ALBERT

Notes: Abstract Small left-lateral strike-slip faults and right-lateral monoclinal kink bands with subvertical fold axes may be related to the formation of a very large right-lateral kink band (Bear Creek kink band), about 8 km wide and at least 15 km long, trending N27W along Bear Creek Valley in the Mt. Abbot quadrangle, Sierra Nevada, California. A foliation within Bear Creek Valley is defined by vertical slabs of granodiorite bounded by joints and faults. Small strike-slip faults and larger fault zones have nucleated along preëxisting joints and accommodated shearing between granodiorite slabs. The orientations of small cracks that occur near the tips of faults or connect adjacent fault segments indicate that the direction of maximum compression was about 20° counterclockwise from traces of joints at the time the faults nucleated. In some places where faults are closely spaced there are small, right-lateral kink bands with widths of 1 to 20 m. The slabs of granodiorite are gently curved through the kink bands, and analysis of the orientations of slabs in the limbs of the small kink bands indicates that the direction of maximum compression during kink-band formation was 15° to 20° counterclockwise from the traces of faults outside the kink bands. The orientation of the maximum compression for the formation of the small cracks at tips of many strike-slip faults and for the formation of the small kink bands, relative to the orientation of the maximum compression inferred from the joints on the limb of Bear Creek kink band, suggests that the foliation within the Bear Creek Valley has reoriented a maximum of 40° to 60° clockwise. Although the various orientations of joints, faults, and kink bands could be explained in terms of different regional compression directions at different places and at different times in the Mt. Abbot quadrangle, a much simpler interpretation, based on analysis of large and small structures in the granodiorite in Bear Creek Valley, is that they all formed in response to one maximum regional compression in the direction N25E.

Notes: Abstract The radial pattern of syenite and syenodiorite dikes of the Spanish Peaks region is analysed using theories of elasticity and dike emplacement. The three basic components of Odé's model for the dike pattern (a pressurized, circular hole; a rigid, planar boundary; and uniform regional stresses) are adopted, but modified to free the regional stresses from the constraint of being orthogonal to the rigid boundary. Dike areal density, the White Peaks intrusion, the strike of the upturned Mesozoic strata, and the contact between these strata and the intensely folded and faulted Paleozoic rocks are used to brient the rigid boundary along a north-south line. The line of dike terminations locates the rigid boundary about 8 km west of West Peak. The location of a circular plug, Goemmer Butte, is chosen as a point of isotropic stress. A map correlating the location of isotropic stress points with regional stress parameters is derived from the theory and used to determine a regional stress orientation (N82E) and a normalized stress magnitude. The stress trajectory map constructed using these parameters mimics the dike pattern exceptionally well. The model indicates that the regional principal stress difference was less than 0.05 times the driving pressure in the West Peak intrusion. The regional stress difference probably did not exced 5 MN/m2.

Notes: Investigates whether the recent emphasis on persuading employers to abandon ageist attitudes and appoint or promote on merit, irrespective of the applicant's age, has been justified by comparing the results of the 1992 Institute of Personnel Management survey with those from 221 post-experience management students from a survey carried out in 1995. In this preliminary analysis of the data, major points of similarity and divergence are examined to see if a "new generation" of managers are thinking in substantially different ways on this long-standing labour market issue.

Notes: [Auszug] The sudden, widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene/Oligocene boundary (∼34 million years ago) (refs 1–4) is one of the most fundamental reorganizations of global climate known in the geologic record. The ...

Notes: Numerous studies have underscored the importance of terrestrial ecosystems as an integral component of the Earth's climate system. This realization has already led to efforts to link simple equilibrium vegetation models with Atmospheric General Circulation Models through iterative coupling procedures. While these linked models have pointed to several possible climate–vegetation feedback mechanisms, they have been limited by two shortcomings: (i) they only consider the equilibrium response of vegetation to shifting climatic conditions and therefore cannot be used to explore transient interactions between climate and vegetation; and (ii) the representations of vegetation processes and land-atmosphere exchange processes are still treated by two separate models and, as a result, may contain physical or ecological inconsistencies.Here we present, as a proof concept, a more tightly integrated framework for simulating global climate and vegetation interactions. The prototype coupled model consists of the GENESIS (version 2) Atmospheric General Circulation Model and the IBIS (version 1) Dynamic Global Vegetation Model. The two models are directly coupled through a common treatment of land surface and ecophysiological processes, which is used to calculate the energy, water, carbon, and momentum fluxes between vegetation, soils, and the atmosphere. On one side of the interface, GENESIS simulates the physics and general circulation of the atmosphere. On the other side, IBIS predicts transient changes in the vegetation structure through changes in the carbon balance and competition among plants within terrestrial ecosystems.As an initial test of this modelling framework, we perform a 30 year simulation in which the coupled model is supplied with modern CO2 concentrations, observed ocean temperatures, and modern insolation. In this exploratory study, we run the GENESIS atmospheric model at relatively coarse horizontal resolution (4.5° latitude by 7.5° longitude) and IBIS at moderate resolution (2° latitude by 2° longitude). We initialize the models with globally uniform climatic conditions and the modern distribution of potential vegetation cover. While the simulation does not fully reach equilibrium by the end of the run, several general features of the coupled model behaviour emerge.We compare the results of the coupled model against the observed patterns of modern climate. The model correctly simulates the basic zonal distribution of temperature and precipitation, but several important regional biases remain. In particular, there is a significant warm bias in the high northern latitudes, and cooler than observed conditions over the Himalayas, central South America, and north-central Africa. In terms of precipitation, the model simulates drier than observed conditions in much of South America, equatorial Africa and Indonesia, with wetter than observed conditions in northern Africa and China.Comparing the model results against observed patterns of vegetation cover shows that the general placement of forests and grasslands is roughly captured by the model. In addition, the model simulates a roughly correct separation of evergreen and deciduous forests in the tropical, temperate and boreal zones. However, the general patterns of global vegetation cover are only approximately correct: there are still significant regional biases in the simulation. In particular, forest cover is not simulated correctly in large portions of central Canada and southern South America, and grasslands extend too far into northern Africa.These preliminary results demonstrate the feasibility of coupling climate models with fully dynamic representations of the terrestrial biosphere. Continued development of fully coupled climate-vegetation models will facilitate the exploration of a broad range of global change issues, including the potential role of vegetation feedbacks within the climate system, and the impact of climate variability and transient climate change on the terrestrial biosphere.

Notes: The LAD estimator of the vector parameter in a linear regression is defined by minimizing the sum of the absolute values of the residuals. This paper provides a direct proof of asymptotic normality for the LAD estimator. The main theorem assumes deterministic carriers. The extension to random carriers includes the case of autoregressions whose error terms have finite second moments. For a first-order autoregression with Cauchy errors the LAD estimator is shown to converge at a 1/n rate.