provenances of the mesozoic sediments in the ordos basin and implications for collision between the north china craton ncc and the south china craton scc abstract to constrain the provenance of the ordos basin and the evolution history of the qinling orogen belt from the triassic to the jurassic 10 samples from the dongsheng area and 28 samples from the yan an area were analyzed for u pb ages and lu hf and sm nd isotopic compositions the results indicate that middle jurassic sediments in the dongsheng area were derived from the khondalite belt langshan mountain and the yinshan terrane mesozoic sediments in the yan an area consist of two parts one part is derived from the north china craton ncc which has u pb age groups of 1 8 ga and 2 5 ga and hf model ages of 2 8 ga the other part is derived from the qilian qinling orogenic belt which has u pb age groups of 600 1500 ma and 100 500 ma and nd and hf isotopic model ages of less than 2 2 ga combining the u pb ages with the hf and nd isotopic model ages mesozoic detrital zircons with u pb age groups of 1 8 ga and 2 5 ga in the yan an area are found to also be derived from the khondalite belt langshan mountain and the yinshan terrane not from the trans china orogen belt from the late late triassic sediments of the yan an area the low average values of the hf 2 03 ga and nd 2 03 ga model ages and the characteristic age population of 600 1500 ma reveal that the main collision or continental subduction between the ncc and the south china craton scc occurred in the late late triassic after the main collision or continental subduction the proportion of sediments from the qinling qilian orogenic belt began to decrease recorded in the early jurassic samples which may be in response to the gradual slowing of the uplift speed of the qinling orogenic belt in the early middle jurassic the sediments have a main u pb age population of 100 500 ma low detrital zircon hf model ages average value is 1 17 ga and low whole rock nd model ages average value is 1 13 ga which suggests that the qilian qinling orogenic belt may have a fast uplift history in the early middle jurassic

triggered surface slips in the salton trough associated with the 1999 hector mine california earthquake surface fracturing occurred along the southern san andreas superstition hills and imperial faults in association with the 16 october 1999 mw 7 1 hector mine earthquake making this at least the eighth time in the past 31 years that a regional earthquake has triggered slip along faults in the salton trough fractures associated with the event formed discontinuous breaks over a 39 km long stretch of the san andreas fault from the mecca hills southeastward to salt creek and durmid hill a distance from the epicenter of 107 to 139 km sense of slip was right lateral only locally was there a minor 1 mm vertical component of slip dextral slip ranged from 1 to 13 mm maximum slip values in 1999 and earlier triggered slips are most common in the central mecca hills field evidence indicates a transient opening as the hector mine seismic waves passed the southern san andreas fault comparison of nearby strong motion records indicates several periods of relative opening with passage of the hector mine seismic wave a similar process may have contributed to the field evidence of a transient opening slip on the superstition hills fault extended at least 9 km at a distance from the hector mine epicenter of about 188 to 196 km this length of slip is a minimum value because we saw fresh surface breakage extending farther northwest than our measurement sites sense of slip was right lateral locally there was a minor 1 mm vertical component of slip dextral slip ranged from 1 to 18 mm with the largest amounts found distributed or skewed away from the hector mine earthquake source slip triggered on the superstition hills fault commonly is skewed away from the earthquake source most notably in 1968 1979 and 1999 surface slip on the imperial fault and within the imperial valley extended about 22 km representing a distance from the hector mine epicenter of about 204 to 226 km sense of slip dominantly was right lateral the right lateral component of slip ranged from 1 to 19 mm locally there was a minor 1 2 mm vertical component of slip larger proportions of vertical slip up to 10 mm occurred in mesquite basin where scarps indicate long term oblique slip motion for this part of the imperial fault slip triggered on the imperial fault appears randomly distributed relative to location along the fault and source direction multiple surface slips both primary and triggered slip indicate that slip repeatedly is small at locations of structural complexity

seismic potential revealed by surface folding 1983 coalinga california earthquake the 2 may 1983 coalinga california earthquake magnitude 6 5 failed to rupture through surface deposits and instead elastically folded the top few kilometers of the crust the subsurface rate of fault slip and the earthquake repeat time are estimated from seismic geodetic and geologic data three larger earthquakes up to magnitude 7 5 during the past 20 years are also shown to have struck on reverse faults concealed beneath active folds

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

strain accumulation in western united states this review is principally concerned with recent geodetic strain measure ments in western united states undertaken by the us geological survey as part of the earthquake studies program and as a consequence is heavily biased toward the author s own publications most of the publications reporting crustal strain measurements in western united states prior to about 1968 have been compiled in one volume national geodetic survey 1973 and more recent work with complete bibliographies is summarized in three successive quadrennial reports to the international union of geodesy and geophysics meade 1971 savage 1975 thatcher 1979b the following conventions are employed in this paper strain a dimensionless quantity is reported in units of 10 6 extension is taken as positive to distinguish between engineering and tensor shear strain we denote the former by y and quote the units as j lrad whereas the latter is denoted by e and given the units of j lstrain uncertainties in all cases are quoted as one standard deviation at the present time geodetic techniques furnish the only reliable measure of strain accumulation in the seismic regions of the world the superiority of geodetic techniques derives principally from the long baseline of the measurements difficulties in coupling fiducial marks to the earth have generally made short baseline measurements of strain accumulation questionable wyatt 1982 however long baselines introduce the dis advantage that the measured strain is not closely localized the current technique of measuring strain accumulation involves the

ice age at the middle late jurassic transition a detailed record of sea surface temperatures in the northern hemisphere based on migration of marine invertebrate fauna ammonites and isotopic thermometry 18o values of shark tooth enamel indicates a severe cooling at the middle late jurassic transition mljt about 160 ma ago the magnitude of refrigeration 1 3 c for lower middle latitudes and its coincidence in time with an abrupt global scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time ice sheets may have developed over the high latitude mountainous regions of far east russia the drastic cooling just post dated the middle late callovian widespread deposition of organic rich marine sediments e g northwestern europe central atlantic and arabian peninsula this thermal deterioration can thus be ascribed to a downdraw in atmospheric co2 via enhanced organic carbon burial which acted as a negative feedback effect i e the inverse greenhouse effect the glacial episode of the mljt climaxed in the late callovian lasted about 2 6 myr and had a pronounced asymmetrical pattern composed of an abrupt 0 8 myr temperature fall opposed to a long term 1 8 myr stepwise recovery the glacial conditions at the mljt reveal that atmospheric co2 levels could have dropped temporarily to values lower than 500 ppmv during mesozoic times

impact experiments on ice the results of cratering and fragmentation experiments on pure ice are reported the projectiles used are cylindrical aluminum poly carbonate teflon and pyrophyllite fired at velocities between 110 m sec and 680 m sec with kinetic energies at impact between 2 and 500 joules crater diameters pit diameters in the ice were about two times larger than craters in the same energy range in basalts the ratios of pit diameter spall diameter are about three and the ratios of depth of crater spall diameter are between 0 1 and 0 3 which are close to the depth diameter ratios observed in basalts the crater diameter in ice is also well expressed as a single function of the late stage effective energy defined recently by mizutani et al 1983 the specific energy for complete destruction of ice target is about 50 j kg which is two orders of magnitude smaller than that of basalt the present experimental data on cratering and fragmentation of ice show that the impacts associated with the largest craters on callisto and mimas must have severely fractured the whole satellites and that those giant impacts with the kinetic energy of 1023 to 1027 joules probably affected significantly the evolution of the satellites

impact crater formation in icy layered terrains on mars we present numerical simulations of crater formation under martian conditions with a single near surface icy layer to investigate changes in crater morphology between glacial and interglacial periods the ice fraction thickness and depth to the icy layer are varied to understand the systematic effects on observable crater features to accurately model impact cratering into ice a new equation of state table and strength model parameters for h2o are fitted to laboratory data the presence of an icy layer significantly modifies the cratering mechanics observable features demonstrated by the modeling include variations in crater morphometry depth and rim height and icy infill of the crater floor during the late stages of crater formation in addition an icy layer modifies the velocities angles and volumes of ejecta leading to deviations of ejecta blanket thickness from the predicted power law the dramatic changes in crater excavation are a result of both the shock impedance and the strength mismatch between layers of icy and rocky materials our simulations suggest that many of the unusual features of martian craters may be explained by the presence of icy layers including shallow craters with well preserved ejecta blankets icy flow related features some layered ejecta structures and crater lakes therefore the cratering record implies that near surface icy layers are widespread on mars

seismotectonics of the easternmost transverse ranges california relevance for seismic potential of the southern san andreas fault earthquake locations depths and focal mechanisms from the southern california regional network 1977 1985 are used to identify the orientation and sense of slip of active subsurface faults in the easternmost transverse ranges etr the etr are separated from the salton trough province by the southernmost strands of the san andreas fault saf much of the seismicity in the etr is concentrated well northeast of the saf at relatively shallow depths under the little san bernardino mountains many of these earthquakes reflect slip on steeply dipping left lateral faults striking northeast to east at relatively high angles to the adjacent saf focal mechanisms in the etr show predominantly strike slip normal or oblique normal faulting and share common near horizontal t axes striking wnw p axes range from near vertical to near horizontal and strike mostly nne in contrast reverse and strike slip focal mechanisms that exhibit persistent north trending near horizontal p axes characterize the san gorgonio pass area immediately to the west these different patterns of strain geometries are inferred to represent changes in local stress regime and clearly establish a boundary between contrasting tectonic styles of contemporary secondary deformation along the saf this boundary which in the coachella valley may be the mission creek fault is also distinguished by abrupt changes in 1 rate and depth of seismic activity 2 topography 3 quaternary vertical deformation 4 strikes and dips of major branches of the saf and 5 seismic velocities in the crust and upper mantle the preponderance of secondary normal faulting in the etr versus secondary reverse faulting in the san gorgonio pass region suggests that fault normal stress is much less across the saf adjacent to the etr if a friction law where strength is proportional to normal stress applies to the saf then a smaller tectonic shear stress would be required tor slip in large earthquakes along the salton trough segment in this case the southernmost saf may have shorter repeat times smaller average displacements and lower moment release rates than earthquakes that rupture through the major restraining bend in san gorgonio pass

composition and structure of the shallow subsurface of ceres revealed by crater morphology the dwarf planet ceres is thought to have an ice rich layer in its shallow subsurface the morphologies of craters however suggest little relaxation by viscous flow has occurred and instead indicate a subsurface that is less than 40 ice

thermal origin of continental red beds in se china an experiment study abstract the origin of continental red beds in se china is the result of high diagenetic temperatures rather than an arid climate during their deposition here we present results from an experimental study where black mud was heated to demonstrate the formation of red beds diffuse reflectance spectroscopy drs of heated samples enables determination of the relative proportion of goethite and hematite iron in black mud is predominantly in the form of goethite that has an initial dehydration temperature of ca 150 c increasing temperature or prolonged heating time is accompanied by decreasing goethite and organic content increasing hematite and red colouration heat provided to subsiding red bed basins is supplied by cooling of an intracrustal granitic magma layer the thermal model can explain vertical colour temperature redox and mineral zonation in red bed sequences from red hematite bearing through green yellow cu zn v sulphide mineralization to grey black hydrocarbon halite bearing sediments the model can also be used to help prospect for hydrocarbon and halite deposits in the se china red bed basins

the south china block indochina collision where when and how this study uses new field observations and existing studies to shed new light on the origin and significance of two nw se striking orogens in nw and ne vietnam we conclude that the architecture of each belt is a stack of ne directed nappes formed either under deep ductile synmetamorphic conditions or under shallow depth in the sw and ne parts respectively the song ma zone and song chay ophiolitic melange represent two ophiolitic sutures however the late permian song da and babu mafic rocks are not ophiolites but intraplate basalts related to the emeishan plume a late triassic unconformity the 225 205 ma postorogenic plutonism and the 250 230 ma syntectonic metamorphism support an early to middle triassic age for these tectonic events both nw and ne belts are due to sw directed subduction with arc magmatism ocean closure and continental collision though two contemporary s dipping subduction zones might explain the structural evolution of the two belts a single convergent system offset by the tertiary red river fault is preferred as this s directed subduction better accounts for the late permian intraplate magmatism this scenario is discussed in the general geodynamic framework of se asia

geomorphic analysis of lobate debris aprons on mars at mars orbiter camera scale evidence for ice sublimation initiated by fractures 1 lobate debris aprons known to be geomorphic landform indicators of the presence of ground ice are of special interest for future missions devoted to the research of water on mars lobate debris aprons in fretted terrains of deuteronilus and protonilus mensae 35 50 n show typical convex shapes interpreted to be the result of viscous deformation at the scale of mars orbiter camera moc high resolution images the surface of these debris aprons shows complex patterns with small pits and buttes these patterns can be explained by the mantling of dust the accumulation of interstitial ice and the subsequent removal of ice by sublimation the sublimation of the ground ice is especially initiated and accelerated by subsurface heterogeneities like fractures theoretical quantification of sublimation rates therefore minimizes sublimation which is not a homogeneous process at least over the landforms studied crater counts show that the sublimation occurred in the last tens of millions of years up to the recent past in the point of view of future searching of subsurface ice only surface layers are submitted to sublimation favoring the conservation of ground ice in deeper layers since the formation of the landform the geophysical survey of lobate debris aprons would give interesting insights into the subsurface distribution of ice and its seasonal variations especially in order to measure current sublimation of ground ice

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

influence of cumulative convergence on lithospheric thrust fault development and topography along the australian pacific plate boundary south of new zealand the development of faulting and topography resulting from initial convergence within oceanic lithosphere is largely unknown we explore relationships among convergence structural development and topography along 1500 km of the submarine australian pacific plate boundary south of new zealand the macquarie ridge complex mrc due to the variable orientation of the boundary and close proximity of the australian pacific poles of rotation individual segments of the plate boundary have experienced different convergence histories since 10 95 ma chron 5o because interaction along the oceanic extent of the boundary involves oceanic lithosphere of broadly the same age and therefore thermal structure structural and morphologic differences can be attributed primarily to variations in angles and rates of convergence with respect to the plate boundary orientation since 10 95 ma we relate plate boundary normal convergence determined from stage pole rotations to structural development focusing on transitions from purely strike slip faulting to partitioned thrust and strike slip faulting between 47 s and 60 s since 10 95 ma our results indicate that boundary normal convergence of 100 km marks the transition from strike slip dominated faulting to partitioned underthrusting and strike slip faulting incipient subduction establishment of subduction at the puysegur trench and incipient subduction at the hjort trench corresponds to convergence at rates between 2 and 4 cm yr angles 30 and with durations of at least 10 m y resulting in 100 km of boundary normal convergence anomalous topographic volumes resulting from tectonic deformation are quantified from swath bathymetry and compared to convergence history results from analysis of the central mrc suggest that prior to lithospheric scale thrust faulting 100 km of boundary normal convergence can be accommodated by crustal deformation 6 km relief from ridge crest to adjacent trough and strike slip faulting our research supports induced forced intraoceanic initiation of subduction

stratigraphical and palaeobiogeographical significance of fossil wood from the mesozoic khorat group of thailand fossil wood from the poorly dated jurassic cretaceous continental sediments of the khorat group northeastern thailand isan is described the khorat group is widely distributed laos cambodia and thailand and despite its poorly known age stratigraphy and palaeoecology is of importance in understanding the sibumasu indochina collision the systematics of wood assemblage and palaeobiogeographical analysis reveal strong relationships with indochina especially vietnam and suggest an age in the range middle jurassic to early cretaceous according to wood taphonomy the corresponding trees grew alongside streams under a rather arid climate although this became wetter during the deposition of the upper formations of the khorat group

xenoxylon a boreal fossil wood in the mesozoic redbeds of southeast asia potential for the stratigraphy of the khorat group and the palinspatic reconstruction of southeast asia abstract the fossil wood genus xenoxylon is reported in situ for the first time in thailand it originates from the indosinian terrane from the mesozoic continental redbeds of the phu kradung formation khorat group palinspatic reconstruction palaeobiogeography and correlation with other occurrences of the genus in southern china as well as in vietnam suggest a middle to late jurassic age for the phu kradung formation level yielding the fossil wood the dating of this formation is still controversial and thus our data is an important step towards a better understanding of its geological history and palaeoecology as well as of the southeast asia mesozoic continental redbeds significance for the evolution of the vertebrates

identification of an anastomosing river system in the early cretaceous khorat basin northeastern thailand using stratigraphy and paleosols abstract the phu kradung and phra wihan formations of the early cretaceous khorat group were investigated to characterize the depositional system and paleoclimate based on stratigraphy paleosol features paleosol profiles and reworked deposits the sediments of both formations are classified into 12 facies on the basis of their primary depositional attributes such as bedding grain size texture and sedimentary structures furthermore these facies are grouped into eight architectural elements based on stratigraphic relationships and outcrop scale macroforms the proportions of each architectural element indicate that the depositional system was that of an anastomosing river the anastomosing river system in the studied section is characterized by a high rate of vertical floodplain aggradation and the development of a relatively stable crevasse channel paleosols are developed mainly in floodplain deposits and are characterized by the development of calcretes a semi arid to sub humid paleoclimate is deduced from the occurrence of the calcretes in addition their microstructures suggest that these calcretes were formed under several different conditions with micritic carbonate precipitating under relatively arid climates and alveolar septal structures under semi arid to sub humid conditions using the thicknesses of the calcrete horizons we conclude that the difference in the amount of precipitation between the wet and dry periods was highly variable without any order during deposition of the studied section the thicknesses of intervals between successive calcrete horizons indicate that the inflow of fine materials occurred randomly across the floodplain partly superimposed multiple calcrete horizons were developed during periods of low sediment supply a random deposition of floodplain sediments appears to characterize the anastomosing river system of the khorat basin

fault slip in southern california measurements of slip on major faults in southern california have been performed over the past 18 yr using principally theodolite alignment arrays and tautwire extensometers they provide geodetic control within a few hundred meters of the fault traces which complements measurements made by other techniques at larger distances approximately constant slip rates of from 0 5 to 5 mm yr over periods of several years have been found for the southwestern portion of the garlock fault the banning and san andreas faults in the coachella valley the coyote creek fault the superstition hills fault and an unnamed fault 20 km west of el centro these slip rates are typically an order of magnitude below displacement rates that have been geodetically measured between points at greater distances from the fault traces exponentially decaying postseismic slip in the horizontal and vertical directions due to the 1979 imperial valley earthquake has been measured it is similar in magnitude to the coseismic displacements analysis of seismic activity adjacent to slipping faults has shown that accumulated seismic moment is insufficient to explain either the constant or the decaying postseismic slip thus the mechanism of motion may differ from that of slipping faults in central california which move at rates close to the plate motion and are accompanied by sufficient seismic moment seismic activity removed from the slipping faults in southern california may be driving their relatively aseismic motion

the geomorphology of ceres introduction observations of ceres the largest object in the asteroid belt have suggested that the dwarf planet is a geologically differentiated body with a silicate core and an ice rich mantle data acquired by the dawn spacecraft were used to perform a three dimensional characterization of the surface to determine if the geomorphology of ceres is consistent with the models of an icy interior rationale instruments on dawn have collected data at a variety of resolutions including both clear filter and color images digital terrain models have been derived from stereo images a preliminary 1 10 m scale geologic map of ceres was constructed using images obtained during the approach and survey orbital phases of the mission we used the map along with higher resolution imagery to assess the geology of ceres at the global scale to identify geomorphic and structural features and to determine the geologic processes that have affected ceres globally results impact craters are the most prevalent geomorphic feature on ceres and several of the craters have fractured floors geomorphic analysis of the fracture patterns shows that they are similar to lunar floor fractured craters ffcs and an analysis of the depth to diameter ratios shows that they are anomalously shallow compared with average ceres craters both of these factors are consistent with ffc floors being uplifted due to an intrusion of cryomagma kilometer scale linear structures cross much of ceres some of these structures are oriented radially to large craters and most likely formed due to impact processes however a set of linear structures present only on a topographically high region do not have any obvious relationship to impact craters geomorphic analysis suggests that they represent subsurface faults and might have formed due to crustal uplift by cryomagmatic intrusion domes identified across the ceres surface present a wide range of sizes 100 km basal shapes and profiles whether a single formation mechanism is responsible for their formation is still an open question cryovolcanic extrusion is one plausible process for the larger domes although most small mounds 10 km diameter are more likely to be impact debris differences in lobate flow morphology suggest that multiple emplacement processes have operated on ceres where three types of flows have been identified type 1 flows are morphologically similar to ice cored flows on earth and mars type 2 flows are comparable to long runout landslides type 3 flows morphologically resemble the fluidized ejecta blankets of rampart craters which are hypothesized to form by impact into ice rich ground conclusion the global trend of lobate flows suggests that differences in their geomorphology could be explained by variations in ice content and temperature at the near surface geomorphic and topographic analyses of the ffcs suggest that cryomagmatism is active on ceres whereas the large domes are possibly formed by extrusions of cryolava although spectroscopic analysis to date has identified water ice in only one location on ceres the identification of these potentially ice related features suggests that there may be more ice within localized regions of ceres crust figure 1 dawn high altitude mapping orbit imagery 140 meters per pixel of example morphologic features a occator crater arrows point to floor fractures b linear structures denoted by arrows c a large dome at 42 n 10 e visible in the elevation map d a small mound at 45 5 s 295 7 e e type 1 lobate flow arrows point to the flow front analysis of dawn spacecraft framing camera image data allows evaluation of the topography and geomorphology of features on the surface of ceres the dwarf planet is dominated by numerous craters but other features are also common linear structures include both those associated with impact craters and those that do not appear to have any correlation to an impact event abundant lobate flows are identified and numerous domical features are found at a range of scales features suggestive of near surface ice cryomagmatism and cryovolcanism have been identified although spectroscopic analysis has currently detected surface water ice at only one location on ceres the identification of these potentially ice related features suggests that there may be at least some ice in localized regions in the crust 1 pending yes

interseismic coupling and refined earthquake potential on the hayward calaveras fault zone interseismic strain accumulation and fault creep is usually estimated from gps and alignment arrays data which provide precise but spatially sparse measurements here we use interferometric synthetic aperture radar to resolve the interseismic deformation associated with the hayward and calaveras faults hf and cf in the east san francisco bay area the large 1992 2011 sar data set permits evaluation of short and long wavelength deformation larger than 2 mm yr without alignment of the velocity field to a gps based model our time series approach in which the interferogram selection is based on the spatial coherence enables deformation mapping in vegetated areas and leads to refined estimates of along fault surface creep rates creep rates vary from 0 2 mm yr on the northern cf to 14 2 mm yr on the central cf south of the hf surface junction we estimate the long term slip rates by inverting the long wavelength deformation and the distribution of shallow slip due to creep by inverting the remaining velocity field this distribution of slip reveals the locations of locked and slowly creeping patches with potential for a m6 8 0 3 on the hf near san leandro a m6 6 0 2 on the northern cf near dublin a m6 5 0 1 on the hf south of fremont and a m6 2 0 2 on the central cf near morgan hill with cascading multisegment ruptures the hf rupturing from berkeley to the cf junction could produce a m6 9 0 1 the northern cf a m6 6 0 1 the central cf a m6 9 0 2 from the junction to gilroy and a joint rupture of the hf and central cf could produce a m7 1 0 1

kinematics of present crust and mantle flow in southern california in the southern california region published geologic studies of prehistoric fault offsets yield at least 81 rates of slip covering various periods of time chiefly since the opening of the gulf of california these rates together with the known geometries of active faults are used to constrain a hand fit block model for present horizontal velocity of the crust the assumptions employed are that these rates apply to the present that the blocks are internally rigid down to the greatest depth of earthquakes and that the over all pacific north american plate motion is correctly given by global models the resulting model fits 67 data within their uncertainties 10 more with a small discrepancy 1 mm yr and fails to accommodate only 4 data 2 of which are inconsistent with other data nominal precision is good 3 mm yr but accuracy and uniqueness are both suspect because many block boundaries are questionable despite its many local defects this model suggests four reliable regional conclusions first the rate of shortening on the south side of the transverse ranges varies from 6 to 14 mm yr increasing eastward which implies an unrecognized seismic hazard unless the motion is taken up by folding or fault creep second the pattern of block rotation rates is quite different from the pattern of rotations shown by tertiary paleomagnetic declinations which implies some major pliocene reorganization of blocks third the great bend left step of the plate boundary fault system in the transverse ranges appears to be straightening gradually by a 3 m y clockwise rotation relative to both plates finally if it is assumed that plate shortening has been occurring at this bend since the early pliocene and that crust and upper mantle velocities are similar then this model predicts mantle lithosphere downwelling to at least 250 km depth beneath the transverse ranges this prediction is consistent with upper mantle seismic velocity structure

tectonics of strike slip restraining and releasing bends restraining and releasing bends are common but enigmatic features of strike slip fault systems occurring in all crustal environments and at regional to microscopic scales of observation regional scale restraining bends are sites of mountain building transpressional deformation and basement exhumation whereas releasing bends are sites of topographic subsidence transtensional deformation basin sedimentation and possible volcanism and economic mineralization because restraining and releasing bends often occur as singular self contained domains of complex deformation they are appealing natural laboratories for earth scientists to study fault processes earthquake seismology active faulting and sedimentation fault and fluid flow relationships links between tectonics and topography tectonic and erosional controls on exhumation and tectonic geomorphology this volume addresses the tectonic complexity and diversity of strike slip restraining and releasing bends with 18 contributions divided into four thematic sections 1 a topical review of fault bends and their global distribution 2 bends sedimentary basins and earthquake hazards 3 restraining bends transpressional deformation and basement controls on development 4 releasing bends transtensional deformation and fluid flow

wood decay of xenoxylon yunnanensis feng sp nov from the middle jurassic of yunnan province china abstract a permineralised gymnosperm wood xenoxylon yunnanensis feng sp nov is described from the middle jurassic shaximiao formation in huize county yunnan province southwest china the pycnoxylic wood consists of thick walled tracheids and thin walled rays it is characterised by uniseriate contiguous compressed bordered pits on the radial walls of tracheids and one large simple pit in each cross field growth rings exhibit narrow latewood the mean sensitivity of analysis of 25 growth rings is 0 2 suggesting that a climate with abundant rainfall and weak seasonality could have prevailed in yunnan at least locally during the middle jurassic the outer portion of the wood is largely decayed and shows poorly preserved cells lacking details decayed tracheids displaying various features including removal of middle lamellae separations of secondary walls presence of thickened corners and appositions are recognised as cell reactions to fungal activity irregularly distributed micro cavities are formed by complete decomposition of tracheids and rays in the wood abundant fungal remains occurring in the wood generally consist of multiple branched hyphae these fungal hyphae are either confined to individual cell lumens or extend through adjacent cells although the probable reproductive structure and typical clamp connection are very rarely observed with few septate hyphae the affinities of these fungal hyphae are somewhat obscure nevertheless our study sheds light on the palaeoecology of middle jurassic terrestrial ecosystems of southwest china

flow patterns of lobate debris aprons and lineated valley fill north of ismeniae fossae mars evidence for extensive mid latitude glaciation in the late amazonian a variety of late amazonian landforms on mars have been attributed to the dynamics of ice related processes evidence for large scale mid latitude glacial episodes existing within the last 100 million to 1 billion years on mars has been presented from analyses of lobate debris aprons lda and lineated valley fill lvf in the northern and southern mid latitudes we test the glacial hypothesis for lda and lvf along the dichotomy boundary in the northern mid latitudes by examining the morphological characteristics of lda and lvf surrounding two large plateaus proximal massifs and the dichotomy boundary escarpment north of ismeniae fossae centered at 45 3n and 39 2e lineations and flow directions within lda and lvf were mapped using images from the context ctx camera the thermal emission imaging spectrometer themis and the high resolution stereo camera hrsc flow directions were then compared to topographic contours derived from the mars orbiter laser altimeter mola to determine the down gradient components of lda and lvf flow observations indicate that flow patterns emerge from numerous alcoves within the plateau walls are integrated over distances of up to tens of kilometers and have down gradient flow directions smaller lobes confined within alcoves and superposed on the main lda and lvf represent a later less extensive glacial phase crater size frequency distributions of lda and lvf suggest a minimum youngest age of 100 ma the presence of ring mold crater morphologies is suggestive that lda and lvf are formed of near surface ice rich bodies from these observations we interpret lda and lvf within our study region to result from formerly active debris covered glacial flow consistent with similar observations in the northern mid latitudes of mars glacial flow was likely initiated from the accumulation and compaction of snow and ice on plateaus and in alcoves within the plateau walls as volatiles were mobilized to the mid latitudes during higher obliquity excursions together with similar analyses elsewhere along the dichotomy boundary these observations suggest that multiple glacial episodes occurred in the late amazonian and that lda and lvf represent significant reservoirs of non polar ice sequestered below a surface lag for hundreds of millions of years

predictions of depth to ice on asteroids based on an asynchronous model of temperature impact stirring and ice loss abstract water ice near the surface of main belt asteroids is gradually lost to space a mantle of low thermal conductivity causes large surface temperature amplitudes and thus increased cooling by thermal re radiation lowering temperatures well below the fast rotator limit a computational barrier for modeling this ice loss is the multi scale character of the problem accurate temperatures require many time steps within a solar day but ice retreats slowly over billions of years this barrier is overcome with asynchronous coupling models of temperature ice loss and impact stirring each use their own time steps and are coupled with one another the model is applied to 1 ceres and 7968 elst pizarro on ceres ice can be expected in the top half meter poleward of 60 latitude on both hemispheres even if excursions of the axis tilt took place and even in the presence of impact gardening at the poles ice can be expected within a centimeter of the surface the retreating ice crust leads to emission of water from the surface mainly at the equator the gradually retreating ice supplies a water exosphere less dense than has been observed by the herschel telescope for main belt comet elst pizarro depths to ice depend on the properties of the surface mantle for a dust mantle estimated depths are on the order of a decimeter for a rocky surface the depth at the pole is on the order of one meter hence it could have been activated by a small impact that exposed buried ice

distribution of phyllosilicates on the surface of ceres the dwarf planet ceres is known to host phyllosilicate minerals at its surface but their distribution and origin have not previously been determined we used the spectrometer onboard the dawn spacecraft to map their spatial distribution on the basis of diagnostic absorption features in the visible and near infrared spectral range 0 25 to 5 0 micrometers we found that magnesium and ammonium bearing minerals are ubiquitous across the surface variations in the strength of the absorption features are spatially correlated and indicate considerable variability in the relative abundance of the phyllosilicates although their composition is fairly uniform these data along with the distinctive spectral properties of ceres relative to other asteroids and carbonaceous meteorites indicate that the phyllosilicates were formed endogenously by a globally widespread and extensive alteration process

pitted terrains on 1 ceres and implications for shallow subsurface volatile distribution prior to the arrival of the dawn spacecraft at ceres the dwarf planet was anticipated to be ice rich searches for morphological features related to ice have been ongoing during dawn s mission at ceres here we report the identification of pitted terrains associated with fresh cerean impact craters the cerean pitted terrains exhibit strong morphological similarities to pitted materials previously identified on mars where ice is implicated in pit development and vesta where the presence of ice is debated we employ numerical models to investigate the formation of pitted materials on ceres and discuss the relative importance of water ice and other volatiles in pit development there we conclude that water ice likely plays an important role in pit development on ceres similar pitted terrains may be common in the asteroid belt and may be of interest to future missions motivated by both astrobiology and in situ resource utilization

sawtooth segmentation and deformation processes on the southern san andreas fault california five contiguous 12 13 km fault segments form a sawtooth geometry on the south ernmost san andreas fault the kinematic and morphologic properties of each segment depend on fault strike despite differences of strike between segments of as little as 3 degrees oblique slip transpression of fault segments within the indio hills mecca hills and durmid hill results from an inferred 8 1 ratio of dex tral slip to convergence across the fault zone triggered slip and creep are confined almost en tirely to transpressive segments of the fault durmid hill has been formed in the last 28 n 6 ka by uplift at an average rate of 3 1 mm a

cratering on ceres implications for its crust and evolution introduction thermochemical models have predicted that the dwarf planet ceres has to some extent formed a mantle moreover due to viscous relaxation these models indicate that ceres should have an icy crust with few or no impact craters however the dawn spacecraft has shown that ceres has elevation excursions of 15 km cliffs graben steep sided mountains and a heavily cratered surface rationale we used dawn s framing camera to study the morphology size frequency and spatial distribution of the craters on ceres these data allow us to infer the structure and evolution of ceres outer shell results a large variety of crater morphologies are present on ceres including bowl shaped craters polygonal craters floor fractured craters terraces central peaks smooth floors flowlike features bright spots secondary craters and crater chains the morphology of some impact craters is consistent with water ice in the subsurface although this might have favored relaxation there are also large unrelaxed craters the transition from bowl shaped simple craters to modified complex craters occurs at diameters of about 7 5 to 12 km craters larger than 300 km are absent but low pass filtering of the digital elevation model suggests the existence of two quasi circular depressions with diameters of 570 km 125 56 e and 19 60 n and 830 km 24 76 w and 0 5 n craters are heterogeneously distributed across ceres surface with more craters in the northern versus the southern hemisphere the lowest crater densities are associated with large well preserved southern hemisphere impact craters such as urvara and yalode because the low crater density lcd terrain extends across a large latitude range in some cases e g urvara and yalode 18 n and 75 s kerwan 30 n and 46 s its spatial distribution is inconsistent with simple relaxation driven by warmer equatorial temperatures we instead propose that impact driven resurfacing is the more likely lcd formation process although we cannot completely rule out an internal endogenic origin we applied two different methodologies to derive absolute model ages from observed crater size frequency distributions the lunar derived model adapts the lunar production and chronology functions to impact conditions on ceres taking into account impact velocities projectile densities current collision probabilities and surface gravity the asteroid derived model derives a production function by scaling the directly observed object size frequency distribution from the main asteroid belt extended to sizes 5 km by a collisional model to the resulting size frequency distribution of cerean craters using similar cerean target parameters as the lunar derived model by dating a smooth region associated with the kerwan crater we determined absolute model ages of 550 million and 720 million years depending on which chronology model is applied conclusion crater morphology and the simple to complex crater transition indicate that ceres outer shell is likely neither pure ice nor pure rock but an ice rock mixture that allows for limited relaxation the heterogeneous crater distribution across the surface indicates crustal heterogeneities and a complex geologic evolution of ceres there is evidence for at least some geologic activity occurring in ceres recent history figure 1 spatial density of craters larger than 20 km on ceres crater rims are shown as black solid circles blue indicates areas with lcds yellow and red represent more highly cratered areas the smallest dashed ellipse denotes the idealized former rim of an extremely degraded impact crater at 48 9 e and 44 9 s which is barely recognizable in imagery but apparent from the global digital elevation model also shown as dashed circles are the outlines of two large putative basins unambiguously recognized basins 300 km in diameter are missing and there are several areas with lcds associated with large impact craters e g yalode urvara kerwan ezinu vinotonus dantu and two unnamed craters northeast and southeast of oxo areas a and b are topographic rises with central depressions that also show lcds thermochemical models have predicted that ceres is to some extent differentiated and should have an icy crust with few or no impact craters we present observations by the dawn spacecraft that reveal a heavily cratered surface a heterogeneous crater distribution and an apparent absence of large craters the morphology of some impact craters is consistent with ice in the subsurface which might have favored relaxation yet large unrelaxed craters are also present numerous craters exhibit polygonal shapes terraces flowlike features slumping smooth deposits and bright spots crater morphology and simple to complex crater transition diameters indicate that the crust of ceres is neither purely icy nor rocky by dating a smooth region associated with the kerwan crater we determined absolute model ages amas of 550 million and 720 million years depending on the applied chronology model 1 pending yes

probabilities of occurrence of large plate rupturing earthquakes for the san andreas san jacinto and imperial faults california 1983 2003 the san andreas san jacinto and imperial faults in california are divided into 19 segments conditional probabilities are calculated that a particular segment will be the site of a large plate rupturing earthquake i e an event that breaks the entire down dip extent of the seismogenic zone during the next 20 years the sizes of such events which account for most of the slip that occurs seismically appear to vary greatly for different segments of these faults repeat time of large shocks coseismic displacement moment release rupture length and seismic magnitude appear to correlate with one another and to be a function of the tectonic style of different parts of those fault zones tectonic inhomogeneities on a scale of about 1 to 100 km are much larger than displacement in any single seismic event and may be regarded as being invariant in their effects upon earthquake generation over many cycles of large shocks it is this invariance that appears to lead to a given segment of a fault rupturing repeatedly in events of nearly the same size since repeat time varies however for a given segment of a fault a simple probabilistic approach is used to forecast the likelihood of large future earthquakes for each segment using as input the time of the last large shock the average recurrence time and the standard deviation of time intervals between events dates of the last large shocks are available for most of the segments investigated repeat times are estimated from times of historic and prehistoric events tectonic similarity and times calculated from coseismic displacement in the last large shock divided by a rate of fault motion or strain buildup the standard deviation of time intervals divided by the average repeat time is close to 1 3 for three fault segments in california for which data are available on historic and prehistoric earthquakes that normalized value is adopted for all calculations of conditional probability magnitudes and seismic moments of future plate rupturing events are estimated for each fault segment several of the segments have well constrained probabilities for rupture during the next 20 years whereas others have large uncertainties eight of the segments constituting about 40 of the total lengths of the three faults have moderate to high probability and thus should be instrumented and studied extensively so as to provide shorter time warnings in some cases two adjacent segments may be nearly in phase in their loading history and may break in a single event the segment of the san andreas fault from opposite san jose to san juan bautista which ruptured less than 1 5 m in 1906 and which probably also broke in 1838 is calculated to have a moderate to high probability of an earthquake of magnitude 6 to during the next 20 years a 325 km section of the southern san andreas between tejon pass and the salton sea has about a 25 chance of rupturing in a shock of magnitude near 8 during the next 20 years all the other segments have only a small chance i e less than 5 to 10 of rupturing in an event of magnitude near 8 during that interval

surface slip subsequent to the 24 november 1987 superstition hills california earthquake monitored by digital creepmeters three creepmeters of new design were operated on the superstition hills fault following the 24 november 1987 earthquake each creepmeter consists of a digital displacement sensor interrogated periodically by a computer at the end of each hour the computer determines a recording rate appropriate to the velocity of the slip on the fault in that hour no data are recorded if the fault is inactive data are recorded at a maximum rate of one sample per minute if slip on the fault is detected the resolution and range of the creepmeters are 10 m and 15 cm respectively fault activity is observed to be confined to periods of episodic slip creep events with mean amplitudes 3 to 6 mm and durations less than 4 hr a total of 80 creep events were recorded during the first week following the earthquake creep events occurred several times each day after 6 months events occurred every 3 weeks this increase in the mean time interval between creep events results in the observed decay in afterslip rate between creep events the fault is inactive although more than 200 microstrain of fault zone deformation may accumulate before each event although creep events were observed to propagate unilaterally in both directions along the fault the most impulsive events appeared to propagate bilaterally from a dilatant offset separating the northern and southern halves of the 24 km long fault zone maximum propagation velocities of 30 m sec were observed aftershocks 2 m 4 7 were observed to occur near the creepmeters following 6 to 9 cm of surface slip on the fault a future aftershock in this region is anticipated in mid 1989 based on afterslip rates in the year following the main shock

geomorphological evidence for ground ice on dwarf planet ceres despite evidence for an ice rich outer shell little water ice has been observed on the surface of ceres lobate morphologies observed on ceres that are increasingly prevalent towards the dwarf planet s poles are consistent with ice rich flows

kalasinemys a new xinjiangchelyid turtle from the late jurassic of ne thailandh tong et al new xinjiangchelyid turtle from ne thailand a new xinjiangchelyid turtle kalasinemys prasarttongosothi n gen n sp is described on the basis of skull and shell material from the upper jurassic phu kradung formation at phu noi locality kalasin province in ne thailand this second xinjiangchelyid turtle from phu noi is distinct from phunoichelys thirakhupti by the smooth shell surface the presence of a cervical notch and vertebral 1 narrower than nuchal the skull presents an arterial system characteristic of the xinjiangchelyidae basal eucryptodira and its outline is similar to that of annemys spp known from the middle late jurassic of china and mongolia but distinct from the latter mainly by the wider triturating surface smaller foramen palatinum posterius and the shape of the prefrontal and frontal as well as that of the basisphenoid and basioccipital based on the turtle assemblages the correlation with mainland asia further supports a late jurassic age for the lower part of the phu kradung formation where phu noi site is located stratigraphically our study provides new insight on the evolution of the basal eucryptodiran turtles in asia

the palaeolatitudinal distribution of fossil wood genera as a proxy for european jurassic terrestrial climate the potential of using the latitudinal distributions of fossil wood genera as a proxy for jurassic terrestrial climate conditions in western laurasia was tested using a database of 386 entries the fossil wood genera brachyoxylon protaxodioxylon and simplicioxylon are southern taxa which have only occasionally extended north of 45 n all latitude references are to palaeolatitudes conversely protocedroxylon and xenoxylon are mostly found at high latitudes the standard deviation of the data on the palaeolatitudes of the northern genera is however much larger than that of the southern genera this is interpreted as resulting from brief periodic southward extensions of the protocedroxylon and xenoxylon distributions while the southern genera remained confined south of 40 n the interval during which the northern genera replaced the southern genera at mid latitudes can be hypothesized to be times of global terrestrial climate cooling or increased rainfall comparisons between the spatiotemporal distributions of these northern taxa and independent climate sensitive indicators clay mineral assemblages oxygen isotopes and neritic carbonate distribution suggest that these genera were adapted to more humid conditions characterizing the mid latitudes of the northern hemisphere accordingly southward migrations of this climatic zone occurred during the early and late pliensbachian early toarcian and early middle oxfordian time intervals these reconstructions are limited by the low resolution and restricted spatial coverage of the wood record therefore further sampling at the ammonite zone level is needed nevertheless the present study suggests that wood taxa distribution represents an underexploited but potentially powerful record of terrestrial environmental changes during the jurassic period

the pliensbachian toarcian paleoclimate transition new insights from organic geochemistry and c h n isotopes in a continental section from central asia the taskomirsay section south kazakhstan is a unique pliensbachian toarcian sequence of lignites clayey layers and silty sandstones deposited in a fluvial lacustrine environment with nearby swampy areas this period characterized by a drastic climate change has been particularly studied in western tethyan marine environments whereas very few studies focused on continental settings paleoflora analyses associated with a multi isotope approach based on well preserved type iii bulk organic nitrogen isotopes a15norg and hydrogen isotopic composition a2h of n alkanes were developed to document paleoclimatic changes in the area sporomorph associations and fossil woods revealed a globally warm to cool temperate climate characterized by xenoxylon a conifer morphogenus biogeographically related to cool humid settings apart from slightly less humid and warmer conditions in the early toarcian warmer conditions are supported by reconstructed mean annual air temperatures maats based on the first branched glycerol dialkyl glycerol tetraethers brgdgts ever recorded in the early jurassic nevertheless no drastic changes were recorded in the a15norg values its signal being attributed to tenuous equilibrium between water and nutrient availability via intense n recycling based on n alkane distributions sources of organic matter were separated in two pools i a purely terrestrial n c27 and ii an aquatic pool n c23 constituted of vegetation that thrived under almost permanent water supply the n alkane a 2h values 248 to 151 as well as their amounts and average chain lengths acl are in agreement with cool temperate conditions in the pliensbachian and less humid warmer conditions in the early toarcian the isotopic difference between a2h values of n c27 and n c23 2hter aq suggests enhanced seasonality during the pliensbachian toarcian transition and low seasonality in the early toarcian in agreement with temperate climate regime finally contrasted response to paleoclimate changes between markers suggests different spatial integration of those proxies the role of sea level variations for a2h values might also resolve this contrasted response

constraints on ceres internal structure and evolution from its shape and gravity measured by the dawn spacecraft ceres is the largest body in the asteroid belt with a radius of approximately 470 km in part due to its large mass ceres more closely approaches hydrostatic equilibrium than major asteroids pre dawn mission shape observations of ceres revealed a shape consistent with a hydrostatic ellipsoid of revolution the dawn spacecraft framing camera has been imaging ceres since march 2015 which has led to high resolution shape models of the dwarf planet while the gravity field has been globally determined to a spherical harmonic degree 14 equivalent to a spatial wavelength of 211 km and locally to 18 a wavelength of 164 km we use these shape and gravity models to constrain ceres internal structure we find a negative correlation and admittance between topography and gravity at degree 2 and order 2 low admittances between spherical harmonic degrees 3 and 16 are well explained by airy isostatic compensation mechanism different models of isostasy give crustal densities between 1 200 and 1 400 kg m3 with our preferred model giving a crustal density of 1 287 70 87 kg m3 the mantle density is constrained to be 2 434 5 8 kg m3 we compute isostatic gravity anomaly and find evidence for mascon like structures in the two biggest basins the topographic power spectrum of ceres and its latitude dependence suggest that viscous relaxation occurred at the long wavelengths 246 km our density constraints combined with finite element modeling of viscous relaxation suggests that the rheology and density of the shallow surface are most consistent with a rock ice salt and clathrate mixture

environment and ecology of east asian dinosaurs during the early cretaceous inferred from stable oxygen and carbon isotopes in apatite abstract during the cold late barremian early albian interval terrestrial environments in east asia were populated by rich and diverse vertebrate faunas characterized by a strong provincialism the latitudinal gradient of temperature and the existence of geographic barriers likely accounted for some aspects of this heterogeneous distribution of faunas other factors however such as local environmental conditions and interactions within vertebrate communities which could have influenced their distribution have not yet been fully identified and understood therefore new and published oxygen and carbon isotope compositions of apatite from chinese and thai reptiles dinosaurs crocodilians and turtles have been analyzed and interpreted in terms of ecology local air temperature and precipitation amounts differences in carbon and oxygen isotope compositions between various groups of sympatric plant eating dinosaurs sauropods ornithopods and ceratopsians indicate food resources partitioning among them most likely to avoid competition mid latitude environments where the jehol biota flourished were submitted to cool temperate climatic conditions with mean air temperature mat of 10 4 c and mean annual precipitations map of about 600 mm yr compatible with the existence of forest environments by contrast sub tropical regions characterized by mat of about 20 25 c were either submitted to high amounts of seasonal precipitations of about 1200 mm yr in thailand or to significant aridity map of about 400 mm yr in south china this difference in precipitation regime between thailand and south china may be attributed to the occurrence of the coastal cordillera extending along the east margin of the south china block these mountain ranges likely prevented humid air masses from the pacific to penetrate some parts of south china thus generating a rain shadow effect mosaic environments characterizing east asia during the late early cretaceous may have acted as a cradle for the origination of advanced dinosaur taxa that subsequently radiated over eurasia and north america during the late cretaceous

palaeocurrent direction estimated in mesozoic redbeds of the khorat plateau lao pdr indochina block using anisotropy of magnetic susceptibility mesozoic redbeds in the western part of central and southern laos are the most abundant rocks of the khorat plateau in earlier studies palaeocurrent directions of the mesozoic redbeds in the khor

cryogenic flow features on ceres implications for crater related cryovolcanism craters on ceres such as haulani kupalo ikapati and occator show postimpact modification by the deposition of extended plains material with pits multiple lobate flows and widely dispersed deposits that form a diffuse veneer on the preexisting surface bright material units in these features have a negative spectral slope in the visible range making it appear bluish with respect to the grey toned overall surface of ceres we calculate the drop height to runout length ratio of several flow features and obtain a coefficient of friction of 0 1 the results imply higher flow efficiency for flow features on ceres than for similar features on other planetary bodies with similar gravity suggesting low viscosity material the special association of flow features with impact craters could either point to an impact melt origin or to an exogenic triggering of cryovolcanic processes

influence of strike slip fault segmentation on drainage evolution and topography a case study the palomares fault zone southeastern betics spain abstract the palomares fault zone pfz is one of the main sinistral strike slip faults in the betics se spain with approximately 16 km of north south displacement the pfz initiated during the tortonian messinian as a transfer structure linking areas subject to nw se shortening during the plio quaternary the fault zone lengthened cutting previous fold structures and widened towards the east displacing the active mountain front to the western border of sierra almagrera sierra almenara these sierras which show moderate uplift rates of 0 05 0 15 m ka formed in response to the oblique slip regime of the pfz the drainage system in the vicinity of the pfz is asymmetric with respect to a main axial valley that runs parallel to the pfz on the downthrown fault block in this block the drainage density is lower and the streams are longer than in the uplifted block furthermore west of the main axial valley the streams describe eastward directed deflections indicating the progressive eastward migration of the main axial valley during the pleistocene the drainage system on the uplifted ranges shows a consequent pattern indicating recent uplift and folding under nnw sse convergence recent activity along segments of the pfz has increased topographical gradients favouring dissection of previous streams by headward erosion of streams transverse to the active fault segments

strain rate profile across the elsinore san jacinto and san andreas faults near palm springs california 1973 81 a profile of the strain accumulation rate along a line trending n50 e across the subparallel elsinore san jacinto and san andreas faults near palm springs california has been constructed from trilateration surveys in the 1973 81 interval the strain accumulation is principally right lateral shear across a vertical plane parallel to fault strike n40 w the strain rate profile for that component exhibits two clearly resolved maxima one centered on the san jacinto fault max 0 35 0 02 rad a and the other on the san andreas fault max 0 40 0 02 rad a no maximum is associated with the elsinore fault this result clearly implies that slip at depth on both the san andreas and san jacinto faults is loading the shallower sections of these faults and that eventually rupture can be expected on both

ceres evolution and current state 1 we modeled several thermal evolution scenarios for ceres to explore the nature of large wet protoplanets and to predict current day evidence that might be found by close inspection such as by the dawn mission the density for ceres is near 2 1 suggesting a water content between 17 and 27 by mass short and long lived radioactive nuclide heating is considered even if only long lived radionuclide heating is assumed the water ice in ceres melts quickly and a water mantle forms but an approximately 10 km crust does not melt the circulating warm water would alter the silicates as heat is lost by conduction through the frozen crust water begins to freeze out at the base of the crust solid state convection begins and transports more heat as well as perhaps material dissolved or entrained in the water to or near the surface ceres water layer eventually but perhaps not entirely freezes forming a layered density structure with perhaps some liquid water remaining today our differentiated models are in agreement with the recently measured difference between the equatorial and polar radii we find that ceres existence and evolution depend critically on it containing water at formation and this depends strongly on the combination of when it accreted and the amount of 26al present in the pre ceres 1 km sized objects slightly more 26al or earlier accretion produces a dry vesta like object melting and freezing plus mineralization would lead to several dimensional changes over time creating topographic features zones of weakness and perhaps disruptions in the crust

peat forming materials and evolution of swamp sequences case analysis of a jurassic inland coal basin in china abstract a case analysis was conducted in the yima coal mine which is located in a jurassic inland basin located in the henan province of central china using data from palynological ecology plant residues coal petrography and some geochemical characteristics the plant community during this coal forming period and the precursors of the coal forming peat were determined the peat forming paleoenvironment and evolutionary sequences within the swamp were reconstructed according to the differences in the spore pollen complex of the coals in the yima mine seven kinds of palynofacies each characterized by predominant species occured within the relative beds seven different types of ecological characteristics are indicated the different stages are represented by the corresponding floral facies six diagnostic properties of the coal facies were determined by studying the petrographic characteristics of each coal and seven different kinds of ancient peat forming swamp paleoenvironments are indicated by the coal facies a genetic model of formation development and evolutionary sequences of the coal forming swamp in the jurassic of central china is proposed

brine volcanism and the interior structures of asteroids and icy satellites abstract cryovolcanism is among the foremost processes responsible for modifying the surfaces of icy satellites volcanic brine petrogenesis in ammonia deficient satellites should mainly involve eutectic melting in relevant salt water systems carbonaceous chondrites provide useful insights into the compositions of salts and aqueously altered rock in icy satellites and asteroids c1 chondrites contain about one fifth by mass of salts in various states of hydration many aspects of the petrogenesis and physical volcanology of icy satellite brines should be well described in the system h2o mgso4 na2so4 minor components include sulfates of k ni mn and ca chondrites also contain abundant carbonates but these are probably not very important in brine magmatism due to their low solubilities under expected conditions chlorides are also unimportant under most circumstances because of the low cosmic abundance ratio of cl s soluble salts may have profound effects on the geology and structure of icy satellites and asteroids in some models late episodes of water volcanism are facilitated by high buoyant forces due to the relatively high densities of sulfate rich mantle and crustal layers in other models early hypersaline brine volcanism quickly yields to plutonic magmatism due to low crustal densities europa probably has a layered crust composed of anhydrous mg na sulfates near the base and a frozen or partially molten eutectic mixture of ice and hydrated mg and na sulfates near the surface ganymede may have a crust about 300 km thick composed of a 10 1 ratio of ice mirabilite and a mantle 500 km thick composed of 50 ice phases plus 50 hydrated mg and na sulfates

tectonic geomorphology of the san andreas fault zone in the southern indio hills coachella valley california geomorphic investigation of the san andreas fault zone in the indio hills indicates many tectonically produced landforms including beheaded streams right lateral deflected and offset streams sags shutter ridges pressure ridges and fault scarps near biskra palms an alluvial fan pediment complex has an apparent cumulative offset of about 0 7 km along the mission creek fault zone north branch san andreas fault many of the tectonic landforms as well as the fracture pattern that has developed during the pleistocene are explainable by simple shear or uplift associated with a small left bend in the main trace of the mission creek fault the ratio of vertical to horizontal displacement in the vicinity of the bend is about 0 04 exposed in pushawalla canyon 5 km northwest of the alluvial fan pediment complex are 1 a sequence of stream terraces 2 folded plio pleistocene fanglomerates and 3 an example of stream capture following a right lateral deflection or offset of several hundred metres a left step of the mission creek fault in pushawalla canyon is a probably cause of folds and sporadic uplift that produced the stream terraces possible cause of recent stream capture are 1 juxtaposition of pushawalla canyon with a relict canyon moving northwestward along the mission creek fault or 2 right lateral deflection or offset of pushawalla canyon along the fault with simultaneous headward erosion of a shorter steep stream flowing toward the coachella valley estimation of a slip rate and identification of paleoseismicity for the san andreas fault in the indio hills is difficult however degree of topographic dissection formation and preservation of desert pavement and relative soil profile development suggest that the age of the offset fan may be as old as 70 000 yr but that most likely it is on the order of 20 000 to 30 000 yr these age estimates for the offset fan indicate a minimum slip rate for the san andreas fault of 10 to 35 mm yr with about 23 to 35 mm yr the most likely the pattern of observed offset drainages is complex but suggests that during the past few thousand years creep events or moderately large earthquakes have periodically produced several metres of right lateral displacement

oxygen isotopes of east asian dinosaurs reveal exceptionally cold early cretaceous climates early cretaceous vertebrate assemblages from east asia and particularly the jehol biota of northeastern china flourished during a period of highly debated climatic history while the unique characters of these continental faunas have been the subject of various speculations about their biogeographic history little attention has been paid to their possible climatic causes here we address this question using the oxygen isotope composition of apatite phosphate from various reptile remains recovered from china thailand and japan values indicate that cold terrestrial climates prevailed at least in this part of asia during the barremian early albian interval estimated mean air temperatures of about 10 4 c at midlatitudes 42 n correspond to present day cool temperate climatic conditions such low temperatures are in agreement with previous reports of cold marine temperatures during this part of the early cretaceous as well as with the widespread occurrence of the temperate fossil wood genus xenoxylon and the absence of thermophilic reptiles such as crocodilians in northeastern china the unique character of the jehol biota is thus not only the result of its evolutionary and biogeographical history but is also due to rather cold local climatic conditions linked to the paleolatitudinal position of northeastern china and global icehouse climates that prevailed during this part of the early cretaceous

the interior structure of ceres as revealed by surface topography abstract ceres the largest body in the asteroid belt 940 km diameter provides a unique opportunity to study the interior structure of a volatile rich dwarf planet variations in a planetary body s subsurface rheology and density affect the rate of topographic relaxation preferential attenuation of long wavelength topography 150 km on ceres suggests that the viscosity of its crust decreases with increasing depth we present finite element fe geodynamical simulations of ceres to identify the internal structures and compositions that best reproduce its topography as observed by the nasa dawn mission we infer that ceres has a mechanically strong crust with maximum effective viscosity 10 25 pa s combined with density constraints this rheology suggests a crustal composition of carbonates or phyllosilicates water ice and at least 30 volume percent vol low density high strength phases most consistent with salt and or clathrate hydrates the inference of these crustal materials supports the past existence of a global ocean consistent with the observed surface composition meanwhile we infer that the uppermost 60 km of the silicate rich mantle is mechanically weak with viscosity 21 pa s suggesting the presence of liquid pore fluids in this region and a low temperature history that avoided igneous differentiation due to late accretion or efficient heat loss through hydrothermal processes

ring mold craters in lineated valley fill and lobate debris aprons on mars evidence for subsurface glacial ice 1 ring mold craters rmcs concentric crater forms shaped like a truncated torus and named for their similarity to the cooking implement are abundant in lobate debris aprons lda and lineated valley fill lvf in the northern mid latitudes on mars but are not seen in surrounding terrain lda and lvf have been interpreted to form by flow of debris but uncertainty remains concerning the mechanism of flow with hypotheses ranging from pore ice assisted creep of talus to debris covered glaciers rmcs average less than a few hundred meters in diameter and occur in association with normal bowl shaped impact craters whose average diameters are commonly less than rmcs on the basis of their morphologic similarities to laboratory impact craters formed in ice and the physics of impact cratering into layered material we interpret the unusual morphology of rmcs to be the result of impact into a relatively pure ice substrate below a thin regolith with strength contrast properties spallation viscous flow and sublimation being factors in the development of the ring mold shape associated smaller bowl shaped craters are interpreted to have formed within a layer of regolith like sublimation till overlying the ice substrate estimates of crater depths of excavation between populations of bowl shaped and ring mold craters suggest that the debris layer is relatively thin these results support the hypothesis that lda and lvf formed as debris covered glaciers and predict that many hundreds of meters of ice remain today in lda and lvf deposits beneath a veneer of sublimation till rmcs can be used in other parts of mars to predict and assess the presence of ancient ice related deposits

new record of fossil wood xenoxylon from the late triassic in the sichuan basin southern china and its paleoclimatic implications abstract fossil wood is one of the significant proxies for terrestrial paleoclimate and paleogeographical reconstruction in earth history abundant and diversified mesozoic fossil woods are well recorded in china however triassic fossil wood is very scarce here we report a new fossil wood from the late triassic xujiahe formation norian to rhaetian in guangyuan of northern sichuan basin southwestern china the fossil wood material consists of two well preserved specimens yielding secondary xylem with distinct growth rings bordered pits on the radial tracheid walls are mostly contiguous biseriate alternate locally uniseriate and strongly flattened cross fields show a large window like pore this anatomy is typical for the important fossil wood morphogenus xenoxylon gothan and based on a novel combination of radial and cross field pitting type and ray height a new species xenoxylon guangyuanense sp nov is recognized the finding of this new fossil wood taxon contributes to a better understanding of the yet poorly documented xenoxylon early radiation during the late triassic as well as of the origin of x meisteri group a peculiar endemic group which diversified in far east asia from the triassic to the early cretaceous xenoxylon is a paleobiogeographically significant genus being bound to cooler and or wetter climates of northern hemisphere throughout its late triassic late cretaceous range the occurrence of xenoxylon in the sichuan basin of southern china may indicate a short term cooling event sandwiched within a period during which warm and wet climate conditions largely prevailed over lower latitude regions of the northern hemisphere such a cooling event in the sichuan basin which was located at a low paleolatitude on the eastern rim of tethys may be in accordance in time with the temperature decline event in norian rhaetian boundary uncovered by oxygen isotope 18 o record in italy of the western rim of tethys