Microscopic feather fractures in the faulting process     

R.E. Conrad II  M. Friedman 《Tectonophysics》1976,33(1-2)

The nature and development of microscopic feather fractures (mff) are investigated in experimentally deformed intact and precut cylinders of room-dry Tennessee and Coconino Sandstone. All specimens are deformed at 25° C, and at a shortening rate of 10⁻⁴ sec⁻¹ ; the intact ones are at confining pressures from 0.5 to 2.5 kbar; and the precut specimens at 1.0 and 1.5 kbar. Mff occur in grains adjacent to induced shear fractures or faults; they are wedge-shaped and die out within one or two grain diameters from the fault; and they make acute angles with the fault such that arrows directed into the apices of these angles on either side of the fault define its sense of shear. Occurrence of mff only after slip on precut surfaces clearly demonstrates that they form as a result of shear displacement. The average angle between the mff and fault is 10° greater than that between the load axis and the fault, and it increases with increasing confining pressure in initially intact specimens. Data suggest that the abundance of mff (mean number per grain) increases with increasing normal stress across the fault and with displacement. The wedgeshaped character of many mff and their consistent orientation at 10° to the load axis are distinguishing characteristics. Mff are shown to be parallel to the local maximum compressive stress and thus are extension microfractures. They are not to be confused with precursive micro fractures developed prior to macroscopic fracture, nor to Riedel shears developed during faulting.  相似文献   

Oxygen isotopes of some trondhjemites,siliceous gneisses,and associated mafic rocks     

Fred Barker  Irving Friedman  D.R. Hunter  J.D. Gleason 《Precambrian Research》1976,3(6):547-557

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Alpha emitters in a coral from Bikini lagoon: A testimony to nuclear blasts in the Western Pacific     

Yitzhal Levy  Donald S. Miller  Gerald M. Friedman  Victor E. Noshkin 《GeoJournal》1977,1(5):91-96

In the years between 1946 and 1958, Bikini Atoll was the site of a series of nuclear device tests which led to the contamination of the calcium-carbonate tests of organisms, including those of corals. Alpha emitters and other radio-nuclides concentrated in these tests. The purpose of our study was to determine where in these test-alpha-emitters concentrated.Petrography of ultra thin sections, in conjunction with solid state alpha-track detectors, shows that it is possible to assign the alpha activity to different parts of the fabric within a coral. The application of this technique to a coral,Favites virens, from the lagoon of Bikini Atoll showed that the theca, septa and dissepiments of the coral skeleton contain very low concentrations of alpha emitters. By contrast, high concentration of alpha emitters occur in damaged parts of the coral. Some of these damaged areas contain cryptocrystalline calcium carbonate, different organisms (algae and/or bryozoan-like tests) and skeletal debris. High concentrations of alpha emitters are associated with the cryptocrystalline calcium carbonate (up to 3000 pCi/g), the skeletal debris (up to 550 pCi/g), bryozoan-like material, and algae (up to 700 pCi/g).

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Application of Sr and O isotope relations to the petrogenesis of the alkaline rocks of the Red Hill complex,New Hampshire,USA     

K. A. Foland  Irving Friedman 《Contributions to Mineralogy and Petrology》1977,65(2):213-225

The Red Hill ring complex in central New Hampshire is composed of apparently cogenetic syenites, nepheline-sodalite syenite, and granite. The ages and petrogenetic relations among five of the six recognized units have been investigated by rubidiumstrontium and oxygen isotope analysis of whole rocks and separated minerals. Whole-rock samples from three syenite units are consistent with a single Rb-Sr isochron which gives an age of 198±3 m.y. and an initial (⁸⁷Sr/⁸⁶Sr)_o ratio of 0.70330±0.00016 (±2 sigma; =1.42× 10^–11y^–1). However, Sr isotope data for two other units, nepheline syenite and granite, are not consistent with this isochron but rather indicate higher initial ratios which range from 0.7033 to about 0.707. Whole-rock O isotope analyses give ¹⁸O values which range from+6.2 to+9.3 Sr and O isotope analyses on mineral separates indicate that observed whole-rock variations in (⁸⁷Sr/⁸⁶Sr)_o are primary and are not due to any secondary process. The fact that the isotope systematics correlate with rock type, suggests that crustal interaction is likely to have played a significant role in the development of this over-and undersaturated association. Such process(es), while still not fully delineated, could be of fundamental importance to the genesis of associations of critically undersaturated and oversaturated intrusives. The data support the idea that interaction between magmas and crustal materials strongly influenced the compositional relations of similar complexes elsewhere including those of the White Mountain magma series.  相似文献   

Global seismicity of 1982: centroid-moment tensor solutions for 308 earthquakes     

A.M. Dziewonski  A. Friedman  D. Giardini  J.H. Woodhouse 《Physics of the Earth and Planetary Interiors》1983,33(2):76-90

The centroid-moment tensor analysis is applied to digital recordings of 308 moderate and large earthquakes that occurred during 1982 and were recorded by the Global Digital Seismograph Network (GDSN) and International Deployment of Accelerometers (IDA) networks. The tables contain numerical results for all events. A graphical representation of the source geometry is shown for the full moment tensor solution, as well as for the “best double couple”.  相似文献   

Origin of dolomite in Miocene Monterey Shale and related formations in the Temblor Range,California     

Irving Friedman  K.J. Murata 《Geochimica et cosmochimica acta》1979,43(8):1357-1365

Dolomites in thick sections of Miocene Monterey Shale and related formations in the Temblor Range of California acquired their isotopic compositions as they formed at shallow depth in the original sediment rich in organic matter, and retained the composition against the vicissitudes of burial diagenesis. The oxygen isotopes of dolomites of successive beds record changes in temperature of bottom water while the carbon isotopes of the same samples indicate changes in the kind of microbial activity (sulfate reduction vs carbohydrate fermentation) that prevailed at shallow depths in the sediment. In an auxiliary study, two samples of dolomite from sediments of Cariaco Basin off Venezuela (DSDP site 147) were found to have δ5C¹³ of ?14.1 and ?9.8 per ml PDB, although they occur in a heavy-carbon zone containing bicarbonate as heavy as +8.4 per ml. These dolomites probably originated at shallow depth in the light-carbon zone of microbial sulfate reducers and were buried under later sediments down into the heavy-carbon zone of microbial fermenters of carbohydrates without losing their original light-carbon composition.  相似文献   

Experimental studies relating to microfracture in sandstone     

J.J. Gallagher Jr  M. Friedman  J. Handin  G.M. Sowers 《Tectonophysics》1974,21(3):203-247

A fundamental understanding of the relation between stress concentrations at grain contacts and microfractures in granular aggregates is obtained through two-dimensional photomechanical model studies and is tested through observational studies of experimentally deformed sandstone discs, glass beads, and quartz sand.In uncemented aggregates, the state of stress in each grain is controlled by the manner in which the applied load is transmitted across grain contacts. The angles between lines connecting pairs of contacts and the axis of the principal load acting at the boundaries of the aggregate determine which of all contacts will be most highly stressed or “critical”. Microfractures follow that maximum principal stress trajectory which connects critical contacts, and they propagate through those points where the magnitude of the local maximum stress difference is the greatest. Microfractures, therefore, are extension fractures. It then follows that both the locations and orientations of fractures can be predicted if the state of stress in the grains is known.Positioning of critical contacts depends primarily on sorting, packing, grain shapes, and the boundary load conditions applied to the aggregate. Some critical contacts and, therefore, microfractures tend to join together in a series or “chain”. Orientations of chains are most strongly influenced by the direction of the maximum compressive load at the boundary of the aggregate. A hydrostatic load applied on the boundaries of an aggregate can cause microfracturing within grains. Orientations for microfractures and contact lines are random in poorly sorted aggregates, but they are influenced by packing in well sorted aggregates.Grains of cemented aggregates are more highly stressed at their centers than at contacts. By analogy, microfracture orientations depend strongly on the position of the greatest load axis and only slightly on the low-magnitude stress concentrations at contacts. These microfractures parallel the greatest principal stress trajectory in regions where the magnitude of the maximum stress difference is greatest. These observations lead to the conclusion that fractures in grains of cemented aggregates are also extension fractures and should exhibit a higher degree of preferred orientation than in uncemented counterparts.These conclusions hold when cementing materials have about the same elastic moduli as the grains. Cements may be so weak that the aggregate behaves as if it were uncemented in terms of microfracture fabric, or so stiff that the major part of the load is transmitted by the cement, and the composite is no longer an aggregate in the mechanical sense.  相似文献   

Sedimentary carbonate minerals: F. Lippmann. Springer-Verlag,Berlin, 1973, 228 pp., 54 figs., 38 tables, $21.50     

Gerald M. Friedman 《Sedimentary Geology》1974,12(1):70-71

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On the Behavior of the Stable Boundary Layer and the Role of Initial Conditions     

Xingzhong Shi  Richard T. McNider  M. P. Singh  David E. England  Mark J. Friedman  William M. Lapenta  William B. Norris 《Pure and Applied Geophysics》2005,162(10):1811-1829

Previous studies of the stable atmospheric boundary layer using techniques of nonlinear dynamical systems (MCNIDER et al., 1995) have shown that the equations support multiple solutions in certain parameter spaces. When geostrophic speed is used as a bifurcation parameter, two stable equilibria are found—a warm solution corresponding to the high-wind regime where the surface layer of the atmosphere stays coupled to the outer layer, and a cold solution corresponding to the low-wind, decoupled case. Between the stable equilibria is an unstable region where multiple solutions exist. The bifurcation diagram is a classic S shape with the foldback region showing the multiple solutions. These studies were carried out using a simple two-layer model of the atmosphere with a fairly complete surface energy budget. This allowed the dynamical analysis to be carried out on a coupled set of four ordinary differential equations. The present paper extends this work by examining additional bifurcation parameters and, more importantly, analyzing a set of partial differential equations with full vertical dependence. Simple mathematical representations of classical problems in dynamical analysis often exhibit interesting behavior, such as multiple solutions, that is not retained in the behavior of more complete representations. In the present case the S-shaped bifurcation diagram remains with only slight variations from the two-layer model. For the parameter space in the foldback region, the evolution of the boundary layer may be dramatically affected by the initial conditions at sunset. An eigenvalue analysis carried out to determine whether the system might support pure limit-cycle behavior showed that purely complex eigenvalues are not found. Thus, any cyclic behavior is likely to be transient.  相似文献   

Editorial     

Mel Friedman 《Tectonophysics》1984,101(3-4)

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