silurian deformation in eastern notre dame bay newfoundland eastern notre dame bay newfoundland is divided into five fault bounded terranes they are from north to south the twillingate terrane the chanceport terrane the new world island terrane the dildo run terrane and the port albert terrane the new world island terrane is characterized by fault repeated sequences of middle ordovician to early silurian turbiditic sandstones sansom formation and conglomerates goldson formation the chanceport terrane has a lower volcanic unit and an upper sedimentary unit consisting of red and green siltstones shales overlain by turdiditic sandstones this sequence is structurally overlain by a mafic and felsic volcanic unit the clastic sedimentary rocks of the chanceport new world island and port albert terranes best record the silurian deformation in the area silurian deformation is divided into two deformation events an early silurian d1 thrusting event and a late silurian d2 dextral ductile faulting event the early silurian joey s cove melange constrains th

redefinition of the wild bight group newfoundland implications for models of island arc evolution in the exploits subzone the wild bight group and correlative plutonic rocks of the south lake igneous complex comprise one of the accreted ordovician peri gondwanan oceanic terranes of the newfoundland appalachians recent field work and isotopic ages from the eastern wild bight group require that the stratigraphic sequence be redefined a package of bimodal volcanic rocks which forms the oldest part of the group and contains all of its volcanogenic massive sulphide deposits is redefined as the glovers harbour formation this formation is correlative with intra oceanic ophiolitic sequences elsewhere in the exploits subzone previous stratigraphic nomenclature for the upper wild bight group is largely retained although the lithological variation within and spatial distribution of the omega point seal bay brook and pennys brook formations are revised and the side harbour formation is included as part of the seal bay brook formation the upper wild bight group is interpreted to represent a second and distinct arc sequence

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

sediment slump structures a review of diagnostic criteria and application to an example from newfoundland abstract in the study of the history of deformed sedimentary rocks it is important that the cause of the deformation and the timing of deformation relative to metamorphic and tectonic events be assessed there is a continuous gradation between the deformation of freshly deposited sediments by gravitational forces and the deformation of well lithified sediments by tectonic forces so determining the degree to which gravity tectonism and lithification influenced deformation can be very difficult the characteristics that may be considered in determining the origin of deformational structures in sedimentary rocks can be divided into five categories ductile deformation structures 1 can provide definitive criteria for recognizing post lithification deformation but not pre lithification deformation this also holds for 2 brittle deformation structures and decollements overprinting of sediment reworking or remobilization structures 3 are the best criteria for recognizing pre lithification structures fabrics 4 can be very useful but are as yet poorly understood and there are misconceptions in the literature about what sort of fabrics are or are not found in unlithified sediments spatial relationships 5 may also tell us a great deal but are most useful when taken in conjunction with other types of evidence complex fold patterns in sandstones on farmer head north central newfoundland provide a case study for criteria that may be used to determine the degree of lithification during deformation although these folds have been interpreted as slump folds by earlier workers fabrics and spatial relationships point to a tectonic post lithification origin for the structures a conclusion which has significant implications for the interpretation of the regional geology

the parkfield prediction fallacy abstract the parkfield earthquake prediction is generally stated as a 95 probability that the next moderate earthquake there should occur before january 1993 that time limit is based on a two sided 95 confidence interval because at the time of the prediction 1985 it was already clear that the earthquake had not occurred prior to 1985 a one sided 95 confidence interval would have been more appropriate that confidence interval ended in october 1991 the parkfield prediction was based on an extrapolation of five of the six events in the 1857 to 1966 earthquake sequence the 1934 event was omitted because it did not fit the regularity exhibited by the other data the fallacy in the prediction is that it did not take account of other less contrived explanations of the parkfield seismicity e g not excluding the 1934 event even if the parkfield earthquake should occur in the near future it would be better explained by less contrived hypotheses

response of the san andreas fault to the 1983 coalinga nunez earthquakes an application of interaction based probabilities for parkfield 1 the parkfield cholame section of the san andreas fault site of an unfulfilled earthquake forecast in 1985 is the best monitored section of the world s most closely watched fault in 1983 the m 6 5 coalinga and m 6 0 nunez events struck 25 km northeast of parkfield seismicity rates climbed for 18 months along the creeping section of the san andreas north of parkfield and dropped for 6 years along the locked section to the south right lateral creep also slowed or reversed from parkfield south here we calculate that the coalinga sequence increased the shear and coulomb stress on the creeping section causing the rate of small shocks to rise until the added stress was shed by additional slip however the 1983 events decreased the shear and coulomb stress on the parkfield segment causing surface creep and seismicity rates to drop we use these observations to cast the likelihood of a parkfield earthquake into an interaction based probability which includes both the renewal of stress following the 1966 parkfield earthquake and the stress transfer from the 1983 coalinga events we calculate that the 1983 shocks dropped the 10 year probability of a m 6 parkfield earthquake by 22 from 54 22 to 42 23 and that the probability did not recover until about 1991 when seismicity and creep resumed our analysis may thus explain why the parkfield earthquake did not strike in the 1980s but not why it was absent in the 1990s we calculate a 58 17 probability of a m 6 parkfield earthquake during 2001 2011 index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 7260 seismology theory and modeling keywords coalinga earthquake parkfield stress change earthquake probability seismicity rate

flow pattern within a permian submarine slump recorded by oblique folds and deformed fossils ulladulla south eastern australia the flow pattern within a slump in permian marine rocks of the southern sydney basin australia is recorded by folds and deformed fossils abundant brachiopod and bryzoan fossils in the slumped rocks are relatively undeformed but fossil crinoid stems have been deformed by relative rotation of individual ossicles measurement of the strain indicates that the deformation of the crinoids is consistent with flexural flow folding within the slump previous models assume that curved slump fold axes remain parallel to the enveloping bedding surface of a slump sheet detailed measurements of the orientation of slump folds in this study found fold axes to be oblique to bedding which is interpreted as a result of folds plunging downward towards the flanks of the slump or slump lobes in the present model fold axes are not generally parallel to the strike of the fold axial surface and this can explain differences between the orientations of slump fold axes and axial surfaces when these are used as directional indicators of slump movement

u pb ages and tectono magmatic evolution of middle ordovician volcanic rocks of the wild bight group newfoundland appalachians the wild bight group and spatially associated south lake igneous complex form one of the ordovician oceanic terranes of the central mobile belt of the newfoundland appalachians an integrated study of these rocks involving detailed mapping geochemistry sm nd isotopic analyses and u pb geochronology has shown that there are two temporally and genetically distinct volcanic sequences within the wild bight group the younger sequence comprises a lower volcanic succession associated with coarse volcaniclastic rocks and an upper volcanic succession interbedded with argillite chert and minor greywacke the lower volcanic succession has calc alkaline affinties and isotopic evidence for minor crustal contamination it is interpreted to represent a volcanic arc formed in proximity to the gondwanan margin above an east dipping subduction zone the age of this volcanic sequence is confined to 472 3 ma by felsic tuffs which occur stratigraphically above and below it the upper volcanic unit has predominantly enriched tholeiitic to alkaline geochemical characteristics with isotopic signatures indicative of little or no crustal contamination and is interpreted to represent arc rifting the age of this sequence was determined indirectly by dating two geochemically related gabbro sills 472 9 ma and 471 4 ma this work shows that despite different lithologies and stratigraphic and structural relationships between early and middle ordovician sequences in the northern and southern exploits subzone they have undergone essentially the same tectono magmatic events the age constraints on the magmatic events in the wild bight group provide evidence for the timing of obduction of early ordovician oceanic sequences and the reversal of subduction polarity along the gondwanan margin suggested by previous workers resume le groupe de wild bight et le complexe de south lake des terrains associes constituent un des terranes oceaniques ordoviciens de la ceinture mobile centrale des appalaches de terre neuve une etude pluridisciplinaire de ces roches incluant la cartographie detaillee la geochimie les analyses isotopiques sm nd et la geochronologie u pb a demontre que le groupe de wild bight est forme de deux sequences volcaniques qui sont genetiquement et

wet sediment deformation in the upper ordovician point leamington formation an active thrust imbricate system during sedimentation notre dame bay north central newfoundland

the grenville front south of val d or quebec abstract the tectonometamorphic history of rock assemblages is unravelled throughout a 50 30 km strip across the grenville front the boundary between the superior and the grenville provinces in the canadian shield this was accomplished by applying geothermobarometric techniques to zoned garnets systematic analysis of garnetiferous assemblages revealed that 1 1 primary garnet grti cores grew during a high t low p metamorphic episode and 2 2 secondary garnet grtii cores as well as most of the grti rims grew during a low low t high p metamorphic episode the two sets of p t conditions can by comparison with available geochronological data be assigned to the kenoran late archaean and grenvillian mid proterozoic orogenies respectively a prominent ductile shear zone traverses the 50 30 km strip and divides the area southeast of the grenville front into two regions with contrasted tectonometamorphic behaviour the eastern region is composed of migmatitic and charnockitic gneisses representing intermediate to lower levels of the archaean crust the western region is composed of migmatitic metasediments which show no evidence of significant crustal thickening during the grenvillian orogeny along a transect across the grenville front eastern region significant offsets of grenvillian paleopressure levels indicate that the thickened crust is a stack of imbricated slices with vertical components of displacement in the order of several kilometres after compensating for the grenvillian movement along the appropriate shear zones offsets remain between some of the archaean paleopressure levels suggesting that delamination of the archaean crust was initiated prior to the peak of grenvillian metamorphism the thrust slices thus identified in the eastern region have thicknesses of a few kilometres but they could be much thinner in the western region here the grenville front is ill defined and lies in a zone of gradual transition between the pontiac group metasediments of the superior province and the lac lambert migmatites of the grenville province the overall deformations of the two regions southeast of the grenville front are incompatible and cause the development of an intervening shear zone although the two regions experienced different tectonometamorphic histories they both belong to the parautochthonous belt of the grenville orogen

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

southwest new world island stratigraphy new fossil data new implications for the history of the central mobile belt newfoundland the identification of fossils from 16 new localities on southwestern new world island has resulted in the refinement and simplification of local stratigraphy and in the correlation of rock units across an intensely deformed area complex stratigraphic classifications of earlier workers are replaced by a simpler scheme consisting of four formations the summerford formation oldest rogers cove formation sansom formation and goldson formation mclange units are fault related and cannot be included in the stratigraphy fossil and lithological data provided here confirm previous indications that the rocks of the summerford formation are the remains of a long lived volcanic island complex this complex is overlain by a markedly diachronous coarsening upwards sequence of marine clastic sediments now represented by the rogers cove sansom and goldson formations the new stratigraphic data combined with structural evidence indicate that the stratigraphy is repeated across several bedding parallel faults significant diachroneity of formation boundaries and the absence of syndepositional high angle faults suggest deposition in one large rnid paleozoic basin rather than in a number of small dynamic basins

distinguishing syn cleavage folds from pre cleavage folds to which cleavage is virtually axial planar examples from the cambrian core of the lower palaeozoic anglo brabant deformation belt belgium abstract within the cambrian jodoigne formation in the easternmost part of the anglo brabant deformation belt sub horizontal to gently plunging folds occur within the limbs of steeply plunging folds the latter folds are cogenetic with cleavage and are attributed to the brabantian deformation event in contrast although cleavage is also 1 virtually axial planar to the sub horizontal to gently plunging higher order folds shows 2 a well developed divergent fanning across these folds 3 an opposing sense of cleavage refraction on opposite fold limbs and 4 only very small cleavage transection angles an analysis of the cleavage bedding intersection lineation suggests that these higher order folds have a pre cleavage origin on the basis of a comparison of structural and sedimentological features these higher order folds are interpreted as slump folds the seemingly normal cleavage fold relationship across the slump folds within the limbs of the large steeply plunging folds is due to the very small angle between cleavage and bedding as such a normal cleavage fold relationship is no guarantee for a syn cleavage fold origin it is not unlikely that also within undeformed recumbent slump folds a well developed compaction fabric formed parallel to the axial surface of the slump folds may show fanning and contrasting senses of cleavage refraction on opposite fold limbs

large scale slumping deduced from structural and sedimentary features in the lower palaeozoic anglo brabant fold belt belgium distinguishing slump folds from tectonic folds in poorly exposed areas can be difficult especially when the scale of the slump folds exceeds outcrop scale in the southeastern part of the single phase deformed lower palaeozoic anglo brabant fold belt a comparison of cleavage fold relationships and stratigraphic polarity shows that a 200 m thick interval of middle caradoc fine grained turbidites in the core of a large synform was overturned prior to tectonic deformation this overturning is attributed to large scale slumping which was most likely a result of middle caradoc seismic activity the exposed portion of the large slump sheet contains only a few small slump folds and intraformational breccias making up less than 5 of the exposed thickness if the beds were not overturned large scale slumping would never be suspected and the small slump folds would probably be interpreted as localized features in an overall stable sedimentary pile this may explain why so few ancient large scale slides and slumps have been reported the small amount of internal deformation makes them very difficult to recognize especially when dealing with poorly exposed areas as such large ancient slides and slumps may be more common than suggested by the geological literature

new u pb zircon age constraints on the timing of deformation in north central newfoundland and implications for early paleozoic appalachian orogenesis u pb zircon ages of five felsic intrusions in eastern notre dame bay bracket the absolute ages of a number of key units and events in the newfoundland appalachians the age of 507 3 2 ma obtained for the twillingate pluton confirms an age obtained by earlier workers it strengthens evidence of widespread cambrian arc volcanism in newfoundland and places a lower limit on the initiation of deformation in central newfoundland the loon bay suite which includes the loon bay batholith and a swarm of quartz and feldsparphyric tonalite dikes has an age of 408 2 ma this age places a late silurian upper limit on the timing of thrust fauting and three generations of folding in the new world island area of notre dame bay this age also constrains the timing of sinistral ductile movement on the reach fault and of initiation of high angle brittle faulting in the region an age of 422 2 ma for a composite mafic and felsic dike on the port albert peninsula places an upper limit on the age of the botwood group in that area this age also supports the correlation between the botwood group and mixed felsic and mafic igneous rocks of the springdale group in western notre dame bay placed in context with the timing of other units and events in the newfoundland appalachians our ages show that the formation and deformation of tectonic terranes making up the orogen did not take place in an orderly sequential fashion instead at any one time more than one tectonic element was being generated subducted or deformed although the locus of strain varied within the orogen deformation occurred continuously from the late cambrian epoch until the end of the paleozoic era

seismic quiescence at parkfield an independent indication of an imminent earthquake the parkfield segment of the san andreas fault midway between san francisco and los angeles has experienced six moderate sized earthquakes since 1850 with an average recurrence time of about 22 years based on this regular behaviour and the occurrence of the most recent earthquake in 1966 a shock of local magnitude ml 5 7 is expected to occur by 19931 2 here we suggest that a current lack of small earthquakes on this segment could be a precursory anomaly to the next characteristic parkfield earthquake only four earthquakes of m 2 5 have occurred on the segment since january 1986 whereas twenty would have been expected extrapolating from the mean background rate comparison with other cases of precursory quiescence suggests that the m 5 7 earthquake should occur in the next two years rupturing the same 35 km fault segment that ruptured in 19663

time dependent changes in failure stress following thrust earthquakes two dimensional 2 d viscoelastic finite element models were used to calculate the time dependent changes in coulomb failure stresses following thrust earthquakes due to respective effects of relaxation of viscous lower crust or upper mantle and postseismic creep on the main fault or its downdip extension results suggest that thrust earthquakes cause a coseismic increase in coulomb stress along antithetic lobes normal to the slip plane following a quake creep processes that reduce stresses in a ductile lower crust or upper mantle are calculated to cause a transfer of stress to the upper crust under certain conditions transfer of stress may lead to a further buildup of high coulomb stress along the base of the upper crust potentially shortening the time to failure of other faults in the region the conditions under which an antithetic lobe of high coulomb stress are favored to expand at the base of the upper crust postseismically within a few decades include the following the lower crust or upper mantle has an effective viscosity not greater than 1019 pa s the thrust fault has a moderate dip angle 40 50 the brittle ductile transition is deep enough to provide a corridor at the base of the upper crust for expansion and the crust has a low apparent coefficient of friction 0 2 postseismic increases in coulomb stress within the upper crust may also be caused by aseismic creep on the fault stress changes due to this mechanism are maximized with a high apparent coefficient of friction analysis of experimentally determined non newtonian flow laws suggests that wet granitic quartz and feldspar aggregates may have a viscosity of the order of 1019 pa s the calculated rate of stress transfer from a viscous lower crust or upper mantle to the upper crust becomes faster with increasing values of the power law exponent and the presence of a regional compressive strain rate results of this 2 d analysis suggest a potentially important role of viscous flow in controlling time dependent postseismic stress changes that warrant further investigation using 3 d viscoelastic analysis

an integrated approach to the study of glaciolacustrine landforms and sediments a case study from hagavatn iceland abstract this paper describes the landform assemblage associated with the neoglacial fluctuation of hagafellsjokull eystri into proglacial hagavatn iceland this landform assemblage is dominated by three components firstly a series of moraines formed both by thrusting within the glacier margin and by proglacial subglacial deformation the internal sedimentary architecture of these moraines ranges from stacked sediment slabs separated by listric thrusts to complexly folded and faulted sequences all in glaciolacustrine sediments the second component is a morainal bank and associated ice contact delta the morainal bank consists of a series of low amplitude ridges composed of laminated silts and clays which have been deformed proglacially during the neoglacial ice advance 1890 this morainal bank helped stabilise the 1890 ice limit within the proglacial lake and was the focus for subaqueous outwash first in the form of a subaqueous out wash fan and subsequently as an ice contact delta the third component is a series of lake bed kame terraces formed by rapid sedimentation in a canal like lake formed as the ice retreated away from the push moraines a range of glaciolacustrine facies is present within the lake bed kame terraces and the sedimentary architecture records a complex pattern of ice marginal oscillations and changes in lake level this detailed case study provides an important analogue for the interpretation of both glaciolacustrine and glaciomarine landform sediment assemblages of pleistocene age and illustrates a range of styles of glaciolacustrine sedimentation and glaciotectonic deformation

the tectonics and depositional history of the ordovician and silurian rocks of notre dame bay newfoundland reply in the notre dame bay region ophiolitic rocks underlie a thick sequence of lower ordovician volcanic arc rocks to the north of the lobster cove chanceport fault neither this fault nor the lukes arm sops head fault shows evidence of very large strike slip movements as parts of the same arc together with much arc derived detritus straddle both faults towards the east this arc derived detritus becomes more distal in aspect and passes laterally into the dunnage melange during the middle ordovician epoch late llandeilo and early caradoc most areas show a marked decrease in volcanic activity and in the amount of coarse detritus deposited coarse turbidites reappear at different times in different areas during the late ordovician these are related to several fault bounded basins and to movements on the lukes arm sops head fault many of these faults particularly in the east are marked by olistostromes several of which can be dated by fossils as late ordovician and early silurian the whole

structural interpretation of the eastern notre dame bay area newfoundland regional post middle silurian thrusting and asymmetrical folding the structural geometry of the eastern notre dame bay area is that of an allochthonous sequence related to f1 thrusting and folding folded by f2 asymmetrical folds and offset by f3 related high angle faults f1 folds are isoclinal and commonly intrafolial f2 folds are asymmetrical generally tight with axial surfaces that dip 30 85 southeast the prominent northeast striking penetrative cleavage s2 is axial planar to f2 folds f3 structures include chevron folds box folds kink bands and local s3 crenulation cleavage f1 folds are overprinted by f2 folds producing coaxial and mushroom interference patterns this and the subhorizontal enveloping surface of f2 indicate that f1 folds were recumbent prior to f2 a zone of f1 folds separating silurian turbidites from subaerial volcanics on the port albert peninsula suggests f1 was related to macroscopic thrusting as does the association of f1 with mesoscopic thrust faults f2 folds are the most obvious structures in the area macroscopic examples in

structural evolution of a transpression zone in north central newfoundland abstract a dextral transpression zone in notre dame bay north central newfoundland was active in middle to late silurian times following the closure of a marginal basin the deformation in the transpression zone was complex and involved several generations of structures deformation was initially distributed over wide low strain zones through the formation of a penetrative regional cleavage with steepening and overturning of the strata the orientation of the sequence was favorable for strike slip bedding parallel movement and the deformation became more efficiently accommodated by shear within the incompetent lithologic horizons forming localized shear zones in high strain zones the sheared incompetent horizons define a belt of melange the boones point complex centered on the contact between a volcanic island arc terrane to the north and a marginal basin terrane to the south two cleavages with similar orientation and morphology were generated at different times during the structural evolution of the transpression zone one of the cleavages is regional in distribution and is transposed by the shear zones folds with no axial planar cleavage but a cleavage cutting obliquely across their hinges are reported they have the geometry of transected folds but are clearly the result of overprinting by a younger generation of cleavage

slump folds and early structures northeastern newfoundland appalachians re examined the bard island area bear path cove presents a well exposed section of complex fold styles that crop out in central notre dame bay newfoundland which have previously been interpreted as a good example of wet sediment deformation a re examination of this classic area shows that the deformation history was more complex than previously thought the earliest phase of deformation in the upper ordovician point leamington formation deep marine turbidites may have occurred while the sediment was semi and or unlithified whether this was a surficial product of slumping or stratigraphically deeper thrusting is not known the majority of structures around bard island are demonstrably the result of hard rock tectonic deformation with the imposition of the late silurian regional acadian d 2 deformation onto previously deformed d 0 d 1 late ordovician rocks the earliest tectonic hard rock folds f1 were westward closing recumbent folds with curvilinear subhorizontal axes n s trending

styles of soft sediment deformation on top of a growing fold system in the gosau group at muttekopf northern calcareous alps austria slumping versus tectonic deformation abstract styles of soft sediment deformation in a syngrowth coarse grained sediment gravity flow system are described from outcrops of the upper gosau subgroup of the northern calcareous alps the deepwater sediments were deposited along the flanks and top of growing folds beside load and fluid escape structures which are commonly found in sediment gravity flow systems soft sediment deformation is mainly related to fluidization of coarse grained beds and downslope gliding of meter thick sediment packages common structures affecting single or several beds are hydroplastic folding of fine grained beds in a coarse grained fluidized matrix symmetric or asymmetric mullions at the base of coarse grained beds and folding of heterolithic units into coarse grained beds folds have varying geometries and styles and fold axes are scattered soft sediment folds also affect thick sediment packages these folds are uniformly verging asymmetric metric to dekametric folds formed at different degrees of lithification rheology of sandstones in such folds ranges from ductile to semi brittle and brittle fold axes tightly cluster about one direction the first group of deformational structures is attributed to slump related deformation whereas the second group represents folds related to tectonic deformation a dislocation model and a shear zone model are used to interpret orientation of folds related to slump deformation this considers processes taking place on the scale of the whole slump sheet and within the shear zone at the base of gliding units both models predict rotation of fold axes toward the transport direction of the slump field data support that fold axes scatter either about the downslope transport direction or about the strike of the slope

mass transport deposits overprinted by contractional tectonics a case study from the southern apennines of italy mass transport deposits mtds created by gravity driven deformation of unlithified sediments and tectonic melanges produced by contractional deformation are characterized by a similar chaotic appearance it follows that distinguishing structures formed by soft sediment deformation during mass transport from those produced by contractional tectonics can be problematic in fact deformation occurring along detachment levels may completely obliterate the original sedimentary fabric although a number of advances have been made during recent decades field criteria for discriminating structures within mtds that are overprinted by later regional contraction are not readily applicable to all the exposed examples we address some of these general issues through a detailed case study of the monte facito formation in italy this triassic unit was formed during the africa europe continental separation and since the miocene has been involved in contractional deformation during the construction of the apennines the monte facito formation consists of a series of stratigraphically coherent units separated by chaotic and often deformed intervals whose origin has been previously attributed to either tectonic or sedimentary processes an example is provided by a characteristic pebbly mudstone or paraconglomerate which has been interpreted as either a triassic gravity flow deposit or alternatively as a product of shearing along regional contractional detachments during the miocene this detailed field based study allows us to recognize structures related to the depositional processes that created these chaotic intervals and which can therefore be interpreted as mtds we also discriminate structures connected to later contractional tectonics that locally produced intense reworking of the mtds