carboniferous petroleum systems around the mid north sea high uk the existence of an extensive prospective visean namurian carboniferous petroleum system in and around the hitherto under explored mid north sea high is documented evidence is drawn from integrated analysis of over 50 000 line kilometres of seismic data and well data together with regional source rock screening reservoir analysis and basin modelling visean namurian marine and non marine mudstones and coal source rocks are interbedded within fluvial and marine reservoir sandstones within a stacked succession up to 5 km thick source rocks are dominantly gas prone with oil prone intervals and have reached oil to gas maturity levels dependent on location burial thermal history modelling indicates a kitchen area on the southern margin of the mid north sea high with northwest and northeastwards migration of gas and oil during mesozoic and cenozoic times a variety of structural and stratigraphic traps are possible including intraformational carboniferous traps with a regional seal at permian zechstein level synthesis of many previously unpublished datasets demonstrates the visean namurian play south of the mid north sea high as part of an extensive petroleum system from the east irish sea across onshore to offshore uk and into the netherlands sector of the north sea the purpose of this synthesis is to highlight future exploration opportunities beneath and northwards of the productive westphalian southern north sea gas basin and to begin to de risk the petroleum systems that are exemplified by the lower carboniferous breagh field in a frontier area of the mature north sea province

assessment of multiple sources of anthropogenic and natural chemical inputs to a morphologically complex basin lake mead usa abstract lakes with complex morphologies and with different geologic and land use characteristics in their sub watersheds could have large differences in natural and anthropogenic chemical inputs to sub basins in the lake lake mead in southern nevada and northern arizona usa is one such lake to assess variations in chemical histories from 1935 to 1998 for major sub basins of lake mead four sediment cores were taken from three different parts of the reservoir two from las vegas bay and one from the overton arm and virgin basin and analyzed for major and trace elements radionuclides and organic compounds as expected anthropogenic contaminant inputs are greatest to las vegas bay reflecting inputs from the las vegas urban area although concentrations are low compared to sediment quality guidelines and to other usa lakes one exception to this pattern was higher hg in the virgin basin core the virgin basin core is located in the main body of the lake colorado river channel and is influenced by the hydrology of the colorado river which changed greatly with completion of glen canyon dam upstream in 1963 major and trace elements in the core show pronounced shifts in the early 1960s and in many cases gradually return to concentrations more typical of pre 1960s by the 1980s and 1990s after the filling of lake powell the overton arm is the sub basin least effected by anthropogenic contaminant inputs but has a complex 137 cs profile with a series of large peaks and valleys over the middle of the core possibly reflecting fallout from nuclear tests in the 1950s at the nevada test site the 137 cs profile suggests a much greater sedimentation rate during testing which we hypothesize results from greatly increased dust fall on the lake and virgin and muddy river watersheds the severe drought in the southwestern usa during the 1950s might also have played a role in variations in sedimentation rate in all of the cores

the role of algal blooms in the formation of lacustrine petroleum source rocks evidence from jiyang depression bohai gulf rift basin eastern china abstract algal blooms are responsible for the laminae in the lacustrine shahejie formation in the jiyang depression one of the sub basins of the bohai gulf rift basin in eastern china about 65 oil fields have been discovered in this depression during the past 40 years and the oil is mainly derived from three types of finely laminated lacustrine rocks of shahejie formation eocene oligocene these lacustrine petroleum source rocks are oil shales calcareous shales and calcareous laminated mudstones optical sem and bsei analyses of these source rocks reveal that there are algal coccoliths and dinoflagellates laminae in the rocks the individual algal lamina is generally composed almost wholly of one species such as reticulofenestra bohaiensis in coccolith laminae and fromea as well as bohaidina in dinoflagellate laminae this distribution suggests that the algal laminae formed from algal blooms in the ancient lake other components of source rocks included organic matter laminae carbonate laminae and clay rich laminae we also discuss the sedimentation of organic matter laminae and carbonate laminae which were related to algal blooms we conclude that the laminated lacustrine petroleum source sediment of jiyang depression formed during episodes of algal blooms alternating with chemical and detrital sedimentation and this represents the primary mechanism responsible for the formation of lacustrine petroleum source rocks

lithium isotope compositions of u s coals and source rocks potential tracer of hydrocarbons abstract kerogen in organic rich rocks contains trace amounts of lithium li that has been overlooked as a contributor to the global li geochemical cycle this study examined a variety of coals where kerogen is concentrated 50 organic carbon and hydrocarbon source rocks of different ages depositional environments and thermal maturity to determine their range of li isotopic compositions 7li and factors that influence their compositions using secondary ion mass spectrometry sims we analyzed 22 coals and 4 hydrocarbon source rocks types i ii iii to determine the 7li of kerogen in situ without chemical isolation of phases that can alter their original isotopic compositions the 7li values of the coals surveyed are distinctly isotopically light nanosims isotopic maps of the lower bakken shale and sims measurements of the green river shale show isotopically light li associated with c dominated areas and heavier 7li with si dominated areas of the hydrocarbon source rocks we conclude that kerogen is a source of isotopically light li that contributes to fluids during thermal maturation and hydrocarbon generation kerogen may be a significant contributor of li to pore fluids and its distinctly light li isotopic composition relative to other terrestrial waters and minerals could provide a tracer of organic inputs to the global geochemical cycle

palaeoseismology of the l aquila faults central italy 2009 mw 6 3 earthquake implications for active fault linkage summary urgent urban planning problems related to the 2009 april mw 6 3 l aquila earthquake prompted immediate excavation of palaeoseismological trenches across the active faults bordering the aterno river valley namely the mt marine mt pettino and paganica faults cross cutting correlations amongst existing and new trenches that were strengthened by radiocarbon ages and archaeological constraints show unambiguously that these three investigated structures have been active since the last glacial maximum period as seen by the metric offset that affected the whole slope alluvial sedimentary succession up to the historical deposits moreover in agreement with both 18th century accounts and previous palaeoseismological data we can affirm now that these faults were responsible for the catastrophic 1703 february 2 earthquake mw 6 7 the data indicate that the paganica san demetrio fault system has ruptured in the past both together with the conterminous mt pettino mt marine fault system along more than 30 km and causing an mw 6 7 earthquake and on its own along ca 19 km as in the recent 2009 event and in the similar 1461 ad event this behaviour of the l aquila faults has important implications in terms of seismic hazard assessment while it also casts new light on the ongoing fault linkage processes amongst these l aquila faults

complete seismic release of tectonic strain and earthquake recurrence in the apennines italy here i compare estimates of tectonic strain rates from dense global positioning system measurements with the seismicity released in the last 500 years in the apennines italy the rates of seismic moment accumulation from geodesy and of historical seismic release by earthquakes agree within the uncertainties ruling out significant aseismic deformation within the considered 400 km long section of the apennines this balance yields an average recurrence interval of 30 75 years for mw 6 5 events without requiring a future earthquake larger than those observed historically mw 7 a minimum estimate of unreleased strain allows mw 6 5 and mw 6 9 events to be released in 35 and 10 of the central southern apennines respectively the definition of the seismic potential for smaller events is more uncertain and their occurrence remains a significant threat throughout the apennines

application of airborne lidar to mapping seismogenic faults in forested mountainous terrain southeastern alps slovenia results are presented of the first airborne lidar survey ever flown in europe for the purpose of mapping the surface expression of earthquake prone faults detailed topographic images derived from lidar data of the idrija and ravne strike slip faults in nw slovenia reveal geomorphological and structural features that shed light on the overall architecture and kinematic history of both fault systems the 1998 mw 5 6 and 2004 mw 5 2 ravne fault earthquakes and the historically devastating 1511 m 6 8 idrija earthquake indicate that both systems pose a serious seismic hazard in the region because both fault systems occur within forested terrain a tree removal algorithm was applied to the data the resulting images reveal surface scarps and tectonic landforms in unprecedented detail importantly two sites were discovered to be potentially suitable for fault trenching and palaeo seismological analysis this study highlights the potential contribution of lidar surveying in both low relief valley terrain and high relief mountainous terrain to a regional seismic hazard assessment programme geoscientists working in other tectonically active regions of the world where earthquake prone faults are obscured by forest cover would also benefit from lidar maps that have been processed to remove the canopy return and reveal the forest floor topography

source controlled carbonates in a small eocene half graben lake basin shulu sag in central hebei province north china carbonate deposits which unconformably overlie the palaeozoic bedrocks extensively occur in the base of the tertiary lake succession in the half graben shulu sag central hebei province north china this study focuses on the basal carbonate successions on the hinged western slope based on seismic borehole and core data nine facies are identified in the carbonate successions and are further grouped into five facies associations mid proximal alluvial fan distal alluvial fan fan fringe moderately deep lake and deep lake the first two facies associations constitute alluvial fans formed by debrisflows at the edge of lake and are dominated by mounded to lobate shaped matrix to clastsupported carbonate rudstones with minor calcretes in the lowermost rudstone units and basinward increase in interfingering with lacustrine carbonate facies the fan fringe moderately deep lake and deep lake associations are dominated by pebbly carbonate arenites or rare carbonate arenites calcisiltitecalcilutites and varve like calcilutites calcareous shales and oil shales respectively widespread occurrences of fine grained limestone packages containing varve like organic rich laminations minor authigenic glauconite and pyrite and planktonic and plant fossils suggest a meromictic anoxic deep lake under a semi humid to humid climate probably with a connection to marine basins similarities in lithology and fossil assemblages e g trilobites of lithoclasts with those of the mid upper cambro ordovician bedrock carbonates suggest that the clastic and dissolved carbonate loads were sourced from this lower palaeozoic catchment and shed off the surrounding highlands into the basin these carbonate facies associations represent the lake lowstand and transgressive deposits of the basal third order sequence ia in which the highstand deposits are composed of lacustrine siliciclastics during the lake lowstand stage or initiation of basin filling under an intermediate climate carbonate alluvial fans occurred mostly subaerially at the bottom of the hinged slope with a narrow shallow lake zone basinwards and locally were perched within the palaeovalley on the mid upper slope during the transgressive deepening stage under a semi humid to humid climate carbonate alluvial fans became smaller in size and episodically stepped backwards upon the slope with greatly expanded and deepened lake nevertheless the carbonate system was switched to an exclusively siliciclastic system during the highstand stage the exhumation and erosion of the mid lower cambrian bedrock dominated by siliciclastics was probably the cause due to further uplift of the drainage basin all these facts indicate

low slip rates and multimillennial return times for mw 7 earthquake faults in southern calabria italy the calabrian arc is the epicentral region of one third of the strongest earthquakes of italy mw 7 0 these are confined within a narrow peninsula which is the emerging portion of a slab related accretionary wedge and all occurred in the past four centuries therefore here more than anywhere in italy historical seismicity alone is not sufficient for seismic hazard assessment we carried out geological and paleoseismological studies in southern calabria that allowed characterizing the seismogenic behavior of the cittanova fault which was responsible for one of the most catastrophic earthquakes to ever occur in europe the mw 7 0 5 february 1783 event we have found out conclusive evidence for four holocene earthquakes prior to 1783 with a recurrence time longer 3 2 kyr than the other apennine faults 0 3 2 4 kyr we have also estimated a robust slip rate for the late upper pleistocene 0 6 mm yr and an extension rate 0 4 mm yr that could reflect the residual back arc opening of the tyrrhenian basin

a depositional model for spherulitic carbonates associated with alkaline volcanic lakes the south atlantic aptian pre salt reservoirs are formed by a combination of spherulitic carbonates and mg rich clays accumulated in volcanic alkaline lake settings with exotic chemistries so far outcrop analogues characterised by metre thick successions deposited in lacustrine scenarios are elusive so disentangling the genesis of spherulitic carbonates represents a major scientific challenge with business impact in particular the controls on spatial distribution and the environment of spherulitic facies formation remain poorly constrained little studied and hotly debated to shed light on this conundrum a spherulitic carbonate rich alkaline volcanic lacustrine succession has been analysed at outcrop scale the carboniferous east kirkton limestone scotland despite clays being very scarce and limited to layers of amorphous mg si minerals a diverse array of spherulitic calcitic components were formed including coated grains crusts and build ups this setting enables the mechanisms of spherulitic calcite development and the patterns of sediment accumulation to be explored in a geobiological and hydrochemical scenario similar to the pre salt subsurface occurrences but divorced from clay influence the integration of logs borehole data outcrop photomosaics and petrographic observations collectively allowed the reconstruction of a depositional model for the east kirkton lacustrine succession in this model calcite spherule nucleation took place at the sediment water interface in the littoral zone driven by the co occurrence of 1 high alkalinity 2 ca mg rich hydrochemistry and 3 microbial derived colloidal exopolymeric substances these environmental conditions permitted the coeval development of spherulitic cementstone build ups and spherulitic grainstone packstone within the wave agitated zone and the accumulation of floatstones and laminites of spherulitic grains in deeper lake regions by means of downslope reworking this model is consistent with the previously documented microbial bloom occurrences and highlights the need to better understand the complex microbe solution interactions before any reliable facies model is envisaged

palaeolimnology of palaeozoic lakes focussing on a single lake cycle in the middle devonian of the orcadian basin scotland there are few palaeolimnological studies of palaeozoic lake deposits using methodologies developed for the study of quaternary lakes new research described here indicates the benefits of applying multidisciplinary high resolution sampling and analysis on the middle devonian lake deposits of the orcadian basin in order to understand lake palaeoecology and response to water chemistry change and possible climate change in a continuously sampled 4 m thick lake cycle in two correlated boreholes in caithness there are two distinct features there is a broad trend in 13c of sedimentary organic matter from high values in the shallow water deposits to lower values in the deeper water deposits attributed to changing contributions from terrestrial plant material 13corg c 28 and algal material 13corg c 33 this variation is consistent with palynological data and is best explained by proximal distal variation as the lake filled a smaller but well correlated up section decreasing 13corg trend occurs over approximately 1 m starting at the cycle centre where the lake was at its deepest since the same feature is seen in two boreholes we suggest that local effects of migrated bitumen diagenesis or facies changes are unlikely to be the cause and that changes in the carbon cycle of the lake are responsible explanations for this trend may relate to the source of carbon that algae utilised as the lake changed from a fresher to a more saline environment and to changes in the carbon isotope composition of the lake water during periods of enhanced productivity

peat marl deposition in a holocene paludal lacustrine basin sucker lake michigan exceptionally thick over 15 m deposits of peat which fill the northern end of sucker lake basin in northcentral michigan document the volumetric importance of allochthonous organic material in a modern coal forming environment organic debris that originates in and is derived from a highly vegetated floodplain immediately upstream is deposited as a lakeward prograding lobe that exhibits features typical of most lacustrine gilbert deltas but is composed almost entirely of organic material this system overlies an additional 7 m of nearly pure brecciated lacustrine carbonate deposited as shallow lake margin benches and emplaced into the deep basin centre by gravity sliding prior to deltaic progradation in the southern end of the basin bottomset beds of fine silt size organic phytoclasts onlap distal facies of progradational bench carbonates which originate in shallow water through calcite encrustation about stems of the dominant macrophyte chara with continued sedimentation a stratigraphic succession in which allochthonous organics will overlie pure allochthonous lacustrine carbonates and in part be overlain by autochthonous carbonates will characterize the northern end of this holocene system in the southern end around the basin margins however autochthonous carbonates will entirely underlie allochthonous organics numerous continuous cores up to 22 m through these units document 1 the importance of sources of allochthonous organic debris in modern coal forming complexes 2 the genetic relationship between nearly pure calcareous and nearly pure carbonaceous facies within these paludal lacustrine settings and 3 the complexity of interrelationships between the several component facies within such continental sedimentary systems

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

paleozoic lake faunas establishing aquatic life on land abstract lakes are important archives for continental records of paleoenvironmental as well as paleoclimatic change they also record a unique macroevolutionary pattern that occurred when faunas invaded the continental realm in order to document that pattern we compiled a database of over one hundred and six lake basins from the neoproterozoic to permian looking at this critical time in lacustrine evolution several patterns emerge for the neoproterozoic through silurian time there is a paucity of documented lake deposits and lake faunal records however the records that are available indicate that lakes were oligotrophic and their nutrient cycling regimes primitive it is not until the establishment of land plants in the silurian that lakes began to respond with higher diversities and more complex physical and chemical conditions during the devonian carboniferous periods diversity was on the rise as trophic structure became more complex most lakes of the devonian and carboniferous formed along continental margins or in tectonic basins with occasional connection to the marine realm the faunas from these types of lakes were commonly comprised of mixed marine and freshwater elements and were far more diverse than other more inland lakes this estuary effect created a gateway or filter through which faunas invaded the continental realm the early history of lake faunas is one of opportunity and amelioration the feedback loops created by the establishment of vascular plants altered the nutrient cycle on land and in lakes all trophic levels were established early but became increasingly complex throughout the paleozoic as roles changed and faunal elements became established groups invading the continents via the estuary effect did so numerous times before establishing themselves permanently this was linked with the episodic re establishment in marine freshwater connections along these continental margins

initial test of the silicic acid leakage hypothesis using sedimentary biomarkers 1 several mechanisms have been proposed for large co2 changes at glacial terminations including shifting the caco3 corg rain ratio by changing surface water nutrient supply altering the balance between diatom and coccolithophore production diatom si n is highest in fe stressed high latitude waters southern ocean fe enrichment studies suggest diatom si demands reduced under fe replete glacial conditions allowing increased silicic acid to leak northward in subducted intermediate water and upwell at lower latitudes we test this silicic acid leakage hypothesis using relative abundances of phytoplankton specific biomarkers in peru margin sediments spanning 0 20 ka results indicate increased coccolithophorid diatom production from 0 5 to 3 between 18 0 15 5 ka temporal correlation with the initial pco2 rise and early deglacial shift in mode water ventilation implicates a coincidental possibly causative reorganization of sub antarctic mode water formation and reduced fe abundance however coccolithophorid production subsequently declined suggesting rain ratio changes were only partly responsible for the co2 deglacial transition

organic facies of the asbian early carboniferous queensferry beds lower oil shale group south queensferry scotland and a brief comparison with other carboniferous north atlantic oil shale deposits abstract the 71 m foreshore exposure of the queensferry beds at south queensferry is currently the best accessible section of the oil shale group of the midland valley of scotland a combination of bulk organic geochemistry and kerogen microscopy palynofacies organic petrology is used to define four organic facies and one variant organic facies 1 occurs in silty mudstones has a mean toc of only 2 and type iii iv gas prone or inert kerogen hi 800 variant 3a is additionally characterised by an abundance of small 4 m spherical cells of possible cyanobacterial origin occurring in one sample adjacent to a stromatolitic limestone organic facies 2 is transitional between 1 and 3 organic facies 4 has atypically low c s ratios and corresponds to the pumpherston marine band these organic facies can also be distinguished using biomarker parameters pr ph oep c25 c15 predominant carbon number etc the hi is very strongly correlated with the relative fluorescence of the organic matter and strongly correlated with the aom phytoclast ratio and the botryococcus and total alginite contents it is inversely correlated with the diameter of black equant phytoclasts the organic rich shales thus correspond to distal lower energy anoxic conditions during periods of meromixis high preservation low dilution similar carboniferous lacustrine source rocks occur in eastern canada and east greenland all are characterised by large lateral extents 500 2 000 km2 a geographic and temporal association with strong syndepositional subsidence generally low botryococcus contents and a dominance of amorphous type ii kerogen