the paleocene eocene transition at mead stream new zealand a southern pacific record of early cenozoic global change mead stream in marlborough new zealand exposes a spectacular 650 m thick stratigraphic section of well bedded micritic limestone chert and marl that was deposited on a south pacific upper continental slope from late cretaceous to middle eocene the 200 m upper paleocene lower eocene succession was examined for its lithology bulk carbonate carbon isotopes and assemblages of radiolarians calcareous nannoplankton and foraminifera so that it could be placed into a global context the interval displays several prominent carbon isotope anomalies and is correlated with south pacific radiolarian zones rp5 to rp9 and calcareous nannofossil zones np6 8 to np12 additionally planktic foraminiferal zones p4 to p6b are identified in uppermost paleocene and lower eocene strata mead stream has a near continuous paleocene lower eocene sediment record and three globally significant climate events the late paleocene carbon isotope maximum pcim the initial eocene thermal maximum ietm and the early eocene climatic optimum eeco have obvious expressions the pcim is a 50 m thick interval of biosiliceous micritic limestone in which 13c is 3 the lower part contains two organic rich biosiliceous mudstone units that may represent expansion of an oxygen minimum zone omz during a global increase in marine biological productivity the ietm is a 4 m thick interval in which 13c drops below 1 5 in a pattern seen at other locations the basal 2 4 m is a distinctive recessed marl rich unit that is defined herein as the dee marl the ietm is marked by a rapid decline in the nannoplankton genus fasciculithus short lived occurrences of discoaster cf araneus and morozovella aequa aequa and significant radiolarian faunal turnover owing to impoverished benthic faunas the benthic foraminiferal extinction event bfee is poorly defined the onset of the eeco is marked by a 1 negative 13c excursion a transition from limestone rich to marl rich facies and a marked decrease in radiolarian abundance compacted sedimentation rates vary between 1 4 2 7 cm kyr for upper paleocene lower eocene strata at mead stream although individual beds with average thickness of 10 cm were deposited too fast to directly represent cycles in orbital parameters time series analysis of bed thicknesses suggests that groups of beds may record milankovitch scale periodicity perhaps with a significant obliquity component thus the relative frequency and thickness of marl and limestone beds in this section is shown to be strongly influenced by climatic changes at a wide range of temporal scales from suborbital and orbital cycles to aberrant short term events and long term trends predominance of marl in ietm and eeco intervals indicates that episodes of extreme global warming resulted in reduced oceanic productivity and increased terrestrial discharge in the high latitude southwestern pacific

reappraisal of early paleogene ccd curves foraminiferal assemblages and stable carbon isotopes across the carbonate facies of perth abyssal plain bulk carbonate content planktic and benthic foraminiferal assemblages stable isotope compositions of bulk carbonate and nuttallides truempyi benthic foraminifera and non carbonate mineralogy were examined across 30 m of carbonate rich paleogene sediment at deep sea drilling project dsdp site 259 on perth abyssal plain off western australia carbonate content mostly reflecting nannofossil abundance ranges from 3 to 80 and generally exceeds 50 between 35 and 57 mbsf a clay rich horizon with a carbonate content of about 37 occurs between 55 17 and 55 37 mbsf the carbonate rich interval spans planktic foraminiferal zones p4c to p6b 57 52 ma with the clay rich horizon near the base of our zone p5 upper p6b throughout the studied interval benthic species dominate foraminiferal assemblages with scarce planktic foraminifera usually of poor preservation and limited species diversity a prominent benthic foraminiferal extinction event bfee occurs across the clay rich horizon with an influx of large acarinina immediately above the 13c records of bulk carbonate and n truempyi exhibit trends similar to those observed in upper paleocene lower eocene 57 52 ma sediment from other locations two successive decreases in bulk carbonate and n truempyi 13c of 0 5 and 1 0 characterize the interval at and immediately above the bfee despite major changes in carbonate content foraminiferal assemblages and carbon isotopes the mineralogy of the non carbonate fraction consistently comprises expanding clay heulandite zeolite quartz feldspar sodic or calcic minor mica and pyrolusite mno2 the uniformity of this mineral assemblage suggests that site 259 received similar non carbonate sediment before during and after pelagic carbonate deposition the carbonate plug at site 259 probably represents a drop in the ccd from 57 to 52 51 ma as also recognized at other locations

leaf waxes as recorders of paleoclimatic changes during the paleocene eocene thermal maximum regional expressions from the belluno basin abstract paired assessments of carbon 13 c lipids and hydrogen isotopic compositions of leaf wax lipids 2 h lipids from warm intervals in earth s history have been used to investigate the relationship between greenhouse gases hydrological cycle and global warming modern studies however show that 2 h lipids can exhibit significant variability due to secondary factors including differences in biosynthetic fractionation and 2 h enrichments in soil and leaf water to evaluate the intrabasinal variability of sedimentary compound specific isotopic records we generated new carbon and hydrogen isotopic compositions of leaf wax lipids for the paleocene eocene thermal maximum petm 55 ma from cicogna creek belluno basin northern italy and compared results with published petm records from the proximal forada creek section similar isotopic trends are observed at both localities the magnitude of the negative carbon isotope excursion at cicogna is 2 5 pre event 2 h enrichment recorded in the forada section is missing at cicogna likely due to a disturbed interval at the paleocene eocene boundary a 2 h depletion of 10 15 during the body of the petm at cicogna is observed in several petm sections implicating a primary change in the global hydrological cycle given the proximity of cicogna and forada isotopic compositions of paleo meteoric water are expected to be similar however a 15 offset between the records is apparent possible reasons include differences in vegetation biomarker transport and precipitation altitude underscoring the complexity of using a single record for zonal reconstructions and data model comparisons ultimately this study shows that while 2 h 1 h trends can be applied for paleoclimate analysis with reasonable certainty absolute magnitudes can be biased by secondary local factors

kinematics of active deformation in the sulaiman lobe and range pakistan the western margin of the indian plate is highly oblique to the direction of convergence between india and asia and represents an excellent example of large scale oblique continent continent collision determining the strain field in western pakistan and how it relates to the plate motion and plate margin geometry affords an exceptional opportunity for understanding oblique margin processes in general through the inversion of regional and teleseismic body waves we have determined the source parameters of 10 moderate sized earthquakes that occurred between 1964 and 1985 in and around the sulaiman range pakistan the earthquakes are dominantly thrust events with slip vectors that are approximately perpendicular to the lobate sulaiman mountain front slip vector orientations rotate 60 70 from a n s to a wnw ese direction of compression consistent with the geometries of the complex festoon shaped mountain belts of this margin we have estimated the spatial variation of the horizontal strain rate and velocity fields within sulaiman using vertically averaged models that accommodate plate motion constraints within a deforming layer the most important factors determining the style of strain rotation in the sulaiman lobe and range are the presence of pure strike slip motion along the chaman fault and the relatively rigid and undeformed katawaz basin that is therefore allowed to translate obliquely relative to india this same conclusion is obtained using either a three dimensional frictional analogue model with significant basal tractions or a thin sheet viscous numerical model without basal tractions thrusting in a predominantly nw se direction in the sulaiman range accommodates 5 14 mm yr of n s motion between india eurasia and 3 6 mm yr of e w shortening seismic moment release this century within the india eurasia plate boundary zone west of the western himalayan syntaxis constitutes roughly 40 of the expected total seismic moment release for this time period particularly significant moment rate deficits exist within the sulaiman range and along the chaman fault

ecological and biogeochemical change in an early paleogene peat forming environment linking biomarkers and palynology abstract sphagnum moss is the dominant plant type in modern boreal and sub arctic ombrotrophic bogs and is of particular interest due to its sensitivity to climate and its important role in wetland biogeochemistry here we reconstruct the occurrence of sphagnum moss and associated biogeochemical change within a thermally immature early paleogene 55 ma lignite from schoningen nw germany using a high resolution multi proxy approach changes in the abundance of sphagnum type spores and the c23 c31 n alkane ratio indicate the expansion of sphagnum moss within the top of the lignite seam this sphagnum moss expansion is associated with the development of waterlogged conditions analogous to what has been observed within modern ombrotrophic bogs the similarity between biomarkers and palynology also indicates that the c23 c31 n alkane ratio may be a reliable chemotaxonomic indicator for sphagnum during the early paleogene the 13c value of bacterial hopanes and mid chain n alkanes indicates that a rise in water table is not associated with a substantial increase in aerobic methanotrophy the absence of very low 13c values within the top of the seam could reflect either less methanogenesis or less efficient methane oxidation under waterlogged sulphate rich conditions

increasing restriction of the egyptian shelf during the early eocene new insights from a southern tethyan carbonate platform the evolution of the isolated galala carbonate platform has been studied intensively with respect to the paleocene eocene thermal maximum petm and the strong climatic variability from the late paleocene to the early eocene in this study we compare the results of different approaches which deal with the early palaeogene evolution of the egyptian shelf including new data from the galala platform microfacies analyses along a platform to basin transect reveal a sedimentological response to a massive tectonic uplift along the syrian arc fold belt in the early eocene this uplift triggered the restriction of the egyptian shelf by modulating and weakening tethyan onshore currents from the north the increasing deposition of quartz and proliferating gastropods green algae and radiolaria which indicate elevated nutrient levels reflect an intensified eutrophication of shallow marine platforms and deeper marine shelf environments strongly depleted carbon isotope ratios in the sediments of the galala succession strongly suggest the presence of restricted conditions throughout the early eocene we assume that a strong climatic divergence with arid conditions on the shelf and humid conditions at the african hinterland triggered intensified chemical weathering at the nubian arabian craton the enhanced riverine transport of terrestrial organic material to the north african shelf caused the increased availability of trophic resources and a strong negative shift of carbon isotope ratios between np10 and np14a the recovery to open ocean conditions is linked to the termination of tectonic uplift along the syrian arc fold belt in the latest early eocene and to stronger ocean currents caused by increasing latitudinal temperature gradients additionally the post petm carbon isotope evolution at the galala platform indicates at least two further negative carbon isotope excursions which reflect hyperthermal events on a global scale the associated reorganization of shallow marine assemblages as described for example for the larger foraminifera turnover at the petm boundary event is however missing we assume that the absence of a foraminiferal reorganization in this region can be linked to an increasing robustness of the major early eocene platform organisms larger benthic foraminifera and their adaption to unfavorable conditions and repeated environmental shifts 2011 elsevier b v

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

high latitude hydrological changes during the eocene thermal maximum 2 abstract the eocene hyperthermals including the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 represent extreme global warming events 56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations an initial study on petm characteristics in the arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound specific carbon and hydrogen isotopic 2h 1h records from sedimentary leaf wax lipids in this study we apply this isotopic and hydrological approach on sediments deposited during etm2 from the lomonosov ridge integrated ocean drilling program expedition 302 our results show similar 2h 1h changes during etm2 as during the petm with a period of 2h enrichment 20 relative to pre event values just prior to the negative carbon isotope shift cie that is often taken as the onset of the hyperthermal and more negative lipid 2h values 15 during peak warming notably lipid 2h enrichment at the base of the event is coeval with colder tex 86 h temperatures if 2h 1h values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation the observed local relationship between temperature and 2h 1h values for the body of etm2 is precisely the opposite of what would be predicted using a simple rayleigh isotope distillation model assuming a meridional vapor trajectory and a reduction in equator pole temperature gradients overall a negative correlation exists between the average chain length of n alkanes and 2h 1h suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes the negative correlation falls across three separate intervals the base of the event the initial cie and during the h2 hyperthermal of which the assignment is not fully certain three possible mechanisms potentially explain 2h enriched signals at the base of the event including 1 intense local drying and cooling leading to evaporative 2h enrichment 2 changes in frequency intensity of storm events and its impact on high latitude amount effects and 3 changes in low latitude temperatures evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases generation of similar high resolution isotopic and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early eocene hyperthermals

high resolution deep sea carbon and oxygen isotope records of eocene thermal maximum 2 and h2 eocene thermal maximum 2 etm2 and h2 were two short lived global warming events that occurred 2 m y after the paleocene eocene thermal maximum petm ca 56 ma we have generated benthic foraminiferal stable carbon and oxygen isotope records of four sites along a depth transect on walvis ridge 3 5 1 5 km paleodepth southeast atlantic ocean and one site on maud rise weddell sea to constrain the pattern and magnitude of their carbon isotope excursions cies and deep sea warming at all sites etm2 is characterized by 3 c warming and a 1 4 cie the h2 event that occurred 100 k y later is associated with 2 c warming and a 0 8 cie the magnitudes of the 13 c and 18 o excursions of both events are signifi cantly smaller than those during the petm but their coherent relation indicates that the 13 c change of the exogenic carbon pool was similarly related to warming during these events despite the much more gradual and transitioned onset of etm2 and h2

significant southern ocean warming event in the late middle eocene a prominent middle eocene warming event is identified in southern ocean deep sea cores indicating that long term cooling through the middle and late eocene was not monotonic at sites on maud rise and the kerguelen plateau a distinct negative shift in 1 8 o values 1 0 is observed ca 41 5 ma this excursion is interpreted as primarily a temperature signal with a transient warming of 4 c over 600 k y affecting both surface and middle bathyal deep waters in the indian atlantic region of the southern ocean this isotopic event is designated as the middle eocene climatic optimum and is interpreted to represent a significant climatic reversal in the midst of middle to late eocene deep sea cooling the lack of a significant negative carbon isotope excursion as observed during the paleocene eocene thermal maximum and the gradual rate of high latitude warming suggest that this event was not triggered by methane hydrate dissociation rather a transient rise in pco 2 levels is suspected possibly as a result of metamorphic decarbonation in the himalayan orogen or increased ridge arc volcanism during the late middle eocene

tectonic implications and seismicity triggering during the 2008 baluchistan pakistan earthquake sequence abstract a damaging and widely felt moderate earthquake mw 6 4 hit the rural mountainous region of southwestern pakistan on october 28 2008 the main shock was followed by another earthquake of identical magnitude mw 6 4 on the next day the spatial distribution of aftershocks and focal mechanism revealed a nw se striking rupture with right lateral strike slip motion which is sympathetic to the nnw sse striking active mapped urghargai fault the occurrence of strike slip earthquakes suggests that along with the thrust faults strike slip faults too are present beneath the fold and thrust belt of sulaiman kirthar ranges and accommodates some of the relative motion of the indian and eurasian plates to assess the characteristics of this sequence the statistical parameters like aftershocks temporal decay b value of g r relationship partitioning of radiated seismic energy due to aftershocks and spatial fractal dimension d value have been examined the b value is estimated as 1 03 0 42 and suggests the tectonic genesis of the sequence and crustal heterogeneity within rock mass the low p value of 0 89 0 07 implies slow decay of aftershocks activity which is probably an evidence for low surface heat flow a value of spatial fractal dimension of 2 08 0 02 indicates random spatial distribution and that the source is a two dimensional plane filled up by fractures the static coseismic coulomb stress changes due to the foreshock mw 5 3 were found to increase stress by more than 0 04 bars at the hypocenter of the main shock thus promoting the failure the cumulative coseismic coulomb stress changes due to the foreshock and mainshocks suggest that most of the aftershocks occurred in the region of increased coulomb stress and to the se to the mainshock rupture

atmospheric pco2 reconstructed across five early eocene global warming events abstract multiple short lived global warming events known as hyperthermals occurred during the early eocene 56 52 ma five of these events the paleocene eocene thermal maximum petm or etm1 h1 or etm2 h2 i1 and i2 are marked by a carbon isotope excursion cie within both marine and terrestrial sediments the magnitude of cie which is a function of the amount and isotopic composition of carbon added to the ocean atmosphere system varies significantly between marine versus terrestrial substrates here we use the increase in carbon isotope fractionation by c3 land plants in response to increased pco2 to reconcile this difference and reconstruct a range of background pco2 and peak pco2 for each cie provided two potential carbon sources methane hydrate destabilization and permafrost thawing organic matter oxidation although the uncertainty on each pco2 estimate using this approach is low e g median uncertainty 23 18 this work highlights the potential for significant systematic bias in the pco2 estimate resulting from sampling resolution substrate type diagenesis and environmental change careful consideration of each of these factors is required especially when applying this approach to a single marine terrestrial cie pair given these limitations we provide an upper estimate for background early eocene pco2 of 463 248 131 ppmv methane hydrate scenario to 806 127 104 ppmv permafrost thawing organic matter oxidation scenario these results which represent the first pco2 proxy estimates directly tied to the eocene hyperthermals demonstrate that early eocene warmth was supported by background pco2 less than 3 5 preindustrial levels and that p co 2 1000 ppmv may have occurred only briefly during hyperthermal events

abrupt increase in seasonal extreme precipitation at the paleocene eocene boundary a prominent increase in atmospheric co at the paleocene eocene boundary ca 55 ma led to the warmest earth of the cenozoic for similar to 100 k y high resolution studies of continental flood plain sediment records across this boundary can provide crucial information on how the hydrological cycle responds to rapidly changing co2 here we show from continental records across the paleocene eocene boundary in the spanish pyrenees a subtropical paleosetting that during the early most intense phase of co2 rise normal semiarid coastal plains with few river channels of 10 200 m width were abruptly replaced by a vast conglomeratic braid plain covering at least 500 km 2 and most likely more than 2000 km 2 this braid plain is interpreted as the proximal parts of a megafan carbonate nodules in the megafan deposits attest to seasonally dry periods and together with megafan development imply a dramatic increase in seasonal rain and an increased intra annual humidity gradient the megafan formed over a few thousand years to similar to 10 k y directly after the paleocene eocene boundary only repeated severe floods and rainstorms could have contributed the water energy required to transport the enormous amounts of large boulders and gravel of the megafan during this short time span the findings represent evidence for considerable changes in regional hydrological cycles following greenhouse gas emissions less

orbital chronology of early eocene hyperthermals from the contessa road section central italy article i nfo article history high resolution geochemical analyses of the lower eocene contessa road section italy reveal orbitally controlled uctuations in the percent concentration of calcium carbonate wt caco3 that include the etm2 elmo and etm3 x hyperthermal events patterns of increased dissolution negative carbon isotope excursions and warmer global climates are intimately linked to maxima in insolation through the global carbon cycle extraction of short and long eccentricity orbital periodicities of the wt caco3 record provides a relative cyclochronologyfortheintervalrangingfrom 52to 55 5 ma thecontessaroadsectioniseasilyaccessibleand offers a continuous integrated stratigraphic record stable isotopes standard calcareous plankton biostrati graphy magnetostratigraphy and cyclostratigraphy thus providing a potential type succession for the study of early eocene hyperthermals

constraints on ocean acidification associated with rapid and massive carbon injections the early paleogene record at ocean drilling program site 1215 equatorial pacific ocean massive amounts of 13c depleted carbon rapidly entered the ocean more than once during the early paleogene providing a geological framework for understanding future perturbations in carbon cycling

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

south pacific intermediate water oxygen depletion at the onset of the paleocene eocene thermal maximum as depicted in new zealand margin sections 1 extreme global warming and massive input of 13c depleted carbon into the exogenic carbon cycle characterize the paleocene eocene thermal maximum petm circa 55 5 ma previous work indicates that dissolved o2 concentrations dropped in some regions of the ocean during this event but spatial temporal and causal relationships between warming carbon input and o2 deficiency remain elusive we present lithologic carbon isotopic and trace fossil results from outcrops in new zealand that clarify this issue sections exposed at mead and dee streams in eastern marlborough south island contain expanded sedimentary intervals that were deposited before during and after the petm on an upper continental slope the petm in these intervals is characterized by enhanced siliciclastic deposition a hallmark negative carbon isotope excursion and a loss of bioturbation importantly however the latter only occurs during the prominent drop in 13c and not during its recovery our results suggest that south pacific intermediate waters became hypoxic coincident to carbon injection at the start of the petm while higher sea surface temperatures throughout the petm would have decreased the dissolved oxygen content of sinking surface waters we argue here that oxygen depletion was driven by some combination of elevated temperature water column stratification and intermediate water methane oxidation

an extraterrestrial 3he based timescale for the paleocene eocene thermal maximum petm from walvis ridge iodp site 1266 in the deep sea the paleocene eocene thermal maximum petm is often marked by clay rich condensed intervals caused by dissolution of carbonate sediments capped by a carbonate rich interval constraining the duration of both the dissolution and subsequent cap carbonate intervals is essential to computing marine carbon fluxes and thus testing hypotheses for the origin of this event to this end we provide new high resolution helium isotope records spanning the paleocene eocene boundary at odp site 1266 in the south atlantic the extraterrestrial 3he 3he et concentrations replicate trends observed at odp site 690 by farley and eltgroth 2003 by assuming a constant flux of 3he et we constrain relative changes in accumulation rates of sediment across the petm and construct a new age model for the event in this new chronology the zero carbonate layer represents 35 kyr some of which reflects clay produced by dissolution of paleocene pre petm sediments above this layer carbonate concentrations increase for 165 kyr and remain higher than in the latest paleocene until 234 48 34 kyr above the base of the clay the new chronology indicates that minimum 13 c values persisted for a maximum of 134 27 19 kyr and the inflection point previously chosen to designate the end of the cie recovery occurs at 217 44 31 kyr this allocation of time differs from that of the cycle based age model of rohl et al 2007 in that it assigns more time to the clay layer followed by a more gradual recovery of carbonate rich sedimentation the new model also suggests a longer sustained 13 c excursion followed by a more rapid recovery to pre petm 13 c values these differences have important implications for constraining the source s of carbon and mechanisms for its subsequent sequestration favoring models that include a sustained release of carbon after an initial pulse

an astronomically dated record of earth s climate and its predictability over the last 66 million years much of our understanding of earth s past climate comes from the measurement of oxygen and carbon isotope variations in deep sea benthic foraminifera yet long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the cenozoic era and to study their dynamics here we present a new highly resolved astronomically dated continuous composite of benthic foraminifer isotope records developed in our laboratories four climate states hothouse warmhouse coolhouse icehouse are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of cenozoic climate dynamics

biostratigraphy and paleoceanographic significance of paleocene radiolarians from offshore eastern new zealand abstract a 100 m thick paleocene sequence of mainly pelagic sediments at odp site 1121 on the eastern flanks of the campbell plateau contains few to common radiolarians of relatively low diversity in the lower 40 m early to early late paleocene and abundant diverse radiolarian assemblages in the upper 60 m mid late paleocene the 150 taxa recorded from the entire paleocene interval are thought to under represent the actual species diversity by at least one half as many morphotypes have not been differentiated below the level of genus assemblages in the lower 40 m are similar to those described from onland new zealand and dsdp site 208 northern lord howe rise they are correlated with south pacific radiolarian zones rp4 and rp5 assemblages in the upper 60 m differ from other known late paleocene assemblages in the great abundance of plagiacanthids and cycladophorids similarities are noted with later cenozoic cool water assemblages this upper interval is correlated with south pacific zone rp6 as revised herein based on comparison with faunas from site 208 and marlborough new zealand the interval is also correlated with the upper part of north atlantic zone rp6 rp6b c based on the presence of aspis velutochlamydosaurus plectodiscus circularis and pterocodon poculum other species such as buryella tetradica and buryella pentadica are valuable for local correlation but exhibit considerable diachroneity between the pacific indian and atlantic oceans an age model for the paleocene interval at site 1121 based on well constrained nannofossil and radiolarian datums indicates that the rate of compacted sediment accumulation doubles from 15 to 30 mm ka at the rp5 rp6 zonal boundary in large part this is due to a sudden and pronounced increase in accumulation rates for all siliceous fossils radiolarians and larger diatoms increase from 10 000 specimens cm2 ka this apparent increase in biosiliceous productivity is age equivalent to a mid paleocene cooling event 57 59 ma identified from global stable isotope records that is associated with the heaviest 13c values for the entire cenozoic

climate and sea level perturbations during the incipient eocene thermal maximum evidence from siliciclastic units in the basque basin ermua zumaia and trabakua pass northern spain abstract based on carbon isotope stratigraphy and lithology a revised high resolution correlation is proposed between sections spanning the incipient eocene thermal maximum ietm in the basque region northern spain in three studied sections the ietm event is represented by a prominent non to low calcareous siliciclastic unit su 4 20 5 m thick during formation of the su sedimentation rates for siliciclastic material increased by a factor of two to five whereas detrital grain size decreased significantly kaolinite and chlorite became more abundant in the clay fraction and calcite dissolution in the water column intensified the su reflects a significant change in climate and hydrological regime towards a warmer and seasonally drier climate the drying caused perennial vegetation cover to collapse and led to increased continental erosion but also to reduced hydrodynamic energy of freshwater debouching into the oceans a coeval relative sea level fall probably related to tectonic uplift or doming affecting major parts of western europe increased the land sea slope and further enhanced erosion rates palynological studies support periodic vegetation during seasonal rain instead of permanent conifer forests prominent caliche soils in coeval continental deposits in northern spain also support warm semiarid conditions during the ietm event net evaporation increased under the subtropical high pressure cells including the basque region whereas more northerly latitudes became more wet the su has a similar origin as detrital units previously assigned to the early palaeogene so called siderolithic discharge in other parts of western europe

an early eocene carbon cycle perturbation at 52 5 ma in the southern alps chronology and biotic response an early eocene carbon cycle perturbation at 52 5 ma from the southern alps chronology and biotic response

hinterland vergent tectonic wedge below the riwat thrust himalayan foreland pakistan implications for hydrocarbon exploration the riwat thrust with a surface trace of over 50 km is one of the major faults in the footwall of the main boundary thrust in the himalayan foreland of pakistan surface geology shows that the riwat thrust is a foreland vergent thrust along which lower to middle siwalik molasse strata are thrust southward over upper siwalik strata seismic reflection interpretation shows that the riwat thrust developed as a roof thrust of a hinterland vergent tectonic wedge triangle zone underlain by evaporites the riwat thrust propagates upsection from a depth of about 4 km at the base of the siwalik group at this depth it merges into a hinterland vergent blind thrust that propagates upsection as a ramp from eocambrian evaporites covering the basement at a depth of about 6 km bounded between this set of conjugate faults a tectonic wedge of eocambrian evaporites to neogene strata is thrust toward the hinterland to form a triangle zone the roof thrusts of triangle zones have been widely mapped as backthrusts in deformed mountain fronts hinterland motion of tectonic wedges as in the riwat thrust triangle zone may be a feature of the fold and thrust belts underlain by evaporites acting as an extremely weak decollement layer their recognition with a trap forming geometry below a thrust is important for interpreting particular fold belts and for hydrocarbon exploration these structures could be predicted by the surface geology data where hinterland vergence of a fold below a thrust is apparent however seismic reflection data appear to be critical in recognizing these structures

structural interpretation of the eastern sulaiman foldbelt and foredeep pakistan the sulaiman foldbelt is an active tectonic feature on the northwestern margin of the indian plate seismic reflection data have been combined with surface geological mapping and drill hole data to interpret the structural style and tectonic shortening of the eastern sulaiman foldbelt and its adjacent foredeep the data show that the basement is more than 8 km deep near the deformation front and that it deepens towards the west the foredeep adjacent to the eastern sulaiman foldbelt is a broad synclinal structure with a steep western limb the more gentle eastern limb has monoclinal dips from near zero to 2 5 several salt cored anticlines are observed on the eastern part of the monocline but the salt structures are lacking in the western foredeep and in the frontal part of the sulaiman foldbelt the basal decollement under the sulaiman lobe lies either in ductile eocambrian salt or within a deep zone of other material that undergoes ductile behavior near the deformation front ramps from the basal detachment become flats in lower triassic and lower cretaceous shales a steep and highly elevated zone immediately to the west of the frontal folds is interpreted to be underlain by a passive roof duplex the culmination wall of this oblique duplex is separated from the overlying roof sequence by a passive roof thrust in lower cretaceous shales the roof thrust has a backthrust sense of movement relative to the forelandward propagating duplex and may extend obliquely 100 km into the interior of the foldbelt fault propagation and fault bend folds are present in the frontal portion of the eastern sulaiman foldbelt palinspastic restoration of a balanced cross section shows 108 km of shortening in the eastern sulaiman foldbelt east of the kingri strike slip fault the presence of more than 11 km of pre neogene strata on top of basement suggests that the mesozoic rifted margin of the indian subcontinent may lie beneath the sulaiman foldbelt this interpretation is also favored by the presence of ophiolites and flysch deposits overthrusted on late cretaceous shelf strata

the india asia collision in north pakistan insight from the u pb detrital zircon provenance of cenozoic foreland basin the northernmost exposures of sub himalayan cenozoic strata in the hazara kashmir syntaxial region of north pakistan comprises the paleocene eocene marine strata in the lower part and oligocene miocene nonmarine strata in the upper part this study provides the detrital zircon u pb geochronology of the cenozoic strata in this area the strong resemblance of u pb age spectra of paleocene hangu lockhart and patala formations with those of himalayan strata indicate an indian plate provenance the first appearance of 100 ma detrital zircon u pb ages within the lower most part of the early eocene margalla hill limestone indicates a shift from an indian to asian provenance geologic mapping shows the existence of a disconformity between the lower and upper most part of the patala formation which is interpreted to have been formed by the migration of a flexural forebulge through this region we consider the upper most part of the patala formation to have been deposited within the distal foredeep of the foreland basin the indian to asian provenance shift and the presence of a possible foreland basin forebulge provide strong evidence that india asia collision was underway in northern pakistan at ca 56 55 ma

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

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

the role of salt in fold and thrust belts davis d m and engelder t 1985 the role of salt in fold and thrust belts in n l carter and s uycda editors collision tectonics deformation of continental lithosphere tectonophysics 119 67 88 the style of deformation in thin skinned fold and thrust belts is critically dependent upon the resistance to sliding along the detachment between the mass of deforming sediments and the underlying rocks evaporites can provide an extremely weak horizon within which a basal detachment can form and along which only a relatively small shear traction can be supported fold and thrust belts that form atop a salt layer such as the appalachian plateau the franklin mountains in northwestern canada and the jura of the alps among others share several readily observable characteristics as predicted by a simple mechanical model for fold and thrust belts a detachment in salt permits a thrust belt to have an extremely narrow cross sectional taper in addition predicted orientations of the principal stress axes over a salt dtcollement are consistent with the commonly observed lack of a consistently dominant vergence direction of structures within the thrust belt other common attributes of salt basal thin skinned deformation include the presence of several widely but regularly spaced folds and abrupt changes in deformational style at the edge of the salt basin

focal mechanisms and depths of earthquakes in central pakistan a tectonic interpretation focal mechanisms and depths for seven earthquakes in central pakistan were determined from an analysis of rayleigh waves of 20 to 50 s periods in east central pakistan the nodal planes for some solutions strike obliquely to the grain of surface structures this observation supports the contention of other workers that a thin surficial unit decoupled from the basement along a surface of decollement characterizes this region in west central pakistan relative movement between the indian and eurasian plates is at least partially accommodated by seismic slip along the chaman fault other faults which are situated to the east of and lie subparallel to the chaman fault may also take up some of the relative plate motion observed activity within the zone of convergent type structure in central pakistan may be a result of the greater component of convergence across the indian eurasian plate boundary north of quetta pakistan appendix is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document b83 010 2 50 payment must accompany order

evaluation of the astronomical time scale for the paleocene and earliest eocene abstract the astronomical tuned time scale is rapidly extended into the paleogene but due to the existence of an eocene gap different tuning options had to be presented for the paleocene these options differ both in number and tuning of 405 kyr eccentricity related cycles and are only partially consistent with recalculated 40 ar 39 ar constraints for the cretaceous paleogene k pg and paleocene eocene p e boundaries in this paper we evaluate the cyclostratigraphic interpretation of records from odp leg 198 and 208 sites and the zumaia section to solve the problem of the different tuning options we found that the interval between the k pg boundary and the early late paleocene biotic event elpe comprises 17 instead of 16 405 kyr eccentricity related cycles as previously proposed while the entire paleocene contains 25 405 kyr cycles starting from 40 ar 39 ar age constraints for the k pg boundary a new tuning to 405 kyr eccentricity is presented for the paleocene and earliest eocene which results in ages of 66 0 and 56 0 ma for the k pg and p e boundaries respectively this tuning introduces considerable differences in age for a number of nannofossil events at odp sites 1209 and 1262 in the interval between 61 and 63 ma but eliminates large and abrupt changes in the seafloor spreading rate the tuning seems further consistent with recalculated 40 ar 39 ar ages for ash layer 17 of early eocene age however despite this apparent consistency with existing radio isotopic constraints an alternative 405 kyr younger or less likely older tuning cannot be excluded at this stage

organic rich sedimentation in the south pacific ocean associated with late paleocene climatic cooling abstract a distinctive organic rich marine mudstone of late paleocene age occurs in most of new zealand s sedimentary basins and has been identified as a potential source rock for oil and gas identified as the waipawa formation in the east coast basin and the tartan formation in the great south and canterbury basins the unit is a relatively uniform massive mudstone that varies greatly in thickness 2 70 m and grades laterally into distinctive facies equivalents notably greensand and a thin bedded siliceous mudstone all these facies are characterised by relatively high toc 0 5 10 wt and 13 c enrichment 13 c toc 24 and we refer to them collectively as waipawa organofacies our detailed stratigraphic and geochemical studies refine the age 58 7 to 59 4 ma distribution and nature of the waipawa organofacies we have determined that deposition occurred in continental margin settings throughout much of the southwest pacific under cool dysoxic conditions associated with a significant influx of terrestrial organic matter high marine productivity a global fall in sea level and a regional unconformity across shallow and deep marine settings the combination of cool temperatures lowered sea level and bathyal erosion suggests that deposition was linked to short lived growth of an antarctic ice sheet in the earliest late paleocene 59 ma

sea level humidity and land erosion records across the initial eocene thermal maximum from a continental marine transect in northern spain in two continental sections in the tremp basin northern spain the initial eocene thermal maximum also known as the paleocene eocene thermal maximum is registered by an 6 fall in 1 3 c values in soil carbonate nodules high resolution correlations using the 1 3 c excursion can be made to nearby shelf and bathyal marine settings allowing a detailed reconstruction of soil formation on land and transport of detritus to the sea during the initial eocene thermal maximum soils that formed before and after the initial eocene thermal maximum in the tremp region reflect arid to semiarid conditions with abundant evaporative minerals whereas initial eocene thermal maximum soils reflect seasonally wetter but generally dry conditions during the initial eocene thermal maximum land erosion was intensified and accumulation rates of terrigenous detritus in the sea increased this reflects both increased topographic relief associated with a prominent sea level lowstand and enhanced seasonal precipitation over a dry landscape with sparse vegetation deeper erosion led to an increase in the flux of kaolinite from buried mesozoic soils to the oceans the association of the initial eocene thermal maximum with a sea level lowstand in northern spain as well as at other marginal north atlantic sites may reflect coeval large scale magmatic activity in the northernmost atlantic

north american continental margin records of the paleocene eocene thermal maximum implications for global carbon and hydrological cycling the impacts of the paleocene eocene thermal maximum petm 55 ma one of the most rapid and extreme warming events in earth history are well characterized in open marine and terrestrial environments but are less so on continental margins a major carbon sink here we present stable isotope carbonate content organic matter content and c n ratio records through the petm from new outcrop sections in california and from cores previously drilled on the new jersey margin foraminifer 18o data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean 5 c 8 c while the carbon isotope excursion cie recorded both in carbonate and organic matter 13c records is slightly larger 3 3 4 5 than documented in open ocean records sediment accumulation rates increase dramatically during the cie in marked contrast to the open ocean sites in parallel mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude the estimated total mass of accumulated carbon in excess of pre cie rates suggests that continental margins at least along north america became carbon sinks during the cie mainly because of weathering feedbacks and rising sea level this result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized

did photosymbiont bleaching lead to the demise of planktic foraminifer morozovella at the early eocene climatic optimum the symbiont bearing mixed layer planktic foraminiferal genera morozovella and acarinina were among the most important calcifiers of early paleogene tropical subtropical oceans a marked and permanent switch in the abundance of these genera is known to have occurred at low latitude sites at the beginning of the early eocene climatic optimum eeco such that the relative abundance of morozovella permanently and significantly decreased along with a progressive reduction in the number of species concomitantly the genus acarinina almost doubled its abundance and diversified here we examine planktic foraminiferal assemblages and stable isotope compositions of their tests at ocean drilling program site 1051 northwest atlantic to detail the timing of this biotic event to document its details at the species level and to test a potential cause the loss of photosymbionts bleaching we also provide stable isotope measurements of bulk carbonate to refine the stratigraphy at site 1051 and to determine when changes in morozovella species composition and their test size occurred we demonstrate that the switch in morozovella and acarinina abundance occurred rapidly and in coincidence with a negative carbon isotope excursion known as the j event 53 ma which marks the start of the eeco we provide evidence of photosymbiont loss after the j event from a size restricted 13c analysis however such inferred bleaching was transitory and also occurred in the acarininids the geologically rapid switch in planktic foraminiferal genera during the early eocene was a major evolutionary change within marine biota but loss of photosymbionts was not the primary causal mechanism

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

high resolution nannofossil biochronology of middle paleocene to early eocene at odp site 1262 implications for calcareous nannoplankton evolution abstract over the last several decades debates on the tempo and mode of evolution have centered on the question whether morphological evolution preferentially occurs gradually or punctuated i e with long periods of stasis alternating with short periods of rapid morphological change and generation of new species another major debate is focused on the question whether long term evolution is driven by or at least strongly influenced by changes in the environment or by interaction with other life forms microfossils offer a unique opportunity to obtain the large datasets as well as the precision in dating of subsequent samples to study both these questions we present high resolution analyses of selected calcareous nannofossils from the deep sea section recovered at odp site 1262 leg 208 in the south eastern atlantic the studied section encompasses nannofossil zones np4 np12 equivalent to cp3 cp10 and chrons c27r c24n we document more than 70 biohorizons occurring over an about 10 myr time interval 62 5 ma to 52 5 ma and discuss their reliability and reproducibility with respect to previous data thus providing an improved biostratigraphic framework which we relate to magnetostratigraphic information and present for two possible options of a new paleocene stratigraphic framework based on cyclostratigraphy this new framework enabled us to tentatively reconstruct steps in the evolution of early paleogene calcareous nannoplankton through documentation of transitional morphotypes between genera and or species and of the phylogenetic relations between the genera fasciculithus heliolithus discoasteroides and discoaster as well as between rhomboaster and tribrachiatus the exceptional record provided by the continuous composite sequence recovered at walvis ridge allows us to describe the mode of evolution among calcareous nannoplankton new genera and or new species usually originated through branching of lineages via gradual but relatively rapid morphological transitions as documented by the presence of intermediate forms between the end member ancestral and descendant forms significant modifications in the calcareous nannofossil assemblages are often related to significant changes in environmental conditions but the appearance of structural innovations and radiations within a single genus also occurred during stable environmental conditions these lines of evidence suggest that nannoplankton evolution is not always directly triggered by stressed environmental conditions but could be also driven by endogenous biotic control

the terminology of structures in thrust belts abstract a review of structures and geometric relationships recognized in thrust belts is presented a thrust is defined as any contractional fault a corollary being that thrusts must cut up section in their transport direction flats are those portions of a thrust surface which were parallel to an arbitrary datum surface at the time of displacement and ramps are those portions of thrusts which cut across datum surfaces ramps are classified on the basis of their orientation relative to the thrust transport direction and whether they are cut offs in the hangingwall or footwall of the thrust lateral variations in the form of staircase trajectories are joined by oblique or lateral ramps which have a component of strike slip movement an array of thrusts which diverge in their transport direction may form by either of two propagation models these are termed piggy back propagation which is foreland directed and overstep propagation which is opposed to the thrust transport direction an array of thrust surfaces is termed an imbricate stack and should these surfaces anastamose upwards a duplex will result the fault bounded blocks are termed horses a duplex is bounded by a higher roof thrust and a lower floor thrust the intersection of any two thrust planes is termed a branch line thrusts can be classified on the basis of their relationship to asymmetric fold limbs which they cut a further classification arises from whether a particular thrust lies in the hangingwall or footwall of another one the movement of thrust sheets over corrugated surfaces or the local development of thrust structures beneath will fold higher thrust sheets these folds are termed culminations and their limbs are termed culmination walls accommodation of this folding may require movement on surfaces within the hangingwall of the active thrust these accommodation surfaces are termed hangingwall detachments and they need not root down into the active thrust this category of detachment includes dip slip hangingwall drop faults which are developed by differential uplift of duplex roofs and out of the syncline thrusts which develop from overtightened fold hinges back thrusts as well as forming as hangingwall detachments may also form due to layer parallel shortening above a sticking thrust or by rotation of the hangingwall above a ramp

the himalayan arc large scale continental subduction oroclinal bending and back arc spreading abstract palaeomagnetic results from the himalayan arc and southern tibet compared with simulated apparent polar wander paths for the indian plate show a consistent pattern of rotations of the himalayan arc relative to the indian shield varying gradually from 45 clockwise in the northwestern himalaya to slightly counterclockwise in the lhasa region this pattern is consistent with continental underthrusting of greater india beneath the tibetan plateau since the early miocene over at least 650 km at the longitude of western nepal and oroclinal bending since the latest miocene available palaeomagnetic observations support the steady state model for the formation of the himalayan arc with refinements as follows 1 collision between greater india s northern boundary and southern asia occurred at equatorial latitudes with progressive suturing from palaeocene in the northwestern himalaya until early eocene in the eastern himalaya 2 continuing convergence and indentation of greater india into southern asia over about 2000 km up to the early miocene resulted in southeastward extrusion of indochina and 3 neogene counterclockwise rotational underthrusting of greater india along the main central thrust with pliocene quaternary oroclinal bending of the himalayan arc

evolution and dynamics of a fold thrust belt the sulaiman range of pakistan we present observations and models of the sulaiman range of western pakistan that shed new light on the evolution and deformation of fold thrust belts earthquake source inversions show that the seismic deformation in the range is concentrated in the thick pile of sediments overlying the underthrusting lithosphere of the indian subcontinent the slip vectors of the earthquakes vary in strike around the margin of the range in tandem with the shape of the topography suggesting that gravitational driving forces arising from the topography play an important role in governing the deformation of the region numerical models suggest that the active deformation and the extreme plan view curvature of the range are governed by the presence of weak sediments in a pre existing basin on the underthrusting indian plate these sediments affect the stress state in the over riding mountain range and allow for the rapid propagation of the nose of the range and the development of extreme curvature and laterally varying surface gradients

a siliciclastic braid delta within a lower paleogene carbonate platform ordesa monte perdido national park southern pyrenees spain record of the paleocene eocene thermal maximum perturbation abstract the la pardina formation is a siliciclastic dominated unit up to 26 m thick intercalated within a 300 m thick danian lower ilerdian succession of shallow marine carbonates in the southern pyrenees the unit is composed of four interdigitated facies three of them of a coarse grained siliciclastic character sf1 sf2 sf3 and the fourth one composed of bioclastic packstones with argillaceous matrix calcareous facies cf the siliciclastic facies make up the bulk of the la pardina formation in the ordesa monte perdido national park while the cf is subordinate in the park but widespread throughout the southern pyrenees biostratigraphic and isotopic data suggest that the cf pertains to the paleocene eocene thermal maximum petm no isotopic or biostratigraphic information could be obtained from the siliciclastic facies but they are also assigned to the petm because of their interfingering with the cf the siliciclastic facies were accumulated in a braid delta system fed by either a major river or by several minor rivers draining the ebro massif the sf3 sf2 and sf1 respectively represent the top set foreset and bottomset parts of the braid delta whereas the cf correspond to the prodelta in proximal parts of the braid delta the sf3 overlies a subaerial surface carved into upper thanetian marine carbonates a proof of a pre petm sea level fall in the remainder of the braid delta the la pardina formation exhibits an overall thickening coarsening up trend that attests to rapid progradation the development of the braid delta implies a dramatic increase in the influx of both coarse and fine grained siliciclastics which temporarily halted a long lasting period of carbonate dominated sedimentation this abrupt change demonstrates that the environmental impact caused by the intensification of the hydrological cycle during the petm was particularly severe at middle latitudes

electro magnetic earthquake bursts and critical rupture of peroxy bond networks in rocks abstract we propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic and electric phenomena which have been associated with earthquakes the mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress the electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice called peroxy bonds or positive hole pairs php where a php represents an o 3 x oo yo 3 with x y si 4 al 3 i e o in a matrix of o 2 of silicates we propose that php are activated by plastic deformations during the slow cooperative build up of stress and the increasingly correlated damage culminating in a large critical earthquake recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit we conjecture that the intermittent and erratic occurrences of em signals are a consequence of the progressive build up of the battery charges in the earth crust and of their release when crack networks percolate through the stressed rock volumes providing a conductive pathway for the battery currents to discharge em signals are thus expected close to the rupture either slightly before or after that is when percolation is most favored the proposed mechanism should be relevant for the broader understanding of fractoemissions

early eocene carbon isotope excursions and landscape destabilization at eccentricity minima green river formation of wyoming repeated global reorganizations of carbon cycling and biotic oceanic and terrestrial processes occurred during the early eocene and appear to have been paced by cyclic variations in the eccentricity of the earth s orbit the phase relationship s between insolation variation terrestrial paleoclimate and atmospheric pco2 during these events remains enigmatic however due to their poorly constrained timing relative to specific orbital configurations here we use tiered interpolation between radioisotopic ages and paleomagnetic polarity chrons to compare high resolution 13c and lithofacies records from the wilkins peak member of the green river formation of western north america to a fe intensity xrf record from the western atlantic ocean and to numerical solutions for earth s orbital configuration wilkins peak member lithofacies stacking patterns record cyclic geomorphic responses to insolation and climate fluctuations spanning an interval of 1 8 ma previous macrostratigraphic analyses using 40ar 39ar and u pb ash bed ages indicate that these cycles reflect long and short eccentricity modulation of precession hydrologic variance appears to have occurred inversely with intervals of maximum sediment advection with carbonate and evaporite dominated lacustrine modes during eccentricity maxima and siliciclastic dominated alluvial modes during eccentricity minima stable carbon isotope analyses of 126 meters of wilkins peak member strata reveal a regular 5 per mil oscillation between high 13c lacustrine modes and low 13c alluvial modes tiered interpolation between paleomagnetically characterized terrestrial ash beds facilitates the integration of 11 radioisotopic ages with the geomagnetic polarity timescale resulting in significant expansion of chron c23 and shortening of chron c22 relative to timescales based on seafloor magnetic anomaly profiles the new proposed timescale permits direct comparison of terrestrial and marine climate proxy records from the early eocene climatic optimum at ca 250 kyr 250 kyr resolution and reveals prominent 100 kyr and 405 kyr scale oscillations within both records wilkins peak member 13c minima which occurred during low eccentricity alluvial modes likely coincided with global 13c minima scenario 1 but may alternatively reflect productivity driven local effects within lake gosiute scenario 2 if scenario 1 proves accurate early eocene negative 13c hyperthermal excursions occurred during eccentricity minima rather than maxima as formerly believed

tropical sea temperatures in the high latitude south pacific during the eocene sea surface temperature sst estimates of 30 c from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the canterbury basin new zealand support paleontological evidence for a warm subtropical to tropical climate in the early eocene high latitude 55 s southwest pacific such warm ssts call into question previous estimates based on oxygen isotopes and present a major challenge to climate modelers even under hypergreenhouse conditions 2240 ppm co2 modeled summer ssts for the new zealand region do not exceed 20 c

multiple early eocene hyperthermals their sedimentary expression on the new zealand continental margin and in the deep sea the paleocene eocene thermal maximum petm ca 55 5 ma was a geologically brief interval characterized by massive influx of isotopically light carbon extreme changes in global climate and profound variations in earth system processes an outstanding issue is whether it was an isolated event or the most prominent example of a recurring phenomenon recent studies of condensed deep sea sections support the latter but this finding remains uncertain here we present and discuss lithologic and carbon isotope records across two lower eocene outcrops on south island new zealand the petm manifests as a marl rich horizon with a significant negative carbon isotope excursion cie above in sediment deposited between 54 and 53 ma are four horizons with similar though less pronounced expressions marl beds of all five horizons represent increased terrigenous sedimentation presumably linked to an accelerated hydrological cycle five corresponding clay rich horizons and cies are found in deep sea records although the lithologic variations represent carbonate dissolution rather than siliciclastic dilution the presence of five intervals with similar systemic responses in different environments suggests a mechanism that repeatedly injected large masses of 13 c depleted carbon during the early eocene

fold and thrust partitioning in a contracting fold belt insights from the 1931 mach earthquake in baluchistan 1 surface deformation associated with the 27 august 1931 earthquake near mach in baluchistan is quantified from spirit leveling data and from detailed structural sections of the region interpreted from seismic reflection data constrained by numerous well logs mean slip on the west dipping dezghat bannh fault system amounted to 1 2 m on a 42 km 72 km thrust plane with slip locally attaining 3 2 m up dip of an inferred locking line at 9 km depth slip also occurred at depths below the interseismic locking line in contrast negligible slip occurred in the 4 km near the interseismic locking line the absence of slip here in the 4 years following the earthquake suggests that elastic energy there must either dissipate slowly in the interseismic cycle or that a slip deficit remains pending its release in a large future earthquake elastic models of the earthquake cycle in this fold and thrust belt suggest that slip on the frontal thrust fault is reduced by a factor of 2 to 8 compared to that anticipated from convergence of the hinterland a partitioning process that is presumably responsible for thickening of the fold and thrust belt at the expense of slip on the frontal thrust near the latitude of quetta gps measurements indicate that convergence is 5 mm yr hence the minimum renewal time between earthquakes with 1 2 m mean displacement should be as little as 240 years however when the partitioning of fold belt convergence to frontal thrust slip is taken into account the minimum renewal time may exceed 2000 years

river sediment discharge to the oceans present day controls and global budgets empirical relationships between river sediment yields and a large number of hydroclimatic biological and geomorphological parameters are investigated at the global scale for a set of 60 major world river basins the environmental characteristics were extracted from various global computer data sets and natural river sediment fluxes were taken from the literature it is found that sediment yields can be best correlated by forming the products of hydroclimatic and geomorphological factors that is runoff intensity basin slope an index characterizing rock hardness and an index characterizing rainfall variability over the year the best parameter combination varies to some extent when the rivers are grouped according to their average climatic situation but it is always a combination of the above mentioned parameters that yields the most significant models in arid climates however regression coefficients are greater than in humid climates indicating that erodibility is much greater than in arid climates when extrapolated to the total continental area on the basis of the corresponding data sets the empirical models result in a total sediment flux of about 16 gigatons discharged to the oceans every year which is in good agreement with previous estimates derived from compilations of world wide river data consequently two global maps are proposed showing the spatial distributions of river sediment yields on the continents as well as the inputs of these sediments to the oceans in a grid point scale by far most of the sediments originate from the young orogenic belts of the continents mainly due to a combination of steep morphologies and high runoff intensities

earthquakes and associated deformation in northern baluchistan 1892 2001 we examine a century of seismicity and earthquake related deformation on the western margin of the indian plate in the pakistan region of northern baluchistan several catalogs of earthquakes for this region currently exist but early catalogs in particular suffer from errors incompleteness inhomogeneity and location bias we form a new catalog of more than 1000 earthquakes using original sources to confirm macroseismic locations and assign m s magnitudes to earthquakes since 1892 in doing so we reveal a systematic east northeast bias in locations caused largely by the uneven global distribution of seismic stations used in their determination an appendix provides narrative accounts and historical references to 34 significant earthquakes in the region the pattern of seismicity in the past century shows activity over a 700 km long 200 km wide segment of the plate boundary with predominantly strike slip faulting to the west and thrust faulting to the east at its narrowest near 29 n transpression of the plate boundary is partitioned into reverse and strike slip components separated by approximately 100 km the m 7 3 1931 mach earthquake slip 1 1 m on a 40 east southeast dipping reverse fault released fault normal stresses that may have unclamped the subsequent m 7 7 left lateral quetta earthquake 4 years later the northern chaman fault system in the past century has been largely inactive suggesting that this time period is not representative of long term activity in the region and that up to 4 m of potential slip is currently available to drive one or more future m 7 earthquakes despite triangulation installed in the late nineteenth and early twentieth centuries no recent geodetic data are available to permit plate boundary velocities to be measured directly

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

gravity and tectonic model across the sulaiman fold belt and the chaman fault zone in western pakistan and eastern afghanistan abstract gravity data from the western boundary of the indian subcontinent have been analysed to infer the gross crustal structure across the indian afghan collision zone seismic reflection profiles reveal the gross structural duplex geometry of the sulaiman fold belt these data show that the wedge which is 10 km thick at the deformation front thickens northwestward to attain a tectonic thickness thickness due to deformation of about 20 km in the hinterland gravity modeling depicts the depth of the moho between 33 and 35 km at the deformation front of the sulaiman fold belt the moho depth shows an upward convexity along an e w profile it decreases northward with a gentle gradient of 1 1 20 m km below the sulaiman fold belt and then deepens abruptly with a gradient of about 7 8 136 m km across the chaman fault zone attaining a depth of about 57 km in eastern afghanistan the model suggests that the sulaiman fold belt is underlain by transitional crust 15 27 km thick in contrast to the continental crust 38 km thick underneath the fold belt of the himalayan collision zone in northern pakistan the about 57 km thick crystalline crust in eastern afghanistan may be due to 1 underplating by crust of the indian subcontinent and 2 structural thickening within the afghan block

eocene 46 44 ma onset of australia pacific plate motion in the southwest pacific inferred from stratigraphy in new caledonia and new zealand

structural interpretation of frontal folds and hydrocarbon exploration western sulaiman fold belt pakistan abstract seismic reflection profiles and borehole data combined with geological mapping was used to analyze foreland structures with 3 d structural variation estimates of shortening and kinematic evolution of western sulaiman fold belt sfb pakistan the western sfb is interpreted with passive roof duplex geometry the floor thrust decollement is interpreted in triassic strata rather than its inference in precambrian cambrian evaporites whereas the roof thrust upper detachment of hinterland vergence is located in eocene ghazij shale based on seismic data the folds in the frontal duplex are interpreted as fault propagation and fault bend type they are located over curved and staircase geometry of blind back thrusts the folds and thrusts of ew trend show right hand en echelon stepping along nw se oriented mountain front due to drag along the western margin of the fold belt the blind thrusts cut across the hanging wall flat of the duplex horse with roots in base triassic at depth of 4 4 5 km 3d surfaces of reservoir strata show three areas of closed elliptical contours as potential prospects over blind thrusts with maximum structural relief of 2200 m shortening of 2100 22 and 9950 m 47 is calculated along with thrusts in the frontal duplex with the interpretation of out of sequence structures passive roof duplex structures between foreland and hinterland vergent back thrusts are reported from mountain belts around the world we have identified out of sequence deformation in the frontal duplex with stacked structures identification of these features adds to our understanding of the development of mountain fronts in the context of anderson s theory of faulting with the presence of a conjugate set of faults and foreland propagation of mountain fronts with secondary out of sequence deformation subsurface seismic data appears to be critical in their recognition for analysis of active foreland deformation and assessment of hydrocarbon plays in the fold belts

triangle zones geometry kinematics mechanics and the need for appreciation of uncertainties abstract triangle zones are important structures found in foreland fold and thrust belts all over the world and are commonly associated with tectonic wedging however tectonic wedging and consequently the formation of passive hinterland verging roof thrusts requires particular mechanic conditions such as pre fractured rocks syntectonic sedimentation or a specific stratigraphic layering with variable mechanically weak and rigid formations in this contribution models of triangle zones and hypotheses regarding their formation are reviewed our results show that the term triangle zone is often used in a contradictory sense and interpretations are affected by large uncertainties passive roof thrusts are not necessarily required in all cases and suggested models of triangle zones even if they are geometrically and kinematically viable are hampered by their mechanical implications with respect to a large number of published triangle zones and associated kinematic as well as mechanic models we present a new definition and classification scheme which is discussed and applied to natural examples worldwide we show that natural examples of triangle zones can be separated into two types 1 detachment dominated and 2 ramp dominated triangle zones both types imply particular mechanic conditions of involved detachments and regional dynamics regarding the large uncertainties associated with triangle zone interpretation we suggest to only use the term triangle zone in a very stringent manner and only if irrefutable evidences for stratigraphic repetitions within a duplex are given the results should then be validated with additional kinematic and mechanic considerations geometric and kinematic uncertainties as well as implications of the proposed model explaining observed triangular structures should be reflected in the nomenclature used

newly discovered paleogene deltaic sequence in katawaz basin pakistan and its tectonic implications in the katawaz basin pakistan the deltaic and turbidite facies of the khojak formation are the paleogene analogue of the modern indus river emptying into the arabian sea to form the indus delta fan system facies identified include upper continental slope to prodelta distal to proximal distributary mouth bar distributary channel interdistributary bay estuary fluvial channel natural levee and flood plains of lower and upper delta plains the proposed model is a fluvial dominated wave modified delta that axially fed khojak submarine fan turbidites exposed in the southwestern part of the basin these sediments were eroded from the early himalayan orogenic highlands and transported southwestward down the axis of the katawaz remnant ocean basin

interpretation of the eastern sulaiman fold and thrust belt pakistan a passive roof duplex abstract surface geology seismic reflection and well data from the eastern sulaiman fold and thrust belt sftb were integrated to analyze its structural geometry deformation style foreland structure development and tectonic shortening the n s oriented fold belt s deformation front has a monoclinal expression over 350 km along the eastern edge of the sftb the cross section shows a 9 km thickness of platform sequences that are detached from the basement by an inferred decollement in paleozoic strata the base of cretaceous strata is 6 km deep in the foredeep syncline rising 7 km in the foreland in the absence of a major thrust and is interpreted as a thin skinned passive roof duplex style of deformation the duplex sequence of jurassic and older strata are separated from the cretaceous and younger roof sequence which is intact over foreland structures for 60 km a balanced structural cross section of this area restores to an original length of 172 km implying 112 km 65 of shortening since 6 2 ma with rates of 18 mm yr this is greater than the 50 shortening along a 359 km long n s balanced cross section across the sftb but is likely to occur along stacked duplexes with high relief along the eastern sftb

early to middle eocene magneto biochronology of the southwest pacific ocean and climate influence on sedimentation insights from the mead stream section new zealand the mead stream section south island new zealand consists of a 650 m thick series of continuous well exposed strata deposited on a south pacific continental slope from the late cretaceous to the middle eocene we examined the uppermost paleocene middle eocene part of the section which consists of 360 m of limestone and marl for detailed magnetic polarity stratigraphy and calcareous nannofossil and foraminifera biostratigraphy magneto biostratigraphic data indicate that the section straddles magnetic polarity chrons from c24r to c18n calcareous nannofossil zones from np9a to np17 cnp11 cne15 following a recently revised paleogene zonation and from the waipawan to the bortonian new zealand stages i e from the base of the ypresian to the bartonian international stages the mead stream section thus encompasses 17 m y 56 39 ma of southwest pacific ocean history the ages of calcareous nannofossil biohorizons are consistent with low to midlatitude data from the literature indicating that during the early middle eocene the low to midlatitude calcareous nannofossil domain extended at least to 50 s 55 s in the south pacific correlation of the magnetic polarity stratigraphy from the mead stream section with the geomagnetic polarity time scale allows us to derive sediment accumulation rates sar which range between 8 and 44 m m y comparing the sar with paleotemperature proxy records we found that two intervals of increased sar occurred during the early eocene climatic optimum 52 50 ma and during the transient warming event peaking with the middle eocene climatic optimum 40 5 ma this correlation indicates that at mead stream the climate evolution of the early middle eocene is recorded in a sedimentation pattern whereby on a million year time scale warmer climate promoted continental weathering transportation and accumulation of terrigenous sediments

the structure of mountain fronts commonly the part of a mountain front which is visible at the surface consists of foreland dipping thrust belt rocks elevated above their regional structural position and overlain more or less conformably by molasse several explanations for their geometry are possible 1 major detachments exist within or beneath the molasse resulting in transport of the foreland basin examples of this geometry come from the swiss molasse plain the southern pyrenees and the mackenzie mountains of canada 2 displacement is lost on major backthrusts beneath the frontal monocline examples cited here are the rockies of alberta the sulaiman ranges of pakistan the mackenzies and the andes in peru 3 thrust sheets travelled over an old land surface and syntectonic molasse contemporaneously offlaps the topographic high of the thrust front this phenomenon occurs along the alpine thrust front in haute provence 4 the frontal fold represents deformation above a large scale thrust tip no unequivocal example of tip line strain at this scale has been recorded although this type of deformation may occur in the brooks range of alaska in many areas mountain fronts show a combination of these idealized geometries

patterns and magnitude of deep sea carbonate dissolution during eocene thermal maximum 2 and h2 walvis ridge southeastern atlantic ocean 1 eocene thermal maximum 2 etm2 or h1 53 7 ma represents a short lived warming episode associated with the injection of a large mass of 13c depleted carbon into the ocean atmosphere system the mass of injected carbon the extent of deep sea dissolution and the amount of warming during etm2 appear to be approximately half of those documented for the paleocene eocene thermal maximum petm 55 5 ma but the pattern of lysocline migration during etm2 has not yet been documented sufficiently to decipher potential differences in carbon sources and sequestration mechanisms we present high resolution carbonate dissolution and bulk stable isotope records across etm2 and the successive h2 event 53 6 ma on a common age model for four sites along the walvis ridge depth transect 1500 to 3600 m paleowater depth to assess lysocline evolution the onset of etm2 is characterized by multiple depth dependent transitions of carbonate dissolution up to 96 of the total flux associated with rapid depletions in bulk carbonate carbon up to 1 1 5 and oxygen up to 0 7 1 5 isotope values h2 shows a 0 7 negative carbon isotope excursion with a coeval decrease in 18o of 0 5 and 80 of carbonate dissolution during etm2 the lysocline recovered within 30 ka we attribute this rapid recovery to terrestrial caco3 neutralization through enhanced chemical weathering of carbonates in soils and rocks according to theory carbonate dissolution was lower after recovery than prior to etm2 indicating carbonate ion oversaturation and a deeper position of the lysocline spectral analysis indicates that the changes in carbonate dissolution and 13c values were precession paced implying that weathering feedbacks and short term perturbations in the carbon cycle were important in determining early eocene background and hyperthermal ocean co32 conditions

mode and tempo of the paleocene eocene thermal maximum in an expanded section from the venetian pre alps mode and tempo of an expanded paleocene eocene thermal maximum section in the venetian pre alps

early eocene climatic optimum environmental impact on the north iberian continental margin the early eocene climatic optimum which constituted the peak of the long term early cenozoic global warming had a significant impact on the environmental evolution of terrestrial and oceanic areas surprisingly however its influence on continental margins is poorly known new insights are provided from a sedimentological stable isotope mineralogical and micropaleontological study of an 1100 m thick lower middle eocene deep marine succession that accumulated on the north iberian continental margin the early eocene climatic optimum is represented by a 410 m thick interval characterized by scarcity of hemipelagic limestones abundance of dark marls which record a reduction in calcium carbonate content and an increase in kaolinite and the occurrence of conspicuous red layers with high siderite and pyrite content series of stratigraphically significant events frame the early eocene climatic optimum based on this analysis the environmental influence of the early eocene climatic optimum started at 52 6 ma and lasted 2 3 m y its onset is marked by rapid drops in 13c and 18o which record the addition of 13c depletedcarbon into the ocean atmosphere system for 80 k y and a concomitant warming a hotter climate and a perennial rainfall regime increased the supply of terrestrial clays organicmatter and iron oxides into the sea eventually these changes affected the deepsea bottom 270 k y after the onset of the early eocene climatic optimum creating conditions in which opportunistic benthic foraminifera thrived and leading to increased methanogenesis in the subsurface which caused the formation of siderite a subsequent gradual recovery culminated abruptly at 50 3 ma with a global cooling episode which is locally recorded by the accumulation of lowstand resedimentation deposits 2015 geological society of america

mechanics of the salt range potwar plateau pakistan a fold and thrust belt underlain by evaporites the salt range and potwar plateau are part of the active foreland fold and thrust belt of the himalaya in northern pakistan in this region the distance from the main boundary thrust mbt to the front of the fold and thrust belt is very wide 100 150 km because a thick evaporite sequence forms the zone of decollement recent studies have combined seismic reflection profiles petroleum exploration wells bouguer gravity anomalies and surface geology to construct cross sections in the eastern central and western salt range potwar plateau areas in this study the sections are compared with a model that considers the mechanics of a fold and thrust belt to be analogous to that of a wedge of snow or soil pushed in front of a bulldozer chapple 1978 davis et al 1983 dahlen et al 1984 dahlen 1984 models which include the effects of evaporites at the base chapple 1978 davis and engelder 1985 suggest that these thrust belts will have 1 narrow 1 cross sectional tapers 2 larger widths than areas not underlain by evaporites 3 symmetrical structures and 4 changes in deformational style at the edge of the evaporite basin the section across the eastern potwar plateau most closely resembles this latter model having 1 a taper of 0 8 0 1 2 a width of 100 150 km 3 thrust faults that verge both to the north and south and 4 structures rotated 30 counterclockwise with respect to the salt range from the observed taper and pore fluid pressures of the eastern potwar plateau estimates of the values for the yield strength of the evaporites o and the coefficient of internal friction of the overlying wedge are calculated as o 1 33 1 50 mpa and 0 95 1 04 which are then applied to the other cross sections in the central and western sections a basement uplift the sargodha high interferes with the front of the fold and thrust belt this feature causes the ramping of the salt range thrust and produces a relatively steep basement slope 2 4 beneath the potwar plateau this dip in the presence of the weak evaporite decollement is sufficient to provide critical taper no topographic slope is necessary and the thrust wedge of the southern potwar plateau is pushed over the decollement without significant internal deformation the northern potwar plateau is strongly folded and faulted yet the topographic slope remains flat although the deformation suggests that evaporites are not present there the observed taper in the northern potwar plateau is best fitted by the model with evaporites at the decollement combining this with published paleomagnetic and geologic constraints a model for the evolution of the northern potwar plateau suggests that the area deformed as a steeply tapered 3 5 5 5 thrust wedge until approximately 2 million years ago when the southward propagating decollement encountered the evaporites between 2 ma and the present the northern potwar plateau has been pushed along the salt decollement without deformation and erosion has reduced its original steep topographic slope to a nearly level surface

lignite deposits of the kutch basin western india carbon isotopic and palynological signatures of the early eocene hyperthermal event etm2 abstract this study presents new results of combined palynological and stable carbon isotope 13 c investigations carried out in the well known lignite sequence at panandhro district kutch in the gujarat state of western india dinoflagellate cysts and associated spore pollen assemblage assign an early eocene ypresian age to the lignitic succession at panandhro furthermore a pronounced negative carbon isotope excursion cie of about 2 7 correlated to the second eocene thermal maximum 53 7 ma a globally recognized hyperthermal event was discovered in the middle part of the succession consistent with the palynological constraints this is the first record of an eocene hyperthermal event etm2 from the kutch basin our data has regional implications for the age of the lignitic sequences across western india as it demonstrates that there is no significant age difference between the lignite deposits of the kutch and cambay basins our results also support a lutetian age for the previously described vertebrate fossils including whales from the panandhro mine section

out of sequence thrusts out of sequence thrusts oost are those thrusts which do not obey the foreland propagating or in sequence deformation style they include both isolated thrusts which develop hindward of the thrust front and sequences of break back thrusts which propagate from the foreland to the hinterland two end members of a series of oost types are recognized 1 older in sequence thrusts which are reactivated along their entire length and 2 completely new thrusts which propagate through already deformed thrust sheets between the two end members are thrusts composed partially of reactivated in sequence thrust sequences and partially of new entirely out of sequence segments oosts can be initiated for a variety of reasons including 1 keeping the orogenic wedge at critical taper 2 break back sequences from the suture zone in the overriding plate 3 ramping to overcome a sticking point which inhibits in sequence thrust propagation and 4 during simultaneous displacement along two stacked thrusts culminations which bow up segment of the upper thrust may be chopped through to permit continued displacement on the upper thrust many different types of thrust behavior including gravity sliding plucking and derivation of isolated horses from ramps may mimic some of the characteristics of oosts consequently it may be difficult to conclusively prove an oost origin for a complex thrust geometry

late cretaceous neogene trends in deep ocean temperature and continental ice volume reconciling records of benthic foraminiferal geochemistry δ18o and mg ca with sea level history 1 we reconstruct trends in ice volume and deep ocean temperature for the past 108 myr resolving variations on timescales of 2 myr and longer we use a sea level record as a proxy for ice volume a benthic foraminiferal mg cabf record as a proxy for temperature and a benthic foraminiferal 18obf record as a proxy for both this allows us to construct dual estimates of temperature and ice volume variations for the interval 10 60 ma extracting temperature from 18obf by using sea level as a proxy for ice volume to constrain the 18osw component and extracting seawater 18osw which reflects ice volume from 18obf by using mg cabf to constrain the temperature component each of these approaches requires numerous assumptions but the range of plausible solutions are concordant on timescales 2 myr and within an uncertainty of 2 c temperature and 0 4 18osw the agreement between the two approaches for the last 50 myr provides empirical justification for the use of 18obf mg cabf and sea level records as robust climate proxies our reconstructions indicate differences between deep ocean cooling and continental ice growth in the late cenozoic cooling occurred gradually in the middle late eocene and late miocene pliocene while ice growth occurred rapidly in the earliest oligocene middle miocene and plio pleistocene these differences are consistent with climate models that imply that temperatures set by the long term co2 equilibrium should change only gradually on timescales 2 myr but growth of continental ice sheets may be rapid in response to climate thresholds due to feedbacks that are not yet fully understood

mari bugti pop up zone in the central sulaiman fold belt pakistan abstract the sulaiman fold and thrust belt is an active tectonic feature of the himalayan mountain system in pakistan seismic reflection profiles borehole surface geology data and bouguer gravity modeling suggested a passive roof duplex geometry over a transitional crust related to the former passive margin of the indian subcontinent in the frontal part of the sulaiman fold belt a passive roof sequence of cretaceous and younger rocks is structurally uplifted at the surface the roof sequence displays a coherent stratigraphy over the underlying duplex sequence of jurassic and older strata the folds in the roof sequence reflect blind faults in the duplex sequence the duplex style of deformation persists throughout the central sulaiman fold belt however unlike the frontal sulaiman fold belt stratigraphy at the surface in the central sulaiman is disrupted by e w and ne trending faults with apparent map lengths of tens of kilometers these foreland and hinterland verging high angle faults juxtapose cretaceous rocks in the cores of tight symmetrical anticlines against eocene ghazij shale and kirthar limestone according to seismic reflection data they have only minor vertical offsets of 1 2 km and are mostly restricted to the roof sequence as a result cretaceous rocks bounded between reverse faults are exposed at the surface in the cores of tight anticlines as pop up structures this implies that 1 the exposed faults in the central sulaiman fold belt are not primary structures with major shortening and 2 recognition of these faults in the roof sequence may reflect an early stage of development of overstep back thrusts from the upper decollement passive roof thrust

large amplitude variations in carbon cycling and terrestrial weathering during the latest paleocene and earliest eocene the record at mead stream new zealand abstractthe late paleocene to early eocene was marked by major changes in earth surface temperature and carbon cycling this included at least two and probably more geologically brief 200 k yr intervals of extreme warming the paleocene eocene thermal maximum petm and the eocene thermal maximum 2 etm 2 the long term rise in warmth and short term hyperthermal events have been linked to massive injections of 13c depleted carbon into the ocean atmosphere system and intense global climate change however the causes environmental impact and relationships remain uncertain because detailed and coupled proxy records do not extend across the entire interval of interest we are still recognizing the exact character of the hyperthermals and developing models to explain their occurrence here we present lithologic and carbon isotope records for a 200 m thick sequence of latest paleocene earliest eocene upper slope limestone exposed along mead stream new zealand new carbon isotope and lithologic anal

oblique convergence and the lobate mountain belts of western pakistan the thin skinned structures of the pakistani convergent margin have formed as a consequence of the relative motion between india and eurasia most of the resultant motion is being accommodated along or near the current edge of the eurasian plate the southwest northeast striking chaman fault zone it has been observed at oblique margins that the total plate motion is resolved into a component parallel to the margin accommodated through strike slip faulting and a component normal to the margin taken up as contraction however the orientations of structures along the pakistani convergent margin in and around the sulaiman lobe and sulaiman range cannot be explained simply by resolving the plate motion vector into components normal and parallel to the plate boundary our modeling suggests that the complex juxtaposition of strike slip faults with thrust faults of various orientations can be explained by the presence of a block centered upon the katawaz basin that translates along the southwest northeast structural barrier of the chaman fault zone moving with respect to both eurasia and india as this relatively rigid block moves northeastward relative to asia it causes deformation of the sedimentary cover and is responsible for much of the structural complexity in the pakistani foreland our simple model explains several first order features of this oblique margin such as the eastward facing sulaiman range the strike slip kingri fault located between the sulaiman lobe and sulaiman range and the reentrant at sibi this leads us to conclude that very complex structural and geometric relationships at oblique convergent plate boundaries can result from the accommodation of strain with simple initial geometric constraints

environmental perturbations at the early eocene etm2 h2 and i1 events as inferred by tethyan calcareous plankton terche section northeastern italy several early eocene hyperthermals have been recently investigated and characterized in terms of temperature anomalies and oceanographic changes the effects of these climatic perturbations on biotic communities are much less constrained here we present new records from the terche section northeastern italy that for the first time integrates data on planktic foraminifera and calcareous nannofossils across three post paleocene eocene thermal maximum petm negative carbon isotope excursions cies the bio magnetostratigraphic framework generated at terche allows us to confidently relate such cies to the eocene thermal maximum 2 etm2 h2 and i1 events each of these events coincides with lithological anomalies characterized by significantly lower calcium carbonate content marly units mus we interpret these mus as mainly linked to an effect of increased terrigenous dilution as dissolution proxies do not display significant variations calcareous plankton assemblages change significantly across these events and radiolarians increase observed changes suggest that transient warming and environmental perturbations though more intense during etm2 occurred during each of the three investigated perturbations variations among calcareous plankton suggest increase in surface water eutrophication with respect to the pre events conditions coupled with a weakening of the upper water column thermal stratification higher nutrient discharge was related to intensification of the hydrological cycle as a consequence of the warmer climate these conditions persisted during the early cie recovery implying slower recovery rates for the environment and biota than for the carbon cycle

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

widespread formation of cherts during the early eocene climate optimum radiolarian cherts in the tethyan realm of jurassic age were recently interpreted as resulting from high biosiliceous productivity along upwelling zones in subequatorial paleolatitudes the locations of which were confirmed by revised paleomagnetic estimates however the widespread occurrence of cherts in the eocene suggests that cherts may not always be reliable proxies of latitude and upwelling zones in a new survey of the global spatio temporal distribution of cenozoic cherts in deep sea drilling project dsdp and ocean drilling program odp sediment cores we found that cherts occur most frequently in the paleocene and early eocene with a peak in occurrences at 50 ma that is coincident with the time of highest bottom water temperatures of the early eocene climatic optimum eeco when the global ocean was presumably characterized by reduced upwelling efficiency and biosiliceous productivity cherts occur less commonly during the subsequent eocene global cooling trend primary paleoclimatic factors rather than secondary diagenetic processes seem therefore to control chert formation this timing of peak eocene chert occurrence which is supported by detailed stratigraphic correlations contradicts currently accepted models that involve an initial loading of large amounts of dissolved silica from enhanced weathering and or volcanism in a supposedly sluggish ocean of the eeco followed during the subsequent middle eocene global cooling by more vigorous oceanic circulation and consequent upwelling that made this silica reservoir available for enhanced biosilicification with the formation of chert as a result of biosilica transformation during diagenesis instead we suggest that basin basin fractionation by deep sea circulation could have raised the concentration of eeco dissolved silica especially in the north atlantic where an alternative mode of silica burial involving widespread direct precipitation and or absorption of silica by clay minerals could have been operative in order to maintain balance between silica input and output during the upwelling deficient conditions of the eeco cherts may therefore not always be proxies of biosiliceous productivity associated with latitudinally focused upwelling zones 2007 elsevier b v all rights reserved

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

passive roof duplex geometry in the frontal structures of the kirthar and sulaiman mountain belts pakistan abstract exploration for hydrocarbons over the past few years has greatly improved our understanding of the geometry of frontal mountain belt structures in this study we introduce and discuss the concept of the passive roof duplex using as the main example the kirthar and sulaiman ranges in the baluchistan province of pakistan structures similar to those described here have been recognized previously in other mountain belts and they appear to exist as a common feature in many more frontal regions of mountain belts our example of a passive roof duplex which we describe from pakistan is compared briefly with similar structures reported by others the passive roof duplex is here defined as a duplex whose roof thrust has backthrust sense passive roof thrust and whose roof sequence those rocks lying above the roof thrust remains relatively stationary during foreland directed piggy back style propagation of horses within the duplex