utility of coal petrology for sequence stratigraphic analysis abstract sequence stratigraphy seeks to predict the depositional architecture of sediments based on the principle that their superposition and lateral arrangement are largely determined by the rate at which accommodation is made below depositional base level relative to the supply rate of sediments depositional base level is generally correlated with sea level which in paralic peat coal deposits controls the position of the groundwater table above which oxidation ablation and erosion would occur the current late quaternary sequence is used to discuss some of the constraints on coal formation that stem from the interaction of short and long period modulations on sequence forming eustatic cycles the results show that the mid transgressive systems tract is unlikely to produce significant coal deposits which is supported by a survey of the relevant literature from eight different countries it reveals a bimodal distribution of coal deposits with the strongest mode being situated in the early transgressive systems tract while a broader secondary mode occurs in the early and mid highstand position this concentration contrasts with the complete absence of any significant coal deposits in the early and mid lowstand systems tract and only a low occupancy of the late highstand systems tracts the reasons for this distribution are briefly discussed and attention is drawn to the possible over stating of the coal forming potential of the late lowstand systems tract following a brief discussion of the sequence stratigraphic interpretation of coal measures emphasis is put on the application of sequence stratigraphy to the study of coal seams and their composition at various levels of petrographic detail while in low rank coals botanical affinities contribute much to the lithotype based analysis a genetic assessment of bituminous coal seams relies primarily on physical and chemical palaeo environmental signatures simple properties such as maximum coal thickness low detrital mineral content and maximum preservation of vitrinite particularly of telovitrinite define a good balance between the former rates of accommodation versus peat accumulation iso metamorphic variations in telovitrinite reflectance and its dispersion measured by the coefficient of variation have also contributed to the palaeo environmental interpretation this paper confirms the identification within coal seams of most of the sequence stratigraphically significant surfaces e g sequence and parasequence boundaries transgressive flooding and maximum flooding surfaces it also gives examples of some new ones referred to as accommodation reversal non marine flooding give up transgressive terrestrialisation and paludification surfaces some of these are specific to coal measures but the give up transgressive and accommodation reversal surfaces may have wider significance

geological and biological heterogeneity of the aleutian margin 1965 4822 m geological biological and biogeochemical characterization of the previously unexplored margin off unimak island alaska between 1965 and 4822 m water depth was conducted to examine 1 the geological processes that shaped the margin 2 the linkages between depth geomorphology and environmental disturbance in structuring benthic communities of varying size classes and 3 the existence composition and nutritional sources of methane seep biota on this margin the study area was mapped and sampled using multibeam sonar a remotely operated vehicle rov and a towed camera system our results provide the first characterization of the aleutian margin mid and lower slope benthic communities microbiota foraminifera macrofauna and megafauna recognizing diverse habitats in a variety of settings our investigations also revealed that the geologic feature known as the ugamak slide is not a slide at all and could not have resulted from a large 1946 earthquake however sediment disturbance appears to be a pervasive feature of this margin we speculate that the deep sea occurrence of high densities of elphidium typically a shallow water foraminiferan results from the influence of sediment redeposition from shallower habitats strong representation of cumacean amphipod and tanaid crustaceans among the unimak macrofauna may also reflect sediment instability although some faunal abundances decline with depth habitat heterogeneity and disturbance generated by canyons and methane seepage appear to influence abundances of biota in ways that supercede any clear depth gradient in organic matter input measures of sediment organic matter and pigment content as well as c and n isotopic signatures were highly heterogeneous although the availability of organic matter and the abundance of microorganisms

utility of coal seams as genetic stratigraphic sequence boundaries in nonmarine basins an example from the gunnedah basin australia concepts of genetic sequence stratigraphy evolved in marginal marine basin settings where widespread episodic marine flooding events provide readily recognizable correlative surfaces that bound successive progradational clastic wedges however application of these concepts to nonmarine aggradational basins has been limited in cases where marine flooding surfaces are absent different criteria for sequence recognition are necessary this paper addresses the utility of regionally extensive coal seams as one type of sequence boundary peat accumulation and preservation as coal can only occur in the absence of significant clastic deposition formation of coal seams of regional extent requires processes capable of interruption in sediment supply at a basin wide scale and can define times of major reorganization in basin tectonics or climate regionally extensive coals can exhibit the essential attributes of sequence boundaries in many cases they are readily recognized and correlated by their unique seam signature or profile which is a function of the original peat forming plants and the physical and chemical conditions imposed during peat swamp evolution the unique seam profile also records numerous isochronous events further emphasizing their time equivalence and potential for accurate dating the concept that regionally extensive coals can serve as genetic stratigraphic sequence boundaries is well illustrated by coal seams from the gunnedah basin australia the hoskissons seam marks the initial change to nonmarine conditions in the basin from underlying deltaic and shallow marine depositional systems the stratigraphically higher breeza seam divides the nonmarine sequence into an underlying quartzose lacustrine bed load fluvial complex and an overlying volcanic lithic mixed load fluvial alluvial fan complex

sequence stratigraphy in lacustrine basins a model for part of the green river formation eocene southwest uinta basin utah u s a abstract in the middle green river formation of central nine mile canyon uinta basin utah several lacustrine dominated intervals 10 m thick comprise aggradational carbonate parasequence sets and a progradational clastic parasequence maximum flooding surfaces are best identified within profundal oil shale that caps some of the clastic parasequences these lacustrine transgressive systems tracts therefore exhibit parasequence stacking patterns unlike typical marine sequences two types of sequence boundary are identified type a sequence boundaries display evidence for a basinward shift in facies across a regionally mappable surface that is an angular or rarely parallel unconformity and they typically juxtapose amalgamated braided fluvial channel sandstone late lowstand systems tract onto the profundal oil shale they also bound depositional sequences that show a distinct asymmetry being dominated by transgressive systems tracts 5 80 m thick highstand systems tracts are less than 4 m thick and may be removed completely by erosion on overlying sequence boundaries other surfaces satisfy only some of the standard criteria of sequence boundaries and are termed type b sequence boundaries type a sequence boundaries mark pronounced base level falls following times when the uinta lake had merged with a lake in an adjacent basin to form a much deeper lake such merging permitted the establishment of a new threshold at higher elevation following lake level balancing type b sequence boundaries are interpreted as marking base level falls from a barely merged lake or a lake that had an outflow over a 200 m stratigraphic thickness type a sequence boundaries are more common upsection indicating that with time a pluvial climate became more pronounced or that the adjacent lake was more easily filled type a sequence boundaries also become angular rather than parallel unconformities upsection suggesting increased tilting of the basin margin over time

sequence stratigraphy of paralic coal bearing strata an overview abstract sequence stratigraphy arose in the late 1980s to fundamentally change the science of stratigraphy former practice of labeling formations and erecting stratigraphic columns gave place to a dynamic genetic stratigraphic analysis where the main concern is about understanding the history of sedimentation and to establish models able to predict facies born and mainly applied to an environment of petroleum prospecting and exploration sequence stratigraphy has gained entrance to other branches of sedimentary geology the present paper gives a short introduction to sequence stratigraphic concepts and shows an overview of its application on coal bearing strata two case studies one from the early permian coals of the parana basin brazil and one from the lower cretaceous coals of the western canada sedimentary basin illustrate the concepts

distribution of chemosynthetic biological communities in monterey bay california we report the first quantitative evaluation of the distribution of seafloor chemosynthetic biological communities on a regional scale the results are based on the analysis of video images and navigation from 792 benthic remotely operated vehicle dives conducted on the continental margin in monterey bay california these communities are common occurring within 5 of the 25 m square grid cells within which there have been bottom observations within 45 km of the bay9s head and within 9 of the visited cells that are below 550 m water depth although it has been previously assumed that these communities are associated with fluid seepage from faults they are not more common within known fault zones surprisingly the communities in monterey bay occur preferentially on steep slopes which are commonly sites of recent erosion

influences of thermal and fluid characteristics of methane and hydrothermal seeps on the stable oxygen isotopes of living benthic foraminifera abstract the serendipitous discovery of methane seep fluids with elevated temperatures 3 6 5 2 c described as a hydrothermal seepage by levin et al 2012 has led to questions about the prevalence of this previously overlooked habitat stable oxygen isotopic analysis of cibicidoides wuellerstorfi schwager 1866 attached to tubeworms near the hydrothermal seep described by levin et al 2012 reflect 18o values consistent with elevated seepage temperatures temperature reconstructions based on c wuellerstorfi 18o from additional seeps in the pacific mounds 11 12 offshore costa rica and hydrate ridge produced variability that is likely a result of influences of seep source temperature and salinity larger ranges in 18o 0 10 paired with traditional isotopic seep indicators e g 13c 0 15 have the potential to geochemically discern whether foraminifera were calcifying in areas of active methane seepage or nearby surrounding off seep environments elevated temperatures derived from foraminiferal reconstructions at jaco scar indicate that it is possible to use foraminiferal 18o to identify the presence and extent of these recently discovered environments seep fluids with elevated temperatures may be common seafloor features and benthic foraminiferal 18o may be an effective means to detect and determine the spatial and temporal extent and possible origin of hydrothermal seepage

modern deep sea benthic foraminifera a brief review of their morphology based biodiversity and trophic diversity most fossil deep sea foraminifera are multichambered and have relatively robust calcareous or agglutinated shells modern assemblages on the other hand include many fragile monothalamous single chambered forms and komokiaceans a superfamily of protist currently placed within the foraminifera with soft test walls these groups are poorly known and most of the hundreds of morphospecies recognized in deep sea samples are undescribed the relative abundance of robust and fragile taxa varies with water depth and food supply calcareous and other hard shelled species tend to predominate in relatively eutrophic areas particularly on continental margins but decrease as a proportion of the entire live fauna i e including soft shelled species with increasing water depth even above the ccd carbonate compensation depth most of the species on which the foraminiferal proxies used in palaeoceanography are based live in these bathyal regions at abyssal depths and particularly below the ccd faunas are largely agglutinated and dominated by monothalamous forms these assemblages have a much lower fossilization potential than those found on continental margins in addition to carbonate dissolution these patterns probably reflect adaptations to increasingly oligotrophic conditions on the ocean floor with increasing depth and distance from land bathyal species include herbivores and opportunistic deposit feeders omnivores that consume labile organic material in addition to deep infaunal deposit feeders and must contribute significantly to carbon cycling many abyssal monothalamous foraminifera in constrast accumulate stercomata waste pellets composed of fine sediment particles and probably ingest sediment associated bacteria and more refractory organic matter some monothalamous species without stercomata may be bacteriovores although they probably process organic carbon at a slower rate than calcareous species the shear abundance of monothalamous taxa at abyssal depths suggests that they are important in carbon cycling on a global scale the loss of a substantial proportion of foraminiferal biomass and biodiversity from the fossil record should be considered when using foraminifera to reconstruct palaeoproductivity for example by using the benthic foraminiferal accummulation rate bfar different dietary preferences among calcareous species have implications for the stable carbon isotope signal preserved in their shell

the influence of microhabitats on the carbon isotopic composition of deep sea benthic foraminifera we report 13c and 18o values for rose bengal stained benthic foraminifera from a set of box cores from continental margin environments in the atlantic and pacific oceans these isotopic results are compared with foraminiferal distribution data and pore water 13c profiles to evaluate the importance of environmental microhabitat effects on the carbon isotopic composition of benthic foraminifera the 13c values of infaunal taxa are consistently lower than those of epifaunal taxa suggesting that microhabitat effects on test composition do exist the 13c differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the 18o differences between benthic foraminifera tests and equilibrium calcite but they do correlate with variations in the chemistry of sediment pore waters however interspecific 18o differences as well as 13c differences between species with similar vertical distributions in the sediments indicate that taxon specific vital effects also influence test composition

structural development of an accretionary prism by thrust and strike slip faulting shumagin region aleutian trench a combination of seabeam swath bathymetric data closely spaced single channel seismic reflection profiles and multichannel seismic reflection profiles from the shumagin islands region indicates that the large scale deformation of the accretionary prism in this segment of the aleutian trench occurs progressively through several stages 1 folding along axes perpendicular to the plate convergence direction in the region 2 thrust faulting in the direction of plate convergence and 3 oblique strike slip faulting along conjugate west northwest trending right lateral and north northeast trending left lateral faults strike slip faults occur in distinct domains with right lateral oblique faults present west of a major transverse fault at long 161 w and left lateral oblique faults prevalent east of 161 w the structural development of the modern aleutian trench fore arc in this region is probably affected by pre eocene inherited structures that are still active in the present day stress regime a major domain boundary fault located at long 161 w is probably part of a strike slip fault system that also bounds sanak basin farther landward on the shumagin shelf this fault zone is nearly coincident with the mapped position of the western edge of the shumagin seismic gap these transverse structures in the shumagin fore arc probably influence the spatial distribution of stress buildup related to subduction and hence the locations of rupture zones of great interplate earthquakes along this segment of the aleutian trench

a study of the chemistry of pore fluids and authigenic carbonates in methane seep environments kodiak trench hydrate ridge monterey bay and eel river basin analyses of the chemical and isotopic composition of carbonates rocks recovered from methane seepage areas of the kodiak trench hydrate ridge monterey bay clam flats and the eel river basin coupled with the studies of the chemistry of the pore fluids have shown that these carbonates have grown within the sediment column geochemical profiles of pore fluids show that in deep water seeps kodiak trench 4450 m monterey bay 1000 m hydrate ridge 650 m 13c dic values are low isotopically light whereas in the eel river area 350 500 m 13c dic values are much higher isotopically heavier in all cases the 13c values indicate that processes of methane oxidation associated with sulfate reduction are dominant in the shallow sediments data on the isotopic composition of authigenic carbonates found at sites in kodiak trench eel river basin south and eel river basin north indicate a variable composition and origin in different geochemical environments some of the authigenic carbonates from the study sites show a trend in their 13c values similar to those of the pore fluids obtained in their vicinity suggesting formation at relatively shallow depths but others indicate formation at greater sediment depths the latter usually consist of high magnesium calcite or dolomite which from their high values of 13c up to 23 and 18o up to 7 5 suggest formation in the deeper horizons of the sediments in the zone of methanogenesis these observations are in agreement with observations by other workers at hydrate ridge in monterey bay and in the eel river basin

nonmarine sequence stratigraphy updip expression of sequence boundaries and systems tracts in a high resolution framework cenomanian dunvegan formation alberta foreland basin canada ten allomembers labeled j a have been mapped in the deltaic dunvegan formation using 2340 wells and 63 outcrop sections each allomember spans about 200 k y is bounded by regional transgressive surfaces and consists of 3 10 component shingles apparently of autogenic origin allomembers h e are discussed in this article their internal stacking patterns and bounding surfaces permit interpretation as depositional sequences sequences h f have a sigmoidal prismatic geometry downlap to the southeast and thin northwest onto the coastal plain no differential thickening exists toward the orogen in the southwest in contrast sequence e thickens markedly toward the northwest the tabular geometry of sequences h f suggests accommodation was controlled by sea level change whereas the wedge geometry of sequence e suggests significant tectonic tilting subaerial unconformities that bound valleys and extend onto adjacent interfluve paleosols can be traced 120 330 km updip into outcrop the base of each sequence is characterized by shoreline backstep of 80 150 km transgressive and highstand shingles in each sequence comprise marine deltaic deposits that pass landward into coastal plain strata falling stage shingles offlap seaward with little or no nonmarine equivalents updip whereas lowstand shingles show renewed coastal onlap in outcrop three nonmarine systems tracts are recognized 1 a channel dominated low accommodation systems tract fills valleys up to 35 m deep and is equivalent to the early transgressive systems tract begin page 1968 2 a lacustrine dominated high accommodation systems tract comprises mudstone enclosing ribbon channel sandstones blankets interfluves and forms the bulk of each sequence it is equivalent to late transgressive and early highstand systems tracts 3 a paleosol dominated low accommodation systems tract occupies the upper part of each sequence and is capped by the sequence boundary it is equivalent to the late highstand systems tract sequence bounding interfluve paleosols represent tens of thousands of years of pedogenesis related to slow aggradation followed by fluvial entrenchment and clastic bypass and represent the late highstand falling stage lowstand and early transgressive systems tracts coastal plain deposits record only part perhaps

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

new kinematic models for pacific north america motion from 3 ma to present i evidence for steady motion and biases in the nuvel 1a model we use velocities derived from 2 4 5 years of continuous gps observations at 21 sites on the pacific and north american plates along with a subset of the nuvel 1a data to examine the steadiness of pacific north america motion since 3 16 ma the transfer of baja california to the pacific plate and the magnitude of biases in the nuvel 1a estimate of pacific north america motion we find that pacific north america motion has remained steady since 3 16 ma but at rates significantly faster than predicted by nuvel 1a in the vicinity of baja california our gps derived model and recent seafloor spreading rates in the southern gulf of california both indicate that the nuvel 1a model underestimates pacific north america rates by 4 2 mm yr 1 steady pacific north america motion since 3 16 myr and increasing seafloor spreading rates since 3 58 myr in the gulf of california imply that pacific north america motion was partitioned between seafloor spreading in the gulf of california and decelerating slip along faults in or offshore from the baja peninsula

sequence stratigraphic distribution of coaly rocks fundamental controls and paralic examples significant volumes of terrigenous organic matter can be preserved to form coals only when and where the overall increase in accommodation approximately equals the production rate of peat accommodation is a function of subsidence and base level for mires base level is very specifically the groundwater table in paralic settings the groundwater table is strongly controlled by sea level and the precipitation evaporation ratio peat accumulates over a range of rates but always with a definite maximum rate set by original organic productivity and space available below depositional base level groundwater table below a threshold accommodation rate nonzero no continuous peats accumulate due to falling or low groundwater table sedimentary bypass and extensive erosion by fluvial channels this is typical of upper highstand lowstand fan and basal lowstand wedge systems tracts higher accommodation rates provide relatively stable conditions with rising groundwater tables mires initiate and copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received september 7 1995 revised manuscript received november 25 1996 final acceptance may 5 1997 2exxon production research company 3120 buffalo speedway houston texas 77096 3exxon production research company 3120 buffalo speedway houston texas 77096 present address conoco inc p o box 2197 houston texas 77252 we benefited from the input and assistance of many people of special assistance were the teams involved in collaborative studies with esso australia and esso malaysia p moore m sloan j emmett b burns a partridge s creaney hanif hussein r hill r lovell and m feeley we also thank the rock springs team r beauboeuf p mclaughlin w devlin a carroll y y chen g grabowski jr k miskell gerhardt m farley r webster and j schwalbach group members d curry and j yeakel were always helpful we also enjoyed and profited from many discussions of these concepts with our colleagues outside exxon c diessel r boyd k shanley b zaitlin p mccabe m hendricks a cohen and m kirschbaum we thank the reviewers of company reports whose careful comments on several generations of this work improved it s creaney m feeley j van wagoner f wehr j yeakel and a young f weber and j zullig provided extensive management support k linke translated our sketches into the fine figures herein we value all the help

a conceptual tectonostratigraphic model for seismic facies migrations in a fluvio lacustrine extensional basin one of the most fundamental differences between lacustrine basins and many marine basins is the stratigraphic response to differential tectonic subsidence because the water volume of a lake is finite tilting of the valley floor redistributes the lake water if the lake water level is below a hinge point fulcrum that experiences no net subsidence the lake shoreline is translated toward the site of subsidence and a deeper lake forms this tectonostratigraphic model for rift lake sedimentation is tested in a seismic and sequence stratigraphic study of deltaic and lacustrine deposits that accumulated in a cenozoic extensional basin beneath goshute valley nevada seismic sequences exhibit an internal cyclic stacking hierarchy of seismic reflections interpreted as the stratigraphic response of a lowstand paleolake to tectonism forced regression and subsequent lake level restoration transgressive and highstand systems tracts

sedimentology and stratigraphic architecture of the late permian betts creek beds queensland australia abstract the late permian betts creek beds form a succession of coal bearing alluvial coastal plain sediments in a basin marginal setting within the northeastern galilee basin queensland australia the unit is 50 60 m in thickness at porcupine creek national park where outcrop is laterally continuous for several kilometers eight facies have been identified within the formation and can be grouped into 2 facies associations a channel deposits and b floodbasin deposits the channel association consists of conglomerate a1 and trough cross bedded multistorey sandstone facies a2 both interpreted as deposits of low sinuosity river systems tidally influenced fluvial channels a3 interbedded sandstone and siltstone a4 interpreted as the abandonment fill of the alluvial systems and diamictite a5 interpreted as debris flows the floodbasin facies association is composed of sandy siltstone b1 proximal distal floodbasin carbonaceous siltstone b2 mire and bioturbated siltstone b3 estuarine facies the overall sediment body architecture can be resolved into 6 unconformity bounded cycles interpreted as sequences in the genetic sense which are sheet like in geometry and in general consist of amalgamated multistorey multilateral braided fluvial deposits at the base overlain by extensive sheet like overbank mudstones carbonaceous shales and coals sea level change is interpreted as the primary control on the sequence architecture of the formation while the internal stratigraphic architecture however varies between sequences and is a function of a combination of sea level tectonic and autogenic controls

habitat heterogeneity of hadal trenches considerations and implications for future studies abstract the hadal zone largely comprises a series of subduction trenches that do not form part of the continental shelf slope rise to abyssal plain continuum instead they form geographically isolated clusters of deep sea 6000 11 000 m water depth environments there is a growing realization in hadal science that ecological patterns and processes are not driven solely by responses to hydrostatic pressure with comparable levels of habitat heterogeneity as observed in other marine biozones furthermore this heterogeneity can be expressed at multiple scales from inter trench levels degrees of geographical isolation and biochemical province to intra trench levels variation between trench flanks and axis topographical features within the trench interior sedimentary basins ridges escarpments deeps seamounts to the substrate of the trench floor seabed sediment composition mass movement deposits bedrock outcrop using best available bathymetry data combined with the largest lander derived imaging dataset that spans the full depth range of three hadal trenches including adjacent slopes the mariana kermadec and new hebrides trenches the topographic variability fine scale habitat heterogeneity and distribution of seabed sediments of these three trenches have been assessed for the first time as well as serving as the first descriptive study of habitat heterogeneity at hadal depths this study also provides guidance for future hadal sampling campaigns taking into account geographic isolation total trench particulate organic matter flux maximum water depth and area

source mechanism of a lower crust earthquake beneath the himalayas and its possible relation to metamorphism abstract the nature of deep crustal intermediate and deep focus earthquakes and their relation to metamorphic reactions is a topic of debate here we seek to better understand a possible link between the earthquake process and metamorphism by analyzing the mechanism of ongoing deep crustal earthquakes we focus on a region in the himalayas with observed seismicity at depths expected to experience active eclogite facies metamorphism and dehydration reactions there are few permanent seismic stations in the region therefore we use waveform data from a temporary seismic array deployment we find two earthquakes with magnitude and station coverage adequate for moment tensor inversion for a given earthquake we estimate its seismic full moment tensors and magnitude together with uncertainties using all available waveforms for the largest earthquake mw 3 7 we obtain a best fitting moment tensor and uncertainties that show a double couple with a tensional crack component in the context of geological records that document similar processes and of laboratory experiments conducted at spatial scales that are 5 6 orders of magnitude smaller this mechanism may be related to dehydration driven stress changes triggering slight crack opening and ambient stresses favoring slip along a fault

sequence stratigraphy and architectural variability in growth fault bounded basin fills a review of plio pleistocene stratal units of the crotone basin southern italy field examples from the pliocene to pleistocene succession of the crotone basin document the variability of stratal architecture in syntectonic units deposited in normal fault bounded basins relatively thick trangressive intervals are common within these successions as shown in the zinga 2 zinga 3 and strongoli stratal units transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones aggradational highstand shallow marine packages are typical of the lower pliocene succession in half graben basins these deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation relatively thick forced regressive deposits are common within basins during phases where the accommodation supply ratio is low e g the middle pleistocene san mauro sandstone these deposits influenced by growth faulting and folding recorded base level lowering linked to glacio eustasy a complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift e g the serra piani stratal unit such variations are thought to be related to the onset of an earliest mid pliocene transpressional tectonic phase the studied deposits therefore show a marked tectonic control that strongly influenced their stratal architecture these examples represent interesting cases of sequence stratigraphic analysis in growth faulted contexts

the destructive 1946 unimak near field tsunami new evidence for a submarine slide source from reprocessed marine geophysical data the mw 8 6 earthquake in 1946 off the pacific shore of unimak island at the end of the alaska peninsula generated a far field tsunami that crossed the pacific to antarctica its tsunami magnitude 9 3 is comparable to the 9 1 magnitude of the 2011 tohoku tsunami on unimak island s pacific shore a runup of 42 m destroyed the lighthouse at scotch cap elsewhere localized tsunamis with such high runups have been interpreted as caused by large submarine landslides however previous to this study no landslide large enough to generate this runup was found in the area that is limited by the time interval between earthquake shaking and tsunami inundation at scotch cap reworking of a seismic reflection transect and colocated multibeam bathymetric surveys reveal a landslide block that may explain the 1946 high runup it is seaward of scotch cap on the midslope terrace and within the time limited area

paleoenvironments and paleogeography of the lower and lower middle jurassic coal measures in the turpan hami oil prone coal basin northwestern china detailed facies and paleogeographical analyses of extensive borehole and outcrop data from lower and lower middle jurassic oil prone coal bearing sequences in the turpan hami oil producing basin of northwest china have led to the reconstruction of a basinwide depositional model a total of 20 distinct lithofacies have been identified and grouped into braided fluvial plain meandering fluvial plain braided delta meandering channel delta and lacustrine depositional systems coal forming swamps occur in each depositional system but the preferred sites of accumulation are interdelta bay and lower delta plain environments in the braided delta and meandering channel depositional systems and it is in these sites that major oil prone source rocks are located a series of age specific basinwide paleogeographical maps have been constructed leading to a depositional model for the basin results indicate that the basin experienced cyclic flooding to produce swamps and lakes and that these characterize the deposition of the lower and lower middle jurassic coal measures analyses indicate that both the bogda and harlik mountains were uplifted prior to the early jurassic and a lake separated the two mountain regions during the early and early middle jurassic from these results it is interpreted that major oil prone coal sequences are to be found in the western part of the taibei depression of the basin and thus the full economic potential of the basin has yet to be fully realized

a possible source mechanism of the 1946 unimak alaska far field tsunami uplift of the mid slope terrace above a splay fault zone in 1946 megathrust seismicity along the unimak segment of the alaska subduction zone generated the largest ever recorded alaska aleutian tsunami the tsunami severely damaged pacific islands and coastal areas from alaska to antarctica it is the charter member of tsunami earthquakes that produce outsized far field tsunamis for the recorded magnitude its source mechanisms were unconstrained by observations because geophysical data for the unimak segment were sparse and of low resolution reprocessing of legacy geophysical data reveals a deep water high angle reverse or splay thrust fault zone that leads megathrust slip upward to the mid slope terrace seafloor rather than along the plate boundary toward the trench axis splay fault uplift elevates the outer mid slope terrace and its inner area subsides multibeam bathymetry along the splay fault zone shows recent but undated seafloor disruption the structural configuration of the nearby semidi segment is similar to that of the unimak segment portending generation of a future large tsunami directed toward the us west coast

on balanced and unbalanced accommodation peat accumulation ratios in the cretaceous coals from gates formation western canada and their sequence stratigraphic significance coal composition was investigated by means of photometric and maceral analyses on closely spaced lithotype based strip samples over the full thickness of several paralic coal seams from the cretaceous gates formation of the western canadian sedimentary basin the aim of this investigation was to test various methods of identifying accommodation trends in coal and use them to refine sequence stratigraphic interpretation of continental sediments conventional sequence stratigraphy derives its subdivisions and significant surfaces from the records left by relative sea level oscillations these records either do not project into the continental realm or are difficult to recognise in clastic non marine sediments paralic coal seams have been selected to study this problem because they are not entirely removed from marine influence and compared with most inorganic deposits coal has stored a greater wealth of information that can be analysed at a higher level of resolution the study has led to the identification of five new surfaces with chronostratigraphic potential in the sequence stratigraphic analysis of non marine sediments two of these surfaces called paludification surface pas and terrestrialisation surface tes occur at the bases of the investigated coal seams while two other surfaces referred to as non marine flooding surface nfs and give up transgressive surface guts form the tops of the coal the fifth and probably most important new surface called the accommodation reversal surface ars is independent of any particular facies and may either coincide with some of the other surfaces or occur separately the proportion of detrital minerals has been used as the chief discriminator between different mire types and accommodation trends other useful indicators of mire type and peat dispersal have been the proportions of sporinite and inertodetrinite as well as some derived maceral and or mineral ratios e g the groundwater influence index and the tissue preservation index isometamorphic variations of telovitrinite reflectance and fluorescence as well as their coefficients of variation were also found to contribute to the identification of cyclic shifts between balanced and unbalanced accommodation peat accumulation ratios some of these cycles which are backed up by clastic stratigraphy appear to correspond to the development of shallowing upward and deepening upward parasequences superimposed high frequency low amplitude perturbations in the coal cycles relate to smaller scale accommodation cycles of sub parasequence level not always recognised in non marine strata these sub parasequence coal cycles do not always continue the shallowing upward trend typical of conventional parasequences several coals were found to contain stacks of small scale cycles with upward increasing accommodation signatures either in their lower or upper halves or over the whole seam section

sequence stratigraphy and paleogeography of the middle jurassic coal measures in the yuqia coalfield northern qaidam basin northwestern china detailed stratigraphic and paleogeographic analyses of data from 72 boreholes for the middle jurassic intermontane fluvial lacustrine coal bearing sequences were conducted in the yuqia coalfield of the northern qaidam basin northwestern china three third order sequences lasting in total ca 10 6 m y and an internal lowstand systems tract lst transgressive systems tract tst highstand systems tract hst and falling stage systems tract fsst have been identified a series of sequence specific paleogeographic maps have been constructed based on the contours of lithological parameters the paleogeographic units include alluvial fan braided meandering fluvial plain upper delta plain lower delta plain subaqueous delta shore shallow lake and deep lake the preferred sites of coal accumulation are interdelta bays upper delta plains lower delta plains and fluvial back swamps the sequence stratigraphic and sedimentological analysis of the middle jurassic coal bearing measures of the yuqia coalfield provides a basis for a comprehensive coal accumulation model that involves a six period evolution from the lst early tst late tst early hst late hst to fsst the major coal seams were accumulated in the early and late tst of the sequences s1 and s2 these results are of practical significance for coal resources exploration and enhance geological effects of prospecting engineering in the northern qaidam basin

sedimentary control on the formation of a multi superimposed gas system in the development of key layers in the sequence framework abstract based on core observations well logs and test results of siderite bearing mudstone from the benxi formation to the member 2 of the shanxi formations in the linxing block northeastern ordos basin a logging identification model for siderite bearing mudstone key layer was established the porosity characteristics and sealing property were quantitatively evaluated by logging data sedimentary control on the formation of multi superimposed gas bearing system in the development of key layers in the sequence framework was also discussed the results showed that the siderite bearing mudstone has obvious logging response characteristics e g high photoelectric absorption cross section index pe high density den high amplitude natural gamma ray gr low acoustic ac low resistivity m2rx and low neutron porosity cncf the quantitatively evaluated results of the porosity characteristics and sealing property for the key layer showed that the key layer has the characteristics of low porosity with an average of 1 20 percent low permeability with an average of 2 29 10 8 m 2 and high breakthrough pressure with an average of 12 32 mpa in the study area this layer acts as an impermeable gas barrier in a multi superimposed gas system the results also indicated that the material composition of the multi superimposed gas bearing system can be established by the sequence stratigraphic framework the sedimentary evolution results in a cyclic rhythm of material composition vertically the spatial distribution of the corresponding transgressive event layer near the maximum flooding surface mfs in the sequence framework restricts the spatial distribution of the key layer with high breakthrough pressure and low porosity which constitutes the gas bearing system boundary the siderite bearing mudstone formed near the mfs in the second order sequence and constitutes a stable comparison of the first order gas bearing system boundary which has a wide range of regional distribution and stable thickness the siderite bearing mudstone formed near the mfs in the third order sequence is often incompletely preserved due to the late underwater diversion channel erosion and cutting this layer forms the coal bearing reservoirs which we termed as a second order gas bearing system in adjacent third order sequences to form a uniform gas bearing system

deposition and deformation of fluvial lacustrine sediments of the upper triassic lower jurassic whitmore point member moenave formation northern arizona abstract the stratigraphic section of the upper triassic lower jurassic whitmore point member of the moenave formation at potter canyon arizona comprises c 26 m of gray to black shales and red mudstones interbedded with mainly sheet like siltstones and sandstones these strata represent deposition from suspension and sheetflow processes in shallow perennial meromictic to ephemeral lakes and on dry mudflats of the terminal floodout of the northward flowing moenave stream system the lakes were small as indicated by the lack of shoreline features and limited evidence for deltas changes in base level likely forced by climate change drove the variations between mudflat and perennial lacustrine conditions lenticular sandstones that occur across the outcrop face in the same stratigraphic interval in the lower part of the sequence represent the bedload fill of channels incised into a coarsening upward lacustrine sequence following a fall in base level these sandstones are distinctive for the common presence of over steepened bedding dewatering structures and less commonly folding deformation of these sandstones is interpreted as aseismic due to the lack of features typically associated with seismicity such as fault graded bedding diapirs brecciated fabrics and clastic dikes rapid deposition of the sands on a fluid rich substrate produced a reverse density gradient that destabilized and potentially fluidized the underlying finer grained sediments this destabilization allowed synsedimentary subsidence of most of the channel sands accompanied by longitudinal rotation and or ductile deformation of the sand bodies

the application of high resolution sequence stratigraphy to fluvial systems a case study from the upper carboniferous breathitt group eastern kentucky usa the pennsylvanian pikeville hyden and four corners formations of the breathitt group in eastern kentucky usa contain six major facies associations along with a number of subassociations these facies associations are offshore siltstone rhythmically bedded mouthbar heteroliths predominantly fine grained floodplain deposits minor channel fills major distributary channels and major stacked fluvial bodies the stacked fluvial bodies are incised into a variety of open marine and delta plain deposits have widths of several kilometres and exhibit a range of sandy fill types these fluvial complexes are interpreted as incised valley fills parasequences and parasequence sets are not identifiable nonetheless it is possible to identify systems tracts on the basis of sequential position facies associations and systematic changes in architectural style and sediment body geometries the studied portion of the breathitt group comprises stacked 4th order sequences which occur in lowstand transgressive and highstand sequence sets related to the development of a lower frequency base level cycle in the lowstand sequence set incision associated with successive 4th order sequence boundaries has commonly removed all the hst and tst of the underlying sequences such that succeeding 4th order incised valley fills are amalgamated within the transgressive sequence set incision is at a minimum and incised valley fills tend to stack discretely with the maximum amount of fine grained tst and hst between them the highstand sequence set is transitional between the lowstand and transgressive sequence sets in terms of the amount of transgressive and highstand deposits preserved incised valley fills tend to stack discretely

sequence stratigraphic interpretation of a pennsylvanian upper carboniferous coal from the central appalachian basin usa peat mires retain a sensitive record of water table base level fluctuations throughout their accumulation on this basis coals provide one of the best opportunities to interpret high resolution base level change in ancient non marine deposits the petrographic composition of 275 samples collected from 11 localities along a 100 km south west to north east transect across the regionally extensive 37 000 km2 pennsylvanian upper carboniferous fire clay coal of the central appalachian basin usa was analysed to determine its internal stratigraphy the coal is positioned within the late lowstand early transgressive systems tract of a fourth order depositional sequence the results of the petrographic analyses reveal a cyclicity in the composition of the fire clay coal which defines six units that are correlated over more than 100 km each coal cycle is characterized by a gradual upward transition from vitrinite dominated to inertinite dominated coal which represents a drying up succession increased concentrations of resistant peat components at the top of the drying up successions indicate reduced peat accumulation rates associated with slowing rate of water table rise and may represent a residue of peat remaining from a phase of exposure and erosion resulting from a falling water table these drying up successions are bound by surfaces that display an abrupt coal facies shift from inertinite rich to vitrinite rich coal representing a rapid water table rise each cycle represents markedly different mire conditions with different aerial distributions which supports the notion of temporal disconnection between each unit of coal and suggests that considerable time may be locked up in unit bounding exposure surfaces recognition that the rate of peat accumulation in a mire may vary considerably through time has important implications for studies which assume that peat and coal successions provide continuous and time invariant records of base level fluctuations or palaeoecological change

sequence architecture depositional systems and controls on development of lacustrine basin fills in part of the erlian basin northeast china sequence architecture and depositional systems of a jurassic cretaceous lacustrine rift succession in the wuliyashitai subbasin and erlian basin in northeastern china were investigated using seismic profiles complemented by well logs and cores five second order or composite sequences are identified on the basis of basin scale unconformities constituent third order sequences are defined by unconformities along the basin margins and correlative conformities within the central basin lowstand transgressive and highstand systems tracts are separated by major lake flooding surfaces depositional systems identified in the basin include alluvial fan incised valley fan delta braid delta and sublacustrine fan three types of lacustrine sequences consisting of distinctive depositional systems formed during different tectonic stages 1 alluvial shallow lacustrine sequences type a developed during the initial rifting stage 2 shallow lacustrine to deep lacustrine sequences type b formed during the early and late periods of rifting and 3 deep lacustrine sequences type c developed in response to rapid tectonic subsidence during the middle maximum rifting stage uplift following each rifting episode related to changes in the paleostress field appears to have been the major control on the formation of high order sequence boundaries second order and some third order sequences block rotation coupled with lake level fluctuations controlled the formation of most third order sequence boundaries forward simulation modeling suggests that development of different lacustrine sequence types can be related to a balance between tectonic subsidence and sediment input begin page 2018 deltaic sandstone bodies and incised valley fills along the hinged margins within the shallow lacustrine and deep lacustrine sequences and sublacustrine fan sandstones in the central basin are the economically most important reservoir sandstones in the basin fan delta deposits along the escarpment margin constitute another potential reservoir type

low δ13c in tests of live epibenthic and endobenthic foraminifera at a site of active methane seepage 1 to investigate the use of benthic foraminifera as a means to document ancient methane release we determined the stable isotopic composition of tests of live rose bengal stained and dead specimens of epibenthic fontbotia wuellerstorfi preferentially used in paleoceanographic reconstructions and of endobenthic high latitude cassidulina neoteretis and cassidulina reniforme from a cold methane venting seep off northern norway we collected foraminiferal tests from three push cores and nine multiple cores obtained with a remotely operated vehicle and a video guided multiple corer respectively all sampled sites except one control site are situated at the hakon mosby mud volcano hmmv on the barents sea continental slope in 1250 m water depth at the hmmv in areas densely populated by pogonophoran tube worms 13c values of cytoplasm containing epibenthic f wuellerstorfi are by up to 4 4 lower than at control site thus representing the lowest values hitherto reported for this species live c neoteretis and c reniforme reach 13c values of 7 5 and 5 5 vienna pee dee belemnite vpdb respectively whereas 13c values of their empty tests are higher by 4 and 3 however 13c values of empty tests are never lower than those of stained specimens although they are still lower than empty tests from the control site this indicates that authigenic calcite precipitates at or below the sediment surface are not significantly influencing the stable isotopic composition of foraminiferal shells the comparatively high 13c results rather from upward convection of pore water and fluid mud during active methane venting phases at these sites these processes mingle tests just recently calcified with older ones secreted at intermittent times of less or no methane discharge since cytoplasm containing specimens of suspension feeder f wuellerstorfi are almost exclusively found attached to pogonophores which protrude up to 3 cm above the sediment and 13c values of bottom water dissolved inorganic carbon dic are not significantly depleted we conclude that low test 13c values of f wuellerstorfi are the result of incorporation of heavily 13c depleted methanotrophic biomass that these specimens feed on rather than because of low bottom water 13cdic alternatively the pogonophores which are rooted at depth in the upper sediment column may serve as a conduit for depleted 13cdic that ultimately influences the calcification process of f wuellerstorfi attached to the pogonophoran tube well above the sediment water interface the lowest 13c of live specimens of the endobenthic c neoteretis and c reniforme are within the range of pore water 13cdic values which exceed those that could be due to organic matter decomposition and thus in fact document active methane release in the sediment

carbon and oxygen isotope geochemistry of live stained benthic foraminifera from the aleutian margin and the southern australian margin article comparisons of ambient bottom water geochemistry and stable isotopic values of the tests of living stained calcareous benthic foraminifera from the north pacific on the aleutian margin water depth 1988 m and murray canyons group in the southern indian ocean australian margin water depths 2476 m and 1634 m provide modern environmental analogs to calibrate paleoenvironmental assessments consistent with the hypothesis that microhabitat preferences influence foraminiferal isotopic values benthic foraminifera from both margins were depleted in 13 c with respect to bottom water dissolved inorganic carbon dic the carbon isotope values of deep infaunal foraminifera chilostomella oolina globobulimina pacifica showed greater differences from estimates of those of dic than shallow benthic foraminifera bulimina mexicana bolivinita quadrilatera pullenia bulloides this study provides new isotopic and ecological information for b quadrilatera the mean 13 c value defined as foraminiferal 13 c values minus estimated ambient 13 c values from the aleutian margin is 0 97 higher for g pacifica than the mean from the murray canyon this difference may result either from genetic or biological differences between the populations or from differences in environmental isotopic influences such as pore water differences that were not accounted for in the equilibrium calculations these analyses provide calibration information for the evaluation of bottom water conditions and circulation patterns of ancient oceans based on fossil foraminiferal geochemistry

determination and uncertainty of moment tensors for microearthquakes at okmok volcano alaska summary efforts to determine general moment tensors mts for microearthquakes in volcanic areas are often hampered by small seismic networks which can lead to poorly constrained hypocentres and inadequate modelling of seismic velocity heterogeneity in addition noisy seismic signals can make it difficult to identify phase arrivals correctly for small magnitude events however small volcanic earthquakes can have source mechanisms that deviate from brittle double couple shear failure due to magmatic and or hydrothermal processes thus determining reliable mts in such conditions is a challenging but potentially rewarding pursuit we pursued such a goal at okmok volcano alaska which erupted recently in 1997 and in 2008 the alaska volcano observatory operates a seismic network of 12 stations at okmok and routinely catalogues recorded seismicity using these data we have determined general mts for seven microearthquakes recorded between 2004 and 2007 by inverting peak amplitude measurements of p and s phases we computed green s functions using precisely relocated hypocentres and a 3 d velocity model we thoroughly assessed the quality of the solutions by computing formal uncertainty estimates conducting a variety of synthetic and sensitivity tests and by comparing the mts to solutions obtained using alternative methods the results show that mts are sensitive to station distribution and errors in the data velocity model and hypocentral parameters although each of the seven mts contains a significant non shear component we judge several of the solutions to be unreliable however several reliable mts are obtained for a group of previously identified repeating events and are interpreted as compensated linear vector dipole events

potential tsunamigenic submarine landslides in active margins abstract a review of modern historical and submarine landslides from the geological record shows that landslides in active continental margins can generate tsunamis the tsunamis may damage coastal and seabed infrastructure and so represent an important element of marine geohazards research due to their potentially significant impacts on society the primary trigger mechanism of tsunamis in this type of setting was thought to be earthquake activity however there are also a number of alternative hypotheses regarding the likely initiation mechanism including the generation of submarine landslides in this paper we briefly review the geological features and trigger mechanisms of tsunamigenic submarine landslides on active margins large tsunamigenic submarine landslides appear to occur mostly on margins characterized by non accretion these observations have implications for tsunami warning systems as the japanese system does not consider the scenario of tsunami excitation by submarine landslides

sequence stratigraphy sedimentary systems and petroleum plays in a low accommodation basin middle to upper members of the lower jurassic sangonghe formation central junggar basin northwestern china abstract the lower jurassic junggar basin is a low accommodation basin in northwestern china because of low subsidence rates and a warm wet climate deposits of the central subbasin of the junggar basin formed from fluvial deltaic shallow lake facies sequence stratigraphy and sedimentary systems of the lower jurassic members of the sangonghe formation j1s were evaluated by observing cores interpreting wireline logs and examining seismic profiles two third order sequences were recognized in the strata the distribution of the sedimentary systems in the systems tracts shows that tectonic movement paleorelief paleoclimate and changes in lake level controlled the architecture of individual sequences during the development of the lowstand systems tract lst the intense structural movement of the basin resulted in a significant fall in the water level in the lake accompanied by rapid accommodation decrease braided rivers and their deltaic systems were also developed in the central junggar basin sediments carried by braided rivers were deposited on upward slopes of the paleorelief and braid delta fronts were deposited on downward slopes during the transgressive systems tract tst the tectonic movement of the basin was quiescent and the climate was warm and humid lake levels rose and accommodation increased quickly shoal lines moved landward and shore to shallow lake deposits sublacustrine fans and deep lake facies were deposited in shallow to deep lake environments during the highstand systems tract hst the accommodation no longer increased but sediment supply continued far exceeding accommodation hst deposits slowly formed in shallow lake to meandering river delta front environments relatively low rates of structural subsidence and low accommodation resulted in coarse grained successions that were fining upward deposits were controlled by structural movement and paleorelief within the lst to tst deposits in the central subbasin fine to medium grained coarsening upward successions developed during the hst the sand bodies of braid delta fronts on the downward slopes of the paleorelief in the lst and the sublacustrine fans in the tst became reservoirs for hydrocarbon accumulation petroleum plays have only been found in the sangonghe formation j1s located on structural ridges that consist of sand bodies comprising these sequences favorable conditions for petroleum plays in hst1 lst2 occur where the sand bodies have been fractured by faults and sealed by denudation and pinch out lines then overlain by deep lake mudstone in tst2 the favorable condition of the sand bodies within tst2 occurs where isolated sand bodies have been fractured by faults

empirical constraints on magnitude distance relationships for seismically induced submarine tsunamigenic landslides abstract seismically induced submarine landslide tsunamis here called silts attract growing attention due to their unique setting damage potential and short warning time a question of key importance especially for tsunami early warning is how far can an earthquake trigger a tsunamigenic slump here we investigate the relationships between earthquake magnitude and the maximal distance between the seismogenic fault and the tsunamigenic slumps rf and between the earthquake epicenter and the slump re and propose empirical constraints on these magnitude distance m d relations the 49 identified silts are spread in various seismotectonic and bathymetric settings in different seas around the globe we found that the maximal distance of the tsunamigenic submarine landslide from the parent earthquake grows with the magnitude and is bounded by an envelope constrained by mw as low as 4 9 for several kilometers the 1968 liguria coast italy and as far as 250 km for mw 7 7 the 1819 rann of kachchh india higher earthquake magnitudes also produce silts seemingly distances lower than 250 km however it is suspected that the available data is limited and unable to reflect the true nature of silt s generation generalized empirical relations between the earthquake magnitude mw and the maximal distance from the seismogenic fault to its generated silt rf in km are log rf 1 17 0 49 mw r2 0 78 the empirical distance between the earthquake epicenter and the corresponding tsunamigenic slump re in km is log re 0 87 0 45 mw r2 0 83 although many earthquakes within the m d bounding envelope did not produce tsunamis the successful events still enable the delineation of the m d zone vulnerable to tsunami generation which in turn can be applied to tsunami early warning procedures this is particularly important for near coast inland earthquakes as their tsunamigenic potential might be overlooked

perspectives on the sequence stratigraphy of continental strata this report is the result of a working group on continental sequence stratigraphy that was set up at the 1991 nuna conference in banff canada to date sequence stratigraphic concepts have been applied mainly to the marine realm but unconformity bounded units have long been recognized in nonmarine strata successful application of sequence stratigraphic concepts to continental strata requires careful consideration of controls on base level and sediment supply as with shallow marine environments relative sea level can be considered as the stratigraphic as well as the geomorphic base level for coastal nonmarine settings farther inland stratigraphic base level which determines accommodation space is more complex and takes various forms such as the graded profile for fluvial strata groundwater tables for some eolian strata and lake level for some intermontane sediments sediment supply is also generally a more complex variable for nonmarine environments than in the marine realm because of the proximity to the source area the influence of climate and tectonism on sediment supply can clearly be seen in many continental sediments the fact that the major controls of climate tectonism and eustasy are somewhat interdependent and that a change in one parameter will most likely be reflected in others is also more readily apparent in continental strata although in its infancy sequence stratigraphic concepts have been applied to a wide variety of continental settings in attempts to explain variations in facies architecture of particular interest are studies that have linked fluvial architecture on coastal plains to variations in relative sea level as indicated by coeval marine strata and studies of lacustrine environments that show marked variation in facies between highstand and lowstand deposits the application of sequence stratigraphy to continental strata will likely result in the development of better correlation techniques and models that better predict the location and nature of fluvial and eolian reservoirs

stratigraphic classification of ancient lakes balancing tectonic and climatic controls lakes and lake deposits present two fundamental paradoxes 1 modern lakes are vastly complicated but the rock records of lakes are relatively simple extensive observations reveal three distinct facies associations of common and widespread occurrence these are referred to here as fluvial lacustrine fluctuating profundal and evaporative facies associations 2 most explanations of modern and ancient lakes attribute their nature to climate but neither modern lake parameters lake size depth and salinity nor the character of ancient lake strata thickness extent lithology correlate with measured or inferred climatic humidity we propose that it is the relative balance of rates of potential accommodation mostly tectonic with sediment water fill mostly a function of climate that controls lake occurrence distribution and character lake basins may be termed overfilled balanced fill or underfilled depending on the balance between these rates we conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales 1 m to hundreds of meters and macroscales hundreds to thousands of meters

relationships between the stable isotopic signatures of living and fossil foraminifera in monterey bay california 1 fossil foraminifera are critical to paleoceanographic reconstructions including estimates of past episodes of methane venting these reconstructions rely on benthic foraminifera incorporating and retaining unaltered the ambient isotopic compositions of pore fluids and bottom waters comparisons are made here of isotopic compositions of abundant live and fossil foraminifera uvigerina peregrina epistominella pacifica bulimina mexicana and globobulimina pacifica collected in monterey bay ca from two cold seeps clam flats and extrovert cliffs and from sediments 5 m outside of the clam flats seep clam flats has steep d 13 cdic gradients to 45 but dic at extrovert cliffs is less enriched in 12 c to approximately 22 oxygen isotope values of fossil foraminifera at clam flats are 1 5 enriched in 18 o over the living foraminifera as well as those of both live and fossil foraminifera at extrovert cliffs suggesting they may have lived during the last glacial maximum statistical comparisons student s t and kolmogorov smirnov tests of d 13 c and d 18 o values indicate that live and fossil foraminifera come from different populations at both clam flats and extrovert cliffs at clam flats the difference appears to result from alteration enriching some fossil foraminifera in 12 c over live foraminifera at extrovert cliffs the fossil foraminifera are enriched in 13 c over the live foraminifera suggesting they lived prior to the onset of venting and thus that venting began recently the short time of venting at extrovert cliffs may be responsible for the less alteration there compared with clam flats these results indicate that preservation of foraminifera is likely to be poor within long lived cold seeps but that foraminifera living in the surrounding sediment may incorporate and preserve broad basin wide changes in isotopic compositions of the ambient water

quantifying fluid flow solute mixing and biogeochemical turnover at cold vents of the eastern aleutian subduction zone in situ oxygen fluxes were measured at vent sites in the aleutian trench at a water depth of almost 5000 m using a tv guided benthic flux chamber the flux was 2 orders of magnitude greater than benthic oxygen fluxes in areas unaffected by venting on the continental margin off alaska porewater profiles taken from the surface sediment below a vent site showed high concentrations of sulfide methane and ammonia the reduced carbon and nitrogen compounds are transported to the vent site by fluids expelled from deeper anoxic sediment layers by the forces of plate convergence the tectonically driven fluid flow was determined from the biochemical turnover in vent communities and was found to be 3 4 0 5 m yr 1 a model was used to quantify the transport of silica ca2 and sulfate via diffusion advection and bioirrigation through the surface sediments of a vent site a nonlocal mixing coefficient of 20 30 yr 1 was determined by fitting the model curves to the measured porewater profiles showing that the transport of solutes within the near surface sediments and across the sediment water interface is dominated by the activity of the vent fauna sulfate containing oceanic bottom water and methane rich vent fluids were mixed below the clam colony to produce sulfide and a caco3 precipitate the vent biota shape their immediate environment and control the sediment water exchange and the benthic fluxes at vent sites the oxygen consumption at vent sites is a major sink for oxygen at the study area

sequence stratigraphy and coal accumulation of lower cretaceous coal bearing series in erlian basin northeastern china the detailed depositional systems and basin evolution of lower cretaceous coal bearing strata in the erlian basin of northeastern china were analyzed based on extensive borehole and outcrop data a total of 7 facies associations are interpreted and consist of 14 distinct lithofacies with lithologies including conglomerates sandstones siltstones mudstones shales and coals five third order sequences were recognized and their internal lowstand transgressive and highstand systems tracts were defined based on six key sequence stratigraphic boundaries these boundaries were represented by regional unconformities basal erosional surfaces of incised valley fills interfluvial paleosols and abrupt depositional facies reversal surfaces sequences i v correspond to the rift initiation stage the early rift climax stage the late rift climax stage the immediate postrift stage and the late postrift stage of the basin respectively the preferred sites for coal accumulation were braided fluvial delta plain meandering fluvial delta plain and littoral shallow lake environments the major coal seams formed during the early and late transgressive systems tract of sequences iii iv and v which were well developed in the eastern northeastern and northeastern parts of the erlian basin respectively three coal depositional models were summarized in the sequence stratigraphic framework including types 1 2 and 3 corresponding to the newark type newark richmond type and richmond type respectively these coal depositional models were closely related to the basin evolution these results could provide preferred depositional environments and favorable areas of coal and coalbed methane cbm for the exploration and development of coal and cbm in the erlian basin with the jiergalangtu huolinhe baiyinhua and a nan sags recommended as the key sags

distribution and isotopic composition of foraminifera at cold seep site 973 4 in the dongsha area northeastern south china sea abstract a 1375 cm long gravity core site 973 4 was acquired from the dongsha cold seep area of the northeastern south china sea scs we measured its stable isotopes of planktonic foraminifera and investigated benthic foraminiferal assemblage compositions accelerator mass spectrometry 14c analysis of planktonic foraminifera shows that some intervals are dated to marine isotope stage mis 3 pulleniatina obliquiloculata has positive 13c 0 25 1 25 except for a negative carbon isotopic excursion up to 13c 1 15 but its light carbon sources remain elusive the benthic 13c values uvigerina of non seep and cold seep boreholes from the scs have no systematic difference therefore the benthic 13c at site 973 4 did not record the enhanced seepage activities if occurred during the last sea level lowstand in the dongsha area in the pre holocene sediments the foraminiferal assemblages have lower diversities shannon wiener indices evenness indices simpson indices and higher calcareous proportions like typical cold seep settings the changes in oxygen levels lower in the glacial period than those in the holocene indicated by foraminiferal indices reflect either bottom water oxygen variations on the glacial interglacial scale or enhanced seepage activities during the last glacial period