structural geometry and kinematic evolution of the eastern cascades foldbelt washington and british columbia the eastern cascades foldbelt is one of three structural domains lying within the complex collision zone between the insular and intermontane composite terranes in northern washington and southern british columbia the foldbelt resides between the high grade metamorphic backbone of the cascade orogen on the west and rocks of the composite intermontane terrane to the east it encompasses the stratigraphically coherent basalt floored jura cretaceous methow basin as well as more chaotically disposed permian jurassic oceanic rocks of the hozameen terrane methow basin rocks are thought to have been sutured above the oceanic rocks prior to the middle cretaceous contractional episode described in this report based on the analysis presented herein between ca 100 and 88 ma the rocks in the foldbelt underwent shortening in an east northeast west southwest direction by 50 km or more largely by displacement on the east vergent jack mountain chuwanten thrust system the early stages of contraction occurred by

paleocave carbonate reservoirs origins burial depth modifications spatial complexity and reservoir implications paleocave systems form an important class of carbonate reservoirs that are products of near surface karst processes and later burial compaction and diagenesis features and origins of fractures breccias and sediment fills associated with paleocave reservoirs have been studied in modern and ancient cave systems information about such cave systems is used in this paper to reconstruct the general evolution of paleocave reservoirs and their associated scale pore networks and spatial complexities spatial complexities in paleocave reservoirs result from near surface and burial processes near surface processes include dissolutional excavation clastic sedimentation chemical precipitation and localized fracturing brecciation and collapse of cave walls and ceilings burial processes begin as cave systems subside into the subsurface remaining cave passages commonly collapse and early formed breccia clasts are rebrecciated differential compaction of strata around and over collapsed passages produces fractures crackle breccias and mosaic breccias near surface and burial processes combine to produce typically complex reservoirs with several scales of heterogeneity hydrocarbon reservoirs of paleocave origin are commonly the product of coalesced collapsed paleocave systems the coalescing of passages in a cave system into larger connected porosity zones results from a combination of multiple cave forming episodes at composite unconformities and from the collapse of cave systems during burial where surrounding host strata are brecciated and fractured this combination of processes creates spatially complex reservoirs that can be hundreds to several thousands of meters across commonly forming large exploration targets final size pore network types and spatial complexities of coalesced collapsed paleocave systems are products of their evolution from near surface development through burial into the deeper subsurface the coalesced collapsed paleocave reservoir hypothesis explains the scale of reservoirs observed and the spatial complexities involved

structural correction of paleomagnetic vectors dispersed about two fold axes and application to the duke island alaska ultramafic complex 1 a new analysis of paleomagnetic data from the mid cretaceous 110 ma ultramafic complex at duke island southeast alaska supports large poleward transport of the insular superterrane relative to north america consistent with the baja british columbia hypothesis previous paleomagnetic work has shown that the characteristic remanence of the ultramafic complex predates kilometer scale deformation of the very well developed cumulate layering but that the layering was not horizontal everywhere before the folding it is possible however to estimate paleohorizontal for the duke island ultramafic complex because the postremanence deformation of the intrusion occurred about two well defined and spatially separate fold axes in such a case the tectonically rotated paleomagnetic directions should be distributed along small circles centered on each of the two fold axes the ancient field direction will lie on both small circles and therefore will be identifiable as one of their two intersection points interpreted this way the tectonically rotated remanence of the duke island ultramafic complex defines a mid cretaceous i e ancient field direction that is within 2 of the paleomagnetic direction found by assuming the cumulate layering was initially horizontal despite the paleomagnetic evidence to the contrary and performing the standard structure correction the inferred mid cretaceous paleolatitude of duke island is 21 2 2350 km anomalous with respect to cratonic north america this result is concordant with southerly paleolatitudes determined by many other workers from bedded rocks of terranes farther inboard in the insular and intermontane superterranes

empirical prediction equations for peak ground velocity derived from strong motion records from europe and the middle east peak ground velocity pgv has many applications in earthquake engineering but there are relatively few prediction equations for this parameter in comparison with the large numbers of equations for estimating peak ground accel eration and response spectral ordinates this lack of empirical equations for pgv has led to widespread use of the practice of scaling peak velocity from the 5 damped response spectral ordinate at 1 sec which is a poor substitute for direct prediction of the parameter responding to the need to provide equations for the prediction of pgv this article derives new equations using the strong motion database for the seismically active areas of europe and the middle east following a new processing of all of the records a total of 532 strong motion accelerograms recorded at distances of up to 100 km from 131 earthquakes with moment magnitudes ranging from m 5 to 7 6 are used to derive equations for both the larger and the geometric mean of the horizontal components the predictions are found to be broadly consistent with those from previous european equations and also with preliminary results from the next generation of attenuation nga project suggesting that systematic differences in ground motions from active crustal regions if any are sufficiently small not to prevent the combined use of strong motion data from southern europe western north america and other tectonically active areas of shallow crustal seismicity

test of goodness of the nga ground motion equations to predict the strong motions of the 2012 ahar varzaghan dual earthquakes in northwestern iran in the first part of this study a set of 87 ground motion records with closest distance to the rupture plane r rup less than 200 km and averaged shear wave velocity over the top 30 m of the subsurface v s 30 between 175 and 1400 m s recorded during the 2012 ahar varzaghan dual earthquakes m w1 6 4 m w2 6 3 were taken into account to examine the predictive capabilities of the next generation attenuation nga ground motion prediction equations gmpes via a set of comparative analyses and tests the first applied method to assess the performance of the nga gmpes is based on the intraevent residual analysis the primary database i e 87 records was also used to develop an event specific gmpe in the case of the ahar varzaghan dual earthquakes by means of regression analyses the derived event specific gmpe has been compared with the nga gmpes for two different site conditions that is v s 30 375 m s rock site and v s 30 375 m s soil site the residual analysis results indicate that the nga gmpes perform better in predicting data recorded at rock sites compared to soil sites for soil sites and at large periods t 2 0 s the observed spectral accelerations are overpredicted by the nga gmpes furthermore as the second part of this study to select the most adequate gmpes 14 strong motion records from the 1997 ardebil earthquake m w 6 1 were added to the primary database the implementation of the likelihood lh and log likelihood methods as modern lh based ranking assessment techniques as well as the nash sutcliffe index reveal that the nga gmpes show good compatibility at short medium periods t 1 0 s on the basis of the data recorded during the 2012 ahar varzaghan dual and 1997 ardebil earthquakes i e 101 records however in the long period range the dispersion in the data does not allow the authors to draw a comprehensible conclusion

monsoon induced errors in paleotemperature estimation based on leaf morphology analysis in central japan abstract models based on the relationship between leaf morphology and climate parameters of different regions have been used for paleoclimate estimation information from japanese floras has been included in some of these models however variation in the distribution pattern of leaf margin within japan caused by the effect of topography and east asian monsoon has not been reflected in these previously published leaf margin analysis models in this study we investigate the relationship between leaf characters and climate parameters under different climate conditions within a small geographical scale and in doing so improve the accuracy of leaf physiognomy based paleoclimate reconstruction we use the local flora in central japan as an example to determine the distribution pattern of leaf margin toothed and untoothed and habit evergreen and deciduous characteristics under monsoon climate conditions in areas along the pacific ocean p zone the leaf margin and habit types correlated with the temperature parameters and growing season precipitation the p zone includes more toothed species than in other regions of the world obtained with published models at a given mean annual temperature in the areas along the sea of japan j zone with deeper snow cover during the winter the percent of sub canopy evergreen shrubs increases especially at higher altitudes no significant relationship between leaf margin characters and climate parameters was observed in this area as heavy snow was a feature of this region since late early pleistocene times paleoclimate estimation based on leaf margin of fossil assemblages younger than early pleistocene from these areas might be less reliable in addition we found that the leaf margin of woody shrub species is less sensitive to the mean annual temperature than tree species

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

eocene continental climates and latitudinal temperature gradients global climate during the mesozoic and early cenozoic is thought to have been warmer than at present but there is debate about winter temperatures paleontological data indicate mild temperatures even at high latitudes and in mid latitude continental interiors whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels foliar physiognomy and floristic composition of 23 eocene floras from the interior of north america and australia indicate cold month means generally 2 c even where the mean annual temperature mat was

late cretaceous terrestrial vegetation a near polar temperature curve quantitative estimates of terrestrial paleotemperatures near the north pole were derived from the physiognomy of the vegetation including leaf margin analysis from rocks of latest albian and late cretaceous age of the north slope of alaska during the latest albian and cenomanian mean annual temperature was approximately 10 3 c during the coniacian mean annual temperature may have been 2 3 c warmer than during the albian cenomanian but no higher than 13 c during the campanian and maastrichtian mean annual temperature would have been about 2 8 c although the ranges for the individual estimates overlap differences among the floras indicate that the relative changes in mean annual temperature did occur

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

amazonis planitia the role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on mars 1 amazonis planitia located between the two main volcanic provinces on mars tharsis and elysium is characterized by extremely smooth topography at several scale lengths as smooth as oceanic abyssal plains topography on earth we use mars global surveyor mgs data primarily very high resolution mars orbiter laser altimeter mola topography and derivative slope maps gradient maps and detrended maps to examine the surface morphology of amazonis planitia and the stratigraphic relationships among previously mapped and newly defined units these new data reveal the presence of a 1300 km diameter noachian impact basin in northwest amazonis planitia and an extensive late hesperian lava flow unit that appears to have originated from the olympus mons source area prior to aureole formation the presence of this previously unrecognized flow unit strongly suggests that olympus mons activity dates back to at least the hesperian as did activity on the tharsis montes emplacement of this 100 meter thick flow unit formed a barrier along the northern margin of amazonis planitia which had a profound influence on the subsequent geologic history of the region formation of olympus mons aureole deposits created an eastern topographic barrier and subsequent tharsis montes lava flows entered the basin from the south flowing around the aureole these three barriers degraded noachian crater rim protoolympus mons flow unit and olympus mons aureole caused subsequent lava flows and outflow channel effluents primarily from the elysium region to the west to pond on the floor of amazonis planitia preferentially smoothing the terrain there mars orbiter camera moc images substantiate that at least two very fluid lava flows alternated with fluvial episodes from elysium planitia flowing through marte valles onto the floor of the amazonis planitia basin within amazonis planitia moc images show flow like textures heavily mantled by sediments and radar data reveal the presence of rough lava flow surfaces underlying the sedimentary debris these data thus suggest that the unique smoothness of amazonis planitia is the result of deposition of thin fluid lava flows and fluvial sediments in an enclosed basin crater counts suggest that the most recent resurfacing may have occurred in the latest amazonian period in the last 1 of the history of mars in light of its unique history it is somewhat ironic to note that amazonis planitia was originally thought to be a typical young martian surface and therefore used to name the amazonian era index terms 6225 planetology solar system objects mars 5415 planetology solid surface planets erosion and weathering 5470 planetology solid surface planets surface materials and properties 5480 planetology solid surface planets volcanism 8450 4267 oceanography general paleoceanography keywords mars water amazonis planitia marte vallis volcanism amazonian citation fuller e r and j w head iii amazonis planitia the role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on mars j geophys res 107 e10 5081 doi 10 1029 2002je001842 2002

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

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

late cretaceous to late eocene palaeogeographic evolution of southwest europe abstract a synthesis of personal research concerning the peri pyrenean region and previously published data is presented as a series of palaeogeographic reconstructions subsequent to the progressive regression at the end of the cretaceous the sea invaded three times parts of the earlier senonian marine domain on both sides of the eastern palaeo pyrenees pre cuisian climatic rewarming combined with cuisian continental epeirogenic deformations resulted in major biogeographic modifications during the cuisian local tectonics forced the sea from the northern pyrenean basin whereas in the southern pyrenean basin the sea retreated much later as a consequence of the pyrenean tectonic phase however the pyrenean tectogenesis seems to have affected a much larger region including the alps shoreline migrations are compared and related to the geodynamic behaviour of the meridional and septentrional european provinces in order to distinguish between tectonic and eustatic causes

the kanaka creek fossil flora huntingdon formation british columbia canada paleoenvironment and evidence for paleocene age using palynology and macroflora paleogene sediments of the huntingdon formation a correlative to the chuckanut formation of neighbouring washington state usa are exposed in the greater vancouver area british columbia canada

recent geological history and modern sedimentary processes along an incipient low energy epicontinental sea coastline northwest florida abstract a major portion of florida s gulf of mexico coastline is a siliciclastic sand starved low wave energy system dominated by marshes that face the open sea because of its location at the center of an enormous 350 000 km2 flooded broad flat ancient carbonate platform this coastline can be viewed as the margin of an incipient epicontinental sea within a 65 km sector along this 300 km long open marine marsh coast four distinctly different morphological sectors have been identified 1 berm ridge marsh shoreline 2 marsh peninsula shoreline 3 marsh archipelago shoreline and 4 shelf embayment shoreline the underlying paleogene limestone bedrock topography results from karstification and dissolution processes this antecedent topography and the distribution of actively discharging freshwater springs affect sedimentary processes facies and stratigraphic units the morphology and processes within the four coastal sectors vary as a function of a northerly decrease in the thickness of relict pleistocene quartz sand cover and an increase in the complexity and relief of the underlying bedrock topography each of the four coastal sectors has a unique distribution of sedimentary products in addition each has responded differently to rising sea level a process that continues to control the spatial distribution of organisms and sediments however the sedimentary lithosomes in all four coastal sectors share a similar fate during landward shoreline translation within the inner continental shelf very little of the marsh stratigraphy or large oyster bioherms is preserved only those sediments that have accumulated within bedrock depressions or sinkholes have the best chance for long term retention thus a condensed stratigraphic section is produced since only thin and discontinuous sediment accumulations are preserved the relief and texture of the bedrock surface due to chemical etching and bioerosion must also be used as clues to the recognition of similar coastal systems in ancient settings

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

jiggling the tropical thermostat in the cretaceous hothouse modern open ocean sea surface temperatures rarely exceed 28 29 8c and the same has been thought to represent a rough maximum for past tropical climates however new isotopic estimates from the uppermost cenomanian in the tropical western north atlantic suggest that mixed layer temperatures reached 33 34 8 c 62 8c during the middle cretaceous hothouse uppermost cenomanian tropical sea surface temperatures may have been as much as 4 7 8c warmer than the highest modern mean annual temperatures such extreme conditions suggest that warm tropical oceans could have driven substantially intensified atmospheric heat transport near the cenomanian turonian boundary the tropical thermostat was set higher than today challenging the hypothesis of tropical climate stability

an istiodactylid pterosaur from the upper cretaceous nanaimo group hornby island british columbia canada an unusual jaw found in a calcite nodule from collishaw point hornby island british columbia off the east coast of vancouver island represents the first definitive pterosaur found in british columbia and the first istiodactylid from canada the nodule was derived from the northumberland formation nanaimo group a fossiliferous formation known for producing numerous plants invertebrates sharks and mosasaurs the pterosaur is represented by the anterior portion of the rostrum including the anterior edge of the nasoantorbital fenestra and numerous small triangular teeth lacking denticles these teeth are similar in overall morphology to the teeth of istiodactylids but are smaller more numerous more tightly packed and have proportionately smaller crowns although fragmentary this specimen is diagnostic and represents a new genus of istiodactylid pterosaur its presence in the upper campanian northumberland formation makes this the latest occurring istiodactylid and extends the stratigraphic

paleoclimate and paleoecology of the latest eocene florissant flora of central colorado u s a abstract the uppermost eocene florissant formation of central colorado u s a contains a diverse flora and fauna preserved in lacustrine facies and represents a key episode in earth history immediately preceding the eocene oligocene boundary laminated shales contain impressions of non monocot angiosperm leaves that were used to estimate paleoecological and paleoclimatic parameters using leaf physiognomic methods including leaf mass per area ma digital leaf physiognomy dilp leaf margin analysis lma and leaf area analysis laa the majority 58 of the morphotypes analyzed for ma suggested a semi evergreen leaf lifespan whereas another 27 indicated a deciduous habit and 15 an evergreen habit there was no significant relationship between ma and insect damage based on a small subset of florissant s leaves higher ma values 73 of leaves one year lifespan coupled with a tendency toward long and narrow leaf shapes and small leaf areas indicate the existence of sclerophyllous vegetation using the global regression for mean annual temperature mat the dilp estimate of mat was anomalously cold 5 5 4 c however using a northern hemisphere regression the dilp mat estimate of 11 6 3 3 c was more plausible using dilp mean annual precipitation map was estimated at 740 608 334 mm yr 1 which supports dry conditions estimates for mat and map using the univariate lma and laa methods overlapped within uncertainty of the dilp results in addition those taxa classified as growing in wet areas riparian had significantly more teeth than non riparian taxa these paleoclimatic and paleoecological results suggest that outside the riparian forest the florissant flora sampled a seasonally dry temperate sclerophyllous shrubland to woodland perhaps similar to modern chaparral forests in the western interior of the u s a just before the transition into the cooler oligocene

equivalent point source modeling of moderate to large magnitude earthquakes and associated ground motion saturation effects we modeled the source and attenuation attributes of well recorded m6 earthquakes based on the equivalent point source approach with the goal of determin ing how to treat ground motion saturation effects within this context we consider ground motions as originating from an equivalent point source and mimic finite fault effects by treating the motion as emanating from a virtual point not a real point on the fault rupture such that ground motions are correctly predicted at close distances this is achieved by using an effective distance metric r d 2 h 2 0 5 in which drup is the closest distance to the rupture and h is a pseudodepth term that accounts for sat uration effects we found that the distance saturation effect is magnitude dependent extending to further distances with increasing magnitude for earthquakes of m 6 we model the saturation term as logh 1 72 0 43 m with a standard deviation of 0 19 in log10 units based on the values obtained from the study earthquakes the apparent source spectra of most m6 earthquakes can be modeled using a simple brune point source model for a few of the m6 earthquakes notably those in california we observed a spectral sag at intermediate frequencies for such earth quakes a two corner point source model provides a better match than the brune model we conclude that an equivalent point source model based on the effective distance concept can successfully predict the average ground motions from m6 earthquakes over a wide distance range including close distances 20 km

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

palaeo mixing zone karst features from palaeocene carbonates of north spain criteria for recognizing a potentially widespread but rarely documented diagenetic system abstract marine meteoric mixing zone dissolution effects are a major feature of present day karst systems in carbonate platforms yet are rarely reported in the geological record an example is described from the upper danian platform limestones of the alava province in the western pyrenees north spain this consists of several narrow zones with sponge like porosity analogous to the swiss cheese features found in present day mixing zones these zones are stained by fe oxides and overlie limestones which are irregularly dolomitized and contain disseminated pyrite these high porosity zones are interpreted as having developed in marine mixing zones where mixing corrosion and microbially mediated processes increased dissolution if collapsed ancient mixing zones could be misinterpreted as terra rossa palaeosols the main criteria to identify them as mixing zone products are their occurrence below a palaeo meteoric phreatic zone their association with stratified oxic and anoxic redox zones and petrographic evidence for highly variable calcite saturation states

the sandstone derived provenance record of the gualala basin northern california u s a abstract detrital zircon u pb ages and pb isotope compositions of detrital feldspars from the late cretaceous eocene gualala basin in northern california indicate that the basin received sediments from the southern sierra nevada the mojave block and the salinian block mesozoic detrital zircon age components and pb isotope compositions of detrital feldspars from the basin are similar to u pb zircon ages and pb isotope compositions from previously studied coeval conglomerate clasts the detrital zircons and feldspars however also include additional age and pb isotope components that are unobserved or poorly represented in the conglomerate based provenance record these new data suggest a more complex provenance history than that inferred from previously studied conglomerate clasts and strongly imply a connection to the mojave desert provenance evolution of the sediments in the basin indicates that significant contribution of sediment from the mojave desert began during the paleocene when it is inferred that the drainage network expanded eastward from its previous extent the presence of mojave derived late permian zircons as well as feldspars that have high 208pb 204pb ratios in the eocene age german rancho formation indicates that the basin remained in the vicinity of the mojave desert until the eocene this result demonstrates that the gualala basin had undergone very little northward motion at that time and consequently requires that no significant northward translation took place prior to 50 ma the results of this study highlight the value of additional provenance constraints combined with age distributions when identifying sediment source terranes

measurements of the cretaceous paleolatitude of vancouver island consistent with the baja british columbia hypothesis a previously unsampled outcrop of gently dipping or flat lying upper cretaceous sedimentary strata in the vancouver island region which contains unaltered aragonitic mollusk fossils yielded a stable remanent magnetization that is biostratigraphically consistent with cretaceous magnetochrons 33r 33n and 32r these results characterized by shallow inclinations indicate an upper cretaceous paleolatitude of about 25 3 degrees north which is equivalent to that of modern day baja california these findings are consistent with the baja british columbia hypothesis which puts the insular superterrane well south of the oregon california border in the late cretaceous

differential dissolution of a pleistocene reef in the ground water mixing zone of coastal yucatan mexico a geochemical explanation is provided for the extensive dissolution observed along the carbonate coast of the yucatan peninsula mexico mixing of fresh ground water with subterranean caribbean seawater generates a highly reactive geochemical zone that enhances aragonite and calcite dissolution and permits neomorphism of aragonite mixing zone dissolution caused by ground water discharge is a major geomorphic process in developing caves coves and crescent shaped beaches along the yucatan coast such dissolution has probably been a significant control on permeability and porosity distribution in carbonate rocks in the geologic record

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

tectonic significance of ductile deformation in low grade sandstones in the mesozoic otago subduction wedge new zealand this study demonstrates how ductile strain measurements can determine the tectonic evolution of a large and long lived subduction wedge we provide a synthesis of the geology of the south island of new zealand with an emphasis on a wedge tectonics perspective that contrasts with a traditional view that interprets new zealand geology in the context of terrane collision and accretion we argue that the otago subduction wedge evolved in a steady fashion throughout its 290 to 105 ma history in response to accretion of trench fill and abyssal plain sediments and slow erosion of a subaerially exposed forearc high maximum temperatures for rocks in the flanks of the forearc high were no greater than 150 to 300 c with solution mass transfer active as the dominant ductile mechanism the 54 studied samples provide information about the absolute ductile strains acquired all along their flow path from the site of accretion to exhumation in the forearc high we use tensor averages to estimate strain at a regional scale these show plane strain uniaxial flattening given that the tensor averages for sy and sx are close to one on average sz is approximately 0 77 and this is balanced by a mass loss of about 23 percent the average z direction is sub horizontal in the prowedge and moderately plunging in the retrowedge a difference attributed to spatial variations in the mode of accretion we infer that rocks presently in the pro side of the otago high were sourced by frontal accretion and those in the retro side were underplated this result highlights the important role of accretion in determining the style of within wedge deformation and also demonstrates the benefit of using a tensor averaging approach to examine regional strain

compaction corrected paleomagnetic paleolatitudes for late cretaceous rudists along the cretaceous california margin evidence for less than 1500 km of post late cretaceous offset for baja british columbia the paleolatitudinal distribution of bivalve rudists has important significance for the baja british columbia baja bc hypothesis that western canadian superterranes from british columbia have been displaced 3000 km since cretaceous time rudists are not observed in baja bc sedimentary rocks yet they are common in late cretaceous strata in california and baja california which have the same paleomagnetically determined paleolatitudes approximately 25 n as baja bc rocks of late cretaceous age in order to resolve this contradiction and to delimit more exactly the southern paleolatitudes of baja bc paleomagnetic inclinations corrected for the effects of burial compaction were used to determine the paleolatitudinal distribution of rudists along the california margin compaction corrected paleomagnetic data from the peninsular ranges and salinia terranes indicate that rudists were restricted to paleolatitudes between 34 and 40 n evidence of coastal upwelling in the latest cretaceous marca shale may explain the northern limit of the rudist distribution these data suggest that baja bc was no farther south than 40 n in the late cretaceous thus limiting its post cretaceous displacement to less than 1500 km and that burial compaction has also affected the paleomagnetism of nanaimo group sedimentary rocks from vancouver island this result also helps resolve the conflict between paleomagnetic results which show 1500 km of post late cretaceous offset between the insular coast plutonic complex superterrane and the intermontane superterrane and geologic observations which can allow only tens of kilometers of offset between these terranes in the methow tyaughton basin

major dextral transcurrent displacements along the northern rocky mountain trench and related lineaments in north central british columbia the northern rocky mountain trench and a number of other prominent lineaments along and east of the eastern margin of the intermontane belt mark faults along which dextral transcurrent movements have been dominant offsets of shelf to off shelf facies boundaries in lower paleozoic rocks indicate a cumulative displacement of at least 750 km and probably 900 km within the system of faults related to those in the northern rocky mountain and the tintina trenches farther west another system of faults appears to offset plutons and stratigraphic assemblages along the eastern margin of the intermontane belt by as much as 300 km these faults including the kutcho and the pinchi connect in part with the teslin suture zone in yukon territory and probably with the fraser river straight creek fault zone in southern british columbia although dextral transcurrent faulting may have taken place between the middle jurassic and early cenozoic the most convincing evidence points to middle cretaceous and particularly to early cenozoic eocene displacements the eocene movements were temporally related to plutonism volcanism lamprophyre dike emplacement high heat flow sedimentation in grabens and rapid uplift of northwesterly trending elongate ranges climactic episodes of granite emplacement particularly in and near the northern omineca crystalline belt at 100 m y 70 m y and 50 m y ago may have been facilitated by changes from dominantly compressional to dominantly transcurrent and related tensional strain

environmental analysis of the mid latitudinal european eocene sites of plant macrofossils and their possible analogues in east asia article i nfo previously known eocene floras of mid latitudinal europe are analysed using statistical methodologies in order to obtain more reliable palaeoclimatological signals to detect possible climatic fluctuations during this time interval only macrofossil assemblages have been taken into account and subjected to the statistical evaluation called the integrated plant record ipr vegetation analysis which is based mostly on percentages of various components additional palaeoclimatic approaches were employed namely the coexistence approach based on autecology of the nearest living relatives and the physiognomic methods of the leaf margin analysis and climate leaf analysis multivariate program clamp the same statistical approaches have been applied to analogous living vegetation of china and japan for comparative purposes additionally an update of objective statistical tools for the selection of the best suited modern vegetation clamp dataset from 144 site physg3br gridmet3br 173 physg3ar gridmet3ar and 189 physgasia1 gridmetasia1 extant biotopes is proposed including its copy paste excel application

quantification of large uncertainties in fossil leaf paleoaltimetry 1 estimates of paleoelevation potentially constrain geodynamic models of continental deformation and inform interpretations of landscape and climate evolution one widely used paleobotanical approach reconstructs paleoelevation from the difference in estimated atmospheric enthalpy between a known sea level and a targeted coeval elevated fossil floral site enthalpy is estimated using climate leaf analysis multivariate program clamp on 31 leaf size and shape variables that have been calibrated in living forests errors related to clamp are significantly greater than often reported and there are many sources of large potential error related to this method that are either difficult to quantify or unquantifiable and are thus not documented here we quantify one significant bias toward underestimation of leaf area in the clamp data set 50 that affects all clamp climate estimates including enthalpy crucially errors in paleoelevation when the leaf size bias is included are in the range of 2 km or more at least 2 times the previous estimates and exceeding the plausible paleoelevations of many fossil sites previously published paleoelevations derived from this technique are unlikely to be accurate either in magnitude or in estimated error

simulation of ground motion in the zagros region of iran using the specific barrier model and the stochastic method abstract physically based ground motion prediction equations for soil and rock sites in the zagros region have been developed based on the specific barrier model sbm used within the context of the stochastic model instead of direct time domain simulation random vibration theory was used to estimate measures of peak motion in terms of the pseudospectral velocity of anelastic harmonic oscillator with 5 viscous damping to avoid the uncertainties calibration of the source model uses a database of carefully selected strong motion data without ambiguity about the site condition therefore only rock sites are selected for determining source parameters also to avoid any inconsistencies caused by magnitude conversion formulas we restricted the dataset only to events with available moment magnitudes regression analysis is performed using the random effects model that considers both interevent and intraevent variabilities to effectively deal with the problem of an unequal number of records from different earthquakes no sign of self similarity breakdown is observed between the source radius and its seismic moment the local and global stress drops derived for the zagros region 39 and 116 bars respectively are more consistent with the values obtained by other authors for an interplate regime than the values for an intraplate region however from the viewpoint of source heterogeneity as the ratio of the stress drops is an indicator of the complexity of the source and heterogeneity of slip on the fault the zagros events which have a stress drop ratio of about three are more homogeneous than other interplate events stochastic simulations are then implemented to predict peak ground motion and response spectra parameters for rock and soil site conditions online material catalog tables of earthquakes and attenuation tables

testing terrane transport an inclusive approach to the baja b c controversy the baja british columbia hypothesis holds that a large segment of the western edge of northern north america baja b c was situated alongside california and northern mexico in middle cretaceous time was displaced northward in the late cretaceous and paleocene by north oblique convergence of the kula plate with north america and arrived near its present location by the early eocene a consistent body of paleomagnetic data supports this hypothesis however doubt persists and various crucial tests of a geologic nature have been proposed one such test concerns the provenance of zircons in cretaceous sedimentary basins of baja b c in this paper we use both paleomagnetic data and zircon occurrences to reconfirm the baja b c hypothesis we first argue that the only truly crucial tests yet performed have been paleomagnetic and that all such tests have been positive second we show that detrital zircon data from the upper cretaceous nanaimo group although not a crucial test provide valuable paleogeographic information available data demonstrate a change in detrital zircon provenance in the nanaimo group that closely matches the position of these rocks predicted by the baja b c hypothesis detrital zircons in the nanaimo group suggest a change from a southwestern north american source rich in grenville and 1 4 1 5 ga rocks to an increasing contribution from older parts of the craton such as the wyoming province together detrital zircons and paleomagnetic inclinations allow us to assemble a detailed schedule of northward tectonic transport of the baja b c terranes

paleomagnetism of the upper cretaceous nanaimo group southwestern canadian cordillera the baja b c model has the insular superterrane and related entities of the canadian cordillera subject to 3000 km of northward displacement with respect to cratonic north america from 90 to 50 ma the upper cretaceous nanaimo group on and about vancouver island british columbia is a prime target to test the model paleomagnetically because of its locality and age we have widely sampled the basin 67 sites from seven islands spread over 150 km santonian to maastrichtian age most samples have low unblocking temperatures 450 c and coercivities 10 mt and strong present field contamination forcing us to reject three quarters of the collection beds are insufficiently tilted to provide a conclusive fold test and we see evidence of relative vertical axis rotations however inclination only analysis indicates pretilting remanence is preserved for many samples both polarities are observed and reversals correlate well to paleontological data proving that primary remanence is observed the mea

plant community ecology and climate on an upland volcanic landscape during the early eocene climatic optimum mcabee fossil beds british columbia canada abstract the mcabee fossil beds in south central british columbia canada provide a record of forest ecosystems within a volcanically active upland landscape during the early eocene climatic optimum eeco to assess plant community ecology and climate within this environment palynology and census style macrofossil collections were investigated from two shale horizons separated in time by likely 103 104 years an ensemble of leaf physiognomic estimates indicates a persistent warm mean annual temperature mat 10 12 c and mesic mean annual precipitation 1000 mm yr 1 climate between the horizons the plant community was similar in both horizons comprising angiosperms e g ulmus fagus alnus betula and carya and gymnosperms e g metasequoia pinus picea and larix plant diversity and the distribution of dicot leaf mass per area ma values were consistent between the two horizons despite intervals of varying tuff thickness and frequency between the horizons differences in macrofossil abundances of ulmus fagus and pinus and a lack of such differences in their respective pollen abundances might be explained by local patch dynamics influenced by spatial heterogeneity resulting from topographic diversity and disturbance ma estimates suggest dicots were predominately deciduous and the distribution of ma is similar to a modern forest in panama influenced by seasonal precipitation the diversity of dicots at mcabee despite relatively lower mean annual temperatures is comparable to fossil plant quarries of similar volume from early eocene sites in patagonia e g laguna del hunco and the denver basin with relatively warmer mats 17 25 c this is best explained by a combination of predominately frost free winters high productivity and an abiotic environment characterized by spatial heterogeneity and high rates of change the sampled paleofloras of this study showcase an eeco plant community likely representing an ecological solution to volcanic disturbance over millennial time scales

cenozoic tectonism in the central basin and range magnitude rate and distribution of upper crustal strain a wealth of pre cenozoic geologic markers across the central basin and range province defined mainly by thrust faults developed within a miogeoclinal wedge makes it one of the best areas on earth to reconstruct large scale continental extension we use this 100 000 km 2 region bounded by the southern sierra nevada on the west and the colorado plateau on the east to illustrate the concepts of correlation and misalignment for regional strain markers and of strain compatibility and kinematic viability in palinspastic reconstructions the results indicate 250 to 300 km of west northwest motion of the sierra away from the plateau accommodated by both crustal thinning and north south shortening tertiary intermontane basin deposits and mineral cooling ages of deeply exhumed rocks constrain the overall kinematics of motion most of the westward motion occurred between 16 and 5 ma at rates near 2 cm yr slowing to 1 to 1 5 cm yr in the last 5 ma we have quantified the partitioning of strain between vertical crustal thinning via normal faults and map view plane strain via conjugate strike slip faults by placing a grid of 10 x 10 km elements on a retrodeformed map of the region and measuring the increase in area of grid elements between the undeformed and present day grids this analysis yields a maximum finite elongation of the basin and range at 36 n to 37 n of 3 4 oriented n73 w map view area balance shows that 20 percent of this elongation is compensated by north south shortening and 80 percent by crustal thinning this yields an average thinning factor for the upper crust of 2 7 between the sierra and plateau inconsistent with the hypothesis that neogene deformation in the central basin and range is predominantly dextral shear plane strain these results in concert with the observation that the southern sierra nevada has similar crustal thickness to the central basin and range support the hypothesis of large scale eastward flow of sierran deep crust during extension

refinement of eocene lapse rates fossil leaf altimetry and north american cordilleran surface elevation estimates abstract estimates of continental paleoelevation using proxy methods are essential for understanding the geodynamic climatic and geomorphoric evolution of ancient orogens fossil leaf paleoaltimetry one of the few quantitative proxy approaches uses fossil leaf traits to quantify differences in temperature or moist enthalpy between coeval coastal and inland sites along latitudes these environmental differences are converted to elevation differences using their rates of change with elevation lapse rate here we evaluate the uncertainty associated with this method using the eocene north american cordillera as a case study to do so we develop a series of paleoclimate simulations for the early 55 49 ma and middle eocene 49 40 ma period using a range of elevation scenarios for the western north american cordillera simulated eocene lapse rates over western north america are 5 c km and 9 8 kj km close to moist adiabatic rates but significantly different from modern rates further using linear lapse rates underestimates high altitude 3 km temperature variability and loss of moist enthalpy induced by non linear circulation changes in response to increasing surface elevation ignoring these changes leads to kilometer scale biases in elevation estimates in addition to these biases we demonstrate that previous elevation estimates of the western cordillera are affected by local climate variability at coastal fossil leaf sites of up to 8 c in temperature and 20 kj in moist enthalpy a factor which further contributes to elevation overestimates of 1 km for early eocene floras located in the laramide foreland basins and underestimates of 1 km for late middle eocene floras in the southern cordillera we suggest a new approach for estimating past elevations by comparing proxy reconstructions directly with simulated distributions of temperature and moist enthalpy under a range of elevation scenarios using this method we estimate mean elevations for the north american cordillera of 2 km using proxy temperatures and 3 km using proxy moist enthalpy this discrepancy is likely related to an inconsistency between the proxy data for temperature and moist enthalpy the combination of temperature and moist enthalpy estimates implies a warm and dry environment which is inconsistent with geological evidence for humid conditions our study emphasizes that lapse rates in warm climate were likely much different than today s and highlights the advantages of using climate models to understand past climate states and regional circulation patterns to derive more accurate paleoelevation estimates using proxy temperature and moist enthalpy

fragment of the coast range ophiolite and the great valley sequence in the san juan islands washington the decatur terrane is a small allochthonous fragment of upper jurassic oceanic crust with an overlying blanket of upper jurassic lower cretaceous sedimentary rocks in the san juan islands the stratigraphy and petrotectonic elements are dissimilar to those of coeval sequences in the pacific northwest oregon washington and southern british columbia but are virtually identical to those of the coast range ophiolite and overlying great valley sequence south of san francisco california this stratigraphic correlation together with regional considerations suggests that the decatur terrane was detached and transported during cretaceous time the resultant displacement is in excess of 1000 km

paleomagnetism of the spences bridge group and northward displacement of the intermontane belt british columbia a second look the spences bridge group is a mid cretaceous 104 ma volcanic succession in the southern intermontane belt of the canadian cordillera 50 5 n 121 w it comprises the pimainus formation mafic to felsic lava volcaniclastic and interbedded epiclastic rocks and the overlying spius formation andesitic lava flows including previous work we have 55 sites distributed among 15 localities representing most of the 3000 m thickness forty seven sites 286 oriented cores 457 specimens mainly andesites yielded acceptable data the beds are gently to moderately tilted partly due to synvolcanic deformation samples taken from a sequence of flows at any one locality have with one exception well grouped magnetization directions polarities are all normal as expected for rocks laid down in the cretaceous normal superchron declinations always are clockwise of that expected of cratonic north america indicating 60 rotation of the spences bridge group as a whole however declinations differ from locality to locality implying relative interlocality rotations about vertical axes hence inclination only analysis has been used to estimate dispersion mean inclination and paleolatitude minimum dispersion for the spius formation 27 sites was achieved after 80 untilting but the changes between 80 and 100 untilting are insignificant indicating that magnetization was acquired predominantly before tilting by contrast minimum dispersion for the pimainus formation 20 sites was achieved after 50 untilting indicating that magnetization was acquired after synvolcanic tilting when buried beneath the overlying spius formation polished thin section studies show that magnetite in the pimainus formation has undergone extensive low temperature hydrothermal alteration whereas magnetite in the spius formation shows little alteration throughout the range of tilt correction from 0 to 100 the mean inclinations of both formations were less than expected from observations obtained from mid cretaceous rocks of cratonic north america the best estimate of paleolatitude from the spius formation is 50 8 5 0 p 0 05 which is 9 5 5 7 less than would be expected had the rocks had been rigidly attached to north america this corresponds to displacement from the south of 1100 600 km displacement between the northern intermontane belt and craton probably was accommodated along major strike slip faults northern rocky mountain trench finlay pinchi etc in the south our results require a major dextral fault the intra quesnellia fault to be situated during late cretaceous or paleocene time within or marginal to the omineca belt along which about 1000 km of dextral motion occurred this could be a southern extension of the pinchi fault whose trace is now obscured by eocene extension and tectonic denudation the results also indicate that the largest tectonic discontinuity in the canadian cordillera occurs not to the east of the intermontane belt as commonly assumed but to the west because the displacements relative to cratonic north america observed from the intermontane belt are only about one third of those observed from the coast belt

a compaction correction for the paleomagnetism of the nanaimo group sedimentary rocks implications for the baja british columbia hypothesis 1 a paleomagnetic and magnetic anisotropy study of the late cretaceous northumberland formation on hornby island british columbia was conducted to determine if burial compaction could have caused its anomalously shallow inclinations the shallow nanaimo group inclinations have been used to support the baja british columbia baja bc model of continental dynamics in which superterranes were transported thousands of kilometers northward along the active north american continental margin in the cretaceous a mean of the site means from the northumberland formation is d 5 8 i 50 9 95 7 9 n 8 anisotropy of magnetic susceptibility ams and anisotropy of anhysteretic remanence aar were measured to identify and correct for any inclination shallowing caused by depositional compactional processes both concretion and fine grained rock samples had typical depositional compactional ams and aar fabrics with bedding perpendicular minimum principal axes a revised correction equation was used to account for the effects of either triaxial magnetic fabrics or small angular deviations of principal axes from the bedding plane the average inclination was increased by 9 6 after the compaction correction d 6 1 i 60 5 95 7 1 n 8 and the mean inclination of concretion and fine grained rock sites was significantly steeper than ward et al s 1997 result i 42 5 placing hornby island and the insular superterrane at a paleolatitude of 41 n in the late cretaceous this paleolatitude indicates that baja bc did translate northward since the late cretaceous by about 1600 km but not by the 3500 km previously indicated

paleomagnetic evidence that the central block of salinia california is not a far traveled terrane new paleomagnetic results from late cretaceous 75 85 m y red beds on the central block of salinia indicate that salinia was located within 6 in latitude of its current cratonal north american position during the late cretaceous after correction for neogene san andreas fault transport the red beds formed as alluvial fan overbank deposits with hematite cement deposited directly on salinian granites in the la panza range paleomagnetic analysis shows two components of magnetization in the red beds a low blocking temperature present day overprint residing in goethite and a high blocking temperature 600 component residing in hematite the hematite magnetization is a chemical remanent magnetization which formed soon after deposition during pedogenesis the bedding corrected hematite remanence contains a magnetic polarity stratigraphy with antipodal normal and reversed directions twenty three class i sites 95 20 have an average hematite direction with inclination 54 4 and declination 18 2 95 6 1 after structural correction these paleomagnetic data suggest that salinia resided at about 35 n latitude during the late cretaceous within 6 of its current location adjacent to cratonal north america by contrast a summary of paleomagnetic data from the peninsular ranges terrane and the sur obispo terrane which are currently outboard of salinia shows northward transport of these terranes of 12 to 22 relative to their current locations in north america since the cretaceous the offsets increase systematically away from the craton with the most outboard sur obispo terrane which is composed of accretionary prism and distal forearc material showing the largest degree of northward translation

is the gulf stream responsible for europe s mild winters is the transport of heat northward by the gulf stream and north atlantic drift and its subsequent release into the midlatitude westerlies the reason why europe s winters are so much milder than those of eastern north america and other places at the same latitude here it is shown that the principal cause of this temperature difference is advection by the mean winds south westerlies bring warm maritime air into europe and north westerlies bring frigid continental air into north eastern north america further analysis of the ocean surface heat budget shows that the majority of the heat released during winter from the ocean to the atmosphere is accounted for by the seasonal release of heat previously absorbed and not by ocean heat flux convergence therefore the existence of the winter temperature contrast between western europe and eastern north america does not require a dynamical ocean two experiments with an atmospheric general circulation model coupled to an ocean mixed layer confirm this conclusion the difference in winter temperatures across the north atlantic and the difference between western europe and western north america is essentially the same in these models whether or not the movement of heat by the ocean is accounted for in an additional experiment with no mountains the flow across the ocean is more zonal western europe is cooled the trough east of the rockies is weakened and the cold of north eastern north america is ameliorated in all experiments the west coast of europe is warmer than the west coast of north america at the same latitude whether or not ocean heat transport is accounted for in summary the deviations from zonal symmetry of winter temperatures in the northern hemisphere are fundamentally caused by the atmospheric circulation interacting with the oceanic mixed layer copyright 2002 royal meteorological society

late paleocene early eocene paleosols and a new measure of the transport distance of alaska s yakutat terrane abstractan intensely weathered paleosol representing a nearly isochronous landscape exists at many places in continental late paleocene early eocene strata in north america most commonly a single siderite spherule bearing horizon is found from which 18o values were obtained to construct a paleolatitudinal gradient for late paleocene early eocene north america comparison of the paleosol siderite spherule 18o composition from the displaced yakutat terrane of alaska to the north american paleolatitudinal gradient indicates that during the late paleocene early eocene the terrane existed at 44 paleonorth thus supporting hypotheses for a far traveled terrane history

paleomagnetic results from the central sierra nevada constraints on reconstructions of the western united states paleomagnetic results from three plutons of the central sierra nevada limit the motion of the sierra nevada relative to the north american craton to 5 8 of poleward motion and 7 11 of clockwise rotation since about 90 ma the indicated rotation and translation are not significant at the 95 confidence level a new tectonic model is presented that is consistent with all available paleomagnetic data from the sierra nevada great valley klamaths oregon coast range cascades and western nevada the paleogeographic reconstructions of this model associate the displacement of major crustal blocks with basin and range extension starting at about 30 ma this model accounts for about 15 of clockwise rotation of the klamaths and southern cascades about 2 of clockwise rotation of the sierra nevada and great valley and 26 of clockwise rotation of the oregon coast range since 30 ma the model is consistent with 40 of clockwise rotation of the oregon coast range before 30 ma as proposed by magill and cox 1980 the amount of basin and range extension in this model at latitude 41 n is 225 km directed e w and at latitude 35 n is 245 km directed wsw ene

submarine fan deposystems and tectonics of a late cretaceous forearc basin along an accretionary convergent plate boundary maccoll ridge formation wrangell mountains alaska analysis of upper cretaceous sedimentary and volcanic strata in the wrangell mountains of south central alaska provides an opportunity to study the tectonics depositional systems and provenance of a forearc basin that developed along an accretionary convergent plate boundary new data from the 1150 m thick maccoll ridge formation indicate that deposition occurred during the campanian on a coarse grained submarine fan that was derived from an uplifted allochthonous terrane exposed in the hanging wall of a fault system that separated the forearc basin from the subduction complex new age controls include palynoflora indicative of a late middle to late campanian age and compatible radiometric age determinations of volcanic vitric crystal tuffs near the top of the formation which have 40ar 39ar isochron ages of 79 4 0 7 and 77 9 2 1 ma sedimentological and paleontological data show that sedimentation occurred on the inner portions of a sand and gravel rich submarine fan system evidence for this inte

large scale dataset from china gives new insights into leaf margin temperature relationships leaf margin analysis lma is an important method of estimating paleotemperatures from fossil leaf floras or modern floras although some calibration has been carried out based upon large scale studies of modern forests most of this research has been in north america and europe with relatively little calibration work in east asia in the present study we used species range maps of 3116 native dicot trees of china to derive synthetic local floras for each county from the chinese humid region and compared the percentage of untoothed leaf margined species with several temperature and precipitation related parameters the results confirm the generally strong relationship between the proportion of species with untoothed leaf margins and climatic parameters within china leaf habit deciduous vs evergreen does not strongly affect this relationship the transfer function obtained from china while not identical is similar to those obtained from other regions and is affected by regional restrictions such as complex topography and relic taxa as such it clarifies the potential range of error inherent in the lma method as applied to paleodimate reconstruction it is possible however that with the close similarity of the modern chinese tree floras to neogene floras in the northern hemisphere the present estimate offers a better transfer function for reconstructing the neogene paleoclimate in various regions without extremely cold conditions across the northern hemisphere c 2014 published by elsevier b v

tilt and northward offset of cordilleran batholiths resolved using igneous barometry considerable controversy surrounds the suggestion based on palaeomagnetic evidence that large segments of the north american cordillera travelled long distances parallel to the coast during the latest cretaceous and early tertiary periods well after the amalgamation of exotic terranes discordant palaeomagnetic data from mid cretaceous plutonic rocks of the peninsular ranges batholith of coastal southern california and baja and the mount stuart batholith of the cascade range in washington play a pivotal role in the controversy the discordant data were originally interpreted to reflect northward transport of 1 000 km relative to cratonal north america after the batholiths cooled through their magnetic blocking temperatures1 5 more recently it has been argued that the discordances arise from local tilting of batholiths rather than northward offset6 7 here we present and implement new methods based on hornblende barometry8 for determining the palaeohorizontal in granitic batholiths and correcting palaeomagnetic data for tilting our results indicate that the peninsular ranges and mount stuart batholiths have undergone northward offsets of 1 000 450 and 2 900 700 km respectively and also significant tilting

megafloral change in the early and middle paleocene in the williston basin north dakota usa abstract this paper presents a quantitative analysis of megafloral changes in composition and diversity using collections of early and middle paleocene floras 65 51 to 58 ma in the williston basin of north dakota usa based on the floral composition and stratigraphic ranges of taxa the williston basin floral record can be subdivided into three megafloral zones wbi wbii and wbiii each representing 1 myr the floral record of the basin implies that local and regional paleoenvironmental and climatic changes contributed to transitions in the early and middle paleocene plant communities the williston basin floral record documents a decrease in species richness that mirrors a decrease in mean annual temperatures from the latest cretaceous to middle paleocene these results combined with previous work from the hanna and bighorn basins suggest that climate may have played an important role in patterns of floral diversity and plant community composition further these data indicate that it took paleocene plant communities in the northern great plains millions of years to reach diversity levels common in the cretaceous

hot summers in the bighorn basin during the early paleogene during the early paleogene climate in continental interiors is thought to have been warmer and more equable than today but estimates of seasonal temperature variations during this period are limited global and regional climate models of the paleogene predict cooler temperatures for continental interiors than are implied by proxy data and predict a seasonal range of temperature that is similar to today here we present a record of summer temperatures derived from carbonate clumped isotope thermometry of paleosol carbonates from paleogene deposits in the bighorn basin wyoming united states our summer temperature estimates are 18 c greater than mean annual temperature estimated from analysis of fossil leaves when coupled these two records yield a seasonal range of temperature similar to that in the region today with winter temperatures that are near freezing these data are consistent with our high resolution climate model output for the early eocene in the bighorn basin we suggest that temperatures in continental interiors during the early paleogene greenhouse were warmer in all seasons but not more equable than today if generally true this removes one of the long standing paradoxes in our understanding of terrestrial climate dynamics under greenhouse conditions

carbonate dissolution in a modern mixing zone the potential for dissolution of calcite and aragonite and precipitation of dolomite by the mixing of fresh and saline ground waters has been demonstrated theoretically1 3 although geologists have used these processes in the explanation of the diagenesis of recent4 7 and ancient8 12 carbonates there has been only limited investigation of the geochemical processes of modern mixing zones13 14 here we report the results of chemical and rock profiling through a modern mixing zone on andros island in the bahamas our results demonstrate undersaturation of the waters in the mixing zone with respect to aragonite and calcite and corresponding pervasive dissolution of the carbonate rocks at this level undersaturation is significantly enhanced by bacterial processes which are also responsible for precipitation of an iron rich crust despite chemical supersaturation precipitation of dolomite was not observed thereby casting some doubt on the mixing zone model of dolomitization

ground motion prediction model for vertical response spectra from mexican interplate earthquakes abstract we present ground motion prediction equations gmpes for vertical response spectra from mexican interplate earthquakes at rock sites national earthquake hazards reduction program b class two options to obtain the vertical response spectrum are presented 1 directly from the vertical attenuation model and 2 by multiplying the horizontal spectral ordinates by the vertical to horizontal ratios the equations were built as functions of magnitude and distance to the fault surface of the earthquake using 40 interplate earthquakes we compared our results with previous attenuation models for inslab and interplate earthquakes in mexico and other vertical attenuation models in the world the predicted intensities from the model were found to be in broad agreement with models derived with other models worldwide not many vertical and or vertical to horizontal attenuation models were found in the literature although the vertical response of structures is used in practice and included in design codes nevertheless it seems to be a trend to pay more attention to this model there was also found to be a lack of gmpes for vertical response spectra applicable to subduction interplate earthquakes for a large range of distances and the region under study therefore an attenuation model for interplate earthquakes was developed for distances up to around 400 km and m w from 5 to 8 the model could be useful for probabilistic seismic hazard assessment and as an aid for code writers

paleoclimatic estimation reveals a weak winter monsoon in southwestern china during the late miocene evidence from plant macrofossils the late miocene xianfeng flora of yunnan province southwestern china was chosen to reconstruct the paleoclimate and the intensity of the asian monsoon three available quantitative climate reconstruction methods from fossil plants i e leaf margin analysis lma the climate leaf analysis multivariate program clamp and the coexistence approach ca were used in this study mats mean annual temperatures resulting from these three approaches i e lma 17 2 2 38 degrees c clamp 15 43 1 25 degrees c ca 17 2 21 7 degrees c appear to have been higher than the present 14 9 degrees c suggesting a much warmer climate in the late miocene both the growing season precipitation gsp from clamp 1908 7 217 7 mm and mean annual precipitation map from ca 1206 0 1613 0 mm estimates are higher than modern values 1003 2 mm gsp and 1038 mm map respectively indicating a more humid climate during the late miocene by comparing these with climates reconstructed from neighboring late miocene floras we conclude that the general late miocene climate appears warmer and more humid than present conditions in southwestern china furthermore the evident differences in estimated monthly temperatures between the summer and winter and precipitations between the humid and dry seasons indicate the existence of seasonality though not as strong as that of today difference in precipitation of dry season indicates a marked strengthening in the winter monsoon since the late miocene a new monsoon intensity index has also been defined based on precipitation seasonality to investigate the intensity of the asian monsoon c 2012 elsevier b v all rights reserved

wood growth indices as climate indicators from the upper cretaceous cenomanian turonian portion of the winton formation australia abstract although the mid to late cretaceous is regarded as a global warm period increasingly a more complex picture of warming and cooling is emerging new techniques allow more precise dating of terrestrial localities opening opportunities for using climate proxy approaches on terrestrial fauna and flora to better capture the complexity of cretaceous climate here an attempt is made to understand the seasonality and inter annual variability of two newly dated localities from the upper preserved portion cenomanian turonian of the winton formation australia primarily quantitative approaches to palaeodendrology are used the results suggest both seasonality and high variability in climate conditions that affect growth between years including evidence for floods the longest series qm f44338 suggests oscillatory patterns of good and poor growth in a 15 year alternating cycle similar to the contemporary pacific decadal oscillation although other potential explanations should be considered and tested

paleoaltimetry incorporating atmospheric physics and botanical estimates of paleoclimate we present a method for deducing paleoaltitudes that incorporates basic physical principles of atmospheric science and inferences of paleoclimates from plant leaf physiognomy we exploit the average west to east flow of the atmosphere at mid latitudes and a thermodynamically conserved variable in the atmosphere moist static energy the combined internal latent heat and gravitational potential energy of moist air to develop a method that relies on a parameter that varies with height in the atmosphere in a predictable fashion because the surface distribution of moist static energy is constrained by atmospheric dynamics and thermodynamics the combined internal and latent heat energies also known as the moist enthalpy should only vary with altitude provided we know the distribution of moist static energy thus we avoid having to make assumptions about the mean annual temperature lapse rate which varies spatially and temporally owing to unpredictable variations in atmospheric water vapor to estimate a paleoaltitude therefore we require 1 a priori knowledge of the spatial distribution of moist static energy for the paleoclimate and 2 the ability to estimate paleoenthalpy for two isochronous locations one at sea level the other at some unknown elevation to achieve this we investigated the spatial distribution of moist static energy for the present day climate of north america to estimate the deviations in moist static energy from zonal invariance in parallel we quantified the relation between moist enthalpy and plant leaf physiognomy of modern forests assuming that such deviations from zonal invariance and such relationships between physiognomy and enthalpy apply to ancient climates and fossil leaves these investigations yield an uncertainty estimate of 910 m in the paleoaltitude difference between two isochronous fossil assemblage locations

regional tilt of the mount stuart batholith washington determined using aluminum in hornblende barometry implications for northward translation of baja british columbia we have developed a new quantitative method to estimate paleohorizontal in granitic plutons using the aluminum in hornblende ah barometer the method is used to correct previously published paleomagnetic data from the 93 96 ma mount stuart batholith of the cascades mountains washington state for the effects of postemplacement tilting ah barometry was done on 46 samples from the batholith using the compositions of hornblende rims coexisting with the full mineral assemblage required for pressureestimation high contrastback scatteredelectronimagingwas usedtoensurethattheanalyzedhornblendeswerenotsignificantly affected by subsolidus alteration the success of the ah barometry is indicated by two observations first increases in the al content of the hornblendes are governed almost entirely by a pressure sensitive tschermak type substitution second amphibole plagioclase thermometry indicates that assemblage equilibration occurred at or very near magmatic conditions 650 c and that temperature has a negligible effect on our pressure estimates ah barometry results indicate that the depth of crystallization across the batholith decreases systematically from 0 3 gpa in the northwest to 0 15 gpa in the southeast consistentwithindependentbarometryforthecontactaureole ofthebatholithandregionalstructuralandstratigraphicrelations using a best fit planar tilt model and bootstrap analysis of uncertainties we estimate that the paleohorizontal plane has a strike of 43 630 4 and dip of 7 62 0 southeast 695 confidence our estimated paleohorizontal allows us to restore the paleomagnetic data of beck et al 1981 and to estimate the original paleolatitude of the mount stuart batholith beck et al found that the southern part of the batholith yielded a number of sites with a well defined high coercivity remanence the carrier of this remanence was not resolved but the following four lines of evidence stronglysuggestthatthepublisheddirectionswereacquiredshortly after emplacement of the batholith 1 the stable sites all came from the shallowest and most rapidly cooled portions of the batholith as indicated by our ah results and concordant k ar ages for hornblende biotite pairs 2 the high coercivity component was always normal in polarity which is consistent with emplacement of the mount stuart batholith at the end of the cretaceous long normal 3 sites from the batholith and the contact aureole gave similar directions 4 the directions show no indication of tilt related smearing after restoration the paleomagnetic data indicate 42 6 11 clockwise rotation and 3100 6 600 km of northward offset

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

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

geometric test for late cretaceous paleogene intracontinental transform faulting in the canadian cordillera the tintina trench northern rocky mountain trench tt nrmt fault zone and the fraser river straight creek fr sc fault zone are separate en echelon concentric small circle fault segments of a composite intracontinental transform fault zone more than 2500 km long that cuts diagonally across the canadian cordillera from the outboard part of a tectonic collage of accreted foreign terranes in the south into the north american preaccretionary continental margin in the north most of the 450 km of right hand slip on the tt nrmt fault zone was transformed southward during the late cretaceous and paleocene into oblique convergence in the southern canadian rockies the remainder probably comprising less than 100 km was transformed southwestward during early and middle eocene time via a zone of distributed shear and east west crustal stretching into right hand slip on the en echelon fr sc fault zone these interpretations based on regional systematic mapping of geologic structures are in conflict with interpretations of paleomagnetic measurements that call for more than 1000 km of post mid cretaceous right hand displacement along the general locus of the tt nrmt fault zone involving foreign terranes and the parts of north america to which they had been accreted this paradox must be resolved

a model for vertical to horizontal response spectral ratios for europe and the middle east in the framework of probabilistic seismic hazard analysis the preferred approach for obtaining the response spectrum of the vertical component of motion is to scale the horizontal spectrum by vertical to horizontal v h spectral ratios in order to apply these ratios to scenario or conditional mean spectra the v h ratios need to be defined as a function of variables such as magnitude distance and site classification a new model for the prediction of v h ratios for peak ground acceleration and spectral accelerations from 0 02 to 3 0 s is developed from the database of strong motion accelerograms from europe and the middle east a simple functional form expres sing the v h ratios as a function of magnitude style of faulting distance and site class is found to be appropriate and the associated aleatory variability is found to be at least as low as that obtained in other studies using more complex models the predicted ratios from the new european model are found to be in broad agreement with recent models derived from predominantly western north america data

角閃石中のアルミニウム圧力計を使って決定された ワシントン州 stuart山バソリスの広域的傾動 バハ ブリティシュコロンビアの北方への転移に関する意味

the cordilleran ribbon continent of north america the north american cordilleran orogen is the result of a two stage process a triassic jurassic accretion within panthalassa forming saybia a composite ribbon continent and b late cretaceous collision of saybia with north america this model requires that a large portion of the continental foreland of the orogen is exotic the exotic continental component of saybia cassiar platform is distinguished from the autochthon on the basis of its a triassic eurasian fauna b involvement in a major late triassic early jurassic orogenic event and c young in part grenvillian basement and mantle a mid cretaceous magmatic arc records west dipping subduction beneath the east margin of saybia the related accretionary prism consists of imbricated shale chert and deep water limestones the medial basin and overlies an isotopically juvenile mantle domain carbonatite complexes delineate the cryptic suture separating saybia and the autochthon paleomagnetic and paleobotanical data place saybia 2000 km to the south relative to the autochthon at 80 ma late cretaceous thrust belt development records transpression between the north moving ribbon continent and the autochthon pinning against the okhotsk chukotka arc in siberia buckled saybia giving rise to the alaskan promontory

a comparison of nga ground motion prediction equations to italian data abstract ground motion prediction equations gmpes have recently been developed in the next generation attenuation nga project for application to shallow crustal earthquakes in tectonically active regions we investigate the compatibility of those models with respect to magnitude scaling distance scaling and site scaling implied by italian strong motion data this is of interest because 1 the italian data are principally from earthquakes in extensional regions that are poorly represented in the nga dataset and 2 past practice in italy has been to use local gmpes based on limited datasets that cannot resolve many significant source path and site effects we find that the magnitude scaling implied by the italian data is compatible with four nga relations however the italian data attenuate faster than implied by the four ngagmpes at short periods the differences are statistically significant comparison with the fifth one was not possible because it was developed for rock conditions only three regression coefficients are reevaluated for the four ngagmpes to reflect the faster attenuation a constant term a term controlling the slope of distance attenuation and a source fictitious depth term the scaling of ground motion with respect to site shear wave velocity is consistent between the nga models and italian data moreover the data are found to contain a nonlinear site effect that is generally compatible with nga site terms the intraevent scatter of italian data is higher than in the nga models although interevent scatter is comparable to nga recommendations when the faster distance attenuation is considered on the basis of these findings we recommend using the nga relations with the aforementioned minor modifications to evaluate ground motions for seismic hazard analysis in italy

a predictive equation for vertical to horizontal response spectral ratios in northern iran abstract the importance of the vertical component of ground motion in damage infliction on a variety of structural systems has been shown in recent years however the available models for ground motion prediction equations gmpes for this component of earthquakes are limited and most of the existing gmpes have been specifically developed for the horizontal component of ground motion alternatively in some cases it is proposed to scale the horizontal spectrum of the earthquake to the vertical one using vertical to horizontal response spectral ratios vhsrs in this work the applicability of some global and regional vhsr models for northern iran are evaluated using several existing statistical approaches the results of these evaluations show inadequate correlation between these models and the observed vhsrs in this region consequently a new vhsr model has been proposed to convert the horizontal earthquake spectrum to the vertical one in the studied region in order to determine the regression coefficients for the proposed vhsr model some 712 three component records with distances less than 300 km from the source from 79 earthquakes with the magnitude ranging from m w 4 1 to 7 3 were used regression coefficients for peak ground acceleration and pseudospectral acceleration for 5 damped systems are determined using a random effect approach a series of comparative studies on the proposed model with respect to the existing vhsrs was performed using the median residuals for the spectral periods in the 0 1 3 s range the results of such investigation show significant reduction of the variability for the proposed model at least 50 compared with the other vhsrs online material database of strong motion records

north american nonmarine climates and vegetation during the late cretaceous abstract analyses of physiognomy of late cretaceous leaf assemblages and of structural adaptations of late cretaceous dicotyledonous woods indicate that megathermal vegetation was an open canopy broad leaved evergreen woodland that existed under low to moderate amounts of rainfall evenly distributed through the year with a moderate increase at about 40 45 n many dicotyledons were probably large massive trees but the tallest trees were evergreen conifers megathermal climate extended up to paleolatitude 45 50 n mesothermal vegetation was at least partially an open broad leaved evergreen woodland perhaps a mosaic of woodland and forest but the evapotranspirational stress was less than in megathermal climate some dicotyledons were large trees but most were shrubs or small trees evergreen conifers were the major tree element some mild seasonality is evidenced in mesothermal woods precipitational levels probably varied markedly from year to year northward of approximately paleolatitude 65 n evergreen vegetation was replaced by predominantly deciduous vegetation this replacement is presumably related primarily to seasonality of light the southern part of the deciduous vegetation probably existed under mesothermal climate comparisons to leaf and wood assemblages from other continents are generally consistent with the vegetational climatic patterns suggested from north american data limited data from equatorial regions suggest low rainfall late cretaceous climates except probably those of the cenomanian had only moderate change through time temperatures generally appear to have warmed into the santonian cooled slightly into the campanian and more markedly into the maastrichtian and then returned to santonian values by the late maastrichtian the early eocene was probably warmer than any period of the late cretaceous latitudinal temperature gradients were lower than at present for the campanian and maastrichtian a gradient of about 0 3 c 1 latitude is inferred equability was high a mean annual range of temperature of about 8 c is inferred for paleolatitude 51 56 n during the campanian most late cretaceous plants evolved in a climate characterized by absence of freezing and low to moderate amounts of precipitation a brief low temperature excursion and a major long lasting increase in precipitation occurred at the cretaceous tertiary boundary in megathermal climates these events selected for plants that could exist in rainforest environments in mesothermal climates deciduousness and contamitant structural adaptations were selected the events at the cretaceous tertiary boundary had a major and long lasting impact on the evolution of land plants and their ecosystems low precipitation at low to middle late cretaceous latitudes is suggested to be the result of high levels of atmospheric co2 which in turn are probably related to inability of warm saline oceans to store large amounts of carbon conditions appear to have rapidly changed at the cretaceous tertiary boundary when oceanic circulation and stratification may have been fundamentally altered after the boundary the oceans were apparently able to store much greater amounts of carbon and the oceans withdrew large amounts of co2 from the atmosphere in turn more precipitation fell at low to middle latitudes the resulting high biomass vegetation formed a second major carbon reservoir to keep atmospheric co2 low relative to the late cretaceous changes in oceanic and atmospheric circulation probably resulted from some factor external to the ocean atmosphere system

simulation of strong ground motion in northern iran using the specific barrier model summary in this study based upon the calibrated specific barrier model sbm against the latest available strong motion data ground motion prediction equations for soil and rock sites in northern iran are developed the sbm may provide the most complete simple and self consistent description of the faulting process which is applicable in both near fault and far field regions consequently the sbm may provide consistent ground motion simulations over the entire necessary frequency range and for all distances of engineering interests to determine source parameters in this study we used 163 three component records of 32 earthquakes with magnitude ranging from mw 4 9 to 7 4 in northern iran in the database records with hypocentral distances less than 200 km are chosen and only earthquakes whose moment magnitude estimates are available have been used furthermore using the best available information recording sites are classified into two main geologic categories rock and soil because of the lack of site amplification information in the most regions of the world including iran we used the h v ratio method for estimating the site amplification moreover the kappa factor that shows diminishing the high frequency amplitude is determined in this study two data sets are considered for determining the source parameters g and l and the h v ratio and the kappa factor only s wave part of signals is used in each analysis regression analysis is performed using random effects method that considers both interseismic event to event and coseismic within event variabilities to effectively deal with the problem of weighting observations from different earthquakes the residuals are controlled against available northern iranian strong ground motion data to verify that the model predictions are unbiased and that there are no significant residual trends with magnitude and distance at first it is assumed that no sign of self similarity breakdown is observed between the source radius and its seismic moment after controlling the results the modified sbm should be used as some deviations have been observed to verify the robustness of the results the number of observations is changed by removing various randomly selected data sets from the original database which results in unchanged results of the model stochastic simulations are then implemented to predict peak ground motion and response spectra parameters the stochastic sbm predictions are in relatively good agreement with other available attenuation relationships proposed for iran europe and middle east it has been shown that the proposed sbm of this study provides unbiased ground motion estimates over the entire frequency range of most engineering applications it provides a reliable and physically realistic yet computationally efficient way to model strong ground motions

paleomagnetism of the mount stuart batholith revisited again what has been learned since 1972 we have collected 20 new paleomagnetic sites from the mount stuart batholith and the adjacent beckler peak stock using thermal and low temperature demagnetization and rock magnetic tests we have found that the remanence in most of the batholith is carried by single domain magnetite the mean of the new mount stuart batholith sites is d 354 2 i 46 2 k 87 2 a95 4 6 n 11 and is similar to those of the beck and noson 1972 and beck and others 1981 studies examination of ar geochronology of hornblende and biotite from the mount stuart batholith finds that the southern part of the batholith cooled through the blocking temperature of magnetite at 91 ma the northern part cooled through the blocking temperature of magnetite at 86 ma and of pyrrhotite at 83 ma from these combined results we conclude that the paleomagnetic directions from the southern part of the batholith were acquired within 0 5 to 1 0 ma of the time at which the ah barometers cooled below their closure temperature use of the ah barometry to establish paleohorizontal for these rocks is thus well justified correcting the mount stuart direction for the tilt indicated by the aluminum in hornblende ah barometry the mean becomes d 355 9 i 50 6 this result places the mount stuart batholith at a latitude of 31 3 3 8 3 4 n at 91 ma by identifying the carrier of remanence in the mount stuart batholith as being single domain sd magnetite we have removed the major remaining uncertainty in interpreting the paleomagnetism of these rocks the characteristic magnetization repeatedly found in the mount stuart rocks clearly supports the microplate tectonic model of beck and noson 1972 presently manifest as the baja british columbia baja bc hypothesis

quantitative reconstruction of the late miocene monsoon climates of southwest china a case study of the lincang flora from yunnan province the miocene lincang leaf assemblage is used in this paper as proxy data to reconstruct the palaeoclimate of southwestern yunnan sw china and the evolution of monsoon intensity three quantitative methods were chosen for this reconstruction i e leaf margin analysis lma climate leaf analysis multivariate program clamp and the coexistence approach ca these methods however yield inconsistent results particularly for the precipitation as also shown in european and other east asian cenozoic floras the wide range of the reconstructed climatic parameters includes the mean annual temperature mat of 18 5 24 7 degrees c and the mean annual precipitation map of 1213 3711 mm compared with the modem lincang climate mat 17 3 degrees c map 1178 7 mm the miocene climate is slightly warmer wetter and has a higher temperature seasonality a detailed comparison on the palaeoclimatic variables with the coeval late miocene xiaolongtan flora from the eastern part of yunnan allows us to investigate the development and interactions of both south asian and east asian monsoons during the late miocene in southwest china now under strong influence of these monsoon systems our results suggest that the monsoon climate has already been established in southwest yunnan during the late miocene furthermore our results support that both southeast asian and east asian monsoons co occurred in yunnan during the late miocene c 2010 elsevier b v all rights reserved

testing the global applicability of ground motion prediction equations for active shallow crustal regions abstract large research initiatives such as the global earthquake model gem or the seismic hazard harmonization in europe share projects concentrate a great collaborative effort on defining a global standard for seismic hazard estimations in this context there is an increasing need for identifying ground motion prediction equations gmpes that can be applied at both global and regional scale with increasing amounts of strong motion records that are now available worldwide observational data can provide a valuable resource to tackle this question using the global dataset of allen and wald 2009 we evaluate the ability of 11 gmpes to predict ground motion in different active shallow crustal regions worldwide adopting the approach of scherbaum et al 2009 we rank these gmpes according to their likelihood of having generated the data in particular we estimate how strongly data support or reject the models with respect to the state of noninformativeness defined by a uniform weighting such rankings derived from this particular global dataset enable us to explore the potential of gmpes to predict ground motions in their host region and also in other regions depending on the magnitude and distance considered in the ranking process we particularly focus on the influence of the distribution of the testing dataset compared with the gmpe s native dataset one of the results of this study is that some nonindigenous models present a high degree of consistency with the data from a target region two models in particular demonstrated a strong power of geographically wide applicability in different geographic regions with respect to the testing dataset the models of akkar and bommer 2010 and chiou et al 2010

the relationship between leaf physiognomy and climate based on a large modern dataset implications for palaeoclimate reconstructions in china abstract in this paper correlation between modern leaf physiognomy and climate in china are examined to optimize the use of leaf characters as a palaeoclimate proxy a large dataset was compiled recording the distribution of leaf physiognomic characters among 3166 native dicot trees species across 732 calibration grids on a county level grids span a range of ecological environments tropical rainforests to alpine shrubs across humid areas thirteen climatic parameters were included for each grid and 22 leaf physiognomic characters were scored for each tree species the correlation between leaf physiognomic characters and climatic parameters were calculated based on single linear regressions slr and multiple linear regressions mlr results indicate clear spatial distribution patterns linked to latitude exist for all leaf characters with temperature coldest month mean temperature cmmt and precipitation growing season precipitation gsp being the main climate controls moreover because leaf characters are more closely correlated with precipitation during the three wettest consecutive months p3wet rather than with precipitation during the three driest consecutive months p3dry seasonal variations in rainfall associated with the asian monsoon might especially influence leaf physiognomic characters closer correlations between leaf physiognomy and climate are seen using mlr compared with slr therefore mean annual temperature mat and mean annual precipitation map based on mlr equations provide the most promising basis for palaeoclimate reconstructions in china

deriving temperature estimates from southern hemisphere leaves abstract the percentage of woody dicots with entire margined leaves in a flora is known to be positively correlated with mean annual temperature leaf margin analysis lma but this relationship is not globally uniform in particular the floras of australia and new zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the northern hemisphere this difference is more marked in new zealand where the lma relationship appears entirely absent here we amass data for both northern and southern hemispheres using standard protocols and show that regional variations in the leaf margin mean annual temperature relationship are real but become less significant when other characters are included even new zealand falls into line and most of the mean annual temperature signal in new zealand floras is encoded in non margin features we introduce a new clamp climate leaf analysis multivariate program calibration dataset for the southern hemisphere comprising leaf physiognomic data from argentina bolivia south africa australia new zealand and other pacific islands that offers comparable precision for climate prediction to similar datasets derived from the northern hemisphere

quantification of calabrian climate in southern primory e far east of russia an integrative case study using multiple proxies abstract early pleistocene climate dynamics in the russian far east southern primory e is studied using multiple quantitative techniques on various palaeobotanical organ types climate data of the time were obtained from a total of 8 macrofloras fruits and seeds woods and leaves and 18 microfloras collected from a 10 m thick terrigenous succession exposed in the pavlovskoe brown coal field according to magnetostratigraphy the studied section covers the last 200 kyr of the calabrian and comprises the early late pleistocene transition a crucial time span involving the transition from obliquity forced cyclicity to the strong eccentricity triggered glacial events in this first integrative study on palaeoclimate of the russian far east we employ growth ring analysis multivariate anatomical analysis leaf margin analysis climate leaf analysis multivariate program and coexistence approach on the different organs partly originating from the same layer the investigation documents the following important outcomes 1 climate data obtained from the various methods are proven to be largely consistent 2 the late calabrian of the southern primory e was characterized by overall cooling and drying our climate record displays 2 small scale cycles warm peaks at 19 4 19 8 and 14 0 14 8 m are tentatively correlated to the global isotope stages mis 25 and mis 21 respectively 3 in the warm phases the calabrian climate of southern primory e was significantly warmer and wetter when compared to the present especially regarding the cold season while in cold phases climate was similar to modern or event slightly cooler 4 as of today early pleistocene climate of southern primory e was warmer and wetter than neighboring areas of the south rfe 5 the effect of the east asian monsoon systems on the climate of the southern primory e was less pronounced compared to the present

topographic evolution of the sierra nevada measured directly by inversion of low temperature thermochronology at present there are at least two competing ideas for the topographic evolution of the sierra nevada one idea is that the sierra nevada was formed as a monocline in the cretaceous marking the transition from the great valley forearc basin to the west and a high nevadaplano plateau to the east similar to the west flank of the modern altiplano of the andes both the thermochronologic imprint of local relief and the stable isotopic evidence of a topographic rain shadow support this hypothesis a second idea supported by geomorphic observations suggests that the sierra gained a large fraction of its present elevation as recently as the pliocene this recent surface uplift could have been driven by convective removal of the lower part of the lithosphere the isostatic response to basin and range faulting and or by changes in dynamic topography associated with deep subduction of the farallon plate here we present the first comprehensive analysis of low temperature thermochronology in the sierra nevada which indicates that both ideas are likely correct we show that thermochronology can resolve surface uplift as well as exhumation by measuring long wavelength topographic evolution relative to sea level uplift measurements are possible whenever there is sufficient constraint on vertical rock velocity the tilting of isochrones defined as surfaces of equal cooling age provide this constraint in the sierra nevada three new factors further distinguish our analysis the first is that we allow for the local relief and the long wavelength topography to evolve independently second we use al in hb barometry to constrain the initial depth of emplacement for the sierra nevada plutons third our analysis is tied to a sea level datum by using the paleo bathymetric record of the great valley basin where it transitions to the sierra nevada batholith results indicate that westward tilting of the sierra nevada accounts for 2 km of uplift since 20 ma topographic relief increased by a factor of 2 these findings suggest that the sierra nevada lost elevation through most of the tertiary but regained much of its initial elevation following the onset of surface uplift in the miocene

plio pleistocene floras of the vildstejn formation in the cheb basin czech republic a floristic and palaeoenvironmental review abstract plant fossil assemblages foliage fruits and seeds pollen wood from the pliocene and early pleistocene deposits in w bohemia the vildstejn formation of the cheb basin tachov cheb doma lice graben are newly analysed using several palaeoenvironmental methods with the aim to reconstruct palaeovegetation and palaeoclimatic changes floras of four subsequent stratigraphic levels show a decrease of exotic elements in the pliocene and a massive immigration of boreal elements in the early pleistocene vegetation changes start with broad leaved deciduous and mixed mesophytic forests and continue towards light forests of the mentioned types in areas of zonal to extrazonal habitats this vegetational change is characterised by an immigration of dry herbaceous and sclerophyllous elements wetland communities from higher positions in the profiles stepwise loose exotic components and point to cool temperate conditions similar to the present conditions palaeoclimatic signals show warmer and more humid conditions for the pliocene levels about 15 c of mean annual temperature 5 c of mean temperature of the coldest month and 25 c of mean temperature of the warmest month more than 900 mm of mean annual precipitation early pleistocene proxy data indicate the beginning of a cooler phase at the plio pleistocene boundary about 7 c of mean annual temperature and decreasing trend of precipitation but conditions not colder than those of the present day in the nw part of the bohemian massif

extremely high sea surface temperatures at low latitudes during the middle cretaceous as revealed by archaeal membrane lipids the middle cretaceous 125 88 ma greenhouse world was characterized by high atmospheric co 2 levels the general absence of polar ice caps and much higher global temperatures than at present both 1 8 o based and model based temperature reconstructions indicate extremely high sea surface temperatures ssts at high latitudes however there are a number of uncertainties with sst reconstructions based on 1 8 o isotope data of foraminifera due to diagenetic overprinting effects and tenuous assumptions with respect to the 1 8 o value of cretaceous seawater the paleoecology of middle cretaceous marine organisms and seawater ph here we applied a novel sst proxy i e text tetraether index of 86 carbon atoms based on the membrane lipids of marine crenarchaeota derived from middle cretaceous sedimentary rocks deposited at low latitudes the text proxy indicates that tropical ssts in the proto north atlantic were at 32 36 c during the early albian and late cenomanian early turonian this finding agrees with sst estimates based on 1 8 o paleothermometry of well preserved foraminifera as well as global circulation model calculations the text proxy indicates cooler ssts 27 32 c for the equatorial pacific during the early aptian which is in agreement with sst estimates based on 1 8 o paleothermometry