isotope geochemistry sr nd pb and petrogenesis of leucite bearing volcanic rocks from colli albani volcano roman magmatic province central italy inferences on volcano evolution and magma genesis the colli albani composite volcano is made up of strongly silica undersaturated leucite bearing rocks magmas were erupted during three main periods but a complex plumbing system dominated by regional tectonics channelled magmas into different reservoirs the most alkali rich magmas restricted to the caldera forming period pre caldera are extremely enriched in incompatible trace elements and display more radiogenic sr 87sr 86sr 0 71057 0 71067 with slightly less radiogenic pb with respect to those of the post caldera period post caldera volcanic activity was concentrated in three different volcanic environments external to the caldera along the caldera edge and within the caldera the post caldera magmas produced melilite to leucitite bearing plagioclase free leucitites in contrast to the pre caldera lavas they are characterised by lower incompatible trace element abundances and less radiogenic sr 87sr 86sr 0 71006 0 71039 magmas evolved through crystal fractionation plus minor crustal assimilation in a large magma chamber during the pre caldera period the multiple caldera collapses dissected and partially obliterated the early magma chamber during the post caldera stage magmas were channelled through several pathways and multiple shallow level magma reservoirs were established a lithospheric mantle wedge previously depleted in the basaltic component and subsequently enriched by metasomatic slab derived component is suggested as the mantle source of colli albani parental magmas two different parental magmas are recognised for the pre and post caldera stages the differences may be related to the interplay between smaller degrees of melting for the pre caldera magmas and more carbonate rich recycled subducted lithologies in the post caldera magmas

petrology and geochemistry of potassic and ultrapotassic volcanism in central italy petrogenesis and inferences on the evolution of the mantle sources major trace element sr isotopic and mineral chemical data are reported for mafic volcanic rocks mg value 65 from the northern central sector of the potassic volcanic belt of central italy the rocks investigated range from potassic series ks and high k series hks to lamproitic lmp and kamafugitic kam through a transitional series trans thus covering the entire compositional spectrum of potassic and ultrapotassic magmas kam rocks are strongly silica undersaturated and compared with the other rock series have low sio2 al2o3 na2o sc and v and high cao k na na k al ks and hks have high al2o3 cao and variable enrichment in k2o and incompatible elements lmp rocks are saturated in silica and have high sio2 k2o k2o na2 mgo ni and cr and low al2o3 cao na2o sc and v trans rocks display intermediate compositional characteristics between lmp and ks all the rocks under study have fractionated hygromagmaphile element patterns with high lil hfs element values and negative anomalies of ti ta nb and ba negative sr anomalies are observed in the lmp and trans rocks lil elements show overall positive correlations with k2o whereas different trends of sr and hfse vs k2o are defined by lmp trans and ks hks kam 87sr 86sr range from about 0 710 to 0 716 ks hks and kam rocks have similar 87sr 86sr values clustering around 0 710 lmp and trans rocks have the highest 87sr 86sr values geochemical and isotopic data reported for the most primitive italian potassic and ultrapotassic rocks support the hypothesis that the interaction between crustal and mantle reservoirs was a main process in the genesis of italian potassic magmatism simple mass balance calculations exclude however an important role of crustal assimilation during ascent of subcrustal magmas to the surface and indicate that the sources of central italy volcanics underwent contamination with fluids and or melts released by upper crustal material previously brought into the mantle by subduction processes different trends of incompatible elements vs k2o observed in the studied rocks suggest distinct metasomatic processes for the sources of the investigated magmas liquids derived by bulk melting of pelitic sediments are believed to be the most likely contaminants of the source of lmp rocks fluids or melts rich in ca sr and with high lile hfse value and sr isotopic composition around 0 710 are the most likely contaminant of the source region of ks hks and kam volcanics variations in cao na2o and ferromagnesian element abundances and ratios suggest that in some zones the mantle source of potassic magmas experienced partial melting with extraction of basaltic liquids prior to metasomatism

40ar 39ar and 14c geochronology of the albano maar deposits implications for defining the age and eruptive style of the most recent explosive activity at colli albani volcanic district central italy abstract new 40 ar 39 ar and 14 c ages have been found for the albano multiple maar pyroclastic units and underlying paleosols to document the most recent explosive activity in the colli albani volcanic district cavd near rome italy consisting of seven eruptions albano 1 oldest both dating methodologies have been applied on several proximal units and on four mid distal fall surge deposits the latter correlated according to two current different views to either the albano or the campi di annibale hydromagmatic center the 40 ar 39 ar ages on leucite phenocrysts from the mid distal units yielded ages of ca 72 ka 73 ka 41 ka and 36 ka bp which are indistinguishable from the previously determined 40 ar 39 ar ages of the proximal albano units 1 2 5 and 7 thus confirming their stratigraphic correspondence twenty one 14 c ages of the paleosols beneath albano units 3 5 6 and 7 were found for samples collected from 13 proximal and distal sections some of which were the same sections sampled for 40 ar 39 ar measurements the 14 c ages were found to be stratigraphically inconsistent and highly scattered and were systematically younger than the 40 ar 39 ar ages ranging from 35 ka to 3 ka considering the significant consistence of the 40 ar 39 ar chronological framework we interpret the scattered and contradictory 14 c ages to be the result of a variable contamination of the paleosols by younger organic carbon deriving from the superficial soil horizons these results suggest that multiple isotopic systems anchored to a robust stratigraphic framework may need to be employed to determine accurately the geochronology of the cavd as well as other volcanic districts

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

origin of the lethal gas burst from lake monoun cameroun abstract on 15 august 1984 a lethal gas burst issued from a submerged 96 m deep crater in lake monoun in cameroun western africa killing 37 people the event was associated with a landslide from the eastern crater rim which slumped into deep water waters below 50 m are anoxic dominated by high fe 2 600 mg l and hco 3 1900 mg l anoxic and supersaturated with siderite which is a major component of the crater floor sediments the unusually high fe 2 levels are attributed to reduction of laterite derived ferric iron gradually brought into the lake as loess and in river input sulfur compounds are below detection limits in both water and gas gases effervescing from depressurized deep waters are dominantly co 2 with minor ch 4 having 13 c of 7 18 and 54 8 per mil respectively bacterial decomposition of organic matter may account for the methane but 14 c of lake water indicates that only 10 of the carbon is modern giving an apparent age of 18 000 years the dominant source of carbon is therefore attributed to long term emission of co 2 as volcanic exhalation from vents within the crater which led to gradual build up of hco 3 in the lake the density stratification of the lake may have been upset by an earthquake and underwater landslide on 15 august which triggered overturn of the lake and caused nucleation of co 2 in the deep water the resultant ebullition of co 2 from deep lake waters led to a gas burst at the surface and locally generated a water wave up to 5 m high people travelling through the gas cloud were asphyxiated presumably from co 2 and suffered skin discoloration from unidentified components

the origin and growth of a recently active fissure ridge travertine over a seismic fault tivoli italy abstract an enigmatic c 2 km long and 15 m high travertine ridge the colle fiorito ridge occurs in the northwestern sector of the tivoli travertine plateau central italy the main questions addressed in this paper concern the origin and mode of growth of this prominent ridge the presence of active structures beneath the studied ridge is inferred by recent and past earthquakes located at shallow depths immediately beneath colle fiorito to understand the surficial structure of the colle fiorito ridge and the travertine depositional environment we constructed a 10 m resolution dem analyzed recent and past aerial photographs and conducted field surveys and meso to micro scale sedimentological analyses to understand the ridge subsurface structure we studied a set of 32 stratigraphic well logs available from previous works and from the local decorative stone industry and realized a 2d electrical resistivity tomography ert across the ridge results show a gentle antiformal structure affected by subvertical zones of strata discontinuity the colle fiorito structure is interpreted as a previously unknown fissure ridge travertine grown at the edge of the tivoli travertine plateau perhaps when the volumetric deposition rate reached its climax in the plateau for the abundance of fluid discharge and the rise of the water table such a fluid pressure may have activated the faults and fractures beneath colle fiorito thus opening new pathways for the ascension of geothermal fluids toward the surface

volcanology history and myths of the lake albano maar colli albani volcano italy abstract the polygenetic albano maar is the most recent centre of the colli albani volcano located just few kilometres to the south east of roma presently the maar hosts a 167 5 m deep crater lake the deepest in europe the maar is to be considered quiescent as phreatic activity is documented throughout the holocene this paper illustrates the close relationships between the activity of the maar and the history of settlement in the roman region as recorded in the geology archaeology history and legends of the area severe fluctuations of the groundwater table and catastrophic overflows of the lake albano from the maar rim had occurred prior to and after the early prehistoric settlements dated in the maar area at the eneolithic times ca iii millennium b c repeated lahars occurred along the northwestern slope of the maar filling in the paleodrainage network and forming a vast plain paleohydraulic analyses on fluvial and lahar deposits originated from the holocene phreatic activity of the albano maar indicate sediment water flows in excess of hundreds of cubic metres per second absolute age determinations of the paleosoil underlying one of the most recent deposits of the lahar succession at 5800 100 yr b p 14 c cal are in perfect agreement with the age of the overlying eneolithic age settlements the last catastrophic overflow is described in the roman literature as a consequence of the anger of poseidon against the romans in 398 b c for their war against the etruscans in 394 b c the romans decided to prevent the repetition of such events by the excavation through the maar crater wall of a 1 5 km long drain tunnel which is still operational keeping the lake 70 m below the lowest point of the maar rim this tunnel drain may be regarded as the first prevention device for volcanic hazard in history and shows an unprecedented development of the engineering technology under the pressure of hazard perception the surprising and still largely unknown results of this study are very important to redefine the hazard of the roman region

patterns and processes of shell fragmentation in modern and ancient marine environments shell fragments are important components of many recent and fossil marine benthic ecosystems and can provide crucial information on past and present environmental conditions interpreting such fragments requires integrated knowledge in various fields and the information potential is therefore rarely optimally utilized this paper uses the definition of a fragment as being a piece of shell having less than 90 of its original form it then outlines the potential characteristics pathways and fates that shells and their fragments can have fragmentation is a key factor shaping the shelly part of death assemblages but it is difficult to interpret because it can be broadly caused by ecological biostratinomic or diagenetic processes and also depends on shell strength strength in turn reflects multifunctionality during ontogeny and depends on a complex set of skeletal and taphonomic factors therefore no particular shell parameter clearly determines strength but thickness microstructure type and degree of organic matrix have the strongest influence on pre and post mortality strength size measurements are usually less important for shell strength than thickness although ecologically complex size refuges from predation do exist similarly shell shape sculptural features and specific aperture types in gastropods provide various defence strategies rather than increasing strength per se key ecological factors of fragmentation include predation due to crushing peeling along with mistaken predation selfinflicted damage during predation and burrowing and more physical aspects such as impacts by stones modern studies must consider damage by benthic commercial fisheries or dredging by scientific vessels key biostratinomic factors include transportinduced abrasion littoral zone of surf washed beaches bioerosion and dissolution mainly sublittoral environments diagenetically fragmentation during compaction mainly occurs when shells are in direct contact with one another or with coarser grains taphonomic features e g drillholes have only minor influence a key step in interpreting fragments is to categorize breakage into repaired versus unrepaired diagnostic versus nondiagnostic and severe versus localized damage quantifying the above categories can then provide useful information on breakage patterns and underlying processes understanding the many characteristics of shells and their fragments is a significant interpretive tool in maximizing the information gain in palaeoecological and taphofacies analyses d 2003 elsevier science b v all rights reserved

the colli albani mafic caldera roma italy stratigraphy structure and petrology new results for the colli albani volcano roma italy surveyed for the geological map of italy at 1 50 000 scale carg project integrated with previous data provide insights on caldera evolution the colli albani a quiescent volcano became active at 600 ka eruptive compositions are consistently mafic 50 km 3 deposits forming the villa senni eruption unit ignimbrites at ca 355 ka two edifices were built within the caldera 1 the horseshoe shaped tuscolano artemisio ta composite edifice or lithosome consists of coalescing peri caldera fissure related scoriae cones interbedded with lava flows the fissure system forms two segments controlled by regional fractures 2 the steep sided faete stratovolcano 949 m a s l filled the caldera the ta and faete lithosomes partly interfinger and were emplaced at 350 260 ka their products indicate reduced eruption rates relative to the vl period and a change to effusive and mildly explosive eruptions the most recent and still active phase of phreatomagmatic activity formed overlapping maars and tuff cones along the western and northern slopes of the volcano collectively named via dei laghi composite lithosome the colli albani caldera is poly phase 1 a piecemeal caldera is associated with large volume ignimbrites of the vl edifice the present shape of the caldera is related to the villa senni eruption 2 the ta composite edifice erupted from peripheral caldera fissures is unrelated to explosive phases of caldera collapse the ta final products cover a morphologically stable caldera wall the peripheral fractures feeding the ta composite edifice are interpreted as volcano tectonic structures activated during the late stage downsag of the caldera reduced eruption rates during the ta and the faete stages 10 1 km 3 1 ka respect to 10 0 km 3 1 ka for the vl edifice suggest a reduced recharge of the magma chamber that may have induced prolonged deflation and downsagging of the caldera floor and the opening of outward dipping peripheral fractures by this interpretation the ta edifice represents the surface expression of ring dykes at depth the absence of similar fissure structures along the western caldera rim may relate to the deep geometry of the ring faults dipping inward in those areas and therefore not favourably oriented for magma intrusion during a period of general subsidence by contrast the following and still active phreatomagmatic phase that has emplaced the via dei laghi composite edifice is located right on the western side of the caldera and may therefore relate to resurgent conditions classical petrological and pers pearce elements ratios analyses indicate that lavas are co genetic and show a differentiation trend up through stratigraphy driven by

conditions for long lasting gas eruptions the 2013 event at fiumicino international airport rome italy abstract a hazardous gas eruption from two very close shallow boreholes occurred near the fiumicino international airport of roma italy from august to december 2013 the erupted gas was mostly co 2 of deep origin and gas output was high and sustained over time reaching values of nearly 20 t day 1 after 3 months the gas flux was still above 5 t day 1 and was only stopped in december 2013 by long and expensive works of closure of the boreholes the gas eruption was uncommon as being associated with the building of two mud volcanoes this style of sustained deep co 2 eruptions contrasts with the more common short lived eruptions of shallow biogenic methane dominated gas pockets in this work we present the chronology of the event the results of geological geochemical and geophysical monitoring and a numerical modeling we propose that the august december 2013 sustained and prolonged event does not relate to the simple degassing of a shallow isolated pocket of gas on the contrary it reflects very specific conditions in a shallow reservoir hosted in a 10 m thick gravel layer at 40 m within the tiber river delta deposits related to the interplay between the total pressure and the fraction of free co 2 initially present across very narrow value ranges around 0 59 mpa and 0 18 respectively the coexistence of short lived and long lived eruptions from the same reservoir suggest that these conditions are not achieved everywhere in the gas reservoir despite its homogeneous properties this consideration implies either a pressure compartmentalization of the reservoir or the occurrence of a transient possibly associated with an impulsive release of gas from greater depths the involvement of deeper and larger gas reservoirs connected along faults is evidenced by geophysical investigations this conceptual model bears significant implications for gas hazard studies

ch 4 consuming microorganisms and the formation of carbonate crusts at cold seeps to understand the role played by microorganisms in the formation of cold seep carbonates we conducted an integrated microbial mineralogical and organic geochemical study of methane related authigenic carbonate crusts formed on eastern mediterranean mud volcanoes we show that supersaturation with respect to carbonate minerals is induced by microbial anaerobic oxidation of methane combined lipid biomarker analysis and 16s rrna gene surveys identified a highly diversified methane consuming archaeal community possibly comprising novel species implying that the anaerobic oxidation of methane is phylogenetically widespread and directly implicating these organisms in the process of crust precipitation moreover pore water sulphate gradients produced by co occurring methane based sulphate reduction exert the main control on aragonite versus magnesian calcite precipitation we propose that this may be the dominant mode of carbonate crust formation at cold seeps world wide in agreement with aquatic chemistry predictions and explaining carbonate mineralogy

co2 release variations during the last 2000 years at the colli albani volcano roma italy from speleothems studies abstract the colli albani is the quiescent volcano that dominates the southwestern skyline of roma italy the last eruption occurred during the holocene from the eccentric albano maar along its western slope the volcano is presently affected by cyclic seismic swarms ground uplift and diffuse co 2 degassing the degassing has caused several deadly incidents during the last years and constitutes a major civil protection concern as the volcano slopes are densely inhabited nevertheless the volcano does not have a permanent monitoring network and the background level and anomalous co 2 levels the relationship between the gas release and the seismic and ground deformation activity at the colli albani are still to be defined the aim of this work is to define the historical record of co 2 release evidences of deep co 2 periodic release during the last 2000 years in the area of colli albani volcano roma italy are offered from speleothems studies a roman age stone mine now used for mushroom cultivation is decorated with actively growing speleothems characterised by depositional hiatuses different levels of four stalactites separated by depositional unconformities and several samples from a single depositional cycle belonging to a stalagmite have been dated by u th method and analysed for their o and c isotopic composition eight cycles of deposition have been identified from 90 110 a d to 1350 1370 a d some of which are recognised across different speleothems the age gap dividing different growth layers is in the order of one to few hundred years giving a temporal span for periodic interruption of speleothems deposition o and c isotopic analyses performed on the samples collected from a single cycle the oldest have shown that the composition of the mother solutions was initially mainly meteoric and that a progressive increase in the input of a deep component rich in co 2 up to a proportion of 20 30 occurred just before the interruption of the speleothem deposition this could be due to a progressive increase of the acidity of the water solutions that caused the undersaturation of fluids if we extrapolate this mechanism to the other cycles of deposition being characterised by analogue isotopic compositions we can hypothesise periods of deposition interrupted by episodes of co 2 release which in the colli albani volcano are often recorded in coincidence with earthquakes therefore we have correlated the hiatuses with some of the largest historical earthquakes interesting to the city of rome

geochemical environments of continental shelf upper slope sediments in the northern gulf of mexico geochemical environments were characterized for 14 sites along the northern gulf of mexico continental shelf and upper slope in an effort to examine the relationship between sediment geochemistry and carbonate shell taphonomy in a long term study shelf and slope experimental taphonomy initiative sseti three groups of environments of preservation seep near seep and shelf and slope were identified based on their geochemical characteristics i e oxygen uptake rate and penetration depth pore water saturation states and carbonate dissolution fluxes diffusive oxygen uptake rate increased in the order of shelf and slope near seep and seep although carbonate dissolution flux did not show significant correlation with o2 flux presumably due to non diffusive behavior at some sites using pore water saturation indices with respect to aragonite and calcite and sedimentation rates we defined a semi quantitative parameter carbonate dissolution index cdi to predict carbonate preservation potential during the taphonomic processes our limited database suggests that both the seep and the shelf and slope sediments may have higher carbonate preservation potential than the near seep sediments

the role of external environmental factors in changing eruption styles of monogenetic volcanoes in a mio pleistocene continental volcanic field in western hungary abstract the occurrence shape structure and eruption style of monogenetic volcanoes such as maars tuff rings tuff cones and scoria cones are generally governed by several internal composition of the magma magmatic flux ascent rate viscosity volatile contents and external conditions regional and local tectonics topography and the presence of surfacial ground and meteoric water these controlling factors are together responsible for the eruption style distribution pattern volcanic facies architecture and morphology of the monogenetic volcanic landforms the late miocene to pleistocene bakony balaton highland volcanic field bbhvf in western hungary is a typical small sized at least 6 volcanic cycles have been identified by cluster analysis time gap between the cycles were vary from 1 66 up to 0 06 ma while the average eruption recurrence rate was 0 1078 ma event the time volume diagram of the volcanism of bbhvf have shown time predictive behavior combined with low magma flux total preserved volume 2 867 km3 and output rates 0 53 km3 ma for the entire volcanic field and 0 90 km3 ma for the last 5 cycles suggesting that volcanism was largely tectonically controlled and not magmatically controlled furthermore the topographic differences between the northern elevated and southern basin like parts of the volcanic field are also important in local differences in dominant fragmentation style because the elevated part of the field was prone to host large more magmatically evolved volcanoes than on the lower water saturated unconsolidated sediments which favored to the magma water interaction driven phreatomagmatic fragmentation the third controlling parameter which seems to play an important role in controlling the eruptive style of monogenetic volcanism at bbhvf was the paleoclimate fluctuation especially during the time interval of 3 0 to 2 5 ma thus mainly the long term environmental changes e g aridification have been response the shifting fragmentation style from phreatomagmatic to more magmatic ones

the 1245 yr bp asososca maar eruption the youngest event along the nejapa miraflores volcanic fault western managua nicaragua abstract the asososca tephra comprises the asymmetrically distributed well stratified phreatomagmatic products of the 1245 125 120 yr bp asososca maar eruption west of managua nicaragua it is the youngest eruptive unit related to the monogenetic volcanism concentrated along the n s trending nejapa miraflores active fault and intersecting e w to ne sw and nw se minor faults the close relationship between monogenetic volcanism and the structural local tectonic framework is evidenced by the lineament domains and vent alignment patterns identified by remotely sensed images and dems of the research area the asososca maar lake bathymetry suggests that the crater was formed by coalescing vents migrating during the eruptive event the asososca tephra dominantly consists of accidental lithics disrupted from the underlying stratigraphic units observed inside and around the maar crater dry base surge bedsets are dominant throughout the eruptive unit showing facies variation from proximal cross stratified beds to mid distal plane parallel and wavy parallel beds grain size analyses indicate that base surges transported dominantly 1 0 and 1 sized particles at the bedload in form of traction carpets while fine ash material in continuous suspension was minimal juvenile fragments were only identified in the finer fractions varying from vesiculated scoriae to dense sideromelane fragments sem analyses suggest that the asososca eruption resulted from a highly efficient fuel coolant interaction between a tholeiitic basaltic melt and an aquifer hosted in a shallow level between 50 and 200 m of olivine bearing scoria ash and lapilli beds the explosion triggered the country rock comminution and the production of moss like fused shaped and blocky ash shards with stepped surfaces quenching cracks pitting alteration skins and adhered particles all indicative of phreatomagmatic fragmentation the very recent age of the asososca maar eruption confirms that the densely inhabited managua area is volcanically active and that hazard studies should focus on the potential for phreatomagmatic eruptions

taphonomic processes affecting late quaternary molluscs along the coastal area of buenos aires province argentina southwestern atlantic molluscan concentrations were abundantly deposited along the coastal area of buenos aires province argentina southwestern atlantic by different sea level episodes during the late quaternary most of them represent holocene ridges highly energetic depositional environments subparallel to the modern shore where the main associations preserved are parautochthonous and others mainly autochthonous associations occurring in tidal flats seaward of the ridges or coastal lagoon deposits accumulated behind them low energetic analysis of three physical taphonomic signatures disarticulation fragmentation and abrasion of the molluscan skeletons of four bivalve species tagelus plebeius mactra isabelleana pitar rostratus brachidontes rodriguezi which exhibit different shell shape and thickness conditions habitats and life habits and represent the most widely distributed and palaeoecologically significant taxa along the area of study support the distinction of both palaeoenvironments characterized by low and high taphonomic grades respectively the taphonomic alteration breakage and abrasion of most shells seems to have been a direct consequence of the amount of reworking of the material especially during periods of exposure along an extensive beach zone more than a consequence of transport from a distant original habitat abrasion signatures are the only probably correlated with after death time span shells showing a near modern aspect and original luster being most probably younger than those with chalky or polished appearance the infaunal species analysed typically living on clays and silts or fine sandy bottoms of the infralittoral or intertidal t plebeius m isabelleana are better preserved less fragmented and abraded than shells of the epibyssate b rodriguezi which lives on hard bottoms of the intertidal and supralittoral areas more exposed to highly unstable conditions with longer episodes of exposure although these nearshore concentrations may represent a time averaging of 1000 yr b p taking into account the ecological requirements of the most constant and dominant taxa together with the taphonomic analysis of shells from parautochthonous and autochthonous associations they still represent valid indicators of past marginal marine conditions in the area but are only reliable to establish long term palaeoenvironmental variations

evidence of episodic fluid gas and sediment venting on the northern gulf of mexico continental slope surficial sediments and sea floor features of the northern gulf of mexico continental slope record dramatic episodic venting and slower seepage of formation fluids brines crude oil gases and fine grained sediments faults activated by massive sediment input during periods of plio pleistocene falling to low sea levels accompanied by compensating salt movement provide avenues of vertical transport to the continental slope surface many of these faults cut thick sedimentary sequences that frequently contain geopressured zones which provide the driving force for fluid and gas expulsion flux rate and fluid characteristics are interpreted as important determinants of modern sea floor geology and biology qualitatively under conditions of rapid flux of sediment rich fluids mud volcanoes up to 1 km wide and 50 m high and extensive sheets of extruded mud result these sediments contain old and displaced microfaunas muds are frequently extruded with large volumes of crude oil and gas both biogenic and thermogenic in water depths greater than approximately 500 m rapid to moderate vertical flux of hydrocarbon gases and fluids results in the construction of relief features composed of gas hydrates ejected mud and authigenic carbonates areas with near surface hydrates frequently support complex chemosynthetic communities with associated hardgrounds containing calcareous remains of mussels clams and associated gastropods slow flux seeps promotes the formation of 13 c depleted carbonate hardgrounds stacked carbonate slabs and moundlike carbonate buildups frequently 20 m relief barite along with carbonate has been found in areas where rapid flux of sediment carrying fluids has waned in the recent past and mineral rich brines are now being ejected crests chimneys and cones of these minerals are found in such settings both recent numerical simulations of fluid release from geopressured zones and direct observations at the sea floor support a pattern of episodic venting short term episodes of venting are probably regulated by fault movement perhaps controlled by local salt adjustment destabilization of gas hydrates by oceanographic processes also causes short term episodic gas expulsion these events occur with interannual to intra annual frequencies longer gas hydrate stabilization destabilization cycles in continental margin settings are forced by hydrostatic loading and unloading at the frequency of sea level change radiometric dating suggests that other long term episodes of venting and major venting expulsion events are also probably modulated by sea level change time scales of thousands of years in response to low stand sedimentary loading results of this summary of vent seep related phenomena suggest that sediment input from the shelf margin associated with cyclic plio pleistocene falling to low sea level periods followed by major listic fault and salt adjustments to a new sediment load have activated venting seepage throughout this period and perhaps longer

why did ancient chemosynthetic seep and vent assemblages occur in shallower water than they do today cold seep communities have relatively low diversity are dominated by one or two taxa present in high density and high biomass in comparison with the surrounding fauna and are restricted to aphotic habitats their associated heterotrophic fauna are usually distinctive from the fauna of their surroundings in contrast a more commonplace chemoautotrophically based community occurs in shallow photic habitats the associated heterotrophic fauna includes many of the species typical of the surrounding communities and typically dominates abundance whereas the species with chemoautotrophic symbionts dominate biomass all modern seep assemblages are deeper than 550 m many fossil seep assemblages occurred in water as shallow as the mid shelf 200 m in contrast communities where species with chemoautotrophic symbionts are biomass dominants but not numerical dominants are common in shallow waters at present but rarely reported in the geological record we suggest that the absence of cold seep communities on the continental shelf presently is due to a combination of predation and competitive exclusion by primary consumers limiting the presence of species dependent on chemoautotrophic symbionts we suggest that cold seep assemblages are more common at shelf depths in the fossil record for two reasons a the biases of preservation have accentuated their distribution by transforming communities where species with chemoautotrophic symbionts dominate by biomass but not numerically into cold seep appearing assemblages b the importance of predation pressure and oligotrophy has varied with decreased predation pressure accompanying increased oligotrophy favoring cold seep communities we suggest that the paucity of shallow water assemblages with species harboring chemoautotrophic symbionts as biomass dominants in the fossil record is based on the reliance of paleoecological analysis on numerical abundance data when energy flow analyses are required to identify these assemblages the distinctiveness of the fossil seep assemblage is intensified by taphonomic processes that bias the assemblage against small individuals and epifaunal species so that diversity declines the small heterotrophic component of the assemblage is significantly reduced and the epifaunal component is minimized the final assemblage is usually dominated by the better preserved large infaunal clams which perchance are also the species with chemoautotrophic symbionts in contrast preservation does not enhance the distinctiveness of these chemoautotroph harboring species in shallow water

preferential dissolution of carbonate shells driven by petroleum seep activity in the gulf of mexico abstract authigenic carbonates are common at deep sea petroleum seeps as a result of excess bicarbonate production during microbial degradation of hydrocarbons coupled to sulfate reduction consequently these seep environments are supersaturated with respect to carbonates this finding conflicts with taphonomic data that dissolution is the most pervasive mode of shell alteration at seeps we provide here the first study linking the preservational process with the chemical characterization of the taphonomically active zone at petroleum seep sites this characterization is made possible using fine scale porewater carbonate chemistry data and skeletal material deployed for 8 years at petroleum seep sites in the northwestern gulf of mexico microelectrode measurements of ph and pco2 identify a very restricted zone of caco3 undersaturation immediately below the sediment water interface in otherwise supersaturated environments i e sandwiched between supersaturated bottom seawater and sediment porewater this zonation characterizes the taphonomically active zone and is a result of a highly compressed redox front between acid generating aerobic oxidation of reduced chemical species including hydrocarbons h2s and planktonic and terrestrial organic carbon and base generating sulfate reduction coupled to ch4 oxidation porewater geochemistry is spatially variable at seep sites and produces variable shell dissolution signatures shells deployed at seep sites have moderate to severe dissolution that is consistent with a much higher flux of total dissolved inorganic carbon dic from the porewater to the bottom water therefore a mosaic of preservational conditions is directly related to the spatially and chemically varying taphonomically active zones found at seep sites these findings support the variability of carbonate preservation reported for globally distributed phanerozoic fossil seeps and the view that data from field taphonomy can significantly upgrade and validate carbonate destruction rates used in geochemical and climatic models carbon mass balance analyses also lead to an important conclusion that carbonate dissolution forms a very important mechanism for benthic carbon recycling possibly accounting for 50 of the benthic dic flux to the bottom water in northern gulf of mexico petroleum seep sediments

plateau versus fissure ridge travertines from quaternary geothermal springs of italy and turkey interactions and feedbacks between fluid discharge paleoclimate and tectonics abstract morphologically different deposits of thermal travertines are known worldwide but what factors controlled their morphology volume and growth for tens of thousands of years is only partially understood two main morphotypes of quaternary thermal travertines are reconsidered here to understand the reasons for their differential growth the fissure ridge travertines of denizli basin western turkey and the travertine plateau of tivoli central italy for comparable longevities and average vertical deposition rates the main differences between the studied travertines are as follows 1 volume of the travertine plateau is about one hundred times larger than each fissure ridge 2 despite a larger volume the travertine plateau does not produce relief whereas the fissure ridges produce a characteristic prominent topography 3 the travertine plateau grew primarily through lateral progradation whereas the fissure ridges through vertical aggradation 4 travertine deposition occurred in different environments principally low energy flat or shallow environments at tivoli and high energy inclined environments at denizli 5 the growth of the tivoli plateau occurred in a subsiding basin whereas the fissure ridges were not influenced by significant subsidence 6 c and o isotope signatures from the two studied travertines are different 7 despite similar annual precipitations the present water discharge in the tivoli area is about ten times greater than that of the denizli basin u series ages from the two deposits are correlated with paleoclimate oscillations at regional and global scales geological field evidence together with paleoclimate correlations suggest that in both the study cases the main body of travertine deposits the bedded travertine grew preferentially when the water table was high warm and or humid periods conversely when the water table was depressed cold and or dry periods the tivoli travertine underwent partial erosion and the denizli ridges were cut by axial veins and lateral sill like structures filled by banded sparitic travertine a comparative model is proposed where the main factor driving the difference in the morphostratigraphic architecture of fissure ridges and travertine plateaus is the volume of water discharge a high discharge rate resulted in the precipitation of caco3 far away from the springs hence driving the lateral progradation of the tivoli plateau a reduced discharge rate caused travertine precipitation close to the springs thus causing the vertical aggradation of the denizli fissure ridges paleoclimate oscillations must have controlled the amount of fluid discharge which in turn must have influenced the opening of the feeding fractures by an increased pore pressure

extreme events in the sedimentary record of maar lake pavin implications for natural hazards assessment in the french massif central a set of sedimentary cores high resolution swath bathymetry and subbottom profiler data provides new insights on sedimentary processes in meromictic maar lake pavin france three sedimentary environments i e littoral plateau and basin have been identified in the lake from sediment composition using bulk organic geochemistry and the analysis of hydroacoustic images various forms of rapidly deposited layers rdls have been identified and radiocarbon dated an up to date stratigraphy of sedimentary events matching coeval rdls across the lake is presented and illustrates a wide range of natural hazards linked to lake pavin during the last 2000 years in ad 600 a sudden lake outburst triggered a slump deposit along with a 9 m lake level drop that drove shifts in sedimentary organic matter composition outside the lake outburst flood deposits have been described downstream and provide sedimentary evidence for this event the lake level drop also favored the generation of gravity reworking processes as shown by 1 a regional earthquake triggered large slope failure on the plateau connected to a masswasting deposit in the basin dated to ad 1300 and 2 a succession of turbidites in ad 1825 and ad 1860 contemporaneous to two historic earthquakes suggesting that this lake is sensitive to earthquakes with a minimum epicentral intensity of v finally past observations of lake water color changes in ad 1783 and ad 1936 similar to reports in other meromictic lakes match iron rich deposits identified in maar lake sediments and suggest that lake pavin could have undergone limnic eruptions

the gas cloud of lake nyos cameroon 1986 results of the italian technical mission abstract on august 21 1986 a gas cloud issued from lake nyos in cameroon killed over 1700 people an italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe on the basis of observations and measurements in the field and of samples collected the origin of the gas outburst is attributed to a phreatic explosion from beneath the bed of the lake this interpretation appears to fit well the observed and reported phenomena and seems perfectly consistent with the geological geothermal conditions of the area

taphonomic implications of shell surface textures in bahia la choya northern gulf of california abstract the author collected shell samples of the bivalve chione from the extensive tidal flat system of bahia la choya northern gulf of california and examined their surfaces under the binocular and scanning electron microscopes samples were collected from environments ranging in degree of tidal exposure energy level and substrate inner tidal flats sandy outer flats rocky outer flats tidal channel estero channel salt marsh beach spit and subtidal surfaces were compared with those of shells experimentally subjected to bioerosion dissolution and abrasion in all more than 1100 shells were examined and described bioerosion by microborers is by far the dominant process attacking shell material in bahia la choya microbored textures dominated shell surfaces from all sedimentary environments with the exception of the beach where abrasion dominated chemical dissolution is important only in the fine grained salt marsh and inner flat environments many shells show composite textures which reflect the concurrent action of more than one taphonomic agent shells from the salt marsh for example frequently show the effects of both microboring and dissolution overprinted textures can document transport among environments

high level triggers for explosive mafic volcanism albano maar italy abstract colli albani is a quiescent caldera complex located within the roman magmatic province rmp italy the recent via dei laghi phreatomagmatic eruptions led to the formation of nested maars albano maar is the largest and has erupted seven times between ca 69 33 ka the highly explosive nature of the albano maar eruptions is at odds with the predominant relatively mafic sio 2 48 52 wt foiditic k 2 o 9 wt composition of the magma the deposits have been previously interpreted as phreatomagmatic however they contain large amounts up to 30 vol of deep seated xenoliths skarns and all pre volcanic subsurface units all of the xenoliths have been excavated from depths of up to 6 km rather than being limited to the depth at which magma and water interaction is likely to have occurred suggesting an alternative trigger for eruption high precision geochemical glass and mineral data of fresh juvenile magmatic clasts from the small volume explosive deposits indicate that the magmas have evolved along one of two evolutionary paths towards foidite or phonolite the foiditic melts record ca 50 mixing between the most primitive magma and ca rich melt late stage prior to eruption a major result of our study is finding that the generation of ca rich melts via assimilation of limestone may provide storage for significant amounts of co 2 that can be released during a mixing event with silicate magma differences in melt evolution are inferred as having been controlled by variations in storage conditions residence time and magma volume

first integrated tephrochronological record for the last 190 kyr from the fucino quaternary lacustrine succession central italy we present the first integrated tephrochronological study major and trace elemental glass composition sr and nd isotope analyses and 40ar 39ar dating for the last one tenth 82 m of the 900 m thick quaternary lacustrine succession of the fucino basin the largest and probably only central apennine intermountain tectonic depression that hosts a continuous lacustrine succession documenting the plio quaternary sedimentary history up to historical times major element glass compositions determined using a wavelength dispersive electron microprobe wds empa yielded the geochemical fingerprinting needed for a reliable identification of most of the 23 stratigraphically ordered tephra layers under investigation these include tephra from italian volcanoes such as campi flegrei etna colli albani ischia vico sabatini and undefined volcanic sources in the neapolitan area and latium region the recognition of key mediterranean marker tephra layers e g x 5 and x 6 is supported by trace element data acquired by laser ablation inductively couple plasma mass spectrometry la icp ms the sr and nd isotope compositions of selected layers where also determined for circumscribing the volcanic source of distal tephra and for supporting correlations with individual eruptive units we also propose a new more expeditious covariation diagram cao feotot vs cl for identifying the volcanic source of trachytic to phonolitic and tephrytic to phonolitic tephra that are the most common compositions of pyroclastic rocks from volcanoes of campania and latium regions finally we present five new 40ar 39ar age determinations including a new analytically well supported and more precise 40ar 39ar age for the widespread y 7 tephra and the first 40ar 39ar age determinations for one tephra from the sabatini volcanic district 126 ka and one tephra from neapolitan volcanic area campi flegrei 159 ka these newly dated tephra are widely dispersed e g monticchio southern italy adriatic sea and lake ohrid macedonia abania and have thus the potential to become important mediterranean mis 5 and mis 6 tephrochronological markers altogether the new geochemical data and 40ar 39ar ages precisely constrain the chronology of the investigated fucino succession spanning the last 190 ka in light of these results and by considering that this sedimentary succession possibly extends back to 2 ma fucino is likely to provide a very long continuous tephrostratigraphic record for the mediterranean area and become a key node in the dense network of tephra correlations of this region

ocean quahogs arctica islandica and atlantic surfclams spisula solidissima on the mid atlantic bight continental shelf and georges bank the death assemblage as a recorder of climate change and the reorganization of the continental shelf benthos abstract the degree to which evidence of range shifts in shelf biomass dominants atlantic surfclams and ocean quahogs as a function of climate change is examined by comparing the dissimilarity in distribution of the living community and the record of habitation ensconced in the death assemblage comparison of the distribution of live animals and dead shells reveals for both species that live animals are rarely found where dead shells were not collected but dead shells were collected at a substantively larger number of sites than where live animals were found the geographic footprint resolved by the dead shells was much broader than that of live animals extensive spatially coherent regions exist inshore and offshore of the present day habitat of occupation where evidence of previous occupation exists sites where ocean quahog shells were found without live ocean quahogs included a portion of the continental shelf inshore of the present day habitable range an area only habitable under colder climatic conditions than observed today surfclam shells were found offshore of the present day habitable region in deeper water additional warming of bottom waters offshore would be necessary for surfclams to occupy the region now occupied solely by dead shells the death assemblage shows that these biomass dominants have repositioned themselves across the continental shelf during the past and this repositioning certainly is driven by changes in bottom water temperature moreover the distribution of surfclam shells indicates that the death assemblage may provide a possible window into the future as movement of the present day population is towards these deeper water previously occupied regions overall the death assemblage may provide an important source of information on range shifts sparing the need to carry out extensive and frequent benthic surveys and may permit reconstruction of ongoing shifts in community composition as a product of climate change when adequate survey data are not available

crystal chemistry of trioctahedral micas in the top sequences of the colli albani volcano roman region central italy abstract trioctahedral mica crystals are frequently found in the volcanoclastic products emplaced during the final stages of the activity of the colli albani volcano roman region central italy in the youngest phreatomagmatic deposits mica is found either as a minor mineral phase in holocrystalline ejecta scoriae and coherent pyroclastics or as loose phenocryst in incoherent pyroclastics based on optical and electron microscope investigations as well as crystal chemical and structural data the micas selected for this study were divided into two groups the first one encompassing brownish fe rich crystals type a phlogopites hereafter referred as t a with 0 68 from a petrological point of view the textural and chemical variations of t a phlogopites are compatible with fractional crystallization processes taking place within the magma chamber t b phlogopites show evidence of a ti oxy substitution mechanism thus suggesting high fo2 conditions textural and paragenetic features observed in t b phlogopite bearing rock samples indicate a genesis by thermal metamorphism of a siliceous dolomitic limestone with the input of a variable amount of a potassic magma possibly the same from which the t a phlogopites formed with the exception of one sample for which a different parental magma is suggested indeed there is an almost continuous spectrum of crystal chemical and structural parameters starting from t b and evolving towards t a phlogopites the t a phlogopites displays complex apparently meaningless relationships in their crystal chemical parameters thus indicating interplay of several substitution mechanisms they possibly formed in polybaric conditions since their cell volumes differ but the total size of the cations hosted in the octahedral sheet is the same

the role of the global carbonate cycle in the regulation and evolution of the earth system we review one of the most ancient of all the global biogeochemical cycles and one which reflects the profound geochemical and biological changes that have occurred as the earth system has evolved through time that of calcium carbonate caco3 in particular we highlight a mid mesozoic revolution in the nature and location of carbonate deposition in the marine environment driven by the ecological success of calcareous plankton this drove the creation of a responsive deep sea sedimentary sink of caco3 the result is that biologically driven carbonate deposition provides a significant buffering of ocean chemistry and of atmospheric co2 in the modern system however the same calcifying organisms that under pin the deep sea carbonate sink are now threatened by the continued atmospheric release of fossil fuel co2 and increasing acidity of the surface ocean we are not yet in a position to predict what the impact on caco3 production will be or how the uptake of fossil fuel co2 by the ocean will be affected this uncertainty in the future trajectory of atmospheric co2 that comes from incomplete understanding of the marine carbonate cycle is cause for concern

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

is burial velocity a master parameter for bioturbation abstract the intensity of biological mixing in a marine sediment is widely believed to be related to the flux of labile organic matter at the same time this flux has been shown to be strongly correlated to the burial velocity one would then expect a significant correlation between biological mixing coefficient d b and burial velocity a nonlinear regression of existing data with a power law eqns 2 and 3 of the text produces a statistically significant correlation the statistical significance of the regression in no way implies causation and in fact it accounts for only about 22 of the total variance in the dataset thus reducing its physical significance a number of additional processes contribute to the large observed variance including timing of mixing events temporal and spatial heterogeneity differences in temporal scales sampling artifacts and specific particle associations with due care the d b relationship may prove useful in defining the likely range of d b values in a particular environment a similar analysis of the tracer identified surface mixed depth shows that it is essentially independent of burial velocity with a worldwide mean of 9 8 4 5 cm depth of mixing is probably more closely related to the energetic costs of deep burrowing

bioerosion and carbonate mud production on high latitude shelves low latitude carbonate muds often are composed either of entire units of skeletons e g algal muds or of precipitates whereas high latitude carbonate muds are bioerosional or result from maceration bioerosion at high latitudes is most intense in the photic zone particularly down to 25 m depth shelly substrata may be crushed bitten drilled bored or scraped clionid sponges endolithic algae acmaeid gastropods and regular echinoids are the most significant agents clionids produce distinctive facetted carbonate silt chips when boring which have been described from both high and low latitudes faecal pellets break down to yield mud sized carbonate particles that are more irregular than those produced by maceration exhumed infaunal bivalves are often preferred to epifaunal organisms as substrata bioerosion occurs very rapidly shells may be totally infested with boring algae in three months a moth eaten appearance therefore does not denote a relict grain reliable rates of fine sediment production are not yet available the mud fraction of northwest european shelf sediment generally contains 10 20 caco3 though an inshore and offshore belt with higher values may be identified some holocene supratidal mud flats exceed 50 caco3 much of the shelf represents a modern day equivalent of the calcareous shale facies common in the geological record instances of synsedimentary cementation are not uncommon particularly in association with heavily burrowed muds

water and gas chemistry of lake nyos and its bearing on the eruptive process abstract the isotopic and chemical composition of water samples collected from lake nyos some two and eight weeks after the eruption of august 21 1986 point to the existence of three distinct mixing regimes involving three water components an essentially homogeneous unmixed body of water at depths 100 m overlain by water increasingly affected by surface evaporation and a 5 10 m layer containing recent but pre eruption rain water the cationic constituents na k mg ca mn fe of the lake water correspond to the dissolution of around 0 1 g of local rock the waters are close to saturation with respect to siderite the composition of the gas dissolved in the deep lake waters 0 65 b w of co2 pco2 4 4b corresponds in mmol mol 1 to 996 co2 2 0 ch4 2 0 n2 0 05 ar 0 004 he 0 0002 h2 0 0001 ne co 2 13 c 3 4 and of he rair 5 5 suggest deep magmatic origins the 13c and 2h content of ch4 organic sedimentary origin the presence of aromatic hydrocarbons indicates very high temperatures of hydrocarbon formation exsolution of gas will first lead to the precipitation of siderite then iron hydroxide the chemistry of the lake waters points to a loss of some 240 000 t of co2 from the upper 100 m of the lake their isotopic composition is consistent with the assumption that the eruption was triggered by the accumulation of cold rain waters at the lake surface prior to the eruption inducing partial convective overturn there is no need to invoke addition of chemical or isotopic constituents from deeper levels during the eruption

magnetic fabric and implications for pyroclastic flow and lahar emplacement albano maar italy 1 the albano polygenetic maar is the youngest eruptive center of the quiescent colli albani volcano located near the city of rome the most recent activity of the albano maar extends from 23 ka into the holocene and produced the small volume basic phreatomagmatic peperino albano pa ignimbrite and more recently phreatomagmatic surge and lahar deposits related to the overspill of the albano maar lake we have performed an anisotropy of magnetic susceptibility ams study in order to define the relationships between the magnetic fabric and the flow mechanisms of the pa and of the phreatomagmatic deposits and lahars ams results indicate different transport and or depositional systems for the veneer and valley pond facies in the pa ignimbrite and for the lahar deposits ams also demonstrates that flow directions are mainly controlled by the paleotopography the paleotopographic control has been interpreted in terms of talweg sedimentation even at proximal locations where deposition occurs from dilute pyroclastic flows furthermore ams results clearly evidence a southward provenance for holocene post pa ignimbrite units cropping out in the ciampino plain and confirm their origin from albano maar lake overspill we demonstrate that ams is a reliable marker to determine paleoflow directions also in small volume phreatomagmatic ignimbrites and in syneruptive lahar deposits and can be successfully used to define their depositional systems

time dependent co2 variations in lake albano associated with seismic activity lake albano alban hills volcanic complex central italy is located in a densely populated area near rome the deep lake waters have significant dissolved co2 concentrations probably related to sub lacustrine fluid discharges fed by a pressurized co2 rich reservoir the analytical results of geochemical surveys carried out in 1989 2010 highlight the episodes of co2 removal from the lake the total mass of dissolved co2 decreased from 5 8 107 kg in 1989 to 0 5 107 kg in 2010 following an exponential decreasing trend calculated values of both dissolved inorganic carbon and co2 concentrations along the vertical profile of the lake indicate that this decrease is caused by co2 release from the epilimnion at depth 9 m combined with 1 water circulation at depth 95 m and 2 co2 diffusion from the deeper lake layers according to this model lake albano was affected by a large co2 input that coincided with the last important seismic swarm at alban hills in 1989 suggesting an intimate relationship between the addition of deep originated co2 to the lake and seismic activity in the case of a co2 degassing event of an order of magnitude larger than the one that occurred in 1989 the deepest part of lake albano would become co2 saturated resulting in conditions compatible with the occurrence of a gas outburst these results reinforce the idea that a sudden co2 input into the lake may cause the release of a dense gas cloud presently representing the major volcanic threat for this densely populated area

taphofacies models for upper cretaceous ammonoids from the kotanbetsu area northwestern hokkaido japan abstract the taphonomic attributes of ammonoid shells in the upper cretaceous of the kotanbetsu area northwestern hokkaido japan are elucidated with reference to sedimentary facies the major attributes are 1 fragmentation rate and fragment separation rate 2 patterns of ammonoid size distribution and mean size 3 shell concentration within calcareous concretions 4 the occurrence of heteromorphic ammonoids and 5 the total number of individuals and species diversity these attributes are classified into four taphofacies analysis of which has lead to the following insights the fragmentation rate and fragment separation rate increase toward shallower environments thus these indices would chiefly reflect the energy level and the frequency of reworking events shells are so abundantly concentrated in storm dominated shelf environments that shell concentrations would be formed by storm and following reworking events the total number of individuals and the diversity differ among the four taphofacies these indices are the largest in the uppermost part of outer shelf these tendencies are inferred to complexly reflect environmental conditions such as energy levels frequency of reworking events and sea level changes

the albano maar lake colli albani volcano italy recent volcanic activity and evidence of pre roman age catastrophic lahar events abstract the evaluation of volcanic hazard in the roman hinterland related to the quiescent colli albani volcano has recently been the subject of renewed attention and several interpretations by many authors however very little was known of the recent history of the volcano making such interpretations rather speculative the most recent activity of colli albani volcano originated from the albano polygenetic maar lake which erupted several phreatomagmatic units the most recent of which the peperino albano ignimbrite has been dated at around 25 ka an area of several square kilometers centered around albano lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards this paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the colli albani volcano and particularly the albano maar lake to the holocene this study allows for the first time to identify a potential hazard related to the albano maar lake withdrawal interpreted to be related to endogenous causes namely co 2 emission the main results of the study are 1 the peperino albano is not as is generally believed the last phreatomagmatic eruption from the colli albani volcano a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the peperino albano and related lahar deposits 2 two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the nw corresponding to the lowest point of the maar rim indicating that catastrophic hydrologic events occurred at the albano lake in recent times rapid and substantial lake level variations and lake withdrawal are reported by roman historians and recorded by the stratigraphy of the albano lake lacustrine sediments 3 microfracturing related to seismic energy release is linked to sudden variation of co 2 flow and upwelling of hydrothermal fluids these occurrences across the lake are the likely causes that triggered during holocene several episodes of lake withdrawal rising the water table and probably triggering convective rollover of the lake water

climatic optimum during the holocene and the distribution of warm water mollusks in the sea of japan abstract the geographical distribution of warm water mollusks has been analyzed and the paleobiogeographical significance of the climatic optimum during the holocene in the formation of the shallow water malacofauna in the sea of japan has been assessed the shift of the southern boundary of the pacific boreal region was 700 800 km to the north compared to its present day position based on bivalve mollusks on the continental coast of the sea of japan this boundary is observed in peter the great bay 43 n and on the japanese side it seems to be at the central part of hokkaido it can be concluded that a temperature increase of the surface water mass of 0 1 0 2 c can cause a shift of about 100 km of the northern boundary of the area of warm water mollusks

facies associations of rain generated versus crater lake withdrawal lahar deposits from quaternary volcanoes central italy abstract two syneruption lahar deposit successions from quaternary italian volcanoes are presented displaying different facies associations interpreted to reflect different water sources the lahar deposits associated with the white trachytic tuff cupa wttc ignimbrites from the quaternary roccamonfina volcano located 150 km to the southeast of rome have been interpreted in terms of rain generated lahars the wttc ignimbrites are made of more than 1 km 3 of loose pumice and lava lithic debris emplaced along the hyperbolic slope of the volcano at ca 300 ka during an interglacial period characterised by mild and wet climate the lahar deposits are organised in a coarsening upward aggradational and back stepping succession of medium to thick bedded progressively juvenile poorer non cohesive debris flow to fluvial deposits box shaped channels cut the wttc ignimbrites along the steep upper slopes channels are filled with lava lithic rich fluvial to hyperconcentrated flow sand and conglomerate which are interpreted as lag deposits related to processes of bulking due to the removal of light pumice and ash debris from the upper slope along the lower slopes of the volcano and in the surrounding ring plains where the average slope inclination decreases to few degrees lahars emplaced an aggradational succession of bedded ash rich hyperconcentrated flow deposits entirely derived from wttc components the succession coarsens upward with increasing presence of lava rich conglomerate lenses fluvial in origin interpreted to record the progressive restoration through time of the drainage network the succession is cut by incised gullies filled with polygenetic fluvial deposits which indicate the restoration of intererruption condition by contrast the ca 23 ka small volume peperino albano phreatomagmatic eruption from colli albani volcano located 30 km to the southeast of rome emplaced a valley ponded block and ash ignimbrite which along the western slope of the volcano grades laterally into a single far reaching thick lahar deposit the lahar deposit coarsens upward from coarse ash hyperconcentrated flow deposit into a lithic block rich debris flow deposit this lahar deposit has been interpreted to be directly derived from a pyroclastic flow and particularly related to the entrance of the pyroclastic flow into a pre existing maar crater lake along the pyroclastic flow path the basal sand size hyperconcentrated flow deposit is interpreted to represent early deposition from the fast frontal flood wave whereas the coarse lithic rich debris flow deposit at the top may represent the rear of the lahar the separation of the two facies can be related to processes of hydraulic sieving operated by the lake water which couples with ash particles leaving behind the coarser fraction

ocean acidification and molluscan shell taphonomy can elevated seawater pco2 influence taphonomy in a naticid predator prey system abstract the size and frequency of gastropod drill holes in shells of their prey are common indicators of predator prey ecology in the fossil record taphonomic processes occurring after predation however can influence the preservation of shells in a given fossil assemblage and can thus influence ecological inferences based on preserved shells to determine if ocean acidification oa has the capacity to influence prey shell taphonomy in a gastropod drilling predation system we tested for effects of elevated pco2 on dissolution rates breakage force and drill hole diameters in non fragmented shells of two prey species of the cannibalistic naticid gastropod euspira heros drilled and non drilled shells of littorina littorea and e heros were exposed to control 300 atm and elevated 800 and 4000 atm pco2 treatments for five weeks dry shell weight and drill hole diameter outer and inner were recorded for individual shells before and after exposure the force required for shell breakage was recorded at the end of the exposure period shell mass loss in 800 and 4000 atm respectively were 1 and 7 for e heros and 0 and 4 for l littorea compared to 0 in the control for both species shell breakage force was unaffected by elevated pco2 but was affected by species and drill hole presence with e heros shells requiring a force of 220 and 269 newtons in drilled and non drilled shells respectively compared to 294 and 415 newtons in l littorea at 4000 atm outer drill hole diameter significantly increased by 12 for e heros while inner drill hole diameter significantly increased by 13 in e heros and 10 in l littorea ultimately this study provides the first documentation of molluscan shell taphonomy in the context of oa for a gastropod drilling predation system and sets the stage for future research

modern sedimentation on the shoreface and inner continental shelf at wrightsville beach north carolina u s a abstract the geologic framework and surficial morphology of the shoreface and inner continental shelf off the wrightsville beach north carolina barrier island were mapped using high resolution sidescan sonar bathymetric and seismic reflection surveying techniques a suite of over 200 diver vibracores and extensive seafloor observations by divers the inner shelf is a sediment starved active surface of marine erosion modern sediments where present form a patchy veneer over tertiary and quaternary units the lithology of the underlying units exerts a primary control on the distribution texture and composition of surficial sediments as well as inner shelf bathymetry the shoreface is dominated by a linear cross shore morphology of rippled scour depressions rsds extending from just seaward of the surf zone onto the inner shelf on the upper shoreface the rsds are incised up to 1 m below surrounding areas of fine sand and have an asymmetric cross section that is steeper sided to the north on the inner shelf the rsds have a similar but more subdued cross sectional profile the depressions are floored primarily by shell hash and quartz gravel vibracore data show a thick up to 1 5 m sequence of rsd sediments that unconformably overlies ancient coastal lithosomes in this sediment starved inner shelf setting rippled scour depressions probably form initially on preexisting coarse sediment substrates such as modern lag deposits of paleofluvial channel lithosomes or ancient tidal inlet thalwegs interannual observations of seafloor morphologic change and the longer term record contained in vibracores suggest that the present seafloor morphology is either relatively stable or represents a recurring preferential morphologic state to which the seafloor returns after storm induced perturbations the apparent stability is interpreted to be the result of interactions at several scales that contribute to a repeating self reinforcing pattern of forcing and sedimentary response which ultimately causes the rsds to be maintained as sediment starved bedforms responding to both along shore and across shore flows sediment accumulation from over 30 years of extensive beach nourishment at wrightsville beach appears to have exceeded the local shoreface accommodation space resulting in the leaking of beach and shoreface sediment to the inner shelf a macroscopically identifiable beach nourishment sediment on the shoreface and inner shelf was used to identify the decadal scale pattern of sediment dispersal the nourishment sediment is present in a seaward thinning wedge that extends from the beach over a kilometer onto the inner shelf to waters depths of 14 m this wedge is best developed offshore of the shoreline segment that has received the greatest volume of beach nourishment

taphonomic degradation of molluscan remains during thirteen years on the continental shelf and slope of the northwestern gulf of mexico abstract in 1993 sseti shelf and slope experimental taphonomy initiative deployed shells of a suite of molluscan species in a variety of environments of preservation eops covering a range of depths and sediment types on the gulf of mexico continental shelf and upper slope with the goal of measuring taphonomic rates over an extended period of time sseti retrieved shells from these eops after 2 8 and 13 years the degree of shell degradation was significantly influenced by species elapsed time since deployment and eop a suite of physical taphonomic processes such as dissolution abrasion discoloration and edge alteration increased in severity over the 13 years fragmentation occurred in some species dissolution proceeded apace however the incidence of chalkiness declined from high levels observed after a few years while the more extreme levels of dissolution such as the development of a soft or deeply dissolved surface rose significantly in frequency the incidence of original color declined while fading of original color increased brown to red and green discoloration rose rapidly in the first eight years and then declined leaving a faded shell surface between habitat differences in degradation rate were significant for most taphonomic attributes between species differences were minor in comparison thus taphofacies the product of the independent actions of a suite of taphonomic processes originate from and provide information on environmental conditions species composition has a lesser inherent influence on the outcome not uncommonly the rates of change in shell condition differed significantly between eops although the direction of change was coincident this was particularly true of the summary indices such as maximum discoloration or the average degree of dissolution the taphonomic process is nonlinear in time nonlinearity is eop dependent becoming a defining attribute leading to disparate taphofacies types some taphonomic processes cannot proceed expeditiously without prior alteration of the shell through other taphonomic means some taphonomic conditions such as chalkiness can be intermediate states the presumption that similar taphonomic characteristics between eops indicate similar environmental processes operating at similar rates is falsified by sseti sites in which similar taphonomic indices at year 13 accrued from different time varying degradational rates during the preceding years

a newly emerged august 2013 artificially triggered fumarole near the fiumicino airport rome italy abstract early in the morning of 24 august 2013 following by hours the drilling of a shallow borehole in the same spot a new fumarole producing emissions of co2 rich gas water and mud suddenly appeared at a crossroad along the fenced area of the fiumicino international airport of rome italy similar episodes have been scientifically documented or simply reported in recent and past years to understand why gases are easily entrapped in the shallow subsurface of the fiumicino area we used five borehole cores drilled by us analyzed the stratigraphy of these and other nearby cores acquired a 2d seismic refraction tomogram and performed chemical and isotopic analyses of water samples collected from aquifers intercepted by two drilled boreholes our boreholes were realized with proper anti gas measures as while drilling we recorded the presence of pressurized gases at a specific permeable gravel level results show that in the study area gases become mainly entrapped in a mid pleistocene gravel horizon at about 40 50 m depth this horizon contains a confined aquifer that stores the endogenous upwelling gases the gravel is interposed between two silty clayey units the lower unit very hard and overconsolidated is affected by fractures that allow ascending gases to bypass the otherwise impermeable shale permeate the gravel and dissolve into the aquifer in contrast the upper unit is impermeable to fluids and seals the gas pressurized aquifer which therefore constitutes a source of hazard during human activities such as well drilling quarrying and various building related excavations as the stratigraphy of the fiumicino area is very common in large portions of the densely populated roman area and as the adjacent volcanic districts are hydrothermally active we conclude that phenomena similar to that observed at fiumicino could again occur both at fiumicino and elsewhere in the surrounding region as a prompt confirmation of our conclusion we signal that while writing this paper new artificially triggered degassing phenomena occurred off fiumicino in connection with the construction of the new harbor

taphonomic signatures in molluscan fossil assemblages from the holocene lagoon system in the northern part of the coastal plain rio grande do sul state brazil abstract molluscan shell accumulations shell beds are very common in shallow marine and estuarine environments in south america and also on the continental shelf between argentina and southern brazil the development of these shell beds is restricted to the quaternary and can provide a great opportunity for taphonomic studies which are rare in this geographic location this study investigates the influence of environmental processes on the destruction of biological remains in a subtropical lagoonal setting by describing the taphonomic signatures occurring in the mollusk shells from the tramandai lagoon northeastern rio grande do sul state brazil this lagoon system originated during the regressive phase that followed a transgressive maximum at 6 0 6 5 ka bp the taphonomic variables fragmentation margin modification surface alteration hinge fine scale alteration and corrosion degree and their damage states were recorded for 1000 shells of erodona mactroides the shells were recovered from two outcrops 8 km apart 14c ams dating were performed on the shells of e mactroides from those outcrops which yielded similar ages from 1060 to 1490 cal yrs bp the ages would indicate that the tramandai lagoon occupied a larger area and must have been subjected to very rapid progradation towards its present position several taphonomic variables such as fragmentation surface alteration and corrasion extent and oxidation presented significant differences p

osl dating of a pleistocene maar birket ram the golan heights abstract direct dating of maars and their phreatomagmatic deposits is difficult due to the dominance of lithic host rock fragments and glassy particles of the juvenile magma in this paper we demonstrate that optically stimulated luminescence osl dating can be successfully used for age determination of phreatomagmatic deposits we studied the tuff deposit of birket ram a basanitic maar located at the northern edge of the golan heights on the western arabian plate the maar is underlain by a thick section of pleistocene basalts and currently hosts a small lake it is filled by approximately 90 m of lacustrine sediments with radiocarbon ages extrapolated to 108 ka at the base osl was applied to quartz grains extracted from tuffs and paleosols in order to set the time frame of the phreatomagmatism at the site a maximum age constraint of 179 13 ka was determined for a paleosol that underlies the maar ejecta quartz grains from two layers in the tuff section yielded a direct age of 129 6 ka for the phreatomagmatic eruption a younger age of 104 7 ka which was determined for a tuff layer underlying a basaltic flow was attributed to thermal resetting during the lava emplacement this was confirmed by an 40 ar 39 ar age of 101 3 ka determined on the overlying basalt the internal consistency of the osl ages and the agreement with the 40 ar 39 ar age determination as well as with previous estimates demonstrates the potential of osl for maar dating

mineralogical and geochemical study of granular xenoliths from the alban hills volcano central italy bearing on evolutionary processes in potassic magma chambers granular xenoliths ejecta from pyroclastic deposits emplaced during the latest stages of activity of the alban hills volcano range from ultramafic to salic ultramafic types consist of various proportions of olivine spinel clinopyroxene and phlogopite they show low sio2 alkalies and incompatible element abundances and very high mgo however cr co and sc are anomalously low at a few ppm level olivine is highly magnesian up to fo 96 and has rather high cao 1 ca and very low ni around a few tens ppm contents these characteristics indicate a genesis of ultramafic ejecta by thermal metamorphism of a siliceous dolomitic limestone probably with input of chemical components from potassic magma the other xenoliths have textures and compositional characteristics which indicate that they represent either intrusive equivalents of lavas or cumulates crystallized from variably evolved ultrapotassic magmas one sample of the former group has major element composition resembling ultrapotassic rocks with kamafugitic affinity some cumulitic rocks have exceedingly high abundances of th 81 84 ppm and light rare earth elements lree la ce 421 498 ppm and extreme ree fractionation la yb 288 1393 not justified by their modal mineralogy which is dominated by sanidine leucite and nepheline finegrained phases are dispersed through the fractures and within the interstices of the main minerals semiquantitative eds analyses show that th and lree occur at concentration levels of several tens of percent in these phases indicating that their presence is responsible for the high concentration of incompatible trace elements in the whole rocks the interstitial position of these phases and their association with fluorite support a secondary origin by deposition from fluorine rich fluids separated from a highly evolved potassic liquid the nd isotopic ratios of the cjecta range from 0 51182 to 0 51217 87sr 86sr ratios range from 0 70900 to 0 71036 with the exception of one sample these values are lower than those of the outcropping lavas which cluster around 0 7105 3 this indicates either the occurrence of several isotopically distinct potassic magmas or a variable interaction between magmas and wall rocks however this latter hypothesis requires selective assimilation of host rocks in order to explain isotopic and geochemical characteristics of lavas and xenoliths the new data indicate that the evolutionary processes in the potassic magmas of the alban hills were much more complex than envisaged by previous studies interaction of magmas with wall rocks may be an important process during magmatic evolution element migration by gaseous transfer often invoked but rarely constrained by sound data is shown to have occurred during the latest stages of magmatic evolution such a process was able to produce selective enrichment of th u lree and to a minor degree ta and hf in the wall rocks of potassic magma chamber finally the occurrence of xenoliths with kamafugitic composition points to the existence of this type of ultrapotassic magma at the alban hills

the influence of molluscan taxon on taphofacies development over a broad range of environments of preservation the sseti experience abstract we utilize information from a suite of molluscan species deployed in a variety of caribbean and gulf of mexico environments of preservation eop by sseti shelf and slope experimental taphonomy initiative to examine to what degree interpretation of the taphofacies is influenced by the mix of species presented to the observer the environment of preservation was the overwhelming determinant of taphonomic state at sseti sites species mix played a subsidiary role a few consistent trends were observed for example arctica islandica strombus luhuanus mytilus edulis and mercenaria mercenaria tended to be more highly dissolved than others mytilus edulis consistently was fragmented more than other species otherwise most species behaved uniquely over a range of eops significant species by eop interactions were the norm a taphofacies model is developed to examine further the role of species on the degradational state of the assemblage two metrics are described a taphonomic degradation score describes the overall degradational state of the assemblage from pristine to highly degraded and a taphonomic signature describes the relative importance of a suite of taphonomic processes model simulations show that the impact of species on degradational state is low initially because all shells are in relatively pristine condition shortly after death the impact is high at intermediate degradational states because factors inherent to the species modulate the time course of taphonomic decay the impact is low again at highly degraded assemblages as the taphonomic process brings shell condition to a common denominator of relatively intense degradation regardless of species fossil assemblages almost certainly express this continuum in some degree the consequence is that better preserved assemblages are ones in which species can affect taphofacies character and so similar eops may be judged distinctive due to differential dominance by one species or another teasing out characteristics that might forewarn the observer in this instance is an important goal simulations show that low evenness is an important warning sign

rollover in volcanic crater lakes a possible cause for lake nyos type disasters abstract seemingly stably stratified fluids that is a heavier layer of fluid underlying an upper layer of lighter fluid can overturn if there is a heat flux through the system such events are termed rollover in the engineering literature occurring for instance in liquid natural gas tanks they take place as well in lakes and ponds in all such cases the stratification starts off with the heavier more dense fluid underlying lighter convection driven mixing at the stratification interface due to the heat flux as well as other processes serves to minimize with time the stabilizing density differences which may eventually cause the stratification to invert if gas has been contained under pressure in the lower layer this gas may explosively vent from the fluid as it suddenly rises to the top such as occurs in liquid natural gas tanks where rollover is a hazard these processes are quantifiable and are applied here to various scenarios that might refer to volcanic crater lakes whose lower layers are charged with volatiles provided herein are some examples of calculated conditions and calculated time of evolution leading to rollover with attendant release of gases from supersaturated ascending fluids these calculations suggest rollover could occur in volcanic lakes the august 1986 gas release at lake nyos is employed as an example these estimates were made taking note that water is commonly supersaturated in co2

the 2009 central italy earthquake seen through 0 5 myr long tectonic history of the l aquila faults system abstract on 6 april 2009 a mw 6 3 earthquake struck l aquila and dozens of neighbouring villages abruzzo central italy causing 308 deaths and with thousands injured within italian seismicity this was the strongest event since 1980 irpinia mw 6 9 and the first located so close to a large city since 1908 messina mw 7 3 consistent data from an integrated approach including stratigraphy geomorphology tephrochronology and paleoseismology have allowed us to identify a 19 km long hitherto poorly known structure as being responsible for this earthquake paganica san demetrio fault system psdfs the fingerprinting of four well dated tephra layers and a detailed outline of the geomorphological and stratigraphic setting have provided the basis for assessing the behaviour of the psdfs since its early activity here dated at least ca 500 ka to the present the slip rate of the structure calculated over different time windows has fluctuated slightly ca 0 5 mm yr paleoseismological analyses revealed the traces of the last surface faulting events thus we unambiguously recognise the offset associated with the mw 6 7 earthquake of 1703 which was previously related to other conterminous structures along with an older comparable strong event speculatively ascribed to an event purely known as the ad 801 central apennine earthquake this study shows that a long term to short term integrated approach is crucial in seismic hazard evaluation especially when dealing with fault systems that are difficult to trace geomorphically despite being capable of generating 2009 like earthquakes or even stronger events when conterminous structures are also involved

mid distal occurrences of the albano maar pyroclastic deposits and their relevance for reassessing the eruptive scenarios of the most recent activity at the colli albani volcanic district central italy abstract the late pleistocene albano maar hosted the most recent volcanic activity of the colli albani volcanic district represented at near vent sections by a thick pyroclastic succession of seven units clustered in two main eruptive cycles dated at around 70 68 and 41 36 ka b p respectively recent stratigraphic investigations allowed us to recognise a pyroclastic succession comprising four eruptive units widely spread in the northeastern sectors of the colli albani volcano up to 15 km eastward from the albano maar integrated tephrostratigraphic morpho pedostratigraphic archaeological petrological and geochemical analyses enable us to recognise them as distal deposits of the first third fifth and seventh albano maar eruptions enlarging significantly their previously supposed dispersion area further tephrostratigraphic studies in central apennine area allowed us to identify the albano maar products in late pleistocene deposits of several intermountain basins extending still further the dispersion area of distal ash fallout as far as 100 120 km from the vent on the basis of the identification and the study of these previously unrecognised mid distal albano maar deposits a reappraisal of the eruptive scenarios and related energetic parameters is proposed

geomorphological evolution and chronology of the eruptive activity of the columba and cuevas volcanoes campo de calatrava volcanic field ciudad real central spain abstract in this study we analyze the geomorphological evolution and chronology of the eruptive phases of the columba and cuevas volcanoes campo de calatrava volcanic field central spain these are two cinder cones located at the margins of the jabalon river valley between the localities of granatula de calatrava and aldea del rey ciudad real in order to generate geomorphological map we conducted fieldwork and photointerpretation of aerial images in addition to morphometric and volcanostratigraphic analyses aimed at correlating the volcanic deposits and fluvial terraces of the jabalon river finally we applied osl optically stimulated luminescence dating to obtain the age of fluvial deposits affected by both volcanoes plus radiocarbon dating to the organic matter of a paleosoil located between the columba volcano deposits the results provide a maximum age of 75 16 4 9 ka for the formation of the cuevas volcano moreover the columba volcano began its activity with a strombolian phase around 33 9 2 36 ka bp followed by a long period of inactivity between 24 9 and 23 2 ka and 14 13 5 ka bp in which the aforementioned paleosoil formed subsequently the eruptive activity resumed with a phreatomagmatic phase followed by another strombolian phase in which a lava flow was emplaced crossing and damming the jabalon river thus forcing the deposition of a 9 m thick fluvial terrace above it at about 6 27 4 28 ka the columba volcano is a good example of polycyclic eruptive behavior in a monogenetic volcanic field whose last eruption occurred between 14 and 6 2 ka ago the interaction between volcanic and fluvial processes was responsible for the morphological evolution of the area the study of which has been crucial to determine the evolution of the eruptive activity its morphological results and the relative chronologies

volcanoes and human history abstract the study of volcanic hazards leads inevitably to questions of how past cultures have lived in volcanically active regions of the world here we summarize linkages between volcanological archaeological and anthropological studies of historic and prehistoric volcanic eruptions with the goal of evaluating the impact of past eruptions on human populations to better prepare for future events we use examples from papers collected in this volume to illustrate ways in which volcanological studies aid archaeological investigations by providing basic stratigraphic markers and information about the nature and timing of specific volcanic events we then turn to archaeological perspectives which provide physical evidence of the direct impacts of volcanic eruptions such as site abandonment and human migration as well as indirect impacts on local cultures as reflected in human artifacts finally we review anthropological studies of societal responses to past and recent volcanic eruptions we pay particular attention to both the psychological impact of catastrophic events and records of these impacts encoded within oral traditions taken together these studies record drastic short term eruption impacts but adaptation to volcanic activity over the longer term largely through strategies of adaptive land use

biodegradation of temperate water skeletal carbonates by boring sponges on the scott shelf british columbia canada abstract boring sponges are a major agent of shell destruction and in the process an important contributor of fine grained carbonate detritus in temperate skeletal carbonate deposits on scott shelf northwestern vancouver island intensive boring is encouraged by the generally low rates of carbonate production and sedimentation skeletal grains become considerably weakened by sponge boring and break preferentially along the directions of sponge excavated tunnels and galleries within the shell boring also facilitates shell dissolution by significantly increasing the surface area weight ratio of shells and by breaking down the organic matrix of shells the large aragonitic bivalves glycymeris and humilaria appear especially susceptible to sponge biodegradation and have become thoroughly bored and corroded within about 1000 years in ambient shelf waters thus their preservation potential is low selective loss of aragonitic biota from ancient cool water shelf skeletal carbonate deposits is anticipated and is evident in many temperate latitude occurrences of new zealand cenozoic limestones

long term accumulation of carbonate shells reflects a 100 fold drop in loss rate shells in modern seabeds can be thousands of years old far older than would be extrapolated from the rapid rates of shell loss detected in short term experiments an extensive shelldating program on the southern california usa shelf permits rigorous modeling of the dynamics of shell loss in the mixed layer discriminating the key rates of carbonate disintegration and sequestration for the first time we find that bivalve shells experience an initially high disintegration rate l 1 decadal half lives but shift abruptly within the first 500 yr postmortem to a 100 fold lower disintegration rate l 2 millennial half lives at sequestration rate t burial and or diagenetic stabilization this drop permits accrual of a long tail of very old shells even when sequestration is very slow and allows only a minority 1 of all shells to survive the first phase these high rates of disintegration and low rates of sequestration are consistent with independent measures of high carbonate loss and slow sedimentation on this shelf our two phase model thus reveals significant spatial and temporal partitioning of car bonate loss rates within the mixed layer and shows how shell age frequency distributions can yield rigorous and realistic estimates of carbonate recycling on geological time scales

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

isotopic and chemical assessment of geothermal potential of the colli albani area latium region italy abstract the chemical and isotopic compositions of low temperature mineral waters discharged over the colli albani region south of rome italy are those of highly immature waters of essentially meteoric origin formed through absorption of gases emanating from greater depth followed by cation leaching of country rock at shallow levels the composition of the gases discharged points to the presence at depth of a co2 producing high temperature system in its waning stage low h2 and unsaturated hydrocarbon contents as well as relative he ar and n2 contents indicate long residence time for the rising gas phase of the order of 1 ma on the basis of these findings temperatures higher than 120 c appear unlikely to exist at shallow depth

incorporating surface indicators of reservoir permeability into reservoir volume calculations application to the colli albani caldera and the central italy geothermal province abstract the quaternary roman volcanic province extends for over 200 km along the tyrrhenian margin of the italian peninsula and is composed of several caldera complexes with significant associated geothermal potential in spite of the massive programs of explorations conducted by the then state owned enel and agip companies between the 1970s and 1990s and the identification of several high enthalpy fields this resource remains so far unexploited although it occurs right below the densely populated metropolitan area of roma capital city the main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain as a consequence almost half of the many exploration deep bore holes drilled in the area reached a dry target this work reviews available data and re assesses the geothermal potential of caldera related systems in central italy by analysing in detail the case of the colli albani caldera system the closest to roma capital city a gis based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential the approach is based on a three dimensional matrix of georeferenced spatial data the a axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data the b axis accounts for the thermal modelling of the crust i e t with depth based on measured thermal gradients both a and b data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs we discuss the implementation of a c axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation we consider datasets on i distribution and density of tectonic lineaments ii temperature and iii electric conductivity of shallow groundwaters iv partial pressure of dissolved co2 in shallow groundwaters the geothermal potential of colli albani and the implications for caldera related geothermal systems in central italy are discussed based on the role of the geometry and structure of reservoirs in relationship with volcano tectonic structures and deep geothermal fluid migration paths

simulation of wave overtopping by an incompressible sph model the paper presents an incompressible smoothed particle hydrodynamics sph model to investigate the wave overtopping of coastal structures the sph method is a grid less lagrangian approach which is capable of tracking the large deformations of the free surface with good accuracy the incompressible algorithm of the model is implemented by enforcing the constant particle density in the pressure projection the sph model is employed to reproduce a transient wave overtopping over a fixed horizontal deck and the regular irregular waves overtopping of a sloping seawall the computations are validated against the experimental and numerical data and a good agreement is observed the sph modelling is shown to provide a promising tool to predict the overtopping characteristics of different waves the present model is expected to be of practical purpose if further improvement in the spatial resolution and cpu time can be adequately made

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

a new interpretation of the left right phenomenon during spatial diffusion and transport of bivalve shells many empty shells of bivalves produced by a local subpopulation will disarticulate into left and right valves between death and final burial in open and shallow seas in areas above the normal wave base wave induced turbulent flows can cause transport of these valves in this study the spatial diffusion of valves is simplified and simulated by a random walk model using a microcomputer in these simulations there were no large differences between the numbers of left and right valves in an infinite area and they are really the same as the mean of the universe but the differences between numbers of left and right valves are sometimes large and various changes are observed depending on the sampling area the different numbers of left and right valves in a finite area shows the magnitude of deviations from the mean of the universe even if the shapes of left and right valves were true mirror images the left right phenomenon of bivalve shells is explainable by one of the statistical laws in a finite are

a review of the stratigraphy of rome italy according to geochronologically and paleomagnetically constrained aggradational successions glacio eustatic forcing and volcano tectonic processes abstract in this paper we provide a critical review of the studies conducted on the geology of rome since the first half of the 20th century aimed at presenting an updated state of the art on the stratigraphy of this area following this introductory summary we present a complete reconstruction of the geological evolution and the resulting chrono litho stratigraphic setting of the greater area of rome according to a series of works that in the last 20 years have adopted an innovative methodological approach based on the conceptual model of aggradational successions deposited in response to sea level rise during the glacial terminations and on the strict geochronologic constraints to the sedimentary record achieved by paleomagnetic investigation of clay sections and 40ar 39ar dating of interbedded volcanic materials we also present a complete overview on the chronostratigraphy of the two volcanic districts of colli albani and monti sabatini located se and nw of rome respectively that has been achieved integrating the field work with the large number of radiometric ages provided in these years on their eruptive products moreover we propose a revised stratigraphic column to compare the most recent official 1 50 000 and 1 10 000 geologic mapping of rome which is intended as a tool of correlation for an international audience of quaternary scientists to approach the study of this area a detailed discussion of the proposed revisions is also provided as supplementary information to this paper

time dependent geochemistry of clinopyroxene from the alban hills central italy clues to the source and evolution of ultrapotassic magmas abstract we investigated chemical and isotopic compositions of clinopyroxene crystals from well age constrained juvenile scoria clasts lava flows and hypoabyssal magmatic ejecta representative of the whole eruptive history of the alban hills volcanic district the alban hills is a quaternary ultra potassic district that was emplaced into thick limestone units along the tyrrhenian margin of italy alban hills volcanic products even the most differentiated are characterised by low sio2 content we suggest that the low silica activity in evolving magmas can be ultimately due to a decarbonation process occurring at the magma limestone interface according to the liquid line of descent we propose the differentiation process is driven by crystallisation of clinopyroxene leucite apatite magnetite coupled with assimilation of a small amount of calcite and or with interaction with crustal co2 by combining age chemical data strontium and oxygen isotopic compositions and ree content of clinopyroxene we give insights into the evolution of primitive ultrapotassic magmas of the alban hills volcanic district over an elapsed period of about 600 kyr geochemical features of clinopyroxene crystals consistent with data coming from other italian ultrapotassic magmas indicate that alban hills primary magmas were generated from a metasomatized lithospheric mantle source in addition our study shows that the 87sr 86sr and lree hree of alban hills magmas continuously diminished during the 600 35 ka time interval of the alban hills eruptive history possibly reflecting the progressive depletion of the metasomatized mantle source of magmas

influence of organic matrix on the post mortem destruction of molluscan shells to examine the role of organic constituents in the destruction of calcium carbonate skeletons we aged fresh shells of the bivalves nucula sulcata organic rich nacreous aragonites with low crystallite surface areas and cerastoderma edule organic poor porcellaneous aragonites high crystallite surface areas under both sterile and non sterile microbial conditions in aragonite undersaturated saturated and supersaturated seawaters for periods up to 11 months deterioration was tracked by sem and weight loss and compared to damage produced by reagents of specific effect the same qualitative sequence of damage was observed in all tanks for both species but rates of deterioration were geq 2 times higher in microbial than in sterile tanks at a given saturation state and were as high or higher in the microbial saturated and supersaturated tanks than in the sterile undersaturated tank damage to shell surfaces was limited almost entirely to loss of organic matrix which eventually exposed and

dead shell assemblages faithfully record living molluscan assemblages at one tree reef abstract reef associated sediments accumulate over time recording the history of biological communities the agreement between live and dead assemblages has been extensively studied because discrepancies between the two can reveal taphonomic bias anthropogenic impact and or a decrease in temporal resolution of dead assemblages to centennial scales i e time averaging given the potential of sedimentary assemblages to provide temporal perspectives on the history of modern communities assessments of live dead agreement in reef mollusk assemblage composition are necessary and timely for understanding rapid environmental change one tree reef otr southern great barrier reef australia has had very little direct anthropogenic influence over the past four decades making it a good system for focusing on taphonomic patterns live n 1335 and dead n 6919 molluscan assemblages were collected from three shallow 6 m carbonate soft sediment lagoons diversity and evenness metrics indicated no significant difference between the live and dead assemblages and dead assemblage rank order abundance explains 82 of that of the live assemblage differences in composition were largely due to sample size the low probability of sampling rare species and to a lesser degree differences in skeletal durability taphonomic factors were responsible for less than 20 of the differences in species composition between live and dead shell assemblages the live molluscan assemblage sampled was similar to the live assemblage sampled 30 years ago given that time averaging is approximately 19 years in the otr lagoon we conclude that the composition of the living assemblage has remained largely unchanged for the last 30 years these findings indicate that dead assemblages preserved in shallow fully carbonate environments primarily reflect the composition of the original source communities making them useful to identify recent changes in coral reef areas where anthropogenic impacts are present

overview and plumbing system implications of monogenetic volcanism in the northernmost andes volcanic province abstract monogenetic volcanic fields are commonly related to rifts and or intraplate tectonic settings however they are also less commonly recognised in subduction zones including both front and back arc volcanoes e g monogenetic volcanoes associated with the llaima volcano in chile or the san agustin volcanic field in colombia here we describe monogenetic volcanic fields associated with subduction related polygenetic volcanism in the northernmost part of the andes northern volcanic zone nvz 2 s to 4 30 n these fields are associated with the main axis of the quaternary volcanoes they are linked to the polygenetic san diego cerro machin volcano tectonic province 140 km long scvtp in colombia the chain that hosts the iconic nevado del ruiz volcano presently three monogenetic volcanic fields with a typical calc alkaline signature have been identified on both sides of this province from south to north they are 1 pijaos monogenetic volcanic field pmvf 2 villamaria termales monogenetic volcanic field vtmvf and 3 samana monogenetic volcanic field smvf pmvf is located 25 km south of cerro machin volcano the southernmost active volcano of the scvtp this field was formed by at least two eruptions with both effusive and explosive eruptive styles three cones and a maar are recognised previous work has defined the volcanoes as basaltic andesitic in composition which we recognised as the most mafic expression mgo 10 11 wt in the whole scvtp its source is related to the same but deeper magma that feeds the volcanoes in the scvtp stratigraphic relationships show that the volcanoes are younger than the underlying alluvial and volcaniclastic ibague fan 5 km of the axis of the province this field is made up of at least 14 volcanoes aligned with the active villamaria termales fault system as previous work has recognised the volcanism has been mainly effusive represented by lava domes and some lava flows since the 1980s studies have framed these andesitic to dacitic volcanoes in the context of the history of the nevado del ruiz volcano it is inferred that the magmatic source is a shallow magma reservoir underneath the scvtp stratigraphic and field relationships have shown that the last eruption occurred

effects of early sea floor processes on the taphonomy of temperate shelf skeletal carbonate deposits abstract cool water shelf carbonates differ from tropical carbonates in their sources modes and rates of deposition geochemistry and diagenesis inorganic precipitation marine cementation and sediment accumulation rates are absent or slow in cool waters so that temperate carbonates remain longer at or near the sea bed early sea floor processes occurring between biogenic calcification and ultimate deposition thus take on an important role and there is the potential for considerable taphonomic loss of skeletal information into the fossilised record of cool water carbonate deposits the physical breakdown processes of dissociation breakage and abrasion are mediated mainly by hydraulic regime and are always destructive impact damage reduces the size of grains removes structure and therefore information and ultimately may transform skeletal material into anonymous particles abrasion is highly selective amongst and within taxa their skeletal form and structure strongly influencing resistance to mechanical breakdown dissolution and precipitation are the end members of a two way chemical equilibrium operating in sea water in cool waters inorganic precipitation is rare there is conflicting opinion about the importance of diagenetic dissolution of carbonate skeletons on the temperate sea floor but test maceration and early loss of aragonite in particular are reported dissolution may relate to undersaturated acidic pore waters generated locally by a combination of microbial metabolisation of organic matter strong bioturbation and oxidation of solid phase sulphides immediately beneath the sea floor in otherwise very slowly accumulating skeletal deposits laboratory experiments demonstrate that surface to volume ratio and skeletal mineralogy are both important in determining skeletal resistance to dissolution biological processes on the sea floor include encrustation and bioerosion encrustation a constructive process may be periodic or seasonal and can be reversed it produces both information and material bioerosion in contrast is destructive and permanent in temperate areas bioerosion may destroy even very large shells during their long residence at the sea floor on the order of hundreds to thousands of years overall processes on the temperate sea floor may combine to destroy more carbonate than they produce and the preservation potential of temperate shelf carbonate into the rock record may be significantly affected where preservation does occur in such a destructive regime the effects of early sea floor processes will be key determinants of the deposit resulting in a taphofacies characteristic of temperate shelf carbonate sediments

taphonomy on the continental shelf and slope two year trends gulf of mexico and bahamas abstract the shelf and slope experimental taphonomy initiative was established to measure taphonomic rates in a range of continental shelf and slope environments of deposition eods over a multiyear period we deployed experiments on the forereef slope off lee stocking island bahamas and on the continental shelf and slope of the gulf of mexico for 2 yr in 18 distinctive eods at depths from 15 to 530 m overall most shells deployed at most sites had relatively minor changes in shell condition most eods generated relatively similar taphonomic signatures a few sites did produce taphonomic signatures clearly distinguishable from the central group and these sites were characterized by one or more of the following high rates of oxidation of reduced compounds presence in the photic zone and significant burial and exhumation events thus unique taphonomic signatures are created by unique combinations of environmental conditions that include variables associated with regional gradients such as depth and light and variables associated with edaphic processes such as the seepage of brine or petroleum or the resuspension and redeposition of sediment most sites however showed similar taphonomic signatures despite the variety of eod characteristics present suggesting that insufficient time had elapsed over 2 yr to generate a more diverse array of taphonomic signatures discoloration and dissolution were by far the dominant processes over the 2 yr deployment period periostracum breakdown loss of shell weight and chipping and breakage was less noticeable eods were chosen based on the expectation that the process of burial and the influence of depth and sediment type should play the greatest roles in determining between eod differences in taphonomic signature eod specific edaphic factors often overrode the influence of geographic scale environmental gradients taphonomic alteration was greater on hardgrounds and in brine exposed sites than on terrigenous muds dissolution was less effective at sites where burial was greatest discoloration occurred most rapidly at shallower sites and on hardgrounds water depth was less influential in determining taphonomic signature than burial state or sediment type the limited influence of water depth is likely due to the presence of shallow sites that for one reason or another were protected from certain taphonomic processes and deeper sites that were characterized by unusually strong taphonomic signals

taphonomic tiering experimental field taphonomy of molluscs and foraminifera above and below the sediment water interface abstract a review and synthesis of field based taphonomic experiments using molluscs and foraminiferans in marine systems reveal differing patterns of hardpart accumulation and destruction for these two major groups of fossil organisms for benthic molluscs most destruction appears to occur at the sediment water interface in siliciclastic settings mollusc preservation is suggested to be high once the shell is buried below the taphonomically active zone although this observation has not been experimentally addressed foraminiferal preservation however depends on microhabitat biogeochemical conditions within the sediments and test composition the taphonomically active zone for foraminiferans appears to be the upper 10 cm in most depositional settings from shallow to deep sea the preservation of tests or shells however has not been examined below the sediment water interface using field based experiments pore water geochemistry and associated microbial processes may be the most important factors in which to examine subsurface taphonomy the term taphonomic tiering is applied to variations in taphonomic activity within the sediments that differentially affect hard parts in essence the subsurface region where hardparts are presumed to be preserved is one of the new frontiers in experimental field taphonomy

recognizing cryptic environmental changes by using paleoecology and taphonomy of pleistocene bivalve assemblages in the oga peninsula northern japan abstract multivariate analyses applied to pleistocene bivalve assemblages from the oga peninsula northern japan discriminate three distinct assemblages the assemblages and their taphonomy were used to recognize environmental settings and changes the astarte cyclocardia glycymeris assemblage indicates shelf environment below the storm wave base where gravels and shells are transported from shallower settings supply of the exotic coarse sediment probably enabled epifaunal bivalves to inhabit the sea floor the glycymeris assemblage is characterized by dominance of g yessoensis and represents current swept shoreface environment above the storm wave base the moerella assemblage is characterized by bivalves inhabiting bay to open marine conditions and diverse deposit feeders indicating a moderately land locked environment such as an open bay or a bay mouth fine grained substrata rich in organic matters in the bay were probably suitable for the deposit feeders ordination also shows the assemblages along two environmental gradients a bathymetrical one and the other related to open marine and bay conditions the environmental changes are explained mainly by glacio eustatic sea level changes and alternation of coastal geomorphology caused by local crustal movements this study also suggests that fossil assemblages can be a powerful tool to reconstruct environments and depositional dynamics even in intensely bioturbated sedimentary facies

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

geology of a continental slope oil seep northern gulf of mexico an oil gas seep was documented by replicate sampling with piston corer abundant high resolution and sparse multichannel seismic reflection profiling and chemical and isotopic analyses the seep occurs on the upper continental slope over a salt ridge interpreted to split and plunge eastward northeastward and northward the relatively shallow diapir over which the seepage occurs is manifested at the surface by a graben in strike section and by a half graben in dip section faulting over the crest is commonly associated with loss of reflected energy or acoustic wipeouts most cores taken in wipeouts with prolonged bottom echoes contain oil and gas the cores also commonly contain secondary carbonate derived from microbial degradation of hydrocarbons the isotopic lightne s of the carbonate and its negative correlation with porosity may be subtle indicators of seepage at sites where oil and gas are not obvious the seepage demonstrates the existence of source rocks and maturation at this site