the bonneville estates rockshelter rodent fauna and changes in late pleistocene middle holocene climates and biogeography in the northern bonneville basin usa abstract excavations at bonneville estates rockshelter nevada recovered rodent remains from stratified deposits spanning the past ca 12 500 14c yr bp 14 800 cal yr bp specimens from horizons dating to the late pleistocene and early holocene include species adapted to montane and moist and cool habitats including yellow bellied marmot marmota flaviventris and bushy tailed woodrat neotoma cinerea shortly after 9000 14c bp 10 200 cal yr bp these mammals became locally extinct or nearly so taxonomic diversity declined and the region became dominated by desert woodrats neotoma lepida and other species well adapted to xeric low elevation settings the timing and nature of changes in the bonneville estates rodent fauna are similar to records reported from nearby homestead and camels back caves and provide corroborative data on terminal pleistocene early holocene environments and mammalian responses to middle holocene desertification moreover the presence of northern pocket gopher thomomys talpoides at bonneville estates adds to a sparse regional record for that species and similar to homestead cave it appears that the ca 9500 14c yr bp 10 800 cal yr bp replacement of the northern pocket gopher by botta s pocket gopher in the great salt lake desert vicinity was also in response to climate change

the dead sea sinkhole hazard geophysical assessment of salt dissolution and collapse abstract a geophysical approach is presented for analyzing processes of subsurface salt dissolution and associated sinkhole hazard along the dead sea the implemented methods include seismic refraction srfr transient electromagnetic method tem electric resistivity tomography ert and ground penetration radar gpr the combination of these methods allows the delineation of the salt layer boundaries estimating its porosity distribution finding cavities within the salt layer and identifying deformations in the overlying sediments this approach is shown to be useful for anticipating the occurrence of specific sinkholes as demonstrated on both shores of the dead sea these sinkholes are observed mainly along the edge of a salt layer deposited during the latest pleistocene when lake lisan receded to later become the dead sea this salt layer is dissolved by aggressive water flowing from adjacent and underlying aquifers which drain to the dead sea sinkhole formation is accelerating today due to the rapid fall of the dead sea levels during the last 30 years caused by anthropogenic use of its water

origin and emplacement of mariana forearc seamounts large seamounts occur on the outer half of the mariana forearc they represent a new class of seamounts consisting of horsts and diapirs of metamorphosed forearc material the degree of metamorphism in this material depends on the amount of water available and the pressure temperature regime of the forearc wedge the major source for the water involved in the metamorphism is most likely the descending slab theoretical models for thermal regimes in convergent margins suggest that the lower grade metamorphic facies will be restricted to the outermost part of a forearc zeolite and chlorite facies rocks predominate in dredge hauls from horsts on the outer 50 km of the mariana forearc thermal models indicate that higher grade greenschist facies should occur farther from the trench seamounts that were probably formed in response to diapiric emplacement of serpentinite predominate from 50 to 120 km from the trench uplift of the horsts and emplacement of the serpentinite diapirs were probably facilitated by vertical tectonic movement in response to subduction of plate seamounts and by fracturing of the mariana forearc

salt karst and tectonics sinkholes development along tension cracks between parallel strike slip faults dead sea jordan this work deals with the tectonic interpretation of an alignment of more than 300 sinkholes stretching along the jordanian coast of the dead sea ghor al haditha area its dimensions are 6 km long with a width of 600 m sinkholes appeared during the last decades as a consequence of the very rapid lowering of the lake level the linear shape was inferred from ground collapse inventories carried out between 1991 and 2008 the lineament is replaced and analyzed in its structural setting at regional and local scales its direction n 24 e is sub parallel to the ones displayed by many focal mechanisms especially the one associated with the earthquake of the 23 april 1979 mb 5 1 n 20 e 5 which is representative of all focal mechanisms calculated on a fault plane compatible with the general direction of the jordan dead sea transform fault system for the east coast of the dead sea area the alignment of sinkholes is constituted by 13 minor linear segments separated by as many empty spaces four minor linear units present an en echelon arrangement from which one can deduce the presence of a local extensional stress field in this context the sinkhole locations provide information of subsurface discontinuities interpreted as hidden fractures in a close future such results could support the work of decision makers and engineers in the projected development of the area copyright 2009 john wiley sons ltd

late quaternary environmental change in the bonneville basin western usa abstract excavation and analyses of small animal remains from stratified raptor deposits spanning the last 11 5 ka together with collection and analysis of over 60 dated fossil woodrat midden samples spanning the last 50 ka provide a detailed record of changing climate in the eastern great basin during the late pleistocene and holocene sagebrush steppe dominated the northern bonneville basin during the full glacial suggesting that conditions were cold and relatively dry in contrast to the southern basin which was also cold but moister limber pine woodlands dominated 13 11 5 ka indicating increased dryness and summer temperatures 6 7 c cooler than present this drying trend accelerated after 11 5 ka causing lake bonneville to drop rapidly eliminating 11 species of fish from the lake from 11 5 8 2 ka xerophytic sagebrush and shadscale scrub replaced more mesophilic shrubs in a step wise fashion a variety of small mammals and plants indicate the early holocene was 3 c cooler and moister than at present not warmer as suggested by a number of climatic models the diversity of plants and animals changed dramatically after 8 2 ka as many species disappeared from the record some of the upland species returned after 4 ka and great salt lake became fresh enough at 3 4 and 1 2 ka to support populations of utah chub

the relation of holocene fluvial terraces to changes in climate and sediment supply south fork payette river idaho abstract well preserved holocene terraces along the south fork payette river in central idaho provide a record of fluvial system behavior in a steep mountain watershed characterized by weathered and erodible idaho batholith granitic rocks terrace deposit ages were provided by 14c dating of charcoal fragments and optically stimulated luminescence osl dating of sandy sediments along with pairing of many terrace tread heights these data indicate episodic downcutting during the holocene with a mean incision rate of 0 9 m ka from 7 ka to present prior to 7 ka the river incised to within 3 m of current bankfull but then aggraded by 5 m over at least a 10 km long reach in an episode centered 7 6 ka aggradation may relate to 1 increased hillslope sediment input from landslides and debris flows in steep tributary basins with abundant grussified granitic bedrock 2 possible local landslide damming of the channel 3 decreased peak discharge or 4 a combination of these factors middle holocene channel aggradation ca 7 6 ka corresponds with a period of prolonged and widespread aridity in the northern rocky mountains between 5 and 1 3 ka the river aggraded slightly and then remained stable forming a prominent terrace tread at 3 m above current bankfull modest aggradation to vertical stability of the south fork payette river at the 1 5 m terrace level 1 0 0 7 ka corresponds with large fire related debris flows in tributaries during medieval droughts three intervals of incision 5 5 5 ka 1 3 1 0 ka and 0 5 ka correspond with frequent but small fire related sedimentation events and generally cooler wetter conditions suggesting increased snowmelt runoff discharges other possible drivers of channel incision include an increase in stochastic or climate modulated large storms and floods and a reduction in delivery of hillslope sediment to the channel aggradation is more confidently tied to climate through increases in hillslope sediment delivery and or decreased stream power both likely related to warmer drier conditions including high severity fires that reduce snowmelt and decrease vegetation cover on steep slopes thus the holocene terraces of the south fork payette river do not reflect simple stepwise incision with periods of vertical stability and lateral migration but record substantial episodes of aggradation as well we infer that increases in hillslope erosion and mass movements combined with reduced discharges during prolonged droughts episodically reverse the post glacial trend of downcutting in particular during the middle holocene the present bedrock dominated channel implies a strong tendency toward incision in the late holocene

kinematics of the philippine sea plate in this study new instantaneous rotation vectors describing the motion of the philippine sea plate relative to surrounding plates are determined that most nearly satisfy all available geological geophysical and seismological observations along the plate margins pacific philippine and caroline pacific poles are generated from a set of trial eurasia philippine poles of rotation using published determinations of the eurasia pacific and caroline philippine poles the pacific philippine caroline pacific and eurasia philippine poles are then checked for agreement with 1 slip vectors determined from focal mechanisms of earthquakes along the ryukyu trench and the nankai trough 2 convergence at the sagami trough 3 extension in the mariana trough 4 extension behind the bonin trench 5 extension in the western sorol trough and 6 convergence at the mussau trench trial eurasia philippine poles are eliminated if predicted plate motions do not match observed plate motions the locations and rotation rates of the three best fitting poles are eurasia philippine 37 0 n 141 0 e 1 60 ma pacific philippine 3 8 n 130 4 e 1 68 ma caroline pacific 16 9 n 141 4 e 0 54 ma the plate motions predicted by these new poles are compared with the spatial distribution of earthquakes and new focal mechanism solutions in the complex region where the philippine pacific and caroline plates intersect intermediate and deep focus earthquake hypocenters along the southern mariana arc show a southward decrease in the length of the seismic zone which qualitatively agrees with the predicted convergence rate as the pole of rotation is approached and as the effect of back arc spreading in the mariana trough disappears the absence of volcanism and intermediate depth seismicity along the southernmost mariana yap and palau sections of the plate boundary is attributed to very low convergence rates a new focal mechanism solution along the trench south of guam is the first clear underthrusting solution found along the mariana trench and agrees with the convergence direction implied by the pacific philippine pole of rotation no clear underthrusting focal mechanism solutions were found along the yap and palau trenches although three high angle thrust solutions demonstrate that compression is occurring in the upper plate perpendicular to the plate boundary

a spatially explicit model of runoff evaporation and lake extent application to modern and late pleistocene lakes in the great basin region western united states 1 a spatially explicit hydrological model was applied to the great basin in the western united states to predict runoff magnitude and lake distributions under modern and late pleistocene conditions the model iteratively routes runoff through depression to find a steady state solution and was calibrated with mean annual precipitation pan evaporation temperature and stream runoff data the predicted lake distribution provides a close match to present day lakes for the late pleistocene the sizes of lakes bonneville and lahontan are well predicted by linear combinations of 0 2 5 8 c decreases in temperature and corresponding increases in precipitation from 2 0 to 1 0 times modern values this corresponds to runoff depths ranging from 1 7 to 4 1 times the present values and yearly evaporation from 0 4 to 1 times modern values to reproduce lake manly however combinations of temperature decreases up to 9 c or precipitation up to 2 8 times the present values were required

palynological evidence for vegetation cycles in a 1 5 million year pollen record from the great salt lake utah usa pollen analysis of the mid lake indian cove well in the great salt lake collected by amoco production co provides a 1 5 ma record of climatic change correlative with the deep sea oxygen isotope record chronologic control for indian cove is provided by the lava creek b 0 60 ma bishop 0 76 ma and huckleberry ridge 2 06 ma volcanic ashes the processing of close interval 3 m ca 8 ka samples is complete for the upper 628 m 1 5 ma of the indian cove well during the last 750 ka interglacial glacial cycles are expressed as the ratio of juniperus ambrosia sarcobatus interglacial vs picea abies and pseudotsuga glacial correlating the peak abundances of this ratio with the odd numbered oxygen isotope stages has refined the time control provided by three volcanic tephra the average pleistocene sedimentation rate is 0 39 m ka 1 huckleberry ridge 2057 ka 797 m based on the refined time scale resulting from correlation with the marine chronology sedimentation reached maximum values during isotope stages 11 9 and was slow between stages 13 and 11 and stages 9 7 development of the bonneville pluvial cycles from 759 to 600 ka is recorded by changes in wetland and aquatic palynomorphs increased pollen concentration above 150 m 310 ka may result from the diversion of the bear river into the great salt lake basin

late holocene hydroclimate inferences for the northern great basin from little lake elko county nevada usa abstract prominent lunette dunes 500 800 m long 50 80 m wide and up to 5 m tall are present on the floor of the independence valley in northeast nevada usa these dunes border the downwind margins of circular playas at the end of a drainage descending from the east humboldt mountains which terminates in an ephemeral water body named little lake gastropod shells from the little lake playa yield radiocarbon ages of 400 cal yr bp after correction for a hard water effect a similar age was obtained for shells from the crest of one of the lunettes deeper sediment in this lunette yielded shell ages clustering around 600 cal yr bp this pattern suggests two intervals of relatively persistent water at little lake both of which ended with lake desiccation and deflation of sediment and shells to the adjacent lunette shells from the crest of another lunette yielded radiocarbon ages between 3800 and 1750 cal yr bp this dune therefore is considerably older and accumulated over a much longer stretch of time using the global surface water explorer years between 1984 and 2018 were identified in which little lake contained water in most of the available summer imagery these years form three clusters 1984 1987 1997 2000 and 2017 2018 snow water equivalent swe is greater in the mountains snow makes up a greater percent of total annual precipitation and palmer drought severity index is more positive in this region in years when water is present in little lake compared with those in which the lake remains dry values of the pdo are also higher in years when little lake holds water although the hydrology of little lake may be influenced to an unknown degree by upstream water diversions this overall pattern implies that the lake and its associated lunettes are a sensitive recorder of late holocene hydroclimate variability in the northern great basin

late pleistocene and early holocene rivers and wetlands in the bonneville basin of western north america abstract field investigations at dugway proving ground in western utah have produced new data on the chronology and human occupation of late pleistocene and early holocene lakes rivers and wetlands in the lake bonneville basin we have classified paleo river channels of these ages as gravel channels and sand channels gravel channels are straight to curved digitate and have abrupt bulbous ends they are composed of fine gravel and coarse sand and are topographically inverted i e they stand higher than the surrounding mudflats sand channels are younger and sand filled with well developed meander scroll morphology that is truncated by deflated mudflat surfaces gravel channels were formed by a river that originated as overflow from the sevier basin along the old river bed during the late regressive phases of lake bonneville after 12 500 and prior to 11 000 14c yr b p dated samples from sand channels and associated fluvial overbank and wetland deposits range in age from 11 000 to 8800 14c yr b p and are probably related to continued sevier basin overflow and to groundwater discharge paleoarchaic foragers occupied numerous sites on gravel channel landforms and adjacent to sand channels in the extensive early holocene wetland habitats reworking of tools and limited toolstone diversity is consistent with theoretical models suggesting paleoarchaic foragers in the old river bed delta were less mobile than elsewhere in the great basin

major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

a speleothem record of holocene paleoclimate from the northern wasatch mountains southeast idaho usa abstract a speleothem stable isotope record from minnetonka cave located in the northern wasatch mountains is shown to be a winter season biased record of holocene paleoclimate the season specific sensitivity of the record provides an opportunity to more robustly evaluate long term variability in large scale pacific teleconnection patterns such as enso and pdo as precipitation anomalies associated with these teleconnection patterns occur primarily in winter seasonal climate composite maps of high and low snowpack years at the study site demonstrate that winter precipitation is strongly linked to the relative strength of the aleutian low and the associated changes from to more meridional or more zonal steering level wind patterns minnetonka cave data suggest wetter cooler than modern early holocene winters and a dry middle holocene with a consistent warming trend from 7400 to 3800 bp after 4000 bp data suggest a return to wetter and or colder than modern winters for much of the late holocene prolonged winter dry intervals are identified from 7400 to 6000 bp and 4200 bp

the 87sr 86sr ratios of lacustrine carbonates and lake level history of the bonneville paleolake system lakes in the bonneville basin have fluctuated dramatically in response to changes in rainfall temperature and drainage diversion during the quaternary we analyzed tufas and shells from shorelines of known ages in orderto develop a relation between 8 7 sr 8 6 sr ratio of carbonates and lake level which then can be used as a basis for constraining lake level from similar analyses on carbonates in cores carbonates from the late quaternary shorelines yield the following average 8 7 sr 8 6 sr ratios 0 71173 for the stansbury shoreline 22 20 1 4 c ka 1350 m 0 71153 for the bonneville shoreline 15 5 14 5 1 4 c ka 1550 m 0 71175 for the provo shoreline 14 4 14 0 1 4 c ka 1450 m 0 71244 for the gilbert shoreline 10 3 10 9 1 4 c ka 1300 m and 0 71469 for the modern great salt lake 1280 m these analyses show that the 8 7 sr 8 6 sr ratio of lacustrine carbonates changes substantially at low to mid lake levels but is invariant at mid to high lake levels sr isotope mixing models of great salt lake and the bonneville paleolake system were constructed to explain these variations in 8 7 sr 8 6 sr ratios with change in lake level our model of the bonneville system produced a 8 7 sr 8 6 sr ratio of 0 71193 very close to the observed ratios from high shoreline tufa and shell the model verifies that the integration of the southern sevier and beaver rivers with the bear and others rivers in the north is responsible for the lower 8 7 sr 8 6 sr ratios in lake bonneville compared to the modern great salt lake we also modeled the 8 7 sr 8 6 sr ratio of lake bonneville with the upper bear river diverted into the snake river basin and obtained an 8 7 sr 8 6 sr ratio of 0 71414 coincidentally this ratio is close to the observed ratio for great salt lake of 0 71469 this means that 8 7 sr 8 6 sr ratios of 0 714 for carbonate can be produced by climatically induced low lake conditions or by diversion of the upper bear river out of the bonneville basin this model result also demonstrates that the upper bear river had to be flowing into the bonneville basin during highstands of other late quaternary lake cycles carbonates from the little valley 130 160 ka and cutler dam 59 5 ka lake cycles returned 8 7 sr 8 6 sr ratios of 0 71166 and 0 71207 respectively and are too low to be produced by a lake without the upper bear river input

holocene fire occurrence and alluvial responses at the leading edge of pinyon juniper migration in the northern great basin usa abstract fire and vegetation records at the city of rocks national reserve ciro south central idaho display the interaction of changing climate fire and vegetation along the migrating front of single leaf pinyon pinus monophylla and utah juniper juniperus osteosperma radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response and fossil woodrat neotoma middens revealed pinyon and juniper arrivals fire peaks occurred 10 700 9500 7200 6700 2400 2000 850 700 and 550 400 cal yr bp whereas 9500 7200 6700 4700 and 1500 1000 cal yr bp are fire free wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late holocene whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid holocene increased fires during the wetter and more variable late holocene suggest variable climate and adequate fuels augment fires at ciro utah juniper and single leaf pinyon colonized ciro by 3800 and 2800 cal yr bp respectively though pinyon did not expand broadly until 700 cal yr bp increased fire related deposition coincided with regional droughts and pinyon infilling 850 700 and 550 400 cal yr bp early and late holocene vegetation change probably played a major role in accelerated fire activity which may be sustained into the future due to pinyon juniper densification and cheatgrass invasion

viscoelastic damage modeling of sinkhole formation abstract the sinkholes along the dead sea coast are observed in two main sedimentary environments alluvial fan sinkholes which usually form abruptly as deep 20 m and narrow 3 m sinkholes and mud flat sinkholes which usually form as shallow a few centimeters and wide 5 m sinkholes and deepen later the mechanical collapse of all sinkholes is triggered by cavities created by the dissolution of an underlying salt layer by relatively fresh groundwater the processes attributed to the mechanical formation of the sinkholes are viscous flow and brittle fracture failure we use a two dimensional viscoelastic damage rheology numerical model to quantitatively explain the brittle and ductile aspects of collapsed sinkholes three cases of the rheology of the collapsed sediments are simulated 1 damage controlled failure 2 viscoelastic controlled failure and 3 an intermediate damage viscoelastic case results show that viscoelasticity cannot be the sole process acting on the deformed layer because all sinkholes are characterized by sharp boundaries the damage accumulation progresses until arched cavities are created in the soil layer because of the geometric heterogeneity of the layer represented by the heterogeneity of the mesh smaller blocks continue to fall after the first breakup into the cavity advancing the arched cavity upwards this propagation finally stops when the cavity is shallow enough to hold the irregular arch the combination of these two processes creates competition within the stress reduction mechanism that may lead to either magnified or reduced deformation the deformation is magnified in high shear stress locations where the dispersion of the viscous flow spreads damage failure and it is reduced in low shear stress locations where viscous flow disperses shear stress before the onset of damage

fault dissolution front relations and the dead sea sinkhole problem abstract there are two conflicting models of sinkhole development along the dead sea ds the first one considers structural control on sinkholes constraining them to tectonic lineaments this hypothesis is based on seismic reflection studies suggesting that sinkholes are the surface manifestations of active neotectonic faults that may serve as conduits for under saturated groundwater enabling its access across aquiclude layers another hypothesis based on results of multidisciplinary geophysical studies considers the salt edge dissolution front as the major site of sinkhole formation this hypothesis associates sinkholes with karstification of the salt edge by deep and shallow undersaturated groundwater our recent seismic reflection and surface wave studies suggest that salt formed along the active neotectonic faults sinkholes form in a narrow strip 60 100 m wide along a paleo shoreline constrained by faults and alluvial fans which determined the edge of the salt layer this scenario reconciles the two major competing frameworks for sinkhole formation

arc volcanic rocks characterize the landward slope of the philippine trench off northeastern mindanao five dredge hauls from the landward flanks 9300 3600 m of the philippine trench at 10 30 n northeast of mindanao recovered densely plagioclase clinopyroxene phyric basalt basaltic andesite and andesite with small amounts of diabase these rocks are all transitional from an arc tholeiitic to arc calcalkaline volcanic series and have low ni and cr 10 30 and 30 70 ppm respectively low tio2 0 7 1 2 and high incompatible element concentrations sr 260 530 ppm ba 170 410 ppm a single dredge on the offshore slope of the trench included aphyric tholeiitic basalt similar to n type ocean ridge basalts sampled from other locations in the west philippine basin tio2 1 0 1 2 ni 70 80 ppm cr 130 ppm ba 2 10 ppm sr 70 85 ppm the landward samples are distinct from the offshore samples and are identical in texture and composition to arc volcanic rocks from southeast and northeast mindanao the mindanao rocks are interpreted to be part of the samar east mindanao arc which collided with the central mindanao sangihe island arc in the late oligocene early miocene the volcanic rocks exposed on the landward slope of the philippine trench are apparently part of the eastern margin of the samar east mindanao arc after the collision the philippine trench was initiated immediately adjacent to the arc massif there is no evidence of any accretion of material from the subducted philippine sea crust the polarity of the samar east mindanao arc is unknown but there is no evidence of either a deformed volcanoclastic apron or an older forearc terrane along the trench such materials must have been limited in extent prior to collision have foundered and been subducted as the trench was initiated or have been faulted or rotated so that they are not locally exposed

gps measurements of current crustal movements along the dead sea fault 1 a network of 11 continuous gps stations was constructed in israel between 1996 and 2001 to monitor current crustal movements across the dead sea fault dsf analysis of the gps measurements with respect to the itrf2000 reference frame yields time series of daily site positions containing both secular and seasonal variations horizontal secular variations station velocities are evaluated with respect to the main tectonic element in the region the dsf we use six velocity vectors west of the dsf to define the itrf2000 pole of the sinai sub plate and rotate the velocity field for all stations into the sinai reference frame srf the velocity vectors reveal that 1 relative station movements are less than 4 mm yr 2 the nine stations located west of the dsf show no statistically significant motion with respect to the srf and 3 the two stations located in the golan heights katz and elro and a station in damascus syria udmc show 1 7 2 8 mm yr northward motion with respect to sinai indicating a left lateral motion along the dsf using locked fault models we estimate the current slip rate across the dsf as 3 3 0 4 mm yr if we exclude the northern sites elro and udmc which are located adjacent to the compressional jog of mount hermon our estimate increases to 3 7 0 4 mm yr the calculated itrf2000 sinai eurasia and nubia poles and a published pole for arabia allow us to calculate the current relative plate motion of sinai arabia and sinai nubia

pine nut use in the early holocene and beyond the danger cave archaeobotanical record abstract nuts of limber pine pinus flexilis from early holocene strata in danger cave utah are distinguishable by seed coat sculpturing from pine nuts of single needled pinyon pinus monophylla which occur in strata dating bp owls and other taphonomic agents may deposit pine nuts in archaeological sites but the morphology of the pine nuts in danger cave strongly indicate they were deposited by human foragers who brought small quantities with them for food for at least the last 7500 years large scale transport of pine nuts to danger cave from distant hinterlands is unlikely however the seamless transition from limber pine to pinyon pine nuts in the danger cave record suggests that foragers who had utilized limber pine as a food resource easily switched to using pinyon pine nuts when pinyon pine migrated into the region at the close of the early holocene

fish remains from homestead cave and lake levels of the past 13 000 years in the bonneville basin abstract a late quaternary ichthyofauna from homestead cave utah provides a new source of information on lake history in the bonneville basin the fish represented by 11 freshwater species were accumulated between 11 200 and 1000 14c yr b p by scavenging owls the 87sr 86sr ratio of lake bonneville varied with its elevation 87sr 86sr values of fish from the lowest stratum of the cave suggest they grew in a lake near the terminal pleistocene gilbert shoreline in the lowest deposits a decrease in fish size and an increase in species tolerant of higher salinities or temperatures suggest multiple die offs associated with declining lake levels an initial catastrophic post provo die off occurred at 11 300 11 200 14c yr b p and was followed by at least one rebound or recolonization of fish populations but fish were gone from lake bonneville sometime before 10 400 14c yr b p this evidence is inconsistent with previous inferences of a near desiccation of lake bonneville between 13 000 and 12 000 14c yr b p peaks in gila atraria frequencies in the upper strata suggest the great salt lake had highstands at 3400 and 1000 14c yr b p

petrology of mariana trough and lau basin basalts the crust of actively opening back arc basins has close chemical and mineralogic similarities to normal mid ocean ridge basalts n morb but some subtle but distinctive differences exist these are largely due to differences in volatiles fe oxidation ratio abundances of large ion lithophile elements lil and some high field strength hfs elements isotope data for sr pb nd he and o are variable but broadly are morb like we present data contrasting mariana trough mtb and lau basin basalts lbb showing how they differ in certain trace element and isotopic signatures and compare both to n morb relative to n morb and lbb the mtb are enriched in alkalis alkaline earths light rare earth elements ree h2o and fe fe even for primitive samples while having morb type he 3 4 7 8 to 8 4 ra sr 87 86 mean 0 70293 and nd e 10 2 the lau basin is zoned with a central area having n morb characteristics for h2o lil ree nd e 8 1 to 9 0 and o but a depletion in hfs elements sr is more radiogenic mean 87 86 0 70347 and 3he 4he 3 4 7 2 to 11 0 ra is high relative to n morb the lau basin has a zone bordering the adjacent island arcs which is like mtb in both back arc basins relatively primitive unfractionated basalts with mg 100 mg fe 62 are found which resemble postulated primitive n morb calculated parental magmas obtained by adding xenocrystic olivine plot near or on 3 and 4 phase boundaries at 1 1 5 gpa for the ol di si system low p fractional crystallization and magma mixing explain most of the observed rock types possible explanations for differences between mtb and lbb include differences in the extent of previous melting episodes of their mantle sources and effects of source metasomatism through dehydration and partial melting of subducted lithosphere the long and complex history of mariana trough mantle sources led to a metasomatized mantle which gives rise to the distinctive mtb in contrast the lau basin is dominated by basalts derived from a source depleted in volatiles lil and hfs elements a previous melting history is implied mixing with a mantle component enriched in 87sr and 3he may be due to mantle counterflow driven by the subduction process

evolution of a forearc basin luzon central valley philippines the cenozoic history of the 14 km thick luzon central valley sequence illustrates the development of a forearc basin forearc basins are important both as major sediment traps and as sites of hydrocarbon accumulations the luzon basin is floored by oceanic crust on the seaward western side and older accreted terranes on the arc eastern side initial sedimentation on this oceanic crust occurred during early tertiary northward translation and emplacement of the crust as an ophiolite along a strike slip or oblique slip zone the basal sediments consist of pelagic limestones and thin ash layers overlain by sandy turbidites derived from uplift and progressive dissection of the ophiolite a sequence of arc derived sediments at least 26 000 ft 8 km thick was shed into the astern arc side of the basin during late paleogene to quaternary convergence along the western margin of luzon by the middle miocene the central valley became a continuous elongate basin fringed by extensive shelf deposits along both the uplifted seaward and arc sides of the basin detritus shed from both flanks filled the subsiding basin and resulted in progressively shallower depths nonmarine deposition began in central portions of the basin in the pliocene and migrated with time both north and south along the basin axis late miocene to holocene movement along the philippine fault zone caused uplift and folding of adjacent parts of the basin exploration models for the central valley predict gas prone hydrocarbon generation in central portions of the basin at times that coincide with and postdate the formation of both structural and stratigraphic traps previous drilling in the basin has either been in areas with thermally immature source rocks or has failed to reach prospective intervals where thermal maturation is inferred the hydrocarbon potential of the central valley has not been determined adequately

age and paleoclimatic significance of the stansbury shoreline of lake bonneville northeastern great basin abstract the stansbury shoreline one of the conspicuous late pleistocene shorelines of lake bonneville consists of tufa cemented gravel and barrier beaches within a vertical zone of about 45 m the lower limit of which is 70 m above the modern average level of great salt lake stratigraphic evidence at a number of localities including new evidence from crater island on the west side of the great salt lake desert shows that the stansbury shoreline formed during the transgressive phase of late pleistocene lake bonneville sometime between about 22 000 and 20 000 yr b p tufa cemented gravel and barrier beaches were deposited in the stansbury shorezone during one or more fluctuations in water level with a maximum total amplitude of 45 m we refer to the fluctuations as the stansbury oscillation the stansbury oscillation cannot have been caused by basin hypsometric factors such as stabilization of lake level at an external overflow threshold or by expansion into an interior subbasin or by changes in drainage basin size therefore changes in climate must have caused the lake level to reverse its general rise to drop about 45 m in altitude reducing its surface area by about 18 5000 km2 and later to resume its rise if the sizes of great basin lakes are controlled by the mean position of storm tracks and the jetstream which as recently postulated may be controlled by the size of the continental ice sheets the stansbury oscillation may have been caused by a shift in the jetstream during a major interstade of the laurentide ice sheet

human induced geological hazards along the dead sea coast the dead sea is a terminal lake whose level is currently dropping at a rate of about 1 m per year due to the over exploitation of all its tributaries the lowering started about four decades ago but geological hazards appeared more and more frequently from the end of the 1980s the water level lowering is matched by a parallel groundwater level drop which results in an increasing intensity of underground and surface water flow the diagonal interface between the dead sea brine and the fresh groundwater is pushed downwards and seawards nowadays sinkholes subsidence landslides and reactivated salt karsts affect wide coastal segments until now mainly infrastructures were damaged and few people animals were injured but the ongoing development of tourism in this very attractive situation will increase the risk if precautionary measures are not included in the development plans this paper discusses the main observations made all around the dead sea and shed a light on the differences between the geological hazards of the western shore israel palestinian authority and the eastern shore jordan it is the first attempt to bring together an overview of the human induced geological hazards encountered along the dead sea coast

reinterpretation of the exposed record of the last two cycles of lake bonneville western united states a substantially modified history of the last two cycles of lake bonneville is proposed the bonneville lake cycle began prior to 26 000 yr b p the lake reached the bonneville shoreline about 16 000 yr b p poor dating control limits our knowledge of the timing of subsequent events lake level was maintained at the bonneville shoreline until about 15 000 yr b p or somewhat later when catastrophic downcutting of the outlet caused a rapid drop of 100 m the provo shoreline was formed as rates of isostatic uplift due to this unloading slowed by 13 000 yr b p the lake had fallen below the provo level and reached one close to that of great salt lake by 11 000 yr b p deposits of the little valley lake cycle are identified by their position below a marked unconformity and by amino acid ratios of their fossil gastropods the maximum level of the little valley lake was well below the bonneville shoreline based on degree of soil development and other evidence the little valley lake cycle may be equivalent in age to marine oxygenisotope stage 6 the proposed lake history has climatic implications for the region first because the fluctuations of lake bonneville and lake lahontan during the last cycle of each were apparently out of phase there may have been significant local differences in the timing and character of late pleistocene climate changes in the great basin second although the bonneville and little valley lake cycles were broadly synchronous with maximum episodes of glaciation environmental conditions necessary to generate large lakes did not exist during early wisconsin time

sinkhole hazards prediction at ghor al haditha dead sea jordan salt edge and tectonic models contribution a rebuttal to geophysical prediction and following development sinkholes in two dead sea areas israel and jordan by ezersky m g eppelbaum l v al zoubi a 3 keydar s abueladas a r akkawi e and medvedev b mikhail ezersky et al have published the article geophysical prediction and following development sinkholes in two dead sea areas israel and jordan february 2013 in which the paper salt karst and tectonics sinkholes development along tension cracks between parallel strike slip faults dead sea jordan published by closson d abou karaki n hallot f in 2009 earth surface processes and landforms 34 10 1408 1421 is questioned in this short paper we propose some clarifications and discuss the criticisms of these authors

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

shoreline tufa and tufaglomerate from pleistocene lake bonneville utah usa stable isotopic and mineralogical records of lake conditions processes and climate shoreline carbonate deposits of pleistocene lake bonneville record the conditions and processes within the lake including the evaporative balance as well as vertical and lateral chemical and isotopic gradients tufas swash zone and tufaglomerates cemented subaqueous colluvium or beachrock on multiple well developed shorelines near the silver island range utah also present an opportunity to examine physicochemical lake processes through time three shorelines are represented by carbonate deposits including the 23 20 ka stansbury stage 15 14 5 ka bonneville stage and 14 5 14 ka provo stage mean 18ovsmow values of all three shorelines are statistically indistinguishable 27 1 when a few bonneville samples of unusual composition are neglected however differences in primary carbonate mineralogy indicate that the correspondence is an artefact of the different fractionation factors between calcite or aragonite and water second in order to sustain a much smaller shallower lake during the colder stansbury stage the climate must have also been relatively dry third 18o values in tufa are higher than tufaglomerate by 0 5 consistent with greater evaporative enrichment of lake water in the swash zone fourth mean 13c values for the provo stansbury and bonneville shorelines 4 4 5 0 and 5 2 respectively show that carbon species were dominated by atmospheric exchange with the variations produced by differences in the oxidation of organic matter comparisons of shoreline carbonates with deep lake marls of the same approximate age indicate that shoreline carbonate was much higher in 13c and 18o values both 2 5 during bonneville time whereas isotopic differences were minor both 1 in stansbury time in particular the bonneville stage may have sustained large vertical or lateral isotopic gradients due to evaporative enrichment effects on 18o values in contrast the lake during the much shallower stansbury stage may have been well mixed differences in the primary mineralogy stansbury and bonneville aragonite calcite provo calcite aragonite reflect profound differences in lake chemistry in terms of open versus closed basin lakes the establishment of a continuous outlet during provo time probably reduced the mg2 ca2 ratio of lake water curiously regardless of primary mineralogy tufaglomerate cements are enriched in na and cl and depleted in mg2 relative to capping tufa of the same age this probably reflects vital or kinetic effects in the swash zone tufa we suspect that abiotic effects may have been important in the dark pore space of developing tufaglomerate where the absence of light suppressed photosynthesis copyright 2005 john wiley sons ltd

a holocene pollen record of persistent droughts from pyramid lake nevada usa pollen and algae microfossils preserved in sediments from pyramid lake nevada provide evidence for periods of persistent drought during the holocene age we analyzed one hundred nineteen 1 cm thick samples for pollen and algae from a set of cores that span the past 7630 years the early middle holocene 7600 to 6300 cal yr b p was found to be the driest period although it included one short but intense wet phase we suggest that lake tahoe was below its rim for most of this period greatly reducing the volume and depth of pyramid lake middle holocene aridity eased between 5000 and 3500 cal yr b p and climate became variable with distinct wet and dry phases lake tahoe probably spilled intermittently during this time no core was recovered that represented the period between 3500 and 2600 cal yr b p the past 2500 years appear to have had recurrent persistent droughts the timing and magnitude of droughts identified in the pollen record compares favorably with previously published y 18 o data from pyramid lake the timing of these droughts also agrees with the ages of submerged rooted stumps in the eastern sierra nevada and woodrat midden data from central nevada prolonged drought episodes appear to correspond with the timing of ice drift minima solar maxima identified from north atlantic marine sediments suggesting that changes in solar irradiance may be a possible mechanism influencing century scale drought in the western great basin d 2004 university of washington all rights reserved

accelerator mass spectrometer ams radiocarbon dating of pleistocene lake sediments in the great basin abstract pleistocene lake sediments in the great basin typically contain little organic carbon and thus are difficult to date reliably by conventional radioccarbon methods paleoenvironmental data are abundant in these sediments but are of limited value without adequate age controls with the advent of accelerator mass spectrometer ams radiocarbon dating it is now possible to date these paleolacustrine sediments ams dates were obtained on sediment cores from the bonneville franklin and lahontan basins in the bonneville basin the ams based chronology compares well with other chronologies constructed from dated shore zone features in the bonneville and franklin basins ams dates delimit unconformities not apparent by other means we found that dispersed organic carbon from sediments deposited during relatively freshwater intervals provided apparently reliable ams radiocarbon dates carbonate microfossils from the lahontan basin also produced results that appear reasonable while bulk carbonate yielded erroneous results

late wisconsin early holocene vegetation in the bonneville basin abstract woodrat middens from the northern bonneville basin allow a reconstruction of vegetation changes from 14 000 to 9000 yr ago cold montane steppe dominated by sagebrush covered much of the western bonneville basin prior to 13 000 yr ago from 13 000 10 800 yr ago the region was vegetated by limber pine woodlands in lower montane settings and a mosaic of limber pine and sagebrush steppe along basin flour margins these low elevation limber pine woodlands began to retreat upslope after about 11 000 yr ago due to increasingly drier climatic conditions and were replaced by relatively more xeric desert scrub dominated by sagebrush and shadscale the growth of limber pine at low elevations suggests that summer temperatures were as much as 6 c lower than at present this evidence is in apparent conflict with the currently accepted post provo lake bonneville chronology especially the magnitude of the postulated near dessication of lake bonneville from ca 13 000 12 200 yr ago

a 13 000 year paleolimnological record from the uinta mountains utah inferred from diatoms and loss on ignition analysis paleolimnological research in mountainous regions of the western united states provide baseline understanding of how these lake systems will respond to ongoing climate change fossil diatom assemblage and loss on ignition data were investigated from a 13 000 year lake sediment core from the uinta mountains northeastern utah usa results indicate the presence of three major zones of environmental change 1 from 12 9 10 9 cal ka modern lake formation began temperatures were cool and water was turbid 2 from 10 9 3 5 cal ka conditions were warmer than present and the lake stratified during the summer and 3 beginning approximately 3 5 cal ka temperatures decreased relative to the previous zone and the lake appears to have become increasingly alkaline shifts in diatom taxa relative abundances within the middle zone ca 8 2 6 5 and 5 0 3 5 cal ka are probably caused by precipitation driven decreases in alkalinity and increases in lake depth this record reflects evolution of the lake system and suggests that currently rising temperatures will reduce ice cover and enhance lake stratification and internal nutrient cycling any future changes in precipitation patterns may also impact lake ecology through shifts in alkalinity and or depth

enhanced development of lacustrine microbialites on gravity flow deposits great salt lake utah usa the great salt lake utah usa is a shallow hypersaline intracontinental lake hosting extensive microbial deposits at a large spatial scale the distribution of these deposits is driven by environmental and geodynamical factors i e water level fluctuations and a fault related framework a detailed mapping of the buffalo point area in the north western part of antelope island indicates the presence of an anomalous concentration of microbial deposits dated ca 5 8 ka bp and distributed along a lobe shaped geometry this uncommon microbial deposit geometry results from an extensive colonization of a conglomerate substrate exhibiting an accumulation of m sized rounded cambrian quartzite boulders we suggest that this conglomerate substrate provides a stable nucleation point that promotes the development and preservation of the lobe shaped microbial deposits microbial deposits may also have protected the conglomerate substrate from erosional processes and thereby increased the preservation potential of the lobe shaped structure based on the characteristics of the conglomerate e g grain size texture and its location i e 200 m beyond the average shoreline this lobe shaped structure likely results from subaqueous debris or a hyperconcentrated density flow that transports sedimentary material from the buffalo point slopes downward to the shore we estimate the age of the conglomerate deposition to be between 21 and 12 ka bp the initiation of the flow may have been triggered by various mechanisms but the existence of a major active normal fault in the vicinity of these deposits suggests that an earthquake could have destabilized the accumulated sediments and resulted in conglomerate emplacement the catastrophic 15 ka bp bonneville flood which led to a drop in the lake level approximately 110 m may also provide an explanation for the initiation of the flow

locating water filled karst caverns and estimating their volume using magnetic resonance soundings magnetic resonance sounding mrs is a geophysical technique developed for groundwater exploration this technique can be used for investigating karst aquifers generally the study ofakarstrequiresa3dfieldsetupandcorrespondingmultichannel data acquisition instruments now only single channel mrs equipment is available i e the time needed for a 3d mrs field survey is multiplied by a factor of four or five where karst caverns are natural hazards as in the dead sea coastal area at nahal hever israel even an approximate localization of potentially dangerous zones and a corresponding estimation of the hazard dimensions are useful we studied numerically the accuracy of mrs estimations of the volume of different 3d targets around nahalhever shiftinga3dtargetinsidethemrsloopandcalculating the volume estimation errors for each target position the calculations covered targets of different sizes the size and position of a target being unknown factors in a field survey the numerical data were considered as random values to be analyzed statistically using a 1d approximation of the mrs solution and assuming a 100 100 m 2 mrs loop the volume of a 3d target under nahal hever conditions is estimated within a 75 error when the target is smaller than the mrs loop and within a 50 error when the target size is about the same as the mrs loop the lower threshold of karst cavity detection with mrs is about 6500 m3 for such estimation only one sounding is

a multi proxy paleolimnological reconstruction of holocene climate conditions in the great basin united states article i nfo article history received 11 february 2009 available online 14 august 2009 a sediment core spanning 7000 cal yr bp recovered from stella lake a small sub alpine lake located in great basin national park nevada was analyzed for subfossil chironomids non biting midges diatoms and organic content estimated by loss on ignition loi subfossil chironomid analysis indicates that stella lake was characterized by a warm middle holocene followed by a cool neoglacial period with the last two millennia characterized by a return to warmer conditions throughout the majority of the core the stella lake diatom community composition is dominated by small periphytic taxa which are suggestive of shallow cool alkaline oligotrophic waters with extensive seasonal ice cover a reconstruction of mean july air temperature mjat was developed by applying a midge based inference model for mjat two component wa pls consisting of 79 lakes and 54 midge taxa rjack 2 0 55 rmsep 0 9 c comparison of the chironomid inferred temperature record to existing regional paleoclimate reconstructions suggests that the midge inferred temperatures correspond well to regional patterns this multi proxy record provides valuable insight into regional holocene climate and environmental conditions by providing a quantitative reconstruction of peak holocene warmth and aquatic ecosystem response to these changes in the great basin a region projected to experience increased aridity and higher temperatures

quaternary palaeolakes in the evolution of semidesert basins with special emphasis on lake bonneville and the great basin u s a abstract this paper reviews attributes of quaternary lakes and lake basins which are often important in the environmental prehistory of semideserts basin floor and basin closure morphometry have set limits on palaeolake sizes lake morphometry and basin drainage patterns have influenced lacustrine processes and water and sediment loads have influenced basin neotectonics information regarding inundated runoff producing and extra basin spatial domains is acquired directly from the palaeolake record including the littoral morphostratigraphic record and indirectly by reconstruction increasingly detailed hypotheses regarding lake bonneville the largest late pleistocene palaeolake in the great basin are subjects for further testing and refinement oscillating transgression of lake bonneville began about 28 ka the highest stage occurred about 15 ka and termination occurred abruptly about 13 ka a final resurgence of perennial lakes probably occurred in many subbasins of the great basin between 11 and 10 ka when the highest stage of great salt lake successor to lake bonneville developed the gilbert shoreline and when the russell shoreline formed 500 600 km away in the carson desert of the lake lahontan basin the highest post gilbert stage of great salt lake which has been one of the few permanent lakes in the great basin during holocene time probably occurred between 3 and 2 ka a set of eighteen general observations regarding geologic aspects of the palaeolake record in semidesert basins is helping to guide quaternary studies in the great basin

geophysical prediction and following development sinkholes in two dead sea areas israel and jordan geophysical methods seismic refraction srfr electrical resistivity tomography ert and microgravity were applied to the dead sea ds sinkhole problem in the ein gedi area at the earlier stage of the sinkhole development 1998 2002 they allowed determining the sinkhole formation mechanism and localizing the sinkhole hazardous zones the srfr method permitted to delineate the underground edge of a salt layer at the depth of 50 m the salt edge was shaped like the sinkhole line on the surface it was concluded that the sinkhole development is linked to the salt edge geoelectrical quasi 3d mapping based on the ert technique detected large resistivity anomalies with 250 300 m2 diameter and 25 35 m deep the ein gedi area has been also mapped by the use of microgravity method the residual bouguer gravity anomaly map shows negative anomalies arranged along the edge of the salt layer those gravity anomalies overall are very similar in plan to the resistivity distribution in this area the results of forward modeling indicate that both high resistivity and residual gravity anomalies are associated with a subsurface decompaction of the soil mass and deep cavity at the sinkhole site following monitoring of the sinkhole development carried out by the geological survey of israel confirmed our suggestions the drilling of numerous boreholes verified the location of the salt edge geographical information system gis database testifies that during 2003 2009 new sinkholes are continuing to develop along the salt edge within a narrow 50 100 m wide strip oriented approximately in north south direction slightly parallel to the shoreline no promotion in west east direction perpendicularly to the ds shoreline was observed in israel collapse of sinkholes and their clustering have been occurred within the area of high resistivity anomaly and negative residual gravity anomaly similar studies carried out at the ghor al haditha area jordan have shown that sinkholes there are also arranged along the winding line conforming to the salt edge in this area sinkholes are slowly moved to the dead sea direction results of geophysical studies in numerous ds sites indicate similar sinkhole development it allowed generating of the sinkhole formation model based on ancient 10 000 11 000 year old salt belt girding the dead sea along its shores

lake size variations in the lahontan and bonneville basins between 13 000 and 9000 14c yr b p abstract recessions of lakes lahontan and bonneville that commenced 13 500 14 c yr b p were interrupted at 11 500 14 c yr b p in the lahontan basin and 12 200 14 c yr b p in the bonneville basin by relatively large perturbations in lake level that persisted for 2000 years minor glacial readvances in the sierra nevada and white mountains of california nevada occurred during the latter half of this interval between 11 000 and 9700 14 c yr b p the hydrologic response of lakes lahontan and bonneville and the mountain glacial advances were concurrent with the allerod younger dryas climatic intervals recorded in vegetational and glacial records of western and central europe

distribution and origin of igneous rocks from the landward slopes of the mariana trench implications for its structure and evolution the landward slope of the mariana trench is composed largely of igneous rocks serpentinites and serpentinized ultramafic rocks occur at nearly all structural levels on the slope from depths of 8000 to 1200 m seamountlike features on the trench slope break are the surface expression of serpentinite diapirs cumulate and massive gabbros are found several varieties of volcanic rocks are common including boninites altered and metamorphosed basalts andesites and dacites the chemical characteristics of the volcanic rocks indicate that nearly all are products of island arc volcanism together with the gabbros these volcanic rocks represent what is probably a late eocene arc complex these rocks were probably the first volcanic products to result from the subduction of the pacific plate beneath the phillippine sea plate their exposure on the trench slope today implies a significant amount of tectonic erosion of the landward slope since eocene time most of this removal of material appears to have occurred during the early stages of subduction there are isolated occurrences on the landward slope of rock assemblages including alkalic basalts chert hyaloclastites upper cretaceous siliceous sediments and shallow water limestones these assemblages are very similar to rocks dredged from seamounts on the offshore flankmore of the trench and their presence on the landward slope suggests that since the cessation of vigorous tectonic erosion there has been episodic accretion of seamount fragments to the landward slope less

oligo miocene lacustrine microbial and metazoan buildups from the limagne basin french massif central the limagne basin french massif central is an extensive continental lacustrine system accommodating microbial and metazoan buildups from chattian to aquitanian age a description of these buildups and their associated biotic components in grand gandaillat and crechy quarries provides insights into their spatio temporal distribution patterns flats cauliflowers domes cones and coalescent columnar morphologies have been identified with a main laminated mesofabric and laminated columnar filamentous and caddisfly coated microfabrics two low gradient margin models emerged based on the changes in the distribution morphology and size of the microbial and metazoan rich deposits through time the first model applies to the chattian deposits in the grand gandaillat quarry and the second to the aquitanian deposits in the crechy quarry this study emphasizes the heterogeneity of marginal lacustrine carbonate siliciclastic cycles the lacustrine palustrine cycles of the limagne basin record i lacustrine deposits composed of microbial and metazoan buildups and organic matter rich marls indicating periods of high accommodation and ii palustrine deposits composed of mudstone and clayey paleosoils indicative of periods of low accommodation the cycles differ with thin and symmetrical deposits that dominate the chattian cycles whereas thicker and asymmetrical deposits mark the aquitanian cycles in addition the chattian buildups are exclusively microbial and only a few centimeters thick whereas the aquitanian ones are multiple meters in height and are composed of both microbes and metazoans climatic tectonism volcanic and local parameters are involved in the deposition of buildups and their organization in each different cycle climate may control the long term arid humid sedimentary succession tectonic may explain the difference in the deposit thickness between two cycles of different ages and localizations as well as the specific distribution of the buildups throughout the basin volcanism may control the chemical lacustrine conditions and local physiography may impact the soil removal ability of the lake margin

late holocene relationships among fire climate and vegetation in a forest sagebrush ecotone of southwestern idaho usa the forest sagebrush ecotone is characterized by a more arid climate than forested regions therefore establishing fire histories using traditional methods e g fire scars from trees charcoal in lake sediments is problematic this study uses radiocarbon dating of charcoal preserved in alluvial deposits to reconstruct a record of fire and geomorphic response in southwestern idaho samples indicate three primary periods of fire related activity 4400 4000 2000 1400 and 650 400 cal yr bp charcoal macrofossil identification and comparison with other regional records indicate this area has likely alternated between a fuel limited system fires limited by lack of fuels and a moisture limited system fires limited by too much moisture with changes in holocene climate over the past 2000 yr samples from this site indicate most fires occurred during wetter times than the record average during overall wetter periods e g little ice age lia 600 100 cal yr bp tree density may have increased

paleodischarge of the late pleistocene bonneville flood snake river idaho computed from new evidence the bonneville flood resulted from catastrophic outflow from pleistocene lake bonneville about 15 000 yr ago when the lake overtopped its rim at red rock pass in southeastern idaho and discharged a vast volume of water down the snake river this paper provides revised estimates of the paleodischarge volume and duration of the bonneville flood based on new evidence of its height and on current understanding of the amount of lowering of lake bonneville evidence for the revised height of the flood is derived from the altitude of erosional features and flood deposits at the head of a constricted reach of the snake river canyon at the mouth of sinker creek and from the altitudes of flood deposits at several places about 53 km upstream using the step backwater method we estimate that peak discharge for the bonneville flood through the constricted reach was from 793 000 to 1 020 000 m 3 s and most likely was 935 000 m 3 s this discharge is 2 2 times the discharge previously reported and is the second largest flood known to have occurred in the world at this rate of discharge the shear stress for the flood would have been 2 500 n m 2 and the unit stream power would have been 75 000 n m s as compared with values of 6 to 10 n m 2 and 12 n m s for recent floods on the mississippi and the amazon other recent studies of the history of lake bonneville show that the volume of water released was 4 700 km 3 or about 3 times greater than the volume previously inferred although this volume indicates a flood duration of 8 weeks at constant peak discharge an accurate estimate of the duration would require dam break modeling at red rock pass from a dam break model flood hydrographs at red rock pass and the hydraulics of the flood wave along the snake river could be computed

origin and evolution of the west philippine basin a new interpretation abstract combined analyses of the magnetic lineations and seafloor structures of the west philippine basin show that it was formed by spreading from the central basin spreading center in two distinctly different spreading phases before and after subduction was initiated along the palau kyushu trend at 45 ma b p these episodes are recognized by differences in the strike of the magnetic lineations spreading rates density and strike of fracture zones and basement relief from 60 45 ma b p spreading was ne sw relative to present orientations at a half rate of 44 mm a at about 45 ma b p the spreading direction changed to a more n s direction with a reconfiguration of the central basin spreading center into numerous short e w segments offset by closely spaced n s transform faults spreading slowed to a half rate of 18 mm a and ceased at 35 ma b p thus the west philippine basin originated at 45 ma b p by the trapping of normal ocean crust west of the initial subduction along the palau kyushu trend the 45 35 ma b p period represents the dying phase of spreading on the central basin spreading center following isolation of the west philippine basin from the plate driving forces of the pacific

late quaternary environments in ruby valley nevada abstract palynological data from sediment cores from the ruby marshes provide a record of environmental and climatic changes over the last 40 000 yr the modern marsh waters are fresh but no deeper than 3 m a shallow saline lake occupied this basin during the middle wisconsin followed by fresh and perhaps deep waters by 18 000 to 15 000 yr b p no sediments were recovered for the period between 15 000 and 11 000 yr b p possibly due to lake desiccation by 10 800 yr b p a fresh water lake was again present and deeper than modern conditions lasted until 6800 yr b p the middle holocene was characterized by very shallow water and perhaps complete desiccation the marsh system deepened after 4700 yr b p and fresh water conditions persisted until modern times vegetation changes in ruby valley were more gradual than those seen in the paleolimno logical record sagebrush steppe was more widespread than at present through the late pleistocene and early holocene giving way somewhat to expanded shadscale vegetation between 8500 and 6800 yr b p shadscale steppe contracted by 4000 yr b p but had greater than modern coverage until 1000 to 500 yr ago pinyon juniper woodland was established in the southern ruby mountains by 4700 yr b p

differential insect and mammalian response to late quaternary climate change in the rocky mountain region of north america abstract of the 200 beetle species identified from rocky mountain late pleistocene insect faunal assemblages 23 are no longer resident in this region none of the 200 species is extinct in contrast to this only 8 of 73 identified mammal species from rocky mountain late pleistocene assemblages are no longer resident in the rockies and 12 species are now extinct since both groups of organisms are highly mobile it would appear that their responses to the large scale fluctuations of climate associated with the last 125 000 years have been considerably different most strikingly contrasting with the insects there are no mammals in the rocky mountain late pleistocene fossil record that are found exclusively today in the pacific northwest pnw region the pnw does have a distinctive modern mammalian fauna but only one of these keen s myotis has a fossil record outside the pnw region in the eastern and central united states no modern pnw vertebrate species have been found in any rocky mountain fossil assemblages based on these data it appears that there has been little or no mammalian faunal exchange between the pnw region and the rocky mountains during the late pleistocene or holocene this is in stark contrast to the fossil beetle record where pnw species are a substantial component in many faunas right through to the late holocene

problems with identifying the 8200 year cold event in terrestrial records of the atlantic seaboard a case study from dooagh achill island ireland the northern hemisphere cooling event 8200 years ago is believed to represent the last known major freshwater pulse into the north atlantic as a result of the final collapse of the north american laurentide ice sheet this pulse of water is generally believed to have occurred indepen dently of orbital variations and provides an analogue for predicted increases in high latitude preci pitation and ice melt as a result of anthropogenically driven future climate change the precise timing duration and magnitude of this event however are uncertain with suggestions that the 100 yr melt water cooling formed part of a longer term cold period in the early holocene here we undertook a multiproxy high resolution investigation of a peat sequence at dooagh achill island on the west coast of ireland to determine whether the 8200 year cold event impacted upon the terrestrial vege tation immediately downwind of the proposed changes in the north atlantic we find clear evidence for an oscillation in the early holocene using various measures of pollen indicating a disruption in the vegetation leading to a grassland dominated landscape most probably driven by changes in precipitation rather than temperature radiocarbon dating was extremely problematic however with bulk peat samples systematically too young for the north atlantic event suggesting significant contamination from downward root penetration the sustained disruption to vegetation over hundreds of years at dooagh indicates the landscape was impacted by a long term cooling event in the early holocene and not the single century length 8200 year meltwater event proposed in many other records in the north atlantic region copyright 2006 john wiley sons ltd

geodynamic setting of izu bonin mariana boninites the izu bonin mariana ibm forearc is characterized by the occurrence of boninite like lavas the study of the cenozoic setting of the genesis of these boninitic lavas in light of modern geodynamic contexts in the tonga and fiji regions lead us to define three tectonic settings that favour the formation of boninites in back arc basins in addition to previous settings that involve the presence of a mantle plume 1 propagation at low angle between a spreading centre and the associated volcanic arc 2 intersection at a high angle of an active spreading centre and a transform fault at the termination of an active volcanic arc and 3 intersection at a right angle between an active spreading centre and a newly created subduction zone a geodynamic model of the philippine sea plate shows that boninites in the bonin islands are related to the second mechanism mentioned above whereas mariana forearc boninites are relevant to the third mechanism in the early eocene the transform plate boundary bounding the eastern margin of the philippine sea plate at the location of the present day mariana arc evolved into a subduction zone that trends perpendicular to the active spreading centre of the west philippine basin some where around 43 47 ma the presence of a mantle plume in the vicinity of the subduction zone bounding the northern ibm arc explains boninites that erupted in its northern part but only in early eocene time

response of bushy tailed woodrats neotoma cinerea to late quaternary climatic change in the colorado plateau abstract temperature profoundly influences the physiology and life history characteristics of organisms particularly in terms of body size because so many critical parameters scale with body mass long term temperature fluctuations can have dramatic impacts we examined the response of a small mammalian herbivore the bushy tailed woodrat neotoma cinerea to temperature change from 20 000 yr b p to present at five sites within the colorado plateau our investigations focused on the relationship between temperature plant composition and abundance and woodrat size body size was estimated by measuring fossil fecal pellets a technique validated in earlier work we found significant and highly covariable patterns in body mass over the five locations suggesting that responses to temperature fluctuations during the late quaternary have been very similar although woodrat mass and the occurrence of several plant species in the fossil record were significantly correlated in virtually all instances changes in woodrat size preceded changes in vegetational composition these results may be due to the greater sensitivity of woodrats to temperature or to the shorter generation times of woodrats as compared to most plants an alternative hypothesis is that winter temperatures increased before summer ones woodrats are highly sensitive to warmer winters whereas little response would be expected from forest woodland plants growing at their lower limits our work suggests that woodrat size is a precise paleothermometer yielding information about temperature variation over relatively short term temporal and regional scales

great salt lake and precursors utah the last 30 000 years sediment cores up to 6 5 m in length from the south arm of great salt lake utah have been correlated radiocarbon ages and volcanic tephra layers indicate a record of greater than 30 000 years a variety of approaches have been employed to collect data used in stratigraphic correlation and lake elevation interpretation these include acoustic stratigraphy sedimentologic analyses mineralogy geochemistry major element c o and s isotopes and organics paleontology and pollen the results indicate that prior to 32 000 year b p an ephemeral saline lake playa system was present in the basin the perennial lake which has occupied the basin since this time rose in a series of three major steps the freshest water conditions and presumably highest altitude was reached at about 17 000 year b p the lake remained fresh for a brief period followed by a rapid increase in salinity and sharp lowering in elevation to levels below that of the present great salt lake the lake remained at low elevations and divided at times into a north and south basin until about 8 000 year b p since that time with the exception of two short rises to about 1290 m the lake level has remained near the present elevation of 1280 m

experimental study of caldera formation scaled experiments have been carried out on caldera collapse mechanisms using silicone as analogue magma and dry sand as analogue rock experiments were carried out in two and three dimensions using a range of roof aspect ratios thickness width 0 2 to 4 5 appropriate for caldera collapse they reveal a general mechanism of collapse only weakly dependent on the shape of the reservoir for low roof aspect ratios 1 subsidence starts by flexure of the roof and the formation of outward dipping reverse ring faults which in turn trigger formation of peripheral inward dipping normal ring faults the subsidence always occurs asymmetrically in cross section the reverse faults delimit a coherent piston bounded on each side by an annular zone of inwardly tilted strata located between the reverse and normal ring fault sets the surface depression consists of a nondeformed area piston surrounded by an annular extensional zone tilted strata for high aspect ratios 1 multiple reverse faults break up the roof into large pieces and subsidence occurred as a series of nested wedges 2 d or cones 3 d the extensional zone dominates the surface depression in the case where preexisting regional faults do not play a major role the collapse mechanics of calderas probably depends strongly on the roof aspect ratio calderas with low roof aspect ratios are predicted to collapse as coherent pistons along reverse faults the annular extensional zone might be the source of the large landslides that generate intracaldera megabreccias collapse into magma reservoirs with high roof aspect ratios may be the origin of some funnel calderas where explosive reaming is not dominant

near infrared spectroscopy of lacustrine sediments in the great salt lake desert an analog study for martian paleolake basins the identification and characterization of aqueous minerals within ancient lacustrine environments on mars are a high priority for determining the past habitability of the red planet terrestrial analog studies are useful both for understanding the mineralogy of lacustrine sediments how the mineralogy varies with location in a lacustrine environment and for validating the use of certain techniques such as visible near infrared vnir spectroscopy in this study sediments from the pilot valley paleolake basin of the great salt lake desert were characterized using vnir as an analog for martian paleolake basins the spectra and subsequent interpretations were then compared to mineralogical characterization by ground truth methods including x ray diffraction automated scanning electron microscopy and several geochemical analysis techniques in general there is good agreement between vnir and ground truth methods on the major classes of minerals present in the lake sediments and vnir spectra can also easily discriminate between clay dominated and salt dominated lacustrine terrains within the paleolake basin however detection of more detailed mineralogy is difficult with vnir spectra alone as some minerals can dominate the spectra even at very low abundances at this site the vnir spectra are dominated by absorption bands that are most consistent with gypsum and smectites though the ground truth methods reveal more diverse mineral assemblages that include a variety of sulfates primary and secondary phyllosilicates carbonates and chlorides this study provides insight into the limitations regarding the use of vnir in characterizing complex mineral assemblages inherent in lacustrine settings

late quaternary environments and biogeography in the great basin abstract plant and animal remains found in packrat neotoma spp middens and cave fill from the eastern and southern great basin region reveal the presence of subalpine conifers and boreal mammals at relatively low elevations during the late wisconsin limber pine pinus flexilis and bristlecone pine p longaeva were important in the late pleistocene plant communities throughout this region spruce picea cf engelmannii and common juniper juniperus communis were present in some of the more northerly localities and douglas fir pseudotsuga menziesii and white fir abies concolor were present in southern and eastern localities single needle pinyon pine pinus monophylla common across this region today was apparently not present north of the sheep range of southern nevada during the late wisconsin pikas ochotona cf princeps small boreal mammals present in only a few great basin mountain ranges today were common throughout the region heather voles phenacomys cf intermedius have been found in two cave fill deposits in nevada though they are unknown in the great basin today limber and bristlecone pines are generally restricted to rocky substrates in modern subalpine habitats in the great basin and this may also have been the case when these plants grew at lower elevations during the late wisconsin subalpine conifers were present on the rock outcrops sampled by the packrat middens but shrub communities perhaps dominated by sagebrush artemisia spp may have been present on alluvial valley bottom substrates forested habitats would thus have been isolated habitat islands as they are today boreal small mammals including pikas and heather voles were able to colonize the great basin mountain ranges during the late pleistocene we suggest that these mammals were able to survive in the intervening valley bottoms under a cool summer climatic regime and that continuous forest or woodland corridors were not necessary for migration

small mammal data on early and middle holocene climates and biotic communities in the bonneville basin usa abstract archaeological investigations in camels back cave western utah recovered a series of small mammal bone assemblages from stratified deposits dating between ca 12 000 and 500 14c yr b p the cave s early holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and or sagebrush e g lepus townsendii marmota flaviventris reithrodontomys megalotis and brachylagus idahoensis which suggest that the region was relatively cool and moist until after 8800 14c yr b p between ca 8600 and 8100 14c yr b p these mammals became locally extinct taxonomic diversity declined and there was an increase in species well adapted to xeric low elevation habitats including ground squirrels lepus californicus and neotoma lepida the early small mammal record from camels back cave is similar to the 11 300 6000 14c yr b p mammalian sequence from homestead cave northwestern utah and provides corroborative data on bonneville basin paleoenvironments and mammalian responses to middle holocene desertification

the late holocene dry period multiproxy evidence for an extended drought between 2800 and 1850 cal yr bp across the central great basin usa abstract evidence of a multi centennial scale dry period between 2800 and 1850 cal yr bp is documented by pollen mollusks diatoms and sediment in spring sediments from stonehouse meadow in spring valley eastern central nevada u s we refer to this period as the late holocene dry period based on sediment recovered stonehouse meadow was either absent or severely restricted in size at 8000 cal yr bp beginning 7500 cal yr bp the meadow became established and persisted to 3000 cal yr bp when it began to dry comparison of the timing of this late holocene drought record to multiple records extending from the eastern sierra nevada across the central great basin to the great salt lake support the interpretation that this dry period was regional the beginning and ending dates vary among sites but all sites record multiple centuries of dry climate between 2500 and 1900 cal yr bp this duration makes it the longest persistent dry period within the late holocene in contrast sites in the northern great basin record either no clear evidence of drought or have wetter than average climate during this period suggesting that the northern boundary between wet and dry climates may have been between about 40 and 42 n latitude this dry in the southwest and wet in the northwest precipitation pattern across the great basin is supported by large scale spatial climate pattern hypotheses involving enso pdo amo and the position of the aleutian low and north pacific high particularly during winter

the younger dryas phase of great salt lake utah usa abstract field investigations at the public shooting grounds a wildlife management area on the northeastern shore of great salt lake and radiocarbon dating show that the great salt lake rose to the gilbert shoreline sometime between 12 9 and 11 2 cal ka we interpret a ripple laminated sand unit exposed at the public shooting grounds and dated to this time interval as the nearshore sediments of great salt lake deposited during the formation of the gilbert shoreline the ripple laminated sand is overlain by channel fill deposits that overlap in age 11 9 11 2 cal ka with the sand and by wetland deposits 11 1 to 10 5 cal ka consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments including those of emergent aquatic plants but mollusk shells from spring and marsh deposits yielded anomalously old ages probably because of a variable radiocarbon reservoir effect the bonneville basin was effectively wet during at least part of the younger dryas global cooling interval however conflicting results from some great basin locations and proxy records indicate that the regional effects of younger dryas cooling are still not well understood

climatic and hydrologic oscillations in the owens lake basin and adjacent sierra nevada california oxygen isotope and total inorganic carbon values of cored sediments from the owens lake basin california indicate that owens lake overflowed most of the time between 52 500 and 12 500 carbon 14 14 c years before present b p owens lake desiccated during or after heinrich event h1 and was hydrologically closed during heinrich event h2 the magnetic susceptibility and organic carbon content of cored sediments indicate that about 19 sierra nevada glaciations occurred between 52 500 and 23 500 14 c years b p most of the glacial advances were accompanied by decreases in the amount of discharge reaching owens lake comparison of the timing of glaciation with the lithic record of north atlantic core v23 81 indicates that the number of mountain glacial cycles and the number of north atlantic lithic events were about equal between 39 000 and 23 500 14 c years b p

comments to publication of d closson and n abu karaki sinkhole hazards prediction at ghor al haditha dead sea jordan salt edge and tectonic models contribution a rebuttal to geophysical prediction and following development sinkholes in two dead sea areas israel and jordan by ezersky m g eppelbaum l v al zoubi a keydar s abueladas a r akkawi e and medvedev b

late pleistocene to early holocene lake level and paleoclimate insights from stansbury island bonneville basin utah abstract this paper reports on recent multiproxy research conducted to determine the chronology of lake level fluctuations recorded in sediments from a natural exposure at a classic bonneville basin site grain size carbonate percentage magnetic susceptibility amount of charcoal and diatom community composition data were collected from the 16 lacustrine units that compose the 122 cm stratigraphic column in stansbury gulch trends observed in the measured proxies reveal several significant changes in lake level and thereby effective moisture over the approximately 14 500 yr time span represented by the sediments results 1 verify the effectiveness of the multiproxy approach in bonneville basin studies which has been underutilized in this region 2 reaffirm the double nature of lake bonneville s stansbury oscillation 3 suggest a previously undocumented post gilbert highstand of great salt lake and 4 identify possible teleconnections between climate events in the bonneville basin and events in the north atlantic at about 20 500 and 7500 14c yr bp

radiocarbon chronology of lake bonneville eastern great basin usa abstract lake bonneville occupied a series of connected topographically closed structural basins in the eastern great basin from about 30 ka to 12 ka the following synthesis of lake bonneville history is based on a critical evaluation of the stratigraphic and geomorphic contexts of 83 radiocarbon ages of a variety of samples including wood charcoal dispersed organic matter mollusk shells and tufa the lake began to rise from levels close to average holocene levels after about 28 ka by 22 ka it had transgressed approximately 100 m between 22 and 20 ka it regressed about 45 m in the stansbury oscillation and the stansbury shoreline was formed transgression after 20 ka proceeded in two phases a rapid phase from 20 to 18 ka and a slower phase from 18 to 15 ka the lake overflowed intermittently at its highest level the bonneville shoreline from about 15 to 14 5 ka then catastrophically dropped 100 m during the bonneville flood to the level of the provo shoreline which it occupied until about 14 ka subsequent closed basin regression was rapid and complete by 12 ka and was followed by a modest transgression to form the gilbert shoreline between 10 9 and 10 3 ka the lake bonneville record is an accurate proxy of the changing water balance in the bonneville basin during the late pleistocene although the nature of the climatic changes during this period are still uncertain

continental margin tectonics forearc processes recent studies of convergent plate margins and the structural development of forearc terranes are summarized in a critical review of u s research from the period 1987 1990 topics addressed include the geometry of accretionary prisms coulomb wedge taper and vertical motion in response to tectonic processes offscraping vs underplating or subduction the response to oblique convergence fluids in forearc settings the thermal framework and the effects of fluid advection and serpentinite seamounts also included is a comprehensive bibliography for the period

geology of the talaud islands molucca sea collision zone northeast indonesia abstract the talaud islands lie at the northern margin of the collision zone between the sangihe and halmahera island arc systems rock units on talaud are neogene marine strata basalt and andesite tectonic melange and ophiolite the units are exposed in n s trending belts that are commonly separated by faults the marine strata consist of tuffaceous siltstone sandstone shale and marl they are strongly deformed by west verging folds with wavelengths of 20 500 m volcanic rocks of island arc affinity are exposed on the east coast of karakelang island and appear to be interbedded with the lowermost marine strata tectonic melanges contain blocks of serpentinite gabbro basalt red middle eocene chert and limestone and greywacke turbidites the blocks range in length from a few millimetres to hundreds of metres and are enclosed in a scaly clay matrix several mappable slabs of ophiolite are separated by tertiary strata or melange the dismembered ophiolites consist of serpentized peridotite gabbro spilites and cherts locally the melanges and ophiolites are thrust over the younger sedimentary rocks along east dipping faults the dominant eastward dips of melange foliation the westward vergence of structures in the neogene strata the eocene ages of the cherts and the miocene age of the strata overlying the ophiolite slabs suggest that the ophiolites are pieces of eocene or older oceanic crust derived from a mid ocean ridge or back arc basin and upper mantle that were emplaced as thrust slices into the lower slope of a west facing arc during the miocene and have been uplifted during arc arc collision

identification of sinkhole development mechanism based on a combined geophysical study in nahal hever south area dead sea coast of israel seismic refraction magnetic resonance sounding mrs and the transient electromagnetic tem method were applied to investigate the geological and hydrogeological conditions in the nahal hever south sinkhole development area at the dead sea ds coast of israel microgravity and mrs results reliably reveal large karst cavity in the central part of investigated area the map of the seismic velocity shows that sinkholes in nahal hever can be divided into two major groups sinkholes close to the salt edge and sinkholes over compact salt formations between a few tens to a hundred meters from the major cavern the present study shows that the formation of sinkholes of the first group is caused by soil collapsing into the cavern in the area occupied by sinkholes of the second group karst was not detected either by mrs or by seismic diffraction methods tem results reveal shallow clay layer saturated with ds brine underlain sinkholes of this group it allows suggestion that the water drainage and intensive water circulation during rain events wash out fine rock particles from the unsaturated zone into the pre existing cavern initiating the formation of sinkholes of the second group karst development takes place at a very low bulk resistivity 1 m of the ds aquifer attesting to the fact that pores are filled with a highly saline solution refilling of the karstic cavities with collapsing and flushed soil slows down sinkhole development in the area the sinkhole formation cycle at the site is estimated at 10 years sinkhole development throughout the studied area is triggered by a drop in the level of the ds which reduces the head of the confined aquifer and the strength of the overlain sediments

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

dead sea sinkholes an ever developing hazard sinkhole development along the western shore of the dead sea became a major concern in 1990 with the appearance of a series of holes 2 15 m diameter and up to 7 m deep in the newe zohar area one of these sinkholes below the asphalt surface of the main road along the western shore of the dead sea was opened by a passing bus repeated infilling and collapse of these holes indicated the extent of this ongoing process and the significance of this developing hazard since then sinkholes have developed in other areas including qalia ein samar ein gedi and mineral beach

cave detection and 4 d monitoring a microgravity case history near the dead sea sinkholes large open holes that result from the earth simply collapsing are a serious environmental problem and hazard around the dead sea figure 1 the largest is about 30 m in diameter and 15 m deep figure 2 the most alarming case is a recent collapse on both sides of the main highway at e n gedi a popular destination for recreation and tourism sinkholes initially opened at a campsite east of the road figure 3 subsequently several sinkholes opened west of the road in a palm grove warning of a possible collapse of the highway

mid holocene drying of the u s great basin recorded in nevada speleothems lake level records point to dramatic changes in great basin water balance over the last 25 ka but the timing and pace of holocene drying in the region remains poorly documented here we present stable isotope and trace metal data from two lehman caves nv speleothems that provide a well dated record of latest pleistocene to mid holocene hydroclimate in the u s great basin together the stalagmites span the interval between 16 4 ka and 3 8 ka with a hiatus from 15 0 ka to 12 7 ka mg ca and d 13 c covary throughout the records consistent with control by the extent of degassing and prior calcite precipitation pcp measurements of modern cave and soil waters support pcp as the primary control on drip water trace element composition we therefore interpret mg ca and d 13 ca s reflecting infiltration rates with higher values corresponding to drier periods both mg ca and d 13 c indicate a wet period at the beginning of the record 12 7e8 2 ka followed by pronounced drying after 8 2 ka this mid holocene drying is consistent with records from around the western united states including a new compilation of great basin lake level records the strong temporal correspondence with the collapse of the laurentide ice sheet over hudson bay suggests that this drying may have been triggered by northward movement of the winter storm track as a result of ice sheet retreat however we cannot rule out an alternative hypothesis that wet early holocene conditions are related to equatorial pacific sea surface temperature regardless our results suggest that great basin water balance in the early holocene was driven by factors other than orbital changes

accreted terranes in the northern part of the philippine archipelago the philippine archipelago consists of a complex array of ophiolites continental fragments and island arc elements that can be identified as accreted terranes similar to those increasingly recognized as components of orogenic zones the northern philippines including luzon mindoro and nearby smaller islands can be divided into at least six of these tectonic elements from west to east across central luzon there are the neogene accretionary prism of the west luzon arc the eocene zambales ophiolite the cretaceous angat ophiolite and a late cretaceous early paleogene volcanic arc built on an older metamorphic basement this arc terrane is repeated by offset along the philippine fault to the south the western luzon terranes are juxtaposed against the metamorphic basement block of mindoro which itself is colliding with the north palawan microcontinental fragment the ophiolites appear to have originated in back arc basins rather than in oceanic plateaus and the metamorphic belts have protoliths indicating deformation along active margins perhaps deep within accretionary prisms the philippine terranes are interpreted as fragments that originated within the complex pacific eurasian plate boundary rather than as intra pacific basin units these terranes have been assembling at least since the oligocene by strike slip and convergent displacements strike slip displacement either along transcurrent faults or as a component of convergence played a very important if not dominant role in this assembly most terranes identified in the northern philippine appear to be plate fragments with attached crust and upper mantle their characteristics contrast with those usually interpreted for terranes in the north american cordillera where near orthogonal convergence and shallow dipping terrane sutures are favored

evolution of dilatancy and permeability in rock salt during hydrostatic compaction and triaxial deformation combined gas permeability and p and s wave velocity measurements were carried out on rock salt samples from the gorleben salt dome and the morsleben salt mine under hydrostatic and triaxial loading condions mostly at room temperature permeabilities in the as received samples vary between 10 16 and 2x10 20 m 2 the initial permeability is primarily due to decompaction induced by drilling core retrieval and sample preparation hydrostatic loading gives rise to a marked decrease of permeability and a coeval significant increase of p and s wave velocities due to progressive closure of grain boundary cracks tending to approach the in situ matrix permeability 18 mpa differential stress at 10 mpa confining pressure to similar to 30 mpa at confining pressures above similar to 70 mpa dilatancy is due to the opening of grain boundary and 100 cleavage cracks and depends on the applied confining pressure the orientation of the open cracks is primarily controlled by the loading geometry system compression extension as a consequence permeability increases dramatically with progressive dilatancy followed by a period of plus minus constant permeability during strain hardening up to 10 axial strain or even more this suggests that the evolution of permeability is not only a function of dilatancy but also of microcrack linkage importantly the anisotropic crack array within the samples causes a strong directional dependence of permeability

contrasting climatic histories for the snake river plain idaho resulting from multiple thermal maxima abstract ten sites near the snake river plain have consistent differences in their climatic histories sites at low elevation reflect the early holocene xerothermic of the pacific northwest whereas most climatic chronologies at high elevation indicate maximum warmth or aridity somewhat later ca 6000 yr ago this elevational contrast in climatic histories is duplicated at three sites from the central snake river plain for sites in such close proximity the different chronologies cannot be explained by changes in atmospheric circulation during the late quaternary rather the differences are best explained by the autecology of the plants involved and the changing seasonal climate the seasonal climatic sequence predicted by multiple thermal maxima explains the high and low elevation chronologies during the early holocene maximum insolation and intensified summer drought in july forced low elevation vegetation upward however moisture was not a limiting factor at high elevation where vegetation moved upward in response to increased length of growing season coincident with maximum september insolation 6000 yr ago

paleoenvironmental implications of the insoluble microparticle record in the gisp2 greenland ice core during the rapidly changing climate of the pleistocene holocene transition oscillations in the time series of insoluble microparticle characteristics between 0 7 and 11 0 m in the greenland ice sheet project 2 gisp2 ice core reflect changes in environmental conditions in the northern hemisphere from 10 500 to 14 000 yr ago elevated values in microparticle number and mass especially during the younger dryas are related to northern hemisphere aridity and the subsequent increase in dust available for long range transport to greenland this scenario occurs with the colder climatic conditions that result from a more expanded spatially and temporally polar vortex peaks in mean grain size based on number mean number diameter are a proxy for increased strength in zonal winds westerlies highs in mean number diameter in the earlier part of the record often coincide with number and mass peaks reflecting the increased temperature and pressure gradients with an expanded polar vortex highs in mean grain size based on mass mean mass diameter reflect greater deposition of the coarser size fraction and thus are a proxy for increased storminess associated with better developed synoptic scale pressure systems in the northernmost atlantic region peaks in mean mass diameter often lead these other parameters by 100 200 yr suggesting an increase in storminess with the initial southward migration of the mean position of the polar front prior to full development of a more expanded polar vortex the general decline in number and mass trends decreased aridity with a contracting polar vortex together with increasing mean number diameter trends strengthening zonal winds following the maxima in the early younger dryas suggest an expansion of mid latitude circulation systems subtropical highs thereby maintaining latitudinal temperature and pressure gradients increased variability in mean mass diameter during the warm preboreal compared to the colder younger dryas may be a function of the greater seasonality during warmer climatic periods and thus more frequent storms associated with higher frequency oscillations in the position of the polar front with changing seasons and increased interannual variability in climate

spatial variability of late quaternary paleoclimates in the western united states abstract paleoclimatic interpretation of proxy data is complicated sometimes by the appearance of heterogeneous patterns of climatic responses across networks of sites modern climate analogues for the western united states similar to those patterns of atmospheric circulation of 18 000 and 9000 yr b p were examined in order to explain such patterns of spatial heterogeneity modern analogues were defined by comparing modern atmospheric circulation patterns with those simulated by general circulation models maps of temperature and precipitation anomalies of the modern analogues reveal patterns of spatial heterogeneity which resemble the patterns of effective moisture compiled from paleoclimatic data january 1957 was found to be a reasonable 18 000 yr b p analogue and it features isolated areas of increased wetness in the northern great basin and increased dryness in the northwest interior analogues for 9000 yr b p from a composite of 11 augusts display patterns of spatial heterogeneity of effective moisture over most of the mountainous areas the analogues suggest that spatial heterogeneity of climate is the rule rather than the exception over much of the western united states with the climatic anomalies at any particular time representing the outcome of the mediation of large scale atmospheric circulation controls by smaller scale topographic features

moisture history and small mammal community richness during the latest pleistocene and holocene northern bonneville basin utah abstract precipitation and net primary productivity are positively correlated in arid environments both variables are in turn correlated with mammal species richness but this relationship is not necessarily positive with increasing precipitation in arid areas of low to moderate productivity mammal richness increases linearly as rainfall and productivity increase beyond this point mammal richness is known to decline in some areas producing a relationship that has been termed unimodal or humped in the great basin of the arid western united states studies of the relationship between rodent species richness and precipitation have revealed only a positive relationship between these two variables it has however been argued that if areas of higher precipitation were to be sampled within this region the decline phase would become evident when latest pleistocene and holocene small mammal assemblages from the northern bonneville basin central utah are examined across a temporal moisture gradient species richness declines as moisture declines since the great basin was significantly moister during the latest pleistocene and early holocene than it has been since that time the unimodal response model does not appear to apply to this region

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds