the lilliput effect in the aftermath of the end permian extinction event early triassic animal body fossils and trace fossils are small relative to those in older and younger intervals size decreases sharply through the end permian extinction event and permian triassic boundary and the smallest sizes are encountered in the parvus and isarcica zones of the earliest induan animals appearing within these two zones are also exceedingly small compared to younger congenerics and conspecifics temporary dramatic size decrease of surviving taxa in the immediate aftermath of the extinction event is an example of the lilliput effect coined by urbanek a 1993 biotic crises in the history of upper silurian graptoloids a palaeobiological model historical biology 7 29 50 body size increases somewhat from the carinata zone mid induan but remains depressed for the duration of the early triassic and pre extinction sizes are not commonly recorded until at least the middle triassic marine and terrestrial faunas appear to be similarly affected the lilliput effect and longer term size reduction could be the result of several factors environmental parameters such as marine anoxia due to low atmospheric concentrations of oxygen at this time coupled with sluggish ocean circulation in a greenhouse world and food shortage are the likely proximal causes for the early triassic lilliput effect no single cause can explain all the observations and a combination of factors are likely to be involved

field test of autogenic control on alluvial stratigraphy ferris formation upper cretaceous paleogene wyoming internally generated autogenic sedimentary processes can obscure signals of tectonic movements climate conditions or sea level fl uctuations in alluvial basins the stratigraphic effects of autogenic dynamics have been considered negligible on time scales of 10 4 10 6 yr however recent physical and numerical models have shown that over basin fi lling time scales self organization in sedimentary systems can produce stratigraphic patterns similar to those resulting from changing basin boundary conditions here we present the fi rst fi eld based test for autogenic control on stratigraphy in an ancient alluvial basin the ferris formation upper cretaceous paleogene hanna basin wyoming is composed of clusters of closely spaced channel deposits separated by intervals dominated by overbank material a pattern that has been proposed as an example of a potentially autogenic stratigraphy in order to evaluate controls on ferris formation stratigraphy spatial patterns of key channel properties were analyzed these variables including sand body dimensions paleofl ow depth maximum clast size paleocurrent direction and sediment provenance were chosen because they can change in response to climate tectonic or sea level forcing and are commonly measurable in ancient alluvial successions no clear statistical trends were detected in the measured variables which suggests that external forces did not likely control stratigraphic organization in the unit this study demonstrates that autogenic dynamics in natural fi eld scale systems can produce organized stratigraphic patterns over much larger spatial and temporal scales than is typically presumed this fi nding emphasizes the need for further understanding of autogenic stratigraphy and greater care interpreting climate tectonic and eustatic changes from alluvial basins

internal tides and tidal cycles of vertical mixing in western long island sound in estuaries tidal period variations in the rate of vertical mixing have been observed to result from various causes in liverpool bay and the york river they have been attributed to tidal straining of the along channel density gradient modulating stratification in the hudson river they arise from tidal modulation of the height of the tidal current bottom boundary layer bbl along continental shelves tidal period fluctuations in mixing have been observed to result from the dissipation of internal waves iws western long island sound wlis moored instrument records indicate that large near bottom increases in dissolved oxygen do and heat and a decrease in salt occur during the middle of the flood tide an analysis of water mass signatures indicates that the transport involved is vertical and not horizontal temperature data from a vertical thermistor array deployed in the wlis for 16 days in august 2009 clearly show a tidal cycle of iw activity creating a mean thermocline depression at midflood of approximately 25 of the water depth with individual iw thermocline depressions of as much as 50 of the water depth contemporaneous adcp measurements show increases in shear due to iws during the flood near bottom internal wave activity is maximal at and after midflood and is correlated with near bottom temperature and do tendencies at both tidal and subtidal scales we conclude that internal tides are an important vertical mixing mechanism in the wlis through both increased shear from iws and displacement of the pycnocline into the region of high shear in the bbl

complex river terrace development in the nenana valley near healy alaska a complex sequence of river terraces in the nenana valley was examined to determine whether the surfaces were depositional or erosional in origin of prime concern was the identification of outwash derived from the healy early wisconsin and riley creek i late wisconsin glaciations two terraces were formed during the healy glacial cycle the higher level represents the depositional surface of the healy outwash the lower level was formed during recession of the healy ice when approximately 18 metres of that outwash was removed the erosion was initiated when glacial lake moody dammed behind the healy moraine spilled over the drainage divide and began excavation of the nenana gorge the surface of riley creek outwash has been offset by faulting near the gorge mouth isolated remnants of that surface stand at different elevations complicating the correlation of downvalley outwash with the riley creek i moraine the evolution of the nenana gorge is associated with spasmodic development of erosional terraces throughout post healy time as the nenana river attempted to establish a new equilibrium condition this erosional trend has been interrupted only by out wash deposition during episodic expansion of the riley creek ice

structure and flow induced variability of the subtidal salinity field in northern san francisco bay abstract the structure of the salinity field in northern san francisco bay and how it is affected by freshwater flow are discussed two datasets are examined the first is 23 years of daily salinity data taken by the u s bureau of reclamation along the axis of northern san francisco bay the second is a set of salinity transects taken by the u s geological survey between 1988 and 1993 central to this paper is a measure of salinity intrusion x2 the distance from the golden gate bridge to where the bottom salinity is 2 psu using x2 to scale distance the authors find that for most flow conditions the mean salinity distribution of the estuary is nearly self similar with a salinity gradient in the center 70 of the region between the golden gate and x2 that is proportional to x 12 analysis of covariability of q and x2 showed a characteristic timescale of adjustment of the salinity field of approximately 2 weeks the steady state response deduced from the x2 time series implies that x2 is proportional

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

stability of giant sand waves in eastern long island sound u s a abstract a combination of a highly accurate bathymetric surveying technique and in situ submersible observations and measurements were used to assess the migrational trends and morphological changes of large sand waves ht 17 m in eastern long island sound although residing in a high energy tidal environment characterized by a net westward sediment flux the large bedforms are relatively stable over the short term over a 7 month period 55 1 of a total 2942 m of sand wave crestline lengths migrated less than the horizontal accuracy limits of navigation 2 m approximately 35 of the remaining sand wave crests migrated less than 4 m net migration of the sand wave crests in the study area was 0 2 m in addition the bulk form center of area in profile view or the base of the sand waves showed little if any movement these data in conjunction with flow data within the sand wave field suggest that net migration rates are greater than the time span of this study and or the sand waves move in response to large residual flows created by high energy aperiodic storm events the latter scenerio suggests that day to day processes only serve to rework and modify the sand waves

impact of the paleocene eocene thermal maximum on the macrobenthic community ichnological record from the zumaia section northern spain article i nfo trace fossil assemblages from the latest paleocene to the earliest eocene were significantly affected by the environmental perturbation of the paleocene eocene thermal maximum petm high resolution ichnolo gical analysis shows well marked different ichnological features pre syn and post event a well developed normal tiered burrowing community is present in the sediments below the petm indicating oxic conditions and normal benthic food availability during the petm the record of trace fossil producers disappeared gradually but rapidly reflecting the global increase in temperature and the concentration of benthic food in the very shallow surface layer and probably the local depletion of oxygen within the sediments although probably not true anoxia the environmental perturbation significantly affected the whole benthic habitat as shown by the correspondence with the main phase of the benthic foraminiferal extinction after the petm the normal tiered burrowing community recovered gradually and slowly in a delayed return to pre petm environmental conditions the changes in the trace fossil assemblage thus document the impact of the petm on the macrobenthic community a decline in oxygen levels during the petm in a globally perturbed habitat due to global warming and the similarities and differences in the response of micro and macrobenthic communities to global phenomena thus ichnological analysis reveals as a very useful additional tool to understanding atmosphere ocean dynamic during petm and a potential way in future climate research 2011 elsevier b v all rights reserved

low frequency sea level variability in the vicinity of the east river tidal strait the east river is a narrow tidal strait connecting long island sound with the lower hudson estuary the sound and estuary both communicate with the new york bight subtidal fluctuations in sea level difference between the ends of the strait which are coherent with barotropic flow through the strait are produced mainly by direct setup in the sound and estuary and by sea level fluctuations primarily wind forced in the bight approximately 70 of the variance in subtidal sea level difference can be accounted for by the two components of wind stress the direction of dominant wind forcing wind stress direction producing maximum response varies considerably with frequency response functions relating sea level difference to wind stress components computed for 128 day series for sea level and winds allow us to interpret the direction of dominant forcing in terms of the relative contributions of direct setup and sea level fluctuations in the bight

exchange between long island sound and adjacent waters 1 we exploit archived salinity data averaged by month for the years 1995 2001 to evaluate exchange of salt between long island sound and shelf waters and treat long island sound as a control volume with eastern and western boundaries at the race and the east river respectively the use of inverse methods to solve a system of equations expressing conservation of salt and water provides estimates of model parameters together with uncertainty estimates and measures of model performance we explore the use of a single exchange coefficient acting on an axial salinity gradient to represent exchange at the race and find that it is necessary to allow the coefficient to depend weakly on variability of freshwater discharge r into the sound i e 0 2 1 600 200 m2 s using established estimates of the mean circulation at the western boundary of the sound we determine a dispersion coefficient in the upper east river of 300 200 m2 s explicitly modeling the advective exchange flow gravitational circulation at the race using a coefficient that varies as the one third power of the normalized discharge indicates that gravitational circulation accounts for less than 10 of the up estuary salt flux in eastern long island sound

environmental changes during the cretaceous paleogene mass extinction and paleocene eocene thermal maximum implications for the anthropocene the cretaceous paleogene boundary kpb mass extinction 66 02 ma and the paleocene eocene thermal maximum petm 55 8 ma are two remarkable climatic and faunal events in earth s history that have implications for the current anthropocene global warming and rapid diversity loss here we evaluate these two events at the stratotype localities in tunisia and egypt based on climate warming and environmental responses recorded in faunal and geochemical proxies the kpb mass extinction is commonly attributed to the chicxulub impact but deccan volcanism appears as a major culprit new mercury analysis reveals that major deccan eruptions accelerated during the last 10 ky and reached the tipping point leading up to the mass extinction during the petm climate warmed rapidly by 5 c which is mainly attributed to methane degassing from seafloor sediments during global warming linked to the north atlantic igneous province naip biological effects were transient marked by temporary absence of most planktic foraminifera due to ocean acidification followed by the return of the pre petm fauna and diversification in contrast the current rapid rise in atmospheric co 2 and climate warming are magnitudes faster than at the kpb or petm events leading to predictions of a petm like response as best case scenario and rapidly approaching sixth mass extinction as worst case scenario

gravitational circulation and its response to the variation in river discharge in the seto inland sea japan 1 in this study gravitational circulation and its response to the variation in river discharge have been investigated in the seto inland sea japan monthly hydrographic surveys have been conducted from 2002 to 2006 in hiuchi nada a basin located between two straits horizontal salinity gradients along the channel varied as the 9 10 power of the river discharge into one end of the basin significant volume fluxes which were proportional to the horizontal salinity gradients were found the relationship between river discharge r m3 s 1 and the volume flux q m3 s 1 was represented as q 13 9r0 88 when river discharge increased vertical density gradients were intensified and then along channel horizontal density gradients were gradually enhanced due to vertical mixing at the western strait these gradients drove gravitational circulations along the channel the gravitational circulations were not uniform across the channel and accompanied by horizontal circulations in the northern part of the basin low salinity water at the eastern end of the basin was directed toward the west and high salinity water was directed toward the east the eastward flows arising from the intrusion of relatively heavy water at the western strait extended from the bottom to the surface in the southern part low salinity water was directed toward the west the westward flows arising from the intrusion of relatively light water at the eastern strait concentrated in the middle layer and formed a plume like structure accompanied by the eastward flow under the plume these situations were responsible for the development of the bulk exchange flux

applied geomorphology and archaeological survey strategy for sites of pleistocene age an example from central alaska abstract the development of a survey strategy for archaeological sites of pleistocene age through the application of historical geomorphology is described geomorphic contexts in the northern foothills of the alaska range with potential for producing archaeological remains from the 30 000 12 000 bp interval were identified and subjected to exploratory testing contexts were selected on the basis of estimated age palaeotopographic setting and geomorphic history and included glaciofluvial outwash side valley fan alluvium loessic colluvium and primary frozen loess testing was eventually focused on formerly deflated terrace surfaces a potential source area for artifacts redeposited in the outwash or alluvium although the results of the exploratory testing were negative and archaeological sites in the region remain confined to loess deposits of the later late glacial 12 000 10 000 bp discoveries in other parts of beringia suggest that sites of earlier late glacial age 14 000 12 000 bp are also likely to be present in the foothills the application of historical geomorphology in surveys for early prehistoric sites is essential for effective use of available resources and for maximizing the significance of the results positive or negative

immigration and extirpation selectivity patterns of brachiopods and bivalves across a carboniferous glacial to non glacial transition pennsylvanian central western argentina and their influence in building the biotic bathymetric gradient abstract the growth and demise of glaciers during the late paleozoic ice age had profound consequences on the marine biota in central western argentina the transition from glacial to non glacial interval during the pennsylvanian caused a major regional turnover which remodeled the bathymetric diversity gradient in order to understand the nature of the environmental changes related to such turnover event we compared selectivity patterns in extirpation and immigration of bivalves and brachiopods using logistic regression we tested for a wide range of potential drivers of extirpation and immigration namely body size geographic range size environmental breadth preferred depth metabolic rates infaunalism and taxonomic identity while extirpation preferentially hit brachiopods and genera having smaller geographic ranges and smaller body sizes immigration was related to genera with preference for deeper environment and small geographic ranges extirpation selectivity was not uniform along the bathymetric gradient both geographic range and body size selectivity are stronger towards deeper environments each clade on the other hand showed idiosyncratic responses to climate change while brachiopods show extirpation selectivity for smaller geographic ranges small sized bivalves were preferentially extirpated these contrasting selectivity regimes however could be reflecting different faunal responses to the same environmental changing factor namely higher thermal amplitude immigration in both brachiopods and bivalves was related to preference to deep environments confirming previous results however brachiopods also showed preferential immigration of small geographic range genera which is puzzling given the extinction selectivity related to the glacial non glacial transition possible explanations point to a brief time span in which an increase in thermal amplitude occurred the rapid climate changes particularly related to a rise in maximum temperatures lead the ecological response of the benthic faunas differences in extinction and immigration selectivity along the bathymetric gradient suggest that the turnover event also remodeled the bathymetric gradient in body size and biogeographic structure and brachiopod bivalve proportions such changes were driven by extirpation contrasting with the remodeling of the bathymetric diversity gradient that was driven by immigration our results therefore highlight that immigration and extirpation can shape different aspects of the bathymetric biotic gradient

global climatic forcing of deep sea benthic foraminiferal test size during the past 120 m y stratigraphic distribution of the maximum diameter of the largest deep water 1500 m water depths calcareous trochospiral benthic foraminiferal tests in samples representing the past 120 m y shows that average values of the maximum diameter have doubled since early cretaceous time fluctuations in test size show six minima and six maxima it is significant that the fluctuations correspond to changes in global climate and in deep water dissolved oxygen conditions this latter synchronism indicates that deep sea foraminiferal test size was likely controlled by fluctuations in the level of dissolved oxygen or related factors in the deep ocean caused by global climatic changes

ichnofossils of the alluvial willwood formation lower eocene bighorn basin northwest wyoming u s a abstract the ichnofossil assemblage of the lower eocene willwood formation consists of at least nine distinct endichnia that are preserved in full relief four forms three ichnogenera and four ichnospecies are new and represent fodinichnia and domichnia of oligochaete worms an insect or spider an unknown vertebrate probably a mammal and domichnia of an unidentified organism other potential trace makers of the ichnofauna include insects mollusks and decapods in contrast to an egyptian oligocene fluvial ichnofauna produced largely by animals that burrowed in stream channel deposits the willwood assemblage is principally of flood plain origin though the ichnofauna occurs in a variety of paleosol types most of the fossils are restricted in distribution to specific sediment and soil types and within paleosols to specific identifiable horizons this attribute will make them valuable indiced of paleoenvironment once they are better known in other ancient alluvial sequences the environment suggested by the willwood trace fossils damp but not wet soils with fluctuating water tables is consistent with the warm temperate to subtropical possibly monsoonal conditions that are interpreted for the willwood formation by independent evidence of body fossils and paleopedology

hydrography and dynamics of the ria de ribadeo nw spain a wave driven estuary the ria de ribadeo a small embayment in nw spain was observed for the first time using three months of adcp acoustic doppler current profiler current meter records and three ctd conductivity temperature depth surveys a wave driven circulation pattern arises from the observations instead of the shelf wind driven circulation of other galician rias based on adcp records a unidirectional flow in the horizontal velocity field coexists with the classic two layer circulation bidirectional flow the proposed horizontal circulation pattern can then be explained as a wave driven inflow this flow enters the ria through the west side describes an anticlockwise gyre inside of it and flows out through the east side numerical simulations run with the hamsom hamburg shelf ocean model agreed with observations confirming the proposed pattern

transient drying during the paleocene eocene thermal maximum petm analysis of paleosols in the bighorn basin wyoming abstract the paleocene eocene thermal maximum petm was a transient episode of global warming that occurred at the paleocene eocene boundary the event is marked by a sharp decline in carbon isotope values that is globally recognized from marine and continental sections the negative isotope excursion has been attributed to the release of methane hydrates from oceanic sediments although studies concur that temperatures rose during the petm changes in precipitation are not well understood alluvial paleosols in the bighorn basin that span the petm interval contain a continuous and highly resolved record of climate including information on precipitation they show a significant but transient decrease in precipitation at the onset of the petm but a gradual return to pre petm levels by the end of the interval the paleosols also show additional although less dramatic wet dry cycles within the petm interval that may correspond to precessional cycles that have been identified in the marine record of the petm this study counters interpretations of increased precipitation for wyoming at this time and shows the importance of detailed case studies of continental strata to test climatic generalizations and models that have been developed for petm precipitation patterns

structure variability and salt flux in a strongly forced salt wedge estuary this researchwas funded by national science foundation grant oce 0452054 ralston also received partial support from the penzance endowed fund in support of assistant scientists and the john f and dorothy h magee fund in support of scientific staff at woods hole oceanographic institution

seafloor environments in the long island sound estuarine system abstract four categories of modern seafloor sedimentary environments have been identified and mapped across the large glaciated topographically complex long island sound estuary by means of an extensive regional set of sidescan sonographs bottom samples and video camera observations and supplemental marine geologic and modeled physical oceanographic data 1 environments of erosion or nondeposition contain sediments which range from boulder fields to gravelly coarse to medium sands and appear on the sonographs either as patterns with isolated reflections caused by outcrops of glacial drift and bedrock or as patterns of strong backscatter caused by coarse lag deposits areas of erosion or nondeposition were found across the rugged seafloor at the eastern entrance of the sound and atop bathymetric highs and within constricted depressions in other parts of the basin 2 environments of bedload transport contain mostly coarse to fine sand with only small amounts of mud and are depicted by sonograph patterns of sand ribbons and sand waves areas of bedload transport were found primarily in the eastern sound where bottom currents have sculptured the surface of a holocene marine delta and are moving these sediments toward the wsw into the estuary 3 environments of sediment sorting and reworking comprise variable amounts of fine sand and mud and are characterized either by patterns of moderate backscatter or by patterns with patches of moderate to weak backscatter that reflect a combination of erosion and deposition areas of sediment sorting and reworking were found around the periphery of the zone of bedload transport in the eastern sound and along the southern nearshore margin they also are located atop low knolls on the flanks of shoal complexes and within segments of the axial depression in the western sound 4 environments of deposition are blanketed by muds and muddy fine sands that produce patterns of uniformly weak backscatter depositional areas occupy broad areas of the basin floor in the western part of the sound the regional distribution of seafloor environments reflects fundamental differences in marine geologic conditions between the eastern and western parts of the sound in the funnel shaped eastern part a gradient of strong tidal currents coupled with the net nontidal estuarine bottom drift produce a westward progression of environments ranging from erosion or nondeposition at the narrow entrance to the sound through an extensive area of bedload transport to a peripheral zone of sediment sorting in the generally broader western part of the sound a weak tidal current regime combined with the production of particle aggregates by biologic or chemical processes cause large areas of deposition that are locally interrupted by a patchy distribution of various other environments where the bottom currents are enhanced by and interact with the seafloor topography

magnetotactic bacterial response to antarctic dust supply during the palaeocene eocene thermal maximum distinct magnetic properties of marine sediments that record the palaeocene eocene thermal maximum petm have been suggested to be due to a bacterial magnetofossil signal that is linked to enhanced weathering conditions during the petm we document the dominance of bacterial magnetite in deep sea sediments from southern kerguelen plateau ocean drilling program hole 738c southern ocean not only during the petm but also before and after the thermal event this occurrence of magnetofossils throughout the petm indicates that the occurrence of bacterial magnetosomes is not due to a preservation effect instead we suggest that it is due to sustained mild iron reducing conditions that dissolved the most labile aeolian derived iron which favoured continued magnetotactic bacterial activity without being strong enough to dissolve the less reactive magnetite and haematite enhanced aeolian haematite abundances at the beginning of the petm indicate drier conditions on the neighbouring antarctic continent at those times our results provide evidence that iron fertilisation by aeolian dust was the main limiting factor that conditioned proliferation of magnetotactic bacteria in the deep sea at the southern kerguelen plateau with the exception of two short periods of rapidly changing palaeoenvironmental conditions at the onset and termination of the petm increased iron supply from aeolian dust that enhanced oceanic primary productivity and subsequent delivery of organic carbon to the seafloor along with mild iron reducing diagenetic conditions seem to have been necessary to provide the iron needed for magnetite biomineralization by magnetotactic bacteria to drive their marked increase in abundance in the studied petm record from southern kerguelen plateau our analyses of a deep sea petm record from hole 1051b at blake nose atlantic ocean failed to identify magnetofossils despite evidence for the occurrence of magnetite and haematite of probable aeolian origin contrasting magnetic properties at these petm sections indicate that further work is needed to understand the palaeoenvironmental and diagenetic factors whose interactions lead to production and preservation of magnetofossils in deep sea sediments

observations of wind induced subtidal variability in the delaware estuary sea level and current observations made in the delaware estuary during autumn of 1982 were examined for evidence of wind forced subtidal variability the large subtidal sea level fluctuations at the mouth of the delaware were found to be forced primarily by the wind stress component over the continental shelf nearly parallel to shore indicating coastal ekman transport to the right of the wind local wind forcing within the estuary is shown to be insignificant the subtidal sea level in the interior of the estuary was found to be driven by the wind through a combination of two remote forcing mechanisms one acting at the mouth of the delaware through direct estuary shelf coupling and a second acting locally over the chesapeake bay and being transmitted from the upper chesapeake through the chesapeake and delaware canal which links the two estuaries in the upper delaware estuary we found predominantly barotropic subtidal current fluctuations superimposed on a much weaker two layer gravitational circulation these current fluctuations were produced primarily by the local subtidal surface slope generated by the difference between the two remote forcing mechanisms the evidence strongly suggests that the chesapeake and delaware canal plays a critical role in the subtidal circulation of the delaware estuary

alluvial fan development and the glacial glaciofluvial cycle nenana valley alaska alluvial fans located downstream from pleistocene glacial margins in the nenana valley of alaska began to form immediately after outwash deposition ended each fan constructed by a major tributary stream rests conformably on the outwash surface of the preceding glacial episode outwash is unweathered where it is covered by thick fan alluvium indicating that no significant time break separated deposition of the two material types except for a thin upper zone development of each fan was completed before trunk river entrenchment occurred prior to the subsequent glacial event it is possible that fans were constructed in a relatively short paraglacial interval when the effects of a nearby glacier were still being felt in the tributary basins a complete fan sequence in any tributary valley near but beyond the downvalley limits of glaciation mirrors the mountain glacial sequence and can be used as a first approximation of the number of glacial episodes

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

a model study of the salish sea estuarine circulation arealistichindcastsimulationofthesalishsea whichencompasses theestuarinesystemsofpugetsound the strait ofjuan de fuca and the strait of georgia is described for the year 2006 the model shows moderate skill when compared against hydrographic velocity and sea surface height observations over tidal and subtidal time scales analysis of the velocity and salinity fields allows the structure and variability of the exchange flow to be estimated for the first time from the shelf into the farthest reaches of puget sound this study utilizes the total exchange flow formalism that calculates volume transports and salt fluxes in an isohaline framework which is then compared to previous estimates of exchange flow in the region from this analysis residence time distributions are estimated for puget sound and its major basins and are found to be markedly shorter than previous estimates the difference arises from the ability of the model and the isohaline method for flux calculations to more accurately estimate the exchange flow in addition evidence is found to support the previously observed spring neap modulation of stratification at the admiralty inlet sill however the exchange flow calculated increases at spring tides exactly opposite to the conclusion reached from an eulerian average of observations

diversity and climate change in the middle late wasatchian early eocene willwood formation central bighorn basin wyoming abstract densely distributed mammal samples from the willwood formation in the central part of wyoming s bighorn basin span episodes of major climate change previous work has focused on dramatic short term 0 5 myr during a 1 myr period of relatively static cool temperatures and a subsequent 1 myr period of warming that begins with the biohorizon b event and ends with the early eocene climatic optimum eeco in which the earth reached the hottest temperatures of the cenozoic geographic information systems is used to create spatially constrained subsamples to limit and explore the effects of the species area relationship on multiple aspects of diversity including the alpha average locality and beta locality differentiation components of species richness and the evenness and relative dominance of species abundance distributions results demonstrate previously unrecognized spatial bias in the upper levels of the section that complicate the interpretation of faunal response to the eeco evenness is strongly related to alpha richness whereas beta richness and dominance vary independently evenness increases significantly and richness becomes significantly more variable during warming richness also increases but the rise in alpha richness is not significant and the rise in beta richness is equivocal the dominance of the fauna by two abundant lineages escalates consistently regardless of changes in temperature diversity is not obviously affected across the biohorizon b event indicating that further study is necessary

particle dynamics of the surface intermediate and benthic nepheloid layers under contrasting conditions of summer monsoon and typhoon winds on the boundary between the taiwan strait and east china sea abstract two shipboard surveys of hydrographics and sediment dynamics were conducted off the mouth of minjiang the min river in july 2012 under contrasting summer monsoon and typhoon wind conditions observations included profiles of conductivity temperature depth fluorescence and suspended particle volume concentration and current velocity in addition water samples were taken for the analyses of mass concentration poc and chlorophyll of suspended sediment seafloor sediment samples were also taken for grain size analysis nepheloid layers nls were observed at surface intermediate and benthic depths snl inl bnl respectively the nl dynamics under the two wind conditions were mainly controlled by 1 the presence of the minjiang river plume and terrigenous material it carries 2 water column stability affected by wind current and waves 3 current induced resuspension of seafloor sediment and 4 physically coupled biological activities the wind field was the major forcing controlling the observed flow field and the upper water column stability in the typical summer condition southerly winds induced offshore directed currents enhancing the seaward dispersal of the minjiang river plume facilitating water column stratification thereby forming 3 nls in the water column phytoplankton growth was enhanced by terrigenous material and sunlight the suspension of the seafloor sediment was the one of the major sources for suspended particles in these nls furthermore the c n ratio of poc in the three nls is 5 72 almost identical to the redfield ratio indicating their predominant marine origin conversely under typhoon related northerly winds the offshore spread of the river plume was restricted the reduced riverine input and enhanced mixing resulted in the disappearance of the snl elevated turbidity in the inl was largely due to the presence of phytoplankton while the bnl was comprised of sediment resuspended off the seafloor and from horizontal advection our results suggest that the presence of the river plume from the minjiang at the study site sets the condition for the snl dynamics the dynamics of inl and bnl were dominated by the wind field and to a lesser degree the wave field and tidal current

a numerical study of salt fluxes in delaware bay estuary the results of a numerical study of delaware bay using the regional ocean modeling system roms are presented the simulations are run over a range of steadyriver inputs and usedm2 ands2tidal components to capture the spring neap variability results provide a description of the spatial and temporal structure of the estuarine exchange flow and the salinity field as well the along channel salt flux in the estuary the alongchannelsaltfluxis decomposedintoanadvectivetermassociatedwith theriverflow asteadysheardispersion feassociated with the estuarineexchangeflow anda tidaloscillatory saltfluxft time seriesoffeandftshow thatbotharelargerduringneaptidethanduringspring thistimevariabilityofft whichiscontrarytoexisting scalings is caused by the lateral flows that bring velocity and salinity out of quadrature and the stronger stratification duringneaptide whichcausesfttobeenhancedrelativetospringtide afitforthesaltintrusion lengthlwithriverdischargeqforanumberofisohalinesisperformed thefunctionaldependencesoflwith q are significantly weaker than q 21 3 scaling it is concluded that the response of the salt field with river discharge is due to the dependence of fe and ft with q and the relative importance of ft to the total upstream salt flux as river discharge increases fe becomes the dominant mechanism once fe dominates the salt field stiffens because of a reduction of the vertical eddy viscosity with increasing q

a simple model of estuarine subtidal fluctuations forced by local and remote wind stress observations of estuarine low subtidal sea level and current fluctuations have often shown domination by the remote effects of the wind acting on the adjacent coastal ocean over the local surface stress acting on the estuary itself the remote effects are transmitted to the estuary by impressment on its mouth of sea level change indtlced by the onshore component of coastal ekman transport and become increasingly dominant as the frequency decreases a simple barotropic model is developed to investigate the joint action of these two wind forcing mechanisms the relative shortness of most estuaries relative to low subtidal estuarine wavelengths explains the dominance of the remote effect for both sea level and barotropic current fluctuations in the estuary for the same reason however surface slope is dominated by local wind setup for an estuary with axis nearly parallel to the coast the two effects will operate either in concert or in opposition depending on hemisphere and orientation of the estuary axis relative to the coast for the geometries of both chesapeake bay and the delawm e estuary the model predicts opposition with the remote effect dominant at lower frequencies consistent with recent observations

response of the marine infauna to triassic jurassic environmental change ichnological data from southern england abstract the trace fossil record through the triassic jurassic boundary interval is examined at three sites in central and southern england st audrie s bay somerset pinhay bay devon and long itchington warwickshire the lower pre planorbis beds of the blue lias formation record low ichnotaxonomic diversity low bioturbation intensity small burrow diameters and an absence of deep tier bioturbation the stepwise reappearance of ichnotaxa following this interval is similar at the three sites suggesting similar rates of recovery in the benthic marine ecosystem and highlighting the potential contribution of these trace fossils to stratigraphic correlation mass extinction in the late triassic is increasingly linked to the emplacement of the central atlantic magmatic province camp timing of the onset of camp volcanism in the uk is currently imperfectly known but potentially occurred within either the westbury formation or the lilstock formation if the onset of camp was within the lilstock formation the modestly diverse trace fossil assemblage of the langport member of the lilstock formation suggests that emplacement of camp had little lasting effect on the marine benthos in central and southern england the decline in benthic activity recorded in the pre planorbis beds appears to be unrelated to the onset of camp and any associated environmental change it is more likely related to an episode of marine anoxia an episode of marine anoxia also provides a suitable causal mechanism for the reduction of infaunal tiering

enhanced primary productivity and magnetotactic bacterial production in response to middle eocene warming in the neo tethys ocean abstract earth s climate experienced a warming event known as the middle eocene climatic optimum meco at 40 ma which was an abrupt reversal of a long term eocene cooling trend this event is characterized in the deep southern atlantic pacific and indian oceans by a distinct negative 18 o excursion over 500 kyr we report results of high resolution paleontological geochemical and rock magnetic investigations of the neo tethyan monte cagnero mca section northeastern apennines italy which can be correlated on the basis of magneto and biostratigraphic results to the meco event recorded in deep sea sections in the mca section an interval with a relative increase in eutrophic nannofossil taxa and decreased abundances of oligotrophic taxa spans the culmination of the meco warming and its aftermath and coincides with a positive carbon isotope excursion and a peak in magnetite and hematite goethite concentration the magnetite peak reflects the appearance of putative magnetofossils while the hematite goethite apex is attributed to an enhanced detrital mineral contribution likely as aeolian dust transported from the continent adjacent to the neo tethys ocean during a drier more seasonal climate during the peak meco warming based on our new geochemical paleontological and magnetic records the meco warming peak and its immediate aftermath are interpreted as a period of high primary productivity sea surface iron fertilization is inferred to have stimulated high phytoplankton productivity increasing organic carbon export to the seafloor and promoting enhanced biomineralization of magnetotactic bacteria which are preserved as putative magnetofossils during the warmest periods of the meco event in the mca section together with previous studies our work reinforces the connection between hyperthermal climatic events and the occurrence or increased abundance of putative magnetofossils in the sedimentary record

remote sensing of coastal sea surface features off northern british columbia this article presents an overview of surface oceanographic features identified by avhrr imagery in hecate strait and adjacent waters surrounding the queen charlotte islands canada an area still poor in in situ observations the observed features and their temporal variability are interpreted in terms of meteorological and hydrological forcing the effects of tidal mixing are discussed through the application of a finite element numerical model

transient dwarfism of soil fauna during the paleocene eocene thermal maximum soil organisms as recorded by trace fossils in paleosols of the willwood formation wyoming show significant body size reductions and increased abundances during the paleocene eocene thermal maximum petm paleobotanical paleopedologic and oxygen isotope studies indicate high temperatures during the petm and sharp declines in precipitation compared with late paleocene estimates insect and oligochaete burrows increase in abundance during the petm suggesting longer periods of soil development and improved drainage conditions crayfish burrows and molluscan body fossils abundant below and above the petm interval are significantly less abundant during the petm likely because of drier floodplain conditions and lower water tables burrow diameters of the most abundant ichnofossils are 30 46 smaller within the petm interval as burrow size is a proxy for body size significant reductions in burrow diameter suggest that their tracemakers were smaller bodied smaller body sizes may have resulted from higher subsurface temperatures lower soil moisture conditions or nutritionally deficient vegetation in the high co2 atmosphere inferred for the petm smaller soil fauna co occur with dwarf mammal taxa during the petm thus a common forcing mechanism may have selected for small size in both above and below ground terrestrial communities we predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric co2 and surface temperatures or that they will exhibit this pattern over the next century we retrodict also that soil fauna across the permian triassic and triassic jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming

seasonal variation of a coastal jet in the long island sound outflow region based on hf radar and doppler current observations 1 surface current hf radar and velocity profile observations obtained as part of the front resolving observational network with telemetry front project over an approximately 2 year period are used to describe the seasonal variability of a coastal jet in the long island sound outflow region the jet is observed in an area of the continental shelf where surface thermal fronts are frequently detected during both summer and winter the current jet is coincident with a band of high summer frontal probability and apparently arises from the interaction between long island sound outflow and larger scale alongshore currents on the shelf the jet reaches peak strength in summer transport of 0 07 sv and is weak or non existent in winter flow is strongest near the surface and weakens with depth with only moderate seasonal variations in the vertical shear the relatively long data set of currents combined with historical hydrographic measurements and buoy wind observations is analyzed to examine the seasonal variability of the terms in the depth averaged momentum balance the depth averaged pressure gradient is partitioned into a steric component evaluated from the hydrography and a non steric component that is estimated as the residual of the computed terms in the momentum equation the depth averaged momentum balance is found to be approximately geostrophic in the across shore direction the seasonal variability in the jet arises due to the shifting balance between buoyancy driven flow that is always downshelf but intensifies somewhat in summer and wind driven flow which dominates in winter when wind stress becomes strongly upwelling favorable

pedogenic carbonate isotopes as evidence for extreme climatic events preceding the triassic jurassic boundary implications for the biotic crisis the triassic jurassic boundary is associated with widespread marine and terrestrial extinctions but there is disagreement regarding the existence and extent of climatic changes that may have driven the biotic crisis here we apply quantitative isotopic climate proxies in order to construct two age equivalent relatively continuous temperature and p co 2 records that span the eight million years preceding the triassic jurassic boundary and that supersede previous terrestrial records in temporal resolution the 18 o data suggest that mean annual temperatures mat increased by 7 9 c from the late norian to the rhaetian in association with the peak increases in p co 2 levels the 13 c data suggest relatively low late norian p co 2 levels 1500 ppmv and at least two periods of extreme p co 2 levels 3000 ppmv preceding the triassic jurassic boundary these estimates are consistent with a recent late triassic climate model that suggests the effects of increased p co 2 levels on pangea would cause severe climatic consequences including a global mat increase of 6 c 10 c in some regions while it is possible that periods of increased aridity could have resulted in erroneously high estimates of both temperature and p co 2 levels it is likely that climate was still fluctuating during the end of the triassic although our data precede the triassic jurassic boundary many studies conclude that the mass extinction took place over a more prolonged period beginning in the late triassic thus climate may have been a significant driving mechanism of the late triassic extinctions

spring summer frontogenesis at the mouth of block island sound 1 a numerical investigation into tidal and buoyancy forced motion 1 the generation and underlying dynamics of late spring temperature and salinity fronts at the mouth of block island sound in the mid atlantic bight are examined using a three dimensional general circulation model the model is forced by tidal velocities at its outer boundaries an estuary shelf salinity gradient and surface warming runs representing the period from 18 april to 23 may 2000 are investigated through direct examination of the model results and diagnostic calculations that isolate individual processes three mechanisms are identified as significantly contributing to the location and structure fronts observed in this region vertical mixing produces the necessary horizontal temperature structure within and near block island sound but the southern frontal boundary is further affected by the subtidal circulation which is divided into two components defined using a momentum budget analysis tidal currents over the complex bathymetry leads to nonlinearly rectified flows including a headland eddy south of montauk point circumscribing this feature is a baroclinically adjusted buoyant outflow from the long island sound estuary while modifications to the buoyancy forcing can modify the frontal position it necessarily remains offshore of the tidally driven circulation analysis of the salinity anomaly fluxes indicates that both tidal and mean advection are responsible for the overall transport of buoyancy

circular plumes in lake pontchartrain estuary under wind straining circular shaped density plumes of low turbidity low fecal indicator escherichia coli and enterococci concentrations and high salinity have been observed near the industrial canal in lake pontchartrain north of the city of new orleans a conceptual model in polar coordinates and a numerical model are developed together with data analysis to illustrate the dense plume it is demonstrated that the northward expansion of the plume occurs under northerly winds the northward expansion of the plume occurs under northerly winds that drive downwind flow at the surface and upwind radial flow at the bottom northerly wind induced straining similar to tidal straining promotes vertical stratification as a result the water becomes stratified near a thin bottom layer 1 m within which density currents are facilitated the stability of the stratified plume suppresses wind induced turbulent mixing inside the plume the bottom water outside of the plume is more effectively stirred by the wind the result being that the suspended sediment concentration outside of the plume area is much higher than inside this contrast in mixing makes the plume visible from the surface by satellites even though the stratification is at the bottom laterally wind stress produces a torque vorticity in areas of non uniform depth such that upwind flow is developed in deep water and downwind flow in shallow water the continuity requirement produces an upwind flow along the axis of the industrial canal ic the upwind flow is balanced by the downwind flow over the shallower peripheral areas along the coast

fronts stratification and mixing in long island and block island sounds spatial patterns of bulk stratification in long island and western block island sounds observed near the fall equinox of 1978 show a strong correlation r 0 79 with contours of the h u3 stratification index derived from tidal stream and depth charts the index delineates stratified transitional and mixed regions with apparent good accuracy with the marginally stratified frontal zones being characterized by log10 h u3 1 5 m 2 s3 these results and theoretical considerations suggest that the index may be a useful parameter in corroborating and predicting frontal boundaries in other moderately stratified estuaries where local buoyancy fluxes are derived from fresh water sources

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

tidally induced residual currents in long island and block island sounds the tidally induced residual currents in the long island sound block island sound lis bis tidal channel are investigated using a previously developed analytic model known first order tidal properties of lis bis are matched using three different models chosen to isolate the effects of the factors potentially controlling the second order currents either breadth depth or eddy viscosity variations the residual currents driven by these first order models agree to within roughly a factor of two indicating that the model is not overly sensitive to these parameters tidally induced currents on the order of observed currents in eastern lis and bis are predicted the outstanding structural feature of the predicted residual currents is a region of strong surface flow divergence and bottom flow convergence centered at a sharp constriction in the channel eulerian and lagrangian observations in eastern lis and bis are reviewed indirect support for the theoretical results is found

subtidal exchange in eastern long island sound abstractlong island sound lis is a large and wide macrotidal estuary with distributed river inputs including the connecticut river the largest freshwater source that flows into the eastern lis near the mouth in 2010 shipboard surveys of salinity temperature and currents were collected along an across estuary transect in eastern lis numerical model results are compared to these observations and used to study the spatial and temporal variability of salinity velocity and freshwater and salt fluxes over a 4 yr period for all low wind conditions observations and model results indicate an outward flowing low salinity wedge on the south side with an inward flowing higher salinity area underneath and to the north observations and model results during the low wind surveys indicate that stratification substantially decreases with increased tidal amplitude and decreased river discharge the velocity field is less variable among surveys model analysis indicates strong sensitivities to both tides and

phytoplankton dynamics across the ordovician silurian boundary at low palaeolatitudes correlations with carbon isotopic and glacial events the late ordovician culminated in a major glacial period that has been related to one of the strongest mass extinctions recorded during the phanerozoic during this interval anticosti island quebec eastern canada was located at low to intermediate palaeolatitudes 15 30 s on the eastern margin of laurentia it displays a relatively complete section across the ordovician silurian o s boundary upper ordovician to lower silurian strata of anticosti studied here comprise the vaureal katian ellis bay hirnantian and becscie latest hirnantian rhuddanian formations phytoplankton dynamics inferred from the acritarch content of these strata are locally compared with new geochemical environmental proxies 13c with recent palynological data from baltica and also with phytoplankton dynamics as described from near polar high latitude localities of the gondwana region two positive excursions of the carbon isotope record have been identified in the lower and upper ellis bay formation overall phytoplankton trends are as follows 1 as with chitinozoans conodonts brachiopods and corals acritarchs from anticosti display a major turn over during the early hirnantian uppermost vaureal formation lower ellis bay formation with the appearance of taxa that exhibit silurian affinities e g tylotopalla sp ammonidium sp oppilatala sp evittia sp dilatisphaera spp high polymorphism for some common taxa is observed in the interval corresponding to the first 13c positive excursion using sequence stratigraphy this period may be related to a first glacially driven sea level drawdown corresponding to terrestrial ice sheet growth on gondwana such as recorded in morocco 2 subsequently during the late hirnantian of anticosti uppermost ellis bay formation phytoplanktic communities suffered a crisis exemplified by the disappearance of several typical large late ordovician taxa i e orthosphaeridium spp peteinosphaeridium spp large baltisphaeridum spp sacculidium sp the lower becscie strata corresponding to the time of deglaciation at the o s boundary interval only contain a low diversity assemblage dominated by large acritarchs of the genus hoegklintia and other morphologically related forms and a few tolerant and long ranging taxa e g evittia remota micrhystridium spp leiospheres despite a possible taphonomic bias in the uppermost ellis bay formation the major crisis in the late hirnantian coincides with the second 13c excursion and a second stronger glacially driven sea level fall corresponding to the time of the maximum extend of the ice sheets on gondwana 3 such phytoplankton events have also been detected in gondwanan ice center area but with typical ordovician taxa crises occurring apparently later when plotted against positive carbon isotope excursions as also observed in baltica this time lag may be linked to a basin configuration of the studied areas where environmental stress consequently differed or linked to the presence of omission surfaces coupled with preservation bias of acritarch assemblages in the uppermost ordovician strata of anticosti in addition to their biostratigraphic and palaeobiogeographic utility acritarchs turn out to be more specific in highlighting palaeoenvironmental conditions

trace fossil evidence suggests widespread dwarfism in response to the end cretaceous mass extinction braggs alabama and brazos river texas as a proxy for the body size of the tracemaker burrow diameter provides information on fundamental characteristics such as organism biology and behavior furthermore changes in this endobenthic parameter provide insight into the timing and recovery of burrowing organisms in response to large scale processes operating in ancient trophic systems we herein report a decrease in burrow size in thalassinoides dominated ichnoassemblages across the cretaceous paleogene k pg boundary in well studied shallow marine sections along the brazos river and cottonmouth creek texas and at braggs alabama at the cottonmouth creek and brazos river localities thalassinoides isp occurring above the previously reported negative 13c shift and the first occurrence of unequivocal danian planktonic foraminifera are 17 smaller in short axis diameter and 22 smaller when diameters are corrected for sediment compaction mean k 27 15 7 12 mm mean pg 21 13 6 88 mm n 53 than those excavated and filled prior to deposition of a hummocky cross bedded ejecta bearing sandstone complex commonly interpreted as the chicxulub event deposit across the k pg boundary at braggs diameters dth of simple maze thalassinoides structures from similar recurring depositional facies abruptly decrease by 22 mean k 13 08 1 86 mm mean pg 10 21 1 87 mm n 26 the cretaceous and paleogene burrows were preserved in beds of similar lithology suggesting that the reduction in size is not attributed to sedimentological factors at both localities up section trends in dth are statistically significant 0 05 equal variance t test non parametric mann whitney u test a reduction in dth above the k pg boundary reflects dwarfing within the post extinction endobenthic community these ichnological trends are similar to those recently documented at more impact distal sites along the new jersey coastal plain dwarfing during the early recovery stages of the end cretaceous mass extinction as recorded by trace fossils was widespread and occurred within siliciclastic carbonate and glauconite producing depositional environments since this ichnological signal in shallow marine successions appears to be a general phenomenon across the crisis interval trace fossil analysis provides a potential in situ field method for constraining and correlating the stratigraphic position of the event particularly in the absence of other macroscopic microscopic and geochemical indicators

exchange fluxes between the ria de vigo and the shelf a bidirectional flow forced by remote wind 1 in the ria de vigo western coast of the iberian peninsula the seasonal pattern associated with shelf winds at these latitudes produces upwelling downwelling episodes that affect the residual circulation the aim of this paper is to go deeply into the interaction between remote winds and the dynamics of the ria aided by an inverse model in the galician r ias the box models inverse models have been developed from a two dimensional 2 d point of view since the classical baroclinic residual circulation in positive estuaries has a vertical distribution freshwater outflow through the surface layer and inflow through the bottom layer however recent work in the ria de vigo has shown the existence of a 3 d residual circulation in the seaward region of the ria during upwelling downwelling conditions a coastal jet enters leaves the ria through the northern mouth and leaves enters through the southern mouth the inverse model developed in this paper is a 3 d kinematic box model based on tracer and volume balances with the constraint of nonnegative vertical exchange coefficients the fluxes obtained confirm during some periods the 3 d residual circulation overlying the classical 2 d scheme it is shown how the 3 d pattern affects the inner ria causing transversal differences in the flow field in addition the model results have been helpful in the discussion of a possible barotropic bidirectional flow associated with remote winds the results have set the basis for the existence of a bidirectional flow originated by a barotropic interaction with the shelf upwelling

dynamics of willapa bay washington a highly unsteady partially mixed estuary results from 3 yr of hydrographic time series are shown for willapa bay washington a macrotidal partially mixed estuary whose river and ocean end members are both highly variable fluctuating ocean conditions alternations between wind driven upwelling and downwelling and intrusions of the buoyant columbia river plume are shown to force order of magnitude changes in salinity gradients on the event 2 10 day scale an effective horizontal diffusivity parameterizing all up estuary salt flux is calculated as a function of riverflow results show that willapa s volume integrated salt balance is almost always far from equilibrium at very high riverflows the top 15 of observations the estuary loses salt on average while at all other riverflow levels it gains salt under summer low riverflow conditions in fact the effective diffusivity k is large enough to drive a net increase in salinity that is 3 6 times the seaward river driven salt flux this diffusion process is amplified not damped by increased tidal forcing contrary to the expectation for baroclinic exchange furthermore k varies along the length of the estuary as 5 of the rms tidal velocity times channel width a scaling consistent with density independent stirring by tidal residuals to summarize willapa s event and seasonal scale variability a simple diagnostic parameter space for unsteady estuarine salt balances is presented a generalization from the hansen and rattray steady state scheme

a simple advection dispersion model for the salt distribution in linearly tapered estuaries 1 we present a simple advection dispersion model for the subtidal salt distribution in estuaries with linearly varying cross sectional area and a nonzero net salt flux a novel analytic solution allows investigation of the dependence of the curvature and gradient of the longitudinal salinity distribution on runoff dispersion coefficient and channel contraction or expansion the model predicts that in estuarine segments that contract toward the fresher boundary the salinity gradient is stronger than in a prismatic channel when the dispersion coefficient is large compared to the salinity intrusion lengthscale the product of segment length and net volume flux divided by cross sectional area at the ocean boundary the curvature of the salt concentration may be negative a characteristic not possible in uniform channel models the main effect of up estuary salt flux is to strengthen the salinity gradient the model can be extended to multiple segments in order to simulate geometrically complicated estuaries the model is employed to estimate an effective dispersion coefficient and to describe the salinity variation in the western 53 km of long island sound where the cross section of the basin varies linearly using 8 years of monthly observations at seven stations we find that since the curvature of the vertically averaged salinity is negative the model and data are consistent only if the net volume flux and salt flux are toward the fresher boundary the east river combining prior estimates of the magnitudes of the fluxes and their uncertainties with the model and salinity observations using a least squares approach we estimate the dispersion coefficient for the western sound as 580 m2 s

clade dependent size response of conodonts to environmental changes during the late smithian extinction abstract in contrast to the benthos whose taxonomic recovery was lagging way behind that of the nekton highly diverse smithian conodont and ammonoid faunas were profoundly decimated during the late smithian ca 2 myr after the permian triassic boundary mass extinction as body size reduction is a common evolutionary response to heavy environmental stress we investigate how the size of the p1 elements of different conodont clades responded during the late smithian crisis based on three sections from the northern indian margin a major and world wide positive carbon excursion is also a consistent signature of the late smithian time interval where adequate ammonoid biochronological control is lacking i e kashmir a new carbonate carbon isotope record provides an independent age proxy for correlations with southern tibet and the salt range assuming a positive correlation between the size of p1 elements and body size we confirm that segminate conodonts underwent a size decrease during the late smithian however segminiplanate conodonts consistently displayed a substantial size increase during the same time interval thus highlighting clade specific diverging answers and precluding any simplistic generalization of size responses to the same stress event additionally a moderate but consistent size increase during the early spathian is documented for both clades thus obscuring any simple general relation between temperature stress and size among conodonts comparison of size time series with the oxygen isotopic composition of conodonts a proxy for sea water temperature suggests that only the size of segminate p1 elements may correlate positively with temperature although at a slower pace the size of segminiplanate p1 elements continued to increase during the early spathian when temperature rose again after the late smithian cooling event therefore temperature alone cannot explain the size variations of segminiplanate conodonts the late smithian was also a time of increasing burial of organic matter on continental shelves but lateral variations of this factor also obscure any relation with the documented size changes last but not least the stratigraphically more comprehensive study in nammal reveals a segminiplanate gap during the middle smithian thermal high the biogeographical expansion of this clade towards the low latitudes during the griesbachian the early smithian the late smithian and the early spathian apparently occurred during the coolest intervals of the early triassic in agreement with their supposed cooler habitat

mammalian community response to the latest paleocene thermal maximum an isotaphonomic study in the northern bighorn basin wyoming new stratigraphic and paleontological information from the mccullough peaks northern bighorn basin wyoming is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest paleocene thermal maximum and coincident earliest wasatchian immigration event on local mammalian community structure surface collections from willwood formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium to large sized components of underlying mammalian communities rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness after this initial increase diversity tapered off to more typical wasatchian levels that were still higher than those in the preceding clarkforkian wasatchian immigrants were rapidly incorporated into the new community organization representing 20 of the taxa and 50 of the individuals immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa causing significant turnover in body size structure and trophic structure there was a significant short term body size decrease in many lineages that may have been prompted by the elevated temperatures and or decreased latitudinal thermal gradients during the latest paleocene thermal maximum rapid short term climatic change transient climates and associated biotic dispersal can have abrupt and long lasting effects on mammalian community evolution

paleoclimatic implications of crayfish mediated prismatic structures in paleosols of the paleogene willwood formation bighorn basin wyoming u s a abstract paleosols at polecat bench northern bighorn basin wyoming show prismatic structures not previously described in the paleogene willwood formation prisms are densely spaced 15 50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long subangular to rounded vertical faces and slightly concave to convex tops prism exteriors are coated commonly by 1 mm thick clay films exteriors also commonly show knobby and striated surficial morphologies prismatic structures are nearly exclusive to thin bedded 1 m thick compound paleosols composed of red to red purple sandy mudrock overlying gray to green gray heterolithic units composed chiefly of fine grained sandstone in addition to prismatic structures these paleosols are characterized by large gray mottles slickensides and calcareous rhizocretions which crosscut or more typically follow prism exteriors the architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies camborygma litonomos at polecat bench an 40 m interval of the willwood formation records a transient episode of global warming known as the paleocene eocene thermal maximum petm the petm interval is characterized by a series of predominantly red cumulative paleosol profiles and increased soil carbonates prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the petm whereas they are locally abundant in red compound paleosols outside the petm interval the changes in paleosol morphology and a sharp decrease in crayfish burrows within the petm interval suggest significantly improved soil drainage conditions and lower water tables on the willwood floodplain during the global warming event

setup and swash on a natural beach wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0 4 to 4 0 m significant wave height when scaled by the incident wave height setup swash height and total runup the sum of setup and half the swash height were found to vary linearly with the surf zone similarity parameter 0 h0 l0 1 2 the foreshore slope appeared the appropriate value for the calculation of 0 although the setup data showed some influence of an offshore bar at low tide for low irribaren numbers the swash height in the incident frequency band becomes saturated while for high irribaren numbers no such signs of saturations were seen thus the infragravity band appears to become dominant in the swash below some value of 0 for these data that value is approximately 1 75 although there is considerable scatter associated with that estimate

response of a large stratified estuary to wind events observations simulations and theory for long island sound abstractthe response to wind events in the long island sound lis a large macrotidal estuary influenced by rotation and stratification is studied using long term ferry based current observations near the mouth unstratified and stratified numerical simulations forced with along estuary winds and analytic solutions based on linear barotropic theory the observed wind event velocity anomalies for down estuary winds have surface intensified downwind flows flanking a deeper central upwind flow response to up estuary wind events has a weaker magnitude and a broader and thicker downwind flow the downwind and upwind flows are more laterally aligned than vertically layered as determined by a newly defined dimensionless lateral alignment index simulation results and analytic solutions share the gross spatial patterns of the observed response though statistical measures indicate weak agreement along estuary variations in the simulation results and analytic solutions follow similar trends and are strongly

early triassic gulliver gastropods spatio temporal distribution and significance for biotic recovery after the end permian mass extinction a reduction in body size lilliput effect has been repeatedly proposed for many marine organisms in the aftermath of the permian triassic pt mass extinction specifically reduced maximum sizes of benthic marine invertebrates have been proposed for the entire early triassic this concept was originally based on observations on early triassic gastropods from the western usa basin and the dolomites n italy and it stimulated subsequent studies on other taxonomic groups however only a few studies have tested the validity of the lilliput effect in gastropods to determine whether the paucity of large sized gastropods is a genuine signal or the result of a poor fossil record and insufficient sampling in combination with a review of the literature we document numerous new abundant large sized gastropods from the griesbachian outcrops of greenland and from the smithian early spathian interval in the southwestern usa we show that large sized gulliver gastropods i were present soon after the pt mass extinction ii occurred in various basins sedimentary facies and environmental contexts from shallow to deeper settings and iii belong to diverse higher rank taxa focusing on the western usa basin we investigate areas from which microgastropod shell beds were previously presented as being typical however we show that gulliver gastropods do occur in the very same areas insufficient sampling effort is probably the main reason for the rarity of reports of large early triassic gastropods which is supported by preliminary rarefaction based simulations finally it appears that the recently documented middle to late smithian climate shifts and the severe end smithian extinction of nekto pelagic faunas did not reduce maximum shell sizes of gastropods

terrestrial evidence for the lilliput effect across the cretaceous paleogene k pg boundary abstract recent research has demonstrated that the lilliput effect reduction of body size in biota associated with the aftermath of mass extinctions affected all trophic levels in the marine realm following the cretaceous paleogene k pg event however it is unclear if this size change was strictly a marine signal or a global phenomenon that also affected continental ecosystems herein we present the results of an ichnological proxy for body size of soil dwelling insects across the k pg boundary in big bend national park texas u s a quantitative efforts focused on naktodemasis bowni which are characterized as unbranching burrows composed of ellipsoidal packets of backfill menisci these traces were likely produced by beetle larvae or cicada nymphs based on previous comparison with structures generated in modern soils and laboratory experiments as an approximation for the body size of the subterranean insects this dataset indicates that a smaller n bowni diameter dn is statistically correlated

estimates of the transport through the east river new york the hydrodynamic characteristics of the east river new york which connects long island sound to new york harbor have been investigated via a high resolution topographically conformal and orthogonal curvilinear grid together with high quality acoustic doppler current profiler measurements the objective is to determine the volume flux of water through this important water body the model was calibrated and validated through comparisons with measured salinities water levels current velocities and data based estimates of volume flux detailed statistical analyses demonstrated that both the tidal and meteorological bands spanning inverse frequencies between 3 hours and 5 days were well simulated by the model the climatological band inverse frequencies greater than 5 days did not exhibit uniformly good agreement because of the paucity of salinity and temperature measurements available for use as model forcing functions results from an 18 month 1988 to 1989 simulation indicate that the net long term flux of water is directed out of long island sound and toward new york harbor the total rate was found to be about 310 m3 s 1 at the eastern end of the east river near its confluence with long island sound the net flow was distinctly two layered with flows of about 260 m3 s 1 directed toward the sound in the surface layer and flows of approximately 570 m3 s 1 in the bottom layer directed toward new york harbor there appeared to be a 100 m3 s 1 monthly variation about the mean transport at the eastern end however on shorter timescales the transport reversed direction for days at a time

effect of the earth s rotation on the circulation in regions of freshwater influence recent surveys in various regions of freshwater influence have shown considerably different flow patterns in each region an analytical model including viscous effects and the earth s rotation is proposed to examine the along channel flow pattern and to explain the differences model results show that the flow pattern is strongly dependent on the ekman number e with a large ekman number e 1 the system is governed by gravitational circulation and thus horizontal density gradients in along channel direction are important the whole water column is in the ekman layer and consequent jet inflow penetrates the surface over a deep depression if the bottom topography varies in a cross channel direction with an intermediate ekman number e 0 1 this jet inflow concentrates in the lower layer in which the viscosity still plays an important role the flow in the upper layer is on the other hand determined by the geostrophic balance the contribution by the geostrophic flow becomes larger so that the cross channel density gradients are important when die ekman number is small e 0 01 since the ekman layer is clung to the bottom the jet inflow exists only in the thin bottom layer the hydrographic and acoustic doppler current profiler surveys were conducted in ise bay japan both the density structure and the flow pattern were different from those observed in many drowned river valleys a strong jet inflow existed in the lower layer over the depression while the flow in the upper layer suggested anticyclonic circulation the estimated ekman number is 0 07 in the bay and thus the observed pattern is consistent with the model result when e 0 1

paleocene eocene carbon isotope excursion in organic carbon and pedogenic carbonate direct comparison in a continental stratigraphic section the negative carbon isotope excursion at the paleocene eocene boundary is a chemo stratigraphic marker widely used for correlation of marine and continental stratigraphic sections it is linked to massive dissociation of sedimentary methane hydrates and helps to explain an important greenhouse thermal event paleocene eocene thermal maximum marine extinctions and mammalian faunal change on three continents we show that the carbon isotope excursion recorded in dispersed organic carbon doc from fine grained terrestrial sedimentary rocks at polecat bench wyoming is very similar to that described in two high resolution studies of pedogenic soil nodule carbonate from the same section all show a rapid onset an 40 m series of excursion values and a slower recovery however the carbon isotope excursion in soil nodule carbonate starts and ends 3 5 m lower stratigraphically than that in doc we hypothesize that enhanced diffusion of atmospheric co2 and subsurface diagenesis in an environment of good drainage and elevated temperature and p co2 may explain this offset the reliability of 13c in doc is attributed to mixing and averaging of isotopic signals from different organic compounds and tissues