glacial cirques and the relationship between equilibrium line altitudes and mountain range height a global gis and literature based analysis of the altitude and relief of more than 14 000 ice free glacial cirques in 56 study areas ranging from 69 n to 77 s shows that average cirque floor altitudes vary with latitude in a zone centered on the quaternary average equilibrium line altitude qa ela in addition relief above cirque floors averages 346 107 m and is rarely 600 m in regions where ice free cirques are abundant cirque relief is independent of modern precipitation rates tectonic regime and relative peak height limiting peaks to within a fixed distance above the qa ela and thus causing them to also parallel the ela we propose a physical process model where under suitable geologic and tectonic conditions climate exerts a first order control on mountain range height in this model glacial erosion excavates a zone of cirques with floors centered on the qa ela while climate driven weathering processes on adjacent slopes limit the peaks to within a few hundred meters above this zone

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

seasonal and diurnal variation of geomagnetic activity russell mcpherron effect during different imf polarity and or extreme solar wind conditions 1 the russell mcpherron r m effect is one of the most prevailing hypotheses accounting for semiannual variation of geomagnetic activity to validate the r m effect and investigate the difference of geomagnetic activity variation under different interplanetary magnetic field imf polarity and during extreme solar wind conditions interplanetary shock we have analyzed 42 years interplanetary magnetic field and geomagnetic indices data and 1270 ssc storm sudden commencement events from the year 1968 to 2010 by defining the r m effect with positive negative imf polarity imf away toward the sun the results obtained in this study have shown that the response of geomagnetic activity to the r m effect with positive negative imf polarity are rather profound the geomagnetic activity is much more intense around fall equinox when the direction of imf is away the sun while much more intense around spring equinox when the direction of imf is toward the sun the seasonal and diurnal variation of geomagnetic activity after sscs can be attributed to both r m effect and the equinoctial hypothesis the r m effect explains most part of variance of southward imf while the equinoctial hypothesis explains similar variance of ring current injection and geomagnetic indices as the r m effect however the r m effect with positive negative imf polarity explains the difference between sscs with positive negative imfbyaccurately while the equinoctial hypothesis cannot explain such difference at the spring and fall equinoxes thus the r m effect with positive negative imf polarity is more reasonable to explain seasonal and diurnal variation of geomagnetic activity under extreme solar wind conditions

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

two component auroral electrojet importance for substorm studies this paper attempts to synthesize the diverse number of observations of electric fields and currents in the high latitude ionosphere during substorms by demonstrating that there are often spatial shifts among regions of high ionospheric conductivity large electric fields and intense currents in the auroral electrojet it is shown that substorm time variations of the current patterns over the entire polar region consist of two basic components the first is related to the two cell convection pattern and the second to the westward electrojet in the dark sector which is in turn related to the three dimensional wedge current system these two components result from the relative strength of electric fields and conductivities in the intensification of the auroral electrojet and are identified as the signatures for directly driven and the unloading components in solar wind magnetosphere interactions we contend that disturbed intervals do not necessitate the presence of substorm expansion phase activity and that the vast number of earlier complex results concerning the auroral electrojet can be ascertained from the high degree of variability of the two components depending on substorm events substorm phases and their own spatial temporal scale sizes it is demonstrated that several major issues that have remained controversial are now accounted for reasonably well in terms of this two component electrojet model we also predict specific features of the substorm auroral electrojet that have not yet been observed

paleomagnetic direction obtained by strain removal in the pyrenean permian redbeds at the col du somport france abstract in order to investigate the possibility and limitations of paleomagnetic works within strained regions a paleomagnetic study related with strain analysis has been conducted in the deformed pyrenean permian redbeds in the col du somport area paleomagnetic sampling together with strain estimates have been conducted in 6 sites through a fold the results obtained by measuring the orientation and axial ratios of elliptical reduction spots show that 1 the shale beds have undergone a penetrative strain 2 the sandy beds can be regarded as tectonically unstrained with reduction spots flattened in the bedding showing that they recorded the compaction it is shown that the total strain recorded in the slaty beds probably results from the superimposition of tectonic strain upon the compaction fabric the paleomagnetic study shows that the primary pretectonic magnetization is widely overprinted by a secondary syn or post tectonic magnetic component as both components appear to be carried by hematite pigment their separation using classical demagnetization procedures has been difficult a characteristic remanent magnetization chrm has however been determined when possible as the hardest component in demagnetization curves then the chrm direction distributions are represented in stereographic density plots although these chrm directions exhibit a clear tendency towards se declinations and shallow inclinations characteristic of permian paleomagnetic field direction for the iberian plate the tilt correction does not induce a clustering of these directions strain is inferred to be responsible for this situation assuming that both pretectonic magnetization directions and bedding planes closely follow the material plane and line strain response model of march 1 an attempt has been made to remove the effect of strain upon the remanent magnetization it is shown that when using a reconstructed tectonic strain tensor i e the total strain tensor as measured in the field corrected for an estimated compaction we obtain a significant clustering of chrm directions the computation of the relevant vgp gives a pole position 210 5 e 42 0 n compatible with the reference apwp for the iberian plate it is therefore inferred that the strain removal technique is a usable tool in order to obtain paleomagnetic results within such strained rocks

ultra high resolution multivariate record and multiscale causal analysis of pridoli late silurian implications for global stratigraphy turnover events and climate biota interactions abstract the upper silurian and especially pridoli epoch is a critical interval for the understanding the evolution of earth s biota since it witnessed series of powerful extinction events global reorganizations of paleocommunities and expansion of new clades which assumed dominance in the subsequent devonian period the stratigraphic record of the eastern part of the silurian baltic basin represents an excellent candidate for the fine scale analysis of paleoecological and paleoceanographic dynamics therefore we presenting here stratigraphic record of the milaiciai 103 core south western lithuania of conodonts brachiopods 13ccarb 18ocarb and a series of various geochemical and geophysical proxies most of which were sampled at a very high resolution 11 ka spanning uppermost ludlow pridoli and the lowermost devonian the analysis revealed that the pridoli was characterized by four distinct long term dynamic states here named i normal pridoli i ii silal negative carbon isotopic excursion and extinction event iii normal pridoli ii and iv klonk positive stable carbon isotopic event and excursion the most significant change in most variables is detected approximately in the middle of the pridoli at the beginning of the delotaxis detorta zone at the recovery after silal event of conodonts and at the onset of collapse of brachiopod communities the analysis of dynamic complexity revealed the strong evidence for the presence of 405 ka metronome milankovitch cycles in the record of 13ccarb which constrains the duration of the pridoli epoch to 4 3 0 2 ma the recurrence plot analyses revealed deterministic coordination between 13ccarband conodont paleocommunity dynamics at all scales finally lead lag analysis using conditional joint recurrence revealed that conodont dynamics as a rule were driven by perturbations in the carbon cycle although silal event interval shown opposite pattern thus confirming the unusual nature of this previously unrecognized coordinated climatic and biotic event

glacial cirques as palaeoenvironmental indicators their potential and limitations abstract glacial cirques are armchair shaped erosional hollows typified by steep headwalls and often overdeepened floors they reflect former regions of glacier initiation and their distribution is therefore linked to palaeoclimate because of this association cirques can be analysed for the information they provide about past environments an approach that has a strong heritage and has seen resurgence over recent years this paper provides a critical assessment of what cirques can tell us about past environments and considers their reliability as palaeoenvironmental proxies specific focus is placed on information that can be obtained from consideration of cirque distribution aspect altitude and morphometry the paper highlights the fact that cirques potentially provide information about the style duration and intensity of former glaciation as well as information about past temperatures precipitation gradients cloud cover and wind directions in all cirques are considered a valuable source of palaeoenvironmental information if used judiciously particularly as they are ubiquitous within formerly glaciated mountain ranges globally thus making regional or even global scale studies possible furthermore cirques often occupy remote and inaccessible regions where other palaeoenvironmental proxies may be limited or lacking

experimental deformation of synthetic magnetite bearing calcite sandstones effects on remanence bulk magnetic properties and magnetic anisotropy we have quantified effects of experimental deformation on the magnetic properties of a set of synthetic calcite sandstone samples containing magnetite the deformation was carried out in a microcomputer controlled apparatus that adjusted the applied differential stress as needed to maintain a constant strain rate of 10 5 s 1 most samples were deformed under dry conditions but a few were deformed with a pore fluid present the samples deformed under dry conditions required substantially higher differential stresses macroscopically ductile shortening strains of up to 25 produced the following irreversible changes in magnetic properties 1 increased bulk coercivity remanence coercivity and mean anhysteretic remanence susceptibility 2 decreased mean low field susceptibility 3 decreases in the component of remanence parallel to shortening 4 smaller decreases for most samples in the component normal to shortening resulting in a net rotation of the remanence away from the shortening axis 5 larger decreases in the normal component in a few samples resulting in a net rotation of the remanence towards the shortening axis 6 increased magnetic anisotropy and 7 increased deformation of initial magnetic ellipsoids a comparison of data for samples deformed under dry and wet conditions higher and lower differential stresses respectively indicates that remanence reorientation and susceptibility anisotropy are controlled primarily by bulk strain i e rotation and displacement of particles whereas coercivity and anhysteretic anisotropy are controlled dominantly by microstrain or intragranular stress

grain scale deformation and the fold test evaluation of syn folding remagnetization the paleomagnetic fold test examines for pre syn or post folding re magnetization generally passive limb rotation is used to restore folded units to their original position and the position of the fisherian maximum deter mines the relationship between folding and magnetization in a more complete analysis the reorientation of material lines in different fold models is used however the magnetic vec tor should not be considered a material line as it represents the sum of vectors in individual magnetic carriers and does not cross grain boundaries therefore the role of grain scale deformation mechanisms was examined using two end mem bers rigid body rotation spin and homogeneous strain from this study it is concluded that 1 the fisherian maximum will in general occur before complete unfolding 2 the sign of the inclination may change during unfolding and consequently cross over unfolding is not representati ve of syn folding remagnetization 3 statistical analysis will not necessarily produce significant results a number of recommendations are given which include stepwise unfol ding and unplunging should be carried out routinely local rather than regional fold tests should be performed both limbs and the hinge of a single folded layer should be exa mined in order to determine the active deformation mecha

syn deformational remanent magnetization of the mount eclipse sandstone central australia summary the palaeomagnetism of the latest devonian early carboniferous mount eclipse sandstone in central australia reveals samples from 16 out of 31 sites having a consistent hightemperature component of natural remanent magnetization site mean directions from the two limbs of the most detailed studied syncline attain their best grouping after 75 per cent of unfolding and further unfolding causes a cross over feature mineralogical studies using microscope and electron microprobe show that this remanance is most likely to be carried by secondary haematite formed by alteration of fe rich minerals during the midcarboniferous deformation four different models are examined to reconstruct the palaeohorizontal for the syn deformational remanence the best estimate of the palaeomagnetic south pole position is lat 33 8 s and long 121 2 e dp 19 2 drn 19 7 close to australia this result indicates a rapid polanvard movement of eastern gondwanaland during the first half of the carboniferous we also suggest that the widespread alice springs orogeny related overprints in central australia were acquired during the beginning of the main phase of deformation in the mid carboniferous

timescale dependence of glacial erosion rates a case study of marinelli glacier cordillera darwin southern patagonia 1 erosion rates have been estimated for a number of glaciated basins around the world mostly based on modern observations last few decades of sediment fluxes to fjords we use time constrained sediment volumes delivered by marinelli glacier 55 s an outlet glacier of the cordillera darwin ice cap southern patagonian andes tierra del fuego to determine erosion rates across different timescales sediment volumes are derived using a dense grid of high and low frequency single channel seismic data and swath bathymetry data along with piston and kasten cores our results show dramatic differences in erosion rates over different timescales erosion rates at marinelli glacier diminish about 80 or by factor of 5 with each ten fold increase in the time span over which erosion rates are averaged 29 3 mm yr for the last 45 years 5 3 mm yr for the last 364 years and 0 5 mm yr for the last 12 500 years these results indicate that modern sediment yields and erosion rates from temperate tidewater glaciers can exceed long term values over the time of deglaciation after the last glacial maximum centennial and millennial timescales by up to 2 orders of magnitude in view of the low exhumation rates of cordillera darwin 0 07 mm yr average for the last 30 myr modern erosion rates could be up to 3 orders of magnitude higher than rates over geological time we conclude that the pattern of erosion rate variation with time reflects the sensitivity of glaciers to climate variability

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

statistical significance of the fold test in palaeomagnetism summary the significance of the change in direction dispersion on applying the fold test in palaeomagnetism is used as the criterion for deciding whether or not the fold test has statistical significance a set of tables is compiled which can be used for quick application of the test

synfolding magnetization in the jurassic preuss sandstone wyoming idaho utah thrust belt the jurassic preuss sandstone exposed in five thrust plates of the wyoming idaho utah thrust belt carries directions of remanent magnetization that group most tightly after only partial unfolding field petrographic and rock magnetic evidence indicates that the carrier of this magnetization is detrital low ti titanomagnetite the detrital titanomagnetite was remagnetized at low temperatures 75 150 c probably completely during folding anisotropy of magnetic susceptibility and petrographic observations indicate that the detrital titanomagnetite has been affected by tectonic strain we suggest that low temperature remagnetization of the detrital titanomagnetite was either a viscous partial thermoremanent magnetization the acquisition of which was enhanced by stress or a piezoremanent magnetization that involved stress induced movement of domain walls during intracrystalline strain or was a combination of the two mechanisms stress may promote remagnetization at temperatures much lower than predicted by current theoretical models other mechanisms such as acquisition of chemical remanent magnetization during folding deflection of a prefolding magnetization by internal strain or combination of components of magnetization with different direction cannot account for the geometry of magnetization in the preuss the locus of acquisition of synfolding magnetization in the preuss migrated in conjunction with deformation in the thrust belt a model is presented in which synfolding magnetization was acquired during cooling and folding as strata moved up thrust ramps a lack of reverse polarity directions remains a puzzling feature of the remanence the remanent direction is tentatively interpreted to reflect the predominant polarity state during its acquisition over an extended rather than a discrete time period during folding in late cretaceous and early tertiary periods of predominantly normal polarity

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

experimental and numerical modeling of irm rotation in deformed synthetic samples abstract the effect of strain upon isothermal remanent magnetization irm carried by hematite particles embedded in a plasticine matrix has been investigated magnetized artificial hand samples were deformed by simple coaxial shortening after deformation the hand samples were cut into 8 15 specimens and each specimen s irm measured hence a mean irm direction was obtained for each shortening step the main results are 1 when the initial direction of irm is parallel to the shortening axis 3 the hand sample mean irm stays parallel to 3 during deformation however individual magnetization directions are deflected towards the flattening plane and thus the specimen directions are scattered by strain this is accompanied by a significant decrease of magnetization intensity 2 in contrast when the initial direction of irm is perpendicular to 3 the shortening results in a clustering of specimen magnetization directions the mean direction being unchanged this is accompanied by a slight increase of magnetization intensity 3 in all other cases where initial irm direction makes an intermediate angle with shortening direction deformation induces a deviation of each specimen irm toward the flattening plane this results in an overall deflection of hand sample mean irm the amount of rotation increases with strain intensity changes of grouping and intensity depend on the initial angle between irm and 3 defining a continuum in behavior between irm directions being either parallel to 3 or perpendicular to 3 finally it is shown that all the experimental changes in irm due to deformation direction grouping intensity can be modeled by a passive marker rotation of hematite planar particles

tilting and transpression of an archaean anorthosite in northern ontario abstract an archaean anorthosite complex crops out over more than 300 km 2 at the junction between an archaean metasedimentary accretionary prism quetico belt and a volcanic greenstone terrain to the north wabigoon belt the anorthosite is feebly deformed and weakly foliated however anisotropies of low field susceptibility ams and anhysteretic remanence aarm define consistent magnetic fabric directions extending over subareas 25 km 2 in extent whereas magnetic fabrics cannot define strain magnitudes they normally provide reliable indications of finite strain orientations even where the fabrics developed by stress controlled nucleation during a progressive noncoaxial strain history the field schistosity s 1 being the oldest foliation rotated closest to the shear plane ams foliation due to preferred crystallographic orientation of silicates and pyrrhotite as well as preferred dimensional orientation of magnetite lies at a greater angle to the shear plane because it formed late then s 1 had less time to rotate the few measurements of the youngest aarm foliation caused by magnetite and pyrrhotite suggest that it may lie at a still greater angle to the shear plane thus s 1 and succeeding magnetic foliations provide a cryptic shear sense indicator they reveal relative motions along the terrain boundary that include transpression due to nw se shortening causing dextral e w shear with a north side up component palaeomagnetic data confirm a progressive northwards steepening of the anorthosite sills that is consistent with northwards subduction of the accretionary prism to the south

folding strain and graham s fold test in palaeomagnetic investigations summary graham s fold test is an important test of stability of magnet ization and is widely used in palaeomagnetic studies the change in dispersion of palaeomagnetic directions achieved by returning layers to their original orientation can give an indication of the relationship between the time of deformation and of magnetization acquisition however mcelhinny s criteria for application of the test are regarded by mcfadden jones to be inappro priate additionally simple rotation of directions about the strike of the layer may not be a sufficient procedure the rock type and style and amount of deformation may often appreciably affect the orientation of a vector or magnetic direction during deformation hence detailed observations are necessary to provide the basis of the steps used in applying the fold test apparent failure of the test may not indicate the absence of pre deformation stable magnetization in a rock although graham s fold test is important in palaeomagnetic and related tectonic investigations of deformed rocks application of the test may be very complex

remanence rotation due to rock strain during folding and the stepwise application of the fold test numerical modeling was conducted to determine the effects of simple models of folding strain on prefolding fisherian distributions of magnetization i found that the constant volume simple shear associated with flexural slip flexural flow folding can rotate a prefolding magnetization to have a maximum precision parameter k value at partial unfolding and thus appear to be synfolding in age if the magnetization is treated as a passive line marker this behavior only occurs for steep initial magnetizations the initial homogeneity of the fisherian precision parameters from each limb is degraded by this type of deformation and may be used to detect a strain modified remanence if the magnetization is carried by rigid mechanically active ellipsoidal or spherical particles a maximum k value at partial unfolding will occur for any initial inclination with the special case that rigid spheres will be rotated to cause a maximum k value at 50 unfolding for any initial inclination homogeneity of limb precisions is not affected in this case a discontinuous model of strain during folding in which pressure solution removes material at an axial planar spaced cleavage and causes limb dips steeper than bedding dips could also produce a maximum k value at partial unfolding strain and remanence studies of flexural slip folding in the allentown formation dolomite and the bloomsburg formation red sandstones and mudstones suggest that 1 the rigid grain model may be a more realistic model of magnetic particle behavior during shear strain and 2 about one quarter to one third of the theoretically predicted simple shear strain occurs in these rocks this amount of strain cannot explain the synfolding behavior observed in the allentown formation but could explain the maximum k values at 80 90 unfolding seen in the bloomsburg formation and perhaps other appalachian clastic rocks

paleomagnetic considerations of the development of the pennsylvania salient in the central appalachians abstract late paleozoic remagnetizations of central appalachian clastic and carbonate rocks of ordovician to devonian age constrain the structural evolution of the pennsylvania salient new paleomagnetic results from 26 sites located on nine folds combined with previously published results from 60 sites yield a mean direction for the northeastern limb of the salient at 172 1 k 49 and a mean direction for sites southwest of the salient at 173 1 k 70 these two directions are not statistically different from each other and are not significantly rotated from the expected permian paleomagnetic direction for north america individual fold test results show that this secondary magnetization is synchronous with or even older than folding across the region these paleomagnetic results suggest that curvature of fold axes around the salient is an original feature of fold growth and not the result of post orogenic oroclinal bending in contrast analysis of the primary magnetization in the silurian bloomsburg formation shows that directions from the two limbs of the salient are significantly different new results from twenty sites yield a mean direction for the northeastern limb at 4 40 k 31 and for the southwestern limb at 338 8 k 23 combining these results with previously published directions from the bloomsburg formation yields a mean direction for the northeastern limb at 1 34 k 32 and for the southeastern limb at 343 34 k 30 the difference in declination does not appear to be the result of internal deformation of the rocks or acquisition of magnetization during a period of rapid apparent polar wander rather these directions indicate that the northeastern limb has been rotated clockwise 18 9 relative to the southwestern limb the sense and amount of this rotation is consistent with the curvature of the orogen around the salient however within each limb of the salient the primary component declinations do not directly correlate with the orientation of the first order fold axes collectively therefore these paleomagnetic results suggest that the structural evolution of the salient included pre orogenic rotations or rotations that occurred early in the alleghanian orogeny followed by later remagnetization and folding of the central appalachian foreland

flexural flow folding and the paleomagnetic fold test an example of strain reorientation of remanence in the mauch chunk formation the relationship between the remanent magnetization and the detailed strain geometry around a first order fold in the appalachian valley and ridge province was investigated to examine whether penetrative strains associated with folding can generate a apparent synfolding geometry from a prefolding magnetization paleomagnetic results from the mississippian mauch chunk formation on both limbs of the frackville anticline near lavelle pennsylvania yield two magnetic components an intermediate unblocking temperature 300 c 600 c kiaman remagnetization and a two polarity high unblocking temperature 650 c 680 c characteristic magnetization when the magnetic directions are incrementally corrected for bedding tilt the intermediate temperature component is most tightly clustered at 85 unfolding d 176 i 3 and the high temperature component is most tightly clustered at 75 unfolding d 184 i 27 mesoscopic and microscopic structural fabric analyses suggest a strain history that includes a significant component of flexural slip flow folding in the coarser grained sandstone units folding has largely been accommodated by slip on bedding while in the finer grained beds folding has been accommodated by grain scale deformation mechanisms such as pressure solution and low temperature plasticity finite strain measurements determined from center to center distances between quartz grains yield strain ellipsoids consistent with this folding model inclination of the characteristic component varies as a function of the magnitude of the finite strain this variation suggests that the characteristic magnetization has been systematically reoriented with respect to bedding during folding remanence directions on the south dipping limb have been rotated to shallower inclinations while those on the north dipping limb have been rotated to steeper directions causing the prefolding magnetization to appear synfolding these rotations are in agreement with models of rigid particle rotation in deforming viscous media unlike the characteristic magnetization the secondary component appears to be unaffected by the deformation and its synfolding behavior is interpreted as the acquisition of a secondary magnetization during alleghenian folding these results show that it is important to consider penetrative strains when evaluating the significance of apparent synfolding magnetizations