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Ohne Zusammenfassung Technische Hochschule Karlsruhe     

Partly-welded pyroclast flow deposits in Dominica,Lesser Antilles

A Pleistocene pyroclast flow of dacitic andesite composition is described from the island of Dominica, Lesser Antilles. Lateral zonation, from welded tuff to a tuffaceous zone of no welding and pumiceous distal facies is observed with distance from the vent. Comparable but less distinct zonation occurs in vertical sections. Variations in physical properties of the pyroclast flow, such as specific gravity, flattening ratio and grain size are described, and related to the degree of welding. Source of the pyroclast flow is located in the former crater of Micotrin volcano, now plugged by a dome. Eleven chemical analyses reveal small, but significant variations in composition, which, together with systematic variations in phenocryst content, are related to crystal sinking in the magma column prior to eruption.     

Etiologies, observations and reporting of estuarine finfish lesions.

Lesions in estuarine finfish are associated with a variety of organisms including parasites and bacterial, viral, and fungal infectious agents. In addition, trauma, suboptimal water quality, and other abiotic stress factors may result in the loss of homeostasis. We have observed solitary ulcerative lesions on menhaden sampled from the Chesapeake Bay, Maryland, the Pimlico River, North Carolina, and the St. Johns River, Florida. Histologically, the lesions demonstrated a marked chronic inflammatory infiltrate and granulomas in response to fungal hyphae throughout large areas of exposed necrotic muscle. Gram-negative rod-shaped bacteria were also observed in the lesions, a common finding in ulcers of aquatic organisms. Similar observations in menhaden and other species have been described previously in the literature as ulcerative mycosis, mycotic granulomatosis, red spot disease, and epizootic ulcerative syndrome. Despite the many different known causes of fish lesions, the popular press and the scientific literature have recently emphasized Pfiesteria piscicida and other Pfiesteria-like dinoflagellates (and their bioactive compounds) as the primary causative agent for finfish lesions, particularly mycotic granulomatous ulcers in Atlantic menhaden. While some laboratory data suggest that Pfiesteria may play a role in field-observed lesions, much more cause-and-effect evidence is needed to determine the importance of other risk factors, both alone or and in combination with Pfiesteria. In order to better understand the etiology of lesion initiation and progression in estuarine finfish, accurate assessments of environmental conditions collected on appropriate temporal and spatial scales, and fish morphological indicators consistent with gross and histological pathologic terminology, should be used for reporting fish lesion observations and kills. Further, this outlook will help to avoid bias and may foster a broader perspective for examining the health of estuarine systems in general.     

Sapphirine-bearing granulites and related high-temperature metamorphic rocks from the Higo metamorphic terrane, west-central Kyushu, Japan

The Higo metamorphic unit in west-central Kyushu island, southwest Japan is an imbricated crustal section in which a sequence of units with increasing metamorphic grade from high (northern part) to low (southern part) structural levels is exposed. The basal part of the metamorphic sequence representing an original depth of 23–24  km consists mainly of garnet–cordierite–biotite gneiss, garnet–orthopyroxene gneiss, orthopyroxene-bearing amphibolite and orthopyroxene-bearing S-type tonalite. These metamorphic rocks underwent high amphibolite-facies up to granulite facies metamorphism with peak P – T  conditions of 720  MPa, 870  °C. In addition sapphirine-bearing granulites and related high-temperature metamorphic rocks also occur as tectonic blocks in a metamorphosed peridotite intrusion. The sapphirine-bearing granulites and their related high-temperature metamorphic rocks can be subdivided into five types of mineral assemblages reflecting their bulk chemical compositions as follows: (1) sapphirine–corundum–spinel–cordierite (2) corundum–spinel–cordierite (3) garnet–corundum–spinel–cordierite (4) garnet–spinel–gedrite–corundum, and (5) orthopyroxene–spinel–gedrite. These metamorphic rocks are characterized by unusually high Al₂O₃ and low SiO₂ contents, which could represent a restitic nature remaining after partial melting of pelitic granulite under the ultra high-temperature contact metamorphism at the peak metamorphic event of the Higo metamorphic unit. The metamorphic conditions are estimated to be about 800  MPa and above 950  °C which took place at about 250  Ma as a result of the thermal effect of the regional gabbroic rock intrusions.     

Field investigation of erosion resistance of common grass species for soil bioengineering in Hong Kong

Grass cover is considered as a sustainable means of controlling soil erosion and enhancing durability of soil slopes. A number of grass species are commonly available for soil bioengineering in Hong Kong, but their capacities to control soil erosion have not been characterized quantitatively. The main objectives of this paper are to study the influence of soil density on characteristics of grass roots, to measure the erodibility parameters of the root-permeated soils at two growth stages, and to select the proper Hong Kong grass species that effectively control soil erosion. Three types of Hong Kong turf grass including Cynodon Dactylon, Paspalum Notatum, and Zoysia Matrella were planted on three soil grounds with degrees of compaction of 80, 90, and 100 %, respectively. The featural parameters of grass roots on each compacted ground, including root mass density, root volume density, and root depth, were measured in two growth stages. A jet index apparatus was applied to measure two erodibility properties (i.e., coefficient of erodibility and critical shear stress) of these vegetated soils in the two test stages. Cynodon Dactylon and Zoysia Matrella have higher root mass density values than Paspalum Notatum does, and reduce the susceptibility of soil erosion more effectively. Therefore, the two grass species are suggested for soil bioengineering in Hong Kong.     

Statistical Analysis of Anisotropic Damage of the Bukit Timah Granite

Summary This paper presents a method to analyze probabilistic anisotropic initial damage of a rock mass. A three-dimensional geometric model of cracks in a rock mass is established in terms of several parameters, such as orientations, spacing and normalized sizes of cracks in the rock mass. The dip, dip direction, spacing, and normalized size of cracks of the Bukit Timah granite in Singapore were obtained from visual inspection of rock cores, color TV imaging, and impression packer tests in the boreholes at a site of geological investigation. Using the measured data, probabilistic distribution laws of geometric parameters of cracks on the surface of the boreholes are derived. Based on these statistical distributions and using Monte-Carlo simulation method, the distribution of anisotropic initial damage of the Bukit Timah granite is derived and found to have a beta distribution. This anisotropic initial damage distribution of a rock mass can be used in probabilistic analysis of rock mass responses to both static and dynamic loads.