3d stratigraphic forward modelling for analysis and prediction of carbonate platform stratigraphies in exploration and production abstract stratigraphic forward modelling sfm has been used to answer important questions in stratigraphic analysis this has been demonstrated through generic modelling of synthetic data and numerous two dimensional 2d real data case studies but the method has rarely been used to further our understanding of specific real three dimensional 3d carbonate data sets by quantitative comparison this paper applies carbonate 3d a sfm program to a hydrocarbon reservoir and outcropping carbonate platforms at both exploration and production scales we show the value of sfm in the exploration and production of hydrocarbons through predicting facies distributions and stratigraphic geometries between wells and by analysing and answering fundamental questions about the formation of specific carbonate strata first the model is tested using the 3d outcrops of a miocene attached carbonate platform at nijar se spain where 78 of mapped facies are matched in the simulations second sfm of an 80 000 km 2 jurassic ramp in ne spain exploration scale predicts new facies in areas without data leads to an improved understanding of ramp evolution modification of the interpreted sea level curve and re interpretation of the main sediment transport direction application to the isolated platform reservoir judy creek devonian canada exemplifies the advantages of applying sfm at reservoir scale the simulations yield information on platform geometries and facies distributions an improved understanding of the factors that control platform evolution and propose a revised sea level history wider applications of sfm in exploration include assessment of the possibilities and probabilities of facies distributions and evaluation and ranking of different interpretations of platform evolution at the reservoir scale facies probability distributions and layer geometries derived from sfm can serve as input into static reservoir models to guide geostatistical simulations

palaeoenvironment of the upper cretaceous coniacian concretion bearing lagerstatten from poland abstract abundantly fossiliferous upper cretaceous sediments including decapod remains in the region of stary waliszow southern poland have been known for many years to date however no study has dealt specifically with detailed palaeoenvironmental and palaeoecological reconstruction the origin of these sediments is still uncertain and has been the source of considerable confusion and controversy mainly due to the strong bioturbation and decalcification of these sediments by using the fossil record comparative taphonomy and geochemical analyses of concretions we provide new insights into the paleoenvironment and the paleoecology of this unique coniacian ecosystem on the basis of ichno and body fossil assemblages composed almost exclusively of benthic organisms such as decapods molluscs and echinoderms which are commonly disarticulated but rarely abraded we suggest that the fossiliferous sediments in stary waliszow were formed in shallow normal saline and well oxygenated waters of the upper sublittoral zone with moderate sedimentation rate and low turbulence of waters the presence of angular terrigenous clasts well preserved delicate land flora and the near absence of planktonic and nektonic fossils strongly imply proximity to the land recorded taxa inhabited a soft bottom environment some organisms were fossilized inside siderite concretions these concretions were formed within the sediment below the zone of active bioturbation during the early stage of diagenesis remarkable preservation of decapod remains is due to phosphatization which replaced the cuticle

segmentation and coalescence of cenozoic carbonate platforms northwestern great bahama bank seismic profiles over the northwestern great bahama bank reveal that it is formed by the coalescence of three smaller platforms and significant lateral progradation this conclusion is contrary to previous models which assumed that the bank is the result of continuous accumulation on one huge buildup in late cretaceous to early tertiary time a north south trending depression the straits of andros separated an eastern platform andros bank from a western platform bimini bank initially the straits of andros had dimensions similar to the modem tongue of the ocean but was progressively filled from east to west in early to middle tertiary time a second depression the bimini embayment formed within bimini bank by folding it had a maximum depth of about 470 m this depression was also filled from east to west in addition prograding systems built the western margin of bimini bank more than 25 km westward into the straits of florida

progradation geometries of carbonate platforms examples from the triassic of the dolomites northern italy various types of progradation of triassic carbonate platforms are described from the dolomites of the southern alps the internal and external geometric relationships are exposed in spectacular natural sections and moreover their scale 500 1000 m of thickness is such that they can be compared with features found in seismic profiles the different types of progradation are controlled by a number of factors which normally interact with each other these factors include rate of basinal sedimentation rate of subsidence width of the platform depth of the surrounding basin and eustatic variations of sea level progradation is not a continuous process but episodic moments of massive debris input during which the platform advances alternate with long periods of negligible progradation during which basinal sediments accrete and onlap the toe of slope upper boundary relationships of the prograding platforms include offlap toplap and erosional truncation lower boundary relationships are horizontal climbing and descending progradations a variety of phenomena and circumstances have caused the cessation of progradation of the triassic platforms they include volcanism collapse of margins drowning rapid relative rise of sea level subaerial exposure relative fall of sea level and probably a natural decay of the system in the triassic of the dolomites two main progradation models can be put forward in the ladinian model progradation took place simultaneously with aggradation relative rise of sea level whereas the characteristic feature of the carnian model is toplap relative stillstand of sea level

combining a computer simulation and eustatic events to date seismic sequence boundaries a case study of the neogene of the bahamas abstract this paper demonstrates that the principles of seismic sequence stratigraphy and the techniques of computer simulation can be combined to date the sedimentary section as an example it uses the neogene section of the western shelf of the straits of andros in the bahamas to this end type i second order seismic sequence boundaries were identified on a seismic cross section from the region these were used as brackets to correlate enclosed third order events with an eustatic sea level curve the interpreted section was then reproduced using a computer simulation program the simulation successfully reproduced the onlapping geometries of the shelf margin identified on the seismic section the early neogene fill of the straits of andros is assumed to have had an uncomplicated and uniform tectonic setting this simplified the inputs to the simulation which focused on capturing the sedimentary response to the eustatic changes inputs included a constant rate of subsidence of 0 009 m ka a uniform linearly increasing rate of carbonate accumulation from 28 5 ma to 11 5 ma and the sea level cycle chart of haq et al 1987 updated for the neogene with the absolute ages provided by berggren et al 1995 the subsequent graphical output shows a good match to the interpreted seismic this suggests that the amplitude and ages of the sea level changes as shown in the eustatic chart can be used to date the sequence boundaries for the neogene of the straits of andros it also establishes that for areas of known subsidence simulation techniques can be used to date seismic sections where biostratigraphic data are poor

integrating palynological and geochemical data in a new approach to palaeoecological studies upper cretaceous of the banterwick barn chalk borehole berkshire uk abstract the dinoflagellate cyst record from an upper cretaceous uppermost cenomanian upper coniacian chalk core drilled at banterwick barn berkshire is described and statistically correlated with elemental and stable isotope bulk sediment geochemical data from the same core seventy two dinocyst species and subspecies are recorded and stable carbon and oxygen isotopic 13 c 18 o trends are documented lithostratigraphy and chemostratigraphic correlation of the 13 c curve with an expanded section at dover kent are used to identify stratigraphically significant marls and determine the positions of macrofossil zones and stage boundaries in the banterwick barn core these data indicate that 30 m of chalk at dover are represented by senoniasphaera rotundata alveolata is proposed which has a fad in the lower turonian and last appears lad in the lower coniacian senoniasphaera rotundata rotundata autonym herein has its fad in the middle turonian first common occurrence in the uppermost turonian and lad in the upper coniacian an extremely impoverished assemblage of dinocysts in the highest cenomanian to lowest turonian is considered to be largely a preservational artefact of intraclastic nodular and calcarenitic chalks and is not related directly to the well documented global oceanic anoxic event oae2 occurring at that time 93 5 ma a sharp increase in dinocyst abundance in the lower turonian corresponds with a change in lithology to more marly chalks a gradual decrease in the number of species is observed through the middle turonian to upper coniacian 18 o records show that this was associated with global climatic cooling cluster analysis of the dinocyst abundance record with geochemical data indicates four distinct species groups with characteristic geochemical associations i e groups 1 4 groups 1 and 2 are associated with phases of increased siliciclastic supply a positive correlation with higher 13 c values differentiates the latter group 3 is independent of carbonate and detrital input and group 4 is associated with high carbonate flux and low detrital supply these groupings suggest that cyst forming dinoflagellates exhibited a range of ecological niches in the late cretaceous although the relationship between the encystment process and the geochemical associations is unclear key environmental factors are likely to be sea level and climate related including water depth turbidity nutrient supply sea surface temperature and environmental stability predictability integrated geochemical and palynological studies have great potential for inter regional correlation and palaeoenvironmental interpretation

coniacian flora of the sudetes south western poland palaeoecological and palaeoclimatic interpretations abstract palaeoecology of the coniacian flora of the sudetes idzikow flora south western poland is reconstructed on the basis of fossil plant morphology palynology and taphonomy four plant communities are reconstructed salt marsh mangrove forest dominated by frenelopsis wetland coastal forest dominated by geinitzia pandanites monheimia riparian forest dominated by ettingshausenia debeya dryophyllum and mesophytic forest dominated by microphyllous angiosperms proxy palaeoclimatic data for the idzikow flora have been estimated using clamp technique the numerical variables are as follows mean annual temperature 17 2 c warm month mean temperature 25 2 c cold month mean temperature 8 7 c length of the growing season 9 4 months growing season precipitation 841 mm mean monthly growing season precipitation 135 mm precipitation during the three consecutive wettest months 484 mm precipitation during the three consecutive driest months 100 mm relative humidity 68 5 specific humidity 8 9 and enthalpy 32 57 the reconstructed vegetation was probably a warm temperate seasonal to tropical forest experiencing hot summers and a short relatively dry season

meso cenozoic cooling and exhumation history of the orlica śnieznik dome sudetes ne bohemian massif central europe insights from apatite fission track thermochronometry

steep microbial boundstone dominated plaform margins abstract seaward progradation of several kilometers has been documented mostly for leeward margin low angle carbonate slope systems with a dominant platform top sediment source however steep and high relief margins fronting deep basins can also prograde and as such are somewhat perplexing characteristics of two prograding carboniferous examples provide a model which may apply elsewhere 1 outcrops in asturias northern spain serve as important analogs for 2 hydrocarbon reservoirs in steep sided isolated platforms of the north caspian basin kazakhstan such as tengiz seismic and well data from tengiz corroborate outcrop patterns for slope development showing progradation of up to 5 and more than 10 km respectively despite the high relief up to 600 m and steep 20 35 nature of these margins the two examples share a highly productive microbial boundstone factory extending from the platform break down the slope to nearly 300 m or more depth and a lower slope dominated by mega breccias and grain flow deposits derived from the margin and slope itself the broad depth range of microbial boundstone increases the potential for production during both lowstands and high stands of sea level and thereby facilitates progradation independent from platform top derived sediment rapid in situ lithification of the boundstone provides stability to the steep slopes but also leads to readjustment through shearing and avalanching what controls the microbial cement boundstone formation remains a debate but its presence is a key factor controlling the progradational geometry of these and possibly other margins this new model of slope shedding has implications for slope readjustment processes and resulting architecture sequence stratigraphic interpretation reservoir characterization and reservoir modeling especially the isotropic character of microbial boundstone will reduce the potential for coherent seismic reflections to develop and possibly invoke under certain stress regimes shattering and fracturing thereby generating significant non matrix permeability key considerations are the contrasts with the bahamian high stand shedding depositional model slope progradation rates that range from 450 to 1500 m my and net growth rates of in situ boundstone of 1000 m my comparable to or higher than accretion rates for metazoan skeletal reef growth

on the use of unconformities in volcanic stratigraphy and mapping insights from the aeolian islands southern italy abstract the approach to volcanic stratigraphy and mapping in the aeolian islands has found the concept of unconformity bounded units ubus extremely useful for purposes of stratigraphic classification and correlation volcanic unconformities erosive and collapse unconformities relative to processes of internal modification of a volcano are classified separately from sea level driven unconformities the erosive unconformities formed during periods of volcanic quiescence are generally characterized by angular relationships and lithological change between the products below and above an unconformity and may be associated with paleosols or epiclastic horizons the collapse unconformities related to calderas and lateral collapses represent surfaces of structural truncation along the collapse borders passing outside of the collapse to erosive unconformities developed during the corresponding repose periods instead the sea level driven unconformities are marine and subaerial erosive surfaces bounding in pairs the depositional cycles relative to sea level highstands which are recorded in raised marine terraces most unconformities can be correlated on a variable scale from local volcanic island to regional inter island by means of careful stratigraphic analysis targeted to identify the corresponding stratigraphic hiatus in the volcanic successions in different points of observation this helps to solve the problems arising from the difficult recognition of the unconformities in the field moving away from the type locality due to their variable features a practical nomenclature scheme for a hierarchy of ubus to be applied in volcanic areas can be established on the basis of the areal magnitude of the bounding unconformities and their importance in the volcano history passing through a slight modification of the international stratigraphic guide s rules combined with lithostratigraphic units mapped rock bodies and lithosomes eruptive centres the ubus provide a useful stratigraphic synthesis of a volcanic area by means of a framework of time stratigraphic unconformable surfaces moreover ubus can be directly interpreted in terms of volcanic activity units with a time stratigraphic significance thus providing the key elements for the eruptive history of a volcano and the definition of its event stratigraphy

paleogene monsoons across india and south china drivers of biotic change monsoonal climates at low latitudes 32 n are an inevitable consequence of seasonal migrations of the inter tropical convergence zone itcz but the character of these monsoons depends on continental configuration orographic expression and the strength of hadley circulation to explore the evolution of monsoon systems across southern asia we compare climate signatures archived in ten paleogene floras from northern india tibet and southern china occupying low palaeolatitudes at a time of extreme global warmth and elevated co2 fossil leaf form reveals that under such hothouse conditions megathermal early eocene to earliest miocene forests were exposed to strong monsoonal climates typical of those experienced today arising from annual migrations of the itcz possibly enhanced by a lower equator to pole temperature gradient throughout the paleogene an elevated tibetan highland produced no discernable modification of this itcz monsoon although rainfall seasonality similar to that of the modern south asia monsoon sam is observed in northern india as early as the beginning of the eocene despite its near equatorial palaeoposition in south china rainfall seasonality increased progressively achieving modern monsoon like wet season dry season precipitation ratios by the early oligocene despite evidencing weak rainfall seasonality overall fossil leaves from south china have exhibited monsoon adapted morphologies comparable to those seen in today s indonesia australia monsoon for at least 45 million years together the indian and south china fossil leaf assemblages show that the evolution of megathermal ecosystems across southern asia has been influenced profoundly by monsoonal climates for at least the last 56 million years the paleogene itcz driven monsoon system strongly impacted india as it transited the equator likely eliminating gondwanan taxa not able to adapt to seasonal precipitation extremes furthermore powerful seasonally reversing winds and associated surface ocean currents are likely to have facilitated two way biotic transfer between india and eurasia long before closure of the tethys ocean

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

late stage volcano geomorphic evolution of the pleistocene san francisco mountain arizona usa based on high resolution dem analysis and 40ar 39ar chronology the cone building volcanic activity and subsequent erosion of san francisco mountain az usa were studied by using high resolution digital elevation model dem analysis and new 40ar 39ar dating by defining remnants or planezes of the volcano flanks in dem derived images the original edifice can be reconstructed we propose a two cone model with adjacent summit vents which were active in different times the reconstructed cones were 4 460 and 4 350 m high a s l corresponding to 2 160 and 2 050 m relative height respectively new 40ar 39ar data allow us to decipher the chronological details of the cone building activity we dated the older and younger andesites of the volcano that according to previous mapping built the stage 2 and stage 3 stratocones respectively the new 40ar 39ar plateau ages yielded 589 556 ka for the older and 514 505 ka for the younger andesites supporting their distinct nature with a possible dormant period between the obtained ages imply an intense final 100 ka long cone building activity terminating 100 ka earlier than indicated by previous k ar ages moreover 40ar 39ar dating constrains the formation of the inner basin an elliptical depression in the center of the volcano initially created by flank collapse a 530 ka age with a 58 4 ka 2 error for a post depression dacite suggests that the collapse event is geochronologically indistinguishable from the termination of the andesitic cone building activity according to our dem analysis the original cone of san francisco mountain had a volume of about 80 km3 of this volume 7 5 km3 was removed by the flank collapse and subsequent glacial erosion creating the present day enlarged inner basin and 2 km3 was removed from the outer valleys by erosion based on volumetric analysis and previous and new radiometric ages the average long term eruption rate of san francisco mountain was 0 2 km3 ka which is a medium rate for long lived stratovolcanoes however according to the new 40ar 39ar dates for the last 100 ka period the final stratovolcanic activity was characterized by a greater 0 3 km3 ka rate

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

the paradox of drowned reefs and carbonate platforms shallow water carbonate platforms and reefs are drowned when tectonic subsidence or rising sea level outpaces carbonate accumulation and benthonic carbonate production ceases drowned platforms are common in the geologic record but they present a paradox if one considers rates of processes involved during the early holocene when sea level rose at rates of 6 000 to 10 000 m yr mm 1 000 yr most reefs and platforms were outpaced by the rising sea during the late holocene with sea level rising 500 to 3 000 m yr in the atlantic caribbean area reefs and platforms started to recover built to sea level and prograded seaward 1 000 m yr is thus a conservative estimate of the average growth potential of modern reefs and platforms independently accumulation rates of prograding platforms in the geologic record suggest growth potential in excess of several hundred microns per year the growth potential of 1 000 m yr exceeds any relative rise of sea level caused by long term processes in the geologic record newly formed ocean crust subsides at a maximum of 250 m yr basin subsidence averages 10 to 100 m yr and sea level rises due to increased sea floor spreading amount to less than 10 m yr rapid pulses of relative rise of sea level or reduction of benthic growth by deterioration of the environment remain the only plausible explanations of drowning the geologic record shows examples of both of these processes global mass extinctions of reefs and platforms occurred in the middle cretaceous eustatic rise due to submarine volcanism or desiccation of a small ocean basin and the late devonian global crisis of ocean environment extraterrestrial cause drowning controlled by regional tectonics prevailed in the jurassic and early cretaceous of the tethyan realm and the drowning of mesozoic platforms in the western north atlantic seems to have been dictated by plate tectonic drift to higher latitudes

foliar physiognomic record of climatic conditions during dormancy climate leaf analysis multivariate program clamp and the cold month mean temperature abstract the extent to which the leaves of woody dicots encode in their physiognomy the climatic conditions that exist during dormancy was tested by sampling 20 sites along an approximately west east transect across european russia the crimean peninsula western siberia and central eastern siberia this transect encompassed the most extreme mean annual temperature range recorded in the modern world where vegetation exists climate leaf analysis multivariate program clamp revealed little change in calibration of the warm month mean temperature compared with the physg3ar data set derived from less extreme sites primarily in north america and japan but significant change with respect to the cold month mean temperature cmmt calibration although clamp underestimated the cmmt by up to 9 c in the coldest sites the addition of the transect sites improved clamp s performance at low temperatures this suggests that winter cold is encoded in foliar physiognomy even though the leaves are functional only duri

the relation of a coastal environment to early diagenetic clinoptilolite zeolite formation new data from the late cretaceous european basin abstract clinoptilolite an authigenic mineral of the zeolite group is commonly considered as a product of rhyolitic volcanic glass transformation during diagenesis of carbonate pelagic hemipelagic sediments of cretaceous paleogene age another subordinate way of clinoptilolite formation that has been suggested in the literature is its precipitation during diagenetic transformation of carbonate sediments enriched with biogenic silica the observations concerning transformation of the latter into zeolite are scarce and mostly based on cretaceous pelagic hemipelagic and shallow marine deposits and post cretaceous sediments in which there was no volcanic material the mechanism of diagenetic clinoptilolite formation in volcanic free sediments as well as the role of the depositional setting in its precipitation is not well understood in carbonates of the nw part of the european basin west side of the ysogory dobrogea archipelago studied here the clinoptilolite is associated with opal ct from the dissolution of sponge spicules and a detrital clays are documented for the first time in a cretaceous coastal environment the carbonates were deposited in a coastal environment which was under the influence of weak currents delivering sponge spicules biogenic opal from the offshore zone and the terrestrial input was transported by rivers from a neighboring island the lush plant vegetation with numerous pteridophytes and conifers within a warm sub tropical or tropical and humid climate enhanced the terrestrial weathering of clays and feldspars this unique combination of elevated silica concentrations from sponge spicules dissolution and aluminum availability from terrestrial weathering of feldspars in a subtropical climate during the early diagenesis combined with alkalinity triggered by organic matter decomposition enhanced the clinoptilolite formation a few centimeters below the seabed the investigation demonstrates a novel route by which pore fluids enriched with silica and aluminum initiate clinoptilolite formation during the very early stage of diagenesis a few centimeters below the seafloor the clinoptilolite distribution in late cretaceous silica rich deposits with no volcanic input of the european basin is always associated with opal ct from sponge spicules and elevated terrestrial input clays taking into account the distinctive campanian maastrichtian sedimentation in the epicontinental european basin composed almost exclusively of pure pelagic carbonates the depositional settings in which the silica and aluminum were available in pore waters was restricted to the part of the basin influenced by terrestrial input this leads to the conclusion that clinoptilolite formation in volcanic free sediment is an indicator of not only enhanced sponge silica availability but also the close proximity of the source area

forward modelling of carbonate platforms sedimentological and diagenetic constraints from an application to a flat topped greenhouse platform triassic southern alps italy abstract quantitative analysis of depositional systems using numerical models can provide insights into the interaction of sedimentological and diagenetic processes difficult to interpret from observation of the geological products alone numerical models can highlight the interactions between controlling parameters and generate best estimate simulations of case studies from the geological record different data sources e g outcrop data uniformitarian constraints paleogeography need to be considered in the process of defining the parameters required to produce models that honour individual case studies we present a best estimate forward model of a high relief triassic carbonate platform southern alps italy generated using carb3d a 3d process based forward modelling package able to simulate sedimentary facies geometries and early diagenesis of isolated carbonate platforms the parameters used for the presented forward model have been deduced by the study of architectural sedimentological and diagenetic features of the platform and by data from modern and ancient analogues sensitivity analysis is used to tune values of the parameters within ranges defined from field laboratory and uniformitarian constraints critical evaluation of the model allowed 1 verification of the validity of the used parameters 2 evaluation of the interaction between controlling parameters 3 development of a numerical model that can be used for quantitative elaborations furthermore the process of generating the numerical model required a detailed interpretation of field and laboratory data crucial to define the required input parameters modelling the studied carbonate platform also enabled evaluation of the effects of the interaction between productivity environmental energy and creation of accommodation space promoting the understanding of their role on the architecture of carbonate systems forward modelling also allows the integration of data from conventional data sets with data from present day observations and seismic geometries promoting a transition from a qualitative to a semi quantitative quantitative sedimentological approach forward models can further be used to parameterise petrophysical properties of complex geobodies with potential application for the management of georesources

strontium isotope stratigraphy of enewetak atoll sup 87 sr sup 86 sr ratios determined for samples from a 350 m core of neogene lagoonal shallow water limestones from enewetak atoll display a remarkably informative trend like the recently published data for deep sea drilling project dsdp carbonates sup 87 sr sup 86 sr at enewetak increases monotonically but not smoothly from the early miocene to the pleistocene the data show intervals of little or no change in sup 87 sr sup 86 sr punctuated by sharp transitions to lower values toward greater core depths the sharp transitions correlate with observed solution disconformities caused by periods of subaerial erosion whereas the intervals of little or no change in sup 87 sr sup 86 sr correspond to intervals of rapid accumulation of shallow water carbonate sediments when converted to numerical ages using the published dsdp 590b trend the best resolved time breaks are at 282 m 12 3 to 18 2 ma missing and 121 6 m 3 0 to 5 3 ma missing below the lagoon floor at enewetak sr isotopes offer a stratigraphic resolution for these shallow marine neogene carbonates comparable to that of nannofossil zonation in deep sea carbonates 0 3 3 m y in addition the correlation of times of sr isotope breaks at enewetak with times of rapid sr isotope change in the dsdp 590b samples confirms the importance ofmore sea level changes in the evolution of global marine sr isotopes and shows that the sr isotope response to sea level falls is rapid less

morphological and statistical characterisation of recent mafic volcanism on tenerife canary islands spain abstract tenerife is the largest island of the canarian archipelago and presents a complex volcanic history the construction of a mafic shield and a phonolitic composite volcano represent the main features of the volcanic evolution of the island both volcanic complexes are still active the first through two main rift zones and the second through the teide pico viejo central complex up to 297 mafic monogenetic volcanoes can be recognised on tenerife most of them corresponding to scoria cones that can been grouped into five geographical volcanic fields characterised by similar volcanological features the large number of these edifices compared to the other existing morphological volcano types indicates that they represent the most common eruptive events occurring during tenerife s recent geological past and therefore the type with the shortest recurrence period and the most likely to occur in the near future in this paper the most frequent mafic monogenetic volcano is defined by means of the statistical analysis of its main volcano morphological features cone height cone width ratio crater width crater depth etc we have applied a simple methodology of our own design based on statistical correlations and modal intervals of the morphological and morphometric parameters best defining the volcanoes morphology the most frequently identified mafic monogenetic volcano corresponds to a scoria cone with strombolian to violent strombolian dynamics 100 high and 3 in volume covering an area of 2 by defining this most common mafic volcano or volcano type we may provide key information on the nature of a potential volcanic event on tenerife in the future

synthetic stratigraphy of carbonate platform and basin systems a forward numerical model of the carbonate platform and basin depositional system aids in understanding the roles played by different variables in controlling the growth patterns of carbonate platforms and thus their internal facies architecture the numerical model simulates the two dimensional development of a carbonate platform and adjacent basin by successively calculating and depositing discrete sediment budgets generated over short time periods 10 sup 4 yr and displaying the results in synthetic cross sections through the carbonate buildup a series of model experiments shows that the effect of changing the eustatic sea level is largely dependent on the rate of subsidence in general sea level fluctuations tend to restrict progradation of the platform by producing periods of exposure of the platform top that decrease the overall sediment budget available for deposition on the marginal slope either increasing the amplitude or decreasing the period of the sea level cycle also restricts progradation which suggests that the higher order short period sea level cycles that are evident in the rock record may play an important role in controlling the cross sectional geometry of carbonate platforms forward models such as the one presented here may provide a basis for creating an inverse model that could be used tomore closely constrain the variables such as sediment production rate subsidence and sea level history that led to the cross sectional geometry observed in the field or in a seismic section less

palaeoclimate estimates for the middle miocene schrotzburg flora s germany a multi method approach we present a detailed palaeoclimate analysis of the middle miocene uppermost badenian lowermost sarmatian schrotzburg locality in s germany based on the fossil macro and micro flora using four different methods for the estimation of palaeoclimate parameters the coexistence approach ca leaf margin analysis lma the climate leaf analysis multivariate program clamp as well as a recently developed multivariate leaf physiognomic approach based on an european calibration dataset elpa considering results of all methods used the following palaeoclimate estimates seem to be most likely mean annual temperature 15 16 c mat coldest month mean temperature 7 c cmmt warmest month mean temperature between 25 and 26 c and mean annual precipiation 1 300 mm although cmmt values may have been colder as indicated by the disappearance of the crocodile diplocynodon and the temperature thresholds derived from modern alligators for most palaeoclimatic parameters estimates derived by clamp significantly differ from those derived by most other methods with respect to the consistency of the results obtained by ca lma and elpa it is suggested that for the schrotzburg locality clamp is probably less reliable than most other methods a possible explanation may be attributed to the correlation between leaf physiognomy and climate as represented by the clamp calibration data set which is largely based on extant floras from n america and e asia and which may be not suitable for application to the european neogene all physiognomic methods used here were affected by taphonomic biasses especially the number of taxa had a great influence on the reliability of the palaeoclimate estimates both multivariate leaf physiognomic approaches are less influenced by such biasses than the univariate lma in combination with previously published results from the european and asian neogene our data suggest that during the neogene in eurasia clamp may produce temperature estimates which are systematically too cold as compared to other evidence this pattern however has to be further investigated using additional palaeofloras

scalloped bank margins beginning of the end for carbonate platforms bathymetric seismic reflection and satellite data have revealed the common existence of a new type of carbonate bank margin scalloped margin throughout the gulf of mexico and the caribbean region these large up to tens of kilometres across irregular convexbankward embayments are interpreted as predominantly erosional features produced by large scale failure of platform margins in tectonically active areas they may be triggered by earthquake shocks whereas in stable regions they may more likely be the result of undercutting by dissolution and or deep water currents scalloped margins are common in the south eastern bahamas this suggests that these relatively small isolated bahama banks may be erosional remnants of once larger platforms the processes that create scalloped margins may result in erosional deep water carbonate basins and potentially the demise and disintegration of carbonate platforms

a comparison of shear strength in calcareous and siliciclastic marine sediments abstract more than 2000 measurements of shear strength versus depth in fine grained marine sediments were collected from the literature and our own experiments in order to study the relationship between carbonate content and strength behavior of marine sediments depositional environments include slope rise and abyssal plain with most data originating from the slopes the depth range is restricted to 6 m subbottom depth in order to minimize diagenetic effects contour plots of shear strength versus depth for calcareous and siliciclastic sediments clearly reveal different trends whereas shear strength in siliciclastic sediments shows low variability and increases only gradually with depth the shear strength in the calcareous population is highly variable and increases rapidly with depth the difference in strength behavior of the two sediment groups has implications for the stability of submarine slopes previous research has shown that carbonate sediments build up steeper and more variable slopes than siliciclastic sediments this difference in slope angle can be explained at least in part by the higher internal strength of the carbonate sediments

morphometrical and geochronological constraints on the youngest eruptive activity in east central europe at the ciomadul csomad lava dome complex east carpathians abstract the timing of late pleistocene volcanic activity of the ciomadul csomad dacitic lava dome complex site of the youngest eruptions in the carpathians has been constrained by morphometric analysis and radiometric chronology pelean domes and asymmetric domes coulees built up the volcano including the central edifice that hosts the youngest twin craters of mohos mohos peat bog and lake st ana szent anna a comparative digital elevation model dem based morphometric analysis of lava domes 29 worldwide examples including 5 domes from ciomadul shows that it is the mean slope of the upper dome flank that correlates best with age although the logarithmic relationship is only moderately strong r 0 80 slope characteristics of the ciomadul domes fit to those of 10 100 ka old domes these young ages contradict the previous k ar dates giving as old as 1 ma ages on a number of domes but are supported by ongoing u pb and u th he zircon dating the latter methods constrain the whole volcanic activity to the past 250 ka and the emplacement of most lava domes within the period of 150 100 ka the volcanism at ciomadul produced alternating effusive and explosive eruptions including lava dome collapses and successive crater formations the latest possibly subplinian explosive event formed the well preserved st ana crater radiocarbon dating of organic remains from a sediment core that reached 11 m into the lacustrine infill of st ana suggests that the crater was formed prior to 26 000 years bp

the use of a resemblance function in the measurement of climatic parameters from the physiognomy of woody dicotyledons abstract wolfe compiled a data set clamp of the physiognomy of woody dicotyledon leaves with a view to using it to extract climatic information from fossil floras attempts made using these data to identify and describe the relationship between plant physiognomy and climate have all searched for a global relationship applicable throughout data space we investigate the possibility that the relation between climate and physiognomy is so non linear that only local relationships should be sought we use a resemblance function to select sites that are physiognomically similar to each unknown site these similar sites alone yield a climatic estimate for the unknown site data collected from new zealand and australia are then added to wolfe s data set in order to test this new method we show that the use of a resemblance function enables us to produce mean annual temperature estimates for all modern sites that lie within 2 6 c of meteorological data for 90 of the sites this method also allows the objective identification of outliers based on their distance in physiognomic space from their nearest neighbours when a method is used that searches for a global relationship between physiognomy and climate the misfit of estimated mean annual temperature for the combined southern hemisphere and clamp sites is almost twice as great 5 c as that to the clamp sites alone in contrast when the resemblance function is used the rms misfit of estimated mean annual temperature increases by only 0 2 c this result demonstrates the robustness of the new method

cenozoic paleotemperatures and leaf physiognomy a european perspective for 21 european leaf floras with a focus on central europe which span a stratigraphic range from the late eocene to the pliocene paleoclimate estimates have been calculated using five different quantitative techniques a leaf margin analysis lma1 using a regression model based on data from east asia b the multivariate climate leaf analysis multivariate programm clamp technique based on data from east asia and n america c a recently developed multivariate technique based on modern european vegetation elpa d a provisional lma regression model based on the vegetation of several wet localities from n america lma2 and e the coexistence approach ca a technique based on comparisons with the nearest living relatives nlrs of fossil taxa according to our results there seems to be certain discrepancies where the different techniques are compared for paleotemperatures estimates depending mainly on the stratigraphic age of the floras for paleogene floras both multivariate leaf physiognomic techniques are in rather good agreement with ca although both techniques may differ considerably from each other in contrast for the neogene clamp shows a tendency to produce estimates that are considerably colder than ca whereas elpa provides generally warmer estimates and is in better agreement with ca and other independent evidence our results and interpretations add some caveats to temperature reconstructions based on leaf physiognomy especially when applied to european floras from older periods i e paleogene cretaceous possible changes of the relationship between climate and leaf physiognomy over time should be taken into account as a possible source of error whenever such techniques are used there is the possibility that the actual correlation between climate and leaf form may be modified by long time evolutionary responses or floral changes leading to erroneous paleoclimate estimates if a calibration data set is used which is not suited for the region and time interval in question however further research will be needed to test whether such changes in the relationship between climate and leaf physiognomy over time can also be detected on other continents or whether this is a problem restricted to europe

bahamian carbonate platform development in response to sea level changes and the closure of the isthmus of panama in this paper we show that the development of the sediment architecture at the leeward toe of slope of great bahama bank ocean drilling project leg 166 bahama transect during the last 6 ma is not only a response to sea level fluctuations but also to major paleo oceanographic and climatic changes a major sequence boundary close to the miocene pliocene boundary dated at 5 6 5 4 ma is interpreted to reflect a major sea level drop that was followed by a sea level rise which led to the re flooding of the mediterranean sea at the end of the messinian and increasing sea surface temperatures at great bahama bank distinct erosional horizons occurred during the pliocene dated at 4 6 and 3 3 3 6 ma related to sea level change and the intensification of the gulf stream when the emergence of the isthmus of panama reached a critical threshold the gulf stream brings warm saline and nutrient poor waters to the bahamas starting at the early late pliocene boundary at 3 6 ma this paleo oceanographic reorganization in combination with enhanced sea level fluctuations associated with the late pliocene main intensification in northern hemisphere glaciation since 3 2 ma led to 1 a gradual change from a ramp type to a flat topped type morphology and 2 a change from a skeletal to a non skeletal dominated sedimentary system mainly peloidal increased sea level fluctuations during the second half of the pleistocene led to an intensified high stand shedding depositional pattern within the surrounding basins

gis methods applied to the degradation of monogenetic volcanic fields a case study of the holocene volcanism of gran canaria canary islands spain abstract modeling of volcanic morphometry provides reliable measurements of parameters that assist in the determination of volcanic landform degradation variations of the original morphology enable the understanding of patterns affecting erosion and their development facilitating the assessment of associated hazards a total of 24 volcanic holocene eruptions were identified in the island of gran canaria canary islands spain 87 of these eruptions occurred in a wet environment while the rest happened in a dry environment 45 of holocene eruptions are located along short barrancos s type less than 10 km in length 20 along large barrancos l type 10 17 km in length and 35 along extra large barrancos xl type more than 17 km in length the erosional history of holocene volcanic edifices is in the first stage of degradation with a geomorphic signature characterized by a fresh young cone with a sharp profile and a pristine lava flow after intensive field work a careful palaeo geomorphological reconstruction of the 24 holocene eruptions of gran canaria was conducted in order to obtain the digital terrain models dtms of the pre and post eruption terrains from the difference between these dtms the degradation volume and the incision rate were obtained the denudation of volcanic cones and lava flows is relatively independent both their geographical location and the climatic environment however local factors such as pre eruption topography and ravine type have the greatest influence on the erosion of holocene volcanic materials in gran canaria although age is a key factor to help understand the morphological evolution of monogenetic volcanic fields the gran canaria holocene volcanism presented in this paper demonstrates that local and regional factors may determine the lack of correlation between morphometric parameters and age consequently the degree of transformation of the volcanic edifices evolves in many cases independently of their age

a pennsylvanian microbial boundstone dominated carbonate shelf in a distal foreland margin picos de europa province nw spain abstract a pennsylvanian bashkirian moscovian high rising microbial boundstone dominated carbonate platform 12 000 km2 developed in the external margin of a variscan foreland basin intensely studied in the northern domain cuera area the stratigraphy and sedimentology of the southern domain the picos de europa province is here revisited distribution of the bashkirian facies valdeteja formation defines a ramp low angle platform with an internal zone central and eastern sectors of the picos de europa province consisting of huge amounts of massive cement rich microbial boundstones surrounded by an external zone comprising lower slope boundstone derived breccias and basinal lime mudstones from the bashkirian moscovian transition to the early kasimovian picos de europa formation the carbonate platform moderately aggraded acquiring a high rising and flat topped geometry and then prograded rapidly into the external zone where platform derived carbonate sediment and clay sourced from the orogen were deposited seismic scale exposures of the western margin of the shelf show angular bedding relationship between basin toe of slope slope and platform top stratal domains with slope inclination up to 32 and a topographic relief of 550 m the platform evolution above described for the picos de europa province significantly differs with respect to the cuera area where platform mostly prograded during the bashkirian and subsequently aggraded during early moscovian the evolutionary differences between these two carbonate domains which are geographically close are interpreted as changes in tectonic subsidence distribution acting as the major factor controlling the large scale platform geometries in the active foreland basin context finally the tectonic overload due to the emplacement of the cuera thrust sheets during the moscovian kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform top cycles in the picos de europa province

growth and erosion rates of the east carpathians volcanoes constrained by numerical models tectonic and climatic implications abstract the east carpathian volcanic range experienced an along arc late miocene to quaternary migration of eruptive activity during its 11 ma long activity here a novel and complex methodology is presented that yields new geochronological and geomorphological constraints on the evolution of the 20 volcanic edifices new unspiked k ar ages either constrain their lifespan 6 79 0 10 6 47 0 09 ma for seaca t tarca 5 47 0 08 4 61 0 07 ma for v rghis or date the youngest volcanic activity central c limani in parallel numerical reconstructions of volcanic paleo topographies were performed to quantify their shape at the end of their construction stage the inferred initial volcano size shows a wide range 3 to 592 km3 making up the four main successive volcanic segments 910 880 279 and 165 km3 for c limani gurghiu north harghita and south harghita segment respectively totalizing 2200 km3 and an average growth rate of 200 km3 ma at range scale at the volcano scale with only consideration to their respective time spans i e avoiding repose periods growth rate is characterized by two major trends a moderate growth rate 137 km3 ma for the older volcanoes 11 3 6 ma followed by a lower growth rate 28 km3 ma obtained for the plio quaternary volcanoes comparing reconstructed and current topographies yielded a total eroded volume of 524 125 km3 defining averaged denudation of 22 and a 20 m ma erosion rate erosion rates for major climatic periods were computed which highlight the contrasting climatic contexts since 11 ma the highest erosion rate 38 m ma occurred during transitional moderate subtropical continental climate period 9 5 8 2 ma an intermediate erosion rate 14 m ma characterized a moderate continental climate period 8 2 6 8 ma when conditions became less humid the lowest erosion rate 7 m ma reflects the prevailing continental but occasionally semi arid climate 6 8 5 8 ma the highest erosion rate 28 m ma was obtained for plio quaternary times during the interglacial glacial cycles such a quantitative morphometric and geochronological approach demonstrates its efficiency to study volcanic dynamism including both constructional and erosional processes through time

reworked paleogene to early neogene planktic foraminifera implications of an intriguing distribution at a late neogene prograding margin bahamas abstract a rich uniquely distributed assemblage 80 species of reworked paleogene to early neogene 66 15 ma planktic foraminifera is documented within 470 m of late neogene 5 7 1 6 ma borehole limestone from the great bahama bank west margin tests vary in size from 0 13 to 1 0 mm and are unusually well preserved where obtainable from the rock the relict species constitute an estimated 20 to 50 of all taxa paleocene faunas occur in upper miocene host rocks eocene species occur in upper miocene and basal upper pliocene rocks and mixed oligocene and early miocene taxa occur throughout the section including the uppermost pliocene i e the oldest groups disappear successively uphole each host rock interval is separated by major disconformities this record provides a substantial proxy for 1 a probable source feature an epipelagic marine tectonic wall escarpment or outcrop composed of pelagic and hemipelagic sediments 2 a probable tectonically active source area northern cuba or southern bahamas and 3 a variety of events that span 60 myr and have wide ranging implications from local progressive isolation of the oldest faunas to regional changes in water depth indicated by the faunas to global hiatuses that correlate with one or more major sequence boundaries in the atlantic bahamas and gulf of mexico as well as proposed eustatic lowstands seven unidentified foraminiferal biozones correspond to a proposed early eocene composite condensed section on the eustatic curve and may have regional implications the relict faunas also have significant implications for the timing and types of paleogene and early neogene sedimentation or nondeposition sea level fluctuations slumping or changing depth of effective marine erosion and regional late neogene events that occurred over 4 myr age of host rocks the direction of the source area from the secondary emplacement site and the estimated percentages of relict faunas indicate that not all the microfossils in the late neogene borehole sediments and by extrapolation therefore along the entire west margin of the platform were locally derived the amount of a possible attendant sedimentary component is not known

computer modeling the internal architecture of carbonate platforms a numerical computer model is described that calculates the internal architecture of carbonate platforms in response to varying values of carbonate production subaerial and submarine erosion sediment redeposition and sea level changes the computer generated sections closely resemble large scale outcrops and interpreted seismic profiles through carbonate platforms stillstand and transgressive sequences have prograding and downlapping platform geometries with lagoons developing in transgressive systems regressive sequences have downlapping clinoforms and erosional upper surfaces glacioeustatic scale cycles have a major control on platform geometry with erosional sequence boundaries developing during low stands and platform drowning occurring during transgressive periods lowstand downlapping wedges are minor features when compared with clastic systems and major progradation and downlap of slope deposits develop with transgressions and flooding of platform tops carbonate erosion rates are varied and have an important effect on the morphology of foodback surfaces which have a major control on platform top production the computer program contributes to the analysis of carbonate systems in two ways it gives a visual picture of the quantitative effects of the many parameters controlling carbonate geometries and it aids quantitative analysis of the architectures and time scales of ancient outcrop or seismic sequences

bahama carbonate platforms the deep and the past abstract carbonate deposition prevailed for 150 ma in the bahama florida segment of the west atlantic margin and provides an interesting test for actualism present day facies patterns on the banks are controlled by the backward decrease of waves and tides and the concomitant increase of temperature and salinity variation in the troughs influx of sand and rubble from gravity flows varies with topography and distance from shallow water sources and allows one to define facies belts a rhythmic sequence of ooze and graded beds on the basin floors subdivided into a basin margin belt of coarse thick turbidites and basin interior with fine turbidites slope facies change with increase in height and declivity from accretionary to by pass to erosional regimes stratigraphic history of the bahamas is not simply a projection of the holo scene back in time both long term natural evolution decrease in subsidence upbuilding of the banks submarine erosion and outside factors climate eustacy have caused significant changes since the jurassic the bahamas seem to have evolved from a clastics evaporite province to a single carbonate evaporite platform and finally to an array of platforms and troughs during the platform trough stage the rate of upbuilding of the platforms decreased submarine canyon erosion increased platform flanks steepened as they grew higher and changed from accretionary to by pass to erosional slopes a change imposed by extraneous factors occurred in the pliocene when the great bahama bank changed from a giant reef rimmed atoll to a flat platform covered by oolites and peloid sands the bahamas share both long term trends as well as random changes by extraneous factors with other platforms in the geologic record compared to ancient platforms however they are unusually long lived and at a more advanced stage of growth they are deeply dissected by erosion their flanks are unusually high and steep and the troughs very narrow the neogene platform sequence is strongly controlled by eustatic sea level fluctuations

reef geometries erosion surfaces and high frequency sea level changes upper miocene reef complex mallorca spain the upper miocene reef complex of mallorca is a 20 km prograding unit which crops out in sea cliffs along the southern side of the island these vertical and exceptionally clean outcrops permit i identification of different facies lagoon reef front reef slope and open platform and their geometries and boundaries at different scales ranging from metre to kilometre and ii construction of a 6 km long high resolution cross section in the direction of reef progradation this cross section shows vertical shifts of the reefal facies and erosion surfaces linked to a general progradational pattern that defines the accretional units four hierarchical orders of magnitude 1 m to 4 m of accretional units are identified by consideration of the vertical facies shifts and by which erosion surfaces are truncated by other erosion surfaces all these orders show similar patterns horizontal beds of lagoonal facies in the upper part landward reefal and slope facies with sigmoidal bedding in the central part and open platform facies with subhorizontal bedding in the lower part basinwards the boundaries are erosion surfaces horizontal over the lagoon facies dipping basinwards over the reef front facies and connecting basinwards with their correlative conformities over the reef slope and open platform facies the four orders of accretional units are interpreted in terms of four 1 m to 4 m hierarchies of sea level cycles because i there is a close relation between the coral growth and the sea surface ii there are vertical shifts in the reefal facies and their relation to the erosion surfaces and iii there was very little tectonic subsidence in the study area during the late miocene additionally all these units can be described in terms of their position relative to the sea level cycle i the reefs prograde on the open platform sediments during low stands of sea level ii aggradation of the lagoon reef and open platform facies dominates during sea level rises and the lagoonal beds onlap landwards upon the previous erosion surface iii reefal progradation occurs during high stands of sea level and iv the 2 m sea level fall produces an off lapping reef and there is progradation with downward shifts of the reefal facies and erosion landward on the emerged older reefal units a erosion surfaces the 3 m and 4 m sea level falls produce only erosion b and c erosion surfaces although precise age data do not exist at present some speculations upon the frequency of these miocene relative sea level cycles can be made by comparisons with pleistocene cyclicity there is a good correlation between the miocene 2 m cycles and the 100 ka pleistocene cycles consequently the 1 m cycles can be assigned to a fourth order in relation to previously proposed global cycles and the 2 m to fifth order cycles all these accretional units could be defined as sequences according to the definition as commonly used in sequence stratigraphy however they represent higher than third order sea level cycles but are not parasequences the term subsequence therefore is suggested to define a part of a sequence bounded by erosion surfaces mostly subaerial and their correlative conformities basinwards a hierarchy of subsequences can be established

late cretaceous campanian leaf and palynoflora from southern skane sweden a late cretaceous campanian leaf megaflora from the vomb trough in southern skane sweden has been investigated on the basis of collections held at the swedish museum of natural history the mai

computer simulation of the influence of basin physiography on condensed section deposition and maximum flooding abstract sequence stratigraphic analysis commonly involves the correlation of condensed sections which are widely used as chronostratigraphic markers condensed sections represent periods of very slow deposition due to sediment starvation and have generally been equated with the maximum flooding surface which is most commonly inferred to occur at sometime between the maximum rate of relative base level rise and the highest point of relative base level however similar sediment starvation can be produced by a rapid landward shift in the shoreline over large distances during the early stages of a base level rise over a very low gradient surface condensed section deposition therefore does not always correspond to a period between the maximum rate of relative base level rise and the highest point of relative base level but can be initiated earlier than the maximum rate of relative base level rise or conclude after the highest point of relative base level the initial timing and the duration of condensed section deposition is therefore influenced by basin physiography basin physiography can also contribute to a diachronous maximum flooding horizon lying at different levels throughout a basin because the rate of change in accommodation during fluctuating base level is partially dependent on the slope of the basin surface these principles are illustrated in the paper by computer simulations

carbonate platform flanks slope angle and sediment fabric more than 20 examples of fossil carbonate platform systems were compared for slope angle and sediment fabric plots of slope angle versus sediment fabric show that grainy non cohesive mud free sediments build steeper slopes than muddy cohesive sediments examples near the end members of grainy and muddy carbonate platform flanks are found in the triassic of the dolomites in northern italy and in the bahamas respectively they document the flank geometry and the processes readjusting the slope profile once the limiting slope angle is exceeded the grainy flank sediments in the dolomites modified by shearing and avalanching produce straight slope profiles with declivities up to 35 whereas the muddy bahamian flank sediments modified by large scale creep and rotational to translational sliding and slumping produce a concave upwards slope profile inclined at less than 4 the comparison between slope angle and sediment fabric indicates that the physical behaviour of sediments in the gravity field angle of shearing and mode of readjustment processes is linked to the composition of the slope sediment among the variables such as sea level subsidence climate plate motion and oceanographic setting windward leeward sediment fabric is suggested to be a major if not the major control on slope angle and slope curvature of carbonate platform flanks besides the recently documented tendency of carbonate sediments to build steeper slopes than siliciclastics this proposed relation sheds new light on the analysis and quantification of the variables influencing the geometry and depositional evolution of carbonate systems furthermore it provides an opportunity to deduce sediment composition from seismic lines and predict lithology prior to drilling

palaeobotanical evidence for a marked temperature increase following the cretaceous tertiary boundary correspondence analysis of dicot leaf physiognomy of modern vegetational samples from a wide range of environments indicates that 70 of physiognomic variation corresponds to water or temperature factors or both despite wide variation in single physiognomic characters overall trends can be used to distinguish between samples from different climates some climate parameters are well correlated with changes in physiognomy so that climate characteristics can be inferred from physiognomic analyses here i apply this climate leaf analysis multivariate program clamp to leaf assemblages from the cretaceous tertiary boundary the results indicate a fourfold increase in precipitation at the boundary and an increase in mean annual temperature of 10 c these levels persisted for 0 5 1 0 myr after which prea cipitation decreased to about three times the values for the latest cretaceous and the mean annual temperature decreased to 5 6 c above latest cretaceous values

the latemar a middle triassic polygonal fault block platform controlled by synsedimentary tectonics abstract detailed field mapping of a middle triassic carbonate buildup the latemar in the western dolomites northern italy has been carried out the latemar is an isolated carbonate buildup that nucleates on a fault bounded structural high horst cut into the underlying late anisian carbonate bank of the contrin fm this study demonstrates that extensional synsedimentary tectonics is the main factor controlling its geometry and provides an age for this tectonic phase in an early phase slopes were mostly composed of well bedded clinostratified grainstones and rudstones in a later stage the deposition of grainstones was accompanied by the emplacement of clinostratified megabreccias the upper portion of slopes is a microbial boundstone with abundant tubiphytes and patches or lenses of grainstone boundstones may occasionally expand into the platform interior and downward to the base of the slope the depositional profile was that of a mounded platform the buildup is dissected by a dense framework of high angle fractures and faults and by magmatic and sedimentary dikes exhibiting two principal directions trending nnw sse and ene wsw faults trending wnw ese were also observed magmatic dikes are related to the emplacement of the nearby predazzo intrusion and are thus upper ladinian kinematic indicators of strike slip activity were observed on fault planes trending nne ssw and nnw sse that can be attributed to cenozoic alpine tectonics faults magmatic dikes and sedimentary dikes show systematic cross cutting relationships with strike slip faults cutting magmatic dikes and magmatic dikes cutting sedimentary neptunian dikes ene wsw and wnw ese faults are cut by all other structures and record the oldest tectonic activity in the region structural analysis attributes this tectonic phase to an extensional stress field with a direction of maximum extension oriented ca n s several lines of evidence including sealed faults and growth wedge geometries allow us to recognize this old tectonic phase as syndepositional and to date it to the latest anisian avisianum and crassus ammonoid biochronozones the horse shoe shape of the platform and its margins rectilinear for long tracts are explained by the existence of a network of extensional faults whose activity lasted for part of the growth of the platform the latemar is thus a polygonal fault block platform controlled by synsedimentary tectonics the resulting sedimentary architecture is that of a growth wedge deposited probably on the uplifted side of a submerged half graben continuous reactivation of faults at platform margins locally determined anomalous facies transitions with well layered platform interior directly in contact with the clinostratified slopes

rates and factors of stratovolcano degradation in a continental climate a complex morphometric analysis for nineteen neogene quaternary crater remnants in the carpathians abstract the systematic age progression of the neogene quaternary volcanic chain in the carpathians manifested in progressively degraded stratovolcanoes from south to north offers a great opportunity to calculate erosion rates and the factors that control degradation in a moderate continental climate using available and newly determined k ar ages for the cessation of volcanism of nineteen stratocones a great number of morphometric variables including crater diameter and perimeter intracraterial valley length valley order and density dip of internal and external crater rim cone diameter relative height cone diameter height above and distance from base level etc has been examined by regression and factor analyses on the one hand the erosion rates which are calculated from the regression equations of a given characteristic versus age seem to answer the question of to what extent the stratovolcanoes are degraded numerical values of crater enlargement 109 m ma internal valley growth 1 3 km ma average cone lowering 31 5 m ma etc are given moreover using multiple regression equations as age equations the age of any volcano in the same climate can be estimated from the measured characteristics on the other hand there are morphometric characteristics e g dip of crater rim crater circularity intracraterial valley density which are not functions of time three major factors i e the time factor about 40 the size depth factor about 24 and the erosional distance factor about 10 account for about 75 of the stratovolcano characteristics variance and two additional factors eruption style magma viscosity and the central manifestation of volcanism may be responsible for a further 13

sedimentary patterns and geometries of the bahamian outer carbonate ramp miocene lower pliocene great bahama bank core logging and high resolution seismic data from odp leg 166 were used to analyse deposits of the neogene miocene lower pliocene bahamian outer carbonate ramp ramp sediments are cyclic alternations of light and dark grey wackestones packstones with interbedded calciturbidite packages and minor slumps cyclicity was driven by high frequency sea level changes light grey layers containing shallow water bioclasts were formed when the ramp exported material whereas the dark grey layers are dominantly pelagic calciturbidites are arranged into mounded lobes with feeder channels internal bedding of the lobes shows a north directed shingling as a result of the asymmetrical growth of these bodies calciturbidite packages occur below and above sequence boundaries indicating that turbidite shedding occurred during third order sea level highstands and lowstands highstand turbidites contain shallow water components such as green algal debris and epiphytic foraminifera whereas lowstand turbidites are dominated by abraded bioclastic detritus gravity flow depocentres shifted from an outer ramp position during the early miocene to a basin floor setting during the late miocene to early pliocene this change was triggered by an intensification of the strength of bottom currents during the tortonian which was also responsible for shaping the convex morphology of the outer ramp the miocene and lower pliocene of the leeward flank of great bahama bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps the contrast between its sedimentary patterns and the well known upper pliocene quaternary slope facies associations of the flat topped great bahama bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base of slope successions

volcanic geomorphology an overview abstract the review examines the role of geomorphology in analyzing the volcanoes on earth five objectives are stressed first classifications of volcanic landforms should be improved to take care of the complexity in volcanic landform generation as magmatic systems style of eruption and the erupted material all influence the morphology second geomorphology should contribute to the science of volcanology through its capability in reconstructing growth stages in complex volcanoes and also in analyzing the structural factors which contribute to the catastrophic collapse of volcanoes third geomorphology can contribute to physical volcanology by assessing the effects of topography on transport erosion and deposition of volcanogenic flows and identifying the sources and climatic tectonic conditions which govern the emplacement of volcaniclastic deposits fourth volcanic geomorphology a identifies sedimentary facies associations b constructs facies models for dynamic volcano delivery systems and c analyzes the characteristics of sediment gravity flows in order to determine relevant parameters for modelling their behaviour fifth process oriented geomorphology is critical in developing accurate methods for measuring rates of geomorphic processes that shape ephemeral volcanic constructs and for evaluating and comparing geomorphic impacts on disturbed catchments and the related hydrologic response before during and after eruptions this should help to refine parameters for the exponential decay model finally volcanic geomorphology is essential for risk assessment through geomorphic hazard zonation and composite risk zonation such treatments are necessary in order to face the enhanced challenge posed by the combination of natural hazards and the increasing number of people who are at risk around volcanoes

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

environmental analysis of the mid latitudinal european eocene sites of plant macrofossils and their possible analogues in east asia article i nfo previously known eocene floras of mid latitudinal europe are analysed using statistical methodologies in order to obtain more reliable palaeoclimatological signals to detect possible climatic fluctuations during this time interval only macrofossil assemblages have been taken into account and subjected to the statistical evaluation called the integrated plant record ipr vegetation analysis which is based mostly on percentages of various components additional palaeoclimatic approaches were employed namely the coexistence approach based on autecology of the nearest living relatives and the physiognomic methods of the leaf margin analysis and climate leaf analysis multivariate program clamp the same statistical approaches have been applied to analogous living vegetation of china and japan for comparative purposes additionally an update of objective statistical tools for the selection of the best suited modern vegetation clamp dataset from 144 site physg3br gridmet3br 173 physg3ar gridmet3ar and 189 physgasia1 gridmetasia1 extant biotopes is proposed including its copy paste excel application

carbplat a computer model to simulate the development of carbonate platforms this paper presents a computer model with two new main components that simulates the development of carbonate platforms first it uses a function for the decrease of carbonate production with depth that combines the photosynthetic growth of carbonate producing organisms and the extinction of light with depth platform growth is simulated with a differential equation incorporating sea level these processes therefore act continuously rather than in steps second it attempts a more realistic approach to predicting carbonate platform slopes by incorporating variation of slope angle with textural composition of the sediment in this model the angle at which slope sedimentation begins depends on the radio between sediment produced on the platform interior mud and that produced on the platform margin sand the shape of the slope is represented by an exponential function that can be changed to accommodate the total amount of slope sediment in the model stratigraphic unconformities due to changing textural composition are produced on the fore reef slopes

quantitative palaeoclimate estimates from late cretaceous and paleocene leaf floras in the northwest of the south island new zealand three new plant macrofossil assemblages were collected from late cretaceous and paleocene fluvio lacustrine sediments of the pakawau and kapuni groups in the northwest of the south island new zealand palaeoenvironmental interpretations were made from each locality and palaeoclimate was deduced from the dicotyledonous angiosperm leaf component of each flora a latest cretaceous pakawau bush road locality flora yielded 58 different dicotyledonous leaf forms the two paleocene collections ian s tip and pillar point track included 23 and 28 dicotyledonous leaf forms respectively quantitative palaeoclimate estimates were obtained using both leaf margin analysis lma and the climate leaf analysis multivariate program clamp temperature estimates suggest that there was a slight cooling from the latest cretaceous into the early paleocene in the northwest nelson region of new zealand supporting similar southern hemisphere palaeoclimate findings from antarctic data consistency in temperature estimates using different methods including lma multivariate leaf morphological analysis clamp oxygen isotope data regional versus local studies and global palaeoclimate models suggests that the mean annual temperature for the pakawau region in the latest cretaceous was between 12 and 15 c lma produced temperature estimates between 6 5 and 8 c for the two paleocene assemblages whereas clamp produced estimates were slightly higher between 9 and 12 5 c 2002 elsevier science b v all rights reserved

volcano basement interaction in the eastern carpathians explaining unusual tectonic features in the eastern transylvanian basin romania abstract evidence of volcano basement interaction related to the neogene quaternary c limani gurghiu harghita volcanic chain cgh in the eastern carpathians romania includes both structural and morphological features the cgh is located roughly between the carpathian thrust and fold arc to the east and the transylvanian basin to the west geological and geophysical data demonstrate basement subsidence along most of the axial part of the volcanic chain the wide volcaniclastic plateau developed preferentially westward by adjoining composite volcanoes extends deep into the transylvanian basin and its surface is tilted toward the chain axis especially in the gurghiu mountains these features strongly suggest late stage or post volcanic basement sagging beneath the volcanoes and related peripheral uplift interpretation of 2d seismic profiles acquired in the transylvanian basin indicates strong influence of the salt related tectonics on the entire post salt sequence the middle to late miocene succession including the volcanic edifices are tilted toward the basin margins the pre salt deposits together with the metamorphic basement are not tilted instead they are progressively uplifted we suggest that the salt related tectonics enhanced by volcano induced compressive tectonics is the main triggering factor the neogene salt tectonics developed under an overall regional compressive stress field the salt withdrawal beneath the upper miocene siliciclastites was amplified by the influence of the weight of the volcanic edifices the post salt succession including the volcanics tilting is related to salt withdrawal processes and rotation of the whole post salt sedimentary succession along the salt layer acting as a detachment surface swarms of small scale west verging reverse faults developed near the cgh volcanic range represent small scale thrust structures accommodating the rotation induced compression in the post salt brittle lithologies the observed tectonic features are characteristic only for the eastern part of the transylvanian basin no such features have been identified along the western margin or elsewhere in the basin the peripheral deformation of the pre volcanic shallow sedimentary basement induced sagging and spreading of the nearby large volcanic edifices this process combined with the effect of increased heat flux may have strongly enhanced salt diapirism as well volcano spreading was asymmetric because the basement at the eastern margin of the volcanic chain consists of brittle mesozoic sedimentary and precambrian metamorphic rocks of the eastern carpathian thrust and fold belt the buttressing effect to the east favored spreading toward the west tectonic features resulted from volcano basement interaction are combined with those related to regional tectonic processes involved in the evolution of the transylvanian basin and the eastern carpathians interplay between regional stress fields and local volcano induced stress may best account for the complexity of tectonic features recorded in the eastern transylvanian basin

seismic architecture and sediment distribution within the holocene barrier reef lagoon complex of mayotte comoro archipelago sw indian ocean twenty gravity cores and a large set of high resolution seismic profiles from various lagoonal settings were studied to determine the holocene sediment distribution and sequence architecture within the mayotte barrier reef lagoon complex the holocene seismic sequence comprises a type 1 sequence with lowstand transgressive and highstand systems tracts the lowstand systems tract consists of a paleosoil horizon formed during subaerial exposure the transgressive systems tract is composed of four depositional systems 1 inner transgressive layer 2 proximal and distal incised valley fills 3 mid lagoonal layer and 4 keep up or catch up fringing and barrier reef sequence the highstand systems tract comprises three depositional systems 1 of a proximal terrigenous wedge 2 mid lagoonal and distal carbonate sands or muds and 3 reefal carbonates our studies show that the nature of the holocene sequence is controlled by the rate and amplitude of sea level rise and environmental changes which are expressed by changes in clastic sediment supply and carbonate production the pre holocene topography and water dynamics steer the vertical and spatial sediment thickness distribution of the holocene additional important parameters are the proximity to a source area carbonate or terrigenous and the width of the depositional area climate dynamics are also of great importance while they determine carbonate production and terrigenous runoff sedimentation rates in the subtidal settings always lacked behind sea level rates thus a steep relief was created keeping most lagoonal parts within the deep subtidal realm in which sediment production was not efficient enough to fill up accommodation space in addition wave and or current energy might prevent the fill up of the lagoon this ultimately resulted in a typical empty bucket morphology only a high amplitude sea level fall would allow the subtidal lagoon to build up to base level unfilled accommodation space therefore must be a very common feature in the geologic record

accumulation of bank top sediment on the western slope of great bahama bank rapid progradation of a carbonate megabank high resolution seismic profiles and submersible observations along the leeward slope of western great bahama bank show large scale export of bank top sediment and rapid progradation of the slope during the holocene a wedge shaped sequence up to 90 m thick is present along most of the slope and consists of predominantly aragonite mud derived from the bank since flooding of the platform 6 8 ka total sediment volume of the slope sequence is 40 80 that of holocene sediment currently retained on the bank maximum rates of vertical accumulation and lateral progradation are 11 15 m ka and 80 110 m ka respectively 10 to 100 times greater than previously known for periplatform muds slope deposition of exported mud during sea level highs appears to have been a major mechanism for the westward progradation of great bahama bank throughout the quaternary this may provide a critical modern analogue for ancient progradational margins

mean annual temperature estimation based on leaf morphology a test from tropical south america abstract are models that predict mean annual temperature mat from leaf morphology applicable globally fifteen models that predict mat from leaf morphology were tested on thirty floral samples from tropical south america to determine the degree to which models based on published data that are primarily from other regions are applicable to floras from tropical south america the models included are based on regional data from north america south america and asia of the fifteen models tested five are simple linear regressions six are multiple linear regressions two are canonical correspondence analyses and two are correspondence analyses followed by nearest neighbor analyses for the seven modern floras with mat 21 c every model overestimates mat for the 23 modern floras with mat 21 c all models produce variable results without a systematic error the range of average model errors is 2 7 7 3 c while the absolute extremes of error are 0 and 15 1 c average 95 predictive confidence intervals range from 1 6 to 6 9 c predicted mat falls within the published standard error of the model for 0 67 of the south american test floras evaluating the seven sites with mat 21 c separately from the 23 sites with mat 21 c shows that no equation accurately estimates mat of the majority of low temperature sites but that four equations accurately estimate 50 of high temperature sites the results suggest that at least for sites of unknown or high elevation mean annual temperature of fossil floras from tropical south america may be better predicted from models based on the leaf morphology of tropical south american floras

the simulation of the sedimentary fill of basins an interactive computer simulation which erects models of sedimentary geometries by filling in a two dimensional basin from both sides with a combination of clastic sediment and or in situ and transported carbonate sediments is described the simulation program is implemented in c using graphical plotting functions data entry including the initial basin configuration the local tectonic behavior the sea level curves the amount and source direction of clastic sediment and the growth rates of carbonates as a function of water depth is performed interactively geometries of clastic and carbonate sediments evolve through time and respond to tectonic movement eustasy and sedimentation clastic modeling includes sedimentary bypass and erosion and sedimentation in alluvial and coastal plains marine shelf basin slope and basin floor settings carbonate modeling includes progradation the development of hard grounds downslope aprons keep up catch up back step and drowned reef settings as well as lagoonal and epeiric settings also included in the model are extensional vertical faulting of the basin sediment compaction and isostatic response to sediment loading sediment geometries are plotted on a graphics terminal as they are computed so the user can immediately view the results based on these observations parameters can be changed and the program rerun until the user is satisfied with the resultant geometry this paper includes output showing the simulation s sensitivity to eustatic sea level variations and variations in sedimentation and subsidence rates also shown are outputs demonstrating the modeling of some examples from the geologic section in the permian basin of west texas and the upper permian of the sichuan basin

offbank transport of carbonate sands along open leeward bank margins northern bahamas abstract vigorous offbank transport of carbonate sands occurs along the west facing leeward open margins of little and great bahama bank large offbank oriented sand waves thick sand bodies covering reefs and shallow water sands mostly non skeletal obtained from adjacent deep flanks all demonstrate the existence of this shallow to deep pathway of sediment transport a variety of data suggests that transport occurs during storms and not during normal tidal current fluctuations an abundance of composite grains as well as vertical sequences of submarine cemented horizons seen via seismic profiling within the marginal sand bodies indicate cyclic periods of relative quiescence followed by moments of intense sediment movement current meter data obtained during six weeks of low wind activity show that critical threshold velocities for sand transport are only barely exceeded during portions of the tidal cycle these flows coupled with higher frequency bottom currents generated by surface gravity waves winnow the sands but do not provide significant net offbank transport offbank sand transport provides material to the shallow and deep bank margins enabling them to expand during sea level highstands each sea level fluctuation is likely to produce within the shallow margins a vertical sequence of basal reefs covered by a thick non skeletal calcarenite capped by a subaerially exposed diagenetically altered surface shallow water sands carried off the marginal escarpment help to construct deep flanks and large sediment drifts

testing a seismic interpretation of great bahama bank with a computer simulation sixty million years of carbonate deposition were simulated to test an interpretation of platform development based on seismic data and limited well control from northwestern great bahama bank seismic profiles of the northwestern great bahama bank document the lateral growth potential of isolated platforms that were welded together by progradation to form the modern bank the mechanism we proposed responsible for an evolution from aggradation to progradation was sediment overproduction on the platform the excess of which was transported offbank and which caused a decrease in accommodation space on the marginal slope progradation occurred in pulses that were interpreted to be the result of third order sea level fluctuations to evaluate the proposed mechanism 15 input p rameters were used to model the platform evolution the simulation program which uses empirical relationships to model basin fill successfully reproduced the geometries seen on the seismic lines indicating that the proposed interplay of mechanisms could have built the observed platform architecture the simulation demonstrated in particular that in a setting like the bahamas a basin must be substantially filled before progradation can take place and that sea level changes can drive the pulses of progradation this implies that laterally stacked sequences often contain the record of sea level changes and therefore have potential use in sequence stratigraphy the simulation can also be used to estimate the quantitative importance of individual factors controlling aggradation and progradation in the bahamas we show how close the balance between aggradation and progradation is and how small changes in the rate of subsidence or accumulation can cause immediate switches from aggradation to progradation in particular we show that the rate of subsidence exerts the major control on the timing of progradation more so than basin width carbonate production rates similar to modern rates were required to produce the necessary sediment input for progradation which suggests that carbonate production has been consistently high since the early tertiary repeated exposure and erosion however have decreased the overall accumulation rate the simula ion also suggests that the asymmetric progradation in the bahamas was only possible where there were extreme differences between windward and leeward conditions with a maximum sediment input of 10 from the windward side

refining clamp investigations towards improving the climate leaf analysis multivariate program clamp climate leaf analysis multivariate program has been used for the past 17 years to estimate palaeoclimatic conditions the reliability and applicability of this method based on leaf physiognomic characters of fossil woody dicots has been widely discussed over the same period the present study focuses on some technical aspects of clamp mainly on its robustness in the context of the theoretical unimodal requirements of canonical correspondence analysis and introduces correction coefficients for these aspects of the statistical approach as a new way of interpreting and improving on clamp estimates this tool was tested on datasets derived from 17 european fossil floras ranging in age from the late oligocene to the pliocene additionally an objective statistical method for the selection of the best suited modern vegetation dataset from 144 site physg3br or 173 physg3ar extant biotopes is proposed

tectonics global changes in sea level and their relationship to stratigraphical sequences at the us atlantic continental margin of geological the principal factors that control the extent of seas through geological time are vertical movements of the lithosphere and global changes in sea level the relative height of the sea surface determines the facies and the thickness of sediments that can accumulate in a sedimentary basin backstripping studies show that the primary factors affecting the subsidence of rifted sedimentary basins are thermal contraction following heating and thinning of the lithosphere at the time of rifting and sedimentary loading factors such as compaction palaeobathymetry erosion and global sea level changes also contribute but their combined affects are small compared to those of thermal contraction and sedimentary loading simple models have been constructed which combine the effects of sedimentary loading and thermal contraction with those of compaction sub aerial erosion and global changes in sea level in the models it was assumed that the lithosphere was heated and thinned by stretching at the time of rifting sedimentary loading occurs by flexure of a lithosphere that progressively increases its flexural rigidity with age following rifting and that sediment compaction and bathymetry change across a basin but do not vary significantly with geological time furthermore different assumptions were made on the magnitude of curves of global sea level changes and the relationship between denudation rate and regional elevation the models show that tectonics in the form of thermal contraction of the lithosphere and flexure and slowly varying global changes in sea level can explain a number of the stratigraphic features of the us atlantic continental margin in this paper some of the implications of these results are examined for studies of a sea level changes through geological time and b the maturation history of continental margin basins

deriving temperature estimates from southern hemisphere leaves abstract the percentage of woody dicots with entire margined leaves in a flora is known to be positively correlated with mean annual temperature leaf margin analysis lma but this relationship is not globally uniform in particular the floras of australia and new zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the northern hemisphere this difference is more marked in new zealand where the lma relationship appears entirely absent here we amass data for both northern and southern hemispheres using standard protocols and show that regional variations in the leaf margin mean annual temperature relationship are real but become less significant when other characters are included even new zealand falls into line and most of the mean annual temperature signal in new zealand floras is encoded in non margin features we introduce a new clamp climate leaf analysis multivariate program calibration dataset for the southern hemisphere comprising leaf physiognomic data from argentina bolivia south africa australia new zealand and other pacific islands that offers comparable precision for climate prediction to similar datasets derived from the northern hemisphere

quantification of large uncertainties in fossil leaf paleoaltimetry 1 estimates of paleoelevation potentially constrain geodynamic models of continental deformation and inform interpretations of landscape and climate evolution one widely used paleobotanical approach reconstructs paleoelevation from the difference in estimated atmospheric enthalpy between a known sea level and a targeted coeval elevated fossil floral site enthalpy is estimated using climate leaf analysis multivariate program clamp on 31 leaf size and shape variables that have been calibrated in living forests errors related to clamp are significantly greater than often reported and there are many sources of large potential error related to this method that are either difficult to quantify or unquantifiable and are thus not documented here we quantify one significant bias toward underestimation of leaf area in the clamp data set 50 that affects all clamp climate estimates including enthalpy crucially errors in paleoelevation when the leaf size bias is included are in the range of 2 km or more at least 2 times the previous estimates and exceeding the plausible paleoelevations of many fossil sites previously published paleoelevations derived from this technique are unlikely to be accurate either in magnitude or in estimated error

magma and sediment ii problems of interpreting palaeovolcanics buried in the stratigraphic column president9s anniversary address 1982 the preservation of volcanoes never more than partial involves a complex interaction of processes and these operate over periods of time which are often undervalued from a review of the relative rates of these processes it seems that short lived structures such as surtseyan ash rings may be preserved albeit in modified form around their whole circumference for larger composite volcanoes however growth and remoulding by activity is balanced by penecontemporaneous and later erosion in such a way that the central and most of the proximal zones are likely to be removed before they can be buried either by transported volcaniclastic or regional epiclastic sediments even the preservation of distal zones may be asymmetrical a one sided hinge line subsidence sedimentation model is therefore suggested to explain the elongate lens shaped aspects of the many extrusive piles known to lie approximately concordantly within stratigraphic sequences formed in both continental and littoral environments

eruptive history of the late quaternary ciomadul csomad volcano east carpathians part ii magma output rates this study which builds on high precision unspiked cassignol gillot k ar age determinations presents an advanced dem based volumetrical analysis to infer long term magma output rates for the late quaternary ciomadul csomad dacitic lava dome complex east carpathians romania the volcanic field of ciomadul developed on the erosional surface of lower cretaceous flysch and 2 ma old andesites and experienced an extended eruptive history from 850 to 30 ka predominantly effusive activity took place during the first stage 850 to 440 ka producing volumetrically minor isolated peripheral domes subsequently after a 250 ky repose interval a voluminous central dome cluster developed in the second stage 200 to 30 ka during the youngest phase of evolution 60 to 30 ka highly explosive eruptions also occurred resulting in the formation of two craters mohos and st ana the calculated 8 00 0 55 km3 total volume of the lava domes which includes the related volcaniclastic 1 57 km3 as well as erosionally removed 0 18 km3 material is in line with dimensions of other medium sized dacitic lava domes worldwide this volume was extruded at an average long term magma output rate of 9 76 km3 my 0 0098 km3 ky however most of the domes 7 53 0 51 km3 were formed in the 200 to 30 ka period implying a significantly increased magma output rate of 37 40 km3 my 0 0374 km3 ky more than 30 times higher than in the first stage within these long term trends individual lava domes of ciomadul e g those with volumes between 0 02 and 0 40 km3 would have been emplaced at much higher rates over a period of years to tens of years the active periods lasting up to hundreds of years would have been followed by repose periods 30 times longer the most recent eruption of ciomadul has been dated here at 27 7 1 4 ka this age which is in agreement with radiocarbon dates for the onset of lake sediment accumulation in st ana crater dates fragmented lava blocks which are possibly related to a disrupted dome this suggests that during the last typically explosive phase of ciomadul lava dome extrusion was still ongoing in a global context the analysis of the volumetric dynamism of ciomadul s activity gives insights into the temporal variations in magma output at lava domes short term day or week scale eruption rates smooth out in long term millenia scale output rates which are tens of times lower

depositional bias and environmental change important factors in sequence stratigraphy abstract differences among depositional systems here called depositional bias strongly influence sequence patterns siliciclastics and shallow water carbonates for instance shed most of their sediment during opposite phases of a sea level cycle lowstand shedding and highstand shedding respectively furthermore the two systems generate their own system specific relief on the sea floor disperse their sediment load along different avenues and differ in the way they are deactivated reefs and carbonate platforms can be drowned whereas siliciclastic deposition can be shut off and renewed at any depth as a consequence of these differences pronounced unconformities drowning unconformities develop where carbonate platforms are terminated and buried by siliciclastics the siliciclastic to carbonate transition tends to be more gradual drowned platforms and drowning unconformities appeared world wide in great abundance in the miocene cretaceous valanginian turonian jurassic toarcian and devonian frasnian famennian examples of drowning unconformities interpreted as sequence boundaries include those of the early cretaceous platforms off new jersey and off morocco the mid cretaceous unconformity in the gulf of mexico and miocene unconformities on top of reefs in the far east the eustatic cycles postulated from sequence stratigraphy are a very unlikely cause for the mass drownings of reefs and platforms either the rates of rise are an order of magnitude lower than the growth potential of platforms or cycle amplitudes are too small or the cycles are too short and subsidence too slow to remove platforms permanently from the photic zone the critical element in the mass drowning seems to be environmental stress that reduces the growth potential of carbonate systems thus drowning unconformities demonstrate the importance of environmental change as a control on sequence development other examples of dominantly environment controlled sequences include slope deposits shaped by shifting currents e g florida and blake plateau and basin fills that were controlled by changes in sediment input related to tectonic alteration of the drainage in the hinterland e g gulf of mexico environmental change must be considered as a third independent factor that competes with eustatic and tectonically driven regional changes of sea level for control of sequences the definition of sequences and sequence boundaries should be broad enough to include the possibility of non sea level controls

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

paleoclimatic estimates from tertiary leaf assemblages a primary obstacle to evaluating numerical modeling of tertiary nonmarine climates has been the significance and reliability of proxy data sloan barron 1990 lacking direct measurements of paleoclimatic parameters inferred paleoclimatic values are based on substitute proxy sources such as fossils or isotopes are proxy data significant that is have they been calibrated in modern environments and to what level is the calibration this is the problem of accuracy validity in the statistical sense second are the proxy data reliable can two workers or even the same worker consistently arrive at the same estimates using the same data set this is the problem of precision repeatability can these two problems be resolved quaternary palynologists have used the concept of transfer functions a methodology originally developed for foraminifera imbrie kipp 1971 applied in palynology a response surface for each palynomorph taxon is constructed for the environmental variables under consideration these transformations can then be subjected to a number of different kinds of multivariate analyses including ordination methodologies bartlein et al 1986 webb bryson 1972 these transfer functions can work for quaternary and especially the lateand post glacial of the last 20 to 30 thousand years pollen assemblages because in most regions where the methodology has been applied the flora is of known diversity and the equivalency of a given palynomorph species to one or a few extant species can be reasonably assumed even in the late neogene 1 5 to 10 million years ago however this assumption can no longer be made we know that the palynomorph assemblages contain exotic genera mccartan et al 1990 and the presence of exotic and or extinct species

tomomorphometry of the somma vesuvius volcano italy 1 a tomomorphometric analysis of the somma vesuvius topography is presented this consists in extracting horizontal cross sections at different altitudes and in determining some morphometric parameters radius of the circle with a surface area equal to the cross section circularity ratio between the major and minor axis of the best fitting ellipse orientation of the ellipse major axis and the x y centroid the somma includes three portions the apron zone the flanks and the summit caldera boundary between 225 m and 525 m is 50 60 between 600 m and 775 m is 130 135 these are the preferred strike of the eruptive fissures affecting the northwestern somma flanks the faults affecting the whole edifice the nodal planes from local earthquakes the somma activity developed along a ne sw structural discontinuity whereas the post caldera activity concentrated along a nw se striking structure somma activity migrates from se to nw

using fossil leaves as paleoprecipitation indicators an eocene example estimates of past precipitation are of broad interest for many areas of inquiry including reconstructions of past environments and topography climate modeling and ocean circulation studies the shapes and sizes of living leaves are highly sensitive to moisture conditions and assemblages of fossil leaves of flowering plants have great potential as paleoprecipitation indicators most quantitative estimates of paleoprecipitation have been based on a multivariate data set of morphological leaf characters measured from samples of living vegetation tied to climate stations however when tested on extant forests this method has consistently overestimated precipitation we present a simpler approach that uses only the mean leaf area of a vegetation sample as a predictor variable but incorporates a broad range of annual precipitation and geographic coverage into the predictor set the significant relationship that results in addition to having value for paleoclimatic reconstruction refines understanding of the long observed positive relationship between leaf area and precipitation seven precipitation estimates for the eocene of the western united states are revised as lower than previously published but remain far wetter than the same areas today abundant moisture may have been an important factor in maintaining warm frost free conditions in the eocene because of the major role of water vapor in retaining and transporting atmospheric heat

dem based morphometry as a tool for reconstructing primary volcanic landforms examples from the borzsony mountains hungary a complex application of digital elevation model dem derivatives is presented for a highly degraded volcanic area the miocene borzsony mountains hungary we propose unconventional geometrical and mathematical transformations of the original dem data in order to enhance the topographic features of the volcanic relief that stem from the primary landforms it is the actual ridges that represent the least degraded surfaces of an original hypothetical volcanic cone therefore the statistical dem properties such as ridge pattern 1 slope angle distribution 2 and higher order slope derivatives 3 should be strongly correlated with the paleosurface automated creation of a ridge pattern image is based on the local histogram of the dem and helps to outline the original surface remnants a local slope angle histogram may point out structurally coherent parts of the original cone for instance tectonic displacements or large scale sector slumping does not affect the slope angle histogram of the original relief evaluating the ridge maps and slope aspect maps of the borzsony mountains allows various cone sectors to be identified and connected to the original volcano structural elements finally the polar coordinate transformed pct image 4 centered on a hypothesized eruptive vent enhances the original radial valley pattern in the case of multiple eruptive centers and or post eruptive tectonic modifications the radial pattern is changed which may be evidenced in the pct image in fact the pct image analysis for the borzsony mountains suggests a complex post eruptive tectonic scenario the presented methods can be recommended to infer the original configuration of highly degraded volcanic structures with poorly known tectonic and erosional history

palaeoclimate analysis of late cretaceous angiosperm leaf floras james ross island antarctica the fossilized remains of cretaceous angiosperm leaves are preserved within sandstones and siltstones of the coniacian hidden lake formation gustav group and the santonian early campanian santa marta formation marambio group in the james ross basin antarctic peninsula region the leaves represent the remains of vegetation that grew at approximately 65 s on an emergent volcanic arc now represented by the antarctic peninsula and were subsequently transported and buried in marine sediments in the adjacent back arc basin some of the angiosperm leaf morphotypes show similarities to leaves of living families such as sterculiaceae lauraceae winteraceae cunoniaceae and myrtaceae palaeoclimate analysis based on physiognomic aspects of the leaves such as leaf margin analysis indicates that the mean annual temperatures for the hidden lake and santa marta formations were 13 21 c mean 17 c and 15 23 c mean 19 c respectively the fossil plants are indicative of warm climates without extended periods of winter temperatures below freezing and with adequate moisture for growth this period of cretaceous warmth in antarctica corresponds with the cretaceous thermal maximum an interval of peak global warmth from the turonian to the early campanian

new developments in clamp calibration using global gridded meteorological data abstract climate leaf analysis multivariate program clamp is a versatile technique for obtaining quantitative estimates for multiple terrestrial palaeoclimate variables from woody dicot leaf assemblages to date it has been most widely applied to the late cretaceous and tertiary of the mid to high latitudes because of concerns over the relative dearth of calibration sites in modern low latitude warm climates and the loss of information associated with the lack of marginal teeth on leaves in paratropical to tropical vegetation this limits clamp s ability to quantify reliably climates at low latitudes in greenhouse worlds of the past one of the reasons for the lack of clamp calibration samples from warm environments is the paucity of climate stations close to potential calibration vegetation sites at low latitudes agriculture and urban development have destroyed most lowland sites and natural vegetation is now largely confined to mountainous areas where climate stations are few and climatic spatial variation is high due to topographic complexity to attempt to overcome this we have utilised a 0 5 0 5 grid of global interpolated climate data based on the data set of new et al 1999 supplemented by the era40 re analysis data for atmospheric temperature at upper levels for each location the 3 d climatology of temperature from the ecmwf re analysis project was used to calculate the mean lower tropospheric lapse rate for each month of the year the gridded data were then corrected to the altitude of the plant site using the monthly lapse rates corrections for humidity were also made from this the commonly returned clamp climate variables were calculated a bilinear interpolation scheme was then used to calculate the climate parameters at the exact lat long of the site when clamp analyses using the physg3br physiognomic data calibrated with the climate station based met3br were compared to analyses using the gridded data at the same locations gridmet3br the results were indistinguishable in that they fell within the range of statistical uncertainty determined for each analysis this opens the way to including natural vegetation anywhere in the world irrespective of the proximity of a meteorological station

incision of a river curvature due to exhumed miocene volcanic landforms danube bend hungary a new model for the formation and relief evolution of the danube bend northern hungary is discussed on geomorphological and volcanological grounds we propose that the present day u shaped loop of the danube bend was partly inherited from the horseshoe caldera morphology of keser s hill volcano a mid miocene ca 15 ma lava dome complex with an eroded central depression open to the north according to combined palaeogeographical data and erosion rate calculations the drainage pattern in the danube bend region was formed when pleistocene tectonic movements resulted in river incision and sedimentary cover removal formation of the present curvature of the river was due to the exhumation of the horseshoe shaped caldera as well as the surrounding resistant volcaniclastic successions i e visegrad castle hill and a hilltop lava dome szent mihaly hill the process accelerated and the present narrow gorge of the danube bend was formed by very rapid as young as late quaternary differential tectonic uplift also enhancing the original volcanic morphology on the basis of comparative long term erosion rate calculations we estimated successive elevation changes of the volcanic edifice including partial burial in late miocene time in comparison with various order of magnitude changes the mid to late quaternary vertical movements show increased rates and or base level drop in the pannonian basin

paleoclimatic estimation reveals a weak winter monsoon in southwestern china during the late miocene evidence from plant macrofossils the late miocene xianfeng flora of yunnan province southwestern china was chosen to reconstruct the paleoclimate and the intensity of the asian monsoon three available quantitative climate reconstruction methods from fossil plants i e leaf margin analysis lma the climate leaf analysis multivariate program clamp and the coexistence approach ca were used in this study mats mean annual temperatures resulting from these three approaches i e lma 17 2 2 38 degrees c clamp 15 43 1 25 degrees c ca 17 2 21 7 degrees c appear to have been higher than the present 14 9 degrees c suggesting a much warmer climate in the late miocene both the growing season precipitation gsp from clamp 1908 7 217 7 mm and mean annual precipitation map from ca 1206 0 1613 0 mm estimates are higher than modern values 1003 2 mm gsp and 1038 mm map respectively indicating a more humid climate during the late miocene by comparing these with climates reconstructed from neighboring late miocene floras we conclude that the general late miocene climate appears warmer and more humid than present conditions in southwestern china furthermore the evident differences in estimated monthly temperatures between the summer and winter and precipitations between the humid and dry seasons indicate the existence of seasonality though not as strong as that of today difference in precipitation of dry season indicates a marked strengthening in the winter monsoon since the late miocene a new monsoon intensity index has also been defined based on precipitation seasonality to investigate the intensity of the asian monsoon c 2012 elsevier b v all rights reserved

stratigraphic simulation of sedimentary basins concepts and calibration a two dimensional stratigraphic simulation program based on semiempirical algorithms has been successfully applied to clastic carbonate and mixed clastic carbonate depositional regimes the program may be used to predict reservoir distribution to constrain interpretations of well and seismic data to test exploration scenarios in frontier basins and to evaluate the fundamental controls on basin stratigraphy applications to seismic and well log data sets from main pass u s gulf coast offshore sarawak malaysia and the baltimore canyon u s east coast demonstrate that the program simulates stratigraphy on a basin wide scale as well as on the scale of individual prospects the main pass section is an offlapping sequence of neogene clastics the model simulates 17 m y of geologic history at a 200 000 yr resolution and reproduces gross basin geometry major sequence boundaries depth and location of nearshore marine sands intervals of sediment bypass into deep water shelf margin positions and paleobathymetry three neogene carbonate buildups of central luconia offshore sarawak malaysia were simulated using a sea level history optimized to reproduce the carbonate growth anatomy the model reproduced observed seismic reflection geometries and transgressive aggradational progradational retrogradational and subaerial exposure phases the program has also simulated jurassic pleistocene basin and stratigraphic sequence geometries and mixed clastic carbonate facies distribution along a 300 km regional dip line of the baltimore canyon trough modeled features of interest include a progradational middle jurassic carbonate margin punctuated by clastic deposition during sea level lowstands and a late jurassic early cretaceous aggradational carbonate margin culminating in the development and subsequent drowning of isolated carbonate buildups simulated bathymetries facies relations and subaerial exposure surfaces for the early cretaceous aggradation margin are consistent with detailed petrographic paleontologic and seismic stratigraphic interpretations

stratigraphy and structure of southern blake plateau northern florida straits and northern bahama platform from multichannel seismic reflection data approximately 2 100 km of 24 fold multichannel seismic reflection data reveal much about the subsurface geology for a large part of the continental margin east of florida discordance between the westward dipping pre breakup sediments and the eastward sloping basement along the edge of the blake plateau is interpreted as an effect of a splinter of continental margin derived from the african plate by a spreading center jump in the middle jurassic early rifting centered under the main part of the blake plateau became inactive as a spreading center jump shifted the active rift to east of the present blake escarpment along the blake spur magnetic anomaly in the northern florida straits the data reveal that the breakup unconformity underlain by triassic lower jurassic arkosic volcaniclastics extends from southern florida to the western bahama banks these volcaniclastics are associated with the rift crust of intermediate nature formed just prior to and during breakup of the north american and african continental plates back reef platform deposits of limestones dolomites and evaporites of late jurassic to albian age extend from the blake bahama escarpment westward beneath florida these deposits formed what once was a megabank extending over a wider area than the present smaller isolated bahama banks the formation of the florida straits and bahama channels occurred during the cenomanian transgression only on the present bahama banks and florida platform did shallow water carbonate deposition persist to maintain a shallow bank environment evidence of recurring scour by current erosion is found in the florida straits erosional events apparently occurred in the middle cenomanian middle paleocene early middle eocene and eocene oligocene which coincidentally are times of lower eustatic sea level according to vail et al 1977a this evidence of florida current scour indicates that the current was present as far back as the cenomanian major faulting appears to have dropped the northeast providence channel relative to the western bahamas after the albian submarine erosion and bank buildup created the channels and smaller relief features like great abaco knoll beginning in about the cenomanian a carbonate bank margin and reef complex was present along the bahama escarpment since the middle jurassic apparently these organic buildups seeded on originally shallow structural relief on oceanic basement created during the spreading center jump to the position of the blake spur magnetic anomaly the bank margin apparently has retreated at least 15 km from a late jurassic earliest cretaceous position now marked by a bench below the au unconformity active faulting occurred along the great abaco fracture zone at least through the late cretaceous and perhaps into the tertiary these relatively young tectonic events together with the post albian faults in providence channel indicate interactions between the atlantic and caribbean plates and that extensions of faulting have taken place far to the northeast of cuba and the greater antilles

erosion rates and erosion patterns of neogene to quaternary stratovolcanoes in the western cordillera of the central andes an srtm dem based analysis abstract erosion patterns and rates of 33 stratovolcanoes in the arid to hyperarid central andean volcanic zone 14 s to 27 s have been constrained by morphometric modelling all selected volcanoes belong to the short lived symmetrical circular andesitic stratocone type with ages spanning 14 ma to recent starting from the initial youthful volcano morphology of this type represented in our study by parinacota volcano and comparing reconstructed volumes of progressively eroded volcanoes such a time span allows us to infer long term erosion rates typical erosion rates of