clay mineral evolution changes in the mechanisms of formation and global distribution of phyllosilicate clay minerals through 4 567 ga of planetary evolution in our solar system reflect evolving tectonic geochemical and biological processes clay minerals were absent prior to planetesimal formation 4 6 billion years ago but today are abundant in all near surface earth environments new clay mineral species and modes of clay mineral paragenesis occurred as a consequence of major events in earth s evolution notably the formation of a mafic crust and oceans the emergence of granite rooted continents the initiation of plate tectonics and subduction the great oxidation event and the rise of the terrestrial biosphere the changing character of clay minerals through time is thus an important part of earth s mineralogical history and exemplifies the principles of mineral evolution

effect of the frasnian famennian extinction event on the stromatoporoids although paleozoic stromatoporoids were drastically reduced in abundance and diversity by the frasnian famennian f f mass extinction event at least 20 genera mostly labechiids and clathrodictyids are known from latest devonian rocks some typical frasnian genera survived the f f crisis to die out in early famennian time and others took part in the strunian resurgence of the stromatoporoids small stromatoporoid reefs are known from famennian and strunian rocks the history of the group suggests a large rapid but progressive environmental change at the f f boundary and the survival of genera better adapted to cool water

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

black shale deposition and faunal overturn in the devonian appalachian basin clastic starvation seasonal water column mixing and efficient biolimiting nutrient recycling integrated geochemical data suggest that black shale deposition in the devonian geneseo formation of western new york was initiated by the coincidence of siliciclastic starvation and the intensification of seasonal water column stratification and mixing once established however black shale deposition was maintained through efficient recycling of biolimiting nutrients which enhanced primary productivity recycling efficiency was achieved through a positive feedback loop of oscillating benthic redox conditions that enhanced n and p regeneration from sediments sustained high primary productivity by returning nutrients to the photic zone during mixing and ensured a downward flux of organic matter that drove or enhanced the episodic development of benthic anoxia during stratification this feedback was ultimately disrupted by rising siliciclastic influx which diluted organic matter and restored benthic redox stability the abrupt overturn of diverse long standing appalachian basin marine communities may have been the result of trophic resource destabilization during geneseo deposition

statistical analysis of mineral diversity and distribution earth s mineralogy is unique abstract earth s mineralogical diversity arises from both deterministic processes and frozen accidents we apply statistical methods and comprehensive mineralogical databases to investigate chance versus necessity in mineral diversity distribution relationships hundreds of mineral species including most common rock forming minerals distinguish an earth like planet from other terrestrial bodies however most of earth s 5000 mineral species are rare known from only a few localities we demonstrate that in spite of deterministic physical chemical and biological factors that control most of our planet s mineral diversity earth s mineralogy is unique in the cosmos

eutrophication by decoupling of the marine biogeochemical cycles of c n and p a mechanism for the late devonian mass extinction the late devonian mass extinction was unusually protracted and ecologically selective with preferential diversity losses among reefbuilding organisms and tropical shallow water faunas in general we have investigated the link between the extinction s unique characteristics and changes in biogeochemical cycling through analyses of the 13 c and c n p atomic ratios of organic matter buried across the kellwasser horizons in western new york state each horizon is characterized by 1 a long term 4 5 excursion in 13 c 3 of which occurs within the horizon and 2 a dramatic increase in the burial ratios of c n p from values of 100 15 1 to an average of 5000 170 1 on the basis of these results we propose that 1 increased efficiency of biolimiting nutrient recycling resulting from cyclic water column stratification and mixing promoted eutrophication during kellwasser deposition in new york and 2 the isotope excursions represent the composite effect of long term global organic c burial and local changes in photosynthetic c isotope fractionation related to nutrient availability this eutrophication model forges a mechanistic link between proposed late devonian climatic cooling and the selective demise of taxa likely to have been narrowly adapted to oligotrophic conditions

ammonoid diversity and disparity track episodes of chaotic carbon cycling during the early mesozoic episodes of mass extinction represent the largest events of biodiversity loss known in the geologic record and may provide tests of biodiversity ecosystem stability hypotheses here we present the first correlation between ammonoid diversity and disparity and ecosystem stability as represented by stable carbon isotopic records spanning the end permian through end triassic mass extinctions ammonoid generic richness from a single biogeographic realm shows that nearly all taxa disappeared coincident with major carbon isotopic shifts to lighter values the intervals following these two major mass extinctions were characterized by multiple positive negative couplets of chaotic carbon cycling and were composed of low richness ammonoid faunas characterized by higher proportions of passively floating non swimming morphotypes than before or after in contrast richness was highest during intervals of stable carbon isotope values we propose that these chaotic carbon episodes reflect the breakdown of functional redundancy in the ecosystem and that the post extinction carbon cycle did not stabilize until redundancy was restored

the late devonian frasnian famennian f f biotic crisis insights from δ13ccarb δ13corg and 87sr 86sr isotopic systematics a severe biotic crisis occurred during the late devonian frasnian famennian f f transition f367 myr here we present d 13 ccarb d 13 corg and 87 sr 86 sr isotopic systematics from identical samples of two sections across f f boundary in south china which directly demonstrate large and frequent climatic fluctuations 200 kyr from warming to cooling during the f f transition these climate fluctuations are interpreted to have been induced initially by increased volcanic outgassing and subsequent enhanced chemical weathering linked to the rapid expansion of vascular plants on land which would have increased riverine delivery to oceans and primary bioproductivity and subsequent burial of organic matter thereby resulting in climate cooling such large and frequent climatic fluctuations together with volcanic induced increases in nutrient e g biolimiting fe toxin sulfide and anoxic water supply and subsequent enhanced riverine fluxes and microbial bloom were likely responsible for the stepwise faunal demise of f f biotic crisis d 2005 elsevier b v all rights reserved

on the nature and significance of rarity in mineralogy more than half of the 5000 approved mineral species are known from five or fewer localities and thus are rare mineralogical rarity arises from different circumstances but all rare mineral species conform to one or more of four criteria 1 p t x range minerals that form only under highly restricted conditions in pressure temperature composition space 2 planetary constraints minerals that incorporate essential elements that are rare or that form at extreme conditions that seldom occur in earth s near surface environment 3 ephemeral phases minerals that rapidly break down under ambient conditions and 4 collection biases phases that are difficult to recognize because they lack crystal faces or are microscopic or minerals that arise in lithological contexts that are difficult to access minerals that conform to criterion 1 2 or 3 are inherently rare whereas those matching criterion 4 may be much more common than represented by reported occurrences rare minerals though playing minimal roles in earth s bulk properties and dynamics are nevertheless of significance for varied reasons uncommon minerals are key to understanding the diversity and disparity of earth s mineralogical environments for example in the prediction of as yet undescribed minerals novel minerals often point to extreme compositional regimes that can arise in earth s shallow crust and they are thus critical to understanding earth as a complex evolving system many rare minerals have unique crystal structures or reveal the crystal chemical plasticity of well known structures as dramatically illustrated by the minerals of boron uncommon minerals may have played essential roles in life s origins conversely many rare minerals arise only as a consequence whether direct or indirect of biological processes the distribution of rare minerals may thus be a robust biosignature while these phases individually and collectively exemplify the co evolution of the geosphere and biosphere finally mineralogical rarities as with novelty in other natural domains are inherently fascinating

global events of the late paleozoic early devonian to middle permian a review abstract the late paleozoic early devonian to middle permian was an interval of profound changes in earth surface systems reflected in dynamic interplay among the biosphere hydrosphere atmosphere and geosphere major events transpired including the colonization of landmasses by vascular plants the assembly of the supercontinent pangea two first order mass extinctions the frasnian famennian and devonian carboniferous boundary events and the most severe icehouse climate mode of the phanerozoic the late paleozoic ice age lpia the goals of the present review are 1 to summarize major global developments in climate oceanography and paleobiology during the late paleozoic 2 to examine the roles of land plant evolution global tectonics and large igneous province magmatism in driving these developments and 3 to serve as an introduction to the 23 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology indicating how they advance our knowledge of various scientific issues related to these developments

anoxic events in the late frasnian causes of the frasnian famennian faunal crisis carbon isotope data collected from five frasnian famennian boundary sections in central europe show two positive 13 c excursions in the late frasnian 367 ma both anomalies coincided with the deposition of the bituminous lower and upper kellwasser horizons the carbon isotope patterns indicate two phases of enhanced burial and subsequent recycling of organic carbon a maximum formation of warm saline waters on the subtropical to tropical epicontinental shelves during late frasnian transgressive episodes may have induced oceanic oxygen deficits variations in the c org burial rates may have resulted in changes in the co 2 concentrations in the oceans and in the atmosphere culminating in global climatic changes we propose that the repeated co occurrences of sea level fluctuations anoxic conditions and global climatic changes during the late frasnian would affect especially the subtropical to tropical shallow water communities and reef ecosystems which were severely affected during the frasnian famennian faunal crisis

fluctuations in the trophic resource continuum a factor in global diversity cycles the trophic resource continuum trc in euphotic zones of the world s oceans is the spectrum of conditions from the richest runoff and upwelling areas to the most nutrient deficient subtropical seas that spectral range has likely varied through geologic history as more efficient phytoplankton taxa evolved as oceanic circulation rates changed and in response to oceanic mixing events reduced rates of oceanic turnover should produce regionally intensified eutrophy and oligotrophy that is trc expansion because oceanic waters as a whole are relatively nutrient rich increased rates of oceanic turnover should prevent extremely eutrophic and extremely oligotrophic conditions from developing causing trc contraction global biotic diversities in the oceans are strongly influenced by communities in oligotrophic environments nutrient deficient waters are more stable and more transparent than richer waters permitting higher degrees of specialization sparse nutrient supplies necessitate smaller phytoplankton and longer more complex food chains preservation potential of oligotrophic biotas is also greater because calcareous taxa are more prevalent and because calcium carbonate is less apt to be bioeroded or dissolved fluctuations in the trc should profoundly affect diversity of habitats within the euphotic zone of the oceans the evolutionary response to a trc expansion diversification would occur in a geologic time frame of millions of years while evolutionary responses to a trc contraction including extinction could occur in a biological time frame of generations a simple model indicates that a reduction in the trophic resource continuum from expansion during a major marine transgression down to modern levels could result in loss of 40 of the euphotic habitats how fluctuations in the trc control diversity of euphotic habitats in the oceans provides an hypothesis by which to interpret global taxonomic diversity cycles as well as taxonomically selective extinctions changes in species dominance and some morphologic trends

frasnian famennian mass extinction and cold water oceans suturing of laurussia and africa elimination of easterly tropical currents and consequent equatorial diversion of cold and possibly dysaerobic waters are suggested as prime causes of the frasnian famennian late devonian extinction these are explained by using a new paleogeographic model evidence for stepdown extinctions that took place from givetian through frasnian time is taken particularly from atrypoid brachiopods one of the most abundant representatives of the global tropical shelly marine benthos during the middle and late devonian only 5 of 17 frasnian genera or subgenera of atrypoids are known to be present in late frasnian sediments and possibly only a single genus spinatrypa was present at the frasnian famennian boundary evidence for stepdown extinction from other invertebrate and vertebrate groups in general corroborates that provided by brachiopods

earth s missing minerals recent studies of mineral diversity and distribution lead to the prediction of 1563 mineral species on earth today that have yet to be described approximately one fourth of the 6394 estimated total mineralogical diversity the distribution of these missing minerals is not uniform with respect to their essential chemical elements of 15 geochemically diverse elements al b c cr cu mg na ni p s si ta te u and v we predict that approximately 25 of the minerals of al b c cr p si and ta remain to be described a percentage similar to that predicted for all minerals almost 35 of the minerals of na are predicted to be undiscovered a situation resulting from more than 50 of na minerals being white poorly crystallized and or water soluble and thus easily overlooked in contrast we predict that fewer than 20 of the minerals of cu mg ni s te u and v remain to be discovered in addition to the economic value of most of these elements their minerals tend to be brightly colored and or well crystallized and thus likely to draw attention and interest these disparities in percentages of undiscovered minerals reflect not only natural processes but also sociological factors in the search discovery and description of mineral species

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

paleomineralogy of the hadean eon a preliminary species list the hadean eon encompassing earth9s first 550 million years was a time of significant planetary evolution nevertheless prebiotic earth9s near surface environment may have held no more than approximately 420 different rock forming or accessory mineral species that were widely distributed and or volumetrically significant this relative hadean mineralogical parsimony is a consequence of the limited modes of mineral paragenesis prior to 4 ga compared to the last 3 0 billion years dominant hadean eon mineralizing processes include the evolution of a diverse suite of intrusive and extrusive igneous lithologies hydrothermal alteration over a wide temperature range notably serpentinization authigenesis in marine sediments diagenesis and low grade metamorphism in near surface environments and impact related processes including shock mineralization creation of marginal hydrothermal zones and excavation of deep metamorphosed terrains on the other hand the hadean eon may have been notably lacking in mineralization generated by plate tectonic processes such as subduction zone volcanism and associated fluid rock interactions which result in massive sulfide deposition convergent boundary orogenesis and consequent extensive granitoid rooted continental landmasses and the selection and concentration of incompatible elements in complex pegmatites with hundreds of accompanying minerals the dramatic mineralogical consequences of life are reflected in the absence of hadean biomineralization for example the lack of extensive carbonate deposits and the associated restricted development of skarn and cave minerals prior to 4 ga most importantly it was not until after the establishment via photosynthesis of significant near surface redox gradients that supergene alteration redox controlled ore deposition and subaerial weathering in an oxidizing environment could diversify earth9s near surface mineralogy these post hadean processes may be responsible for over 4000 of the more than 4800 approved mineral species any scenario for life9s origins that invokes minerals as agents of molecular synthesis selection protection or organization must take into account the limited mineralogical repertoire of the time

cobalt mineral ecology minerals containing cobalt as an essential element display systematic trends in their diversity and distribution we employ data for 66 approved co mineral species as tabulated by the official mineral list of the international mineralogical association http rruff info ima as of 1 march 2016 representing 3554 mineral species locality pairs www mindat org and other sources as of 1 march 2016 we find that cobalt containing mineral species for which 20 are known at only one locality and more than half are known from five or fewer localities conform to a large number of rare events lnre distribution our model predicts that at least 81 co minerals exist in earth s crust today indicating that at least 15 species have yet to be discovered a minimum estimate because it assumes that new minerals will be found only using the same methods as in the past numerous additional cobalt minerals likely await discovery using micro analytical methods primary co minerals include 26 species most of which are hydrothermally deposited chalcogenides we identify 33 additional plausible as yet undiscovered primary cobalt chalcogenide minerals including 28 phases with spinel nickeline pyrite and marcasite structural topologies all 40 secondary cobalt minerals are oxides and 37 of these phases also incorporate hydrogen we tabulate an additional 117 plausible secondary co minerals that are related compositionally and or structurally to known species new cobalt minerals are likely to be discovered in specimens collected at the 10 most prolific co localities all of which are mining districts with hydrothermal co mineralization and hosting at least 10 different primary and secondary co species

phanerozoic large igneous provinces lips heatt haline euxinic acidic thermal transgression episodes and mass extinctions abstract the phanerozoic consists of three mutually exclusive climate states icehouse greenhouse and hothouse the greenhouse is the default state representing 70 of the phanerozoic it is characterized by a weak thermal mode pole driven deep water formation with little or no continental sea ice and weakly oxic cool water sinking near the poles nitrogen limitation characterizes greenhouse oceans in which ammonium may be the dominant bioavailable form of nitrogen the steady state greenhouse default must be forced to produce either of the other two states continent continent collision produces the intense chemical weathering that draws down atmospheric co2 and results in the icehouse state that comprises 20 25 of the phanerozoic icehouses have ice caps in contact with the ocean that produce icebergs and foster sea ice formation sea ice formation fills the ocean with highly oxic phosphorus limited icewater except for a thin layer of warm surface water in the tropics of the 23 most conspicuous mass extinctions of the phanerozoic including the late ediacaran 4 are associated with ice volume related regressions and 3 are problematic we suggest that the other 16 mass extinctions occurred when greenhouse climate was forced to hothouse climate large igneous provinces lips can trigger the heatt haline euxinic acidic thermal transgression mechanism which can force greenhouse climate to a hothouse climate state the rapid voluminous co2 emissions of lips cause a series of events that result in very slow but pronounced haline mode circulation mid latitude driven deep water formation that produces warm saline bottom water at very dry hot subtropical and middle latitudes this water upwells at the poles causing warm and moist equable climate hothouse development promotes deep sea anoxia that is generated in concert with co2 buildup and warming the spread of anoxia favors reduced nitrogen over nitrate and limited iron dust curtails nitrogen fixation this leads to dominance of primary productivity by primitive green algae and or cyanobacteria progression to euxinia that reaches the photic zone severely curtails primary productivity via poisoning even as availability of usable nitrogen plummets the result is eukaryotic mass extinction we suggest that the 16 phanerozoic mass extinctions referred to above resulted at least in part from the heatt process evidence for this relationship at 11 of the most severe extinctions is convincing data sets for the other 5 are strongly suggestive of heatt related mass extinction but do not yet have enough documentation to reliably characterize them as heatt episodes

the late devonian frasnian famennian event in south china patterns and causes of extinctions sea level changes and isotope variations abstract the frasnian famennian f f event may be recognized in various facies areas in south china in the pelagic cherty basin facies both lower and upper kellwasser events can seemingly be recognized in the deeper water carbonate facies the f f event level is well controlled in light of conodont biostratigraphy in the shallow water carbonate and mixed carbonate shale facies the f f boundary may be defined by clear taxonomic distinction in benthic fossils articulate brachiopods and corals as well as evidence from minor pelagic fossils post extinction recovery rate of benthic organisms differs in different facies settings and different taxonomic groups in open shallow water platform to inter platform depression areas brachiopods seem to recover quickly probably in the middle pa triangularis zone benthic ostracodes seem to recover at a later stage recovery of rugose corals did not happen until the uppermost famennian three steps of the f f mass extinction are postulated 1 extinction of diverse brachiopods including most atrypids 2 extinction of pelagic conodonts 3 extinction of both benthic faunas very abundant and diverse rugose corals and ostracodes and pelagic conodonts evidence of an end frasnian regression in south china is clear particularly in shallow water settings however in deeper water settings the picture is complicated with evidence of both sea level rise and fall in the latest frasnian it may be assumed from overall data so far known that crustal evolution itself and associated multiple volcanic hydrothermal activities may have mainly caused frequent and rapid climatically warming cooling alterations and sea level changes as well as marine ecologic collapse eutrophication microbial blooming seawater acidification and anoxia which may explain the f f extinction pattern in south china

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

how many boron minerals occur in earth s upper crust the current rate of discovery of new boron minerals 65 species or potential species described from 2008 to 2017 is higher than at any prior 10 year period implying that rates of b mineral discovery could increase further with no obvious limit to boron mineral diversity in earth s crust in contrast large number of rare events lnre models calculated from the 295 species of b minerals discovered through 2017 give a total predicted b mineral endowment in earth s crust of 459 65 5 and 523 species using a finite zipf mandelbrot fzm model and sichel s generalized inverse gauss poisson model gigp respectively i e there is a very real predicted limit of no more than 500 species as cautioned by hazen hystad and their co authors lnre modeling presumes no changes in how minerals are discovered from the beginning of mineral discoveries in the late 18th century to early 2017 however this condition is clearly not the case and thus changes could explain the discrepant indications the most important changes are 1 the advent of the electron microprobe which became widely used for chemical analysis of b minerals in 1978 2 technological advances in single crystal x ray diffractrometry 3 technological advances in electron microscopy including advent of electron backscattered diffraction 4 advent of micro raman spectroscopy and 5 changes in mineralogical nomenclatures particularly of the tourmaline supergroup changes 1 to 4 are expected to reduce the size of the mineral grains that can be studied thereby increasing the number of species accessible to study furthermore should species have a fractal distribution i e diversity is independent of scale examination of increasingly smaller grains will turn up an even larger number of species to evaluate the impact of these changes on the lnre modeling we modeled the 146 b minerals discovered up through 1978 which was selected as the cutoff because of 1 the important role played subsequently by the electron microprobe and 2 the number of species was 50 of the current number this modeling gave 306 fzm and 359 gigp for total species i e the access to smaller grains afforded by advanced analytical instrumentation has resulted in an increased estimate of total endowment by 50 from 1978 whether the fzm or gigp distribution is applied we doubt that the 500 b species estimate is the end of the story as we expect there will be further technological advances in the future a more realistic finale might come when we reach the natural limit imposed by the minimum number of unit cells needed for new mineral to be viable and thus lnre modeling might yet show that earth s total endowment of b minerals is finite a review of past patterns of discovery of new boron minerals which can inform us what to expect in future discoveries reveal that only 19 of b minerals were synthesized prior to discovery we conclude that synthetic compounds are not a particularly promising source of potential new b minerals in contrast 22 of b minerals were discovered prior to synthesis and 29 have unique structures i e they have no synthetic analogs and are not isostructural with a known mineral accordingly 41 of b minerals could not be predicted and we conclude that the realm of as yet undiscovered b minerals holds a significant number of surprises

mountain building enhanced continental weathering and organic carbon burial as major causes for climatic cooling at the frasnian famennian boundary c 376 ma the late devonian was a period of drastic environmental changes as exemplified by a major biotic crisis at the frasnian famennian boundary ffb and the onset in famennian times of glaciations across southern gondwana worldwide evidence for the coeval development of the major acadian eovariscan belt led us to propose a model relating the late frasnian famennian environmental perturbations to extensive continental uplift through two atmospheric co2 depleting mechanisms 1 the intensification of silicate weathering on the continental areas as attested by a major rise in the 87 sr 86 sr composition of sea water at the ffb and 2 the massive burial of organic carbon kellwasser events in partially confined basins due to the collisional induced reduction of equatorial oceanic communications between the palaeotethysian and panthalassic oceans this process is also suggested to have been controlled by an important primary productivity connected to an increased nutrient availability triggered by the enhanced continental run off

a coupled model for laplace s tidal equations in a fluid with one horizontal dimension and variable depth abstracttide topography interactions dominate the transfer of tidal energy from large to small scales at present it is poorly understood how low mode internal tides reflect and scatter along the continental margins here the coupling equations for linear tides model celt are derived to determine the independent modal solutions to laplace s tidal equations lte over stepwise topography in one horizontal dimension celt is i applicable to arbitrary one dimensional topography and realistic stratification without requiring numerically expensive simulations and ii formulated to quantify scattering because it implicitly separates incident and reflected waves energy fluxes and horizontal velocities obtained using celt are shown to converge to analytical solutions indicating that flat bottom modes which evolve according to lte are also relevant in describing tides over sloping topography the theoretical framework presented can then be used to quantify simultaneous incident and reflected energy fl

the global frasnian famennian kellwasser event during the uppermostp gigas conodont zone p linguiformis zone the stepwise frasnian extinction culminates in the global transgressive regressive frasnian famennian kellwasser event most pelagic organisms of the tropical marine environment are more or less affected by this mass extinction during the early upper devonian extinction rates are clearly related to the deposition of black shales and the storage of a great amount of organic carbon in the shelf sediments contemporaneous positive excursions of the 13c recorded from pelagic limestones of europe and australia prove a worldwide change in the co2 content of the oceans surface water which is in balance with the atmosphere if the climate is controlled by the co2 content of the atmosphere a cyclic operation process might have developed with the succession transgression high organic production deposition of organic carbon lowering of co2 in the atmosphere icehouse effect polar glaciation regression erosion of organic carbon and re supply of co2 to the ocean and atmosphere greenhouse effect deglaciation transgression during the change from a greenhouse to an icehouse effect an overturn of the anoxic oceans probably was one of the causes for the mass killing of low latitude marine organisms

chromium mineral ecology minerals containing chromium cr as an essential element display systematic trends in their diversity and distribution we employ data for 72 approved terrestrial cr mineral species http rruff info ima as of 15 april 2016 representing 4089 mineral species locality pairs http mindat org and other sources as of 15 april 2016 we find that cr containing mineral species for which 30 are known at only one locality and more than half are known from three or fewer localities conform to a large number of rare events lnre distribution our model predicts that at least 100 13 1 cr minerals exist in earth s crust today indicating that 28 13 1 species have yet to be discovered a minimum estimate because our model assumes that new minerals will be found only using the same methods as in the past numerous additional cr minerals likely await discovery using micro analytical methods we propose 117 compounds as plausible cr minerals to be discovered including 7 oxides 11 sulfides 7 silicates 7 sulfates and 82 chromates depending on their compositions and crystal structures new cr minerals are likely to be discovered in various environments including meteorites basalt evaporites and oxidized pb ore deposits

water column structure during deposition of middle devonian lower mississippian black and green gray shales of the illinois and michigan basins a biomarker approach abstract the extractable organic matter of organic rich black shales and associated organic poor bioturbated green gray shales of the illinois and michigan basins of north america is analyzed to constrain the water column structure during their deposition all black shale samples contain derivatives of the biomarker isorenieratene a diaromatic carotenoid pigment produced exclusively by the brown strain of the green sulfur bacteria chlorobiaceae chlorobiaceae are phototrophic organisms requiring euxinic anoxic and sulfidic conditions to survive and the presence of isorenieratene derivatives indicates that the middle devonian early mississippian epeiric seas of north america experienced bottom water euxinic conditions during black shale deposition analysis of green gray shales also reveals the presence of isorenieratene derivatives and in some cases isorenieratane the highly bioturbated fabric of these sediments indicates the presence of oxygen in bottom waters during their deposition thus we suggest that short term shoaling of the oxycline across the basin slope may have occurred during their deposition though they were deposited predominantly under an oxygenated water column i e above the chemocline most green gray shales contain three pseudohomologous series of branched alkanes with quaternary substituted carbon atoms baqcs which are absent in black shale samples recent studies suggest that baqcs are produced by benthic chemoautotrophs dwelling at the redox boundary separating anoxic sediments from moderately oxygenated waters comparison of the biomarker content i e regular isoprenoid baqcs between black and green gray shales indicates different sources of organic matter and suggests that phytoplanktonic productivity in the upper water column was enhanced during black shale deposition the results of this study indicate that the alternation of green gray and black shales in these basins results from the vertical fluctuations of the chemocline these fluctuations seem to be driven by changes in phytoplanktonic productivity our data when associated to previous studies of other black shales from canada and europe confirm that photic zone euxinia was a widespread feature of low latitude epeiric seas during the middle devonian lower mississippian

benthic phosphorus regeneration net primary production and ocean anoxia a model of the coupled marine biogeochemical cycles of carbon and phosphorus we examine the relationships between ocean ventilation primary production water column anoxia and benthic regeneration of phosphorus using a mass balance model of the coupled marine biogeochemical cycles of carbon c and phosphorus p the elemental cycles are coupled via the redfield c p ratio of marine phytoplankton and the c p ratio of organic matter preserved in marine sediments the model assumes that on geologic timescales net primary production in the oceans is limited by the upwelling of dissolved phosphorus to the photic zone the model incorporates the dependence on bottom water oxygenation of the regeneration of nutrient phosphorus from particulate matter deposited at the water sediment interface evidence from marine and lacustrine settings modern and ancient demonstrates that sedimentary burial of phosphorus associated with organic matter and ferric oxyhydroxides decreases when bottom water anoxia dysoxia expands steady state simulations show that a reduction in the rate of thermohaline circulation or a decrease of the oxygen content of downwelling water masses intensifies water column anoxia dysoxia and at the same time increases surface water productivity the first effect reflects the declining supply of oxygen to the deeper parts of the ocean the second effect is caused by the enhanced benthic regeneration of phosphorus from organic matter and ferric oxyhydroxides sedimentary burial of organic carbon and authigenic calcium phosphate mineral francolite on the other hand is promoted by reduced ocean ventilation according to the model global scale anoxia dysoxia leads to a more efficient recycling of reactive phosphorus within the ocean system consequently higher rates of primary production and organic carbon burial can be achieved even when the continental supply of reactive phosphorus to the oceans remains unchanged

comparison of organic and inorganic carbon isotope patterns across the frasnian famennian boundary abstract the carbon isotopic composition of organic matter is reported for two frasnian famennian boundary sections from the rheinische schiefergebirge germany during the late frasnian 13 c org values commonly range from 27 5 to 26 highest 13 c org values around 24 are encountered immediately above and below the kellwasser horizons all samples from the kellwasser horizons are depleted in 13 c org by 2 5 to 4 7 this depletion is explained by a higher proportion of biomass derived from isotopically depleted chemoautotrophic bacteria a comparison of the positive 13 c excursions shows that the 13 c org shifts precede the 13 c carb shifts by some 10 5 years consequently 13 c values document a shift towards lower values below the upper kellwasser horizon a contribution of terrestrial organic matter as well as a thermal alteration of the 13 c org signals do not provide compelling explanations for the earlier 13 c org shift increases in primary productivity or carbon burial rate will change the co 2 aq content of surface waters affect the carbon isotope fractionation during photosynthetic carbon uptake and thus enrich organic carbon in 13 c however both processes cannot account for the earlier onset of the 13 c org shift because the 13 c carb record should document the resulting 13 c enrichment in surface waters as well a reduction in the calcium carbonate precipitation rate due to the global extinction of the reef ecosystem may have played an important role in reducing the co 2 aq content of surface waters without changing the isotopic composition of surface waters whether this process or other factors such as a rise in sea surface temperature or a change in the phytoplankton association account for the earlier onset of the positive shift in the 13 c org curve must be determined by further studies that may be able to confirm the global significance of the reported 13 c org pattern in frasnian famennian boundary sections from other parts of the globe

beryllium mineral evolution beryllium is a quintessential upper crustal element being enriched in the upper crust by a factor of 30 relative to primitive mantle 2 1 vs 0 07 ppm most of the 112 minerals with be as an essential element are found in granitic pegmatites and alkalic rocks or in hydrothermal deposits associated with volcanic and shallow level plutonic rocks and skarns because of the extensive differentiation needed to enrich rocks sufficiently in beryllium for beryllium minerals to form these minerals are relative latecomers in the geologic record the oldest known is beryl in pegmatites associated with the sinceni pluton swaziland 3000 ma in general beryllium mineral diversity reflects the diversity in the chemical elements available for incorporation in the minerals and increases with the passage of geologic time furthermore the increase is episodic that is steep increases at specific times are separated by longer time intervals with little or no increase in diversity nonetheless a closer examination of the record suggests that at about 1700 ma the rate of increase in diversity decreases and eventually levels off at 35 species formed in a given 50 ma time interval between 1125 and 475 ma then increases to 39 species at 125 ma except for four spikes before dropping off to 30 species for the last 100 ma these features appear to reflect several trends at work 1 diversifications at 2475 1775 and 525 ma which are associated with highly fractionated rare element granitic pegmatites and with skarns at langban and similar deposits in the bergslagen ore region of central sweden and which are inferred to correspond to the collisional phases of the supercontinents kenorland nuna and gondwana respectively 2 diversification at 1175 ma due to the rich assemblage of beryllium minerals in the ilimaussaq peralkaline complex gardar province west greenland in an extensional environment 3 diversification at 275 ma which is largely attributable to granitic pegmatites appalachian mountains u s a and urals russia and the larvik alkalic complex norway but nonetheless related to continental collision and 4 limited exhumation of environments where beryllium minerals could have formed in the last 100 ma that the maximum diversity of be minerals in any one geologic environment could be finite is suggested by the marked slowing of the increase in the number of species formed in a given 50 ma time interval whereas the drop off at 100 ma could be due to 100 myr being too short a time interval to exhume the deep seated occurrences where many be minerals had formed the relative roles of chance vs necessity in complex evolving systems has been a matter of considerable debate one equally applicable to what extent the temporal distribution of beryllium minerals is a matter of contingency on the one hand the appearance of the most abundant be minerals such as beryl and phenakite early in the history of be mineralization appears to be a deterministic aspect since these minerals only require the abundant cations al and si and crystallize at relatively low concentrations of be in aqueous solution or granitic magmas on the other hand it could be argued that the very existence of most other be minerals as well as the temporal sequence of their appearance is a matter of chance since 55 of the 112 approved be minerals are known from a single locality and many of these phases require an unusual combination of relatively rare elements consequently we cannot exclude the possibility that other equally rare and thus contingent potential be minerals await discovery in as yet unexposed subsurface deposits on earth and we suggest that details of be mineral evolution on other earth like planets could differ significantly from those on earth

influence of water column anoxia on the elemental fractionation of carbon and phosphorus during sediment diagenesis abstract organic carbon oxidation and benthic total phosphorus flux measurements from sites covering a range of bottom water oxygen concentrations have been compiled the data show that p regeneration relative to carbon oxidation is much more extensive in sediments overlain by oxygen depleted waters these results are consistent with studies showing that low oxygen bottom water concentrations correlate with reduced total phosphorus burial efficiencies and enhanced organic carbon burial efficiencies based on these observations a positive feedback is proposed between water column anoxia enhanced benthic phosphorus regeneration and marine productivity this feedback may help explain the widespread accumulation of organic rich marine sediments from anoxic waters observed in the geologic record

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response