facies architecture and sequence stratigraphy in glacially influenced basins basic problems and water level glacier input point controls with an example from the quaternary of ontario canada abstract sequence architecture is controlled by two fundamental factors the water level relative to the depositional surface which controls accommodation space and the points or areas of sediment injection which control how this space is filled in relative water level accommodation space and injection points normally vary together and various genetic terms are used to define systems tracts but in glacially influenced basins accommodation space is controlled not only by water level but also by the glacier injection points are similarly dually controlled by water level and by the terminus of the glacier during high lake levels the injection point of the glacier may be underwater at the base of the slope genetic terms like highstand and lowstand therefore are meaningless in successions controlled by sediment input points which are independent of water levels and accommodation space distinct water level and glacier input point systems can occur side by side the water level system controlled by lake level or sea level the glacier input point system controlled by the position of the subaqueous glacier front and both can form juxtaposed systems passing laterally into each other a bewildering and incompatible terminology is needed if the terms of genetic sequence stratigraphy are used for both water level and glacier input point systems because the sedimentary injection points and sequence boundaries of the two systems fluctuate out of phase with one another sequences developed by movement of the glacier are completely independent of those controlled by water levels if genetic sequence stratigraphy is applied to a basin with both lake level and glacier input point systems then each needs separate genetic terminologies to describe them which leads only to confusion however descriptive sequence stratigraphy allostratigraphy can be readily applied to successions like the quaternary of lake ontario we therefore suggest that genetic sequence terms be discarded and simpler allostratigraphic terminology used in glacially influenced basins

phanerozoic continental drift abstract an account is given of phanerozoic continental drift a series of paleocontinental maps is presented for ten intervals from 600 to 25 my ago post triassic maps were reconstructed using the plate tectonic model based mainly on ocean floor spreading evidence continental edge fits and apparent polar wander apw paths the middle carboniferous triassic maps are less certain lacking ocean floor spreading evidence but continental positions are constrained by the assumptions of minimum relative continental motions the pre carboniferous maps are based on poorly defined apw paths and minimum motions and can only indicate probable configurations during that period the main theme is that the late precambrian pan african pangea has been progressively fragmented during the phanerozoic pieces broken off in the paleozoic have now collided with one another forming the present northern continents which have grown at the expense of pangea except for india fragments broken off in the mesozoic and cenozoic are still unattached and form the present southern continents

facies architecture and sequence stratigraphy of fine grained lacustrine deltas along the eastern margin of late pleistocene lake bonneville northern utah and southern idaho this study documents the effects of changing lake level limnostasy tectonics sediment yield and basin physiography on the facies architecture sequence stratigraphy and reservoir quality of three fine grained deltas deposited along the eastern margin of late pleistocene lake bonneville analysis of facies architecture indicates that the weber and spanish fork deltas were strongly wave modified because they were situated along openly exposed portions of the shoreline the bear river delta nestled in a relatively isolated northeast arm of the lake records both fluvial and wave processes these fine grained deltas were fed by low gradient rivers that drained large regions that were sparsely glaciated whereas other contemporaneous coarse grained gilbert deltas were fed by steep gradient rivers that drained local source areas that were strongly influenced by glaciers limnostasy tectonics and sediment yield were similar for all three fine grained deltas implying that the most influential forcing parameter on sequence stratigraphy is basin physiography basin physiography specifically ramp length and accommodation most strongly controlled the external and internal geometry of the lowstand systems tract of each delta potential hydrocarbon reservoir quality e g grain size and sorting is largely a product of drainage basin size and stream gradient relative differences in ramp lengths seemed to determine thickness and lateral continuity of delta front deposits relative differences in accommodation appeared to determine the internal geometry of the delta front deposits especially in the lowstand systems tract these deltas can serve as analogs for lacustrine exploration and production where many forcing parameters typically are unknown

sequence stratigraphy in lacustrine basins a model for part of the green river formation eocene southwest uinta basin utah u s a abstract in the middle green river formation of central nine mile canyon uinta basin utah several lacustrine dominated intervals 10 m thick comprise aggradational carbonate parasequence sets and a progradational clastic parasequence maximum flooding surfaces are best identified within profundal oil shale that caps some of the clastic parasequences these lacustrine transgressive systems tracts therefore exhibit parasequence stacking patterns unlike typical marine sequences two types of sequence boundary are identified type a sequence boundaries display evidence for a basinward shift in facies across a regionally mappable surface that is an angular or rarely parallel unconformity and they typically juxtapose amalgamated braided fluvial channel sandstone late lowstand systems tract onto the profundal oil shale they also bound depositional sequences that show a distinct asymmetry being dominated by transgressive systems tracts 5 80 m thick highstand systems tracts are less than 4 m thick and may be removed completely by erosion on overlying sequence boundaries other surfaces satisfy only some of the standard criteria of sequence boundaries and are termed type b sequence boundaries type a sequence boundaries mark pronounced base level falls following times when the uinta lake had merged with a lake in an adjacent basin to form a much deeper lake such merging permitted the establishment of a new threshold at higher elevation following lake level balancing type b sequence boundaries are interpreted as marking base level falls from a barely merged lake or a lake that had an outflow over a 200 m stratigraphic thickness type a sequence boundaries are more common upsection indicating that with time a pluvial climate became more pronounced or that the adjacent lake was more easily filled type a sequence boundaries also become angular rather than parallel unconformities upsection suggesting increased tilting of the basin margin over time

geomorphology applied to flooding problems of closed basin lakes specifically great salt lake utah abstract closed basin lakes fluctuate in level and area in response to variations in the climate over their drainage basins rises of the level of these lakes present severe flooding hazards to developments on the lake bed effective planning for development of these lake beds requires a knowledge of the lake level fluctuations that should be anticipated and also the effect of wind earthquakes and human activity on flooding the historic record of fluctuations of the closed basin lakes of the great basin of the western united states is too short to adequately define the recurrence intervals of high lake levels geomorphic evidence can supplement the historic record great salt lake is the largest closed basin lake in the great basin and its lake bed has been the most extensively developed in the 1980s the level of great salt lake rose dramatically in response to a period of much above average precipitation the resulting flooding caused extensive damage to developments on the lake bed and posed serious dilemmas to federal state and local governments studies subsequent to the flooding reveal how geomorphic evidence can supplement the historic record and provide sufficient understanding of the lake s flooding hazard to guide development and planning under the climatic conditions that have existed for the past several thousand years the still water level of great salt lake can be expected to rise to near the historic highstand or slightly above about once every one hundred years wind action extends flooding in some locations to elevations 2 m above the still water elevation of the lake if an understanding of flooding hazards guides the planning and engineering of developments on and around the lake losses from future high lake cycles can be significantly reduced

paleoshoreline geomorphology of boon tsagaan nuur tsagaan nuur and orog nuur the valley of lakes mongolia abstract we conducted a preliminary study of paleoshoreline features associated with boon tsagaan nuur tsagaan nuur and orog nuur lakes located in the gobi altai transition zone of the valley of lakes dolina ozor which stretches from central to western mongolia the paleoshoreline features were first identified on radarsat satellite sar imagery we investigated the features during the 1998 field season of the joint mongolian russian american archaeological expedition to the gobi altai region we identified paleoshorelines of multiple elevations in the field which are considered to be relict beach ridges and wave cut terraces other paleolake landforms include spits and gilbert type deltas these landforms are complex large and well established implying that the paleolakes were stable for extended periods the reconstructed paleolakes cover extensive areas of the valley floor implying that hydrological and climatic conditions were very different in the past paleolake expansions may have occurred under a variety of circumstances one hypothesis is that the high lake stands occurred during the wetter period corresponding to the oxygen isotope stage 3 prior to the last glacial maximum lgm during the warmest early holocene and the late holocene or during all these periods if low evaporation rates due to lower temperatures glacier meltwater and possibly increased precipitation are important factors then the expansions may have occurred during the terminal late glacial period after the last glacial maximum the greatly expanded lakes in the gobi altai could have significantly affected the quaternary human demography and migration in the region

variability of the wind stress curl over the north pacific implications for the oceanic response the subinertial frequency wavenumber structure and spatial coherence of wind stress curl and their spatial and temporal variability are described with the emphasis on characteristics which affect the ocean s response to the wind stress curl forcing function wind stress curl over the north pacific between 25 o and 60on was computed for 3 years 1985 1988 from the fleet numerical oceanography center wind product the range from winter peak to summer trough for the mean and variance are typically a factor of 3 4 and 10 respectively with superimposed interannual changes of up to a factor of 2 power spectra vary seasonally and interannually in an essentially frequency independent manner that is consistent with the curl variance however the spectrum over the period band 5 100 days often fails a statistical test for whiteness at the 95 level zonal and meridional wavenumber spectra were estimated for 13 sites distributed around the central eastern north pacific using the maximum likelihood method directional trends with frequency are comparable to those from earlier studies if 3 year long data segments are analyzed with approximate wavenumber symmetry except for the zonal term at mid latitudes for periods shorter than 10 days where eastward propagation is dominant however spectra for shorter data sections sometimes display eastward and westward excursions which are only weakly similar over distances of 1000 km and essentially dissimilar over longer separations the spatial correlation structure of wind stress curl is shown typically to have a main lobe of 1000 km and multiple intercorrelation lobes separated by 2000 km the strength and location of the intercorrelation peaks vary slowly with time these results suggest that curl behavior is more complex than was previously believed that the use of long term averages of or simple parameterizations for the frequency wavenumber spectrum of wind stress curl in model studies may be unrealistic and that more attention to actual curl characteristics at the time oceanic measurements are collected will be required to reconcile models with observations

paleomagnetic investigation of the bonneville alloformation lake bonneville utah abstract paleomagnetic secular variation in a portion of the bonneville alloformation is compared with secular variation in lacustrine sediments in the mono basin california and with secular variation in lake lahontan sediments in the northwestern great basin the comparison places an age of about 18 000 yr b p and a span of 1000 to 3000 yr on part of a transgressive stage of lake bonneville near delta utah that is coeval with a wet period in the lahontan basin

paleomagnetic investigation of lake lahontan sediments and its application for dating pluvial events in the northwestern great basin abstract a comparison of paleomagnetic secular variation in sediment of pleistocene lake lahontan in the northwestern great basin with secular variation in lake sediment in the mono basin california indicates that lake lahontan was in the valley of the truckee river between pyramid lake and wadsworth nevada from about 19 000 to 13 000 yr b p the secular variation in older lake lahontan sediment in the truckee river valley has the general features of secular variation in middle pleistocene lacustrine sediments near rye patch dam nevada 125 km to the east on the basis of field mapping and tephrochronology the sections of older lacustrine sediments are not coeval the apparent but erroneous correlation of those sediments emphasizes the need for multiple dating methods when paleomagnetic secular variation is used to date stratigraphy

hierarchical dynamic stratigraphy in various quaternary gravel deposits rhine glacier area sw germany implications for hydrostratigraphy the approach of dynamic stratigraphy aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales this approach was used to investigate quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties facies analysis within 62 gravel pits laboratory permeability measurements of field samples and geophysical surveys 3 d georadar 2 d seismic reflection led to the detection and classification of sedimentary heterogeneity according to the following six scales whereby each scale can be translated into defined hydrostratigraphic units 1 particles and pores micro scale that reflect depositional and diagenetic fluid dynamics as well as source material behaviour e g grain size roundness lithological composition this was found to be important for the hydrogeochemistry of groundwater in gravel aquifers e g higher sorption capacity of carbon rich limestone particles for organic pollutants 2 strata meso scale contain the recognition of sorting fabric texture and stratinomic features which can give an indication of transport and depositional dynamics five major lithofacies groups for example were distinguished within fluvial gravel bed deposits their variable hydraulic properties led to their subdivision into 12 hydrofacies types they form the smallest mappable hydrostratigraphic units which may result in either preferred pathways for fluid flow or flow barriers 3 depositional elements macro scale enable reconstruction of sedimentary geomorphic elements and their dynamics within a depositional system e g gravel bed braided river systems are dominated by gravel sheet gravel dunes and scour pool depositional elements hydrostratigraphically the architecture of depositional elements influences the hydraulic connectivity and local permeability structure distribution within an aquifer body five types of depositional elements in fluvial gravel bed deposits were distinguished and their geometries dimensions quantified 4 facies bodies mega scale composed of a stack of depositional elements and strata recording distinct environmental systems and their dynamics e g a coarse grained prograding delta system hydrostratigraphically facies bodies represent major compartments of an aquifer six major types of meltwater controlled facies bodies were identified in the study area 5 genetic sequences mega scale reflect the shifts of depositional environments caused by allocyclic changes e g glacial advance recorded by a coarsening upward sequence or autocyclic changes of landscape shaping events these sequences may form separate hydrostratigraphic units or aquifer storeys 6 basin fill giga scale comprising the lateral and vertical stacking of facies bodies and genetic sequences controlled by either long term glacier dynamics or short term flood events the regional distribution of permeable gravel units and for example less permeable diamicts builds the larger scale hydrostratigraphy

geomorphology and quaternary stratigraphy the roles of morpho litho and allostratigraphy abstract the subdivision and ordering of quaternary sediments and landforms is very often based on geomorphology quaternary landforms such as moraines river terraces palaeoshorelines and indeed any other landform can be arranged and ordered in time based on their relative position in the landscape morphostratigraphy is the subdivision of sedimentary units primarily on the basis of surface form whilst surface form is often used as a criterion for separating sedimentary units morphostratigraphy also usually incorporates lithological criteria to aid stratigraphical subdivision and morpho and lithostratigraphy are often interlinked in quaternary science however another approach allostratigraphy has increasingly been applied to subdivide and order quaternary sediment landforms allostratigraphy uses discontinuities to subdivide sedimentary successions allostratigraphy enables lateral variations in lithology to be included within the same stratigraphical unit furthermore it enables lithologically similar sediments stacked on top of each other to be divided into separate units based on discontinuities this paper examines the applications of morpho litho and allostratigraphy to subdivide sediment landform assemblages and critically reviews their role in quaternary stratigraphy

geochronology and stratigraphy of late pleistocene lake cycles on the southern bolivian altiplano implications for causes of tropical climate change large paleolakes 33 000 60 000 km2 that once occupied the high altitude poopo coipasa and uyuni basins in southern bolivia 18 22 s provide evidence of major changes in low latitude moisture in these now dry or oligosaline basins extensive natural exposure reveals evidence for two deep lake and several minor lake cycles over the past 120 k y fifty three new u th and 87 new 14c dates provide a chronologic framework for changes in lake level deposits from the ouki deep lake cycle are extensively exposed in the poopo basin but no deep lakes are apparent in the record between 98 and 18 1 ka the ouki lake cycle was 80 m deep and nineteen u th dates place this deep lake cycle between 120 and 98 ka shallow lakes were present in the terminal uyuni basin between 95 and 80 ka salinas lake cycle at ca 46 inca huasi lake cycle and between 24 and 20 5 ka sajsi lake cycle the tauca deep lake cycle occurred between 18 1 and 14 1 ka resulting in the deepest 140 m and largest lake in the basin over the past 120 ka multiple 14c and u th dates constrain the highest stand of lake tauca along a topographically conspicuous shoreline between 16 4 and 14 1 ka a probable post tauca lake cycle the coipasa produced a 55 m deep lake that is tentatively dated between 13 and 11 ka we suggest that paleolakes on the bolivian altiplano expanded in response to increased moisture in the amazon and enhanced transport of that moisture onto the altiplano by strengthened trade winds or southward displacement of the intertropical convergence zone itcz pole to equator sea surface temperature sst and atmospheric gradients may have influenced the position of the itcz affecting moisture balance over the altiplano and at other locations in the amazon basin links between the position of the itcz and the ca 23 ka precessional solar cycle have been postulated march insolation over the altiplano is a relatively good fit to our lake record but no single season or latitude of solar cycling has yet to emerge as the primary driver of climate over the entire amazon basin temperature may influence altiplano lake levels indirectly as potentially dry glacial periods in the amazon basin are linked to dry conditions on the altiplano intensification of the trade winds associated with la nina like conditions currently brings increased precipitation on the altiplano and deep lake development during the tauca lake cycle coincided with apparently intense and persistent la nina like conditions in the central pacific this suggests that sst gradients in the pacific are also a major influence on deep lake development on the altiplano

sequence stratigraphy of lacustrine deposits a quaternary example from the bonneville basin utah the late quaternary lacustrine sedimentary record in the bonneville lake basin in the eastern great basin provides an excellent example of sequence stratigraphy two sequences referred to as the little valley and bonneville alloformations are exposed in the bluffs of the sevier river where it has entrenched its pleistocene delta between leamington and delta utah both alloformations contain offshore marl units and fine grained deltaic or underflow fan deposits they can be identified and mapped by tracing the unconformity separating them and employing a number of geochronometric tools including amino acid epimerization in fossil gastropods radiocarbon and thorium 230 ages and basaltic tephrochronology thin transgressive sand of the little valley alloformation is overlain by deeper water marl and down lapping regressive phase deltaic silt the bonneville alloformation lies unconformably above the little valley deposits fine grained deltaic sediments deposited during the transgressive phase of lake bonneville fill the entrenched sevier river valley that was eroded subsequent to the little valley lake cycle marl deposited during the deep water phase is overlain by down lapping deposits of the regressive phase below the provo shoreline but is the uppermost unit in the altitudinal range where the lake was lowered catastrophically during the bonneville flood the sequence stratigraphic interpretation leads to the conclusion that the sevier river delta as a whole is probably made up of a number of sediment sequences each composed of several facies recognition of this complexity could be important in potential applications of the stratigraphic model

holocene paleolakes of lake canyon colorado plateau paleoclimate and landscape response from sedimentology and allostratigraphy middle and late holocene paleoclimate can be inferred from lake level fluctuations recorded in the sediment of two fresh groundwater controlled paleolakes in lake canyon southeast utah the record from lake canyon contributes proxy climate data for the region as well as insight into climate controls on sedimentation the paleolakes were formed immediately upcanyon of side stream confluences where disproportionately large volumes of alluvium were focused into the bedrock canyon excellent exposure allows a depositional facies model to be developed and allostratigraphic units to be defined a facies based proxy for the past shoreline position is applied to the allostratigraphy and radiocarbon based chronostratigraphy to produce a record of lake level through time that is corroborated by diatom proxy data the earliest known lake formed during an episode of aggradation that began just before 5180 14 c yr b p and an arroyo cutting event drained the lake before 3050 14 cy r b p the lake canyon record for the past 3 k y is composed of wet dry cycles that have a periodicity of 520 yr matching cycles resolved by the regional tree ring record and the timing of the medieval warm period and little ice age lake level rose after 420 14 c yr b p and aggradation continued until an advancing arroyo headcut drained the upper lake in a d 1915 fluvial and lacustrine aggradation in lake canyon accompanied shifts to wetter climate when sediment stored in upper reaches of the drainage basin was delivered to the canyon whereas arroyo cutting in the canyon is more a function of sediment supply and internal complex response mechanisms than dry climate conditions correlation with other records is hindered by differences in resolution and the influence of local controls on alluvial stratigraphy the lake canyon record confirms that episodes of high flood frequency in holocene time have been wetter overall but not all wet periods have been marked by high flood frequency

transgressive stratigraphic record and possible oscillations of late pleistocene lake bonneville northern hogup mountains utah u s a abstract distinct mappable facies changes make the stratigraphic record of the shorezone of late pleistocene lake bonneville the most robust indicator for past lake level oscillations unfortunately clear stratigraphic evidence of transgressive and regressive deposits has been generally lacking new stratigraphic and chronological data within the lacustrine shorezone sediments of the hogup mountains of northwestern utah provide some of the best evidence yet for oscillations within the overall transgressive phase of the lake this study documents two previously unknown oscillations hereby named the lower hogup 22 cal ka and upper hogup 20 6 cal ka oscillations and provides further evidence for the previously proposed u2 oscillation 21 3 cal ka the study suggests that the water level of the lake changed dramatically up to 25 of the lake s total volume during the transgressive phase 30 15 cal ka with the additional oscillations documented in this study there are seven proposed oscillatory events during the transgressive phase of the lake these events likely correlate to rapid but short term regional climatic fluctuations during the broader climatic trends of the last glacial maximum however it is still unknown what specific climatic drivers are causing these oscillations and if these events can be correlated to other global climatic events

amino acid paleothermometry of quaternary ostracodes from the bonneville basin utah abstract unlike many other proxy climate recorders temperature dependent chemical reactions that take place in fossils are independent of paleoprecipitation changes and therefore allow paleotemperatures to be calculated uniquely in this study i use the extent of amino acid racemization in fossil ostracode shells to reconstruct the temperature history of the bonneville basin utah the enantiomeric composition d l ratios of 64 ostracode samples each comprising an average of 18 subsamples from 25 sites were analyzed by reverse phase hplc the effective diagenetic temperature edt for five intervals of the quaternary including the last full glacial period was calculated for two amino acids aspartic and glutamic acids errors associated with the edt calculations were derived using a monte carlo procedure age control was provided by both new and previously published ams 14 c luminescence tephra and amino acid geochronology the edt for the southern bonneville basin during the middle pleistocene interval from 620 150 ka oxygen isotope stages ois 16 6 was 5 7 1 5 c this compares with an edt of 10 9 1 3 c for the late holocene last 5 8 cal ka and a current mean annual temperature of about 9 4 c at nearby sites 40 n latitude the edt then decreased to 3 3 1 3 c for the interval from ois 6 2 150 12 cal ka during the last full glacial period 24 12 cal ka ois 2 the edt was 1 1 2 5 c or about 10 3 c lower than during the late holocene paleotemperatures this low suggest that reduced evaporation rather than increased precipitation could have accounted for the increased effective moisture and the growth of lake bonneville

orbital control of long term moisture in the southwestern usa 1 regional lake sediment records including late pleistocene lake estancia new mexico show that the southwestern usa was wetter than present over the last glacial maximum and drier during the holocene chronology of speleothems that mark groundwater levels in cavenee caverns near lake estancia indicates water level lowering through the cave during the early to middle holocene 8500 yr bp consistent with the timing of desiccation of lake estancia and deflation of the basin floor the speleothem record also shows the same wetter to drier climatic shift during the penultimate glacial and interglacial transition at 134 kyr bp subaqueous crusts formed when cave submerged to 121 kyr bp cave rafts formed during water table drop our data support wet glacials and dry interglacials as being a general feature of pleistocene climate in the southwestern usa the timing suggests that the process is orbitally controlled

pre late wisconsinan pleistocene biota from southeastern michigan u s a abstract fossiliferous sediments underlie the late wisconsinan mill creek and fisher road tills at the mill creek site northwest of port huron michigan fragmentary remains of 5 fish and 11 mammal taxa occur with 39 taxa of molluscs 6 of ostracodes and a pine spruce pollen assemblage while the fish are wide ranging the mammals include distinctly northern elements such as dicrostonyx sp lemmus sp mictomys borealis and microtus xanthognathus the molluscs include a mixture of cold vertigo alpestris oughtoni and v modesta and warm lioplax sulculosa taxa none of the vertebrates have been found at michigan sub till sites before and lioplax is new to michigan fossil or living vertigo hannai is known only as a pleistocene fossil at present the age of the biota is indeterminate the stratigraphy indicates a middle wisconsinan or greater age a finite 14c age of 48 3 0 8 ka ql 1215 was later supplemented by a tl date of 57 9 ka but perhaps as old as 300 ka two clusters of amino acid allo isoleucine isoleucine values obtained from six genera of molluscs are interpreted to represent the co occurrence of early sangamonian aile ile values ranging from approximately 0 15 to 0 25 and illinoian aile ile values ranging from approximately 0 25 to 0 35 mollusc fossils at the mill creek site these results highlight the need for more reliable quaternary dating methods

sedimentology and allostratigraphy of post 240 ka to pre 26 5 ka lacustrine terraces at intracaldera lake rotorua taupo volcanic zone new zealand abstract lake rotorua partially occupies a nearly circular 20 km diameter volcano tectonic depression formed at c 240 ka by eruption of the voluminous mamaku ignimbrite three distinct lacustrine littoral terraces defined on the basis of contrasting geomorphology and field relations and separated by tephrostratigraphically dateable unconformities and basin floor disconformities fringe much of the lake basin they are here correlated with former high stands of the lake which resulted from the blockage and re establishment of a number of alternative outlets due to tectonic activity and volcanism at both the host and adjacent volcanic centres the unconformities allow division of the deposits into three allostratigraphic units each of which is then characterised by elevation and sediment provenance the

reconstructing low levels of lake lisan by correlating fan delta and lacustrine deposits abstract reconstruction of paleo shorelines of lake lisan the late pleistocene precursor of the dead sea is based on sequence stratigraphy of fan delta and lacustrine deposits that are exposed at the perazim valley southwest of the dead sea the shoreline sediments are physically correlated with lacustrine aragonites their ages are determined by u series dating to establish a lake level curve for the time interval between 55 and 35 kyr during most of this period lake lisan was at a relatively low level which fluctuated between 280 and 290 m below sea level m bsl the minimum lake stand 330 m bsl was reached at 47 kyr and lasted for 3 4 kyr this episode is marked by a depositional hiatus in the section and formation of an erosional channel the studied period correlates with the global marine isotope stage 3 the low stand of lake lisan during most of this period indicates relative dry climatic conditions in the region

eruption dynamics at pahvant butte volcano utah western usa insights from ash sheet dispersal grain size and geochemical data shallow to emergent subaqueous basaltic explosive eruptions here referred to as surtseyan are a source of pyroclastic material expelled from subaqueous vents and transferred to the water column and atmosphere they can threaten coastal communities in different ways and one of these is through the generation of pyroclastic density currents travelling over water once the eruption becomes subaerial these may be preceded or accompanied by eruption fed currents moving along the sea lake floor one approach for studying these eruptions is through analysis of their deposits but these are commonly either inaccessible under water or poorly preserved by the time they are exposed subaerially the site selected for this work pahvant butte ut usa avoids these limitations the volcano was formed at 18 600 cal year b p in the giant pleistocene lake bonneville by an eruption initiated at a relatively shallow water depth 85 m the water is now drained and deposits of the edifice and of the ash sheet at medial distances on the old lake floor medial lake are accessible and well preserved the ash sheet deposits allow us to investigate dispersal of ash from a surtseyan eruption including the subaqueous phase of edifice building by comparing edifice deposits with ash sheet deposits correlated using geochemistry and textural analysis results suggest that medial deposited ash from pahvant butte travelled at least 25 km from the vent in eruption fed pyroclastic density currents moving along the lake floor this transport began early in the eruption apparently prior to the volcano s subaerial emergence

lake bonneville fluctuations and global climate change lake bonneville the largest late pleistocene closed basin lake in the north american great basin fluctuated widely in response to changes in climate the geochemistry and mineralogy of endogenic calcium carbonate deposited in deep water and stratigraphic studies of shore zone deposits provide evidence of millennial scale lake level fluctuations that had amplitudes of about 50 m between 30 and 10 ka falling lake events occurred at 21 18 5 19 17 5 16 15 5 14 13 and 10 ka radiocarbon years synchronously with the terminations of heinrich events h1 and h2 and other smaller scale iceberg rafting events a b c and younger dryas in the north atlantic ocean the lake bonneville results thus support other climate records that suggest that late pleistocene millennial scale climate change was global in extent the size and shape of the northern hemisphere ice sheets which determined the mean positions of storm tracks may have been the primary control on late pleistocene water budgets of great basin lakes

evolution of colpan barrier and lagoon complex lake van turkey sedimentological and hydrological approach abstract the northeastern coast of the lake van eastern anatolia turkey is exposed to energetic waves inducing large sediment transport rates intense wave activity on coastal environment shows the shaping impact on the shoreline either erosional or depositional processes sedimentation is characterized by gravelly beaches spit formation and barrier lagoon complex colpan barrier and lagoon complex forming the subject of this study occurred in these swashed environmental conditions this study aims to introduce formation and evolution of the colpan barrier and lagoon complex and to assess the future development of the coastal area around the lake van characteristics of barrier sediments as shape size provenance sedimentary structures and palaeocurrent directions are determined with field investigations smooth flattened and rounded polygenetic sediments compose the barrier drifted to the shoreline with coastal processes as wave and longshore currents colpan barrier was created a lagoon completely isolated from lake van this wetland constitutes a habitat for some animals and plants with relatively dilute water than sodic lake van s water level fluctuation is an important element for the constructive and destructive processes for the barrier and lagoon complex

fluvial response to an historic lowstand of the great salt lake utah understanding fluvial adjustments to base level changes benefits the fields of sequence stratigraphy geomorphology and petroleum geology this investigation is a modern case study of the channel dynamics of lee creek and the goggin drain two streams that are part of the jordan river drainage into the endorheic great salt lake of northern utah a lacustrine system that has experienced multiple decadal scale base level changes since 1965 the lake level has fluctuated in elevation more than 6 m transitioning from an historic lowstand 1284 m a s l and in 2009 2010 approaching an historic lowstand this study uses detailed aerial images fieldwork and lidar data to link the modern geomorphology and channel hydraulics to specific variations in sediment transport channel form and avulsion behavior although lee creek and the goggin drain are situated only a few kilometers apart and share similar shore zone gradients substrates and vegetation patterns and have been subjected to the same changes in lake level their channel forms have evolved very differently differences in discharge patterns are likely the most influential factor causing the meandering form of lee creek and the braiding channel of the goggin drain despite the differences in discharge total sediment eroded from the two streams is comparable and can be attributed to similar stream power unit stream width in the two streams although lee creek has not recently been avulsive three major avulsions of the goggin drain have taken place since 1965 two possible styles of avulsion are interpreted an allogenic response to changing base level and an autogenic response dictated by channel morphology and hydraulics despite a wealth of available information avulsions cannot be unequivocally attributed to one style or another caution should be used when attempting to link the complex process of avulsion to causal mechanisms copyright 2011 john wiley sons ltd