neogene tectonic rotation of the santa ynez range western transverse ranges california suggested by paleomagnetic investigation of the monterey formation a paleomagnetic investigation was conducted on dolomite beds in the middle and upper miocene monterey formation in order to determine the timing and amount of post early miocene tectonic rotation experienced by the santa ynez range part of the western transverse ranges province of california five stratigraphic sections of the monterey formation exposed along the coastline west of santa barbara were extensively sampled the sections were correlated using tuff beds and ages were assigned to each dolomite bed on the basis of magnetostratigraphy and diatom biostratigraphy the dolomite beds possess stable primary remanent magnetic directions which pass fold tests and reversal tests and show a consistent decrease in magnetic declination with decreasing age rocks 14 8 to 15 8 m y old have a mean magnetic declination of 92 7 whereas rocks 8 to 11 m y old have a mean magnetic declination of 36 7 the consistent upsection decrease in magnetic declination within these stratigraphic sections is attributed to a rapid 56 10 clockwise rotation of the entire santa ynez range between 15 2 0 1 and 10 1 m y b p the mean magnetic declination of 36 7 in rocks 8 to 11 m y old is probably due to continued clockwise rotation of the santa ynez range during the plio pleistocene an early miocene palinspastic reconstruction is proposed in which the area of the presently east west trending santa ynez range is restored to an initially north south orientation

tectonic implications of paleomagnetic and geochronologic data from the yukon koyukuk province alaska the paleomagnetic and geochronologic record of alaska is complicated by overprints that make it difficult to relate the terranes of northern and southern alaska to each other and to north america to better understand these relationships and the overprinting paleomagnetic and k ar dating samples were analyzed from the three major geologic units of the yukon koyukuk province ykp of central alaska these units consist of a basal jurassic early cretaceous volcanic island arc assemblage albian cenomanian clastic sedimentary rocks and bimodal eocene volcanic rocks k ar age determinations of the early tertiary volcanic rocks form two distinct groups the older group 65 49 ma is mostly felsic and probably represents the maximum inboard penetration of low angle subduction related volcanism these older rocks were deformed during the regional deformation of the ykp the younger group 44 43 ma is post deformational and composed dominantly of basalt these results bracket a time 49 44 ma when deformation ceased in the province this time interval is coincident with a major transition from convergence to strike slip and extensional tectonic style throughout alaska the geologic units of the ykp display two characteristic paleomagnetic signatures primary directions based on positive reversal conglomerate and or bedding tilt stability tests were obtained from the albian cenomanian sedimentary rocks and eocene volcanic rocks the mid cretaceous sedimentary rocks show about 15 of poleward motion between 90 56 ma a time of high rates of convergence between alaska and the pacific and eurasian plates age equivalent rocks from neighboring regions st matthew island and the alaskan north slope also indicate similar amounts of poleward northward motion which suggests that the whole of western and northern alaska may have moved northward about 10 relative to north america as a more or less coherent block paleomagnetic results from the eocene volcanic rocks indicate that the ykp was in place by 56 ma and formed part of the accretionary nucleus that served as a backstop for the accreted terranes of southern alaska secondary remagnetized directions are recorded in the basal island arc assemblage and in albian cenomanian sediments near younger igneous occurrences the clustering of secondary directions in the geographic reference frame indicates that they were acquired after deformation ceased 49 44 ma which is consistent with the coincidence of the mean of these directions and the 54 44 ma north american reference direction

accretion of southern alaska abstract paleomagnetic data from southern alaska indicate that the wrangellia and peninsular terranes collided with central alaska probably by 65 ma ago and certainly no later than 55 ma ago the accretion of these terranes to the mainland was followed by the arrival of the ghost rocks volcanic assemblage at the southern margin of kodiak island poleward movement of these terranes can be explained by rapid motion of the kula oceanic plate mainly from 85 to 43 ma ago according to recent reconstructions derived from the hot spot reference frame after accretion much of southwestern alaska underwent a counterclockwise rotation of about 50 as indicated by paleomagnetic poles from volcanic rocks of late cretaceous and early tertiary age compression between north america and asia during opening of the north atlantic 68 44 ma ago may account for the rotation

strike slip faulting and block rotation in the lake mead fault system strike slip faults in the basin and range province have often been considered passive boundaries between differentially extended domains of tilted normal faults and are thus considered secondary in accommodating regional horizontal deformation paleomagnotic investigation of late miocene age volcanic rocks displaced by the left lateral fault system of lake mead nevada shows 1 that these rocks have not been affected by significant structural tilt the difference between observed and expected inclinations being only 0 6 14 9 and 2 a significant horizontal counterclockwise rotation of 29 4 8 5 about a vertical axis this rotation was accommodated by slip on northwest trending right lateral strike slip faults this implies significant west northwest elongation results of the investigation indicate that strike slip faulting is the primary process accommodating crustal deformation along the lake mead fault system and that tilting in response to normal faulting is secondary

oroclinal bending of the southern sierra nevada batholith structural magmatic and isotopic features of the southern sierra nevada batholith are deflected clockwise with respect to its central and northern parts directions of magnetization at three localities in the southern sierra nevada are progressively deflected this is consistent with the hypothesis that the region was tectonically rotated in an orocline no paleomagnetic deflection was observed northwest of the white wolf kern canyon fault system oroclinal bending ofa block bounded by the san andreas garlock and white wolf kern canyon faults may have occurred before about 16 x l06 years ago the deformation may have been a response to shear at the western boundary of the north american plate caused by oblique subduction

paleomagnetism of cretaceous volcanic rocks from central chile and implications for the tectonics of the andes the mean direction of remanent magnetization in well dated structurally and petrologically simple cretaceous ash flow tuffs from the central valley of chile near santiago indicates that the region has undergone a small about 14 clockwise rotation two other paleomagnetic studies on cretaceous rocks from coastal chile give a similar result we tentatively attribute these rotations to dextral shear caused by oblique subduction of the nazca plate beneath south america in contrast cretaceous rocks from peru seem from paleomagnetic evidence to have been rotated counterclockwise relative to the stable interior of the continent this sense of apparent rotation agrees with the sense of deflection of geologic trends from north south to north northwest at about the peru chile border the arica deflection on the basis of these observations several authors have suggested that the arica deflection is an orocline however uncertainty in all such paleomagnetic interpretations is introduced by what seems to be a very streaked distribution of cretaceous reference poles from the south american craton the cause of this streaking is not known

mesozoic paleomagnetism and northward translation of the baja california peninsula paleomagnetic data from cretaceous igneous and sedimentary rocks of the peninsular ranges and continental borderland of the baja california peninsula yield an average pole position of 83 n 344 e a95 3 4 suggesting that the peninsula as a whole has moved northward 11 and rotated 32 clockwise with respect to the north american craton since cretaceous time only a small portion of this movement is due to the neogene opening of the gulf of california results from stratified rocks giving both positive and negative fold tests are included in the average cretaceous pole the rocks that fail fold tests have been deformed and remagnetized by nearby intrusives that are only slightly younger unconnected directions from these sites closely match corrected directions from sites where the fold tests are positive oceanic rocks were also sampled in the continental borderland from upper triassic and upper jurassic tectonostratigraphic terranes which are apparently allochthonous with respect to the western baja peninsula and each other these oceanic rocks show magnetizations indicating low paleolatitudes although the hemisphere of origin is presently unknown the cretaceous rocks of the baja california peninsula may have originally formed adjacent to the now truncated continental margin along the northern middle america trench northward transport of the peninsula probably occurred by transcurrent faulting associated with oblique subduction of the farallon plate beneath western north america between late cretaceous and late miocene time

application of paleomagnetism to accretionary tectonics and structural geology the use of paleomagnetism to determine translations and rotations of geologic terranes has contributed to a better understanding of deformation within accretionary complexes shear zones and rifts in this report to the i u g g we review the progress resulting from paleomagnetic studies during the last four years in the cordillera of north america the appalachian orogen and the circum pacific region

additional paleomagnetic results from the sierra nevada further constraints on basin and range extension and northward displacement in the western united states modal analysis of new paleomagnetic results that have a skewed distribution from four plutons in the kings canyon national park area central sierra nevada produces a pole position concordant with the results of frei and others 1984 from the yosemite area these studies suggest a that stable magnetization resides in the more mafic plutons and inclusions in the sierra nevada and b that the amount of internal deformation within the central sierra nevada does not exceed a few degrees at the 95 confidence level the mean pole of both studies limits the relative displacement between the sierra nevada and cratonal north america to 6 8 of clockwise rotation and 6 6 of poleward displacement the clockwise rotation agrees well with the model of frei and others 1984 for basin and range extension which predicts 2 of clockwise rotation for the sierra nevada the poleward displacement suggests right lateral shear of 600 km within the basin and range between 90 and 35 ma

paleomagnetic study of devonian rocks from ste cecile st sebastien region quebec appalachians three devonian rock units were collected for paleomagnetic study from the ste cecile st sebastien region located in the gaspe connecticut valley synclinorium of quebec appalachians 15 sites 48 samples from the metasediments subgreenschist facies siltstones sandstones of the compton formation early middle to late early devonian age based on fossil plants which were tightly folded during middle devonian acadian orogeny 14 sites 61 samples from the ste cecile st sebastien granitic body 362 m y k ar age which intruded the metasediments 14 sites 62 samples from the hornfels created subsequent to the emplacement of the intrusive detailed thermal cleaning of the metasediments yielded a mean remanence direction characterized by linear vector trajectories after tilt correction at d 209 i 20 k 30 95 7 2 with unblocking temperature spectrum 300 550 c carried probably by magnetite the predeformational origin of this remanence is tested at 99 confidence level as well as antipodal normal and reverse polarity directions the corresponding paleomagnetic pole ms falls at 28 n 77 e dp dm 6 11 in agreement with the recently reported poles which are mostly early devonian in age and derived from the southeastern margin of the presumed proto atlantic ocean af demagnetization of granites resulted in a univectorial mean remanence at 1 d 332 i 39 k 31 for n 5 sites in fine grained granite fg unit 2 d 313 i 25 k 19 for n 9 sites in medium grained granite mg unit and 3 d 319 i 30 k 17 for all the total n 14 granite g sites af demagnetization of hornfels revealed a post intrusive mean remanence direction hf at d 346 i 22 k 8 for n 14 sites the individual site mean remanence directions with coercivity spectra 10 60 mt from both granites and hornfels suffer from a large declination spread of about 60 but the confidence ovals for the fg and hf remanences overlap this indicates that the fg and hf remanences are indistinguishable from each other and therefore are proximal in time and probably originated during middle to late devonian period interpretation of this kind is speculative in the absence of a convincing evidence for a two fg younger than mg or three phase intrusive history of the pluton since the pole positions of g 18 n 150 e mg 18 n 158 e fg 18 n 137 e and hf 32 n 125 e spread over 40 in longitude these data cannot confirm or negate the possibility of a mid paleozoic transcurrent motion proposed for northern appalachians we regard only the pole ms with probable late early or early middle devonian age as reliable for the apparent polar path construction

block rotation by strike slip faulting structural and paleomagnetic evidence geometric analysis shows that motion of sets of strike slip faults should cause block rotation otherwise the distorted fault domain would not fit with its surrounding the sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults all of which can be obtained from structural data the predictions of the geometric model can then be independently tested by paleomagnetic measurements the model was tested in northern israel structural data reveal several domains of contemporaneous right and left lateral strike slip faults paleomagnetic measurements show that in a domain of nnw trending left lateral faults blocks rotated 23 3 8 2 clockwise and in a domain of right lateral faults blocks rotated 22 4 9 0 anticlockwise these results are in agreement with the prediction of the geometric analysis of the structure the combined results of the heterogenous deformation of the area resembles a pure shear which allows n s extension by about 1 3 in other domains rotations of 34 6 9 1 and 53 1 11 0 were found in their original orientation the left and right lateral faults intersected at angles of 60 70 enclosing the principal axis of shortening in accordance with theories of brittle failure as a result of block rotations this angle is now larger and may reach 110 the results demonstrate large block rotations in different senses in domains of strike slip faults the independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model northern israel is considered to be a good model for this efficient mechanism of intraplate deformation which is expected to occur in similar tectonic settings elsewhere

paleomagnetic evidence for spatially distributed post miocene rotation of western washington and oregon anomalous paleomagnetic directions have been determined for 17 sites in the frenchmans springs member of the wanapum basalt formation columbia river basalt group these sites are located in the ginkgo flows from near vantage washington to portland oregon a distance of approximately 300 km the average paleomagnetic direction for six of these sites centered around vantage is d 147 i 41 95 4 5 the expected miocene field direction is d 355 i 65 at some localities there are two distinct ginkgo flows in direct stratigraphic succession with statistically identical anomalous directions their anomalous paleomagnetic direction makes these flows a valuable marker horizon in the columbia river basalt group the nondipole field direction of the ginkgo flows correlates well with available results from the miocene cape foulweather basalts of oregon this correlation strongly supports the hypothesis that these coastal basalts of oregon are the distal ends of columbia plateau derived basalt flows the spatial distribution of these anomalous field directions suggests about 14 of clockwise rotation between vantage and portland combining these data with data from the oregon coast basalts allows a maximum declination difference of about 35 the increase in declination can be best explained by clockwise rotation about nearby vertical axes increasing to the southwest across the columbia plateau and oregon coast

observations and modeling of thermally induced stresses in first year sea ice during spring 1992 ice property geophone meteorological and stress data were collected on first year ice southwest of cornwallis island within the canadian archipelago one of the goals of the study was to specify the average characteristics of the ice use these characteristics in a model of thermally induced stresses in the ice and examine the fracturing associated with the occurrence of those stresses the results of simulations with a thermal stress model indicate that stress variations within the ice can be reasonably approximated by a viscoelastic rheology the rheology takes into consideration thermally induced strains generated locally as well as strains generated elsewhere and then mechanically transmitted through the ice the geophone data showed both ice borne and water borne propagation paths for individual fracturing events the data imply a detection radius out to 500 600 m for the ice borne signatures of fractures an investigation of a region after fracturing showed that 1 fracturing occurred in an area with a 10 to 15 cm snow cover 2 the snow cover had been scored down to the surface of the ice and 3 cracks in the ice were found under each location where the snow had been scored the cracks were 5 6 m long and at least 15 cm deep a review of these and other experimental results draw us to the conclusion that the forces required to produce fractures in response to natural forcing is greater for first year floes than for multiyear floes

post 12 million year clockwise rotation in the central columbia plateau washington the pomona flow 12 m y b p of the columbia river basalt group was sampled for paleomagnetic analysis at 32 sites in the yakima fold belt of the central columbia plateau to assess the pattern of deformation field directions from anticlinal ridges are found to be rotated clockwise relative to sites from synclinal areas two geographic patterns of rotation are present the primary pattern is one in which the greatest amount of rotation occurs in the crest hinge area of the anticlines and decreases into synclines a secondary pattern in which the amount of rotation is consistent within a geometric segment but varies among them is superimposed on the primary pattern the pattern of clockwise rotation is interpreted to be the result of local tectonic rotation occurring along a closely spaced north northwest trending primary shear system and northeast trending secondary shear system the shear system and concurrent rotation are interpreted to have developed during the growth of the yakima folds the relationship between the paleomagnetic data and the geologic structures can be used to constrain tectonic models for the columbia plateau the data reported in this study indicate that clockwise rotation can not be attributed to rigid block or microplate rotation but support models that predict localized dextral shear furthermore it is postulated that this mechanism may contribute to clockwise rotation observed in other parts of the western united states

paleomagnetism of the bonin islands and its tectonic significance abstract paleomagnetic samples were collected from six of the bonin islands located on the northeastern margin 27 n 142 e of the philippine sea these volcanic islands are of eocene age both lava flows and dikes were collected at each of 34 sites with chichi jima the largest island being sampled most extensively mean directions of the 27 sites on chichi jima are divisible into two groups showing antipolar relationships at the 95 confidence level a between site mean direction after tilt correction of 22 of the 27 sites is i 7 d 110 95 14 while that of the remaining sites is i 10 d 273 95 32 the seven sites on the other three bonin islands as a whole seem to cluster well around the mean of i 3 d 213 with a95 19 which differs significantly from both mean directions determined for chichi jima the low inclinations and deflected declinations of the bonin islands are interpreted as being due to tectonic rotation the islands have undergone a northward migration of at least 30 from the equatorial region together with possibly clockwise rotation of 30 to over 90 around the vertical axis since the northward drift and clockwise rotation are consistent with the tectonic movement inferred for the west philippine basin by previous studies the bonin islands appear to have been part of the basin before opening of the shikoku and parece vela basins during the miocene

cretaceous magnetizations in northwestern nevada and tectonic implications paleozoic and mesozoic arc related rocks of the black rock desert region of northwestern nevada have acquired a very stable postfolding secondary magnetization probably in late cretaceous time the remagnetization which appears to be of regional extent probably accompanied emplacement of granitic plutons in a northeast trending belt across northwestern nevada near the end of mesozoic time the region has experienced no appreciable tectonic rotation since that time

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

polar wander and paleomagnetic reference pole controversies the purpose of this paper is to review the progress made over the past four years in studies of phanerozoic and precambrian polar wander with an emphasis on the contributions made by u s scientists we perceive a general theme embracing the notion that the accuracy of cratonic reference poles and therefore of apparent polar wander apw paths is not as good as was generally believed four years ago a renewed interest in research concerning cratonic reference poles is largely the result of paleomagnetic studies in orogenic belts namely the western cordillera and appalachians of north america the andes of south america and elsewhere which seek to document the existence or non existence of displacements of suspect terranes i e rotation and or translation with respect to their presently associated cratons some of the results of this research are reviewed in this volume by hillhouse and mcwilliams an important realization of which paleomagnetists have long been aware but which was demonstrated recently by a number of sobering examples for both the paleozoic and mesozoic apw paths for north america is that the reliability of concordance discordance parameters that define terrane displacement is dependent not only on the precision and accuracy of the individual paleomagnetic study but also on the precision and accuracy of the appropriate cratonic reference pole

paleomagnetic results for eocene volcanic rocks from northeastern washington and the tertiary tectonics of the pacific northwest the direction of remanent magnetization for 102 sites in eocene volcanic and volcaniclastic rocks of the o brien creek formation sanpoil volcanics and klondike mountain formation suggests approximately 25 of clockwise rotation of a 100 by 200 km area in northeastern washington the volcanic rocks consist chiefly of rhyodacite and quartz latite flows with intercalated ash flow tuff and volcaniclastic layers these rocks have been sampled at 102 sites distributed among five volcanotectonic depressions the toroda creek republic keller and first thought grabens and the spokane enterprise lineament the volcanic rocks probably range in age from 55 m y to about 48 m y and the 50 to 48 m y old volcanic rocks within this suite appear to be rotated as much as the older rocks previous investigators have shown that 40 m y old and younger plutonic rocks of northwestern washington are not rotated hence we infer that the north central washington rocks were rotated to their present declination between 48 and 40 m y b p during the middle and or late eocene during early eocene time this region was extended in a westward direction through crustal necking gneiss doming diking and graben formation internal deformation of the region related to this crustal extension was extreme but most bedrock units that were formed concurrent with the crustal extension were probably in place prior to the rotation hence we infer that the rotation was chiefly accommodated by movement on faults peripheral to the sampled area faults active during paleogene time appear to define boundaries of a triangular crustal block the sanpoil block encompassing much of northeastern washington northern idaho northwestern montana and adjacent parts of british columbia the faults include the laramide thrusts of the rocky mountain thrust belt the strike slip faults of the lewis and clark line and strike slip faults of the straight creek fraser zone we suggest that during early eocene time the sanpoil block was extended westward through crustal necking and dilation and then during the middle eocene was rotated clockwise and thrust over the craton in a final stage of laramide thrusting the motor driving these deformations presumably was interaction of north america with oceanic lithosphere off its western margin such interaction probably involved right oblique underthrusting and dextral shear

palaeomagnetism of volcanic rocks of the kodiak islands indicates northward latitudinal displacement in the past decade it has become widely accepted that southern alaska is composed of allochthonous terranes1 4 but the times of amalgamation and their accretion to north america remain controversial palaeomagnetists and geologists generally agree that the talkeetna superterrane consisting of the wrangellia and peninsular terranes fig 1 was far to the south of its present position with respect to north america in triassic and jurassic time1 4 this consensus is lost when it comes to the question of the relative position of these terranes in the tertiary previously limited palaeomagnetic evidence suggested that the peninsular terrane may have lain substantially south of its present position4 but the timing of deformational and thermal events and the apparent absence of a tertiary suture zone argue for a cretaceous docking of wrangellia and the peninsular terrane5 6 here we present new palaeomagnetic results demonstrating that the kodiak islands were indeed at a more southerly latitude 62 myr ago around 43 n and discuss the implications of this conclusion

magnetostratigraphy of displaced upper cretaceous strata in southern california a magnetostratigraphic study of upper cretaceous marine strata from the santa ana mountains in southern california has identified a campanian reversed magnetozone this reversed interval corresponding to marine magnetic anomaly 33 34 chron 33r of campanian age can be correlated with a campanian reversed magnetozone that has been reported from strata of the great valley sequence in central california the late cretaceous paleolatitude of the santa ana mountains is estimated from this study to be 26 6 n this is significantly different from the region9s expected cretaceous paleolatitude of 43 8 n as part of the north american stable craton and indicates that this region part of the peninsular ranges terrane was 1900 km farther south in cretaceous time relative to the stable craton

paleomagnetism of the paleocene ghost rocks formation prince william terrane alaska the mean paleomagnetic inclination of paleocene volcanics from two regions on kodiak island in the ghost rocks formation suggests that the prince william terrane originated at mid latitudes about 25 south of its expected alaskan latitude in paleocene time the remanent magnetization of these rocks passes both the fold and reversal tests and is well constrained in age the mean declinations of the two regions however differ by approximately 120 suggesting they have rotated with respect to each other perhaps during emplacement we suggest that despite the lack of evidence for a major tertiary suture zone between the prince william terrane and central alaska the prince william and perhaps adjacent terranes may have lain substantially south of their present position in the early tertiary

paleomagnetism and the motion of large and small plates the focus of paleomagnetic research during past decades has varied greatly the first generation in paleomagnetism might be defined as beginning with the pioneering studies aimed at discovering whether the geomagnetic field has been a reliable reference frame for measuring and timing continental displacements an enormous effort followed in the form of individual paleomagnetic studies of cratonic rocks culminating with the construction of apw apparent polar wander paths for the continents which could be used to test paleogeographic reconstructions coupled with parallel research in marine geophysics and geology the refined apwp which result from this effort have helped to develop a reasonable first order history of cenozoic mesozoic paleogeography for the major plates

paleomagnetic study of thrust sheet rotation during foreland impingement in the wyoming idaho overthrust belt upper jurassic and lower cretaceous strata in the darby and absaroka thrust sheets were sampled in order to paleomagnetically evaluate thrust sheet rotation in the wyoming idaho overthrust belt no significant rotations were found lack of rotation in these thrust sheets suggests that previously reported rotation of the prospect thrust sheet was not transmitted to the older darby and absaroka thrust sheets indicating that the prospect thrust sheet only experienced local rotations in response to collision with the teton gros ventre uplift the upper jurassic stump formation possesses a magnetization that passes the fold test and gives a paleomagnetic pole at 64 n 170 e k 18 a95 15 in good agreement with other published upper jurassic poles for cratonic north america samples from all lower cretaceous sites are believed to possess a synfolding remagnetization of chemical origin

southern hemisphere origin of the cretaceous laytonville limestone of california new paleomagnetic paleontologic and stratigraphic data from outcrops of the laytonville limestone 101 to 88 million years old support a southern hemisphere origin a paleomagnetic megaconglomerate test is statistically significant and suggests magnetization at 14 5 south predating late cretaceous to eocene 70 to 50 million years ago accretion rapid kula plate movement or the existence and demise of a now vanished oceanic plate or both are required to accommodate the greater than 50 of poleward displacement implied by the paleomagnetic data this rapid motion brings into question the validity of a speed limit for absolute plate velocity based on present day plate motions

evidence against large scale carboniferous strike slip faulting in the appalachian caledonian orogen kent and opdyke1 have argued that during the late devonian and early carboniferous the eastern part of the northern appalachians acadia was situated 1 500 km further south relative to cratonic north america than it is at present and that it moved to its present position sometime later in the carboniferous fig 1 van der voo and scotese2 proposed an even greater displacement of 2 000 km which they attribute to motion between cratonic north america and europe acadia being attached to europe fig 1 the argument is that palaeolatitudes p derived palaeomagnetically from upper devonian and lower carboniferous rocks of cratonic north america are 15 20 more northerly than those of acadia and europe the proposed shear zone passes through central newfoundland using palaeomagnetic results from eastern and western newfoundland we show here that no such motion occurred we also show that kiaman late carboniferous and permian overprinting is widespread in newfoundland and that these secondary magnetizations agree with two exceptions attributed to dextral rotation of the colorado pleateau with observations from late devonian and early carboniferous rocks of the north american craton confirming the proposal3 that magnetizations of the cratonic early carboniferous rocks are kiaman not early carboniferous in age our results also enable us to extend this proposal3 to late devonian rocks of the craton hence the palaeolatitudinal offset of fig 1 is almost certainly not tectonic but is an artefact of the wrong assumption of the equivalence of rock and magnetization ages

early tertiary paleomagnetic evidence and the displacement of southern alaska paleomagnetic data from early paleocene lavas a few kilometers north of lake clark just inboard of the peninsular terrane indicate modest post early tertiary latitudinal displacement and about 55 sup 0 of counterclockwise rotation of this region with respect to north america a nearby middle eocene sequence of lava flows however gives no indication of displacement or rotation south of lake clark the paleomagnetism of five paleogene 30 to 40 ma volcanic sequences that are a part of the peninsular terrane proper shows no northward translation and no rotation a major part of the northward movement documented by other studies in the gulf of alaska region may be accounted for by cumulatively significant intraterrane displacements 32 references 3 figures 1 table

cretaceous and early tertiary paleomagnetic results from the antarctic peninsula paleomagnetic results are presented for early tertiary and cretaceous igneous and volcanic units from the northern antarctic peninsula when combined with previously published data they permit the construction of a polar wander path that is very similar to one derived for the east antarctic craton by rotating tertiary and cretaceous poles from india and australia into the antarctic frame of reference when considered in this context the paleomagnetic data from the orville coast which was previously interpreted as evidence in favor of oroclinal bending or relative rotation of the southern antarctic peninsula with respect to the northern part may be considered as an in situ resulte the implications of the new data are as follows 1 the antarctic peninsula down to the orville coast has been a part of the antarctic plate since 100 m y ago 2 movement of the antarctic peninsula required to avoid overlap in reconstructions of gondwanaland must have occurred before 100 m y ago

role of interannual kelvin wave propagations in the equatorial atlantic on the angola benguela current system the link between equatorial atlantic ocean variability and the coastal region of angola namibia is investigated at interannual time scales from 1998 to 2012 an index of equatorial kelvin wave activity is defined based on prediction and research moored array in the tropical atlantic pirata along the equator results show a significant correlation between interannual pirata monthly dynamic height anomalies altimetric monthly sea surface height anomalies ssha and ssha calculated with an ocean linear model this allows us to interpret pirata records in terms of equatorial kelvin waves estimated phase speed of eastward propagations from pirata equatorial mooring remains in agreement with the linear theory emphasizing the dominance of the second baroclinic mode systematic analysis of all strong interannual equatorial ssha shows that they precede by 1 2 months extreme interannual sea surface temperature anomalies along the african coast which confirms the hypothesis that major warm and cold events in the angola benguela current system are remotely forced by ocean atmosphere interactions in the equatorial atlantic equatorial wave dynamics is at the origin of their developments wind anomalies in the western equatorial atlantic force equatorial downwelling and upwelling kelvin waves that propagate eastward along the equator and then polewards along the african coast triggering extreme warm and cold events respectively a proxy index based on linear ocean dynamics appears to be significantly more correlated with coastal variability than an index based on wind variability results show a seasonal phasing with significantly higher correlations between our equatorial index and coastal ssta in october april season

paleomagnetism of middle tertiary volcanic rocks from the western cascade series northern california the western cascade series wcs is a 3 5 km thick crudely homoclinal east dipping calcalkaline volcanic sequence of mid oligocene to early miocene age that crops out near the southern tip of the cascade range in northern california the mean direction of remanent magnetization in the wcs is d 4 9 i 57 6 n 53 k 14 4 95 5 3 when compared to a reference direction for the north american craton the wcs direction indicates that the southern cascade range has rotated 14 0 9 0 since the wcs accumulated a difference in mean direction between the lower and upper halves of the wcs suggests that much of this rotation occurred during the late oligocene six other paleomagnetic studies of rock units of an age roughly comparable to the wcs also are available from western oregon northwestern california and southwestern washington all show statistically significant clockwise rotation inclinations of all but one are concordant comparison of directions indicates that the pacific northwest did not rotate as a rigid body but neither did it behave as a collection of small independently rotating domains the amount of rotation found throughout the area increases to the west or northwest suggesting a driving force for rotation operating at the continental margin