raman spectroscopic analysis of carbonaceous matter and silica in the test walls of recent and fossil agglutinated foraminifera raman spectroscopy has been used extensively in thermal maturation studies of kerogen but has not been used to examine the maturation of organic cements in agglutinated foraminifera here we use raman spectroscopy to document the existence of carbonaceous matter and silica in recent and fossil agglutinated foraminifera and to measure thermal alteration effects in fossil foraminifera the distribution of carbonaceous matter through the test shell walls of agglutinated foraminifera suggests that this carbonaceous material is derived from primary organic cement and not from random contamination fossil specimens exhibit three broad stages of maturation 1 immature specimens are characterized by moderately strong fluorescence broad low intensity raman peaks relative to fluorescence and a tendency for the g band to occur at lower wave numbers these attributes are consistent with the presence of amorphous carbonaceous matter and minor organic degradation 2 mature samples oil window exhibit high fluorescence increased relative d and g band intensities and a decreased width of the d band 3 postmature samples exhibit low levels of fluorescence and high relative d and g band intensities a tendency for the g band to be located at higher wave numbers an increase in the d g band ratio and an increase of the relative intensity of the silica peak this stage is consistent with the presence of highly ordered carbonaceous matter and diagenetic quartz these findings indicate that raman spectroscopic analysis of fossil agglutinated foraminifera can be used as a quick and easy tool to assess thermal maturity and estimate optimal temperatures for hydrocarbon generation

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

coherent and subsequent incoherent ringwoodite growth in olivine of shocked l6 chondrites abstract pervasive replacement of original olivine grains by ringwoodite adjacent to a shock melt vein of yamato 791384 l6 chondrite was observed with a feg sem in these olivines we observed three distinct olivine ringwoodite textures arranged in a spatially successive arrangement from the wall of the shock melt vein into the olivine grains 1 polycrystalline ringwoodite 2 oriented several sets of ringwoodite lamellae and 3 oriented single lamellae tem images show that the polycrystalline and oriented several sets of lamellae parts consist of polycrystalline ringwoodite indicating that phase transformation from olivine to ringwoodite is controlled by incoherent growth mechanism on the other hand the set of oriented single lamellae consists of thin ringwoodite platelets

shock induced melting recrystallization and exsolution in plagioclase from the martian lherzolitic shergottite grv 99027 plagioclase in the martian lherzolitic shergottite grove mountains grv 99027 was shocked melted and recrystallized the recrystallized plagioclase contains lamellae of pyroxene olivine and minor ilmenite 1 m wide both the pyroxene and the olivine inclusions enclosed in plagioclase and grains neighboring the plagioclase were partially melted into plagioclase melt pools the formation of these lamellar inclusions in plagioclase is attributed to exsolution from recrystallizing melt distinct from other martian meteorites grv 99027 contains no maskelynite but does contain recrystallized plagioclase this shows that the meteorite experienced a slower cooling than maskelynite bearing meteorites we suggest that the parent rock of grv 99027 could have been embedded in hot rocks which facilitated a more protracted cooling history

uv raman spectroscopy of hydrocarbon bearing inclusions in rock salt from the dongying sag eastern china abstract compositions of hydrocarbon bearing inclusions in rock salt halite from the shahejie formation in the dongying sag bohai bay basin eastern china have been analysed by raman spectroscopy coupled with a 244 nm uv laser source the fluorescence effect caused by the conventional visible laser excitation of the aromatic fractions of hc bearing inclusions can be effectively avoided six types of hc bearing inclusions belonging to two generations have been identified in halite according to their hydrocarbon types and petrographic characteristics the presence of hc bearing inclusions in halite provides evidence of crystal fracturing and healing plastic deformation and dynamic recrystallization of rock salt in the dongying sag this proves that rock salt may have repeatedly lost and then recovered its sealing capacity during two stages of oil emplacement water and hydrocarbons were detected by uv raman spectroscopy in the studied samples in both hc bearing inclusions and aqueous inclusions these results are important for understanding the formation conditions of these fluid inclusions and the interactions between the formation water and petroleum in reservoirs our results show that uv raman spectroscopy has a potential to become a powerful tool for analyzing hydrocarbon bearing fluid inclusions trapped in various elements of a petroleum system

the viscous creep component in shallow clayey soil and the influence of tree load on creep rates creep tests carried out on silty clay samples of a terres noires colluvium show that even in shallow soils 1 m in depth stress conditions can be high enough to initiate measurable creep displacements by the mechanism of continuous viscous creep it is therefore not necessary to think exclusively of a shrink swell mechanism seasonal creep in order to explain these slow movements in the soil the creep tests also show a negative correlation between effective normal stress and the viscosity of the soil material therefore in shallow soils removal of an external load forest clearing might increase the creep rate at lower slope angles and therefore decrease the stability of the slopes at higher slope angles removal of external load decreases the creep rate

stones from mohave county arizona multiple falls in the franconia strewn field one of the most productive and well sampled dense collection areas for meteorites on earth is the franconia strewn field in mohave county arizona which since 2002 has yielded hundreds of meteorites in an ellipsoidal area approximately 5 16 km across based on petrographic mineral chemical and terrestrial age data we conclude that among 14 meteorites examined there are at least 6 and possibly 8 distinct meteorites represented which fell over a period of approximately 0 20 kyr ago these include equilibrated h chondrites such as franconia h5 and buck mountains bm 001 h6 h3 6 breccias such as buck mountains wash and bm 004 and l6 chondrites such as bm 002 and bm 003 which may be paired palo verde mine and bm 005 to confidently pair such meteorites often requires thorough petrographic examination mineral chemical analyses and terrestrial ages we estimate that 50 10 of the larger specimens in this area are paired yielding a relatively high value of approximately 2 3 2 9 distinct meteorites km 2 the meteorite flux estimated for franconia area is higher than the flux inferred from contemporary fireball data for larger masses we suggest that one large h3 6 meteoroid fell in the area most likely that of buck mountains wash approximately 4 kyr ago which produced an elliptical strewn field with masses generally increasing toward one end and which raised the meteorite productivity in the recovery area

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

raman spectroscopy as a tool for the non destructive identification of organic minerals in the geological record abstract organic minerals can be considered as a forgotten group of organic components in the geological record they are salts of organic acids originating directly in plant metabolic processes pure crystalline terpenes formed from precursor conifer decomposition products and polycyclic aromatic hydrocarbons originating in the accumulation of fractions generated by natural high temperature distillation from specific precursors the presence of some of these minerals in quaternary or tertiary continental sedimentary environments in soils and peats is known as are rare occurrences in lignite shales and other rocks from older geological formations raman spectral signatures have been identified for mellite the hydrated aluminium salt of benzene hexacarboxylic acid the terpenoids fichtelite norabietane and hartite phyllocladane as well as for idrialite a complex polycyclic aromatic hydrocarbon mineral the survival of organic minerals such as oxalates terpenoid hydrocarbons and aromatic minerals in the geological record is important for an appreciation of the diversity of molecular compounds that need to be assessed in the search for life detection signatures in terrestrial and extraterrestrial scenarios

accordant summit heights summit levels and the origin of the upper denudation level in the serra do mar se brazil sao paulo a study of hillslope forms and processes abstract in southern sao paulo the serra do mar is characterized by three distinct terrain types 1 highly dissected areas with closely spaced ridges and accordant summit heights 2 multiconvex hills and 3 terrains with highly elevated watershed areas irregular summit heights and locally subdued relief the development of this landscape is considered to be the result of the cenozoic block faulting and of the influences that are exerted by the differing lithological and structural setting of block faulted compartments on weathering and erosion processes in areas characterized by pronounced accordant summits the close coincidence between hillslope angle and the angle of limiting stability against landsliding points to a close adjustment of hillslope gradients and the mechanical properties of the regolith the relative height of the hillslopes is functionally related to the spacing of the valleys and the gradient of the hillslopes in areas with a regular spacing of v shaped valleys and uniform rocks this leads to the intersection of valley side slopes in summits and ridges at a certain elevation this elevation is determined by the length and steepness of the valley side slopes therefore the heights of the summits are geometrically constrained and are likely to indicate the upper limit of summit heights or an upper denudation level that is adjusted by hillslope processes to the incising streams accordant summit heights of this type are poor indicators of formerly more extensive denudation surfaces as it is also likely that they are a result of the long term adjustment of hillslopes to river incision the steep mountain flanks of block faulted compartments on the other hand comprise regolith covered hillslopes that are closely adjusted to the maximum stable gradient as well as rock slopes that are controlled by the rock mass strength their summits are usually not accommodated into uniform summit levels highly elevated watershed areas exhibiting a subdued relief are detached from the base level response on granitoid rocks these areas are often characterized by the rocky hills and domal rock outcrops however differences in the elevation of interfluves and summits between rocks of differing resistance and in the elevation of lithologically distinct individual fault blocks imply that long term weathering and erosion has transformed and lowered these landscapes therefore these areas cannot be interpreted as a remnant of a pre uplift topography and it appears to be unlikely that the height of the summits correlates with formerly more widespread planation surfaces in the far hinterland the studies indicate that concepts such as the parallel retreat of hillslopes cannot account for the observed differences in the landscape it is suggested that the serra do mar is consumed from the atlantic and the inland side by spatially non uniform developmental states these states are determined by local differences in the coupling and distance to the regional base level and sea level or are due to lithological and structural controls between and within the block faulted compartments

raman spectroscopic and scanning electron microscopic analysis of a novel biological colonisation of volcanic rocks a novel type of colonisation of a basaltic rock collected on the arctic island of svalbard norway during the amase expedition in 2004 was characterised using raman spectroscopy and scanning electron microscopy sem the sample contains two different types of extremophile communities one occurring behind a radial white crystallisation and the other occurring inside a dark vacuole several types of minerals and microbial colonies have been identified by both raman spectroscopy and sem analyses it is the first time that photosynthetic communities have been documented to colonise the inside of dark basaltic rocks our discovery has important implications for planetary exploration because it extends the analytical capability and our understanding of microbial rock colonisations to subaerial volcanic outcrops and has wide implications towards the search for life in extraterrestrial planets in this work we also demonstrate that the use of different laser wavelengths for raman spectroscopic studies and complementary microscopic analysis are critical for a comprehensive organic and inorganic compound identification

paleoecology reconstruction from trapped gases in a fulgurite from the late pleistocene of the libyan desert when lightning strikes the ground it heats melts and fuses the sand in soils to form glass tubes known as fulgurites we report here the composition of co 2 co and no contained within the glassy bubbles of a fulgurite from the libyan desert the results show that the fulgurite formed when the ground contained 0 1 wt organic carbon with a c n ratio of 10 15 and a 13 c of 13 96 compositions similar to those found in the present day semiarid region of the sahel where the vegetation is dominated by c 4 plants thermoluminescence dating indicates that this fulgurite formed 15 k y ago these results imply that the semiarid sahel at 17 n reached at least to 24 n at this time and demonstrate that fulgurite gases and luminescence geochronology can be used in quantitative paleoecology

types chemical and porosity characteristics of hydrocarbon generating organisms of the lower paleozoic south china taking longmaxi formation and qiongzhusi formation in sichuan basin as examples abstract in this study the biotypes chemical structures and porosity characteristics of hydrocarbon generating organisms in the wufeng formation longmaxi formation of the well jiaoye 1 and in the qiongzhusi formation of the well jinye 1 sichuan basin are studied through the systematic organic petrology and geochemical analysis the hydrocarbon generating organisms in the wufeng formation longmaxi formation mainly consist acritarchs and graptolites with other animal fossils observed the hydrocarbon generating organisms of the qiongzhusi formation are mainly acritarchs benthic macroalgae and cyanobacteria together with some animal fossils such as embryos sponge spicules besides cryptospore fossils are found in the bottom of qiongzhusi formation fortunian of the lower cambrian for the first time ever according to raman parameters the change of pyritized acritarch and bitumen in the same thermal evolution process is greater followed by that of organic acritarch and the structural change of graptolite is the smallest ftir spectra shows ether bonds a few aromatic rings some aliphatic chains in the structures of acritarchs and very low content of aliphatic hydrocarbon a large amount of carboxyl groups ether bonds aromatic rings in both graptolite and chitinozoan the acritarch has well developed pores which is of excellent connectivity the epidermis of graptolite is composed of multiple layers of fiber between which develop a lot of narrow pores of good connectivity conodont has many isolated nano pores while the pores of chitinozoan are not developed

non destructive analysis of amber artefacts from the prehistoric cioclovina hoard romania abstract amber beads from the cioclovina hoard hunedoara county romania dating from the transitional period between the late bronze age and the iron age were analysed by fourier transform infrared spectroscopy variable angle reflectance ftir var and fourier transform raman spectroscopy ft raman the aim was to determine if the raw material came from the shores of the baltic sea on the amber route which crosses central europe or if it originated from the area of the main amber occurrences in romania in buz u county around the village of col i all applied analyses strongly suggest that a large part of the amber from the cioclovina deposit has a romanian origin and thus no connection with the amber route

petrology and geochemistry of olivine phyric shergottites lar 12095 and lar 12240 implications for their petrogenetic history on mars larkman nunatak lar 12095 and lar 12240 are recent olivine phyric shergottite lnds we report the results of petrographic and chemical analyses of these two samples to understand their petrogenesis on mars based on our analyses we suggest that these samples are likely paired and are most similar to other depleted olivine phyric shergottites particularly dar al gani dag 476 and sayh al uhaymir sau 005 and samples paired with those the olivine megacryst cores in lar 12095 and lar 12240 are not in equilibrium with the groundmass olivines we infer that these megacrysts are phenocrysts and their major element compositions have been homogenized by diffusion the cores of the olivine megacrysts have mg 70 whereas megacryst rims and groundmass olivines typically have mg 58 60 the rare earth element ree microdistributions in the various phases olivine low and high ca pyroxene maskelynite and merrillite in both samples are similar and support the likelihood that these two shergottites are indeed paired the calculated parent melt i e in equilibrium with the low ca pyroxene which is one of the earliest formed ree bearing minerals has an ree pattern parallel to that of melt in equilibrium with merrillite i e one of the last formed minerals this suggests that the lar 12095 12240 paired shergottites represent the product of closed system fractional crystallization following magma emplacement and crystal accumulation utilizing the europium oxybarometer we estimate that the magmatic oxygen fugacity early in the crystallization sequence was iw finally petrographic evidence indicates that lar 12095 12240 experienced extensive shock prior to being ejected from mars

weddellite occurrence in peats and other organic rich sediments of florida abstract the mineral weddellite calcium oxalate dihydrate is rarely reported in sediments although it is common in biologic materials including plants forest soils and the urinary stones of mammals research designed to evaluate the factors influencing the fuel grade potential of peat deposits in florida has now documented the occurrence of weddellite as a primary constituent in the inorganic ash fraction of peat and other organic rich soils weddellite is believed to originate within the peat forming basin rather than as a product of sample storage or laboratory preparations the mineral s origin is genetically related to the metabolic activity of abundant plant life at the depositional site and its concentration in the basin is directly related to the percentage of organic matter pr served in the sediments scanning electron micrographs reveal that the mineral s characteristic prismatic needle shape is preserved in peat differential thermal analysis shows initial water loss endotherms at approximately 100 c and 200 c followed by exothermic transformations to caco3 at 300 c and to cao near 780 c

biomarkers of holocene buried conifer logs from bella coola and north vancouver british columbia canada abstract the biomarker compositions of a holocene seep oil liquefied resin originating from a buried log of douglas fir pseudotsuga menziesii from bella coola bc canada and a holocene pine wood pinus sp sample from north vancouver bc canada were analyzed using gas chromatography mass spectrometry gc ms the total extract of the bella coola sample contains the sesquiterpenoid derivative calamenene and diterpenoids of the labdane abietane pimarane and phyllocladane classes a novel series of successively degraded labdane derivatives labdan 15 oic acid norlabdanoic acids drimenoic acid was detected in the polar fraction and a diagenetic pathway is proposed aromatic abietanes are the major components in the neutral fraction the neutral fraction of the pine wood contains two sesquiterpenoids calamenene cadalene diterpenoids of the abietane pimarane isopimarane and kaurane classes and a series of steroids 18 norabieta 8 11 13 triene dehydroabietin is the major component among the predominantly aromatic abietanes based on the compositions of the terpenoids it is concluded that the diagenesis of the pine and douglas fir logs probably occurred under anaerobic conditions leading to reductive reactions such as decarboxylation of resin acids with concurrent oxidation reactions to form the aromatic derivatives

petrogenesis of miller range 07273 a new type of anomalous melt breccia implications for impact effects on the h chondrite asteroid miller range 07273 is a chondritic melt breccia that contains clasts of equilibrated ordinary chondrite set in a fine grained 3 gpa possibly to 15 19 gpa and temperature 1350 c possibly to 2000 c the higher pressures and temperatures would have involved back reaction of high pressure polymorphs to pyroxene and olivine upon cooling silicates outside of melt matrix have compositions that were relatively unchanged owing to brief heating duration

shock metamorphism of ordinary chondrites a revised petrographic classification of progressive stages of shock metamorphism of ordinary chondrites is proposed six stages of shock s1 to s6 are defined based on shock effects in olivine and plagioclase as recognized by thin section microscopy the characteristic shock effects of each shock stage are s1 unshocked sharp optical extinction of olivine s2 very weakly shocked undulatory extinction of olivine s3 weakly shocked planar fractures in olivine s4 moderately shocked mosaicism in olivine s5 strongly shocked isotropization of plagioclase maskelynite and planar deformation features in olivine and s6 very strongly shocked recrystallization of olivine sometimes combined with phase transformations ringwoodite and or phases produced by dissociation reactions s6 effects are always restricted to regions adjacent to melted portions of a sample which is otherwise only strongly shocked in stages s3 to s6 localized melting results from stress and temperature peaks which locally deviate from the equilibration shock pressure due to differences in shock impedance these melting effects are a opaque melt veins shock veins b melt pockets with interconnecting melt veins c melt dikes and d troilite metal deposits in fractures based on a critical evaluation of data from shock recovery experiments a shock pressure calibration for the six shock stages is proposed which defines the s1 s2 s2 s3 s3 s4 s4 s5 and s5 s6 transitions at 5 5 10 15 20 30 35 and 45 55 gpa respectively whole rock melting and formation of impact melt rocks or melt breccias occurs at about 75 90 gpa the symbol for the shock stage may be used in combination with the symbol for the petrologic type to abbreviate the complete classification of a chondrite e g h5 s3 we propose this new shock classification and pressure calibration system to replace previous systems which are out of date with respect to the pressure calibration nominally restricted to l chondrites and based on incomplete and in part illdefined sets of shock effects we have classified seventy six ordinary chondrites using the new classification system and conclude the following 1 1 shock effects and the sequence of progressively increasing degrees of shock metamorphism are very similar in h l and ll groups differences in the frequency distribution of shock stages are relatively minor e g l chondrites appear to have the largest fraction with stages s5 and s6 this suggests that the collisional histories of the h l and ll parent bodies were similar 2 2 petrologic type 3 chondrites are deficient in stages s4 to s6 and with increasing petrologic type the frequency of stages s4 to s6 increases we suggest that the more porous and volatile rich type 3 chondrites are subject to melting at a lower shock pressure than the nonporous chondrites of higher petrologic type volatiles trapped in pores cause shock induced dispersal of the shocked and melted material into small particles which are not expected to survive as meteorites 3 3 stage s3 is the most abundant in nearly all petrologic types 4 4 at shock pressures in excess of about 35 gpa s5 and s6 4he and 40ar are almost completely lost pressures below 10 gpa s1 and s2 do not cause noble gas losses

use of alloformations for definition of holocene meander belts in the middle amite river southeastern louisiana geomorphological studies in drainage basins of the northern gulf of mexico coastal plain have indicated similarities in flood plain character and comparable influences on basin evolution alluvial morphology and stratigraphy can be linked to flood plain evolution through the use of alloformations unconformity bounded stratigraphic units this procedure extends classical terrace mapping concepts to conform with formally defined stratigraphic procedures a meander belt segment of the middle amite river valley in southeastern louisiana was selected to test the applicability of alloformation mapping in part of a regional scale 5 000 km 2 drainage basin three alloformations identified as magnolia bridge mag denham springs ds and watson wat can be differentiated by unconformable boundaries landscape morphology and relative pedogenic development the valley fill consists of a lower sandy and upper silty facies preserved deposits consist of channel lag point bar and scroll bar channel fill and overbank sequences lithofacies and sedimentary environments are dependent on fluvial process and a suite of meander belt environments can be identified within each alloformation surface horizons of alluvial soils are all similar ochric epipedons but subsoil horizons are chiefly stratified parent material on the mag entisols cambic horizons on the ds inceptisols and minimally developed argillic horizons on the wat alfisols allostratigraphy provides an objective method for definition of geologic units that contain genetically related but heterogeneous sedimentary deposits alluvial sediments are differentiated in a manner that successfully integrates geomorphic sedimentologic and pedologic data into significant stratigraphic models this approach is applicable to a wide variety of quaternary settings where prior stratigraphic techniques have resulted in ambiguity

submerged late pleistocene reefs on the tectonically stable s e florida margin high precision geochronology stratigraphy resolution of substage 5a sea level elevation and orbital forcing abstract a well preserved submerged in situ fossil reef tract lies offshore of the southeast florida carbonate margin in the florida keys cores in two transects enabled reconstruction of reef stratigraphy and paleoenvironments paleo water depths and paleo sea levels because florida is tectonically stable the elevation data required correction only for the known minor subsidence rate twenty eight pristine aragonitic corals were dated via high precision tims u series methods to produce a comprehensive late pleistocene and early holocene geochronology the pleistocene section of the fossil reef includes a thick section of substage 5a reef growth recorded from 15 to 11 m msl spanning an age range of 86 2 80 9 ka paleoenvironmental reconstruction local water quality constraints and elevations of concurrent bahamian speleothem growth combine to limit sea level to 9 0 m msl at 83 ka this coincides unlagged with the 82 ka 65 n july insolation peak the absence of any lag suggests that the earlier peak in obliquity at 92 ka also controls paleoclimate and sea level a below present sea level estimate for substage 5a from the florida fossil reef data coincides more closely with uplift corrected reef data estimates of 15 to 13 m msl from tectonic margins such as barbados and haiti than with higher than present sea levels derived from detrital corals from bermuda and the u s atlantic coastal plain the best tims dates on corals and speleothem constraining sea level combine to produce a new regional sea level curve for the atlantic caribbean region for late isotope stage 5 and early stage 4

variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite nwa 5298 and improved u pb dating of solar system events abstract the accurate dating of igneous and impact events is vital for the understanding of solar system evolution but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole rock isotopic systems used for geochronology baddeleyite monoclinic zro2 is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust u pb isotopic systematics but there is little understanding of shock effects on this phase here we present new nano structural measurements of baddeleyite grains in a thin section of the highly shocked basaltic shergottite northwest africa nwa 5298 using high resolution electron backscattered diffraction ebsd and scanning transmission electron microscopy stem techniques to investigate shock effects and their linkage with u pb isotopic disturbance that has previously been documented by in situ u pb isotopic analyses the shock altered state of originally igneous baddeleyite grains is highly variable across the thin section and often within single grains analyzed grains range from those that preserve primary magmatic twinning and trace element zonation baddeleyite shock group 1 to quasi amorphous zro2 group 2 and to recrystallized micro granular domains of baddeleyite group 3 these groups correlate closely with measured u pb isotope compositions primary igneous features in group 1 baddeleyites n 5 are retained in high shock impedance grain environments and an average of these grains yields a revised late amazonian magmatic crystallization age of 175 30 ma for this shergottite the youngest u pb dates occur from group 3 recrystallized nano to micro granular baddeleyite grains indicating that it is post shock heating and new mineral growth that drives much of the isotopic disturbance rather than just shock deformation and phase transitions our data demonstrate that a systematic multi stage microstructural evolution in baddeleyite results from a single cycle of shock loading heating and cooling during transit to space and that this leads to variable disturbance of the u pb isotope system furthermore by linking in situ u pb isotopic measurements with detailed micro to nano structural analyses it is possible to resolve the timing of both endogenic crustal processes and impact events in highly shocked planetary materials using baddeleyite this opens up new opportunities to refine the timing of major events across the solar system

shock induced deformation of shergottites shock pressures and perturbations of magmatic ages on mars shergottites and chassignites practiced major deformation effects whose nature magnitude and relevance were controversially evaluated and disputatively debated our studies of many shocked shergottites present contrary to numerous previous reports ample evidence for pervasive shock induced melting amounting of at least 23 vol of the shergottite consisting of maskelynite and pyrrhotite partial melting of pyroxene titanomagnetite ilmenite and finding of several high pressure polymorphs and pressure induced dissociation reactions our results cast considerable doubt on using the refractive index ri or cathodoluminescence cl spectra of maskelynite in estimating the magnitudes of peak shock pressure in both shergottites and ordinary chondrites ri of maskelynite was set after quenching of the feldspar liquid before decompression to maskelynite glass followed by glass relaxation after decompression at the closure temperature of relaxation the ri procedure widely practiced in the past 38 years revealed unrealistic very high pressure estimates discrepant with the high pressure mineral inventory in shocked shergottites and ordinary chondrites and with results obtained by robust laboratory static experiments shergottites contain the silica high pressure polymorphs the scrutinyite structured polymorph seifertite a monoclinic ultra dense polymorph of silica with zro2 structure stishovite a dense liquidus assemblage consisting of stishovite na hexa aluminosilicate na cas and both k lingunite and ca lingunite applying individual high pressure silica polymorphs alone like stishovite to estimate the equilibrium shock pressure is inadequate due to the considerable shift of their nominal upper pressure bounds intrinsically induced by spatially variable absorptions of minor oxides like al2o3 na2o feo mgo and tio2 this practice revealed variable pressure estimates even within the same shergottite subjected to the same peak shock pressure occurrence of na cas stishovite lack of the naalsio4 ca ferrite structured polymorph or jadeite indicates that the peak shock pressures barely exceeded 22 gpa we present convincing and ample evidence refuting the claim that the shock induced high pressure inventory in shergottites and ordinary chondrites are disequilibrium assemblages resulted from local pressure spikes in excess of 80 gpa and during the decompression stage such scenario calls for a series of incomplete and quenched retrograde reactions starting with the crystallization of mg silicate perovskite magnesiowustite if the claimed peak shock pressure was in excess of 80 gpa this would be followed by replacement of this pair by majorite pyrope ss magnesiowustite or akimotoite magnesiowustite below 23 gpa and 2000 degrees c polycrystalline ringwoodite above 16 gpa respectively and finally replacement by polycrystalline olivine below 16 gpa such incomplete retrograde reactions were never encountered in any shergottite chassignite or shocked ordinary chondrite so far olivine ringwoodite phase transformation in the l6 y 791384 commences with the coherent mechanism producing ringwoodite lamellae with their 111 planes parallel to the 100 of olivine followed by the incoherent mechanism due to build up of strain in the parental olivine this is in accord with the olivine ringwoodite settings produced in static laboratory experiments in a multi anvil device olivine ringwoodite phase transitions were also encountered in comparable settings in the shergottite nwa 1068 application of experimentally obtained kinetic parameters of the olivine ringwoodite phase transitions reveals possible duration of the natural dynamic events up to few seconds thus unambiguously refuting the claimed disequilibrium decompression mechanism the shock induced pervasive melting of labradorite pyrrhotite titanomagnetite ilmenite and partial melting of clinopyroxene strongly suggests shock induced partial to complete resetting of the ar ar rb sr sm nd re os u pb and lu hf radiometric systems this also casts considerable doubt on the radiometric ages shorter than 575 ma reported in the past 38 years to allegedly be the igneous crystallization ages these short ages probably resulted from partial or total shock induced age resetting c 2012 elsevier ltd all rights reserved

alkaline rocks from continental brazil abstract the present literature review on brazilian alkaline rocks stresses mainly the petrographic and geologic aspects at least eight different rock associations are represented agewise four groups are found among southern brazilian outcrops an older one about 240 m y only that is still poorly known the massifs clustered around jacupiranga about 130 m y old a few occurrences 100 110 m y old tunas itapirapua and the youngest and most important one with an age spread from about 80 m y to about 53 m y recent research shows a clear tectonic control both on local and on regional scales of alkaline occurrences in southern brazil alkaline magmatism was set off by pre drift and drift activity and is at its onset geologically related to basaltic activity emplacement of many massifs is also locally controlled by old lineaments e g in the minas gerais goias belt as is emphasized by geophysical data on a petrographic and chronologic basis several alkaline provinces are distinguished in southern brazil preliminary data on the cambrian precambrian rocks from southern bahia state a province with undersaturated syenites and litchfieldites and from cratonic areas in northern brazil are also presented

shock metamorphism and petrography of the shergotty achondrite the shergotty subsamples 1 and 12 consist of augite and pigeonite 67 5 maskelynite 24 ilmenite and titanomagnetite 2 pyrrhotite 0 4 whitlockite 1 8 apatite 0 1 quartz 0 5 baddeleyite trace fayalite 0 4 mesostasis 3 and shock induced local polymineralic melt products 0 6 the overall modal composition is similar to other shergotty samples except for the rather high whitlockite content the shock effects observed in the mineral constituents include mosaicism deformation bands planar fractures and mechanical twin lamellae in clinopyroxene isotropization of plagioclase with very rare remnants of birefringence planar deformation structures mosaicism and strongly reduced birefringence in quartz mechanical twinning of ilmenite localized in situ melting of neighbouring minerals at the contact of low and high density phases based on the refractive index of maskelynite average 1 5467 with average an content of 49 and the degree of isotropization of the plagioclase an equilibrium shock pressure of 29 1 gpa is derived the inferred post shock temperature is 200 20 c no heating event could have exceeded 400 c duke 1968 local stress and temperature concentrations reach 60 80 gpa and 1600 2000 c the observed shock effects can be explained by a single shock event a second weaker shock event as found by others appears to be highly improbable equilibrium shock pressures and post shock temperatures for the other known shergottites are 31 2 gpa and 220 50 c zagami 43 2 gpa and 400 800 c alha 77005 the pressure estimate for eeta 79001 by lambert 1985 is confirmed 34 1 gpa the post shock temperature is 250 50 c the abundance and textural setting of localized melt products in these meteorites confirm increasing shock pressures in the sequence shergotty zagami eeta 79001 alha 77005 undoubtedly the melts could have been formed by the same single shock which produced the equilibrium shock effects e g maskelynitization in these meteorites the shock induced particle velocities inferred from hugoniot data of basalts are in the 1 5 2 0 km s range for the parental rocks of the shergottites ejection velocities are therefore in the order of 3 4 km s special ejection mechanisms are required in order to exceed the escape velocity of a planet like mars without producing higher degrees of shock e g melting than those observed in the shergottites

the effect of land plants on weathering rates of silicate minerals abstract land plants and their associated microbiota directly affect silicate mineral weathering in several ways by generation of chelating ligands by modifying ph through production of co2 or organic acids and by altering the physical properties of a soil particularly the exposed surface areas of minerals and the residence time of water in laboratory experiments far from equilibrium 1 mm oxalate a strong chelator of al has a negligible effect on the dissolution rate of alkali feldspars but some effect on calcic feldspars and olivine by analogy to oxalate the overall effect of organic ligands on the weathering rate of silicate minerals in nature is likely to be small except perhaps in microenvironments adjacent to roots and fungal hyphae the effect of ph on silicate mineral dissolution rate depends on ph below ph 4 5 the rate increases with decreasing ph in the circumneutral region the rate is ph independent and at ph values above around 8 the rate increases with increasing ph vegetation should thus cause an increase in weathering rate through the ph effect only where the ph is below 4 5 as an overall generalization the effect of plants on weathering rate through changes in soil solution chemistry is probably small for granitic rocks it may be greater for more mafic rocks it is the release of ca and mg from mafic rocks that has the greatest influence on the global co2 budget the effect of changes in soil physical properties on weathering rate can be major by binding fine particles plants can greatly increase weathering rates in areas of high physical erosion where erosion rates are lower the effect of plants is less clear on long timescales plants may decrease chemical weathering by binding secondary products and isolating unweathered minerals from meteoric water a major unknown in estimating the effect of the advent of land plants on weathering rates is the nature thickness particle size distribution permeability of the regolith on the pre silurian continents the indirect effect of vegetation through changing the regional distribution of precipitation may be as important as the direct effects

sea level and deep water temperature changes derived from benthic foraminifera isotopic records we show that robust regressions can be established between relative sea level rsl data and benthic foraminifera oxygen isotopic ratios from the north atlantic and equatorial pacific ocean over the last climatic cycle we then apply these regressions to long benthic isotopic records retrieved at one north atlantic and one equatorial pacific site to build a composite rsl curve as well as the associated confidence interval over the last four climatic cycles our proposed reconstruction of rsl is in good agreement with the sparse rsl data available prior to the last climatic cycle we compute bottom water temperature changes at the two sites and at one southern indian ocean site taking into account potential variations in north atlantic local deep water 18o our results indicate that a last glacial maximum lgm enrichment of the ocean mean oxygen isotopic ratio of 0 95 is the lowest value compatible with unfrozen deep waters in the southern indian ocean if local deep water 18o did not increase during glacials with respect to present such a value of the lgm mean ocean isotopic enrichment would impose a maximum decrease in local bottom water 18o at the north atlantic site of 0 30 during glacials

nanoscale chemical characterisation of phase separation solid state transformation and recrystallization in feldspar and maskelynite using atom probe tomography the feldspar minerals occur in a wide variety of lithologies throughout the solar system often containing a variety of chemical and structural features indicative of the crystallization conditions cooling history and deformational state of the crystal such phenomena are often poorly resolved in micrometre scale analyses here atom probe tomography apt is conducted on ca rich bytownite and na rich albite plagioclase reference materials experimentally exsolved k feldspar sanidine shock induced plagioclase glass labradorite composition and shocked and recrystallized plagioclase to directly test the application of apt to feldspar and yield new insights into crystallographic features such as amorphisation and exsolution undeformed plagioclase reference materials amelia albite and stillwater bytownite appear chemically homogenous and yield compositions largely within uncertainty of published data within microstructurally complex materials apt can resolve chemical variations across a 20 nm wide exsolution lamella and define major element na k diffusion profiles across the lamella boundaries which appear gradational over a 10 nm length scale in experimentally exsolved k feldspar nnpp 04b the plagioclase glass within the zagami shergottite shows no heterogeneity in the distribution of major elements although the enrichment of fe mg and sr in the bulk microtip points to at least minor incorporation of surrounding phases pyroxene and with that supports a shock melt origin for the glass maskelynite the recrystallization of feldspar during post shock annealing such as in poikilitic shergottite nwa 6342 appears to induce a range of chemical nanostructures that locally effect the composition of the material these findings demonstrate the ability of apt to yield new insights into nanoscale composition and chemical structures of alumniosilicate phases highlighting an exciting new avenue with which to analyse these key rock forming minerals

biomarkers and their raman spectroscopic signatures a spectral challenge for analytical astrobiology the remote robotic exploration of extraterrestrial scenarios for evidence of biological colonization in search for life missions using raman spectroscopy is critically dependent on two major factors firstly the raman spectral recognition of characteristic biochemical spectral signatures in the presence of mineral matrix features and secondly the positive unambiguous identification of molecular biomaterials which are indicative of extinct or extant life both of these factors are considered here the most important criterion is the clear definition of which biochemicals truly represent biomarkers whose presence in the planetary geological record from an analytical astrobiological standpoint will unambiguously be indicative of life as recognized from its remote instrumental interrogation also discussed in this paper are chemical compounds which are associated with living systems including biominerals which may not in themselves be definitive signatures of life processes and origins but whose presence provides an indicator of potential life bearing matrices

age and duration of weathering by 40k 40ar and 40ar 39ar analysis of potassium manganese oxides supergene cryptomelane k1 2 mn3 mn4 8o16 h2o samples from deeply weathered pegmatites in southeastern brazil subjected to 40k 40ar and 40ar 39ar analysis yielded 40k 40ar dates ranging from 10 1 0 5 to 5 6 0 2 ma million years ago laser probe 40ar 39ar step heating of the two most disparate samples yielded plateau dates of 9 94 0 05 and 5 59 0 10 ma corresponding within 2 to the 40k 40ar dates the results imply that deep weathering profiles along the eastern brazilian margin do not reflect present climatic conditions but are the result of a long term process that was already advanced by the late miocene weathering ages predate pulses of continental sedimentation along the eastern brazilian margin and suggest that there was a time lag between weathering and erosion processes and sedimentation processes

mineral chemistry of muses c regio inferred from analysis of dust particles collected from the first and second touchdown sites on asteroid itokawa the mineralogy and mineral chemistry of itokawa dust particles captured during the first and second touchdowns on the muses c regio were characterized by synchrotron radiation x ray diffraction and field emission electron microprobe analysis olivine and low and high ca pyroxene plagioclase and merrillite compositions of the first touchdown particles are similar to those of the second touchdown particles the two touchdown sites are separated by approximately 100 meters and therefore the similarity suggests that muses c regio is covered with dust particles of uniform mineral chemistry of ll chondrites quantitative compositional properties of 48 dust particles including both first and second touchdown samples indicate that dust particles of muses c regio have experienced prolonged thermal metamorphism but they are not fully equilibrated in terms of chemical composition this suggests that muses c particles were heated in a single asteroid at different temperatures during slow cooling from a peak temperature of approximately 800 c chemical compositions of plagioclase and k feldspar seem to have been modified ab and or contents changed during cooling but an did not this compositional modification is reproduced by a numerical simulation that modeled the cooling process of a 50 km sized itokawa parent asteroid after cooling some particles have been heavily impacted and heated which resulted in heterogeneous distributions of na and k within plagioclase crystals impact induced chemical modification of plagioclase was verified by a comparison to a shock vein in the kilabo ll6 ordinary chondrite where na k distributions of plagioclase have been disturbed

carbon isotopic composition of whewellite cac2o4 h2o from different geological environments and its significance carbon isotopic composition of whewellite cac2o4 h2o varies significantly among individual types of occurrences from the bohemian massif czech republic the 13c values of whewellite found inside pelosiderite concretions in the coal bearing carboniferous kladno basin are unusually high from 3 2 to 14 7 indicating influence of bacterial activity on the oxalate carbon isotopic composition in the tertiary northern bohemian basin where the depth of burial and coalification grades are much lower the 13c values of two whewellite samples are 6 9 and 14 2 whewellites from low temperature hydrothermal veins of the p ibram uranium deposits where bacterial processes are highly unlikely have 13c values of 31 7 to 28 4 identical to carbon isotopic composition of underlying black shales

rapid and widespread response of the lower mississippi river to eustatic forcing during the last glacial interglacial cycle discussion shen et al 2012 1 address critical issues related to fluctuating late pleistocene sea levels associated climate phases and their likely impact during erosion and aggradation episodes in the lower and middle mississippi river valley nineteen new pleistocene optically stimulated luminescence

geological investigation and optical dating of quaternary siliciclastic sediments near apalachicola north west florida usa ground penetrating radar and single aliquot regenerative dose optically stimulated luminescence were used to determine the depositional environments and age of unconsolidated siliciclastic sediments near apalachicola florida five direct push cores five vibracores and 28 optically stimulated luminescence samples were collected as well as 7 km of ground penetrating radar data a new model of cosmic dose rate calculation which removes the effect of a much younger aeolian cap was utilized to calculate more representative optically stimulated luminescence ages five radar facies were identified based on reflector amplitude and orientation the resulting data indicate that the tertiary quaternary shelly sediments were deposited before marine isotope stage 6 the quaternary alluvium was deposited during marine isotope stage 6 and the quaternary beach ridge and dune was deposited during the marine isotope stage 5e sea level highstand which peaked at approximately 2 5 m above present sea level in this area

modern day tectonic subsidence in coastal louisiana subsidence is leading to the slow inundation of communities and wetlands of louisiana mississippi texas and alabama united states by the gulf of mexico the prevailing paradigm considers subsidence to be the result of young sediment compaction and or consolidation and human activities this paper describes the results of a test of this theory based on an examination of historic motions of benchmark in the michoud area of orleans parish louisiana this methodology allowed for an assessment of vertical change at different levels over time relative to a precise vertical datum north american vertical datum of 1988 navd88 data do not support the current theory on the origins of subsidence they demonstrate that tectonic causes dominate in the study area during 1969 1971 and 1971 1977 tectonism was responsible for 16 9 mm yr and 7 1 mm yr of subsidence respectively these contributions account for 73 and 50 of the total subsidence during these intervals the change in deep subsidence is attributed to renewed motion along a large normal fault michoud fault over the same time intervals intermediate depth subsidence due to compaction of pleistocene to middle miocene strata was constant 4 6 mm yr similarly subsidence due to shallow processes i e sediment compaction and groundwater offtake was 1 5 mm yr and 2 5 mm yr subsidence associated with petroleum extraction was not a factor due to the lack of local production

gulf coastal plain evolution in west louisiana heavy mineral provenance and pleistocene alluvial chronology abstract high resolution heavy mineral analysis hrhma of late pleistocene terrace samples their tertiary source rocks and modern river sediments provided an effective tool for reconstructing sediment provenance and mapping heavy mineral provinces in southwest louisiana each province linked to a discrete source region represents pleistocene fluvial channel belts within which depositional activity was controlled by periods of climate sediment supply and sea level changes four coastal heavy mineral provinces have been identified the northern province np drained by the lower reaches of the sabine and calcasieu rivers underlies level mid and late pleistocene coastal terrace surfaces and is distinguished by high grade metamorphic assemblages kyanite staurolite sillimanite and abundant zircon probably of ouachita mts derivation transporting eroded cretaceous tertiary and pleistocene coastal plain deposits the modern calcasieu and sabine river sands in west central and southwest louisiana and east texas display identical heavy mineral composition to that of the np level late pleistocene coastal terrace areas in the east represent the red river province rrp with dominant epidote tourmaline garnet and zircon its mineralogy is influenced significantly by paleozoic mesozoic sedimentary units that frame the drainage basin upstream modern red river sands differ in their spectra both from red river pleistocene coastal terrace and valley terrace deposits interpreted by temporal fluctuations in sediment supply initiating a variable contribution of detritus from different sources tributaries that drain formations with high concentrations of high grade metamorphic minerals also affected red river valley pleistocene terrace deposits in west central louisiana enriching them in kyanite and staurolite the mississippi province mp occupies the eastern southeastern area of the low flat gently seaward sloping prairie coastal terrace whereas modern mississippi alluvium is dominated by hornblende pyroxenes and epidote as the result of post depositional dissolution pyroxenes are rare in the mp the mixed suite province msp reflects mp rrp and to a lesser degree np signatures and forms the prairie fluvial coastal plain surface closer to the texas state line raw data of the principal heavy minerals were used for statistical analysis statistical parameters proved consistent with mineralogy derived reconstruction of sediment provenance and provinciality of heavy mineral suites thus providing an independent and objective support to data interpretation optical and thermal luminescence dating at other gulf locations otvos e g 2005 numerical chronology of pleistocene coastal plain and valley development extensive aggradation during glacial low sea levels quaternary internat 135 91 113 supports the pre sangamon ages of the intermediate pleistocene terraces in the np area sangamon 135 116 ka eowisconsin 114 76 ka and wisconsin 74 36 ka dates characterize the four provinces in the low level northern gulf prairie coastal plain refuting earlier assumptions that coastal plain aggradation occurred only during marine highstand phases thermal and optical luminescence dates indicated that despite the low eowisconsin and wisconsin eustatic sea levels of several preglacial and glacial stages and substages coastal plain alluviation paradoxically recurred between 106 and 35 ka bp an interesting outcome of our heavy mineral study is the recognition and dating of a previously undocumented rare ash fall event that originated in caribbean andesitic volcanoes it was identified by the presence of a volcanogenic heavy mineral suite composed of pristine euhedral clinopyroxene sphene zircon apatite and hexagonal biotite unaffected by fluvial reworking this suite was recovered from a mp sample dated ca 86 ka bp

shock events in the solar system the message from minerals in terrestrial planets and asteroids impacts are central to the origin and evolution of planets of the solar system the shapes of craters which can reach up to 1 000 km in diameter on the moon provide critical information on the large scale dynamics of the impact and related shock minerals formed at high pressure and temperature found in shocked terrestrial rocks and meteorites give additional and complementary insights on the shock process at a smaller scale typically from a few micrometers to a few millimeters local flaws in rocks such as voids and mineral interfaces are the preferential sites for the formation of high pressure melts and minerals calculations based on the physics of shocks and the thermodynamics and kinetics of mineral transformations provide orders of magnitude for the duration transient pressure and prevailing temperature conditions of shock events case studies on shocked terrestrial and extraterrestrial materials illustrate the links between these parameters and impact duration many of the high pressure min

a new natural high pressure na ca hexaluminosilicate caxna1 x al3 xsi3 xo11 in shocked martian meteorites a ca na hexaluminosilicate whose ca end member was previously synthesized in numerous high pressure experiments has been identified by raman spectroscopy in heavily shocked martian meteorites this mineral has a structural formula close to caxna1 x al3 xsi3 xo11 and is similar to the calcium aluminum silicate phase previously synthesized in high pressure experiments performed on anorthite and rocks of basaltic composition this new mineral occurs in shock melt pockets in two distinct settings and is intimately intergrown with sio2 stishovite the first setting encountered in zagami consists of idiomorphic equant crystals overgrown by acicular stishovite that crystallized from a melt of labradorite composition the second setting contains the na ca hexaluminosilicate phase intergrown with stishovite and hollandite and was formed during partial melting at high pressures the mineralogical association na ca hexaluminosilicate stishovite was observed in shock melt pockets which have distinct bulk compositions in seven martian shergottites this new mineral represents after majorite the second natural occurrence of a silicate mineral with silicon in both four and six coordination the assemblage stishovite na ca hexalummosilicate sets constraints on the pressure and temperature conditions that prevailed during shock in some of the studied meteorites the na ca hexaluminosilicate mineral is a potential carrier of al and na during subduction of oceanic crust in the lower mantle of the earth c 2003 elsevier b v all rights reserved

first early mesozoic amber in the western hemisphere detrital amber pebbles and granules have been discovered in upper triassic strata on the colorado plateau although amber pre viously has been reported from pennsylvanian jurassic cretaceous and tertiary strata we know of no other reported triassic occurrence in north america or the western hemisphere the newly discovered occurrences of amber are at two localities in the lower part of the petrified forest member of the upper triassic chinle formation in petrified forest national park arizona the paper coals and carbonaceous paper shales containing the amber also contain fossil palynomorph assemblages that indicate a late carnian age for these occurrences

conversion of carbonaceous material to graphite within the greywacke zone of the eastern alps morphology and reflectance of carbonaceous material cm in late carboniferous metasediments of the eastern greywacke zone eastern alps indicate a mixture of vitrinite grainy textured and lamellar shaped particles as imaged by high resolution atomic force microscopy vitrinite and the grainy textured particles show mesophase structures which can be described as facetted nanocrystals within the carbon matrix high resolution transmission electron microscopy has revealed two types of microtextures representing different degrees of graphitization the first type is characterized by elongated ring shaped microtextures whereas the second type is characterized by graphite lamellae and polygonal flakes with long range ordered aromatic layers in spite of the heterogeneity of the cms the geographical distribution of quantitative metamorphic parameter raman spectra parameter x ray diffraction pattern microscopic reflectance suggests a graphitization process which is promoted by advective heat transport during post collisional processes in a tentative pressure time path late cretaceous thrusting results in a turbostratic ordering of the aromatic layer ordering to long range ordered aromatic layers was achieved during the late cretaceous paleogene exhumation of mid crustal rocks beneath the eastern greywacke zone

176lu 176hf and 147sm 143nd ages of the martian shergottites evaluation of the shock resetting hypothesis through diffusion kinetic experiments and modeling and petrological observations abstract we address the age controversy of the shergottite suite of martian meteorites 200 ma dates determined by 176lu 176hf 147sm 143nd and various other decay systems as opposed to a 4 ga whole rock pb pb date by calculating the timescales needed to reset hf and nd isotopes in clinopyroxene which is the primary host of rare earth elements amongst the minerals used to compose the 176lu 176hf and 147sm 143nd isochrons at the peak and post shock p t conditions likely to have been experienced by the shergottites it is concluded that impact heating is highly unlikely to have significantly reset the 176lu 176hf and or 147sm 143nd mineral isochrons of these meteorites this conclusion is bolstered by the nature of measured concentration profiles of cr and fe across olivine maskelynite boundaries and ti profiles across clinopyroxene maskelynite melt interfaces in the shergottite rbt 04262 the lack of any evidence of diffusion in the measured concentration profiles coupled with the qualitative incompatibility of the measured crystal melt fractionation trends at these interfaces with the nature of fractionation expected from equilibrium partitioning provides strong evidence that no substantial chemical exchange took place between the solid and melt phases during peak shock p t conditions furthermore we find that the compositional profiles of major elements in coexisting augite and pigeonite are homogenous and reflect a magmatic temperature of 1143 9 c we argue that the pyroxene compositions and consequently the 176lu 176hf and 147sm 143nd geochronometers were highly unlikely to have been reset by the thermal effect of a shock event x ray mapping of a selected section of rbt 04262 shows no evidence of enhanced grain boundary diffusion we thus conclude that the 200 ma dates recorded by the 176lu 176hf and 147sm 143nd geochronometers most likely record the crystallization age of the shergottites

formation of feldspathic and metallic melts by shock in enstatite chondrite reckling peak a80259 the enstatite chondrite reckling peak rkp a80259 contains feldspathic glass kamacite troilite and unusual sets of parallel fine grained enstatite prisms that formed by rapid cooling of shock melts metallic fe ni and troilite occur as spherical inclusions in feldspathic glass reflecting the immiscible fe ni s and feldspathic melts generated during the impact the fe ni s and feldspathic liquids were injected into fractures in coarse grained enstatite and cooled rapidly resulting in thin 10 m semicontinuous to discontinuous veins and inclusion trails in host enstatite whole rock melt veins characteristic of heavily shocked ordinary chondrites are conspicuously absent raman spectroscopy shows that the feldspathic material is a glass elevated mgo and sio2 contents of the glass indicate that some enstatite and silica were incorporated in the feldspathic melt metallic fe ni globules are enclosed by sulfide and exhibit nienrichment along their margins characteristic of rapid crystallization from a fe ni s liquid metal enclosed by sulfide is higher in si and p than metal in feldspathic glass and enstatite possibly indicating lower o fugacities in metal sulfide than in silicate domains fine grained elongate enstatite prisms in troilite or feldspathic glass crystallized from local pyroxene melts that formed along precursor grain boundaries but most of the enstatite in the target rock remained solid during the impact and occurs as deformed coarsegrained crystals with lower cao al2o3 and feo than the fine grained enstatite reckling peak a80259 represents an intermediate stage of shock melting between unmelted e chondrites and whole rock shock melts and melt breccias documented by previous workers the shock petrogenesis of rkpa80259 reflects the extensive impact processing of the enstatite chondrite parent bodies relative to those of other chondrite types

defining the mechanisms that disturb the sm nd isotopic systematics of the martian meteorites examples from dar al gani 476 and allan hills 77005 microbeam studies of martian meteorites dar al gani dag 476 and allan hills alh 77005 have been conducted to identify potential causes of disequilibrium exhibited in their sm nd isotopic systematics olivine and maskelynite mineral fractions on the dag 476 isochron are displaced relative to their positions as dictated by measured mineral compositions the olivine mineral fractions from alh 77005 not only have a relatively low sm nd ratio but appear to contain an unradiogenic component that shifts the olivine mineral fraction off the isochron defined by the pyroxene and maskelynite mineral fractions trace components such as melt inclusions impact melt high si mesostasis and altered olivine were analyzed using scanning electron microscopy quantitative electron microscopy and secondary ion mass spectrometry to determine their potential for disturbing the isotopic systematics of the mineral fractions assuming that the mineral fractions were not completely pure mixing models indicate that the presence of melt inclusions in the dag 476 olivine mineral fraction lowered its sm nd ratio the maskelynite mineral fraction contains a related but more evolved mesostasis component that raised the sm nd ratio of the fraction the position of two olivine mineral fractions below the alh 77005 isochron is interpreted to reflect small additions of impact melt with a light rare earth element enriched pattern and a non indigenous unradiogenic nd component furthermore the presence of rare earth elements in olivine and maskelynite from both igneous and non igneous components such as melt inclusions mesostasis and impact melt is observed on a fine 30 m scale despite the addition of this material the sm nd ages are not affected this study demonstrates that detailed mineral separation procedures as employed by modern geochronology laboratories permit reliable ages to be derived from shocked and altered samples

shock experiments on pre heated α and β quartz ii x ray and tem investigations quartz single crystals pre heated to different temperatures 20 275 540 and 630 c were experimentally shocked to pressures ranging from 20 to 40 gpa with the shock front propagating parallel to 1010 or 0001 shocked quartz pre heated to 630 c is nearly x ray amorphous at 26 gpa while quartz shocked at room temperature still displays several x ray diffraction lines up to 30 gpa all samples that were still crystalline when shocked above 25 gpa exhibit lattice expansion internal strain and reduced crystallite sizes lattice expansion was up to 1 for the constants a o and co and up to 3 for the cell volume v o quartz shocked parallel to 1010 always shows larger lattice constants and is more strained than quartz shocked parallel to 0001 indicating that shock effects are controlled by the structural anisotropy internal strain is anisotropic with minimum strain in the planes belonging to 1012 the dominant shock defect revealed by tem are sets of parallel lamellae consisting of pure sio 2 glass so called planar deformation features pdfs below 25 gpa pdfs are extremely rare and thin 30 nm at pressures above 25 gpa however pdfs occur frequently and are about ten times thicker this qualitative observation of increasing pdf frequency and thickness with increasing pressure is quantified by calculations of the amount of glass using x ray and density data the results of this study substantiate the crucial role of pdfs for the lattice expansion of quartz and the formation of diaplectic glass and lechatelierite lattice expansion is ascribed to the enormous expansion of pdfs during decompression leading to elastic stretching in adjacent crystalline areas the observation that pdfs occur predominantly parallel to 1012 where minimum strain is present supports this hypothesis the increasing amount of pdfs above 25 gpa is interpreted as the cause for the formation of diaplectic glass shock temperature calculations support the assumption that these pdfs consist under compression of superheated melt the heat is possibly sufficient to melt crystalline areas adjacent to the superheated pdfs at enhanced pressures such molten bands coalesce to a total melt which is quenched upon decompression thus diaplectic glass represents a quenched high pressure melt while lechatelierite sio 2 glass with a fluidal texture is interpreted as quenched low pressure melt

lunar highland meteorite dhofar 026 and apollo sample 15418 two strongly shocked partially melted granulitic breccias studies of lunar meteorite dhofar 026 and comparison to apollo sample 15418 indicate that dhofar 026 is a strongly shocked granulitic breccia or a fragmental breccia consisting almost entirely of granulitic breccia clasts that experienced considerable post shock heating probably as a result of diffusion of heat into the rock from an external hotter source the shock converted plagioclase to maskelynite indicating that the shock pressure was between 30 and 45 gpa the post shock heating raised the rock s temperature to about 1200 c as a result the maskelynite devitrified and extensive partial melting took place the melting was concentrated in pyroxene rich areas all pyroxene melted as the rock cooled the partial melts crystallized with fine grained subophitic poikilitic textures sample 15418 is a strongly shocked granulitic breccia that had a similar history but evidence for this history is better preserved than in dhofar 026 the fact that dhofar 026 was previously interpreted as an impact melt breccia underscores the importance of detailed petrographic study in interpretation of lunar rocks that have complex textures the name impact melt has in past studies been applied only to rocks in which the melt fraction formed by shock induced total fusion recently however this name has also been applied to rocks containing melt formed by heating of the rocks by conductive heat transfer assuming that impact is the ultimate source of the heat we urge that the name impact melt be restricted to rocks in which the bulk of the melt formed by shock induced fusion to avoid confusion engendered by applying the same name to rocks melted by different processes

equilibrium scale and inheritance in geomorphology abstract of the many equilibrium terms that have been proposed only two are needed dynamic equilibrium in the original sense of g k gilbert 1877 and steady state the former refers to the relationship between the process components of a system the latter to the system as a whole the tendency towards establishing a dynamic equilibrium is inherent in all natural systems that contain negative feedbacks between processes capable of compensating each other in geomorphology equilibrium tendencies of the mass budget are more relevant than those of the energy budget the validity of the equilibrium concept is discussed at several scales from a slope point to entire slopes drainage basins and mountain ranges the effects of eksystemic changes vary depending upon the length of the intervals between such changes in comparison to the length of the required relaxation times this relationship also applies to the influence of inherited forms patterns and materials that have become components of present day systems

depositional environment of the late miocene hausruck lignite alpine foreland basin insights from petrography organic geochemistry and stable carbon isotopes abstract lignites and fossil wood from two boreholes in the late miocene hausruck district alpine foreland basin austria were investigated with respect to organic carbon and total sulfur contents ash yields maceral composition organic geochemistry and stable carbon isotope ratios the lignites from the two sampled profiles differ in sulfur contents and petrography based facies indicators gelification index gi tissue preservation index tpi the results point to drier and more acidic conditions in the part of the mire sampled at drill site lukasberg whereas the lignites from kalletsberg formed under near neutral conditions due to a raised ground water table the different depositional environments are supported by the paleogeographic positions of the boreholes borehole lukasberg is located within a paleo valley whereas borehole kalletsberg is located at the deeper part of a basin situated south and southwest of the hausruck area environmental changes with time within the mire are confirmed by the molecular composition of the soluble organic matter som differences in pristane phytane ratio isomerisation of hopanes at position 17 concentrations of hopanes and in the ratio of hopanes to hop 17 21 enes are related to the extent of gelification of plant tissue sulfur content and ph values caused by differences in ground water table the variable contents of individual terpenoid hydrocarbons derived from land plants indicate that angiosperms and conifers contribute to peat formation in the hausruck district in variable proportions overall angiosperm biomarkers slightly predominate the tissue preservation index tpi within the kalletsberg profile is probably governed by the proportion of decay resistant conifers as indicated by the correlation between tpi and biomarker composition of the coals correlations between 13 c values of the lignites between 24 9 and 27 4 and their non hopanoid terpenoid composition indicate the major influence of changes in peat forming vegetation on the carbon isotopic composition of the coals in the hausruck district carbon isotope data of macrofossils are consistent with their taxonomical classification as conifers 13 c between 22 7 and 25 1 and angiosperms 13 c between 25 5 and 26 6 respectively the 13 c data of the extracted cellulose reveal clear differences between fossil wood from gymnosperms average 13 c 21 0 and angiosperms mean 13 c 23 4

the nature of maskelynite in shocked meteorites not diaplectic glass but a glass quenched from shock induced dense melt at high pressures abstract maskelynite an important constituent of shocked meteorites once thought to be diaplectic plagioclase glass formed by shock induced solid state transformation our systematic investigation of shocked l chondrites and snc meteorites indicates that maskelynite does not contain inherited fractures or cleavage and shock induced fractures we found no evidence for models calling for melting that initiated in pdfs and affected the whole crystals maskelynite grains are smooth and display radiating cracks emerging from their surfaces into neighboring pyroxene this is indicative of shock induced melting and quenching of the dense melt at high pressure thus erasing the inherited and shock induced fractures this was followed by relaxation of the dense plagioclase glass which induced the expansion cracks in pyroxene and olivine enrichment in potassium deviation from stoichiometry degradation of igneous zoning the presence of offshoots of maskelynite in pyroxene the lack of vesiculation in the melt pockets melt veins and molten mesostasis are clear evidence for melting and quenching under high pressure our investigations present unequivocal evidence that maskelynite in meteorites is not diaplectic plagioclase glass formed by solid state transformation but a dense quenched glass the duration of the shock pulse in natural events can be several orders of magnitude longer than in shock experiments since kinetic effects are crucial factors in promoting phase transitions vitrification and melting experimentally induced solid state vitrification of plagioclase produced in dynamic experiments is inadequate for calibration of peak shock pressures in maskelynite bearing natural samples

plagioclase breakdown as an indicator for shock conditions of meteorites the collision history of asteroids in the early solar system is difficult to reconstruct a study of plagioclase breakdown using x ray diffraction measurements under increasing pressures and temperatures suggests that peak pressures in collisions that formed shocked meteorites have been overestimated shocked meteorites that were formed when their parent body underwent shock metamorphism often contain the mineral plagioclase either in an amorphous form or in its high pressure phase the peak pressures in shock metamorphism can be constrained by shock recovery experiments that determine the amorphization pressures of plagioclase1 2 3 however in these experiments temperatures have been unrealistically low and timescales much shorter than those in natural events here we present in situ x ray diffraction measurements of two kinds of plagioclase feldspar in conditions of increasing pressures and temperatures we find that the amorphization pressure of plagioclase decreases with increasing temperature suggesting that previous studies overestimated this parameter1 2 3 we also found that the mineral jadeite forms first from amorphous plagioclase whereas the nucleation of other minerals such as stishovite or garnet is significantly delayed the occurrence of jadeite in shocked meteorites that do not contain stishovite4 5 6 7 8 can therefore be explained as a result of the crystallization kinetics we conclude that the study of plagioclase breakdown can constrain the pressure temperature time history of shock events and thus help to reconstruct the collisional history of asteroids in the early solar system

shock barometer using cathodoluminescence of alkali feldspar 1 color cathodoluminescence cl images of unshocked and experimentally shocked sanidine at pressures up to 40 1 gpa showed red violet emission below 20 0 gpa and blue emission above 20 0 gpa the phases in these shock recovered samples were identified as crystalline feldspar for red violet emitting areas and as diaplectic feldspar glass for blue emitting ones by micro raman spectroscopy cl spectra of these shocked sanidine have emissions at 330 380 and 400 420 nm of which intensities increase with an increase in shock pressure similar uv blue emissions were found in alkali feldspar and the glass in martian meteorites and ries crater impactite the deconvolution of these cl spectra provides the emission component at 2 948 ev assigned to shock induced defect center where this intensity correlates linearly with peak shock induced pressure on sanidine with little dependence on composition and structure the correlation gives quantitative values of the shock pressures experienced by the feldspar resulting in estimated shock pressures of martian meteorites and ries crater impactite the cl intensity of feldspar has a potential for a universal shock barometer with high spatial resolution 1 m and in a wide pressure range theoretically 4 5 40 1 gpa this leads to a breakthrough in understanding the impact histories on earth moon and mars

breccia formation at a complex impact crater slate islands lake superior ontario canada abstract the slate islands impact structure is the eroded remnant of a 30 32 km diameter complex impact structure located in northern lake superior ontario canada target rocks are archean supracrustal and igneous rocks and proterozoic metavolcanics metasediments and diabase a wide variety of breccias occurs on the islands many of which contain fragments exhibiting shock metamorphic features aphanitic narrow and inclusion poor pseudotachylite veins commonly with more or less parallel boundaries and apophyses branching off them represent the earlist breccias formed during the compression stage of the impact process coarse grained polymictic clastic matrix breccias form small to very large inclusion rich dikes and irregularly shaped bodies that may contain altered glass fragments these breccias have sharp contacts with their host rocks and include a wide range of fragment types some of which were transported over minimum distances of 2 km away from the center of the structure they cut across pseudotachylite veins and contain inclusions of them field and petrographic evidence indicate that these polymictic breccias formed predominantly during the excavation and central uplift stages of the impact process monomictic breccias characterized by angular fragments and transitional contacts with their host rocks occur in parautochthonous target rocks mainly on the outlying islands of the slate islands archipelago a few contain fragmented and disrupted coarse grained polymictic clastic matrix breccia dikes this is an indication that at least some of these monomictic breccias formed late in the impact process and that they are probably related to a late crater modification stage a small number of relatively large occurrences of glass poor suevitic breccias occur at the flanks of the central uplift and along the inner flank of the outer ring of the slate islands complex crater a coarse glass free allogenic breccia containing shatter coned fragments derived from proterozoic target rocks upper target strata observed at two locations may be analogous to the bunte breccia of the ries crater in germany at one of these locations this breccia lies close to a crater suevite deposit at the other it overlies parautochthonous monomictic breccia the slate islands impact breccias are superbly exposed much better than breccias in most other terrestrial impact structures observations including those indicative of multiple and sequential processes provide insight on how impact breccias form and how they relate to the various phases of the impact process eventually they will lead to an improved understanding of planetary impact processes

petrogenesis of the northwest africa 4734 basaltic lunar meteorite we report the petrography mineralogy trace element abundance geochemistry and pb pb geochronology of the lunar meteorite northwest africa nwa 4734 and make a comparison with the lapaz icefield lap 02205 02224 low ti lunar basaltic meteorites nwa 4734 is an unbrecciated low ti mare basalt composed mainly of subophitic textured pyroxene 60 vol and plagioclase 30 pyroxene plagioclase and olivine exhibit large compositional variations and intra grain chemical zoning pyroxene and plagioclase in nwa 4734 have rare earth element ree concentrations and patterns similar to those of the laps the crystallization age of nwa 4734 determined in situ in baddeleyite is 3073 15 ma 2 sigma nearly identical to that of the laps 3039 12 ma nwa 4734 and the laps have similar textures modal abundances mineral chemistry and crystallization ages and are most likely source crater paired on the moon

alluvial pedogenesis in pleistocene and holocene mississippi river deposits effects of relative sea level change comparison of pleistocene and holocene soils developed in mississippi river meander belt deposits in louisiana illustrates the influence of relative sea level change on pedogenesis holocene and pleistocene meander belts have similar landscape morphologies lithofacies and soil characteristics and probably formed under similar hydrologic regimes the pleistocene avoyelles prairie meander belt is now terraced but it was originally graded to a lower relative sea level position than the holocene flood plain holocene alluvial soils are generally weakly expressed cumulative profiles with abundant redoximorphic features and formed on an aggrading flood plain with a shallow fluctuating water table the soil morphology varies with respect to landscape position and overbank lithofacies pleistocene alluvial paleosols show evidence for two stages of pedogenesis during the first stage of pedogenesis water table fluctuations and flood plain aggradation produced profiles with color mottles iron and carbonate nodules and weak b and c horizons similar to holocene flood plain soils the second stage of pedogenesis occurred after the avoyelles prairie was terraced and the regional water table fell a minimum of 30 m improved soil drainage created oxidizing and acidic conditions removed free carbonates dehydrated iron oxides and transformed clay minerals this stage produced pleistocene profiles with brighter matrix and mottle hues lower ph values larger and harder iron nodules and greater kaolinite contents than comparable holocene flood plain soils the primary influence on regional water table lowering in the southern lower mississippi valley was relative sea level fall mississippi river flood plain lowering adjacent to the avoyelles prairie most likely occurred between the end of oxygen isotope stage 3 and the maximum period of valley entrenchment during oxygen isotope stage 2 water table fall affected pedogenic processes a minimum of 400 km upvalley of the continental shelf margin pleistocene mississippi river paleosols represent excellent analogs for interpreting ancient alluvial paleosols formed during episodes of base level fall and valley incision as fluvial entrenchment terraced the meandering avoyelles prairie a pedogenic threshold was crossed that altered the pathway of chemical weathering the complexity of a multiple step pedogenic history also highlights the fact that interpretation of relative profile development as a function of time can be problematic

formation mechanisms of planar deformation features in naturally shocked quartz abstract shock waves induce peculiar defects in quartz shock mosaics high pressure polymorphs coesite and stishovite diaplectic glass and planar deformation features pdfs together these features are the indices of shock metamorphism pdfs appear under the optical microscope as straight and narrow defects parallel to the 10 1n rhombohedral planes with n 3 and 2 as most frequent values although n 1 4 and i e basal plane are also found we report in the first part of this paper a detailed investigation by transmission electron microscopy of the fine structure of pdfs in shocked quartz grains from a variety of sites slate islands la malbaie and manson in north america the vredefort complex in south africa the ries crater in germany and the cretaceous tertiary boundary layer at raton basin colorado we distinguish four pdf fine structures 1 bands of dislocations 2 lamellae of mixtures in various proportions of amorphous silica and small crystallites 3 thin brazil twin lamellae 4 short parallel lamellae forming serrated ladder structures the possible formation mechanisms of these pdfs are discussed in the second part of the paper it is suggested that the dislocation bands are probably not original pdf structures but stem from a later recrystallization stage the brazil twins have been produced by relatively large deviatoric stresses which accompanied the shock wave the other pdf structures which consist of partial amorphization in the 10 1 n planes must result from elastic instabilities of the shear modulus of the quartz structure at high pressure in these planes theoretical estimates of the elastic stiffness coefficients indicate that amorphization should start at approximately 10 gpa the growth of the straight and narrow amorphous lamellae would be driven by the front of the shock wave

rapid and widespread response of the lower mississippi river to eustatic forcing during the last glacial interglacial cycle the lower mississippi valley provides an exceptional fi eld example for studying the response of a continental scale alluvial system to upstream and downstream forcing associated with the large orbitally controlled glacialinter glacial cycles of the late quaternary however the lack of a numerical chronology for the widespread pleistocene strata assemblage known as the prairie complex which borders the holocene fl oodplain of the lower mississippi river has so far precluded such an analysis here we apply optically stimulated luminescence osl dating mainly on silt sized quartz from prairie complex strata in total 27 osl ages indicate that the prairie complex consists of multiple allostratigraphic units that formed mainly during marine isotope stages 7 5e and 5a thus the aggradation of the prairie complex is strongly correlated with the sea level highstands of the last two glacialinterglacial cycles fluvial incision during the sea level fall associated with the mis 5a mis 4 transition extended as far inland as 600 km from the present day shoreline testifying to the dominant downstream control of fl stratigraphic architecture in the lower mississippi valley in addition the short reaction time of the lower mississippi river suggests that large fl uvial systems can respond much more rapidly to allogenic forcing than is commonly believed

raman spectroscopy of volcanic lavas and inclusions of relevance to astrobiological exploration volcanic eruptions and lava flows comprise one of the most highly stressed terrestrial environments for the survival of biological organisms the destruction of botanical and biological colonies by molten lava pyroclastic flows lahars poisonous gas emissions and the deposition of highly toxic materials from fumaroles is the normal expectation from such events however the role of lichens and cyanobacteria in the earlier colonization of volcanic lava outcrops has now been recognized in this paper we build upon earlier raman spectroscopic studies on extremophilic colonies in old lava flows to assess the potential of finding evidence of biological colonization in more recent lava deposits that would inform first the new colonization of these rocks and also provide evidence for the relict presence of biological colonies that existed before the volcanism occurred and were engulfed by the lava in this research samples were collected from a recent expedition to the active volcano at kilauea hawaii which comprises very recent lava flows active fumaroles and volcanic rocks that had broken through to the ocean and had engulfed a coral reef the raman spectra indicated that biological and geobiological signatures could be identified in the presence of geological matrices which is encouraging for the planned exploration of mars where it is believed that there is evidence of an active volcanism that perhaps could have preserved traces of biological activity that once existed on the planet s surface especially in sites near the old martian oceans

shock and thermal history of martian meteorite allan hills 84001 from transmission electron microscopy microstructures in the allan hills 84001 meteorite were studied using optical and electron microscopy putting emphasis on shock effects which are widespread some orthopyroxene exhibits only 100 slip but more typical grains suffered extensive slip microfracturing and frequently contain 100 clino inversion lamellae in fracture zones shock deformation of orthopyroxene has produced all three effects in profusion together with intergranular pockets of orthopyroxene glass and intragranular glass lamellae which were apparently created by shearing on low index planes usually 100 or 110 both types of plane are loci that pseudo planar fractures tend to follow thus the glass lamellae which have not been observed in other meteorites probably formed by frictional heating during the sliding of microscale corrugated surfaces one over another leading to local melting we infer that the orthopyroxene glass and the fracture zones both formed from shear stresses created by strong shock ubiquitous undeformed micrometer and submicrometer euhedral chromites in orthopyroxene and plagioclase glasses and carbonate probably crystallized after shock heating and fracture zone formation nanocrystals of eskolaite cr2o3 coating silica glass grains are probably also a result of shock induced thermal decomposition of chromite iron sulfides pyrite and pyrrhotite were identified tended to be associated with plagioclase glass a carbonate disk showing no evidence for shock deformation had a substructure of elongated slightly misoriented subcells in the exterior interior regions had more eqiaxed subcells both microstructures probably formed during growth but the conditions are undetermined chemical composition varied on a micron scale but the rim of the disk was more ferroan oxide precipitates and voids were widely distributed as in fracture filling carbonates if the fracture zones and opx glass are the result of strong shock as we deduce it is very unlikely that pores could have filled by carbonate long after the fracture zones formed we infer that the carbonate like the phosphate olivine pyrrhotite eskolaite and many euhedral submicrometer chromites crystallized during the final stages of the impact that created the fracture zones and glasses with compositions of plagioclase silica and orthopyroxene

response of coastal plain rivers to falling relative sea level allogenic controls on the aggradational phase this study combines mathematical modelling and supporting flume experiments to address the problem of how coastal plain rivers respond to a steady fall in relative sea level the theoretical component of the study focuses on the development of a moving boundary model of fluviodeltaic progradation that treats rigorously the dynamics of the shoreline and alluvial basement transition the upstream limit of the alluvial river system dimensional analysis and numerical solutions to the model governing equations together suggest that at first order coastal plain rivers will remain aggradational on a timescale that varies with allogenic sediment and water supply and the fall rate of relative sea level in natural fluviodeltaic systems this intrinsic timescale is likely to vary by several orders of magnitude suggesting that the aggradational phase of river response can be geologically long lived at second order the duration of alluvial aggradation is controlled by two dimensionless numbers that embody system geometry and the kinematics of alluvial sediment transport model predictions were tested in a series of carefully scaled flume experiments the level of agreement between predicted and measured trajectories for the shoreline and alluvial basement transition strongly suggests that the moving boundary theory developed here successfully captures the response of small scale fluviodeltaic systems to falling sea level the results of this study have several sequence stratigraphic implications a fall in relative sea level at the shoreline is not a sufficient condition for river incision the onset of alluvial degradation and sequence boundary formation need not coincide with a maximum in the rate of sea level fall and the onset of sequence boundary formation is sensitive to allogenic sediment supply

carbonates and oxalates in sediments and landfill monitors of death and decay in natural and artificial systems subaqueous sediments and landfill waste disposal sites are both natural locations for anaerobic microbiological metabolism where sulphates are reduced to sulphide and organic matter particularly acetate is oxidized and degraded to produce ultimately co 2 and ch 4 the microbiologically mediated geochemical processes in each case are similar however natural sedimentary porewaters can be difficult to sample and monitor whereas landfill sites are relatively easily accessible yielding leachate samples that are routinely monitored over periods of time in both environments carbonate precipitation is predicted to be a normal consequence of anaerobic microbiological activity consistent with changes in leachate composition and the predictions of geochemical modelling initial investigation of scale from a landfill drainage system confirms the presence of calcite together with gypsum and iron minerals calcium oxalate minerals whewellite and weddelite are widespread in their occurrence within septarian concretions from a number of geological formations whewellite is reportedly stable up to 160 c the solubility of calcium oxalate is very low and precipitation readily takes place when oxalate oxalic acid is present derived from fungal processes in sediments and soils calcium oxalate minerals should be expected wherever vegetable matter is decomposing this link can be demonstrated for natural sediments but has yet to be proven for landfill

the influence of lithology on hillslope development in the area of the jacupiranga alkaline complex and its surroundings sao paulo brazil abstract the area of the jacupiranga alkaline complex and its surroundings is characterized by a variety of slope forms their spatial differentiation and the differences in relative relief and hilltop heights are a function of lithology significant contrasts exist particularly between the ultramafic rocks of the alkaline complex and the quartz rich rocks of the surrounding precambrian basement although climatic conditions are uniform the physical and chemical properties of the weathering products formed on the various rock types are very different through their properties they affect the hillslope processes and thereby influence the hillslope development slope forming processes on deeply weathered ultramafic rocks are slow mass movements and chemical denudation on the more resistant ultramafic rocks wash processes appear to be more important wash and rapid mass movements predominate on gneisses granites and mica schists the geomorphological development of the jacupiranga alkaline complex can be explained in terms of a long continuous downwearing the large differences in elevation within the alkaline complex suggest that the development towards a more differentiated relief may extend well back into the tertiary the mutual adjustment of slope forms processes and lithological controls favoured the development of rock dependent summit heights where heights are determined by the steepness of the slopes and the spacing of the drainage lines climatic fluctuations in the pleistocene failed to produce any fundamental change in the long term development of the hillslopes as their duration was too short with respect to the relaxation time of the hillslopes or their influence was not great enough to alter the overall trend of slope development

prospects for interregional correlations using wisconsin and holocene aridity episodes northern gulf of mexico coastal plain abstract luminescence dating of extensive dune fields and associated eolian sandsheets provided a chronology of recently recognized pleistocene and early holocene dry climate episodes in the currently humid warm temperate northern northeastern gulf of mexico region scattered parabolic dunes and clusters of intersecting parabolic dunes along with elongated shore transverse and shore parallel dunes developed these landforms occur in a 390 km long and 2 to 3 km wide semicontinuous belt in southeast alabama and northwestern florida dune elevations reach 22 m sangamon coastal barrier sectors were the primary source of the eolian sand deflation was coeval with early wisconsin to mid holocene marine low sea levels and associated distant shorelines early holocene dune dates were synchronous with indications of a hypsithermal dry interval in southeast louisiana the yucatan and the south atlantic seaboard overlapping with dry episodes in yucatan and the high plains texas dunes and louisiana and texas prairie mounds especially in the southwest texas coast still dominated by dry climate suggests intervals of early to late holocene drought the dates provide the basis for identifying and correlating wisconsin early and late holocene climate phases between currently semiarid and humid coastal and interior areas they contribute to future studies including interregional paleoclimate modeling although pleistocene coastal eolian deposition coincided with glaciation in the northern interior and with cooler temperatures of a reduced gulf of mexico holocene aridity phases may have been related to major variations in the position of high pressure cells storm tracks and branches of the jet stream and even to prolonged la nina conditions

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

age and temperature of shock metamorphism of martian meteorite los angeles from u th he thermochronometry mineralogic features attributed to impact induced shock metamorphism are commonly observed in meteorites and terrestrial impact craters partly because the duration of shock metamorphism is very short constraining the timing and temperature of shock events has been problematic we measured u th he ages of single grains of merrillite and chlorapatite from the martian meteorite los angeles la merrillite and chlorapatite ages cluster at 3 28 6 0 15 ma 2s and 2 18 6 0 19 2s ma respectively the mean age of the merrillites which are larger than chlorapatites is indistinguishable from cosmic ray exposure ages 3 1 6 0 2 ma suggesting that impact induced shock metamorphism was coeval with ejection of the la precursor from mars to constrain the initial temperature of shock metamorphism in the la precursor body we modeled diffusive loss of he from merrillite as a function of diffusion domain size la precursor body size and ablation depth from these calculations we suggest that the metamorphic temperature of the shock event was higher than 450 8c these results support the idea that shock pressures of the martian meteorite shergotty were higher than 45 gpa as inferred from the presence of post stishovite sio2 polymorphs single grain u th he dating of phosphates may provide unique constraints on the timing and pressure temperature dynamics of shock metamorphism in a wide variety of extraterrestrial materials

exposure of late pleistocene mississippi river meander belt facies at mt pleasant louisiana abstract exposure of a sedimentary sequence along a mississippi river bluff at mt pleasant louisiana provides insight into the constructional development of the prairie terraces this site serves as a type section for a late pleistocene meander belt of the mississippi river and stratigraphic features have been traced beneath the prairie terraces in southeastern louisiana a 76 6 ft 23 35 m measured section reveals upper units of peoria loess and mixed loess loessial sediments overlie proximal flood plain deposits of a meandering river system the upper flood plain deposits are stratified natural levee facies consisting of coarse silt to fine sand with small scale trough cross stratifications horizontal stratifications climbing ripples scour surfaces and various soft sediment deformation structures within this deposit a silt loam paleosol was identified with moderately developed blocky structure clay films and oxide stains concentrated along root traces the flood plain sequence grades downward into abandoned channel fill facies with five distinct cycles recognized by textural gradations each cycle fines upward from basal loamy or sandy textures to silt loam or silty clay textures oxide stains and concretions are common in the upper fine grained parts of each cycle the third channel fill cycle is characterized by a mottled paleosol with blocky structure clay films and oxide stains in its upper part this paleosol represents an unconformable surface upon which the overlying fluvial sequence was deposited about 1300 ft 400 m downstream from the measured section is a point bar sequence consisting of fine sand to granule gravel with large and small scale trough cross stratifications horizontal stratifications scour surfaces and clay drapes the vertical and lateral successions of strata at mt pleasant bluff indicate deposition by a large scale mixed load meandering fluvial system the modern mississippi river has facies characteristics analogous to those described in the late pleistocene sequence correlation of individual strata away from the mt pleasant bluff measured section is difficult however the upper contact between mixed loess and stratified natural levee facies and the underlying upper paleosol can be traced along the mississippi river bluffs for considerable distances identification of the lower paleosol away from mt pleasant bluff is more difficult due to its limited exposure and possible lateral variability the described meander belt facies are of a probable wisconsin age and are considered as a unit here named the mt pleasant bluff alloformation the age designation is based on position in the stratigraphic section degree of preservation of sedimentary facies character and degree of development of the upper paleosol preservation of constructional topography beneath the loess and correlation of this sequence to nearby sites with wisconsin age radiocarbon dates

the last interglacial stage definitions and marine highstand north america and eurasia abstract delineation of the boundary between the last interglacial lig and the last wisconsinan glacial stage in north america represents a critical yet unresolved issue subdivisions of the late pleistocene are based on oxygen isotope ice cover and pollen stratigraphic data boundaries defined by isotope chronology hinge on complex interrelationships between 18o in foraminifer tests ice volumes stored on land and coeval sea level position in the absence of adequate pollen stratigraphic documentation pleistocene subdivision boundaries were harder to establish in north america than in europe time transgressive pollen zones revealed increased lengths of the climatically floristically defined lig from the european subarctic to the mediterranean conflicting definitions of sangamon as representing only the last interglacial of minimum ice cover and higher temperatures or broadly defined sensu lato also incorporating early part of the last wisconsinan glacial stage persist in the north american literature the exclusively interglacial age of the sangamon geosol originally used in dating the sangamonian stage proved untenable designation of an eowisconsinan interval corresponding to susbtages mis 5d a also lacks merit despite climate and vegetation related discrepancies pollen and coastal deposit based comparisons between europe and north america during mis 5 and the holocene are useful in establishing the climate history of the north american sangamonian and subsequent early wisconsinan substages an overarching mis 5 cooling trend represented by scattered subarctic and high mountain ice accumulation events followed the mis 5e eemian sangamonian temperature peak adoption of the general european practice that asymmetrically splits mis 5 into a short mis 5e interglacial and a long early wisconsinan glacial mis 5d a interval is preferred in north america as well subdivisions in the normalized 18o curve that serve as the chronological framework and the wealth of european pollen data support this approach while multiple pre sangamon pleistocene marine paralic intervals do occur on the nw gulf coast all pre sangamon pleistocene marine and brackish inshore deposits had been removed by erosion in the ne coastal plain a single inshore nearshore marine sediment and highstand interval is well documented in this region the lig highstand sequence correlates with varied eemian marine and paralic mis 5e deposits encountered along northern and western european siberian and additional shores apart from reliably dated sangamonian s florida coral reefs identification and dating of lig highstand deposits remain highly problematical in se atlantic shore terraces

multiple origins of xenoliths and xenocrysts in the elephant moraine 79001 lithology a olivine phyric shergottite

natural high pressure polymorph of merrillite in the shock veins of the suizhou meteorite abstract a new high pressure polymorph of merrillite with the structure of trigonal ca 3 po 4 2 was found in the shock produced veins of the suizhou meteorite where it coexists with ringwoodite majorite naalsi 3 o 8 hollandite and majorite pyrope garnet the crystallographic nature of this natural ca 3 po 4 2 phase was characterized by raman spectroscopy and x ray diffraction and all data compare favorably to the same data obtained from ca 3 po 4 2 synthesized at 14 gpa and 1400 c the cell parameters of this new high pressure mineral are a 5 258 1 angstroms and c 18 727 3 angstroms space group r 3m and density 3 447 g cm 3 where the number in parentheses are standard deviations in the last significant digits the natural occurrence of the ca 3 po 4 2 phase together with other high pressure minerals constrains the pressure of the shock veins at about 23 gpa the suizhou meteorite provides the first naturally occurring example of ca 3 po 4 2 polymorph

an experimental study of the effects of base level change on fluvial coastal plain and shelf systems abstract several of the concepts of sequence stratigraphic models were tested by experiments in a large flume using different gradients for successive runs a physical model of a fluvial drainage basin coastal plain continental shelf and continental slope was constructed in all experiments initial gradients of the coastal plain and shelf were identical systematic raising and lowering of the water surface simulated the changes in relative sea level i e base level that are similar to most sequence stratigraphic models base level changes significantly affected the shelf area but they had little effect on the fluvial drainage basin during base level falls fluvio deltaic progradation occurred fluvial aggradation occurred only during periods of base level stillstand or rise because of the slow rate of head ward erosion of incised valleys a significant time gap existed from the time base level first fell below the shelfbreak and the development of a cross shelf bypass valley during this lag time deposition occurred on the exposed shelf to form a fluvial braid plain concurrently channels developed at the shelfbreak and grew by headward erosion at various rates continuous incision and widening of these channels formed valleys these valleys were not linked directly to the main drainage basin unt l ultimately one captured the flow from that drainage at that point other valleys were abandoned and ceased to grow during the subsequent base level rise the single large cross shelf valley filled with coarser sediments while the other valleys partially filled with finer suspended load sediments the main cross shelf valley also supplied coarser sediments to the slope