some aspects of the seismicity associated with the 1982 eruption of el chichon volcano chiapas mexico we review the different phases of the seismicity related to the 1982 eruption of el chichon volcano chiapas mexico the pre eruption seismicity was already anomalous by late 1980 became significant by late 1981 and increased towards 28 march 1982 when the first eruptive event occurred a noticeable feature within the 7 day period of unrest is the occurrence of three earthquake swarms before the devastating explosions of 3 and 4 april 1982 local time the periodicity and appearance of the swarms close to the time of maximum tidal strain suggests a large overpressure in the magmatic system and the triggering of the events by the earth tides the post eruption seismicity occurred mostly in a radius 5 km from the crater and a depth range 11 to 15 km suggesting that this region was a deeper reservoir of the erupted magma

some regularity in the process of re awakening of andesite and dacite volcanoes specific features of the 1982 el chichon volcano mexico reactivation el chichon volcano is an andesite stratovolcano in southern mexico it erupted in march 1982 after about 550 years of quiescence the 1982 eruption of el chichon has not been followed by the growth of a lava dome within the newly formed crater this is rather anomalous since the construction of a new dome after the destruction of an old one is a common process during the eruptions at andesite and dacite volcanoes to discuss this anomalous aspect of the el chichon eruption some regularity in the process of re awakening of dormant here defined as a period of quiescence of more than 100 years andesite and dacite volcanoes are studied based on the seismic activity recorded at the volcanoes bezymianny mount st helens el chichon unzen pinatubo and soufriere hills three stages were identified in the re awakening activity of these volcanoes 1 preliminary seismic activity leading up to the first phreatic explosion 2 activity between the first and the largest explosions 3 post explosion dome building process the eruptions were divided into two groups low vei volcanic explosivity index and the long duration stage 1 events unzen 1991 and soufriere hills volcano 1995 and high vei and the short duration stage 1 events bezymianny 1956 mount st helens 1980 el chichon 1982 and pinatubo 1992 the comparative analysis of the seismo eruptive activity of two eruptions of the second group the 1980 of mt st helens and the 1982 of el chichon produced an explanation the absence of new dome building during the 1982 eruption of el chichon volcano it may be explained in terms of the unusually rapid emission of gas and water from the magmatic and hydrothermal system beneath the volcano during a relatively short sequence of large explosions that could have sharply increased the viscosity of the magma making impossible its exit to the surface

major and trace element geochemistry of neutral and acidic thermal springs at el chichon volcano mexico implications for monitoring of the volcanic activity abstract four groups of thermal springs with temperatures from 50 to 80 c are located on the s sw w slopes of el chichon volcano a composite dome tephra edifice which exploded in 1982 with a 1 km wide 160 m deep crater left very dynamic thermal activity inside the crater variations in chemistry and migration of pools and fumaroles drastic changes in the crater lake volume and chemistry contrasts with the stable behavior of the flank hot springs during the time of observations 1974 2005 all known groups of hot springs are located on the contact of the basement and volcanic edifice and only on the w sw s slopes of the volcano at almost same elevations 600 650 m asl and less than 3 km of direct distance from the crater three groups of near neutral ph 6 springs at sw s slopes have the total thermal water outflow rate higher than 300 l s and are similar in composition the fourth and farthest group on the western slope discharges acidic ph 2 saline 10 g kg of cl water with a much lower outflow rate water rock interaction modeling of main types of the el chichon thermal waters using regular log q k graphs saturation indices vs temperature showed maximum equilibrium temperature slightly higher than 200 c acidic waters are equilibrated with some clay minerals at about 120 c three main sources of the salinity of thermal water are suggested on the basis of mixing plots and isotopic data a magmatic source for co2 boron sulfur and a limited part of cl volcanic rock source for the major cations and trace elements the oil bearing evaporitic basement source oil field brine for nacl br a part of ca and some trace elements all flank thermal springs end up in the river rio magdalena that has a variable seasonal flow rates from 4 to 20 m3 s any changes in the chemistry of springs must notably change the composition of the streams draining hot springs and eventually rio magdalena a monthly geochemical monitoring of rio magdalena and streams draining main hot springs would be a useful tool for surveying the activity of the volcano

intrusive reawakening of el chichon volcano prior to its holocene eruptive hyperactivity abstract el chichon volcano in southeastern mexico chiapas has produced compositionally homogeneous trachyandesite throughout its ca 372 kyr eruptive history but crystal scale heterogeneity reveals a complex interplay between magmas generated and stored at different crustal levels high sensitivity ion microprobe 238u 230th zircon dating from the last two eruptions of el chichon 1982 and 550 bp demonstrates that most zircon crystallized between 0 and ca 40 ka few zircon crystals date back to ca 130 kyr and none to the middle pleistocene phase of eruptions trace elements and oxygen isotope variations in zircon indicate fairly stable conditions in the magma chamber between ca 20 and 130 ka with average ti in zircon temperatures estimated at 712 c and 18o values of 6 6 however excursions to high ti in zircon temperatures and high 18o values in zircon occurred at ca 24 ka these excursions also mark the onset of subsequent progressive changes to occasionally higher ti in zircon temperatures lower 18o values and more primitive magma compositions e g high eu eu zr hf and th u systematic rim ward decrease in 18o is recorded by juvenile zircon domains which quasi continuously crystallized for up to 30 kyr prior to eruption textural relationships and o isotopic variations within single zircon crystals are thus evidence for magma recharge causing initial resorption of xenocrystic zircon rapid zircon re saturation driven by local supersaturation and effective magma mixing with sediment contaminated high 18o melts from a boundary layer at the contact of the magma reservoir to country rock initial thermal and compositional defrosting of an intermediate boundary layer and its crystal cargo may have been rapid due to the brief duration of high temperature recharge events as evidenced by the preservation of zircon xenocrysts the delay of at least 12 kyr between major recharge episodes recorded by zircon and the onset of holocene eruptions at brief recurrence intervals suggests that frequent eruptions only started when trachybasaltic magma recharge continued or intensified during the holocene

a review of the biogeochemical controls on the occurrence and distribution of polycyclic aromatic compounds pacs in coals abstract the organic matter in coal contains polycyclic aromatic compounds pacs of varying quantities in diverse soluble and insoluble forms pacs in coal are of special interest for organic geochemical studies because they have been successfully used as biological marker compounds biomarkers and indicators of thermal maturity in addition they could provide critical information to understand the structural and compositional evolution of the coal organic matters during coalification and to predict pac releasing characteristics during coal utilization the main purpose of this paper is to provide a critical review on the current state of knowledge on the potential use of pac composition to understand the underlying biogeochemical factors that control pac occurrence and distribution in coal the published pac data of world coal are first compiled according to their ranks natural coke anthracite semi anthracite bituminous coal low volatile bituminous coal medium volatile bituminous coal high volatile bituminous coal sub bituminous coal lignite countries brazil canada china france germany japan usa formation periods carboniferous permian jurassic cretaceous early middle cenozoic then the biogeochemical factors affecting the occurrence and distribution of pacs in coal including biogenic precursor materials coal rank maceral composition depositional environment and geological settings are comprehensively reviewed the results show that the geochemical parameters of pacs in coal are robust tools to trace the coalification processes from the molecular perspectives and to understand the corresponding biogeochemical process e g depositional environment geological settings igneous intrusion occurring during coal formation

energy partition in the 1982 eruption of el chichon volcano chiapas mexico abstract the 1982 eruption of el chichon volcano chiapas mexico has been extensively investigated from various standpoints including seismicity tephra geology atmospheric effects and tectonic structure in this paper the six largest of a series of explosions are isolated considering various sources of information then the seismic energy released by volcanic earthquakes and tremor is estimated using seismograms of low magnification in order to avoid saturation of seismic wave amplitudes the explosion kinetic energy is evaluated by two methods one by the initial velocity of the ejecta and the other by the air wave data recorded at a distance both the results are roughly coincident the thermal energy is classified into two components that transferred by volcanic ejecta and that consumed by convective clouds the thermal energy released by the explosions is very large compared with that of mechanical energy such as the seismic energy and explosion kinetic energy after the last major explosion of april 4 a type volcanic earthquakes swarmed till the end of april their occurrence rate decreased with time in an aftershock like sequence these earthquake swarms may have been due to post eruptive readjustment of the stress field within and near the volcano such seismic activity contrasts with other examples of similar major eruptions which were followed by growth of lava domes in the new craters after the paroxysmal eruptions the 1982 eruption of el chichon volcano has not been followed by the growth of a lava dome within the newly formed crater

the effect of maturity on the relative abundances of cadalene and isocadalene in sediments from the gippsland basin australia abstract two sedimentary sequences from the gippsland basin australia have been analysed for cadelene and 3 isopropyl 1 6 dimethylnaphthalene isocadalene the relative abundance of these compounds changes with increasing depth maturity of the sediments and is associated with an increase in the abundance of 1 6 dimethylnaphthalene relative to other dimethylnaphthalene isomers these changes have been attributed to dealkylation and isomerization reactions of cadalene in the sediments because analogous changes have been demonstrated in laboratory heating experiments in which cadalene was converted into a mixture containing mainly 1 6 dimethylnaphthalene and isocadalene when heated in the presence of aluminum smectite the ratio of isocadalene and cadalene may be a useful maturity parameter for some sediments and crude oils which contain these compounds

a 550 year old plinian eruption at el chichon volcano chiapas mexico explosive volcanism linked to reheating of the magma reservoir 1 some 550 years ago 1320 1433 a d a powerful plinian eruption at el chichon volcano in southern mexico produced a widespread pumice fall deposit we subdivided the deposit into three parts on the basis of structural and textural characteristics pumice lithology and density granulometry and petrologic geochemical attributes the deposit covers an area of 1500 km2 within the 1 cm isopach and has a minimum estimated bulk volume of 2 8 km3 1 1 km3 dense rock equivalent dre its eruptive column reached an altitude of 31 km consideration of field evidence the presence and nature of mafic enclaves and chemical data strongly suggest that the 550 year b p eruption is linked with the intrusion of a high temperature basaltic magma into preexisting but stagnated trachyandesitic magma beneath el chichon thorough mixing of the two magmas produced a compositionally uniform hybrid trachyandesite magma average sio2 55 3 wt which subsequently underwent crystal growth and gas exsolution ultimately overpressurizing the zoned magmatic system to erupt explosively on the basis of el chichon s known eruptive history the intrusion mixing event occurred sometime after the 900 year b p eruption the hybrid magma had a preeruption temperature of 820 830 c and was water undersaturated 5 6 wt h2o at pressures of 2 2 5 kbar

petrographic examination of low rank coals from saskatchewan and british columbia canada including reflected and fluorescent light microscopy sem and laboratory oxidation procedures the response to oxidation of eight coals of lignite and subbituminous rank from saskatchewan and hat creek british columbia was studied by means of maceral distribution fluorescence and scanning electron microscopy sem the oxidizing agent used was schulze s solution with some modification of reaction time from that normally employed in palynological maceration these eight samples were chosen to represent different macroscopically described lithotypes maceral analysis indicates that the huminite macerals behave differently when oxidized densinite seems to be the most susceptible to destruction along with gelinite humotelinite eu ulminite and texto ulminite is more resistant and in four of the eight samples shows a slight increase in concentration oxidation increases the relative content of liptinite along with some of the inertinite macerals fusinite and semifusinite among the liptinite macerals resinite appears to be preferentially concentrated suggesting that the modified oxidation pr

deposition temperature of some pdc deposits from the 1982 eruption of el chichon volcano chiapas mexico inferred from rock magnetic data abstract thermal remanent magnetization trm analyses were carried out on lithic fragments from two different typologies of pyroclastic density current pdc deposits of the 1982 eruption of el chichon volcano in order to estimate their equilibrium temperature tdep after deposition the estimated tdep range is 360 400 c which overlaps the direct measurements of temperature carried out four days after the eruption on the pdc deposits this overlap demonstrates the reliability of the trm method to estimate the tdep of pyroclastic deposits and to approximate their depositional temperature these results also constraint the time needed for reaching thermal equilibrium within four days for the studied pdc deposits in agreement with predictions of theoretical models sedimentological analysis demonstrates that different thickness of aggrading granular dominated pulses does not affect significantly the estimated tdep for the two studied pdcs the component analysis highlights how the entrapment of a significant amount of pre heated lithic fragments from the dome and the conduit walls reduced the cooling of the pyroclastic mixture

reappraisal of the 1982 eruptions of el chichon volcano chiapas mexico new data from proximal deposits additional data from proximal areas enable a reconstruction of the stratigraphy and the eruptive chronology of phases iii and iv of the 1982 eruption of el chichon volcano phase iii began on 4 april at 0135 gmt with a powerful hydromagmatic explosion that generated radially fast moving 100 ms 1 pyroclastic clouds that produced a surge deposit s1 due to the sudden reduction in the confining pressure the process continued by tapping of magma from a deeper source causing a new explosion the ejected juvenile material mixed with large amounts of fragmented dome and wall rock which were dispersed laterally in several pulses as lithic rich block and ash flow f1 partial evacuation of juvenile material from the magmatic system prompted the entrance of external water to generate a series of hydromagmatic explosions that dispersed moisture rich surge clouds and small volume block and ash flows iu up to distances of 3 km from the crater the eruption continued by further decompression of the magmatic system with the ensuing emission of smaller amounts of gas rich magma which with the strong erosion of the volcanic conduit formed a lithic rich plinian column that deposited fallout layer b associated with the widening of the vent an increase in the effective density of the uprising column took place causing its collapse block and ash flows arising from the column collapse traveled along valleys as a dense laminar flow f2 in some places flow regime changes due to topographic obstacles promoted transformation into a turbulent surge s2 which attained minimum velocities of approximately 77 ms 1 near the volcano the process continued with the formation of a new column on 4 april at 1135 gmt phase iv that emplaced fall deposit c and was followed by hydromagmatic explosions which produced pyroclastic surges s3

evolution of the seismic activity from the 1982 eruption of el chichon volcano chiapas mexico we analyzed more than 1700 earthquakes related to the 1982 eruption of el chichon volcano in southern mexico the data were recorded at specific periods throughout the whole eruptive interval of march to april 1982 by three different networks the seismic activity began several months before the first eruption on 28 march during this period the seismicity consisted of hybrid and long period shallow earthquakes most likely related to processes of faulting fracturing and fluid movement underneath the volcano the foci of events occurring before the eruption circumscribe an aseismic zone from approximately 7 to 13 km below the volcano after the eruption the seismic activity consisted of tectonic type earthquakes that peaked at 1200 events h this later activity occurred over a wide range of depths mostly between 5 and 20 km that includes the former aseismic zone and is roughly limited by the major tectonic faults in the area

the slow boiling of magma chambers and the dynamics of explosive eruptions abstract explosive eruptions are fed by shallow magma chambers and are mainly characterized by a water saturated magma a temporal increasing eruption rate and deep seismicity following the later stages of eruption we develop two simple physical models based on the decompression of a water saturated magma and the non equilibrium growth of bubbles that drives the magma out of the chamber the eruption ends when sufficient decompression is attained to cause magma chamber collapse and restoration of the initial pressure conditions the first model considers a single step decompression the second one a multi step decompression the models predict that the duration of the eruptive phase is mainly controlled by the bubble number densities and the initial decompression pressure decrease of the order 0 1 1 mpa results in eruption lasting days hours the erupted volume magnitude and eruption rate intensity are mainly controlled by the volume of the magma chamber by the strength of the rocks surrounding the reservoir and the physical properties of the magma water diffusivity and bubble density we simulated the eruptions at mt st helens 1980 and vesuvius 79 ad the models correctly predict the duration and evolution of the eruptions with the initial phases characterized by a slow eruption rate with the formation of a plinian column and the subsequent increase resulting eventually in pyroclastic flow activity

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

the 1982 eruptions of el chichon volcano mexico stratigraphy of pyroclastic deposits abstract following a repose period of 500 to 600 years el chichon volcano in se mexico erupted explosively during the months of march and april 1982 three major eruptions involving trachyandesite magma injected ash into the stratosphere on 29 march at 0515 gmt and on 4 april at 0139 and 1110 gmt the first major eruption generated only tephra fall which was dispersed ene in the troposphere over the yucatan peninsula and wsw in the stratosphere towards the pacific ocean the second eruption produced tephra fall and pyroelastic surges and pyroclastic flows by repeated collapse of a lithicrich eruption column the surge and flow activity devastated a roughly circular area 153 km 2 around el chichon to a distance of about 6 km from the vent nine villages within the zone were either partially or completely destroyed and loss of human life was perhaps as high as 2000 pyroclastic flows and surges were also generated during the third eruption although ash fall was the primary activity as a result of both the second and third eruptions tephra was transported ene in the troposphere and wsw in the stratosphere the total volume of material ejected during the three major eruptions 0 50 km 3 d r e is represented by tephra fall 0 37 km 3 pyroclastic surges 0 09 km 3 and pyroclastic flows and debris flows 0 04 km 3 as a result of the eruptions a new 1 km wide and 300 m deep crater was formed by the disruption and excavation of a pre existing summit dome

depositional environments of late cretaceous gongila and fika formations chad bornu basin northeast nigeria abstract organic geochemical and palynofacies studies of 172 ditch cuttings samples of possible source rock shales from the late cretaceous gongila and fika formations in the chad basin of ne nigeria were carried out to determine their paleoenvironments of deposition although dominated by amorphous organic matter c s ratios and molecular parameters suggest the mostly organic lean shales toc contents typically below 1 5 were deposited in a normal marine environment levels of oxygenation influenced by water depth in the depositional environment appear to control organic richness and quality of the dark grey shales the organic rich toc 2 0 upper part of the fika formation was deposited under anoxic conditions during the late cretaceous and could represent an oceanic anoxic event mature intervals where such conditions prevailed would have generated liquid hydrocarbon although none were sampled here a trend of increasing organic richness towards the central part of the larger chad basin observed in this and other studies supports the development of organic rich marine shales average toc contents of 2 3 of equivalent age in the termit basin where water depth would have been deeper and oxygen conditions at levels that permitted preservation of marine organic matter

geochemical characteristics of tertiary coal bearing source rocks in xihu depression east china sea basin abstract this study aims at investigating hydrocarbon generation potential and biological organic source for the tertiary coal bearing source rocks of pinghu formation middle upper eocene in xihu depression east china sea shelf basin another goal is to differentiate coal and mudstone with respect to their geochemical properties the coal bearing sequence has a variable organofacies and is mainly gas prone the coals and carbonaceous mudstones in comparison with mudstones have a higher liquid hydrocarbon generation potential as reflected by evidently higher hi values averaging 286 mg hc g c and h c atomic ratios round 0 9 the molecular composition in the coal bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes dominant c29 sterane over c27 and c28 homologues and high amount of terrigenous related aromatic biomarkers such as retene cadalene and 1 7 dimethylphenanthrene indicating a predominantly terrigenous organic source the source rocks show high pr ph ratios ranging mostly from 3 5 to 8 5 and low mdbts mdbfs ratios

timing and duration of the central atlantic magmatic province in the newark and culpeper basins eastern u s a abstract new major and trace element data and 40ar 39ar plateau ages constrain the timing duration and time related geochemical evolution of the central atlantic magmatic province in the u s a newark and culpeper basins and refine correlations with basaltic lava flows from other late triassic early jurassic circum atlantic basins the precise statistically robust 40ar 39ar plateau ages were obtained on biotite and on fresh plagioclase and calculated using the latest 40k decay constants these ages are supported by a general consistency of the ca k calculated from 37ar 39ar of the plateau steps and the ca k obtained by detailed electron microprobe analyses on plagioclase phenocrysts the ages of five analyzed basalt lava flows from all three lava flow units in the newark basins and the ages of two sill samples are indistinguishable indicating a brief magmatic peak phase at 201 8 0 7 ma recalibrated 40ar 39ar plateau ages from the entire province indicate a near synchronous onset and peak volcanic activity at the triassic jurassic boundary within the circum atlantic basins from the u s a canada and morocco the early erupted magmas moroccan lower to upper basalts the fundy basin north mountain basalt and orange mountain and equivalent u s a flows yield an enriched geochemical signature e g with relatively high la yb whereas late magmas in the u s a hook mountain and hampden basalts and morocco recurrent basalt yield relatively depleted geochemical compositions low la yb a slight but significant age difference for eruption of hook mountain and hampden basalts 200 3 0 9 ma and recurrent basalts 198 2 1 1 ma is interpreted as evidence of a diachronous northward rift drift transition during break up of pangea our data indicate also a prolonged intrusive sequence that continued until about 195 ma at the palisades sill and is consistent with sporadic late camp magmatism for dykes from the south eastern u s a and for intrusions from guinea

aromatic hydrocarbon biomarkers in terrestrial organic matter of devonian to permian age abstract this paper presents the results of a detailed study on the occurrence and distribution of alkylnaphthalenes and alkylphenanthrenes in 39 coal and sediment samples from the late palaeozoic containing predominantly terrestrial organic matter most of the samples represent the euramerian flora realm and originate from locations beyond the variscan front in eastern northern and central europe i e especially england and the moscow basin the samples are of relatively low maturity 0 32 to 1 80 rr and consist mainly of mixtures of type iii and ii kerogen quantification of the c0 to c4 naphthalenes and the c0 to c4 phenanthrenes showed that these compound classes were highly abundant in all samples aromatic hydrocarbon maturity parameters in general are in good agreement with measured vitrinite reflectance values 1 2 7 trimethylnaphthalene an assumed diagenetic product of oleanane type biomarkers was present in all investigated samples this observation provides evidence that oleanane type lipids were biosynthesised by organisms predating the evolution of angiosperms or that assumed formation pathways for 1 2 7 trimethylnaphthalene are insecure 1 2 8 trimethylphenanthrene was significantly enriched in samples from the permian and the one sample from the devonian investigated in this study the precursor s of 1 2 8 trimethylphenanthrene therefore may have been produced by organisms which were least abundant in the carboniferous depositional environments represented by our samples

occurrence and geochemical significance of 1 2 5 6 tetramethylnaphthalene analysis of aromatic hydrocarbon fractions of selected coal and shale samples reveals the predominance of two specific polyalkylnaphthalenes which have been identified as 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnaphthalene the maturity of the samples is such that the source effect on the formation of individual molecules from biological precursors is expected to be recognisable these alkylnaphthalenes are thought to be diagenetically derived from pentacyclic triterpenoids via 8 14 seco triterpenoids which are also detectable in some of the samples investigated it is proposed that 1 2 5 6 tetramethylnaphthalene in the coal samples is formed by cleavage and methyl shift reactions from geminal c 4 methylated triterpenoids which contain a leaving group in position 3 for the shale samples degradation of monoaromatic secohopanoids must be considered as an alternative pathway

the effects of varying tissue preservation on the aliphatic hydrocarbons within a high volatile bituminous coal detailed petrographic analyses of the barrett coal an upper permian high volatile bituminous coal in the hunter coalfield australia reveal cycles of peat formation defined by the tissue preservation index these cycles correspond to coal plies that are separated by dirtbands the petrographic cyclicity is also manifested by a corresponding stratigraphic cyclicity in the biomarker composition of the extracted aliphatic hydrocarbons higher amounts of hopanes and lower carbon preference index values n c22 to n c30 show greater bacterial contribution in samples characterised by low values of tissue preservation index the inherited biodegradation signal from the diagenetic stage has now been partially diluted by the generation of new hydrocarbons from the macromolecule the c31 22s22s 22r hopane and c29 20s20s 20r sterane ratios show least variation through the seam the homohopane epimer ratios have attained equilibrium whilst the hopane moretane ratios are typical of coals with unsupressed vitrinite reflectance of 0 65 however other hopane and sterane maturity ratios appear slightly affected by the degree of preservation of organic matter the c29 and c29 20s20s 20r sterane ratios were not found to be useful for maturity comparisons with other coals because of the low values average 0 18 and 0 43 respectively due to heating rate effects these and other biomarker distributions are syndepositional features of the coal precursor and therefore are controlled by the environmental conditions during the stage of peat accumulation and its subsequent coalification all these changes are evident in a coal member only 2 2 m in thickness the petrographic and geochemical evidence suggest that the environmental affinity of the barrett coal is that of a delta plain depositional setting

volcano tectonic earthquakes a new tool for estimating intrusive volumes and forecasting eruptions abstract we present data on 136 high frequency earthquakes and swarms termed volcano tectonic vt seismicity which preceded 111 eruptions at 83 volcanoes plus data on vt swarms that preceded intrusions at 21 other volcanoes we find that vt seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from vei 0 to ultraplinian vei 6 at such previously long dormant volcanoes because large eruptions occur most commonly during resumption of activity at long dormant volcanoes vt seismicity is an important precursor for the earth s most dangerous eruptions vt seismicity precedes all explosive eruptions of vei 5 and most if not all vei 4 eruptions in our data set surprisingly we find that the vt seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption and rarely if ever starts beneath the eruption site itself the distal vt swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance beyond which hypocenter depths level out we summarize several important characteristics of this distal vt seismicity including swarm like nature onset days to years prior to the beginning of magmatic eruptions peaking of activity at the time of the initial eruption whether phreatic or magmatic and large non double couple component to focal mechanisms most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the vt seismicity from log10 v 0 77 log moment 5 32 with volume v in cubic meters and seismic moment in newton meters because the cumulative seismic moment can be approximated from the size of just the few largest events and is quite insensitive to precise locations the intruded magma volume can be quickly and easily estimated with few short period seismic stations notable cases in which distal vt events preceded eruptions at long dormant volcanoes include nevado del ruiz 1984 1985 pinatubo 1991 unzen 1989 1995 soufriere hills 1995 shishaldin 1989 1999 tacana 1985 1986 pacaya 1980 1984 rabaul 1994 and cotopaxi 2001 additional cases are recognized at frequently active volcanoes including popocateptl 2001 2003 and mauna loa 1984 we present four case studies pinatubo soufriere hills unzen and tacana in which we demonstrate the above mentioned vt characteristics prior to eruptions using regional data recorded by neic we recognized in near real time that a huge distal vt swarm was occurring deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant sulu range new britain island papua new guinea that it was likely to lead to eruptive activity and warned rabaul volcano observatory days before a phreatic eruption occurred this confirms the value of this technique for eruption forecasting we also present a counter example where we deduced that a vt swarm at volcan cosiguina nicaragua indicated a small intrusion insufficient to reach the surface and erupt finally we discuss limitations of the method and propose a mechanism by which this distal vt seismicity is triggered by magmatic intrusion

deposit temperature of pyroclastic density currents emplaced during the el chichon 1982 and colima 1913 eruptions new data on the pyroclastic density current pdc deposit temperature t dep are provided for two prominent eruptions of mexican volcanoes of the twentieth century the 1982 eruption of el chichon and the 1913 eruption of colima in spite of similar lithofacies magma composition and pre eruptive conditions the t dep of the pdcs from the 1982 el chichon and 1913 colima eruptions differ significantly with intervals of t dep of 360 420 c and 250 330 c respectively these new data emphasize that a full understanding of the physical mechanisms responsible for equilibrium temperature attainment within a pyroclastic deposit has not yet been realized the t dep measured for el chichon pdc deposits confirm the preliminary data published elsewhere while colima magnetic temperatures provide different values to those published previously

multiple paleosols of the late albian boulder creek formation british columbia canada fifteen lithified paleosols closely spaced in vertical sequence occur in the top 90 m of the late albian boulder creek formation in the foothills of northeastern british columbia canada the paleosols have well developed profiles 0 5 to 1 5 m thick including a b and c horizons the paleosols are characterized by their grey colour cutans vertical roots peds spherulitic siderite and absence of sedimentary structures the paleosols formed during a period when one or more basin wide unconformities occurred as a result of either eustatic sea level fluctuations or local tectonic events these unconformities represent the terrestrial record of a lowered base level which caused valley incision and decreased rates of sedimentation on the incised flood plain the climate was humid to subhumid overall the environment in which these soils developed was of low relief and subject to little erosion the water table was high for part of the year but there is also evidence of periodic drying and oxidation of organic debris cumulatively the paleosols in this interval may represent 150000 yr of non deposition

comment on synchrony between the central atlantic magmatic province and the triassic jurassic mass extinction event by whiteside et al 2007 a dipartimento di geoscienze universita di padova and igg cnr via giotto 1 35100 padova italy b laboratoire des sciences de la terre umr cnrs 5570 ecole normale superieure de lyon and ucbl 46 allee d italie 69364 lyon france c department of the geophysical sciences 5734 s ellis ave hgs 237 university of chicago chicago il 60637 usa d dipartimento di scienze della terra universita di perugia piazza universita 1 06100 perugia italy e cea uvsq umr 1572 lsce orme orme des merisiers 91191 gif sur yvette cedex france f berkeley geochronology center 2455 ridge road ca94709 berkeley usa and department of earth and planetary science university of california berkeley usa g unsa umr geosciences azur parc valrose 06108 nice france h department of geology cadi ayyad university boulevard prince moulay abdellah marrakech morocco i section des sciences de la terre universite de geneve 13 rue des maraichers 1205 geneve switzerland

saturated and aromatic diterpenoids and triterpenoids in eocene coals and mudstones from china several series of saturated diaromatic triaromatic c ring cleaved and triaromatic diterpenoids and triterpenoids have been detected in 4 immature coal and mudstone samples a number of these compounds appear to represent intermediates in a series of postulated pathways for progressive aromatization of biogenic diterpenoids and triterpenoids diagenetic pathways for the formation of tricyclic aromatic hydrocarbons from abietane and pimarane type diterpenoid precursors and for the formation of diaromatic triaromatic c cleaved and triaromatic hydrocarbons from amyrin and other triterpenoid precursors are proposed saturated and aromatized abietanes pimaranes and phyllocladanes which are the most abundant compounds in all 4 samples indicate a predominant higher plant input which can be related to the coniferales group but not to individual plant families amyrin and other triterpenoid derived triaromatic and triaromatic c ring cleaved hydrocarbons with triterpenoid structures are thought to be characteristic for angiosperms the relative concentrations of the triaromatic and triaromatic c ring cleaved hydrocarbons are higher in samples 9602 mudstone and 9603 coal than samples 9601 coal and 9604 mudstone indicating samples 9602 mudstone and 9603 coal contain relatively more angiosperm derived organic matter than samples 9601 coal and 9604 mudstone the distribution patterns and the relative concentrations of saturated and aromatic diterpenoids and triterpenoids thus are valuable markers for the determination of the relative contents of biological sources of organic material in geological samples

trimethylnaphthalenes in crude oils and sediments effects of source and maturity abstract three sedimentary sequences and a number of crude oils have been analysed for trimethylnaphthalenes tmns using gas chromatography the sediments were found to contain enhanced relative abundances of 1 2 5 tmn and 1 2 7 tmn in samples of cretaceous age and younger this was especially pronounced in lower maturity sediments containing type iii organic matter older samples containing type iii organic matter were found to contain enhanced relative abundances of 1 2 5 tmn and lower relative abundances of 1 2 7 tmn 1 2 7 tmn appears to be derived directly from the structural degradation of oleanane type triterpenoids present in angiosperms and as such is proposed as a marker for this class of plant and indirectly therefore also for samples deposited since the early cretaceous the crude oils have been classified according to their trimethylnaphthalene compositions this classification enables crudes of higher plant origin to be identified and to be further classified according to whether the organic matter pre dated or post dated the evolution of angiosperms

comparison of resinite related aromatic biomarker distributions in cretaceous tertiary coals from canada and germany a set of 13 cretaceous tertiary coals from western canadian coal deposits and two cretaneous coals from the southern part of the lower saxony basin of germany have been investigated using microscopial and organic geochemical methods the coals are in the ranl range of lignite to medium volatile bituminous 0 37 1 13 rr petrographically the coals are characterized by varying proportions in vitrinite inertinite and liptinite groups in most of the coals resinite constitutes the major liptinite component both of the german wealden coals are composed exclusively of conifer needles gc ms analyses indicate differences in the composition of resin related molecular biomarkers comparing samples from both deposits in the canadian coals of moderate rank 0 4 0 8 rr resin related napthalene derivatives are associated with tricyclic aromatic hydrocarbons such as retene abieta 6 8 11 13 tetraene simonellite and c5 phenanthrene samples higher in rank about 1 1 rr provide fully aromatized and partly desalkylated phenanthrene homologues generation of 1 methylphenanthrene from retene during maturation affects molecular rank parameters like mpr and mpi 1 additionally an intra seam homogenization of resin derived aromatic hydrocarbon is observed in comparison the german wealden coal extracts are dominated by bicyclic aromatic hydrocarbons and they are poor in tricyclic hydrocarbons analyses of hand picked macerals resinites and cutinites by thermodesorption coupled to gc ms indicate the presence of two potential sources for the naphthalene derivatives c4 tetralin is primarily associated with the resins of abietites linkii 1 2 5 trimethylnaphthalene and 1 2 5 6 tetramethylnapthhalene are probably derived from the fluorinite filling of the conifer needles

earthquake classification location and error analysis in a volcanic environment implications for the magmatic system of the 1989 1990 eruptions at redoubt volcano alaska abstract determination of the precise locations of seismic events associated with the 1989 1990 eruptions of redoubt volcano posed a number of problems including poorly known crustal velocities a sparse station distribution and an abundance of events with emergent phase onsets in addition the high relief of the volcano could not be incorporated into the hypoellipse earthquake location algorithm this algorithm was modified to allow hypocenters to be located above the elevation of the seismic stations the velocity model was calibrated on the basis of a posteruptive seismic survey in which four chemical explosions were recorded by eight stations of the permanent network supplemented with 20 temporary seismographs deployed on and around the volcanic edifice the model consists of a stack of homogeneous horizontal layers setting the top of the model at the summit allows events to be located anywhere within the volcanic edifice detailed analysis of hypocentral errors shows that the long period lp events constituting the vigorous 23 hour swarm that preceded the initial eruption on december 14 could have originated from a point 1 4 km below the crater floor a similar analysis of lp events in the swarm preceding the major eruption on january 2 shows they also could have originated from a point the location of which is shifted 0 8 km northwest and 0 7 km deeper than the source of the initial swarm we suggest this shift in lp activity reflects a northward jump in the pathway for magmatic gases caused by the sealing of the initial pathway by magma extrusion during the last half of december volcano tectonic vt earthquakes did not occur until after the initial 23 hour long swarm they began slowly just below the lp source and their rate of occurrence increased after the eruption of 01 52 ast on december 15 when they shifted to depths of 6 to 10 km after january 2 the vt activity migrated gradually northward this migration suggests northward propagating withdrawal of magma from a plexus of dikes and or sills located in the 6 to 10 km depth range precise relocations of selected events prior to january 2 clearly resolve a narrow steeply dipping pencil shaped concentration of activity in the depth range of 1 7 km which illuminates the conduit along which magma was transported to the surface a third event type named hybrid which blends the characteristics of both vt and lp events originates just below the lp source and may reflect brittle failure along a zone intersecting a fluid filled crack the distribution of hybrid events is elongated 0 2 0 4 km in an east west direction this distribution may offer constraints on the orientation and size of the fluid filled crack inferred to be the source of the lp events

changes in hydrocarbon maturity indices with coal rank and type buller coalfield new zealand abstract the buller coalfield south island new zealand is an inverted late paleogene basin that contains middle eocene bituminous coals which exhibit considerable variation in both coal rank across basin and coal type in seam twenty two fractionated bitumen extracts of brunner coal measures coal samples from 12 drillholes were analyzed by gc and gc ms to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window 0 56 1 26 ro max the carbon preference index pristane phytane and isoprenoid n alkane ratios evolve throughout the high volatile bituminous b rank stage while other biomarker ratios 18 h 22 29 30 trisnorneohopane 17 h 22 29 30 trisnorhopane ts tm 18 h 21 h 30 norneohopane c 29 ts 17 h 21 h 30 norhopane and c 30 diahopane hopane do not show appreciable change in value until medium volatile bituminous rank various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window in particular the methylphenanthrene index and vitrinite reflectance are positively correlated over the entire bituminous rank range however subtle changes in depositional conditions variable coal type complicate these rank estimates within a given coal seam variation in cpi isoprenoid n alkane and hopane sterane ratios appear to be related to the hydrogen content of the coal while the homohopane index and the oleanane hopane ratio covary with sulfur content as with depressed vitrinite reflectance values mpi is similarly lowered in the perhydrous samples the mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted however changes in bacterial activity and community with marine incursion appear to play an important role due to these anomalies none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

organic geochemistry and petrography of tertiary coals and carbonaceous shales from argentina a series of eight tertiary coal and carbonaceous shale samples with vitrinite reflectance values between 0 50 and 0 58 were extracted fractionated and the saturated and aromatic hydrocarbons analysed for characteristic components by gc and gc ms additionally a microscopical study was undertaken in order to obtain a more precise picture of the samples under investigation the saturated hydrocarbon fractions displayed the typical n alkane distribution for coals of this rank with cpi values between 2 0 and 3 1 among the branched cyclic compounds pristane and homohopane were recognised as relevant components pointing to an oxic depositional environment detection of benzohopanes c32 c35 in the aromatic hydrocarbon fractions suggests that bacteriohopanetetrol was a significant constituent of the coal biomass taking into consideration the pr ph ratios ash contents and microscopical characteristics of the samples aspects of the possible degradation of hopanetetrol to homohopane are discussed resin derived diterpenoids with the phyllocladane and kaurane skeleton were tentatively identified and although minor compounds they are interpreted to be a sign of the contribution of podocarpaceae and araucareaceae to the coal swamp aromatic compounds were dominated by alkylnaphthalene derivatives presumably formed by c ring cleavage and aromatisation of higher plant derived pentacyclic triterpenois which were main components in the high boiling range of the fractions investigated angiosperms especially fagaceae are postulated as source for these polycyclic compounds and hence for some of the polyalkylated aromatic bicyclics detected

higher plant biomarker signatures of early eocene sediments of north eastern india abstract the biomarkers molecular fossils of paleobiota have been studied in detail from a coal bearing sequence of early eocene lakadong sandstone member of sylhet formation of upper assam basin ne india using gas chromatography mass spectrometry corresponding hydrocarbon source potential of the same unit has been studied using rock eval pyrolysis the rock eval data suggest dominant terrestrial land plant contribution i e type iii kerogen and the sediments of the section had entered the early stage of catagenesis the alkane and isoprenoid distributions are characterized by odd over even preference oep 1 1 1 2 of n alkanes and high pristane phytane ratio 2 9 7 6 which corroborate the rock eval data the distribution of aliphatic biomarkers is characterized by dominance of c24 tetracyclics over c23 tricyclics high concentration of des e hopane moderate to high c29 c30 hopane ratio extremely low oleanane index and low c35 homohopane index the extremely low oleanane index is correlated with a high degree of aromatization of oleanane skeleton favoured by acidic swampy depositional environment the presence of diterpanes at the base of the early eocene section indicates contribution from gymnosperms coniferales order of land plants whereas angiospermous biomarkers with oleanoid skeleton are also preserved this pattern subsequently evolved to angiosperm dominated towards the top of the section with no gymnosperm signature indicating possible climatic variation during the early eocene towards the top of the section presence of bicadinanes indicates contribution of dipterocarpaceae family of trees and advent of the evergreen tropical rain forest element in eastern india in early eocene similar to the pattern found in western india e g cambay and kutch basins

occurrence and palaeoenvironmental significance of aromatic hydrocarbon biomarkers in oligocene sediments from the mallik 5l 38 gas hydrate production research well canada abstract the aromatic hydrocarbon biomarker distributions of thirty oligocene sediment samples with different lithology lignite clay and sand from the japex jnoc gsc et al mallik 5l 38 gas hydrate production research well canada were analyzed using gas chromatography mass spectrometry gc ms the compositions vary with lithology indicating a change in palaeoenvironmental conditions at the time of deposition aromatic diterpenoids of the abietane type are more abundant in the lignite samples than in the clay samples and represent a gymnosperm e g conifer dominated palaeovegetation in contrast in the clay samples aromatic triterpenoids are generally preserved as major constituents indicating angiosperm dominated vegetation the sand samples contain only minor amounts of aromatic terpenoids but show a preference for diterpenoid gymnosperm markers to recognise gymnosperm versus angiosperm dominated palaeoenvironments a new ratio termed the angiosperm gymnosperm aromatic ratio agar has been developed thus the terpenoid distribution in the deltaic sediments provides information on the compositional changes in the plant community at the mallik site lignites and the hinterland clays over time concomitantly the changing dominance in the plant communities allows an insight into varying climatic conditions during the late oligocene in the area additionally the aromatic biomarker composition has been used to assess the level of thermal maturity of the organic matter in the mallik samples and indicates a prevailing immature character