discrepancies between different organic maturity indicators in a coal series affected by an abnormal thermal event visean niger abstract classical petrographical and geochemical approaches have been used to study visean coal seams sampled in two areas 50 km apart in northern niger t max values given by rock eval pyrolysis and individual molecular ratios determined on hopanes and steranes are in agreement with the burial history of the two sets of samples studied the difference of maturity of the two sample sets revealed by these various parameters is consistent with their current difference in burial depth 400 m only small changes of these parameters with depth were observed owing to the small depth interval sampled at both sites 15 and 40 m these variations also appear to be related to normal burial diagenesis no maturity differences between the two sample sets are revealed by vitrinite reflectance data and atomic h c ratios which are in the same range at both sites but display very large variations with depth r v 0 60 1 40 and h c at 0 80 0 90 to 0 55 these data indicate rapid entrance into the oil window this conclusion also being supported by microspectrofluorimetric observations showing oil production and expulsion and by the presence of pyrobitumens containing large devolatilization vacuoles in the deepest samples the abnormally high maturity gradient could have been caused by a hydrothermal event the present observations on coals confirm and supplement previous conclusions drawn from the study of organic materials disseminated in zn pb sulfide ore bearing sedimentary rocks the difference in sensitivity shown by the various maturity indicators is considered very likely to be due to differences in the kinetics of the transformations on which they each depend

liquefaction evidence for strong earthquakes of holocene and latest pleistocene ages in the states of indiana and illinois usa abstract sand and gravel filled clastic dikes of seismic liquefaction origin occur throughout much of southern indiana and illinois nearly all of these dikes originated from prehistoric earthquakes centered in the study area in this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the holocene and at least one during the latest pleistocene the recognition of different earthquakes has been based mainly on timing of liquefaction in combination with the regional pattern of liquefaction effects but some have been recognized only by geotechnical testing at sites of liquefaction most paleo earthquakes presently recognized lie in indiana but equally as many may have occurred in illinois studies in illinois have not yet narrowly bracketed the age of clastic dikes at many sites which sometimes causes uncertainty in defining the causative earthquake but even in illinois the largest paleo earthquakes probably have been identified prehistoric magnitudes were probably as high as about moment magnitude m 7 5 this greatly exceeds the largest historic earthquake of m 5 5 centered in indiana or illinois the strongest paleo earthquakes struck in the vicinity of the concentration of strongest historic seismicity elsewhere paleo earthquakes on the order of m 6 7 have occurred even where there has been little or no historic seismicity both geologic and geotechnical methods of analysis have been essential for verification of seismic origin for the dikes and for back calculating prehistoric magnitudes methods developed largely as part of this study should be of great value in unraveling the paleoseismic record elsewhere

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

structural analysis and interpretation of the surface deformations of the el asnam earthquake of october 10 1980 the el asnam earthquake of october 10 1980 represents the major seismotectonic event of these last decades in the west mediterranean area it has induced a large amount of surface breaks this earthquake reveals the importance of compressional phenomena that characterize nowadays the tectonics of north africa the tectonic analysis of surface rupture shows the complexity of the deformation mechanism the principal mechanism consists of the activation of a nw se trending thrust fault accompanied with a left lateral motion and with an intense deformation of the northwestern overthrusting block an accurate description of these deformations shows that for a large part the breaks geometry depends closely on the substratum structure finally the analysis of the dislocations on irrigation ducts just above the fault traces allowed a quantitative study of the deformation

preliminary observations from the 3 january 2017 m w 5 6 manu tripura india earthquake abstract on 3 january 2017 a m w 5 6 earthquake occurred in dhalai district in tripura india at 14 39 03 ist 09 09 03 utc with an epicentre at 24 018 n 4 9 km and 91 964 e 4 4 km and a focal depth of 31 6 0 km the focal mechanism solution determined after evaluating data from seismological observatories in india indicated a predominantly strike slip motion on a steeply dipping plane the estimated focal depth and focal mechanism solution places this earthquake in the indian plate that lies beneath the overlying indo burmese wedge as in the 2016 manipur earthquake a strong motion record from shillong india appears to suggest site amplification possibly due to topographic effects in the epicentral region in tripura damage assessed from a field survey and from media reports indicated that the macroseismic intensity approached 6 7 ems with damage also reported in adjacent parts of bangladesh a striking feature of this earthquake were the numerous reports of liquefaction that were forthcoming from fluvial locales in the epicentral region in tripura and at anomalous distances farther north in bangladesh the occurrence of the 2017 manu earthquake emphasises the hazard posed by intraplate earthquakes in tripura and in the neighbouring bengal basin region where records of past earthquakes are scanty or vague and where the presence of unconsolidated deltaic sediments and poor implementation of building codes pose a significant societal and economic threat during larger earthquakes in the future

an integrated model of extrusive sand injectites in cohesionless sediments clastic injection and surface expression of subsurface sediment remobilization is a phenomenon which is becoming increasingly recognized however understanding of the physical mechanisms that control these features remains limited dominated by inference from outcrop and seismic studies here this limitation is addressed through a set of experiments focused on the development and evolution of fluidization features in non cohesive bedded sequences fluidization and the onset of piping are shown to occur progressively through a sequence of discrete phases with initial void formation development of infiltration horizons rupture and finally pipe formation critically the style of piping the stability of piping and the temporal evolution of venting are shown to exhibit considerable variability in particular pipes may either be stable or very mobile migrating laterally over large distances these produce deposits that are typically interpreted in outcrop as being the product of en masse liquefaction rather than localized dynamic fluidization these differing elements are synthesized to produce a model of sand extrudites in addition the implications of this model are explored

neogene sedimentary deformation in the chilean forearc and implications for andean basin development seismicity and uplift neogene sediments in the northern chilean forearc display a wide range of near syndepositional structures analysis of the origin and distribution of these structures in space and time offers new insights into the development of the forearc basins the structures are described in detail and show many features associated with soft sediment deformation pseudo diapirism and slope failure synsedimentary deformation reached a peak in the late miocene to early pliocene while the sediments were saturated in a largely plastic state and many of the structures were probably triggered by seismic shock late stage tilting of the forearc generated shear stresses in the sediments leading to slumping and sliding base level revision and drainage incision led to sediment bypass and cessation of lacustrine sedimentation that was not necessarily linked to climate change compaction and dewatering of the basins caused transition of the sediments from a plastic to a brittle state the age and distribution of structures associated with seismicity appears to correlate with increasing subduction erosion and westward drift of south america but not with basin subsidence shortening rates or plate convergence this suggests that upper crustal deformation is at least partly decoupled from plate movement

holocene soft sediment deformation of the santa fe sopetran basin northern colombian andes evidence for pre hispanic seismic activity abstract the detailed study of four deformed intervals from the holocene fluvio lacustrine deposits of the santa fe sopetran basin in northern colombia shows 17 types of soft sediment deformation ssd structures evidence indicates that seismic activity was responsible for the ssd structures a conclusion reached after considering the environmental conditions at the time of sediment deposition and shortly after and the detailed analysis of the driving force systems other triggers i e overloading and rapid sedimentation however are not discarded intervals showing ssd structures occurred at centennial frequencies and apparently resulted from mw 6 7 earthquakes the holocene age of these major shaking events should be seriously considered when evaluating the seismic hazard and risk for the middle cauca valley and the nearby city of medellin with 3 million inhabitants

early diagenetic oxidation and maturation trends in organic matter extracted from eocene chalks and cherts abstract kerogen and humic acid extracted from eocene chalks and cherts display composition variations which do not follow normal thermal maturation trends decrease in the h c ratio is followed by an increase of the o c s c and n c ratios and the 12 c is also enriched the humic acids are always heavier in their 13 c composition than the kerogens extracted from the same samples their h c o c and s c ratios are usually higher and their structure is more aliphatic and less aromatic the compositional trends observed in the humic acids and kerogens apparently result mostly from increased microbial oxidation of aliphatic chains into carboxyl groups by sulfate reducing bacteria this process is corroborated by infrared spectra which reveal a negative correlation between aliphatic and oxygen containing groups coinciding with the negative h c o c relationship the change from humic acids to kerogen on the other hand is the result of thermal maturation accompanied by microbial oxidation since the chert and chalk samples reflect the same evolution trends it appears that the microbial oxidation affected the organic matter prior to chertification

multiscale organisation of organic matter associated with gold and uranium minerals in the witwatersrand basin south africa abstract organic matter from the northern part of the early proterozoic witwatersrand basin carbon leader reef was investigated using optical om and transmission electron tem microscopes completed by xrd analysis the multiscale organization texture microtexture structure of the organic matter was observed in order to gain information about the processes which affected organic material after its deposition in sediments in the micrometre scale optical microscope the shape and size of the reflectance indicating surface ris of the organic matter were determined the organic matter reveals a prevailing biaxial symmetry the size of ris is generally dependent on uranium and increases with increasing uranium concentration furthermore it appears that more than one ris is present within the scale of a single sample each with a different symmetry and size the presence of domains differing in organisation of the aromatic framework was confirmed by tem observation in the df mode the aromatic skeleton of organic matter is composed of short often crumpled mostly isolated non stacked polyaromatic layers whose fringe length corresponds to 3 16 aromatic rings the data indicate reorganization of the polyaromatic organic matter structure under stress in high pressure and relatively low temperature conditions the organic matter was in a solid state within the rocks before the pressure event

evidence for a buried fault system in the coastal plain of the carolinas and virginia implications for neotectonics in the southeastern united states geomorphic geologic and geophysical data suggest the presence of an 600 km long north northeast trending buried fault system in the coastal plain of the carolinas and virginia herein named the east coast fault system the east coast fault system is expressed by anomalous changes in fluvial geomorphology that locally coincide with one or more of the following features linear aeromagnetic anomalies buried faults interpreted from seismic reflection data surface faults offsetting pliocene pleistocene surficial units locally brecciated phyllites and argillites gently upwarped sediments topographic highs and seismicity near summerville south carolina river anomalies where the rivers traverse unconsolidated upper pleistocene holocene flood plain sediments are evidence of deformation along the east coast fault system during the past 130 to 10 k y which may be ongoing the fault system traverses the epicentral area of the 1886 charleston south carolina earthquake and lies west of paleoliquefaction sites along the outer south carolina coastal plain thus the fault system could be the source of the charleston earthquake and other large prehistoric earthquakes therefore confirmation and demarcation of the east coast fault system and elucidation of its history will help better assess seismic hazards in the southeastern united states

diagenetic trends of a tertiary low rank coal series abstract the mahakam delta kalimantan indonesia coals represent all the evolution stages between freshly deposited plant peat material lignites and bituminous coals the geochemical techniques used to study this coal series included elemental analysis extraction of humic compounds infrared spectroscopy and 13 c nuclear magnetic resonance of the total coal the main mechanisms of early maturation in this series are loss of oxygenated compounds aromatisation and condensation of the organic matter these changes which have already been suggested for other coal series and partially reported for sedimentary organic matter were confirmed and described in more detail for the mahakam coal series

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

geochemical and petrographic characterization of humic coals considered as possible oil source rocks abstract recently several groups of authors have argued that coals should be considered as possible source rocks for oil as well as being source rocks for gas the present study was undertaken with the objective of evaluating the various methods of characterization of maturation levels and oil potentials of coals from within the oil window it was found that the degree of maturation of a coal could not be specified exactly no matter what parameter describing coal rank was used this lack of precision obviously makes it difficult to compare coals especially from the point of view of their petroleum potential which varies during the course of coalification furthermore quantitative evalution of the oil potential of coals is difficult particularly the present day petrographic concept of exinite does not seem very well adapted to this quantitative evaluation differences in oil potential might in fact be better explained by the relative proportions of the various vitrinite macerals which are present rather than by the proportion of exinite in the coal

radiolytic alteration of biopolymers in the mulga rock australia uranium deposit abstract we investigated the effect of ionizing radiation on organic matter om in the carbonaceous uranium u mineralization at the mulga rock deposit western australia samples were collected from mineralized layers between 53 and 58 5 m depths in the ambassador prospect containing

abraded sand volcanoes as a tool for recognizing paleo earthquakes with examples from the cisuralian talchir formation near angul orissa eastern india abstract one of the bedding planes of a sandstone unit belonging to the cisuralian talchir formation is well exposed along the nandir jhor river in eastern india it shows a few dozens of circular structures commonly with diameters of a few decimetres a concentration is found in an area of some 50 m 2 where 12 well developed specimens occur the structures are interpreted as abraded sand volcanoes which interpretation is supported by the occurrence on the same bedding plane of a sand volcano with a diameter of over a meter the concentrated structures thus represent a sand volcano field a phenomenon that has not been recognized earlier in the pre holocene geological record but that in recent times seems always to be related to an earthquake the structures described here might therefore help to recognize earthquakes that occurred in the geological past

on the nature of an unusual wave train observed in the northern tien shan region we describe an unusual wave group that propagates in the northern tien shan region along the border between mountain ranges and the chu and ili depressions to the north this wave group which we call s l stands out against the short period coda on the recordings of local earthquakes and quarry explosions at distances up to 100 km the time t m needed for the s l group to reach maximum amplitude varies between 98 and 131 sec and at the same time the t m value does not depend on epicentral distance at distances up to 30 km the s l group has a very narrow spectrum t 1 5 1 8 sec but when the epicentral distance increases the predominant period also increases up to approximately 2 3 sec at 100 km characteristics of the wave group are significantly different for the zaili fault zone than for the regions to the west of 76 e and to the east of 79 e in the zaili fault region the s l group is characterized by great variability of velocity amplitude and polarization parameters even for nearby paths the s l group maintains an amplitude within 0 7 of its maximum for 4 36 sec depending on the path the polarization of the s l group is in the vertical plane in the zaili fault zone region and in the horizontal plane in other regions particle motion is elliptical or almost circular we suggest that the s l group consists of shear waves propagating in a subvertical wave guide and reflected from a thin upper mantle layer

a second order bulk boundary layer model abstract bulk mass flux models represent the large eddies that are primarily responsible for the turbulent fluxes in the planetary boundary layer as convective circulations with an associated convective mass flux in order for such models to be useful it is necessary to determine the fractional area covered by rising motion in the convective circulations this fraction can be used as an estimate of the cloud amount under certain conditions matching conditions have been developed that relate the convective mass flux to the ventilation and entrainment mass fluxes these are based on conservation equations for the scalar means and variances in the entrainment and ventilation layers methods are presented to determine both the fractional area covered by rising motion and the convective mass flux the requirement of variance balance is used to relax the well mixed assumption the vertical structures of the mean state and the turbulent fluxes are determined analytically several aspects of this simple m

stream networks and long term surface uplift in the new madrid seismic zone stream networks are sensitive to low rates of surface uplift and can be used to decipher the history of large earthquakes even where faults do not rupture the surface as in intraplate seismic zones statistical analysis of alluvial network data from topographic maps in the new madrid seismic zone in the central united states shows that stream segment gradients deviate the most from an estimated natural stream profile where surface uplift is greatest evidence of cumulative deformation distilled from stream network patterns represents at least several meters of differential surface uplift during holocene time which suggests that more than one cycle of surface deformation occurred

the armenian earthquake of 1988 december 7 faulting and folding neotectonics and palaeoseismicity summary the spitak earthquake of 1988 december 7 is the first well documented event directly associated with surface breaks in the transcaucasian regions of the ussr the earthquake was located within the ese wnw oriented pambak sevan thrust and fold zone corresponding to the southern front of the lesser caucasus the mechanism of the earthquake is consistent with the nearly ns compressive tectonics due to the active continental collision between the arabian block and the russian platform the rupture is composed by several branches two of which reach the surface the first branch oriented n140 begins near the village of alavar has a length of 11 km and disappears at about 4 km se of spitak it consists of a right lateral en echelon system of strike slip faults with a maximum offset of 50 cm the second branch is the main one and breaks for about 8 km between spitak and gekhasar with a general orientation n120 showing reverse faulting dipping to the north with a right lateral component surface ruptures between gekhasar and spitak show either a narrow band of pressure ridges in alluvial deposits and soil or a fault scarp in the bed rocks when soil is absent maximum displacements observed between spitak and gekhasar attain 160 cm of vertical motion and 90 cm of horizontal dextral offset the displacement also varies within this branch showing finer segmentation few secondary deformations are observed some normal faults near gekhasar correspond to the collapse of the uplifted block an anticline fold oriented parallel to the fault scarp and situated along its northwestern prolongation emphasizes the regional compressive tectonics landslides were activated on its flanks a 200 m long reverse fault break observed along the hinge of a secondary fold suggests the occurrence of a blind thrust at depth and that the hidden branches which continue the main central segment towards the nw are associated to surface folding therefore the total length of the fault and fold zone is about 40 km in agreement with the rupture length and seismic moment obtained on the basis of surface wave modelling well developed uplifted terraces in the northern block and subsiding valleys in the southern block indicate past quaternary activity in the fault region palaeoseismological evidence of ancient earthquakes has been recognized in trenches across the spitak fault one old event occurred between 17 000 years bp and the beginning of the formation of present day soil

chemical transformations of type iii organic matter associated with the akouta uranium deposit niger geological implications abstract pure vitrinites from the akouta uranium deposit niger have been characterized using rock eval pyrolysis c h o analysis infrared and raman spectroscopies and reflectance measurements the organic matter sampled in the sandy guezouman formation is land derived type iii elemental analyses plotted in a h c vs o c diagram define three types of evolution the first one corresponds to a maturation trend and has been related to a w e geothermal gradient the second one corresponds to a slow rate diagenetic oxidation affecting organic matter located far from the ore zone the third one can be compared with a late oxidation it is related to the mineralizing process and results from both oxidation reduction and radiolysis effects the different alteration trends have been compared to mineralogical and microthermometric data in order to draw geological implications

nested simulations of perpetual january climate over the australian region a limited area grid point model is nested at resolutions of 250 km and 125 km within a spectral general circulation model for simulations of perpetual january climate over the australian region the spectral model is run for 300 days and provides the lateral boundary conditions for the nested model runs in these experiments the physical parameterizations are kept as similar as possible the results show that the limited area model significantly improves the simulation of january climate particularly in regions of steep topography some problems are described regarding the integration of the two models including the generation of spurious precipitation near the boundaries of the nested model and limitations of the soil temperature scheme problems relating to the applicability of the technique to tropical domains are also discussed the simulation in the interior of the domain is good in particular the simulation of precipitation is significantly improved compared to that of the general circulation model

late pleistocene evolution of the lower mississippi river valley southern missouri to arkansas the mississippi river served as the principal conduit for meltwaters discharging from the southern margins of north american ice sheets the northern half of the mississippi river alluvial valley in missouri and arkansas can be subdivided into two distinct channel courses the western and eastern lowlands which are separated by crowleys ridge the eastern lowlands contain two entry points the bell city oran and thebes gaps the latter is a narrow bedrock gorge that contains the modern river this paper summarizes a model for evolution of channel courses in the western and eastern lowlands during the illinoian and wisconsin glacial stages for the western lowlands stratigraphic relations between loess units and subjacent fluvial deposits show that major continuous terrace surfaces or valley trains are illinoian or late wisconsin in age investigations of tributary valley fills further show the western lowlands were deeply incised during the early to middle wisconsin stage then aggraded during the late wisconsin stage to such an extent that tributary valleys were backfilled with slackwater deposits moreover analysis of loess thinning and fining trends shows that early to middle wisconsin roxana silt and the late wisconsin peoria loess covers on western lowlands valley trains were derived from deflation of valley trains in the eastern lowlands we conclude that the western lowlands were the primary mississippi river course during illinoian deglaciation but were abandoned shortly thereafter then episodically reoccupied during the late wisconsin stage for the eastern lowlands course valley trains of early to middle wisconsin age are not preserved with the exception of a small remnant where the mississippi river broke through a gap in the southern margins of crowleys ridge and reentered the western lowlands all valley trains in the eastern lowlands are late wisconsin age a series of discontinuous terrace surfaces in the bell city oran gap represent dissected remnants of the primary late wisconsin full glacial and early late glacial course of the mississippi river or combined mississippi and ohio rivers whereas younger continuous braided stream surfaces in the bell city oran and thebes gap courses represent valley trains of latest wisconsin and earliest holocene age hence the bell city oran gap was the primary course during the entire wisconsin stage and the thebes gap was permanently occupied in earliest holocene time as much as 5 m difference in elevation between successive late wisconsin terrace surfaces of the eastern lowlands indicates that valley trains were rapidly constructed incised and abandoned in response to fluctuations in the delivery of meltwater and outwash from the former ice margin moreover a variety of data indicates that deglacial meltwater floods were commonly of sufficient magnitude to overflow from the primary course in the bell city oran gap throughout the late wisconsin substage floodwaters overflowed into the western lowlands constructed a series of secondary valley trains and filled tributary valleys with slackwater deposits during the latest wisconsin stage perhaps in association with the drainage of glacial lake agassiz floodwaters overflowed into the western lowlands and broke through the thebes gap the charleston fan represents the initial deposits of the thebes gap course following deposition of a large crevasse splay at the western lowlands entrance that course was no longer active but flow was routed through the thebes gap during periods of high magnitude flooding until the bell city oran gap was abandoned and the thebes gap course was permanently occupied during earliest holocene time

the first stage in the formation of the uranium deposit of arlit niger role of a new non continental organic matter abstract the uranium deposits of arlit are located in fluvial sandstone rich in organic matter of continental origin type iii deposited in palaeochannels previous studies on arlit deposits documented that organic matter of continental origin type iii was the main contributor to the reduction of uranium from the oxidation state of uranium vi u vi to uranium iv u iv this study shows that migrated oils of non continental origin strongly contributed to the genesis of uranium mineralization the petrographic analyses showed that i solid bitumen resulting from the polymerization of migrated oils is present in abundance in the porosity of the sandstone and fractures at the level of the channels of the tarat formation tamou takriza southern taza and guezouman formation mine sector of akouta and ii uranium mineralization is mainly associated with this migrated organic matter currently expressed in the form of solid bitumen the association occurs at an infra micrometric scale in the solid bitumen the geochemical analysis rock eval py gc ms and gc ms and the analysis of different indicators and biomarkers n alkanes pr ph steranes indicate the presence of a second organic matter with a different signature to type iii the oils present in the porosity of the sandstone of the guezouman and tarat formations confirm that channels of these two formations are the traps of the oil migration

fault slip rates in the modern new madrid seismic zone structural and geomorphic analysis of late holocene sediments in the lake county region of the new madrid seismic zone indicates that they are deformed by fault related folding above the blind reelfoot thrust fault the widths of narrow kink bands exposed in trenches were used to model the reelfoot scarp as a forelimb on a fault bend fold this coupled with the age of folded sediment yields a slip rate on the blind thrust of 6 1 0 7 mm year for the past 2300 100 years an alternative method used structural relief across the scarp and the estimated dip of the underlying blind thrust to calculate a slip rate of 4 8 0 2 mm year geometric relations suggest that the right lateral slip rate on the new madrid seismic zone is 1 8 to 2 0 mm year

structural imprints at the front of the choco panama indenter field data from the north cauca valley basin central colombia abstract the northern andes are a complex area where tectonics is dominated by the interaction between three major plates and accessory blocks in particular the choco panama and northern andes blocks the studied cauca valley basin is located at the front of the choco panama indenter where the major romeral fault system active since the cretaceous changes its kinematics from right lateral in the south to left lateral in the north structural studies were performed at various scales dem observations in the central cordillera between 4 and 5 7 n aerial photograph analyses and field work in the folded oligo miocene rocks of the serrania de santa barbara and in the flat lying pleistocene quindio risaralda volcaniclastic sediments interfingering with the lacustrine to fluviatile sediments of the zarzal formation the data acquired allowed the detection of structures with a similar orientation at every scale and in all lithologies these families of structures are arranged similarly to riedel shears in a right lateral shear zone and are superimposed on the cretaceous romeral suture they appear in the central cordillera north of 4 5 n and define a broad zone where 060 oriented right lateral distributed shear strain affects the continental crust the romeral fault system stays active and strain partitioning occurs among both systems the southern limit of the distributed shear strain affecting the central cordillera corresponds to the e w trending garrapatas ibague shear zone constituted by several right stepping en echelon right lateral active faults and some lineaments north of this shear zone the romeral fault system strike changes from nne to n paleostress calculations gave a wnw ese trending maximum horizontal stress and 69 of compressive tensors the orientation of 1 is consistent with the orientation of the right lateral distributed shear strain and the compressive state characterizing the romeral fault system in the area it bisects the synthetic and antithetic riedels and is sub perpendicular to the active romeral fault system it is proposed that the continued movement of the choco panama indenter may be responsible for the 060 oriented right lateral distributed shear strain and may have closed the northern part of the cauca valley thereby forming the cauca valley basin conjugate extensional faults observed at surface in the flat lying sediments of the zarzal formation and quindio risaralda volcaniclastic fan are associatedwith soft sediment deformations these faults are attributed to lateral spreading of the superficial layers during earthquakes and testify to the continuous tectonic activity from pleistocene to present finally results presented here bring newinformation about the understanding of the seismic hazard in this area whereas the romeral fault systemwas so far thought to be themost likely source of earthquakes themore recent cross cutting fault systems described herein are another potential hazard to be considered

earthquake signals in tree ring data from the new madrid seismic zone and implications for paleoseismicity severe ground shaking and the formation of reelfoot lake during the great new madrid earthquakes of a d 1811 1812 had a profound effect on baldcypress trees that still survive in reelfoot lake of northwestern tennessee inundation greatly increased baldcypress radial growth from 1812 to 1819 and permanently decreased wood density after 1811 ground shaking fractured the baldcypress stems that were present during the 1811 1812 event but fractures are absent in the post 1811 growth in contrast the growth of old baldcypress trees in the st francis sunkland of northeastern arkansas was severely suppressed for almost 50 yr following the 1811 1812 new madrid earthquakes thus there are two opposite but profound growth responses to the same earthquake events preserved in baldcypress trees of the new madrid seismic zone the tree ring chronology at reelfoot lake extends from a d 1682 to 1990 but the 1812 1819 growth surge was the only extreme growth anomaly in this 309 yr period the st francis sunkland chronology extends from a d 1321 to 1990 and the 1812 1857 growth suppression is the most severe and prolonged growth anomaly of this entire 670 year period thus the tree ring record indicates that there was not a great earthquake during the 129 yr prior to 1811 in the reelfoot lake basin nor during the 490 yr prior to 1811 in the st francis sunkland

hotspot origin of the mississippi embayment and its possible impact on contemporary seismicity abstract previous authors have related the late cretaceous early tertiary subsidence of the mississippi embayment to the opening of the gulf of mexico but the gulf opened earlier in triassic jurassic time we offer an alternative hypothesis that development of the embayment was coeval with the passage of the mississippi valley graben system over the bermuda hotspot about 90 ma several lines of evidence of significant uplift of the embayment axis accompanying mid cretaceous magmatism and prior to late cretaceous subsidence support this proposal first reactivation of the pascola arch in the northern embayment is recorded by flanking deposits of basal upper cretaceous gravel second beneath a regional mid cretaceous unconformity subcrops of jurassic and early cretaceous strata define a pronounced southwest plunging arch in the southern embayment this arch is collinear with an arch revealed in paleozoic rocks after restoration to mid cretaceous structural geometries third a deep weathering profile on mid cretaceous alkalic plutons along the western embayment margin is nonconformably overlain by paleocene sediments and rapid mid cretaceous cooling of these intrusions has been interpreted from apatite fission tracks moreover exploratory holes along the embayment axis encountered similar weathered alkalic intrusions nonconformably overlain by basal upper cretaceous strata fourth there was an anomalous influx of clastic sediment into the northern gulf of mexico during mid cretaceous time and subsequent clastic facies patterns suggest the mississippi river drainage began to enter the gulf in the late cretaceous passage of the mississippi valley graben over the bermuda hotspot during elevated hotspot activity of cretaceous time may have significantly weakened the previously rifted lithosphere rifted continental margin at charleston south carolina also passed over this hotspot in latest cretaceous time similarly the st lawrence rift system passed over the great meteor hotspot during the cretaceous it is important to note that these rift systems are the principal loci of strong seismicity in eastern north america and thus weakening by increased cretaceous hotspot activity may be an important common factor for these seismic rift zones

organic geochemical analysis of sedimentary organic matter associated with uranium abstract samples of sedimentary organic matter from several geologic environments and ages which are enriched in uranium 56 ppm to 12 have been characterized the three analytical techniqyes used to study the samples were rock eval pyrolysis pyrolysis gas chromatography mass spectrometry and solid state c 13 nuclear magnetic resonance nmr spectroscopy in samples with low uranium content the pyrolysis gas chromatography products contain oxygenated functional groups as hydroxyl and molecules with both aliphatic and aromatic carbon atoms these samples with low uranium content give measurable rock eval hydrocarbon and organic co 2 yields and c 13 nmr values of 30 aliphatic carbon in contrast uranium rich samples have few hydrocarbon pyrolysis products increased rock eval organic co 2 contents and 70 aromatic carbon contents from c 13 nmr the increase in aromaticity and decrease in hydrocarbon pyrolysis yield are related to the amount of uranium and the age of the uranium minerals which correspond to the degree of radiation damage the three analytical techniques give complementary results increase in rock eval organic co 2 yield correlates with uranium content for samples from the grants uranium region calculations show that the amount of organic co 2 corresponds to the quantity of uranium chemically reduced by the organic matter for the grants uranium region samples

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

seasonal simulations of the planetary boundary layer and boundary layer stratocumulus clouds with a general circulation model abstract the ucla general circulation model gcm has been used to simulate the seasonally varying planetary boundary layer pbl as well as boundary layer stratus and stratocumulus clouds the pbl depth is a prognostic variable of the gcm incorporated through the use of a vertical coordinate system in which the pbl is identified with the lowest model layer stratocumulus clouds are assumed to occur whenever the upper portion of the pbl becomes saturated provided that the cloud top entrainment instability does not occur as indicated by arakawa and schubert cumulus clouds are assumed to originate at the pbl top and tend to make the pbl shallow by drawing on its mass results are presented from a three year simulation starting from a 31 december initial condition obtained from an earlier run with a different version of the model the simulated seasonally varying climates of the boundary layer and free troposphere are realistic the observed geographical and seasonal variations of stratocumulus cloudi

late wisconsin to holocene deformation in the new madrid seismic zone the new madrid earthquakes of 1811 1812 produced regional deformation in northwestern tennessee southeastern missouri and northeastern arkansas landforms such as the lake county uplift reelfoot lake and the sunklands of northeast arkansas either formed or were reactivated during these great earthquakes two hundred and fifty three cores were used to construct a structure contour map of the unconformity between the eocene strata and the overlying quaternary mississippi river alluvium in the new madrid seismic zone this map reveals relief that mirrors the surface deformation and provides additional data on the distribution of regional deformation we interpret the structure contour map as a representation of the late wisconsin to the present strain field of the new madrid seismic zone this map provides constraints for future kinematic analyses of late quaternary new madrid faulting and allows forecasting of future coseismic deformation

luminescence chronometry and geomorphic evidence of active fold growth along the kachchh mainland fault kmf kachchh india seismotectonic implications abstract the kachchh region of western india is a pericratonic basin experiencing periodic high magnitude earthquakes events in 2001 a catastrophic seismic event occurred at bhuj measuring mw 7 7 the epicenters of both the 1956 and 2001 earthquakes were along the kachchh mainland fault kmf proximal to the eastern end of the northern hill range nhr the latter is a topographic expression of an active fault related fold on the hanging wall and is controlled by a south dipping blind thrust the present study deals with the eastern sector of nhr and uses optical dating to reconstruct the chronology of tectonically caused incisions along the backlimb of the nhr incision ages on channel fills and valley fill terraces progressively decrease from 12 ka to 4 3 ka this age progression along with geomorphic evidences decrease in topographic relief drainage capture and drainage migration across the fold nose suggests an active vertical and lateral fold growth along the kmf optical ages suggest that during the late holocene the average uplift rate along the eastern nhr was 10 1 mm a recent gps based estimates on crustal shortening are 12 mm a the kmf and the south wagad fault swf represent the bounding faults of a transtensional basin that formed during the initial rifting this basin is termed as the samakhiali basin the compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate shaped anticlines along kmf and swf zone these anticlines subsequently coalesced and formed linked and overlap segments the present study suggests that eastward lateral deformation across the eastern portion of kmf has continued and has now resulted in its interaction with a left step over transfer fault called the south wagad master fault swmf this implies an increasing transpersional deformation of the samakhiali basin we therefore suggest that the eastward nhr ridge propagation along kmf resulted in the thrust faulting on the south dipping swmf resulting in the bhuj 2001 event the increasing strain on this basin may cause enhanced seismicity in the future along the eastern kmf and wagad region

neotectonics of the upper mississippi embayment abstract although the upper mississippi embayment is an area of low relief the region has been subjected to tectonic influence throughout its history and continues to be so today tectonic activity can be recognized through seismicity patterns and geological indicators of activity either those as a direct result of earthquakes or longer term geomorphic structural and sedimentological signatures the rate of seismic activity in the upper mississippi embayment is generally lower than at the margins of tectonic plates the embayment however is the most seismically active region east of the rocky mountains with activity concentrated in the new madrid seismic zone this zone produced the very large new madrid earthquakes of 1811 and 1812 geological and geophysical evidence of neotectonic activity in the upper mississippi embayment includes faulting in the benton hills and thebes gap in missouri paleoliquefaction in the western lowlands of missouri subsurface faulting beneath and tilting of crowley s ridge in northeastern arkansas and southeastern missouri subsurface faulting along the crittenden county fault zone near memphis tennessee faulting along the east flank of the tiptonville dome and numerous indicators of historic and prehistoric large earthquakes in the new madrid seismic zone paleoearthquake studies in the new madrid seismic zone have used trenching seismic reflection shallow coring pedology geomorphology archaeology and dendrochronology to identify and date faulting deposits of liquefied sand and areas of uplift and subsidence the cause of today s relatively high rate of tectonic activity in the mississippi embayment remains elusive it is also not clear whether this activity rate is a short term phenomenon or has been constant over millions of years ongoing geodetic and geological studies should provide more insight as to the precise manner in which crustal strain is accumulating and perhaps allow improved regional neotectonic models

an integrated global model of present day plate motions and plate boundary deformation summary in this paper we present a global model gsrm 1 of both horizontal velocities on the earth s surface and horizontal strain rates for almost all deforming plate boundary zones a model strain rate field is obtained jointly with a global velocity field in the process of solving for a global velocity gradient tensor field in our model we perform a least squares fit between model velocities and observed geodetic velocities as well as between model strain rates and observed geological strain rates model velocities and strain rates are interpolated over a spherical earth using bi cubic bessel splines we include 3000 geodetic velocities from 50 different mostly published studies geological strain rates are obtained for central asia only and they are inferred from quaternary fault slip rates for all areas where no geological information is included a priori constraints are placed on the style and direction but not magnitude of the model strain rate field these constraints are taken from a seismic strain rate field inferred from normalized focal mechanisms of shallow earthquakes we present a global solution of the second invariant of the model strain rate field as well as strain rate solutions for a few selected plate boundary zones generally the strain rate tensor field is consistent with geological and seismological data with the assumption of plate rigidity for all areas other than the plate boundary zones we also present relative angular velocities for most plate pairs we find that in general there is a good agreement between the present day plate motions we obtain and longterm plate motions but a few significant differences exist the rotation rates for the indian arabian and nubian plates relative to eurasia are 30 13 and 50 per cent slower than the nuvel1a estimate respectively and the rotation rate for the nazca plate relative to south america is 17 per cent slower on the other hand caribbean north america motion is 76 per cent faster than the nuvel 1a estimate while crustal blocks in the india eurasia collision zone move significantly and self consistently with respect to bounding plates only a very small motion is predicted between the nubian and somalian plates by integrating plate boundary zone deformation with the traditional modelling of angular velocities of rigid plates we have obtained a model that has already been proven valuable in for instance redefining a no net rotation model of surface motions and by confirming a global correlation between seismicity rates and tectonic moment rates along subduction zones and within zones of continental deformation

soil liquefaction during the arequipa mw 8 4 june 23 2001 earthquake southern coastal peru abstract the arequipa june 23 2001 earthquake with a moment magnitude of mw 8 4 struck southern peru northern chile and western bolivia this shallow 29 km deep interplate event occurring in the coupled zone of the nazca subduction next to the southeast of the subducting nazca ridge triggered very localized but widely outspread soil liquefaction although sand blows and lateral spreading of river banks and road bridge abutments were observed 390 km away from the epicenter in the southeast direction nearing the town of tacna close to the chile border liquefaction features were only observed in major river valleys and delta and coastal plains in the meizoseismal area this was strongly controlled by the aridity along the coastal strip of southern peru from the sand blow distribution along the coastal area a first relationship of isolated sand blow diameter versus epicentral distance for a single event is ever proposed the most significant outcome from this liquefaction field reconnaissance is that energy propagation during the main june 23 2001 event is further supported by the distribution and size of the isolated sand blows in the meizoseismal area the sand blows are larger to the southeast of the epicenter than its northwestern equivalents this can be stated in other words as well the area affected by liquefaction to the northwest is less spread out than to the southeast implications of these results in future paleoliquefaction investigations for earthquake magnitude and epicentral determinations are extremely important in cases of highly asymmetrical distribution of liquefaction features such as this one where rupture propagation tends to be mono directional it can be reliably determined an epicentral distance between earthquake and liquefaction evidence and an earthquake magnitude only if the largest sand blow is found therefore magnitude estimation using this uneven liquefaction occurrence will surely lead to underrating if only the shortest side of the meizoseismal area is unluckily studied which can eventually be the only part exhibiting liquefaction evidence depending on the earthquake location and the distribution of liquefaction prone environments

a comparison of the impact of an envelope orography and of a parametrization of orographic gravity wave drag on model simulations results are presented from extended annual cycle integrations of the meteorological office 11 layer atmospheric general circulation model an 8 year control integration produces a good simulation in the southern hemisphere in both summer and winter and also in the northern hemisphere in summer in northern winter however there is excessive westerly near surface flow polewards of about 40 n it is argued that this indicates a lack of orographic forcing of the flow by the major mountain ranges two solutions which have been proposed for this problem are investigated the first is envelope orography and the second is a parametrization of the effects of orographic gravity wave drag each was included separately in 3 1 2 year integrations in parallel with the control both produce substantial changes in the model s climatology but envelope orography does not improve the westerly problem over the european area and it also degrades the summer circulation the gravity wave drag scheme however gives results which in general are in very good agreement with the observations in both hemispheres and seasons comparison of the zonally averaged torques from the three experiments demonstrates that with envelope orography the northern hemisphere near surface westerlies are reduced because of a dramatic increase in the mountain pressure torque in the experiment with the gravity wave scheme however the reduction is due to the gravity wave drag and the mountain torque is similar in magnitude to that in the control a study of the variability of the 500mb height fields on synoptic timescales demonstrates the improvement in the positions of the northern hemisphere storm tracks in this integration some remaining errors in the simulations are identified particularly in the stratosphere finally it is argued that despite these results it may be too early to come to a final conclusion as to the role of gravity wave drag in the general circulation and also as to the relative importance of dynamical and radiative processes in the polar winter stratosphere

a moist pbl parameterization for large scale models and its application to subtropical cloud topped marine boundary layers abstract a new general purpose boundary layer parameterization that permits realistic treatment of stratocumulus capped boundary layers scbls with coarse vertical resolution is described it combines a 1 5 order turbulent closure model with an entrainment closure at the boundary layer top three different implementations of the entrainment closure in which the boundary layer height is respectively prognosed reconstructed from thermodynamic values at the grid points or restricted to lie on a flux level of the host model grid are tested in a single column modeling framework at both fine and coarse vertical resolution the first two approaches permit a stratocumulus top and base to lie between grid levels and evolve continuously with time but are more complicated to implement in a three dimensional model the model performs very well in cases of dry convection whatever the inversion implementation and the vertical resolution with 15 mb or better vertical resolution all approaches properly simulate

response of alluvial rivers to slow active tectonic movement alluvial rivers respond to valley slope deformation caused by active tectonics in various ways depending on the rate and amount of surficial deformation and on the type of river on the basis of experimental results and field examples hypothetical models of river response to anticlinal uplift and synclinal subsidence were developed for different types of alluvial rivers an experimental braided channel responded to anticlinal uplift across the channel with degradation and terrace formation in the central part of the uplift with subsidence aggradation in the central reach was the main response transverse bars developed downstream of the subsidence axis an experimental meandering channel responded to slope steepening with a sinuosity increase bank erosion and point bar growth occurred downstream of the anticlinal axis and upstream of the synclinal axis upstream of the uplift axis and downstream of the subsidence axis where the slope was flattened water flooded over bars local convexity in longitudinal profiles of the middle rio grande new mexico is considered to be formed by a domal uplift local aggradation and degradation could be explained by the effect of uplift the san joaquin river california which is now highly controlled does not show clear adjustment to the rapid subsidence due to ground water withdrawal it shows however a channel pattern adjustment to active tectonic subsidence that has been occurring for a long time the san antonio and guadalupe rivers in texas both increase their sinuosity significantly where monoclinal movements steepen valley slopes

origin and age of the manila high and associated big lake sunklands in the new madrid seismic zone northeastern arkansas uplift of the manila high and subsidence of the south flowing little river during the great new madrid earthquakes of 1811 1812 formed the present lake in big lake basin of northern arkansas this is the most recent deformation of the 19 km long manila high that began between 11 000 and 5400 yr ago and is time transgressive toward the south at least 4 m of holocene uplift occurred on the northern portion of the manila high prior to initiation of the little river distributary in mid holocene time the distributary is deflected around the high and overbank sediment derived from it thins and is locally absent across the northern highest portion of the high deformation along the southern end of the high began between 3500 and 2000 yr ago since 3500 yr b p 2 m of uplift appears to have caused a reduction in gradient anastomosing upstream of the uplift and incision of the little river across the uplift north of the manila high in the big lake basin the little river has an increased aggradation rate 10 times that of the preuplift rate cores collected in and adjacent to big lake indicate that the little river was ponded twice apparently in response to deformation in 1811 1812 and between 90 b c and a d 1640

stream response to repeated coseismic folding tiptonville dome new madrid seismic zone abstract fluvial response to tectonic deformation is dependent on the amount and style of surface deformation and the relative size of the stream active folding in the new madrid seismic zone nmsz forms the tiptonville dome a 15 km long and 5 km wide surface fold with up to 11 m of late holocene structural relief the fold is crossed by streams of varying size from the mississippi river to small flood plain streams fluvial response of these streams to repeated coseismic folding has only been preserved for the past 2 3 ka since the tiptonville meander of the mississippi river migrated across the area forming the present flood plain this surface comprises a sandy point bar deposit locally overlain by clayey overbank and silty sand crevasse splay deposits an abandoned chute channel infilled with laminated sandy silt and silty clay and an abandoned neck cutoff filled with a sandy cutoff bar and silty clay oxbow lake deposits dating various stream responses to coseismic folding has more tightly constrained the timing of earthquake events in the central nmsz and provides a means of partitioning the deformation amount into individual seismic events three earthquakes have been dated in the reelfoot lake area ca a d 900 1470 and 1812 the latter two earthquakes had large local coseismic deformation both of these events were responsible for numerous stream responses such as shifting depocenters modification of mississippi river channel geometry and derangement of small streams overbank sedimentation ceased on the dome as it was uplifted above the normal flood stage and sedimentation of crevasse splay deposits from the mississippi river colluvium from the scarp and lacustrine sediment accumulated in the adjacent reelfoot basin the much larger mississippi river channel responded to uplift by increasing its sinuosity across the uplift relative to both upstream and downstream increasing its width depth ratio across and downstream of the uplift and decreasing the width depth ratio upstream of the uplift despite the size of the mississippi river it has not yet attained equilibrium since the latest uplift 190 years ago small channels that could not downcut through the uplift were filled locally reversed flow direction or formed a lake where they were dammed uplift and stream response to folding along the tiptonville dome is less dramatic between 2 3 and 0 53 ka during this interval abandoned channel fill and overbank deposition across the dome suggests that it was not a high relief feature one earthquake event occurred during this interval ca a d 900 but coseismic stream response was probably limited to a slight aggradation of a small flood plain stream

alluvial river response to neotectonic deformation in louisiana and mississippi repeat geodetic surveys show uplift of the monroe and wiggins anticlines in louisiana and mississippi there are deformed quaternary terraces which indicate long term deformation in the valleys of the alluvial rivers that cross these structures and there are floodplain and channel convexities that provide evidence of modern deformation in addition the channels show significant variations of morphology sinuosity gradient and depth and behavior appropriate to reaches of increased and decreased valley slope these alluvial rivers are adjusting to modern deformation and their adjustment confirms two geodetic leveling anomalies

organic geochemistry of the pine point lead zinc ore field and region northwest territories canada middle devonian barrier complex within the pine point lead zinc ore field located within the immature to marginally mature zone with respect to petroleum generation certain of the host rocks of the ore field were deposited in highly reducing conditions such that organic matter of algal or microbial origin has been preserved to a remarkable degree yields of extractable soluble material relative to organic carbon are extremely high which has resulted in the local migration of immature bitumens and heavy oil within the shallow regime polymerization of nitrogen sulfur and oxygen compounds and asphaltenes biodegradation of bitumens is a relatively late process the question of a genetic relationship between lead zinc sulfide and organic matter remains open modified journal abstract

experimental evidence of uraninite formation from diagenesis of uranium rich organic matter abstract this study focuses on the experimental diagenetic evolution of an uranium rich lignite from the coutras uranium deposit gironde france located in eocene sediments three samples containing 6 to 15 5 wt uranium were analysed and compared to two barren samples located outside the ore deposit in a stratigraphically equivalent unit uranium in the mineralized samples is present as uranyl carboxylic complexes dry thermal maturation was simulated in a cold seal autoclave at 150 200 250 300 and 350 c at 100 mpa for 24 h with increasing temperature uranyl carboxylic complexes decompose while uraninite forms the chemical composition of the experimentally matured barren samples when plotted in a van krevelen diagram h c vs o c parallels the natural trend of land derived type ill organic matter evolution while mineralized samples are characterized by a higher loss of hydrogen above 250 c reduction to form uraninite is directly related to the dehydrogenation of lignite the resulting uraninite has a similar unit cell edge to that of natural uraninites observed in sedimentary environments uraninite not only forms in the pore space but also replaces the lignite constituents the results demonstrate that uraninite may form during thermal evolution of uranium rich organic matter during diagenesis

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

geometry numerical models and revised slip rate for the reelfoot fault and trishear fault propagation fold new madrid seismic zone abstract the geometry and structural relief of late holocene sediments folded across the reelfoot scarp are characterized with trench excavations shallow borings a digital elevation model dem of topography and reelfoot lake rl bathymetry results suggest the scarp forms by heterogeneous shear in the forelimb of a fault propagation fold seismic data and the accompanying structural analysis support the argument that the reelfoot fault does not offset the surface and that the reelfoot scarp is a fold limb structural relief measured across the reelfoot scarp is slightly higher than previous determinations and varies from 7 to 11 m along the western shoreline of rl numerical models based on trishear kinematics constrain growth of the reelfoot monocline and indicate that the underlying reelfoot thrust fault is steeply dipping the shallowest portion of the central reelfoot thrust segment dips 75 where the fault tip has propagated upward from 911 m to its current location 465 m beneath the surface the models indicate that the shallowest section of the southern thrust segment in the reelfoot thrust system dips even more steeply at 80 but has propagated upward only a few tens of meters to its present location 1016 m beneath the surface the thrust is flatter at deeper levels based on the location of earthquake hypocenters strain across the reelfoot scarp is partitioned into two or three separate fold scarps that collectively record a late holocene fault slip rate of 3 9 0 1 mm yr the slip rate is based on 9 m of structural relief the 2290 60 ybp age of folded sediment and a 75 dip for the fault this implies a rate of horizontal contraction in the seismic zone of 1 0 mm yr this rate is strongly dependent on the dip of the thrust calculated by the structural analysis the numerical models argue for reactivation of faults that previously offset paleozoic strata

displacement history and slip rate on the reelfoot fault of the new madrid seismic zone abstract a displacement history and slip rates were determined for the reelfoot fault in the new madrid seismic zone from a seismic reflection profile and trench data based on calculations from the seismic reflection line the average slip rate over the last 80 million years is 0 0009 mm year 1 slip rate during the late cretaceous was 0 0007 mm year 1 0 002 mm year 1 during the paleocene midway group 0 001 mm year 1 during paleocene eocene wilcox formation time 0 0003 mm year 1 during the post wilcox pre holocene period and a holocene slip rate of 1 8 mm year 1 based on trench data slip rate on the reelfoot fault has been 4 4 mm year 1 over the last 2400 years and a maximum of 6 2 mm year 1 during the two most recent earthquake cycles between ad 900 and ad 1812 the holocene slip rate is at least four orders of magnitude higher than the average late cretaceous and cenozoic slip rates for the reelfoot fault it would appear that there has been a quaternary change in the stress field in the central united states or the reelfoot fault is experiencing a short lived burst of seismic activity

changes in the tectonic regime above a subduction zone of andean type the andes of peru and bolivia during the pliocene pleistocene this paper adresses the changes in the tectonic regime in the peruvian and bolivian andes that have occurred since the upper miocene when the present day elevation of the cordillera above sea level has been almost reached the stress patterns are deduced essentially from a field study of fault kinematics and a numerical inversion of the slip vector data measured on the fault planes the cuzco fault system in southern peru is chosen as an example to illustrate the methodology used in this region striations on both active and holocene faults are in agreement with a n s extension but faults affecting early pleistocene deposits exhibit two families of striations the younger results from the previous n s extension the older involving reverse motions results from either an e w or a n s compression faults affecting pliocene formations often show an oldest family of striations resulting from a ne sw or an e w trending extension thus three tectonic regimes are demonstrated which are also supported by regional unconformities and sedimentological data 1 a pliocene extensional regime 2 a lower pleistocene compressional regime and 3 a mid pleistocene present day extensional regime similar analyses conducted in the pacific and sub andean lowlands allow sketching of the successive pliocene pleistocene stress patterns in the central andes the quaternary and present day stress pattern is characterized by a n s extension in the high andes and in the pacific lowlands and by an e w compression in the sub andean lowlands and at the contact between the nazca and south american plates this stress pattern is interpreted at a large wavelength 100 km as an effect of compensated topography this model supposes that the vertical lithospheric stress zz increases with the topography the crustal thickness and the low density mantle beneath and that the lithospheric maximum compressional horizontal stress hmax trending e w roughly parallel to the convergence is fairly constant on both edges of the andes the tectonics being compressional zz is 3 and hmax is 1 in the high andes zz becomes 1 then the e w trending hmax is 2 and hmin trending n s is 3 allowing extension to occur in this direction the pliocene stress pattern was characterized by a ne sw or an e w trending extension in the high andes in the pacific lowlands and possibly in the sub andean lowlands this stress pattern was clearly different from the present day one because the e w trending stress was hmin this required a weak push or eventually tractional boundary forces acting on the south american lithosphere it is suggested that this might result from a strong slab pull due to a long steeply dipping slab which decreased the value of the xx stress transmitted to the overriding plate the early pleistocene state of stress was compressional since the elevation of the andes had not markedly decreased during this period this required an increase of the e w trending stress value this resulted from a strong coupling between the two lithospheric plates possibly due to a rupture of a long slab under its own weight other spatial changes in the stress pattern are related to the particular situation of the forearc to the subduction of the buoyant nazca ridge and to the different dips of the slab extension in the high andes is of small magnitude of the order of 1 during the last 1 2 m y in a few basins it may have attained 40 during the pliocene 5 3 m y

review and update of the applications of organic petrology part 2 geological and multidisciplinary applications abstract the present paper is focused on organic petrology applied to unconventional and multidisciplinary investigations and is the second part of a two part review that describes the geological applications and uses of this branch of earth sciences therefore this paper reviews the use of organic petrology in investigations of i ore genesis when organic matter occurs associated with mineralization ii the behavior of organic matter in coal fires self heating and self combustion iii environmental and anthropogenic impacts associated with the management and industrial utilization of coal iv archeology and the nature and geographical provenance of objects of organic nature such as jet amber other artifacts and coal from archeological sites and v forensic science connected with criminal behavior or disasters this second part of the review outlines the most recent research and applications of organic petrology in those fields

erroneous maturity assessment given by tmax and hi rock eval parameters on highly mature weathered coals abstract two sets of mature coals have been collected at outcrop on two dipping coal seams in the ales carboniferous coalfield massif central france visual examination petrographic observations and rock eval pyrolysis studies unequivocally suggest that these coals have been weathered the intensity of this alteration increasing progressively towards the soil according to the reflectance rr values of 1 7 1 8 these coals have reached low volatile bituminous rank in contrast to the reflectance which does not exhibit any marked variation along the studied sections tmax although classically considered as a rank parameter increases progressively with decreasing distance from the surface this tmax increase is accompanied by a decrease in the hydrogen index hi and with an increase in oxygen index oi all these changes are undoubtedly consequential to weathering thus in the present case tmax must not be considered as a maturity indicator but as an oxidation parameter like oi and the o c atomic ratio this conclusion is also supported by the positive correlation between tmax and proportion of oxidised vitrinites i e bearing oxidation marks provided by maceral analysis this peculiar behaviour of tmax in response to the weathering of mature coals is in total contrast with its invariance during low mature coal alteration this finding obliges us to moderate or even to revise the conclusions of a previous work on mature coals sampled at outcrop int j coal geol 44 2000 49 where higher tmax than expected from rr values were supposed to have been necessarily caused by warm and oxidizing fluids

the origin of crowley s ridge northeastern arkansas erosional remnant or tectonic uplift the geomorphology of crowley s ridge apparent quaternary reactivation of the ridge bounding faults and orientation of the faults to the present stress field suggest that the faults bounding crowley s ridge and the western margin of the reelfoot rift may be seismogenic fifteen high resolution seismic reflection lines were acquired across and adjacent to the margins of crowley s ridge to test the hypothesis that corwley s ridge is fault bounded eleven of the reflection lines were 24 channel mini sosie data with 1 sec record length and four lines were 24 channel shotgun source data with 0 25 sec record length nine lines traversed the margins and adjacent areas of the northern segment of the ridge near jonesboro arkansas and the other six were located south of jonesboro on the southern segment the reflection data show that paleozoic through eocene wilcox sections have been uplifted beneath crowley s ridge from 60 to 30 m across ridge bounding faults however eocene or pliocene pleistocene near surface strata appear to be displaced a maximum of 7 5 m based on reflection and geomorphologic data we believe that reactivation of the bounding faults of crowley s ridge occurred concurrently with and strongly influenced wisconsin denudation of the mississippi valley

quasi stationary waves in the southern hemisphere part ii generation mechanisms abstract in this part ii the authors investigate the role that antarctic elevations the rest of the world orography thermal forcing from lower latitudes and the transient eddy component of the flow play on the generation of the quasi stationary wave field in the southern hemisphere an approach based on the ucla gcm is followed results from a control simulation with full orography and from experiments without the antarctic elevations and without the rest of the world orography suggest that the quasi stationary wave with zonal wavenumber 1 qs wave 1 around antarctica is primarily generated by mechanisms other than the antarctic elevations comparison of a three dimensional eliassen palm flux vector in the control simulation and those where the antarctic elevation and the rest of the world orography are removed suggests that wave activity propagates both from the subtropics and from polar latitudes although in qualitative agreement with results of part i the horizontal and vertical structure of t

a new parameterization for shallow cumulus convection and its application to marine subtropical cloud topped boundary layers part ii regional simulations of marine boundary layer clouds abstract the impact of physical parameterizations on simulations of cloud topped marine boundary layers is investigated using the fifth generation pennsylvania state university ncar mesoscale model mm5 three month mm5 simulations of the northeast and southeast pacific during june august 1987 are boundary forced with time varying ecmwf analyses runs with four planetary boundary layer pbl parameterizations already implemented in mm5 are compared with runs using new parameterizations of boundary layer turbulence and shallow cumulus convection shcu described in a companion paper numerous modifications to the mm5 that allow it to be used as a regional climate model are described the simulated 3 month mean shortwave cloud radiative forcing swcf and vertical structure of cloud topped boundary layers in the northeast pacific are sensitive to the pbl shallow convection schemes all four current mm5 pbl schemes the blackadar medium range forecast mrf burk thompson and gayno seaman schemes produc

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

andean tectonics related to geometry of subducted nazca plate seismological and geological data show that tectonic segmentation of the andes coincides with segmentation of the subducted nazca plate which has nearly horizontal segments and 30 east dipping segments andean tectonics above a flat subducting segment between 28 s to 33 s are characterized by from west to east 1 a steady topographic rise from the coast to the crest of the andes 2 no significant quaternary and possibly neogene magmatism 3 a narrow belt of eastward migrating apparently thin skinned neogene to quaternary shortening of the andes and 4 plio pleistocene uplift of the crystalline basement on reverse faults in the pampeanas ranges from about 15 to 24 s over a 30 dipping subducted plate a west to east andes cross section includes 1 a longitudinal valley east of coastal mountains 2 an active neogene and holocene andesitic volcanic axis 3 the altiplano puna high plateau 4 a high neogene but inactive thrust belt eastern cordillera and 5 an active eastward migrating subandean thin skinned thrust belt tectonics above a steeply subducting segment south of 33 s are similar west of the volcanic axis but quite different to the east early cenozoic tectonics of western north america were quite similar to the neogene andes however duration of segmentation was longer and the width of deformation was greater in the western united states patterns of crustal seismicity are systematically related to plio quaternary structural provinces implying that current deformational processes have persisted since at least the pliocene horizontal compression parallel to the plate convergence direction is indicated to a distance of 800 km from the trench above flat subducting segments crustal seismicity occurs over a broad region whereas over steep segments it is confined to the narrow thrust belt strain patterns in the forearc region are complex and perhaps extensional and a broad region of the altiplano puna and eastern cordillera appears to be aseismic

seismically induced soft sediment deformation structures associated with the magallanes fagnano fault system isla grande de tierra del fuego argentina abstract in this paper evidence of paleoearthquake induced soft sediment deformation structures associated with the magallanes fagnano fault system in the isla grande de tierra del fuego southern argentina has been identified well preserved soft sediment deformation structures were found in a holocene sequence of the udaeta pond these structures were analyzed in terms of their geometrical characteristics deformation mechanism driving force system and possible trigger agent they were also grouped in different morphological types sand dykes convolute lamination load structures and faulted soft sediment deformation features udaeta a small pond in argentina tierra del fuego is considered a quaternary pull apart basin related to the magallanes fagnano fault system the recognition of these seismically induced features is an essential tool for paleoseismic studies since the three main urban centers in the tierra del fuego province of argentina ushuaia rio grande and tolhuin have undergone an explosive growth in recent years the results of this study will hopefully contribute to future analyses of the seismic risk of the region

geomorphic and sedimentary response of rivers to tectonic deformation a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings abstract rivers are extremely sensitive to subtle changes in their grade caused by tectonic tilting as such recognition of tectonic tilting effects on rivers and their resultant sediments can be a useful tool for identifying the often cryptic warping associated with incipient and smaller scale epeirogenic deformation in both modern and ancient settings tectonic warping may result in either longitudinal parallel to floodplain orientation or lateral normal to floodplain orientation tilting of alluvial river profiles alluvial rivers may respond to deformation of longitudinal profile by 1 deflection around zones of uplift and into zones of subsidence 2 aggradation in backtilted and degradation in foretilted reaches 3 compensation of slope alteration by shifts in channel pattern 4 increase in frequency of overbank flooding for foretilted and decrease for backtilted reaches and 5 increased bedload grain size in foretilted reaches and decreased bedload grain size in backtilted reaches lateral tilting causes down tilt avulsion of streams where tilt rates are high and steady down tilt migration combing where tilt rates are lower each of the above effects may have profound impacts on lithofacies geometry and distribution that may potentially be preserved in the rock record fluvial sedimentary evidence for past tilting is traditionally based on the assumption that depositional features reminiscent of modern fluvial tectonic effects are evidence for past tectonic effects where it is closely associated with historically active structures or where non tectonic causes cannot be invoked however caution must be exercised when using these effects as criteria for past or current tectonic warping as these effects may be caused by non tectonic factors these non tectonic causes must be eliminated before tectonic interpretations are made

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

geoarchaeological evidence of strong prehistoric earthquakes in the new madrid missouri seismic zone sand blows and fissures that cover 10 500 km sup 2 in northeastern arkansas and southeastern missouri attest to the severity of the 1811 1812 earthquake series in the new madrid seismic zone however except for one occurence near new madrid missouri the region has been devoid of any evidence of other major shocks for at least 1 3 ka prior to 1811 and possibly for 9 ka stratigraphic relations and radiocarbon dating at a recently excavated archaeological site near east prairie missouri have revealed liquifaction phenomena attributable to a shock dated to within about 100 yr prior to a d 539 and a probable second one dated between about a d 539 and 991

structure of the lake county uplift new madrid seismic zone abstract the central segment of the new madrid seismic zone lies within a left step over zone between two northeast striking right lateral strike slip fault systems within this compressional step over zone is the topographically and structurally high lake county uplift which includes the tiptonville dome and ridgely ridge we believe these structures are a consequence of deformation in the hanging wall above the northwest striking southwest dipping reelfoot reverse fault reelfoot fault dips 73 from the surface to the top of the precambrian at a depth of approximately 4 km from 4 to 12 km depth the fault dips 32 and is seismically active based on a fault bend fold model we believe that the reelfoot fault becomes horizontal and aseismic at the top of the quartz brittle ductile transition zone at approximately 12 km depth our data indicate that the western margin of the tiptonville dome ridgely ridge and the western margin of the lake county uplift are bounded by east dipping kink bands backthrusts recent work suggests that the reelfoot fault is responsible for the 7 february 1812 m 8 new madrid earthquake however the reelfoot fault has a surface area that is less than that necessary for an m 8 earthquake a possible solution to this discrepancy between magnitude and fault plane area is that the associated backthrusts are seismogenic

new evidence for a large earthquake in the new madrid seismic zone between a d 1400 and 1670 in an integrated geological archaeological and geophysical study in the new madrid seismic zone of the southeastern united states we documented a prehistoric sand blow and related feeder dikes at an archaeological site near steele missouri archaeological analysis combined with radiocarbon dating suggest that the earthquake induced features formed between a d 1400 and 1670 this paleoseismic study provides the best evidence to date for a large earthquake occurring in the zone within 400 yr prior to the 1811 1812 new madrid earthquake sequence to determine an optimal location for excavating at the study site we mapped surficial artifact density and conducted geophysical surveys in doing so we were able to reveal critical relationships for constraining the age of the prehistoric earthquake with minimal impact to the archaeological site

hadley cell dynamics in a virtually dry snowball earth atmosphere the hadley cell of a virtually dry snowball earth atmosphere under equinox insolation is studied in a comprehensive atmospheric general circulation model in contrast to the hadley cell of modern earth momentum transport by dry convection which is modeled as vertical diffusion of momentum is important in the upper branch of the snowball earth hadley cell in the zonal momentum balance mean meridional advection of mean absolute vorticity is not only balanced by eddies but also by vertical diffusion of zonal momentum vertical diffusion also contributes to the meridional momentum balance by decelerating the hadley cell through downgradient mixing of meridional momentum between its upper and lower branches when vertical diffusion of momentum is suppressed in the upper branch the hadley cell strengthens by a factor of about 2 this is in line with the effect of vertical diffusion in the meridional momentum balance but incontrastwithitseffectinthezonalmomentumbalance neitheraxisymmetrichadleycelltheoriesbasedon angular momentum conservation nor eddy permitting hadley cell theories that neglect vertical diffusion of momentum are applicable to the snowball earth hadley cell because the snowball earth hadley cell is a particular realization of a dry hadley cell these results show that an appropriate description of dry hadley cells should take into account vertical transport of momentum by dry convection

faulting along the southern margin of reelfoot lake tennessee abstract the reelfoot lake basin tennessee is structurally complex and of great interest seismologically because it is located at the junction of two seismicity trends of the new madrid seismic zone to better understand the structure at this location a 7 5 km long seismic reflection profile was acquired on roads along the southern margin of reelfoot lake the seismic line reveals a westerly dipping basin bounded on the west by the reelfoot reverse fault zone the ridgely right lateral transpressive fault zone on the east and the cottonwood grove right lateral strike slip fault in the middle of the basin the displacement history of the reelfoot fault zone appears to be the same as the ridgely fault zone thus suggesting that movement on these fault zones has been synchronous perhaps since the cretaceous since the reelfoot and ridgely fault systems are believed responsible for two of the main shocks of 1811 1812 the fault history revealed in the reelfoot lake profile suggests that multiple mainshocks may be typical of the new madrid seismic zone the ridgely fault zone consists of two northeast striking faults that lie at the base of and within the mississippi valley bluff line this fault zone has 15 m of post eocene up to the east displacement and appears to locally control the eastern limit of mississippi river migration the cottonwood grove fault zone passes through the center of the seismic line and has approximately 5 m of up to the east displacement correlation of the cottonwood grove fault with a possible fault scarp on the floor of reelfoot lake and the new markham fault north of the lake suggests the cottonwood grove fault may change to a northerly strike at reelfoot lake thereby linking the northeast trending zones of seismicity in the new madrid seismic zone