tectonic and environmental evolution of quaternary intramontane basins in southern apennines italy insights from palaeomagnetic and rock magnetic investigations summary southern apennines is characterized by active extensional tectonics with ne sw stretching direction the seismicity of the region is very well understood and continuously monitored in contrast the onset of extensional tectonics is chronologically poorly constrained the aim of this study is that to give important constraints on the development of extensional regime and the onset of the continental deposition during quaternary in southern apennines we report the results of palaeomagnetic and rock magnetic analyses from four quaternary small intramontane basins in the picentini mountains southern apennines the sedimentary sequences are located at different altitudes from 600 to 1200 m a s l and were deposited in fluvial lacustrine environments we sampled 29 sites in clays and lacustrine limestones from tizzano piano del gaudo and acerno basins and in red palaeosoils and matrix supported conglomerates from the iumaiano basins in the clay and limestones samples magnetite titano magnetite hematite and iron sulphide have been recognized as the main magnetic carriers whereas magnetite and hematite characterize the iumaiano conglomerates and red soils palaeomagnetic results have been integrated with published radiometric data in order to constrain the age of each sedimentary basins sites from the iumaiano basin which represents the substrate of the tizzano and piano del gaudo basins show a reverse polarity and therefore have been attributed to the lower matuyama chron in contrast palaeomagnetic data from tizzano basin show a transition from reversed to normal polarity along the exposed section which has been interpreted as the matuyama brunhes transition sites from acerno and piano del gaudo basins show a normal polarity which according to radiometric and pollen data have been correlated to the brunhes epoch on the base of such results we discuss the tectonostratigraphic evolution of the basins and the role of extensional tectonics in this portion of the southern apennine during the quaternary

pennsylvanian uplands were forested by giant cordaitalean trees the precise timing of when upland terrains first became forested is highly controversial pennsylvanian palynoflora and megaflora transported into marine highstand deposits imply that emergent topographic highs may have supported cordaitalean forests the discovery of a new pennsylvanian bolsovian plant assemblage in southwest newfoundland confirms this hypothesis and allows the architecture of these upland trees to be reconstructed in detail the assemblage includes several hundred calcareously permineralized stumps trunks and branches and represents the remains of shallowly rooted cordaitalean trees that were 48 5 m high when mature the fossils occur in alluvial conglomerates that constitute a 10 km diameter outlier on the margins of the paleoequatorial variscan foreland the paleogeographic setting together with plant taphonomic inferences strongly indicate that these giant trees were transported from nearby upland alluvial plains and deposited in an elevated intermontane basin this interpretation is supported by analysis of rootstock morphology which implies tree growth in thin soils consistent with an alluvial gravel substrate this improved understanding of pennsylvanian upland forests has important implications for geochemical modeling of the global carbon cycle

transpression and extensional collapse steep belts and flat belts in the appalachian central mobile belt northern new brunswick canada models of the appalachian caledonian orogen infer oblique collision and an enigmatic reversal from sinistral silurian to dextral devonian transpression the miramichi highlands in canada are relevant to such models because 1 they are a subductional thrust complex in which the inferred reversal coincided with recumbent folding and 2 its kinematic indicators include rotated thrust structures and conjugate sets of coeval structures both are easily mistaken as evidence for sinistral and dextral transpression the thrust complex is part of the appalachian central mobile belt and is partitioned into steep belts and flat belts according to the attitude of the schistosity we argue that the steep belts are coeval with late silurian plutonism and low pressure metamorphism representing transpressional zones d 2 in which the extension lineation of d 1 thrusting was tilted twice first from gentle to steep then back to a gentle plunge the transpression was synchronous with exhumation as well as sedimentation flat belts represent a later flattening d 3 that probably resulted from extensional collapse and preceded early devonian dextral transpression d 4 along the central mobile belt our model for the flat belts differs principally from models proposed for equivalent flat belts in newfoundland

devonian extension in northwestern newfoundland 40ar 39ar and u pb data from the ming s bight area baie verte peninsula abstract the ming s bight group of northwestern newfoundland an outlier of humber zone continental margin rocks is entirely surrounded by ophiolitic rocks of the dunnage zone structures in the ming s bight group and adjacent units record three main phases of deformation the earliest structures relate to silurian sinistral transpression previously documented in the region two later phases of extensional deformation produced a series of dextral oblique normal shear zones and faults that now separate the ming s bight group in the footwall from ophiolitic and granitoid rocks in the hangingwall 40ar 39ar and u pb data constrain the times of oblique normal shear and cooling metagabbro in the point rousse ophiolite complex which lies in the hangingwall preserves disturbed ordovician hornblende 40ar 39ar ages whereas adjacent shear zones record devonian ages hornblendes in pacquet harbour group amphibolites within extensional shear zones mainly record 40ar 39ar ages of 390 380 ma synkinematic titanite

river channel change during the last 50 years in the middle yangtze river the jianli reach intensive anthropogenic disturbances have affected the channel of the middle yangtze river since the 1950s this paper selects the jianli reach as an example to examine human impact on channel change in the middle yangtze river 1 100 000 channel distribution maps from 1951 1961 and 1975 and 1 25 000 navigation charts from 1981 and 1997 were employed to reconstruct channel change in the study reach the result indicates that the channel under the constraint of levees along the riverbanks underwent a minor widening but frequent bank failure due to susceptible bank structure and increase in water discharge the bank failure promoted bar growth in the channel cross section changes and quantitative calculations of erosion and deposition based on the dem derived from navigation charts present a pattern of over bank sedimentation and riverbed incision the stage and duration of floods have increased following levee construction and bank revetment

channel adjustments to reservoir construction and gravel extraction along stony creek california stony creek drainage area 1920 km2 a tributary to the sacramento river 200 km north of san francisco has experienced channel adjustments to both dam construction and instream gravel extraction black butte dam constructed in 1963 reduced flood peaks and trapped the annual 100 000 m3 of bedload sediment formerly delivered from the upper watershed the reach below the dam changed from an active braided channel to an incised single thread channel shortly after dam construction about 25 km downstream of the dam large instream gravel mines annually extract 230 000 580 000 m su3 and have induced channel incision of over 5 m necessitating bridge repairs costing us 1 4 million

deformation path partitioning within a transpressive shear zone marble cove newfoundland detailed study of the structures in marble cove newfoundland indicates that they formed during a single transpressional event during which deformation was partitioned between dominantly strike slip and dominantly dip slip domains marble cove exhibits steeply dipping foliations steeply to shallowly plunging stretching lineations greenschist facies mineral assemblages and abundant quartz veins within the broad domain where stretching lineations plunge steeply sense of shear indicators and asymmetry of quartz c axis distributions in mylonitized quartz veins indicate dominantly reverse motion with a component of dextral shear adjacent greenschists exhibit orthorhombic symmetry and apparently accommodated pure shear the abrupt transition to a narrow high strain domain of shallowly plunging stretching lineations is accommodated by a rheologically distinct serpentinite body shear bands in this domain indicate dextral strike slip movement with a reverse component smaller conjugate shear bands are evident in thin section indicating a component of pure shear sense of shear indicators and asymmetry of c axis distributions in mylonitized quartz veins also record dextral strike slip and reverse shear with a component of pure shear crenulations and asymmetric folds in foliation overprint all other fabrics in marble cove and record a final phase of reverse shear with a dextral component with partitioning of this kind structures recording strike slip movement may be limited in areal extent and therefore less likely to be exposed than structures recording dip slip motion such partitioning within transpressional shear zones may therefore impede recognition of strike parallel motions within orogenic belts

dating transcurrent terrane accretion an example from the meguma and avalon composite terranes in the northern appalachians the polygenetic minas geofracture separates the meguma and avalon composite terranes of the maritime appalachians dynamically recrystallized muscovite and biotite occur within d3 shear zones which developed during dextral movement along the geofracture these record 40ar 39ar plateau ages between circa 360 and 370 ma comparable plateau ages are recorded by micas within undeformed portions of granitic plutons and their low pressure contact metamorphic aureoles these are similar to u pb ages previously reported for igneous monazite therefore indicating relatively rapid postmagmatic cooling at shallow crustal levels the d3 fabrics were superimposed on earlier s1 structures which formed during initial amalgamation of the meguma and avalon composite terranes whole rock slate phyllite samples collected outside high temperature portions of the plutonic contact aureoles yield 40ar 39ar plateau ages which correspond to groupings of circa 400 395 ma 390 385 ma and 380 375 ma these are interpreted to date diachronous formation of the s1 fabrics and concomitant low grade regional metamorphism in the circa 25 ma between initial amalgamation and granitic plutonism it is inferred that there was a slow rise of isotherms through the crust as a result of overthrust tectonic thickening this led to crustal melting and the production of widespread granitic magmas which were emplaced immediately prior to d3 dextral shearing

structural history of continental margin sediments beneath the bay of islands ophiolite newfoundland deformed continental margin sediments of the curling group underlie the bay of islands ophiolite in the humber arm allochthon of western newfoundland within the allochthon tectonic slices of sediments are separated by zones of melange the earliest structures in the slices are synsedimentary features produced by soft sediment deformation on the continental slope or rise later west facing asymmetrical f 1 folds without penetrative axial plane cleavage were probably produced during the emplacement of the allochthon in the middle ordovician taconic orogeny associated extensional structures include shear fracture and extension fracture boudins pervasive cataclastic shearing of shale and boudinage of competent beds produced melange between slices shear surfaces and the original bed parallel fissility of the shale both contribute to the anastomosing fabric of the melange matrix a subsequent folding event of probable acadian age produced upright to moderately inclined f 2 folds with axial plane cleavage increasing in intensity eastwards across the allochthon this event refolded the folds thrust slices and melange zones produced during emplacement later gentle cross folds associated with sporadic development of crenulation cleavage produced culminations and depressions on the f 2 fold hinges

geoinformatics in morphological study of river paglia tiber river basin central italy this work reports the results of a geomorphological study on the river paglia tiber basin central italy to analyse the historical evolution of the riverbed floodplain system in its lower valley reaches upstream the confluence of river tiber a morphological sedimentological approach has been used starting with an historical analysis and a survey of the forms and sediments in the riverbed alluvial plain system in order to reconstruct the current evolutionary trend and to identify the causes and processes leading to changes in natural trends this approach is not in contrast to the hydrologic hydraulic one normally applied in engineering fields but it is integrated with it in a complementary and parallel manner in order to achieve the complete knowledge of the river system result of an investigation multidisciplinary aimed to define its physical state historical data cartographic documents digital terrain models dtm topographic surveys aerial photographs etc indicate clear cut narrowing and deepening of the active channel manifested after the second world war and due to the considerable changes which affected the entire fluvial system from the recovery of land for agriculture near the river to sediments taken from its bed over the past few decades the result is a state of great disequilibrium which is shown in the passage from a braided morphology observed in the 1950s to a single channel with low sinuosity wandering type this type of morphology is certainly more unstable in fact the narrowing and deepening of fluvial sections provide a better hydraulic efficiency for the upstream so the peak discharge does not overflow such peak discharge arrives downstream next to the confluence with the tiber river not laminated causing serious flooding effects an increased vulnerability is observed in the last reach in the areas pertaining to the river where most of the industrial economic activities are concentrated and where transportation infrastructures of nationwide importance italy s most important motorway the a1 and the rome florence milan high speed rail links are located the evolution of the paglia which is not substantially different from that of many streams in italy and in general throughout europe is affected by severe anthropic constraints and intense exploitation of resources which have produced a state of disequilibrium approaching irreversibility in an already vulnerable system finally some suggestions for the correct management of the river system are pointed out with the aim of mitigating the flood risk in the lower paglia valley

high resolution analysis of early diagenetic effects on magnetic minerals in post middle holocene continental shelf sediments from the korea strait 1 two studied sediment cores from the korea strait contain mud sequences 14 m and 32 62 m in thickness that were deposited during the last 6 000 years the sediments have uniform lithology and geochemical properties however marked down core changes in magnetic properties suggest that diagenesis has significantly impacted the magnetic properties an expanded view of early diagenetic reactions that affect magnetic mineral assemblages is evident in these rapidly deposited continental shelf sediments compared to deep sea sediments the studied sediments are divided into four descending intervals based on magnetic property variations interval 1 is least affected by diagenesis and has the highest concentrations of detrital magnetite and hematite and the lowest solid phase sulfur contents interval 2 is characterized by the presence of paramagnetic pyrite and sharply decreasing magnetite and hematite concentrations which suggest active reductive dissolution of detrital magnetic minerals interval 3 is marked by a progressive loss of hematite with depth and coincides with the minimum magnetite concentration interval 4 has an increasing down core enhancement of authigenic greigite which apparently formed at depths of 3 30 m below the sediment water interface due to arrested pyritization reactions these results indicate delays of thousands of years for acquisition of magnetizations carried by greigite which suggests that studies of geomagnetic field behavior from greigite bearing continental shelf sediments should be conducted with care also virtually complete destruction of detrital magnetic minerals at depth suggests that magnetic studies of rapidly deposited shelf sediments are unlikely to provide a meaningful signature associated with syn depositional environmental processes

acadian dextral transpression and synorogenic sedimentary successions in the appalachians the successive seboomook littleton northern appalachians and catskill pocono central appalachians clastic wedges suggest oblique convergence and southwestward migration of acadian orogeny beginning in early devonian and continuing into early mississippian wrench fault movement in maritime canada coincided with deposition of all but the earliest components of the catskill pocono clastic wedge and continued into the pennsylvanian contrasts between a thin lower to middle devonian shallow shelf facies in the alabama appalachian fold thrust belt and a time equivalent thick shallowing upward sedimentary to volcanic succession in the adjacent talladega slate belt are interpreted to reflect a wrench fault basin a wrench fault setting for devonian rocks in alabama integrated with manifestations of oblique convergence during the acadian orogeny in the central and northern appalachians can be accommodated in dextral transpression along the entire length of the acadian appalachian orogen

recent channel adjustments in alluvial rivers of tuscany central italy drastic channel adjustments have affected the main alluvial rivers of tuscany central italy during the 20th century bed level adjustments were identified both by comparing available topographic longitudinal profiles of different years and through field observations changes in channel width were investigated by comparing available aerial photographs 1954 and 1993 98 bed incision represents the dominant type of vertical adjustment and is generalized along all the fluvial systems investigated the arno river system is the most affected by bed level lowering up to 9 m whereas lower incision generally less than 2 m is observed along the rivers of the southern part of the region human disturbances appear to be the dominant factors of adjustments the main phase of vertical change occurred during the period 1945 80 in concomitance with the phase of maximum sediment mining activity at the regional scale the second dominant type of adjustment that involved most of the rivers in the region consists of a narrowing of the active channel based on measurements of channel width conducted on aerial photographs 38 of the reaches analysed experienced a narrowing greater than 50 of the initial channel width the largest values of channel narrowing were observed along initially braided or sinuous with alternate bars morphologies in the southern portion of the region a regional scheme of channel adjustments is derived based on initial channel morphology and on the amounts of incision and narrowing different styles of channel adjustments are described rivers that were originally sinuous with alternate bars to braided generally became adjusted by a moderate incision and a moderate to intense narrowing in contrast sinuous meandering channels mainly adjusted vertically with a minor amount of narrowing copyright 2003 john wiley sons ltd

post taconian shortening inversion and strike slip in the stephenville area western newfoundland appalachians deformed terrigenous and carbonate sedimentary rocks representing the early paleozoic laurentian continental margin form a series of elongate fault bounded blocks that plunge north beneath the humber arm allochthon in the stephenville area west newfoundland appalachians the continental shelf succession was folded and thrust faulted after emplacement of the humber arm allochthon in the west of the area table mountain is cut by a pop up structure bounded by downward converging reverse faults structures at the east margin of table mountain indicate both dextral and reverse slip the phillips brook structure farther east contains multiple fault bounded carbonate slices one slice carried by the west blanche brook fault is thrust over the humber arm allochthon the western edge of the indian head massif consisting of grenville basement is also a thrust contact these reverse faults and thrusts which cut the carbonate succession and postdate emplacement of the humber arm allochthon are in turn

channel incision gravel mining and bedload transport in the rhone river upstream of lyon france canal de miribel the miribel canal is a former arm of the rhone embanked between 1848 and 1857 over a length of 18 km to improve navigation at low discharges the impact of this was a hydraulic tilting of the long profile characterised by 4 m of degradation upstream and 4 6 m of aggradation of bedload downstream this phenomenon increased downstream flooding since 1937 a diversion dam has controlled upstream water input thus reducing the transit of the pebble bedload however excessive harvesting of sands and gravels occurred between 1970 and 1980 resulting in a general lowering of the river bed and the accompanying water table with ecological consequences in the alluvial plain and for water supply this development made it all the more necessary to obtain knowledge about the bedload discharges passing through the miribel canal and more broadly about the hydraulic conditions as functions of the varying discharge calculation of shear stresses and grain size measurements on the lateral bars after several floods in 1989 90 show that movement of bed material is initiated at a discharge of 440 m3 s 1 equalled or exceeded 40 days year 1 and becomes general at 550 m3 s 1 equalled or exceeded 30 days year 1 transport discharge is thus relatively frequent and involves distal fluvio glacial deposits composed of fine grained materials potential transport calculated by the meyer peter formula is around 60 000 t year 1 for the range of discharges between 440 and 850 m3 s 1 for these discharge values the canal experiences a loss of materials without replacement from upstream for higher rates of discharge the floodgates let through an unknown quantity of materials which partially make up the loss gravel harvesting ceased in 1991 but the diversion dam will have to be operated in a different way in order to increase the input of bedload into the canal

basin evolution in western newfoundland new insights from hydrocarbon exploration the humber zone is the most external zone of the appalachian orogen in western newfoundland it records multiphase deformation of the cambrian ordovician passive margin and of the ordovician to devonian foreland basins by the taconian salinian and acadian orogenic events the recent phase of exploration drilling has provided new evidence for structural stratigraphic reservoir and source rock maturation models of western newfoundland the first well port au port 1 supported the hypothesis that the round head thrust had an earlier extensional history prior to the acadian compressional inversion that created the present day structural high of the port au port peninsula the well tested a small anticline formed in a footwall shortcut fault of the round head thrust the second well long point m 16 was drilled at the northern tip of long point to test a triangle zone identified by previous workers this well demonstrates that the frontal monocline at the western edge of the triangle zone is elevated by a stack of imbricate thrusts composed of rocks of the taconian allochthon and compressional basement involved faults that have uplifted the cambrian ordovician carbonate platform the structural model developed in the port au port area with the aid of these wells has been extended throughout the humber zone in western newfoundland changes in structural style illustrated by regional cross sections suggest that prospective trap geometries are only developed in the southern and central parts of the region the reservoir model proposed invokes exposure and karsting of the footwalls of extensional faults formed as the carbonate platform collapsed during a middle ordovician hiatus the st george unconformity structural relief became more pronounced as extensional collapse continued through the middle ordovician begin page 394 these structurally high fault footwalls became the foci for dolomitizing and mineralizing fluids that used major faults as fluid conduits during the devonian fluids deposited sulphide ores and created zebra and sparry dolomite and some sucrosic hydrothermal dolomites in the st george group and the table point formation the reservoir model maturity and source rock data and the structural models have been combined with seismic and onshore surface geology this enables the prospectivity of the western newfoundland cambrian ordovician play trend to be evaluated for further exploration

rock magnetism and palaeomagnetism of greigite bearing mudstones in the italian peninsula magnetic measurements were carried out on a collection of samples from different geological settings throughout the italian peninsula the samples display magnetic properties that indicate the presence of ferrimagnetic iron sulphide minerals paired samples were also investigated to compare the palaeomagnetic behaviour with respect to different demagnetization treatments thermal static and tumbling alternating field af demagnetization greigite fe3s4 was positively identified in most samples in agreement with previous studies of greigite the sediments display thermal decomposition of the magnetic carriers at temperatures above ca 230 c resulting in decreased magnetic susceptibility values and maximum unblocking temperatures tub mostly in the range 320 350 c high saturation isothermal remanent magnetization sirm to low field magnetic susceptibility k ratios sirm k 10 ka m hysteresis ratios that are typical for single domain sd grains mrs ms 0 5 and b0 cr b0 c 1 5 where mrs is the saturation remanence ms is the saturation magnetization b0 c is the coercive force and b0 cr is the coercivity of remanence moderate coercivity with b0 cr values that range between 52 and 81 mt and a tendency to acquire a significant rotational remanent magnetization rrm we also found that greigite bearing sediments are particularly sensitive to field impressed anisotropy we propose a new magnetic parameter that can be used as a rapid mean to screen a rock sample for the presence of greigite which relies on its sd behaviour in field impressed anisotropy experiments in greigite bearing sediments the magnetic susceptibility measured in a given direction is increased by the application of a relatively high magnetic field 0 9 t in our experiments at right angles to this direction the susceptibility increase is directly correlated to the concentration of greigite in the sediment the comparative palaeomagnetic analysis of standard demagnetization techniques indicates that thermal demagnetization in close steps up to 350 380 c is clearly the most effective treatment for the isolation of the remanent magnetization carried by greigite whereas af demagnetization treatments display significant acquisition of unwanted magnetic remanences gyroremanent remanent magnetization grm and rrm at fields above ca 40 mt

stratigraphy and depositional environments of the upper mississippian codroy group port au port peninsula western newfoundland upper mississippian middle visean biohermal limestones siliciclastics evaporites and red beds of the lower codroy group correlative with the lower windsor group in nova scotia bevel a rugged paleokarst of late devonian early mississippian age on the port au port peninsula western newfoundland laminated limestones ship cove formation and overlying evaporites codroy road formation are similar to the sequence in the bay st george subbasin southwestern newfoundland in the port au port region this sequence is laterally equivalent to biohermal limestones and plant bearing siliciclastics of the proposed big cove formation and red beds of the lower cove formation lithostratigraphic correlation is supported by miospore and conodont biostratigraphies use of macrofaunal subzones is cautioned because there is evidence for the need to reevaluate the ranges of fossils that have previously been considered key indicators e g martinia galataea bell for parts of the codroy and windsor groups the na

medium and short term channel planform changes on the rivers tay and tummel scotland abstract channel planform change was analysed using a variety of data sources for the medium term 25 years and

timing of peak metamorphism and deformation along the appalachian margin of laurentia in newfoundland silurian not ordovician u pb and ar ar isotopic age data from the corner brook lake region of the eastern appalachian humber zone in western newfoundland indicate that regional deformation and peak amphibolite facies metamorphism are early silurian a lower limit on deformation is provided by a u pb zircon age of 434 2 3 ma for a pegmatite that is affected by the regional foliation and is interpreted to be syntectonic monazite and rutile from a garnet kyanite staurolite schist which records peak metamorphic conditions and in which porphyroblasts have overgrown the regional foliation gave u pb ages of 430 2 ma and 437 6 ma respectively ar ar cooling ages for hornblende from amphibolites and muscovite from psammitic and pelitic schists range from 430 to 420 ma a silurian age for deformation and metamorphism of the laurentian margin is coincident with the timing of similar events along the newfound land gondwana margin and suggests that the silurian was a period of major continent continent collision

strain induced mineral growth in ductile shear zones and a preliminary study of ductile shearing in western newfoundland in the fleur de lys and the central gneiss terranes the presence of strain induced mineral growth characteristic of ductile shear zones within zones of rocks with mylonitic fabrics indicates the existence of major belts of layer parallel ductile shearing with complex evolutionary sequences kinematic markers in several of these shear belts indicate that shearing movements on initially probably gently inclined surfaces directed not normal to the axial trend of the orogen but parallel to it are tectonically important in western newfoundland the shear belts are in excess of 1 km thick and one well exposed example exhibits a pattern in which zones of the highest strain anastomose on the map scale the base of the fleur de lys supergroup is marked by one such major zone of shearing decollement in which kinematic indicators record movements directed to the north and to the south before the regional attitude of the rocks was steepened along the baie verte line earlier north and south directed movements

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

bay of islands and little port complexes revisited age geochemical and isotopic evidence confirm suprasubduction zone origin the bay of islands complex of the humber arm allochthon west newfoundland contains the best exposed ophiolite in the appalachian orogen associated structural slices the little port and skinner cove complexes also contain rocks formed in an oceanic domain although their relationship to the bay of islands complex remains controversial to constrain the origin of the complexes and obtain a better understanding of the geology of the humber arm allochthon we have undertaken an integrated geochronological geochemical and isotopic study a u pb zircon age of ma for the little port complex and a zircon and baddeleyite age of 484 5 ma for the bay of islands complex have been obtained geochemical and isotopic data on trondhjemitic rocks from the two complexes indicate that petrogenetic models for these rocks must account for fundamental differences in source materials and mineralogy during differentiation the little port complex trondhjemites are characterized by initial end of 1 to 1 whereas those

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

stratal disruption and development of melange western newfoundland effect of high fluid pressure in an accretionary terrain during ophiolite emplacement abstract the bay of islands ophiolite was emplaced onto the continental margin of north america during the mid ordovician taconic orogeny when tectonic slices of continental margin sediments were accreted to the moving allochthon tectonic slices grade into and are surrounded by melange early fracture in sandstones formed without grain breakage and allowed penetration of liquid petroleum along fracture planes other fractures involved cataclastic flow and were sometimes re activated during formation of later pressure solution cleavage shear fracture and extension fracture boudinage affect competent strata extensional veins cut cement in limestone beds and are filled by shale quartz calcite and bitumen folds also formed at a time when siltstone and sandstone were at least partially lithified melange matrix shows abundant shear and extension fractures in a variety of orientations coaxial extension responsible for disruption of bedding can be explained by a brittle accretionary wedge model in which high fluid pressures resulted from tectonic dewatering of shales surface slope decreased as fluid pressure rose beneath the ophiolite causing horizontal extension of the wedge after escape of excess water the surface slope steepened again as renewed stacking occurred

spatio temporal patterns of channel changes in response to a major flood event the case of the magra river central northern italy on october 25th 2011 the magra river central northern italy was affected by a significant flood event with an estimated return interval ranging from 30 to 200 years this study investigates the morphological responses of the magra river to this major flood event with the aims of i documenting the channel changes which occurred in response to the flood ii analysing this response within the context of the historical trend of width changes iii investigating the possible factors controlling the spatial pattern and the intensity of the observed changes significant channel widening was documented along the entire length studied about 34 km ranging from 3 to 90 of the pre flood channel width braided reaches were characterized by the most severe planimetric changes although characterized by high rates of change these variations are however amply included in the historical range of channel width variability over approximately the last 150 years from 1877 to present day and are comparable with though generally lower than the channel width of the 1950s statistical analyses simple and multiple regressions between the observed changes in channel width and a series of selected morphological and hydraulic controlling factors showed no robust correlations to explain the spatial pattern and the variability of channel adjustments instead major adjustments occurred along reaches characterized by the confluence of those streams draining the sub catchments where the storm was concentrated copyright 2014 john wiley sons ltd

late tertiary quaternary tectonics of the southern apennines italy new evidences from the tyrrhenian slope this paper summarises the results of combined structural and geomorphological investigations we carried out in two key areas in order to obtain new data on the structure and evolution of the tyrrhenian slope of the southern apennines analysis by a stress inversion method angelier j 1994 fault slip analysis and paleostress reconstruction in continental deformation p l hancock ed pergamon press oxford 53 100 of fault slip data from mesozoic to quaternary formations allowed the reconstruction of states of stress at different time intervals by integrating these data with those deriving from the stratigraphic and morphotectonic records chronology and timing of the sequence of the deformation events was obtained the tectonic history of the region can be related to four deformation events structures related to the first event that was dominated by a strike slip regime with a nw se oriented 1 and was active since mid late miocene do not significantly affect the present day landscape as they were strongly displaced and overprinted by subsequent deformation events and or deleted by erosion the second and third events that may be considered as the main responsible for the morphostructural signature of the region are comparable with the stretching phases recognised offshore and considered to be responsible for the opening and widening of the tyrrhenian basin in particular the second event with an e w oriented 3 took place in the late miocene earliest pliocene and was first dominated by a strike slip regime that was also responsible for thrusting and folding since late pliocene it was dominated by an extensional regime that created large vertical offsets along n s to nw se trending faults the third event that was dominated by extension with a nw se oriented 3 started in the early pleistocene and was responsible for formation of the horst and graben structure with ne sw trend that characterises the tyrrhenian margin of the southern apennines the fourth deformation event which is characterised by an extensional regime with a ne sw trending 3 started in the late middle pleistocene and is currently active

lithoprobe onshore seismic reflection transects across the newfoundland appalachians vibroseis seismic reflection data have been recorded to 18 s two way traveltime along three transects across the island of newfoundland the upper crust has both steep and subhorizontal reflectors consistent with a ramp flat style of deformation whereas the middle and lower crust are largely free of regional flats reflectors descend through ca 20 km of vertical section in the middle and lower crust to flatten into the moho or perhaps cut through it in places the moho is interpreted to be no younger than the dipping reflectors reflection fabrics interpreted to be indicators of dominantly mid ordovician to mid silurian strain show consistent orientations among the transects and divide the crust into two blocks a northwestern block is characterized by upper and middle crustal reflectors dipping mostly southeast at variable angles this block is underlain to the southeast by supposedly younger and dominantly northwesterly dipping reflectors that define a northwest tapering wedge shaped block floored

deformation styles at the appalachian structural front western newfoundland implications of new industry seismic reflection data new seismic reflection data gathered during hydrocarbon exploration in and adjacent to the external humber zone western newfoundland have important implications for the interpretation of structural style at the appalachian front these new data indicate that the structural front is influenced by both thin skinned and thick skinned structures where the structural front is thin skinned it is characterized by a triangle zone or tectonic wedge similar to structures observed at the southeastern margin of the canadian cordillera and at other orogenic fronts the thin skinned tectonic wedge is overridden locally by thick skinned thrusts which are generally emergent but are locally blind forming a thick skinned tectonic wedge timing relationships indicate that although initial motion occurred during the early to middle ordovician taconian orogeny the thin skinned allochthonous slices in western newfoundland were not emplaced until devonian time the acadian orogeny thick skinned deformation which p

post deformational growth of late diagenetic greigite in lacustrine sediments from southern italy 1 paleomagnetic rock magnetic and micro textural analyses from a middle pleistocene lacustrine sequence in the southern apennines italy indicate the presence of greigite and magnetite as the main magnetic minerals at different stratigraphic levels in all cases a normal polarity characteristic remanent magnetization chrm was observed in agreement with an 40ar 39ar age of 0 712 0 018 ma from volcaniclastic sanidine after correction for bedding tilt chrm directions carried by greigite do not coincide with the expected geocentric axial dipole field direction at the site latitude whereas the magnetite chrms directions do the data indicate that the greigite magnetization was acquired after tilting and after lock in of the magnetite chrm the estimated delay for the remanence carried by greigite with respect to deposition is 300 ka scanning electron microscope analyses indicate that alteration of detrital volcanic minerals has occurred and that authigenic greigite is generally present in agglomerates and around volcanic grains this observation is consistent with a late diagenetic origin of greigite due to anoxic conditions and availability of dissolved sulfide associated with decomposition of organic matter in the paleolake documentation of a late diagenetic magnetization confirms that care should be taken when using greigite bearing sediments for magnetostratigraphic and tectonic studies

a reevaluation of the position of the baie verte brompton line in the quebec appalachians the influence of middle devonian strike slip faulting in gaspe peninsula the baie verte brompton line bbl the surface expression of the taconian suture in the canadian appalachian orogen extends from southern quebec to the northeast end of newfoundland in the que

carbonate platform to foreland basin revised stratigraphy of the table head group middle ordovician western newfoundland carbonates of the table head group and associated strata were deposited along the western margin of a foreland basin during initial stages of the taconian orogeny and record collapse and cannibalization of a long lived carbonate platform the stratigraphy of klappa opalinski and james is here revised to reflect better understanding of lithologic units within this complex tectono stratigraphic assemblage the table head group now contains only three formations the table point and table cove formations as originally defined and the cape cormorant formation redefined and restricted to western port au port peninsula black cove formation shales are removed from the table head distinctive conglomerates once placed in the cape cormorant are now recognized as separate units within the overlying flysch and called the daniel s harbour member the foreland basin developed in three stages 1 fragmentation uplift and erosion of the platform and subsequent deposition of shallow water limestones table point

structure of the appalachian deformation front in western newfoundland implications of multichannel seismic reflection data petroleum industry multichannel marine seismic data in the public domain do not support the traditional interpretation of the acadian deformation front in the appalachians of western newfoundland they show that the late ordovician to latest silurian long point clam bank succession is folded in a northwest facing monocline whereas the underlying cambrian ordovician platform succession dips southeast we interpret the intervening region as a structural triangle zone similar to those at the foreland edges of other thrust belts the contact between the long point group and the underlying humber arm allochthon previously interpreted as unconformable on port au port peninsula is the southeast vergent upper detachment surface of the triangle zone the platform succession on the peninsula is probably within the triangle zone and is therefore allochthonous at least 30 km of acadian silurian devonian northwest transport is implied the triangle zone continues to the northeast offshore the bay of islands suggesting that grenvillian basement of the long range massif is also allochthonous

flexural modeling of paleozoic foreland basin subsidence offshore western newfoundland evidence for substantial post taconian thrust transport multichannel seismic reflection data gathered by the petroleum industry offshore of western newfoundland constrain the absolute thicknesses of the middle ordovician and post middle ordovician portions of the anticosti foreland basin immediately adjacent to the appalachian structural front these seismic lines which include 1970s vintage data in the public domain and recently acquired proprietary data indicate that the middle ordovician taconian portion of the foreland basin is more than an order of magnitude thinner than the preserved post middle ordovician salinian acadian portion the mechanical lithospheric coupling of foreland basins and their adjacent overthrust belts is a well understood phenomenon a thin taconian foreland succession and a thick salinian acadian succession imply that the overthrust loads responsible for flexural depression of the anticosti basin were much more distant and or much smaller during the middle ordovician taconian orogeny than they are today we quantify thi

environmental magnetism past present and future environmental magnetism involves the application of rock and mineral magnetic techniques to situations in which the transport deposition or transformation of magnetic grains is influenced by environmental processes in the atmosphere hydrosphere and lithosphere the first explicit description of environmental magnetism as a distinct field was in 1980 since that time environmental magnetism has become a broad field that is finding application in an ever increasing array of scientific disciplines in this review of the present state of environmental magnetic studies we divide the field into three broad but arbitrary categories the first involves the use of mineral magnetic assemblages in the geological record to study physical processes in depositional environments this category includes the correlation of sediment cores using magnetic susceptibility measurements studies of geomagnetic field behavior the analysis of depositional and postdepositional mechanical processes that affect sediments and the examination of magnetic parameters that might represent proxies for paleoclimatic variation the second category encompasses studies of the processes responsible for variations in the magnetic minerals brought into a sedimentary environment these provenance investigations include studies of changes in catchment derived sediment in lakes fluctuations in contributions from terrigenous aeolian and glaciogenic components in deep sea sediments and the origin of atmospheric particulates the final category addresses in situ changes and transformations of magnetic minerals in sedimentary environments including pedogenesis authigenetic diagenetic formation of ferrimagnetic phases dissolution of magnetic minerals due to reductive diagenesis and contributions of biomagnetism to sedimentary magnetism because environmental magnetism can address problems in so many disciplines and because many of these problems may be inaccessible to other techniques it is likely that the scope of environmental magnetism will continue to expand rapidly environmental magnetism is capable of providing important data for studies of global environmental change climatic processes and the impact of humans on the environment all of which are major research initiatives in the international scientific community these factors suggest that environmental magnetism has a bright and diverse future

mid paleozoic thrusting at the appalachian deformation front port au port peninsula western newfoundland structures exposed on port au port peninsula in western newfoundland record the nature of the appalachian deformation front which forms the western boundary of the humber tectono stratigraphic zone the major structures affect the late ordovician to late silurian long point clam bank succession but not the unconformably overlying carboniferous rocks they are probably of devonian age at the west coast of the peninsula long point and clam bank strata are affected by both east vergent and west vergent structures the basal surface of the succession is interpreted as an east vergent thrust forming the upper detachment of a triangle zone and correlates with a similarly located contact seen in offshore multichannel seismic profiles within the succession east vergent deformation zones locally duplicate the stratigraphy west vergent structures including a map scale overturned fold north of round head mountain are probably younger farther south middle ordovician foreland basin sediments are also af

sense of displacement on the cobequid chedabucto fault system nova scotia canada the cobequid chedabucto fault system of the canadian appalachians is a major anastomosing fault system over 300 km in length it separates the meguma terrane of southern nova scotia from the avalon terrane to the north these terranes are distinct tectonic and lithological entities in the appalachian orogen two areas at either end of this fault system have been examined in detail to determine the sense and history of offset along it both areas are situated on major component fault zones of the system and both exhibit structures due to early intense ductile shearing that are overprinted by semi brittle to brittle structures caused by later faulting along the eastern chedabucto fault zone area a ductile structures were examined this area is characterized by the progressive development of s c textures and shear bands rotated syntectonic porphyroblasts and asymmetric minor folds features indicative of and caused by ductile shearing along the western cobequid fault zone area b semi brittle and b

melanges and disrupted rocks at the leading edge of the humber arm allochthon w newfoundland appalachians deformation under high fluid pressure abstract the humber arm allochthon was structurally emplaced onto the laurentian margin in western newfoundland during taconian ordovician and acadian devonian deformation on port au port peninsula disrupted allochthonous rocks previously mapped as melange and scaly shale include three mappable variably disrupted stratigraphic units in addition mixed rocks constitute melange with much smaller area than previously mapped at outcrop scale a qualitative assessment of disruption distinguishes broken but coherent stratigraphy from a more disrupted and mixed melange unit within coherent regions three generations of folds are probably related to taconian acadian and carboniferous deformation events more disrupted regions show an average of 24 blocks to 76 matrix with block sizes 0 5 158 cm a new sampling technique allowed recovery of oriented melange samples for thin section multiple orientations of extensional fractures suggest approximately coaxial extension abundant carbonate and less common bitumen filled veins suggest that high fluid pressure played a role in the emplacement of the allochthon high fluid pressure was probably also responsible for dewatering structures sandstone dykes and partially brecciated carbonate beds map relationships outcrop and thin section scale observations lead to a reinterpreted structural history for western newfoundland in which an early taconian west bay thrust sheet was rapidly emplaced onto the laurentian margin during emplacement debris flows initially contributed igneous blocks to the allochthon but the majority of fragmentation took place in an environment of horizontal tectonic extension promoted by high fluid pressure that encouraged brittle fracture the west bay thrust sheet was subsequently overridden by the out of sequence lourdes thrust parts of the allochthon were probably re imbricated in later events but because of previous disruption an organized imbricated thrust belt was not developed at the tip of an advancing thrust wedge a clear distinction between tectonic and surficial processes of melange formation may not be possible

basin development and inversion at the appalachian structural front port au port peninsula western newfoundland appalachians in the humber zone of the newfoundland appalachians cambro ordovician shelf and foreland basin successions are affected by middle ordovician taconian orogeny and devonian acadian orogeny deformation on port au port peninsula the presence of the late ordovician to late silurian long point clam bank succession allows these episodes to be separated the taconian foreland basin stratigraphy on port au port peninsula is highly variable on the west coast platform carbonates are overlain by megaconglomerates of the cape cormorant formation which record progressive exposure of 1 km of the platform succession the conglomerates are restricted to a narrow zone consistent with derivation from a fault scarp originally immediately west of the outcrops in palinspastic restoration farther east at victors brook the cape cormorant formation is absent but the overlying almost undeformed goose tickle group contains conglomerate derived both from the upper part of the platform succession and from the tacon

recent geomorphological changes of the middle and lower calore river campania southern italy the geomorphological changes experienced by the middle and lower calore river southern italy between 1957 and 1998 were investigated data derived from field surveys and interpretation of topographic maps and aerial photos were introduced into a geographic information system gis and processed the results showed that the calore river underwent a mean narrowing of 66 with a peak of 86 the channel length increased by approximately 75 m and the sinuosity from 1 311 to 1 314 the extension of fluvial bars reduced by more than 83 while their number increased from 151 to 381 field evidence of riverbed lowering such as river terraces formed in the considered time span and exhumation of foundations of bridges and flood walls were also constantly detected due to these channel adjustments the calore river morphology changed from transitional to single thread these results were coherent with those reported in the pre existing literature about channel adjustments experienced by many rivers during the twentieth century they all were explainable with a reduction of the bedload transport this latter in turn is completely in accordance with the environmental changes that affected the calore river system in the considered period i e damming and or channelization of the main tributaries reduction of liquid discharge due to water withdrawals and sediment mining from the riverbed

plinian fall deposits from vulsini volcanic district central italy stratigraphic investigations of the vulsini volcanic district indicate the existence of five prominent plinian fall deposits deposited over a period of about 0 34 ma the oldest deposit basal pumices crops out mainly in the peripheral areas and is one of the largest plinian events in the vulsini district with a volume of about 9 km3 and a calculated column height exceeding 30 km subcircular patterns of isopachs and isopleths around the bolsena lake indicate emplacement in wind free conditions and suggest a source vent location in the northernmost sector of the present bolsena lake where it is possible that an older central volcanic structure existed the four younger plinian fall deposits are related to bolsena activity the oldest of these named the ponticello and orvieto bagnoregio pumices are mainly distributed on the north eastern sector of the vulsini district their volumes are an order of magnitude lower than that of the basal unit and the estimated column heights do not exceed 20 km the younger ospedaletto pumice deposit has a ne sw dispersal axis whereas the youngest casetta pumice deposit is found only in the north eastern sector of the district their estimated volumes are respectively 1 2 and 0 1 km3 whereas the inferred vent areas appear to be located slightly to the east of the ponticello and orvieto bagnoregio pumice deposit source areas the chronology of the ospedaletto and casetta pumices indicates that the final plinian activity from the bolsena complex is contemporaneous with the latera activity the decreasing volumes from the oldest to the youngest units together with the progressive shifting northeastwards of the source vents may be related to the volcano tectonic subsidence of the bolsena area the source vents for the post basal pumices events are mainly clustered just north of bolsena village where the greatest displacement during subsidence occurred accordingly source vent shifting appears to be related to the progressive opening of normal faults from the inner to the outer margin of the bolsena depression

bed level adjustments in the arno river central italy abstract two distinct phases of bed level adjustment over the last 150 years are identified for the principal alluvial reaches of the arno river upper valdarno and lower valdarno the planimetric configuration of the river in these reaches is the result of a series of hydraulic works canalization rectification artificial cut offs etc carried out particularly between the 18th and the 19th centuries subsequently a series of interventions at basin level construction of weirs variations in land use intense instream gravel mining after world war ii and the construction of two dams on the arno river caused widespread degradation of the streambed since about 1900 total lowering of the channel bed is typically between 2 and 4 m in the upper valdarno reach and between 5 and 8 m in some areas of the lower valdarno reach bed level adjustments with time are analyzed for a large number of cross sections and described by an exponential decay function this analysis identified the existence of two main phases of lowering the first triggered at the end of the past century the second triggered in the interval 1945 1960 and characterized by more intense degradation of the streambed the first phase derived from changes in land use and land management practices the second phase is the result of the superimposition of two factors intense instream mining of gravel and the construction of the levane and la penna dams