A pre-Ipswichian cold stage mammalian fauna from the Balderton Sand and Gravel,Lincolnshire, England     

Adrian M. Lister  Allan Brandon 《第四纪科学杂志》1991,6(2):139-157

The Balderton Sand and Gravel has yielded one of very few mammalian faunas dated to the penultimate Cold Stage in Britain. The assemblage is dominated by mammoth and woolly rhinoceros, with subordinate horse, red deer, bison, straight-tusked elephant, musk ox, reindeer, wolf, lion, brown bear and cf. narrow-nosed rhinoceros. This fauna indicates cold stage conditions, probably including one or more interstadial episodes. The presence of straight-tusked elephant and cf. narrow-nosed rhinoceros supports its pre-Devensian age, and provides corroboration for the occurrence of these taxa in the British Wolstonian. An attempt is made to analyse the fossil collection by preservation type and adhering sediment: the occurrence of individual species appears to be largely uncorrelated with lithology. The Balderton assemblage corresponds well to other British mammal faunas assigned to a cold interval between the Hoxnian and Ipswichian Interglacials.  相似文献   

Tectonic and Topographic Framework of Political Division     

Brandon J. McElroy  Bruce H. Wilkinson  Edward D. Rothman 《Mathematical Geology》2005,37(2):197-206

Boundaries between the various topographic, geologic, and socio-political entities that span the Earths continental surfaces are determined by a myriad of complexly interrelated natural and/or cultural factors. Areas of large river basins, of lithologic units on geologic maps, and of nations exhibit size frequency distributions that are closely approximated by density functions in which diameters of individual areas are distributed exponentially. As such, size distributions of each type of surface unit are closely modeled as randomly delimited areas. In other words, if one were to walk in a straight line across any particular continent, each step along that transect would embody some random continuous probability of passing out of a major drainage basin, or out of an area of more or less homogeneous rock type, or from one country to another. Moreover, this simple truism gives rise to area frequency distributions for large river basin or outcrop or nation area that are primarily dependent on the number of basins or outcrops or countries that exist across that particular landmass. As a consequence, the size frequencies of these areal units can be closely predicted knowing only the total area under consideration and the number of drainage basins, outcrop areas, or nations that exist within the area. The similarity between area frequencies of large river basins and rock types and nations suggests a nontrivial component of geologic influence on the partitioning of continental surfaces into major political divisions, and implies that cultural and economic factors, which serve to divide and unite political entities, do so within a geological framework.  相似文献   

Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: III. Physical stratigraphy and charcoal analysis     

Manuel?R.?Palacios-FestEmail author  Andrew?S.?Cohen  Kiram?Lezzar  Louis?Nahimana  Brandon?M.?Tanner 《Journal of Paleolimnology》2005,34(1):31-49

Documenting the history of catchment deforestation using paleolimnological data involves understanding both the timing and magnitude of change in the input of erosional products to the downstream lake. These products include both physically-eroded soil and the byproducts of burning, primarily charcoal, which arise from both intentional and climatically-induced changes in fire frequency. As a part of the Lake Tanganyika Biodiversity Projects special study on sedimentation, we have investigated the sedimentological composition of seven dated cores from six deltas or delta complexes along the east coast of Lake Tanganyika: the Lubulungu River delta, the Kabesi River delta, the Nyasanga/Kahama River delta, and the Mwamgongo River delta in Tanzania, and the Nyamusenyi River delta and Karonge/Kirasa River delta in Burundi. Changes in sediment mass accumulation rates, composition, and charcoal flux in the littoral and sublittoral zones of the lake that can be linked to watershed disturbance factors in the deltas were examined. Total organic carbon accumulation rates, in particular, are strongly linked to higher sediment mass accumulation from terrestrial sources, and show striking mid-20th century increases at disturbed watershed deltas that may indicate a connection between increased watershed erosion and increased nearshore productivity. However, changes in sedimentation patterns are not solely correlated with the 20th century period of increasing human population in the basin. Fire activity, as recorded by charcoal accumulation rates, was also elevated during arid intervals of the 13th–early 19th centuries. Some differences between northern and southern sedimentation histories appear to be correlated with different histories of human population in central Tanzania in contrast with northern Tanzania and Burundi.  相似文献   

Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: IV. Lacustrine paleoecology     

Manuel?R.?Palacios-FestEmail author  Simone?R.?Alin  Andrew?S.?Cohen  Brandon?Tanner  Heather?Heuser 《Journal of Paleolimnology》2005,34(1):51-71

Fossil invertebrates from cores collected in Lake Tanganyika provide a record of probable nearshore ecological response to recent watershed deforestation and sediment erosion in several East African watersheds. We compared paleoecological profiles (primarily from ostracodes) from watersheds spanning a range of sizes and present-day deforestation disturbance levels to understand the timing and magnitude of faunal changes, and their relationship in time to terrestrially-derived disturbance indicators. Profiles from the Lubulungu and Nyasanga/Kahama Rivers (Tanzania) provide a record of faunal variability in watersheds that are currently undisturbed with respect to deforestation. These records indicate continuous faunal turnover through time. However, this pattern of turnover is accompanied by relatively high levels of diversity throughout the record, with no wholesale extinction events. Ostracode taphonomic data and other fossil abundance data from the Lubulungu area provide strong evidence in support of at least two episodes of lower lake levels, associated with episodes of Late Holocene aridity. Records from deltas of disturbed watersheds at the Kabesi River (Tanzania) and those of Northern Burundi all show a combination of profound and abrupt faunal turnover, in some cases accompanied by local extinction and establishment of a few dominant taxa. At the Mwamgongo River delta, fed from a very small, disturbed watershed, species turnover was subtler. In disturbed watershed cores showing abrupt faunal changes the transitions mostly occurred in the late 19th to early 20th centuries, predating the major mid-20th century increase in sediment mass accumulation rates, with the latter only correlated with changing fossil abundance and flux. However, the earlier faunal community changes are contemporaneous with both palynological and geochemical changes in the core profiles indicative of changing land-use patterns. This suggests that lacustrine ecosystem response to deforestation was a two-stage process, with an earlier phase of response to changing quality of sediments or dissolved matter being discharged from the watershed, and a subsequent phase responding to increased quantity of sediment.  相似文献   

Constructing a coherent joint prior while respecting biological realism: application to marine mammal stock assessments   总被引：1，自引：0，他引：1  

Brandon  John R.; Breiwick  Jeffrey M.; Punt  Andre E.; Wade  Paul R. 《ICES Journal of Marine Science》2007,64(6):1085-1100

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Impact of Partially Cemented and Non-persistent Natural Fractures on Hydraulic Fracture Propagation     

Wei Fu  Brandon C. Ames  Andrew P. Bunger  Alexei A. Savitski 《Rock Mechanics and Rock Engineering》2016,49(11):4519-4526

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Imprints of mass accretion on properties of galaxy clusters     

Andreas Faltenbacher  Brandon Allgood  Stefan Gottlöber  Gustavo Yepes  Yehuda Hoffman 《Monthly notices of the Royal Astronomical Society》2005,362(3):1099-1108

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Bandlimited implicit Runge–Kutta integration for Astrodynamics     

Ben K. Bradley  Brandon A. Jones  Gregory Beylkin  Kristian Sandberg  Penina Axelrad 《Celestial Mechanics and Dynamical Astronomy》2014,119(2):143-168

We describe a new method for numerical integration, dubbed bandlimited collocation implicit Runge–Kutta (BLC-IRK), and compare its efficiency in propagating orbits to existing techniques commonly used in Astrodynamics. The BLC-IRK scheme uses generalized Gaussian quadratures for bandlimited functions. This new method allows us to use significantly fewer force function evaluations than explicit Runge–Kutta schemes. In particular, we use a low-fidelity force model for most of the iterations, thus minimizing the number of high-fidelity force model evaluations. We also investigate the dense output capability of the new scheme, quantifying its accuracy for Earth orbits. We demonstrate that this numerical integration technique is faster than explicit methods of Dormand and Prince 5(4) and 8(7), Runge–Kutta–Fehlberg 7(8), and approaches the efficiency of the 8th-order Gauss–Jackson multistep method. We anticipate a significant acceleration of the scheme in a multiprocessor environment.  相似文献   

Tools for gauging the capacity of salmon spawning substrates          下载免费PDF全文

Brandon T. Overstreet  Clifford S. Riebe  John K. Wooster  Leonard S. Sklar  Dino Bellugi 《地球表面变化过程与地形》2016,41(1):130-142

We present a set of river management tools based on a recently developed method for estimating the amount of salmon spawning habitat in coarse‐bedded rivers. The method, which was developed from a mechanistic model of redd building by female salmon, combines empirical relationships between fish length, redd area, and the sizes of particles moved by fish during spawning. Model inputs are the grain‐size indices D₅₀ and D₈₄ and an estimate of female fish length, which is used to predict the size of the redd that they will build and the size of the largest particle that they can move on the bed. Outputs include predictions of the fraction of the bed that the fish can use for redd building and the number of redds that they can build within the useable area. We cast the model into easy‐to‐use look‐up tables, charts, an Excel worksheet, a JavaScript web applet, and a MATLAB user interface. We explain how these tools can be used in a new, mechanistic approach to assessing spawning substrates and optimizing gravel augmentation projects in coarse‐bedded rivers. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Re-evaluating Nd/Nd in lunar mare basalts with implications for the early evolution and bulk Sm/Nd of the Moon     

Alan D. Brandon  Thomas J. Lapen  Brian L. Beard  Clive Neal 《Geochimica et cosmochimica acta》2009,73(20):6421-17609

The Moon likely accreted from melt and vapor ejected during a cataclysmic collision between Proto-Earth and a Mars-sized impactor very early in solar system history. The identical W, O, K, and Cr isotope compositions between materials from the Earth and Moon require that the material from the two bodies were well-homogenized during the collision process. As such, the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the Earth. Two recent studies to obtain high-precision ¹⁴²Nd/¹⁴⁴Nd ratios of lunar mare basalts yielded contrasting results. In one study, after correction of neutron fluence effects imparted to the Nd isotope compositions of the samples, the coupled ¹⁴²Nd-¹⁴³Nd systematics were interpreted to be consistent with a bulk Moon having a chondritic Sm/Nd ratio [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372]. The other study found that their data on the same and similar lunar mare basalts were consistent with a bulk Moon having a superchondritic Sm/Nd ratio [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516]. Delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the Moon and for constraining the types of materials available for accretion into large terrestrial planets such as Earth.To further examine this issue, the same six lunar mare basalt samples measured in Rankenburg et al. [Rankenburg K., Brandon A. D. and Neal C. R. (2006) Neodymium isotope evidence for a chondritic composition of the Moon. Science312, 1369-1372] were re-measured for high-precision Nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than ±3 ppm (2σ) for ¹⁴²Nd/¹⁴⁴Nd ratios. The measurements were repeated in a distinct second analytical campaign to further test their reproducibility. Evaluation of accuracy and neutron fluence corrections indicates that the multidynamic Nd isotope measurements in this study and the 3 in Boyet and Carlson [Boyet M. and Carlson R. W. (2007) A highly depleted Moon or a non-magma origin for the lunar crust? Earth Planet. Sci. Lett.262, 505-516] are reproducible, while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk Moon with either chondritic or superchondritic Sm/Nd ratios. The multidynamic data are best explained by a bulk Moon with a superchondritic Sm/Nd ratio that is similar to the present-day average for depleted MORB. Hafnium isotope data were collected on the same aliquots measured for their ¹⁴²Nd/¹⁴⁴Nd isotope ratios in order to assess if the correlation line for ¹⁴²Nd-¹⁴³Nd systematics reflect mixing processes or times at which lunar mantle sources formed. Based on the combined ¹⁴²Nd-¹⁴³Nd-¹⁷⁶Hf obtained we conclude that the ¹⁴²Nd-¹⁴³Nd correlation line measured in this study is best interpreted as an isochron with an age of 229⁺²⁴₋₂₀Ma after the onset of nebular condensation. The uncertainties in the data permit the sources of these samples to have formed over a 44 Ma time interval. These new results for lunar mare basalts are thus consistent with a later Sm-Nd isotope closure time of their source regions than some recent studies have postulated, and a superchondritic bulk Sm/Nd ratio of the Moon and Earth. The superchondritic Sm/Nd signature was inherited from the materials that accreted to make up the Earth-Moon system. Although collisional erosion of crust from planetesimals is favored here to remove subchondritic Sm/Nd portions and drive the bulk of these bodies to superchondritic in composition, removal of explosive basalt material via gravitational escape from such bodies, or chondrule sorting in the inner solar system, may also explain the compositional features that deviate from average chondrites that make up the Earth-Moon system. This inferred superchondritic nature for the Earth similar to the modern convecting mantle means that there is no reason to invoke a missing, subchondritic reservoir to mass balance the Earth back to chondritic for Sm/Nd ratios. However, to account for the subchondritic Sm/Nd ratios of continental crust, a second superchondritic Sm/Nd mantle reservoir is required.  相似文献