oxygen and carbon isotope record of east pacific core v19 30 implications for the formation of deep water in the late pleistocene north atlantic abstract a detailed oxygen and carbon isotope record has been obtained from benthic foraminifera in core v19 30 from the carnegie ridge on the south side of the panama basin expressing these records and the oxygen and carbon isotope records previously published for atlantic core m 12392 on a common timescale it is apparent that the oxygen isotope records are very similar but that the carbon isotope records are quite different by obtaining the carbon isotope gradient between the two sites as a function of time we show that the production of north atlantic deep water has varied over a wide range during the late pleistocene and that the pattern of variation is not simply related to the well known oxygen isotope record although the two oxygen isotope records are very similar changes in the interoceanic gradient are detectable and support the hypothesis that in the glacial mode the north atlantic was colder and less oxygenated than it is today shackleton s 1 1977 interpretation whereby the carbon isotope record from the atlantic core reflects changes in the terrestrial biomass is an over simplification however the record from the pacific core v19 30 probably can be explained in these terms since it probably approximates the carbon isotope record of global mean oceanic dissolved co 2

significant changes in land vegetation and oceanic redox across the cretaceous paleogene boundary abstract the impact of an extraterrestrial body 65 5 ma caused the so called cretaceous paleogene k pg event that resulted in a mass extinction and rapid changes in the surface environment on earth here we report changes in land vegetation and oceanic redox across the k pg boundary at caravaca southeastern spain using biomarkers the results reveal that the basal 3 mm thick layer of the k pg boundary clay is marked by a rapid increase in the concentration of terrestrial long chain n alkanes and dibenzofuran indicating the destruction of land vegetation and an increase in the supply of terrestrial organic matter into the marine environment during the deposition of the k pg boundary clay this layer also records a rapid increase in the concentration of dibenzothiophenes which indicates a change in redox conditions from oxic to anoxic euxinic conditions in the intermediate water over the seafloor the low oxygen conditions could have been caused by an increase in the influx of terrestrial organic matter into the ocean a rapid increase in the concentration of retene and retene cadalene occurred during the deposition of the upper part of the boundary clay 10 kyr after the mass extinction indicating the recovery of conifers which greatly decreased at the k pg boundary

mass mortality and its environmental and evolutionary consequences the latest mesozoic and earliest tertiary sediments at deep sea drilling project site 524 provide an amplified record of environmental and biostratographic changes at the end of cretaceous closely spaced samples representing time intervals as short as 102 or 103 years were analyzed for their bulk carbonate and trace metal compositions and for oxygen and carbon isotopic compositions the data indicate that at the end of cretaceous when a high proportion of the ocean9s planktic organisms were eliminated an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere this resulted in a large increase of the atmospheric carbon dioxide during the next 50 000 years which is believed to have caused a temperature rise revealed by the oxygen isotope data the lowermost tertiary sediments at site 524 include fossils with cretaceous affinities which may include both reworked individuals and some forms that survived for a while after the catastrophe our data indicate that many of the cretaceous pelagic organisms became extinct over a period of a few tens of thousands of years and do not contradict the scenario of cometary impact as a cause of mass mortality in the oceans as suggested by an iridium anomaly at the cretaceous tertiary boundary

continental growth comments on the archean proterozoic transition evidence from guyana and montana by a k gibbs c w montgomery p a o day and e a erslev

iridium sulfur isotopes and rare earth elements in the cretaceous tertiary boundary clay at stevns klint denmark microbial activity and redox controlled precipitation have been of major importance in the process of metal accumulation in the strongly ir enriched cretaceous tertiary k t boundary clay the fish clay at stevns klint in denmark two important findings support this view 1 1 kerogen recovered by leaching the fish clay in hcl and hf shows an ir concentration of 1100 ppb this represents about 50 of the ir present in the bulk sample fish clay strong organometallic complexes is the most probable carrier phase for this fraction of ir kerogen separated from the k t boundary clay at caravaca spain similarly exhibits enhanced ir concentrations 2 2 sulfur isotope analyses of metal rich pyrite spherules which occur in extreme abundance about 10 by weight in the basal fish clay give a 34s value of 32 this very low value shows that sulfide formation by anaerobic bacteria was intensive in the fish clay during early diagenesis since the pyrite spherules are major carriers of elements such as ni co as sb and zn microbial activity may have played an important role for concentrating these elements in the fish clay large amounts of rare earth elements have precipitated from sea water on fish scales analyses reveal that compared with sea water the fish clay is only about four times less enriched in sea water derived lanthanides than in ir this shows that a sea water origin is plausible for elements that are strongly enriched in the clay but whose origin cannot be accounted for by a lithogenic precursor

a sulfur isotope event at the end of the permian abstract a hypothesis of light sulfur injection to the ocean atmosphere system at the end of the permian was presented by kaiho et al kaiho k kajiwara y nakano t miura y kawahata h tazaki k ueshima m chen z q shi g r 2001 end permian catastrophe by a bolide impact evidence of a gigantic release of sulfur from the mantle geology 29 815 818 based on a negative shift of 34 s 32 s ratio of carbonate associated sulfate in south china this hypothesis was discussed in some papers with additional data in other areas however the cause and distribution of the negative shift has not been clarified here we show that a significant decrease in the 34 s 32 s ratio of carbonate associated sulfate occurred simultaneously in south china and hungary at the end of the permian coincident with the end permian mass extinction the cause of the abrupt negative shift of 34 s 32 s in these two distant sites is the injection of light sulfur to the surface ocean from the deep ocean rich in h 2 s or deposits rich in sulfide or the mantle this sulfur isotope event was likely caused by either an abrupt warming a bolide impact to the ocean mantle plume induced volcanism or a harmonizing of these possible direct causes are 1 massive release of h 2 s gas from the euxinic surface and intermediate waters due to abrupt warming by volcanic co 2 or impact shock wave in the ocean 2 a huge volcanism penetrated sediments or ore rich in sulfide 3 an extraterrestrial impact to sulfide rich sediments or ore deposit and 4 release of mantle origin sulfur by an impact of 70 km asteroid to the ocean these are four possible causes for a mass extinction there is also a possibility of a local oceanic event only in the tethys

the cretaceous tertiary boundary carbon and oxygen isotope stratigraphy diagenesis and paleoceanography at zumaya spain carbon and oxygen isotope analysis of 240 m of upper cretaceous and lower tertiary limestones and marlstones from zumaya spain has revealed three distinct negative carbon isotope excursions of up to 2 per mil occurring both before and during the cretaceous tertiary k t transition although diagenesis has affected these rocks to varying degrees during burial and lithification we believe that these excursions may reflect paleoceanographic changes sr ca electron microscopic and petrographic analysis have been used to assess the type and magnitude of diagenesis allowing us to distinguish samples with significantly altered isotopic values carbon isotopes of rocks at zumaya exhibit absolute values and ranges similar to semiconsolidated sediments of the same age oxygen isotopes of these rocks however exhibit a 1 2 per mil or more depletion defined here as a diagenetic overprint in comparison with values from semi consolidated sediments of the same age ammonite and inoceramid macrofossils disappear in this section 12 5 and 120 m below the k t boundary coincident with two distinct episodes of negative 13c values these may reflect localized paleoceanographic or ecological changes the last and largest of the isotope excursions corresponds with the k t boundary marl and mass extinctions of calcareous plankton the k t boundary carbon isotope excursion is one of three that took place during the last 1 million years of the cretaceous each one possibly being associated with biotic changes in the oceanic realm the k t boundary excursion coincides with iridium concentration and spherules of unidentified origin perhaps indicating that paleoceanographic change coincided with either extraterrestrial impacts or volcanic events that amplified their effects and accelerated biotic changes during times of stressed oceanic ecosystems

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

the cretaceous tertiary boundary event in the north pacific planktonic foraminiferal results from deep sea drilling project site 577 shatsky rise a detailed micropaleontologic analysis of sediments from deep sea drilling project site 577 from the shatsky rise north pacific was undertaken to describe extinction and radiation patterns of plank tonic foraminifera in a continuous carbonate sequence spanning the cretaceous tertiary k t boundary a 15 m section containing the boundary was closely sampled and contained planktonic foraminiferal assemblages characteristic of the late maastrichtian abathomphalus mayaroensis zone through the danian globorotalia uncinata zone the cretaceous tertiary boundary was placed at the abrupt disappearance of almost all maastrichtian planktonic foraminifera coincident with these extinctions was the presence of a large number of microtektitelike spherules the most important faunal change in the late maastrichtian was an abrupt increase in the relative abundance of the high latitude species hedbergella monmouthensis together with the appearance of diminutive populations of guembelitria cretacea and globigerina eugubina approximately 20 000 years before the boundary these changes are interpreted as indicating a cooling of surface water conditions globigerina eugubina and g cretacea were the only planktonic foraminiferal species to survive the cretaceous tertiary boundary event at this locality the o 18 and c 13 values of g eugubina from below the k t boundary are nearly the same as those from above the boundary but in both cases the o 18 values indicate relatively cooler paleotemperatures than those from other coexisting planktonic foraminiferal species in addition the c 13 values of g eugubina are lighter than those of the other planktonic foraminifera such a relationship might suggest that g eugubina lived in cooler shallow intermediate water masses advected from higher latitudes during a latest maastrichtian cooling episode better preservation of planktonic foraminifera a progressive change in the c 13 of benthic foraminifera and a brief positive excursion in c 13 of the carbonate fine fraction and of planktonic foraminifera within 20 to 30 cm below the k t boundary all suggest important paleoceanographic changes that preceded the extinction event a large population of aberrant g eugubina and eoglobigerina was observed in the earliest danian these forms are characterized by the development of secondary apertures bullae and abnormal final chambers these abnormal morphotypes are considered to be ecophenotypic variants reflecting ecologic stress or instability in the earliest cenozoic marine environment

a low extinction rate of intermediate water benthic foraminifera at the cretaceous tertiary boundary the contrast between the high extinction rates of calcareous marine plankton and low extinction rates of deep water calcareous benthic foraminifera across the cretaceous tertiary k t boundary is now recognized however the water depth at which the vertical change in extinction rates of marine organisms occurred at the k t boundary is not yet known because of the lack of data on the extinction rates of intermediate water organisms the extinction rate of intermediate water benthic foraminiferal species from kawaruppu hokkaido japan was determined by distinguishing locally extinct species a distinctly low extinction rate 10 for calcareous benthic foraminiferal fauna from the upper part of the intermediate water is documented for the first time this rate is almost equal to the extinction rate of deep water benthic foraminifera 10 and is much smaller than the planktic foraminiferal extinction rate 81 the extinction rate curve for calcareous foraminifera in a vertical water column indicates that a rapid change from a high extinction rate 80 to a low extinction rate 10 took place at a water depth of about 150 m this depth of change is equivalent to the boundary depth between the surface and intermediate waters and between the euphotic and aphotic zones furthermore this coincidence is consistent with the hypothesis that acid rain and a darkness induced breakdown of the marine food chain produced by a cometary or asteroidal impact at the k t boundary were the main causes of the mass extinction of calcareous planktic organisms in surface waters

geochemistry of late permian to early triassic pelagic cherts from southwest japan implications for an oceanic redox change major trace and rare earth element abundances were determined for the southwestern japanese pelagic chert sequence from the early late permian to early early triassic to investigate a redox change in deep sea pelagic environments before and at the permo triassic boundary ptb 251 ma the sequence was primarily deposited in the deep sea of the superocean panthalassa and then was accreted to japan in the middle jurassic a remarkable lithostratigraphic change from red chert to siliceous carbonaceous claystone through gray chert is observed in this sequence constituent elements for these sedimentary rocks are essentially derived from two sources 1 an ancient seawater via biogenic mainly radiolarian hydrothermal and authigenic materials and 2 an average shale like terrigenous material the present measurement demonstrates significant stratigraphic changes of the ce cenon ter value estimated ce anomaly value of non terrigenous component recalculated by subtraction of terrigenous rees from bulk rees and the mn te sample mn te paas value excess mn component other than terrigenous one te terrigenous elements including ti al nb hf th paas post archean average australian shale in the permian chert the ce cenon ter values increase from 0 2 to 1 and the mn te sample mn te paas values decrease up section suggesting that the redox condition of deep sea open ocean changed from oxic to suboxic in an interval of approximately 10 myr the fe te sample fe te paas and mn te sample mn te paas values of carbonaceous claystone near or at the ptb are less than unity suggesting that reductive dissolution of iron and manganese occurred under an anoxic condition this supports the idea of the ptb oceanic anoxia in the superocean panthalassa the present data suggest that the anoxic condition prevailed in the deep sea pelagic regions for an extremely long period much more than 10 myr from the middle late permian to early early triassic this long term development of widespread oceanic anoxia may have been linked to the greatest mass extinction of the phanerozoic

geological and biological consequences of giant impacts it seems inescapable that large impacts have been an ongoing phenomenon throughout geological time in the phanerozoic the estimated frequency of impact by bodies of 5 km diameter or more is on the order of 1 0 every 1 00 myr the 5 km lower limit is chosen arbitrarily but it is shown in this review that such a body is certainly large enough to cause very large terrestrial effects a small decrease in this size limit would lead to a large increase in the frequency of occurrence it may be claimed that bodies of a size likely to have drastic and sudden effects on niany physical and biological features of the earth have arrived with a frequency comparable to the average duration of a biostratigraphic stage nothing is said of the interval between arrivals which may be random i e stochastic currently there is not enough geological evidence to allow recognition of other than random spacing between a few positively identified events during the phanerozoic since impacts by extraterrestrial bodies have been clearly established it is reasonable to postulate that they must leave a record in the stratigraphic column why then do we currently have so few horizons that have been claimed to contain evidence of a global impact event since the effects we are considering are unquestionably global in this paper we bring together evidence from several disciplines that

the cretaceous tertiary transition the fossil sequences from cores across the cretaceous tertiary boundary show a range of transition times and transition time intervals depending on the fossil indicators and the location of the site these variations together with the pattern of iridium distribution with depth at some sites differences in total amounts of iridium variations in noble metal abundances normalized to extraterrestrial concentrations the depositional effects that might be expected in a reducing environment and the clay mineralogy of the boundary layer clays put into question the interpretation that an extraterrestrial event was the cause of the faunal changes and the iridium anomaly in the vicinity of the cretaceous tertiary transition it seems more likely that an explanation for the changes during the transition will come from continued examination of the great variety of terrestrial events that took place at that time including extensive volcanism major regression of the sea from the land geochemical changes and paleoclimatic and paleoceanographic changes

metal precipitation in the cretaceous tertiary boundary clay at stevns klint denmark abstract alvarez et al 1980 explained anomalous ir concentrations in the cretaceous tertiary k t boundary informal type sediment the fish clay in denmark in terms of a global fall out of extraterrestrial matter however geochemical and mineralogical analyses of the various sublayers in the clay reveal that not only ir but also elements such as ni co zn mo as se and sb are substantially enriched in the clay the enrichments may be due to precipitation of elements as sulfides at a redoxcline the facts supporting this view are 1 1 the over all chalcophile element abundance pattern in the clay 2 2 the occurrence of a redoxcline deduced from the distribution of organic matter and oxidized iron in the clay 3 3 the large amounts of small pyrite spheroids present at this redoxcline 4 4 the high concentration of trace elements in these spheroids also ni co and ir elements that have previously been presumed to have a meteoritic origin are substantially enriched in the spheroids a model is suggested in which metal bearing pore solutions lose their metals by precipitation upon passing the boundary between the oxic cretaceous chalk and the overlying anoxic and hydrogen sulnde rich fish clay the great similarity in geochemistry and lithological appearance between several strongly ir enriched clays suggest that the model may also be applied to other k t boundary clays

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

stable isotope evidence for gradual environmental changes and species survivorship across the cretaceous tertiary boundary high resolution 13c and 18o records have been generated from analyses of the planktonic foraminiferal species heterohelix globulosa and the benthonic foraminiferal taxon lenticulina spp from 3 m of a cored section spanning the cretaceous tertiary k t boundary at brazos river texas these are the first stable isotope records across the k t boundary based on monospecific and monogeneric foraminiferal samples they show a gradual decrease in 13c values of about 2 5 permil beginning at the k t boundary as defined by the first appearance of tertiary planktonic foraminifera and continuing 17 20 cm above the boundary approximately 40 000 years later gradual 13c depletion contrasts with the sudden 13c drop at the k t boundary observed in many deep sea sections the surface to bottom 13c gradient decreased to less than zero approximately 25 000 30 000 years after the k t boundary and remained negative for at least the next 140 000 years concomitant with change in 13c values is a gradual decrease of about 2 5 permil in 18c values which has not been observed at other localities this 18o depletion suggests changes in temperature and or salinity in the earliest paleocene gulf of mexico no extinction of foraminiferal species is associated with the k t boundary or the onset of 18o and 13c depletions instead two phases of cretaceous species extinctions occur one extinction phase is below the k t boundary and below the tsunami bed of bourgeois et al 1988 and may be linked to sea level regression and environmental perturbations the second extinction phase coincides with the minimum in 13c and 18o values in the early danian zone p0 pla and appears directly related to environmental changes reflected in the isotopic record h globulosa which is commonly present in maastrichtian and danian sediments exhibits significantly lower 18o 16o and 13c 12c ratios in tertiary sediments relative to specimens from maastrichtian sediments demonstrating the survival of this important cretaceous taxon after the k t boundary event

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

oceanic anoxia at the cretaceous tertiary boundary supported by the sulfur isotopic record abstract a temporary and drastic increase in 34s 32s ratio of whole rock sulfide has been recognized just at the cretaceous tertiary boundary within the continuous marine sedimentary sequence of the kawaruppu section in eastern hokkaido japan the apparent extent of fractionation with respect to inferred contemporaneous seawater sulfate in the anomaly zone which includes the boundary claystone at the bottom lies in the range of 25 10 whereas that in the lower and upper siltstone strata is roughly twice as much giving the values in the range of 49 10 the former is quantitatively equivalent in magnitude with the range of kinetic isotope effect in bacterial dissimilatory sulfate reduction and the latter with the typical variation range as observed in sedimentary diagenetic sulfides in ordinary oxic marine basins the present data would strongly support the temporary occurrence of an aerobe free anoxic oceanic sedimentary environment beginning just at the cretaceous tertiary boundary and continuing for approximately 70 000 years probably as a consequence of a certain catastrophic event responsible for the terminal cretaceous mass extinction

end cretaceous devastation of terrestrial flora in the boreal far east a continuous marine sedimentary sequence spanning the cretaceous tertiary k t boundary has been identified in eastern hokkaido japan on the basis of planktonic foraminifera the k t boundary is marked by a 6 10 cm thick layer of pyrite rich fossil poor greyish black claystone1 which is lithologically similar to the well known boundary clay of the classical european k t boundary sections2 4 we show here that terrestrial palyno morphs from the hokkaido section record sudden changes in the floristic composition precisely at the base of the boundary claystone layer in particular both angiosperm and gymnosperm pollen abundances decline markedly and these changes are accompanied by an abrupt rise in the proportion of fern spores return to the original moderate level of fern dominance occurs within a few centimetres above the boundary layer a sharp increase of fern spores has also been reported at the palynologically defined k t boundary in the western interior of north america5 which coincides with the top of an iridium rich clay layer6 7 the possibly synchronous occurrence of analogous floral changes at these widely separated regions implies a devastation of the land flora which although geologically brief was intercontinental in scope and which was probably caused by a major catastrophic event such as the impact of a massive meteorite7

bolide impacts acid rain and biospheric traumas at the cretaceous tertiary boundary abstract large projectiles impacting the earth will cause severe shock heating and chemical reprocessing of the earth s atmosphere this occurs during atmospheric entry and more importantly as a result of the supersonic plume ejected on impact in particular very large amounts of nitric oxide would result from the impact of the putative cretaceous tertiary bolide s we present models of the shock chemistry the conversion of no to no2 and thence to nitrous and nitric acids and the global dispersion of the no2 and acids two plausible projectiles are considered an ice rich long period comet and a much smaller rock metal asteroid the comet produces semi global atmospheric no2 mixing ratios of 0 1 while the asteroid produces these high mixing ratios only in the immediate region of the impact the comet produces concentrated nitrous and nitric acid rain with aph 0 1 5 globally the asteroid produces rain with aph 0 1 near the impact and 4 5 globally immediate environmental effects of these nitrogen species include inhibition of photosynthesis due to extinction of solar radiation by no2 foliage damage due to exposure to no2 and hno3 toxicosis resulting from massive mobilization of soil trace metals and respiratory damage due to exposure to no2 the acid rain decreases the ph of the oceanic mixed layer affecting the stability of calcite with important implications for the survival of calcareous shelled organisms and for exhalation of co2 from the mixed layer to the atmosphere longer term environmental effects perhaps 1000years in duration include a global warming due to the sudden co2 injection and the simultaneous extinction of the ocean micro organisms which normally help remove co2 from the atmosphere mixed layer system havens for survival include carbonate buffered lakes and burrows this acid rain theory therefore serves to explain the peculiar selectivity of the extinctions seen at the cretaceous tertiary boundary the first few years of acid rain will lead to massive weathering rates of continental soils characterized by large ratios of the relatively insoluble metals e g be2 al3 hg2 cu fe2 fe3 tl3 pb2 cd2 mn2 sr2 to the more soluble metals ca2 mg2 which should have left a clear signal in the fossils of neritic organisms and in unperturbed neritic sediments near river deltas if such sediments still exist for the cretaceous tertiary time frame

the structure of an exhumed intraplate seismogenic fault in crystalline basement abstract the 600 m thick gole larghe fault zone glfz is hosted in jointed crystalline basement and exposed across glacier polished outcrops in the italian alps ancient seismicity is attested by the widespread occurrence of cataclasites associated with pseudotachylytes solidified frictional melts formed at 9 11 km depth and ambient temperatures of 250 300 c previous work focused on the southern part of the fault zone here we quantitatively document fault zone structure across the full width of the glfz and surrounding tonalite host rocks by using a combination of structural line transects and image analysis of samples collected across fault strike these new datasets indicate that the glfz has a broadly symmetric across strike damage structure and contains distinct southern central and northern zones distinguished by large variations in fracture density distribution of pseudotachylytes volume of fault rock materials and microfracture sealing characteristics the c 100 m wide central zone is bound by two thick 2 m and laterally continuous 1 km protocataclastic to ultracataclastic horizons within and immediately surrounding the central zone fracture density is relatively high due to cataclastic fault fracture networks that reworked earlier formed pseudotachylytes the fault fracture networks were associated with pervasive microcracking and fluid rock interaction resulting in the development of a c 200 m thick alteration zone delimited by lobate fluid infiltration fronts in the c 250 m thick southern and northern zones fracture densities are much lower and pseudotachylytes systematically overprint cataclastic faults that exploited pre existing magmatic cooling joints analysis of the structure of the glfz suggests that it shares certain characteristics with the seismogenic source responsible for the 2002 au sable forks intraplate earthquake sequence in the northeastern usa including seismicity distributed across a fault zone 500 1000 m thick and large 100 mpa static stress drops associated with frictional melting