the meandering gulf stream as seen by the geosat altimeter surface transport position and velocity variance from 73 to 46 w the surface geostrophic velocity field for the gulf stream region was analyzed for the position structure and surface transport of the gulf stream for 2 5 years of the geosat altimeter exact repeat mission synthetic data using a gaussian velocity profile were generated and fit to the sea surface residual heights to create a synthetic mean sea surface height field and profiles of absolute geostrophic currents most of cross track velocity variance was due to the meandering of the gulf stream rather than to rings or complicated velocity profiles which suggested that the simple model parameters are an efficient description of the gulf stream fluctuations an analysis of the model parameters and the actual geostrophic velocity profiles revealed two different flow regimes for the gulf stream connected by a narrow transition region coincident with the new england seamount chain the upstream region was characterized by relatively straight gulf stream paths long eulerian time scales and eastward propagating meanders the downstream region had more large meanders no consistent propagation direction and shorter eulerian time scales a 25 reduction in surface transport occurred in the transition region with a corresponding reduction in current speed and no change in gulf stream width a significant anomaly in surface transport near 69 w suggested the existence of small scale recirculation gyres there the highest variance empirical orthogonal functions of position and surface transport were significantly correlated with larger surface transports leading more northerly positions by a month

c1c8 hydrocarbons in sediments from guaymas basin gulf of california comparison to peru margin japan trench and california borderlands surface seafloor sediments hydrothermal vent samples and deep sea drilling project sediments hole 481a from the guaymas basin were examined for c1c8 hydrocarbons the proportions of various classes of compounds were examined and compared to those from other geographic areas peru upwelling region and japan trench to gain insight into the relative importance of thermal generation migration and biodegradation concentrations of c2c7 hydrocarbons were about 10 10 000 times higher in geothermally warm estimated to have been exposed to maximum temperatures in the range of 30 150 c guaymas basin sediments in comparison to the low concentrations 0 1 10 ppb per compound typical of geothermally cold maximum thermal exposure less than 20 c seafloor and dsdp diatomaceous sediments however one sediment sample from dsdp site 477 estimated to have been exposed to temperatures of 300 c or higher in the past showed only a limited hydrocarbon composition consisting of c1c3 alkanes and aromatic hydrocarbons only alkene alkane ratios of 0 1 or greater were typical of both geothermally cold sediments and also of very hydrocarbon richalvin samples recovered from the seafloor because little or no alkene was generally detected in buried sediments exposed to geothermal temperatures greater than 30 c it is suggested that the alkenes are produced by biogenic processes normal alkenes predominated over cyclic and branched structures in geothermally cooler 20 c sediments with the proportion of cyclic and branched compounds increasing in hotter sediments concentrations ofgem dimethyl and aromatic compounds generally remained approximately constant or increased slightly with temperature in comparison with geothermally cold shallow sediments similarities in compositions of branched and cyclic compounds were observed in some pairs of bitumen rich guaymas seafloor samples recovered from different areas suggesting common mechanisms of light hydrocarbon generation and or migration localized increases in ratios of specific cycloalkane ratios were observed adjacent to sill intrusions

hydrothermal petroleum from lacustrine sedimentary organic matter in the east african rift cape kalamba oil seeps occur at the south end of the ubwari peninsula at the intersection of faults controlling the morphology of the northern basin of the tanganyika rift east africa oil samples collected at the surface of the lake 3 4 km offshore from cape kalamba have been studied the aliphatic hydrocarbon and biomarker compositions with the absence of the typical suite of polynuclear aromatic hydrocarbons indicate an origin from hydrothermal alteration of immature microbial biomass in the sediments these data show a similarity between a tar sample from the beach and the petroleum from the oil seeps and confirm that the source of these oils is from organic matter consisting mainly of bacterial and degraded algal biomass altered by hydrothermal activity the compositions also demonstrate a 200 degrees c temperature for formation generation of this hydrothermal petroleum similar to the fluid temperature identified for the pemba hydrothermal site located 150 km north of cape kalamba the 14c age of 25 6 ka b p obtained for the tar ball suggests that pleistocene lake sediments could be the source rock hydrothermal generation may have occurred slightly before 25 ka b p during a dry climatic environment when the lake level was lower than today these results also suggest that the cape kalamba hydrothermal activity did not occur in connection with an increased flux of meteoric water higher water tables and lake levels as demonstrated in the kenya rift and for the pemba site hydrothermal petroleum formation is a facile process also in continental rift systems and should be considered in exploration for energy resources in such locales

a vertical section of eddy kinetic energy through the gulf stream system ocean current observations made by drifting buoys sofar floats and current meters are combined to produce the first section of eddy kinetic energy through the gulf stream and subtropical gyre along 55 w eddy kinetic energy peaks at 2000 cm2 s 2 in the surface gulf stream near 39 n and decreases latitudinally and vertically to a low of 0 5 cm2 s 2 in the abyssal gyre interior 4000 m 28 n still further south eddy energy increases slightly in the region of the north equatorial current

surface currents in the caribbean sea as deduced from lagrangian observations the results of a satellite tracked drifting buoy experiment conducted in the caribbean sea from october 1975 through june 1976 are presented the buoy trajectories suggest that the aves rise beata ridge and nicaraguan rise are regions where considerable mesoscale variability occurs in the surface flow the variability is in the form of current deflections small diameter eddies ranging in size from 20 to 100 km large amplitude meanders with amplitudes greater than 150 km and large diameter eddies with diameters greater than 200 km which form on and near these rises and ridges in the central caribbean where the topographic relief is not as dramatic the flow is predominantly zonal intensifications in the surface flow occur off the coast of colombia south of the nicaraguan rise and south of the yucatan strait

mid latitude mesoscale variability neither homogeneous quasi geostrophic turbulence nor the effect of eddies on the interior ocean circulation remains the major focus of mesoscale research as was the case for much of the preceding 20 years following identification of the phenomena concentration on basin wide geographical exploration of eddy properties was rather well established by 1978 over the last few years a promising zero order description and rationalization of the mesoscale field has become available that is eddy energy is largest near strong flows intensification not only in western boundary currents but along their mid latitude open ocean extension roughly as indicated by gyre scale numerical models where eddies develop as a result of instability processes in the mid latitude jet and recirculation regimes and then propagate into the ocean interior our point of view is that mesoscale eddies drive recirculations but do not play a crucial role in the dynamics of the mean flow in the ocean interior in the north atlantic for example the idea is that the downstream increase in transport of the gulf stream is eddy driven but not the flow through the florida straits in addition the fluctuating response to forcing by variable winds may now be widely perceived as forming the horizontally homogeneous background signal in subtropical gyres the time dependent field associated with thermohaline flows at abyssal depths also has a special character

gulf stream trajectories measured with free drifting buoys abstract during 1975 78 35 free drifting buoys measured surface currents in the gulf stream region the buoy trajectories trace numerous paths of the stream and show that the stream is strongly influenced by the new england seamounts this influence is manifested as 1 a quasi permanent 100 km southeastward deflection of the stream and the frequent occurrence of a ring meander over the seamounts 2 large amplitude meanders beginning at the seamounts and extending eastward and 3 small 20 km diameter eddies which appear to be generated locally by individual seamounts a chart of the mean temperature field at a depth of 450 m agrees with several of the patterns seen in the buoy trajectories west of the seamounts the mean path of the gulf stream is eastward over the seamounts the path turns sharply northeastward and the isotherms in the stream abruptly diverge

comparison of 14c ages of hydrothermal petroleums abstract in order to set limits on the time frame of formation of hydrothermal petroleum we have obtained 14 c ages on samples from three diverse regions gulf of california guaymas basin northeast pacific ocean escanaba trough and middle valley and the east african rift tanganyika trough the results date the source of carbon and therefore provide maximum ages for the formation and emplacement of the hydrothermal petroleums the youngest petroleum occurs iin the souther trough of guaymas basin 3200 6600 yr mean 4692 yr in the northern trough the petroleum is slightly older 7400 yr significantly older hydrothermal petroleum occurs in escanaba trough 17 000 yr and middle valley 29 000 yr a continental example from the east african rift has an age of 25 000 yr comparable to the ages observed in the oceanic samples from the northeast pacific ocean these ages affirm that hydrothermal petroleum formation is a very rapid process and took place some time between the latest pleistocene and the present in these active hydrothermal systems

formation of nanoporous pyrobitumen residues during maturation of the barnett shale fort worth basin abstract hydrocarbon generation reactions occur within organic rich shales as a response to thermal maturation here we report observations on samples from the organic rich mississippian barnett shale gas system fort worth basin texas usa at varying stages of thermal maturation a multiscale characterization was achieved using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm and transmission electron microscopy tem we document the chemical evolution of the macromolecular structure of barnett shale kerogen with increasing maturity from an immature kerogen containing a significant aliphatic component and an important concentration of oxygen and sulfur containing functional groups to an overmature kerogen dominated by poorly condensed aromatic structures in addition to the presence of bitumen in samples of oil window maturity very likely genetically derived from thermally degraded kerogen the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by secondary cracking of bitumen compounds

dynamic transfer of simulated altimeter data into subsurface information by a numerical ocean model a global eddy resolving capability to predict the ocean circulation is technologically feasible within the next decade for this purpose the satellite altimeter is the most promising operational source of oceanic data with global coverage but only at the surface a comparable source of subsurface data is not on the horizon this investigation demonstrates the ability of a numerical ocean model to dynamically transfer simulated altimeter data into subsurface information this was done for a variety of dynamical regimes with 1 barotropic baroclinic mixed and episodic instabilities 2 flat bottoms or large amplitude topography 3 relatively vigorous or gentle exchange of energy between the layers and 4 major time scales that are short 60 days long 1 year or both in all cases the pattern of the deep pressure field is much different from the one for the current related variations in the sea surface elevation and sometimes not obviously related to it the model was able to reconstruct the deep pressure field even in situations with energetic shallow and deep circulations baroclinic instability and a vigorous vertical exchange of energy however in such experiments the frequency of updating for the free surface elevation was critical in this study the maximum update interval that allowed successful dynamic surface to subsurface transfer was about half the shortest major time scale smts e g 50 60 days in the experiments with baroclinic instability without knowledge of the deep pressure field numerical predictions of the surface pressure field and the depth of the pycnocline typically were better than climatology for 1 4 to 1 2 the smts but with successful dynamic surface to subsurface transfer forecasts without updating were better than climatology for the smts or more the time scale for predictive skill can be substantially longer than the maximum update interval permitted because the update interval must be short enough to allow decreasing error in the deep pressure field from one free surface update to the next until the error asymptotes at some acceptable level approximately 30 50 in these results forecasts of nondispersive isolated eddies with beta rossby number o 1 demonstrated predictive skill for 3 months or more even when the subsurface initial state was unknown a serendipitous result of the study is some progress in understanding the generation of cyclonic eddies associated with the loop current in the eastern gulf of mexico section 5 5

survey of hydrothermally generated petroleums from the guaymas basin spreading center abstract the guaymas basin spreading center and hydrothermal system are generating an assortment of petroleum like bitumens by pyrolysis of organic matter in the overlying uncosolidated sediments samples collected by d s v alvin from hydrothermal fields in the southern trough exhibit large variations in the quantities and character of the solvent soluble organic materials various pyrolytic regimes combined with fluctuating thermal gradients and migration velocities may impart a compositional fractionation possibly by differential gaseous solubilization and hydrodynamic alteration of the multi component fluids the data suggest that differential condensation solidification biodegradation and water washing cause selective removal of components at the seabed many hydrothermal oils are unlike normal reservoir petroleums because they contain significant concentrations of polar material due to their rapid genesis and transport and probable solubilization or advection of polar immature components the biomarker distributions confirm high temperature pyrolysis at depth with variable entrainment of less thermally mature bitumens during transport data for shallow core samples from the northern trough indicate that those locations experienced variable influx predominantly volatiles of a low temperature pyrolysate

the near surface flow in the subtropical gyre south of the azores this study presents evidence that the azores current azc is a permanent feature of the north atlantic subtropical gyre and that it feeds the north equatorial current nec the azc path is located south of the azores its velocity is mostly geostrophic and the energy level in the mesoscale range is higher than in the nec the nec velocity appears to be mostly ageostrophic and the wind driven surface velocity is at about 15 to the right of the mean wind field

hydrothermal petroleum genesis migration and deposition in guaymas basin gulf of california hydrothermal activity and seabed mounds have been explored in guaymas basin by the deep sea drilling project dsdp piston coring dredging and diving with the deep submersible research vessel dsrv alvin sedimentary organic matter derived primarily from immature degraded microbial detritus is easily converted to petroleum under the hydrothermal regime these petroleums are mature and migrate in the fluids and by diffusion to the seabed the fluid migration is aided by near critical aqueous solution and supercritical carbon dioxide and hydrocarbons petroleum compositions vary from condensates to naphthenic to waxy all with significant amounts of asphaltenes and hydrothermal products such as olefins and toxic polynuclear aromatic hydrocarbons pah the heavy ends condense at the seabed depositing mainly as a cement with the sulfides and other minerals and to a lesser extent as entrapped oil and crystalline wax in vugs and conduits of the mounds the pah are high temperature resynthesis aromatiza

relay ramp forms and normal fault linkages canyonlands national park utah fieldwork within a series of mesoscale grabens in southeast utah has revealed a particularly well exposed system of interlinked extensional faults a series of down faulted grabens are developed within a 460 m thick brittle layer of upper paleozoic sandstone and shale which overlies a ductile layer with a high gypsum content all the major grabens consist of two or more overlapping elements which are composed of fault segments these segments may be hard linked fault surfaces are joined or soft linked fault surfaces are isolated but linked by ductile strain of the rock volume between them in map view relay structures are defined as zones connecting the footwalls and hanging walls of overlapping fault segments representing soft linkage of fault segments in the canyonlands grabens the transfer of displacement between soft linked fault segments is characterized by well de fined dipping relay ramps commonly rotated and extended to accommodate the ductile strain between the overlapping fault segments relay ramps develop as ephemeral structures eventually becoming breached by hard linkage of the fault segments breakdown of ramps by breaching is part of the process of fault growth by segment linkage within the canyonlands graben system four orders of segmentation are present this may be a consequence of different scales of mechanical heterogeneity but evidence from the canyonlands grabens and elsewhere points to a fundamental process of discontinuous fault growth by segment linkage

numerical simulation of the gulf stream system the loop current and the deep circulation 1 the loop current and the deep circulation in the gulf of mexico are numerically investigated by a primitive equation sigma coordinate ocean model with realistic surface fluxes obtained from an atmospheric forecast model a deep cyclonic circulation bounded by the deep basin in the eastern gulf of mexico is spun up by the loop current the deep cyclonic circulation is coincident with a southward current of the loop current eastern limb and weakens after loop current ring separation and cessation of the southward current the anticyclonic semienclosed loop current also induces anticyclonic lower layer columnar eddies in the eastern gulf these lower layer eddies decouple from the upper layer loop current the westward translation speed of a loop current ring is about 2 16 5 18 km d 1 the lower layer eddies have a higher speed and lead the rings into the central gulf the time averaged surface circulation of the gulf of mexico basin is anticyclonic mainly because of the transport of anticyclonic vorticity by loop current rings in the surface layer an average lower layer cyclonic circulation occurs along the continental slope of the basin

surface circulation at the tip of the antarctic peninsula from drifters an array of 40 surface drifters drogued at 15 m depth was deployed in february 2007 to the east of the tip of the antarctic peninsula as part of the antarctic drifter experiment links to isobaths and ecosystems adelie project data obtained from these drifters and from a select number of local historical drifters provide the most detailed observations to date of the surface circulation in the northwestern weddell sea the antarctic slope front asf characterized by a 20 cm s 1 current following the 1000 m isobath is the dominant feature east of the peninsula the slope front bifurcates when it encounters the south scotia ridge with the drifters following one of three paths drifters i are carried westward into bransfield strait ii follow the 1000 m isobath to the east along the southern edge of the south scotia ridge or iii become entrained in a large standing eddy over the south scotia ridge drifters are strongly steered by contours of f h coriolis frequency depth as shown by calculations of the first two moments of displacement in both geographic coordinates and coordinates locally aligned with contours of f h an eddy mean decomposition of the drifter velocities indicates that shear in the mean flow makes the dominant contribution to dispersion in the along f h direction but eddy processes are more important in dispersing particles across contours of f h the results of the adelie study suggest that the circulation near the tip of the antarctic peninsula may influence ecosystem dynamics in the southern ocean through antarctic krill transport and the export of nutrients

structural geology and 4d evolution of a half graben new digital outcrop modelling techniques applied to the nukhul half graben suez rift egypt abstract lidar based digital outcrop mapping in conjunction with a new surface modelling approach specifically designed to deal with outcrop datasets is used to examine the evolution of a half graben scale normal fault array in the suez rift syn rift deposition in the nukhul half graben was controlled by the graben bounding nukhul fault the fault can be divided into four segments based on the strike of the fault the morphology of hangingwall strata and the variation in throw along strike the segments of the fault became geometrically linked within the first 2 5 m y of rifting as evidenced by the presence of early syn rift abu zenima formation strata at the segment linkage points fault perpendicular folds in the hangingwall related to along strike variations in throw associated with precursor fault segments persist for a further 1 8 m y after linkage of the segments suggesting that the fault remains kinematically segmented we suggest this occurs because of sudden changes in fault strike at the segment linkage points that inhibit earthquake rupture propagation or because displacement is geometrically inhibited at fault linkage points where the orientation of the intersection line of the segments is significantly different from the orientation of the slip vector on the fault system length throw plots and throw contour patterns for minor faults show that some faults initiated in pre rift strata whereas late east striking faults initiated in the syn rift basin fill the late initiating faults are spatially associated with the east striking baba markha fault which was active throughout the rift history but developed as a transfer fault between major block bounding fault systems around 6 7 ma after rift initiation

the growth of fault bounded tilt blocks a series of uniformly tilted fault bounded blocks is a common feature in actively extending regions such as the basin and range province if the tilted blocks were produced by rigid domino style rotation one would predict large voids at either end of a series of these blocks using tilt data and a simple flexural calculation we suggest that much of the apparent rigid behavior could also be produced by internal block deformation in our model of normal fault growth isostatic elastic uplift of the footwall is coupled with hanging wall downdrop within the region between faults resulting in the appearance of a tilted rigid block we present tilt data sampled at varying distances from several block defining faults within the northeast basin and range province tilt measurements between a series of 30 km spaced block defining faults are found to be uniform while tilts between more widely spaced faults exhibit a pattern of tilt that diminishes to zero in less than 30 km using a simple flexural calculation for internal block deformation we show that for this region the patterns of tilt are consistent with a flexural length scale of 8 12 km and deflections of 2 4 km these estimates are compatible with both the lower limit to seismicity and basin depth determined from earthquake and seismic reflection studies

geometry and development of relay ramps in normal fault systems relay ramps occur between normal fault segments that overstep in map view the geometry and evolution of exposure scale relay ramps are described from the somerset coast england and are compared with larger scale ramps from elsewhere relay ramps can be classified into four groups based on the degree of interaction and linkage between the overstepping segments these groups are interpreted as being evolutionary stages in stage 1 the segments do not interact stage 2 involves the reorientation of bedding between two interacting faults to produce a relay ramp in stage 3 connecting fractures start to break the relay ramp stage 4 is when the relay ramp is destroyed to produce a single fault that has an along strike bend these evolutionary stages can develop through ti e but they can also be seen spatially a branch line between normal faults or an along strike bend may represent a stage 4 relay with progressively earlier stages occurring updip or downdip characteristic variability in displacement distance profiles for fault segments and linked faults accompanies the interaction and linkage processes displacement transfer by relay ramps is accompanied by steep displacement gradients along fault segments at oversteps relay ramps often contribute to a minimum in total fault displacement at a linkage point

lithospheric structure of the malawi rift implications for magma poor rifting processes this project was supported by the national science foundation continental dynamics nsf cd grant ear 1255233 and office of international and integrative activities oiia grant iia 1358150 this project is also supported by the nsf earthcube integration grant 1740627 we thank the computational infrastructure for geodynamics geodynamics org which is funded by the national science foundation under award ear 0949446 and ear 1550901 for supporting the development of advanced solver for problems in earth s convection

variations of the gulf stream s north wall east of cape hatteras abstract twelve years 1977 1988 of noaa infrared imagery data were used to study the variations of the north wall displacements of the gulf stream east of cape hatteras i e between 74 w and 65 w the variations of the north wall displacements were compared with the variations in the straits of florida transport which was estimated using a multifrequency model based on the sea level differences between siboney cuba and key west florida for the period 1977 1988 and with transport measurements based on the submarine cable between jupiter florida and settlement point in the bahamas for the period 1982 1988 the north wall reached a maximum northward position in 1985 when the cable data indicated that the straits of florida transport was a maximum the north wall reached a maximum southward position in 1981 cable data were not available before 1982 but the available data suggested that there may have been a minimum transport in 1981 a weak annual cycle of the north wall was found with a maximum northward position in the fall and a maximum southward position in the spring no relationship was found between the annual cycle of the gulf stream s north wall and the annual cycle of the straits of florida transport

a transform continental margin rich in hydrocarbons gulf of california conventional and near bottom geophysical surveys mapped shallow deformational structures and sediment accumulation patterns along part of the actively shearing continental margin of sonora including the intersection with a guaymas basin spreading center the principal strike slip faults occupy a zone 1 2 km 0 6 1 2 mi wide along the lower slope with a ridge of tightly folded sediments raised by uplift of sheared basement at the abrupt boundary between continental and oceanic crust this transform ridge and a continental rise on its seaward slope grows as the fault zone ages away from the spreading center intersection shoaling at a net rate of 500 m m y 1 600 ft m y despite erosion of its crest a clathrate horizon in the upper 80 m 260 ft of sediment is inferre from bottom simulating reflectors in the rise and lower slope hydrocarbon seeps occur at 1 600 m 1 mi below sea level along the crest of the transform ridge and patchy gas accumulation and seepage are recognized on a young marginal plateau

a mechanism to explain rift basin subsidence and stratigraphic patterns through fault array evolution rift basin stratigraphy commonly records an early stage of slow subsidence followed by an abrupt increase in subsidence rate the physical basis for this transition is not well understood although an increase in extension rate is commonly implied here a numerical fault growth model is used to investigate the influence of segment linkage on fault displacement rate patterns along an evolving normal fault array the linkage process we describe is controlled by a stress feedback mechanism which leads to enhanced growth of optimally positioned faults model results indicate that even with constant extension rates slow displacement rates prevail during an initial phase of distributed extension followed by an increase in displacement rates as strain becomes localized on linked fault arrays this is due to the dynamics of fault interactions rather than mechanical weakening comparison of model simulations with rift basin subsidence and stratigraphic patterns in the gulf of suez and north sea suggests that the occurrence and timing of rapid basin deepening can be explained by the mechanics of fault zone evolution without invoking a change in regional extension rates

novel phenolic biomarker triterpenoids of fossil laticifers in eocene brown coal from geiseltal germany abstract novel phenolic triterpenoids were tentatively identified with known mono tri and tetraaromatic oleanane ursane and lupane hydrocarbons and natural product precursors amyrone amyrin in the extract of eocene fossil laticifers called affenhaar from the geiseltal lignites germany the novel phenolic terpenoids are mono and triaromatic hydroxytriterpenoids oh at position 1 2 or 3 of the oleanane ursane and lupane classes hydroxy 24 25 dinoroleana 1 3 5 10 12 tetraene hydroxy 24 25 dinorlupa 1 3 5 10 triene hydroxy 24 25 dinorlupa 1 3 5 10 19 22 tetraene hydroxy 24 25 26 27 tetranorursa 1 3 5 7 9 11 13 heptaene hydroxy 24 25 26 27 tetranoroleana 1 3 5 7 9 11 13 heptaene and hydroxy 24 25 26 27 tetranorlupa 1 3 5 7 9 11 13 heptaene the structures of the novel compounds were proposed based on the interpretation of the gas chromatography mass spectrometry data of the underivatized and silylated total extract

phenols in hydrothermal petroleums and sediment bitumen from guaymas basin gulf of california the aliphatic aromatic and polar nso fractions of seabed petroleums and sediment bitumen extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry free and silylated the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolyzates that have migrated to the seafloor by hydrothermal fluid circulation the downcore sediments are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds in samples with a high degree of thermal maturity phenols are one class of oxygenated compounds found in these samples a group of methyl dimethyl and trimethyl isoprenoidyl phenols c27 c29 is present in all of the seabed nso fractions with the methyl and dimethyl isoprenoidyl phenols occurring as major components and a trimethyl isoprenoidyl phenol as a minor component a homologous series of n alkylphenols c13 c33 has also been found in the seabed petroleums these phenols are most likely derived from the hydrothermal alteration of sedimentary organic matter the n alkylphenols are probably synthesized under hydrothermal conditions but the isoprenoidyl phenols are probably hydrothermal alteration products of natural product precursors the suites of phenols do not appear to be useful tracers of high temperature hydrothermal processes

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

organic geochemistry of deep sea drilling project sediments from the gulf of calofornia hydrothermal effects on unconsolidated diatom ooze abstract the effects of intrusive thermal stress have been studied on a number of pleistocene sediment samples obtained from leg 64 of the dsdp ipod program in the gulf of california samples were selected from sites 477 478 and 481 where the organic matter was subjected to thermal stress from sill intrusions for comparison purposes samples from sites 474 and 479 were selected as representative of unaltered material the gc and gc ms data show that lipids of the thermally unaltered samples were derived from microbial and terrestrial higher plant detritus samples from sill proximities were found to contain thermally derived distillates and those adjacent to sills contained essentially no lipids curie point pyrolysis combined with gc and gc ms was used to show that kerogens from the unaltered samples reflected their predominantly autochthonous microbial origin pyrograms of the altered kerogens were much less complex than the unaltered samples reflecting the thermal effects the kerogens adjacent to the sills produce little or no pyrolysis products since these intrusions into unconsolidated wet sediments resulted in in situ pyrolysis of the organic matter examination of the kerogens by esr showed that spin density and line width pass through a maximum during the course of alteration but esr g values show no correlation with maturity stable carbon isotope 13 c values of kerogens decrease by 1 1 5 near the sills at sites 477 and 481 and the atomic n c decreases slightly with proximity to a smaller sill at site 478 differences in maturation behavior between site 477 and 481 and site 478 are attributed to dissimilarities in thermal stress and to chemical and isotopic heterogeneity of guaymas basin protokerogen

mass and nutrient fluxes around sedlo seamount abstract we use data from a hydrographic cruise in november 2003 over sedlo seamount in conjunction with historical hydrographic and altimeter data to describe the circulation patterns near the seamount and within the region a mixing model that incorporates two water types and two water masses assesses the water composition within the region and an inverse model provides estimates of mass transports within different water strata eastern north atlantic central water dominates for the upper neutral density n levels n n 27 7 band in the 27 5 n 27 8 band mediterranean water constitutes slightly more than 10 except in the northwestern portion where this water type is less abundant for 27 7 n 27 9 labrador sea water becomes the predominant water mass the results from the inverse model and direct velocity measurements draw a gross picture of central waters flowing northwest along the northeastern margin of the seamount while the net fluxes of labrador sea water are relatively small the central water flow appears to be topographically guided with a region of high eddy kinetic energy over a spur that stretches southeast from the mid atlantic ridge a gross calculation suggests the existence of significant net nutrient transport into the seamount that would support an enhanced level of primary production

concentrations distributions and energy yields of dissolved neutral aldoses in a shallow hydrothermal vent system of vulcano italy abstract large numbers of heterotrophic microorganisms inhabit hydrothermal systems but few organic geochemistry studies have been carried out on these environments this study presents the first data on total dissolved neutral aldose tdna composition in a shallow hydrothermal system on the island of vulcano italy samples were collected from geothermal wells sediment seeps and shallow submarine vents temperatures and geochemical conditions varied between sample locations concentrations of tdna were 56 55 128 nm a larger range than those reported for non hydrothermal systems tdna yields ranged from 0 47 to 16 54 the highest yields were observed in sediment seeps and these yields are higher than any reported for non hydrothermal systems similar to other marine environments glucose and galactose had the highest mole fractions in most samples mole fractions of the deoxysugars fucose and rhamnose were low indicating that algal material is not a likely source for tdna high tdna concentrations correlated with high amino acid aa concentrations indicating that the source and sink processes for aa and tdna may be similar high concentrations of both tdna and aa occurred in samples with low ph and high temperature but only ph showed a significant correlation with organic parameters at the in situ geochemical conditions and per mole of aldose reacted fermentation yields 220 420 kj anaerobic respiration yields 500 2400 kj and aerobic respiration yields 2750 kj the generally high aldose yields indicate a large fraction of biologically labile material and energy calculations show that aldose respiration is more exergonic than chemolithotrophic reactions within the system

dynamics at an elongated intermediate depth seamount in the north atlantic sedlo seamount 40 20 n 26 40 w abstract observations from a five mooring array deployed in the vicinity of sedlo seamount over a 4 month period together with supporting hydrographic and underway adcp measurements are described sedlo seamount is an elongated intermediate depth seamount with three separate peaks rising from 2200 m water depth to summit peaks between 950 and 780 m depth located at 40 20 n 26 40w currents measured in depth range 750 and 820 m the layer close to the summit depth of the shallowest southeast peak showed a mean anti cyclonic flow around the seamount with residual current velocities of 2 5 cm s 1 significant mesoscale variability was present at this level and this is attributed to the weak and variable background impinging flow stronger more persistent currents were found at the summit mooring as a result of tidal rectification and some weak amplification below 1300 m currents were extremely weak even close to the seabed time series of relative vorticity for the depth layer 750 820 m showed persistent anti cyclonic vorticity except for two periods of cyclonic vorticity a mean relative vorticity of 0 06f f the local coriolis frequency was calculated from a triangle of current meters located at the flanks of the seamount modelling results confirmed that anti cyclonic flow above the seamount was likely due to taylor cone generation driven by a combination of steady impinging and tidally rectified flow the closed circulation pattern over the seamount was found to extend to 150 m above the summit level consistent with simple idealised theory and the supporting hydrographic observations at shallower depths

some examples of detection of oceanic mesoscale eddies by the seasat synthetic aperture radar this note presents images of three dynamically different regions in the ocean to demonstrate the variety of mesoscale variabilities detected by the seasat synthetic aperture radar sar south of the grand banks of newfoundland a cold eddy is observed to form as the result of the southward intrusion of labrador sea water perhaps having led to the birth of a gulf stream extension ring off the northern coast of california features resulting from the offshore intrusions of cold upwelling water are observed two topographically generated eddies are detected near misteriosa bank on the cayman ridge in the northwestern caribbean comparisons are made with concurrent noaa 5 infrared images whenever the eddies have thermal signatures

processes controlling water and hydrocarbon composition in seeps from the salton sea geothermal system california usa water mud gas and petroleum bearing seeps are part of the salton sea geothermal system ssgs in southern california seeps in the davis schrimpf seep fi eld 14 000 m 2 show considerable variations in water temperature ph density and solute content water rich springs have low densities 98 vol halogen geochemistry of the waters indicates that mixing of deep and shallow waters occurs and that near surface dissolution of halite may overprint the original fl uid compositions carbon isotopic analyses suggest that hydrocarbon seep gases have a thermogenic origin this hypothesis is supported by the presence of petroleum in a water dominated spring composed of 53 saturated compounds 35 aromatics and 12 polar compounds the abundance of polyaromatic hydrocarbons and immature biomarkers suggests a hydrothermal formation of the petroleum making the ssgs a relevant analogue to less accessible hydrothermal seep systems e g the guaymas basin in the gulf of california

sea surface temperature variability and deep water reorganisation in the subtropical north atlantic during isotope stage 2 4 abstract two sediment cores from a high accumulation sediment drift at 3000 m water depth in the western north atlantic are investigated in order to examine possible linkages between subtropical surface and bottom water properties and global climate oscillations during the last glacial interglacial cycle planktonic foraminiferal assemblages and the 18 o of globigerinoides ruber both document large sea surface temperature oscillations 3 4 c that appear to co vary with greenland ice core records short episodes of sea surface cooling as far south as the blake outer ridge at 33 n are inferred from increased abundance of the polar species neogloboquadrina pachyderma sinistral during the ice core stadials events nutrient proxy records suggest that the deep waters flooding the site alternated between a northern north atlantic deep water and a southern southern ocean water source in most cases warm surface water conditions interstadials were accompanied by a strong north atlantic deep water component in the bottom water circulation however the transitions into interstadial 14 and 12 seem to be marked by a 1500 yr lag between surface water warming and the deep water circulation shift as recorded by caco 3 and 13 c of benthonic foraminifera

geochemistry of shallow sediments in guaymas basin gulf of california hydrothermal gas and oil migration and effects of mineralogy offset of prograde hydrothermal alterations by retrograde reactions is evident in sediments from a piston core pc6 8 m long from the guaymas basin gulf of california geochemical and mineralogical analyses of sediments and pore fluids show superimposed geochemical signals that indicate currently active reactions are modifying previously formed secondary solids hydrothermal barite was formed in a previously active flow channel between 150 and 250 cm depth hydrothermal gypsum is presently dissolving at depths 780 cm below which hydrothermal fluid flow is channeled by a secondary dolomite layer thermal stress of organic matter generates hydrothermal gas and petroleum having wide ranges of compositions and maturities a significant amount of hydrothermally generated oil has been transported laterally through a porous debris flow approx 240 cm subbottom overwhelming the indigenous bituminous matter water soluble petroleum constituents have disseminated throughout the cored sediments from 400 to 700 cm depth the immature organic matter continues to experience thermally enhanced diagenesis and an even higher thermal stress has occurred at the bottom of the core enhanced bacterial degradation of organic matter has led to depletion of pore water sulfate and enrichment of ammonium nh4 in both pore fluid and sediment resulting in formation of nh4 bearing secondary clay minerals at depths below 780 cm

abyssal eddies near the gulf stream a comparison is made of long 8 12 months records of three near bottom current meters with satellite derived frontal positions of gulf stream meanders and rings energetic fluctuations with time scales 0 30 90 days coincide with and most probably result from the movement of gulf stream meanders and rings

ketones in hydrothermal petroleums and sediment extracts from guaymas basin gulf of california the polar compound nso fractions of seabed petroleums and sediment extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolysates that have migrated to the seafloor by hydrothermal fluid circulation the downcore samples are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds correlated with samples exhibiting a high degree of thermal maturity several homologous series of related ketone isomers are enriched in the interiors of the hydrothermal vent samples or in hydrothermally altered sequences of the downcore sediments dsdp holes 477 and 481a the n alkanones range in carbon number from c11 to c33 with a cmax from 14 to 23 distributions that are similar to those of the n alkanes the alkan 2 ones are usually in highest concentrations with lower amounts of 3 4 5 6 7 and higher alkanones and they exhibit no carbon number preference there is an odd carbon number preference of alkanones observed for downcore samples the alkanones are enriched in the interiors of the hydrothermal vent spires or in downcore hydrothermally altered sediments indicating an origin at depth or in the hydrothermal fluids and not from an external biogenic deposition minor amounts of c13 and c18 isoprenoid ketones are also present simulation of the natural hydrothermal alternation process by laboratory hydrous pyrolysis techniques provided information regarding the mode of alkanone formation hydrous pyrolysis of n c32h66 at 350 c for 72 h with water only or water with inorganic additives has been studied using a stainless steel reaction vessel in each experiment oxygenated hydrocarbons including alkanones were formed from the n alkane the product distributions indicate a reaction pathway consisting of n alkanes and olefins as primary cracking products with internal olefins and alkanones as secondary reaction products hydrous pyrolyses of messel shale spiked with molecular probes have been performed under similar time and temperature constraints to produce alkanone distributions like those found in the hydrothermal vent petroleums

evidence for spreading rate dependence in the displacement length ratios of abyssal hill faults at mid ocean ridges new data from the eastern flank of the mid atlantic ridge 25 27 n show that slow spreading abyssal hill faults maintain maximum displacement length ratios that are systematically greater than those reported on the fast spreading east pacific rise lower displacement length ratios in the fast spreading environment may reflect the importance of fault linkage rather than lateral propagation in determining the lengths of abyssal hill faults and the limited ability of fault systems that evolve within an extremely thin lithosphere to acquire additional displacement during or following linkage

geochemical evolution of organic rich shales with increasing maturity a stxm and tem study of the posidonia shale lower toarcian northern germany hydrocarbon generation and retention processes occurring within gas shales as a response to increases in thermal maturation are still poorly constrained while efforts have been directed at unravelling the resource potential composition and textures of these economically important unconventional systems their spatial variability in chemistry and structure is still poorly documented at the sub micrometer scale here we have characterized samples of the lower toarcian posidonia shale samples from northern germany at varying stages of thermal maturation using a combination of compositional organic geochemistry and spectromicroscopy techniques including synchrotron based scanning transmission x ray microscopy stxm we document geochemical and mineralogical heterogeneities down to the nanometer scale within the investigated samples as a function of their level of thermal maturity in particular authigenic albite crystals containing nanometric halite inclusions have been documented within the investigated mature and overmature samples the presence of such tracers of palaeobrine carbonate interactions supports a maturation scenario for the lower toarcian posidonia shale intimately related to ascending brine fluids rather than a maturation scenario solely resulting from high heat flows in addition various types of asphaltene and nso rich bitumen have been detected within the same samples very likely genetically derived from thermally degraded organic precursors furthermore the formation of nanoporous pyrobitumen has been inferred for samples of gas window maturity likely resulting from the formation of gaseous hydrocarbons by providing in situ insights into the fate of bitumen and pyrobitumen as a response to the thermal evolution of the macromolecular structure of kerogen the results reported here constitute an important step towards better constraining hydrocarbon generation processes during natural shale gas maturation

growth of a normal fault system observations from the lake malawi basin of the east african rift abstract we have studied the growth history of the usisya normal fault system which bounds the west side of the lake malawi basin one of the largest rift basins in the east african rift system the lake malawi rift basin is a complex of intrabasins and intrabasin highs formed by three major fault segments each about 100 km in length the basin has been actively subsiding since the late miocene and has a maximum depth of about 3 km unlike the majority of previous studies of fault systems we are able to define the temporal evolution of this fault system using the patterns of sediment infill this is due almost exclusively to the availability of a high density seismic reflection network in combination with several clearly identifiable temporal marker beds an analysis of the seismic reflection data reveals that growth of the basin bounding faults occurred in the following sequence 1 in the early stages of rifting starting about 8 6 ma the northern fault was the most active 2 then extension shifted to the southernmost fault segment and lasted until about 2 5 ma 3 during the interval between about 2 3 ma and 1 6 ma the central segment was most active prior to the last interval the central segment accrued the least total displacement of the three segments this contradicts the common notion that the location of maximum displacement remains at a fixed location from fault inception or that the largest fault in any population of faults always maintained the highest displacement rate consistent with observations on smaller faults there is a marked increase in the displacement gradient on individual faults in the regions of overlapping segments although there is an observable asymmetry in individual segment displacement profiles there is a clear evolution toward a flattened bell shaped total displacement profile for the fault system that is consistent with the shape and scaling relationships of displacement vs length that are observed on a wide range of individual normal faults this suggests that the irregularities in the shape and scaling relationships observed in complex fault systems will eventually smooth out moreover the observed growth pattern suggests that the profile of the fault system will progress toward that of isolated faults provided the system is allowed sufficient time to evolve this in turn describes a process for maintaining a self similar scaling observed in large populations of faults which span several orders of magnitude in fault length

slip tapers at the tips of faults and earthquake ruptures 1 slip gradients near the tips of earthquake ruptures and faults are typically linear for non interacting faults or earthquake ruptures tip tapers are scale invariant and about 1 2 orders of magnitude larger for faults than for earthquakes for fault tips interacting with other faults the taper can be as much as a factor of 10 greater than for non interacting faults for earthquake ruptures taper is also greater by as much as a factor of 10 for tips of rupture segments in the interior of the main rupture tips in which the earthquake has propagated to the end of the fault and tips which interact with the stress drop of a previous earthquake on the same fault tip taper for faults increases with the strength of the wall rock these observations are consistent with fracture mechanics models in which inelastic deformation occurs in a volume surrounding the crack tip

implications of structural inheritance in oblique rift zones for basin compartmentalization nkhata basin malawi rift ears abstract the cenozoic east african rift system ears is an exceptional example of active continental extension providing opportunities for furthering our understanding of hydrocarbon plays within rifts it is divided into structurally distinct western and eastern branches the western branch comprises deep rift basins separated by transfer zones commonly localised onto pre existing structures offering good regional scale hydrocarbon traps at a basin scale local discrete inherited structures might also play an important role on fault localisation and hydrocarbon distribution here we consider the evolution of the central basin of the malawi rift in particular the influence of pre existing structural fabrics integrating basin scale multichannel 2d and high resolution seismic datasets we constrain the border mlowe nkhata fault system mnf to the west of the basin and smaller mbamba fault mf to the east and document their evolution intra basin structures define a series of horsts which initiated as convergent transfers along the basin axis the horsts are offset along a ne sw striking transfer fault parallel to and along strike of the onshore karoo permo triassic ruhuhu graben discrete pre existing structures probably determined its location and oriented obliquely to the extension orientation it accommodated predominantly strike slip deformation with more slowly accrued dip slip to the north of this transfer fault the overall basin architecture is asymmetric thickening to the west throughout while to the south an initially symmetric graben architecture became increasingly asymmetric in sediment distribution as strain localised onto the western mnf the presence of the axial horst increasingly focussed sediment supply to the west as the transfer fault increased its displacement so this axial supply was interrupted effectively starving the south east while ponding sediments between the western horst margin and the transfer fault this asymmetric bathymetry and partitioned sedimentation continues to the present day overprinting the early basin symmetry and configuration sediments deposited earlier become increasingly dissected and fault juxtapositions changed at a small 10 100 m scale the observed influence of basin scale transfer faults on sediment dispersal and fault compartmentalization due to pre existing structures oblique to the extension orientation is relevant to analogous exploration settings

temperature and velocity structure of the gulf stream northeast of cape hatteras modes of variability thirty five expendable bathythermograph sections and 10 pegasus velocity sections taken approximately normal to the gulf stream northeast of cape hatteras were used to examine the variability of the current s structure the regridded profiles were superimposed in a stream coordinate system such that the temperature variance associated with the superposition was minimized the resulting variance field was examined using empirical orthogonal functions the temperature variability is heavily weighted by seasonal warming hence the following results exclude temperatures from the upper 200 m the first mode 48 of the variance is due to a deepening of the thermocline relative to the mean on the offshore side of the gulf stream and a shoaling on the inshore edge associated with a change of geostrophic velocity and baroclinic transport the amplitudes of this transport mode indicate a slight downstream increase in baroclinic transport 2 per 100 km and a seasonal modulation 5 sverdrups rms that peaks in may june the second temperature mode below 200 m 13 21 of the variance is associated with a change in horizontal shear a vorticity mode and is positively correlated with measured path curvature and layer thickness the directly observed pegasus velocity sections were combined with corresponding temperature sections to compute their joint empirical modes the dominant combined mode has a thermocline structure change as in the transport mode that is coupled with an increase in alongstream velocity and for levels above the main thermocline an inflow from both sides toward the center both temperature and velocity data indicate that high transport in the gulf stream is associated with lateral displacement offshore of its mean position

general circulation of the western subtropical north atlantic observed using profiling floats 1 the general circulation of the subtropical western north atlantic is described using hydrography and subsurface velocity measured simultaneously by 71 profiling floats during the period july 1997 to december 2002 subsurface trajectories of the floats revealed a strong topographic influence and depth dependence of the gulf stream its recirculation gyres and the north atlantic current we discuss eddy like and nonsteady flows in several subregions especially near the major topographic features the seasonal cycle of volume transport estimated using the absolute geostrophic velocity in the upper 900 m was shown to be a maximum in winter and minimum in summer the eddy kinetic energy and eddy diffusivity derived from the float data and mapped over the subtopical gyre show seasonal variability in the vicinity of the gulf stream with a maximum in spring and minimum in winter for both quantities

gulf stream path analysis near the new england seamounts as part of the naval ocean research and development activity s regional energetics experiment 12 inverted echo sounders iess were deployed from june 1985 to july 1986 in two arrays across the historical mean path of the gulf stream near 67 w and 58 w slightly upstream and downstream of the new england seamount chain gulf stream positions and directions were computed at half day intervals for adjacent ies pairs levels of variability at the two array locations were similar but the characteristics of the meanders in terms of propagation and current direction were quite different evidence was found for a quasi stationary meander near 58 w features deduced from ies measurements are compared with concurrent infrared air dropped expendable bathythermograph and geosat altimetry observations

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

evolution of the stress field in southern california and triggering of moderate size earthquakes a 200 year perspective changes in stress in southern california are modeled from 1812 to 2025 using as input 1 stress drops associated with six large 7 0 7 5 earthquakes through 1995 and 2 stress buildup associated with major faults with slip rates 3 mm yr as constrained by geodetic paleoseismic and seismic measurements evolution of stress and the triggering of moderate to large earthquakes are treated in a tensoffal rather than a scalar manner we present snapshots of the cumulative coulomb failure function acff as a function of time for faults of various strike dip and rake throughout southern california we take acff to be zero everywhere just prior to the great shock of 1812 we find that about 95 of those well located m 6 earthquakes whose mechanisms involve either strike slip or reverse faulting are consistent with the coulomb stress evolutionary model that is they occurred in areas of positive acff the interaction between slow moving faults and stresses generated by faster moving faults significantly advanced the occurrence of the 1933 long beach and 1992 landers events in their earthquake cycles coulomb stresses near major thrust faults of the western and central transverse ranges have been accumulating for a long time future great earthquakes along the san andreas fault especially if the san bernardino and coachella valley segments rupture together can trigger moderate to large earthquakes in the transverse ranges as appears to have happened in the santa barbara earthquake that occurred 13 days after the great san andreas shock of 1812 maps of current acff provide additional guides to long term earthquake prediction

surface and deep ocean variability in the northern sargasso sea during marine isotope stage 3 new geochemical proxy data from bermuda rise piston cores reveal ocean and climate conditions in the northern sargasso sea during marine isotope stage 3 using 18o on the planktonic foraminifer globigerinoides ruber we can correlate explicitly with every stadial interstadial change in greenland ice between 32 and 58 ka these data suggest repetitive changes of 4 c in the annual average sea surface temperature sst with maximum cooling comparable to or greater than sst during glacial maximum conditions the extent of sst depression is about the same for typical stadial events and for heinrich events 4 and 5 which we have identified on the bermuda rise by traces of ice rafting benthic foraminiferal 13c decreases during every stadial event consistent with reduced production of the deepest component of north atlantic deep water and shoaling of its interface with antarctic bottom water this interpretation is supported by benthic cd ca data from the climate cycle associated with interstadial 8

14c ages of hydrothermal petroleum and carbonate in guaymas basin gulf of california implications for oil generation expulsion and migration sup 14 c dates have been obtained by accelerator mass spectrometry and by conventional techniques from hydrothermally derived petroleum calcite and vent water from the southern trough of guaymas basin gulf of california the ages for petroleum range from 4240 to 5705 b p whereas those for calcite range from 7340 to 33 168 b p the co sub 2 in a sample of hydrothermal vent fluid 24 end member yielded an apparent age of 14 820 b p which is within the calcite age range these are not true ages but rather they reflect the age of carbon within these materials the data indicate that the conversion of sedimentary organic matter to petroleum occurs very rapidly and that the petroleum is mobilized from sedimentary organic matter in the upper 30 m of the sediment column le 500 m thick underlying the sea floor deposits the large difference in ages between the petroleum and most of the calcites indicates that the carbon source in the calcites is more complex the inorganic carbon pool probably originates from the dissolution of older detrital carbonates and autochthonous biogenic carbonates in the shallow sediments and or the decarboxylation of organic matter at greater depth with a magmatic component of dead carbon

eddy kinetic energy in the north atlantic from surface drifters one hundred ten satellite tracked freely drifting buoys measured velocities and trajectories of the near surface currents in the north atlantic mean velocity values and the velocity variance about the mean were calculated for different regions a horizontal map of eddy kinetic energy was prepared on a 2 2 grid between latitudes 20 and 55 n maximum eddy energy 3000 cm2 s 2 coincides with the high speed gulf stream jet where it begins large amplitude meanders near 37 n 67 w a tongue of high eddy energy coincides with the stream s path eastward and around the grand banks into the newfoundland basin where values of 1000 cm2 s 2 are found a weaker tongue extends eastward across the mid atlantic ridge near 45 n a second weak extension reaches southeastward from the stream and crosses the mid atlantic ridge between 30 and 35 n north and south of the stream eddy energy diminishes rapidly reaching an e folding at 300 km from the axis values of 200 cm2 s 2 were observed in the mid gyre region and 100 cm2 s 2 in the eastern north atlantic and north equatorial current although the gross distribution of eddy energy is similar to that determined from ship drift measurements there are significant differences eddy energy from drifters amounts to about twice the value measured by ship drift in the gulf stream and one half the ship drift values in the mid gyre it is suggested that these differences are due to the horizontal averaging of mesoscale motion and the errors in navigation both of which are problems with the ship drift technique

overlapping faults intrabasin highs and the growth of normal faults normal fault systems bounding extensional basins are typically adjoined by a series of subbasins separated by intrabasin highs the strata within these basins form syndepositional anticlines and synclines whose axes are transverse to the strike of the main bounding fault one possible explanation for these intrabasin highs is that they result from persistent along strike deficits in fault displacement such deficits are incompatible with scaling relationships observed between fault displacement and length based on large populations of faults we present data from active normal faults within the basin and range province and from inactive normal faults of the newark basin of eastern north america demonstrating a clear correlation between the along strike position of overlapping splay faults and the location of intrabasin highs as well as syndepositional transverse folds summed displacements for all faults within an intrabasin high are comparable to the displacements on faults bounding flanking subbasins o

morphotectonic analysis of the long term surface expression of the 2009 l aquila earthquake fault central italy using airborne lidar data abstract in this paper we present a morphotectonic study of the paganica san demetrio fault system psdfs responsible for the mw6 1 april 6 2009 earthquake l aquila central italy the discrepancy observed between the length of the seismologic geodetic modeled fault the limited size of the primary coseismic surface ruptures and the significant morphological expression of the psdfs stimulated a debate about the maximum rupture length of the psdfs and its capability to generate larger magnitude events to image the psdfs long term morphological expression and define its surface geometrical arrangement length number of fault splays and boundaries we took advantage of a high resolution airborne lidar dataset lidar topography substantially increased our confidence in detecting even subtle tectonic controlled morphologies we define the psdfs as a 19 km long fault system that displays a complex structural setting characterized by two different sectors 1 the paganica sector to the nw with a narrow deformation zone and 2 the san demetrio sector to se where the strain is accommodated by several fault splays dissecting a wider quaternary basin we also defined a first order hierarchy among the numerous fault splays across the psdfs the long term geomorphic expression of the psdfs suggests that it ruptured also involving the whole 19 km long structure besides rupturing only small sections as it occurred in 2009 this suggests a variable slip behavior empirical relations applied to this hypothesis allow up to m 6 6 earthquakes along the psdfs these results have a critical impact on the seismic hazard assessment of the area when compared with a m 6 1 event as the 2009

on the temporal variability of the surface gulf stream and near bottom flows long 3 4 years time series of the surface gulf stream position and near bottom flow south of nova scotia support earlier findings of a barotropic semimonthly periodicity in the region a bimodal gulf stream path downstream of the new england seamount chain and a seasonal shift in the gulf stream position new results are 1 a marked reduction of the meridional shifts of the surface gulf stream when it is in its north position mode 2 the semimonthly periodicity seeming to be related at times to the mf tide the most energetic long period tide and 3 an energetic highly coherent but out of phase motion with a near 40 day period in the surface gulf stream position and near bottom flow

displacement rates of normal faults previous estimates of displacement rates on individual faults have been limited to neotectonic faults and averaged over time intervals of about 200 kyr or less1 2 3 4 5 these estimates have been highly variable which has led to a belief that longer term displacement rates on individual faults are likely to be variable as well here we report estimates of long term normal fault displacement rates averaged over time intervals ranging from 1 to 40 myr and based on observed decreases in displacement of progressively younger horizons intersected by syn sedimentary faults we find that displacement rates are remarkably stable over these longer time periods and within a given fault system the rates are strongly dependent on the relative size of the fault as measured by cumulative vertical displacement taken together these results indicate that faults become large relative to nearby faults by having higher displacement rates even when small rather than as a consequence of having been active for longer our analyses also show that high regional strain rates tend to be accommodated by high fault displacement rates rather than high fault densities

five year climatological survey of the gulf stream system and its associated rings a 5 year climatological survey of the gulf stream system s landward surface edge defines the mean standard deviation extreme limits annual and interannual variabilities and frequency distributions along 0 5 longitudinal transects from 91 to 44 w the climatology covers the loop current in the gulf of mexico and the gulf stream in the northwest atlantic ocean autocorrelations and power spectra are derived for longitudinal transects between 79 5 and 57 5 w the study also investigates the observed warm core ring and cold core ring movements and their areal extent the observed data are compiled from the oceanographic analysis charts produced by the national oceanic and atmospheric administration which utilize infrared satellite imagery and in situ observations east of cape hatteras the gulf stream system landward surface edge exhibits both interannual and annual signals the interannual variability is equal to the annual variability the mean monthly gulf stream position for the longitudinal band 70 44 w shifts from farthest north in september to farthest south in february the magnitude of the annual shift is largest near the grand banks frequency distributions of the gulf stream system position are quasi normal nearly everywhere autocorrelation plots from the 5 year time series of gulf stream positions at longitudinal transects 79 5 57 5 w exhibit three well defined e folding time regimes with a maximum time of 10 weeks at 72 w power spectrums from 79 5 to 57 5 w are red spectrums having dominant peaks of 1 year period or greater the largest total spectra energies are found at 61 w the loop current sheds rings at two apparent spatial scales which are labeled major 307 km mean and minor 185 km mean warm core rings annually the loop current sheds about one major warm core ring which translates into the western basin of the gulf of mexico and one minor warm core ring which is usually reabsorbed by the loop current the major loop current warm core ring sheddings have no seasonal preference loop current warm core rings have a mean velocity of 2 4 km d west southwest an average of 22 gulf stream warm core rings are formed and absorbed annually between 75 and 44 w the largest frequency of warm core ring formations is seen near the new england seamounts while the largest frequency of warm core ring absorptions is found near cape hatteras gulf stream warm core rings can absorb each other as occurred in 14 of the absorption cases with the highest frequency just upstream of the new england seamounts the gulf stream warm core rings have a surface diameter decay rate of 0 026 per week loop current warm core rings are similar the gulf stream warm core rings have a mean velocity of 2 4 km d west southwest cold core rings have a mean cool core surface diameter of 105 km and a mean velocity of 1 km d southwest more definitive conclusions on cold core rings are not possible as ring identification and tracking by satellite infrared imagery is tentative

formation of segmented normal faults a 3 d perspective the interpretation of fault kinematics from geometric data is an essential step in developing an understanding of the growth of fault systems constraints on fault geometry are however often restricted to 2 d maps or cross sections in this article we consider the extent to which kinematic interpretations of faulting benefit from a 3 d rather than 2 d geometrical perspective concentrating on relay zones and segmented normal fault arrays we suggest that very different interpretations of their evolution arise from the recognition that the propagation directions of faults and fault segments will rarely be contained within the inspection plane of 2 d data a 3 d perspective favours an interpretation in which the segments of a fault array are kinematically interrelated from their initiation individual segments in such systems may link into a single fault surface out of the plane of inspection or may be unconnected in 3 d we argue that this interpretation which conflicts with the often suggested model of incidental overlap of originally isolated faults should be the preferred model for the generation and growth of segmented normal fault arrays

hydrocarbons in surface sediments from a guaymas basin hydrothermal vent site petroleum like materials found at the guaymas basin hydothermal vent site gulf of california are derived from pyrolysis of organic matter two characteristics surface sediment cores differing in temperature profiles and other parameters were collected by dsv alvin sectioned and analyzed for hydrocarbons the quantitative and qualitative composition of alkanes steranes diasteranes and triterpanes differed between these cores as well as within sections of the same core these differences apparent for scales of tens of centimeters are related to interactive physical chemical and microbial processes as well as the influence of multiple sources for the petroleum

tectonic controls on rift basin morphology evolution of the northern malawi nyasa rift radiometric k ar and ar 40 ar 39 age determinations of volcanic and volcaniclastic rocks combined with structural gravity and seismic reflection data are used to constrain the age of sedimentary strata contained within the seismically and volcanically active northern malawi nyasa rift and to characterize changes in basin and flank morphologies with time faulting and volcanism within the tukuyu karonga basin began at approximately 8 6 ma when sediments were deposited in abroad initially asymmetric lake basin bounded on its northeastern side by a border fault system with minor topographic relief extensions primarily by a slip along the border fault and subsequent regional isostatic compensation led to the development of a 5 km deep basin bounded by broad uplifted flanks along the low relief basin margin opposite border fault younger stratigraphic sequences commonly onlap older wedge shaped sequences although their internal geometry is often progradational intrabasinal faulting flankuplift and basaltic and felsic volcanism from centers at the northern end of the basin became more important at about 2 5 ma when cross rift transfer faults developed to link the tukuyu karonga basin to the rukwa basin local uplift and volcanic construction at the northern end of the basin led to a southeastward shift in the basin s depocenter sequence boundaries are commonly erosional along this low relief hanging wall margin and conformable in the deep lake basin the geometry of stratigraphic sequences and the distribution of the erosion indicate that horizontal and vertical crustal movements both across and along the length of the rift basin led to changes in levels of the lake irrespective of paleoclimatic fluctuations