Structural Geology

The Pinnacles Volcanic Formation and the Neenach Volcanic Formation originated from a series of common eruptive centers during the early Miocene. The once contiguous units were subsequently split and separated 314 km from each other by movement along the San
Andreas fault. The actual site of the eruptions has important implications for the age of the 'big bend' segment of the San Andreas fault.
If the eruptions occurred in southern California with the Pinnacles Volcanic Formation moving northward, then the big bend segment must
have been active during early Miocene time.  Alternatively, if the eruptions occurred in northern California with the Neenach Volcanic
Formation moving southward, the big bend segment of the fault need be no older than Pliocene-Pleistocene. Early Miocene paleogeographic
reconstructions which do not place the Pinnacles and Neenach areas adjacent to each other are probably not valid.

The only occurrence of monoclines along the eastern flank of the Colorado Front Range is near Llvermore at the northern end of the tten echelonrl fold-and-fault belt (Fig. l). The monocl ines I ie along the Kawuneeche-Livermore Iineament (h/ork and tlatthev,rs, in preparatlon). sedimentary rocks elsewhere along the eastern flank of the Front Range were deformed into either homoclines, anticllnes, or syn-clines during the Laramide orogeny. Erosion has removed the sedlmentary rock cover from the Precambrian basement on the western edge of the area of monoclinal folding. Thus, the area pro-vldes an unusual opportunlty for studying the role of structural basement in the formation of the monocllnes. Our study comblned detalled field work with photo-interpretation of NASA U-2 photography stereo-pa I rs. DESCR I PT ION OF I1ONOCL lNES Northeast of Llvermore, Colorado the Paleozoic and l.lesozoic strata are folded into a series of narrov't linear monoclines (Flgs. 2r3)" The monoctines separate large areas where the strata are planar and lilanuscript received, February 18, 1976; accepted, llarch 3, 1976. fhe Mowttain Geologiet u. 73, no. 2 (Aprti lszol p. 61-66 6]. ABSTMCT: Honoclinal foldlng is the dominant style of deformation in Paleozoic and }lesozolc sedimentary strata northeast of Livermore, Colorado. The markedly llnear monocllnes are narrow and bound large areas of nearly flat-lylng strata. Axes of the monoclines are not parallel, which indlcates that they did not form as a resutt of reglonal horizontal compression. Several mlles to the west, eroslon has stripped the sedimentary cover from the underlylng Precambrian basement. The basement is characterized by brittle deformation in the form of dlfferentlally upllfted fault blocks. The pre-Pennsylvanian erosion surface developed on top of the Precambrlan igneous and metamorphlc rocks Is only sllghtly tilted. Where the faults ln the basement pass under the Paleozoic sedimentary cover to the east, the sedlmentary rocks are folded into unfaulted monoclines. This suggests that the monocllnes in the area are formed by passive draping of sedimentary rocks over dlfferentially uplifted basement blocks. Such an interpretation ls conslstent with the geometrlcal relationships of the monocllnes, with burlal conditlons durlng the Laramlde orogeny, and with experimental results on the behavior of rock materlals.

Debate over the question of whether basement rocks folded or faulted during the Laramide orogeny in the Wyoming province of the Rocky Mountain foreland has raged for many years. Proponentsbl one view or the olher have drawn support for their case from theorctical arguments, from experimental laboratory results, from interpretations of seismic and subsurface borehole data, and from direct observation of surlace outcrops and subsurface miie exposu/es. An anatysis of the validity and applicability ot these various approaches included the generation of synthetic ielsmrc sections and an evaluation of balanced cross sectlons, This analysis indicated that the notion of a folded basement is supported only bl the interpretation of seismic and borehole data whereas the concept of brittle defotmation of the basementls s upportea by ilt of thes; tines of rcasoning, interprctation, and observation. The conclusion is that structural basement did not fotd during the Laramide orogeny.

Within the framework of the International Continental Drilling Program (ICDP) we propose a comprehensive initiative to drill the continental crust bordering modern and ancient convergent and collisional plate boundaries. These zones host the vast majority of modern megacities and industrial installations on Planet Earth, and at the same time are loci of major earthquakes , tsunamis, volcanic eruptions and other associated great natural threats to human life and to economies. In-depth understanding of dynamic Earthprocesses at convergent and collisional plate boundaries is not possible without scientific drilling embedded into integrated research programmes. The set of scientific questions identified here is rooted in the plate tec-tonic paradigm of a dynamic Earth. Proposed studies derived from these questions target on (1) the dynamics of active subduction and collision zones, with focus on the seismogenic zone at the plate interface, and the distribution of deformation and seismicity in general, (2) the role of mantle plumes in orogeny, (3) supra-subduction magmatism in arc systems, (4) the geological manifestation of deep subduction and exhumation of the lithosphere, and (5) aspects relating to continental birth and growth through Earth history. ICDP drilling in convergent and collisional plate margins faces unprecedented challenges regarding drilling technology, drilling depth and requirements for long-term monitoring of Earth processes in downhole observatories.

Structural and morphotectonic analyses were carried out in the catchments of the Das Cinzas and Itararé rivers, tributaries of the left bank of the Paranapanema River, in order to demonstrate the tectonic-structural evolution of the studied area, which involves the northeast region of Paraná and southwest of São Paulo, and is underlain by sedimentary rocks from the Paraná, Itararé, Guatá, and São Bento Groups, of the Paraná Sedimentary Basin, and including mesozoic volcanic rocks from the Serra Geral Formation. The topography of the studied area is moderate to steep, with elevations varying between 360 and 1,360 meters. The main magnetic/structural alignments that affect and/or are contiguous to the study area are the Santo-Anastácio/Paranapanema (NW-SE), Guaxupé (NE-SW) and Jacutinga lineaments (NE-SW), to the north; São Sebastião lineament (EW) in the central portion; São Jerônimo-Curiúva (NW-SE) and Taxaquara lineaments (NE-SW) in the southern portion. The method aplied consisted of classical structural analysis, processing and photointerpretation of DEMs (SRTM), extraction of longitudinal profiles of rivers and lineaments of relief and drainage. In order to assess morphometric parameters, we performed analyses of the drainage patterns and anomalies, slope of the terrain, drainage basin asymmetry factor, knickpoints and probable drainage captures. The Itararé River catchment flows from south to north and is elongated in shape, bordered by the large NW-SE lineaments, corresponding to the fault zones of Santo Anastácio/Paranapanema and São Jerônimo-Curiúva. It is moderately asymmetrical and follows the traces of the extensive NE-SW lineaments, related to the fault zones of Taxaquara, Jacutinga and Guaxupé. The Itararé River is predominantly straight, with meandraments restricted to the portion of the middle course. The drainages are characterized by the mean to low density, accentuated angularity and conspicuous structural control, whose characteristics imply the subdendritic to rectangular pattern, elbow-like, parallel and aligned segments, according to directions NE-SW, NNW-SSE, NS and E-W. The analysis of longitudinal profiles revealed that the knickpoints are aligned mainly in the directions NE-SW and NW-SE, which indicate a possible tectonic control. The relief lineaments occur in two preferential orientations NE-SW and NW-SE and, secondarily, N-S, NNW-SSE, E-W and ENE-WSW, showing influence throughout the studied area. The structural data collected characterize the predominance of strik-slip and oblique faults, which cut the sedimentary sequence and the rocks of the Serra Geral Formation, marked by consistent kinematic indicators of tectonic processes, surely in the Cenozoic. There are predominant right-lateral strike-slip faults, E-W-oriented, and secondarily directed to WNW-ESE, NNE-SSW and N-S. Less frequent are those oriented to NE-SW, ENE-WSW, NNW-SSE and NW-SE. Left-lateral strike-slip faults are also widely observed, with directions NE-SW, WNW-ESE, E-W, N-S and NNE-SSW, and secondarily ENE-WSW and NNW-SSE. Normal and/or oblique faults oriented to WNWESE and E-W, and secondarily ENE-WSW and NW-SE to NNW-SSE, are frequent, however, there are indications that they are sectioned by a strike-slip system. Finally, the reverse faults, with directions NNE-SSW and E-W, are uncommon. The paleostress analysis indicates an evolution of the landscape associated with at least four tectonic pulses with compressive SHmax oriented to NE-SW, N-S, NW-SE and E-W, described by several authors for the southern and southeastern regions of Brazil, which would be active, respectively, in the Neocretaceous-Paleogen, Plio-Pleistocene, Pleistocene and Holocene. Keywords: Neotectonics; cenozoic; tectonic geomorphology; morphometry.

This is part of a collection of files for my paper on the structure of the Clark, Mescal and Ivanpah mountains of San Bernardino County, California. On Academia.com I have posted the following sections:

Abstract
Structure (Text)
Comparative Stratigraphic Table
Generalized Geologic Map
Detailed Geologic Mosaic
Geologic Mosaic Index
References

These parts are linked at

http://www.greggwilkerson.com/ivanpah-mescal-and-clark-mountains.html

The main magma source for eruptions on Etna (Italy) is poorly constrained. Here we use data on the size distributions of volcanic fissures/feeder-dykes, crater cones, dyke thicknesses, and lava flows to estimate the average magma volume flowing out of the chamber during eruptions and the volume of the chamber. For the past four centuries the average magma volume leaving the chamber during each eruption is estimated at 0.064 km 3. From the theory of poroelasticity the estimated chamber volume is then between 69 and 206 km 3. For comparison, a sill-like, circular chamber (an oblate ellipsoid) 1 km thick and 14 km in diameter would have a volume of about 154 km 3. the elastic strain energy stored in the host rock during inflation of such a chamber is about 2.8 × 10 14 J. estimating the surface energy of a typical dyke-fracture as about 10 7 J m −2 , the results suggest that the stored strain energy is sufficient to generate a dyke-fracture with an area of about 28 km 2. the average strike-dimension of volcanic fissures/feeder-dykes in Etna is about 2.7 km. It follows that the estimated strain energy is sufficient to generate a feeder-dyke with a strike-dimension of 2-3 km and with a dip-dimension as great as 10 km, agreeing with the maximum estimated depth of the magma chamber.

Volcanoes are open thermodynamic systems: they exchange energy and matter with their surroundings. In particular, volcanoes receive heat and magma from their source chambers. Volcanoes also store elastic (mainly strain) energy, both through work done on them by external (e.g. spreading-related) forces and, in particular, through magma-chamber expansion and inflation during unrest periods 1. The elastic energy is partly transformed into surface energy for the formation of fractures, such as tension fractures, normal faults, and dykes. In order to estimate the elastic energy available to form a feeder-dyke and squeeze magma out of the chamber and to the surface, information on the magma-chamber size is needed. Here we report for the first time the statistical size distributions of various types of volcanotectonic structures compiled from measurements on a single volcano, namely Etna (Italy), and show how these can be used to estimate its magma-chamber volume and elastic energy during inflation. The features measured include (i) lengths and orientations of volcanic (eruptive) fissures, (ii) thicknesses and orientations of dykes, (iii) diameters, volumes, and orientations of scoria cones, and (iv) combined volumes of feeder-dykes and lava flows. We show that the size distributions generally follow power laws. Using the combined volumes of feeder-dykes and lava flows together with basic poroelasticity theory, we estimate the likely volume of the main magma chamber of Etna. From the chamber volume we estimate the elastic strain energy stored in the volcano during inflation periods. From the estimated strain energy, we infer the potential of dykes injected from the magma chamber to reach the surface so as to supply magma to eruptions in Etna. Volcanotectonic setting and activity of etna. The activity of the Etna volcano, located along the eastern coast of Sicily (Italy), began at ~0.6 Ma 2 ; it is presently one of the world's most active volcanoes. Etna shows all the geochemical features of an 'anorogenic' volcano 3 although its location at the front of the Apennines

Continuous positive airway pressure (CPAP) is worldwide considered as the standard treatment of sleep apnea/hypopnea syndrome (SAHS) although studies on the effectiveness of this treatment are limited. The aim of our study was to evaluate the effectiveness of CPAP in improving SAHS-related symptoms, daytime function, perceived health status, and quality of life in patients with moderate to severe SAHS. The effect of conservative treatment (CT) measures-sleep hygiene and weight loss- was compared with CT + CPAP. We included 105 consecutive patients (13 females, age 53 +/- 10 yr, body mass index [BMI] = 32 +/- 6 kg/m2, apnea/hypopnea index [AHI] = 56 +/- 20, Epworth sleepiness scale [ESS] = 12 +/- 5) who met our criteria for CPAP treatment. Patients were randomly allocated in two groups of similar characteristics. Group 1 (n = 37) was asked to improve sleep hygiene and started a weight loss program. Group 2 (n = 68) received, in addition, treatment with CPAP. Both groups were followed through weekly telephone calls and appointments. Sleepiness, other symptoms related to SAHS, daytime function, perceived health status, and quality of life were assessed through questionnaires at inclusion and after 3 mo of treatment. The relief of sleepiness and other SAHS-related clinical symptoms and improvement in perceived health status was much greater in Group 2 receiving CT + CPAP compared with Group 1, only receiving CT. The odds of experiencing a treatment response with CPAP + CT compared with CT alone was 6.52 (odds ratio [OR] = 2.51 to 17.6, 95% confidence interval [95% CI]). CPAP is currently the treatment of choice. At this time, the indication of CPAP treatment in moderate to severe SAHS is adequately supported.