a historical perspective of atmospheric chemicals deposited on a mountain top peat bog in pennsylvania abstract a chronology of a mountain top peat bog in pennsylvania has been developed using 210 pb techniques checked with fallout 137 cs from nuclear weapons tests and applied to measurements of the deposition of sulfur nitrogen bromine and trace metals the local wind precipitation patterns and vegetation at the bog increased the deposition of materials two to five times more than expected the trace metals nutrients and magnetic materials found in the core profiles originate regionally as well as from across the great plains of north america and illustrate the history of industrial and domestic activities since 1800 land use changes from virgin forest to clear cutting to reforestation are recorded by the development of the bog the rate of mass and specific element deposition increased during the logging operation to a maximum at the time of clear cutting 1909 and then decreased to the present the deposition of refractory elements also increased to a maximum and then decreased however the deposition of volatile elements and iron showed a steady increase from 1830 to 1983 annual sulfur and bromine deposition appears to have increased some 20 times and nitrogen some 45 times since 1817

paleomagnetic age for hominid fossils at atapuerca archaeological site spain a paleomagnetic investigation at the gran dolina site excavation atapuerca spain shows that the sediments containing the recently discovered human occupation were deposited more than 780 000 years ago near the time of the matuyama brunhes boundary forty one oriented samples were obtained from 22 sites along an 18 meter section of the gran dolina karst filling the lower 16 sites displayed reversed polarity magnetizations whereas the upper six sites were normal the reversal spans the hominid finds at stratigraphic level td6 the aurora stratum and these hominid fossils are therefore the oldest in southern europe

a late pleistocene palaeoclimate record based on mineral magnetic properties of the entrance facies sediments of kulna cave czech republic summary kulna cave is located in the moravian karst a well developed karstic region formed in devonian limestones in the eastern part of the czech republic the entrance facies sediments in the cave consist of interbedded layers of silts loess and clay rich silts loam that were either directly blown into the cave entrance or redeposited in the cave by slope processes during the last glacial stage the layers of loess and loam overlie fluvial sands and gravels deposited during the last interglacial previous research at kulna concentrated on the archaeology palaeontology and dendrology of these entrance facies sediments from these data palaeoenvironmental conditions in the vicinity of the cave were reconstructed our results suggest that susceptibility variations and in particular variations in pedogenic susceptibility yield a more detailed record of the palaeoenvironmental conditions at the cave during the last glacial stage magnetic susceptibility was measured on approximately 700 samples collected throughout three well studied profiles in the cave entrance the record is well defined and correlates from one profile to another mineral magnetic measurements fd arm sirm s ratio t suggest that variations in the kulna sediments from the last glacial stage are controlled by the concentration of magnetite and or maghemite formed during pedogenesis after the removal of the effects of fine carbonate debris and detrital ferromagnetic minerals on the bulk record we obtained a record of pedogenic susceptibility p that serves to quantify the concentration of magnetic minerals formed during pedogenesis therefore p can be thought of as a proxy reflecting the intensity of pedogenesis which in turn is controlled by climate our p record is also in good agreement with the median grain size record of the kulna sediments another proxy for climatic change we suggest that in the case of kulna p is more sensitive to climate change than bulk the kulna pedogenic susceptibility record shows variations on both long and short timescales the long term trends are in good agreement with the deep sea specmap record while the short term oscillations correlate well with rapid changes in the north atlantic sea surface temperatures our results suggest that central european climate during the last glacial stage was strongly controlled by the sea surface temperatures in the north atlantic short term warmer events and perhaps higher precipitation over the mid continent increased the intensity of pedogenesis given the number of independent climate proxies determined from the entrance facies of the cave and their high resolution kulna is an extremely important site for studying late pleistocene climate

3 d rotation of double couple earthquake sources summary we discuss 3 d rotations by which one double couple earthquake source can be rotated into another arbitrary double couple due to the symmetry of double couple sources there are four such rotations an algorithm is obtained in analytical form which is also available as a computer program solving the inverse problem of 3 d rotation of double couple earthquake sources i e for each pair of focal mechanisms or seismic moment tensor solutions the program finds all four rotations which rotate one mechanism into another this algorithm may be used in a wide variety of studies of stress field causing earthquakes investigations of the relationship between the focal mechanisms and the tectonic features of a seismogenic region etc the same inversion algorithm can be used to study the 3 d rotation of any symmetric second rank tensor such as the stress or strain tensor

impurity sources of f cl no3 and so4 2 in greenland and antarctic precipitation five polar impurity sources are proposed anthropogenic no3 and so42 in recent greenland but not antarctic snow marine aerosols the dominant cl source volcanic eruptions which produce detectable but variable peaks in so42 f and or cl concentrations biogenic sulfurous gases from soil and coastal waters the dominant source for so42 in nonvolcanic strata an unidentified source of background nitrate which is more active in the northern hemisphere and which displays a summer concentration maximum solar activity and supernova events do not modulate no3 concentrations in greenland snow

the palaeomagnetism and magnetic fabric of sediments from peak cavern derbyshire summary this paper describes the magnetic remanence and susceptibility anisotropy of 42 samples of laminated clay from peak cavern the sediments are shown to have acquired a stable remanent magnetization due to the depositional alignment of magnetite grains the magnetic fabric data confirm the existence of alteration within a reddened surface layer a record of geomagnetic secular variation in the underlying clay is compared to a dated lake sediment magnetostratigraphy to suggest that deposition occurred around 7000 yr bp a method for estimating water current directions based on the renianence and magnetic fabric data is critically assessed before deducing the sense of palaeoflow in the cave

magnetochronological sequence of the early pleistocene gigantopithecus faunas in chongzuo guangxi southern china abstract the gigantopithecus fauna the most important mammalian fauna during the early pleistocene in southern china was usually excavated from cave or fissure deposits without precise age constraints here we present new magnetostratigraphy results for four cave sedimentary sequences in chongzuo guangxi zhuang autonomous region of southern china from the highest and oldest to the lowest and youngest including baikong cave juyuan cave sanhe cave and queque cave magnetite was identified as the major carrier of characteristic remnant magnetizations in the cave deposits correlation to the geomagnetic polarity time scale was achieved by combining magnetostratigraphic and biochronologic data our correlation suggests that the cave sedimentary sequences span from the pre olduvai matuyama chron to the jaramillo subchron the combined magneto biochronology leads to the establishment of a chronological framework for the early pleistocene gigantopithecus faunas in chongzuo area the gigantopithecus faunal succession of early pleistocene were assigned to estimated ages of 2 0 ma baikong cave 1 8 ma juyuan cave 1 2 ma sanhe cave and 1 0 ma queque cave respectively the river incision rate in chongzuo area during this time span was estimated to be 14 mm ky

the tsunami earthquake of 13 april 1923 in northern kamchatka seismological and hydrodynamic investigations we present a seismological and hydrodynamic investigation of the earthquake of 13 april 1923 at ust kamchatsk northern kamchatka which generated a more powerful and damaging tsunami than the larger event of 03 february 1923 thus qualifying as a so called tsunami earthquake on the basis of modern relocations we suggest that it took place outside the fault area of the mainshock across the oblique pacific north america plate boundary a model confirmed by a limited dataset of mantle waves which also confirms the slow nature of the source characteristic of tsunami earthquakes however numerical simulations for a number of legitimate seismic models fail to reproduce the sharply peaked distribution of tsunami wave amplitudes reported in the literature by contrast we can reproduce the distribution of reported wave amplitudes using an underwater landslide as a source of the tsunami itself triggered by the earthquake inside the kamchatskiy bight

luminescence chronology and palaeoenvironmental significance of limnic relics from the badain jaran desert northern china abstract the badain jaran desert in northern china is well known for the highest mega dunes on earth and unique alternating megadune lake landform and various formation mechanisms have been proposed although the relics of interdune lakes are generally considered as good palaeoenvironmental records their evolutions and relevance to paleoenvironment change are poorly understood due to limited age control in this study quartz optically stimulated luminescence osl and k feldspar post infrared infrared stimulated luminescence pirir were used to establish a chronological framework for limnic relics in order to reconstruct the evolution of interdune lakes our results indicate that limnic relics were deposited in mis 5 and mis 1 due to a lake level transgression and humid environmental condition during the holocene humid conditions occurred at early to middle holocene immediately preceded and followed by aridity the last 600 years have been characterized by high rates of aeolian activity based on field observation and luminescence ages we propose that climate fluctuations since the late pleistocene have played a pivotal role in the formation of the unique landform assemblages

a re evaluation of the great aleutian and chilean earthquakes of 1906 august 17 summary we investigate two great earthquakes that occurred in the aleutian islands and chile within 30 min of each other on 1906 august 17 based on a collection of seismograms compiled shortly after the events by scientists at strasbourg the method of preliminary determination of focal mechanisms pdfm is applied to 14 mantle waves from seven stations in order to resolve the moment tensors of the two shocks it is complemented by examination of body wave polarities at japanese stations to lift the remaining indeterminacy in focal mechanism the chilean earthquake occurring second is a regular subduction event whose moment 2 8 1028 dyn cm is revised downwards from previous estimates except kanamori s suggesting that its rupture did not involve more than 200 km of fault the aleutian earthquake occurring first has a larger moment 3 8 1028 dyn cm but features mantle wave radiation patterns and body wave polarities incompatible with both underthrusting at the aleutian subduction zone and tensional buckling at the outer rise rather we suggest that it is an intraplate somewhat deeper 50 km earthquake this is supported by tentative relocation of available arrival times north of it the origin of the earthquake may be related to the presence of the bowers ridge north of the amchitka pass in the epicentral area finally hydrodynamic simulations using our source mechanisms support the observation that the chilean event was the source of the reported transpacific tsunami the report of a 3 5 m wave at maui constitutes a misassociation as its timing is shown to be non causal for both events

intraplate seismicity of the pacific basin 1913 1988 we establish here a comprehensive database of intraplate seismicity in the pacific basin relocation and analysis of 894 earthquakes yield 403 reliable intraplate earthquakes during 1913 1988 these numbers do not include earthquake swarms which account for another 838 events most of the remainder 304 events are actually plate boundary earthquakes that have been erroneously located in intraplate regions a significant number occur in recent years when location capabilities should have guarded against this situation relocations involve a careful linear inversion of p and s arrivals accompanied by a monte carlo statistical analysis we have also attentively removed the high number of clerical errors and nuclear tests that exist in epicenter bulletins

multiple cmt source analysis of the 2004 sumatra earthquake while it is agreed that the great sumatra earthquake of december 26 2004 was among the largest earthquakes of the past century there has been disagreement on how large it was which part of the fault ruptured and how the rupture took place we present a centroid moment tensor cmt analysis of the earthquake in which multiple point sources are used in the inversion to mimic a propagating slip pulse the final model consists of five point sources with the southernmost sources accounting for the majority of the moment release the presumed fault planes of the southern sources strike northwest while those in the north strike northeast consistent with the geometry of the subduction trench slip on the fault is found to be more oblique in the north than in the south the inversion with five sources leads to a moment magnitude for the sumatra earthquake of m w 9 3 consistent with estimates from long period normal mode amplitudes

preliminary determination of focal mechanisms from the inversion of spectral amplitudes of mantle waves abstract we present a method for the preliminary determination of focal mechanisms pdfm based on the inversion of deviatoric moment tensor components from depleted datasets of mantle wave spectral amplitudes the latter are found to be largely insensitive to errors in epicentral estimates which can hamper the inversion of the full complex spectrum under real time operational conditions robust solutions can be obtained from rayleigh wave spectra at as few as three stations and from a combination of rayleigh and love waves at only two stations provided they sample 60 in azimuth the systematic application of this method to a dataset of 43 large earthquakes during 1996 1999 yielded mechanisms rotated an average of only 17 from the published harvard cmt a figure comparing favorably with the case of other catalogues such as the usgs moment tensor solutions

sedimentation and diagenesis of chinese loess implications for the preservation of continuous high resolution climate records chinese loess has been extensively utilized to produce continuous and high resolution climate records of the late cenozoic such work assumes uninterrupted loess deposition and limited diagenesis here closely spaced optically stimulated luminescence osl dates are used to characterize the holocene and late pleistocene sedimentation histories of three sites across a nw se transect of the chinese loess plateau the results suggest that sedimentation is episodic at subglacial interglacial time scales with rates rapidly varying within units and between sites unconformities noneolian deposition and mixing of sediments also appear to be common existing understanding of loess deposition therefore requires reexamination while previous reconstructions of rapid climate change not dated using absolute methods should be regarded with caution loess deposits may still yield detailed climate records from specific high sedimentation rate strata and evidence for rapid climate change may yet be obtainable by targeting these units through absolute dating the rapid changes in sedimentation presented here indicate the east asian monsoon has the capacity to vary on millennial scales

the implication of the geophysical data and drilling records for the formation and paleoenvironment of the hobq desert china abstract the hobq desert hd locates at the northern margin of the ordos plateau china and the transition zone to the hetao basin it is one of the main proximal deserts of the loess plateau and its formation was controlled by the evolution of the yellow river and the ordos plateau it is still worthy of discussing the regional structure to enhance the understanding of the desert formation and paleoenvironment especially with the additional works in the eastern part geophysical methods including gravity magnetic em electromagnetic are often used to analyse the regional and near surface structure as for drilling records they could show the lithology sequence directly and be applied for the environmental study e g osl dating therefore in this paper we used the satellite gravity data gpr ground penetrating radar tem transient electromagnetic method and drilling records with borehole resistivity data to analyse the desert structure from different scales and the paleoenvironment trough the upward continuation and park oldenburg calculation for the gravity data the thickness of quaternary deposits is 0 85 1 55 km the inferred faults indicated the performance of the hetao basin and the ordos plateau s uplift in pleistocene which also contributed to hd s formation and existing topography a three part structure within 350 m was revealed in the profile at eastern hd by em data the upper layer within 80 90 m was the aeolian dry sand the middle one was mainly fluviolacustrine saturated sand with the occurrence of clay and grey calcareous root tubes and the lower one might be the aeolian sand this near surface structure was consistent to the western part and the forming period for the sand in the upper zone was thereby estimated no earlier than 80 ka moreover during this period millennial scale changes in paleo effective moisture occurred although it was dominated by the arid climate

magnetostratigraphy in pursuit of missing links since the last quadrennial report magneto stratigraphy has continued to flourish the primary issues have been 1 refinements to the geomagnetic reversal time scale grts including recalibrations correlation of biostratigraphic data to the crts and revision of the terminology 2 use of magnetostratigraphic data for estimating rates of such processes as sediment accumulation evolution and faunal migration and 3 magnetic mineralogy and the origin of remanence for convenience we have divided the publications into studies of continental and marine sediments and highlight the most exciting issues within each of these sub headings in the first section of this review we will concentrate on the development of the geomagnetic reversal time scale grts with particular emphasis on refinements from the last few years we then turn our attention to applications of magnetostratigraphy in marine and continental sequences

far field tsunami hazard from mega thrust earthquakes in the indian ocean summary we evaluate far field tsunami hazard in the indian ocean basin based on hydrodynamic simulations of ten case studies of possible mega earthquakes at the major seismic zones surrounding the basin they represent worst case scenarios of seismic rupture along the full extent of seismogenic faults having supported large earthquakes in the historical record in a series of numerical experiments in which the source parameters of the 2004 sumatra tsunami are allowed to vary one by one while keeping the seismic moment and the fault orientation unchanged we document that the main patterns of far field tsunami amplitudes are remarkably robust with respect to nominal variations in such parameters as hypocentral depth exact centroid location and slip distribution on the fault plane these results validate the concept of modelling case scenarios of potential future earthquakes whose source is by definition imprecise we consider seismic sources located at the extremities of the 2004 sumatra andaman rupture namely along the southern coast of sumatra and in the andaman myanmar province along the makran coast of pakistan and iran and also along the southern coast of java where the possibility of a large interplate thrust earthquake cannot be entirely dismissed the results of our hydrodynamic simulations indicate that the distribution of maximum amplitudes in the indian ocean basin is primarily controlled by the classical effect of source directivity and additionally by refraction and focusing along bathymetric features as a result many provinces in the basin could be threatened by higher tsunami amplitudes than in 2004 this pattern is particularly important along the coast of east africa from somalia to and including south africa in madagascar and the mascarene islands especially under a south sumatra scenario involving an earthquake comparable to or even possibly larger than the 1833 event whose epicentral area is widely believed to be under enhanced seismic risk as a result of stress transfer from the 2004 and 2005 ruptures to the northwest possibly even in the wake of the 2007 bengkulu earthquakes

magnitudes of large shallow earthquakes from 1904 to 1980 abstract in order to obtain a uniform magnitude catalogue surface wave magnitudes ms and broad band body wave magnitudes mb have been determined for large shallow earthquakes from 1904 to 1980 in making the catalogue homogeneous the author consistently adheres to the original definitions of ms and mb given by gutenberg 1945 and gutenberg and richter 1956 the determinations of ms and mb are all based on the amplitude and period data listed in gutenberg and richter s unpublished notes bulletins from stations worldwide and other basic information mb is measured on broad band instruments in periods of 8 s consistency of the magnitude determinations from these different sources is carefully checked in detail more than 900 shallow shocks of magnitude 7 and over are catalogued the meaning of the magnitude scales in various catalogues is examined in terms of ms and mb most of the magnitudes listed by gutenberg and richter 1954 in their seismicity of the earth are basically ms for large shocks shallower than 40 km but are basically mb for large shocks at depths of 40 60 km the surface wave magnitudes given by earthquake data reports are higher than ms by 0 2 unit whether the combined horizontal amplitude or the vertical amplitude is used mb and the currently used 1 s body wave magnitude are measured at different periods and should not be directly compared

coseismic slip and afterslip of the great mw 9 15 sumatra andaman earthquake of 2004 we determine coseismic and the first month postseismic deformation associated with the sumatra andaman earthquake of 26 december 2004 from near field global positioning system gps surveys in northwestern sumatra and along the nicobar andaman islands continuous and campaign gps measurements from thailand and malaysia and in situ and remotely sensed observations of the vertical motion of coral reefs the coseismic model shows that the sunda subduction mega thrust ruptured over a distance of about 1500 km and a width of less than 150 km releasing a total moment of 6 7 7 0 10 22 n m equivalent to a magnitude m w 9 15 the latitudinal distribution of released moment in our model has three distinct peaks at about 4 n 7 n and 9 n which compares well to the latitudinal variations seen in the seismic inversion and of the analysis of radiated t waves our coseismic model is also consistent with interpretation of normal modes and with the amplitude of very long period surface waves the tsunami predicted from this model fits rela tively well the altimetric measurements made by the jason and topex satellites neither slow nor delayed slip is needed to explain the normal modes and the tsunami wave the near field geodetic data that encompass both coseismic deformation and up to 40 days of postseismic deformation require that slip must have continued on the plate interface after the 500 sec long seismic rupture the postseismic geodetic moment of about 2 4 10 22 nm mw 8 8 is equal to about 30 5 of the coseismic moment release evolution of postseismic deformation is consistent with rate strengthening frictional afterslip online material summary of geodetic data used in this study

a chronology of natural and anthropogenic influences on coastal sedimentation new zealand 14c and 137cs chronologies of sediment accumulation were obtained from five sediment cores taken from wellington harbour new zealand a 10 000 year chronology records the holocene transgression european colonisation and variations in the general sediment accumulation rate caused by earthquake uplift and anthropogenic activity rates vary from a high of 60 to a low of 0 1 mm a 1 in general rates increased at the beginning of the holocene marine transgression but by 5000 yr bp they reached a stable level harbour wide these rates remained stable until the second half of the 19th century when deforestation by european settlers caused order of magnitude increases in sediment accumulation in the past 40 80 years rates have increased again as a result of urban growth and river channel management although the effects are less pervasive harbour wide influences can be placed in two categories natural and anthropogenic the latter being recent contributions to a sedimentary regime dominated by the holocene marine transgression sediment accumulation rates indicate that two major earthquake uplift events had only a local effect on harbour sediments anthropogenic influences are considered to be more significant sedimentologically than earthquake activity

environmental changes in the ulan buh desert southern inner mongolia china since the middle pleistocene based on sedimentology chronology and proxy indexes abstract the ulan buh desert ubd in southwestern inner mongolia is one of the main dune fields and dust source areas in northern china the formation of the desert and associated environmental changes since the middle pleistocene are still unclear due to a lack of depositional records and environmental proxy index analyses in this study quartz and k feldspar optical dating environmental proxy indexes of grain size loss on ignition pollen and ostracod analysis were employed to supplement the sediment record of a 120 5 m drill core wl12zk 1 from the southern ubd in combination with previous stratigraphic records obtained from drill cores wl10zk 1 35 m deep and wl10zk 2 32 m deep from the northern ubd and drill core wl12zk 2 80 m deep from the northeastern ubd these proxies indicate there has been essentially an arid environment in the ubd with desert or steppe vegetation since the middle pleistocene and that sand dunes were widely distributed in the ubd beginning at least 230 ka ago the yellow river filled a freshwater paleolake beginning 15 ka ago that covered both the ubd and the adjacent hetao plain the paleolake lasted until 87 ka and was associated with wetlands along its margins steppe vegetation was present in the surrounding region an arid environment appeared again after 87 ka and there is no evidence of a large stable lake in the ubd at any time thereafter sand dune deposition and a very arid desert environment were present throughout the last glacial period and lasted into the early holocene during the holocene these arid conditions were interrupted by minor wetland intervals deserts in southern inner mongolia formed at least since the middle pleistocene expanded during the last glaciation and into the early holocene and again after 2 ka we suggest that a combination of tectonic activity and climate change may be responsible for desert formation and environmental changes in southern inner mongolia since the middle pleistocene with additional human influence exacerbating these conditions in the late holocene

the behaviour of major and trace elements in complete vertical peat profiles from three sphagnum bogs the distribution of major elements al ca k mg na in peat profiles from two contrasting ombrotrophic sphagnum bogs is interpreted in respect to the abundance and mineralogical composition of ash atmospheric deposition plant bioaccumulation and leaching high concentrations of ca are found in the minerotrophic peats from a continental bog underlain by calcareous sediments luther bog ontario aluminum is more abundant in the minerotrophic peats from a coastal bog in a siliceous terrain barrington bog nova scotia the peats at the coastal site contain an average of 3 times as much na and mg as the peats from the continental bog because of sea spray potassium is highly enriched in the surface peats at both sites because of plant bioaccumulation the behaviour of trace metals cr cu fe mn ni pb u v zn in peat profiles is explained in terms of the abundance and distribution of mineral matter plant bioaccumulation the response of metals to acidic anaerobic conditions and anthropogenic atmospheric deposition the distribution of ni v and cr in the peats from a third bog galbraith bog ontario follows that of mineral matter content and the metals are highly correlated with ash relative to the mean composition of the underlying mineral sediments clays collected at 30 other sites the peats are neither significantly 2 times enriched nor depleted in ni v and cr manganese is strongly enriched in surface and near surface peat layers because of plant bioaccumulation in contrast fe and mn are relatively depleted in subsurface peats due to their enhanced solubilities in acidic anaerobic waters the opposite is true for cu and u which accumulate in peats because of their diminished solubilities in anaerobic environments enrichments of zn and pb also occur but these are restricted to surface peats and are due to anthropogenic metal deposition

late quaternary downcutting rates of the qianyou river from u th speleothem dates qinling mountains china abstract dating deposits in caves formed by rivers may yield insight into rates and processes of bedrock incision three cave passages at different levels have developed in the walls of the qianyou river valley in the qinling mountains south of the city of xian china twelve speleothem samples near the position of palaeowater tables in three cave passages are dated by the 230th dating method the results show that the river cut down at the rate of 0 23 0 02 mm yr from 358 000 38 000 to 247 000 28 000 yr ago 0 19 0 03 mm yr from 247 000 28 000 to 118 000 19 000 yr ago and 0 51 0 08 mm yr from 118 000 19 000 yr ago until today these fall very close to the glacial interglacial transition following marine oxygen isotope stages 10 8 and 6 respectively the increase in downcutting rates during the interglacial period is consistent with warm wet weather increasing rates of erosion this may lead us toward an underlying mechanism for modulating incision that is not in a direct response to the presence of headwater glaciers

mm a variable period mantle magnitude this paper lays the theoretical groundwork for a variable period mantle magnitude mm based on the measurement of the spectral amplitude x of very long period rayleigh waves we retain the concept of magnitude by restricting ourselves to single station measurements ignoring the focal mechanism and the exact depth of the shallow earthquakes considered our measurements are made at a series of periods in all cases greater than 40 s and the largest value is retained this procedure effectively avoids the well known interference effects leading to saturation of magnitude scales defined at a fixed period two corrections are used a period dependent distance correction cd and a source correction cs also period dependent compensating for the variation of the excitation of rayleigh waves with period both of these corrections are fully predictable on the basis of standard surface wave excitation and dispersion theory the result is a formula of the type mm log10 x cd cs c0 in which all coefficients including the constant c0 are justifiable on sound theoretical grounds the analysis of a data set of 256 records from the broadband seismograph at papeete tahiti the ultra long period system at pasadena and stations of the geoscope network shows that the mean error in the estimation of the seismic moment is on the order of 0 1 0 2 units of magnitude with the standard deviation at each station also on the order of 0 2 units of magnitude no significant trend with either distance period or station can be identified the method can also be transposed to the time domain under some simple assumptions which are justifiable theoretically for typical teleseismic distances across the pacific basin both versions of the method lend themselves well to automation thus by providing a real time estimate of the seismic moment of distant earthquakes mm has considerable potential for tsunami warning purposes its concept can easily be extended to love waves and also to intermediate and deep earthquakes

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

sulfur during early diagenesis in sphagnum peat insights from δ34s ratio profiles in 21pb dated peat cores pb chronologies and depth profiles of stable s isotope ratios 834s and concentrations of organic and inorganic s fractions were determined in peat cores from nine sites in the u s and the czech republic results indicate that depth profiles in s concentrations s accumulation and 634s ratios in peat deposits are affected not only by historical patterns in atmospheric s deposition but also by ongoing depth dependent changes in s reduction oxidation and s immobilization mineralization processes within a peat deposit these processes impart a certain degree of mobility to s in peat bringing into question the validity of reconstructing historical records of s accumulation using dated peat profiles over long term diagenesis isotopically light s may be continually released from deep peat this release may result in redistribution of s and s isotopes in peat and suggests that short term patterns in s accumulation may not persist over much longer time scales

the large andaman islands earthquake of 26 june 1941 why no significant tsunami we present a modern seismological study of the earthquake of 26 june 1941 in the andaman islands the largest pre 2004 event along that section of the india burma plate boundary despite a large conventional magnitude m text pas 8 1 it generated at best a mediocre tsunami for which no definitive quantitative reports are available we show that the 1941 earthquake took place under the andaman accretionary prism and consisted of a composite event whose nucleating phase had a strike slip mechanism incompatible with a data set of spectral amplitudes of mantle rayleigh and love waves combining this initial phase with a larger normal faulting mechanism can reconcile them with p wave first motions reports of subsidence on the eastern coast of the andaman islands and the small amplitudes of any putative tsunami the small tsunami results from a combination of that mechanism and of a source located under the islands themselves and in shallow water implying a reduction in amplitude under green s law when transitioning to a deeper basin

large scale controls on the development of sand seas in northern china abstract although sand seas are located in arid regions given that the proportions of dune areas vary greatly from region to region they are clearly influenced by other factors as well as aridity this paper discusses the distribution pattern and major features of sand seas and large fields of stabilized dunes in northern china and demonstrates the main influences on their development it appears that the availability of onsite loose sediments not wind strength is critical to the occurrence of the sand seas on a regional scale tectonic endorheic basins or areas of alluvial fans or forelands of mountain ranges are advantageous to the accumulation of fluvial sediments and thus are ideal locations of large sand seas in an arid climate the large dune fields currently stabilized by vegetation were active sand seas during the drier periods of the late pleistocene and early holocene the distribution patterns of chinese sand seas suggest that the height or size of the dunes in the sand seas are determined more by the availability of sands than any other potential factors as the sand seas in china account for a large portion of deserts in the middle latitudes of the northern hemisphere taklamakan is the second largest sand sea on earth knowledge of these sand seas past changes is important for understanding climatic changes in the terrestrial regions of mid latitudes

magnetostratigraphy of cave sediments wyandotte ridge crawford county indiana towards a regional correlation abstract the polarity of 42 sediment samples obtained from 21 sites in wyandotte cave and five smaller satellite caves in wyandotte ridge southern indiana is used as a basis for a magnetostratigraphic correlation with sediments in mammoth cave kentucky sediments in caves at elevations between 137 and 162 m have a normal polarity but the fill between 168 and 171 m exhibits a polarity reversal the reversal is interpreted to represent the most recent polarity change suggesting that the upper level of wyandotte cave was last active at about the same time not less than 0 78 ma as the c level in mammoth cave which lies at approximately the same elevation the local base level control in both cave systems is provided by tributaries of the ohio river thus the correlation is most likely a consequence of the contemporaneous abandonment of upper level passages in wyandotte and mammoth caves during the early pleistocene reconstruction of the ohio river drainage sediments in caves between 236 and 241 m have a normal polarity the fill in these little wildcat and galley door caves is probably at least 2 6 ma old it appears to correlate with the residuum that delimits the upper mitchell plain surface the pennyroyal plateau in kentucky and on the basis of our interpretation of the magnetostratigraphy is older than the fill in the highest a and b levels in mammoth cave

weathering and soil development on fan surfaces as a function of height above modern drainageways roan mountain north carolina abstract a relative age chronosequence has been established for fan surfaces on the west and south piedmont slopes of roan mountain north carolina based on measurements of weathering and soil development indices at 20 sites in addition to standard soil properties measurements were made of amphibolite clast weathering rind thickness maximum surface boulder size and mean size and sorting of a 10 kg whole sediment sample from the c horizon soils lacking bt horizons occur only at high altitudes at or near the heads of young fans excepting these locations the youngest fan surfaces have soils with bt horizons generally less than 60 cm thick hues of 10 7 5yr maximum clay contents less than 35 percent rind thicknesses less than 1 2 mm and maximum boulder diameters of 1 2 m soils of the oldest fan surfaces have bt horizons 75 200 cm thick hues of 5 2 5yr rind thicknesses of 6 14 mm maximum clay contents of 40 60 percent and maximum boulder diameters less than 0 75 m although the youngest fan surfaces are close to the level of modern drainageways the oldest stand as much as 20 m above these drainageways and are obviously relict features an index of fan height above modern drainageways was devised that combines height above lateral drainageways with height above the main stream of the valley into which the fan debouches many weathering and soil development properties correlate significantly with this height index including weathering rind thickness r 0 86 munsell hue 0 65 maximum percent clay 0 59 graphic mean phi units of whole sediment particle size analysis 0 54 maximum boulder diameter 0 52 maximum percent free iron in b horizon 0 50 and thickness of bt horizon 0 49 a soil weathering soil development index using these parameters shows a 0 82 correlation coefficient with the height index a cluster analysis shows that the 20 sites can be placed into three distinct groups suggesting that the formation of fan surfaces may be episodic on long time scales a comparison of the fan map with a county soils map shows that the oldest fan surface is fairly consistently mapped as dillsboro series but that the younger fan surfaces show no consistent relationship to soils mapping

the isc gem global instrumental earthquake catalogue 1900 2009 introduction abstract in this introductory article we give a general description of the isc gem global instrumental earthquake catalogue 1900 2009 we also provide the background for four further articles that describe the effort in collecting and digitizing parametric earthquake bulletin data as well as the methodologies developed to compute homogeneous earthquake parameters the result of the two and a half year project is a catalogue of approximately 20 000 large earthquakes covering 110 years with hypocentres and uncertainties computed using the same technique and velocity model we show that the overall homogeneity of the main earthquake parameters in the catalogue was achieved despite changes in instrumentation and routine measurement practices concurrent with developments in instrumental seismology from almost a ground level to its current state for each earthquake mw magnitude values and uncertainties were computed either based on available estimates of seismic moment or using new empirical relationships between mw ms and mb further important results of this project include the electronic availability of a considerable volume of seismic wave arrival time and amplitude measurements from early instrumental printed station bulletins these newly recovered amplitude measurements provided a basis for computation of many previously unavailable ms magnitudes with uncertainties in this article we describe why such a catalogue is required for a comprehensive assessment of global and regional seismic hazard we also describe other potential uses of the catalogue in many other fields of earth sciences we discuss the catalogue availability and lay out the plans of further development

three dimensional tsunami generation simulation due to sea bottom deformation and its interpretation based on the linear theory summary the present study investigates the tsunami generation process by using 3 d numerical simulations and the linear potential theory first we evaluate the relation between sea bottom elevation and sea surface elevation as function of source size l sea depth h and source duration t based on 3 d numerical simulations the surface elevation decreases with increasing sea depth and source duration the difference between the sea bottom and the sea surface elevation appears when the source size is smaller than approximately 10 times the sea depth for a short source duration the linear potential theory can precisely predict the numerical simulation results based on the theory we can consider the tsunami generation as two spatial lowpass filter processes in which the cut off wavenumbers are given by the sea depth and the source duration the criteria for small source size and short source duration are given as l 13h and t l 8c respectively where c is the phase velocity of the tsunami we then simulate the tsunami generation of the 1896 sanriku tsunami earthquake japan the simulated sea surface elevation is significantly different from the sea bottom elevation which suggests the need for correction of the sea depth and source duration for the precise evaluation of the initial water height distribution to include these effects in 2 d simulations we can use the impulse response function and add the fractional sea surface uplift within the time step to the sea surface for each time step

late quaternary optically stimulated luminescence osl chronology and environmental changes in the hobq desert northern china abstract the hobq desert hd is distributed along the south bank of the yellow river in northern china proximation to the east asian summer monsoon limit makes this desert sensitive to fluctuations of monsoonal intensity however environmental changes in the hd during late quaternary are poorly known due to lack of extensive field investigation and appropriate dating materials for radiocarbon dating in this study seven field profiles were examined and a chronology framework based on quartz optically stimulated luminescence osl was established to reconstruct environmental changes in the hd the results suggested two possible periods when lake existed during late quaternary the older paleo lake covering most part of the hd was likely to be formed before 160 ka and vanish at 100 ka whereas the younger paleo lake which was much smaller existed at 10 ka the vanishment of the older paleo lake was probably triggered by a tectonic event while the existence of the younger paleo lake was assumed as a response to humid climate in the beginning of holocene meanwhile the results also showed that modern desert landscape in the hd began at 27 ka and kept expanding during the holocene the climate variations dominated the development of desert landscape in the beginning and human activity enhanced the desertification at least since 1 ka

morphology and tectonics of the andaman forearc northeastern indian ocean summary the andaman sea has developed as the result of highly oblique subduction at the western sunda trench leading to partitioning of convergence into trench perpendicular and trench parallel components and the formation of a northward moving sliver plate to accommodate the trench parallel motion the andaman forearc contains structures resulting from both components of motion the main elements of the forearc are the accretionary prism and outerarc ridge a series of forearc basins and major n s faults the accretionary prism is an imbricate stack of fault slices and folds consisting of ophiolites and sediments scrapped off the subducting indian plate the western outer slope of the accretionary prism is very steep rising to depths of 1500 2000 m within a distance of 30 km there is a difference in the short wavelength morphology between the western and eastern portions of the accretionary prism the outer portion consists of a series of faulted anticlines and synclines with amplitudes of a few 100 to 1000 m and widths of 5 15 km resulting from ongoing deformation of the sediments the inner portion is smoother with lower slopes and forms a strong backstop the width of the deforming portion of the accretionary prism narrows from 80 to 100 km in the south to about 40 km between 10 n and 11 30 n it remains at about 40 km to 14 40 n north of there the inner trench wall becomes a single steep slope up to the myanmar shelf the eastern edge of the outerarc ridge is fault bounded and north of the nicobar islands a forearc basin is located immediately to the east a deep gravity low with very steep gradients lies directly over the forearc basin the west andaman fault waf and or the seulimeum strand of the sumatra fault system form the boundary between the burma and sunda plates south of the andaman spreading centre the waf is the most prominent morphologic feature of the andaman sea and divides the sea into a shallow forearc and a deeper backarc region the diligent fault runs through the forearc basin east of little andaman island although it has the general appearance of a normal fault multichannel seismic data show that it is a compressional feature that probably resulted from deformation of the hanging wall of the eastern margin fault this could occur if the forearc basins were formed by subduction erosion of the underlying crust rather than by east west extension

magnetostratigraphy of sediments in mammoth cave kentucky clastic sediment deposits found within the caves of mammoth cave national park have yielded a magnetostratigraphic pattern of magnetic polarity reversals which indicates that they were deposited over a range of at least 1 million and most likely 2 million years

the depth of the deepest historical earthquakes we usep ands times listed in the international seismological summary to relocate 23 historical earthquakes 1927 1963 reported as occurring at or below 670 km in all cases our relocated hypocenters are shallower than the starting depths furthermore all events converge to 691 km or less with a precision estimated at 10 km this study upholds the results of stark and frohlich who had usedpp p times of post wwssn earthquakes to constrain reliable hypocentral depths to no greater than 684 km in particular we reject rothe s claim that a 1963 event in the vicinity of new guinea occurred at a depth of more than 780 km

holocene environmental changes in the central inner mongolia based on single aliquot quartz optical dating and multi proxy study of dune sands abstract alternating units of dune sands and paleosols in the central inner mongolia imply multiple episodes of dune building and stabilization in response to the waxing and waning of the east asian monsoon such eolian deposits were dated by using the single aliquot quartz optical dating method combined with the multi proxy study on the deposits the past environmental changes during the holocene have been reconstructed our results indicate that widespread eolian sand mobilization occurred in the studied region during the beginning of the early holocene from 11 5 ka to 9 ka the climate became warm and humid during the period between 9 ka and 5 6 ka holocene optimum after 5 6 ka the region again became arid as inferred from dune building however the environmental changes during the late holocene have been affected by both climate and human impacts and the presence of desert environment in such semiarid region is not only the result of climatic drought of the late holocene but also related to poor land use practices

landscape evolution of the ulan buh desert in northern china during the late quaternary the evolution of arid environments in northern china was a major environmental change during the quaternary here we present the dating and environmental proxy results from a 35 m long core a wl10zk 1 collected from the ulan buh desert ubd along with supplemental data from four other cores the ubd is one of the main desert dune fields in china and our results indicate the ubd has undergone complex evolution during the late quaternary most of the present ubd was covered by a jilantai hetao mega paleolake lasting until similar to 90 ka ago a sandy desert environment prevailed throughout the ubd during the last glacial period and early holocene a wetland environment characterized by the formation of numerous interdunal ponds in the northern ubd occurred at similar to 8 7 ka although a dune field persisted in the southern ubd the modern ubd landscape formed after these wetlands dried up during the last 2000 years eolian sand from the badain jaran desert has invaded the northern ubd while farming and overgrazing resulted in the formation of the eastern ubd we suggest that the formation of ubd landforms is related to the disintegration of the megalake jilantai hetao and to summer monsoon changes during the last glaciation and holocene c 2013 university of washington published by elsevier inc all rights reserved

observations of ultra long period normal modes from the 2004 sumatra andaman earthquake abstract the great december 2004 sumatra andaman earthquake was the first giant or extreme moment magnitude mw 9 earthquake recorded by broadband digital seismometers whose data were rapidly available to investigators worldwide as a result analysis of the earth s longest period normal modes became a primary tool for studying the earthquake rather than an elegant afterthought the mode data provided the first evidence that the earthquake was much larger mw 9 3 than initially inferred from surface wave data and involved slip on a much longer fault than initially inferred from body wave data these observations in turn yielded important insight into the likely recurrence of similar earthquakes and the resulting tsunamis both on the segment of the trench that ruptured and on neighboring segments the normal mode data are more numerous and much higher quality than previously available they thus provide the first direct evidence for effects that had been theoretically predicted such as the control of the splitting pattern by receiver latitude and the splitting of torsional modes they similarly yield better results for mode properties such as the attenuation of the longest period radial modes found in agreement with existing models of intrinsic earth attenuation

hydrological and climatic changes in deserts of china since the late pleistocene article i nfo article history large areas in western china were wetlands or less arid between 40 and 30 ka corresponding to the greatest lake period on the adjacent tibetan plateau during the last glacial maximum some of these western chinese deserts again experienced wetter conditions however at the same time the sandy lands in the eastern chinese desert belt experienced an activation of aeolian dunes while interpretations of the mid holocene environment in the deserts of china are controversial it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems as well as other paleoenvironmental proxies such as the artemisia chenopodiaceae ratio should be interpreted with greater caution facing the highlighted uncertainties in our understanding of climate changes in chinese deserts it is hoped that this special issue will improve our knowledge considerably

apparent increasing rates of stream incision in the eastern united states during the late cenozoic stream incision rates were obtained from 16 studies of terraces or stream associated cave levels in the eastern united states a log log regression of age against height above modern river level arl shows that age increases approximately as the square of height arl this relation may indicate an increasing rate of stream incision through time alternatively the relation may simply reflect an inherent effect of measured time interval on process rate as described by gardner et al who found that data from hundreds of studies showed a tendency for geologic process rates to decrease for increasing measurement intervals a regression equation for landscape denudation rates showed that the thickness removed increased as the 0 82 power of the time interval over which the denudation was measured gardner et al suggested that this bias could be removed by the use of statistically derived scaling functions however a similar regression equation for the data in this study shows a slope of 0 38 representing a much more rapid decrease in rate with increasing measurement interval than found by gardner et al even after applying the scaling function calculated by gardner et al my data show a 19 fold decrease in incision rate for a 103 increase in the measured time interval this result suggests that the observed decrease in stream incision rates with greater time spans may be at least partly real

kinematics and source zone properties of the 2004 sumatra andaman earthquake and tsunami nonlinear joint inversion of tide gauge satellite altimetry and gps data 1 we re analyzed the source of the 26 december 2004 sumatra andaman earthquake and tsunami through a nonlinear joint inversion of an inhomogeneous data set made up of tide gauges satellite altimetry and far field gps recordings the purpose is twofold 1 the retrieval of the main kinematics rupture parameters slip rake and rupture velocity and 2 the inference of the rigidity of the source zone we independently estimate the slip from tsunami data and the seismic moment from geodetic data to derive the rigidity our results confirm that the source of the 2004 sumatra andaman earthquake has a complex geometry constituted by three main slip patches with slip peaking at 30 m in the southern part of the source the rake direction rotates counterclockwise at the northern part of the source according to the direction of convergence along the trench the rupture velocity is higher in the deeper than in the shallower part of the source consistent with the expected increase of rigidity with depth it is also lower in the northern part consistent with known variations of the incoming plate properties and shear velocity our model features a rigidity 20 30 gpa that is lower than the preliminary reference earth model prem average for the seismogenic volume the source rigidity is one of the factors controlling the tsunami genesis for a given seismic moment the lower the rigidity the higher the induced seafloor displacement the general consistence between our source model and previous studies supports the effectiveness of our approach to the joint inversion of geodetic and tsunami data for the rigidity estimation

chronology and the upper dating limit for loess samples from luochuan section in the chinese loess plateau using quartz osl sar protocol abstract luminescence dating of loess older than 100 ka has long been a challenge it has been recently reported that using optically stimulated luminescence osl of fine grained quartz 4 11 m extracted from loess the range of luminescence dating could be pushed to 0 6 ma with osl ages being in agreement with independent ages watanuki t murray a s tsukamoto s 2005 quartz and polymineral luminescence dating of japanese loess over the last 0 6 ma comparison with an independent chronology earth and planetary science letters 240 774 789 the aim of this study is to provide a luminescence chronology 20 samples for the standard luochuan loess section and to further examine the upper limit of quartz osl dating for chinese loess the growth curve does not saturate at 700 gy and should allow reliable equivalent dose d e determination up to at least 400 gy however when compared with independent chronological control the d e that could be treated as reliable is less than 230 gy corresponding to 70 ka in age for chinese loess and the d e larger than 230 gy should be underestimated ages for samples from the lower part of palaeosol s1 are severely underestimated with the maximum age of 95 ka for a sample from the bottom of this palaeosol much younger than the expected age of 128 ka the maximum d e obtained for sample l9 m collected from loess layer l9 which is below the matuyama brunhes b m boundary whose age is 780 ka is only 403 gy which corresponds to an age of 107 ka the cause of underestimation is not yet clear the previous results by watunuki et al 2005 on the extension of osl dating of loess to 0 6 ma is not confirmed when evaluating the validity of osl ages in s1 another possibility is to question the already established chronological frame for luochuan section which is based on the hypothesis of continuous dust deposition the assumption of an erosion hiatus between l2 and s1 could make the osl ages look reasonable however if this is the case then it is difficult to explain why the age of sample l9 m is only 107 ka which could be treated as a saturation age while the osl can provide a correct age for loess as old as 94 9 ka for sample lc22 collected from the bottom of s1 much work is required to clarify these confusions

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

desert paleoenvironmental data from cave speleothems with examples from the chihuahuan somali chalbi and kalahari deserts abstract pollen bearing lake bog and spring sediments are relatively scarce in many arid and semiarid regions of the world and few are dateable beyond the 14c range we have obtained pollen spectra from speleothems collected from caves in the somali chalbi and kalahari deserts suggesting that these deposits may be an important future source of desert paleovegetation data as cave speleothems can be dated by the 230th 234u method to c 350 000 yr b p and by the tl and esr methods potentially to 1 m y b p and can sometimes give paleotemperature and paleohydrologic data they could provide a first glimpse of desert paleoenvironments during isotope stages 4 9 ages of speleothems from the chihuahuan kalahari and somali chalbi deserts suggest that there was more available moisture in the southwestern u s a and in northwestern bostwana during glacials and interstadials of the last c 300 000 years but that wetter conditions in the horn of africa corresponded with interglacials and perhaps to a lesser extent with interstadials pollen from three northern somalia speleothems indicate more mesic conditions in the horn of africa at 10 000 11 800 and 176 500 yr b p while speleothem pollen spectra from matupi cave in northeastern zaire presently surrounded by tropical rainforest suggest a savanna grassland at this cave c 14 000 yr b p

source area and rupture parameters of the 31 december 1881 mw 7 9 car nicobar earthquake estimated from tsunamis recorded in the bay of bengal 1 on the morning of 31 december 1881 a submarine earthquake beneath the andaman islands generated a tsunami with a maximum crest height of 0 8 m that was recorded by eight tide gauges surrounding the bay of bengal since the earthquake occurred 8 years before the construction of the world s first teleseismic recording seismometer little has been known about its rupture parameters or location waveform and amplitude modeling of the tsunami indicate that it was generated by a mw 7 9 0 1 rupture on the india andaman plate boundary resulting in 10 60 cm of uplift of the island of car nicobar the rupture consisted of two segments the northern 40 km long segment is separated from the southern 150 km long segment by a 100 km region corresponding to the westward projection of the west andaman spreading center the main rupture occurred between 8 5 n and 10 n with a total area of 150 km 60 km dipping 20 e with a mean slip of 2 7 m the recurrence time for 1881 type events is estimated to be 114 200 years on the basis of inferred gps convergence rates and inferred plate closure vectors although slip partitioning in the region may extend this estimate by as much as 30

unprecedented last glacial mass accumulation rates determined by luminescence dating of loess from western nebraska abstract a high resolution chronology for peoria last glacial period loess from three sites in nebraska midcontinental north america is determined by applying optically stimulated luminescence osl dating to 35 50 m quartz at bignell hill nebraska an osl age of 25 000 yr near the contact of peoria loess with the underlying gilman canyon formation shows that dust accumulation occurred early during the last glacial maximum lgm whereas at devil s den and eustis nebraska basal osl ages are significantly younger 18 000 and 21 000 yr respectively at all three localities dust accumulation ended at some time after 14 000 yr ago mass accumulation rates mars for western nebraska calculated using the osl ages are extremely high from 18 000 to 14 000 yr much higher than those calculated for any other pre holocene location worldwide these unprecedented mars coincide with the timing of a mismatch between paleoenvironmental evidence from central north america and the paleoclimate simulations from atmospheric global circulation models agcms we infer that the high atmospheric dust loading implied by these mars may have played an important role through radiative forcing in maintaining a colder than present climate over central north america for several thousand years after summer insolation exceeded present day values

bioturbation minimal effects on the magnetic fabric of some natural and experimental sediments magnetic fabric measurements have been performed on three suites of sediment samples to contrast biologically disturbed and undisturbed sediments the first of these analyses includes samples from laminated relatively undisturbed and bioturbated totally disturbed horizons found in an athabasca oil sand core the second includes samples from biologically undisturbed sediments from mammoth cave in kentucky the third includes evaluation of the evolution of a magnetite horizon which was established by the author in december of 1982 in a biologically active tidal flat on sapelo island georgia changes in this magnetite horizon were monitored by periodic subsampling results from these suites of samples indicate that the measured magnetic fabric in bioturbated sediments may exhibit primary sedimentary characteristics similar to undisturbed sediments such primary indicators include the anisotropy of magnetic susceptibility ams parametersv used by graham always greater than 45 q used by rees and hamilton always less than 0 69 and a subhorizontal magnetic foliation plane i infer that the presence of apparently primary fabric distributions in these bioturbated sediments indicates that physical not biological factors are responsible for the observed fabric these factors include dewatering and simple low magnitude compaction the data indicate that it cannot be assumed a priori that poor fabric distributions are the result of bioturbation on the contrary for the sapelo island experiments the magnetic fabric actually improved with bioturbation and the athabasca bioturbated magnetic fabric is very similar to that from the athabasca laminated sediment data from the sapelo island georgia tidal flat experiment are interpreted to indicate that long axis ams alignments develop within the sediment such alignments are the result of water movement through sediment which exhibits increased porosity due to high rates of burrowing it is also observed that rm precision improves during the experiment in spite of bioturbation

a palaeomagnetic secular variation record from c 120 000 yr old new zealand cave sediments summary a record of palaeomagnetic secular variations has been obtained from a 5 m section of cave sediments in new zealand the uppermost horizon has been dated at 120 000 yr and the section probably spans about 10 000 yr the mean direction of remanence is close to the field direction expected at the site from an axial geocentric dipole in the upper part of the record the palaeomagnetic vector describes three open clockwise loops ending in a swing to anomalously low inclinations this swing is tentatively associated with a weakening of the main dipole field prior to the blake geomagnetic event

back arc extension in the andaman sea tectonic and magmatic processes imaged by high precision teleseismic double difference earthquake relocation 1 the geometry kinematics and mode of back arc extension along the andaman sea plate boundary are refined using a new set of significantly improved hypocenters global centroid moment tensor cmt solutions and high resolution bathymetry by applying cross correlation and double difference dd algorithms to regional and teleseismic waveforms and arrival times from international seismological centre and national earthquake information center bulletins 1964 2009 we resolve the fine scale structure and spatiotemporal behavior of active faults in the andaman sea the new data reveal that back arc extension is primarily accommodated at the andaman back arc spreading center absc at 10 which hosted three major earthquake swarms in 1984 2006 and 2009 short term spreading rates estimated from extensional moment tensors account for less than 10 of the long term 3 0 3 8 cm yr spreading rate indicating that spreading by intrusion and the formation of new crust make up for the difference a spatiotemporal analysis of the swarms and coulomb stress modeling show that dike intrusions are the primary driver for brittle failure in the absc while spreading direction is close to ridge normal it is oblique to the adjacent transforms the resulting component of e w extension across the transforms is expressed by deep basins on either side of the rift and a change to extensional faulting along the west andaman fault system after the mw 9 2 sumatra andaman earthquake of 2004 a possible skew in slip vectors of earthquakes in the eastern part of the absc indicates an en echelon arrangement of extensional structures suggesting that the present segment geometry is not in equilibrium with current plate motion demands and thus the ridge experiences ongoing re adjustment

pliocene pleistocene incision of the green river kentucky determined from radioactive decay of cosmogenic 26al and 10be in mammoth cave sediments cosmogenic 26al and 10be in sediments washed into mammoth cave kentucky record the history of 3 5 m y of water table position governed by incision and aggradation of the green river a tributary of the ohio river upper levels of the cave formed during a period of slow river incision and were later filled with sediment due to river aggradation at 2 3 2 4 ma a brief surge of river incision ca 2 ma was followed by river stability and cave passage formation at a lower level rapid incision through 15 m of bedrock ca 1 5 ma was prompted by repositioning of the ohio river to its present course along an ice sheet margin renewed incision ca 1 2 ma and aggradation at 0 7 0 8 ma correlate with major ice advances in the ohio river basin measurements of 26al and 10be also indicate that sandstone capped uplands have maintained slow erosion rates of 2 7 m m y for the past 3 5 m y despite accelerated pleistocene river incision rates of 30 m m y

the palaeomagnetism and magnetic fabric of cave sediments from gronligrotta and jordbrugrotta norway summary twenty four oriented specimens of laminated clay were obtained from vertical sections in two caves in northern norway studies of the magnetic remanence and susceptibility anisotropy show that the magnetization is depositional in origin and due to magnetite the palaeomagnetic record in one section is correlated with results from a swiss lake sediment core to suggest an age of 9600 6800 yr bp for the cave clay it is shown that the susceptibility lineation produced on gently sloping surfaces was predominantly controlled by gravity and cannot therefore be used directly to estimate the palaeoflow or palaeofield directions

paleoflood events recorded by speleothems in caves speleothems are usually composed of thin layers of calcite or aragonite however cemented detrital materials interlayered between laminae of speleothemic carbonate have been also observed in many caves flowstones comprising discontinuous carbonate layers form due to flowing water films while flood events introduce fluviokarstic sediments in caves that on occasion are recorded as clayey layers inside flowstones and stalagmites this record provides a potential means of understanding the frequency of palaeofloods using cave records in this work we investigate the origin of this type of detrital deposit in el soplao cave northern spain the age of the lowest aragonite layer of a flowstone reveals that the earliest flood period occurred before 500 ka though most of the flowstone formed between 422 69 43 ka and 400 66 42 ka this suggests that the cave was periodically affected by palaeoflood events that introduced detrital sediments from the surface as a result of occasional extreme rainfall events especially at around 400 ka the mineralogical data enable an evolutionary model for this flowstone to be generated based on the alternation of flood events with laminar flows and carbonate layers precipitation that can be extrapolated to other caves in which detrital sediments inside speleothems have been found copyright 2014 john wiley sons ltd

concurrent tectonism and aquifer evolution 100 000 years recorded in cave sediments dinaric karst slovenia a natural conduit that had formed along a fault was exposed in upper cretaceous limestones during construction of a tunnel near postojna slovenia the conduit is filled with poorly indurated clastic sediments slickensides found on the margin of the sediment deposit show sinistral fault motion that is consistent with regional tectonism analysis of the sediments revealed reversed magnetic polarity the minimum age for latest movement on the fault origin of the cave and deposition of these sediments is 780 ka present day tectonic stresses are concordant with the fault movement and it is likely that the fault has been continuously active throughout growth infilling and hydrologic abandonment of the conduit based upon known and modeled growth rates for conduits this system is recording a period of growth and abandonment that exceeds100 000 years the role that rock discontinuities play in groundwater flow may vary over these timescales and it may be important to account for tectonism when evaluating the long term evolution of aquifers

a new chronology for the age of appalachian erosional surfaces determined by cosmogenic nuclides in cave sediments the relative chronology of landscape evolution across the unglaciated appalachian plateaus of kentucky and tennessee is well documented for more than a century geomorphologists have carefully mapped and correlated upland erosional surfaces inset by wide valley straths and smaller terraces constraining the timing of river incision into the appalachian uplands was difficult in the past due to unsuitable dating methods and poorly preserved surface materials today burial dating using the differential decay of cosmogenic 26al and 10be in clastic cave sediments reveals more than five million years of landscape evolution preserved underground multilevel caves linked hydrologically to the incision history of the cumberland river contain in situ sediments equivalent to fluvial deposits found scattered across the eastern highland rim erosional surface cave sediments correlate with 1 thick lafayette type gravels on the eastern highland rim deposited between c 5 7 and c 3 5 ma 2 initial incision of the cumberland river into the eastern highland rim after c 3 5 ma 3 formation of the parker strath between c 3 5 ma and c 2 0 ma 4 incision into the parker strath at c 2 ma 5 formation of a major terrace between c 2 0 ma and c 1 5 ma 6 shorter cycles of accelerated incision and base level stability beginning at c 1 5 ma and 7 regional aggradation at c 0 85 ma initial incision into the appalachian uplands is interpreted as a response to eustasy at 3 2 3 1 ma incision of the parker strath is interpreted as a response to eustasy at 2 5 2 4 ma a third incision event at c 1 5 ma corresponds with glacial reorganization of the ohio river basin widespread aggradation of cave passages at c 0 85 ma is interpreted as the beginning of intense glacial interglacial cycling associated with global climate change copyright 2006 john wiley sons ltd

comparison of u th paleomagnetism and cosmogenic burial methods for dating caves implications for landscape evolution studies caves are useful in landscape evolution studies because they often mark the level of previous water tables and when dated yield incision rates dating caves is problematic however because their ages are only constrained by the oldest deposits contained within which may be far younger than the cave itself we dated cave deposits in the sierra nevada using u th dating of speleothems paleomagnetic dating of fine sediment and cosmogenic 26 al 10 be burial dating of coarse sediment the sampled caves formed sequentially as the water table lowered providing an important stratigraphic test for the dating methods large discrepancies between deposit ages from similar cave levels demonstrate that even when accurately determined deposit ages can seriously underestimate the timing of cave development drip type speleothems are most prone to this minimum age bias because they can accumulate long after caves form and because the u th method is limited to 400 ka paleomagnetic dating requires correlation with the global reversal chronology and is hindered by a lack of continuous stratigraphy the fine sediment analyzed for paleomagnetism is also highly susceptible to remobilization and deposition in cave passages well above base level cosmogenic 26 al 10 be dates bedload material deposited when caves were at or very near river level and can date material as old as 5 ma in the sierra nevada speleothem u th ages and sediment burial ages from the same cave levels differ by as much as an order of magnitude these results suggest speleothem ages alone may significantly underestimate cave ages