weathering rinds and the evolution of piedmont slopes in the southern blue ridge mountains the piedmont slopes on the west side of rich and snake mountains in the blue ridge province are composed of dozens of fans and fan remnants of various ages the fans consist of a few meters of flood and debris flow deposits overlying saprolite and deeply weathered bedrock the deposits are rich in amphibolite clasts the weathering rinds of which allowed fan surfaces to be classified into six relative age categories on the basis of rind thickness the presence of reversed remanent magnetism in one old fan deposit indicates an age of at least 780 ka however the magnetization appears to reside in secondary hematite produced by weathering rather than in original magnetite grains so that a minimum age on the order of 1 ma is more likely transverse profiles surveyed across 15 fans and fan remnants show that old surfaces may attain heights as great as 30 m above younger surfaces but that a better index of age is the convexity of the profile young surfaces show only slight transverse convexities but old su

rates of weathering rind formation on costa rican basalt weathering rind thicknesses were measured on 200 basaltic clasts collected from three regionally extensive alluvial fill terraces qt 1 qt 2 and qt 3 preserved along the pacific coast of costa rica mass balance calculations suggest that conversion of unweathered basaltic core minerals plagioclase and augite to authigenic minerals in the porous rind kaolinite allophane gibbsite fe oxyhydroxides is iso volumetric and ti and zr are relatively immobile the hierarchy of cation mobility ca na k mg si al fe p is similar to other tropical weathering profiles and is indicative of differential rates of mineral weathering anorthite albite hypersthene orthoclase apatite alteration profiles across the cm thick rinds document dissolution of plagioclase and augite and the growth of kaolinite with subsequent dissolution of kaolinite and precipitation of gibbsite as weathering rinds age the rate of weathering rind advance is evaluated using a diffusion limited model which predicts a parabolic rate law for weathering rind thickness rr as a function of time t rr t and an interface limited model which predicts a linear rate law for weathering rind thickness as a function of time rr kappt in these rate laws is a diffusion parameter and kapp is an apparent rate constant the rate of advance is best fit by the interface model terrace exposures are confined to the lower reaches of streams draining the pacific slope near the coast where the stream gradient is less than 3 m km and terrace deposition is influenced by eustatic sea level fluctuations geomorphological evidence is consistent with terrace deposition coincident with sea level maxima when the stream gradient would be lowest assigning the most weathered regionally extensive terrace qt 1 mean rind thickness 6 9 0 6cm to oxygen isotope stage ois 7 ca 240 ka and assuming that at time 0 rind thickness 0 it is inferred that terrace qt 2 rr 2 9 0 1 cm is coincident with stage 5e ca 125 ka and that qt 3 rr 0 9 0 1 cm is consistent with ois 3 ca 37 ka these assignments yield a value of kapp of 8 6 10 13 cm s 1 r 2 0 99 only this value satisfies both the existing age controls and yields ages coincident with sea level maxima using this value elemental weathering release fluxes across a weathering rind from qt 2 range from 6 0 10 9 mol si m 2 s 1 to 2 5 10 11 mol km 2 s 1 the rate of rind advance for the costa rican terraces is 2 8 10 7 my r 1 basalt rind formation rates in lower temperature settings described in the literature are also consistent with interface controlled weathering with an apparent activation energy of about 50 kj mol 1 rates of rind formation in costa rica are an order of magnitude slower than reported for global averages of soil formation rates copyright 2004 elsevier ltd

a paleoclimate interpretation derived from pedogenic clay minerals from the piedmont province virginia abstract oxygen isotope ratios of pedogenic kaolinites were measured to estimate the ambient climate conditions during the formation of a saprolite in the piedmont province woodbridge va kaolinite is the predominant pedogenic clay mineral in this saprolite it is formed mostly from weathering of muscovite and to a lesser extent from weathering of microcline a dioctahedral smectite vermiculite phase formed by weathering muscovite is present in minor amounts the 18o 16o ratios indicate that most if not all the kaolinite formed in a cooler climatic regime in which meteoric waters were more depleted in 18o than most present meteoric waters it is possible that the pedogenic kaolinite formed shortly after or during the pleistocene glacial stage in north america this interpretation is consistent with the age of this saprolite derived from 10be dating methods the oxygen isotopic signatures of these kaolinites are not consistent with an older middle or early miocene age for this saprolite

appalachian piedmont landscapes from the permian to the holocene abstract between the potomac and susquehanna rivers and from the blue ridge to the fall zone landscapes of the piedmont are illustrated for times in the holocene late wisconsin early miocene early cretaceous late triassic and permian landscape evolution took place in tectonic settings marked by major plate collisions permian arching and rifting late triassic and development of the atlantic passive margin by sea floor spreading early cretaceous erosion proceeded concurrently with tectonic uplift and continued after cessation of major tectonic activity atlantic outer continental shelf sediments record three major erosional periods 1 late triassic early jurassic 2 late jurassic early cretaceous and 3 middle miocene holocene the middle miocene holocene pulse is related to neotectonic activity and major climatic fluctuations in the piedmont upland the holocene landscape is interpreted as an upland surface of low relief undergoing dissection major rivers and streams are incised into a landscape on which the landforms show a delicate adjustment to rock lithologies the fall zone has apparently evolved from a combination of warping faulting and differential erosion since late miocene the periglacial environment of the late wisconsin and earlier glacial epochs resulted in increased physical erosion and reduced chemical weathering even with lowered saprolitization rates geochemical modeling suggests that 80 m or more of saprolite may have formed since late miocene this volume of saprolite suggests major erosion of upland surfaces and seemingly contradicts available field evidence greatly subdued relief characterized the early miocene time near the end of a prolonged interval of tropical morphogenesis the ancestral susquehanna and potomac rivers occupied approximately their present locations in early cretaceous time local relief may have been as much as 900 m and a major axial river draining both the piedmont and appalachians flowed southeast past baltimore the late triassic landscape was influenced by rift basin development streams drained into a hydrologically closed basin no through flowing rivers seem to have been present a limestone escarpment along the blue ridge may have existed as a consequence of a semi arid climate the permian may have been a time of himalayan like mountains and mountain glaciers streams and glaciers generally flowed southwest and west

regolith residence time and the concept of surface age of the piedmont peneplain the common upland weathering profile on foliated metamorphic rocks on the appalachian piedmont between alabama and maryland includes a 50 cm 1 m thick clay rich soil b horizon over 10 20 m of saprolite the saprolite retains the volume fabric and structure of the underlying parent rock but has lost about one third of the mass of the parent rock where the saprolite is thickest beneath upland drainage divides those divides are of loow slope and relief the flatness of the piedmont drainage divides provides the appearance of a planation surface of accordant summits or peneplain i interpret this flatness to be the result of three active processes volume reduction during compaction of saprolite into soil loss of mass in dissolved solids draining the soil b horizon and loss of mass from the soil surface by erosion of clay size particles the cumulative effects of these upland processes are to convert saprolite into soil to limit soil thickness and residence time and to limit the age of the oldest residual soils on the surface this results in a continual lowering of the piedmont peneplain surface this interpretation is corroborated by evidence of topographic inversion of fluvial gravels since the miocene near the fall line study of baseflow dissolved solids draining piedmont basins indicates a minimum rate of saprolite production of about 4 m ma 1 this minimum rate of production near the fall line is less than the estimated rate of surface lowering and saprolite consumption during the late tertiary and quaternary periods of topographic inversion measurement of cosmogenic 10be inventories in two 15 20 mores of piedmont upland regolith indicate a minimum residence time of residual soil and saprolite of about 1 ma this indicates a possible maximum rate of saprolite production and erosion of about 20 m ma 1 using the best available evidence therefore the typical piedmont upland regolith has a residence time of between 1 and 5 ma residence times may not be the same everywhere and ages may vary systematically across the surface the geomorphic evidence of topographic inversion and similar regolith profiles in other humid temperate and tropical regions strongly suggests that production and removal of piedmont saprolite has been an ongoing quaternary process and that most of the piedmont regolith is significantly younger than 5 ma independent geophysical evidence suggests that the rate of uplift probably involving tilting of parts of the piedmont blue ridge and valley and ridge has averaged between 5 and 20 m ma 1 through the cenozoic

glacial and periglacial erosion of the appalachians abstract the marine 18 o record indicates that the first ice advance into the appalachians equivalent to that of the late wisconsin occurred in the pliocene at about 2 4 ma only periodic localized glacial and periglacial activity occurred in the northern appalachians from 2 33 to 0 85 ma after 0 85 ma middle to late pleistocene eight out of ten glaciations covered the northern appalachians and brought periglacial conditions to the southern appalachians during the last 850 000 years glaciation extended to the late wisconsin limit within the appalachians for 15 of the time and extended to the early wisconsin limit just north of the appalachians for 25 of the time pleistocene glacial erosion of the appalachians of 120 200 m is necessary to account for the estimated volume of pleistocene ocean sediment derived from the appalachians and the estimated volume of pliocene pleistocene glaciogenic ocean sediment derived from the entire laurentide ice sheet this amount of glacial erosion occurring over the maximum expectable duration of pliocene pleistocene ice cover of 247 000 years yields glacial erosion rates from 0 5 0 8 m ka 1 such depths of erosion by thick warm based ice streams were localized in the lowlands and estuaries of the northern appalachians in the maritimes the presence of thin cold based ice caused minimal erosion of uplands periglacial landforms and tundra boreal forest were distributed throughout the appalachian highlands and the northern coastal plain during the glacial maxima periglacial erosion of 0 15 0 30 m ka 1 near the ice in pennsylvania decline to 0 1 0 2 m ka 1 in the southern piedmont each cold period almost completely renewed the regolith by eroding slopes and filling valleys the cumulative effect of the eight to ten major cold events could have produced as much as a few ten s of meters of periglacial ridge top lowering during the pleistocene both estimated glacial and periglacial erosion rates greatly exceed estimated current fluvial erosion rates therefore glacial and periglacial processes should be considered the dominant processes in shaping the present appalachian landscape the northern appalachians may be evolving towards a form where the landscape provides just the shape necessary to permit the least work conveyance of the ice across the region during glacial maxima the southern appalachians may be evolving towards a form where the landscape provides just the hillslope form necessary to transport the debris provided by periglacial conditions

chemical weathering of crystalline rocks in contrasting climatic conditions using geochemical proxies an overview abstract weathering profiles of granitoid rocks from the sila massif southern italy have been studied to characterize weathering processes that affect this area chemical weathering indices of the sila massif weathered granitoids were compared to those of different areas of the world characterized by different climates malaysia puerto rico georgia china nigeria colorado switzerland and sweden to decipher their weathering characteristics the geochemical indices show values of cia chemical index of alteration ranging from 55 to 97 ciw chemical index of weathering ranging from 60 to 100 pia plagioclase index of alteration ranging from 55 to 100 wip weathering index of parker ranging from 7 to 64 and rr ruxton ratio ranging from 2 14 to 3 96 all these geochemical proxies closely resemble each other and show variations mainly related to the different climatic and tectonic settings malaysia and puerto rico granitoids showing high cia values respectively 97 and 95 on average underwent very intensive chemical weathering alteration georgia china and nigeria showing medium high cia values respectively 86 90 and 92 on average underwent moderate intensive chemical weathering alteration southern italy and colorado granitoids showing medium low cia values 68 on average underwent moderate weak chemical weathering alteration whereas switzerland and sweden granitoids showing low cia values respectively 58 and 55 on average underwent weak chemical weathering alteration those values are mainly related to the climatic conditions in term of temperature and precipitation of each area cia vs climate histograms display a shift towards higher cia values with increasing of warm humidity tropical conditions whereas granitoids weathered under conditions inferred to be cold arid polar climate show lower cia values

mass balance modeling of mineral weathering rates and co2 consumption in the forested metabasaltic hauver branch watershed catoctin mountain maryland usa mineral weathering rates and a forest macronutrient uptake stoichiometry were determined for the forested metabasaltic hauver branch watershed in north central maryland usa previous studies of hauver branch have had an insufficient number of analytes to permit determination of rates of all the minerals involved in chemical weathering including biomass more equations in the mass balance matrix were added using existing mineralogic information the stoichiometry of a deciduous biomass term was determined using multi year weekly to biweekly stream water chemistry for a nearby watershed which drains relatively unreactive quartzite bedrock at hauver branch calcite hosts 38 mol of the calcium ion ca2 contained in weathering minerals but its weathering provides 90 of the stream water ca2 this occurs in a landscape with a regolith residence time of more than several ka kiloannum previous studies indicate that such old regolith does not typically contain dissolving calcite that affects stream ca2 na ratios the relatively high calcite dissolution rate likely reflects dissolution of calcite in fractures of the deep critical zone of the carbon dioxide co2 consumed by mineral weathering calcite is responsible for approximately 27 with the silicate weathering consumption rate far exceeding that of the global average the chemical weathering of mafic terrains in decaying orogens thus may be capable of influencing global geochemical cycles and therefore climate on geological timescales based on carbon balance calculations atmospheric derived sulfuric acid is responsible for approximately 22 of the mineral weathering occurring in the watershed our results suggest that rising air temperatures driven by global warming and resulting in higher precipitation will cause the rate of chemical weathering in the hauver branch watershed to increase until a threshold temperature is reached beyond the threshold temperature increased recharge would produce a shallower groundwater table and reduced chemical weathering rates copyright 2013 john wiley sons ltd

fluvial terraces of the lower susquehanna river abstract fluvial terraces of the lower susquehanna river offer a unique opportunity to investigate the late stage geologic and geomorphic evolution of the u s atlantic passive margin petrography and elevation distinguish and provide a basis for correlation of two groups of terraces the upland terraces and lower terraces through the piedmont newark basin and great valley downstream correlation to dated upper coastal plain and fall zone fluvial deposits relative weathering and soil profile development characteristics establish terrace age upland terraces tg1 tg2 and tg3 middle to late miocene strath terraces 80 to 140 m above the present channel occur only along the piedmont reach they are underlain by unstratified texturally mature quartz dominated roundstone diamictons lower terraces qtg qt1 qt6 pliocene and pleistocene strath and thin aggradational terraces within 45 m of the present channel are underlain by stratified and unstratified texturally and compositionally immature sand gravel and pebbly silt terrace age and longitudinal profiles suggest complex interactions among relative base level long term flexural isostatic processes climate and river grade our model for terrace genesis requires the susquehanna river to attain and maintain a characteristics graded longitudinal profile over graded time for the u s atlantic margin we propose that straths are continually cut along this graded profile during periods of relative base level stability achieved by slow steady isostatic continental uplift acting in concert with eustatic rise change in an external modulating factor such as eustatic fall or climate change results in fluvial incision and subsequent genesis of strath terraces longitudinal profiles of lower susquehanna river terraces which converge at the river mouth diverge through the piedmont and reconverge north of the piedmont contrast with their hypothesized original concave up profiles progressive and cumulative flexural upwarping of the atlantic margin accounts for terrace profile deformation suggesting flexural isostasy as a first order regional deformation mechanism these results offer new interpretations of terrace age correlation and geologic significance that require modification of previous studies suggesting uplifted or anticlinically warped peneplains on the u s atlantic margin

coupling chemical weathering with soil production across soil mantled landscapes soil covered upland landscapes constitute a critical part of the habitable world our understanding of how they evolve as a function of different climatic tectonic and geological regimes is important across a wide range of disciplines and depends in part on understanding the links between chemical and physical weathering processes extensive previous work has shown that soil production rates decrease with increasing soil column thickness but chemical weathering rates were not measured here we examine a granitic soil mantled hillslope at point reyes california where soil production rates were determined using in situ produced cosmogenic nuclides 10be and 26al and we quantify the extent as well as the rates of chemical weathering of the saprolite from beneath soil from across the landscape we collected saprolite samples from the base of soil pits and analysed them for abrasion ph as well as for major and trace elements by x ray fluorescence spectroscopy and for clay mineralogy by x ray diffraction spectroscopy our results show for the first time that chemical weathering rates decrease with increasing soil thickness and account for 13 to 51 per cent of total denudation we also show that spatial variation in chemical weathering appears to be topographically controlled weathering rate decreases with slope across the divergent ridge and increases with upslope contributing area in the convergent swale furthermore to determine the best measure for the extent of saprolite weathering we compared four different chemical weathering indices the vogt ratio the chemical index of alteration cia parker s index and the silicon aluminium ratio with saprolite ph measurements of the cia were the most closely correlated with saprolite ph showing that weathering intensity decreases linearly with an increase in saprolite ph from 4 7 to almost 7 data presented here are among the first to couple directly rates of soil production and chemical weathering with how topography is likely to control weathering at a hillslope scale copyright 2006 john wiley sons ltd

climatic impact on isovolumetric weathering of a coarse grained schist in the northern piedmont province of the central atlantic states the possible impact of periglacial climates on the rate of chemical weathering of a coarse grained plagioclase muscovite quartz schist has been determined for a small watershed near baltimore maryland the isovolumetric chemical weathering model formulated from the geochemical mass balance study of the watershed shows that the weathering front advances at a velocity of 9 1 m m y if the modern environmental parameters remain the same back through time however recent surficial geological mapping demonstrates that periglacial climates have impacted the area such an impact significantly affects two key chemical weathering parameters the concentration of co2 in the soil and groundwater moving past the weathering front depending upon the assumptions used in the model the rate of saprolitization varies from 2 2 to 5 3 m m y the possible impact of periglacial processes suggested by the chemical weathering rates indicates a need to reconsider theories of landscape evolution as they apply to the northern piedmont province of the mid atlantic states i suggest that from the late miocene to the present that the major rivers have become incised in their present locations this incision has enhanced groundwater circulation and chemical weathering such that crystalline rocks beneath interfluvial areas remain mantled by saprolite and the saprolite mantle has been partially stripped as periglacial conditions alternate with humid temperate conditions

post late glacial calcareous tufas from the kurai fault zone southeastern gorny altai russia abstract calcareous tufa deposits have been discovered in the chibitka river valley near lake cheybek kohl at the junction of the kurai and teletsk kurai large active faults in the southeastern gorny altai russia at an altitude of 1800 2000 m fossil tufa is composed of calcite and cements holocene grey colluvium and glacial till deposited by the late glacial chibitka glacier current tufa precipitation has been observed from a low flow spring with cold 10 c hco 3 so 4 ca mg water 6 86 the stable isotope composition of spring water is 5 8 vpdb 13 c of dissolved inorganic carbon and 14 5 vsmow 18 o modern tufa consists of thin laminated mg calcite and sr aragonite crusts with abundant algae and biofilms on their surfaces both modern and fossil tufas are depleted in ree a total of 0 40 16 4 ppm and 0 40 3 80 ppm respectively and share similar paas normalised ree y spectra with hree enrichment and slight progressive lree depletion the modern tufas show positive 13 c values of 0 1 to 0 9 vpdb while the fossil ones have an isotopically lighter composition of 13 c 4 1 to 1 9 vpdb the 18 o range is very narrow 13 0 to 13 8 vpdb both stable isotope and trace element signatures including ree patterns of the tufas indicate precipitation from cold groundwaters subjected to prolonged interaction with a carbonate aquifer the baratal group of limestone and dolostone in a cold continental climate similar to the present conditions tufa deposition in the lake cheybek kohl area began with the onset of post late glacial global warming and permafrost degradation unlike the fossil tufa formation current precipitation of freshwater carbonates has been microbially mediated the discovered tufa deposits provide new palaeoclimatic and active tectonic proxies in the southeastern gorny altai

rates and time scales of clay mineral formation by weathering in saprolitic regoliths of the southern appalachians from geochemical mass balance rates of clay formation in three watersheds located at the coweeta hydrologic laboratory western north carolina have been determined from solute flux based mass balance methods a system of mass balance equations with enough equations and unknowns to allow calculation of secondary mineral formation rates as well as the more commonly determined primary mineral dissolution rates was achieved by including rare earth elements ree in the mass balance rates of clay mineral formation determined by mass balance methods have been used to calculate the time needed for a 5 50 g kg 1 change in relative clay abundance in the saprolite at coweeta this corresponds to the response time of the clay mineral to for example a change in climate the 5 change in relative clay abundance is the smallest change that can generally be detected using x ray diffraction xrd response times range from tens of thousands to hundreds of thousands of years extrapolating the coweeta clay formation rates to other southern appalachian regoliths the time required to form measured clay abundances production times in eastern blue ridge and inner piedmont regolith have been calculated the production times of clay mineral assemblages range from 2 k y to 2 m y with mean values ranging from 50 k y to 1 m y the results of this study are consistent with the arguments of thiry 2000 1 that the best resolution of the paleoclimatic record in marine clay rich sediments and mudrocks is 1 or 2 m y 1 ref 107

late cenozoic flexural deformation of the middle u s atlantic passive margin despite the century long recognition of regional epeirogeny along the middle atlantic passive margin relatively few studies have focused on understanding postrift uplift mechanisms here we demonstrate that epeirogenic uplift of the central appalachian piedmont and subsidence of the salisbury embayment represent first order flexural isostatic processes driven by continental denudation and offshore deposition our results show that regional epeirogenic processes present on all atlantic type passive margins are best resolved by specific stratigraphic and geomorphic relationships rather than topography a simple one dimensional geodynamic model constrained by well dated baltimore canyon trough coastal plain and lower susquehanna river piedmont stratigraphy simulates flexural deformation of the u s atlantic margin the model represents the passive margin lithosphere as a uniformly thick elastic plate without horizontal compressive stresses that deforms flexurally under the stress of strike averaged vertically applied line loads model results illustrate a complex interaction among margin stratigraphy and geomorphology the isostatic response to denudational and depositional processes and the modulating influence of exogenic forces such as eustasy the current elevation with respect to modern sea level of fluvial terraces and correlative coastal plain deposits or unconformities is successfully predicted through the synthesis of paleotopography eustatic change and margin flexure results suggest that the middle u s atlantic margin landward of east coast magnetic anomaly is underlain by lithosphere with an average elastic thickness of 40 km flexural rigidity d 4 1023 n m the margin experiences an average long term denudation rate of approximately 10 m m y and the piedmont has been flexurally upwarped between 35 and 130 meters in the last 15 m y long term isostatic continental uplift resulting from denudation and basin subsidence resulting from sediment loading are accommodated primarily by a convex up flexural hinge physiographically represented by the fall zone our results elucidate an inherent danger in using topography alone to constrain late stage passive margin deformation mechanisms only through careful synthesis of field stratigraphic and geomorphic elements such as fluvial terraces coastal plain deposits and offshore stratigraphy can age control be extended from the offshore depositional setting to the erosionally dominated continent this study demonstrates that despite a relatively subdued topography the middle u s atlantic margin experiences progressive flexural isostatic deformation similar to that proposed for high relief margins characterized by great escarpments thus margin topographic diversity remains a function of other factors such as lithospheric composition and or structure supracrustal stratigraphy and structure degree of drainage integration drainage divide migration and climate

long term average mineral weathering rates from watershed geochemical mass balance methods using mineral modal abundances to solve more equations in more unknowns abstract the number of phases for which weathering rates can be determined by watershed geochemical mass balance is limited by the number of equations that can be constructed from elemental flux losses from the watershed and mineral stoichiometries mass balance studies of watershed weathering rates routinely use the flux losses of the six major cations sio 2 al na k mg and ca analyses of these species in water are common but following matrix algebraic methods limits the number of weathering rates that can be calculated to six for the brubaker run watershed located in the northern piedmont physiographic province of pennsylvania usa long term 10 3 10 6 year watershed chemical flux losses have been determined using 10 be derived total denudation rates and zirconium normalized total chemical concentrations from bedrock and soils chemical flux losses calculated from solid phase data have three advantages they 1 permit generation of a relatively large number of equations because both major and trace analyses are included 2 eliminate the need for many years of regular e g weekly sampling and chemical analyses of stream water and atmospheric precipitation and measurement of hydrologic parameters i e precipitation stream discharge etc and 3 long term weathering rate calculations need not address biomass for brubaker run eight minerals are involved in weathering the five primary minerals are ree rich epidote ankerite almandine spessartine garnet muscovite chlorite and the three secondary products are weathered muscovite kaolinite and gibbsite the long term average weathering rates of these minerals were calculated using the six major cations and two trace elements selected from rb sr ba la pr nd sm gd and dy despite having the eight equations needed geochemically reasonable weathering rates e g positive primary mineral rates that reflect destruction could not be achieved regardless of the two trace elements used in the mass balance calculations for brubaker run this is primarily attributable to the natural heterogeneity of the trace element concentrations within the host mineral grains with trace element stoichiometries in some minerals varying by as much as an order of magnitude because the trace elements are hosted by a relatively small number of minerals the computed weathering rates of other minerals become very sensitive to small variations in trace cation stoichiometry ree rich epidote garnet and ankerite within the brubaker run watershed together host nearly all of the ca in the bedrock and completely dissolve at or near the weathering front consequently approximately all of the ca in bedrock is lost from the regolith in bedrock the mole percentages of ca hosted by ree rich epidote garnet and ankerite are 49 mol 4 mol and 43 mol respectively and are determined by the modal abundance of the mineral in the bedrock and its ca stoichiometry the weathering rates of ree rich epidote garnet and ankerite can be determined by distributing to each mineral that fraction of the total watershed ca flux loss for which it is responsible based on its mole percent ca in bedrock by using a base cation that is completely lost from the regolith and knowing the mole percentage of that element in the mineral s undergoing weathering additional equations may be added to the mass balance matrix we term this technique the flux distribution method the flux distribution method eliminates the need for additional equations established using trace elements based on the mineral weathering rates for the brubaker run watershed determined using the flux distribution method the rates at which the weathering front penetrated the bedrock the saprolitization rate are 4 5 m myr 1 and 6 5 m myr 1 for chlorite and muscovite respectively these measured long term average saprolitization rates compare very favorably with published theoretical values for the nearby northern maryland piedmont which range from 2 2 to 5 3 m myr 1

periglacial geomorphology of the appalachian highlands and interior highlands south of the glacial border a review abstract many features reported in the appalachian region have been assigned a paleoperiglacial origin based on field relationships and their similarities with analogs active in present day actuoperiglacial environments these forms include but are not limited to sorted and nonsorted varieties of patterned ground grezes litees block fields block slopes and block streams cryoplanation terraces and hillslope and river terrace landscapes although very small scale features generally less than 1 m in plan or section dimension and some larger forms on steep hillslopes are known to be at least sporadically active today the large scale features discussed here are interpreted as either inactive or truly fossil periglacial phenomena thus they hav implications for paleoclimatic reconstruction and significance as indicators of relative landscape stability since the time s of their development this paper briefly reviews the historical dimension of early researchs work present selected examples of recent results and gives authors conclusions

a generalized 3 d geological and hydrogeological conceptual model of granite aquifers controlled by single or multiphase weathering summary the weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas these weathering profiles generally develop under both stable geodynamic conditions weathering rate erosion rate and a hydrolysing climate they are composed of thick stratiform layers that follow the paleo landscape paleotopography and thus present a gently dipping sequence at a regional scale the structure and the hydrodynamic properties of the weathering profile of a granitic area 53 km 2 maheshwaram catchment state of andhra pradesh india were characterized in detail and mapped from observations on outcrops 80 vertical electric soundings and lithologs from 45 borewells in which flowmeter measurements and injection tests were also performed to characterize the hydraulic conductivities of the conductive fissure zones the structure of the weathering profile results from a multiphase process an ancient weathering profile was partly eroded down to its fissured layer it was later re weathered more or less parallel to the current topographic surface this peculiar structure is linked to the geodynamic history of the indian peninsula that underwent alternate weathering and erosion dominated phases the profile is thus composed from top to bottom up to a total depth of 35 m of sandy regolith saprolite 1 3 m 10 15 m of laminated saprolite containing unusual preserved fissures and a 15 20 m thick fissured layer by comparing various case studies in similar terrain a generalized 3 d geological and hydrogeological conceptual model of granite type aquifers granites gneisses etc is proposed in granite type rocks single weathering or multiphase weathering and erosion processes induce similar geological structures a few main geological differences arise from the comparison of single phase and multiphase weathering profiles i in the later the respective thicknesses of the various layers can be deeply modified ii the ancient fissured layer can be re weathered and the resulting new laminated layer may contain quite well preserved and conductive ancient fissures and iii the upper part of the fissured layer is more densely fissured as a result of the same weathering processes the fissures from the fissured layer of single phase or multi phase profiles exhibit very similar hydraulic conductivities and show both a higher density of conductive fissures at the top of the layer the preserved ancient fissures within the laminated layer of a multiphase profile are partly obliterated by the recent weathering their hydraulic conductivity is thus significantly reduced nevertheless they do significantly contribute to borewell yield these weathering induced fissures provide most of the aquifer permeability the use of such a conceptual model for the precise geological mapping of the weathering structure appears to be a prerequisite for groundwater development and management in hard rock areas as it answers to several key issues

rates and patterns of late cenozoic denudation in the northernmost atlantic coastal plain and piedmont topography of a 2800 km 2 section of the u s atlantic coastal plain and piedmont is reconstructed at five times from the late miocene to the holocene the reconstructions are based on mapping of fluvial colluvial and marginal marine deposits that are dated by radiocarbon palynostratigraphy and correlation to adjacent glacial and marine units denudation rates and patterns are calculated by subtracting successive topographies with 60 m horizontal resolution and 6 m vertical resolution the overall late miocene to holocene denudation rate of 10 m m y is similar to other estimates of long term denudation in the region the overall rate resolves spatially into a wide range of local rates varying from a minimum of 0 2 m m y on residual uplands to as high as 600 m m y in glacially rerouted stream channels the distribution of local rates shows that denudation is accomplished by stream incision in response to long term glacio eustatic decline followed by slope retreat into residual uplands from the incised channels slope retreat replaces the uplands with pediments and straths pediment landforms and sediments and observation of modern scarps and valley heads indicate that groundwater seepage from the base of residual uplands is an important mechanism of slope retreat this process is self limiting because as the volume of residual upland is reduced seepage diminishes and slope retreat slows until small residuals undergo little or no further reduction thus relict topography is preserved even as most of the landscape actively erodes

weathering the escarpment chemical and physical rates and processes south eastern australia differences in chemical weathering extent and character are expected to exist across topographic escarpments due to spatial gradients of climatic and or tectonic forcing the passive margin escarpment of south eastern australia has a debated but generally accepted model of propagation in which it retreated within 40 ma to near its current position following rifting between australia and new zealand 85 100 ma before present we focus on this escarpment to quantify chemical weathering rates and processes and how they may provide insight into scarp evolution and retreat we compare chemical weathering extents and rates above and below the escarpment using a mass balance approach coupling major and trace element analyses with previous measurements of denudation rates using cosmogenic nuclides 10be and 26al we find a slight gradient in saprolite chemical weathering rate as a percentage of total weathering rate across the escarpment the lowlands area encompassing the region extending from the base of the escarpment to the coast experiences a greater extent of chemical weathering than the highland region above the escarpment percents of denudation attributable to saprolite weathering average 57 6 and 47 7 at low and high sites respectively furthermore the chemical index of alteration cia a ratio of immobile to mobile oxides in granitic material that increases with weathering extent have corresponding average values of 73 7 3 9 and 65 5 3 4 indicating lower extents of weathering above the escarpment finally we quantify variations in the rates and extent of chemical weathering at the hillslope scale across the escarpment to suggest new insight into how climate differences and hillslope topography help drive landscape evolution potentially overprinting longer term tectonic forcing copyright 2009 john wiley sons ltd

sea valleys and related depositional systems in the gulf of lion and ebro continental margins 1 four main types of sea valleys submarine canyons gullies channels of turbidite systems and a mid ocean channel have been characterized in the ebro and the gulf of lion distal margins in the catalan sea together with three main types of depositional bodies pyrenean canyon deep sedimentary body pcdsb apron deposits and channel levee complexes related to the development of these sea valleys erosion and deposition mainly during the quaternary have formed the majority of these sea valleys although some structurally controlled sea valleys also exist as an example a messinian entrenchment has been confirmed in the petit rhone canyon the evolution of the drainage patterns is established from the detailed analysis of the sedimentary structure this analysis revea s the presence of buried sedimentary bodies and older drainage systems differing from those observed in the bathymetric charts specific factors determine the evolutionary differences between both margins including the absence or presence of underlying evaporitic messinian layers and the regional geodynamic evolution during and after the alpine orogeny we propose a dual evolutionary model from the end of the miocene to the quaternary

nonequilibrium regolith thickness in the ouachita mountains abstract interpretations of regolith and soil thickness in the context of landscape evolution are typically based on the notion that thickness is controlled by the interaction of weathering rates and erosion and tuned to topography on sideslopes of the ouachita mountains arkansas however there is a high degree of local spatial variability that is largely unrelated to topography this indicates nonequilibrium in the sense that there is no evidence of a balance between rates of weathering and removal as is postulated in some conceptual models in geomorphology and pedology johnson s soil thickness model is applied as an alternative to interpret local variations in regolith thickness at the study sites regolith thickness is not generally related to slope curvature elevation or pedogenic development in the solum this indicates that variability in thickness is related chiefly to processes and controls acting in the lower regolith below the solum the primary controls of variability are local lithol

quality of samples retrieved from great depth and its influence on consolidation properties pleistocene sediments deposited in osaka bay have been extensively investigated to depths of up to 400 m consolidation properties especially preconsolidation pressure are somewhat scattered with depth the quality of samples retrieved from great depths has been evaluated based on the indices calculated from the volumetric strain or the void ratio changes in the recompression process the study reveals that these indices do not simply increase with an increase in sampling depth the potential for sample disturbance during sample setting in the constant rate of strain crs oedometer was also investigated these tests have revealed that the preconsolidation pressure as measured in the laboratory is not influenced significantly by swelling in addition preconsolidation pressures indicate that the sediments are slightly overconsolidated with a departure from normally consolidated behaviour that could be explained by cementation key words sampling preconsolidation pressure sample disturbance oedomet

chemical weathering in a tropical watershed luquillo mountains puerto rico i long term versus short term weathering fluxes abstract the pristine rio icacos watershed in the luquillo mountains in eastern puerto rico has the fastest documented weathering rate of silicate rocks on the earth s surface a regolith propagation rate of 58 m ma 1 calculated from iso volumetric saprolite formation from quartz diorite is comparable to the estimated denudation rate 25 50 ma 1 but is an order of magnitude faster than the global average weathering rate 6 ma 1 weathering occurs in two distinct environments plagioclase and hornblende react at the saprock interface and biotite and quartz weather in the overlying thick saprolitic regolith these environments produce distinctly different water chemistries with k mg and si increasing linearly with depth in saprolite porewaters and with stream waters dominated by ca na and si such differences are atypical of less intense weathering in temperate watersheds porewater chemistry in the shallow regolith is controlled by closed system recycling of inorganic nutrients such as k long term elemental fluxes through the regolith e g si 1 7 10 8 moles m 2 s 1 are calculated from mass losses based on changes in porosity and chemistry between the regolith and bedrock and from the age of the regolith surface 200 ma mass losses attributed to solute fluxes are determined using a step wise infiltration model which calculates mineral inputs to the shallow and deep saprolite porewaters and to stream water pressure heads decrease with depth in the shallow regolith 2 03 m h2o m 1 indicating that both increasing capillary tension and graviometric potential control porewater infiltration interpolation of experimental hydraulic conductivities produces an infiltration rate of 1 m yr 1 at average field moisture saturation which is comparable with libr tracer tests and with base discharge from the watershed short term weathering fluxes calculated from solute chemistries and infiltration rates e g si 1 4 10 8 moles m 2 s 1 are compared to watershed flux rates e g si 2 7 10 8 moles m 2 s 1 consistency between three independently determined sets of weathering fluxes imply that possible changes in precipitation temperature and vegetation over the last several hundred thousand years have not significantly impacted weathering rates in the luquillo mountains of puerto rico this has important ramifications for tropical environments and global climate change

slope failure dynamics and impacts from seafloor and shallow sub seafloor geophysical data case studies from the costa project holocene and slightly pre holocene submarine landslide are found both in high latitude glacial dominated margins and in lower latitude river dominated margins this paper constitutes a major assessment on some of the best studied submarine instabilities in the world we review and update from original data and literature reports the current state of knowledge of storegga traenadjupet and finneidfjord slides from the mid norwegian margin afen slide from the faeroe shetland channel big 95 slide and central adriatic deformation belt cadeb from continental slope and inner continental shelf settings off the ebro and po rivers in the mediterranean sea canary slide west of the westernmost youngest canary islands and gebra slide off the northern tip of the antarctic peninsula in the southern hemisphere i e those studied in the continental slope stability costa project the investigated slides range in size from the gigantic 90 000 km2 and almost 3000 km3 storegga slide to the tiny 1 km2 and 0 001 km3 finneidfjord slide not only do individual submarine landslides rarely involve processes precisely fitting with pre established categories mostly based on subaerial research but also they display complex mechanical behaviors within the elastic and plastic fields individual events can involve simultaneous or successive vertical to translational movements including block detachment block gliding debris flow mud flow and turbidity currents the need for an in depth revision of the classification criteria and eventually for a new classification system based on the new imaging capabilities provided by modern techniques is more than obvious we suggest a new system which for the moment is restricted to debris flows and debris avalanches volume calculation methods are critically reviewed and the relations between some key geomorphic parameters are established for the selected slides the assumed volume missing from scar areas does not necessarily match the actual volume of sediment remobilised by an individual event since in situ sediment can be remoulded and eventually incorporated during the slide downslope journey cadeb a shore parallel prodelta detached from its source is the exception to the good correlation found between across slope width and alongslope length with slide area height drop measured from the headwall upper rim to its foot correlates with the debris deposit maximum thickness unless the slide moves into restricted areas which prevent farther forward expansion of the deposit such as gebra and big 95 in such cases over thickened deposits are found a particularly loose and fluid behavior can be deduced for slides showing an over thinned character such as the canary slide that traveled 600 km scar areas and slip planes have been investigated with particular emphasis although slide headwalls might present locally steep gradients up to 23 for storegga slide the slope gradients of both the failed segment margins and the main slip planes are very low max 2 and usually around 1 and less an exception is the finneidfjord slide 20 5 that occurred in 1996 because of a combination of climatic and anthropogenic factors leading to excess pore pressure and failure mechanically distinct low permeable clayey weak layers often correspond to slip planes beyond the slide headwall since not only formation of these weak layers but also sedimentation rates are climatically controlled we can state that slide pre conditioning is climatically driven too run out distances reflect the degree of disintegration of the failed mass of sediment the total volume of initially failed material and transport mechanisms including hydroplanning commonly specific run outs could be attributed to distinct elements such as cohesive blocks and looser matrix as nicely illustrated by the big 95 slide total run outs usually correspond to matrix run outs since the coarser elements tend to rest at shorter distances outrunner blocks are finally a very common feature proving the ability of those elements to glide over long distances with independence of the rest of the failed mass in addition to pre conditioning factors related to geological setting and sedimentation conditions a final trigger is required for submarine landslides to take place which is most often assumed to be an earthquake in high latitude margins earthquake magnitude intensification because of post glacial isostatic rebound has likely played a major role in triggering landslides although it cannot be totally ruled out there is little proof at least amongst the costa slides that gas hydrate destabilisation or other processes linked to the presence of shallow gas have acted as final triggers

grus weathering mantles problems of interpretation abstract grus is an ill defined product of deep weathering of coarse grained rocks whose relationships to other weathering changes remain unclear this paper attempts to address this issue by reviewing a number of examples of coarse saprolites from a variety of climatic and topographic settings grus is the category of weathering mantle that possesses the following characteristics sand gravel 75 100 silt clay

overpressure within upper continental slope sediments from cptu data gulf of lion nw mediterranean sea data from in situ piezocone tests cptu and laboratory analyses are utilized for the interpretation of the stress history of quaternary sedimentary sequences in the upper continental slope of the gulf of lion northwestern mediterranean sea a cptu based preconsolidation pressure profile referenced to the current effective stress indicates that the deposit is underconsolidated from 12 meters below the seafloor mbsf down to at least 150 mbsf excess pore pressure below 12 mbsf is further supported by results from oedometer and dissipation tests subseafloor pockmarks and indications of free gas in seismic reflection profiles reveal four main overpressure sources si siv with overpressure ratios 0 3 at subseafloor depths coinciding with levels where the dominantly silty clayey sediment contains increased proportions of sand we relate the excess pore pressure related to free gas due to gas exsolution processes and sea level variations driven by pleistocene sea level changes

implications of salt sediment interactions on the architecture of the gulf of lions deep water sedimentary systems western mediterranean sea we integrated structural analysis of multichannel seismic data and isopach maps of the quaternary sedimentary cover to evaluate how salt tectonics has influenced the stratigraphic evolution offshore the gulf of lions the interplay between salt tectonics and sedimentation occurs at two scales at local scale listric normal faults create bathymetric relief able to deviate sediment transport axes with implications on depocenters configuration at depocenter scale overburden vertical movements due to salt evacuation or salt diapiric rise create sub basins providing accommodation space for clastic deposition these mechanisms have significant implications on the architecture and the internal organization of turbidite systems offshore the gulf of lions

sortable silt and fine sediment size composition slicing parameters for palaeocurrent speed and palaeoceanography fine sediment size 63 ixm is best measured by a sedimentation technique which records the whole size distribution repeated size measurement with intermediate steps of removal of components by dissolution allows inference of the size distribution of the removed component as well as the residue in this way the size of the biogenic and lithogenic noncarbonate fractions can be determined observations of many size distributions suggest a minimum in grain size frequency curves at 8 to 10 ixm the dynamics of sediment erosion deposition and aggregate breakup suggest that fine sediment behavior is dominantly cohesive below 10 1xm grain size and noncohesive above that size thus silt coarser than 10 ixm displays size sorting in response to hydrodynamlc processes and its properties may be used to infer current speed silt that is f mer than 10 ixm behaves in the same way as clay 2 xm useful parameters of the distribution are the 10 63 ixm mean size and the percentage 10 63 ixm in the fine fraction we cannot use size distributions to distinguish the nature of the currents therefore to infer water mass advection speeds i e the mean kinetic energy of the flow ku regions of high eddy kinetic energy ke must be avoided at the present such abyssal regions lie under the high surface k e of major current systems gulf stream kuroshio agulhas antarctic circmpolar current and brazil falldand currents in the argenthe basin this is probably a satisfactory guide for the pleistocene with regard to the carbonate subfraction of the size spectrum size modes due to both cocco iths and foramlnlferal fragments can be recognized and analyzed with the boundary between them again at about 10 lm the flux of less than 10 lm carbonate at pelagic sites above the lysocline is another candidate for a productivity indicator