source mechanisms of micro earthquakes induced in a fluid injection experiment at the hdr site soultz sous forets alsace in 2003 and their temporal and spatial variations we have inverted the peak amplitudes of direct p waves of 45 micro earthquakes with magnitudes between m 1 4 and 2 9 which occurred during and after the 2003 massive fluid injection in the gpk3 borehole of the soultz sous for ets hot dry rock facility these events were recorded by a surface seismic network of 15 stations operated by the ecole et observatoire des sciences de la terre university of strasbourg the unconstrained moment tensor mt expression of the mechanism was applied allowing the description of a general system of dipoles that is both double couple dc and non dc sources as tensile fractures the mechanisms of all but one event are dominantly dcs with a few per cent additional components at the most we have checked carefully the reliability of the mt retrieval in bootstrap trials eliminating some data by simulating the mislocation of the hypocentre and by applying simplified velocity models of the area in constructing green s functions in some of the trials non dc components amounting to several tens of per cent appear but the f test classifies them as insignificant even the only micro earthquake with an exceptionally high non dc mechanism cannot be classified unambiguously the f test assigns similar significance to the pure dc solution the massive dominance of the dc indicates the shear slip as the mechanism of the micro earthquakes investigated the mechanisms display large variability and are of normal dip slip oblique normal to strike slip types the t axes are fairly stable being concentrated subhorizontally roughly in the e w direction on the contrary the p axes are ill constrained varying in the n s direction from nearly vertical to nearly horizontal which points to heterogeneous stress in the soultz injected volume this is in agreement with the stress pattern from in situ measurements the minimum stress axis is well constrained to e w whereas the maximum and intermediate stress values are close to one another enabling the ambiguity of the p axis direction we found no significant dependence of source mechanisms either on magnitudes or depths the time space distribution of the events analysed suggests that the injection activated two segments of the natural faults existing in the area i and ii in our notation showing different source mechanism patterns the dip slip regime is characteristic of fault segment i where the seismicity occurred during and also after injection whereas the strike slip regime prevails in segment ii where the seismicity was triggered only after the injection shut in this indicates that the tensile fractures which are assumed to be created during injection may have occurred on a smaller scale than the pure shear micro earthquakes investigated

cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

timing of early cretaceous angiosperm diversification and possible links to major paleoenvironmental change palynological records from the western portuguese and algarve basins portugal provide new insights on the timing and pattern of the early diversification of angiosperms flowering plants and its relationship to global environmental perturbations during the late early cretaceous angiosperm pollen displays a stepwise increase in both diversity and relative abundance during the late barremian to middle albian interval ca 124 104 ma reflecting the incipient radiation of flowering plants in lower midlatitude floras our results provide new evidence for the age interpretation of the previously described angiosperm mesofossil floras and associated in situ pollen assemblages from the western portuguese basin until now interpreted as barremian or possibly aptian in age biostratigraphic and sedimentologic evidence indicates a post aptian age for these assemblages hence demonstrating a major radiation phase of angiosperms during the early albian correlation of the angiosperm pollen record with data on global paleoenvironmental changes suggests a link between the rapid adaptive radiation of flowering plants and major climatic and oceanographic perturbations during the late early cretaceous

influences of quaternary climatic changes on processes of soil development on desert loess deposits of the cima volcanic field california summary soils formed in loess are evidence of both relict and buried landscapes developed on pliocene to latest pleistocene basalt flows of the cima volcanic field in the eastern mojave desert california the characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow four distinct phases of soil development are recognized phase 1 weakly developed soils on flows less than 0 18 m y old phase 2 strongly developed soils with thick argillic horizons on 0 18 0 7 m y old flows phase 3 strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0 7 to 1 1 m y old flows and phase 4 degraded soils with petrocalcic rubble on pliocene flows a critical aspect of the development of stage 1 soils is the evolution of a vesicular a horizon which profoundly affects the infiltration characteristics of the loess parent materials laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development slight reddening of the interiors of peds from vesicular a horizons of phase 1 soils and presence of weakly developed b horizons indicates a slight degree of in situ chemical alteration however clay and fe oxide contents of these soils show that these constituents as well as carbonates and soluble salts are incorporated as eolian dust in contrast to phase 1 soils chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in situ chemical alteration these data the abundant clay films and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist flow age data and soil stratigraphic evidence also indicate that several major loess deposition events occurred during the past 1 0 m y loess events are attributed to past changes in climate such as the pleistocene to holocene climatic change that periodically caused regional desiccation of pluvial lakes reduction of vegetational density and exposure of loose unconsolidated fine materials during times of warmer interglacial climates precipitation infiltrates to shallower depths than during glacial periods extensive saline playas which developed in the mojave desert during the holocene are a likely source of much of the carbonates and soluble salts that are accumulating at shallow depths both in phase 1 soils and in the formerly noncalcareous nongypsiferous argillic horizons of phase 2 and 3 soils

amplitude ratios for complete moment tensor retrieval 1 we generalized the snoke s method of inversion of amplitude ratios and polarities p sh sv designed to determine double couple earthquake focal mechanism snoke 2003 we search for a general dipole source described by unconstrained seismic moment tensor i e non double couple non dc source components are allowed as well based on synthetic tests simulating various configurations of seismic stations from sparse to dense networks and from low to high number of stations conditions for successful inversion were found we specified minimum amount of data i e number of stations used and amplitude ratios employed for reliable retrieval of non shear source components we showed that processing of non dc data by traditional dc constrained algorithm could provide distorted fault plane solution the approach is demonstrated with local data 1st arrival amplitudes from 1997 west bohemia czechia earthquake swarm and from 2000 injection experiment in ktb germany

influence of late quaternary climatic changes on geomorphic and pedogenic processes on a desert piedmont eastern mojave desert california radiocarbon dating of late quaternary deposits and shorelines of lake mojave and cation ratio numerical age dating of stone pavements dorn 1984 on the adjacent soda mountains piedmont provide age constraints for alluvial and eolian deposits these deposits are associated with climatically controlled stands of lake mojave during the past 15 000 yr six alluvial fan units and three eolian stratigraphic units were assigned ages based on field relations with dated shorelines and piedmont surfaces as well as on soil geomorphic data all but one of these stratigraphic units were deposited in response to time transgressive climatic changes beginning approximately 10 000 yr ago increased eolian flux rates occurred in response to the lowering of lake mojave and a consequent increase in fine sediment availability increased rates of deposition of eolian fines and associated salts influenced pedogenesis stone pavement development and runoff infiltration relations by 1 enhancing mechanical weathering of fan surfaces and hillslopes and 2 forming clay and silt rich surface horizons which decrease infiltration changes in alluvial fan source areas from hillslopes to piedmonts during the holocene reflect runoff reduction on hillslopes caused by colluvial mantle development and runoff enhancement on piedmonts caused by the development of less permeable soils inferred increased in early to middle holocene monsoonal activity resulted in high magnitude paleo sheetflood events on older fan pavements this runoff triggered piedmont dissection which in turn caused increased sediment availability along channel walls thus runoff infiltration changes during the late quaternary have occurred in response to eolian deposition of fines pedogenesis increased sheetflood activity in the holocene and vegetational changes which are related to many complicated linkages among climatic change lake fluctuations and eolian hillslope and alluvial fan processes

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

cyclostratigraphy and orbital tuning of the terrestrial upper santonian lower danian in songliao basin northeastern china abstract the songke 1 north sk 1n borehole recovered a continuous 1541 66 m late santonian early danian terrestrial succession in songliao basin sb northeastern china it provides a unique record for improving our understanding of continental paleoclimate and ecological system in cretaceous greenhouse world here we use thorium th logging data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic study on the sk 1n core power spectra evolutionary fast fourier transformation and wavelet analysis all reveal significant decameter to meter scale sedimentary cycles in the nenjiang k 2 n sifangtai k 2 s and mingshui k 2 m formations the ratios of cycle wavelengths in these stratigraphic units are 20 5 2 1 and are interpreted as milankovitch cycles of 405 kyr and 100 kyr eccentricity 38 4 kyr obliquity and 20 kyr precession cycles respectively an astronomical time scale ats is established by tuning filtered 405 kyr eccentricity cycles to a target curve of the astronomical solution la2010d based on the magnetostratigraphic time framework of the sk 1n borehole this ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the cretaceous paleogene k pg campanian maastrichtian santonian campanian boundaries are estimated at core depths of 318 m 752 8 m and 1751 1 m respectively a 3 8 myr long hiatus between the nenjiang k 2 n and sifangtai k 2 s formations occurs from 76 1 to 79 9 million years ago the ages and durations of magnetochrons c33r to c30n are precisely estimated and provide new constraints on the late cretaceous geomagnetic polarity time scale gpts and south atlantic sea floor spreading rates

paleoatmospheric pco2 fluctuations across the cretaceous tertiary boundary recorded from paleosol carbonates in ne china abstract a dramatic change in atmospheric composition has been postulated because of global carbon cycle disruption during the cretaceous k tertiary t transition following the chicxulub impact and deccan trap eruptions here pedogenic carbonates were collected from drill core of a borehole sk 1 n straddling the late cretaceous and early paleocene strata in the songliao basin northeast china to reconstruct atmospheric co 2 concentrations using a paleosol paleobarometer our estimates for atmospheric pco 2 from paleosol carbonates range between 277 115 ppmv and 837 164 ppmv between 67 8 ma and 63 1 ma one large 66 65 5 ma and several small co 2 spikes 64 7 64 2 ma during the latest maastrichtian to earliest danian are reported here and incorporated with previously published pco 2 estimates also estimated from paleosol carbonates these co 2 spikes are attributed to one million year long emplacement of the large deccan flood basalts along with the extraterrestrial impact at the k t boundary

40ar 39ar geochronology of the eocene green river formation wyoming the deposits of eocene lake gosiute that constitute the green river formation of wyoming contain numerous tuff beds that represent isochronous correlatable stratigraphic markers tuff beds selected for 40ar 39ar analysis occur within laminated mudstone are matrix supported and lack evidence of reworking these tuffs contain 2 15 euhedral phenocrysts of quartz plagioclase sanidine biotite and minor amphibole pyroxene and zircon encased in a matrix of altered glassy ash air abrasion and handpicking under refractive index oils were required to obtain clean unaltered phenocrysts of sanidine 40ar 39ar age determinations from single crystal and 1 mg multigrain aliquots of sanidine and biotite allowed the identification and exclusion of xenocrystic contamination laser fusion experiments on phenocrysts from the rife firehole c bed grey main sixth and analcite tuff beds from the tipton wilkins peak and laney members yielded weighted mean ages 2 analytical uncertainties of 51 25 0 31 ma 50 70 0 14 ma 50 56 0 26 ma 50 39 0 13 ma 49 96 0 08 ma 49 70 0 10 ma and 48 94 0 12 ma respectively ages for sanidine and biotite from the main tuff are indistinguishable when presumably xenocrystic contaminants are excluded from the age calculation moreover the 40ar 39ar ages are consistent with the stratigraphic order of the tuff beds and with provenance in the absaroka and challis volcanic fields our 40ar 39ar based age model indicates that sediment accumulated three times more rapidly 327 86 m yr during the evaporative wilkins peak phase than the freshwater to saline tipton 88 34 m yr and laney 104 18 m yr phases the much lower accumulation rates for the tipton and laney members are permissive of an annual origin for 1 mm thick laminae and precessional forcing of 1 3 m thick depositional cycles in these units however previously described cycles in the wilkins peak member have average durations that are significantly shorter than the 19 23 k y precessional modes the green river formation encompasses an 5 m y period between ca 53 5 and 48 5 ma spanning magnetic chrons 24n through 21r the green river formation was therefore deposited during the warmest period of the cenozoic corresponding to the early eocene climatic optimum as defined by the global marine o isotope record deposition of bedded evaporites trona of the wilkins peak member began at ca 51 ma or 2 m y after the onset of the highest inferred temperatures of the climatic optimum the bridgerian wasatchian faunal turnover occurred subsequently during wilkins peak time at ca 50 6 ma thus our 40ar 39ar ages strongly suggest that wilkins peak evaporite deposition and the turnover from wasatchian to bridgerian fauna were not directly caused by the initiation of maximum greenhouse conditions

stable isotopic evidence for climate and basin evolution of the late cretaceous songliao basin china abstract because of the need to understand the links and feedbacks of the carbon cycle during times of global greenhouse conditions numerous studies have focused on the cretaceous climate much of what we know about this warm period in earth s history comes from the study of ocean sediments recovered from both ocean drill cores and marine sediments exposed at the earth s surface in contrast there are few studies of cretaceous terrestrial sediments the songliao basin located in northeast china offers a unique opportunity to understand cretaceous paleoclimate of terrestrial settings because it contains a nearly complete record of lacustrine sediments deposited throughout the cretaceous and there is an active drilling program to recover core from this paleolake we present carbon oxygen and strontium isotopic data from ostracods collected from two drill cores sk 1 n and sk 1 s that cover a time interval that extends from the turonian through the maastrichtian these data record robust isotopic trends with numerous carbon and oxygen isotope shifts that are both rapid and long term we tentatively interpret this record to reflect changes in both global climate and regional basin evolution in the turonian and coniacian qingshankou formation we observe several carbon isotope shifts that appear to be correlative to marine isotopic records based upon timing and magnitude of the isotopic changes we suggest that the carbon isotope record in the songliao basin reflect the decrease in carbon isotope ratios following the strong positive excursion at the cenomanian turonian boundary a positive isotope excursion in the late turonian and the negative isotope shift that occurs at the turonian coniacian boundary upward in the section however the marine and songliao isotopic records diverge as sediment sources shift from the southwest east and north to more northerly strontium isotopes record the change in source region as they increase markedly between the coniacian santonian yaojia and santonian campanian nenjiang formations as this is the first isotopic record of the songliao basin we are cautious about many of our interpretations of these isotopic data yet it is clear that with tighter age constraints and focused sampling centered on many of the isotope excursions presented here will allow for a deeper understanding of the terrestrial response to changing climate and the hydrologic response to basin evolution

cretaceous provenance change in the hegang basin and its connection with the songliao basin ne china evidence for lithospheric extension driven by palaeo pacific roll back

the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary the cretaceous paleogene boundary similar to 65 5 million years ago marks one of the three largest mass extinctions in the past 500 million years the extinction event coincided with a large asteroid impact at chicxulub mexico and occurred within the time of deccan flood basalt volcanism in india here we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction notably a single ejecta rich deposit compositionally linked to the chicxulub impact is globally distributed at the cretaceous paleogene boundary the temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations for example darkness and cooling lead us to conclude that the chicxulub impact triggered the mass extinction

moment tensor inversion of lp events recorded on etna in 2004 using constraints obtained from wave simulation tests 1 the persistent occurrence of long period lp events at mt etna became apparent with the installation of the first fixed broad band seismic network in late 2003 repeating similar lp events from nov 03 to sept 04 indicate a non destructive source process we perform moment tensor mt inversions on a stacked high s n ratio representative lp signal conducting a grid search for the source geometry and l2 inversion for the source time function results indicate a nnw sse oriented resonating sub vertical crack as the most probable source this result is consistent with deformation and gps observations crucial to this result are constraints imposed by detailed 3d full waveform numerical simulations in a heterogeneous tomographic model with topography and in particular a detailed assessment of the influence of very near surface velocity structure on lp signals pulsating gas injection is hypothesised as the most likely lp trigger

rock magnetic records of the qingshankou formation of sk 1 south borehole in songliao basin northeast china and their paleoclimate implications abstract the south borehole sk 1s of the china cretaceous continental scientific drilling project songke 1 penetrated the late cretaceous lacustrine sediments in the central depression of the songliao basin northeast china in order to reveal the terrestrial records of the cretaceous climate changes high resolution rock magnetic records were obtained on the qingshankou formation k 2 qn of sk 1s the results indicate that detrital magnetite is the main remanence carrier of the k 2 qn formation while both magnetite and paramagnetic minerals including clay minerals and pyrite dominantly contribute to magnetic susceptibility although reductive diagenesis may have more or less effect on the magnetic signals of the k 2 qn formation they recorded ancient lake level changes well resulting both from the tectonic development of the basin and from the milankovitch astronomical paleoclimatic changes the first order vertical trends of the rock magnetic records were controlled by the shallowing upwards of the lake level caused by the tectonic uplift of the basin the short term variations of the rock magnetic records were controlled by the lake level periodical drift caused by the fluctuations of the rainfall of the catchment area of the basin which were controlled by astronomical orbital forcing in addition the magnetic records also distinguished two most anoxic periods during the lacustrine anoxic event 1 lae1 the sections of 1758 1761 m and 1769 1771 5 m which may suggest the two most active periods of surface productivity of the lake

the kirchrode i and ii boreholes technical details and evidence on tectonics and the palaeoceanographic development during the albian abstract the technical details of drilling and coring at the kirchrode i and ii sites are presented at these sites a sequence of claystones and marlstones from an albian shelf basin was recovered constraints on the ages of the sediments in the two boreholes are provided by the occurrence of the inoceramid bivalve actinoceramus sulcatus the first appearance of which is used to define the middle upper albian boundary and by observed facies changes that can be correlated to the established lithostratigraphy the cores from the two boreholes provide a rather complete 285 m long sequence of the upper albian with a 155 5 m long overlap analysis of the tectonic structures showed considerable shortening in the middle and lower albian part of the sequence due to normal faulting of the upper albian only the lowermost part is affected by faults the increase in sedimentation rates of terrigenous detritus and of marine biogenic carbonate which occurs in the basal part of the c auritus subzone is interpreted to reflect a regional change to a more humid climate and regional tectonic movements uplift of the rhenish bohemian massif subsidence of the lower saxony basin intensified locally by halokinetic movements the further increase in marine productivity in the latest albian may be related to upwelling of more nutrient rich deep water along submarine relief in this shelf sea identification of milankovitch cyclicity documented by the fluctuating caco3 contents of the sediments is used i to constrain the minimum time represented by the upper albian deposits and ii to determine the duration of the sea level cycles cycle v 1 6 ma cycle vi 2 ma and iii to establish the duration of the late albian ammonite subzones e g callihoplites auritus subzone 2 1 ma average sedimentation rates determined from the identified 100 ka eccentricity cycles show a stepwise increase in sedimentation rates from 1 2 cm 1000 a in the lower albian dark claystones to 7 13 cm 1000 a in the late late albian in addition to the general deepening trend through the late albian two nearly completely documented 3rd order sea level cycles in the upper albian of kirchrode i were recognised plus another one cut short by faulting at the base of the upper albian documented in kirchrode ii these global sea level cycles were identified on the basis a of the sequence of the abundance maxima of selected benthos and plankton groups b of trends in the fluctuations of the caco3 content and c of the abundance of glauconite the transgression periods in this upper albian deep shelf basin are characterised by intensified circulation this intensified circulation is found to have affected first the surface near waters resulting e g in an increase in the abundance of immigrant plankton and nekton species from the tethys at a later stage the deep water was affected supporting then an increased population of suspension feeding benthos and causing condensation and erosion in the sediment at the sea floor

cretaceous terrestrial paleoenvironments of northeastern asia suggested from carbon isotope stratigraphy increased atmospheric pco2 induced climate abstract terrestrial organic carbon from cenomanian turonian sequences in hokkaido island japan has retained an isotopic record of the response of terrestrial higher plants to the paleoenvironment superimposed on a carbon isotope ratio fluctuation of atmospheric co 2 the stratigraphic record of organic carbon isotopic compositions from the hokkaido sections has been correlated to the carbonate carbon isotope record from europe and north america however considerable discrepancy in the long term time stratigraphic pattern of these isotope ratio curves exists through the middle upper cenomanian and lower turonian contrary to the marine carbonate profiles from europe and north america which show consistent positive migration through the upper cenomanian terrestrial organic carbon isotope values display a negative shift through the upper cenomanian followed by a positive recovery in the lower turonian environmental pressures that only affected carbon isotope values of terrestrial organic carbon but not those of carbonate carbon are causal factors for this discrepancy variations in atmospheric temperature and humidity and related conditions of carbon cycling in forests may have acted as factors to shift isotope values of terrestrial organic carbon negatively this causal relationship between climate and carbon isotope ratio fractionation is best explained when an increasing atmospheric p co 2 as suggested from a decoupling between isotope ratio curves of marine organic carbon and carbonate is understood as a driving force for a climatic optimum during the middle cenomanian through early turonian

lower mantle convection and geomagnetism the statistical properties of recent marine magnetic anomaly time scales covering the period from 165 ma to the present are analyzed via the methods presented in the companion paper mcfadden this issue the data no longer support the hypothesis that during the last 86 ma there were two periods separated by a discontinuity at about 45 ma when the properties were stationary instead there is strong evidence that the rate of reversals decreased in an approximately linear manner with time from 165 ma until it reached zero resulting in the cretaceous normal polarity interval at about 86 ma ago the process of reversals began again and the rate of reversals increased linearly with time there is a slight indication that the rate of reversals reached a maximum about 10 ma ago and is again decreasing analysis of the reversal sequences shows there is no good evidence for the concept of differences in the relative stabilities of the two polarity states nor need such a concept be invoked to explain long intervals without reversals such as the cretaceous normal polarity interval quite clearly there has been some form of thermal perturbation at the base of the mantle with a characteristic time of the order of 108 years our interpretations require convection deep within the mantle and suggest that the temperature at the base of the mantle attains a maximum during long magnetic quiet intervals

a multiple proxy and model study of cretaceous upper ocean temperatures and atmospheric co2 concentrations foraminiferal d 18 o and mg ca suggests that the ratio of magnesium to calcium in the turonian coniacian ocean may have been lower than in the albian cenomanian ocean perhaps coincident with an ocean 87 sr 86 sr minimum the carbon isotopic compositions of distinct marine algal biomarkers were measured in the same sediment samples the d 13 c values of phytane combined with foraminiferal d 13 c and inferred temperatures were used to estimate atmospheric carbon dioxide concentrations through this interval estimates of atmospheric co2 concentrations range between 600 and 2400 ppmv within the uncertainty in the various proxies there is only a weak overall correspondence between higher lower tropical temperatures and more less atmospheric co2 the genesis climate model underpredicts tropical atlantic temperatures inferred from odp leg 207 foraminiferal d 18 o and mg ca when we specify approximate co2 concentrations estimated from the biomarker isotopes in the same samples possible errors in the temperature and co2 estimates and possible deficiencies in the model are discussed the potential for and effects of substantially higher atmospheric methane during cretaceous anoxic events perhaps derived from high fluxes from the oxygen minimum zone are considered in light of recent work that shows a quadratic relation between increased methane flux and atmospheric ch4 concentrations with 50 ppm ch4 genesis sea surface temperatures approximate the minimum upper ocean temperatures inferred from proxy data when co2 concentrations specified to the model are near those inferred using the phytane d 13 c proxy however atmospheric co2 concentrations of 3500 ppm or more are still required in the model in order to reproduce inferred maximum temperatures

detailed mapping of shallow landslides in eastern oklahoma and western arkansas and potential triggering by oklahoma earthquakes abstract landslides have long been considered one of the main erosive drivers that sculpt hillslopes over time tectonic forces raise slopes that can be sculpted by climate and the degree to which they can be sculpted depends upon the underlying lithology and hillslope geomorphology landslides destroy life and property and contribute to the evolution of mountain landscapes by generating and transporting hillslope sediments in this study we investigate the dynamics of soil mantled hillslopes in eastern oklahoma and western arkansas usa by mapping shallow landslides evaluating the frequency and magnitude of the landslides and quantifying the surface geometries we mapped 185 shallow landslides in a 150 km2 area the approximate ages of landslides and the frequencies and magnitudes area volume and runout were estimated using historical aerial photographs the landslide database was then used to compute rate of landslide occurrence and sediment yield in addition landslide surface geometries including slope curvature and surface roughness were determined from 10 m ned and 2 m lidar elevation data the hillslope susceptibility studies derived from elevation data were augmented by our review of common historical accounts that link landslides in the study region to the 1952 m 5 4 el reno oklahoma earthquake 300 km away in light of that case study we determined the frequency of historical earthquakes that impart 2 kpa dynamic stresses for the study area since 1900 and find an increased potential for dynamic stress perturbation of landslide activity since 2010 all these characteristics were then evaluated to understand the dynamics of hillslopes and hillslope susceptibility to shallow landslides frequency assessment of mapped landslides suggested that frequency of landslides increased significantly during 2005 2016 compared to 1995 2005 on average 10 shallow landslides occurred every year during 2005 2016 these landslides alone contributed 1 5 105 m3 yr sediment yield rate 0 10 cm yr of sediments surface roughness values were relatively higher in landslide areas compared to that of surrounding non landslide areas the surface roughness index mapped 84 of observed landslides and suggests that the index could be used to map hillslope susceptibility to landslides for future planned studies

morokweng south africa a large impact structure of jurassic cretaceous boundary age geophysical petrographical and geochemical data indicate the presence of a large impact structure in the area around morokweng northwest province south africa possibly up to 340 km in diameter drill cores from the center of the structure show a thick layer of impact melt rocks with high abundances of cr ni co and the platinum group elements consistent with the presence of up to 5 of a chondritic component ion probe dating of zircons extracted from the impact melt yielded a 206 pb 238 u age of 146 2 1 5 ma and a 208 pb 232 th age of 144 7 1 9 ma these are indistinguishable from the age of the jurassic cretaceous boundary following the identification of the chicxulub impact structure of cretaceous tertiary boundary age the discovery of a second large impact structure at a previously established major chronostratigraphic boundary strengthens suggestions that large impact events have been major factors in the evolution of the earth

co2 forced climate thresholds during the phanerozoic abstract the correspondence between atmospheric co2 concentrations and globally averaged surface temperatures in the recent past suggests that this coupling may be of great antiquity here i compare 490 published proxy records of co2 spanning the ordovician to neogene with records of global cool events to evaluate the strength of co2 temperature coupling over the phanerozoic last 542 my for periods with sufficient co2 coverage all cool events are associated with co2 levels below 1000 ppm a co2 threshold of below 500 ppm is suggested for the initiation of widespread continental glaciations although this threshold was likely higher during the paleozoic due to a lower solar luminosity at that time also based on data from the jurassic and cretaceous a co2 threshold of below 1000 ppm is proposed for the initiation of cool non glacial conditions a pervasive tight correlation between co2 and temperature is found both at coarse 10 my timescales and fine resolutions up to the temporal limits of the data set million year timescales indicating that co2 operating in combination with many other factors such as solar luminosity and paleogeography has imparted strong control over global temperatures for much of the phanerozoic

a biomarker study of depositional paleoenvironments and source inputs for the massive formation of upper cretaceous lacustrine source rocks in the songliao basin china abstract the abundance and composition of total organic carbon aliphatic and aromatic hydrocarbons including biomarkers and the 13c composition of total organic matter and individual compounds in core samples of the nenjiang formation from the sk 1 borehole of the songliao basin provide information on the paleoenvironmental conditions of lacustrine sediments formed during the upper cretaceous the distribution of n alkanes and their 13c composition and 4 methylsteranes and dinosteranes in the first member of the nenjiang formation k2n1 indicate that the organic matter largely originated from algal organisms and is dominated by types i and ii kerogen the occurrence of gammacerane aryl isoprenoids isorenieratane and low pristane phytane and diasterane sterane ratios further suggest a salinity stratified water column associated with anoxic bottom waters as well as possible photic zone oxygen depletion conditions during major source rock deposition of the k2n1 the organic geochemical data also indicate significantly different depositional environments for the second member of the nenjiang formation k2n2 sediments which are interpreted to have been deposited under a uniform salinity non stratified oxic water column consequently although the organic matter in the k2n2 sediments was largely derived from algal and bacterial sources the kerogen types are dominantly iib and iii due to the oxidative degradation of organic matter combined with a gradual increase in land plant input furthermore the occurrence and shift of two saw toothed distribution patterns of the 13c composition of c29 to c33 n alkanes with w and m patterns being isotopically heavy odd and even numbered alkanes respectively is suggestive of organic input shift or an unknown mechanism of carbon uptake or isotopic fractionation in particular the heavy even carbon numbered high molecular weight n alkanes is rare and needs further investigation

chronology of the terrestrial upper cretaceous in the songliao basin northeast asia the cretaceous was a period of great environmental biological and geodynamical change but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records here we present an integrated chronology for the terrestrial upper cretaceous in east asia based on new high resolution magnetostratigraphic results and previously published sims u pb zircon analyses of the cretaceous continental scientific drilling borehole sequence from the songliao basin in northeast china hereafter termed ccsd sk i which consists of a sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and sims u pb zircon geochronologic data and lithostratigraphy our correlation suggests that the ccsd sk i sedimentary sequence spans from the upper chron c34n to chron c29r the age of the sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m in the songliao basin can thus be constrained to an interval from the turonian to the maastrichtian ages in addition our correlation puts the cretaceous paleogene boundary in the upper part of member 2 of the mingshui formation k2m2 the constructed comprehensive chronology allows the precise correlation of the terrestrial upper cretaceous of the songliao basin to marine strata as well as other continental sequences

alluvial sediment or playas what is the dominant source of sand and silt in desert soil vesicular a horizons southwest usa 1 vesicular a av soil horizons form beneath desert pavements from the accretion of aeolian sediment dust commonly thought to be derived primarily from desiccating pluvial lakes and playas with contributions from ephemeral washes and alluvial fans particle size distributions of av horizons are typically bimodal with primary modes of very fine silt and fine sand suggesting that the horizon matrix is derived from multiple sources here we conduct detailed chemical and physical analysis of both av horizon soil samples and potential sources of aeolian sediment to better constrain the relative contributions of dust associated with the development of av horizons geochemical data from both sand 125 250 m and silt 2 32 m fractions in av horizons and potential dust sources in the eastern mojave desert and western sonora desert usa point to large contributions from nearby sources including distal alluvial fans and washes and comparably lower contributions from regional sources such as playas the silt mode is derived from suspension transport of dust and the fine sand mode is derived from saltating sand the desiccation of pluvial lakes in the mojave desert is commonly believed to have driven episodes of aeolian activity contributing to sand dunes and av horizon formation we propose that alluvial fans and washes are underappreciated as desert dust sources and that pulses of dust from late pleistocene and holocene alluvial fans dwarfed pulses of dust from desiccating pluvial lakes in the eastern mojave desert

the influence of debris flow rheology on fan morphology owens valley california we have investigated factors controlling the surface morphology of debris flow fans comprising the bajada along the western slope of owens valley california these fans have average slopes of 4 an extensive network of abandoned boulder lined channels rough undulatory surfaces near the range front and smooth distal surfaces field relationships and mechanical considerations indicate that the channels of the bajada are products of fluvial incision and not debris flow scour this is significant because detailed geomorphic maps indicate that the channels strongly influence the pattern of debris flow deposition the locus of debris flow deposition on a channelized fan surface is set by the interaction of debris flows with the channel system and is controlled by channel size channel gradient flow volume flow hydrograph and flow rheology debris flow behavior is most directly controlled by variations in bulk sediment concentration and its influence on flow rheology whereas low sediment concentration debris flows tend to smooth the surface of the lower fan spreading into thin sheets and filling channels and surface undulations repeated deposition of high sediment concentration debris flows produces the rugged topography of the upper fan the texture of the fan surface rough or smooth is determined by the relative volumetric importance of these two types of debris flow in addition channel avulsions and the associated long term shifting of depositional loci are driven by in channel deposition of debris flows with the highest sediment concentrations these debris flows therefore play a critical role in determining both the structure of the channel network and the long term pattern of deposition on the fan surface as a whole we infer that the frequency distribution of debris flow rheologies set by source terrain geology and hydrology is an important control on fan morphology

holocene environmental change and vegetation contraction in the sonoran desert abstract two types of microtopographic features plant scar mounds and plant scar depressions on surfaces of barren desert pavements provide a unique record of the former presence of large perennial plants evidence of bioturbation by burrowing animals extends more than 1 m beneath each type of plant scar indicating that both features originated as large bioturbation mounds formation of bioturbation mounds in desertscrub environments is generally restricted to areas beneath widely separated large perennial plants the contrasting forms of plant scars mounds vs depressions represent time dependent changes following disappearance of the large plants and eventual cessation of bioturbation plant scar mounds represent a geologically recent episode of plant mortality whereas plant scar depressions represent the disappearance of plants at a considerably earlier time possibly at the pleistocene holocene transition contrasting spatial distributions of the two kinds of plant scars indicate that vegetation on alluvial fans has progressively contracted from a more diffuse former vegetation cover yielding the wide barren pavement surfaces present today in less arid portions of the sonoran desert spatial distribution of recent plant mortality due to persistent severe drought provides an analog of the progressive loss of plants from different parts of the landscape in the past

isotopic evidence for glaciation during the cretaceous supergreenhouse the turonian 93 5 to 89 3 million years ago was one of the warmest periods of the phanerozoic eon with tropical sea surface temperatures over 35 c high amplitude sea level changes and positive 18 o excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth new 18 o data from the tropical atlantic show synchronous shifts 91 2 million years ago for both the surface and deep ocean that are consistent with an approximately 200 000 year period of glaciation with ice sheets of about half the size of the modern antarctic ice cap even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets calling into question the common assumption that the poles were always ice free during past periods of intense global warming

application of a soil water balance model to evaluate the influence of holocene climate change on calcic soils mojave desert california u s a abstract we used a process based soil water balance model to simulate the downward flux of soil water under varied conditions of climate vegetation and soil texture to determine the potential impact of episodic periods of wetter pluvial climate during the holocene on calcic soils in the mojave desert that have a bimodal distribution of carbonate daily weather data associated with a relatively wet climate years with extreme increases in annual rainfall 33 cm yr and dry climate historic average annual rainfall 15 cm yr was used to simulate the affects of pleistocene and holocene climate change on soil water balance linkages among atmospheric circulation patterns regional increases in precipitation and historic flooding in the mojave desert california suggest that historic wet years provide an analog for wetter climates that occurred during the last glacial period latest pleistocene and episodically during holocene periods of pluvial activity modeling results indicate that soil water balance for dry and wet years strongly corresponds with the upper and lower zones of carbonate accumulation respectively soil water only reached the lower zone of carbonate during a wet year when extreme increases in winter spring storm activity resulted in a significant increase in precipitation and the downward flux of soil water the linkage between increases in frontal storm activity and pluvial events suggests that the shallow zone of the bimodal distribution of carbonate is a result of periods of significant decreases in winter and spring rainfall and not primarily due to increases in holocene temperature or the development of clay rich horizons calculation of carbonate solubility and accumulation rates suggests that the bimodal distribution of carbonates in soils may have also been impacted by episodic periods of extreme increases in precipitation associated with perennial lakes during the holocene results suggests that much of the carbonate in the upper 75 cm of pleistocene soils may have accumulated during the late holocene rather than throughout the entire holocene

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

warm tropical ocean surface and global anoxia during the mid cretaceous period the middle of the cretaceous period about 120 to 80 myr ago was a time of unusually warm polar temperatures1 repeated reef drowning in the tropics2 and a series of oceanic anoxic events oaes that promoted both the widespread deposition of organic carbon rich marine sediments and high biological turnover3 4 5 6 7 8 the cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide7 8 9 10 11 12 in contrast there is no consensus on the climatic causes and effects of the oaes with both high biological productivity and ocean stagnation being invoked as the cause of ocean anoxia3 4 5 6 7 8 here we show using stable isotope records from multiple species of well preserved foraminifera that the thermal structure of surface waters in the western tropical atlantic ocean underwent pronounced variability about 100 myr ago with maximum sea surface temperatures 3 5 c warmer than today this variability culminated in a collapse of upper ocean stratification during oae 1d the breistroffer event a globally significant period of organic carbon burial that we show to have fundamental stratigraphically valuable geochemical similarities to the main oaes of the mesozoic era our records are consistent with greenhouse forcing being responsible for the warm temperatures but are inconsistent both with explanations for oaes based on ocean stagnation and with the traditional view reviewed in ref 12 that past warm periods were more stable than today s climate

cretaceous paleogeography and paleoclimate and the setting of ski borehole sites in songliao basin northeast china article i nfo as a paradigm of greenhouse climate in earth s history the cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate the songliao basin among the longest dura tion 85 90 m y of continental sedimentary basins provides an excellent opportunity to recover a nearly complete cretaceous terrestrial sedimentary record extensive lake deposits ten kilometers deep and cover ing an area of 260 000 km 2 of the songliao basin provide unique detailed records that can be tied to the glob al stratigraphic time scale thereby improving our understanding of the continental paleoclimate and ecological system the two coreholes at skis and skin sites were drilled into this basin and completed with a total length of 2485 89 m of recovered core that spanned the complete middle to upper cretaceous strata in the basin the unique geological setting of long term continuous subsidence within the largest cretaceous landmass in the world makes the cretaceous songliao basin of northeastern china an ideal place to study cretaceous climate change on the continent this paper reviews the literature on the paleogeography and paleoclimate of the northern east asia and the songliao basin during the cretaceous based on the climatolog ically sensitive deposits oxygen isotope studies and paleontology the climate during the cretaceous in the songliao basin was temperate and humid with relatively abundant rainfall during the period significant changes four cooling three warming and three semiarid events are generally consistent with the oxygen isotope data from east asia and the four cooling events in berriasian valanginian aptian albian early santonian and campanian maastrichtian may be related to potential glaciations in cretaceous

osmium isotope evidence for the regulation of atmospheric co2 by continental weathering the long term stability of earth9s climate throughout the phanerozoic stands in marked contrast to the dramatic fluctuations that have taken place on time scales as short as a few years reflecting the high efficiency of longer term climate regulation through negative feedbacks a fundamental mechanism is thought to involve control of co 2 in the ocean atmosphere system through continental weathering although unambiguous high resolution data supporting this hypothesis have hitherto not been available organic rich mud rocks from yorkshire england which were deposited during the toarcian oceanic anoxic event ca 181 ma early jurassic contain evidence of an exceptionally large excursion in the 187 os 188 os ratio of contemporaneous seawater from 0 4 to 1 0 the most likely explanation for this excursion is that it resulted from a transient increase in global continental weathering rates of 400 800 the os isotope excursion coincided with a well documented global 13 c excursion of 6 that affected all the major biospheric reservoirs of the time higher mean global temperatures caused global chemical weathering rates to increase substantially while in turn chemical weathering was very effective in reducing the elevated levels of atmospheric co 2 and the high temperatures to preexcursion levels

deposition of playa windblown dust over geologic time scales thick eolian deposits are commonly observed beneath desert pavements downwind of dust emitting playas these deposits play an important role in piedmont surface evolution controlling surface hydrologic conductivity and rates of pedogenesis to better understand the factors controlling the spatial distribution of eolian deposition we developed a numerical model that treats deposition from spatially distributed playa sources using analytic point source solutions for deposition from a gaussian plume the model also accounts for complex downwind topography as a test case model predictions were compared to eolian deposit thicknesses on eagle mountain piedmont southern amargosa valley california which receives dust from nearby franklin lake playa the close relationship between the model predictions and mapped thicknesses suggests that eolian transport and deposition can be modeled from basin to regional scales within this framework these results have important implications for hydrologic pedogenic and air quality problems

stress state differences between sedimentary cover and basement of the songliao basin ne china in situ stress measurements at 6 7 km depth of an icdp scientific drilling borehole sk ii abstract the stress state down to the basement within sedimentary basins yet remains poorly understood the anelastic strain recovery asr method was employed to measure the stress state in the sk ii borehole in the songliao basin northeast china the results show that the stress state differs significantly between the sedimentary cover and basement in the sedimentary cover 6296 6335 m the maximum principal stress 1 is nearly vertical which is in the normal faulting stress regime dominated by gravitation in accordance with the normal faults observed on seismic reflection profiles within the sedimentary cover in contrast the basement 6646 6846 m shows that 1 is nearly horizontal suggesting a strike slip or reverse faulting regime the stress state of the basement is close to the reasonable stress condition for the eurasian plate far from a western pacific plate subduction zone and consistent with the focal mechanisms of earthquakes 7 15 km in the vicinity of icdp sk ii borehole the difference of stress state may imply that the far field stress generated by the western pacific plate has limited effects on the sedimentary cover an increase in thickness correlates with an increasing influence of tectonic stress with depth

high precision u pb geochronologic constraints on the late cretaceous terrestrial cyclostratigraphy and geomagnetic polarity from the songliao basin northeast china abstract the cretaceous continental sedimentary records are essential to our understanding of how the terrestrial geologic and ecologic systems responded to past climate fluctuations under greenhouse conditions and our ability to forecast climate change in the future the songliao basin of northeast china preserves a near complete predominantly lacustrine cretaceous succession with sedimentary cyclicity that has been tied to milankocitch forcing of the climate over 900 meters of drill core recovered from the upper cretaceous turonian to campanian of the songliao basin has provided a unique opportunity for detailed analyses of its depositional and paleoenvironmental records through integrated and high resolution cyclostratigraphic magnetostratigraphic and geochronologic investigations here we report high precision u pb zircon dates ca id tims method from four interbedded bentonites from the drill core that offer substantial improvements in accuracy and a ten fold enhancement in precision compared to the previous u pb sims geochronology and allow a critical evaluation of the songliao astrochronological time scale the results indicate appreciable deviations of the astrochronologic model from the absolute radioisotope geochronology which more likely reflect cyclostratigraphic tuning inaccuracies and omitted cycles due to depositional hiatuses rather than suspected limitations of astronomical models applied to distant geologic time age interpolation based on our new high resolution geochronologic framework and the calibrated cyclostratigraphy places the end of the cretaceous normal superchon c34n c33r chron boundary in the songliao basin at 83 07 0 15 ma this date also serves as a new and improved estimate for the global santonian campanian stage boundary

predictive mapping of soil landscape relationships in the arid southwest united states abstract multi scale geospatial and absolute variation of surface and near surface soil physical and chemical properties can be mapped and quantified by coupling digital soil mapping techniques with high resolution remote sensing products the goal of this research was to advance data driven digital soil mapping techniques by developing an approach that can integrate multi scale digital surface topography and reflectance derived remote sensing products and characterize multi scale soil landscape relations of quaternary alluvial and eolian deposits the study area spanned the arid landscape encompassed by the barry m goldwater range west bmgrw which is administered by the marine corps air station yuma in southwestern arizona usa an iterative principal component analysis ipca was implemented for lidar elevation and landsat etm derived soil predictors termed environmental covariates principal components that characterize 95 of covariate space variability were then integrated and classified using an isodata iterative self organizing data unsupervised technique the classified map was further segmented into polygons based on a region growing algorithm yielding multi scale maps of soil landscape relations that were compared with maps of soil landforms identified from aerial photographs satellite images and field observation the approach identified and mapped the spatial variability of soil landscape relationships in alluvial and eolian deposits and illustrated the applicability of coupling covariate selection and integration by ipca isodata classification of integrated data layers and image segmentation for effective spatial prediction of soil landscape characteristics the approach developed here is data driven applicable for multi scale mapping allows incorporation of a wide variety of covariates and maps spatially homogenous soil landscape units that are necessary for hydrologic models land and ecosystem management decisions and hazard assessment

cretaceous paleogeography in china abstract the paleogeography of china is represented by four maps the neocomian aptian albian cenomanian santonian and the campanian maastrichtian the continental interior of china was characterized by large lake systems in tectonic depressions and intermontane basins with little or no marine influence shallow epicontinental cretaceous seas were limited by the eastern margins and to the tectonic troughs of the southern and western tibetan plateau in contrast to the detailed knowledge of the interior cretaceous deposits of china the record of the marine invasions is known only in a general way

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

evolution of the geomagnetic reversal rate since 160 ma is the process continuous two main interpretations have been advanced for the evolution of the geomagnetic reversal rate since about 160 ma these interpretations have quite different implications for earth history and associated events and processes our own interpretation is that gradually and continuously decreased from its value of about 41 2 per million years at about 160 ma to zero at about 118 ma then at about 83 ma began to recover again gradually and continuously until reaching its present value of about 41 2 per million years the cretaceous superchron occurred from about 118 to about 83 ma when the reversal rate was zero recently gallet and hulot 1997 suggested an alternative interpretation where 1 was constant from 160 ma to about 130 ma at which time the process was rapidly and strongly perturbed this perturbation led to a discontinuous increase in the mean length of intervals and caused the cretaceous superchron the process then gradually recovered from the strong perturbation with the mean length gradually decreasing until the reversal process again became stationary at about 25 ma this interpretation is predicated on being constant from 160 to 130 ma whereas our interpretation requires a gradual increase in over this time interval consequently a new statistic is suggested to distinguish between the null hypothesis that the reversal process is stationary against the specific alternative that there is a trend in the mean length application of this statistic shows that the data require a trend toward larger values of in the reversal process going from 160 to 130 ma and that this trend continues strongly to the beginning of the superchron thus the addition of a discontinuity at 130 ma is neither required nor supported by the data furthermore application of this statistic shows that the trend toward smaller values of from 83 to 25 ma appears to continue from 83 ma to at least 12 ma certainly there is no requirement for a change in the style of process at 25 ma overall the gallet and hulot interpretation seems untenable with the available data despite this the gallet and hulot interpretation has great value in that it is inherently testable and our ability to reject it has increased our knowledge about the reversal process

new quantitative palaeocolimate data for the late cretaceous arctic evidence for a warm polar ocean abstract physiognomic analysis of four taphofloras one from the coniacian of n alaska one from the coniacian of kamchatka one from the turonian of kamchatka and one from the turonian of novaya sibir island using the clamp technique of wolfe 1993 yielded quantitative data on the mean annual warm month mean and cold month mean temperatures the length of the growing season mean annual precipitation mean growing season precipitation mean monthly growing season precipitation and the precipitation during the three consecutive driest months these new results represent the first application of multivariate statistical analysis of foliar physiognomy to determine palaeoclimatic parameters clamp to arctic cretaceous floras and demonstrate its robustness even in the context of vegetation which has no living analogues these new estimates were comparable to those from previous quantitative or qualitative sedimentological or palaeobotanical data where they were available but offer greater measurable precision the results also suggest that an arctic ocean with a winter surface temperature of approximately 6 c maintained n alaska coastal temperatures above freezing locally reversing the equator to pole temperature gradient a phenomenon not seen in the northern proto pacific this anomalously warm arctic ocean could have been produced by marine poleward heat transport precipitation in alaska kamchatka and novaya sibir island was predicted to have been high e g 1760 mm yr in the coniacian of n alaska reflecting a very weak polar high pressure cell and substantially different precipitation patterns to present

combined dna and lipid analyses of sediments reveal changes in holocene haptophyte and diatom populations in an antarctic lake preserved ribosomal dna of planktonic phototrophic algae was recovered from holocene anoxic sediments of ace lake antarctica and the ancient community members were identified based on comparative sequence analysis the similar concentration profiles of dna of haptophytes and their traditional lipid biomarkers alkenones and alkenoates revealed that fossil rdna also served as quantitative biomarkers in this environment the dna data clearly revealed the presence of six novel phylotypes related to known alkenone and alkenoate biosynthesizing haptophytes with isochrysis galbana uio 102 as their closest relative the relative abundance of these phylotypes changed as the lake chemistry particularly salinity evolved over time changes in the alkenone distributions reflect these population changes rather than a physiological response to salinity by a single haptophyte using this novel paleo ecological approach of combining data from lipid biomarkers and preserved dna we showed that the post glacial development of ace lake from freshwater basin to marine inlet and the present day lacustrine saline system caused major qualitative and quantitative changes in the biodiversity of the planktonic populations over time

marine transgressional events in the gigantic freshwater lake songliao paleontological and geochemical evidence abstract the fossil remains of euryhaline organisms in the mesozoic cenozoic non marine sedimentary records of eastern china may have resulted from either marine transgressions or inland hypersaline lacustrine environments paleontological and organic geochemical results of this study have provided new evidence for marine transgressional events in the gigantic freshwater lake songliao during the late cretaceous

post rift geodynamics of the songliao basin ne china origin and significance of t11 coniacian unconformity abstract the t11 unconformity lies between the qingshankou and yaojia formations in the post rifting sequence of the cretaceous songliao basin ne china it is intimately associated with petroleum reservoirs and considered to be a disconformity forming in the tectonic quiet stage we present the interpretations from new seismic surveys and cored sections of the cretaceous continental scientific drilling borehole ccsd sk 1 in order to resolve the nature and origin of t11 unconformity the t11 is often a low angle unconformity with underlying qingshankou formation having been deformed and eroded prior to deposition of the yaojia formation in the post rift evolution of the basin it marks an abrupt change from a deep lake to shallow lake or subaerial environment documented by reddening of the lacustrine mudstone extinction of the ostracod assemblages and a great increase of coarse detrital inputs the sharp change of depositional environment the truncation of gentle folds and the cluster of volcanic and paleoearthquake activities all happened simultaneously immediately before the development of t11 unconformity indicating a significant regional compressional uplift event in the basin the timing of the t11 unconformity formation is within the interval 88 86 2 ma correlations with coeval unconformities in other cretaceous sedimentary basins in eastern asia indicate that this compressional uplift coincided with an episode of global plate reorganization between the eurasian and paleo pacific plates that culminated at 88 87 ma during this short interval the northeast asian margin in eastern china south korea japan and russian far east experienced widespread violent volcanic and granite emplacement activity triggered by compression resulting from rapid and orthogonal slab subduction the post rift basin tectonic inversion occurred during t11 coniacian time thereafter the basin again evolved in an extension regime two subsidence phases in post rift history took place as the direct consequence of coniacian compression peak which defined the distribution of oil sources and reservoirs

clay mineralogy of the middle mingshui formation upper campanian to lower maastrichtian from the skin borehole in the songliao basin ne china implications for palaeoclimate and provenance abstract clay mineralogy of a 60 m thick section of the middle mingshui formation upper campanian to lower maastrichtian from the skin borehole songliao basin in ne china has been studied to assess the palaeoclimate and provenance the sedimentary succession is composed of shore to shallow lacustrine mudstones and siltstones in the lower part and meandering fluvial sandstone mudstone sequences in the upper part the clay mineral assemblage is characterized by the predominance of smectitic minerals with some exceptions of illite rich layers and trace amounts of kaolinite and chlorite the high smectite content 90 on average in lacustrine sediments could source from erosion of smetitic soils and volcanic materials in source areas the lesser xing an zhangguangcai range was the potential provenance area for the sediments with volcanic activity occurring at 70 ma when the temperate semi humid palaeoclimate was favorable for the clay formation smectite presented in meandering fluvial sandstones is of early diagenetic origin formed by hydrolysis and alteration of primary minerals after deposition illite in overbank deposits is interpreted as a result of erosion of granitic rocks and sorting in sedimentation processes the clay mineralogy of the studied strata contains information on palaeoclimate and provenance although early diagenetic processes may have influenced the mineralogical composition in some intervals of sandstones

stationary and nonstationary behaviour within the geomagnetic polarity time scale we analyse the geomagnetic polarity time scale gpts since the upper jurassic by displaying the successive lengths of polarity intervals as a function of their order of occurrence the sequence consists of three segments between the upper jurassic and the lower cretaceous segment a comprises intervals of short duration with a mean duration of about 0 29 my and no clear long term evolution segment b begins around 130 ma displays a sudden increase of the duration of the magnetic intervals an interval of maximum duration the normal cretaceous superchron and a long and erratic sequence of intervals with decreasing average duration between 85 ma and about 25 ma from 25 ma to the present segment c consists of intervals of short duration with a mean value of 0 23 my this description suggests that the earth s magnetic field could have experienced a fairly stationary regime until slightly before the onset of the cretaceous superchron when the regime has been rapidly and strongly perturbed before progressively returning to another stationary regime about 25 ma ago a geophysical explanation for this sequence of events could be that the geodynamo has been perturbed by the arrival of some cold material at the core mantle boundary as this material would have heated up the geodynamo would have been brought back to its stationary regime

deep sea paleotemperature record of extreme warmth during the cretaceous oxygen isotope analyses of well preserved foraminifera from blake nose 30 n paleolatitude north atlantic and globally distributed deep sea sites provide a long term paleotemperature record for the late albian maastrichtian interval that is difficult to reconcile with the existence of significant cretaceous ice sheets given reasonable assumptions about the isotopic composition of cretaceous seawater our results suggest that middle bathyal water temperatures at blake nose increased from 12 c in the late albian through middle cenomanian to a maximum of 20 c during the latest cenomanian and earliest turonian bottom waters were again 12 c during the middle campanian and cooled to a minimum of 9 c during the maastrichtian correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from blake nose comparison of global bottom water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late albian through late cenomanian to a hot greenhouse phase during the latest cenomanian through early campanian then to cool greenhouse conditions during the mid campanian through maastrichtian

an integrated approach to flood hazard assessment on alluvial fans using numerical modeling field mapping and remote sensing millions of people in the western united states live near the dynamic distributary channel networks of alluvial fans where flood behavior is complex and poorly constrained here we test a new comprehensive approach to alluvial fan flood hazard assessment that uses four complementary methods two dimensional raster based hydraulic modeling satellite image change detection field based mapping of recent flood inundation and surficial geologic mapping each of these methods provides spatial detail lacking in the standard method and each provides critical information for a comprehensive assessment our numerical model simultaneously solves the continuity equation and manning s equation chow 1959 using an implicit numerical method it provides a robust numerical tool for predicting flood flows using the large high resolution digital elevation models dems necessary to resolve the numerous small channels on the typical alluvial fan inundation extents and flow depths of historic floods can be reconstructed with the numerical model and validated against field and satellite based flood maps a probabilistic flood hazard map can also be constructed by modeling multiple flood events with a range of specified discharges this map can be used in conjunction with a surficial geologic map to further refine floodplain delineation on fans to test the accuracy of the numerical model we compared model predictions of flood inundation and flow depths against field and satellite based flood maps for two recent extreme events on the southern tortolita and harquahala piedmonts in arizona model predictions match the field and satellite based maps closely probabilistic flood hazard maps based on the 10 yr 100 yr and maximum floods were also constructed for the study areas using stream gage records and paleoflood deposits the resulting maps predict spatially complex flood hazards that strongly reflect small scale topography and are consistent with surficial geology in contrast fema flood insurance rate maps firms based on the fan model predict uniformly high flood risk across the study areas without regard for small scale topography and surficial geology

characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data 1 range front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages these distinct landforms are often defined by descriptions of their surface morphology desert varnish accumulation clast rubification desert pavement formation soil development and stratigraphy although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past high resolution airborne laser swath mapping alsm digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail here we use alsm data to calculate surface roughness on two alluvial fans in northern death valley california we define surface roughness as the standard deviation of slope in a 5 m by 5 m moving window comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99 confidence level furthermore there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10be and 36cl surface exposure ages of 70 ka beyond 70 ka alluvial landforms become progressively rougher with age these data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces

synoptic reconstruction of a major ancient lake system eocene green river formation western united states numerous 40ar 39ar experiments on sanidine and biotite from 22 ash beds and 3 volcaniclastic sand beds from the greater green river piceance creek and uinta basins of wyoming colorado and utah constrain 8 m y of the eocene epoch multiple analyses were conducted per sample using laser fusion and incremental heating techniques to differentiate inheritance 40ar loss and 39ar recoil when considered in conjunction with existing radioisotopic ages and lithostratigraphy biostratigraphy and magnetostratigraphy these new age determinations facilitate temporal correlation of linked eocene lake basins in the laramide rocky mountain region at a significantly increased level of precision to compare our results to the geomagnetic polarity time scale and the regional volcanic record the ages of eocene magnetic anomalies c24 through c20 were recalibrated using seven 40ar 39ar ages overall the ages obtained for this study are consistent with the isochroneity of north american land mammal ages throughout the study area and provide precise radioisotopic constraints on several important biostratigraphic boundaries applying these new ages average sediment accumulation rates in the greater green river basin wyoming were approximately three times faster at the center of the basin versus its ramp like northern margin during deposition of the underfilled wilkins peak member in contrast sediment accumulation occurred faster at the edge of the basin during deposition of the balanced filled to overfilled tipton and laney members sediment accumulation patterns thus reflect basin center focused accumulation rates when the basin was underfilled and supply limited accumulation when the basin was balanced filled to overfilled sediment accumulation in the uinta basin at indian canyon utah was relatively constant at 150 mm k y during deposition of over 5 m y of both evaporative and fluctuating profundal facies which likely reflects the basin margin position of the measured section the most rapid sediment accumulation for the entire system 1 m k y occurred between 49 0 and 47 5 ma when volcaniclastic materials from the absaroka and or challis volcanic fields entered the green river formation lakes from the north our new ages combined with existing paleomagnetic and biostratigraphic control permit the first detailed synoptic comparison of lacustrine depositional environments in all the green river formation basins coupled with previously published paleocurrent observations our detailed correlations show that relatively freshwater lakes commonly drained into more saline downstream lakes the overall character of eocene lake deposits was therefore governed in part by the geomorphic evolution of drainage patterns in the surrounding laramide landscape freshwater overfilled lakes were initially dominant 53 5 52 0 ma possibly related to high erosion rates of remnant cretaceous strata on adjacent uplifts expansion of balanced fill lakes first occurred in all green river formation basins at 52 0 51 3 ma and again between 49 6 and 48 5 ma evaporative underfilled lakes occurred in various basins between 51 3 and 45 1 ma coincident with the end of the early eocene climatic optima and subsequent onset of global cooling defined from marine record however evaporite intervals in the different depocenters were deposited at different times rather than being confined to a single episode of arid climate evaporative terminal sinks were initially located in the greater green river and piceance creek basins 51 3 48 9 ma then gradually migrated southward to the uinta basin 47 1 45 2 ma this history is likely related to progressive southward construction of the absaroka volcanic province which constituted a major topographic and thermal anomaly that contributed to a regional north to south hydrologic gradient the greater green river and piceance creek basins were eventually filled from north to south with absarokaderived detritus at sedimentation rates 1 2 orders of magnitude greater than the underlying lake deposits

astrochronology of the early turonian early campanian terrestrial succession in the songliao basin northeastern china and its implication for long period behavior of the solar system abstract the first complete early turonian early campanian lacustrine succession has been recovered from the sk i south sk is borehole in the songliao basin slb northeastern china we conducted a detailed cyclostratigraphic study of natural gamma ray gr log thorium th log and magnetic susceptibility ms data from this core spectral analysis of the upper quantou formation k 2 q 3 4 qingshankou formation k 2 qn yaojia formation k 2 y and lower nenjiang formation k 2 n 1 2 reveals a hierarchy of meter to decameter scale cycling in the data the wavelength ratios of the cycles in these stratigraphic units are 20 5 2 1 corresponding with those of milankovitch cycle periods of 405 kyr long eccentricity 100 kyr short eccentricity 37 kyr obliquity 20 kyr precession indicating astronomical control on sedimentation an astronomical time scale ats was established by tuning interpreted 405 kyr cycles to a 405 kyr orbital eccentricity target curve and to four sims u pb zircon radioisotope ages this absolute ats provides precise numerical ages for stratigraphic boundaries biozones geological and geophysical events and serves as a basis for correlation of strata and events between marine and terrestrial systems the ages of the c33r c34n geomagnetic polarity boundary in k 2 n 2 and three short reversal events in k 2 y are estimated as 83 633 ma 84 819 84 862 ma 84 982 85 092 ma and 85 240 85 629 ma respectively long period amplitude modulations in the obliquity and eccentricity bands of the 405 kyr tuned gr th series provide strong evidence that long period orbital forcing influenced climate change and depositional processes in the slb the extracted amplitude modulations provide evidence that the orbits of earth and mars were not in secular resonance and were undergoing chaotic interactions during this time although the modulations do not match those of recent astronomical models

carbon isotope composition of lower cretaceous fossil wood ocean atmosphere chemistry and relation to sea level change the carbon isotope composition of fossil wood fragments collected through a biostratigraphically well constructed aptian lower cretaceous shallow marine siliciclastic succession on the isle of wight southern britain shows distinct variations with time the results indicate that the stratigraphic signature of delta sup 13 c sub wood through the aptian was influenced primarily by fluctuations in the isotopic composition of co sub 2 in the global ocean atmosphere system as registered in marine carbonates elsewhere and was not governed by local paleoenvironmental and or paleoecological factors negative and positive excursions in delta sup 13 c sub wood through the lower aptian occur in phase with inferred transgressions and regressions respectively a pattern that contrasts with that observed in many previous studies for different time intervals the relationship between delta sup 13 c variations and relative sea level change is tentatively interpreted as a response to various climatic and eustatic factors relating to rapid sea floor spreading thermal uplift of ocean floor emplacement of plateaus volcanic co sub 2 emissions weathering and sedimentary rate

determination and uncertainty of moment tensors for microearthquakes at okmok volcano alaska summary efforts to determine general moment tensors mts for microearthquakes in volcanic areas are often hampered by small seismic networks which can lead to poorly constrained hypocentres and inadequate modelling of seismic velocity heterogeneity in addition noisy seismic signals can make it difficult to identify phase arrivals correctly for small magnitude events however small volcanic earthquakes can have source mechanisms that deviate from brittle double couple shear failure due to magmatic and or hydrothermal processes thus determining reliable mts in such conditions is a challenging but potentially rewarding pursuit we pursued such a goal at okmok volcano alaska which erupted recently in 1997 and in 2008 the alaska volcano observatory operates a seismic network of 12 stations at okmok and routinely catalogues recorded seismicity using these data we have determined general mts for seven microearthquakes recorded between 2004 and 2007 by inverting peak amplitude measurements of p and s phases we computed green s functions using precisely relocated hypocentres and a 3 d velocity model we thoroughly assessed the quality of the solutions by computing formal uncertainty estimates conducting a variety of synthetic and sensitivity tests and by comparing the mts to solutions obtained using alternative methods the results show that mts are sensitive to station distribution and errors in the data velocity model and hypocentral parameters although each of the seven mts contains a significant non shear component we judge several of the solutions to be unreliable however several reliable mts are obtained for a group of previously identified repeating events and are interpreted as compensated linear vector dipole events

mesozoic cenozoic basin inversion and geodynamics in east china a review abstract east china experienced alternating tectonic extension and compression with ambiguous tectonic settings in the mesozoic cenozoic interval long term extensional episodes associated with the subduction retreat of the paleo pacific and pacific slabs have been widely studied the compressional events of which basin inversion is a typical case are less concerned but important in understanding the tectonic evolution and geodynamics in east china we made a systematic study involving tectonics sedimentation apatite fission track and dynamic topography on the mesozoic cenozoic basin inversion in east china four phases of basin inversion were concluded 1 early late cretaceous inversion occurred at 115 100 ma in southeast china and at 100 89 ma in northeast china showing a northward migration due to the diachronous collision of the northward moving okhotomorsk block with east asia 2 the latest cretaceous early paleogene inversion was widely developed throughout east china it is associated with the increasingly younger subducted oceanic crust of the izanagi plate which caused the progressively increasing buoyancy beneath east china and an uplift in dynamic topography cenozoic inversion showed an eastward migration from 3 the western part of each basin at the late paleogene to 4 the eastern part at the neogene due to the subduction retreat of the pacific plate

40ar 39ar and k ar dating on the volcanic rocks in the songliao basin ne china constraints on stratigraphy and basin dynamics precise 40ar 39ar and k ar ages were determined on sanidine and whole rock separates of volcanic rocks in the songliao basin sb the volcanism is characterized by a series of continual and episodic eruptions in the late jurassic 147 157 ma and early cretaceous 113 136 ma a fairly accurate chronostratigraphic column was first established based on those data the volcanic activities happened synchronously with closure of the mongolia okhotsk ocean north to the sb structures of the volcanogenic successions are s dipping or se dipping fault blocks coupled with n dipping or nw dipping major detachment systems distribution of the volcanics revealed by high resolution seismic reflections is neither restricted within nor in agreement with the framework of the overlying sedimentary sequence striking nne this new evidence fits the overlap model proposed in the present paper that formation of the volcanic successions in the sb is related to the subduction of the mongolia okhotsk plate under the mongolia north china block during the jurassic and early cretaceous whereas the overlying sedimentary sequence unconformably on the volcanics is tectonically controlled by the oblique subduction of the pacific plate under the eurasian plate since late aptian in addition the coal bearing epiclastic sediments intercalating the volcanics were deposited at the subduction quiescence episodes when extensional collapse occurred

mid latitude terrestrial climate of east asia linked to global climate in the late cretaceous reply the late cretaceous late campanian to maastrichtian was characterized by a variable greenhouse climate with evidence for cooling and or glaciation and warming events most of these climatic signals are derived from marine records and knowledge of the terrestrial climate especially in the mid latitudes is limited due to fragmentary geological records on continents here we report mid latitude terrestrial stable oxygen and carbon isotope data from pedogenic carbonates in the nearly continuous late cretaceous age sk 1 core drilled in the songliao basin northeastern china our data indicate a punctuated mid latitude terrestrial climate in the late cretaceous we interpret the negative excursion of pedogenic carbonate 18o in the early maastrichtian to be the result of decreasing temperature and or strengthened westerlies during global cooling and possible glaciation providing valuable mid latitude terrestrial evidence for this event the negative 13c isotopic excursion ca 66 ma is modeled as higher primary productivity caused by increasing temperature and precipitation in response to a warming climate in the latest cretaceous our continuous stable isotopic records in the songliao basin are in accordance with previously published global late cretaceous records of climate variability from marine and terrestrial regions and demonstrate the sensitivity of mid latitude terrestrial climate in a greenhouse world

continental scientific drilling project of cretaceous songliao basin scientific objectives and drilling technology abstract the continental scientific drilling project at the cretaceous age songliao basin is a drilling initiative under the framework of the international continental scientific drilling program to recover a nearly complete cretaceous terrestrial sedimentary record in the songliao basin northeastern china the recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the cretaceous greenhouse world and provide a documentation of geological events relevant to the carbon cycle during this time period this drilling project will address significant geological questions such as the identification of important stratigraphic boundaries and the marine terrestrial correlations of stratigraphy the reasons for the biotic response to the terrestrial environmental changes the terrestrial response to the cretaceous oceanic anoxic events the formation of terrestrial petroleum source rocks and the mechanisms for the cretaceous magnetic normal superchron cns in the first stage of this drilling project the ski drilling rock cores of 2485 89 m in total length were recovered and the recovery ratio reached 96 46 a series of drilling and coring technologies including regular confined directional and sealed coring were utilized to ensure a higher recovery ratio for the core and will be described at the end of this paper well loggings were conducted right after coring core handling and storage were arranged in such a way that the scientific research was conducted on half of each core whereas the other half of each core was preserved for long term storage the upcoming second stage the skii drilling will combine with data from the existing ski to provide complete high resolution climate records of the terrestrial environment for the whole cretaceous time period

toward age determination of the m0r barremian aptian boundary of the early cretaceous china most 973 program 2006cb701403 national natural science foundation of china 90714010 40573040 40634024 40221402 chinese academy of sciences kzcx3 sw 142

timing and distribution of alluvial fan sedimentation in response to strengthening of late holocene enso variability in the sonoran desert southwestern arizona usa abstract the integration of geomorphic mapping soil stratigraphy and radiocarbon dating of alluvial deposits offers insight to the timing magnitude and paleoclimatic context of holocene fan sedimentation near yuma arizona mapping of 3400 km2 indicates about 10 of the area aggraded in the late holocene and formed regionally extensive alluvial fan and alluvial plain cut and fill terraces fan deposits have weakly developed gravelly soils and yielded a date of 3200 2950 cal yr bp from carbonized wood alluvial plain deposits have weakly developed buried sandy soils and provided a date of 2460 2300 cal yr bp from a terrestrial snail shell precipitation records were analyzed to form historical analogues to the late holocene aggradation and to consider the role of climatic variability and extreme hydrologic events as drivers of the sedimentation the historical precipitation record indicates numerous above average events correlated to the southern oscillation index soi in the region but lacks any significant reactivation of alluvial fan surfaces the timing of aggradation from 3200 to 2300 cal yr bp correlates well with other paleoclimatic proxy records in the southwestern u s and eastern pacific region which indicate an intensification of the el nino southern oscillation enso climatic pattern and rapid climate change during this period

an 11 million year long record of astronomically forced fluvial alluvial deposition and paleoclimate change in the early cretaceous songliao synrift basin china abstract in the cretaceous songliao basin northeastern china boreholes have recovered detailed geologic data from sub basins that developed during the early rifting of the basin among these the lower cretaceous shahezi formation k1s in the songshen 4 ss4 well is represented by an 836 m thick succession of fluvial alluvial deposits with coals distributed throughout the upper part of the formation gamma ray gr logging data are quantitatively related to grain size defined litho facies that recur throughout the succession with high gr values in mudstones and low gr values in sandstones cyclostratigraphic analysis of the gr log reveals depositional cycling at frequencies that are consistent with those of the earth s astronomical parameters the results also indicate that occurrence of coal beds occur every 100 kyr when development of vegetation at the depositional site was promoted by humid climate we propose a model of astronomically forced hydroclimate change to explain the cycling of depositional environments between fluvial and alluvial conditions the model describes a principally fluvial environment that episodically experienced at one extreme advancing alluvial conditions involving a drop in base level lake recession and increased aridity conglomerates and coarse sands and at the other extreme an advancing lakeshore with a rise in base level and increased humidity fine sands silts muds and coal a floating astronomical time scale was established by calibrating long orbital eccentricity 405 kyr cycles interpreted along the gr series the results indicate that the duration of the k1s is 11 14 myr 27 5405 kyr long orbital eccentricity cycles corresponding to an average sedimentation rate of 6 55 cm kyr the recognition of astronomical forcing in this early cretaceous fluvial alluvial dominated depositional setting offers a new framework for interpreting the sedimentary cyclicity and dynamics of early rift basins and for developing time scales

non double couple mechanisms of microearthquakes induced by hydraulic fracturing 1 we have inverted polarity and amplitude information of representative microearthquakes to investigate source mechanisms of seismicity induced by hydraulic fracturing in the carthage cotton valley east texas gas field with vertical arrays of four and eight three component geophones in two monitoring wells respectively we were able to reliably determine source mechanisms of the strongest events with the best signal to noise ratio our analysis indicates predominantly non double couple source mechanisms with positive volumetric component consistent with opening cracks oriented close to expected hydraulic fracture orientation our observations suggest the induced events are directly the result of opening cracks by fluid injection in contrast to many previous studies where the seismicity is interpreted to be primarily shearing caused by pore pressure diffusion into the surrounding rock or associated with shear stresses created at the hydraulic fracture tip

do superchrons occur without any palaeomagnetic warning abstract the mainly dipolar geomagnetic field generated by the geodynamo within the earth s liquid core has reversed its polarity many times in the past this succession of intervals of alternate polarity defines the geomagnetic polarity time scale gpts usually interpreted as resulting from a gamma renewal process the rate of which would be controlled by the boundary conditions imposed by the mantle on the core in this interpretation boundary conditions would have occasionally evolved towards being unfavourable to reversals leading the reversal rate of the process to progressively decrease and reach zero at least twice causing the onset of the so called kiaman and cretaceous very long polarity intervals superchrons here we reconsider this causal link analysing the latest and best constrained gpts thanks to the continuous record provided by marine magnetic anomalies describing the past 160 myr we found that contrary to earlier claims no long term behaviour over the 40 myr preceding the cretaceous superchron can be seen in the reversal rate that could explain its onset at 120 ma more generally it turns out that hardly any special behaviour can be identified in the gpts which could have announced this superchron only the occurrence of the longest of all pre superchron intervals cm1n 3 myr before the onset of the superchron could be identified as a precursor such a behaviour could possibly be the consequence of medium term on the 10 myr time scale changes in the boundary conditions imposed by the mantle on the core but we note that the sole analysis of the gpts does not allow this to be tested in fact it appears that a single stationary process could also explain the entire pre superchron gpts with the only possible exception of cm1n this suggests that the occurrence of superchrons does not necessarily require changes in boundary conditions and could simply attest for a sudden non linear transition between a reversing and a non reversing state of the geodynamo

late cretaceous stratigraphy songliao basin ne china sk1 cores abstract the songliao basin is the largest cretaceous oil and gas producing lacustrine basin in china with its greatest aerial extent in the middle cretaceous a coring program sk1 has to date yielded 2485 89 m of continuous core 96 46 recovery and provides significant material for cretaceous research the sequence of the core consists mainly of lacustrine sandstone dark grey mudstone shale and oil shale the upper cretaceous stratigraphic section has been subdivided into the quantou qingshankou yaojia nenjiang sifangtai and mingshui formations in ascending order late cretaceous microfossils are diverse and abundant a detailed biostratigraphic study has subdivided the sequence into high precision biozones 21 ostracode assemblages 10 phytoplankton assemblages 7 palynological zones and 4 charophyta assemblages respectively in addition marine foraminifera were first discovered from the basin three 206pb 238u ages and one 40ar 39ar age were analysed ten local magnetozones have been recognised in the sk1 north and two magnetozones have been indicated in the sk1 south based on biostratigraphy high resolution magnetostratigraphy and sims u pb zircon analyses the sk1 stratigraphy is correlated with upper cretaceous stages in the international geologic time scale the upper part of the quantou formation is the lower turonian the qingshankou formation is the upper turonian lower coniacian the yaojia formation is from the upper coniacian to middle santonian the nenjiang formation is the upper santonian to middle campanian the sifangtai formation is limited to the upper campanian and the mingshui formation is the uppermost campanian to maastrichtian it is likely that the upper part of the mingshui formation belongs to the paleocene and the k pg boundary is within the member 2 of the mingshui formation around the depth of 328 m by new micropalaeontologic and magnetostratigraphic data

reconstruction of short term palaeoceanographic changes during the formation of the late albian niveau breistroffer black shales oceanic anoxic event 1d se france the niveau breistroffer black shale succession in the vocontian basin se france is the regional equivalent of the widely distributed late albian oceanic anoxic event 1d the studied black shale rich interval at the col de palluel section is 6 28 m thick and comprises four black shale units with up to 2 5 wt total organic carbon toc intercalated with marlstones calcareous nannofossil palynomorph planktic foraminifera and stable isotopic data from the niveau breistroffer succession suggest that short term climate changes influenced its deposition with relatively warm and humid climate during black shale formation in comparison with relatively cool and dry climatic conditions during marlstone deposition an increase in the terrigenous marine ratio of palynomorphs indicates enhanced humidity and higher runoff during black shale formation a nutrient index based on calcareous nannofossils and the abundance pattern of small 63 125 m hedbergellid foraminifera show short term changes in the productivity of the surface water surface water productivity was reduced during black shale formation and increased during marlstone deposition a calcareous nannofossil temperature index and bulk rock oxygen isotope data indicate relative temperature changes with warmer surface waters for black shale samples at these times warm humid climate and reduced surface water productivity were accompanied by greater abundances of subsurface dwelling calcareous nannofossils nannoconids and planktic foraminifera rotaliporids these taxa presumably indicate more stratified surface water conditions we suggest that the formation of the niveau breistroffer black shales occurred during orbitally induced increase in monsoonal activity that led to increasing humidity during periods of black shale formation this in turn caused a decrease in low latitude deep water formation and probably an increase in surface water stratification the combination of these two mechanisms caused depleted o 2 concentrations in the bottom water that increased the preservation potential of organic matter

formation of holocene sedimentary laminae in the black sea and the role of the benthic flocculent layer holocene black sea sediments recovered in 1988 and 1993 from box cores and gravity cores were analyzed geochemically microscopically and with backscattered electron imagery bsei in order to determine the temporal geochemical and sedimentological relationships between the benthic flocculent layer often referred to as the fluff layer and the formation of underlying laminated unit i sediments existence of a permanent benthic fluff layer in the black sea basin is suggested acting as a geochemical transition layer within which all sedimentary particles are hydraulically sorted and particles subject to dissolution or organic remineralization are altered prior to accumulation we propose that particle residence time within the benthic fluff layer is a key factor in determining sedimentary microfabric and geochemical composition of laminated unit i sediments we present a schematic model depicting the above relationships and use it to propose a paleoflux scenario for laminae formation in the unit ii sapropel

mapping quaternary alluvial fans in the southwestern united states based on multiparameter surface roughness of lidar topographic data 1 quaternary alluvial fans have diverse surface morphologies related to both depositional and weathering processes numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition but only recently has there been an effort to utilize high resolution topographic data to differentiate alluvial fans by surface age with automated and quantifiable routines we developed a quantitative model for mapping the relative age of alluvial fan surfaces based on multiparameter surface roughness values computed from 1 m resolution lidar topographic data roughness is defined as a function of observational scale and integration of slope curvature and aspect topographic parameters alluvial fan roughness values were computed across multiple observation scales 3 3 m to 150 150 m based on the standard deviation sd of slope curvature tangential and aspect topographic parameters plots of roughness value versus size of observation scale suggest that the sd of each parameter over a 7 7 m observation window best identified the signature of surface roughness elements roughness maps derived from slope curvature and aspect at this scale were integrated using fuzzy logic the integrated roughness map was then classified into five relative morphostratigraphic surface age categories active wash to 400 ka and statistically compared with a similar fivefold surface age map of alluvial fans developed using traditional field surveys and aerial photographic interpretation the model correctly predicted the distribution and relative surface age of 61 of alluvial fan landforms based on traditional mapping techniques

use of multiparameter relative age methods for age estimation and correlation of alluvial fan surfaces on a desert piedmont eastern mojave desert california numerical and calibrated age determinations of the late quaternary alluvial fan deposits of the soda mountains piedmont in the mojave desert provide an opportunity to study the utility of the multiparameter relative age ra method for distinguishing and mapping geomorphic surfaces on a desert piedmont most ra parameters could not discriminate between deposits of holocene age although pavements have formed over locally significant parts of surfaces as young as middle holocene several parameters including lithologic composition particle size soil development and varnish cover permit distinguishing between holocene surfaces and late pleistocene surfaces statistically significant differences in initial particle size and lithology of the deposits inferred to be the result of complex interaction among hillslope alluvial fan and eolian processes and climatic change create conditions unfavorable for use of most ra techniques in contrast soil profile development and varnish cover data are successful in discrimination among deposits of holocene and pleistocene age this is attributed to the development of pedogenic features and varnish that are strongly dependent on dust influx and to the relatively minor dependence of these features on differences in the depositional character of the fan

mjolnir structure an impact crater in the barents sea a systematic search for impact indicators was conducted on a core of late jurassic early cretaceous sedimentary strata from the vicinity of the proposed mjolnir impact structure barents sea a 0 8 m thick section of the core was found to contain unequivocal indicators of meteoritic impact shocked quartz grains and a strong enrichment in iridium the ejecta bearing strata were discovered only 30 km north northeast of the structure within a stratigraphic interval corresponding to the seismically defined deformation event at mjolnir further study of this unusually well presented impact crater ejecta layer pair may help constrain poorly understood aspects of large magnitude meteorite impacts into the oceans 14 refs 4 figs

quantifying dust emissions from desert landforms eastern mojave desert usa abstract the measurement of natural dust emissions from desert landforms is crucial in environmental hazard assessment and field checking the accuracy of global dust models more than 500 individual dust measurements from eight common desert landforms in southern california were collected using the pi swerl portable in situ wind erosion lab the largest emitters of dust are dry washes 13 787 to 0 007 mg m 2 s 1 dunes playa margins distal alluvial fans and lacustrine beaches low emitters include salt crusted playas 0 692 to 0 002 mg m 2 s 1 silt clay crusted playas and desert pavements high emissions are a function of saltating sand that bombards the surface liberating dust sized particles for entrainment low dust emissions are primarily a function of surface crusting gravel armoring and vegetation density pi swerl measurements reveal that emission rates can vary by at least three orders of magnitude reflecting local variability in soil texture and continuity of surface crusts shear stress partitioning models can be applied to dust data measured by the pi swerl to account for large surface roughness features such as vegetation the results presented here give an approximation of the contributions to atmospheric dust loading by landforms in the mojave desert and can potentially be used to improve atmospheric dust models

marine incursion events in the late cretaceous songliao basin constraints from sulfur geochemistry records abstract songliao basin in ne china developed the most productive oilfield in the world sourced from terrestrial rocks the main source rock of the basin includes member 1 of the qingshankou k2qn1 and members 1 and 2 of the nenjiang formation k2nj1 2 however the exact reasons for the formation of the source rock especially the k2qn1 are still controversial former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of k2qn1 but further geochemical evidence is needed this paper explores the distinct sulfate levels that distinguish marine from fresh waters of the songliao paleo lake we undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the quantou formation k1q4 to top of member 1 of the qingshankou k2qn1 the ratio of organic carbon to the pyrite sulfur toc pys proved the previously suggested saline conditions during the deposition of k2qn1 and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for k2qn1 but also for top of k1q4 the exact time for the beginning of marine incursion is to be determined the marine incursion within k2qn1 is not strong and partially controlled by the fluctuation of paleo lake level the present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the songliao paleo lake although further studies are still needed

geomorphological controls on soil fertility of semi arid alluvial fans a case study of the joghatay mountains northeast iran abstract alluvial fans are ideal locations to examine the effect of geomorphic processes and landforms on the soil characteristics the rate of soil development and fertility differs between active surfaces exposed to aggradation and old or relict surfaces subject to degradation the aim of this research is to evaluate the effect of landforms and processes on soil fertility based on the studies on three alluvial fans of different ages relict old and young a total of 36 soil samples were collected from these three alluvial fan surfaces the samples were gathered from different locations of fans apex and toe and landforms gully beds interfluves swales and bars and for each sample nine variables including soil texture acidity ph electrical conductivity ec total neutralizing value tnv available phosphorus ap available potassium ak total nitrogen tn total organic carbon toc and hydraulic conductivity k were measured the results show that the values of tnv ap ak tn and toc increase as clay increases in the relict and old fans the values of tnv toc tn ap ak clay and silt are higher in the interfluves than in the gully beds also in the relict and old fans the rates of clay silt toc tn and ap are higher in the apexes than in the toes in the young fan the values of most variables are higher in the toe compared to the apex the wide and relatively flat interfluves of the apex of old and relict fans have soils that are more fertile compared to the extensively entrenched surfaces of relict and old fan toes with relatively steep sloped interfluves the less fertile soils in the apex of young fan can be attributed to its coarse textured soils and also to repeated flooding and depositional processes overall this study reveals that geomorphological landforms and processes such as aggradation and degradation play an important role in the spatial variation of soil fertility

moment tensor analysis of near field broadband waveforms observed at aso volcano japan abstract locations and focal mechanisms of long period volcanic events observed at aso volcano japan are determined by waveform inversion near field broadband three component seismograms of four to seven stations are simultaneously inverted in the time domain in order to find the six component seismic moment tensor a linear inversion is performed at each point of a 3d grid located under the volcano in order to constrain the centroid position and the focal mechanism of the source the complete displacements including near field waves in a homogeneous half space for a general point source are taken into account inversions of 43 long period tremors and six phreatic eruptions exhibit mainly an isotropic mechanism with a minor deviatoric component that may originate from a north south trending crack these events are all located in a small region at about 1 3 km depth beneath the active crater the high accuracy both of locations a few hundred meters and of focal mechanisms given by the inversion is partly attributed to the rapid variation of the amplitude of the static displacement seen in the long period part of the near field seismograms