evaluating the reliability of the stream tracer approach to characterize stream subsurface water exchange stream water was locally recharged into shallow groundwater flow paths that returned to the stream hyporheic exchange in st kevin gulch a rocky mountain stream in colorado contaminated by acid mine drainage two approaches were used to characterize hyporheic exchange sub reach scale measurement of hydraulic heads and hydraulic conductivity to compute streambed fluxes hydrometric approach and reachscale modeling of in stream solute tracer injections to determine characteristic length and timescales of exchange with storage zones stream tracer approach subsurface data were the standard of comparison used to evaluate the reliability of the stream tracer approach to characterize hyporheic exchange the reach averaged hyporheic exchange flux 1 5 ml s 1 m 1 determined by hydrometric methods was largest when stream base flow was low 10 l s 1 hyporheic exchange persisted when base flow was 10 fold higher decreasing by approximately 30 reliability of the stream tracer approach to detect hyporheic exchange was assessed using first order uncertainty analysis that considered model parameter sensitivity the stream tracer approach did not reliably characterize hyporheic exchange at high base flow the model was apparently more sensitive to exchange with surface water storage zones than with the hyporheic zone at low base flow the stream tracer approach reliably characterized exchange between the stream and gravel streambed timescale of hours but was relatively insensitive to slower exchange with deeper alluvium timescale of tens of hours that was detected by subsurface measurements the stream tracer approach was therefore not equally sensitive to all timescales of hyporheic exchange we conclude that while the stream tracer approach is an efficient means to characterize surface subsurface exchange future studies will need to more routinely consider decreasing sensitivities of tracer methods at higher base flow and a potential bias toward characterizing only a fast component of hyporheic exchange stream tracer models with multiple rate constants to consider both fast exchange with streambed gravel and slower exchange with deeper alluvium appear to be warranted

solute transport in rivers with multiple storage zones the stir model solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges between the surface stream and distinct retention zones this paper presents a residence time model for strea

kilometre scale folding in the teslin zone northern canadian cordillera and its tectonic implications for the accretion of the yukon tanana terrane to north america reply the teslin zone in south central yukon has previously been described as a discrete zone with a steep foliation unique to the zone it includes the anvil assemblage and the narrowest portion of the

the sylvester allochthon upper paleozoic marginal basin and island arc terranes in northern british columbia the sylvester allochthon is a composite klippe of upper paleozoic ophiolitic island arc and pericratonic assemblages which rests directly on the cassiar terrane a displaced sliver of ancestral north america each tectonic assemblage occurs at a distinct and consistent structural level within the allochthon they are assigned respectively to the slide mountain harper ranch and yukon tanana terranes the sylvester allochthon provides a view of the structural relationships between these terranes prior to early cretaceous early tertiary strike slip dismemberment as well as possible sedimentological links to late paleozoic north america slide mountain terrane assemblages designated divisions i and ii form the lowest structural panels chert quartz sandstones are interbedded with lower mississippian deep water sediments in division i and ocean floor basalts and deep water sediments in division ii they are similar in age and character to sandstones in the autochthonous earn group division ii as

surface subsurface water interactions in an alluviated mountain stream channel data from an instream tracer experiment performed in north fork dry run shenandoah national park virginia illustrate that the transport of water and conservative solute in the stream is greatly influenced by interaction with water present in both the relatively shallow gravel bed and in the relatively deeper alluvial infill material the shape of concentration time curves from the field tracer experiment exhibit storage of tracer in the subsurface short term storage imposed by exchange with the gravel bed and long term storage by exchange with the deeper alluvial infill time series models fit the observed concentration data very well estimates of mixing volumes generated by the time series analysis indicate that a large volume of the gravel bed participates in rapid mixing with the surface stream at one point along the study reach a second order time series model is supported by the data suggesting two independent parallel flow paths observations of tracer in wells more than 10 m from the stream and the very extended recession of the tracer in the stream where it flows over a bedrock ledge support the contention that the deeper alluvium plays an important role in transient storage of solute in north fork dry run the work implies that physically based models to predict transport and storage in alluviated mountain catchments may have to account for interactions between the stream and large portions of its floodplain

backflow and margin parallel shear within an ancient subduction complex lineated and foliated tectonites of the teslin suture zone yukon represent the deep seated part of a west dipping subduction complex that formed seaward of western north america in permian triassic time the tectonites were progressively underplated onto the hanging wall plate during b type subduction with continued subduction and underplating the boundary between the hanging wall and subduction channel migrated oceanward resulting in growth of the hanging wail plate at depth these tectonites preserve a progressive record of backflow dextral margin parallel shear and downflow within the subduction channel early jurassic a type subduction of the leading edge of western north america resulted in eastward overthrusting of the tectonites as a coherent block onto north american strata these tectonites provide empirical evidence that backflow margin parallel displacement and downflow can all occur within the deeper parts of subduction zones

the cordilleran ribbon continent of north america the north american cordilleran orogen is the result of a two stage process a triassic jurassic accretion within panthalassa forming saybia a composite ribbon continent and b late cretaceous collision of saybia with north america this model requires that a large portion of the continental foreland of the orogen is exotic the exotic continental component of saybia cassiar platform is distinguished from the autochthon on the basis of its a triassic eurasian fauna b involvement in a major late triassic early jurassic orogenic event and c young in part grenvillian basement and mantle a mid cretaceous magmatic arc records west dipping subduction beneath the east margin of saybia the related accretionary prism consists of imbricated shale chert and deep water limestones the medial basin and overlies an isotopically juvenile mantle domain carbonatite complexes delineate the cryptic suture separating saybia and the autochthon paleomagnetic and paleobotanical data place saybia 2000 km to the south relative to the autochthon at 80 ma late cretaceous thrust belt development records transpression between the north moving ribbon continent and the autochthon pinning against the okhotsk chukotka arc in siberia buckled saybia giving rise to the alaskan promontory

seismic and gravity constraints on the crustal architecture of the intermontane terranes central yukon in 2004 two seismic reflection lines were shot across the mesozoic whitehorse trough and adjacent terranes three dimensional first arrival tomographic inversion is used to constrain lithology to 800 1200 m depth and surface structures are extrapolated into the middle crust using the coincident reflection data in the yukon tanana terrane the metasedimentary snowcap assemblage is characterized by velocities of 4 5 5 5 km s while in quesnellia velocities of 5 0 6 0 km s occur at 500 m depth and probably represent igneous rocks of the tatchun batholith across the whitehorse trough velocities 4 0 km s correspond to clastic rocks of the jurassic laberge and triassic lewes river groups velocities 4 0 km s probably present the clastic jurassic to cretaceous tantalus formation several near surface units with velocities of 2 0 3 0 km s are identified some correlate well with volcanic rocks of the upper cretaceous carmacks group but others could be attributable to alluvial deposits or faulting the b

the effect of streambed topography on surface subsurface water exchange in mountain catchments a numerical hydrological simulation suggested that water exchange between stream channels and adjacent aquifers is enhanced by convexities and concavities in streambed topography at st kevin gulch an effluent stream in the rocky mountains of colorado subsurface hydraulic gradients and movement of ionic tracers indicated that stream water was locally recharged into well defined flow paths through the alluvium stream water filled flow paths in the alluvium referred to as substream flow paths returned to the stream a short distance downstream 1 to 10 m recharge to the substream flow paths occurred where stream water slope increased at the transition from pools 1 to steeper channel units 5 20 return of substream flow paths to the stream occurred where stream water slope decreased at the transition from steeper channel units to pools a net water flux calculation is typically used to characterize water and solute fluxes between surface and subsurface zones of catchments along our study reach at st kevin gulch the net inflow of water from subsurface to stream 1 6 ml s 1 m 1 underestimated the gross inflow 2 7 ml s 1 m 1 by 40 the influence of streambed topography is to enhance hydrological fluxes between stream water and subsurface zones and to prolong water sediment contact times these effects could have important consequences for solute transport retention and transformation in catchments

jurassic location of the yukon tanana terrane from palaeomagnetism of the folded mississippian tatlmain batholith and ragged stock

evolution of the yukon tanana terrane evidence from southeastern yukon territory the yukon tanana terrane ytt in southeastern yukon consists predominantly of a mid paleozoic volcanic plutonic arc assemblage built on continental crust the ytt had experienced strong deformation and metamorphism by late triassic time by mid cretaceous the metamorphic complex and late triassic clastic rocks derived from it were imbricated with middle and upper paleozoic ophiolitic sheets the ytt differs markedly from adjacent parts of the north american continental margin in both its depositional and tectonic histories the composition and tectonic history of the ytt is comparable to that of the kootenay and barkerville terranes of southern and central british columbia from which the ytt may have been displaced

transfer of nonsorbing solutes to a streambed with bed forms theory a theoretical analysis of the exchange of nonsorbing solutes between a permeable streambed and the overlying water of a stream or river is presented in this paper in a companion paper elliott and brooks this issue the results of experimental studies of such exchange are presented the analysis focuses on water movements into within and out of the bed which result from the presence of bed forms ripples and dunes and highlights the mechanisms of pumping and turnover pumping is the movement of fluid through the bed induced by steady dynamic pressure variations over bed forms turnover occurs as moving bed forms trap and release interstitial fluid the detailed analysis was used to generate the distribution of the residence time of solute within the bed which can be used to calculate the net mass exchange due to pumping and turnover

convective transport within stable river sediments local pressure variations of the order of 100 1000 n m2 can be observed between the upstream and downstream faces of the typically triangular shaped dunelike sediment structures that form at the sediment water interface of rivers laboratory experiments were conducted examining the influence of this localized pressure variation on contaminant transport processes within the sediment numerical modeling of the in bed flow via boundary element methods was also undertaken in order to predict convective transport under typical field conditions the laboratory experiments and numerical simulation of the in bed flow in several rivers verified that the pressure distribution observed on the sediment surface and the resulting interstitial fluid convection can control transport of chemically inert nonsorbed contaminants in stable sediments in bed peclet numbers were of the order of 100 1000 indicating the negligible influence of diffusion under the conditions examined

timing of high pressure metamorphism in the yukon tanana terrane canadian cordillera constraints from u pb zircon dating of eclogite from the teslin tectonic zone zircon from eclogite near last peak in the teslin tectonic zone yielded a u pb isotopic age of 269 2 ma 2 the first precise age for such a rock in the yukon tanana terrane of the canadian cordillera both the morphology and geochemistry of the eclogitic zircons indicate a metamorphic origin and the u pb age therefore constrains the timing of peak high pressure metamorphism in this rock the u pb age demonstrates for the first time that an early permian high pressure metamorphic event occurred in rocks now making up the teslin tectonic zone and possibly elsewhere in the yukon tanana terrane this u pb age provides a new geochronologic pin in the evolution of the yukon tanana terrane prior to its mesozoic accretion to the north american continental margin and combined with recent 40ar 39ar muscovite data indicates that high pressure metamorphism at this time was a relatively short lived event

the slide mountain terrane and the structural evolution of the finlayson lake fault zone southeastern yukon the finlayson lake fault zone forms a fundamental but little studied tectonic boundary between strata of autochthonous north america and the accreted slide mountain and yukon tanana terranes in southeastern yukon a structural and petrologic study was undertaken to examine the depositional environment of the slide mountain terrane its tectono thermal evolution in the fault zone and its relationship with the yukon tanana terrane the slide mountain and yukon tanana terranes are divisible into units dominated by metavolcanic and metasedimentary rocks field observations and whole rock geochemistry indicate that slide mountain greenstone is ocean floor basalt deposited in a deep submarine basin with a proximal terrigenous sediment influx either a marginal or ocean basin setting is supported by the data slide mountain greenstone is thrust northeastward over metasedimentary rocks of slide mountain terrane and southwestward over rocks of the yukon tanana terrane regional metamorphic grade ranges from su

the 3d geophysical investigation of a middle cretaceous to paleocene regional decollement in the cordillera of northern canada and alaska

structural divergence and transpression in the teslin tectonic zone southern yukon territory the structural and tectonic evolution of the teslin tectonic zone a complex belt of ductilely deformed rocks forming the southern extension of the yukon tanana terrane in the northern canadian cordillera is elucidated with new field data and by the reinterpretation of existing data the zone includes greenschist to amphibolite facies metasedimentary and metaplutonic rocks of the nisutlin and anvil assemblages characterized by s and l s tectonite fabrics primary contact relationships and ages show that most rocks in the zone were contiguous by mississippian time mapping identified a number of strain domains which preserve s fabrics dipping northeasterly or southwesterly variable mineral lineation orientations and a variety of shear directions including easterly and westerly vergent thrust shear down to the east and down to the west normal shear and dextral strike slip shear regional constraints and microstructures suggest that latest ductile deformation was late triassic to early jurassic in age structural characteristics are explained most effectively by convergent dominated transpression in combination with tectonic wedging and associated back thrusting above a low angle west dipping detachment oblique eastward and upward movement of the rocks over the detachment which may have coincided with the top of thinned north american continental crust produced easterly vergent shear and localized or widespread tectonic wedging and back thrusting produced westerly vergent shear the transpressive deformation postdates formation of the nisutlin assemblage by mississippian time and subduction of the slide mountain ocean beneath the nisutlin assemblage in permian to early triassic time the western margin of the teslin tectonic zone was truncated by cretaceous strike slip faults and translated northward rocks of the peraluminous orthogneiss assemblage of the yukon tanana terrane in central yukon acted as the tectonic wedge and were overthrust by rocks of the nisutlin and anvil assemblages in early jurassic time before unroofing by local extension in cretaceous time

precambrian crust beneath the mesozoic northern canadian cordillera discovered by lithoprobe seismic reflection profiling 1 the cordillera in northern canada is underlain by westward tapering layers that can be followed from outcrops of proterozoic strata in the foreland belt to the lowermost crust of the orogenic interior a distance of as much as 500 km across strike they are interpreted as stratified proterozoic rocks including 1 8 0 7 ga supracrustal rocks and their basement the layering was discovered on two new deep seismic reflection profiles in the yukon line 3 650 km and northern british columbia line 2 1245 km in two segments that were acquired as part of the lithoprobe slave northern cordillera lithospheric evolution snorcle transect in the mackenzie mountains of the eastern yukon the layering in line 3 is visible between 5 0 and 12 0 s 15 to 36 km depth it is followed southwestward for nearly 650 km 500 km across strike and thins to less than 1 0 s 3 0 3 5 km thickness near the moho at the yukon alaska international boundary in the northern rocky mountains of british columbia the upper part of the layering on line 2 correlates with outcrops of proterozoic 1 76 1 0 ga strata in the muskwa anticlinorium at this location the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for 700 km 300 km across strike it disappears as a thin taper at the base of the crust 150 km east of the coast of the alaskan panhandle the only significant disruption in the layering occurs at the tintina fault zone a late to postorogenic strike slip fault with up to 800 km of displacement which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles 300 km apart the base of the layered reflection zone coincides with the moho which exhibits variable character and undulates in a series of broad arches with widths of 150 km in general the mantle appears to have few reflections however at the southwest end of line 3 near the alaska british columbia border a reflection dips eastward from 14 0 s to 21 0 s 45 to 73 km depth beneath exposed eocene magmatic rocks it is interpreted as a relict subduction surface of the kula plate our interpretation of proterozoic layered rocks beneath most of the northern cordillera suggests a much different crustal structure than previously considered 1 ancient north american crust comprising up to 25 km of metamorphosed proterozoic to paleozoic sediments plus 5 10 km of pre 1 8 ga crystalline basement projects westward beneath most of the northern canadian cordillera 2 the lateral 500 km by at least 1000 km and vertical up to 25 km extent of the proterozoic layers and their internal deformation are consistent with a long lived margin for northwestern north america with alternating episodes of extension and contraction 3 the detachments that carry deformed rocks of the mackenzie mountains and northern rocky mountains are largely confined to the upper crustal region above the layering 4 accreted terranes include thin klippen that were thrust over north american pericratonic strata e g yukon tanana and terranes such as nisling and stikinia that thicken westward as the underlying proterozoic layers taper and disappear 5 the ages of exposed rocks are not necessarily indicative of the ages of underlying crust a frequent observation in lithoprobe interpretations so that estimates of crustal growth based on surface geology may not be representative

nina creek group and lay range assemblage north central british columbia remnants of late paleozoic oceanic and arc terranes in north central british columbia a belt of upper paleozoic volcanic and sedimentary rocks lies between mesozoic arc rocks of quesnellia and ancestral north america these rocks belong to two distinct terranes the nina creek group of the slide mountain terrane and the lay range assemblage of the quesnel terrane the nina creek group is composed of mississippian to late permian argillite chert and mid ocean ridge tholeiitic basalt formed in an ocean floor setting the sedimentary and volcanic rocks the mount howell and pillow ridge successions respectively form discrete generally coeval sequences interpreted as facies equivalents that have been interleaved by thrusting the entire assemblage has been faulted against the cassiar terrane of the north american miogeocline west of the nina creek group is the lay range assemblage correlated with the harper ranch subterrane of quesnellia it includes a lower division of mississippian to early pennsylvanian sedimentary and volcanic rocks some with con

cobalt and nickel concentrations in the komatiite component of apollo 16 polymict samples reply to r l korotev abstract we agree with korotev that the abundances of siderophiles in apollo 16 breccias are anomalously large but do not accept his hypothesis that they were supplied by the impact of a hitherto unknown type of meteorite possessing a grossly non chondritic composition co ni and other siderophiles in apollo 16 breccias display systematic relationships which imply that a substantial proportion of these siderophiles were present as oxidised species in the lunar crust prior to the impacts of chondritic type meteorites with the lunar surface these pre existing indigenous lunar siderophiles were reduced to the metallic state to varying degrees during impact bombardment and became alloyed with chondritic meteoritic metal in this manner the metallic particles of complex and unusual compositions now present at the a16 site were formed the indigenous siderophiles present in the a16 crust prior to meteoritic bombardment may themselves have been derived from two distinct sources one endogenous and the other exogenous the first corresponds to basic and ultrabasic magmas formed by partial melting of the moon s deep interior which were erupted and then and intimately mixed into the lunar crust the latter represents basic and ultrabasic material ejected from the earth s primitive crust by early meteorite bombardment which then fell upon the lunar surface the siderophiles present in each of these components display terrestrial like abundance patterns because they are both ultimately of terrestrial origin the anomalously high abundances of siderophiles at the a16 site may reflect an important contribution from ejected terrestrial material overall the siderophile abundance patterns present in lunar highland breccias represent mixtures of terrestrial and chondritic components

paleozoic and mesozoic high pressure metamorphism at the margin of ancestral north america in central yukon eclogite and blueschist in the yukon tanana and slide mountain terranes in the yukon and alaska preserve a partial record of middle paleozoic late paleozoic and early mesozoic subduction and subsequent unroofing near faro eclogites are commonly mylonitized and partially retrogressed the analysis of fe mg exchange between garnet and clinopyroxene suggests temperatures t in the 400 500 c range for eclogite and jadeite 40 mol quartz suggest minimum pressures p of 11 13 kilobar at that temperature range clinopyroxene garnet epidote quartz suggest pressure near 15 kilobar p h 2 o p s eclogite near last peak which contains brown hornblende late stage oligoclase and biotite yielded p t estimates up to 625 c at a minimum pressure of 14 kilobar eclogite near ross river yielded temperatures near 525 c and a minimum pressure near 13 kilobar the previously proposed permian triassic age of high pressure tectonism for the entire yukon tanana terrane in the yukon was inferred from isotopic dating of one eclogite and one blueschist in separate localities in this study isotopic 40 ar 39 ar analysis of white mica from eclogite in the simpson range yielded a date of 344 1 ma eclogite and blueschist from ross river yielded white mica 40 ar 39 ar dates of 267 3 ma and 273 3 ma respectively white mica in eclogite from faro was dated at 260 3 ma white mica in two eclogites from stewart lake about 2 km apart yielded 40 ar 39 ar dates of 228 1 ma and 346 3 ma white mica in last peak eclogite for which a concordant u pb zircon date is 269 ma yielded an integrated date of 236 1 ma overprinting in the blueschist facies and final cooling in some localities predated eclogite metamorphism in others the cooling ages indicate significant plate convergence as early as carboniferous time and either the existence of more than one subduction zone or continuous convergence and episodic exhumation above a single zone when this is considered together with the range of ages of other high pressure occurrences the north american cordillera is seen to be characterized by multiepisodic and diachronous high pressure metamorphism

effects of current bed form induced fluid flow on the thermal regime of sediments 1 heat transport associated with current bed form fluid exchange affects biogeochemical and ecological process in a variety of aquatic settings we simulate turbulent flow over dunes induced darcy flow in sediments and sediment heat transport forced by a diel variation of water column temperature heat conduction dominates when the water column current cannot induce rapid fluid exchange heat advection becomes important with increasing sediment permeability and or current velocity resulting in a complicated space time temperature pattern weak temperature variations are found beneath dune crests where water upwells out of the sediments strong variations are located below dune stoss faces where water downwells the relative dominance of heat conduction versus advection is captured by a global peclet number that depends on dune geometry and hydrodynamic and thermal properties including the period of thermal forcing thermally induced fluid viscosity variations cause periodic but nonsymmetric changes in fluid flux through the sediments but do not significantly influence temperature patterns

geology and juxtaposition history of the yukon tanana slide mountain and cassiar terranes in the glenlyon area of central yukon in central yukon the pericratonic yukon tanana terrane yt is juxtaposed with the cassiar terrane ct parautochthonous north america along the tummel fault zone tfz a 3 4 km wide northwest trending belt comprising imbricate fault slices of slide mountain terrane sm greenstone chert serpentinite and synorogenic clastic rocks north east of the tfz the ct comprises paleozoic metapelitic rocks marble and amphibolite of continental margin affinity to the southwest the yt consists of a pre late devonian metasedimentary complex overlain and intruded by mississippian clastic volcanic and plutonic successions of continental arc affinity in the tfz middle to late permian ocean floor basalt of the sm shows evidence of crustal contamination suggesting deposition at the edge of a marginal ocean basin deformation features in the tfz include early ductile fabrics overprinted by younger brittle structures triassic synorogenic clastic rocks in the tfz and at the base of a klippen above the yt suggest that terrane imbrication began shortly after the early triassic 40 ar 39 ar mica ages from the region suggest cooling of the yt sm and part of ct below 300 c by early jurassic time pervasive brittle structures in the ragged lake klippe which roots into the tfz indicate brittle thrusting of the sm over the ct in post triassic time early cretaceous plutons intrude the ct glenlyon batholith and the tfz leucogabbro and impose a contact aureole that extends westward into the yt steep brittle structures that deformed the tfz also affect in part the glenlyon batholith but do not significantly offset its contact aureole consequently little displacement can have occurred along the tfz after early cretaceous time

geophysical investigation and reconstruction of lithospheric structure and its control on geology structure and mineralization in the cordillera of northern canada and eastern alaska a reconstruction of the tintina fault is applied to regional geophysical and topographic data facilitating the definition of west trending lineaments within the lower crust and or mantle lithosphere oblique to the nw trending structure of the cordilleran terranes the lineaments which exhibit a range of geophysical and geological signatures are interpreted to be related to the liard transfer zone continuous to the denali fault that divided lower and upper plates during late proterozoic cambrian rifting of the laurentian margin three dimensional gravity models show a density increase in the lower crust and mantle lithosphere to the north the transfer zone also divides bimodal mantle xenolith suites to the south from unimodal suites to the north these conclusions suggest that extended north american basement related to laurentian margin rifting that would have brought mantle lithosphere rocks to a shallow depth continuously underlies a thin carapace of accreted terranes in western yukon and eastern alaska the interpreted continuity of north american basement reaffirms that if oroclinal bending of the intermontane terranes occurred then it was prior to its emplacement upon the rifted basement examination of the spatial relationships between mineral occurrences and postaccretionary cretaceous lithospheric lineaments from their manifestation in geophysical geological and topographic data suggest that the late proterozoic lineaments influenced mesozoic mineralization through influence on the development of the shallow crustal structure intrusion and exhumation and erosion

structural and kinematic evolution of the teslin suture zone yukon record of an ancient transpressional margin abstract the teslin suture zone tsz yukon which forms the fundamental boundary between rocks deposited along the ancient margin of north america and allochthonous terranes to the west preserves a complex history of pre mid jurassic convergence and dextral strike slip translation which is overprinted locally by late cretaceous dextral strike slip shear the tsz comprised of a 15 20 km thick structural sequence of ductilely deformed sedimentary and volcanic strata basalt peridotite and granitoids is divisible into distinct elongate structural domains based on the distribution of two well defined but differently oriented stretching lineations lds and lss lds and lss both formed during non coaxial ductile deformation lds trends e w and plunges down dip whereas lss trends nnw sse and plunges shallowly two 1 2 km wide nnw trending anastomosing shear zones of lss cross cut lds structures indicating lss is younger other field relations indicate further that lds began forming earlier than lss followed by a period of coeval lds and lss formation latest motion was dominantly parallel to lss synkinematic mineral assemblages associated with both lds and lss related structures record greenschist to albite epidote amphibolite facies conditions lds tectonites record a complex movement history to the west textural asymmetries indicate west side down or normal shear whereas in eastern domains top to the east thrust style asymmetries dominate lss tectonites consistently record dextral or top to the north shear parallel to lss tectonic motion began as chiefly penetrative dip slip shear lds at a high angle to the present trend of the tsz and evolved to dominantly dextral strike slip shear lss parallel to the trend of the zone the geometry kinematics and sequence of deformation in tsz tectonites evoke a general model of terrane accretion during oblique plate convergence involving initial shortening at a high angle to the convergent margin and progression to margin parallel translation

determining in channel dead zone transient storage by comparing solute transport in a bedrock channel alluvial channel sequence oregon 1 current stream tracer techniques do not allow separation of in channel dead zone e g eddies and out of channel hyporheic transient storage yet this separation is important to understanding stream biogeochemical processes we characterize in channel transient storage with a rhodamine wt solute tracer experiment in a 304 m cascade pool type bedrock reach with no hyporheic zone we compare the solute breakthrough curve btc from this reach to that of an adjacent 367 m alluvial reach with significant hyporheic exchange in the bedrock reach transient storage has an exponential residence time distribution with a mean residence time of 3 0 hours and a ratio of transient storage to stream volume of 0 14 demonstrating that at moderate discharge bedrock in channel storage zones provide a small volume of transient storage with substantial residence time in the alluvial reach though pools are similar in size to those in the bedrock reach transient storage has a power law residence time distribution with a mean residence time of 100 hours estimated at nearly 1200 hours and a ratio of storage to stream volume of 105 because the in channel hydraulics of bedrock reaches are simpler than alluvial step pool reaches the bedrock results are probably a lower end member with respect to volume and residence time though they demonstrate that in channel storage may be appreciable in some reaches these results suggest that in stream dead zone transient storage may be accurately simulated by exponential rtds but that hyporheic exchange is better simulated with a power law rtd as a consequence of more complicated flow path and exchange dynamics