folsom drought and episodic drying on the southern high plains from 10 900 10 200 14c yr b p the paleoenvironments of late pleistocene and early holocene time on the southern high plains have been studied for decades but regionally extensive or long term easily recoverable proxy climate indicators are difficult to find the stratigraphy of valley fill and upland eolian deposits and stable carbon isotope data in addition to geographically limited paleontological data now provide clues to the environment during this time which includes the earliest or paleoindian period 11 200 8000 14c yr b p of human occupation during the clovis occupation 11 200 10 900 14c yr b p valleys contained perennial streams this was followed in folsom time 10 900 10 200 14c yr b p by an abrupt change to lakes and ponds with water levels fluctuating between several meters depth and no surface water and marshes and accumulation of sheet sands on uplands starting the earliest phase of construction of the regional dune fields these changing conditions indicate a shift from relatively wetter to relatively drier conditions with episodic drought stable c isotopes further indicate that warming characterized the clovis folsom transition during the rest of the paleoindian period the environment was relatively cool but fluctuated between wetter and drier conditions with an overall trend toward drying that resulted in further enlargement of the dune fields and culminated in the warm dry altithermal beginning 8000 14c yr b p clovis time probably was the wettest of any paleoindian period in terms of runoff and spring discharge the folsom period was drier and was the earliest episode of regional wind erosion and eolian deposition and may have been the warmest of paleoindian times evidence of a previously hypothesized clovis drought in this region is sparse

reconstruction of early phase deformations by integrated magnetic and mesotectonic data evaluation abstract markers of brittle faulting are widely used for recovering past deformation phases rocks often have oriented magnetic fabrics which can be interpreted as connected to ductile deformation before cementation of the sediment this paper reports a novel statistical procedure for simultaneous evaluation of ams anisotropy of magnetic susceptibility and fault slip data the new method analyzes the ams data without linearization techniques so that weak ams lineation and rotational ams can be assessed that are beyond the scope of classical methods this idea is extended to the evaluation of fault slip data while the traditional assumptions of stress inversion are not rejected the method recovers the stress field via statistical hypothesis testing in addition it provides statistical information needed for the combined evaluation of the ams and the mesotectonic 0 1 to 10 m data in the combined evaluation a statistical test is carried out that helps to decide if the ams lineation and the mesotectonic markers in case of repeated deformation of the oldest set of markers were formed in the same or different deformation phases if this condition is met the combined evaluation can improve the precision of the reconstruction when the two data sets do not have a common solution for the direction of the extension the deformational origin of the ams is questionable in this case the orientation of the stress field responsible for the ams lineation might be different from that which caused the brittle deformation although most of the examples demonstrate the reconstruction of weak deformations in sediments the new method is readily applicable to investigate the ductile brittle transition of any rock formation as long as ams and fault slip data are available

a reexamination of late pleistocene boreal forest reconstructions for the southern high plains previous paleoecological research on the southern high plains resulted in development of a late quaternary chronology of pollen analytical episodes and the proposal that boreal forest existed in the region in the late pleistocene these interpretations are now considered untenable because 1 a number of the radiocarbon ages are questionable 2 there are serious problems of differential pollen preservation and reproducibility of the pollen data 3 there is an absence of supporting geological or paleontological data and 4 the soils of the area contain none of the distinctive pedological characteristics produced by a boreal forest available data suggest that the region was primarily an open grassland or grassland with some nonconiferous trees through most of the quaternary

an 18 ka to present pollen and phytolith based vegetation reconstruction from hall s cave south central texas usa pollen spores phytoliths and microscopic charcoal from a sedimentary column in hall s cave south central texas provide information for local and regional vegetation change during the last deglaciation and the holocene in the context of broader regional and global climatic changes the combination of paleoenvironmental proxy data from the cave indicates that between about 18 000 and 16 500 cal yr bp the cave area was dominated by an open plant community consisting of herbaceous vegetation dominated by c 3 grasses and scattered trees primarily quercus and pinus species after about 16 500 cal yr bp the arboreal component fluctuated attaining a peak between 14 000 and 13 000 cal yr bp with relatively equal proportions of c 3 and c 4 grasses including a sizable proportion of panicoideae grasses the younger dryas is marked by a conspicuous decrease in arboreal pollen with an apparent increase of c 4 grasses toward its termination early holocene recovery of arboreal vegetation is followed by a drying trend marked by the increasing dominance of c 4 drought tolerant chloridoideae grasses increasing human use of the cave in middle to late holocene times creates noise in the climatic significance of pollen phytolith and other proxies a factor to consider when interpreting paleoenvironmental proxies in other cave sedimentary records

new data on the stratigraphy and pedology of the clovis and plainview sites southern high plains abstract the well known clovis and plainview archaeological sites of new mexico and texas have yielded new data on regional late quaternary geologic paleoclimatic and pedologic histories eolian sedimentation at the clovis site from about 10 000 to less than 8500 yr b p was followed by the formation of a cumulic soil between 8500 and 5000 yr b p episodic eolian and slope wash deposition then culminated in massive eolian sedimentation about 5000 yr b p after which a haplustalf formed then was subsequently buried by part of a dune system within the last 1000 yr at the plainview site a basal stream gravel contains plainview cultural material ca 10 000 yr b p which is followed by a localized early holocene lacustrine deposit two eolian deposits the younger dating to about 5000 yr b p and a marsh deposit which slowly accreted as an argiustoll formed in the younger eolian unit the data indicate that on the southern high plains 1 between 12 000 and 8500 yr b p sedimentation varied from site to site 2 there was a regional climate change toward warming and drying in the early holocene 3 two episodes of severe drought apparently occurred in the middle holocene 6500 to 4500 yr b p 4 between 4500 yr b p and the present an essentially modern climate existed but with several shifts toward aridity within the last 1000 yr 5 argillic horizons have developed in late holocene soils 6 clay illuviation can occur in calcareous soils and 7 long distance correlation of holocene stratigraphy in the region is possible particularly with the aid of soil morphology

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

formation uplift and tectonic integration of a periadriatic intrusive complex pohorje slovenia as reflected in magnetic parameters and palaeomagnetic directions summary the periadriatic lineament is a 700 km long first order tectonic boundary in the alps along which several tertiary intrusions are located that were emplaced while tectonic processes were active the pohorje pluton is one of the periadriatic magmatic suites and comprises a pluton and a dacite stock that were emplaced at depths of about 10 and 2 km respectively oriented samples were collected from 33 sites in the magmatic and three in the surrounding metamorphic rocks and subjected them to standard palaeomagnetic and magnetic susceptibility anisotropy processing there is extreme variation in susceptibility although the magnetic mineral are always magnetite and in its anisotropy within the pluton lowest values are in the mafic members in the gabbro the oldest and in some lamprophyres the youngest member of the plutonic suite while the tonalite granodiorite exhibits extreme variation far exceeding those observed for other periadriatic plutons the abnormality of the pohorje pluton is attributed to the complex history that involves assimilation fractional crystallization stratification in the magma chamber incorporation of wall rocks variable degree of k metasomatism and hydrothermal alteration despite the above described heterogenities and sometimes very high degree of susceptibility anisotropy much higher that in the metamorphic samples in the acid member the palaeomagnetic directions observed for the pluton define three clear cut groups the directions show no dependence on the degree of magnetic susceptibility anisotropy in the order of crystallization they exhibit decreasing degree of clockwise declination deviation from north the dacite stock is characterized by counter clockwise rotated declinations as the pohorje pluton was uplifted very fast within the right lateral periadriatic shear zone system it is interpreted that the palaeomagnetic directions observed for the pluton are evidence for a clockwise rotation during exhumation the palaeomagnetic directions for the dacite which formed after the climax of the external forces fits the regional pattern of counter clockwise rotation observed in the neogene sediments around the pohorje pluton this shows that by the time of the dacite intrusion the pohorje pluton was already incorporated into the block that was driven by counter clockwise rotated adriatic microplate

interpreting magmatic fabric patterns in plutons abstract most plutons have widespread magmatic fabrics the interpretation of which remains controversial we propose a method to constrain likely causes of fabric patterns the application of which indicates the following 1 preserved fabric patterns often form after chamber construction and only rarely provide information about ascent or emplacement 2 fabrics are poor recorders of total strain and are easily reset preserving only the last increment of strain during crystallization 3 in magmatic systems mechanically decoupled from host rocks patterns may result from strain during internally driven flow filter pressing or porous flow in relatively static chambers or by final increments of strain during emplacement 4 with greater emplacement depths fabric patterns increasingly reflect strain caused by regional deformation and 5 given that magmatic fabrics are easily reset and reflect only the last increment of strain of comparatively weak materials they may provide a relatively direct record of paleostress in orogenic belts

emplacement and fabric forming conditions of the alous en tides granite eastern border of the tin seririne tin mersoi basin algeria magnetic and visible fabrics analysis abstract the alous en tides pluton intruded within one of the most important late panafrican n s shear zones the 7 30 shear zone in the southern hoggar shield a magnetic fabric study points out strong preferred orientations of the magnetite grains the orientation is coherent in the whole massif however it cannot be correlated with any of the visible structures in the field or in thin section strongly oriented magnetites are thus disseminated within all the rock the main rock forming minerals in this pluton were not preferably oriented during their crystallization showing that magma was emplaced without strongly oriented stresses magnetite orientations on the contrary reflect a strong stress field strike slip movements along the 7 30 shear zone probably generated local relative distension allowing pluton emplacement during the last magmatic phase they put the intrusion under the regional compressional stress field causing orientation of the magnetite the magnetic fabric then reveals the regional ene wsw stress field during late panafrican times in part of the pluton which was later affected by very intense solid state deformation during dextral movement the magnetic fabric remains mainly in connection with this initial magnetite fabric

granite tectonics revisited insights from comparison of k feldspar shape fabric anisotropy of magnetic susceptibility ams and brittle fractures in the jizera granite bohemian massif in the jizera granite of the krkonose jizera plutonic complex northern bohemian massif contrasting patterns of magmatic k feldspar fabrics and brittle fractures characterize different structural levels of the pluton the uppermost exposed level at 800 1 100 m above sea level is dominated by flat foliation that overprints two steep foliations in contrast k feldspar shape fabric in an underground tunnel 660 m above sea level shows complex variations in orientation and intensity magnetic fabric carried by coaxial contributions of biotite magnetite and maghemite is homogeneous along the examined section of the tunnel and is decoupled from the k feldspar fabric the jizera granite is crosscut by two regional sets of subvertical fractures ne sw and nw se and by near surface exfoliation joints the multiple fabrics are inferred to reflect a complex magmatic strain history at different structural levels of the pluton bearing little or no relationship to the fracture network in contrast to the original concept of hans cloos granite tectonics we conclude that no simple genetic relationship exists between fabrics and fractures in plutons an alternative classification of fractures in plutons thus should avoid relationships to magmatic fabrics and should instead consist of cooling syntectonic uplift and post uplift fractures

incorrect when uncorrected reconstructing vegetation history using n alkane biomarkers in loess paleosol sequences a case study from the saxonian loess region germany abstract this study aims at contributing to the reconstruction of the paleoenvironment of the saxonian loess region by investigating sedimentary n alkanes as plant leaf wax derived biomarkers in two loess paleosol sequences lpss namely the gleina and the rottewitz lpss the weichselian paleosols are characterised by n alkane concentration maxima when compared to the loess layers when this coincides with high odd over even predominances oeps this points not only to increased n alkane input and or production but also to increased n alkane preservation in the soils namely in gleysols with water logged edaphic conditions by contrast the buried cambisols reveal low oeps indicating accelerated degradation under aerobic edaphic conditions the n alkane concentrations in the truncated eemian interglacial paleosol are very low this reflects the removal of the formerly n alkane enriched eemian topsoil low n alkane input into the b t s d horizon subsoil horizon of the eemian luvisol and or strong soil organic matter mineralization four investigated n alkane ratios show distinct variations during the weichselian tempting inferences of vegetation changes in terms of varying contributions of tree shrub derived dominated by n c 27 or n c 29 versus grass derived dominated by n c 31 or n c 33 n alkanes however using the oep as a proxy for degradation and considering that n alkane ratios are prone to degradation effects the above interpretation is very likely incorrect degradation can account for most variability of the n alkane ratios applying an endmember model based on a modern n alkane reference dataset allows estimating the contribution of tree shrub versus grass derived n alkanes semi quantitatively these modelling results suggest that both the gleina and the rottewitz lpss were formed under prevailing grassland minor contributions of trees shrubs are only likely for the gleinaer soil complex in rottewitz lps for the top of a brown gleysol in gleina lps and the holocene soil the weichselian vegetation changes as inferred from the uncorrected n alkane ratios are not confirmed overall the n alkane results support the idea that the gleinaer soil complex in gleina and rottewitz lps respectively are not identical but rather are chronostratigraphic equivalents more favourable regional climatic conditions presumably occurred in the southwesterly exposed rottewitz locality and allowed tree shrub vegetation to grow during favourable periods of the weichselian a major shortcoming of the n alkane biomarker method is that only vegetation changes of deciduous woodland to grassland and vice versa can be reconstructed because coniferous trees exhibit by two to three orders of magnitude lower n alkane concentrations

impacts of paleohydrological changes on n alkane biomarker compositions of a holocene peat sequence in the eastern european russian arctic coupled analyses of n alkane biomarkers and plant macrofossils from a peat plateau deposit in the northeast european russian arctic were carried out to assess the effects of past hydrology on the m

charcoal and wood remains for radiocarbon dating upper pleistocene loess sequences in eastern europe and central siberia abstract the present paper concerns long upper pleistocene loess sequences from eastern europe with multiple upper palaeolithic occupations rich in charcoal as well as loess sequences from central siberia with abundant wood remains these complementary records have allowed establishing a high resolution climatic sequence integrating 24 interstadial episodes between ca 42 5 and 10 kyr bp here we discuss the methodology of dating used to fix the chronological framework of this climatic sequence based on a set of 240 available radiocarbon dates mainly produced on charcoal and wood remains special attention is paid to the strategy of sampling charcoal and wood material in strict accordance with stratigraphy as well as to the preparation process in the laboratory for extraction cleaning identification and selection of the best fragments to date careful stratigraphic drawing and detailed positioning of the samples for each geological layer are also considered in order to clarify the relationship of the obtained dates with respect to any sedimentary pedological or archaeological event to be dated the reliability and accuracy of the dates obtained from loess sequences are further controlled by the internal consistency with regard to stratigraphy palaeoenvironmental implications are also discussed

paleogene early miocene igneous rocks and geodynamics of the alpine carpathian pannonian dinaric region an integrated approach a review of paleogene early miocene igneous rocks of the alpine carpathianpannonian dinaric region is presented in this paper we attempt to reveal the geodynamic link between paleogene early miocene igneous rocks of the mid hungarian zone and those of the alps and dinarides our summary suggests that paleogene early miocene igneous rocks of all these areas were formed along a single subduction related magmatic arc the study also highlights orthopyroxene rich websterite mantle xenoliths from west hungary and east serbia that were formed in the vicinity of a subducted slab we discuss the location and polarity of all potential subduction zones of the area that may account for the igneous rocks and orthopyroxene rich mantle rocks however results of seismic tomography on subducted slabs beneath the studied area combined with geological data demonstrate that igneous rocks and mantle rocks cannot be explained by the same subduction process we propose that the paleogene early miocene arc was mainly generated by the budva pindos subduction zone subordinately by penninic subduction whereas mantle rocks were possibly formed in the vicinity of the older vardar subduction zone continental blocks possibly moved together with their mantle lithosphere the present diverging shape of the proposed arc has been achieved by considerable shear and rotations of those lithospheric blocks

middle holocene drought on the southern high plains abstract the climate of the southern high plains during the middle holocene is indicated by data from a variety of sources stratigraphic geomorphic and pedologic research at six localities in draws several dune sites and one playa lake basin show that widespread eolian erosion and sedimentation began in some areas by 9000 yr b p and culminated 6000 4500 yr b p probably because of warmer drier conditions that reduced the vegetative cover archaeological investigations at three sites provide evidence for the excavation of wells at this time apparently because of a declining water table studies of a few vertebrate and invertebrate faunas also indicate warming and drying in the middle holocene climate models and very limited isotopic data from bison bone suggest that summers in the middle holocene were warmer than present with reduced effective precipitation all lines of evidence indicate that the southern high plains was subjected to prolonged drought in the middle holocene with a maximum between 6500 and 4500 yr b p conforming climatically and chronologically to the altithermal

the alpine overprints of the magnetic fabrics in the basement and cover rocks of the veporic unit western carpathians slovakia abstract in the veporic unit building up the central areas of the western carpathians the magnetic fabrics are more or less coplanar and coaxial in metamorphic early palaeozoic in age granitic early to late palaeozoic in age and sedimentary cover rocks permian triassic in age the magnetic fabrics in metamorphic and granitoid basement rocks as well as in sedimentary volcanic cover rocks appear to reflect a very wide p t conditions of cretaceous originally variscan basement reactivation connected with a prograde metamorphism of the sedimentary cover rocks in lower greenschist in the north veporic area or the upper greenschist to lower amphibolite facies in the south veporic area during collisional burial in a collisional wedge in addition there are deformation zones where the magnetic fabrics formed due to a ductile deformation associated with extensional exhumation along sinistral lateral strike slip and normal faults the late open folds did not principally change the former magnetic fabrics the magnetic fabrics in sedimentary cover rocks of the north veporic area are either related to still recognizable bedding planes in competent layers with parallel superimposed metamorphic schistosity or they are conformable to subparallel or oblique metamorphic cleavages in the south veporic area they are undoubtedly related to the metamorphic mylonitic fabrics of the basement granitoids and their metamorphic mantle rocks the magnetic fabrics in granitoid rocks of the south veporic area s of the pohorela sinistral strike slip fault are influenced with micromechanisms of dominated low temperature ductile deformation and partial dynamic recrystallization we ascribe the observed coaxial magnetic fabrics in metamorphic granitic and sedimentary rocks to an alpine collision 110 95 ma p max 8 9 kbar t max 530 c and extension tectonometamorphic events 95 80 ma up to p 4 5 kbar t 300 c of cretaceous age the magnetic fabrics seem not to be strongly dependent on temperatures until the medium part of the amphibolite facies as in this example but they are strongly following simultaneous deformational low temperature to medium temperature meso and microfabrics

magma emplacement during exhumation of the lower to mid crustal orogenic root the jihlava syenitoid pluton moldanubian unit bohemian massif in this study we present structural and ams data from the w335 ma ultrapotassic jihlava syenitoid pluton which intruded the lower to midcrustal orogenic root moldanubian unit in the bohemian massif central european variscides the emplacement of the pluton was accommodated by multiple processes such as ductile host rock shortening formation of sheeted zones by magma wedging magmatic stoping and possibly host rock displacement within a wide transtensional zone magmatic fabrics preserved in the pluton reflect both intrusive processes and regional strain margin parallel and weneewsw foliations which probably formed by strain during emplacement of inner magma pulses were overprinted by tectonic strain within a zone of distributed wrench dominated dextral transtension this zone probably accommodated exhumation of different segments in the eastern part of the moldanubian unit during pluton emplacement in contrast to existing models we emphasize that the jihlava pluton as well as other ultrapotassic plutons widespread in the moldanubian unit are structurally highly variable bodies emplaced by multiple intrusive processes our case study illustrates how careful documentation of structural relations around these ultrapotassic plutons may constrain the kinematic framework and local exhumation histories in different segments of the orogenic root during and shortly after the w340 ma mechanical event in the central european variscides 2006 elsevier ltd all rights reserved

cenozoic granitoids in the dinarides of southern serbia age of intrusion isotope geochemistry exhumation history and significance for the geodynamic evolution of the balkan peninsula two age groups were determined for the cenozoic granitoids in the dinarides of southern serbia by high precision single grain u pb dating of thermally annealed and chemically abraded zircons 1 oligocene ages kopaonik drenje eljin ranging from 31 7 to 30 6 ma 2 miocene ages golija and polumir at 20 58 20 17 and 18 06 17 74 ma respectively apatite fission track central ages modelling combined with zircon central ages and additionally local structural observations constrain the subsequent exhumation history of the magmatic rocks they indicate rapid cooling from above 300 c to ca 80 c between 16 and 10 ma for both age groups induced by extensional exhumation of the plutons located in the footwall of core complexes hence miocene magmatism and core complex formation not only affected the pannonian basin but also a part of the mountainous areas of the internal dinarides based on an extensive set of existing age data combined with our own analyses we propose a geodynamical model for the balkan peninsula the late eocene to oligocene magmatism which affects the adria derived lower plate units of the internal dinarides was caused by delamination of the adriatic mantle from the overlying crust associated with post collisional convergence that propagated outward into the external dinarides miocene magmatism on the other hand is associated with core complex formation along the southern margin of the pannonian basin probably associated with the w directed subduction of the european lithosphere beneath the carpathians and interfering with ongoing dinaridic hellenic back arc extension

the late quaternary loess record of tokaj hungary reconstructing palaeoenvironment vegetation and climate using stable c and n isotopes and biomarkers abstract large areas of southeast europe are covered by pleistocene loess deposits with interbedded palaeosol layers reflecting interglacials or stadials these loess palaeosol sequences are valuable terrestrial archives for continuous palaeoclimatic and palaeoenvironmental information in recent years the traditional paradigm of treeless full glacial palaeoenvironments has increasingly been called into question as there is palynological anthracological and malacological evidence for the continuous presence of trees from loess palaeosol sequences in the carpathian basin this paper aims at contributing to this discussion by applying biogeochemical geophysical and sedimentological methods to a late quaternary loess palaeosol profile at tokaj ne hungary previous studies at the same location have focused on molluscs and charcoal while this study concentrated on stable c and n isotopes and lipid biomarkers long chain n alkanes c 23 c 33 which form major constituents of plant leaf waxes have successfully been used as biomarkers over the last years and allow for a reconstruction of palaeovegetation based on the differentiation of grassland vs shrubs and trees stable carbon isotopes were used to further differentiate between c 3 and c 4 palaeovegetation and stable n isotopes to reconstruct the n cycle and climatic variations magnetic susceptibility ms organic carbon and grain size distribution which may serve as proxies for e g the intensity of pedegenesis weathering and palaeowind strength were measured to complement the biogeochemical results and to establish a pedo and biostratigraphy although the results do not agree in every detail with previous studies there are surprising matches and similarities in the data alkane and stable n isotopic data indicate that pedogenesis occurred under productive fertile steppe grasslands probably in an intensified seasonal climate and during reduced sedimentation two short treeless steppe periods were found between 26 and 12 ka bp however periods characterised by a cooler climate in which trees and shrubs expanded were also found this interpretation is also supported by previous mollusc data that provide evidence for several periods of favourable conditions for tree growth

palaeomagnetic evidence for tertiary counterclockwise rotation of adria abstract with the aim of obtaining tertiary palaeomagnetic directions for the adriatic foreland of the dinaric nappe system we carried out a palaeomagnetic study on platform carbonates from stable istria from the northwestern and the central dalmatia segment of imbricated adria despite the weak to very weak natural remanences of these rocks we obtained tectonically useful palaeomagnetic directions for 25 sites from 20 localities all exhibit westerly declinations both before and after tilt correction concerning the age of the magnetizations we conclude that five subhorizontal and magnetite bearing eocene localities from stable istria are likely to carry primary remanence whereas three tilted and hematite bearing ones were remagnetized in the northwestern segment of imbricated adria the cluster of the mean directions improved after tectonic correction indicating pre tilting magnetization in contrast maastrichtian eocene platform carbonates from central dalmatian were remagnetized in connection with the late eocene oligocene deformation or miocene hydrocarbon migration based on the appropriate site locality means we calculate mean palaeomagnetic directions for the above three areas and suggest an alternative interpretation of the data of kissel et al j geophys res 100 1995 14999 for the flysch of central dalmatia the four area mean direction define a regional palaeomagnetic direction of dec 336 inc 52 k 107 95 9 from these data we conclude that stable istria in close coordination with imbricated adria must have rotated by 30 counterclockwise in the tertiary relative to africa and stable europe we suggest that the latest miocene early pliocene counterclockwise rotations observed in northwestern croatia and northeastern slovenia were driven by that of the adriatic foreland i e the rotation of the latter took place between 6 and 4 ma

archaeological geology of the lubbock lake site southern high plains of texas the lubbock lake site is a well stratified archaeological locality in yellowhouse draw on the southern high plains of texas it has a cultural record that spans the past 11 000 yr that is contained within a thick sequence of sediments and soils the sequence at lubbock lake is one of the most closely integrated records of late quaternary human occupation sedimentation and soil formation documented in north america stratum 1 11000 yr b p and older was deposited by a meandering stream and contains clovis age cultural remains stratum 2 is composed of lacustrine sediments 11000 to 10000 yr b p and overlying marsh deposits 10000 to 8500 yr b p with paleoindian material in both units the firstview soil 8500 to 6300 yr b p formed in the top of stratum 2 stratum 3 6300 to 5000 yr b p contains early archaic material eolian and marsh deposits suggestive of warm arid conditions and the yellowhouse soil indicating a brief period of landscape stability stratum 4 5000 to 4500 yr b p is primarily an eolian unit that marks the second of two periods of severe drought in the middle holocene the lubbock lake soil formed in stratum 4 beginning 4500 yr b p coincides with the late archaic and ceramic periods and documents landscape stability and a return to climatic conditions similar to those of today stratum 5 contains late ceramic protohistoric and historic archaeological material within eolian and slopewash sediments and the apache and singer soils which indicate several shifts toward aridity within the past 1 000 yr

magnetic fabrics in the holum granite vest agder southernmost norway implications for the late evolution of the sveconorwegian grenvillian orogen of sw scandinavia abstract the holum granite vest agder southernmost norway has been considered to be the oldest 980 ma undeformed post tectonic pluton of a late sveconorwegian granitoid series that form two belts in southern norway and sw sweden an integrated structural study of this granite pluton based on a survey of its anisotropy of low field magnetic susceptibility ams complemented by microstructural observations optical microscopy and rock magnetism investigations including measurements of partial anhysteretic remanent magnetization and its anisotropy paarm is presented here the magnetic susceptibility and the ams of the holum granite are carried by large magnetite grains coaxiality between the magnetite controlled ams fabric and the rock fabric is verified which allows the use of the former as a proxy for the latter microstructural evidence of a deformation continuum in the granite from magmatic to solid state and homogeneity and continuity of the ams fabrics across the pluton demonstrate that the holum granite is not post tectonic but that it was emplaced in a tectonic strain field a model of emplacement and deformation during the last sveconorwegian regional folding phase evidenced in the country rocks of the pluton is proposed

soils and landscape evolution of eolian plains the southern high plains of texas and new mexico holliday v t 1990 soils and landscape evolution of eolian plains the southern high plains of texas and new mexico in p l k knuepfer and l d mcfadden editors soils and landscape evolution geomorphology 3 489 515 sheets of eolian sediment cover many areas of the earth s surface sand seas dune fields and loess sheets being the best known examples of such features less well known are deposits of sandy eolian sediment forming extensive plains an excellent example of such a region is the semi arid southern high plains northwest texas and eastern new mexico the level landscape of the area was created by depositon of multiple extensive 80 000 km 2 sheets of eolian sediment biackwater draw formation over the past 1 4 ma this deposit grades from sandy southwest to silty and clayey northeast and is up to 27 m thick surface soils at least 30 000 and possibly 120 000 years old are well developed 5yr hues agrillic horizons 1 2 m thick with prismatic structure stage ii iii calcic horizons and are generally paleustolls and paleustalfs with some paleargids and haplargids morphologic variation is due mainly to textural variation of the eolian parent material although locally thickness of the parent material and wind erosion and cumulization are important factors and locally slight variation in effective precipitation may be significant the blackwater draw formation contains as many as six well developed buried soils each formed in individual layers of eolian sediment similar to or more strongly expressed 2 syr hues higher illuvial clay content than the regional surface soils the presence of the buried soils indicates that sedimentation was episodic and separated by long periods of relative landscape stability eolian processes also appear to have been important during the periods of stability and pedogenesis by providing clayey calcareous dust that was added to the soil promoting formation of the argillic and calcic horizons the sedimentologic and pedologic uniformity of the deposit suggests that the regional environment has not varied significantly during the quaternary except for periods of increased sedimentation or wind deflation underlying the blackwater draw formation is an upper tertiary deposit up to 36 m thick of eolian sand silt and clay ogallala formation this deposit contains buried soils very similar to those in the blackwater draw formation suggesting that the geomorphic processes that created the quaternary landscape of the southern high plains began to operate in the late tertiary perhaps as much as 11 million years ago

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

structural and magnetic fabric study of the marimanha granite axial zone of the pyrenees the structural and magnetic fabric study of the marimanha granite axial zone of the pyrenees provides new data to characterize the zonation and the internal structure of the pluton the marimanha granite intrudes cambro ordovician clastic rocks and silurian devonian limestones and slates the zonation of the low field magnetic susceptibility consistent with the petrological zonation of the igneous body indicates a concentric arrangement of rock types with more basic compositions at the external areas this pluton is characterized by a low susceptibility and rock magnetic studies indicate a majority of paramagnetic samples magnetic foliations strike parallel to petrographic contacts and to contours of zonation of magnetic susceptibility and show a dominant ne sw strike steeply dipping towards the north locally in the northern border of the pluton foliation directions become perpendicular to petrographic contacts and depict sigmoidal trajectories magnetic lineations are characterized by the predominance of ne sw trends with shallow plunges to the ne and sw these foliations and lineations are parallel to the slight elongation of internal petrographic zonation magnetic fabric within the granitoid body and internal elliptical shape of petrographic zonation suggest an intrusion contemporary with a transpressional regime and nnw sse shortening syntectonic with the late stages of the variscan orogeny these results are in accordance with anisotropy of magnetic susceptibility studies of others plutons in the pyrenees to explain the origin of the marimanha granite we propose magma ascent through faults at depth and emplacement by ballooning in situ at the rheological boundary between cambro ordovician and siluro devonian metasediments

soil geomorphic relations of lamellae in eolian sand on the high plains of texas and new mexico clay lamellae are ubiquitous features in sands in a wide variety of settings around the world most studies of lamellae focus on 1 a few or individual locales or on 2 formation by experimental methods in the laboratory this study reports on lamellae from eight localities in three late quaternary dune fields on the southern high plains of northwest texas and eastern new mexico most lamellae observed are illuvial and they increase in number and thickness through time a few 1 3 thin 1 2 mm lamellae formed in historic sediments lamellae are more numerous 3 12 and thicker 3 5 mm in older late holocene b 1000 14 c years bp and middle holocene b 7600 14 c years bp sands soils that formed through the late pleistocene and into the early holocene 14 300 7600 14 c years bp or soils that formed throughout the holocene can exhibit as many as 30 lamellae or lamellae of 10 12 mm thickness the micromorphology of the lamellae shows that argillans on sand grains are thicker more laminated more continuous and cap and link more grains through time other variables affect lamella morphology within individual dunes the lamellae are best expressed where the sand is thickest they decrease in number and thickness as sand thins the lamellae also form only in clean well drained sand poor drainage and or bioturbation result in formation of a continuous argillic horizon encasing lamellae d 2005 elsevier b v all rights reserved

grassland vegetation in the southern great plains during the last glacial maximum abstract new pollen records from white lake in the southern high plains and from friesenhahn cave on the southeastern edwards plateau of texas indicate that the glacial age vegetation of the southern great plains was a grassland the high plains was a treeless artemisia grassland and the edwards plateau at the south edge of the great plains was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats the glacial age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog the dominance of prairie vegetation during the last glacial maximum is compatible with late pleistocene mammalian faunas and late glacial grassland pollen records from the region earlier interpretations of a pine spruce forest on the high plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration resulting in differential preservation of conifer pollen grains accordingly the tahoka pluvial and other climatic episodes defined by high plains pollen records are abandoned

the emplacement of the rieserferner pluton eastern alps tyrol constraints from field observations magnetic fabrics and microstructures abstract within the alpine chain several tertiary intrusions e g bergell adamello intruded along the periadriatic lineament this study attempts to show how the rieserferner pluton vedrette di ries is related to the defereggen antholz vals dav line for a survey of the fabric pattern over the pluton the anisotropy of the magnetic susceptibility ams was determined on nearly 170 samples low bulk susceptibilities of k vol 6 si and a total degree of anisotropy p

simulation of the climate of 18 000 years bp results for the north american north atlantic european sector and comparison with the geologic record of north america abstract the large ice sheets in north america and europe and the extensive sea ice cover in the north atlantic at the time of the last glacial maximum must have greatly modified the surface temperature patterns and in turn the location and intensity of the surface winds and jet streams a general circulation model was used to simulate the january and july patterns of temperature precipitation and wind for 18 ka bp boundary conditions for the model consisting of ice sheet location and height sea ice location and sea surface temperature were prescribed from climap 1981 the model results are illustrated and described for the north american north atlantic european sector the jet stream splits around the north american ice sheet and the southern branch strengthens considerably compared to present over the southern portion of the united states the sea ice margin of the north atlantic and the southern edge of the european ice sheet geologic evidence principally from north america of wind temperature and moisture conditions is assessed from sand dune and loess records estimates of snowline depression pollen records and lake level studies the geologic evidence is generally compatible with the model simulation

the motion of adria during the late jurassic and cretaceous new paleomagnetic results from stable istria abstract the motion of adria the largest lithospheric fragment in the central mediterranean region has played an important role in the tectonic development of the surrounding mountain chains and even of distant areas like the eastern alps or the pannonian basin the available paleomagnetic data were insufficient to constrain this motion except in a general way in this paper new paleomagnetic results are presented from one of the stable parts of adria which emerge from the adriatic sea the results were obtained on weakly magnetic platform carbonates of the mud supported type collected from 21 geographically distributed localities the results combined with mean paleomagnetic directions from selected localities from a pioneer study in istria that were chosen using statistical criteria were divided into three age groups tithonian aptian albian cenomanian turonian coniacian the paleomagnetic poles calculated for each of them tithonian aptian n 47 e 275 k 67 95 9 4 n 5 albian cenomanian n 58 e 253 k 145 95 4 3 n 9 turonian coniacian n 63 e 261 k 50 95 7 3 n 9 reveal a moderate shift during the cretataceous which is comparable with that calculated from the african reference poles however the istrian apparent polar wander path is slightly displaced from the african curve as a consequence of about 10 counterclockwise rotation of istria with respect to africa this rotation angle is more that 10 smaller than the difference measured for the mid late eocene between the paleomagnetic direction of platform carbonates from istria and the african reference direction this difference may be the consequence of a small clockwise rotation of istria with respect to africa most probably at the end of cretaceous