geochemical and textural evidence for early shallow diagenetic growth of stratigraphically confined carbonate concretions upper devonian rhinestreet black shale western new york laterally persistent carbonate concretionary horizons are conspicuous to the upper devonian frasnian rhinestreet black shale of the western new york state appalachian plateau field observations including randomly tilted concretions and differential compaction of host sediment laminae around concretions are consistent with early diagenetic growth in unconsolidated sediment further estimates of pre cementation host sediment porosity based on the volume percentage of caco3 cement 74 93 and perhaps most importantly the preservation of a cardhouse clay fabric in mudstones collected from concretion pressure shadow regions suggest that concretionary growth occurred rapidly within perhaps a meter of the seafloor petrographic examination sem of matrix carbonate samples collected from six concretions reveals a relatively porous 4 7 framework of calcite micrite and microsparite euhedral pyrite most abundant near concretion rims disseminated pyrite framboids and randomly oriented detrital clay platelets and domains c isotopic compositions of rhinestreet concretion matrix carbonate range from 13 9 to 1 7 pdb suggesting derivation of c from a mixed source that included depleted and isotopically heavy c slightly to moderately depleted o isotopic compositions 3 8 to 6 8 pdb do not corroborate the shallow depth of concretion growth suggested by field and textural observations the vertically confined nature of most rhinestreet concretions their large size oblate ellipsoidal shape variable c isotope compositions and absence of any evidence that concretions were sited at local concentrations of organic matter suggest an origin by anaerobic ch4 oxidation early pre concretion sulfate reduction and associated pyrite framboid formation that occurred throughout the host sediment was renewed in thin shallow zones of uncompacted sediment the concretionary horizons by ch4 and isotopically heavy dissolved carbonate diffusing upward from the zone of biogenic methanogenesis to the base of the sulfate reduction zone probably little more than a meter below the seabed local variations in the mix of isotopically light ch4 and heavier dissolved carbonate may have been responsible for the wide range of 13c isotopic compositions of rhinestreet concretions crucial to this mechanism is a pause in deposition that would have held the zone of carbonate precipitation at a fixed distance below the ocean floor long enough for the large concretions to grow evidence that sedimentation slowed or even stopped during concretion growth includes 1 laminae that can be traced through concretions with no observed systematic changes in thickness and 2 minimal concretion center to edge variations in estimated pre cementation porosity a resumption of sedimentation and related burial brought concretion growth in each horizon to an end the moderately depleted 18o values of rhinestreet concretions probably reflect the resetting of o isotopic compositions by warm fluids migrating through the permeable concretions during burial

structural evolution of the sarandi del yi shear zone uruguay kinematics deformation conditions and tectonic significance the sarandi del yi shear zone is a crustal scale shear zone that separates the piedra alta terrane from the nico perez terrane and the dom feliciano belt in southern uruguay it represents the eastern margin of the rio de la plata craton and consequently one of the main structural features of the precambrian basement of western gondwana this shear zone first underwent dextral shearing under upper to middle amphibolite facies conditions giving rise to the reactivation of pre existing crustal fabrics in the easternmost piedra alta terrane afterwards pure shear dominated sinistral shearing with contemporaneous magmatism took place under lower amphibolite to upper greenschist facies conditions the mylonites resulting from this event were then locally reactivated by a cataclastic deformation this evolution points to strain localization under progressively retrograde conditions with time indicating that the sarandi del yi shear zone represents an example of a thinning shear zone related to the collisional to post collisional evolution of the dom feliciano belt that occurred between the meso to neoproterozoic 600 ma and late ediacaran lower cambrian times

geochemistry and sedimentology of the lower silurian longmaxi mudstone in southwestern china implications for depositional controls on organic matter accumulation abstract spatial and temporal changes of lithofacies and abundance of organic matter in mudstones control distribution of prospective unconventional petroleum reservoirs in a sedimentary basin lithofacies characterization is an essential prerequisite to understanding of organic matter accumulation depositional processes and water column chemistry this research combines geochemical analyses and detailed sedimentologic observations in order to investigate the depositional controls on organic matter abundance in the prolific black mudstone of the long 1 member of the lower silurian longmaxi formation in southwestern china six primary lithofacies deposited at variable marine water depths and under differing water column chemistry were identified from an 83 m long core based on microscopic observations of sediment texture and structure and biota and analyses of total organic carbon toc content mineralogy and trace element abundances our results show that toc content is well correlated to biogenic quartz content and the non detrital components of v u mo ni and cu suggesting the accumulation of organic matter in the studied mudstone was controlled by high paleoproductivity and anoxic water conditions the good correlations also suggest that the abundant organic matter was produced by algal blooms which are typically associated with radiolarian thrive because of the symbiotic relationship between algal and radiolarian the low mo toc ratios of the three lithofacies formed in deep anoxic environments were similar to the ratios of modern sediments deposited in anoxic euxinic environments suggesting moderate basin restriction during deposition the mudstone in the lower longmaxi formation may be part of the globally abundant organic rich mudstones of early silurian age whose depositional mechanism have yet to be fully explored the distribution of lithofacies in the studied interval shows an overall trend from deep water to shallow water depositional environments we developed a detailed depositional model to interpret the evolution of depositional environments of the lower longmaxi formation this study provides an example to how better characterize unconventional hydrocarbon systems through coupling of rigorous geochemical and sedimentological analysis

andean rolling mosses gather on stone pavements geoecology of grimmia longirostris hook in a high periglacial paramo abstract rolling mosses of grimmia longirostris hook were studied in paramo piedras blancas a high andean area in venezuela using a geoecological research framework focused on interactions between geomorphic ecological and soil processes spatial patterns of mosses were analyzed downslope from granitic outcrops on three slopes at 4445 4480 m elevation fragments from epilithic mosses on the apex outcrops were the source of other mosses distance of moss transport below rocks was measured at all sites mosses on the gentlest 4 34 m long slope were censused along a belt transect on 17 contiguous quadrats density of moss growth forms stone size percent of bare soil cover and surface soil properties were determined surface clast morphology and profile characteristics of a periglacial stone pavement at the slope base were also examined mosses on this site included four growth forms epilithic mosses on outcrops mobile rolling moss balls epilithic mosses on loose clasts and unattached elongated mosses moss balls density 0 87 mosses m2 lay on upper transect plots over bare soils 92 cover disturbed by needle ice soils here contained 43 51 fine grains 0 063 mm and 2 9 5 9 organic matter this made them exceptionally prone to ice segregation and needle ice formation lower transect plots showed 78 100 stone cover cobbles and blocks but little exposed soil mosses attached to loose clasts were exceedingly abundant 31 m2 on this section unattached elongated mosses often resting along boundaries between adjacent stones were also common 5 5 m2 the basal stone pavement showed a shallow 7 cm rock veneer over a 24 cm thick profile with exceptionally fine soil up to 83 2 fine grains 8 6 organic matter a conceptual developmental model emphasizing the close linkages among the spatial distribution of mosses patterns of surface clasts and characteristics of soils and stone pavements is proposed i stones and mosses are transported downhill by needle ice and other frost agents moss fragments gradually assume a globular shape forming rolling moss balls ii when these reach the stones and pavements on the basal slope they cannot be transported any further and remain immobile iii some mosses come to rest along boundaries between stones and develop into unattached elongated mosses or iv they may become gradually attached to cobbles on the stone pavement clasts with epilithic mosses can continue moving toward the basin floor v some mosses become fragmented and provide a source of elongated mosses or remain partially attached to clasts stone pavements develop by a combination of rock accumulation following needle ice transport rock upheaving and sorting by ground frost slope runoff and downward soil illuviation

phyllosilicate orientation demonstrates early timing of compactional stabilization in calcite cemented concretions in the barnett shale late mississippian fort worth basin texas u s a abstract calcite cemented zones in the prolific gas producing barnett shale ft worth basin texas preserve very early compactional fabrics that contrast markedly with fabrics in the enclosing host rocks the compactional state of these zones based upon alignments of phyllosilicates as determined by high resolution x ray goniometry hrxtg complemented by x ray powder diffraction xrpd back scattered electron imaging and elemental x ray mapping points to a prelithification near syndepositional timing of initial authigenic calcite emplacement thus these carbonate cemented zones are of particular interest for the information they provide on the character of grain assemblages and sediment types at the time of deposition and also on the early post depositional environmental chemistry of the barnett shale strata

biogeomorphic relationships between slope processes and globular grimmia mosses in haleakala s crater maui hawai i abstract globular mosses were found in haleakala s crater maui at five locations between 2175 and 2725 m the highest altitude site with abundant epilithic mosses growing on alkali olivine basalt outcrops and a large mossball population was studied mossballs form when moss cushions are dislodged from rocks but continue growing unattached to substrate detachment agents include rainsplash desiccation wind frost and disturbance by birds dark rumped petrels that burrow nests under outcrops or by goats when loosened moss polsters are transported down steep 26 34 slopes by different geomorphic processes including frost mainly needle ice activity runoff and wind mossballs contained two species grimmia trichophylla grev and grimmia torquata drumm growing separately or commingled weight size and various shape indices were determined for 260 specimens shape and size were correlated larger mosses become less spheroidal because heavier specimens are less disturbed by needle ice remaining immobile for increasingly longer time periods thus becoming flattened distance of downslope transport from source rockwalls was measured for 330 specimens 83 shifted 100 cm but only 5 had moved 200 839 cm heavier mossballs moved short distances thus 88 of all biomass remained within 200 cm from outcrops substrate soils were compared with those within globoids surface site soils were much coarser than mossball grains twelve substrate samples had on average 21 3 gravel 2 mm 6 1 fines 0 063 mm and 2 1 organic matter in contrast 12 mossballs contained this area is frequently subjected to freezing temperatures while fog interception from incoming tradewinds contributes significant moisture amounts to precipitation ground disturbance by frost activity seemed significant needle ice grows frequently on this slope as evidenced by widespread presence of miniature sorted stripes striated soils fine earth flags below stones gaps around stones and fine soil raised patches observed during multiple visits biogeomorphic interactions between mossballs and substrate at haleakala are briefly discussed from the perspective of self organized criticality and interpreted to represent a self replicating moss dispersal system dependent on slope geomorphic processes

u pb and th pb whole rock isochrons from metavolcanic rocks of the carolina slate belt felsic volcaniclastic rocks and massive pyrite of a part of the carolina slate belt in south carolina referred to as the haile brewer block seem to have remained closed systems with respect to u th and pb since 465 ma u pb and th pb whole rock isochrons indicate ages of 466 40 2 and 462 53 ma respectively the pb pb secondary isochron age of the volcaniclastic rocks is 455 ma because of the divergent ways in which u th and pb have behaved during the various alteration events that have affected the haile brewer block metamorphism post tectonic intrusion weathering the isochronous relationships most likely represent the emplacement age of the rocks the preservation of u pb and th pb isochrons is thought to be due to the originally glassy nature of the volcaniclastic rocks and to the relatively impermeable character of the rocks which may have been aided by the sealing of pore space by infiltration of penecon temporaneous silica rich hydrothermal fluids the u pb and th pb whole rock ages are considerably younger than the 550 ma age inferred from u pb zircon ages and ediacaran fossil assemblages for the slate belt in north carolina the younger ages agree however with the presence of sponge spicules no older than middle cambrian in the haile brewer block the younger age of the haile brewer block with respect to other parts of the carolina slate belt indicates that the belt is more complex than has been thought

is the central piedmont suture a low angle normal fault in the crystalline southern appalachians the carolina are terrane is in fault contact with the piedmont terrane along a seismically reflective surface dipping toward the hinterland and called the central piedmont suture the central piedmont suture may be interpreted as a thrust but existing data also support a silurian devonian normal slip origin 1 there are lower grade rocks in the hanging wall than in the footwall 2 a normal fault solution allows simultaneous metamorphism of the piedmont terrane and carolina terrane prior to their juxtaposition along the central piedmont suture 3 mineral ages in the piedmont terrane are older in the west than in the east consistent with an eastward progressive unroofing 4 along the western edge of the carolina terrane a linear belt of devonian subalkalic to alkalic granitoids and gabbro norites with low initial 87sr 86sr ratios may represent mantle derived magmas along the axis of rifting that are contemporary with major crustal extension the westernmost piedmont terrane includes the chauga belt the chauga belt comprises metavolcanic and metaplutonic units similar in rock type and age to those of the western carolina terrane chauga belt rocks are interpreted to be the westernmost exposures of the carolina terrane translated west on the lower plate by extension the piedmont and carolina terranes may thus compose a single lithotectonic element the piedmont terrane would represent the basement on which the arc was constructed the terrane was uplifted during extension along a major low angle normal fault recognized today as the central piedmont suture

cocorp seismic profiling of the appalachian orogen beneath the coastal plain of georgia a southeastward extension onto the coastal plain of an earlier cocorp traverse which confirmed large scale thin skinned thrusting of crystalline rocks of the southern appalachians has provided some of the most spectacular reflections yet seen in crustal seismic data most of the reflectors can be interpreted as either fault surfaces or as metamorphosed strata of late precambrian early paleozoic age they are consistent with the hypothesis that a major detachment extends eastward beneath this part of the orogen although other interpretations with a more complex pattern of detachments or sutures are also possible large scale overthrusting provides a mechanism for incorporating sedimentary rocks into the lower crust and may help to explain many of the layered features on crustal seismic data reflections from deep beneath the coastal plain indicate that the structural configuration of the rocks is complex and that the remains of a collision zone are being observed several east dipping horizons which bear strong similarities to thrust faults in valley and ridge sedimentary rocks are seen in the basement at shallow and mid crustal levels beneath the coastal plain the augusta fault for example displays a reflection which extends at a low angle some 80 km or more southeast of its surface position in conjunction with surface geologic information these new data demonstrate that late paleozoic compressive deformation was pervasive and resulted in lateral movements in the upper crust extending from the valley and ridge to the crystalline rocks beneath the coastal plain a distance of 400 km or more a large antiform cresting at about 2 3 sec or about 6 km below the surface and other structures beneath the coastal plain of georgia deserve further consideration for petroleum exploration although metamorphism may have eliminated petroleum from these rocks refracted arrivals and fault geometries indicate two triassic rift basins beneath coastal plain sedimentary rocks one of which has apparently not been recognized previously

kinematics u pb geochronology and 40ar 39ar thermochronology of the gold hill shear zone north carolina the cherokee orogeny in carolinia southern appalachians the gold hill shear zone is the most prominent pre carboniferous structure in the southern appalachian peri gondwanan tract of carolinia common perception based on indirect evidence holds that it is an acadian dextral strike slip shear zone however our recent structural and geochronologic studies directed at the shear zone indicate that it is a complex structure in both time and space structural studies in central north carolina kinematically link deformation in the shear zone to regional shortening structures in both the hanging wall and footwall and indicate that there was a sinistral component to the deformation collectively these structures constitute a regional sinistral transpressional system we obtained nine new u pb zircon ages ediacaran devonian and 12 new 40 ar 39 ar muscovite ages late ordovician middle mississippian these data in conjunction with the regional geology indicate that the shear zone has 12 km of stratigraphic throw and that the main motion on the zone was late ordovician collectively geologic relations structures and the distribution of 40 ar 39 ar ages indicate that the shear zone was reactivated in the late devonian and the middle mississippian the regional late ordovician silurian sinistral transpressive system of which the gold hill shear zone is part represents the most widespread tectonism documented in carolinia it overlaps in time with the ordovician silurian cherokee unconformity in laurentian strata and late ordovician silurian suprasubduction zone magmatism and metamorphism in peri laurentian rocks and consequently is considered a manifestation of the southern appalachian cherokee orogeny marking the accretion of carolinia to laurentia

reprocessing and reinterpretation of cocorp southern appalachian profiles abstract reprocessing of cocorp southern appalachian data was focused on basic seismic evidence for continuation of sediments beneath a master decollement the most important evidence is a nearly continuous series of subhorizontal reflections extending from the valley and ridge province into the piedmont province continuity of subhorizontal reflections becomes tenuous in the inner piedmont careful reprocessing has yielded evidence for termination of strong reflections beneath the allochthon and the beginning of a relatively weak and complex series of events termination of sedimentary rocks beneath the piedmont is interpreted from true amplitude seismic data a zone of detachment continues southeast of the sediment termination as far as the master decollement root zone research on stacking velocities has indicated that complex velocity structures could create apparent low stacking velocities this phenomenon may occur in the charlotte belt of georgia bouguer gravity can be modeled as a former craton of normal density with an accreted margin of very slightly higher density variation in crustal thickness also contributes to the bouguer gravity gradient no continuous large scale overthrust is needed southeast of the interpreted master decollement root zone located beneath the kings mountain belt and charlotte belt

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

carbon oxygen and sulphur isotope variations in concretions from the upper lias of n e england carbon oxygen and sulphur isotope data for transects across two pyrite bearmg carbonate concretions and their host sediments from the upper lias of n e england show symmetrical zonation 13cpdb values of the calcite cement 12 9 to 15 4 indicate that most of it originated from organic matter by bacterial reduction of sulphate augmented with marine and to a lesser extent fermentation derived carbonate organic carbon 13cpdb 26 1 to 37 0 reflects the admixture of allochtho nous terrestrial organic matter with marine material and the selective preservation of isotopically light organic material through microbiological degradation two phases of pyrite are present in each concretion the earlier framboidal pyrite formed throughout the sediment prior to concretionary growth and has 34scd values of 22 to 26 indicating formation by open system sulphate reduction the later euhedral phase is more abundant and reaches values of 2 5 to 5 5 at concretion margins this phase of sulphate reduction provided the carbonate source for concretionary growth and occurred in a partially closed system the 13c and 34s data are consistent with mineralogical and chemical evidence which suggest that both concretions formed close to the sediment surface the 18o values of the calcite in one concretion 18opdb 2 3 to 4 8 indicate precipitation in pore waters whose temperature and isotopic composition was close to that of overlying seawater the other concretion is isotopically much lighter 18opdb 8 9 to 9 9 and large 18o differences between concretions in closely spaced horizons imply that local factors control the isotopic composition of pore waters

rotation of fabric elements in convergent shear zones with examples from the southern appalachians plane strain shear zones between rigid walls which do not rotate but which converge and move laterally relative to each other are here in referred to as convergent shear zones analysis of the deformation in convergent shear zones indicates the existence of two flow apophyses one parallel to the shear zone wall and the other inclined to the wall modeling of the development of fabrics in convergent shear zones indicates the occurrence of stable orientations in which s and c do not rotate and are oppositely inclined to the shear zone boundary the stable c orientation is parallel to the inclined flow apophysis and also is parallel to the approach velocity vector of the opposing walls of the shear zone if it can be demonstrated from field relationships that the walls of a shear zone were rigid and remained parallel then the occurrence of a flow apophysis inclined in the direction of shear is diagnostic of convergent shear s and c fabrics in the ridge road and gundy creek shear zones of the southern appalachian piedmont are interpreted to indicate a convergent shear regime with an approach velocity vector oriented 10 13 clockwise from the strike of the zones

pyritization induced by anaerobic oxidation of methane aom an example from the upper devonian shale succession western new york usa abstract the diagenetic history of the upper devonian rhinestreet shale of the western new york region of the appalachian basin appears to reflect the upward diffusion of methane through these deposits shortly after their accumulation the most obvious diagenetic signature of this process is numerous horizons of authigenic calcium carbonate concretions interpreted to reflect mineralization induced by the anaerobic oxidation of methane aom focused along the sulfate methane transition smt zone additionally a 2 m thick section of the lower rhinestreet preserves a diagenetic record consistent with aom in the form of two pyritiferous stratigraphic horizons the stratigraphically lowest horizon is a 2 cm thick layer containing abundant 34 s enriched 11 8 and 18 4 v cdt coarsely crystalline pyrite the thinness of this interval suggests that aom related diagenesis remained fixed at this stratigraphic position for a brief period of time before these deposits were buried below the smt or the smt shifted position within the sediment column a second paleo smt appears to have stabilized 60 to 80 cm above the 2 cm thick pyritiferous horizon meter scale carbonate concretions being the most obvious evidence of this episode of aom more than this though the apparently fe limited nature of the host black shale induced the downward diffusion of 34 s enriched hydrogen sulfide produced by aom resulting in the precipitation of 34 s enriched 23 1 to 27 3 v cdt pyrite below the smt the maximum depth of diffusion of the sulfidization front was limited by the amount of hydrogen sulfide produced within and near the smt as well as by the availability of reactive iron in underlying deposits the focusing of aom related diagenesis at the two stratigraphic positions was likely caused by non steady state sedimentation however it is impossible to decipher relative timing of formation of the two paleo smts

subaerial river bank erosion processes and their interaction with other bank erosion mechanisms on the river arrow warwickshire uk river bank erosion occurs primarily through a combination of three mechanisms mass failure fluvial entrainment and subaerial weakening and weathering subaerial processes are often viewed as preparatory processes weakening the bank face prior to fluvial erosion within a river basin downstream process domains occur with subaerial processes dominating the upper reaches fluvial erosion the middle and mass failure the lower reaches of a river the aim of this paper is to demonstrate that a subaerial processes may be underestimated as an erosive agent and b process dominance has a temporal as well as spatial aspect bank erosion on the river arrow warwickshire uk was monitored for 16 months december 1996 to march 1998 using erosion pins variations in the rate and aerial extent of erosion are considered with reference to meteorological data throughout the first 15 months all erosion recorded was subaerial resulting in up to 181 mm a 1 of bank retreat compared with 13 to 27 mm a 1 reported by previous researchers while the role of subaerial processes as preparatory is not contended it is suggested that such processes can also be erosive the three bank erosion mechanisms operate at different levels of magnitude and frequency and the river arrow data demonstrate this thus the concept of process dominance has a temporal as well as spatial aspect particularly over the short time periods often used for studying processes in the field perception of the relative efficacy of each erosive mechanism will therefore be influenced by the temporal scale at which the bank is considered with the advent of global climate change both these magnitude frequency characteristics and the consequent interaction of bank erosion mechanisms may alter it is therefore likely that recognition of this temporal aspect of process dominance will become increasingly important to studies of bank erosion processes copyright 2001 john wiley sons ltd

the carolina terrane in northwestern south carolina u s a late precambrian cambrian deformation and metamorphism in a peri gondwanan oceanic arc the carolina terrane comprises an exotic volcanic island arc in the hinterland of the southern appalachian orogen the western portions of the carolina terrane consist of zoned mafic ultramafic plutonic complexes intruded into a pile of basalts and basaltic andesites this sequence of rocks has been interpreted to represent an episode of intra arc rifting prior to regional metamorphism and deformation new u pb zircon ages from the mean crossroads complex in northwestern south carolina along the central piedmont suture confirm relative ages inferred from detailed mapping two foliated metadiorites yield u pb dates of 579 4 and 571 16 ma interpreted to be crystallization ages a foliated metaquartz diorite yields a u pb date of 538 5 ma interpreted to be a crystallization age an undeformed unmetamorpbosed diorite intruding these metamorphosed zoned complex intrusive rocks yields an age of 535 ma hence we believe that intra arc rifting and regional metamorphism and foliation development both occurred between 580 and 535 ma while petrographic and ar ar studies support subsequent middle to late paleozoic regional metamorphic overprint s or at least static recrystallization and or uplift through hornblende biotite muscovite blocking temperatures for ar the 535 ma undeformed unmetamorphosed intrusion suggests late precambrian early cambrian regional metamorphism and deformation was the event responsible for the regional metamorphic fabric in this area of the piedmont these observations contradict the idea that this metamorphism and fabric development are related to presumed early paleozoic accretion of the carolina arc to laurentia as well as correlations with middle ordovician fabric elements in the eastern piedmont instead this fabric is interpreted to record a changing plate kinematics e g migration of triple junction or change in relative motion vectors during semicontinuous diachronous development of an island arc on the gondwanide margin

particle sorting due to off road vehicle traffic in a high andean paramo summary in the paramo de piedras blancas venezuelan andes unrestricted access by off road vehicles orv s within the past 10 years has caused widespread soil damage by generating numerous tire tracks pebbles and vagant lichens thamnolia vermicularis have been sharply segregated in the vicinity of the tracks both are concentrated in the elongated depressions creating an unusual type of sorted stripes materials migrate to tire tracks due to frequent ground frost and formation of needle ice a ubiquitous geomorphic agent of this high paramo lichens also have been concentrated in the tracks by wind activity the role of needle ice in transporting pebbles to hollow depressions is discussed and illustrated with other examples of recent patterned ground from this paramo

particle interaction in fjord suspended sediment abstract glacial flour enters the surface layer of howe sound a fjord in southwestern british columbia as a sediment plume which moves quickly down inlet while gradually mixing with the sea water flocculation occurs in the lower brackish waters of the surface layer although mixing and diffusion are the dominant processes for sediment to enter the marine water once in the underlying marine water zooplankton pelletization and biologic agglomeration of inorganic floccules predominate this generates a response in the order of days between the two layers in terms of sedimentation of particulate matter most particles settling in the fjord environment fall as 1 sand and silt grains containing attached clay particles 2 clay clasts possibly related to river mudballs 3 mineral bearing fecal pellets from pelagic zooplankton 4 large grain inorganic and colloidal floccules and 5 inorganic biogenic agglomerates analysis of sediment trap data has led to the following conclusions 1 water turbidity cannot be used to infer the downward flux of particles 2 size distributions of sediment deposited on the sea bed are a function of non lognormal size distributions from particles composing sub laminae

the orientation of sorted stripes in the maritime subantarctic marion island the orientation of sorted stripes developed in glacial deposits on marion island is examined this study confirms earlier reports of preferential occurrence of sorted stripes on windward slopes however sorted stripes were also found to occur on low angle leeward slopes mechanisms for the orientation of sorted stripes by wind action are discussed copyright 2001 john wiley sons ltd

siderite concretions indicators of early diagenesis in the gammon shale cretaceous the upper cretaceous gammon shale in the northern great plains contains abundant siderite concretions that formed during the early compactional history of the fine grained marine sediments the relative depth of siderite precipitation can be estimated on the basis of textural mineralogical and isotopic evidence siderite concretions that formed at shallow depths in the sediment column contain a large volume percent carbonate 75 85 preserve uncompacted sediment textures and have oxygen isotope ratios similar to those of carbonates precipitated in equilibrium with seawater delta 18 o nearly equal e 0 to 2 per thousand pdb in contrast lower volume percent carbonate values 55 75 and relative decreases in 18 o 16 o values characterize concretions that formed longer after deposition and or at greater depths in the accumulating sediments both volume percent carbonate and delta 18 o values are strongly correlated with independently determined sediment accumulation rates concretions in rapidly deposited sediments formed at shallow depths 200 m later in the burial history the gammon served as both source rock and reservoir for accumulations of biogenic methane and like the siderite concretions the methane was generated during early diagenesis both siderite precipitation and methane accumulation require interstitial pore waters that have sufficiently high bicarbonate activities and that are depleted in dissolved sulfur and free oxygen because of chemical requirements siderite did not precipitate until after the onset of methane generation therefore if the depth of siderite formation is known the minimum depth for the onset of methane accumulation can be inferred the presence of abundant pyrite in slowly accumulated gammon sediments suggests by analogy to data from recent sediments that the depth of siderite precipitation and methane accumulation was controlled by the sedimentation rate in slowly accumulating sediments most organic matter was probably consumed by aerobic organisms and sulfate reducing anaerobic bacteria whereas in areas of more rapid deposition large quantities of organic matter were available for methane generation

sorted stripes on sub antarctic kerguelen island observations of sorted stripes at nine different localities on sub antarctic kerguelen island are presented the study sites range from 25 600 m above sea level and are of varying aspect it is found that there is a strong relationship between stripe orientation and the wind direction to the extent that at one locality stripes were orientated across a slope stripe width was seen to increase with altitude and in addition the coarse stripe was dominant at lower elevations and the fine stripe at higher elevations at one site a secondary set of stripes was observed to occur within the fine stripe of a primary larger set on a trachyte plug there was evidence of lateral squeezing in the formation of the stripes a number of minor observations pertaining to the possible mechanism of stripe formation are given

clay fabric of selected submarine sediments fundamental properties and models abstract clay fabric of selected mississippi delta sediment and a red clay from the eastern equatorial pacific is related to void ratio and depth of burial relatively high void ratio naturally consolidated delta sediment is characterized by a fabric of randomly oriented domains and short linking chains with particles in edge to face and face to face contacts lower intermediate void ratio sediment showed greater particle to particle packing but a consistent predominance of randomly oriented domains with a few chains and a slight development of larger domains than observed in the high void ratio sediment the deeply buried very low void ratio sediment has highly oriented domains and thin long voids the red clay sample is characterized by flocs connected by long linking chains and a very hi h void ratio domains and turbostratic type clay fabric are characteristic of high porosity high void ratio mississippi delta sediments highly oriented domains and long chains are diagnostic of the deeply buried very low porosity delta muds the clay fabric of natural undisturbed samples was compared with laboratory remolded samples for comparison with models suggested by earlier researchers observations using the transmission electron microscope tem support the proposed fabric models for remolded sediment selected samples were studied using the scanning electron microscope sem tentative clay fabric models for undisturbed submarine sediment are proposed and related to void ratios

deep in the heart of dixie pre alleghanian eclogite and hp granulite metamorphism in the carolina terrane south carolina usa the central part of the carolina terrane in western south carolina comprises a 30 to 40 km wide zone of high grade gneisses that are distinct from greenschist facies metavolcanic rocks of the carolina slate belt to the se and amphibolite facies metavolcanic and metaplutonic rocks of the charlotte belt to the nw this region termed the silverstreet domain is characterized by penetratively deformed felsic gneisses granitic gneisses and amphibolites mineral assemblages and textures suggest that these rocks formed under high pressure metamorphic conditions ranging from eclogite facies through high p granulite to upper amphibolite facies mafic rocks occur as amphibolite dykes as metre scale blocks of coarse grained garnet clinopyroxene amphibolite in felsic gneiss and as residual boulders in deeply weathered felsic gneiss inferred omphacite has been replaced by a vermicular symplectite of sodic plagioclase in diopside consistent with decompression at moderate to high temperatures and a change from eclogite to granulite facies con ditions all samples have been partially or wholly retrograded to amphibolite assemblages we infer the following p t t history 1 eclogite facies p t conditions at 1 4 gpa 650 730 c 2 high p granulite facies p t conditions at 1 2 1 5 gpa 700 800 c 3 retrograde amphibolite facies p t conditions at 0 9 1 2 gpa and 720 660 c this metamorphic evolution must predate intrusion of the 415 ma newberry granite and must postdate formation of the charlotte belt and slate belt arcs 620 to 550 ma comparison with other medium temperature eclogites and high pressure granulites suggests that these assemblages are most likely to form during collisional orogenesis eclogite and high p granulite facies metamorphism in the silverstreet domain may coincide with a 570 535 ma event documented in the western charlotte belt or to a late ordovician early silurian event the occurrence of these high p assemblages within the carolina terrane implies that prior to this event the western carolina terrane charlotte belt and the eastern carolina terrane carolina slate belt formed separate terranes the collisional event represented by these high pressure assemblages implies amalgamation of these formerly separate terranes into a single composite terrane prior to its accretion to laurentia

a comparison of stream bank erosion processes on forested and moorland streams in the balquhidder catchments central scotland stream bank erosion rates measured over a two year period on a moorland and a forested stream in the institute of hydrology s balquhidder paired catchments in central scotland were compared bank erosion rates are generally higher on the mainstream of the moorland catchment and highest in wintger on both streams bank erosion is correlated with the incidence of frost minimum temperatures measured on stream banks of the forested stream were an average of 3 7 c higher than on stream banks both outside the forest and on the moorland stream this makes the incidence of frost on forested stream banks half as frequent volumes of material eroded from the mainstreams were combined with bulk density measurements and it is estimated that erosion of the mainstream banks is contributing 1 5 and 7 3 per cent of the sediment yield of the forested and moorland catchments respectively analysis of the vertical distribution of erosion on the banks of both streams suggests an undercutting mechanism which is more pronounced in the moorland stream the influence of trees on bank erosion and possible implications for the management of forest streams are discussed 1997 by john wiley sons ltd

reinterpretation of adcoh and cocorp seismic reflection data with constraints from detailed forward modeling of potential field data implications for laurentia peri gondwana suture abstract to better constrain the structure of the laurentian peri gondwana suture zone maps and a 2 dimensional regional cross section model constrained by seismic data and surface geology have been developed by forward and inverse modeling the aeromagnetic and gravity fields the central piedmont suture cps the boundary between the laurentian inner piedmont and the peri gondwanan carolina terrane is a low angle thrust fault 30 ramping up from an alleghanian mid crustal detachment at depths of about 12 km adcoh and cocorp seismic data image anticlinal structures in the footwalls of the hayesville thrust and the cps above the alleghanian decollement the footwall rocks have previously been interpreted as paleozoic shelf strata on the basis of sub horizontal seismic reflectors however the high densities required to fit the observed gravity anomaly suggest that the folded footwall reflectors may need to be reinterpreted as horse blocks or duplex structures of grenvillian basement the appalachian paired gravity anomaly can be explained by an increase in crustal thickness and a decrease in upper crustal density moving northwestward from the carolina terrane toward the appalachian core a change in lower crustal density is not required so that grenville basement rocks may extend farther to the southeast than previously thought the 5 to 10 km of alleghanian uplift and exhumation predicted by p t crystallization data compiled in this paper can be easily accommodated by thrusting on four major low angle thrust systems great smoky mountain thrust gsmt hayesville brevard and cps unroofing of metamorphic core complexes by normal faulting may therefore not be required to explain the observed exhumation alleghanian collision along the southeastern appalachian margin was predominately orthogonal to strike consistent with the previous reconstructions that call for the counter clockwise rotation of gondwanan west africa creating head on collision in the southern appalachians and at least 370 km of shortening

fabric anisotropy induced by primary depositional variations in the silt clay ratio in two fine grained slope fan complexes texas gulf coast and northern north sea article i nfo high resolution x ray texture goniometry hrxtg has been used to quantify the alignment anisotropy of phyllosilicate minerals in a series of diagenetically altered mudstone samples from the deep subsurface of the texas gulf coast and the northern north sea the sampled formations have undergone a simple burial history with no overprint of tectonic deformation that may have influenced the phyllosilicate orientation observations have been made in two constrained temperature windows 148 150 c north sea data and 169 210 c texas gulf coast wherein less than 20 smectite remains in the mixed layer phase illite smectite quantitative x ray powder diffraction xrpd shows quartz which is dominantly detrital and phyllosilicate content having an inverse relationship quantified illite smectite fabric intensity phyllosi licate alignments ranges from low alignment values of 2 42 m r d multiples of a random distribution to high alignment values 6 75 m r d and chlorite kaolinite ranges from 1 80 to 6 46 m r d we propose that the broad range of phyllosilicate fabric intensity observed reflects the range of quartz phyllosilicate ratios that are the imprint of depositional setting bedform truncation and initial grain size detrital quartz acts to disrupt fabric intensity by being non platy producing areas sheltered from effective stress pressure shadows and acting as a matrix support there is no evidence that bioturbation is a significant control on phyllosilicate alignment in these quartz phyllosilicate mixtures these findings have important implications for the role of grain scale alignment on seismic anisotropy in mudstone systems fabric intensity in post diagenetic samples can be predicted from 1 quartz content and 2 total clay content where

ages of regional metamorphism and ductile deformation in the central and southern appalachians abstract a summary of available geochronology of deformational fabrics formed at greenschist and higher grades in the central and southern appalachians is presented as a map showing the ages of regional metamorphism and ductile deformation the ca 480 435 ma taconic event affected most of the piedmont and blue ridge provinces the ca 380 340 ma acadian event was milder and was centered in the west central piedmont and eastern blue ridge the 330 230 ma alleghanian event exhibits an abrupt ductile deformation front in the eastern piedmont and extends an unknown distance eastward below the atlantic coastal plain

new field evidence for an exposure of the appalachian decollement at the east end of the pine mountain terrane georgia detailed field mapping at the east end of the pine mountain terrane in central georgia indicates that the box ankle fault is an 4 km thick ductile shear zone separating grenvillian basement of laurentian affinity in the footwall from allochthonous accreted terranes in the hanging wall fabric data from the box ankle fault indicate that it is a gently southeast dipping northwest vergent thrust fault recently discovered structural relations together with geochronological data indicate that the box ankle fault is of late paleozoic age we argue that the box ankle fault is a surface exposure of the appalachian decollement the east end of the pine mountain terrane may be the only place in the entire orogen where this fundamentally important structure is exposed for study

the hyco shear zone in north carolina and southern virginia implications for the piedmont zone carolina zone boundary in the southern appalachians the recently recognized hyco shear zone is a first order structure in the southern appalachians that separates sharply contrasting rocks of the carolina and milton terranes in north central north carolina and southern virginia traditionally this boundary has been viewed as a comformable contact between infrastructural milton rocks and suprastructural carolina rocks in contrast our work indicates that shallowly dipping sillimanite gneisses of the milton terrane comprise the footwall of the ductile shear zone whereas moderately to steeply dipping greenschist to amphibolite facies carolina terrane gneisses and metavolcanics form the hangingwall the hyco shear zone has a sharply arcuate surface trace it trends east northeast in the area of hyco lake north carolina and abruptly changes trend to north northeast near the north carolina virginia state line the zone is moderately to steeply south southeast dipping along the hyco lake segment and structures there indicate dominantly dextral strike slip along the virginia segment the zone is moderately to shallowly east dipping with structures indicating thrusting of the carolina terrane over the milton terrane timing constraints on synkinematic plutons indicate that the shear zone is an early alleghanian feature the geometry kinematics and timing of the shear zone are compatible with the interpretation that the hyco lake and virginia segments of the zone represent lateral and frontal ramps respectively in an overall alleghanian thrust regime recognition of the shear zone in conjunction with geological geophysical and isotopic contrasts across the zone negates established views that the milton rocks are a comformable higher grade portion of the carolina terrane these contrasting features instead are remarkably similar to those found along the central piedmont suture the tectonic boundary between the piedmont and carolina zones from south carolina to central north carolina we propose that the hyco shear zone is the northern equivalent of this structure thus our new data on the hyco shear zone have significant regional implications concerning the nature timing and kinematics of this zone boundary

effects of silt clay content on the susceptibility of river banks to subaerial erosion abstract the aim of this paper is to demonstrate how subaerial processes vary with the silt clay content of river bank soil and to consider this variation in the context of erosion observed in the field in particular spatial and temporal variations in erosion interactions with other bank erosion processes and the implications for bank morphology are explored a number of soil blocks of known silt clay content were subjected to a series of freeze thaw and drying wetting cycles changes in the dimensions of the soil blocks were recorded and the mass of soil eroded from each block together with maximum size of eroding aggregates were measured limitations to this methodology are acknowledged including a limited ability to replicate the forces to which a river bank may be subject restrictions imposed by the available equipment in producing temperature and humidity cycles which reflect those occurring in the field and issues of scale the results indicate that river banks with high silt clay contents are the most susceptible to erosion by subaerial processes high susceptibility may influence spatial variations in bank erosion processes and rates including downstream changes in the effectiveness and significance of subaerial erosion a vertical zoning of processes on a river bank is recognised whereby the upper part of the bank is subject to subaerial erosion and the lower part to fluvial erosion given that a high silt clay content tends to indicate increased susceptibility to subaerial erosion but increased resistance to fluvial erosion this vertical zoning may have implications for bank morphology

the geometrical relationship between the stretching lineation and the movement direction of shear zones abstract the geometrical relationship between foliations and lineations in shear zones is considered quantitatively assuming that the internal structures of shear zones have monoclinic symmetry the common practice of directly correlating the pitch or plunge of the stretching lineation with the obliquity of the shear direction is challenged it is the orthogonal projection of the stretching lineation on the shear zone boundary that is parallel to the shear direction a shear zone is parallel to a plane containing both the pole to the symmetry plane and the strike of the shear zone and the shear direction is parallel to the intersection of the symmetry plane and the shear zone boundary the symmetry plane is determined by the stretching lineation and the poles to the s foliation the implications of this study for the interpretation of shear zones are discussed with reference to an actual example

chemical model for the origin of minor limestone shale cycles by anaerobic methane oxidation chemical and isotopic studies of jurassic carbonate concretions indicate an origin by anaerobic methane oxidation concretion growth occurred within the top 1 m of sediment in a thin zone where methane was consumed to stimulate a late rejuvenated phase of sulfate reduction similar chemical and isotopic characteristics are shown by diagenetic carbonate in several limestone shale sequences and an origin by anaerobic methane oxidation is proposed for these sequences also the evolution of isolated concretions into diagenetic limestones depends on the extent of and depth variations in carbonate supersaturation arising from anaerobic methane oxidation and the persistence of a reduced sedimentation rate or a depositional hiatus diagenetic limestones formed in this way can often be recognized by their association with a later pyrite phase that is more abundant and has more positive sup 34 s values than the adjacent shales

ocmulgee fault the piedmont avalon terrane boundary in central georgia the ocmulgee fault is a fundamental boundary within the piedmont of central georgia separating north american piedmont terrane rocks from exotic rocks of the avalon carolina terrane contrasts in stratigraphy metamorphic grade and aeromagnetic signature coincide with the fault trace the fault comprises a broad zone ca 2 km of foliation dipping steeply southeast and containing localized syn and post thermal peak right lateral strike slip shear zones oblique dextral convergence between the avalon and peidmont terranes most likely around 350 ma produced the steep zone and its attendant dextral shear zones steep foliation within the fault zone resulted in its predisposition to later faulting

generation segregation ascent and emplacement of alleghanian plutons in the southern appalachians the carboniferous permian alleghanian orogeny in the southern appalachians produced a distinctive 45 m y long intrusive event that formed a ne trending band of dispersed composite plutons covering 10 500 km 2 of these plutons 75 are metaluminous biotite or amphibole biotite granitoids with lower crustal sources and 20 are peraluminous biotite muscovite garnet or cordierite biotite granitoids with more evolved crustal sources the remaining 5 are gabbroids intermediate rocks and possible alkaline granitoids the granitoid to gabbroid intermediate rock area ratio is 180 1 the exposed intrusive rocks were produced at a relatively slow rate of 2 km 3 linear km m y along the orogen indicating an inability of the source to produce much melt inefficient melting mechanisms or difficulty of magma segregation and ascent the absence of spatial trends in rock composition and age of emplacement the small amount but relative abundance of the granitoids and coincidence with con

top seal development in the shale dominated upper devonian catskill delta complex western new york state the preferential generation of vertical natural hydraulic fractures at the contact of the upper devonian hanover gray shale and overlying dunkirk black shale of the catskill delta complex western new york state suggests that the latter served as a hydraulic top seal to formation fluids migrating upward from deeper in the sediment pile petrophysical properties and small scale textural characteristics of these siliceous fine grained rocks confirm the crucial role of depositional environment and sequence stratigraphic position of a shale lithotype in determining its sealing capacity the especially high sealing capacity of the basal interval of the dunkirk shale inferred early high stand systems tract hst strata reflects the anoxic depositional environment of these deposits that favored the preservation of their abundant organic matter and finely laminated depositional texture the absence of bioturbation enabled the undisrupted sediment notably carbonaceous clay rich laminae to undergo rapid mechanical compaction platy grain reorientation and porosity reduction compaction induced squeezing of ductile organic matter into void spaces further reduced pore throat diameters immediately underlying heavily bioturbated deposits of the organic lean hanover shale inferred upper hst or low stand wedge sediments accumulated in a dysoxic depositional environment disruption of layering and homogenization of sediment by burrowing organisms produced a more porous and permeable microfabric through which formation fluids moved only to be arrested by the high capillary entry pressures at the base of the dunkirk shale natural hydraulic fractures some of which propagated into the dunkirk shale formed when fluid pressure at the top of the hanover shale reached the fracture gradient the high sealing capacity of the basal dunkirk shale was probably enhanced by its finely laminated nature and the generation of biogenic methane both of which contributed to the formation of a near impermeable gas capillary seal

docking carolina mid paleozoic accretion in the southern appalachians accretion of the extensive carolina zone to laurentia is one of the most critical unresolved problems in southern appalachian tectonics synthesis of southern appalachian tectonism reveals three lines of evidence from across the orogen that indicate a late ordovician to silurian time of accretion a tectonic unconformity in native laurentian rocks an extensive magmatic pulse in the piedmont zone of the orogen and active uplift in the carolina zone are all related to this accretionary event structural geometries in the carolina zone suggest that accretion involved sinistral transpression this new model for carolina accretion is consistent with models for the accretion of northern appalachian peri gondwanan terranes collectively their timing and mode of accretion to laurentia place tectonic constraints on paleozoic global reconstructions

growth mechanisms and geochemistry of carbonate concretions from the cambrian wheeler formation utah usa carbonate concretions provide unique records of ancient biogeochemical processes in marine sediments typically they form in organic rich mudstones where a significant fraction of the bicarbonate required for carbonate precipitation is supplied from the decomposition of organic matter in the sediments as a result carbonates that comprise concretions are usually characterized by broad ranges in 13c and include values that are significantly depleted relative to seawater this article reports results from a physical petrographic and geochemical analysis of 238 concretions from the wheeler formation cambrian series 3 utah usa which are unusual in several respects most prominently they formed in organic poor mudstones total organic carbon 0 1 to 0 5 and are characterized by a narrow range of 13c that onlaps the range of contemporaneous seawater values subtle centre to edge trends in 13c demonstrate that concretion precipitation was initiated by local chemical gradients set up by microbial activity in the sediments but was sustained during growth by a large pool of inorganic bicarbonate probably derived from alkaline bottom waters the large inorganic pool appears to have been important in facilitating rapid precipitation of the concretion matrix which occurred via both displacive and replacive carbonate precipitation during early diagenesis stable isotope data from cogenetic pyrite 34s and silica 18o phases provide insight into the evolution of biogeochemical processes during concretion growth and suggest that concretions were formed almost entirely during sulphate reduction with only minor modification thereafter concretions of the wheeler formation appear to represent an end member system of concretion formation in which rapid growth was promoted by ions supplied from sea water as such they offer insight into the spectrum of processes that may influence the growth of carbonate concretions in marine sediments

confirmation of the carolina slate belt as an exotic terrane an assemblage of middle cambrian atlantic faunal province trilobites has been found in the rocks of the carolina slate belt near batesburg south carolina geologic and paleomagnetic data suggest that the carolina slate belt and the adjacent charlotte belt constitute an exotic terrane that was accreted to north america in early to middle paleozoic time

the association of folds and veins in shear zones abstract paired hook shaped asymmetric folds with shared limbs cut by axial planar veins dikes or fractures are common in glaciers and rocks the sense of offset across the vein or fracture is characteristically opposite to that expected from the sense of fold asymmetry the kinematics of development of the folds and the relationship of the folds to the fractures or veins can be understood by considering the nature of glacial flow and by utilizing simple clay experiments in zones of simple shear dilational fractures may form at about 45 to the shear zone boundaries the perturbation of strain around such a fracture during its development and subsequent rotation and closure under continued deformation causes layers or pre existing foliation cut by the fracture to become folded thus folding is a consequence of the fracturing and not vice versa the precise shape of the fold depends on the nature of the perturbation and particularly whether or not the fracture remains for a time open or fluid filled and thus has walls unable to sustain a shear stress during vein rotation paired hook folds provide evidence for non coaxial strain and are good sense of shear indicators however not all folds with veins parallel to their axial surfaces form in the way described in this paper in some cases vein emplacement occurs late during fold development or post dates folding in these cases offsets along the veins are consistent with fold asymmetry

shear zone between the inner piedmont and kings mountain belts in the carolinas the kings mountain shear zone which marks the boundary between the inner piedmont and kings mountain belts near the north carolina south carolina state line is a northeast striking steeply to moderately dipping zone of ductile mylonitic deformation and late stage semibrittle deformation the zone is at least 60 km long and is no more than a few hundred metres wide it truncates rock units of both belts the juxtaposition of two lithologically different terranes suggests that displacement may be considerable probably on the order of kilometres inconclusive evidence suggests that the northwest inner piedmont side is upthrown the kings mountain zone is one of several in the southern appalachian piedmont that were active during a middle to late devonian acadian deformational event and it may be part of a regional fault system extending from alabama to virginia the kings mountain lowndesville and towaliga zones may be a single zone more than 550 km long

character of the alleghanian orogeny in the southern appalachians part iii regional tectonic relations geological and geochronological studies in the eastern piedmont of the southern appalachians have documented a polyphase late paleozoic deformational chronology d 2 d 4 that is contemporaneous with the alleghanian orogeny recorded in the western appalachian foreland the scale and vergence of d 3 anticlinoria in the eastern piedmont are similar to those of anticlinoria in the western appalachians which are related to ramping of underlying thrust surfaces we suggest that the appalachian decollement extends southeastward beneath the entire piedmont province and that all of the piedmont rocks were displaced at least 175 km northwestward relative to north america during the alleghanian orogeny late paleozoic deformational effects in the eastern piedmont thus are considered cogenetic with alleghanian foreland deformation we interpret the alleghanian orogeny to be the result of oblique dextral convergence and collision of gondwana and laurentia

compaction of quartz kaolinite mixtures the influence of the pore fluid composition on the development of their microstructure and elastic anisotropy abstract shales play important roles in sedimentary basins acting as both seals and reservoir rocks and knowledge of their anisotropic velocity trends is of practical importance for correct seismic image processing and inversion and for seismic to well tie whereas velocity depth trends are extensively studied for conventional reservoirs and critical factors that control their compaction are well understood little work has been done on shales compaction trends of shaly formations are controlled by a number of parameters such as clay mineralogy silt fraction and depositional environment this large number of parameters which are difficult if not impossible to control in naturally deposited shales make the study of shale compaction a statistically complex multivariate and non unique problem in such a situation laboratory experiments that allow precise planning of mixture mineralogy and chemical compositions of pore fluids as well as an accurate control of microstructural changes seems to be an attractive alternative in this work we have conducted two sets of compaction experiments on quartz kaolinite mixtures with 100 75 and 60 of kaolinite powders dry weight in the first set the use of a kcl brine solution to saturate the mixtures has led to the aggregation of the existing clay particles with each other and with silt particles in the other set the mixtures have been treated with a dispersant to separate existing clay aggregates into individual platelets the mixtures have been further compacted in an oedometric cell at uniaxial stresses up to 30 mpa compressional in vertical and horizontal directions and shear in vertical direction ultrasonic wave velocities have been measured during these compaction experiments and the p wave anisotropy has been estimated the effect of the chemical composition of the pore fluid on shale microstructure has been studied using the micro ct and sem image analysis neutron diffraction experiments have been conducted to understand the orientation of clay platelets at the final stage of the compaction our research shows that the chemical composition of pore fluid significantly affects the microstructure of the clay component and via this the elastic properties of the artificial shales the samples with the dispersed clay microstructure dcm have shown larger elastic anisotropies at the same porosity and significantly larger anisotropies at the same stress the dispersed clay platelets have orientated preferably parallel to bedding plane while the clay platelets in the samples with the aggregated clay microstructure acm show a wider angle distribution in the absence of quartz particles 100 kaolinite samples in the case of 40 of quartz fraction though the clay particles are more aligned in the acm sample than in the dcm one

evaluation of southern eastern overthrust belt beneath blue ridge piedmont thrust seismic reflection surveys in the southern part of the eastern overthrust reveal that crystalline rocks of the blue ridge and piedmont were thrust westward burying a large segment of sedimentary rocks of the valley and ridge surface and subsurface data suggest that the buried segment includes cambrian and lower ordovician shallow shelf clastic and carbonate rocks overlain by middle ordovician foredeep black shale because eastward increasing regional thermal patterns existed prior to thrusting westward movement of thrust sheets disrupted and telescoped that pattern by placing more thermally mature eastern rocks over less mature western rocks the original thermal pattern can be reconstructed by restoring the thrust sheets to their prethrust position the reconstruction mphasizes that rocks less metamorphosed than greenschist facies are contained in only two thrust sheets all of the saltville and part of the pulaski because subgreenschist rocks of the saltville and pulaski thrust sheets appear to be confined to the subsurface of the blue ridge and westward it is most likely that rocks with commercial gas potential will not be present in the subsurface of the piedmont east of the brevard fault nevertheless the concealed area of the southern eastern overthrust with possible gas potential is about as wide as its exposed part thus the combined surface and subsurface area for future exploration in the southern appalachians is about doubled in size

seasonal changes in the sediment flux on steep hillslopes in a humid diurnal frost environment mountain hillslopes are generally shaped by a combination of various types of sediment transport processes e g surface erosion soil creep and dry ravel which can occur simultaneously in the same area since sediment transport is generally affected by multiple microclimatic factors such as heavy rainfall and changes in ground temperature the types of predominant sediment transport processes vary by season we conducted field observations in the southern japanese alps in the period from 2009 to 2013 using sediment traps and time lapse cameras to investigate the seasonal changes in the type and flux of hillslope sediment transport on steep mountains in which both rainfall and diurnal freeze thaw triggered sediment transport in winter and early spring sediment transport via diurnal freeze thaw soil creep and dry ravel was highly active whereas rainfall induced soil creep and selective transport by overland flow were active in summer and autumn when precipitation is abundant average sediment flux of 0 033 and 0 074 kg m 1 day 1 respectively sediment flux was spatially variable and was affected by the form of the slope sediment flux on the concave slope was higher than on the ridge shaped slope during both freeze thaw and rainfall periods sediment flux on an old landslide exceeded that in second growth forest regardless of the slope shape temporal changes in the sediment flux were not completely synchronized among monitoring plots and were affected by slope shape grain size and episodic sediment supply events such as release of sediment from woody debris copyright 2016 john wiley sons ltd

seismic velocity and anisotropy in mylonites and the reflectivity of deep crystal fault zones compressional wave velocity anisotropy has been measured to 1 kb confining pressure in several mylonites in one cataclasite and in their protoliths no significant difference in the velocity or density was found between the protolith and the tectonically altered rock at 1 kb strong seismic anisotropy greater than 10 was present in only two of nine mylonites measured the anisotropy was due to their aphanitic texture high content of layered silicates and pervasive foliation most mylonitic rocks studied were not strongly anisotropic despite a well developed macroscopic foliation where anisotropy was present velocities usually were slowest perpendicular to the foliation and fastest parallel to both foliation and lineation these preliminary results suggest that ductile fault zones in the crust are not strong seismic reflectors unless mylonites in the fault zone are aphanitic and contain large amounts of foliated phyllosilicates it is also possible that anomalous environmental conditions such as high pore pressure in the fault zone in situ may explain observed seismic reflectivity

origin of shale fabric by mechanical compaction of flocculated clay evidence from the upper devonian rhinestreet shale western new york u s a abstract most workers attribute the preferred grain orientation that defines the shale fabric to the mechanical collapse of a high porosity clay microfabric under increasing overburden pressure scanning electron microscope analysis of samples of the upper devonian frasnian rhinestreet shale of western new york state collected from near early diagenetic carbonate concretions provides further evidence of this mechanism specifically mudstones recovered from pressure shadows immediately adjacent to lateral edges of concretions are characterized by an open fabric of randomly arranged clay domains the cardhouse fabric laterally equivalent shale samples collected only 0 2 to 0 3 m distant the pressure shadows however reveal a low porosity strongly oriented shale fabric in which clay particles mold around incompressible quartz silt and euhedral pyrite grains and pyrite framboids these observations suggest that the organic rhinestreet shale accumulated as water rich flocculated clay the open clay fabric observed in pressure shadow mudstones was preserved by the incompressible concretions during burial flocculated clay beyond the shielding effect of the concretions however collapsed during progressive burial to form the strongly oriented shale fabric

gaining insights into interrill erosion processes using rare earth element tracers abstract increasing interest in developing process based erosion models requires better understanding of the relationships among soil detachment transportation and deposition the objectives are to 1 identify the limiting process between soil detachment and sediment transport for interrill erosion 2 understand the dynamic relationships between transport and deposition by tracking sediment fate with multiple tracers and 3 verify the effects of slope length on interrill soil erosion five rare earth element ree tracers were applied in five bands or segments to track sediment dynamics on a 10 4 4 m long uniform slope under simulated rainfall a silt loam soil with 8 clay and 87 silt was used six rain events were applied the first four with 60 mm h 1 and the last two with 90 mm h 1 sediment in runoff and deposition along the slope were measured results confirmed that interrill soil erosion was controlled by the transport process thus soil erodibility estimated with many interrill erosion models was actually sediment transportability as the slope length increased soil erosion rates initially increased and then decreased indicating that the upper section was dominated by erosion and the lower section by transport raindrop driven creeping prevailed in the upper section while flow driven rolling dominated in the lower section sediment influx from upslope clearly suppressed soil detachment downslope moreover the steady state sediment discharge from a segment was positively correlated to the amount of sediment deposited downslope from that segment implying that 1 re detachment transport and deposition occurred simultaneously in the system and 2 sediment was transported in a form of bedload mainly rolling or creeping on interrill areas sediment delivery ratios of each segment tended to slightly increase downslope suggesting the flow driven transport was more efficient than the raindrop driven transport the sequence of sediment discharged from different slope positions was inconsistent with the transport distance theory however interrill erosion processes vary with soil slope and rainfall properties and the findings here need to be verified in different conditions

character of the alleghanian orogeny in the southern appalachians part ii geochronological constraints on the tectonothermal evolution of the eastern piedmont in south carolina a nearly concordant u pb zircon age of 550 4 ma is interpreted to closely date crystallization of the epizonal little mountain metatonalite in the southeastern part of the charlotte belt in south carolina this confirms field studies which indicate that the charlotte belt contains a plutonic metaigneous complex that developed as a sub volcanic arc infrastructure contemporaneous with vulcanism manifested in the carolina slate belt both paleontological and geochronological controls indicate that the south carolina slate belt is mostly younger than 570 ma cambrian whereas the slate belt in north carolina and virginia is mostly of late proterozoic age a regionally significant mid paleozoic ca 340 360 ma thermal event is suggested by discordant 40ar 39ar whole rock age spectra of slate phyllite in the northwestern carolina slate belt and from hornblende in the southeastern charlotte belt it is uncertain if this event was associated with deformation in the eastern piedmont however mid paleozoic deformation has been previously documented elsewhere in the western piedmont a slightly disconcordant u pb zircon age of 317 4 ma is interpreted to closely date initial crystallization of the deformed edge field granite and confirms a record of late paleozoic penetrative deformation in the kiokee belt of south carolina u pb isotope data for the lake murray orthogneiss and clouds creek granite are discordant and suggest that the magmas of these plutons were derived by partial melting of a sialic precam brian source and then emplaced in the eastern piedmont at ca 315 ma prior to or during the early stages of the alleghanian orogeny the thermal maximum of alleghanian regional metamorphism amphibolite facies in the kiokee belt greenschist facies in the southeastern part of the carolina slate belt occurred during ca 295 315 ma during the late carboniferous and early permian the eastern piedmont experienced differential uplift erosion and relatively rapid postmeta morphic cooling isothermal surfaces were folded into an antiform synform antiform configuration corresponding to the kiokee carolina slate and charlotte belts respectively the geochronological data provide the following calibration for the late paleozoic deformational chronology recorded in the kiokee and carolina slate belts d2 lake murray deformation ca 295 315 ma d3 clarks hill deformation ca 285 295 ma and d4 irmo deformation ca 268 290 ma

the evolution of the avalonian plate abstract the avalon platform of newfoundland is the type locality of the avalonian plate that is characterized by late precambrian volcanic and clastic rocks marine at the bottom and terrestrial at the top all are intruded by 650 550 ma granites late precambrian rocks in the southern british isles are similar in both areas northeastern parts of the belt are affected by deformation and metamorphism that have orogenic aspects the orogeny is referred to as the avalonian in newfoundland and monian in britain to the southeast of the avalonian rocks in europe lies another late precambrian cadomian orogenic belt of rocks as a part of the pan african orogenic belt the cadomian and avalonian belts extend into north africa morocco since these belts are ophiolite bearing it is suggested that the plate was bordered by oceanic domains it is therefore proposed that a microcontinental volcanic arc that was generated in the late precambrian was orogenically deformed by collision with north america europe and africa and survived as a coherent terrain until the late carboniferous

microfabric and rock properties of experimentally compressed silt clay mixtures abstract oedometric mechanical compaction tests were performed on brine saturated synthetic samples consisting of silt clay mixtures to study changes in microfabric and rock properties as a function of effective stress the silt consisted of crushed quartz 100 with grain size range between 4 and 40 m whereas the clay consisted of 81 kaolinite 14 mica illite and 5 microcline of grain size between 0 4 and 30 m five sample pairs ranging in composition from pure silt to pure clay were compacted to 5 and 50 mpa effective stress respectively sem studies were carried out to investigate microfabric changes in the mechanically compacted silt clay mixtures the degree of alignment of the different minerals present quartz mica illite and kaolinite were computed by using an image analysis software experimental compaction have measured the changes in the rock properties such as porosity and velocity as a function of effective stress for different mixtures of clay and silt clay rich samples showed a higher degree of mineral orientation and lower porosity compared to silt dominated samples as a function of effective stress pure clay sample had 11 porosity at 50 mpa effective stress whereas the pure silt sample retained about 29 porosity at the same effective stress the experiments showed that low porosity down to 11 is possible by mechanical compaction only a systematic increase in strain was observed in the silt clay mixtures with increasing clay content but the porosity values found for the 50 50 silt clay mixture were lower than that of 25 75 silt clay mixture no preferential mineral orientation is expected before compaction owing to the high initial porosity suggesting that the final fabric is a direct result of the effective stress both p and s wave velocities increased in all silt clay mixtures with increasing effective stress the maximum p and s wave velocities were observed in the 25 75 silt clay mixture whereas the minimum vp and vs were recorded in the pure silt mixture at 50 mpa effective stress p wave velocities as high as 3 km s resulted from experimental mechanical compaction alone the results show that fine grained sediment porosity and velocity are dependent on microfabric which in turn is a function of grain size distribution particle shape sediment composition and stress at 5 mpa effective stress quartz orientation increased as a function of the amount of clay indicating that clay facilitate rotation of angular quartz grains adding clay from 25 to 75 in the silt clay mixtures at 50 mpa effective stress decreased the quartz alignment the clay mineral orientation increased by increasing both the amount of clay and the effective stress the mica illite fabric alignment being systematically higher than that of kaolinite even small amount of silt 25 added to pure clay reduced the degree of clay alignment significantly this study demonstrates that experimental compaction of well characterized synthetic mudstones can be a useful tool to understand microfabric and rock properties of shallow natural mudstones where mechanical compaction is the dominant process

interactions between a cushion plant azorella selago and surface sediment transport on sub antarctic marion island on sub antarctic marion island cushions of the dominant vascular plant species azorella selago interact with the geomorphology of fellfield landscapes by affecting sediment distribution and ultimately terrace formation here to understand the consequences of azorella cushions for substrate movement and sorting we quantified the size and shape of azorella cushions and the grain size distribution of sediment surrounding these cushions using a combination of image analysis approaches results show that as cushions become larger they tend to become more elongated and grow more perpendicular to the slope mean and variance of grain size were greater upslope of azorella cushions while the number of particles was higher downslope of cushions although these differences were not significant at all sites studied differences between upslope and downslope particle sizes were however not related to cushion elongation or growth angle as had been expected the observed sediment partitioning is likely caused by a combination of frost related sediment transport and azorella cushions acting as sediment obstructions understanding these interactions between azorella cushions and the landscape is especially important in the light of recent warming and drying on the island as particle size affects soil properties such as water holding capacity and frost susceptibility

isotopic evidence for a tectonic boundary between the kings mountain and inner piedmont belts southern appalachians concordant u pb zircon ages of 320 ma for the deformed high shoals granite of the kings mountain belt kmb extend the range of known alleghanian late paleozoic deformation and metamorphism in the southern appalachian piedmont isotope systematics in kmb rocks suggest an affinity with terranes to the southeast rather than with the inner piedmont belt to the northwest lead isotope systematics in meta igneous rocks of the kmb suggest direct or indirect mantle derivation with little or no crustal contamination

an analysis of horizontal microcracking during catagenesis example from the catskill delta complex horizontal bitumen filled microcracks are common within clay laminae of the finely laminated organic carbon rich shale in the lower half of the heavily jointed upper devonian dunkirk shale western new york state such cracks are not found higher in the dunkirk shale where moderate bioturbation resulted in a relatively porous and permeable microfabric horizontal microcracks in a hydrocarbon source rock that carries regional vertical joints indicating a horizontal least principal stress owe their presence to material properties of the fractured shale and the magnitude and orientation of the crack driving stress during kerogen maturation three material properties favored the horizontal initiation of microcracks in the dunkirk shale 1 the abundance of flat kerogen grains oriented parallel to layering 2 a marked strength anisotropy in large part caused by the laminated nature of the rock and 3 the tight strongly oriented planar clay grain fabric produced by gravitational compaction of flocculated clay at shallow burial depth the latter was especially important to sustaining elevated pore pressure the crack driving stress which was generated by the conversion of kerogen to bitumen poroelastic deformation of the low permeability laminated shale pressurized by catagenesis perhaps enhanced by compaction disequilibrium prior to kerogen conversion elevated the in situ horizontal stress in excess of the vertical stress which remained constant during pore pressure buildup thereby favoring the propagation of microcracks in the horizontal plane

interactive property of large thrust sheets with footwall rocks the sub thrust interactive duplex hypothesis a mechanism of dome formation in thrust sheets abstract recently acquired appalachian ultradeep core hole adcoh project site investigation seismic reflection data and geologic data from the appalachians and several other orogenic belts suggest an important mutually interdependent relationship exists between emplacement of large crystalline thrust sheets and the deforming foreland rocks beneath this relationship suggests isolated domes beneath crystalline thrust sheets may be produced by passive folding of the sheet as a result of formation of an antiformal stack duplex in the platform sedimentary sequence beneath suggestions that domes in crystalline thrust sheets formed by interference of late open folds is doubtlessly still valid in places but the platform duplex mechanism is probably also valid to explain the late doming of many crystalline and other large thrust sheets the dome beneath the shooting creek and brasstown bald windows in the adcoh site region is imaged as an antiformal stack duplex at depth the tallulah falls dome grandfather mountain and mountain city windows and smokies foothills duplex in the site region and elsewhere in the southern blue ridge are all late isolated domes and all are probably or demonstrably underlain by antiformal stack duplexes beneath the blue ridge piedmont composite crystalline thrust sheet the assynt window and footwall duplex benath the arnabol and moine thrusts in scotland and the engadine window in the alps may be similar structures

did the taconic appalachians continue into southern south america the appalachian mountains now terminating abruptly at the gulf of mexico coastal plain may have formerly continued into southern south america rocks forming the basement of the argentine andes can be interpreted as remnants of an early paleozoic orogen the famatinian belt not unlike the taconic appalachians both orogens are bordered to the west present coordinates by lower paleozoic carbonate platforms bearing the olenellid trilobite fauna that is characteristic of laurentia paleomagnetic and geologic data indicate that they could have formed as one continuous mountain chain possibly extending into antarctica during ordovician closure of an ocean basin southern iapetus between laurentia and gondwana the taconic and famatinian segments of the chain may have been truncated during late ordovician separation of laurentia and gondwana along the preexisting late neoproterozoic to cambrian rift system that initiated formation of the ouachita embayment and the southern margin of north america

paleomagnetism and 40ar 39ar ages from the carolina slate belt albemarle north carolina implications for terrane amalgamation with north america paleomagnetic and sup 40 ar sup 39 ar dating studies of late proterozoic metamorphic rocks from the carolina slate belt were undertaken to gain insight into the history of this suspect lithostratigraphic terrane geochronological data suggest a peak metamorphic age of ca 455 ma and a later thermal overprint at ca 185 ma thermal demagnetization indicates two magnetization components a low temperature component yields a pole close to 180 190 ma segments of the north american apparent polar wander path a high temperature component postdates folding and is inferred to have been acquired at ca 455 ma corresponding paleomagnetic pole is lat 20 sup 0 n long 80 sup 0 e although paleomagnetic data from the carolina slate belt remain too ambiguous for construction of a unique polar wander path consideration of available paleolatitudes suggests that the terrane may have been proximal to cratonic north america after ca 455 ma this result contrasts markedly with high southerly ordovician paleolatitudes inferred from paleomagnetic studies within central and northern appalachian terranes

greigite from carbonate concretions of the ediacaran doushantuo formation in south china and its environmental implications abstract greigite fe 3 s 4 is a ferrimagnetic iron sulfide that commonly forms as a precursor of pyrite in anoxic environments where the supply of reactive fe outpaces that of sulfide h 2 s and hs because of its metastability and sensitivity to redox changes during burial greigite has been rarely documented in rocks older than the cretaceous here we report well preserved greigite in carbonate concretions of the upper doushantuo formation ca 551 ma in the yangtze gorge area south china greigite in the carbonate concretions coexists with anhedral and framboidal pyrite and is distributed in clay rich carbonates with card house microtextures and dolomitic spherical structures indicative of early diagenetic formation during shallow burial preservation of greigite in carbonate concretions of the upper doushantuo formation implies that these concretions maintained a closed micro system since their formation and that they provide information about the ancient depositional and early diagenetic environments

a modified version of archie s law to estimate effective diffusion coefficients of radionuclides in argillaceous rocks and its application in safety analysis studies abstract because of the very low hydraulic conductivity of clay rocks molecular diffusion is the main process responsible for the transport of radionuclides released from the waste matrix into the host rock diffusion values are thus important input parameters in safety analyses because diffusion measurements are very time consuming it is impossible to measure diffusion coefficients for all radionuclides of interest it is therefore important to develop procedures for doing reliable estimates of diffusion coefficients diffusion data of mainly tritiated water hto and anions i cl measured in different sedimentary rocks were taken from the literature the effective diffusion coefficient could be related to the transport porosity by an extended version of archie s law e archie d e d w e m 1 b e m 2 the extended version deviates from the classical law at porosity values below ca 0 1 effective diffusion coefficients of hto 36cl and 22na were measured for a series of swiss clay rocks brauner dogger effingen member opalinus clay and helvetic marls and for one hungarian rock boda claystone formation and could be satisfactorily described by the extended version of archie s law bounded by an upper and a lower curve a method was developed based on e archie for estimating effective diffusion coefficients for a series of radionuclides important input parameters are the accessible porosity of the rock and the diffusion coefficient of the radionuclide in water in case of cations showing surface diffusion a correction term was introduced based on the work of gimmi and kosakowski 2011

ordovician docking of the carolina slate belt paleomagnetic data paleomagnetic results from eight sites in argillaceous metasediments from union county north carolina in the central carolina slate belt yield a consistent high blocking temperature magnetization component the precision of the mean declination and inclination of all site means is maximized at 50 tilt correction and the improvement in grouping relative to 0 and 100 tilt correction is significant at the 95 confidence level this tends to indicate that the high blocking temperature component was acquired during folding the metamorphism and deformation in this area are rather well constrained by recent 40ar 39ar data to the late ordovician 450 ma we therefore interpret the computed pole position 29 6 n 122 1 e 95 5 11 as late ordovician in age and note that it lies close to some of the late ordovician poles for cratonic north america the paleolatitude 22 2 s of the sampling site is certainly unlike those derived from armorica and gondwana for this time interval and is rather similar to that proposed for the iapetus coast of laurentia during the late ordovician indeed the magnetization and deformation may be contemporaneous with the docking of the carolina slate belt onto the laurentian continent

master decollement root zone beneath the southern appalachians and crystal balance a root zone of the southern appalachian master decollement is postulated to exist beneath kings mountain belt on the basis of an alternative interpretation of cocorp seismic profiles palin spastic restoration of the entire crust and earlier geological and geophysical interpretations mildly deformed cambrian metased imentary rocks beneath the decollement end beneath the piedmont in the vicinity of danielsville georgia reflections farther southeast are probably from ultramylonites weak subhorizontal reflections continue southeasterly to the kings mountain belt where a series of east dipping 30 reflections dominate the section to a depth of 20 km beneath the charlotte belt reflections southeast of the root zone are possibly all related to the structure in an accreted island arc

suspect terranes and accretionary history of the appalachian orogen the north american connection or the grenvillian continental crust that separated from eastern north america during the initiation of the appalachian orogenic cycle is poorly defined within the present orogen a variety of terranes occur outboard of the north american miogeocline all structurally uncoupled and therefore suspect stratigraphic analysis indicates that appalachian accretion progressed from the miogeocline outward the boundaries of the earliest accreted western terranes are marked by melange and ophiolite complexes later boundaries between eastern terranes are steep mylonitic zones and brittle faults accretionary events defined by stratigraphic analysis correspond to times of major deformation plutonism and metamorphism in the history of the orogen

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

bouguer gravity in northeastern georgia a buried suture a surface suture and granites a bouguer gravity map of an area of northeastern georgia encompassing parts of the inner piedmont charlotte belt and carolina slate belt has been constructed from gravity stations spaced 2 km apart anomalies in the charlotte carolina slate belts are due to metamorphosed mafic rocks in the upper crust depth extent

soil creep the driving factors evidence and significance for biogeomorphic and pedogenic domains and systems a critical literature review abstract soil and regolith creep have been analyzed for at least the last 140 years using many methodological configurations and temporal and spatial scales the general concept of creeping soil and its mechanism first proposed by w m davis and g k gilbert at the end of the 19th century evolved since the 1940s towards theoretical models and precise short and long term field measurements this fruitful epoch continued with results enhanced at the turn of the 20th century by the application of new research methods e g radiometry and a redefinition of the term soil creep to encompass the sum of stochastic shallow subsurface and near surface processes causing net downslope movement of soil or regolith simultaneously another possibility of creep detection was noticed in dendrochronology and since the 1970s in the formally defined discipline of dendrogeomorphology indirect evaluations of creep activity were performed based on tree ring analyses of bent trees this method found many followers but was also heavily criticized as imprecise and lacking in evidence of which kind of tree trunk curvature e g pistol butt like deformation s shape curvature could be ascribed to creep movement from the beginning soil creep was associated with the activity of living organisms on hillslopes however this aspect of creep studies has never been fully developed in spite of the solid foundations and directions of potential studies pointed out by charles darwin at the end of the 19th century in this paper we focus on the historical context of soil creep studies and highlight forest ecosystems as probably the most active environment of biogenic creep mainly due to tree uprooting and other biomechanical effects of living and dead trees root channel infilling tree root mounding etc that are a factors in biotransport in the final sections the position of biogenic creep in the structure of biogeomorphic systems is discussed in relation to such important conceptual frameworks as the biogeomorphic ecosystem biogeomorphic feedback window and ecosystem engineering we also describe several hypotheses that should be carefully tested in the future and propose several research methods that have the ability to further our knowledge about soil creep radiometry laser scanning and soil micromorphology

a kinematic model for the collision and complete suturing between gondwanaland and laurussia in the carboniferous maps of middle to late carboniferous strike slip faults in western europe northern africa and eastern north america have been compiled from geological gravity and magnetic onshore and offshore data a large majority of these faults can be interpreted in terms of a logical syn to post collisional pattern superimposed on the initial suture between the african i e gondwana and north american european laurussian continental margins the pre collision positions of the major continents are derived from paleomagnetic data and when combined with the general distribution of the strike slip faults lead to a kinematic model of the complex middle late carboniferous collision in this model the west african precambrian craton acted as a rigid promontory or die with respect to the partially rigid plastic zones between it and the large north american craton these partially rigid plastic zones comprise the external appalachian and canadian maritime margins the mauritanide and hercynian margins of north

needle ice formation induced frost heave and frost creep a case study through photogrammetry at stelvio pass italian central alps abstract needle ice growth is one of the more widespread and easily visible but less studied climate related processes shaping soil evolution surface dynamics and ecosystem changes in the alpine environments here we show the results of the monitoring of needle ice development at four plots located at 2670 m a s l close to the stelvio pass in the italian central alps during 2016 needle ice formation and evolution with time was monitored through the photogrammetric technique of the structure from motion sfm our monitoring data included also quantitative measurements of some selected physical and climatic parameters like air temperature ground temperature and ground water content at depths of 2 and 5 cm our data demonstrate that needle ice can develop with a relatively low ground water content 13 2 at a relatively high minimum ground temperature 0 3 c and with a low cooling rate the total frost heave seems to be related to the abundance of fine material although we couldn t demonstrate it statistically the absence of statistically significant relationships between frost heave and frost creep could be probably due to the importance of the observed needle ice toppling and the possible sliding of the clasts during the melting phases

structural analysis of the carolina inner piedmont terrane boundary implications for the age and kinematics of the central piedmont suture a terrane boundary that records paleozoic laurentia gondwana interactions new field mapping along the carolina inner piedmont terrane boundary in south carolina and eastern georgia reveals preaccretionary synaccretionary and postaccretionary faults the dextral strike slip lowndesville shear zone is adjacent to a 50 km long segment of the terrane boundary however the lowndesville shear zone is correlated eastward with the dextral strike slip beaver creek shear zone which is within the carolina terrane and predates 415 ma the lowndesville shear zone is overprinted by a dextral strike slip phyllonite zone named the deal creek shear zone the deal creek shear zone is correlated eastward with the gold hill silver hill shear zone which is also within the carolina terrane and records dextral strike slip motion between 400 and 325 ma the cross anchor and mulberry creek faults both truncate the lowndesville and the deal creek shear zones and form the terrane boundary the mulberry creek fault probably of triassic jurassic age juxtaposes the lowndesville shear zone adjacent to the carolina inner piedmont terrane boundary west of waterloo south carolina the cross anchor fault is the terrane boundary east of waterloo south carolina and forms the southeastern boundary of the whitmire reentrant crosscutting relationships indicate that the cross anchor fault is the oldest fault which juxtaposes the carolina and inner piedmont terranes in the study area these structural interpretations and available geochronological data indicate that the cross anchor fault is a 325 ma thrust fault and may be the central piedmont suture an early alleghanian suture resolves the problem of inserting the carolina terrane into the western iapetus ocean

analogous tectonic evolution of the ordovician foredeeps southern and central appalachians new stratigraphic data suggest that the diachronous evolution of the ordovician foredeeps in the southern and central appalachians was remarkably similar stratigraphic features that characterize the middle ordovician sevier basin in tennessee and the middle and late ordovician martinsbuirg basin in pennsylvania are in identical ascending order 1 disconformity on the knox group beekmantown group 2 shelf carbonates 3 slope deposits 4 submarine fan turbidites and 5 contourites and muddy turbidites we propose that diachronous attempted subduction of the north american craton beneath southeastern microplates and or volcanic arcs resulted in uplift and erosion of the western shelf followed by its rapid subsidence basinward migration of eastern and northeastern terrigenous source areas and associated submarine fan turbidites resulted from continued convergence and filled the basins finally tectonic stabilization and lowering of the source area is recorded by contourites and muddy turbidites the evolutionary model proposed for the sevier and martinsburg basins closely resembles present day tectonics of the timor foredeep and the adjoining sahul shelf north of australia similar comparisons have also been made for ordovician basins in the northern appalachians analogous tectonic mechanisms therefore appear to have operated diachronously along the eastern margin of north america from tennessee to new england and possibly to newfoundland during ordovician time

soil moisture and texture controls of selected parameters of needle ice growth needle ice was grown in the laboratory to determine the limits of soil moisture and texture on the growth of needle ice as the percentage of fines in the soil increases the lower limit of soil moisture required for growth decreases and may be defined by a linear boundary the efficiency of conversion of soil water to needle ice in soil samples used peaked at about 16 per cent soil fines contrary to expectations the finer textured soils produced significantly thicker ice crystals quantity of soil lifted by needle ice was related to ice height the ice mass to atmospheric void ratio soil texture and moisture and soil surface roughness however no definite quantitative relationships could be determined a test to determine if needle ice is selective in the grain sizes of particles lifted suggested no selectivity

mudrock hosted carbonate concretions a review of growth mechanisms and their influence on chemical and isotopic composition existing interpretations of cement textures and isotopic compositions may significantly under estimate the depth and duration of concretionary growth minus cement porosities can commonly under estimate depths of concretionary growth for some or all of the following reasons i cements might not passively replace host sediment porosity ii non cement carbonate phases such as replaced bioclastic carbonate can be significant iii sediment compaction models over estimate rates of porosity loss at shallow carbon isotope data from modern sediments show that dissolved carbonate in the methanogenic zone has a continuum of values from 30 to 15 and thus overlaps 13 c depleted values normally considered characteristic of sulphate reduction many concretions previously thought to have grown entirely during sulphate reduction may therefore have continued cementation during methanogenesis indicating a deeper and more prolonged cementation history the necessary carbonate supersaturation for concretionary growth could either occur throughout the porewaters the equilibrium model or be generated in situ by organic matter decay the local equilibrium model or created where external fluids are introduced the fluid mixing model

probing the structure of the deep continental crust old buried deformed crystalline rocks apparently make up most of the 40 kilometer thick continental crust this part of the earth is poorly explored and constitutes a major frontier of modern earth science two techniques seismic reflection profiling and drilling which were developed by industry for other purposes offer special potential for such exploration seismic profiling of the deep crust by cocorp the consortium for continental reflection profiling has already produced important information including evidence for extensive thin skinned thrusting of older rocks over a continental margin as the corresponding ocean basin closed deep drilling of crystalline rocks of the continents for scientific purposes is so far relatively unexploited in the united states but is already being carried on elsewhere in general big science is likely to become more important in basic geology as this frontier is explored

biogeographical significance of cambrian trilobites from the carolina slate belt abundant middle middle cambrian trilobites of the ptychagnostus atavus interval zone are described from the upper asbill pond formation informal name near batesburg south carolina the fauna containing at least nine species has strong affinities with cool water faunas of both armorica and baltica but little affinity with warm water shelf faunas of laurentia this is compatible with previous conclusions that the carolina slate belt is an exotic terrane that was accreted to north america during the early or middle paleozoic further evaluation however introduces an alternative possibility that the fauna could have lived in deep cool water environments along the periphery of laurentia and subsequent displacement need not necessarily have been great combined faunal and stratigraphic components of the carolina slate belt do not precisely match those of any known region but may be closest to those of bohemia although a southpolar location in proximity to armorica baltica and gondwana seems likely a definitive placement in a reconstruction of the cambrian world is not yet possible included in the trilobite fauna are the agnostoids hypagnostus mammillatus h parvifrons peronopsis fallax ptychagnostus sp and tomagnostus fissus the polymeroids include agraulos sp paradoxides cf polonicus paradoxides sp and skreiaspis sp

significance of stable carbon isotope trends in carbonate concretions formed in association with anaerobic oxidation of methane aom middle and upper devonian shale succession western new york state usa abstract carbonate concretions are concentrated along discrete stratigraphic horizons within middle and upper devonian carbonaceous black and organic deficient gray shale of western new york state textural characteristics preserved throughout studied concretions including a clay grain microfabric typical of flocculated clay and spherical algal cysts are consistent with a model entailing the formation of low density compaction resistant calcium carbonate masses at shallow burial depth within the zone of bacterial sulfate reduction burial of nascent concretions to the sulfate methane transition zone smtz was accompanied by the nearly complete infilling of porosity the diagenetic consequence of the anaerobic oxidation of methane aom each concretionary horizon then defines the position of the smtz stabilized during an episode of reduced sedimentation rate most analyzed concretions 75 of the middle devonian marcellus formation into the upper devonian gowanda formation display center to edge profiles of increasing bulk 13c far fewer concretions are characterized by radial profiles of decreasing 13c the common radial profiles of increasing 13c can be attributed to aom related kinetic carbon isotope fractionation under diagenetic conditions of limited methane which favors the production of dissolved inorganic carbon of increasing 13c less common concretions displaying center to edge profiles of diminishing 13c may record the anaerobic oxidation of more strongly 13c depleted methane produced by carbon dioxide reduction methanogenesis related to the degradation of organic matter within and near the smtz or aom back flux an enzyme mediated equilibrium isotope effect these processes are favored by sulfate limited diagenetic conditions more typical of the lower smtz and immediately underlying upper methanogenic zone mez contradictory isotope profiles of texturally similar concretions can be accounted for by diagenesis associated with an extended smtz esmtz comprising the methane limited smtz and the underlying sulfate deficient upper mez vertical shifts of the diagenetic horizons of the esmtz induced by variable methane flux would have juxtaposed concretions displaying seemingly incompatible isotopic histories