location of the southern edge of the gorda slab and evidence for an adjacent asthenospheric window results from seismic profiling and gravity as the mendocino triple junction migrates northward along the california margin it is widely presumed to leave a slab free or asthenospheric window in its wake a 250 km long south north seismic refraction reflection profile crossing the transition from transform to subduction regimes allows us to compare and contrast crust and upper mantle of the north american margin before and after it is modified by passage of the mendocino triple junction from the seismic data we have determined that 1 the crust is laterally homogeneous in velocity to a depth of 20 km interpreted by us as franciscan complex 2 below 20 km depth the crust is characterized by velocities of 7 0 km s for the southern half of the profile and by velocities of 3 2 g cm 3 is required on the southern end of the profile we interpret these combined results to indicate that our profile crosses the southern edge of the gorda plate and that directly adjacent to this edge is an asthenospheric window with overlying mafic rocks in the crust these mafic rocks and a reforming lithospheric mantle increase in thickness southward

raman microspectroscopy of funginite from the upper silesian coal basin poland abstract raman spectral characteristics of funginite were compared with that of fusinite and semifusinite from the same coals inertinite concentrates prepared from four samples of coking coals from the upper silesian coal basin of poland were examined the examination reveals that funginite spectral characteristics have common features with that of fusinite or to smaller extent to semifusinite this suggests that the high reflectance of funginite might result from charring during wildfire activity

transition from slab to slabless results from the 1993 mendocino triple junction seismic experiment three seismic refraction reflection profiles part of the mendocino triple junction seismicexperiment allowustocompareandcontrastcrustanduppermantleofthenorth american margin before and after it is modified by passage of the mendocino triple junction upper crustal velocity models reveal an asymmetric great valley basin overlying sierran or ophiolitic rocks at the latitude of fort bragg california and overlying sierran or klamath rocks near redding california in addition the upper crustal velocity structure indicates that franciscan rocks underlie the klamath terrane east of eureka california thefranciscancomplexis onaverage laterallyhomogeneousandisthickestinthe triple junction region north of the triple junction the gorda slab can be traced 150 km inboardfromthecascadiasubductionzone southofthetriplejunction strongprecritical reflections indicate partial melt and or metamorphicfluids at the base of the crust or in theuppermantle breaksinthesereflectionsarecorrelatedwiththemaacamaandbartlett springs faults suggesting that these faults extend at least to the mantle we interpret our datatoindicatetectonicthickeningofthefranciscancomplexinresponsetopassageofthe mendocino triple junction and an associated thinning of these rocks south of the triple junction due to assimilation into melt triggered by upwelling asthenosphere the region of thickenedfranciscancomplexoverliesazoneofincreasedscattering intrinsicattenuation or both resulting from mechanical mixing of lithologies and or partial melt beneath the onshore projection of the mendocino fracture zone our data reveal that we have crossed thesouthernedgeofthegordaslabandthatthisedgeand ortheoverlyingnorthamerican crust may have fragmented because of the change in stress presented by the edge

a critical re examination of the petrology of the no 5 block coal in eastern kentucky with special attention to the origin of inertinite macerals in the splint lithotypes abstract the pennsylvanian no 5 block coal bed in eastern kentucky is one of several coals considered to be among the splint coals of the central appalachians the coals are generally noted for their inertinite rich dull lithotypes petrographic aspects of the lithologies reveal both fire derived and degradation derived inertinites in the assemblages fire is not an exclusive contributor to the origin to inertinite macerals there are many other biological factors such as the actions and interactions of fungi bacteria and insects which must be considered in the alteration of plant materials to form inertinite macerals fungi physically and chemically alter plant tissues to form macerals with a distinct morphology and chemistry different than those formed from fire and other abiological processes insects as secondary sources of wood degradation within a mire are responsible for physical such as boreholes from wood consuming insects and chemical alteration of plants degradation observed in macrinite may be boreholes from wood consuming insects such as mites some inertinite macerals in particular macrinite may be the result of inert fecal pellet conglomerates preserved in the mire overall macerals of the same name can form from multiple and complex biological and abiological processes

revisiting coos bay oregon a re examination of funginite huminite relationships in eocene subbituminous coals coal petrography has advanced significantly since reinhardt theissen and james schopf pioneered the use of thin sections to examine coals from coos bay oregon and to many coal petrographers the nomenclature used in that study is irrelevant the schopf 1947 study was a ground breaking examination of maceral relationships that need to be part of the working vocabulary of modern petrographers to support this a re examination of the coos bay thin section collection was undertaken using modern nomenclature for low rank coals under reflected light this particular collection was chosen in part because of the abundance of fungal material reported by schopf fungal material in coal and its association with huminite vitrinite macerals provides important information about the decompositional history of the coal and allows coal dominated by oxic processes to be differentiated from coal dominated by anoxic processes in the coos bay samples predominantly oxic intervals contain well preserved fungi including spores sclerotia and hyphae while anoxic intervals contain no fungi

notes on the origin of the resinite rich pine needle lithotype of the cretaceous cambria coal weston county wyoming abstract the cretaceous cambria coal located in the western part of the black hills in weston county wyoming was mined in the late 1800 s and early 1900 s primarily to serve the burlington and missouri river railroad on its route from lincoln nebraska to billings montana the coal bed contains a distinctive resinite rich lithotype commonly known as the pine needle coal the coal is characterized by a collodetrinite inertodetrinite liptodetrinite lithotype and the liptodetrinite including the resinite represents a degraded residue of what was originally a deposit with a greater representation of wood derived material

early holocene climate oscillations recorded in three greenland ice cores a new ice core chronology for the greenland dye 3 grip and ngrip ice cores has been constructed making it possible to compare the 18 o and accumulation signals recorded in the three cores on an almost annual scale throughout the holocene we here introduce the new time scale and investigate 18 o and accumulation anoma lies that are common to the three cores in the early holocene 7 9 11 7 ka before present three time periods with significant and synchronous anomalies in the 18 o and accumulation signals stand out the well known 8 2 ka event an event of shorter duration but of almost similar amplitude around 9 3 ka before present and the preboreal oscillation during the first centuries of the holocene for each of these sections we present a 18 o anomaly curve and a common accumulation signal that represents regional changes in the accumulation rate over the greenland ice cap

late holocene tectonics and paleoseismicity southern cascadia subduction zone holocene deformation indicative of large subduction zone earthquakes has occurred on two large thrust fault systems in the humboldt bay region of northern california displaced stratigraphic markers record three offsets of 5 to 7 meters each on the little salmon fault during the past 1700 years smaller and less frequent holocene displacements have occurred in the mad river fault zone elsewhere as many as five episodes of sudden subsidence of marsh peats and fossil forests and uplift of marine terraces are recorded carbon 14 dates suggest that the faulting subsidence and uplift events were synchronous relations between magnitude and various fault offset parameters indicate that earthquakes accompanying displacements on the little salmon fault had magnitudes of at least 7 6 to 7 8 more likely this faulting accompanied rupture of the boundary between the gorda and north american plates and magnitudes were about 8 4 or greater

precise radiocarbon dating of late glacial cooling in mid latitude south america abstract variability of atmospheric 14c content often complicates radiocarbon based chronologies however specific features such as periods of constant 14c age or steep changes in radiocarbon ages can be useful stratigraphic markers the younger dryas event in the northern hemisphere is one of those periods showing conspicuous 14c wiggles although the origin of those variations is not fully understood we can make practical use of them and determine i whether the younger dryas was global in extent if so ii were the initial cooling and the final warming synchronous worldwide and iii what are the implications of these similarities differences here we report high resolution ams 14c chronologies from the mid latitudes of south america that pinpoint a cool episode between 11 400 and 10 20014c yr b p the onset of the final cool episode of the late glacial in the southern mid latitudes i e the huelmo mascardi cold reversal preceded the onset of the younger dryas cold event by 550 calendar years both events ended during a radiocarbon age plateau at 10 20014c yr b p thus the huelmo mascardi cold reversal encompasses the younger dryas as well as a couple of short term cool warm oscillations that immediately preceded its onset in the north atlantic region

wide angle seismic constraints on the evolution of the deep san andreas plate boundary by mendocino triple junction migration recent wide angle seismic observations that constrain the existence and structure of a mafic layer in the lower crust place strong constraints on the evolution of the san andreas plate boundary system in northern and central california northward migration of the mendocino triple junction and the subducted juan de fuca lithospheric slab creates a gap under the continent in the new strike slip system this gap must be filled by either asthenospheric upwelling or a northward migrating slab attached to the pacific plate both processes emplace a mafic layer either magmatic underplating or oceanic crust beneath the california coast ranges a slab of oceanic lithosphere attached to the pacific plate is inconsistent with the seismic observation that the strike slip faults cut through the mafic layer to the mantle detaching the layer from the pacific plate the layer could only be attached to the pacific plate if large vertical offsets and other complex structures observed beneath several strike slip faults are original oceanic structures that are not caused by the faults otherwise if oceanic slabs exist beneath california they do not migrate north to fill the growing slab gap the extreme heat pulse created by asthenospheric upwelling is inconsistent with several constraints from the seismic data including a shallower depth to the slab gap than is predicted by heat flow models seismic velocity and structure that are inconsistent with melting or metamorphism of the overlying silicic crust and a high seismic velocity in the upper mantle yet either the pacific slab model or the asthenospheric upwelling model must be correct while the mafic material in the lower crust could have been emplaced prior to triple junction migration the deeper slab gap must still be filled a preexisting mafic layer does not reduce the inconsistencies of the pacific slab model such material could however compensate for the decrease in mafic magma that would be produced if asthenospheric upwelling occurred at a lower temperature these low temperatures however may be inconsistent with asthenospheric rheology

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

molecular characterization of fossil and extant dammar resin extracts insights into diagenetic fate of sesqui and triterpenoids abstract the composition of sesquiterpenoids and triterpenoids in the solvent extract of extant miocene and eocene dammar i e class ii resins has been determined and compared to investigate the vulnerability of these biomarkers to diagenesis molecular evidence e g absence of bicadinanes and low rock eval maturity values tmax

the little ice age glacier advance in the central andes 35 s argentina abstract this paper documents the occurrence of the little ice age lia in the el azufre and el penon glaciers at 35 s and in the las choicas and las damas glaciers at 34 55 s in the headwaters of the rio grande basin in the central andes of argentina moraine morphology stratigraphic relationships radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the lia advance in this area the lia maximum advance occurred between cal yr 1550 and 1720 ad and a readvance occurred around cal yr 1830 ad in addition glacier fluctuations of the las vacas and gussfeltd glaciers 33 s and el penon and el azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs and satellite images the glaciers showed a marked retreat during 1894 2007 minor readvances occurred in the 1980s and 1990s which could be related with strong warm enso events during these decades our results are consistent with observations made by other authors in the region

global changes in intensity of the earth s magnetic field during the past 800kyr recent advances in palaeomagnetic and dating techniques have led to increasingly precise records of the relative intensity of the earth s past magnetic field at numerous field sites the compilation and analysis of these records can provide important constraints on changes in global magnetic field intensity and therefore on the earth s geodynamo itself a previous compilation for the past 200 kyr integrated 17 marine records into a composite curve1 with the geomagnetic origin of the signal supported by an independent analysis of 10be production made on different cores2 the persistence of long term features in the earth s magnetic intensity or the existence of long term periodic changes cannot however be resolved in this relatively short time span here we present the integration of 33 records of relative palaeointensity3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 into a composite curve spanning the past 800 kyr we find that the intensity of the earth s dipole field has experienced large amplitude variations over this time period with pronounced intensity minima coinciding with known excursions in field direction reflecting the emergence of non dipole components no stable periodicity was found in our composite record and therefore our data set does not support the hypothesis that the earth s orbital parameters have a direct and strong influence on the geodynamo

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

paleoecology of the fire clay coal bed in a portion of the eastern kentucky coal field vertically continuous increment samples of the fire clay coal bed mid middle pennsylvanian late westphalian b collected from a portion of the central appalachian basin were studied palynologically petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient fire clay paleomire results indicate that four compositional groups can be identified they are 1 a lycospora vitrinite dominant group characterized by high percentages of lycospora and vitrinite macerals and generally low but variable ash yields and sulfur contents 2 a mixed palynoflora high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora 3 a mixed palynoflora moderate low vitrinite group characterized by various admixtures of lycopsid fern and calamite miospores increased percentages of liptinite and inertinite macerals and low ash yields and sulfur contents and 4 a mixed palynoflora high ash yield group characterized by high percentages of small lycopsid fern and occasionally calamite and cordaite miospores high liptinite and inertinite contents high ash yields and moderate to high sulfur contents the fire clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches these two benches upper and lower are highly disparte in occurrence appearance and composition in the study area the lower bench generally is thin 0 5 m laterally discontinuous and mainly composed of dull mainly durain coal lithotypes ash yields typically are high sulfur contents generally are moderate to high compositional group 4 the mixed palynoflora high ash yield group defines all of the increments examined from the lower bench in contrast the upper bench is thick 0 75 m laterally continous and mainly comprised of bright mainly clarain coal lithotypes overall ash yields and sulfur contents for this bench are generally low although vertical variation is apparent all of the compositional groups occur in the upper bench in some columns notably those that are thick and uninterrupted by clastic partings groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers other columns especially those taken in areas of thin 0 5 m fire clay coal are dominated by groups 1 and 4

petrography and geochemistry of oligocene bituminous coal from the jiu valley petrosani basin southern carpathian mountains romania abstract belt samples of oligocene chattian bituminous coal from 10 underground mines located in the jiu valley hunedoara county petrosani basin romania have been examined and analyzed for proximate and ultimate analysis major minor and trace element chemistry organic petrography and vitrinite reflectance the mineral chemistry and mode of occurrence of trace elements also have been investigated using sem and electron microprobe techniques twenty coal beds occur in the jiu valley and most of the samples are from bed no 3 the most productive bed of the dilja uricani formation of oligocene age the petrosani basin oriented sw ne is 48 km long 10 km wide at the eastern part and 2 km wide at the western part the coal mines are distributed along the center of the valley generally following the jiu de vest river reflectance measurements indicate that the rank of the coals ranges from high volatile b to high volatile a bituminous overall rank decreases from the southwest to the northeast in bed no 3 r max varies from 0 75 in the northeast to 0 93 in the southwest although most oligocene coals in romania and adjacent countries are lignite in rank the jiu valley bituminous coals have been affected by regional metamorphism and attending hydrothermal fluids related to the alpine orogenic event the coals are all dominated by vitrinite resinite and funginite are important minor macerals in most of the coals pyrite and carbonate generally dominate the mineral assemblages with carbonate more abundant in the northwest siderite occurs as nodules and masses within the macerals generally vitrinite dolomite and calcite occur as fracture fillings plant cell fillings and in other authigenic forms late stage fracture fillings are siderite dolomite calcite and ankerite in one instance two populations of siderite 35 and 45 wt feo plus ankerite fill a large fracture late stage pyrite framboid alteration is ni and cu bearing with ni rich pyrite hydrated ni fe sulfate chalcopyrite and rare pentlandite and clausthalite some of the mines sampled in 2001 have been closed as romania has undergone severe economic and environmental reforms in preparation for its 2007 entry into the european union eu romania s continued efforts to adapt to a market economy within the environmental and economic constraints of the eu make this collection of data valuable as the eventual fate of the other mines in jiu valley is unknown

classification of debris covered glaciers and rock glaciers in the andes of central chile in the dry andes of chile 17 to 35 s debris covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover thickness of surface debris and ice content internal ice is preserved by an insulating cover of thick debris which acts as a storage reservoir to release water during the summer and early fall these landforms are more numerous than glaciers in the central andes however the existing legislation only recognizes uncovered or semicovered glaciers as a water resource glaciers debris covered glaciers and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains in addition agricultural expansion and population growth in this region have placed additional demands on water resources in a warmer climate as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season rock glaciers and debris covered glaciers contribute a larger component of base flow to rivers and streams as a result identifying and locating these features to implement sustainable regional planning for water resources is important the objective of this study is to develop a classification system to identify debris covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs the classification system is linked to field observations and measurements of ice content debris covered glaciers have three subclasses surface coverage of semi class 1 and fully covered class 2 glaciers differentiates the first two forms whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris based on field observations the amount of ice decreases from more than 85 to 65 85 to 45 65 for semi fully and buried debris covered glaciers respectively rock glaciers are characterized by three stages class 4 rock glaciers have pronounced transverse ridges and furrows that arch across the surface which indicates flow produced via ice class 5 rock glaciers have ridges and furrows that appear linear in the direction of flow indicating reduced flow from limited internal ice and class 6 rock glaciers have subdued surface topography because the movement of the rock glacier has ceased ice content decreases from 25 45 to 10 25 to 10 from class 4 to 6 respectively examples from digital imagery aerial photographs and field photographs are provided for each class the classification scheme can be used to identify and map debris covered glaciers and rock glaciers to create an inventory this will help improve recognition of these landforms as an important water resource in the dry andes of chile which will aid in sustainable planning and development in basins that hold the majority of the population and support a large share of the economic activity in chile

post middle miocene accretion of franciscan rocks northwestern california deformed sedimentary rocks assigned to the franciscan assemblage in the king range south of cape mendocino northern california are dominantly deep water argillite and sandstone occurring as thick to thin bedded locally channelized marine turbidites of arkosic to andesitic volcani clastic composition these rocks structurally overlie late cretaceous coniacian to campanian basaltic pillow flows flow breccias diabase sills and arkosic sandstone turbidites that also are assignable to the franciscan assemblage and are well exposed along the coast at point delgada radiolarians and planktic and benthic foraminifers indicate that the oldest rocks in the king range may be early tertiary and that the youngest rocks are middle miocene or younger the youngest rocks yet reported from the franciscan assemblage partly coeval miocene relizian and luisian to quaternary rocks representing shallower sedimentary facies of the inner shelf to outer continental slope occupy the eel river basin and isolated fault bounded slivers adjacent to the king range on the north and east wide zones of penetrative shearing that may delineate a middle miocene or younger suture separate the deep water franciscan rocks of the king range from less severely deformed neogene rocks of the eel river basin the king range appears to be a displaced terrane of oceanic basement overlain by paleogene and neogene sedimentary and igneous rocks of continental and oceanic derivation this terrane may have been displaced north or eastward and obductively accreted to california 15 m y ago before or perhaps during northward passage of the pacific farallon north american plate junction

notes on the origin of inertinite macerals in coals funginite associations with cutinite and suberinite abstract the association of fungus with plant leaves and roots is ubiquitous while many of these occurrences are considered to be pathogenic mycorrhizzal fungal associations with roots are essential for plant growth despite the common knowledge of such relationships in plant science with a few exceptions the fungus leaf root stem association as the macerals funginite cutinite and suberinite in coals has not been extensively studied in this work examples of funginite associations with cutinite and suberinite are discussed

the cape mendocino california earthquakes of april 1992 subduction at the triple junction the 25 april 1992 magnitude 7 1 cape mendocino thrust earthquake demonstrated that the north america gorda plate boundary is seismogenic and illustrated hazards that could result from much larger earthquakes forecast for the cascadia region the shock occurred just north of the mendocino triple junction and caused strong ground motion and moderate damage in the immediate area rupture initiated onshore at a depth of 10 5 kilometers and propagated up dip and seaward slip on steep faults in the gorda plate generated two magnitude 6 6 aftershocks on 26 april the main shock did not produce surface rupture on land but caused coastal uplift and a tsunami the emerging picture of seismicity and faulting at the triple junction suggests that the region is likely to continue experiencing significant seismicity

petrology mineralogy and geochemistry of the ge rich coal from the wulantuga ge ore deposit inner mongolia china new data and genetic implications abstract the early cretaceous wulantuga high ge coal deposit in inner mongolia is one of the major coal hosted ge deposits in china this paper reports new data on the petrological mineralogical and geochemical compositions of 13 bench samples of the high ge no 6 coal from the wulantuga deposit and provides new insight into the origin and modes of occurrence of the minerals and elements present the no 6 coal has a low rank ro max 0 45 and is a low ash coal 8 77 the total content of inertinite 52 5 vol on average in most coal benches is higher than that of huminite 46 8 vol on average the dominant huminite maceral is textinite averages 43 9 and the dominant inertinite macerals are mainly fusinite averages 33 and semifusinite 12 5 along with trace portions of intertodetrinite secretinite funginite and macrinite fungus seen as the maceral funginite played a role in the development of degraded maceral forms in the wulantuga coals funginite is present in samples examined in this study but is not easily extracted during palynological studies recovered fungal taxa are saprophytes indicating woody decomposition prior to incorporation in the mire palynology revealed a sparse flora that is consistent with the early cretaceous age minerals in the coal include quartz kaolinite illite and or illite smectite gypsum pyrite and traces of rutile and anatase a varying proportion of bassanite was observed in the low temperature ashes ltas bassanite in the ltas was derived both from the dehydration of gypsum in the raw coals and from the interaction between organically associated ca and s during the low temperature ashing in addition to a proportion of detrital quartz fine grained and cell filling quartz of authigenic origin is also present pyrite is of syngenetic origin and derived from sulfate rich hydrothermal fluids compared to common chinese and world low rank coals the no 6 coal is enriched in be 25 7 g g f 336 g g ge 274 g g as 499 g g sb 240 g g cs 5 29 g g w 115 g g hg 3 165 g g and tl 3 15 g g germanium in the coal is organically associated and its enrichment is attributed to hydrothermal fluids from the adjacent granitoids beryllium is probably associated with ca and mn bearing carbonate minerals and to a lesser extent with clay minerals rather than with organic matter fluorine largely occurs in clay minerals kaolinite and illite the elevated concentrations of tl hg as and sb are mainly distributed in pyrite and were derived from the same hydrothermal source the high w in the coal occurs in both the organic matter and the authigenic quartz illite is the major carrier of cs in the coal the accumulation of rare earth elements ree in the coals had a polygenetic and multistage nature including two syngenetic stages early hydrothermal and terrigenous and one diagenetic late hydrothermal stage the ree distribution patterns of the early hydrothermal and terrigenous stages were characterized by the enrichment of medium ree m type ree and light ree l type ree respectively a h type ree distribution pattern hree enrichment occurred in the late diagenetic hydrothermal stage the high ge wulantuga coals are also abnormally enriched in precious metals gold pt and pd in the coals calculated from their concentrations in the ltas are 3 5 25 8

comparing maceral ratios from tropical peatlands with assumptions from coal studies do classic coal petrographic interpretation methods have to be discarded petrographic investigations of tropical peat deposits from the tasek bera basin malaysia show that petrographic methods can contribute valuable information about paleoecological settings of mire deposits comparing modern peat forming environments and the pre maceral composition of peat samples allows the reconstruction of paleoecological conditions such as floral composition fires microbial activity etc and gives insight into paleodepositional environments in the past maceral ratios of coals have been used to interpret paleodepositional settings of coal deposits such a procedure assumes that coal texture and coal maceral composition are dictated solely by the depositional environment and thus different depositional environments should be clearly discriminated based on maceral ratios in the modern peat deposits of tasek bera divergent petrographic results occur in similar depositional environments hence poor correlation occurs between the petrography the degree of decomposition and the depositional environment furthermore from the time of peat deposition peat is subject to considerable alteration during subsequent diagenesis preservation of structured and strongly altered material such as inertinite gelified material or funginite is favoured and results in biased coal maceral compositions because maceral indexes in modern peat studies are of little utility in the reconstruction of paleoenvironmental settings it follows that coal maceral indexes should not be utilized in the future to interpret paleodepositional environments of coals

notes on the origin of inertinite macerals in coals observations on the importance of fungi in the origin of macrinite macrinite is a generally rare inertinite maceral often incorporating remnants and fragments of other macerals including vitrinite liptinite and other inertinite the associated inertinites include multiple forms of funginite funginite is also commonly found in association with vitrinite of slightly elevated reflectance and with degraded varieties of vitrinite together with the highly degraded macrinite the latter two associations are here inferred to be part of a continuum of fungal and microbial degradation of peat in any case the origin of some macrinite is potentially distinct from that of inertinite generated by fire

magnetostratigraphy and magnetic susceptibility of the las carreras loess paleosol sequence in valle de tafi tucuman nw argentina abstract stratigraphic studies on loess deposits in the intramontane basin of valle de tafi 27 s 66 w revealed up to 31 intercalated paleosols in order to clarify the chronostratigraphic position of the sediments we performed paleomagnetic investigations in the 50 m thick las carreras section the characteristic remanent magnetization chrm obtained after alternating field af demagnetization gives clear evidence of the matuyama brunhes boundary mbb at a profile depth of 26 7 m and of the jaramillo subchron at depths from 38 7 to 44 9 m we assign a minimum age of 1 15 ma to the onset of loess sedimentation which calls for a complete reassessment of the antiquity of loess in the region thus the las carreras sequence which is probably continuous and complete represents one of the longest quaternary terrestrial paleoclimatic records reported from the southern hemisphere the magnetic susceptibility signal follows the behavior known for argentinian eolian sediments though with certain restrictions and an overall weak correlation with pedostratigraphy this behavior is opposite to the pattern reported from the chinese loess plateau clp and seems to be influenced strongly by changing source materials contributing to the susceptibility signal in valle de tafi

structure and seismotectonics of the mendocino triple junction california 1 we analyze and interpret two marine multichannel seismic reflection onshore offshore ocean bottom seismometer obs seismic profiles that cross in the region of the mendocino triple junction over the fault plane of the 1992 petrolia california ms 7 1 earthquake from the offshore reflection data and the wide angle constraints provided by the onshore offshore and obs data we have determined a rough three dimensional view of crustal and uppermost mantle structure beneath the triple junction region this structure is also consistent with gravity data the upper and mid crust has seismic velocities and densities consistent with accretionary complex rocks of the franciscan terrane a ubiquitous lower crustal layer with velocities of 6 5 7 1 km s 1 is 5 7 km thick throughout most of the region over an area extending at least 25 km to the south and 60 km to the west of the triple junction the lower crustal layer is up to 12 km thick this area is overlain by undisturbed pre 11 ma sediments indicating little deformation since that date the thick lower crust extends beneath the coast suggesting that the deep boundary between pacific and north american terranes lies onshore the northeastern edge of the thick lower crustal layer is marked by concentrated seismicity with the hypocenter of the 1992 petrolia earthquake lying close to the ne corner we speculate that at depth the pacific lower crust acts an asperity acting to concentrate stress from which the petrolia earthquake ruptured

spatial variability in modern tropical peat deposits from sarawak malaysia and sumatra indonesia analogues for coal petrographic and chemical variability in two tropical low ash domed peat deposits of similar age and physiographic setting but different external morphology were examined as modern analogues for coal both occur in microtidal alluvial to deltaic plain settings support similar arborescent vegetation and have accumulated in the past 5 000 years one deposit is an extremely convex mature done with a surface that rises 10 m above river level the other is a low gradient dome rising only 3 m above river level but with a concave base up to 6 m below both deposits have been eroded by adjacent rivers yet peat in the mature dome has accumulated remote from persistent flooding and exhibits distinctive internal stratigraphy decomposed sapric peat floors the deposits and is overlain by increasingly better preserved woody hemic and a cap of coarse fibrous peat derived from less arborescent vegetation consistent flooding in the low gradient dome has maintained conditions for the accumulation of predominantly woody hemic peat which interfingers with and is overlain by oxidised sapric peat and levee derived clastic sediments peat types in both deposits exhibit distinctive polymodal textures and organo chemical signatures that correspond to botanical input and degree of decay due to the abundance of pre huminite vitrinite macerals in all peat types from these deposits megascopic and microscopic texture is a better discriminator for comparison to ancient coal types it is suggested that the upward vertical sequence of decreasing woodiness and increasing lightness in colour observed in the mature dome might best be compared to sequences observed in tertiary brown coals this typical sequence can be modified or overprinted due to flooding in the burial process

crustal velocity structure north of the mendocino triple junction a 140 km long refraction wide angle reflection profile recently recorded by stanford university and the u s geological survey imaged the subducting gorda slab beneath northern california the profile which is subparallel to the coast from cape mendocino northward indicates that the north american plate is 13 to 14 km thick along the coast north of cape mendocino the crust is characterized by relatively uniform low velocities of 6 km s interpreted as franciscan rocks two strong reflections define the upper and lower boundaries of the subducting gorda crust our data indicate that the subducting gorda crust thickens northward from cape mendocino from 7 km thick just north of cape mendocino to 10 km thick 120 km to the north this change in thickness is coincident with a change in velocity from 6 7 km s south to 6 2 km s north mantle velocities of 7 7 km s are observed for offsets greater than c 80 km we interpret our model to indicate that the gorda slab is not imbricated on a crustal scale beneath our profile that sediments and or a tectonically thickened oceanic layer 2 are present to the north but not in the vicinity of cape mendocino and that proximity to the mendocino triple junction affects the way sediments are subducted

micromorphology and osl dating of the basal part of the loess paleosol sequence at la mesada in tucuman province northwest argentina abstract the basal part of the 42 m loess paleosol sequence at la mesada near tucuman in nw argentina reported by zinck and sayago j s am earth sci 12 1999 293 quat int 78 2001 11 is re examined here using a combination of micromorphology and optically stimulated luminescence osl dating depth distributions of microstructure clay coatings and secondary carbonate features enable the development of this part of the sequence to be reconstructed in terms of a series of pedosedimentary stages stage one involved accretionary pedogenesis with loess being modified by bioturbation and possibly leaching processes as it accumulated stage two was marked by a reduction in loess deposition and establishment of a relatively stable surface at which bioturbation leaching and clay translocation processes were dominant stage three represented a return to accretionary pedogenesis followed by establishment of a new relatively stable surface and vertical leaching and clay translocation processes with some welding of secondary carbonate features on the underlying older soil the three osl dates ranging from ca 150 to 195 ka bp suggest that the whole sequence is significantly older than indicated by the radiocarbon chronology ka bp reported in the works of zink and sayago cited above however assuming that the pedosedimentary changes reflect alternating periods of dry cool and moist warm conditions as suggested in the works of zink and sayago cited above the succession still potentially provides the highest resolution proxy climatic record so far reported in argentina

petrographic changes induced by artificial coalification of peat comparison of two planar facies rhizophora and cladium from the everglades mangrove complex of florida and a domed facies cyrilla from the okefenokee swamp of georgia abstract petrographic changes during coalification of three peat samples were investigated by artificial coalification experiments using a semi open reactor system compressions of from 83 to 88 produced dark brown to black shiny flattened pellets exhibiting microscopic banding overall amounts of compression inversely correlated with the framework to matrix ratios f m although certain tissue fragments remained relatively uncompressed due to the presence of tanniniferous cell fillings and also hypothetically to the presence of colorless plant secretions or gelified wall materials that were present in the cells but only recognizable after a change in color during coalification the most distinct microscopic banding longest and widest bands developed in samples of the dome formed peat facies which had the highest framework to matrix ratios of any type and the greatest contents of surface litter composing the framework i e highest s n ratio the planar root dominated rhizophora facies showed the greatest change in microbanding character during coalification in that the numerous lens like bands produced by the compressed roots were very distinct at the 60 2100 psi 121 4 kg cm 2 stage but nearly disappeared at the 175 5000 psi 289 1 kg cm 2 stage this is explained as a result of differences in rates of coalification of the different telinitic precursors in the roots multilinear vitrinization and could explain why roots are significant components of many modern peats and ancient coal ball concretions but are difficult to recognize in bituminous coals similarly separation of cuticles from leaves in modern peat forming environments due to irreversible shriveling and subsequent enhanced microbiological decay partially explains why leaf remains are also difficult to recognize in most coals even those with abundant cutinites microcracks developed in all pellets with dominant orientations of cracks being either perpendicular to induced banding or horizontal to it minute vertical microcracks interpreted as dewatering features were observed primarily in gelinitic bands especially in the most fire prone cladium coal facies but these rarely extended into juxtaposed microlithotypes as did most of the larger vertical cracks horizontal cracks tended to form at microband boundaries almost all humotelinitic and humocollinitic precursors showed some changes in color during artificial coalification with humotelinites exhibiting less or slower changes than humocolinites or humodetrinites finer grained matrix material additionally nearly all dark brown degraded tissues in the peats became dark orange or red during coalification but many of these tissue masses were observed to contain significant amounts of minute inertinite derived from microorganisms pseudomicrinite that only became prominent after coalification and subsequent change in color of surrounding macerals fusinite precursors were only found in the fire prone cladium facies and although the coalified doming generated cyrilla facies exhibited evidence of significant drying events i e occasional bands or parts of bands containing significant pseudomicrinites macrinites and sclerotinites it was dominated by huminitic vitrinitic components liptinites were most common in the coalified dome formed cyrilla facies and displayed a slight qualitative increase in red green fluorescence during coalification and some possible flow of components into nearby cracks changes in mean random reflectance of huminitic macerals although still requiring more data and only measured to the 60 c 2100 psi 121 4 kg cm 2 level indicated increasing directions of change during artificial coalification with humocollinitic macerals progressing from an average of about 0 21 to 0 32 and humotelinitic macerals which consistently had lower inherent reflectances in the peats progressing from 0 15 to 0 25 the above petrographic results along with previously reported chemical results all suggest that the methods that we have used in these experiments have produced changes that might reasonably be expected to occur during natural coalification despite the fact that we have speeded up the process although more work needs to be done to verify and refine these results and to establish a correlation between these artificial coalification steps and true coalification the new observations and conclusions from these studies might still be helpful in constructing models to predict or interpret coal seam characteristics and to establish the timing and release potential of gaseous or liquid hydrocarbons from coals

nature and causes of quaternary climate variation of tropical south america abstract this selective review of the quaternary paleoclimate of the south american summer monsoon sasm domain presents viewpoints regarding a range of key issues in the field many of which are unresolved and some of which are controversial 1 el nino southern oscillation variability while the most important global scale mode of interannual climate variation is insufficient to explain most of the variation of tropical south american climate observed in both the instrumental and the paleoclimate records 2 significant climate variation in tropical south america occurs on seasonal to orbital i e multi millennial time scales as a result of sea surface temperature sst variation and ocean atmosphere interactions of the tropical atlantic 3 decadal scale climate variability linked with this tropical atlantic variability has been a persistent characteristic of climate in tropical south america for at least the past half millennium and likely far beyond 4 centennial to millennial climate events in tropical south america were of longer duration and perhaps larger amplitude than any observed in the instrumental period which is little more than a century long in tropical south america these were superimposed upon both precession paced insolation changes that caused significant variation in sasm precipitation and eccentricity paced global glacial boundary conditions that caused significant changes in the tropical south american moisture balance as a result river sediment and water discharge increased and decreased across tropical south america lake levels rose and fell paleolakes arose and disappeared on the altiplano glaciers waxed and waned in the tropical andes and the tropical rainforest underwent significant changes in composition and extent to further evaluate climate forcing over the last glacial cycle 125 ka we developed a climate forcing model that combines summer insolation forcing and a proxy for north atlantic sst forcing to reconstruct long term precipitation variation in the sasm domain the success of this model reinforces our confidence in assigning causation to observed reconstructions of precipitation in addition we propose a critical correction for speleothem stable oxygen isotopic ratios which are among the most significant of paleoclimate proxies in tropical south america for reconstruction of variation of paleo precipitation or sasm intensity however it is already well known that any particular 18o value observed in speleothem carbonate is affected by two processes that have nothing to do with changes in precipitation amount the influence of temperature on carbonate water isotopic fractionation in the cave and the influence of changing 18o of seawater quantitatively accounting for both artifacts can significantly alter the interpretations of speleothem records in tropical south america both adjustments act in the same direction and have the tendency to increase the true amplitude of the paleo hydrologic signal but by different amounts in glacial and inter glacial stages these corrections have even graver implications for the interpretation of tropical northern hemisphere speleothem records e g chinese speleothems where the combined adjustments tend to decrease or even eliminate the true signal amplitude

influence of geochemical organo petrographical and palynofacies assemblages on hydrocarbon generation a study from upper oligocene coal and shale of the makum coal basin assam india abstract the makum coal basin of northeast india comprises important coal and shale reserves of upper oligocene age a total of twenty samples were collected to evaluate the kerogen type hydrocarbon generation potential and thermal maturity through geochemically organo petrographically and palynofacies analyses the samples are characterized by high toc total organic carbon and large s2 remaining heavier hydrocarbons meet the required standards as good to excellent generation potential the coal and shale are marked by mixed type iii ii kerogen with minor occurrence of type i kerogen moderate to high hydrogen index hi values and are considered to generate thermogenic gas with some condensate oil the reflectance values indicate samples are mostly immature and close to the oil birth line the amount of vt60 grains also suggests that the samples can produce some condensate oil along with thermogenic gas the rock eval pyrolysis rep data stands with the interpretation through petrographic palynofacies and fourier transform infrared spectroscopy ftir in determining kerogen type and generation potential the generation potential is also controlled by the degree of organic matters reactivity the estimated reactivity indicates that besides vitrinite and liptinite up to 70 vol of the inertinite macerals have the potential to generate hydrocarbon the occurrence of a substantial amount of reactive macerals i e collotelinite vitrodetrinite collodetrinte corpogelinite alginite resinite and bituminite within the samples makes them more potential to generate hydrocarbons the diagram proposed based on our data of macerals and palynofacies assemblages may also be a convenient tool in detecting kerogen type s and nature of hydrocarbons

geomorphological response to the lateglacial holocene palaeoenvironmental changes in the ne piedmont of the sierra de aconquija tafi valley nw argentina abstract fluvial basins located on the ne side of the sierra de aconquija and facing the tafi valley nw argentina enable a study of the sedimentary records of valleys and alluvial fans that have been subject to glacial and periglacial dynamics since the fini pleistocene to upper holocene i the oldest morphosedimentary unit h1a encompasses the late glacial and early holocene a relationship was established linking fluvioglacial terraces to records from el rincon profile younger dryas belonging to the most important glacial phase g1 in the cirques found in the ne of aconquija ii similarly there is a g2 glacial phase neoglacial that could be connected with the h1b records of the munoz river and dated to early middle holocene iii the final units h2 and h3 from upper holocene form a stepped terrace in the valleys and were interpreted as corresponding to the rock glacier phases from the high mountains and highlighting those that were active during the lia

seismic potential associated with subduction in the northwestern united states despite good evidence of present day convergence of the juan de fuca and north american plates there has been remarkably little historical seismic activity along the shallow part of the juan de fuca subduction zone although we cannot completely rule out the possibility that the plate motion is being accommodated by aseismic creep we find that the juan de fuca subduction zone shares many features with other subduction zones that have experienced great earthquakes

influence of the mendocino triple junction on the tectonics of coastal california abstract the migration of the mendocino triple junction through central and northern california over the past 25 30 million years has led to a profound change in plate interactions along coastal california the tectonic consequences of the abrupt change from subduction plate interactions north of the triple junction to the development of the san andreas transform system south of the triple junction can be seen in the geologic record and geophysical observations the primary driver of this tectonism is a coupling among the subducting juan de fuca gorda north american and pacific plates that migrates with the triple junction this coupling leads to ephemeral thickening of the overlying north american crust associated uplift and subsequent subsidence and a distinctive sequence of fault development and volcanism

case study of igneous intrusion effects on coal nitrogen functionalities this study presents the results of the nitrogen xps analysis performed on a set of four bukit asam indonesia low rank coals and on a related natural pyrolysis product formed after an igneous intrusion low rank coal nitrogen xps sub peak is dominantly pyrrolic with subordinate quaternary and pyridinic dike intrusions are responsible for transformation of these nitrogen forms nitrogen to graphitic quaternary nitrogen the transformation of nitrogen is similar to that exhibited by laboratory prepared pyrolysis products of other coals

fossil wood from the middle cretaceous moreno hill formation unique expressions of wood mineralization and implications for the processes of wood preservation abstract the cretaceous turonian moreno hill formation of west central new mexico provides an opportune isotaphonomic setting to study wood preservation because both carbonized and mineralized wood are commonly found within the same sediments and often within individual specimens petrographic reflectance maceral and chemical analyses were used to compare and characterize mineralized and carbonized wood from the study site to investigate biases which influence mode of preservation coal in the form of coal inclusions is the most common form of fossil wood and mineralized wood is also widespread in the formation two striking specimens of in situ coalified stumps are particularly informative because each includes a mineralized ring that appears to represent the former location of sapwood most of the mineralized samples are primarily composed of quartz but a few specimens are predominantly mineralized with apatite calcite is present in charcoal samples where it permineralized but never replaced organic carbon this study points to two key factors that influence mineralization wood permeability and the chemical alteration of the wood prior to incorporation into the sediment the patterns of mineralization are consistent with hypothesized microbial involvement in the mineralization process the coexistence of coal and mineralized tissues in some samples suggests that the processes of silicification and phosphatization co occurred with coalification and that these processes are competitive within individual pieces of wood as such various stages of wood degradation have been preserved in mineralized samples from the moreno hill formation the study suggests that coal inclusions and mineralized wood coal associations may also be common in other ancient sediments even though weathering may obscure their presence such information is important for paleoecological and paleoenvironmental studies which utilize the occurrence of fossil wood to help reconstruct floral composition or climatic conditions

a kinematic model for the evolution of the gorda plate the magnetic lineation pattern produced by the gorda rise reflects a complex tectonic history marked by propagating ridges and nonrigid deformation of the gorda plate the pacific side lineation pattern is matched using a kinematic model which incorporates northward and southward propagating ridge segments and ridge rotation by superimposing flexural slip style deformation on the resulting gorda side lineations and allowing convergent motion at the mendocino fracture zone the gorda magnetic pattern is also successfully predicted a similar model but one which does not allow convergence at the mendocino fracture zone fails to produce the observed lineation pattern model predictions of the amount of material that would be obducted at the mendocino due to convergence between the gorda and pacific agree with bathymetric and density estimates of the amount of material located along the mendocino ridge

three dimensional crustal structure of the mendocino triple junction region from local earthquake travel times the large scale three dimensional geometry of the mendocino triple junction at cape mendocino california was investigated by inverting nearly 19 000 p wave arrival times from over 1400 local earthquakes to estimate the three dimensional velocity structure and hypocentral parameters a velocity grid 175 km n s by 125 km e w centered near garberville california was constructed with 25 km horizontal and 5 fan vertical node spacing the model was well resolved near cape mendocino where the earthquakes and stations are concentrated at about 40 6 n latitude a high velocity gradient between 6 5 and 7 5 km s dips gently to the south and east from about 15 km depth near the coast relocated hypocenters concentrate below this high gradient which we interpret as the oceanic crust of the subducted gorda plate therefore the depth to the top of the gorda plate near cape mendocino is interpreted to be 15 km the gorda plate appears intact and dipping 8 eastward due to subduction and flexing downward 6 12 to the south both hypocenters and velocity structure suggest that the southern edge of the plate intersects the coastline at 40 3 n latitude and maintains a linear trend 15 south of east to at least 123 w longitude the top of a large low velocity region at 20 30 km depth extends about 50 km n s and 75 km e w roughly between garberville and covelo and is located above and south of the southern edge of the gorda plate we interpret this low velocity area to be locally thickened crust 8 10 km due to either local compressional forces associated with north south compression caused by the northward impingement of the rigid pacific plate or by underthrusting of the base of the accretionary subduction complex at the southern terminous of the cascadia subduction zone south of cape mendocino and southwest of the garberville fault high velocities indicative of oceanic crust are detected at 15 km depth we interpret this evidence as tectonic underplating of the pacific oceanic crust beneath the coastal franciscan complex similar to the situation seismically imaged in central coastal california page and brocher 1994 this geometry indicates that the westernmost portion of the slab window has been filled by tectonic underplating and crustal thickening while deep seated mantle upwelling is confined to an area centered about 75 km north of clear lake benz et al 1992 zandt et al 1992

lithospheric structure of northern california from teleseismic images of the upper mantle teleseismic p wave travel time residuals from 120 earthquakes recorded across the u s geological survey california seismic network were used to determine the lithosphere p wave velocity structure beneath northern california a region characterized by complex interactions between the pacific north american and gorda plates lateral p wave velocity variations beneath the array were determined by inversion of 9383 travel time residuals inversion results for the crust show strong correlations to volcanic features the active volcanic fields shasta medicine lake lassen and clear lake are characterized by crustal low velocity anomalies that average approximately 6 possibly identifying partially molten magma bodies cooled solidified magma bodies beneath the extinct volcanic fields sonoma southern clear lake and sutler buttes are denoted by relative velocity highs averaging 3 the largest upper mantle velocity variations occur in the depth range 30 110 km where velocities vary from 5 5 to 9 5 these velocity variations reflect changes in the thickness and geometry of the pacific north american and gorda plates where they interact at the mendocino triple junction north of the mendocino triple junction the steep 70 east dipping portion of the gorda plate is imaged as a 5 velocity high to depths near 270 km a presumed segment of the gorda plate observed beneath the northern great valley and south of the inferred edge of the plate is characterized by a 9 velocity high in the depth range 30 70 km beneath the northern coast ranges shallow asthenosphere is imaged in the depth range 30 100 km as a pronounced southward tapering 4 low velocity zone which we interpret as the slab window results from this study provide improved constraints on gorda plate subduction evolution of the san andreas fault system and development of the lithosphere beneath western north america

late pleistocene glaciations of the arid subtropical andes and new results from the chajnantor plateau northern chile abstract the spatiotemporal pattern of glaciation along the andes mountains is an important proxy record reflecting the varying influence of global and regional circulation features on south american climate however the timing and extent of glaciation in key parts of the orogen particularly the deglaciated arid andes are poorly constrained we present new cosmogenic 10 be and 36 cl exposure ages for glacial features on and near the chajnantor plateau 23 s the new dates although scattered due to cosmogenic inheritance imply that the most recent extensive glacial occupation ended before or during the global last glacial maximum lgm we discuss this new record in the context of published glacial chronologies from glacial features in peru bolivia and northern chile rescaled using the latest cosmogenic 10 be production rate calibration for the tropical andes the results imply regionally synchronous moraine stabilization ca 25 40 ka 15 17 ka and 12 14 ka with the youngest of these moraines absent in records south of 20 s including in our new chajnantor area chronology this spatial pattern implicates easterly moisture in generating sufficient snowfall to glaciate the driest parts of the andes while allowing a role for westerly moisture possibly modulated by the migration of the southern westerly wind belt in the regions near and south of the atacama desert

average pleistocene climatic patterns in the southern central andes controls on mountain glaciation and paleoclimate implications abstract despite elevations of 5000 6800 m modern glaciers occur along the southern puna plateau and the northern sierras pampeanas in the southern central andes the modern snowline rises from 5100 m in sierra aconquija to 5800 m in the puna as a result of a westward decrease in precipitation from 450 to less than 100 mm yr during the pleistocene these arid highlands experienced multiple cirque and valley glaciation that likely postdate the last interglacial period although lack of age control prevents an absolute chronology glaciation in the puna and along the eastern puna edge produced a 300 m pleistocene snowline psl depression while in the sierras pampeanas the psl depression was at least 900 m the greater psl depression in the sierras pampeanas is best explained by a combination of cooling and increase of easterly moisture whereas the psl depression in the puna appears more sensitive to moisture increases than temperature previously glaciations in this region have been explained by increa

organic geochemical and petrographic characteristics of tertiary coals in the northwest sarawak malaysia implications for palaeoenvironmental conditions and hydrocarbon generation potential abstract tertiary coals from mukah and balingian coalfields in the northwest sarawak malaysia were investigated to evaluate their regional rank variation petroleum generative potential and to reconstruct the palaeoenvironment conditions during peat accumulation the tertiary coals are characterized by high total organic carbon contents toc and yield of bitumen extraction ranging from 31 3 to 55 9 wt and 25 724 9 92 143 7 ppm respectively meet the standard as a good source rock potential the mukah and balingian coals were generally plotted in an area of type iii kerogen and mixed type ii iii kerogens with hi values between 90 and 289 mg hc g toc whereby the coals were derived from plant materials of terrigenous origin this shows that the balingian coals are dominated by type iii terrigenous kerogen while mukah coals are dominated by type ii iii kerogens and are thus considered to be generate mainly gas prone and limited oil prone this is also supported by macerals composition and open system pyrolysis gas chromatography py gc the mukah and balingian coals are thermally immature in rang from lignite to sub bituminous c rank possessing huminite reflectance in the range of 0 26 0 39 this immaturity has a considerable influence on the proximate analysis particularly on relatively high moisture and volatile matter contents and relatively low fixed carbon content petrographically it was observed that the mukah and balingian coals are dominated by huminite with low to high amounts of liptinite and relatively low amounts of inertinite pointing to predominantly anaerobic deposition conditions in the paleomires with limited thermal and oxidative tissue destruction the palaeoenvironment conditions of the coals are generally interpreted as a lower deltaic plain wet peat swamp depositional setting which are generally characterised by low tpi and high gi values and are plotted on the marsh field of the diessel s diagram this is usually consistent with generate relatively high ash yield as is the case of the mukah and balingian coals

seismicity of the gorda plate structure of the continental margin and an eastward jump of the mendocino triple junction analysis of 9 years of data from the humboldt bay seismic network sheds new light on the structure and evolution of the gorda plate and mendocino triple junction significant findings include the buttressing effect of the pacific plate which demonstrates that there is no underthrusting of the gorda plate along the mendocino fault and the pattern of left lateral northeast trending faults which demonstrates how the gorda plate accommodates n s shortening without such underthrusting focal mechanisms are consistent with northward compression of the gorda plate by the pacific plate until the gorda plate passes the triple junction beyond which the n s compressive stress is effectively removed and the focal mechanisms show a change from strike slip to normal faulting with downslab tension another significant feature is the shallow benioff zone 10 40 km which shows a double seismogenic layer unlike most other double seismic layers in deep subduction zones this one appears to be due to underplating with a new subduction zone being developed east of the former one a corner of continental margin material has been partially subducted we attribute this double seismic zone to reactivation of both the old and new subduction boundaries under n s compression produced by pacific gorda plate interaction at the triple junction because the geometry of this triple junction indicates that it is unstable and because there is evidence that as part of its evolution the san andreas fault has migrated eastward we have constructed a model that accounts for both the eastward migration of the san andreas fault and the doubling of the seismic zone in the gorda plate this can be done by assuming that at the time of the last eastward jump of the fault the overriding continental margin north of the triple junction was broken and underthrust producing a new subduction zone that is collinear with the san andreas fault other scenarios for the evolution of the mendocino triple junction do not require that the subduction zone migrate eastward however the position and dip of the double zone indicate that an eastward jump of 100 km some 5 my ago could have taken place this is consistent with other evidence for an eastward jump of the san andreas fault

a kinematic model for the gorda deformation zone as a diffuse southern boundary of the juan de fuca plate several lines of evidence indicate that the space problem caused by southeastward motion of the juan de fuca plate toward the east west mendocino transform is resolved by distributed deformation of the oceanic crust north of the transform a kinematic model for this deformation based on the assumption of nondivergent flow conservation of area within the area known as the gorda plate and on the assumption of no subduction along the mendocino transform successfully matches the isochron pattern inferred from magnetic anomalies the model assumes strain rate decreasing to zero approaching the rigid juan de fuca plate with no sharp boundary or separate rigid area that would imply a discrete gorda plate this interpretation allows magnetic anomalies from south of the blanco fracture zone to be used to constrain the kinematics of the juan de fuca plate these anomalies imply a substantial change in the distance to the rotation pole at roughly 3 ma in addition to the clockwise shift in motion direction at 5 ma

evidence for a 180 km long subducted slab beneath northern california we present new seismic data for subduction of a 180 km long segment of the gorda plate beneath cape mendocino in northern california the inclined seismic zone dips 10 to 11 in the direction s68 e for a length of 120 km to depths of 30 to 35 km then steepens in dip to 25 and plunges to depths of at least 60 km p wave focal mechanisms of two earthquakes at depths of 30 and 58 km are consistent with downdip tension and imply that these events resulted from stresses within the slab and not from gorda north american plate interaction

glacier and climate reconstruction at tres lagunas nw argentina based on 10be surface exposure dating and lake sediment analyses abstract we present 35 10 be surface exposure ages from quartzite moraine boulders at tres lagunas in the sierra de santa victoria nw argentina additionally an 8 m sediment core from a glacial lake was investigated to provide independent radiocarbon age control the oldest and most extensive glaciation occurred 116 3 ka and likely coincides with the lake transgression phase ouki on the altiplano maximum glaciation in phase with the global last glacial maximum lgm is dated to 22 25 ka and documents a glacial mass balance response to substantially lower temperatures and minor precipitation increase in phase with the sajsi lake transgression phase after initial deglaciation and formation of a small paleolake at tres lagunas a glacial readvance is documented by an outwash diamict in the sediment core and radiocarbon dated to 19 17 ka as well as by a moraine surface exposure dated to 17 ka the most prominent moraine was deposited at 14 5 ka coinciding with the lake transgression phase tauca on the altiplano this late glacial advance reflects the massive intensification of the south american summer monsoon sasm in response to northern hemispheric cooling during heinrich i and the resultant southward shift of the intertropical convergence zone itcz and la nina like conditions in the eastern equatorial pacific rapid deglaciation started after 14 5 ka interrupted only by minor glacial still stands at 13 8 1 5 ka and 12 0 1 5 ka the latter one correlating with the coipasa transgression phase on the altiplano and the younger dryas

three dimensional compressional wave attenuation tomography for the crust and uppermost mantle of northern and central california i present a frequency independent three dimensional 3 d compressional wave attenuation model indicated by quality factor qp for the crust and uppermost mantle of northern and central california the tomographic inversion used t values measured from amplitude spectra of 80 988 p wave arrivals of 3247 events recorded by 463 network stations through a 3 d seismic velocity model the model has a uniform horizontal grid spacing of 15 km and the vertical node intervals range between 2 and 10 km down to 45 km depth in general the resulting qp values increase with depth and agree with the surface geology at shallow depth layers the most significant features observed in the qp model are the high qp values in the sierra nevada mountains and low qp anomalies in the western fault zones low qp values are also imaged in owens valley and long valley at shallow depths and the cape mendocino region in the lower crust 25 km depth an overall contrast of qp values across the fault is observed in the creeping parkfield and cholame carrizo sections of the san andreas fault the new 3 d qp model provides an important complement to the existing regional scale velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area

northern california seismic attenuation 3d qp and qs models the geological complexity of northern california and its accreted terranes produces pronounced regional variations in the attenuation 1 q of earthquake waves using local earthquakes 3d q p and q s models have been obtained for this region that includes the san andreas fault system the great valley the sierra nevada batholith and the gorda subduction volcanic system path attenuation t values were determined from p and s spectra of 959 spatially distributed earthquakes magnitude 2 5 6 0 using 1254 stations from northern california earthquake data center networks and mendocino and sierra nevada temporary arrays the t data were used in q inversions using existing 3d velocity models and basic 10 km node spacing uneven data coverage was accommodated with linking nodes into larger areas for useful q images across the 3d volume results at shallow depth show very low q in the sacramento delta the eureka area and parts of the san francisco bay area in the brittle crust low q tends to be associated with regions of fault zones and microearthquakes in the ductile lower crust low q is observed below fault zones with large cumulative displacement and inferred grain size reduction with apparent broad ductile shear zones across the fault system in the coast ranges underlying active arc volcanoes low q features are apparent below 20 km depth under the long valley caldera two distinct partial melt features at 3 and 15 km depth are inferred moderately high q is associated with sierra nevada and salinian igneous rocks whereas the franciscan subduction complex shows moderately low q prominent high q relates to the great valley ophiolite the pattern of path specific attenuation rate from 3d q is generally similar to the pattern of psuedospectral acceleration residuals for the south napa earthquake indicating that it may be beneficial to incorporate 3d q models into future ground motion prediction equations for northern california online material figures of q p and q s resolution and station delays for t and table of q p v p q s and v s

retrieving a common accumulation record from greenland ice cores for the past 1800 years 1 in the accumulation zone of the greenland ice sheet the annual accumulation rate may be determined through identification of the annual cycle in the isotopic climate signal and other parameters that exhibit seasonal variations on an annual basis the accumulation rate in different greenland ice cores is highly variable and the degree of correlation between accumulation series from different ice cores is low however when using multiyear averages of the different accumulation records the correlation increases significantly a statistical model has been developed to estimate the common climate signal in the different accumulation records through optimization of the ratio between the variance of the common signal and of the residual using this model a common greenland accumulation record for the past 1800 years has been extracted the record shows significant 11 9 years periodicity a sharp transition to very dry conditions is found just before a d 1200 and very dry conditions during the 13th century together with dry and cold spells during the 14th century may have put extra strain on the norse population in greenland and may have contributed to their extinction accumulation rates gradually decrease from a distinct maximum in a d 1394 to very dry conditions in the late 17th century and thus reflect the little ice age

funginite resinite associations in coal abstract petrographic examination of a series of indian tertiary age coal seams some with 38 resinite mineral free basis showed that several had associations of funginite in resinite there are three primary mechanisms for incorporation of fungus into resinite 1 as an accidental inclusion for example as a fungal infection on an insect encapsulated in resin 2 infestation of fungus into tree whether into a wound or other point of entry with encapsulation by resin as a defense mechanism by the tree alternatively fungal hyphae could also be growing from another portion of the tree that is already infected and 3 resinicolous fungus using the resin as a food source in the coal samples examined while incidental fungal inclusion on invading insects cannot be eliminated we have seen no direct evidence for insects both encapsulation of invading fungus by resin and resinicolous relationships are among the associations observed

quaternary glaciations in the rio mendoza valley argentine andes in the rio mendoza valley five pleistocene drifts and one holocene drift are distinguished by multiple relative age criteria including surface rock weathering development of rock varnish moraine morphology soil profile development and stratigraphic relationships several absolute ages suggest a preliminary chronology during the oldest uspallata glaciation a system of valley glaciers flowed 110 km from the andean drainage divide and 80 km from cerro aconcagua to terminate at 1850 m drift of this ice advance is older than a widespread tephra dated by fission track at 360 000 36 000 yr during the punta de vacas advance ice terminated at 2350 m while during the subsequent penitentes advance the glacier system ended at 2500 m a travertine layer overlying penitentes drift has u series age of 24 200 2000 yr b p the distribution of horcones drift which is inferred to represent the last glacial maximum delimits an independent ice stream that flowed 22 km down horcones valley to 2750 m a later readvance almacenes reached 3250 m confluencia drift is considered to be neoglacial in age and extends downvalley to 3300 m the moraine sequence is compared with those studied by caviedes 1972 along rio aconcagua on the chilean flank of the andes

deformation of the so called gorda plate a new compilation of magnetic anomaly identifications recent side scan sonar data and other data provide constraints on the mechanism of deformation of the area commonly known as the gorda plate a sharp boundary between the rigid juan de fuca plate and deformed material trends southeast from the northern part of the gorda ridge in material older than 2 3 ma the boundary is gradational and trends more to the east previous observations that the anomalies east of the ridge are shorter than their counterparts on the pacific plate are confirmed there is no evidence for subduction or obduction along the mendocino transform adjacent to the ridge the deformation is interpreted to be distributed nw se right lateral simple shear possibly controlled by ductile deformation of the lower crust deformation of this sense is capable of producing the observed shortening the anomalies away from the ridge apparently in crust of age 2 3 ma there must be a transition to deformation on observed ne sw left lateral faults parallel to the original spreading fabric

fungal origin of oxidised plant material in the palangkaraya peat deposit kalimantan tengah indonesia implications for inertinite formation in coal abstract the top 1 0 1 5 m of the 6 m thick palangkaraya peat deposit in indonesia is decaying aerobically and contains up to 22 oxidised plant material i e inertinite in contrast intervals below the level of water table fluctuation contain less than 5 oxidised material analysis of fungal remains in the peat show there is a coincident increase in total aggregate hyphal length a measure of fungal activity with the proportion of oxidised plant constituents macroscopically the top of the peat which contains the greatest proportion of oxidised material is black lacks wood fragments and would be classed as a sapric or sapric hemic peat oxidised material in the peat is predominantly epidermal cell walls of primary roots these cell walls are abnormally thickened and display a distinctive dentate structure in cross section the texture of the cell walls are either laminated or granular and often contains intercellular nodules these features together with the absence of charcoal layers in the peat suggest that oxidised constituents were derived from fungal alteration furthermore the coincident increase in fungal hyphal length with the proportion of oxidised material may suggest a causal link based on texture morphology and size the same types of oxidised plant material found in the palangkaraya peat deposit have been identified in coal beds of tertiary age from indonesia new zealand and the u s a this indicates similar fungal alteration occurred in the past and may account for some of the oxidised constituents found in coal if the palangkaraya mire is used as a model fungal alteration zones may be recognised in coals as relatively thick 0 5 2 0 m laterally extensive macroscopically dull coal

evidence of widespread wildfires in coal seams from the middle jurassic of northwest china and its impact on paleoclimate abstract today wildfire is an important disturbance in many continental ecosystems and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions one way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo wildfires a total of 140 jurassic samples including 122 coal samples and 18 rock samples from roof and floor of coal seams were collected from 4 coalfields in northwestern china the samples were analyzed by macropetrography microscopy scanning electron microscopy gas chromatography and gas chromatography mass spectrometry to study the evidences of wildfires and their impact on the paleoclimate high contents of pyrogenic inertinites charcoal natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early middle jurassic in all over northwestern china additionally high molecular weight polycyclic aromatic hydrocarbons were detected in the coal samples these aromatic compounds were formed under high temperature and provide further evidence of wildfires according to a carbon emission model for modern forest fires the total carbon and gas emissions from wildfires in peat swamps of the middle jurassic in northwest china were calculated by the data from 21 575 coal samples of number of 1567 drill core samples the total carbon released from peat swamp forest wildfires was at least 1207 gt corresponding to emissions of co2 co and ch4 of 1926 gt 163 gt and 8 8 gt respectively the huge amount of co2 released by forest fires in the peat swamp systems of the middle jurassic in northwestern china alone was equivalent to 64 20 of the total co2 in the atmosphere at present 3000gt the large amounts of greenhouse gases released by wildfires must have led to long term changes in the atmospheric composition and have caused global warming which could have the reason of affected the paleoclimate

geochemistry and petrology of selected coal samples from sumatra kalimantan sulawesi and papua indonesia abstract indonesia has become the world s largest exporter of thermal coal and is a major supplier to the asian coal market particularly as the people s republic of china is now 2007 and perhaps may remain a net importer of coal indonesia has had a long history of coal production mainly in sumatra and kalimantan but only in the last two decades have government and commercial forces resulted in a remarkable coal boom a recent assessment of indonesian coal bed methane cbm potential has motivated active cbm exploration most of the coal is paleogene and neogene low to moderate rank and has low ash yield and sulfur generally

southward younging apatite u th he ages in the northern california coast ranges due to a northward migrating crustal welt abstract u th he in apatite dating of franciscan formation samples from between 39 47 n and 39 08 n in the northern california coast ranges nccr reveals a southward and downward younging pattern of ages 21 8 0 6 ma to 7 9 0 9 ma these ages are interpreted to represent a northward or northeastward dipping fossil he partial retention zone that was tilted and exhumed by a northward migrating pulse of crustal thickening that begins 150 200 km ahead of the migrating mendocino triple junction mtj k p furlong r govers ephemeral crustal thickening at a triple junction the mendocino crustal conveyor geology 27 1999 127 130 the 8 ma ages from the southern end of the sample transect are interpreted to come from rocks that were immediately below the he partial retention zone when crustal thickening began 5 my before the mtj passed by these rocks have now reached the surface 3 my after passage of the mtj the older ages from the central and northern portions of the sample transect are interpreted to represent rocks that were within the he partial retention zone prior to crustal thickening ahead of the mtj and which therefore record ages transitional from older subduction related cooling and exhumation to more recent transform related cooling and exhumation in addition to providing support for the model of a migrating crustal welt associated with the mtj the existence of an essentially intact gently tilted fossil partial retention zone in the northern california coast range raises the possibility of using isochronous surfaces as neotectonic structural markers in this geologically complex and heavily vegetated region

geology of the eel river basin and adjacent region implications for late cenozoic tectonics of the southern cascadia subduction zone and mendocino triple junction two upper cenozoic depositional sequences of principally marine strata about 4000 m thick overlie accreted basement terranes of the central and coastal belts of the franciscan complex in the onshore offshore eel river basin of northwestern california the older depositional sequence is early to middle miocene in age and represents slope basin and slope blanket deposition whereas the younger sequence late miocene to middle pleistocene in age consists largely of forearc basin deposits youthful tectonic activity related to gorda north american plate convergence indicates an active cascadia subduction zone and strong partial coupling between these plates structures of the northeastern margin of the eel river basin are principally north northwest trending east northeast dipping thrust and reverse faults that form imbricate thrust fans many faults merge downward into sole thrusts that extend to or near the gorda north american plate interface in the southern part of the region these structures have been modified by northward encroachment of the pacific plate the coastal belt fault the early tertiary accretionary suture between the franciscan central and coastal belts can be traced from arcata bay northward offshore to the southern oregon border it is tentatively extended farther northward based on aeromagnetic data to an offshore position west of cape blanco thereafter it may coincide with the offshore fulmar fault if so the franciscan coastal belt in california is correlative with the offshore fulmar terrane in oregon the cascadia subduction zone csz does not join the mendocino transform fault at the commonly depicted offshore location of the mendocino triple junction mtj instead the csz extends southeastward around the southern eel river basin and shoreward along mendocino canyon to join the petrolia shear zone similarly the mendocino fault may extend shoreward via mattole canyon and join the cooskie shear zone these two shear zones intersect onshore north of the king range and the area of their intersection is the probable location of the mtj

p wave detection thresholds pn velocity estimates and t wave location uncertainty from oceanic hydrophones p wave arrivals recorded by the u s navy s sound surveillance system sosus hydrophone arrays were used to estimate earthquake detection thresholds and pn velocities in the northeast pacific ocean the navy hydrophones have been used successfully to detect and locate oceanic earthquakes using their waterborne acoustic tertiary t waves however use of these hydrophones for seismic body wave detection allows regional seismic analyses to be extended to the oceanic environment the p wave detection threshold of the sosus hydrophones was quantified using the epicentral distance and magnitude of 250 northeast pacific ocean earthquakes earthquakes with body wave magnitudes as low as 2 have detectable p wave arrivals at epicentral distances of 500 km earthquakes with mb between 3 5 and 5 were detected 50 of the time at distances of 100 1500 km while events with mb 5 were all detected even out to distances of 1000 1500 km both p and t wave hydrophone arrival times were used to estimate the epicenters of 100 earthquakes the peak amplitude of the t wave coda and the onset of the p wave were used as the earthquake arrival times to estimate event locations t wave arrival time residuals have a gaussian distribution with zero mean which implies that using t wave peak amplitude is consistent with using the p wave onset as the arrival time there are typically 6 stations used to derive a t wave based location hence location error ellipses are not well constrained a monte carlo technique was employed to estimate t wave event location uncertainty t wave locations have error bars of 1 km in latitude and longitude when 3 hydrophones are used for a location estimate the detected p wave arrivals and earthquake locations were used to measure pn velocities pn velocity values of 7 9 0 1 and 8 0 0 1 km s were found for the pacific and juan de fuca plates respectively a pn velocity of 7 5 0 1 km s was measured for rays traveling northward from the mendocino triple junction along the cascadia subduction zone a pn velocity of 7 7 0 3 km s was estimated for ray paths originating onshore western north america and traveling to the offshore hydrophones

holocene glacier chronology of valenzuela valley mendoza andes argentina glacial geologic evidence and radiocarbon dated glacial deposits provide evidence of glacier fluctuations during the last 5 ka years in the andes radiocarbon dated moraines morphological and stratigraphical studies permit the reconstruction of glacier fluctuations during the holocene in the valenzuela area of the mendoza andes valley located at 35s in the upper rio grande basin the holocene record in this part of the andes is mostly unknown so this research is relevant for palaeoclimatic reconstructions in south america in the rio valenzuela glacier variations were dated in the el azufre and el pefion valleys the first neoglacial advance occurred at c 5700 yr bp and a very close re advance of similar magnitude occurred at 4700 4300 yr bp which formed well preserved lateral terminal moraines the first neoglacial advance occurred in the el pefion valley at c 4400 yr bp and a well preserved terminal moraine is observed a second neoglacial advance reached its maxima at c 2500 2200 yr bp in the el

pedostratigraphy and pedological and geochemical characterization of las carreras loess paleosol sequence valle de tafi nw argentina abstract the las carreras loess paleosol sequence is considered the most complete quaternary pedostratigraphic record in south america it consists of 32 paleosols formed during the past 1 15 ma chronological control is provided by magnetostratigraphy sediment and paleosol characterization is based on a variety of methods including soil chemistry geochemistry and micromorphology the main pedogenic processes identified are carbonate leaching and reprecipitation ped formation and translocation of clay and organic matter in many cases the boundaries between individual paleosols are not clearly defined due to indistinct transitional zones based on both pedological and sedimentological characteristics the sequence was subdivided into three units with paleosols in units i and iii designated as luvisols and paleosols in unit ii tentatively classified as luvic kastanozems this subdivision reflects environmental changes associated with the mid pleistocene transition overall geochemical variability is low and largely related to pedogenesis the homogeneity suggests a rather constant provenance that seems to be linked to the central andes pursuant to the chaco model of iriondo 1997 models of deposition of loess and loessoids in the upper quaternary of south america journal of south american earth sciences 10 71 79 and includes direct volcanic ash falls and local sources in a subordinate manner in a paleoclimatic context loess paleosol alternation is interpreted to reflect climatic cycles that were primarily caused by the variability of the south american monsoon system

petrographic geochemical and mycological aspects of miocene coals from the novaky and handlova mining districts slovakia abstract fungi have once again become a topic of interest to coal scientists in their roles as agents of maceral formation recent works have demonstrated that fungi occur in association with woody remains resins and cuticles in coalified materials of a variety of ages in addition to coal balls and compression impression fossils where they are already well known these forms however have only been viewed as cross sections along a polished plane assigning the fungi to family much less determining which fungi they represent is very difficult in this orientation fungal identifications are necessary to the continuance of this research into the origin of coal macerals because of the need to know if macrinite begins to form prior to incorporation into the peat which could be demonstrated by its association with symbiotic and parasitic rather than saprophytic fungi this study examines the fungal remains recovered from eight coal samples from miocene age coals in the novaky and handlova mining districts of slovakia with the aim of making this distinction these samples were collected in slovakia as part of the us geological survey s world coal quality inventory program and provided to the authors the samples were processed using the o keefe technique for subbituminous coals and mounted for observation in transmitted light forms were identified using published works and consultation with a modern mycologist forms recovered through palynologic processing were compared to and correlated with forms seen in cross section under reflected light

petrography and taphonomic significance of the vertebrate bearing cannel coal of linton ohio westphalian d upper carboniferous abstract petrographic study of a vertebrate bearing cannel coal which underlies the upper freeport coal late westphalian d upper carboniferous in the area of linton ohio provides information on the depositional conditions represented by fossiliferous sapropelic coals samples of the cannel obtained from an approximately 10 km long curvilinear area were prepared as polished blocks and point counted in reflected light the cannel typically consists of over 50 percent very finely grained micrinite rich groundmass approximately 25 percent exinite and 10 percent pyrite and varying amounts of vitrinite and inertinite sporinite is the most abundant exinite but no alginite occurs euhedra and framboids are the most common forms of pyrite and vitrinite is poorly preserved and virtually struc ureless vertebrate scales teeth and bones preserved in the cannel show no significant mineralogic alteration these petrographic findings agree with results from an investigation of the physical paleoenvironment of the linton deposit and together these data sets indicate that the vertebrate bearing cannel represents a freshwater sapropelic peat that formed within abandoned segments of a fluviodeltaic channel in the absence of clastic influx macerated plant debris and resistant spores accumulated in the bottom of the channel and decay of these organic rich sediments led to anaerobic conditions in which sulfate reducing bacteria thrived vertebrate remains introduced from the overlying oxygenated waters were not subjected to scavenging in this anoxic nonacidic setting but slowly rotted leaving skeletal parts intact

a major advance of tropical andean glaciers during the antarctic cold reversal a moraine chronology determined by surface exposure dating shows that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas stadial 12 800 to 11 500 years ago contrary to previous studies as a result previous chronologies and climate interpretations from tropical glaciers may need to be revisited the younger dryas was a cold period immediately prior to the present warm interglacial period there is clear evidence that it occurred throughout much of the northern hemisphere but its global extent remains debatable prior work in the tropical andes suggested extensive glacial advances during the younger dryas vincent favier and colleagues present new cosmogenic dating of glacial deposits and a reassessment of existing datasets from other glaciated andean landscapes to show that instead maximal glacial advances took place in the preceding antarctic cold reversal rather than a major advance the younger dryas now appears to have been associated with modest glacial retreat the younger dryas stadial a cold event spanning 12 800 to 11 500 years ago during the last deglaciation is thought to coincide with the last major glacial re advance in the tropical andes1 this interpretation relies mainly on cosmic ray exposure dating of glacial deposits recent studies however have established new production rates2 3 4 for cosmogenic 10be and 3he which make it necessary to update all chronologies in this region1 5 6 7 8 9 10 11 12 13 14 15 and revise our understanding of cryospheric responses to climate variability here we present a new 10be moraine chronology in colombia showing that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas on the basis of a homogenized chronology of all 10be and 3he moraine ages across the tropical andes we show that this behaviour was common to the northern and southern tropical andes transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration during the antarctic cold reversal glaciers advanced primarily in response to cold sea surface temperatures over much of the southern hemisphere during the younger dryas however northern tropical andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land surface feedbacks triggered by a weakened atlantic meridional overturning circulation conversely glacier retreat during the younger dryas in the southern tropical andes occurred as a result of progressive warming probably influenced by an increase in atmospheric carbon dioxide considered with evidence from mid latitude andean glaciers16 our results argue for a common glacier response to cold conditions in the antarctic cold reversal exceeding that of the younger dryas

an explanation for the double seismic layers north of the mendocino triple junction we propose that the gently eastward dipping double planed seismic zone observed at 15 25 km depths in the southern cascadia subduction zone just north of the mendocino triple junction is a direct consequence of the thermally controlled rheology as the oceanic lithosphere subducts to a depth of about 15 km the temperature regime causes a brittle plastic transition to occur within the oceanic crust thus a ductile layer forms in the lower oceanic crust sandwiched between the brittle upper crust and brittle upper mantle the very high strain rates near the triple junction caused by the northward push of the pacific plate on the gorda plate increase the seismicity and thus accentuate the double seismic zone in this region this model explains the focal mechanisms observed in the seismic zone and their spatial change the double seismic layers clearly define the position of the subducting gorda plate previously uncertain in the cape mendocino region

late pleistocene glacial fluctuations in cordillera oriental subtropical andes abstract the behavior of subtropical glaciers during middle to late pleistocene global glacial maxima and abrupt climate change events specifically in earth s most arid low latitude regions remains an outstanding problem in paleoclimatology the present day climate of cordillera oriental in arid northwestern argentina is influenced by shifts in subtropical climate systems including the south american summer monsoon to understand better past glacier subtropical climates during the global last glacial maximum lgm 26 5 19 ka and other time periods we combined geomorphic features with forty two precise 10 be ages on moraine boulders and reconstructed paleo equilibrium line altitudes ela at nevado de chani 24 s in the arid subtropical andes we found a major glacial expansion at 23 1 6 ka that is during the global lgm additional glacial expansions are observed before the global lgm at 52 39 ka and after at 15 0 5 and 12 0 6 ka the 15 ka glacial event was found on both sides of chani and the 12 ka event is only recorded on the east side reconstructed elas of the former glaciers exhibit a rise from east to west that resembles the present subtropical climate trajectory from the atlantic side of the continent hence we infer that this climate pattern must have been present in the past based on comparison with other low latitude paleoclimate records such as those from lakes and caves we infer that both temperature and precipitation influenced past glacial occurrence in this sector of the arid andes our findings also imply that abrupt deglacial climate events associated with the north atlantic specifically curtailed meridional overturning circulation and regional cooling may have had attendant impacts on low subtropical southern hemisphere latitudes including the climate systems that affect glacial activity around nevado de chani

vertical extent of the newborn san andreas fault at the mendocino triple junction three dimensional seismic refraction data reveal the structure of the plate boundaries at the mendocino triple junction first arrival traveltimes were inverted to obtain a three dimensional seismic velocity model the tomography results indicate a strong lateral velocity contrast in the lower crust this velocity contrast is beneath the surface trace of the san andreas fault and tracks along the fault to the triple junction and then along the mendocino fracture zone velocity values appropriate for mafic rocks are more than 5 km shallower on the pacific plate than east of the san andreas fault and 1 3 km shallower than under the cascadia accretionary prism the model suggests that the san andreas fault which is growing as the triple junction migrates northward cuts steeply through the entire crust pacific oceanic crust does not extend beneath north america at this location the slabless window south of the triple junction and east of the san andreas fault must be filled with upwelling asthenosphere the sharp corner of the pacific plate migrates northward displacing the cascadia accretionary prism and forcing the prism material to move north or east

glaciation in the andes during the lateglacial and holocene this review updates the chronology of andean glaciation during the lateglacial and the holocene from the numerous articles and reviews published over the past three decades the andes which include some of the world s wettest and driest mountainous regions offer an unparalleled opportunity to elucidate spatial and temporal patterns of glaciation along a continuous 68 degree meridional transect the geographic and altitudinal extent of modern glaciers and the sensitivity of both modern and former glaciers to respond to changes in specific climatic variables reflect broad scale atmospheric circulation and consequent regional moisture patterns glaciers in the tropical andes and in the mid latitude andes are likely to have been far more sensitive to changes in temperature than glaciers in the dry subtropical andes broad scale temporal and spatial patterns of glaciation during the lateglacial are apparent in the southernmost andes the lateglacial chronology appears to have a strong antarctic signature with the best dated moraines correlating closely with the antarctic cold reversal the southernmost andes do not appear to have experienced a significant ice advance coeval with the younger dryas yd climatic reversal at the other end of the andes from w 0t o 9 n a stronger yd connection may exist but critical stratigraphic and geochronologic work is required before a yd ice advance can be fully demonstrated in the central andes of peru well dated moraines record a significant ice readvance at the onset of the yd but ice was retreating during much of the remaining yd interval the spatial temporal pattern of holocene glaciation exhibits tantalizing but incomplete evidence for an early to mid holocene ice advance s in many regions but not in the arid subtropical andes where moraines deposited during or slightly prior to the little ice age lia record the most extensive advance of the holocene in many regions there is strong evidence for neoglacial advances in the interval between 1 0 and 2 5 ka moraines that correlate with the lia of the northern hemisphere are seen in all presently glacierized mountain ranges most of these date to within the past 450 years outboard of these moraines in many regions are moraines of a slightly more extensive advance that occurred several hundred years prior to the onset of the lia priorities for future work include filling in several prominent spatial gaps in the distribution of chronologic studies for the lateglacial these gaps include the arid regions of northern chile and argentina the southern peruvian andes between 11 5 and 13 5 s and the andes of northern peru and

terpenoid composition of fossil resins from western india new insights into the occurrence of resin producing trees in early paleogene equatorial rainforest of asia abstract the terpenoid composition of well preserved fresh and oxidized fossil resins ambers from early paleogene lignite bearing sequences of india have been examined using gas chromatography mass spectrometry for determining their botanical origin the samples were collected from two sedimentary basins viz barmer akli formation and bikaner nagaur palana formation western india the total extracts of the studied ambers are represented by hydronaphthalenes sesquiterpenoids and significant occurrence of diterpenoids such terpenoid distribution is typical for gymnosperm especially conifer derived sources the diterpenoids are comprised of majorly abietane phyllocladane kaurane pimarane isopimarane and podocarpane class compounds tertracyclic diterpenoids such as 18 norkauranes ent 16 h kaurane and 16 h phyllocladane and a rearranged tricyclic diterpenoid rosane are detected in the fossil resins from barmer basin the occurrence of tetracyclic diterpenoids and rosane together with 8 13 dimethyl 16 norpodocarpa 6 ene suggests that podocarpaceae family is the possible source of the ambers however chemotaxonomic assignment at family level for the fossil resin from bikaner nagaur basin is difficult due to the absence of source specific diterpenoids previous reports had documented the occurrence of angiosperm derived dammar resins from early paleogene sediments of india dutta et al 2009 rust et al 2010 the present study suggests that the early paleogene resins of the equatorial rainforests were not always represented by the dammar resins derived from dipterocarpaceae a family of angiosperm some of them were also contributed by the conifers

geomorphological dynamic changes during the holocene through ephemeral stream analyses from northwest argentina abstract this paper studies the changes in the geomorphological dynamics recorded in 18 ephemeral streams located on the east side of loma pelada tafi valley a part of the sierras subandinas northwest argentina the applied methodology is based on photointerpretation field survey and descriptions of the holocene alluvial fillings dated by tephras archaeological artefacts and absolute datings the records show a coupled system of slope terrace alluvial fans resulting from the environmental changes of four alternating aggradation degradation stages the oldest stage 1 was generated by climatic causes and covers early to mid holocene ca 13 000 10 000 bp to ca 4200 bp after the incision of these accumulations a new aggradation stage 2 was triggered by anthropogenic activity occurring from right before 2500 bp to the 15th century during that time human occupations of the tafi valley were intense two wetter events occurred around 4200 and 2800 bp in the area related to global cooling phases lastly two more recent phases 3 and 4 are associated with the climatic variability of the lia and the present warm period the results highlight the sensitivity of headwater catchments of dry subtropical mountainous areas to climate changes anthropogenic impact and their relationship with global climatic data

fluctuations of outlet and valley glaciers in the southern andes argentina during the past 13 000 years abstract in the southern argentine andes ten advances of valley glaciers were used to reconstruct the late glacial and holocene glacier history the accumulation areas of these glaciers lie in the precordillera and are thus independent of fluctuations of the south patagonian icefield like the viedma outlet glacier the valley glaciers advanced three times during late glacial time 14 000 10 000 yr b p the youngest advance correlates with the younger dryas stade based on two minimum ams 14 c dates of 9588 and 9482 yr b p the second oldest advance occurred before 11 800 yr b p during the first half of the holocene ca 10 000 5000 yr b p advances culminated about 8500 8000 7500 and 5800 5500 yr b p during the second half of the holocene advances occurred between ca 4500 and 4200 yr b p as well as between 3600 and 3300 yr b p in the rio condor valley three subsequent advances have been identified