three dimensional geometry of the reelfoot blind thrust implications for moment release and earthquake magnitude in the new madrid seismic zone mapping of the reelfoot blind thrust using portable array for numerical data acquisition panda seismicity suggests that it is a complex fault that changes its geometry along strike the thrust appears to be bounded to the north by an east trending strike slip fault the southern end of the thrust is defined by seismicity and does not terminate at a known transverse fault the northern portion of the thrust steepens at shallow levels forming a listric concave upward shape in cross section the southern segment of the thrust is interpreted to flatten near the top of the precambrian basement although some segmentation of the blind thrust is observed from the mapping of 3 km wide strips of seismicity oriented perpendicular to the fault it does not appear to be significant enough to prevent rupture along its entire length the area of the blind thrust 1301 km 2 coupled with several estimates of displacement in the 7 february 1812 event is used to determine the moment released during the event the values of m 0 range from 6 8 10 26 to 1 4 10 27 dyne cm with preferred values between 6 8 10 26 and 8 7 10 26 dyne cm similar calculations for an earthquake in a d 1450 yield a moment release of 1 0 10 27 dyne cm computed moment magnitude for the 7 february 1812 event ranges from m w 7 2 to 7 4 with preferred values between m w 7 2 and 7 3 the moment magnitude for the a d 1450 event is computed as m w 7 3 these values for the magnitude of the 1812 earthquake are lower than previous estimates based on historical records of shaking however this does not imply a lowered seismic risk in the new madrid seismic zone as site effects in the mississippi embayment may significantly amplify the ground motion caused by earthquakes of a given magnitude

estimating severity of seismically induced landslides and lateral spreads using threshold water levels abstract the potential for an earthquake induced landslide increases when the shear strength of a slope decreases and the hydrostatic pressure increases from the dynamic stresses induced by seismic shaking and or heavy rainfalls this paper presents an assessment of seismically induced slope failure in the st louis mo usa area it emphasizes water elevations as the controlling factor realizing that such levels vary over space and time we estimated the threshold water table depths to initiate seismically induced landslides in the uplands and liquefaction induced lateral spreads in the alluvial floodplains under an m7 5 earthquake with a peak ground acceleration of 0 20 to 0 40 g these threshold water table depths were computed as a function of ground steepness using the newmark model for rigid block landslides and an empirical regression for lateral spreads the seismic microzonation was prepared by comparing the map of threshold water table depths and maps of average water levels the resultant hazard maps suggest that the river bluffs are prone to seismically induced landslides only when the water reaches its highest recorded levels while much of the floodplains are prone to lateral spreads lateral spreads occur more extensively when the water exceeds its normal level

topography and tectonics of the central new madrid seismic zone results of numerical experiments using a three dimensional boundary element program we present results of a series of numerical experiments designed to test hypothetical mechanisms that drive deformation in the new madrid seismic zone experiments are constrained by subtle topography and the distribution of seismicity in the region we use a new boundary element algorithm that permits calculation of the three dimensional deformation field surface displacement fields are calculated for the new madrid zone under both far field plate tectonic scale and locally derived driving strains results demonstrate that surface displacement fields cannot distinguish between either a far field simple or pure shear strain field or one that involves a deep shear zone beneath the upper crustal faults thus neither geomorphic nor geodetic studies alone are expected to reveal the ultimate driving mechanism behind the present day deformation we have also tested hypotheses about strain accommodation within the new madrid contractional step over by including linking faults two southwest dipping and one vertical recently inferred from microearthquake data only those models with step over faults are able to predict the observed topography surface displacement fields for long term relaxed deformation predict the distribution of uplift and subsidence in the contractional step over remarkably well generation of these displacement fields appear to require slip on both the two northeast trending vertical faults and the two dipping faults in the step over region with very minor displacements occurring during the interseismic period when the northeast trending vertical faults are locked these models suggest that the gently dipping central step over fault is a reverse fault and that the steeper fault extending to the southeast of the step over acts as a normal fault over the long term

structure and composition of organic reefs and carbonate mud mounds concepts and categories defined here as essentially in place calcareous deposits created by sessile organisms organic reefs are diverse and complex structures with a long geological history their classification has been the subject of fierce debate often characterized by reliance on subjective features such as wave resistance and qualitative attempts to discriminate between first and second class reefs in contrast emphasis is here placed on the objective characteristic of the type of sedimentary support which largely determines the sedimentary composition of the deposit constructional and depositional processes result in three principal sedimentary components matrix m essentially in place skeletons s and cavity cement c whose proportions can be represented on msc triangular plots separately or together these components also provide the structural support for the reef on these compositional and structural bases three main categories of organic reef are recognized 1 matrix supported reefs agglutinated microbial reefs cluster reefs segment reefs 2 skeleton supported reefs frame reefs 3 cement supported reefs cement reefs agglutinated microbial reefs possess laminated clotted or aphanitic fabrics created by microbial trapping of particulate sediment in place skeletons and large primary cavities are rare early cementation may provide added support topographic relief is limited by the need for currents to provide sediment to accreting surfaces cluster reefs skeletal reefs in which essentially in place skeletons are adjacent but not in contact resulting in matrix support characterized by relatively high matrix skeleton ratios and low volumes of extra skeletal early cement sediment trapping is an important corollary of skeletal growth and cluster reef organisms are tolerant of loose sediment absence of framework limits the topographic relief that cluster reefs can attain relative to spatial extent and may permit bedding to develop within the reef close cluster reefs have skeletons up to 1 unit distance apart spaced cluster reefs have skeletons more than 1 and up to 2 unit distances apart with increasing separation of skeletons they grade to level bottom communities segment reefs matrix supported reefs in which skeletons are adjacent and may be in contact but are mostly disarticulated and mainly parauthochtonous matrix abundance is high and early cement relatively low moderate relief can develop in response to intense on reef sediment production frame reefs skeletal reefs in which essentially in place skeletons including calcified microbes are in contact characterized by relatively high skeleton matrix ratio skeletal support enables them to raise themselves above the substrate independently of cementation and particulate sedimentation simultaneously by creating partly open shelter cavities skeletal support may facilitate early cementation both relief and early lithification promote marginal talus formation skeletal shape and orientation distinguish conical stick like dendritic domical and laminar frames each of these may be open or filled open frame reefs

tectonic geomorphology of the southeastern mississippi embayment in northern mississippi usa we analyzed drainage basin geometry in part of the southeastern mississippi embayment near the new madrid seismic zone in order to detect areas of lateral stream migration that could indicate recent tectonism toward this goal a field of drainage basin asymmetry vectors was generated from a digital terrain model and compared to geologic structure lithofacies seismicity remotely sensed lineaments and major drainage divides transverse topographical drainage basin asymmetry t index results define geomorphic domains in northern mississippi 33 to 35 n 88 5 to 90 25 w that may reflect deep crustal blocks bounded by active faults or flexures t index measurements a proxy for lateral stream migration of more than 4500 second order drainage basins produced a two dimensional field of 282 spatially averaged vectors from which we interpreted 12 domains some domain boundaries correspond to mapped faults of two paleozoic fault systems in our study area the northeast striking mississippi valley graben system and the northwest striking ouachita thrust belt and foreland faults several other prominent domain boundaries may be previously unmapped faults flexures parallel to these systems this interpretation is supported by satellite image analysis of the northeastern study area which reveals lineaments consistent with our domain boundaries that have strikes that reflect the regional subsurface structural grain

organic buildups and reefs on the palaeozoic carbonate platform margin pechora urals russia abstract in the pechora urals palaeozoic organic structures are widespread and are represented by various types from small bioherms to large barrier reefs which can be observed throughout upper ordovician lower permian strata in the pre orogenic history of palaeozoic carbonate sedimentation and reef growth three stages are distinguished each stage is characterized by a distinct reef geometry growth rate and depositional setting 1 the reefs of the lower palaeozoic ashgillian lower emsian stage were restricted to the outer shelf margin and they were wave resistant stromatolite rich frameworks except for upper llandoverian knoll and patch reefs the total thickness of the lower palaeozoic reefs is 60 1200 m 2 the middle palaeozoic middle frasnian lower tournaisian organic buildups are quiet water carbonate bank type structures generally between 300 and 700 m thick they were formed on both the outer and the inner shelf margin however they are better developed and more characteristic of the latter setting stromatoporoid microbial and microbial associations form the main buildup facies separated by bedded interbuildup sediments the upper palaeozoic upper visean sakmarian organic structures are represented by both isolated wave resistant shelf margin reefs up to 200 m thick and quiet water carbonate banks up to 330 m thick these buildups were located in the outer and inner shelf margin framework builders were mainly branching and platy stromatoporoids associated with stromatolites in the reefs and calcified microbes and phylloid algae in the carbonate banks the distribution and geometry of the buildups was mainly determined by regional tectonic events caused by the passive to active margin transition of the northeastern european platform the size of the reefs depended on the magnitude and duration of sea level fluctuations

faunal evidence for a cool boundary current and decoupled regional climate cooling in the permian of western laurentia abstract deglaciation following the late paleozoic ice age was a complex climate transition marked by smaller glacial interglacial transitions superimposed on an overall permian warming trend in contrast to this growing recognition of a dynamic climate system few studies have investigated geographic variations in postglacial climate changes which may have been as dynamic as the temporal variations because temperature and ocean circulation are important controls on the biogeography of marine invertebrates many permian taxa were characteristic of either paleotropical or high latitude faunal realms this study takes advantage of that temperature sensitivity using a database of more than 5000 permian fossil collections from northwestern pangea to reconstruct spatial variations in permian climate changes throughout the region cluster analysis demonstrates that localities in the phosphoria basin nevada idaho wyoming were taxonomically distinct from coeval faunas in texas and occupied the transitional zone between paleoequatorial and boreal realms quantitative scoring of the faunal affinity of all taxa in 1 by 1 paleolatitudinal bins suggests that the western margin of laurentia was affected by a persistent southward flowing cool boundary current and that the effects of the current became more pronounced throughout the permian in conjunction with cooling in the boreal ocean the increasingly cool water nature of phosphoria basin faunas contrasted with warming in texas and implies that northern and northwest pangea were decoupled from the broader global warming trend following the late paleozoic ice age

carbon isotope chemostratigraphy and implications of palaeoclimatic changes during the cisuralian early permian in the southern urals russia abstract in order to meet the requirements for potential gssps in the cisuralian series early permian isotopic chemostratigraphy from the carboniferous permian boundary to middle artinskian using bulk carbonates was investigated under high resolution biostratigraphical and new geochronologic constrains from three gssp candidate sections at usolka kondurovsky and dal ny tulkas in the southern urals russia a gradually increasing trend in carbonate carbon isotope 13 c has been observed in the interval from the base of asselian to early sakmarian which is generally consistent in timing with the increasing development of glacial iii or p1 from the latest carboniferous to early sakmarian early permian which prevailed in southern gondwana an excursion with double negative shifts in 13 c value is present around the asselian sakmarian boundary in both the usolka and kondurovsky sections which may have great potential to serve as chemostratigraphical marks for intercontinental correlation the following highly positive excursion of 13 c in early sakmarian indicates the maximium expansion of glacial iii or p1 the negative 13 c shift in the middle sakmarian is possibly related to the quick collapse of glacial iii or p1 on the gondwanaland this negative shift is largely correlative with those documented in other areas of russia the north american craton and south china but further precise biostratigraphical and geochronologic constrains are neccessary to confirm this global signal the late sakmarian is characterized by a strong oscillation stage of 13 c which probably indicates a complex climate transition marked by smaller alternating glacial interglacial transitions during glacial p2 superimposed on an overall warming trend the sharp negative 13 c shift around the sakmarian artinskian boundary at the dal ny tulkus section is difficult to interpret this is followed by long term low values 13 c values in the artinskian at the dal ny tulkas section might result regionally from the enhanced input of organic carbon after the melt out of ice sheets and the subsequent degradation and isotopic refractionation of the microbial chemosynthetic processes on the buried organic matter

near surface structural model for deformation associated with the february 7 1812 new madrid missouri earthquake the february 7 1812 new madrid missouri earthquake m moment magnitude 8 was the third and final large magnitude event to rock the northern mississippi embayment during the winter of 1811 1812 although ground shaking was so strong that it rang church bells stopped clocks buckled pavement and rocked buildings up and down the eastern seaboard little coseismic surface deformation exists today in the new madrid area the fault s that ruptured during this event have remained enigmatic we have integrated geomorphic data documenting differential surficial deformation supplemented by historical accounts of surficial deformation and earthquake induced mississippi river waterfalls and rapids with the interpretation of existing and recently acquired seismic reflection data to develop a tectonic model of the near surface structures in the new madrid missouri area this model consists of two primary components a north northwest trending thrust fault and a series of northeast trending strike slip tear faults we conclude that the reelfoot fault is a thrust fault that is at least 30 km long we also infer that tear faults in the near surface partitioned the hanging wall into subparallel blocks that have undergone differential displacement during episodes of faulting the northeast trending tear faults bound an area documented to have been uplifted at least 0 5 m during the february 7 1812 earthquake these faults also appear to bound changes in the surface density of epicenters that are within the modern seismicity which is occurring in the stepover zone of the left stepping right lateral strike slip fault system of the modern new madrid seismic zone

coelobiontic communities in neptunian fissures of synsedimentary tectonic origin in permian reef southern urals russia sedimentary dykes in the permian reef complexes of the russian platform are well preserved and important in providing information about reef growth the reef biota and particularly cavity dwelling organisms and sediment sources two main fissure assemblages are recognized with n80 and n170 late asselian early sakmarian and n130 140 and n60 sakmarian artinskian orientations these contemporaneous orthogonal dyke sets present orientations corresponding to the regional tectonic fabric and a tectonic origin for fracturing associated with the foreland basin development the largest dykes record eight lithofacies and several stages of fracture opening stromatoids and centimetre thick deposits of peloidal grainstones packstones thromboids which form in situ within microbial laminae on the fissure walls preceded filling by skeletal and terrigenous sediments the fissures contain a well preserved biota similar to the lower permian cavity dwelling organisms observed within the reef the coelobiontic habitat was episodically enlarged by successive synsedimentary fracturing episodes reflecting several phases of encrustation and infill of recurrent lithofacies the pioneer microbialites grew when nothing else was deposited in the fissures immediately after fracturing gastropods and ostracods occur as dense clusters probably indicating in situ growth or are considered as reworked material from the subsurface others organisms such as crinoids bryozoans tubiphytes conodonts brachiopods ammonoids and spiculate sponges are also found within fractures as reworked shells and skeletons indicating that they were washed in from the overlying sea floor the biota in the dykes is mainly represented by the dweller guilds living on the reef surface whereas members of the binding and frame building guilds are poorly represented the dykes formed during reef development and the last stage of argillaceous wackestone sedimentation within the fractures is related to a major flooding event corresponding to upper artinskian drowning of the russian platform biostratigraphically significant fossils in the dykes date the ages of the host rock and of the fissure formation and filling from late asselian to upper artinskian the tratau reef thus provides an instructive example of the interaction between carbonate accumulation and tectonic events

early permian location of western north american terranes based on brachiopod fusulinid and coral biogeography abstract brachiopod rugose coral and fusulinid faunas present in early permian rocks along northern and western margins of north america in both cratonal localities and accreted terranes have been compared statistically allowing refinement in placement of these terranes relative to the north american continental margin at that time statistical tests including conventional and probabilistic indices of similarity as well as multivariate analysis show that the faunas of wrangellia alexander are most similar to those of stikinia and quesnellia and to the yukon canadian rocky mountains part of the continental margin they also show that faunas of the eastern klamath terrane are most similar to those of stikinia quesnellia and the central cordilleran part of the continental margin these results suggest that during the early permian wrangellia alexander was the northernmost of these terranes lying west of the yukon canadian rocky mountains region and the eastern klamath terrane was the southernmost lying west of the central cordillera stikinia and quesnellia were in intermediate positions these relative latitudes are compatible with latitudinal determinations based on paleomagnetic data faunal diversity in the eastern klamath and stikine terranes is similar to that at similar latitudes on the craton whereas diversity in the wrangellia alexander terrane is considerably lower than that of the latitudinally similar yukon canadian rocky mountains area as diversity is in part a function of temperature this may suggest water around the wrangellia alexander terrane was cooler than that along the continental margin therefore we suggest that warm water currents bathed the southern terranes and the southern and central parts of coastal north america whereas cool water currents influenced the northernmost terrane wrangellia alexander revised otsuka similarity coefficients for corals show higher similarities between western north american terranes and the western continental margin than previously published but they still are relatively low this and the overall patterns of similarity and limits on distribution of tethyan corals and fusulinids in the eastern panthalassa suggest that wrangellia alexander stikinia and the eastern klamath terranes were at approximately the same distance estimated at 2000 3000 km from their latitudinally equivalent segments of the north american craton

triggered seismicity and deformation between the landers california and little skull mountain nevada earthquakes this article presents evidence for the channeling of strain energy released by the ms 7 4 landers california earthquake within the eastern california shear zone ecsz we document an increase in seismicity levels during the 22 hr period starting with the landers earthquake and culminating 22 hr later with the ms 5 4 little skull mountain lsm nevada earthquake we evaluate the completeness of regional seismicity catalogs during this period and find that the continuity of post landers strain release within the ecsz is even more pronounced than is evident from the catalog data we hypothesize that regional scale connectivity of faults within the ecsz and lsm region is a critical ingredient in the unprecedented scale and distribution of remotely triggered earthquakes and geodetically manifest strain changes that followed the landers earthquake the viability of static strain changes as triggering agents is tested using numerical models modeling results illustrate that regional scale fault connectivity can increase the static strain changes by approximately an order of magnitude at distances of at least 280 km the distance between the landers and lsm epicenters this is possible for models that include both a network of connected faults that slip sympathetically and realistic levels of tectonic prestrain alternatively if dynamic strains are a more significant triggering agent than static strains ecsz structure may still be important in determining the distribution of triggered seismic and aseismic deformation

faunal turnover and changing oceanography late palaeozoic warm to cool water carbonates sverdrup basin canadian arctic archipelago abstract carbonate sedimentary rocks in the fosheim hamilton sub basin at the eastern end of the sverdrup basin contain a particularly sensitive record of changing palaeoceanography and faunal turnover during the northward movement of pangaea through the late palaeozoic carboniferous and earliest permian inner ramp carbonates are a photozoan association of colonial corals fusulinids algae and ooids with sparse heterozoan elements crinoids brachiopods and bryozoans based on modern analogues these biotic components reflect warm water oligotrophic marine environments contemporaneous mid ramp and basin biotas are dominated by a heterozoan fauna solitary corals crinoids bryozoans and brachiopods that grew in cooler deeper waters that may have been beneath a thermocline initial cooling began in the latest sakmarian with an influx of cool deep water and climatic deterioration allowing cool and warm waters to mix disrupting the thermocline and producing a sub tropical marine biota whose remains were reworked by storms and re deposited as tempestites faunas are heterozoan crinoids bryozoans brachiopods and sponges with photozoan elements colonial corals and symbiont bearing fusulinids prominent only in inner ramp facies by late artinskian these photozoan components are only present in shallowest basin margin environments artinskian subtropical waters contained somewhat elevated trophic resources that together with mixing of photozoan and heterozoan elements in the subtropical inner ramp produced the greatest faunal diversity seen in the sverdrup basin the biota was completely boreal in nature and warm shallow waters with a warm refuge biota were now supplemented by cool waters derived from the panthalassa ocean profound change took place in the kungurian coincident with localised uplift during the melville disturbance and increased siliciclastic input neritic storm dominated sediments are wholly heterozoan brachiopods bryozoans crinoids and sponges with no remaining photozoan elements nutrient levels are elevated but not eutrophic as indicated by phosphate and glauconite extensive bioerosion numerous infaunal foraminifers and an impressive and diverse shelly biota that during times of high siliciclastic input was replaced by a profuse zoophycos infauna brachiopod and bryozoan faunas are distinctly boreal continued cooling relatively high nutrients as indicated by abundant glauconite and phosphate and decreased siliciclastic input eventually resulted in an abundant heterozoan biota brachiopods bryozoans crinoids and sponges with local gigantism but reduced brachiopod and bryozoan diversity these middle permian rocks may be the coolest water deposits in the sverdrup basin the faunas are still part of a boreal arctic province with strong ties to cool water faunas of uralian basin the succession ends with late permian biosiliceous spiculitic cherts containing accessory heterozoan components brachiopods bryozoans and few crinoids these sediments in part coeval with evaporites and terrestrial red beds on the eastern european platform are interpreted to reflect a combination of cool waters elevated nutrients and mid latitude storminess

climate environment and society in southern italy during the last 2000 years a review of the environmental historical and archaeological evidence abstract this paper examines the interrelationship between the natural and human history of sicily over the last 2000 years it presents a close comparison of the data from the key multi proxy site of lago di pergusa located inland in the eastern part of sicily with the existing archaeological and textual evidence on the socio economic processes the article also includes a review of the available natural proxy archives from the central mediterranean on the basis of the isotope and pollen data from the lago di pergusa core prg2 we identified two humid periods ca 450 750 ad and ca 1400 1800 ad as well as a dry one ca 1100 1350 ad our evidence corresponds closely with other environmental palaeoclimate proxies from the mediterranean region in our synthesis of the environmental historical and archaeological evidence from southern italy we argue that during both periods of increased humidity that is during the late antique byzantine times and during the late medieval and early modern periods intense agricultural use of the sicilian landscape developed on an unprecedented scale this in turn contributed to the impressive demographic and economic expansion visible during these periods a sudden period of aridity followed the first of these eras of humidity related agricultural growth this climatic shift dated to around 750 ad corresponds to a decrease in synanthropic taxa and a recovery of arboreal vegetation we argue that in this case a climatic change contributed to socio economic decline moreover as this change occurred prior to the arab invasion of sicily in ad 827 the environmental processes may help to explain the collapse of byzantine society on sicily which in turn made the muslim conquest possible after this event there occurred a longer period of agricultural decline lasting until around 1000 ad after which we see the first signs of a slow recovery ongoing research in nearby archaeological sites will help defining if it was a local change or a regional potentially climate induced phenomenon although textual evidence records considerable population losses during the later middle ages as a result of the black death the effects of the plague are not obviously apparent in the pollen data except for some short term fluctuations

late palaeozoic environmental changes an introduction the idea of this volume arose from our proposal to the palaeoclimatic session held at the european geosciences union general assembly 2011 conference in vienna austria although the original scope was broader the included contributions focus on palaeoenvironmental changes during the late palaeozoic late palaeozoic history is especially important in that it records an increase of tectonics diastrophism frequent sea level fluctuations and climatic changes all finally leading to the most geocratic time of earth s history with the formation of the supercontinent pangaea this volume includes a number of articles that discuss the fossil record around the late palaeozoic ice age and its decline during the carboniferous with its unusual plant proliferation soon after when the hottest and driest period in earth s history in the permian caused the development of huge sand seas on the land finally a biotic event the largest mass extinction in earth history at the permian triassic transition ends the palaeozoic world this volume addresses two key issues the palaeoclimate and depositional cycles both of which have a strong impact on the record of palaeoenvironmental changes and the understanding of environmental perturbations the vigorous current debate on the future climate of the globe inevitably increases our interest in past climates from a geological perspective climatic perturbations occurred many times before humans were on the planet climate varies on several timescales depends on many high order factors including tectonic uplift and the orbital wandering of the earth and as a result it changes through time consequently palaeoclimatic reconstructions are growing in their importance as they enable us to use the past as a key to the future the earth s system experiences various cycles of very different origin scale frequency amplitude phase and basic level from a geological perspective the cyclicity appears unidirectional like brownian motion however in the past the complex interaction of these cycles has led to catastrophic changes in earth s systems such as those during the late palaeozoic when palaeoclimatic and geotectonic cycles coincided these cycles are also influencing our lives and will do so in our future so their impact needs to be understood the geological archives record both the climatic and cyclic phenomena on local to regional scales including in the late palaeozoic as documented in this volume understanding these records will improve our predictions about climate phenomena in the future they also show that the present climatic perturbations are insignificant from a geological point of view changes in the late palaeozoic earth system are illustrated in this volume by case studies of fossil records from north and south america east and south asia south africa and australia and as regional reviews section one the methods include palaeoenvironmental analysis including palaeobiological sedimentological stratigraphic sequence stratigraphy palaeomagnetic and geochemical methods they describe various environmental settings from palaeodeserts through marine associated giant salt pans to shallow to deep marine records the articles report new data from less known study areas provide up to date data ordering and expand our knowledge of the evolution of marine and terrestrial environments climatic changes and biotic events in late palaeozoic time this special publication is divided into five chapters the first comprising articles focused on the broad descriptive character of late carboniferous to early triassic palaeoclimatic changes and stratigraphy with the latest part of this period in europe i e zechstein subsequent articles include more detailed studies of the geological periods grouped into the latest devonian to early carboniferous section two late carboniferous to early permian section three middle to late permian section four and finally the permian triassic transition section five a brief synopsis of individual papers is given below wopfner 2012 reviews westphalian early triassic palaeoclimatic conditions between samfrau comprising the southern margins of south america and south africa extending via antarctica

a 2540 year record of moisture variations derived from lacustrine sediment sasikul lake on the pamir plateau although the pamir plateau is an ideal place to investigate paleo environmental changes in the westerlies dominated high central asia there are only few holocene records from this region we present a sub centennially resolved lacustrine record of moisture variations from sasikul lake central pamir plateau based on geochemical sedimentological and mineralogical proxies our results show that generally dry conditions at sasikul lake during the past 2540 years were interrupted by a pronounced wet period between ad 1550 and 1900 corresponding to the little ice age lia more negative values of carbonate 18o lower total inorganic carbon tic and sand content during the lia all indicate a relatively wet period with higher lake level higher tic during the medieval warm period mwp ad 950 1200 reveals a lower lake level relative to the lia low 18o during this time is probably attributed to changes in the isotopic composition of input water and or upstream moisture sources the significant incr

the plio pleistocene geologic and climatic record of the kashmir valley india a review and new data abstract the kashmir valley located in the northwestern himalayas provides an intermontane valley fill comprising unconsolidated fluvio lacustrine sediments of more than a km thickness datable at 4 myr these sediments have been investigated for the last 7 years under an interdisciplinary multi agency project using a variety of proxy climatic data techniques and other analyses to decipher climatic change as a result of this study a variety of proxy climatic data from a long continental record is available now from northernmost south asia in this paper we briefly review the lithostratigraphic and chronologic framework of the sediment profile and proxy climatic data based on flora fauna stable isotopes pedology mineral magnetics and sedimentology lastly the climatic events are put in an absolute time frame for comparison with the global climatic trends the chronology is based on 14c thermoluminescence tl palaeomagnetic and fission track techniques

modern heterozoan carbonates from a eutrophic tropical shelf mauritania abstract heterozoan or foramol production is typical in extratropical carbonate sedimentary systems however under mesotrophic to eutrophic conditions heterozoan carbonates also form in tropical settings but such heterozoan tropical sedimentary systems are poorly understood nevertheless distinction between tropical and extratropical heterozoan carbonates in ancient successions is crucial for accurate paleoenvironmental and paleoclimate reconstructions here surficial holocene and pleistocene sediments of the northern mauritanian shelf are studied as an example of a tropical eutrophic carbonate depositional system 11 g l 1 chl a chlorophyll a upwelling nutrient rich waters push onto the wide mauritanian shelf where they can warm up to in excess of 25 c this condition favors production of heterozoan carbonates dominated by bivalves and foraminifers even in this tropical setting in addition sediments are provided by eolian input from the desertic hinterland the resulting sediments are carbonate and mixed carbonate siliciclastic facies in which the carbonates are characterized by a mixture of tropical and cosmopolitan taxa benthic photosynthetic biota are absent while suspension feeding organisms are dominant this foramol grain association on a shelf scale is reminiscent of cool water carbonates therefore recognition of warm water heterozoan carbonates relies on key taxa related to tropical waters within the biota assemblages associated with a highly productive environment

why the new madrid earthquakes are m 7 8 and the charleston earthquake is m 7 estimates of magnitudes of large historical earthquakes are an essential input to and can seriously affect seismic hazard estimates the earthquake intensity observations modified mercalli intensities mmi and assigned magnitudes m of the 1811 1812 new madrid events have been reinterpreted several times in the last decade and have been a source of controversy in making seismic hazard estimates in the central united states observations support the concept that the larger the earthquake the greater the maximum felt distance for the same crustal attenuation and local soil conditions magnitude should be the main influence on intensity values at large distances we apply this concept by comparing the mean mmi at distances of 600 1200 km for each of the four largest new madrid 1811 1812 earthquakes the 1886 charleston south carolina earthquake the 1929 m 7 2 grand banks earthquake and the 2001 m 7 6 bhuj india earthquake we fit the intensity observations using the form mmi a c dist 0 8 log dist to better define intensity attenuation in eastern north america ena the intensity attenuation in cratonic india differs from ena and is corrected to ena using both the above estimate and published intensity relations we evaluate source marine geophysical q and stress drop information as well as a 1929 milne shaw record at chicago to confirm that the 1929 grand banks earthquake occurred in ena crust our direct comparison of mean intensities beyond 600 km suggests m 7 5 7 3 7 7 and 6 9 for the three new madrid 1811 1812 mainshocks and the largest aftershock and m 7 0 for the 1886 charleston south carolina earthquake with an estimated uncertainty of 0 3 units at the 95 confidence level based on a monte carlo analysis our mean new madrid and charleston mainshock magnitudes are similar to those of bakun and hopper 2004 and are much higher than those of hough and page 2011 for new madrid online material tables of mean modified mercalli intensity for 800 1200 and 600 1000 km distance ranges and figures of least squares fit for all intensity measures used and for frequency dependent q in easternmost canada

warm water carbonates in proximity to gondwanan ice sheets a record from the upper paleozoic of iran abstract sedimentologic and paleontologic proxies recovered from the alborz basin the sanandaj sirjan zone and additional iranian peri gondwanan continental blocks near the arabian margin of northeastern gondwana record the formation of warm water shallow marine carbonates throughout the late pennsylvanian earliest permian this reflects a prevailing favorable climatic and environmental regime that contrasts with the cold conditions of slightly more southerly gondwanan regions that experienced profound glaciations the sedimentologic and paleobiologic properties of these iranian carbonates also differ greatly from coeval cool water carbonates of bolivia that developed at equivalent paleolatitudes along the northwestern margin of gondwana the complex climatic patterns reflected in the dispersal of marine taxa and their colonization of ecosystems relatively remote to their customary habitats and climate zones are interpreted to record the influence of ocean circulation based on these sedimentologic and paleobiologic data we utilized a climate model community climate system model version 3 ccsm3 to help resolve the mechanisms responsible for enabling transport of warm water to higher latitudes in northeastern gondwana these simulations reveal that spatial variations in sea surface temperatures exerted a strong forcing on paleo tethyan oceanic circulation and thereby governed the distribution diversity and abundance of taxa in late paleozoic marine ecosystems based on this outcome we conclude that the climatic contrasts registered across upper pennsylvanian lower permian carbonate platforms of the paleo tethys and panthalassic ocean originated through oceanic circulation driven by geographic differences in sea surface temperature

analysing the 1811 1812 new madrid earthquakes with recent instrumentally recorded aftershocks although dynamic stress changes associated with the passage of seismic waves are thought to trigger earthquakes at great distances more than 60 per cent of all aftershocks appear to be triggered by static stress changes within two rupture lengths of a mainshock1 2 3 4 5 the observed distribution of aftershocks may thus be used to infer details of mainshock rupture geometry6 aftershocks following large mid continental earthquakes where background stressing rates are low are known to persist for centuries7 8 and models based on rate and state friction laws provide theoretical support for this inference9 most past studies of the new madrid earthquake sequence have indeed assumed ongoing microseismicity to be a continuing aftershock sequence10 11 12 here we use instrumentally recorded aftershock locations and models of elastic stress change to develop a kinematically consistent rupture scenario for three of the four largest earthquakes of the 1811 1812 new madrid sequence our results suggest that these three events occurred on two contiguous faults producing lobes of increased stress near fault intersections and end points in areas where present day microearthquakes have been hitherto interpreted as evidence of primary mainshock rupture we infer that the remaining new madrid mainshock may have occurred more than 200 km north of this region in the wabash valley of southern indiana and illinois an area that contains abundant modern microseismicity and where substantial liquefaction was documented by historic accounts our results suggest that future large mid plate earthquake sequences may extend over a much broader region than previously suspected

microcodium an extensive review and a proposed non rhizogenic biologically induced origin for its formation abstract microcodium has been previously described as a mainly cenozoic calcification pattern ascribed to various organisms a review of the available literature and our data reveal two peaks in microcodium abundance the moscovian early permian and the latest cretaceous paleogene a detailed analysis of late paleozoic and cenozoic examples leads to the following new conclusions typical microcodium forming unilayered corn cob aggregates of elongated grains and thick multilayered palisade replacing structures cannot be linked to smaller grained intracellular root calcifications as became widely accepted after the work of klappa klappa c f 1979 calcified filaments in quaternary calcretes organo mineral interactions in the subaerial vadose environment j sediment petrol 49 955 968 typical microcodium is recognized from the early carboniferous with doubtful devonian reports to quaternary as a biologically induced mineralization formed via dissolution precipitation processes in various aerobic ca rich soil and subsoil terrestrial environments morphology and 13c signatures of microcodium suggest that neither plants algae or roots and root associated mycorrhiza regulate the formation of these fossil structures non recrystallized microcodium grains basically consist of slender 1 5 4 m curved radiating monocrystalline prisms with occasionally preserved hyphae like morphology thin 0 5 3 m hypha like canals can also be observed these supposed hyphae may belong to actinobacteria however thin fungal mycelia cannot be excluded we propose a model of microcodium formation involving a mycelial saprotrophic organism responsible for substrate corrosion and associated bacteria capable of consuming acidic metabolites and caco3 reprecipitation into the microcodium structures

on the modified mercalli intensities and magnitudes of the 1811 1812 new madrid earthquakes we reexamine original felt reports from the 1811 1812 new madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks in many cases we interpret lower values than those assigned by earlier studies in some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues additionally earlier studies had assigned modified mercalli intensity mmi values of v vii to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high we investigate several approaches to contouring the mmi values using both analytical and subjective methods for the first mainshock on 02 15 lt december 16 1811 our preferred contouring yields m 7 2 7 3 using the area moment regressions of johnston 1996 for the 08 00 lt on january 23 1812 and 03 45 lt on february 7 1812 mainshocks we obtain m 7 0 and m 7 4 7 5 respectively our magnitude for the february mainshock is consistent with the established geometry of the reelfoot fault which all evidence suggests to have been the causative structure for this event we note that the inference of lower magnitudes for the new madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern united states we also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811 1812 sequence

estimating earthquake magnitudes from reported intensities in the central and eastern united states a new macroseismic intensity prediction equation is derived for the central and eastern united states and is used to estimate the magnitudes of the 1811 1812 new madrid missouri and 1886 charleston south carolina earthquakes this work improves upon previous derivations of intensity prediction equations by including additional intensity data correcting magnitudes in the intensity datasets to moment magnitude and accounting for the spatial and temporal population distributions the new relation leads to moment magnitude estimates for the new madrid earthquakes that are toward the lower range of previous studies depending on the intensity dataset to which the new macroseismic intensity prediction equation is applied mean estimates for the 16 december 1811 23 january 1812 and 7 february 1812 mainshocks and 16 december 1811 dawn aftershock range from 6 9 to 7 1 6 8 to 7 1 7 3 to 7 6 and 6 3 to 6 5 respectively one sigma uncertainties on any given estimate could be as high as 0 3 0 4 magnitude units we also estimate a magnitude of 6 9 0 3 for the 1886 charleston south carolina earthquake we find a greater range of magnitude estimates when also accounting for multiple macroseismic intensity prediction equations the inability to accurately and precisely ascertain magnitude from intensities increases the uncertainty of the central united states earthquake hazard by nearly a factor of two relative to the 2008 national seismic hazard maps our range of possible 1811 1812 new madrid earthquake magnitudes increases the coefficient of variation of seismic hazard estimates for memphis tennessee by 35 42 for ground motions expected to be exceeded with a 2 probability in 50 years and by 27 35 for ground motions expected to be exceeded with a 10 probability in 50 years

late palaeozoic evolution of the north atlantic margin of pangea abstract eleven palaeogeographic maps spanning the earliest carboniferous tournaisian to late permian kazanian have been constructed for the northern north atlantic based on available onshore and offshore data each palaeogeographic map corresponds to an epoch i e 4 17 ma there are no reconstructions of the serpukhovian and tatarian and the kungurian ufimian are treated as one the palaeogeographic reconstructions outline a change in the overall depositional environment of the barents sea north greenland area from huge humid flood plains in the early carboniferous over shallow warm seas in the mid carboniferous to mid permian to cooler and possibly deeper marine environments in the late permian in east greenland non marine conditions occurred during the entire carboniferous and following a prolonged early permian hiatus warm water carbonates were deposited during the late permian the changes reflect large scale shifts in palaeoclimatic and subsidence patterns related to the northward drift of the area and ongoing rifting in the region

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

permian ice volume and palaeoclimate history oxygen isotope proxies revisited abstract a high resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in south china usa and iran was composed in order to unravel permian palaeotemperature and ice volume history the conodont apatite 18 o record is compared to published brachiopod calcite 18 o records brachiopods and conodonts from different palaeocontinents show significantly different 18 o values suggesting differences in local climatic conditions e g evaporation precipitation ratio as a consequence secular changes in palaeotemperature and oxygen isotope composition of permian sea water cannot be reconstructed from records combined from different areas but have to be based on records from a specific area oxygen isotope analyses of different conodont taxa suggest that streptognathodus and hindeodus lived in near surface seawater and recorded surface water temperature whereas the habitat of gondolellid genera was variable depending on sea level with both near surface and deeper waters as potential life habitat the oxygen isotope record measured on conodonts from south china exhibits relative high values between 22 and 23 vsmow during the glaciated early permian translating into warm seawater temperature between 26 and 30 c assuming that the late palaeozoic ice volumes were comparable to the pleistocene glacial maxima in contrast to the earlier view that the late palaeozoic ice age lpia terminated in the late sakmarian the south china conodont apatite oxygen isotope record suggests waning of the ice sheets in the kungurian ice melting is indicated by a pronounced decrease in 18 o of 2 vsmow which is interpreted as reflecting the combined effect of climatic warming and glacial ice melting significant temperature fluctuations 4 c warming succeeded by 6 to 8 c cooling are observed during the guadalupian lopingian transition interpreted as combined climate changes induced by emeishan volcanism and changes in habitat depth of gondolellid conodonts oxygen isotope values increase to 22 vsmow in the changhsingian which suggests climate cooling and clarkina moving to deeper waters because of the changhsingian sea level rise across the permian triassic boundary 18 o values decrease from 22 to 19 vsmow parallel to the significant negative carbon isotope excursion and the eruption of the siberian traps the latter is pointing to a cause effect relationship as a consequence of the massive release of volcanic greenhouse gases derived from the siberian volcanism and related processes

paleoenvironmental shifts spanning the last 6000 years and recent anthropogenic controls inferred from a high altitude temperate lake anchar lake nw himalaya integrating multiproxy results geochemistry mineral magnetism grain size and c n ratio variability supported by 14c ams dating obtained from a 1 4 m sediment core retrieved from high altitude

holocene lake level variations on the qinghai tibetan plateau paleoshorelines indicative of multiple high lake stages can be found around many lakes on the qinghai tibetan plateau qtp conspicuous paleoshorelines associated with the most recent highstands can be readily observed on satellite images and during field investigations however earlier paleoshorelines have been identified at only a few sites around these lakes due to a lack of clear shoreline features and limited spatial extension of those that can be identified we investigated past lake highstands using published chronologies aster dem google earth and arcgis 9 2 software these data suggest that 1 paleoshorelines of the most recent lake highstand were formed during the holocene 2 during this highstand lake levels reached more than 90 60 90 and 30 60 m higher than present in the central gangdise and western qiangtang areas while in the eastern qiangtang holxil yushu and northeastern qtp areas highstands did not exceed 30 m above modern 3 during the early holocene some lakes on the southwestern qtp combined to form large lakes while lakes in the inland areas of the qtp were only a little larger during the holocene high lake level stages

seismic moment assessment of earthquakes in stable continental regions iii new madrid 1811 1812 charleston 1886 and lisbon 1755 summary the sizes of three major or great historical earthquakes are reassessed using the isoseismal area regression tools developed in parts i and ii of this study of stable continental region scr seismicity the earthquakes are 1811 new madrid central united states and its following sequence 1886 charleston coastal south carolina and 1755 lisbon oceanic intraplate off the continental shelf of portugal the analysis confirms the large size of these events and for the first time places constraints on the uncertainty of their seismic moment release because of the exceptionally low seismic wave attenuation of eastern north america ena a separate north american regression of seismic moment on isoseismal area was developed additionally the unknown western extents of the new madrid isoseismal areas were calibrated with the patterns of the m 6 3 6 6 1843 and 1895 earthquakes application of part ii analysis procedures with these corrections yields new madrid size estimates expressed as moment magnitude of m 8 1 0 31 for the 1811 december 16 m 7 8 0 33 for the 1812 january 23 and m 8 0 0 33 for the 1812 february 7 principal events the charleston earthquake s magnitude decreases from m 7 4 to m 7 3 0 26 after compensation for the effect of coastal plain sediments on its inner isoseismals intensity regressions for lisbon are calibrated against the isoseismal pattern of the nearly co located m 7 8 1969 st vincent earthquake which in this case increases the predicted size of lisbon from m 8 4 to m 8 7 0 39 these size estimates are supported by data from independent phenomena extent and severity of liquefaction the maximum distance of induced landslides and for lisbon tsunami wave amplitudes estimated source parameters are controlled by crustal or lithospheric temperature which governs the depth extent of brittle faulting using estimated continental and oceanic geotherms viable fault lengths are 30 80 km for charleston 120 180 km for 1811 new madrid and 180 280 km for lisbon for average displacements of 2 4 m 8 11 m and 10 14 m respectively and for average static stress and strain drops at the estimated seismic moments of this study the 1811 new madrid and the 1755 lisbon events are respectively the largest known scr and oceanic lithosphere earthquakes

estimating locations and magnitudes of earthquakes in eastern north america from modified mercalli intensities we use 28 calibration events 3 7 m 7 3 from texas to the grand banks newfoundland to develop a modified mercalli intensity mmi model and associated site corrections for estimating source parameters of historical earthquakes in eastern north america the model batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm mmi 1 41 1 68 times mathbf m 0 00345 times delta 2 08 mathrm log delta end document where is the distance in kilometers from the epicenter and m is moment magnitude provides unbiased estimates of m and its uncertainty and if site corrections are used of source location the model can be used for the analysis of historical earthquakes with only a few mmi assignments we use this model mmi site corrections and bakun and wentworth s 1997 technique to estimate m and the epicenter for three important historical earthquakes the intensity magnitude m i is 6 1 for the 18 november 1755 earthquake near cape ann massachusetts 6 0 for the 5 january 1843 earthquake near marked tree arkansas and 6 0 for the 31 october 1895 earthquake the 1895 event probably occurred in southern illinois about 100 km north of the site of significant ground failure effects near charleston missouri manuscript received 14 march 2002

seismic hazard map of southeast missouri and likely magnitude of the february 1812 new madrid earthquake abstract the new madrid seismic zone lies beneath the upper mississippi embayment straddling the border between southeastern missouri and northwestern tennessee in late 1811 and early 1812 it produced five earthquakes of magnitudes 6 5 violently shaking the central and eastern united states ceus its magnitude and recurrence are of concern to today s central united states regions by considering the effects of local geology deterministic scenario maps m w 7 3 and 7 7 were produced for ground motions intended to simulate the 7 february 1812 event nm3 which was the largest felt these maps include spatial estimates of peak ground acceleration and of 0 2 s and 1 0 s spectral acceleration sa compared with the isoseismic map of modified mercalli intensities mmis in southeast missouri the mmis converted from 0 2 s sa suggest that m w 7 7 is a plausible scenario for nm3 to better constrain its magnitude other ceus sites shaken during nm3 were also examined local site conditions were studied and evaluated before calculating the threshold magnitude for the reported mmis these results indicate that the magnitude of nm3 was at least m w 7 6 which validates our estimated size of m w 7 7 for southeastern missouri

magnitude estimates of two large aftershocks of the 16 december 1811 new madrid earthquake the three principal new madrid mainshocks of 1811 1812 were followed by extensive aftershock sequences that included numerous felt events although no instrumental data are available for either the mainshocks or the aftershocks available historical accounts do provide information that can be used to estimate magnitudes and locations for the large events in this article we investigate two of the largest aftershocks one near dawn following the first mainshock on 16 december 1811 and one near midday on 17 december 1811 we reinterpret original felt reports to obtain a set of 48 and 20 modified mercalli intensity values of the two aftershocks respectively for the dawn aftershock we infer a m w of approximately 7 0 based on a comparison of its intensities with those of the smallest new madrid mainshock based on a detailed account that appears to describe near field ground motions we further propose a new fault rupture scenario for the dawn aftershock we suggest that the aftershock had a thrust mechanism and occurred on a southeastern limb of the reelfoot fault for the 17 december 1811 aftershock we infer a m w of approximately 6 1 0 2 this value is determined using the method of bakun et al 2002 which is based on a new calibration of intensity versus distance for earthquakes in central and eastern north america the location of this event is not well constrained but the available accounts suggest an epicenter beyond the southern end of the new madrid seismic zone

preliminary assessment of sand blows in the southern mississippi embayment trenching of sand blows in two liquefaction fields on late to mid holocene alluvium within the southern mississippi embayment was conducted to determine the origin of the sand blows and their possible relationship to new madrid seismic zone events trench stratigraphy and crosscutting relationships show evidence of multiple events of seismically induced sand venting these two fields of moderate to intense liquefaction are 175 km and 240 km southwest of the southern limit of similarly intense sand blows within the new madrid seismic zone nmsz liquefaction field the southernmost field ashley county arkansas is 25 km in diameter and sand blows are densely spaced sand blows are more sparsely spaced in the larger 30 km by 45 km northern field desha county arkansas various correlations of liquefaction events between these two fields and between each of these fields and the nmsz can be accommodated by our radiocarbon and infrared stimulated luminescence irsl ages of sediments predating and postdating vented sand deposits in our trenches these ages show a major liquefaction event at both the ashley and desha county fields between 4600 and 5500 years ago and a major event at the ashley county field approximately 700 years ago the early venting episode is older than the documented nmsz chronology and so a nmsz seismic source cannot be assessed the age of the later venting episode falls between two postulated nmsz events so it may reflect seismicity from a different source zone our trench logs show at least three other moderate to minor sand venting episodes at the ashley county field and two at the desha county field and one may be the same event at both fields about 2200 years ago if these sand blows formed during large nmsz events 175 km northeast the area of strong ground motion for this seismic source has been underestimated alternatively if these liquefaction fields formed due to local seismicity then additional significant seismic source zones are present in the mississippi embayment outside the nmsz each of the two fields sits astride seismicity alignments associated with the margins of a previously identified active fault block between the arkansas river fault zone that projects through the desha county field and the saline river fault zone that projects through the ashley county field

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

oxygen isotope values from high latitudes clues for permian sea surface temperature gradients and late palaeozoic deglaciation abstract the permian was a period of waning large scale continental glaciations in the southern hemisphere the waning of these ice sheets during the early permian led to discharge of 18o depleted ice melt water into the oceans this coupled with rising seawater temperatures resulted in a concomitant decline of about 2 5 in the 18o of seawater as recorded by brachiopod shells from low latitude

toward a consistent model for strain accrual and release for the new madrid seismic zone central united states 1 at the heart of the conundrum of seismogenesis in the new madrid seismic zone is the apparently substantial discrepancy between low strain rate and high recent seismic moment release in this study we revisit the magnitudes of the four principal 1811 1812 earthquakes using intensity values determined from individual assessments from four experts using these values and the grid search method of bakun and wentworth 1997 we estimate magnitudes around 7 0 for all four events values that are significantly lower than previously published magnitude estimates based on macroseismic intensities we further show that the strain rate predicted from postglacial rebound is sufficient to produce a sequence with the moment release of one mmax6 8 every 500 years a rate that is much lower than previous estimates of late holocene moment release however mw6 8 is at the low end of the uncertainty range inferred from analysis of intensities for the largest 1811 1812 event we show that mw6 8 is also a reasonable value for the largest main shock given a plausible rupture scenario one can also construct a range of consistent models that permit a somewhat higher mmax with a longer average recurrence rate it is thus possible to reconcile predicted strain and seismic moment release rates with alternative models one in which 1811 1812 sequences occur every 500 years with the largest events being mmax 6 8 or one in which sequences occur on average less frequently with mmax of 7 0 both models predict that the late holocene rate of activity will continue for the next few to 10 thousand years

paleoclimatic significance of phanerozoic reefs a database of pre quaternary phanerozoic reefs is used to test the significance of ancient reefs as paleoclimatic tracers the compilation of reef paleolatitudes through time and comparison with published paleoclimate curves shows that neither the width of the tropical reef zone nor the total latitudinal range of reefs is correlated with published estimates of paleotemperature however reefs trace paleoclimate indirectly algal reefs tend to prevail during icehouse climatic intervals and distinct high latitude reefs are only developed in cold intervals whereas during greenhouse episodes the reef zone usually ended abruptly at a particular latitudinal boundary in the subtropics additionally different biotic reef types tended to be concentrated in different latitudes the lowest latitudes have usually been occupied by coralline sponge or microbial reefs coral reefs tended to grow in intermediate latitudes and bryozoan reefs constantly occupied the highest latitudinal position

carbonate minerals oxygen and carbon isotopes in modern temperate bryozoa eastern tasmania australia abstract x ray analysis of cool temperate bryozoa from eastern shelf carbonates indicates the occurrence of a spectrum of low mg calcite to high mg calcite with variable amounts of aragonite bryozoa contain variable amounts of caco3 cements in bryozoa 18o values increase and 13c values decrease with increasing aragonite content probably due to the occurrence of vaterite aragonite contents decrease with decreasing water temperatures as established by oxygen isotope thermometry tasmanian bryozoa may be enriched in 18o up to 0 7 due to aragonite and high mg calcite contents 13c values of bryozoa composed of pure calcite are similar to those of associated brachiopods 18o and 13c values of bryozoa are unaffected by kinetic and metabolic effects the isotopic field of temperate bryozoa differs from tropical carbonates by having heavier 18o 1 3 0 5 and lighter 13c 1 8 0 8 values than bulk tropical carbonates the bryozoa are in equilibrium with upwelling deep seawater and surface subantarctic water and therefore intersect seafloor diagenesis and upwelling water trend lines mol mgco3 content ranges from 2 to 11 in calcite and corresponds to 5 14 c water temperatures the 18o values of bryozoa give a range of temperatures from 7 to 13 c slightly less than the 4 15 c obtained from 18o of tasmanian brachiopods this discrepancy is probably due to either minor biochemical fractionation or to bryozoa being in equilibrium with warmer waters

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

microbial community from the lower permian artinskian kungurian paleoclimatic transition mid panthalassan akiyoshi atoll japan abstract large oncoids up to 14 cm and microbialites are abundant in the artinskian lower permian section of mid panthalassan akiyoshi atoll carbonates the oncoids and microbialites consist mainly of a tubular microproblematicum girvanellid cyanobacterial filaments microbial micrite crusts and pore filling sparry calcite cements they are surrounded by intraclastic bioclastic grainstone rudstone indicative of moderate to slightly high energy subtidal conditions the microbial community was the primary boundstone forming organisms on the akiyoshi atoll during this time it represents a transitional stage in a mid panthalassan reef succession between a cooler water autotrophic palaeoaplysina microencruster community in the gzhelian asselian and a warmer water heterotrophic calcareous sponge microencruster community in the middle permian the flourishing mid panthalassan microbial community during the late early permian is related to enhanced alkalinity increasing nutrient levels elevated sea surface temperatures and the absence of major reef building metazoans which resulted from gondwanan deglaciation climatic changes and a pulse of active volcanism

cool water carbonates in a paleoequatorial shallow water environment the paradox of the auernig cyclic sediments upper pennsylvanian carnic alps austria italy and its implications distinct parts of limestones within the upper paleozoic auernig group of the carnic alps austria and italy are characteristic of cool water carbonates the carnic alps were between 5 n and 10 s paleolatitude during the late carboniferous a position confirmed by dasyclad algae and fossil plants the floral association occurrence of coal seams and absence of evaporites indicate a humid tropical environment the entire section lacks abiotic components of typical warm water limestones no ooids and no aggregates occur within the auernig group parts of the limestones show surprisingly a cool water association of high diversity bryozoans brachiopods crinoids red algae sponge spicules and entomozoan ostracodes the genesis of these limestones atypical for a paleoequatorial setting cannot be explained by changes in salinity bathymetry or terrigenous input the water temperature possibly linked with upwelling nutrient supply and paleoceanographic currents is the most convincing cause of this unusual association paleoceanographic changes are interpreted as linked to contemporaneous glaciation deglaciation cycles in gondwana this paper shows that cool water carbonates in shallow water environments are not necessarily nontropical as generally interpreted future studies should consider water temperature oceanic circulation and availability of nutrients supplementary to bathymetry salinity and latitude related climate in interpretation of carbonate components

multiple late holocene earthquakes along the reelfoot fault central new madrid seismic zone the reelfoot fault is an east vergent reverse fault underlying the lake county uplift a low amplitude late holocene anticline bordered on the east by the 32 km long reelfoot scarp fluvial deposits across the scarp define an 8 m high east facing monocline most near surface deformation along the scarp is accommodated via folding rather than faulting we interpret the scarp as a fault propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data trench exposurcs provide evidence for three episodes of deformation along the reelfoot fault within thc past approximately 2400 years between a d 780 and 1000 between a d 1260 and 1650 and during a d 1812 our best estimate of the average recurrence interval for deformation along the scarp is 400 500 years each episode of deformation had a slightly different style the third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault the second most recent earthquake produced about 1 3 m of throw in the graben as well as folding along the updip projection of the reverse fault and development of the scarp thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude the 1811 1812 episode of deformation produced abundant liquefaction prominent folding of fluvial strata along the scarp and minor faulting in the graben

paleoseismology of the southeastern reelfoot rift in western tennessee and implications for intraplate fault zone evolution 1 the southeastern reelfoot rift margin is expressed as a series of collinear scarps across western tennessee and shallow s wave reflection profiles coring and trenches show late quaternary faulting along this lineament at the north end our seismic profile and coring suggest 1 5 m of wisconsin down to the nw faulting coring and trenches across the central lineament show 3 m of up to the nw and 8 15 m of right lateral late wisconsin holocene faulting averaged late quaternary right lateral slip has been 0 85 0 37 mm yr on one fault plane at this locality suggesting that total slip across all southeast rift margin fault planes may accommodate much of the regional strain our seismic profile at this site shows up to the west faulting of eocene strata folded down to the west indicating structural inversion seismic profiles electrical surveys coring and a trench across the southern lineament segment show holocene faulting trenching exposed a vertical fault with 0 5 m of late holocene down to the nw displacement nearby coring and electrical surveys show 0 5 m of late holocene up to the nw faulting we conclude the southeastern reelfoot rift margin is a right lateral system with high angle faults showing both up to the nw and down to the nw separations age constraints permit an earthquake circa 2500 to 2000 years b p on the southwestern central segment of this fault system that ruptured 80 km we suggest the northeastern segment of the southeastern rift margin turned off in holocene when the reelfoot step over thrust turned on

estimating earthquake location and magnitude from seismic intensity data analysis of modified mercalli intensity mmi observations for a training set of 22 california earthquakes suggests a strategy for bounding the epicentral region and moment magnitude m from mmi observations only we define an intensity magnitude m i that is calibrated to be equal in the mean to m m i mean m i where m i mmi i 3 29 0 0206 i 1 68 and i is the epicentral distance km of observation mmi i the epicentral region is bounded by contours of rms m i rms m i m i rms m i m i where rms is the root mean square rms m i m i is the minimum rms over a grid of assumed epicenters and empirical site corrections and a distance weighting function are used empirical contour values for bounding the epicenter location and empirical bounds for m estimated from m i appropriate for different levels of confidence and different quantities of intensity observations are tabulated the epicentral region bounds and m i obtained for an independent test set of western california earthquakes are consistent with the instrumental epicenters and moment magnitudes of these earthquakes the analysis strategy is particularly appropriate for the evaluation of pre 1900 earthquakes for which the only available data are a sparse set of intensity observations

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

from isolated buildups to buildup mosaics 3d seismic sheds new light on upper carboniferous permian fault controlled carbonate buildups norwegian barents sea abstract carbonate buildups are a common feature of many ancient carbonate platforms and were especially abundant during the palaeozoic our present understanding of buildup distribution and the ability to better predict their location is however hampered by the fact that maps of buildups rarely show evidence of widespread spatial organisation and indeed their distribution often appears chaotic a previously unrecognized pattern of buildup distribution has been revealed by three dimensional 3d seismic data recently acquired from the loppa high norwegian barents sea here syn rift carboniferous permian buildups are not isolated but are instead linked into a mosaic of laterally extensive ridges the buildups location is controlled by the intersection of three trends of syndepositional faults systematic organisation of buildup height width density and external form across the study area appears to have been controlled by changes in accommodation space driven by differential subsidence the buildups were remarkably long lived and developed over an interval of 35 ma despite this longevity buildup location remained relatively static and true to the underlying pattern of basement faults indicating that their progradation was likely restricted by a combination of factors including limited highstand production their depositional relief

carbonate deposition during a time of mid latitude ocean cooling early permian subtropical sedimentation in the sverdrup basin arctic canada abstract carbonate rocks of the lower permian sakmarian to kungurian raanes and great bear cape formations accumulated in the sverdrup basin during a critical transition period when ocean waters cooled dramatically these rocks have many attributes similar to sediments deposited in modern subtropical zones the biota is dominated by a heterozoan assemblage of pelmatozoans bryozoans and brachiopods with the addition of photozoan elements such as fusulinids and colonial corals associated with the change in the sverdrup basin from a tropical to subtropical environment is the first occurrence of glauconite iron oxides and storm deposits the shift in depositional conditions is interpreted to reflect decreased seawater temperature that was brought about by a northward migration to a mid latitude position frequented by storms oceanographic change however was not unidirectional but was complicated by concomitant variations in sea level and oceanography recorded as three distinct phases determined by water depth and temperature 1 rocks of the raanes and lower great bear cape are deep water and heterozoan 2 the middle great bear cape records shallow water subtropical conditions with fusulinids and large colonial corals 3 the upper great bear cape is entirely heterozoan in all locations and by implication all depths all post raanes and great bear cape rocks of the sverdrup basin are entirely heterozoan taking caution for possible evolutionary changes subtropical carbonates can be recognized in rocks much older than previously believed the most important components for identifying subtropical carbonates of the past are large benthic foraminifers in an otherwise heterozoan assemblage and as such the ability to delineate this carbonate realm in the past is currently restricted to times when large benthic foraminifers grew in shallow marine environments