trishear kinematic modeling of extensional fault propagation folding we present a new non linear 2 d numerical trishear model that is capable of modeling both symmetrical and asymmetrical trishear zones and a strain prediction approach based on the velocity field within the trishear zone a simple relationship exists between the shape factor r of the velocity field the hanging wall apical angle and footwall apical angle the implication of this relationship is that when dealing with a real deformed state cross section one can measure the hanging wall and footwall apical angles to determine the r value to specify the velocity field within the trishear zone for either the forward modeling or restoration the new trishear model can accurately reproduce the geometry of two experimental clay models and an extensional fault propagation fold from the gulf of suez predicted strain is greatest directly above the fault tip and decreases with distance from the fault tip as in the experimental models greater strain occurs in the hanging wall because of the greater velocity gradient there whereas the footwall is much less intensely deformed consequently secondary faulting and fracturing if present should be better developed along the fault tip line or in the hanging wall the orientation of fractures or minor faults can be predicted from the strain ellipses calculated from the trishear velocity field

microfloral diversity patterns of the late paleocene eocene interval in colombia northern south america the late paleocene early eocene interval was characterized by a long period of global warming that culminated with the highest temperatures of the tertiary this interval was also associated with plant extinctions and a subsequent increase in plant diversity in temperate latitudes however tropical regions remain largely unknown we compare the microfloral diversity of the late paleocene with the late early to middle eocene in flood plain coastal plain and estuarine facies of a section in the colombian eastern andes several techniques such as range through method rarefaction bootstrap detrended correspondence analysis and simpson index were used to assess the significance of the diversity pattern observed throughout the section the microfloral record indicates a distinct diverse paleocene flora declining toward the end of the paleocene being replaced by a different and much more diverse eocene flora it is uncertain however how these floral changes correlate with the latest paleocene thermal maximum and eocene thermal maximum events

evolution of the lithosphere in the area of the rhine rift system the rhine rift system rrs forms part of the european cenozoic rift system ecris and transects the variscan orogen permo carboniferous troughs and late permian to mesozoic thermal sag basins crustal and lithospheric thicknesses range in the rrs area between 24 36 km and 50 120 km respectively we discuss processes controlling the transformation of the orogenically destabilised variscan lithosphere into an end mesozoic stabilised cratonic lithosphere as well as its renewed destabilisation during the cenozoic development of ecris by end westphalian times the major sutures of the variscan orogen were associated with 45 60 km deep crustal roots during the stephanian early permian regional exhumation of the variscides was controlled by their wrench deformation detachment of subducted lithospheric slabs asthenospheric upwelling and thermal thinning of the mantle lithosphere by late early permian times when asthenospheric temperatures returned to ambient levels lithospheric thicknesses ranged between 40 km and 80 km whilst the thickness of the crust was reduced to 28 35 km in response to its regional erosional and local tectonic unroofing and the interaction of mantle derived melts with its basal parts re equilibration of the lithosphere asthenosphere system governed the subsidence of late permian mesozoic thermal sag basins that covered much of the rrs area by end cretaceous times lithospheric thicknesses had increased to 100 120 km paleocene mantle plumes caused renewed thermal weakening of the lithosphere starting in the late eocene ecris evolved in the pyrenean and alpine foreland by passive rifting under a collision related north directed compressional stress field following end oligocene consolidation of the pyrenees west and northwest directed stresses originating in the alps controlled further development of ecris the rrs remained active until the present whilst the southern branch of ecris aborted in the early miocene extensional strain across ecris amounts to some 7 km plume related thermal thinning of the lithosphere underlies uplift of the rhenish massif and massif central lithospheric folding controlled uplift of the vosges black forest arch

extensional forced folding and decollement of the pre rift series along the rhine graben and their influence on the geometry of the syn rift sequences

new palynology based astronomical and revised 40ar 39ar ages for the eocene maar lake of messel germany the annually laminated oil shale from the eocene maar lake at messel federal state of hessen germany provides unique paleoenvironmental data for a time interval of 640 ka during the paleogene greenhouse phase as a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake the lacustrine laminites can now be astronomically tuned dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical la2010a la2010d solutions in combination with a revised 40ar 39ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments depending on different newly suggested ages for the fish canyon sanidine used as monitor for neutron irradiation the age for the eruption at messel is between 48 27 0 22 and 48 11 0 22 ma this allows for the first time the exact correlation of a paleogene lacustrine sequence to the marine record in central europe the messel oil shale becomes now slightly older than previously assumed and includes the ypresian lutetian boundary that moves the base of the european land mammal age geiseltalian mp 11 into the lower eocene this opens a window for establishing an independent chronostratigraphic framework for paleogene terrestrial records and their correlation to the marine realm furthermore the study reveals that higher amounts of pollen from wet and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well expressed eccentricity minimum

tectonic evolution of the european variscan belt constrained by palaeomagnetic structural and anisotropy of magnetic susceptibility data from the northern vosges magmatic arc eastern france geochronology structural and anisotropy of magnetic susceptibility data from the northern vosges batholith which belongs to the northern vosges mid german crystalline rise arc show contrasting emplacement modes of southern granodiorites and northern granites the ene wsw trending fabrics of granodiorites 346 334 ma are parallel to the metamorphic cleavage affecting the host rocks developed during regional compression the nnw sse trending fabrics of younger granitoids c 330 ma reveal an extensional emplacement mode associated with a normal shear zone separating the two magmatic suites palaeomagnetism shows that the switch from a compressive to an extensional regime coincides with a regional counterclockwise rotation the 330 325 ma extension is further supported by palaeomagnetic and seismic data indicating southeastward tilt of the whole batholith finally the system is rotated clockwise without any structural overprint data from the early carboniferous northern vosges magmatic arc and remote bohemian massif suggest that this evolution is valid for the whole eastern branch of the european variscan belt for which the following model is proposed 1 late devonian early carboniferous east west shortening of the variscides above the rhenohercynian subduction zone 2 axial nnw sse shortening of the assembled variscan orogen associated with 3 internal sinistral rotation of inherited rhenohercynian transform faults and shortening of intervening blocks 4 east west extension and dextral external rotation of blocks between dextrally reactivated transforms supplementary materials analytical procedures for geochronology magnetism anisotropy of magnetic susceptibility and palaeomagnetism are available at www geolsoc org uk sup18635

the rhinegraben extension subsidence and shoulder uplift abstract we apply a numerical model of the thermal evolution of a continental lithosphere undergoing extensional deformation to the rhinegraben using reasonable parameters the results of computations are in agreement with the present configuration of the rift and of its shoulders as well as with their evolution since the oligocene contrasting evolutions are reconstructed in the northern and southern rhinegraben whereas the northern history is accounted for by a simple model of homogeneous stretching of the lithosphere the history of the southern rhinegraben cannot be explained without introducing two main periods of heterogeneous stretching the results are locally supported by structural analyses of extensional patterns factors of extension average 1 2 in the axial portion of the rhinegraben and 1 15 for the whole rift section suggesting that the total amount of e w extension reaches 6 km

crustal structure and dynamics in the rhine graben and the alpine foreland summary the rhine graben rift stretches for 300 km from basel to frankfurt the axis of maximum subsidence switches from west in the southern graben to east in the northern graben subsidence in the south began in the upper eocene and was interrupted in the mid miocene by a broad uplift of 1 1 5 km in the vosges schwarzwald black forest region whereas subsidence in the north proceeded continuously from the lower oligocene to the present a combined geophysical and geological interpretation of the rhine graben is presented in the form of a 3 d gravity model and 2 d flexural plate modelling from the alps across the alpine foreland to the rhenish massif modelling is based on crustal structure revealed by geologic gravity and seismic data including ecors dekorp and egt profiles the 3 d gravity modelling supports a modest density contrast of 0 3 g cm 3 at the crust mantle boundary since there is no evidence of a large scale upper mantle anomaly a dense lower crust 2 9 3 0 g cm 3 is proposed as the cause of this modest density contrast the presence of a dense mafic lower crust in south west germany is corroborated by lower crustal xenoliths elevated p wave velocities 6 7 7 2 km s 1 and high poisson s ratios 0 26 0 29 residual gravity and magnetic data reveal strong crustal heterogeneities particularly from the dense magnetic saxothuringian terrane to the light non magnetic moldanubian terrane the polarity of the asymmetric rhine graben reverses at this variscan tectonic boundary light graben fill can account for nearly the entire 20 40 mgal short wavelength gravity minimum but the presence of intrusive bodies ranging from granitic to mafic composition can also strongly influence the local gravity field 2 d modelling of the flexure of the european lithosphere along seven 1000 km long profiles indicates a flexural bulge of 1 1 5 km in the alpine foreland of southern germany which corresponds to an ene trending moho uplift of the same magnitude and to a band of free air gravity highs longer flexural wavelengths in the east indicate increasing lithospheric rigidity and increasing elastic thickness towards the bohemian massif the vosges schwarzwald dome is interpreted as the intersection of the oligocene rhine graben rift and associated rift flank uplift with the mid miocene flexural bulge

kinematic and geometric analysis of fault related folds in a rift setting the dannemarie basin upper rhine graben france abstract the upper rhine graben urg developed in the alpine foreland from mid eocene to pliocene as part of the west european rift system the dannemarie basin occupies the sw termination of the urg and is bordered by the vosges fault zone west and the illfurth fault zone east we constructed a 3d model of faults and principal pre and syn rift stratigraphic surfaces using all available subsurface and surface geological and geophysical data the model shows 1 syn rift strata thinning across kilometre scale fault parallel monoclinal flexures associated with basin margin faults and 2 major basin margin faults terminating laterally into major flexures sequential cross section restorations show that these flexures accommodated deposition of over 1300 m of syn rift strata salt series which is 42 63 of the basin fill these folds are interpreted as syn rift fault propagation folds that developed above normal faults their geometry is replicated in a trishear numerical model using reasonable parameter values fold development was controlled principally by 1 reactivation of favourably oriented basement faults 2 the presence of a thick viscous layer principally triassic evaporites allowing decoupling between crystalline basement and competent jurassic cover and 3 a relatively slow deformation rate

evidence for rapid climate change in north america during the latest paleocene thermal maximum oxygen isotope compositions of biogenic phosphate from the bighorn basin wyoming oxygen isotope records of cenozoic sea water temperatures indicate that a rapid warming event known as the latest paleocene thermal maximum lptm occurred during the otherwise gradual increase in world temperatures during the late paleocene and early eocene oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river dwelling fish from the bighorn basin in wyoming were made to investigate corresponding changes in the terrestrial climate a comparison of carbonate and phosphate isotope data from modern and fossil material indicates that some diagenetic alteration of the fossil material has occurred although systematically larger intra tooth ranges in the oxygen isotope composition of carbonate indicate that it is more likely to have been affected than phosphate carbonate and phosphate from the ecologically diverse mammals and fishes both record a shift to higher oxygen isotope ratios at the same time and of the same duration as the lptm these shifts reflect a change in the isotopic composition of regional precipitation which in turn provides the first evidence for continental climate change during the lptm assuming the present day relation between the oxygen isotope composition of precipitation and temperature applies to conditions in the past and that animal physiology and behavior is relatively invariant over time the isotopic shift is equivalent to an increase of surface temperature in western north america of several degrees this result is consistent with the magnitude of high latitude ocean warming and provides a basis for relating marine and terrestrial oxygen isotope records to records of terrestrial biotic change 1998 elsevier science b v all rights reserved

effects of magnetic anisotropy on total magnetic field anomalies modeling of magnetic anomaly data is a powerful technique to gain information on the shape of subsurface rock bodies most models are based on the assumption that the magnetization in the source body is parallel to the direction of the earth s magnetic field it has long been recognized that remanent magnetization affects the magnetization direction intensity and shape of the anomaly and therefore the interpreted structure the effects of anisotropy however have only received little attention so far this study uses synthetic models and a case study to investigate how anisotropy affects magnetization and anomalies over a thick dipping sheet and determines expected errors in interpreted magnetic properties and geometry of the source body for various anisotropy degrees and field inclinations anisotropy affects both the shape and amplitude of anomalies for an oblate uniaxial fabric with the minimum susceptibility normal to the sheet and p 1 5 errors in interpreted dip are up to 12 depending on the field inclination dip and profile orientation and errors in estimated mean susceptibility are up to 30 20 if anisotropy is not taken into account during modeling these effects are larger for higher degrees of anisotropy a case study over the mcu ive layer in the bjerkreim sokndal layered intrusion norway investigates the contributions of an isotropic induced and remanent magnetizations to the total field anomalies there the influence of anisotropy is mainly related to remanence deflection the results shown here will help to further improve interpretation of magnetic potential field data

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

the northern upper rhine graben basin geometry and early syn rift tectono sedimentary evolution a large scale transfer zone subdivides the northern parts of the upper rhine graben into a northern and a southern sub basin these sub basins display the geometry of asymmetric half grabens with opposing tilt directions the transfer zone connects the western master fault of the northern half graben with the eastern master fault of the southern half graben in the northern upper rhine graben early syn rift sedimentation late priabonian to late rupelian was controlled by the tectonically induced subsidence of these half grabens autogenetic as well as by regional third order sea level variations allogenetic within the graben lateral changes in subsidence rates in dip and strike direction of fault blocks controlled the development of accommodation space and thus sediment thickness and facies furthermore a low displacement segment along the western border fault acted as a sediment entry point tectonics controlled the distribution of early syn rift deposits and the palaeogeography of the northern upper rhine graben

late paleocene early eocene tethyan carbonate platform evolution a response to long and short term paleoclimatic change abstract the early paleogene experienced the most pronounced long term warming trend of the cenozoic superimposed by transient warming events such as the paleocene eocene thermal maximum petm the consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored today modern carbonate platforms especially coral reefs are highly sensitive to environmental and climatic change which raises the question how sub tropical reef systems of the early paleogene reacted to gradual and sudden global warming eutrophication of shelf areas enhanced co 2 levels in an ocean with low mg ca ratios the answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising co 2 levels here we present a synthesis of tethyan carbonate platform evolution in the early paleogene 59 55 ma concentrating on coral reefs and larger foraminifera two important organism groups during this time interval we discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early paleogene detailed analyses of two carbonate platform areas at low egypt and middle spain paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late paleocene to early eocene tethys stage i late paleocene coralgal dominated platforms at low to middle paleolatitudes stage ii a transitional latest paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera dominated miscellanea ranikothalia assilina platforms at low paleolatitudes and stage iii early eocene larger foraminifera dominated alveolina orbitolites nummulites platforms at low to middle paleolatitudes the onset of the latter prominent larger foraminifera dominated platform correlates with the paleocene eocene thermal maximum the causes for the change from coral dominated platforms to larger foraminifera dominated platforms are multilayered the decline of coralgal reefs in low latitudes during platform stage ii is related to overall warming leading to sea surface temperatures in the tropics beyond the maximum temperature range of corals the overall low occurrence of coral reefs in the paleogene might be related to the presence of a calcite sea at the same time larger foraminifera started to flourish after their near extinction at the cretaceous paleogene boundary the demise of coralgal reefs at all studied paleolatitudes in platform stage iii can be founded on the effects of the petm resulting in short term warming eutrophic conditions on the shelves and acidification of the oceans hampering the growth of aragonitic corals while calcitic larger foraminifera flourished in the absence of other successful carbonate producing organisms larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant leading to a stepwise tethyan platform stage evolution around the paleocene eocene boundary this szenario might be also effective for threatened coral reef sites

tectonic implications of transpression and transtension upper rhine graben 1 seismic reflection data from the upper rhine graben urg show a series of synclines along the linear eastern boundary faults from north of karlsruhe to the jura mountains similar structures do not characterize the northern segment of the graben the synclinal shape is portrayed by inversion related to transpression on the linear boundary faults coupled with the conserved easterly dip of the sediments farther inside the tilted hanging block the onset of transpression preceded the known early burdigalian unconformity but was also an early miocene event it suggests that the regional compression axis 1 in early miocene had a trend between 315 and 0 the continuous transtension in the northern segment suggests that at no time during the history of the urg was the regional 1 horizontal with a ne sw trend the lack of transpressional structures in the younger plio pleistocene sediments along the entire eastern boundary of the urg suggests a late change in the regional stress field the main eastern boundary faults and synclines north and south of baden baden are all continuous and have the same trend kinematically they form a single graben segment and respond to the regional stress in the same way

cool tropics in the middle eocene evidence from the changchang flora hainan island china abstract the middle eocene lutetian bartonian 48 6 37 2 ma near equatorial megafossil flora from swamp and lacustrine facies of the lower changchang formation hainan island south china 19 631463 n 110 445049 e is highly diverse 200 taxa dominated by an unusual mixture of angiosperms typical of modern temperate subtropical and tropical evergreen and deciduous forms it is also rich in palms multivariate analysis of the architecture of minimally transported woody dicot leaves reveals a mean annual air temperature mat of 22 4 7 c with a marked thermal seasonality range of 21 c the year round humid climate lacked any monsoonal signature the overall climate signal is compatible with the growth characteristics exhibited by fossil wood but is warmer than the climate signal derived from pollen and spores using co existence analysis corrections for possible palaeoelevation of the basin bring the megafossil derived mat estimate in line with 54 52 ma sea surface and soil temperatures obtained from the gulf coast usa palaeolatitude 30 n using multiple geochemical proxies and supports the claim that the low latitude eocene climate was not uniformly warm this challenges previous conclusions based on 18 o analysis of unaltered calcareous microfossils our air temperature data also adds to the challenge of understanding heat transport away from the equator to higher latitudes during hothouse climate regimes

plant and mammal diversity in the paleocene to early eocene of the bighorn basin abstract abundant plant and vertebrate fossils have been recovered from fluvial sediments deposited in the bighorn basin wyoming during the first 13 m y of the tertiary here we outline and discuss changes in the composition and diversity of floras and faunas during this period which includes the recovery of terrestrial ecosystems from the k t boundary extinctions and later during the paleocene eocene transition the greatest global warming of the cenozoic floral diversity has been studied at three levels of spatial resolution sub local at individual collecting sites local along a single bed or stratigraphic horizon and basin wide regional sub local diversity shows a moderate increase from the early to late paleocene followed by a decrease across the paleocene eocene boundary then an increase into the later early eocene local heterogeneity was lower in paleocene backswamp floras although distinct groups of species dominated in different local fluvial settings such as backswamps and alluvial ridges heterogeneity of backswamp forests increased by about 65 from the early to late wasatchian early eocene the number of plant species inferred from the bighorn basin dataset rose gradually from the puercan to an early clarkforkian peak of about 40 species declined sharply to about 25 species by the clarkforkian wasatchian boundary then rose through the wasatchian to about 50 species a regional analysis of mammalian genera shows high turnover and a rapidly increasing number of genera within a million years of the k t boundary 10 50 genera a slight decline to 40 genera by the early clarkforkian then an increase from 40 to 75 genera by the late wasatchian our analyses found no major extinctions in mammals during the paleocene and early eocene in the bighorn basin but a one third decrease in the number of plant species at about the paleocene eocene boundary rates of taxonomic turnover were much higher for mammals than plants the diversity trends for plants and mammals show little congruence implying that the two groups responded in a very different manner to post k t extinction opportunities there is also little congruence between plant diversity levels and change in mean annual temperature mat as inferred from foliar physiognomy

dynamic response of the shallow marine benthic ecosystem to regional and pan tethyan environmental change at the paleocene eocene boundary the indus basin of pakistan preserves a record of a late paleocene early eocene shallow marine carbonate ecosystem in the east tethys and of its response to an interval of marked climate change and regional tectonic reconfiguration local palaeoecological conditions and or the tethyan latitudinal temperature gradient favoured meso oligotrophic biotic assemblages of mainly larger benthic foraminifera lbfs and dasycladacean algae in the late paleocene early thanetian of east tethys whereas coral algal assemblages dominated west tethys the appearance of oligotrophic lbfs miscellanids and ranikothalids in the indus basin during latest paleocene late thanetian time is comparable with west tethys and suggests a pan tethyan response to long term early paleogene warming however the response of the shallow marine biota to profound earliest eocene environmental change in east tethys was remarkably different from that apparent in the west the larger foraminifer turnover lft and rapid radiation of typical eocene lbfs e g alveolina nummulites and orbitolites seen in the west does not occur in the east during the earliest eocene a relict late paleocene fauna mainly miscellanids and ranikothalids persisted in east tethys but this shows profound morphological and ecological modifications with palaeo depth ranges compressed to shallower environments the delayed lft in the indus basin indicates the complex response of the shallow marine biota to the earliest eocene climate perturbation in the east india asia collision at the paleocene eocene boundary may have produced local biogeographic barriers increased seasonal runoff and altered oceanic gateways and oceanic circulation delaying the lft later in the early eocene pan tethyan environmental conditions were restored and alveolina and nummulites migrated east

numerical modeling of trishear fault propagation folding in contrast to kink band migration modeling methods trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges modeled fold hinges tighten and converge downward within a triangular zone of distributed deformation which is focused on the fault tip such features have been reported from field studies and are also seen in analogue models of compressional deformation however apart from its initial application to laramide folds little quantitative work has been undertaken on trishear fault propagation folding in other settings in addition no study has been undertaken into the growth strata which might be associated with such structures this paper uses an equivalent velocity description of the geometric model of trishear together with models of erosion and sedimentation to investigate trishear fault propagation folding of both pregrowth and growth strata the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement the models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata when total slip on a structure is high the model predicts overturned pregrowth and growth strata during the initial stages of deformation beds in the forelimb thicken but later thin when they become steep or overturned the effect of variations in fault propagation to slip ratios on two dimensional finite strain in the models is assessed by the use of initially circular strain markers high fault propagation to slip p s ratios lead to narrow zones of high finite strain while lower p s ratios lead to more ductile deformation and broader zones of high strain in all cases hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault modeled structures are compared with natural examples

net effect of rainfall activity on salt marsh sediment distribution it has been established that increased suspended sediment concentrations in tidal waters adjacent to salt marshes occur during periods following heavy rainfall events in this work we present experimental data for concentration and sediment flux measurements during periods of natural moderate rainfall events from a microtidal alochthonous salt marsh system north inlet south carolina usa the results indicate that rainfall events although responsible for increasing sediment concentration levels do not alter the sediment flux of the system in our results the sediment mobilized by the rain was re introduced to the system further using the geochemical signatures of suspended particles from the same location we found that the sediment mobilized by rainfall events is the same as the sediment present in the tidal creeks suggesting that rainfall mobilizes only recently deposited non consolidated sediment and does not erode the substrate of the marsh surface

on the use of aeromagnetism for geological interpretation 1 comparison of scalar and vector magnetometers for aeromagnetic surveys and an equivalent source interpolator for combining gridding and transforming fixed altitude and draping data sets

eocene continental climates and latitudinal temperature gradients global climate during the mesozoic and early cenozoic is thought to have been warmer than at present but there is debate about winter temperatures paleontological data indicate mild temperatures even at high latitudes and in mid latitude continental interiors whereas computer simulations of continental paleoclimates produce winter temperatures closer to modern levels foliar physiognomy and floristic composition of 23 eocene floras from the interior of north america and australia indicate cold month means generally 2 c even where the mean annual temperature mat was

palaeozoic evolution of the variscan vosges mountains a geological synthesis of the palaeozoic vosges mountains ne france is presented using existing observations and new data the geodynamic evolution involves 1 early palaeozoic sedimentation and magmatism 2 late devonian subduction triggering back arc spreading 3 early lower carboniferous continental subduction continent continent collision and polyphase deformation and metamorphism of the orogenic root and 4 late lower carboniferous orogenic collapse driven by thermal weakening of the middle crust the evolution is integrated within the framework of the european variscan belt the northern vosges comprise sediments of rhenohercynian affinity separated from tepla barrandian metasediments by a lower carboniferous magmatic arc the latter is correlated with the mid german crystalline rise and is ascribed to the south directed subduction of the rhenohercynian basin the saxothuringian moldanubian suture is thought to be obliterated by the magmatic arc while the lalaye lubine fault is interpreted as the tepla barrandian moldanubian boundary the central vosges are paralleled with the moldanubian domain of the bohemian massif where identical lithologies record the devonian carboniferous se directed subduction of the saxothuringian passive margin below the moldanubian upper plate the southern vosges represent the upper moldanubian crust and are linked to the southern black forest the presence of an oceanic domain to the south of the vosges black forest remains unclear

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

eocene pliocene time scale and stratigraphy of the upper rhine graben urg and the swiss molasse basin smb we present a general stratigraphic synthesis for the upper rhine graben urg and the swiss molasse basin smb from eocene to pliocene times the stratigraphic data were compiled both from literature and from research carried out by the authors during the past 6 years an index of the stratigraphically most important localitites is provided we distinguish 14 geographical areas from the helvetic domain in the south to the hanau basin in the north for each geographical area we give a synthesis of the biostratigraphy lithofacies and chronostratigraphic ranges the relationships between this stratigraphic record and the global sea level changes are generally disturbed by the geodynamic e g subsidence evolution of the basins however global sea level changes probably affected the dynamic of transgression regression in the urg e g middle pechelbronn beds and serie grise corresponding with sea level rise between ru1 ru2 and ru2 ru3 sequences respectively as well as in the molasse basin regression of the umm corresponding with the sea level drop at the ch1 sequence the urgent project upper rhine graben evolution and neotectonics provided an unique opportunity to carry out and present this synthesis discussions with scientists addressing sedimentology tectonics geophysics and geochemistry permitted the comparison of the sedimentary history and stratigraphy of the basin with processes controlling its geodynamic evolution data presented here back up the palaeogeographic reconstructions presented in a companion paper by the same authors see berger et al in int j earth sci 2005

palaeocene eocene paratropical floral change in north america responses to climate change and plant immigration the initial eocene thermal maximum ietm at c 55 ma represents a period of rapid global warming that lasted less than 200 ka the response of vegetation to such an event and particularly warm adapted highly diverse vegetation types is poorly understood using pollen floral clay mineral and stable carbon isotope analyses of sediments from the upper tuscahoma formation on the eastern us gulf coast eastern mississippi and western alabama we document paratropical floral changes across the palaeocene eocene boundary from the wahalak 2 and lower harrell cores data indicate strong changes in the abundance of kaolinite that correlate with changes in relative abundance of native pollen taxa there is no evidence for a transient extra tropical flora on the us gulf coast that may characterize the ietm immigration and extinction are not associated with this event instead early eocene plant immigration occurs in pulses and therefore is not associated directly with climate change during the ietm the two cores share the same regional species pool but compositional differences are stronger between cores than they are either through changes in environment increased soil erosion or chemical weathering or through the introduction of non native plants our data suggest that vegetation change across the palaeocene eocene boundary is not a single event but rather a sequence of cascading events

the deep thermal field of the upper rhine graben abstract the upper rhine graben has a significant socioeconomic relevance as it provides a great potential for geothermal energy production the key for the utilisation of this energy resource is to understand the controlling factors of the thermal field in this area we have therefore built a data based lithospheric scale 3d structural model of the upper rhine graben and its adjacent areas in addition 3d gravity modelling was performed to constrain the internal structure of the crystalline crust consistent with seismic information based on this lithosphere scale 3d structural model the present day conductive thermal field was calculated and compared to measured temperatures our results show that the regional thermal field is mainly controlled by the configuration of the upper crust which has different thermal properties characteristic for the variscan and alpine domains temperature maxima are predicted for the upper rhine graben where thick insulating cenozoic sediments cause a thermal blanketing effect and where the underlying crustal units are characterised by high radiogenic heat production the comparison of calculated and measured temperatures overall shows a reasonable fit while locally occuring model deviations indicate where a larger influence of groundwater flow may be expected

tertiary tectonics of the dannemarie basin upper rhine graben and regional implications recently released seismic reflection data together with previous seismic and well data are used to describe the development of the dannemarie basin in the sw end of the upper rhine graben the dannemarie basin was formed during the main rifting phase of the upper rhine graben as an asymmetrical graben trending ne sw post rift tectonism shifted the depocenter southward and changed the overall shape of the basin miocene jura compression did not result in the formation of folds as in the adjacent mulhouse horst strike slip faulting was dominant in the post rift period and new faults were created most notably the north trending and transpressional belfort fault the boundary of the dannemarie basin with the vosges mountains is part of a restraining bend which may account for the uplift of the southernmost part of the vosges mountains

tectonostratigraphy of the west alpine foreland correlation of tertiary sedimentary sequences changes in eustatic sea level and stress regimes abstract analysis of the tertiary depositional history of the west alpine foreland shows that its different basins were governed by essentially synchronous tectonostratigraphic scenarios the tectono sedimentary records of the west alpine foredeep and molasse basin and the rhone and massif central grabens demonstrate successions of tectonic deformation events and so called cenozoic rift and foredeep crf sequences which correlate to both changes in eustatic sea level and coeval modification in foreland stress regime since correlative successions developed in the north alpine foreland it seems likely that the western and northern alpine foreland stress fields were repeatedly modified at the same time compressional stresses associated with the intermittent tectonic and sedimentary changes in the foreland originated firstly from the alpine and pyrenean orogens in conjunction with the episodic history of the foreland stress regime the syn orogenic accumulation of widespread tectono sedimentary sequences reflects sequential kinematic events in the adjacent mountain chains the apparent synchroneity of the tectonostratigraphic events in the principal basins of the west alpine foreland testifies for a common geodynamic cause for the occurrence of correlative series of widespread tectonic phases and crf subdivisions

high resolution leaf fossil record spanning the cretaceous tertiary boundary theories that explain the extinctions characterizing the cretaceous tertiary k t boundary1 3 need to be tested by analyses of thoroughly sampled biotas palynological studies are the primary means for stratigraphic placement of the terrestrial boundary and for estimates of plant extinction4 12 but have not been combined with quantitative analyses of fossil leaves megaflora megafloral studies complement palynology by representing local floras with assemblages capable of high taxonomic resolution13 but have previously lacked the sample size and stratigraphic spacing needed to resolve latest cretaceous floral history5 14 18 we have now combined megafloral data from a 100 m thick composite k t boundary section in north dakota with detailed palynological analysis here the boundary is marked by a 30 palynofloral extinction coincident with iridium and shocked mineral anomalies and lies 2 m above the highest dinosaur remains the megaflora undergoes a 79 turnover across the boundary and smaller changes 17 and 25 m below it this pattern is consistent with latest cretaceous climatic warming preceding a bolide impact

us gulf coast vegetation dynamics during the latest palaeocene abstract pollen and spore floras from the bear creek section in western alabama us gulf coast record vegetation events from the lower to middle tuscahoma formation late palaeocene mid np9 sporomorphs are abundant and well preserved in these sediments and are used as a proxy to record vegetation change over time we present results from both palynofloral and clay mineral analyses in the interval approximately 0 4 0 1 my before the paleocene eocene thermal maximum petm a period of transient and intense global warming that had a profound effect on animal and plant groups in high latitudes an important factor that has a significant bearing on our understanding of turnover across the petm is that of climate environmental stability prior to the petm in terrestrial ecosystems palynological analysis with a between sample resolution of 4 10 5 yr clay mineral suites show the dominance of smectite and illite throughout the studied section with minor fluctuations in the abundance of kaolinite ranging from 2 to 10 that indicates a high seasonality of precipitation throughout our studied section the exact stratigraphic position of the petm is unknown on the us gulf coast but data from existing publications suggests there is little change in the vegetation type across the palaeocene eocene boundary with no major immigration or turnover events dinocysts are restricted in both diversity and occurrence but apectodinium homomorphum is present with 30 abundance throughout the studied section and provides some evidence that the apectodinium acme is not correlative with the petm at middle latitudes

high frequency floral changes at the paleocene eocene boundary revealed by comparative biomarker and palynological studies abstract the cap d ailly area upper normandy france shows several terrestrial lagoonal sections recording the negative carbon isotope excursion cie associated with the paleocene eocene thermal maximum petm 55 8 ma a study of the biomarkers and spore pollen content of the vasterival section gave complementary information on paleofloral changes that occurred around the paleocene eocene p e boundary aliphatic hydrocarbon fractions revealed a high abundance of vascular plant biomarkers including tricyclic diterpanes derived from conifers fernenes derived from ferns and des a triterpenes derived from angiosperms whereas the vegetation of the depositional environment surroundings seemed alternately dominated by ferns and angiosperms revealed from biomarkers the regional flora seemed dominated strictly by angiosperms such as juglandaceae revealed by pollen spore pollen assemblages revealed no major turnover in the paleovegetation but slight variation in vegetation composition however both biomarkers and spores pollen exhibited two intervals of rapid floral change the first occurred around the p e boundary and the second at the top of the strictly terrestrial unit that coincides with a marine transgression comparison of the data with published paleoclimatic results obtained from the same samples indicated that the first interval of floral change correlates with strong paleohydrological perturbations whereas the second is linked to an increasing marine influence

an alternative age model for the paleocene eocene thermal maximum using extraterrestrial 3he a continuous age model for the brief climate excursion at the paleocene eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3he 3he et to the seafloor 3he et measurements from odp site 690 provide quantitative evidence for the rapid onset few kyr and short duration 120 kyr of global warming and of the associated disturbance to the earth s surficial carbon budget at this time these observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon possibly from seafloor methane hydrate as the proximal cause of the event however the 3he et technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre event values the 3he et based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle and so may indicate additional or accelerated mechanisms of carbon removal from the ocean atmosphere system during this period 3he et was also measured at odp site 1051 to test the validity of the site 690 chronology comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at site 1051 an observation consistent with sediment structures and previous age modeling efforts the site 1051 age model shows a 30 kyr period in which climate proxies return toward pre event values after which they remain invariant for 80 kyr if this rise represents the recovery interval identified at site 690 then the 3he et based age models of the two sites are in good agreement however alternative interpretations are possible and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion regardless of these details this work shows that the 3he et technique can provide useful independent evidence for the development and testing of astronomically calibrated age models

plio pleistocene transpressional reactivation of paleozoic and paleogene structures in the rhine bresse transform zone northern switzerland and eastern france pliocene to recent uplift and shortening in the southern rhinegraben is documented by deformation of pliocene fluvial gravels deposited on a nearly planar surface as well as by progressive deflection and capture of rivers this deformation is suggested to result from thick skinned tectonic movements as evidenced by ob servations on seismic records which demonstrate a spatial coincidence between en chelon anticlines at the surface and faults located in the crystalline basement these findings contradict the often invoked thin skinned tectonism in the recent tectonic history of the rhine graben in particular the transfer zone between the rhinegraben and the bressegraben is very suitable for reactivation under the present day stress field thick skinned reactivation of faults in the basement is also expressed by focal plane mechanisms of recent earth quakes showing strike slip rather than reverse faulting characteristics this is of importance for the densely populated and industrialised southern rhinegraben pre viously affected by large earthquakes in historical times e g basel 1356

growth and linkage of a segmented normal fault zone the late jurassic murchison statfjord north fault northern north sea abstract the structure of the 25 km long northeastern portion of the murchison statfjord north fault zone and adjacent syn rift stratigraphy are integrated to reconstruct the temporal and spatial evolution during c 30 5 myr of late jurassic north sea rifting based on a structural analysis d d data alone approximately 14 precursor fault strands are identified incorporation of stratigraphic data shows that only six of these strands were important in controlling stratal architecture and distribution three main stages in the evolution of the fault zone are recorded in the syn rift stratigraphy and are biostratigraphically constrained these are 1 following initiation of rifting six isolated fault strands developed each 9 km long fault segments separated by a 2 km wide relay ramp that controlled the stratigraphy for at least the following c 10 5 myr and 3 the two fault segments hard linked forming a single continuous fault trace during the final c 7 myr of rifting the results of this study reveal the necessity to adopt an integrated structural and stratigraphic approach when reconstructing the evolution of normal fault zones the results may also help to further constrain models of fault evolution

graben width controlling syn rift sedimentation the palaeogene southern upper rhine graben as an example eocene to early oligocene syn rift deposits of the southern upper rhine graben urg accumulated in restricted environments sedimentation was controlled by local clastic supply from the graben flanks as well as by strong intra basinal variations in accommodation space due to differential tectonic subsidence that in turn led to pronounced lateral variations in depositional environment three large scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions they form three major base level cycles that can be traced throughout the basin each of them representing a stratigraphic sub unit a relatively constant amount of horizontal extension l in the range of 4 5 km has been estimated for the urg from numerous cross sections the width of the rift lf however varies between 35 and more than 60 km resulting in a variable crustal stretching factor between the bounding masterfaults apart from block tilting tectonic subsidence was therefore largely controlled by changes in the initial rift width l0 the along strike variations of the graben width are responsible for the development of a deep trough like evaporite basin potash basin in the narrowest part of the southern urg adjacent to shallow areas in the wider parts of the rift such as the colmar swell in the north and the rhine bresse transfer zone that delimits the urg to the south under a constant amount of extension the along strike variation in rift width is the principal factor controlling depo centre development in extensional basins

structural heritage reactivation and distribution of fault and fracture network in a rifting context case study of the western shoulder of the upper rhine graben abstract in fractured reservoirs in the basement of extensional basins fault and fracture parameters like density spacing and length distribution are key properties for modelling and prediction of reservoir properties and fluids flow as only large faults are detectable using basin scale geophysical investigations these fine scale parameters need to be inferred from faults and fractures in analogous rocks at the outcrop in this study we use the western shoulder of the upper rhine graben as an outcropping analogue of several deep borehole projects in the basement of the graben geological regional data dtm digital terrain model mapping and outcrop studies with scanlines are used to determine the spatial arrangement of the faults from the regional to the reservoir scale the data shows that 1 the fault network can be hierarchized in three different orders of scale and structural blocks with a characteristic structuration this is consistent with other basement rocks studies in other rifting system allowing the extrapolation of the important parameters for modelling 2 in the structural blocks the fracture network linked to the faults is linked to the interplay between rock facies variation linked to the rock emplacement and the rifting event

upper rhine graben role of preexisting structures during rift evolution 1 the evolution of the cenozoic upper rhine graben was controlled by a repeatedly changing stress field and the reactivation of a complex set of crustal discontinuities that had come into evidence during permo carboniferous times a comparison of the spatial and temporal thickness distribution of synrift deposits with preexisting fault patterns permits to infer a sequence of distinct basin subsidence phases that can be related to changes in the ambient stress field reactivation of a system of late palaeozoic fault systems outlining troughs and highs controlled the nucleation of initially separated middle and late eocene basins the depocenters of which coincided with a preexisting wsw ene trend during oligocene crustal extension the individual basins coalesced resulting in the development of the ssw nne striking upper rhine graben during the late oligocene chattian change in stress field the upper rhine graben was probably reactivated as a dextral strike slip system with the central graben segment forming a releasing bend during the early miocene aquitanian a major reorientation of the regional stress field is held responsible for the main subsidence phase of the northern parts of the upper rhine graben this is reflected by a counterclockwise rotation and northeastward shift of the depocenter axis and later by the middle miocene uplift and erosion of the southern parts of the upper rhine graben during the plio quaternary the upper rhine graben was reactivated as a sinistral strike slip system with the central graben segment forming a restraining bend

cool equatorial terrestrial temperatures and the south asian monsoon in the early eocene evidence from the gurha mine rajasthan india abstract early eocene 55 52 ma laminated lacustrine sediments overlying lignites in the gurha mine 27 87398 n 72 86709 e rajasthan india yield a diversity of fossil leaves flowers fruits seeds and insects clamp multivariate foliar physiognomic analysis of two horizons separated by an estimated several tens of thousands of years of deposition indicates cool equatorial 10 n temperatures and a pronounced monsoon signature a lower assemblage consisting of 54 leaf morphotypes and an upper assemblage of 57 leaf forms yielded mean annual temperatures mat of 24 7 and 23 9 c respectively the uncertainty 2 82 c means these temperature regimes are identical despite few similarities in the morphotypes between the two assemblages the mean annual range of temperature mart was approximately 9 7 c for both assemblages when corrected for evapotranspirational cooling these temperature regimes are similar to those experienced today at 10 n on the west coast of india and surprisingly cool for the tropics at a time of extreme global warmth growth was year round the tropical to paratropical fossil floras also suggest a moist regime 80 annual relative humidity and high mean annual precipitation of 1800 mm for both assemblages but with a pronounced wet dry seasonality indicative of a pronounced monsoonal regime the lower assemblage has a stronger monsoon index 11 8 than the upper assemblage 8 8 the two assemblages seem to have been deposited less than 100 ka apart this suggests that not only a pronounced south asian monsoon existed when india and asia first made contact but also a variation in monsoon strength existed that cannot be ascribed to tectonic drivers

analysis of fluvial suspended sediment load contribution through anthropocene history to the south atlantic bight coastal zone u s a abstract discerning the effects of anthropogenic activities i e reservoir construction land use change as opposed to those of natural processes i e climate variability on suspended sediment flux has become an increasingly difficult challenge this contribution presents water and suspended sediment flux from five major watersheds that discharge into the southeastern u s atlantic a region that is currently considered sediment starved three periods of anthropocene time were defined and evaluated 1 pre european conditions 1680 1700 2 pre dam conditions 1905 1925 and 3 post dam conditions 1985 2005 physical and hydrologic watershed data were used to run a climate driven hydrological transport numerical model hydrotrend to estimate suspended sediment flux for each period results indicate that the suspended sediment contribution to the south atlantic bight coastal zone increased by up to 145 as a result of accelerated soil erosion conditions caused by the arrival of europe

late paleocene early eocene climate changes in southwestern wyoming paleobotanical analysis the warmest global temperatures of the cenozoic era occurred in early eocene time following a warming trend that started in late paleocene time the greater green river basin of southwestern wyoming is one of the best areas in the rocky mountains for paleobotanical investigation of the paleocene eocene climatic transition intensive sampling has resulted in the recovery of an estimated 189 species of plant macrofossils from the tiffanian clarkforkian wasatchian and bridgerian land mammal ages the leaf morphologies and taxonomic affinities of these fossils were used in combination with other indicators to evaluate paleocene eocene climates following cool humid conditions in the tiffanian the clarkforkian was humid and subtropical and several plant families with modern tropical affinities appeared however as in the tiffanian clarkforkian floras had low diversity and were dominated by a single species in the birch family mean annual temperature mat rose from an estimated 12 c in the tiffanian to 19 c in the clarkforkian while mean annual precipitation map for the tiffanian and clarkforkian is estimated to have been 130 150 cm little fossil plant material is preserved from the latest clarkforkian or the earliest wasatchian which is thought to have contained an interval of cooling and drying followed by renewed warming by the middle wasatchian the time of the cenozoic thermal maximum the inferred mat was about 21 c and the map was near 140 cm a second influx of plant families with tropical affinities appeared in the area and diversity increased significantly but most plant families known from the clarkforkian persisted species turnover from the clarkforkian to the wasatchian was greater than 80 a second turnover of more than 80 of species but not families from the wasatchian to the early bridgerian accompanied drying and increased seasonality of precipitation the early bridgerian mat is inferred to have been near 20 c and the map to have been about 80 cm except for the tiffanian and possibly portions of the early wasatchian paleoclimates during the study interval were predominantly frost free although the moderating influence of the green river lake system has been suggested as a possible explanation for mild eocene winters in wyoming this study shows that virtually frostfree climates existed in the area prior to and independent of significant lake development

oxygen isotope and paleobotanical estimates of temperature and δ18o latitude gradients over north america during the early eocene empirical estimates of climate parameters such as mean annual temperature mat are essential to describe both ancient climate and to ground truth climate model simulations of past climates in terrestrial settings no single proxy record is able to provide detailed temporal yet geographically widespread information and it thus becomes essential that paleoclimatic information obtained from different proxies be comparable as an example of how to compare estimates and to illustrate what can be learned by doing so we measured oxygen isotope ratios of phosphate in the tooth enamel of fossil mammals and the body scales of freshwater fish in order to estimate the mean annual temperature mat in which they lived the samples were collected from paleogene rocks of the bighorn green river and powder river basins of wyoming earliest eocene samples provide mat estimates that are similar to mat estimates for the same times and areas obtained from leaf margin analysis furthermore isotopic data from the paleocene eocene thermal maximum petm which has not yet yielded fossil floras indicate a significantly higher mat of 26 c we also used temperature estimates obtained by both methods to investigate paleoelevation and to reconstruct geographic patterns of mat over north america for the early eocene larger laramide basins have higher temperatures and lower inferred elevations compared to associated volcanic highlands where cooler temperatures are consistent with substantial elevations in turn latitudinal gradients in temperature indicate that warming centered on polar regions played an important role during the eocene hothouse lastly we show that the reconstructed eocene relation between oxygen isotope ratios of precipitation and mat is significantly different from the modern relation between these two variables because the relation has changed over time the modern correlation should not be used to estimate paleo mat from measurements of oxygen isotope ratios in fossil material

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

paratropical floral extinction in the late palaeocene early eocene the palaeocene eocene thermal maximum petm at c 55 8 ma marks a transient c 100 ka duration interval of rapid greenhouse warming that had profound effects on marine and terrestrial biota plant communities responded rapidly with major compositional turnover the long term effects on tropical vegetation communities that stem from the brief period of global warming are unclear we present pollen data from the paratropical us gulf coast eastern mississippi western alabama and georgia which had background palaeogene mean annual temperatures of 26 27 c sporomorph data pollen and spores demonstrate that taxonomic diversity increases over c 1 ma in the late palaeocene but this trend is replaced with the first occurrences of taxa that mark the early eocene by a pronounced extinction into the early eocene c 20 of the palynoflora taxonomic diversity also decreases by up to 38 in the early eocene the timing of the extinction is not clearly resolved but may be restricted to the earliest part of the early eocene two richness estimators chao 2 and jackknife 2 both demonstrate that late palaeocene samples contain significantly more taxa than those in the early eocene extinction on the us gulf coast proves that ancient tropical ecosystems were highly susceptible to changes in diversity mediated directly or indirectly by environmental change even during equable greenhouse climates in the early palaeogene

discrete element modelling of the influence of cover strength on basement involved fault propagation folding abstract a discrete element model is used to investigate the influence of sedimentary cover strength on the development of basement involved fault propagation folds we find that uniformly weak cover best promotes the development of classical trishear like fault related folds showing marked anticlinal thinning and synclinal thickening with cover dips increasing downwards towards the fault tip uniformly strong cover results in more rounded fold forms with only minor hinge thickening thinning and significant basement fault propagation into the sedimentary cover heterogeneous layered cover sequences with marked differences in strength promote the development of more complex and variable fold forms with a close juxtaposition of brittle and macroscopically ductile features which diverge from the predictions of simple kinematic models in these structures the upper layers are often poor indicators of deeper structure in addition we find that in layered cover sequences fault propagation into the cover is a complex process and is strongly buffered by the weaker cover units

short term fluctuations in vegetation and phytoplankton during the middle eocene greenhouse climate a 640 kyr record from the messel oil shale germany the palaeogene was the most recent greenhouse period on earth especially for the late palaeocene and early eocene several superimposed short term hyperthermal events have been described including extremes such as the palaeocene eocene thermal maximum major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events high resolution palynological analysis of the early middle eocene maar lake sediments at messel near darmstadt germany provides an insight into the dynamics of a climax vegetation during the middle eocene greenhouse climate in a time span without significant climatic excursions numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long term trends in the vegetation through a time interval of approximately 640 kyr based on the numerical zoning of the pollen diagram three phases in the development of the vegetation may be distinguished throughout these phases the climax vegetation did not change substantially in qualitative composition but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized a shift in algal population from the freshwater dinoflagellate cyst messelodinium thielepfeifferae to a dominance of botryococcus in the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake time series analyses of pollen assemblages show that variations in the milankovitch range of eccentricity obliquity and precession can be distinguished in addition fluctuations in the sub milankovitch range are indicated this demonstrates that floral changes during steady depositional conditions in the middle eocene of messel were controlled by orbital forcing

aerial magnetic mapping with an unmanned aerial vehicle and a fluxgate magnetometer a new method for rapid mapping and upscaling from the field to regional scale abstract magnetic measurements with an unmanned aerial vehicle are ideal for filling the gap between ground and airborne magnetic surveying however to obtain accurate aeromagnetic data the compensation of magnetic effects of the unmanned aerial vehicle is a challenge typically scalar magnetometers are towed several metres under the unmanned aerial vehicle to minimize its magnetic field in this study a fluxgate three component magnetometer is attached 42 cm in front of the unmanned aerial vehicle at the tip of a composite pipe using a scalar calibration the sensor can be calibrated and the permanent and induced magnetic fields of the unmanned aerial vehicle can be compensated the contributions of the magnetic measurements at different altitudes to the unmanned aerial vehicle results were tested over an area of 1 km in the northern vosges mountains the area is located in a hamlet surrounded by a forest where few geological outcrops are observed three magnetic surveys of the same area are obtained at different altitudes 100 30 and 1 m above the ground the unmanned aerial vehicle magnetic data are compared with a helicopter aeromagnetic survey at 300 m above the ground and a ground magnetic survey using upward continuations of the maps to compare the results the magnetic maps 300 100 30 and 1 m above the ground show very different magnetic anomaly patterns e g amplitude shape wavelength and orientation the magnetic data at different altitudes improve the understanding of the geology from the local to more general scales

plate interactions at the southern end of the rhine graben abstract the southern end of the rhine graben in the basel area originated in the early tertiary as an extensional structure it is the site of a transfer zone that connected the rhine graben with the bresse rhone grabens this transfer zone is located in an area into which a late paleozic trough projects which apparently was reactivated from the beginning of miocene to recent times three distinct phases of slight compression were superimposed on the southern end of the rhine graben the first one in the aquitanian early burdigalian is coeval with the development of the helvetic nappes and the insubric fault zone in the alps the second one in the langhian tortonian interval occurred when the external massifs and an important part of the lombardic fold thrust belt in the southern alps developed and the third pliocene to recent one is contemporaneous with the inactivation of this belt and its incorporation into the foredeep of the northern apennines in the aquitanian the forebulge of the alpine orogen is recognizable as a system of flexures that developed preferably on the margin of the late paleozoic trough the middle late miocene one gave rise to uplift of the black forest vosges domain and a river system flowing from this high to the south in the pliocene to recent one alpine rivers made their appearance flowing first to the west into the rhone system and then as the rhine to the north the pliocene to recent phase seems to be decoupled from the body of the central and southern alps

lower triassic sequence stratigraphy of the western part of the germanic basin west of black forest fluvial system evolution through time and space abstract the aim of this paper is to analyse the fluvial evolution of the lower triassic in the western part of the germanic basin through time and space as well as the impact of the geodynamic and climatic setting on the preservation of fluvial deposits the lower triassic crops out only in the vosges massif and the black forest so well log studies are required to realise sequence stratigraphy correlations and establish comparisons with others parts of the germanic basin in a first step we use well log data analyses to characterise the electrofacies associations in the triassic and then define the well log signatures of each formation in a second step the characterisation and recognition of genetic sequences and their stacking pattern allow us to define seven minor cycles integrated into two major cycles finally the quantification of the lithologies at different stages of basin evolution leads to the reconstruction of paleoenvironmental maps to illustrate facies evolution through space and time a comparison with cycles defined in the germanic basin allows us to propose correlations of the lower triassic on either side of the rhine graben and leads to a discussion of the evolution of fluvial systems through time and space during the scythian the fluvial style is characterised by braided fluvial systems evolving laterally into lake deposits towards the central part of the germanic basin during this stage the basin was a huge depression with very few marine connections in its extreme eastern part the stratigraphic cycles represent rhythmic fluctuations in relative lake level that could be attributed to sediment supply and or lake level variations in an arid setting four minor stratigraphic cycles are observed that are integrated within a single major stratigraphic cycle during the period of the stratigraphic base level rise of the major cycle a maximum of 233 m of sediment would represent a duration of sedimentation in the paris basin of at least 1 8 m y during the period of the stratigraphic base level fall of the major cycle a maximum of 65 m of sediment would have accumulated over 2 5 m y on the western edge of the germanic basin the top of the scythian is marked by a major sedimentary break characterised by a planation surface with preservation of the first paleosols followed by the hardegsen unconformity this unconformity is tectonically deformed leading to the development of a new sedimentation area in the west of the basin the fluvial sedimentation above this discontinuity shows a trend towards enhanced development of floodplain or lacustrine type environments at its western margin with the formation of paleosols the fluvial systems are linked with sabkhas and then with a shallow sea connected to the tethys ocean in this context the stratigraphic cycles are caused by variations in relative sea level and or sediment supply the fluvial deposits are preserved in an exoreic basin

the variscan tectonic inheritance of the upper rhine graben evidence of reactivations in the lias late eocene oligocene up to the recent processing of gravity and magnetic maps shows that the basement of the upper rhine graben area is characterized by a series of ne sw trending discontinuities and elongated structures identified in outcrops in the vosges black forest and the odenwald mountains they form a 40 km wide n30 40 striking sinistral wrench zone that in the visean shifted the variscan and pre variscan structures by at least 43 km to the ne wrenching was associated with emplacement of several generations of plutonic bodies emplaced in the time range 340 325 ma the sub vertical ne sw trending discontinuities in the basement acted as zones of weakness susceptible to reactivation by subsequent tectonism the first reactivation marked by mineralizations and palaeomagnetic overprinting along ne sw faults of the vosges mountains results from the liassic nw se extension contemporaneous with the break up of pangea the major reactivation occurred during the late eocene n s compression and the early middle oligocene e w extension the ne sw striking basement discontinuities were successively reactivated as sinistral strike slip faults and as oblique normal faults elongated depocenters appear to form in association with reactivated variscan wrench faults some of the recent earthquakes are located on ne sw striking variscan fault zones and show sinistral strike slip focal mechanisms with the same direction suggesting also present reactivation

simultaneous normal faulting and extensional flexuring during rifting an example from the southernmost upper rhine graben the southern end of the upper rhine graben urg is formed by a major continental transfer zone which was localised by the reactivation of ene oriented basement faults of late palaeozoic origin a combination of subcrop data derived from exploration wells and reflection seismic lines and palaeostress analysis provided new constraints on the timing and kinematics of interacting basement faults rifting in the southern urg began in the upper priabonian under regional wnw ese directed extension oriented roughly perpendicular to the graben axis in the study area this led to the formation of nne trending half grabens simultaneously ene trending basement faults situated in the area of the future rhine bresse transfer zone rbtz were reactivated in a sinistrally transtensive mode in the sedimentary cover the strike slip component was accommodated by the development of en echelon aligned extensional flexures flexuring and interference between the differently oriented basement faults imposed additional but locally confined extension in the sedimentary cover which deviated by as much as 90 from the regional wnw ese extension the interference of regional and local stresses led to a regime approaching radial extension at the intersection between the urg and rbtz

style and sequence of deformation during extensional fault propagation folding examples from the hammam faraun and el qaa fault blocks suez rift egypt kilometre scale fault parallel folds are identified adjacent to normal faults in the oligo miocene suez rift egypt and are interpreted to have formed in response to fault propagation folding above upward propagating blind faults the geometry scale and distribution of secondary structures within the folds and their cross cutting relationships with the master faults allow the style and sequence of deformation during fault propagation folding to be established and suggest that during the initial stages of folding the proto footwall underwent extension which was accommodated by layer parallel slip in encasing mudstone horizons and linked normal faulting and block rotation in carbonate and sandstone units the proto hanging wall also contains dominantly extensional normal faults although locally where the master fault had a convex into the footwall map view trace reverse faulting and fracturing occurred secondary structures adjacent to the master fault were not all active simultaneously but initiated and died at different stages during the evolution of the fault propagation fold the results of this study confirm many key predictions of numerical and physical analogue models but also highlight several important controls on the evolution of fault propagation folds in extensional settings which existing models cannot capture such as the influence of the map view trace of the propagating fault and lateral variations in cover stratigraphy lithology and strength on the style and magnitude of secondary deformation

intra annual isotopic variation in venericardia bivalves implications for early eocene temperature seasonality and salinity on the u s gulf coast abstract stable isotope compositions were determined for 166 microsamples of aragonite from the bivalve venericardia hatcheplata collected from the early eocene hatchetigbee formation in southwestern alabama these were milled from two transects one across the left valve hinge plate and one along the growth axis amplitude and spacing of about nine years of seasonal variation is very regular with peaks and troughs occurring at equal intervals and reaching consistent compositions except for some attenuation in both parameters during the last three years of life assuming an ice free world with an ocean 18o value of about 1 0 and using the aragonite water fractionation equation of grossman and ku 1986 isotope derived paleotemperatures are somewhat warmer 31 c than temperatures presently recorded anywhere on the earth s surface and exhibit significantly greater seasonality 12 c than regions with the warmest mean temperatures it is therefore likely that these very negative and extremely seasonal 18o values reflect the influence of seasonal discharge of 18o depleted river water into the eocene gulf of mexico comparison of these data with 1 mean annual temperature versus seasonal temperature variation from modern climates 2 isotopic compositions reported from coeval molluscs and 3 isotopic compositions of global meteoric precipitation and united states rivers suggest that mean annual temperature along this portion of the eocene gulf coast was in fact about 26 c and varied seasonally from a winter low of about 25 c to a summer high of 27 c differences between these temperatures and those derived from direct conversion of oxygen isotope values reflect the influence of seasonal influx of fresh 18o value of 4 7 water during deposition of this portion of the hatchetigbee formation ambient water 18o values varied between winter values of about 1 0 to less than 3 5 during the summer freshwater discharge served to seasonally depress salinity to 10 to 16 ppt along this part of the gulf coast the early eocene was perhaps the warmest time interval of the past 65 million years primarily manifest as lower equator to pole temperature gradients in this context an eocene mean annual temperature of 26 c is not much higher than modern surface water temperatures of about 24 c at 29 30 n immediately off the modern alabama coast seasonal temperature variation of 2 to 3 c about a mean of 26 c however is significantly lower than that off coastal alabama 19 to 30 c and occurs only along modern equatorial coasts at latitudes less than 19 this implies that early eocene tropical conditions extended well beyond modern latitudinal limits

mammalian community response to the latest paleocene thermal maximum an isotaphonomic study in the northern bighorn basin wyoming new stratigraphic and paleontological information from the mccullough peaks northern bighorn basin wyoming is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest paleocene thermal maximum and coincident earliest wasatchian immigration event on local mammalian community structure surface collections from willwood formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium to large sized components of underlying mammalian communities rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness after this initial increase diversity tapered off to more typical wasatchian levels that were still higher than those in the preceding clarkforkian wasatchian immigrants were rapidly incorporated into the new community organization representing 20 of the taxa and 50 of the individuals immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa causing significant turnover in body size structure and trophic structure there was a significant short term body size decrease in many lineages that may have been prompted by the elevated temperatures and or decreased latitudinal thermal gradients during the latest paleocene thermal maximum rapid short term climatic change transient climates and associated biotic dispersal can have abrupt and long lasting effects on mammalian community evolution

deep crustal structure of the rhine graben from dekorp ecors seismic reflection data a summary abstract results of two deep reflection seismic lines crossing the northern and southern part of the rhine graben which were recorded in 1988 by the french ecors and the german dekorp teams indicate that the asymmetry of this rift persists to the base of the crust the brittle ductile transition zone approximately coincides with the top of the lower crust ductile shear zones appear to affect the crust mantle boundary upper crustal extension by faulting accounts for a divergence of the graben flanks by 5 7 km whereas the crustal configuration of the rhine graben suggest an extension value of some 17 km

normal fault growth displacement localisation and the evolution of normal fault populations the hammam faraun fault block suez rift egypt abstract fault segment linkage migration of the locus of fault activity and displacement localisation were important processes controlling the late oligocene recent evolution of the normal fault population of the hammam faraun fault block suez rift initial fault activity was distributed across the fault block on fault segments that had attained their final length within 1 2 my of rifting these initial segments then either grew by increasing displacement and linked to form longer segmented fault zones or died during a rift initiation phase that lasted 6 8 my following this rift initiation phase displacement became localised onto 25 km long border fault zones bounding the fault block and many of the early high displacement intra block fault zones died following displacement localisation onto the major faults bounding the fault block the locus of maximum displacement continued to migrate with post middle miocene displacement focused on the western margin of the fault block this migration of fault activity between major crustal scale normal faults can be viewed in terms of strain localisation at the rift scale the results from this study question conventional fault growth models based on final displacement distributions and highlight the sequential nature of faulting on major normal faults bounding domino style tilted fault blocks

long term resilience decline in plant ecosystems across the danian dan c2 hyperthermal event boltysh crater ukraine mass balance calculations indicate that a massive amount of 13 c depleted carbon was released into the early danian atmosphere in volumes comparable with the younger paleocene eocene thermal maximum petm this danian hyperthermal event the dan c2 has been documented from the fill of the boltysh meteorite crater ukraine palynofloras recovered from the boltysh crater fill show a trend from mesic forest to savannah ecosystem dominance on a millennial scale across the hyperthermal inception with no abrupt compositional shift this longer term trend is overprinted by moisture availability oscillations reflecting orbital forcing forcing is not directly tracked by the oscillations which are composed of mesic forest and savannah palynofloras separated by rapid critical transitions the absence of an ecological collapse at the dan c2 indicates that plant ecosystems experienced dominant forcing from orbital cyclicity rather than a stochastic temperature rise

magnetostratigraphic correlation of paleogene sequences from northwest europe and north america using all available biostratigraphic information and our own extensive magnetostratigraphic database we have attempted to assess the synchronicity of depositional cycles recorded in the paleogene epicontinental deposits on both sides of the north atlantic as stage two of a four stage global assessment of the eustatic sea level model our conclusion is that the depositional histories of the u s gulf of mexico atlantic coastal plain and the north sea basin show many similarities on a variety of time scales over the interval 60 46 ma considering the tectonic imprint of the northeast atlantic opening on the north sea basin sea level record for part of this time it must give some weight to the claim that eustasy is the dominant mechanism controlling deposition on passive continental margins

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

paleomagnetic investigations and k ar dating on the variscan plutonic massif of the champ du feu and its volcanic sedimentary environment northern vosges france abstract paleomagnetic investigations have been carried out on samples from the plutonic series of the champ du feu massif and the devonian ordovician host rocks in order to date the different phases of magnetization a series of samples has been selected for k ar analysis on micas amphiboles and feldspars the diorites granodiorites diabases and hornfelses are characterized by high susceptibilities of up to 10 1 si thermal demagnetization reveals several groups of directions of characteristic magnetization the a direction d 202 i 23 49 n 153 e is consistent with the permian virtual geomagnetic pole for europe the b 1 direction d 59 i 22 11 n 128 5 e was obtained from the effusive parts of the kagenfels granite dated at 284 ma diorites microdiorites and volcanics emplaced a short time after the intrusion of the natzwiller granite dated at 344 and 351 ma display three groups of directions the c 1 direction d 328 i 15 27 n 223 5 e the c 2 d 323 i 38 13 s 222 e and the c 3 d 272 i 41 16 s 260 e the c 1 and c 2 directions agree well with those obtained previously for visean volcanics from the southern vosges in the host rocks we have identified b and c overprintings despite the lack of tectonic control the paleomagnetic data demonstrate at least two important motions of the vosges first a rotation of undetermined direction relative to stable europe which affected the variscan belt between the late visean and 320 ma and second a clockwise rotation which occurred during the stephanian autunian in late variscan time

paleogeography of the upper rhine graben urg and the swiss molasse basin smb from eocene to pliocene twenty paleogeographic maps are presented for middle eocene lutetian to late pliocene times according to the stratigraphical data given in the companion paper by berger et al this volume following a first lacustrine continental sedimentation during the middle eocene two and locally three rupelian transgressive events were identified with the first corresponding with the early rupelian middle pechelbronn beds and the second and third with the late rupelian serie grise fischschiefer and equivalents during the early rupelian middle pechelbronn beds a connection between north sea and urg is clearly demonstrated but a general connection between north sea urg and paratethys via the alpine sea is proposed but not proved during the late rupelian whereas in the southern urg a major hiatus spans early aquitanian to pliocene times early and middle miocene marine brackish and freshwater facies occur in the northern urg and in the molasse basin omm osm however no marine connections between these basins could be demonstrated during this time after the deposition of the molasse series a very complex drainage pattern developed during the late miocene and pliocene with a clear connection to the bresse graben during the piacenzian sundgau gravels during the late miocene pliocene and quaternary sedimentation persisted in the northern urg with hardly any interruptions the present drainage pattern of the rhine river from alpine area to the lower rhine embayment was not established before the early pleistocene

rapid carbon sequestration at the termination of the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum warm event about 56 million years ago was caused by the release of large amounts of carbon to the ocean and atmosphere estimates of the rate of recovery from the event suggest that about 2 000 pg of the carbon released was sequestered as organic carbon

kinematic modelling of extensional fault propagation folding abstract many studies have shown that in extensional basins discrete faulting at depth is commonly linked to more distributed deformation in particular folding at higher levels such extensional fault propagation folds are particularly common where there is a distinct mechanical contrast between faulted basement and sedimentary cover outcrop and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation monoclines above discrete faults at depth with increasing displacement strain the folds are cut by faults as they propagate upwards into the cover to date however there has been little investigation into the kinematics of linked basement faulting and extensional fault propagation folding here we present a two dimensional kinematic model of linked basement faulting and fault propagation folding which is based upon trishear the model allows investigation of the influence of shear zone geometry and the rate of fault propagation upon the style of folds and the strains associated with them the evolution of linked basement faulting and folding predicted by the model is compared in detail to that observed in an analogue model the kinematic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies

influence of varying tidal prism on hydrodynamics and sedimentary processes in a hypertidal salt marsh creek recent initiatives directing tidal power development in the bay of fundy have raised questions about far field environmental impacts related to energy extraction it is understood that commercial scale tidal power installations in the minas passage will result in an overall decrease in tidal amplitude in the minas basin corresponding changes in sedimentation patterns may or may not be within the natural range of variability and it is hypothesized that intertidal sedimentation rates will demonstrate a non linear response to modification of the tidal energy regime this research considers acoustic doppler velocimeter adv and optical backscatter sensor obs data from a sheltered tidal creek in the minas basin for analysis of tidal characteristics in a hypertidal creek environment over spring and neap tidal cycles sediment deposition in the creek was also measured results show a first order control of topography on flow magnitude in the tidal creek which impacts net sediment deposition through resuspension and removal of newly introduced material this study demonstrates that tides which peak around the bankfull level show reduced early ebb stage turbulence and flow velocity and encourage an extended depositional period the dynamics of marshfull tides may be responsible for the maximum sediment deposition in tidal creeks providing large amounts of material that is eventually distributed to and deposited on marsh surfaces copyright 2012 john wiley sons ltd