ground temperatures landforms and processes in an atlantic mountain cantabrian mountains northern spain abstract ground temperatures determine significant geomorphological processes in a wet and temperate mountain with a narrow high elevation range belt twenty five temperature data loggers were buried at a shallow depth in different locations and altitudes and at specifically cold locations at two massifs in the cantabrian mountains north spain picos de europa and fuentes carrionas this paper analyses the ground thermal regime and associated parameters e g freeze index duration and depth of freeze freeze and thaw cycles and correlates them with active geomorphological processes and landforms the thermal regime varies in accordance to the topoclimatic conditions and it was possible to determinate annual phases in function of snow cover behaviour main active processes and landforms stop their activity with a large snow cover which thermally protects the ground and in consequence avoids the freeze and thaw cycles during this period the records allow to asseverate the evidence of seasonal freeze grounds in several locations permafrost was not discover on the ground at any of the thermometers except one located at the vicinity of a relict ice patch with the help of geomorphological maps and previous works we got to establish the relation between geomorphological processes landforms snow cover and ground thermal regime

relay zone geometry and displacement transfer between normal faults recorded in coal mine plans abstract overlap lengths separations and throw gradients were measured on 132 relay zones recorded on coal mine plans throws on the relay bounding fault traces are usually 2 m and individual structures are recorded on only one seam throw gradients associated with relay zones are not always higher than on single faults but asymmetry of throw profiles is diagnostic of relay zones bed geometries around larger faults in opencast mines are used to assess the displacement accommodated by shear in the vertical plane normal to the faults and displacement transfer accommodated by shear in the fault parallel plane three dimensional structure is defined for two relay zones each recorded on five seam plans these relay zones are effectively holes through the fault surfaces and overlap occurs between salients or lobes of the parent fault surfaces lobes initially terminated at tip lines but as the faults grew gradually rejoined the main fault surfaces along branch lines this type of relay zone originates by bifurcation of a single fault surface at a locally retarded tip line and is an almost inevitable result of a tip line irregularity

soil temperatures in an atlantic high mountain environment the forcadona buried ice patch picos de europa nw spain the present study focuses on the analysis of the ground and near rock surface air thermal conditions at the forcadona glacial cirque 2227 m a s l located in the western massif of the picos de europa spain temperatures have been monitored in three distinct geomorphological and topographical sites in the forcadona area over the period 2006 11 the forcadona buried ice patch is the remnant of a little ice age glacier located in the bottom of a glacial cirque its location in a deep cirque determines abundant snow accumulation with snow cover between 8 and 12 months the presence of snow favours stable soil temperatures and geomorphic stability similarly to other cantabrian mountains the annual thermal regime of the soil is defined by two seasonal periods continuous thaw with daily oscillations and isothermal regime as well as two short transition periods however the results showed evidence of a significantly different annual thermal regime at the ground and near rock surface air relatively stable soil thermal regimes were observed at the moraine and talus sites while a more dynamic pattern was recorded at the rock wall site here a higher interannual variability in the number of freeze thaw days was also detected which showed evidence of the important role of the snow cover as a ground surface insulator in the area seasonal frost conditions are widespread today in the high lands of the massif no permafrost regime was detected in the area though mean temperatures measured at 0 5 m depth at the forcadona buried ice patch during 2006 07 0 1 c suggest that permanent negative values may be reached at deeper layers

long term soil temperature dynamics in the sierra nevada spain abstract soil temperatures play a key role on the dynamics of geomorphological processes in periglacial environments however little is known about soil thermal dynamics in periglacial environments of semiarid mid latitude mountains where seasonal frost is dominant from september 2006 to august 2012 we have monitored soil temperatures at different depths 2 10 20 50 and 100 cm in a solifluction landform located at 3005 m a s l in the summit area of the sierra nevada south spain mean annual temperatures in the first meter of the soil ranged from 3 6 to 3 9 c while the mean annual air temperature at the nearby veleta peak was 0 08 c therefore these data point out the inexistence of widespread permafrost conditions today in this massif seasonal frost controls the geomorphodynamics even in the highest lands climate conditions have shown a large interannual variability as it is characteristic in a high mountainous mediterranean environment these variations are reflected in the patterns of soil thermal dynamics the depth and duration of the frozen layer are strongly conditioned by the thickness of the snow cover the date of the first significant snowfalls conditioned the beginning and rhythm of freezing of the soil wet years resulted in a thick snow cover which insulated the ground from external climate oscillations and favored a shallow frost layer 2008 2009 2009 2010 and 2010 2011 on the other hand years with low precipitations promoted deeper freezing of the soil down to 60 70 cm extending until late may or early june 2006 2007 2007 2008 and 2011 2012 when snow melted a high increase of temperatures of 10 12 c in few weeks was recorded at all depths at this time of the year periglacial activity is enhanced due to higher water availability and the existence of freeze thaw cycles these were recorded mostly in spring and autumn in the first 50 cm depth of the soil ranging from 9 8 days at 2 cm to 3 7 days at 50 cm however the inactivity of solifluction landforms suggests that the combination of present day soil temperatures together with moisture conditions is not favorable to promote solifluction activity in the periglacial belt of the sierra nevada future climate scenarios point to a temperature increase and precipitation decrease in the area which would entail deeper but shorter frozen soil layers these conditions would not be favorable for active periglacial slope processes in the sierra nevada

kinematic analysis of faults in a physical model of growth faulting above a viscous salt analogue abstract syn sedimentary faults overlying an extended ductile layer within a sand model provide an analogue for studying some aspects of the geometry and kinematics of basin scale extensional listric faults associated with salt rollers the displacement analysis techniques used to examine displacement variations over fault surfaces within the sand model show that displacement varies in a regular and predictable manner deviations from simple fault displacement patterns are due to transfers of displacement onto adjacent synthetic faults aggregation of the displacements on adjacent synthetic faults produces more regular patterns of displacement distribution and demonstrates the geometric coherence of the aggregated faults rapid upward decreases in displacement on the model faults are due to fault growth during sedimentation elsewhere in the model post sedimentary faulting is associated with very low upward displacement gradients and pre and syn faulting sedimentation are readily distinguished on cross sectional fault traces in three dimensions a non horizontal line separating the pre faulting and syn faulting sequences tracks the lateral extent of a fault through time backstripping of fault displacements by subtracting the fault displacement of a sedimentary horizon from the displacements of underlying horizons gives the displacement distribution on a fault surface at the time of deposition of the backstripped horizon backstripped fault displacement distributions also allow examination of the general fault structure through time backstripping of fault displacements on one of the larger faults within the model and on an associated hanging wall synthetic splay shows that the two structures originated as a relay zone which was breached by lateral propagation of one of the overlapping faults which form the relay zone the backstripping technique allows determination of the geometrical changes during growth of a fault system

incremental growth of normal faults insights from a laser equipped analog experiment we conducted a laser equipped analog experiment aimed at quasi continuously monitoring the growth of a dense population of normal faults in homogeneous conditions to further understand the way geological faults progressively gain in slip and length as they accumulate more strain we measured with great precision the incremental slip and length changes that the analog faults sustain as they grow these measurements show that the analog faults share common features with the natural ones in particular during their growth the faults develop and maintain cumulative slip profiles that are generally triangular and asymmetric the growth takes place through two distinct phases an initial short period of rapid lateral lengthening followed by a longer phase of slip accumulation with little or no lengthening the incremental slip is found to be highly variable in both space along the faults and time resulting in variable slip rates in particular short and long term slip rates are markedly different we also find that slip measurements at local points on fault traces do not contain clear information on the slip increment repeat mode finally while the fault growth process is highly heterogeneous when considered at the scale of a few slip events it appears homogeneous and self similar at longer time scales which integrate many slip increments this is likely to be the result of a feedback between stress heterogeneities and slip development the long term scale homogeneity also implies that the long term faulting process is primarily insensitive to the short term heterogeneities that are rapidly smoothed or redistributed we propose a new conceptual scenario of fault growth that integrates the above observations and we suggest that faults grow in a bimodal way as a result of a self driven and self sustaining process

growth and linkage of the east tanka fault zone suez rift structural style and syn rift stratigraphic response abstract an integrated tectono stratigraphic analysis of the east tanka fault zone suez rift indicates fault growth by linkage of initially isolated fault segments that is consistent with fault growth models based on displacement length d l scaling laws during the initial 2 4 ma of rifting the east tanka fault zone was composed of two en echelon fault segments c 1 1 5 km long separated by a hanging wall intrabasin high that controlled the geometry of depocentres filled with continental deposits alluvial fan conglomerates were fed through the region between the two fault segments and form a discrete coarse grained body preserved in the immediate hanging wall of the fault zone subsequent stratigraphic patterns indicate that the two faults hard linked to form a single fault zone c 3 5 km long hard linkage of the segments resulted in migration of the zone of maximum displacement and subsidence into the zone of linkage uplift due to the migration of activity caused modification of drainage in the footwall of the fault zone that terminated the growth of the alluvial fan this study demonstrates the need to integrate structural and stratigraphic data when attempting to reconstruct the temporal and spatial evolution of normal fault zones additionally the fault dynamics illustrated have implications for tectono stratigraphic models of rift basins and syn rift stratigraphic evolution

progressive localisation of strain during the evolution of a normal fault population abstract the evolution of a syn sedimentary normal fault population has been established from the analysis of a high quality 3d seismic reflection survey from the timor sea offshore nw australia growth of the fault population which initiated ca 6 ma ago occurred in three distinct but temporally overlapping stages the initial stage of fault population evolution was characterised by rapid growth of fault length in the first 1 2 ma of extension displacement rates of individual faults were established during this stage and were constant throughout subsequent fault growth the second stage involved amplification of fault displacements on existing fault traces with minimal fault propagation during the third stage shortening of the traces of active faults and high mortality rates for small faults resulted in a net decrease in fault trace length on successively younger horizons this stage was accompanied by a declining extension rate fault throw populations have constant slopes on each syn faulting horizon however an up sequence shallowing of the slope of length and geometric moment populations demonstrates a progressive concentration of strain onto fewer and larger faults through time if extension were to continue beyond the present value of 4 5 this strain localisation might culminate in the formation of a single active through going fault

lateral propagation of the surface trace of the south alkyonides normal fault segment central greece its impact on models of fault growth and displacement length relationships abstract the evolution of deformed marine terraces and drainage systems have been examined in order to investigate the growth and lateral propagation of an active normal fault geological mapping has revealed three distinct raised marine terraces in the immediate footwall of the western end of the active south alkyonides fault segment safs gulf of corinth central greece we correlate these terraces with sea level highstands at 125 240 and 330 ka using elevation estimates of the inner edges of the terraces we show that uplift rates decrease towards the perachora fault segment boundary at the western end of the safs analysis of terraces and drainage wind gaps in the footwall of the fault shows that the surface trace of the safs propagated westwards at a rate of 12 1 16 7 mm y over at least the last 330 ka whilst the surface trace length has increased analysis of the geometry and kinematics of fault slip suggests that fault length at depth has remained fixed implying progressive increase in the values for the displacement length ratio if this is correct growth is not self similar and fault length has been established early in the evolution of the system i e before 330 ka

snow control on active layer thickness in steep alpine rock walls aiguille du midi 3842 m a s l mont blanc massif since the early 2000s a remarkable amount of rockfalls has been observed in permafrost areas of the mid latitude mountain ranges concurrently to hot summers this study explores the seasonal thaw st in permafrost rock walls of the aiguille du midi site 3842 m a s l mont blanc massif we first analyse six years of temperature records in three 10 m deep boreholes against air temperature at and a four year time series of pictures showing the snow conditions on two rock faces then we test the sensitivity of the active layer against eight snow fall scenarios using the 1 d surface energy balance and heat conduction model cryogrid 3 forced by in situ measurements from a vertical face snow falls occur all the year round at this elevation and play an important role for the active layer thickness alt but the snow cover and its control are highly heterogeneous a long lasting of a snow cover during spring early summer delays the st and reduces the alt the thicker and the more spatially continuous is the snow cover the stronger are the delay and alt reduction convective clouds could also reinforce this pattern the summer at and heat waves are the dominant controlling factors of the alt but summer snow falls can sometimes persist for several days on the rock surface and reduce the effect of the heat waves active layer can thicken during the early fall except if the snow starts to accumulate on the rock surface and favours the refreezing the timing of the snow fall is the most critical parameter to determine the snow effect on the alt this study suggests that the characteristics of the bedrock and snow accumulation steepness surface roughness and sun exposure must be taken into account to better understand the formation and changes of the active layer and its possible implications for rockfall triggering

mountain permafrost development and challenges of a young research field an overview is given of the relatively short history important issues and primary challenges of research on permafrost in cold mountain regions the systematic application of diverse approaches and technologies contributes to a rapidly growing knowledge base about the existence characteristics and evolution in time of perennially frozen ground at high altitudes and on steep slopes these approaches and technologies include 1 drilling borehole measurement geophysical sounding photogrammetry laser altimetry gps sar surveying and miniature temperature data logging in remote areas that are often difficult to access 2 laboratory investigations e g rheology and stability of ice rock mixtures 3 analyses of digital terrain information 4 numerical simulations e g subsurface thermal conditions under complex topography and 5 spatial models e g distribution of permafrost where surface and microclimatic conditions are highly variable spatially a sound knowledge base and improved understanding of governing processes are urgently needed to deal effectively with the consequences of climate change on the evolution of mountain landscapes and especially of steep mountain slope hazards as the stabilizing permafrost warms and degrades interactions between glaciers and permafrost in cold mountain regions have so far received comparatively little attention and need more systematic investigation

supra salt normal fault growth during the rise and fall of a diapir perspectives from 3d seismic reflection data norwegian north sea abstract normal faulting and the deep subsurface flow of salt are key processes controlling the structural development of many salt bearing sedimentary basins however our detailed understanding of the spatial and temporal relationship between normal faulting and salt movement is poor due to a lack of natural examples constraining their geometric and kinematic relationship in three dimensions to improve our understanding of these processes we here use 3d seismic reflection and borehole data from the egersund basin offshore norway to determine the structure and growth of a normal fault array formed during the birth growth and decay of an array of salt structures we show that the fault array and salt structures developed in response to i late triassic to middle jurassic extension which involved thick skinned sub salt and thin skinned supra salt faulting with the latter driving reactive diapirism ii early cretaceous extensional collapse of the walls and iii jurassic to neogene active and passive diapirism which was at least partly coeval with and occurred along strike from areas of reactive diapirism and wall collapse our study supports physical model predictions showcasing a three dimensional example of how protracted multiphase salt diapirism can influence the structure and growth of normal fault arrays

lateral flow in a layered profile of an infinite uniform slope a numerical solution was used to calculate vertical infiltration of rainfall into a periodic layered profile of an infinite uniform slope the calculated pressure head distribution within the profile was then used to evaluate transient un saturated lateral flow in the slope which is not limited to the existence of an impervious barrier because of the pressure line distribution within the layers the horizontal component of the lateral flow changes direction from one layer to another as a result the net discharge across the profile can be directed upstream during the initial stages of infiltration into a relatively dry profile over longer times it is always directed downstream and its value is proportional to the slope this indicates that the layered soil profile behaves as an anisotropy media on the point scales and on the average for a two periodic layered profile the total volume that passes in the direction parallel to the slope is very nearly proportional to the square of the total rainfall and it is represented versus the accumulated rainwater by one curve for all rainfall intensities thus the total rainfall is controlling the rate of lateral flow rather than the rainfall intensity the thickness of the soil layers has only a secondary effect on lateral flow the net volume that moves horizontally is a potential source for water accumulation at concave parts of a regular slope this water accumulation can form saturated or near saturated wedges that may contribute to surface runoff generation at these partial areas for cases of low rainfall intensities and short ponding times these wet zones of the hillslope may also contribute massive recharge of water and chemicals if exist to groundwater in narrow columns

long term slip rates and fault interactions under low contractional strain wanganui basin new zealand the newly mapped kapiti manawatu fault system kmfs in southern north island new zealand accommodated 3 5 km of basement throw over the last 3 myr along strike throw profiles are generated using seven stratigraphic markers interpreted from seismic reflection profiles acquired 3 km apart the profiles are symmetrical about their point of maximum displacement and cumulative profiles suggest that the reverse fault system behaves coherently the kmfs originates from the reactivation of extensional structures with fault lengths remaining constant over time contractional deformation started at circa 1750 400 ka maximum dip slip rates along individual faults are 1 77 0 53 and 0 74 0 22 mm yr 1 for the 0 120 and 120 1350 ka periods respectively the maximum cumulative throw rates across the kmfs are 4 9 1 5 and 1 5 0 5 mm yr 1 for the same periods long term strain rates across the kmfs are 2 5 times smaller than strain rates in the forearc basin of the hikurangi subduction margin located less than 100 km to the east the faults of the kmfs may extend to depth and link with the subducted pacific plate

displacement loss on growth faults due to sediment compaction compaction models of normal growth faults combined with displacement data from a natural growth fault cape egmont fault new zealand are used to quantify the loss of displacement arising from compaction in circumstances where growth faults are blanketed and buried by compacting sediment in both footwall and hangingwall comparison of imposed tectonic displacements with the preserved displacements indicates that although the thicknesses of sand shale sequences may decrease by up to c 55 due to compaction associated losses in displacement on growth faults are typically 70 and post faulting burial is large i e km scale

deformed streams reveal growth and linkage of a normal fault array in the canyonlands graben utah we use the deformation of streams by the growth of active normal faults within the canyonlands graben of southeastern utah to constrain the displacement evolution of a fault array during segment interaction and linkage coupling fault displacement data with geomorphic analysis of present day streams and paleostreams permits sequential reconstruction of a three segment fault array from initial component segments to its final displacement geometry our results show that although segment interaction causes enhanced displacement addition at overlap zones postlinkage displacement accumulation is significant and permits array equilibration to a displacement length ratio characteristic of a single fault evidence of stream disequilibrium indicates that this postlinkage displacement addition was rapid compared to that during the fault interaction phase

evolution of a salt related listric growth fault near the d 1 well block 5605 danish north sea displacement history and salt kinematics abstract the top chalk surface and the tertiary sediments of the danish north sea are cut by only a few major faults which are often related to or controlled by the mobile zechstein salt a single listric growth fault the d 1 fault and its adjacent area have been mapped in detail in order to unravel the fault geometry and kinematics the spatial distribution of displacements and lateral dimensions of the fault are used to examine the interaction between salt movements and the evolution of the fault the displacement distribution on the fault is systematic with contours of equal displacement forming concentric semi ellipses centred on the point of maximum displacement with displacement decreasing upwards and laterally approaching the displacement configuration for the upper part of an ideal simple blind fault furthermore within the volume surrounding the fault vertical displacement shows similar contour patterns for the hangingwall and footwall respectively the lateral displacement variation during fault growth and reconstructed displacement geometries indicate that footwall uplift was mainly a result of salt flow despite the complicated nature of salt dynamics the evolution of the d 1 fault resulted in a systematic fault displacement geometry within the rock volume surrounding the fault

relay ramps as pathways for turbidity currents a study combining analogue sandbox experiments and numerical flow simulations unlike for subaerial settings the impact of subaqueous relay ramps on sediment dispersal is still poorly understood a combination of analogue laboratory experiments in a sandbox with numerical flow calculations is used to simulate relay ramp topographies on rifting continental margins and to analyse the resulting turbidity current pathways and their deposits various scenarios are investigated including inflow perpendicular and oblique to the relay ramp axis as well as flow constrained by an incised channel on the ramp and by a landward directed tilt of the ramp without channelling most sedimentation takes place on the basin floor because the bulk of the flow follows the steepest gradient down the fault and into the rift basin with a channel along the relay ramp significant flow occurs initially down the ramp axis but channel spillover and basinward ramp tilting combine to redirect much of the sediment down the fault slope into the basin when the relay ramp has a landward oriented tilt most of the current flows down the ramp and deposits its sediment load there and at the foot of the ramp however also here a considerable amount of the flow is shed over the hanging wall fault and into the basin forming a secondary depocentre while ponding redistributes thin deposits over a wider area of the basin the quantitative dependence of these results on the specific ramp geometries remains to be investigated further but may bear great importance for refined sedimentary models in subaqueous rifted settings as well as for hydrocarbon exploration therein 2009 the authors journal compilation 2009 international association of sedimentologists

active layer dynamics in three topographically distinct lake catchments in byers peninsula livingston island antarctica abstract topography exerts a key role in controlling permafrost distribution in areas where mean annual temperatures are slightly negative one such case is the low altitude environments of maritime antarctica where permafrost is sporadic to discontinuous below 20 40 m asl and continuous at higher areas and active layer dynamics are thus strongly conditioned by geomorphological setting in january 2014 we installed three sites for monitoring active layer temperatures across byers peninsula livingston island south shetland islands at elevations between 45 and 100 m the sites are situated in lake catchments lakes escondido cerro negro and domo that have different geomorphological and topographical conditions our objective was to examine the role of topography and microclimatic conditions in determining the active layer thermal regime in order to identify the factors that control geomorphic processes in these lake catchments at each site a set of loggers was installed to monitor air temperature at snow thickness swt and soil temperature st down to 80 cm depth mean annual air temperatures maat showed similar values in the three sites 2 7 to 2 6 c whereas soil temperatures showed varying active layer thicknesses at the three catchments the ground thermal regime was strongly controlled by soil properties and snow cover thickness and duration which is influenced by local topography geomorphological processes operating at the lake catchment scale control lacustrine sedimentation processes and both are dependent on the combination of topographical and climatic conditions therefore the interpretation of lake sediment records from these three lakes requires that soil thermal regime and snow conditions at each site be taken into account in order to properly isolate the geomorphological environmental and climatic signals preserved in these lake records

the effect of relay ramps on sediment routes and deposition a review abstract a better understanding of the interplay between rift basin evolution and sediment transport paths can improve the success rate of locating hydrocarbon reservoirs at passive rift margins this paper reviews the current knowledge and suggests future research directions relay ramps at extensional basin margins can form drainage entry points if tectonic activity exceeds sedimentation and incision rates leading to a diversion of sedimentary flow paths towards the ramp during base level lowstands channels and canyons may incise into the relay ramp and provide flow paths from the basin margin into the basin their orientation and geometry mainly develops as a response to faulting and fracturing and their activity is influenced by base level fluctuations flow constraints such as channels parallel to the ramp axis direct flows to the foot of the relay ramp where sediment accumulates in response to the basin topography in subaqueous settings however turbidity currents are likely to spill at least partly over channel levees and flow down the fault slope into the basin depositing its load adjacent to the en echelon boundary faults channels and canyons with oblique and perpendicular orientations to the boundary faults can funnel flows down the hanging wall fault onto the basin floor by passing the relay ramp the prevalent basinward tilt of relay ramps can direct unconstrained subaqueous gravity flows also directly into the basin in subaerial settings the duration of channel activity in relation to relay ramp evolution strongly depends on the ratio between flow incision rates and tectonic uplift drainage direction on the footwall may revert if footwall uplift exceeds incision rates and the feeding of former depocentres terminates in the course of rift margin development relay ramp bounding faults may link causing the breaching of relay ramps and eventually their burial the effect of continued rifting on ramp remnants and associated syn rift deposits however is not sufficiently known and needs further investigation

active layer thermal monitoring of a dry valley of the ellsworth mountains continental antarctica abstract the ellsworth mountains are located along the southern edge of the ronne filchner ice shelf and are subdivided by the minnesota glacier into the heritage range to the east and the sentinel range to the west figure 1 the climate of the ellsworth mountains is strongly controlled by proximity to the ronne filchner ice shelf and elevation the entire ice free area is underlain by continuous permafrost of unknown thickness most in the form of dry permafrost active layer depths in drift sheets of the ellsworth mountains range from 15 to 50 cm detailed knowledge on antarctic permafrost is patchy especially at the continent two adjacent active layer monitoring sites were installed at mt dolence ellsworth mountains in the summer of 2012 two dry valley soils at mt dolence area on quartzite drift deposits were studied i a convex slope site exposed to the wind lithic haplorthel 886 m asl 5 cm 10 cm 30 cm and a sheltered concave slope site protected from winds lithic anhyorthel 850 m asl 5 cm 10 cm 30 cm data was recorded at hourly intervals from january 2nd 2012 until december 29th 2013 the soil climate temperature at 5 cm reaches a maximum daily mean in late december reaching a minimum in mid july at both sites active layer thickness reaches a maximum of 48 4 cm at p1 on january 17th 2013 and 47 8 cm at p2 on january 7th 2012 the soil thermal regime at the dry valley of mt dolence ellsworth mountains is characteristic of cold desert affected by dry frozen permafrost although air temperature does not reach elevated positive values variations in soil temperature are intense showing the soil s response to solar radiation the origins of typical surface periglacial features and landform on the widespread ellsworth drifts may be inherited from past events of warmer climates since liquid water is unlikely to play any significant role under the present climate

evaluation of frozen ground conditions along a coastal topographic gradient at byers peninsula livingston island antarctica by geophysical and geoecological methods abstract geophysical surveying and geoelectrical methods are effective to study permafrost distribution and conditions in polar environments geoelectrical methods are particularly suited to study the spatial distribution of permafrost because of its high electrical resistivity in comparison with that of soil or rock above 0 c in the south shetland islands permafrost is considered to be discontinuous up to elevations of 20 40 m a s l changing to continuous at higher altitudes there are no specific data about the distribution of permafrost in byers peninsula in livingston island which is the largest ice free area in the south shetland islands with the purpose of better understanding the occurrence of permanent frozen conditions in this area a geophysical survey using an electrical resistivity tomography ert methodology was conducted during the january 2015 field season combined with geomorphological and ecological studies three overlapping electrical resistivity tomographies of 78 m each were done along the same profile which ran from the coast to the highest raised beaches the three electrical resistivity tomographies are combined in an electrical resistivity model which represents the distribution of the electrical resistivity of the ground to depths of about 13 m along 158 m several patches of high electrical resistivity were found and interpreted as patches of sporadic permafrost the lower limits of sporadic to discontinuous permafrost in the area are confirmed by the presence of permafrost related landforms nearby there is a close correspondence between moss patches and permafrost patches along the geoelectrical transect

segmentation and growth of an obliquely reactivated normal fault abstract detailed kinematic analysis of a large 1800 m maximum displacement reactivated normal fault in the taranaki basin new zealand has been conducted using high quality 3d seismic data the parihaka fault is approximately north south striking in basement where it accrued late cretaceous to early eocene displacements in response to east west extension and was obliquely reactivated by nw se extension in the pliocene reactivation resulted in upward propagation newly formed segmentation and up dip clockwise rotation of the fault surface by up to 20 from the strike of the basement fault fault segmentation and map view soft linkage by relay zones in post miocene strata was synchronous with the formation of antithetic faults in late miocene strata at bends in the fault surface fault segment lengths antithetic faults and relay zone dimensions were formed geologically instantaneously during initial reactivation of the main fault at 3 7 3 4 ma i e within the first 10 of faulting rapid formation of pliocene fault segments is followed by displacement accumulation without an increase in fault segment length until eventual relay breaching when continued ramp rotation is unsustainable this evolutionary history is consistent with a model in which arrays of fault segments are from inception components of a single coherent structure

growth and linkage of a segmented normal fault zone the late jurassic murchison statfjord north fault northern north sea abstract the structure of the 25 km long northeastern portion of the murchison statfjord north fault zone and adjacent syn rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c 30 5 myr of late jurassic north sea rifting based on a structural analysis d d data alone approximately 14 precursor fault strands are identified incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution three main stages in the evolution of the fault zone are recorded in the syn rift stratigraphy and are biostratigraphically constrained these are 1 following initiation of rifting six isolated fault strands developed each 9 km long fault segments separated by a 2 km wide relay ramp that controlled the stratigraphy for at least the following c 10 5 myr and 3 the two fault segments hard linked forming a single continuous fault trace during the final c 7 myr of rifting the results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones the results may also help to further constrain models of fault evolution

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

extensional fault propagation folding in mechanically layered rocks the case against the frictional drag mechanism abstract fault drag deflection of beds or other markers into folds that are convex in the direction of relative slip is often interpreted as the product of frictional sliding along a fault and progressive tilting of beds with increased amount of displacement along a fault we analyze two sets of normal faults with throws ranging from 0 5 m to 5 m and associated fault related folds in mechanically layered upper cretaceous carbonate anhydrite and shale in central texas for each fault set we interpret the fault displacement and fault related folds exposed in outcrop to represent different stages in the developmental sequence in both fault sets faults in dolostone or limestone lose displacement and tip into less competent anhydrite or shale where deformation is accommodated by folding and smaller scale deformation fold wavelength is established early and at small displacement

growth of a normal fault system observations from the lake malawi basin of the east african rift abstract we have studied the growth history of the usisya normal fault system which bounds the west side of the lake malawi basin one of the largest rift basins in the east african rift system the lake malawi rift basin is a complex of intrabasins and intrabasin highs formed by three major fault segments each about 100 km in length the basin has been actively subsiding since the late miocene and has a maximum depth of about 3 km unlike the majority of previous studies of fault systems we are able to define the temporal evolution of this fault system using the patterns of sediment infill this is due almost exclusively to the availability of a high density seismic reflection network in combination with several clearly identifiable temporal marker beds an analysis of the seismic reflection data reveals that growth of the basin bounding faults occurred in the following sequence 1 in the early stages of rifting starting about 8 6 ma the northern fault was the most active 2 then extension shifted to the southernmost fault segment and lasted until about 2 5 ma 3 during the interval between about 2 3 ma and 1 6 ma the central segment was most active prior to the last interval the central segment accrued the least total displacement of the three segments this contradicts the common notion that the location of maximum displacement remains at a fixed location from fault inception or that the largest fault in any population of faults always maintained the highest displacement rate consistent with observations on smaller faults there is a marked increase in the displacement gradient on individual faults in the regions of overlapping segments although there is an observable asymmetry in individual segment displacement profiles there is a clear evolution toward a flattened bell shaped total displacement profile for the fault system that is consistent with the shape and scaling relationships of displacement vs length that are observed on a wide range of individual normal faults this suggests that the irregularities in the shape and scaling relationships observed in complex fault systems will eventually smooth out moreover the observed growth pattern suggests that the profile of the fault system will progress toward that of isolated faults provided the system is allowed sufficient time to evolve this in turn describes a process for maintaining a self similar scaling observed in large populations of faults which span several orders of magnitude in fault length

thermal regimes at the snow ground interface and their implications for permafrost investigation abstract snow cover is a critical factor determining the presence or absence of permafrost in mid latitude high mountain regions this paper discusses the relation between temporal changes in temperature at the snow ground interface and permafrost distribution four fundamental types of temporal change in winter ground surface temperature gst are identified 1 nearly constant at 0 c 2 short term fluctuation 3 gradual increase without short term fluctuation and 4 gradual decrease without short term fluctuation the latter three are favorable for permafrost growth and result from direct cold penetration throughout winter ground cooling before the onset of seasonal snow cover and cold air funneling and concentrating in voids between coarse blocks respectively the fourth thermal effect predominantly contributes to growth of permafrost and thus should be included in the bottom temperature of snow cover bts concept which involves mainly the third effect monitoring gst over a winter provides a new tool for investigating the distribution of permafrost as well as information on the thermal regimes that control permafrost development

nucleation growth and linkage of faults in oblique rift zones results from experimental clay models and implications for maximum fault size we use scaled clay models to study the temporal evolution of fault populations in experiments of moderately oblique a5 608 and highly oblique a5 308 distributed extension where a is the angle between the rift axis and the direction of displacement faults nucleate at random heterogeneities enhancing nucleation of diffuse clusters of new faults in the highly oblique model clusters of displacement normal faults form parallel arrays leading to fault growth dominated by tip propagation and along strike linkage until maximum length is achieved subsequent growth of rift subparallel faults leads to a phase of growth characterized by linkage and formation of branching faults in the moderately oblique model clusters form in a stepping geometry leading to growth dominated by linkage faults nucleate and grow more rapidly and their growth is less restricted than in the highly oblique model our results have implications for the maximum size earthquake to be expected in an oblique rift setting

fault growth by linkage observations and implications from analogue models abstract using time sequence analyses of extensional fault models we demonstrate the pivotal role played by fault segmentation in the accumulation of displacement and length during the growth of faults experiments are described in which incremental steps during the development of individual faults have been reconstructed from time lapse photographs taken during model deformation these records confirm the composite segment hierarchy of fault structure a pattern that is frequently recognised in many natural arrays they reveal the progressive enlargement of individual faults to be the product of a repetitive cycle of tip line propagation overlap and linkage between nearest neighbours by contrasting the displacement patterns of successive increments during growth convincing evidence is also presented to suggest that individual segments of faults may remain kinematically independent once they are physically linked this behaviour is shown to be responsible for the characteristic saw tooth patterns often recognised in strike parallel fault displacement profiles such patterns are believed to arise where relict segment boundaries remain preserved as asperities to slip so that displacement is confined to discrete parts of a fault plane surface growth in this way also causes the maximum displacement d and surface length l of faults to continually change by different proportions incremental displacement records presented here corroborate field evidence which shows that linkage between fault segments during growth is responsible for a significant component of the spread of values often recorded in d versus l compilations finally we speculate that linkage between fault segments also accounts for transient irregularities recorded in the frequency distribution of the fault length populations of each model

the growth and propagation of synsedimentary faults abstract offset of each syn fault horizon across a synsedimentary i e growth fault records the throw subsequent to its deposition allowing successive growth stages of a fault to be determined this technique has been applied to synsedimentary faults mapped on 3d seismic datasets to distinguish between faults which propagated laterally during growth faults which did not propagate laterally for significant growth periods and faults in which the lateral dimensions of the active surface decreased during their growth these different fault tip line behaviours result in characteristic lateral and dip parallel fault displacement variations fault propagation rates have been measured for 10 fault tips the maximum propagation rate is 15 km my for gravity driven faults and 3 km my for tectonically driven faults rates of fault propagation decrease with elapsed time from the initiation of faulting with tip line stasis and retreat becoming dominant in the later stages of fault growth static and retreating lateral tip lines are associated with overlap of the fault strain field with that of a neighbouring fault most often with the formation of a fault relay zone

syndepositional faulting in the gres d annot formation se france high resolution kinematic analysis and stratigraphic response to growth faulting

3d seismic characterisation of an array of blind normal faults in the levant basin eastern mediterranean the geometry throw distribution and kinematics of an array of blind normal faults were investigated using a high resolution 3d seismic dataset located in the levant basin offshore israel to establish criteria allowing true blind faults to be distinguished from minor synsedimentary faults a detailed analysis of throw distribution on the fault planes shows that the displacement exhibits a crudely concentric pattern about a maximum region located centrally on a fault plane as expected for ideal blind faults however vertical displacement profiles do not exhibit classical linear or triangular profiles but are mostly flat topped or hybrid in type comparison of unrestricted blind faults to those that interacted with a mechanical boundary or another structure suggests that such interactions significantly modify the throw spatial distribution on a fault plane to distinguish small synsedimentary faults from blind faults we use a combination of three criteria to assess whether a fault grew by blind propagation 1 plunging upper tip region and complementary pattern in the throw contours 2 presence of upper tip propagation fold and 3 absence of stratigraphic evidence that the fault interacted with the free surface

the role of aridification in constraining the elevation range of holocene solifluction processes and associated landforms in the periglacial belt of the sierra nevada southern spain climate variability during the mid late holocene has influenced the activity of geomorphic processes in the current periglacial belt of the sierra nevada we studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi arid massif solifluction landforms and mountain lake sediments lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp although present day climate conditions do not promote active solifluction processes in the sierra nevada colder and wetter periods during the holocene triggered solifluction and transported coarse grained sediments into the lakes by contrast warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys diminishing the grain size of the particles reaching the lakes lake sediments record an aridification trend in the massif intensifying since 4 2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations during major cooler phases such as the little ice age active solifluction was recorded back down to 2500 m altitude copyright 2010 john wiley sons ltd

solifluction rates processes and landforms a global review abstract field data on the rates of solifluction and associated parameters are compiled from the literature in an attempt to evaluate factors controlling the spatial variability in solifluction processes and landforms with special attention on the climate solifluction relationship the analyzed data originate from 46 sites over a wide range of periglacial environments from antarctic nunataks to tropical high mountains solifluction broadly defined as slow mass wasting resulting from freeze thaw action in fine textured soils involves several components needle ice creep and diurnal frost creep originating from diurnal freeze thaw action annual frost creep gelifluction and plug like flow originating from annual freeze thaw action and retrograde movement caused by soil cohesion the depth and thickness of ice lenses and freeze thaw frequency are the major controls on the spatial variation in solifluction processes near the warm margin of the solifluction affected environment diurnal freeze thaw action induces shallow but relatively rapid movement of a superficial layer 5 10 cm thick on average often creating the thin stone banked lobes typically seen on tropical high mountains in addition to diurnal movement annual frost creep and gelifluction may occur on slopes with soil climates of seasonal frost to warm permafrost dislocating a soil layer shallower than 60 cm at a rate of centimeters per year and eventually producing medium size solifluction lobes in high arctic cold permafrost regions two sided freezing can induce plug like flow of a soil mass 60 cm or thicker the correlation between process and landform suggests that the riser height of lobes is indicative of the maximum depth of movement and prevailing freeze thaw type climate change may result in new different ground freezing conditions thereby influencing the surface velocity and maximum depth of soil movement soil moisture and topography also control solifluction high moisture availability in the seasonal freezing period enhances diurnal freeze thaw action and subsequent seasonal frost heaving the latter contributes to raising the moisture content of the thawed layer and promotes gelifluction during the thawing period the slope angle defines the upper limit of the surface velocity of solifluction a diagram correlating the potential frost creep with the actual surface velocity permits an inter site comparison of the relative magnitude of solifluction components physically based modelling of periglacial slope evolution requires synthetic and more detailed field monitoring and laboratory simulations of solifluction processes

growth of normal faults in multilayer sequences a 3d seismic case study from the egersund basin norwegian north sea abstract we investigate the structural style and evolution of a salt influenced extensional fault array in the egersund basin norwegian north sea through analysis of 3d reflection seismic and well data analysis of fault geometry morphology throw distribution and syn kinematic strata reveal an intricate but systematic style of displacement and growth suggesting an evolution of 1 initial syn sedimentary fault growth contemporaneous with salt mobilization initiated during the late triassic 2 cessation of fault activity and burial of the stagnant fault tips and 3 subsequent nucleation of new faults in the cover above contemporaneous salt re mobilization initiated during the late cretaceous with downward propagation and linkage with faults stage 3 was apparently largely controlled by salt mobilization in response to basin inversion as reactivated faults are located where the underlying salt is thick while the non reactivated faults are found where salt is depleted based on the 3d throw analyses we conclude that a combination of basement faulting and salt re mobilization is the driving mechanisms behind fault activation and reactivation even though the sub and supra salt faults are mainly geometrically decoupled through the salt a kinematic coupling must have existed as sub salt faults still affected nucleation and localization of the cover faults

stratigraphic classification of ancient lakes balancing tectonic and climatic controls lakes and lake deposits present two fundamental paradoxes 1 modern lakes are vastly complicated but the rock records of lakes are relatively simple extensive observations reveal three distinct facies associations of common and widespread occurrence these are referred to here as fluvial lacustrine fluctuating profundal and evaporative facies associations 2 most explanations of modern and ancient lakes attribute their nature to climate but neither modern lake parameters lake size depth and salinity nor the character of ancient lake strata thickness extent lithology correlate with measured or inferred climatic humidity we propose that it is the relative balance of rates of potential accommodation mostly tectonic with sediment water fill mostly a function of climate that controls lake occurrence distribution and character lake basins may be termed overfilled balanced fill or underfilled depending on the balance between these rates we conclude that climate and tectonics exert coequal influence on lake deposits at both mesoscales 1 m to hundreds of meters and macroscales hundreds to thousands of meters

active layer thermal dynamics at two lithologically different sites on james ross island eastern antarctic peninsula abstract the active layer thermal regime was studied at two sites with different lithological properties located on james ross island eastern antarctic peninsula to assess the main driving factors the abernethy flats site 41 m a s l is located in cretaceous calcareous sandstones and siltstones of the santa marta formation in contrast the berry hill slopes site 56 m is composed of muddy to intermediate diamictites tuffaceous siltstones to fine grained sandstones of the mendel formation the data of air temperature at 2 m and ground temperature at two 75 cm deep profiles were analysed for the period 1 january 2012 to 31 december 2014 small differences were found when comparing mean air temperatures and ground temperatures at 5 50 and 75 cm depths in the period 2012 2014 while the mean air temperatures varied between 7 7 c and 7 0 c the average ground temperatures oscillated between 6 6 c and 6 1 c at 5 cm 6 7 c and 6 0 c at 50 cm and 6 9 c and 6 0 c at 75 cm at abernethy flats and berry hill slopes respectively the increasing difference of ground temperature with depth and a significant difference in active layer thickness 52 to 64 cm at abernethy flats and 85 to 90 cm at berry hill slopes respectively suggests the significant effect of lithology the higher proportion of fine particles and more thermally conductive minerals together with higher water saturation has been found to be fundamental for higher active layer thickness documented at berry hill slopes

recent shallowing of the thaw depth at crater lake deception island antarctica 2006 2014 abstract the western antarctic peninsula region is one of the hot spots of climate change and one of the most ecologically sensitive regions of antarctica where permafrost is near its climatic limits the research was conducted in deception island an active stratovolcano in the south shetlands archipelago off the northern tip of the antarctic peninsula the climate is polar oceanic with high precipitation and mean annual air temperatures maat close to 3 c the soils are composed by ashes and pyroclasts with high porosity and high water content with ice rich permafrost at 0 8 c at the depth of zero annual amplitude with an active layer of about 30 cm results from thaw depth ground temperature and snow cover monitoring at the crater lake calm s site over the period 2006 to 2014 are analyzed thaw depth td was measured by mechanical probing once per year in the end of january or early february in a 100 100 m with a 10 m spacing grid the results show a trend for decreasing thaw depth from ci 36 cm in 2006 to 23 cm in 2014 while maat as well as ground temperatures at the base of the active layer remained stable however the duration of the snow cover at the calm s site measured through the snow pack factor sf showed an increase from 2006 to 2014 especially with longer lasting snow cover in the spring and early summer the negative correlation between sf and the thaw depth supports the significance of the influence of the increasing snow cover in thaw depth even with no trend in the maat the lack of observed ground cooling in the base of the active layer is probably linked to the high ice water content at the transient layer the pyroclastic soils of deception island with high porosity are key to the shallow active layer depths when compared to other sites in the western antarctic peninsula wap these findings support the lack of linearity between atmospheric warming and permafrost warming and induce an extra complexity to the understanding of the effects of climate change in the ice free areas of the wap especially in scenarios with increased precipitation as snow fall

an alternative model for the growth of faults conventional growth models suggest that faults become larger due to systematic increases in both maximum displacement and length we propose an alternative growth model where fault lengths are near constant from an early stage and growth is achieved mainly by increase in cumulative displacement the model reconciles the scaling properties of faults and earthquakes and predicts a progressive increase in fault displacement to length ratios as a fault system matures this growth scheme is directly applicable to reactivated fault systems in which fault lengths were inherited from underlying structure and established rapidly the model may also apply to some non reactivated fault systems near constant fault lengths during subsequent growth are attributed to retardation of lateral propagation by interaction between fault tips the model is validated using kinematic constraints from growth strata which are displaced by a system of reactivated normal faults in the timor sea nw australia

normal fault growth displacement localisation and the evolution of normal fault populations the hammam faraun fault block suez rift egypt abstract fault segment linkage migration of the locus of fault activity and displacement localisation were important processes controlling the late oligocene recent evolution of the normal fault population of the hammam faraun fault block suez rift initial fault activity was distributed across the fault block on fault segments that had attained their final length within 1 2 my of rifting these initial segments then either grew by increasing displacement and linked to form longer segmented fault zones or died during a rift initiation phase that lasted 6 8 my following this rift initiation phase displacement became localised onto 25 km long border fault zones bounding the fault block and many of the early high displacement intra block fault zones died following displacement localisation onto the major faults bounding the fault block the locus of maximum displacement continued to migrate with post middle miocene displacement focused on the western margin of the fault block this migration of fault activity between major crustal scale normal faults can be viewed in terms of strain localisation at the rift scale the results from this study question conventional fault growth models based on final displacement distributions and highlight the sequential nature of faulting on major normal faults bounding domino style tilted fault blocks

four dimensional analysis of the sembo relay system offshore angola implications for fault growth in salt detached settings subsurface mapping of several relay ramps from a raft related fault array in the lower congo basin offshore angola reveals a full spectrum of fault linkage styles a comprehensive three dimensional geometric and kinematic appraisal of a more complex relay system within the fault array the sembo relay system srs highlights differences with current structural models of relay ramp genesis evolution and breaching the srs is a rearward upper ramp breached relay system with a maximum fault overlap and spacing of 9500 and 3600 m 31 000 and 11 800 ft respectively this system is characterized by a structural geometry that becomes increasingly complex with depth as the relay system is gradually assimilated into the structural architecture of a separate and structurally deeper fault system a detailed kinematic appraisal of the srs indicates that the throw patterns on the frontal and rearward segments are intrinsically different throw backstripping reveals different initiation ages for the rearward and frontal segments of about 5 5 and 2 5 ma respectively mutual overlap is estimated to first occur about 2 5 ma at the 5 0 ma structural level with fault linkage and ramp breaching occurring subsequently the srs therefore represents a complex amalgamation of faults that have each developed independently at different times the genesis and evolution of the srs have been governed through time by both salt withdrawal and associated fault detachment histories in conjunction with increased congo fan progradation and sedimentation rates and phases of tectonic tilting of the underlying salt detachment surface

3d seismic analysis of the structure and evolution of a salt influenced normal fault zone a test of competing fault growth models abstract in this paper we determine the structure and evolution of a normal fault system by applying qualitative and quantitative fault analysis techniques to a 3d seismic reflection dataset from the suez rift egypt our analysis indicates that the october fault zone is composed of two fault systems that are locally decoupled across a salt bearing interval of late miocene messinian age the sub salt system offsets pre rift crystalline basement and was active during the late oligocene early middle miocene it is composed of four planar nw se striking segments that are hard linked by n s striking segments and up to 2 km of displacement occurs at top basement suggesting that this fault system nucleated at or more likely below this structural level the supra salt system was active during the pliocene holocene and is composed of four nw se striking listric fault segments which are soft linked by unbreached relay zones segments in the supra salt fault system nucleated within pliocene strata and have maximum throws of up to 482 m locally the segments of the supra salt fault system breach the messinian salt to hard link downwards with the underlying sub salt fault system thus forming the upper part of a fault zone composed of i a single amalgamated fault system below the salt and ii a fault system composed of multiple soft linked segments above the salt analysis of throw distance t x and throw depth t z plots for the supra salt fault system isopach maps of the associated growth strata and backstripping of intervening relay zones indicates that these faults rapidly established their lengths during the early stages of their slip history the fault tips were then effectively pinned and the faults accumulated displacement via predominantly downward propagation we interpret that the october fault zone had the following evolutionary trend i growth of the sub salt fault system during the oligocene to early middle miocene ii cessation of activity on the sub salt fault system during the middle miocene to early pliocene iii stretching of the sub and supra salt intervals during pliocene regional extension which resulted in mild reactivation of the sub salt fault system and nucleation of the segmented supra salt fault system which at this time was geometrically decoupled from the sub salt fault system and iv pliocene to holocene growth of the supra salt fault system by downwards vertical tip line propagation which resulted in downward breaching of the salt and dip linkage with the sub salt fault system the structure of the october fault zone and the rapid establishment of supra salt fault lengths are compatible with the predictions of the coherent fault model although we note that individual segments in the supra salt array grew in accordance with the isolated fault model our study thereby indicates that both coherent and isolated fault models may be applicable to the growth of kilometre scale basin bounding faults furthermore we highlight the role that fault reactivation and dip linkage in mechanically layered sequences can play in controlling the three dimensional geometry of normal faults

formation of segmented normal faults a 3 d perspective the interpretation of fault kinematics from geometric data is an essential step in developing an understanding of the growth of fault systems constraints on fault geometry are however often restricted to 2 d maps or cross sections in this article we consider the extent to which kinematic interpretations of faulting benefit from a 3 d rather than 2 d geometrical perspective concentrating on relay zones and segmented normal fault arrays we suggest that very different interpretations of their evolution arise from the recognition that the propagation directions of faults and fault segments will rarely be contained within the inspection plane of 2 d data a 3 d perspective favours an interpretation in which the segments of a fault array are kinematically interrelated from their initiation individual segments in such systems may link into a single fault surface out of the plane of inspection or may be unconnected in 3 d we argue that this interpretation which conflicts with the often suggested model of incidental overlap of originally isolated faults should be the preferred model for the generation and growth of segmented normal fault arrays