the basal onaping intrusion in the north range roof rocks of the sudbury igneous complex the 1 85 ga sudbury impact structure is one of the largest impact structures on earth igneous bodies the so called basal onaping intrusion occur at the contact between the sudbury igneous complex sic and the overlying onaping formation and occupy 50 of this contact zone the basal onaping intrusion is presently considered part of the onaping formation which is a complex series of breccias here we present petrological and geochemical data from two drill cores and field data from the north range of the sudbury structure which suggests that the basal onaping intrusion is not part of the onaping formation our observations indicate that the basal onaping intrusion crystallized from a melt and has a groundmass comprising a skeletal intergrowth of feldspar and quartz that points to simultaneous cooling of both components increasing grain size and decreasing amounts of clasts with increasing depth are general features of roof rocks of coherent impact melt rocks at other impact structures and the basal onaping intrusion planar deformation features within quartz clasts of the basal onaping intrusion are indicators for shock metamorphism and together with the melt matrix point to the basal onaping intrusion as being an impact melt rock by definition importantly the contact between granophyre of the sic and basal onaping intrusion is transitional and we suggest that the basal onaping intrusion is what remains of the roof rocks of the sic and thus is a unit of the sic and not the onaping formation we suggest henceforth that this unit be referred to as the upper contact unit of the sic

3 d kinematic restoration of the eastern sudbury igneous complex canada and its importance for cu ni pge sulphide exploration abstract kinematic restorations of deformed igneous terranes have rarely been attempted due to the general absence of 1 planar primary lithological contacts 2 tightly constrained deformation kinematics and 3 geometric constraints on lithologies and structures at depth because of the vast number of exploration drill holes the deformed and layered 1 85 ga sudbury igneous complex sic in ontario canada is reasonably well understood with respect to 1 and 3 we therefore explored the kinematics of folding and faulting in the eastern sic and use the subsurface geometry of faults extracted from a model integrating surface mapping and drill core logs in an attempt to restore the geometry of part of the sic specifically we identified rotation magnitudes and the tilt axis of a kilometer scale plunging fold the west bay anticline which appears to have folded the eastern part of the sic we combined a 3 d model of the faults and lithological contacts of the sic fault kinematics calculated from the inversion of brittle shear faults at surface and limb rotations of the west bay anticline to kinematically restore the eastern part of the sic results of restorations using simple shear and flexural slip algorithms highlight the importance of slip on prominent curved faults that displaced the sic and facilitated its folding flexural slip appears to be the more plausible mechanism of the two as it removed the curvature of and displacement on prominent faults flexural slip restoration helps to estimate primary thickness variations of the sic and the results show that thickened parts of the main mass of the sic correspond spatially with known cu ni pge sulfide deposits this result demonstrates that 3 d restoration can be an important tool for mineral exploration in igneous terranes

diagnosing the imbalance of yanamarey glacier in the cordillera blanca of peru a detailed glaciological observation program was conducted on the yanamarey glacier in the cordillera blanca of peru including the monitoring of net balance and ice flow velocity during 1977 1988 and mappings of the surface topography in 1973 1982 and 1988 these observations are here evaluated to combine net balance surface lowering and ice flow into a consistent picture of the mode of operation of a tropical glacier on the scale of a decade the glacier extends between 5100 and 4500 m with a total area of 9 105 m2 and length of about 1 3 km maximum flow velocity is 17 4 m yr 1 and maximum volume flux 336 103 m3 yr 1 in the ablation area net balance is about 6 m yr 1 and surface lowering 3 m yr 1 about half of the mean annual water discharge from the glacier of 80 l s 1 is not renewed by precipitation but supplied by the ice thinning the rate of surface lowering of 1 5 m yr 1 liquid water equivalent translates to a glacier average departure heat supply for melting of 16 w m 2 sensitivity analyses indicate that this could be produced by a cloudiness increase of less than one tenth an air temperature decrease of 2 c an increment in specific humidity of less than 1 g kg 1 or some combination of heat budget processes such changes in the atmospheric environment would be required to stabilize the glacier at its recent volume as another indication of the recent imbalance the maximum volume flux is found some 100 m below the equilibrium line altitude under continuation of the recent climatic conditions the glacier may survive for more than half a century

seismicity and crustal structure in the orozco fracture zone project rose phase ii a total of 301 earthquakes were recorded in the vicinity of the orozco fracture zone by seven texas ocean bottom seismograph stations during the 2 week period of the rivera ocean seismic experiment rose phase ii using data from the entire rose array hypocenters of 50 earthquakes were determined these revealed two distinct zones of seismic activity within the fracture zone in addition to these earthquake families many very small events were detected by a station located very close to the spreading center of the east pacific rise the magnitudes of these earthquakes defined by their duration times were so small that most of them were recorded only at this station station 14 in continual or swarmlike occurrences the slope of the frequency magnitude distribution of these events is significantly larger than those of other earthquake groups detected during the experiment i e they appear to have an unusually high b value these results suggest that this new population of earthquakes may be associated with volcanic activity or stress release within highly fractured crustal material refraction studies in the fracture zone reveal the presence of a rather high velocity crustal layer 6 9 7 0 km s beneath the experiment zone the moho velocity and the crustal thickness are estimated at 7 8 km s and 6 2 km respectively

quantifying global warming from the retreat of glaciers records of glacier fluctuations compiled by the world glacier monitoring service can be used to derive an independent estimate of global warming during the last 100 years records of different glaciers are made comparable by a two step scaling procedure one allowing for differences in glacier geometry the other for differences in climate sensitivity the retreat of glaciers during the last 100 years appears to be coherent over the globe on the basis of modeling of the climate sensitivity of glaciers the observed glacier retreat can be explained by a linear warming trend of 0 66 kelvin per century

terrestrial impact melt rocks and glasses abstract the effects of meteorite and comet impact on earth are rock brecciation the formation of shock metamorphic features rock melting and the formation of impact structures i e simple craters complex craters and multi ring basins large events such as the 65 ma chicxulub impact are believed to have had catastrophic environmental effects that profoundly influenced the development of life on earth in this review an attempt is made to summarize some of the voluminous literature on impact melting one important aspect of planetary impact provide some comments on this process and to make suggestions for future research the products of impact melting are glasses impact melt rocks and pseudotachylites our treatise deals mainly with the geological setting petrography and major element chemistry of melt rocks and glasses impact glasses in several petrographic aspects are similar to volcanic glasses but they are associated with shock metamorphosed mineral and rock fragments and in places with siderophile element anomalies suggestive of meteoritic contamination they are found in allogenic breccia deposits within fall back suevite and outside fall out suevite impact craters and as spherules in distal ejecta large events such as the k t boundary chicxulub impact are responsible for the formation of worldwide ejecta horizons which are associated with siderophile element anomalies and shock metamorphosed mineral and rock debris impact glasses have a bulk chemical composition that is homogeneous but exemptions to this rule are common on a microscopic scale however impact glasses are commonly strikingly heterogeneous tektites are glasses ejected from craters over large distances they are characterized by very low water and volatile contents and element abundances and ratios that are evidence that tektites formed by melting of upper crustal sedimentary rocks four tektite strewn fields are known three of which can be tied to specific impact craters impact melt rocks form sheets lenses and dike like bodies within or beneath allogenic fallback breccia deposits in the impact crater and possibly on crater terraces and flanks dikes of impact melt rocks also intrude the rocks of the crater floor they commonly contain shock metamorphosed target rock and mineral fragments in various stages of assimilation and are glassy or fine to coarse grained chemically they are strikingly homogeneous but as with impact glasses exemptions to this rule do exist large and thick melt bodies such as the sudbury igneous complex sic are differentiated or may represent a combination of impact melt rocks sensu strictu and impact triggered deep crustal melts a concerted multidisciplinary approach to future research on impact melting and on other aspects of meteorite and comet impact is advocated impact models are models only and uncritical reliance on their validity will not lead to a better understanding of impact processes especially of melting excavation and deposition of allogenic breccias and the spatial position of breccias in relation to sheets and lenses of melt rocks within the crater impact triggered pressure release melting of target rocks beneath the excavation cavity may be responsible for the existence of melt rocks beneath the impact melt rocks sensu strictu this controversial idea needs to be tested by a re evaluation of existing data and models be they based on field or laboratory research only a relatively small number of terrestrial impact structures has been investigated in sufficient detail as it relates to geological and geophysical mapping in this review we summarize observations made on impact melt rocks and impact glasses in a number of north american brent haughton manicouagan new quebec sudbury wanapitei all in canada asian popigai russia zhamanshin kazakhstan two south african structures morokweng and vredefort the henbury crater field of australia and one european crater ries germany our tables listing major element chemical compositions of impact glasses and melt rocks however include also data from structures not dealt with in further detail

the sudbury structure ontario canada a tectonically deformed multi ring impact basin the occurrence of shock metamorphic features substantiates an impact origin for the 1 85 ga old sudbury structure but this has not been universally accepted recent improvements in knowledge of large scale impact processes combined with new petrographic geochemical geophysical lithoprobe and structural data allow the sudbury structure to be interpreted as a multi ring impact structure the structure consists of the following lithologies sudbury breccia dike breccias occurring up to 80 km from the sudbury igneous complex sic footwall rocks and footwall breccia brecciated shocked crater floor materials in part thermally metamorphosed by the overlying sic sublayer and offset dikes main mass of the sic and basal member of the onaping formation of geochemically heterogeneous coherent impact melt complex ranging from inclusion rich basal unit through a dominantly inclusion free to a capping inclusion rich impact melt rock grey member of of melt rich impact breccia suevite green member of of thin layer of fall back ejecta black member of of reworked and redeposited breccia material onwatin and chelmsford formations post impact sediments observational and analytical data support an integrated step by step impact model for the genesis of these units analysis of the present spatial distribution of various impact related lithologies and shock metamorphic effects result in an estimated original rim to rim diameter of the final crater of 200 or even 280 km for the sudbury structure prior to tectonic thrusting and deformation during the penokean orogeny

optimizing photogrammetric dems for glacier volume change assessment using laser scanning derived ground control points photogrammetric processing of archival stereo imagery offers the opportunity to reconstruct glacier volume changes for regions where no such data exist and to better constrain the contribution to sea level rise from small glaciers and ice caps the ability to derive digital elevation model dem measurements of glacier volume from photogrammetry relies on good quality well distributed ground reference data which may be difficult to acquire this study shows that ground control points gcps can be identified and extracted from point cloud airborne lidar data and used to control photogrammetric glacier models the technique is applied to midtre lovenbreen a small valley glacier in northwest svalbard we show that the amount of ground control measured and the elevation accuracy of gcp coordinates based on known and theoretical error considerations has a significant effect on photogrammetric model statistics dem accuracy and the subsequent geodetic measurement of glacier volume change models controlled with fewer than 20 lidar control points or gcps from sub optimal areas within the swath footprint overestimated volume change by 14 53 over a 2 year period dems derived from models utilizing 20 25 or more gcps however gave volume change estimates within 4 of those from repeat lidar data 0 51 m a 1 between 2003 and 2005 our results have important implications for the measurement of glacier volume change from archival stereo imagery sources

crater floor topography and impact melt sheet geometry of the sudbury impact structure canada terra nova 00 000 000 2010 abstract based on high resolution topography data and the geometry of geological contact traces at the surface we determined the orientation of layer interfaces of the sudbury igneous complex sic our analysis provides for the first time quantitative structural evidence for the thickness variation of its layers which supports an impact melt origin of the sic the present crater floor topography varies up to 400 m over distances of hundreds of metres to a few kilometres and up to 1500 m over a distance of about 25 km crater floor depressions are spatially associated with economically important sulphide mineral deposits which points to a viable exploration strategy finally observed variations in the width of the thermal aureole imparted by the sic on its host rocks are due to primary thickness variations of the sic rather than post impact deformation

the suevite conundrum part 1 the ries suevite and sudbury onaping formation compared the term suevite has been applied to various impact melt bearing breccias found in different stratigraphic settings within terrestrial impact craters suevite was coined initially for impact glass bearing breccias from the ries impact structure germany which is the type locality various working hypotheses have been proposed to account for the formation of the ries suevite deposits over the past several decades with the most recent being molten fuel coolant interaction mfci between an impact melt pool and water this mechanism is also the working hypothesis for the origin of the bulk of the onaping formation at the sudbury impact structure canada in this study the key characteristics of the ries suevite the onaping formation and mfci deposits from phreatomagmatic volcanic eruptions are compared the conclusion is that there are clear and significant lithological stratigraphic and petrographic observational differences between the onaping formation and the ries suevite the onaping formation however shares many key similarities with mfci deposits including the presence of layering their well sorted and fine grained nature and the predominance of vitric particles with similar shapes and lacking included mineral and lithic clasts these differences argue against the viability of mfci as a working hypothesis for genesis of the ries suevite and for a required alternative mechanism for its formation

ice flow and mass continuity of shumsky glacier in the djungarski alatau range of kazakhstan central asia the glaciological monitoring program on the shumsky glacier in the djungarski alatau range of southeastern kazakhstan has included measurements of horizontal surface ice flow velocity net balance and emergence velocity at a network of more than 200 stakes during 1967 1991 as well as mappings of the ice surface topography by double theodolite triangulation and determination of ice thickness and of bedrock topography by radio echo sounding in 1984 these observations are here evaluated together to deduce the long term average dynamic behavior of shumsky glacier the glacier extends between 3100 and 4400 m with a total area of 3 km2 and length of nearly 4 km maximum surface velocity is 20 m yr 1 and maximum volume flux 9 105 m3 yr 1 located near the equilibrium line altitude around 3680 m the ice volume equivalent net balance is 0 5 m yr 1 in the average over the accumulation area changing to about 1 5 m yr 1 near the terminus the submergent flow in the accumulation area changes to emergence of 1 m yr 1 in the lower glacier the rate of ice thinning is less than 0 1 m yr 1 in the middle glacier increases to 2 5 m yr 1 near the terminus and averages 0 12 m yr 1 for the glacier as whole in fact the shumsky glacier differs little from equilibrium being in a more favorable location that the other glaciers of the djungarski alatau however trends toward slower ice flow more negative net balance and faster rate of ice thinning indicate response to a progressively adverse climatic environment

organic geochemistry of impactites from the haughton impact structure devon island nunavut canada organic matter in impactites from the 24 km wide and 39 ma old haughton impact structure canadian high arctic is a mixture of fossil and modern biological components the fossil component represents a conventional oil that was generated from lower palaeozoic marine source material before impact and permeates bedrock dolomites biomarker maturity parameters record the thermal effect of the mid tertiary impact maturity influenced sterane rearranged hopanoid and triaromatic steroid ratios all increase towards the centre of the impact structure where thermal alteration was greatest the heating was probably dominated by an impact related hydrothermal system as such systems last long enough for kinetically based thermal alteration to occur kinetically related biomarker data suggest that the hydrothermal heating lasted for c 5000 years biomarkers are also preserved in dolomite clasts within impact melt breccia and indicate strong thermal alteration modern biological contamination of the rocks is responsible for the superposition of two geochemical signatures which could be cyanobacteria non marine algae or higher plant matter onto the fossil component but they can be recognized and distinguished the data show that the impact structure system holds a record of both the pre impact organic signature and the thermal signature of the impact and thereby indicates that organic geochemistry is a valuable tool in documenting the response of rocks to impacts

origin of the sudbury complex by meteoritic impact neodymium isotopic evidence samarium neodymium isotopic data on whole rocks and minerals of the sudbury complex in canada gave an igneous crystallization age of 1840 21 x 10 6 years the initial epsilon neodymium values for 15 whole rocks are similar to those for average upper continental crust falling on the crustal trend of neodymium isotopic evolution as defined by shales the rare earth element concentration patterns of sudbury rocks are also similar to upper crustal averages these data suggest that the sudbury complex formed from melts generated in the upper crust and are consistent with a meteoritic impact

the evolution of the onaping formation at the sudbury impact structure the 1 4 1 6 km thick onaping formation consists of a complex series of breccias and melt bodies lying above the sudbury igneous complex sic at the sudbury impact structure based on the presence of shocked lithic clasts and various glassy phases the onaping has been described as a suevitic breccia with an origin at least in part as fallback material recent mapping and a redefined stratigraphy have emphasized similarities and differences in its various vitric phases both as clast types and discrete intrusive bodies the nature of the onaping and that of other suevitic breccias overlying impact melt sheets is reviewed the relative thickness internal stratigraphic and lithological character and the relative chronology of depositional units indicate multiple processes were involved over some time in the formation of the onaping the sudbury structure formed in a foreland basin and water played an essential role in the evolution of the onaping as indicated by a major hydrothermal system generated during its formation taken together observations and interpretations of the onaping suggest a working hypothesis for the origin of the onaping that includes not only impact but also the interaction of sea water with the impact melt resulting in repeated explosive interactions involving proto sic materials and mixing with pre existing lithologies this is complicated by additional brecciation events due to the intrusion of proto sic materials into the evolving and thickening onaping fragmentation mechanisms changed as the system evolved and involved vesiculation in the formation of the upper two thirds of the onaping

structural characteristics of the sudbury impact structure canada impact induced versus orogenic deformation a review orogenic deformation both preceding and following the impact event at sudbury strongly hinders a straightforward assessment of impact induced geological processes that generated the sudbury impact structure central to understanding these processes is the state of strain of the sudbury igneous complex the solidified impact melt sheet its underlying target rocks overlying impact breccias and post impact sedimentary rocks this review addresses 1 major structural metamorphic and magmatic characteristics of the impact melt sheet and associated dikes 2 attempts that have been made to constrain the primary geometry of the igneous complex 3 modes of impact induced deformation as well as 4 mechanisms of pre and post impact orogenic deformation the latter have important consequences for estimating parameters such as magnitude of structural uplift tilting of pre impact huronian strata and displacement on major discontinuities which collectively have not yet been considered in impact models in this regard a mechanism for the emplacement of offset dikes is suggested that accounts for the geometry of the dikes and magmatic characteristics as well as the occurrence of sulfides in the dikes moreover re interpretation of published paleomagnetic data suggests that orogenic folding of the solidified melt sheet commenced shortly after the impact uncertainties still exist as to whether the sudbury impact structure was a peak ring or a multi ring basin and the deformation mechanisms of rock flow during transient cavity formation and crater modification

distribution petrography and shock metamorphism of the ejecta of the ries crater in germany a review abstract the lithologies and distribution of the various ejecta formations from the ries crater germany are described they may be subdivided into 1 low shock level 10 gpa represented by polymict crystalline breccias fall out suevites crater suevite and tektites moldavites the ejecta from the mesozoic sedimentary column do not show effects of shock pressures exceeding 10 gpa and only basement gneisses were shock melted to yield suevite glasses it is therefore concluded that the maximum impact energy was transferred from the impactor to the target rocks at a depth of at least 1000 m below ground level where a complex of gneisses underlies shallower granitic intrusions the estimated depth of the transient crater was about 2700 m and its diameter was 12 13 km bunte breccia megablocks of sedimentary rocks and crystalline breccias and megablocks were ejected in ballistic trajectories and form the earliest ejecta deposits extending up to a radius of 22 km fall out suevites are understood to have been lofted from the transient crater by an expanding plume of vaporized rocks and deposited outside the crater as fluidized turbulent masses on top of the earlier ejecta in contrast the crater suevite never left the crater cavity it represents the main mass of suevite moldavites are understood to have been formed during the first encounter of the impactor with the ground by condensation from vaporized and ionizised tertiary sands covering the surface of the target area

the sudbury structure controversial or misunderstood the origins of the sudbury structure and associated igneous complex have been controversial most models call for a major impact event followed by impact induced igneous activity although totally igneous models are still being proposed much of the controversy is due in our opinion to a misunderstanding of the size of the original sudbury structure by analogy with other terrestrial impact structures the spatial distribution of shock features and huronian cover rocks at the sudbury structure suggest that the transient cavity was 100 km in diameter which places the original final structural rim diameter in the range of 150 200 km theoretical calculations and empirical relationships indicate that the formation of an impact structure of this size will result in 104 km3 of impact melt more than sufficient to produce a melt body the size of the igneous complex present volume 4 8 103 km3 for the igneous complex to be an impact melt sheet it must have a composition similar to that of the target rocks evidence for this has been presented previously for sr and nd isotopic data which suggest a crustal origin here we also present new evidence from least squares mixing models that the average composition of the igneous complex corresponds to a mix of archean granite greenstone terrain with possibly a small component of huronian cover rocks this is a geologically reasonable mix based on the interpreted target rock geology and the geometry of melt formation in an impact event of this size the igneous complex is differentiated which is not a characteristic of previously studied terrestrial impact melt sheets this can be ascribed however to its great thickness and slower cooling that large impact melt sheets can differentiate has important implications for how the lunar samples and the early geologic history of the lunar highlands are interpreted if this working hypothesis is accepted namely that both the sudbury structure and the igneous complex are impact in origin then previous hybrid impact igneous hypotheses can be discarded and the sudbury structure can be studied specifically for the constraints it provides to large scale cratering and the formation of basin sized multiring impact structures

the south range breccia belt of the sudbury impact structure a possible terrace collapse feature the south range breccia belt srbb is an arcuate 45 km long zone of sudbury breccia in the south range of the 1 85 ga sudbury impact structure the belt varies in thickness between tens of meters to hundreds of meters and is composed of a polymict assemblage of huronian supergroup 2 49 2 20 ga nipissing diabase 2 2 ga and proterozoic granitoid breccia fragments ranging in size from a few millimeters to tens of meters the srbb matrix is composed of a fine grained 100 m assemblage of biotite quartz and ilmenite with trace amounts of plagioclase zircon titanite epidote pyrite chalcopyrite pyrrhotite and occasionally chlorite the srbb hosts the frood stobie vermilion and kirkwood quartz diorite offset dykes the former being associated with one of the largest ni cu pge sulphide deposits in the world optical petrography and whole rock geochemistry concur with previous studies that have suggested that the matrix of the srbb is derived from comminution and at least partial frictional melting of the wall rock huronian supergroup lithologies rare earth element ree data from all sampled lithologies associated with the srbb exhibit crustal signatures when normalized to c1 chondrite values additionally ree data from the quartz diorites disseminated sulphides in sudbury breccia and a sample of an aphanitic biotite hornblende tonalite dyke exhibit flat slopes when compared to the mafic and felsic norites quartz gabbro and granophyre units of the sudbury igneous complex sic which suggests that these lithologies are representative of bulk sic melt we suggest that the srbb was formed by high strain rate 1 m s gravity driven seismogenic slip of the inner ring of the sudbury impact structure during postimpact crustal readjustment crater modification stage failure of the hanging wall may have facilitated the injection of bulk sic melt into the srbb along with the ni cu pge sulphides of the frood stobie deposit postimpact penokean 1 9 1 7 ga tectonism particularly northwest directed shearing along the south range shear zone and associated thrust faulting could account for the present subvertical orientation of the srbb and the apparent lack of a connection at depth with the sic