correlation and provenance of upper cretaceous campanian fluvial strata utah u s a from zircon u pb geochronology and petrography abstract detrital zircon and petrographic provenance analysis of upper cretaceous campanian strata corroborate correlation of the fluvial kaiparowits formation in southern utah with post castlegate strata of the mesaverde group in eastcentral utah sandstone samples of the kaiparowits formation in the kaiparowits plateau and mesaverde group neslen bluecastle tongue of castlegate farrer and tuscher formations in gray canyon north of green river utah contain six u pb detrital zircon age populations ranging in age from archean to late cretaceous thrust belt derived sublitharenite and quartzarenite of the lower part of the mesaverde group neslen and bluecastle lack or have only rare mesozoic grains but contain abundant archean proterozoic and paleozoic grains that record recycling of proterozoic paleozoic and jurassic sandstones exposed in uplifted thrust sheets to the west south and southwest derived feldspathic litharenite of the kaiparowits and farrer formations contains proterozoic grains and a diverse population of mesozoic grain ages archean grains are rare to absent maximum depositional ages interpreted from young zircon grains in two kaiparowits samples statistically overlap 40ar 39ar ages 76 74 ma from interbedded bentonitic tuffs and weighted mean ages of young grains from the farrer formation kolmogorov smirnoff statistics in conjunction with young grain ages and detrital age spectra corroborate petrographic evidence which indicates that the kaiparowits rivers were connected northward with a river system that deposited the farrer formation the young grain ages although imprecise indicate that the uppermost mesaverde group strata of the tuscher formation are younger than the kaiparowits formation and record partitioning of the former foreland basin by laramide uplifts

base level buffers and buttresses a model for upstream versus downstream control on fluvial geometry and architecture within sequences abstract the effects of downstream base level control on fluvial architecture and geometry are well explored in several broadly similar sequence stratigraphic models cretaceous dakota group strata u s western interior have characteristics reflecting combined downstream and upstream base level controls that these models cannot address particularly three layers of amalgamated channel belt sandstone within this group thicken and are continuous for distances 300 km along dip that stretch the reasonable lengths for which these models are intended to apply as well architecture in up dip reaches records repeated valley scale cut and fill cycles this contrasts with equivalent strata down dip which record channel scale lateral migration with no such valley scale cycles apparent we here introduce the concept of buffers and buttresses to address these observations we assume that river longitudinal profiles are each anchored down dip to some physical barrier e g the sea strand etc that we refer to as a buttress buttress shift is considered the primary downstream control on base level profiles extrapolated up dip from the buttress over any modeled duration of buttress shift can range widely because of high frequency variability in upstream base level controls e g discharge etc all these potential profiles however are bounded above by the profile of highest possible aggradation and below by the profile of maximum possible incision these upper and lower profiles are buffers and they envelop the available fluvial preservation space thickness of the buffer zone is determined by variability in upstream controls and should increase up dip to the limit of downstream profile dominance dakota valley scale surfaces record repeated cut and fill cycles driven by up dip controls and are confined between thick stable buffers equivalent strata down dip record lateral reworking within a thinner channel scale buffer zone that was positioned by downstream controls regression exposed slopes similar to the buffer zone thus buffers were stable for long distances and durations this prompted dip extensive lateral reworking of strata into upstream valley scale and downstream channel scale sheets buffers and buttresses provide a broadly applicable model for fluvial preservation that captures upstream vs downstream base level controls on geometry and architecture the model lends general insights into dip oriented variations in fluvial architecture production of sheet vs lens geometry total preservation volumes for fluvial systems and variations in these factors related to contrasting climatic conditions and basin physiography the model can be amended to existing sequence stratigraphic approaches in order to capture dip oriented variations in sequence architecture

integrated climate model oxygen isotope evidence for a north american monsoon during the late cretaceous abstract during the late cretaceous western north america was characterized by a close geographic association between the sevier highlands and the western interior seaway in this paper an atmospheric general circulation model agcm is used to simulate the impact of this geographic association on surface pressure wind direction and precipitation and it is predicted that seasonal changes in these variables resulted in a strong monsoon along the eastern flank of the sevier highlands confirmation that these model simulations are accurate is provided by isotopic data from foreland basin sediments in particular oxygen isotope records from different environments large rivers small streams and ponds and proxies unionid bivalve shells and paleosol carbonates indicate that foreland basin streams were recharged by local precipitation with high oxygen isotope ratios while large trunk rivers were recharged by high elevation precipitation this hydrologic pattern is observed from alberta to utah and is consistent with east to west monsoonal air mass movements and associated seasonal rainfall recognition of a highland driven monsoon has implication in regard to studies of fossil taphonomy of water vapor transport and of links between climate and mountain uplift and exhumation in this region

high resolution water column survey to identify active sublacustrine hydrothermal discharge zones within lake rotomahana north island new zealand abstract autonomous underwater vehicles were used to conduct a high resolution water column survey of lake rotomahana using temperature ph turbidity and oxidation reduction potential orp to identify active hydrothermal discharge zones within the lake five areas with active sublacustrine venting were identified 1 the area of the historic pink terraces 2 adjacent to the western shoreline subaerial steaming cliffs boiling springs and geyser 3 along the northern shoreline to the east of the pink terrace site 4 the newly discovered patiti hydrothermal system along the south margin of the 1886 tarawera eruption rift zone and 5 a location in the east basin northeast of patiti island the pink terrace hydrothermal system was active prior to the 1886 eruption of mount tarawera but venting along the western shoreline in the east basin and the patiti hydrothermal system appear to have been initiated in the aftermath of the eruption similar to waimangu valley to the southwest different combinations of turbidity ph anomalies both positive and negative and orp responses suggest vent fluid compositions vary over short distances within the lake the seasonal period of stratification limits vertical transport of heat to the surface layer and the hypolimnion temperature of lake rotomahana consequently increases with an average warming rate of 0 010 c day due to both convective hydrothermal discharge and conductive geothermal heating a sudden temperature increase occurred during our 2011 survey and was likely the response to an earthquake swarm just 11 days prior

facies analysis of the kosi megafan deposits abstract the kosi river shows distinct changes in its channel pattern from chatra where the river enters the indogangetic plains to kursela where it joins the ganga river i e gravelly sandy braided zone 1 sandy braided zone 2 and straight zone 3 to meandering zone 4 facies analysis of the kosi channel deposits suggests that in zones 1 and 2 mid channel bars islands side bars 3 d dunes and various types of linguoid dunes are the most common features large linguoid dunes with lengths of up to 1 km and with superimposed smaller 3 d dunes are also common the deeper parts of the channel are probably characterized by longitudinal bars in zone 1 and sandwaves in zone 2 lateral accretion of sandy bars is a significant process in these zones zone 3 is characterized by side bars with deposition by lateral accretion as on point bars linguoid dunes may migrate up a side bar or move across it subparallel to the main channel thalweg the uppermost sedimentary sequence 8 10 m thick of the kosi megafan consists of mainly sands and minor gravels in the proximal northern half and sand and mud 45 vol in the distal southern half of the megafan this downfan trend reflects the change from braided to straight channel pattern numerous spring fed streams rework the surficial sediments of the megafan and produce a fining upward sequence up to 4 7 m thick on top of braided straight channel deposits of the megafan

fluvial form in modern continental sedimentary basins distributive fluvial systems comment weissmann et al 2010 1 discuss what they term distributary fluvial systems dfs to address a key question in the earth sciences what modern systems are appropriate analogues to the rock record they conclude since dfss dominate depositional patterns in all continental sedimentary

sandstone body variability in the medial distal part of an ancient distributive fluvial system salt wash member of the morrison formation utah u s a abstract plan view exposures of the salt wash member of the morrison formation in central utah provide unique insights into the characteristics of fluvial sandstone bodies associated with ancient distributive fluvial systems dfs here we use field based observations and data from an unmanned aerial vehicle and structure from motion photogrammetry to document and interpret sandstone bodies across a 10 km2 area from the medial distal portion of the salt wash dfs we divide the fluvial sandstone bodies into four distinct groups very narrow narrow and medium width sandstone bodies as well as an additional classification of other sandstones very narrow sandstone bodies are 100 m and poorly exposed the sandstone bodies record a portion of the dfs that was occupied by fluvial channels with multiple orientations sizes and plan view morphologies similar to the variety of channels observed on modern dfs because the fluvial deposits are composed of distinct sandstone body types mean values from the combined data set tend to obscure important aspects of the depositional history cyclical deposits in the salt wash member suggest that autogenic processes were important in this region consistent with modern dfs overall dfs depositional models derived from regional scale studies provide an excellent framework for interpreting dfs strata however smaller scale details of these deposits particularly the variability in sandstone body orientations are not addressed by existing models

tidal current effects on temperature in diffuse hydrothermal flow guaymas basin a twelve day record of temperature collected from the diffuse flow area of a guaymas basin hydrothermal site exhibits variations from a minimum of 3 05 c to a maximum of 4 87 c whose periodicity is correlated with tides measured at the nearby town of guaymas a simple model based on the hypothesis that temperature variations result as changes in tidal bottom currents induce changes in the height of the thermal boundary layer is in good quantitative agreement with observed temperatures for most of the record the success of this model illustrates that the effects of tidal currents can be strong enough to dominate the time variability of a temperature signal at a fixed point in hydrothermal flow therefore tidal currents must be taken into account when using temperature measurements to estimate time varying heat fluxes from hydrothermal diffuse flow regions

integrating sandstone petrology and nonmarine sequence stratigraphy application to the late cretaceous fluvial systems of southwestern utah u s a abstract petrographic and dispersal data are essential to correct interpretation of mechanisms that create continental sequence stratigraphic architecture a case study from southern utah demonstrates that upper cretaceous upper santonian campanian alluvial successions in the southernmost part of the cordilleran foreland basin were deposited by fluvial systems of contrasting drainage directions and provenance and suggests that different mechanisms governed their sequence architecture most of the rivers flowed northeast subparallel to the basin foredeep less common fluvial systems flowed to the east southeast the fluvial sandstones fall naturally into four petrofacies 1 quartzofeldspatholithic mean qt61f19l20 2 feldspatholithic qt29f19l52 3 quartzolithic qt75f6l20 and 4 quartzose qt99f1l1 petrofacies 1 and 2 were derived from mixed supracrustal and basement sources to the southwest and south respectively whereas petrofacies 3 and 4 were derived from uplifted thrust sheets of the sevier orogenic belt to the southwest and west respectively only the east southeast flowing rivers transported the quartzose petrofacies the fluvial strata which include the uppermost straight cliffs wahweap and kaiparowits formations form two large scale stratigraphic successions typically interpreted as continental stratigraphic sequences hundreds of meters thick each succession begins with an amalgamated braided fluvial deposit grades to mudstone rich strata with low sandstone body connectivity and culminates in highly connected sandstone bodies with multistory stacking the basal amalgamated deposits of each succession are architecturally similar but their compositional and dispersal characteristics are different quartzofeldspatholithic quartzolithic and quartzose sandstones above the lower base level shift are variable but generally similar in compositional and dispersal characteristics to both underlying and overlying strata a phenomenon termed here congruence in contrast quartzose amalgamated fluvial sandstone above the upper base level shift differs sharply in composition and dispersal direction from underlying and overlying lithic rich strata the foredeep axis controlled the progradation direction of the congruent shift which was likely driven by climatically induced sediment influx a eustatic fall or both in the case of the incongruent shift increased sediment supply permitted the rivers to cross the foredeep temporal association of the upper amalgamated deposit with active structures in the thrust belt and foreland basin indicates that syntectonic thrust uplift not isostatic uplift or climate caused the influx of quartz

facies control on sandstone composition and influence of statistical methods on interpretations in the john henry member straight cliffs formation southern utah usa abstract the upper cretaceous john henry member of the straight cliffs formation preserves regressive shoreface and channel facies and transgressive lagoonal tidal inlet facies that suggest distinct modal sandstone compositions detrital modes from six sandstone facies upper shoreface lower shoreface deflected mouth bars fluvial channels tidal inlets and washover fans and their spatial and temporal variations provide additional data regarding the depositional environments and setting of the john henry member three statistical methods were utilized univariate standard deviation and confidence interval and multivariate logratio transformations to assess the compositional difference between facies using estimation of means both univariate statistical methods have some inherent problems standard deviation does not account for sample size while the confidence interval method incorporates a t test to account for only some of the uncertainty of small sample size the results of the univariate methods differ slightly and both indicate statistically distinct sandstone compositions based on facies multivariate statistics are much more robust and suggest similar trends yet display different compositional means and have inconclusive confidence fields as they incorporate all of the uncertainty associated with small sampling sizes in general sandstone compositions become more quartz rich and compositionally mature as sediment is transported from proximal fluvial environments to distal upper shoreface environments this trend reflects the degree of preferential reworking or winnowing of unstable grains prior to lithification more complicated relationships are observed as facies distributions shift through space and time sandstone compositions support a deflected wave dominated deltaic interpretation for the john henry member in this area sandstone compositions become more lithic rich from north to south corresponding to the facies distribution of upper shoreface and deflected mouth bars respectively mouth bars occur at the intersection of the fluvial channel and the coastline where sand is deflected via longshore drift to the southern portion of the field area upper shoreface facies located further away from mouth bar facies are heavily reworked by wave processes and contain more mature quartz rich modal compositions additionally high feldspathic and lithic concentrations in tidal inlet facies suggest that this facies was sourced closer to mouth bars rather than updrift upper shoreface sediments a shift in sandstone composition occurs at the end of the second transgressive regressive cycle of the john henry member throughout the rogers canyon area this compositional change is concurrent with a relatively large basinward shift in facies which suggests that it reflects the transition from regressive to transgressive facies associated with the relative sea level fall rather than a change in the main sediment source area

fluid density control on vapor liquid partitioning of metals in hydrothermal systems hot aqueous fluids both vapor and saline liquid are primary transporting media for metals in hydrothermal magmatic systems despite the growing geological evidence that the vapor phase formed through boiling of magmatic ore bearing fluids can selectively concentrate and transport metals the physical chemical mechanisms that control the metal vapor liquid fractionation remain poorly understood we performed systematic experiments to investigate the metal vapor liquid partitioning in model water salt gas systems h2o nacl kcl hcl at hydrothermal conditions measurements show that equilibrium vapor liquid fractionation patterns of many metals are directly related to the densities of the coexisting vapor and liquid phases despite differences in the vapor phase chemistry of various metals that form hydroxide chloride or sulfide gaseous molecules of contrasting volatile properties water solute interaction is a key factor that controls the metal transfer by vapor like fluids in earth s crust these findings allow quantitative prediction of the vapor liquid distribution patterns and vapor phase metal transport in a wide range of conditions our density model accounts well for the vapor brine distribution patterns of na si fe zn as sb and ag observed in fluid inclusions from magmatic hydrothermal deposits for au and cu the partitioning in favor of the liquid phase predicted in a sulfur free system contrasts with the copper and gold enrichment observed in natural vapor like inclusions the formation of stable complexes of cu and au with reduced sulfur may allow for their enhanced transport by sulfur enriched magmatic hydrothermal vapors

spatial and temporal evolution of coastal depositional systems and regional depositional process regimes campanian western interior seaway u s a abstract this paper provides a critical review and regional synthesis of late cretaceous shallow marine deposits along part of the western margin of the western interior seaway of north america which contains the most extensively documented outcrop based studies of siliciclastic coastal depositional systems in the world the results of this synthesis are presented in the form of paleogeographic maps covering present day new mexico utah colorado and wyoming usa for five timeslices in the campanian these maps are used to evaluate the spatial and temporal evolution of regional depositional process regimes along a large 1000 m stretch of coastline the evolution of regional depositional process regimes is linked to tectonic and paleoceanographic controls on the western interior seaway which enables the results of this synthesis to be applied to prediction of depositional process regimes in other less intensively studied basins six gross depositional environments have been mapped for each timeslice 1 alluvial to coastal plain sandstones 2 coastal plain coals mudstones and sandstones 3 shoreline sandstones 4 marine mudstones 5 gravity flow siltstones and sandstones and 6 marine marls and chalk shoreline sandstones in each timeslice are interpreted in further detail using documented evidence for the three principal classes of depositional process wave tidal and fluvial and published reconstructions of coastal morphology which is widely considered to reflect depositional process regime based on these interpretations shoreline sandstones are assigned to five categories of depositional process regime 1 regressive wave dominated shorefaces and delta fronts 2 regressive river dominated delta fronts 3 regressive mixed tide and wave influenced delta fronts 4 regressive tide dominated delta fronts and 5 transgressive barrier islands back barrier lagoons and estuaries the accuracy of and uncertainty in classification of depositional process regime are critically evaluated additionally stratal thickness and sediment routing pathways have been interpreted in order to assess the impact of tectonic and paleoceanographic controls on spatial and temporal changes in all of the evaluated shallow marine successions thin tide influenced intervals were deposited in back barrier and lagoon systems associated with net transgressive shorefaces and estuaries however it is notable that all preserved tide dominated and tide influenced regressive deltaic systems are located along the northern margin of the utah bight a tectonically related embayment that had a pronounced expression during the middle campanian the southern margin of the embayment and coastlines to the north are conspicuously more wave dominated which supports their exposure to a larger wave fetch in contrast the northern margin of the embayment was relatively wave protected it is concluded that tidal range was amplified due to resonance of the principal semidiurnal tide in the strongly embayed geometry of the middle campanian utah bight

flexural subsidence and basement tectonics of the cretaceous western interior basin united states the flexural subsidence history recorded in cenomanian to early campanian 97 to 80 ma strata in the cretaceous u s western interior basin was studied with two dimensional flexural backstripping techniques results indicate that the flexural subsidence resulting from thrust loading was superimposed on epeirogenic subsidence in the foreland basin the flexural component exhibits significant spatial and temporal variations along both the strike and dip relative to the sevier thrust belt the greatest cumulative subsidence occurred in southwestern wyoming and northern utah concurrent subsidence in northwestern montana and southern utah was insignificant temporal trends in subsidence also show a distinct regional pattern from the cenomanian to late turonian 97 to 90 ma subsidence rates were high in utah and much lower in wyoming and montana in contrast during the coniacian and santonian 90 to 85 ma subsidence accelerated rapidly in wyoming increased slightly in montana and decreased in utah we suggest that these spatially and temporally varying subsidence patterns reflect the interplay of several geodynamic factors including 1 temporal and spatial variation in emplacement of the thrust loads 2 segmentation of the basement into adjacent blocks with different rheological properties 3 reactivation of basement fault trends and 4 regional dynamic topographic effects

in situ measurement of dissolved chloride in high temperature hydrothermal fluids abstract the ability to continuously monitor chemical properties of hydrothermal vent effluents for extended periods of time is essential to understanding dynamic processes responsible for the temporally variable nature of mid ocean ridge hydrothermal systems although instruments do exist for some parameters there has been no sensor capable of measuring the chloride concentration an indicator of possible phase separation on a real time and long term basis in this article we discuss the construction of a novel instrument which measures solution resistance as a proxy for chloride concentration the sensor consists of four gold electrodes embedded in a cylindrical zro 2 ceramic housing it has been successfully deployed in several high temperature vents at the main endeavour field mef on the juan de fuca ridge in the ne pacific and calibrated under simulated hydrothermal conditions ranging up to 380 c and 300 bar the in situ data clearly demonstrate a tidal influence on the effluent from some high temperature vents possibly relating to a subsurface mixing process involving non seawater end members non tidal changes are used to constrain the sequence and type of controls operating on fluids circulating within the subsurface

tide influenced acidic hydrothermal system offshore ne taiwan elemental sulfur and hydrogen sulfide emitted offshore of northeastern taiwan known to local fishermen for generations but never studied until recently are found to have originated from a cluster of shallow 92 with small amounts of h2s helium isotopic ratios 7 5 times that of air indicate that these gases originate from the mantle high temperature hydrothermal fluids have measured temperatures of 78 116 degrees c and ph 25 degrees c values as low as 1 52 likely the lowest to be found in world records low temperature vents 30 65 degrees c have higher ph values continuous temperature records from one vent show a close correlation with diumal tides suggesting rapid circulation of the hydrothermal fluids c 2005 elsevier b v all rights reserved

rare earth element distribution in 400 c hot hydrothermal fluids from 5 s mar the role of anhydrite in controlling highly variable distribution patterns abstract two submarine hydrothermal vent fields at 5 s mid atlantic ridge mar turtle pits and comfortless cove emanate vapor phase fluids at conditions close to the critical point of seawater 407 c 298 bars in this study the concentration and distribution of rare earth element ree and yttrium y has been investigated independent of the major element composition the fluids display a strong temporal variability of their ree y concentrations and relative distributions at different time scales of minutes to years chondrite normalized distributions range from common fluid patterns with light ree enrichment relative to the heavy ree accompanied by positive eu anomalies type i to strongly ree y enriched patterns with a concave downward distribution with a maximum enrichment of sm and weakly positive or even negative eu anomalies type ii the larger the sum of ree the smaller cecn ybcn and eu eu we also observed a strong variability in fluid flow and changing fluid temperatures correlating with the compositional variability as evident by the positive correlation of total ree ca and sr concentrations in turtle pits and comfortless cove fluids precipitation dissolution of hydrothermal anhydrite controls the variability in ree concentrations and distributions in these fluids and the transformation of one fluid type to the other the variable distribution of ree can be explained by the accumulation of particulate anhydrite with concave downward ree distribution and negative eu anomaly into a fluid with common ree distribution type i followed by the modification of the ree fluid signature due to dissolution of incorporated anhydrite a second model in which the type ii fluids represent a primary ree reaction zone fluid pattern which is variably modified by precipitation of anhydrite can also explain the observed correlations of total ree fractionation of lree hree and size of eu anomaly as well as ca sr the emanation of such a fluid may be favored in a young hydrothermal system in its high activity phase with short migration paths and limited exchange with secondary minerals however this model is not as well constrained as the other and requires further investigations the strongly variable ree fluid signature is restricted to the very hot actively phase separating hydrothermal systems turtle pits and comfortless cove at 5 s and has not been observed at the neighboring red lion vent field which continuously emanates 350 c hot fluid and displays a stable ree distribution type i

anomalous clastic wedge development during the sevier laramide transition north american cordilleran foreland basin usa new high resolution regional correlation and isopach maps provide evidence that 1 laramide style deformation began as early as ca 77 ma in central utah and 2 rapid 208 km m y 1 and extensive 400 km progradation of a clastic wedge was facilitated by reduced subsidence during the transition from sevier to laramide style deformation this study defi nes three campanian alluvialto marine clastic wedges that traversed 200 400 km eastward across the utah colorado segment of the cordilleran foreland basin wedges a and c are thicker successions with rising trajectory shoreline stacking patterns blackhawk formation and lower castlegate sandstone bluecastle tongue and rollins sandstone that refl ect relatively slow overall progradation 50 81 km m y 1 of narrow 10 20 km wide wave dominated shorelines in contrast wedge b consists of lower volume successions with a fl at to falling shoreline stacking pattern middle castlegate sandstone sego sandstone neslen formation corcoran and cozzette members of the iles formation that suggests rapid progradation 208 km m y 1 of embayed 60 80 km wide mixed energy wave and tide infl uenced shore lines wedges a and c prograded 200 250 km in more than 3 m y whereas wedge b prograded 340 400 km in 2 m y 170 km m y 1 the anomalously extensive wedge b is unique in the utah colorado segment because of its long extent rapid progradation rate dominance of tidally infl uenced facies long transit transgressions regressions and low accommodation nested sequence architecture stratigraphic relationships indicate development of wedge b coeval with both sevier and laramide style deformation in utah assuming a constant sediment supply the extensive 300 400 km sheet like amalgamated wedge wedge b may have been caused by 1 reduced subsidence driven by a fl exural interference pattern whereby two short wavelength 200 km fl exural profi les are superimposed during the uplift of both basement cored and thin skinned thrust belt 2 an increase in or eastward migration of dynamic subsidence during tectonic transitions associated with slab fl attening or rollback i e long wavelength fl exure or 3 reduced subsidence due to short wavelength fl exural interference augmented by the reduction or migration of long wavelength fl

thrusting and gravel progradation in foreland basins a test of post thrusting gravel dispersal the use of gravels as syntectonic indicators of thrusting has recently been questioned by foreland basin models that assign gravels to a post thrusting interval of progradation except in very proximal areas on the basis of precise temporal control provided by magnetostratigraphically dated sections the history of gravel progradation after a major thrusting and uplift event in the northwestern himalaya is shown to be a virtually syntectonic phenomenon despite considerable crustal subsidence driven by a thick skinned thrust gravels prograded approximately 70 km during a 1 5 m y long thrusting event by 3 m y after the start of thrusting gravels extended more than 110 km into the basin although delayed gravel progradation appears appropriate for many rocky mountain foreland basins it is clearly not valid for the himalaya the authors attribute the difference in depositional response between these basins to difference in the quantity of sediment supplied to them sediment starved vs overfilled the availability of resistates in the source area and the size of the antecedent drainage

late cretaceous fluvial megafan and axial river systems in the southern cordilleran foreland basin drip tank member of straight cliffs formation and adjacent strata southern utah u s a abstract the upper cretaceous lower campanian drip tank member of the straight cliffs formation in the grand staircase region of southern utah is an upward coarsening sandstone rich low sinuosity fluvial deposit in the cordilleran foreland basin the drip tank member thins from 75 m to 30 m eastward across the basin foredeep approximately parallel to its dominant eastward sediment dispersal direction and thins southward along the foredeep to as little as 17 m near its southern outcrop extent along modern cliff lines it overlies and underlies mudstone rich fluvial strata of the john henry member of the straight cliffs formation and lower member of the wahweap formation respectively both of which were deposited by northeast flowing rivers the john henry drip tank contact lies in an interfingering progradational stratigraphic transition from medium grained lenticular sandstone bodies to tabular coarse grained amalgamated sandstone bodies the contact with the overlying wahweap formation is locally a prominent surface of erosion or sediment reworking sandstone petrography and detrital zircon age populations of the strata indicate detrital sources in basement south of the foreland basin thrust sheets to the west and magmatic arc rocks to the southwest the uppermost part of the john henry member contains as much as 10 feldspar and abundant 1 84 1 60 ga detrital zircons derived from yavapai mazatzal basement rocks in the mogollon highlands the drip tank member ranges from quartzarenite to chert bearing sublitharenite with grenville 1 2 1 1 ga neoproterozoic and early paleozoic detrital zircons derived from proterozoic through jurassic strata exposed in the sevier orogenic belt lower member wahweap litharenites contain abundant thrust belt derived detrital carbonate grains absent from compositionally mature drip tank sandstones as well as a broad range of zircon ages the drip tank member constitutes deposits of a sand rich fluvial megafan or distributive fluvial system that displaced a subjacent but partly time equivalent axial fluvial system eastward as the megafan driven in part by seasonally high discharge fed by monsoonal precipitation prograded across the basin foredeep a thick amalgamated fan axis succession present in northern exposures contrasts with a thinner fan flank succession in southern localities tabular sixth order lithosomes each containing channels on the order of 7 m deep define three individual fluvial fans or fan lobes in the megafan system younger wahweap fluvial channels eroded uppermost drip tank deposits of the fan axis and fan flank transverse fan progradation across the foredeep recorded falling accommodation sediment supply in an aggradational to progradational systems tract erosion and reworking of the upper fan surface record decreased accommodation sediment bypass and erosion prior to reoccupation of the foredeep by the wahweap axial fluvial system the upper contact of the drip tank member is thus the primary sequence boundary in this multi component fluvial system and the lower wahweap represents transitional systems tract deposits accumulated as accommodation sediment supply increased

a tidal influenced hydrothermal system temporarily cooled by a tropical storm abstract the lutao hydrothermal field is an intertidal arc volcanic system located offshore southeast taiwan hosting a zhudanqu zdq vent and a huwaichi hwc spring with strongly contrasting fluid chemistry low mg moderately enriched cl and h with respect to seawater indicate that the zdq endmember was derived from the brine phase that was formed during low degree subcritical phase separation in contrast the endmember for the hwc vent fluids is related to the vapor phase temperature and pressure of the phase separation were estimated as 150 c and 7 bar respectively the water rock ratio was roughly calculated as about 2 the lutao hydrothermal system was slightly affected by semi diurnal tides by some combination of tidal loading and tidal currents the time delay between tides and the response of the hydrothermal system was about 3 h while freshwater was almost absent in the hwc vent fluids at normal conditions the typhoon fung wong on sep 21st 2014 led to intrusions of freshwater into the vent fluids with a percentage of 16 both the zdq and the hwc endmember compositions showed some changes after the typhoon event suggesting a cooling of the reaction zone after the typhoon passed by the hydrothermal system began to recover evidenced by increasing percentages of the hwc endmember and decreasing freshwater contributions the flux of the hwc endmember was estimated as 460 560 l h 1 based on these observations this study for the first time reports a shallow depth tidal influenced hydrothermal system that was temporarily cooled by a tropical storm

quartz solubility in the two phase and critical region of the nacl kcl h2o system implications for submarine hydrothermal vent systems at 9 50 n east pacific rise abstract experiments were performed to investigate quartz solubility in cl bearing aqueous solutions at temperature 365 430 c and pressure conditions 219 381 bars near and within the two phase region of the nacl kcl h2o system dissolved sio2 concentrations increased with pressure along a given isotherm although the magnitude of this decreased with increasing proximity to the two phase boundary upon intersection of the two phase boundary however significant concentrations of dissolved sio2 characterized vapor rich fluids at both subcritical and supercritical conditions for these fluids dissolved silica concentrations ranged from 2 81 to 14 6 mmolal increasing with dissolved chloride concentration the experimental data permit regression of a density based relationship taking account of non ideal activity concentration effects which can be used to better constrain temperatures and pressures from dissolved sio2 and chloride in high temperature vent fluids at mid ocean ridges accordingly pressure and temperature conditions in subseafloor hydrothermal reaction zones at 9 50 n east pacific rise epr were estimated applying data from this experimental study to interval 1991 2002 and new field data 2004 results indicate reaction zone at conditions ranging from 420 to 430 c at 600 to 1500 m below seafloor thus conditions predicted for 9 50 n east pacific rise epr vent fluids suggest that supercritical phase separation might be more common than previously thought

modeling of cretaceous foreland basin parasequences utah with implications for timing of sevier thrusting computer modeling suggests that thrusting order can be discriminated on the basis of foreland basin geometry and parasequence stacking patterns the position of sequential thrust sheets relative to the basin affects the amount and distribution of subsidence source terrain elevation and distance from the shoreline and sediment transport into the basin for this study a forward numerical model was constructed to quantitatively simulate the interaction of geologic processes active in the foreland basin setting including thrusting and orogenic development lithospheric flexure orogenic denudation sediment transport across the coastal plain and nearshore deposition in order to isolate the effects of tectonics and sediment supply on nearshore deposition eustatic sea level is held constant model runs simulate two different thrusting sequences foreland stepping in sequence and hinterland stepping out of sequence when in sequence thrusting is modeled sediment is trapped in intra orogen basins because sediment is prevented from reaching the shoreline the basin is underfilled when out of sequence thrusting is modeled sediment is transported from the orogen to the shoreline episodes of thrusting result in subsidence and marine flooding surfaces and resulting accommodation space allows for parasequence development comparing model output to stratigraphy observed in eastern utah suggests that late cretaceous out of sequence uplift and thrust loading resulted in aggradational and progradational parasequence stacking in the campanian blackhawk formation this result supports the theory that the pavant thrust system was active prior to deposition of the blackhawk formation and that the location of thrust shortening shifted toward the hinterland prior to or during blackhawk formation deposition

eco geochemical dynamics of a shallow water hydrothermal vent system at milos island aegean sea eastern mediterranean shallow water hydrothermal vents are extreme environments that share many characteristics with their deep sea analogs however despite ease of access much less is known about the geochemical dynamics of these ecosystems here we report on the spatial and temporal geochemical dynamics of a shallow water vent system at paleochori bay milos island greece our multi analyte voltammetric profiles of dissolved o2 and hydrothermal tracers e g fe2 fesaq mn2 on sediment cores taken along a transection in hydrothermally affected sediments indicate three different areas the central vent area highest temperature with a deeper penetration of oxygen into the sediment and a lack of dissolved fe2 and mn2 a middle area 0 5 m away rich in dissolved fe2 and mn2 exceeding 2 mm and high free sulfide with potential for microbial sulfide oxidation as suggested by the presence of white mats at the sediment surface and finally an outer rim area 1 1 5 m away with lower concentrations of fe2 and mn2 and higher signals of fesaq indicating an aged hydrothermal fluid contribution in addition high frequency temperature series and continuous in situ h2s measurements with voltammetric sensors over a 6 day time period at a distance 0 5 m away from the vent center showed substantial variability in temperature 31 6 to 46 4 c and total sulfide 488 to 1329 m in the upper sediment layer the analysis of these data suggests that tidal and wind forcing and abrupt geodynamic events generate intermittent mixing conditions lasting for several hours to days despite substantial variability the concentration of sulfide available for chemoautotrophic microbes remained high however the availability of electron acceptors originating from seawater might be more intermittent which in turn has an effect on the reestablishment of the white mats after wave induced disturbances our results emphasize the importance of transient events in the development of chemoautotrophic communities in the hydrothermally influenced sediments of paleochori bay

isotopic geochemical and temporal characterization of proterozoic basement rocks in the quitovac region northwestern sonora mexico implications for the reconstruction of the southwestern margin of laurentia a detailed geochemical characterization of 19 representative proterozoic basement rocks in the quitovac region in northwestern sonora mexico has identified two distinct paleoproterozoic basement blocks that coincide spatially with the previously proposed caborca and north america blocks new u pb zircon geochronology revises their age ranges the caborca 1 78 1 69 ga and north america 1 71 1 66 ga blocks at quitovac and precludes a simple age differentiation between them in addition grenvillian age granitoids ca 1 1 ga spatially associated with the caborca block have been identified at quitovac nd isotopes and major and trace element geochemistry support the distinction of these paleoproterozoic blocks granitoids of the north america block are characterized by depleted end values 3 4 3 9 and younger nd model ages 1800 1740 ma and have lower k 2 o y rb ba th ree and fe mg values than coeval rocks of the caborca block the caborca block granitoids are likewise characterized by slightly less depleted end 0 6 2 6 and older nd model ages 2070 1880 ma despite the subtle differences granitoids from both the caborca and north america blocks exhibit island arc like affinities we propose that the proterozoic basement rocks from the quitovac region are an extension of the proterozoic crustal provinces in the southwestern united states specifically rocks of the caborca block exhibit an affinity to rocks of either the yavapai province or the mojave yavapai transition zone whereas rocks of the north america block have signatures similar to those of the mazatzal province or possibly the yavapai province of arizona the new isotopic ages and geochemical data do not support the existence of the late jurassic mojave sonora megashear at quitovac as originally proposed however the quitovac region accounts only for a small fraction of the proterozoic basement in sonora so these findings do not eliminate the possibility of a megashear elsewhere in northern sonora our new data create the possibility of alternative hypotheses for the distribution of paleoproterozoic crustal provinces in southwestern north america that affect reconstructions of the original southwestern margin of laurentia and reduce uncertainties in the configuration timing and existence of the proterozoic supercontinent rodinia

kosi megafan historical records geomorphology and the recent avulsion of the kosi river abstract it has been proposed that the kosi river continuously migrated 113 km westward across the surface of the megafan over the last two centuries examination of a number of old maps published between 1760 and 1960 shows that during most of this period the kosi river occupied a position slightly east of the megafan axis the apparent channel movement shown in these maps is oscillating in nature and not unidirectional instead of encountering deposits left behind by a sweeping braided kosi like stream a preliminary study of the uppermost 2 5 m succession in the north central part of the megafan reveals overwhelming dominance of meandering stream deposits assuming the existing notion of kosi river migration the rate of deposition averaged over 100 200 years for the uppermost 5 10 m of megafan deposits works out to be unusually high 50 mm y all these observations question the soundness of the hypothesis of rapid westward migration of the kosi river over the last two centuries the existing facies model for the uppermost 8 10 m of the megafan deposits also appears untenable the three dimensional geometry of the kosi megafan is similar to those of typical alluvial fans but with much gentler gradient 0 05 0 01 and with larger area 10 000 km 2 based mainly on the patterns of paleo and modern channels recognised in the satellite images three major accretionary lobes can be identified on the kosi megafan relative age of the lobes determined from the truncating relationship of the paleochannels indicates a random shift of the trunk channel forming these lobes similar multilobate form and evidences of random switching of the loci of lobe aggradation are also found to be common in the tista and taquari megafans the factors known to favour avulsion and the results of the recent simulation studies of alluvial deposits are inconsistent with the notion of unidirectional shift of the channels for more than 100 km across the entire megafan surface this study suggests that the relocation of the kosi river in the past was through random nodal avulsion rather than systematic unidirectional shift the recent avulsion of the kosi channel by a large distance to the east follows this expected pattern further study and age dating is required for a comprehensive understanding of the depositional dynamics of the megafan and the pattern of channel movement on it future flood predictions and disaster management plans should be based on such comprehensive understanding

river systems and their sediment flux indo gangetic plains northern bihar india river systems of part of the himalayan foreland northern bihar plains india are described in terms of their channel morphology hydrology and suspended sediment characteristics a simple classification of the river systems based mainly on the source area characteristics is proposed i mountain fed ii foothills fed iii plains fed and iv mixed fed rivers distinct differences are noted between these classes of river systems most rivers show evidence of channel movement mainly by avulsion but cut offs also occur locally the mountain fed rivers are characterized by very high discharge and low suspended sediment concentration and the plains fed rivers have relatively low discharge and high suspended sediment concentration the foothill fed rivers have moderate values of discharge and suspended sediment concentration the mountain fed rivers have built megafans of large extent whereas the foothills fed and plains fed rivers have formed muddy interfan areas semi quantitative estimates of water and sediment flux suggest that about 99 9 of the mass transfer into the plains is water with the remaining 0 1 being sediment and that 10 s of the latter 0 01 of the total is retained in the basin the remainder being transferred to the bengal fan

trace element partitioning between vapor brine and halite under extreme phase separation conditions abstract experiments were conducted to investigate the partitioning of li br rb cs and b between vapor brine and halite during subcritical and supercritical phase separation in the nacl h2o system 388 550 c 250 350 bars results indicate that li and br partition preferentially into the low salinity vapor fluids while rb and cs become more enriched in the coexisting brines under more extreme conditions of pressure and temperature in the two phase region especially near the vapor brine halite boundary strong salting out effects imposed on neutral aqueous species enhance significantly partitioning of all trace elements into the low salinity fluid dissolved boron is strongly affected by this and a particularly strong enrichment into vapors is observed a trend that can be effectively correlated with changes in reduced density exclusion of li br rb cs and b from halite when precipitated further increases the solubility of these species in the coexisting cl poor fluid in general the lack of distortion in the partitioning behavior of trace elements between vapor brine and or halite with the transition from subcritical to supercritical conditions in the nacl h2o system precludes the need for special reference to the critical point of seawater when interpreting phase relations in submarine hydrothermal systems the combination of experimentally determined trace element partitioning data with constraints imposed by mineral solubility provides a means to better understand the origin and evolution of hot spring vent fluids for example in brandon hydrothermal system 21 s epr supercritical phase separation and subseafloor mixing appear to be the main heat and mass transport mechanisms fueled by a shallow magmatic intrusion with boron systematics ruling out major contributions from magmatic degassing processes accompanying the near seafloor volcanism

correlation of jurassic eolian strata between the magmatic arc and the colorado plateau new u pb geochronologic data from southern arizona mature quartz rich sandstone interbedded with mesozoic magmatic arc strata in southern arizona has been previously considered correlative with the eolian pleinsbachian to toarcian navajo sandstone on the colorado plateau new u pb zircon data from the mount wrightson formation in the santa rita mountains and from the strata of cobre ridge in the pajarito mountains and in the arivaca area in southern arizona support the hypothesis that sand derived from the navajo sandstone probably did gain access to the magmatic arc and further indicate that sands extending from younger eolian units on the colorado plateau are probably present as well the mount wrightson formation accumulated from 190 ma to 170 ma corresponding to late pleinsbachian to aalenian time time scale of harland 1990 isotopic ratios from zircon fractions from the lower member of the mount wrightson formation define a discordia line with lower intercept of 184 8 ma the lower member is approximately coeval with the 188 2 ma piper gulch monzonite dated by asmerom and others 1990 which intrudes it the middle and upper members of the formation yield somewhat less precise dates that indicate deposition between 183 2 ma and 170 ma quartz rich sandstone occurs in all three members though most abundantly in the middle and upper members and in many places contains sedimentary structures diagnostic of eolian sedimentation our results suggest that sands related to lower jurassic navajo ergs and middle jurassic temple capergs gained access to the arc the age of the strata of cobre ridge is 170 5 ma eighteen fractions taken from three samples of the tuff lie in a cluster near concordia a best fit age of 169 ma is based on near concordance of one fraction and on model discordia trajectories using assumed upper intercepts sandstone horizons interbedded within the strata of cobre ridge in many cases contain sedimentary structures diagnostic of eolian sedimentation and although quartz rich in general have more volcanic detritus than sandstones in the mount wrightson formation the interval between 165 175 ma corresponds to the aalenian and bajocian stages and is within the time span represented by the temple cap and page sandstones of southern utah and northern arizona sandstone interstratified with the strata of cobre ridge may be correlative with either of those units the possibility cannot be discounted however that unconsolidated or weathered navajo equivalent sands from the upper member of the mount wrightson formation were recycled into the strata of cobre ridge these results support the models busby spera 1988 riggs and busby spera 1990 1991 suggesting that during early to middle jurassic time the magmatic arc in southern arizona was low standing and did not constitute an impediment to the south and southwestward movement of continental sediments we suggest that much of the region between the colorado plateau and the arc was topographically low and that tectonic and volcanic basins within the arc provided traps for windblown mature sands for as long as 35 m y we speculate that early to middle jurassic tectonic subsidence within the magmatic arc may have been more continuous than subsidence on the colorado plateau thus providing a depocenter in which major tectonically induced unconformities that characterize the mesozoic record in the back arc are masked by ongoing volcanic activity

shifting of the kosi river northern india the kosi river shifts laterally over the himalaya foreland plain by continual minor cutoffs and bank cutting and by episodic major shifts across watersheds by moving into and then out of preexisting adjacent less actively aggrading streams migration is unidirectional because after a channel is filled to instability floodwater will drain preferentially into a new adjacent low rather than across it to the next watershed or back to the last abandoned channel major shifts seem stochastic and autocyclic they do not correlate with the many severe quakes and floods that undoubtedly helped prime the system for shifts

the castlegate sandstone of the book cliffs utah sequence stratigraphy paleogeography and tectonic controls abstract earlier stratigraphic work had predicted that at the type section of the castlegate formation the castle gate near price utah the unit consists of two sequences separated by a sequence boundary representing approximately one million years of unrecorded time although the type section is well exposed it consists of a monotonous succession of braided fluvial sandstones and no obvious boundary can be identified using facies criteria this is a good example of a cryptic sequence boundary petrographic data indicate however a significant change in detrital composition 20 m above the base of the section at a through going erosion surface that is therefore interpreted as the sequence boundary revised sequence correlations together with other petrographic data and regional paleocurrent patterns provide the basis for a model of the paleogeographic evolution of the area rocks assigned to the castlegate sandstone comprise two or possibly three sequences formed at times of slow regional subsidence erosional sequence boundaries and tilts in paleoslope between each sequence record thrust loading and unloading of the basin and the growing influence of intrabasinal upwarps movement of which was beginning to be affected by laramide movements toward the end of castlegate sedimentation

tracing submarine hydrothermal inputs into a coastal bay in baja california using radon abstract hydrothermal fluid fluxes into deep ocean environments can be obtained from heat balance approaches however in shallow systems hydrothermal heat fluxes can be masked by solar heating in this paper we use radon 222rn as a naturally occurring geochemical tracer to map the location of hydrothermal fluid inputs as well as low temperature groundwater discharges and quantify fluxes into concepcion bay baja california mexico this fault bound bay contains intertidal seeps with salinities ranging from 5 3 to 25 6 temperatures reaching 64 c and nitrate reaching 900 m the bay is subject to natural eutrophication and frequent red tide events a detailed 222rn survey around the 100 km perimeter of concepcion bay allowed us to map the location of enhanced submarine groundwater inputs moorings at three contrasting coastal sites indicated that radon concentrations were higher at low tide and during the winter modeled hydrothermal fluid inputs ranged between 0 4 cm day in the middle of the bay and 43 9 cm day at the largest hydrothermal coastal seep site apparently faults allow meteoric water to be heated and serve as conduits for its subsequent discharge through permeable marine sediments when conservatively extrapolated to the entire bay using weighted distributions these fluxes are estimated at 17 5 m3 s a flow much higher than local ephemeral rivers about 42 of the fluxes described consisted of fresh groundwater with the remaining made up of recirculated seawater new nitrogen inputs associated with groundwater pathways are estimated to directly account for at least 15 of the local primary productivity our combined spatial survey time series strategy can be very useful to quantify hydrothermal fluid inputs in particular at vent sites where a temperature signal in shallow surface waters is difficult to be observed

sequence stratigraphy of nonmarine jurassic cretaceous rocks central cordilleran foreland basin system an analysis of the upper jurassic lower cretaceous morrison and cedar mountain formations of utah and colorado has resulted in a general sequence stratigraphic model for nonmarine rocks in this model nonmarine deposition is governed by changes in basin accommodation development and corresponding shifts in depositional base level these fluctuations result in deposition of systematically varying facies and architectural elements that allow nonmarine depositional sequences to be recognized internally nonmarine depositional sequences comprise three systems tracts degradational transitional and aggradational which are analogous to the lowstand transgressive and highstand systems tracts of marine depositional sequences degradational systems tracts overlie sequence bounding unconformities and consist of relatively coarse grained low sinuosity fluvial deposits that are either contained within incised valleys or deposited as widespread thin sheets above shallow erosion surfaces transitional systems tracts represent an increase in basin accommodation development following degradational systems tract deposition they are marked by the transition from laterally continuous low sinuosity fluvial channel sandstones and conglomerates to lenticular and ribbon like meandering and anastomosing channel sandstones aggradational systems tracts are characterized by meandering anastomosing channel sandstones and abundant fine grained overbank and lacustrine deposits the upper jurassic lower cretaceous nonmarine rocks of the study area contain three depositional sequences the first of these the uj 1 sequence consists primarily of an aggradational systems tract overlain by a sequence bounding unconformity however the lower parts of this sequence are transitional with older marine rocks and can be considered the late stages of a marine highstand systems tract the upper morrison sequence uj 2 consists of degradational transitional and aggradational systems tracts above the uj 2 sequence are a sequence bounding unconformity and degradational and transitional systems tracts of the lk 1 sequence represented by the buckhorn conglomerate the buckhorn is overlain by a sequence bounding unconformity and transitional aggradational systems tracts of the lk 2 sequence that is composed of the upper part of the cedar mountain formation the upper jurassic lower cretaceous sequences in utah and colorado can be traced regionally and correlated with nonmarine depositional sequences in central utah and sequences that contain nonmarine transitional and marine rocks in central wyoming these sequences were deposited in the back bulge forebulge and distal foredeep depozones of the late jurassic early cretaceous foreland basin system

architecture and formation of transgressive regressive cycles in marginal marine strata of the john henry member straight cliffs formation upper cretaceous of southern utah usa marginal marine deposits of the john henry member upper cretaceous straight cliffs formation were deposited within a moderately high accommodation and high sediment supply setting that facilitated preservation of both transgressive and regressive marginal marine deposits complete transgressive regressive cycles comprising barrier island lagoonal transgressive deposits interfingered with regressive shoreface facies are distinguished based on their internal facies architecture and bounding surfaces two main types of boundaries occur between the transgressive and regressive portions of each cycle i surfaces that record the maximum regression and onset of transgression bounding surface a and ii surfaces that place deeper facies on top of shallower facies bounding surface b the base of a transgressive facies bounding surface a is defined by a process change from wave dominated to tide dominated facies or a coaly shelly interval indicating a shift from a regressive to a transgressive regime the surface recording such a process change can be erosional or non erosive and conformable a shift to deeper facies occurs at the base of regressive shoreface deposits along both flooding surfaces and wave ravinement surfaces bounding surface b these two main bounding surfaces and their subtypes generate three distinct transgressive regressive cycle architectures i tabular shoaling upward marine parasequences that are bounded by flooding surfaces ii transgressive and regressive unit wedges that thin basinward and landward respectively and iii tabular transgressive lagoonal shales with intervening regressive coaly intervals the preservation of transgressive facies under moderately high accommodation and sediment supply conditions greatly affects stratigraphic architecture of transgressive regressive cycles acknowledging variation in transgressive regressive cycles and recognizing transgressive successions that correlate to flooding surfaces basinward are both critical to achieving an accurate sequence stratigraphic interpretation of high frequency cycles

provenance of upper cretaceous paleogene sandstones in the foreland basin system of the sierra madre oriental northeastern mexico and its bearing on fluvial dispersal systems of the mexican laramide province sandstone petrography and detrital zircon u pb analysis of upper cretaceous paleogene sandstones in the foreland basin of the sierra madre oriental in northeastern mexico indicate long distance sediment transport from arc basement and thrust belt sources lying to the west northwest and south the basin fill termed the difunta group consists of sublitharenites litharenites feldspathic litharenites and lithic arkoses derived from mixed sources that included sedimentary rocks magmatic arc rocks and subordinate basement rocks six age populations comprise the detrital zircon content of the sandstones proterozoic 1900 900 ma early paleozoic 500 400 ma late paleozoic early triassic 288 235 ma jurassic 180 151 ma early cretaceous 150 111 ma and late cretaceous paleogene 110 54 ma these grains were derived from several arc terranes ranging in age from permian to paleogene in western mexico and the southwestern united states from sedimentary rocks and possibly interbedded tuffs of the sierra madre oriental orogen and from basement sources or their derivative sandstones of the southwestern united states the petrographic and geochronologic provenance data corroborate existing models for derivation of much foreland detritus from arc sources to the west identify the sierra madre orogen itself as an important source for sediment and these data modify the late cretaceous paleogene paleogeography of mexico to include a long orogen parallel fluvial system with headwaters in the southwestern united states the difference in average ages of the youngest grains in the sandstones and their inferred depositional ages is 10 5 m y indicating that the initial coarse fill of the foreland basin was derived from early laramide uplift and eastward arc migration in northwestern mexico and the southwestern united states

a synthetic stratigraphic model of foreland basin development the processes of erosion and deposition must be included in foreland basin models to predict correctly basin geometry and stratigraphy we present a synthetic stratigraphic model of the development of nonmarine foreland basins that predicts progressive geometry topography and facies patterns in the model steady crustal shortening occurs according to a wedgethickening model erosion and deposition follow a diffusive process and the lithosphere is compensated elastically erosion and deposition are controlled by the transport coefficients r of the diffusion equation for a range of thrust velocities and lithospheric rigidities transport coefficients are of order 102 103 m yr in the mountain belt these values are much higher than those derived from the study of scarp degradation in the sedimentary basin transport coefficients of order 104 m2 yr are appropriate and are compatible with previous studies of fluvial and deltaic deposition rapid thrusting results in a narrow underfilled basin while slow thrusting results in a wide overfilled basin in addition by varying the erosional and depositional transport coefficients while holding other parameters constant we generate both overfilled and underfilled basins these results suggest that changes in the rate of thrust loading the climate or the source rock lithology can create stratigraphic signatures that have been interpreted to record viscoelastic relaxation of the lithosphere clearly to understand either the long term behavior of the lithosphere or to interpret orogenic history from preserved foreland strata the manner in which a basin was filled must be considered we apply the model to the evolution of the modern sub andean foreland and find that an erosional transport coefficient of 3000 m2 yr and a depositional transport coefficient of 20 000 m2 yr successfully predict the observed basin geometry

basin scale predictive models of alluvial architecture constraints from the palaeocene eocene bighorn basin wyoming usa this work was supported by phase 2 of the fluvial systems research group bp bg chevron conocophillips and total ae thanks the university of aberdeen for additional funding and mgms thanks the sao paulo research foundation fapesp 2014 13937 3 the authors also wish to thank numerous residents of the bighorn basin for their kind hospitality and access to land and isobel buchanan and alistair swan for assistance in the field the authors also thank reviewers luca colombera and sian davies vollum and ae christopher fielding for helpful comments on this manuscript

controls on synorogenic alluvial fan architecture beartooth conglomerate palaeocene wyoming and montana late palaeocene uplift of the beartooth range in northwestern wyoming and southwestern montana generated the beartooth conglomerate along the eastern and northeastern flanks of the range systematic unroofing sequences and intraformational unconformities folds and faults in the conglomerate attest to deposition during uplift along the eastern flank at least three ancient alluvial fan systems and a braidplain system can be distinguished on the bases of petrofacies and lithofacies the two southern fans consist of 700 m of sedimentary clast conglomerate and subordinate sandstone dominated by hyperconcentratedflow and stream flow facies the next fan to the north is dominated by plutonic and metamorphic clasts and contains abundant mud matrix supported debris flow facies as well as stream flow facies the northernmost depositional system consists of arkosic channellized fluvial conglomerate and sandstone overbank mudstone and crevasse splay sandstone units palaeocurrent data indicate eastward dispersal away from the beartooth range outstanding exposure of the beartooth conglomerate allows facies to be mapped on lateral photographic mosaics a seven fold hierarchy of bounding surfaces and enclosed lithosomes exists in the beartooth conglomerate first through fourth order surfaces are analogous to first through fourth order surfaces that recently have been documented in sandy fluvial facies with one exception sediment gravity flows are bounded by first order surfaces fifth order surfaces are either erosional e g lateral migration of fanhead trench or accretionary e g aggradation of fan surface during backfilling of trench and construction of lobes on lower fan during entrenchment on upper fan some fifth order surfaces coincide with intraformational angular unconformities and are thus the result of long term fanhead entrenchment following uplift of the upper part of the fan sixth order surfaces bound individual fan packages that are several hundred metres thick and 10 km2 in area the enclosed sixth order lithosomes are distinguishable in terms of petrofacies and lithofacies a single seventh order surface bounds the entire beartooth conglomerate lower order lithosomes are produced by intrinsic processes of fan construction fifth order lithosomes can be attributed to both extrinsic and intrinsic controls sixth and seventh order lithosomes are generated by extrinsic controls

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

modeling the effects of tidal loading on mid ocean ridge hydrothermal systems 1 tidal signals are observed in numerous time series measurements obtained from mid ocean ridge hydrothermal systems in some instances these tidal signals are clearly the result of ocean currents but in other instances it appears that the signals may originate in the subseafloor formation in order to explore the effect of ocean tidal loading on mid ocean ridge hydrothermal systems we apply a one dimensional analytical model of tidal loading on a poroelastic half space and develop a two dimensional numerical model of tidal loading on a poroelastic convection cell the one dimensional models show that for a reasonable range of fluid elastic and hydrological properties the loading efficiency may vary from near zero to near unity and the diffusive penetration depth for tidal pressure signals may vary from tens of meters to kilometers the two dimensional models demonstrate that tides may generate significant vertical and horizontal pressure gradients in mid ocean ridge hydrothermal systems as a result of spatial variations in fluid temperatures and the elastic and hydrological properties of the crust these continuum models predict that outflow temperature perturbations will be very small 10 4 c but in real systems where the continuum hypothesis does not always apply the perturbations may be on the order of 0 1 c the models predict relatively large perturbations to fluid velocity at the seafloor for high temperature vents the outflow perturbations normalized to the mean flow velocity increase as the permeability decreases flow reversals at the seafloor are predicted in some regions of net low temperature outflow and net inflow during the tidal cycle in the subseafloor tidally induced flow perturbations are likely to significantly enhance mixing and fluid exchange below the seafloor in regions of slow flow and in regions where there are strong gradients in temperature or in the mechanical and hydrological properties of the crust tidally enhanced mixing and fluid exchange may significantly influence the extent and character of microbial production in the subseafloor

provenance of impure calclithites in the laramide foreland of southwestern montana abstract the sphinx conglomerate is an uppermost cretaceous and paleocene synorogenic clastic wedge derived from a laramide uplift in southwestern montana conglomerate petrology documents unroofing of the thick phanerozoic section that covered the uplift the active tectonic setting resulted in close correspondence between source lithologies and derived conglomerates and sandstones sandstone detrital modes determined using the gazzi dickinson point counting method further document the unroofing sequence all sphinx sandstones consist of mixtures of siliciclastic and carbonatoclastic detritus detrital modes correspond to the recycled orogenic provenance of other workers in addition to these general modal compositions vertical trends in qfl q and qfl l and in proportions of types of sedimentary lithic fragments mimic trends in the inverted phanerozoic stratigraphic section total quartz q decreases upsection in the sphinx corresponding to decreases of both sandstone the only source for qm and chert source for qp in the inverted phanerozoic section upward increases occur in unstable lithic fragments in the sphinx and in carbonate units in the inverted phanerozoic section carbonate sedimentary lithic fragments lsc increase vertically in proportion to silicic sedimentary lithic fragments lss and chert qp fragments again mimicking the inverted phanerozoic section detailed modal analysis of recycled orogenic sandstones should include study of subcategories of sedimentary lithic fragments for example qplsslsc and qlsslsc plots standard qfl and qplvmlsm plots are useful in assessing the overall tectonic setting of foreland sandstones but are insensitive to temporal changes in source areas supracrustal sources contribute most or all of the detritus to foreland sandstones therefore proportions of sedimentary lithic fragments record tectonic and erosional processes in source areas through time

direct observation of the evolution of a seafloor black smoker from vapor to brine a single hydrothermal vent f vent occurring on very young crust at 9 16 8 n east pacific rise was sampled in 1991 and 1994 in 1991 at the measured temperature of 388 c and seafloor pressure of 258 bar the fluids from this vent were on the two phase curve for seawater these fluids were very low in chlorinity and other dissolved species and high in gases compared to seawater and most sampled seafloor hydrothermal vent fluids in 1994 when this vent was next sampled it had cooled to 351 c and was venting fluids 1 5 times seawater chlorinity this is the first reported example of a single seafloor hydrothermal vent evolving from vapor to brine the 1991 and 1994 fluids sampled from this vent are compositionally conjugate pairs to one another these results support the hypothesis that vapor phase fluids vent in the early period following a volcanic eruption and that the liquid phase brines are stored within the oceanic crust and vent at a later time in this case 3 years these results demonstrate that the venting of brines can occur in the same location in fact from the same sulfide edifice where the vapor phase fluids vented previously

alteration of the oceanic crust implications for geochemical cycles of lithium and boron abstract fresh tholeiitic basalt glass has been reacted with seawater at 150 c water rock mass ratio of 10 and fresh diabase has been reacted with a na k ca cl fluid at 375 c water rock mass ratios of 1 2 and 5 to understand better the role of temperature basalt composition and water rock mass ratio on the direction and magnitude of b and li exchange during basalt alteration at 150 c slight but nevertheless significant amounts of b and li were removed from seawater and incorporated into a dominantly smectite alteration phase at 375 c however b and li were leached from basalt b behaved as a soluble element and attained concentrations in solution limited only by the b concentration in basalt and the water rock mass ratio li however was less mobile for example at water rock mass ratios of 1 2 and 5 the percent of li leached from basalt was 58 70 and 92 respectively this suggests some mineralogic control on li mobility during hydrothermal alteration of basalt especially at low water rock mass ratios in general these results as well as those for b are consistent with the temperature dependent chemistry of altered seafloor basalt and the chemistry of ridge crest hydrothermal fluids based on the distribution and chemistry of products of seafloor weathering low 150 c and high temperature hydrothermal alteration of basalt and the chemistry of ridge crest hydrothermal fluids it was estimated that alteration of the oceanic crust is a li source for seawater this is not true for b however since the hot spring flux estimated for b is balanced by low temperature basalt alteration these data coupled with b and li flux estimates for other processes e g continental weathering clay mineral adsorption authigenic silicate formation and formation of siliceous skeletal material yield new insight into the b and li geochemical cycles calculations performed here indicate relatively good agreement between the magnitude of b and li sources and sinks the geochemical cycle of b however may be affected by serpentinization of mantle derived peridotite in oceanic fracture zones serpentinites are conspicuously enriched in b and if the b source for these rocks is seawater then an additional b sink exists which must be integrated into the b geochemical cycle however until more data are available in terms of areal extent of serpentinization serpentite chemistry and isotopic composition the importance of b in these rocks with respect to the b geochemical cycle remains speculative at best

influence of inherited taper on structural variability and conglomerate distribution cordilleran fold and thrust belt western united states north south changes in thickness of the prethrust stratigraphy of the north american cordillera within the united states controlled kinematic development of the late mesozoic sevier fold and thrust belt variation in stratigraphic thickness determined the initial slope o of the basal decollement beneath the thrust wedge as predicted by critical wedge theory segments of the sevier thrust belt with initially thick precambrian and paleozoic stratigraphic sections are structurally simple and are composed of few thrust sheets segments with thin prethrust stratigraphy and comparably low values of o are intensely imbricated the difference in structural style resulted because wedge segments with higher values of o required less internal deformation to build and maintain the critical taper required for thrust wedge advance transverse structural zones across which kinematic style differed formed at the terminations of thrust belt segments and controlled the locations of long lived antecedent drainage systems that transported gravel to the foreland therefore along strike changes in prethrust stratigraphic thickness resulted in an observed disjunct distribution of conglomerate in synorogenic deposits of the thrust wedge and foreland basin

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

hydrothermal venting at pressure temperature conditions above the critical point of seawater 5 s on the mid atlantic ridge hydrothermal circulation within oceanic crust depends on pressure p and temperature t the critical point cp of seawater at 298 bar and 407 c represents the threshold between subcritical and supercritical conditions here we present data from the first hydrothermal system in which the sampled fluids fall on and above the cp the vent system discovered at 5 s on the mid atlantic ridge is characterized by multiple fluid emanations at variable temperatures in water depths of 3000 m vigorous vapor phase bubbling stable emanation of superhot fluid at 407 c and decreased salinity indicate phase separation at conditions above the cp at one site at another site the measured maximum t of 464 c during a 20 s interval is by far the hottest fluid ever measured at the seafloor and falls into the vapor phase supercritical region of seawater besides these two separate fields with ongoing phase separation and extremely hot fluids a third vent field emanates non phase separated fluids at 349 c and is used as a reference site fluid chemistry shows that supercritical fluids evolve differently than subcritical fluids making this vent system a unique natural laboratory to investigate processes at high p t conditions the stability of the high temperature and fluid geochemistry measured in 2005 and 2006 after the assumed seismic trigger event in 2002 supports this as an exceptional site along the mid atlantic ridge

sequence stratigraphic relationships and facies architecture of turonian campanian strata kaiparowits plateau south central utah outcrop study of the straight cliffs formation in the kaiparowits plateau allows examination of facies tract development within a sequence stratigraphic framework this approach provides a new perspective to regional chronostratigraphic and lithostratigraphic relationships of turonian through campanian strata these strata are arranged in geometric patterns that can be related to lowstand transgressive and highstand system tracts

high resolution correlation of the upper cretaceous stratigraphy between the book cliffs and the western henry mountains syncline utah u s a abstract exposures of upper cretaceous strata in the book cliffs have played a key role in the formulation of modern sequence stratigraphic concepts and yet correlations with time equivalent strata in nearby regions remain uncertain resulting in an incomplete understanding of regional paleogeography this study presents detailed high resolution correlations of the upper cretaceous stratigraphy between the book cliffs the wasatch plateau and the western henry mountains syncline in utah with emphasis on the campanian interval two newly acquired measured vertical sections at coal canyon near green river in the book cliffs and blind trail in the henry mountains inform the correlations which also incorporate the substantial body of previous research correlations are further constrained by vertical and lateral facies stacking patterns and changes in sediment dispersal directions at discrete stratigraphic horizons derived from paleocurrent measurements much of the campanian succession can be characterized as a single low frequency third order depositional sequence within which are nested numerous high frequency sequences while it is not possible to correlate every high frequency sequence recognized in individual outcrop areas we define four intervals numbered 1 4 in ascending stratigraphic order that we correlate across the entire region interval 1 basal campanian is represented by initially deltaic and later wave dominated shoreface strata of the star point sandstone and equivalent basal muley canyon sandstone interval 2 lower campanian comprises coastal plain facies passing eastward into shallow marine strata of the lower blackhawk formation and equivalent muley canyon sandstone interval 3 lower to mid middle campanian comprises a thick aggradational stack of coastal plain fluvial strata that pass eastward into coastal and shallow marine facies blackhawk formation and equivalent masuk formation interval 4 overlying a major facies dislocation third order sequence boundary comprises amalgamated sheet fluvial deposits of the lower castlegate sandstone and equivalent tarantula mesa sandstone during the early to middle campanian the northern wasatch plateau and western henry mountains regions were along depositional strike with respect to one another the book cliffs near green river were located obliquely down depositional dip from the western henry mountains region during the campanian these new correlations and the improved understanding of paleogeography that derive from them have the potential to inform basin scale stratigraphic interpretations to a greater extent than has been hitherto possible

seasonal controls of aragonite saturation states in the gulf of maine the gulf of maine gome is a shelf region especially vulnerable to ocean acidification oa due to natural conditions of low ph and aragonite saturation states ar this study is the first to assess the major oceanic processes controlling seasonal variability of the carbonate system and its linkages with pteropod abundance in wilkinson basin in the gome two years of seasonal sampling cruises suggest that water column carbonate chemistry in the region undergoes a seasonal cycle wherein the annual cycle of stratification overturn primary production respiration remineralization and mixing all play important roles at distinct spatiotemporal scales surface production was tightly coupled with remineralization in the benthic nepheloid layer during high production seasons which results in occasional aragonite undersaturation from spring to summer carbonate chemistry in the surface across wilkinson basin reflects a transition from a production respiration balanced system to a net autotropic system mean water column ar and abundance of large thecosomatous pteropods show some correlation although patchiness and discrete cohort reproductive success likely also influence their abundance overall photosynthesis respiration is the primary driving force controlling ar variability during the spring to summer transition as well as over the seasonal cycle however calcium carbonate caco3 dissolution appears to occur near bottom in fall and winter when bottom water ar is generally low but slightly above 1 this is accompanied by a decrease in pteropod abundance that is consistent with previous caco3 flux trap measurements the region might experience persistent subsurface aragonite undersaturation in 30 40 years under continued ocean acidification

thrust timing growth of structural culminations and synorogenic sedimentation in the type sevier orogenic belt western united states most of the regional shortening in the type area of the sevier orogenic belt in central utah was accommodated by displacement on the canyon range neocomian aptian pavant aptian albian paxton cenomanian campanian and gunnison late campanian paleocene thrust systems inception of each thrust system generated synorogenic sediment associated with frontal thrust tip anticlines or triangle zones and older thrust sheets that were elevated above major ramps farther toward the hinterland the sevier culmination a large antiformal duplex cored by crystalline basement rocks developed during paxton and gunnison thrusting west of and structurally beneath the canyon range and pavant thrusts growth of the sevier culmination was coeval with reactivation of the canyon range and pavant thrust systems and produced a second culmination in proterozoic lower cambrian rocks in the canyon range these structural highs provided much of the sediment to the adjacent foreland basin from late cenomanian to late paleocene time and may have helped to maintain critical taper in the thrust belt

stratigraphic and provenance variations in the early evolution of the magallanes austral foreland basin implications for the role of longitudinal versus transverse sediment dispersal during arc continent collision resolving the role of longitudinal versus transverse sediment dispersal in ancient sedimentary basins is paramount for understanding filling history and the timing of source area exhumation the southern patagonian andes provide a unique opportunity for constraining these relationships because upper cretaceous shallow and deep marine strata that record the longitudinal filling history of the magallanes austral foreland basin are exposed along a 500 km outcrop belt new stratigraphic sedimentologic and facies analyses of the cenomanian aged lago viedma formation indicate a protracted phase of a dominantly shoreface and foreshore depositional setting at the northern end of the basin austral basin sector whereas 200 km to the south age equivalent strata of the punta barrosa formation are characterized by southward flowing deep water fan systems new sandstone compositional data from both formations are rich in intermediate volcanic grains and suggest an undissected to transitional volcanic arc source however detrital zircon populations from the shallow marine lago viedma formation are dominated by arc sources 126 75 ma whereas deep water strata of the punta barrosa formation contain much greater abundances of jurassic 199 161 ma and pre jurassic 200 ma ages this indicates that deep water fan systems were not linked to a shelfal sediment dispersal system by a simple northward point source model despite consistent southward directed paleocurrents in deep water strata time transgressive provenance variations continue southward along strike where lithostratigraphic equivalents in the ultima esperanza and fuegian sectors of the basin contain a mix of arc and pre jurassic metamorphic basement sources and a paucity of jurassic ages we interpret these along strike provenance variations to be the result of significant local sediment contributions from transverse sources the influence of transverse tributaries during the early history of the magallanes austral foreland basin suggests that the diachronous onset of coarse clastic deposition in the basin was likely due to the progressive delivery and initiation of more locally derived coarse clastic sediment we attribute this to southward progressing thrust belt development associated with progressive north to south collision or suturing of the parautochthonous patagonian arc with attenuated continental crust of south america