identifying the origin of groundwater samples in a multi layer aquifer system with random forest classification summary accurate identification of the origin of groundwater samples is not always possible in complex multilayered aquifers this poses a major difficulty for a reliable interpretation of geochemical results the problem is especially severe when the information on the tubewells design is hard to obtain this paper shows a supervised classification method based on the random forest rf machine learning technique to identify the layer from where groundwater samples were extracted the classification rules were based on the major ion composition of the samples we applied this method to the campo de cartagena multi layer aquifer system in southeastern spain a large amount of hydrogeochemical data was available but only a limited fraction of the sampled tubewells included a reliable determination of the borehole design and consequently of the aquifer layer being exploited added difficulty was the very similar compositions of water samples extracted from different aquifer layers moreover not all groundwater samples included the same geochemical variables despite of the difficulty of such a background the random forest classification reached accuracies over 90 these results were much better than the linear discriminant analysis lda and decision trees cart supervised classification methods from a total of 1549 samples 805 proceeded from one unique identified aquifer 409 proceeded from a possible blend of waters from several aquifers and 335 were of unknown origin only 468 of the 805 unique aquifer samples included all the chemical variables needed to calibrate and validate the models finally 107 of the groundwater samples of unknown origin could be classified most unclassified samples did not feature a complete dataset the uncertainty on the identification of training samples was taken in account to enhance the model most of the samples that could not be identified had an incomplete dataset

recurrent hierarchical patterns and the fractal distribution of fossil localities understanding the spatial structure of fossil localities is critical for interpreting earth system processes based on their geographic distribution coordinates of marine and terrestrial sites in the conterminous united states for 17 time bins were analyzed using point pattern statistics lacunarity analysis shows that the spatial distributions of sites are fractal for almost every studied interval indicating that clumping of localities occurs at multiple scales random hierarchical multiplicative processes provide a theoretical null model for the distribution of collecting sites consistent with their occurrence being a complex product of numerous biological geological and anthropogenic processes acting at many spatial and temporal scales mechanistic models for the formation preservation and exposure of fossil localities and other geologic entities can be tested using point pattern and related spatial statistics

influence of granite mineralogy rainfall vegetation and relief on stream water chemistry vosges mountains north eastern france abstract the influence of rock mineralogy climate vegetation and relief on stream water composition and export as a result of weathering is a major scientific concern both at the local scale because of the link between stream chemistry and biodiversity and at the global scale in relation to global climate changes environmental factors influencing stream chemistry at baseflow were studied for 95 forested catchments located in the granite part of the vosges mountains ne france mean annual rainfall slope altitude catchment area forest cover and granite composition were attributed to each catchment using a geographic information system gis and spatially distributed databases these variables were then used to model stream water concentrations in so4 ca mg k na si anc acid neutralizing capacity and ph via linear regression analyses sulfate concentration is mainly negatively correlated to the mean altitude of the catchment silica and na concentrations are strongly correlated and negatively related to the mean annual rainfall and not to altitude ph is positively related to the sum of ca mg and k but not to so4 for any type of granite ca mg and ph are generally negatively related to the mean annual rainfall and positively related to the catchment area calcium is best explained by the rock content in hornblende mg by the rock contents of biotite and hornblende k by the content in k feldspar nevertheless models differ for each granite type in relation to the availability of weatherable minerals and probably to water pathways this study shows the interest of spatial analysis methods for understanding stream water concentrations at the mountain range scale in combination with local process studies and modelling at the catchment scale

use of regression based models to map sensitivity of aquatic resources to atmospheric deposition in yosemite national park usa 1 an abundance of exposed bedrock sparse soil and vegetation and fast hydrologic flushing rates make aquatic ecosystems in yosemite national park susceptible to nutrient enrichment and episodic acidification due to atmospheric deposition of nitrogen n and sulfur s in this study multiple linear regression mlr models were created to estimate fall season nitrate and acid neutralizing capacity anc in surface water in yosemite wilderness input data included estimated winter n deposition fall season surface water chemistry measurements at 52 sites and basin characteristics derived from geographic information system layers of topography geology and vegetation the mlr models accounted for 84 and 70 of the variance in surface water nitrate and anc respectively explanatory variables and the sign of their coefficients for nitrate included elevation positive and the abundance of neoglacial and talus deposits positive unvegetated terrain positive alluvium negative and riparian negative areas in the basins explanatory variables for anc included basin area positive and the abundance of metamorphic rocks positive unvegetated terrain negative water negative and winter n deposition negative in the basins the mlr equations were applied to 1407 stream reaches delineated in the national hydrography data set for yosemite and maps of predicted surface water nitrate and anc concentrations were created predicted surface water nitrate concentrations were highest in small high elevation cirques and concentrations declined downstream predicted anc concentrations showed the opposite pattern except in high elevation areas underlain by metamorphic rocks along the sierran crest which had relatively high predicted anc 200 eq l 1 maps were created to show where basin characteristics predispose aquatic resources to nutrient enrichment and acidification effects from n and s deposition the maps can be used to help guide development of water quality programs designed to monitor and protect natural resources in national parks

automated upscaling of river networks for macroscale hydrological modeling 1 we developed a hierarchical dominant river tracing drt algorithm for automated extraction and spatial upscaling of basin flow directions and river networks using fine scale hydrography inputs e g flow direction river networks and flow accumulation in contrast with previous upscaling methods the drt algorithm utilizes information on global and local drainage patterns from baseline fine scale hydrography to determine upscaled flow directions and other critical variables including upscaled basin area basin shape and river lengths the drt algorithm preserves the original baseline hierarchical drainage structure by tracing each entire flow path from headwater to river mouth at fine scale while prioritizing successively higher order basins and rivers for tracing we applied the algorithm to produce a series of global hydrography data sets from 1 16 to 2 spatial scales in two geographic projections wgs84 and lambert azimuthal equal area the drt results were evaluated against other alternative upscaling methods and hydrography data sets for continental u s and global domains these results show favorable drt upscaling performance in preserving baseline fine scale river network information including 1 improved automated extraction of flow directions and river networks at any spatial scale without the need for manual correction 2 consistency of river network basin shape basin area river length and basin internal drainage structure between upscaled and baseline fine scale hydrography and 3 performance largely independent of spatial scale geographic region and projection the results of this study include an initial set of drt upscaled global hydrography maps derived from hydro1k baseline fine scale hydrography inputs these digital data are available online for public access at ftp ftp ntsg umt edu pub data drt

sources of weathering derived solutes in two granitic catchments with contrasting forest growth chemical weathering is one of the controlling factors for landform evolution here we present deductions about the location and rate of chemical weathering within catchments based on chemical observations of soil water groundwater springs and streams in two granitic catchments with contrasting forest growth conditions forested and non vegetated and soil development the two catchments are located in the tanakami mountains of central japan and share the same climate in both catchments sio2 and na are the dominant weathering derived solutes in the first order stream using hydrological evidence the contribution to the sio2 and na fluxes from soil and bedrock were partitioned despite the difference in mean soil depth net fluxes of sio2 and na from the soil profile do not differ much between the two catchments suggesting low levels of easily weatherable minerals in the forest soil net sio2 and na fluxes from bedrock are about three times greater in the forested catchment than in the bare catchment and these differences contribute largely to the difference in net fluxes from the catchments net fluxes of sio2 and na from the forested catchment are about twice those from the bare catchment part of this increase may be related to the greater proton production in forested catchment consequently about 60 to 70 of the net sio2 and na fluxes from the non vegetated catchment and 70 to 90 from the forested catchment are derived from bedrock suggesting that the contribution of bedrock to the export of these weathering products increased with forest growth and soil formation copyright 2004 john wiley sons ltd

facies analysis and palaeoenvironmental interpretation of the late oligocene attard member lower coralline limestone formation malta the oligocene represents a key interval during which coralline algae became dominant on carbonate ramps and luxuriant coral reefs emerged on a global scale so far few studies have considered the impact that these early reefs had on ramp development consequently this study aimed at presenting a high resolution analysis of the attard member of the lower coralline limestone formation late oligocene malta in order to decipher the internal and external factors controlling the architecture of a typical late oligocene platform excellent exposures of the lower coralline limestone formation occurring along continuous outcrops adjacent to the victoria lines fault reveal in detail the three dimensional distribution of the reef associated facies a total of four sedimentary facies have been recognized and are grouped into two depositional environments that correspond to the inner and middle carbonate ramp the inner ramp was characterized by a very high energy shallow water setting influenced by tide and wave processes this setting passed downslope into an inner ramp depositional environment which was colonized by seagrass and interfingered with adjacent areas containing scattered corals the middle ramp lithofacies were deposited in the oligophotic zone the sediments being generated from combined in situ production and sediments swept from the shallower inner ramp by currents compositional characteristics and facies distributions of the attard ramp are more similar to the miocene ramps than to those of the eocene an important factor controlling this similarity may be the expansion of the seagrass colonization within the euphotic zone this expansion may have commenced in the late oligocene and was associated with a concomitant reduction in the aerial extent of the larger benthonic foraminifera facies stacking pattern analysis shows that the depositional units parasequences at the study section are arranged into transgressive regressive facies cycles this cyclicity is superimposed on the overall regressive phase recorded by the attard succession furthermore a minor highstand correlated with the ru4 ch1 sequence and subsequent minor lowstand ch2 sequence have been recognized the biota assemblages of the attard member suggest that carbonate sedimentation took place in subtropical waters and oligotrophic to slightly mesotrophic conditions the apparent low capacity of corals to form wave resistant reef structures is considered to have been a significant factor affecting substrate stability at this time the resulting lack of resistant mid ramp reef frameworks left this zone exposed to wave and storm activity thereby encouraging the widespread development of coralline algal associations dominated by rhodoliths

carbonate lithofacies as paleolatitude indicators problems and limitations abstract detailed study of miocene carbonates in the mediterranean region and their analogues on modern carbonate shelves in the mediterranean sea brazil and other areas reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef chlorozoan lithofacies a chloralgal lithofacies similar to the chlorozoan but without hermatypic corals b rhodalgal lithofacies characterized by abundant encrusting coralline algae and c molechfor lithofacies consisting of benthic foraminifers molluscs echinoids bryozoans and barnacles these carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature although other factors e g water circulation river discharge suspended sediment controlling water salinity and temperature nutrient content light penetration etc also play important roles chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end members the chlorozoan lithofacies which characterizes shallow tropical shelves and the molechfor lithofacies which characterizes colder and or deeper areas detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks

geological and land use control on δ34s and δ18o of river dissolved sulfate the moselle river basin france abstract the upper part of the moselle river basin northeastern france shows contrasting lithology and topography granitic formations upstream in the vosges mountains and carbonate platform downstream on the lorraine plateau we measured concentration and isotopic composition of dissolved so 4 in the moselle river and its main tributaries in order to identify the sources of sulfate rainwater lichens s fertilizers and natural gypsum were also analyzed as potential sulfate sources along the moselle river dissolved so 4 concentrations and s o isotopes display relationships which suggest two major sources of sulfates 1 a low concentration and low delta values 34 s of 6 9 and 18 o of 6 9 component upstream and 2 a high concentration and high delta values 34 s of up to 17 and 18 o of up to 13 these are likely 1 atmospheric s input with some retention time in forest soils as carbon bonded sulfur and 2 sulfates from the dissolution of evaporites from the muschelkalk and keuper formations of the lorraine plateau the madon tributary drains a basin largely used for agriculture 35 of the land surface and formed by carbonate and evaporite rocks deviation from the general 34 s 18 o trend for dissolved so 4 was found to be seasonal and related to land use and agricultural practices and are interpreted as a significant input of sulfates from fertilizers used in the area isotope mixing models indicate that between 1 1 10 7 and 1 9 10 7 mol of anthropogenic so 4 are annually exported through the madon river these values compared well with the expected annual fertilizer spreading rates in the area and demonstrate the powerful source tracing done by using s isotopes in dissolved sulfates this implies that combining isotopic fingerprinting approach to knowledge of the catchment i e land use agricultural practices river flow would provide key information for decision makers in the context of river basin management

ordered hierarchy versus scale invariance in sequence stratigraphy sequence stratigraphy has been applied in a wide range of scales of time and space from decimeter thick layers formed within hours to kilometer thick basin fills formed during hundreds of millions of years the traditional approach to practice sequence stratigraphy in this wide range of scales is to subdivide the sediment piles into an ordered hierarchy of sequence cycles of different duration and different architecture an alternative are scale invariant models with fractal characteristics published data confirm two predictions of the ordered hierarchy model sequences of very short duration 200 106 years are symmetrical transgressive regressive cycles however the sequence record in the range of 1 104 200 106 years the principal domain of sequence stratigraphy shows a rather irregular succession of sequences with variable symmetry and bounded by flooding surfaces or exposure surfaces for these time scales scale invariant models are a good first approximation particularly because the evidence for scale invariance and randomness in the stratigraphic record is strong frequency spectra of sea level change as well as rates of sedimentation and rates of accommodation change plotted against length of observation span show basic trends indistinguishable from random walk these trends combined with scale invariant sequence models may be the most efficient tools for across the board predictions on sequences and for locating islands of order in the sequence record

quantitative biostratigraphy achieving finer resolution in global correlation abstract the fossil record preserves a wide range of events that might be used to build timescales and correlate strata from place to place the events include the originations and extinctions of species the occurrence of distinctive faunal assemblages magnetic field reversals changes in ocean chemistry and volcanic ash falls the fundamental task is to determine the global sequence of all these events modern computer algorithms can build high resolution timescales by sequencing and calibrating thousands of such events from hundreds of localities each successful sequencing algorithm can be understood in terms of a simple two dimensional visual device graphic correlation permutable sequences permutable matrices and slotting devices are each suited to a different data problem such as contradictory evidence of sequence a lack of information about sequence or uncertain correspondence of events algorithms based upon permutable sequences and evolutionary programming heuristics have the flexibili

solute flux and mineral mass balance approaches to the quantification of plant effects on silicate weathering the weathering of calcium and magnesium silicate minerals on the continents has exerted a major control on atmospheric co 2 over geologic time and vascular plants may have played an important role in this process we have examined the role of plants in weathering in western iceland by two methods a solute flux approach and a mineral mass balance approach using the chemistry of weathering products and of waters draining adjacent areas of basaltic rocks that are either barren with a partial cover of mosses and lichens or populated by trees the study area was chosen to maximize vegetational differences and to minimize differences in microclimate slope and lithology while avoiding hydrothermal waters and anthropogenic acid rain solute flux results including data on cation uptake by growing trees indicate that the rate of weathering release of ca and mg to streams is about 4 times higher in vegetated areas than in bare areas mineral mass balance results show that trees increase plagioclase weathering by a factor of 2 and pyroxene weathering by a factor of 10 possibly as a result of preferential weathering of pyroxene by the vegetation biomass normalized weathering fluxes from the birch trees are greater than those from the conifers suggesting that angiosperms enhance weathering to a greater degree than gymnosperms results indicate a perpetual short term sink for atmospheric c as tree induced leakage of hco super 3 from the forest ecosystem to rivers and streams in addition to the finite sink of c in forest biomass the findings also suggest a major role for vascular plants as they invaded upland portions of the continents between 410 and 360 my ago in accelerating weathering and thereby lowering atmospheric co 2

macrostratigraphy of north america abstract the geological record is a three dimensional mosaic of gap bound rock bodies that at any given scale of temporal resolution were emplaced more or less continuously at any geographic location the irregular alternation of processes responsible for the formation and destruction of rock bodies results in the preservation of hiatus bound rock packages that have a distinct time of first occurrence base or oldest portion a time of last occurrence top or youngest portion and a suite of defining characters e g lithologies thickness fossils etc many important aspects of the geologic record can be quantified by compiling the stratigraphic ranges of such gap bound rock packages these include the quantity and spatial and temporal distribution of preserved rock rates of rock formation sequence stratigraphic architecture and area weighted rates of expansion and contraction erosional truncation of rock emplacement settings this approach to characterizing the rock record is scalable per

the ties linking rock and fossil records and why they are important for palaeobiodiversity studies a correlation exists between the quality of the rock record and the diversity of fossils recorded from that rock record but what drives that correlation and how consistent that correlation is across different environments remain to be determined palaeontologists wishing to investigate past diversity patterns need to first address issues of geological bias in their data the fossil record provides the only empirical evidence of how life has diversified over geological time but it needs to be interpreted with caution for many years the history of diversity was estimated simply by summing up the numbers of taxa species genera families palaeontologists have recorded from successive geological time intervals or extrapolated from their first and last occurrences in the geological record this time series approach led to what is now a classic view of how diversity has changed over time sepkoski et al 1981 benton 1995 sepkoski 1997 such counts take the fossil record at face value or assume that biases or errors are randomly distributed in such a way that the overall effect is negligible we now realize that this is only a first crude approximation that may be subject to a number of strong biases that arise because of the nature of the sedimentary rock record time series analysis requires that sampling be carefully controlled for best results ideally data should be collected so that sampling from each time interval is uniform or at least sampled fairly using the shareholder quorum subsampling method alroy 2010 otherwise apparent changes in diversity may arise for spurious reasons for example because a a time intervals being sampled are of variable duration longer time intervals 1 4 more recorded diversity or b a time interval has been more intensively sampled more localities specimens habitats formations sampled 1 4 more recorded diversity while for a biological survey it is easy to plan a sampling strategy that will give approximately equal effort and coverage for observations palaeontologists are faced with a much more difficult task firstly the time bins they work with are irregular and highly variable in their duration for example the durations of one of the most widely used time scales has intervals spanning two orders of magnitude gradstein et al 2004 secondly and much more critically palaeontologists are collecting from an already incomplete and highly biased set of rocks which in turn skew the range of taxa and habitats that can be sampled zuschin et al 2011 bluntly put we cannot sample what is not preserved in the rock record although phylogenetic and molecular approaches can attempt to compensate pol norrell 2006 bininda emonds et al 2007 wills 2007 o connor et al 2011 so while it may be possible to standardize for sampling effort from the rock record that remains those rocks might provide a far from uniform sample of the sediments and palaeoenvironments that were originally present palaeontologists cannot therefore assume uniform sampling of the fossil record and must try to assess how the rock record they have to work with has affected their ability to sample evenly and then develop methods that compensate appropriately for this variation in recent years therefore palaeobiodiversity studies have become more probabilistic in their approach concerned with establishing confidence limits around estimates that try to correct for uneven sampling alroy et al 2001 2008 and testing empirical patterns against model predictions foote 2001 smith mcgowan 2007 mcgowan smith 2008 if we are to improve our estimates of biodiversity over time then sampling parameters need to be better quantified and we need to better understand the complex interrelationship between rock and fossil records this is no simple task and requires a more systematic approach to recording culture as well as better documentation of the variables benton et al 2011 figure 1 summarizes the problem as we see it palaeontologists estimate past diversity from remains preserved in the rock record as with any from mcgowan a j smith a b eds comparing the geological and fossil records implications for biodiversity studies geological society london special publications 358 1 7 doi 10 1144 sp358 1 0305 8719 11 15 00 the geological society of london 2011 biological survey variation of sampling effort of the surviving rock record needs to be factored out but this rock record has already passed through a geological filter that has altered and distorted not only the rock area that survives to sample but also the proportions of facies and the preservational quality of its fossil record were this geological filter to remain approximately constant over time there would be little problem of interpreting the biological signal however it is far from uniform with amounts of rock to sample proportions of facies represented by those rocks and preservation potential all varying from one time interval to the next to interpret observed changes in sampled biodiversity estimates correctly we must therefore first understand the role of the geological filter variability of the rock and fossil records

discussion facies analysis and palaeoenvironmental interpretation of the late oligocene attard member lower coralline limestone formation malta by brandano et al 2009 sedimentology 56 1138 1158 peter a gattdepartment of earth sciences university of durham south road durham dh1 3le uk e mail p a gatt durham ac uk introductionthis discussion of the paper by brandano et al 2009 evaluates the 40 km wide and 60 m in the maltese islands gattet al 2009 andnot10to15 masindicatedintheir g 1c in their g 2a the authors present logs of theirmeasured sections of the attard member how ever the lowermost 3ae5 m thick coral bioclasticwackestone oatstone facies in their section ii described as having a matrix with a high percent age of micrite 40 actually forms the top part ofthe maghlaq member which was deposited in aprotected lagoonal environment 20 m thick maghlaq member that cropsout at the mosta quarry grid reference 489 757 located ca 1ae5 km to the north east of the siteshown in their g 2 the maghlaq member isdominated by miliolids in a micritic matrix whereas micrite in the overlying attard memberis only abundant in intermittent 1 m thick bedsrecorded by brandano et al 2009 in some oftheir measured sections the topmost section iiiand ca 3 m below the top of section iv parasequences in the logged sections by brand ano et al 2009 are described as basal trans gressive porcelaneous foraminiferal grainstonespassing upward to the rhodolith oatstone rud stone facies i e a deepening upward sequence however the ca 3 m thick parasequence sets seenin the nearby mosta quarry and other localitiesare distinctly shallowing upward these succes sive parasequences begin with subtidal rhodolithand coral facies and terminate with a 20 cmthick laminar micritic bed of microbial origin thatwas deposited in a peritidal environment theparasequences are capped by a ooding surfacewhich consists of a thin bed of sub tidal micritethat thickens towards the east which wasburrowed intensely by the bivalve kuphus in their g 2d brandano et al 2009 make anattempt at dating their sections using biostratig raphy they correlate their logged sections in g 2 with the large benthic foraminiferal bio zones of cahuzac poignant 1997 and with theglobal sea level curve of haq et al 1987 andidentify the sequence boundary ch2 of hardenbolet al 1998 this sequence boundary is markedin their g 2d but not indicated in their logs ofmeasured sections in g 2a and consequently is dismissed as being of minor importance how ever a sequence boundary extending to the mostasedimentology 2010 57 1152 1154

predicting natural base flow stream water chemistry in the western united states 1 robust predictions of stream solute concentrations expected under natural reference conditions would help establish more realistic water quality standards and improve stream ecological assessments models predicting solute concentrations from environmental factors would also help identify the relative importance of different factors that influence water chemistry although data are available describing the major factors controlling water chemistry i e geology climate atmospheric deposition soils vegetation topography geologic maps do not adequately convey how rocks vary in their chemical and physical properties we addressed this issue by associating rock chemical and physical properties with geological map units to produce continuous maps of percentages of cao mgo s uniaxial compressive strength and hydraulic conductivity for western united states lithologies we used catchment summaries of these geologic properties and other environmental factors to develop multiple linear regression lr and random forest rf models to predict base flow electrical conductivity ec acid neutralization capacity anc ca mg and so4 models were derived from observations at 1414 reference quality streams rf models were superior to lr models explaining 71 of the variance in ec 61 in anc 92 in ca 58 in mg and 74 in so4 when assessed with independent observations the root mean square error for predictions on validation sites were all temperature precipitation soil atmospheric deposition vegetation amount of rock water contact topography

using remote sensing and a geographic information system to quantify rock exposure area in england and wales implications for paleodiversity studies rock outcrop area and number of sedimentary formations have been widely used as sampling proxies in paleodiversity studies and have often been found to correlate with apparent paleodiversity however rock exposure area is a better proxy for the amount of sedimentary rock available for study than the widely used measures of outcrop area i e map area or number of formations with the use of remote sensing and a geographic information system gis it is possible to quantify rock exposure area accurately on a regional scale rock exposure area does not correlate well with either outcrop area or number of sedimentary formations and the proportion of rock exposed in different areas can vary considerably with proximity to the coast bedrock age lithology land use and elevation therefore this suggests that the correlation of paleodiversity and rock volume estimates is best explained by a common cause hypothesis rather than a geologic sampling bias hypothesis gis methods offer an efficient and accurate method of quantifying regional sedimentary rock exposure and may provide a helpful approach to assessing rock record bias on patterns in the fossil record

covariation in macrostratigraphic and macroevolutionary patterns in the marine record of north america students of earth history have long recog nized the correlation between the quantity of preserved sedimentary rock and the diversity of life recorded as fossils but paleontologists have yet to determine whether this pattern refl ects a causal relationship or a unidirec tional sampling bias in fossil data imposed by preserved rock quantity distinguishing between these two alternatives has been com plicated by the fact that many of the basic patterns of paleontologic and lithologic co variation have yet to be quantifi ed rigorously here we present the fi rst analyses of the co variation between the macrostratigraphic and macroevolutionary histories of north america based on geographically and tem porally explicit co occurrences of rocks and fossils the analyses use independent quan titative summaries of the stratigraphic and fossil records by integrating the paleobiology database paleodb and macrostrat a mac rostratigraphy database for north america which allows a more direct comparison of the stratigraphic and biological histories of the continent than has heretofore been possible within the macrostrat database the rock re cord is divided into discrete packages of sedi ment that are bound by hiatuses resolvable at the stage level using per interval per pack age rates of sediment package initiation and truncation and genus fi rst and last appear ances herein regional origination and extinc tion we fia substantially stronger positive correlation between sediments and biology for extinction like parameters than we do for origination like parameters four of the largest coincident pulses of regional extinc tion and sediment truncation occur during the widely recognized end ordovician late permian end triassic and end cretaceous mass extinction intervals a further compari son of the global ranges of north american genera to north american macrostratigra phy indicates that the regional and global extinction of genera are more likely to oc cur in the same stage than are global and regional originations together these results suggest that our general understanding of biodiversity dynamics from the fossil record may not be strongly biased by the preserva tion of sediments and leaves open the pos sibility that certain large perturbations to the earth system are responsible for major changes of state in both the sedimentary and biological systems

measured rates of sedimentation what exactly are we estimating and why abstract data on rates of sedimentation are essential in studies of sedimentation systems these data are obtained in three main study contexts 1 the study of sedimentation systems that are active today 2 the source to sink study of sedimentation systems that no longer are active and 3 the study of the relationship between accumulation rate and measurement timespan the aim of this paper is to question the meaning of measured rates of sedimentation and their interpretability particularly in these three contexts individual measurements of rate of sedimentation must always be interpreted with care firstly there are different definitions for instance with different statistical support or measurement dimension values that are defined differently cannot be compared directly secondly appropriate sampling schemes must have been used for the measurement this minimises sampling bias thirdly the inherent limitations of the data sources must be taken into account rates of sedimentation can usually be measured successfully in active sedimentation systems the same is not true for systems that are no longer active these can only be studied using the stratigraphic successions left behind rates of erosion can never be measured successfully in stratigraphic successions rate of sedimentation is essentially a ratio an amount of sedimentation per length of time therefore the obvious strategy to use in determining it is first to measure the amount and the time independently then to combine the values the amount can be measured in terms of thickness or volume or mass per unit area the duration of the time interval can be preset using quasi continuous measurement techniques or site reoccupation or it can be identified from interval specific sedimentary structures or it can be measured using dated horizons an alternative strategy is to use a surrogate measurement variable rates of erosion in ancient systems are usually measured in this way using cosmogenic radionuclide concentrations these two strategies are reviewed in this paper sets of measurements made in systems that are active today can certainly be used to estimate the rate of sedimentation for the system as a whole this estimation is best carried out using geostatistical estimation techniques the alternative is simply to average the measured rate values this latter approach should not be used however because the mean sedimentation rate in a system gives information only about the net sediment movement at the system boundaries it says nothing at all about how the system is operating or about its spatial and temporal variability measurements of rates of sedimentation made for source to sink studies are necessarily made in stratigraphic successions the measurements are used to estimate quantities in the sediment mass budget equation the amount of decumulation is inherently incapable of being measured in stratigraphic successions therefore there are always unknowns in the mass budget equation whenever the lithic surface at the start of the time interval considered cannot be recognised everywhere this means that the mass budget equation is applicable in practice only when all the systems involved in the study are entirely non erosional for that entire time interval a highly unrealistic situation the consistently inverse relationship documented between accumulation rates and measurement timespan is taken usually to indicate that this relationship is substantially scale invariant this in turn is often taken as indicating that the stratigraphic record is fractal in nature there are nevertheless grounds for doubt all of which relate to the ways that the data are collected and used for estimation the relationship is in fact the natural mathematical result of last in first out lifo operation and is produced in any type of system in which addition and removal processes both operate it says nothing particular about sedimentation processes the future analysis of accumulation rate data collected from stratigraphic successions will sensibly be framed in the context of estimating the parameters of a lifo model

stochastic and deterministic controls on stratigraphic completeness and fidelity compilations of sedimentation rates determined across a large range of time spans and different sedimentary environments attest to the discontinuous nature of sedimentation and support the reasoning that hiatuses pervade sedimentary successions at multiple spatial and temporal scales the relationship between sedimentation rate and time span of observation also emphasises how stratigraphic completeness is a time span dependent concept the scaling of stratigraphic completeness with time span alludes to the likely stochastic and fractal nature of the stratigraphic record it also implies that the relationship between stratal thickness and time is inherently non linear and this has obvious implications for the way we should expect temporal processes to be recorded stratigraphically order within the stratigraphic record may arise from deterministic processes in stratigraphy most notably through astronomically influenced sedimentation intuitively a strongly ordered stratigraphic record due to the presence of cyclicity in sedimentation increases stratigraphic completeness at time spans equal to and longer than the time span of the cyclicity and minimises the non linearity between stratal thickness and time here geological data and simple modelling are used to support this supposition but these results also highlight how stochastic variability inherent in depositional processes may sensitise certain successions to missed cycles and incompleteness even in the presence of strong cyclicity this stochastic variability has the potential to mask evidence of astronomical forcing of sedimentation it is also shown how hiatuses affect the ability of a succession to faithfully record temporal processes and this is true regardless of whether hiatuses are deterministically controlled or random or indeed whether a succession is considered complete or not consequently stratigraphic completeness and stratigraphic fidelity are not synonymous terms

completeness of the fossil record and the validity of sampling proxies a case study from the triassic of england and wales many studies have highlighted correlations between palaeodiversity and sampling proxies these correlations have been interpreted as evidence for bias common cause or redundancy between signals here we compare a number of sampling proxies representing sedimentary rock volume rock accessibility and worker effort with palaeodiversity through the predominantly terrestrial triassic system in england and wales we find that proxies for sedimentary rock volume and accessibility do not correlate with palaeodiversity until the removal of facies related preservational and palaeoecological factors this indicates that a weak sampling signal may be present but the effects of changing palaeoenvironments are far more important at the regional scale significant correlations between worker effort and palaeodiversity are detected although this is likely to be a result of the preferential sampling of formations already known to be rich in fossils the fact that there is little evidence for sedimentary rock bias in the fossil record of the triassic of england and wales suggests that either 1 sampling bias is not a major source of error at the regional scale or 2 sampling proxies are inadequate representations of geological and human sampling bias supplementary material correlation test results and raw time series data from the study are available at www geolsoc org uk sup18567

the dissolution kinetics of major sedimentary carbonate minerals abstract among the most important set of chemical reactions occurring under near earth surface conditions are those involved in the dissolution of sedimentary carbonate minerals these minerals comprise about 20 of phanerozoic sedimentary rocks calcite and to a significantly lesser extent dolomite are the major carbonate minerals in sedimentary rocks in modern sediments aragonite and high magnesian calcites dominate in shallow water environments however calcite is by far the most abundant carbonate mineral in deep sea sediments an understanding of the factors that control their dissolution rates is important for modeling of geochemical cycles and the impact of fossil fuel co 2 on climate diagenesis of sediments and sedimentary rocks it also has practical application for areas such as the behavior of carbonates in petroleum and natural gas reservoirs and the preservation of buildings and monuments constructed from limestone and marble in this paper we summarize important findings from the hundreds of papers constituting the large literature on this topic that has steadily evolved over the last half century our primary focus is the chemical kinetics controlling the rates of reaction between sedimentary carbonate minerals and solutions we will not attempt to address the many applications of these results to such topics as mass transport of carbonate components in the subsurface or the accumulation of calcium carbonate in deep sea sediments such complex topics are clearly worthy of review papers on their own merits calcite has been by far the most studied mineral over a wide range of conditions and solution compositions in recent years there has been a substantial shift in emphasis from measuring changes in solution composition to determine batch reaction rates to the direct observation of processes occurring on mineral surfaces using techniques such as atomic force microscopy afm however there remain major challenges in integrating these two very different approaches a general theory of surface dissolution mechanisms currently lacking although see lasaga and luttge science 291 2001 2400 is required to satisfactorily relate observations of mineral surfaces and the concentration of dissolved components studies of aragonite high magnesian calcites magnesite and dolomite dissolution kinetics are much more limited in number and scope than those for calcite and provide at best a rather rudimentary understanding of how these minerals are likely to behave in natural systems although the influences of a limited number of reaction inhibitors have been studied probably the greatest weakness in application of experimental results to natural systems is understanding the often profound influences of foreign ions and organic matter on the near equilibrium dissolution kinetics of carbonate minerals

near channel versus watershed controls on sediment rating curves predicting riverine suspended sediment flux is a fundamental problem in geomorphology with important implications for water quality land and water resource management and aquatic ecosystem health to advance understanding we evaluated environmental and landscape factors that influence sediment rating curves srcs we generated srcs with recent total suspended solids tsss and discharge data from 45 gages on 36 rivers throughout the state of minnesota usa watersheds range from 32 to 14 600 km2 and represent distinct settings regarding topography land cover and geologic history rivers exhibited three distinct src shapes simple power functions threshold power functions and peaked or negative slope functions we computed src exponents and coefficients describing the steepness of the relation and the tss concentration at median flows respectively in addition to quantifying watershed topography climate hydrology geology soil type and land cover we used lidar topography to characterize the near channel environment upstream of gages we used random forest models to analyze relations between src parameters and attributes of the watershed and the near channel environment the models correctly classify 78 of src shapes and explain 37 60 of variance in src parameters we find that src steepness exponent is strongly related to near channel morphological characteristics including near channel relief channel gradient and presence of lakes along the local channel network but not to land use in contrast land use influences tss concentrations at moderate and low flow these findings suggest that the near channel environment controls changes in tss as flows increase whereas land use drives median and low flow tss conditions

exceptionally preserved fossil assemblages through geologic time and space abstract geologic deposits containing fossils with remains of non biomineralized tissues i e konservat lagerstatten provide key insights into ancient organisms and ecosystems such deposits are not evenly distributed through geologic time or space suggesting that global phenomena play a key role in exceptional fossil preservation nonetheless establishing the influence of global phenomena requires documenting temporal and spatial trends in occurrences of exceptionally preserved fossil assemblages to this end we compiled and analyzed a dataset of 694 globally distributed exceptional fossil assemblages spanning the history of complex eukaryotic life 610 to 3 ma our analyses demonstrate that assemblages with similar ages and depositional settings commonly occur in clusters each signifying an ancient geographic region up to hundreds of kilometers in scale which repeatedly developed conditions conducive to soft tissue preservation using a novel hierarchical clustering approach we show that these clusters decrease in number and shift from open marine to transitional and non marine settings across the cambrian ordovician interval conditions conducive to exceptional preservation declined worldwide during the early paleozoic in response to transformations of near surface environments that promoted degradation of tissues and curbed authigenic mineralization potential we propose a holistic explanation relating these environmental transitions to ocean oxygenation and bioturbation which affected virtually all taphonomic pathways in addition to changes in seawater chemistry that disproportionately affected processes of soft tissue conservation after these transitions exceptional preservation rarely occurred in open marine settings excepting times of widespread oceanic anoxia when low oxygen levels set the stage with these patterns non marine cluster count is correlated with non marine rock quantity and generally decreases with age this result suggests that geologic processes which progressively destroy terrestrial rocks over time limit sampling of non marine deposits on a global scale future efforts should aim to assess the impacts of such phenomena on evolutionary and ecological patterns in the fossil record