volcanism and faulting of the campania margin eastern tyrrhenian sea italy a three dimensional visualization of a new volcanic field off campi flegrei by means of information technology 3d digital geologic models are increasingly the best methods of constraining interpretations of geology at depth visualization in three dimensions has allowed us to develop solutions that explain the stratigraphic and structural complexity of the campania margin of the eastern tyrrhenian sea especially the lateral relationships among volcanoes and underlying normal faults using seismic and sequence stratigraphy and structural geology approaches in a dedicated gis environment we interpreted a seismic grid and investigated a subsurface volcanic field in gaeta bay off campi flegrei located within the campania margin the gaeta bay basin fill is characterized by several volcanic units that were analyzed using 2d structure contour maps and isochron maps these volcanoes are comparable in size to the edifices of campi flegrei vesuvius and the submerged volcanoes of the bay of naples their age spans from the lower pleistocene for the isolated v0 volcano sited in central gaeta bay to 0 4 0 1 ma for the volcanic field of southern gaeta bay the study of the interplay between volcanic units and faults allowed us to distinguish 1 the oldest fault buried by the lower pleistocene v0 volcano in central gaeta bay 2 a normal fault swarm ne sw that in the middle pleistocene gave rise to a half graben filled by the v1 v5 volcanic field in southern gaeta bay and 3 post 0 4 ma normal faults that downthrow the v1 and v3 volcanoes we correlated the 1 500 m thick late quaternary volcanoes of southern gaeta bay to the buried lava volcanoes interlayered with volcanoclastic deposits drilled at campi flegrei geothermal wells

simulation of groundwater exchange between an unconfined aquifer and a discrete fracture network with laminar and turbulent flows abstract in this study a new approach is developed to simulate groundwater flow through both an overlying unconfined aquifer and an underlying discrete fracture network the groundwater exchange between the aquifer and the fracture network including magnitude and direction is explicitly simulated based on the mass conservation which depends on a variety of parameters related to flow and network characteristics in the overlying unconfined aquifer we approximate the flow using the dupuit assumptions in the underlying fracture network we use the cubic law and forchheimer s law to iteratively simulate laminar or turbulent flow in individual fractures depending on the reynolds number explicitly separating laminar and turbulent flows in the fractures results in a system of nonlinear equations which is iteratively solved while the flow from the overlying unconfined aquifer is a small portion of the overall flow in the underlying fracture network incorrect use of the laminar or turbulent flow equation in the fractures can lead to significant errors in simulating the flow exchange as apertures increase both the portion of the total flowrate in the aquifer and the portion of the flow in the fractures coming from the aquifer decrease as the overall hydraulic gradient increases both the portion of the total flow in the aquifer and the portion of the fracture flow that comes from the aquifer increase the portion of the total flow in the aquifer increases with the aquifer thickness while the portion of fracture flow coming from the overlying aquifer decreases

three dimensional implicit stratigraphic model building from remote sensing data on tetrahedral meshes theory and application to a regional model of la popa basin ne mexico remote sensing data provide significant information to constrain the geometry of geological structures at depth however the use of intraformational geomorphologic features such as flatirons and incised valleys often calls for tedious user interaction during 3 d model building we propose a new method to generate 3 d models of stratigraphic formations based primarily on remote sensing images and digital elevation models this method is based on interpretations of the main relief markers and interpolation of a stratigraphic property on a tetahedral mesh covering the domain of study the tetrahedral mesh provides a convenient way to integrate available data during the interpolation while accounting for discontinuities such as faults interpretive expert input may be provided through constrained interactive editing on arbitrary cross sections and additional surface or subsurface data may also be integrated in the modeling we demonstrate this global workflow on a structurally complex basin in the sierra madre oriental northeastern mexico

long term cycles of triassic climate change a new δ18o record from conodont apatite jat and isw gratefully acknowledge financial support from the australian research council dp1096252 mr is grateful for financial support from progetto d ateneo 2009 cpda090175 09 and 2012 cpda 121100 and prin 2008 2008bef5z7 005

water table fluctuations near an incised stream walnut creek iowa abstract incised channels are common features in many agricultural watersheds but the effects of channel incision on riparian water table conditions have been poorly documented in this study we evaluate the water table fluctuations in the floodplain near an incised stream walnut creek iowa and investigate the roles that channel incision and variable recharge play in modifying the water table configuration in the floodplain groundwater flows from higher landscape positions towards walnut creek under hydraulic gradients that were steepest near the upland floodplain contact and in the near stream riparian zone annually water table fluctuations on the floodplain were greatest in wells located 30 m from the creek midway between the creek and upland water levels monitored continuously during a runoff event indicated that bank storage was confined to a narrow zone adjacent to the channel a steady state one dimensional analytical model was developed to describe the shape of the water table surface near an incised stream and evaluate how variable groundwater recharge and channel bed lowering has affected the shape of the water table surface results from this study have implications for managing the riparian buffers of incised streams with successful establishment dependent upon matching buffer vegetation to riparian water table conditions

climate controlled early dolomite late triassic cyclic platform carbonates hungary abstract the 2 km thick late triassic hungarian carbonate platform has a completely dolomitized lower part and a limestone dominated upper part the platform succession is made up of meter scale possibly precessional 20 ky carbonate cycles in the lower platform main dolomite cycles are completely dolomitized and capped by caliche laminites and pisolites in the upper platform dachstein limestone dolomite is confined to laminite caps of cycles that are bounded by clayey paleosols most of the dolomitization in the platform interior occurred early in tidal flat settings during each high frequency cycle subtidal dolomites are slightly coarser grained are low in fe2 and mn2 and have the heaviest 18o signature this indicates they formed from evaporative oxidizing brines sourced from supratidal flats intertidal supratidal dolomites are fine grained commonly fe2 and or mn2 rich and slightly enriched in 18o compared to the marine calcite cement they formed from marine water that was weakly to moderately reducing dachstein paleosols have light 18o and 13c signatures reflecting meteoric soil waters repeated emergence stabilized the dolomites to low sr2 and na dolomite similar to cenozoic platform dolomites in contrast to these early cyclic dolomites coarse grained platform margin dolomites with very low mn2 and fe2 and light 18o signatures formed as thermally driven warm oxidizing marine water associated with jurassic rifting of the neo tethys pennini ocean circulated through the margin early dolomitization of cycles may have been controlled by high frequency sea level changes but the overall vertical distribution of early dolomite on the platform does not reflect long term eustasy rather the intense dolomitization of the lower platform reflects a semiarid hot subtropical seasonal setting and megamonsoonal climate global cooling and increased humidity toward the latest triassic and early jurassic inhibited pervasive early dolomitization leaving the upper platform largely as limestone

geologic stereo mapping of geologic structures with spot satellite data geologic note 1 the spot imaging system launched in 1986 by the french national space agency cnes provides two significant advances for mapping geological structures from satellite imagery increased spatial resolution of key structural and stratigraphic elements and stereoscopic capabilities for making strike and dip measurements quantitative stereo mapping with spot data may be done using hard copy images and conventional equipment such as stereo plotters or by displaying images on a video monitor in stereo viewing format the latter method is a new remote sensing technique particularly relevant to the exploration community this technique allows development with minor expenditure and training of an effective stereo mapping capability on existing image processing systems or o stand alone personal computers spot stereo data is particularly useful for mapping low amplitude and highly deformed structures surface structure maps generated from stereo imagery data can be applied to exploration at two levels at early stages such maps can be used to establish the style trend size and spatial distribution of structures in a basin and to investigate key tectonic elements at more advanced prospecting stages these maps can be used to constrain subsurface mapping of structures located in areas of poor seismic data quality this latter technique however may require the support of higher resolution stereo aerial photography

the carnian pluvial episode from discovery through obscurity to acceptance the discovery of the carnian pluvial episode arose through a chance conversation bringing together two seemingly unrelated strands of research the extinction of some triassic crinoids and the stratigraphy of the non marine mercia mudstone group investigations revealed a hitherto unrecognized period of climate change seemingly linked to a largely overlooked episode of biotic turnover ignored for more than a decade an upsurge of interest in recent years has validated our original findings and answered some of the key questions concerning its extent and ultimate cause

rainfall infiltration derived submarine groundwater discharge from multi layered aquifer system terminating at the coastline this article investigates the quantity of submarine groundwater discharge sgd from a coastal multi layered aquifer system in response to constant rainfall infiltration the system comprises an unconfined aquifer a leaky confined aquifer and an aquitard between them and terminates at the coastline an approximate analytical solution is derived based on the following assumptions i flow is horizontal in the aquifers and vertical in the aquitard and ii flow in the unconfined aquifer is described by nonlinear boussinesq equation the analytical solution is compared with numerical solutions of the strictly two dimensional nonlinear model to validate the model assumptions used for the analytical solution the sgd from the leaky confined aquifer increases with the inland rainfall infiltration recharge and the specific leakage of aquitard the maximum sgd ranges from 1 87 to 10 37 m3 per day per meter of shoreline when rainfall infiltration ranges from 18 2 to 182 mm year and the specific leakage of aquitard varies from 10 9 to 10 1 l day copyright 2011 john wiley sons ltd

lower eocene alluvial paleosols willwood formation northwest wyoming u s a and their significance for paleoecology paleoclimatology and basin analysis abstract the lower eocene willwood formation of northwest wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones nearly all of which show paleopedogenic modifications pedogenesis of willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation early local cementation by calcium carbonate and thin illuviation cutans on clastic grains pedogenesis in willwood mudstones is indicated by plant bioturbation insect and other invertebrate burrow casts and lebensspuren free iron aluminum and manganese mobilization including hydromorphic gleying sesquioxide and calcareous glaebule formation in lower parts of the solum presence of clay rich and organic carbon rich zones and well differentiated epipedons and albic and spodic horizons probable a horizons are also locally well developed occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin lenticular and unconnected fluvial sandstones in the willwood formation of the central and southeast bighorn basin suggest that these soils formed during times of rapid sediment accumulation the tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that willwood floodplains were broad and essentially featureless all willwood paleosols were developed on alluvial parent materials and are complex in that b horizons of younger paleosols were commonly superimposed upon and mask properties of suspected a and b horizons of the next older paleosols the soils appear to be wet varieties of the spodosol and entisol groups aquods and ferrods and aquents respectively though thick superposed and less mottled red purple and yellow paleosols resemble some ultisols most willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and or fluctuating water tables the up section decrease in frequency of gley mottles increase in numerical proportion and thickness of red versus orange coloration and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late willwood time this drying is believed to be related to creation of rain shadows and spacing of rainfall but not necessarily decrease in absolute rainfall due to progressive tectonic structural elevation of the mountainous margins of the bighorn basin

triassic climates state of the art and perspectives abstract the climate of the triassic period was characterized by a non zonal pattern dictated by a strong global monsoon system with effects that are most evident in the tethys realm this strong monsoonal regime is related to the aggregation of the pangaean supercontinent which by triassic time was already completed climate oscillations existed within this framework the harsh hot house climatic conditions that characterized the late permian and perhaps precipitated the end permian mass extinction were probably maintained during the early triassic and may account for the impoverished but distinctive faunal and floral lower triassic associations although metazoan reef builders were probably the most affected group carbonate production remained high at least in the western tethys realm the middle triassic was characterized locally by humid episodes although their geographical distribution has yet to be clarified the carnian pluvial event marks an episode of increased rainfall documented worldwide was the most distinctive climate change within the triassic different hypotheses have been proposed for its causes changes of atmospheric or ocean circulation driven by plate tectonics a peak of the global monsoon due to maximum continent aggregation or triggering by the eruption of a large igneous province subsequently the late carnian and norian seem to have been climatically stable although minor climatic changes have recently been described even from this time period finally the end triassic extinction event is also associated with climate change specifically warming and increased rainfall but this evidence comes mostly from the northern parts of the central atlantic magmatic province and the global pattern of climate change at the triassic jurassic boundary has still to be resolved many facets of triassic climate are intriguing and deserve further research however palaeoclimate studies on the triassic have so far been carried out only locally with different proxies those proxies will require inter calibration in order to depict correctly the temporal and geographical patterns of triassic climate

3 d modeling of geologic maps from surface data recent discoveries in earth sciences are mostly related to technologies allowing graphical representations of volumes we present a way to produce mathematically and geometrically correct three dimensional 3 d geologic maps consisting of the volume and shape of all geologic features of a given area the method is innovative in that it only uses surface information based on the combination of a standard geologic map a satellite image and a digital elevation model it is based on a modeling algorithm that only uses surfaces calculated from scattered data points and that intersects them following a series of geologically sound rules the major advantage of using such technology is that it provides the user with a way to quantify geology to illustrate how a 3 d geologic map can be computed we explain the steps taken to build a dummy model with simple faulting and depositional sequencing the case study chosen to illustrate the method is the beirut watershed lebanon an area with relatively simple geology the 3 d visualization and cross sections help in the understanding of the geometrical relationship between the different geologic features allowing a reexamination of the tectonic history of the area during the late mesozoic

the carnian pluvial event in western europe new data from iberia and correlation with the western neotethys and eastern north america nw africa regions abstract at the beginning of the late triassic a period of increased precipitation occurred over large tracts of central pangea the carnian pluvial event it was a short lived event 1 ma coeval with a marked sea level fall and active rifting new and classical sections of carnian age in the iberian peninsula have been studied and a new correlation scheme is proposed for the iberian domain integrating field data and subsurface electric log data this is the first time that the portuguese and spanish late triassic carnian sediments are correlated the carnian pluvial event is identified in the iberian peninsula as a continental clastic wedge manuel fm and coeval sediments in between marine evaporite formations during a marked sea level drop event its age is considered to be julian early carnian by palynological and paleogeographic considerations a new correlation of the late triassic sediments of the iberian peninsula with coeval sediments of western europe nw africa and eastern north america is proposed and a new paleogeographical map of central eastern pangea for this period is presented in order to demonstrate that the geographical extent of the siliciclastic sediments related to the carnian pluvial event was much larger than accepted before

palaeoenvironments of the late triassic rhaetian sea implications from oxygen and strontium isotopes of hybodont shark teeth the oxygen and strontium isotopic composition of 125 teeth of the hybodont sharks lissodus and hybodus from various late triassic rhaetian bone bed localities in the central european basin are used as environmental and ecological tracers for the shallow epicontinental rhaetian sea the preservation of tooth enameloid was ascertained by cathodoluminescence microscopy mean 18op values differ regionally across the rhaetian sea with values of 18 6 0 6 near the western gate 16 1 0 8 in the east 15 4 0 6 in the southeast and 17 7 0 9 in the south the 18op values in the eastern rhaetian sea are 4 5 lower relative to tethyan seawater while teeth from the southern and western parts close to the marine gates are less fractionated the strontium isotopic composition of teeth from most localities is more radiogenic in comparison to late triassic seawater the observed spatial 18op trend in the rhaetian sea indicates a shift from marine to brackish conditions in the south and west towards extensively brackish conditions with salinities of less than 16 in the east thus confirming the existence of two marine gates brackish conditions persisted throughout early rhaetian times and were maintained by increased fluvial discharge from the vindelician bohemian and fennoscandian highs as a result of enhanced atmospheric moisture availability in the course of the rhaetian transgression the 18op values of lissodus and hybodus indicate euryhaline behaviour of rhaetian hybodonts by exceeding modern shark intraspecific variability the lack of accordance in 18op values between different isotopically conspicuous localities in the rhaetian sea contradicts a basin wide migration pattern differences between co site taxa might indicate some degree of niche partitioning

taphonomy of the prosauropod dinosaur sellosaurus and its implications for carnivore faunas and feeding habits in the late triassic abstract the stubensandstein upper triassic norian is a complex system of fluvial deposits in southwest germany and yields one of the most diverse records of fossil vertebrates from the european continental triassic taphonomic data from 17 partial skeletons of the prosauropod dinosaur sellosaurus gracilis are presented with emphasis on a recently rediscovered field sketch of one particular specimen the preservational states and burial postures of individuals forming a practically monospecific prosauropod assemblage indicates in situ preservation of single specimens most likely by miring in unconsolidated fluvial sands covered by floodplain deposits shed teeth of carnivores and the mode of preservation suggest that one of the prosauropod carcasses was scavenged at least two different types of predators several individuals of a large indeterminate primitive archosaur and a phytosaur left traces of their activities during scavenging on the carcass the prosauropod carnivore tooth assemblage provides the first evidence that deep snouted phytosaurs with heterodont dentitions were capable of manipulating and feeding on large terrestrial prey moreover scavenger prey assemblages in the norian of central europe support the hypothesis that large carnivorous basal archosaurs as represented for example by rauisuchians were replaced by theropod dinosaurs in the late triassic

a review of mesozoic climates there is overwhelming evidence based on the distribution of distinctive sediments and fossils and oxygen isotope data that the climate of the mesozoic world was appreciably more equable than that of today with no polar ice caps but precise quantitative data are not available except for an episode of late cretaceous cooling there is no good documentation of any significant change in global temperature distributions through the era the distribution of coals and evaporites together with other criteria indicates a pattern of humid arid and zones appreciably different in important respects from that of today during the triassic and jurassic western pangaea in low to middle latitudes was largely arid but in the early cretaceous the lands on the margin of the newly opening central atlantic and western tethys experienced a humid climate by late cretaceous times arid zones had become very restricted in extent because of insufficient suitable data attempts at climatic modelling have had only modest success and only to a limited extent can the major long term changes in climate between the permian and the present be explained in terms of changing geography the most probable explanation of mesozoic equability is an increased atmospheric co 2 content a number of enigmas remain such as the existence of flourishing forests in polar palaeolatitudes whereas for the late cenozoic short term climatic changes can be related successfully to variations in the geometry and mechanics of the earth sun system there is a long way to go before comparable success can be claimed for the mesozoic

dissected paleotopography and base level changes in a triassic fluvial sequence at one stratigraphic level in petrified forest national park in arizona fluvial mudrocks of the chinle formation are truncated by areally extensive deep scours that are filled dominantly by pedogenically modified mudrocks color differences between paleosols developed on scoured and scour fill deposits facilitate recognition of the dissected interval the mudstone filled scour system records a period of channel incision and widespread gullying caused by lowered base level although it is difficult to document subsidence rates in the chinle basin the tectonic setting suggests that the enormous scour system could be the result of fluctuations in regional thermal activity during late triassic time similar scour and fill should occur in other fluvial sequences however because they both truncate and are filled by mudrocks identification can be difficult recognition of them is important because they are indicators of base level fluctuations and thus are useful in unraveling the depositional history of a basin

carnian norian late triassic climate change evidence from conodont oxygen isotope thermometry with implications for reef development and wrangellian tectonics abstract the carnian norian c n transition late triassic has long been postulated as an interval of major climatic changes though the nature of such changes and their ecological impact remains largely unexplored we use oxygen isotopes measured on monogeneric conodont assemblages 18 opo4 from the canadian cordillera to trace seawater temperature evolution at the western margin of pangea and in the allochthonous wrangellia terrane different conodont taxa show conspicuous offsets in 18 opo4 suggesting that they had preferential habitat depths and genus specific temperature corrections must be applied thus 18 opo4 from the williston lake sections indicates low mid latitude sea surface temperatures ssts ranging from 28 to 35 c favouring a generally warm late triassic climate scenario the parvus subzone of c n transition which marks the peak faunal turnover records major climatic perturbations ssts peaking at 34 c then decreasing to 29 c this is followed by a quick temperature rebound and a second pulse of cooling from 33 to 27 c in the asymmetrica norigondolella subzone marking the coldest temperatures in the 20 myr study interval a secular warming trend towards the late norian reinstated after the transient cooling in the earliest norian coinciding with reef expansions in the late triassic the middle late norian alaunian 3 sevatian 1 represents a hothouse climate comparable to the paleocene eocene thermal maximum and its warmth supressed both diversity and origination rates of reef building biota early norian 18 opo4 data from frederick island haida gwaii part of the wrangellia terrane are more depleted in 18o compared to coeval samples from the black bear ridge indicating 3 5 c warmer temperatures than the laurentian epicontinental sea the temperature difference supports a more southern probably sub equatorial position for at least part of the wrangellia terrane during the earliest norian

evolution of the permian and triassic tetrapod communities of eastern europe abstract the permo triassic terrestrial and freshwater tetrapod communities of eastern europe are reconstructed as food webs the late permian theriodont dinocephalian community ocher mezen isheyevo changes to a latest permian theriodont pareiasaur community north dvina vyazniki after a major extinction the triassic thecodontian dicynodont communities appear a lystrosaurid one in the early triassic lower and upper vetluga and a kannemeyerid one in the later early triassic yarenga and the mid triassic donguz bukobay similar stages are represented in the evolution of aquatic communities the late permian temnospondyl community ocher isheyevo the latest permian chroniosuchian one north dvina vyazniki the lower and middle triassic new temnospondyl one from vetluga to bukobay the faunal changes in eastern europe are mirrored in other parts of the world although there are some endemic russian forms

recharge to aquifers with mixed boundaries abstract the problem of localized groundwater recharge from a strip basin to an aquifer bounded by stream and impermeable boundaries was solved by the use of extended finite fourier transforms the solution was evaluated by comparison with the method of images and with numerical and experimental results the existing expression for the inverse of the extended finite fourier cosine transform was corrected

cyclicity of triassic to lower jurassic continental red beds of the argana valley morocco implications for palaeoclimate and basin evolution abstract cyclical playa deposits form a prominent part of the continental clastic succession of the argana valley western high atlas of morocco the red beds formed in triassic to lower jurassic times during rifting of the north american and african plates detailed stratigraphic work revealed asymmetrical metre scale cycles in mudstone dominated successions that constitute the intermediate and upper portion of the basin fill sedimentary cycles commonly comprise ephemeral lake shales at the base playa mudflat mudstones in the intermediate part and both fluvial and aeolian sandstones at the top cycles of the aglegal member t4 are mainly characterized by analcime rich playa mudflat deposits displaying features indicative of palaeo vertisols cycles of the sidi mansour t7 and hasseine t8 members are represented by ephemeral lake or dry playa mudflat deposits grading into saline mudflat mudstones that are overlain by sheet flow and minor aeolian sandstones sedimentary cycles of the imerhrane member t9 comprise sheet delta sandstones at the base overlain by ephemeral lake and dry playa mudflat mudstones upper cycle portions consist of aeolian dune and sand sheet sandstones cyclicity is attributed to palaeoclimatic and associated palaeohydrological fluctuations probably within the milankovitch frequency band sedimentary facies of each cycle provide evidence for a gradual climatic drying with time the asymmetrical drying upward cycles possibly record the precession cycle since they are modulated by symmetrical i e oscillating drying wetting cycles of a lower frequency indicative of eccentricity a long term change in palaeoclimate ranging from semi arid conditions with seasonal precipitation t4 towards an arid non seasonal climate t8 is preserved within the cyclical units spanning a time interval of several million years individual cycles can be traced laterally for tens of kilometres correlative sections are almost identical in thickness suggesting a phase of tectonic quiescence during their deposition sediment accumulation was not restricted to small scale grabens but took place continuously throughout the exposed area of the argana valley implying that accommodation space has not been controlled by syndepositional tectonism

wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western united states a comparison panfish j t and peterson f 1988 wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western united states a comparison in g kocurek editor late paleozoic and mesozoic eolian deposits of the western interior of the united states sediment geol 56 261 282 wind directions for middle pennsylvanian through jurassic time are predicted from global circulation models for the western united states these predictions are compared with paleowind directions interpreted from eofian sandstones of middle permsylvanian through jurassic age predicted regional wind directions correspond with at least three quarters of the paleowind data from the sandstones the rest of the data may indicate problems with correlation local effects of paleogeography on winds and lack of resolution of the circulation models the data and predictions suggest the following paleoclimatic developments through the time interval studied predominance of winter subtropical high pressure circulation in the late pennsylvanian predominance of summer subtropical high pressure circulation in the permian predominance of summer monsoonal circulation in the triassic and earliest jurassic and during the remainder of the jurassic influence of both summer subtropical and summer monsoonal circulation with the boundary between the two systems over the western united states this sequence of climatic changes is largely owing to paleogeographic changes which influenced the buildup and breakdown of the monsoonal circulation and possibly owing partly to a decrease in the global temperature gradient which might have lessened the influence of the subtropical high pressure circulation the atypical humidity of triassic time probably resulted from the monsoonal circulation created by the geography of pangaea this circulation is predicted to have been at a maximum in the triassic and was likely to have been powerful enough to draw moisture along the equator from the ocean to the west

a geographical information system gis study of triassic vertebrate biochronology geographical information systems gis have been applied extensively to analyse spatial data relating to varied environmental issues but have not so far been used to address biostratigraphical or macroevolutionary questions over extended spatial and temporal scales here we use gis techniques to test the stability validity and utility of proposed middle and late triassic land vertebrate faunachrons lvfs a global biostratigraphical framework based upon terrestrial freshwater tetrapod occurrences a database of tetrapod and megafloral localities was constructed for north america and western europe that also incorporated information on relevant palaeoenvironmental variables this database was subjected to various spatial analysis techniques our gis analysis found support at a global level for eocyclotosaurus as an anisian index taxon and probably aetosaurus as a norian indicator other tetrapod taxa are useful biostratigraphical biochronological markers on a regional basis such as longosuchus and doswellia for late carnian time other potential index fossils are hampered however by taxonomic instability mastodonsaurus metoposaurus typothorax paleorhinus pseudopalatus redondasaurus redondasuchus and or are not clearly restricted in temporal distribution paleorhinus angistorhinus stagonolepis metoposaurus and rutiodon this leads to instability in lvf diagnosis we found only in the western northern hemisphere is there some evidence for an anisian ladinian biochronological unit amalgamating the perovkan and berdyankian lvfs and a possible late carnian unit integrating the otischalkian and adamanian megaplants are generally not useful for biostratigraphical correlation in the middle and upper triassic of the study area but there is some evidence for a carnian age floral assemblage that corresponds to the combined otischalkian and adamanian lvfs environmental biases do not appear to strongly affect the spatial distribution of either the tetrapods or megaplants that have been proposed as index taxa in biostratigraphical schemes though several examples of apparent environmental bias were detected by the analysis consequently we argue that further revision and refinement of middle and late triassic lvfs is needed before they can be used to support global or multi regional biostratigraphical correlations caution should therefore be exercised when using the current scheme as a platform for macroevolutionary or palaeoecological hypotheses finally this study demonstrates the potential of gis as a powerful tool for tackling palaeontological questions over extended timescales

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

the end triassic bivalve extinction event one of the most important episodes of mass extinction of animal groups in the whole of the phanerozoic took place in the latter part of the triassic but the time of major faunal turnover of the vertebrates preceded that of marine invertebrates by several million years as shown by ammonites brachiopods and conodonts decline from a carnian early norian diversity peak was followed by a significant extinction episode at the end of the period this pattern is confirmed at generic and subgeneric level by the bivalve molluscs probably the most abundant and diverse macroinvertebrate group this paper analyses the bivalves in detail and attempts to seek a relationship of the extinction event to environmental changes as recorded by late triassic facies stratigraphy of the youngest triassic is briefly discussed following a recent recommendation the rhaetian stage is dropped and the upper norian sevatian subdivided into three new ammonite zones it is suggested that the classic northwest european rhaetic correlates with the kossen and zlambach beds of the alps and corresponds at least approximately with the upper two of these zones it is estimated that nearly half the existing bivalve genera and nearly all the species failed to survive the end triassic extinction event the trigonioid unionoid and hippuritoid orders were especially strongly affected but most of the pholadomyoid genera survived three major ecological categories are distinguished a shallow neritic group to which most taxa belong a euryhaline group that could tolerate marginal marine and lagoonal conditions and a deep neritic group notably halobia and monotis all groups were strongly affected by the extinction but species of the deep neritic group were apparently the most susceptible seven biogeographic regions are distinguished for the purpose of analysis and it is shown that provinciality is slight but some important taxa are endemic to the tethyan and pacific regions endemic genera prove to have been much more subject to extinction than cosmopolitans there are very few places in the world with a more or less continuous marine sequence of deposits across the triassic jurassic boundary details are given of sections in the alps northwest europe and nevada and briefer mention made of others with regard to late triassic palaeogeographic changes those involving climate were neglibible but there was a more or less progressive regression of epicontinental seas following a ladinian early carnian transgressive maximum with a corresponding shallowing in the more continuously marine tethyan region that this first order effect was due to a eustatic lowering of sea level is fairly certain but the situation is less clear for second order transgressive regressive cycles the late late norian rhaetian cycle is probably however the results of a minor eustatic event by the end of the triassic the sea had regressed substantially and the mass extinction event is though to be bound up partly with this phenomenon and partly with the phase of widespread anoxicity that occurred during the succeeding hettangian transgression

breccia hosted manganese rich minerals of alpi apuane italy a marine redox generated deposit mn rich beds occur within the brecce di seravezza formation bsfm intercalated between norian metadolostone megalodontic marble and hettangian marble in the alpi apuane italy the bsfm is a rockfall talus deposit that accumulates at the base of the footwall scarp of normal faults bordering extensional marine coastal basins the type sequence of metabreccia ends with a bed of chloritoid schist interpreted as the metamorphic equivalent of lateritic soils the four main types of mn mineral assemblages are 1 braunite piemontite and rare hausmannite 2 piemontite braunite hollandite and minor rhodochrosite and kutnahorite 3 braunite hollandite and rare piemontite the other minerals are quartz calcite muscovite phlogopite baryte and minor hematite rutile and apatite during the alpine orogeny pressures of 4 6 kb and temperatures of 350 380 c were attained mn assemblages with hematite and phlogopite indicate o2 10 8 for t 350 c and o2 10 6 when braunite appears on the mn rich rocks ti fe nb sn ta hf th ga rb pr k na nd were identified as detrital in origin and are positively correlated with al u is positively correlated with co pb bi mo the rare earth element patterns normalized to seawater show a negative slope towards the heavy rare earth elements with positive ce anomalies in some samples positive ce and eu anomalies in other samples and negative ce and positive eu anomalies in a third group the eu concentrations are nearly constant and the eu anomalies reflect differences in the concentration of other rare earth elements for ce a positive correlation with al2o3 sio2 indicate that a detrital signature prevails on that produced by duration of seawater exposure but a significant good correlation of la tm lu with mg could indicate at least for these elements a seawater signature only in some samples ba eu sr show anomalously high concentrations likely of hydrothermal origin however generally in all the chemical variation diagrams the bsfm samples fall outside the field of hydrothermal and hydrogenous deposits as defined in the literature for other mn deposits in addition metabasites and metavolcaniclastic beds are absent from the bsfm sequence and bsfm coastal basins were for the most part separated from the open ocean and related streams that must be excluded as possible mn sources owing to the arid climate of late triassic the runoff was negligible and the groundwater oxidizing and alkaline were unable to mobilize mn the bsfm basins are then the most suitable depositional environment for mn the water column was stagnant and stratified only where bottom of the basin was deeper than the oxic anoxic boundary reducing marine bottom waters percolated within the fractured basement and leached mn from disseminated minerals of metamorphic rocks and then rising along fault and fractures supplied mn to the bottom waters afterwards when tectonic uplift and sealevel drop brought the bottom into the oxic field mn precipitated and formed the mn rich matrix of the bsfm deposits

reconstructing extensional basin architecture and provenance in the marrakech high atlas of morocco implications for rift basins and inversion tectonics

more than one event in the late triassic mass extinction the recent hypothesis that mass extinctions are discrete phenomena that have occurred with great regularity during the history of life1 2 is testable in several ways two essential elements of the hypothesis are 1 that each extinction event represents a significant departure from normal or background rates of extinction and 2 that such mass extinction events are spaced equally in time the analyses of the cyclicity of mass extinctions so far have concentrated on the past 250 myr with the first event occuring at the permian triassic boundary 245 myr ago1 5 the second event followed 26 33 myr later1 6 in the late triassic here i present a detailed analysis of the fossil record of marine and non marine life during the late triassic which suggests that there were at least two phases of mass extinction during that time separated by 12 17 myr

upper plate deformation as marker for the northern step fault of the ionian slab tyrrhenian sea central mediterranean abstract the eastern tyrrhenian margin etm the active boundary of the tyrrhenian sea backarc basin is the key for understanding the geodynamics of the central mediterranean numerous seismic tomography studies have been carried out in this region proposing different reconstructions of the lower subducting plate and cause of the slab break off existing beneath the southern apennines however the area and mode of the recent deformation of the tyrrhenian sea are still not fully defined and understood in this study we combine the analysis of a recent seismic tomography model and geological data in order to understand the relationship between the subducting lower plate and the tectonic evolution of the sedimentary basins formed on the upper plate with this aim we interpreted a large data set of seismic reflection profiles and several well logs the results consist in 2d and 3d geological models of the basins sedimentary infill and fault networks taking into account the geological data of the etm and those of the adjacent inner flank of the apennines we observe i a system of linked sedimentary basins developed on a narrow deformation belt bounded by transform fault zones ii a polyphase rifting within the upper plate iii an abrupt change of the direction of extension 90 from ne oriented in the lower pleistocene to se oriented in the middle pleistocene since these etm features are not the typical expressions of the current backarc extensional models we propose a link between the evolution of upper plate and the onset and development of a step subduction transform edge propagator fault along the northern margin of the ionian slab

late triassic ecosystem variations inferred by palynological records from hechuan southern sichuan basin china the late triassic deposits of the sichuan basin southwestern china are significant for hosting abundant and diverse fossil assemblages including plants containing spores and pollen bivalves and insects however the late triassic palaeoecological variations are still poorly documented in this region here we present results from a palynological study from the upper triassic xujiahe formation in hechuan of chongqing southern sichuan basin the palynological analysis revealed a well preserved terrestrial palynoflora of high diversity comprising 184 species in 75 genera of spores and pollen three palynological assemblages were recognized reflecting terrestrial successions throughout the entire interval with significant changes in the vegetation cycads bennettites ginkgophytes and conifers show an increasing trend into younger deposits while ferns and lycopsids decrease in relative abundance the late triassic vegetation underwent changes from lowland fern forest to a mixed forest with more canopy trees we applied the spore pollen morphological group smg method and sporomorph ecogroup seg model to interpret the palaeoclimate features the results reveal that the lower part of the xujiahe formation was deposited under relatively warm and humid conditions with an overall cooling and drying trend from latest norian to rhaetian time accompanied by a general decrease of ferns and simultaneous increase of gymnosperms and a decline in diversity of miospores this study presents data on variations within the terrestrial ecosystem prior to the end triassic extinction event in the sichuan basin and therefore provides important information for understanding the changes in the vegetation preceding the end triassic event

infiltration mechanism simulation of artificial groundwater recharge a case study at pingtung plain taiwan this paper discusses the artificial groundwater recharge effect of high infiltration basins for this purpose the hydrogeological parameters of the study area are collected to construct a conceptualized physical model the tough2 numerical simulation software is then used to simulate the infiltration behavior of an artificial recharge into an underground aquifer four wells mw 1 mw 2 mw 3 and mw 4 are observed at the field site after which the groundwater levels are compared with the simulation results it is found that good agreement exists between the observed and numerical data for mw 1 and mw 2 however the observed groundwater level in mw 3 is higher than the simulated level we also find that mw 3 is at the edge of the artificial recharge lake and that the high groundwater level may well be the result of a portion of the infiltration load following the well border into the well screen conversely the groundwater level in mw 4 is found to be lower than in the simulated well due to local permeability in the well location finally the numerical results predict that the groundwater level will attain a steady state at approximately 47 h after the onset of infiltration

transient groundwater flow between reservoirs and water table aquifers abstract transient groundwater flow between a reservoir and a semi infinite unconfined aquifer has been one of the fundamental research topics in hydrogeology prediction of water level changes in the aquifer due to water level variations in the reservoir is of importance in contamination control irrigation and hydrology the movement of groundwater under this condition is described by the nonlinear boussinesq equation analytical solutions to this equation are limited to some special cases and often require tedious computations in this study a new solution technique is developed in which the boltzmann transformation is used to reduce the boussinesq equation to a nonlinear ordinary differential equation and the water level distributions are calculated using the newton raphson method the solution procedure requires very little computational effort and the solution has been verified by comparing with analytical and numerical solutions this solution should have application in verifying other analytical or numerical solutions and in many practical hydrogeological problems two linearized solutions are evaluated using the new analytical solution developed in this study the linearized solution with respect to h 2 gives a better result than that linearized with respect to h

giant polygons in the triassic salt of cheshire england a thermal contraction model for their origin abstract the triassic salt in cheshire england has large polygonal patterns on bedding surfaces the polygons are bounded by deep v shaped fissures the fissures have a banded internal structure made up of individual units of pure secondary salt and clastic rich halite the salt was deposited from shallow brines in an arid environment a thermal contraction model is proposed here for the formation of the polygons calculations of the depth of penetration of thermal waves and the net contraction of salt beds indicate that annual temperature fluctuations would produce fissures of the observed depth and width it is suggested that thermal contraction is the most important factor in the initiation of all polygonal patterns on salt surfaces and that the polygon form that eventually develops is de endent on the thickness of the salt bed and the availability of brines to the salt surface

three dimensional reconstruction of geological surfaces an example of growth strata and turbidite systems from the ainsa basin pyrenees spain the external and internal geometry of four turbidite systems outcropping around the buil syncline ainsa basin spanish pyrenees has been reconstructed with reservoir scale resolution in three dimensions 3 d the irregular geometry of the syncline and the resolution required for the reconstruction cannot be resolved with cross sections therefore reconstruction has been carried out with a new methodology that applies a 3 d dip domain geometrical model and 3 d restoration techniques to achieve reservoir scale resolution in kilometric scale reconstructions this methodology is aimed at resolving 3 d geometries in folded areas and regions with variable thickness stratigraphy the 3 d reconstruction of the buil syncline reveals the synsedimentary growth of an intrabasinal anticline and the foreland lithospheric flexure associated with tectonic loading north of the ainsa basin

senonian basin inversion and rejuvenation of rifting in africa and arabia synthesis and implications to plate scale tectonics abstract the late paleozoic to tertiary stratigraphic record of much of the african plate reflects the effects of continental rifting and passive margin development several short lived but widespread and tectonically important compressional or wrench dominated events occurred however during the permian to recent evolution of africa we focus here on the best documented of these events which occurred during the late santonian at that time older sedimentary basins mostly ene wsw trending were folded and inverted including some basins along the tethyan margin from morocco to the syrian arc and the intraplate benue southern chad basins and the lugh mandera basin in oman ophiolites were obducted following the santonian tectonism an extensive phase of rifting occurred in central and north africa and northern arabia spanning from campanian to maastrichtian or paleocene times rejuvenation or acceleration of subsidence occurred in several basins located along the tethyan margin along the atlantic and indian ocean margins as well as within the intraplate domain rifting was sometimes accompanied by magmatic activity especially in offshore northern libya and along the indian ocean margin compressional deformations rejuvenated or developed by latest maastrichtian times along the tethyan margin and locally within the intraplate domain one of the most remarkable attributes of the santonian tectonic event which we consider representative of the major trans african stress field changes is the rapidity with which the change was reflected stratigraphically across north and central africa and its short duration the cause of the santonian compressional event is directly linked to the change in poles of rotation for the opening of the atlantic at 83 85 ma the end of the cretaceous normal magnetic quiet zone this was also synchronous with the obduction of ophiolites along the northeast margin of arabia oman the onset of separation between india and madagascar with formation of the mascarene oceanic basin and the development of the european alpine chain we interpret these phenomena as causally related aspects of a global tectonic event the santonian compressional event as well as the campanian maastrichtian rifting event and the end cretaceous compressional event illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries

groundwater visualisation system gvs a software framework for integrated display and interrogation of conceptual hydrogeological models data and time series animation summary management of groundwater systems requires realistic conceptual hydrogeological models as a framework for numerical simulation modelling but also for system understanding and communicating this to stakeholders and the broader community to help overcome these challenges we developed gvs groundwater visualisation system a stand alone desktop software package that uses interactive 3d visualisation and animation techniques the goal was a user friendly groundwater management tool that could support a range of existing real world and pre processed data both surface and subsurface including geology and various types of temporal hydrological information gvs allows these data to be integrated into a single conceptual hydrogeological model in addition 3d geological models produced externally using other software packages can readily be imported into gvs models as can outputs of simulations e g piezometric surfaces produced by software such as modflow or feflow boreholes can be integrated showing any down hole data and properties including screen information intersected geology water level data and water chemistry animation is used to display spatial and temporal changes with time series data such as rainfall standing water levels and electrical conductivity displaying dynamic processes time and space variations can be presented using a range of contouring and colour mapping techniques in addition to interactive plots of time series parameters other types of data for example demographics and cultural information can also be readily incorporated the gvs software can execute on a standard windows or linux based pc with a minimum of 2 gb ram and the model output is easy and inexpensive to distribute by download or via usb dvd cd example models are described here for three groundwater systems in queensland northeastern australia two unconfined alluvial groundwater systems with intensive irrigation the lockyer valley and the upper condamine valley and the surat basin a large sedimentary basin of confined artesian aquifers this latter example required more detail in the hydrostratigraphy correlation of formations with drillholes and visualisation of simulation piezometric surfaces both alluvial system gvs models were developed during drought conditions to support government strategies to implement groundwater management the surat basin model was industry sponsored research for coal seam gas groundwater management and community information and consultation the virtual groundwater systems in these 3d gvs models can be interactively interrogated by standard functions plus production of 2d cross sections data selection from the 3d scene rear end database and plot displays a unique feature is that gvs allows investigation of time series data across different display modes both 2d and 3d gvs has been used successfully as a tool to enhance community stakeholder understanding and knowledge of groundwater systems and is of value for training and educational purposes projects completed confirm that gvs provides a powerful support to management and decision making and as a tool for interpretation of groundwater system hydrological processes a highly effective visualisation output is the production of short videos e g 2 5 min based on sequences of camera fly throughs and screen images further work involves developing support for multi screen displays and touch screen technologies distributed rendering gestural interaction systems to highlight the visualisation and animation capability of the gvs software links to related multimedia hosted online sites are included in the references

remote surface mapping using orthophotos and geologic maps draped over digital elevation models application to the sheep mountain anticline wyoming remote mapping of surface structures can be conducted by draping digital orthophotos and geologic maps over digital elevation models in geographic information systems formational contacts can be mapped by viewing the intersections of these contacts with the topography on a true to scale three dimensional image bedding orientations can be determined from 1 the trends and slopes of dip slopes or 2 best fit planes to multiple points of intersection of a bedding surface with the topography the methods are tested against mapped formation contacts and bedding attitudes for the sheep mountain anticline in the bighorn basin wyoming detailed mapping of formation contacts is improved by careful observations of the contacts on three dimensional images interpreted bedding attitudes from slope and multiple point solutions show strong positive correlations with field measurements this mapping method provides an efficient and accurate alternative to stereoscopic mapping using aerial photographs and satellite images particularly for remote and inaccessible areas

vertebrate preservation in fluvial channels abstract two taphonomic modes for attritional vertebrate assemblages in channels are proposed based on the sedimentary context of the vertebrate remains and taphonomic features of the bones themselves the channel lag mode includes bones that are buried with coarse lithologies near the bases of active channels the channel fill mode occurs in fine grained to mixed fills of abandoned channels the extreme for a channel lag assemblage would be a cluster of allochthonous abraded unidentifiable fragments and the extreme for a channel fill assemblage would be a cluster of autochthonous unbraded complete skeletons between these extremes there is a broad spectrum of possible taphonomic histories for bones in channels but distinct channel lag vs channel fill modes can be recognized in fluvial deposits in different tectonic and climatic settings throughout the phanerozoic physical and biological processes that affect the different modes produce different samples of vertebrate paleocommunities with bones in the channel lag mode representing transported remains from a variety of habitats whereas channel fill assemblages are more autochthonous and habitat specific channel facies channel pattern and alluvial architecture are used to develop hypotheses concerning how the taphonomic modes relate to different scales of fluvial processes fluvial systems with numerous abandoned channels provide more sites for preservation of relatively complete fossil vertebrates in channel fills while systems that continually rework sediments by lateral migration preserve more vertebrate remains as channel lags large scale physical controls on channel pattern and fluvial architecture probably have had significant effects on the quality and quantity of the vertebrate record throughout the history of land vertebrates taphonomic modes provide a basis for comparing faunas with similar preservational histories throughout the geologic record and they can help to minimize biases in important paleobiological parameters such as diversity estimates and the timing of appearance and extinction events

geologic stereo mapping of geologic structures with spot satellite data reply the spot imaging system launched in 1986 by the french national space agency cnes provides two significant advances for mapping geological structures from satellite imagery increased spatial resolution of key structural and stratigraphic elements and stereoscopic capabilities for making strike and dip measurements quantitative stereo mapping with spot data may be done using hard copy images and conventional equipment such as stereo plotters or by displaying images on a video monitor in stereo viewing format the latter method is a new remote sensing technique particularly relevant to the exploration community this technique allows development with minor expenditure and training of an effective stereo mapping capability on existing image processing systems or on stand alone personal computers spot stereo data is particularly useful for mapping low amplitude and highly deformed structures surface structure maps generated from stereo imagery data can be applied to exploration at two levels at early stages such maps can be used to establish the style trend size and spatial distribution of structures in a basin and to investigate key tectonic elements at more advanced prospecting stages these maps can be used to constrain subsurface mapping of structures located in areas of poor seismic data quality this latter technique however may require the support of highermore resolution stereo aerial photography less

some outstanding issues in the geology of lebanon and their importance in the tectonic evolution of the levantine region abstract the concept of pervasive and disruptive late neogene quaternary strike slip tectonics in lebanon has made establishing a satisfactory pre neogene palaeogeographic and palaeotectonic history for the area difficult research has allowed clarification of three fundamental issues that permit the setting of lebanon against its adjacent regions to be more firmly assigned the first issue is the identification of the significance of the 100 km long nne ssw trending monocline of the western lebanon flexure this feature is interpreted as a modified and rejuvenated early mesozoic hinge line that is presumed to be the northern continuation of the carmel sinai hinge line to the south the second issue is the correlation of the mount lebanon bekaa and anti lebanon complex with the adjacent intracontinental palmyride fold belt of syria through recognition in each of common divisions in structural style between a higher northern zone dominated by broadly spaced box folds and a lower southern zone with more numerous closely spaced and more internally complex folds the third issue involves the identification of major two stage late cretaceous to palaeogene syrian arc tectonism within lebanon resolution of these issues suggests a tectonic model for the region whereby the levantine region formed in two main phases the first of these was the multiphase late palaeozoic early mesozoic rifting of the area which imposed a fundamental extensional fabric over much of the region the second tectonic phase was the subsequent inversion of these extensional structures in the two stage syrian arc deformation of senonian and late palaeogene age which gave rise to the main lebanon structures it is this syrian arc tectonism rather than the late cenozoic strike slip that was probably the main structuring agent which affected the lebanon area the transpression from the braided dead sea fault motion although locally complex is an essentially neotectonic overprint on an already existing fabric offset of syrian arc structures in lebanon suggests that the total sinistral motion of the yammouneh fault segment of the dead sea fault is around 47 km

recharge from rectangular areas to finite aquifers abstract a generalized analytical solution is derived for the growth of groundwater mound in finite aquifers bounded by open water bodies in response to recharge from rectangular areas finite fourier transforms are used to solve the linearized differential equation of groundwater flow unlike earlier solutions the method presented here does not require the use of tables for evaluation of complicated functions the solution is evaluated by comparison with existing numerical and analytical results in stream aquifer systems similar to those described above application of the proposed solution is more realistic than using solutions available for infinite aquifers

modelling of water table variation in response to time varying recharge from multiple basins using the linearised boussinesq equation a mathematical model is presented to describe the variations of the water table in an unconfined aquifer due to time varying recharge applied from four rectangular basins the model is developed by solving the linearised boussinesq equation using the extended finite fourier cosine transform the time varying recharge rate is approximated by a number of piecewise linear elements of different lengths and slopes depending on the nature of the variation in recharge rate application of this model for the prediction of water table fluctuations and in the sensitivity analysis of various controlling parameters on the aquifer response is demonstrated in an example

groundwater dynamics due to general stream fluctuations in an unconfined single or dual porosity aquifer subjected to general areal recharge abstract analytical solutions of groundwater dynamics in an elongated aquifer subjected to general time dependent recharge are presented the lateral boundaries are specified heads with the head variations governed by general time dependent functions general recharge function was not considered in previous works of this kind both single and double porosity aquifers are considered the solution is obtained using fourier sine and laplace transformations followed by an inverse fourier laplace transform involving residue theorem and convolutional integral for the unconfined single porosity aquifer case the exact time domain solution is obtained using the residue theorem for the unconfined double porosity aquifer case the time domain head is calculated using the de hoog inverse laplace algorithm the presented solution can be used to estimate the hydraulic parameters of 1 groundwater head variation of a river basin aquifer subjected to general lateral head variation and recharge 2 groundwater head variation in a double porosity elongated fractured anticline 3 groundwater depletion of an elongated fractured anticline subjected to recharge due to rainfall or snowmelt to its adjacent alluvial aquifer in addition the presented solution can be utilized to optimize the irrigation pattern in a cropland between two trench drains to control the groundwater mound

the response of groundwater to artificial recharge schemes analytic solutions are presented for the groundwater flow in an unconfined aquifer under seasonal artificial recharge schemes of variable duration the results can be used for a preliminary assessment of the response of groundwater to artificial recharge variations in storage and outflow from the aquifer apart from the siting of recharge are also highly dependent on both the aquifer characteristics and the duration of recharge

quantitative structural analysis with stereoscopic remote sensing imagery we employ powerful stereoscopic methods with satellite imagery to obtain surface bedding attitude measurements these data are used to constrain geologic structures in three dimensions using quantitative structural models we document a numerical method for measuring the strike and dip of bedding using stereoscopic pairs of air photos as well as landsat thematic mapper and spot images in examples from the north american and andean cordilleras these remote measurements prove consistent with direct surface control and subsurface structures imaged in seismic reflection profiles remotely derived measurements are combined with subsurface data to generate balanced structural interpretations that define complex structural traps using fault related folding theory these remote sensing methods can provide a low cost and rapid means of delineating prospects and leads

vertebrate paleoecology of the chinle formation late triassic of the southwestern united states abstract the late triassic chinle formation is an extensive series of fluvial and lacustrine sediments exposed mostly in the colorado plateau region fossil vertebrates occur in local concentrations throughout the vertical and horizontal extent of the formation although the most diverse accumulations occur within the petrified forest member in arizona and new mexico successive faunas are known from the lower and upper units of the petrified forest member and can be subdivided into terrestrial and aquatic communities faunal turnover occurs among herbivores phytosaurs and metoposaurs between the lower and upper units no major change is observed in fish faunas throughout chinle deposition mass accumulations of vertebrate fossils in the chinle occurred on floodplains in bogs and small ponds and in or near fluvial channels paleontological and sedimentological evidence supports the interpretation of chinle paleoclimates as having significant precipitation but being strongly seasonal vertebrate occurrences do not clearly reflect the gradual aridification at the end of chinle deposition suggested by sedimentological study

some analytical solutions of the linearized boussinesq equation with recharge for a sloping aquifer subsurface flow from a hillslope can be described by the hydraulic groundwater theory as formulated by the boussinesq equation several attempts have been made to solve this partial differential equation and exact solutions have been found for specific situations in the case of a sloping aquifer brutsaert 1994 suggested linearizing the equation to calculate the unit response of the hillslope in this paper we first apply the work of brutsaert by assuming a constant recharge to the groundwater table the solution describes the groundwater table levels and the outflow in function of time then an analytical expression is derived for the steady state solution by allowing time to approach infinity this steady state water table is used as an initial condition to derive another analytical solution of the boussinesq equation this can then be used in a quasi steady state approach to compute outflow under changing recharge conditions subsurface flow from a hillslope can be described by the hydraulic groundwater theory as formulated by the boussinesq equation several attempts have been made to solve this partial differential equation and exact solutions have been found for specific situations in the case of a sloping aquifer brutsaert 1994 suggested linearizing the equation to calculate the unit response of the hillslope in this paper we first apply the work of brutsaert by assuming a constant recharge to the groundwater table the solution describes the groundwater table levels and the outflow in function of time then an analytical expression is derived for the steady state solution by allowing time to approach infinity this steady state water table is used as an initial condition to derive another analytical solution of the boussinesq equation this can then be used in a quasi steady state approach to compute outflow under changing recharge conditions

carbonate facies of the upper triassic ojo huelos member san pedro arroyo formation chinle group southern new mexico paleoclimatic implications abstract the upper triassic adamanian lvf ojo huelos member of the san pedro arroyo formation chinle group is a distinctive carbonate rich unit that occurs in the lower chinle section of central new mexico the member consists mainly of micritic lime mudstones ostracodal wackestones to grainstones peloidal grainstones and distinctive pisolitic rudstones interbedded with fine grained siliciclastic mudstones most limestones exhibit some evidence of pedogenic brecciation and root penetration and porous fabrics similar to those of modern limestone tufas occur locally the interbedded mudstones are typically lenticular and commonly display a blocky ped fabric in which subequant peds are separated by sparry calcite veins fossils from the ojo huelos member are freshwater darwinulid ostracodes various freshwater fishes and aquatic amphibious tetrapods metoposaurs and phytosaurs we interpret the carbonate facies as the deposits of carbonate lakes ponds and wetlands that were partly spring fed whereas the interbedded and surrounding mudstones were alluvial in origin the groundwater and overland hydrology of the region was likely controlled by the relative proximity to an upland recharge area in the mogollon highlands to the south but sedimentary fabrics record strong overprinting by desiccation and pedogenic reworking consequently we interpret the ojo huelos member as recording a climate that varied from subhumid to semi arid which caused episodic falls in the hydrologic base level this resulted in landscape degradation exemplified by significant pedogenic and erosional reworking of the carbonate sediments and fluvial incision

events around the triassic jurassic boundary in northern and eastern spain a review abstract more than 20 successions containing the triassic jurassic t j boundary were studied in five of the major geological units of spain the data are from outcrop cored boreholes and interpreted well logs a consistent 3 4 13 c org isotope excursion starting in the rhaetian and continuing in the hettangian was recorded in asturias climate changes in the t j transition show a warming episode in the early hettangian other climate changes are indicated by an increase in hygrophytic miospores above the t j boundary this reflects a more humid episode at the beginning of the hettangian the messejana dyke in southeastern iberia is part of the central atlantic magmatic province camp co 2 outgassing related to extensive magmatic activity in the camp is thought to be one of the possible factors responsible for the end triassic mass extinction no major sea level changes or unconformities were recorded at the t j boundary only in the asturias area was there a well defined shallow carbonate platform during the t j transition the other areas of eastern and northern spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions the biotic crisis around the t j boundary is reflected in the palynomorph record in asturias seven species do not persist beyond the late rhaetian and only six appeared in the triassic jurassic transition however 22 taxa appeared in the early hettangian

triassic environments climates and reptile evolution abstract a consideration of all the available data on triassic vertebrate faunas and their stratigraphic location reveals a relatively sudden extinction event among the last of the mammal like reptiles and the herbivorous rhynchosaurs in the norian of the upper triassic this event was apparently quickly followed by the radiation of the dinosaurs also in the norian this conclusion suggests that competition was not the main factor in the initial success of the dinosaurs but opportunistic radiation following the extinction of major reptile groups a global review of triassic sedimentary facies shows that there were climatic and floral changes towards the end of the triassic it is envisaged that increasing aridity in the later triassic resulting from plate motions and particularly affecting gondwanaland and southwestern laurasia brought about floral changes and then the reptile extinctions with the rapid evolution of new floras of conifers and bennettitaleans the dinosaurs came to dominate all terrestrial faunas within the space of only a few million years

the age origin and tectonic significance of mesozoic sediment filled fissures in the mendip hills sw england implications for extension models and jurassic sea level curves in the eastern mendip hills on the northern margin of the wessex basin sw england the carboniferous limestone is cut by numerous fissures that are filled with mesozoic sediments sedimentary dykes neptunian dykes the fissures contain a record of triassic lower jurassic sediments that are only sparingly preserved in their normal stratigraphical position between the carboniferous limestone and the unconformably overlying upper inferior oolite of bajocian age detailed analysis of cross cutting relationships facies analysis biostratigraphy lithostratigraphy and strontium isotope ages of relevant mesozoic sediments has allowed the construction of an upper triassic lower jurassic fissure fill stratigraphy for the eastern mendip area most fissures were clearly formed by rapid influx of unlithified sediment from the land surface or sea floor some smaller cavities or larger cavities with restricted access to the unconformity were apparently filled by sediment that trickled down into the fissure system the vast majority of the mendip fissures are interpreted as having formed as a response of the carboniferous limestone north of major basin bounding faults to pulses of tectonic extension during ladinian norian rhaetian late hettangian early sinemurian late sinemurian early pliensbachian late pliensbachian and bajocian times triassic earliest jurassic fissures have a broad spread of strike from e w to nw se to n s accommodating extension in a roughly ne sw direction younger jurassic fissures show well defined e w and n s trends with the former becoming dominant through time total extension of 4 7 n s and 0 6 e w was produced by the formation of triassic jurassic fissures within the carboniferous limestone such patterns of extension are thought likely to be characteristic of the subsurface geology in much of southern england and wales major implications of this study are that 1 the presence of seismically unresolvable sediment filled fissures in supposedly rigid fault blocks can lead to a significant underestimate of regional extension based on the restoration of motion on normal faults on seismic reflection profiles and 2 the isolation of pulses of tectonic activity with a temporal resolution of 10 5 10 6 years may provide a means of identifying a tectonic signal in relative sea level curves derived from the jurassic sedimentary record

analytical solutions for two dimensional groundwater flow with subsurface drainage tiles summary the tile drainage problem in an unconfined aquifer was investigated a mathematical model was established that describes two dimensional groundwater flow in an unconfined aquifer near a river with a linearized boussinesq equation time dependent sources and a sloped tile analytical solutions for groundwater level and discharge were derived and used to compare hydrologic conditions in a system with and without tile natural drainage we found that the spatial and temporal variations of groundwater level and discharge were significantly altered by the presence of drainage tile in an aquifer with tile drainage the groundwater level was lower and total groundwater discharge to the river increased compared to an aquifer with no tile application of the solutions to a synthetic case demonstrates that the analytical solutions derived can be used to quantify effect of tiles on nitrate loads in the baseflow of a river and assess the effectiveness of various conservation practices

analytical solutions for strip basin recharge to aquifers with cauchy boundary conditions abstract analytical solutions for groundwater recharge from strip basins to finite aquifers are presented the problem concerns the impact of either continuous or periodic seasonal recharge schemes on aquifers with a boundary condition of the third kind cauchy the solutions can be useful for assessing aquifer response as well as for calibrating numerical computer models

recharge to finite aquifers from strip basins abstract the problem of groundwater recharge from strip basins to finite aquifers is solved analytically by the method of finite fourier transforms both impermeable and recharge boundaries are considered the analytical solutions are evaluated by comparison with experimental results in sand tank models reported in the literature

a new analytical method for groundwater recharge and discharge estimation summary a new analytical method was proposed for groundwater recharge and discharge estimation in an unconfined aquifer the method is based on an analytical solution to the boussinesq equation linearized in terms of h2 where h is the water table elevation with a time dependent source term the solution derived was validated with numerical simulation and was shown to be a better approximation than an existing solution to the boussinesq equation linearized in terms of h by calibrating against the observed water levels in a monitoring well during a period of 100 days we shown that the method proposed in this study can be used to estimate daily recharge r and evapotranspiration et as well as the lateral drainage it was shown that the total r was reasonably estimated with a water table fluctuation wtf method if the water table measurements away from a fixed head boundary were used but the total et was overestimated and the total net recharge was underestimated because of the lack of consideration of lateral drainage and aquifer storage in the wtf method

analytical and experimental solutions for drainage of sloping lands with time varying recharge m j boussinesq s 1904 nonlinear partial differential equation for unsteady state flow of water through a phreatic aquifer resting on a sloping impervious barrier and receiving time varying recharge has been solved two patterns of recharge rates i e linearly increasing and exponentially declining with time were considered the initial conditions of the water table were taken at the drain level transformations were devised to transform the resulting approximate linearized boussinesq equation to the form of a one dimensional heat flow equation for each case of recharge pattern and analytical solutions for the height of the water table between parallel drains were obtained in the form of a convergent series the analytical solutions were experimentally verified with a hele shaw model a reasonably close agreement was found in the computed and observed phreatic surfaces the results showed that the analytical solutions presented herein can be used with reasonable accuracy for designing subsurface drainage in sloping phreatic aquifers

analytical solutions for periodic well recharge in rectangular aquifers with third kind boundary conditions abstract analytical solutions for groundwater flow in rectangular aquifers are presented in the case of single well recharge the problem concerns the impact of a seasonal periodic recharge scheme of variable duration on aquifers with various boundary conditions of which at least one is of the third kind results can be obtained for any combination of boundary conditions and can be used in a preliminary assessment of the groundwater response to artificial recharge schemes

estimating recharge based on long term groundwater table fluctuation monitoring in a shallow aquifer of malaysian tropical rainforest catchment a practical and reliable approach was applied to investigate the groundwater dynamics and obtain natural direct recharge based on the time series of water table fluctuation in moderately flat coastal area with a shallow water table and tropical rainforest weather drainage rate was about 0 034 m day in the study area as estimated by falling groundwater table in period of no rainfall and specific yield values ranged between 0 11 and 0 23 by calculating depth dependent specific yield based on soil water storage for layering soils the method was applied to the monthly data of shallow aquifer at eight field sites in north kelantan river catchment in the period of 1991 2011 the cross correlation and partial cross correlation reveal the acceptable correlation between the water table fluctuation and the rainfall data assuming the time lag from precipitation to water table response is negligible due to shallow water table recharge rates vary with the field sites and mainly depend on soil type and rainfall rather than surface geology although computer simulation with mrcr code was implemented with limited data two series still results are just slightly greater than the field data which indicated the method successfully employed and can be applied in areas with similar conditions in future

seasonal climatic fluctuations in the late triassic tropics high resolution oxygen isotope records from aragonitic bivalve shells cassian formation northern italy abstract three megalodontoid bivalves from the upper triassic cassian formation n italy dolomites were sampled for 13 c and 18 o sclerochronology n 270 with more than 1000 described invertebrate species the cassian formation has one of the best records of an early mesozoic tropical fauna in addition the cassian formation is one of the very few triassic occurrences with original aragonite preservation with all studied shells consisting of pristine aragonite the presence of aragonite and crossed lamellar as well as fibrous prismatic shell microstructures shown for the first time for triassic megalodontoids suggests absence or minimal impact of diagenetic alteration the 13 c values range from 3 6 to 5 8 and show a distinct cyclicity in two studied shells whereas a third shell shows no obvious cyclicity in one bivalve specimen the cycles are somewhat offset from 18 o cycles and in the other specimen 18 o and 13 c curves are inversely correlated seasonal variation in freshwater runoff including nutrient input and subsequent changes in plankton productivity during dry and wet seasons may explain 13 c cyclicity 18 o values show a pronounced cyclicity within each of the studied shells varying from 3 6 to 1 4 the variations in 18 o suggest a pronounced seasonality in late triassic tropical shallow waters of the western tethys with inferred seasonal temperature changes ranging from 24 to 32 c influx of fresh water during the rainy seasons mega monsoon or upwelling might also explain part of the variation in 18 o the presented data suggest that the diverse cassian fauna lived under conditions characterized by warm sea surface waters with a pronounced seasonality similar conditions are reported for some modern tropical settings

li b rich rhaetian metabauxite tuscany italy reworking of older bauxites and igneous rocks abstract li b rich metabauxite layers occur in two outcrops of talus metabreccias intercalated between norian and liassic marbles in the alpi apuane tuscany italy field evidence petrographical geochemical and paleogeographic paleoclimatologic considerations suggest that bauxitic material was derived from a multistage reworking of late carboniferous early autunian primary deposits now completely removed the identified lithotypes are cookeite rich metabauxite cookeite bearing metabreccia chloritoid schist and chloritoid phyllite the mg content of calcite and the si content of muscovite and mineral assemblages indicate temperatures of 350 380 c pressures of f o 2 values of 10 30 to 10 24 for the alpine metamorphism in comparison with the average mesozoic bauxite of bronevoy et al 1985 the metabauxite is strongly enriched in si k ca mg li b be ni and ce it shows comparable contents of co la eu tb ta and th it is depleted in ga cr v zn mn hf u and is strongly depleted in sr f cu a metabauxite layer shows decreasing abundance of fe and ga from bottom to top with a pattern opposite to that of primary bauxite deposits inverted profile the strong enrichment of li and b is not related to evaporitic conditions since the mgo na 2 o and sr contents are too low and indicator minerals such as dravitic tourmaline albite and scapolite are missing during the permian volcanic products similar to the coeval peralkaline peraluminous rocks of corsica sardinia were widespread in tuscany b li rich minerals were produced by circulation of hot hydrothermal fluids within the permian volcanic rocks during and soon after their emplacement the erosion of such hydrothermal products supplied detrital material to the talus metabreccia

foraminiferal biostratigraphy and sequence stratigraphy of peritidal carbonates at the triassic jurassic boundary karaburun peninsula western turkey abstract continuous shallow marine carbonates spanning the triassic jurassic boundary are exposed in the karaburun peninsula western turkey the studied section tahtaiskele section consists of upper triassic cyclic shallow marine carbonates intercalated with clastics overlain by lower liassic carbonates based on the microfacies stacking patterns three main types of shallowing upward cycles have been recognized cycles are mostly composed of subtidal facies at the bottom intertidal supratidal facies and or subaerial exposure structures at the top the duration of the cycles suggests that cycles were driven by the precessional milankovitch rhytmicity in the sequence stratigraphic frame of the tahtaiskele section 4 sequence boundaries were detected and globally correlated the first sequence boundary is located at the alaunian sevatian boundary nearly coinciding with the first appearance of triasina hantkeni the second falls in the rhaetian corresponding to a major sea level fall which led to the invasion of forced regressive siliciclastic deposits over the peritidal carbonates the third occurs close to the t j boundary and the fourth lies slightly above the base of the jurassic in the studied section extinction survival and recovery intervals have been recognized based on the stratigraphic occurrence patterns of benthic foraminifera and algae foraminifers became nearly totally extinct in the inner carbonate shelves at the triassic jurassic boundary and an interval of approximately 0 5 my passed before the begining of the recovery of jurassic foraminifera

outer ramp cycles in the upper muschelkalk of the catalan basin northeast spain the upper muschelkalk triassic of the catalan basin eastern spain was deposited upon a carbonate ramp of homoclinal type located in an intracratonic setting the rasquera unit in the upper muschelkalk mostly consists of outer ramp carbonates arranged in upward shallowing cycles five cycles from 1 5 to 12 m thick are recognised each cycle shows an upward coarsening of grain size an upward increase in bed thickness and an upward change in fossil content reflecting an upward shallowing of the environment in the complete cycle marlstone and shale pass up into marlstone with thin bedded line mudstones containing pelagic bivalves the succeeding thin bedded and nodular limestones with shaley partings contain a more varied fauna and are bioturbated they pass up into thick bedded skeletal wackestones packstone coquinas locally cap the cycles and have a diverse benthic fauna as well as the alga tubiphytes occurring as bioclasts encrustations around skeletal grains and forming microbuildups although some of the thin beds were deposited during weak storms there is little evidence of intense storm activity petrological sedimentological and palaeontological criteria and the geological setting allow the recognition of distal intermediate and proximal facies on a relatively deepwater carbonate ramp

lungfish burrows in the upper triassic chinle and dolores formations colorado plateau abstract vertical to inclined cylindrical trace fossils that occur in the upper triassic chinle and dolores formations on the colorado plateau are interpreted to be the casts of lungfish burrows the casts which are as much as 11 cm in diameter and as much as 1 6 m long were formed by passive silicilastic and carbonate sedimentation into apparently abandoned lungfish burrows locally the burrow fillings are overwhelmingly abundant and many intersect and have destroyed former burrow fillings superposition of bioturbation episodes has obliterated most primary sedimentary structures this bioturbation has contributed to the mottled coloration and the knobby weathering texture of the rocks the burrow fillings occur ubiquitously in three lithofacies comprising 1 purple and white mottled ilicified sandstone and siltstone 2 red and brown siltstone and mudstone and 3 pink and green limestone these strata were deposited in a continental environment that included fluvial channels and floodplains sand sheets and playa mudflats and lacustrine basins marshes and deltas the identification of the trace fossils as the positive casts of lungfish burrows is based on their morphologic similarity to previously identified lungfish burrows and to available hand specimens the widespread occurrence of the lungfish burrows in the chinle and dolores formations attests to the extensive habitat that supported lungfish in the late triassic and to conditions favorable for burrow preservation analogy with the environments that support modern lungfish populations suggests that the late triassic climate in the study area provided sufficient moisture to support large populations of lungfish and that this climate was probably punctuated by seasonally dry periods

fragmentation of asia in the permian asia is a composite continent formed by the accretion of crustal blocks1 3 a likely sequence of events is that siberia collided with a kazakhstan block which together then collided with europe along the urals in permo triassic times2 this was followed by the sucessive accretion of various blocks of south and east asia to siberia culminating in the collision of india with asia during the cenozoic palaeomagnetic data have already demonstrated that the kolyma and sikhote alin blocks of eastern asia collided with the main continent along the late mesozoic fold belts of verkhoyansk and sikhote alin4 furthermore results from the malay peninsula5 and japan6 suggest that south east asia and japan were situated near the equator in permian times and were therefore separated from the asian continent we report here some palaeomagnetic results from the permian of the sino korean and yangtze blocks of china that show they were also situated near the equator were not in their present relationship to one another and were widely separated from siberia

a metahillslope model based on an analytical solution to a linearized boussinesq equation for temporally variable recharge rates 1 in hydrology the slow subsurface component of the discharge is usually referred to as base flow one method to model base flow is the conceptual approach in which the complex physical reality is simplified using hypotheses and assumptions and the various physical processes are described mathematically the purpose of this paper is to develop and validate a conceptual method based on hydraulic theory to calculate the base flow of a catchment under observed precipitation rates the governing groundwater equation the boussinesq equation valid for a unit width sloping aquifer is linearized and solved for a temporally variable recharge rate the solution allows the calculation of the transient water table profile in and the outflow from an aquifer under temporally variable recharge rates when a catchment is considered a metahillslope the solution can be used when coupled to a routing model to calculate the catchment base flow the model is applied to the zwalm catchment and four subcatchments in belgium the results suggest that it is possible to model base flow at the catchment scale using a boussinesq based metahillslope model the results further indicate that it is sufficient to use a relatively simple formulation of the infiltration overland flow and base flow processes to obtain reasonable estimates of the total catchment discharge

steady state groundwater recharge in trapezoidal shaped aquifers a semi analytical approach based on variational calculus summary this study presents a semi analytical solution for steady groundwater flow in trapezoidal shaped aquifers in response to an areal diffusive recharge the aquifer is homogeneous anisotropic and interacts with four surrounding streams of constant head flow field in this laterally bounded aquifer system is efficiently constructed by means of variational calculus this is accomplished by minimizing a properly defined penalty function for the associated boundary value problem simple yet demonstrative scenarios are defined to investigate anisotropy effects on the water table variation qualitative examination of the resulting equipotential contour maps and velocity vector field illustrates the validity of the method especially in the vicinity of boundary lines extension to the case of triangular shaped aquifer with or without an impervious boundary line is also demonstrated through a hypothetical example problem the present solution benefits from an extremely simple mathematical expression and exhibits strictly close agreement with the numerical results obtained from modflow overall the solution may be used to conduct sensitivity analysis on various hydrogeological parameters that affect water table variation in aquifers defined in trapezoidal or triangular shaped domains

the origin and early radiation of dinosaurs abstract dinosaurs were remarkably successful during the mesozoic and one subgroup birds remain an important component of modern ecosystems although the extinction of non avian dinosaurs at the end of the cretaceous has been the subject of intense debate comparatively little attention has been given to the origin and early evolution of dinosaurs during the late triassic and early jurassic one of the most important evolutionary radiations in earth history our understanding of this keystone event has dramatically changed over the past 25 years thanks to an influx of new fossil discoveries reinterpretations of long ignored specimens and quantitative macroevolutionary analyses that synthesize anatomical and geological data here we provide an overview of the first 50 million years of dinosaur history with a focus on the large scale patterns that characterize the ascent of dinosaurs from a small almost marginal group of reptiles in the late triassic to the preeminent terrestrial vertebrates of the jurassic and cretaceous we provide both a biological and geological background for early dinosaur history dinosaurs are deeply nested among the archosaurian reptiles diagnosed by only a small number of characters and are subdivided into a number of major lineages the first unequivocal dinosaurs are known from the late carnian of south america but the presence of their sister group in the middle triassic implies that dinosaurs possibly originated much earlier the three major dinosaur lineages theropods sauropodomorphs and ornithischians are all known from the triassic when continents were joined into the supercontinent pangaea and global climates were hot and arid although many researchers have long suggested that dinosaurs outcompeted other reptile groups during the triassic we argue that the ascent of dinosaurs was more of a matter of contingency and opportunism dinosaurs were overshadowed in most late triassic ecosystems by crocodile line archosaurs and showed no signs of outcompeting their rivals instead the rise of dinosaurs was a two stage process as dinosaurs expanded in taxonomic diversity morphological disparity and absolute faunal abundance only after the extinction of most crocodile line reptiles and other groups

climatic and biotic change in the late triassic generally arid conditions that pervaded much of europe and north america during the late triassic were interrupted by a wet monsoonal climatic phase during middle and late carnian times extensive fluviatile sandstones deposited at this time throughout the region occur within a thick sequence of playa lake mudstones the sandstones occasionally contain kaolinite suggesting a humid climate an extreme 13 c depletion in a shallow marine sequence of this age in israel has been interpreted as evidence for an influx of freshwater a widespread change from carbonates to clastics in marine sequences at this time may also be climate related water course cave systems in limestone areas exposed during the late triassic indicate high levels of runoff during the middle and late carnian the marine invertebrate fauna shows a significant turnover at the end of the early carnian the terrestrial fauna and flora were relatively unaffected at this time but subsequently diversified prior to a major biotic turnover at the carnian norian boundary these periods of biotic change appear to be synchronous with the onset and cessation of a carnian humid phase the change to a monsoonal climate during this interval has been documented over more than 90 of longitude between 5 and 50 north of the triassic equator it may have been caused by rising atmospheric co 2 levels due to volcanism associated with the incipient dispersal of pangaea

modelling of groundwater mound formation resulting from transient recharge an analytical solution of a linearized boussinesq equation is obtained to predict water table fluctuations as a result of time varying recharge from a strip basin for any number of recharge cycles the analytical solution is obtained by using finite fourier sine transform applications of the solution for the prediction of water table fluctuations and sensitivity analysis are demonstrated with the help of example problems copyright 2001 john wiley sons ltd

straight thinking about groundwater recession while in catchment and hillslope hydrology a more nuanced approach is now taken to streamflow recession analysis in the context of major aquifers it is commonly still assumed that the groundwater head recession rate will take exponential form an idea originally proposed in the 19th century however it is shown here that in early times the groundwater head recession in a major aquifer should take an almost straight line form with a rate approximately equal to the long term recharge rate divided by the aquifer storage coefficient the length of this phase can be estimated from an analytical expression derived in the paper which depends on the aquifer diffusivity length scale and the position of the monitoring point a transitional phase then leads to an exponential phase after some critical time which is independent of the position of the monitoring point major aquifers in a state of periodic quasi steady state are expected to have rates of groundwater flux recession which deviate little from the average rate of groundwater recharge where quasi exponential groundwater declines are observed in nature their form may be diagnostic of particular types of aquifer properties and or boundary effects such as proximity to drainage boundaries variations in transmissivity with hydraulic head storage changes due to pumping nonequilibrium flow at a range of spatial and temporal scales and variations in specific yield with depth recession analysis has applicability to a range of groundwater problems and is powerful way of gaining insight into the hydrologic functioning of an aquifer