been observed that a zone extending some 5 to 6 km on both sides of this moderately dipping thrust upto 45 n nne has undergone homogeneous ductile deformation strain measurements across this zone reveal a characteristic profile in which the mct coincides with the highest strains earlier pre mct folds and their interference patterns are absent around the thrust towards which there is a gradual increase in the intensity of deformation and grade of metamorphism in the framework of the himalaya the mct coincides with a line of hot springs and seismic activity the rocks around the mct appear to have undergone marked superimposition of homogeneous ductile strain in the light of our studies the mct has been regarded as a ductile thrust of deep intracrustal character involving a vertical displacement of about 18 km for the crystalline slab which today constitutes the greater himalaya a model of the mct is presented and its wider implications are discussed

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 sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

marine 187os 188os isotope stratigraphy reveals the interaction of volcanism and ocean circulation during oceanic anoxic event 2 high resolution osmium os isotope stratigraphy across the cenomanian turonian boundary interval from 6 sections for four transcontinental settings has produced a record of seawater chemistry that demonstrates regional variability as a function of terrestrial and hydrothermal inputs revealing the impact of palaeoenvironmental processes in every section the 187os 188os profiles show a comparable trend radiogenic values in the lead up to oceanic anoxic event 2 oae 2 an abrupt unradiogenic trend at the onset of oae 2 an unradiogenic interval during the first part of oae 2 and a return to radiogenic values towards the end of the event above the cenomanian turonian boundary the unradiogenic trend in 187os 188os is synchronous in all sections previous work suggests that activity of the caribbean lip large igneous province was the source of unradiogenic os across the oae 2 and possibly an instigator of anoxia in the oceans here we assess this hypothesis and consider the influence of activity from other lips such as the high arctic lip a brief shift to high radiogenic 187os 188os values occurred in the western interior seaway before the onset of oae 2 we evaluate this trend and suggest that a combination of factors collectively played critical roles in the initiation of oae 2 differential input of nutrients from continental and volcanogenic sources coupled with efficient palaeocirculation of the global ocean and epeiric seas enhanced productivity due to higher nutrient availability which permitted penecontemporaneous transport of continental and lip derived nutrients to trans equatorial basins

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

ground subsidence quaternary faults and vulnerability of utilities and transportation networks in thessaly greece ground fissures and subsidence have caused extensive damage in structures and the utility networks roads railroad line larisa nato airport telecommunication network in the plain of thessaly central greece in the last 20 years the fact that these fissures are parallel to quaternary faults controlling the structural evolution of the thessaly basin marked by intense recent seismic activity led some scientists to regard them as manifestation of tectonic creep even premonitory phenomena of major future seismic events a careful study of the geometric characteristics and of the kinematics of these ground fissures however revealed that they only reflect shear failure of the ground due to compaction of loose sediments following significant decline of the groundwater level due to over pumping i e a geotechnical and not a tectonic process furthermore theoretical considerations and modeling predict surface fissuring along zones of anomalous basement normal fault controlled topography this explains the correlation between ground fissures and active quaternary normal faults

wavelength amplitude characteristics of polyphase folds in the precambrian bundelkhand complex india abstract on the basis of wavelength amplitude measurements on minor folds in a precambrian complex of central india it is demonstrated that the folds related to a particular generation are characterised by some definite values of their wavelength amplitude ratio the wavelength amplitude plots show that the folds related to a particular generation are all confined to certain definite fields

velocity and deformation fields in the north aegean domain greece and implications for fault kinematics derived from gps data 1993 2009 abstract gps rates based on data of an extended continuous and campaign type gps network in the north aegean domain are presented the data processed for the time period 1993 2009 is used to analyze the complex kinematic and deformation fields in the north aegean sea and adjacent regions the presence of slowly deforming areas is investigated southern bulgaria eastern macedonia and thrace move uniformly southward relative to eurasia 1 5 3 5 mm yr western macedonia epirus thessaly and central greece rotate rather coherently clockwise the region comprising the islands of limnos agios efstratios and alonnisos moves like a counterclockwise rotating slowly deforming block the new gps rates allow a quantification of the spatial change of strike slip motion and locking depth along the north aegean trough dextral strike slip motion diminishes from east toward west amounting to 21 2 mm yr along the saros basin and 12 5 mm yr south of the chalkidiki peninsula less than 5 mm yr 50 nstrain yr shear strain rate is transferred from the sporades islands pelion toward northern evia the locking depth is shallow for the ganos fault and the western saros basin 5 6 8 9 km it is deeper between the sporades islands and pelion 17 7 km corresponding to a more diffuse shear zone an elementary finite element model is applied to derive slip rates of the three main ene wsw to ne sw trending dextral strike slip faults in the north aegean large scale n s to nne ssw extension in the north aegean domain is analyzed by employing finite element and gps based strain rate analyses pronounced extension 100 nstrain is associated with known tectonic structures e g mygdonian graben northern gulf of evia in offshore areas such as the sporades basin the correspondence between gps derived extension rates and active fault structures is not entirely evident however important constraints are provided for seismotectonic interpretations

geodetic constraints to the kinematics of the kapareli fault reactivated during the 1981 gulf of corinth earthquakes abstract comparison of historical and of post seismic triangulation data is used to model vertical crustal movements in the vicinity of the kapareli fault or the alkynonides earthquakes north fault one of the two antithetic normal faults which reactivated during the 1981 gulf of corinth ms 6 7 earthquakes this fault is characterized by a much smaller geomorphological signature than the south or perachora fault of the same seismic sequence analysis of geodetic data on the basis of polynomial filtering and elastic dislocation modelling as well as analysis of structural and coastal change data permits us to conclude that the upper bound in the uncertainty level of most of the available elevation changes is 20 30 cm usually lower than the corresponding dislocation signal in addition the available geodetic data have a systematic pattern and are consistent with structural data for this reason they permit more precise constraints on the geometry and the role of the kapareli fault or the alkyonides earthquakes north fault its total length is estimated about 17 km about 50 longer than its surface trace about 30 40 cm subsidence of its hanging wall as well as at least 15 cm maximum uplift of its footwall is also inferred this new evidence suggests that although in the long term the kapareli fault may represent a rather secondary antithetic fault to the alkyonides earthquakes south perachora fault during the 1981 earthquakes it probably had a more important structural role

axial obliquity control on the greenhouse carbon budget through middle to high latitude reservoirs carbon sources and sinks are key components of the climate feedback system yet their response to external forcing remains poorly constrained particularly for past greenhouse climates carbon isotope data indicate systematic million year scale transfers of carbon between surface reservoirs during and immediately after the late cretaceous thermal maximum peaking in the cenomanian turonian circa 97 91 million years myr ago here we calibrate albian to campanian 108 72 myr ago high resolution carbon isotope records with a refined chronology and demonstrate how net transfers between reservoirs are plausibly controlled by 1 myr changes in the amplitude of axial obliquity the amplitude modulating terms are absent from the frequency domain representation of insolation series and require a nonlinear cumulative mechanism to become expressed in power spectra of isotope time series mass balance modeling suggests that the residence time of carbon in the ocean atmosphere system is by itself insufficient to explain the myr scale variability it is proposed that the astronomical control was imparted by a transient storage of organic matter or methane in quasi stable reservoirs wetlands soils marginal zones of marine euxinic strata and potentially permafrost that responded nonlinearly to obliquity driven changes in high latitude insolation and or meridional insolation gradients while these reservoirs are probably underrepresented in the geological record due to their quasi stable character they might have provided an important control on the dynamics and stability of the greenhouse climate

earthquake clustering in the eastern mediterranean during historical times most coastal sectors which show evidence of holocene coseismic uplift in greece and the eastern mediterranean were raised during a short period called here the early byzantine tectonic paroxysm ebtp between the middle of the fourth and the middle of the sixth century a d the areas uplifted at that time include cephalonia and zante in the ionian islands lechaion and the perachora peninsula in the gulf of corinth the pelion coast of thessaly antikythira and the whole of western crete a coastal sector near alanya in southern turkey and the entire levant coast from hatay turkey to syria and the lebanon the amount of the ebtp uplift was generally between 0 5 m and 1 0 m but reached a maximum of about 9 m in southwestern crete in several areas zante pelion coast antikythira western crete alanya the ebtp uplifted shoreline is the only evidence of holocene emergence in other areas however a similar uplift occurred earlier in the holocene levant coast or more recently cephalonia evidence of preseismic subsidence prior to the ebtp uplift has been reported from thessaly antikythira and crete in both the latter islands the ebtp uplift was preceded by a series of about 10 coseismic small subsidence movements each measuring some tens of centimeters which took place in the preceding 3000 years no evidence was observed of postseismic vertical displacements

the 1978 earthquake sequence near thessaloniki northern greece summary this paper presents a detailed study of teleseismically and locally recorded foreshocks and aftershocks of the 1978 thessaloniki earthquake sequence and discusses the relations between the locations and mechanisms of these shocks and the three dimensional geometry of faulting in the source region sixteen teleseismically recorded events were relocated using a relative relocation method and positioned geographically using the accurate locally determined location of the largest aftershock all these shocks had depths shallower than 15 km the spatial distribution of the foreshocks showed that the activity was initiated at the central part of the epicentral region progressed westwards and for about 20 days clustered in the region of the imminent mainshock no teleseismically recorded foreshock was located west of the mainshock location in less than 1 hr after the mainshock large aftershocks occurred west of it and in later stages spanned the entire western part of the epicentral region no teleseismically recorded aftershocks were located east of the mainshock locally recorded aftershocks were accurately located and provided a more detailed picture of the seismic deformation they occurred at depths between 3 and 12 km and in three distinct clusters separated by well defined gaps the largest foreshock on may 23 had a moment of 5 6 1024dyne cm and a mean displacement of 31cm the mainshock on june 20 had a moment of 5 2 1025dyne cm a strain drop of 4 0 10 5 static stress drop of 12 bar and a mean displacement of 64 cm these values are for one of the two possible interpretations of the aftershock distribution which suggests that the largest earthquakes of the sequence occurred on two different but adjacent fault segments the first event 1 on may 23 occurred along the central fault segment and was followed 28 days later by the second event 2 on june 20 along a western fault segment finally 61 days later another smaller earthquake event 3 occurred along another fault east of event 1

subsidence and evolution of the thessaloniki plain greece based on historical leveling and gps data comparison of historical leveling and of recent gps data reveal that the wider thessaloniki plain north greece a 2500 years old delta has subsided in the last 50 years up to 3 5 m these results are consistent with independent estimates of subsidence in the suburbs of thessaloniki and testify to a plain wide effect rather localized increased subsidence resulting from hydrocompaction due to intense pumping is superimposed on the plain wide subsidence the latter seems to mimic the long term tendency of landscape change as the correlation between recent surface deformation and deformation derived from boreholes reveals furthermore differential subsidence seems to control the flow of rivers and the overall morphology of the delta the significance and necessity of geoid corrections in the comparison of historical and gps data is also indicated

recent vertical movements across the atalandi fault zone central greece repeated leveling data collected over a 14 km long traverse crossing the atalandi fault that last broke in 1894 revealed small amplitude motions for the interval 1969 1984 these motions are significant against random errors and are probably free of systematic errors in addition no local or superficial ground effect may account for the observed elevation changes which correlate with the tectonic pattern in the area as they show a relative downward motion of the hanging wall of a normal fault this motion is similar to the co seismic slip geomorphological observations and observations of submerged archaeological sites on the other hand corroborate long term motions which are unlikely to be explained as cumulative co seismic slip and are possibly similar to the short term motions leveling data reveal

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

significant increases in global weathering during oceanic anoxic events 1a and 2 indicated by calcium isotopes abstract calcium isotope ratios 44 42ca were measured in carbonate rich sedimentary sections deposited during oceanic anoxic events 1a early aptian and 2 cenomanian turonian in sections from resolution guyot mid pacific mountains coppitella italy and the english chalk at eastbourne and south ferriby uk a negative excursion in 44 42ca of 0 20 and 0 10 is observed for the two events these 44 42ca excursions occur at the same stratigraphic level as the carbon isotope excursions that define the events but do not correlate with evidence for carbonate dissolution or lithological changes diagenetic and temperature effects on the calcium isotope ratios can be discounted leaving changes in global seawater composition as the most probable explanation for 44 42ca changes in four different carbonate sections an oceanic box model with coupled strontium and calcium isotope systems indicates that a global weathering increase is likely to be the dominant driver of transient excursions in calcium isotope ratios the model suggests that contributions from hydrothermal activity and carbonate dissolution are too small and short lived to affect the oceanic calcium reservoir measurably a modelled increase in weathering flux on the order of three times the modern flux combined with increased hydrothermal activity due to formation of the ontong java plateau oae1a and caribbean plateau oae2 can produce trends in both calcium and strontium isotopes that match the signals recorded in the carbonate sections this study presents the first major element record of a weathering response to oceanic anoxic events

cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode oceanic anoxic events oaes were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen deficient bottom waters oae2 occurring at the cenomanian turonian boundary about 93 5 myr ago is the most widespread and best defined oae of the mid cretaceous although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios the actual trigger mechanism corresponding closely to the onset of these episodes of increased carbon sequestration has not been clearly identified it has been postulated that large scale magmatic activity initially triggered oae2 refs 4 5 but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of oae2 has not yet been found here we report seawater osmium isotope ratios in organic rich sediments from two distant sites we find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of oae2 using a simple two component mixing equation we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin a approximately 30 50 fold increase relative to pre oae conditions furthermore the magmatic osmium isotope signal appears slightly before the oae2 as indicated by carbon isotope ratios suggesting a time lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial which may reflect the reaction time of the global ocean system our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of oae2 which may have triggered the subsequent deposition of large amounts of organic matter

obliquity forcing of organic matter accumulation during oceanic anoxic event 2 1 an analysis of orbitally influenced climate sensitive sedimentation is conducted across a meridional transect of the proto north atlantic to reconstruct the behavior of the carbon cycle and climate during oceanic anoxic event 2 oae 2 94 ma midlatitude to near equatorial sites spanning deep ocean to shelf environments are evaluated using a new inverse method for the identification and calibration of orbital influence in ancient strata the results yield consistent independent astrochronologies at each location compatible with the recently published radioisotopic astrochronologic time scale at the cenomanian turonian gssp and thus provide a unified high resolution temporal context for evaluation of the event the proto north atlantic astrochronologies document an amplification of obliquity power during oae 2 indicating that obliquity was the dominant pacemaker of organic matter accumulation by the latter portion of the event the strong obliquity signal suggests an influence of high latitude climate processes across midlatitude deep ocean to tropical shelf environments changes in oceanic circulation during oae 2 represent a likely mechanism for the propagation of a high latitude signal and proxy data from demerara rise reveal the development of a new intermediate water mass source synchronous with the record of obliquity amplification we hypothesize that a dense high latitude water mass displaced a pre existing nutrient rich anoxic deep water layer in the proto north atlantic augmented by enhanced volcanism driving an episode of high productivity that lasted 700 800 ka the development and intensification of the new intermediate deep water source was potentially driven by eustatic sea level rise which created expansive seaways in mid to high latitudes

astronomical tuning of the cenomanian scaglia bianca formation at furlo italy abstract the astronomical tuning of the upper cenomanian rhythmic succession of marine limestones and black shales that prelude to the bonarelli level oceanic anoxic event 2 in the classic furlo section of central italy was achieved using cyclostratigraphic analyses on environmentally controlled rock magnetic properties and the caco 3 content of the limestones the astronomical tuning was based on the stable 405 kyr long eccentricity cycle observed in the rock magnetic record and correlated to the orbital solution of laskar et al 2004 and the phase relationship was established by the eccentricity modulated precession signal observed in the caco 3 record according to our tuning pre bonarelli black shales formed during eccentricity minima and reduced seasonality when reduced deep water circulation sea bottom ventilation in a paleogeographically constricted alpine tethys central atlantic ocean promoted organic matter preservation and possibly a reduced carbonate dissolution resulting in a higher sedimentation rate in compliance the onset of the oae2 at furlo corresponds to the eccentricity minimum nominally placed at 93 92 ma with the full development of oae2 persisting much longer than any black shale precursor across at least one long eccentricity maximum

litho bio and chemostratigraphy across the cenomanian turonian boundary oae 2 in the vocontian basin of southeastern france the oceanic anoxic event 2 oae 2 was one of at least two large oceanic anoxic events during the cretaceous period and it is characterized in the stratigraphic record by double positive peaks in the 13c curves of carbonate and organic carbon since the positive 13c shift is believed to have resulted from massive burial of isotopically depleted organic carbon generated globally in anoxic oceanic environments the positive 13c shift tend to coincide with widespread deposition of organic rich sediments in the case of oae 2 however the organic rich horizons do not accord exactly with the two intervals with positive 13c shifts at many sites such as pueblo tarfaya eastbourne and gubbio e g tsikos h jenkyns h c walsworth bell b petrizzo m r forster a kolonic s erba e premoli silva i baas m wagner t sinninghe dameste j s 2004 carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities journal of the geological society london 161 711 719 the thomel level of the cenomanian turonian c t boundary in the vocontian basin southeastern france accumulated during the oae 2 and it is marked by frequent intercalations of black shale and organic rich marl detailed litho bio and chemostratigraphy analyses across the c t boundary in the vocontian basin indicate that the 13ccarbonate profile fluctuation across the thomel level corresponds well with changes in lithofacies total organic carbon toc and calcium carbonate caco3 abundance positive 13c excursions within the oae 2 correlate with basal and middle parts of the thomel level that are characterized by high toc low caco3 and predominantly contain organic rich sediments such as black shale and dark gray marl on the other hand negative 13c intervals within the oae 2 correspond with lower and upper parts of the thomel level that consist of marly limestone and limy marl with low toc and high caco3 values since the fluctuation of redox conditions during thomel level deposition in the vocontian basin coincides well with the global carbon burial rate indicated by its 13c profile the thomel level could be an ideal candidate for the reference section of the oae 2

a quantitative study of hinge thickness of natural folds some implications for fold development abstract a quantitative analysis of some natural folds showing thickened hinges designated here as t folds has been carried out two parameters of a fold have been recognized here a the axial angle is the angle for a given trace or arc as subtended at its apex hinge and b the thickness ratio t is the ratio between the hinge th and limb tl thicknesses the t plots for a variety of natural folds yield a very typical curve that not only reflects interdependence of hinge thickening and axial angle but also bears significant implications for fold development assuming the initiation of folding due to buckling it appears that under a system of compressive forces the naturally deformed buckled folds may retain their parallel fold geometry down to the axial angle of about 130 thereafter i e between 130 and 70 the hinge thickening appears to be a rather slow process with more enhanced deformation i e between 70 and 30 when elevated temperatures also appear to play their part the folds develop great mechanical instability and undergo marked flowage and mass transfer towards the hinge zone flattening at

modeling organic carbon burial during sea level rise with reference to the cretaceous after three decades of research on the correlation between sea level and various proxies there has been very little quantification of the first order influence of sea level change on nutrient inventory marine productivity and burial of organic carbon we present a model aimed at quantifying the burial of organic carbon as a function of sea level rise the biogeochemical model explicitly considers the mean surface area distribution of the earth as a function of elevation also included is dissolved inorganic phosphate dip liberated from coastal sediments during transgression we quantify how sea level rise of magnitudes inferred for the mid cretaceous influences the phosphorus cycle and burial of organic carbon the burial efficiency is greater on the shelf therefore in the model the larger shelf area under high sea level results in more efficient burial of marine organic carbon for a given dip concentration and associated new production of organic matter np with a late cretaceous model shelf area the residence time of dip decreases by 60 relative to the present day reference thus in the final steady state dip and np in the open ocean are reduced compared to today when the biologically reactive phosphorus preac fluxes to the ocean from land are held constant the lower new production reduces the oxygen demand for respiration and results in a significant oxygenation of the global ocean finally the global organic carbon burial decreases by 30 relative to today in the model this decrease results from feedbacks between the flux of organic carbon to the seafloor and the ratio of organic carbon to preac in buried sediments in contrast during sea level rise coastal erosion may increase the preac flux to the ocean by up to 20 relative to today and cause a temporary increase in dip concentration in the ocean the resulting increase in organic carbon burial is equivalent to a carbon isotope event of 0 5 to 1 larger carbon isotope events can be triggered by sea level rise only when the ocean is sufficiently close to anoxia in the oxygen minimum zone just prior to the sea level rise

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

late cretaceous orbitally paced carbon isotope stratigraphy from the bottaccione gorge italy abstract a refined astronomical tuning of the upper albian lower campanian is proposed from the bottaccione reference section gubbio central italy long term eccentricity cycles filtered from a high resolution 13c record were tuned to the highly stable 405 kyr cycles of the new la2010 astronomical solution for the earth s orbital elements the achieved orbital tuning provides a new precise and accurate age model for dating biostratigraphic magnetostratigraphic and carbon isotope events through a 23 myr long record cycles of 8 0 4 7 3 4 and 2 4 myr modulate the entire 13c record thus extending their detection from the cenozoic to 100 ma and represent primary and stable long term oscillation modes of earth s climate ocean system although an ultimate driver of these long term periodicities is lacking we speculate that specifically the periodicity at 4 7 myr represents a homologue of the present eccentricity grand cycles evolved by the chaotic behaviour of solar system planets during the mesozoic the long term periodicities potentially reflect an unexplored expression of the low frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients particularly phosphorus associated with modulation of inputs to the ocean in turn triggered by high order marine transgressions and formation of highly productive shelf seas this very long term eccentricity control modulated by periodic low energy cycles is suggested to play a crucial role in carbon cycling controlling a chain of climate sensitive global biogeochemical processes on the earth finally these grand cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the solar system

geodetic constraints on the fault pattern of the 1978 thessaloniki northern greece earthquake ms 6 4 summary repeated measurement of a 110 km long high precision spirit levelling traverse indicates that between 1958 and 1978 about 25 cm of subsidence occurred along a distance of 30 km in the mygdonian quaternary graben near thessaloniki northern greece observed displacements are significant against random and systematic errors and most are unrelated to near surface effects and can be assigned to the 1978 thessaloniki destructive earthquakes the available data do not permit a formal inversion but an elastic dislocation analysis indicates that the main shock of the seismic sequence ms 6 4 was probably associated with a ne dipping wnw trending blind normal fault marking the southwestern margin of the mygdonian graben in agreement with seismological and structural data there also exists evidence for incipient faulting in the central southern part of the mygdonian graben

a southern hemisphere record of global trace metal drawdown and orbital modulation of organic matter burial across the cenomanian turonian boundary ocean drilling program site 1138 kerguelen plateau despite its assumed global nature there are very few detailed stratigraphic records of the late cenomanian to the early turonian oceanic anoxic event 2 from the southern hemisphere a highly resolved record of environmental changes across the cenomanian turonian boundary interval is presented from ocean drilling program site 1138 on the central kerguelen plateau southern indian ocean the new data lead to three key observations firstly detailed biostratigraphy and chemostratigraphy indicate that the record of oceanic anoxic event 2 is not complete with a hiatus spanning the onset of the event a decrease in glauconite and highly weathered clays after the onset of oceanic anoxic event 2 marks the end of the hiatus interval which can be explained by a relative sea level rise that increased sediment accommodation space on the kerguelen plateau margin this change in depositional environment controlled the timing of the delayed peak in organic matter burial during oceanic anoxic event 2 at site 1138 compared with other oceanic anoxic event 2 locations worldwide a second key observation is the presence of cyclic fluctuations in the quantity and composition of organic matter being buried on the central kerguelen plateau throughout the latter stages of oceanic anoxic event 2 and the early turonian a close correspondence between organic matter sedimentary elemental compositions and sediments recording sea floor oxygenation suggests that the cycles were mainly productivity driven phenomena available age control points constrain the periodicity of the coupled changes in sedimentary parameters to ca 15 to 50 ka suggesting a link between carbon burial and astronomically forced climatic variations precession or obliquity in the southern hemisphere mid latitudes both during and after oceanic anoxic event 2 fluctuations that were superimposed on the impact of global scale processes finally trace metal data from the non sulphidic black shale unit at site 1138 provide the first evidence from outside of the proto north atlantic region for a global drawdown of seawater trace metal mo inventories during oceanic anoxic event 2 this article is protected by copyright all rights reserved

toward an orbital chronology for the early aptian oceanic anoxic event oae1a 120 ma abstract the early aptian oceanic anoxic event oae1a 120 ma represents a geologically brief time interval in the mid cretaceous greenhouse world that is characterized by increased organic carbon accumulation in marine sediments sudden biotic changes and abrupt carbon isotope excursions indicative of significant perturbations to global carbon cycling the brevity of these drastic environmental changes

milankovitch climatic origin of mid cretaceous black shale rhythms in central italy the earth s orbital variations reflected in pleistocene ice volume were also recorded in non glacial times carbonate production in pelagic mid cretaceous sediments quantified by calcium carbonate and optical densitometry time series reflects the orbital eccentricity and precessional cycles minimal eccentricity brought deep sea anoxia most of the sedimentary variability of this 100 myr old sequence lies within the milankovitch orbital frequency band

cenomanian to campanian carbon isotope chemostratigraphy from the western interior basin u s a abstract late cretaceous carbon isotope curves generated for localities in europe asia and the deep sea records have provided the foundation for development of a contiguous intercontinental chemostratigraphic framework despite the development of carbon isotope records from selected stratigraphic intervals in the western interior basin however a comprehensive 13c record comparable to those developed in europe and asia and from odp sites had not yet been completed this study reports a new high resolution cenomanian to campanian carbon isotope record for the central western interior basin of north america that makes a key contribution to the intercontinental correlation the curve is correlated to the well developed molluscan biostratigraphic framework for the western interior basin as well as a revised geochronology based on integration of new radioisotopic dating and astrochronology developed in the same core records from where the 13c data were derived the new 13c record reflects not only major perturbations in the global carbon cycle such as the mid cenomanian event and the cenomanian turonian ocean anoxic event 2 but also smaller excursions that have been recognized in records from europe and asia this shows that the western interior shallow epeiric sea was not isolated for any appreciable part of cenomanian to early campanian time it consistently recorded changes in the global marine carbon cycle observed elsewhere a critical attribute of the chemostratigraphic dataset produced in this study is its linkage with a revised late cretaceous time scale assignment of revised ages to western interior carbon isotope events that are globally expressed will allow export of the improved time scale to localities within and outside the western interior where similar carbon isotope records have been generated this chronostratigraphic tool will allow a number of stratigraphic and geochemical hypotheses to be more rigorously tested

cyanobacteria proliferation in the cenomanian turonian boundary interval of the apennine carbonate platform immediate response to the environmental perturbations associated with oae 2

a perturbed hydrological cycle during oceanic anoxic event 2 the late cretaceous oceanic anoxic event 2 oae2 ca 94 ma was one of the largest global carbon cycle perturbations during the phanerozoic oae2 represents an important although extreme case study for modern trends because widespread anoxia and enhanced organic carbon burial during oae2 were linked to exceptionally warm climates and high atmospheric co 2 concentrations however the consequences of this warmth for the hydrological cycle remain poorly understood hampering our understanding of its impact on biogeochemical cycles during this greenhouse episode here we show evidence for changes in the hydrological cycle during oae2 based on combined geochemical and palynological data for the stratigraphically expanded coastal oae2 succession at bass river located on the new jersey shelf ocean drilling program leg 174ax eastern united states paleothermometry based on tex86 indicates sea surface warming at the onset of oae2 and a subsequent pronounced cooling event palynological data show that these changes in temperature were associated with strong variations in precipitation and runoff we suggest that an acceleration of the hydrological cycle during oae2 played a key role in supplying nutrients to coastal waters and enhancing stratification thus contributing to the development of ocean anoxia

fault parameters of the 1980 mw 6 5 volos central greece earthquake from inversion of repeated leveling data the 1980 volos almyros seismic sequence the last of an unusual clustering of earthquakes with surface magnitude 6 0 7 0 which hit thessaly central greece between 1930 and 1980 is among the least studied recent earthquakes in greece repeated measurement of three first order spirit leveling traverses crossing the meizoseismal area of the seismic sequence indicates that between 1970 1971 and 1988 1989 a subsidence of about 35 cm is observed at the almyros neogene quaternary graben the observed displacements are significant against random and systematic errors and can be assigned to the 1980 earthquake sequence inversion of leveling data using an elastic dislocation model constrained by structural and seis mological data indicates that the mainshock mw 6 5 and the largest aftershock mw 6 1 were probably associated with reactivation of two subparallel homothetic nor mal faults marking the northern margin of the almyros neogene quaternary graben

the geometrical evolution of normal fault systems abstract the purpose of this paper is to examine the kinematic behaviour of normal fault systems and see what general conditions govern their geometrical evolution we pay particular attention to seismological and surface data from regions of present day active normal faulting as the instantaneous three dimensional geometry at the time of fault movement is better known in active regions than in areas where the faults are now static most normal faults are concave upward or listric this shape can be produced by geometric constraints either because the faults reactivate curved thrusts or because they must be curved to accommodate rotations another effect which will produce curved faults is the variation of rheology with depth brittle failure at shallow depths produces less fault rotation than does distributed creep in the lower part of the crust an important geometric feature of normal faulting is the uplift of the footwall the amount of such uplift is related not only to the elastic properties of the lithosphere but also to the throw and dip of the fault a striking feature of active normal faults is that they occur in groups in which all the faults dip in the same direction this behaviour arises because the faults cannot intersect if they do one must cease to be active the rotation which such fault systems produce reduces the dip of the faults until a new steeply dipping fault is formed once a new fault cuts pre existing faults the earlier faults become locked and a new set of faults must propagate rapidly across the whole region involved many of these geometric constraints also apply to thrust faulting

lithium isotope evidence for enhanced weathering during oceanic anoxic event 2 the ocean anoxic event 2 oae2 about 93 5 million years ago was marked by high atmospheric co2 concentration rapid global warming and marine anoxia and euxinia the event lasted for about 440 000 years and led to habitat loss and mass extinction the marine anoxia is thought to be linked to enhanced biological productivity but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery here we use lithium isotope measurements from carbonates spanning the interval including oae2 to assess the role of silicate weathering we find the lightest values of the li isotope ratio 7li during oae2 indicating high levels of weathering and therefore atmospheric co2 removal which we attribute to an enhanced hydrological cycle we use a geochemical model to simulate the evolution of 7li and the ca sr and os isotope tracers our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric co2 concentrations and rapid global warming which initiated oae2 the simulated warming was accompanied by a roughly 200 000 year pulse of accelerated weathering of mafic silicate rocks which removed co2 from the atmosphere the weathering also delivered nutrients to the oceans that stimulated primary productivity we suggest that this process together with the burial of organic carbon allowed the rapid recovery and stabilization from the greenhouse state

the floating astronomical time scale for the terrestrial late cretaceous qingshankou formation from the songliao basin of northeast china and its stratigraphic and paleoclimate implications abstract the upper cretaceous qingshankou formation k 2 qn in the songliao basin slb of northeast china consists of up to 550 m thick lacustrine mudstone and shale that constitute one of the most important source rocks of the daqing oil field a high resolution cyclostratigraphic analysis of the natural gamma ray logging from 10 wells of the qingshankou formation k 2 qn reveals orbital cycles of precession 20 ka obliquity 40 ka and eccentricity 100 ka and 405 ka providing strong evidence for astronomically driven climate changes in the late cretaceous terrestrial environments floating astronomical time scales ats are established for all sections which demonstrate variable durations of k 2 qn across the basin 1 09 ma 5 20 ma and strong diachroneity of the lacustrine strata four periods of high depositional rates can be identified in the central parts of the basin possibly recording deposition during times of sustained wet climate and high chemical weathering an ats established from well m206 in the central depression zone of the basin where the most complete and stable milankovitch cycles are present suggests that the maximum duration of the k 2 qn is 5 20 ma from 94 27 ma to 89 07 ma late cenomanian to early coniacian the lacustrine anoxic event 1 lae1 at the cenomanian turonian boundary lasted 210 310 ka during which the most prolific petroleum source rocks in slb were deposited the onset 94 21 94 18 ma and duration 210 310 ka of lae1 in slb are comparable to those of the oceanic anoxic event 2 oae2 onset at 94 21 ma and duration of 320 900 ka suggesting that the same trigger mechanism such as increased atmospheric co 2 from large scale igneous activity may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems

a climatic control on reorganization of ocean circulation during the mid cenomanian event and cenomanian turonian oceanic anoxic event oae 2 nd isotope evidence although ocean circulation plays a vital role in the climate system its response to major carbon cycle perturbations during the mid cretaceous including mid cenomanian event i mce i and the cenomanian turonian oceanic anoxic event oae 2 is poorly constrained here we present nd isotope evidence for episodic increases in the influence of boreal seawater in the european epicontinental sea during mce i the start of this circulation reorganization lagged the onset of the 13c positive excursion defining mce i this sequence of change is similar to that observed during oae 2 in the same area showing a consistent response of regional circulation to changes in the global carbon cycle brief intervals of invasion of boreal fauna to mid latitude seas two during mce i and one during oae 2 plenus cold event all started after the influence of boreal seawater was enhanced implying a slower biological response to climate cooling rather than passive transport of fauna by boreal waters the lack of an nd isotope positive excursion in our record across mce i supports a volcanic origin for prominent increases in seawater nd isotope values found in the european epicontinental sea and the tropical atlantic during oae 2 the observed tight circulation carbon cycle coupling may help the upper ocean replenish nutrients from deep waters and or volcanic sources providing a critical feedback allowing continuation of mce i and oae 2 over long durations

origin of limestone marlstone cycles astronomic forcing of organic rich sedimentary rocks from the cenomanian to early coniacian of the cretaceous western interior seaway usa abstract we present an integrated multidisciplinary study of limestone marlstone couplets from a continuously cored section including parts of the upper buda limestone the entire eagle ford group boquillas formation and lower austin chalk from the shell iona 1 research borehole texas usa which provides a 8 million year myr distal clastic sediment starved intrashelf basin record of the early cenomanian to the earliest coniacian stages results show that despite variable yet minimal diagenetic overprints several unambiguous primary environmental signals are preserved and support greater water mass ventilation and current activity promoting increased silica carbonate productivity during the deposition of limestone beds compared to deposition of marlstone beds which reflect greater organic matter productivity and preservation furthermore our astronomical analyses demonstrate that the limestone marlstone couplets in the iona 1 core reflect climatic forcing driven by solar insolation resulting from integrated milankovitch periodicities in particular we propose that obliquity and precession forcing on the latitudinal distribution of solar insolation may have been responsible for the observed lithological and environmental variations through the cenomanian turonian and coniacian in this mid latitude epicontinental sea setting our data also suggests that rhythmic lithological alternations deposited in greenhouse periods in general may simply reflect climate driven cycles related to earth sun dynamics without the need to invoke significant sea level variations

contemporaneous massive subaerial volcanism and late cretaceous oceanic anoxic event 2 abstract oceanic anoxic events oaes are geological time intervals characterized by extremely high burial rates of organic carbon that led to deposition of organic rich black shales in the global ocean it has been proposed that oceanic anoxic events are ultimately caused by massive volcanism associated with formation of large igneous provinces lips because of chronological similarities but no general consensus has developed yet to investigate the possibility of lip volcanism instigating oaes we measured stable isotopic compositions of bulk organic carbon 13 c org and lead pb isotopic compositions in the silicate sediment fraction across the bonarelli black shale italy a type stratigraphic section for the end cenomanian oae oae 2 94 ma ultra high resolution 13 c org records determined every 1 5 mm capture a 3 sharp negative shift at the base of the bonarelli at the same stratigraphic level pb isotopic compositions in the silicate sediment fraction exhibit significant shifts toward characteristic values of volcanic rocks from contemporaneous lips caribbean and madagascar flood basalts these data suggest a rapid substantial increase in the relative supply of silicate minerals from the two lips massive subaerial volcanism associated with lip formation provides a simple explanation for these two isotopic geochemical signals via release of a huge amount of carbon dioxide 10 5 gt co 2 and particulate materials into the atmosphere which resulted in a rapid negative shift of 13 c in sea water and changes in pb isotopic compositions in the silicate sediment fraction respectively we interpret that massive volcanism triggered significant climatic changes inducing biotic crises and oceanic anoxia

historical coseismic uplift on euboea island greece abstract in the aegean region it is usually accepted that uplift is confined to the southern areas near the outer island arc whereas subsidence prevails in the inner basin areas however we give evidence of elevated notches andlithophaga shells dated by ams14c showing that holocene coseismic uplift of the order of about a metre occurred in inner aegean areas too and affected parts of the coasts of north and central euboea island between 510 and 380 b c and also possibly between 1050 and 900 b c

intercalibration of radioisotopic and astrochronologic time scales for the cenomanian turonian boundary interval western interior basin usa we develop an intercalibrated astrochronologic and radioisotopic time scale for the cenomanian turonian boundary ctb interval near the global stratotype section and point in colorado usa where orbitally influenced rhythmic strata host bentonites that contain sanidine and zircon suitable for 40ar 39ar and u pb dating paired 40ar 39ar and u pb ages are determined from four bentonites that span the vascoceras diartianum to pseudaspidoceras flexuosum ammonite biozones utilizing both newly collected material and legacy sanidine samples of j obradovich comparison of the 40ar 39ar and u pb results underscores the strengths and limitations of each system and supports an astronomically calibrated fish canyon sanidine standard age of 28 201 ma the radioisotopic data and published astrochronology are employed to develop a new ctb time scale using two statistical approaches 1 a simple integration that yields a ctb age of 93 89 0 14 ma 2 total radioisotopic uncertainty and 2 a bayesian intercalibration that explicitly accounts for orbital time scale uncertainty and yields a ctb age of 93 90 0 15 ma 95 credible interval total radioisotopic and orbital time scale uncertainty both approaches firmly anchor the floating orbital time scale and the bayesian technique yields astronomically recalibrated radioisotopic ages for individual bentonites with analytical uncertainties at the permil level of resolution and total uncertainties below 2 using our new results the duration between the cenomanian turonian and the cretaceous paleogene boundaries is 27 94 0 16 ma with an uncertainty of less than one half of a long eccentricity cycle

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

north aegean crustal deformation an active fault imaged to 10 km depth by reflection seismic data three multichannel seismic profiles imaged a normal fault to at least 10 km depth in the north aegean trough and thermaikos basin the fault is active and recent forming a scarp at sea bottom and crossing the quaternary deltaic front on the northern slope of the trough controlled to the south by the north anatolian fault prestack depth migration imaged the fault as a seismic reflector cutting steeply across the sedimentary rocks and flattening in the basement from the seismic image the n100 e strike of the fault scarp and the orientations of the three profiles the true fault dip is constrained to an average 20 in the basement a low angle dip the throw and age estimated from the geometry in the sedimentary rocks document recent onset of the motion that must have occurred at a high rate both the direction and the rate of slip are consistent with the instantaneous motion as measured by space based geodesy which shows the fault to be forming by pure normal slip large earthquakes that have occurred in the basin may relate to such normal faults whereas the north anatolian fault with its current strike slip earthquakes appears to slip here under low resolved shear stress

a study of the 1980 summer seismic sequence in the magnesia region of central greece summary properties of the seismic sequence foreshocks and aftershocks of the 1980 july 9 m 6 5 earthquake in the magnesia region of central greece are investigated fault plane solutions of the three major shocks of the sequence distribution of epicentres geological data and field observations show that the seismic fault is a normal trending ene wsw and dipping sse evidence that its dip angle decreases with depth is presented the parameter b in the frequency magnitude relation was found equal to 0 84 for the foreshocks and equal to 1 28 for the aftershocks while the decay parameter p of the time distribution of the aftershock frequency was found equal to 0 72 the frequency of foreshocks which started on july 4 increased till july 6 but after that decreased till the occurrence of the main shock while their average magnitude decreased continuously between july 4 and 9 a striking similarity between the focal properties of shocks of this sequence and of shocks of two other sequences which occurred in 1978 and 1981 in the back arc aegean area is attributed to tensional forces acting in this area since the middle pleistocene

the expression of the cenomanian turonian oceanic anoxic event in tibet the gongzha section of tibet china is located at the northern margin of the indian plate se tethys and is characterized by hemipelagic grey marls and marly limestones light grey limestones and silty limestones but no organic rich sediments high resolution biostratigraphy reveals an expanded cenomanian turonian ct boundary interval and the 13c record includes the main features of the classical positive carbon isotope excursion that characterizes the ct oceanic anoxic event the biotic response inferred from the foraminifera suggests that oxic to dysoxic conditions prevailed except for a short interval marked by peak abundance of heterohelix that indicates a significantly dysoxic environment during the 13c b peak excursion the overall decreasing trend in redox sensitive trace elements rste during the maximum 13c excursion confirms the absence of significant longer lasting anoxia in the gongzha section enrichments in rste are linked to phases of increased detrital input chemical weathering indices suggest that the upper cenomanian sediments accumulated under an increasingly hot and humid climate that culminated near the ct boundary in the early turonian lower weathering indices suggest a warm drier climatic regime with reduced continental runoff phosphorus mass accumulation rates show a significant peak at the onset of the positive 13c excursion followed by a decrease up to the basal turonian this pattern is positively correlated with the long term decrease in detrital index as also observed in numerous other ct boundary sections e g eastbourne pueblo and whadi el ghaib sinai long term phosphorus accumulation in the gongzha section is therefore associated with changes in detrital input the overall decreased detrital input can be explained by the increasingly remote continental sources due to the major transgression at the end of cenomanian coupled with changes in continental weathering intensity linked to increasingly more arid climate conditions

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

cretaceous rhythmic bedding sequences a plausible link between orbital variations and climate abstract simple oscillation cycles have been recognized in cretaceous pelagic sequences as a marked periodicity in carbonate and or organic carbon content the estimated periodicities of these cycles resemble milankovitch type variations in orbital elements however during warm geologic periods the nature of the link between orbital variations and the sedimentary record has been problematic climate model studies show that the intensity of continental margin precipitation in specific low latitude regions is a function of land sea thermal contrast which is sensitive to orbital variations cretaceous climate model simulations are characterized by regions of intense precipitation the locations of which are controlled by geographic configuration in particular in the model simulation the northern margin of the tethys ocean has all the climatic characteristics necessary to exhibit a sensitivity to orbital variations detailed studies of the biota sedimentology and geochemistry of the bedding rhythms in greenhorn cyclothem in the western interior seaway of north america are best interpreted in terms of variations in precipitation runoff and stable stratification of the seaway combined the geologic and model studies support a link between orbital periodicities variations of intense precipitation associated with specific paleogeographic situations and cretaceous bedding patterns this hypothesis has important implications for the sensitivity of the atmosphere hydrosphere lithosphere system to external forcing

biochemostratigraphy of an upper albian turonian succession from the southeastern neo tethys margin sw iran abstract a neo tethyan upper albian turonian hemi pelagic carbonate succession sarvak formation accessible in outcrop in the zagros sw iran was investigated using sedimentology microfacies analysis planktonic foraminifera biostratigraphy and carbon isotope stratigraphy the succession contains six biozones including thalmanninella th appenninica th globotruncanoides rotalipora cushmani whiteinella archaeocretacea helvetoglobotruncana helvetica and marginotruncana schneegansi some of these biozones show variable stratigraphic positions throughout the tethyan and boreal realms that hinder correlation of the studied iranian section with european reference sections therefore the correlation of the existing biostratigraphic framework was complemented by carbonate carbon isotope stratigraphy based on bulk carbonate material despite the low resolution of the presented carbon isotope record pronounced global events including the late turonian events cenomanian turonian boundary ctb event oae 2 and albian cenomanian boundary acb event can be distinguished the 13c excursions provide global synchronous time lines for correlation the distinguished biozones were compared among the sections regarding their stratigraphic positions relative to these time lines the correlation tentatively suggests that the biostratigraphic datum marking the acb is diachronous with an se nw trend first appearance datum fad of th appenninica varies from the upper albian to the lower cenomanian the fad of th globotruncanoides is also variable from the upper albian to the lower cenomanian however the middle cenomanian turonian biozones including rotalipora cushmani and whiteinella archaeocretacea zones are synchronous elevated pco2 contributed to the gradual increase of the sst sea surface temperature during the cenomanian and the dramatic climax at the earliest turonian this trend closely correlates with the change from the diachronous acb biozones to synchronous ctb biozones possibly increasing ssts provided temperature tolerance range for the species throughout different latitudes and assisted their rapid distribution moreover the warming raised the sea level from the latest albian to turonian that inundated landbridges resulting in an enhanced marine circulation and faster distribution of planktonic species throughout the neo tethys ocean

stress tensor inversions along the westernmost north anatolian fault zone and its continuation into the north aegean sea summary gephart forsyth s method has been applied to estimate stress orientations from earthquake fault plane solutions of the westernmost north anatolian fault zone nafz its westward continuation in the northern aegean sea where it interacts with the normal faulting of central greece and of the western coastal parts of anatolia in total 163 fault plane solutions were used to invert for the stress tensor of 9 seismotectonic subregions magnitudes range from 1 1 to 7 4 all events have shallow focal depths most occurred in the uppermost 15 km and very few in the 15 to 40 km depth range the region studied is characterized by strike slip nafz by transtension central greece and western anatolia and by a strong signature of transpression in the marmara area from nafz to central greece the 3 axis changes continuously and smoothly its orientation from n35 e in the westernmost nafz to nearly north south in continental central greece and the maximum horizontal stress hmax changes from wnw ese to e w the total angle of lateral variation in the direction of either hmax or 3 is 40 in central western anatolia the orientation of 3 is nne ssw n10 e while in southern western anatolia it is nnw sse n33 w in both cases the development of the major grabens simav gediz menderes is in agreement with the resolved stress tensor at the termination of the nafz against central greece the regime is complex the dextral shear motion transferred from the east crosses the pilion peninsula and northern evia island where it interacts with the major normal faults of continental greece these faults have variable orientations the e w trending quaternary fault system and the nw se trending fault system which is inherited from the past the latter faults under the presently acting stress field are reactivated either as strike slip faults with sinistral strike slip component when oriented at small angle in respect to 3 or as normal faults with small sinistral strike slip component when oriented at high angle in respect to 3 the occurrence of the recent 2001 july 26 skyros event which was clearly connected to a nnw sse fault with sinistral strike slip motion provides strong seismological evidence that the old structures can equally well be reactivated under the presently active stress field

greater india basin hypothesis and a two stage cenozoic collision between india and asia cenozoic convergence between the indian and asian plates pro duced the archetypical continental collision zone comprising the himalaya mountain belt and the tibetan plateau how and where india asia convergence was accommodated after collision at or be fore 52 ma remains a long standing controversy since 52 ma the two plates have converged up to 3 600 35 km yet the upper crustal shortening documented from the geological record of asia and the himalaya is up to approximately 2 350 km less here we show that the discrepancy between the convergence and the shortening can be explained by subduction of highly extended continental and oceanic indian lithosphere within the himalaya be tween approximately 50 and 25 ma paleomagnetic data show that this extended continental and oceanic greater india promontory resulted from 2 675 700 km of north south extension between 120 and 70 ma accommodated between the tibetan himalaya and cratonic india we suggest that the approximately 50 ma india asia collision was a collision of a tibetan himalayan microconti nent with asia followed by subduction of the largely oceanic greater india basin along a subduction zone at the location of the greater himalaya the hard india asia collision with thicker and contiguous indian continental lithosphere occurred around 25 20 ma this hard collision is coincident with far field deforma tion in central asia and rapid exhumation of greater himalaya crys talline rocks and may be linked to intensification of the asian monsoon system this two stage collision between india and asia is also reflected in the deep mantle remnants of subduction imaged with seismic tomography

testing the astronomical time scale for oceanic anoxic event 2 and its extension into cenomanian strata of the western interior basin usa the development of integrated astronomical and radioisotopic time scales from rhythmic strata of the western interior basin wib has played a fundamental role in the refi nement of late cretaceous chronostratigraphy in this study x ray fl uorescence xrf core scanning is utilized to develop a new elemental data set for cyclostratigraphic investigation of cenomanianturonian strata in the wib using material from the aristocrat angus 12 8 core northcentral colorado the xrf data set yields the fi rst continuous 5 mm resolution analysis of lithogenic biogenic and syngeneticauthigenic proxies through the uppermost lincoln limestone member the hartland shale member and the bridge creek limestone member including oceanic anoxic event 2 oae 2 the 40 ar 39 ar ages from ashes in three biozones including a new age from the dunveganoceras pondi biozone uppermost lincoln limestone member provide geochronologic constraints for the cyclostratigraphic analysis astrochronologic testing of the 5 mm resolution xrf weight percent caco3 data via average spectral misfi t analysis yields strong evidence for astronomical infl uence on climate and sedimentation results from the bridge creek limestone member are consistent with the previously published astrochronology from the u s geological survey 1 portland core central colorado and identifi cation of an astronomical signal in the underlying hartland shale member now permits extension of the wib astrochronology into the earlier cenomanian prior to oae 2 high rates of sedimentation in the angus core during the interval of oae 2 initiation as compared to the portland core allow recognition of a strong precessional control on bedding development as a consequence the new results provide a rare high resolution chronometer for the onset of oae 2 and the timing of proposed hydrothermal trace metal enrichment as observed in the 5 mm xrf data

the neotectonics of the aegean an alternative view minor reverse faults in widely dispersed neogene outcrops in the central aegean have led several people to suggest that the regional extension which started in the lower pliocene or earlier was interrupted by short periods of compression the durations of these postulated compressional episodes are short compared to the time scale on which convective forces acting on the base of the lithosphere can change thus possible mechanisms for driving such motions are limited in this paper we offer alternative explanations for these observations and in particular show that these apparently compressional episodes are probably not regional in extent and may not be truly compressional in origin in some places they are more likely to be a consequence of the considerable rotation that is found in extensional terranes the plio quaternary paleogeography of the central aegean is satisfactorily explained by uplift in the footwall blocks of normal faults and does not require regional compression studies of the faulting associated with recent large earthquakes suggest that the sort of microtectonic analysis which is typically carried out on small faults in surficial sediments is more likely to reflect the internal deformation of blocks bounded by major fault structures than be a reliable indicator of regional stress patterns

the cenomanian turonian extinction and oceanic anoxic event evidence from southern tibet deep shelf locations on the perigondwanan margin of southern tibet record a major extinction of foraminifera and calcareous nannoplankton in the latest cenomanian top of the rotalipora cushmani zone this is followed by a low diversity survival interval that straddles the cenomanian turonian boundary whiteinella archaeocretacea zone during which only low diversity surface water dwelling foraminifera and nannoplankton and microfilaments are present rapid recovery in the early turonian saw the appearance of new species the reappearance of many lazarus species and the reestablishment of a diverse community of planktonic foraminifera that included a range of shallow to deep water column dwellers the extinction and survival intervals coincide with the development of dysaerobic facies characterised by small sized burrows and moderately large sized framboid pyrite populations at no time does the water column appear to have become sulfidic this study indicates that the end cenomanian oceanic anoxic and extinction events were also manifested in moderately high southerly palaeolatitudes on the southern margin of the tethyan ocean thereby increasing the known extent of this global event albeit with the proviso that the anoxic event was a dysoxic one

cyclostratigraphic analysis of pelagic carbonates at monte dei corvi ancona italy and astronomical correlation of the serravallian tortonian boundary cyclostratigraphic analysis of pelagic carbonates at monte dei corvi ancona italy and astronomical correlation of the serravallian tortonian boundary spectral analysis of high resolution calcium carbonate data from a 2 m y long section from the upper miocene pelagic limestone marl sequence at monte dei corvi italy indicates orbital forcing of depositional cycles at frequencies corresponding to eccentricity obliquity and precessional cycles identification of these milankovitch cycles dated by 4 0 ar 3 9 ar ages from two biotite rich volcanic ash layers within the section allows us to correlate this section with the astronomical time scale by matching low frequency variations in calcium carbonate content with the orbital eccentricity this correlation yields precise numerical ages for any stratigraphic level within the analyzed section including the two volcanic ash layers and the serravallian tortonian boundary dated here as 11 32 ma the eccentricity based correlation also allows us to tune the data resulting in enhanced power in the obliquity and precessional frequencies supporting the initial hypothesis of orbital control of these lithologic cycles

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

microseismicity and focal mechanisms at the western termination of the north anatolian fault and their implications for continental tectonics summary for seven weeks a temporary network of 68 seismological stations was operated in central greece in the region of thessaly and evia located at the western termination of the north anatolian fault system we recorded 510 earthquakes and computed 80 focal mechanisms seismic activity is associated with the ne sw dextral north aegean fault or with very young e w striking normal faults that are located around the gulf of volos and the gulf of lamia the important nw se striking faults bounding the pilion or the basins of larissa and karditsa are not seismically active suggesting that it is easier to break continental crust creating new faults perpendicular to the principal stresses than to reactivate faults that strike obliquely to the principal stress axes

upper cretaceous carbon and oxygen isotope stratigraphy of hemipelagic carbonate facies from southern tibet china a high resolution carbon isotope curve derived from upper cretaceous hemipelagic sediments cropping out at tingri southern tibet shows similarities to patterns established on other continents notably in the presence of a well defined positive excursion across the cenomanian turonian boundary where 13 c values exceed 3 5 from the upper turonian to the lower campanian 13 c values generally decline apart from a minor positive excursion in the middle coniacian a trend that departs from that recorded from europe relatively low 13 c values c 1 at the santonian campanian and campanian maastrichtian boundaries in tibet define a prominent broad positive excursion centred in the middle campanian and terminated by an abrupt fall towards the close of the stage when compared with data from europe and north africa the 13 c values of the tibetan section are generally lower by c 1 5 except for the middle campanian positive excursion where values 13 c c 2 are comparable with those documented from europe and north africa these differences are interpreted as reflecting variable mixing of water masses carrying different carbon isotope signatures such that areas close to the major sinks of marine organic carbon recorded higher 13 c values than those located in more distal regions oxygen isotope ratios albeit affected by diagenesis may record a palaeotemperature signal

black shale deposition atmospheric co2 drawdown and cooling during the cenomanian turonian oceanic anoxic event 1 oceanic anoxic event 2 oae2 spanning the cenomanian turonian boundary ctb represents one of the largest perturbations in the global carbon cycle in the last 100 myr the 13ccarb 13corg and 18o chemostratigraphy of a black shale bearing ctb succession in the vocontian basin of france is described and correlated at high resolution to the european ctb reference section at eastbourne england and to successions in germany the equatorial and midlatitude proto north atlantic and the u s western interior seaway wis 13c offset between 13ccarb and 13corg is shown to be a good pco2 proxy that is consistent with pco2 records obtained using biomarker 13c data from atlantic black shales and leaf stomata data from wis sections boreal chalk 18o records show sea surface temperature sst changes that closely follow the 13c pco2 proxy and confirm tex86 results from deep ocean sites rising pco2 and sst during the late cenomanian is attributed to volcanic degassing pco2 and sst maxima occurred at the onset of black shale deposition followed by falling pco2 and cooling due to carbon sequestration by marine organic productivity and preservation and increased silicate weathering a marked pco2 minimum 25 fall occurred with a sst minimum plenus cold event showing 4 c of cooling in 40 kyr renewed increases in pco2 sst and 13c during latest cenomanian black shale deposition suggest that a continuing volcanogenic co2 flux overrode further drawdown effects maximum pco2 and sst followed the end of oae2 associated with a falling nutrient supply during the early turonian eustatic highstand

frequency modulation reveals the phasing of orbital eccentricity during cretaceous oceanic anoxic event ii and the eocene hyperthermals abstract major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods amplitudes and phases of the milankovitch cycles of precession obliquity and eccentricity while numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data limitations in radioisotopic dating and instability of the theoretical astronomical solutions beyond 50 myr ago can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies here we demonstrate that interference patterns accompanying frequency modulation fm of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data one and two dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the fm method and indicate that pristine eccentricity fm can be readily distinguished in paleo records apart from paleoclimatic implications the fm approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions and for refining chronologies for the deep past we present two case studies that use the fm approach to evaluate major carbon cycle perturbations of the eocene and late cretaceous interference patterns in the short eccentricity band reveal that eocene hyperthermals etm2 elmo h2 i1 and etm3 x 52 54 myr ago were associated with maxima in the 405 kyr cycle of orbital eccentricity the same eccentricity configuration favored regional anoxic episodes in the mediterranean during the middle and late cenomanian 94 5 97 myr ago the initial phase of the global oceanic anoxic event ii oae ii 93 9 94 5 myr ago coincides with maximum and falling 405 kyr eccentricity and the recovery phase occurs during minimum and rising 405 kyr eccentricity on a myr scale the event overlaps with a node in eccentricity amplitudes both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times

astrochronology of the early turonian early campanian terrestrial succession in the songliao basin northeastern china and its implication for long period behavior of the solar system abstract the first complete early turonian early campanian lacustrine succession has been recovered from the sk i south sk is borehole in the songliao basin slb northeastern china we conducted a detailed cyclostratigraphic study of natural gamma ray gr log thorium th log and magnetic susceptibility ms data from this core spectral analysis of the upper quantou formation k 2 q 3 4 qingshankou formation k 2 qn yaojia formation k 2 y and lower nenjiang formation k 2 n 1 2 reveals a hierarchy of meter to decameter scale cycling in the data the wavelength ratios of the cycles in these stratigraphic units are 20 5 2 1 corresponding with those of milankovitch cycle periods of 405 kyr long eccentricity 100 kyr short eccentricity 37 kyr obliquity 20 kyr precession indicating astronomical control on sedimentation an astronomical time scale ats was established by tuning interpreted 405 kyr cycles to a 405 kyr orbital eccentricity target curve and to four sims u pb zircon radioisotope ages this absolute ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the ages of the c33r c34n geomagnetic polarity boundary in k 2 n 2 and three short reversal events in k 2 y are estimated as 83 633 ma 84 819 84 862 ma 84 982 85 092 ma and 85 240 85 629 ma respectively long period amplitude modulations in the obliquity and eccentricity bands of the 405 kyr tuned gr th series provide strong evidence that long period orbital forcing influenced climate change and depositional processes in the slb the extracted amplitude modulations provide evidence that the orbits of earth and mars were not in secular resonance and were undergoing chaotic interactions during this time although the modulations do not match those of recent astronomical models

seismicity and associated strain of central greece between 1890 and 1988 summary we examined the seismicity of central greece between 1890 and 1988 using macroseismic and instrumental data to ask two questions 1 does the seismicity of this period reveal all the major tectonic structures that are known to be active and 2 what are the likely strains associated with the seismicity over this period many known active structures have been effectively aseismic for the last hundred years and even the inclusion of all known large events earlier than 1890 reveals no activity associated with the ne coast of evia gulf of argos or graben ne of mt parnassos it is clear that even 100 years data are inadequate for either a reasonable assessment of seismic risk or for a confident estimation of maximum magnitude however we are aware of no earthquakes in central greece during the last 200 yr that were larger than ms 7 0 it is probable that the maximum magnitude is restricted by the maximum length of fault segments which appears to be around 15 20 km the earthquakes of ms 5 8 during 1890 1988 can account for a n s displacement of around 45 70 cm with maximum and minimum estimates a factor of two greater and smaller than this across part of a 1890 1900 triangulation network in central greece that was resurveyed in 1988 the contribution of smaller events may increase this displacement by about 50 per cent this cumulative seismic displacement is similar to that estimated from the geodetic work about 100 cm but a detailed comparison of the two sets of observations will be reported elsewhere a re evaluation of all the important earthquakes of 1890 1988 in central greece is presented in the appendix which summarizes information of use to both earth scientists and engineers

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

late cainozoic geodynamic evolution of thessaly and surroundings central northern greece abstract in the framework of the late alpide deformation of greece and of the recent and active extensional tectonism of the aegean region the geotectonic evolution of the thessaly region central northern greece has been examined using a quantitative and qualitative structural analysis stratigraphie sedimentological morphotectonic and seismological data the geometry of the faults their architecture and the knowledge of the stress pattern are used to explain some aspects of the tectonics and crustal dynamics of thessaly and the surrounding area the oldest compressional phases taken into account show a mean ene wsw trending direction of shortening and have been defined as late alpide early aquitanian and langhian a later late miocene pliocene ne sw oriented extensional phase has been related to the hellenic post orogenic collapse which developed behind the collisional front between the aegean eurasia and african plates this phenomenon diachronically migrated from the east central macedonia thermaikos basin towards the west epirus albania where it is still active as a consequence of this second phase the area forms a basin and range like structure the third and last phase middle pleistocene present is characterized by a n s direction of extension and affects the entire aegean region it generated new e w trending basins superimposed on the inherited ones this gave as a final result the complex block pattern we can see today the recent and active right lateral strike slip movements along the north aegean trough seem to stop in the sporades basin and do not affect the uppermost crust of mainland greece a further wnw ese directed extension observed occasionally in central and northern greece could be explained by local events or as block related deformation

black shale deposition on the northwest african shelf during the cenomanian turonian oceanic anoxic event climate coupling and global organic carbon burial high resolution geochemical records from a depth transect through the cenomanian turonian c t tarfaya basin northwest african shelf reveal high amplitude fluctuations in accumulation rates of organic carbon oc redox sensitive and sulphide forming trace metals and biomarkers indicative of photic zone euxinia these fluctuations are in general coeval and thus imply a strong relationship of oc burial and water column redox conditions the pacing and regularity of the records and the absence of a prominent continental signature suggest a dynamic depositional setting linked to orbital and higher frequency forcing determining the dominant frequency depends on the definition of the most pronounced oceanic anoxic event oae2 and its duration we propose that eccentricity is the main forcing factor at tarfaya and controlled fluctuations in wind driven upwelling of nutrient rich oxygen depleted intermediate waters from the adjacent atlantic and the periodic development of photic zone and bottom water euxinia on the mid cretaceous northwest african shelf accumulation records clearly identify the basin center as the primary site of sediment deposition with highest temporal variability and an up to six fold increase in oc burial from similar to2 g m 2 yr prior to the oae2 to similar to12 g m 2 yr during the oae2 photic zone and bottom water euxinia alternated with periods of greater oxygenation of the water column in response to climate forcing mass balance calculations imply that similar to2 of the overall global excess oc burial associated with the oae2 was deposited in the tarfaya basin an area that represented only similar to0 05 of the total global c t ocean floor in fact the lateral extent of similar black shales along the african continental margin indicates that this part of the ocean contributed significantly to the global increase in organic carbon burial during the oae2

trace element abundances in the rock canyon anticline pueblo colorado marine sedimentary section and their relationship to caribbean plateau construction and oxygen anoxic event 2 1 rapid eruption of submarine lava flows during formation of the caribbean plateau correlates closely with ocean anoxic event 2 oae2 which bracketed the cenomanian turonian boundary 93 5 ma these events also correspond with a positive excursion in carbon isotopic composition of seawater hydrothermal activity associated with large scale submarine volcanism may have been responsible for this abrupt change in ocean chemistry we determined the distribution of major minor and trace element abundances in the rock canyon marine sedimentary section pueblo colorado after normalizing element concentrations to zr to remove the variable contribution of terrigenous material to these sediments we detected an interval of concentrated metal abundance anomalies that coincides with the abrupt beginning of the positive 13c isotope excursion the metal abundance anomalies indicate that intermittent hydrothermal activity in the form of both water rock exchange and magmatic degassing introduced large concentrations of trace metals into the cretaceous ocean at the same time that extinctions of benthic species turnover in plankton communities and increases in isotopically light organic carbon burial occurred the stratigraphic position of this interval of trace metal anomalies matches events associated with oae2 and indicates that intermittent hydrothermal activity on a massive scale triggered abrupt changes in carbon burial and deep ocean oxygen contents

astronomical constraints on global carbon cycle perturbation during oceanic anoxic event 2 oae2 abstract oceanic anoxic event 2 oae2 was a major disturbance in global carbon cycling and transient climate disruption triggered by a pulse of volcanic co2 although this well studied perturbation to the ocean atmosphere system offers a unique opportunity to better understand abrupt climate change in response to co2 forcing the origin evolution and duration of the event are still debated due in large part to the temporal resolution of existing oae2 records and uncertainty over the duration of the overall perturbation and c cycle shifts within it here we report coupled magnetic susceptibility ms and carbon isotope time series of 2 5 to 5 0 5 kyr resolution from an expanded oae2 interval from southern tibet china ms cyclicity indicates short eccentricity modulation permitting the construction of a high precision orbital timescale which when integrated with the high resolution 13 c carb record fully constrains the timing and nature of onset through recovery of oae2 revealing finer scale structure than previously recognized abrupt coupled shifts in 13 c carb and ms and changing phase relationships in step with transitions between high and low long eccentricity indicate orbitally linked changes in marine carbon cycling and monsoon dynamics superimposed on repeated wholesale oceanographic changes in particular the high resolution tibetan record reveals dynamic shifts in the phasing relationship of ms and 13 c which suggests that the initiation of ocean anoxia was probably not orbitally forced this finding is in sharp contrast with the paradigm of orbitally forced ocean anoxia conversely the new record suggests that termination of anoxia was likely orbitally forced and superimposed on a dramatic oceanographic change

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

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb

changing ocean circulation and hydrothermal inputs during ocean anoxic event 2 cenomanian turonian evidence from nd isotopes in the european shelf sea nd isotopes of fish debris collected from the english chalk at eastbourne sussex uk are used to reconstruct the history of ocean circulation in the nw european shelf sea during oceanic anoxic event 2 oae 2 cenomanian turonian the eastbourne end record exhibits a 1 unit negative excursion decreasing from 9 to 10 immediately followed by a 3 unit positive excursion reaching 7 the onset of the negative end excursion lags the global 13c rise characteristic of oae 2 suggesting stable patterns of ocean circulation in the nw european shelf sea at this time both negative and positive nd isotope excursions took place during a transient cooling episode within oae 2 the negative end excursion is interpreted as due to a change in ocean circulation with northerly sourced water masses becoming the dominant bottom waters at eastbourne the positive excursion is best explained by the transport of radiogenic nd derived from a volcanic source possibly the high arctic or caribbean large igneous province lip an input of volcanic nd may reconcile the eastbourne record with coeval end records on demerara rise in the western tropical atlantic the broad synchroneity of high end values 7 registered at both sites suggests a possible period with efficient oceanic mixing between the tropical atlantic and the nw european shelf sea during the cooling episode the eastbourne end record of oae 2 together with coeval temperature reconstructions provides evidence for the coincidence of changes in ocean circulation and transient climatic cooling implying a tight coupling between the two phenomena during this interval

paleomagnetic calibration of milankovitch cyclicity in lower cretaceous sediments abstract bedded pelagic limestones of early to mid cretaceous age may record cyclic climate variability driven by changes in the earth s orbit milankovitch cycles if properly calibrated the lithologic cycles could provide sedimentary chronometry at far shorter time scales than biostratigraphy and magnetic stratigraphy the lower cretaceous maiolica formation of northern and central italy displays rythmic bedding in sections whose magnetic reversal sequence is clearly correlated to the upper m series marine anomalies the magnetic reversals divide measured sections into 0 5 2 myr increments in which sedimentation rate assuming continous deposition can be measured to 15 25 accuracy paleomagnetically estimated sedimentation rates over a number of polarity zones establish with one exception a narrow range in periods of the carbonate cycles carbonate couplets have an estimated mean period of 23 5 kyr and prominent modulations in bedding thickness bundling have a mean period of 117 kyr kent and gradstein 1985 time scale the close match of sedimentary periodicities to orbital repeat times implies that the carbonate cycles reflect a combination of professional and eccentricity climatic forcing comparison of measured sections from different locations shows that bed to bed correlations are possible regionally cosistent with the milankovitch hypothesis episodes of barremian black shale deposition occur in the troughs of the short eccentricity cycle as roughly one half of the carbonate marl couplet or about 10 kyr duration it is possible to estimate both the timing relative to the top of reversed chron m 0 and duration of a period of unusual organic carbon rich deposition selli horizon in the early part of the cretaceous long normal magnetic polarity interval by tracing the sedimentary cycles up from the barremian strata