Discrete Fault Research Articles

Tectonic relationships between the Proterozoic Gawler and Willyama orogenic domains, Australia

Stratotectonic and morphotectonic data from the two principal exposed domains (pre-Adelaidean rocks) of the Gawler sub-province are used to characterize the Proterozoic Olarian orogeny and to distinguish its effects from those of the later Phanerozoic Delamerian orogeny. The principal metasedimentary sequences in the Gawler domain and in the Willama domain are inferred to have been deposited in a single broad zone of early Proterozoic shallow-water sedimentation on older (presumed Archaean) continental crust. The sequence becomes more pelitic upwards and may be interpreted as a transgressive sequence with more distal facies to the east. Three main phases of deformation are recognized, and each phase has similar characteristics and age in both domains. D1 2nd D2 can be dated between 1850 and 1650 Ma, while D3 appears to be about 1650-1540 Ma. In high grade rocks, D1 gave rise to a layer-parallel schistosity, while D2 is characterized by tight folds with a high-grade axial-plane schistosity. The whole subprovince was characterized by high geothermal gradients so that medium- to highgrade metamorphism affected the lower parts of the succession before and during the D1 and D2 deformation episodes. No distinct tectonic zones can be recognized but large-scale stratigraphic inversions (i.e. nappe tectonics) during D1 have been recognized only in the east of the Willyama domain. The higher parts of the stratigraphic succession are generally less deformed and exhibit only low-grade metamorphism. D3 produced relatively open, upright macroscopic folds and was characteristically associated with retrogression, but was demonstrably of pre-Adelaidea n age. The Gawler domain exhibits D3 structures although it lies in the platform west of the Adelaide Geosyncline and was not affected by deformation during Adelaidean sedimentation or by the subsequent Delamerian orogeny. A network of retrograde shear zones is the principal expression of post-Olarian deformation in the Willyama domain which forms part of the basement to the Adelaide Geosyncline. The trends of D2 and D3 folding in the two domains are similar and it is shown therefore that no large-scale rotations of one domain relative to the other has been produced by the Delamerian orogeny. Large-scale translations on discrete faults or on broad zones of simple shear in the basement are not easily ruled out, but if they exist, are probably largely of pre-Adelaidea n age. However, a significant relationship between Olarian structures and variable Adelaidean fold trends has been deduced. The Olarian orogeny may have occurred in close proximity to a continental margin to the east and may thus be related to subduction processes. It differs from linear gneissic belts in Phanerozoic orogenies since it occurs in a more stable stratotectonic environment and over a wider area.

Petroleum Prospects of Lebanon: Reevaluation

Lebanon occupies 10,170 sq km along the eastern Mediterranean seaboard. The country is mainly mountainous and includes two north-northeast-south-southwest-trending ranges separated by a structural depression. Seven exploratory wells have been drilled in Lebanon, six relatively deep tests and one shallow. None tested formations older than those cropping out in Lebanon. These wells were drilled between 1947 and 1967. About 5,800 m of predominantly marine sedimentary rocks, ranging in age from Early Jurassic to recent, are exposed in Lebanon. Paleogeographic considerations of facies and thickness indicate that the country was the site of marine sedimentation during the Paleozoic Era also, and that 2,800 to 3,300 m of sedimentary rocks of Paleozoic through Early Jurassic age lie below the oldest exposures. The tectonic style is almost entirely vertical movement on discrete fault blocks, with minor compression caused by jostling between blocks. As a result, the exposed competent carbonate rocks in the succession are highly fractured and meteoric waters have invaded subsurface reservoirs where structures are near the main faults or elevated outcrop recharge areas. However, indications of petroleum are plentiful, and commercial accumulations are likely where cover is unbreached. Such accumulations should occur mainly in formations of pre-Jurassic age, because these strata should include many interbeds of shale, marl, and evaporite which would not be fractured seriously by major faulting. Evaluation of wells drilled shows that several were not sited correctly in relation to structure. Future efforts should be concentrated on the continental shelf for upper Paleozoic-Cretaceous objectives, and on the major closed structures in the mountains for tests of the pre-Jurassic sequence to basement.

Inspection of sheet materials--model and data.

In the inspection of sheet materials in industry, two interrelated tasks are involved: Visual search and decisionmaking. When these tasks have been studied separately, it has been found that both exhibit a speed/error trade-off. As more time is allowed for the task, errors usually decrease. However the speed/error trade-off in industrial inspection studies shows that, as time per item is increased, Type 2 errors (accepting faulty items) decrease while Type 1 (rejecting good items) errors actually increase. A model combining visual search and decision theory is postulated and tested on the inspection of flat glass for discrete faults. Separate experiments are performed to test the ability of inspectors to (1) search for and locate known defects in sheets of glass, and (2) decide whether a small fixated circular dot is above or below the standard required. The results of these two experiments are used to derive model parameters and the model used to predict performance in the factory situation. The model predicts the same change in errors with increasing time per item as results obtained previously in flat-glass inspection.

Control of resistivity, microstructure, and stress in electron beam evaporated tungsten films : A. K. Sinhaet al. J. Vac. Sci. Technol. 10 (3), 436–444 (May-June 1973)

Electrical power distribution systems are composed of heterogeneous components, which include continuous power sources, discrete relays, passive and active loads, and fast-switching power conversion subsystems. This heterogeneity introduces significant challenges for model-based diagnosis, such as building accurate models, and generating fast and accurate diagnoses while ensuring robustness to measurement noise and modeling errors. In this paper, we present a comprehensive methodology for the diagnosis of parametric and discrete faults in electrical power distribution systems that include dc and ac components. We use a hybrid bond graph modeling language to systematically develop computational models and algorithms for hybrid state estimation, robust fault detection, and efficient fault isolation. Simulation and experimental results on a real-world electrical power distribution system demonstrate the effectiveness of our methodology.

Sedimentary Rock Deformation Related to Structure in Basement: ABSTRACT

Petroleum exploration and development in areas of deformed sedimentary rocks commonly must be concerned with the interrelations between sedimentary rock deformation and the structure of the basement. Concern with the changes in the nature and attitudes of structures with increasing depth, and increased emphasis on understanding regional structural styles, necessitate an understanding of expected basement behavior during deformation of the overlying sedimentary rocks. The basement comprises those igneous and metamorphic rocks of the earth's crust which unconformably underlie the unmetamorphosed, dominantly sedimentary rocks of a particular region. As defined here the term bears no connotation of specific age. Although for most of North America the basement is Precambrian, it is Mesozoic in parts of California and Paleozoic in parts of the New England Upland the Appalachian Piedmont. The widespread occurrence in the basement of severely deformed metasedimentary rocks in association with igneous intrusives typically reveals a long and complex history of deformation under confining pressures ranging up to 5,000-8,000 bars and at temperatures commonly in the order of 300°-800°C. Thus the environment which originally produced the basement rocks was much different from that of the relatively low energy levels in which the overlying sedimentary rocks were deposited and subsequently deformed, and the resulting mechanical properties of basement-type rocks are very different from those of most sedimentary rocks. It is clear that the interface between the basement and the overlying sedimentary rocks is a mechanical discontinuity as well as a stratigraphic and structural one. Especially in those regions where the basement was closely involved in the deformation of the superjacent sedimentary rocks is a knowledge of the expected mechanical behavior of the basement essential End_Page 1836------------------------------ to understanding the regional structural framework and the changes in the nature and attitudes of local structures with increasing depth. Triaxial compression tests by several workers on typical basement rocks indicate that the expected mode of failure of the basement in submetamorphic environments is principally fracturing and faulting. This is consonant with numerous field data from many structural provinces in North America and elsewhere. Present understanding of sedimentary rock deformation related to basement structures is best for regions of relatively thin sedimentary cover, such as in the foreland of the Rocky Mountains. Here the dominant structure of the Laramide orogeny is basement block faulting of diverse trends and great structural relief. Individual blocks are bounded by upthrust faults which commonly die out upward into monoclinal flexures in the overlying sedimentary rocks. Horizontal compression structures on a wide range of scales may be formed even though differential vertical uplift characterizes the fundamental structural style. The deformation of the sedimentary rocks is demonstrably a direct result of differential movement of discrete fault blocks in the underlying basement. This style of deformatio , so well defined in the Rocky Mountains foreland, is at least partly developed in other structural provinces where differential vertical uplift of a rigid basement with a sedimentary rock cover has been recognized. The roles of lithologic inhomogeneities and fabric anisotropies of the basement in controlling the locus and style of basement-related deformation of sedimentary rocks are complex and not well understood. Pertinent experimental work on the problem is very limited in amount and scope, and field data commonly are conflicting and inconsistent. The much-cited zone-of-weakness concept of basement-related structures is deemed not to have real operational significance in the present state of knowledge, but it remains a promising field for continued study. End_of_Article - Last_Page 1837------------

Basement-Controlled Deformation in Wyoming Province of Rocky Mountains Foreland

The Laramide deformation of the Rocky Mountains foreland in Montana, Wyoming, Colorado, and New Mexico is characterized by a distinctive structural style. Because the Laramide structure of Wyoming east of about 110° W. Long. well typifies that structural style, the term Wyoming Province is here used for the conterminous area characterized by it. The Precambrian basement of the Wyoming Province was closely involved in the Laramide deformation of the region. During the Laramide deformation the basement was covered generally by 8,000-15,000 feet of sedimentary rocks. The dominant structural style of the Wyoming Province is basement block faulting of diverse trends and great structural relief. Individual blocks are bounded by upthrust faults which commonly die out upward into monoclinal flexures in the overlying sedimentary rocks. Tilting of basement fault blocks produces a characteristic asymmetry of individual uplifts and basins. The deformation of the sedimentary rocks is mostly a direct consequence of differential movement of discrete fault blocks in the underlying basement. Originally horizontal sedimentary beds have been ch nged in attitude by (1) bodily tilting in unity with the underlying basement block, (2) drag along faults, (3) substitution of flexing for faulting along the strike of, or updip along, basement faults which extend into the overlying sedimentary rocks, and (4) buckling in local zones of horizontal compression related to upthrust faulting. Field studies in the Wyoming Province do not substantiate the widely held concept that there is a cause-and-effect relationship between either inherent fabric anisotropies or lithologic inhomogeneities in the basement and the style and locus of Laramide deformation. However, present inability to evaluate definitely such factors in controlling the style and locus of Laramide deformation of both basement and overlying sedimentary rocks does not necessarily invalidate that concept. Experimental rock deformation and other lines of evidence ultimately may provide a basis for relating inherent basement features to subsequent deformation.