de glauconiarum origine the glauconitic facies is widespread on present day continental shelves from 50 s to 65 n and at water depths between 50 and 500 m and is in particularly great abundance on the upper slope and outer shelf between 200 and 300 m it is also common in many ancient rocks of post late precambrian age it occurs as sand to pebble sized essentially green particles granular facies but also as a surface coating on particles and hardgrounds and as a diffuse impregnation film and diffuse facies we suggest the replacement of the term glauconite which has been interchangeably used to designate a morphological form and a specific mineral by glaucony facies and glauconitic smectite and glauconitic mica as end members of the glauconitic mineral family the widely accepted model of burst and hower for glauconitization requires a degraded micaceous 2 1 layer lattice structure parent clay mineral however detailed analysis of numerous samples of recent glaucony reveals that such a parent substrate is exceptional the model therefore requires modification generally the parent material is carbonate particles argillaceous kaolinitic faecal pellets infillings of foraminiferal tests various mineral grains and rock fragments that pass gradually into the commonly occurring green grains we show that the process of glauconitization is achieved by de novo authigenic growth of automorphous crystallites in the pores of the substrate accompanied by progressive alteration and replacement of the substrate it is this two fold evolution that causes the verdissement of granular substrates macrofossils and hardgrounds the authigenic mineral is an iron rich and potassium poor glauconitic smectite while new smectites are growing into the remaining pore space the earlier smectites are modified by incorporation of potassium producing decreasingly expandable minerals with a non expandable glauconitic mica as the end member this mineralogical diversity of the glauconitic mineral family explains the highly variable physical and chemical properties of glaucony four categories nascent little evolved evolved and highly evolved glaucony are distinguished glauconitization appears to be controlled by a delicate balance between degree of physical confinement of a particle and the amount of ionic exchange between the micro environment and ambient open marine sea water the optimum conditions for glauconitization are those of semi confinement as a result the interior of a grain is more glauconitized than its less confined periphery similarly for identical substrate types large grains 500 m provide more favourable substrates for glauconitization than lesser confined small grains on a larger scale the formation of glaucony is governed by the availability of iron and potassium and the balance between detrital influx and winnowing low accumulation rates expose grains to the open marine environment for sufficiently long times 105 106 years for highly evolved glaucony

influence of tidal effects on the periodicity of earthquake activity in diverse geological settings with particular emphasis on submarine hydrothermal systems abstract hydrothermal earthquakes may be defined as earthquakes caused by the hydrofracturing of the oceanic crust by submarine hydrothermal fluids it is suggested that they correspond to the cracking of the ocean crust at the brittle ductile transition that marks the downward limit of seawater circulation into the ocean crust semi diurnal variations in submarine hydrothermal discharge in backarc settings and at the crests of mid ocean ridges have been detected by hydrophone but no influence of tidal effects on the periodicity of microearthquakes around submarine hydrothermal vents has been observed so far although tidal stresses are too small to initiate earthquakes themselves they may trigger earthquake activity when imposed on slowly increasing tectonic stress these effects therefore tend to be observed in geologically active regions where stress levels in the earth s crust are high the influence of tides on the periodicity of microearthquakes tends to be complex because the effects of ocean and earth tides are not uniform at the surface of the earth and because the microearthquakes occur in a wide variety of geological settings earth tides cause compression and dilatation of the oceanic crust which may be the most significant factor in initiating changes in fluid flow rate and microseismicity in submarine hydrothermal systems much of the information now available on the tidal periodicity of microearthquakes is based on relatively short term monitoring which lacks statistical validity the development and installation of deep sea monitoring stations will permit rigorous long term monitoring programmes to be carried out which will lead to a better understanding of the nature and periodicity of microearthquakes around submarine hydrothermal vents

long term seismicity and ground deformation at axial volcano juan de fuca ridge seismicity along the juan de fuca ridge jdfr has been monitored since august 1991 using u s navy hydrophones in the northeast pacific ocean during this time the focus of jdfr seismicity has been axial volcano where a total of 9055 earthquakes have been detected 1669 located this activity occurred within 48 discrete swarms along the summit caldera and flank rift zones from august 1991 to may 1996 axial volcano exhibited only one swarm with 50 earthquakes from may 1996 to november 1997 swarm activity increased significantly with five swarms of 50 earthquakes activity culminated at the volcano in january 1998 with an 11 day 8247 event swarm that was the result of a major eruption along the summit and southern flank seafloor deformation sensors indicated pre eruption swarms in october 1995 may 1996 and june 1996 coincided with subsidence of the caldera floor the 1996 1997 swarm activity increase also coincided with horizontal extension of the north rift zone consistent with pre eruption deformation of the volcano following the 1998 eruption swarm activity dramatically decreased and no earthquakes have been detected since april 1998 this is the longest aseismic period 1 yr observed at the volcano since acoustic monitoring began suggesting the january 1998 swarm marked the end of an eruptive cycle at axial volcano

the glauconite fe illite fe smectite problem a critical review iron silicate minerals are a significant component of sedimentary systems but their modes of formation remain controversial our analysis of published data identifies end member compositions and mixtures and allows us to recognize controls of formation of different mineral species the compositional fields of glaucony fe illite fe al smectites are determined in the m 4si vs fe sum of octahedral cations m interlayer charge solid solutions could exist between these phases the fe al and fe rich clay minerals form two distinct solid solutions the earliest phases to be formed are fe al smectites or berthierine depending on the sedimentation rate reductive microsystems appear in the vicinity of organic debris in unconsolidated sediments the fe is incorporated first in pyrite and then in silicates after oxidation potassium ions diffuse from the sea water sediment interface if not interrupted the diffusion process is active until reaction completion is reached i e formation of fe illite or glauconite or a mineral assemblage berthierine nontronite according to the available al ion amounts in the microsystem mixed layer minerals are formed when the diffusion process is interrupted because of sedimentation compaction or cementation despite the common belief of their value as palaeoenvironment indicators these minerals can form in a variety of environments and over a period of millions of years during sediment burial

deep downward fluid percolation driven by localized crust dilatation in iceland from a detailed seismic survey on a transform like plate setting in iceland we propose a spatial relationship between highly deformed crustal columns and areas of low vp vs ratio which are best explained by high fluid pressures at the base of the seismogenic crust combined with geological observations our seismic data suggest transient and local increases in crust permeability at specific highly dilating areas triggered by dynamical stresses from high magnitude regional earthquakes fluids are then trapped at supercritical conditions in the deep brittle crust which in turn increases the capacity of the rocks to deform through cracking and faulting

relationship between mass extinction and iridium across the cretaceous paleogene boundary in new jersey we directly link iridium ir anomalies in new jersey to the mass extinction of marine plankton marking the cretaceous paleogene k pg boundary we confirm previous reports of an ir anomaly 20 cm below the extinction of cretaceous macrofauna the pinna bed with new results from a muddy sand section from tighe park freehold new jersey united states but we also show that ir anomalies correlate with marine mass extinctions at three other clay rich new jersey sections thus we attribute the anomaly at freehold to the downward movement of ir and reaffirm the link between impact and mass extinction

long term seismicity of the reykjanes ridge north atlantic recorded by a regional hydrophone array summary the seismicity of the northern mid atlantic ridge was recorded by two hydrophone networks moored in the sound fixing and ranging sofar channel on the flanks of the mid atlantic ridge north and south of the azores during its period of operation 05 2002 09 2003 the northern sirena network deployed between latitudes 40 20 n and 50 30 n recorded acoustic signals generated by 809 earthquakes on the hotspot influenced reykjanes ridge this activity was distributed between five spatio temporal event clusters each initiated by a moderate to large magnitude 4 0 5 6 m earthquake the rate of earthquake occurrence within the initial portion of the largest sequence which began on 2002 october 6 is described adequately by a modified omori law aftershock model although this is consistent with triggering by tectonic processes none of the reykjanes ridge sequences are dominated by a single large magnitude earthquake and they appear to be of relatively short duration 0 35 4 5 d when compared to previously described mid ocean ridge aftershock sequences the occurrence of several near equal magnitude events distributed throughout each sequence is inconsistent with the simple relaxation of mainshock induced stresses and may reflect the involvement of magmatic or fluid processes along this deep 2000 m section of the reykjanes ridge

does ice drive early maastrichtian eustasy a large 30 40 m rapid 1 m y earliest maastrichtian sea level drop inferred from new jersey sequence stratigraphic records correlates with synchronous 18o increases in deep water benthic and low latitude surface dwelling planktonic foraminifera the coincidence of these events argues for the development of a moderate sized ice sheet during the early maastrichtian

a record of appalachian denudation in postrift mesozoic and cenozoic sedimentary deposits of the u s middle atlantic continental margin abstract the complex interplay between source terrain uplift basin subsidence paleoclimatic shifts and sea level change left an extensive sedimentary record in the contiguous offshore basins of the u s middle atlantic margin salisbury embayment baltimore canyon trough and hatteras basin isopach maps of 23 postrift lower jurassic to quaternary a allostratigraphic units coupled with a revised stratigraphic framework reveal that tectonism by regulating sediment supply accumulation rate dominated the interplay of forcing mechanisms tectonic pulses are evidenced by abruptly accelerated sediment accumulation marked latitudinal shifts in the location of depocenters and regional changes in lithofacies relatively rapid tectonic subsidence during the early and middle jurassic history of the basins may have enhanced sediment accumulation rates beginning in the late jurassic however subsidence rates decreased significantly though occasional short pulses of subsidence may have effected relative sea level rises sea level change heavily influenced the distribution and redistribution of sediments one they reached the basins and paleoclimate regulated the relative abundance of carbonates and evaporites in the basins we conclude that source terrains of the central appalachian highlands were tectonically uplifted intensely weathered and rapidly eroded three times since the late triassic 1 early to middle jurassic aalenian to callovian 2 mid early cretaceous barremian and 3 late cenozoic middle miocene intervals of tectonic quiescence following these three tectonic pulses provided conditions suitable for the formation of regional erosion surfaces geomorphic features commonly reported to characterize the central appalachian highlands this series of three irregularly spaced tectonic quiescent cycles does not however match the traditional four cycle concept of post triassic appalachian peneplanation

segmentation volcanism and deformation of oblique spreading centres a quantitative study of the reykjanes ridge abstract new multi beam swath bathymetry charts and high resolution side scan sonar imagery provide detailed evidence for volcanic and magmatic segmentation along the reykjanes ridge by combining these data sets we have quantified some relationships between different orders of segmentation various characteristics of volcanism and changes in tectonism along the ridge axis three orders of segmentation along the reykjanes ridge have been recognised 1 a long wavelength depth variation or swell that is related to the shoaling of the ridge towards iceland 2 intermediate wavelength rises of the order of 40 120 km and 3 a short wavelength volcanic segmentation of the order of 5 30 km the long wavelength depth variation which is probably controlled by the temperature of the underlying asthenosphere has a maximum positive deviation from a predicted depth curve that forms a break in slope at 59 60 n this feature migrated southward along the ridge at between 5 and 10 cm yr at least four times in the past 10 ma the intermediate wavelength rises which are also temporally and spatially unstable are probably related to local rayleigh taylor style asthenospheric instabilities the short wavelength segments have an evolutionary life cycle starting with eruption via fissure volcanoes and progressing by increasing magma flux to the formation of conical and then shield like volcanoes these segments are tectonically dismembered by extensional faulting following a rapid decrease in magma supply we propose a model for the construction of the volcanic layer of the reykjanes ridge which involves a cyclicity of magmatic and tectonic activity

hypercanes a possible link in global extinction scenarios bolide impacts and large scale volcanic eruptions have been proposed as possible causes of the massive extinction of life that has occurred episodically in earth s history in spite of the catastrophic disruption of the local environment that accompanies bolide impacts and volcanic eruptions it has been difficult to explain why these events sometimes lead to global extinction of species we propose that in some cases the missing link may be provided by hypercanes runaway hurricanes that are capable of injecting massive amounts of water and aerosols into the middle and upper stratosphere where they may have profound effects on atmospheric chemistry and radiative transfer hypercanes are theorized to occur when the sea surface temperature exceeds a critical threshold which may occur when sea water is locally heated by bolide impact shallow sea volcanism or possibly by overturning of superheated brine pools formed by underwater volcanic activity simulations using a convection resolving nonhydrostatic axisymmetric numerical model show that hypercanes can indeed develop when the sea surface temperature is high and that they inject large amounts of mass into the stratosphere

the northern mid atlantic and reykjanes ridges spreading center morphology between 55 50 n and 63 00 n seamarc ii and hydrosweep acoustic imagery and bathymetry reveal that the northern mid atlantic ridge mar and reykjanes ridge between 55 50 n and 63 00 n are segmented seafloor spreading centers that exhibit structural morphologies that vary with distance from iceland the northern 100 km of the mar 55 50 n 56 47 n is oriented 005 perpendicular to the spreading azimuth and contains four third order spreading segments separated along strike by right and left stepping axial discontinuities the boundary between mar and reykjanes ridge occurs at 56 47 n where the bight transform fault offsets the neo volcanic axis 15 km right laterally across a single linear fault oriented 092 this is the only transform fault between 55 50 n and 63 00 n and is inferred to have generated the bight fracture zone the reykjanes ridge lies between the bight transform and iceland s reykjanes peninsula and is oriented 30 oblique to the spreading orthogonal direction axial faults and volcanic systems on the reykjanes ridge are arranged in a right stepping en echelon pattern and display strikes intermediate between the spreading orthogonal direction and the strike of the ridge which is compatible with experimental models of oblique extension spreading segments on the northern mar and reykjanes ridge are defined structurally and bathymetrically at the smallest scale the volcanic axis is segmented into individual volcanic systems 4 45 km long which are separated along strike by intervolcano gaps or offsets these features are analogous to fourth order spreading segments documented elsewhere on the mar axial volcanic systems are superimposed on intermediate wavelength 13 65 km axial topographic highs that constitute third or second order spreading segments segment boundaries occur at axial depth maxima which correspond to offsets in the volcanic axis four primary characteristics of the spreading axis axial valley depth axial boundary fault throw relief along the neovolcanic axis and degree of inter segment structural discontinuity decrease toward the north this variation is consistent with higher crustal temperatures near iceland due to either thicker crust or elevated mantle temperatures

detailed distribution of microearthquakes along the northern reykjanes ridge off sw iceland we have obtained a snapshot image of the earthquake activity along the northern reykjanes ridge rr using a dense ocean bottom seismometer obs array the earthquakes are narrowly concentrated along the ne sw trending ridge crest the seismicity is segmented into clusters by the en echelon nne ssw trending axial volcanic systems which characterize the obliquely spreading ridge the hypocenters are concentrated at somewhat greater depths 3 7 km than on the reykjanes peninsula rp where the crust is thicker normal faulting dominates at the ridge crest the focal planes are oriented more ne sw than nne ssw i e parallel to the ridge crest and its peripheral faults rather than the trend of individual axial volcanic systems and associated faults

associations of vertebrate skeletal concentrations and discontinuity surfaces in terrestrial and shallow marine records a test in the cretaceous of montana abstract although lags of bones and teeth are commonly cited criteria for marine unconformities the consistency of the association of vertebrate fossils and discontinuity surfaces as well as the taphonomic postmortem controls on this relationship are poorly understood a field test across fluvial paralic and shallow marine facies in the campanian two medicine and judith river formations of montana indicates that the distribution of vertebrate skeletal concentrations is poorly correlated with the inferred durations of erosional and omissional hiatuses instead vertebrate concentrations associated with discontinuities of all durations tend to be patchy and closely track the abundance of fossil material in underlying and lateral facies based on the analysis of 83 measured sections we found first that erosional bases of channels and minor scours within channels yield vertebrate lags tidally influenced fluvial deposits are more productive than are upland fluvial deposits second erosional shorefa

unusual occurrence of glauconite in a shallow lagoonal environment lower cretaceous northern aquitaine basin sw france some minerals are considered to be representative of specific natural environments among them glauconite is considered to be formed in marine deep platform conditions however the term glauconitic is misused to designate green minerals formed in marine outer shelf environments x ray diffraction scanning electron microscopy and energy dispersive x ray analyses of individual green materials were carried out leading to the identification of glauconite in the purbeckian facies green glauconite grains predominantly occur as burrow fills and occasionally as faecal pellet replacements two depositional environments have been identified from bottom to top of the succession 1 an argillaceous dolomitic lagoonal sediment formed in saline shallow water 2 a marl limestone alternation deposited in a brackish water estuary the crystallochemical properties of the glauconites change abruptly these findings show that glauconite may form in coastal environments and not only in mid shelf to upper deep water platform environments as classically assumed moreover the glauconite composition changes with the chemical conditions imposed by the local environment

glaucony from the eocene of the isle of wight southern uk implications for basin analysis and sequence stratigraphic interpretation the lower middle eocene sequence of the hampshire basin which includes an alternation of sands silts and clays interpreted as fluvial to open marine deposits is exposed at two locations on the western alum bay and eastern whitecliff bay margin of the isle of wight glaucony is encountered throughout the study units sand clay alternations of lagoonal origin and estuarine channel fill sands include less than 10 of predominantly poorly evolved allochthonous glaucony shelf silts and sands generally comprise more than 20 of evolved mostly autochthonous glaucony vertical changes in maturity of glaucony confirm the trend predicted by recent models indicating an overall upward increase in the transgressive systems tracts and decrease in the highstand systems tracts with maximum values in coincidence with the condensed sections where a remarkable peak in glaucony concentration is invariably recorded comparison of glaucony characteristics at different sites of depositional sequences shows a slight increase in maturity and abundance from the proximal to the distal areas this lateral tendency is interpreted to reflect more suitable conditions for glauconitization in open marine environments than in shallow waters despite documented intrasequential variability of glaucony characteristics glaucony assemblages from distinct depositional sequences may be generally identified on the basis of more pronounced differences in maturity consequently glaucony attributes can be used as an index for characterization of third order sedimentary cycles

origin of a widespread marine bonebed deposited during the middle miocene climatic optimum bonebeds are vertebrate bioclast concentrations in beds that are local to basinal in extent the middle miocene sharktooth hill bonebed in the southeastern san joaquin basin of california is among the largest of such deposits exposed over 15 km and containing a rich assemblage of marine vertebrates with a mean density of 200 specimens m 2 it ranks among the most widespread and richest bonebeds known yet its genesis is poorly understood hypotheses for its origin and formation include mass death from shark predation volcanic or red tide poisoning accumulation from a calving ground for marine mammals and condensed accumulation over a long period of time based on multiple kinds of evidence we conclude that the bonebed formed over a protracted time interval of little to no net clastic sedimentation coincident with a significant transgressive regressive cycle between 16 and 15 ma ago during the middle miocene climatic optimum mmco geochronological constraints bracket the duration of bonebed formation to no longer than 700 ka indicating that time averaging is a critical consideration for paleoecological analyses of north pacific ocean biotic richness during the mmco

increase in basin sediment yield from landslides in storms following major seismic disturbance the landslide area along the tachia river catchment of central taiwan was investigated using the remote sensing images of various typhoon and earthquake events taken from 1996 to 2004 and the sediment discharge measured at hydrometric stations our findings indicate that 88 of the coseismic landslides triggered by the 1999 chi chi earthquake were first time occurrences after the chi chi earthquake 59 of the landslide area was reactivated during typhoon toraji and 66 during typhoon mindulle the landslides prone to reactivation were on the formations with closely spaced discontinuities it is suggested that further rock mass defects in the formations were added or opened by the earthquake and that the landslide areas continued to extend until the end of 2004 post 1999 rainstorms delivered large amounts of colluvial sediment into the main channel leading to a 2 fold increase in post seismic sediment discharge while the precipitation was only half that of the pre earthquake rate

glauconite composition and morphology shocked quartz and the origin of the cretaceous main fossiliferous layer mfl in southern new jersey u s a abstract the main fossiliferous layer mfl is a concentration of vertebrate and invertebrate fossils 20 to 30 cm thick preserved in a sequence of glauconitic sand at or near the cretaceous paleogene boundary in the new jersey usa coastal plain several hypotheses have been proposed to explain the origin and age of the mfl including marine transgression and formation of lag deposits of reworked bones and shells formation of a condensed section and attritional accumulation of fossil material and catastrophic collapse of late cretaceous ecosystems following the end cretaceous bolide impact at chicxulub we use new data on glauconite morphology concentrations geochemistry and presence of shocked quartz coupled with previous data on sedimentology taphonomy and rare earth element geochemistry of fossil vertebrates to interpret the genesis of the mfl glauconite concentration and maturity steadily increases from latest cretaceous sediments of the navesink new egypt formation through the mfl and into the paleogene upper hornerstown formation suggesting that marine transgression and decreasing sedimentation rates were a factor in the formation of the glauconite but not the mfl rare earth element patterns in fossil bones from the mfl which are acquired during fossilization are different from those of cretaceous and paleogene specimens indicating that vertebrate remains in the mfl fossilized in situ and were not reworked from older underlying units vertebrate fossils from the mfl are preserved as isolated to articulated specimens while isolated specimens would be common in a transgressive lag articulated specimens would not articulated specimens could be concentrated by attritional accumulation along a defined surface during a period of slow sedimentation but the lack of a distinct increase in glauconite maturity or concentrations of elements associated with heavy mineral accumulations at the navesink new egypt hornerstown contact or mfl which would be expected during a period of reduced sedimentation hiatus or unconformity are absent at the localities studied shocked quartz was identified in a burrow fill directly beneath the mfl at the contact of the navesink and hornerstown formations clay clasts with latest cretaceous microfossils along with reworked invertebrate fossils with infills of latest cretaceous sediment have been recovered from the mfl the association of shocked quartz mixture of isolated and articulated vertebrates with distinct rare earth signatures lack of a punctuated period of increased glauconite maturity and presence of reworked late cretaceous invertebrates and clay clasts with late cretaceous microfossils suggests that the mfl may represent a thanatocoenosis that was the direct result of environmental disturbance associated with the end cretaceous impact event at chicxulub

volcanism and hydrothermalism on a hotspot influenced ridge comparing reykjanes peninsula and reykjanes ridge iceland abstract current estimates indicate that the number of high temperature vents one of the primary pathways for the heat extraction from the earth s mantle at least 1 per 100 km of axial length scales with spreading rate and should scale with crustal thickness but up to present shallow ridge axes underlain by thick crust show anomalously low incidences of high temperature activity here we compare the reykjanes ridge an abnormally shallow ridge with thick crust and only one high temperature vent known over 900 km axial length to the adjacent subaerial reykjanes peninsula rp which is characterized by high temperature geothermal sites confined to four volcanic systems transected by fissure swarms with young holocene volcanic activity multiple faults cracks and fissures and continuous seismic activity new high resolution bathymetry gridded at 60 m of the reykjanes ridge between 62 30 n and 63 30 n shows seven axial volcanic ridges avr that based on their morphology geometry and tectonic regime are analogues for the volcanic systems and fissure swarms on land we investigate in detail the volcano tectonic features of all mapped avrs and show that they do not fit with the previously suggested 4 stage evolution model for avr construction instead we suggest that avr morphology reflects the robust or weak melt supply to the system and two or more eruption mechanisms may co exist on one avr in contrast to 4 stage evolution model our interpretations indicate that unlike on the reykjanes peninsula faults on and around avrs do not cluster in orientation domains but all are subparallel to the overall strike of avrs orthogonal to spreading direction high abundance of seamounts shows that the region centered at 62 47 n and 25 04 w between avr 5 and 6 is volcanically robust while the highest fault density implies that avr 1 and southern part of avr 6 rather undergo period of melt starvation based on our observations and interpretations we expect all of the avrs on reykjanes ridge to be hydrothermally active but morphological and hydrographic settings of this ridge may cause hydrothermal plumes to be quickly dispersed and diluted due to exposure to strong bottom currents therefore combined ctd and autonomous vehicles surveys are probably the most efficient methods for hydrothermal exploration along the reykjanes ridge