the interrelation of glaciotectonic and glaciodepositional processes within the glacial environment abstract in recent years it has been recognised that ice sediment coupling occurred beneath the quaternary ice sheets that advanced over the soft sediments of lowland areas this paper looks in detail at the effects of this coupling on the sediments which results in glaciotectonic deformation and also discusses the interaction of deformation and deposition within the subglacial environment two types of glaciotectonic deformation are discussed that are produced by the active movement of ice 1 proglacial tectonics at the margin which include compressive fold styles such as listric thrusts and faults and open folding 2 subglacial tectonics formed beneath the glacier which include fold styles resulting from simple shear and represent a soft rock purely dynamic shear zone styles of deformation associated with stagnant ice are also investigated we argue that glaciotectonic deformation is a common phenomenon and an integral part of geological record from continental ice sheets it is suggested that zones of deformation within the sediment are related to similar zones of strain in the ice sheet and complex deformation sequences are produced by the superimposition of these differing styles upon one another as the ice sheet advances and retreats it is also argued that subglacial deposition and deformation are related and that on soft beds underformed till is rare whilst deformed till is very common

basal ice facies and supraglacial melt out till of the laurentide ice sheet tuktoyaktuk coastlands western arctic canada glacially deformed massive ice and icy sediments mi is in the eskimo lakes fingerlands and summer island area of the tuktoyaktuk coastlands western arctic canada show in the same stratigraphic sequences features characteristic of both basal glacier ice and intrasedimental ice basal ice features comprise 1 ice facies and facies groupings similar to those from the basal ice layers of contemporary glaciers and ice sheets in alaska greenland and iceland 2 ice crystal fabrics similar to those from basal ice in antarctica and ice cored moraines on axel heiberg island canada and 3 a thaw or erosional unconformity along the top of the mi is buried by glacigenic or aeolian sediments intrasedimental ice consists of pore ice and segregated ice formed within pleistocene sands deposited before glacial overriding the co existence of basal and intrasedimental ice within the mi is records their occurrence within the basal ice layer of the laurentide ice sheet stagnation of the ice sheet and melt out of till from the ice surface allowed burial and preservation of the basal ice layer on a regional scale the widespread occurrence of supraglacial melt out till with clast fabrics similar to those in the underlying ice suggests that such till can be well preserved during partial thaw of a continental ice sheet in lowlands underlain by continuous permafrost

geometry and distribution of regional joint sets in a non homogeneous stress field case study in the ebro basin spain abstract three regional joint sets striking n s e w and wnw ese affect the tertiary rocks of the central ebro basin from analysis of their chronological relationships and spatial distribution it is concluded that they correspond to two different tectonic events the n s set oldest and the e w set younger are present in the southern and central sectors while the wnw ese joint set predominates in the northern one the n s joints propagated in response to joint normal and fluid loads under an intraplate stress field with shmax oriented near n s related to forces caused by the convergence of africa iberia and europe and rifting at the valencia trough during the sedimentary infilling of the basin these joints are only present in the southern part of the area the e w joint set in the southern central sector records the same fracturing event as the wnw ese set does in the northern one its orientation was modified by the presence of the older n s set in the south which perturbed the regional stress field the younger wnw ese and e w joint sets are interpreted as unloading joints these propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the pyrenees and the ebro foreland basin a numerical approach is used to explain the inhomogeneous distribution of the n s joint set in terms of their absence being controlled by the depth of the water table at the time of their formation

a model for deformation in long valley california 1980 1983 geodetic data collected in long valley california from 1975 through 1983 define a pattern of uplift and strain which is evidently associated with a sequence of earthquakes occurring in may 1980 and subsequent swarm activity continuing until the present we have constructed a model to explain the deformation observed since may 1980 in terms of inflation of two subsurface magma chambers faulting in the south moat region of the caldera and slip on the hilton creek fault the most significant new feature of the model is the shallow magma chamber at 5 km depth located a few hundred meters to the east of the casa diablo hot spring area inflation of this chamber causes stresses which show consistency with various aspects of the seismicity in the south moat of the caldera calculations of stress across vertical planes over the magma chamber can be used together with failure criteria to estimate the inflation volume at which the rock layers intervening between the chamber and the surface will fail by extensional fracture

palaeostress analysis of the northern nijar and southern vera basins constraints for the neogene displacement history of major strike slip faults in the betic cordilleras se spain this paper presents the results of a detailed structural analysis of the northern nijar and southern vera basins with special emphasis on the evolution of the regional stress field and the associated timing of movement of the serrata gafarillos and palomares strike slip fault zones these major fault zones control the neogene deformation of the se internal betic cordilleras in spain detailed stress analysis on neogene sediments of the vera and nijar basins shows a strike slip regime with nw se oriented subhorizontal maximum principal stress 1 during tortonian and earliest messinian times under the influence of this stress field dextral displacement along the n090e trending gafarillos fault zone resulted in deformation of the sediments of the southern sorbas and northeastern nijar basins during the early messinian a clock wise rotation of the stress field occurred stress analysis in rocks with late early messinian up to quaternary ages in the nijar and vera basins indicates a strike slip regime with n s oriented subhorizontal maximum principal stress 1 under the influence of this stress field the main activity along the n010e striking palomares strike slip fault zone took place resulting in deformation of the neogene sediments of the southeastern vera basin and culminating in a maximum sinistral displacement of more than 20 km at the same time the stress field was not suitably oriented to exert a large shear component on the gafarillos fault zone which activity ended after the earliest messinian fault and outcrop patterns of syntectonic neogene sediments in the vera basin show that displacement along the palomares fault zone decreased at the end of the middle miocene although minor displacement phases may still have occurred during the late miocene and possibly even pliocene from the middle miocene onward deformation in the nijar basin was controlled by sinistral displacement along the n040e trending serrata strike slip fault zone

the origin of deep buried channels of elsterian age in northwest germany buried channels cut to a depth of over 100m into the underlying substratum of north germany are almost exclusively of elsterian age evaluation of geophysical well logs in the hamburg area for the first time allows the construction of detailed longitudinal and transverse profiles it can be shown that an apparently chaotic infill known from borehole records in some cases is actually a regular sedimentary sequence fining from proximal to distal channel formation seems to have been the result of catastrophic meltwater release in the marginal parts of the ice sheet the channel infill reflects these episodic outbursts of meltwater during deglaciation the channel remnants became infilled with fine sediments the channels ceased to exist as morphologically detectable forms at the end of the holsteinian stage

use of a viscous model of till rheology to describe gravitational loading instabilities in glacial sediments this paper models the operation of loading rayleigh taylor instabilities in sediments using an effective pressure dependent viscosity such has been used to model the deformation of sediment beneath glaciers a particular feature is a strong increase of viscosity with depth resulting from the fact that the effective pressure increases with depth observations suggest that more than one wavelength is generally present e g diapirism and loadcasting which requires at least three layers with uniform properties to be present three layers permit wavelength growth maxima at two distinct wavelengths we investigate whether an effective pressure dependent rheology is consistent with rt instabilities and whether the non uniformity it produces is able to increase the number of growth rate maxima the investigation starts from the point where sediment in an underlying layer is less dense than the overlying sediment and the rayleigh taylor instability starts to operate the mechanics of two layers of finite thickness but infinite extent are modelled by the stokes equations the equation set is linearized and the fourier transform taken in order to describe the periodic horizontal variation of flow fields at a specified wavelength the influences of layer thickness and viscosity ratio on the flow fields are considered it is found that for a given wavelength layer thickness has a far stronger influence on flow fields than does viscosity ratio for all configurations inspected the dependence of growth rate on wavenumber exhibited one maximum meaning that a variable viscosity model does not produce multiple wavelengths maximum growth rates occur at wavelengths corresponding to the layer thicknesses we infer that loading instabilities occurring at wavelengths around the layer thicknesses are consistent with the effective pressure dependent viscous model

constraints on the preservation of diamict facies melt out tills at the margins of stagnant glaciers abstract this paper reviews the formation and preservation of diamict facies melt out till generated in situ by the downwasting of stagnant ice at the margins of continental glaciers melt out tills are commonly envisaged as being the product of the top supraglacial or bottom subglacial melt of stagnant debris rich glacier ice but such deposits are relatively uncommon in modern glacier environments where they are thin laterally discontinuous and have a low preservation potential theoretical considerations of the distribution of englacial debris in continental ice sheets show that only the glacier margin is likely to contain the necessary volumes of englacial debris for melt out to be a significant diamict forming process however the application of thaw consolidation theory to the formation of such deposits shows that substantial porewater pressures and self sediment deformations can be induced during melt out especially in matrix rich debris the classic melt out mechanism widely invoked in the literature since 1875 and involving passive in situ aggregation from thawing englacial debris can be seen to operate under restricted conditions diamict facies produced by melt out are likely to form spatially disjunct and laterally discontinuous elements within complex and ice marginal stratigraphics the melt out process is not a mechanism whereby regionally extensive diamiet ite units can be deposited across glaciated basins

synthesis of the quaternary in the almeria littoral neotectonic activity and its morphologic features western betics spain a sequence of marine and continental quaternary episodes is established as are their interrelationships the zone s tectonics have in most cases remained active to the present and control the factors all the tyrrhenian levels containing strombus bubonius are affected by the many faults that cross the lateral fringe and continue onto the shelf among these are the loma del viento fault n120 e a normal fault with certain leftward characteristics the el alquian faults n140 160 e which coincide according to several authors bousquet 1979 with the surface feature of a great dextral deep accident and the carboneras fault or the serrata fault n40 45 e left strike slip fault given the varying behaviour of the shoreline we have chosen to divide it into four sectors campo de dalias el alquian cabo de gata mojacar garrucha and campo de nijar serrata due to its geographical location no marine continental relationships exist in the latter a chart has been made in an attempt to synthesize the most significant stratigraphic genetic and tectonic characteristics of each sector lastly the influence of tectonics on the distribution and heights of the quaternary shorelines is clearly shown in a chart of the transgressive maxima of the tyrrhenian episodes

nucleation linkage and active propagation of a segmented quaternary normal dextral fault the loma del viento fault campo de dalias eastern betic cordillera se spain active faults from the campo de dalias se betic cordillera allow us to constrain the deformation styles involved in the development of segmented oblique slip faults this sector constitutes the widest outcrop of plio quaternary sediments in the northern boundary of the alboran sea it has emerged since the late pliocene and therefore provides recent deformation markers that are not disturbed by erosive processes the faults started to grow during the pleistocene reactivating previous hybrid joints with a normal dextral slip we present a detailed map of the largest fault in the area the loma del viento fault comprising six onshore segments based on field work and aerial photography the distributions of the contiguous joints have been mapped and the joints reactivated as faults are identified some of these fault segments are hard linked and fault slip enhances toward the linkage sectors between them with associated sedimentary depocenters an electrical tomography profile reveals the wedge geometry of a unit of pleistocene conglomerates and red silts that were coevally deposited during the fault movement long term slip rate in the central part of the fault is estimated at 0 07 0 03 mm y in addition a seismic crisis nucleated close to the loma del viento fault during november 2010 was recorded moment tensor analysis of the two mainshocks mw 3 5 and 4 2 provides a focal solution indicating a n120 e striking right lateral strike slip fault the corrugated morphology of the loma del viento fault may have influenced its seismic behavior some of the fault segments are oblique to the general motion of the fault these oblique segments would provide higher resistance against the general fault motion and could lock the fault leading to accumulate elastic energy

evidence of suppression of the unequal refraction error in geodetic leveling analyses of historic data indicate that procedures in force since the nineteenth century have effectively suppressed the unequal refraction error ure in geodetic leveling although theoretical considerations argue that large refraction errors should accumulate where levelings traverse gentle slopes permitting long sight lengths extensive examination of routinely developed results lends little support to this argument our analyses of the historic record consider 1 height differences based on otherwise similar levelings over the same route but characterized by substantially different sight length 2 modeled refraction error differences and actually measured elevation changes on both a section by section and a line by line basis 3 misclosures produced from levelings identified with significantly different procedural constraints in technically stable areas of comparable variation in terrain and climate and 4 alternatively and sequentially developed heights in areas of tectonic stability and areas of persisting instability all of these analyses indicate that the ure is generally small and unpredictable and hence inconsistent with both theoretical expectations and the results of two conceptually different experimental studies this inconsistency probably is attributable to the inability of the theoretical models and the failure of the experiments to incorporate in their design those procedures especially the rejection criteria at the setup section and circuit level that normally minimize refraction error traditionally invoked procedural specifications may have suppressed the ure through biasing of observations toward less refractive conditions whereas all of the theoretical models assume an averaged sampling of the atmosphere alternatively a variety of real world complexities that are disregarded in the models may take on added importance in normally constrained leveling thus refraction corrections based on simplified models and mean atmospheric and terrain conditions tend to overcompensate substantially for refraction errors associated with routinely constrained surveys

mechanisms and environments of deposition of late precambrian geosynclinal tillites scotland and east greenland abstract the late precambrian tillites in scotland and east greenland lie in marine geosynclinal sequences and extend for hundreds of kilometers both tillite formations are hundreds of meters thick and contain largely conformable internal stratigraphies with many individual mixtite beds separated by sandstone siltstone conglomerate and dolomite interbeds direct evidence for deposition of the mixtures from grounded ice sheets is provided by the angular unconformities beneath the tillite formations by the huge rafts of deformed sediment in the great breccia in scotland and by the bedded horizons within mixtites which are often lenticular as a result of deposition in sub or englacial tunnels indirect evidence that the surface of deposition was mostly too shallow for icebergs or was even above sea level comes from algal stromatolites mudcracks tidal palaeocurrent patterns and coarse beach conglomerates from the several internal marine erosion surfaces in scotland and from the sandstone wedges inferred to be of subaerial permafrost origin both tillite formations thus record complex glacial histories with 17 main glacial advances in scotland and 2 in greenland the tillites are compared with the thick but little known quaternary sequences of the north sea basin they may have accumulated on continental shelves that were more gentle and extensive than the latter

fabric and origin of multiple diamictons within the pre illinoian kennedy drift east of waterton glacier international peace park alberta canada and montana usa pebble fabrics and sedimentological properties indicate a glacigenic origin for multiple superposed diamictons within the pre illinoian kennedy drift east of waterton glacier international peace park alberta canada and montana usa determining the origin of these diamictons is particularly important in light of their antiquity eight diamictons on mokowan butte saint mary ridge and two medicine ridge have reversed magnetic polarity and are correlated with the matuyama chron 2 6 0 78 ma on mokowan butte two diamictons with normal polarity underlying two reversed diamictons are correlated with the gauss chron 3 6 2 6 ma or possibly the reunion or olduvai events 2 23 2 20 and 1 93 1 76 ma respectively fabrics were taken from 17 units within the kennedy drift on five interfluves on the basis of comparison of properties of these diamictons with those of modern glacial deposits eight including the uppermost one or two units on each interfluve are probably undeformed lodgment tills these are typically massive matrix supported bouldery sandy loam with strong unimodal fabric orientations relatively high eigenvalue s 1 s 3 ratios and striations on resistant clasts some include boulder pavements bullet shaped boulders and weak fissility eight other units have weaker fabrics typical of either deformed lodgment tills or glacigenic sediment flows because these also include bullet shaped boulders stone pavements and striated clasts most are probably deformed lodgment tills a colluvial or mudflow origin for the material is ruled out on the basis of the lateral and vertical extent of the diamictons at least 300 m wide and 5 10 m thick wide range of clast lithologies and sizes and distance from the mountain front 2 10 km as well as pebble fabrics and sedimentological properties

deformation in neogene sediments of the sorbas and vera basins se spain constraints on simple shear deformation and rigid body rotation along major strike slip faults abstract detailed structural analyses are presented of the neogene sorbas basin adjacent to the e w striking gafarillos fault zone and the vera basin adjacent to the 020 striking palomares fault zone in southeastern spain a stress regime with an e w oriented subhorizontal maximum principal stress 1 existed in pre tortonian 11 3 ma time a strike slip regime with nw se oriented compression during tortonian and earliest messinian time caused dextral displacement along the e w trending gafarillos fault of approximately 10 km structural analysis indicates that most displacement took place in the early tortonian deformational patterns within the adjacent pull apart basin reflect a dextral simple shear zone of at least 500 m width kinematical analysis of folds in the sorbas basin suggests however that rotational effects are largely caused by rigid body rotation without much internal deformation sinistral strike slip displacements occurred along the palomares fault zone under the influence of the same stress regime an abrupt change in the orientation of the stress field to n s directed compression in earliest messinian time 6 5 ma caused the termination of displacements along the gafarillos fault zone whereas the 020 trending palomares fault zone continued to accumulate sinistral strike slip displacements of about 25 km volcanism occurred along splays of the fault zone a wider shear zone of a few kilometers width evolved in which considerable anti clockwise rotation of folds occurred kinematic analysis of these folds shows that these rotational effects are again dominantly rigid body rotations assuming rotations are merely caused by simple shear deformation overestimates the amounts of strain a better way to deal with simple shear deformation is to compare observed shortening caused by folding with the magnitude of rotation of fold hinges

seismicity and geometry of a 110 km long blind thrust fault 1 the 1985 kettleman hills california earthquake the august 4 1985 kettleman hills earthquake was the third in a sequence of moderate shocks to occur beneath the northern half of a 110 km long fold chain bounding the eastern california coast ranges the 1982 mw 5 4 new idria 1983 mw 6 5 coalinga and 1985 mw 6 1 kettleman hills events define a southward progression of seismic activity beneath the fold we use teleseismic waveforms geodetic modeling hypocenters relocated in a three dimensional velocity model and subsurface structural data to investigate the kettleman hills earthquake the main shock results from motion on a shallowly dipping thrust fault buried at 10 km depth aftershocks and coseismic fault slip extend 20 km along the fold axis nearly the full extent of the kettleman hills north dome anticline aftershocks occur primarily several kilometers in front of the fault tip and in the core of the anticline the main shock and several foreshocks occurred at a 2 km right step in the quaternary fold axis which also corresponds to the southern end of the 1983 coalinga and northern end of the 1985 kettleman hills aftershock zones from this we infer that the step in the fold is caused by an offset or tear in the underlying fault the scalar seismic moment is 1 6 1018 n m consistent with the geodetic deformation and the duration of rupture is 16 s 3 4 times greater than for the average earthquake with this scalar moment the slow rate of moment release provides an explanation for the low level of ground shaking and low local magnitude reported for the event the peak of the geodetic uplift is located 5 km perpendicular to the quaternary fold axis we argue that the fault is propagating northeast into the undeformed san joaquin valley sediments and that the overlying fold is growing at about 0 5 mm yr

on the reconstruction of pleistocene ice sheets a review abstract pleistocene ice sheets can be reconstructed through three separate approaches 1 evidence based on glacial geological studies such as erratic trains till composition crossing striations and exposures of multiple tills nonglacial sediments 2 reconstructions based on glaciological theory and observations these can be either two or three dimensional models they can be constrained by known ice margins at specific times or they can be open ended with the history of growth and retreat controlled by parameters resting entirely within the model 3 glacial isostatic rebound after deglaciation provides a measure of the distribution of mass ice across a region a best fit ice sheet model can be developed that closely approximates a series of relative sea level curves within an area of a former ice sheet in addition the model should also provide a reasonable sea level fit to relative sea level curves at sites well removed from glaciation this paper reviews some of the results of a variety of ice sheet reconstructions and concentrates on the various attempts to reconstruct the ice sheets of the last wisconsin weischelian wurm devensian glaciation evidence from glacial geology suggests flow patterns at variance with simple single domed ice sheets over north america and europe in addition reconstruction of ice sheets from glacial isostatic sea level data suggests that the ice sheets were significantly thinner than estimates based on 18 ka equilibrium ice sheets cf denton and hughes 1981 the review indicates it is important to differentiate between ice divides which control the directions of glacial flow and areas of maximum ice thickness which control the glacial isostatic rebound of the crust upon deglaciation recent studies from the laurentide ice sheet region indicate that the center of mass was not over hudson bay that a major ice divide lay east of hudson bay so that flow across the hudson bay and james bay lowlands was from the northeast that hudson bay was probably open to marine invasions two or three times during the wisconsin glaciation and that the laurentide ice sheet was thinner than an equilibrium reconstruction would suggest

hybrid veins from the southern margin of the bristol channel basin uk sinistral and dextral en echelon hybrid calcite veins are exposed on the southern margin of the bristol channel basin north somerset on a liassic carbonate platform these hybrid veins are transitional between pure extensional mode i and shear fractures mode ii mode iii and experienced both extensional and shear displacements during their formation in the study area they occur in conjugate sets with the conjugate angle ranging between 10 and 50 based on the kinematic analysis of these veins a new model for the opening of the bristol channel is proposed

sediment deformation beneath glaciers rheology and geological consequences experiments beneath breidamerkurjokull in iceland have led to development of flow laws for the subglacial till relating strain rate to shear stress and effective pressure and assuming either bingham fluid or nonlinearly viscous fluid behavior water pressures in the till are less than ice pressures and it is suggested that this may lead to infiltration of ice into the sediment which inhibits sliding at the ice sediment interface where water pressures are equal or near to ice pressures infiltration does not occur and sliding may result a one dimensional theory of subglacial deformation is developed in which the empirical flow law is coupled with a model of subglacial hydrology and consolidation this predicts stable states in which subglacial sediment either does not deform or a dilatant deforming horizon forms with positive effective pressures at the ice bed interface or unstable states where zero or negative effective pressures are predicted time dependent analyses show that response times following perturbations of the system may be of the order of 103 years and thus that unsteady behavior may be normal on glaciers flowing over unlithified sediment beds it is suggested that the natural variability of material properties in subglacial sediment beds leads to the development of drumlins on the glacier bed it is suggested that unstable deformation at zero or negative effective stress leads to piping in subglacial sediments at the glacier terminus and the growth of sediment floored subglacial tunnels their frequency is that which is sufficient to draw down subglacial water pressures so as to prevent unstable deformation where they discharge large water volumes subglacial sediments flow laterally toward them producing tunnel valleys this sediment is then removed by water flowing along the axial tunnel tunnel valleys can be regarded as the equivalent in soft sediment areas of eskers in bedrock areas

leveling precision and bench mark motions pinon flat observatory california the reliability of relative vertical motions detected by levelings of bench marks installed at pinyon flat is highly dependent on the kinds of bench marks installed for monitoring purposes the most stable marks are the end monuments for two 535 m long fluid tiltmeters nine direct measurements of average slope between tiltmeter end monuments agree to within a standard deviation about the mean of 0 2 mm 0 4 rads comparable to the slope measured by the tiltmeters themselves motions of class b steel rod marks are random with standard deviations ranging from 0 5 to 3 2 mm averaging 1 0 mm the motions of nearly all rod marks decreased greatly in the fourth year evidently because of a time dependent establishment of stability in the decomposed granite fundament other kinds of bench marks are stable between 0 5 and 0 8 mm tectonic tilt is not revealed in 15 levelings of the array in 4 years consistent with the tiltmeters but the random bench mark motions dominate the errors in the estimated tilt

resolving denudational histories in orogenic belts with apatite fission track thermochronology and structural data an example from southern spain interpreting apatite fission track thermochronology aftt data obtained from orogenic belts presents a considerable challenge because of the complexity of denudational processes operating in this tectonic setting an approach which integrates kinematic foliation and thermochronologic data is advocated and an example from southern spain is used as an illustration aftt ages from the sierra nevada are negatively correlated with their elevation precluding interpretation in terms of simple erosive denudation however when additional structural data is included in the analysis a complex denudation history is obtained an initial phase of tectonic denudation was responsible for the cooling that produced the oldest apparent ages thereafter folding accompanied by differential erosive denudation caused cooling of samples inferred to have been as much as 4 5 km below the detachment the second phase of cooling began in the late miocene early pliocene

modifications to the theory of intraglacial waterways for the case of subglacial ones on defend l idee que dans les glaciers de montagne temperes les voies d eau sont sous glaciaires pour un conduit noye sous glaciaire il faut introduire deux processus importants l accroissement de la deformation plastique sur les cotes amont des bosses et la chaleur apportee par l eau des sources qui en hiver rend compte de la plus grande partie du debit la theorie explique pourquoi rothlisberger 1972 dut adopter une valeur non realiste pour le parametre rheologique de la glace elle conduit a la conclusion que dans les zones non surcreusees la plus grande partie de l annee les conduits sous glaciaires doivent rester non noyes et a la pression atmospherique cas des surcreusements l incidence de ce nouveau modele sur la theorie du glissement des glaciers

sedimentation in glacial environments and the identification of tills and tillites in ancient sedimentary sequences abstract tills and tillites are defined and subdivided into primary tills comprising lodgement tills melt out tills and sublimation tills and secondary tills comprising flow tills and deformation tills they are defined on the basis of their mode of deposition which endows them with their distinctive properties another category of till that of supra till is defined on the basis of its debris source derived supraglacially from valley sides and nunataks which gives these tills a coarse grained character the processes of till deposition and of outwash sedimentation are associated in several recurrent combinations which allow the definition of three principal glacial sediment associations and land systems which define the character of the sequences within which tills tend to occur the criteria which allow tills of different genesis to be identified and to be distinguished from non till diamictons are reviewed there are several features which are uniquely characteristic of till but unfortunately these are few it has been found generally necessary to employ an array of characteristics which though not individually unique to till when taken together can be strong evidence for particular till types the recognition of several typical and repetitive facies sequences which form in the major glacial sedimentary environments can also be important indicators of till genesis

a direct comparison of spirit and compensator leveling rumpf and meurisch 1981 conclude that any magnetic field including particularly that of the earth can deflect the line of sight of compensator or automatic self leveling levels since the city of los angeles has observed many lines of geodetic leveling using a zeiss ni 1 level a field investigation was designed to assess the potential impact of this error source the observations were made along a line that had been releveled several times over a period of years this generally north south line runs from tidal 8 san pedro to the vicinity of the jet propulsion laboratory in lacanada figure 1 an additional line of leveling was also observed in an east west direction our investigation seems to confirm the existence of an azimuth dependent error as suggested by rumpf meurisch

the temporal relationship between joints and faults abstract examples are presented of three temporal relationships between joints and faults joints that pre date faults joints that are precursors to or synchronous with faults and joints that post date faults emphasis is placed on strike slip faults in carbonate beds but other examples are used general rules are given for identifying the three temporal relationships between joints and faults joints that formed before faults can be dilated sheared or affected by pressure solution during faulting depending on their orientation in relation to the applied stress system faulted joints can preserve some original geometry of a joint pattern with pinnate joints or veins commonly developing where faulted joints interact joints formed synchronously with faults reflect the same stress system that caused the faulting and tend to increase in frequency toward faults in contrast joints that pre or post date faults tend not to increase in frequency towards the fault joints that post date a fault may cut across or abut the fault and fault related veins without being displaced by the fault they may also lack dilation near the fault even if the fault has associated veins joints formed either syn or post faulting may curve into the fault indicating stress perturbation around the fault different joint patterns may exist across the fault because of mechanical variations geometric features may therefore be used in the field to identify the temporal relationships between faults and joints especially where early joints affect or control fault development or where the distribution of late joints are influenced by faults

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

uplift across long valley caldera california the results of levelings along u s highway 395 between lee vining and toms place california in 1957 1975 1980 1982 and 1983 define the development of a dome shaped uplift across the long valley caldera these levelings indicate that toms place remained virtually invariant with respect to lee vining during the full interval 1957 1983 implying that the end points of the survey route lie beyond the range of the developing dome no significant uplift occurred before 1975 but by october 1980 the uplift near casa diablo hot springs reached 0 25 m and the half width of the dome was of the order of 25 km the uplift of casa diablo hot springs increased to 0 35 m by august 1982 and to about 0 40 m by august 1983 without any appreciable increase in the lateral extent of the dome the august 1982 to august 1983 uplift apparently occurred before february 1983 with little or no uplift during the period february august 1983 the 1975 1983 uplift is attributed to the injection of 0 19 km3 of magma into a spherical chamber at a depth of 10 km beneath the southern quadrant of the ancient resurgent dome within the caldera examination of the full vertical control record through the long valley area indicates that the 1975 1983 uplift is unique within the period 1905 1983 although comparisons of the results of a 1932 leveling against a 1914 datum disclose a 1914 1932 down to the northwest tilt of about 10 rad over the reach between toms place and lee vining this tilt if real is more reasonably attributed to regional tectonic deformation than it is to the movement of magma at depth

till stratigraphy and sedimentology at the margins of terrestrially terminating ice streams case study of the western canadian prairies and high plains complex glacigenic sediment sequences arranged in large arcuate assemblages and demarcating the lobate termini of fast ice flow corridors in western canada represent the terrestrial equivalents of the trough mouth fans of the marine palaeo ice stream record intensive sedimentological and stratigraphic investigations at a regional scale are employed in the interpretation of thick units or sequences of diamicton and two depositional scenarios are proposed first glacier marginal till thickening and the stacking of till wedges takes place in areas where an ice stream margin was stationary for short periods of time stacks of subglacial traction tills potentially record annual sub marginal incremental thickening at ice stream margins especially in areas where densely spaced recessional push moraines appear to record seasonal climatic forcing second proglacial lake and valley infilling with glacilacustrine rhythmites and mass flow diamictons is associated with the advection of sub marginal till into preglacial bedrock depressions and records ice stream marginal oscillations and debris influx into discontinuous proglacial lakes which act as subaqueous sediment sinks for materials that would otherwise have been used to construct sub marginal till wedges and moraines glacial overriding modifies the deposits produced in both scenarios through deformation and the dislocation and entrainment of bedrock and sediment rafts at the margins of bedrock valley walls resulting in the widespread development of glacitectonites and megablocks the occurrence of the thickest deposits as preglacial valley fills may be significant in groundwater siphoning away from subglacial deforming layers and the promotion of sticky spots

on the role of mechanical energy in maintaining subglacial water conduits at atmospheric pressure recent theo retical studies of glacier hydrology have assumed that subglacial conduits are completely filled with water under steady state conditions this however is not necessarily the case where discharges are larger than a few tens of liters per second and the down glacier slope of the bed is more than a few degrees the potential energy released by water descending this slope may be capable of melting the walls of a subglacial conduit many times faster than the conduit can close by plastic flow of the ice as a result the pressure in such tunnels may normally be atmospheric or possibly even at the triple point pressure if there is no open connection to the glacier surface simple calcu lations suggest that such pressures in subglacial conduits may be more common than herclofore anticipated the positions of such open conduits may be unstable to small per turbations in discharge or ice veloci ty this is because the mechanical energy available in excess of that needed to balance closure can instead offset the gene ral flow of the ice cond ui ts can thus trend diago nally across the direction of ice aow if an increase in the angle which such a conduit makes with the ice flow direction also results in an increase in slope of he conduit more mechanical energy will become available resulting in a positive feedback process subglacial channels at atmospheric pressure may inauence the origin and morphology of certain glacial landforms such as eskers and plastically molded features resume sur le role de l inergie newtonnienne dam le maintien du riseau aquiflrl sous glaciaire cl la pression almosph irique de recentes etudes theoriques d hydrologie glaciaire ont suppose que le reseau sous glaci aire clait corn pletement rempli d eau en condition d cquil ibre stable ceci neanmoins n est pas necess airement le cas lorsque les debits sonl superieurs a quelques dizaines de litres par seconde et que la pente du lit du glacier est superieure a quelques degres i energie potentielle mise en oeuvre par i eau descendant celle pente peut ire capable de fondre les parois d un chenal sous glaciaire beaucoup plus vite que le chenal ne peut se refermer par le auage plastique de la glace il en resuhe que la pression dans de tels chenaux peut nor rnalement etre atrnospherique

quaternary geology and geomorphology of the dinosaur provincial park area and surrounding plains alberta canada the identification of former glacial lobes drainage diversions and meltwater flood tracks abstract the quaternary geology and geomorphology of the lower red deer river drainage basin centred on the dinosaur provincial park badlands provides information on pre late wisconsinan drainage patterns and the dynamics of former lobes of the laurentide ice sheet in western canada patterns of deglaciation proglacial lake evolution and spillway incision are also reconstructed based upon the distribution of surface materials and glacial glaciofluvial landforms the empress group fluvial and glaciolacustrine sediments which could be as young as 27 ka bp infill the precursor red deer river and its tributaries and document the initial advance of glacier ice into southern alberta glaciotectonic disturbance of older sediments and bedrock the production of deformation tills and the construction of a megafluting complex and cupola hills record the advances of a glacier lobe centred over the study area stratified inter and intra till beds record pulses of subglacial meltwater between phases of subsole deformation the thickening of tills towards the margin of the lobe represents a till wedge an expected product of sediment advection by glaciers moving over deformable beds the eastern margin of the glacier lobe is demarcated by the interlobate suffield hummocky moraine belt which contains overprinted thrust ridges which record diachronous oscillations of neighbouring lobes within the ice sheet proglacial and glaciofluvial sediments were deposited in the area in association with proglacial lake bassano patricia which drained eastwards when the suffield moraine was dissected by spillways changes in the size of glacial lake bassano patricia are clearly documented by a sequence of spillway incisions which culminated in the erosion of scabland topography and the initiation of a new course for the red deer river a 15 km southward diversion of the main channel in distinct contrast to the documented incision histories of other small rivers in alberta one tree creek and little sandhill creek did not start major incisions of the quaternary sediments over buried valley positions until the late holocene when environmental conditions were characterized by higher precipitation

preservation of basal ice sediment texture in ice sheet moraines ice sheet moraines near kangerlussuaq in west greenland inherit distinctive particle size distributions from basal ice although debris structures from the basal ice are commonly destroyed by deposition and resedimentation processes the abundance of clay and silt in the dispersed faciesa basal ice at the ice sheet margin is clearly re ected in the sedimentology of the ice sheet moraine geographical variations in the texture or grain size of moraine sediments may thus re ect geographical variations in basal ice this o ers a new approach to reconstructing the basal ice characteristics and hence the thermal and dynamic properties of former ice sheets 2000 elsevier science ltd all rights reserved

characterization of pebble fabrics in modern terrestrial glacigenic sediments pebble fabric data are available from several facies of glacigenic sediments deposited by modern glaciers where sedimentary processes can be observed or inferred with relatively little ambiguity over 100 samples from contemporary environments illustrate fabrics characterizing melt out till deformed and undeformed lodgement till sediment flow deposits and ice slope colluvium lodgement till fabric variability is related to the two layer structure of these sediments a structureless friable upper layer with low shear strength and high consolidation coefficient overlying a very compact material of horizontal platy structure fabric strength assessed by eigenvalue analysis is weaker and pebble dip is more dispersed in the upper structureless horizon stronger fabrics in the lower platy horizon may be primary depositional fabrics which are destroyed by subglacial shearing to give weaker fabrics in the upper horizon alternatively upper horizon fabrics may be characteristic of all recently deposited lodgement tills with stronger fabrics developing at depth by dewatering and consolidation there is a general reduction in fabric strength and an increase in particle dip associated with the transition from melt out tills through undeformed and deformed lodgement tills to sediment flow deposits and ice slope colluvium there is however considerable overlap in the fabric strengths characteristic of sediment flow deposits and deformed lodgement tills fabric data from modern glacial sedimentary facies are used to assist in interpreting the mode of deposition of some quaternary glacial sediments relatively strong fabrics characteristic of melt out tills and undeformed lodgement tills are more likely to be diagnostic of genesis than weaker fabrics associated with deformed sediments

rogen moraine an example of glacial reshaping of pre existing landforms abstract rogen moraine is widely distributed in the core areas of the former scandinavian and laurentide ice sheets it is generally agreed upon that these gently arched ice flow transverse ridges can be used in reconstructions of paleo ice flow patterns and that they indicate a melted bed or poly thermal basal ice regime however the processes of ridge generation have been contentious this study proposes a two stage formation of rogen moraine based on detailed sedimentological and structural investigations in excavated trenches in a rogen moraine landscape in the province of dalarna central sweden field data suggest that rogen moraine ridges are the reshaped remains of pre existing transverse moraine ridges originally deposited from ice cored moraines in an ice marginal zone due to back and down wasting of ice cores inter ridge troughs were filled with debris flow and fluvial deposits which after landscape inversion were transformed to areas of transverse and hummocky moraines it is proposed that this primary landscape formation occurred during an early weichselian deglaciation this relict landscape was later preserved beneath cold based mid to late weichselian ice sheet s which turned wet based during the preboreal deglaciation phase and re moulded the precursor landforms into rogen moraine

melt out till in the edmonton area alberta canada till at two localities in the edmonton area alberta was formed mainly by passive melt out from glacier ice and not by lodgment by active ice or as a result of supraglacially derived flows this interpretation is based on the implications of in situ stratified glacial sediment below and within till and of large unlithified clasts of sediment derived from subtill deposits the interpretation is also supported by more general regional stratigraphic and structural observations such associated properties as subtill deformation a sharply planar till preglacial sediment contact sole marks and fabric support formation by melt out or illustrate local exceptions to this process regionally consistent preferred orientation of clasts is interpreted to represent preferred englacial orientation collective analysis of the principal eigenvectors of individual englacial fabrics and flow or resedimented till fabrics from a modem glacial environment and similar analysis for till at villeneuve near edmonton show the edmonton till to occupy the intermediate position in terms of orientation strength predicted by the melt out hypothesis in places preferred orientation is considered to have been disturbed by flow and diapirism induced by the process of thaw consolidation thus preferred clast orientation in till may show considerable deviation from a regional trend stratigraphy and sedimentology are used to classify the till and to relate individual exposures to regional environments of deposition

glacial dynamics and transport of debris during the final phases of the weichselian glaciation southwest skane sweden late weichselian glacial sediments were studied in three sections west of lund southwest sweden the lowermost sedimentary unit is a lodgement till containing rock fragments derived from the northeast east fabric analyses indicate successive ice flow directions from the northeast east northeast south southeast and then east the last active ice movement in the area was from the east above the lodgement till are deglaciation sediments consisting of meltout till flow till and glaciofluvial sand and gravel deposited in a subaerial stagnant ice environment the uppermost unit consists of glaciolacustrine clay and silt containing abundant ice rafted debris deposited during a short lived transgression phase when stagnant ice was still present in the area at the westernmost site investigated the petrographical composition of the deglaciation deposits displays a gradual change with upwards increasing components of cretaceous chalky limestone the presence of this rock type requires a period of glacial transport from the south this stratigraphy cannot be explained with traditional glaciodynamic models a possible scenario can however be constructed using a previously published model lagerlund 1987 where marginal ice domes in the southwestern baltic area interact with the main scandinavian ice sheet

postseismic deformation at el asnam algeria in the seismotectonic context of northwestern algeria summary we use a combination of seismicity tectonic features focal mechanisms seismic strain and postseismic movement to study the western part of north algeria the el asnam region and its surrounding area in particular a seismotectonic map of this part of algeria delimited by the mediterranean sea in the north and the tellian mountains in the south was built from available geological and seismological data an examination of this map shows that the most significant earthquakes are concentrated along tectonic features and quaternary basins elongated in an east west direction suggesting nnw sse compressional movements during the large el asnam earthquake of 1980 october 10 m 7 1 vertical movement was measured along a 40 km northeastsouthwest thrust fault these movements were determined geodetically in 198 1 with reference to a basic network previously measured in 1976 in order to control postseismic movement and to ensure the monitoring of the seismic area a dense geodetic network has been regularly measured since 1986 both in planemetry and altimetry the results of the altimetric remeasurements show significant vertical movements the elevation changes of the benchmarks have been deduced from precise levelling measurements a remarkable uplift 5 1 5 1 9 mm yr of the northwestern block during the 1986 91 period has been observed whereas the southeastern block is seen to be relatively stable the sar el maiirouf anticline situated along the central segment of the el asnam surface breaks appears to be growing with a maximum postseismic slip rate of 9 6 1 4 mm yr i the mean uplift rates computed for the northwestern block support the view that the 1954 earthquake did not occur on the same reverse fault as the 1980 event

faulted joints kinematics displacement length scaling relations and criteria for their identification structural geometries and kinematics based on two sets of joints pinnate joints and fault striations reveal that some mesoscale faults at split mountain utah originated as joints unlike many other types of faults displacements d across faulted joints do not scale with lengths l and therefore do not adhere to published fault scaling laws rather fault size corresponds initially to original joint length which in turn is controlled by bed thickness for bed confined joints although faulted joints will grow in length with increasing slip the total change in length is negligible compared to the original length leading to an independence of d from l during early stages of joint reactivation therefore attempts to predict fault length gouge thickness or hydrologic properties based solely upon d lscaling laws could yield misleading results for faulted joints pinnate joints distinguishable from wing cracks developed within the dilational quadrants along faulted joints and help to constrain the kinematics of joint reactivation q 2001 elsevier science ltd all rights reserved

deposition and palaeogeography of a glacigenic neoproterozoic succession in the east kimberley australia facies provenance and palaeocurrent analysis of the predominantly siliciclastic neoproterozoic succession of the east kimberley district of northwestern australia indicates southwesterly directed regional palaeoice flow directions associated with continental glaciation facies relationships at three key study sites in the east kimberley record glacial advance retreat and marine transgression and the likely effects of ice dynamics on local basin depositional history ice scour linked with provenance data indicate ice advance from the northeast additional ice flow data from the west kimberley and the daly river area of northern territory are consistent and record a regional palaeoice flow direction towards the southwest palaeocurrent data and facies relationships in the east kimberley however suggest that sediment transport directions within the east kimberley basin were influenced by a combination of ice induced lithospheric flexure pre existing topography and modification of basin topography and sediment dispersal paths by ice induced redistribution of debris a basin evolution model incorporating these concepts within the framework of ice advance retreat and marine inundation is proposed identification of regional ice flow trends of this scale should ultimately prove a useful tool in testing possible palaeogeographic reconstructions of continent configurations in a post rodinian world

identification of basal layer debris in ice marginal moraines russell glacier west greenland different processes of ice formation and deformation at the glacier bed create distinctive basal ice facies the geographical distribution of these facies at the glacier margin can indicate the distribution of subglacial environments previous research has shown that debris in dispersed facies basal ice at the margin of the greenland ice sheet has a distinctive particle size distribution that can also be recognised in moraines deposited where the dispersed facies is present this permits reconstruction of the distribution of basal ice characteristics and subglacial conditions from moraine sediments here we study stratified and debris band facies of the basal ice layer at the same site we find that contrary to previous suggestions these two facies can also be distinguished sedimentologically co variant plots of the c40 aggregate shape and ra aggregate roundness indices show that pebble and cobble sized clasts 2 to 7 in the debris bands are statistically more angular than those in the stratified facies sedimentological characteristics of the parent facies are retained in ice marginal moraines combined with previous work these new observations suggest that the geographical distribution of basal ice facies at a glacier margin can be reconstructed from sedimentological characteristics preserved in moraines

quaternary tectonic activity of the carboneras fault in the la serrata range se iberia geomorphological and chronological constraints the eastern betic shear zone ebsz in southern iberia is known to accommodate part of the 4 5 mm yr convergence between africa and iberia but its seismic hazard is not sufficiently understood for an accurate risk assessment one of the main structures of the ebsz the left lateral 150 km long carboneras fault displays no clear instrumental and historical activity despite being morphologically expressive detailed geomorphological mapping geochronological analysis and structural observation on the la serrata segment of the carboneras fault were designed to investigate its recent evolution quaternary sediments and geomorphic features were targeted and 42 new numerical ages were obtained based on 66 samples thermoluminescence u series 14c 10be the chronological framework of la serrata was constructed by combining these numerical ages with a conceptual model previously developed in the region which assumes that alluvial fan aggradation was produced during cold and dry periods glacials and stadials whereas stability and phases of calcrete formation were favored during warm and wetter periods interglacials and interstadials the spatial distribution of dated alluvial fans suggests an early phase of uplift that probably occurred between 1 ma and 56 6 ka in the northeastern portion of the study area whereas in the southwest sector the main uplift phase occurred later than 110 3 ka a decline in fault activity would have taken place after 30 8 ka vertically offset dated units indicate minimum dip slip rates of 0 05 mm yr and 0 18 mm yr averaged for the last 1 ma and the last 110 3 ka respectively deflected channels and associated dated units yield a minimum left lateral strike slip rate of 1 31 mm yr averaged for the last 110 3 ka the most recent fault movement of the fault could be younger than ad 637 our results suggest therefore that the carboneras fault is among the fastest in iberia and should be considered in future hazard analyses

experiments on the production of transverse grain alignment in a sheared dispersion a series of experiments was designed to investigate grain orientation in flows with concentrations of granular solids in the range from 0 5 to 15 fourteen experiments were carried out in which sand sized material was dispersed in liquid plaster of paris and the dispersion allowed to flow down a slope until it came to rest the preferred orientation of the grains was then estimated by measuring the anisotropy of magnetic susceptibility of specimens cut from the solidified flows five of the experiments showed signs of deformation both in the gross characteristics of the flow and in the grain alignment the remaining nine had grain alignment dependent on grain concentration at concentrations of 1 2 and less and 11 1 and more by volume alignment of long axes was parallel to flow these observations were consistent with the existing theories for low concentrations in which preferred alignment is shown to result from the varying rate of rotation of grains in a shearing flow and for high concentrations in which preferred alignment results from the transfer of angular momentum between colliding grains at some intermediate concentrations transverse alignment was observed a theoretical explanation combining the theories of the extreme cases is suggested the observation of transverse alignment is compared with a similar observation in some turbidites

quaternary sediments in central edmonton alberta canada stratigraphy distribution and geotechnical implications abstract borehole logs were used to determine the stratigraphy and distribution of sedimentary units in central edmonton the quaternary sediments overlying upper cretaceous sedimentary bedrock consist of preglacial fluvial sand and some gravel glaciofluvial sand and gravel a glacial diamicton complex composed of melt out and flow diamictons glaciofluvial sand and silt glaciolacustrine silt and clay and minor deposits of postglacial fluvial sand the glacial sediments represent deposition during one major glaciation in the late wisconsinan the diamicton complex has an intermediate stratigraphic position in the quaternary sequence is generally thick and laterally continuous and serves as a satisfactory substrate for many deep foundations and tunnels including part of the light rail transit system seepage and block failures during tunnelling in the diamicton complex are mainly due to abundant saturated sand lenses in the upper part of the complex the lateral continuity of the diamicton complex is interrupted by sand infilling a meltwater channel incised into bedrock tunnelling is difficult and costly within the sand due to seepage and collapse mapping of the meltwater channel and associated outwash deposits allowed adjustment of the tunnel alignment to avoid intersection with the channel over the meltwater channel deposits of outwash sediments and flow diamictons form a broad surface ridge

hummocky moraine sedimentary record of stagnant laurentide ice sheet lobes resting on soft beds abstract over large areas of the western interior plains of north america hummocky moraine hm formed at the margins of laurentide ice sheet lis lobes that flowed upslope against topographic highs current depositional models argue that hm was deposited supraglacially from stagnant debris rich ice disintegration moraine across southern alberta canada map and outcrop data show that hm is composed of fine grained till as much as 25 m thick containing rafts of soft glaciotectonized bedrock and sediment chaotic non oriented hm commonly passes downslope into weakly oriented hummocks washboard moraine that are transitional to drumlins in topographic lows the same subsurface stratigraphy and till facies is present throughout these landforms and others such as doughnut like rim ridges flat topped moraine plateaux and linear disintegration ridges are identified as belonging to subglacially deposited soft bed terrain this terrain is the record of ice lobes moving over deformation till derived from weakly lithified bentonite rich shale drumlins record continued active ice flow in topographic lows during deglaciation whereas hm was produced below the outer stagnant margins of ice lobes by gravitational loading pressing of remnant dead ice blocks into wet plastic till intervening zones of washboard moraine mark the former boundary of active and stagnant ice and show hybrid drumlins whose streamlined form has been altered by subglacial pressing humdrums below dead ice the presence of hummocky moraine over a very large area of interior north america provides additional support for glaciological models of a soft bedded laurentide ice sheet

temporal changes in subglacial meltwater activity field evidence from the late devensian in the north of ireland abstract temporal changes in meltwater abundance distribution and characteristics controlling subglacial processes and ice sheet dynamics can be inferred from subglacial sediment successions field evidence for changes in subglacial meltwater characteristics over time is presented from two sites doonan drummee near a former late weichselian devensian ice centre in the north of ireland on a macroscale both sites investigated show subglacial diamicton overlying glacially planated bedrock platforms in more detail primary sedimentary structures and facies variability show a complex relationship between depositional processes and meltwater characteristics at the ice bed interface ibi sedimentary evidence suggests sediment transport and deposition took place by low viscosity subglacial slurries mobile sediment meltwater admixtures which are part of a continuum between the processes of subglacial sediment deformation and subglacial meltwater flooding subtle changes in meltwater abundance and distribution at the ibi controlled slurry rheology mechanisms of particle support and detailed sediment depositional processes

neogene evolution of the sorbas basin se spain determined by paleostress analysis abstract the neogene subsidence history of the sorbas basin situated in the internal zone of the betic cordilleras of southeastern spain is strongly controlled by strike slip deformation the sedimentary sequence of the basin offers a good control on the timing of separate phases of fault activation the southern border of the sorbas basin is formed by a major east west trending fault zone the gafarillos fault zone which consists of intermixed slivers of pre neogene basement blocks and neogene basin sediments fault patterns and paleostress analysis both indicate that major displacement along this fault zone was dextral with a n310e oriented maximum principal stress axis strike slip movement along the east west oriented faults ended during the earliest messinian after a minimum of 6 ma of activation paleostress analysis indicates a subsequent phase of strike slip fault movement present in sites of up to early pliocene age the maximum principal stress axis orientation is n350e for this phase this deformation is synchronous with sinistral displacement along the palomares fault zone situated directly to the east of the study area subsequently our paleostress analysis indicates an extensional regime during the late pliocene to quaternary however extensional tensors were calculated at a number of sites possibly representing local stress regimes coexisting with the main strike slip deformation and sorbas basin subsidence folding of tortonian sediments points out that local compressional deformation took place as well during the neogene basin history observed wide ranges for the ellipsoid shapes of the calculated tensors support the existence of lateral stress variations

a comparison of clast fabric and shape in late precambrian and modern glacigenic sediments abstract northeastern svalbard contains a well preserved glacigenic sequence of vendian late precambrian age in which terrestrial lacustrine intertidal and marine glacial facies are represented diamictite facies are of two main types massive and weakly to strongly bedded diamictite field appearance and relationships with other facies however provide insufficient information to allow a clear interpretation of the precise mode of glacial deposition by combining this information with data concerning the fabric of clasts in modern glacigenic sediments where the mode of glacial deposition is better known a wider understanding of the processes of glacial deposition in vendian time is obtained several diamictite samples were interpreted to be of lodgement tillite facies and material o water laid and glacigenic sediment flow origin was also recorded clast shape analyses indicate that most glacial debris was transported at least for a time at the glacier bed little angular supraglacial debris was present implying that the ice mass was of ice cap or ice sheet dimensions with few subaerial rock exposures clast shape in the late precambrian deposits was not useful in distinguishing between the variety of lithofacies derived from basally transported glacial material too few systematic studies of clast striation in modern glacigenic sediments are yet available for this criterion to be helpful in distinguishing between tillite facies lithofacies analysis together with clast fabric and shape studies provide useful and complementary lines of evidence concerning the ode of deposition of ancient diamictite sequences an understanding of the depositional processes and patterns of modern glacial sedimentation provides a fundamental framework for such studies

soft zones in the glacial till in downtown edmonton high rise buildings in downtown edmonton have generally been founded on spread footings in glacial till early geotechnical work proposed a geological model comprising uniform very dense basal lodgement till however recent work shows that the till is more complex being variable in both material type and consistency a case history is described that exemplifies this variability it is concluded that early experience with the dense tills has led to an overconfident approach to soil investigation in this area and that a thorough site investigation is required

sedimentary signatures of basal ice formation and their preservation in ice marginal sediments reconstruction of subglacial processes from sedimentological evidence is central to our understanding of glaciological conditions beneath former ice masses at svinafellsjokull southeast iceland we assess the extent to which two different processes of basal ice formation regelation and glaciohydraulic supercooling can be identified from ice marginal sediments our results indicate that the sedimentary characteristics of deposits produced by these two processes can be distinguished from one another and that it may be possible to recognise evidence of these processes in quaternary sediments and to reconstruct their spatial pervasiveness sediments derived from the melting of regelation basal ice have i a massive structure ii a sediment matrix 0 to 10 dominated by coarse sand and iii a higher proportion of angular clasts than supercool basal ice and associated sediments sediments derived from supercool basal ice i can be either massive or layered ii tend to have a silt dominated matrix and iii contain a slightly higher proportion of rounded and well rounded clasts than regelation basal ice and sediments previous studies indicate that the dominance of silt within supercool basal ice may be unique to this process and hence supercooling should leave a readily recognisable signature in the sedimentary record our results from svinafellsjokull lend support to that idea although we suggest that further work is required to assess whether silt dominance is a process signature diagnostic of supercooling and in particular the extent to which subglacial sediment supply determines the sedimentary character of basal ice facies and associated sediments

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

the carstairs kames lanarkshire scotland morphology sedimentology and formation the carstairs kames have been the subject of debate for over 150 yr a synthesis of previous work along with new sedimentological data is used to reappraise this classic british esker locality three morphological elements are recognised i large sinuous and anastomosing ridges ii large irregular linear mounds and iii small low and irregular mounds the main ridge system is composed of a core of boulder gravel with sand pebble gravel above and adjacent to the core the large linear mounds contain a varied facies range which include glaciolacustrine sediments deltaic sequences laminites and dropstones debris flows and glaciofluvial channel systems all the deposits both in the main ridges and in the adjacent linear mounds contain syn and post depositional subsidence structures including normal faults synclinal folds and growth faults a range of potential origins for these landforms is reviewed and it is suggested that glaciofluvial sedimentation in a supraglacial environment controlled by a topography of ice cored ridges is the most appropriate depositional model 1997 john wiley sons ltd

density driven deformation structures in glacigenic consolidated diamicts examples from traeth y mwnt cardiganshire wales u k abstract density driven deformation may occur when a sediment of higher bulk wet density is deposited on top of one of a lower bulk wet density and occurs commonly in glacigenic sediments by recognizing density driven deformation of gravels and sands embedded in diamicts it is possible to reconstruct relative preconsolidation states of the diamicts density driven structures indicate that during deformation the diamict behaved as a viscous fluid thus providing important evidence for the viscosity and physical state of diamicts after deposition which has implications for the depositional environment the density driven process and its implications for reconstructing depositional environments is discussed criteria are given for the recognition of density driven deformation stages of gravels and sands deposited on top of a viscous mud

melt out till and ribbed moraine formation a case study from south sweden abstract hummocky moraine with dispersed agglomerations of ribbed moraine here named asnen type ribbed moraine forms a 20 40 km wide zone over smaland south sweden terminated to the north by a sharp boundary to streamlined terrain the hummocky ribbed moraine zone can be geomorphologically linked to the subaqueous goteborg moraine formed at an oscillation stand still phase during the deglaciation of the swedish west coast based on detailed sedimentological and structural investigations of ribbed moraine ridges it is concluded that diamict sequences and associated sorted sediment were deposited due to passive melt out from stagnant debris rich ice with synsedimentary deposition of sorted sediments preferentially at a melting ice bed interface to accommodate for the geomorphological expression such an interpretation further implies that debris rich ice formed in an intermediate adfreezing zone between ice at the pressure melting point and a frontal frozen zone at deglaciation basal debris rich ice was stacked into transversally arranged zones controlled moraine forming ribbed moraine embryos the active phase of ridge formation the stacked sequences of debris rich ice eventually melted out beneath a stable and melt retarding supraglacial ablation complex to form the final moraine ridges the passive phase of ridge formation in areas with no stable supraglacial ablation complex the resulting landform after final de icing was a hummocky moraine landscape internal composition of moraine hummocks suggests that most of them are composed of sediment gravity flow sediments intercalated with stream deposited sediments all resting on a platform of subglacial melt out till de icing of the zone now occupied by hummocky and ribbed moraine took a considerable time deglacial 14 c age differences from lake basins on either side of the geomorphic boundary to the streamlined terrain indicate a separation between active and stagnant ice along that boundary and that it took another 200 300 yr for the stagnant ice zone to melt during the final formation of present day landforms

controlled moraines origins characteristics and palaeoglaciological implications abstract controlled moraines are supraglacial debris concentrations that become hummocky moraine upon de icing and possess clear linearity due to the inheritance of the former pattern of debris rich folia in the parent ice linearity is most striking wherever glacier ice cores still exist but it increasingly deteriorates with progressive melt out as a result moraine linearity has a low preservation potential in deglaciated terrains but hummocky moraine tracts previously interpreted as evidence of areal stagnation may instead record receding polythermal glacier margins in which debris rich ice was concentrated in frozen toe zones recent applications of modern glaciological analogues to palaeoglaciological reconstructions have implied that a controlled moraine development can be ascribed to a specific process e g englacial thrusting or supercooling and b controlled moraine preservation potential is good enough to imply the occurrence of the specific process in former glacier snouts e g ancient polythermal or supercooled snouts these assumptions are tested using case studies of controlled moraine construction in which a wide range of debris entrainment and debris rich ice thickening mechanisms are seen to produce the same geomorphic features polythermal conditions are crucial to the concentration of supraglacial debris and controlled moraines in glacier snouts via processes that are most effective at the glacier permafrost interface end moraines lie on a process form continuum constrained by basal thermal regime the morphological expression of englacial structures in controlled moraine ridges is most striking while the moraines retain ice cores but the final deposits landforms tend to consist of discontinuous transverse ridges with intervening hummocks preserving only a weak impression of the former englacial structure these are arranged in arcuate zones of hummocky moraine up to 2 km wide containing ice walled lake plains and lying down flow of streamlined landforms produced by warm based ice a variety of debris entrainment mechanisms can produce the same geomorphic signature spatial and temporal variability in process form relationships will lead to the sequential development of different types of end moraines during the recession of a glacier or ice sheet margin

glacigenic deposits at the edmonton convention centre edmonton alberta four main stratigraphic units are present at the edmonton convention centre site in downtown edmonton the lowermost sediment exposed is cretaceous sandstone of the horseshoe canyon formation this is overlain by preglacial sands and gravels of uncertain age which contain recumbent drag folds developed by glacial overriding of previously existing periglacial involutions these sediments are surmounted by a glacigenic complex consisting of subglacially modified sand and four till facies formed through passive melt out the uppermost quaternary sediment present is a proglacial lacustrine unit dominated by silts and clays with interbedded diamictons a single glacial episode is recorded in the sediments stratigraphic relationships with other exposures throughout the edmonton region indicate that the glacigenic complex formed during the final ice advance variation in the orientation of glacially induced deformations in the preglacial sands and gravels and the basal glacigenic sand indicate that the directi

vertical surface displacements at yellowstone caldera wyoming 1976 1986 between first order leveling surveys in 1976 and 1986 the east central floor of yellowstone caldera rose 15 4 1 4 mm yr and the west central floor rose 17 0 2 0 mm yr with respect to points on the south caldera rim the same pattern has prevailed since an initial survey in 1923 except that the western caldera rose 30 faster during 1976 1986 than during 1923 1976 the 1976 1986 uplift extends beyond the northwest caldera rim near the adjacent hebgen lake fault zone site of a magnitude 7 3 earthquake in august 1959 marginally significant displacements in the eastern caldera suggest that uplift continued during 1983 1984 stopped during 1984 1985 and reversed to subsidence during 1985 1986 thus long term uplift may accumulate episodically historical uplift is especially noteworthy because regional crustal extension and thermal contraction during cooling would cause the caldera floor to subside if other processes were not acting to warp it upward the pattern and dimensions of the uplift indicate a source in the upper crust beneath yellowstone caldera probably a reservoir of rhyolite magma within a cooling granitic pluton a simple point source model would suggest a source 10 15 km deep but the reservoir is probably lens shaped and closer to the surface uplift may be caused by basaltic intrusions near the base of the reservoir or accumulation of magmatic fluids during cooling and crystallization within the reservoir subsidence might be a response to regional tectonic extension or release of trapped magmatic fluids magmatic inflation volatile accumulation and crustal extension may culminate eventually in renewed eruptive activity but there is no evidence of an imminent volcanic hazard

laurentide glaciation in west central alberta a single late wisconsinan event the grande prairie region in west central alberta shows evidence of late wisconsinan laurentide glaciation in the form of a widespread till containing abundant erratic clasts derived from the canadian shield two sections located on the smoky river at watino and on the simonette river 80 km to the southwest expose sediment lying stratigraphically below the till a similar sequence is exposed in both localities 5 10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt the gravel contains no laurentide erratics and is thus preglacial the contact between the basal gravel and the overlying sand and silt is sharp and conformable 14c dates from the base of the simonette section and throughout the watino section suggest a middle wisconsinan age thus the sediment exposed is interpreted as a conformable middle wisconsinan sequence the sedimentary sequences were deposited in a moderate to low energy braided stream system flowing towards the north the general fining up trend in the

vertical movement and gravity change near the la grande 2 reservoir quebec leveling and precise gravity observations were made along a 50 km profile before and after the filling of the la grande 2 reservoir 53 7 n 77 w in 1979 anomalous relative vertical uplift of 4 cm and relative changes in gravity of 14 gal 140 nm s2 were observed along the profile the observed changes are anomalous with respect to theoretical results for loading of a layered elastic earth homogeneous isotropic porous elastic models with reasonable hydraulic properties are also unable to explain the observations in an effort to account for the discrepancies the accuracies of the leveling and the gravity data were investigated corrections were made to the leveling data for refraction errors rod calibrations magnetic effects and deflection of the vertical by the water mass although the corrections for systematic errors were significant the discrepancy with respect to homogeneous isotropic loading models remains the anomalous increase in gravity is thought to be the result of lateral transport of water in a high permeability formerly undersaturated zone hydraulically coupled to the reservoir the anomalous uplift is thought to be the result of elastic expansion of cracks and fractures of low aspect ratio in the high permeability zone or the result of an unexpectedly high rate of regional tilting in the lagrande 2 area

recent tectonic structures in a transect of the central betic cordillera the betic cordillera has undergone recent alpine deformations related to the eurasian african plate interaction boundary most of the present day relief has been built up since tortonian times and is related to the development of folds and faults that are overprinted on older deformations and some of the faults may be considered as out of sequence the combination of geophysical and geological data makes it possible to determine the main features of the recent tectonic structures or those recently active in its central transect the main fault is a crustal detachment that separates a footwall constituted by the iberian massif and a hanging wall formed by the rocks of the betic cordillera while the footwall is practically undeformed the hanging wall has been folded and faulted the folds are mainly e w to ne sw and have larger sizes and higher related relieves towards the south the reverse faults are mainly concentrated in the northern mountain front however normal faults affect the southern part of the cordillera and are associated with the development of large asymmetrical basins such as the granada depression in this setting the slip along the crustal detachment is variable and should increase southwards the model of the recent tectonics in the central transect of the cordillera is compatible with the presence of an active subduction in the alboran sea and contrasts notably with the setting of the eastern betic cordillera mainly deformed by transcurrent faults

glacial sedimentary processes and environmental reconstruction based on lithofacies glacigenic sediments exposed in pits around villeneuve near edmonton alberta are subdivided into facies based on grain size sedimentary structure glacially induced deformation and faulting and groove marks two diamicton facies are recognised one of which is interpreted as a primary till deposited directly from glacier ice and the other as a product of mass movement the diamicton facies are closely associated with current bedded facies interpreted as fluvioglacial deposits the stratigraphic sedimentological and tectonic aspects of these fluvial deposits suggest subglacial deposition in channels and cavities at any one place the glacier appears to have alternated between being attached to the bed causing thrusting and sole marking and being separated from the bed by a cavity in which fluvial and mass movement sediments accumulated the net result is a highly complex and laterally variable stratigraphy produced by a single glacial advance the correct interpretation of such sequences is essential if lithostratigraphy is to be used to establish glacial history in addition the interpretations presented here have implications regarding the formation of soft zones in till they indicate that the soft zones are beds of sorted sediment redeposited by mass movement

on the effects of bedrock protuberances upon the depositional and relief forming processes in different marginal environments of spitsbergen glaciers abstract the problem formulated in the title is considered on the basis of examples drawn from two retreating spitsbergen glaciers anreasbreen and aavatsmarkbreen which are though to be representative of two mahor types of ice marginal environmnts differing from each other in respect of the geometry and dynamic conditions of the terminal zones these are type a associated with an active steep fronted glacier snout and type b associated with a stagnant terminal zone the environments of type b related the depositional and relief forming processes to the dynamic state of ice prior to stagnation on this basis two sub types are distinguished b 1 associated with a stagnant terminal zone which experienced extending or uniform flow prior to stagnation and b 2 associated with a stagnant terminal zone which experienced compressive flow prior to stagnation larger obstacles to glacier flow on the bed bring about enhanced debris supply at the glacier surface and consequently formation of ice cored moraines equally in all of these environments however the processes involved in the formation of ice cored features as well as their location are different in each in environment of type a ice cored moraines are formed on the lee side of the protuberances in associated with dump moraines while in environments of sub types b 1 and b 2 they tend to be located immediately on the top of the bedbrock protuberances or in close down glacier vicinity and do not differ genetically from the overall ice cored morphology a particularly efficient relief forming process in environments of type b both b 1 and b 2 is thermo erosion by supraglacial meltwater streams there is a general tendency to smooth the pre existing glacier bed irregularities in environment of type a and to accentuate them in environments of type b

interaction of aquifer wetland in a zone of intensive agriculture the case of campo de dalias almeria se spain the campo de dalias almeria south eastern spain was the backdrop for the development of intensive agricultural activity during the 1970s due to the poor natural soil development the agriculturalists opted for a system that involved quarrying silt and clay deposits that could be used as soil in the greenhouses in parallel poor water quality in the upper aquifer caused the gradual abandonment of boreholes and a generalised rise in piezometric levels these factors have favoured the formation of a series of artificial wetlands in the abandoned clay pits onayar cabriles and balsa del sapo toad pond being the most significant in balsa del sapo the water column rose 3 5 m between october 2007 and february 2011 there has been a continuous fall in the electrical conductivity of the surface water which has gone from 14 500 s cm 1 in 2004 to 4 100 s cm 1 in 2013 the most recent concentrations are close to those found in the groundwater the same situation is detected for cl so4 and na ion concentrations in the surface and groundwater these data show the groundwater surface water interaction in the balsa del sapo nevertheless the sharp rise in surface water level has created a flood hazard due to the shallow topography of the area both for people living in the vicinity and their property this is an endorheic zone where a number of ramblas gullies draining the southern face of the sierra de gador mountains converge the campo de dalias is a spectacular example of the changes that can occur in a semiarid agricultural area as a result of intensive groundwater abstraction these changes are directly related to the management of water resources the most recent consequence of which is the increased risk of flooding hence there is a need to consider the management of these water resources to achieve a more sustainable use which is compatible with the environmental protection of the wetland and which will give some guarantee of flood protection for people and property

characteristics and origins of lee side stratification sequences in late pleistocene drumlins northern ireland spindle and parabolic shaped drumlins examined at fifty five localities in northern ireland possess stratification sequences on their lee side flanks these forms lack the distinctive steep stoss and tapering lee ends of classical drumlins and tend to occur in linear zones transverse to late pleistocene ice flow in most cases 90 per cent the stratified deposits infill embayments excavated in the lee side of barkhanoid forms and in the remainder 10 per cent they are superimposed on the lee side of whaleback forms the stratification sequences developed as a result of sedimentation in interconnected subglacial water filled cavities and are unlike remanie proglacial sediments moulded by ice into drumlin form stratigraphic evidence indicates that the lee side sequences developed during drumlin streamlining which supports the view that subglacial hydraulic processes played an important role in drumlin formation

subaqueous outwash deposits in the ingraham ridge chazy new york a 1 5 km segment of ingraham ridge a stratified sand and gravel ridge in northeastern new york is composed dominantly of subaqueous outwash deposits the core of the ridge segment may include subordinate subglacial tunnel deposits the subaqueous outwash is composed mainly of interbedded sediment gravity flow bar dune and ripple deposits that occur in channels sheetlike cross stratified and cross laminated deposits also are common particularly on the distal western margin of the ridge segment the ridge segment is draped by glaciolacustrine laminated sand silt and clay and glaciomarine massive mud westward decrease in grain size and scale of sedimentary structures is attributed to confining ice walls of an asymmetric embayment sediments are deformed in part by the melting of adjacent and buried ice the ridge was modified during champlain sea regression and the reworked deposits were colonized by shallow water organisms reworking may have been minor and the broad low morphology of the ridge

the betic segment of the lithospheric trans alboran shear zone during the late miocene abstract the betic sinistral transcurrent shear zone betic cordilleras crosses the southeastern part of spain the study of the geodynamics of this area is approached from tectonic sedimentary magmatic and geophysical data large strike slip movements tectono sedimentary processes and magmatic events are seen at the boundary between two different lithospheric slabs they are located in a thinned compartment with a high geothermal gradient the large scale movements vertical and horizontal and the intensity of magmatic activity are the expression of the mechanical behaviour of this hot and thin crust all the geological events from the late miocene to recent are integrated in a crustal scale cross section which shows that the betic sinistral transcurrent shear zone widely affects the lithosphere it appears that subduction zones are not the only geodynamic context in which calc alkaline magmatism occurs

depositional controls on the magnetic characteristics of lodgement tills and other glacial diamict facies genetic interpretation of massive unstructured diamict and diamictite facies is a commonly encountered problem faced by sedimentologists data are presented concerning the magnetic characteristics namely anisotropy of magnetic susceptibility ams and natural remanent magnetism nrm of facies deposited by 1 lodgement processes at a glacier base lodgement till and 2 subaqueously by pelagic mud deposition and ice rafting rain out diamicts lodgement tills have an nrm that is distorted around the geomagnetic pole position to form a girdle approximately 90 in length either transverse or parallel to ice flow direction this distension appears to be the result of subglacial shear processes because other diamicts deposited passively by melt out below stagnant ice and modelled by a laboratory experiment show a nondeformed nrm clustering around the geomagnetic pole the ams data show that lodgement tills have only a weakly orientated magnetic microfabric glaciolacustrine rain out diamicts show

vertical deformation 1952 1987 in the salton trough california from water level recordings analysis of 36 years of water level data from three sites on the shore of the salton sea reveals a history of vertical deformation in the salton trough data from two sites allow estimation of tilt along a 36 km nw se baseline between 1952 and 1970 since 1970 the addition of a 13 km wnw ese baseline allows the full tilt vector to be estimated we find down to the southeast tilting at an average rate of about 0 01 0 01 rad yr from the early 1960s to 1987 an anomalous period of more rapid 0 2 0 04 rad yr tilting occurs between the mid 1950s and early 1960s but this coincides with a period from which we have been unable to examine all the original data a previous analysis of the 1952 1978 data suggested a precursory increase in tilt rate prior to the 1968 borrego mountain earthquake and a tilt reversal in 1972 we show that there was no significant tilt change prior to the 1968 earthquake and that the apparent 1972 reversal resulted from uncorrected offsets in the water level observations tilts derived from water level and from reliable first order leveling surveys show limited agreement but the leveling data contain evidence for nonuniform tilting recent analyses of leveling data by others using different techniques show 20 30 cm uplift and subsidence events in the salton trough between 1968 and 1978 our data constrain the relative elevations of the three water level sites to be stable within 1 2 cm during these proposed events

faulted hybrid joints an example from the campo de dalias betic cordilleras spain abstract the development of hybrid and faulted joints has not been studied in detail in natural outcrops this field study in the campo de dalias betic cordilleras establishes the distinctive features of these structures as compared with those predicted by theoretical studies hybrid joints appear as two sets of vertical joints forming variable angles but generally about 25 with opening directions orthogonal to joint planes their development requires low differential stresses with a tensile minimum stress the main criteria that indicate the existence of faulted joints are 1 the presence of subvertical fault planes with oblique slip forming a complex pattern of dextral and sinistral faults developed under a single stress regime 2 faults with similar geometries as joints in the same outcrop showing an inconsistent cross cutting relationship and 3 the development of small basins with variable polarity of asymmetric wedge filling a permutation in stress orientation since the tortonian in the campo de dalias was responsible for the development of a faulted hybrid joint system with a constant ene wsw extension trend and a switch of 1 between nnw sse and vertical

correlation of late wisconsin glacial phases in the western great lakes area late wisconsin glacial phases of the superior lobe in wisconsin and adjacent minnesota are tentatively correlated across northern wisconsin and adjacent michigan to phases of the green bay and lake michigan lobes spanning the period from about 26 000 yr b p to about 9500 yr b p 7 phases of the late wisconsin laurentide ice sheet are discussed but only 2 of these are precisely dated ice advanced out of the basins of lakes superior and michigan and stabilized during the st croix hancock phase the most extensive late wisconsin phase in most of the area between about 18 000 and 15 000 yr ago following the st croix hancock phase the general wasting of the ice was interrupted by stillstands or readvances of the ice margin during the intermediate and mountain phases the ice then wasted into the superior basin before readvancing over a landscape containing ice masses from earlier phases during the winegar early athelstane phase this phase is believed to have occurred just prior to growth of the two creeks forest in eastern wisconsin the ice then wasted back and advanced three more times during the marenisco late athelstane porcupine about 11 000 yr b p and marquette about 9900 yr b p phases

the 1890 surge end moraine at eyjabakkajokull iceland a re assessment of a classic glaciotectonic locality abstract the glaciotectonic architecture and sequential evolution of the eyjabakkajokull 1890 surge end moraines in iceland were studied for understanding better the formation and evolution of glaciotectonic end moraines and their relation to glacier dynamics based on morphological geological and geophysical data from terrain cross profiles cross sections and ground penetrating radar profiles we demonstrate that three different qualitative and conceptual models are required to explain the genesis of the eyjabakkajokull moraines firstly a narrow single crested moraine ridge at the distal end of a marginal sediment wedge formed in response to decoupling of the subglacial sediment from the bedrock and associated downglacier sediment transport secondly large lobate end moraine ridges with multiple closely spaced narrow asymmetric crests formed by proglacial piggy back thrusting thirdly a new model shows that moraine ridges with different morphologies may reflect different members of an end moraine continuum this is true for the eastern and western parts of the eyjabakkajokull moraines as they show similar morphological and structural styles which developed to different degrees the former represents an intermediate member with decollement at 4 5 m depth and 27 33 shortening through multiple open anticlines that are reflected as moderately spaced symmetric crests on the surface the latter represents an end member with decollement at about 27 m depth and 39 horizontal shortening through multiple high amplitude overturned and overthrusted anticlines appearing as broadly spaced symmetric crests we propose that the opposite end member would be a moraine of multiple symmetric wide open anticlinal crests of low amplitude our data suggest that the glacier coupled to the foreland to initiate the end moraine formation when it had surged to within 70 190 m of its terminal position this indicates a time frame of 2 6 days for the formation of the end moraines

changes in morphology at the margin of the greenland ice sheet leverett glacier in the period 1943 1992 a quantitative analysis changes in ice marginal morphology near leverett glacier a small outlet glacier at the western margin of the greenland ice sheet are determined from a photogrammetrical analysis to be able to compare two datasets from subsequent years with measurements at different coordinates kriging was used for interpolation in this study the kriging standard error is used to evaluate the relative accuracy of the resulting maps aerial photographs of 1943 1968 and 1985 were compared in the period 1943 1968 an area of 0 2 106 m2 was deglaciated approximately 1 1 10 m3 of material is deposited in this area the southern part of the deglaciated area is characterized by ice cored moraines while moraines without ice core were formed in the north differences in depositional products reflect differences in meltwater activity and probably ice marginal thermal regime during deglaciation a small proglacial sandur decreased in altitude by 3 2 0 1 m from the early 1970s leverett glacier advanced over a previously deglaciated area during this advance small ice marginal accumulations were incorporated and eroded by the advancing glacier erosion products were for a substantial part stored in the proglacial sandur about 1 2 105 m2 of the northern part of an ice cored moraine complex decreased in altitude by 3 6 0 1 m from 1943 to 1968 and over 2 7 104 m2 by 2 7 0 1 m during 1968 1985 the spatial patterns of altitude change were analysed in relation to topomorphological parameters as exposition and slope angle and areas occupied by lakes the estimated energy used to melt the subsurface ice of the ice cored moraine is 1 4 2 2 w m2 1943 1968 and 1 0 1 6 w m2 1968 1985 these values are 30 50 times larger than the geothermal heat flux for the expected average debris concentration of the ice core 10 per cent by volume the deviation of the surface energy balance forced by climate change will be small and encompass an insignificant part of the total estimated energy used for melting

sedimentation and stratigraphy at eyjabakkajokull an icelandic surging glacier a model for sedimentation by surging glaciers is developed from analysis of the debris load sedimentary processes and proglacial stratigraphy observed at the icelandic surging glacier eyjabakkajokull three aspects of the behavior of surging glaciers explain the distinctive landformsediment associations which they may produce a sudden loading of proglacial sediments during rapid glacier advances results in the buildup of excess pore pressures failure and glacitectonic deformation of the overridden sediments b reactivation of stagnant marginal ice by the downglacier propagation of surges is associated with large longitudinal compressive stresses these induce intense folding and thrusting during which basal debris rich ice is elevated into an englacial position in a narrow marginal zone as the terminal area of the glacier stagnates between surges debris from this ice is released supraglacially and deposited by meltout and sediment flows c local variations in overburden pressure beneath stagnant crevassed ice cause subglacial lodgement tills which are sheared during surges to flow into open crevasses and form crevasse fill ridges

subglacial till a physical framework for its properties and processes the continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized the proposed framework is provisional in two senses the constitutive description of till will require improvement and not all potentially significant processes have been included till is treated as a three component mixture of water clasts coarse grained solids and fine grained matrix solids these components obey mass balance equations and their behavior is subject to constitutive relations that describe such processes as darcian water transport fine grained sediment transport consolidation shear deformation dilatancy and comminution five state variables uniquely determine the compressibility permeability shear strength and other physical properties numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment

the relative locations of multiplets in the vicinity of the western almeria southern spain earthquake series of 1993 1994 summary we have analysed 721 earthquakes 1 5jmbj5 0 of the 1993 1994 western almero a southern spain series and the following seismicity in the area until 1998 among the data there are several multiplets events characterized by very similar seismograms at the short period stations of the local network we detected similar seismograms using crosscorrelation analysis of the p and s arrivals and classified similar events into families or clusters we found 39 multiplet clusters of 3 33 events within each cluster relocations relative to a master event have been calculated by using the interpolated cross correlation maxima for the precise relative timing of p and s phases at each station relative arrival times have been compared for all the possible selections of the master event and adjusted by forming the mean value after removing the outliers the distribution of the stations does not permit a satisfactory resolution of focal depths but relative epicentres have been determined with an accuracy of a few tens of metres typically they draw well defined lineaments and show two dominant strike directions n120u 130ue and n60u 70ue these directions are coincident with known fault systems in the area and with the source parameters of three of the largest events mw 4 8 3 6 and 4 9 which were estimated from waveform modelling of near field acceleration records at a single station consistent with previous studies distances within multiplets typically several tens of metres are for the most part clearly smaller than the fracture radii of these events this indicates repeated slip on the same fault segment it was possible to obtain precise relative locations between several nearby clusters thereby imaging a very heterogeneous seismotectonic fine structure of the source area i e the positions of adjacent active fault segments and the fragmentation of the crust into small approximately 1 km tectonic blocks

smooth folds favoring gypsum precipitation in the messinian poniente marginal basin western mediterranean abstract the poniente basin lies in a folded sector located at the boundary between the eastern betic cordillera and the alboran sea we reconstruct its 3d geometry combining depth migrated 2d seismic reflection sections with borehole and surface structural data the folds have been interplaying with sedimentation since late miocene time growth strata allow us to reconstruct both the folding history and the average shortening rate two isolated antiforms began to grow during the late tortonian separated by an antiformal saddle point a rectilinear fold linkage sector between initially isolated short segments developed during the messinian eventually forming a subcylindrical ene wsw trending antiform that has continued growing symmetrically since the pleistocene the antiform formed a barrier that favored messinian evaporite deposition along the contiguous synform to the north the vertical breakup between the lower parts of the synform and the barrier anticline culmination ranges from 500 to 700 m in the last 7 2 ma the analyzed folds accommodated a shortening of 52 m ma along a 20 km wide band at a mediterranean scale our study sheds light on the propagation mode of barriers that favor the precipitation of gypsum in peripheral basins by restricting water exchange with the open sea before the main phase of evaporite deposition occurred in the deep basin