the upper ordovician black shales of southern quebec canada and their significance for naturally occurring hydrocarbons in shallow groundwater abstract shale gas exploration in the st lawrence platform of southern quebec eastern canada focussed on the upper ordovician utica shale from 2006 to 2010 during which 28 wells were drilled 18 of which were fracked the st lawrence platform is thus considered as a pristine geological domain where potential environmental effects of fracking can be evaluated relative to the natural baseline conditions of the shallow aquifers in the saint edouard area southwest of quebec city it has been shown that groundwater carries variable and locally high levels of naturally occurring dissolved hydrocarbons in which thermogenic ethane and propane can be found fifteen shallow 30 147 m wells were drilled into bedrock and sampled cores and cuttings with the purpose of characterizing the shallow bedrock in a shale gas pre development context the shallow bedrock geology is made of three upper ordovician clastic formations the lotbiniere and les fonds formations are time and facies correlative with the utica shale present at a depth of 1 5 to 2 km in this area they are dominated by calcareous black shales with minor siltstone and micrite beds the nicolet formation is the youngest unit of the area and consists of gray to dark gray shales with locally abundant thick siltstone and fine grained sandstone beds the organic matter in the lotbiniere and les fonds formations is represented by solid bitumen with subordinate liptinite algae graptolites and chitinozoans representing normal marine type ii kerogen both formations are at the post peak hydrocarbon generation as indicated by the equivalent random vitrinite reflectance of 0 94 to 1 04 rock eval data support the type ii nature of the kerogen and the late oil window maturation level hydrocarbon extracts from the three formations have yielded high to low concentrations of c1 to c6 for all units an upward decrease in total volatiles c1 c2 c3 together with an increase in the gas dryness ratio c1 c2 c3 is recorded the transitions occurring at depths shallower than 50 m where the shales are more fractured the upward increase in the gas dryness ratio results from the more significant reduction of ethane and propane concentrations compared to that of methane consistent with the dryness ratio trend the 13 c vpdb values of methane change from thermogenic values 50 for deeper samples to more biogenic negative values 2 h vsmow trend of more negative values at shallower depths is noted the 13 c vpdb and 2 h vsmow values of rock hosted methane indicate that samples at shallow depth recorded a microbial influence it is proposed that diffusion and some microbial degradation of hydrocarbons are responsible for the decrease of rock volatiles and the in situ generation of biogenic methane in the shales at shallow depths to mix with the in situ thermogenic methane the utica shale is a very good source rock with high generation potential however thermogenic volatiles can also originate from shallower units with much shorter migration pathways the mixed thermogenic and biogenic methane in the groundwater results from fracture enhanced diffusion and biodegradation of volatiles at shallow depths

depositional environment and oil generation in ordovician source rocks from southwestern ontario canada organic geochemical and petrological approach the ordovician trenton group sherman fall and cobourg formations and the lindsay collingwood member and blue mountain formations of southwestern ontario were examined using rock eval pyrolysis gas chromatography gas chromatography mass spectrometry and incident light microscopy to evaluate their paleodepositional environments thermal maturities and source rock potential all units contain sufficient amount of oil prone type ii predominantly marine organic matter to be considered as petroleum source rocks unstructured bituminite with varying proportions of unicellular alginite are the dominant dispersed organic matter macerals the bituminite typically occurs in massive to laminated granular or patchy populations that commonly show microtextural relationships persistent inclusions of leiosphaeridia telalganite demonstrate that planktonic algal debris was a primary organic substrate for blooming microbes disseminated coccoidal gloeocapsomorpha prisca is found in minor amounts usually in association with common to abundant acritarchs zooclasts chitinozoa graptolites scolecodonts and solid bitumen also are present as maceral inclusions within the bituminite network the biomarker distributions for all of the studied units are those expected for marine organic matter deposited in a clastic dominated environment the extracts are characterized by a smooth n alkane profile with low abundance of c20 members typical for marine derived organic matter pristane phytane ratios range from 0 97 to 1 72 indicating dysoxic conditions during deposition smooth c31 c35 homohopane profiles ts tm ratios typically above 1 0 and a higher concentration of diasteranes relative to regular steranes all appear to indicate the clay bearing character of these rocks the predominance of c30 hopane over c29 regular sterane is interpreted to reflect a primary microbial input and extensive reworking of the organic matter optical reflectance fluorescence and geochemical tmax biomarker data thermal maturity parameters indicate that the trenton and blue mountain strata are within the zone of prolific oil generation throughout the whole area of study the collingwood shales are mature with respect to petroleum generation in the eastern part toronto area and only marginally mature in the northern part georgian bay area of the study area in general the biomarker composition of the extracts from all examined units is compatible with that of the oils found in the trenton reservoirs of southwestern ontario however geochemical and geological evidence suggests that the organic rich shaly laminae within the trenton group are the principal source of these oils accumulation of organic carbon in the ordovician sediments of southern ontario is suggested to derive from low energy normal marine environments grading from shallow shelf into deep shelf and open basinal settings the nutrient availability and consequently higher bioproductivity more intense consumption of oxygen and progressing anoxia controlled by a low latitude location diminished water circulation stratification of the water column and a depressed pycnocline resulted in high preservation rates the amorphous nature of kerogen reflects significant microbial interaction at the water sediment interface and within the sediments where reducing conditions must have periodically predominated

internal structure and volcanic hazard potential of mt tongariro new zealand from 3d gravity and magnetic models abstract a new 3d geophysical model of the mt tongariro volcanic massif tgvm new zealand provides a high resolution view of the volcano s internal structure and hydrothermal system from which we derive implications for volcanic hazards geologically constrained 3d inversions of potential field data provides a greater level of insight into the volcanic structure than is possible from unconstrained models a complex region of gravity highs and lows 6 mgal is set within a broader 20 mgal gravity low a magnetic high 1300 nt is associated with mt ngauruhoe while a substantial thick demagnetised area occurs to the north coincident with a gravity low and interpreted as representing the hydrothermal system the hydrothermal system is constrained to the west by major faults interpreted as an impermeable barrier to fluid migration and extends to basement depth these faults are considered low probability areas for future eruption sites as there is little to indicate they have acted as magmatic pathways where the hydrothermal system coincides with steep topographic slopes an increased likelihood of landslides is present and the newly delineated hydrothermal system maps the area most likely to have phreatic eruptions such eruptions while small on a global scale are important hazards at the tgvm as it is a popular hiking area with hundreds of visitors per day in close proximity to eruption sites the model shows that the volume of volcanic material erupted over the lifespan of the tgvm is five to six times greater than previous estimates suggesting a higher rate of magma supply in line with global rates of andesite production we suggest that our model of physical property distribution can be used to provide constraints for other models of dynamic geophysical processes occurring at the tgvm

thermal expansion contraction and slope instability of a fumarole field inferred from geodetic measurements at vulcano between 1987 and 1993 fumarole temperatures at the fossa crater of vulcano italy were characterized by the highest values since the 1920 s increasing from about 300 c in 1987 to 690 c in may 1993 before decreasing to 400 c by 1996 1997 during 1990 vulcano s electronic distance measurement edm network was expanded to provide more detailed coverage of the northern sector of the fossa crater and in particular to monitor the movement of the northern flank the fossa cone measurements carried out between 1990 and 1994 showed shortening by about 6 to 7 cm along baselines measured to a small section of the northern rim over the following four years these baselines showed a slow extension by about 3 cm to gradually recover part of the previous deformation we believe that the shortening and lengthening of the edm baselines was respectively due to the increasing and decreasing temperature of the rock body lying close to the deforming area this caused thermal expansion followed by contraction the positive movement of the rim was not completely matched by a negative recovery suggesting that a non recoverable sliding movement was also responsible for some of the shortening of the baselines we verified our hypothesis by calculating the expected dilatation of a rock body as a function of the volume of rock heated and its thermal expansion coefficient and compared the expected deformation to that observed the geodetic investigation showed that the unstable portion affects a small length of the rim about 100 m long and involves a volume of about 0 8 106 m3 however this zone lies directly above a particularly unstable portion of the flank as well as the main village and port on the island

chitinozoan graptolite and scolecodont reflectance as an alternative to vitrinite and pyrobitumen reflectance in ordovician and silurian strata anticosti island quebec canada because of the absence of vitrinite in lower paleozoic sediments the reflectance of pyrobitumen is used as an indicator of thermal maturation a new technique of preparing organic matter permits discrimination among types of zooclasts and solid bitumen including pyrobitumen and leads to more precise reflectance histograms studies of organic matter from ordovician silurian strata of anticosti island show that reflectance of zooclasts is different from that of solid bitumen and that each group of the following zooclasts chitinozoans graptolites and scolecodonts has a specific reflectance evolution path with increasing depth on a logarithmic scale the paths of the three groups of zooclasts are linear highly correlated and converging however reflectance of solid bitumen is not linear throughout the range studied solid bitumen becomes linear only where the reflectance is greater than 0 75 comparing the relations between zooclasts and solid bitumen with the vitrinite solid bitumen correlation in the literature suggests that a hypothetical vitrinite evolution line in the anticosti island basin should be subparallel with that of chitinozoans and graptolites but 0 4 0 8 lower in the 1 2 range however scolecodonts and vitrinite should have the same reflectance at 1 but scolecodont reflectance should be slightly 0 2 higher for a vitrinite reflectance of 2

failure of volcano slopes magmatic intrusions can initiate and sustain massive and catastrophic volcano collapse their role is twofold involving both driving and resisting forces first flank stability is diminished by magmastatic and magma overpressures and steepened slopes that accompany intrusion second excess pore pressures in potential failure zones can be generated as a result of intrusion related mechanical or thermal straining of the rock fluid medium pressurized retrograde boiling in high level magma chambers or hydrothermal fluid circulation also earthquakes may aid collapse through inertial forces and shaking induced pore pressure generation these excess pore pressures reduce the sliding resistance as shown for wedge shaped slide blocks for selected cases the destabilizing influence of mechanically induced pore pressures is maximized as the intruded width or corresponding overpressure of the intrusion is increased the destabilizing influence of thermally induced pore pressures is conditioned by the seve

graptolites as indicators of the temperature histories of rocks a pilot study of the optical properties of graptolite skeletal materials shows progressive changes of reflectance bireflectance refractive index and absorptive index produced by temperature changes related to depth of burial samples of lower ordovician to upper silurian graptolites were selected from across canada from locations where the conodont alteration indices of adjacent conodont collections provide a control index of temperature the reaction to temperature of graptolite skeletal material appears to be similar to that of bitumen but somewhat different to that of the vitrinite and liptinite maceral components of coal maximum reflectance in oil and bireflectance appear to be the characteristics most diagnostic of maximum temperature and both show progressively higher rates of increase at higher temperatures these factors show potential for more sensitive discrimination of temperatures at high levels of conodont alteration indices the optical properties of graptolites may perhaps provide a useful tool for unravelling the post depositional histories of lower palaeozoic rocks in deformed belts

instability of exogenous lava lobes during intense rainfall on many volcanoes there is evidence of a relationship between dome collapse and periods of high precipitation we propose a mechanism for this relationship and investigate the conditions that optimize failure by this process observations of elongate lobes that evolve through exogenous growth of lava domes reveal that they commonly develop tensile fractures perpendicular to the direction of motion these cracks can increase in depth by localized cooling and volumetric contraction during periods of high rainfall water can fill these cracks and the increase in fluid pressure on the base of the lobes and within the crack can trigger the collapse of the hot exogenous lava domes using limit equilibrium analysis it is possible to calculate the water and vapor forces acting on the rear and base of the potentially unstable part of the lobe the model presented is rectangular in cross section with material properties representative of andesitic dome rocks vapor pressures at the base of cracks are sealed by the penetrating rainfall which forms a saturated cap within the lobe this leads to an increase in fluid pressurization both through the underlying gas pressure and the downslope component of the liquid water cap fluid pressurization increases as the penetration depth increases this rainfall penetration depth is dependent on the thermal properties of the rocks antecedent temperature lobe geometry and the intensity and duration of precipitation dominant parameters influencing the stability of the lobe are principally lobe thickness duration and intensity of rainfall and antecedent lobe temperature our modeling reveals that thicker lobes are intrinsically more unstable due to the amplification of downslope forces in comparison to cohesive strength the increase in the duration and intensity of rainfall events also increases the potential for collapse as it leads to deeper liquid penetration deeper penetration depths are also achieved through lower antecedent temperatures since less fluid is lost through vaporization thus the potential for rain triggered collapse increases with time from emplacement

soils in the bipartite sediments within the moscow glacial limits of the russian plain sedimentary environment pedogenesis paleolandscape implication abstract the basal tills of the late moscow mis 6 cryochrone form an important component of landscapes in northern europe including the center of the russian plain the till is often covered only with a thin cover layer 30 50 cm as an average veneers of sands sandy loams or silty loams so that surface soils retisols are formed in the bipartite sediments the study of such soils allows identifying a set of pre depositional syn depositional and post depositional pedogenic and cryogenic features an assemblage of macro meso and micro morphological features together with analytical data confirmed that soils had been formed within several climatic cycles starting from the late moscow time till now including the last thermochrone when the well developed argic horizon had been formed modern pedogenesis forms embedded profiles within the cover layer depending on the bioclimatic parameters with humic protospodic or cambic horizons the clear record of the final stages of sedimentation and ancient pedogenesis within profiles of soils in bipartite sediments may help to derive paleoclimatic interpretations from the last interglacial glacial cycle till present correlation of these records with other archives in glacial and periglacial areas opens attractive research perspectives

long term stress strain analysis of volcano flank instability the eastern sector of etna from 1980 to 2012 1 we investigated the evolution of seismicity and deformation in the unstable eastern flank of etna volcano over a 30 year period from 1980 to 2012 a significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border pernicana fault system of the sliding flank and the deformation of the eastern flank two marked phases have been observed in 1984 1986 and in the years following 2002 these two phases are separated by an intermediate phase from 1987 to 2001 in which the flank sliding slowed down and the seismicity dropped drastically this common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding this interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface the two intense phases of flank acceleration are representative of two main different sources volcano flank instability stretching the eastern sector in the first 1984 1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002 2003 eruption establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding etna s mechanical behavior and provides insights into the processes regulating the unstable flank response

geological constraints of a structural model of sector collapse at stromboli volcano italy this study is focused on the reconstruction of the structure and dynamics of the first lateral collapse that occurred at stromboli during the holocene which represents the structure inherited by all the following collapses that formed the present sciara del fuoco depression the first lateral collapse of stromboli occurred at the end of the vancori volcano activity at about 13 ka ago the neostromboli lava cone grew within this collapse amphitheater based on a comprehensive geologic and structural analysis of both vancori and neostromboli products we propose an innovative interpretation of the sliding surface once considered to be a homogeneous landslide along a deep seated sliding surface we demonstrate that the upper vancori failure was accommodated by a more complex deformation regime comprising an upper proximal domain of tilted megablocks toreva and a lower distal domain of fragmental landslide transport and deposition

application of acritarch fluorescence in thermal maturity studies the relative fluorescence of acritarchs 400 700 nm range was investigated as an alternative technique of determining the level of thermal maturity of marine paleozoic source rocks in canada the sedimentary strata examined include the blue mountain lindsay collingwood mbr guelph eramosa mbr and marcellus formations from southern ontario yeoman and winnipegosis formations from saskatchewan as well as the manitoba and elk point groups from saskatchewan and alberta respectively the examined strata contain oil prone predominantly marine organic matter type ii and i kerogen with varying proportions of bituminite and alginite as the dominant maceral components acritarchs which occur as persistent maceral inclusions within such organic facies show excellent potential in thermal maturity estimations the fluorescence of acritarchs shows a progressive red shift throughout the initial and main stages of oil generation with a trend parallel to that of alginite however as a result of their lower sensitivity to increasing burial temperature the amax and q values of acritarchs are lower than the corresponding amax and q of gloeocapsomorpha prisca and leiosphaeridia alginite with the difference becoming more pronounced with increasing thermal maturity correlations with optical and geochemical maturity indicators such as reflectance of chitinozoa chr o bitumen br o and vitrinite vr o rock eval tmax and the isomerization ratio of regular steranes s s r indicate that in kerogen type ii organic matrix both amax and q values of acritarchs vary little until the onset of oil generation at this maturity level corresponding to vr o 0 5 and tmax 435 c amax values are commonly 450 nm or less whereas q is below 0 5 within the zone of the initial phase of oil generation the amax shows a steady increase to 480 nm and then a more rapid raise throughout the oil window 520 550 nm these changes in amax are not accompanied by a meaningful increase in q values which in general remain around 0 5 in kerogen type i organic matrix no significant variations in amax and q have been observed up to a maturity level corresponding to vr o 1 and tmax up to 460 c

holocene environments of the central great plains multi proxy evidence from alluvial sequences southeastern nebraska abstract pollen plant macrofossils phytoliths carbon isotopes and alluvial history from sediments exposed along the south fork of the big nemaha river southeastern nebraska usa provide an integrated reconstruction of changes in holocene vegetation climate and fluvial activity from 9000 to 8500 uncalibrated 14 c yr bp climate became more arid and the floodplain and alluvial fans in the main valley aggraded rapidly upland deciduous forest declined and prairie attained its holocene dominance from 8500 to 5800 yr bp upland forest elements disappeared and even riparian trees were sparse under dry climatic conditions alluvial fans continued to aggrade but aggradation in the main valley was interrupted by a stable episode 7000 yr bp from 5800 to 3100 yr bp riparian forests returned to prominence and droughts were intermittent alluviation was slower and punctuated by two major episodes of channel incision and terrace formation in the main valley aggradation on alluvial fans slowed and finally ceased near the end of this period during a short dry interval from 3100 to 2700 yr bp riparian trees except elm disappeared and prairie and weedy species became more abundant this interval is represented by the organic roberts creek member and the alluvial setting was a slightly incised meandering channel belt habitats became similar to presettlement conditions during the last 2700 yr bp weedy taxa dominate modern samples reflecting widespread disturbance alluvial fans and terrace surfaces were stable during the last 2500 years but episodes of floodplain aggradation were punctuated by incision of the main channel

hybrid collapse mechanism at piton de la fournaise volcano reunion island indian ocean 1 recent studies have shown that hydrothermal alteration in the core of volcanoes may weaken the edifice and trigger sector collapse lopez and williams 1993 day 1996 voight and elsworth 1997 van wyk de vries et al 2000 reid et al 2001 alteration of volcanic products must take place over long periods of times before collapse can occur so this process is considered to be less frequent than volcanic failure generated by magmatic intrusion and flank spreading however acceleration of this slow process may occur along one direction as a result of a weak lateral confinement following outward gravitational sliding of a flank of the volcano we present here evidence that the enclos fouque depression of piton de la fournaise volcano results from such a hybrid mechanism seaward sliding of the grand brule trough on top of an ancient hypovolcanic complex led to a lateral unconfined boundary along which collapse of the altered core of the edifice took place the result is a caldera like structure breached on the grand brule slide scaled experiments to simulate this process of pseudocaldera formation reveal tectonic features remarkably similar to those encountered in the field and demonstrate the mechanical consistency of the model similar processes may have played a role in the evolution of other volcanoes

cyclic eruptions and sector collapses at monowai submarine volcano kermadec arc 1998 2007 1 repeated multibeam bathymetric surveys at monowai cone a shallow submarine basaltic volcano and part of the monowai volcanic center in the northern kermadec arc were conducted in 1998 2004 and 2007 these surveys document dramatic depth changes at the volcano including negative changes up to 176 m from two sector collapses and positive changes up to 138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars one sector collapse occurred on the se slope between 1998 and 2004 with a volume of 0 09 km3 and another occurred on the sw slope between 2004 and 2007 with a volume of 0 04 km3 the volume of positive depth change due to addition of volcanic material by eruption is of the same order 0 05 km3 between 1998 and 2004 and 0 06 km3 between 2004 and 2007 during these time intervals monitoring by the polynesian seismic network detected frequent t wave swarms at monowai indicative of explosive eruptive activity every few months an unusual t wave swarm on 24 may 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys but no similarly anomalous t waves were detected between 2004 and 2007 probably because the polynesian seismic network stations were acoustically shadowed from the second slide event we interpret that the sector collapses on monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano 20 moreover there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano volumetric rate calculations suggest that these two processes may be more or less in equilibrium the repeated collapses at monowai are relatively modest in volume involving only 0 1 0 5 of the edifice volume have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes and may be characteristic of how persistently active shallow submarine arc volcanoes grow

assessing thermal maturity of palaeozoic rocks from reflectance of chitinozoa as constrained by geochemical indicators an example from southern ontario canada the reflectance of chitinozoa chr0 was investigated as an alternative technique of determining the level of thermal maturity of organic rich palaeozoic rocks in southern ontario these sedimentary strata which include the ordovician collingwood member and the blue mountain formation as well as the devonian marcellus formation lack vitrinite precluding the application of a standard vitrinite reflectance vr0 technique chr0 shows a proportional increase at marginal to moderate maturities being on average 20 to 25 higher than expected vitrinite reflectance the reflectance data fall into a very narrow range showing a high degree of consistency for each lithostratigraphic unit the average chr0 are as follows collingwood mbr 0 63 georgian bay area and 0 88 toronto area blue mountain fm 0 92 marcellus fm 0 68 correlation with more conventional optical and geochemical maturity parameters obtained from the same set of samples fluorescence of tasmanites leiosphaeridia and gloeocapsomorpha alginite rock eval tmax extract data distribution of terpanes and steranes in extracts indicates that within the area of study the beginning of the catagenetic stage corresponds to chr0 0 65 equivalent vr 0 50 whereas the threshold of significant oil generation is reached at chr0 0 9 equivalent vr 0 70 therefore the blue mountain formation is thermally mature with respect to hydrocarbon generation throughout the whole area of study the collingwood shales are mature only in the toronto area while those occurring in the georgian bay area as well as the marcellus shales have yet to enter the main stage of hydrocarbon generation this integrated approach of assessing thermal maturity shows that chr0 when constrained with other maturity parameters is a very reliable indicator of thermal maturity in lower to middle palaeozoic sedimentary rocks

organic petrology of source rocks history and state of the art abstract the development of organic source rock petrology depended on the methods applied a procedure derived from coal petrology is the study of polished sections of the untreated rock under incident light this method combined with the fluorescence techniques is best suited to characterize and identify the discrete organic matter macerals and permits the most reliabble maturity measurements on the basis of vitrinite reflectance and of various fluorescence parameters another common method treats the rock with acids and studies strew slides of organic matter concentrates this destroys the natural texture of the rock and often some of the individual macerals as well but on the other hand it allows recognition of extremely fine particles which are not resolvable in polished sections maturity studies based on maceral colour changes as observed in strew slides are rapid and practical although they are rather subjective the relative merits of the various methods are discussed the individual organic constituents as seen in the whole rock and in organic matter concentrates are described and illustrated in two colour plates some classification systems are compared in tabular form finally the history of microscopic observations and measurements with respect to the generation of petroleum like substances in coal is briefly reviewed

correction to chronological evolution of the channel functional units in association with palaeo hydrogeomorphological environment in the ancient delta fan of subarnarekha basin india the original article has been published inadvertently with some errors in figures and their caption figs 1 2 3 and errors only in captions of figures figs 4 5 7 8 9 also errors in tables and their caption tables 1 5 6 7 and errors only in captions of tables tables 2 3

the chimborazo sector collapse and debris avalanche deposit characteristics as evidence of emplacement mechanisms abstract chimborazo is a late pleistocene to holocene stratovolcano located at the southwest end of the main ecuadorian volcanic arc it experienced a large sector collapse and debris avalanche da of the initial edifice ch i this left a 4 km wide scar removing 8 0 0 5 km 3 of the edifice the debris avalanche deposit dad is abundantly exposed throughout the riobamba basin to the rio chambo more than 35 km southeast of the volcano the dad averages a thickness of 40 m covers about 280 km 2 and has a volume of 11 km 3 two main dad facies are recognized block and mixed facies the block facies is derived predominantly from edifice lava and forms 80 vol of the dad with a probable volume increase of 15 25 vol the mixed facies was essentially created by mixing brecciated edifice rock with substratum and is found mainly in distal and marginal areas the dad has clear surface ridges and hummocks and internal structures such as jigsaw cracks injections and shear zone features are widespread structures such as stretched blocks along the base contact indicate high basal shear substratum incorporation is directly observed at the base and is inferred from the presence of substratum derived material in the dad body based on the facies and structural interpretation we propose an emplacement model of a lava rich avalanche strongly cataclased before and or during failure initiation the flow mobilises and incorporates significant substrata 10 14 vol while developing a fine lubricating basal layer the substrata dominated mixed facies is transported to the dad interior and top in dykes invading previously formed fractures

subaerial submarine evidence of structures feeding magma to stromboli volcano italy and relations with edifice flank failure and creep abstract structural field data including parameters of 109 sheets strike mostly n10 55 e average dip angle mostly 70 90 average thickness two peaks at 1 2 m and 4 2 m and of 14 eruptive fissures and vents as well as bathymetric and numerical data suggest that stromboli experienced the development of a volcanic rift zone across the cone summit with a tendency to widen towards the lower submarine flanks during the last 100 ka inside this rift zone intrusive sheets mostly strike ne and become more abundant more steeply dipping and thicker on approaching the rift axis this rift persistence reflects the edifice s state of stress with a nw se horizontal least principal stress on the magma intrusion paths after 13 ka ago sheets mainly intruded with a horseshoe shaped geometry in plan view along the boundaries of the northwestern unstable volcano flank where four main lateral collapses occurred during the last 13 ka they also intruded with a ne strike across the volcano summit and the northeastern volcano flank the horseshoe shaped geometry is influenced by the lateral creep of the volcano flank which provides space for intrusion along the transtensional boundaries of the unstable sector where thinner sheets were emplaced when the collapse depression was filled up by new deposits ne striking thicker dykes emplaced across the northwestern volcano flank indicating a rapid re establishment of regional tectonic forces across the cone unbuttressing due to the present sciara del fuoco depression and ongoing flank creeping can account for intrusions also inside the sciara del fuoco the latter in 2007

hydrous pyrolysis maturation of vitrinite like and humic vitrinite macerals implications for thermal maturity analysis abstract the evaluation of thermal maturity of lower paleozoic sedimentary rocks is somewhat complex mainly because of the absence of humic vitrinite maceral material various sedimentary basins of this age contain a syndepositional vitrinite like maceral that resembles vitrinite but has a lower reflectance samples of shales from outcrops and boreholes from the ponta grossa formation middle devonian or older in the parana basin were studied for maturation assessment hydrous pyrolysis assays were conducted for 27 combinations of time and temperature to compare the reflectances of the vitrinite like maceral and humic vitrinite in response to increasing temperature and time this data confirmed that the maturation pathway of the vitrinite like maceral is lower than that of humic vitrinite the spore coloration index for the outcrop samples was also evaluated for natural series studies the combination of the natural and artificial series led to the development of two stage linear regression equations that estimate the equivalent vitrinite reflectance values from measured vitrinite like maceral reflectances to validate the proposed equations reported measurements of vitrinite like maceral reflectances from sedimentary basins in china north america and europe were selected from the literature for comparison the validations showed that the values obtained from the proposed equations correlated well with other maturity parameters

diagenesis to very low grade metamorphism in lower palaeozoic sediments a case study from deep borehole tobolka 1 the barrandian basin czech republic abstract the diagenetic grade of a 2 7 km thick sequence of lower palaeozoic marine sediments in the tobolka 1 deep exploration borehole was investigated by analysing organic and mineral components and fluid inclusions embedded in vein minerals the reflectance of organic matter r r increases down section from values of about 0 77 at the top of the devonian srbsko formation to values around 3 at the base of the ordovician letna formation in the devonian and silurian sediments the reflectance values of vitrinite like and graptolite fragments 0 77 1 13 r r and 1 09 1 46 r r respectively and the composition of fluid inclusions entrapped in vein minerals ch 4 co 2 complex saline solutions light gaseous hydrocarbons liquid petroleum t h 170 230 c collectively indicate organic maturation within the high temperature part of the oil window to the wet gas stage in the ordovician sediments below 1000 m chitinozoan reflectance values 1 38 3 03 r r and the ch 4 dominated composition of the fluid inclusions t h 250 310 c indicate a wet gas condensate stage to an advanced dry gas stage the clay mineral assemblage remains uniform throughout the whole succession and consists of illite mixed layered illite smectite is chlorite and kaolinite below 1400 m the illite content gradually increases down hole forming up to 45 55 of the clay fraction in the deeply buried ordovician sediments throughout the borehole the is displays uniformly low expandability 7 12 3 of smectite layers and an isii ordering the illite crystallinity broadly correlates with organic matter reflectance values and improves with depth from 1 1 to 0 54 2 according to the crystallinity index standard cis scale indicating high grade diagenesis to incipient anchimetamorphism the chlorite crystallinity chc index however shows no systematic correlations with depth the combined evidence from organic matter clay minerals and fluid inclusions points to maximum paleotemperatures of 100 230 c in the silurian devonian strata and up to 250 c or even higher in the ordovician strata apatite fission track analysis afta data suggests that maximum heating occurred between 340 and 380 ma i e during variscan orogenic deformations these paleotemperatures and the degree of diagenesis may have been produced by a post middle devonian burial or tectonic load that was subsequently eroded or by higher paleogeothermal gradients or by a combination of both

active thrusting landscape evolution and late pleistocene sector collapse of baru volcano above the cocos nazca slab tear southern central america in this paper stratigraphy geochronology and geologic mapping are used to characterize a sequence of quaternary deposits associated with edifice failure of baru volcano which together with balanced cross sections illustrate the upper plate s response to along strike variations in subduction properties that occur across the tear in the subducting slab located at the panama fracture zone the subducting panama fracture zone is an active transform that separates disparate styles of subduction between the thick rapid and flat subduction of the cocos plate to the west and the thinner more oblique and steeper subduction of the nazca plate to the east we focus on the arc forearc region above the cocos nazca slab tear where both the fila costena inner forearc fold and thrust belt and the exhumed cordillera de talamanca terminate along strike to the southeast the fila costena thrust belt imbricates an eocene late miocene forearc basin sequence with up to 40 km of shortening inboard of cocos plate subduction and crosscuts a sequence of pleistocene and younger volcano sedimentary units on the southwestern flanks of the active baru volcano at its southeastern termination these units constrained in age by radiocarbon dating n 11 soil color and 40 ar 39 ar n 5 data include a sequence of late pleistocene to holocene debris avalanche and lahar deposits landscape morphology the areal distribution of units and new shortening estimates from balanced cross sections collectively suggest that the southeastern termination of the fila costena thrust belt actively propagates to the southeast coeval with migration of the panama triple junction the prevailing map pattern suggests that the forearc s response to southeastward migration of the slab tear varies with distance to the trench in contrast to deformation patterns in the outermost forearc plate boundary tractions associated with shallow subduction and cocos caribbean convergence are more influential in the development of arc forearc deformation than either oblique subduction of the 2 km bathymetric scarp or right lateral shear which both occur astride the subducting panama fracture zone

long term pedolithogenic rhythms in the holocene abstract soil sedimentary series in subordinate accumulative and trans accumulative landscapes represent the most complete and detailed record of the development of soils topographic forms and local geosystems in the holocene a new conception of centuries long rhythms of soil formation and erosion is offered on the basis of literature analysis and original data on 80 pits within the east european plain supplied with 180 radiocarbon dates it is established that the holocene the last 10 500 years comprises seven stages of soil formation alternating with stages of intensive erosion and sediment accumulation 450 950 2300 2700 4200 4700 6300 6600 7700 8100 9500 10 200 bp the intervals of 450 150 1050 2300 2800 4200 4700 6200 6600 7700 8300 9500 and 10 200 10 400 bp correspond to the formation of soils in the geochemically subordinate footslopes gully bottoms floodplains landscapes the erosion lithogenetic stages are characterized by humid warm and cold and also arid cold climatic conditions the pedogenetic stages in subordinate landscapes of the forest steppe and forest zones fall mainly into arid warm and sometimes humid warm and arid cold climatic phases of the 2000 year long rhythm known as the shnitnikov rhythm

revisions to the stratigraphy of the upper ordovician collingwood beds of ontario a potential oil shale preliminary results from a drilling programme aimed at evaluating the oil shale potential of the whitby formation upper ordovician of ontario showed that the craigleith member of this unit possessed the greatest promise however some preliminary lithostratigraphic observations contradicted those of earlier workers prompting a detailed analysis of the lithostratigraphy log response and organic geochemistry of this unit of organic rich interbedded shale and limestone also known informally as the collingwood shales previously grouped with overlying non calcareous shales these strata are found to be in gradational contact with underlying limestones of the lindsay formation this together with a sharp decrease in carbonate and organic carbon contents at their top leads to their redefinition as the collingwood member of the lindsay formation analysis of subsurface data shows that the unit now termed the collingwood formation in well records does not contain any of the collingwood strata as origi

forecasting catastrophic stratovolcano collapse a model based on mount taranaki new zealand regular large scale edifice collapse and regrowth is a common pattern during the long lifespans of andesitic stratovolcanoes worldwide the 130 k y history of mount taranaki new zealand is punctuated by at least 14 catastrophic collapses producing debris avalanche deposits of 1 to 7 5 km 3 the largest of these sudden events removed as much as one third of the present day equivalent cone the resulting deposits show similar sedimentary and geomorphic features suggesting similar proto edifice characteristics failure trigger mechanisms and runout path conditions each collapse was followed by sustained renewed volcanism and cone regrowth although there are no matching stepwise geochemical changes in the magma erupted instead a stable slowly evolving magmatic system has prevailed last glacial climatic variations are also uncorrelated with the timing or magnitudes of edifice collapse we demonstrate here that if the magmatic composition erupted from stratovolcanoes is constant and basement geology conditions are stable large scale edifice collapse and the generation of catastrophic debris avalanches will be governed by the magma supply rate using a mass balance approach a volume frequency model can be applied to forecasting both the probable timing and volume of future edifice failure of such stratovolcanoes in the mount taranaki case the maximum potential size of a present collapse is estimated to be 7 9 km 3 while the maximum interval before the next collapse is 3

climate forcing of volcano lateral collapse evidence from mount etna sicily in this study we present evidence for early holocene climatic conditions providing circumstances favourable to major lateral collapse at mount etna sicily the volcano s most notable topographic feature is the valle del bove a 5 x 8 km cliff bounded amphitheatre excavated from the eastern flank of the volcano its origin due to prehistoric lateral collapse is corroborated by sturtzstrom deposits adjacent to the amphitheatre s downslope outlet but the age nature and cause of amphitheatre excavation remain matters for debate cosmogenic 3 he exposure ages determined for eroded surfaces within an abandoned watershed flanking the valle del bove support channel abandonment ca 7 5 ka bp as a consequence of its excavation in a catastrophic collapse event watershed development was largely dictated by pluvial conditions during the early holocene which are also implicated in slope failure a viable trigger is magma emplacement into rift zones in the eastern flank of a water saturated edifice leading to the development of excess pore pressures consequent reduction in sliding resistance detachment and collapse such a mechanism is presented as one potential driver of future lateral collapse in volcanic landscapes forecast to experience increased precipitation or melting of ice cover as a consequence of anthropogenic warming

magnitude and chronology of extreme floods in the last 2 ka based on the stratigraphy of a riverine archeological site schurovo settlement middle oka river central european russia

new pollen data from paleosols in the moskva river floodplain nikolina gora natural and anthropogenic environmental changes during the holocene abstract in the floodplain of the moskva river near nikolina gora 3 well developed buried soils have been revealed the lower soil of boreal atlantic age a chernozem contains pollen of steppe plants but no pollen of conifers subboreal and subatlantic soils have light humus eluvial horizons subatlantic soils also have a well developed bt horizon the pollen data shows the distribution of the spruce forests in the second half of the holocene some signs of economic activities such as the pollen of ruderal plants and coal appear at the end of the formation of the atlantic soil and correspond to the neolithic in the subatlantic soils there are many traces of intensive development of the floodplain associated with the economic activity of the population of iron age and early middle ages the pollen and soil characteristics indicate deforestation of the floodplain and the continued existence of anthropogenic grasslands and meadows within a radius of 1 km from the settlements

how to cope with volcano flank dynamics a conceptual model behind possible scenarios for mt etna abstract volcano flank dynamics poses a serious hazard also involving the inhabited lower slopes mt etna is a well studied unstable volcano and a significant amount of data has been collected on the dynamics of its eastern and southern flanks we first propose a conceptual model to describe and explain flank dynamics at etna we identify the preconditions as due to the differential unbuttressing conditions at the volcano base and the triggering factors as shallow magmatic sources dikes reservoirs evidence and parameters and or observations for flank dynamics are listed summarizing the 1994 2010 period of activity based on this we then propose a set of scenarios possibly occurring in case of unrest of the unstable flanks of mt etna flank unrest is a variation in the steady state condition of the volcano flanks possibly accompanied by significant ground deformation seismicity and eruptions the scenarios may provide a general reference and recommendation in case of five types of multi hazard processes related either as a cause or effect to flank dynamics 1 edifice inflation 2 emplacement of dikes along the ne and or s rifts 3 seismicity along pernicana fault system 4 seismicity on the s sector 5 seismicity along timpe fault system each scenario is analyzed and recommendations are given the scenarios may or may not be related to each other in the sense that the probability of occurrence of one scenario may or may not be contingent or dependent upon the prior occurrence of another these scenarios provide a qualitative analysis of the multi hazard processes related to flank dynamics a more quantitative i e probabilistic characterization is under consideration

sedimentary signatures of cyclic growth and destruction of stratovolcanoes a case study from mt taranaki new zealand abstract the long term behaviour of andesite stratovolcanoes is characterised by a repetition of edifice growth phases followed by collapse this cyclic pattern represents a natural frequency at varying timescales in the growth dynamics of stratovolcanoes worldwide around the 130 ka mt taranaki egmont volcano new zealand coastal cliff successions at 20 40 km distance comprise repeating packages of lithologically and sedimentologically distinctive mass flow deposits varying depositional mechanisms and source properties of these units record growth and collapse cycles of the central edifice these are used to construct a model for cyclic volcaniclastic sedimentation in the surrounds of stratovolcanoes during edifice construction phases thick packages of tabular predominantly monolithologic hyperconcentrated flow and debris flow deposits accumulate with intercalated tephra beds the mass flow units commonly contain large proportions of fresh pumice or juvenile lithic andesite intervals of quiescence separating eruptive periods are characterised by landscape re adjustment accompanied by deposition of fluvial and aeolian sediments along with steady accretion of medial ash in contrast brief episodes of destruction are marked by wide spread distinctively clay rich polylithologic debris avalanche deposits and related marginal debris flow units the growth stages can be terminated by an eruption triggered sector collapse or by external forces once the edifice exceeds a critical stable height or profile dependent on eruptive style and local geo tectonic conditions once the edifice becomes metastable regional tectonic earthquakes or shallow level intrusion events are likely triggers for collapse although the resulting debris avalanches represent the greatest individual hazard from such andesite stratovolcanoes their frequency is relatively low compared with other types of mass flows generated during edifice growth phases accurate forecasts of future hazard from mass flow events are therefore dependent on recognition of both the frequency of a stratovolcano s growth cycle and its current position in that cycle

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

diagenesis of ordovician carbonates from the north east michigan basin manitoulin island area ontario evidence from petrography stable isotopes and fluid inclusions middle to late ordovician subtidal carbonates in the manitoulin island area of ontario are predominantly limestone in composition but non ferroan and ferroan dolomite is a common cement as well as a selective or locally pervasive replacement phase integration of field petrographic geochemical 6i3c 6 o and fluid inclusion data indicates that lithification of these carbonates occurred during burial diagenesis with much of the alteration controlled by regional fracturing and hydrothermal influences aqueous type 1 fluid inclusions in early calcite pre dolomite and dolomite are saline 29 wt nacl eq solutions with ca and or mg in excess of na and display homogenization temperatures with modes of 95 and 101 c respectively these temperatures can be explained by significantly more burial than can be accounted for either by the available stratigraphic information or by an unusually high palaeogeothermal gradient which also is not well supported the fluid inclusion temperatures are interpreted to have resulted from hydrothermal fluids which circulated during the burial diagenesis of these strata type 1 inclusions in late post dolomite calcite are less saline 19 wt nacl eq and have a bimodal distribution of homogenizatign temperatures with a relatively well defined low temperature peak similar to those in early calcite and dolomite and a broad higher temperature grouping with a mode at 183 c a small proportion of methane and light hydrocarbon bearing fluid inclusions type 2 are present in all stages of carbonate dolomitizing fluids were derived from burial compaction of argillaceous sediments in the more central parts of the michigan basin and the updip migration of these brines along fractures to the basin margin where the carbonates of the manitoulin island area were dolomitized alternatively migration of dolomitizing brines downward from the overlying pervasively dolomitized silurian sequence into fractures in the ordovician carbonates may have occurred integration of the aqueous fluid inclusion data into the diagenetic history of these carbonates remains equivocal because most of the inclusions are secondary or indeterminate in origin nevertheless high salinities resulting from interaction with evaporitic strata and hydrothermal effects are clearly implicated although the origin of the latter remains unclear the alteration styles of the ordovician carbonates in the manitoulin area are similar to those of ordovician hydrocarbon reservoirs described from other parts of the michigan basin they indicate that fracture related diagenesis occurred on a basin wide scale and that hydrothermal effects were important

caldera rim collapse a hidden volcanic hazard following the emblematic flank collapse of mount st helens in 1981 numerous models of flank sliding have been proposed these models have allowed to largely improve the understanding of mechanisms involved in such landslides which represent a tremendous risk for populations living around volcanoes in this article a new mode of landslide formation related to buried calderas is described the model emphasizes the paramount importance of the hidden ring fault that even when the caldera is buried still remains a plane of weakness in the core of the edifice under certain conditions this plane of weakness becomes activated as the upper part of a pre existing critical slip surface and is used in the emplacement of huge landslides which travel downslope at a very high velocity a natural example is taken from piton de la fournaise volcano la reunion island indian ocean it reveals that the primary cause triggering caldera rim collapse is partial unbuttressing of the flank of the volcano in the natural example this occurs through regressive erosion that excavates deep canyon in the direction of the buried caldera but other mechanisms may exist on account of the large volumes of material involved in caldera rim collapse as well as their long runout distances such a volcanic hazard should be taken into account on every volcano where buried calderas are suspected

emplacement mechanisms of contrasting debris avalanches at volcan mombacho nicaragua provided by structural and facies analysis we study the lithology structure and emplacement of two debris avalanche deposits dads with contrasting origins and materials from the quaternary holocene mombacho volcano nicaragua a clear comparison is possible because both dads were emplaced onto similar nearly flat 3 slope topography with no apparent barrier to transport this lack of confinement allows us to study in nature the perfect case scenario of a freely spreading avalanche in addition there is good evidence that no substratum was incorporated in the events during flow so facies changes are related only to internal dynamics mombacho shows evidence of at least three large flank collapses producing the two well preserved debris avalanches of this study one on its northern flank las isletas directed northeast and the other on its southern flank el crater directed south other south eastern features indicate that the debris avalanche corresponding to the third collapse la danta occurred before las isletas and el crater events the materials involved in each event were similar except in their alteration state and in the amount of substrata initially included in the collapse while el crater avalanche shows no signs of substratum involvement and has characteristics of a hydrothermal weakening related collapse the las isletas avalanche involves significant substratum and was generated by gravity spreading related failure the latter avalanche may have interacted with lake nicaragua during transport in which case its run out could have been modified through a detailed morphological and structural description of the mombacho avalanches we provide two contrasting examples of non eruptive volcanic flank collapse we show that remarkably even with two distinct collapse mechanisms the debris avalanches developed the same gross stratigraphy of a coarse layer above a fine layer this fine layer provided a low friction basal slide layer whereas dad layering and the run outs are roughly similar the distribution of structures is different and related to lithology las isletas has clear proximal faults replaced distally by inter hummock depressions where basal unit zones are exhumed whereas el crater has faults throughout but the basal layer is hidden in the distal zone hummocky forms depend on material type with steep hummocks being formed of coherent lava units and low hummocks by matrix rich units in both avalanches extensional structures predominate the upper layers exclusively underwent longitudinal and lateral extension this is consistent with evidence of only small amounts of block to block interactions during bulk horizontal spreading the base of the moving mass accommodated transport by large amounts of simple shear we suggest that contractional structures and inter block collisions seen in many other avalanches are artifacts related to topographic confinement

contributions to geotechnique 1948 2008 engineering geology rock mechanics and rock engineering throughout its history geotechnique has regularly published papers on the fundamentals of engineering geology the core concepts of rock mechanics and the practice of rock engineering in totality these papers provide a concise history of the development of these areas of geotechnics here a review of many of these papers is presented in terms of the specific themes of engineering geology rock slope instability behaviour of intact rock and discontinuities in rock field measurements in rock mechanics discontinuous rock masses numerical modelling and rock engineering papers covering a wide range of issues within these themes are outlined together with an indication of how they have influenced later developments the review clearly demonstrates how geotechnique has been at the forefront of rock mechanics rock engineering and engineering geology for the whole of its 60 year existence

dike emplacement and flank instability at mount etna constraints from a poro elastic model of flank collapse this work was funded by istituto nazionale di geofisica e vulcanologia ingv and the italian dipartimento per la protezione civile dpc dpc ingv project v4 flank

quantitative diamondoid analysis indicates oil cosourcing from a deep petroleum system onshore niger delta basin the niger delta basin is one of the most prolific hydrocarbon provinces in the world yet the origin of the vast amounts of oil and gas found in the numerous sub basins across the delta remains contested a total of 180 oil samples from more than 40 oil fields in the niger delta were analyzed by gas chromatography gc gc mass spectrometry gc ms and selected samples by gc tandem mass spectrometry gc msms the interpreted thermal maturity and source depositional environments of these hydrocarbons show significant variation depending on the components analyzed and allow no clear correlation to a single source rock but rather imply extensive mixed contributions diamondoid hydrocarbon parameters were used for the first time on these paleogene neogene reservoired oils to investigate source thermal maturity and mixing effects and to perform cross correlations of these oils the diamondoid abundances and distributions support the hypothesis of co sourcing of oil from a thermally cracked sub delta type ii marine source which was then mixed with oils of relatively lower maturities in the paleogene neogene reservoirs future geochemical interpretations should treat the niger delta oils as potential mixtures of oils of variable maturities from different sources often with the most important source biomarkers depleted because of the extent of thermal cracking

buried late holocene luvisols of the oka and moskva river floodplains and their anthropogenic evolution according to soil and pollen data abstract according to radiocarbon dating the ages of the four major soils developed on the floodplains are as follows 1 modern 2 2500 800 cal bp 3 4700 3000 cal bp and 4 7000 5300 cal bp the late holocene soil 2 is usually defined as albeluvisol or luvisol it has a developed profile with clearly expressed argic horizons bt it is markedly different from the underdeveloped soil 1 fluvisol and soil 4 phaeozem or chernozem that have a dark humus mollic chernic horizon soil 2 has a typical light gray color of the humus horizon and is characterized by the accumulation of clay fraction in the bt horizon as compared with the overlying e horizon micromorphological data indicate that the bt horizon has well developed clay films on pore walls and on the surface of aggregates cultural layers belonging to the iron age or early middle ages are sometimes located in soil 2 pollen analysis of this soil attests to its development under forest vegetation which corresponds to the genesis of luvisols and albeluvisols however in some places near ancient settlements characteristic features of the e and bt horizons become weakly pronounced and a well developed dark humus umbric horizon is diagnosed in the soil profiles these soils are marked by the abundance of pollen of herbs including cultivated cereals and weeds this is evidently related to the anthropogenic activity and the propagation of secondary grassy and ruderal vegetation that replaced forests on the floodplains floodplain environments are considered unsuitable for the development of luvisols and albeluvisols within a larger part of the holocene these soils appeared on the floodplains in the late holocene in relation to the propagation of forest vegetation and extremely low floods within a relatively long time

buried paleoindian age landscapes in stream valleys of the central plains usa abstract a systematic study of late quaternary landscape evolution in the central plains documented widespread deeply buried paleosols that represent paleoindian age landscapes in terrace fills of large streams 5th order in alluvial fans and in draws in areas of western kansas with a thick loess mantle alluvial stratigraphic sections were investigated along a steep bio climatic gradient extending from the moist subhumid forest prairie border of the east central plains to the dry subhumid and semi arid shortgrass prairie of the west central plains radiocarbon ages indicate that most large streams were characterized by slow aggradation accompanied by cumulic soil development from ca 11 500 to 10 000 14c yr b p in the valleys of some large streams such as the ninnescah and saline rivers these processes continued into the early holocene the soil stratigraphic record in the draws of western kansas indicates slow aggradation punctuated by episodes of landscape stability and pedogenesis beginning as early as ca 13 300 14c yr b p and spanning the pleistocene holocene boundary the development record of alluvial fans in western kansas is similar to the record in the draws slow aggradation was punctuated by multiple episodes of soil development between ca 13 000 and 9000 14c yr b p in eastern kansas and nebraska development of alluvial fans was common during the early and middle holocene but evidence shows fan development as early as ca 11 300 14c yr b p buried soils dating between ca 12 600 and 9000 14c yr b p were documented in fans throughout the region in stream valleys across the central plains rapid alluviation after ca 9000 14c yr b p resulted in deeply buried soils that may harbor paleoindian cultural deposits hence the paucity of recorded stratified paleoindian sites in the central plains is probably related to poor visibility i e deep burial in alluvial deposits instead of limited human occupation in the region during the terminal pleistocene and early holocene the thick dark cumulic a horizons of soils representing buried paleoindian age landscapes are targets for future archaeological surveys

active tectonic features and structural dynamics of the summit area of mt etna italy revealed by soil co2 and soil temperature surveying project cgl2005 07509 cli ministry of education and science of spain dpc ingv project flank istituto nazionale di geofisica e vulcanologia osservatorio etneo sezione di catania

chitinozoan reflectance a lower palaeozoic thermal maturity indicator abstract chitinozoan reflectance r ch is an innovative technique of thermal maturation determination suitable for lower palaeozoic sediments where the established reflectance scale vitrinite reflectance r v is not applicable due to the lack of vitrinite reflectance measurements are taken from polished sections of chitinozoa a group of lower palaeozoic organic walled marine microfossils these vase shaped palynomorphs are optically isotropic have thick homogeneous test walls and are easy to identify making then ideal for organic petrology from over 1000 samples collected 54 possessed both chitinozoa and vitrinite enabling direct calibration of the two scales a clear linear relationship exists between the two parameters the equation resulting from this study is r ch 1 152 r v 0 08 with a correlation coefficient of 0 989 there is a suggestion of a maturity discontinuity between 1 and 2 r ch but due to the high sample redundancy rate only 5 of samples possessed both vitrinite and chitinozoa it was not possible to supply more data at this maturity level chitinozoan reflectance is a powerful thermal maturity indicator for lower palaeozoic sediments the technique has significant advantages over its maln rivals particularly the ease of particle identification and the fact that it is independent of facies thus quantitative maturity data with a high spatial and temporal resolution can be gained from pre devonian marine sedimentary sequences

reflected light microscopy of chitinozoan fragments abstract certain optical properties of some silurian ordovician chitinozoans have been measured and their morphology described using polished block mounted samples and polished thin sections the chitinozoans were found to be optically isotropic and many fine details of their morphology were observed using reflected light microscopy it has also proved possible to recognize chitinozoan fragments in sections made from kerogen concentrates and whole rock samples from early palaeozoic sediments using reflected light microscopy reflectance studies indicate their potential use as maturity indicators

a global synthesis of lava lake dynamics abstract active lava lakes represent a variety of open vent volcanism in which a sizable body of lava accumulates at the top of the magma column constrained by the vent and or crater geometry the longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface and input of hot and gas rich magma from below due to their longevity and relative accessibility lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing convection and cooling this article examines all seven lakes that existed at the time of writing in 2018 located in the pacific antarctica africa and south and central america these lakes span all tectonic environments and a range of magma compositions we focus on analysis of the lake surface motion using image velocimetry which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes we identify two categories of lake behavior organized erta ale nyiragongo k lauea after 2011 and erebus and chaotic villarrica masaya marum this division does not map directly to lake size viscosity gas emission rate or temperature instead when examined together we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area this relationship points to the combined importance of both flux and lake size in addition to the total volume of gas emission and suggests that a shared deep mechanism controls the supply of heat and gas to all lakes on the other hand the differences between chaotic and organized lakes highlight the important role of the geometry of the conduit lake transition which superimposes a shallow signal on that of the deep circulation the spatial patterns of surface motion we document suggest that the release of gas bubbles at chaotic lakes is more efficient i e bubbles are less likely to be retained and recycled compared with organized lakes in addition the data presented here indicate that the solidified crust of organized lakes plays a role in regulating convection and outgassing in lava lakes

evolution of landscapes of the moskva river floodplain in the atlantic and subboreal pedological and palynological records abstract floodplain deposits in the valley of the moskva river contain a series of buried soils of the holocene age which can be an important source of paleoecological information these soils were dated as follows soil 1 100 bp soil 2 cal 1200 ad 500 bc soil 3 900 2700 bc and soil 4 3700 6000 bc archeological monuments associated with these soils belong to the neolithic soil 4 early bronze age soil 3 and iron age and middle ages soil 2 buried soils have well developed profiles and diagnostic features dark colored soils of the atlantic period soil 4 in most cases can be attributed to phaeozems pollen analysis shows that these soils were formed under forest steppe communities buried soils of the subatlantic period soil 2 are usually referred to as luvisols unlike them the soils of the subboreal period soil 3 are traced in rare cases and have no clear diagnostic features allowing reconstruction of the paleoenvironment these soils have a light colored humus horizon which does not allow them to be classified as phaeozems however they do not have the bt horizon characteristic of luvisols this paper describes the results of a new comprehensive study of the moskva river floodplain near the zvenigorod biological station zbs of moscow state university the buried soils of the atlantic and subboreal periods were studied by palaeopedological and palynological methods the findings confirmed previously obtained results and indicated that the buried soil 3 at the zbs site could be developed under mixed forests dominated by spruce these results suggest that the landscapes of the lower levels of the valley changed dramatically between 5000 and 4500 cal bp the forest steppe communities were replaced by dense forests due to the early subboreal climate change the paper also examines the specifics of soil and pollen records of the landscape evolution the anthropogenic influence on the floodplain landscapes is also considered

optical properties of organic matter in relation to thermal gradients and structural deformation the general response of macerals to the coalification process the effectiveness of organic geochemical and petrological parameters as estimators of coalification and the applicability of different microscopical parameters in the assessment of rank are reviewed the central role of vitrinite reflectance as the most widely used estimator of coalification from brown coals to the low grade metamorphic zone is established on the basis of its relatively uniform variation with rank specificity ease and rapidity of measurement and cheapness factors influencing the optical properties ofvitrinites are considered temperature has the dominant influence in modifying optical properties with rank but time static pressure and stress can all have significant influences upon the course of optical properties depending upon particular geological conditions static pressure has a retarding effect on the coalification process but it is also responsible for creating increasing anisotropy within the condensing aromatic structures as rank rises hydrostatic pressures and pore pressures can contribute to the overpressuring of sediments thus affecting their thermal conductivities and consequently the rate of coalification stress is responsible for the development of biaxicity in the reflectance indicatrix fast and high levels of heating from igneous bodies cause textural effects on vitrinites as a result of carbonization that are quite different from those of coalification recognizing these different influences upon the optical properties of vitrinites examples are given of the use and application of vitrinite reflectance in the preparation of rank maps in the burial histories of basins in the timing of coalification in relation to orogenesis and igneous activity and in the zones of anchimetamorphism and low grade metamorphism consideration is also given to the problem of provincialism in correlations between chemical and physical parameters and to the future development of optical studies in organic petrology and their relation to organic geochemical investigations

distinct evolution trends of nanometer scale pores displayed by the pyrolysis of organic matter rich lacustrine shales implications for the pore development mechanisms abstract organic matter om compositions greatly affect hydrocarbon generation and expulsion processes which are critical for the organic porosity development in shale lacustrine shale samples of low thermal maturity were pyrolyzed using two pyrolysis systems closed and semi closed systems pore development was measured by low pressure gas adsorption and field emission scanning electron microscopy fe sem and bulk porosity was modeled utilizing organic geochemical data the gas adsorption analysis indicated that shale samples of different om compositions differed in pore volume evolution with thermal maturity mainly related to the different amounts of hydrocarbon generated and expelled residual bitumen significantly reduced the pore volume of om rich oil generative shale samples and restricted the micro meso and macro pore volumes to different extents calculations and experiments both showed that om rich and oil generative shale experienced a greater increase in pore volume after the oil peak in addition it was observed that variations in the main pore types were associated both with shale compositions and with exerted overburden pressure increase in overburden pressure were found to greatly facilitate the development of nanometer size spongy and complex om pores in shales containing type kerogens possibly as a result of the expulsion of gaseous hydrocarbons by contrast the shale with abundant type kerogen tended mainly to develop relatively large pores following oil expulsion regardless of overburden pressure the modeled organic porosity of pyrolyzed samples of type iii om was similar to the porosity of geological shale but the porosity of om rich oil generative shale samples with high expulsion efficiency at the oil generation stage was two to three times the measured porosity of the geological shale in some cases the higher modeled shale porosity might be related to the higher expulsion efficiency for geological shales of expulsion efficiency comparable to the pyrolyzed samples geological processes e g compaction and cementation may have greatly reduced the om associated pore volume

some consequences of volcanic edifice destruction for eruption conditions abstract destruction of a volcanic edifice by landslides or phreatic explosions unloads the upper crust induced changes of stress field around and of magmatic pressure within a magma reservoir are investigated with an analytical model for the deformation of a liquid filled cavity within an elastic half space unloading affects the reservoir pressure and hence the net result depends on how the liquid filled reservoir responds to a change of remote stress magma compressibility is taken into account and may dampen changes of internal pressure in small volatile rich reservoirs the main consequence of edifice destruction is a decrease of magmatic pressure and stresses on the reservoir walls in some cases this may be responsible for dyke closure at the reservoir walls which stops magma withdrawal and may prevent eruption if an eruption does occur edifice destruction affects the volume of magma erupted depending on edifice size magma reservoir size and depth the erupted volume may be smaller or larger than that which would be erupted with no damage to the edifice these results suggest that major phreatic explosions may prevent magmatic eruptions

morphology of river channels and surface runoff in the volga river basin east european plain during the late glacial period abstract morphology of the large palaeochannels over the entire periglacial belt of the northern hemisphere shows distinct evidence of high surface runoff at the late glacial time channel width and meander wavelength of 73 well preserved fragments of large palaeochannels were measured in the volga river basin east european plain palynological studies of palaeo moskva river alluvium make it possible to locate the climatic and hydrological region analogues of the late glacial landscapes these analogues allowed reconstruction of the former surface runoff of the late glacial rivers as well as the total volume of flow to the caspian sea using the transform functions these reconstructions support the climatic hypothesis of the khvalyn transgression of the caspian sea and explain high water levels during this transgression without melt water inflow from the receding scandinavian ice sheet

reflectance measurements of zooclasts and solid bitumen in lower paleozoic shales southern scandinavia correlation to vitrinite reflectance abstract reflectance measurements have been carried out on zooclasts graptolites chitinozoans and vase shaped microfossils and other organic particles vitrinite like particles porous granular vitrinite like particles and solid bitumen in middle cambrian to upper silurian shales from central and southern sweden and the danish island of bornholm baltic sea the most abundant organic components in all the shales are fragments of graptolites and vitrinite like particles the reflectance distribution of these two types of components is largely identical and it is suggested that the vitrinite like particles are fragments of graptolites without any recognizable morphology reflectance measurements of graptolites and vitrinite like particles yield well defined reflectance populations in samples with average r graptolite and average r vitrinite like of 0 75 r o the reflectance distributions are bimodal because of increasing bireflectance and the average reflectance value of the well defined lower reflecting population is arbitrarily used as maturity indicator our results suggest that with increasing thermal maturity the reflectance of graptolites increases faster than the predicted vitrinite reflectance the relationship between graptolite reflectance and equivalent vitrinite reflectance can be expressed by the equation vr eqv 0 73 r graptolite vitrinite like low 0 16 the gas generation window which normally is considered to begin at a vitrinite reflectance of 1 3 r o in post lower paleozoic rocks containing vitrinite starts accordingly at 1 56 r o graptolite reflectance porous granular vitrinite like particles occur in minor amounts and they may represent graptolite fragments with a non smooth surface they generally yield slightly higher reflectance than non granular vitrinite like particles and graptolite fragments the middle cambrian to furongian upper cambrian shales may contain sparse fragments of vase shaped microfossils vsm that seem to follow the maturation trend of chitinozoans in the present sample set the reflectance of chitinozoans and vsm is comparable to that of graptolites at the same level of maturity reflectance measurements of solid bitumen are a poor maturity indicator probably because bitumen can have various origins and morphologies and it may not be indigenous to the host rock

palaeohydrology of the seim river basin mid russian upland based on palaeochannel morphology and palynological data abstract morphological geological geochronological and palynological analyses show that the landscape climate and hydrological history of the seim river basin includes 1 a period of sandy terrace 1 formation by shallow flows with the surface transformation by cryogenic and aeolian processes close to the last glaciation maximum 2 a cold and dry period about 16 14 k radiocarbon years b p with very high surface runoff and extremely large meandering channel formation 3 a period between the oldest dryas and the preboreal of non steady surface runoff decrease large meander abandonment and formation of smaller channels against the background of climate warming 4 a period of relative stability of hydrological regime and small variations of water runoff as in modern rivers throughout the holocene

fluvial chronology in the east european plain over the last 20 ka and its palaeohydrological implications abstract a database containing 983 absolute ages of fluvial deposits was interpreted in palaeohydrological terms and 646 dates were found associated with 754 local palaeofluvial events geomorphic or sedimentological traces of changing fluvial activity combined probability density functions of high and low activity dates were used to detect time intervals of different palaeohydrological status after low fluvial activity during lgm two palaeohydrological epochs were designated extremely high activity in the end of mis 2 ca 18 11 7 ka before ce 2000 b2k and much lower activity in the holocene within the holocene two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude regional palaeohydrological phases centuries to few millennia and regional palaeofluvial episodes decades to few centuries tendency is rather clear of activity lowering in the first half and rise in the second half of the holocene extremes within the palaeohydrological phases were designated as 19 palaeofluvial episodes 7 high activity ha episodes 8 low activity stability la episodes and 4 contrast or complex ca episodes in most cases changes of fluvial activity were most likely induced by changing amounts of spring snowmelt runoff most distinct correlation of temperature and hydrological regimes was found in the late holocene high fluvial activity corresponded to cold climatic phases little ice age low activity to warm phases medieval climatic optimum current climate warming the suggested fluvial chronology was compared with independent hydroclimatic archives such as palaeosoils and lake levels correlation with soil formation alluviation epochs was found very close with some exceptions in the early holocene correspondence of fluvial activity to the caspian sea level changes is rather high in the second part of the holocene and is poor before 4 5 ka b2k which can be explained by insufficient data behind both types of reconstructions correlation of changes in fluvial activity within a west east transect over europe revealed relatively poor correlation in the early and mid holocene and much higher synchronism since 3 0 ka b2k which may indicate increasing role of westerlies in controlling european climates in the late holocene throughout the whole holocene changes of fluvial activity over eep were governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion

conditions favouring catastrophic landslides on tenerife canary islands catastrophic failures of volcano flanks represent one of the most hazardous geological phenomena these immense mass movements originate either by increasing the destabilizing forces driving forces or by reducing the strength of the materials involved or both the study of large volcanic landslides on tenerife suggests that the presence of weak residual soils palaeosols in combination with the pre existence of deep narrow canyons created by fluvial erosion have played a fundamental role in the initiation of large scale sector collapses of the volcanic edifice regardless of the triggering mechanism considered residual soils strongly reduce the material strength during undrained loading while pre existing canyons control the lateral limits of the landslide the existence of a wet climate in some sectors of the island favours these circumstances

correlations among the reflectances of vitrinite chitinozoans graptolites and scolecodonts abstract paleozoic marine sequences sampled in outcrops and wells of northeastern gaspe peninsula quebec appalachians yield kerogen composed in part of vitrinite and zooclasts chitinozoans scolecodonts and graptolites on which reflectance measurements were made the comparison between means of random measurements show that reflectance of chitinozoans is similar to that of telinite vitrinite with a cellular texture and that the reflectance of scolecodonts is significantly lower than that of telinite in the lower range of studied values at higher reflectivities differences decrease but at the end of the condensate gas zone reflectancea are not yet identical as shown by previous studies reflectance of graptolites is slightly less than that of telinite pyrobitumen reflectance is related to the lithology of the host rock and no generalized correlation can be established between the reflectance of pyrobitumen and that of vitrinite

application of organic petrography in north american shale petroleum systems a review abstract organic petrography via incident light microscopy has broad application to shale petroleum systems including delineation of thermal maturity windows and determination of organo facies incident light microscopy allows practitioners the ability to identify various types of organic components and demonstrates that solid bitumen is the dominant organic matter occurring in shale plays of peak oil and gas window thermal maturity whereas oil prone type i ii kerogens have converted to hydrocarbons and are not present high magnification sem observation of an interconnected organic porosity occurring in the solid bitumen of thermally mature shale reservoirs has enabled major advances in our understanding of hydrocarbon migration and storage in shale but suffers from inability to confirm the type of organic matter present herein we review organic petrography applications in the north american shale plays through discussion of incident light photographic examples in the first part of the manuscript we provide basic practical information on the measurement of organic reflectance and outline fluorescence microscopy and other petrographic approaches to the determination of thermal maturity in the second half of the paper we discuss applications of organic petrography and sem in all of the major shale petroleum systems in north america including tight oil plays such as the bakken eagle ford and niobrara and shale gas and condensate plays including the barnett duvernay haynesville bossier marcellus utica and woodford among others our review suggests systematic research employing correlative high resolution imaging techniques and in situ geochemical probing is needed to better document hydrocarbon storage migration and wettability properties of solid bitumen at the pressure and temperature conditions of shale reservoirs

dispersed organic matter from silurian shales of the barrandian basin czech republic optical properties chemical composition and thermal maturity abstract samples of lower silurian liten and kopanina formations dark shales from the barrandian basin czech republic were examined using reflected light microscopy fourier transform infrared spectroscopy ft ir and gas chromatography mass spectrometry gc ms the samples contained uniform assemblage of organic material that included dominant graptolites chitinozoa bitumens and minor anthracite to meta anthracite rank particle of unknown origin two types of graptolite morphologies were recognized a nongranular blocky type and a granular type bitumen is also common in these rocks and forms discrete oval bodies resembling droplets or angular particles with granular internal fabrics the thermal maturity of the sediments was examined by measuring random reflectance of organic particles the variations in graptolite reflectance in between three localities in the western part of the basin were relatively minor suggesting a similar level of diagenetic transformation the values range from 0 78 to 1 53 rr the reflectance of graptolites was correlated with the reflectance of chitinozoa and bitumen and also indirectly with illite crystallinity data which indicates thermal maturation levels in the high temperature part of the oil window to the onset of wet gas condensate zone mature petroleum that commonly impregnates veins crosscutting the sequence further supports a maturation level within the oil window graptolite and bitumen reflectance values markedly elevated above the regional diagenetic background were found in several centimeter wide contact zones immediately adjacent to basalt sills that locally penetrate the silurian strata as shown by computer modeling heating in the range of 600 800 c which lasted only several years was sufficient to promote an increase in reflectance up to 2 2 5 rr in the contact samples with increasing thermal stress the graptolite periderm undergoes progressive optical and structural changes being gradually converted into a highly condensed aromatic residuum structurally and chemically similar to highly matured kerogen on a basin wide scale however the overall impact of basalt intrusions on organic maturity of enclosing shales was minimal

deformed symmetrical volcanoes analog modeling of volcanic cones traversed by strike slip faulting was conducted and the cones were analyzed for deformation characteristics the study shows that symmetrical volcanoes that have undergone basal strike slip offset may be deformed internally without manifesting any change in their conical shape volcanoes deformed by strike slip faulting may already have well developed fractures in their interior yet still appear as a symmetrical cone exhibiting concentric contours when viewed on a topographic map moreover slight changes in the basal shape of the cone induced by strike slip movement can be restored by the relatively faster resurfacing and reshaping processes from the deposition of younger eruptive products these findings pose a subtle but significant point in the assessment of volcanic landslide hazards not all perfect cones are undisturbed the detection of concealed deformation is important because fractures induce further instability in volcanoes and act as slip planes during volcano collapse events there are many examples of symmetrical volcanoes in nature the faultless appearance of such perfect cones can be misleading which requires careful attention in hazards assessment

development of characteristic volcanic debris avalanche deposit structures new insight from distinct element simulations large scale catastrophic collapse of volcanic edifices is a relatively common phenomenon in the geologic record however the processes that occur during debris avalanche emplacement remain poorly understood and must generally be inferred from analysis of avalanche deposits in the field which are recognized to contain a suite of recurrent features such as conical surface hummocks and toreva block ridges this study uses the distinct element numerical modelling method to investigate debris avalanche emplacement processes because it allows brittle deformation of the failure mass to be examined after describing the material calibration and model setup necessary for modelling the geomechanical behaviour of a failed edifice flank a sequence of emplacement snapshots is described the simulated debris avalanche is seen to evolve from initial block sliding through extension with horst and graben structures defined by propagation and offset of large scale discontinuities to a final stage in which the avalanche flows down valley the numerical model is consistent with emplacement theory in the literature and allows for a more precise view of the processes at work during failure and the deposits created thereby for example toreva blocks are formed in the medial and proximal sections of the failure through top down propagation of normally offset discontinuities developed from upper surface tension a mechanism for surface hummock formation is also recognized involving the retention of surface blocks as these and other characteristic deposit features are formed from a flank with homogeneous material properties brittle deformation of the initially listric shaped failure mass and associated macroscopic structural evolution are recognized as important factors in failure evolution and subsequent deposit morphology

geochemical and petrographic characterization of the upper ordovician utica shale southern quebec canada abstract the utica shale is a potential unconventional tight gas reservoir from southern quebec the utica shale is a calcareous shale with intervals of fine grained siltstone with total organic content of 1 2 wt median n 408 the major organic matter constituents are migrabitumen and zooclasts chitinozoan and graptolite macerals the primary kerogen is characterized as marine due to the presence of chitinozoan and marine derived prasinophyte algae such as tasmanites a significant portion of the bulk organic matter is dominated by migrabitumen the present hydrocarbon potential s2 mg hc g rock of the utica shale is largely controlled by distribution of solid migrabitumen throughout the unit hydrogen index hi declines with increasing maturity which is controlled by greater burial from shallow to deep sections oxygen index oi remains low in most samples which is attributed to lack of terrestrial input however organic lean intervals show significantly inflated oi due to interference of mineral carbon possibly siderite random reflectance measurements on matrix solid bitumen and chitinozoans are robust indicators of thermal maturity the maturity ranges from the late oil window in the shallow utica to the wet and dry gas windows in the intermediate and deep utica respectively the results suggest that matrix bitumen formed during migration and dissemination of hydrocarbon into the clay fraction of the rock this is associated with significant bacterial sulfate reduction possibly in the early stages of generation and migration of oil it appears that the porous siltstone facies in the deeply buried section of the utica shale acts as a reservoir for the migrated bitumen from organic rich strata within the section and or possibly overlying source rock

a new indicator for dividing sedimentary rhythms in alluvial deposits a pollen based method abstract yellow river flooding has occurred many times near kaifeng city resulting in the formation of a relatively complete sedimentary sequence which provides a rare research carrier for exploring sedimentary rhythms in alluvium in this paper two 25 m long cores were respectively obtained from suburban jm core and urban sz core areas of kaifeng city china using detailed pollen data grain size and our previous studies we explore the effect of yellow river flood events on the characteristics of alluvial pollen assemblages through cluster analysis of the pollen assemblages and pollen concentrations we determined that there are 16 and at least 14 pollen zones subzones i e pollen rhythms in the jm core and sz core respectively to aid an objective analysis we define a comprehensive rhythm from three other indicators namely grain size black carbon and anthropogenic biological elements for the suburban jm core less disturbed by human activity each pollen rhythm has its corresponding comprehensive rhythm and the upper and lower boundaries are basically the same however the number of pollen rhythms is found to be greater than the number of comprehensive rhythms suggesting the precision of the pollen proxy is higher than the other three indicators similar phenomena were found in the sz core with significant human disturbance which also suggests that the pollen proxy is less susceptible to human disturbance and can accurately identify sedimentary rhythms furthermore the pollen concentration and its assemblage characteristics can indicate floods to some extent even small scale floods this is thought to be related to circumstances where some yellow river floods may have lasted for a long time during which time there were several relatively short flood intervals due to seasonal and flood path changes nevertheless pollen rhythms can also be identified consequently a pollen rhythm may not indicate a specific flood event

study of a silurian sequence of dornes region central iberian zone portugal the contribution of organic petrology and palynofacies abstract a wenlock silurian sedimentary continuous sequence was sampled in the dornes region central iberian zone portugal to characterize the organic matter type using different microscopic analyses organic petrology and palynofacies total organic carbon toc was also determined samples are part of foz da serta formation and correspond to mudstone punctually with sandstone rich in organic matter mean toc value of 5 1 whole rock samples showed a dominance of non granular graptolites lath and blocky shape and solid bitumen lath shape graptolites display the characteristic segmented structure in the blocky shape graptolites the fusellar layers of the graptolite wall are well marked and are an important distinctive feature foz da serta graptolites are optically anisotropic as well as the solid bitumen non granular graptolite s maximum reflectance varies from 1 43 to 3 94 and solid bitumen maximum reflectance oscillates between 1 09 and 2 22 vitrinite reflectance equivalent was calculated using bertrand and malo s equation values between 1 97 and 3 72 denoting a post mature stage for the organic matter no relation was established with confidence between graptolite maximum reflectance and solid bitumen maximum reflectance the palynofacies study confirmed not only the presence of graptolite and solid bitumen but also amorphous material derived from graptolite under transmitted white light graptolite features were not noticed to improve the palynofacies characterization reflected white light was used on slides thus exposing distinctive graptolite features the different lights and preparation types used allowed a better characterization of the organic matter present in foz da serta formation samples mainly the graptolites the use of reflected white light in the palynofacies study proved to be extremely important in the description of the graptolite features

organic petrology and organic geochemistry of devonian black shales in southwestern ontario canada abstract the hydrocarbon source rock potential of the devonian marcellus and kettle point black shales in southern ontario has been assessed using rock eval pyrolysis gas chromatography gas chromatography mass spectrometry and incident light microscopy both formations contain sufficient hydrogen rich organic matter type ii to be considered possible source rocks the kerogen is predominantly marine in origin this organic matter was deposited in a clastic algal dominated environment and mainly consists of unstructured bituminite and unicellular alginite the organic microfacies indicate shelf paleodepositional settings with a transition to an open basinal region the optical reflectance fluorescence and geochemical rock eval tmax extract yields distributions of steranes and terpanes maturity data indicate that the organic matter in the kettle point formation is immature whereas in the marcellus formation it has reached the early stages of hydrocarbon generation and expulsion some devonian oils occurring in this area have characteristics similar to the marcellus extracts suggesting that more mature equivalent units from the appalchian basin could be their source

review of ten years of volcano deformations recorded by the ground based insar monitoring system at stromboli volcano a tool to mitigate volcano flank dynamics and intense volcanic activity abstract stromboli volcano southern italy is one of the most monitored volcano in the world with a surveillance network that includes a permanently sited ground based sar interferometer gbinsar this work is the review of the gbinsar data gained from the last decade of monitoring activity the analysis of the entire dataset of gbinsar measurements allowed the assessment of the deformation field of the northern part of the summit crater area and the sciara del fuoco depression in detail the main displacements recognized can be related to different factors 1 the inflation deflation respectively immediately before and after each new effusive event 2 the bulging of localized sectors of the volcano involved in the vent opening 3 the gravitational sliding of the sciara del fuoco infill 4 the movement of lava flows accelerations in this sector are related to sheet intrusions while the possibility of vent opening associated with small sliding or catastrophic flank failure are related to highly overpressurized sheets able to produce high displacement rate in the sciara del fuoco in the summit crater area the increases in the displacement rate are related to the pressurization of the shallow conduit system as the consequence of the variation in the magma level magmastatic pressure or to the lateral magma migration lateral conduit expansion or dike intrusion in response to the increase of the overpressure component fluctuations in the displacement rate in the summit crater area can be related to the magma overturning within the conduit with the increases in displacement rate during the upwelling of less dense magma while displacement rate decreases as the degassed magma column is pushed out from the conduit lava flows or overflows instead the decrease in the displacement rate without coeval lava outpouring could be related to the sink of the degassed magma due to density contrast between the gas poor and the gas charged magmas using the displacement rate in the summit crater area as a proxy for the variation in the pressure condition in conduit both magmastatic and overpressure components thresholds for the crises characterized by the occurrence of overflows eventually associated with major explosions and flank effusions eventually associated with paroxysmal explosions are identified small conduit overpressure will produce overflows sometimes associated with crater rim collapses while large magma overpressure will laterally expand the conduit forming ne sw striking sheets feeding eruptive vents at the base of the summit crater area and within the sciara del fuoco generating conditions of instability that can evolve into catastrophic collapse of the instable flank

geological and geomechanical models of the pre landslide volcanic edifice of guimar and la orotava mega landslides tenerife abstract the geological and geomechanical characterizations of the volcanic rock mass succession affected by the guimar and la orotava mega landslides tenerife canary island are presented here for the first time the estimated subaerial volume of rocks mobilized by each of these landslides is in the range of 30 50 km 3 one of the largest known in the world field data gallery surveys and borehole drilling have allowed the main types of materials and their structural arrangement to be identified based on these information a geological model of the pre landslide volcanic edifice is proposed a palaeo morphological reconstruction has been produced and possible slope angles and heights of the pre landslide volcanic edifice are presented five main lithological units have been identified in the emerged part of the edifice three of them forming the flanks and two forming the structural axis of the island on the flanks lava flows predominate with different degrees of alteration and proportion of dikes increasing near the structural axis the predominant materials on the structural axis are pyroclastic deposits lava flows and dikes in the submarine edifice four main lithological units have been distinguished formed by hyaloclastites pillow lavas dikes and gravitational deposits slope and basin facies the geomechanical characterization of these materials has been obtained from field data boreholes laboratory tests and literature review the geological and geomechanical models obtained provide the fundamental basis for the explanation of the instability processes that generated the guimar and la orotava mega landslides

geomorphic development of white island volcano based on slope stability modelling abstract white island shows many geomorphic features associated with stratovolcanoes that have undergone major sector collapse most notably the flat floored amphitheatre comprising the present crater arcgis is used to develop a reconstructed pre failure cone and 2d limiting equilibrium stability analysis is undertaken of the reconstructed cone water table ranges from 0 dry to 100 saturated are assumed and earthquake accelerations of 0 0 5 g bracket the likely range of accelerations expected in a volcanic setting geotechnical data from moon et al moon v bradshaw j smith r and de lange w 2005 geotechnical characterization of stratocone crater wall sequences white island volcano new zealand engineering geology 81 146 178 are used the models suggest that flank failure is a feasible explanation for the present day geomorphology and indicate that there were at least two retrogressive failures the best model sees a core of hydrothermally altered material overlying relatively unaltered andesite lavas and breccias where accelerations of 0 17 g saturated slope to 0 45 g dry slope are required to initiate failure f 1 0 the failure modelled was relatively small volume of 0 21 km3 and would have mostly involved hydrothermally altered materials with some fresh rock mass two toreva blocks are recognised occupying the seaward margin of the amphitheatre with a lobe of debris offshore suggested as the debris avalanche deposits modification of both the outer slopes of the island and the inner crater walls has occurred since the failure event especially on the southwestern margin of the crater modelling suggests that further failure of the inner walls is likely and poses a significant hazard to tourists visiting the island further outer slope failures are unlikely

investigation of thermal maturity of lower palaeozoic hydrocarbon source rocks by means of vitrinite like maceral reflectance a tarim basin case study evaluation of the maturity of chinese lower palaeozoic sediments has not been satisfactorily accomplished because of the absence of vitrinite and the relatively high level of maturity of the organic matter in the tarim basin one of the largest petroliferous basins in china important lower palaeozoic marine sediments contain a widely distributed type of maceral resembling vitrinite especially characterised by syndepositional occurrence elongate shape homogenous texture and weak anisotropy the term vitrinite like maceral is used to describe the maceral in this paper because of insufficient evidence for its origin thirty five lower palaeozoic source rocks mainly from five boreholes in the tarim basin have been investigated by organic petrologic methods and a positive correlation between the vitrinite like maceral reflectance and sample depth has been recognized this correlation is better than that between bitumen reflectance and depth artificial maturation data show that the maturation pathway of vitrinite like macerals is quite different from that of vitrinite there is a distinct step in the development of reflectance of vitrinite like macerals with increasing maturation by combining the reflectance data from naturally and artificially matured samples the relationship between vitrinite like maceral reflectance and vitrinite reflectance can be divided into three stages which are well represented by three linear regression equations the equations provide a convenient method to evaluate the maturity of lower palaeozoic sediments by allowing an equivalent vitrinite reflectance to be derived from the measured vitrinite like maceral reflectance

tracking precursors and degassing by radon monitoring during major eruptions at stromboli volcano aeolian islands italy 1 we monitored radon anomalies before during and after the recent paroxysmal eruptions of stromboli major eruptive events are preceded by relative minima in radon emissions at stations located at the base of the cone whereas three of the summit stations reached peak values 20 000 bq m3 or higher 12 to 14 days before major eruptions and are nearly coeval with earth tides radon emissions at or above such high threshold values are proposed to result from the dynamic response of the fracture network due to degassing processes associated with magma ascent relative minima recorded at the base of the cone are related to fractures self sealing within the hydrothermal system eventually coupled with the atmospheric stack effect the coexistence of the above anomalies is interpreted as the first precursory signals to major eruptive events

from steep slope volcano to flat caldera floor 1 most laboratory experiments of caldera collapse have dealt with reservoir emptying below a flat lying overburden without an overlying analogue volcanic edifice on top the overload and the role of topography are then neglected so that the final flat floor within the caldera is directly linked to the initial one in addition caldera subsidence is commonly attributed to the collapse of the top of a magma chamber linked to eruptions delivering large amounts of volcanic products analogue experiments show that the deformation of a weak clay rich core resulting from the hydrothermal alteration in a volcanic edifice can in certain conditions reproduce the structures of a caldera in particular it is a way to explain the flat floor of a caldera when resurfacing resulting from new eruptions or destructive processes seems unlikely

the strength of heterogeneous volcanic rocks a 2d approximation abstract volcanic rocks typically contain heterogeneities in the form of crystals and pores we investigate here the influence of such heterogeneity on the strength of volcanic rocks using an elastic damage mechanics model in which we numerically deform two dimensional samples comprising low strength elements representing crystals and zero strength elements representing pores these circular elements are stochastically generated so that there is no overlap in a medium representing the groundmass our modelling indicates that increasing the fraction of pores and or crystals reduces the strength of volcanic rocks and that increasing the pore fraction results in larger strength reductions than increasing the crystal fraction the model also highlights an important weakening role for pore diameter but finds that crystal diameter has a less significant influence for strength to account for heterogeneity pores and crystals we propose an effective medium approach where we define an effective pore fraction p v p v p v g where v p and v g are the pore and groundmass fractions respectively highly heterogeneous samples containing high pore and or crystal fractions will therefore have high values of p and vice versa when we express our numerical samples more than 200 simulations spanning a wide range of crystal and pore fractions in terms of p we find that their strengths can be described by a single curve for a given pore diameter to provide a predictive tool for the strength of heterogeneous volcanic rocks we propose a modified version of 2d solution for the sammis and ashby 1986 pore emanating crack model a micromechanical model designed to estimate strength using microstructural attributes such as porosity pore radius and fracture toughness the model reformulated to include p and therefore crystal fraction captures the strength curves for our numerical simulations over a sample heterogeneity range relevant to volcanic systems we find that published experimental data for which the porosity and crystal fraction is known correlate well with our modelled curves adding validity to our approach we present herein a 2d analytical tool to estimate the strength of volcanic rock that can be used when the porosity crystal fraction and maximum pore diameter are known

the vanishing cryovolcanoes of ceres ahuna mons is a 4 km tall mountain on ceres interpreted as a geologically young cryovolcanic dome other possible cryovolcanic features are more ambiguous implying that cryovolcanism is only a recent phenomenon or that other cryovolcanic structures have been modified beyond easy identification we test the hypothesis that cerean cryovolcanic domes viscously relax precluding ancient domes from recognition we use numerical models to predict flow velocities of ahuna mons to be 10 500 m myr depending upon assumptions about ice content rheology grain size and thermal parameters slower flow rates in this range are sufficiently fast to induce extensive relaxation of cryovolcanic structures over 108 109 years but gradual enough for ahuna mons to remain identifiable today positive topographic features including a tholus underlying ahuna mons may represent relaxed cryovolcanic structures a composition for ahuna mons of 40 ice explains the observed distribution of cryovolcanic structures because viscous relaxation renders old cryovolcanoes unrecognizable

fluorescence properties of palaeozoic oil prone alginite in relation to hydrocarbon generation williston basin saskatchewan canada abstract alginite macerals the oil prone microscopic components of hydrocarbon source rocks fluoresce in the visible region when irradiated with ultraviolet light the fluorescence properties max and red green quotient of coccoidal unicellular and filamentous alginite macerals were investigated in palaeozoic potential hydrocarbon source rocks northern williston basin saskatchewan canada this study documents the variation in fluorescence properties of alginite during thermal maturation and the onset of petroleum generation values of max nm of disseminated coccoidal gloeocapsomorpha alginite from upper cambrian siliciclastics and upper ordovician carbonates show different magnitudes of red shift with increasing thermal maturity gloeocapsomorpha prisca disseminated alginite and g prisca stromatolitic alginite from upper ordovician kukersites exhibit unique fluorescence properties with increasing thermal maturity the former undergoes a greater red shift in fluorescence than the latter over an 1800 m change in depth of burial devonian and mississippian unicellular prasinophyte leiosphaeridia and tasmanites alginite show a minimal change in fluorescence properties max 450 500 nm between vitrinite reflectance values of 0 35 and 0 65 ro beyond 0 65 ro vitrinite reflectance prasinophyte alginites show a marked red shift to a max of 560 600 nm this phenomenon is coincident with peak hydrocarbon generation from a type ii filamentous alginite bituminite kerogen within middle devonian carbonate source rocks a comparison of the fluorescence properties of palaeozoic prasinophytes with the fluorescence properties of mesozoic prasinophytes reveals that the latter undergo a substantially greater red shift in max with increasing thermal maturity relative to the former this conspicuous difference is interpreted as a reflection of the well documented distinct difference in species and abundance of leiosphaeridia and tasmanites alginite between the geological eras

investigating collapse structures in oceanic islands using magnetotelluric surveys the case of fogo island in cape verde abstract one of the most remarkable natural events on earth are the large lateral flank collapses of oceanic volcanoes involving volumes of rock exceeding tens of km3 these collapses are relatively frequent in recent geological times as supported by evidence found in the geomorphology of volcanic island edifices and associated debris flows deposited on the proximal ocean floor the island of fogo in the cape verde archipelago is one of the most active and prominent oceanic volcanoes on earth the island has an average diameter of 25 km and reaches a maximum elevation of 2829 m above sea level m a s l at pico do fogo a young stratovolcano located within a summit depression open eastward due to a large lateral flank collapse the sudden collapse of the eastern flank of fogo island produced a megatsunami 73 ky ago the limits of the flank collapse were deduced as well from geomorphologic markers within the island the headwall of the collapse scar is interpreted as either being located beneath the post collapse volcanic infill of the summit depression or located further west corresponding to the bordeira wall that partially surrounds it the magnetotelluric mt method provides a depth distribution of the ground resistivity obtained by the simultaneous measurement of the natural variations of the electric and magnetic field of the earth two n s magnetotelluric profiles were acquired across the collapsed area to determine its geometry and boundaries the acquired mt data allowed the determination of the limits of the collapsed area more accurately as well as its morphology at depth and thickness of the post collapse infill according to the newly obtained mt data and the bathymetry of the eastern submarine flank of fogo the volume involved in the flank collapse is estimated in 110 km3 this volume the first calculated onshore stands between the previously published more conservative and excessive calculations offshore that were exclusively based in geomorphic evidence the model for the summit depression proposing two caldera collapses preceding the collapse of the eastern flank of fogo is supported by the mt data

discrete element simulations of gravitational volcanic deformation 1 deformation structures and geometries 1 we have carried out two dimensional particle dynamics simulations of granular piles subject to frictional coulomb failure criteria to gain a first order understanding of different modes of gravitational deformation within volcanoes under uniform basal and internal strength conditions granular piles grow self similarly developing distinctive stratigraphies morphologies and structures piles constructed upon cohesive substrates exhibit particle avalanching forming outward dipping strata and angle of repose slopes systematic decreases in basal strength lead to progressively deeper and steeper internal detachment faults and slip along a basal decollement landslide forms grade from shallow slumps to deep seated landslide and finally to axial subsidence and outward flank displacements or volcanic spreading surface slopes decrease and develop concave up morphologies with decreasing decollement strength depositional layers tilt progressively inward spatial variations in basal strength cause lateral transitions in pile structure stratigraphy and morphology this approximation of volcanoes as coulomb granular piles reproduces the richness of deformational structures and surface morphologies in many volcanic settings the gentle slopes of hawaiian volcanoes and olympus mons on mars suggest weak basal decollements that enable volcanic spreading high angle normal faults favored above weak decollements are interpreted in both settings and may explain catastrophic sector collapse in hawaii and broad aureole deposits surrounding olympus mons in contrast steeper slopes and shallow detachment faults predominate in the canary islands thought to lack a weak decollement favoring smaller more frequent slope failures than predicted for hawaii the numerical results provide a useful predictive tool for interpreting dynamic behavior and associated geologic hazards of active volcanoes