climatic and tectonic signature in the fluvial infill of a late pliocene valley siena basin northern apennines italy abstract incised valleys entirely filled with fluvial deposits are rarely described in the literature and even rarer are accounts of incised valleys whose filling is not driven by relative sea level changes valleys of this type have not been widely recognized in the stratigraphic record because they are likely to occur in areas undergoing intense erosion or to be encased within alluvial deposits with no strong lithologic contrast in this paper an upper pliocene fluvial valley fill encased within shallow marine middle pliocene deposits and pre neogene bedrock eastern siena basin northern apennines italy and accumulated in response to tectonics and climate changes is described the recognition of this fluvial body up to 40 m thick in an incised valley setting is based on its overall geometry lithofacies characteristics gravel composition and fossil content upvalley fill is represented by amalgamated gravels emplaced by heavily sediment laden flows whereas downvalley fill shows a more organized depositional style and consists of two fining upward successions notable is the presence at the top of the lower succession of decameter thick floodplain fines which extend from one valley wall to another and have no fine grained correlatives in the upvalley fill valley incision resulted from a drop in relative sea level arising from late middle pliocene regional uplift stratigraphic and paleontological data constrain valley filling to the late pliocene early pleistocene time span such a filling stemmed from an increase in sediment supply which resulted from the interplay between uplift of the chianti ridge and a climatic change toward humid conditions as recorded in the coeval strata of the adjacent valdarno basin beyond the regional significance an important implication of the case study is that the incision and filling factors need not be genetically related moreover the stratigraphic architecture of the studied fluvial fill is discussed in terms of the relations between sediment supply and sediment storage en route from the source area to the depositional site and their association with tectonic movements specifically the valley wide floodplain fines are thought to record the response of the fluvial system to a tectonic rejuvenation of catchments which modified the valley gradient and promoted upstream gravel storage whereas the overlying gravels manifest the reestablishment of a new equilibrium river profile

astronomical calibration of the danian stage early paleocene revisited settling chronologies of sedimentary records across the atlantic and pacific oceans abstract astronomical tuning of sedimentary records to precise orbital solutions has led to unprecedented resolution in the geological time scale however the construction of a consistent astronomical time scale for the paleocene is controversial due to uncertainties in the recognition of the exact number of 405 kyr eccentricity cycles and accurate correlation between key records here we present a new danian integrated stratigraphic framework using the land based zumaia and sopelana hemipelagic sections from the basque basin and deep sea records drilled during ocean drilling program odp legs 198 shatsky rise north pacific and 208 walvis ridge south atlantic that solves previous discrepancies the new coherent stratigraphy utilises composite images from odp cores a new whole rock 13c isotope record at zumaia and new magnetostratigraphic data from sopelana we consistently observe 11 405 kyr eccentricity cycles in all studied danian successions we achieve a robust correlation of bioevents and stable isotope events between all studied sections at the 100 kyr short eccentricity level a prerequisite for paleoclimatic interpretations comparison with and subsequent tuning of the records to the latest orbital solution la2011 provides astronomically calibrated ages of 66 022 0 040 ma and 61 607 0 040 ma for the cretaceous paleogene k pg and danian selandian d s boundaries respectively low sedimentation rates appear common in all records in the mid danian interval including conspicuous condensed intervals in the oceanic records that in the past have hampered the proper identification of cycles the comprehensive interbasinal approach applied here reveals pitfalls in time scale construction filtering techniques in particular and indicates that some caution and scrutiny has to be applied when building orbital chronologies finally the zumaia section already hosting the selandian global boundary stratotype section and point gssp could serve as the global danian unit stratotype in the future

climate and biomes in the west mediterranean area during the pliocene a new pollen derived method of climatic quantification based on the mutual climatic range of plant taxa has been applied to 17 pliocene pollen sequences in the west mediterranean area the latitudinal gradient observed in the pollen data was confirmed by the climatic reconstructions there is a gradient from north to south both for temperatures and precipitation at the beginning of the pliocene 5 32 5 ma the climate in the north mediterranean area was on average warmer and more humid than today respectively 1 4oc and 400 700 mm in the south mediterranean region the climate was both warmer and drier than today respectively equal to or 5oc higher and drier or equal humidity the pollen based climate estimates were then used to reconstruct biomes for the region the results show the occurrence of three biomes the broad leaved evergreen warm mixed forest the xerophytic woods scrub biome and the warm grass shrub biome these biomes are still represented today in the mediterranean region despite different thermic and water conditions

untangling the palaeocene climatic rhythm an astronomically calibrated early palaeocene magnetostratigraphy and biostratigraphy at zumaia basque basin northern spain abstract the magnetostratigraphy of a 54 m long section above the cretaceous tertiary boundary at the sea cliff section of zumaia in the basque basin northern spain has been established the section encompasses the entire danian and the lower part of the selandian stages as indicated by calcareous plankton biostratigraphy the studied interval consists of hemi pelagic limestone marl alternations in the form of couplets and bundles which range from centimetre decimetre to metre scale respectively and a few thin bedded calcareous turbidites the magnetostratigraphy based on samples from about 200 stratigraphic levels allows the identification of six reversal boundaries from chron c29r to c26r at a bed level the spatial or temporal evolution of periodicities from a lithologically coded series is studied with the continuous wavelet transform technique a preliminary age model based on the standard ck95 gpts indicates that the basic lithologic carbonate marl couplet corresponds to the 19 23 kyr precession cycle 21 31 cm cycle in the depth domain and that a bundle cycle usually groups of four to six basic couplets with global periodicity centred at 1 22 m corresponds to the 110 kyr eccentricity cycle we have tuned the bundle cycles to the va03 r7 eccentricity orbital solution astrophys j 592 2003 620 630 following an initial match of a node of the 2 4 ma eccentricity modulatory cycle in the target time series to particularly carbonate rich bundles from the upper part of the zumaia section that displays significant power of a 4 4 m period cycle corresponding to the 404 kyr eccentricity cycle consistency between lithologic patterns and characteristics in the eccentricity target is reasonably met although the 404 kyr eccentricity cycle is not persistent throughout the tuning however appears robust as it brings the age of the k t boundary at 65 8 ma it is argued that a sea level signal tectonically driven is superimposed on the climatic forcing at the milankovitch band masking the full expression of the low frequency astronomical periods we provide a cycle tuned duration for all intervening early palaeocene polarity chrons and estimate relative ages for bioevents the cycle tuned chronology indicates that the ck95 gpts overestimates the duration of chrons c28 and c27 by 20 and 26 respectively our data may prove useful to better constrain early palaeocene biostratigraphy of calcareous plankton and in the redefinition of the boundary between the danian and selandian stages

joint petrophysical and structural inversion of electromagnetic and seismic data based on volume integral equation method a joint petrophysical and structural inversion method for electromagnetic em and seismic data based on the volume integral equation vie is proposed in this paper in the forward em problem only the contrast of conductivity is solved by the electric field integral equation method however in the forward seismic problem both the contrasts of velocity and mass density are solved by the combined field vie method both forward solvers are accelerated by the fast fourier transform in the inversion problem by using the petrophysical equations about the porosity and saturation and applying the chain rule we fuse the em and seismic data and construct the joint petrophysical inversion equations which can be solved by the variational born iteration method then in order to further enhance the reconstructed results of the joint petrophysical inversion we enforce the structural similarity constraint between porosity and water saturation and add the cross gradient function to the joint petrophysical inversion cost function two typical geophysical models based on the remote sensing measurement are used to validate the proposed methods one is the cross well model and the other is the marine surface exploration model the advantage of the joint inversion compared with the separate inversion is evaluated based on the resolution and the data misfits of the reconstructed profiles as well as the antinoise ability

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

closing the mid palaeocene gap toward a complete astronomically tuned palaeocene epoch and selandian and thanetian gssps at zumaia basque basin w pyrenees abstract an integrated magneto bio and cyclostratigraphic framework is presented for the mid palaeocene interval from the hemi pelagic sea cliff section of zumaia in the basque basin the new 55 m long studied section expands about 3 5 myr and closes the gap between previously published integrated studies in the section the occurrence of magnetochron c26n is now documented and its duration complemented also by data from the ibaeta section and that for chrons c26r and c25r is estimated by counting precession related lithologic couplets assigned to have 21 kyr duration c25r 1449 kyr c26n 231 kyr c26r 2877 kyr consequently the zumaia section now provides the first complete palaeocene astronomically derived chronology rendering this section a master reference section due to limitations in the orbital calculations and uncertainties in the radiometric dating method no robust tuning and absolute ages can be given for the moment however the fos first occurrences of key calcareous plankton species and the mid palaeocene biotic event mpbe are placed within the magnetostratigraphic and cyclostratigraphic template along the studied mid palaeocene interval in addition the dataset provides the key elements for a proper settling of the thanetian and selandian global stratotype section and point gssps which is one of the primary objectives of the ics international commission of stratigraphy we consider the base of chron c26n and the criteria associated to the lithostratigraphic change between the danian limestone fm and the itzurun marl fm at zumaia as the respective delimiting points for the thanetian and selandian bases as recently agreed by the paleocene working group of the international subcommission of the paleogene stratigraphy of the ics consequently the duration of the thanetian selandian and danian component stages can be estimated at zumaia to be about 3129 kyr 2163 kyr and 4324 kyr respectively see text for error considerations however the mpbe located 8 precession cycles below the base of c26n in correspondence to a short eccentricity maxima at zumaia could also serve as a guiding criteria to approximate or redefine the thanetian base if this level demonstrated synchronous

oceanographic and climatic implications of the palaeocene carbon isotope maximum we have compared detailed planktonic and benthonic foraminiferal carbon and oxygen isotope records from the palaeocene and early eocene successions at dsdp site 577 shatsky rise north pacific a composite section derived from dsdp leg 74 sites walvis ridge south atlantic and a composite section from odp leg 113 sites maud rise weddell sea the 13c records of palaeocene and early eocene foraminifera at site 577 and the leg 74 sites show that an increase in 13c values in surface waters at 64 ma end of zone p1 resulted in increased vertical carbon isotope gradients 13c between surface and deeper dwelling planktonic foraminifera and between surface dwelling planktonics and benthonic foraminifera which became progressively steeper until the iniddle late palaeocene zone p4 this steepening also occurs in the latest palaeocene of the composite leg 113 section and can be explained by an increase in surface ocean productivity this increase in productivity probably resulted in an expansion of the oxygen minimum zone omz benthonic 13c values increased during the late palaeocene in site 577 and the composite leg 74 section suggesting that the palaeocene carbon isotope maximum was composed of both within ocean reservoir increased surface water productivity and between reservoir organic carbon burial ftactionation effects the benthonic 13c increase lags the surface ocean 13c increase in the early palaeocene 63 64 ma suggesting that surface water productivity increase probably led an increase in the burial rate of organic carbon relative to carbonate sedimentation moreover inter site 13c comparisons suggest that the locus of deep to intermediate water formation for the majority of the palaeocene and the earliest eocene was more likely to have been in the high southern latitudes than in the lower latitudes oxygen isotope data show a decline in deeper water temperatures in the early and early late palaeocene followed by a temperature increase in the late palaeocene and across the palaeoceneeocene boundary we speculate that these changes in deeper water temperatures were related to the flux of co2 between the oceans and the atmosphere through a mechanism operating at the high southern latitudes

a hybrid 3 d electromagnetic method for induction detection of hydraulic fractures through a tilted cased borehole in planar stratified media as one of the most important nondestructive characterization techniques electromagnetic em methods can be used in the subsurface fracture detection especially for hydraulic fracture evaluation in unconventional petroleum exploration and development the multiscale nature of long but extremely thin 3 d fractures is difficult for conventional em modeling methods such as the finite element method fem in numerical simulation the problem becomes even more challenging when the effects of tilted borehole casing and planar stratified media need to be considered so far modeling a tilted borehole in layered media is still a major challenge for conventional methods in this paper we present the hybrid numerical mode matching method with the stabilized biconjugate gradient fast fourier transform method as the forward modeling algorithm that can efficiently model 3 d fractures in planar stratified media with a cased borehole environment numerical results validate the accuracy of the hybrid forward method and show orders of magnitude higher efficiency of this forward solver than the fem

the tyrrhenian apennines system structural setting and seismotectogenesis abstract the available geological geophysical and seismological data of the tyrrhenian apennines system are briefly reviewed and synthesized in a number of sketch maps integrating and comparing these data a large scale simple shear kinematic model is proposed for the tyrrhenian apennines system that is here interpreted as an oblique asymmetric passive continental margin developed during the progressive counterclockwise rotation of the adriatic foreland from the late miocene to the present in the frame of this working hypothesis the thinning and stretching of the tyrrhenian crust were accommodated by progressive eastward motion of extensional allochthonous slices bounded by low angle west dipping oblique shear zones rotating above a common detachment that penetrates into the mantle lithosphere at any given time the most external eastward moving slice is bounded by a transtensional shear zone at the top and by a transpressional one at the bottom the displacement within the hanging wall of the transtensional shear zone is accommodated by high angle normal faults and en echelon grabens the displacement within the hanging wall of the transpressional shear zone is instead accommodated by co axial en echelon sets of folds thrusts and high angle strike slip faults thus the development of the late miocene pliocene pleistocene contractional strain field of the apennines of italy might not be a consequence of complex subduction processes but subordinate to the deformation processes that lead to the progressive opening of the tyrrhenian sea the seismicity of the crustal apennines of italy is analyzed in the frame of the above history of progressive deformation and a seismotectogenetic model is outlined

reconstruction of high contrast proppant in hydraulic fractures with galvanic measurements hydraulic fracturing is a technique to fracture rocks by pumping high pressure fluid into a segment of a well the created fractures help to release a hydrocarbon resource such as oil or natural gas from the rock a group of small scaled fracturing field tests are performed by the advanced energy consortium to investigate the feasibility of using the galvanic electromagnetic em method to map fractures the injected proppants are designed with high em contrasts e g conductivity and permittivity to generate detectable signals at electrode type sensors to map the created fractures an efficient 3 d em inversion method is introduced to simultaneously reconstruct conductivity and permittivity profiles in fractures first to test the capability of the inversion solver and the designed experimental setting for successful fracture mapping the noise polluted synthetic data are used to reconstruct the fracture on a theoretical model it shows that the designed experimental setting can be used to map the fracture and the inversion solver is able to reconstruct the fracture in both conductivity and permittivity the inversion method is then applied to two hydraulic fracturing field tests with injected high contrast proppants loresco coke breeze and steel shot the fracture conductivity and permittivity are reconstructed based on the voltage signals difference between the postfracturing and prefracturing data the reconstructed fracture profiles are compared with the coring samplings to show the reliability of the inversion results their good agreement demonstrates that the experimental setting and the galvanic inverse solver are able to estimate the fracture size and location reliably

paleocene oceanography of the eastern subtropical indian ocean an integrated magnetobiostratigraphic and stable isotope study of odp hole 761b wombat plateau surface and deep water circulation patterns in the eastern indian ocean during the paleocene epoch are inferred based on an integrated magnetobiostratigraphic and stable isotope investigation of ocean drilling program hole 761b drilled on the wombat plateau a combination of magnetostratigraphy biostratigraphy and isotope stratigraphy demonstrates that numerous deep sea sites that have been considered to show continuous or nearly continuous sedimentation through the paleocene are punctuated by a series of hiatuses some of which exceeding a duration of 1 myr therefore our study is based on a detailed temporal interpretation of the stratigraphic successions we used for paleoceanographic reconstructions we compare detailed planktonic and benthic foraminiferal carbon and oxygen isotope records from hole 761b with several temporally correlative records published from different oceanic provinces in order to distinguish between local and global patterns within the eastern indian ocean although site 761 was situated at low latitudes during the paleocene its surface waters were predominantly influenced by circulation originating from the southern ocean as indicated by inferred cool sea surface temperatures and reduced surface to deep water temperature gradients we suggest that deep waters in the eastern indian ocean were not directly fed by the southern or tethys oceans rather the more negative n 13 c composition of the bottom waters recorded by benthic foraminifera implies the presence and or active contribution of aged deep waters from the pacific during this time at least prior to v60 2 ma and subsequent to v59 0 ma the indian continent ninetyeast ridge kerguelen plateau and broken ridge may have played a significant role as submarine barriers to deep water circulation during the paleocene 2002 elsevier science b v all rights reserved

hole to surface resistivity measurements hole to surface resistivity measurements over a layered volcanic tuff sequence illustrate procedures for gathering reducing and interpreting hole to surface resistivity data the magnitude and direction of the total surface electric field resulting from a buried current source is calculated from orthogonal potential difference measurements for a grid of closely spaced stations a contour map of these data provides a detailed map of the distribution of the electric field away from the drill hole resistivity anomalies can be enhanced by calculating the difference between apparent resistivities calculated from the total surface electric field and apparent resistivities for a layered earth model lateral discontinutities in the geoelectric section are verified by repeating the surface field measurments for current sources in several drill holes a qualitative interpretation of the anomalous bodies within a layered earth can be made by using a three dimensional 3 d resistivity model in a homogeneous half

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

the palaeocene top chron c27n transient greenhouse episode evidence from marine pelagic atlantic and peri tethyan sections terra nova 24 477 486 2012 abstract the early cenozoic which is punctuated by several negative carbon isotope excursions cies was a time of climatic and oceanographic transition from greenhouse to icehouse conditions the occurrence of a 0 5 cie starting at the top of chron c27n tc27n is reconfirmed with stable isotope data from zumaia spain and bjala bulgaria localities spectral analysis on respective carbonate magnetic susceptibility proxy records substantiates the orbital cyclostratigraphy allowing correlation to a high resolution benthic foraminifera isotope record from odp pacific site 1209 that indicates a coeval 2 c transient warming the hyperthermal event lasts 200 ka contrasting with other short lived events from the eocene and displays a relatively rapid onset and a longer tailing back to pre event values similar to the palaeocene eocene thermal maximum petm though lower in amplitude that a causal trigger for the tc27n event may be the onset of volcanism in the north atlantic igneous province naip can be inferred from a 200 m thick lava pile erupted during c27n c26r polarity transition in the e greenland margin

astronomical calibration of the paleocene time the first complete cyclic sedimentary successions for the early paleogene from drilling multiple holes have been retrieved during two odp expeditions leg 198 shatsky rise nw pacific ocean and leg 208 walvis ridge se atlantic ocean these new records allow us to construct a comprehensive astronomically calibrated stratigraphic framework with an unprecedented accuracy for both the atlantic and the pacific oceans covering the entire paleocene epoch based on the identification of the stable long eccentricity cycle 405 kyr high resolution x ray fluorescence xrf core scanner and non destructive core logging data from sites 1209 through 1211 leg 198 and sites 1262 1267 leg 208 are the basis for such a robust chronostratigraphy former investigated marine odp sites 1001 and 1051 and land based e g zumaia sections have been integrated as well the high fidelity chronology is the prerequisite for deciphering mechanisms in relation to prominent transient climatic events as well as completely new insights into greenhouse climate variability in the early paleogene we demonstrate that the paleocene epoch covers 24 long eccentricity cycles we also show that no definite absolute age datums for the k pg boundary or the paleocene eocene thermal maximum petm can be provided by now because of still existing uncertainties in orbital solutions and radiometric dating however we provide two options for tuning of the paleocene which are only offset by 405 kyr our orbitally calibrated integrated leg 208 magnetostratigraphy is used to revise the geomagnetic polarity time scale gpts for chron c29 to c25 we established a high resolution calcareous nannofossil biostratigraphy for the south atlantic which allows a much more detailed relative scaling of stages with biozones the re evaluation of the south atlantic spreading rate model features higher frequent oscillations in spreading rates for magnetochron c28r c27n and c26n

paleoenvironmental change at the danian selandian transition in tunisia foraminifera organic walled dinoflagellate cyst and calcareous nannofossil records abstract in the present study we document paleoenvironmental change across the danian selandian transition planktic foraminiferal interval p2 p3b calcareous nannofossil zone np4 subzones ntp6 ntp8a 61 59 ma in nw tunisia diversifications of paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages morozovella acarinina and igorina and of the biostratigraphically important nannofossils genus fasciculithus are recorded within this interval the present study aims to understand early paleogene environmental changes in the southern tethys by analyzing the evolution of surface water and to a lesser extent seafloor conditions three localities were investigated ain settara elles and el kef all representing outer neritic deposition in the same basin the tunisian trough paleoenvironmental changes are explored by combining planktic foraminiferal organic dinocyst and calcareous nannofossils assemblages and several proxy parameters planktic benthic ratio numbers of planktic foraminifera per gram peridinioid gonyaulacoid ratio terrestrial marine palynomorph ratio in addition also some geochemical parameters calcite content and stable isotopes are examined our records indicate that the environment evolved from an initially oligotrophic open marine deep outer neritic setting in p2 p3a towards a shallower and nutrient rich setting from the base of subzone p3b this change is seen in the foraminiferal assemblages with the substitution of praemurica by morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa also the organic dinocyst assemblages show a peak of peridinioid cysts cerodinium and lejeunecysta associated to these dinocyst assemblages the lowest occurrence of apectodinium is recorded which seem to have evolved in this region possibly in response to enhanced nutrient levels on the shelf additionally a distinct change in calcareous nannofossil assemblages is also described marked by the lowest appearance of chiasmolithus edentulus the lowest consistent occurrence of fasciculithus and a slight increase in near shore taxa essentially pontosphaera this project provides an accurate understanding of paleoenvironmental change across the danian selandian transition in tunisia especially integrating different proxies demonstrates a paleobathymetric shallowing from the danian to the selandian associated to increase surface paleoproductivity furthermore the results are compared with those from other localities along the southern tethyan margin egypt and jordan and a more regional paleoclimatic paleoceanographic perturbation in the southern tethys is suggested

a complete high resolution paleocene benthic stable isotope record for the central pacific odp site 1209 1 we have compiled the first stratigraphically continuous high resolution benthic foraminiferal stable isotope record for the paleocene from a single site utilizing cores recovered at pacific odp site 1209 the long term trend in the benthic isotope record suggests a close coupling of volcanic co2 input and deep sea warming over the short term the record is characterized by slow excursions with a pronounced periodic beat related to the short 100 kyr and long 405 kyr eccentricity cycle the phase relationship between the benthic isotope record and eccentricity is similar to patterns documented for the oligocene and miocene confirming the role of orbital forcing as the pace maker for paleoclimatic variability on milankovitch time scales in addition the record documents an unusual transient warming of 2 c coeval with a 0 6 carbon isotope excursion and a decrease in carbonate content at 61 75 ma this event which bears some resemblance to eocene hyperthermals marks the onset of a long term decline in 13c the timing indicates it might be related to the initiation of volcanism along greenland margin

paleoenvironmental evolution of the pliocene villarroya lake northern spain a multidisciplinary approach abstract the pliocene villarroya basin fill consists of lacustrine and alluvial deposits over 100 m thick the lacustrine deposits up to 30 m thick comprise three sequences the two lower sequences consist of profundal laminated deposits formed by mostly terrigenous facies that are overlain by charophytic carbonates and varves the uppermost third sequence made up of massive bioturbated mudstones corresponds to a very shallow lacustrine palustrine environment bulk mineralogy comprises carbonates clay minerals quartz and feldspars the carbonates are exogenic biogenic calcite and biogenic aragonite biogenic calcite constitutes ostracod shells and charophyte stem encrustations whereas aragonite forms gastropod shells and in some varve intervals charophyte encrustations the clay minerals are illite kaolinite palygorskite chlorite and paragonite which are inherited from source rocks and smectite and interstratified clays which are probably formed in the soils of the source area variations in clay mineralogy reflect the interplay between the climate tectonic rejuvenation and the paleogeography of the basin the pollen assemblages indicate significant variations in climate a first phase of varying climate was followed by cool temperate and sub humid phases that culminated in a temperate and dry episode which is recorded in the lower part of the second lacustrine sequence this was succeeded by a marked warm and humid episode which may be correlated with the mid pliocene warmth about 3 0 ma and the subsequent cooling phase which is recorded in the upper third sequence in the two lower sequences profundal lacustrine deposits ostracods indicate oligosaline to mesosaline waters with salinity variations and some warm and na cl episodes molluscs are characterized by hydrobiids suggesting a salinity stress in the upper palustrine deposits the ostracods and aquatic mollusc assemblages indicate fresh cold waters faunal records indicate that changes in salinity do not correlate with climate suggesting phases of significant saline inputs to the lake which were recorded in the lower first sequence and in the upper part of the second sequence the lacustrine sequence of villarroya record pronounced variations in climate and in the lacustrine environment however there are no consistent relationships between the climate conditions inferred from the pollen data and the sedimentary record of the environmental changes showing that other factors especially tectonics have exerted an influence on the paleoenvironmental evolution and on the sedimentary record of the pliocene villarroya lake

on the duration of the paleocene eocene thermal maximum petm 1 the paleocene eocene thermal maximum petm is one of the best known examples of a transient climate perturbation associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle from injection of isotopically light carbon into the ocean atmosphere system one key to quantifying the mass of carbon released identifying the source s and understanding the ultimate fate of this carbon is to develop high resolution age models two independent strategies have been employed cycle stratigraphy and analysis of extraterrestrial helium heet both of which were first tested on ocean drilling program odp site 690 these two methods are in agreement for the onset of the petm and initial recovery or the clay layer main body but seem to differ in the final recovery phase of the event above the clay layer where the carbonate contents rise and carbon isotope values return toward background values here we present a state of the art age model for the petm derived from a new orbital chronology developed with cycle stratigraphic records from sites drilled during odp leg 208 walvis ridge southeastern atlantic integrated with published records from site 690 weddell sea southern ocean odp leg 113 during leg 208 five paleocene eocene p e boundary sections sites 1262 to 1267 were recovered in multiple holes over a depth transect of more than 2200 m at the walvis ridge yielding the first stratigraphically complete p e deep sea sequence with moderate to relatively high sedimentation rates 1 to 3 cm ka where a is years a detailed chronology was developed with nondestructive x ray fluorescence xrf core scanning records on the scale of precession cycles with a total duration of the petm now estimated to be 170 ka the revised cycle stratigraphic record confirms original estimates for the duration of the onset and initial recovery but suggests a new duration for the final recovery that is intermediate to the previous estimates by cycle stratigraphy and heet

palaeocene oceans and climate an isotopic perspective abstract the early cenozoic was a time of climatic and oceanographic transition from the cretaceous greenhouse world to the icehouse world of the neogene 18 o measurements shed light on ocean temperature and possible polar ice fluctuations during this interval while 13 c measurements monitor fluctuations in ocean productivity deep water circulation and atmospheric co 2 the major features from 18 o analysis of the early cenozoic are general cooling of surface waters with some evidence for transient cooling across the k t boundary surface water temperatures were at a cenozoic maximum in the early eocene whereas deep waters cooled then warmed during the palaeocene the 13 c of bulk carbonates is at a minimum at the start of the cenozoic due to the profound crisis in ocean surface water productivity associated with the extinctions of marine plankton at the cretaceous tertiary boundary thereafter 13 c values increase in bulk carbonates as well as planktonic and benthonic foraminifera to their cenozoic maximum in the late palaeocene c 60 ma after which time they again decrease over an interval of c 4 5 m y to a cenozoic low in the early eocene the increase in 13 c values characteristic of the palaeocene period is probably related to a combination of increasing surface water productivity and accelerated burial of organic carbon conversely the decline in 13 c into the early eocene is probably related to a decrease in ocean productivity and a deceleration in the rate of organic carbon burial benthic 13 c comparisons suggest that deep waters appear to have been predominantly formed in the high southern latitudes with the exception of a short lived interval near the palaeocene eocene boundary possibly associated with a transient climatic anomaly the late palaeocene thermal maximum the thermal change of palaeocene deep waters may be related to the changing productivity of surface waters by controlling atmospheric co 2 flux in a similar way to that proposed for the control of the pleistocene glacial cycles

aragonite laminae in hot water travertine crusts rapolano terme italy small 5 30 m aggregates of aragonite needles occur in calcite crystal crusts of present day hot water slope travertines at rapolano terme in tuscany italy the aggregates are mainly concentrated in irregular wispy and dark laminae which cross cut calcite crystal feathers to create a pervasive millimetre scale banded appearance in the deposit they also occur less commonly scattered irregularly through the calcite layers the aragonite needle aggregates are in the form of crosses fascicles sheaf shaped bundles or dumbbell shaped rosettes and spherulites locally irregular masses of needles also occur the fascicles rosettes and spherulites have hollow centres which resemble microbial components fungal spores bacterial colonies and pollen suggesting that the aragonite crystals are biotically nucleated the lamination is interpreted to reflect diurnal control stimulation of microbial activity during daylight concentrates cells in laminae and promotes aragonite calcification calcite feather crystals although traversed by the aragonite aggregate laminae have a clear appearance under the light microscope they form more or less continuously through the diurnal cycle by abiotic precipitation the constant association of aragonite with organic nuclei irrespective of whether the latter are in laminae or scattered through the calcite layers supports a biotic control on aragonite formation lamination in pleistocene travertines is superficially similar to that in the present day deposits but is diagenetically altered in the pleistocene deposits the calcite feathers appear dark under the light microscope and the aragonite aggregates where they are not altered to dark calcite are dissolved together with parts of the adjacent spar calcite and therefore appear light coloured

archean granite greenstone tectonics at kolar south india interplay of diapirism and bulk inhomogeneous contraction during juvenile magmatic accretion 1 the structural study of the kolar greenstone belt and surrounding granite gneiss terrains combined with u pb dating reveals that the middle and lower crustal tectonoplutonic pattern of the eastern dharwar craton developed during a major magmatic accretion event between 2550 and 2530 ma the granite greenstone pattern resulted from the interference of gravity driven sagging of the greenstones i e diapirism e w bulk inhomogeneous shortening combined with horizontal n s stretching and syntectonic juvenile pluton emplacement bulk inhomogeneous contraction is accommodated by the synchronous development of a pervasive n s trending vertical foliation shallow stretching lineation and conjugate strike slip shear zone pattern within and outside the greenstone belt resulting in regional horizontal pure shear deformation the plutons around the greenstone belt record regional contraction by developing one set of strike slip c s fabrics of the shear zone pattern the development of the granite greenstone pattern was coeval and compatible with deformation during juvenile magmatic accretion melting and granulite metamorphism in the lower crust the kolar example points to a specific crustal rheology that allowed sagduction of the greenstones and regional distributed bulk inhomogeneous strain due to mechanical homogeneity and low viscosity provided by large scale melting during the accretion event this example further suggests specific boundary conditions to the craton that allowed e w inhomogeneous shortening to be accommodated by n s stretching and spreading of the crust without significant tectonic thickening such tectonoplutonic pattern is specific to the archean and may develop as a consequence of mantle plume activity in intracontinental settings

origin and diagenesis of quaternary travertine shrub fabrics rapolano terme central italy millimetre to centimetre sized arborescent shrub like calcite precipitates are common constituents of hot water travertine shallow pool deposits of quaternary age at rapolano terme tuscany italy in the presently forming travertines the shrubs consist of apparently random associations of i micrite aggregates and ii subhedral to euhedral rhombic spar crystal aggregates in thin section the micrite aggregates appear dark and the spar rhomb aggregates light giving the shrubs a mottled appearance travertines are basically produced by caco3 precipitation due to degassing and evaporation of the spring waters although biological influence may also stimulate precipitation the formation of masses of erect shrubs rather than dense crystal crusts that form on slopes is probably due to limited water flow in the pool environments microbes including bacteria and diatoms are important influences on shrub microfabric and external shape the micrite aggregates are associated with bacteriform bodies seen as tiny rods and spheres the micrite precipitates around these bodies and in adjacent biofilm spar rhomb precipitation appears to be external to the biofilm and may be related to the presence of diatoms which are locally closely associated with the spar rhombs although an essentially inorganic origin particularly for the more euhedral rhombs cannot be ruled out in the older quaternary travertines the original microfabric of the shrubs has been diagenetically altered the original mottled appearance of the shrubs has become uniformly dark and micritic and the evidence for the dual micritic and spar rhomb origin of the shrubs is obscured or destroyed spar micritization of the shrubs is probably due to abiotic and locally biotic dissolution previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity

cover thrust reactivations related to internal basement involvement during neogene quaternary evolution of the northern apennines up to recently the neogene quaternary evolution of the northern apennines italy has been described by the classic model of a migrating eastward compressive external front with an extensional regime in the back areas connected with the tyrrhenian basin formation however in the last few years new structural data have been collected in the internal marine and continental episutural basins and in the external exposed thrust belt a complex structural evolution has now been reconstructed with coeval main tectonic phases that affect both areas with stress field change four main tectonic phases have been identified since late tortonian times these are dated as messinian late pliocene middle and late pleistocene the thrust belt has a complex evolution detected in a wide external area of the chain after the first emplacement of the main thrust sheets with reactivations and out of sequence thrusting these reactivation phases fit very well with the compressive phases affecting the sediments of the internal basins suggesting a direct relationship within a single evolutive model the increased knowledge of the deep structure of the northern apennines through geophysical and subsurface data acquired in the last few years indicates the basement involvement at least for the internal side of the northern apennines this basement involvement also played an important role in the tectonic evolution of the external sector of the apennines in this paper a new model is proposed that integrates field data geophysical evidence and geodynamic constraints the thrust reactivations and the out of sequence structures of the external area are related to internal crustal thrust activity the deformed sediments of the neogene quaternary basins are dating the thrust activity all the evidences point to a late neogene rejuvenation of the tectonic evolution but some inferences can be drawn on the development of the foredeep

sedimentary response to paleocene eocene thermal maximum carbon release a model data comparison possible sources of carbon that may have caused global warming at the paleocene eocene boundary are constrained using an intermediate complexity earth system model confi gured with early eocene paleogeography we fi that 6800 pg c 13 c of 22 is the smallest pulse modeled here to reasonably reproduce observations of the extent of seafl oor caco 3 dis solution this pulse could not have been solely the result of methane hydrate destabilization suggesting that additional sources of co 2 such as volcanic co 2 the oxidation of sedimentary organic carbon or thermogenic methane must also have contributed observed contrasts in dissolution intensity between atlantic and pacifi c sites are reproduced in the model by reduc ing bioturbation in the atlantic during the event simulating a potential consequence of the spread of low oxygen bottom waters

architecture of fluvial dominated valley fill deposits in the cretaceous fall river formation the fall river formation is a 45 m thick layer of fluvial dominated valley fills and shore zone strata deposited on the stable cratonic margin of the cretaceous western interior seaway fall river deposits in red canyon in the south west corner of south dakota usa expose a cross section of a 3 5 km wide valley fill sandstone and laterally adjacent marine deposits the marine deposits comprise three 10 m thick upward shoaling sequences each composed of multiple metres thick upward coarsening successions the lower two of these sequences are laterally cut by the valley fill sandstone and are capped by metres thick muddy palaeosols the upper sequence spans the top of the valley fill sandstone and is overlain by the skull creek shale the 30 m thick valley sandstone is partitioned into four distinct fills by major erosion surfaces and each of these fills contain many metres thick channel form bodies deposits in the lower parts of these fills are sheet like top truncated channel bodies whereas deposits in the upper parts of fills are upward concave laterally amalgamated channel bodies more completely preserved heterolithic channel bodies or wave deposited sheets each valley fill basal erosion surface records an episode of valley incision and relative sea level fall and the gradual progression from fluvial to more estuarine deposits upwards within each fill records relative sea level rise all fills are dominantly channel deposits and are capped by marine flooding surfaces the dominance of channel deposits the gradual change to more estuarine facies in the upper parts of fills and the location of flooding surfaces at valley fill tops all suggest that sediment supply initially kept pace with relative sea level rise and valleys filled during late marine lowstand and transgression not during subsequent highstands recently proposed facies models have focused on variations in the relative strength of tide wave and river currents as controls on valley fill deposits however relative rates of sediment supply and basin accommodation change and the shift in this ratio along the depositional profile during multiple scale cycles in relative sea level are equally important controls on the style of valley fill deposits

paleoceanographic changes across the latest danian event in the south atlantic ocean and planktic foraminiferal response abstract a number of short warming events occurred during paleocene and eocene of which the paleocene eocene thermal maximum petm 56 ma is the most severe and most investigated event the less known latest danian event lde at 62 2 ma represents a 200 ky lasting warming phase superimposed on a long term cooling trend after the early paleocene south atlantic odp site 1262 data covering 1 myr indicate a warming of the entire water column by 1 5 2 6 c accompanying a prominent negative carbon isotope excursion 0 9 1 1 and a long term re organization of the planktic foraminiferal fauna associated with the lde this study unravels a different paleoceanographic evolution of the upper ocean structure compared to results from pacific odp site 1210 unlike the pacific the atlantic site lacks an apparent change of stratification as well as an overall dominance of thermocline dwelling planktic foraminifera species and a low abundance of surface dwelling photosymbiotic foraminifera within the lde indications for a slightly enhanced stratification of the upper water column and transient warming were indicated when surface dwelling planktic foraminifera became temporarily more abundant the long term evolution in planktic foraminifera with the disappearance of praemurica at the lde onset and a contemporaneous rise in morozovella is similar to the trends reported from shatsky rise odp site 1210

three dimensional mise a la masse modeling applied to mapping fracture zones a numerical scheme applying the method of volume integral equations has been developed for borehole to borehole and borehole to surface modeling of the apparent resistivity response of a thin conductive body in a half space the inhomogeneity simulates a fracture zone in a geothermal system the algorithm is applicable for the direct current case when the buried electrode is either inside mise a la masse or outside near miss the body in implementing the scheme the integral equation is transformed into a matrix equation as a result of discretizing the inhomogeneity into rectangular cells all physical properties are assumed constant within each cell the rectangular cells are used through out execution of the algorithm the computed surface and subsurface apparent resistivity responses are examined for bodies of similar shape and size but with different orientations 1 vertical 2 horizontal 3 dipping at 60 degrees and 4 dipping at 30 degrees the four bodies produce apparent resistivity cr

extension and compression in the northern apennines italy hinterland evidence from the late miocene pliocene siena radicofani basin and relations with basement structures 1 the northern apennines na hinterland area is characterized by a complex neogene quaternary tectonics where both crustal extension associated with the tyrrhenian basin opening and crustal shortening in the onshore area took part in the deformation analysis of synorogenic deposits preserved in the nnw trending siena radicofani basin srb extending along a large part of the na hinterland documents the evolution of deformation of this sector during the last 9 ma information from subsurface geology deep seismic lines commercial seismic lines and deep wells surface geology mapping and structural analysis and from analogue modeling was integrated and used to infer the tectono sedimentary history of the srb and its relation with structures in the substratum as well as the possible implications for the evolution of the na hinterland the results we obtain indicate that the srb and the adjoining hinterland basins were bounded by thrust anticlines controlling basin development and deformation seismic lines across the srb display various examples of compressional structures affecting the basin fill and the substratum such as thrust anticlines and reverse faults notably these basin scale structures exhibit a good correlation with those observed in the field and are consistent with the kinematics of the outcrop scale compressional structures the thrust anticlines bounding the basins are often cored by triassic evaporites burano formation suggesting that this weak layer decoupling the sedimentary cover from the underlying crystalline basement controlled their evolution in this circumstance three series of scaled brittle ductile physical models have been used to investigate the development of a basement cover system with a decollement ductile layer at the base of the sedimentary cover these models simulate the evolution of the northern apennines hinterland where the basement is involved in the thrusting and the sedimentary cover is shortened above a basal ductile layer given by the burano formation longitudinal models cross sections display similar deformation patterns to those observed in the na hinterland such as characteristic wavelength of both basement and cover structures as well as detachment and fault propagation folding in the cover extensional tectonics is instead found to control sedimentation in the southern part of the srb at 8 ma or representing recent deformation the older extensional event is here related to the forelandward propagation of tyrrhenian related extension that could reactivate suitably oriented basement thrusts transfer zones produced a differential propagation of extension such that along strike sectors of the hinterland were eventually deformed by different stress fields analysis of the srb and of other adjoining basins reveals that the na hinterland experienced alternated periods of forward and backward migration of the compression extension transition in our interpretation the competition between extension and compression in the hinterland is related to the nnw directed africa pelagian indentation responsible for the lateral extrusion of the na and the contemporaneous opening of the tyrrhenian basin in the inner zone increased marginal loading at the foreland promoting reactivation of hinterland thrusts may have influenced this process as well

latest cretaceous paleocene deep sea ostracode fauna at iodp site u1407 western north atlantic with special reference to the cretaceous paleogene boundary and the latest danian event abstract during the paleocene the marine plankton community recovered its diversity after a severe diversity loss at the cretaceous paleogene k pg boundary in general changes in paleocene deep sea ostracode faunas are poorly understood it is still unclear how the deep sea ostracode faunas changed during compelling events such as the k pg boundary 66 04 ma and the latest danian event lde 62 18 ma a transient paleocene warming event in this report we describe a study on the latest cretaceous late paleocene ostracodes from integrated ocean drilling program site u1407 off newfoundland in the northwestern atlantic thirty six ostracode taxa were obtained from 202 discrete samples that were collected from the interval between 66 3 and 57 3 ma near the k pg boundary 8 2 of 25 of the maastrichtian taxa became extinct the extinction rate is estimated to be at most 0 12 e msy 1 which is equal to extinction rate of 12 per one million years and is in the same range as the background level extinction rate comparing the extinction rates between different ocean basins such as maud rise and blake nose the ostracode extinction at the k pg boundary displays striking geographical heterogeneity between the maastrichtian and danian the ostracode faunas change from a biofacies dominated by shallow bathyal taxa to one dominated by deep bathyal taxa during the lde ostracode faunas display an increase in their benthic ostracode accumulation rates and taxonomic diversity as well as an increase in the relative abundance of krithe crassicaudata simultaneously with a decline in carbonate content a similar change is commonly documented in fauna from the northeastern atlantic during the paleocene eocene thermal maximum petm 56 0 ma in contrast to the petm fauna an extinction event is not recognized near the danian selandian boundary the ostracodes show an increase in export productivity after the danian the ostracodes form a community that appears to tolerate warm and acidified water export productivity remains high during the selandian and thanetian

magnetostratigraphic and cyclostratigraphic calibration of a prospective palaeocene eocene stratotype at zumaia basque basin northern spain detailed magnetostratigraphic work at the palaeocene eocene boundary interval in the zumaia section has led to a precise delineation of the position of polarity chron c25n from 35 0 m or 35 7 m to 25 2 m below the base of the carbon isotopic excursion that marks the palaeocene eocene boundary this chronostratigraphic constraint suggests that the lithological carbonate marl couplets making up most of the studied section are the expression of orbital precession cycles and confirms the expanded and continuous nature of the section with mean sediment accumulation rates of 2 5 cm kyr 1 the new data render zumaia a unique land based marine section with available magnetostratigraphic data coupled to cyclostratigraphy the revised chronostratigraphic framework presented supports previous cyclostratigraphic calibration of the latest palaeocene geomagnetic timescale it should facilitate better assessment of the different chemobiostratigraphic events that span this critical interval as a consequence of past climate and oceanographic change consequently the zumaia section is proposed as a candidate global stratotype section and point gssp for the palaeocene eocene boundary

early paleogene biosiliceous sedimentation in the atlantic ocean testing the inorganic origin hypothesis for paleocene and eocene chert and porcellanite abstract the widespread occurrence of lower eocene chert and porcellanite has been viewed as a major paleoceanographic issue since the advent of ocean drilling and both biotic and abiotic forcings have been proposed to explain it we present a reconstruction of indurated siliceous sediment iss and preserved biosiliceous sediment pbs occurrences in the atlantic ocean through the paleocene and eocene 66 through 34 ma iss and pbs distributions reveal dissimilar temporal trends with the peak of iss occurrences coinciding with the early eocene climatic optimum in line with previous studies pbs occurrences show a generally increasing trend culminating between 44 and 43 ma the common co occurrence of iss and pbs and their coherent geographic distribution lends strong support to the biogenic origin of the precursor to the widespread paleogene iss and argues against an inorganic mode of early cenozoic chert and porcellanite precipitation weight per cent biogenic opal records and trends in linear sedimentation rates indicate two plausible modes of silicification 1 silicification due to prolonged exposure of biogenic opal rich sediments to corrosive bottom waters and 2 silicification due to elevated pressures and temperatures caused by rapid burial of biogenic opal rich deposits the confinement of iss and pbs to proximal sites along continental margins points to the reliance of siliceous sedimentation through the paleocene and eocene on terrestrial supply of dissolved silicon consistent with this quantitative siliceous microfossil assemblage records from the blake nose in the nw atlantic indicate that the nutrient rich marginal rather than oligotrophic pelagic settings hosted the majority of siliceous plankton production through the early paleogene the inorganic sio2 precipitation model is unlikely to have been the dominant mechanism responsible for ubiquitous occurrences of early paleogene iss we favor the biogenic iss precursor scenario and reconcile it with the low productivity early cenozoic oceans by showing that large volumes of biogenic silica were supplied to the western north atlantic ocean from the north american margin through the paleocene and eocene dissolution of this surplus silica was facilitated by an early southwestward flow of young sio2 depleted waters from the north atlantic all these factors contributed to iss and pbs focusing in the western north atlantic through the early paleogene

through casing hydraulic fracture evaluation by induction logging ii the inversion algorithm and experimental validations evaluation of hydraulic fractures has been under intensive study since the last decade among published works only a few have included casing effects this paper focuses on the through casing electromagnetic em induction imaging method that evaluates hydraulic fractures with enhanced contrasts an experimental system and an inverse scattering algorithm are presented the laboratory scaled experimental system is built for the feasibility study of the em induction imaging method for the through casing hydraulic fracture evaluation to develop the inverse scattering algorithm fractures outside boreholes with metallic casing are modeled by a novel hybrid approximation method this method combines the distorted born approximation and the mixed order stabilized bi conjugate gradient fast fourier transform method to solve the forward scattering problem the variational born iterative method is applied to solve the nonlinear inverse problem iteratively experimental results show that the inverse scattering algorithm is effective for em contrast enhanced through casing hydraulic fracture evaluation

the sequence stratigraphy of fluvial depositional systems the role of floodplain sediment storage abstract the currently used model for alluvial sequence stratigraphy has been criticised miall 1991 and an alternative model is offered here in this model alluviation mainly takes place during transgressive and not highstand phases when accommodation space allows sediment storage the high capacity for some river systems to store floodplain sediments is a critical consideration the effects of climatic and intrinsic geomorphic changes during fluvial deposition are likely to greatly complicate simple base level controlled sequence models and recognising higher order fourth and fifth order cycles will be particularly difficult

debris flow and hyperconcentrated flood flow deposits in an alluvial fan northwestern part of the cretaceous yongdong basin central korea abstract the alluvial fan deposits in the cretaceous yongdong basin korea consist of conglomerates with a muddy or sandy matrix and sandstones with thick or thin laminations the conglomerates and sandstones occur commonly in couplets constituting apparently single sedimentation units facies transitions in the deposits can be summed up in a tripartite facies sequence 1 a clast supported conglomerate with a muddy or sandy matrix and parallel clast alignment facies a and b 2 a matrix supported coarse tail normally graded conglomerate with random clast orientation facies c and thickly stratified pebbly sandstone facies d and 3 laminated sandstone facies e the clast supported conglomerate is interpreted as deposits of debris flows dominated by frictional grain interactions development of pervasive parallel clast alignment lacking large floating clasts and inverse grading suggests deposition via incremental aggradation rather than en masse freezing the matrix supported conglomerate an

high resolution iridium δ13c δ18o foraminifera and nannofossil profiles across the latest paleocene benthic extinction event at zumaya spain in the expanded upper paleocene lower eocene section 30 m of zone p5 sediments at zumaya northern spain the highest occurrence of many late paleocene deep sea benthic foraminifera species 40 extinction coincides with a transition from marl to calcite free clay our high resolution studies chemical elements 613c 6180 calcareous nannofossils planktic and benthic foraminifera show that below the marl clay transition there is a 40 50 cm thick interval corresponding to 10 20 kyr containing a detailed record of a gradual succession of faunal and geochemical events culminating in the benthic extinctions planktic foraminiferal and nannofossil changes e g the onset of demise in fasciculithus genus occur a few meters below the marl clay transition in the limestone 50 cm below the base of the clay a prominent glauconite maximum indicates that sea floor oxygenation suddenly decreased glauconite continues to be common until the onset of clay deposition a whole rock negative 613c shift 1 6 0 most likely reflecting an original sea water trend is gradually developed over the 40 cm of greenish brown marls immediately below the clay at the base of these marls there is a small significant iridium anomaly of 133 ppt ir compared with an average background of 38 ppt in the marls the demise of the fasciculithus species accelerates gavelinella beccariiformis becomes extinct and the abundance of acarinina species begins to increase the superjacent 4 m of clay is devoid of original calcite in its lower part and has a low calcareous content higher up at calcareous levels in the clay an unusual planktic foraminifera fauna occurs dominated by acarinina species when marl deposition returns 613c gradually increases and then stabilizes at values about 0 5 o lower than before the isotopic excursion the 613c excursion spans in total 5 m probably corresponding to 200 400 kyr the fasciculiths disappear shortly after the stabilization of 613c here we also present a whole rock 6 3c profile through the entire paleocene section at zumaya the profile is very similar to previous profiles registered in well preserved deep sea material suggesting that whole rock 613c at zumaya can be used for correlation

3 d full wave inversion of helicopter transient electromagnetic data in frequency domain helicopter transient airborne electromagnetics htem has become a useful tool in mineral explorations and geological or environmental detection in recent decades this article presents the frequency domain 3 d full wave inversion of the electromagnetic data recorded by a newly built htem system in the forward process the secondary magnetic field is calculated through the volume electric field integral equation efie in the inversion process the secondary field is first extracted from the total field measured by the htem system then the born iterative method bim is adopted to solve the nonlinear inverse scattering problem for the 3 d reconstruction of conductivity it is first applied to the synthetic models to verify their effectiveness and accuracy the effects of adjacent underground anomalies on the 3 d inversion performed in a local region within the long flight lines are studied and discussed then the bim solver is used to invert for the underground anomalies using the field measured data recorded by the newly built htem system the 2 d slices from the reconstruction are compared with the nomogram it is found that the locations of the high conductivity regions in the bim results are consistent with locations of the peaks in the nomogram the reconstructed profiles are also compared with the drilling data obtained near one flight line the good agreement shows that the 3 d bim inversion algorithm can be used to reconstruct the underground ore in htem surveys

environmental instability during the latest paleocene at zumaia basque cantabric basin the bellwether of the paleocene eocene thermal maximum abstract the paleocene eocene transition is well represented in the bathyal zumaia section basque cantabric basin northern spain where numerous studies have documented the sedimentological environmental and biotic effects of the paleocene eocene thermal maximum petm the extinction of more than half of the species of deep sea benthic foraminifera has been previously reported but the triggering causes and the exact sequence of events leading the to the extinction event still remain uncertain the combined study of benthic foraminifera and geochemical proxies allowed us to assess the consequences of an extreme global warming event and to investigate its environmental precursors with special attention to the analysis of the uppermost paleocene geochemical and micropaleontological data indicate that environmental instability started 42 6 kyr before the onset of the carbon isotope excursion cie that officially marks the paleocene eocene boundary perturbations during the late paleocene include fluctuations in trophic and redox conditions as well as in detrital input previous studies on calcareous nannofossils suggest that early warming started during the last 18 8 12 kyr of the paleocene the gradual but rapid disappearance of benthic foraminifera reveals significant environmental stress during the last 12 kyr of the paleocene and the main phase of extinction of benthic foraminifera coincided with the onset of the negative cie the gradual onset of the extinction is recorded across an interval with high caco3 content suggesting that carbonate corrosiveness was not the main trigger of the extinctions geochemical and micropaleontological data point to oligotrophy and increased temperatures in surface waters prior to the onset of the cie the increasing food demand of benthic foraminifera due to accelerated metabolic rates at higher temperatures was exacerbated by more oligotrophic conditions during the last 12 kyr of the paleocene possibly triggering the gradual but rapid extinction which culminated during the onset of the cie when carbonate dissolution was pervasive at zumaia dilution of carbonate rich material by terrigenous matter combined with effects of dissolution resulted in a very low caco3 content in the lowermost 350 cm of the eocene the environmental changes observed during the late paleocene are the bellwether of the petm and are in line with the early warming recorded prior to the petm at other locations

an integrated stratigraphic record from the paleocene of the chijiang basin jiangxi province china implications for mammalian turnover and asian block rotations new paleomagnetic and isotopic results from a similar to 1000 meter thick paleocene stratigraphic section in the chijiang basin of china s jiangxi province provide chromostratigraphic constraints on the shanghuan nongshanian asian land mammal age boundary and allow for a more accurate determination of an early paleogene paleomagnetic pole for the south china block paleomagnetic analysis of 121 sites 326 samples reveals that the shanghuan nongshanian boundary lies close to a normal to reverse polarity change stable carbon isotope analysis of dispersed organic matter and paleosol carbonates indicate a secular increase of similar to 1 5 superimposed on higher frequency variations correlation of this magnetochemostratigraphic pattern to the global timescale suggests that the polarity reversal near the shanghuan nongshanian boundary likely represents the chron c27n c26r transition the torrejonian tiffanian north american land mammal age boundary is closely correlated to this same polarity transition indicating nearly synchronous global mammalian turnover at this time because both land mammal age boundaries are thought to record turnover of mostly endemic taxa it is unlikely that the synchroneity of faunal change is due to intercontinental dispersal as documented for other early paleogene faunal transitions e g paleocene eocene boundary instead these mammalian faunal transitions may represent independent ecological or evolutionary responses to environmental changes that have been interpreted from marine records at this time e g top chron 27n event these new paleomagnetic results from the chijiang basin are also used to augment other published data and to calculate a paleocene paleomagnetic pole for the south china block the new pole shows no significant vertical axis rotation compared to the paleocene reference pole for eurasia indicating that much of the clockwise rotation that has been documented for the south china block from cretaceous deposits cannot be the result of extrusion tectonics associated with the early paleogene india asia collision observed cretaceous rotations of the south china block may be the result of late cretaceous early paleocene rifting in the backarc of the kula pacific subduction zone c 2008 elsevier b v all rights reserved

high resolution calcareous nannofossil biostratigraphy and paleoecology across the latest danian event lde in central eastern desert egypt abstract a detailed study of the calcareous nannofossil assemblages of latest danian to early selandian age from wadi qena the qreiya 1 qreiya 2 and araas sections in the central eastern desert and the gebel duwi section at the red sea coast has been carried out to understand the local phytoplankton paleocommunities for the first time in egypt four calcareous nannofossil zones ntp6 ntp7 ntp8 ntp9 and five subzones ntp7a ntp7b ntp8a ntp8b and ntp8c were distinguished subdividing the standard np4 and np5 zones the calcareous nannofossil zones were correlated with nannofossil zonations from the tethyan region e g tunisia and the zumaia section the gssp for the danian selandian boundary the calcareous nannofossil assemblages are moderately to well preserved the event beds are characterized by a dark brown shaley marl bed rich in organic carbon and coprolites three main assemblages are distinguished a pre event assemblage a transitional assemblage and a post event assemblage the paleoenvironments vary from cool eutrophic water below and above the event to warm oligotrophic conditions during the event the result of this study concludes that the latest danian event lde may represent an early paleocene hyperthermal

high resolution intra and interbasinal correlation of the danian selandian transition early paleocene the bjala section bulgaria and the selandian gssp at zumaia spain abstract the danian selandian d s boundary has been identified for the first time in the black sea coast at bjala bulgaria based on a new integrated bio magneto and cyclostratigraphic study several correlation criteria as established for the basal selandian gssp from zumaia basque basin are evaluated noteworthy is the almost complete lack of calcareous nannoplankton species braarudosphaera bigelowi in the bulgarian sections a sharp decrease of which was indicated as suitable criteria for defining the d s boundary as it occurred both at zumaia and in the classical locations of the north sea basin conversely the second evolutionary radiation of the calcareous nannofossil genus fasciculithus together with the occurrence of fasciculithus tympaniformis that define the np4 np5 zonal boundary seem to be reliable criteria to approximate the d s boundary in detail however the best approach is to integrate biostratigraphic data within a magnetostratigraphic and or cyclostratigraphic framework refinements on the placement of chron c27n at zumaia and robust bed by bed correlation between several basque sections and bjala indicates that the d s boundary is located 30 precession cycles 630 ky above c27n in addition to the precession related marl limestone couplets and 100 ky eccentricity bundles recognized in the studied sections expression of the stable 405 ky long eccentricity allows direct tuning to the astronomical solutions a correlation of the land based sections with previously tuned data from odp site1262 from the southern atlantic is challenged our choice is consistent with original tuning at zumaia but shifts one 100 ky cycle older previous tuning from site 1262 along the interval above c27n under the preferred tuning scheme the d s boundary can be given an age of 61 641 0 040 ma on the la04 orbital solution

latest danian carbon isotope anomaly and associated environmental change in the southern tethys nile basin egypt abstract during the palaeocene and eocene epochs 65 5 33 9 ma the earth experienced the warmest conditions of the cenozoic this palaeogene greenhouse episode is characterized by several short lived negative carbon isotope 13 c excursions which are usually interpreted as transient warming events hyperthermals9 as indicated by rising temperatures of surface and bottom waters and accompanied carbonate dissolution in deep sea settings among these events the palaeocene eocene thermal maximum petm c 55 5 ma is globally the best documented and most prominent further negative 13 c anomalies have recently been identified in the eocene but the early to middle palaeocene has mostly been neglected here benthic foraminiferal 13 c records are presented from four upper danian lower selandian sections in the nile basin eastern egypt all records show a negative 13 c shift with an amplitude of up to 2 at the base of planktonic foraminiferal subzone p3b c 61 ma the supra regional nature of this event is emphasized by correlation with a well dated similar 13 c record from zumaia spain lithological changes the 13 c signature and biotic responses strongly resemble those of the petm in egypt which leads to the hypothesis that this latest danian event9 lde may represent another early palaeocene hyperthermal

orbitally driven fertility cycles in the palaeocene pelagic sequences of the southern alps northern italy abstract palaeocene pelagic sequences cropping out in the southern alps are often characterized by a cyclic alternation of marly and calcareous lithologies in particular two sets of limestone marlstone couplets are well exposed in the ponte nelle alpi and tabiago sections both danian to thanetian in age located in the belluno region venetian prealps and in the brianza region central prealps respectively a multidisciplinary approach was adopted to determine the nature of these alternations by analyzing for each semicouplet the abundance and composition of planktonic foraminiferal faunas the degree of bioturbation and the carbonate content both sections show similar general features the marly semicouplets of ponte nelle alpi and tabiago sections are poor in planktonic foraminifera but enriched in more tolerant for nutrients and temperature foraminiferal forms and they record more oxygenated conditions a possible interpretation of the lithological rhythms suggests that the marly semicouplets were deposited in periods of high seasonality a marked seasonality leading to an increased circulation of water masses induced a nutrient enrichment in surface waters and oxygenated conditions at the seafloor the data prove that the marly semicouplets represents fertile surface waters whereas the calcareous ones record the opposite conditions low seasonality sluggish circulation and fewer nutrients at the sea surface spectral analysis was applied to evaluate the possible periodicities that could have driven the observed cyclicity the periodicities recorded agree with those predicted by the palaeoclimatic milankovitch theory for the precession obliquity and eccentricity cycles the stronger signal associated to obliquity has also been recorded during the mid cretaceous confined to some intervals this inconstancy is probably attributable to the response of the earth to a signal that may only be detected in the low latitudes when climatic or oceanic conditions are particularly favorable to its transmission

palaeoenvironmental changes during the danian selandian boundary interval the ichnological record at the sopelana section basque basin w pyrenees abstract ichnological analysis was conducted in the danian selandian d s boundary interval from the sopelana section basque basin northern spain to improve characterization of the recently defined global stratotype section and point of the base of the selandian stage middle paleocene in the nearby zumaia section and to interpret the danian selandian boundary event with its associated palaeoenvironmental changes the trace fossil assemblage of the boundary interval is relatively scarce and shows low diversity consisting of chondrites planolites thalassinoides trichichnus and zoophycos which cross cut a diffuse burrow mottled background typical of a normal burrowing tiered community distribution of trace fossils shows local drops in abundance and diversity just above the d s boundary and about half a metre upwards into the succeeding selandian generally the selandian part of the section has slightly lower trace fossil diversity and abundance this is interpreted as due to a higher detrital food supply corresponding to a sea level fall in contrast to a decreased food supply during the selandian sea level rise smaller scale fluctuations of trace fossil diversity and abundance are also interpreted as due more to food content fluctuations in the sediment than to oxygenation of pore waters results reveal the minor influence of an extreme warming event hyperthermal conditions at the d s boundary which affected the whole benthic habitat contrarily a probable major effect of sea level fluctuations can be envisaged which determined variations in siliciclastic input and food content

microfossil turnover across the uppermost danian at caravaca spain paleoenvironmental inferences and identification of the latest danian event abstract the latest danian event lde or top chron c27n hyperthermal event has been identified in the caravaca section southern spain by means of calcareous nannofossil biozones subzone ntp7b and the recognition of a prominent negative 0 6 per mille carbon isotope excursion measured in benthic foraminiferal tests this is the first time that this danian hyperthermal event has been identified in a deep water middle to lower bathyal setting from the western tethyan realm the analysis of benthic foraminiferal assemblages shows gradual changes in the assemblages prior to the onset of the lde and an increase in food supply to the seafloor during the lde in agreement with results from shallower southern tethyan settings the benthic assemblage changes across the lde at caravaca share some characteristics with other hyperthermal events including the negative carbon isotope excursion the increased abundance of buliminids or the common occurrence of a aragonensis an opportunistic species that proliferated during other paleogene hyperthermal events in addition the increased abundance of nuttallides truempyi a dissolution resistant form that thrived during the paleocene eocene thermal maximum and the abundance of calcareous infaunal morphogroups which calcify in less carbonate undersaturated pore waters indicate slightly caco3 corrosive bottom waters during the lde turnover of calcareous plankton across the lde is similar to other sites globally distributed including the evolution of photosymbiotic foraminiferal lineages and the radiation of the nannofossil fasciculiths group the occurrence of innovative morphostructures diantholitha and lithoptychius towards the base of the lde may indicate a more efficient biological pump this hypothesis is supported by increased percentages of benthic infaunal morphogroups and a decrease in the abundance of oligotrophic species a reworked interval has been identified immediately above the lde higher up in the section benthic and planktic assemblages from the post lde interval point to the recovery of the environmental conditions including a decrease in the food supply to the seafloor

analysis of electromagnetic induction for hydraulic fracture diagnostics in open and cased boreholes in this paper the sensitivity and detectability of an electromagnetic induction tool for hydraulic fracture detection are analyzed by calculating the electromagnetic response from an orthogonal transverse fracture otf in an open or cased borehole using the improved numerical mode matching method the otf is modeled as a slim circular disk which is axially symmetric with respect to the borehole axis and filled with a conductive or magnetic proppant the feasibility of the induction tool for fracture diagnostics was validated via scaled down experimental measurements we then quantitatively analyze the induction response sensitivity to different proppant parameters such as conductivity and permeability to evaluate the effectiveness of the induction logging tool for fracture detection the analysis reveals that the short spaced receiver can accurately locate the fracture position and distinguish small sized fractures while the long spaced receiver can differentiate fractures with large dimension casings with different thicknesses conductivities and permeabilities are modeled together with the fracture to investigate their effects in fracture detection finally the application of the induction tool to a fracture network is evaluated

the c27n c26r geomagnetic polarity reversal recorded in the west greenland flood basalt province how complex is the transitional field 1 we present a paleomagnetic record of the c27n c26r 60 9 ma geomagnetic polarity reversal gpr sampled in two separate lava sequences in the vaigat formation west greenland flood basalt province the two profiles distanced 16 km apart consist of 45 and 35 sampled lava flows of which 31 and 23 respectively record transitional field directions a prominent feature of each profile is the presence of successive flows with similar paleomagnetic directions which based on geological geochemical and paleomagnetic evidences are interpreted to represent flow fields i e lavas erupted in a short period of time rather than periods when the geomagnetic field stood still multimodel photogrammetry shows that the typical flow length of vaigat formation picritic lavas is 2 km which explains why flow to flow correlation of paleomagnetic directions between the two profiles 16 km apart is not possible the two profiles therefore record different and independent time series of the same gpr allowing us to cast light on some of the questions that have arisen from single records particularly noteworthy is the fact that the two high resolution paleomagnetic records share no general trends clearly indicating that the c27n c26r transitional field was more complex and faster changing than can be resolved by either record in addition we obtained stable polarity paleomagnetic data from both pretransitional c27n and posttransitional c26r yielding a paleomagnetic pole latitude 64 8 n longitude 141 5 e n 14 k 19 8 a95 9 2 that passes reversal test

detection and quantification of three dimensional hydraulic fractures with horizontal borehole resistivity measurements this paper investigates the suitability of low frequency borehole resistivity measurements for detecting and appraising hydraulic fractures the effects of the borehole logging tool s transmitter receiver spacing orientation and operating frequency as well as the fracture s shape cross sectional area dip and electrical conductivity contrast with the embedding formation are quantified using an fast fourier transform fft accelerated integral equation solver simulation results for a logging tool that consists of one transmitter and two receivers in a homogeneous shale formation of 1 3 s m conductivity show the following 1 longer transmitter receiver spacings can differentiate larger fractures while shorter transmitter receiver spacings can detect smaller fractures specifically the tool can differentiate fractures up to 1000 m 2 in area if the receivers are 18 and 19 2 m away from the transmitter but this long spacing configuration cannot detect fractures smaller than 10 m 2 in area and requires the effective electrical conductivity of the fracture to be larger than 100 s m in comparison the tool can detect fractures as small as 1 m 2 in area if the receivers are 1 2 and 1 5 m away from the transmitter even if the effective electrical conductivity of the fracture is only 10 s m but this short spacing configuration cannot distinguish fractures larger than 10 m 2 in area 2 coaxial measurements are sensitive to the fracture cross sectional area but cannot differentiate fractures of the same area with different cross sectional shapes or dips transverse copolarized measurements can discern axially symmetric fractures from asymmetric ones for example in long spacing configuration they can differentiate elliptical fractures with an aspect ratio of 8 from circular or square fractures if their areas are within 1 m 2 to 1000 m 2 cross polarized measurements can quantify fracture dip and become more sensitive as the dip angle increases for example in long spacing configuration they can detect 15 dipping fractures that are larger than 100 m 2 in area but cannot distinguish them while they can detect and distinguish 60 dipping fractures if their areas are in the range of 100 1000 m 2 3 the measurements are mostly insensitive to the operating frequency in the 10 hz 1 khz range in the short spacing configuration and depend moderately on the operating frequency in the long spacing configuration 4 the relative strength of the measured signals is proportional to the fracture effective electrical conductivity when the fracture is more than ten times conductive compared to the embedding rock formation 5 short spacing measurements exhibit higher resolution the tool can differentiate two fractures as long as they are more than 1 m 4 m away from each other in the short spacing long spacing configuration 6 in complex fracture networks not only major branches but intermediate and small branches contribute to the shape and magnitude of measured signals the contributions depend mainly on the area and position of the branches

induction logging through casing by detecting lateral waves a numerical analysis induction logging through casing iltc is of significant importance to the evaluation of residual oils traditional induction logging fails to work in cased wells due to the shielding effect of metallic casings to date the feasibility of iltc remains an open question in this article we propose an iltc based on the detection of lateral waves that carry the formation information based on the analytical equations derived to describe the hybrid modes of total magnetic fields that can be detected inside cased wells numerical analyses aiming to describe the behavior of lateral waves were carried out in both frequency and time domains the obtained results comply with full wave simulations and existing scaled experiments our results indicate that if an iltc tool can be properly configured to work in a region dominated by lateral waves and the casing effect and the primary field of the lateral waves can be effectively compensated it is feasible to implement an iltc to detect formation conductivities ranging from 0 01 to 5 s m

foraminiferal and δ13c isotopic event stratigraphy across the danian selandian transition at zumaya northern spain chronostratigraphic implications unconformity characterized by a ma jor lithological shift from greyish white oxic limestone chalk of the danskekalk fm upper danian to suboxic glauconitic green sand of the lellinge greensand fm lower selan dian overlain by grey marl and clay of the kerteminde marl fm middle selandian this unconformity was correlated with the sequence bound ary between cycles ta 1 3 and ta 1 4 abstract the zumaya section northern spain is a suitable candidate to define the global stratotype section and point for the base of the selandian stage palaeocene because of its excellent accessibility exposure and stratigraphic continuity uncertain ties exist however with regard to the stratigraphic horizon where to place the danian selandian d s boundary five potential stratigraphic horizons hds1 to hds5 to define the d s boundary have been identified at zumaya based on integrated stratigraphic studies that include quantitative plank tic and benthic foraminiferal results as well as d 13 c isotopic and lithological data two of these horizons hds2 and hds4 placed in zone c26r appear to have particularly good potential for serving as the d s boundary marker because they may represent significant global palaeoceanographic palaeoclimatic and eustatic events

new paleomagnetic and stable isotope results from the nanxiong basin china implications for the k t boundary and the timing of paleocene mammalian turnover abstract the nanxiong basin guangdong province china preserves the most complete asian stratigraphic record of the cretaceous paleogene k pg boundary extinction and the subsequent paleocene mammalian radiation despite extensive study the precise placement of the k pg boundary in the nanxiong basin sequence has been controversial and the timing of subsequent mammalian turnover is poorly constrained we present new paleomagnetic and geochemical data from the late cretaceous pingling formation nanxiong group and the overlying paleocene shanghu nongshan and guchengcun formations luofozhai group our samples are directly correlated with previous geochemical and paleontological sampling localities allowing for easy comparison with other local proxy records results indicate that the traditional placement of the k pg boundary at the base of a chaotic channel sandstone bed marking the highest stratigraphic appearance of dinosaur eggshell fragments and lowest stratigraphic appearance of paleocene ma

pronounced biotic and environmental change across the latest danian warming event lde at shatsky rise pacific ocean odp site 1210 abstract the early paleogene is characterized by numerous hyperthermals transient nuttallides umbonifera dominated assemblage yet 200 kyr before the lde benthic foraminiferal assemblages with increased relative abundance of endobenthic morphotypes and benthic foraminiferal accumulation rates indicate a slightly enhanced food flux a temperature increase 40 kyr before the first carbon isotope excursion cie of the lde lde1 is associated with a rise in abundance of tappanina selmensis suggesting episodic input of fresh phytodetritus at the start of lde1 and through the second cie lde2 the seafloor returned to more oligotrophic conditions between 220 and 430 kyr after the onset of the lde a second phase of episodic fresh phytodetritus input is suggested by a renewed dominance of t selmensis although the patterns of faunal change during hyperthermals relate to local conditions circulation patterns the magnitude of faunal change is probably more related to an absolute temperature threshold

buried inset valleys in the eastern yilgarn craton western australia geomorphology age and allogenic control abstract a contributory network of narrow fluvially incised valleys filled with a distinctive sequence of tertiary continental to shallow marine sediments is widespread throughout the eastern yilgarn craton in southwestern australia previously referred to as deep leads or paleochannels these are herein termed inset valleys to more accurately reflect their geomorphic expression and emphasize their subordinate and entrenched position with the bedrock surface of a much broader and older system of primary valleys owing to minimal denudation and tectonic deformation during the late cenozoic the inset valleys are excellently preserved and can be readily traced in boreholes and open cut mines throughout the eastern yilgarn craton and possibly also adjacent parts of southwestern australia with a combined catchment areal extent of at least documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmary

multiscale hydraulic fracture modeling with discontinuous galerkin frequency domain method and impedance transition boundary condition to facilitate the detection of hydraulic fractures by electromagnetic survey a discontinuous galerkin frequency domain dgfd method is introduced in this paper to efficiently model the fracture responses under complicated geophysical environments in the proposed dgfd method the computational domain can be split into multiple subdomains with nonconformal meshes the riemann solver upwind flux is introduced to evaluate the numerical flux the impedance transition boundary condition itbc is employed to facilitate fracture modeling by approximating fractures as surfaces numerical results show that the itbc works well for different fracture conductivities dipping angles operation frequencies as well as different sources for both small and large scale fractures it also shows good agreement with the references the responses of fractures increase as their conductivities become larger large dipping angles can cause spikes on the responses in a borehole for a magnetic source higher operation frequencies can enhance the signal level while for an electric source the sensitivity to frequency is small when no borehole is considered the responses due to an electric source are in general larger than those due to a magnetic one however when a borehole with conductive mud is included the responses can be reversed for the electric and magnetic sources for multiple fractures outside a cased borehole the signal level of an electric source is significantly reduced while that of a magnetic source remains at a similar level compared with the scenario without a casing with the proposed technique multiscale modeling of hydraulic fractures in complicated geophysical environments becomes possible

facies and basin architecture of the late carboniferous salvan dorenaz continental basin western alps switzerland france the salvan dorenaz basin formed during the late palaeozoic within the aiguilles rouges crystalline basement western alps as an asymmetric intramontane graben elongated in a ne sw direction and bounded by active faults at least 1700 m of fluvial alluvial fan and volcanic deposits provide evidence for a strong tectonic influence on deposition with long term average subsidence rates of 0ae 2m m yr 1 the early basin fill was associated with coarse grained alluvial fans that were dominated by braided channels unit i these issued from the south western margin of the basin the fans then retreated to a marginal position and were overlain by muddy floodplain deposits of an anastomosed fluvial system unit ii that drained towards the ne deposition of thick muds resulted from a reduction in the axial fluvial gradient caused by accelerated tectonic subsidence overlying sand rich meandering river deposits unit iii document a reversal in the drainage direction from the ne to the sw caused by synsedimentary tectonism reflecting large scale topographic reorganization in this part of the variscides with subsidence now preferentially in the w and sw and uplift in the e and ne coarse grained alluvial fan deposits unit iv repeatedly prograded into and retreated from the basin as documented by coarsening upward cycles tens of metres thick reflecting smaller scale tectonic cycles volcanism was active throughout the evolution of the basin and u pb isotopic dating of the volcanic deposits restricts the time of basin development to the late carboniferous 308 295 ma 40 ar 39 ar ages of detrital white mica indicate rapid tectonic movements and exhumation of the nearby basement in unit i youngest ages are close to that of the host sediment but the age spectrum is wide in unit ii high subsidence and or sedimentation rates coincide with very narrow age spectra indicating small homogeneous catchment areas in unit iii age spectra became wider again and indicate growing catchment areas

integrated bio chemostratigraphical correlations and climatic evolution across the danian selandian boundary at low latitudes abstract the global boundary stratotype section and point for the base of the selandian stage is defined in the zumaia section spain at an abrupt change in lithology base of itzurun formation which coincides with the onset of a negative carbonate carbon isotope shift however this lithological change is not always very well expressed in other sections in order to document the stratigraphic position of the danian selandian boundary dsb on a more global scale we have investigated three sections across the dsb the zumaia reference section gssp the loubieng section auxiliary dsb reference section france and the sidi nasseur section tunisia the danian selandian boundary interval is subdivided and correlated throughout low latitudes from the altlantic bay of biscay to the southern tethys on the basis of seven calcareous nannofossil and planktonic foraminiferal events e events the base of the selandian is proved to coincide with the end of the braarudosphaera acme which correlates with the lowest consistent occurrence lcso of lithoptychius aff bitectus fasciculithus janii sensu steurbaut and sztrakos 2008 event e4 but which is slightly posterior to the second radiation of the fasciculiths up to now considered to represent the primary correlation tool of the dsb a short term 13 c org negative excursion associated with an increase in p co 2 is recorded at the very base of the selandian it is interpreted as a short period of global warming hyperthermal the duration of which is estimated at 30 kyr it is followed in all the three studied sections by a long term decoupled carbon isotope event marked by increasing 13 c org and decreasing 13 c carb values it may reflect a period of climatic cooling of a few 100 kyr interpreted as a possible precursor of the global cooling event marking the late paleocene in the north atlantic realm the integration of the biostratigraphic and the isotope data indicates major differences in sedimentation rates during the early selandian in the studied sections but there is no evidence of substantial breaks in sedimentation in any of the sections during this interval the lithological shift at the base of the selandian points to an abrupt palaeoenvironmental reorganisation although our integrated bio chemostratigraphical investigation does not allow for estimating its duration nor the presence of a hiatus at that time

arid climate 2 5 ma in the plio pleistocene valdarno basin northern apennines italy abstract distinctive eolian dominated sandy deposits 35 m thick exposed along the sw margin of the plio pleistocene valdarno basin in the northern apennines italy reflect an unusually arid period in the region paleomagnetic investigation and 40 ar 39 ar dating of a tephra layer 10 m above the eolian sand suggest that the sand was deposited between about 2 7 and 2 4 ma this age is coeval with the global climatic deterioration that occurred at the middle upper pliocene transition eolian sediments are represented by cross bedded sand rippled sand and horizontal bedded sand the alluvial deposits associated with the eolian sediment consist of sheet like beds of coarse sand and erosively based pebbly sand bodies eolian sand together with fluvial sandy deposits was formed in the medial distal portion of an alluvial system and represents the rena bianca sand unit the eolian and alluvial deposits are arranged into sedimentary cycles 2 6 m thick displaying a wetting drying wetting upward trend recording second order climatic oscillations of ca 40 ka each cycle is enclosed between major bounding surfaces defined by iron mineral encrustations these bounding surfaces represent periods of reduced eolian sand accumulation caused by a rising water table during the 2 5 ma global cooling the valdarno basin experienced a period of arid conditions owing to the influence of cold and dry easterly and northeasterly winds in contrast during the pleistocene the uplift of the pratomagno ridge protected the valdarno basin from easterly and northeasterly winds giving rise to relatively warm and wet conditions and mitigating the regional and global climatic changes

development of tectonic cyclothems in rift pull apart and foreland basins sedimentary response to episodic tectonism the thickest part of asymmetric rift pull apart and foreland basin fills commonly consists of large scale hundreds to thousands of metres thick tectonically generated cyclothems of fine grained marine lacustrine or longitudinal fluvial deposits and coarse grained transverse braid plain or alluvial fan deposits the appearance of coarse clastics in these basin fills is typically noted as the time of tectonically rejuvenated source area uplift based on the conceptual tie between relief and coarse grain size and on the application of the davis theory of landform development we propose the opposite interpretation that the commencement of fine grained sedimentation above coarse grained deposits in a tectonic cyclothem is the best indicator of renewed tectonic activity this reinterpretation is more consistent with 1 modern examples 2 the consideration of source area and sedimentary basin geomorphology 3 the disparity between the reaction rates of the various environments to subsidence 4 the disparity between the rates of tectonic uplift and erosion and 5 the controls on elastic wedge progradation in our model extensive coarse grained clastic wedge progradation is an indicator of tectonically quiescent phases

tempo and scale of late paleocene and early eocene carbon isotope cycles implications for the origin of hyperthermals abstract the upper paleocene and lower eocene are marked by several prominent 1 carbon isotope 13c excursions cie that coincide with transient global warmings or thermal maxima including the paleocene eocene thermal maximum petm the cie which are recorded mainly in marine sedimentary sequences have also been identified in continental sequences occurred episodically and yet appear to be paced or triggered by orbital forcing to constrain the timing and scale of the cie relative to long term baseline variability we have constructed a 4 52 million year myr long high resolution 3 kyr bulk sediment carbon isotope record spanning the lower eocene to upper paleocene c25r c24n from a pelagic sediment section recovered at odp site 1262 in the southeast atlantic this section which was orbitally tuned utilizing high resolution core log physical property and geochemical records is the most stratigraphically complete upper paleocene to lower eocene sequence recovered to date time series analysis of the carbon isotope record along with a high resolution fe intensity record obtained by xrf core scanner reveal cyclicity with variance concentrated primarily in the precession 21 kyr and eccentricity bands 100 and 400 kyr throughout the upper paleocene lower eocene in general minima in 13c correspond with peaks in fe i e carbonate dissolution both of which appear to be in phase with maxima in eccentricity this covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity this relationship includes all late paleocene and early eocene cie confirming pacing by orbital forcing the lone exception is the petm which appears to be out of phase with the 400 kyr cycle though possibly in phase with the 100 kyr cycle reinforcing the notion that a mechanism other than orbital forcing and or an additional source of carbon is required to account for the occurrence and unusual scale of this event

evidence of an abrupt environmental disruption during the mid paleocene biotic event zumaia section western pyrenees an abrupt environmental disruption occurred in the photic zone and at the seafloor during the mid paleocene biotic event mpbe calcareous nannoplankton planktic foraminifer and benthic foraminifer assemblages at zumaia section western pyrenees underwent a rapid and remarkable transformation the major calcareous plankton assemblage changes suggest a shift from relatively cooler mesotrophic to warmer more oligotrophic conditions indicating a disturbed environment due to the warming of the ocean benthic foraminifer assemblages were also significantly affected by the mpbe diversity of the assemblages and buliminids show net decline and the low food and opportunistic taxa increase in abundance the reorganization of the planktic ecosystem possibly involved changes in the food flux type and quantity to the seafloor thus triggering changes in the benthic communities a 1 negative 13 c shift and a 30 carbonate content decrease are recorded in connection with the biotic event this suggests that during the mpbe as in the paleocene eocene thermal maximum petm an input of a large mass of isotopically depleted carbon into the ocean and atmosphere could have lowered the deep sea ph triggering a rapid shoaling of the lysocline and contributing to greenhouse warming the mpbe was short lived according to the counting of limestonemarl couplets the stratigraphic expression of precession cycles throughout the zumaia section the mpbe lasted for 52 53 k y with the core of the event representing 10 11 k y the zumaia section is the first land based locality in which the mpbe is recognized and described in detail due to its expanded character and excellent paleontological record this section may prove to be a global reference section for the study of this short lived event