chemically striking regions on mars and stealth revisited 1 the mars odyssey gamma ray spectrometer suite has yielded global chemical information for mars in this work we establish regions of unusual chemical composition relative to average mars primarily on the basis of ca cl fe h k si and th using data from mars odyssey the mars exploration rovers the mars reconnaissance orbiter imaging and 3 5 cm and 1 35 cm radar observations from earth we examine a chemically striking 2 e6 km2 region and find it to overlap significantly with a radar stealth region on mars it is remarkably enriched in cl and depleted in fe and si along with minor variations in h k and th relative to average mars surface dust observed at the two rover sites mixed with and indurated by ca mg bearing sulfate salts would be a reasonable chemical and physical analog to meter scale depths we describe potential scenarios that may have contributed to the unique properties of this region the bulk dust component may be an air fall deposit of compositionally uniform dust as observed in situ hydrothermal acid fog reactions on the flanks of nearby volcanoes may have generated sulfates with subsequent deflation and transport alternatively sulfates may have been produced by low temperature regional scale activity of ground ice driven brine and or regional scale deposition of acidified h2o snowfall

the burgess shale and associated cambrian formations west of the fossil gully fault zone on mount stephen british columbia west of the fossil gully fault zone on mount stephen the three lowest members only of the burgess shale formation are preserved the kicking horse shale the yoho river limestone and the campsite cliff shale the formation rests unconformably upon the takakkaw tongue formation whose dark basinal limestones conformably overlie paler shelf like limestones of the mount whyte formation mapping has resolved a long standing problem and shown that the stratigraphical position of the famous mount stephen trilobite beds lies within the campsite cliff shale it has also revealed some of the complexities of the fossil gully fault zone among which different periods and directions of component fault movements are indicated faunal evidence shows that the plagiura kochaspis to albertella and albertella to glossopleura zonal boundaries lie within the takakkaw tongue sequence within the burgess shale three distinct soft bodied communities occur at different stratigraphical levels on this mountain slope the oldest

viking landing sites remote sensing observations and physical properties of martian surface materials abstract important problems that confront future scientific exploration of mars include the physical properties of martian surface materials and the geologic processes that formed the materials the design of landing spacecraft roving vehicles and sampling devices and the selection of landing sites vehicle traverses and sample sites will be in part guided by the physical properties of the materials four materials occur in the sample fields of the viking landers 1 drift 2 crusty to cloddy 3 blocky and 4 rock the first three are soillike drift materials is weak loose and porous we estimate that it has a dielectric constant near 2 4 and a thermal inertia near 1 10 3 to 3 10 3 cal cm 2 sec 1 2 k 1 because of its low bulk density fine grain size and small cohesion crusty to cloddy material is expected to have a dielectric constant near 2 8 and a thermal inertia near 4 10 3 to 7 10 3 because of its moderate bulk density and cementation of grains blocky material should have a dielectric constant near 3 3 and a thermal inertia near 7 10 3 to 9 10 3 because of its moderate bulk density and cementation common basaltic rocks have dielectric constans near 8 and thermal inertias near 30 10 3 to 60 10 3 comparisons of estimated dielectric constants and thermal inertias of the materials at the landing sites with those obtained remotely by earth based radars and viking orbiter thermal sensors suggest that the materials at the landing sites are good analogs for materials elsewhere on mars correlation of remotely estimated dielectric constant and thermal inertias indicates two modal values for paired values of dielectric constants and thermal inertias near a 2 and 2 10 3 and b 3 and 6 10 3 respectively these two modes are comparable to the dielectric constants and thermal inertias for drift and crusty to cloddy material respectively dielectric constants and thermal inertias for blocky material are larger but conistent with values in the northern plains our interprertations are compatible with an aeolian origin for drift and similar materials elsewhere on mars the postulate that moderate dielectric constants and thermal inertias larger than 3 or 4 10 3 are produced by cementation of soillike materials is partly consistent with the data the average dielectric constant and thermal inertia and their correlation with one another suggest that most of the surface of mars should present few difficulties to future surface exploration but some surfaces may present difficulties for spacecraft that are not suitably designed

bioturbation in burgess shale type lagerstatten case study of trace fossil body fossil association from the kaili biota cambrian series 3 guizhou china abstract cruziana gordia planolites rusophycus and trichophycus are common ichnological elements of the kaili biota new discoveries based on the examination of 323 specimens include eldoniids echinoderms trilobites monoplacophorans and non biomineralizing arthropods that are associated with trace fossils based on the observed effects of bioturbation on the preservation of five different animal groups it is clear that infaunal scavengers deposit feeders were periodically active on the kaili sea floor and were able to reach historic layers yielding exceptionally preserved fossils in general the average level of infaunal activity is absent to moderate ichnofabric index i i 1 to 3 in the kaili substrate by contrast the phycodes beds are completely disturbed by infaunal activity i i 5 observed burrow diameter ranges from diminutive 0 2 mm to normal up to 4 2 mm computed tomography allows us to visualize the precise geometry of the trace fossil body fossil association in three dimensions we concluded that although some kaili infaunal animals could bore through the biomineralized echinoderms they did not appear to have scavenged upon these echinoderms based on our three dimensional reconstruction furthermore kaili burrowers can reach the historic layers containing exceptionally preserved fossils without altering soft tissue preservation on the other hand we used conventional techniques to reveal that one burrow is filled with fecal pellets 100 200 m at its terminal end because most burrows are filled with yellow brown coarse sediment and because there is no compositional difference between the fecal pellets and the surrounding coarse sediment within the burrow the origin of the yellow brown coarse sediment is interpreted here as parautochthonous and or autochthonous and as a result of sediment reworking by deposit or suspension feeders the relative scarcity of soft part preservation in the kaili biota compared to the older chengjiang biota and the younger burgess shale biota may be the result of post burial bio disturbance due to the relatively high intensity of local bioturbation it is plausible that oxygenation in deeper sediments facilitated by bioturbation allowed carcasses in the kaili biota to undergo a more extensive period of normal decay prior to final burial than in other cambrian konservat lagerstatten

convective vortices on mars a reanalysis of viking lander 2 meteorological data sols 1 60 dust devil data from mars is limited by a lack of data relating to diurnal dust devil behaviour previous work looking at the viking lander meteorological data highlighted seasonal changes in temporal occurrence of dust devils and gave an indication of typical dust devil diameter size and internal dynamics the meteorological data from viking lander 2 for sols 1 to 60 have been revisited to provide detailed diurnal dust devil statistics results of our analysis show that the viking lander 2 experienced a possible 38 convective vortices in the first 60 sols of its mission with a higher occurrence in the morning compared to earth possibly as a result of turbulence generated by the lander body dust devil events have been categorised by statistical confidence and intensity some initial analysis and discussion of the results is also presented assuming a similar dust loading to the vortices seen by mars pathfinder it is estimated that the amount of dust lofted in the locality of the lander is approximately 800 10 kgsol 1km 2

a case study of recurring slope lineae rsl at tivat crater implications for rsl origins abstract the origin or origins of recurring slope lineae rsl on mars are enigmatic these seasonally dark linear features correlate with temperatures appropriate for liquid water or brine they also progress slowly downslope and fade disappear when inactive similar to shallow subsurface groundwater flows that wick moisture to the surface if liquid water or brine does indeed flow so near the surface and is sufficiently dilute it could have profound implications for the modern habitability of mars we present the results of a case study at tivat crater in the southern midlatitudes that provide new insights into rsl including their potential origins at tivat these results include comprehensive maps of rsl extents in four mars years detailed rsl evolution across one growth season rockfall markings and dust devil tracks in two well constrained years rsl and rockfall markings which are more widely distributed than rsl fade at the same time suggesting a fading mechanism that acts across tivat based on relative albedo analyses rsl and rockfall markings at tivat fade because their host slopes darken which is most easily explained by the widespread removal of dust such a dry fading mechanism would favor a dry origin for rsl we also present a wide range of other rsl observations including highly variable growth pooling like behavior where slopes shallow to roughly 30 and total areal extents that decrease each year across a span of five years we discuss the implications of these observations for various rsl formation models including a new conceptual model that primarily mobilizes dust taken together our observations seem to favor a dry mass movement origin for rsl at tivat but significant challenges remain for each examined model

chemosynthetic mussels at a brine filled pockmark in the northern gulf of mexico a large 540 square meters bed of bathymodiolus n sp mytilidae bivalvia rings a pool of hypersaline 121 35 practical salinity units brine at a water depth of 650 meters on the continental slope south of louisiana the anoxic brine dissolved oxygen 0 17 milliliters per liter contains high concentrations of methane which nourishes methanotrophic symbionts in the mussels the brine which originates from a salt cored diapir that penetrates to within 500 meters ofthe sea floor fills a depression that was evidently excavated by escaping gas the spatial continuity of the mussel bed indicates that the brine level has remained fairly constant however demographic differences between the inner and outer parts of the bed record small fluctuations

chronology of early cambrian biomineralization data on the first appearances of major animal groups with mineralized skeletons on the siberian platform and worldwide are revised and summarized herein with references to an improved carbon isotope stratigraphy and radiometric dating in order to reconstruct the cambrian radiation popularly known as the cambrian explosion with a higher precision and provide a basis for the definition of cambrian stages 2 to 4 the lophotrochozoa and probably chaetognatha were first among protostomians to achieve biomineralization during the terreneuvian epoch mainly the fortunian age fast evolutionary radiation within the lophotrochozoa was followed by radiation of the sclerotized and biomineralized ecdysozoa during stage 3 the first mineralized skeletons of the deuterostomia represented by echinoderms appeared in the middle of cambrian stage 3 the fossil record of sponges and cnidarians suggests that they acquired biomineralized skeletons in the late neoproterozoic but diversification of both definite sponges and cnidarians was in parallel to that of bilaterians the distribution of calcium carbonate skeletal mineralogies from the upper ediacaran to lower cambrian reflects fluctuations in the global ocean chemistry and shows that the cambrian radiation occurred mainly during a time of aragonite and high magnesium calcite seas

textures of the soils and rocks at gusev crater from spirit s microscopic imager the microscopic imager on the spirit rover analyzed the textures of the soil and rocks at gusev crater on mars at a resolution of 100 micrometers weakly bound agglomerates of dust are present in the soil near the columbia memorial station some of the brushed or abraded rock surfaces show igneous textures and evidence for alteration rinds coatings and veins consistent with secondary mineralization the rock textures are consistent with a volcanic origin and subsequent alteration and or weathering by impact events wind and possibly water

laboratory studies of aeolian sediment transport processes on planetary surfaces abstract we review selected experimental saltation studies performed in laboratory wind tunnels and collision experiments performed in splash laboratory facilities that allow detailed observations between impinging particles on a stationary bed we also discuss progress in understanding aeolian transport in nonterrestrial environments saltation studies in terrestrial wind tunnels can be divided into two groups the first group comprises studies using a short test bed typically 1 4 m long and focuses on the transitional behavior near the upwind roughness discontinuity where saltation starts the other group focuses on studies using long test beds typically 6 m or more where the saturated saltation takes place under equilibrium conditions between wind flow and the underlying rough bed splash studies using upscaled model experiments allow collision simulations with large spherical particles to be recorded with a high speed video camera the findings indicate that the number of ejected particles per impact scales linearly with the impact velocity of the saltating particles studies of saturated saltation in several facilities using predominantly particle tracking velocimetry or laser doppler velocimetry indicate that the velocity of the few particles having high trajectories increases with increasing friction velocity however the speed of the majority of particles that do not reach much higher than bagnold s focal point is virtually independent of shields parameter at least for low or intermediate u values in this case mass flux depends on friction velocity squared and not cubed as originally suggested by bagnold over short beds particle velocity shows stronger dependence on friction velocity and profiles of particle velocity deviate from those obtained over long beds measurements using horizontally segmented traps give average saltation jump lengths near 60 70 mm and appear to be only weakly dependent on friction velocity which is in agreement with some but not all older or recent wind tunnel observations similarly some measurements performed with uniform sand samples having grain diameters of the order of 0 25 0 40 mm indicate that ripple spacing depends on friction velocity in a similar way as particle jump length the observations are thus in agreement with a recent ripple model that link the typical jump length to ripple spacing a possible explanation for contradictory observations in some experiments may be that long observation sequences are required in order to assure that equilibrium exists between ripple geometry and wind flow quantitative understanding of saltation characteristics on mars still lacks important elements based upon image analysis and numerical predictions aeolian ripples have been thought to consist of relatively large grains diameter 0 6 mm and that saltation occurs at high wind speeds 26 m s involving trajectories that are significantly longer than those on earth by a factor of 10 100 however this is not supported by recent observations from the surface of mars which shows that active ripples in their geometry and composition have characteristics compatible with those of terrestrial ripples sullivan et al 2008 also the highest average wind speeds on mars have been measured to be electrification is seen as a dominant factor in the transport dynamics of dust on mars affecting the structure adhesive properties and detachment entrainment mechanisms specifically through the formation of aggregates merrison et al 2012 conversely for terrestrial conditions electric fields typically observed are not intense enough to significantly affect sand transport rates while little is known in the case of extra terrestrial environments

the middle cambrian burgess shale and its relationship to the stephen formation in the southern canadian rocky mountains the burgess shale has been an anomalous geologic unit ever since walcott named it in 1911 as the geographic equivalent of the ogygopsis shale in the middle cambrian stephen formation of southeastern british columbia but it has never been recognized outside of its type locality so its status relative to the stephen formation remained uncertain the geologic setting of the burgess shale was determined by aitken and fritz in 1968 when they recognized the cathedral escarpment and divided the stephen formation into a thin platformal succession on top of the escarpment and a thick basinal succession which included walcott s burgess shale in front fieldwork by royal ontario museum parties between 1982 and 1997 has now demonstrated that the thin and thick stephen successions lie within different facies belts and should be regarded as separate formations the stephen shale formation is part of the middle carbonate belt succession whereas the name burgess shale formation is applied to the thick basinal

reinterpretation of middle cambrian stratigraphy of the rifted western laurentian margin burgess shale formation and contiguous units sauk ii megasequence rocky mountains canada abstract until recently research on the renowned fossil animals of the burgess shale has advanced to a greater degree than an understanding of the rocks in which they are found studies addressing lithostratigraphy and hydrothermal petrography of the so called inner carbonate belt and adjacent chancellor group however have begun to re evaluate long standing hypotheses on the middle cambrian of western canada tectonic activity along the kicking horse rim buried remnants of neoproterozoic rifting during the cambrian period had more influence on local sedimentation than previously thought notably large scale collapse of the cathedral carbonate platform margin at 509 ma bp is evidence of reactivated basement faults these failures produced listric megatruncation surfaces having near vertical escarpments 150 m in height where they terminate against the platform the majority of what have been interpreted as shed olistoliths from the cathedral platform margin is herein shown instead to be carbonate mud mounds these grew in situ along the face of the cathedral escarpment and are associated with fossiliferous intervals in overlying basinal mudstones at three distinct stratigraphic horizons two within the burgess shale during the delamaran and marjuman stages the mounds nucleated where deep seated normal faults intersected the seafloor building primarily during periods of relative sea level transgression mound growth is associated with syndepositional exhalative activity inferred from stratigraphic relations sedimentology and geochemistry the new name monarch formation is proposed for the initial post collapse beds and mounds deposited against the cathedral escarpment early glossopleura zone the variably defined term takakkaw tongue is thereby confined to pre collapse slope deposits coeval to and correlative with the cathedral formation

atmospheric imaging results from the mars exploration rovers spirit and opportunity a visible atmospheric optical depth of 0 9 was measured by the spirit rover at gusev crater and by the opportunity rover at meridiani planum optical depth decreased by about 0 6 to 0 7 per sol through both 90 sol primary missions the vertical distribution of atmospheric dust at gusev crater was consistent with uniform mixing with a measured scale height of 11 56 0 62 kilometers the dust s cross section weighted mean radius was 1 47 0 21 micrometers mm at gusev and 1 52 0 18 mm at meridiani comparison of visible optical depths with 9 mm optical depths shows a visible to infrared optical depth ratio of 2 0 0 2 for comparison with previous monitoring of infrared optical depths

morphological development of the florida escarpment observations on the generation of time transgressive unconformities in carbonate terrains abstract an unconformity of 100 m yr magnitude continues to form on the western edge of the florida bahama platform near 26 n where distal mississippi fan sediments are progressively burying the florida escarpment multiple perspectives of the developing unconformity s morphology are revealed using available technologies including gloria images of the entire platform s edge seabeam bathymetric contours and deep tow s high resolution side scan data calibrated with bottom photographs the structure and stratigraphy of the buried escarpment and the associated unconformity are resolved by airgun sparker and deep tow s 4 khz seismic reflection data we summarize the morphological data on the exposed part of the unconformity and the sedimentary deposits accumulating in the basin above the unconformity the exposed cliff face is composed of a staircase of bedding plane terraces which are developed along joint planes the terraces extend 100 1000 m along the escarpment s face and the intervening vertical walls are up to 100 m high the jointed morphology of this mesozoic limestone cliff apparently reflects erosional exposure of its interior anatomy rather than its accretionary shape the change in slope between the platform face and the abyssal plain is very abrupt in places along the contact between the escarpment and fan sediments reduced chemical charged brine seeps occur which locally cause carbonate dissolution and precipitation sulfide mineralization and the deposition of a fossiliferous and organic carbon rich lens associated with chemosynthetic communities these seep deposits and escarpment derived megabreccias intercalate with basinal sediments that overlie the unconformity because surface seismic reflection data do not produce images of the escarpment s face that closely reflect the exposed escarpment s morphology they must also be of limited value in characterizing the surface of similar steeply dipping buried escarpments thus the downslope extent of the heavily eroded platform edge is unclear

basaltic sand ripples at eagle crater as indirect evidence for the hysteresis effect in martian saltation abstract the rover opportunity documented small basaltic sand ripples at the bottom of eagle crater meridiani planum on mars these ripples are composed of fine basaltic sand 100 m diameter and their average wavelength and height are 10 cm and 1 cm respectively present theories on the transition between saltation and suspension predict that such light particles are suspended by turbulence at the fluid threshold which is the minimum wind speed required to initiate saltation consequently the existence of these 100 m ripples on mars indicates that either current suspension theories are incorrect or that saltation can take place at wind speeds substantially below the fluid threshold indeed recent studies point to the occurrence of hysteresis in martian saltation that is once initiated hysteresis can be maintained at much lower wind speeds than the fluid threshold we investigated the possible role of hysteresis in the formation of fine grained ripples on mars by coupling for the first time a detailed numerical saltation model comsalt with a dynamic model for sand ripple formation the results from the coupled model indicate that ripples with properties similar to those observed at eagle crater can be developed by the impact mechanism at shear velocities far below the fluid threshold these findings are consistent with the occurrence of hysteresis in martian saltation and support the hypothesis that hysteresis plays a role in the surprisingly large sand mobility observed at several locations on mars

convective vortices and dust devils at the phoenix mars mission landing site 1 the phoenix mars lander detected a larger number of short 20 s pressure drops that probably indicate the passage of convective vortices or dust devils near continuous pressure measurements have allowed for monitoring the frequency of these events and data from other instruments and orbiting spacecraft give information on how these pressure events relate to the seasons and weather phenomena at the phoenix landing site here 502 vortices were identified with a pressure drop larger than 0 3 pa occurring in the 151 sol mission ls 76 to 148 the diurnal distributions show a peak in convective vortices around noon agreeing with current theory and previous observations the few events detected at night might have been mechanically forced by turbulent eddies caused by the nearby heimdal crater a general increase with major peaks in the convective vortex activity occurs during the mission around ls 111 this correlates with changes in midsol surface heat flux increasing wind speeds at the landing site and increases in vortex density comparisons with orbiter imaging show that in contrast to the lower latitudes on mars the dust devil activity at the phoenix landing site is influenced more by active weather events passing by the area than by local forcing

active dust devils in gusev crater mars observations from the mars exploration rover spirit 1 a full dust devil season was observed from spirit from 10 march 2005 sol 421 first active dust devil observed to 12 december 2005 sol 691 last dust devil seen this corresponds to the period ls 173 2 to 339 5 or the southern spring and summer on mars thermal emission spectrometer data suggest a correlation between high surface temperatures and a positive thermal gradient with active dust devils in gusev and that spirit landed in the waning stages of a dust devil season as temperatures decreased 533 active dust devils were observed enabling new characterizations they ranged in diameter from 2 to 276 m with most in the range of 10 20 m in diameter and occurred from about 0930 to 1630 hours local true solar time with the maximum forming around 1300 hours and a peak occurrence in southern late spring ls 250 horizontal speeds of the dust devils ranged from 1 to 21 m s while vertical wind speeds within the dust devils ranged from 0 2 to 8 8 m s these data when combined with estimates of the dust content within the dust devils yield dust fluxes of 3 95 10 9 to 4 59 4 kg m2 s analysis of the dust devil frequency distribution over the inferred dust devil zone within gusev crater yields 50 active dust devils km2 sol suggesting a dust loading into the atmosphere of 19 kg km2 sol this value is less than one tenth the estimates by cantor et al 2001 for regional dust storms on mars

new burgess shale fossil sites reveal middle cambrian faunal complex soft bodied and lightly sclerotized burgess shale fossils have been found at more than a dozen new localities in an area extending for 20 kilometers along the front of the cathedral escarpment in the middle cambrian stephen formation of the canadian rockies five different fossil assemblages from four stratigraphic levels have been recognized these assemblages represent distinct penecontemporaneous marine communities that together make up a normal fore reef faunal complex

localization and physical properties experiments conducted by spirit at gusev crater the precise location and relative elevation of spirit during its traverses from the columbia memorial station to bonneville crater were determined with bundle adjusted retrievals from rover wheel turns suspension and tilt angles and overlapping images physical properties experiments show a decrease of 0 2 per mars solar day in solar cell output resulting from deposition of airborne dust cohesive soil like deposits in plains and hollows bright and dark rock coatings and relatively weak volcanic rocks of basaltic composition volcanic impact aeolian and water related processes produced the encountered landforms and materials

miocene shallow marine cold seep carbonate in fold and thrust western foothills sw taiwan a mound shaped authigenic carbonate buildup 50 m wide and 5 m high occurred in the middle part of the late miocene shallow marine succession the hunghuatzu formation exposed along the nantzuhsien river sw taiwan the carbonate concretions are classified into four types based on morphology which appeared to develop in upward sequence with vague boundaries 1 flat pipe shaped nodules highly dolomitic small pipes or nodules subparallel to the host strata 2 bulb shaped nodules discrete or combined small mesoclots with subspherical to irregular shapes 3 mushroom shaped concretions large mushroom like or irregular shaped blocks with chimney or vent structures and 4 carbonated layers with sedimentary structures these concretions are mainly composed of dolomite micrites quartz feldspar muscovite and clay minerals ubiquitously interweaved with blackish brown colored low magnesium calcite lmc veins low delta c 13 vpdb values 51 8 parts per thousand to 29 8 parts per thousand of all types of the carbonates reveal that the carbonates were mainly derived from anaerobic oxidation of hydrocarbons many samples are also o 18 depleted delta o 18 vpdb 11 5 parts per thousand to 1 00 parts per thousand due to the mixture with isotopically light lmc veins likely precipitated from meteoric waters there are numerous chemosymbiotic bivalve fossils genus monitilora diameter 3 4 cm in growth position just above the carbonate buildup according to the geological and isotopic signatures the hunghuatzu carbonates are related to a cold seep pseudobioherm which formed in a very shallow marine environment like tidal flat in a passive margin setting exposures of the hunghuatzu pseudobioherm may provide clues for tracking and comparing the evolution history of gas reservoir systems and hints of active tectonics of the sw taiwan region c 2012 elsevier ltd all rights reserved

threshold for particle entrainment into suspension laboratory observations regarding the limit conditions for particle entrainment into suspension are presented a high speed video system was used to investigate conditions for the entrainment of sediment particles and glass beads lying over a smooth boundary as well as over a rough bed the results extend experimental conditions of previous studies towards finer particle sizes a criterion for the limit of entrainment into suspension is proposed which is a function of the ratio between the flow shear velocity and particle settling velocity observations indicate that particles totally immersed within the viscous sublayer can be entrained into suspension by the flow which contradicts the conclusions of previous researchers a theoretical analysis of the entrainment process within the viscous sublayer based on force balance considerations is used to show that this phenomenon is related to turbulent flow events of high instantaneous values of the reynolds stress in agreement with previous observations in the case of experiments with a rough bed a hiding effect was observed which tends to preclude the entrainment of particles finer than the roughness elements this implies that as the ratio between particle and roughness element sizes becomes smaller progressively higher bed shear stresses are required to entrain particles into suspension on the other hand an overexposure effect was also observed which indicates that a particle moving on a smooth bed is more prone to be entrained than the same particle moving on a bed formed by identical particles

comparison of geochemical and distinctive mineralogical features associated with the kinzers and burgess shale formations and their associated units article i nfo article history accepted 12 august 2007 this paper compares two north american occurrences of fossils that exhibit burgess shale type preservation bst the middle cambrian burgess shale formation of southeastern british columbia and the lower to middle cambrian kinzers fm of southeastern pennsylvania redox sensitive trace elements mo ni co v sc indicate that palaeo oxygenation conditions varied with respect to faunal assemblage and location ogygopsis bearing fauna in both the burgess shale and kinzers formations are associated with a dysoxic metal signature burgess shale type preservation in the kinzers fm was deposited in a fluctuating oxycline whereas the bst fossil beds of fossil ridge and mt stephen burgess shale fm yield a geochemical signature that consistently indicates oxic conditions thus sustained low oxygen conditions do not correlate with higher quality of fossil preservation at these sites ogygopsis is associated with dysoxic conditions in both localities and may therefore be a faunal indicator of such environments in middle cambrian strata carbonate units associated with both the burgess shale and kinzers formations contain large generally concordant near surface cavities that contain herringbone calcite cements that show no significant enrichment in the potential calcite inhibitor ions such as reduced fe sr s pb and zn the abundance of micro inclusions of dolomite suggests that mg may have been the calcite inhibitor ion responsible for herringbone cement in these cambrian occurrences another distinctive mineralogical feature is the presence of doubly terminated euhedral zoned authigenic quartz as a conspicuous part of a carbonate host rock replacement assemblage the association of both herringbone calcite and zoned quartz crystals in units associated with the burgess shale and kinzers formations suggest a common feature in the depositional and diagenetic environment of these two regions in which burgess shale type fossil preservation occur syn depositional brine flow is the likely cause of these distinct mineralogical features brine seeps in the depositional environment may have provided nutrients for stable high abundance faunal communities in a slope setting thereby accounting for the abundance of fossil material furthermore high salinity brine in the pore waters of carcass bearing cambrian muds may have further limited shallow burrowing scavenging and decomposition rates accounting for the exceptional preservation in these two localities

active aeolian processes on mars a regional study in arabia and meridiani terrae 1 we present evidence of widespread aeolian activity in the arabia terra meridiani region mars where different kinds of aeolian modifications have been detected and classified passing from the regional to the local scale we describe one particular dune field in meridiani planum where two ripple populations are distinguished by means of different migration rates moreover a consistent change in the ripple pattern is accompanied by significant dune advancement between 0 4 1 meter in one martian year that is locally triggered by large avalanche features this suggests that dune advancement may be common throughout the martian tropics

middle cambrian carbonate platform collapse southeastern canadian rocky mountains regional erosion features termed megatruncation surfaces at the seaward margin of a middle cambrian carbonate platform in southeastern british columbia are inferred to be the proximal parts of gravity slide scars comparable in scale and morphology to modern examples in the caribbean region the surfaces truncate up to 200 m of outer platform strata and have low angle to near vertical headwalls they can be traced a minimum of 56 km along depositional strike and appear to extend at least 8 km basinward of the platform edge they therefore profoundly affect regional stratigraphy

continental margin brine seeps their geological consequences local dissolution observed at the base of the florida escarpment appears to result from acid generated by sea floor oxidation of dissolved sulfide species carried in brines that seep from the base of the escarpment the extent of seep corrosion depends upon the amount of sulfide that has exited the platform and the efficiency with which the acid attacks the limestones of the escarpment calculations suggest that brine seepage influences the shape of these escarpments by undercutting and steepening the carbonate continental margin edges other processes competing for the dissolved sulfides are bacterial chemosynthesis and sulfide mineralization which produces organic carbon and sulfide mineral rich deposits along the unconformity that separates the buried escarpment from onlapping abyssal sediments

dust devils on mars observed by the high resolution stereo camera fourteen active dust devils were observed by the high resolution stereo camera hrsc on mars express which enable the first analysis of the forward speed of dust devils on mars determined from orbit results show speeds on the order of 20 m s which compares favorably with values of the wind profiles estimated from the martian climate database for higher altitudes smaller dust devils of 1 km height and very small diameters were found moving only at 1 5 to 6 0 m s in agreement with surface wind speeds

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

saltation under martian gravity and its influence on the global dust distribution abstract dust and sand motion are a common sight on mars understanding the interaction of atmosphere and martian soil is fundamental to describe the planet s weather climate and surface morphology we set up a wind tunnel to study the lift of a mixture between very fine sand and dust in a mars simulant soil the experiments were carried out under martian gravity in a parabolic flight the reduced gravity was provided by a centrifuge under external microgravity the onset of saltation was measured for a fluid threshold shear velocity of 0 82 0 04 m s this is considerably lower than found under earth gravity in addition to a reduction in weight this low threshold can be attributed to gravity dependent cohesive forces within the sand bed which drop by 2 3 under martian gravity the new threshold for saltation leads to a simulation of the annual dust cycle with a mars gcm that is in agreement with observations

martian aeolian activity at the bagnold dunes gale crater the view from the surface and orbit the first in situ investigation of an active dune field on another planetary surface occurred in 2015 2016 when the msl curiosity rover investigated the bagnold dunes on mars hirise images show clear seasonal variations that are in good agreement with atmospheric model predictions of intra annual sand flux and migration directions that together indicate that the campaign occurred during a period of low wind activity curiosity surface images show that limited changes nevertheless occurred with movement of large grains particularly on freshly exposed surfaces two occurrences of secondary grain flow on the slip face of namib dune and a slump on a freshly exposed surface of a large ripple these changes are seen at sol to sol time scales grains on a rippled sand deposit and unconsolidated dump piles show limited movement of large grains over a few hours during which mean friction speeds are estimated at 0 3 0 4 m s 1 overall the correlation between changes and peak rems winds is moderate with high wind events associated with changes in some cases but not in others suggesting that other factors are also at work the distribution of rems 1 hz wind speeds show a tail up to the 20 m s 1 showing that even higher speed winds occur non aeolian triggering mechanisms are also possible the low activity period at the dunes documented by curiosity provides clues to processes that dominated in the martian past under conditions of lower obliquity

a new middle cambrian burgess shale type biota bolaspidella zone chancellor basin southeastern british columbia abstract a newly discovered burgess shale type bst biota occurs in southeastern british columbia on haiduk and tangle peaks the fossiliferous rocks of the informally named vermilion sub unit and duchesnay unit occur in the bolaspidella zone one trilobite biozone younger than the burgess shale formation the younger rocks abut the eldon escarpment in a stratigraphic and depositional relationship that mirrors that of the burgess shale formation and cathedral escarpment the biota concentrated at the eldon escarpment is hosted predominantly in the duchesnay unit and includes burgess shale genera of sponges worms some arthropods and brachiopods new taxa include an arborescent benthic graptolite with preserved fuselli microbial fossils including vendotaenid bacteria are locally abundant and range up to 750 m basinward of the escarpment in both the vermilion sub unit and duchesnay unit while concentrations of animal fossils are restricted to within 100 m in the vermilion sub unit large autochthonous carbonate mud mounds previously interpreted as platform derived olistoliths originated at the base of the escarpment probably over fluid conduits and then slid downslope bulldozing and entraining sediments in their paths local magnesian and barian rich brine pool deposits occur up to 750 m distal of the escarpment fractionation of the fluids may explain the differing geochemistries at least one mgo rich brine pool deposit on haiduk peak is fringed by abundant animal fossils including concentrations of priapulid worms this assemblage together with high density low diversity assemblages on tangle peak likely represent fringing fauna facies around brine seeps a model erected for similar fossil concentrations and distributions in the burgess shale intrabasinal comparison of the vermilion sub unit and duchesnay unit with the burgess shale formation reveals an identical stratigraphic ordering of carbonates and shales brine pool deposits major debris flow deposits carbonate mud mound growth and fossiliferous deposits the eldon and cathedral platform formations are known to share complimentary brine derived characteristics as well the stratigraphic patterns signify that the depositional processes producing the suite of older lithofacies recurred during deposition of the younger units interbasinal correlation with the wheeler and marjum formations utah identifies the duchesnay unit deposit as the youngest basinal burgess shale type deposit in north america decreasing abundance of animal fossils away from the eldon and cathedral escarpments is generally attributed to increasing development of tectonic fabrics however on haiduk peak rocks hundreds of metres basinward of the escarpment contact are essentially undeformed and contain rare planolites brachiopods and trilobites as the only macrofauna locally abundant vendotaenids and morania are evidence that bst preservation occurred at these distances the concentration of animal fossils at the escarpment is therefore a primary ecological feature not due to a preservational or rheological bias communities were clustered at the face of the escarpment where brines were seeping

the opportunity rover s athena science investigation at meridiani planum mars the mars exploration rover opportunity has investigated the landing site in eagle crater and the nearby plains within meridiani planum the soils consist of fine grained basaltic sand and a surface lag of hematite rich spherules spherule fragments and other granules wind ripples are common underlying the thin soil layer and exposed within small impact craters and troughs are flat lying sedimentary rocks these rocks are finely laminated are rich in sulfur and contain abundant sulfate salts small scale cross lamination in some locations provides evidence for deposition in flowing liquid water we interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water followed by evaporation exposure and desiccation hematite rich spherules are embedded in the rock and eroding from them we interpret these spherules to be concretions formed by postdepositional diagenesis again involving liquid water

the spirit rover s athena science investigation at gusev crater mars the mars exploration rover spirit and its athena science payload have been used to investigate a landing site in gusev crater gusev is hypothesized to be the site of a former lake but no clear evidence for lacustrine sedimentation has been found to date instead the dominant lithology is basalt and the dominant geologic processes are impact events and eolian transport many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration any lacustrine sediments that may exist at this location within gusev apparently have been buried by lavas that have undergone subsequent impact disruption

geochemical evidence for oxygenated bottom waters during deposition of fossiliferous strata of the burgess shale formation abstract deciphering the oxygenation potential of bottom waters during deposition of the fossiliferous strata of the burgess shale is key to understanding the paleoecology of the organisms preserved as fossils and the processes involved in their preservation methods of paleo redox determination that are based upon trace fossils organic carbon content or size analysis of pyrite framboids are problematic when applied to the burgess shale fortunately patterns in redox sensitive trace elements hold great potential for determining paleo redox conditions for these greenschist facies rocks because they are independent of both age and metamorphic grade four burgess shale type bst fossil bearing sections were studied three lie within the burgess shale formation whereas one lies within the slightly younger duchesnay unit of the middle chancellor formation the geochemical proxies of seawater redox conditions that were used are mo u th v cr v v ni ni co and v sc each of these redox sensitive indices suggests that oxygenated conditions prevailed in the overlying seawater during deposition of beds within which bst preservation developed non fossiliferous beds at the base of the mt stephen trilobite beds yield three geochemical indices v v ni v sc ni co that indicate deposition under dysoxic to anoxic conditions thus the only beds to have been deposited under anoxic conditions are barren of fossils of soft bodied taxa further contradicting the notion that bottom water anoxia is a factor in bst preservation the laminated nature of the burgess shale and evidence for subsurface anoxia coupled with evidence for oxygenated bottom waters presence of bacterial mats and surficial trace fossils suggest that the burgess shale was deposited in the exaerobic zone oxic anoxic boundary at the water sediment interface implications of this reinterpretation of the depositional environment of the burgess shale include 1 taphonomic models for bst preservation must account for the presence of oxygen in bottom waters 2 paleoecological interpretations of the burgess shale need to account for a probable autochthonous benthic component in what is a complex assemblage of fossils that includes elements derived from the platform and 3 the possibility of burgess shale communities based upon chemosynthesis and or bacteria grazing must be considered

wind driven particle mobility on mars insights from mars exploration rover observations at el dorado and surroundings at gusev crater 1 the ripple field known as el dorado was a unique stop on spirit s traverse where dust raising active mafic sand ripples and larger inactive coarse grained ripples interact illuminating several long standing issues of martian dust mobility sand mobility and the origin of transverse aeolian ridges strong regional wind events endured by spirit caused perceptible migration of ripple crests in deposits sse of el dorado erasure of tracks in sandy areas and changes to dust mantling the site localized thermal vortices swept across el dorado leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests from orbit winds responsible for frequently raising clay sized dust into the atmosphere do not seem to significantly affect dunes composed of more easily entrained sand sized particles a long standing paradox this disparity between dust mobilization and sand mobilization on mars is due largely to two factors 1 dust occurs on the surface as fragile low density sand sized aggregates that are easily entrained and disrupted compared with clay sized air fall particles and 2 induration of regolith is pervasive light toned bed forms investigated at gusev are coarse grained ripples an interpretation we propose for many of the smallest linear light toned bed forms of uncertain origin seen in high resolution orbital images across mars on earth wind can organize bimodal or poorly sorted loose sediment into coarse grained ripples coarse grained ripples could be relatively common on mars because development of durable well sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing

introduction to the special issue commemorating the 30th anniversary of the royal tyrrell museum of palaeontology with a summary of the museum s early history and its research contributions located just west of drumheller in southern alberta canada the royal tyrrell museum of palaeontology rtmp is nestled among outcrops of the upper cretaceous horseshoe canyon formation exposed along the red deer river valley fig 1 since it officially opened on 25 september 19851 the museum has become one of alberta s must see tourist attractions a significant contributor to the local economy and earned an international reputation for the quality of its palaeontological collections and the research conducted by its scientists the rtmp is unique within canada in being the only government supported museum dedicated to palaeontology and it is one of the few such institutions in the world fig 1 the royal tyrrell museum of palaeontology a front of museum and main entrance circa 2010 looking westwards and with horizontal beds of the upper cretaceous horseshoe canyon formation exposed in the walls of the red deer river valley in the distance b aerial photograph oblique angle and looking to the north northeast the museum sits on top of the number 7 coal seam sensu gibson 1977 and at the base of the horsethief member of the horseshoe canyon formation d a eberth pers comm 2015 that stratigraphic position correlates with an age of about 71 5 ma i e late campanian and lies within the upper part of the edmontosaurus regalis pachyrhinosaurus canadensis dinosaur assemblage zone see eberth et al 2013 fig 6 c the iconic running theropod logo that until recently graced the exterior of the museum below a life sized tyrannosaurid sculpture by brian cooley one of many such sculptures by cooley that have been featured at the museum since its opening in 1985 and with the education wing opened in 2003 as the atco tyrrell learning centre in the background d the cretaceous alberta life sized diorama opened in 2007 an example of a rtmp exhibit that relies heavily on discoveries and interpretations by museum researchers in this case work done in the albertosaurus bonebed and at other localities throughout the horseshoe canyon formation all photographs courtesy of the royal tyrrell museum of palaeontology this special issue of the canadian journal of earth sciences presents a collection of papers commemorating the rtmp s 30th or pearl anniversary our rationale for doing a 30th anniversary volume was two fold first it is an opportunity to showcase the breadth of research conducted by current and former museum scientists as well as by some colleagues having a history of collaboration with the rtmp the 13 invited papers included in this volume are a mix of review and original research papers all thematically focused on the geology and palaeontology of alberta to varying degrees each contribution is the result of work supported by the rtmp and relies on specimens housed in the museum s collections second the 30th anniversary is an opportunity to reflect on the rtmp s history and its research program as is typical for most institutions the rtmp has done little to formally document its own history this year likely will be the last major milestone for which the original generation of museum staff are still working and available to share their recollections about the museum fieldwork and research already deaths and departures have winnowed away part of the original

aeolian contributions to the development of hillslopes and scree sediments in graenagil torfajokull iceland abstract scree cones and slopes are common sedimentary landforms created by rock fall and rock particle fall in mountainous environments these formative processes are attributed to various weathering and particle detachment mechanisms however the aeolian contributions to the weathering of rock faces and formation of scree sediments are poorly understood and often underestimated a case study in the southern highlands of iceland provided a geological setting in a subarctic environment where the contribution of various erosion and deposition mechanisms to the development of scree deposits could be studied here moderately cohesive subglacial volcanic eruption products are continuously undercut by local streams creating exposed and steep sided canyon walls where scree cones and slopes are formed by dominant influences of freeze thaw cycles and the wind on rock particle fall the stratigraphy and the morphometry of these sedimentary landforms indicate that wet formative processes can contribute but are not as dominant avalanching of accumulated material occurs in dry conditions and creates distinct stratified sediments the aeolian contribution to the scree development was studied by determining the physical requirements of particle detachment using wind tunnel simulations simulated threshold wind speeds of the removal of fines show that these wind and gust conditions are common in these areas in iceland a detailed particle analysis of the sediment from an isolated scree cone and the contributing rock face showed that sediments were depleted in the silt fractions field observations confirmed the influence of deflation where fine material is removed by the wind from exposed sediments whereas larger particles are excavated by the deflation of the surrounding matrix on the overlying rock face the outcomes highlight the role that aeolian processes can fulfil in subarctic environments as similar glassy materials are also found on other planets the studied processes can for example offer insights in hillslope processes at the surface of planet mars

dust devils on earth and mars 1 dust devils particle loaded vertical convective vortices found on both earth and mars are characterized by high rotating wind speeds significant electrostatic fields and reduced pressure and enhanced temperature at their centers on earth they are subordinate to boundary layer winds in the dust cycle and except possibly in arid regions are only nuisance level phenomena on mars though they seem to support the persistent background atmospheric haze to influence the surface albedo through the formation of tracks on the surface and to possibly endanger future exploration because of their high dust load and large potential gradients high resolution numerical simulations and thermophysical scaling models successfully describe dust devil like vortices on mars but fitting dust devil action into the martian global dust cycle is still problematic reliable parameterizations of their erosional abilities and solid temporal and spatial distribution data are still required to build and test a complete model of dust devil action

determination of the wind induced detachment threshold for granular material on mars using wind tunnel simulations experimental results are presented of wind induced grain detachment under mars simulation conditions a simple force balance equation is applied to quantify the wind shear stress required for removal of glass spheres from a sand bed the transport of fine grained martian dust is simulated by the detachment of hollow glass spheres which resemble low mass density dust aggregates observed to form during simulations when using mars analogue material the results agree well with observations of dust removal and wind speed measurements made by the nasa viking landers at the martian surface this work supports the suggestion that dust aggregate fragmentation allows wind induced dust entrainment at substantially lower wind shear than that of solid sand grains and has direct application to the study of global dust transport and martian climatology

wind related processes detected by the spirit rover at gusev crater mars wind abraded rocks ripples drifts and other deposits of windblown sediments are seen at the columbia memorial station where the spirit rover landed orientations of these features suggest formative winds from the north northwest consistent with predictions from atmospheric models of afternoon winds in gusev crater cuttings from the rover rock abrasion tool are asymmetrically distributed toward the south southeast suggesting active winds from the north northwest at the time midday of the abrasion operations characteristics of some rocks such as a two toned appearance suggest that they were possibly buried and exhumed on the order of 5 to 60 centimeters by wind deflation depending on location

aeolian slipface dynamics and grainflow morphologies on earth and mars abstract in 2015 an active dune field on mars was visited up close by the curiosity rover in gale crater providing the first high resolution ground images of fine scale windblown features not previously resolved from orbital based imagery for the first time these images allow for direct comparison with terrestrial aeolian dynamics and provide critical ground truth data to bridge the gap between model predictions and satellite observations the image data from the slipface on the namib dune within the bagnold dune field shows grainflow morphologies that are similar to dunes on earth quantitative estimates of flow thickness based on shadow length are presented for the grainflows on the namib dune slipface and compared to grainflow characteristics measured by terrestrial laser scans from the maspalomas dune field located in gran canaria spain using observations from maspalomas to support interpretations of martian slipface dynamics we discuss implications for the local wind regime style of grainflow seasonal activity and dune migration the presence of multiple large magnitude grainflows on the namib slipface suggests an active aeolian environment capable of delivering enough sediment to the slipface to initiate these flows and transport sediment to the bottom of the lee slope however the thinness of grainflows on the namib dune the formation of smaller grainflows directly below the dune brink and limited grainfall suggest a lower wind energy environment at least for the most recent slipface activity large actively migrating stoss ripples obliquely oriented to the dune crest regularly deposit sediment on to the upper slipface and may be a mechanism in which larger grainflow occur during seemingly low energy wind events this mechanism of sediment delivery may also explain the existence of a variety of slipface morphologies both young and old which are otherwise quickly erased on earth due to sediment redistribution and grainfall

preliminary investigation of the crustal structure of the southern urals by geomagnetic methods abstract two different methods have been used to interpret the deep magnetic structure of the southern urals the first employed data from long east west aeromagnetic traverses extending across the orogenic belt the data were interpreted using a two dimensional inversion program which generates a set of magnetic sources and or topography on magnetic interfaces that together can replicate the anomalous magnetic field closely the second method involved the construction of generalised three dimensional models of the deep magnetic basement in the region using wavenumber domain routines both interpretation methods indicate that the uralide orogenic belt is characterised by relatively low average magnetisation compared with the crust to the east and west on the basis of estimates of the probable range of values for the bulk magnetisation of large volumes of crustal rocks we infer that the structures responsible are likely to have depth extents in excess of 20 km our preferred interpretation is that the contrast is between magnetic crystalline basement of the east european craton to the west and a kazakhstan continent to the east and the intervening terranes which appear to have a significantly lower average magnetisation in the area under investigation it appears that the less magnetic zone is in part composed of a thick sequence of riphean rocks which may have been accreted against the margin of the east european craton in pre uralian times

ripple migration and dune activity on mars evidence for dynamic wind processes 1 in this report we show evidence of widespread ripple migration over the stoss side of dark barchan dunes in nili patera on mars the measured average migration of 1 7 meters in less than 4 terrestrial months clearly indicates that active sand saltation is occurring in the study area in addition we document widespread changes in the dune base ground surface contact and in the slip face structures showing that not only the ripples but the whole dunes are actually migrating in the present day atmospheric setting these results provide unequivocal evidence of recent aeolian activity and suggest that other dunes and ripples on mars may also be active

unsteady saltation on mars abstract saltation is an important process on mars as it contributes to dust raising bedform dynamics and aeolian abrasion lander measurements and mesoscale meteorological models suggest that winds in the martian atmosphere rarely exceed the fluid threshold value that is necessary to aerodynamically initiate saltation a fact in stark contrast to the existence of dunes and ripples on the planet many of which are in an active state of migration in an attempt to reconcile these observations we perform an unsteady simulation with a simple turbulence model to calculate the saltation transport rate sinusoidal wind variations are imposed on the saltation layer the numerical simulations verify that gusty transport is one of the main manifestations of martian sediment transport events a formula for the saltation transport rate is reported q m u u it p where u and u it are the friction velocity and impact threshold friction velocity the power p varies in the range of 0 7 1 8 on mars and 1 5 on earth depending on the period and amplitude of the gusty inflow wind our results show that the law of martian and terrestrial transport rate are not universal and hence one should be cautious when trying to extrapolate existing terrestrial results to mars

three mars years viking lander 1 imaging observations the mutch memorial station viking lander 1 on mars acquired imaging and meteorological data over a period of 2245 martian days 3 3 martian years this article discusses the deposition and erosion of thin deposits ten to hundreds of micrometers of bright red dust associated with global dust storms and the removal of centimeter amounts of material in selected areas during a dust storm late in the third winter atmospheric pressure data acquired during the period of intense erosion imply that baroclinic disturbances and strong diurnal solar tidal heating combined to produce strong winds erosion occurred principally in areas where soil cohesion was reduced by earlier surface sampler activities except for redistribution of thin layers of materials the surface appears to be remarkably stable perhaps because of cohesion of the undisturbed surface material

palaeontology and depositional environments of ancient brine seeps in the middle cambrian burgess shale at the monarch british columbia canada abstract the monarch a mountain in southeastern british columbia exposes the cathedral escarpment which abuts the basinal burgess shale and an underlying limestone the upper takakkaw tongue at one section a dolomitized megabreccia representing an intraformational collapsed cavern forms the cathedral escarpment wall the megabreccia is cross cut by the subsequent megatruncation event marking the collapse of the cathedral margin which supports previous hypotheses that dolomitizing brines were active at the cathedral margin prior to and during deposition of the burgess shale epiphyton rich carbonate megablocks within the basinal strata previously interpreted as olistoliths spalled off the escarpment are unlike the peritidal strata comprising the cathedral margin and are more likely deep water carbonate mud mounds that grew in the basin near the escarpment face evidence for early brines in basinal environments at this locality includes lenses of dark magnesium rich clinochlore 30 wt mgo vs 2 in background shales within the burgess shale at the escarpment wall these clinochlores are interpreted as precipitates from seafloor brine seeps analogous to ones currently found at the foot of the florida escarpment and on the distal shelf and slope of the northern gulf of mexico like the gulf examples the brines formed standing pools on the cambrian seafloor and hosted abundant organisms in a narrow fringe around their peripheries but not within the pools sponges priapulid worms hyoliths linguliform brachiopods and trilobites predominate shales only a few metres basinward from the pools are nearly barren of animal fossils increased biologic productivity localized at the seeps would account for the patchy distribution of fossils in the burgess shale in a narrow zone close to the escarpment the discovery of brine seep deposits and associated fringing communities at the monarch shows that at least some assemblages in the burgess shale were preserved within their habitat and were supported by chemosynthesis