asphalt volcanoes as a potential source of methane to late pleistocene coastal waters natural petroleum seepage emits large volumes of oil and methane to the oceans every year accompanied by the formation of asphalt volcanoes on the sea floor the discovery of seven asphalt volcanoes off the coast of southern california may help to explain high methane emissions recorded during the late pleistocene

the role of the critical angle in brightness reversals on sunglint images of the sea surface 1 a wide variety of oceanic and atmospheric phenomena are often observed in and around the sunglint region on optical images of the sea surface the appearance of these phenomena depends strongly on the viewing geometry with areas on the sea surface that are rougher or smoother than the background appearing as either brighter or darker than the background depending on their position relative to the specular point to understand these sea surface signature variations this paper introduces the concept of a critical sensor viewing angle defined as the sensor zenith angle at which different sea surface roughness variances produce identical sunglint radiance it is when the imaging geometry transitions through the critical angle that a surface feature goes through a brightness reversal knowledge of where this transition takes place is important for properly interpreting the characteristics of the sea surface signature of these phenomena the theory behind the concept of the critical angle is presented and then applied to sunglint imagery acquired over the ocean from space by the moderate resolution imaging spectroradiometer onboard nasa s aqua and terra satellites

sm nd evidence for a major 1 5 ga crust forming event in the central grenville province the majority of gray gneisses from an 80 000 km 2 area in the central quebec grenville province define a sm nd isochron that yields an age of 1 53 0 07 ga major element trace element and initial nd isotopic data all point to a subduction related orogenic source for this terrane it is attributed to a major crustal extraction event that formed a mid proterozoic island arc the age of the terrane agrees with published data from the eastern and western grenville province in newfoundland and ontario respectively we suggest that 1 5 ga are fragments were accreted along much of the length of the laurentian foreland within 100 m y of their formation in an event marked by widespread granitoid plutonism

joint sun glitter and radar imagery of surface slicks a method is proposed to retrieve and interpret fine spatial variations of the sea surface roughness in sun glitter imagery observed sun glitter brightness anomalies are converted using a transfer function determined from the smoothed shape of sun glitter brightness the method is applied to modis and meris sun glitter imagery of natural oil seeps and the catastrophic deepwater horizon oil spill in the gulf of mexico the short scale roughness variations in the presence of mineral oils slicks are consistently extracted and compared to variations associated with the biogenic slicks in doing so the wind speed dependency on the roughness anomalies is also considered a comparison to normalized radar cross section nrcs anomalies taken from the corresponding high resolution asar images is performed and similarities as well as differences are investigated the results document significant benefit from the synergetic use of sun glitter and radar imagery for detection and monitoring of surface slicks

detecting surface oil slick related to gas hydrate petroleum on the ocean bed of south china sea by envi asar radar data abstract for exploring the distribution of oil slick related to gas hydrate or petroleum in the northern part of south china sea and evaluating the potential of envi asar radar data for detecting oil slick this paper tries to detect the oil slick on ocean surface of some potential areas in south china sea and map oil slick from anomaly area in radar image seven surface oil slicks in qiongdongnan basin and four potential targets of oil slicks in taixi dongsha basin were detected and extracted by using eniv asar data the anomalies of the radar image representing oil slick are validated by in site sampling and laboratory analyzing the gas chromatograph gc results of the extracted oil from the water samples gathered from the sites of detected oil slick demonstrate a typical composition of oil rather than that of ocean microbial origins and total organic carbon toc concentrations in two designed vertical profiles keep steady in different depths showing that the organic contents in water column are steady from the deep area to ocean surface these results suggest the detected oil slick is a thin floating oil rather than a thick spill influencing factors to the results of oil slick detection including wind speed current small islands and capes as well as deep sea petroleum reservoirs are discussed the results in this study exhibit that extracting the anomaly signals related to oil slick related to oil gas seeps using image processing techniques from envi asar data is helpful to predict anomaly areas as potential targets for further exploration in this area

mesoproterozoic and paleoproterozoic crustal growth in the eastern grenville province nd isotope evidence from the long range inlier of the appalachian orogen

crustal formation in the grenville province nd isotope evidence ninety eight new nd isotope analyses are presented for gneissic rocks from the grenville province when combined with over 250 published nd analyses and some unpublished analyses these data can be used to establish a first order crustal formation age map for most of the grenville parautochthon and allochthonous polycyclic belt in particular the geographic extents of a juvenile labradorian arc labradoria and a juvenile 1 5 ga arc quebecia are defined each with an area probably in excess of 100 000 km2 in addition pre 1 75 ga arcs are identified in ontario barilia and labrador makkovikia this work largely fills the last major gap in the continent wide crustal formation age map of the precambrian shield of north america

sar imaging of ocean surface oil seep trajectories induced by near inertial oscillation abstract in the gulf of mexico repeated satellite synthetic aperture radar sar observations show circular trajectories of oil slicks with a radius of several km some circles overlay onto each other while in other cases the circles are modified by the ambient current to form a train of spirals we show that these sar observed features originate from oil seeps of the ocean bottom and the circles are induced by near inertial oscillation nio from the sar images we have estimated the ambient current velocity from a train of spiral like circles and verified the nio by calculating its oscillation period in this study we also analyze time series of wind and velocity profiles obtained from a moored buoy and acoustic doppler current profilers mounted on oil platforms in the area covered by the sar images the ocean current analysis confirms that during the sar imaging times there were nios buoy measurements also show that moderate wind of 7 ms 1 existed 24 h prior to a sar observation and it diminished to 2 ms 1 in 6 h and remained very low for the next 18 h a condition ideal for producing nios

mapping sea surface oil slicks using radarsat 2 quad polarization sar image 1 polarimetric sar decomposition parameters average alpha angle and entropy h are estimated for oil slick contaminated sea surfaces and slick free conditions using a radarsat 2 quad polarization sar image the values of h and within oil slick areas are significantly higher than those of the ambient sea surface indicating the dominance of bragg scattering for the slick free ocean and non bragg scattering for the oil slick area in land classification the conformity coefficient is often used to discriminate surface scattering with double bounce or volume scattering based on this rationale we also develop a method using as a logical scalar descriptor to map oil slicks under low to moderate wind conditions the proposed method is assessed using a radarsat 2 quad polarization sar image of oil slicks in the gulf of mexico analysis shows that when is positive the sea surface is slick free whereas is negative for oil slick areas this method provides a simple and effective mapping technique for oil slick detection

the location of the allochthon boundary thrust and the archean proterozoic suture in the mattawa area of the grenville province nd isotope evidence abstract over 100 nd isotope analyses are used to map the crustal formation ages of grenville orthogneisses in a 10 000 km 2 area near mattawa on the ontario quebec border lithotectonic terranes with mapped outcrops of eclogite or coronitic metagabbro have nd model ages less than 1 8 ga and are interpreted as fragments of the allochthonous polycyclic belt however large areas of orthogneiss to the north of mattawa have model ages of 1 9 2 9 ga interpreted as archean crust that was extensively plutonised in paleo and mesoproterozoic magmatic events based on this evidence a revised location is proposed for the allochthon boundary thrust abt which passes to the south of the bonfield batholith and mattawa but then trends to the north and is correlated with the lac watson shear zone some allochthonous klippen are identified northwest of the main trace of the abt representing the dissected remains of what was originally a large allochthonous thrust sheet within the parautochthon a major step in depleted mantle model ages is observed in the vicinity of the mattawa fault separating archean and paleoproterozoic crustal blocks this boundary is interpreted as an ancient crustal suture reactivated by faulting associated with the ottawa bonnechere graben it is concluded that nd isotope analysis is a useful technique for detailed mapping of major tectonic boundaries in highly metamorphosed orogenic belts such as the grenville province

observation of sea surface roughness at a pixel scale using multi angle sun glitter images acquired by the aster sensor abstract sea surface roughness ssr is commonly used to describe the state of the sea surface sun glitter sg caused by direct specular reflection of sunlight from the sea surface and its intensity are strongly affected by ssr here we propose a new model for estimating ssr at a pixel scale using multi angle sg images to test our model high resolution multi angle sg images acquired by the advanced spaceborne thermal emission and reflection radiometer aster sensor were used to estimate ssr the modal value of ssr was more suitable for describing the background ssr induced by wind and these data were then converted into wind speed for accuracy evaluation the estimated wind matched reasonably well with corresponding reanalysis wind data from the european centre for medium range weather forecasting and buoy wind data from the national data buoy center the results showed that the proposed model has an inversion accuracy that is comparable to other remote sensing methods next we presented three examples of high resolution ssr images of an oil slick submarine topography and internal wave information to illustrate the applications of the model these estimated ssr images showed detailed oceanographic features with low noise and quantitative changes in ssr at a pixel scale the results of this study demonstrate that it is feasible to estimate ssr at a high resolution using multi angle sg images and high resolution ssr observations have considerable applicability to oceanographic phenomena

did deepwater horizon hydrocarbons transit to the west florida continental shelf abstract hydrocarbons that originated from deepwater horizon were observed at the surface along west florida s northern coastline in june 2010 the farthest eastward advance nearly to cape san blas occurred during the last week of june before the surface oil retreated back westward and dissipated surface oil was not observed on the portion of the west florida continental shelf wfs situated to the southeast of cape san blas nevertheless there were numerous anecdotal occurrences of reef fish caught on the wfs with lesions and other deformities subsequent systematic sampling of wfs reef fish provided additional evidence for damage that extended as far south as the dry tortugas here we examine the possibility that hydrocarbons of deepwater horizon origin transited to the wfs beneath the surface we use a numerical circulation model simulation run for the entirety of 2010 and quantitatively gauged against in situ observations a passive tracer is introduced into the model to mimic the movement of subsurface hydrocarbons either dissolved or of sufficiently small particle size to effectively be dissolved the tracer driven primarily by an anomalously strong and persistent upwelling circulation eventually covered most of the wfs using reasonable estimates of what the initial tracer concentration may have been with respect to hydrocarbons we conclude that the transport of subsurface hydrocarbons to the wfs is both plausible and consistent with the observed distribution of fish lesions fish liver chemistry and other chemical and ecological evidence

natural oil slicks in the gulf of mexico visible from space natural oil seepage in the gulf of mexico causes persistent surface slicks that are visible from space in predictable locations a photograph of the sun glint pattern offshore from louisiana taken from the space shuttle atlantis on may 5 1989 shows at least 124 slicks in an area of about 15 000 km2 a thematic mapper tm image collected by the landsat orbiter on july 31 1991 shows at least 66 slicks in a cloud free area of 8200 km2 that overlaps the area of the photograph samples and descriptions made from a surface ship from aircraft and from a submarine confirmed the presence of crude oil in floating slicks the imagery data show surface slicks near eight locations where chemosynthetic communities dependent upon seeping hydrocarbons are known to occur on the seafloor additionally a large surface slick above the location of an active mud volcano was evident in the tm image in one location the combined set of observations confirmed the presence of a flourishing chemosynthetic community active seafloor oil and gas seepage crude oil on the sea surface and slick features that were visible in both images we derived an analytical expression for the formation of floating slicks based on a parameterization of seafloor flow rate downstream movement on the surface half life of floating oil and threshold thickness for detection applying this equation to the lengths of observed slicks suggested that the slicks in the atlantis photograph and in the tm image represent seepage rates of 2 2 30 m3 1000 km 2 d 1 and 1 4 18 m3 1000 km 2 d 1 respectively generalizing to an annual rate suggests that total natural seepage in this region is of the order of at least 20 000 m3 yr 1 120 000 barrels yr 1

evidence and quantification of the correlation between radar backscatter and ocean colour supported by simultaneously acquired in situ sea truth 1 near simultaneously within 2 hours acquired ers 2 synthetic aperture radar sar and sea viewing wide field of view scanner seawifs data over an upwelling region shows remarkable similarity in feature s location scale and boundary under uniform wind and sea states reduction of normalised radar cross section nrcs from sar is found highly correlated with the increase of seawifs chlorophyll a chl a concentration typically 1 mg m3 of chlorophyll a is correspondent with a 5 db reduction of nrcs this relationship is supported by simultaneously collected in situ sea truth measurements this work provides a direct evidence and exceptional quantification of the relationship between radar backscatter and ocean colour that has long been speculated

monitoring of natural oil seepage in the lower congo basin using sar observations abstract synthetic aperture radar sar is a spaceborne tool allowing near real time imagery over large ground footprints of areas hundreds of kilometres wide sar also allows persistent observations of the process of oil discharges benefiting from 1 day and night observations 2 independence of cloud cover and 3 high revisiting frequencies the interpretation of 82 sar scenes over the lower congo basin for the 1994 2012 period allowed the recognition of 1400 natural seepage slicks associated with 102 individual seep sites we acquired an additional sar data set with a short revisit time over a selected prolific area the data set consisted of 22 sar scenes acquired over a 10 day period meaning a maximum revisiting period of 12 h between subsequent sar acquisitions the short term approach shows that seepage slicks were detected with wind speeds between 1 5 and 6 5 m s 2 91 to 12 63 knots both long term and short term monitoring evidences that seepage events are intermittent with the occurrence rate of oil release ranging from 5 to 80 short term monitoring shows that the seepage pace is independent between seep sites suggesting contrasted controlling factors it also shows that the residence time of seepage slicks is systematically shorter than 12 h which is far below reported values understanding the seepage slick residence time is essential to provide an accurate estimation of the fluid flow and to compute the volumetric outflow the integration of in situ mooring points measuring the current velocity 10 m below the sea surface in addition to local wind field and slick length allowed us to more accurately estimate the residence time of oil slicks at the sea surface before vanishing the results show that the sea surface residence time of oil slicks is limited to a few hours with a median value of 3 h 15 min these new residence time estimations allowed us to propose a quantification of the regional oil output in the lower congo basin estimated at 4380 m3 year this area may therefore be considered as the world s third biggest oil supplying province from natural leakages

nd isotope mapping of a pinwarian age composite arc belt in the quebecia terrane of the central grenville province canada abstract there continues to be confusion in the geological community concerning the ages of crustal formation and crustal accretion within the central grenville province of quebec to clarify the geological history of crustal growth in the eastern part of the quebecia terrane sixty new nd isotope analyses are presented from a 60 000 km2 area northwest of baie comeau most samples yield pinwarian nd model ages that suggest them to be derived from juvenile oceanic arc terranes however two large slivers with paleoproterozoic tdm ages attest to the existence of hidden blocks of old crust which divide the area of juvenile pinwarian crust into a composite arc belt of smaller accreted terranes the old crustal blocks probably do not reach the present surface but represent an igneous crustal protolith of younger i type magmatism by comparison with a mesozoic tectonic analogue it is proposed that accreted juvenile arc crust with attached slivers of older crust were rifted away from an active margin to the west and translated eastwards until blocked by the previously accreted labradoria terrane although the quebecia composite arc belt consists of over 95 of pinwarian juvenile arc crust the age of arc accretion was post pinwarian the proposed oblique nature of the accretion process may explain the lack of a major collisional orogen at that time this paper shows the usefulness of large scale nd isotope mapping of precambrian crustal terranes to clarify complex processes of crustal formation and arc accretion

a comparison of nd model ages and u pb zircon ages of grenville granitoids constraints on the evolution of the laurentian margin from 1 5 to 1 0 ga terra nova 24 7 15 2012 abstract concordance and discordance between nd model ages and u pb ages is still widely misunderstood in the geological community in the sw grenville province plutonic orthogneisses often yield tdm ages significantly older than u pb crystallization ages but this can be understood in a model where a series of crustal nd isotope evolution lines departs at intervals from the depleted mantle dm evolution line seven samples with concordant u pb and nd model ages have initial e nd on the dm line attributed to melting of juvenile crust generated in an elzevirian back arc rift zone in contrast plutons with discordant u pb and nd model ages lie near crustal evolution lines defined by suites of basement gneisses on the flanks of the rift zone this study shows that nd data from large suites of geographically constrained undated grey gneiss provide a crustal evolution framework for orogen scale interpretation of more scattered but precisely dated plutons

ocean sand ridge signatures in the bohai sea observed by satellite ocean color and synthetic aperture radar measurements abstract satellite measurements from synthetic aperture radar sar and the moderate resolution imaging spectroradiometer modis onboard the aqua platform are used to study the ocean sand ridges in the eastern bohai sea in china even though the imaging mechanisms for sar and modis aqua remote sensing are different the sand ridges are shown to have exactly the same patterns in images from both sensors therefore the location extension and coverage of the ocean sand ridges can be detected and cross examined by both sar and modis aqua observations satellite images show quite different sand ridge distribution pattern from the published bathymetry map based on in situ data that shows six sand ridges in the area 10 finger shaped sand ridges are identified from satellite observations the tidal current sand ridge interaction driven physical and optical changes are assessed and evaluated the existence of sand ridges causes enhanced water diffuse attenuation coefficient k d 490 and elevated normalized water leaving radiance at the red and near infrared nir wavelengths the sea surface over the sand ridges experiences significant seasonal variability of water turbidity and shows remarkable differences from nearby ocean regions during winter k d 490 values are about 2 3 m 1 over the ridges while the maximum k d 490 in the neighboring oceans is approximately 1 5 m 1 in summer the enhancement of the sea surface turbidity is less significant than that which occurs in winter

u pb geochronologic constraints on the crustal evolution of the long range inlier newfoundland the long range mountains of newfoundland expose the northeastern most basement inlier of the appalachian orogen u pb results for two samples of basement gneiss reveal crustal formation ages of 1466 10 ma western brook pond charnockite and 1530 8 ma cat arm road gneiss indicating an affinity with pinwarian magmatism 1510 1450 ma in labrador a third sample of basement gneiss from the cat arm road dam site yielded a minimum formation age of 1631 ma these basement gneisses were intruded by granite plutons during two periods of grenvillian magmatism group i at 1032 1022 ma and group ii at 993 985 ma group i intrusions include the 1032 0 1 5 ma lomond river granite and the 1022 0 2 0 ma lake michel igneous suite group ii intrusions include the 999 4 ma potato hill charnockite 993 7 ma horse chops granite 984 9 1 6 ma cloud river granite and may include the apsy granite the metamorphic history of the long range inlier is complex and three discrete proterozoic metamorphic events can

magnetization of extraterrestrial allende material may relate to terrestrial descend abstract the origin of magnetization in allende may have significant implications for our understanding of core formation differentiation dynamo processes in chondrite parent bodies the magnetic allende data may contain information that could constrain the magnetic history of allende the measurements on allende chondrules reveal an existence of magnetization component that was likely acquired during the meteorite transit to terrestrial conditions both the pyrrhotite carrying magnetic remanence intensity and direction of the chondrules change erratically when subjecting the allende meteorite s chondrules to temperatures near 77 k and back to room temperature chondrules with more intense original magnetization are denser and contain larger inverse thermoremanent magnetization itrm temperature dependent monitoring of itrm revealed that magnetization was acquired at temperature near 270 k such temperature is consistent with the condition when in addition to temperature increase the atmospheric uniaxial pressure applied during the meteorite entry on the porous material was responsible for meteorite break up in the atmosphere during this process collapse of the pore space in the matrix and some chondrules would generate crystalline anisotropy energy accumulation within pyrrhotite grains in form of parasitic magnetic transition

new tectonic divisions of the grenville province southeast canadian shield on the basis of geological geophysical and geochronological data the grenville province has been divided into three first order longitudinal belts the parautochthonous belt pb allochthonous polycyclic belt apb and allochthonous monocyclic belt amb these are set apart by three first order tectonic boundaries the grenville front gf allochthon boundary thrust abt and monocyclic belt boundary zone mbbz the belts are subdivided into terranes based on internal lithological character the gf separates the archean to proterozoic foreland northwest of the orogen from reworked equivalents to the southeast continuous at the scale of the orogen its main characteristic is that of a crustal scale contraction fault the pb although less clearly identified along the length of the orogen in most places represents upgraded and tectonically reworked rocks of the adjacent foreland the boundary between the pb and the apb to the southeast the abt is most clearly delineated in the eastern half of the province it is the locus of major crustal delamination along which high grade mostly middle proterozoic polycyclic terranes were tectonically transported northwest toward and onto the pb the amb comprises two separate areas underlain by the wakeham supergroup and what is currently known as the grenville supergroup respectively its basal contact the mbbz is a decollement zone of variable kinematic significance between older polycyclic rocks and tectonically overlying monocyclic rocks this first order zonation implies a tectonic polarity to the grenville province superimposed on which are second order features evident from contrasting tectonic styles and radiometric ages these characteristics are consistent with a diachronous or oblique collisional model for the grenville orogen

styles of proterozoic crustal growth on the southeast margin of laurentia evidence from the central grenville province northwest of lac st jean quebec the southeast margin of laurentia was a very long lived active continental margin part of whose history is recorded in the grenville province of the canadian shield within this province nd isotope mapping can be used to define the boundaries between terranes with a variety of crustal formation ages and can also distinguish between crustal growth by oceanic and continental arc magmatism the former gives rise to large terranes with homogeneous nd isotope signatures and well defined boundaries whereas the latter leads to areas with heterogeneous nd isotope signatures one of the best examples of continental arc magmatism in the grenville province is provided by the region northwest of lac st jean quebec eighty new nd isotope analyses are used along with aeromagnetic data to divide this area into three blocks bounded by abrupt changes in nd model age the western block consists almost exclusively of tonalitic grey gneisses with archean model ages the eastern block is composed almost exclusively of

detection of natural oil slicks in the nw gulf of mexico using modis imagery i we demonstrate the unique capability of the modis instruments in detecting oil slicks in an open ocean environment on 13 may 2006 in the nw gulf of mexico where water depth ranges from 50 to 2500 m one 250 m resolution modis image showed at least 164 surface slicks under sun glint glint reflectance l g ranged between 0 0001 and 0 06 sr 1 after discounting other possible causes we believe these are the result of natural seeps our analysis showed total coverage of 1900 km 2 with individual slicks varying in surface area 1 1 7 14 8 km 2 and length 19 2 12 4 km concurrent sar imagery showed similar area estimates to within 30 this estimate based on a single image is higher than earlier estimates from a database of multi date sar images for the same region inspection of 200 images for the month of may between 2000 and 2008 revealed similar slicks on at least 50 images on 2 june 2005 slicks were detected under sun glint with both negative contrast l g 0 05 sr 1 these slicks could not be detected in glint free modis images collected on the same day because of the near daily revisit and wide sun glint coverage e g 800 km e w between march and october at 25 n systematic and global application of the modis 250 m imagery can help locate natural seeps and improve estimates of seepage rates in the world s ocean

nd isotope mapping of allochthonous grenvillian klippen evidence for widespread ramp flat thrust geometry in the sw grenville province abstract over sixty new nd isotope analyses are used to constrain the extent of several small grenvillian lithotectonic domains that form erosional outliers of the grenvillian allochthonous polycyclic belt the identification of these tectonic klippen when combined with previous mapping of large nappes shows that the allochthonous polycyclic belt forms a mid upper crustal sub horizontal thrust sheet that was transported to the nw over the archean proterozoic parautochthon this thrust sheet was corrugated by folding and dissected by erosion leaving the klippen as synformal remnants nd isotope mapping of these remnants when coupled with seismic reflection data from the lithoprobe programme suggests that these thrust sheets were exhumed on relatively steep crustal scale ramps before transportation to the nw on sub horizontal shear zones this type of thrust geometry previously observed in the central eastern grenville province was termed ramp flat geometry by rivers et al 2012 re examination of lithoprobe seismic data for the georgian bay transect shows that reflectors under the parry sound klippe have a synformal character in the mid crust suggesting that this is also part of an undulose sub horizontal thrust sheet exhumed on a steep crustal scale ramp rather than the previous model of a very long ramp with low inclination hence we argue that the georgian bay section has a geometry resembling the ramp flat trajectory of the allochthon boundary thrust previously discerned elsewhere in the grenville province

nd isotope mapping of the allochthon boundary thrust on the shores of georgian bay ontario significance for grenvillian crustal structure and evolution nearly 50 new nd isotope analyses are presented for the shawanaga region of georgian bay ontario to study crustal evolution in the grenvillian central gneiss belt depleted mantle t dm nd model ages are used to map a major grenvillian tectonic boundary the allochthon boundary thrust abt which in the shawanaga area separates gneisses with t dm ages above and below 1 65 ga this is lower than the 1 8 ga age cut off observed further north and is attributed to a southward increase in mesoproterozoic magmatic reworking of an original palaeoproterozoic continental margin causing a progressive southward decrease in nd model ages between shawanaga island and franklin island nd isotope mapping yields an abt trajectory that closely matches published geological mapping and passes within 100 m of four retrogressed eclogite bodies typically associated with the thrust boundary this validation of the method gives confidence in the mapped trajectory south of snake island where sparse outcrop inhibits lithological mapping the new results suggest that published 1 7 1 9 ga t dm ages in the lower go home domain of the central gneiss belt further south are also indicative of parautochthonous crust hence we propose that the main ramp of the abt is located in the immediate hangingwall of the go home domain much further south than generally recognized this has important implications for the large scale crustal structure of the sw grenville province suggesting that the abt ramp has a similar curved trajectory to the grenville front and the central metasedimentary belt boundary thrust

mesoproterozoic basement of the lac st jean anorthosite suite and younger grenvillian intrusions in the saguenay region quebec structural relationships and u pb geochronology

nd isotopes and the origin of 1 9 1 7 ga penokean continental crust of the lake superior region nd isotopic data on 26 samples demonstrate the origin of the early proterozoic crust of the penokean orogen the three major components are 1 the marquette range supergroup a predominantly miogeoclinal continental margin sequence deposited before 1 85 ga on archean basement 2 ca 1 88 ga felsic metavolcanic rocks of the wisconsin magmatic terrane to the south of evolved island arc affinity and 3 1 87 1 76 ga granitoids that intrude the metavolcanic rocks initial nd values for the metavolcanic rocks of the magmatic terrane range between 0 0 and 2 4 and t dm ages between 1 9 and 2 2 b y the volcanic rocks primarily represent new crustal material that had only a limited archean input probably through mixing of subducted sediments into the magma source area nd t values for sedimentary rocks in the lower part of the marquette range supergroup indicate an archean source most likely the 2 7 ga superior province to the north on the other hand the sedimentary rocks in the upper part of the marquette range supergroup graywackes of the upper michigamme formation have initial nd values between 0 8 and 1 5 indicative of an early proterozoic source these graywackes probably are foredeep deposits derived from the volcanic rocks of the wisconsin magmatic terrane to the south thus the time of deposition of the upper michigamme formation dates the final convergence of the wisconsin magmatic terrane with the continental margin the granitoids of the wisconsin magmatic terrane have a wide range of nd t values from 4 5 to 4 0 they represent mixtures of variable amounts of new crustal material and recycled archean detritus the more negative nd t values occur in samples close to the northern boundary of the wisconsin magmatic terrane which is marked by a mylonitic shear zone the niagara fault zone we suggest that the miogeoclinal lower marquette range supergroup rocks having an archean nd signature became involved in magma genesis close to the collisional boundary whereas increasingly lesser amounts of this older material were available for mixing farther away from the suture the 1 9 1 7 ga penokean events involved major growth of new crust from the mantle

nd isotope mapping of the grenvillian allochthon boundary thrust in algonquin park ontario over 50 new nd isotope analyses are presented for high grade orthogneisses from algonquin park and surrounding region to map major grenvillian thrust boundaries nd model ages display a consistent

compact polarimetric synthetic aperture radar for marine oil platform and slick detection compact polarimetric cp synthetic aperture radar sar can provide ocean surface observations with large coverage swath and abundant polarimetric scattering information these distinctive characteristics make cp sar a potential tool for operational monitoring oil slicks and oil platforms overcoming the shortcomings of small spatial coverage by the traditional quad polarization quad pol sar in this paper we use the radarsat 2 c band quad pol sar data to generate cp covariance matrix elements and subsequently construct pseudoquad pol backscatter coefficients using two cp reconstruction algorithms to evaluate cp sar s applications in detection of oil slicks and oil platforms the reconstructed co and cross polarization data show good agreement with original radar observations acquired at different incidence angles and wind speeds furthermore we develop an unsupervised classification method using the relative phase a logical scalar threshold that separates odd and multiple scattering events as an indicator to discriminate oil slicks and platforms from clean ocean waters the relative phase is positive for clean ocean surfaces where odd scattering is dominant but negative for oil platforms and oil slick covered areas associated with multiple scattering the detections of oil spills and oil platforms are validated against known oil platform geographic positions and optical aircraft surveys of the oil slicks the proposed method provides a promising technique to detect oil slicks and oil platforms from cp imaging mode sar data i e as may be acquired by the risat 1 alos 2 and the future radarsat constellation mission

isotopic mapping of the allochthon boundary thrust in the grenville province of ontario canada abstract nd isotope analyses of orthogneissic rocks were conducted in the vicinity of the allochthon boundary thrust abt in the central gneiss belt of ontario canada gneisses from the parautochthonous belt have relatively homogeneous nd isotope signatures with an average tdm model age of 1 91 ga consistent with an origin as an accreted paleoproterozoic arc terrane barilia orthogneissic rocks from the overlying allochthonous belt have a wider range of model ages from 1 46 to 1 79 ga consistent with a more complex geological history that may involve reworking of sedimentary material in a long lived ensialic arc algonquia the isotopic boundary between these terranes represented by the abt is consistent with the distribution of distinct types of metabasic rock previously used as a criterion for recognising rocks of the allochthonous and parautochthonous belts of the grenville province however the location of the abt proposed on the basis of isotopic analysis has been modified from that of other workers because nd isotopes provide a much more detailed tool for mapping the original zone of convergence thrusting between allochthonous and parautochthonous terranes with distinct crustal formation ages the isotopic boundary is also supported by field based mapping of high strain zones in critical areas other mapped shear zones may represent later extensional structures with lesser geological significance

imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data a synergetic approach for quantitative analysis of high resolution ocean synthetic aperture radar sar and imaging spectrometer data including the infrared ir channels is suggested this approach first clearly demonstrates that sea surface roughness anomalies derived from sun glitter imagery compare very well to sar roughness anomalies as further revealed using these fine resolution similar to 1 km observations the derived roughness anomaly fields are spatially correlated with sharp gradients of the sea surface temperature sst field to quantitatively interpret sar and optical in visible and ir ranges images equations are derived to relate the surface roughness signatures to the upper ocean flow characteristics as developed a direct link between surface observations and divergence of the sea surface current field is anticipated from these satellite observations intense cross frontal dynamics and vertical motions are then found to occur near sharp horizontal gradients of the sst field as a plausible mechanism it is suggested that interactions of the wind driven upper layer with the quasi geostrophic current field via ekman advective and mixing mechanisms result in the generation of secondary ageostrophic circulation producing convergence and divergence of the surface currents the proposed synergetic approach combining sst sun glitter brightness and radar backscatter anomalies possibly augmented by other satellite data e g altimetry scatterometry ocean color can thus provide consistent and quantitative determination of the location and intensity of the surface current convergence divergence upwelling downwelling this in turn establishes an important step toward advances in the quantitative interpretation of the upper ocean dynamics from their two dimensional satellite surface expressions