tidal modeling of an ancient tide dominated seaway part 1 model validation and application to global early cretaceous aptian tides abstract the utility of deep time global paleotidal modeling is evaluated with a series of modeling experiments focused on the early cretaceous aptian the results from a series of paleobathymetry sensitivity experiments indicate that despite paleogeographic and paleobathymetric uncertainty appropriate use of global paleotidal models complements and enhances stratigraphic and sedimentological methods before being applied to global paleotidal modeling the imperial college ocean model icom is validated for the computation of modern global tides the icom results only deviate slightly from a state of the art published model and were achieved with considerably less computational expense and without data assimilation the results from global paleotidal modeling of the early cretaceous aptian were assessed by comparison with the published geological record icom predicts high mesotidal to macrotidal ranges on the arabian platform around india especially to the north and west along the pacific coast between north and south america northeast of australia and around southeast asia the model predicts low microtidal ranges in the proto south atlantic ocean and weddell sea a further validation test assessed the ability of the model to predict the dominant tidal constituents diurnal or semidiurnal in the aptian lower greensand seaway of southeastern england and northern france during the aptian this region was connected to the boreal proto atlantic and neotethys oceans and now preserves superbly documented tidal deposits the model predicts low microtidal ranges in the proto central atlantic ocean and boreal ocean suggesting that they had little impact on tides in the lower greensand seaway higher tidal amplitudes especially of diurnal once daily tides are predicted in the northwestern neotethys ocean suggesting that this ocean was an important source of tidal energy to the lower greensand seaway sensitivity tests to paleogeographic and paleobathymetric uncertainty indicate that the model predictions are robust the prediction of predominantly diurnal tides is supported by published analyses of large dune scale deposits in the lower greensand of southeast england

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

active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea shallow seismic profiles and borehole data revealed active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea the ridges consist of relatively clean well sorted sands with fairly uniform sequences the microfossil assemblage exhibits a high diversity including both euryhaline and stenohaline species the ridges are huge elongated sand bodies several kilometres wide 10 60 km long and up to 20 m thick and occur in groups with a spacing of several to 10 km normally they are parallel with each other extending in the direction of the tidal currents the field of tidal sand ridges on the east china sea shelf covers an area of 57 000 km2 tidal sand ridges in the east china sea and the southern yellow sea were formed in estuarine and shallow shelf environments where strong tidal currents reworked transported and redeposited large amounts of relict sands from older deltaic and fluvial sediments the development of tidal sand ridges in estuary mouth areas is accompanied by a net sand transport from the shelf into the estuary the evolution of tidal sand ridges is closely related to transgressions active tidal sand ridges are formed during sea level rises they show distinct morphology and active migrations in a lateral as well as in a landward direction they are generally in equilibrium with present day tidal processes and their distribution patterns are related to the flow field of the tidal currents as the sea level rises further these tidal sand ridges become moribund sand bodies with less distinct morphologies their upper surfaces are covered by a thin calcareous rich layer with very high contents of foraminifera tests reflecting a submarine hiatus condition on the shelf during the highstand period during the subsequent steady fall in sea level tidal sand ridges are often buried by fine grained shelf and prodelta sediments they have therefore a good chance of being preserved in stratigraphic records the sequential buildup during a sea level rise tr tract and a subsequent sea level fall hs and ls tract would consist of estuarine channel and tidal flat facies tidal sand ridge facies shelf mud facies delta facies and fluvial facies in an ascending order tidally dominated estuary conditions may also occur when a major distributary is abandoned such as at the northern branch of the modern changjiang river mouth where the accumulation of sand from an abandoned delta lobe and the development of tidal sand ridges have been observed the observed features have important implications for the subsurface recognition of fossil tidal sand ridges for the reconstruction of the regional palaeogeography and transgressional history and for the prediction of potential reservoir sandstones

interactions between axial and transverse drainage systems in the late cretaceous cordilleran foreland basin evidence from detrital zircons in the straight cliffs formation southern utah usa new detrital zircon geochronologic data from the straight cliffs formation of southern utah provide insight into the controls on stratigraphic architecture of the western interior basin during turonian early campanian time detrital zircon ages n 40 n 3650 derived from linked fluvial and shallow marine depositional systems of the kaiparowits plateau indicate the majority of zircons in fluvial strata were derived from the mogollon highlands 1 25 1 90 ga 67 of fluvial zircons with subordinate contributions delivered from the sevier fold and thrust belt 265 1250 ma 17 and cordilleran magmatic sources 81 265 ma 16 integration of these data with fluvial facies distributions petrography clast counts and evidence of magmatic arc sources from the mohave region of california implies the presence of a northeast flowing axial fluvial system this system was fed by rivers draining the mogollon highlands to the south and by transverse drainages from the sevier fold and thrust belt to the west compared to the fluvial deposits shallow marine sandstones have a greater proportion of sevier fold and thrust belt derived zircons 42 which were delivered via longshore currents from the north shallow marine samples also contain less mogollon input 44 compared to contemporaneous fluvial systems and similar input from the magmatic arc 14 although proterozoic zircons associated with the mogollon highlands are also present in the sevier fold and thrust belt several lines of evidence argue for a distinct southerly source for the straight cliffs formation these include 1 moderate proportions of feldspar and angular quartz grains in fluvial sandstones which favor a felsic intrusive source and 2 prominent 1 4 and 1 7 ga zircon populations the 1 4 and 1 7 ga peaks are the only dominant proterozoic peaks in samples from the straight cliffs formation whereas samples derived more directly from the sevier fold and thrust belt tend to have a broader distribution of proterozoic age peaks up section architectural trends in the straight cliffs formation are linked to trends in detrital zircon geochronologic data underscoring the likelihood of common drivers and controls the axial system depositing straight cliffs fluvial strata was primarily fed by drainages originating in the mogollon highlands during a pulse of tectonic activity in the maria fold and thrust belt and generally high subsidence rates in the foreland basin turonian santonian over time activation of the paxton duplex in the sevier fold and thrust belt early campanian exhumed proximal foreland basin strata and enabled drainage systems from the sevier fold and thrust belt to feed into the basin more prominently the results presented here underscore the potential significance of axial fluvial systems and their complex interplay with transverse drainage networks in foreland basins

the first antarctic geomagnetic reference model arm 1 spherical cap harmonic analysis has been applied to obtain a reference model of geomagnetic secular change for antarctica valid for the last forty years in this paper we use the latest available observatory data to update this model and to compare it with the 8th generation igrf in addition the selected set of total field values used for the generation of the oersted initial field model have been employed together with observatory data to develop the first complete antarctic reference model arm this model improves the fit to the secular variation deduced from observatory data by about 60 relative to igrf and the fit to observatory and satellite field data by 8 the model allows merging data sets taken at different altitudes and epochs in antarctica where significant temporal geomagnetic variations occur

numerical simulations of tidal and wind driven circulation in the cretaceous interior seaway of north america twenty two numerical experiments using a multi layer numerical model of turbulent flow in shallow seas better define fluid circulation and sediment transport paths in the cretaceous interior seaway of north america each experiment consists of a different combination of paleogeography paleobathymetry coriolis acceleration boundary tidal amplitudes wind stresses and bed friction the paleogeographies and paleobathymetries represent three seaway configurations a seaway of intermediate size and depth 200 m during a transgressive peak t5 in late albian time a seaway of maximum size and depth 400 m during peak transgression t6 in early turonian time and a seaway of minimum size and depth 100 m during a peak regression r8 in the campanian values for the other key model parameters are m 2 co oscillating boundary tides of 0 1 to 0 2 m range at the arctic ocean boundary and 0 5 to 1 m range at the proto gulf of mexico boundary coriolis accelerations corresponding to 30 n 45 n and 60 n latitude chezy friction factors ranging from 31 to 70 m s 1 and average winter winds and two winter storms computed by the community climate model at the national center for atmospheric research for paleogeographic conditions during the late albian results of the numerical experiments and comparison of these results with geologic observations allow the following conclusions 1 circulation in the seaway was generally storm dominated 2 typical winter storms crossing the seaway from west to east generated 0 3 m s 1 shore parallel geostrophic currents on the shelves north of arizona at first flowing weakly to the north but later during the storm flowing strongly to the south 3 extreme storms could have produced 0 8 m s 1 currents over the shelves and 0 3 m s 1 currents in 200 m of water 4 co oscillating tides propagated into the seaway as progressive kelvin waves and therefore tidal ranges in the seaway were mesotidal to macrofdal along the southeastern margin but microtidal everywhere else 5 significant deep water wave heights and periods of the fully developed wave field are predicted to have been 5 to 6 m high and 10 s respectively the northwestern shore of the seaway would have experienced these storm waves approaching from the north and thus net sediment drift should have been to the south limited available field data support these conclusions

pinch out style and position of tidally influenced strata in a regressive transgressive wave dominated deltaic sandbody twentymile sandstone mesaverde group nw colorado the upper cretaceous twentymile sandstone of the mesaverde group in nw colorado usa has been analysed with respect to its pinch out style and the stratigraphic position of tidally influenced facies within the sandstone tongue detailed sedimentological analysis has revealed that the twentymile sandstone as a whole is a deltaic shoreface sandstone tongue up to 50 m thick proximally facies change character vertically from very fine grained storm wave dominated shelf sandstones and mudstones to fine grained wave dominated sandstones and finally to fine to coarse grained tidally dominated sandstones the pinch out style is characterized by a basinward splitting of the massive proximal sandbody into seven coarsening upward fourth order sequences consisting of a lower shaly part and an upper sandy part sandstone tongue these are stacked overall to reflect the regressive to transgressive development of the tongue each of the lower sandstone tongues 1 3 are gradationally based very fine grained and dominated by hummocky cross stratification and were deposited on the lower to upper shoreface sandstone tongues 4 and 5 prograded further basinwards than the underlying tongues are erosively based fine to coarse grained and mainly hummocky herringbone and trough cross stratified especially in tongue 5 tidal indicators such as bipolar foresets and double mud drapes are common these tongues were deposited as upper shoreface and tidal channel sandstones respectively sandstone tongues 6 and 7 retrograded in relation to tongue 5 are very fine to fine grained and hummocky cross stratified these tongues were deposited in lower shoreface to offshore transition environments the two lower fourth order sequences were deposited during normal regressions during slowly rising or stable relative sea level and represent the highstand systems tract the three succeeding fourth order sequences which show succeedingly increasing evidence of tidal influence were deposited during falling and lowstand of relative sea level and represent the falling stage forced regressive and lowstand systems tracts the uppermost two fourth order sequences were deposited during rapidly rising sea level in the transgressive systems tract the maximum tidal influence occurred during lowstand progradation in contrast to most other published examples reporting maximum tidal influence during transgression

sedimentary facies of the tide dominated paleo changjiang yangtze estuary during the last transgression abstract a large estuary was formed by marine inundation of the paleo changjiang yangtze incised valley during the transgression after the last glacial maximum this paper presents the sedimentary facies and architecture of the estuary fill based on the analysis of three sediment cores cm97 js98 and hq98 obtained from the present changjiang delta plain estuary fill deposits showing an upward fining succession were grouped into five depositional facies tidal river distributary channel muddy intertidal to subtidal flats transgressive lag and estuary front based on sedimentary textures lithology and physical sedimentary structures sand mud couplets are common in these deposits indicating that tides played a significant role in producing these sedimentary structures and that the estuary type was tide dominated some of the successive sand mud couplets probably recorded neap spring cycles as well as semidiurnal tidal cycles the nature of the estuary was very different from other representative tide dominated estuaries in sediment facies its distribution and sediment source for estuarine fill unlike the other estuaries that receive sediments mainly from the sea the paleo changjiang estuarine fill deposits were supplied largely from the river this difference would also have a great influence on the sedimentological and morphological component in the estuary the sediment distribution of the estuary showed fining seaward and estuary mouth sand bodies fed by marine source sand were absent the architecture model of tide dominated estuaries should be divided into two types by the degree of fluvial sediment supply the paleo changjiang estuary shows a good example for an estuary of large rivers

fault chronology and uplift history of the southern wind river range wyoming implications for laramide and post laramide deformation in the rocky mountain foreland the stratigraphy provenance and structural involvement of tectogenic sedimentary rocks along the southern and western margins of the wind river range in western wyoming record a complex laramide and later uplift history and identify the timing and position of individual faulting events the chronology of these events is 1 main uplift of the range by displacement on the wind river fault between 90 and 49 to 50 ma 2 the formation of reverse faults in the hanging wall of the wind river fault ca 50 to 51 ma 3 sagging of the toe of the wind river fault into sedimentary fill of the green river basin between 46 and 23 ma 4 uplift of the core of the range along reactivated precambrian shear zones between 30 and 23 ma and 5 collapse of the southern part of the range along normal faults beginning at 13 ma the sedimentary record of uplift and erosion indicates that erosion and basin fill kept pace or caught up with uplift so that by the end of the laramide there was little topographic relief between the crest of the range and the adjacent green river basin the present topography of the range characterized by a high level erosion surface and distinct crestal ridge derives from uplift of the erosion surface by the late laramide reverse faulting post laramide uplift of the crest of the range and neogene exhumation initial uplift of the range as early as 110 ma and prior to displacement on the wind river fault suggests either a pre laramide event of unknown origin or that laramide crustal shortening began nearly 35 m y earlier than commonly assumed

transgressive origin of channeled estuarine deposits in the point lookout sandstone northwestern new mexico a model for upper cretaceous cyclic regressive parasequences of the u s western interior 1 regionally correlatable regressions recorded in upper cretaceous strata from the united states western interior represent low order cyclic progradations of the epeiric seaway shoreline stratigraphic intertonguing of coastal sandstone deposits and marine shales developed in response to higher order depositional cycles where episodic transgressions interrupt regressions a simple model based on walther s law of facies has most often been used to interpret these deposits including channeled estuarine sandstones commonly found at the top of the sequence the regressive phase history is presumed to reflect progradation of a barrier island and its associated environments whereas transgressions are presumed to be mainly erosive i propose an alternative explanation for these deposits based on time stratigraphic architecture and component facies distributions of the point lookout sandstone in the northwestern san juan basin new mexico interpretations of outcrop measured sections and well log correlations suggest an individual parasequence is actually the product of a depositional couplet that includes a regressive phase and a transgressive phase strand plain progradation during the regressive phase produced upward coarsening shoreline deposits deposition during the transgressive phase occurred mainly in a zone landward of a reworked shoreline trend and comprises a lagoonal estuarine system specific examples of transgressive backbarrier deposits are described from outcrops of the point lookout sandstone these facies include an areally extensive fine grained variably stratified lagoonal deposit and an upward fining cross bedded sandstone deposited in highly migratory tidal channels the channeled estuary developed by infilling of the backbarrier lagoon the deposition of these backbarrier facies during episodic transgressions is significant for reinterpreting the typical vertical lithologic succession in cyclic regressive stratigraphic sequences the backbarrier deposits are separated from the strand plain deposits by a flooding surface and do not represent environments that translated seaward during shoreline progradation transgressive estuarine deposits appear to be an important potential reservoir facies in the point lookout section each estuarine sandstone is developed as a discrete reservoir unit at the landward limit of a parasequence these sandstones can be correlated into the subsurface and their distribution mapped parallel to depositional strike the distribution of channeled estuarine reservoirs can be predicted and effectively exploited based on the depositional couplet model

hummocky cross stratification tropical hurricanes and intense winter storms most previous workers have inferred a storm origin for hummocky cross stratification which typically occurs in shallow marine deposits on the modern earth the only storms capable of profoundly affecting shallow marine depositional environments are severe tropical cyclones hurricanes and mid latitude winter wave cyclones intense winter storms this paper examines the palaeogeographic distribution including palaeolatitude and palaeogeographic setting of 107 occurrences of hummocky cross stratification ranging in age from the proterozoic to recent in each of these stratigraphic units both palaeolatitude and palaeogeography are consistent with a direct storm influence associated with the passage of hurricanes or winter storms directly over the site of deposition this palaeogeographic evidence lends support to the inferred storm origin for hummocky cross stratification further the distribution of the structure suggests that most occurrences 73 were generated by tropical hurricanes the remaining 27 being generated by intense mid latitude winter storms the preferential generation of hummocky cross stratification by hurricanes is consistent with 1 the known differences in the nature of the bottom flows generated by the two major storm types and 2 the inferred nature of the flows which form hummocky cross stratification hurricanes couple less effectively with the water column than do intense winter storms due to this ineffective coupling hurricane generated bottom flows tend to be oscillatory or multidirectional dominant with only minor unidirectional components of motion in contrast intense winter storms generally do couple effectively with the water column generating bottom flows which possess a dominant or significant unidirectional component most previous workers have suggested that hummocky cross stratification forms under oscillatory or multidirectional dominant flow thus it is conceptually reasonable that the vast majority of ancient occurrences of hummocky cross stratification were probably hurricane generated as suggested by the aforementioned palaeogeographic distribution the proterozoic palaeozoic neogene and quaternary were times when global climate was similar to that of today the distribution of hummocky cross stratification deposited during these times suggests that both hurricanes and intense winter storms occupied latitudinal belts during these times which were essentially identical to those occupied by their modern counterparts the mesozoic and palaeogene were non glacial times when global climate was much warmer than that of today the distribution of hummocky cross stratification deposited during this interval suggests that hurricanes occurred more frequently at higher latitudes during non glacial times than they do at present the possibility of a broadened hurricane belt during the mesozoic and palaeogene is consistent with climatic considerations a limited number of mesozoic and palaeogene rock units containing hummocky cross stratification were deposited in palaeogeographic settings that preclude a direct hurricane influence these examples were deposited in the middle latitudes suggesting that intense winter storms continued to form hummocky cross stratification in the middle latitudes during these much warmer times some previous workers have suggested that tsunamis may be capable of generating hummocky cross stratification the palaeogeographic distribution of the structure does not support an origin due to tsunamis lacustrine examples of hummocky cross stratification reported herein are the first known non marine occurrences they suggest that storm effects strongly influence the sedimentary record of some lakes

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

high resolution sequence stratigraphic analysis of the shannon sandstone in wyoming using a template for regional correlation abstract recent interpretations of the lower campanian shannon sandstone in the powder river basin wyoming have suggested that it was deposited in falling stage and lowstand incised shorefaces rather than in stacked shelf ridges up to 160 km from shore despite these detailed studies there is no published correlation of the outcrop deposits at salt creek anticline with the subsurface deposits in the hartzog draw heldt draw hd hd area a complete high resolution sequence stratigraphic analysis of the shannon requires that the outcrops at salt creek be correlated with the subsurface fields at hd hd there is little core control in the approximately 30 km between these areas so correlations are based almost entirely on well logs a template has been constructed in the hd hd area where ther is good core and well log control which embodies data from facies facies successions well log signatures and bounding discontinuities the template consists of a regressive surface of erosion rse that forms the base of an incised shoreface sandbody and a transgressive surface of erosion tse that truncates the top of the sandbody and the rse two cross sections have been constructed and the template has been used to guide correlations between salt creek and the hd hd area from the cross sections six progradational events and six transgressions have been defined during shannon time the positions of the rses and tses allow estimates of between a few meters and 60 m for the magnitude of sea level fluctuations that controlled shannon deposition the proposed correlations confirm and reinforce the interpretation of the shannon as a series of incised shoreface sandbodies separated by transgressive systems tract mudstone deposits

variability of lowstand wedges and their distinction from forced regressive wedges in the mesaverde group southeast wyoming the debate on the geometry and origin of shelf sandbodies has evolved from a discussion of how sands and gravels managed to move from shorelines far out onto muddy shelves to an acceptance that many of these sandbodies did not originate on the shelf but were simply resident there after a fall and subsequent rise of sea level in the efforts to reinterpret these sandstones there has been some tendency to underestimate how varied they can be data from eight such shelf sandstone tongues campanian in southeast wyoming are used to illustrate how variable lowstand prograding wedges can be and how these should in addition be distinguished from forced regressive wedges the depositional environments encountered in these two types of wedges are surprisingly different and the lowstand wedges which are frequently tidally influenced show a greater affinity with the overlying transgressive tract than with the preceding wave dominated forced regressive shoreface deposits

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

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

integrated paleoenvironmental analysis of the niobrara formation cretaceous western interior seaway northern colorado abstract this study presents a regional chronostratigraphic framework and paleoenvironmental reconstruction of the niobrara formation in northern colorado based upon multidisciplinary biostratigraphic and lithostratigraphic data a local biostratigraphic zonation is described for the coniacian to earliest campanian of this region of the western interior seaway based primarily upon the distribution of calcareous nannofossils three key paleoenvironmental packages are also identified and linked to the evolution of regional sedimentary facies during the early to late coniacian tethyan water masses interacted with boreal surface currents to produce regional upwelling along tectonically controlled bathymetric highs a well mixed relatively well oxygenated water column with warm surface water temperatures and high fertility sustained a rich microflora fauna and promoted higher carbonate production enhanced fluvial input and a weakening of tethyan influence during the early santonian mark the onset of a regional environmental shift this period of transition extends through the middle santonian and is characterized by pulses of transported material and relatively frequent turnover of faunal associations increased terrigenous runoff likely produced eutrophic surface waters and intensified water column stratification leading to a general deterioration of the bottom water environment in a progressively dysoxic setting continued strengthening of fluvial input during the late santonian to early campanian resulted in surface water freshening and sustained primary productivity this surface water environment in conjunction with stifled vertical mixing promoted the development of a stagnant and intensely stratified water column the basin was therefore severely dysoxic possibly anoxic and corrosive with chemically reducing bottom waters and an expanded oxygen minimum zone thereby limiting biotic development and causing the deposition of finely laminated mud rich carbonate poor seciments

tidal hydrodynamics and fine grained sediment transport on the radial sand ridge system in the southern yellow sea abstract the large radial sand ridge rsr system located in the southern yellow sea off the jiangsu coast is characterized by a radial current field and high suspended sediment concentrations sscs significant rectilinear currents are present over the northern sand ridge area whereas rotary currents prevail over the southern area the transition between the two being dominated by a locally generated trapped wave observations undertaken in 2006 and 2007 indicate a seasonal pattern in the ssc and associated dynamic characteristics the results of a calibrated hydrodynamic model show that the m2 tide dominates the rsr area the maximum tidal amplitude in the core region close to land being approximately 2 m an amphidromic point is located some distance north of the rsr off the abandoned yellow river mouth 121 686 e 34 6 n specifically the eulerian and lagrangian residual currents flow southward in both summer and winter whereas the stokes drift is directed southward in the north and northward in the south moreover in deep water the lagrangian residual current is mainly determined by the eulerian residual current whereas it is strongly influenced by the stokes drift in shallow water the seasonal variation in the residual current in the southern yellow sea is a good indicator for the location of the yellow sea warm current yswc in both summer and winter measurements show that a ssc peak appears off the abandoned yellow river delta in response to the strong currents and plentiful supply of fine grained sediment from coastal erosion another ssc peak lying close to the north branch of the changjiang river mouth is related to the abundant suspended sediment supplied by the river seasonal variations in ssc are observed in the study area maximum average values and widest diffusion from land occurring in winter this being contrasted by minimum mean values in summer sensitivity experiments demonstrate that the main factor influencing the distribution of ssc is the tide while river discharge wind and wave effects are small and very localized to explain the seasonal variation in ssc the role of hydrodynamics initial conditions and temperature are tested in the model the results show that the hydrodynamics play a significant role whereas the initial conditions only have a minor regional influence temperature on the other hand is also shown to greatly influence the seasonal variation in ssc because of substantial changes in the viscosity of the water and the erosion shear stress the modeled results are used to calculate sediment fluxes which are shown to be consistent with the lagrangian residual current pattern while wind waves can significantly change the fluxes in winter bed elevations change substantially on a monthly time scale in general the deep channels are undergoing erosion while the shallow ridges and coastal tidal flats are accreting the net sediment transport being directed towards the coastal tidal flat and the changjiang yangtze river subaqueous delta

basin dimensions and morphology as controls on amplification of tidal motions the early miocene north hungarian bay following the late aquitanian sea level fall tide influenced deposition started in the north hungarian bay an embayment in the paratethys open to the north east the relatively narrow funnel shape of the bay supported amplification of tidal movements resulting in the generation of strong tidal currents the length and the depth of the north hungarian bay and the connecting seaway through east slovakia fell into the tidal amplification window and thus fulfilled the conditions needed for resonant amplification of semidiurnal m2 tides tide influenced deposits were formed at both sides of the north hungarian bay they reflect dominant currents in opposite directions and of different strengths at either side of the basin this difference was the result of bottom tide interactions cyclonic anticlockwise residual currents were induced above the asymmetrical central depression in the bay and were superimposed upon the tidal currents producing an anticlockwise time and velocity asymmetrical current system the north hungarian bay and other examples show that amplification of tidal motions and formation of tide influenced deposits may occur if basin dimensions pass through the tidal amplification window this window represents ideal conditions for resonant or amphidromic amplification of tidal currents it determines an ideal length depth or width depth ratio relative to the wavelength of the astronomical tides thus signs of strong tidal influence in fossil basin fills can be used to reconstruct the dimensions length depth and width of such basins

the mesozoic mogollon highlands arizona an early cretaceous rift shoulder the mogollon highlands have long been considered the southern source terrane for much of the early to middle mesozoic fluvial sedimentary rocks of the southern colorado plateau because of the lack of mesozoic sedimentary strata in the mogollon region many workers have suggested these highlands were located in central arizona and new mexico new evidence suggests that during the triassic and most of the jurassic a large highland did not exist in central arizona new mexico but was present as a continental margin volcanic arc in southern arizona and northern mexico at this time central arizona would be more aptly called the mogollon slope early jurassic navajo equivalent sands were blown south from the colorado plateau area across the mogollon slope to become intercalated with volcanics along the northeast side of the arc the first good evidence for a structural and topographic highland in the mogollon area is in the early cretaceous when the uplifted northeast flank of the bisbee rift basin tilted

pleistocene forced regressions and tidal sand ridges in the east china sea abstract tidal sand ridges are common features on modern shelves but only few examples of such preserved sand bodies are described in pleistocene deposits in the stratigraphic record some sand bodies encased in shales previously interpreted as sand ridges have been reinterpreted as shoreface deposits more than 5000 km of high resolution seismic data from the east china sea correlated to geotechnical boreholes and shallow cores demonstrate the potential of sand ridge preservation and allow reconstruction of the depositional history of pleistocene fourth order 100 kyr depositional sequences a high subsidence rate of about 300 m myr allows the preservation of three elementary sedimentary facies constitutive of a motif which was repeated during glacio eustatic cycles they consist of 1 regressive marine prodeltaic prograding wedges 2 estuarine and continental deltaic facies and 3 transgressive sand ridges similar in shape and orientation to modern sand ridges major discontinuities traceable over the entire outer continental shelf along distances of hundreds of kilometers are transgressive and regressive surfaces of marine erosion whereas sequence boundaries formed by fluvial erosion are difficult to identify on this low gradient shelf because of the asymmetry of the pleistocene glacio eustatic cycles most of the preserved sedimentary record with the exception of sand ridges corresponds to forced regressive deposits deposits that formed during a seaward shift of the shoreline due to relative sea level lowering

modelling tidal current induced bed shear stress and palaeocirculation in an epicontinental seaway the bohemian cretaceous basin central europe lower to middle turonian deposits within the bohemian cretaceous basin central europe consist of coarse grained deltaic sandstones passing distally into fine grained offshore sediments dune scale cross beds superimposed on delta front clinoforms indicate a vigorous basinal palaeocirculation capable of transporting coarse grained sand across the entire depth range of the clinoforms ca 35 m bi directional alongshore oriented trough cross set axes silt drapes and reactivation surfaces indicate tidal activity however the bohemian cretaceous basin at this time was over a thousand kilometres from the shelf break and separated from the open ocean by a series of small islands the presence of tidally influenced deposits in a setting where co oscillating tides are likely to have been damped down by seabed friction and blocked by emergent land masses is problematic the imperial college ocean model a fully hydrodynamic unstructured mesh finite element model is used to test the hypothesis that tidal circulation in this isolated region was capable of generating the observed grain size distributions bedform types and palaeocurrent orientations the model is first validated for the prediction of bed shear stress magnitudes and sediment transport pathways against the present day north european shelf seas that surround the british isles the model predicts a microtidal to mesotidal regime for the bohemian cretaceous basin across a range of sensitivity tests with elevated tidal ranges in local embayments funnelling associated with straits increases tidal current velocities generating bed shear stresses that were capable of forming the sedimentary structures observed in the field the model also predicts instantaneous bi directional currents with orientations comparable with those measured in the field overall the imperial college ocean model predicts a vigorous tide driven palaeocirculation within the bohemian cretaceous basin that would indisputably have influenced sediment dispersal and facies distributions palaeocurrent vectors and sediment transport pathways however vary markedly in the different sensitivity tests accurate modelling of these parameters in this instance requires greater palaeogeographic certainty than can be extracted from the available rock record

trace fossil model for reconstructing oxygenation histories of ancient marine bottom waters application to upper cretaceous niobrara formation colorado abstract trends of decreasing trace fossil diversity burrow size and penetration depth with diminishing oxygen availability in contemporary marine settings have been incorporated with the concept of trace fossil tiering to develop a model for reconstructing the oxygenation history of ancient basin bottom waters more sensitive than traditionally employed criteria the model permits detailed evaluation of relative degree of oxygenation through the recognition of oxygen related ichnocoenosis ori units or units of strata deposited under similar levels of bottom water oxygenation when employed in detailed vertical sequence analyses the model may also be used to construct interpreted oxygenation curves that reflect rates and magnitudes of temporal change in redox conditions the utility of the model is demonstrated by its application to rhythmically bedded calcareous strata of the niobrara formation upper cretaceous exposed in colorado non laminated strata of the niobrara are characterized by four recurring trace fossil suites referred to as the 1 chondrites 2 zoophycos teichichnus 3 planolites and 4 thalassinoides assemblages on the basis of trends in trace fossil diversity burrow diameter and penetration depth these assemblages are recognized as oxygen related ichnocoenoses interpreted oxygenation curves for the basal fort hays member reflect high magnitude redox cycles characterized by rapid deoxygenation events followed by gradual reoxygenation phases curves for the overlying smoky hill member reflect an overall lower degree of oxygenation with more irregular lower magnitude redox fluctuations significant correlation between interpreted levels of paleooxygenation and organic carbon content illustrate the model s potential for evaluating the distribution of organic rich fine grained strata co interpretation of these variables with carbonate content supports the premise that deposition was controlled by paleoceanographic perturbations modulated by milankovitch like climatic cycles comparison with traditionally emphasized macroinvertebrate body fossil criteria clearly demonstrates the greater utility of the trace fossil approach for evaluating paleo oxygenation

late cretaceous subsidence in wyoming quantifying the dynamic component the late cretaceous western interior basin of north america is generally considered to have been a retroarc foreland basin flexural backstripping of the stratigraphic record from 97 2 ma to 73 4 ma along a section perpendicular to the wyoming idaho salient of the sevier belt clearly demonstrates that there were components of subsidence in addition to those driven by the thrust and associated sediment loads the simulation demonstrates that the flexural foredeep is only 180 120 km wide and shows a forebulge located near the subsequent laramide rock springs uplift foredeep strata between the rock springs uplift on the east and the thrust front to the west were mostly involved in the eastward overlapping thrust belt or deeply truncated by inferred rebound after 78 5 ma the difference between the observed decompacted cumulative subsidence and the amount of subsidence that can be explained by simple flexural loading the residual subsidence increases from 800 m in eastern wyoming to 1 8 km near the thrust belt the westward thickening upper cretaceous sediment wedge filled the accommodation space generated by downward tilting to the west of the north american cratonic margin by underplating and mantle flow associated with the shallowly subducted farallon plate

style contrast between forced regressive and lowstand transgressive wedges in the campanian of south central wyoming hatfield member of the haystack mountains formation

tectonic control on coarse grained foreland basin sequences an example from the cordilleran foreland basin utah newly released reflection seismic and borehole data combined with sedimentological provenance and biostratigraphic data from upper cretaceous paleocene strata in the proximal part of the cordilleran foreland basin system in utah establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin during campanian time coarse grained sand and gravel were derived from the internally shortening charleston nebo salient of the sevier thrust belt a rapid regional campanian progradational event in the distal foreland basin 200 km from the thrust belt in 8 m y can be tied directly to active thrust generated growth structures and an influx of quartzose detritus derived from the charleston nebo salient eustatic sea level variation exerted a minimal role in sequence progradation

the cliff house sandstone san juan basin new mexico model for the stacking of transgressive barrier complexes abstract the upper cretaceous cliff house sandstone in the san juan basin new mexico is characterized by en echelon nw se elongated linear sandstone complexes representing successive phases of coastal sedimentation along the western margin of the cretaceous seaway detailed analysis of the lithofacies spatial facies relations and geometry of the stratigraphically highest cliff house sandstone complex in the southern part of the basin indicates a storm dominated tidal linear barrier island coast as the depositional environment the complex consists of four stacked sandstone bodies each body is bounded above and below by a sharp erosion surface offsets of the stacked sandstone bodies along the erosion surfaces mark minor transgressive and regressive shifts of the cliff house coast the cliff house sandstone is generally known as a transgressive sequence accumulation of barrier sands however took place during the regressive intervals in subsequent transgressive intervals part of the accumulated sediment was eroded and only topographicall low lying parts of the barrier e g shoreface tidal inlets and lagoonal sediment were preserved

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

source processes of the thermal waters from the phlegraean fields naples italy by means of the study of selected minor and trace elements distribution abstract the geochemical characteristics of hydrothermal waters from the phlegraean fields p f naples italy were analysed for minor and trace elements selectively mobilised in hydrothermal systems such as b f hg as pb and tl the water samples collected from a shallow aquifer likely to be fed by deeper fluids showed various geochemical features resulting from the mixing of three components 1 surface waters of meteoric origin 2 hot deep waters deriving from water rock interaction and including deep waters of marine origin 3 magmatic fluids rising from the local magma chamber lying a few kilometres below the town of pozzuoli this setting although very complex provides a reliable means of studying the distribution of the investigated trace elements in particular within the phlegraean area high contents of b 0 1 48 mg l f 0 5 8 mg l as 16 6050 g l and hg 0 7 232 g l were observed the levels of thallium in the springs close to solfatara about 7 g l were in line with those normally recorded in hydrothermal areas whereas high levels of this element up to 23 3 g l were identified in other wells of the study area lead 1 3 to 29 1 g l appears to be anomalous with respect to its normal content in groundwater about 1 g l owing to the presence of high density brines at depth which enhance the solubility of pb in volcanic rocks under hydrothermal conditions the distribution of the investigated trace elements in the phlegraean fields thermal area is probably related to the different ascent pathways of the fluids clearly apart from the influence exerted by anomalous thermal conditions each element shows a different behaviour depending on its geochemical affinity with mineral phases and as a consequence of the different enthalpy values which determine ion partitioning in gaseous phases based on geochemical evidences and on the distribution of minor and trace elements the source processes of the investigated hydrothermal waters were defined five main groups were identified 1 acid sulphate waters resulting from mixing of meteoric water with magmatic gases mainly h 2 s 2 high sulphate chloride waters from a deep reservoir located in the major upflow zone 3 waters associated with significant degassing of magmatic co 2 4 waters from a deep geothermal neutral chloride reservoir resulting from heating of marine water modified by water rock interaction processes 5 cold waters from the inner area influenced by low temperature water rock interaction processes

sharp based tide dominated deltas of the sego sandstone book cliffs utah usa the lower part of the cretaceous sego sandstone member of the mancos shale in east central utah contains three 10 to 20 m thick layers of tide deposited sandstone arranged in a forward and then backward stepping stacking pattern each layer of tidal sandstone formed during an episode of shoreline regression and transgression and offshore wave influenced marine deposits separating these layers formed after subsequent shoreline transgression and marine ravinement detailed facies architecture studies of these deposits suggest sandstone layers formed on broad tide influenced river deltas during a time of fluctuating relative sea level shale dominated offshore marine deposits gradually shoal and become more sandstone rich upward to the base of a tidal sandstone layer the tidal sandstones have sharp erosional bases that formed as falling relative sea level allowed tides to scour offshore marine deposits the tidal sandstones were deposited as ebb migrating tidal bars aggraded on delta fronts most delta top deposits were stripped during transgression where the distal edge of a deltaic sandstone is exposed a sharp based stack of tidal bar deposits successively fines upward recording a landward shift in deposition after maximum lowstand where more proximal parts of a deltaic sandstone are exposed a sharp based upward coarsening succession of late highstand tidal bar deposits is locally cut by fluvial valleys or tide eroded estuaries formed during relative sea level lowstand or early stages of a subsequent transgression estuary fills are highly variable reflecting local depositional processes and variable rates of sediment supply along the coastline lateral juxtaposition of regressive deltaic deposits and incised transgressive estuarine fills produced marked facies changes in sandstone layers along strike estuarine fills cut into the forward stepped deltaic sandstone tend to be more deeply incised and richer in sandstone than those cut into the backward stepped deltaic sandstone tidal currents strongly influenced deposition during both forced regression and subsequent transgression of shorelines this contrasts with sandstones in similar basinal settings elsewhere which have been interpreted as tidally influenced only in transgressive parts of depositional successions

subaqueous deltaic formation of the old yellow river ad 1128 1855 on the western south yellow sea abstract the yellow river presently flows into the bohai sea but during the period ad 1128 1855 the river called the old yellow river oyr flowed into the western south yellow sea sys where the dispersal of its sediment load was controlled by the interactions among alongshore currents waves and tides and shelf morphology in this study high resolution shallow seismic profiles vibrocores boreholes and water depth data which were obtained during geological surveys in the western sys in recent years are used to examine the depositional pattern and stratigraphic record related to the oyr entering the sea our data reveal compound clinoform morphologies double clinoforms a subaerial subaqueous delta couplet sourced by the oyr in the western sys the subaerial delta comprises the currently onshore delta plain and deltafront extending to 17 m in water depth while the subaqueous delta is composed of a wide gently inclined topset and a relatively narrow steeply sloping foreset stretching seaward about 160 km away from the shoreline and showing a morphological asymmetry with a generally southward deflection relative to the oyr mouth the topset is 25 100 km wide in a shore normal direction at water depths of 10 25 m but is generally less than 4 m thick the foreset is much narrower and thicker than the topset is generally 5 30 km wide at 10 45 m water depth and is mostly 4 16 m thick with a maximum thickness of 20 m it shows seaward dipping internal reflectors generally 0 3 0 5 the rollover points topset foreset transition of the subaqueous clinoform range mostly between 10 and 25 m water depth results of 210pb and 137cs geochronology indicate that maximum sediment accumulation rates 1 06 to 2 16 cm yr correspond to the foreset region with much lower rates in the topset and surrounding shallow sea regions 97 in ad 1128 1855 has accumulated on the subaerial delta and that about 10 16 of the total load on the subaqueous delta our data also reveal that the subaqueous delta related to the oyr is underlain by a large scale clinoform broadly confined to 2 5 9 8 cal kyr bp in age as thick as 4 13 m with seaward dipping lower angled

anatomy of a transgressive lag panther tongue sandstone star point formation central utah the panther tongue of the star point formation in central utah contains a variety of transgressive lag deposits that when mapped regionally show a sensitive dependence upon pre existing topography of the palaeoshoreline the panther tongue consists of a coarsening upward sandstone wedge that prograded into the western interior seaway during late cretaceous santonian time high resolution sequence stratigraphic analysis revealed that this member was deposited during the long distance 50 km regression and transgression of a delta into shallow marine environments containing basal highstand forced regression lowstand and transgressive systems tracts based on grain size clast composition lateral extent and stratigraphic position the coarse sandstones on top of the panther tongue were classified into four types 1 simple 2 dispersed 3 oxidized and 4 local lags the simple lag is composed of dark grey coarse sandstone with oyster fragments and shark teeth this lag is typically extensively bioturbated and massive laminated and cross bedded units are also common this type of coarse sandstone is interpreted as a typical transgressive lag the dispersed lag differs in that it contains abundant mud and commonly occurs as multiple beds in thick intervals of muddy sandstone mixing of bay estuarine and shallow marine mud with simple lag sand may be responsible for deposition of this type of coarse sandstone the oxidized lag is distinctive in its reddish colour with extensive bioturbation and is commonly overlain by a simple lag the local lag is composed of thin bedded dark grey coarse sandstone occurring locally between the mouth bar and distributary channel the variation in types grain size and bed thickness of the coarse grained lags was mainly controlled by antecedent topography as suggested by immediately underlying lithofacies relatively thick 30 cm simple lags are present on top of mouth bar sandstones whereas dispersed lags are common on top of the distributary channel sandstone and in bay estuarine and shallow marine mudstones erosion of topographic highs mouth bar resulted in relatively thick accumulation of simple lags in topographic low areas such as distributary channel estuary bay and shallow marine environments fine grained muddy sands that were eroded from the nearby topographic highs were redeposited intermittent storm waves transported coarse sands both landward and seaward forming a dispersed lag the net effect was reworking of local topographic relief during overall transgression forming an apparently planar transgressive surface of erosion

sequence stratigraphy and marine to nonmarine facies architecture of foreland basin strata book cliffs utah u s a the desert member of the blackhawk formation and the castlegate sandstone in the book cliffs of utah and colorado were analyzed to develop a model of sequence stratigraphy and facies architecture in foreland basins stratal architecture of these rocks is controlled by two regionally extensive surfaces of incision and subaerial exposure interpreted as major sequence boundaries and at least six surfaces of incision and subaerial exposure with more limited lateral extent interpreted as minor sequence boundaries each sequence boundary is a regionally correlatable single surface major sequence boundaries can be traced from marine into proximal alluvial plain environments sequence boundaries have different physical expressions depending upon where in the basin they are observed strata beneath sequence boundaries are unrelated to strata above and time lines cannot be carried across these boundaries flooding surfaces called parasequence or parasequence set boundaries also exert an important control on facies architecture based on parasequence stacking patterns position of sequence boundaries and facies associations the desert member and castlegate sandstone have been divided into sequences with durations of 200 000 to 300 000 yr there are an order of magnitude more sequences in this interval than are predicted by the global sea level chart of haq et al 1988 the major sequences have been divided into the following systems tracts or sequence sets 1 grassy highstand sequence set below the desert sequence boundary named for the grassy member of the blackhawk formation 2 desert lowstand transgressive and highstand systems tracts between the desert and castlegate sequence boundaries 3 castlegate lowstand sequence set resting on the castlegate sequence boundary and 4 castlegate transgressive systems tract parasequence stacking patterns suggest that the grassy highstand sequence set and the desert highstand systems tract were deposited during a relative rise in baselevel the grassy highstand sequence set is punctuated by minor relative falls in baselevel both of these stratal units contain thick

evidence of across shelf transport of fine grained sediments turbidite filled shelf channels in the campanian aberdeen member book cliffs utah usa the shore normal transport of fine grained sediments by shelf turbidity currents has been the focus of intense debate over the last 20 years many have argued that turbidity currents are unlikely to be a major depositional agent on the shelf however sedimentological architectural stratigraphic and palaeogeographic data from the campanian aberdeen member book cliffs eastern utah suggests otherwise and clearly demonstrates that storm generated and river flood generated underflows can transport a significant volume of fine grained sediments across the shelf these across shelf flowing turbidity currents cut large subaqueous channel complexes up to 7 m deep tens of kilometres basinward of their time equivalent shoreface the shelf channels were filled with organic rich siltstones mudstones and very fine to fine grained bouma like sandstone beds including wave modified turbidites hyperpycnites and classical turbidites deposition was above storm wave base palaeocurrent data reveal an overwhelmingly dominant across shelf east south east offshore directed transport trend tectonic activity and or concomitant palaeogeographic reorganization of the basin may favour the generation of these turbidite rich shelf deposits by altering the relative balance of wave versus fluvial energy increased erosion and sediment supply rates because of tectonic uplift of the hinterland may have increased the probability of fluvial dominance along the coastline and hence the possibility of submarine channelization in front of the river mouths additionally the coastline may have become more sheltered from direct wave energy thus allowing the fluvial processes to dominate seasonal increases in rainfall and storm activity may also favour the generation of across shelf underflows on wave dominated shorelines isolated shelf channels and lobes are most likely to be found down dip of fluvial feeder systems in relatively high sediment supply settings these features are also most likely to occur in systems tracts that straddle a sequence boundary especially those which are tectonically generated as these would enhance the potential for altering basin morphology and hence the balance of fluvial and wave energy isolated shelf channels are recognized in older and younger strata in the book cliffs region implying that wave supported gravity flows were a recurrent phenomena in the campanian of utah it is probable that isolated shelf bodies are preserved in other stratigraphic intervals in the cretaceous western interior of north america and other basins worldwide and are currently being overlooked or misidentified shoreface to shelf facies models should be revised to incorporate turbidite rich shelf deposits in some shelf settings

facies architecture and geometry of landward stepping shoreface tongues the upper cretaceous cliff house sandstone mancos canyon south west colorado the campanian cliff house formation represents a series of individually progradational shoreface tongues preserved in an overall landward stepping system in the mancos canyon area the formation consists of four 50 to 55 m thick and 10 to 20 km wide sandstone tongues which pinch out landwards into lower coastal plain and lagoonal deposits of the upper menefee formation and seawards into offshore shales of the lewis shale formation photogrammetric mapping of lithofacies along the steep and well exposed canyon walls was combined with sedimentary facies analysis and mapping of the detailed facies architecture two major facies associations have been identified one comprising the mostly muddy and organic rich facies of lagoonal and lower coastal plain origin and one comprising the sandstone dominated facies of shoreface origin key stratigraphic surfaces were identified by combining the mapped geometry of the lithofacies units with the interpretation of depositional processes the stratigraphic surfaces master ravinement surface shoreface coastal plain contact transgressive surface maximum flooding surface and the sequence boundary allow each major sandstone tongue to be divided into a simple sequence consisting of a basal transgressive system tract tst overlain by a highstand system tract hst within each sandstone tongue a higher frequency cyclicity is evident the high frequency cycles show a complex stacking pattern development and are commonly truncated in the downdip direction by surfaces of regressive marine erosion the complexities of the cliff house sandstone tongues are believed to reflect changes in the rate of sea level rise combined with the responses of the depositional system to these changes synsedimentary compaction causing a thickness increase in the sandstone tongues above intervals of previously uncompacted lagoonal coastal plain sediments also played a role this study of the facies architecture geometry and sequence stratigraphy of the cliff house formation highlights the fact that there may be some problems in applying conventional sequence stratigraphical methods to landward stepping systems in general these difficulties stem from the fact that no single stratigraphic surface can easily be identified and followed from the non marine to the fully marine realm i e from the landward to the basinward pinch out of the sandstone tongues in addition the effects of synsedimentary compaction and changes in the shoreface dynamics are not easily recognized in limited data sets such as from the subsurface

quantifying clinothem geometry in a forced regressive river dominated delta panther tongue member utah usa this study presents a methodology for the quantitative description of small scale delta clinothems the quantitative bed data analysis is based on three dimensional virtual outcrop models generated by ground based laser scanning light detection and ranging a large number of clinothem bed measurements have been collected from the ancient forced regressive delta system of the panther tongue that crops out in utah usa in river dominated marginal marine environments clinothems separated by clinoform surfaces represent the former position of the delta front as it prograded systematic collection of data from virtual outcrop models has allowed for accurate spatially constrained measurement of individual bed thicknesses and the compilation of a detailed database on clinothems and associated clinoform geometries measurement locations were selected so that each measurement was 10 m down depositional dip from the previous one the study area covers 5 km2 within which 2376 measurements were made from 50 separate clinothems in 320 different positions within the virtual outcrop a bed taper parameter permitted the thinning of the clinothems to be described as a single number and thus allowed relative comparison between beds combined measurements were also used to calculate the average dip angle of the clinothems analysis of the vertical and lateral stacking of the clinothems has revealed a series of stratigraphic cycles which are termed bedsets stream mouth bars the surfaces that bound the bedsets are unremarkable and it is unlikely that their significance would be recognized without this style of detailed analysis a cyclic depositional pattern interpreted as related to autocyclic processes and compensational stacking of mouth bars is proposed as the origin of these packages mapped length thickness trends constrain the spread of these variables and can be used to constrain subsurface models of analogous hydrocarbon reservoirs

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

a model for migrating shelf bar sandstones in upper mancos shale campanian northwestern colorado the duffy mountain sandstone was deposited by migrating submarine shelf bars that are now completely encased in marine mudstones of the mancos shale upper cretaceous the shelf bars were deposited at least 10 mi 16 km offshore and stood approximately 100 to 150 ft 30 to 46 m above a shallow shelf the bars were never emergent but were shallow enough for fair weather waves to form ripples along their crests these elongate sand bodies trend northeast southwest approximately parallel to the shoreline the sediment was probably derived from reworking of transgressed littoral deposits in southwestern wyoming four subenvironments are recognized 1 landward flank of the shelf bar the back bar 2 the axial crest of central bar 3 a seaward facing ramp subfacies and 4 the shelf upon which the shelf bars migrated two major processes were active during deposition 1 fair weather longshore southwesterly currents and 2 storm erosion and westerly across the shelf bar sediment transport during fair weather sand waves transported sediment along the central bar while the back bar and shelf were being bioturbated storms eroded the seaward face of the bar and portions of the central bar creating hummocky erosion surfaces eroded sediment transported across the bar was deposited in coarsening upward spillover lobes in the back bar after the storm waned sediments deposited in t e back bar were bioturbated and sand waves were deposited on the eroded central bar migration of sand waves onto the eroded face of the bar formed the ramp facies as the shelf bar migrated the central bar facies climbed stratigraphically over the back bar facies the direction of shelf bar migration was probably controlled by the interaction of fair weather and storm sediment transport