diviner lunar radiometer observations of cold traps in the moon s south polar region diviner lunar radiometer experiment surface temperature maps reveal the existence of widespread surface and near surface cryogenic regions that extend beyond the boundaries of persistent shadow the lunar crater observation and sensing satellite lcross struck one of the coldest of these regions where subsurface temperatures are estimated to be 38 kelvin large areas of the lunar polar regions are currently cold enough to cold trap water ice as well as a range of both more volatile and less volatile species the diverse mixture of water and high volatility compounds detected in the lcross ejecta plume is strong evidence for the impact delivery and cold trapping of volatiles derived from primitive outer solar system bodies

kinematic models of fluvial terraces over active detachment folds constraints on the growth mechanism of the kashi atushi fold system chinese tian shan during detachment folding the relationship between differential uplift and shortening depends on the mechanism of fold growth such as limb rotation or hinge migration and may vary over the lifetime of a fold thus neither long term shortening rates nor the present fold geometry unambiguously constrain the kinematics of fold growth where rivers cut through growing anticlines flights of abandoned fluvial terraces act as passive kinematic markers as shortening progresses the terraces become deformed and thereby preserve critical information about the kinematics and evolution of active fold growth to constrain recent fold growth across three detachment folds in the kashi atushi fold system in the sw tian shan china we surveyed flights of deformed terraces and compared them with geometric models of successively emplaced horizontal unconformities terraces across pregrowth strata deformed by hinge migration limb rotation and a combination of the two migration of angular hinges and curved hinge zones were also compared each kinematic model predicts both a distinct geometry for the deformed terraces and contrasting angular relationships between the terraces and the pregrowth strata notably limb rotation and migration of curved hinge zones result in progressively rotated terraces that cut across pregrowth strata whereas all limb lengthening models result in parallelism between pregrowth strata and terrace straths across much of the fold the kashi atushi terraces show clear evidence of abandoned axial surfaces concentrated deformation near the core of the folds and progressive tilting with age when compared to the model predictions the folds are likely growing by a combination of limb rotation in the tight cores of the folds and hinge zone migration of pregrowth strata across the flanks of the folds

geometric and kinematic models for detachment folds with fixed and variable detachment depths abstract detachment folds are defined by competent rock units and are cored by incompetent units deformed internally above a detachment horizon we have developed two geometric models to constrain possible geometries and kinematic paths for ideal detachment folds the models each independently relate fold geometry to shortening and to detachment depth model assumptions include plane strain constant competent bedlength constant cross sectional area chevron fold geometry and no bed parallel shear outside the fold detachment depth is constant in one model but may vary in the other thus allowing evaluation of the implications for fold geometry and kinematics of fixed vs variable detachment depth detachment folds formed above a detachment unit of constant thickness constant detachment depth must be initially symmetrical and cannot grow with fixed hinges fixed arc length or a self similar geometry detachment folds formed above a detachment unit of variable thickness variable detachment depth must also be initially symmetrical but any one fold geometry can have a range of possible initial and final detachment depths kinematic paths for folds with fixed hinges fixed arc lengths migrating hinges variable arc lengths and selfsimilar geometries are all possible if detachment depth varies the change in detachment depth during deformation can be determined using the variable detachment depth model if either initial or final detachment depth is known the models demonstrate a wider range of variability in the geometry and kinematics of ideal detachment folds particularly for the variable depth model than is the case for ideal fault bend and fault propagation folds this variability limits the usefulness of simple geometric models for reconstructing the geometry of natural detachment folds balancing cross sections over a sufficient area and evaluating strain may compensate for these limitations

further evidence for inclination shallowing in red beds red beds and related shallow marine siliciclastic sediments within the extensional catalan neogene basins offer a unique opportunity to study the relationship between sediment anisotropy remanence acquisition and inclination shallowing on the basis of the dominant fabric features sedimentary facies are grouped into laminated massive and bioturbated the bulk susceptibility appears to be dominated by paramagnetic phyllosilicates and clay minerals the magnetic susceptibility fabric is dominantly foliated while the degree of anisotropy is very variable and is dependent on the facies type strong foliation dominates in the laminated sediments whereas weak anisotropy characterizes the bioturbated and massive mass flow facies moreover we observe a correlation between facies type and remanence inclination the undisrupted thinly laminated facies provides the most biased inclination values 20 as opposed to 60 of the expected geomagnetic field steeper inclinations are reported from bioturbated muds while the best record of the geomagnetic inclination is found in the weakly anisotropic mass flow deposits

paleomagnetism of carboniferous strata from the stellarton gap deposition of carboniferous sediments within the stellarton graben of nova scotia was controlled by displacements on the bounding hollow and cobequid fault systems periods of both normal and transcurrent faulting have occurred on both faults as a result models for the development of the stellarton basin have included a pull apart basin and a thermal subsidence basin paleomagnetic study of stratigraphic sequences from within the graben showed evidence for three separate periods of remanence acquisition st3 st2 st1 ordering the acquisition sequence for these three magnetizations is mainly circumstantial being based on the distribution of each remanence phase relative to stratigraphic position and deformation of the strata the oldest magnetization st3 is grossly divergent from previously reported carboniferous results suggesting an early period of large scale clockwise rotation magnetization st2 has a similar pole position to many others from maritime carboniferous basins located within the app

the fold test in palaeomagnetism summary the fold test suggested by mcelhinny is shown to be inappropriate more correctly one should determine whether the mean direction of a group of sites from one limb of a fold may be distinguished statistically from the mean direction of a group of sites from another limb details of the application of this test are given with examples it is shown that the test indicates significance under far less severe folding than does the test suggested by mcelhinny

bed length does not remain constant during deformation recognition and why it matters abstract we apply multiple balancing restoration methods to three examples of fault bend folds exhibiting increasing levels of complexity and uncertainty three methods the chamberlin depth to detachment calculation direct measurement of fault displacement and flexural slip restoration balancing assume that bed lengths and thicknesses blt remain constant during deformation the area depth strain ads method allows bed lengths and thicknesses to vary during deformation for a kinematic model the agreement among methods is exact to within measurement error for an experimental sand model the disagreement among methods is substantial the ads relationship shows that the sand model has significant layer parallel shortening and an area increase of 4 a previously published interpretation of a seismically imaged fault bend fold from the rosario oil field venezuela is nearly line length balanced but the ads relationship indicates small but significant anomalies including an area deficit for the deeper stratigraphic levels a revised interpretation with a more internally consistent ads relationship suggests that much of the footwall uplift is real and not a velocity pull up our comparisons of the results of the various balancing restoration techniques show the resolving power of the ads method to detect sub resolution changes in bed lengths and thicknesses and to identify footwall structures overlooked by the constant blt methods

geometric analysis of fold development in overthrust terranes abstract fault bend folding fault propagation folding and detachment or decollement folding are three distinct scenarios for fold thrust interaction in overthrust terranes simple kink hinge models are used to determine the geometric associations implicit in each scenario bedding maintains constant thickness in the models except in the forelimb of the fold the forelimb is allowed to thicken or thin without limit the models address individual folds and the calculated fold geometries are balanced structures each mode of fold thrust interaction has a distinct set of geometric relationships final fold geometry is adequate in itself to discern many fault bend folds this is not the case for fault propagation and detachment folds these two fold forms have very similar geometric relationships some knowledge of the nature of the underlying thrust or decollement zone is usually needed to distinguish between them the geometry of a fold is altered in a predictable fashion by transport through an upper ramp hinge and by fault parallel shearing of the structure the shearing results in a tighter fold whereas transport through the ramp hinge produces a broader fold the viability of the geometric analysis technique is demonstrated through its application to a pair of detachment folds from the canadian cordillera the geometric analysis is also used to evaluate cross sections through subsurface structures in an example from the turner valley oil field the analysis indicates how the interpretation should be altered so as to balance the cross section the analysis reveals hidden assumptions and specific inconsistencies in structural interpretations

compaction corrected inclinations from southern california cretaceous marine sedimentary rocks indicate no paleolatitudinal offset for the peninsular ranges terrane paleomagnetic data have been used extensively to delineate the terrane displacement and accretion history of the western margin of north america however the anomalously shallow paleomagnetic inclinations used to indicate large scale northward translation might be alternatively interpreted as due to postmagnetization tilting of batholithic rocks and compaction of marine sediments to understand the magnitude of burial compaction effects on the post cretaceous motion history of the peninsular ranges baja borderlands terrane a rock magnetic compaction and paleomagnetic study of the ladd formation and the point loma formation from southern california was conducted the anhysteretic anisotropy of remanence of the characteristic remanence carrying grains and individual magnetic grain anisotropy were used to correct the inclinations of each formation individual magnetic grain anisotropy was determined by both compaction experiments and redeposition of a magnetic separate in a dc magnetic field standard paleomagnetic studies of the units indicated that previous ladd formation results could be reproduced and a correction was made at the sample level we were unable to adequately reproduce earlier results of the point loma formation so the average remanence anisotropy was used to correct the previously reported mean direction the mean inclination of the ladd formation was conected from 46 95 8 to 58 95 4 and the mean inclination of the point loma formation was conected from 39 5 5 4 normal and 36 4 16 6 reversed to 56 0 5 1 normal and 53 0 16 7 reversed these results suggest that the peninsular ranges baja borderland terrane has been part of the western north america since the late cretaceous and that clay containing sedimentary rocks may typically experience from 10 to 15 of inclination shallowing due to burial compaction

bed by bed fold growth by kink band migration sant llorenc de morunys eastern pyrenees ahstract rowth strata deposited over and against the flank of the sant llorenc de morunys fold during its final stages of deformation have been mapped at high resolution as the basis for unraveling the kinematics of fold growth we use restoration techniques based on normal balancing assumptions to decipher the detailed kinematic history of folding the progressive restorations as well as balanced forward modeling show that the last few hundred meters of fold growth were dominated by kink band migration of a sort that is typical of much faultrelated folding the kink band migration has produced complex anticlinal hinge zone geometry including segmented fold hinges linked by disconformities and unconformities which has direct and detailed explanation in terms of fluctuations in deposition rate relative to curved hinge kink band migration rate large fluctuations in the convolution of non steady sedimentation and deformation are demonstrated although the absolute fluctuations in deformation and sedimentation are unknown at a length scale of 100 m kink band migration with little or no deposition is interspersed with sedimentation with little or no deformation at the length scale of 500 m deposition ranges from 200 to 50 of uplift 0 1997 elsevier science ltd all rights reserved

lithologic and structural controls on natural fracture distribution and behavior within the lisburne group northeastern brooks range and north slope subsurface alaska the carboniferous lisburne group of northern alaska has been deformed into a variety of map scale structures in both compressional and extensional structural settings thus providing a series of natural experiments for observing the formation distribution and behavior of fractures in this thick carbonate unit two fracture sets dominate the lisburne group carbonates of the north slope subsurface and the nearby northeastern brooks range fold and thrust belt north northwest striking regional extension fractures probably formed in front of the northeastern brooks range fold and thrust belt in the north slope subsurface this fracture set overprints east northeast striking fractures related to earlier extensional deformation in contrast in the fold and thrust belt the north northwest striking fracture set is overprinted by younger east northeast striking fractures related to subsequent contractional deformation lithology is the primary control on the fracture density of both sets in mildly deformed lisburne copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received february 20 1996 revised manuscript received november 25 1996 final acceptance june 5 1997 2geophysical institute university of alaska fairbanks fairbanks alaska 99775 3sandia national laboratories ms 0705 albuquerque new mexico 87185 4department of petroleum natural gas engineering new mexico institute of mining technology socorro new mexico 87801 and sandla national laboratories ms 0705 albuquerque new mexico 87185 this study was supported by a department of energy subcontract administered by sandia national laboratories additional support was provided by arco alaska bp alaska chevron exxon mobil and japan national oil company we would like to thank arco alaska and bp alaska for giving us permission to view selected lisburne group cores w wallace for helpful discussions on deformational styles of detachment folds a j mansure for help in interpreting the interference tests and w wallace k biddle w belfield n hurley and j kelley for helpful reviews of the manuscript

paleomagnetism of rocks from burin peninsula newfoundland hypothesis of late paleozoic displacement of acadia criticized the posttectonic st lawrence granite 360 5 ma and associated subvertical dikes have two magnetizations n and h n points north with an intermediate upward inclination declination 005 inclination 50 alpha 95 10 paleopole 12 n 120 e we consider n to have been acquired close to the time of initial cooling the h magnetization points south with low inclination h is also the dominant magnetization in the nearby permo carboniferous spanish room formation h is considered to be an overprint acquired chemically during the kiaman reversed superchron late carboniferous and permian the n magnetization corresponds to a paleolatitude of 31 7 s very different from the near equatorial values expected from the commonly accepted late devonian and earliest carboniferous tournaisian reference paleofields for cratonic north america this is generally consistent with the hypothesis of a southerly displaced acadia proposed by kent and opdyke although the displacement is much greater 30 rather than 15 however we show that all inclinations observed from middle to upper devonian and tournaisian rocks from the craton are not significantly different either from the kiaman paleofield or from the h overprints observed from newfoundland some of these cratonic studies are not very detailed but it is noteworthy that the declination observed in the most comprehensive of them catskill red beds also agrees with the kiaman paleofield and with the h overprints from newfoundland declinations in some other cratonic studies show small departures of only a few degrees with one exception based on limited sampling and two from the colorado plateau which may have been rotated which could be caused by experimental inaccuracies moreover the directions obtained from cratonic studies are 97 reversed as they are in rocks with kiaman magnetizations we suggest therefore that the commonly accepted late devonian to earliest carboniferous reference paleofield for north america is either entirely kiaman in age or has been seriously affected by kiaman overprinting consequently the 30 of southerly displacement which the n magnetization of the st lawrence granite apears to indicate and the 15 invoked by kent and opdyke we consider to be illusory three late precambrian rock units 623 to 606 ma have scattered declinations but similar inclinations yielding paleolatitudes of about 35 the scattered declinations presumable were caused by local pre carboniferous relative rotations there is little or no evidence of kiaman overprinting in precambrian rocks indicating that overprinting is comparatively superficial and is probably related to late paleozoic groundwater circulation

a plagioclase rich rock measured by yutu 2 rover in von karman crater on the far side of the moon abstract the chang e 4 spacecraft successfully landed in von karman crater inside the south pole aitken basin on the lunar far side on january 3 2019 and the yutu 2 rover has performed explorations on the lunar surface for nine lunar days as of september 2019 our earlier analysis of the visible and near infrared spectrometer measurements made by the yutu 2 rover during the first two lunar days shows that the regolith of the landing site may have come from the nearby finsen crater and is dominated by plagioclase with lesser amount of mafic minerals during its third lunar day explorations the yutu 2 photographed a small piece of lunar rock and measured its reflectance spectra compared with the spectra of its surrounding regolith this rock s spectrum has deeper absorption features indicating its fresher nature to obtain the mineralogy of the rock we compared the rock s spectrum with the spectral library data of nasa s reflectance experiment laboratory of returned lunar rocks and lunar meteorites we found that this rock is also plagioclase rich with a possible plagioclase abundance of 60 80 vol a source region analysis using the moon mineralogy mapper s remote sensing observations indicates this rock was ejected from the zhinyu crater about 30 km west of the landing site rather than directly from the finsen crater numerical simulations of the zhinyu crater on the impact cratering process and ejecta thickness distribution confirmed our findings and imply that the surficial materials at the ce 4 landing site experienced a complicated evolution rather than simply retaining the pristine or primordial ejecta directly from the finsen crater

photometric anomalies in the apollo landing sites as seen from the lunar reconnaissance orbiter abstract phase ratio imagery is a new tool of qualitative photometric analyses of the upper layer of the lunar regolith which allows the identification of natural surface structure anomalies and artificially altered regolith we apply phase ratio imagery to analyze the apollo 14 15 and 17 landing sites this reveals photometric anomalies of 170 120 m size that are characterized by lower values of the phase function steepness indicating a smoothing of the surface microstructure caused by the engine jets of the landing modules other photometric anomalies characterized by higher phase function slopes are the result of regolith loosening by astronaut boots and the wheels of the modular equipment transporter and the lunar roving vehicle we also provide a possible explanation for the high brightness of the wheel tracks seen in on surface images acquired at very large phase angles

submillimeter scale topography of the lunar regolith we have applied computer stereophotogrammetry to apollo lunar surface closeup camera alscc pictures of the lunar surface to construct the first ever digital topographic relief maps of undisturbed lunar soil over spatial scales from 85 m to 8 5 cm using elevation histograms fractal analysis and hapke s photometric roughness model we show that apollo 14 fra mauro imbrium ejecta is rougher than average apollo 11 mare tranquilitatis and apollo 12 oceanus procellarum mare surfaces at submillimeter to decimeter size scales we confirm the early result of k lumme et al 1985 earth moon planets33 19 29 that the cumulative distribution of elevations for lunar soil is typically well described by gaussian statistics however cumulative distributions are insensitive to asymmetries in the shapes of elevation histograms of 11 discrete elevation histograms we measured about half exhibit significant deviations from gaussian behavior we also confirm lumme et al s finding that the roughnesses of all lunar surfaces increase with decreasing size scale we further show that the scale dependence of roughness is well represented by fractal statistics the rates of change of roughness with size scale represented by fractal dimension d are remarkably similar among terrians after correcting for the contribution of large scale roughness our average value of d 2 31 0 06 falls within the range 2 0 d 2 4 reported from lunar radar studies the amplitude of roughness which we characterize with the rms slope angle at 1 mm scale varies significantly among terrains for lunar mare the average rms slope angle is 16 4 3 and that for fra mauro regolith is 25 1 by comparison to radar data we suggest that the roughness of fra mauro imbrium ejecta regolith is similar to that of lunar highland terrains we find that the gaussian slope distribution assumed in b w hapke s model 1984 icarus59 41 59 adequately describes typical lunar regolith surfaces a revised form of hapke s equation that models realistic particle phase functions and the coherent backscatter opposition effect was fitted to disk resolved lunar photometric observations and yields estimates of 27 1 for highland and 24 1 for mare regolith these values of as well as the implied relative highland mare photometric roughness ratio are best matched in our elevation data by the cummulative contributions of surface topography covering all scales greater than 0 1 mm less than 5 of the photometrically detected roughness of lunar regolith is contributed by surface relief at scales larger than 8 cm this conclusion implies that values of derived from whole disk and disk resolved photometry respectively may be taken to represent the same physical quantity in addition particulate samples used in goniophotometric measurements should not be assumed to be photometrically smooth i e 0 as is often done in laboratory applications of hapke s photometric model the predicted photometric roughness at size scales of 0 1 mm and less significantly exceed photometric estimates and suggests that there exists a measurable size scale below which topographic relief either is not photometrically detectable or is not represented in the hapke model as macroscopic roughness

the role of strain in area constant detachment folding abstract the classical constant area relationship for balancing cross sections is reformulated to accommodate layer parallel strain leading to a general equation for the layer parallel strain in a fold formed above a stratigraphically fixed detachment horizon the strain required for area balance can be calculated from a knowledge of the fold shape and the depth to detachment the strains predicted from a simple kinematic model are realistic in the order of 10 30 layer parallel shortening the strain may be penetrative or occur as small scale disharmonic folds and faults the tip top anticline a fold at the leading edge of the wyoming thrust belt is used to illustrate the applicability of this reformulation the computed layer parallel strains in the well controlled upper portion of the structure are less than 5 because most of the shortening is accommodated by second order folds and faults

fluid inclusion technique for determining maximum temperature in calcite and its comparison to the vitrinite reflectance geothermometer theory laboratory experiments and empirical observation suggest that many aqueous fluid inclusions in calcite reequilibrate during overheating and therefore some homogenization temperatures t h record a temperature close to the maximum reached by the rock this characteristic suggests that aqueous fluid inclusions in calcite can be used to establish maximum temperature t peak to test this hypothesis we have compiled fluid inclusion t peak mean random vitrinite reflectance r m and present day t peak from 46 diverse geologic systems that have been at t peak from 10 4 to 10 6 yr present t peak ranged from 65 to 345 c t h modes and means ranged from 59 to 350 c and r m data ranged from 0 4 to 4 6 spanning the temperature and thermal maturity range associated with burial diagenesis hydrothermal alteration and low grade metamorphism plots of t h and t peak data for systems thought to be currently at maximum temperature demonstrate close agreement between t h and present t peak in sedimentary basins although caution should be applied the relation suggests that t h of aqueous fluid inclusions in calcite may be a useful measure of maximum temperature this study also compares t h to mean random vitrinite reflectance r m to offer further support for the use of t h as a measure of t peak and to provide a better understanding of r m t h correlates well with r m and results in a curve similar to r m vs t peak calibrations determined by other workers the strong correlation correlation coefficient r 0 93 between t peak and r m in these systems suggests that maximum temperature is the major control on thermal maturation

lunar surface roughness derived from lro diviner radiometer observations abstract sunlit and shaded slopes have a variety of temperatures based on their orientation with respect to the sun generally greater slope angles lead to higher anisothermality within the field of view this anisothermality is detected by measuring changing emitted radiance as a function of viewing angle or by measuring the difference in brightness temperatures with respect to observation wavelength thermal infrared measurements from the lunar reconnaissance orbiter diviner radiometer were used to derive lunar surface roughness via two observation types 1 nadir multispectral observations with full diurnal coverage and 2 multiple emission angle targeted observations measurements were compared to simulated radiance from a radiative equilibrium thermal model and gaussian slope distribution model nadir observations most closely match a 20 rms slope distribution and multiple emission angle observations can be modeled using 20 35 rms slope distributions limited sampling of the lunar surface did not show any clear variation in roughness among surface units two dimensional modeling shows that surfaces separated by distances greater than 0 5 5 mm can remain thermally isolated in the lunar environment indicating the length scale of the roughness features non equilibrium conditions are prevalent at night and near sunrise and sunset preventing the use of the equilibrium thermal model for roughness derivations using data acquired at these local times multiple emission angle observations also show a significant decrease in radiance at high emission angles in both daytime and nighttime observations and hemispherical emissivity is lower than is apparent from nadir observations these observations and models serve as a basis for comparison with similar measurements of other airless bodies and as an initial template for the interpretation of tir measurements acquired under a variety of geometric conditions

the roles of complex mechanical stratigraphy and syn kinematic sedimentation in fold development insights from discrete element modelling and application to the pico del aguila anticline external sierras southern pyrenees

palaeomagnetism of the early carboniferous deer lake group western newfoundland no evidence for mid carboniferous displacement of acadia early carboniferous visean to possibly earliest namurian sedimentary rocks of the deer lake group of western newfoundland rest unconformably on grenvillian basement rocks of the canadian shield which form the western border of the early palaeozoic appalachian orogen in addition to magnetically soft magnetizations directed along the present field three families of magnetization directions are found two of them referred to as n north and s south are antiparallel and prefolding and were probably acquired during the depositional process n and s are roughly of equal frequency they have a mean direction irrespective of sign of 0 7 35 2 k 40 95 8 9 and a palaeopole 21 5 n 121 8 e 10 3 6 0 corresponding to a palaeolatitude of 20 6 s this agrees with the palaeolatitude 17 5 s determined from the somewhat older early carboniferous tournaisian terenceville formation of the avalon platform on the eastern side of the appalachian orogen in newfoundland the third magnetization referred to as h roughly horizontal has a mean direction 156 8 13 3 k 37 95 10 1 and a palaeopole 45 4 n 140 3 e 10 3 5 3 corresponding to a palaeolatitude of 7 4 n we interpret this to be an early kiaman latest carboniferous to early permian overprint probably acquired chemically the palaeolatitude determined from the h overprint agrees with that determined from early carboniferous rocks of cratonic north america west of the appalachians therefore we argue early carboniferous palaeofield determinations for cratonic north america have been strongly biased by unremoved kiaman overprints because of this and because of the good agreement between early carboniferous palaeolatitudes obtained from opposite margins of the appalachian orogen we suggest that there is at present no palaeomagnetic evidence for the previously proposed 1500 km displacement from the south of an eastern portion of the appalachians acadia relative to cratonic north america during the carboniferous

a compositional study of the aristarchus region of the moon using near infrared reflectance spectroscopy newly obtained near infrared reflectance spectra for features on or near the aristarchus plateau demonstrate the diversity of compositions in the region highland units are of three probable compositions a feldspar and clinopyroxene assemblage a probable clinopyroxene olivine and possibly feldspar assemblage and an assemblage composed of olivine or olivine and feldspar the feldspar clinopyroxene assemblage is tentatively correlated with the major th anomaly centered on aristarchus crater the regional pyroclastic deposits on the plateau are composed of greater than 90 fe2 bearing glass the aristarchus cratering event fully penetrated any mare or pyroclastics in the target evidence for mare related material is found in the ejecta on the mare side of the mare plateau contact

spectroscopic observations of the moon at the lunar surface abstract the moon s reflectance spectrum records many of its important properties however prior to chang e 3 ce 3 no spectra had previously been measured on the lunar surface here we show the in situ reflectance spectra of the moon acquired on the lunar surface by the visible near infrared spectrometer vnis onboard the ce 3 rover the vnis detected thermal radiation from the lunar regolith though with much shorter wavelength range than typical thermal radiometer the measured temperatures are higher than expected from theoretical model indicating low thermal inertia of the lunar soil and the effects of grain facet on soil temperature in submillimeter scale the in situ spectra also reveal that 1 brightness changes visible from orbit are related to the reduction in maturity due to the removal of the fine and weathered particles by the lander s rocket exhaust not the smoothing of the surface and 2 the spectra of the uppermost soil detected by remote sensing exhibit substantial differences with that immediately beneath which has important implications for the remote compositional analysis the reflectance spectra measured by vnis not only reveal the thermal compositional and space weathering properties of the moon but also provide a means for the calibration of optical instruments that view the surface remotely

mesozoic paleomagnetic results of the tarim craton tertiary relative motion between china and siberia paleomagnetic poles from two late jurassic to late cretaceous stratigraphic sections on the northern boundary of the tarim craton in western china are concordant with poles of similar age from eastern china when combined with previously published data these new results suggest that the major tectonic blocks which comprise china the tarim yangtze and sino korean cratons have been arranged in approximately their present relative configuration since cretaceous times the averaged cretaceous paleomagnetic pole for china is significantly different from the averaged cretaceous pole for siberia the difference may reflect significant relative post cretaceous motion between the composite china terrane and the siberian craton alternatively the cretaceous pole for siberia may not be reliable

stratigraphic controls on eformation patterns in fault related folds a detachment fold example from the sierra madre oriental northeast mexico abstract deformation patterns are described by the style intensity and distribution of structures throughout a volume of rock in fault related folds presently observed deformation patterns are controlled by structural factors like kinematic history environmental factors like burial history and stratigraphic factors like layer thickness and competence to demonstrate the role of stratigraphy in controlling fold related deformation patterns we document the stratigraphic variability of mesostructures at one structural position on a map scale detachment fold unique assemblages of faults fractures and cleavages in certain stratigraphic intervals define a mechanical stratigraphy comprised of several units each exhibiting a characteristic deformation response to the folding process the varying response of each mechanical unit suggests that folding mechanisms such as orthogonal flexure flexural slip or flexural flow were sequentially or coevally operative in each of the units using the simple theoretical strain distributions associated with each folding mechanism and the fact that each mechanical unit accommodates fold related strain by developing a characteristic set of mesostructures we are able to predict general deformation patterns elsewhere in the fold the significance of this approach is that it recognizes that even in a single structure fold kinematics and deformation response may be dramatically different in various parts of a stratigraphic section because of this the quality and character of reservoir rocks in anticlinal traps may change markedly over short stratigraphic distances predictions of fold related deformation based solely on fold kinematics are unlikely to resolve these variations

mobile hinge kinking in layered rocks and models abstract an unresolved question in structural geology is whether kink folds grow by the gradual rotation of the fold limbs about a fixed hinge by the nucleation of kink bands that grow by fold hinge migration or by some combination of these mechanisms the importance of mobile hinge kinking has previously been recognized in experimentally deformed slate and phyllite as well as decks of paper cards but its importance in the folding of multilayers consisting of alternating competent and incompetent layers has been uncertain this study shows that mobile hinge kinking can be an important folding mechanism in both natural and experimental multilayers the natural folds are in pelagic limestones from the umbria marche apennines of italy the geometrical properties of these folds as well as the small scale structures in the rocks indicate that these folds formed by the nucleation and expansion of kink bands with mobile hinges not by a fixed hinge folding mechanism the experimental folds were produced by the deformation of multilayered models consisting of layers of lead separated by layers of wax impregnated cloth the progressive growth of these folds by the nucleation and expansion of kink bands was directly observable a rough estimate of the rate at which fold hinges migrated through the apennine limestones was obtained indirectly using the displacement history recorded by calcite fibers on a fault which cuts a kink fold and was active during the formation of the fold it appears that the rate at which fold hinges migrated was approximately 100 times greater than the displacement rate along a fault that was moving by pressure solution slip

relief and shortening in detachment folds we present new thickness relief methods for determining shortening s z mean shortening s z and curvimetric shortening sc z as a function of height in well imaged structures thickness relief measurements allow us to constrain the fractions of the deformation that are layer parallel pure shear simple shear and flexural and to measure the excess area ae of fold cores caused for example by flow of evaporites the key measurements are made in the thickness domain which allows for more certain determination of regional stratigraphic gradients which is required for reliable separation of structural relief from primary stratigraphic thickness variations we apply these methods to a diverse set of active detachment folds from the fronts of the nankai trough japan cascadia accretionary wedge oregon southern tianshan china and agbami anticline deep water niger delta three of these folds can be approximated by pure shear detachment fold models because more than 95 of the shortening is by layer parallel heterogeneous pure shear plus horizontal compaction for this reason curvimetric shortening is one to two orders of magnitude less than total shortening in contrast agbami anticline shows layer parallel stretching above the excess area of the fold core in all examples the layer parallel simple shear component is negligible or absent 2006 elsevier ltd all rights reserved

a visible and near infrared photometric correction for moon mineralogy mapper m 3 observations of the moon obtained by the moon mineralogy mapper m 3 instrument were acquired at various local viewing geometries to compensate for this a visible near infrared photometric correction for the m 3 observations of the lunar surface has been derived images are corrected to the standard geometry of 30 phase angle with an incidence of 30 and an emission of 0 the photometric correction is optimized for highland materials but is also a good approximation for mare deposits the results are compared with ground based observations of the lunar surface to validate the absolute reflectance of the m 3 observations this photometric model has been used to produce the v1 0 level 2 delivery of the

2 d and 3 d modeling of detachment folds with hinterland inflation a natural example from the monterrey salient northeastern mexico abstract geologists now recognize the presence and abundance of detachment folds in various contractional settings several two dimensional geometric and kinematic models exist to describe the development of such structures these models typically are area balanced are interpreted to develop by hinge migration limb rotation or a combination of the two processes and possess a constant regional level outside the fold itself we present two new two dimensional geometric and kinematic models for detachment folds that incorporate hinge migration and limb rotation as their deformation mechanisms these area balanced models differ from previous models however in that they allow hinterland inflation to occur thereby creating a higher local regional level in the hinterland relative to the foreland this local regional difference across the detachment fold may reflect hinterland uplift due to thickening of the incompetent unit foreland deflation of the incompetent unit as material migrates into the fold core during fold growth and or migration of material out of the fold core as the fold tightens we illustrate the utility of these models by constructing pseudo three dimensional representations of the western termination of the nuncios fold complex in the monterrey salient northeastern mexico our results suggest that the limb rotation model more accurately portrays the overall three dimensional fold geometry for the nuncios fold complex matches the observed hinterland inflation and predicts more reasonable detachment depths for the structure along its length these results agree with interpreted kinematics based on field observations and illustrate how this modeling approach may help constrain interpretations of detachment folds with hinterland inflation in areas lacking sufficient data

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

detachment folds with fixed hinges and variable detachment depth northeastern brooks range alaska abstract detachment anticlines in the northeastern brooks range accommodated displacement above a detachment by buckling of a competent unit over an incompetent unit meso and microstructures in hinges and a lack of relict hinge structures in limbs suggest that these folds grew with fixed hinges the structural thickness of the incompetent unit beneath the folds detachment depth varies from less than to greater than the stratigraphic thickness a model in which incompetent unit thickness varies with fold area better approximates the geometry of the folds than does a more conventional constant depth model additional discrepancies between modelled and observed incompetent unit thickness and field observations suggest non plane strain and or transport of material through the boundaries of the fold in the plane of the cross section the results of this study suggest a typical evolutionary sequence for detachment folds in the northeastern brooks range which may be applicable elsewhere anticlines initiate as fixed hinge buckle folds rapid initial increase in anticlinal cross sectional area results in a decrease in incompetent unit thickness fold area begins to decrease with tightening beyond an interlimb angle of 90 dg decreasing fold area is accommodated through some combination of structural thickening of the incompetent unit transport of solid or dissolved material out of the plane of section transport of material through the boundaries of the fold in the plane of the cross section and or truncation by thrust faults

the kinematics of break thrust folds abstract the kinematics of asymmetric open to close often overturned thrust related folds are commonly explained with fault propagation or detachment fold models field observations of thrust related folds exposed in tennessee virginia wyoming and montana that exhibit this geometry indicate that models of fault propagation and detachment folds do not adequately describe the kinematics of these structures existing models of fault propagation and detachment folding employ migrating kink shaped hinges and relate fold geometry entirely to fault geometry slip and to the thickness of the basal detachment layers the models exclude the relation between fold shape and amplitude and they do not predict a correlation between competent layer thickness and fold wavelength as expected from buckling theory thrust related folds examined in this study exhibit unique distributions of fabrics in the hinges and forelimbs which demonstrate a lack of hinge migration furthermore the ratios of dominant member thickness to fold wavelenght agree with those expected for folds controlled by a single layer and they are within the expected range for folds with multiple evenly spaced harmonically deforming layers our analyses suggest these folds evolved from an initial brief stage of sinusoidal buckling to a later stage of fixed hinge kinking and thrusting thrust related folds which exhibit a geometry and mesofabric distribution suggesting this type of evolution are defined as break thrust folds

a new framework for modeling sediment fining during transport with fragmentation and abrasion 1 a new framework for modeling sediment fining during transport is proposed the model is based on a physical description of both abrasion and fragmentation processes it attempts to describe and explain the changes in the grain size distribution of sediments during their transport in a water flow abrasion and fragmentation are modeled through the use of breakage frequency functions and daughter size distributions these functions are determined experimentally for the specific case study which is presented comparison between the predictions from the model and experimental data from the case study show that 1 both abrasion and fragmentation are involved in the degradation 2 fragmentation efficiency decreases during the experiment and 3 the shape of the pebbles provides feedback between abrasion and fragmentation this type of model is therefore appropriate for explaining degradation mechanisms which is promising for a future application to rivers

a quantitative study of hinge thickness of natural folds some implications for fold development abstract a quantitative analysis of some natural folds showing thickened hinges designated here as t folds has been carried out two parameters of a fold have been recognized here a the axial angle is the angle for a given trace or arc as subtended at its apex hinge and b the thickness ratio t is the ratio between the hinge th and limb tl thicknesses the t plots for a variety of natural folds yield a very typical curve that not only reflects interdependence of hinge thickening and axial angle but also bears significant implications for fold development assuming the initiation of folding due to buckling it appears that under a system of compressive forces the naturally deformed buckled folds may retain their parallel fold geometry down to the axial angle of about 130 thereafter i e between 130 and 70 the hinge thickening appears to be a rather slow process with more enhanced deformation i e between 70 and 30 when elevated temperatures also appear to play their part the folds develop great mechanical instability and undergo marked flowage and mass transfer towards the hinge zone flattening at

dual polarity early carboniferous remagnetization of the fisset brook formation cape breton island nova scotia summary red siltstones and volcanic flows of the fisset brook formation of cape breton island nova scotia were folded or tilted in two phases one of late tournaisian and the other of mid namurian age upon thermal demagnetization both rock types yield three components of magnetization herein denoted as l i and h the l component has low unblocking temperatures and a direction conforming to that of the present day geomagnetic field l is inferred to be of recent origin the intermediate i component carried by haematite is of synfolding origin directions could be obtained through vector subtraction for the demagnetization interval of 300 550 c and yield a mean of d i 160 38 k 90 8 ag5 s lo after 39 per cent of the tilt correction is applied the h component has even higher unblocking temperatures which overlap to a large degree with those of the i component but analysis of intersecting great circles appears to yield a best fit direction for h which is nearly antipodal to that of the i component h is also synfolding and yields a mean direction of d i 342 38 k 120 9 ag5 6 9 after 60 per cent of tilt correction both components are interpreted as secondary chemical remanent magnetizations of late tournaisian to early namurian age a comparison of all available carboniferous results from the craton and the northern appalachians indicates that palaeolatitudes for nova scotia changed from about 20 s to about 10 s in the interval between the early and late namurian and that they changed again from about 10 s to 0 between the late namurian and the stephanian declinations show good agreement between newfoundland nova scotia new brunswick and the craton with the exception of the meguma terrain which underwent a counterclockwise rotation with respect to the mainland in the late carboniferous as noted previously by spariosu kent keppie 1984

competent unit thickness variation in detachment folds in the northeastern brooks range alaska geometric analysis and a conceptual model detailed measurements of six map scale detachment folds in the northeastern brooks range alaska document significant variations in structural thickness of the competent lisburne limestone thickness variations occur mainly by parasitic folding and penetrative strain and may be controlled by differences in mechanical stratigraphy relative thicknesses of the competent and incompetent units and structural relief of the underlying basement the geometry of these detachment folds is not consistent with key assumptions of existing geometric and kinematic models such as constant competent unit thickness or constant detachment depth we propose a new model that allows both competent and incompetent unit thicknesses to vary throughout the fold this model allows a more realistic geometric description of some natural detachment folds than previous models but the number of variables makes unique reconstruction of specific fold geometries or kinematics difficult comparison of models with natural folds demonstrates that significant error can result if shortening estimates are based on models that incorrectly assume constant competent unit thickness or constant detachment depth use of surveying techniques to quantify map scale fold geometry can provide better reconstructions of fold geometry better shortening estimates and information to constrain kinematic reconstructions

thrust breakthrough of asymmetric anticlines observational constraints from surveys in the brooks range alaska abstract to gain insights into the processes governing the thrust truncation of anticlines we conducted a field study of the thrust truncated folds in the remote brooks range of northern alaska where there is a transition in fold style from symmetric detachment folds to thrust truncated asymmetric folds in order to document the detailed geometry of the km scale folds exposed in cliff forming largely inaccessible outcrops a new surveying technique was developed that combines data from a theodolite and laser range finder the field observations survey profiles and cross section reconstructions indicate that late stage thrust breakthrough of the anticlines within the mechanically competent lisburne group carbonates accommodated continued shortening when other mechanisms became unfeasible including fold tightening forelimb rotation and parasitic folding in the anticline forelimbs these results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold and thrust belts worldwide

moon near infrared spectral reflectance a first good look a positive identification of the minerals olivine plagioclase and several types of pyroxenes were made at several locations on the lunar surface by using remote measurements for example the crater aristarchus is found to have an average pyroxene composition of augite and plagioclase is obviously present a dark mantle deposit in the crater j herschel is at least partly composed of a mixture of 70o7o olivine and 30o7o pyroxene these determinations were possible because the reflectance spectra for 10 20 km diameter lunar areas have been measured for the first time in the ir spectral region 0 65 2 5 m with sufficient spectral resolution and photometric precision to define mineral electronic absorption bands the reflectance for all lunar regions observed over 100 to present continues to increase toward longer wavelengths to at least 2 5 m and several mineral absorption bands appear the telescopic spectra are of similar quality and contain features similar to laboratory spectra of lunar samples the absorption features in several spectra have been quantitatively analyzed using newly developed computer processing techniques including thermal flux removal and absorption band fitting to produce these mineral identifications detection and quantitative analysis of these absorptions provide a much improved basis for remotely determining and mapping surface mineralogy quantitatively from the ground or using airborne or spacecraft platforms

fracture paragenesis and microthermometry in lisburne group detachment folds implications for the thermal and structural evolution of the northeastern brooks range alaska the distribution character and relative age of fractures in detachment folded mississippian pennsylvanian lisburne group carbonates and overlying permian triassic clastic rocks in the northeastern brooks range of northern alaska provide important clues to the thermal and deformational sequence experienced by these rocks although paleothermal indices in the host rock limit the conditions of folding to temperatures equal to or less than 280c field and petrographic relationships suggest that different fracture sets formed at different times during the deformational history of the rocks providing a record of deformation under changing temperature and pressure conditions these rocks probably initially entered the oil generation window 80 140c during the early cretaceous formation of the colville basin via thrust loading by the brooks range to the south regional fractures formed during this time as a result of high pore pressures and low in situ differential stresses shortening in these rocks related to the advancing northeastern brooks range fold and thrust belt began during the late cretaceous to early tertiary early phases of detachment folding were via flexural slip with associated fracturing with continued shortening and growth of detachment folds structural thickening resulted in deeper burial of the bottom part of the deforming wedge early fold related fractures were subsequently overprinted by penetrative strain during peak folding at temperatures of approximately 280c continued shortening resulted in uplift and erosional unroofing at approximately 60 ma late fold related fractures formed at about 150c subsequent uplift of the thickened wedge through 60c occurred after about 25 ma late pervasive extension fractures related to unroofing and or regional stresses formed at relatively shallow depths and low temperatures overprinting all the earlier fractures and penetrative structures

photometric characterization of the chang e 3 landing site using lroc nac images abstract china s robotic chang e 3 spacecraft carrying the yutu rover touched down in mare imbrium on the lunar surface on 14 december 2013 the lunar reconnaissance orbiter lro narrow angle camera nac imaged the site both before and after landing multi temporal nac images taken before and after the landing phase ratio images made from nac images taken after the landing and hapke photometric techniques were used to evaluate surface changes caused by the disturbance of regolith at the landing site blast zone by the descent engines of the chang e 3 spacecraft the reflectance of the landing site increased by 10 1 from i f 0 040 to 0 044 at 30 phase angle as a result of the landing a value similar to reflectance increases estimated for the apollo luna and surveyor landing sites the spatial extent of the disturbed area at the chang e 3 landing site 2530 m 2 also falls close to what is predicted on the basis of correlations between lander mass thrust and blast zone areas for the historic landed missions a multi temporal ratio image of the chang e 3 landing site reveals a main blast zone slightly elongate in the n s direction 75 m across n s and 43 m across in the e w direction and an extended diffuse irregular halo that is less reflective than the main blast zone extending 40 50 m in the n s direction and 10 15 m in the e w direction beyond the main blast zone the n s elongation of the blast zone likely resulted from maneuvering during hazard avoidance just prior to landing the phase ratio image reveals that the blast zone is less backscattering than surrounding undisturbed areas the similarities in magnitude of increased reflectance between the chang e 3 landing site and the surveyor apollo and luna landing sites suggest that lunar soil reflectance changes caused by interaction with rocket exhaust are not significantly altered over a period of 40 50 years the reflectance changes are independent of regolith composition indicating that they are caused by a change in the physical properties of the regolith likely microscopic to macroscopic smoothing of the surface and possibly a change in surface maturity by removal of highly mature very fine grained regolith components

geometric constraints derived from the law of conservation of volume and applied to evolutionary models for detachment folding this paper presents geometric arguments for modifying the conventional concept for the evolution of concentric fold trains above nonductile detachment zones the common geometric model for concentric folding above a detachment invokes a wave train with fixed fold axes regularly spaced along the fold panel limb lengths from crest to trough remain constant as the limb dips increase to uplift the anticlinal crests while the synclinal troughs slide parallel to the detachment plane the basic depth to detachment calculation which derives from the law of conservation of volume requires that the area of uplift above regional for a concentric anticline be equal to the arithmetic product of the shortening and the depth to detachment this imposes a geometric constraint with which a constant limb length anticline growing by increasing limb dip above a fixed detachment plane cannot comply unless in the early stages mobile material in the detachment zone flows from the synclinal troughs to the anticlinal crests and then in the later stages the flow direction reverses relatively few detachment zones contain a significant amount of mobile salt or shale therefore in most concentric detachment fold trains a basic geometric incompatibility exists between the conventional geometric model and themore law of conservation of volume the conflict can be resolved by an evolutionary fold model wherein the anticlinal fold limbs are short at the inception of folding and grow longer as dips increase and the fold grows in this model the anticlinal axes generally are fixed and the synclinal axes active which has structural and economic implications for the distribution of permeability and syntectonic sediments as well as for the migration and entrapment of hydrocarbons 18 figs less

effects of ph and salinity on the intensity of magnetization in redeposited sediments abstract the intensity of magnetization in redeposited sediments was measured as a function of salinity and ph of the sediment water mixture the intensity was relatively low at high salinity or low ph under these conditions inter particle bonds are enhanced which lead to the formation of larger flocs ferromagnetic minerals magnetite in our sediment are incorporated in the flocs consisting mainly of non magnetic minerals and orientation along an applied field is resisted by the drag proportional to the third power of the diameter of the floc higher intensity is recorded at lower salinity and higher ph when inter particle forces are weaker and floc sizes are smaller the increase of magnetization as a function of ph stops at a ph of about 5 which is the pzc of the edge of illite the dominant non magnetic mineral in our sediment above this ph both the edge and face of the illite grains are negative and there is net repulsion which retards flocculation the interactions between clay particles therefore have a larger effect on the intensity of magnetization than interactions between magnetite and clay this suggests that magnetite is always included in a clay magnetite domain and this domain is the smallest unit that is reoriented by a magnetic field

paleomagnetism of fluorite veins in the devonian st lawrence granite newfoundland canada paleomagnetic results are reported from the devonian st lawrence granite and the fluorite veins within the granite or its related porphyry dikes paleomagnetic analysis of 359 specimens from 29 sites shows that there is no statistically significant difference at 95 confidence between the site mean characteristic remanent magnetization chrm directions carried by pyrrhotite and or magnetite of the granite and fluorite veins no post granite metamorphic event is known in the area thus these concordant directions indicate that the granite and fluorite veins are coeval and retain a primary remanence however the mean chrm direction of 25 vein and granite sites yields an early pennsylvanian paleopole of 316 ma on the north american apparent polar wander path at 35 5 n 129 2 e a95 3 4 that is younger than the 374 2 ma devonian u pb zircon age for the granite two intersecting vertical vein sets indicate that the st lawrence granite has not been tilted since emplacement of the fluorite veins t

kinematics of decollement folding in the lost river range idaho decollement folding of massive 2 m thick carbonate beds of the scott peak formation within the willow creek anticline northern lost river range idaho was associated with the development of thin 0 25 m widely spaced deformation zones incremental strain histories determined from fibrous overgrowths in strain fringes from the deformation zones provide a basis for kinematic analysis of the anticline plane strain is indicated by coaxial up dip extension on cleavage xy planes and a lack of extension in the y direction in xz sections coaxial incremental strain histories characterize fold hinges and document pinned hinges during folding the sense of rotation on opposing limbs indicates that the fiber curvature records primarily the spin of layers through fixed moderately steep 66 12 dg l diverging extension directions the magnitude of the external rotation for each sample is typically less than the bedding dip suggesting that the external rotation also includes a component of internal rotation related to layer parallel shear toward the upper flat panel or the hinge pin line the magnitude of this internal rotation varies within and between layers

evolving mechanical stratigraphy during detachment folding abstract the combination of a complex lithostratigraphy and shortening can lead to a mechanical stratigraphy that changes character and mode of deformation during detachment folding in the detachment folded carbonates of the carboniferous lisburne group of northern alaska a complex lithostragraphy led to a mechanical stratigraphy that evolved during folding with mechanical unit thickness decreasing as deformation progressed and the fold tightened newly forming mechanical boundaries changed the dominant deformation behavior and subsequent geometry during folding of a given horizon during early folding flexural slip dominated in units comprised of thick bedded competent lithologies while flexural flow dominated in units composed of thinner bedded incompetent lithologies after fold lock up homogeneous flattening dominated in the less competent mechanical units the final result was a fold with a complex geometry and a suite of fractures and other structures indicative of both flexural slip flexural flow folding and homogeneous flattening

the flexural slip mechanism abstract detailed field studies of turbiditic sequences from south georgia south atlantic north devon england and cardigan bay wales show that flexural slip occurs on discrete movement horizons between rock packets in which the beds have welded contacts stair stepping displacements of sedimentary dykes and of early quartz veins show that the movement horizons generally have a decimetre to metre spacing and are marked by bedding parallel quartz veins these veins are from 1 mm to several cm thick and can be used to identify movement horizons in the absence of displaced markers they consist of several sheets of quartz fibres which each carry a slickenfibre lineation and which together preserve a record of the displacements on an individual surface complex slickenfibre patterns and departures from ideal behaviour in which slip occurs orthogonal to the fold hinge probably result from changes in slip vector on the limbs of growing non cylindrical folds movement horizons show many of the features associated with large scale thrusting such as ramps duplexes and imbricate structures and the shear sense given by fibre steps on these surfaces and by duplexes within stratigraphically restricted packages changes across fold hinges chevron folds are thought to develop mainly by flexural flow in the early stages with flexural slip becoming dominant later as the beds become lithified new slip surfaces are generated as the dip of the fold limbs increases

in situ optical measurements of chang e 3 landing site in mare imbrium 1 mineral abundances inferred from spectral reflectance the visible and near infrared imaging spectrometer on board the yutu rover of chinese chang e 3 mission measured the lunar surface reflectance at a close distance similar to 1m and collected four spectra at four different sites these in situ lunar spectra have revealed less mature features than that measured remotely by spaceborne sensors such as the moon mineralogy mapper instrument on board the chandrayaan 1 mission and the spectral profiler on board the kaguya over the same region mineral composition analysis using a spectral lookup table populated with a radiative transfer mixing model has shown that the regolith at the landing site contains high abundance of olivine themineral abundance results are consistent with that inferred from the compound measurement made by the on board alpha particle x ray spectrometer

the nature and origin of rims on lunar soil grains abstract space weathering processes that operate in the lunar regolith modify the surfaces of lunar soil grains transmission electron microscope analysis of the lunar soil grains from the fine size fraction of several lunar soils show that most grains are surrounded by thin 60 200 nm thick rims the microstructure and chemical compositions of the rims can be used to classify rims into four broad categories amorphous inclusion rich multiple and vesicular amorphous rims are noncrystalline generally lack crystalline inclusions show evidence for preferential sputtering of cations and are produced largely by solar wind irradiation damage inclusion rich rims contain abundant nanometer sized grains of fe metal as randomly dispersed inclusions or as distinct layers embedded in an amorphous silica rich matrix inclusion rich rims are compositionally distinct from their host grains and typically contain accumulations of elements that are not indigenous to the host inclusion rich rims are formed largely by the deposition of impact generated vapors with a contribution from the deposition of sputtered ions a continuum in the chemical and microstructural properties exists between typical amorphous rims and typical inclusion rich rims multiple rims consist of a distinct radiation damaged layer up to 50 nm thick that is overlain by vapor deposited material of comparable thickness vesicular rims are compositionally similar to their hosts and are characterized by an abundance of small the formation of rims on lunar soils is complex and involves several processes whose effects may be superimposed from this study it is shown that one process does not dominate and that the relative importance of vapor deposition is comparable to radiation damage in the formation of rims on lunar silicate grains the presence of rims on lunar soil grains particularly those with nanometer sized fe metal inclusions may have a major influence on the optical and magnetic properties of lunar soils

paleomagnetism of the lawrenceton formation volcanic rocks silurian botwood group change islands newfoundland paleomagnetic sampling of the lawrenceton formation of the silurian botwood group in northeastern newfoundland was combined with detailed structural mapping of the area in order to determine the deformation history and make adequate structural corrections to the paleomagnetic data structural analysis indicates that the lawrenceton formation experienced at least two folding events i a regional northeast southwest trending siluro devonian folding episode that produced a well developed axial plane cleavage and ii an episode of local north trending folding bedding regional cleavage relationships indicate that the latter event is older than the regional folding thermal demagnetization of the lawrenceton formation yielded univectorial southerly and shallow directions in situ a fold test on an early mesoscale fold indicates that the magnetization of the botwood postdates this folding event however our results combined with an earlier paleomagnetic study of nearby lawrenceton formation rocks demo

paleomagnetism of the distal member of the new glasgow formation nova scotia canada new constraints on magnetic polarity stratigraphy near the base of the kiaman superchron abstract the ca 315 260 ma kiaman reversed permo carboniferous magnetic superchron is an important time marker that can be used for correlation of stratigraphic sequences from a local to a global scale earlier workers from a paleomagnetic study of the joggins stratigraphic section of the western cumberland basin of nova scotia demonstrated that the base of the superchron lies above redbeds of the lowermost portion of the late namurian westphalian a boss point formation although a detailed sequence of reversals was observed below this point no normal magnetic polarity zones were recognized above it in our study samples were collected from redbeds of the distal member of the westphalian a new glasgow formation of the eastern cumberland basin which directly overlie the gray sandstones of the boss point formation most sampling sites carry a normal polarity magnetization probably acquired at about the time of deposition therefore the base of the kiaman reversed superchron lies within or above th

paleomagnetic evidence for post devonian displacement of the avalon platform newfoundland the possibility that the avalon platform where the avalonian lithotectonic belt is best developed was involved in late paleozoic displacement was tested by paleomagnetic study of red sandstones of the upper devonian terrenceville formation of eastern newfoundland two magnetization directions were identified by thermal demagnetization analysis of 60 oriented samples from 10 sites a high blocking temperature thermally discrete a component of normal and reversed polarity and an intermediate blocking temperature thermally distributed b component of reversed polarity the b component d 185 9 i 3 3 a95 7 2 for n 8 sites is interpreted as a postfolding secondary magnetization and gives a paleomagnetic pole position latitude 43 6 n longitude 117 1 e near early to late permian paleopoles for north america the a component d 181 6 i 28 0 a95 10 1 for n 9 sites is interpreted as the characteristic magnetization possibly dating from near the time of deposition of the terrence ville formation the corresponding paleomagnetic pole position latitude 27 4 n longitude 123 5 e falls within a group of late devonian early carboniferous paleopoles obtained from the acadia displaced terrain encompassing the coastal areas of new england and the canadian maritimes which form another part of the avalonian belt these paleopoles are systematically offset by 15 to 20 in latitude from coeval pole positions obtained from cratonic north america thus the avalonian belt of the northern appalachians which is thought to represent a remnant of a precambrian and early paleozoic microcontinent on tectonostratigraphic considerations appears to correspond to a late paleozoic displaced terrain on the basis of paleomagnetic evidence

paleomagnetism of certain constituents of the bay st george sub basin western newfoundland abstract paleomagnetic studies have been made of certain constituents of the bay st george sub basin specifically results are reported from the spout falls formation tournaisian the jeffreys village member of the robinsons river formation visean and the searston formation namurian westphalian the following magnetizations have been isolated spout falls a tournaisian with d 343 5 i 22 7 k 61 2 95 7 1 and the corresponding pole at 28 6 n 139 5 e 4 5 8 5 spout falls b kiaman with d 166 7 i 12 2 k 51 7 95 10 7 and the corresponding pole at 34 5 s 42 7 w 5 5 10 9 jeffreys village a visean with d 351 2 i 27 3 k 54 0 95 7 6 and the corresponding pole at 26 5 n 130 7 e 4 5 8 3 searston a namurian with d 161 7 i 11 7 k 107 95 7 4 and the corresponding pole at 33 9 s 37 2 w 3 8 7 5 and searston c with d 111 6 i 13 8 k 28 8 95 14 5 and the corresponding pole at 19 6 s 19 0 e 7 6 14 8 after comparison with paleopoles of similar ages derived from eastern and western newfoundland rocks from constituents of the east coast basin and for interior north america it is concluded that 1 it is unlikely that any large scale relative motion took place since the early carboniferous between eastern and western newfoundland 2 it is unlikely that any north south relative motion took place between the east coast basin and the bay st george sub basin and 3 the bay st george sub basin results do not support the earlier proposed displaced terrane hypothesis of the northern appalachians in as much as the motions during the carboniferous are not supported there is evidence of the northward motion of the appalachians and north america as a whole during the carboniferous the magnetostratigraphic horizon marker in the carboniferous separating a dominant normal and reversed magnetization on the older side and an entirely reversed kiaman magnetization on the younger side may be placed in the bay st george sub basin at the base of the searston formation

review of major shale dominated detachment and thrust characteristics in the diagenetic zone part i meso and macro scopic scale there is considerable variability in the thickness structure and macroscopic deformation style within shale prone major thrust zones which also impacts the structural style in the overlying and sometimes the underlying section the properties and percentages of clay minerals and percentages of organic material quartz and calcite affect fault zone weakness and behaviour the distribution of competent units within a shale prone zone can also significantly affect fault zone architecture even over short strike distance of 10s to 100s of metres other influences include high pore fluid pressures and associated veins deformation of the fault zone may disrupt the original principal displacement zones and force them to relocate including switching lithologies calcite veins can become concentrated locally in the fault zone and become a focus of fault zone weakness we still need many more descriptions of shale prone fault zones to understand the potential variations in thrust sheet structural style caused by differences in shale detachment characteristics the variations in structural style in the hanging walls of shale detachments are broad and range between the sledge runner style in many appalachian examples and the extensive closely spaced imbricate style of the osen roa detachment southern norway such contrasts are related to several factors including thrust sheet mechanical stratigraphy thickness of the overburden lateral continuity of the detachment detachment mechanical properties composition pore fluid pressures presence absence of higher level detachments and strain rate in many structural locations and at many scales shale prone sequences will pile up to produce over thickened masses cleavage duplexes s c fabrics duplexes imbricates pseudo duplexes and vein formation can all contribute to the thickening at nested scales a mixture of brittle and solution diffusion processes overall cause the affected unit to exhibit flow like characteristics while the broad principles are now well established considerable work remains to be done understanding the full range of structural geometries associated with shale detachments what factors regarding the nature of the detachments affect overlying structural styles rates of deformation and the controls on deformation mechanisms within the thrust zones

geometry and kinematics of single layer detachment folds detachment folds form above below or above and below bed parallel thrusts where thrust displacement is transferred into folding geometric and kinematic models are developed for individual single layer detachment folds formed above the tip line of a thrust we analyze three different detachment fold shapes kink bands chevron and box detachment folds and consider three principal detachment fold models 1 constant limb dip where the detachment fold grows by limb lengthening 2 constant limb length where the detachment fold grows by limb rotation and 3 variable limb length and variable limb dip where the detachment fold grows by both limb rotation and limb lengthening the allowance for variable forelimb thickness and excess layer parallel shear enables us to de elop a wide range of possible detachment fold geometry the geometric validity fields for folds with excess parallel shear are reduced when forelimb thinning takes place folds formed with constant limb length are likely to lock up in the initial amplification stages whereas larger amounts of shortening can be taken up by folds formed with variable limb length the manner in which a fold evolves affects the fracture and porosity features of the folded strata therefore determining which mechanism operated to form a specific detachment fold is of particular importance in hydrocarbon exploration the models we present are aimed at permitting more accurate geometric and kinematic interpretations of individual detachment folds examples of detachment folds are analyzed to illustrate the po ential benefits and limitations of the geometric model presented

growth stratal records of instantaneous and progressive limb rotation in the precordillera thrust belt and bermejo basin argentina analysis of synorogenic deposits preserved near the thrust front zone of the precordillera fold and thrust belt and in the bermejo foreland basin in central argentina documents the evolution of deformation during the last 5 myr as well as the thrust system kinematics seismic lines across the area display examples of progressive and instantaneous limb rotations the easternmost thrust plate of the central precordillera the niquivil thrust experienced episodic motion in two main stages a first thrust movement as a fault propagation fold and a second movement as a high angle anticlinal breakthrough fault after a period of quiescence growth strata deposited in the la pareja intermontane basin and the las salinas and bermejo anticline recorded continuous growth of eastern precordilleran structures beginning at 2 7 ma with uplift rates of 0 3 mm yr for the niquivil anticline 1 08 mm yr for the las salinas anticline and between 0 6 and 0 38 mm yr during the last 2 myr for the bermejo anticline once the eastern precordillera began to grow the propagation of the niquivil thrust stopped restricting the deformation to the young vallecito out of sequence thrust the complex geometry of growth strata deposited on the back limb of the las salinas anticline can be explained by using a model of a two step fault propagation fold with constant layer thickness the bermejo anticline of the eastern precordillera is formed by the simultaneous propagation of a shallow fault responsible for the fold shape and a deep fault that produced vertical uplift a growth triangle that documents instantaneous forelimb rotation for a fault propagation fold is recorded for the first time in a published seismic line

the occurrence and origin of late paleozoic remagnetization in the sedimentary rocks of north america although it has been known for 25 years that some paleozoic sedimentary rock units in europe and north america were remagnetized during pennsylvanian or permian time it is only very recently that the complex and widespread nature of the late paleozoic remagnetization phenomenon has been generally acknowledged it is now recognized that many paleozoic paleomagnetic poles for north america that were once considered reliable are in fact the result of remagnetization and as a consequence the paleomagnetic data base for the paleozoic is undergoing rapid and drastic revision the causes of late paleozoic remagnetization in north america are currently the focus of much interest and active research the remagnetization can reside in either hematite or magnetite and different remagnetization mechanisms have been important in different settings chemical remagnetization processes some related to specific diagenetic events are dominant in hematite bearing sandstones and carbonates in magnetite bearing carbonates both chemical and thermoviscous remagnetization processes appear to have been important but it is difficult to determine which process is the dominant one in some settings some of the observed remagnetizations can be linked to the migration of chemically active and perhaps hot fluids during the mountain building events that affected much of the continent during the late paleozoic paleomagnetic studies promise to be important in assessing the role of orogeny in driving fluid migrations within sedimentary basins and in constraining the age of the migrations and the nature of the fluids

kinematic model of detachment folding including limb rotation fixed hinges and layer parallel strain abstract detachment anticlines formed above a stratigraphically fixed detachment horizon and without thinning in the syncline will in general require layer parallel shortening a kinematic model for detachment folds is presented that has planar limbs and is area balanced but requires bed length changes that can be expressed as layer parallel strain the fold grows primarily by limb rotation not by limb lengthening at constant dip the kinematic evolution of the geometry and strain is examined fold geometry is well predicted and the strain estimated in applications of the model to two map scale detachment folds a triangle zone from the front of the wyoming thrust belt and a duplex cored anticline from the appalachian plateau

book review the techniques of modern structural geology volume 2 folds and fractures john g ramsay and martin i huber academic press london 1987 xi 309 398 pp price stg17 50 us 34 50 paperback

geometry and kinematics of the nuncios detachment fold complex implications for lithotectonics in northeastern mexico 1 using recent geologic mapping combined with digital elevation data aerial photo interpretation and cross section balancing we describe the three dimensional 3 d geometry and kinematics of the nuncios fold complex in the monterrey salient of northeastern mexico this map scale evaporite cored detachment fold structure involves upper jurassic through cretaceous rocks deformed during the laramide orogeny and comprises two westward plunging anticlines and an intervening eastward plunging syncline seven balanced cross sections and a 3 d model of this north vergent structure document substantial along strike variations in both fold geometry and detachment depth suggesting that 3 d flow of the detachment layer may have occurred during folding comparison of folds in the monterrey salient with those in the neighboring parras basin suggests that the latter south vergent folds root to a shallower detachment we suggest that northward transport of the monterrey salient folds on the lower evaporite detachment may have been inhibited by a thick sequence of foreland basin rocks in the northeastern parras and southern la popa basins and that the smaller south verging folds formed where the lower detachment was abandoned and slip was transferred to the shallower detachment forming a triangle zone at the front of the sierra madre orogenic wedge

optical effects of space weathering the role of the finest fraction the optical properties of lunar softs are different than those of rocks from which they are derived as a consequence of lunar space weathering soils are darker and exhibit a distinctive red sloped continuum and weaker mineral absorption bands the accumulation of dark glass welded aggregates agglutinates has been thought to account for these optical effects of space weathering on lunar soils spectroscopic analyses of agglutinate separates and size fractions for a suite of lunar softs presented here indicate that the agglutinate paradigm is insufficient to fully account for lunar optical alteration it is the finest fraction of lunar soils 25 gm which constitute 25 wt that dominates the optical properties of the bulk soil unlike size fractions of most silicates for which the finest fraction is the brightest the lunar soil size fractions all have comparable albedos in the short wavelength visible in the near infrared however it is the finest fraction that exhibits the steep red continuum and weak absorption bands the properties of the finest fraction cannot be duplicated by preparing a fine fraction by grinding larger agglutinate rich soil particles these results suggest space weathering on airless bodies is dominated by surface correlated processes perhaps associated with the development of fine grained fe o on or near the surface of grains and the accumulation of the larger agglutinates is not necessarily required to account for lunar optical alteration

multispectral photometry of the moon and absolute calibration of the clementine uv vis camera abstract we present a multispectral photometric study of the moon between solar phase angles of 0 and 85 using clementine images obtained between 0 4 and 1 0 m we produce a comprehensive study of the lunar surface containing the following results 1 empirical photometric functions for the spectral range and viewing and illumination geometries mentioned 2 photometric modeling that derives the physical properties of the upper regolith and includes a detailed study of the causes for the lunar opposition surge 3 an absolute calibration of the clementine uv vis camera the calibration procedure given on the clementine calibration web site produces reflectances relative to a halon standard and further appear significantly higher than those seen in groundbased observations by comparing clementine observations with prior groundbased observations of 15 sites on the moon we have determined a good absolute calibration of the clementine uv vis camera a correction factor of 0 532 has been determined to convert the web site www planetary brown edu clementine calibration html reflectances to absolute values from the calibrated data we calculate empirical phase functions useful for performing photometric corrections to observations of the moon between solar phase angles of 0 and 85 and in the spectral range 0 4 to 1 0 m finally the calibrated data is used to fit a version of hapke s photometric model modified to incorporate a new formulation developed in this paper of the lunar opposition surge which includes coherent backscatter recent studies of the lunar opposition effect have yielded contradictory results as to the mechanism responsible shadow hiding coherent backscatter or both we find that most of the surge can be explained by shadow hiding with a halfwidth of 8 however for the brightest regions the highlands at 0 75 1 0 m a small additional narrow component halfwidth of

petroleum geology of northern part of arctic national wildlife refuge northeastern alaska abstract the northern part of the arctic national wildlife refuge and adjacent native lands an area between the brooks range and the beaufort sea encompassing about 2 4 million ac is judged to have the geologic characteristics of a major petroleum province except for the undeformed northwest quarter the area is involved in an east west trending and northeast trending north verging imbricate fold and thrust fault system related to brooks range deformation analyses of hydrocarbons from oil seeps and oil stained rocks in out crop suggest that three types of oil are present all dissimilar to oils from the prudhoe bay area the hue shale is postulated to be the most important source rock for oil with a present day geothermal gradient of about 30 sup 0 c km 1 6 sup 0 f 100 ft oil generation is expected to occur between depths of 3 7 and 6 9 km 12 000 22 500 ft mostly within the thick cretaceous and tertiary brookian sequence oil generation accompanied by clay mineral transformation and abnormal fluid pressure development probably began about 50 ma at the southern edge of the coastal plain and progressed northward reaching the coastline about 10 ma

new insights into deformation mechanisms in the gravitationally driven niger delta deep water fold and thrust belt we use two and three dimensional seismic reflection data from the deep water niger delta fold and thrust belt to document evidence for two discrete postfaulting deformation mechanisms an early phase of thrust propagation folding is followed by folding caused by thickness changes within the basal shale detachment unit the later phase of folding is caused by a lateral redistribution of the strata within the basal detachment unit this example of late deformation occurred over a 4 5 m y period as a result of the displacement of approximately 590 km3 370 mi3 of the underlying strata within the detachment unit in another deformation event in the basal detachment unit about 160 km3 100 mi3 moved laterally creating a synform in the overburden and parallel onlap fill indicative of the relatively rapid creation of accommodation space on the basis of seismic reflection data from the delta and a consideration of the volumes and rates of movement of sedimentary rock we conclude that the poorly imaged succession commonly referred to as mobile shale cannot deform solely by ductile mechanisms as interpretations of shale tectonic provinces have commonly suggested but instead by brittle processes that involve thickening by thrust faulting and subseismic accommodation structures processes such as liquefaction where a complete loss of shear strength is observed had a minimal function therefore the term mobile shale in this setting is widely exaggerated an awareness of postfaulting deformation mechanisms will be important for the successful exploration of gravitationally driven fold and thrust belts

the youngest paleozoic plutonism of the newfoundland appalachians u pb ages from the st lawrence and francois granites the posttectonic st lawrence and francois granites have long been regarded as the youngest paleozoic plutonic suites of the newfoundland appalachians their u pb ages of 374 2 and 378 2 ma respectively define a middle to late devonian magmatic event mid carboniferous magmatic and or rifting events suggested on the basis of earlier rb sr dating of the st lawrence granite are not supported by these new data both granites intrude major ductile and brittle structures that were active during the early paleozoic and they provide a younger age limit for major tectonic activity in the avalon zone and on the south coast of newfoundland the granites may correlate with plutons of closely similar age reported from the aspy and mira terranes of cape breton island nova scotia

genesis of the st lawrence fluorspar deposits as indicated by fluid inclusion rare earth element and isotopic data more than 40 separate fluorspar veins are associated with the lower carboniferous st lawrence granite of southeastern newfoundland with more than 3 4 million short tons mined since 1933 and a further 9 million short tons of reserves contained in the three main veins it is estimated from these tonnages that fluorine concentrations in the magma of only 19 ppm would have been adequate to form the veins much less than the average of 1 567 ppm f found in the granite fluid inclusions show that salinities remain within the range of 5 to 15 equivalent weight percent nacl although homogenization temperatures fluctuate between 100 degrees and 500 degrees c evidence for boiling between 450 degrees and 223 degrees c indicates that the homogenization temperatures are trapping temperatures at low pressures between 65 and 650 bars some 18 o depletion in the aqueous fluids owing to unmixing and loss of co 2 in the fluorite veins delta 18 o quartz is approximately 14 per mil and calculated fluid delta values are 10 per mil 450 degrees c to 6 per mil 120 degrees c waters released from low temperature magmatic fluids which underwent transient mixing with a cool low 18 o meteoric reservoir modified journal abstract

effects of rocket exhaust on lunar soil reflectance properties abstract high resolution images of the surveyor luna and apollo landing sites obtained by the lunar reconnaissance orbiter camera lroc narrow angle camera nac show regions around the landers where reflectivity of the surface was modified we interpret the change in reflectance properties of these regions mainly as disturbance of the regolith by rocket exhaust during descent of the spacecraft and we refer to these areas herein as blast zones bzs the bzs consist of an area of lower reflectance lr bz compared to the surroundings that extends up to a few meters out from the landers as well as a broader halo of higher reflectance hr bz that extends tens to hundreds of meters away from the landers when approximated as an ellipse the average apollo bz area is 29 000 m2 175 60 m by 200 27 m which is 10 larger than the average luna bz and over 100 larger than the average surveyor bz the lr bzs are most evident at the apollo sites especially where astronaut activity disturbed the soil leading to a 15 30 relative to background undisturbed areas reduction in reflectance at 30 phase angle the lr bzs at the surveyor and luna sites are less evident and are unresolvable with nac images the average reflectance in the hr bzs as determined for 30 phase angle is 3 12 higher than in the undisturbed surrounding areas this magnitude is the same within uncertainty for all sites indicating a common process or combination of processes causing differences in reflectance properties of the regolith phase ratio images and photometric data collected over a range of illumination geometries show that a greater separation in reflectance occurs between the hr bzs and undisturbed areas at phase angles between 0 and 70 and indicates that the hr bzs are less backscattering than undisturbed areas the lr bzs are affected by macroscopic disruption of the surface and astronaut activity at the apollo sites for the hr bz areas reflectance has likely been affected by scouring from particles entrained by exhaust gases with low angle trajectories regolith particle interactions with surface soil within hr bzs may destroy fine scale surface structure e g fairy castle and decrease macroscopic roughness contributing to a decrease in backscattering character within the hr bzs and an increase in backscattering character within the lr bzs redistribution of fine particles from the lr bz to the hr bz may have also contributed to the changed reflectance photometric modeling is consistent with one or a combination of these processes

regional fractures i a mechanism for the formation of regional fractures at depth in flat lying reservoirs 1 regional fractures may form slowly at depth in extension and parallel to regional horizontal tectonic compression such fracture sets can be common in reservoirs despite the absence of flexure of the strata and are commonly important contributors to reservoir permeability such fractures make good targets for deviated wells high formation pore pressure is crucial to creating low effective confining stresses and brittle rock properties in the reservoirs conditions conducive to fracturing despite deep burial but pore pressure does not exceed the least principal stress and does not cause tensile fracturing the mechanism of natural hydraulic fracturing is incompatible with the characteristics of most regional fracture sets rather many regional fractures form duri g far field compression initiate at locally induced tensile stresses caused by flaws in the rock and propagate in the plane of the maximum and intermediate compressive stresses the differential stress required for initiation and propagation of regional fractures is well below that necessary for shear failure in the presence of high pore pressure fractures can be held open at depth by a tectonic basinwide dilatancy of the strata and the open void space commonly becomes mineralized

paleomagnetism of the deadman s bay diabase dikes from northeastern central newfoundland twenty six oriented samples were collected from six diabase dikes cutting the deadman s bay granite of northeastern central newfoundland for the purpose of paleomagnetic investigations the dikes probably form part of a general swarm of diabase dikes in this area of devonian age 40ar 39ar age of 370 10 ma stepwise thermal demagnetization of individual specimens followed by vector subtraction based on zijderveld plots revealed two characteristic magnetizations one a poorly grouped magnetization of 78 0 95 17 4 16 carried by multidomain magnetite and a better grouped magnetization of 4 0 95 10 0 42 residing in hematite a baked contact test of the host rock deadman s bay granite intruded by the diabase dikes revealed a steep well grouped magnetization which is not dissimilar to that carried by magnetite in the dikes the magnetization of the host rock seems to be well grouped irrespective of distance away from the dike thus making the contact test inconclusive

chang e 4 initial spectroscopic identification of lunar far side mantle derived materials over 60 years of spacecraft exploration has revealed that the earth s moon is characterized by a lunar crust1 dominated by the mineral plagioclase overlying a more mafic richer in iron and magnesium mantle of uncertain composition both crust and mantle formed during the earliest stages of lunar evolution when late stage accretional energy caused a molten rock magma ocean flotation of the light plagioclase sinking of the denser iron rich minerals such as olivine and pyroxene and eventually solidification2 very large impact craters can potentially penetrate through the crust and sample the lunar mantle the largest of these craters is the approximately 2 500 kilometre diameter south pole aitken spa basin3 on the lunar far side evidence obtained from orbiting spacecraft shows that the floor of the spa basin is rich in mafic minerals4 but their mantle origin is controversial and their in situ geologic settings are poorly known china s chang e 4 lunar far side lander recently touched down in the von karman crater5 6 to explore the floor of the huge spa basin and deployed its rover yutu 2 here we report on the initial spectral observations of the visible and near infrared spectrometer vnis 7 onboard yutu 2 which we interpret to represent the presence of low calcium ortho pyroxene and olivine materials that may originate from the lunar mantle geological context6 suggests that these materials were excavated from below the spa floor by the nearby 72 km diameter finsen impact crater event and transported to the landing site continued exploration by yutu 2 will target these materials on the floor of the von karman crater to understand their geologic context origin and abundance and to assess the possibility of sample return scenarios initial spectral observations by china s chang e 4 far side lunar rover suggest the presence of materials that may originate from the moon s mantle

reverse modelling of detachment folds application to the pico del aguila anticline in the south central pyrenees spain abstract a simple method to estimate fold amplification and thrust movement rates for detachment folds is documented and illustrated by its application to a symmetrical detachment fold in the southern pyrenees spain the technique provides a complete record of the kinematic evolution of detachment folds and is based on the application of equations for detachment folds involving limb rotation the method uses the stratal pattern of the syntectonic sediments and assumes that these growth strata were deposited horizontally that the folds involve a homogeneous competent unit detached over a ductile horizon and that the folds can be represented by chevronkink bands the procedure is applicable to any detachment fold with associated growth strata that display wedge geometries progressive unconformities indicating limb rotation through time this method can be used for both detachment folds formed with constant limb length or variable limb length and it can also accommodate undecompacted or decompacted growth strata

new paleomagnetic data from carboniferous volcanics and red beds from central new brunswick it has long been argued on the basis of paleomagnetic data derived from devonian carboniferous and permian lithological units from eastern north america that a sinistral megashear of carboniferous age parallels and lies within the faults delimiting the appalachian caledonian chains recent paleomagnetic studies in the northern appalachians have cast doubt on the models of a carboniferous offset the geologic evidence suggests that only a small amount of dextral and not sinistral strike slip has occurred on faults which are parallel with pre acadian paleogeographic realms the purpose of this paleomagnetic study is to test the validity of the proposed left lateral motion at one of the sites of its presumed passage in central new brunswick six sites 80 oriented specimens in carboniferous red beds and volcanics were collected on both sides of the fredericton fault and other parallel faults after af and thermal cleaning the mean direction of magnetization is 158 38 the fold test is indecisive the corresponding paleopole is 135 e 21 n and the paleolatitude 20 s the paleopole positions and paleolatitudes are not significantly different on either side of the fredericton fault and no left lateral motion was detected by paleomagnetic means as no such motion was detected in south central new brunswick and newfoundland it is possible but unlikely that it took place in northern new brunswick and in the western gaspe peninsula this contribution is useful in discussing possible motions of acadia

the mineralogy of late stage lunar volcanism as observed by the moon mineralogy mapper on chandrayaan 1 1 the last major phases of lunar volcanism produced spectrally unique high titanium basalts on the western nearside of the moon the moon mineralogy mapper m3 on chandrayaan 1 has provided detailed measurements of these basalts at spatial and spectral resolutions necessary for mineralogical interpretation and mapping of distinct compositional units the m3 imaging spectrometer acquired data in 85 spectral bands from 430 to 3000 nm at 140 to 280 m pixel in its global mapping mode during the first half of 2009 reflectance data of several key sites in the western maria were also acquired at higher spatial and spectral resolutions using m3 s target mode prior to the end of the chandrayaan 1 mission these new observations confirm that both fresh craters and mare soils within the western high ti basalts display strong 1 m and weak 2 m absorptions consistent with olivine rich basaltic compositions the inferred abundance of olivine is observed to correlate with stratigraphic sequence across different mare regions and absolute ages the apparent stratigraphic evolution and fe rich compositions of these basalts as a whole suggest an origin from evolved residual melts rather than through the assimilation of more primitive olivine rich sources mare deposits with spectral properties similar to these late stage high ti basalts appear to be very limited outside the procellarum imbrium region of the moon and where present appear to occur as small areas of late stage regional volcanism detailed analyses of these new data and supporting measurements are in progress to provide further constraints on the mineralogy olivine abundance and compositions of these final products of lunar volcanism and the nature and evolution of their source regions