gas hydrates clathrates causing pore water freshening and oxygen isotope fractionation in deep water sedimentary sections of terrigenous continental margins the occurrence of gas hydrates in deep water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep sea drilling results on the pacific continental slope off guatemala gas hydrates were brought up for the first time from two holes 497 498a drilled during leg 67 of the dsdp in water depths of 2360 and 5500 m respectively the hydrates occur in organic matter rich pleistocene to miocene terrigenous sediments in the hydrate bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10 20 m subbottom depth pore waters at the bottom of the holes near 400 m subbottom have as little as half the chlorinity of seawater i e 9 similar but less pronounced trends were observed during previous legs of the dsdp in other hydrate prone segments of the continental margins where recharge of fresh water from the continent can be excluded e g leg 11 the crystallization of hydrates like ice excludes salt ions from the crystal structure during burial the dissolved salts are separated from the solids subsidence results in a downward motion of the solids including hydrates relative to the pore fluids thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation the volume of the latter decreases downhole thus causing downward decreasing salinity chlorinity hydrate formation is responsible for oxygen isotope fractionation with18o enrichment in the hydrate explaining increasingly more positive 18o values in the pore fluids recovered after hydrate dissociation with depth

in situ gas hydrate hydrate saturation estimated from various well logs at the mount elbert gas hydrate stratigraphic test well alaska north slope abstract in 2006 the u s geological survey usgs completed detailed analysis and interpretation of available 2 d and 3 d seismic data and proposed a viable method for identifying sub permafrost gas hydrate prospects within the gas hydrate stability zone in the milne point area of northern alaska to validate the predictions of the usgs and to acquire critical reservoir data needed to develop a long term production testing program a well was drilled at the mount elbert prospect in february 2007 numerous well log data and cores were acquired to estimate in situ gas hydrate saturations and reservoir properties gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance nmr p and s wave velocity and electrical resistivity logs along with pore water salinity gas hydrate saturations from the nmr log agree well with those estimated from p and s wave velocity data because of the low salinity of the connate water and the low formation temperature the resistivity of connate water is comparable to that of shale therefore the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data two highly gas hydrate saturated intervals are identified an upper 43 ft zone with an average gas hydrate saturation of 54 and a lower 53 ft zone with an average gas hydrate saturation of 50 both zones reach a maximum of about 75 saturation

fault generated mountain fronts in southeast spain geomorphologic assessment of tectonic and seismic activity abstract tectonic activity of se spain is evaluated through the application of a general morphometric analysis over 17 different mountain fronts the selected fronts are distributed along the two most prominent crustal scale structures of the mediterranean sector of spain the eastern betic shear zone ebsz and the valencia trough geomorphic indexes used in this study are mountain front sinuosity index smf and valley floor width ratio vf this work is largely based on the smf vf regression analysis of the studied fronts together with previous available data from sw usa the development of mountain fronts in both different lithologies and tectonic contexts enabled characteristic morphometric signatures for different activity scenarios tectonic activity classes to be obtained this study thus indicates that variations of mountain front geomorphology triggered by different styles of faulting can be detected by morphometric analysis it is demonstrated that discrete uplift rates of 0 15 0 08 m ka are sufficient to keep relatively low smf values down to 1 4 in active fronts class 1 taking into account the reported uplift rates and preliminary palaeoseismic data for some of the class 1 studied fronts recurrence periods for surface rupture events can be theoretically bracketed for se spain recurrence periods for class 1 fronts could theoretically range between 10 000 and 12 500 years for maximum slip conditions and 1750 and 2600 years for minimum slip conditions inactive fronts class 3 develop under uplift rates down to 0 03 m ka and tested recurrence intervals for rupture events range between 25 000 and 50 000 years class 2 fronts of intermediate characteristics and activity display uplift rates between 0 07 and 0 03 m ka

crustal structure and rift architecture across the krishna godavari basin in the central eastern continental margin of india based on analysis of gravity and seismic data abstract the krishna godavari basin is a rifted passive margin basin that developed orthogonally to the nw se trending pranhita godavari graben along the central eastern continental margin of india in response to the continental rifting process and the subsequent seafloor spreading between india and eastern antarctica during the early cretaceous period the 3 d gravity interpretation of both the onshore and offshore sections of the basin integrated with detailed seismic reflection and refraction data provided significant new information about the crustal architecture and the early breakup history of the basin the gravity derived crustal models indicate that the crust at the eastern indian shield margin is 39 41 km thick and thins to as much as 20 23 km at the ocean continent transition oct in the offshore there is a significant variation in the nature of crust and the configuration along the margin between the three crustal domains encompassing the basin the cuddapah basin pranhita godavari graben and the eastern ghat mobile belt that indicates the lateral segmentation of the margin a zone of high density 3 0 g cm3 crustal material at the oct separates the pure continental and oceanic crusts on either side the moho is shallowest along this zone and brought the upper mantle notably close to the surface which indicates that it could be comprised of proto oceanic crustal rocks furthermore the present study highlights a major basement structural high in the deep offshore area of the margin the geophysical signatures over this structure suggest that it is a crustal scale feature that is characterized by intrusive volcanic rocks comprised of low density crust and lies close to the oct towards offshore based on the inferred tectonic reconstruction we believe that this structural high could be a continental fragment that was left behind during the process of breakup between india and the elan bank

pressure core analysis of geomechanical and fluid flow properties of seals associated with gas hydrate bearing reservoirs in the krishna godavari basin offshore india abstract physical properties of the sediment directly overlying a gas hydrate reservoir provide important controls on the effectiveness of depressurizing that reservoir to extract methane from gas hydrate as an energy resource the permeability of overlying sediment determines if a gas hydrate reservoir s upper contact will provide an effective seal that enables efficient reservoir depressurization compressibility stiffness and strength indicate how overlying sediment will deform as the in situ stress changes during production providing engineering data for well designs assessing these properties requires minimally disturbed sediment india s national gas hydrates program expedition 2 nghp 02 provided an opportunity to study these seal sediment properties reducing disturbance from gas exsolution and bubble growth by collecting a pressure core from the seal sediment just above the primary gas hydrate reservoir at site nghp 02 08 in area c of the krishna godavari basin the effective stress chamber esc and the direct shear chamber dsc devices in the suite of pressure core characterization tools pccts were used to measure permeability compressibility stiffness and shear strength at the in situ vertical stress geotechnical properties of the predominantly fine grained seal layer at in situ vertical stress are in typical clay sediment ranges with low measured permeability 0 02 md high compressibility c c 0 26 0 33 and low shear strength 404 kpa though pressure and temperature were maintained throughout the collection and measurement process to stabilize gas hydrate the lack of effective stress in the pressure core storage chamber and the chamber pressurization with methane free water caused core expansion and gas hydrate in a thin coarser grained layer to dissolve the pccts can reapply in situ stress with incremental loading steps during a consolidation test to account for sediment compaction gas hydrate dissolution can be limited by storing cores just above freezing temperatures and by using solid spacers to reduce the storage chamber s free volume

morphodynamic evolution of the orb river languedoc france evidence of eustatic tectonic and climatic controls this study aims to reconstruct the cenozoic and pleistocene morphodynamic evolution of the orb a mediterranean river which crosses all the structural units of the south massif central border a geomorphological and sedimentological analysis of detrital deposits was carried out as a basis for correlating the different formations and reconstructing the palaeodrainage heavy minerals were used to reconstruct the main sedimentary palaeochannels since the messinian the successive orb longitudinal profiles show anomalies which can be caused by structure and by interactions between fluvial dynamics and tectonics evidence of volcanic heavy minerals on the faugeres mountains and in the upper pliocene deposits of the languedocian piedmont demonstrates that a north south flow took place during the upper pliocene nevertheless a palaeo orb existed at the place of the present course when the basaltic lava flows were spreading but headward erosion did not reach them until the upper pleistocene because the orb middle and high terraces do not contain volcanic minerals sourced from the escandorgue the successive orb longitudinal profiles show that headward erosion due to pleistocene low sea levels does not reach beyond beziers and that a tectonic hinge has functioned near the shoreline the non lithologic knickpoints are explained by the montagne noire and avant monts uplift up until the pleistocene a progressive continental uplift is necessary to explain the orb terraces staircase in the beziers district and the fluctuations of incision from upstream to downstream are due to laterally differential movements which are isostatic effects of thick regressive deposits on the gulf of lion shelf during the cold periods copyright 2008 john wiley sons ltd

preferential mode of gas invasion in sediments grain scale mechanistic model of coupled multiphase fluid flow and sediment mechanics 1 we present a discrete element model for simulating at the grain scale gas migration in brine saturated deformable media we rigorously account for the presence of two fluids in the pore space by incorporating forces on grains due to pore fluid pressures and surface tension between fluids this model which couples multiphase fluid flow with sediment mechanics permits investigation of the upward migration of gas through a brine filled sediment column we elucidate the ways in which gas migration may take place 1 by capillary invasion in a rigid like medium and 2 by initiation and propagation of a fracture we find that grain size is the main factor controlling the mode of gas transport in the sediment and we show that coarse grain sediments favor capillary invasion whereas fracturing dominates in fine grain media the results have important implications for understanding vent sites and pockmarks in the ocean floor deep subseabed storage of carbon dioxide and gas hydrate accumulations in ocean sediments and permafrost regions our results predict that in fine sediments hydrate will likely form in veins following a fracture network pattern and the hydrate concentration will likely be quite low in coarse sediments the buoyant methane gas is likely to invade the pore space more uniformly in a process akin to invasion percolation and the overall pore occupancy is likely to be much higher than for a fracture dominated regime these implications are consistent with laboratory experiments and field observations of methane hydrates in natural systems

numerical simulations of sand migration during gas production in hydrate bearing sands interbedded with thin mud layers at site nghp 02 16 abstract the geomechanical behavior of gas hydrate bearing sands during gas production is complex involving changes in hydrate dependent mechanical characteristics and also redistribution of stresses carried by the hydrate when an interbedded mud layer is present the complex response of the hydrate bearing sediments is more pronounced because hydrate dissociation tends to occur preferentially in the sands adjacent to the hydrate free mud layer which can act as a heat source this leads to non uniform sediment deformation and potentially to shearing deformation along the sand mud layers in addition since the hydrate bearing sand permeability becomes far greater than the mud permeability with hydrate dissociation a greater hydraulic gradient may exist along the interface between the sand mud layers these two behaviors may contribute to sand migration and thus a thorough study on the effect of a thin interbedded mud layer on the extent of sand migration is necessary this paper presents numerical sand migration modeling of sand mud interbedded hydrate bearing sediments found at site nghp 02 16 one of 25 sites drilled as a part of national gas hydrate program expedition 02 nghp 02 in the offshore of india subjected to depressurization for a comparison and better understanding simulation of homogeneous hydrate bearing sediments is also conducted it is found that greater sand migration occurs when the interbedded mud layer is present because of greater shearing deformation and greater pressure gradients at sand mud interface

recognition of insufficient bleaching by small aliquots of quartz for reconstructing soil erosion in greece optical dating of sediments requires sufficient bleaching of the material to be dated using single aliquot techniques the statistical parameter of the coefficient of variation v in combination with the reduction of mineral grains per aliquot enables the detection of insufficiently bleached samples this was empirically tested on quartz extracts from the greek study area which were artificially bleached differently dosed and then mixed to simulate insufficiently bleached samples the single aliquot regenerative dose protocol was applied the test measurements show that for the studied quartz material the detection of insufficient bleaching is possible if small aliquots of 200 500 grains and a threshold value of v 10 are used the technique was applied to the age determination of colluvial and alluvial torrential deposits from the study area the basin of phlious in greece the optically stimulated luminescence age data allow reconstruction of the history of holocene soil erosion which essentially started in the 7th millennium bc simultaneous with the onset of agricultural activities in the early neolithic

india national gas hydrate program expedition 02 operational and technical summary abstract the india national gas hydrate program is being steered by the government of india s ministry of petroleum and natural gas mopng with participation of directorate general of hydrocarbons dgh oil and natural gas corporation limited ongc and the national oil companies and research institutes of india the india national gas hydrate program expedition 01 nghp 01 established the presence of gas hydrate in the krishna godavari kg and mahanadi basins and in the offshore area of the andaman sea basin however the gas hydrates discovered during nghp 01 were mainly distributed as fracture filling material in fine grained clay rich sediments the india national gas hydrate program expedition 02 nghp 02 was carried out with an objective to discover gas hydrate in sand rich sediment along the eastern offshore margin of india ongc planned and executed nghp 02 on the behalf of the mopng nghp 02 started on march 3 2015 and was completed on july 28 2015 total 147 days using the japanese scientific drilling vessel chikyu d v chikyu during nghp 02 42 holes at 25 sites were drilled cored and or surveyed with downhole logging tools these sites were located in four areas along the eastern margin of india and formally named area a mahanadi basin three sites area b northern part of the kg basin twelve sites area c central part of the kg basin six sites and area e southern part to the kg basin four sites all 25 sites established during nghp 02 were first drilled and logged with logging while drilling lwd tools and an additional 17 holes were then drilled and or cored with conventional coring tools hpcs escs or pressure coring tools pctb wireline logging was conducted in 10 holes and formation tests using a dual packer modular formation dynamics tester mdt tool were carried out in two holes the onboard science team used the laboratory facilities on the d v chikyu to examine and analyse the physical properties geochemistry and sedimentology of all the cores collected during the expedition core samples were also analysed in additional post expedition shore based studies conducted in numerous domestic and international gas hydrate research laboratories the nghp 02 sediment cores were archived at the national gas hydrate core repository in mumbai india which is associated with the ongc gas hydrate research and technology centre ghrtc the necessary data for characterizing the occurrence of gas hydrate such as interstitial water chlorinities core derived gas chemistry physical and sedimentological properties thermal images of the recovered cores pressure core and downhole measured logging data lwd and or conventional wireline log data were obtained from most of the drill sites established during nghp 02 almost all the drill sites yielded evidence for the occurrence of gas hydrate however the inferred in situ concentration of gas hydrate varied substantially from site to site for the most part the interpretation of downhole logging data core thermal images interstitial water analyses and pressure core images from the sites established during nghp 02 indicate that the occurrence of concentrated gas hydrate is mostly associated with coarser grained sand rich sediments this paper presents the operational and technical summary of nghp 02

tectonic implications of paleomagnetic data from sills and dykes in the sverdrup basin canadian arctic mesozoic intrusives 71 sills and 12 dykes from different structures in the folded eastern sverdrup basin contain stable well grouped paleomagnetic directions of both normal and reverse polarity the mean direction is 274 79 k 173 95 3 7 with a corresponding pole position at 157 67 n k 61 a95 6 6 the paleomagnetic fold test shows that the major deformation involving tilting of strata around strike postdated the emplacement of sills and dykes minor preintrusion deformation may also have occurred but more importantly an offset of the paleopole from the cretaceous section of the polar wander path permits a postintrusion anticlockwise rotation of eastern sverdrup basin of about 15 20 with respect to stable north america if the intrusives are cretaceous the degree of rotation is close to that 11 estimated for greenland during the opening of the labrador sea no positive evidence has been found to support models of distributed shear with block rotations to accommodate the contentious northeast translation of greenland along the nares strait

palaeoflood and floodplain records from spain evidence for long term climate variability and environmental changes abstract palaeoflood chronologies from seven spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed these fluvial records were divided in to two sub sets namely atlantic 10 ka record and mediterranean 3 ka record river basins which represent distinct modern hydroclimatic conditions in atlantic basins floods result from intense widespread rainfalls associated with atlantic frontal systems transported by westerly airflow mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems mcss during autumn months evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10 750 10 240 9550 9130 4820 4440 2865 2350 960 790 and 520 290 cal bp despite the different flood producing weather conditions in atlantic and mediterranean rivers the radiocarbon sample clusters overlap and indicate changes in large scale atmospheric circulation and climatic conditions in the iberian peninsula comparison with proxy records of mean temperature for the northern hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases e g the 2650 yr bp climatic event or ad 1590 1650 period of the little ice age radiocarbon dates from aggraded floodplain sediments were clustered at 2710 2320 2000 1830 and 910 500 cal bp the first cluster period is in phase with the timing of slackwater deposition whereas the third 910 500 cal bp occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records it is argued that the 910 500 cal bp floodplain aggradation period reflects the first post roman evidence of environmental change related to generalised land use changes at the catchment scale which produced high sediment load transported to overbank areas during high flows

rise of the base of the gas hydrate zone since the last glacial recorded by rock magnetism gas hydrate a clathrate of methane and water widespread on continental margins has been implicated as a trigger of climate change and submarine slides as a result of methane release when the base of its stability zone moves upward rapidly direct tests of these hypotheses are made difficult by the ephemeral record of gas hydrate in sediment in places a seismic reflector double bottom simulating reflector bsr appears to mark the old base of the gas hydrate layer but the occurrence of this feature is patchy and its interpretation is controversial microbial activity is stimulated in the presence of gas hydrate and results in the production of magnetic iron sulfides the base of the gas hydrate interval is marked by a sharp reduction in the magnetic hysteresis parameter d j h at hydrate ridge on the cascadia margin sampled during ocean drilling program leg 204 this signature occurs between 20 and 65 m below the present day base of the gas hydrate zone at a depth consistent with predictions for the base of gas hydrate stability given water depths and bottom water temperatures appropriate for the last glacial maximum seismic evidence for a double bsr over part of hydrate ridge corroborates the rock magnetic interpretation

origin of gas in gas hydrates as interpreted from geochemistry data obtained during the national gas hydrate program expedition 02 krishna godavari basin offshore india abstract this report presents the result of geochemical studies carried out on cores recovered from krishna godavari basin k g basin during the national gas hydrate program expedition 02 nghp 02 nghp 02 targeted gas hydrate accumulations in sand facies in the k g basin off the east coast of the indian peninsula three areas area b area c and area e in the k g basin were investigated during this expedition 10 research sites in k g basin were cored and samples for geochemistry analysis were collected high toc tn ratios indicate an input from terrestrial organic matter analysis of gas samples from pressure cores also acquired during nghp 02 were composed of mostly methane carbon isotopic studies show that methane gas sampled from recovered gas hydrate samples were derived from biogenic microbial sources this list of factors appears to indicate that the gas associated with the recovered hydrate bearing core samples were derived from a microbial source however the biogeochemical processes responsible for generating the microbial gases found with the recovered gas hydrates may not have been limited to current limits off the gas hydrate stability zone it is important to note here that microbial process likely extend to more than 1 km deep into the basin so gas coming from below the gh stability zone can still be from a microbial source in addition the microbial gas within the stability zone was likely in part recycled from hydrate accumulations that has passed through the base of the gas hydrate stability zone as a product of sedimentation with the dissociated microbial gas migration again vertically in the section entering the gas hydrate stability zone and reforming gas hydrates although the organic carbon required for in situ methanogenesis and gas hydrate formation is abundant in the shallow sedimentary section of the kg basin the faulted fractured and deformed stratigraphy observed in the kg basin coupled with high pore filling gas hydrate saturations at many sites suggests that advective processes may be contributing to the supply of methane to the gas hydrates in the kg basin the possible migration of gas from greater depths is also supported by seismic evidence of through going migration pathways that can connect the gas hydrate system with deeper petroleum systems it is important to note here that the deep conventional gas accumulations in the basin also contain microbially sourced gas

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

climatic and human influence on river systems and glacier fluctuations in southeast spain since the last glacial maximum abstract the semi desert environments of the mediterranean region are most sensitive to climatic changes and human land exploitation this paper is focused on the late pleistocene and holocene geomorphic evolution of southeast spain one of the driest regions in europe late pleistocene and holocene chronosequences of river terraces were established for the antas and aguas valleys respectively the deposition of up to four fluvial terraces during isotope stage 2 points to important erosion and accumulation processes at the end of late pleistocene in the vera basin in contrast to the stage 2 deposits the holocene terraces are composed of point bar deposits accumulated by meandering rivers with less sediment discharge according to the obtained 14c dating and extracted pottery fragments holocene terrace deposition occurred during the atlantic period early middle ages little ice age lia and the 20th century the most outstanding site in southern spain for studying holocene glacier shifts up to five end moraines is the veleta cirque in sierra nevada where the southernmost glacier of europe persisted during the little ice age the climate changes of the lia probably are recorded by two glacier fluctuations as indicated by 210pb dating and historical data the reconstruction of the evolution of the aguas and antas valleys stress that the aggradations of the lower terraces is mostly climate induced although during the last 500 years human interference in the landscape christian conquest mining boom of the 19th century etc may have played an important role to river dynamics

pleistocene and holocene fluvial development of the ecemis valley central anatolia turkey abstract the ecemis river developed during the pleistocene and holocene in the ecemis basin the basin developed because of tectonic movement on the ecemis fault which is west of the aladag mountains in the pleistocene glacial interglacial climate changes directly affected the regimes and discharges of rivers causing changes in river levels along the ecemis channel fluvial formations became extremely complicated when active tectonic movements accompanied the changes resulting from the climatic conditions the rivers embedded in their beds according to new local base levels in interglacials terraces formed due to interruptions in the cycle of morphological development along the ecemis river from the morphologic structure of these terraces and their positions in the ecemis valley two groups and five levels of terraces were defined in the ecemis valley modern terraces 1 5 m formed in the holocene while low terrace systems 5 10 m and 15 20 m and high terrace systems 30 40 and 70 80 m formed in the pleistocene

paleohydrological implications of late quaternary fluvial deposits in and around archaeological sites in syria abstract the importance of fluvial processes to the development of late quaternary landforms in arid regions is well established particularly for the american southwest in contrast much less information exists about past fluvial processes for other arid regions such as arabic countries in the middle east this paper reviews the characteristics of late quaternary fluvial deposits and landforms in syria an arid country with little previous quaternary geomorphic research relatively detailed information has been obtained from areas adjacent to archaeological sites because of collaborative activities with geomorphologists and other geoscientists such activities have resulted in intensive field surveys and associated results of complementary archaeological studies of lithic artifacts are useful for establishing the chronology of fluvial deposits although the number of existing studies is limited the available information points to marked changes in the mode of fluvial processes in response to late quaternary climatic change fluvial sedimentation was enhanced during the wet periods of mis 3 4 the pleistocene holocene transition and the mid holocene in contrast the lgm was characterized by limited fluvial sedimentation under a drier climate as well as enhanced carbonate precipitation near the land surface to form calcrete and oncoids

long timescale variation in bulk and clay mineral composition of indian continental margin sediments in the bay of bengal arabian sea and andaman sea abstract this study documents x ray diffraction results from bulk powders and oriented clay size aggregates using samples from sites drilled and cored during the indian national gas hydrate expedition 01 nghp01 these sites are located in the krishna godavari basin mahanadi basin and andaman accretionary wedge of the bay of bengal and the kerala konkan basin of the arabian sea calcite is more abundant at the pelagic sites of the andaman sea and kerala konkan basin which is consistent with previous studies of biological productivity and dilution by lithogenous influx hemipelagic sediments in the krishna godavari basin and mahanadi basin are comprised primarily of smectite rich and illite rich clay mineral assemblages respectively we attribute those contrasts to differences in detrital sources between the deccan basalts smectite sources and precambrian rocks of the eastern ghats belt those sources remained consistent over the entire history of sedimentation 0 9 ma higher quartz content in the mahanadi basin and higher feldspar content at the krishna godavari basin reinforce these interpretations of detrital provenance smectite is the most abundant clay mineral in the andaman sea sediments likely due to weathering of volcanic sources along the sunda arc strata from the kerala konkan basin show a shift at 23 ma from a smectite kaolinite clay mineral assemblage to an increasingly illite rich assemblage we also see steady decreases in kaolinite and increases in chlorite and quartz over the 30 myr record which indicates increasing influences of material derived from physical weathering the higher abundance of fully hydrated smectite in the krishna godavari basin may play a minor role in gas hydrate formation by sustaining higher permeabilities at any given value of mudstone porosity or void ratio

multi measurement approach for establishing the base of gas hydrate occurrence in the krishna godavari basin for sites cored during expedition nghp 02 in the offshore of india abstract the 2015 national gas hydrate program of india s second expedition nghp 02 acquired logging and coring datasets for constraining the base of the gas hydrate occurrence zone deepest gh and the theoretical base of gas hydrate stability zone bghs these data are used here for two primary goals to constrain the deepest occurrence of gas hydrate relative to predicted stability limits and the observed bsr and to characterize the nature of the contact between gas hydrate bearing sediment and the underlying gas hydrate free sediment a consensus depth for the deepest gh is derived for each nghp 02 coring site from downhole indicators of gas hydrate occurrence obtained from well log electrical resistivity and acoustic data pressure core compressional wave velocity measurements and conventional core measurements of anomalously low temperatures to establish the theoretical bghs models of gas hydrate phase stability with depth are compared with downhole temperature profiles derived from 1 assuming a constant geothermal gradient consistent with downhole temperature measurements and 2 assuming constant heat flow using a geotherm through the downhole temperature measurements and incorporating thermal conductivity calculated from borehole logging data although the deepest nghp 02 gh occurrences are controlled at several sites by a lithologic boundary most sites have deepest gh occurrences within a single coarse grained lithology cutoffs within a single coarse grained lithology which occur for the primary nghp 02 area b gas hydrate reservoir will inhibit pore pressure drawdowns used to extract methane from gas hydrate as an energy resource

human impacts on fluvial systems in the mediterranean region the long history of substantial human impacts on the landscape of the mediterranean region and their effects on fluvial systems is documented these effects have included impacts of deforestation and other land use changes agricultural terracing on a wide scale water transfers and irrigation schemes during the 20th century major changes were made directly to channels through channelisation construction of dams of various sizes and extraction of gravel and indirectly by reforestation these changes have caused a major phase of incision on some rivers runoff and soil erosion have been affected by types of crops and agricultural practices as well as by the varying extent of cultivation and grazing some recent agricultural practices involve wholescale relandscaping of the topography and alteration of surface properties of material the importance of analysing the connectivity within different land units and of the spatial position of human activity within a catchment is illustrated the analysis of connectivity is the key to understanding the variability of impact and the extent of propagation of effects

the gulf of valencia continental shelf extensional tectonics in neogene and quaternary sediments abstract seismic reflection profiles obtained with mud penetrator 3 5 khz sparker 3000 j uniboom 300 j and side scan sonar 100 khz enabled us to map recent morphostructural features extensional structures in neogene and quaternary sediments of the gulf of valencia shelf these structures are dominated by a group of normal faults trending subparallel to the coast the faults produced a series of steps in the neogene quaternary depositional series these sedimentary formations are very thick throughout the area decreasing southward in the direction of the betic system this distensive regime is still active today producing structures which affect the morphology of the shelf

paleomagnetism of permian through early triassic sequences in central spitsbergen implications for paleogeography upper carboniferous through lower triassic sediments from spitsbergen have yielded paleomagnetic results with those for the late gzhelian early permian being the more reliable the corresponding pole 38 n 171 e is fully concordant with the early permian segment of the apparent polar wander path for baltica it does not support hypotheses about post carboniferous mobilism of spitsbergen with respect to stable europe neither mesozoic nor later rifting processes changed the position of spitsbergen considerably in relation to the stable europe

comparison of the physical and geotechnical properties of gas hydrate bearing sediments from offshore india and other gas hydrate reservoir systems abstract the sediment characteristics of hydrate bearing reservoirs profoundly affect the formation distribution and morphology of gas hydrate the presence and type of gas porewater chemistry fluid migration and subbottom temperature may govern the hydrate formation process but it is the host sediment that commonly dictates final hydrate habit and whether hydrate may be economically developed in this paper the physical properties of hydrate bearing regions offshore eastern india krishna godavari and mahanadi basins and the andaman islands determined from expedition nghp 01 cores are compared to each other well logs and published results of other hydrate reservoirs properties from the hydrate free kerala konkan basin off the west coast of india are also presented coarser grained reservoirs permafrost related and marine may contain high gas hydrate pore saturations while finer grained reservoirs may contain low saturation disseminated or more complex gas hydrates including nodules layers and high angle planar and rotational veins however even in these fine grained sediments gas hydrate preferentially forms in coarser sediment or fractures when present the presence of hydrate in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the andaman islands properties of individual nghp 01 wells and regional trends are discussed in detail however comparison of marine and permafrost related arctic reservoirs provides insight into the inter relationships and common traits between physical properties and the morphology of gas hydrate reservoirs regardless of location extrapolation of properties from one location to another also enhances our understanding of gas hydrate reservoir systems grain size and porosity effects on permeability are critical both locally to trap gas and regionally to provide fluid flow to hydrate reservoirs index properties corroborate more advanced consolidation and triaxial strength test results and can be used for predicting behavior in other nghp 01 regions pseudo overconsolidation is present near the seafloor and is underlain by underconsolidation at depth at some nghp 01 locations

infilled valleys in the central ebro basin spain abstract the infilled valleys are one of the most frequent landforms that we have found in the central ebro basin area this study concerns those developed in the ebro basin near the city of zaragoza in a large number of these valleys as many as three levels of fill have been recognized these correspond to different accumulative stages and are separated by other periods with a dominant fluvial incision at present the principal process which acts in this area is gully erosion this fact has allowed us to observe the deposit characteristics these deposits are composed of gravels sands and thick levels of silts they have a large variety of sedimentary structures from these we know they are generated by ephemeral streams but there is also a slope material contribution in several cases there are archaeological fragments within the deposits thus we were able to determine the age of some of the levels the oldest fill has a post roman age the middle could have a post medieval age but we could not confirm that the youngest has been produced in recent times alternating sedimentation incision could be produced by the interaction between climatic and human action

potential freshening impacts on fines migration and pore throat clogging during gas hydrate production 2 d micromodel study with diatomaceous ubgh2 sediments abstract the methane gas hydrate stored in natural sediments is considered a potential gas resource countries such as china india japan and korea are interested in commercializing this resource and offshore field pilot tests for gas production have been conducted using depressurization methods to destabilize gas hydrate and facilitate the migration of methane to the production well however fine grained sediments fines which are present even in coarse grained gas hydrate bearing sediments can be resuspended in the production fluid subsequently clogging pore throats in the formation and reducing the overall production efficiency we conducted laboratory tests to evaluate the suspension and clogging potential of fines collected from the ulleung basin east sea korea during the 2010 ulleung basin gas hydrate expedition 2 ubgh2 experimental results reveal that diatoms are prevalent in the sediment and largely control the suspension and clogging behavior fluid flow experiments in 2d micromodels show clogging occurs even when injecting the minimum sediment concentration 0 1 wt in the fluid through micromodels with pore throat widths at the high end of the anticipated range for ubgh2 gas hydrate bearing sands 100 m mobile gas fluid interfaces forming during gas hydrate dissociation accentuate clogging by concentrating and mobilizing fines sedimentation tests show pore water freshening during dissociation is not anticipated to change the potential for diatoms to become entrained in the pore water flow even for the observed gas hydrate saturations of 80 muscovite and illite are also significant components of the tested sediment however and pore water freshening increases their potential for resuspension and clogging overall the resuspension and clogging potential of these fine sediments should increase as gas hydrate dissociation progresses in the thin gas hydrate bearing sands investigated in the ulleung basin

late holocene fluvial chronology of spain the role of climatic variability and human impact abstract a database of published and unpublished radiocarbon dates from late holocene fluvial environments in spain was critically analysed in order to obtain a fluvial chronology for this period the principal types of depositional environment represented in the record were slackwater flood deposits 28 dates alluvial overbank facies 12 dates and alluvial channel facies 7 dates the sedimentary context of each date was classified in order to identify those samples that specifically dated change in the fluvial environment analysis of the different depositional environment data sets using summed probability plots identified phases of alluviation at 2800 2350 and 800 500 cal bp increased frequency of large magnitude floods occurred at 2850 2500 1000 800 and 520 250 cal bp the results indicate that in mediterranean regions slackwater flood deposits are valuable archives of climatic variability even during periods of increased human impact

hydrate morphology physical properties of sands with patchy hydrate saturation 1 the physical properties of gas hydrate bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase the host sediment grain size and the state of effective stress determine the hydrate morphology in sediments this information can be used to significantly constrain estimates of the physical properties of hydrate bearing sediments including the coarse grained sands subjected to high effective stress that are of interest as potential energy resources reported data and physical analyses suggest hydrate bearing sands contain a heterogeneous patchy hydrate distribution whereby zones with 100 pore space hydrate saturation are embedded in hydrate free sand accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate bearing sands and captures observed physical property dependencies on hydrate saturation for example numerical modeling results of sands with patchy saturation agree with experimental observation showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations the hydrate patch size itself impacts the physical properties of hydrate bearing sediments for example at constant hydrate saturation we find that conductivity electrical hydraulic and thermal increases as the number of hydrate saturated patches increases this increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross section of the specimen

predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio this paper assesses methods to predict the saturated hydraulic conductivity k of clean sand and gravel currently in engineering the most widely used predictive methods are those of hazen and t

a review of paleomagnetic results from the carboniferous of north america the concept of carboniferous geomagnetic field horizon markers results from the east coast carboniferous basin contain an important time stratigraphic horizon of possible global significance late carboniferous units are found to have mostly reversed magnetizations while older carboniferous units may have normal reverse or most frequently dual polarity magnetizations this feature records the change in geomagnetic field from a period of common polarity changes to a period of mainly reversed polarity the kiaman magnetic interval recognition of the stratigraphic position of this polarity feature provides a time line for correlation of units within and among carboniferous basins in the east coast carboniferous basin of atlantic canada this horizon has now been located at the riversdale group level early pennsylvanian namurian westphalian boundary since remanence acquisition of red sediments is often a lengthy process possibly spanning field reversal time scales red bed units pre dating and post dating this time line can in most instances be readily distinguished the former generally recording both polarities and the latter just one reverse polarity a polar displacement of at least 16 is recorded in the results from the east coast carboniferous basin paleolatitude maps show that the area was located near the equator and was displaced northwards by about 8 during the pennsylvanian it cannot be ascertained if those observations are representative of the whole of north america or merely the atlantic seaboard poles derived from other areas of north america do not all fit the regular pattern observed on the atlantic coast using the horizon marker as a tool it is suggested that those poles are post time line in age so that none of them is representative of the position of north america prior to the time line

compressional and shear wave velocities in uncemented sediment containing gas hydrate 1 the competing hypotheses for gas hydrate formation at the particle scale in sediments describe processes of pore filling frame building or cementation new measurements of compressional vp and shear wave vs velocities in fine grained sands subjected to low confinement and monitored during formation of tetrahydrofuran hydrate indicate that hydrate nucleates in the pore space presumably at grain boundaries and grows with limited impact on the sediment shear stiffness vp and vs until crystals begin to interact with the granular skeleton at 40 hydrate concentration vs increases significantly more than vp at higher hydrate concentrations reflecting larger changes in the specimen s shear stiffness than its bulk stiffness the results indicate that seismic velocities and or their ratio vp vs have limited capability for locating hydrate or constraining hydrate concentrations

thermal properties of highly saturated methane hydrate bearing sediments recovered from the krishna godavari basin abstract we measured the thermal constants including conductivity specific heat and thermal diffusivity of methane hydrate mh bearing sediment samples recovered in 2015 from the krishna godavari basin in india these samples were recovered through the national gas hydrate program expedition 02 nghp 02 the measurements were performed using the single sided transient plane source tps method to investigate the influence of the sediment composition on the thermal properties of mh bearing sediments the thermal constants of mh bearing sediments were measured at 5 c and 10 mpa over a porosity range of 41 51 and mh saturation sh range of 17 sh 74 in addition density and mineral compositional measurements of the dry sediment grain samples were conducted the measured thermal conductivity slightly decreases with increasing and is independent of sh the measured specific heat increased with increasing whereas it decreased with increasing sh the measured thermal diffusivity decreased with increasing whereas it increased with increasing sh various models were used to estimate the thermal constants to examine the applicability of these models to natural mh bearing sediments the distribution model using a geometric mean model is valid from the low to high mh saturations however the thermal properties of clay rich layers are not likely reproducible by the distribution model from the mineral compositions this indicates that the low value of the observed thermal conductivity in the clay rich samples is likely a product of the sediment s small grain size

thermal conductivity of hydrate bearing sediments 1 a thorough understanding of the thermal conductivity of hydrate bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone the coexistence of multiple phases gas hydrate liquid and gas pore fill and solid sediment grains and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate bearing sediments previous studies have been unable to capture the full parameter space covered by variations in grain size specific surface degree of saturation nature of pore filling material and effective stress for hydrate bearing samples here we report on systematic measurements of the thermal conductivity of air dry water and tetrohydrofuran thf saturated and thf hydrate saturated sand and clay samples at vertical effective stress of 0 05 to 1 mpa corresponding to depths as great as 100 m below seafloor results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size effective stress porosity and fluid versus hydrate filled pore spaces the thermal conductivity of thf hydrate bearing soils increases upon hydrate formation although the thermal conductivities of thf solution and thf hydrate are almost the same several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment increased mean effective stress due to hydrate formation under zero lateral strain conditions and decreased interface thermal impedance as grain liquid interfaces are transformed into grain hydrate interfaces

use of alloformations for definition of holocene meander belts in the middle amite river southeastern louisiana geomorphological studies in drainage basins of the northern gulf of mexico coastal plain have indicated similarities in flood plain character and comparable influences on basin evolution alluvial morphology and stratigraphy can be linked to flood plain evolution through the use of alloformations unconformity bounded stratigraphic units this procedure extends classical terrace mapping concepts to conform with formally defined stratigraphic procedures a meander belt segment of the middle amite river valley in southeastern louisiana was selected to test the applicability of alloformation mapping in part of a regional scale 5 000 km 2 drainage basin three alloformations identified as magnolia bridge mag denham springs ds and watson wat can be differentiated by unconformable boundaries landscape morphology and relative pedogenic development the valley fill consists of a lower sandy and upper silty facies preserved deposits consist of channel lag point bar and scroll bar channel fill and overbank sequences lithofacies and sedimentary environments are dependent on fluvial process and a suite of meander belt environments can be identified within each alloformation surface horizons of alluvial soils are all similar ochric epipedons but subsoil horizons are chiefly stratified parent material on the mag entisols cambic horizons on the ds inceptisols and minimally developed argillic horizons on the wat alfisols allostratigraphy provides an objective method for definition of geologic units that contain genetically related but heterogeneous sedimentary deposits alluvial sediments are differentiated in a manner that successfully integrates geomorphic sedimentologic and pedologic data into significant stratigraphic models this approach is applicable to a wide variety of quaternary settings where prior stratigraphic techniques have resulted in ambiguity

paleomagnetic constraints on the assembly of the old red continent abstract a model is proposed on the basis of paleomagnetic and geological arguments for the assembly of the old red continent which in the devonian comprised north america the baltic shield and russian platform as well as a third element called armorica the latter is thought to have included most of hercynian europe and southern england and wales as well as possibly the avalonian terranes of northeastern north america and perhaps some parts of the atlas ranges and moroccan meseta the model envisions a late ordovician taconic collision of north america and armorica which are joined in the late silurian by the baltic shield and russian platform not until the late early carboniferous did gondwana join the old red continent in a collision responsible for a large internal megashear parallel to the caledonian orogenic belt as well as the hercynian alleghenian orogeny subduction of the large siluro devonian ocean between gondwana and the old red continent is held responsible for the mid devonian acadian orogeny

weichselian palynological records from southern europe correlation and chronology abstract the high resolution independently dated palynostratigraphic record from lago grande di monticchio spanning the last 101 530 calendar years provides a basis for re evaluating the correlations between palaeoenvironmental events in europe during the last glacial as well as a means to determine their chronology the interstadial events recorded from various localities throughout europe are combined into a single scheme of correlations and a chronological framework is suggested this provides a basis for assessing the evolution of the vegetation and environmental patterns across europe during the last glacial revealing a general tendency for the latitudinal climatic gradient to have been steeper than it has been during the holocene the vegetation has also generally been subject to greater moisture deficiency either because of prevailing climatic conditions or as a reflection of the lower atmospheric concentration of co 2 the scheme of correlations is shown to be capable of being extended beyond europe not only to marine and ice core records from the north atlantic region but also to a palynological record from north west north america

gas hydrate saturations estimated from fractured reservoir at site nghp 01 10 krishna godavari basin india 1 during the indian national gas hydrate program expedition 01 nghp 01 one of the richest marine gas hydrate accumulations was discovered at site nghp 01 10 in the krishna godavari basin the occurrence of concentrated gas hydrate at this site is primarily controlled by the presence of fractures assuming the resistivity of gas hydrate bearing sediments is isotropic the conventional archie analysis using the logging while drilling resistivity log yields gas hydrate saturations greater than 50 as high as 80 of the pore space for the depth interval between 25 and 160 m below seafloor on the other hand gas hydrate saturations estimated from pressure cores from nearby wells were less than 26 of the pore space although intrasite variability may contribute to the difference the primary cause of the saturation difference is attributed to the anisotropic nature of the reservoir due to gas hydrate in high angle fractures archie s law can be used to estimate gas hydrate saturations in anisotropic reservoir with additional information such as elastic velocities to constrain archie cementation parameters m and the saturation exponent n theory indicates that m and n depend on the direction of the measurement relative to fracture orientation as well as depending on gas hydrate saturation by using higher values of m and n in the resistivity analysis for fractured reservoirs the difference between saturation estimates is significantly reduced although a sizable difference remains to better understand the nature of fractured reservoirs wireline p and s wave velocities were also incorporated into the analysis

paleoposition of the northern margin of armorica in late devonian times paleomagnetic and rock magnetic results from the frankenstein intrusive complex mid german crystalline rise a detailed rockmagnetic and paleomagnetic study of the frankenstein intrusive complex fic 363 7 ma in age southwestern germany has been carried out in order to test whether the paleomagnetic declinations within the internal parts of the european variscides follow a common trend controlled by the structural grain of the orogen or whether the distribution of declinations follows a random pattern in addition new paleomagnetic data will contribute to further refine the drift history of the armorican terrane assemblage during late paleozoic times the unmetamorphosed frankenstein igneous complex forms part of the mid german crystalline rise within the armorican terrane assemblage amalgamated to avalonia and baltica during the variscan orogeny stepwise thermal and alternating field af demagnetization experiments identify four components a b c n and c r of magnetization component a is a recent viscous overprint that parallels the present day geomagnetic field the high unblocking temperatures of a in some samples can be explained by the presence of multidomain magnetite component b is carried by hematite and is considered to be a late carboniferous remagnetization components c r and c n found in 110 samples from 20 sites are antiparallel and pass a class c reversal test their primary origin is further supported by a contact test c r and c n have maximum unblocking temperatures of up to 580 c and occasionally above over 600 c indicating magnetite and hematite to carry the characteristic remanent magnetization ore microscopy revealed that primary hematite lamellae in ilmenite carry c r and c n and that a secondary generation of hematite is the carrier of b the overall site mean direction of c r and c n 20 sites based on endpoints and remagnetization circle analysis of 198 40 declination inclination with a 95 confidence limit 95 of 4 9 and a precision parameter k of 45 0 defines a paleopole at 15 s 9 w when comparing to the apparent polar wander path for stable europe this result indicates up to 27 counterclockwise rotation of the fic region this is significantly less than reported previously for the odenwald spessart black forest and the vosges massifs of the central european variscides furthermore the resulting paleolatitude indicates significant separation between baltica and this sector of the armorican terrane assemblage in the latest devonian

gas hydrate saturation and reservoir characterization at sites nghp 02 17 and nghp 02 19 krishna godavari basin eastern margin of india abstract we have characterized the gas hydrate reservoir at sites nghp 02 17 and nghp 02 19 based on isotropic and anisotropic velocity modeling by utilizing both the wireline wl and logging while drilling lwd data independently the isotropic study is carried out using the simplified three phase biot equation stpbe with density derived porosity and calculated bulk density of sediments as inputs the anisotropic study uses the transverse isotropic theory for laminated media by considering a layered reservoir model composed of two components i fractures filled with 100 gas hydrates and ii isotropic medium composed of water saturated sediments in the anisotropic velocity modeling the reservoir is modeled by incorporating fractures with varying dip angles from 0 to 90 we estimated gas hydrate saturations using isotropic and anisotropic velocity analysis at both sites nghp 02 17 and nghp 02 19 in both the cases the lwd data derived isotropic model yielded what appears to be the most accurate values an average saturation of 45 8 in the high velocity interval between 269 and 285 5 mbsf at site nghp 02 17 and 33 8 in the high velocity interval between 306 and 312 mbsf in nghp 02 19

sediment budget of the rhone delta shoreface since the middle of the 19th century this study analyses long term 1841 1872 1895 1974 changes in the grand rhone prodeltaic lobe to 1 quantify the accumulation 2 determine the evolution of relict prodeltaic lobes and 3 establish long term relationships between river sediment discharge the shoreface and the continental shelf our results show a reduction of the sedimentation of the prodeltaic lobe at the main river mouth since 150 yr by a factor of 3 7 12 63 to 3 41 10 6 m 3 yr 1 at the minor mouth of the river erosion dominates and speeds up during the same period 0 53 to 1 34 10 6 m 3 yr 1 these changes are found to directly result from the river sediment input decrease related to the natural decreasing of the frequency of major floods end of the little ice age the reforestation in the catchment area the dam construction and the dredging activities since the 1950s our results indicate that while there is large sediment accumulation in the area around a growing prodeltaic lobe there is also a reduced contribution of the river sediments to the non adjacent beaches of the mouth following a shift in the river channel and mouth the relict prodeltaic lobes petit rhone st ferreol bras de fer and pegoulier are reworked by waves and their sediments contribute partially to the growth of the spits espiguette beauduc and gracieuse this suggests that there is a time shift between the input of river sediment to the sea and the build up of a beach the chronic erosion of the coastline is likely to continue in the future since 1 a river shift is not possible because the river channels are controlled by dykes and human intervention 2 the decrease of river sediment input and 3 the relict prodeltaic lobes constitute sedimentary reservoirs that are gradually being used up 2006 published by elsevier b v

osl dating of coarse grain fluvial quartz using single aliquot protocols on sediments from ne peloponnese greece abstract optical ages of quartz extracts in holocene sediments from the north eastern peloponnese greece are reported the single aliquot regenerative dose protocol proposed by murray and wintle 2000 radiation measurements 32 57 73 was used to estimate the equivalent dose in these samples a large inter aliquot scatter in d e values was observed for all samples this is ascribed to heterogeneous bleaching of the samples at deposition to estimate a d e for age calculation a technique is suggested based on the analysis of the d e scatter obtained from nine different quartz samples which were artificially bleached and irradiated this procedure is especially useful when the sample quantity is limited the optical age estimates increase with sampling depth an average aggradation rate of 1 5 mm yr is derived using the osl ages this value is consistent with the known uplift rate of 1 2 mm yr

sedimentation stratigraphy and petroleum potential of krishna godavari basin east coast of india the krishna godavari basin is located in the central part of the eastern passive continental margin of india the structural grain of the basin is northeast southwest exposures of upper cretaceous sedimentary rocks demarcate the basin margin toward the north west where the northwest southeast trending pranahita godavari graben abuts the basin the basin contains thick sequences of sediments with several cycles of deposition ranging in age from late carboniferous to holocene a major delta with a thick argillaceous facies that has prograded seaward since the late cretaceous is a hydrocarbon exploration target magnetic and gravity data predicted the basin architecture which was subsequently confirmed by a multichannel seismic sur vey the basin is divided into subbasins by fault controlled ridges sediments accumulated in subbasins more than 5 km thick above the basement ridges thin sediments are found until the jurassic period sediments were deposited in the rift valley and in topo graphic lows this sequence is completely overlain by a lower cretaceous transgressive sedimentary wedge later continued delta progradation characterized basin sedimentation with an areal extent of approximately 45 000 km2 this proven petroliferous basin has potential reservoirs ranging in age from the permian to the pliocene exploratory drilling of more than 350 wells in more than 160 structures has resulted in the discovery of 42 oil and gas bearing structures good source rocks are known from sequences ranging in age from permian carboniferous to early miocene because the reservoir sand bodies have limited lateral variation understanding the stratigraphy and depositional sub environments in different sequences is essential to decipher the favorable locales for reservoir sands tilted fault blocks growth faults and related rollover anticlines provide the structural traps begin page 1624

numerical analysis of gas production potential from a gas hydrate reservoir at site nghp 02 16 the krishna godavari basin offshore india feasibility of depressurization method for ultra deepwater environment abstract sandy gas hydrate reservoirs are considered to be promising deposits for gas recovery but the feasibility of the depressurization method in ultra deepwater environments remains unclear because high pressure gradient induced by depressurization may increase the water production and reduce the gas water ratio of produced fluid in numerical simulations this study predicts the gas production behavior of a hydrate reservoir site nghp 02 16 in the krishna godavari basin offshore india located in ultra deepwater depth 2546 5 m the reservoir properties such as the hydrate saturation and initial effective in situ permeability were determined from log data and pressure core analysis by comparing the hydrate saturations calculated from resistivity log with the estimations from p wave velocities of pressure cores the model parameters a m and n of archie s equation were determined as 1 8 2 0 and 2 9 respectively the initial effective permeability of the hydrate bearing layers with up to 78 hydrate saturation was estimated to range from approximately 0 01 to 1 0 millidarcy md at day 180 after the start of depressurization in a single vertical well the gas production rates ranged from 320 to 9500 sm3 d depending on the bottom hole pressure lowering the bottom hole pressure increased the gas production rate and gas water ratio of the produced fluid the bottom hole pressure of 10 mpa or less is recommended for the production test condition in this site however aquifer below the gas hydrate bearing zone and poor hydraulic sealing of the over and under burden increased the water production hydraulic isolation of the gas hydrate bearing layers is essential when applying depressurization in an ultra deepwater environment

geomorphology and quaternary stratigraphy the roles of morpho litho and allostratigraphy abstract the subdivision and ordering of quaternary sediments and landforms is very often based on geomorphology quaternary landforms such as moraines river terraces palaeoshorelines and indeed any other landform can be arranged and ordered in time based on their relative position in the landscape morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form whilst surface form is often used as a criterion for separating sedimentary units morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision and morpho and lithostratigraphy are often interlinked in quaternary science however another approach allostratigraphy has increasingly been applied to subdivide and order quaternary sediment landforms allostratigraphy uses discontinuities to subdivide sedimentary successions allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit furthermore it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities this paper examines the applications of morpho litho and allostratigraphy to subdivide sediment landform assemblages and critically reviews their role in quaternary stratigraphy

gas hydrate reservoir identification delineation and characterization in the krishna godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition offshore india abstract during the national gas hydrate program expedition 02 nghp 02 logging while drilling conventional coring and pressure coring wire line logging vertical seismic profiling and formation pressure measurements were carried out in deep water portions of the krishna godavari k g and mahanadi basins along the eastern continental margin of india a total of 42 research holes were completed for comprehensive data collection and measurements related to gas hydrate reservoir and host sediments properties with an objective to identify producible gas hydrate in sand rich reservoirs that would be suitable for a future pilot production test shipboard and post cruise evaluation of physical properties measurements pressure core dissociation studies and gas analysis of recovered core samples have confirmed the occurrence of sand hosted gas hydrate deposits in three operational areas named during nghp 02 as area b area c and area e in the deep water portion of the k g basin the energy resource potential of the discovered gas hydrate deposits in the k g basin depends on many factors including the quantity of available gas trapped as gas hydrate in the basin therefore this study was undertaken to identify characterize and delineate the discovered and confirmed gas hydrate prospects in the k g basin based on the integrated analysis of regional seismic data and nghp 02 acquired borehole data a total of 8 sand rich reservoir constrained gas hydrate prospects have been identified and mapped in the k g basin areas b c and e as described in this report

an international code comparison study on coupled thermal hydrologic and geomechanical processes of natural gas hydrate bearing sediments abstract geologic reservoirs containing gas hydrate occur beneath permafrost environments and within marine continental slope sediments representing a potentially vast natural gas source numerical simulators provide scientists and engineers with tools for understanding how production efficiency depends on the numerous interdependent coupled processes associated with potential production strategies for these gas hydrate reservoirs confidence in the modeling and forecasting abilities of these gas hydrate reservoir simulators ghrss grows with successful comparisons against laboratory and field test results but such results are rare particularly in natural settings the hydrate community recognized another approach to building confidence in the ghrs comparing simulation results between independently developed and executed computer codes on structured problems specifically tailored to the interdependent processes relevant for gas hydrate bearing systems the united states department of energy national energy technology laboratory doe netl sponsored the first international gas hydrate code comparison study ighccs1 in the early 2000s ighccs1 focused on coupled thermal and hydrologic processes associated with producing gas hydrates from geologic reservoirs via depressurization and thermal stimulation subsequently ghrss have advanced to model more complex production technologies and incorporate geomechanical processes into the existing framework of coupled thermal and hydrologic modeling this paper contributes to the validation of these recent ghrs developments by providing results from a second ghrs code comparison study ighccs2 also sponsored by doe netl ighccs2 includes participants from an international collection of universities research institutes industry national laboratories and national geologic surveys study participants developed a series of five benchmark problems principally involving gas hydrate processes with geomechanical components the five problems range from simple geometries with analytical solutions to a representation of the world s first offshore production test of methane hydrates which was conducted with the depressurization method off the coast of japan to identify strengths and limitations in the various ghrss study participants submitted solutions for the benchmark problems and discussed differing results via teleconferences the ghrss evolved over the course of ighccs2 as researchers modified their simulators to reflect new insights lessons learned and suggested performance enhancements the five benchmark problems final sample solutions and lessons learned that are presented here document the study outcomes and serve as a reference guide for developing and testing gas hydrate reservoir simulators

pre holocene sediments in the barranco de las lenas central ebro basin spain as indicators for climate induced fluvial activities abstract in the central inner ebro basin valleys infilled with young alluvial sediments are very common they are usually incised by deep gullies previously these sediments were assumed to be of holocene age and their infilling was seen in connection with different periods of climatic deterioration and increasing human impact in the barranco de las lenas an eastern tributary of the huerva river south of zaragoza the sediments are up to 15 m thick and consist of 20 60 cm thick interbedded layers of argillaceous silt pure silt sandy loamy silt sandy silt with fine grit which are interrupted by 5 25 cm thick discontinuous cobble and gravel layers with silty matrix the sediments contain horizontal organic layers and charcoal pieces of remarkable size a 2 2 m high outcrop in the upper part near the recent end of the incision was radiocarbon dated with the ages ranging from 17765 15440 cal bp to 13140 12650 cal bp a 1 2 m sediment sequence between two organic mud layers with an age of 14040 12975 cal bp at the base and 13140 12650 cal bp at the top indicates a climatically induced highly active phase of morphodynamic processes within a period of 1400 years at the longest older sediments from the pleniglacial have been reworked the analyses of the sediments and data suggest that these few single events are indicators for strong climatic changes in the late glacial allerod period the results show that similar highly dynamic processes can occur without human impact these results strongly contrast with previously published investigations that dated such fillings as younger holocene

baltica a synopsis of vendian permian palaeomagnetic data and their palaeotectonic implications torsvlk t h smethurst m a van der voo r trench a abrahamsen n and halvorsen e 1992 baltlca a synopsis of vendlan permmn palaeomagnetic data and their palaeotectonlc implications earth sci rev 33 133 152 in light of recent additions to the palaeozoic palaeo magnetlc data base particularly for the ordovlclan era a revised apparent polar wander apw path for baltica has been constructed following a rigorous synthesis of all late precambrlan perm lan data the apw path is characterized by two prominent loops firstly a late precambrlan camb rlan loop probably relating to a rifting event and secondly a younger loop relating to a mid silurian scandlan colhsion event these features imply major change in plate tectonic reconfiguratlon baltlca probably represented an individual continental unit m early palaeozoic times and was positioned m high southerly latitudes in an inverted geographic orientation in such a reconstruction baltlca was separated from the northern margin of gondwana by the tornqulst sea and from laurentla by the iapetus ocean the tornqulst zone is thus interpreted as a passive or dextral transform margin during the early palaeozoic while undergoing counter clockwise rotations up to 1 6 ma baltica drifted northward through most ol the palaeozoic except for a short period of southerly movement in late silurian early devonian times after colhslon with laurentla rapid movements in latitude up to 9 cm yr are noted m late precambrlan earl y palaeozoic times and slgmficant decrease in velocities throughout palaeozoic time probably reflect the progressive amalgamation of a larger continent by early devonian euramerlca and permian pangea times the tornqulst sea had a principal component of palaeo east west orientation hence it is difficult to be precise in the timing of when micro continents such as eastern avalonla and the european masslfs ultimately collided along the southwestern margin of baltica these micro continents are considered to have been peripheral to gondwana m high southerly latitudes during the early ordovlclan eastern avalonla clearly had rifted off gondwana by llanvlrn llanded o times and may have collided with baltlca during late ordovlclan times although the present available sdunan palaeomagnetlc data from eastern avalonia may suggest colhslon in late silurian times across the lapetus facing margin of baltica laurentla was s tuated in equatorml to southerly latitudes during most of the lower palaeozoic these continents collided in mid silurian times l e a first collision between southwestern norway and greenland scotla nd which gave rise to the early scandlan orogeny 425 ma in southwestern norway possible followed by a later but less dramatic scandlan event in northern norway at around 410 ma since baltlca was geographically reverted m early palaeozoic times the colhsional margin could not have been a margin that once rifted off laurentm as assumed in a number of plate tectonic models

electrical anisotropy due to gas hydrate filled fractures in 2006 the indian national gas hydrate program expedition01 ornghp 01 discoveredgashydrateasfillinnearvertical fractures in unconsolidated sediments at several drillingsitesontheindiancontinentalmargins thesegashydrate filled fractures were identified on logging while drilling resistivity images the gas hydrate filled fracture intervals coincide with high measured resistivity at the nghp 01 sites high measured resistivity translates into high hydrate saturationsviaarchie sequation however thesehighsaturations contradict lower gas hydrate saturations determined from pressure core and chlorinity measurements also in intervalswithnear verticalgashydrate filledfractures thereis considerable separation between phase shift and attenuation resistivity logs with 2 mhz resistivity measurements being significantly higher than 400 khz resistivity measurements we modeled the sensitivity of the propagation resistivity measurements in the gas hydrate filled fracture intervals at nghp 01 sites 5 and 10 near vertical hydrate filled fracturescancausetheabnormallyhighresistivitymeasurements in vertical holes due to electrical anisotropy the model suggests the gas hydrate saturations in situ are usually significantlylowerthanthosecalculatedfromarchie sequation in addition these modeled gas hydrate saturations generally agree with the lower gas hydrate saturations obtained from pressure core and chlorinity measurements at nghp 01 sites5and10

the valencian coast western mediterranean neotectonics and geomorphology abstract an analysis of terrestrial and marine data has shown the coastal fringe of the emerged continent to be naturally divided into five distinct morphosedimentary sectors whereas three clearly different large domains are visible in the submarine shelf this geographic coastal space corresponds to an area of wide tectonic activity where the internal and external units of betic ranges meet showing a morphological expression of the substratum structure on the contrary the continental shelf located to the north in the gulf of valencia is subsiding and has important accumulations of sediments as a consequence of the influence of units linked to the iberic orogeny the detailed analysis of the tectonic and geomorphic elements illustrated a correlation between the morphosedimentary sectors of the emerged coastal area and the corresponding ones in the inner and middle continental shelf this reveals that the littoral is affected by a general increase in structural and morphological complexity from north to south

physical property characteristics of gas hydrate bearing reservoir and associated seal sediments collected during nghp 02 in the krishna godavari basin in the offshore of india abstract india s national gas hydrate program expedition 02 nghp 02 was conducted to better understand geologic controls on gas hydrate occurrence and morphology targeting coarse grained sediments along the lower continental slope offshore eastern india this study combines seismic logging while drilling data and a petroleum system approach to provide a regional geologic and lithologic context for 1 gas hydrate morphology and distribution and 2 effects of fine grained sediments clays and other grains smaller than 63 m on gas production in nghp 02 area b in the krishna godavari basin area b seismic data show a buried anticline syncline structure with strong reflectors r1 and r2 that delineate two of the five lithologic units unit i shallowest ii r1 iii iv r2 and v below the bas of gas hydrate stability throughout area b gas hydrate morphology depends on its placement within these units specifically core and grain scale measurements indicate fines content exerts a primary control on the gas hydrate distribution and morphology units i ii and iii are generally fine grained on the anticline crest these units host primarily grain displacing gas hydrate veins linked to pore occupying gas hydrate in thin localized coarser grained deposits diatoms in unit iii increase porosity with depth reaching 70 where it contacts unit iv the gas hydrate reservoir associated with reflector r2 the unit iii lithology and porosity allow fluid and dissolved phase methane to escape unit iv and form gas hydrate in the fine grained overburden within unit iv fine grained layers are interbedded with coarser grained gas hydrate reservoir sands and the fines content even in the sands is high enough to impact hydraulic and mechanical properties during gas production fluid motion during gas production can mobilize fines which can then clog pore throats limiting production rates pore water freshening during gas hydrate dissociation can increase fines mobilization particularly given the smectite identified in the fine grained interbeds

regional stratigraphic framework and gas hydrate occurrence offshore eastern india core log seismic integration of national gas hydrate program expedition 02 nghp 02 area b drill sites abstract the indian national gas hydrate program expedition 02 nghp 02 was designed to study the occurrence of gas hydrate along the passive continental margin of the indian peninsula in the bay of bengal twelve holes were logged and measured with logging while drilling lwd and five holes were cored in area b of nghp 02 the lwd and coring results in area b helped to understand the geological significance of sequence stratigraphy in krishna godavari basin and identified the occurrence of gas hydrate this study summarized the log and litho units in area b and establish three integrated units based on the core log seismic integration most of the downhole log and core inferred gas hydrate occurrences are in the late miocene integrated unit b with several sets of reservoir sections exhibiting favorable conditions for hosting gas hydrate the gas hydrates reservoirs associated with reflectors r1 and r2 were identified and the r1 reservoirs are characterized by fracture and pore filling gas hydrate and the r2 is in sand rich sediments with pore filling gas hydrate at high saturations the thickness variations associated with the r1 and r2 are possibly associated with the development anticlinal structure and are likely related to syn sedimentary growth of the folding structures major gas hydrate zones exist in and around the r1 and r2 near the bsr depth and mostly have coincident with the fractures and mass transport deposits the spatial distribution of gas hydrate in the r1 and r2 reservoirs is highly influenced by the anticlinal structure this study can be considered a good case for the future gas hydrate studies and explorations in the nearby areas

sub millennial climate shifts in the western mediterranean during the last glacial period recorded in a speleothem from mallorca spain very few high resolution and directly dated terrestrial archives of the last glacial period exist for the western mediterranean region yet this is a key locality for recording sub millennial north atlantic and mediterranean climate change here we present evidence of effective precipitation changes based on growth history and 13c of calcite in a mallorcan stalagmite that grew between 112 and 48 ka effective precipitation in mallorca appears to have been sensitive to proximal sea surface temperature variations and at certain times ca 76 ka for example changed rapidly from moist to arid conditions in only a few centuries a sea level highstand during marine isotope stage mis 5a interrupted growth regrowth started promptly after this but effective precipitation decreased markedly for much of the later part of mis 5a and also for shorter periods correlative with heinrich events h8 ca 90 ka and h6 ca 65 ka with growth ceasing during h5 ca 48 ka arid episodes in mallorca appear to be expressions of extremely cold periods recorded further north in europe and occur contemporaneously with rapid decreases in greenland temperature copyright 2008 john wiley sons ltd

cenozoic landscape development within the central iberian chain spain abstract in the central iberian chain spain covering an area of some 7400 km 2 up to seven stepped erosion surfaces are determined from aerial photographs and field observations these planation surfaces situated between 1000 and 1600 m a s l are separated by erosional scarp slopes most parts of the erosion surfaces are developed on mesozoic limestones and form stepped rims around the main elevations of the iberian chain it is proposed that the surfaces were formed by erosional events associated with periods of uplift related to eocene miocene compressional tectonic activity the palaeogene uplift was related with syntectonic sedimentation in internal basins with up to 3500 m of accumulated thickness during the neogene middle miocene pliocene post tectonic period the lowered synclinal areas formed residual internally drained basins that were filled with non marine deposits mainly clays and limestones the filling of the internally drained sedimentary basins located within the iberian chain onlapped onto the ancient erosional surfaces covering the lower younger levels the recent landscape evolution of the whole area is controlled by the capture of the internal basins and the dissection of the ancient relief by the present day fluvial network this process is related with the transition from internal to external drainage of the ebro basin

gas hydrate occurrence and distribution controlled by regional geological structure off eastern india estimates from logging while drilling in area b national gas hydrate program expedition 02 nghp 02 abstract the national gas hydrate program expedition 02 nghp 02 was designed to examine gas hydrate occurrences off the eastern margin of the indian peninsula twelve holes were logged with logging while drilling lwd tools and nine holes at five sites were cored in area b of nghp 02 five logging units were defined based on the characteristics in logging data responses distinctive logging units r1 and r2 characterized by high gamma ray log values and composed of quartz and biotite rich medium sized sand grain units that act as gas hydrate resevoirs and correlated to strong seismic reflectors hydrate bearing intervals can be identified by resistivity and sonic velocity logs and classified into pore filling type fracture filling type and a mixture of pore and fracture filling types based on borehole image characteristics pore filling type gas hydrate is typically developed in the case where the depths of r1 and or r2 is close to the seismic inferred bottom simulating reflector bsr fracture filling type hydrates associated the r1 section occur above the bsr associated with the anticline in area b the occurrence of pore filling and fracture filling gas hydrate represent different processes of hydrate formation related to the regional geological structure the stratigraphic layered pore filling gas hydrate occurrences are generated along often dipping sand layers which are also conduits for methane bearing fluid migrating from below the bsr in many settings fracture filling type gas hydrate is an alternative mechanism for the occurrence of gas hydrate in mudstone rich sediments above the bsr and found associated with the anticline in area b this structural constraint of the hydrate bearing fractures in the area b anticline suggest that the fracture dominated reservoirs possibly formed by anticlinal flexure and the upward flow of methane bearing fluids along porous sedimentary layers and the subsequent formation of pore filling gas hydrate occurrences account for the range of gas hydrate accumulations discovered during nghp 02

reconstructions of the continents around the north atlantic at about the 60th parallel abstract late carboniferous early tertiary apparent polar wander apw paths 300 40 ma for north america and europe have been tested in various reconstructions these paths demonstrate that the 500 fathom bullard et al fit is excellent from late carboniferous to late triassic times but the continental configuration in northern pangea changed systematically between the late triassic ca 214 ma and the mid jurassic ca 170 ma due to pre drift extension best fit north atlantic reconstructions minimize differences in the late carboniferous early jurassic and late cretaceous tertiary segments of the apw paths but an enigmatic difference exists in the paths for most of the jurassic whereas for the early cretaceous the data from europe are nearly non existent greenland s position is problematic in a bullard et al fit because of a late triassic early jurassic regime of compression 300 km that would be inherently required for the norwegian shelf and the barents sea but which is geologically not defensible we suggest a radically new fit for greenland in between europe and north america in the early mesozoic this fit keeps greenland locked to europe for the late paleozoic early mesozoic and maintains a reconstruction that better complies with the offshore geological history of the norwegian shelf and the barents sea pre drift a24 extension amounted to approximately 450 km on the mid norwegian shelf but with peak extension in the late cretaceous

luminescence chronology of late pleistocene raised beaches in southern italy new data of relative sea level changes abstract littoral sediments forming terraces along the crotone peninsula coast southern italian have been investigated using sedimentological analysis and luminescence dating techniques and adopting assessments from previous work on fossil assemblages all sediment layers analysed were deposited in the nearshore environment between 20 m below and few metres above sea level during the falling sea level of a temperate warm climate interval the restoration of almost identical environmental conditions occurred in oxygen isotope substages 5e and 5a and in oxygen isotope stage 3 limits given by luminescence physics prevented accurate dating of the uppermost lying terrace former crotonian stage terrace and the presence of a substage 5c terrace is masked by the lack of suitable material for dating constraints on the positions of relative sea level from the reliable data set show that the sea level fell from 2 m during substage 5e to 29 m during substage 5a and then rose to 15 m during stage 3 observations for oxygen isotope stage 3 sea level at the crotone peninsula coast are inconsistent with those at the huon peninsula new guinea and in the western pacific the disagreement highlights the lack of knowledge concerning mediterranean thermohaline circulations and sea water exchanges between the atlantic and mediterranean seas during glacial cycles

combining allostratigraphic and lithostratigraphic perspectives to compile subregional records of fluvial responsiveness the case of the sustainably entrenching palancia river watershed mediterranean coast ne spain abstract we use a combined allostratigraphic and morpholithostratigraphic approach to establish a relative stratigraphy of macroscale sediment landform units in the mediterranean palancia river watershed 986 km2 ne spain four alloformations signifying important changes in sub regional scale geomorphic valley floor evolution were identified based on data from 1120 field sites and age determinations and from analyzing high resolution geodata the formation of the widespread and thick pleistocene alloformation can be attributed to climatically induced excessive sediment supply and flood activities during pleistocene cold intervals rather than representing time lagging response to plio pleistocene neotectonic uplift triggered by the turn to holocene climatic conditions three successively inset alloformations illustrate how stream grading and floodplain narrowing continuously have progressed over the holocene the overall degradational valley floor evolution in the holocene is interpreted as a response to the antecedent overly valley floor aggradation allostratigraphic and morphostratigraphic data suggest that the abandonment of the two earlier holocene alloformations geomorphologically represents a pulsed turn toward intensified entrenchment rather than pulsed sedimentation the most important benefit of amalgamating allostratigraphic and morpho lithostratigraphic concepts is that allostratigraphic ordering provides a formally conclusive approach to scale up morpho lithostratigraphic information from the reach scale to much larger scales of geographical extent consequently applying allostratigraphic principles opens a perspective to moving forward toward analyzing the relationships between climate neotectonics sea level change human impact and fluvial response in coupled hinterland coastal systems that require to evaluate sedimentary information at larger spatial scales

palaeomagnetic investigations in the hercynian mountain belt of central europe abstract the palaeomagnetism of sediments and volcanics of middle devonian to early carboniferous age has been studied in the hercynian realm of the vosges harz and franconian forest france and germany after appropriate cleaning characteristic directions of natural remanent magnetization nrm have been determined which are considered to be of pretectonic origin according to rock magnetic and structural geological evidence a mean palaeopole for the devonian rocks in the areas investigated was determined at 29 7 n and 9 0 e the site latitude derived from the devonian rocks agrees very well with that observed in great britain and britanny the significant difference in longitude between our devonian poles and the other european data may be due to an anticlockwise rotation of central europe with respect to the northern hercynian foreland the carboniferous rocks yield a mean palaeopole at 41 7 n and 340 4 e matching the carboniferous part of the european polar wander path a fold test within carboniferous greywackes from the harz mountains proves a pre folding origin of the nrm of these rocks however this stable magnetization direction indicates local or regional tectonic displacement our results do not support any major latitudinal motions of continental segments in central europe during the hercynian orogeny the palaeozoic palaeomagnetic data from the vosges franconian forest harz britanny and central massif can be used to interpret the hercynides in terms of a large scale shear belt

the tectonic implications of solundian upper devonian magnetization of the devonian rocks of kvamshesten western norway the allochthonous old red sandstone of kvamshesten western norway records polyphase orogenic deformation and palaeomagnetic results from both the devonian sediments and mylonites associated with the basal thrust define a syn to post tectonic magnetization withd 218 i 3 and 95 9 7 the corresponding pole position lat 21 s long 324 e suggests a late devonian early carboniferous magnetization age solundian and probably dates the time of thrust movements

global and regional factors controlling changes of coastlines in southern iberia spain during the holocene the interaction between global glacio eustatic sea level rise and regional factors oceanographic and tectonic has controlled the evolution of coastline during the holocene in southem iberia at ca 10 000 14c years bp a deceleration of relative sea level rise took place both in the atlantic and mediterranean littorals with a maximum transgression at 6450 14c years bp in subsiding areas present tidal flats estuaries illustrate a clear marine influence recorded both in sediments and the fauna while in uplifting areas prograding spit bar systems developed two phases of major progradation are distinguished in these systems the first one between 6450 and 3000 14c years bp with a sedimentary gap at ca 4000 14c years bp and the second one from 2750 14c years bp up to present with an intervening gap between 1200 and 1050 14c years bp these progradation phases develop during stillstands followed by relative sea level fall while the sedimentary gaps represent relative high sea level in the mediterranean areas with a higher uplift rate marine terraces almost coeval to those gaps occur the most pronounced modifications in littoral dynamics occurred at between 3000 and 2750 14c years bp represented by changes in the direction of longshore drift and prevailing winds and in the predominance of progradation over aggradation processes at ca 1000 14c years bp the estuaries record a greater fluvial than marine influence and at 500 years ago an extraordinary increase in coastal progradation took place in all littoral zones the european medieval warm period is characterized at least during its initial phase by low pressure climate conditions while during the little ice age anticyclonic conditions gave rise to a strong coastal progradation

assessing the geomechanical stability of interbedded hydrate bearing sediments under gas production by depressurization at nghp 02 site 16 abstract establishing the geomechanical stability of marine sediments in the vicinity of a production well is one of the key design considerations in planning offshore gas production from marine hydrate reservoirs this paper presents an assessment of the sediment stability at india s national gas hydrate program expedition 2 nghp 02 site 16 area b offshore eastern india for which gas production is to be carried out by depressurization one important feature of the study is that extensive calibration of constitutive model parameters has been conducted based on laboratory test data from pressured core samples from analysis perspective the site is challenging because the hydrate reservoir consists of thin layers of hydrate bearing sands interbedded with mud moreover depressurization at the depth of a reservoir more than 2750 m below sea surface will lead to a pore pressure drop and accordingly an effective confining stress increase as high as 25 mpa in dealing with thin interbedded hydrate bearing strata meshing requirements for flow and geomechanical analysis are quite different from those for reservoirs with thicker massive layers an axisymmetric model and one way coupling simulations were thus adopted for this study in which the geomechanical study utilizes pore pressure and hydrate saturation output from the flow study but the flow study does not takes the porosity changes from the geomechanical analysis instead the reduction of porosity due to sediment deformation in the flow study is based on a pressure dependent pore compressibility relationship derived from geomechanical modeling the rationality is validated through back computing the pore compressibility from the geomechanical deformation results the study shows that large compression in the reservoir will result in movement of the sediments from above and below as well as laterally in smaller magnitudes and the sediment is deemed stable during the gas production period

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

a kinematic model for the collision and complete suturing between gondwanaland and laurussia in the carboniferous maps of middle to late carboniferous strike slip faults in western europe northern africa and eastern north america have been compiled from geological gravity and magnetic onshore and offshore data a large majority of these faults can be interpreted in terms of a logical syn to post collisional pattern superimposed on the initial suture between the african i e gondwana and north american european laurussian continental margins the pre collision positions of the major continents are derived from paleomagnetic data and when combined with the general distribution of the strike slip faults lead to a kinematic model of the complex middle late carboniferous collision in this model the west african precambrian craton acted as a rigid promontory or die with respect to the partially rigid plastic zones between it and the large north american craton these partially rigid plastic zones comprise the external appalachian and canadian maritime margins the mauritanide and hercynian margins of north

goodbye hazen hello kozeny carman the century old hazen formula for predicting the permeability of sand is based only on the d10 particle size whereas the half century old kozeny carman formula is based on the entire particle size distribution the particle shape and the void ratio as a consequence the hazen formula is less accurate than the kozeny carman formula it is recommended that the former be retired and the latter be adopted

fluvial networks of the iberian peninsula a chronological framework abstract knowledge of the evolution of spanish fluvial networks has improved during recent years as more river systems have been studied and more geochronological data has become available however the chronological framework is a major issue as the range of applications is limited by methodological constraints and spatial coverage is sparse integration of absolute dating methods with biostratigraphy and palaeomagnetism permits the recent evolution of these river systems to be reviewed the timing of incision from the late neogene to the present varies between the major iberian fluvial systems depending on the substrata and tectonic settings early pleistocene and older fluvial sequences in the core areas of the iberian peninsula provide a more extensive record of fluvial evolution and are better preserved than the terrace flights in the coastal lowlands middle pleistocene sequences are well developed in most of the major river systems in iberia particularly those of the tajo guadalquivir and aguas river and frequently represent the principal climatic cycles of that period although tectonic and sea level effects can also be seen for late pleistocene to holocene times the scheme becomes more complex our review suggests that each river system has responded differently to local and regional climate control glacial and periglacial processes in headwaters in high mountain areas glacio eustatic sea level changes and local and regional tectonic patterns

climatic and tectonic significance of late pleistocene and holocene tufa deposits in the mijares river canyon eastern iberian range northeast spain

geoarchaeology and aggradation around kinet hoyuk an archaeological mound in the eastern mediterranean turkey we examined the alluvial history of the plain near kinet hoyuk an archaeological mound or tell with a sequence of six millennia of occupation on the southeast mediterranean coast of turkey through 17 excavations over a 1000 m transect near the mound excavations ranged from 2 to 6 m deep and up to 20 m across this low gradient alluvial plain shows significantly different rates and processes of near mound sedimentation with one unit having nearly 4 m of late bronze age habitation and flood deposits and another having 4 m of hellenistic channel and floodplain deposition this flat alluvial surface turns out to be a rich geoarchaeological landscape that shrouds early and late bronze age settlements hellenistic walls and two epochs of roman roads one widespread phenomenon was a hellenistic or earlier paleosol and occupation level covered by channel gravels and overbank deposits mostly from the hellenistic to the late roman period these channel and floodplain deposits filled in and flattened out the off mound settlements blanketing the pre hellenistic topography and silting in a long active port this glut of alluvium correlates in time with drier conditions and the most intensive land uses in the watershed where roman and hellenistic sites today are severely eroded

lithofacies characterization of gas hydrate prospects discovered during the national gas hydrate program expedition 02 offshore krishna godavari basin india abstract lithofacies of host sediments associated with gas hydrate reservoirs may have a significant influence on the formation of hydrates the type of sediments and the depositional processes responsible for the gas hydrate bearing sediments along the eastern margin of the india have been studied by integrating core data and logging while drilling downhole logs borehole data correlated with seismic data were used for the interpretation of geological process responsible for gas hydrate formation the acquired seismic profiles were correlated with the downhole logs by identifying the shape of the well logs curves that indicate finning up and blocky patterns turbidite sands and debris flows were also identified from the log and core sediment studies this study identified two prominent types of depositional systems 1 turbidity currents and 2 debris flows were mainly responsible for the deposition of gas hydrate bearing reservoirs in the study area based on these studies two well developed gas hydrate systems have been identified in the krishna godavari basin and hydrates were determined to be distributed mostly in sand dominated facies fine grained sand in the identified turbidite deposits were shown to be a good hydrate reservoir the hydrate bearing sediments in the central part of the krishna godavari basin area c in d6 block consist of mostly debris flows which is consistent with scattered gravel and sand silt sized grains in channel levee systems

quaternary development and evolution of the sedimentary environments in the central mediterranean spanish coast abstract the reconstruction of the evolutive phases of the mediterranean spanish central sector during the late quaternary is the aim of this work from geomorphological sedimentological and chronometrical studies different morphostratigraphic units are determined results point out the development of several transgressive phases the older one go back to isotope stage 7 the eemian transgression is broadly recorded and its coastline was near the present one during the flandrian episode the sea surpassed the current coastline in the northern coastal plain while in the meridional littoral erosive notches were formed between 1 and 2 m during the regressive events we find the progradation of the continental sediments with alluvial and colluvial facies we note the terminal phases of the wurmiam glaciation because of their marked climatic aridic characteristics