middle miocene deduction and late miocene beginning of collision registered in the hengchun peninsula geodynamic implications for the evolution of taiwan abstract taiwan is located in the axis of the manila trench it results from an oblique collision between the northernmost part of the luzon arc and the chinese passive margin this active collision follows the subduction of the oligocene miocene oceanic crust of the south china sea along the manila trench the tectonized chinese margin emerged in the hengchun peninsula south taiwan gentle folds which are delineated by the quaternary reefal limestones demonstrate recent deformations these folds deformed a thick detrital sequence of miocene age ssuchung chi series which was previously strongly folded and thrust westward axis ns n20 upon the renting melange of latest miocene age these main deformations sealed by the middle pliocene are the evidence for the onset of collision in this part of taiwan at the end of the miocene because of its obliquity the collision started already in the northern part of taiwan during the late miocene 6 7 8 ma the ssuchung chi series a sequence of proximal turbidites has contained since the middle miocene nn 6 13 ma fragments of an oligocene to lower miocene oceanic crust this ophiolitic material is very similar to the east taiwan ophiolite of the coastal range it originated most probably from a slice of south china sea crust obducted in middle miocene times 13 14 ma upon the chinese margin north of the hengchun peninsula this obduction occurred 7 to 8 ma before the beginning of collision these results make it possible to propose an evolutionary model for taiwan from the oligocene to the recent with the different phases of a collision between a volcanic arc and a passive margin

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

evidence for increased latent heat transport during the cretaceous albian greenhouse warming quantitative estimates of increased heat transfer by atmospheric h2o vapor during the albian greenhouse warming suggest that the intensified hydrologic cycle played a greater role in warming high latitudes than at present and thus represents a viable alternative to oceanic heat transport sphaerosiderite d 18 o values in paleosols of the north american cretaceous western interior basin are a proxy for meteoric d 18 o values and massbalance modeling results suggest that albian precipitation rates exceeded modern rates at both mid and high latitudes comparison of modeled albian and modern precipitation minus evaporation values suggests amplification of the albian moisture deficit in the tropics and moisture surplus in the mid to high latitudes the tropical moisture deficit represents an average heat loss of 75 w m 2 at 108n paleolatitude at present 21 w m 2 the increased precipitation at higher latitudes implies an average heat gain of 83 w m 2 at 458n at present 23 w m 2 and of 19 w m 2 at 758n at present 4 w m 2 these estimates of increased poleward heat transfer by h2o vapor during the albian may help to explain the reduced equator to pole temperature gradients

meteoric sphaerosiderite lines and their use for paleohydrology and paleoclimatology sphaerosiderite a morphologically distinct millimeter scale spherulitic siderite feco 3 forms predominantly in wetland soils and sediments and is common in the geologic record ancient sphaerosiderites are found in paleosol horizons within coal bearing stratigraphic intervals and like their modern counterparts are interpreted as having formed in water saturated environments here we report on sphaerosiderites from four different stratigraphic units each of which has highly variable 13 c and relatively stable 18 o compositions the unique isotopic trends are analogous to well documented meteoric calcite lines which we define here as meteoric sphaerosiderite lines meteoric sphaerosiderite lines provide a new means of constraining ground water 18 o and thus allow evaluation of paleohydrology and paleoclimate in humid

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

is taiwan the result of arc continent or arc arc collision abstract conventionally it has been accepted that the formation of taiwan results from the collision of the luzon arc with the eurasian continental margin we suggest that taiwan results from the collision of the luzon arc with the former ryukyu subduction zone before the collision the latter extended a few hundred kilometres southwest of its present day termination in the early to middle miocene the subduction became inactive in its southwest portion and the manila trench migrated northeastward giving rise to the formation of the luzon arc the collision started in the late miocene by closing the oceanic domain located between the luzon arc and the former ryukyu arc because the luzon arc moved northwestward with respect to the former ne sw trending ryukyu arc the oblique collision first resulted in the indentation on the south ryukyu arc west of 123 5 e and the narrowing of the corresponding portion of the okinawa trough prior to the uplift of taiwan today the hsuehshan and backbone ranges represent the uplifted portion of the backarc basin and the longitudinal valley corresponds to the suture zone between the former ryukyu and the luzon arcs in this model we propose to link although they are not of the same age two truncated backarc basins the active okinawa trough to the northeast and the former active tainan backarc basin to the southwest the former backarc basin extended from southwest of taiwan to southern japan and could have been initiated near the paleo location of taiwan as early as the eocene oligocene the result of the collision is the truncation of the ancient backarc basin associated with the shortening deformation and uplift of the ancient outer arc and related backarc region which provides the fundamental mechanism of the taiwan mountain building this model is in agreement with a counterclockwise rotation of the portion of taiwan located west of the coastal range belonging to the luzon arc and a clockwise rotation of the south ryukyu arc earthquake focal mechanisms geodetic observations and the distribution of the petrologic and structural features are also consistent with the proposed arc arc collision model

dynamics of the polish and eastern slovakian parts of the carpathian accretionary wedge insights from palaeostress analyses the arcuate outer carpathian accretionary wedge formed in front of the east alpine carpathian pannonian alcapa megablock during the eocene sarmatian the wedge accreted sediments of the subducting remnants of the carpathian flysch basin a large oceanic tract left in front of the alpine orogen the palaeostress data for the orogenic hinterland particularly the data related to the early miocene extension that was expanding towards the ne combined with coeval subduction related volcanism that was expanding towards the ne indicate that the uneven roll back of the subduction zone was the main mechanism controlling the development of the northern west carpathian arc the palaeostress data for the tertiary accretionary wedge from the same time period are characterized by outward fanning 1 trajectories that changed gradually during the wedge development in contrast the palaeostress data for the hinterland are characterized by preferred directional stress events that changed abruptly during the wedge development these palaeostress results are in accordance with the behaviour of the wedge and the hinterland as the wedge behaved as a weak continuum and the hinterland behaved as a block mosaic with weak boundaries the fault traces of the northern west carpathian arc converge to both ends of the arc and suggest that the pre existing basin was the factor that controlled the arc location these fault trace patterns are asymmetric indicating a slightly oblique overall convergence in a ne sw direction in accordance with this convergence the palaeostress data for the accretionary wedge indicate that the western part of the wedge which is characterized by nw se oriented maximum principal compressional stress 1 was undergoing sinistral transpression meanwhile the eastern part which is characterized by ne sw oriented 1 was undergoing compression apparently the dynamics of the accretionary wedge was further influenced by the shape of an elongated ne sw trending alcapa megablock which was located behind the wedge and advanced in the direction of the general early miocene convergence during the most pronounced stages of the wedge development this megablock served as the local indenter as its strength surpassed that of the accretionary wedge located to its front further dynamic complexities were added because of the complex shape of the magura unit which was located in the most proximal portion of the wedge and was stronger than the units in front of it wedge outcrops indicate that the large scale shortening which is characterized by the development of detachments and ramps was preceded by an initial layer parallel shortening this is indicated by scaly fabrics and minor reverse faults that rotated into locked positions during the later accretion several outcrops with a wedge detachment fault indicate that there was a relatively low amount of friction during its development the decollement zone is several hundred metres thick and shows evidence of transient fluid flow that was driven by pressure gradients this is documented by frequent hydrofracturing sandstone dykes and fibrous veins that opened against the weight of the whole wedge all of which indicate cycles of higher pore fluid pressures that lowered the basal friction

formation of siderite mg calcite iron sulphide concretions in intertidal marsh and sandflat sediments north norfolk england concretions cemented mainly by siderite mg calcite and iron monosulphide are common in late holocene marsh and sandflat sediments on parts of the north norfolk coast field experiments have shown that the concretions are actively forming in reduced sediments in which sulphate reducing bacteria are active 13c values ranging from 3 to 11 8 mean 5 9 0 suggest that the carbonate in the concretions is derived partly from marine sources and partly from microbial degradation of organic matter 18o values ranged from 6 4 to 0 8 mean 1 0 suggesting that carbonate precipitated in porewaters ranging from pure sea water to sea water diluted with meteoric water chemical analysis of porewaters showed no evidence of significant sulphate depletion at the depth of concretion formation some concretions have formed around fragments of wood or metal but others contain no apparent nucleus in field experiments siderite fes and mg calcite were precipitated around several different nuclei within a period of six months we suggest that siderite may form wherever the rate of iron reduction exceeds the rate of sulphate reduction such that insufficient dissolved sulphide is available to precipitate all the available dissolved ferrous iron

phanerozoic atmospheric co2 change evaluating geochemical and paleobiological approaches abstract the theory and use of geochemical modeling of the long term carbon cycle and four paleo pco 2 proxies are reviewed and discussed in order to discern the best applications for each method geochemical models provide pco 2 predictions for the entire phanerozoic but most existing models present 5 10 m y means and so often do not resolve short term excursions error estimates based on sensitivity analyses range from 75 200 ppmv for the tertiary to as much as 3000 ppmv during the early paleozoic the 13 c of pedogenic carbonates provide the best proxy based pco 2 estimates for the pre tertiary with error estimates ranging from 500 1000 ppmv pre devonian estimates should be treated cautiously error estimates for tertiary reconstructions via this proxy are higher than other proxies and models 400 500 ppmv and should not be solely relied upon we also show the importance of measuring the 13 c of coexisting organic matter instead of inferring its value from marine carbonates the 13 c of the organic remains of phytoplankton from sediment cores provide high temporal resolution up to 10 3 10 4 year high precision 25 100 ppmv for the tertiary to 150 200 ppmv for the cretaceous pco 2 estimates that can be near continuous for most of the tertiary its high temporal resolution and availability of continuous sequences is advantageous for studies aiming to discern short term excursions this method however must correct for changes in growth rate and oxygen level at elevated pco 2 750 1250 ppmv this proxy loses its sensitivity and is not useful the stomatal density and stomatal index of land plants also provide high temporal resolution 2 year high precision 10 40 ppmv for the tertiary and possibly cretaceous pco 2 estimates and so also is ideal for discerning short term excursions unfortunately this proxy also loses sensitivity at some level of pco 2 above 350 ppmv which currently is largely undetermined our analysis of the recently developed 11 b technique shows that it currently is not yet well constrained most importantly it requires the assumption that the boron isotopic composition of the ocean remains nearly constant through time in addition it assumes that there are no biological or temperature effects and that diagenetic alteration of the boron isotopic composition does not occur a fifth co 2 proxy based on the redox chemistry of marine cerium has several fundamental flaws and is not discussed in detail here

timing of early angiosperm radiation recalibrating the classical succession new stratigraphically controlled pollen data from the late early cretaceous of portugal allow a recalibration of the classical continental succession of the potomac group usa which has long been used to demonstrate the gradual morphological changes of angiosperm leaves and pollen the portuguese record represents the best dated succession of angiosperm pollen assemblages of the interval between the late barremian and the mid albian comparison of the angiosperm pollen record of the potomac group with the pollen assemblages from portugal and with other independently dated records indicates that the distinct differences in the angiosperm pollen assemblages between the three formations of this group the patuxent formation arundel clay formation and patapsco formation are related to discontinuities our revised age model for the potomac group implies a major discontinuity between the arundel clay of early albian age and the patapsco formation of mid albian early cenomanian age the portuguese record reveals a so far undocumented radiation phase of angiosperms within the early aptian to mid albian in which monocolpate angiosperm pollen of monocot and or magnoliid affinity appear as a highly diversified group these new findings imply that the onset of the radiation of monocots magnoliids preceded the radiation of eudicots by at least 10 ma

collision and stress trajectories in taiwan a finite element model abstract field analyses of plio quaternary compressional deformations in taiwan have enabled us to reconstruct the paleostress trajectories resulting from the collision of the luzon arc philippine sea plate with the chinese continental margin eurasian plate the direction of the maximum compressional stress 1 shows a fan shaped pattern that we interpret as resulting from the collision of a rigid body the luzon arc indenting a more deformable material the thick sediments of the chinese continental margin simple analytical models qualitatively explain the fan shaped pattern but the influence of various parameters such as boundary conditions and rheology cannot be quantitatively accounted for by this approach consequently we have used a finite element technique to compute the stresses and strains induced by the push of a rigid body against a two dimensional viscous material the boundary conditions are the velocities based on plate kinematics a motion in the n300 e direction best explains the stress trajectories observed in central taiwan viscosity contrasts as well as small changes in the shape of the northern edge of the indenter have little influence on the computed stress pattern the most important parameter is the direction of convergence our model quantitatively explains the general pattern of the stress trajectories observed in the collision zone of taiwan between the philippine sea plate and eurasia

thrust related river terrace development in relation to the 1999 chi chi earthquake rupture western foothills central taiwan abstract the 21 september 1999 earthquake mw 7 6 produced a surface rupture that extended for 100 km in a general north south direction in front of the western foothills central taiwan the study area located in a segment of the fold thrust belt of central taiwan provides an important natural laboratory to study the relationship between active thrust deformation and fluvial terrace development we recognize from west to east three subparallel thrusts the sanyi houli and shihkang faults in the northern part of the earthquake disaster area the 1999 earthquake rupture occurred only along the shihkang fault whereas the other two faults were inactive along the tachia river in the hanging wall of the shihkang fault eight well developed terrace levels are observed and can be subdivided into lateritic lt5 lt1 and non lateritic terraces ft3 ft1 five levels of lateritic terrace lt5 lt1 are located in the hanging wall of the houli fault and a lateritic terrace lt5 is present in the hanging wall of the sanyi fault stratigraphic and elevation correlations between these well developed fluvial terraces in relationship to nearby geologic structures show that the sanyi fault is the oldest structure lateritic terraces of at least 10 000 yr bp for example overlie the sanyi fault but correlative terraces associated with the houli fault are offset these types of terrace correlations allow us to define the progressive development of the thrust system within the western foothills

the mid cretaceous water bearer isotope mass balance quantification of the albian hydrologic cycle a latitudinal gradient in meteoric n 18 o compositions compiled from paleosol sphaerosiderites throughout the cretaceous western interior basin kwib 34 75 n paleolatitude exhibits a steeper more depleted trend than modern predicted values 3 0x 34 n latitude to 9 7x 75 n lighter furthermore the sphaerosiderite meteoric n 18 o latitudinal gradient is significantly steeper and more depleted 5 8x 34 n to 13 8x 75 n lighter than a predicted gradient for the warm mid cretaceous using modern empirical temperature n 18 o precipitation relationships we have suggested that the steeper and more depleted relative to the modern theoretical gradient meteoric sphaerosiderite n 18 o latitudinal gradient resulted from increased air mass rainout effects in coastal areas of the kwib during the mid cretaceous the sphaerosiderite isotopic data have been used to constrain a mass balance model of the hydrologic cycle in the northern hemisphere and to quantify precipitation rates of the equable greenhouse albian stage in the kwib the mass balance model tracks the evolving isotopic composition of an air mass and its precipitation and is driven by latitudinal temperature gradients our simulations indicate that significant increases in albian precipitation 34 52 and evaporation fluxes 76 96 are required to reproduce the difference between modern and albian meteoric siderite n 18 o latitudinal gradients calculations of precipitation rates from model outputs suggest mid high latitude precipitation rates greatly exceeded modern rates 156 220 greater in mid latitudes 2600 3300 mm yr 99 greater at high latitudes 550 mm yr the calculated precipitation rates are significantly different from the precipitation rates predicted by some recent general circulation models gcms for the warm cretaceous particularly in the mid to high latitudes our mass balance model by no means replaces gcms however it is a simple and effective means of obtaining quantitative data regarding the mid cretaceous hydrologic cycle in the kwib our goal is to encourage the incorporation of isotopic tracers into gcm simulations of the midcretaceous and to show how our empirical data and mass balance model estimates help constrain the boundary conditions

equation for compaction of paleosols due to burial existing empirically derived compaction curves for marine sediments fail to estimate the compaction of paleosols flood plain sediments and peats as indicated by deformation of clastic dikes dinosaur footprints and sandstone paleochannels yet compaction estimates are vital to reconstructing paleoclimate and geochemical profiles of paleosols to modeling sediment accumulation rates of nonmarine rocks and to tectonic flexural modeling of molasse facies this paper presents a compaction equation and physically derived constants that make geologically realistic estimates of compaction of paleosols and other nonmarine sediments a protocol for the application of the equation is suggested that would allow the following equation to solve for burial compaction c as a fraction of original thickness given depth of burial d in km as c s i f e d k 1 this equation can be applied to nonmarine sedimentary rocks or paleosols given appropriate empirical data on the physical constants in the equation such as initial solidity s i initial porosity f and the corresponding curve fitting constant k data on physical constants useful for this equation are compiled here for a range of paleosol and nonmarine sediment types

distinguishing base level change and climate signals in a cretaceous alluvial sequence we present the results of oxygen isotope and electron microprobe analyses of sphaerosiderites obtained from cretaceous paleosols in iowa the sphaerosiderite d 18 o values record creta ceous meteoric groundwater chemistry and an overall waning of brackish groundwater inundation during alluvial plain aggrada tion and soil genesis we focus on horizons that precipitated from freshwater in which d 18 o values ranging from 23 3 to 26 8 relative to the peedee belemnite standard are interpreted to record variations in the cretaceous atmospheric hydrologic cycle during relative sea level highstands moisture was derived from the cre taceous western interior seaway whereas during lowstands when the seaway narrowed and occasionally withdrew from the midcon tinent the dominance of hemispheric scale atmospheric moisture transport initiated in the tropical tethys ocean led to decreased precipitation rates these processes did not operate like a switch but rather as a continuum of competing moisture sources and mechanisms of transport between the nearby epicontinental sea and the distant tropics the sphaerosiderite data demonstrate 1 temporal variation in the intensity of hemispheric scale atmospher ic moisture transport and 2 long term amplification of the global hydrologic cycle marked by extreme 18 o depletion at the albian cenomanian boundary

phanerozoic atmospheric oxygen new results using the geocarbsulf model modifications of the geocarbsulf model for phanerozoic atmospheric oxygen have been made to account for new carbon isotopic data reconsideration of the fractionation of carbon isotopes between carbonate and organic matter deposited in sediments and different rates of weathering of volcanic rocks versus granitic rocks results indicate distinctly higher o2 values than geocarbsulf for the mesozoic and cenozoic lack of an appreciable drop in o2 below 15 percent at any time and a small late cenozoic decline of o2 to the present

distal alluvial deposits in a foreland basin setting the lower freshwater molasse lower miocene switzerland sedimentology architecture and palaeosols the lower freshwater molasse untere susswasser molasse crops out over a wide area of the swiss molasse basin coarse grained alluvial fan conglomerates dominate in proximal basin areas along the alpine front these conglomerates pass northwards into sandstones and mudstones of an extensive northeastward draining meandering river system which ran parallel to the basin axis sedimentological study of outcrops quarry exposures and boreholes in the basal miocene aquitanian has permitted detailed facies analysis of this distal alluvial sequence the distal aquitanian is made up of distinct architectural elements characterized by their geometries and sedimentary structures each may be assigned to a particular depositional setting meander belt levees crevasse channels and splays overbank fines and palaeosols and lacustrine meander belt sandstones were deposited in mixed load channels with a dominant bedload component sandstones commonly comprise amalgamated and locally stacked ribbon bodies 2 15 m thick and 150 1500 m wide interbedded rippled laminated and mottled fine grained levee sandstones and siltstones form lenticular packages up to 3 m thick and 30 100 m across small scale crevasse channel sandstones 2 4 m thick and 5 10 m across pass laterally into metre scale medium to fine grained crevasse sandstone sheets rare laminated lacustrine siltstones occur only in the north east part of the basin floodplain mudstones and marls make up the remainder of the succession these display a variety of pedogenic features recording cyclical palaeosol development palaeosols show strong variations in morphology and maturity both laterally across the floodplain and downstream along the basin axis reflecting local variation in aggradation rate associated with proximity to alluvial channel courses as well as regional variation in subsidence and floodplain drainage analysis of the organization and distribution of the various sediment bodies permits reconstruction of the fluvial system and allows development of a model for the sedimentary architecture of the lower freshwater molasse in the study area integration of palaeosol studies into a well defined architectural framework assists recognition of areal facies belts and may aid location of sand prone sequences in the subsurface

basin scale changes in floodplain paleosols implications for interpreting alluvial architecture abstract floodplain paleosols in time equivalent strata of the willwood for mation differ in terms of paleodrainage and degree of pedogenic development ancient soils were more poorly drained and more strongly developed in one area compared to a second area about 45 km away this difference in drainage is attributed to parent material the more poorly drained paleosols formed in an area with less permeable clay rich floodplain deposits in the stratigraphic interval that accumulated more slowly paleosols are more strongly developed less numerous and thicker than in the more rapidly accumulating stratigraphic interval these differences are attributed not only to different sediment accumulation rates which are commonly considered to control the degree of ped ogenic development but also to differences in avulsion frequency a simple model is offered to show how paleosols change with varying basin subsidence rates and the relationship between avulsion frequency and accumulation rate when avulsion frequency increases more rapidly than sediment accumulation rate an increase in subsidence rate causes strongly developed paleosols to be overlain by a stratigraphic interval with paleosols that are less well developed thinner and more densely spaced when avulsion frequency is not related to accumulation rate as early models of alluvial architecture assumed an increase in subsidence rate produces a stratigraphic section in which strongly developed paleosols are overlain by paleosols that are less well developed thicker and more widely spaced study of the thickness and degree of development of floodplain paleosols can be used together with more traditional studies of alluvial architecture to provide a clearer understanding of the factors that influenced the stratigraphic architecture in a particular alluvial basin

quantification of a greenhouse hydrologic cycle from equatorial to polar latitudes the mid cretaceous water bearer revisited article this study aims to investigate the global hydrologic cycle during the mid cretaceous greenhouse by utilizing the oxygen isotopic composition of pedogenic carbonates calcite and siderite as proxies for the oxygen isotopic composition of precipitation the data set builds on the aptian albian sphaerosiderite 18 o data set presented by ufnar et al 2002 by incorporating additional low latitude data including pedogenic and early meteoric diagenetic calcite 18 o ufnar et al 2002 used the proxy data derived from the north american cretaceous western interior basin kwib in a mass balance model to estimate precipitation evaporation fluxes we have revised this mass balance model to handle sphaerosiderite and calcite proxies and to account for longitudinal travel by tropical air masses we use empirical and general circulation model gcm temperature gradients for the mid cretaceous and the empirically derived 18 o composition of groundwater as constraints in our mass balance model precipitation flux evaporation flux relative humidity seawater composition and continental feedback are adjusted to generate model calculated groundwater 18 o

lower to mid cretaceous sequence stratigraphy and characterization of co2 storage potential in the mid atlantic u s coastal plain abstract the mid atlantic u s coastal plain new jersey delaware maryland and northern virginia contains thick 500 m mid cretaceous sand sandstone reservoirs confined by thick clay shale confining units and thus has high potential for storage of co 2 captured from nearby point sources the predictability of the continuity of the reservoir and confining units can be improved by applying principles of sequence stratigraphy including integration of lithostratigraphy biostratigraphy paleoenvironmental proxies and a novel application of fluvial aggradation cycles facs we evaluate the storage and confinement potential for the lower cretaceous waste gate formation and mid cretaceous potomac formation group in new jersey and maryland which we divide into three major reservoirs waste gate potomac unit i potomac unit ii and potomac unit iii we use new core data to ground truth well logs and paleoenvironmental changes sequence stratigraphic stacking patterns including facs and pollen biostratigraphy to update previous well log correlations in new jersey and extend these correlations into deep holes in maryland while individual sand beds are typically local in extent zones of sands are broadly correlative over distances of 60 km these regionally traceable sand prone zones should be useful for carbon storage cenomanian potomac unit iii sands are relatively thick 70 m in new jersey but generally thin average of 50 m into maryland they are near the updip limit for supercritical storage 800 m in new jersey and maryland and may not be suitable due to updip migration above the supercritical level potomac unit ii sands albian pollen zone ii appear to be discontinuous and less suitable in both states potomac unit i aptian pollen zone i and waste gate formation sands early aptian to berriasian pre pollen zone i are relatively thick 88 223 m and 81 288 m respectively and confined in new jersey and appear to be widespread and continuous the updip confinement of this reservoir in maryland is less certain volume storage estimates for the potomac i waste gate in the mid atlantic coastal plain are 8 4 33 5 gt co 2 adequate to store co 2 captured from 24 95 gw of natural gas generation for a century

determining terrestrial paleotemperatures using the oxygen isotopic composition of pedogenic carbonate abstract quantifying terrestrial paleotemperatures has proven to be a challenging endeavor this paper explores the use of the oxygen isotopic composition of pedogenic calcite for terrestrial paleotemperature reconstructions we generate three paleotemperature equations two of them derived by simultaneous solution of equations that describe the fractionation of oxygen isotopes in the exogenic cycle while the third equation is derived using a linear regression through modern 18occ mat oxygen isotopic composition of pedogenic calcite versus mean annual temperature data we use the paleotemperature equations to evaluate climate change across the k t boundary by analyzing the oxygen isotopic composition of pedogenic carbonates from a series of stacked paleosols in west texas the fabrics in the calcite nodules were evaluated in order to identify soil carbonate components that have the best chance of containing isotopic information that represents ancient pedogenic conditions the average temperature for west texas during the time period studied is 18 0 5 c two temperature excursions are recognized prior to the k t boundary in which terrestrial temperatures increase by about 4 c for relatively short periods of time these short greenhouse events documented in west texas correlate with changes in marine temperatures as well as terrestrial temperatures in north dakota during the same time period latitudinal temperature gradients generated using the west texas and north dakota data indicate that the spatial simultaneous solution yields the most reliable temperature reconstructions of the three equations considered in this study

focal mechanism determination in taiwan by genetic algorithm we determined the focal mechanism solutions for earthquakes with mag nitude ml 4 0 that occurred in the taiwan region between 1991 and 2005 first motion polarities of p waves recorded at over 700 seismic stations in taiwan were used because of the large number of events and stations involved we implemented the genetic algorithm in a nonlinear global search for the focal mechanism solutions the algorithm was tuned and validated through synthetic tests we finally determined the focal mechanisms of 1635 events with good qualities among 4188 earthquakes focal mechanism solutions for a majority of the earthquakes display a dominant pat tern of thrust fault type reflecting the compressive stress field due to the plate colli sion normal fault events occurred at intermediate depths in subduction zones which is likely the result of the bending of the subducting slabs strike slip faults are also found within the eurasia plate around the peikang basement high and in collision zones near ilan where the geometry of the colliding plates is complex our study pro vides a database of focal mechanisms for studying seismogenic structures and plate tectonics this database can also be used by structural seismologists to compute syn thetics for waveform tomography studies

neotectonic regime on the passive continental margin of the northern south china sea abstract between 1989 and 1994 more than 6600 km of reflection seismic profiles were obtained in the south china sea off hong kong with the german research vessel sonne during cruises so 50b so 72a and so 95 a seismo stratigraphic interpretation of this data set leads to a new age assignment of the unconformity t0 which we place within the pleistocene both neogene unconformities t1 and t0 are generated by uplift of the dongsha rise and truncation of their overlying strata this uplift is caused by intrusion of magma into the upper crust our seismic profiles show plutons which have penetrated the sedimentary cover whereby their original stratification in the contact zone is eliminated these magmato tectonic events may be correlated to the two main collision phases between taiwan and the continental margin of east china 5 3 and 3 0 ma ago the collisional events subsequent to the nnw to wnw drift of taiwan transformed the compression into strike slip movements along the continental margin of southeastern china the accompanying stress regime is transtensional with subsidence of the cooling oceanic crust since the cessation of rifting and its consumption beneath the manila trench providing the extensional stress the strike slip movements remobilized many of the rift and drift faults providing pathways for magma ascent the tectonic framework of the northern south china sea is characterized by miocene faults trending ne sw these faults are scarce but are distributed throughout the study area pliocene faults striking ene wsw to ne sw are concentrated west of the dongsha islands and are mostly strike slip in character recent faults are generally oriented ne sw subparallel to the synrift faults they result in part from local uplifts where they are normal in character but strike slip motion also occurs most of the faults involve the basement and represent reactivated zones of weakness of the rift and drift phases

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

precipitation rates and atmospheric heat transport during the cenomanian greenhouse warming in north america estimates from a stable isotope mass balance model stable isotope mass balance modeling results of meteoric 18o values from the cenomanian stage of the cretaceous western interior basin kwib suggest that precipitation and evaporation fluxes were greater than that of the present and significantly different from simulations of albian kwib paleohydrology sphaerosiderite meteoric 18o values have been compiled from the lower tuscaloosa formation of southwestern mississippi 25 n paleolatitude the dakota formation rose creek pit fairbury nebraska 35 n and the dunvegan formation of eastern british columbia 55 n paleolatitude these paleosol siderite 18o values define a paleolatitudinal gradient ranging from 4 2 vpdb at 25 n to 12 5 vpdb at 55 n this trend is significantly steeper and more depleted than a modern theoretical siderite gradient 25 n 1 7 65 n 5 6 vpdb and a holocene meteoric calcite trend 27 n 3 6 67 n 7 4 vpdb the cenomanian gradient is also comparatively steeper than the albian trend determined for the kwib in the mid to high latitudes the steep latitudinal trend in meteoric 18o values may be the result of increased precipitation and evaporation fluxes amount effects under a more vigorous greenhouse world hydrologic cycle a stable isotope mass balance model has been used to generate estimates of precipitation and evaporation fluxes and precipitation rates estimates of cenomanian precipitation rates based upon the mass balance modeling of the kwib range from 1400 mm yr at 25 n paleolatitude to 3600 mm yr at 45 n paleolatitude the precipitation evaporation p e flux values were used to delineate zones of moisture surplus and moisture deficit comparisons between cenomanian p e and modern theoretical siderite and holocene calcite latitudinal trends shows an amplification of low latitude moisture deficits between 5 25 n paleolatitude and moisture surpluses between 40 60 n paleolatitude the low latitude moisture deficits correlate with a mean annual average heat loss of 48 w m2 at 10 n paleolatitude present 8 w m2 at 15 n the increased precipitation flux and moisture surplus in the mid latitudes corresponds to a mean average annual heat gain of 180 w m2 at 50 n paleolatitude present 17 w m2 at 50 n the cenomanian low latitude moisture deficit is similar to that of the albian however the mid latitude 40 60 n precipitation flux values and precipitation rates are significantly higher albian 2200 mm yr at 45 n cenomanian 3600 mm yr at 45 n furthermore the heat transferred to the atmosphere via latent heat of condensation was approximately 10 6 that of the present at 50 n the intensified hydrologic cycle of the mid cretaceous greenhouse warming may have played a significant role in the poleward transfer of heat and more equable global conditions paleoclimatological reconstructions from multiple time periods during the mid cretaceous will aid in a better understanding of the dynamics of the hydrologic cycle and latent heat flux during greenhouse world conditions

insights into active tectonics of eastern taiwan from analyses of geodetic and geologic data 1 about 50 mm yr of convergence between the philippine sea and eurasian plates is absorbed in eastern taiwan and it remains unclear how the convergence is partitioned among active faults the longitudinal valley fault lvf the most seismically active fault in eastern taiwan creeps at the surface in the south and not in the north however it is unclear how much of the fault is locked or creeping at depth to address these problems we model holocene and interseismic deformation of elastic lithospheric blocks moving over a viscoelastic asthenosphere in eastern taiwan through a fully probabilistic scheme we invert gps interferometric synthetic aperture radar creepmeter and holocene marine terrace data for block motions fault slip rates and distribution of interseismic creep the data are explained with four blocks separated by three faults central range fault lvf and an offshore fault the model explains the essential features of interseismic and holocene deformation we find that 35 55 mm yr of slip on the offshore fault is necessary to fit marine terrace uplift rates which is a larger fraction of the plate convergence than previously recognized the lvf has a holocene slip rate of 20 30 mm yr with approximately equal magnitudes of reverse slip and left lateral strike slip components only about half of the surface area of the longitudinal valley fault appears to be locked the southern segment of the lvf creeps at a rate of 5 28 mm yr down to a depth of 15 20 km while the northern segment is locked from the surface to a depth of 20 km

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

quaternary transfer faulting and belt front deformation at pakuashan western taiwan the arcuate pakuashan anticline is located in the outermost front units of the western foothills of taiwan this oblique feature of the deformation front is investigated in terms of combined morphostructural analysis based on imagery and digital elevation model as well as microtectonic analysis of fault slip data a subsurface structural study based on available seismic and well data was also carried out resulting in improved mapping of the neogene series and associated structures this mapping allowed construction of several along strike cross sections such combined analyses revealed that the transverse pakuashan fold is located above a major transfer fault zone this active fault zone accommodates differential westward propagation of thrust units its kinematic evolution is principally controlled by the geometry of the foreland peikang high behaving as a buttress for the west verging thrust sheets a preliminary analytical model of the oblique thrusting at pakuashan is based on similar cases studied by apotria et al 1992 it involves quaternary transfer faulting accommodating the motion of connected thrust sheets moving over oblique ramps linked to a preexisting major basement boundary the hinge fault of the peikang high this analytical modeling accounts for the occurrence of local extension at the intersection of oblique ramps in the southern pakuashan numerous complementary structural and tectonic evidences led us to establish a complete deformation model involving local rotation in southern pakuashan which caused differential slips in northern pakuashan resulting in tear faulting these evidences include large extension at the intersection of oblique ramps distributed extension in the transverse zone regional wrench deformation absence of major reorientation of local stress inside the transverse zone along strike variation of structural styles coupled with low to high uplift rate from the northern to the southern part of the pakuashan fold thus a synthetic reconstruction of the pakua transfer fault zone evolution is proposed as a typical example of active transfer faulting evolving gradually from a primary tear fault with a slight curvature to the left lateral tear fault or transfer fault that offsets two distinct frontal thrust and fold sheets

stratigraphic implications of meteoric sphaerosiderite 18o values in paleosols of the cretaceous albian boulder creek formation ne british columbia foothills canada abstract the md 80 08 coal exploration core from the albian boulder creek formation of northeastern british columbia contains 90 m of alluvial strata that underwent extensive pedogenic modification gleyed colors pedogenic slickensides clay coatings mottling sphaerosiderite and sedimentary pyrite characterize the paleosols the isotopic compositions of 30 sphaerosiderite bearing horizons commonly show trends of invariant 18o and variable 13c values equal area plots of 18o vs 13c were used to construct meteoric sphaerosiderite lines msls the msls indicate that meteoric groundwater compositions ranged from approximately 11o oo to 16o oo smow the sphaerosiderite 18o values indicate formation in shallow groundwaters predominantly recharged by local precipitation the sphaerosiderite isotopic compositions are a proxy record of mid cretaceous precipitation and are useful for quantifying changes in the hydrologic cycle during humid greenhouse periods micromorphology of a 1 15 meter interval 69 75 68 6 m with a 1 31o oo increase in the average 18o values records a polygenetic history of paleosol development the pedocomplex has a four stage developmental history characterized by 1 an initial well drained phase with wet dry cycles and relatively low baselevel 2 erosion baselevel rise and coarser grained sedimentation 3 saturated reducing soil conditions high baselevel with some marine influence on pedogenesis and 4 meteoric water dominated hydromorphic soil conditions high baselevel and sphaerosiderite precipitation the 18o excursion recorded through this interval reflects minor mixing of marine and meteoric groundwaters the modal abundance of pyrite and increased mg ca mg and mg fe cation ratios in the sphaerosiderites further substantiate marine influence on pedogenesis the alluvial section of the boulder creek formation is aggradational and several changes in baselevel recorded in the paleosols are interpreted to have been driven by minor parasequence scale changes in relative sea level

paleogeographic reconstruction and origin of the philippine sea abstract our reconstruction of the philippine sea suggests that it formed by two distinct episodes of back arc spreading each of which resulted from seaward retreat of the trench in the first episode the protoizu bonin trench retreated northward and the west philippine basin formed behind the northern half of the palau kyushu ridge in the second episode the izu mariana trench retreated eastward and the shikoku and parece vela basins formed behind it during the last 17 ma the philippine sea basin has been moving northwestward with respect to eurasia shifting the ttt triple junction off central japan westward by about 50 km the motion of the philippine sea with respect to eurasia at the triple junction changed from north northwestward to west northwestward 10 5 ma ago for the period before 17 ma ago we construct two models retreating trench model and anchored slab model the izu bonin trench migrated from south to northeast rotating in a clock wise sense since 48 ma ago in the retreating trench model in the anchored slab model the trench has been fixed with respect to eurasian margin since 43 ma ago we prefer the retreating trench model because the deformation of the plate boundary along the eastern margin of eurasia during 30 17 ma ago is much simpler for this model than for the anchored slab model furthermore rotations of the bonin mariana islands are consistent with those predicted from the retreating trench model the 48 ma ages of the northern part of the palau kyushu ridge and of chichi jima of the bonin islands indicate that there was subduction beneath the northern half of the ridge beginning at least 48 ma ago from this and the subparallelism in trend between the northern part of the palau kyushu ridge and the central basin ridge we propose that the major part of the west philippine basin formed by back arc spreading in a n s direction behind the northern part of the palau kyushu ridge the pacific plate was moving northward with respect to hot spots from 48 to 43 ma ago which implies that the pacific plate is not likely to have been subducting beneath the west philippine basin during this time we speculate that another plate existed south of the pacific plate and thai it was subducting beneath both tile west philippine basin and australia the annihilation of this plate might he a cause for the sudden change of the pacific plate motion at 43 ma ago

transverse fold evolution in the external sierra southern pyrenees spain fault slip data are used to reconstruct varying tectonic regimes associated with transverse fold development along the eastern and southern margins of the jaca basin southern pyrenees spain the spanish pyrenean foreland consists of thrust sheets and leading edge decollement folds which developed within piggyback basins guara formation limestones on the margins of the jaca basin were deposited synchronously with deformation and are exposed in the external sierra within the transverse folds principal shortening axes determined from p and t dihedra plots of fault slip data show a shift from steep shortening in stratigraphically older beds to nne ssw horizontal shortening in younger beds older strata are characterized by extensional faults interpreted to result from halotectonic salt tectonics deformation whereas younger strata are characterized by contraction and strike slip faults interpreted to result from thrust sheet emplacement the interpretation of the timing for the shortening axes in the younger strata is supported by the observation that these axes are parallel to shortening axes determined from finite strain analysis calcite twins and regional thrusting directions determined from fault related folds and slickenlines this study shows that fault population analysis in syntectonic strata provides an opportunity to constrain kinematic evolution during orogeny

a pedotype approach to latest cretaceous and earliest tertiary paleosols in eastern montana a pedotype approach to the study of paleosols emphasizes individual profiles it is an alternative approach to the study of geosols which are laterally extensive suites of paleosols or pedofacies which are pedogenically distinctive sedimentary facies this is the first pedotype study of paleosols across the cretaceous tertiary boundary in eastern montana pedotypes allow assessment of sedimentation and fossilization the sequence of paleosols across the cretaceous tertiary boundary at bug creek is one of high temporal resolution because most available geological time can be accounted for by differing degree of development inferred for each pedotype paleosols at bug creek include pedotypes that preserve plant fossils well but were unfavorable for preservation of fossil vertebrates pedotypes also allow reassessment of ecosystem change despite indications of catastrophe at the cretaceous tertiary boundary the array of paleocene and cretaceous pedotypes are not strikingly different the upper cretaceous hell creek formation includes pedotypes interpreted as gleyed alfisols inceptisols and entisols probably formed under seasonally water logged forest and mean annual rainfall of the order of 900 1200 mm most paleosols of the lower paleocene tullock formation were histosols but some can be interpreted as gleyed inceptisols and entisols probably formed under bald cypress swamps in a humid climate with 1200 mm mean annual rainfall broadly comparable pedotypes were present before and after the cretaceous tertiary boundary although paleocene flood plain forest lived in paleosols chemically a little more oligotrophic than cretaceous paleosols this modest difference supports the idea that change to coaly facies in the earliest paleocene was a local shift in sedimentary environment such local changes do not begin to account for profound disruption in specific composition of plant and animal communities at the cretaceous tertiary boundary in eastern montana

micromorphology and stable isotope geochemistry of historical pedogenic siderite formed in pah contaminated alluvial clay soils tennessee u s a abstract alluvial clay soil samples from six boreholes advanced to depths of 400 450 cm top of limestone bedrock from the chattanooga coke plant ccp site were examined micromorphologically and geochemically in order to determine if pedogenic siderite feco3 was present and whether siderite occurrence was related to organic contaminant distribution samples from shallow depths were generally more heavily contaminated with polycyclic aromatic hydrocarbons pahs than those at greater depth the upper 1 m in most boreholes consisted of mixtures of anthropogenically remolded clay soil fill containing coal clinker cinder grains and limestone gravel most layers of coarse fill were impregnated with creosote and coal tar most undisturbed soil below 1 m depth consisted of highly structured clays exhibiting fine subangular blocky ped structures as well as redox related features pedogenic siderite was abundant in the upper 2 m of most cores and in demonstrably historical 100 years old soil matrices two morphologies were identified 1 sphaerosiderite crystal spherulites ranging from 10 to 200 m in diameter and 2 coccoid siderite comprising grape like clusters of crystals 5 20 m in diameter the siderite formed in both macropores and within fine grained clay matrices indicates development of localized anaerobic low eh conditions possibly due to microbial degradation of organic contaminants stable isotope compositions of the siderite have 13c values spanning over 25 7 to 18 vpdb indicating fractionation of dic by multiple microbial metabolic pathways but with relatively constant 18o values 4 8 0 66 vpdb defining a meteoric sphaerosiderite line msl calculated isotope equilibrium water 18o values from pedogenic siderites at the ccp site are from 1 to 5 per mil lighter than the groundwater 18o values that we estimate for the site if confirmed by field studies in progress this observation might call for a reevaluation of low temperature siderite water 18o fractionations investigations at the ccp site thus provide valuable information on the geochemical conditions under which siderite can form in modern soils and thus insight on controls on siderite formation in ancient soils

extensional collapse of the northern taiwan mountain belt as an active collision zone between the luzon arc and the china continental margin the taiwan mountain belt particularly its south central part is undergoing crustal shortening and rapid uplift the northern part of the orogen is however subjected to crustal stretching and rifting as a result of flipping of subduction from the northwest facing luzon arc system to the south facing ryukyu arc system taiwan and its neighboring southern ryukyu used to be part of the rifted china continental margin before the collision started in late miocene time engineered by the northwest movement of the philippine sea plate in the past 5 m y the north south trending luzon arc obliquely overrode the northeast southwest trending continental margin and tectonized it into a collision orogen that progressively enlarged and migrated from northeast to southwest following the southwest propagating collision the north dipping philippine sea plate which was subducting beneath the ryukyu arc also extended westward and caused flipping of subduction in the northern part of the collision orogen in consequence the orogen lost the compressive support by the colliding plates and became subjected to lithospheric stretching induced by the trench suction the collision orogen collapsed as a result of crustal thinning and its central part foundered into a deep submerged basin a whole spectrum of active tectonic scenarios ranging from orogenic buildup by collision to orogenic collapse by rifting and subsidence can be readily observed in the taiwan ryukyu area and provides a vivid example for the process of orogenic collapse

vertisol carbonate properties in relation to mean annual precipitation implications for paleoprecipitation estimates abstract previous publications combining the properties of multiple soil orders show that depth to carbonate dtc increases systematically between 350 and 1000 mm of mean annual precipitation map we hypothesize that carbonate in vertisols clay rich shrink swell soils respond differently to water flux than other soil orders because of lower permeability to test this hypothesis we compiled soil description and characterization data from multiple published sources across a late pleistocene climosequence of the coast prairie of texas to assess the relationship between map 700 1400 mm and dtc the dtc of carbonate nodules represents an index of accumulation and the dtc of calcium carbonate equivalent total carbonate 2 0 mm diam an index of leaching the dtc for 1 2 and 5 abundances were assessed using regression analysis the r2 values were highest for the dtc of 2 nodules and of 1 calcium carbonate equivalent in vertisol microlows surprisingly relatively high r2 values were calculated

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

sem and light microscopic observations of minerals in bog ores of the belgian campine abstract stoops g 1983 sem and light microscopic observations of minerals in bog ores of the belgian campine geoderma 30 179 186 soft bog ore deposits are frequently present in alluvial soils of the nete valley province of antwerp belgium a profile was studied consisting of four layers of which the upper three were analyzed with the light microscope and sem scanning electron microscope the top layer consisted mainly of clay and fragmented diatom shells isotropic fe oxihydrates and radiating goethite needles were present in the underlying limonitic layer siderite and vivianite were found in the third layer the former often present in the wall of root channels whereas the latter was frequently found within the channels vivianite was also found associated with decaying roots or alone inside root channels pyrite framboids were also found in the lower part of the profile the presence close to each other of different minerals such as goethite pyrite siderite and vivianite cannot be explained by macroenvironmental mineral equilibria alone it requires the existence of different microenvironments which can vary in time and place the study of such microenvironments however requires additional in situ microchemical submicroscopic techniques

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

plate collision and paleostress trajectories in a fold thrust belt the foothills of taiwan abstract field analyses of compressional faulting and folding in the foothills of western taiwan enable us to reconstruct paleostress trajectories over a large area and to establish the relative chronology of tectonic events two main compressional events have contributed to the present structure of the fold thrust belt stratigraphic data show that these events are plio pliocene in age older normal faulting indicates nnw sse extension across the chinesse passive continental margin during the neogene the two main compressional events of the taiwan collision correspond to similar fan shaped distributions of maximum compressive stress trajectories with a counterclockwise shift of 30 50 between the two events using the relationship between recent stress trajectories and the direction of recent plate motion as a guide we reconstruct the direction of plate convergence for the older event we suspect that the relative motion philippine sea plate eurasia has rotated counterclockwise of at least 35 45 in taiwan during collision this conclusion is in agreement with independent plate tectonic reconstructions several problems provide objectives to further tectonic and paleomagnetic studies including the duration and diachronism of compressional events as well as possible clockwise rotation of northernmost taiwan

geocarbsulf a combined model for phanerozoic atmospheric o2 and co2 abstract a model for the combined long term cycles of carbon and sulfur has been constructed which combines all the factors modifying weathering and degassing of the geocarb iii model berner r a kothavala z 2001 geocarb iii a revised model of atmospheric co2 over phanerozoic time am j sci 301 182 204 for co2 with rapid recycling and oxygen dependent carbon and sulfur isotope fractionation of an isotope mass balance model for o2 berner r a 2001 modeling atmospheric o2 over phanerozoic time geochim cosmochim acta 65 685 694 new isotopic data for both carbon and sulfur are used and new feedbacks are created by combining the models sensitivity analysis is done by determining 1 the effect on weathering rates of using rapid recycling rapid recycling treats carbon and sulfur weathering in terms of young rapidly weathering rocks and older more slowly weathering rocks 2 the effect on o2 of using different initial starting conditions 3 the effect on o2 of using different data for carbon isotope fractionation during photosynthesis and alternative values of oceanic 13c for the past 200 million years 4 the effect on sulfur isotope fractionation and on o2 of varying the size of o2 feedback during sedimentary pyrite formation 5 the effect on o2 of varying the dependence of organic matter and pyrite weathering on tectonic uplift plus erosion and the degree of exposure of coastal lands by sea level change 6 the effect on co2 of adding the variability of volcanic rock weathering over time berner r a 2006 inclusion of the weathering of volcanic rocks in the geocarbsulf model am j sci 306 in press results show a similar trend of atmospheric co2 over the phanerozoic to the results of geocarb iii but with some differences during the early paleozoic and for variable volcanic rock weathering lower co2 values during the mesozoic atmospheric oxygen shows a major broad late paleozoic peak with a maximum value of about 30 o2 in the permian a secondary less broad peak centered near the silurian devonian boundary variation between 15 and 20 o2 during the cambrian and ordovician a very sharp drop from 30 to 15 o2 at the permo triassic boundary and a more or less continuous rise in o2 from the late triassic to the present

middle cretaceous greenhouse hydrologic cycle of north america we present a paleolatitudinal precipitation reconstruction for the greenhouse setting of mid latitude north america based on the oxygen isotopic composition of sphaerosiderites found in middle cretaceous wetland paleosols our reconstructed middle cretaceous d 18 o values of precipitation are 4 less than values from comparable modern low elevation coastal settings free of monsoons the data fit a conceptual model in which the precipitation source for the eastern margin of the cretaceous western interior seaway of north america is an 18 o enriched oceanic coastal jet in this subtropical tropical setting midcretaceous precipitation rates are interpreted to range from 2500 to 4100 mm yr

jiggling the tropical thermostat in the cretaceous hothouse modern open ocean sea surface temperatures rarely exceed 28 29 8c and the same has been thought to represent a rough maximum for past tropical climates however new isotopic estimates from the uppermost cenomanian in the tropical western north atlantic suggest that mixed layer temperatures reached 33 34 8 c 62 8c during the middle cretaceous hothouse uppermost cenomanian tropical sea surface temperatures may have been as much as 4 7 8c warmer than the highest modern mean annual temperatures such extreme conditions suggest that warm tropical oceans could have driven substantially intensified atmospheric heat transport near the cenomanian turonian boundary the tropical thermostat was set higher than today challenging the hypothesis of tropical climate stability

paleosols in clastic sedimentary rocks their geologic applications interest in pre quaternary paleosols has increased over the past decade in large part because they have proved to be beneficial in solving diverse geological problems the majority of paleosols are described from continental deposits most commonly from alluvial strata criteria for recognizing these paleosols have been extensively described however classifying them has proved more complicated pre quaternary paleosols are generally classified according to one or more modern soil classification systems although one new classification has been proposed exclusively for paleosols to avoid problems using the modern soil classifications in addition to taxonomic classification paleosols can be categorized according to the interplay among deposition erosion and the rate of pedogenesis when they formed paleosols can be solitary if they formed during a period of landscape stability following the development of an unconformity such paleosols are commonly thick and extremely well developed more commonly paleosols are vertically stacked or multistory because they formed in sedimentary systems undergoing net aggradation if erosion was insignificant and sedimentation was rapid and unsteady compound paleosols generally formed if the rate of pedogenesis exceeded the rate of deposition composite paleosols developed thick cumulative paleosols indicate that erosion was insignificant and that sedimentation was relatively steady both autogenic and allogenic processes can influence depositional and erosion patterns and thus affect the kinds of soils that form consequently paleosols can help to interpret the history of sediment deposition and the autogenic and allogenic processes that influenced a sedimentary basin paleosols are also helpful in stratigraphic studies including sequence stratigraphic analyses they are used for stratigraphic correlations at the local and basinal scale and some workers have calculated sediment accumulation rates based on the degree of paleosol development in addition to their stratigraphic applications paleosols can be used to interpret landscapes of the past by analyzing paleosol landscape associations at different spatial scales ranging from local to basin wide in scope at the local scale lateral changes in paleosol properties are largely the result of variations in grain size and topography at the scale of the sedimentary basin paleosols in different locations differ because of basinal variations in topography grain size climate and subsidence rate paleosols are used to reconstruct ancient climates even to estimate ancient mean annual precipitation map and mean annual temperature mat ancient climatic conditions can be interpreted from modern soil analogs or by identifying particular pedogenic properties that modern studies show to have climatic significance stable carbon and oxygen isotopes are also used to interpret ancient climate and some effort has been made to estimate mat from isotopic composition on the basis of

cretaceous plate tectonic reconstructions abstract plate tectonic reconstructions for each cretaceous stage are produced as base maps for cretaceous paleogeography and for oceanic and continental data both geologic and geophysical data are utilized to determine the relative rotations of cretaceous plates with respect to north america a sea floor spreading history is generated from the relative rotations this history is consistent with data from the deep sea drilling project paleolatitude lines are derived using average paleomagnetic pole positions these reconstructions are significantly more comprehensive than previous global reconstructions although there are still many areas which remain controversial

response of intracontinental deformation in the central andes to late cenozoic reorganization of south american plate motions new stratigraphic chronologic and fault kinematic data from the quebrada del toro in northwestern argentina provide a detailed view of late cenozoic kinematic reorganization in the southern central andes the quebrada del toro is a thrust bounded basin filled with 2 km of synorogenic clastic deposits ranging in age from early miocene to holocene as observed elsewhere in northwestern argentina faults in the quebrada del toro record an early phase of horizontal nw se contraction beginning between early and late miocene and ending after 0 98 ma and a later phase of horizontal ne sw contraction beginning between late miocene and 4 17 ma and still active these results require both kinematic regimes to have been active between 4 17 and 0 98 ma compatible with timing and kinematic data from the adjacent central andes and best explained by a temporal pattern of serial recurrence of the kinematic regimes a hypothesis that intraplate deformation in the central andes is driven by the absolute motion of the south american plate with respect to the hotspot reference frame is tested by comparing quebrada del toro kinematics to plate reconstructions and space based geodetic results nazca south america relative motion and absolute nazca plate motion show consistent azimuths throughout the past 20 5 myr in contrast absolute south american plate motion azimuths mimic the changing contraction directions determined from intraplate andean faults although the timing of the south american plate motion change is poorly resolved by current data it is compatible with the quebrada del toro data absolute upper plate motion might control intraplate kinematics along many of the earth s convergent margins

holocene changes in trophic states of shallow lakes from the pampa plain of argentina changes in trophic status of shallow lakes from the southeastern pampa plain of argentina are evaluated based on the relative presence of submerged macrophytes and phytoplankton the evolution of lake lonkoy is reconstructed for the last 5000 years using pollen non pollen palynomorphs npps and macrofossil remain analyses revealing three main lake stages a macrophyte dominated clear lake prevailed until 670 cal yr bp afterwards the lake changed to a turbid phytoplankton dominated state recently the lake has turned to a turbid phase caused by resuspended sediment these results are compared with two other paleolimnological records from the region lakes hinojales and nahuel ruca revealing a similar late holocene evolution with a shift from a macrophyte to phytoplankton dominated lake occurring at broadly the same time the shift of states may be attributed to a shift in climate after 1000 cal yr bp towards wetter conditions during the medieval climate anomaly