Cosmic-ray exposure ages of the ordinary chondrites and their significance for parent body stratigraphy

²¹Ne cosmic-ray exposure ages have been calculated from literature data for 201 H, 203 L and 38 LL chondrites, corrected for shielding differences when possible. The distributions of exposure ages again show the familiar peaks at 4.5 and 20 Myr for the H's, but no outstanding events for the L's and LL's. If the L-chondrite distribution is interpreted as a series of discrete events, then at least 6 peaks between 1 and 35 Myr are needed to model it. The observations, that every petrologic type occurs in every large peak and that even the higher petrologic types contain solar wind gases, suggest that the parent bodies have been fragmented and reassembled into a megabreccia. For the H chondrites, both large and small peaks contain about 15% solar-gas bearing meteorites, which could mean that surface material has been mixed to depths represented by the largest event, on the order of a kilometer. In contrast, only 3% of the L's contain solar wind, which may be related to breakup of their parent planet. Those L's with especially low radiogenic He (U,Th-He ages < 1 AE) tend to have low exposure ages: their distribution may be biased by a subgroup that had orbits coupling short capture lifetimes with significant solar heating.     

Environmental changes during the past 2000 years in north-central Wisconsin: Analysis of pollen,charcoal, and seeds from varved lake sediments

A 2000-year accumulation of varved sediments from Hell's Kitchen Lake in north-central Wisconsin was analyzed for pollen, charcoal, and seeds. The varves provided an accurate time scale for the study. The pollen record indicates changes on two different time scales. Short-term changes lasting several decades appear to be superimposed on long-term changes lasting several centuries. The short-term changes are related to individual fires, and the long-term changes result from increases or decreases in the frequency of these perturbations. From 2000 to 1150 years ago the average interval between fires was about 100 years, and from 1150 to 120 years ago the interval increased to about 140 years. Evidence from pollen, seeds, and charcoal at Hell's Kitchen Lake suggests that at least two “moist” intervals occurred during the past 2000 years, one between 2000 and 1700 years ago and the other between 600 and 100 years ago. A third but minor “moist” period occurred about 1150 to 850 years ago. A pollen and seed diagram shows that these intervals are characterized by increased percentages of white pine pollen, hemlock pollen, and yellow birch seeds, and by decreased levels of charcoal. The “dry” interval of 1700 to 1150 years ago is characterized by increased percentages of paper birch seeds, oak pollen, and aspen pollen, along with high levels of charcoal. The times of climatic change indicated at Hell's Kitchen Lake are nearly synchronous with those based on studies of tree rings, soils, glacial activity, and other pollen studies from various regions of North America, but the direction of these inferred changes is not always the same. This result suggests that the long-wave pattern of the general circulation has been variable during the past 2000 years.     

Who’s afraid of red, yellow and green?: Redlining in Rotterdam

Redlining research is common practice in the US but not in other countries. Does this imply redlining does not take place elsewhere? This paper presents evidence from Rotterdam, the second largest city of the Netherlands, showing that in the 1990s it was impossible to get a home mortgage in large parts of the city. However, after Rotterdam joined the National Mortgage Guarantee (an institutional control measure) in 2000, hardly any evidence of redlining was found. This paper not only shows that redlining takes place outside of the US context, but also that a (discursive) treatment based on case study research has the possibility to gain a fuller understanding of redlining practices than a statistical/correlation analysis of mortgage data. Interviews with key actors are instrumental to unravelling how, why and when those in power make their decisions: agents are structured by the existing system while, at the same time, some of these agents have the power to re-produce as well as re-structure (transform) the system. One of the geographical outcomes of the agency-structure interaction is that credit is “redirected away from poorer to richer (and therefore “safer”) groups” as part of a strategy of risk avoidance [Leyshon and Thrift, 1997]. Thus redlining, like any other form of financial exclusion, deepens and accentuates prevailing levels of uneven development by creating geographical variations in access to the financial system [Dymski and Veitch, 1992].     

The ecological role of fire in the Jackson Hole area,northwestern Wyoming

Fire-history investigations in the Jackson Hole area of northwestern Wyoming reveal that most current stands of aspen and lodgepole pine regenerated following extensive fires between 1840 and 1890 and that widespread fires occurred in the 1600s and 1700s. White man's major effect on the fire incidence has been the successful suppression during the past 30–80 yr. Successional changes in the absence of fire include the deterioration of aspen stands, massive invasions of subalpine fir in lodgepole pine stands, great increase in conifer cover, heavy fuel buildups in lodgepole pine and Douglas fir stands, and increase in sagebrush and other shrubs. Steps are being taken, starting in 1972, to allow fire to play a more natural role in Grand Teton and Yellowstone National Parks. Teton National Forest plans experimental prescribed burning to determine whether fire can stimulate successful aspen regeneration in the presence of large numbers of wintering elk.     

Water and magmas: application of the Gibbs-Duhem equation

Burnham (1975a, b) has shown that in several alumino-silicate systems Henry's law constant is independent of silicate melt composition up to X^melt_H2O = 0.5. He has used this fact to conclude that such silicate melts behave ideally over a wide range of compositions based on the application of the Gibbs-Duhem relation. Unless Henry's law is valid up to X^melt_H2O = 1.0, the application of the Gibbs—Duhem relation to three component systems only shows that if one component obeys Henry's law, the other two components follow the two component Gibbs-Duhem equation. There is no thermodynamic requirement of ideality.     

松辽盆地南部白垩纪-古近纪挤压构造的发现与盆地性质探讨

松辽盆地位于欧亚板块东部,毗邻太平洋板块,是叠置于华北板块和西伯利亚板块之间的晚古生代碰撞造山带之上规模最大的中-新生代陆相含油气盆地,具有断、坳双重结构。自白垩纪以来,松辽盆地南部主要经历两期挤压作用:NW-SE向挤压作用发生在下白垩统营城组碎屑岩段-上白垩统泉头组沉积时期,挤压作用持续了18Myr;近E-W向挤压作用发生在四方台组-古近系沉积时期,挤压作用至少持续了39.1Myr。两期挤压作用都表现出东强西弱的特点,第二期挤压作用的变形强度远大于第一期,并且在明水组沉积晚期变形强度最大,这期挤压作用奠定了松辽盆地现今的构造格局。下白垩统营城组上部碎屑岩段-上白垩统泉头组和四方台组-古近系的沉积作用分别记录了第一期、第二期挤压作用形成的反转构造和断层相关褶皱的变形过程。上述构造在不同时期隆升速率与沉积速率之间的关系,控制了盆地的沉积范围、沉积地层的厚度和接触关系在空间上的变化。松辽盆地在上述两个构造演化阶段都处于活动大陆边缘的陆内区域,盆地性质都应属于陆内挤压坳陷盆地。     

The stable carbon isotopes in enstatite chondrites and Cumberland Falls

The carbon isotopic composition of the total carbon in the enstatite chondrites Indarch, Abee, St. Marks, Pillistfer, Hvittis and Daniel's Kuil and the enstatite achondrite Cumberland Falls has been measured. The empirical relationhip between carbon isotopic composition and total carbon content is distinct from that of carbonaceous and ordinary chondrites. Within the enstatite chondrite group the average ¹³C content increases with petrographic type: E4 < E5 < E6. Daniel's Kuil shows the largest ¹³C enrichment in the bulk carbon of any meteorite. The carbon isotopic composition is most clearly correlated with the abundance of the elements Zn, Cd and In. Insofar as these elements may hold the key to the understanding of enstatite chondrites, more detailed combined carbon isotope and trace element studies of these meteorites will play an important role in the deciphering of their history.     

Mekometer measurements in the Imperial Valley, California

A network of about 130 bench marks, mostly about 800 m apart at road intersections and forming a continuous chain of quadrilaterals crossing the Imperial Valley in the vicinity of El Centro, has been measured three times, in 1971, 1973 and 1975. The instrument used was a Mekometer, a superior short-range electronic-distance-measuring (EDM) instrument having a sensitivity of 0.1 mm and a potential accuracy of better than 1 ppm. In 1975 the network was extended, particularly where it crosses the Imperial fault, to about 200 bench marks defining about 500 lines.For various reasons, it has not been possible to achieve standard errors of much less than 3 ppm in the distance measurements. Even so, about one line in three shows significant change at the 95% level in one or more of the three intervals 1971–1973, 1973–1975 and 1971–1975. Adopting stringent consistency criteria, the number of places where significant changes occurred can be reduced to seven. One of these is almost certainly associated with the Heber geothermal anomaly, one with the Imperial fault, and the others with one or other of the faults identified on the ground further to the north. The largest and most consistent changes occur on the Imperial fault, and imply an aseismic slip on it averaging about 8 mm/yr.The data also lend themselves to regional strain analysis. The results are consistent with a linear strain rate of about 0.3 ppm/yr, which is comparable with the rate deduced from large-scale geodetic surveys of the area.     

The locational policies and geographical expansion of multiple retail companies: A case study of M.F.I.

M.F.I. has emerged as the major retailer of self-assembly furniture in the United Kingdom and their trading philosophy has led to a search for suburban retail sites. This paper outlines M.F.I.'s locational policies and traces the company's geographical expansion.     

Crustal deformation in the Central Ionian Islands (Greece): Results from DGPS and DInSAR analyses (1995–2006)

Ground deformation studies based on Differential GPS (DGPS) and Differential Interferometric SAR (DInSAR) analyses have been conducted in the seismically active area of the Central Ionian Islands. Local GPS networks were installed in Cephallonia (2001) and Zakynthos (2005). The Cephallonian network has been remeasured five times and Zakynthos' once as of July 2006. The studies have yielded detailed information regarding both local and regional deformations that are occurring in the area.For Lefkas Island, DInSAR analysis (March to September 2003) revealed 56 mm of uplift in the central and western parts and is attributed to the August 2003 earthquake (M_w = 6.3) that occurred offshore to the west. Synthetic DInSAR modelling of the magnitude and extent of deformation is consistent with the seismologically deduced parameters for the ruptured segment along the Lefkas Transform Fault. Subsidence (< 28 mm) along the northern part of the island is attributed to local conditions unrelated to the earthquake. For Zakynthos Island, large-magnitude earthquakes that occurred offshore to the south in October 2005 and April 2006 most likely contributed to the observed deformation as deduced from DGPS measurements for an encompassing period (August 2005 to July 2006). The largest amount of horizontal deformation occurred in the south, where its western part moved in a W–NW direction, while the eastern part moved towards the NE, with magnitudes ranging from 15 to 26 mm. The southern part of the island uplifted a maximum of 65 mm whereas the north subsided from 12 to 28 mm.For Cephallonia Island, DInSAR analysis (1995 to 1998) indicated ground deformation up to 28 mm located in small sections of the island. Further interferometric analysis for the period 2003 to 2004, encompassing the occurrence of the Lefkas earthquake in August 2003, indicated 28 mm of uplift in the northern part, while during the next two years (2004 to 2005), further uplift of at least 56 mm had taken place at the western and northern part of the island.DGPS measurements for the period 2001 to 2006 revealed a clockwise rotation of the island with respect to a centrally located station on Aenos Mt. The horizontal component of deformation generally ranged from 6 to 34 mm, with the largest values at the western and northern parts of the island. Considering the vertical deformation, two periods are distinguished. The first one (2001 to 2003) is consistent with anticipated motions associated with the main geological and tectonic features of the island. The second one (2003 to 2006) has been tentatively attributed to dilatancy in which relatively small uplift (20–40 mm) occurred along the southern and southeastern parts of the island, while larger magnitudes (> 50 mm) happened at the western part (Paliki Peninsula). These large magnitudes of uplift over an extended area (> 50 km), in conjunction with an accelerated Benioff strain determined from the analysis of the seismicity in the broader region, are consistent with dilatancy. This effect commenced some time after 2003 and is probably centered in the area between Zakynthos and Cephallonia. If this interpretation is correct, it may foreshadow the occurrence of a very strong earthquake(s) sometime during 2007 to 2008 in the above designated region.     

Evolution of CaAl-rich bodies in the earliest solar system: growth by incorporation

Many Type B CaAl-rich inclusions (CAI's) in the Allende carbonaceous chondrite contain two types of spinel structures, “framboids” and “palisades.” Framboids are clumps of spinel grains generally <100 μm across. Experimental studies (Wark and Lovering, 1982) show that they probably formed in situ by solid state growth processes. Palisades are texturally different and consist of ovoid shells of spinel grains that appear in thin sections as long arcs or rings with diameters ranging from ～50 μm up to 2 cm. No in situ formation process seems able to explain the variety of sizes and morphologies of palisades nor the different compositions and textures of the enclosed and enclosing materials. We therefore suggest that palisades are the spinel rims of smaller, earlier-formed Type B CAI's that were incorporated into other CAI material in various ways—by capture into liquid drops, by solid condensate overgrowths and by the partial melting or welding of agglomerates containing the bodies. As some Type B bodies have been found inside Type A host material it appears that in at least some regions, and probably generally, Type A CAI's formed after Type B. We propose that Type B CAI's are residues from the heating and incomplete evaporation of interstellar dust during the accretion of the protosolar nebula, and that Type A CAI's are later condensates from completely evaporated dust whose exotic ¹⁶O-rich component became more diluted in the gas phase.     

Government assistance and the changing distribution of dairyfarming in Australia

An important proportion of Australian dairy production has been destined for export markets, where prices are below those received on the home market. This degree of dependence on international prices has adversely affected dairy farm incomes and thereby influenced both Government responses to the industry's problems and dairymen's decisions about levels of production and farm viability. Examination of the spatial impact on the now declining Australian dairy industry of Government-funded subsidies and of schemes for reconstruction of non-viable dairy farms, has indicated that withdrawal of farmers from the industry has not been areally uniform at the national level; but study of a major dairying region whose industry has undergone substantial decline suggests that this uneven pattern reflects industry and regional characteristics more than the deliberate or inadvertent results of Government intervention. Although Government policy has been broadly directed towards reducing the numbers of dairymen, and hence dependence on overseas prices for production surpluses, industry change has been greatest in regions where viable economic alternatives have been available for low-income dairymen.     

Cataclysmic Late pleistocene flooding from glacial Lake Missoula: A review

Late Wisconsin floods from glacial Lake Missoula occurred between approximately 16 and 12 ka BP. Many floods occurred; some were demonstrably cataclysmic. Early studies of Missoula flooding centered on the anomalous physiography of the Channeled Scabland, which J. Harlen Bretz hypothesized in 1923 to have developed during a debacle that he named ‘The Spokane Flood’. Among the ironies in the controversy over this hypothesis was a mistaken view of uniformitarianism held by Bretz's adversaries. After resolution of the scabland's origin by cataclysmic outburst flooding from glacial Lake Missoula, research since 1960 emphasized details of flood magnitudes, frequency, routing and number.Studies of flood hydraulics and other physical parameters need to utilize modern computerized procedures for flow modeling, lake-burst simulation, and sediment-transport analysis. Preliminary simulation models indicate the probability of multiple Late Wisconsin jökulhlaups from Lake Missoula, although these models predict a wide range of flood magnitudes.Major advances have been made in the study of low-energy, rhythmically bedded sediments that accumulated in flood slack-water areas. The ‘forty floods’ hypothesis postulates that each rhythmite represents the deposition in such slack-water areas of separate, distinct cataclysmic floods that can be traced from Lake Missoula to the vicinity of Portland, Oregon. However, the hypothesis has numerous unsubstantiated implications concerning flood magnitudes, sources, routing and sedimentation dynamics.There were multiple great Late Wisconsin floods in the Columbia River system of the northwestern United States. Studies of high-energy, high altitude flood deposits are necessary to evaluate the magnitudes of these floods. Improved geochronologic studies throughout the immense region impacted by the flooding will be required to properly evaluate flood frequency. The cataclysmic flood concept championed by J. Harlen Bretz continues to stimulate exciting and controversial research.     

On cenozoic and older glaciationsZur frage känozoischer und älterer vereisungenLes glaciations cénozoíques et antérieures

The distribution of solar radiation on the Earth's surface produces regular climatic zones, including essential ice covers in the polar regions. Thus it is unjustified to speak of glacial and interglacial periods in a global sense. Climatic zones and polar ice caps have been displaced from time to time by polar wandering both on smaller circular paths during one great epoch of Earth history as well as on long straight courses at the limits of these epochs. Polar wanderings are linked among others with expansion processes of the Earth. Alterations in intensity of solar radiation and in atmospheric processes have influenced the transitional climatic zones and caused an alternation of perlglacial and interperiglacial periods in the belts around the ice caps.     

“Fluffy” Type A Ca-, Al-rich inclusions in the Allende meteorite

Allende “fluffy” Type A's (FTA's) are a distinct sub-group of Ca-, Al-rich inclusions whose primary mineral assemblage consists of Al-rich melilite (Åk 0–33), spinel that is commonly very V-rich, perovskite and, frequently, hibonite. Some contain relatively coarse-grained melilite (up to 1.5 mm) that is intensely kink-banded and commonly reversely-zoned, hibonite and V-rich spinel. Others contain much finer-grained and strain-free melilite (?50 μm) and have not been found to contain hibonite or V-rich spinel. Some FTA's contain both coarser- and finer-grained melilite and textural relationships indicate that the latter is replacing the former. FTA's are characterized by extremely irregular shapes and 60–75 volume per cent of fine-grained, secondary alteration products. Many are aggregates of innumerable nodules, each of which is surrounded by a Wark-Lovering-type rim sequence. These nodules are frequently separated from one another by matrix-like clastic rim material. Other FTA's do not have nodular structure. Structural and mineralogical characteristics of their Wark-Lovering rims suggest that FTA's did not achieve their shapes by deformation of a liquid or a hot, plastic solid. In contrast to those in Type B inclusions, formation of reverse zoning in the coarser-grained melilite crystals in FTA's cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure. Further evidence against a liquid origin is the wide range of spinel compositions within individual coarser-grained FTA's. The fact that the reversely-zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues. FTA's are aggregates in some of which are preserved vapor-solid condensate grains that formed at high temperature in the solar nebula.     

Are C1 chondrites chemically fractionated? a trace element study

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for the elements Ag, Au, Bi, Br, Cd, Ce, Cs, Eu, Ge, In, Ir, Lu, Nd, Ni, Os, Pd, Pt, Rb, Re, Sb, Se, Sn, Tb, Te, Tl, Yb, and Zn. The data were combined with 9 earlier analyses from this laboratory and examined for evidence of chemical fractionation in C1 chondrites.A number of elements (Br, Rb, Cs, Au, Re, Os, Ni, Pd, Sb, Bi, In, Te) show small but correlated variations. Those of the first 8 probably reflect hydrothermal alteration in the meteorite parent body, whereas those of Sb, Bi, In, and Te may at least in part involve nebular processes. Br and Au show systematic abundance differences from meteorite to meteorite, which suggests hydrothermal transport on a kilometer scale. The remaining elements vary from sample to sample, suggesting transport on a centimeter scale.There is no conclusive evidence for nebular fractionation affecting C1 's. Though C1 chondrites have lower $\text{Zr}\text{Hf}$ and $\text{Ir}\text{Re}$ ratios than do other chondrite classes, these ratios vary in other classes, suggesting that those classes rather than C1's are fractionated. Three fractionation-prone REE—Ce, Eu, and Yb have essentially the same relative abundances in C1's and all other chondrite classes, and hence apparently are not fractionated in C1's. We did not confirm the large Tb and Yb variations in C1's reported by other workers.We present revised mean C1 abundances for 35 elements, based on the new data and a critical selection of literature data. Changes are generally less than 10%, except for Br, Rb, Ag, Sb, Te, Au, and the REE.The Plainview C2 xenolith has normal trace element abundances, except for 3 elements falling appreciably above the C2 range: Rb, Cs, and Bi. Hydrothermal alteration may be the reason for all 3, though nebular fractionation remains a possibility for Bi.     

Mineralogy and petrology of chondrules and inclusions in the Mokoia CV3 chondrite

All objects >100 μm in apparent diameter in five polished thin sections of the Mokoia CV3 chondrite were studied and classified. Number and volume percentages and mean apparent size of each type of chondrule and inclusion were determined. Three major types of olivine chondrules were observed: igneous chondrules, recrystallized chondrules, and chondrules that appear to be accretional aggregates. Coarse-grained CAI's have igneous textures and mineral parageneses, while fine-grained CAI's are aggregates containing varying proportions of Al-rich concentric objects, Ca-rich chaotic material, and inclusion matrix. Chondrules and refractory inclusions in Mokoia and Allende are broadly similar in texture and mineral chemistry, but Mokoia refractory inclusions contain phyllosilicates rather than feldspathoids, and melilite-rich CAI's are more abundant in Allende.We think that most CAI's formed during the metamorphism, partial melting, and incomplete distillation of primitive dust aggregates when they were heated in the solar nebula. In the process, Ca-rich melt appears to have been physically separated from Al-rich residues, producing the observed fractionation of Ca from Al into distinct constituents of CAI's. Some CAI's may be aggregates of devitrified, amorphous metastable condensates. Inclusion matrix may have condensed from silicate-rich vapors produced during distillation. Mokoia inclusion matrix contains phyllosilicates that are probably primitive nebular material.     

Time-lag of dunes in unsteady flows: An analysis of nasner's data from the R. Weser,Germany

In order to contribute towards the development of a sound actualistic basis for the interpretation of dune structures, phase diagrams and related graphs are presented for six-year time-series of daily mean dune wavelength, daily mean dune height, and daily freshwater discharge obtained by Nasner from four fixed sites on the R. Weser. Dune dimensions at these sites vary out of phase with the freshwater discharge, in a year of typical discharges by approximately π/2 rad in the case of wavelength, and by roughly 3 π/2 rad in terms of height. The mean annual wavelength (daily wavelength averaged over a hydrological year, equal to one flow cycle) is independent of the mean annual discharge, but the relative range of wavelength over the cycle increases with this discharge. The relative range of dune height also increases with the mean annual discharge. However, the mean annual dune height is inversely proportional to the mean annual discharge. Related modes of behaviour may be expected of dunes in other environments where unsteady flows prevail, but their recognition will depend on sampling carried out at sufficiently small time intervals over protracted periods. The analysis of Nasner's data suggests that although in natural environments the dimensions of dunes are related in defineable ways to hydraulic conditions, the relationships are likely to prove complex and multi-valued, rather than simple as has commonly been supposed by sedimentologists in the past.     

A hidden suture within the northern Paleotethyan margin: Paleogeographic/paleo-tectonic constraints on the late Paleozoic 'Veles Series' (Vardar Zone,North Macedonia)

There is little consensus in characterizing the effects of the migrated late Pan-African/Lower Paleozoic configuration (western Paleotethys and precursory Paleozoic oceans) and its Variscan, late Variscan, and Eo-Cimmerian involvement. Constrained by a limited choice of the geological, biostratigraphical, and paleogeographical constraints, the focus of this regional geological synthesis is the little-known Devonian – Lower Carboniferous polymetamorphic 'Veles Series' (southern Vardar-Axios Zone, Northeast Mediterranean). Kinematic reconstructions indicate that the drifted carbonate platform assemblage of the 'Veles Series' including its Lower Carboniferous collision occurred along an active margin of southwestern Moesia, Laurussian foreland. Despite the fact that the dominant, low-grade metamorphic imprint across the 'Veles Series' is compatible with the ‘soft’ Eo-Cimmerian docking (i.e. Triassic), the documented Lower Carboniferous age suggests a Variscan involvement.A distinctive Late Paleozoic age is consistent with the north Gondwana and Variscan developments, reflected by the peculiar protoliths pallet portraying the presence of the oceanic crust to deep-marine equivalents. Accommodated to the west (paleo-south) of the late Cadomian Serbo-Macedonian Unit (a segment of the former peri-Gondwanan terrane assembly) and to the north of the Cimmerian Minoan system (East Mediterranean), the 'Veles Series' reflects a migrated rift to carbonate platform system. Despite the significant Alpine overprinting, based on this regional geological synthesis we propose that the 'Veles Series' is a 60 km-long suture segment documenting a so far rather poorly explored Variscan segment of the Paleotethyan lithosphere exposed within Balkans/Northeast Mediterranean.