assessing lnrf fr and ahp models in landslide susceptibility mapping index a comparative study of nojian watershed in lorestan province iran landslides and slope instabilities are major risks for human activities which often lead to economic losses and human fatalities all over the world the main purpose of this study is to evaluate and compare the results of landslide nominal risk factor lnrf frequency ratio fr and analytical hierarchy process ahp models in mapping landslide susceptibility index lsi the study case nojian watershed with an area of 344 91 km2 is located in lorestan province of iran the procedure was as follows first the effective factors of the landslide basin were prepared for each layer in the gis software then the layers and the landslides of the basin were also prepared using aerial photographs satellite images and fieldwork next the effective factors of the layers were overlapped with the map of landslide distribution to specify the role of units in such distribution finally nine factors including lithology slope aspect altitude distance from the fault distance from river fault land use rainfall and altitude were found to be effective elements in landslide occurrence of the basin the final maps of lsi were prepared based on seven factors using lnrf fr and ahp models in gis the index of the quality sum qs was also used to assess the accuracy of the lsi maps the results of the three models with lnrf 40 fr 39 and ahp 44 indicated that the whole study area was located in the classes of high to very high hazard the qs values for the three models above were also found to be 0 51 0 70 and 0 70 respectively in comparison according to the amount of qs the results of ahp and fr models have slightly better performed than the lnrf model in determining the lsi maps in the study area finally the study watershed was classified into five classes based on lsi as very low low moderate high and very high the landslide susceptibility maps can be helpful to select sites and mitigate landslide hazards in the study area and the regions with similar conditions

e i corrected paleolatitudes for the sedimentary rocks of the baja british columbia hypothesis paleomagnetic inclinations from sediments of the western terranes of canada are consistently too shallow for their reconstructed paleogeographic positions two contradicting explanations for these discrepancies are 1 terranes have been displaced northward with respect to the stable american craton by several thousands of kilometres between the late cretaceous 75 ma and the eocene 50 ma and 2 sedimentary inclination error has caused a shallow bias in the paleomagnetic directions here we apply the elongation inclination e i method to paleomagnetic data sets from sedimentary rocks of supposedly allochtonous terranes of western north america to correct for inclination flattening our results indicate that the paleomagnetic directions from the continental silverquick sediments 95 92 ma of southern british colombia are not seriously affected by inclination error because the magnetic signal most likely concerns a chemical remanent magnetisation crm in contrast the marine sediments of the nanaimo group 84 72 ma of vancouver island region appear seriously affected by inclination flattening f 0 7 and the e i corrected mean inclinations are about 98 steeper than the original data we arrive at corrected inclinations paleolatitudes of i 578 k 388n for the silverquick and i 558 k 368n for the nanaimo sediments our corrected paleolatitudes indicate that the canadian terranes were indeed located adjacent to the baja californian margin during the late cretaceous thus supporting the baja bc hypothesis d 2005 elsevier b v all rights reserved

arc and intraplate volcanism in the spences bridge group implications for cretaceous tectonics in the canadian cordillera the spences bridge group a late albian 100 ma age volcanic succession built on the western margin of superterrane i comprises two stratigraphic units with contrasting geochemistry the lower unit the pimainus formation represents a set of stratovolcanoes with calcalkaline character lavas of the overlying spins formation deposited as a shield volcano are hybrids between pimainus arc magma and spins type melts of intraplate affinity integration of regional geology suggests that the pimainus formation was produced by short lived easterly dipping subduction beneath superterrane i that convergence closed a narrow oceanic basin now represented by the methow tyaughton trough bringing superterrane ii into collision with superterrane 1 accretion in the latest albian resulted in cessation of pimainus are volcanism the eruption of spins lavas and easterly directed deformation of methow tyaughton strata early to middle cretaceous are volcanism of the gambier group on superterrane ii was produced by a separate concurrently active subduction zone

ni speciation in a new caledonian lateritic regolith a quantitative x ray absorption spectroscopy investigation abstract changes in ni speciation in a 64 m vertical profile of a new caledonian saprolitic lateritic regolith developed over ultramafic rocks under tropical weathering conditions were investigated by exafs spectroscopy quantitative analysis of the exafs spectra by linear combination least squares fitting lc lsf using a large set of model compound spectra showed that ni hosted in primary silicate minerals olivine and serpentine in the bedrock is incorporated in secondary phyllosilicates serpentine and fe oxides goethite in the saprolite unit and mainly in goethite in the laterite unit a significant concentration of ni up to 30 of total ni is also hosted by mn oxides in the transition laterite i e the lowest part of the laterite unit which contains large amounts of mn oxides however the amount of ni associated with mn oxides does not exceed 20 of the total ni in the overlying laterite unit this sequence of ni species from bedrock to laterite yields information about the behavior of ni during tropical weathering of ultramafic rocks the different ni distributions in phyllosilicates in the bedrock randomly distributed and in the saprolite unit clustered indicate two generations of ni bearing phyllosilicates the first which formed at higher temperature is related to serpentinization of oceanic crust whereas the second one which formed at lower temperature is associated with post obduction weathering of ultramafic rocks in addition the observed decrease in the proportion of ni hosted by mn oxides from the transition laterite to the upper lateritic horizons indicates dissolution of mn oxides during the last stages of differentiation of the lateritic regolith i e lateritization finally the ubiquitous occurrence of ni bearing goethite emphasizes the major role of this phase in ni speciation at the different weathering stages and suggests that goethite represents the major host for ni in the final tropical weathering stages of new caledonian ultramafic rocks

provenance of albian cenomanian rocks of the methow and tyaughton basins southern british columbia a mid cretaceous link between north america and the insular terrane basin analysis of albian cenomanian rocks of the tyaughton and methow basins suggests that the two basins were filled by three principle petrofacies during a regionally significant contractional ev

soil development on basic and ultrabasic rocks in cold environments of russia traced by mineralogical composition and pore space characteristics abstract recent soils from basic amphibolite and meta gabbro amphibolite and ultrabasic serpentinous dunite rocks formed in cold and humid climates of northern eurasia russia were studied to detail the characterization of soils and rocks with special attention to the interdependence of porosity system and rock mineralogy the study plots were located in taiga and tundra zones of east fennoscandia and the polar ural mountains a variety of methods was used including optical microscopy x ray diffraction and rietveld analysis and three supplemental methods for the determination of pore space characteristics in rocks i mercury intrusion porosimetry ii a modification of this method using the intrusion of a molten alloy wood s metal and iii scanning atomic force microscopy the results illustrate that the specification of the porosity system is a significant factor in tracing the clay mineralogy in soils formed from hard rocks ultrabasic rock is the most sensitive to weathering as determined by i the high value of small pores especially those with a radius of despite the presence of low proportions of phyllosilicates in both types of basic rocks only soil from meta gabbro amphibolite is enriched by clay minerals and is most probably affected by small pores

eocene paleo physiography and drainage directions southern interior plateau british columbia a map of reconstructed eocene physiography and drainage directions is presented for the southern interior plateau region british columbia south of 53 n eocene landforms are inferred from the distribution and depositional paleoenvironment of eocene rocks and from crosscutting relationships between regional scale geomorphology and bedrock geology of known age eocene drainage directions are inferred from physiography relief and base level elevations of the sub eocene unconformity and the documented distribution provenance and paleocurrents of early cenozoic fluvial sediments the eocene landscape of the southern interior plateau resembled its modern counterpart with highlands plains and deeply incised drainages except regional drainage was to the north an anabranching valley system trending west and northwest from quesnel and shuswap highlands across the cariboo plateau to the fraser river valley contained north flowing streams from eocene to early quaternary time other valleys dating back at least to middle eocene time include the north thompson valley south of clearwater thompson valley from kamloops to spences bridge the valley containing nicola lake bridge river valley and okanagan lake valley during the early cenozoic highlands existed where the coast mountains are today southward drainage along the modern fraser chilcotin and thompson river valleys was established after the late miocene

contrasting isotopic signatures between anthropogenic and geogenic zn and evidence for post depositional fractionation processes in smelter impacted soils from northern france abstract zinc isotopes have been studied along two smelter impacted soil profiles sampled near one of the largest pb and zn processing plants in europe located in northern france about 50 km south of lille mean 66zn values along these two soil profiles range from 0 22 0 17 2 to 0 34 0 17 2 at the lowest horizons and from 0 38 0 45 2 to 0 76 0 14 2 near the surface the 66zn values in the lowest horizons of the soils are interpreted as being representative of the local geochemical background mean value 0 31 0 38 whereas heavier 66zn values near the surface of the two soils are related to anthropogenic zn this anthropogenic zn occurs in the form of franklinite znfe2o4 bearing slag grains originating from processing wastes at the smelter site and exhibiting 66zn values of 0 81 0 20 2 the presence of franklinite is indicated by exafs analysis of the topsoil samples from both soil profiles as well as by micro xanes analysis of the surface horizon of a third smelter impacted soil from a distant site these results indicate that naturally occurring zn and smelter derived zn exhibit significantly different 66zn values which suggests that zinc isotopes can be used to distinguish between geogenic and anthropogenic sources of zn in smelter impacted soils in addition to a possible influence of additional past sources of light zn likely zn sulfides and zn sulfates directly emitted by the smelter the light 66zn values in the surface horizons compared to smelter derived slag materials are interpreted as resulting mainly from fractionation processes associated with biotic and or abiotic pedological processes zn bearing mineral precipitation zn complexation by organic matter and plant uptake of zn this conclusion emphasizes the need for additional zn isotopic studies before being able to use zn isotopes to trace sources and pathways of this element in surface environments

mesoscale and regional kinematics of the northwestern yalakom fault system major paleogene dextral faulting in british columbia canada the northwestern yalakom fault system yfs lies on the eastern margin of the coast belt in southwestern british columbia the yalakom fault is the most significant structure in the fault system with at least 115 km of dextral slip mostly of early tertiary age the nw yfs is up to 25 km wide and is bounded on the southwest by the tchaikazan fault zone which had 5 km or more of dextral slip kinematic and paleostress analysis of mesofaults and map scale structures shows that secondary faults within the nw yfs had both dextral and sinistral oblique slip three large synclines had increasing amounts of clockwise vertical axis rotation from southeast to northwest block rotation between two synthetic strike slip faults with large offset yalakom and moderate offset tchaikazan is similar to current kinematics between the san andreas and san jacinto faults in southern california the nw yfs was active from latest cretaceous to mainly eocene time and postdates early late cretaceous thrust faulting to the southwest early stage mesofaults are compatible with the thrust belt and suggest that open folds developed in the foreland of the thrust belt before strike slip faulting commenced the abrupt northwest termination of the yfs may be related to extension within the adjacent tatla lake metamorphic complex some dextral slip may have been transferred farther northwest through the coast belt but these structures have not been documented in west central british columbia most of the 120 km of dextral slip on the yfs was transferred to the north via a mosaic of normal and strike slip faults in central british columbia thus the yfs forms the southwestern margin of a broad zone of transtensional structures that extends to the tintina rocky mountain trench fault zone these structures accommodated northwestward displacement of the northwestern cordillera in paleogene time

the coast belt thrust system evidence of late cretaceous shortening in southwest british columbia the coast belt thrust system cbts is the leading edge of a west vergent contractional belt that formed along the inboard margin of the insular superterrane in late cretaceous time the foreland of this contractional belt comprises a system of east dipping frontal thrusts that imbricate jurassic and early cretaceous supracrustal arc sequences and related plutonic suites of the western coast belt wcb these faults root eastward into an imbricate zone of folded thrusts and out of sequence reverse faults across which the metamorphic gradient has been structurally inverted to the east and structurally above the imbricate zone is a folded stack of high pressure thrust sheets comprising metamorphosed island arc and oceanic rocks of the central coast belt ccb these rocks represent the exhumed crustal root of the cbts metamorphosed volcanic and volcaniclastic rocks that occur in thrust sheets of the imbricate zone yield u pb zircon dates which support a correlation with lower plate jurassic and early cretaceous arc sequences of the wcb structural and geochronologic data indicate a two stage history of late cretaceous shortening during the early stage of shortening supracrustal arc and related basin sequences along the inboard margin of the insular superterrane were structurally imbricated and accreted to the toe footwall of a westward prograding accretionary complex made up of previously assembled terranes of the ccb these early stage structures are represented by folded thrusts in the imbricate and hinterland zones of the cbts the timing of this early stage thrusting is bracketed by the emplacement of synorogenic plutonic suites which yield u pb zircon dates of 97 1 ma and 96 6 3 ma late stage shortening involved both thin skinned thrusting and folding of jura cretaceous arc sequences in the wcb foreland and out of sequence thrusting of higher grade thrust sheets in the imbricate and hinterland zones of the cbts in the foreland this episode of deformation is bracketed by late and postkinematic plutons which yield u pb zircon dates of 94 2 ma and 91 4 3 ma respectively in the imbricate zone this episode of deformation is bracketed by the emplacement of synkinematic and postkinematic plutons which yield u pb zircon dates of 96 6 3 ma and 94 6 5 ma respectively the development of thick skinned out of sequence thrusts in the imbricate and hinterland zones of the cbts signals a northeastward migration of the deformation front in late cretaceous time this shift in the locus of thrusting resulted in southwestward telescoping and structural inversion of the metamorphic hinterland and may account for the complex stacking order and thermal history of the southern coast belt

lithostratigraphic and tectonic framework of jurassic and cretaceous intermontane sedimentary basins of south central british columbia1this article is one of a series of papers published in this special issue on the theme of new insights in cordilleran intermontane geoscience reducing exploration risk in the mountain pine beetle affected area british columbia the south central intermontane belt of british columbia has a complex architecture comprising late paleozoic to mesozoic volcanic and plutonic arc magmatic suites marine and nonmarine clastic basins high grade metamorphic complexes and accretionary rocks jurassic and cretaceous clastic basins within this framework contain stratigraphy with hydrocarbon potential the geology is complicated by cretaceous to eocene deformation dismemberment and dislocation the eocene to neogene history of the southern intermontane belt is dominated by non arc volcanism followed by pleistocene to recent glaciation the volcanic and glacial cover makes this a difficult region to explore for resources much recent work has involved re evaluating the challenges that the overlying volcanic cover has historically presented to geophysical imaging of the sedimentary rocks in this region in light of technological advances in geophysical data collection and analysis this paper summarizes the lithological and stratigraphic fra

deciphering shallow paleomagnetic inclinations 1 implications from correlation of albian volcanic rocks along the insular intermontane superterrane boundary in the southern canadian cordillera 1 geologic and paleomagnetic data lead to two contradictory hypotheses regarding the paleoposition of the insular and intermontane superterranes that presently constitute the western canadian cordillera paleomagnetic data from the insular and intermontane superterranes suggest a southerly origin coinciding with the latitude of mexico and the northwest united states respectively during the mid cretaceous geologic evidence points to a northerly origin for these same tectonic entities during this period both models cannot be correct geologic and paleomagnetic data from the empire valley churn creek area in south central british columbia 51 5 n 122 5 w are critical to resolving these contradictory hypotheses late cretaceous rocks correlated to the insular superterrane with large paleomagnetic displacements unconformably overlie mid cretaceous rocks correlative to the spences bridge group of the intermontane superterrane we provide paleomagnetic evidence of this correlation based on similar magnetic properties opaque mineral assemblages demagnetization behavior fold test results mean inclinations clockwise vertical axes rotations and statistically indistinguishable paleomagnetic poles and displacement estimates this correlation and the observed geologic relationships in the empire valley churn creek area indicate that the insular and intermontane superterranes were linked by the mid cretaceous sites from the two previous spences bridge group studies are combined with their correlatives in the empire valley churn creek area to give 81 sites that yield a paleomagnetic pole of 60 5 n 304 5 e dp 3 7 dm 5 5 which corresponds to 1050 450 km of displacement from the south this new displacement estimate suggests that the spences bridge arc formed at the latitude of southern oregon during the mid cretaceous

deciphering shallow paleomagnetic inclinations 2 implications from late cretaceous strata overlapping the insular intermontane superterrane boundary in the southern canadian cordillera 1 significant discrepancies exist between paleomagnetic and geologic estimates of the timing and magnitude of terrane displacement in the southern canadian cordillera lithostratigraphic palynological geochronologic geochemical and structural data to which we add paleomagnetic data demonstrate that upper cretaceous strata in churn creek are laterally equivalent facies of the silverquick powell creek spc succession these rocks therefore comprise a single overlap sequence linking the insular and intermontane superterranes by late albian cenomanian time 95 ma contradicting previous assertions based solely on paleomagnetic interpretation that major 2000 km latitudinal displacement separated the two regions the churn creek succession retains primary magnetic remanence as demonstrated by positive fold conglomerate and contact tests the sediments do not hold the anisotropy signature of compaction shallowed inclinations the mean inclination of all spc sites from both mount tatlow and churn creek is 55 6 2 3 n 36 sites corresponding to a paleolatitude of 36 1 2 4 this reflects northward translation of the composite insular intermontane superterrane of 3050 450 km between 85 and 50 ma the silverquick powell creek succession at churn creek unconformably overlies the northern end of the spences bridge group a late early cretaceous volcanic arc assemblage on the intermontane superterrane paleomagnetic data in the companion paper place it 1050 450 km south of its current position between 100 and 105 ma integration of these new data sets require that the insular and intermontane superterranes formed a single enormous crustal block that underwent complex episodic south north translation between circa 105 and 50 ma the timing rate and vectors of translation are problematic in terms of geologic constraints along the continental margin

mobility of ni cr and co in serpentine soils derived on various ultrabasic bedrocks under temperate climate abstract serpentine soil is a common name for soils derived either from igneous peridotites or metamorphic serpentinites however differences in mineralogy of these rocks are responsible for some differences between soils occurring on peridotites and serpentinites in this study we analyze the mobility of ni cr and co in six serpentine sites derived from a variety of parent substrates from partially serpentinized peridotites through serpentinites containing relics of primary minerals and textures to proper serpentinites the mobility of ni cr and co determined using the edta extraction is the highest for ni whereas cr is the least mobile element in all soils studied no relationship between type of parent rock and cr mobility is found the lowest proportions of edta extractable fractions of ni and co up to 7 and 4 of total concentrations respectively are observed in soils derived from proper serpentinites devoid of primary minerals e g olivine pyroxene and having non pseudomorphic texture the highest proportions of edta extractable ni and co are noted in soils derived from partially serpentinized peridotite hornblende peridotite and serpentinite having typical pseudomorphic texture containing primary al rich magnesiochromite up to 18 and 16 of total concentration respectively it is therefore justified that type and origin of ultrabasic parent rock affect metal mobility at least in the case of ni and co in serpentine soils furthermore several soil characteristics such as ph total organic c soil mineralogy also play an important role in the mobility of ni cr and co however relationships between soil properties and metal availability are more pronounced for soils developed on proper serpentinites than for soils deriving from rocks that experienced less advanced serpentinization

paleomagnetism of the upper cretaceous strata of mount tatlow evidence for 3000 km of northward displacement of the eastern coast belt british columbia this study contributes the first paleomagnetic data from dated cretaceous units of the coast belt 51 3 n 123 8 w in which paleohorizontal bedding surfaces can be identified with certainty we sampled 38 sites through a 1 5 km stratigraphic interval of cenomanian silverquick sedimentary strata and cenomanian to campanian powell creek volcanics in the tatlow syncline in the tyaughton methow basin magnetizations at 21 sites have high unblocking temperatures tub and pass the tilt test precision k 5 before untilting maximum k 48 after 100 untilting magnetic minerals of volcanics show original textures mean declinations in volcanic and sedimentary rocks are statistically identical and polarity is consistently normal the mean inclination 55 4 3 4 probability p 0 05 of this pretilting magnetization is 20 1 4 0 shallower than that expected if the rocks were deposited in their present position relative to cratonic north america field and laboratory observations rule out other causes for these anomalous shallow inclinations these rocks therefore have been displaced northward by 3000 500 km relative to cratonic north america since mid cretaceous time this displacement is almost 3 times greater than that estimated from mid cretaceous volcanics in the now adjacent intermontane belt evidently the two belts were not amalgamated until latest cretaceous or early tertiary time these results are inconsistent with all previous geologically based tectonic reconstructions of the cordillera magnetizations at eight sites in silverquick and powell creek beds have low tub and directional characteristics similar to those in three younger diorite intrusions reversed and normal polarities occur the rocks are commonly highly altered and maximum precision occurs after 40 untilting the magnetizations therefore are interpreted as overprints of latest cretaceous age acquired during folding

on determining paleohorizontal and latitudinal shifts paleomagnetism of spences bridge group british columbia the spences bridge group of late albian age palynology and u pb zircon date of 104 5 ma is situated in the intermontane belt of the southern canadian cordillera zeolite grade andesite lavas and interbedded volcaniclastic rocks have been sampled through a thickness of about 2900 m sampling has been confined to localities whose bedding attitudes are well defined and to rocks that have not undergone internal deformation of the 27 sites studied 25 gave single component magnetizations with well grouped directions high coercivities and high unblocking temperatures applying corrections for geological tilt to all 25 sites yielded minimum dispersion after 65 untilting analysis indicates that this is a consequence of the interaction of two modes of behavior one exhibited by y magnetizations at 8 sites in which minimum dispersion occurs after 35 untilting and one x magnetizations at 17 sites in which minimum dispersion occurs after 100 correction actually the dispersion is essentially constant in the range 88 to 100 correction the y magnetizations are uninterpretable in terms of the paleofield because no estimate of paleohorizontal can be made because of their positive response to the tilt test the x magnetizations were acquired before tilting and it is argued that geologically determined bedding planes are good estimators of paleohorizontal at the time of remanence aquisition there may be errors because of paleoslope but arguments are presented for believing that these are small on this basis the best estimate of the mean direction of the paleofield in spences bridge time is estimated to be d i declination inclination 38 7 63 9 17 sites k 44 compared with k 11 in situ 95 5 4 with a paleopole at 64 4 n 321 0 e k 24 compared with k 5 in situ a95 7 5 when compared with the cratonic reference field for mid cretaceous time this pretilting magnetization indicates a clockwise rotation of the study area of 66 3 11 8 p 0 05 and an apparent displacement from the south of 15 5 7 1 1725 790 km when these and other data previously obtained from cretaceous rocks of the pacific northwest are compiled they show an increase in apparent displacement from east to west across the cordillera this result is discussed in terms of three hypotheses 1 no translation but systematic tilts of about 30 to the southwest 2 translation of a substantial part of the pacific northwest referred to as baja british columbia and is defined more exactly in the text by variable amounts up to more than 2000 km from the south together with clockwise rotations and 3 lesser translation of baja british columbia by about 1500 km combined with variable tilting predominantly to the south it is concluded that paleomagnetic data as they are presently known are consistent with hypotheses 2 and 3 but unless serious sources of error are present are not consistent with hypothesis 1 the most likely candidate for such errors is the uncertainty in estimating initial dip of beds paleoslope in volcanic rock units

interpretation of structures in the southeastern nechako basin british columbia from seismic reflection well log and potential field data1this article is one of a series of papers published in this special issue on the theme of new insights in cordilleran intermontane geoscience reducing exploration risk in the mountain pine beetle affected area british columbia 2geological survey of canada contribution 20100002 the structure and stratigraphy of the southeast nechako basin which are poorly understood primarily because of substantial volcanic cover are investigated in an analysis of seismic reflection well and potential field data formation and development of the se nechako basin resulted in sub basins containing cretaceous and eocene rocks interpretation reveals that dextral transtension in the early to middle eocene created nnw trending en echelon strike slip faults linked by pull apart basins which locally contain a thickness of eocene volcaniclastic rocks of 3 km this structural pattern is consistent with regional observations that suggest the transfer of slip from the yalakom fault to the north via a series of en echelon strike slip faults in the middle to late eocene faults associated with a change in the direction of stress echoed by the north trending right lateral fraser fault reactivated and cut earlier structures a simple model agrees with local observations that northeast directed comp

using leaf margin analysis to estimate the mid cretaceous albian paleolatitude of the baja bc block abstract the baja bc hypothesis which postulates that western washington state british columbia and southern alaska originated at the latitude of mexico has pitted paleomagnetic results against long held interpretations about the tectonic evolution of western north america in this paper we develop a new paleobotanical method for estimating paleolatitude and apply it to this problem we start by showing that the modern mat field for north america is well correlated with latitude demonstrating the feasibility of using mat to estimate paleolatitude a compilation of mat and floral data from 84 modern sites in central and north america is used to establish a new prediction relationship mat 1 32 28 99p where p is the proportion of smooth margined species within a floral sample at a site our analysis also includes a more complete estimate of the uncertainties associated with estimating mat from a measurement of p using modern data we show that mat and p can be used to estimate latitude as well we then apply this approach to resolve the paleolatitude of baja bc eleven floral sites from stable north america are used to establish the latitudinal mat profile for north america during the albian and cenomanian a floral site from the winthrop formation a mid cretaceous 110 100 ma fluvial unit in the methow basin of northern washington state is linked to the baja bc block and predates its proposed northward offset forty three morphospecies of dicotyledonous angiosperm leaves from the winthrop formation give p 0 76 which is equivalent to a mat of 23 4 c indicating a subtropical to tropical climate we use the north american mat profile to estimate a paleolatitude of 38 4 n for the winthrop flora indicating 2200 km of northward offset relative to stable north america

the rattlesnake creek terrane klamath mountains california an early mesozoic volcanic arc and its basement of tectonically disrupted oceanic crust the rattlesnake creek terrane in the south western klamath mountains consists of a serpentinite matrix melange basement unconformably overlain by a coherent cover sequence of upper triassic and lower jurassic volcanic hemipelagic and clastic sedimentary rocks both the meelange and cover sequence are intruded by a suite of ca 193 207 ma u pb zircon gabbroic to quartz dioritic plutons these rocks collectively record a complex multistage evolution through several distinct tectonic environments blocks in the meelange basement include peridotite greenstone amphibolite pillow basalt various generally mafic plutonic rocks metachert and limestone all suspended in a matrix of sheared serpentinite trace element chemistry indicates that basalt amphibolite and greenstone blocks were derived from normal to enriched mid oceanic ridge basalt n morb to e morb and within plate basalt wpb protoliths there is no geochemical evidence that any blocks were derived from a magmatic arc nor do any of the sedimentary rocks contained within the meelange reflect deposition near a terrigenous sediment source collectively these relations indicate that the basement meelange was derived by disruption of oceanic crust and upper mantle in a setting far removed from either an arc or a terrigenous landmass and are most consistent with an interpretation that meelange formation oc curred in an oceanic fracture zone the overlying cover sequence is divisible into a stratigraphically lower salt creek assemblage and a stratigraphically higher dubakella mountain assemblage both deposited in a marine setting volcanic rocks in the lower assemblage are basaltic pillow lava and pillow breccia with the trace element characteristics of a primitive island arc tholeiite suite whereas those in the upper assemblage are predominantly chnopyroxene phyric basalt to basaltic andesite and compositionally similar volcaniclastic rocks with the geochemical characteristics of a more evolved cale alkaline to shoshonitic volcanic arc suite the geochemical character of these volcanic rocks is indistinguishable from that of the coeval early mesozoic plutons leading to the conclusion that these plutons represent the intrusive roots of the volcanic succession collectively these rocks reflect construction of a late triassic to early jurassic island arc and indicate that subduction had initiated within or near the under lying fracture zone assemblage by at least the late triassic the latest stages of crustal disruption in the basement thus probably occurred in a subduction zone environment both cover sequence units also contain inter layered chert and argillite as well as coarse epiclastic rocks with an abundance of quartzose sedimentary and metasedimentary grains these elastic rocks provide the first evidence for terrigenous input into the rattle snake creek terrane and indicate that the early mesozoic arc developed in proximity to a terrigenous sediment source probably paleozoic rocks of the western north american cordillera several lines of evidence suggest that early mesozoic arc magmatism was accompanied by an episode of extensional tectonism these include structural evidence for an early mesozoic phase of high angle faulting that appears to have localized cover sequence deposition in fault bounded grabens sedimentologic evidence indicating that both the basement and terrigenous sediment sources experienced episodic pulses of uplift and erosion during cover sequence deposition and widespread intrusion of arc plutons into the upper crustal levels of the are carapace both the basement complex and the early mesozoic arc assemblage of the rattlesnake creek terrane were then deformed by thrust faulting folding and penetrative foliation development during over thrusting from the east by the western hayfork terrane in the middle jurassic regional de formation was in response to northeast south west directed shortening and was accompanied by metamorphism to subgreenschist grade insofar as the western hayfork terrane represents part of a middle jurassic arc whose plutonic roots intrude most klamath mountain terranes east of and including the rattle snake creek terrane it is clear that the rattlesnake creek terrane formed part of the klamath mountain province by middle jurassic time the paleogeographic and tectonic relation of the rattlesnake creek terrane to the rest of the klamath mountains prior to the middle jurassic however is unclear

topographic and soil differences from peridotite to serpentinite pedologists commonly lump peridotite and serpentinite soils together without reporting differences between them peridotite and serpentinite are chemically similar but mineralogically quite different a detailed soil survey in which soils with peridotite and serpentinite parent materials were separated in mapping revealed appreciable differences in geomorphic and pedologic features between these two types of ultramafic rocks in mountainous terrain of the klamath mountains california and oregon slopes tend to be steeper on peridotite and the soils redder more luvisols alfisols were found on peridotite and more phaeozems mollisols on serpentinite very shallow soils 7 of the area which are leptosols mostly mollisols and entisols few alfisols are more common on serpentinite sparsely vegetated barrens are commonly fragmental colluvium talus on peridotite and erodible slightly to moderately stony summits and sideslopes on serpentinite large landslides are much more extensive in serpentinite terrain vegetative cover differences from peridotite to serpentinite are much less pronounced than the topographic and soil differences the plant differences are obvious only on shallow soils

the gang ranch big bar area south central british columbia stratigraphy geochronology and palynology of the tertiary beds and their relationship to the fraser fault tertiary rocks in the gang ranch big bar area south central british columbia consist of 1 early or middle eocene 50 ma lavas breccias and tuffs capped by a mappable unit of conglomerate a

mid cretaceous thrusting in the southern coast belt british columbia and washington after strike slip fault reconstruction a major thrust system of mid cretaceous age is present along much of the coast belt of northwestern north america thrusting was concurrent and spatially coincided with emplacement of a great volume of arc intrusives and minor local strike slip faulting in the southern coast belt 52 to 47 n thrusting was followed by major dextral slip faulting which resulted in significant translational shuffling of the thrust system in this paper we restore the displacements on major dextral slip faults of the southern coast belt and then analyze the mid cretaceous thrust system two reconstructions were made that use dextral faulting on the yalakom fault 115 km castle pass and ross lake faults 10 km and fraser fault 100 km the reconstructions differ in the amount of dextral offset on the straight creek fault 160 and 100 km and how much the ne part of the cascades crystalline core expanded 30 km and 0 km during eocene extension reconstruction a produces the best match of lithotectonic units and thrust systems our synthesis shows that the southern coast belt thrust system was 250 180 km wide after thrusting the thrust system was mainly southwest vergent but had a belt of northeast vergent back thrusts on the northeast side associated with the tyaughton methow basin which may indicate large scale tectonic wedging thrust faults are commonly low to moderate angle but high angle faults also occur especially as late stage out of sequence structures involving plutons the amount of thrust displacement across the system is unknown but must be at least 100 km and may be many hundreds of kilometers most thrusting occurred from 100 to 80 ma and did not migrate systematically until after 90 ma when thrusting and magmatism shifted to the northeast for a few million years widespread thrusting occurred both near plutons and where there are no or small plutons which strongly suggests that thrust faulting was caused by regional to plate scale forces such as rapid plate convergence and or arc continent collision

the eocene oligocene magmatic hiatus in the south central canadian cordillera a capture of the kula plate by the pacific plate the tertiary paleogene and neogene geological record in south central canadian cordillera is dominated by the 350 400 km wide lower eocene volcanic arc and the overlying miocene recent back arc lavas that are separated by a hiatus in magmatic activity between 48 and 24 ma in the black dome area 240 km north of vancouver the eocene volcanic rocks are mainly continental margin calc alkaline andesite and dacite resulting from the melting of a juvenile mafic source at the base of the crust in contrast the miocene volcanic rocks resemble continental flood basalts both eocene and miocene rocks from the black dome volcanic complex have high positive end values 7 2 to 7 4 and 6 4 to 7 6 respectively and low initial sr isotopic ratios 0 702 516 0 703 528 and 0 703 376 0 703 392 respectively comparable to modern oceanic basalts the onset of the hiatus in magmatism at 48 ma coincides with capture of the kula plate by the pacific plate resulting in a change in convergence direction with the

the conglomerate of churn creek late cretaceous basin evolution along the insular intermontane superterrane boundary southern british columbia upper cretaceous coarse clastic rocks exposed in the canyon of churn creek south central british columbia record active basin tectonism and coeval volcanism adjacent to the boundary between the intermontane and insular superterranes mid to late albian 104 ma u pb calc alkaline andesite and basaltic andesite flows with minor conglomerate and reworked epiclastic deposits and tuffs correlative with the spences bridge group of the intermontane superterrane are exposed in the canyon in depositional contact above the volcanic rocks is the conglomerate of churn creek which contains a thick 1 km sequence of complexly intertonguing conglomerate and sandstone that is divided into two members composed of four lithofacies the lower member was deposited unconformably on the underlying albian volcanic unit and contains late albian cenomanian chert pebble 50 chert conglomerate and interbedded chert and volcanic lithic sandstone it is interpreted to have been deposited in a braided stream system flowi

syntectonic remagnetization in the southern methow block resolving large displacements in the southern canadian cordillera 1 the upper cretaceous ventura member of the goat wall unit in the southern methow block of southern british columbia and northern washington state holds a syntectonic magnetization eight new sites from manning park in british columbia give a mean direction of d 27 5 i 60 1 k 304 7 95 3 2 after optimal partial tilt correction of five groups of bedded sites from farther south in the basin reported by bazard et al 1990 four have a syntectonic remanence with a direction similar to what we observe the exception is one group which has optimal concentration of remanence directions on 100 untilting and an abherent direction which must be rejected combining the accepted sites the optimal differential syntilting direction is d 11 8 i 61 5 k 39 3 95 3 4 n 47 giving a mean pole of 79 8 n 359 2 e k 19 5 and a95 4 8 the age of the remagnetization is constrained to be between 88 and 80 ma compared to cratonic north america this result indicates that the southern methow block was displaced from the south by 1800 500 km meaning it lay south of the sierra nevada subduction zone but well north of other paleomagnetically constrained cretaceous rock units from the insular superterrane including correlative strata of the mount tatlow area in the northern methow block among several possibilities to reconcile this discrepancy the most plausible has the whole methow block translated coherently but with the southern methow block strata remagnetized during transit

landslide susceptibility mapping in bijar city kurdistan province iran a comparative study by logistic regression and ahp models landslides and instability slopes are major risks for human activities which often lead to losing economic resources and damaging properties and structures the main aims of this study are identifying the underlying effective factors of landslide occurrence in bijar kurdistan province and evaluating the regions prone to landslide to prepare the susceptibility map using the logistic regression lr and analytical hierarchy process ahp at first using field surveys questionnaires geological and topographic maps and reviewing the related studies ten effective factors including the elevation of sea level slope inclination slope aspect geology distance from the linear elements fault road and river precipitation and land use were recognized then they were processed using arc gis 10 and ilwis 33 the dependent variable included 144 of slopes prone to landslide selected across the region as the landslide data code 1 and also 144 stable landslide slopes were randomly selected as landslide free data code 0 the results of the evaluation showed that lr model with pcpt index equals to 83 4 2ll index equals to 229 226 and roc index equals to 98 5 and landslide susceptibility map based on scai index had high verification in the case study therefore 75 489 of the area had very low susceptibility 10 037 low susceptibility 3 628 moderate susceptibility 4 062 high susceptibility and 6 784 very high susceptibility based on the preferences of the ahp method the weighting of selected parameters was logically performed so that the parameters could be arranged according to their priorities the results of the ahp model showed that 3 4 of the area had very low susceptibility 30 43 low susceptibility 46 68 moderate susceptibility 18 14 high susceptibility and 1 33 very high susceptibility