87sr86sr in late proterozoic carbonates evidence for a mantle event at 900 ma ago abstract strontium isotopic measurements were made on late proterozoic carbonates from west african craton comparison of samples with acceptable trace element patterns with coeval data from southern africa and with the published australian results suggests that the 87 sr 86 sr ratio of the late proterozoic sea water evolved in the following manner about 0 7075 at 1000 50 ma 0 7056 to 0 7074 at 900 50 ma 0 7068 to 0 7091 0 7106 at 800 50 ma 0 7074 to 0 7077 at 700 50 ma and 0 7076 to 0 7089 0 7096 at 600 50 ma ago the variations are comparable in magnitude and frequency to those described previously for the phanerozoic strontium isotopic values in the radiogenic part of this range suggest that the continental river flux of sr into late proterozoic oceans was of comparable isotopic composition to its present day counterpart 0 711 consequently the non radiogenic 87 sr 86 sr value at 900 50 ma ago signifies a large flux of mantle strontium into the ocean at this time because the present time resolution is only about 75 25ma additional sampling as well as better stratigraphie resolution and more definite selection criteria are required for construction of a more detailed late proterozoic sea water curve

object oriented classification of a high spatial resolution spot5 image for mapping geology and landforms of active volcanoes semeru case study indonesia the present work explores the object oriented classification ooc of high spatial resolution hsr satellite panchromatic imagery for mapping the geology of the persistently active semeru volcano and its ring plain east java indonesia a panchromatic spot5 image and a digital elevation model dem have been used to identify geologic units structures landforms and deposits the panchromatic image was georeferenced and enhanced using histogram equalization the enhanced image was segmented into polygons using the envifx exelis software the polygons were delineated and classified on the basis of spectral panchromatic hues and textures topographic slope elevation information and geologic geomorphic processes the validity of classification was evaluated by interpreting google earth images aerial photographs and limited field observations the classification consists of three hierarchical levels across the volcanic area of about 745 km2 the first operational spatial level includes seven large volcano domains based on the spectral content of the volcanic tectonic and lithological structures and principal catchments the second operational level based on contextual relationships topography drainage network vegetation cover type stratigraphy and slope dynamics encompasses 20 geological units that range between 30 and 80 km2 in area among the units the third operational level distinguishes as many as 47 geomorphological sub units 0 25 25 km2 according to slope gradient deposit type mass wasting process and weathering the resulting map provides a detailed pattern of geologic and geomorphic features unlike previous geologic maps that identified only 11 stratigraphic units we show that the high spatial resolution panchromatic spot5 scene can help to safely map the geology and landforms of persistently active volcanoes such as semeru we have applied the ooc technique on one hsr geoeye panchromatic image to map another active volcano merapi in central java after considerable geomorphic changes due to the large eruption in 2010

sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

the lamongan volcanic field east java indonesia physical volcanology historic activity and hazards abstract the lamongan volcanic field lvf in east java indonesia consists of up to 61 basaltic cinder or spatter cones a minimum of 29 prehistoric maars and a central compound complex comprising three main vents including the historically active lamongan volcano the field lies on the sunda volcanic arc and abuts onto the currently active tengger caldera semeru complex to the west between 1799 and 1898 lamongan was persistently active and discharged up to 15 lava flows of basaltic to basaltic andesite composition which is probably more than what was erupted by any other indonesian volcano in that period several seismic crises have been recorded in the lvf since lamongan s last eruption there are no existing records of cinder cone or maar forming eruptions in the area despite the possible hazards posed by future activity in the lvf the history and structure of the field have been subject to little scrutiny this contribution presents the results of a detailed morphometric and volumetric investigation of prehistoric vents and historic lava flows in the lvf using field data historic records satellite imagery and modelling of erupted volumes a typical lvf maar is characterised as a crater with a diameter of 450 m generated by an eruption with a model ejecta volume of 0 016 km 3 dense rock equivalent dre and a model juvenile component volume of 0 0096 km 3 dre diameter depth ratios of some maars display a morphological freshness comparable to recently formed phreatomagmatic eruption craters elsewhere the median lvf cinder spatter cone has a basal diameter of 600 m a height of 75 m a volume of 0 009 km 3 and a model total erupted volume of 0 014 km 3 variation in cone basal diameter to height ratios indicates that the age of some prehistoric cones may not exceed a few centuries and morphological classification identifies the youngest prehistoric vents on the northern flanks of the central edifice historic activity from vents on the western flanks of lamongan produced at least 0 05 km 3 of basaltic to basaltic andesite lava resurfacing rates at lamongan in the 19th century imply an age of 900 2100 years for the surface of the volcano the steady state eruptive rate from 1843 1898 is evaluated as 0 025 m 3 s 1 which is low in comparison to estimates from many presently active systems using eruptive rate and volume data the age of the lvf is estimated as between 13 and 40 ka placing it among the youngest dated indonesian volcanoes complex regional tectonics in conjunction with magmatic pressure have probably been the major influences on the distribution of volcanism in the lvf the occurrence of maar forming eruptions may have been controlled by a porous substrate possibly a deposit from the holocene iyang argapura complex to the east volcanic hazards from future eruptions in the lvf include base surges ash flows ashfall and ejected blocks associated with phreatomagmatic activity and ashfall and ejecta from magmatic eruptions

ultrastructure of a middle cambrian primary nonpelletal phosphorite and its early transformation into phosphate vadoids georgina basin australia abstract mudstone phosphorites collophane mudstones and mini profiles composed of phosphate coated grains from the duchess phosphate deposit of early middle cambrian age in the georgina basin australia are described in detail the mudstone phosphorites form thin beds and laminae interlayered with transported peloidal phosphorites in thin section the mudstone phosphorites are characterized by predominately homogeneous micritic phosphate under the scanning electron microscope sem they are mostly composed of globose structures of 10 25 m diameter and tubules these structures are interpreted as the preserved phosphatized remnants of solitary and colonial unicells and sheaths that once formed part of a larger microbial mat community intermittent subaerial exposure of the microbi lly constructed mudstone phosphorites resulted in their in situ vadose transformation into mini profiles composed of coated phosphate grains these profiles are characterized by poorly laminated coated phosphate grains inverse grading hollow rims gravitational cements and a fitted fabric transition zones between the mudstone phosphorites and the overlying mini profiles allow the steps involved in the transformation to be understood the mudstone phosphorites and mini profiles are characterized by distinctive structures identical to those found in many transported phosphate grains as these surfaces are frequently laterally discontinuous and eroded at their margins they are probably important contributors of grains to the deposits

development of an apatite oxygen paleobarometer experimental characterization of sm3 substituted apatite fluorescence as a function of oxygen availability abstract global apatite bearing phosphorites represent unique biogeochemical periods coincident with major transitions in biological evolution and particularly marine oxygenation however current understanding of such oxygenation is limited by qualitative and not uncommonly contrasting interpretations of the marine redox conditions evidenced by sedimentary isotope and trace element abundances a potentially novel measure of ancient marine oxygenation has previously been indicated by fluorescence signatures detected in sm3 substituted microfossil preserving apatite from early cambrian phosphorites consistent with experimental studies demonstrating an oxygen dependent mechanism for sm3 incorporation quantitative calibration of these signatures would enable the interpretation of oxygen concentrations during sedimentary apatite formation in the experiments described heat promoted substitution of sm3 in apatite powder pellets has been conducted under gaseous oxygen concentrations ranging from 0 to 20 9 the resulting fluorescence signals provide a comparison to those observed in naturally occurring phosphorites that should reflect the levels of oxygen in the immediate precipitating environment these analyses suggest that a metric describing the relative spectral characteristics derived from end member oxic and anoxic experiments here described as an apatite oxygen paleobarometer aop robustly correlates with gaseous oxygen concentrations the application of this quantifiable metric to phosphorite apatite is expected to provide a fundamentally new dataset by which to probe ancient marine redox conditions particularly during the neoproterozoic cambrian phosphogenic event and diversification of early metazoans

potential photosynthetic impact on phosphate stromatolite formation after the marinoan glaciation paleoceanographic implications abstract this study investigated the origin and the depositional age of phosphate stromatolites contained in the neoproterozoic salitre formation brazil the stromatolites exhibited columnar shapes and were intercalated with laminated dolostones their depositional environment was interpreted to have been an evaporitic ramp where erosion and reworking by waves prevailed laser ablation inductively coupled plasma mass spectrometry measurements of the stromatolites yielded a u pb age of 616 32 ma suggesting that they were deposited after the marinoan glaciation several types of filamentous structures were recognized in the stromatolites many of them were pseudofossil ambient inclusion trails but some were possibly microfossils to consider the general presence of photosynthetic microorganisms on the surface of shallow water stromatolites the involvement of microbial photosynthesis in phosphate stromatolite formation was expected numerical calculations determined that photosynthesis could have induced phosphate mineral precipitation at the time of deposition if the phosphorus concentration was above ca 5 m to achieve such high concentration at the shallow ocean globally elevated phosphorus concentration was considered to be the ultimate factor in addition to the local process es including upwelling and or evaporation therefore the phosphate stromatolites in the salitre formation are evidence of the development of a phosphorus rich ocean after the marinoan glaciation

timing the breakup of a proterozoic supercontinent evidence from australian intracratonic basins in the late proterozoic several broad shallow intracratonic depressions appeared across a vast area of central australia the basins which all contain shallow marine to fluvial successions appear to have been tenuously interconnected through much of their history analysis of their fill by means of tectonic subsidence curves suggests that they are the product of two separate and distinct periods of crustal extension one at about 900 ma and a second at about 600 ma these extensional episodes were probably the result of failed rifting events that almost fragmented the australian continent during the late proterozoic the second period of extension almost certainly relates to the breakup of a proterozoic supercontinent the results suggest that sediments preserved in the relatively protected environment of interior basins may provide a more subtle record of major tectonic events than continental margin sequences that were exposed to major continental interactions

controls on phosphorus regeneration and burial during formation of eastern mediterranean sapropels the carbon c and phosphorus p geochemistry of sapropels from four sites in the eastern mediterranean sea was determined to obtain more insight into the role of differences in sediment accumulation rates and bottom water anoxia on p regeneration and burial in sediments sediment corg porg with org organic ratios above redfield indicate enhanced regeneration of p relative to c from organic matter during formation of the most recent sapropel s1 and a pliocene sapropel odp site 969e i 282c release of p from fe oxides was relatively unimportant increased burial of ca p authigenic carbonate fluorapatite and or biogenic hydroxyapatite occurred but was of minor importance compared to the enhanced p release from organic matter for sapropel s1 corg porg and corg preac with reac reactive defined as the sum of organic fe bound authigenic and biogenic ca p ratios decreased with increasing sedimentation rate and oxygen exposure and decreasing water depth whether the water column in the deep basin was dysoxic semi euxinic s1 or euxinic pliocene does not appear to affect the estimated burial efficiencies of porg and preac enhanced corg burial under the euxinic water column explains the much higher corg porg and corg preac ratios in the pliocene sapropel on average 2860 and 760 respectively compared to sapropel s1 on average 530 and 160 respectively

application of synthetic aperture radar sar imagery to volcano mapping in the humid tropics a case study in east java indonesia volcanoes in humid tropical environments are frequently cloud covered typically densely vegetated and rapidly eroded these factors complicate field and laboratory studies and even the basic identification of potentially active volcanoes numerous previous studies have highlighted the potential value of radar remote sensing for volcanology in equatorial regions here cloud and vegetation penetrating lhh band 24 cm synthetic aperture radar sar data from the japanese earth resources satellite jers 1 are used to investigate persistently active volcanoes and prehistoric calderas in east java indonesia the lhh band jers 1 sar produces high spatial resolution 18 m imagery with relatively high incidence angle that highlights structures and topographic variations at or greater than the wavelength scale while minimising geometrical distortions such as layover and foreshortening these images along with internet browse data derived from the canadian radarsat mission provide new evidence relating regional tectonics to volcanism throughout east java volcanic events such as caldera collapse at the tengger caldera appear to have been partly controlled by northwest aligned faults related to intra arc sedimentary basins similar regional controls appear important at historically active lamongan volcano which is encircled by numerous flank maars and cinder cones a previously undocumented pyroclastic sheet and debris avalanche deposit from the jambangan caldera complex is also manifested in the synoptic radar images at the currently active semeru volcano these data permit identification of recent pyroclastic flow and lahar deposits radar data therefore offer a valuable tool for mapping and hazard assessment at late quaternary volcanoes the criteria developed in the analysis here could be applied to other regions in the humid tropics

surface deformation and coherence measurements of kilauea volcano hawaii from sir c radar interferometry the shuttle imaging radar c x synthetic aperture radar sir c x sar radar on board the space shuttle endeavor imaged kilauea volcano hawaii in april and october 1994 for the purpose of measuring active surface deformation by the methods of repeat pass differential radar interferometry observations at 24 cm l band and 5 6 cm c band wavelengths were reduced to interferograms showing apparent surface deformation over the 6 month interval and over a succession of 1 day intervals in october a statistically significant local phase signature in the 6 month interferogram is coincident with the pu u o o lava vent interpreted as deformation the signal implies centimeter scale deflation in an area several kilometers wide surrounding the vent peak deflation is roughly 14 cm if the deformation is purely vertical centered southward of the pu u o o caldera delays in the radar signal phase induced by atmospheric refractivity anomalies introduce spurious apparent deformation signatures at the level of 12 cm peak to peak in the radar line of sight direction though the phase observations are suggestive of the wide area deformation measured by global positioning system gps methods the atmospheric effects are large enough to limit the interpretation of the result it is difficult to characterize centimeter scale deformations spatially distributed over tens of kilometers using differential interferometry without supporting simultaneous spatially distributed measurements of refractivity along the radar line of sight studies of the interferometric correlation of images acquired at different times show that l band is far superior to c band in the vegetated areas even when the observations are separated by only 1 day these results imply longer wavelength instruments are more appropriate for studying surfaces by repeat pass observations

influence of late cenozoic mountain building on ocean geochemical cycles in a steady state ocean input fluxes of dissolved salts to the sea must be balanced in mass and isotopic value by output fluxes for the elements strontium calcium and carbon rivers provide the primary input whereas marine biogenic sedimentation dominates removal dissolved fluxes in rivers are related to rates of continental weathering which in turn are strongly dependent on rates of uplift the largest dissolved fluxes today arise in the himalayan and andean mountain ranges and the tibetan plateau during the past 5 m y uplift rates in these areas have increased significantly this suggests that weathering rates and river fluxes may have increased also the oceanic records of carbonate sedimentation level of the calcite compensation depth and delta sup 13 c and delta sup 87 sr in biogenic sediments are consistent with a global increase in river fluxes since the late miocene the cooling of global climate over the past few million years may be linked to a decrease in atmospheric co sub 2 driven by enhanced continental weathering in these tectonically active regions

high resolution strontium isotope stratigraphy across the cambrian ordovician transition we have analyzed 214 fossil apatite samples from nine stratigraphic sections worldwide that cover the lower cambrian to lower ordovician for their strontium isotope ratios of these samples 180 from six sections that cover the cambrian ordovician transition 5 ma reveal how the extent of isotopic alteration can differ greatly according to lithology and sample type from three limestone sections 126 euconodont samples yield the most consistent 87sr 86sr ratios and are used in this article to constrain seawater 87sr 86sr across the cambrian ordovician boundary by contrast protoconodonts paraconodonts and inarticulate brachiopods are far less likely to retain a primary 87sr 86sr signature and appear to be of only limited value for chemostratigraphy seawater 87sr 86sr fell from maximum values for the phanerozoic of more than 0 7092 during the early late cambrian to 0 7090 by the earliest ordovician high resolution sampling has permitted the recognition of sinusoidal variations with a wavelength on the order of 1 ma that are superimposed on the overall fall in 87sr 86sr these variations may be caused by high order cycles in seawater 87sr 86sr or diagenetic alteration

geology and petrology of the hormuz dolomite infra cambrian implications for the formation of the salt cored halul and shraouh islands offshore state of qatar abstract geological investigations of the halul and the shraouh islands offshore qatar indicate that most of their calcareous rocks which display abundant stromatolitic bedding belong to the infra cambrian hormuz series mineralogical petrological and geochemical analyses show that these calcareous rocks consist dominantly of dolomite and have formed in a reducing depositional environment faint laminations and small streaks of organic matter furnish evidence for the involvement of algal mats in their genesis and indicate their formation in an intertidal to supratidal setting the halul and shraouh dolomites experienced extensive recrystallization and sulfatization during the emplacement of the halul and shraouh salt domes that form the cores of the islands during mobilization and ascent of the salt the dolomite recrystallized and its sr initial ratios were abnormally enhanced by the incorporation of 87sr from a source which is more radiogenic than the attendant seawater at the time of the dolomite formation near the proterozoic cambrian boundary geochemical analysis show that si al ti zr and of insoluble residue are highly correlative suggesting the presence of detrital minerals such as rutile and zircon a paleosabkha model may well agree with this chemical signature however the infra cambrian age of the hormuz rocks and the presence of stromatolitic layers containing organic materials in the studied rocks suggest that organogenic dolomitization could be an alternative dolomitization model

potentially active volcanoes of peru observations using landsat thematic mapper and space shuttle imagery landsat thematic mapper tm images and space shuttle color photograph have been used to make a synoptic study of the volcanoes of southern peru 14 17 s the northernmost portin of the central volcanic zone cvz 14 28 s of the andes apart from providing consistent coverage the chief merit of the tm for this study has been the spatial resolution provided by the 30 m pixel size the optimal 20 m resolution variable lighting and viewing geometry and stereo capability of the shuttle photography provided an invaluable ancilliary data set at the resolution available subtle glacial morphological features such as valley and terminal moraines can be confidently identified and these features have been used to determine the relative ages of volcanoes volcanoes have been classified as potentially active if they have i a well preserved summit crater ii pristine lava flow texture and morphology iii flank lava flows with low albedo and iv evidence of postglacial 10 000 years activity eight major volcanoes are postulated to be potentially active most are large dominantly andesitic composite cones with edifice heights of up to 2500 m some of which threaten nearby settlements one of them sabancaya was active as recently as july 1988 other little known postglacial volcanic features include huaynaputina site of a major explosive rhyolitic eruption in 1600 a d and several fields of monogenetic scoria cones and lava flows the active volcanic front is some 200 km east of the peru chile trench and the volcanoes lie on a trenchparallel trend oblique to the ew subduction this narrow volcanic zone is thought to reflect the steep dip of the nazca plate through the zone of magma generation the break in the trend of the volcanic front in the northern extremity of the volcanic zone is thought to reflect the complexity of the crustal stress field above a major segment boundary in the subducting plate the fields of mafic monogenetic centers also occur in this region in comparison with the southern part of the cvz the general paucity of older volcanic edifices north of 17 s suggests a more recent onset of volcanism north of this latitude probably resulting from the oblique subduction of the nazca ridge and the consequent northward migration of its intersection with the pere chile trench this coupled with the lack of any large silicic caldera systems and youthful dacite domes like those found further south suggest that there are real differences between the volcanic evolution of different parts of the cvz

velocity models and site effects at kawah ijen volcano and ijen caldera indonesia determined from ambient noise cross correlations and directional energy density spectral ratios abstract two different ambient seismic noise techniques allow the determination of velocity models at ijen caldera and kawah ijen volcano at ijen caldera two average velocity models are constrained down to a depth of 3 km by inverting the stacked dispersion curve obtained by ambient noise cross correlation in addition four local velocity models were obtained by inverting the horizontal to vertical spectral ratio of the directional energy densities of ambient noise dedhvr i e computed through auto correlation of ambient noise this set of velocity models is then compared to the geology of the caldera and the local discontinuities are evidenced at kawah ijen volcano a map of local dominant frequencies is provided by the dedhvr measurements recorded at 87 sites around kawah ijen volcano the horizontality of the shallow layers and the great outcrop of the crater rim facilitate the interpretation of the dedhvrs furthermore the inversion of several juxtaposed dedhvrs provided a complete 2 d velocity model of the flank of the crater unlike other stratovolcanoes the kawah ijen appears to have a remarkably homogeneous structure the dedhvr technique is used for the first time in a volcanic environment and shows a great potential for an accurate and fast computation of the velocity model on volcanoes

mapping the 2010 merapi pyroclastic deposits using dual polarization synthetic aperture radar sar data l band alos palsar images acquired before during and after the 2010 merapi eruption have been used to classify and map the pyroclastic deposits emplaced during this vei 4 event we characterize the deposits using direct polarized and cross polarized l band sar data and by combining the information of amplitude evolution with temporal decorrelation changes in amplitude of the radar signal enable us to map the pyroclastic density currents pdcs and tephra fall deposits radar amplitudes in direct hh and cross hv polarizations decrease where the valley confined and overbank block and ash flow baf deposits d1 are emplaced rainfall and runoff reworked pdc deposits d2 are characterized by an increase in ground backscattering for hh polarization and a decrease for hv polarization ground backscattering transiently increases in both polarizations after pyroclastic surge d3 and tephra fall d4 deposition we use a supervised classification method based on maximum likelihood to map the deposits d1 d4 the temporal decorrelation of the radar signal and the amplitude evolution improve the quality of classification results classification derived from alos palsar images using the maximum likelihood classification provides a result with 70 classification accuracy for deposits overall the estimated areas of valley confined and overbank pdc deposits either primary or reworked by rainfall and runoff are consistent with the areas measured by other studies while the large discrepancy in area estimated for pyroclastic surge deposits can be partly explained by the strong erosion due to intense rainfall that removed a large part of these thin deposits

oblique synoptic images produced from digital data display strong evidence of a new caldera in southwestern guatemala abstract the synoptic view of broad regions of the earth s surface as displayed in landsat and other satellite images has greatly aided in the recognition of calderas ignimbrite plateaus and other geologic landforms remote sensing images that include visual representation of depth are an even more powerful tool for geologic interpretation of landscapes but their use has been largely restricted to the exploration of planets other than earth by combining landsat images with digitized topography we have generated regional oblique views that display compelling evidence for a previously undocumented late cenozoic caldera within the active volcanic zone of southwestern guatemala this new caldera herein called xela is a depression about 30 km wide and 400 600 m deep which includes the quezaltenango basin the caldera depression is breached only by a single river canyon the caldera outline is broadly circular but a locally scalloped form suggests the occurrence of multiple caldera collapse events or local slumping of steep caldera walls or both within its northern part xela caldera contains a toreva block about 500 m high and 2 km long that may be incompletely foundered pre caldera bedrock xela contains several post caldera volcanoes some of which are active a bouguer gravity low tens of milligals in amplitude is approximately co located with the proposed caldera the oblique images also display an extensive plateau that dips about 2 away from the north margin of xela caldera we interpret this landform to be underlain by pyroclastic outflow from xela and nearby atitlan calderas field mapping by others has documented a voluminous rhyolitic pumiceous fallout deposit immediately east of xela caldera we speculate that xela caldera was the source of this deposit if so the age of at least part of the caldera is between about 84 ka and 126 ka the ages of deposits that stratigraphically bracket this fallout most of the floor of xela caldera is covered with los chocoyos pyroclastics 84 ka deposits erupted from atitlan caldera oblique images produced from digital data are unique tools that can greatly facilitate initial geologic interpretation of morphologically young volcanic and other terrains where field access is limited especially because conventional visual representations commonly lack depth perspective and may cover only part of the region of interest

petrology and geochemistry of the lamongan volcanic field east java indonesia primitive sunda arc magmas in an extensional tectonic setting new geochemical data are presented from prehistoric and historical multifarious process involving possible inputs from the subducted oceanic lithosphere subducted oceanic sedieruptive products of the lamongan volcanic field lvf east java a region of the sunda arc covering 260 km and containing ments and fluids the asthenospheric and lithospheric portions of the mantle wedge above the subduction zone 90 eruptive vents plus the historically active lamongan volcano lvf lavas include medium k basalts and basaltic andesites from and the arc crust e g tatsumi eggins 1995 following melt generation processes such as crystal fractionation historical eruptions of lamongan and prehistoric eruptions in the eastern lvf along with a high k suite represented by prehistoric accumulation and crustal assimilation during transit to the surface may obscure the true nature of the magma deposits in the western lvf although lacking some of the characteristics of truly primary basalts the least evolved lavas identified source region the effects of these processes on the compositions of erupted lavas must therefore be removed in the lvf have some of the lowest sio2 contents 43 wt sio2 yet reported in sunda arc volcanic rocks mass balance before models of arc magma genesis can be tested for this reason it is desirable to sample magmas that considerations indicate that two chemically distinct lvf magmas may be parental to suites currently being erupted from the neighbouring have suffered minimal modification since segregation from their source region the compositions of the primary volcanoes semeru and bromo lamongan s historical lavas can be related to the medium k andesitic products of semeru by fractional or primitive magmas from different arcs provide a window on the diverse mechanisms of and the components crystallization despite the former s location at the same distance from the trench as bromo a high k volcano extensional tectonics involved in melt production at convergent margins and as such are essential to our understanding of the possibly related to arc segmentation in the region of the lvf creating subduction zone environment conditions that promote the rapid ascent of parental magmas is many studies have highlighted the correlation between probably responsible for this and several other features of the complex extensional tectonics in volcanic arcs and the eruption of lavas with primitive chemical characteristics e g luhr carmichael 1981 knittel oles 1995 bacon et al

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

kawah ijen volcanic activity a review kawah ijen is a composite volcano located at the easternmost part of java island in indonesia and hosts the largest natural acidic lake in the world we have gathered all available historical reports on kawah ijen s activity since 1770 with the purpose of reviewing the temporal evolution of its activity most of these observations and studies have been conducted from a geochemical perspective and in punctuated scientific campaigns starting in 1991 the seismic activity and a set of volcanic lake parameters began to be weekly available we present a database of those measurements that combined with historical reports allow us to review each eruption unrest that occurred during the last two centuries as of 2010 the volcanic activity is monitored by a new multi disciplinary network including digital seismic stations and lake level and temperature measurements this detailed monitoring provides an opportunity for better classifying seismic events and forecasting volcanic unrest at kawah ijen but only with the understanding of the characteristics of this volcanic system gained from the historical review presented here

preliminary analyses of sir b radar data for recent hawaii lava flows abstract the shuttle imaging radar sir b experiment acquired two l band 23 cm wavelength radar images at about 28 and 48 incidence angles over the kilauea volcano area of southeastern hawaii geologic analysis of these data indicates that although as lava flows and pyroclastic deposits can be discriminated pahoehoe lava flows are not readily distinguished from surrounding low return materials preliminary analysis of data extracted from isolated flows indicates that flow type i e as or pahoehoe and relative age can be determined from their basic statistics and illumination angle

sir b radar imagery of volcanic deposits in the andes the andean cordillera of western south america between 16 s and 28 s and south of 34 s latitude have been two of the most volcanically active areas in the world for the last 25 million years ma synthetic aperture radar imagery from the shuttle imaging radar mission b sir b was collected in october 1984 over the central andes between 20 s and 24 s and also south of 42 s despite signal strength problems that drastically reduced the signal to noise s n ratio of the images volcanic features of both areas show up well in particular ignimbrite sheets formed by large explosive eruptions stand out as very strong radar reflectors due to their characteristically rough erosional surface high backscatter is apparently caused by erosional relief on the ignimbrites at scales ranging from the radar wavelength 23 cm for sir b to the 30 200 m scale of quebradas gullies and canyons the quebradas are steep sided and straight and have a similar southeast orientation in ignimbrites separated by as much as 450 km spatially and 6 ma temporally the consistent regional erosional pattern appears unrelated to the emplacement of the ignimbrites and is probably caused by preferential eolian erosion in the direction of the prevailing wind hand held space photographs ground observations and landsat thematic mapper tm imagery support the interpretation of the ignimbrite radar signature the chilean volcano michinmahuida 43 s was imaged by four radar data takes at different incidence angles which show tectonic glacial and volcanic features of that nearly inaccessible and often cloud covered region

geology tectonics and the 2002 2003 eruption of the semeru volcano indonesia interpreted from high spatial resolution satellite imagery abstract the paper illustrates the application of high spatial resolution satellite images in interpreting volcanic structures and eruption impacts in the tengger semeru massif in east java indonesia we use high spatial resolution images ikonos and spot 5 and aerial photos in order to analyze the structures of semeru volcano and map the deposits geological and tectonic mapping is based on two dems and on the interpretation of aerial photos and four spot and ikonos optical satellite images acquired between 1996 and 2002 we also compared two thermal surface kinetic temperature aster images before and after the 2002 2003 eruption in order to delineate and evaluate the impacts of the pyroclastic density currents semeru s principal structural features are probably due to the tectonic setting of the volcano a structural map of the tengger semeru massif shows four groups of faults orientated n40 n160 n75 and n105 to n140 conspicuous structures such as the se trending horseshoe shaped scar on semeru s summit cone coincide with the n160 trending faults the direction of minor scars on the east flank parallels the first and second groups of faults the semeru composite cone hosts the currently active jonggring seloko vent this is located on and buttressed against the mahameru edifice at the head of a large scar that may reflect a failure plane at shallow depth dipping 35 towards the se this failure plane may correspond to a weak basal layer of weathered volcaniclastic rocks of tertiary age we suggest that the deformation pattern of semeru and its large scar may be induced by flank spreading over the weak basal layer of the volcano it is therefore necessary to consider the potential for flank and summit collapse in the future the last major eruption took place in december 2002 january 2003 and involved emplacement of block and ash flows we have used the 2003 aster surface kinetic temperature image to map the 2002 2003 pyroclastic density current deposits we have also compared two 10 m pixel images acquired before and after the event to describe the extent and impact of an estimated volume of 5 45 106 m3 of block and ash flow deposits an ash rich pyroclastic surge escaped from one of the valley confined block and ash flows at 5 to 8 km distance from the crater and swept across the forest and tilled land on the sw side of the bang river valley downvalley the temperature of the pyroclastic surge decreased and a mud rich deposit coated the banks of the bang river valley thus hazard mitigation at semeru should combine 1 continuous monitoring of the eruptive activity through an early warning system and 2 continuous remote sensing of the morphological changes in the drainage system due to the impact of frequent pyroclastic density currents and lahars

an approach using sar ers images to relate extension fractures to volcanic vents examples from iceland and madagascar abstract a new approach to the study of geometric relationships between tectonic structures and volcanic vents is presented it is based on the mapping of tectonic and volcanic features using high resolution imagery including synthetic aperture radar sar images of the european remote sensing satellite number one ers 1 we have evidenced new faults 1 n striking normal faults in the husavik fault zone of the north atlantic ridge and 2 nw striking faults belonging to the husavik transform fault zone associated to drag folds which testify to a dextral strike slip movement component we show that most of the volcanic edifices are located on extension fractures responsible for fissure eruptions volcanic linear clusters and elongated volcanoes this relationship is studied first in iceland where the geodynamics is well known using sar ers 1 imagery applied to the montagne d ambre in northern madagascar using aerial photographs this approach makes it possible to identify faults and the regional plio quaternary direction of extension i e n65 e to n85 e volcanoes forming linear clusters together with elongated volcanoes are interpreted to be located on extension fractures s or z shape of the linear clusters allowed us to determine the tips of extension fractures and consequently the orientation of the regional tension alignments of extension fractures depending on their s or z shape permitted us to infer conjugated faults

relations between geomorphic form and sedimentologic stratigraphic variability holocene ooid sand shoal lily bank bahamas although the linkages among surface sediments geomorphic forms and hydrodynamics in holocene ooid tidal sand shoals have been evaluated recently how these factors are reflected in the geomorphic evolution and stratigraphic record of shoals is less constrained yet such understanding is essential to developing meaningful predictive conceptual models of three dimensional architecture of ancient reservoir analogs integrating remote sensing imagery high frequency seismic data and core characterization from lily bank a modern tidally dominated bahamian ooid shoal in which sedimentologic processes are well documented reveals the stratigraphic record of geomorphic change an irregular gently dipping rocky surface interpreted as the top pleistocene with no pronounced topographic high underlies the holocene oolitic succession a 6 m 20 ft thick poorly sorted gravelly muddy sand with few ooids overlies this basal surface this lower interval is overlain by sand with an upward increase in proportion of ooids sorting and grain size the uppermost unit present only under active bar forms is well sorted oolitic medium sand with accretionary foresets sediments vary stratigraphically and geomorphically the lower unit is finer and less well sorted than the upper units and in the oolitic upper unit sediment size and sorting on bar crests are distinct from bar flanks collectively these results suggest that a marked antecedent bump is not necessary for occurrence of ooid shoals and that the stratigraphic record of analogous ooid shoal systems may preserve clues of geomorphic position as well as geobody size and orientation

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

sea level changes facies changes and the late precambrian early cambrian evolutionary explosion abstract an explosive increase in the fossil record coincided with a major rise in sea level during latest precambrian early cambrian times the artefactual and real effects of an onshore offshore environmental gradient upon taxonomic diversity are considered with particular reference to 14 fossiliferous sections from around the world within taxon and within habitat evolution through the early cambrian are also discussed the evidence suggests that evolution was a diversity dependent i e kinetic growth process made possible by the colonisation and gradual filling of habitats that were growing both in variety and area archaeocyatha diversified rapidly at first but may have suffered later decline and extinction because facies changes in late early cambrian times reduced their area of habitat

the threat of hazards in the semeru volcano region ineast java indonesia abstract semeru volcano 3676 m the highest volcano in java is one of the most active volcanoes in indonesia its activity has occurred almost continuously since 1967 the activity is manifested by mostly strombolian type eruptions with lava extrusions which extend into a lava tongue in kobokan breach southeast slope of the volcano the lava tongue is unstable after reaching a certain volume the tongue collapses and causes pyroclastic flows to the southeast direction traveling a maximum of about 11 km downslope the collapse is sometimes triggered by volcanic eruptions the main dangers are not due to eruption and collapse of the lava tongue but caused by the secondary dangers the secondary dangers are more destructive and distributed over a wider area tens of kilometres from the source the natural hazards in the semeru region are not only related to volcanic activity which is so called lahar but also non volcanic processes such as debris flow this phenomenon is related to the heavy rainfall which causes landslides in the altered volcanic deposit areas the flow of the mixture of water and landslide materials has devastated large areas the occurrences of the secondary flow is unpredictable and its viscosity is much lower than lahar this flow is distributed over a wide area and threatens cultivated land and densely populated and developing urban areas

analysis of coregistered landsat seasat and sir a images of varied terrain types multisensor image data sir a seasat sar and landsat mss over areas in nothern algeria and eastern utah have been coregistered in order to assess the complementary effects of the orbital sensors for geologic mapping in two very different terrains this first attempt at registering such a data set shows that the radar backscatter information provided by the sir a image increases the classification accuracy of several geologic units over the landsat image alone and over combined landsat and seasat images

isotopic composition of disseminated sulfur in precambrian sedimentary rocks abstract isotopic analyses of trace sulfur in precambrian carbonates and clastic sedimentary rocks support the results of previous studies which have shown that 34s measurements of archean sedimentary sulfur cluster mostly around mantle like values and that a significant overall dispersion of 34 s 32 s ratios commenced at about 2 7 ga ago the outstanding feature of the proterozoic record is the predominance of heavy 34ssulfide values mostly in excess of 0 cdm consideration of these data in combination with the sparse 534s record for proterozoic sulfates suggests that 34ssulfide sulfide may have been smaller than was the case during the phanerozoic a possible scenario that is compatible with the above data is based on a proposition that the terrestrial exogenic sulfur cycle evolved in a tripartite manner in the archean it was coupled to and controlled by the magmatic endogenic cycle the proterozoic for the most part represents a transitional stage into a phanerozoic like exogenic cycle the latter essentially decoupled from its endogenic counterpart and its redox balance maintained and mediated by the biosphere the indication that the mean combined 34s of proterozoic sulfate and sulfide may have significantly exceeded the phanerozoic mean value of 2 cdm is enigmatic and poses problems for balance considerations

anomalous geochemical signals from phosphatic middle cambrian rocks in the southern georgina basin australia middle cambrian rocks of the georgina basin contain both phosphatic and organic rich sediments the former often occurring as commercially viable phosphate deposits and the latter as minor oil shale occurrences both kinds of rocks occur in the hay river formation penetrated by bureau of mineral resources bmr stratigraphic corehole tobermory 14 detailed sampling and analysis of this core has been undertaken to assess the chemostratigraphy of the hay river formation to examine the possible use as a palaeoceanographic tool of changes in 13c values of carbonates and kerogens and to gain an understanding of phosphate deposition in this part of the basin the upper hay river formation was deposited in a normal marine environment characterized by oxic bottom conditions it contains several episodes of significant trace metal enrichment which appear to indicate periodic replacement of the water body the lower hay river formation however was deposited in an abnormal marine environment low in sulphate and mo and enriched in p its carbonate phase has positive 13c values 1 1 5 0 enriched over the accepted cambrian marine carbonate value of 0 57 0 17 0 the very low sulphate concentration mo depletion and spiking of carbonate 18o values suggests there was an influx of deeper ocean water of sufficient volume to maintain prolonged stable anoxic bottom waters these data support a previous suggestion that phosphogenesis in the georgina basin was related to oceanic anoxic events

cambrian phoscrete profiles coated grains and microbial processes in phosphogenesis georgina basin australia abstract middle cambrian phoscrete profiles occurring within phosphatic carbonates that surround the phosphate deposits of the georgina basin australia are described in detail the profiles occur within a mixed mineralogy suite of rocks and are characterized by fabrics and textures identical to those developed in calcretes phoscrete profiles are subdivided into an overlying laminar phoscrete crust and an underlying phoscrete modified substrate diagenesis in the substrate results in the elimination of primary structures producing a coated to vaguely pelleted texture micritic phosphate cements dominate the phosphate profiles these cements occur as irregular coatings on 1 grains and 2 thread like structures which criss cross interparticle spaces scanning electron microscope examination f these cements indicates that they are coatings on tubular structures herein interpreted as chasmolithic and epilithic filaments the preferential occurrence of phosphate on organic substrates suggests that organic matter plays a dual role in phosphogenesis it provides both a source of phosphate to the pore waters via bacterial degradation and it also provides a substrate on which phosphate preferentially nucleates phosphate particles derived from the erosion of phoscrete profiles vary from friable aggregates and lumps to peloids and coated grains whereas the composite particles were unlikely to survive sediment transport peloids and coated grains were coherent particles able to survive transport and sorting this suggests that some of these particles may occur in the phosphate d posits

application of stable carbon isotopes to early biochemical evolution on earth the emergence and early evolution of life on earth have long been intriguing subjects for scientific inquiry and a continuous source of intel lectual excitement current work at this frontier proceeds along a number of different avenues and comprises a variety of disciplinary approaches that together strongly suggest that the earth was inhabited by life as early as almost 4 gyr ago the present state of the field as inferred from the results of a broad interdisciplinary approach has recently been summarized by j w schopf and coworkers cf schopf 1 983 it is with the advantage of such a synoptic view that the present review addresses a single facet of the theme namely the potential isotopic infer ences of the presence of co2 fixing autotrophic organisms for the carbon cycle of the early earth with biologically derived organic carbon as well as carbonates limestone dolomite etc abundantly preserved in sediments relevant isotopic evidence should have been encoded in the geologic record from its onset about 3 8 gyr ago it has been known since the pioneering studies by nier gulbransen 1939 murphey nier 1941 and rankama 1948 that the trans formation of inorganic carbon into living matter entails a marked bias in favor of the light isotope c2c with the heavy species l3c retained in the inorganic reservoir subsequent work performed by many investigators e g craig 1953 park epstein 1960 has confirmed that all common

pyrite and organic matter in normal marine sediments of middle cambrian age southern georgina basin australia normal marine sedimentary rocks of middle cambrian floran undillan age from the southern georgina basin have pyrite sorganic c ratios with a mean value of 0 65 and show a significant positive correlation with an extension of the line of best fit through zero the sc ratio of 0 65 determined in this study is close to the mean ratio for all cambrian sediments of 0 7 but differs markedly from the recently reported sc ratio of 2 for normal marine early palaeozoic rocks mainly from the united kingdom the variations shown by these figures indicate that if the oxidation state of the crust ocean atmosphere over geological time is to be fully understood and related to possible world wide trends further assessment of early palaeozoic sulfur and carbon burial rates is needed furthermore as sc burial rates are known to vary the ages of the sediments being analysed need to be more precisely known

geochemistry of cambro ordovician arbuckle limestone oklahoma implications for diagenetic δ18o alteration and secular δ13c and variation abstract isotopic analyses of 227 limestone samples from the cambro ordovician arbuckle group oklahoma document slow secular changes in the chemistry of the limestones from late cambrian to early ordovician the 18o values of the limestones increase from 10 to 7 pdb 13c values decrease from 0 to 2 pdb and 87 sr 86 sr ratios decrease from 0 7091 to 0 7088 the light 18o values suggest that all arbuckle limestones underwent diagenetic alteration probably caused by meteoric water recharged during the development of the overlying pre middle ordovician unconformity the gradual 18o increase from late cambrian to early ordovician reflects reduced 18o depletion with decreasing burial temperature during alteration although the presence of additional primary secular 18o variation cannot be ruled out the 13c and 87 sr 86 sr variations in accord with 13c and 87 sr 86 sr variations in the literature represent primary secular variations the variations indicate that the 13c value and 87 sr 86 sr ratio of early paleozoic surface seawater decreased from late cambrian to early ordovician the 13c variation during this time period seems to correlate with sea level variation specifically during sea level fall an increase in the rate of oxidation of organic matter caused 13c depletion of inorganic bicarbonate in seawater as a result early ordovician carbonates probably deposited during the regression stage of the latest precambrian to latest early ordovician cycle became 13c depleted relative to late cambrian carbonates the decrease of seawater 87 sr 86 sr ratio from late cambrian to early ordovician may have resulted from decreased riverine sr input caused by decreased rate of continental weathering

geologic analyses of shuttle imaging radar sir b data of kilauea volcano hawaii analyses of imaging radar data of volcanic terranes on earth and venus have emphasized the need for a clearer understanding of how these data can be most effectively used to accomplish important volcanological goals including the interpretation of eruptive styles and the characterization of the geologic history of volcanic centers the second shuttle imaging radar experiment sir b obtained two digital images over the summit caldera and the southwest rift zone of kilauea volcano in 1984 our geologic analyses of these images indicate that sir b data are particularly useful for delineating the distribution and surface textural variations of a9a lava flows for mapping large scale topographic features with radar facing slopes and for identifying an areally extensive pyroclastic deposit analyses of the sir b data of kilauea however do not permit unambiguous identification of landforms such as pahoehoe lava flows cinder cones and fissures although separation of low return units such as pahoehoe lava flows and adjacent pyroclastic ash is not greatly improved using standard image enhancement techniques the texture analysis technique applied here did facilitate discrimination of such smooth surfaced volcanic deposits although analyses of the sir b data permit a generally accurate interpretation of the eruptive history of kilauea the inability to distinguish low return pahoehoe flows results in misinterpretation of several aspects of kilauea volcanism suggesting that caution should be exercised in the interpretation of sar data of volcanic terranes

preliminary observations of volcanoes with the sir c radar the two flights of the shuttle imaging radar sir c x sar in april and october 1994 provided a wealth of new image data over many of the world s volcanoes including 13 of the 15 international decade volcanoes a first look at these data shows that mapping of remote volcanoes e g nyiragongo and nyamuragira in africa will now be easier especially when aided by the collection of multi parameter radar data over better known analogous volcanoes such as kilauea hi the utility of the radar to identify different types of lava flows is shown for fernandina volcano galapagos islands growth of mudflow deposits lahars that were emplaced on mount pinatubo philippines during the six months between the two missions is also illustrated additionally interferometric radar data were collected over several active volcanoes the potential uses of these data for topographic mapping and ground deformation studies are discussed

isotope shifts in the late permian of the delaware basin texas precisely timed by varved sediments closely spaced samples 285 in number of varved sediments from the upper permian in delaware basin texas have been analyzed for 13ccarb 13corg 18ocarb corg ccarb and calcite dolomite 13c records a dramatic rise from 2 8 to 5 7 in only 4400 years detected in three sections across the basin extrapolating smoothly through a 600 year interruption by a local west side of the basin fresh water inflow evidenced by low 18o this continuity and low corg within the basin both indicate that the excess net deposition of corg necessary to generate the rise in 13c took place in the ocean external to the delaware basin correlation with similar records from the zechstein basin suggest that the event was world wide although this poses obvious difficulties for the carbon cycle the rate of rise of 13c and its sustained high level must imply conversions of oxidized carbon to reduced carbon that are very large depending on which reservoirs were involved

preliminary ers 1 observations of alaskan and aleutian volcanoes abstract we used ers 1 radar images collected between october 1991 and february 1993 to study volcanic landforms of the alaska peninsula and aleutian islands these data were used to map a little eroded even textured unit that is a thick low mobility pyroclastic deposit around aniakchak caldera also we have identified possible caldera remnants at black peak and located volcanically related collapse pits and depressions in the summit glacier of veniaminof observations of westdahl and mt spurr both of which erupted during our observation period demonstrate that new lava flows and debris flows can be mapped by virtue of their high radar backscatter and contrast with the surrounding terrain these data demonstrate the utility of frequent orbital radar observations in this area regional mapping can be carried out for volcanoes that are difficult to study in the field due to adverse working conditions e g frequent cloud cover bad weather long periods of darkness during winter and remote locations timely acquisition of images soon after or during an eruption can assist in the monitoring of active volcanoes the 23 incidence angle causes strong foreshortening and there is sometimes up to 35 days between repeat observations of certain locations however we conclude that the routine collection of sar data from ers 1 can provide valuable rapid information for assessing volcanic hazards in this region whatever the weather or time of year the situation will be improved with the additional use of jers 1 data and the launch of the radarsat spacecraft in 1995

volcanic hazards at mount semeru east java indonesia with emphasis on lahars mt semeru the highest mountain in java 3 676 m is one of the few persistently active composite volcanoes on earth with a plain supporting about 1 million people we present the geology of the edifice review its historical eruptive activity and assess hazards posed by the current activity highlighting the lahar threat the composite andesite cone of semeru results from the growth of two edifices the mahameru old semeru and the seloko young semeru on the se flank of the summit cone a n130 trending scar branched on the active jonggring seloko vent is the current pathway for rockslides and pyroclastic flows produced by dome growth the eruptive activity recorded since 1818 shows three styles 1 the persistent vulcanian and phreatomagmatic regime consists of short lived eruption columns several times a day 2 increase in activity every 5 to 7 years produces several kilometer high eruption columns ballistic bombs and thick tephra fall around the vent and ash fall 40 km downwind dome extrusion in the vent and subsequent collapses produce block and ash flows that travel toward the se as far as 11 km from the summit and 3 flank lava flows erupted on the lower se and e flanks in 1895 and in 1941 1942 pyroclastic flows recur every 5 years on average while large scale lahars exceeding 5 million m3 each have occurred at least five times since 1884 lumajang a city home to 85 000 people located 35 km e of the summit was devastated by lahars in 1909 in 2000 the catchment of the curah lengkong river on the ese flank shows an annual sediment yield of 2 7 105 m3 km 2 and a denudation rate of 4 105 t km 2 yr 1 comparable with values reported at other active composite cones in wet environment unlike catchments affected by high magnitude eruptions sediment yield at mt semeru however does not decline drastically within the first post eruption years this is due to the daily supply of pyroclastic debris shed over the summit cone which is remobilised by runoff during the rainy season three hazard prone areas are delineated at mt semeru 1 a triangle shaped area open toward the se has been frequently swept by dome collapse avalanches and pyroclastic flows 2 the s and se valleys convey tens of rain triggered lahars each year within a distance of 20 km toward the ring plain 3 valleys 25 km s se and the ring plain 35 km e toward lumajang can be affected by debris avalanches and debris flows if the steep sided summit cone fails

carbon isotope excursions in precambrian cambrian boundary beds morocco the precambrian cambrian boundary is one of the most significant points on the geological timescale because it marks the change in the fossil record from soft bodied organisms to skeletonized faunas the cambrian explosion or radiation event1 saw the evolution of many new life forms especially various molluscs and archaeocyathids from the base of the cambrian tommotian stage others including the trilobites and bivalves evolved a little later in the succeeding atdabanian stage2 3 a massive increase in the biomass of the photic zone through phytoplankton blooms has also been postulated for this time4 particularly in the late riphean early vendian and in the early cambrian5 there has been much discussion concerning where precisely to place the boundary6 7 and here are several contenders in the world for the type section8 i present here a carbon isotope profile from the precambrian cambrian boundary beds in morocco where two distinctive positive 13c excursions are revealed these are interpreted as records of increased organic productivity as part of the precambrian cambrian explosion of life 13c excursions could be useful points for correlation between boundary sections

sar and gravity change based characterization of the distribution pattern of pyroclastic flow deposits at mt merapi during the past 10 years mt merapi indonesia is one of the most active and dangerous volcanoes in the torrid zone this volcano has erupted frequently and has produced pyroclastic flows following the collapse of the summit lava dome we used synthetic aperture radar sar data acquired by jers 1 and radarsat 1 satellites from april 1996 to july 2006 to clarify the distribution patterns of the pyroclastic flow deposits the extent of the deposits termed p zones was accurately extracted by ratio operation and low level feature extraction from sar intensity images these images highlighted temporal changes of the distribution area perimeter flow distance included angle and collapse direction to validate the image processing results reflectance spectra of the rock samples collected after the eruption in june 2006 were measured in a laboratory the reflectance spectra of all samples showed similar characteristics to the reference spectra which were derived from atmospheric correction of hyperion sensor image data covering the lava dome at the summit therefore p zones were confirmed to be the pyroclastic flow deposits originating from destruction of the lava dome at the summit the image processing results clarified that the extent of the distribution areas perimeter flow distances and included angle of the p zones were variable among the eruptions while the collapse direction had a constant pattern the collapse pattern followed a clockwise change from the south toward the west by comparing the ratio maps of bouguer gravity anomaly data in two periods the change was interpreted to originate from the inclination of the conduit and the formation of shallow and deep magma reservoirs

two decades of research on the proterozoic phanerozoic transition 1972 1991 the most radical global change involving the biology chemistry and physics of life occurred near and at the stratigraphical level of the boundary between the neoproterozoic system precambrian and the cambrian system this stratigraphical level is held by consensus to be the proterozoic eonothem phanerozoic eonothem boundary and is regarded as being of fundamental importance research has involved not only archaeocyathans shelly small problematica earliest trilobites stromatolites and algae trace fossils soft bodied metazoans microphytolites and acritarchs but also physical and chemical aspects radio isotope dating carbon strontium and oxygen isotope stratigraphy polar wandering relating to palaeogeography and magnetostratigraphy a selected bibliography 1985 1990 is appended to enable further reading of the extensive research contributions

geologic interpretation of space shuttle radar images of indonesia the national aeronautics and space administration nasa space shuttle mission in november 1981 acquired images of parts of the earth with a synthetic aperture radar system at a wavelength of 23 5 cm 9 3 in and spatial resolution of 38 m 125 ft this report describes the geologic interpretation of 1 250 000 scale images of irian jaya and eastern kalimantan indonesia where the all weather capability of radar penetrates the persistent cloud cover the inclined look direction of radar enhances subtle topographic features that may be the expression of geologic structures on the indonesian images the following terrain categories are recognizable for geologic mapping carbonate clastic volcanic alluvial and coastal melange and metamorphic as well as undifferentia ed bedrock regional and local geologic structures are well expressed on the images in the vogelkop region of irian jaya the major tectonic elements tamrau mountains sorong fault kemum block bintuni basin and lengguru foldbelt are readily mapped on the image of the sorong fault geomorphic features offset drainage shutterridges aligned notches provide clear evidence for left lateral strike slip displacement several lineaments on the image correlate with previously mapped faults other lineaments may be the expression of previously unrecognized faults on the image of the mainland of irian jaya a belt of metamorphic and melange terrain marks the zone of collision between the pacific plate and the australian plate the high central range of irian jaya is located south of the metamorphic and melange belt the generally homoclinal structure of the central range is interrupted in the paniai lake region by a series of southward directed thrust plates indicated by belts of carbonate terrain new guinea limestone group that alternate with belts of clastic terrain kembelangan formation in the image of eastern kalimantan several major foldbelts are clearly expressed these limited examples of space shuttle radar images demonstrate their value for geologic interpretation of indonesia it is recommended that future shuttle missions acquire complete radar coverage of the main islands of indonesia for use in geologic mapping and energy exploration shuttle radar images would also be valuable for other cloud covered forested regions

lava flow characterization at pisgah volcanic field california with multiparameter imaging radar multi incidence angle in the 25 to 55 range radar data acquired by the nasa jpl airborne synthetic aperture radar airsar at three wavelengths simultaneously and displayed at three polarizations are examined for their utility in characterizing lava flows at pisgah volcanic field california pisgah lava flows were erupted in three phases flow textures consist of hummocky pahoehoe smooth pahoehoe and aa with and without thin sedimentary cover of the eight airsar images used here four were calibrated to within an accuracy of 2 db with trihedral corner reflectors and data from these calibrations were used to process the additional images to a conservatively estimated 5 db level of accuracy calibrated radar backscatter data in db were plotted as a function of incidence angle at three wavelengths p band 68 cm l band 24 cm and c band 5 6 cm and three polarizations hh horizontal transmit horizontal receive hv horizontal transmit vertical receive and vv vertical transmit vertical receive for eight major units at pisgah for which multi incidence angle airsar data were available the eight units consist of near vent and distal aa flows near vent and distal hummocky pahoehoe flows a mantled hummocky pahoehoe flow a platform pahoehoe flow an alluvial fan and a playa analyses of these backscatter data show that major unmodified volcanic units at pisgah are readily distinguishable from each other and that they exhibit diffuse hh vv and or multiple hv scattering behavior typical of rough surfaces at these wavelengths these analyses show that discrimination of smooth lavas platform pahoehoe from mantled units with greater primary roughness hummocky pahoehoe is difficult and must rely on supporting observations such as evidence of localized weathering and or sediment deposition contrast with surrounding units and superposition of flow units l band backscatter and image data at hv polarization show the best discrimination of pisgah lava flows with optimal unit separation observed between 40 and 50 incidence angles backscatter data shown as a function of relative age of pisgah flows indicate that dating of lava flows on the basis of average radar backscatter may yield ambiguous results if primary flow textures and modification processes are not well understood

phosphorus phosphorites and skeletal evolution at the precambrian cambrian boundary clustering of sedimentary phosphate deposits around the precambrian cambrian boundary is related to a global phosphogenic event this event probably resulted from a complex interplay of factors and had a profound effect on the biota with high concentrations of phosphorus in the photic zone producing an increase in the total shallow marine biomass faunal diversification the precipitation of skeletal structures and explosive evolution

redox fluctuations trace metal enrichment and phosphogenesis in the 2 0 ga zaonega formation abstract the 2 0 ga zaonega formation zf holds one of the oldest phosphorites in the geologic record reaching 15 p2o5 understanding the depositional conditions that enabled sedimentary phosphorus enrichment in this unit will thus help us to interpret the significance of the temporal distribution of phosphorites in earth s early history here we use an array of major and trace element data to constrain the redox conditions in the water column and extent of basinal restriction during deposition of the zf we also present new selenium se abundance and isotopic data to provide firmer constraints on fluctuations across high redox potentials which might be critical for phosphogenesis we find that se isotope ratios shift over a range of 3 in the zf with the earliest stratigraphically resolved negative se isotope excursion in the geologic record implying at least temporarily suboxic waters in the basin furthermore we find that redox sensitive element rse enrichments coincide with episodes of p enrichment thereby implicating a common set of environmental controls on these processes together our dataset implies deposition under a predominantly anoxic water column with periodic fluctuations to more oxidizing conditions because of connections to a large oxic reservoir containing se oxyanions and other rse s as well as sulfate in the open ocean this is broadly consistent with the depositional setting of many modern and recent phosphorites thereby tying these ancient deposits to a common depositional mechanism in light of these data we propose that the broader prevalence of phosphogenesis in the paleoproterozoic era was driven by growth of the seawater oxidant reservoir namely sulfate thus enabling diagenetic apatite precipitation in basins with high rates of export production particularly by facilitating the activity of sulfide oxidizing bacteria this suggests that the muted authigenic p burial observed in marginal marine siliciclastic sedimentary rocks during other intervals of the precambrian was not merely a result of low dissolved p levels in the global deep ocean but also was influenced by sulfate scarcity and strongly reducing bottom water conditions

palaeoenvironment and carbon isotope stratigraphy of upper proterozoic carbonates of the yangtze platform the 13c values for phanerozoic marine carbonates display secular trends mainly in the range 1 to 2 1 these have been interpreted as primary features reflecting changes in the carbon isotope composition of dissolved bicarbonate in seawater brought about largely by variations in the proportions of carbon being sequestered in the oxidized and reduced carbon reservoirs1 2 carbon isotope trends are not as well established for the precambrian but there are indications that upper proterozoic sequences contain carbonates with unusually high 13c values3 9 here we present the results of the first carbon isotopic study of the upper proterozoic carbonate strata from the type locality of the sinian system in the yangtze gorges sections near yichang south china and discuss their implications for accumulation of organic matter we also compare the results for these chinese strata with 13c trends in other upper proterozoic cambrian sequences and assess the extent to which such isotopic data can be used to make stratigraphic correlations between widely spaced sequences

sedimentary manganese metallogenesis in response to the evolution of the earth system abstract the concentration of manganese in solution and its precipitation in inorganic systems are primarily redox controlled guided by several earth processes most of which were tectonically induced the early archean atmosphere hydrosphere system was extremely o2 deficient thus the very high mantle heat flux producing superplumes severe outgassing and high temperature hydrothermal activity introduced substantial mn2 in anoxic oceans but prevented its precipitation during the late archean centered at ca 2 75 ga the introduction of photosystem ii and decrease of the oxygen sinks led to a limited buildup of surface o2 content locally initiating modest deposition of manganese in shallow basin margin oxygenated niches e g deposits in india and brazil rapid burial of organic matter decline of reduced gases from a progressively oxygenated mantle and a net increase in photosynthetic oxygen marked the archean proterozoic transition concurrently a massive drawdown of atmospheric co2 owing to increased weathering rates on the tectonically expanded freeboard of the assembled supercontinents caused paleoproterozoic glaciations 2 45 2 22 ga the spectacular sedimentary manganese deposits at ca 2 4 ga of transvaal supergroup south africa were formed by oxidation of hydrothermally derived mn2 transferred from a stratified ocean to the continental shelf by transgression episodes of increased burial rate of organic matter during ca 2 4 and 2 06 ga are correlatable to ocean stratification and further rise of oxygen in the atmosphere black shale hosted mn carbonate deposits in the birimian sequence ca 2 3 2 0 ga west africa its equivalents in south america and those in the francevillian sequence ca 2 2 2 1 ga gabon are correlatable to this period tectonically forced doming up attenuation and substantial increase in freeboard areas prompted increased silicate weathering and atmospheric co2 drawdown causing glaciation on the neoproterozoic rodinia supercontinent tectonic rifting and mantle outgassing led to deglaciation dissolved mn2 and fe2 concentrated earlier in highly saline stagnant seawater below the ice cover were exported to shallow shelves by transgression during deglaciation during the sturtian glacial interglacial event ca 750 700 ma interstratified mn oxide and bif deposits of damara sequence namibia was formed the varangian marinoan ca 600 ma cryogenic event produced mn oxide and bif deposits at urucum jacadigo group brazil the datangpo interglacial sequence south china liantuo nantuo varangian event contains black shale hosted mn carbonate deposits the early paleozoic witnessed several glacioeustatic sea level changes producing small mn carbonate deposits of tiantaishan early cambrian and taojiang mid ordovician in black shale sequences china and the major mn oxide carbonate deposits of karadzhal type central kazakhstan late devonian the mesozoic period of intense plate movements and volcanism produced greenhouse climate and stratified oceans during the early jurassic oae organic rich sediments host many mn carbonate deposits in europe e g urkut hungary in black shale sequences the late jurassic giant mn carbonate deposit at molango mexico was also genetically related to sea level change mn carbonates were always derived from mn oxyhydroxides during early diagenesis large mn oxide deposits of cretaceous age at groote eylandt australia and imini tasdremt morocco were also formed during transgression regression in greenhouse climate the early oligocene giant mn oxide carbonate deposit of chiatura georgia and nikopol ukraine were developed in a similar situation thereafter manganese sedimentation was entirely shifted to the deep seafloor and since ca 15 ma b p was climatically controlled glaciation deglaciation assisted by oxygenated polar bottom currents aabw nadw the changes in climate and the sea level were mainly tectonically forced

chemostratigraphy of paleoproterozoic carbonate successions of the wyoming craton tectonic forcing of biogeochemical change the archean wyoming craton is flanked on the south and east by belts of paleoproterozoic supracrustal successions whose correlation is complicated by lack of geochronologic constraints and continuous outcrop however carbonate units in these successions may be correlated by integrating carbon isotope stratigraphy with lithostratigraphy the 10 km thick paleoproterozoic snowy pass supergroup in the medicine bow mountains was deposited on the present day southern flank of the wyoming craton it contains three discrete levels of glacial diamictite correlative with those in the huronian supergroup on the southern margin of the superior craton the nash fork formation of the upper snowy pass supergroup is significantly younger than the uppermost diamictite and was deposited after the end of the paleoproterozoic glacial epoch carbonates at the base of the nash fork formation record remarkable 13 cenrichment up to 28 v pdb whereas those from overlying members of the lower nash fork formation have d 13 c values between 6 and 8 carbonates from the upper nash fork formation above the carbonaceous shale have carbon isotope values ranging between 0 and 2 5 the transition from high carbon isotope values to those near 0 in the nash fork formation is similar to that at the end of the ca 2 2 2 1 ga carbon isotope excursion in fennoscandia this chemostratigraphic trend and deposition of bifs mn rich lithologies carbonaceous shales and phosphorites at the end of the global ca 2 2 2 1 ga carbon isotope excursion are likely related to ocean overturn associated with the final breakup of the kenorland supercontinent correlative carbonates from the slaughterhouse formation in the sierra madre wy and from the whalen group in the rawhide creek area in the hartville uplift wy have highly positive carbon isotope values in contrast carbonates from other exposures of the whalen group in the hartville uplift and all carbonate units in the black hills sd have carbon isotope values close to 0 combined with existing geochronologic and stratigraphic constraints these data suggest that the slaughterhouse formation and the succession exposed in the rawhide creek area of the hartville uplift are correlative with the lower and middle nash fork formation and were deposited during the ca 2 2 2 1 ga carbon isotope excursion the estes and roberts draw formations in the black hills and carbonates from other exposures in the hartville uplift postdate the ca 2 2 2 1 ga

on the late neoproterozoic early cambrian transition events in parts of east gondwanaland abstract the east gondwanaland evolved as a result of break up of the rodinia supercontinent the late neoproterozoic early cambrian geochemical events documented in the rocks of the east gondwanaland and siberia suggest variations in the c s and sr isotopic compositions of the contemporary seawater and systematic distribution of phosphorite and evaporite deposits the geochemical records in the peninsular india himalaya south china iran and oman regions have been discussed and used for establishing late neoproterozoic links of these widely separated sedimentary basins

diagenesis of late proterozoic carbonates the beck spring dolomite of eastern california abstract petrographic and compositional attributes of limestone and dolostone in the beck spring dolomite of eastern california indicate that late proterozoic mineralogies isotopic compositions and diagenetic processes were similar to those inferred for younger phanerozoic marine carbonate sequences allochems in limestones include strontium rich ooids with well preserved concentric banding and cortices of equant neomorphic calcite that commonly exhibit dissolution and compaction features cements include microdolomite rich columnar marine calcite and equant spar calcites are depleted relative to dolomites and become enriched with stratigraphic depth acicular and columnar marine cement and allochems in dolostones display fabrics identical to those in limestones but are isotopically distinct dolomite ooids columnar and acicular cement crystal silt and early luminescent spar cement from four stratigraphic sections define overlapping positive oxygen carbon covariant fields that trend toward depleted calcite compositions early luminescent dolomite spar cement is unconformably overlain by depleted ferroan dolospar fabric data suggest that marine cement and ooids were precipitated as magnesian calcite and aragonite isotopic data suggest that metastable components locally stabilized to calcite during subaerial exposure while laterally dolomitization took place in mixed marine meteoric waters early dolospar precipitation began during replacive dolomitization and late ferroan dolospar precipitated during burial lack of evidence for hypersaline conditions suggests that late proterozoic normal marine carbonate isotopic composition was 0 5 2 018o and 5 3 0 5913c

sm nd in marine carbonates and phosphates implications for nd isotopes in seawater and crustal ages this study explores the possibility of establishing nd isotopic variations in seawater over geologic time calcite aragonite and apatite are examined as possible phases recording seawater values of nd modern biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have nd concentrations of from 0 2 to 70 ppb showing that primary marine caco 3 contains little ree and that nd ca is not greatly enhanced relative to seawater during carbonate precipitation very young marine limestone and dolomite containing no continental detritus have 200 ppb nd all the carbonates are lree enriched 0 16 sm nd 0 45 modern and very young atlantic and pacific carbonates have nd in the range of shallow atlantic and pacific seawater respectively implying that they derive their ree from local seawater the nd in well preserved carbonate fossils is 4 10 4 ppb much greater than in their modern counterparts but like the high values found for carbonates in other studies we believe the high ree contents at the 500 ppb level in some detritusfree carbonates are due to ree rich fe hydroxide in on the carbonate in favorable cases such material may record seawater nd values however introduction of extraneous ree may obscure the original isotopic composition of pure caco 3 because of its very low intrinsic primary ree abundance modern biogenic apatite is also shown to have very low ree content 150 ppb nd but appears to quickly scavenge ree from seawater inorganically precipitated apatite from phosphorites has high concentrations of seawater derived ree young phosphorite apatite from the atlantic and pacific oceans has nd in the range of the seawater from these oceans older apatite samples of similar age from different localities bordering common oceans record similar values of nd t sedimentary apatite has sr t values in good agreement with the curves for 87 sr 86 sr of seawater as a function of time individual conodonts from a single formation yield the same sr t and nd t other workers have shown that sedimentary apatite preserves seawater ree patterns these characteristics suggest that sedimentary apatite can be used to determine nd t in ancient seawater the seawater values so inferred range between 1 7 and 8 9 over the last 700 my and lie in the range of modern seawater showing no evidence for drastic changes high values of seawater nd t in the triassic and latest precambrian may correlate with the breakup of large continental landmasses the initial nd t 15 0 of a 2 ae old phosphorite implies the presence of 1 5 ae old continental crust at 2 ae ago the approach outlined here can be used to constrain the age of the exposed crust as a function of time

soil gas emanations as precursory indicators of volcanic eruptions field measurements conducted on several active volcanoes in italy the lesser antilles and indonesia demonstrate the common occurrence of diffuse soil gas emanations from the volcanic piles at distances from active craters or fumarolic zones these emanations consist essentially of carbon dioxide and rare gases and their genetic link with crater fumaroles and or magma degassing at depth can be verified both chemically and isotopically we emphasize here the potential use of these fluids for continuous volcano monitoring and eruption forecasting

the effect of varying acquisition parameters on the interpretation of sir c radar data the virunga volcanic chain abstract in 1994 the spaceborne imaging radar experiment c sir c acquired five data takes with different acquisition parameters over the virunga volcanic chain zaire changes in incidence angle 20 0 48 1 look direction west and east looking and pulse bandwidth 10 mhz 20 mhz and 40 mhz affect the geologic interpretations drawn from these data we examine differences in spatial distortion of features near the summit of nyiragongo volcano finding that opposite look direction data are helpful in interpreting volcanic features such as the shape of small craters in areas of high relief the relative brightness of lava flows and vegetation change and actually reverse for different wavelengths and polarizations although l band data are best for mapping the outline of the flows c and x band cross polarization data show differences in backscatter intensity between and within flows in addition our ability to discriminate lava flows and vents from surrounding vegetation is strongly influenced by pulse bandwidth resolution and angle of incidence pulse bandwidth is the most important parameter in mapping small topographic features such as volcanic cones and a set of particularly thick flows on the flanks of karisimbi volcano these examples illustrate important considerations of the tradeoffs and priorities in acquisition parameters for future missions such as envisat as well as potential pitfalls for interpretation of existing data