sediment dispersal and quantitative stratigraphic architecture across an ancient shelf two large 200 to 300 km near continuous outcrop transects and extensive well log data ca 2800 wells allow analysis of sedimentological characteristics and stratigraphic architecture across a large area ca 60 000 km2 of the latest santonian to middle campanian shelf along the western margin of the western interior seaway in eastern utah and western colorado usa genetically linked depositional systems are mapped at high chronostratigraphic resolution ca 0 1 to 0 5 ma within their sequence stratigraphic context in the lower part of the studied interval sediment was dispersed via wave dominated deltaic systems with a compound clinoform geomorphology in which an inner wave dominated shoreface clinoform was separated by a muddy subaqueous topset from an outer clinoform containing sand poor gravity flow deposits these strata are characterized by relatively steep net regressive shoreline trajectories 0 1 with concave landward geometries narrow nearshore belts of storm reworked sandstones 2 to 22 km wide offshore mudstone belts 250 km and relatively high sediment accumulation rates ca 0 27 mm year 1 the middle and upper parts of the studied interval also contain wave dominated shorefaces but coeval offshore mudstones enclose abundant isolated tide influenced sandstones that were transported sub parallel to the regional palaeoshoreline by basinal hydrodynamic tidal circulation these strata are characterized by relatively shallow net regressive shoreline trajectories 190 km and relatively low sediment accumulation rates ca 0 11 mm year 1 the change in shelfal sediment dispersal and stratigraphic architecture from i compound clinoform deltas characterized by across shelf sediment transport to ii wave dominated shorelines with isolated tide influenced sandbodies characterized by along shelf sediment transport is interpreted as reflecting increased interaction with the hydrodynamic regime in the seaway as successive shelfal depositional systems advanced out of a sheltered embayment utah bight this advance was driven by a decreasing tectonic subsidence rate which also suppressed autogenic controls on stratigraphic architecture

estimation of kerogen porosity in source rocks as a function of thermal transformation example from the mowry shale in the powder river basin of wyoming evaluations of porosity relevant to hydrocarbon storage capacity in kerogen rich mudrocks i e source rocks have thus far been plagued with ambiguity in large part because conventional core and petrophysical techniques were not designed for this rock type the growing recognition of an intraparticle organic nanopore system that is related to thermal maturity is beginning to clarify this ambiguity this mode of porosity likely evolved with the thermal transformation of labile kerogen and probably neither depends nor interacts except perhaps chemically with previously assumed matrix or mineral porosity that is dominated by bound water and that may be largely irrelevant to hydrocarbon storage capacity in these rocks to address this newly recognized and important nonmatrix kerogen pore system that is arguably the dominant hydrocarbon storage and mobility network in these rocks we introduce a relatively simple kinetic model that describes porosity development within kerogen as a function of thermal maturation kerogen porosity development is estimated within the upper albian mowry shale in the powder river basin of wyoming to illustrate the approach relevant storage capacity is considered to have evolved with thermal decomposition of organic matter during catagenesis where we estimate that kerogen porosity does not typically exceed 3 of bulk rock volume modeled oil in place estimates are comparable to residual oil estimates from pyrolysis data s1 at lower maturities but exceed pyrolytic s1 yields at higher maturities we hypothesize therefore that a subsurface kinetic porosity model might represent a means to account for s1 losses at surface conditions and to circumvent difficulties surrounding estimations of expulsion efficiencies that are inherent to more traditional mass balance calculations

magmatic epidote and its petrologic significance epidote is a major magmatic mineral in tonalite and granodiorite in a belt coextensive with the mesozoic accreted terranes between northern california and southeastern alaska textural and chemical evidence indicates that epidote crystallized as a relatively late but magmatic mineral that formed through reaction with hornblende in the presence of a melt phase the observed relations concur with experimental data on crystallization of epidote from synthetic granodiorite at 8 kbar total pressure plutonic rocks bearing magmatic epidote must have formed under moderately high pressures corresponding to lower crustal depths under fairly oxidizing conditions

subaqueous delta of the ganges brahmaputra river system abstract the ganges brahmaputra is among the world s three largest river systems in terms of sediment load but until now no high resolution seismic data have been obtained to document the nature of the sediment deposit seaward of the rivers mouths the other two amazon huanghe discharge into energetic coastal environments and form subaqueous deltas with characteristic clinoform stratigraphy high resolution seismic reflection profiles of the bengal shelf reveal similar stratigraphy topset beds dip gently 0 036 and diverge offshore more steeply dipping foreset beds 0 190 converge farther seaward and relatively thin gently dipping bottomset beds 0 022 extend across the outer shelf overlying an erosional surface presumed to be of late pleistocene age sediment accumulation rates are highest in the foreset region 5 cm year and reduced in the bottomset region

structural geometry and kinematic evolution of the eastern cascades foldbelt washington and british columbia the eastern cascades foldbelt is one of three structural domains lying within the complex collision zone between the insular and intermontane composite terranes in northern washington and southern british columbia the foldbelt resides between the high grade metamorphic backbone of the cascade orogen on the west and rocks of the composite intermontane terrane to the east it encompasses the stratigraphically coherent basalt floored jura cretaceous methow basin as well as more chaotically disposed permian jurassic oceanic rocks of the hozameen terrane methow basin rocks are thought to have been sutured above the oceanic rocks prior to the middle cretaceous contractional episode described in this report based on the analysis presented herein between ca 100 and 88 ma the rocks in the foldbelt underwent shortening in an east northeast west southwest direction by 50 km or more largely by displacement on the east vergent jack mountain chuwanten thrust system the early stages of contraction occurred by

seismic anisotropy of the pacific ocean inferred from long period surface waves dispersion abstract the dispersion of surface rayleigh and love waves in the period range 40 300 s along a large number of paths allows the estimation of both the azimuthal anisotropy and the shear wave polarization anisotropy the regional dispersion is determined taking into account simultaneously its dependence with age and an azimuthal factor the pacific ocean has been divided into 5 regions for rayleigh waves and into 3 regions for love waves this partition discriminates the regions of extreme age which show a fast variation of dispersion with age from the regions of intermediate age where the variation is weak a variation of 2 of rayleigh wave group velocity with the azimuth of the path measured with respect to the direction of spreading is displayed up to very long period on the contrary the azimuthal anisotropy for love waves is difficult to resolve for rayleigh waves the present day direction of plate motion seems to agree best with the direction of maximum velocity on the other hand the isotropic inversion of the regional dispersion curves indicates except for young regions a discrepancy between rayleigh wave and love wave models with this hypothesis sh velocities are higher than sv velocities for the regions older than 23 ma down to a depth of 300 km which is indicative of the presence of polarization anisotropy the latter very weak for the young part of the ocean increases with age and reaches 7 for the oldest region

global anisotropy in the upper mantle inferred from the regionalization of phase velocities a data set of 2600 paths for rayleigh waves and 2170 paths for love waves was selected in order to resolve azimuthal anisotropy of surface waves in the period range 70 250 s the epicenters were chosen so that the paths provide uniform spatial and azimuthal coverage of earth a synthetic seismogram is computed for each path and compared to the observed seismogram in order to infer the phase velocity along each path to process such a large data set a new tomographic technique is designed a good correlation is found with surface tectonics in the whole period range for love waves and at shorter periods for rayleigh waves the directions of maximum velocities are also well correlated with plate tectonics motions for the 2 azimuthal term of rayleigh waves when the power spectrum of heterogeneities is computed it is found that for love waves the even orders are usually larger than the odd orders for rayleigh waves the degrees 2 and 6 dominate only at long periods suggesting a deep origin for these components

lateral heterogeneity and azimuthal anisotropy of the upper mantle love and rayleigh waves 100 250 s the lateral heterogeneity and apparent anisotropy of the upper mantle are studied by measuring rayleigh and love wave phase velocities in the period range 100 250 s spherical harmonic descriptions of the lateral heterogeneity are obtained for order and degree up to 1 m 10 slow regions are evident at the east pacific rise northeast africa tibet tasman sea southwestern north america and triple junctions in the northern atlantic and indian oceans fast regions occur in australia western pacific and the southern atlantic these features are also found by a completely different analysis based on the backus gilbert method the backus gilbert method also shows that the obtained phase velocities are averaged values within an area of about 2000 km radius and the errors are about 1 of the phase velocity in the zeroth order spherically symmetric earth inversion for azimuthal dependence shows that for low angular order the fast phase velocity directions seem to correlate well with the plate motion vectors however resolution analysis by the backus gilbert method shows that the current data do not have enough resolution for everywhere on the globe only a few regions currently have adequate azimuthal coverage thus confirmation of the above correlation requires a more complete data set

the late holocene gargano subaqueous delta adriatic shelf sediment pathways and supply fluctuations the gargano subaqueous delta formed on the eastern and southeastern sides of the gargano promontory in the western adriatic this subaqueous deposit represents the southernmost portion of the late holocene highstand systems tract hst growing along the western side of the adriatic as an extensive wedge of deltaic and shallow marine mud the late holocene hst rests above a regional downlap surface that marks the time of maximum landward shift of the shoreline attained around 5 5 cal kyr bp at the end of the late pleistocene holocene sea level rise high resolution seismic stratigraphic and tephra correlation indicate the presence of a thin basal unit recording condensed deposition between 5 5 and 3 7 cal kyr bp over much of the basin above this unit sediment accumulation rates increased to high values as much as 1 5 cm yr 1 reflecting the stabilisation of relative sea level and the forcing from high frequency climatic or anthropogenic changes affecting river dynamics the late holocene mud wedge of which the gargano subaqueous delta is a significant component reaches up to 35 m in thickness and has a volume of ca 180 km3 the shore parallel thickness distribution of the mud wedge reflects the dominant oceanographic regime of the basin and the asymmetric location of the mostly western sediment sources with a combined modern delivery of 51 7 106 t yr 1 of mean suspended load in sections perpendicular to the coast the late holocene mud wedge appears composed of forestepping clinoforms with gently dipping foresets typically 0 5 the gargano subaqueous delta is characterised by a submarine topset in water depths shallower than 25 28 m and accounts for about 1 7th of the total volume of the late holocene mud wedge despite the absence of direct river supply to the gargano area in the area of maximum interaction between shore parallel currents and basin morphology progradation occurs onto a flat and barren bedrock outcrop in about 50 80 m water depth the rapid transition from a thickness of 30 m of late holocene mud to nil is a good indication of the role of southward flowing bottom hugging shelf currents in causing the redistribution of sediment along the adriatic inner shelf additional evidence of this regime comes from 1 the most recent sigmoid defined at seismic stratigraphic scale deposited since the onset of the little ice age showing a shore parallel thickness distribution and a main depocentre to the southeast of the gargano promontory 2 the maximum values of sediment accumulation rates over the last century documented by 210pb measurements defining a narrow shore parallel belt immediately seaward of the depocentre of the most recent sigmoid the gargano subaqueous delta grows from the outbuilding of progressively younger progradational sigmoids that tend to parallel the previous ones the gargano subaqueous delta differs from other documented late holocene subaqueous deltas because its growth reflects 1 sediment transport dominated by bottom currents sub parallel to the strike of the composing clinoforms 2 a complex supply regime including the po delta 350 km to the north and several coalescing apennine rivers acting as line source 3 several alternating intervals of enhanced outbuilding and condensed deposition and 4 an in phase growth of the most recent sigmoid with the major progradation of the po delta during the little ice age

mud deposition and diagenesis within an early palaeozoic clinothem power steps formation newfoundland canada the early ordovician 385 ma power steps formation newfoundland canada exposes a well preserved mudstone dominated clinothem that serves as an excellent archive for understanding how mud has been produced transported and converted into mudstone prior to the evolution of globally widespread deep soil horizons sedimentological analysis of four sandstone and five mudstone facies along the ochre cove clinothem reveal that mud and sand were delivered by unidirectional currents and experienced episodic reworking by storm waves petrographic examination and x ray diffraction from described mudstone facies reveal significant variability in the distribution of illite versus chlorite between the lower and upper part of the ochre cove clinothem this research highlights that in the present day clay mineral fraction illite is often detrital whereas chlorite originated via the alteration of silt sized highly unstable mafic volcanoclastic grains throughout all sedimentologic facies albeit in different proportions these mafic lithic grains were diagenetically altered via in situ weathering before significant compaction occurred resulting in the precipitation of significant volumes of pore bridging silica and iron rich chlorite cement compositional diagenetic and textural attributes across the ochre cove mud clinothem vary as a function of starting composition hydrodynamic sorting and grain density given that a significant proportion of clay minerals has been generated via in situ transformation of a mafic non stable precursor assemblage we recommend future studies to incorporate detailed petrographic description along with x ray diffraction analyses when aiming to employ trends in whole rock clay mineral data as a proxy in provenance and palaeoclimate studies of very old pre devonian mudstones and sandstones

depositional and stratigraphic architecture of the santonian emery sandstone of the mancos shale implications for late cretaceous evolution of the western interior foreland basin of central utah u s a abstract the santonian emery sandstone member of the mancos shale is a continental to shallow marine succession that prograded into the cretaceous western interior seaway of western north america sediment sourced from the uplifted sevier orogen to the west fed a shoreline in the adjacent subsiding north south trending foredeep these sandstones are now superbly exposed along a 120 km long strike parallel continuous outcrop in the cliffs of the wasatch plateau of central utah shoreface parasequences are composed of coarsening upward successions of hummocky cross stratified and intensely bioturbated sandstones indicating deposition at a storm dominated shoreline two distinct depositional complexes record eastward and northeastward shoreline progradation at the northern and southernmost extremities of the plateau respectively in the subsurface emery strata comprise a thick succession of coal bearing coastal plain deposits the emery sandstone records a period of long term paralic progradation to aggradation containing at least 17 parasequences arranged into three 600 kyr regressive transgressive cycles that are recognizable in both complexes each cycle comprises only highstand and transgressive systems tracts and erosional sequence boundaries are absent absence of erosional sequence boundaries is attributed to high rates of subsidence in the foreland basin at this time santonian glacio eustatic sea level fluctuations are proposed to account for the high frequency cyclicity whilst longer term aggradation may be a function of organic controls on shoreface stacking patterns by immobile raised coal mires lying landward of the shorefaces when placed in a temporal and spatial context the emery sandstone provides a missing link in the understanding of long term controls on late cretaceous depositional systems in the central utah segment of the foreland basin and allows inferences to be made regarding foreland basin dynamics in particular thrust tectonics is postulated to have played a major role in governing the architecture of late cretaceous strata in central utah marked along strike thickening of the emery sandstone in particular is attributed to long lived elevated rates of subsidence in northern utah and southern wyoming during the late cretaceous that is adjacent to concentrated zones of thrust nappes a north dipping depositional slope is inferred from this subsidence distribution aligned approximately parallel to the structural grain of the hinterland load northeastward progradational directions of successive turonian santonian and early campanian regressive wedges in this part of the western interior basin are attributed to the presence of this tectonically induced regional slope gradient sediment sourced to these late cretaceous shorefaces is likely to have been sourced through structural recesses within the thrust front resulting in a spatial alignment of several successive regressive wedges and implicates an important long lived kinematic control on sediment supply of late cretaceous regressive wedges only the emery sandstone does not temporally coincide with reported periods of active thrusting suggesting that the regression was a consequence of factors other than uplift related elevated rates of sediment supply

late cretaceous paleocene synorogenic sedimentation and kinematic history of the sevier thrust belt northeast utah and southwest wyoming integration of cross cutting structural relationships overlapping sedimentary units new conglomerate provenance data and radiometric and palynological dates provides a basis for reinterpretation of the distribution and timing of late cretaceous through paleocene thrust faulting in the northeast utah southwest wyoming part of the sevier thrust belt these data indicate a general eastward progression of deformation that was punctuated by local out of sequence and hinterlandward verging events provenance data delimit a sequential restoration of a regional cross section the principal thrust systems in northeast utah and southwest wyoming are the willard ogden crawford absaroka and hogsback thrusts the willard is the westernmost structurally highest and oldest of the thrusts it carries a unique section of thick proterozoic sedimentary rocks as well as paleozoic rocks and was folded during displacement on younger thrust systems the next youngest thrust system is the ogden which comprises several basement rooted imbricate thrusts that together form a large antiformal stack with a structural culmination in the wasatch range growth of the wasatch culmination took place during coniacian through paleocene time contemporaneous with sequential displacement on the frontal crawford absaroka and hogsback thrusts total shortening in this part of the thrust belt was 100 km and structural relief of 25 km developed in the area of the wasatch culmination during coniacian through paleocene time thrusting followed an overall eastward progression that was interrupted by local out of sequence and hinterlandward verging events several episodes of synchronous displacement on two or more thrusts can be demonstrated shortening occurred in three main episodes the first episode 89 84 ma involved 33 km of shortening on the crawford thrust and its footwall imbricates approximately 19 km of structural relief on the basement cover contact developed in the area of the wasatch culmination the second episode 84 62 ma with a break between 75 69 ma involved 30 km of shortening mainly on the absaroka thrust and development of an additional 6 km of structural relief in the culmination the third episode of shortening 56 50 ma took place on the hogsback thrust involved 21 km of horizontal shortening and produced no significant increase in structural relief in the culmination long term rates of shortening ranged between 3 0 mm yr and 6 6 mm yr these three episodes of shortening produced three large accumulations of synorogenic conglomerate totaling 3 km in thickness the henefer formation and echo canyon and weber canyon conglomerates were deposited during crawford thrusting the evanston formation was deposited during and after absaroka thrusting and the lower conglomeratic part of the wasatch formation was deposited during and after hogsback thrusting most of the sediment in these synorogenic units however was derived from repeated uplift of the willard thrust sheet and from the eastern flank of the wasatch culmination in the rear part of the thrust belt only local minor accumulations were derived from the frontal ramp anticlines sediment accumulation and structural deformation were generally out of phase periods of regional shortening and uplift were marked by development of unconformities and sediment bypassing to distal parts of the foreland basin periods of structural inactivity were marked by accumulation of aerially widespread braided river conglomerate on top of the thrust belt one exception to this pattern is the henefer echo canyon weber canyon conglomerate deposit which contains evidence of progressive deformation in close proximity to the tip of the crawford thrust comparison of the sequential restoration with the late cretaceous subsidence history and isopach patterns in the distal foreland basin of western wyoming demonstrates that the principal controls on regional subsidence and sediment supply were the growth and erosion of the wasatch culmination growth of the duplex beneath the culmination may have been a means of maintaining critical taper in the thrust wedge

application of sequence stratigraphic concepts to the upper cretaceous tununk shale member of the mancos shale formation south central utah parasequence styles in shelfal mudstone strata

seismic structure of the upper mantle beneath the western philippine sea abstract we investigate the seismic structure of the western philippine sea using two sets of seismological observations scs reverberations which provide the layering framework for a regional upper mantle model and observations of frequency dependent phase delays for direct s waves surface reflected phases ss ss sss and surface waves r1 g1 which constrain the velocity and anisotropy structure within the layers the combined data set comprising 17 discontinuity amplitudes and layer travel times from the scs reverberation stack and more than 1000 frequency dependent phase delays was inverted for a path averaged radially anisotropic model mineralogical estimates of the bulk sound velocity and density are incorporated as complementary constraints the final model phb3 is characterized by a 11 5 km thick crust an anisotropic lid bounded by a sharp negative g discontinuity at 89 km an anisotropic low velocity layer extending to 166 km a subjacent high gradient region and transition zone discontinuities at depths of 408 km 520 km and 664 km the lid is slower than in a comparable model for the tonga hawaii corridor pa5 but also significantly thicker requiring a compositional variation between the two regions we explore the hypothesis that the thickness of the oceanic lid is controlled by the melting depth at the spreading centers during crust formation and that the thicker crust and lid in the philippine sea results from deeper melting owing to a higher potential temperature and perhaps a higher water content in the upper mantle

flux and fate of yangtze river sediment delivered to the east china sea numerous cores and dating show the yangtze river has accumulated about 1 16 x 10 12 t sediment in its delta plain and proximal subaqueous delta during holocene high resolution seismic profiling and coring in the southern east china sea during 2003 and 2004 cruises has revealed an elongated similar to 800 km distal subaqueous mud wedge extending from the yangtze river mouth southward off the zhejiang and fujian coasts into the taiwan strait overlying what appears to be a transgressive sand layer this distal clinoform thins offshore from similar to 40 in thickness between the 20 and 30 m water depth to 1 2 in between 60 and 90 m water depth corresponding to an across shelf distance of less than 100 km total volume of this distal mud wedge is about 4 5 x 10 11 m 3 equivalent to similar to 5 4 x 10 11 t of sediment most of the sediment in this mud wedge comes from the yangtze river with some input presumably coming from local smaller rivers thus the total yangtze derived sediments accumulated in its deltaic system and east china sea inner shelf have amounted to about 1 7 x 10 12 t preliminary analyses suggest this longshore and across shelf transported clinoform mainly formed in the past 7000 yrs after postglacial sea level reached its mid holocene highstand and after re intensification of the chinese longshore current system sedimentation accumulation apparently increased around 2000 yrs bp reflecting the evolution of the yangtze estuary and increased land erosion due to human activities such as fanning and deforestation the southward flowing china coastal current the northward flowing taiwan warm current and the kuroshio current appear to have played critical roles in transporting and trapping most of yangtze derived materials in the inner shelf and hence preventing the sediment escape into the deep ocean c 2006 elsevier b v all rights reserved

traces in the dark sedimentary processes and facies gradients in the upper shale member of the upper devonian lower mississippian bakken formation williston basin north dakota u s a abstract black organic rich rocks of the upper shale member of the upper devonian lower mississippian bakken formation a world class petroleum source rock in the williston basin of the united states and canada contain a diverse suite of mudstone lithofacies that were deposited in distinct facies belts the succession consists of three discrete facies associations fas these comprise 1 siliceous mudstones 2 quartz and carbonate bearing laminated mudstones and 3 macrofossil debris bearing massive mudstones these fas were deposited in three facies belts that reflect proximal to distal relationships in this mudstone system the macrofossil debris bearing massive mudstones fa 3 occur in the proximal facies belt and contain erosion surfaces some with overlying conodont and phosphate lithoclast lag deposits mudstones with abundant millimeter scale siltstone laminae showing irregular lateral thickness changes and shell debris in the medial facies belt quartz and carbonate bearing laminated mudstones dominate exhibiting sub millimeter thick siltstone layers with variable lateral thicknesses and localized mudstone ripples in the distal siliceous mudstone facies belt radiolarites radiolarian bearing mudstones and quartz and carbonate bearing laminated mudstones dominate overall total organic carbon toc contents range between about 3 and 10 wt with a general proximal to distal decrease in toc content abundant evidence of bioturbation exists in all fas and the lithological and toc variations are paralleled by changes in burrowing style and trace fossil abundance while two horizontal traces and two types of fecal strings are recognized in the proximal facies belt only a single horizontal trace fossil and one type of fecal string characterize mudstones in the distal facies belt radiolarites intercalated into the most distal mudstones are devoid of traces and fecal strings bedload transport processes likely caused by storm induced turbidity currents were active across all facies belts suspended sediment settling from near the ocean surface however most likely played a role in the deposition of some of the mudstones and was probably responsible for deposition of the radiolarites the distribution pattern of high toc sediments in proximal and lower toc deposits in some distal facies is interpreted as a function of higher accumulation rates during radiolarian depositional events leading to a decrease in suspension derived organic carbon in radiolarite laminae the presence of burrows in all fas and nearly all facies in the upper bakken shale member indicates that dysoxic conditions prevailed during its deposition this study shows that in intracratonic high toc mudstone successions such as the upper bakken shale member bed load processes most likely dominated sedimentation and conditions promoted a thriving infaunal benthic community as such deposition of the upper bakken shale member through dynamic processes in an overall dysoxic environment represents an alternative to conventional anoxic depositional models for world class source rocks

bioturbation sedimentation rates and preservation of flood events in deltas abstract we examine the nature and number of event beds preserved in heterolithic prodelta and delta front strata in five proximal accumulation dominated pad north american delta systems including the quaternary gulf of mexico and the late cretaceous western interior seaway we also explore the continuum between pad more distal deposits of mud belts and thicker subaqueous delta clinoforms sdc sediment accumulation rates in modern pad and sdc systems are commonly on the order of several to severaltens of centimeters per year they also show that several event beds may be created annually with preservation depending on supply and reworking the pad heterolithics commonly comprise interbedded sand silt and clay these show normal and inverse grading and bouma sequences indicating deposition from turbidity currents and hyperpycnal flows that are interpreted as the products of river plumes generated during flood episodes re equilibrated rosselia socialis in stacked delta front turbidite bedsets in the cretaceous examples show that floods may occur as a cluster of events over several months shelf areas adjacent to river mouths may experience high rates of sediment delivery from rivers but oceanographic processes are instrumental in moving much of the silt and clay farther along the shelf direct hyperpycnal delivery from a river mouth on a low gradient shelf i e typically

the offshore bar revisited a new depositional model for isolated shallow marine sandstones in the cretaceous frontier formation of the northern uinta basin utah u s a abstract shallow marine sandstone bodies isolated within marine mudrock successions are still incompletely understood a robust understanding of such bodies is of interest not only scientifically but also in order to facilitate successful exploration for and production of petroleum and other natural resources such bodies are preserved in the turonian frontier formation of the northern uinta basin in utah and colorado u s a where they have been previously interpreted as the products of offshore bars a reappraisal of these bodies in the uppermost frontier formation herein defined as the turonian ashley valley member reveals three northeast southwest elongate incised highstand forced regressive and lowstand offshore sandstone bodies partially to fully encased in offshore marine mudrock these bodies are herein named the buckskin hills kane hollow and raven ridge sandstones from oldest to youngest five lithofacies were identified from 47 measured outcrop sections located along the western and southern margins of dinosaur national monument they are 1 marine shelf claystones and siltstones 2 lower upper offshore marine admixed siltstone and sandstone 3 lower upper offshore thin bedded sandstones and siltstones 4 distal lower shoreface heavily bioturbated very fine grained sandstone and 5 transgressive lag conglomerate wireline logs from 112 drillhole locations throughout the uinta basin were calibrated with nearby outcrop locations to construct cross sections and net sandstone isochore maps from these regionally traceable horizons flooding surfaces and internal erosion surfaces facilitated an analysis of stacking patterns development of a stratigraphic framework and a depositional environment interpretation overall the ashley valley member preserves a basinward offlapping stacking pattern indicative of shoreline progradation in response to the late turonian greenhorn global eustatic regression that was interrupted by two high frequency transgression regression cycles this nested cyclicity cannot be explained by global eustasy alone and instead is suggestive of a secondary allogenic control likely related to western cordilleran foreland basin wcfb geodynamic driving mechanisms as a result the ashley valley member provides an example of tectonic forcing on stratal stacking patterns highlighting the importance of intrabasinal tectonic processes on dispersal patterns and high frequency relative base level fluctuations within the wcfb stratigraphic record

location of love to rayleigh conversion due to lateral heterogeneity or azimuthal anisotropy in the upper mantle love waves can be converted to rayleigh waves which are sometimes called quasi love waves in laterally heterogeneous or azimuthally anisotropic mantle a local four station network of broadband seismometers in hokkaido japan records the quasi love waves from the earthquakes located in and around oregon and california usa we infer that these quasi love waves are generated by lateral heterogeneity or azimuthal anisotropy beneath the aleutian or kuril trench we attempt to locate the love to rayleigh conversion areas for the august 17 1991 off coast of northern california earthquake by using the group velocities of the observed surface waves the locations of the love to rayleigh conversion areas concentrate near the kuril trench the concentration is the most clear at a low frequency of 8 mhz this successful location of the conversion areas provides us with an important constraint on the generation of the quasi love waves

parasequences allostratigraphic misfits in sequence stratigraphy abstract parasequences were introduced as the building blocks of seismic scale systems tracts in the context of low resolution seismic stratigraphy pitfalls of this concept relate to the definition of parasequence boundaries as lithological discontinuities that mark episodes of abrupt water deepening with this general meaning flooding surfaces may be facies contacts within transgressive deposits or may coincide with different types of sequence stratigraphic surfaces maximum regressive transgressive ravinement or maximum flooding in all cases flooding surfaces are allostratigraphic contacts restricted to coastal and shallow water settings where evidence of abrupt water deepening can be demonstrated flooding surfaces may also be absent from the shallow water systems where conformable successions accumulate during gradual water deepening it follows that 1 parasequences have smaller extent than systems tracts and 2 systems tracts do not always consist of stacked parasequences these limitations prevent the dependable use of the parasequence concept in sequence stratigraphy advances in high resolution sequence stratigraphy show that the scales of sequences and parasequences are not mutually exclusive the two types of units define different approaches to the delineation of stratigraphic cycles at high resolution scales sequences that develop at parasequence scales provide a more reliable alternative for correlation both within and outside of the coastal and shallow water settings rendering parasequences obsolete every transgression that affords the formation of a flooding surface starts from a maximum regressive surface and ends with a maximum flooding surface observed at the scale of that transgression these systems tract boundaries are invariably more extensive than any facies contacts that may form during the transgression flooding surfaces remain relevant to the description of facies relationships but their stratigraphic meaning needs to be assessed on a case by case basis the use of sequences and systems tracts in high resolution studies provides consistency in methodology and nomenclature at all stratigraphic scales irrespective of geological setting and the types and resolution of the data available

evidence from neodymium isotopes for mantle contributions to phanerozoic crustal genesis in the canadian cordillera sm nd and rb sr isotopic studies of several phanerozoic orogenic belts have shown that much of the crust in these belts is composed of reworked pre existing continental crust in contrast isotopic data collected from two of the largest terranes in the canadian cordilleran orogenic belt the alexander and stikine terranes show that these tectonic fragments are composed of mantle derived continental crust in many respects the style and rate of crustal accretion of these and related terranes appear similar to those of some proterozoic crustal regions

hydrodynamic controls on muddy sedimentary fabric development on the southwest louisiana subaqueous delta abstract this study examines the sedimentary products of current wave enhanced sediment gravity flows cwesgfs on the muddy southwest louisiana swla subaqueous delta where the combined effects of gravity currents and wave orbital velocity exert a strong control on sedimentary fabric development and contribute to development of a muddy inner shelf clinothem cwesgf microstratigraphy from the swla subaqueous delta displays an overall structure similar that is similar to the tripartite layering of wesgfs previously documented on the eel shelf where wave enhanced sediment gravity flow deposits were first described basal crossbeds intermediate planar interlaminations of clay and silt topmost clay rich drape however on the swla subaqueous delta a shorter wave period appears to impart more rapid alternations in turbulent and laminar conditions than for the eel shelf reducing the prominence of the intermediate planar laminations that are thought to develop during laminar flow conditions only a novel framework for relating the sedimentary products of cwesgfs to interacting unidirectional wave driven and gravity driven flow is used to place our results in a global context with respect to other modern examples this is an important contribution as it may provide insights into paleo depositional conditions represented by sedimentary structures in ancient strata and provide the basis for developing additional recognition criteria for cwesgfs an important and diverse class of sediment gravity flows

mud re distribution in epicontinental basins exploring likely processes abstract fine grained clastic sediments are very common in the interior deposits of ancient epicontinental seas not only do they make up the gross lithology in these basins but they can also be traced for more than 1000 km offshore from basin margins given that epicontinental seas were overall shallow and in many parts most likely less than 100 m deep basin floor slopes can safely be expected to be in the 0 01 to 0 001 range for much of depositional history known processes that bring muds to the basin margin and beyond are hypopycnal river plumes hyperpycnal fluvial discharge events storm setup relaxation flows and gravity driven fluidized muds with the exception of river plumes all of these processes require the presence of sufficient slope for sustained movement due to that constraint these processes combined might in the majority of situations have been able to move muddy sediments on the order of 100 km offshore whereas this is sufficient to distribute mud across marginal shelf seas it becomes problematic in the case of much larger epicontinental seas for example those of upper devonian or upper cretaceous times extended in places for thousands of kilometers and thus a process is needed that can move muddy sediments the rest of the way flume studies of the bedload transport of mud combined with observations from the rock record suggest that wind or tide induced bottom current circulation was most likely essential for moving muddy sediments from the periphery of epicontiental seas to their interiors remobilization of seafloor muds during frequently recurring lowering of sea level is likely to have aided in this process

detailed facies analysis of the upper cretaceous tununk shale member henry mountains region utah implications for mudstone depositional models in epicontinental seas abstract lower middle turonian strata of the tununk shale member of the greater mancos shale were deposited along the western margin of the cretaceous western interior seaway during the greenhorn second order sea level cycle in order to examine depositional controls on facies development in this mudstone rich succession this study delineates temporal and spatial relationships in a process sedimentologic based approach the 3 dimensional expression of mudstone facies associations and their stratal architecture is assessed through a fully integrative physical and biologic characterization as exposed in outcrops in south central utah sedimentologic characteristics from the millimeter to kilometer scale are documented in order to fully address the complex nature of sediment transport mechanisms observed in this shelf muddy environment the resulting facies model developed from this characterization consists of a stack of four lithofacies packages including 1 carbonate bearing silty and sandy mudstone cssm 2 silt bearing calcareous mudstone scm 3 carbonate bearing silty mudstone to muddy siltstone cms and 4 non calcareous silty and sandy mudstone ssm spatial and temporal variations in lithofacies type and sedimentary facies characteristics indicate that the depositional environments of the tununk shale shifted in response to the 2nd order greenhorn transgressive regressive sea level cycle during this eustatic event the tununk shows a characteristic vertical shift from distal middle shelf to outer shelf cssm to scm facies then from outer shelf to inner shelf environment scm to cms and to ssm facies shifting depositional environments as well as changes in dominant paleocurrent direction throughout this succession indicate multiple source areas and transport mechanisms i e longshore currents offshore directed underflows storm reworking this study provides a rare documentation of the greenhorn cycle as exposed across the entire shelf setting high resolution mapping of genetically related packages facilitate the development of process based depositional models that can be utilized for lateral correlations into the equivalent foredeep strata of the cretaceous interior

foreland basin structural growth recorded in the turonian ferron sandstone of the western interior seaway basin usa tectonic forcing of stratigraphic architecture is likely in foreland basins tectonic driving forces are increasingly being invoked to explain stratigraphic patterns in the cretaceous western interior seaway basin of north america yet the evidence is largely circumstantial and the details of driving forces remain elusive in this paper i show direct stratigraphic evidence for syndepositional growth of a structural arch with at least 50 m of relief during accumulation of the upper turonian ferron sandstone in south central utah united states progressive growth of the arch was superimposed on several high frequency stratal cycles that were driven by a more regionally extensive process geodynamic or eustatic and that produced laterally amalgamated sandstone bodies in a depositional strike parallel orientation north south all of this stratigraphy was then truncated by a more or less planar erosion surface sequence boundary that can be traced physically over at least 67 km north south this surface was later tilted northward such that the upper member of the ferron sandstone thins progressively southward from 50 to 10 m over 67 km the facies juxtapositions revealed by the ferron sandstone could if seen in exposure of limited lateral extent be wrongly interpreted as recording regionally extensive relative sea level drops and potentially used in error as evidence for substantial eustatic sea level falls during the turonian the folding and tilting documented in this study can be clearly attributed to geodynamic and or tectonic driving forces likely related to migration of a forebulge

structural geology and accretionary history of the northwest cascades system washington and british columbia pre tertiary rock units on the western flank of the cascades in washington and southern british columbia constitute the northwest cascades system nwcs this litho tectonic package is characterized by predominantly oceanic lithologies subjected to high p t metamorphism and structurally mixed to form a regional melange although the focus of this report is on rocks of the nwcs as originally defined survey of the regional geology suggests broadening of the limits of this system to include the san juan islands the pacific rim complex and pre tertiary rocks on the western flank of the central and southern washington cascades the shuksan metamorphic suite a relatively coherent and broadly exposed unit of the nwcs contains a regionally consistent stretching lineation which provides evidence of east northeast directed underthrusting subduction during the early cretaceous blue schist metamorphism metamorphic f2 folds are approximately normal to the stretching lineation and appear to have developed late in the same deformational event the melange structure postdates the high pressure regional metamorphism it is characterized by a tectonic assemblage of diverse and unrelated rock units occurring as fragments as much as 10 or more kilometres in breadth and separated by a network of low to high angle north northwest striking faults pre fault restoration is impossible argillaceous or serpentinitic material commonly occurs in deformation zones between more competent lithologies mylonite zones as much as several metres thick are widely developed and display stretched clast lineations indicating a north northwest south southeast transport direction for both low and high angle faults the high angle faults are therefore strike slip in nature shear sense indicators are mixed in thrust fault zones but many indicate dextral movement for the strike slip faults k ar whole rock ages of mylonites range from 20 127 ma but two late cretaceous ages of 87 and 91 3 ma are considered as best representing the time of faulting the inferred shift in direction of tectonic transport from east northeast west southwest during early cretaceous metamorphism to north northwest south southeast during late cretaceous faulting and melange formation is correlated with a mid cretaceous change in plate interaction between the north american and farallon kula plates from high to low angle convergence the nwcs melange is interpreted to have formed during large dextral transform motion along the continental margin and to have reached final emplacement by thrusting against the southern end of wrangellia and the coast plutonic complex

seismic structure of the upper mantle in a central pacific corridor the seismic structure of the tonga hawaii corridor has been investigated by combining two data sets revenaugh and jordan s reflectivity profile from scs reverberations which provides travel times to and impedance contrasts across the major mantle discontinuities and 1500 new observations of frequency dependent phase delays for the three component s ss and sss body waves and the r1 and g1 surface waves which constrain the velocity structure within this layered framework the shear waves turning in the upper mantle showed significant splitting of the sh and sv components indicative of shallow polarization anisotropy the data set was inverted in conjunction with attenuation and mineralogical constraints to obtain a complete spherically symmetric radially anisotropic structure the final model pa5 is characterized by a high velocity anisotropic lid bounded at 68 km depth by a large negative g discontinuity a low velocity anisotropic layer below g extending to a small l discontinuity at 166 km an isotropic steep gradient region between 166 km and 415 km and transition zone discontinuities at 415 507 and 651 km the depth of the radial anisotropy in pa5 is shallower than in most previous studies based on surface waves and higher modes the average value of radial shear anisotropy in the lid 3 7 is consistent with the magnitude expected from the spreading controlled models of olivine orientation while anisotropy in the low velocity zone which is required by our data set could be induced either by paleostrains that took place near the ridge crest or by shearing in the asthenosphere as a result of present day plate motions on the basis of recent work by hirth and kohlstedt we suggest that the g discontinuity is caused by a rapid increase in the water content of mantle minerals with depth marking the fossilized lower boundary of the melt separation zone active during crust formation the high gradient zone between 200 and 400 km is a characteristic feature of convecting oceanic upper mantle and is probably controlled by a steady decrease in the homologous temperature over this depth interval the average shear velocity gradient in the transition zone is lower than in most previous seismic models in better agreement with the predictions for a pyrolitic composition

geologic analysis of the upper jurassic haynesville shale in east texas and west louisiana the upper jurassic haynesville shale is currently regarded as one of the most prolific emerging shale gas plays in the continental united states it has estimated play resources of several hundred trillion cubic feet and per well reserves estimated as much as 7 5 bcf the reservoir spans more than 16 counties along the boundary of eastern texas and western louisiana although this basin has a long history of exploration and analysis of its mesozoic section a comprehensive subsurface study characterizing the haynesville shale has not been conducted this article is the first to address the structural setting stratigraphy depositional environment and facies fracturing and production challenges of the haynesville shale gas play basement structures and salt movement influenced carbonate and siliciclastic sedimentation associated with the opening of the gulf of mexico the haynesville shale is an organic and carbonate rich mudrock that was deposited in a deep partly euxinic and anoxic basin during the kimmeridgian to the early tithonian related to a second order transgression that deposited organic rich black shales worldwide the haynesville basin was surrounded by carbonate shelves of the smackover and haynesville lime louark sequence in the north and west several rivers supplied sand and mud from the northwest north and northeast into the basin haynesville mudrocks contain a spectrum of facies ranging from bioturbated calcareous mudstone laminated calcareous mudstone and silty peloidal siliceous mudstone to unlaminated siliceous organic rich mudstone framboidal to colloidal pyrite is variably present in the form of concretions laminae and individual framboids and replaces calcite cement and mollusk shells haynesville reservoirs are characterized by overpressuring porosity averaging 8 to 12 sw of 20 to 30 nanodarcy permeabilities reservoir thickness of 200 to 300 ft 70 to100 m and initial production of as much as 30 mmcf day reservoir depth ranges from 9000 to 14 000 ft 3000 to 4700 m and lateral drilling distances are 3000 to 5000 ft 1000 to 1700 m typical haynesville wells exhibit a steeper decline curve 80 in the first year than other shale gas plays which is attributed to a very high overpressure

the vaca muerta quintuco system tithonian valanginian in the neuquen basin argentina a view from the outcrops in the chos malal fold and thrust belt the vaca muerta quintuco system uppermost lower tithonian lower valanginian is a thick shallowing upward sedimentary cycle consisting of dark bituminous shales marlstones limestones and sandstones cropping out in the neuquen basin west central argentina this paper analyzes three outcrop sections in chos malal area northem neuquen province detailed facies analysis allows us to differentiate six facies associations representing basinal to proximal outer ramp facies of a homoclinal carbonate ramp system vaca muerta formation and basinal to shoreface facies of a mixed carbonate siliciclastic shelf system quintuco formation prograding westward from the eastern margin of the basin two sequence hierarchies were recognized 5 composite depositional sequences third order and 15 high frequency sequences fourth order fluctuations in organic matter content within the vaca muerta formation suggest a relationship with depositional sequences finding the highest values associated with transgressive systems tract whereas the transition to the quintuco formation shows a strong decrease in total organic carbon the x ray diffraction studies show an increase of clay minerals and quartz in the transgressive systems tract of the vaca muerta formation and an increase in the content of calcite in highstand systems tracts this pattern is reversed in the quintuco formation our sequence stratigraphic approach contributes to the understanding of the relationship between organic matter clay minerals facies stacking pattern and relative sea level changes in this exceptional shale oil and shale gas unconventional reservoir this study may be helpful for a better postulate of petrophysical and geomechanical models for unconventional exploration

a depositional model for offshore deposits of the lower blue gate member mancos shale uinta basin utah usa depositional models that use heterogeneity in mud dominated successions to distinguish and diagnose environments within the offshore realm are still in their infancy despite significant recent advances in understanding the complex and dynamic processes of mud deposition six cored intervals of the main body of the mancos shale the lower blue gate member uinta basin were examined sedimentologically stratigraphically and geochemically in order to evaluate facies heterogeneity and depositional mechanisms unique sedimentological and geochemical features are used to identify three offshore environments of deposition the prodelta the mudbelt and the sediment starved shelf prodelta deposits consist of interlaminated siltstone and sandstone and exhibit variable and stressed trace fossil assemblages and indicators of high sedimentation rates the prodelta was dominated by river fed hyperpycnal flow mudbelt deposits consist of interlaminated siltstone and sandstone and are characterized by higher bioturbation indices and more diverse trace fossil assemblages ripples scours truncations and normally graded laminations are abundant in prodelta and mudbelt deposits indicating dynamic current conditions mudbelt sediment dispersal was achieved by both combined flow above storm wave base and current enhanced and wave enhanced sediment gravity flows below storm wave base sediment starved shelf deposits are dominantly siltstone to claystone with the highest calcite and organic content bioturbation is limited to absent sediment starved shelf deposits were the result of a combination of shelfal currents and hypopycnal settling of sediment despite representing the smallest volume sediment starved shelf deposits are the most prospective for shale hydrocarbon resource development due to elevated organic and carbonate content sediment starved shelf deposits are found in either retrogradational to aggradational parasequence sets or early distal aggradational to progradational parasequence sets bounding the maximum flooding surface an improved framework classification of offshore mudstone depositional processes based on diagnostic sedimentary criteria advances our predictive ability in complex and dynamic mud dominated environments and informs resource prospectivity

lithofacies and sequence stratigraphy of the barnett shale in east central fort worth basin texas ten barnett shale lithofacies have been recognized in a 223 ft 68 m long core from johnson county texas eight of these lithofacies match those previously identified in the main producing area of the newark east barnett shale field in the northern part of the fort worth basin but two new lithofacies have been identified in this core resedimented spiculitic mudstone lithofacies and lag deposits both of which are indicative of a relatively higher energy environment and downslope resedimentation of shallower water deposits the recognition of cyclical stacking patterns of the lithofacies condensed sections css and transgressive surfaces of erosion were the keys to establishing the sequence stratigraphic framework in these fine grained rocks which consists of seven stratigraphic intervals in the lower barnett shale and nine stratigraphic intervals in the upper barnett shale spectral gamma ray uranium and thorium logs aided in this objective and are recommended for future sequence stratigraphic studies of these and other shales the sequence stratigraphic framework reveals that the lower barnett shale in this area was deposited mainly in a low energy relatively deep water environment somewhat far from a terrigenous source area which probably lies to the northwest by contrast the upper barnett shale was deposited in an oxygenated shallower water environment which had a source area from the west and southwest sides of the basin the higher frequency of sea level fluctuation during development of the upper barnett shale most probably indicates periodic tectonic activity perhaps associated with a structural high that was susceptible to sea level fluctuations alternatively it could have resulted from the onset of glaciations in gondwanaland during this time this higher frequency may indicate that the upper barnett is chesterian in age because cyclicity was higher than during the osagean and meramecian stages if so there may be more high frequency cycles than recognized in this core siliceous sponge spicules are more common in this core than in more northerly cores so more brittle facies might prevail in the southern part of the fort worth basin high gamma ray log responses which are caused by a high total organic carbon and or in situ phosphate minerals are commonly found in css and can be used for regional correlations however high gamma ray phosphatic deposits that have been resedimented to downslope positions by sediment gravity flows are an exception to the previous statement correlation of the barnett stratigraphic intervals now provides a north to southeast stratigraphic framework along the fort worth basin relative hydrocarbon potential rhp is an organic geochemical parameter applied to this core and found to provide an indicator of marine transgressions and regressions we recommend continued testing and use of the rhp parameter for high frequency sequence stratigraphic analysis of unconventional gas shales

paleogeographic and paleotectonic setting of laramide sedimentary basins in the central rocky mountain region in the rocky mountain region between central montana and central new mexico sedimentologically isolated nonmarine basins were produced by basement deformation during the laramide orogeny within the area formerly occupied by a broad late cretaceous foreland basin in which laterally continuous marine facies had accumulated previously laramide structures of varying trend and scale reflect heterogeneity of crustal strain caused by shear between the continental lithosphere and an underlying subhorizontal slab of subducted oceanic lithosphere laramide basins include perimeter basins along the cratonic periphery of the arcuate laramide province axial basins along a north south intramontane trend and ponded basins located farther west closer to the overthrust belt twelve specific stratigraphic and sedimentologic criteria for the onset duration and termination of laramide deformation allow the chronology of basin development to be inferred independently for each basin maastrichtian initiation of laramide deformation was approximately synchronous throughout the laramide province but termination of laramide deformation was systematically diachronous from north to south between early and late eocene time widespread eocene erosion surfaces truncate syntectonic laramide sequences and are overlain by largely volcanic and volcaniclastic post laramide strata of eocene age in the north and oligocene age in the south fluvial depositional systems draining toward the great plains were dominant in perimeter and axial basins but ponded basins were occupied at times by large lakes that served as regional sediment traps paleocene drainages from ponded basins also led eastward toward the continental interior but partly interconnected lakes that developed within several ponded basins by mid eocene time were either closed hydrologically or else they drained westward into the tyee paleoriver of the pacific northwest

rayleigh wave phase velocities in the pacific with implications for azimuthal anisotropy and lateral heterogeneities summary the lateral distribution of fundamental mode rayleigh wave phase velocities in the pacific has been calculated in order to determine the variation in velocity as a function of the age of the oceanic plate the importance of azimuthal anisotropy and the presence of secondary lateral heterogeneities the data set used in this study consists of phase velocity measurements in the period range 20 125 s for 178 paths traversing the pacific both the pure path and spherical harmonic inversion techniques are used in this investigation with an emphasis placed on determining the effectiveness and resolving power of these methods in calculating the velocity distribution in an oceanic regime the first order velocity age relation which dominantly characterizes surface wave dispersion in an oceanic environment can be adequately modelled by either the pure path or spherical harmonic techniques azimuthal anisotropy is the dominant second order effect and is best developed in regions less than 80 myr in age in this age zone the faster direction of wave propagation is either in the direction of fossil seafloor spreading or in the direction of present day absolute plate motion in the western pacific there is a correlation with paleo relative motion fossil seafloor spreading for periods less than 50 s lateral velocity heterogeneities which are not related to the age of the oceanic plate are found by pure path inversions and are correlated with regions associated with shallow residual depth anomalies this effect slow velocities with respect to the velocity age model monotonically decreases as a function of period and is indicative of a shallow origin age independent anomalies were also modelled by the application of the pure path and spherical harmonic methods in a sequential inversion

evaluating along strike variation using thin bedded facies analysis upper cretaceous ferron notom delta utah thin bedded delta front and prodelta facies of the upper cretaceous ferron notom delta complex near hanksville in southern utah usa show significant along strike facies variability primary initiation processes that form these thin beds include surge type turbidity currents hyperpycnal flows and storm surges the relative proportion of sedimentary structures generated by each of these depositional processes events has been calculated from a series of measured sedimentological sections within a single parasequence ps6 1 which is exposed continuously along depositional strike for each measured section sedimentological data including grain size lithology bedding thickness sedimentary structures and ichnological suites have been documented parasequence 6 1 shows a strong along strike variation with a wave dominated environment in the north passing abruptly into a fluvial dominated area then to an environment with varying degrees of fluvial and wave influence southward and back to a wave dominated environment further to the south east the lateral facies variations integrated with palaeocurrent data indicate that parasequence 6 1 is deposited as a storm dominated symmetrical delta with a large river dominated bayhead system linked to an updip fluvial feeder valley this article indicates that it is practical to quantify the relative importance of depositional processes and determine the along strike variation within an ancient delta system using thin bedded facies analysis the wide range of vertical stratification and grading sequences present in these event beds also allows construction of conceptual models of deposition from turbidity currents i e surge type turbidity currents and hyperpycnal flows and storm surges and shows that there are significant interactions and linkages of these often paired processes

amplitude and phase data inversions for phase velocity anomalies in the pacific ocean basin summary rayleigh wave phase velocities at periods 30 80 s in the pacific ocean are calculated by inverting phase and amplitude anomaly data using the paraxial ray approximation and the gaussian beam method the region is divided into 5 x 5 blocks and approximately 200 source receiver pairs from 18 well studied events around the pacific ocean are used first we assume phase anomalies for the lithospheric age dependent model next conventional phase data inversions are conducted assuming great circle paths so that the phase discrepancies are reduced to less than t this procedure is essential for later inversions using amplitude data we then determine the residuals of both amplitude and phase terms by calculating ray synthetic seismograms using the born approximation for a 2 d wave equation a nonlinear iterative inversion for phase velocities is performed with both residuals frbchet derivatives for the inversion consist primarily of two wavefields 1 the wavefield at the model point from the source and 2 the green s function from the model point to the receiver these wavefields are also calculated by the paraxial ray approximation and gaussian beam methods in the inverse formulations the simple use of the conventional backus gilbert approach yields undesirable results in the non linear iterative case and an extra term is necessary to control the model perturbations in order to minimize departures from the a priori model the use of this additional term guarantees that we are able to obtain a fairly reliable phase velocity model even in the present non linear problem in most cases residual variances are significantly reduced after two or three iterations as far as the starting model is fairly correct compared with the phase data inversions this inverse scheme gives more reliable resolution and most of the inverted features in phase velocities are significantly larger than the uncertainty level while some features obtained by the great circle phase data

three dimensional velocity map of the upper mantle beneath the pacific ocean as determined from rayleigh wave dispersion abstract a three dimensional shear wave velocity model of the upper mantle beneath the pacific is determined from rayleigh wave phase velocities at periods 60 200 s without any a priori regionalization the results clearly indicate that the velocity distribution in the uppermost 150 km is correlated with the surface tectonics the seismic velocities of the young regions such as the east pacific rise and the west coast of north america are lower than the average pacific structure by 2 5 and those of the old regions such as the northwest pacific are higher by 2 4 as the depth increases the low velocity region in the southeast pacific seems to move to the northwest a wide area of the central pacific shows low velocity below depths of 200 250 km an area off the coast of western canada exhibits a velocity lower by 4 5 above 200 km but changes to a velocity higher by 4 5 below that depth cross sections of the marginal sea regions around the pacific the tasman sea the philippine sea the sea of japan the okhotsk sea and the bering sea have quite different features from each other the bering sea has a velocity lower by 1 2 above 100 km and below 300 km and higher by 1 at depths 150 250 km the philippine sea and the sea of japan have a velocity lower by 1 2 at depths 50 150 km and a velocity higher by 1 2 at depths 200 400 km the bismark islands region and the south fiji basin show similar velocity changes at a depth of about 250 km and 150 km respectively the tasman sea is characterized by low velocity in the upper 400 km there is a good correlation between high velocity and seismicity below 150 km in the marginal sea regions

mid cretaceous strike slip and contractional fault zones in the western intermontane terrane washington and their relation to the north cascades southeastern coast belt orogen structural and geochronologic data from the 111 114 ma okanogan range batholith in north central washington are used to characterize the timing and style of deformation during the early stages of the mid to late cretaceous north cascades southeastern coast belt nc secb orogen the pasayten fault zone bounds jurassic cretaceous sedimentary and volcanic rocks of the methow basin to the west against predominantly mesozoic igneous rocks of the intermontane terrane to the east the pasayten fault zone accommodated intrusion of the western units of the okanogan range batholith during high angle slip then approximately 20 km of left lateral strike slip at 109 95 ma south of the pasayten fault zone the red shirt and methow river thrust zones accommodated 1 west vergent contraction at amphibolite grade that began by 113 ma and ended by 112 ma based on new u pb zircon dates for deformed and undeformed granitoids and 2 northwest vergent contraction in the methow river thrust zone followed by west vergent contraction in the red shirt thrust zone both at greenschist grade prior to 104 ma these contractional displacements thrust the methow basin 10 20 km southeastward beneath the western okanogan range batholith deformation in the nc secb thus began by earliest albian time earlier than previously thought and was characterized by coeval sinistral transcurrent and west vergent contractional faulting sinistral strike slip in the pasayten fault zone may have reflected the pre 100 ma sense of oblique plate convergence or relatively minor southward tectonic escape of the adjacent methow basin during contractional deformation the slip history of the pasayten fault zone is undocumented between approximately 80 ma and 60 ma when on the basis of paleomagnetic data some workers have proposed that the methow basin moved 1700 km northward to its present position relative to the intermontane terrane however significant late cretaceous to early eocene dextral slip on the pasayten fault zone is unlikely because the western intrusive units of the okanogan range batholith continue without disruption across its southeastward trend

role of crustal thickening and extensional collapse in the tectonic evolution of the sevier laramide orogeny western united states the effects of crustal thickening and extensional collapse of continental crust combined with variations in plate convergence forces provide a coherent explanation for evolution of the cretaceous early tertiary sevier laramide orogeny crustal thickening of the sevier laramide hinterland region was triggered by the combination of compressive plate convergence forces and subduction induced conductive heating of the crust eastward progradation of the locus of sevier laramide deformation through time reflects the progressive widening of the region of crustal thickening the region of maximum crustal thickening migrated outward until about 80 to 75 ma when it encountered excessively strong lithosphere of the colorado plateau the locus of deformation was then transmitted laterally across both a hinterland that had attained maximum crustal thickness and the rigid colorado plateau into the laramide rocky mountain foreland an episode of vigorous extensional collapse of orogenically thickened crust affected the southern cordillera between about 75 and 35 ma early tertiary waning of plate convergence rates and continued subduction induced conductive heating of thickened crust allowed extensional collapse along the southern cordillera region to drive the colorado plateau block northward the result was the late laramide phase of rocky mountain foreland deformation because of this compressive deformation in the central and southern laramide rocky mountain region continued through eocene time rather than ceasing at 56 ma as it did in the northern cordillera

geometric effects of global lateral heterogeneity on long period surface wave propagation long period rayleigh waves from iranian earthquakes have large amplitude asymmetries between minor arc and major arc arrivals e g r 2 and r 3 at digital stations in the azimuth range n20 w to n60 e these asymmetries are as large as a factor of 2 at a period of 256 s and persist to periods greater than 300 s in some cases the entire rayleigh wave group arrival spanning periods from 100 to 300 s is either uniformly enhanced in amplitude or diminished to such a degree that the group arrival appears to be missing the amplitude anomalies are generally not accompanied by significant phase anomalies the irregular azimuthal distribution of the amplitude asymmetries and their occurrence for events with different focal mechanisms and epicentral separations of several hundred kilometers preclude an explanation of these observations by source complexity events in the mediterranean and nepal do not produce similar amplitude asymmetries at the same stations the anomalies are thus most likely due to focusing and defocusing propagation effects as a preliminary investigation of the effects of lateral heterogeneity of upper mantle velocity structure on long period surface wave amplitudes surface wave ray tracing calculations are performed using recently proposed global phase velocity distributions dramatic deviations from great circle paths are predicted for long propagation paths e g r 3 the particular spatial distribution of lateral velocity gradients around a given source location determines whether substantial amplitude asymmetries will be observed between minor arc and major arc arrivals and whether these will persist for sequential great circle orbits the 200 s period amplitude asymmetry observed at kip for the iranian source region r 2 4 r 3 is well predicted by the ray tracing results the absence of this anomaly for the other source regions is also predicted other observed anomalies are not all well predicted but it is clear that geometric effects can contribute significantly to the observed variations of rayleigh and love wave amplitudes this is the probable explanation for the instability of q estimates made from surface waves other source regions producing large surface wave amplitude anomalies include japan and southeastern alaska

the deltaic nature of amazon shelf sedimentation despite the annual discharge of more than a billion tons of sediment by the amazon river the sedimentary environment near the river mouth has little subaerial expression and thus does not meet the classic definition of a delta the river mouth however is not an estuary either these observations raise a major question as to what type of sedimentary environment the amazon river mouth represents seismic stratigraphy has been examined on the continental shelf at the mouth of the amazon river using high frequency 3 5 khz seismic records from about 6 000 km of ship track these records demonstrate three regions 1 the amazon river has built a subaqueous feature which stretches for hundreds of kilometres offshore and alongshore from its mouth the feature is prograding seaward and accreting upward and it contains fine scale stratification typical of classic deltas the feature forming at the mouth of the amazon is a subaqueous delta it differs from classic deltas primarily in its lack of subaerial expression subaqueous deltas such as the amazon represent the general case of a major river entering an energetic oceanic regime

a sedimentological and sequence stratigraphic reinterpretation of the upper cretaceous prairie canyon member mancos b and associated strata book cliffs area utah usa the mancos shale book cliffs eastern utah usa represents the open marine mudstones of the cretaceous western interior seaway and encloses the prairie canyon member which is located over 50 km seaward of interpreted contemporaneous highstand shoreline deposits in the blackhawk formation examination of the member reveals that it does not wholly represent offshore deposition as previously interpreted but instead contains three nearshore facies associations 1 tidally influenced fluvial channel fills 2 fluvial dominated delta fronts and 3 weakly storm influenced shorefaces tidally influenced fluvial channel fills are commonly stacked into multistory bodies that can be traced for tens of kilometers at discrete stratigraphic levels defining incised valley fill networks four such incised valley networks are identified at outcrop fluvial dominated deltas and weakly storm influenced shorefaces are eroded into by and lie at the down dip terminations of incised valley fills and are interpreted as forced regressive and lowstand shoreface deposits one incised valley fill appears to be onlapped by additional fluvial dominated deltas which represent pulses of shoreface progradation during an overall transgression forced regressive lowstand and transgressive shorefaces in the prairie canyon member differ significantly from highstand shorefaces in the blackhawk formation the former are sand poor and weakly wave storm influenced whereas the latter are sand rich and wave dominated this change in shoreface style reflects increased mud supply and an enhanced embayment paleogeography during periods of relative lowering of sea level

seismic anisotropy and global geodynamics for many years seismic anisotropy was often neglected mostly because of the inherent heavy mathematical and computational tools needed to describe and model its effects on seismic waves the usual basic knowledge about propagation in isotropic media cannot easily apply to anisotropic media where new phenomena come up such as birefringence or shear wave splitting or difference between directions of propagation of phase velocity and of group velocity consequently geophysicists often claimed that it was a second order effect and considered the earth as isotropic this hypothesis was assumed to be a good approximation because of the random orientation of crystals in most parts of the earth and of the random sampling of anisotropic regions by seismic rays this assumption furthermore made easier the description of wave propagation as well as the parameterization of media in inverse problems an isotropic elastic medium can be described by two independent elastic parameters and lame parameters but the simplest anisotropic medium transverse isotropy with a vertical symmetry axis requires 5 independent parameters love 1927 anderson 1961 to date seismic observations have been explained in terms of isotropic and often thermal lateral heterogeneities ignoring manifestations of anisotropy however since the 1960s it was recognized that most parts of the earth are not only laterally heterogeneous but also anisotropic and that seismic anisotropy provides a simple explanation of different observational data seismic anisotropy contrary to isotropy is reflecting some inherent

lithospheric thickness beneath the pitcairn hot spot trail as inferred from rayleigh wave dispersion abstract we have determined the s velocity model beneath the pitcairn hot spot trail from rayleigh wave phase velocities in order to examine the plate reheating model in which the lithosphere is expected to be thinned by reheating due to a hot spot the rayleigh wave dispersion for the pitcairn hotspot trail was measured by the two station method the phase velocity dispersion obtained for the pitcairn hot spot trail is consistent with oceanic upper mantle models with lithospheric ages corresponding to the pitcairn hot spot trail the dispersion data were inverted for s velocity structure using a hybrid method combining a grid search method and a non linear inversion method the lithospheric thickness was constrained to be from 50 to 80 km which is consistent to the thickness of the corresponding age indicating that the oceanic lithosphere is not anomalously thinned beneath the studied region

upper mantle low anisotropy channels below the pacific plate a new 3d anisotropic model has been obtained at a global scale by using a massive dataset of seismic surface waves though seismic heterogeneities are usually interpreted in terms of heterogeneous temperature field a large part of lateral variations are also induced by seismic anisotropy of upper mantle minerals new insight into convection processes can be gained by taking seismic anisotropy into account in the inversion procedure the model is best resolved in the pacific plate the largest and the most active tectonic plate superimposed on the large scale radial parameter and azimuthal anisotropy of vsv velocity within and below the lithosphere correlated with present or past pacific plate motions are smaller scale 1000 km lateral variations of anisotropy not predicted by plate tectonics channels of low anisotropy down to a depth of 200 km hereafter referred to as lac are observed and are the best resolved anomalies one east west channel between easter island and the tonga kermadec subduction zones observed on both radial and azimuthal anisotropies and a second one only observed on azimuthal anisotropy extending from the south west pacific up to south east hawaii and passing through the polynesia hotspot group for plate older than about 40 ma these features provide strong constraints on the decoupling between the plate and asthenosphere they are presumably related to cracking within the pacific plate and or to secondary convection below the rigid lithosphere predicted by numerical and analog experiments the existence and location of these lacs might be related to the current active volcanoes and hotspots possibly plumes in the central pacific lacs which are dividing the pacific plate into smaller units might indicate a future reorganization of plates with ridge migrations in the pacific ocean

muddy prodeltaic hyperpycnites in the lower genesee group of central new york usa implications for mud transport in epicontinental seas abstract recent studies of marine continental shelves show that hyperpycnal flows are responsible for offshore transport of large volumes of sediment detailed facies analysis and petrography of the lower genesee group in the northern appalachian basin nab shows a wealth of sedimentary textures and fabrics that indicate mud deposition by lateral transport across and along the shelf under energetic conditions intervals of silt rich mudstones and muddy siltstones with internal scours diffuse stratification soft sediment deformation normal and inverse lamina set grading and a reduced intensity and diversity of bioturbation occur in multiple facies types and interrupt what appears to be the overall background sedimentation these intervals and their sedimentary features are interpreted as products of high density fluvial discharge events which generated turbulent flows that carried fine grained clastics several tens of kilometers offshore from the paleoshoreline recognizing these sediments as products of river flood and storm wave generated offshore directed underflows challenges previous depositional models for organic rich mudstones in the lower genesee succession which call for clastic starvation and suspension settling of clay and silt in a deep stratified basin rapid deposition of fine grained intervals from hyperpycnal plumes in a setting favoring preservation of organic rich mudstones calls for a reappraisal of the depositional setting of not only the genesee group but also of comparable mudstone successions in the appalachian basin and elsewhere

regional and azimuthal dependence of phase velocities of mantle rayleigh waves in the pacific ocean abstract the lateral heterogeneity and azimuthal anisotropy of the upper mantle in the pacific ocean are investigated by analysing rayleigh wave phase velocities in the period range 60 200 s rayleigh waves at periods below 150 s travel fast in the direction parallel to the present day plate motion rayleigh wave velocities at longer periods show a similar azimuthal dependence in most parts of the pacific the average magnitude of the velocity anisotropy in the pacific ocean changes from 1 at 60 s to 0 4 at 200 s the azimuth independent phase velocities increase with the increase in age of the sea floor in the period range 60 120 s but the correlation is weak at longer periods the trade off between the lateral variation and the azimuthal variation is weak except for marginal places of the studied area

where can seismic anisotropy be detected in the earth s mantle in boundary layers during the last 30 years considerable evidence of seismic anisotropy has accumulated demonstrating that it is present at all scales but not in all depth ranges we detail which conditions are necessary to detect large scale seismic anisotropy firstly minerals must display a strong anisotropy at the microscopic scale and or the medium must be finely layered secondly the relative orientations of symmetry axes in the different crystals must not counteract in destroying the intrinsic anisotropy of each mineral and there must be efficient mechanisms of orientation of minerals and aggregates finally the strain field must be coherent at large scale in order to preserve long wavelength anisotropy part of shallow anisotropy can be related to the past strain field frozen in anisotropy however the deep anisotropy is due to the present strain field all these conditions are fulfilled only in boundary layers of convective mantle we review in this paper the seismic data sets which provide insight into the location at depth of large scale anisotropy from the d layer up to the lithosphere in addition to the well documented seismic anisotropy in the lithosphere and asthenosphere there is new evidence of seismic anisotropy in the upper 400 660 km and lower 660 900 km transition zones and in the d layer nonetheless the bulk of the lower mantle seems close to isotropy if we assume the hypothesis that seismic anisotropy is associated with boundary layers in convective systems these observations strongly suggest that the transition zone is a boundary layer which makes the pasage of matter between the upper and the lower mantle difficult however this general statement does not rule out flow circulation between the upper and lower mantles finally the geophysical mineral physics and geological applications are briefly reviewed an intercomparison between surface wave anisotropy and body wave anisotropy data sets is presented we discuss the scientific potential of seismic anisotropy and how it makes it possible to gain more insight into continental root deformation and geodynamics processes

shoreface tongue geometry constrains history of relative sea level fall examples from late cretaceous strata in the book cliffs area utah progradational shoreface tongues preserve a near complete depositional record of relative sea level highstands falls and lowstands two distinct styles of progradational shoreface tongue are examined in an extensive outcrop and subsurface dataset from late cretaceous strata of the book cliffs area utah representing i highstand through attached lowstand progradation and ii highstand through detached lowstand progradation using this dataset key geometrical attributes of the shoreface tongues and their internal facies architecture are identified and quantified that enable the reconstruction of relative sea level fall history for example attached wave dominated lowstand shoreface deposits record a slow 0 2 0 3 mm yr 1 low magnitude 14 m relative sea level fall punctuated by minor rises detached weakly wave influenced lowstand shoreface deposits record a more rapid 0 4 0 5 mm yr 1 high magnitude 45 m relative sea level fall synchronous with a marked change in sediment delivery and depositional process regime at the shoreline

seismic anisotropy the state of the art ii summary the theory causes observations and possible applications of seismic anisotropy in the earth have developed considerably since the previous state of the art paper was published in 1977 the behaviour of waves in layered anisotropic media is now much better understood and the evidence for seismic anisotropy indicates that anisotropy is likely to be present throughout much of the crust and upper mantle the top few hundred kilometres of the mantle appears to be anisotropic with the orientations aligned by the present or palaeo stress field the upper part of the crust is frequently anisotropic probably due to cracks differentially aligned by the non lithostatic stresses the possibility of being able to monitor crack geometry by seismic techniques opens a wide range of applications in currently important activities

phase velocity structure from rayleigh and love waves in tibet and its neighboring regions deep geodynamic processes involved in the continental collision between india and asia are still controversial to address this issue phase velocities of 619 rayleigh waves and 254 love waves have been inverted by using an anisotropic tomographic technique such a technique enables us not only to retrieve phase velocity distributions but also to map azimuthal anisotropy on a large scale only phase velocity anomalies in the period range 50 200 s are dealt with here but the azimuthal anisotropy has been taken into account in the inversion process moreover because of the important influence of shallow layers on the inversion results an inversion of phase velocities corrected for shallow layers has been performed to correct raw phase velocities the 3smac crust heterogeneous reference earth model has been used the comparison of phase velocity distributions for love and rayleigh waves with and without corrections of surficial layers implies that much of the low velocity zone visible at short periods in central tibet can be explained by unusually thick crust at periods longer than 100 s tibet is overall characterized by high velocity anomalies such anomalies seem to converge toward the center of the plateau as period increases we conclude that the phase velocity structure beneath tibet results at short periods from thick crust and possible partial melting in the uppermost lithosphere and at long periods from the inward plunge of the cold lithospheric mantle surrounding the high plateau

the quantification and application of handheld energy dispersive x ray fluorescence ed xrf in mudrock chemostratigraphy and geochemistry abstract traditionally analytical techniques such as wavelength dispersive x ray fluorescence wd xrf inductively coupled plasma icp and mass spectrometry icp ms instrumental neutron activation analysis inaa or stationary bench top energy dispersive x ray fluorescence ed xrf have been used to generate quantitative geochemical results however a more efficient means of data collection using portable ed xrf instrumentation now allows the investigator to acquire rapid non destructive quantitative measurements on drill core and clean flat rock surfaces in addition to pressed powder pellets typically used in wd xrf analysis similar to traditional xrf methods quantification using the handheld ed xrf requires a matrix specific calibration unfortunately very few internationally accepted mudrock or shale reference materials exist and their elemental ranges provide inadequate coverage for the geochemical diversity of mudrocks in order to return reliable calibrated results a unique set of reference materials has been developed that incorporates a wide range of mudrock elemental compositions the current method provides elemental calibrations for major elements heavier than sodium and the following trace elements ba v cr ni cu zn rb sr y zr nb mo th and u a comparison of handheld energy dispersive and wavelength dispersive x ray fluorescence ed xrf and wd xrf results from pressed powder pellets of mississippian age barnett shale of north central texas usa is presented in order to evaluate the reliability of the reference calibration and the quantification of unknown samples using two different instrument platforms it will be demonstrated that calibrated results from the handheld ed xrf effectively define chemostratigraphic changes in real time as a consequence quantified results can be used immediately to assess changes in bulk mineralogy paleo redox conditions and to link down core geochemical changes to stratigraphic sedimentological and paleoenvironmental observations

marine triassic faunas of north america their significance for assessing plate and terrane movements the distribution of marine triassic invertebrate faunas in north america is reviewed to recognize forms that may have paleolatitudinal significance

u pb and k ar dates related to the timing of magmatism and deformation in the cache creek terrane and quesnellia southern british columbia u pb dating of zircon from the guichon creek batholith indicates an emplacement age of 210 3 ma comparison with previously published k ar 211 188 ma and rb sr 205 and 196 ma dates reveals that intrusion mineralization cooling and uplift of the batholith took some 20 ma spanning the triassic jurassic boundary on the decade of north american geology dnag time scale the mount martley pluton and tiffin creek stock yield late jurassic dates of 155 2 ma u pb zircon and 152 5 ma k ar hornblende respectively and provide a reliable minimum age kimmeridgian for penetrative deformation in the cache creek terrane k ar whole rock dates from cache creek terrane and ashcroft formation argillites range from early permian 266 8 ma and early jurassic 194 6 ma to late jurassic kimmeridgian 154 5 ma we interpret the younger dates as recording middle late jurassic tectonism and the older ones as possible relics from earlier deformation episodes an early cretaceous k ar date 129 5 ma for a lamprophyre dike that cuts the nicola group suggests that the early cretaceous magmatic arc of the coast plutonic complex had an eastern alkalic fringe in the intermontane belt

ichnology of prodeltaic hyperpycnite turbidite channel complexes and lobes from the upper cretaceous prairie canyon member of the mancos shale book cliffs utah usa

geochronometry of the eagle plutonic complex and the coquihalla area southwestern british columbia new u pb k ar and rb sr dates from the eagle plutonic complex and adjacent map units place timing constraints on intrusive and deformational events along the southwestern margin of the intermontane belt u pb zircon minimum dates for eagle tonalite and gneiss 148 6 156 4 and 157 4 ma document previously unrecognized middle to late jurassic magmatism and syn intrusive deformation along the eastern margin of the eagle plutonic complex and the southwestern margin of the intermontane terrane widespread mid cretaceous albian cenomanian resetting of k ar and rb sr isotopic systematics in jurassic and older rocks is coeval and cogenetic with emplacement of plutons of the fallslake plutonic suite 110 5 2 ma u pb which crosscut jurassic plutons and structures but were themselves ductilely deformed along the pasayten fault during sinistral east side up reverse displacement k ar and rb sr cooling dates for the fallslake suite of ca 100 ma including dates from mylonites along the pasayten fau

thickness trends and sequence stratigraphy of the middle devonian marcellus formation appalachian basin implications for acadian foreland basin evolution analysis of more than 900 wireline logs indicates that the middle devonian marcellus formation encompasses two third order transgressive regressive t r sequences mss1 and mss2 in ascending order compositional elements of the marcellus formation crucial to the successful development of this emerging shale gas play including quartz clay carbonate pyrite and organic carbon vary predictably within the proposed sequence stratigraphic framework thickness trends of marcellus t r sequences and lithostratigraphic units reflect the interplay of acadian thrust load induced subsidence short term base level fluctuations and recurrent basement structures rapid thickening of both t r sequences especially mss2 toward the northeastern region of the basin preserves a record of greater accommodation space and proximity to clastic sources early in the acadian orogeny however local variations in t r sequence thickness in the western more distal area of the basin may reflect the reactivation of inherited eocambrian basement structures including the rome trough and northwest striking cross structural discontinuities induced by acadian plate convergence episodes of block displacement locally warped the basin into northeast southwest trending regions of starved sedimentation and or erosion adjacent to depocenters in which regressive systems tract deposits were ponded block movement appears to have initiated in late early devonian time resulting first in thinning and local erosion of the oriskany sandstone in northwest pennsylvania this study in addition to providing the basis for a predictive sequence stratigraphic model that can be used to further marcellus exploration tells of a foreland basin more tectonically complex than accounted for by simple flexural models

how to relate body wave and surface wave anisotropy seismic anisotropy is one of the most efficient geological and geodynamical tools for understanding the dynamics of the earth upper mantle anisotropy is evident in seismic data sets for the last 30 years primarily from surface wave dispersion curves and body wave sks data we demonstrate in this paper that surface wave and body wave derived anisotropy can be explained by the same anisotropic parameters l gc gs in the simplest case of a horizontal fast symmetry axis one application of this method is to display the sks delay time and the corresponding azimuth which can be derived from surface wave global with a lateral resolution of around 2000 km and regional lateral resolution of 350 km anisotropy tomography a global scale comparison is disappointing since there are only a few areas where both data types are correctly retrieved at the same spatial scale same lateral resolution the anisotropy is well resolved in oceanic basins from surface waves whereas most measurements of sks splitting are available below continents however there is a good agreement between surface wave and body wave anisotropy in regions where large scale processes primarily tectonic are taking place such as the western united states and in central asia in particular we show that at high frequency 1hz the observed sks delay time and azimuth depend on the order in which s waves propagate through the layers a comparison between synthetic and observed sks phases in central asia highlights the varying sensitivity of sks waves at depth we can obtain a good correlation between synthetic and observed sks by considering anisotropy only between 80 and 200 km depth in the tomographic model rather than in the entire upper mantle however it is more difficult to explain the discrepancy between synthetic and observed sks under the eastern united states where a large scale coherent sks anisotropy is present such results call for more sophisticated sks waveform modeling and for enhanced lateral resolution in anisotropic tomographic models

the cambrian revolutions trace fossil record timing links and geobiological impact several concepts pertaining to the dramatic changes that occurred during the cambrian have been proposed namely the agronomic revolution ar the cambrian substrate revolution csr and the cambrian information revolution cir the original concept of the ar refers to the replacement of precambrian type substrates matgrounds by phanerozoic type ones mixgrounds the csr highlights the evolutionary and ecological effects of cambrian substrate changes on epifaunal sessile metazoans the cir involves the distribution of signals in an environment that an organism can potentially respond to underscoring an increased complexity and heterogeneity of marine ecosystems which may have played a major role as a driving force of further evolutionary change during the cambrian a systematic review of the ediacaran cambrian ichnofossil record allows to provide some temporal resolution for these cambrian revolutions and to explore the synergies among these evolutionary breakthroughs and possible geobiological outcomes the ar is not coincident with the ediacaran cambrian boundary but rather it is manifested by cambrian age 2 because the csr focuses on the response of the epifauna to newly evolved mixgrounds and the late cambrian appearance of hardgrounds it may be understood at least in part as a consequence of the ar in contrast the cir involved the appearance of sophisticated innovative feeding strategies that allowed benthic organisms to successfully exploit resources in an increasingly more heterogeneous sea bottom the occurrence in the fortunian of highly patterned grazing trails reflects the establishment of efficient navigational devices although the cir signals the appearance of novel body plans and novel ways of animal substrate interactions strategies involving matground exploitation were still widespread in the fortunian more dramatic changes took place in cambrian age 2 as revealed by the onset of the ar and later the effects on epifaunal sessile organisms and communities during the csr signalling to the transition to shallow marine ecosystems of modern aspect

wave enhanced sediment gravity flows and mud dispersal across continental shelves reappraising sediment transport processes operating in ancient mudstone successions recent studies of marine shelf sediment dispersal show that wave enhanced sediment gravity flows are widespread phenomena and can transport large volumes of fluid mud rapidly across low gradient shelves flow evolution is controlled by sediment supply seabed gradient and spatial distribution of wave energy at the seabed using existing flow models we predict that such flows in mud dominated sediments will develop a three part microstratigraphy produced by changing flow conditions beginning with wave induced turbulent resuspension then development of a wave enhanced sediment gravity flow prior to lutocline collapse and suspension settling petrographic examination of modern flow deposits collected from the eel shelf reveals that resultant beds possess a microstratigraphy consistent with our hypothesis a silt rich basal subunit with curved ripple laminae abruptly overlain by a subunit composed of continuous intercalated silt clay laminae and an upper clay rich drape analyses of beds from ancient mud rich outer shelf and basinal successions cleveland ironstone jurassic uk and mowry shale cretaceous united states show that they too contain beds with this three part organization suggesting that such flows were active in these ancient settings too recognition of these microstructures in these ancient mud dominated successions demonstrates that sediment in these settings was commonly reworked and transported advectively downslope by high energy events contrasting with previous interpretations of these units that deposition was dominated by quiescent suspension settling identification of these recognition criteria now allows the products of this newly recognized sediment dispersal mechanism to be identified in other shale dominated successions

jurassic and cretaceous plutonic and structural styles of the eagle plutonic complex southwestern british columbia and their regional significance the eagle plutonic complex is an elongate north northwest trending body of deformed middle to late jurassic and middle cretaceous rocks which underlies the southwestern margin of the intermontane terrane new mapping of the complex and its country rocks in concert with geochronometry has defined episodes of contractional ductile deformation in the middle to late jurassic and middle cretaceous as well as brittle deformation in tertiary time synkinematic middle to late jurassic eagle tonalite at the eastern margin of the eagle complex intrudes mylonitic nicola group rocks and structurally overlies them along a southwest dipping belt of high strain eagle shear zone with a structural thickness of 1 km and a strike length of 100 km in the central and western eagle complex eagle tonalite grades into tonalite orthogneiss eagle gneiss and both are crosscut by mid cretaceous muscovite bearing plutons of the fallslake plutonic suite fallslake suite rocks are themselves ductilely deformed along the

bottomset and foreset sedimentary processes in the mixed carbonate siliciclastic upper jurassic lower cretaceous vaca muerta formation picun leufu area argentina abstract the upper jurassic lower cretaceous vaca muerta formation at the picun leufu area constitutes bottomset and foreset marine deposits comprising open bay siliciclastic basin and mixed carbonate siliciclastic shelf facies detailed sedimentological ichnological and sequence stratigraphic analysis of six stratigraphic sections allows establishing two depositional sequences depositional sequence 1 ds1 begins with lowstand eolian deposits included in the quebrada del sapo formation and continues with thin retrograding transgressive open bay facies of the vaca muerta formation encompassing coastal sand sheet and dune marginal marine bay margin and distal bay facies above the transgressive deposits the regressive hemicycle of ds1 consists of bottomset deposits representing a siliciclastic basin facies association lobe and lobe fringe hyperpycnal flow sedimentation alternated with hemipelagic basinal deposition in an oxygen deficient environment a relative sea level fall generated a sequence boundary which coincides with an angular unconformity that marks the base of depositional sequence 2 ds2 this sea level fall triggered the formation of an extensive lowstand channel fill and lobe complex at the base of the slope followed by retrogradational lobe facies during the subsequent transgression the regressive hemicycle of ds2 represents foreset mixed carbonate siliciclastic shelf facies forming a slope mud belt and slope sand bodies near the top sedimentation in a foreset topset transition resulted in the accumulation of bioturbated mixed slope and sandy shoal deposits sand bars and lagoonal facies occur on top of all sections and are truncated by a sequence boundary the combined analysis provides insights into the sedimentary processes affecting bottomset and foreset deposition underscoring the role of wave influenced hyperpycnal flows and the effect on organic matter dilution in one of the most important unconventional reservoirs from argentina