Olivine-normative dolerite dikes from western South Carolina: Mineralogy,chemical composition and petrogenesis

This investigation describes five Mesozoic dolerite dikes which intrude Paleozoic metamorphic and igneous rocks of the Inner Piedmont of western South Carolina. The dikes are vertical or nearly so and strike approximately N40° W. Three major northeast-trending faults also occur in the study area. Left lateral displacement of one dolerite is documented at a locality near Cleveland, South Carolina. Elsewhere, several of the dolerite dikes appear to terminate at or near the faults. — The dolerite dikes have subophitic to microporphyritic textures and consist principally of plagioclase (generally An_70–80), olivine (dominantly Fo_80–90) and augite with subordinate pigeonite, titanomagnetite, chromite and brown, partly glassy mesostasis. In one dike pyroxene compositions trend from augite to ferroaugite in contrast to an augitesubcalcic augitepigeonite trend characteristic of the other dolerites. The contrasting trends primarily result from differences in SiO₂ abundance in the dolerite magmas. — Major and trace element analyses indicate the presence of two different olivine-normative dolerite magma types. The two magma types are not related by near surface crystal fractionation. Models for genesis of the olivine-normative dolerite magmas by partial melting of a plagioclase peridotite upper mantle source region are presented. The models require that the source region be enriched in LREE and incompatible elements such as Rb, Ba, Hf and Th relative to Cl chondritic abundances. One magma type appears to represent a primary dolerite magma that ascended from the source region with little subsequent compositional change. The second magma type most likely experienced assimilation of clinopyroxene-garnet (eclogite) during ascent, thereby acquiring a REE pattern with a less steep negative slope for the LREE and a slight positive slope in the HREE.     

Ultra-rapid landscape response and sediment yield following glacier retreat, Icy Bay, southern Alaska

The páramo is a neotropical alpine ecosystem that covers more than 75,000 km² of the northern Andes of Colombia, Ecuador, Venezuela, and Peru. It provides important environmental services: more than 10 million people in the Andean highlands benefit from the water supply and regulation function, which is attributed to the volcanic soils that underlie the ecosystem. The soils are also major carbon sinks of global significance. Severe land use changes and soil degradation threaten both the hydrology and carbon sink function. Nevertheless, soil genesis and properties in the páramo is rather poorly understood, nor are their ecological functions well documented. The impact of the geomorphology of the páramo on soil genesis was studied in the rio Paute basin, south Ecuador. Two toposequences were described and analysed. In each toposequence, four pedons were selected representing summit, backslope, undrained plain situation, and valley bottom positions in the landscape. The soils are classified as Hydric Andosols in the World Reference Base for Soil Resources and Epiaquands or Hydrudands in Soil Taxonomy. They are very acidic and have a high organic matter content, high P deficiency, and Al toxicity. Their water content ranges from 2.64 g g^− 1 at saturation, down to 1.24 g g^− 1 at wilting point, resulting in a large water storage capacity. Two major soil forming processes are identified: (1) volcanic ash deposition and (2) accumulation of organic carbon. Volcanic ash deposits may vary in depth as a result of regional geomorphological factors such as parent material, orientation, slope, and altitude. Organic carbon accumulation is an interaction of both waterlogging, which depends on the position in the landscape, and the formation of organometallic complexes with Al and Fe released during volcanic ash breakdown. Despite the high variability in parent material and topography, the soil is characterised by a notable homogeneity in physico-chemical properties. Statistical analysis reveals that only topographic location has a slight but significant influence on soil pH as well as the organic matter content, saturated conductivity and water retention at high pressure. Finally, the exceptional properties of these soils provide useful insights to improve classification of the Andosols reference group of the FAO World reference Base for Soil Resources.     

Changes and patterns of origin regions of international tourism

The dramatic political and economic changes in Europe, Asia, and the Middle East during the early 1990s have had a dramatic impact on international tourism. Between 1974 and 1990 there have been significant shifts in international tourist originations. The purpose of this paper is to describe and analyze the changing patterns and to compare the two time periods. A key component of the study is the construction of a Population-Adjusted Travel Index which assesses the capability of a country to generate tourists relative to population characteristics. Findings indicate that Europe is still the leader in trips generated, even though the proportion from this region is declining over time. Asian countries exhibited the most marked improvement due primarily to the tremendous economic expansion taking place on the Pacific Rim. In contrast countries of the Middle East have declined in importance relative to international tourism. This is due to political and economic instability in the region.     

Lamprothamnium prosperity in permannetly hypersaline water

The leuco-halophytic charophyte,Lamprothamnium papulosum, readily germinates, grows and reproduces in C1 Pond of ICI's solar saltworks near Port Alma, a permanently hypersaline waterbody in Queensland, Australia. Its morphology very much resembles that ofChara corallina, although the two central cells of the axial node are subdivided, a feature found inLamprothamnium but not inChara. Some of the characteristics of the Port Alma population, like the occurrence of a considerable proportion of pedicellate gametangia among the normal sessile ones, or the deviation in the sizes of some plant parts from the ranges that have been reported previously, are unusual, even for this highly variable species. Florida Agricultural Experiment Station Journal Series No. 6876     

Effects of weathering on site response

Nearly all studies of site response under seismic excitation employ idealized site models in which uniform layers of homogeneous soils are separated by perfect interfaces. The impedance mismatch at each interface gives rise to wave reflections which strongly affect the calculated free surface response. In reality, these perfect interfaces may often not exist. Instead, a zone in which materials from both above and below are mingled may form a blurred interface between layers. This article examines the effects of such weathered zones. The zone is modelled by a linearly varying shear modulus so that no abrupt impedance change occurs. Significant differences in response of weathered and unweathered profiles are found.