displaced carbonates in the zechstein of the uk north sea abstract the cored zechstein 2 interval of amoco well 38 24 1 drilled on the southern margin of the mid north sea high contains deformed conglomeratic and brecciated dolostones which are interpreted as displaced distal shelf sediments redeposited in deeper water the displaced dolostones indicate disruption and sliding of consolidated rock down a slope accompanied by slumping of semi consolidated sediment minor collapse brecciation also occurred as a result of the partial removal of underlying evaporites such features have not hitherto been described from cored wells in the uk north sea nor have their petrophysical attributes been discussed the best reservoir properties occur in the slumped deposits showing plastic deformation brecciated beds have unpredictable and wide ranging porosity and permeability values which are attributable to variable anhydrite cementation and clasts with different textures and very variable fabric displaced zechstein carbonates on or at the foot of unstable palaeo slopes for example in the vicinity of the mid north sea high can develop moderately attractive reservoir characteristics and might in places be thick enough to be of economic importance

shifting zonal patterns of the southern boreal forest in eastern canada associated with changing fire regime during the holocene this research aims at uncovering the stand scale holocene fire history of balsam fir forest stands from two bioclimatic zones of the boreal forest and assessing the existence of a sub continental shift in past fire activity that could have triggered a change in the holocene zonal pattern in eastern canada the extant closed crown boreal forest corresponds to two ecological regions separated along 49 n the northern black spruce zone and the southern balsam fir zone we sampled balsam fir stands from the southern fir zone n 7 and among the northernmost patches of fir forest located far beyond the fir zone boundary into the spruce zone n 6 macrofossil analysis of charcoal in mineral soils was used to reconstruct both the stand scale and regional holocene fire histories data were interpreted in the context of published palaeoecological evidence stands of the balsam fir zone were submitted to recurrent fire disturbances between c 9000 and 5000 cal yr b p local fire histories suggested that four sites within the fir zone escaped fire during the holocene such fire protected sites allowed the continuous maintenance of the balsam fir forest in the southern boreal landscape stands of the spruce zone have been affected by recurrent fires from 5000 cal yr b p to present local fire histories indicated that no site escaped fire in this zone published palaeoecological data suggested that balsam fir migrated to its current northern limit sometime between 7300 and 6200 cal yr b p a change of the fire regime 5000 years ago caused the regional decline of an historical northern balsam fir forest and its replacement by black spruce forest the consequence was a sub continental reshuffling of the fir and spruce zones within the closed crown boreal forest the macrofossil analysis of charcoal in mineral soils was instrumental to the reconstruction of stand scale holocene fire history at sites where no other in situ fire proxies were available

the trow point bed a deposit of upper permian marine oncoids peloids and columnar stromatolites in the zechstein of ne england

upper permian zechstein supergroup carbonate evaporite platform palaeomorphology in the uk southern north sea abstract seismic interpretation geological mapping and depth conversion of the zechstein supergroup z2 cycle using high quality well calibrated three dimensional 3 d seismic has revealed the complex palaeomorphology of a deeply buried ancient carbonate shelf margin on the southwestern margin of the southern permian basin the new mapping shows that the margin comprises a series of corrugated embayments and promontories which extend up to 5 km 3 mi into the basin and locally have a palaeobathymetric relief of 200 m 650 ft well calibration across the margin demonstrates a strongly bipartite lateral thickness distribution between a high velocity anhydrite dominated shelf and a lower velocity halite dominated basin strong lateral and vertical velocity variations in the upper permian zechstein supergroup are known to have major impacts upon seismic imaging and depth conversion in the spb the resulting uncertainty remains one of the major challenges when interpreting and assessing the prospectivity of the underlying upper permian rotliegend group leman sandstone formation reservoirs in the uk southern north sea an understanding of the zechstein shelf edge s 3 d physiography and its velocity variation has implications for the delineation of traps containing the prospective reservoirs that lie below recognition of the complexity and effects of this shelf margin contributed to the recent juliet discovery whose position outside of the presently defined rotliegend group play fairway suggests that prospectivity is more extensive along the basin margin than previously thought as such the work provides a means by which to identify and delineate new structures and extend the life of this mature yet prolific gas province

formation of fine grained metal and silicate precipitates on a bacterial surface bacillus subtilis abstract the ability of the gram positive bacterium b subtilis to bind and nucleate precipitates from silicate anions has been studied over 24 weeks in the presence of fe and a1 at concentrations close to those levels in soils and at slightly acid 5 5 and basic 8 0 ph in all cases formation of silicate crystallites quasi crystalline precipitates on the bacterial surfaces was observed bacterially mediated minerals were more diverse in composition and morphology less crystalline smaller and sometimes more abundant than those that were abiotically formed fe pretreatment of the bacterial cells enhanced the binding of silicate at ph 8 0 walls which were not pretreated with fe bound silicate more favourably at acid values when heavy metals pb cd zn cr ni cu were added to the mixture at ph 4 5 silicate retention was greatly favoured giving greater retention of either si or metals than was seen in abiotic controls experiments with only heavy metals showed a high affinity of the bacterial walls for the metals even at low temperatures 4 c it is postulated that a cationic bridging mechanism is involved in the binding of silicate anions by bacterial cell walls

bacteria as nucleation sites for authigenic minerals in a metal contaminated lake sediment abstract sediment samples contaminated with metals arising from mine tailings drainage were obtained from lower moose lake in the onaping region near sudbury ontario canada the samples were examined by electron microscopy selected area electron diffraction and energy dispersive x ray spectroscopy individual bacterial cells and their remains were prominent as nucleation sites for both metal sulfides and a complex polymorphic fe al silicate the principal metal sulfide species associated with the bacteria were amorphous mackinawite fes 1 x and microcrystalline millerite nis trace amounts of cu and zu were also detected in some of the sulfide precipitates at least two structural forms of the fe al silicate were present and energy dispersive x ray spectroscopy point analyses revealed corresponding differences in chemical composition poorly ordered limonitic clay type phases had a granular morphology and contained less fe than well developed crystalline material which generated hexagonal diffraction patterns with reflections d 4 60 and 2 55 characteristic of an interstratified chamositic clay

metal sorption and mineral precipitation by bacteria in two amazonian river systems rio solimoes and rio negro brazil the surfaces of epiphytic and episammic bacteria from the solute rich waters of the rio solimoes brazil interacted with available cations in solution and provided major sites for iron deposition once bound to the bacteria the iron served as nucleation sites for the formation and growth of fine grained authigenic mineral phases because of progressive mineralization the precipitates exhibited a wide range of morphologies from amorphous gel like to crystalline structures complete encrustation of some bacterial cells was observed the most abundant mineral phase associated with the bacteria was a complex fe al silicate with a variable composition energy dispersive x ray spectroscopy suggested that the gel like structures were similar in composition to a chamositic clay whereas the crystalline phases were increasingly kaolinitic bacteria collected from the solute deficient waters of the rio negro remained conspicuously unmineralized suggesting that metal sorption and biomineralization largely reflect the availability of dissolved metals in the water column in a solute rich river system the fate of the metal loaded bacteria has profound implications for the transfer of metals from the hydrosphere to the sediment through diagenesis the bound metals may either be recycled to the overlying water column or become immobilized as stable mineral phases if the latter occurs microorganisms will have played an important role in metal deposition low temperature clay formation and invariably mudstone diagenesis this implies that in the geologic record microorganisms may have been instrumental in the genesis of many sedimentary rocks of fluvial origin

geochemistry of dissolved aluminum at low ph hydrobasaluminite formation and interaction with trace metals silica and microbial cells under anoxic conditions abstract the precipitation of dissolved aluminum is among the most important geochemical processes affecting the water chemistry and trace metal dynamics of acid mine drainage amd in this study we focus on the in situ formation of al precipitates and their subsequent interaction with trace metals dissolved silica and microbial cells under anoxic conditions e g deep strata of pit lakes flooded underground mines in the presence of sulfate 0 1 0 2 m dissolved aluminum precipitates at ph 4 0 and forms an amorphous globular hydroxysulfate precipitate with composition corresponding to hydrobasaluminite this proto hydrobasaluminite shows an important capacity to incorporate sio 2 aq divalent metal cations fe ii pb ii be ii and many anion forming trace elements as cr sb v se u by coprecipitation removal efficiencies obtained experimentally with freshly formed hydrobasaluminite under anoxic and oxic conditions were consistent with metal profiles obtained in the pit lakes and suggest that the behaviour of many toxic metals is closely linked to the al particles detailed transmission electron microscopy tem shows that hydrobasaluminite may coexist with more crystalline minerals like gibbsite bayerite and or allophane which are present as nanocrystals embedded in the amorphous matrix and appear to form by transformation of the former hydrobasaluminite precipitation is favoured by the activity of iron and sulfate reducing microbes in the water column and at the sediment water interface our study shows that at solubility equilibrium microbial cells often serve as nuclei for al precipitation further chemical mapping of al coated cells by scanning tem shows an important incorporation of sio 2 fe 2 valence confirmed by electron energy loss spectroscopy and other metal cations e g mg 2 in the al cell coatings as compared to al particles presumed to form via abiotic precipitation these al cell coatings are amorphous to x rays and their compositions likely result from coprecipitation of sio 2 and fe 2 resulting in si rich and fe ii rich hydrobasaluminite the disparity between field and laboratory data the serendipitous detection of nontronite like smectite in precipitates formed in the acidic waters under laboratory conditions and the apparent saturation with respect to different clay minerals e g kaolinite halloysite are all evidences suggesting thermodynamic feasibility of aluminosilicate precursor formation in these systems

acid mine drainage in the iberian pyrite belt odiel river watershed huelva sw spain geochemistry mineralogy and environmental implications abstract this work reports the physical properties and water chemistry of 64 amd discharges from 25 different mines in the ipb draining to the odiel river watershed which have been investigated during the hydrologic year 2003 2004 these amd solutions vary largely in flow rate and chemical composition both spatially between the different mine sites suggesting a strong geologic control on amd chemistry and seasonally due to marked hydrologic variations and include cases with very low ph mostly in the range 1 4 4 and extreme sulphate up to 44 g l so 4 2 and metal content e g up to 7 7 g l fe 2 6 g l al or 1 4 g l zn different hydrogeochemical facies of amd namely fe ii anoxic fe iii suboxic and aluminous oxic are recognized in the field as a response to the continuous oxidation and hydrolysis of dissolved fe relevant geochemical aspects of these amd environments are discussed including i the redox chemistry of the fe ii fe iii couple ii the reaction rates for bacterially catalyzed oxidation of fe ii and hydrolysis of fe iii iii the role played by dissolved fe and al in the acidity and chemical buffering of the amd systems and iv the solubility and trace metal retention capacity of the fe oxyhydroxysulphate and hydrated sulphate minerals commonly associated with amd in addition the mineralogy and chemistry of the fe precipitates schwertmannite jarosite goethite ferrihydrite al phases e g basaluminite and mg fe al efflorescent so4 salts e g epsomite hexahydrite copiapite halotrichite rozenite coquimbite present in the amd generating mine sites have also been studied the mineralogy of the fe precipitates is well correlated with the water ph with jarosite at ph 2 schwertmannite at ph 2 4 basaluminite at ph 4 5 and ferrihydrite at ph 6 schwertmannite appears to be the most important mineral phase both in controlling the fe solubility at ph 2 4 and as sorbent of trace elements as cu zn which favours natural attenuation finally a basin scale environmental perspective is given in order to evaluate the impact of amd on the water quality including calculation of metal loadings transported by amd from the most important mine districts in the province

soil charcoal stability over the holocene comment to the paper published by de lafontaine and asselin quaternary research v 76 2011 pp 196 200

sequence stratigraphy and cyclic development of basal zechstein carbonate evaporite deposits with emphasis on zechstein 2 off platform carbonates upper permian northeast germany abstract although the basal zechstein is classically subdivided into two cycles z1 and z2 lower part it can alternatively be subdivided into three complete third order depositional sequences zs1 zs3 and the associated lowstand systems tract transgressive systems tract of a fourth sequence zs4 third and higher order sea level fluctuations influenced the depositional and diagenetic history of the carbonate evaporite alternations within the basal zechstein the main subject of the present study the zechstein 2 carbonate stassfurt carbonate or ca2 is interpreted to encompass both transgressive predominantly in slope and basinal settings and highstand systems tracts of zechstein sequence zs3 as well as part of the lowstand systems tract of the fourth zechstein sequence zs4 in northeastern germany hydrocarbon reservoirs of the ca2 developed along both northern and southern margins of the southern permian basin on top of the topography of the zechstein 1 cycle z1 this z1 topography resulted from deposition of the werra anhydrite a1 the highstand systems tract of the second zechstein sequence zs2 the northern ca2 carbonate platform is consistently narrow and fringed by coated grain and composite grain bars and shoals it is characterized by a steep fault controlled slope which precluded the formation of in situ shallow water grain dominated carbonates during relative sea level lowstands displaced shallow water coated grain and composite grain packstones wackestones may however occur as slope fan deposits turbidites in contrast the southern carbonate platform is wide tectonically dissected and fringed by grain dominated shallow water carbonates coated grain and composite grain bars and shoals zechstein 2 shallow water carbonates detectable by basal zechstein seismic anomalies also developed on pre existing topographical highs in off platform positions three depositional cycles ca2 cycles i ii and iii most probably reflecting high amplitude fourth order sea level fluctuations can be identified within the stassfurt carbonate our observations suggest that sea level variations possibly reflecting cyclicity in the milankovitch frequency band 0 1 0 4 ma and the pre zechstein topography pronounced during formation of the werra anhydrite were the most important factors in controlling the depositional as well as the diagenetic history of the zechstein 2 carbonate in off platform positions

evolution of the nw margin of the north permian basin uk north sea mapping of depositional zones within the zechstein supergroup using semi regional 2d and 3dseismic data constrains the geological evolution of the northwestern margin of the north permian basinin uk offshore quadrants 14 15 19 20 and 21 four depositional zones are identified on the basis of mappable seismic facies which are assumed to vary with halite content well control characterizes the most reflective seismic facies as an interbedded carbonate and anhydrite shelf succession which grades laterally through clastic rich sequences to the least reflective a thick halite basinal equivalent the trendsof the depositional zones illustrate the geometry of the north permian basin and may have been locally controlled by basement lineaments within the north permian basin a n s trending axis devil s hole high characterized by thick reflective facies separates the central north sea from the forth approaches basin basement fault blocks control facies type and thickness along the northwest margin of the north permian basin in the moray firth area permian tilt of the zechstein shelf related to regional flexure played a role in precipitating gravity driven tectonics within the seismically reflective facies on the east flank of the devil s hole high this permian phase of salt tectonics resulted in numerous intra zechstein structures which can be interpreted as rafted and folded zones of interbedded halite carbonate sulphate and clastics the rafts initially slid downdip towards the main halite basin then their evolution became dominated by differential subsidence of the interbeds which forced salt layers into adjacent passive diapirs this episode predates deposition of the triassic smith bank shales which rest upon the zechstein with local angular unconformity the spatial distribution of zechstein facies influenced the tectonostratigraphy of the triassic jurassic and cretaceous systems boundaries between zechstein facies correspond to the limit of triassic halokinesis on the west central shelf and the limit of detachment of jurassic and lower cretaceous thin skinned tectonics in moray firth half graben

aluminum mobility in mildly acidic mine drainage interactions between hydrobasaluminite silica and trace metals from the nano to the meso scale abstract aluminum precipitates control the hydrochemistry and mineralogy of a broad variety of environments on earth e g acid mine drainage amd coastal wetlands boreal and alpine streams tropical acid sulfate soils laterites and bauxites however the geochemical and mineralogical processes controlling al and other associated metals and metalloids transport and removal in those environments are not fully understood the geochemical system of paradise portal colorado usa comprises sulfate rich mildly acidic waters the hydrochemistry of which is directly controlled by the massive precipitation of hydrobasaluminite al4 so4 oh 10 12 36h2o three connected but discernible aluminum precipitation stages were identified and described 1 nanoparticle formation and size decrease along the creek 2 hydrobasaluminite neoformation on the riverbed and 3 precipitate accretion and accumulation on the riverbed leading to al and fe banded formations the co occurrence of al and si in the system was observed recording significant amounts of si accompanying the three different components of the system i e nanoparticles and fresh and aged al precipitates also abrupt and minor changes in the sedimentary record were described and proposed to be the response of the system to seasonal and interannual changes in amd chemistry concerning the mobility of other metals and metalloids p th v w ti and b showed a tendency to be preferentially incorporated into hydrobasaluminite while others like be as se or ba tend to remain dissolved in the water

sequence stratigraphy of carbonate evaporite basins models and application to the upper permian zechstein of northeast england and adjoining north sea the successions of carbonate evaporite basins which are periodically cut off from the world ocean are considered in terms of their sequence stratigraphy two basin types are distinguished those where incomplete drawdown takes place and those showing complete drawdown and wholesale basin desiccation it is argued that following relative sea level falls sequences begin with the evaporites precipitated as marginal lowstand gypsum wedges in the first basin type and as lowstand basin centre halite fills in the second the evaporites pass up into carbonate sediments which are mainly deposited on shallow water platforms around the basin during transgressive and highstand systems tracts the concepts and models developed are applied to the zechstein upper permian strata of northeast england and adjoining north sea seven sequences are proposed with some containing thin parasequences the sequence approach to carbonate evaporite basins which considers both basin margin and basin centre facies gives a more encompassing perspective of sedimentation than the traditional cycle concept with its emphasis on the basin centre

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

local structure and ageing of basaluminite at different ph values and sulphate concentrations abstract basaluminite is a poorly crystalline aluminium sulphate oxyhydroxide that precipitates in acid mine drainage waters and acid sulphate soils when ph increases above 4 5 approximately the ph increase can be due to mixing with natural waters or by the addition of an alkaline reagent a method commonly used in remediation treatments basaluminite is a scavenger of elements such as se as sb mo p and rare earth elements rees and acts as a vector for their transport in the environment the retention of these elements has important environmental and economic impact due to their toxicity and to the potential extraction of rees for technological applications despite the long history of basaluminite initially described as a mineral in the late 40s little is known about its stability and its eventual transformation in other less metastable phases here the stability of synthetic basaluminite in aqueous solutions with different ph values and sulphate concentrations was studied for 81 days chemical analyses of the aqueous phase combined with high energy x ray diffraction and pair distribution function pdf analyses of the solids were used to characterize the ageing process in contact with water basaluminite incongruently dissolves precipitating amorphous al hydroxide and releasing sulphate to the solution this process and the recrystallization of amorphous al hydroxide into nanoboehmite were enhanced with increasing ph however for high so4 concentrations such as those found in acid mine waters the transformation to nanoboehmite was partially inhibited the ageing processes highlighted here point to a potential pathway for the desorption of trace elements upon neutralization of acid mine drainage furthermore pdf analyses of basaluminite show a high similarity with the local structure of a synthetic amorphous al hydroxide