a unified approach to orbital solar and lunar forcing based on the earth s latitudinal insolation temperature gradient widespread empirical evidence suggests that extraterrestrial forcing influences the earth s climate but how this could occur remains unclear here we describe a new approach to this problem that unifies orbital solar and lunar forcing based on their common control of the earth s latitudinal insolation gradient lig the lig influences the climate system through differential solar heating between the tropics and the poles that gives rise to the latitudinal temperature gradient ltg which drives the earth s atmospheric and wind driven ocean circulation we use spectral analysis of recent changes in the earth s ltg to support earlier work on orbital timescales davis and brewer 2009 that suggests the climate system may be unusually sensitive to changes in the lig identification of lig forcing of the ltg is possible because the lig varies according to seasonally specific periodicities based on obliquity in summer 41 kyr orbital and 18 6 yr lunar cycle and precession 21 kyr orbital cycle and total solar irradiance 11 yr solar cycle in winter we analyse changes in the northern hemisphere ltg over the last 120 years and find significant 99 peaks in spectral frequencies corresponding to 11 years in winter and 18 6 years in summer consistent with lig forcing the cross seasonal and multi frequency nature of the lig signal and the diffuse effect of the ltg driver on the climate system may account for the complexity of the response to extraterrestrial forcing as seen throughout the climatic record this hypersensitivity of the ltg to the lig appears poorly reproduced in climate models but would be consistent with the controversial theory that the ltg is finely balanced to maximise entropy c 2011 elsevier ltd all rights reserved

crossing the several scales of strain accomplishing mechanisms in the hinterland of the central andean fold thrust belt bolivia depictions of structures at outcrop regional and tectonic scales enforce horizontal shortening and vertical thickening as the predominant style of deformation at all scales within the hinterland of the central andean fold thrust belt outcrop scale structures document a progression of strain that created 1 flexural slip folds 2 fold flattening via axial planar cleavage 3 vertical stretching via boudinage and late stage faulting and finally 4 kink folding these examples of intraformational deformation are generally concentrated just beyond the tip lines of thrust faults where fault propagation folds and related structures are well developed fault propagation folding accommodated the accrual of strain indicated by outcrop scale structures while the structures themselves indicate how deformation developed within each individual fold fault propagation fold geometries at a regional scale emerge from the construction of regional balanced cross sections the sections were drawn with careful attention to 1 known map relationships 2 field inspection of key contacts 3 bedding orientation data 4 local seismic control and 5 principles of balance the pervasive ese wnw shortening and vertical elongation seen at the outcrop and regional scales developed during the formation of the central andean backthrust belt in the hinterland of the andes the central andean backthrust belt is a large scale west vergent thrust system along the western side of the eastern cordillera in the generally east vergent andean fold thrust belt of bolivia strain accrual within this west verging zone of deformation is proposed to be a taper building mechanism that allowed the fold thrust belt to continue propagating eastward

a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

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

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

the geometry and kinematics of the main boundary thrust and related neotectonics in the darjiling himalayan fold and thrust belt west bengal india abstract the main boundary thrust mbt is well exposed in a section of the tista river valley in the darjiling himalayan fold and thrust belt the fault trace trends e w across the n s flowing tista and thrusts gondwana permian age sandstones over lower siwalik miocene age sandstones the mbt has been folded into a fault propagation synform antiform pair by tectonic activity along a younger south kalijhora thrust skt in its footwall that transports lower siwalik rocks over middle siwalik sandstones the skt cuts through the fault propagation structure preserving the mbt fault propagation fold pair in its hanging wall the motion along the skt rotated the bedding and the limbs of the folded mbt in its hanging wall footwall imbrication in front of the skt further rotated the folded mbt footwall imbrication continued to about 30 km south of the study area in the middle siwalik and younger section the region has been subsequently reactivated as evident from uplifted gravel beds and strath terraces along the folded trace of the mbt fault zone and also in the footwall of the skt the reactivation resulted in the formation of connective splays off the existing faults probably forming horses of a connecting splay duplex in the sub surface within the siwalik section the motion along these splays passively folded overlying beds and formed uplifted gravel beds and strath terraces along the local drainage the rotations resulting from footwall imbrication and reactivated splays probably caused the southern limb of the fault propagation synform to become overturned the duplexing also raised the river bed and arrested the flow of the river tista causing the river to pond and deposit its load resulting in the formation of a bar upstream of the mbt trace the tectonic reactivation of the area points to taper building activities in a subcritical wedge probably in response to monsoon induced excessive erosion in the middle of the darjiling sikkim tibet himalayan thrust wedge

compositional and temporal investigation of exposed lunar basalts in the mare imbrium region abstract this paper presents an updated stratigraphical and compositional study of the exposed maria within the imbrium basin on the moon clementine multispectral data were employed to derive tio2 and feo wt abundance estimates of potentially distinct basaltic flows additionally nasa lunar orbiter images were used to estimate flow ages using crater count statistics mare imbrium shows evidence of a complex suite of low to high ti basaltic lava units infilling the basin over an 800 million year timescale more than a third 37 of identified mare basalts were found to contain 1 3 wt tio2 two other major mare lithological units representing about 25 of the surface each show tio2 values between 3 5 and 7 9 wt the dominant fraction 55 of the sampled maria contain feo between 16 and 18 wt followed by 27 of maria having 18 20 wt and the remaining 18 14 16 wt feo a crater frequency count for diameters 500 m shows that in three quarters of the sampled mare crater counts range between 3 5 and 5 5 10 2 per km2 which translates according to a lunar cratering model chronology into estimated emplacement ages between 3 3 and 2 5 ga a compositional convergence trend between the variations of iron and titanium oxides was identified in particular for materials with tio2 and feo content broadly above 5 and 17 wt respectively suggesting a related petrogenesis and evolution according to these findings three major periods of mare infill are exposed in the imbrium basin despite each period showing a range of basaltic compositions classified according to their tio2 content it is apparent that at least within these local geological settings the igneous petrogenesis generally evolved through time towards more tio2 and feo rich melts

the distribution of deformation in parallel fault related folds with migrating axial surfaces comparison between fault propagation and fault bend folding abstract in fault related folds that form by axial surface migration rocks undergo deformation as they pass through axial surfaces the distribution and intensity of deformation in these structures has been impacted by the history of axial surface migration upon fold initiation unique dip panels develop each with a characteristic deformation intensity depending on their history during fold growth rocks that pass through axial surfaces are transported between dip panels and accumulate additional deformation by tracking the pattern of axial surface migration in model folds we predict the distribution of relative deformation intensity in simple step parallel fault bend and fault propagation anticlines in both cases the deformation is partitioned into unique domains we call deformation panels for a given rheology of the folded multilayer deformation intensity will be homogeneously distributed in each deformation panel fold limbs are always deformed the flat crests of fault propagation anticlines are always undeformed two asymmetric deformation panels develop in fault propagation folds above ramp angles exceeding 29 for lower ramp angles an additional more intensely deformed panel develops at the transition between the crest and the forelimb deformation in the flat crests of fault bend anticlines occurs when fault displacement exceeds the length of the footwall ramp but is never found immediately hinterland of the crest to forelimb transition in environments dominated by brittle deformation our models may serve as a first order approximation of the distribution of fractures in fault related folds

the pliocene pleistocene stratigraphic and tectonic evolution of the central sector of the western periadriatic basin of italy abstract the central portion of the western periadriatic basin is a foreland basins systems associated to the central apennine outer orogenic wedge that stretches along the marche and abruzzi regions of italy an area that has been studied since long time and where a plenty of surface and subsurface data are available the present study is aimed to review and synthetize these data add new surface and subsurface data in order to define a firm stratigraphic and tectonic framework that is base for the reconstruction of the pliocene pleistocene tectonic stratigraphic evolution of the central portion of the western periadriatic basin the study integrates field mapping published geological maps seismic lines well logs and an updated chronostratigraphic scheme six major nne ssw thrust stacks and eight unconformity bounded stratigraphic units have been defined then a ne sw oriented zone separates a northern from a southern sector which have differences in structural styles amount of shortening basins widths and thicknesses of stratigraphic units despite these differences the deformation timing the depositional history and the migration of basins system are common in both sectors and eight tectonic stratigraphic evolutionary stages have been reconstructed with sequential restoration of two representative cross sections the results highlight that the pliocene pleistocene stratigraphic and tectonic evolution of the central western periadriatic basin preserves the records of supra regional and global controls which drive thrust propagation orogen growth basins migration and basins sedimentary infill in particular the stratigraphy preserves global third order eustatic climatic changes that have a strict feed back and concomitance with tectonic pulses the latter are regulated 1 by cyclic growth of an orogenic wedge undergoing coeval erosion and sedimentation and 2 by eastward retreat of a westward subducting and flexing continental lithosphere

phenomenological solar signature in 400 years of reconstructed northern hemisphere temperature record 1 we study the solar impact on 400 years of a global surface temperature record since 1600 this period includes the pre industrial era roughly 1600 1800 or 1600 1900 when negligible amount of anthropogenic added climate forcing was present and the sun realistically was the only climate force affecting climate on a secular scale and the industrial era roughly since 1800 1900 when anthropogenic added climate forcing has been present in some degree we use a recent secular northern hemisphere temperature reconstruction moberg et al 2005 three alternative total solar irradiance tsi proxy reconstructions lean et al 1995 lean 2000 wang et al 2005 and a scale by scale transfer climate sensitivity model to solar changes scafetta and west 2005 2006 the phenomenological approach we propose is an alternative to the more traditional computer based climate model approach and yields results proven to be almost independent on the secular tsi proxy reconstruction used we find good correspondence between global temperature and solar induced temperature curves during the pre industrial period such as the cooling periods occurring during the maunder minimum 1645 1715 and the dalton minimum 1795 1825 the sun might have contributed approximately 50 of the observed global warming since 1900 scafetta and west 2006 we briefly discuss the global cooling that occurred from the medieval maximum 1000 1100 ad to the 17th century minimum

on lunar asymmetries 1 tilted convection and crustal asymmetry 1 it is proposed that lunar crustal asymmetries are the result of convective processes acting early in the moon s history during the magma ocean phase and after synchronous rotation was established buoyant anorthositic crystals were transported to the farside by a large scale circulation called tilted convection known to occur spontaneously in chaotic convective systems the circulation was oriented toward the farside of the moon by a small temperature contrast produced by radiative thermal shielding due to the proximity of earth crustal thickening near the equator resulted from the modification of tilted convection by the coriolis force the anorthosite that was transported to the farside and equator may be a major cause of the observed crustal asymmetries and of the associated offset of the center of figure from the center of mass and bimodal hyposgram the selective transport may have resulted in a nearside excess of incompatible elements leading to the formation of the procellarium kreep terrane

the role of magma buoyancy on the eruption of lunar basalts it has long been recognized that mare basalts on the moon are preferentially located both on the earth facing hemisphere and within large impact basins a popular model that accounts for this observation assumes that these magmas were denser than the lunar crust that they accumulated at the crust mantle interface and that eruptions occurred only when this magma chamber became overpressurized in this paper we re evaluate this model and argue that it is not consistent with the available data nor with models of dike propagation as an alternative hypothesis we propose that magma buoyancy is the predominant factor that determines whether mare basalts erupt at the surface or form crustal intrusions instead we have computed the densities of mare basaltic magmas and find that some are in fact less dense than the moon s upper anorthositic crust based on the widely accepted view that the lunar crust becomes more mafic with depth we also show that all mare basaltic magmas should be less dense than the lower portion of the crust thus if the upper anorthositic crust was regionally removed by an impact event then any mare basaltic magma could have risen to the surface there based on buoyancy considerations alone in support of this model we note that mare basalts are indeed found wherever geophysical crustal thickness models predict the upper crust to be absent furthermore many of the basalts that erupted within the anorthositic highlands are predicted to be less dense than the underlying crust based on remote sensing data the high titanium flows within oceanus procellarum are somewhat problematical to our model in that an anorthositic crust is predicted to be present beneath them using results from recent lunar thermal models we suggest that these magmas may have overcome their negative buoyancy in the crust by possessing superliquidus temperatures if magma buoyancy does indeed control whether or not a basaltic eruption will occur then this implies that the quantity of magma produced beneath the south pole aitken basin was about 10 times less than that of the nearside fl 2001 elsevier science b v all rights reserved

origin of a thrust related fold geometric vs kinematic tests abstract geometric tests to determine the origin of fault related folds are common but as is typical in structural geology more than one fold origin may yield the final natural geometry thus the results of geometric tests are usually non unique in contrast kinematic tests of origin which employ both geometry and data about deformation commonly yield more constrained if not unique results unfortunately the necessary data collection requires much more work than for a geometric test in this study the thrust related barclay anticline is analyzed both geometrically and kinematically to determine which test is more effective geometric tests using angular relationships indicate three possible origins fault bend fault arrest and break thrust for the kinematic test predicted deformations for interlayer and flexural slip flexural flow simple shear and bending strains are compared to micro and mesostructural distributions solution strain and finite strain from the anticline strain measurements indicate that microscale deformation is uniformly distributed through the structure and is lithification dominated the microscale deformation does not match kinematic predictions and did not accommodate fold formation fold growth was achieved primarily through layer parallel slip restricted mostly to the forelimb and absent in the hinge which eliminates fault bend and fault arrest origins that require material transport from forelimb to backlimb the barclay anticline is therefore interpreted to be a break thrust structure interestingly a suite of contraction faults in the forelimb and hinge indicates material transport from forelimb to backlimb such transport has been discounted for break thrust folds the most important result of this study is that a kinematic test was a necessary step for distinguishing fold origin geometric testing alone was insufficient given that the barclay anticline has geometric characteristics typical of many thrust related folds kinematic testing appears necessary to determine their structural origin

the effects of pre existing normal faults on thrust ramp development an example from the northern apennines italy the umbria marche foreland fold and thrust belt in the northern apennines of italy provides excellent evidence to test the hypothesis of synsedimentary structural control on thrust ramp development this orogenic belt consists of platform and pelagic carbonates late triassic to miocene in age whose deposition was controlled by significant synsedimentary extension normal faulting mainly active from jurassic through late cretaceous paleogene time resulted in significant lateral thickness variability within the related stratigraphic sequences by late miocene time the sedimentary cover was detached from the underlying basement and was deformed by east verging folds and west dipping thrusts two restored balanced cross sections through the southernmost part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps these evidences suggest that synsedimentary tectonic structures such as faults and the related lithological lateral changes can be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic inversion processes

topography and palaeogeographic evolution of a middle miocene foredeep basin plain northern apennines italy abstract the marnoso arenacea basin was a narrow northwest southeast trending foredeep of middle late miocene age bounded to the southwest by the apennine thrust front the basin configuration and evolution were strongly controlled by tectonics geometrical and sedimentological analysis of serravallian turbidites deposited within the marnoso arenacea foredeep combined with palaeocurrent data turbidite flow provenance reflection and deflection identify topographic irregularities in a basin plain setting in the form of confined troughs the more internal mandrioli sub basin and the external s sofia sub basin separated by an intrabasinal structural high this basin configuration was generated by the propagation of a blind thrust striking northwest to southeast parallel to the main trend of the apennines thrust belt ongoing thrust induced sea bed deformation marked by the emplacement of large submarine landslides drove the evolution of the two sub basins in an early stage the growth and lateral propagation of a fault related anticline promoted the development of open foredeep sub basins that were replaced progressively by wedge top or piggy back basins partially or completely isolated from the main foredeep meanwhile the depocenter shifted to a more external position and the sub basins were incorporated within an accretionary thrust belt

strains developed in the hangingwalls of thrusts due to their slip propagation rate a dislocation model reply abstract fault planes propagate radially from a point source and this failure propagation process is very similar to the movement of a dislocation through a crystal lattice an elastic strain represented by an extra half plane is necessarily imparted to the lattice at an edge dislocation and this is equivalent to the ductile bead which accompanies the propagating tip of a thrust fault this ductile bead migrates with the fault tip and imparts a characteristic internal strain to the thrust sheet a two dimensional model is presented to illustrate the inter relationship between fault plane slip fault tip propagation and internal strain in multilayered sequences internal strain is usually represented by asymmetric folds verging in the thrust transport direction a simple technique the displacement distance plot utilizes the fact that displacement dies out towards the fault tip this plot can be used to quantify the relative stretch measured parallel to the fault movement which is dependent on the slip propagation rate and it may be used to define exactly the position of the fault tip on a cross section examples of fold thrust structures from devon england and pembrokeshire wales are used to illustrate the technique

sequential development of selected pyrenean thrust faults new mapping structural analysis and magnetostratigraphy reveal a polyphase deformational history at the leading edge of the spanish pyrenean foreland fold and thrust belt the present structural architecture is the consequence of three discrete periods of deformation map relationships between four syntectonic units and major structures provide tight geometric and age constraints for each deformational period d1 55 to 42 ma d2 30 1 to 28 0 ma d3 27 9 to 25 8 ma most of the shortening in the area accumulated during d2 thrusting at rates which varied from 0 7 mm y 1 to 2 8 mm y 1 along strike from northwest to southeast respectively removal of d2 and d3 displacement on thrust faults restores folds formed during d1 a sequential kinematic history during which an individual structure accommodates shortening by folding tightening of the fold and subsequent truncation by thrust faulting is inferred sequential restoration of three serial cross sections demonstrates that nearly every structure active during d1 was also active during d2 distributed deformation characterizes the temporal and spatial pattern on all time scales from structures active during each individual deformational period to the long term history encompassed by the total deformation

three dimensional kinematic history at an oblique ramp leamington zone sevier belt utah abstract differences in kinematics in adjoining salients in fold thrust belts are typically accommodated along bounding transverse zones the leamington zone is an oblique ramp that accommodates slip between structures in the provo salient and the central utah segment of the sevier fold thrust belt the leamington zone consists of the leamington canyon thrust associated second order asymmetric folds and an out of syncline reverse fault the leamington canyon thrust is a rotated se dipping thrust fault with top to southeast motion it represents an oblique ramp of the folded canyon range thrust fold tightening of the syncline se of the folded leamington canyon thrust trace during later emplacement of underlying structures caused out of syncline reverse faulting in the fold core analysis of the finite strain minor fault populations and conjugate fracture sets were used in interpreting the 3 d kinematic history along the leamington zone restored maximum stretching directions of finite strain ellipsoids trend eastward overall inferred motion planes from populations of slickenlines on minor faults are consistent with overall southeastward motion acute bisectors of conjugate fracture sets may reflect more southward directions later in the deformation history these superimposed deformations with local relative chronologies of plastic and brittle structures using cross cutting relationships indicate that the leamington zone area shows overall clockwise changes in kinematic directions from e to ese to sse during successive pulses of deformation the temporal changes in kinematic directions along the leamington zone most likely reflect variations in kinematics over the oblique ramp as the overall easterly displaced 3 d fold thrust belt wedge interacted with the pre existing oblique ramp structure with small magnitudes of superimposed local vertical axis rotations during later folding and fold tightening of the leamington canyon thrust

geometry and kinematics of main frontal thrust related fault propagation folding in the mohand range northwest himalaya abstract the main frontal thrust mft shapes the 2500 km long frontal himalayan arc between two syntaxes surprisingly the structural geometry and kinematics of the mft sheet remains poorly constrained along portions of this arc even though it is a major seismogenic plate boundary hazard that affects 53 million people living in the himalaya and roughly 600 million living in the combined himalayan drainage basin apollo 2017 here we integrate methods to constrain and quantify mft deformation and its associated topographic growth in the mohand range at the northwestern himalayan front we use a new structural data and trishear modeling to detail the mft related structural geometry across a portion of the range and confirm it to be a fault propagation fold with an exposed monocline in the hanging wall as previously hypothesized srivastava et al 2016 and b microstructural finite strain and grain size analysis from 11 transport parallel thin section samples of middle siwalik sandstones to propose that the fold formed by near surface 1 5 km frictional sliding and block supported cataclastic flow new luminescence dating of fault gouge and uplifted sand bodies indicate that mft activity is older 105 ka in the central compared to the western 15 ka mohand range implying that recent mft motion has been variable and segmented we next present boundary element method based dislocation modeling results along 3 transects to confirm that the along strike topographic growth is variable but consistent with the existing data and our interpretations balanced cross sections indicate that a maximum of 23 26 km2 area was eroded from the mohand range since folding began modern era estimates of minimum erosion from our dislocation modeling compared to existing topographic profiles suggest that 1 km2 erosion occurred in the range our integrated approach helps us to better constrain resolve reported inconsistencies and advance our understanding of mft related deformation topographic growth and erosion within the dehradun recess and across its outboard range front himalayan arc segmentation into salients and recesses likely impacts along strike earthquake rupture propagation thus it is important to understand how each segment behaves evolves and perhaps interrelates as part of a larger perspective towards evaluating active collisional wedge fronts and their potential seismic hazards

deriving thrust fault slip rates from geological modeling examples from the marche coastal and offshore contraction belt northern apennines italy abstract we present a reconstruction of the central marche thrust system in the central northern adriatic domain aimed at constraining the geometry of the active faults deemed to be potential sources of moderate to large earthquakes in this region and at evaluating their long term slip rates this system of contractional structures is associated with fault propagation folds outcropping along the coast or buried in the offshore that have been active at least since about 3 myr the ongoing deformation of the coastal and offshore marche thrust system is associated with moderate historical and instrumental seismicity and recorded in sedimentary and geomorphic features in this study we use subsurface data coming from both published and original sources these comprise cross sections seismic lines subsurface maps and borehole data to constrain geometrically coherent local 3d geological models with particular focus on the pliocene and pleistocene units two sections crossing five main faults and correlative anticlines are extracted to calculate slip rates on the driving thrust faults our slip rate calculation procedure includes a the assessment of the onset time which is based on the sedimentary and structural architecture b the decompaction of clastic units where necessary and c the restoration of the slip on the fault planes the assessment of the differential compaction history of clastic rocks eliminates the effects of compaction induced subsidence which determine unwanted overestimation of slip rates to restore the displacement along the analyzed structures we use two different methods on the basis of the deformation style the fault parallel flow algorithm for faulted horizons and the trishear algorithm for fault propagation folds the time of fault onset ranges between 5 3 and 2 2 myr overall the average slip rates of the various thrusts are in the range of 0 26 1 35 mm yr

topographic compositional units on the moon and the early evolution of the lunar crust the distribution of elevations on the moon determined by clementine deviates strongly from a normal distribution suggesting that several geologic processes have influenced the topography the hypsograms for the near side and far side of the moon are distinctly different and these differences correlate with differences in composition as determined by apollo orbital geochemistry clementine global multispectral imaging and ground based spectroscopy the hypsograms and compositional data indicate the presence of at least five compositional altimetric units the lack of fill of the south pole aitken basin by mare basalts suggests poor production efficiency of mare basalt in the mantle of this area of the moon

structural evolution of the frontal fold thrust belt nw himalayas from sequential restoration of balanced cross sections and its hydrocarbon potential abstract two sedimentary lithotectonic zones are traditionally recognized in the northwestern himalayan frontal fold thrust belt in the nahan salient the lesser himalaya zone lhz and the sub himalaya zone shz the lhz is made up of a sequence of proterozoic to early cambrian rocks and the shz is made up of cenozoic rock sequences which were deposited subsequent to the india asia collision serial balanced cross sections show that the structural geometries become increasingly complex from independent ramp anticlines near the foreland through imbricate fan duplex to stacked up horses towards the hinterland sequential restoration suggests a structural evolution in which a foreland propagating in sequence thrusting event was followed by out of sequence thrusting in an approximately break back style during the out of sequence movement some of the ramps formed during in sequence thrusting were repeatedly reactivated leading to very complex structural geometries particularly in the lhz in such a complexly deformed terrain a rigorous structural modelling approach combined with a robust geochemical and geochronological database should be used to carry out calibrated petroleum system modelling and thus reduce exploration risk

progressive rollover fault propagation folding a possible kinematic mechanism to generate regional scale recumbent folds in shallow foreland belts the occurrence of strongly overturned to recumbent anticlines in shallow foreland thrust fold belts is not well explained by the available geometric models of thrust related folding when a very large amount of forward shear cannot be assumed and for growth anticlines when the tectonic uplift rate is greater than the sedimentation rate we have developed new geometries for fault propagation folding progressive rollover fault propagation folding that are suitable for overcoming these problems in our configuration an outer right way up sector and an overturned sector can grow simultaneously in the forelimb of the tip anticline they are linked to a recumbent leading syncline a semiquantitative computation of fracture strain during folding allowed us to define six homo eneously strained rock panels the location of the most strained panels suggests that an anticlinal breakthrough or a synclinal breakthrough is likely to affect the structure later in its evolution the outer morphology of the tip anticline in progressive rollover fault propagation folding resembles a fault bend fold this model produces geometries suitable for hydrocarbon trapping

on lunar asymmetries 2 origin and distribution of mare basalts and mascons 1 a novel mechanism is proposed for the emplacement of mare basalts and the formation of mascons that does not involve melting or remelting of the source region the source magmas are the remnants of the primordial lunar magma ocean and are rich in incompatible elements including radioactive isotopes potassium rare earth elements and phosphorus kreep and volatiles exsolution of volatiles as the magmas cooled and crystallized a process called second boiling produced overpressures which drove the dense basalts upward to the surface creating the mascons this process occurred preferentially beneath nearside mare basins where the crust is thinnest and lithostatic pressure is lowest the delay between impact and magmatic extrusion reflects the time needed for the volatile rich magma to cool to its second boiling point radioactive heating buffered the magmas against cooling and solidification allowing for an extended period of magmatism

stratigraphy and depositional setting of slurry and contained reflected beds in the marnoso arenacea formation langhian serravallian northern apennines italy this work presents the stratigraphy and facies analysis of an interval of about 2500 m in the langhian and serravallian stratigraphic succession of the foredeep turbidites of the marnoso arenacea formation a high resolution stratigraphic analysis was performed by measuring seven stratigraphic logs between the sillaro and marecchia lines 60 km apart for a total thickness of about 6700 m the data suggest that the stratigraphy and depositional setting of the studied interval was influenced by syndepositional structural deformations the studied stratigraphic succession has been subdivided into five informal stratigraphic units on the basis of how structurally controlled topographic highs and depocentres a consequence of thrust propagation change over time these physiographic changes of the foredeep basin have also been reconstructed through the progressive appearance and disappearance of thrust related mass transport complexes and of five bed types interpreted as being related to structurally controlled basin morphology apart from bouma like type 4 beds type 1 tripartite beds characterized by an internal slurry unit tend to increase especially in structurally controlled stratigraphic units where intrabasinal topographic highs and depocentres with slope changes favour both mud erosion and decelerations type 2 beds with an internal slump type chaotic unit characterize the basal boundary of structurally controlled stratigraphic units and are interpreted as indicating tectonic uplift type 3 beds are contained reflected beds that indicate different degrees of basin confinement while type 5 are thin and fine grained beds deposited by dilute reflected turbulent flows able to rise up the topographic highs the vertical and lateral distribution of these beds has been used to understand the synsedimentary structural control of the studied stratigraphic succession represented in the marnoso arenacea formation by subtle topographic highs and depocentres created by thrust propagation folds and emplacements of large mass transport complexes

constraints on the depth geometry and kinematics of blind detachment faults provided by fault propagation folds an example from the mesozoic fold belt of south china abstract the mesozoic multi layered thin skinned fault related fold belt in south china is characterized by propagation chevron folding and thrust faulting we examine the geometry and depth of blind detachment faults in this belt using faults and folds that crop out along a well defined cross section a combination of parameters such as backlimb dip angle 2 interlimb angle height of anticline h thickness of the referenced layer h0 width of the anticline ab and thickness change ratio of layering within the forelimb tf t are used to develop new equations to estimate the geometry and depth of the detachment faults in the cross section the huangdushan chevron anticline has parameters revealing a blind fault with a ramp angle of 42 and a flattened segment at a depth of 4 9 km based on existing seismic data we interpret this blind fault as a backthrust developed over an in sequence imbricated duplex of cambrian to ordovician strata a chevron anticline at qiyueshan also reveals a backthrust fault however a broad anticline in lengzhuba and a small cylindrical sinusoidal anticline in yupize reveal a flat ramp flat detachment fault with flat segments at depths of 7 4 and 3 4 km respectively suggesting that the sinian strata were thickened probably by an out of sequence imbricated duplex our results indicate that the flat ramp flat detachment fault along the bottom of the sinian strata produced the out of sequence imbricated duplex and cylindrical sinusoidal folds the in sequence imbricated duplex produced backthrusts and related chevron anticlines we consider that this fault related fold belt was produced by collision between the yangtze block and north china blocks

thrust surface geometry implications for thrust belt evolution and section balancing techniques abstract the application of modern concepts of thrust tectonics to orogenic belts has yielded many detailed restorable sections thrusts generally restore with a staircase geometry onto the undeformed stratigraphic template since the work of rich 1934 it has been generally assumed that thrusts have propagated with a staircase trajectory and that hangingwall structures result from the movement of the thrust sheet up footwall ramps however thrusts often cut through previously folded strata with a smooth trajectory smooth trajectory thrusts can be identified from footwall geometry and strain state once a smooth trajectory thrust has been identified it is insufficient to produce a balanced deformed section and its restored counterpart sequential balanced sections must be constructed reversing the deformation history the restoration of thrusts to a staircase trajectory has no mechanical significance as the thrust is merely acting as a marker if restored back beyond the time at which it propagated thrust ramps are not necessarily actual steps in the thrust surface they are often just zones where the thrust cuts through bedding in a smoothly curving trajectory ductile deformation in thrust belts can reduce bed length at depth thus removing the need for structures which are necessary to preserve constant bed lengths ductile deformation in the internal zones of orogenic belts renders the construction of balanced sections in these zones highly problematical

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

growth stratal architectures associated to decollement folds and fault propagation folds inferences on fold kinematics abstract in many thrust and fold belts asymmetric folds with overturned or steeply dipping forelimbs and gently dipping backlimbs are commonly interpreted as thrust related folds determining the folding mechanism exclusively from the final fold geometry in the pre growth units is possible only for a limited suite of structures the nature of fold thrust interaction in shallow structures can be inferred by coupling the fold geometric analysis with the study of the syntectonic sediment stratal architectures several factors such as axial surface activity fold uplift limb rotation and limb widening rates together with sedimentation and erosion rates control growth strata patterns because the evolutionary path of most of these parameters depends on the folding kinematics different growth stratal architectures are expected for different thrust related anticlines in this paper we examine the influence of the above factors on growth stratal geometries associated to a simple kink band and then we apply the same approach to kinematic models of decollement folding and fault propagation folding four geometric approaches are used to account for the geometry and kinematics of anticlines located at the tip of a blind thrust fault propagation folding with no excess layer parallel shear fault propagation folding with progressive layer parallel shear constant limb length decollement folding and variable limb length decollement folding whereas fault propagation folding with no excess layer parallel shear is a self similar folding mechanism the other three types involve limb rotation coherent geometries between growth and pre growth sequences develop at high sedimentation rates in the crest of fault propagation folds and incoherent ones in decollement folds minor differences within growth strata patterns occur at low sedimentation rates and when erosion affects the crest of the anticlines

structural analysis of the lombard thrust sheet and adjacent areas in the helena salient southwest montana usa abstract the helena salient is a prominent craton convex curve in the cordillera thrust belt of montana usa the lombard thrust sheet is the primary sheet in the salient structural analysis of fold trends cleavage attitudes and movement on minor faults is used to better understand both the geometry of the lombard thrust and the kinematic development of the salient early w e to wnw ene shortening directions in the lombard sheet are indicated by fold trends in the center of the thrust sheet the same narrow range of shortening directions is inferred from kinematic analysis of movement on minor faults and the orientations of unrotated cleavage planes along the southern lateral ramp boundary of the salient as the salient developed the amount and direction of shortening were locally modified as listric detachment faults rotated some tight folds to the nw and as right lateral simple shear caused by lock up and folding of the jefferson canyon fault above the lateral ramp rotated other folds northeastward where the lateral ramp and frontal oblique ramp intersect folds were rotated back to the nw our interpretation of dominant w e to wnw ese shortening in the lombard sheet later altered by local rotations supports a model of salient formation by primary parallel transport modified by interactions with a lateral ramp

fault propagation folds above thrusts with constant dip abstract previous models of fault propagation folds have been extended to include the case where folding initiates above a thrust ramp of constant dip the model may be useful in analyses of fold thrust structures in thin and thick skinned compressional terrains it may be most applicable to fault propagation folds that develop as a fault propagates from a thick massive brittle unit into a thinly layered anisotropic unit

detachment folding related miocene submarine slope instability in the romagna apennines italy 1 the relationships between slope failure and growing thrust related structures have been explored in the miocene marnoso arenacea foredeep basin romagna apennines impressive fossil slump layers are distributed along the footwall of the regional mount nero thrust which evolved from detachment fold to breakthrough thrust during the detachment fold stage development of growth strata on the rotating forelimb was preceded by the emplacement of slump layers that are currently part of the mount nero thrust footwall in this process sliding is assumed to nucleate along the contacts between different lithologies in the semiconsolidated rock mass the conditions of sliding specifically the critical angle of sliding crit are quantified by adding the influence of cohesion of sediments to the equilibrium analysis reported in hubbert and rubey s 1959 classical work the resulting angles crit are discussed with respect to the depth of the basal surface of sliding and pore fluid pressure states on the basis of such an analysis and field work results an evolutionary model is proposed in which slide sheets come from the crest and upper forelimb of growing detachment folds and attain a deeper detachment depth as the forelimb rotates and steepens pore fluid pressure is found to play a major role by radically decreasing the critical angle of sliding likewise localization of overpressures may also control the depth of sliding during progressive forelimb rotation to allow sliding along gently dipping bedding surfaces slope failure is interpreted as being related to the reactivation of anisotropies represented by lithological discontinuities

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

the origin and evolution of lunar high ti basalts periodic melting of a single source at mare tranquillitatis abstract five groups of basalts a b1 b2 b3 d with three principal ages exist at the apollo 11 site these range from the low k low rare earth element ree groups b1 b2 and b3 to the low k high ree group d basalts to the high k high ree group a basalts the group a basalts are the only high k 0 2 wt k2o basalts and youngest with an age of 3 59 02 ga groups b3 and b1 are 3 71 02 and 3 67 02 ga respectively group b2 basalts are the oldest at 3 85 02 ga group d basalts have not been dated fractionation modelling for major and trace elements indicates that the b1 basalts could have formed from a b3 like parent liquid the b2 and d basalts can also be related to liquids similar to the b3 b1 composition through the presence of varying amounts of modal whitlockite thus the entirety of low k high ti basalts at apollo 11 may have formed through melting of the same source region the group a basalt compositions are consistent with formation from a different parent liquid with the composition of apollo 11 orange glass modelling of major and trace elements in the apollo 11 orange glass indicate that the composition of the group a basalts is consistent with fractionation of this glass coupled with some assimilation 7 5 15 of an evolved kreep like material however this component is much younger than primitive kreep 4 4 ga this neukreep component similar to the composition of quartz monzodiorites described from the apollo 15 site probably represents evolved material formed during plutonism prior to the formation of the apollo 11 orange glass liquid

late miocene seep carbonates and fluid migration on top of the montepetra intrabasinal high northern apennines italy relations with synsedimentary folding abstract during the miocene hydrocarbon seep carbonates located atop intrabasinal highs and associated with sediment instability formed commonly at the deformation front of the northern apennine collisional orogen the parallelism between the structural trend and the distribution of seep carbonates suggests a close relationship between tectonics and gas fluid emission the montepetra intrabasinal high was formed during the closure stage of the foredeep being related to the synsedimentary growth of an anticline field geometry suggests that detachment folding was the leading mechanism of anticline growth and synsedimentary instability along the anticline flanks ten different bodies of seep carbonates occur in the tortonian early messinian sediments nine in the hinge zone and one in the southern backlimb of the anticline foraminiferal study geochemistry facies investigation and the three dimensional geometry of carbonate bodies with respect to the encasing terrigenous sediments indicate a protracted late tortonian early messinian activity of fluid migration with re mobilization and ascent of sediments from the core of the anticline stabilization of chemosynthesis related communities and in situ brecciation seepage atop the intrabasinal high was fed by different circuits one related to the compaction dewatering of shallow tortonian early messinian sediments and a deeper one related to the deformation of the anticline core and to the activity of detachment surfaces and of faults propagating through the sedimentary cover

a kinematic model for the origin of footwall synclines abstract the origin of footwall synclines at the base of thrust ramps can be related to the kinematic evolution of fault propagation folds the conventional fault propagation fold model does not predict the development of footwall synclines because it assumes a high propagation to slip ratio for development of the lower flat which does not allow for folding before the thrust cuts up section an alternative model where the propagation to slip ratio remains finite throughout the development of the fault propagation fold produces a detachment fold at the thrust tip during propagation of the thrust along the lower flat if the thrust cuts up through the ductile core of the detachment fold during ramp formation it will leave behind the forelimb of the detachment fold as part of a footwall syncline

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

thick skinned and thin skinned tectonics of the zagros orogen iran constraints from structural microstructural and kinematics analyses abstract our understanding of the geological structures and kinematics of thick skinned and thin skinned tectonics during the evolution of an orogenic system is strongly related to field evidence of decollement dominated tectonics or deformation involving the entire middle and lower continental crust in this paper we compare thin skinned and thick skinned deformation of the zagros orogen from small to large scales in the foreland thin skinned region sedimentary rocks with several decollement horizons have undergone in sequence thrusting with dominant nw striking ne dipping and sw verging displacement the gneissic basement of the foreland underwent permo triassic rifting and the normal faults were reactivated as thrust or strike slip faults during subduction to collision orogenic system there is no field exposures of deformed basement windows in this external part of orogen however in the internal parts of the orogen the newly recognized hinterland fold and thrust belt and slate belt there are outcrops of gneissic basement slices mylonitic shear zones and granite gneissic flow the tutak granite gneiss dome is associated with sole thrusts therefore it contains deformed margins of both continents thus in deformation in this part of the orogen was thick skinned measurements of quartz c axis opening angles of the exhumed mylonite nappes document high temperature 642 43 and 424 31 c relationship between kinematic vorticity number wk wm 0 76 0 06 of the mylonite nappes which are related to the hinterland fold and thrust belt indicate 55 7 8 simple shear and 45 7 4 pure shear components for instantaneous 2d flow which indicate sub simple shear deformation on the more thickened side of the zagros deformed basement involved contains continuous to discontinuous shear band boudins of eclogite and slices of blue schist this provide kinematic indicators suggesting simultaneous dip slip and strike slip and shear zones accelerating inclined lateral exhumation of the high pressure metamorphic rocks of oceanic and continental crustal origin both the thin and thick skinned portions of the zagros on three major cross sections indicate the intensity of deformation in the nw and se parts of the belt that display the opposite senses of shear on the two sides we infer that both senses of shear were developed coevally under a bulk sub simple shear regional scale deformation along a curved inclined transpression study of crustal scale cross sections of the paleozoic and mesozoic sequences shows that asymmetrical to symmetrical folding an d thrusting in the central part of the zagros foreland fold and and thrust belts in the fars area are gentle in comparison with those in the se and nw of the orogen the highest intensity of deformation occurs in the rotated asymmetrical folding and thrusting near the bandar abbas syntaxis

double edge fault propagation folding geometry and kinematics abstract fault propagation folding is a common folding mechanism in thrust and fold belts and accretionary prisms several geometrical models relating the fold shape to the ramp shape have been proposed in all these models ramps always emanate from a basal fault and propagate upwards we have developed a new kinematic and geometric model of fault propagation folding named double edge fault propagation folding the model simulates folding at thrust ramps as a function of their nucleation site and propagation history within the folded multilayer the fold shape depends on the initial length and location of the ramp its dip and the s p ratio i e incremental ramp slip versus propagation of both the upper and lower ramp tips this solution increases the geometrical flexibility of fault propagation folding reducing for example the direct dependence between the backlimb dip and the ramp dip as double edge fault propagation folding is characterised by a backlimb panel not necessary parallel to the ramp non parallelism between the ramp and the backlimb is commonly observed in thrust related anticlines within fold and thrust belts and accretionary prisms the excess layer parallel shear imposed by the development of double edge fault propagation folding can be easily accommodated by discrete faulting and or penetrative deformation the dependence of the fold shape on the fault behaviour provides a tool for including the role of mechanical stratigraphy and environmental conditions of deformation into kinematic models natural examples of anticlines that could be modelled by double edge fault propagation are presented

frontal part of the northern apennines fold and thrust belt in the romagna marche area italy shallow and deep structural styles in this study surface geological data resulting from a detailed field survey including structural and biostratigraphic analysis have been integrated with subsurface seismic lines and well logs data in order to reconstruct the tectonic evolution of the external zones of the northern italian apennines in the romagna marche foothills and adriatic sea areas this integrated analysis shows 1 a late messinian to lower pleistocene progression of structural development from the hinterland to the foreland of the studied sector of the thrust belt 2 relatively limited 20 southward increasing amounts of shortening obtained by the construction of line length balanced and restored geological cross sections 3 a regional deformation style characterized by the presence of backthrusts associated with most foreland vergent thrust ramps leading to quasi symmetric uplift and a low critical taper for the wedge typical of foreland fold and thrust belts with a weak basal decollement triassic anhydrites in the present case 4 an important influence of basement faulting which despite a general basement cover decoupling appears to control stress localization in the latter producing linkage of basement and cover stuctures in a combination of thin and thick skinned tectonic styles and 5 contrasting structural styles characterizing deep features as imaged by seismic reflection profiles and shallow ones deep stuctures consist of growth anticlines bounded by major thrust ramps and back limb back thrusts separated by broader open synclines both involving a mesozoic paleogene mainly carbonate passive margin succession in the crestal zones of major anticlines shallow structures affecting neogene terrigenous foredeep sediments show a complex pattern of upright to recumbent folds of tens to hundreds of meters wavelength related to minor thrusts and backthrusts deformation of the mesozoic paleogene multilayer appears to be dominated by thrust propagation in the cores of early formed anticlines developed by buckling instabilities the overlying neogene deposits are detached from the carbonate substratum along the base of the foredeep succession bedding parallel slip occurring along this detachment level appears to be accommodated by the complex structures in the crests of major anticlines where the thrusts lramp to the surface cutting up section complex shallow structures interpreted to accommodate at shallow structural levels the deep deformation would therefore represent a geometrical requirement for maintaining strain compatibility across the shallow detachment level located at the base of the foredeep succession

anatomy of turbidites and linked debrites based on long distance 120 x 30 km bed correlation marnoso arenacea formation northern apennines italy much of our understanding of submarine sediment laden density flows that transport very large volumes ca 1 to 100 km3 of sediment into the deep ocean comes from careful analysis of their deposits direct monitoring of these destructive and relatively inaccessible and infrequent flows is problematic in order to understand how submarine sediment laden density flows evolve in space and time lateral changes within individual flow deposits need to be documented the geometry of beds and lithofacies intervals can be used to test existing depositional models and to assess the validity of experimental and numerical modelling of submarine flow events this study of the miocene marnoso arenacea formation italy provides the most extensive correlation of individual turbidity current and submarine debris flow deposits yet achieved in any ancient sequence one hundred and nine sections were logged through a ca 30 m thick interval of time equivalent strata between the contessa mega bed and an overlying columbine marker bed correlations extend for 120 km along the axis of the foreland basin in a direction parallel to flow and for 30 km across the foredeep outcrop as a result of post depositional thrust faulting and shortening this represents an across flow distance of over 60 km at the time of deposition the correlation of beds containing thick 40 cm sandstone intervals are documented almost all thick beds extend across the entire outcrop area most becoming thinly bedded 40 cm in distal sections palaeocurrent directions for flow deposits are sub parallel and indicate confinement by the lateral margins of the elongate foredeep flows were able to traverse the basin in opposing directions suggesting a basin plain with a very low gradient small fractional changes in stratal thickness define several depocentres on either side of the verghereto high area the extensive bed continuity and limited evidence for flow defection suggest that intrabasinal bathymetric relief was subtle substantially less than the thickness of flows thick beds contain two distinct types of sandstone ungraded mud rich sandstone intervals record evidence of en masse debrite deposition graded mud poor sandstone intervals are inferred to result from progressive grain by grain turbidite deposition clast rich muddy sandstone intervals pinch out abruptly in downflow and crossflow directions in a fashion consistent with en masse debrite deposition the tapered shape of mud poor sandstone intervals is consistent with an origin through progressive grain by grain turbidite deposition most correlated beds comprise both turbidite and debrite sandstone intervals intrabed transitions from exclusive turbidite sandstone to turbidite sandstone overlain by debrite sandstone are common in the downflow and crossflow directions this spatial arrangement suggests either i bypass of an initial debris flow past proximal sections ii localized input of debris flows away from available sections or iii generation of debris flows by transformation of turbidity currents on the basin plain because of seafloor erosion and or abrupt flow deceleration a single submarine flow event can comprise multiple flow phases and deposit a bed with complex lateral changes between mud rich and mud poor sandstone

kinematic evolution of thrust related structures in the umbro romagnan parautochthon northern apennines italy in the internal part of the umbro marchean romagnan apennines the foredeep clastic wedge constituting the neogene part of the sedimentary cover is completely detached from the underlying mesozoic palaeogene succession the resulting umbro romagnan parautochthon consists of tectonostratigraphic units with a general geometry of broad synclinal blocks separated by narrow faulted anticlines thrust related structures observed in the field require thrust ramp propagation to have occurred within already folded rocks therefore they cannot be restored using simple fault bend fold or fault propagation folding models evidence for a passive fold origin in the studied rocks suggests that an early detachment folding episode preceded ramp propagation the latter was facilitated by the enhanced thickness of incompetent material in the cores of detachment anticlines which became the preferential sites where thrust ramps cut up section depending on the trajectory of such thrust ramps different types of fault related structures could develop hanging wall anticlines which give way to monoclinal structures higher up in the section are associated with listric thrust ramps whereas hanging wall monoclines approximately parallel to the underlying fault surface are associated with straight trajectory ramps this kinematic evolution which occurred partly during syn depositional compression also accounts for the observed lithofacies distribution the latter reflects an early differentiation of the foredeep trough into sub basins that are progressively younger towards the foreland the detachment anticlines that originally bounded such sub basins were the site of later thrust propagation leading to a tectonic juxtaposition of different tectonostratigraphic units consisting of broad nw se elongate synclinal blocks

distribution of fault slip in outcrop scale fault related folds appalachian mountains abstract current kinematic models of ramp related folds predict a direct relationship between ramp angle and fold shape and imply specific sequences of deformation analyses of outcrop scale structures in the valley and ridge province of the appalachians reveal configurations that depart from model predictions the models fail to account for the presence of footwall synclines and are inconsistent with measured displacement distributions on some natural faults observations support the interpretation that faults can grow by propagation both up and down dip from a nucleation point fault propagation in either direction may result in the formation of folds primarily on the side of the fault that is displaced in the direction of fault propagation

strains and folds within thrust sheets an analysis of the heilam sheet northwest scotland abstract the changes of shape and orientation of fossil worm burrows have been used to carry out a detailed strain analysis of the heilam thrust sheet in the moine thrust zone northwest scotland the strains have been factorised into components of layer parallel shear 1 layer normal shear 2 and layer parallel shortening or elongation variations in the 1 shear are largely lithologically controlled some strain is due to flexural processes as the thrusts and overlying beds change dip over thrust ramps or are tightened by later deformation while there may also be a component of drag which increases towards the overlying thrust this predating the shear due to flexure a contoured map of the values suggests that major folds within the thrust sheet developed as a result of stick or drag on the floor thrust prior to ramp climb this led to differential movement in the transport direction causing layer parallel shortening accompanied or followed by buckling of the layers a map showing layer normal shear strains 2 suggests that the heilam sheet forms a major surge zone the central part having moved further wnw than the northern and southern parts this has led to components of lateral shear along parts of the sheet especially in the north producing curvature of the imbricate faults

structural evolution of a foreland fold and thrust belt the umbria marche apennines italy abstract outcrop scale structures that record a progressive sequence of deformation can be used to clarify the kinematic evolution of an entire fold and thrust belt the temporal progression of the compressional deformation as reconstructed by means of a mesoscopic structural analysis provides a key for unraveling the kinematic history of the umbria marche apennines central italy overprinting relationships at outcrop scale allow for the recognition of three distinct structural stages which are in sequence a layer parallel shortening b folding c thrusting individual stages are explained in the framework of a progressive deformation model where shortening of the sedimentary cover was continuous and occurred during a single contractional episode as a consequence of tip line folding processes a comparison of this history with those reported from other fold and thrust belts shows that layer parallel shortening folding and thrusting are sequentially dominant processes in areas which have experienced compressional deformation

on glacier retreat and drought cycles in the rocky mountains of montana and canada abstract the enigma of why mountain glacier started to retreat in the 1850s in the rocky mountains and elsewhere remains unresolved the most important factor affecting climate change presumably was a change in the mode of operation of the sun one or two decades earlier from irregular periodicity and low output to regular periods and greater brightness but the direct cause appears to have been the onset of drought in the 1830s interestingly there is no obvious solar information in the drought narrative in montana and southwestern canada the presence of tidal lines in the spectrum of the pacific decadal oscillation together with the presence of lines that could be interpreted as beat periods between solar and tidal forcing in the drought series suggests that the energy of solar variation is preempted for interference with tidal forcing within the system of oscillations informing precipitation patterns in the region the suggestion is supported by the presence of a strikingly dominant 12 5 year period in the drought series which is interpreted as a difference tone between the main sunspot cycle at 10 8 and a tidal period at 5 8 also this period is close to 2 3 of the nodal tide at 18 61

authigenic seep carbonates cementing coarse grained deposits in a fan delta depositional system middle miocene marnoso arenacea formation central italy seep carbonates 13 c depleted are present at different levels within the miocene terrigenous succession of deruta marnoso arenacea formation central italy they are associated with pebbly sandstones and conglomerates in a tectonically active fan delta slope depositional system most of these seepcarbonates are included in slide slump horizons as scattered blocks the occurrence of seep carbonates is clear evidence of the flow of methane rich fluids pervading the sediments fluids probably of biogenic origin may have reached the sea bottom through thrust faults and selectively infiltrated the more permeable coarse grained horizons deposited along the slope different stages of fluid emissions are documented slow flux stage corresponding to the development of large carbonate bodies and dense chemosynthetic communities and fast fluid flow associated with intense carbonate brecciation pipes and veins large amounts of authigenic carbonates are reworked by slope failures triggered by tectonics and fluids reducing sediment strength in situ cementation of slide blocks may also have occurred due to remobilization of methane rich fluids by mass wasting processes

a dynamic origin for the global asymmetry of lunar mare basalts we propose that the hemispheric asymmetry fig 1 of mare basalts may be explained as a result of hydrodynamic instabilities associated with a layer of mixed ilmenite rich cumulates ic and olivine orthopyroxene opx overlying a metallic core this mixed layer mic should form shortly after the solidification of the magma ocean p c hess and e m parmentier earth planet sci lett 134 1995 501 514 because of gravitational differentiation of chemically dense ic material that is expected to form below the anorthositic crust in the final stages of magma ocean crystallization a e ringwood and s e kesson proc lunar planet sci conf 7 1976 1697 1722 ic material is rich in heat producing elements and thermal expansion due to radiogenic heating causes the mic layer to become less dense than overlying mantle the time required for the mic layer to become thermally buoyant may explain a delay of mare volcanism until about 500 ma after solidification of the magma ocean our analyses of the resulting rayleigh taylor instability and numerical modeling of thermo chemical convection show that the instabilities produce spherical harmonic degree 1 thermal and compositional structure if a lunar metallic core is sufficiently small less than 250 km in radius fl 2000 elsevier science b v all rights reserved

the use of finite strain data in constructing a retrodeformable cross section of the meade thrust sheet southeastern idaho u s a abstract a method for drawing a balanced cross section is presented which uses the constraint of both the interpretation of the geometry and the analysis of the internal deformation within the meade thrust sheet southeastern idaho u s a earliest deformation associated with the meade thrust sheet is layer parallel shortening which is indicated by a spaced solution cleavage and deformed fossils in the jurassic twin creek formation this early layer parallel shortening fabric is rotated by folding in front of the main meade thrust sheet these folds are then truncated by the meade thrust locally finite strain markers indicate fault parallel shear

the procellarum kreep terrane implications for mare volcanism and lunar evolution geophysical remote sensing and sample data demonstrate that the procellarum and imbrium regions of the moon make up a unique geochemical crustal province here dubbed the procellarum kreep terrane geochemical studies of imbrium s ejecta and the crustal structure of the imbrium and serenitatis basins both suggest that a large portion of the lunar crust in this locale is composed of a material similar in composition to apollo 15 kreep basalt kreep basalt has about 300 times more uranium and thorium than chondrites so this implies that a large portion of moon s heat producing elements is located within this single crustal province the spatial distribution of mare volcanism closely parallels the confines of the procellarum kreep terrane and this suggests a causal relationship between the two phenomena we have modeled the moon s thermal evolution using a simple thermal conduction model and show that as a result of the high abundance of heat producing elements that are found in the procellarum kreep terrane partial melting of the underlying mantle is an inevitable outcome specifically by placing a 10 km kreep basalt layer at the base of the crust there our model predicts that mare volcanism should span most of the moon s history and that the depth of melting should increase with time to a maximum depth of about 600 km we suggest that the 500 km seismic discontinuity that is observed in the apollo seismic data may represent this maximum depth of melting our model also predicts that the kreep basalt layer should remain partially molten for a few billion years thus the imbrium impact event most likely excavated into a partially molten kreep basalt magma chamber we postulate that the kreep basalt composition is a by product of mixing urkreep with shallow partial melts of the underlying mantle since mg suite rocks are likely derived from crystallizing kreep basalt the provenance of these plutonic rocks is likely to be unique to this region of the moon

structural evolution along the inner forearc of the obliquely convergent hikurangi margin new zealand the accretionary margin of the hikurangi forearc on the southeast coast of the north island of new zealand is part of the leading edge of the australian plate which is overriding the obliquely converging pacific plate we investigate the last 10 m y of deformation history of the innermost western quarter of the total width of the forearc through analysis of the sedimentologic and structural evolution of the eketahuna area on the east coast of the north island the eketahuna area is ideal for such a study because emergence of the margin in the quaternary has exposed a complete late neogene rock record this record has allowed us to chronicle the strain history from 10 ma to about 2 5 ma this forearc region was the locus of subsidence and marine deposition in the latest pliocene this part of the margin began to shorten through folding and reverse faulting bringing an end to basin filling the period of shortening was brief and by the late pleistocene reverse faulting had ceased and was immediately succeeded by dextral strike slip faulting in some cases along the same faults presently the dominant strain regime in the inner quarter of the forearc is strike slip faulting this structural history illustrates that over time the pattern of strain partitioning has changed in the hikurangi forearc the switch from crustal shortening to dextral shear along the major faults in this area in the last 1 m y may be a response to more than 10 of clockwise rotation in the southern hikurangi forearc in pliocene and pleistocene time this rotation is a consequence of the fact that the accretionary margin is undergoing continuous deformation between the obliquely converging australian and pacific plates in this area at the southernmost end of the kermadec hikurangi subduction system the inboard portion of this young accretionary margin is exceptionally well exposed today probably in part because of the late neogene subduction of relatively thick buoyant crust of the hikurangi chatham plateau

fault bend folding as an end member solution of double edge fault propagation folding fault bend folding is the most commonly used kinematic mechanism to interpret the architecture and evolution of thrust related anticlines in thrust wedges however its basic requirement of an instantaneous propagation of the entire fault before hangingwall deformation limits its kinematic effectiveness to overcome this limitation we used the interdependence between fold shape and fault slip vs propagation rate s p ratio implemented in double edge faultpropagation folding we show that very small s p values produce fault propagation anticlines that when transported

clementine observations of the aristarchus region of the moon multispectral and topographic data acquired by the clementine spacecraft provide information on the composition and geologic history of the aristarchus region of the moon altimetry profiles show the aristarchus plateau dipping about 1 to the north northwest and rising about 2 kilometers above the surrounding lavas of oceanus procellarum to the south dark reddish pyroclastic glass covers the plateau to average depths of 10 to 30 meters as determined from the estimated excavation depths of 100 to 1000 meter diameter craters that have exposed materials below the pyroclastics these craters and the walls of sinuous rilles also show that mare basalts underlie the pyroclastics across much of the plateau near infrared images of aristarchus crater reveal olivine rich materials and two kilometer sized outcrops of anorthosite in the central peaks the anorthosite could be either a derivative of local magnesium suite magmatism or a remnant of the ferroan anorthosite crust that formed over the primordial magma ocean

late pliocene quaternary evolution of outermost hinterland basins of the northern apennines italy and their relevance to active tectonics abstract we examine the tectonic evolution and structural characteristics of the quaternary intermontane mugello casentino and sansepolcro basins in the northern apennines fold and thrust belt these basins have been classically interpreted to have developed under an extensional regime and to mark the extension compression transition the results of our study have instead allowed framing the formation of these basins into a compressive setting tied to the activity of backthrust faults at their northeastern margin syndepositional activity of these structures is manifested by consistent architecture of sediments and outcrop scale deformation after this phase the mugello and sansepolcro basins experienced a phase of normal faulting extending from the middle pleistocene until present basin evolution can be thus basically framed into a two phase history with extensional tectonics superposed onto compressional structures analysis of morphologic features has revealed the occurrence of fresh fault scarps and interaction of faulting with drainage systems which have been interpreted as evidence for potential ongoing activity of normal faults extensional tectonics is also manifested by recent seismicity and likely caused the strong historical earthquakes affecting the mugello and sansepolcro basins qualitative comparison of surface information with depth converted seismic data suggests the basins to represent discrete subsiding areas within the seismic belt extending along the axial zone of the apennines the inferred chronology of deformation and the timing of activity of normal faults have an obvious impact on the elaboration of seismic hazard models

mare tranquillitatis basalt emplacement history and relation to lunar samples galileo and clementine multispectral data of the mare tranquillitatis region have been analyzed to investigate the stratigraphy of basaltic units and the effects of lateral and vertical mixing processes within the mare the distribution of compositionally distinct mare units is observed to be correlated with previous uv vis ratio images although estimates of soil titanium contents are low in some areas as a result of mixing of local basalts with nonmare feldspathic materials basalt units identified by their spectral properties and spectral mixture analysis are compared with groups of apollo 11 samples defined by previous workers on the basis of age and chemistry spectral studies presented here indicate that the apollo 11 site lies at the edge of a localized western mare unit which includes the youngest and most titanium rich basalts in tranquillitatis apollo 11 high k high ti samples in southern tranquillitatis these basalts have been contaminated by a large degree of mixing with nonmare feldspathic materials nonmare materials near the apollo 11 site are attributed largely to crater rays from theophilus 100 km in diameter which is located approximately 300 km to the south a more extensive and stratigraphically older unit exposed near apollo 11 is related to the low k high ti apollo 11 samples and appears to extend as a coherent surface unit as far north as the apollo 17 site in southern serenitatis the distribution of this spectrally identified basalt unit supports petrologic and geochemical evidence for the grouping of the high ti low k apollo 11 and 17 basalt samples into the same regional volcanic events multispectral analysis of tranquillitatis deposits also identify low titanium basalts in the northeastern and southeastern portions of the basin that are older than the high ti basalts and are believed to be unsampled by apollo 11 several lines of evidence suggest that the cayley formation along the western tranquillitatis margin may indeed lie on top of an ancient mare deposit buried by imbrium basin ejecta e g a cryptomare deposit the distribution of vertically excavated feldspathic premare material within the mare provides information on the depth of the mare units and the proximity of the underlying basin topography compositional stratigraphy observed in both sets of multispectral data supports an asymmetric premare fill basin topography containing thicker basalts in the northwestern portion of the basin than previously predicted by crater flooding data

the lunar crust global structure and signature of major basins new lunar gravity and topography data from the clementine mission provide a global bouguer anomaly map corrected for the gravitational attraction of mare fill in mascon basins most of the gravity signal remaining after corrections for the attraction of topography and mare fill can be attributed to variations in depth to the lunar moho and therefore crustal thickness the large range of global crustal thickness 20 120 km is indicative of major spatial variations in melting of the lunar exterior and or significant impact related redistribution the 61 km average crustal thickness constrained by a depth to moho measured during the apollo 12 and 14 missions is preferentially distributed toward the farside accounting for much of the offset in center of figure from the center of mass while the average farside thickness is 12 km greater than the nearside the distribution is nonuniform with dramatic thinning beneath the farside south pole aitken basin with the global crustal thickness map as a constraint regional inversions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km in order to yield crustal thickness maps with the maximum horizontal resolution permitted by the data the downward continuation of the bouguer gravity is stabilized by a three dimensional minimum slope and curvature algorithm both mare and non mare basins are characterized by a central upwarped moho that is surrounded by rings of thickened crust lying mainly within the basin rims the inferred relief at this density interface suggests a deep structural component to the surficial features of multiring lunar impact basins for large 300 km diameter basins moho relief appears uncorrelated with diameter but is negatively correlated with basin age in several cases it appears that the multiring structures were out of isostatic equilibrium prior to mare emplacement suggesting that the lithosphere was strong enough to maintain their state of stress to the present

tectonics in the cuddapah fold thrust belt in the indian shield andhra pradesh india and its implication on the crustal amalgamation of india and rayner craton of antarctica during neoproterozoic orogenesis neoproterozoic orogenesis in east antarctica and india led to the amalgamation of northern prince charles mountains rayner complex of antarctica with the krishna province of india along the present eastern coast of india with the development of 990 900 ma old fold thrust belt the frontal part of the fold thrust belt henceforth called the cuddapah fold thrust belt cftb recognized in the intercratonic palaeoproterozoic neoproterozoic cuddapah basin includes two frontal thrust sheets carried by the eastern velikonda and the western nallamalai thrusts along with a part of the undeformed foreland constituting frontal part of a larger fold thrust belt now fragmented and separated in different continents of gondwanaland therefore the intercratonic deformation now preserved in the palaeoproterozoic neoproterozoic cuddapah basin is related to the collision of the indian shield to the antarctic block during the amalgamation of the rodinia supercontinent cftb is dominated by quasi plastic deformational structures representing exhumed deeper level fault propagation folding related to the velikonda thrust while the nallamalai thrust represents the forelandward thrust of the cftb dominated by elastico frictional deformation structures

duplexes as slip transfer zones application to the himalayan fold thrust belt abstract duplex fault zones and imbricate fans originally termed schuppen schuppenstruktur or imbricate structure were first described in the late 1800s from the alps nw highlands scotland and montana rockies lewis thrust sheet as originally defined duplexes contained shingled imbricate slices bounded above and below by through going thrusts these duplex fault zones commonly occur along the base of major regional thrust sheets or within the body of such sheets accommodating regional bed parallel shortening and transferring slip from a lower stratigraphic horizon to a higher one thereby providing a mechanical advantage to the emplacement of large thrust sheets however faulting is not the only means of layer parallel shortening lps and displacement transfer within duplexes lps cleavage and detachment folds are also common and can play the same role as imbricate faults based on some selected examples we recognize three types of duplexes 1 fault duplex 2 cleavage duplex and 3 fold duplex the style of duplex that forms is likely a function of mechanical stratigraphy and deformation conditions the relationships among the three basic duplex styles can be plotted on a ternary diagram each duplex type constituting an apex given the complexities of most sedimentary sequences hybrid duplexes with a mix of fault fold and cleavage shortening can also form hybrid duplexes plot along the side of the triangle as fault fold fold cleavage and fault cleavage duplexes while those combining all three mechanisms plot in the middle if the partitioning of shortening by the different mechanisms can be quantified the ternary diagram provides a means of representing the contributions of the three mechanisms in shortening and slip transfer along much of the himalayan fold thrust belt a significant portion of the lesser himalayan shortening is taken up by the lesser himalayan duplex a first order fault duplex with subsidiary cleavage and fold development the geometry of and shortening within the duplex varies significantly along the length of the himalaya

fault related folding in sandbox analogue models of thrust wedges abstract the nucleation and growth of thrust fault related folds has been simulated using high resolution sandbox coulomb wedge type analogue models thrust related anticlines grew progressively from initial layerparallel shortening to decollement folding thrust tip folding and eventually thrust ramp folding thrust ramps nucleated in the central sector of the overturned forelimb of decollement folds as a consequence of limb thinning thrust tip folding occurred during outward migration of the ramp tips the fault propagation rate was greater at the lower ramp tip which quickly joined the basal thrust flat while folding continued beyond the upper tip the development of the analogue model thrust fault related folds by progressive changes in kinematics from decollement folding to thrust tip folding and finally thrust ramp folding compares well with analyses of naturally occurring thrust fault related folds

a 70th degree lunar gravity model glgm 2 from clementine and other tracking data a spherical harmonic model of the lunar gravity field complete to degree and order 70 has been developed from s band doppler tracking data from the clementine mission as well as historical tracking data from lunar orbiters 1 5 and the apollo 15 and 16 subsatellites the model combines 361 000 doppler observations from clementine with 347 000 historical observations the historical data consist of mostly 60 s doppler with a noise of 0 25 to several mm s the clementine data consist of mostly 10 s doppler data with a data noise of 0 25 mm s for the observations from the deep space network and 2 5 mm s for the data from a naval tracking station at pomonkey maryland observations provided clementine provide the strongest satellite constraint on the moon s low degree field in contrast the historical data collected by spacecraft that had lower periapsis altitudes provide distributed regions of high resolution coverage within 29 of the nearside lunar equator to obtain the solution for a high degree field in the absence of a uniform distribution of observations we applied an a priori power law constraint of the form 15 10 5 l2 which had the effect of limiting the gravitational power and noise at short wavelengths coefficients through degree and order 18 are not significantly affected by the constraint and so the model permits geophysical analysis of effects of the major basins at degrees 10 12 the glgm 2 model confirms major features of the lunar gravity field shown in previous gravitational field models but also reveals significantly more detail particularly at intermediate wavelengths 103 km free air gravity anomaly maps derived from the new model show the nearside and farside highlands to be gravitationally smooth reflecting a state of isostatic compensation mascon basins including imbrium serenitatis crisium smythii and humorum are denoted by gravity highs first recognized from lunar orbiter tracking all of the major mascons are bounded by annuli of negative anomalies representing significant subsurface mass deficiencies mare orientale appears as a minor mascon surrounded by a horseshoe shaped gravity low centered on the inner and outer rook rings that is evidence of significant subsurface structural heterogeneity although direct tracking is not available over a significant part of the lunar farside glgm 2 resolves negative anomalies that correlate with many farside basins including south pole aitken hertzsprung korolev moscoviense tsiolkovsky and freundlich sharonov

remelting mechanisms for shallow source regions of mare basalts abstract two mechanisms are studied which could induce remelting at shallow depths within the moon a radioactive heating model in which remelting is the result of lateral variations of the heat source concentration emplaced by the end of the initial differentiation event and a thermal insulation model in which remelting is induced by lateral variations of near surface conductivity as a result of a high porosity ejecta blanket created by basin forming impacts the effects of these perturbations are studied by evaluating the thermal evolution of an otherwise radially symmetric lunar model the radioactive heating models predict extensive pre basin volcanism which would probably remove from the source region many of the heat producing elements potentially responsible for melting therefore localized high concentrations of heat producing elements emplaced early would most probably not be heat sources for the basin filling mare basalts however they are plausible heat sources for pre basin mare basalts the thermal insulation model predicts a delay of about 200 m y between impact and volcanism thermal insulation may also allow for the persistence of source regions for young basalts at shallow depths if greater basin ages are correct from 4 2 to 3 9 ga and most volcanism occurred between 3 8 and 3 6 ga then the thermal insulation model may explain the delay between impact and basin filling if the basins formed during a terminal cataclysmic event at about 3 9 ga then the earliest stages of basin filling at about 3 8 ga may have been a result of melting beneath the basin as a result of mantle uplift basin filling may have been characterized by a migration of the source region from beneath the basin to beneath the adjacent highlands cooling of the top 200 km beneath the basin after 200 m y because of its high surface conductivity is consistent with the mascon support requirement

fault displacement gradient folds and the structure at lost hills california u s a abstract geometric models of fault propagation folds require that the underlying fault tip propagate upward across layering however related folds can be generated if the tip remains stationary or even moves back along the ramp as a pre existing fault is reactivated fault propagation folds detachment folds as well as those produced when there is no propagation are generated by a displacement gradient along the underlying fault and as a general class can be called fault displacement gradient folds new geometric equations are derived which relate fold shape to displacement gradient and fault propagation folds are a special case of these more general equations growth sequences associated with these structures have been used to distinguish fault propagation folds from fault bend folds when the underlying structure is obscured a displacement gradient fold in which the fault tip retreats back down the ramp generates a growth sequence that in some cases could be confused with that of a fault bend fold the structure at lost hills in the san joaquin valley of california u s a has been interpreted as a fault bend fold but it may be a displacement gradient fold which formed as a pre existing fault was reactivated during a pliocene change in plate motion

sedimentary facies control on mechanical and fracture stratigraphy in turbidites natural fracture networks exert a first order control on the exploitation of resources such as aquifers hydrocarbons and geothermal reservoirs and on environmental issues like underground gas storage and waste disposal fractures and the mechanical stratigraphy of layered sequences have been intensively studied to unravel the relationships between bed thickness and fracture spacing but less attention has been paid to intrabed fracturing patterns due to the intrinsic local variability of sedimentary processes and products among sedimentary rocks turbidites show great lateral and vertical variability of textural characteristics and depositional facies which are expected to strongly influence the location and density of fractures to better understand the contribution of stratigraphic sedimentologic and petrophysical properties on fracture patterns we performed a high resolution study on a selected stratigraphic interval of jointed foredeep turbidites in the miocene marnoso arenacea formation northern apennines italy cumulative statistical relations of field and laboratory structural sedimentologic and petrophysical data significantly improved when analyzed at the sedimentary facies scale in particular for facies recording different cross flow i e longitudinal to the paleocurrents depositional conditions within the parent turbidity currents we observed three dimensional anisotropies of rock hardness i e uniaxial compression that were positively correlated with normalized fracture intensities indicating a primary sedimentary control on fracture distribution this type of intrabed joint distribution has crucial practical implications for the lateral prediction and evaluation of mesoscale fracture patterns in turbidite sequences

three dimensional visualization of the neogene structures of an external sector of the northern apennines italy a three dimensional 3 d visualization technique is used to build a structural model linking a complex series of thrust sheets in an external area of the northern apennines central italy this foreland fold and thrust belt consists of faulted anticlines and broad syn clines involving a triassic paleogene succession that is detached from the underlying basement reactivation of basement faults has influenced the geometry and kinematics of the overlying structures in a mix of thin skinned and thick skinned tectonics upper de tachment horizons within the sedimentary succession form shallow structures in the crestal zone of the major anticlines all the struc tures are scantily cylindrical and the model demonstrates the soft linkages between oblique and frontal structures through relay ramps

global surface temperatures over the past two millennia 1 we present reconstructions of northern and southern hemisphere mean surface temperature over the past two millennia based on high resolution proxy temperature data which retain millennial scale variability these reconstructions indicate that late 20th century warmth is unprecedented for at least roughly the past two millennia for the northern hemisphere conclusions for the southern hemisphere and global mean temperature are limited by the sparseness of available proxy data in the southern hemisphere at present

fault related folding a review of kinematic models and their application abstract folding that is directly related to fault activity is an important deformation feature that occurs all over the world in mountain belts accretionary wedges fold and thrust belts and intra plate settings in either strike slip compressional or extensional regimes due to their widespread occurrence knowledge about the development of these structures is important to a broad spectrum of geoscience sub disciplines such as structural geology seismology geomorphology petroleum geology and quaternary geology fault related folding has been analyzed intensively over the last 140 years for the sake of this review we divide the folds according to the way the faults and the folds form that is into detachment fault bend and fault propagation folds all fault related folds are caused by changes in fault parameters the simplest method to produce folds is to transport material along faults that have stepped flat ramp flat geometries fault bend fold alternatively the slip can decrease along the length of the fault and depending on whether the fault remains within a detachment layer or steps up through mechanical stratigraphy either a detachment fold or a fault propagation fold is formed respectively detachment folding was first investigated in the early 20th century whereas the full significance of fault propagation folds was recognized quite late in the 1980s seminal work on fault related folding was carried out in the 1930s but quantitative kinematic models have only been available in the last 30 years these models are extremely valuable because they allow a comprehensive understanding of the evolution of fault related folds and lead to more accurate predictions of the sub surface structure from the mid 1990s onwards numerical simulations have been used to identify how fault parameters such as dip and fault bend angle propagation to slip ratio and shape of the trishear zone influence the geometry of the related folding this is directly applicable to the analysis of the shape of anticlines produced however this does not mean that fold geometry is uniquely related to fault geometry on the contrary different kinematic approaches can lead to a similar fold shape

progressive development of block in matrix fabric in a shale dominated shear zone insights from the bobbio tectonic window northern apennines italy 1 block in matrix is a common fabric characterizing highly deformed to apparently chaotic rocks originated by sedimentary tectonic and mud diapiric processes in many exposed orogenic belts a true melange originates when this fabric is associated with mixing of rocks of different ages and provenance as that characterizing the main decollement shear zone developed between the highly allochthonous ligurian nappe and its substratum of foredeep deposits at the margins of the bobbio tectonic window trebbia valley northern apennines mixing of rocks by both mass transport processes and synsedimentary thrusting occurs at the front and tectonic erosion at the base of the nappe during its emplacement evidence of polyphased deformations spanning from liquefaction related and hydroplastic structures to pseudo hydrofracturing features and mineralized veining have been recognized within the marginal portions and along the sheared contacts of blocks encased within a scaly matrix crosscutting relationships testify a progressive deformation involving a transition from mesoscopic ductile to brittle conditions with the significant contribution of fluid overpressure a novel evolutionary scheme for block in matrix fabric development is here proposed involving the progressive dismembering of already highly deformed units originally developed in non to poorly lithified conditions through a generalized simple shearing achieved during the evolution of the shear zone coupled with strain hardening due to tectonic compaction synkinematic diagenesis and fluid expulsion

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

triggering basaltic volcanic eruptions by bubble melt separation understanding the processes by which volcanic eruptions are triggered is crucial for volcanic hazard prediction and assessment in intermediate and silicic magmas where water is the dominant volatile phase1 2 second boiling provides an effective eruption trigger1 as the magma cools and crystallizes volatiles are increasingly concentrated in the residual melt where they eventually become saturated and are exsolved thereby raising the magma pressure to the point of eruption1 2 in contrast in basaltic magma chambers in which carbon dioxide is the dominant volatile phase the effect of second boiling is to decrease the chamber pressure but basaltic magmas are also relatively inviscid so volatile bubbles can separate from the turbulently convecting melt to produce a foam layer at the chamber roof3 4 decompression of the rising bubbles can increase the chamber pressure and so trigger an eruption5 6 here we model the complex competition between the processes of magma cooling and bubble ascent we find that in basalt of very low viscosity 1 10pas bubble separation dominates and can increase the reservoir pressure by as much as 10 mpa sufficient to trigger an eruption7 on timescales of 1 10 years comparable to the duration of eruptive episodes at kilauea volcano hawaii4 8

tectonic thickening of hanging wall units over a ramp in this article we use results of analogue models and published numerical models to study the elements that influence the amount of thickening of hanging wall units during their transport over a ramp the models consisting of granular layers were shortened over a single pass rigid ramp dipping at 15 30 or 45 and friction coefficient that was large 0 67 intermediate 0 42 or null model results show that the amount of thickening depends on the ramp angle and its friction thickening increases dramatically with increasing ramp friction and dip the maximum amount of thickening 80 is observed over steepest ramps 45 with largest ramp friction 0 67 whereas the minimum amount of thickening 2 5 occurs over frictionless ramps dipping 15 for the same friction coefficient along the ramp steeper ramps cause larger amounts of thickening the tectonic thickening demonstrated by our models was compared with thickening of hanging wall units of natural examples and other experimental and model studies this comparison shows that thickening occurs whether the material considered is brittle viscous or plastic it also confirms the importance to thickening of ramp angle and fault friction finally it reveals also that ramp shape round or sharp bend its changes due to footwall deformations and the topographic relief are additional boundary conditions for thickening more generally our model results and other published model results demonstrate that retardation during the transport of hanging wall units over a ramp results in hanging wall thickening

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

mirror image thrusting in the south china orogenic belt tectonic evidence from western fujian southeastern china abstract the mesozoic orogenic belt in south china is readily divided into two fold and thrust belts and a central multiply deformed zone of ductile deformation dominated by folds with steeply dipping axial planes southeast directed thrusting in the eastern belt and northwest directed thrusting in the western belt resulted in a mirror image of one another during the mesozoic the eastern fold and thrust belt can be further divided into three domains that overlap one another and exhibit a southeast verging wedge like geometry and kinematics deviatoric stress has been calculated from quartz dislocation density at 91 5 mpa 74 5 mpa and 73 8 mpa decreasing toward the southeast upper devonian and lower carboniferous sandstones have been used to constrain bed length for cross section balancing to estimate crustal shortening from three typical areas these indicate 45 41 6 and 37 3 shortening and suggest that 110 km of contraction has been achieved as a result of thrusting this orogen correlates with the ogcheon belt in south korea to the northeast to the southwest it appears to correlate with a thrust belt in western guangdong this southeast verging thrusting may be at least partially controlled by cathaysia to the east

deformation pattern and evolution of the structures in the penganga group the pranhita godavari valley india probable effects of grenvillian movement on a mesoproterozoic basin abstract recent studies reveal imprints of tectonic deformation in the mesoproterozoic rocks of the pranhita godavari p g valley india outcrop scale structures that record a progressive sequence of deformation can thus be used to clarify the kinematic evolution of the penganga group a mesoproterozoic succession in the northern and central parts along the sw marginal proterozoic belt of the pg valley overprinting relationships among the structures in the northern part indicate three distinct structural stages 1 layer parallel shortening 2 thrusting and folding in combination and 3 extensional joint and fracture opening the former two stages are explained in the framework of a progressive deformation model the extensional structures were produced during exhumation similar structures are also developed in the central part of the sw belt of the pg valley though the two areas slightly differ in the overall pattern of deformation the geometry of the progressive deformation structures from both regions of the belt suggests that they were produced under a regime of ne sw ene wsw directed regional compression the deformation in the proterozoic basin is possibly related to the grenvillian orogeny recorded in the eastern ghats mobile belt and may represent a small scale meso neoproterozoic convergence event