Geologic interpretation of the aeromagnetic survey in the Agourai area (Central Morocco)

Abstract The aim of this work is to interpret the geologic structures of the Agourai area (Paleozoic and Mesozoic structures) from processed magnetic maps. The detected magnetic anomalies from different standard methods used in aeromagnetism (Residual map, RTP map, horizontal gradient map) were compared to geologic structures and permit enhancing the mapping quality of some areas, and thus defining many geologic features. Existing geologic maps and geologic field studies allow interpreting some detected anomalies. It was thus possible to define the limits between the Paleozoic basement and the Mesozoic cover, to determine magnetic anomalies according to NE-SW trends compatible with the regional geologic structures and finally to detect a NE to SW-oriented fault system in the Mesozoic cover of the Agourai Plateau. Despite the reliability of this approach, some folded basaltic sills occurring in this region were not well detected, probably because of their reduced thickness

Location of geologic structures from interpretation of ERTS-1 imagery, Carbon County, Wyoming

The author has identified the following significant results. Possible geologic structures in the basin sediments of Carbon County and vicinity were located by interpretation of ERTS-1 imagery. These same structures are not evident on existing conventional geologic maps of the area. Subsequent field checks confirmed much of the geologic interpretation, but revealed that two apparent closed structures identified on the ERTS-1 imagery were actually topographic pseudostructures in flat or homoclinal sediments. Stereoscopic coverage (where available) allows the interpreter to avoid such misinterpretations

Mapping magnetized geologic structures from space: The effect of orbital and body parameters

When comparing previous satellite magnetometer missions (such as MAGSAT) with proposed new programs (for example, Geopotential Research Mission, GRM) it is important to quantify the difference in scientific information obtained. The ability to resolve separate magnetic blocks (simulating geological units) is used as a parameter for evaluating the expected geologic information from each mission. The effect of satellite orbital altitude on the ability to resolve two magnetic blocks with varying separations is evaluated and quantified. A systematic, nonlinear, relationship exists between resolution and distance between magnetic blocks as a function of orbital altitude. The proposed GRM would provide an order-of-magnitude greater anomaly resolution than the earlier MAGSAT mission for widely separated bodies. The resolution achieved at any particular altitude varies depending on the location of the bodies and orientation

Forestry, geology and hydrological investigations from ERTS-1 imagery in two areas of Ecuador, South America

The author has identified the following significant results. In the Oriente area, well-drained forests containing commercially valuable hardwoods can be recognized confidently and delineated quickly on the ERTS imagery. In the tropical rainforest, ERTS can provide an abundance of inferential information about large scale geologic structures. ERTS imagery is better than normal aerial photography for recognizing linears. The imagery is particularly useful for updating maps of the distributary system of the Guagas River Basin and of any other river with a similarly rapid changing channel pattern

ERTS-1 image contributes to understanding of geologic structures related to Managua earthquake, 1972

ERTS-1 imaged the western portion of Nicaragua on December 24, 1972, one day after the central part of the city of Managua was devastated by a major earthquake which measured 5.6 on the Richter scale. ERTS-1 images reveal sets of lineaments (which may reflect fault systems) along any one of which movement could have taken place. One set includes a line of active volcanoes that parallels the coast and constitutes the southwestern edge of the Nicaraguan Depression, a regional graben which cuts obliquely across the Central American isthmus. This trend is offset approximately 10km in a right lateral geometric sense just west of the city of Managua. A parallel lineament, north of Lake Managua, marks the northeast edge of the graben. A second set, extends northward to northwestward from the mouth of the Rio Grande (Viejo) north of Lake Managua and can be projected southward across the lake to Managua. It is this set along which geometric offset of the volcanic lineament appears to have taken place

Lineaments in the Grand Canyon area, northern Arizona - A radar analysis

Side-looking radar analysis of Grand Canyon Arizona geomorpholog

Lineaments of Texas---Possible Surface Expressions of Deep-Seated Phenomena

Geologic structures are important controls on geothermal resources. Buried plutons, intrusions, or diapirs may provide either localized areas of high heat flow or zones of high thermal conductivity. Various structures such as faults, joints, folds, or buried massifs may affect underground fluid flow and thus may alter local thermal regimes. These subsurface hydrologic effects may either enhance or detract from geothermal potential because upwelling of deep-seated fluids increases local geothermal gradient, but recharge decreases geothermal gradient. Geologic structures provide direct controls on heat flow and indirect controls on geothermal gradients via hydrologic processes. Understanding geologic structures, especially buried structures, will therefore aid in assessing the geothermal potential of a given area. Some lineaments are surface indicators of geologic structures. An analysis of lineaments and an awareness of general hydrologic regimes provide means for delimiting promising areas for geothermal development. Lineaments, however, are polygenetic; not all linear features are related to earth structures at depth. Some are expressions of surface processes alone. Others seem to be essentially random alignments of features such as drainage, topography, soils, or vegetation, and the cause of many such features is unknown or ambiguous. Because of the varying quality of information imparted by individual lineaments, a high "noise-to-signal" ratio exists in lineament data. The geologist's task, in collecting lineament data and in subsequently analyzing them, is to winnow noise from signal—that is, to eliminate patterns that impart no geologic information, and thereby to ascertain which features are significant with respect to local or regional geologic structures. This process entails correlation of lineaments with other mapped features. For geothermal assessment, special emphasis must be placed on recognition of buried structures or other irregularities that may control thermal conditions in subsurface fluids. Using lineament analysis for ascertaining geothermal potential entails a consideration of the structural (subsurface) control on surface features—especially the recurring motifs of aligned features that constitute regional or statewide linear trends or "grain." In places, lineaments are clearly correlative with buried structures. But lineaments also occur in areas without known subsurface discontinuities, and lineaments also occur in many places that have no geothermal potential. Thus, lineament analysis as a prospecting tool must be used carefully. Some workers have tended to assume that the very presence of a lineament invariably implies geologic control. The data we obtained do not support such a view, but they do indicate that many lineaments are expressions of local structural conditions that may be otherwise hidden or subtle.Bureau of Economic Geolog

Dilated Spatial Generative Adversarial Networks for Ergodic Image Generation

Generative models have recently received renewed attention as a result of adversarial learning. Generative adversarial networks consist of samples generation model and a discrimination model able to distinguish between genuine and synthetic samples. In combination with convolutional (for the discriminator) and de-convolutional (for the generator) layers, they are particularly suitable for image generation, especially of natural scenes. However, the presence of fully connected layers adds global dependencies in the generated images. This may lead to high and global variations in the generated sample for small local variations in the input noise. In this work we propose to use architec-tures based on fully convolutional networks (including among others dilated layers), architectures specifically designed to generate globally ergodic images, that is images without global dependencies. Conducted experiments reveal that these architectures are well suited for generating natural textures such as geologic structures

Geological Structure of the Jornada del Muerto and Adjoining Bolson Plains

The recent visits of a number of the members of the Academy to the Tulerosa district and contiguous plains in New Mexico makes it seem worthwhile to call attention to some of the major geologic structures of the region

Evaluation of LANDSAT-2 (ERTS) images applied to geologic structures and mineral resources of South America

The author has identified the following significant results. The Salar of Coposa is located in northern Chile along the frontier with Bolivia. The surface was divided into six general classes of materials. Analysis of LANDSAT image 1243-14001 by use of interactive multispectral computer (Image 100) enabled accurate repetition of these general classes based on reflectance. The Salar of Uyuni is the largest of the South American evaporite deposits. Using image 1243-13595, and parallel piped computer classification of reflectance units, the Salar was divided into nine classes ranging from deep to shallow water, water over salt, salt saturated with water, and several classes of dry salt