crustal structure and surface zonation of the canadian appalachians implications of deep seismic reflection data in 1986 1181 km of marine seismic reflection data was collected to 18 20 s of two way traveltime in the gulf of st lawrence area the seismic profiles sample all major surface tectono stratigraphic zones of the canadian appalachians they complement the 1984 deep reflection survey northeast of newfoundland together the seismic profiles reveal the regional three dimensional geometry of the orogen three lower crustal blocks are distinguished on the seismic data they are referred to as the grenville central and avalon blocks from west to east the grenville block is wedge shaped in section and its subsurface edge follows the form of the appalachian structural front the grenville block abuts the central block at mid crustal to mantle depths the avalon block meets the central block at a steep junction that penetrates the entire crust consistent differences in the seismic character of the moho help identify boundaries of the deep crustal blocks the moho signature varies from uniform over extended di

the impact of ground based glaciogenic seeding on clouds and precipitation over mountains a case study of a shallow orographic cloud with large supercooled droplets this paper examines the impact of ground based glaciogenic seeding on a shallow lightly precipitating orographic cloud with rather large 35 m supercooled droplets the storm was observed on 22 february 2012 as part of the agi silver iodide seeding cloud impact investigation experiment in wyoming the cloud base top temperature was about 5 c 12 c vertical velocity data from an airborne doppler w band 3 mm profiling wyoming cloud radar wcr indicate broad ascent due to the strong wind 20 m s 1 impinging on the terrain and small pockets of intense updrafts the large droplets low droplet and ice particle concentrations and strong updrafts lead to natural snow growth mainly by accretion riming the treated seeded period is compared with the preceding untreated period the main target site located on a mountain pass was impacted by agi seeding according to a trace chemistry analysis of the falling snow data from three radar systems were used in the analysis of the impact of seeding on snow growth the wcr two ka band 1 2 cm profiling micro rain radars and an x band 3 cm scanning polarization doppler on wheels radar this case is complicated somewhat by a natural increase in cloud liquid water and in snow growth by riming starting halfway during the seeding period and continuing after seeding ended composite data from the centimeter wave radar systems indicate an increase in low level reflectivity during seeding even after accounting for the natural trend observed in the upwind control region a precipitation particle probe at the main target site shows an increase in concentration of both small and large hydrometeors

stratigraphie framework for the cambrian ordovician rift and passive margin successions from southern quebec to western newfoundland the taconian humber zone stretches from western newfoundland to southern quebec the early cambrian slope succession in newfoundland is found in the curling group whereas in quebec various units were deposited during that first time slice biostratigraphic data allow correlation of the curling group with the labrador group in newfoundland and with the newly time constrained slope succession in quebec the end of the rift drift transition is marked by a sea level lowstand at the end of the early cambrian the middle cambrian to latest early ordovician passive margin history recorded five cyclic sea level fluctuations three of these cycles are recorded in the shallow marine middle to late cambrian platform port au port group and slope sediments preserved in the cow head and northern head groups in newfoundland the biostratigraphic information assists correlation with cambrian passive margin units in quebec major sea level lowstands are recognized along the continental margin in early middle late camb

paleogeography and tectono sedimentary history at the margin of laurentia during silurian to earliest devonian time the gaspe belt quebec the silurian lower devonian sequence of the gaspe belt at the laurentia margin south of the quebec reentrant and st lawrence promontory was deposited during the period between the two main orogenies that created the northern appalachians the late ordovician taconian and the middle devonian acadian orogenies although this sequence is traditionally considered to have been deposited during a period of quiescence between both orogenies significant tectonic activity attributed to the salinic disturbance began during late llandoverian telychian time and persisted until the acadian orogeny this tectonic activity has profoundly influenced the composition and distribution of the silurian earliest devonian sedimentary facies the shelf and shelf edge history at the laurentia margin along the quebec reentrant st lawrence promontory is summarized according to four broad phases phase 1 is a llandoverian wenlockian regressive phase r1 related to post taconian successor basin filling that culminated with extensive carbonate platform development phase 2 is a late wenlockian ludlovian transgressive phase t1 phase 3 corresponds to a later ludlovian pridolian second regressive phase r2 phases 2 and 3 were accompanied by extensional tectonics that produced shelf faulting and block tilting on top of which block reefs and reef complexes settled and built a reef tract all the way along the gaspe temiscouata shelf phase 4 is an early devonian phase of accelerated subsidence transgression t2 affecting the northwestern part of the segment quebec reentrant area while the southeastern part st lawrence promontory area was already uplifted due to the ongoing collision between laurentia and the western margin of gondwana related terranes to the south composition and distribution of sedimentary facies were controlled by the interaction of tectonics sediment influx and sea level fluctuations construction of a post taconian pre acadian palinspastic map to plot facies has proven to be basic to obtaining a realistic picture of the paleogeography of the shelf and shelf edge of the gaspe temiscouata segment at the margin of the laurentia craton during the silurian earliest devonian time interval

bathymetric and isotopic evidence for a short lived late ordovician glaciation in a greenhouse period the end ordovician glaciation is distinct among phanerozoic glaciations in that co 2 levels were generally high yet major continental ice sheets accumulated on the gondwana supercontinent new oxygen isotopic data indicate substantial changes in sea water temperatures and ice volume coinciding with glacio eustatic changes in sea level reflecting the growth and decay of the gondwana ice cap major glaciation was apparently confined to the hirnantian and was 0 5 1 m y long rather than the 35 m y of earlier estimates carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep water circulation and then back again we believe that the changes in the carbon cycle effected a reduction in p co 2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world

age and composition of the ruisseau isabelle melange along the shickshock sud fault zone constraints on the timing of melanges formation in the gaspe appalachians melanges are common in the humber and dunnage zones of the quebec appalachians humber zone melanges are spatially associated with taconian nappes and believed to be of tectonic origin dunnage zone melanges are interpreted as relicts of an ordovician accretionary prism the ruisseau isabelle melange rim in the gaspe ap palachians was first interpreted as a dunnage zone melange because of its tectonic position along the baie verte brompton line and lithological components such as dark mudstone blocks of ultramafic rocks and greenish chromite bearing sandstone the rim comprises sedimentary rock assemblages composite shale black shale and chromite bearing sandstone assemblages an exotic block a pebbly mudstone assemblage and slivers of serpentinized peridotite and metamorphic tectonite most melanges of the dunnage zone in the quebec appalachians contain partly similar rocks but their age is not well constrained recent work on the rim and cap chat melange of the humber zone and new fossil finds in the rim rock assemblages allow us to conclude that previous distinction between melanges of the dunnage and humber zones on the basis of rock type associations is not valid according to the age of the rim rock assemblages melanges in the northern gaspe appalachians continued forming after the mid caradocian later than the dunnage zone melanges of southern gaspe appalachians the juxtaposition and structural features of the rim rock assemblages result from repeated faulting along the shickshock sud fault from late ordovi cian to middle devonian

significance of new potassium argon ages from the goldens ranch and moroni formations sanpete sevier valley area central utah exposures of volcanic sedimentary strata are widely distributed within central utah we believe that these volcanic and stratified sedimentary rocks known by different formational names in different parts of this region are in fact segments of one and the same suite of rocks that formed during the early and middle tertiary the volcanic sedimentary complex is exposed on both sides of a north trending lowland formed by the collinear juab and sevier valleys west of the lowland the complex has been named the goldens ranch formation east of the lowland it has been called the moroni formation both formations are stratigraphically alike in that each consists of a lower unit composed predominantly of water laid variably cemented sediments and sedimentary rocks with some tuff beds near the base and an upper unit of intermediate composition volcanic rocks chiefly ash flow tuffs and volcanic breccias both formations contain abundant exotic clasts of andesite tan and purple quartzite and dark blue limestone and dolomite both formations are folded and faulted along with the underlying sedimentary units potassium argon ages indicate that both the goldens ranch and moroni formations formed during the late eocene to middle oligocene the geochronology and stratigraphic relations are strong evidence that the goldens ranch and moroni formations are correlative and that they are one and the same depositional unit during the latest oligocene earliest miocene minor monzonitic bodies intruded sedimentary units in the area the new k ar data bear on the matter of the origin of the complex structural deformation in central utah different workers have attributed the singular deformation either to recurrent episodes of compression stemming from the sevier orogeny or to repeated episodes of salt diapirism we recognize two sequences of repeated deformation one that occurred prior to deposition and consolidation of the goldens ranch and moroni formations and a second that occurred after these formations were emplaced in essence after early oligocene time the sevier orogeny ended in paleocene time thus the compression and thrusting stemming from the sevier orogeny could be responsible for the structural complexity that marks pre paleocene units these same orogenic forces do not seem to be viable explanations for the broad flexures and monoclinal downwarps that mark the goldens ranch moroni and younger formations in our view multiple episodes of salt diapirism more reasonably explain the structural complexity in central utah

biostratigraphic paleogeographic and tectonic implications of late ordovician conodonts from the grog brook group northwestern new brunswick diverse conodont faunas recovered from the grog brook group in northwestern new brunswick indicate a late ordovician probably gamachian age the conodonts are of mixed provincial affinity including components of the north atlantic province e g hamarodus icriodella periodon and protopanderodus and taxa representing shallow e g rhipidognathus to deeper water environments e g phragmodus in the midcontinent province elements of amorphognathus ordovicicus branson and mehl numerically dominate the faunas that together with sparse representatives of gamachignathus ensifer mccracken nowlan and barnes suggest a latest ordovician age the beds from which the conodont faunas have been recovered are interpreted as distal debris flows that originated at the basin margin and brought midcontinent province conodonts down the slope to mix with indigenous north atlantic province faunas the faunas are correlative with those from the matapedia group previously thought to overlie the grog brook group and

regional metamorphism of the appalachian humber zone of gaspe peninsula 40ar 39ar evidence for crustal thickening during the taconian orogeny geochronological studies on the timing of deformation and metamorphism along the laurentian margin have shown that the ages of metamorphic events change along strike within the newfoundland southern quebec segment of the canadian appalachians the gaspe peninsula is located at mid point of the two extremities of this segment new single grain laser 40ar 39ar plateau ages solely reflect latest middle late ordovician metamorphism samples taken within the internal humber zone in the shickshock group rocks yield 40ar 39ar muscovite and hornblende ages ranging from 457 to 454 ma samples from the amphibolite du diable the metamorphic sole of the mont albert ophiolite yield 40ar 39ar muscovite and hornblende ages ranging from 459 to 457 ma ordovician ages of the internal humber zone are consistent with 40ar 39ar ages from southern quebec and are interpreted as the result of the emplacement onto the margin of both the ophiolite and its metamorphic sole

ordovician arc collision and foredeep evolution in the gaspe peninsula quebec the taconic orogeny in canada and its bearing on the grampian orogeny in scotland the middle to upper ordovician deslandes cloridorme and garin formations in the eastern gaspe peninsula quebec are some of the most extensively exposed foredeep successions along the northern appalachian portion of the taconic caledonian orogen their depositional and biostratigraphic frameworks n gracilis to c spiniferus zones approximate correlatives to the n gracilis to d clingani british zones indicate that foredeep evolution spanned c 10 ma and was essentially synchronous with the convergence and accretion of the popelogan arc to the laurentian margin during the caradoc c 458 449 ma these results when combined with metamorphic and radiometric age data synthesized from across the laurentian segments of the northern appalachian and northwestern ireland taconic caledonian orogen further substantiate that orogenesis consisted of several short lived c 10 20 ma deformational episodes confined to arenig through ashgill time c 485 440 ma this indicates that the total duration of orogeny as recorded by arc magmatism metamorphism and laurentian foredeep development spanned no more than c 45 ma in that the scottish caledonides are a consanguineous part of this orogen their tectonostratigraphic evolution i e grampian orogeny should be similar accordingly the results detailed above are geodynamically compatible with and thereby support tectonic models that define the grampian orogeny in scotland as a mostly early to mid ordovician c 480 460 ma tectonic episode of short rather than long duration

evidence of liquid dependent ice nucleation in high latitude stratiform clouds from surface remote sensors 1 ground based lidar radar and microwave radiometer observations at eureka canada barrow alaska and over the western arctic ocean measure physical characteristics and morphology of stratiform clouds despite transition of a cold atmosphere 15 c through ice supersaturated conditions ice is not observed until soon after a liquid layer several cases illustrating this phenomenon are presented in addition to long term observations from three measurement sites characterizing cloud phase frequency this analysis demonstrates that clouds composed entirely of ice occur less frequently than liquid topped mixed phase clouds at temperatures warmer than 25 to 30 c these results indicate ice formation generally occurs in conjunction with liquid at these temperatures and suggest the importance of liquid dependent ice nucleation mechanisms

stratigraphy and tectono sedimentary evolution of the late ordovician to middle devonian gaspe belt in northern new brunswick evidence from the restigouche area the gaspe belt in the restigouche area comprises three successions separated by a late silurian salinic disconformity and an early devonian angular unconformity the lower upper ordovician to lower silurian sequence consists of siliciclastic turbidites of the boland brook and whites brook formations grog brook group overlain by calcareous turbidites of the pabos and white head formations matapedia group and slope and shelf deposits of the upsalquitch and limestone point formations lower chaleurs group above the salinic disconformity the upper chaleurs group and the dalhousie group record a transgressive regressive cycle the former comprises pridolian carbonate rocks of the west point formation and overlying pridolian to lochkovian sedimentary rocks of the indian point formation the chaleurs group is conformably overlain by lochkovian to early emsian subaerial volcanic rocks of the dalhousie group val d amour formation which is unconformably overlain by alluvial lacustrine deposits of the late emsian campbellton formation acadian orogenesis began during the emsian and is characterized by open to closed folding heterogenous cleavage development and reverse and strike slip faults the salinic orogeny is manifested in extensional block faulting within plate volcanism and uplift and deep erosion of early silurian strata early devonian high level intrusion of the matapedia group white head clasts in indian point conglomerate and thermal maturation data all indicate an extended period of late silurian early devonian uplift in parts of the restigouche area thermal maturities of west point and indian point strata are within the oil and condensate windows and suggest potential for hydrocarbons in the study area

paleogeography of the matapedia basin in the gaspe appalachians initiation of the gaspe belt successor basin the matapedia basin consists of the uppermost ordovician lowermost silurian deep water fine grained carbonate siliciclastic rocks of the honorat garin formation and matapedia groups pabos and white head formations the lower rock assemblage of the gaspe belt in the gaspe appalachians paleogeographic maps of eight time slices from the caradocian to the llandoverian are presented to better understand the tectonosedimentary evolution of the matapedia basin deposition evolved from siliciclastic garin fm to argillaceous limestones pabos fm to limestones white head fm the overall change from terrigenous garin fm to limestone facies white head fm reflects a change in the source area paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the garin formation which is believed to be the inliers of the humber and dunnage zones in the southern gaspe and new brunswick appalachians lime muds deposited by turbidity currents coming from the nor

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

a stratigraphical and faunal revision of the ordovician silurian strata of the perce area quebec the ordovician silurian strata of the perce area are assigned to the matapedia group they occur in a southwestern monoclinal sequence unconformably overlying cambrian strata and are assigned to the pabos and white head formations the pabos formation is preponderantly a terrigenous sequence whereas the white head is preponderantly a carbonate sequence the pabos strata of this area are included in the new rouge member in which four brachiopod dominated communities are recognized the dalmanella catazyga sowerbyella and epitomyonia communities within which trilobites occur sporadically the white head formation is divided into three new limestone members and a new mudstone member the basal burmingham member has yielded a catazyga community and a sowerbyella like community the cote de la surprise member is composed of mudstones with the previously described hirnantia community the rouge burmingham and cote de la surprise members are ashgillian upper ordovician but the uppermost two members

the origin of ice in mountain cap clouds abstract ice crystal development in relatively simple layer clouds was studied using airborne instrumentation the patterns in the development of ice in those clouds suggest that the ice originates in association with the initial condensation process near the upwind edge of the cloud since continued ice production does not occur beyond that region the ice development can be attributed to nucleation there is no evidence for secondary ice generation either condensation freezing or contact nucleation could account for the observed nucleation process but special properties are required for the nuclei in either case ice crystal concentrations show a clear temperature trend as expected for a nucleation process

palinspastic restoration of a post taconian successor basin deformed within a transpressive regime northern appalachians restoration of transpressional orogens requires a three dimensional analysis of the strain state in order to take into account both the pure shear and simple shear components of the deformation and assess their relative contribution throughout the deformation history restoration of the post taconian successor basin the gaspe belt located within the external part of the acadian orogen in the canadian appalachians was performed by using a step by step method based on the successive removal of strain increments the pure shear component contributed 70 of the total strain during the first stages of the deformation whereas the simple shear component contributed 30 of the total strain during the last stages three retrodeformation steps are defined starting with restoration of the last deformation stage and working back to the first deformation stage the first step is to restore slip along acadian strike slip faults the second step is to restore shortening related to the horizontal extension during the acadian regional simple shear event finally the third step is to restore vertical extension related to the pure shear event by removing slip along the reverse faults unfolding and removing internal strain associated with cleavage development retrodeformation of the simple shear component of the transpressive deformation during the first two steps is performed on a horizontal view of the gaspe belt basin which contains the horizontal extension direction and which is perpendicular to the acadian nw se directed compression likewise restoration of the pure shear component is performed in vertical sections which contain the vertical extension and which are perpendicular to the acadian nw se directed compression the palinspastic map presented here is a much more appropriate base map for the basin and allows for a more realistic paleogeographic interpretation of the gaspe belt

observation of playa salts as nuclei in orographic wave clouds during the ice in clouds experiment layer clouds ice l dry lakebed or playa salts from the great basin region of the united states were observed as cloud nuclei in orographic wave clouds over wyoming using a counterflow virtual impactor in series with a single particle mass spectrometer sodium potassium magnesium calcium chloride salts were identified as residues of cloud droplets importantly these salts produced similar mass spectral signatures to playa salts with elevated cloud condensation nuclei ccn efficiencies close to sea salt using a suite of chemical characterization instrumentation the playa salts were observed to be internally mixed with oxidized organics presumably produced by cloud processing as well as carbonate these salt particles were enriched as residues of large droplets 19 m compared to smaller droplets 7 m in addition a small fraction of silicate containing playa salts were hypothesized to be important in the observed heterogeneous ice nucleation processes while the high ccn activity of sea salt has been demonstrated to play an important role in cloud formation in marine environments this study provides direct evidence of the importance of playa salts in cloud formation in continental north america has not been shown previously studies are needed to model and quantify the impact of playas on climate globally particularly because of the abundance of playas and expected increases in the frequency and intensity of dust storms in the future due to climate and land use changes

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

along strike acadian structural variations in the quebec appalachians consequence of a collision along an irregular margin the quebec appalachians have been shaped by two major orogenies the middle to late ordovician taconian and the middle devonian acadian thrust faults and nappe structures characterized the taconian deformation throughout the quebec appalachians whereas structural styles pertaining to the acadian orogeny differ from southern quebec to the gaspe peninsula structural analysis of late ordovician to middle devonian supracrustal rocks shows two different acadian deformational regimes strike slip tectonics in the gaspe peninsula and thrust or dip slip tectonics in southern quebec in southern quebec acadian regional deformation produced folds which vary from upright to overturned and tight to isoclinal from the nw to the se major faults e g la guadeloupe are northwestward directed thrust faults marked by highly ductile shear zones outlined by mylonite in the gaspe peninsula structural trend is ne and major e w dextral strike slip faults transect this trend folds are open and upright inclined and tighter near the major faults where they have a clockwise rotation like the regional cleavage major faults e g grand pabos follow corridors delimiting high strain zones where the fabrics developed are indicative of a ductilebrittle regime of deformation in the temiscouata region major structural features of both southern quebec and the gaspe peninsula are recognized structures of this region consist of ene trending dextral strike slip faults and high angle wnw verging reverse faults parallel to major nne folds these structures reflect the transition from purely horizontal movement along major strike slip faults of the gaspe peninsula to vertical movement along thrust faults in southern quebec acadian structural variations within the quebec appalachians are interpreted in terms of a continental collision of gondwana along the irregular margin of laurentian and its taconian accreted terranes