generation and propagation of near inertial waves in a baroclinic current on the tasmanian shelf abstractnear inertial waves niws are often an energetic component of the internal wave field on windy continental shelves the effect of baroclinic geostrophic currents which introduce both rela

fluvio lacustrine sedimentation and volcanism in a late carboniferous tensional intra arc basin northern chile abstract extensive outcrops of late carboniferous to triassic volcanoplutonic magnetic arc complexes occur in the andes of northern chile in the salar de atacama area terrestrial volcanosedimentary successions include a 200 600 m thick fluvio lacustrine sequence miembro medio the terrestrial basin which accommodated this sequence formed during the latest carboniferous on top of the deposits of the pre existing carboniferous composite volcanoes the lower part of the miembro medio consists of green limnic and multicoloured alluvial fan deposits the upper part is made up of red fluvial sedimentary rocks basic volcanic rocks occur locally throughout the sequence the climate is inferred to have been warm and humid the limnic freshwater environment had a minimum extension of 300 100 km limnic facies is inferred from the existence of fine parallel bedded sediments ooliths and a limnic benthic fauna lake shore deposits prevail in the outcrops in some sections the green limnic sequence is followed by red fine grained floodplain or alluvial plain and fluvial channel deposits the framework composition of the miembro medio is dominated by volcanogenic detritus presumably eroded from the successions of the previous late carboniferous volcanic arc another volcanogenic clast type was provided by syndepositional basalto andesitic phreatomagmatic activity which also produced peperitic sills dykes and lavas the limnic alluvial fan facies association the predominance of volcanogenic detritus and the accompanying intrabasinal basic calc alkaline volcanism together with the considerable size of the basin point to a nw se trending half graben setting controlled by trans tensional arc tectonics with regard to the late carboniferous triassic volcanosedimentary successions of northern chile this latest carboniferous tensional setting is the only feature in this area supporting those models which inferred an extensional magmatic arc for the entire central and southern andes during the permo triassic

evolution of near inertial waves during an upwelling event on the new jersey inner shelf abstract a 1996 field program provided a nearly three dimensional view of the temporal evolution of near inertial motion toward the end of an upwelling event on new jersey s inner shelf the appearance of near inertial motion is marked by a rapid rise in kinetic energy at the surface that is of the same magnitude and temporal structure of the work done by the wind indicating that the inertial motions are forced by local winds the incipient near inertial motion is surface intensified and spatially coherent it has a horizontal wavelength of 300 km and a mean kinetic energy of 0 04 m2 s 2 both of which decrease to less than 100 km and 0 01 m2 s 2 within two inertial periods an energy budget suggests that the rapid decline in surface kinetic energy is primarily due to vertical propagation into the thermocline near inertial motion in the thermocline is heterogeneous suggesting interaction between near inertial motion and subinertial shears the heterogeneous nature of near inertial waves poses a practica

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

last interglacial sediments of the don valley brickyard toronto canada and their paleoenvironmental significance the don valley brickyard in toronto is an internationally designated type site in recognition of diverse faunal remains in the don beds of last sangamonian interglacial age pollen in overlying strata record the climatic deterioration marking the onset of the last wisconsinan glacial cycle new sedimentological descriptions show that the don beds about 8 m thick were deposited in a lacustrine lower shoreface environment subject to episodic storms storm deposited sand facies are interbedded with peaty muds that are extensively bioturbated water depths derived from wave formed ripples using linear wave theory appear to have increased during deposition of the don beds from about 2 m to about 18 m 12 28 m above the modern lake level a change that is recorded by an overall fining up sequence increasing water depths may have been the result of isostatic recovery of the lake outlet to the east the don beds overlie a thin bouldery deposit possibly a remnant of older illinoian glacial sediments yo

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

hydrologic effects on water level changes associated with episodic fault creep near parkfield california as part of the parkfield california earthquake prediction experiment water level is monitored in a well 460 m from the main trace of the san andreas fault on middle mountain in the preparation zone of the anticipated parkfield earthquake the well configuration allows water level to be monitored in two fluid reservoirs at depths of 85 and 250 m below land surface during 1987 water level changes were recorded during 12 of the 18 episodes of accelerated fault creep detected by a creep meter spanning the fault trace 750 m northwest of the well the creep related water level changes in the shallow reservoir have durations of less than 1 day whereas in the deeper reservoir the changes persist for as long as 2 months these data suggest that the transient nature of the water level changes in the shallow interval is due to vertical flow to the water table and is not evidence that creep events propagate past the well phase leads of earth tidal constituents in the water level data from the shallow interval relative to the same constituents in the local volume strain tide support the interpretation of significant flow to the water table at periods of 1 day or less the form of the water level changes in the deep interval is affected by horizontal flow to the well bore this effect can be removed from the water level records using a theoretical response curve constrained by the phases of earth tidal constituents in the deep interval relative to the local volume strain tide for the events where the signal in the shallow interval has been large enough to measure the sizes of the simultaneous water level changes in the two reservoirs are consistent with the same amounts of volume strain occurring at both depths

the influence of diurnal winds on phytoplankton dynamics in a coastal upwelling system off southwestern africa abstract at a coastal upwelling zone near 30 s latitude diurnal wind variability forced energetic inertial current oscillations 0 5 m s 1 that materially influenced phytoplankton distribution and productivity the diurnal inertial band resonance found at this latitude in the benguela upwelling system allowed rapid efficient transfer of energy from counterclockwise rotating winds into anticyclonic currents upon the onset of the transition from relaxation to upwelling conditions these inertial band oscillations caused regular pycnocline outcropping at the surface and the vertical advection of nutrient rich waters in the coastal zone vertical pycnocline outcropping was coincident with the vertical redistribution of chlorophyll a fluorescence from a subsurface maximum to entrainment into the surface mixed layer in effect turning vertical phytoplankton gradients into horizontal ones the shear caused by the vertical structure of the inertial oscillations during and after the onset of wind forcing was intense enough to erode the strong stratification established during a prior relaxation period according to richardson number and strain analyses this diapycnal mixing also had the consequence of mixing heat and chlorophyll downwards and nutrient rich water upwards such that the surface nitrate concentration became non zero chlorophyll concentrations thereafter increased in what qualitatively appeared to be a phytoplankton bloom this diurnal inertial resonance driven mechanism for mixing driven nutrient flux embedded within the low frequency advective vertical flux forced by ekman dynamics enhanced the efficiency of wind forcing to produce high phytoplankton productivity and is likely to be of first order importance in bloom dynamics in the study area including harmful algal blooms our results argue that in general high frequency physical dynamics should be considered when studying the bottom up forcing of algal blooms and red tide events

the energy flux from the wind to near inertial motions in the surface mixed layer abstract time series of wind stress computed from long term meteorological buoy data off north america are used to examine the forcing of surface inertial currents by the wind a simple damped slab model of the mixed layer is used to compute h the average flux of energy from the wind to mixed layer inertial currents in a mixed layer of fixed depth h the forcing of mixed layer inertial motions is highly intermittent most of the forcing occurs during the winter months with a few dozen events accounting for typically over half the total energy flux major forcing events are usually associated with translating cold fronts or small lows with scales of about 100 km the larger synoptic scale features have little energy at the inertial frequency and thus result in only weak forcing of inertial currents a strong seasonal signal exists in the inertial forcing at ows p 50 n 145 w 50 m is largest from october to february and is a factor of 12 above the june and july values if seasonally varying

paleoclimatic significance of the lacustrine carboniferous deposits in northwest argentina abstract the origin and probable paleoclimatic significance of carboniferous lacustrine deposits in northwest argentina are discussed these rocks are developed extensively throughout northwestern argentina but are described in the present paper only from the region of the sistema del famatina five lithofacies have been identified a laminated siltstones and claystones b thinly interbedded mudstones and sandstones c interlayered mudstones and sandstones with sole structures flute marks and tool marks d conglomerates and fine sandstones e sandstones and diamictites these lithofacies are interpreted as lacustrine deposits formed during the final episode of the carboniferous glaciation lithofacies a originated as a suspension load deposit in the central and intermediate parts of the lake the presence of dropstones in this lithofacies suggests coeval ice rafting processes underflow currents probably formed lithofacies b and lacustrine turbidites lithofacies c lithofacies d and e were deposited in marginal environments and represent in some cases shoreline bars and small deltas the age of the lacustrine episode is deduced from paleobotanical information both palynological and megafloristic data suggest that these deposits were formed during the middle carboniferous a palynological assemblage dominated by cristatisporites like spores characterizes these sediments

internal wave mixing in the baltic sea near inertial waves in the absence of tides 1 the dynamics of near inertial motions and their relation to mixing is investigated here with an extensive data set including turbulence and high resolution velocity observations from two cruises conducted in 2008 summer and 2010 winter in the bornholm basin of the baltic sea in the absence of tides it is found that the basin scale energetics are governed by inertial oscillations and low mode near inertial wave motions that are generated near the lateral slopes of the basin these motions are shown to be associated with persistent narrow shear bands strongly correlated with bands of enhanced dissipation rates that are the major source of mixing inside the permanent halocline of the basin in spite of different stratification near inertial wave structure and atmospheric forcing during summer and winter conditions respectively the observed dissipation rates were found to scale with local shear and stratification in a nearly identical way this scaling was different from the gregg henyey type models used for the open ocean but largely consistent with the mackinnon gregg scaling developed for the continental shelf

the effect of a bottom shelf front upon the generation and propagation of near inertial internal waves in the coastal ocean abstract a three dimensional nonlinear baroclinic model in cross sectional form is used to study the generation and propagation of wind forced near inertial internal waves in a coastal region in the presence of a bottom front initially calculations are performed with the front in an infinite domain region by this means coastal effects are removed the initial response is in terms of inertial oscillations in the surface layer however in the frontal area these are modified by interaction through the nonlinear momentum terms with regions of positive and negative vorticity associated with the alongfront flow this leads to a change in amplitude phase and frequency of the inertial current and a resulting ekman pumping that drives near inertial internal waves in the frontal region on the positive vorticity side of the front these waves are at the superinertial frequency and rapidly propagate away on the negative side they are at the subinertial frequency and are trapped and inertial energy leaks to dep

the relation of near inertial motions observed in the mixed layer during the jasin 1978 experiment to the local wind stress and to the quasi geostrophic flow field abstract oscillations with near inertial frequencies were an energetic component of the upper ocean velocity field observed at each of two moorings separated by 44 km during the joint air sea interaction jasin experiment during the late summer of 1978 at each mooring the amplitude of the inertial motion was highest in the mixed layer where it was nearly depth independent previous work pollard and millard 1970 pollard 1980 had found that the amplitude and phase of inertial motion in the mixed layer was related to the local wind stress in this case the loacal winds measured at each mooring were coherent but the time series of mixed layer near inertial motion at one mooring bore little resemblance to that at the other mooring during jasin 1978 the differences in the inertial response at the two moorings coincided with differences in the quasi geostrophic flow field in the vicinity of the two moorings inclusion of the horizontal gradients of the quasi geostrophic flow in model equations prov

observations of the semidiurnal internal tide on the southern california slope and shelf 1 we give a detailed description of the semidiurnal band current and temperature variability observed during the internal waves on the continental margin iwaves field experiments of 1996 and 1997 off of mission beach california this variability was dominated by the internal tide and the structure of the internal tide on the slope and shelfbreak region was different from that on the narrow shelf on the slope and shelfbreak the internal tide was dominated by alongshore propagating coastal trapped waves in this region semidiurnal band currents were predominantly oriented in the alongshore direction in the lower half of the water column at a water depth h of 350 m current and temperature variability were consonant with a short wavelength 8 km bottom trapped wave propagating in the alongshore direction to the north in the upper 120 m of the water column above the depth of the shelfbreak slope and shelfbreak currents were highly coherent with a zero phase lag that is there was no phase propagation in the cross shore direction on the narrow 10 km shelf cross shore currents u were much more energetic than on the slope and had the structure of a mode one internal wave the alongshore currents v decreased monotonically from the surface to the bottom of the water column with a phase that did not change with depth the near bottom u signal propagated toward the coast during all mooring deployments faster in the summer than in the fall the near bottom u and mid column temperature relative phase was neither consistent with a purely progressive nor a purely standing mode one internal wave we conclude that the internal tide on the shelf was partially reflected

possible strain events reflected in water levels in wells along san jacinto fault zone southern california water levels have been monitored in wells along the san jacinto fault zone since 1977 the three largest earthquakes to occur within 30 km of the segment of the san jacinto fault zone being monitored with continuous recorders showed magnitudesm of 4 5 4 8 and 5 5 two wells in borrego valley 31 to 32 km southeast of them 5 5 earthquake on 25 february 1980 showed anomalous spikes recording a probable strain event 88 hours before the earthquake two other wells 12 km northwest of the epicenter showed no water level anomalies no water level anomalies preceded them 4 8 earthquake near anza on 15 june 1982 anomalous water level fluctuations occurred in a well near ocotillo wells 13 km northeast of them 4 5 earthquake on 22 march 1982 19 to 23 days prior to the earthquake similar fluctuations in other wells have not been followed by sizable earthquakes a simultaneous drop in water level occurred in four wells on 8 september 1982 this possible strain event was not associated with a sizable earthquake the presumed strain events occur only in wells that show earth tides and may have been the result of creep on strands of the san jacinto fault zone although water level anomalies have occurred in only one or two wells prior to two out of three moderate m 4 5 5 5 earthquakes the simultaneous drop in water level on 8 september 1982 and the spikes in two wells before them 5 5 earthquake on 25 february 1980 suggest that wells responsive to earth tides may detect strain events

eolian permian deposits in west and northwest argentina abstract the sedimentary and stratigraphic characteristics of eolian permian deposits exposed in mendoza la rioja and san juan provinces west and northwest argentina are described in this paper the eolianites are fine and medium sandstones with large scale cross bedding multiple parallel truncation planes and some asymmetrical ripples three genetic types of deposits have been identified dune facies eolian sand sheet facies and mixed fluvial eolian facies fine and medium sandstones with large scale cross bedding and multiple parallel truncation planes are here interpreted as dune deposits mainly crescentic dunes and unstratified or flat bedded sandstones as eolian sand sheet deposits mixed fluvial and eolian sequences composed of sandstones mudstones and some matrix supported conglomerates represent a transitional facies between those formed in eolian and fluvial environments this considerable deposition of eolian sediments was probably brought about by the existence of an extensive medium to low latitude continent and the withdrawal of marine environments the environments with highest aridity occurred towards the south and west of the region the eolian circulation pattern was controlled by a long ensialic volcanic arc emerging towards the west of the basin

near inertial ocean response to tropical cyclone forcing on the australian north west shelf the regional ocean modeling system roms was applied to the australian north west shelf nws to hindcast the ocean response to four intense historical tropical cyclones tcs while the four cyclones had very different trajectories across the nws all passed within 150 km of a long term vertical mooring located on the continental shelf in 125 m depth the observed ocean response at this relatively shallow southern hemisphere shelf site was characterized by the development of a peak in the counter clockwise ccw near inertial kinetic energy mixed layer deepening and subsequent restratification strong near inertial isotherm oscillations were also observed following two of the cyclones roms reproduced these features and also showed that the peak in the near inertial ccw kinetic energy was observed on the left side of each cyclone trajectory the time rate of change of near inertial kinetic energy depended strongly on the storm rossby number i e defined based on the storm speed the storm length scale and the coriolis frequency the shallow water depth on the nws resulted in first a more rapid decay of near inertial oscillations than in the deep ocean and second a generation efficiency the ratio of near inertial power to the rate of wind work of up to 10 smaller than found for cyclones propagating across deeper water the total energy put into near inertial motions is nevertheless large compared to the background tidal energy the rapid decay of near inertial motions emphasizes the importance of frictional effects in characterizing the response to cyclone forcing in shallow seas

near inertial waves on the new england shelf the role of evolving stratification turbulent dissipation and bottom drag abstract energetic variable near inertial internal waves were observed on the springtime new england shelf as part of the coastal mixing and optics cmo project surface warming and freshwater advection tripled the average stratification during a 3 week observational period in april may 1997 the wave field was dominated by near inertial internal waves generated by passing storms wave evolution was controlled by a balance among wind stress bottom drag and turbulent dissipation as the stratification evolved the vertical structure of these near inertial waves switched from mode 1 to mode 2 with associated changes in the magnitude and location of wave shear the growth of mode 2 waves was attributable to a combination of changing wind stress forcing and a nonlinear coupling between the first and second vertical modes through quadratic bottom stress to explore both forcing mechanisms an open ocean mixed layer model is adapted to the continental shelf in this model surface wind stress and bottom stre

late paleozoic paleoclimatology of central west argentina abstract based on sedimentologic and paleontological characteristics present in the sedimentary record of the calingasta uspallata and paganzo basins a model of paleoclimatic evolution for the late paleozoic of central west argentina is proposed additional evidence is also provided by data from other basins of southern san rafael and tepuel basins and northern tarija basin west argentina five paleoclimatic stages have been defined paleoclimatic stage i tournalism visean early carboniferous is characterized by temperature and humid preglacial conditions as evidencedin the el raton and maliman formations calingasta uspallata basin plant remains of archeosigillaria and lepidodendropsis zone are present in both units the paleoclimatic stage ii namurian early westphalian middle carboniferous comprises widespread glacial deposits including glaciomarine sequence in the westernmost basins calingasta uspallata western paganzo san rafael and tepuel and terrestrial tillites and glaciolacustrine fine clastics in some areas of the paganzo basin fossils of the levipustula fauna are distinctive in the glaciomarine deposits of this stage and in the overlying postglacial fine clastics of the basal portion of stage iii substage iiia the paleoclimatic stage iii of middle carboniferous late westphalian age corresponds to postglacial transgressions that flooded the previously glaciated shelves in the calingasta uspallata and tepuel basins terminal glaciolacustrine deposits substage iiia indicate of the demise of glacial conditions and coal measures of fluvial affinity in the paganzo basin substage iiib probably this postglacial stage was characterized by high humidity and moderate temperatures this stage is paleobiologi defined by a floral assemblage known as nbg nothorhacopteris botrychiopsis and ginkgophyllum the paleoclimatic stage iv late carboniferous stephanian early permian corresponds to a time interval characterized by seasonally dry climates and a progressive amelioration in humidity clear evidence of these climatic conditions is present in several localities in the paganzo basin the first astherothecae and glossopteris leaves are found finally paleoclimatic stage v middle late permian is dominated by red beds thick eolian sequences and saline lake facies deposited under arid to semi arid conditions coeval volcanism derived from the west is expressed by interbedded tuffs and agglomerates calingasta uspallata paganzo and san rafael basins

lacustrine environment during lower beaufort upper permian karoo deposition in northern malawi abstract this paper provides the first detailed sedimentological facies analyses of a lower beaufort upper permian gondwana sequence from mt chombe are in northern malawi approximately 300 m of undeformed non marine mudstones siltstones and sandstones are preserved in isolated grabens exposed along the mzuzu karonga highway where it crosses the lake malawi escarpment five lithofacies are distinguished a finely laminated paper shales and muddy siltstones deposited in lakes with anoxic bottom waters b massive muddy siltstones and siltstones deposited in oxic lake waters c thinly bedded horizontally stratified siltstones from episodic sheet flows into a lake d cross stratified and flaser bedded siltstones and sandstones of higher energy lake environments and e massive and cross bedded coarse grained sandstones with small channels and intraformational pebble layers interpreted as marginal lacustrine deposits new dates by pollen indicate an uppermost permian interval the whole sequence appears to have been deposited in a large shallow lake complex as none of the strata displays subaerial features such as desiccation cracks pedogenesis or rootlets all facies are reworked as is also suggested by the lack of in situ faunal or floral remains organic matter is mainly land derived although some algal dominated intervals occur clastic mineralogy is immature uniform and dominated by feldspar and quartz clay minerals include smectite kaolinite and illite carbonate contents greater than 5 and up to 40 are taken as an evidence of periods of authigenic precipitation in a freshwater lake setting the mt chombe sequence is lithologically similar but differs in significant sedimentology aspects from equivalent sequences in the adjacent luwanga and ruhuhu basins where sub aerial deposition has been reported although all three basins are part of a stable cratonic palaeoenvironment the absence of the lower permian upper coal measures from karoo sequences in northern malawi is taken as evidence of some syndepositional topographic relief in the region

the bude formation lower westphalian sw england siliciclastic shelf sedimentation in a large equatorial lake the 1300 m thick turbiditic bude formation was deposited in a lake lake bude but disagreement persists over whether the environment was a deltaic or deep water fan the tectonic setting of the lake was the northern flank of a northerly advancing variscan foreland basin close to the westphalian palaeo equator palaeocurrents indicate sediment sourcing from all quadrants except the south there is a dm m scale cyclicity whereby sandstone bodies comprising amalgamated event beds alternate with mudstone intervals containing non amalgamated event beds the ideal cycle is a symmetrical coarsening up fining up cycle consisting of three facies i 2 and 3 arranged in 12321 order facies 3 in the middle of the cycle is an amalgamated sandstone body up to 10 m thick which interfingers laterally with thin cm mudstone layers the sandstone body comprises amalgamated beds of very fine sandstone which are largely massive and up to 0 4 m thick channels are absent except for scours up to 0 2 m deep which truncate the interfingering mudstone layers sandstone bodies are inferred to be tongue shaped in three dimensions facies 1 and 2 completing the 12321 cycle are respectively dark grey fine and light grey coarse varved mudstone containing thin 0 4 m sandstone event beds fossils and burrows indicate that facies 1 and 2 were deposited respectively in brackish rarely marine and fresh water hence the ideal cycle 12321 reflects an upward decrease then increase in salinity brackish fresh brackish this is attributed to the lake sill being periodically overtopped by the sea due to glacio euitatic sea level oscillations the resulting oscillations in lake depth produced the coarsening up fining up regressivetransgressive cyclicity the central sandstone body representing the regressive maximum event beds are interpreted as river fed turbidites deposited during catastrophic storm floods combinedflow ripples and other wave influenced structures occur in event beds throughout the ideal cycle suggesting deposition of the entire bude formation above storm wave base the proposed environment is a shelf of continental shelf dimensions but lacustrine instead of marine sandstone bodies are interpreted to be river connected tongues or lobes the absence of cycles containing nearshore or emergent facies is attributed to i the lake sill preventing the water level from falling below sill level thereby insulating the lake floor from eustatically forced emergence and ii relatively distal deposition beyond the reach of shoreline progradations the lack of palaeoflow from the south is attributed to a now eroded deep water trough lying to the south in front of the northerly advancing orogen some facies 2 laminated mudstone beds grade laterally into massive and or contorted beds interpreted as in situ seismites facies 4 consistent with an active foreland basin setting development of seismites was possibly facilitated by gas bubbles and or weak cohesion in the fresh water bottom mud the late quaternary black sea with its broad northwestern shelf is probably a good physiographical analogue of lake bude and was likewise fresh at times

tidally driven vorticity diurnal shear and turbulence atop fieberling seamount abstract fine and microstructure profiles collected over fieberling seamount at 32 26 n in the eastern north pacific reveal a variety of intensified baroclinic motions driven by astronomical diurnal tides the forced response consists of three phenomena coexisting in a layer 200 m thick above the summit plain i an anticyclonic vortex cap of core relative vorticity 0 5f ii diurnal fluctuations of 15 cm s 1 amplitude and 200 m vertical wavelength and iii turbulence levels corresponding to an eddy diffusivity e 10 10 4 m2 s 1 the vortex cannot be explained by taylor proudman dynamics because of its 0 3fn2 negative potential vorticity anomaly the 0 3f fortnightly cycle in the vortex s strength suggests that it is at least partially maintained against dissipative erosion by tidal rectification the diurnal motions are slightly subinertial turning clockwise in time and counterclockwise with depth over the summit plain they also exhibit a fortnightly cycle in their amplitude pointing to

evidence for late palaeozoic glaciation in southern tanzania abstract new observations from basal karoo beds of the ruhuhu basin in southern tanzania prove the existence of the late palaeozoic glaciation in the region bordering lake nyasa evidence for the glaciation includes the identification of tillites and varved lacustrine siltstones with dropstones the tillites contain abundant striated and facetted pebbles and cobbles floating in a rock flour matrix consisting of finely ground quartz and feldspar features supporting subglacial transport of the rudaceous sediments are microstriations on clasts pressure flaked edges of grains and cleavage breakage observed under the sem the topography of the pre karoo surface suggests continental glaciation the onset of the glaciation was concomitant with late carboniferous to early permian taphrogenic movements which established the large ne trending karoo trough of tanzania

about the potential of wells to reflect stress variations within inhomogeneous crust abstract kumpel h j 1992 about the potential of wells to reflect stress variations within inhomogeneous crust in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 317 336 numerous pre co and post seismic well level changes that are believed to reflect stress variations in the crust have been observed in various parts of the world so far analysis of these data has not favoured a distinct model of the processes that could be involved the benefit from the signals is in fact limited because understanding of the underlying physical mechanisms is poor the paper discusses the impact that inhomogeneities in the brittle crust can have on the observations in particular the following problems are considered 1 could the well level signals be induced by the invasion of pressurized pore fluid at some place 2 could the hydrological conditions close to the observation well modulate any remote pore pressure variation 3 which features of the crust are most likely to dominate the process of stress transfer in the crust 4 how should a stress sensitive well be designed the results can be summarized as follows 1 stress diffusion due to the invasion of pressurized pore fluid can lead to significant well level changes only when the source region is at closer distance than a few kilometres probably less than a few hundred metres from the well 2 local inhomogeneities in the vicinity of the observation well may strongly influence the well s response to remote pressure changes even sign reversal of the anomaly may be encountered 3 there is increasing evidence that the wide range of stiffness values of natural rocks from 100 mpa or less till 100 gpa manifested in a fractal distribution of fault like weak zones within relatively stiff formations dominates stress transfer in the brittle crust uncertainty about the effective rheology for time scales from 10 4 to 103 years limits the inversion of many geophysical observations at present 4 of various configurations a well tapping an extensive hydraulic fracture could act best as a sensitive stress sensor provided that the fracture volume is isolated from the pore space of the host rock however experimental evidence of the practicability of such configuration is still due the weakness of conventional wells as stress sensors results from the fact that the process of fluid flow often lacks a sufficient control on attenuation mechanisms for low frequency well level variations regardless of whether the wells end in stiff or weak formations to a large extent the presented findings are compiled from publications of investigators working in various fields

model studies of near inertial waves in flow over the oregon continental shelf abstract two dimensional primitive equation model studies of wind forced flow over a continental shelf show that under upwelling conditions high levels of near inertial wave energy are found in the interior over the shelf the regions of elevated wave energy with maximum wave amplitudes of around 0 2 m s 1 persist for up to two weeks and have spatial scales of 20 40 m vertically and 5 20 km horizontally relatively high dissipation levels are associated with these concentrations of wave energy when forced with downwelling favorable winds model results show very little subsurface inertial energy on the shelf a comparison of inertial wave propagation using the primitive equation model and a linearized version of the model demonstrates strong dependence on the background flow field the behavior of inertial waves using the linearized model is completely different very little subsurface inertial energy is seen on the shelf in either upwelling or downwelling conditions except where the bottom slope

lacustrine deltas in a mesozoic alluvial sequence from camp hill antarctica sedimentary rocks of late mesozoic age exposed at camp hill northern antarctic peninsula are associated with calc alkaline volcanic rocks they represent deposition on a fault controlled floodplain with marginal alluvial fans on a volcanic arc finely laminated mudstone and occasional graded laminae were deposited from suspension and by density underflow currents respectively in small shallow lakes thickening and coarsening upward sandstone bodies overlying the lake deposits are interpreted as lacustrine deltas of which two types are preserved 1 gilbert type with steep foresets and 2 mouth bar type which lack steep foresets sections through the latter type reveal the presence of sub environments characteristic of fluvial dominated marine deltas i e prodelta distributary mouth bar and distributary channel abandoned mouth bars resulting from avulsion are recognized it is suggested that the processes which operated during formation of the mouth bar deltas resulted from hyperpycnal flow by contrast the gilbert type delta is thought to be the consequence of a reduced inflow of suspended sediment causing homopycnal flow and thorough mixing of the river and lake waters

half graben lacustrine sedimentary rocks of the lower carboniferous strathlorne formation horton group cape breton island nova scotia canada the strathlorne formation is the middle formation of a three part horton group stratigraphy present throughout the post acadian orogeny maritimes basin in atlantic canada it is up to 600 m in thickness and is of tournaisian age the formation was deposited in a complex lacustrine system during the period of maximum fault bounded extensional subsidence within two asymmetric half graben sub basin segments of a large rift this rift was located at a palaeolatitude of 10 15 s four facies assemblages are identified and interpreted 1 dark grey mudstone open lacustrine 2 grey very fine to fine grained sandstone nearshore shoreline 3 grey medium grained sandstone to conglomerate fan delta and 4 red siltstone to fine grained sandstone interdeltaic mudflat interpreted structural asymmetry of the fault bounded sub basins is evidenced by asymmetry of sediment input facies distribution and palaeoflow in the lacustrine sedimentary fill these indicators suggest that the sub basins which were linked end to end had opposed polarity of structural asymmetry during deposition of the strathlorne formation open lacustrine sediments are typified by stacked shallowing upward sequences each representing deepening due to sub basin wide subsidence events followed by gradual infilling to shallow water depths sub basin asymmetry is also reflected in the contrast of thick sequences and grouped thinner sequences at marginal and axial positions respectively the lakes which occupied the sub basins were large up to 100 50 km tens to hundreds of metres deep and periodically stratified presence of an anoxic hypolimnion at least near sub basin axes

inertial oscillations in the korea strait inertial oscillations io are examined in the korea strait based on measurements from 13 acoustic doppler current profilers covering the time period may 1999 through march 2000 strong io responses to wind stress occur during summer a simple linear model predicts that winter wind stress is expected to generate inertial responses of the same order of magnitude as those in summer however the observed winter io response is much weaker than predicted during summer the currents within the mixed layer and below the mixed layer are of comparable amplitude but in opposite directions the depth at which the currents reverse directions varies throughout the year as the mixed layer deepens from about 40 m during summer to the bottom of the water column in november during winter the velocity structure is more uniform in depth with currents in the same direction throughout the water column one possible explanation for these phenomena is related to the combined effect of the strait boundaries and the strong summer stratification the stratification prevents the wind stress momentum flux from mixing downward below the thermocline and thus allows the development of a bottom current separate from the surface current such a velocity structure is necessary to satisfy the no flow condition through the land boundaries

permo carboniferous proglacial lake sedimentation in the sahajuri gondwana basin india abstract the study of lithological associations sedimentary structures and their interrelation suggests that the talchir rocks of the sahajuri gondwana basin were deposited in a proglacial lake the lowermost lithological association of diamictites and chaotic boulder beds deposited mainly as sediment gravity flows represent a transitional phase between terminoglacial and proglacial sub environments the coarsening upward sequence coarse steeply dipping sandstone and fining upward sequence together represent bottomset foreset and topset respectively of a gilbert type delta the delta progradation to the southwest was mainly controlled by decaying of buried ice in the lake floor and consequent enlargement of the lake the diamictites were emplaced mainly as debris flow and the chaotic boulder bed by downslope slumping

observations of diurnal coastal trapped waves with a thermocline intensified velocity field abstractusing 18 days of field observations we investigate the diurnal d1 frequency wave dynamics on the tasmanian eastern continental shelf at this latitude the d1 frequency is subinertial an

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

recent movement on the garlock fault as suggested by water level fluctuations in a well in fremont valley california water levels have been continuously recorded since march 1978 in a well in fremont valley where several strands of the adjacent garlock fault zone have exhibited both left lateral displacement and components of normal displacement differences in water levels indicate that a fault segment lies between the observation well and a nearby irrigation well during the 4 year recording period six sharp fluctuations or spikes were noted these fluctuations occurring over 2 to 4 day periods have amplitudes of 15 30 cm they appear to be the result of creep events on a nearby fault two types of creep events are plausible 1 normal slip on an en echelon trace of the garlock fault less than 300 m south of the well with the north side up relative to fremont valley or 2 left lateral slip on the same fault because of the nature of the fluctuations we favor the latter interpretation dislocation models utilizing exponential arc tangent and skewed cosine functions were used to analyze the water level fluctuations associated pressure distribution and fault displacements the results suggest that creep on the fault ranges from several millimeters to a centimeter for individual events estimates of cumulative creep for the period 1978 1982 range from 20 to 50 mm depending on the particular model employed

interpretation of changes in water level accompanying fault creep and implications for earthquake prediction quantitative calculations for the effect of a fault creep event on observations of changes in water level in wells provide an approach to the tectonic interpretation of these phenomena for the pore pressure field associated with an idealized creep event having an exponential displacement versus time curve an analytic expression has been obtained in terms of exponential integral functions the pore pressure versus time curves for observation points near the fault are pulselike a sharp pressure increase or decrease depending on the direction of propagation is followed by more gradual decay to the normal level after the creep event the time function of the water level change may be obtained by applying the filter derived by a g johnson and others to determine the influence of atmospheric pressure on water level to the analytic pore pressure versus time curves the resulting water level curves show a fairly rapid increase or decrease and then a very gradual return to normal the results of this analytic model do not reproduce the steplike changes in water level observed by johnson and others if the procedure used to obtain the water level from the pore pressure is correct these results suggest that steplike changes in water level are not produced by smoothly propagating creep events but by creep events that propagate discontinously by changes in the bulk properties of the region around the well or by some other mechanism in addition simplistic calculations show that significant pressure field variations and water level changes near the surface may be expected to accompany a propagating creep event on a buried fault water level changes of as much as several meters may be expected at the surface for a creep event having a dislocation amplitude of l m on a semi infinite dislocation surface extending downward from a depth of 10 km and propagating horizontally at a rate of 10 km day the maximum near surface effect should be observed at a horizontal distance from the fault about equal to the depth of the top of the dislocation surface these results are consistent with the observations made in china of large water level changes preceding large earthquakes if some sort of aseismic creep event at depth precedes these earthquakes

the inertial chimney the near inertial energy drainage from the ocean surface to the deep layer a three dimensional primitive equation numerical model is used to study the behavior of near inertial waves generated by surface wind stress on an plane the model is fixed depth with a rigid lid on the surface and is horizontally periodic this study shows the behaviors of the wind generated near inertial waves for four different eddies 1 a subtropical cold core eddy 2 a subtropical warm core eddy 3 a california subsurface warm core eddy and 4 the gulf stream warm core ring the mean secondary circulation generated by the wind eddy interaction has magnitude to comparable to that of the ekman current and its characteristics are determined by the relative angle between wind and current the propagation characteristics of near inertial waves are quite different depending upon the sign of the relative vorticity in a cyclonic eddy near inertial wave propagation is outward from the core of the eddy the propagation direction in an anticyclonic eddy is downward and toward the core vertically propagating waves inside the eddy are trapped above a critical layer and slowly dissipated by parameterized viscous effects the model shows that anticyclones efficiently drain near inertial energy from the surface to the deep layer below the thermocline

paleozoic lake faunas establishing aquatic life on land abstract lakes are important archives for continental records of paleoenvironmental as well as paleoclimatic change they also record a unique macroevolutionary pattern that occurred when faunas invaded the continental realm in order to document that pattern we compiled a database of over one hundred and six lake basins from the neoproterozoic to permian looking at this critical time in lacustrine evolution several patterns emerge for the neoproterozoic through silurian time there is a paucity of documented lake deposits and lake faunal records however the records that are available indicate that lakes were oligotrophic and their nutrient cycling regimes primitive it is not until the establishment of land plants in the silurian that lakes began to respond with higher diversities and more complex physical and chemical conditions during the devonian carboniferous periods diversity was on the rise as trophic structure became more complex most lakes of the devonian and carboniferous formed along continental margins or in tectonic basins with occasional connection to the marine realm the faunas from these types of lakes were commonly comprised of mixed marine and freshwater elements and were far more diverse than other more inland lakes this estuary effect created a gateway or filter through which faunas invaded the continental realm the early history of lake faunas is one of opportunity and amelioration the feedback loops created by the establishment of vascular plants altered the nutrient cycle on land and in lakes all trophic levels were established early but became increasingly complex throughout the paleozoic as roles changed and faunal elements became established groups invading the continents via the estuary effect did so numerous times before establishing themselves permanently this was linked with the episodic re establishment in marine freshwater connections along these continental margins

observations and modeling of coastal internal waves driven by a diurnal sea breeze during the internal waves on the continental margin iwaves field experi ments of 1996 and 1997 off of mission beach california 32 75on we observed energetic diurnal band motions across the entire study site in water depths ranging from 15 to 500 rn and spanning a cross shore distance of 15 km the spectral peak of the currents was at the diurnal frequency av 1 cpd and was sufficiently well resolved to be clearly separated from the slightly higher local inertial frequency f 1 08 cpd these motions were surface enhanced and clockwise circularly polarized and had an upward phase propagation speed of 68 m d l suggesting that the motions were driven predominantly by the diurnal sea breeze however the downward energy upward phase propagation seems irrecon cilable with the subinertial diurnal period and moreover the intermittent diurnal current events were not obviously associated with diurnal sea breeze events we rationalize these features using a flat bottomed linear modal sum internal wave model that includes advection and refraction due to subtidal alongshore flow v z t fluctuations in v at the observing site can change the effective local coriolis parameter f vz by as much as 50 thus making the diurnal motions at different times effectively either subinertial or superinertial the model is integrated numerically for 200 days at a latitude of 32 75on under different wind and subtidal flow conditions purely diurnal winds and no v purely diurnal winds and a time independent v narrow band diurnal winds and no v and narrow band diurnal winds and subtidal time dependent v model diurnal currents forced by narrow band diurnal winds and subtidal v show complex offshore structure with realistic intermittency and spectral broadening this study suggests that continental margins in the vicinity of the 30 o latitude where av f are regions that could potentially produce energetic sea breeze driven baroclinic motions and that these motions could be regulated by the vorticity of the local subtidal currents

sedimentary dynamics and evolutionary history of a late carboniferous gondwanic lake in north western argentina lacustrine deposits are well represented in the lower part of the late carboniferous agua colorada formation in the north west sierra de narvbez catamarca province argentina lake narvbez was one of the several water bodies formed in the region immediately after the gondwana glaciation shallow lake and deep lake delta progradation proceeded from the ese coarse grained delta plain and turbidite delta front deposits suggest that the delta was formed close to the headwaters short headed stream delta type during periods of high discharge river mouths acted as bypass zones and fine and very fine sands were transported further into the lake by underflow currents the clastic material supplied by the deltaic system was partially reworked by wave action sands accumulated in unstable conditions at the upper delta front as a consequence of delta progradation as a result of the addition of clastics in the steep delta front turbidity currents were formed spreading their load along the lower delta slope deep lacustrine deposits are typically stacked forming two different kinds of progradational turbidite lobe sequences type i lobes were formed in a basinal setting and were probably detached from their feeder systems as a result of sediment bypassing in a shallow lake during periods of low lake level these turbidite lobes are replaced upwards by type i1 lobes which were formed on the delta slope during periods of lake level rise that allowed the onset of delta progradation the presence of highly deformed sandstone bodies suggests rapid depositional rates in a high slope setting whereas the occurrence of hummocky cross stratified sandstones indicates wave reworking of the sands initially emplaced by turbidity currents therefore the inner part of type i1 lobes was formed above storm wave base the depositional history of lake narvaez can be traced through four evolutionary stages lake transgression formation of type i lobes formation of type i1 lobes and delta progradation tectonic activity was probably important at the early stage of lake evolution but the subsequent depositional history was mainly controlled by fluctuations of lake level the lacustrine transport system has been divided into three distinct zones delta

lithofacies and depositional processes from a carboniferous lake sierra de narvaez northwest argentina abstract thick and widespread late carboniferous lacustrine successions occur in the sierra de narvaez area northwest argentina a detailed lithofacies analysis forms the basis for the definition of fourteen lithofacies clustered into three assemblages the delta assemblage consists of channelized cobble to pebble conglomerates quartz rich sandstones and carbonaceous mudstones this assemblage is present at the top of the lake succession and records the progradation of a short headed stream delta wave and current rippled sandstones and a heterolithic facies make up the shallow lake assemblage the nearshore area was probably composed of small bars shoreline sand flats and low energy sand mud flats the deep lake assemblage is represented by two types of coarsening and thickening upward lithofacies sequences the first type consists from bottom to top of laminated mudstones thin bedded turbidites classic turbidites and massive sandstones each sequence is thought to represent turbidite lobe progradation in a basinal setting the second type of sequence consists from base to top of underflow current sandstones and mudstones thin bedded and classic turbidites deformed sandstones and hummocky cross stratified sandstones each sequence records progradation of turbidite lobes on the delta front the analyzed lithofacies record deposition in a hydrologically open lake final lake infill was related to the progradation of a deltaic system it is suggested that four distinct processes controlled sediment transport and deposition in the carboniferous lake 1 delta progradation 2 episodic sediment density surges 3 river plume dispersion and 4 wave action during periods of high discharge fine to very fine sand and silt bypassed mouth bar zones and were deposited farther into the lake by underflow currents sands supplied by the delta system accumulated in the upper delta front in unstable conditions and were later redeposited by episodic turbidity currents wave action was able to rework shallow water sands supplied by the delta system or emplaced by turbidity currents