Geological evolution of two crustal scale shear zones. Part I. The Rand thrust complex, northwestern Mojave Desert, California. Part II. The Magdalena metamorphic core complex, north central Sonora, Mexico

The geology and structure of two crustal scale shear zones were studied to understand the partitioning of strain within intracontinental orogenic belts. Movement histories and regional tectonic implications are deduced from observational data. The two widely separated study areas bear the imprint of intense Late Mesozoic through Middle Cenozoic tectonic activity. A regional transition from Late Cretaceous-Early Tertiary plutonism, metamorphism, and shortening strain to Middle Tertiary extension and magmatism is preserved in each area, with contrasting environments and mechanisms. Compressional phases of this tectonic history are better displayed in the Rand Mountains, whereas younger extensional structures dominate rock fabrics in the Magdalena area.

In the northwestern Mojave desert, the Rand Thrust Complex reveals a stack of four distinctive tectonic plates offset along the Garlock Fault. The lowermost plate, Rand Schist, is composed of greenschist facies metagraywacke, metachert, and metabasalt. Rand Schist is structurally overlain by Johannesburg Gneiss (= garnet-amphibolite grade orthogneisses, marbles and quartzites), which in turn is overlain by a Late Cretaceous hornblende-biotite granodiorite. Biotite granite forms the fourth and highest plate. Initial assembly of the tectonic stack involved a Late Cretaceous? south or southwest vergent overthrusting event in which Johannesburg Gneiss was imbricated and attenuated between Rand Schist and hornblende-biotite granodiorite. Thrusting postdated metamorphism and deformation of the lower two plates in separate environments. A post-kinematic stock, the Late Cretaceous Randsburg Granodiorite, intrudes deep levels of the complex and contains xenoliths of both Rand Schist and mylonitized Johannesburg? gneiss. Minimum shortening implied by the map patterns is 20 kilometers.

Some low angle faults of the Rand Thrust Complex formed or were reactivated between Late Cretaceous and Early Miocene time. South-southwest directed mylonites derived from Johannesburg Gneiss are commonly overprinted by less penetrative north-northeast vergent structures. Available kinematic information at shallower structural levels indicates that late disturbance(s) culminated in northward transport of the uppermost plate. Persistence of brittle fabrics along certain structural horizons suggests a possible association of late movement(s) with regionally known detachment faults. The four plates were juxtaposed and significant intraplate movements had ceased prior to Early Miocene emplacement of rhyolite porphyry dikes.

In the Magdalena region of north central Sonora, components of a pre-Middle Cretaceous stratigraphy are used as strain markers in tracking the evolution of a long lived orogenic belt. Important elements of the tectonic history include: (1) Compression during the Late Cretaceous and Early Tertiary, accompanied by plutonism, metamorphism, and ductile strain at depth, and thrust driven? syntectonic sedimentation at the surface. (2) Middle Tertiary transition to crustal extension, initially recorded by intrusion of leucogranites, inflation of the previously shortened middle and upper crustal section, and surface volcanism. (3) Gravity induced development of a normal sense ductile shear zone at mid crustal levels, with eventual detachment and southwestward displacement of the upper crustal stratigraphy by Early Miocene time.

Elucidation of the metamorphic core complex evolution just described was facilitated by fortuitous preservation of a unique assemblage of rocks and structures. The "type" stratigraphy utilized for regional correlation and strain analysis includes a Jurassic volcanic arc assemblage overlain by an Upper Jurassic-Lower Cretaceous quartz pebble conglomerate, in turn overlain by marine strata with fossiliferous Aptian-Albian limestones. The Jurassic strata, comprised of (a) rhyolite porphyries interstratified with quartz arenites, (b) rhyolite cobble conglomerate, and (c) intrusive granite porphyries, are known to rest on Precambrian basement north and east of the study area. The quartz pebble conglomerate is correlated with the Glance Conglomerate of southeastern Arizona and northeastern Sonora. The marine sequence represents part of an isolated arm? of the Bisbee Basin.

Crosscutting structural relationships between the pre-Middle Cretaceous supracrustal section, younger plutons, and deformational fabrics allow the tectonic sequence to be determined. Earliest phases of a Late Cretaceous-Early Tertiary orogeny are marked by emplacement of the 78 ± 3 Ma Guacomea Granodiorite (U/Pb zircon, Anderson et al., 1980) as a sill into deep levels of the layered Jurassic series. Subsequent regional metamorphism and ductile strain is recorded by a penetrative schistosity and lineation, and east-west trending folds. These fabrics are intruded by post-kinematic Early Tertiary? two mica granites. At shallower crustal levels, the orogeny is represented by north directed thrust faulting, formation of a large intermontane basin, and development of a pronounced unconformity. A second important phase of ductile strain followed Middle Tertiary? emplacement of leucogranites as sills and northwest trending dikes into intermediate levels of the deformed section (surficial volcanism was also active during this transitional period to regional extension). Gravitational instabilities resulting from crustal swelling via intrusion and thermal expansion led to development of a ductile shear zone within the stratigraphic horizon occupied by a laterally extensive leucogranite sill. With continued extension, upper crustal brittle normal faults (detachment faults) enhanced the uplift and tectonic denudation of this mylonite zone, ultimately resulting in southwestward displacement of the upper crustal stratigraphy.

Strains associated with the two ductile deformation events have been successfully partitioned through a multifaceted analysis. R_f/Ø measurements on various markers from the "type" stratigraphy allow a gradient representing cumulative strain since Middle Cretaceous time to be determined. From this gradient, noncoaxial strains accrued since emplacement of the leucogranites may be removed. Irrotational components of the postleucogranite strain are measured from quartz grain shapes in deformed granites; rotational components (shear strains) are determined from S-C fabrics and from restoration of rotated dike and vein networks. Structural observations and strain data are compatable with a deformation path of: (1) coaxial strain (pure shear?), followed by (2) injection of leucogranites as dikes (perpendicular to the minimum principle stress) and sills (parallel to the minimum principle stress), then (3) southwest directed simple shear. Modeling the late strain gradient as a simple shear zone permits a minimum displacement of 10 kilometers on the Magdalena mylonite zone/detachment fault system. Removal of the Middle Tertiary noncoaxial strains yields a residual (or pre-existing) strain gradient representative of the Late Cretaceous-Early Tertiary deformation. Several partially destrained cross sections, restored to the time of leucogranite emplacement, illustrate the idea that the upper plate of the core complex bas been detached from a region of significant topographic relief. 50% to 100% bulk extension across a 50 kilometer wide corridor is demonstrated.

Late Cenozoic tectonics of the Magdalena region are dominated by Basin and Range style faulting. Northeast and north-northwest trending high angle normal faults have interacted to extend the crust in an east-west direction. Net extension for this period is minor (10% to 15%) in comparison to the Middle Tertiary detachment related extensional episode.

Market Instruments and CO2 Mitigation: A General Equilibrium Analysis for Spain

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Seismic structure along transitions from flat to normal subduction: central Mexico, southern Peru, and southwest Japan

The fine-scale seismic structure of the central Mexico, southern Peru, and southwest Japan subduction zones is studied using intraslab earthquakes recorded by temporary and permanent regional seismic arrays. The morphology of the transition from flat to normal subduction is explored in central Mexico and southern Peru, while in southwest Japan the spatial coincidence of a thin ultra-slow velocity layer (USL) atop the flat slab with locations of slow slip events (SSEs) is explored. This USL is also observed in central Mexico and southern Peru, where its lateral extent is used as one constraint on the nature of the flat-to-normal transitions.

In western central Mexico, I find an edge to this USL which is coincident with the western boundary of the projected Orozco Fracture Zone (OFZ) region. Forward modeling of the 2D structure of the subducted Cocos plate using a finite-difference algorithm provides constraints on the velocity and geometry of the slab’s seismic structure in this region and confirms the location of the USL edge. I propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ, by a process analogous to that which occurred when the Rivera plate separated from the proto-Cocos plate 10 Ma.

In eastern central Mexico, observations of a sharp transition in slab dip near the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a possible slab tear located within the subducted South Cocos plate. The eastern lateral extent of the USL is found to be coincident with these features and with the western boundary of a zone of decreased seismicity, indicating a change in structure which I interpret as evidence of a possible tear. Analysis of intraslab seismicity patterns and focal mechanism orientations and faulting types provides further support for a possible tear in the South Cocos slab. This potential tear, together with the tear along the projection of the OFZ to the northwest, indicates a slab rollback mechanism in which separate slab segments move independently, allowing for mantle flow between the segments.

In southern Peru, observations of a gradual increase in slab dip coupled with a lack of any gaps or vertical offsets in the intraslab seismicity suggest a smooth contortion of the slab. Concentrations of focal mechanisms at orientations which are indicative of slab bending are also observed along the change in slab geometry. The lateral extent of the USL atop the horizontal Nazca slab is found to be coincident with the margin of the projected linear continuation of the subducting Nazca Ridge, implying a causal relationship, but not a slab tear. Waveform modeling of the 2D structure in southern Peru provides constraints on the velocity and geometry of the slab’s seismic structure and confirms the absence of any tears in the slab.

In southwest Japan, I estimate the location of a possible USL along the Philippine Sea slab surface and find this region of low velocity to be coincident with locations of SSEs that have occurred in this region. I interpret the source of the possible USL in this region as fluids dehydrated from the subducting plate, forming a high pore-fluid pressure layer, which would be expected to decrease the coupling on the plate interface and promote SSEs.

Freshwater biological research in Mexico: A brief historical review

Apart from a couple of early papers in the 1600s, the development of freshwater biology as a science in Mexico began in the last century. Taxonomic studies were made especially on algae, aquatic insects, crustaceans, annelid worms and aquatic plants. The great impetus acquired by limnology in Europe and America in the first half of the 20th Century stimulated foreign researchers to come and work in Mexico. During this period the Instituto de Biologia, belonging to the Universidad Nacional Autonoma de Mexico, was created in 1930. The Institute had a section of Hydrobiology that contributed to the limnological characterization of Mexican lakes and ponds. In 1962, the Instituto Nacional de Investigaciones Biologico-Pesqueras was created to bring together the work of several institutes working on the native ichthyofauna, the restocking of reservoirs, and aquaculture.

The aquatic biota of the now extinct lacustrine complex of the Mexico basin

The commonest organisms of the original Mexico lake complex are listed, including those that exist today in the Lago Viejo. In addition, a brief hydraulic history of this endorheic basin is given.

The lakes of Michoacan (Mexico): A brief history and alternative point of view

This article is intended to open a discussion about the historical development of lakes Zirahuen, Patzcuaro and Cuitzeo in the state of Michoacan, and the postulated relationships between lake ecology and evolution. Dr Fernando De Buen was the first man dedicated to limnology in Mexico who came to the country in the 1930s. He was adviser at the Estacion Limnologica de Patzcuaro and wrote outstanding papers dealing with Mexican lakes. The lakes of Michoacan probably formed in the late Pliocene or Holocene, and were part of a tributary to the Lerma River, which became isolated by successive volanic barriers to form lake basins. Lake Zirahuen is a warm monomictic waterbody with unique water dynamics amongst the Michoacan lakes. Because it is relatively deep (max depth 40m), seasonal patterns of alternating circulation and thermal stratification develop in the lake, a feature not shared by the other two polymictic shallow lakes, Patzcuaro and Cuitzeo.

Multipole moments in general relativity and dynamical perturbations of black-hole magnetospheres

This thesis consists of two parts. In Part I, we develop a multipole moment formalism in general relativity and use it to analyze the motion and precession of compact bodies. More specifically, the generic, vacuum, dynamical gravitational field of the exterior universe in the vicinity of a freely moving body is expanded in positive powers of the distance r away from the body's spatial origin (i.e., in the distance r from its timelike-geodesic world line). The expansion coefficients, called "external multipole moments,'' are defined covariantly in terms of the Riemann curvature tensor and its spatial derivatives evaluated on the body's central world line. In a carefully chosen class of de Donder coordinates, the expansion of the external field involves only integral powers of r ; no logarithmic terms occur. The expansion is used to derive higher-order corrections to previously known laws of motion and precession for black holes and other bodies. The resulting laws of motion and precession are expressed in terms of couplings of the time derivatives of the body's quadrupole and octopole moments to the external moments, i.e., to the external curvature and its gradient.

In part II, we study the interaction of magnetohydrodynamic (MHD) waves in a black-hole magnetosphere with the "dragging of inertial frames" effect of the hole's rotation - i.e., with the hole's "gravitomagnetic field." More specifically: we first rewrite the laws of perfect general relativistic magnetohydrodynamics (GRMHD) in 3+1 language in a general spacetime, in terms of quantities (magnetic field, flow velocity, ...) that would be measured by the ''fiducial observers” whose world lines are orthogonal to (arbitrarily chosen) hypersurfaces of constant time. We then specialize to a stationary spacetime and MHD flow with one arbitrary spatial symmetry (e.g., the stationary magnetosphere of a Kerr black hole); and for this spacetime we reduce the GRMHD equations to a set of algebraic equations. The general features of the resulting stationary, symmetric GRMHD magnetospheric solutions are discussed, including the Blandford-Znajek effect in which the gravitomagnetic field interacts with the magnetosphere to produce an outflowing jet. Then in a specific model spacetime with two spatial symmetries, which captures the key features of the Kerr geometry, we derive the GRMHD equations which govern weak, linealized perturbations of a stationary magnetosphere with outflowing jet. These perturbation equations are then Fourier analyzed in time t and in the symmetry coordinate x, and subsequently solved numerically. The numerical solutions describe the interaction of MHD waves with the gravitomagnetic field. It is found that, among other features, when an oscillatory external force is applied to the region of the magnetosphere where plasma (e⁺e^-) is being created, the magnetosphere responds especially strongly at a particular, resonant, driving frequency. The resonant frequency is that for which the perturbations appear to be stationary (time independent) in the common rest frame of the freshly created plasma and the rotating magnetic field lines. The magnetosphere of a rotating black hole, when buffeted by nonaxisymmetric magnetic fields anchored in a surrounding accretion disk, might exhibit an analogous resonance. If so then the hole's outflowing jet might be modulated at resonant frequencies ω=(m/2) Ω_H where m is an integer and Ω_H is the hole's angular velocity.

Applications of a Concise and General Strategy for the Syntheses of Transtaganolide and Basiliolide Natural Products

Herein are described the total syntheses of all members of the transtaganolide and basiliolide natural product family. Utilitzation of an Ireland–Claisen rearrangement/Diels–Alder cycloaddition cascade (ICR/DA) allowed for rapid assembly of the transtaganolide and basiliolide oxabicyclo[2.2.2]octane core. This methodology is general and was applicable to all members of the natural product family.

A brief introduction outlines all the synthetic progress previously disclosed by Lee, Dudley, and Johansson. This also includes the initial syntheses of transtaganolides C and D, as well as basiliolide B and epi-basiliolide B accomplished by Stoltz in 2011. Lastly, we discuss our racemic synthesis of basililide C and epi-basiliolide C, which utilized an ICR/DA cascade to constuct the oxabicyclo[2.2.2]octane core and formal [5+2] annulation to form the ketene-acetal containing 7-membered C-ring.

Next, we describe a strategy for an asymmetric ICR/DA cascade, by incorporation of a chiral silane directing group. This allowed for enantioselective construction of the C8 all-carbon quaternary center formed in the Ireland–Claisen rearrangement. Furthermore, a single hydride reduction and subsequent translactonization of a C4 methylester bearing oxabicyclo[2.2.2]octane core demonstrated a viable strategy for the desired skeletal rearrangement to obtain pentacyclic transtaganolides A and B. Application of the asymmetric strategy culminated in the total syntheses of (–)-transtaganolide A, (+)-transtaganolide B, (+)-transtaganolide C, and (–)-transtaganolide D. Comparison of the optical rotation data of the synthetically derived transtaganolides to that from the isolated counterparts has overarching biosynthetic implications which are discussed.

Lastly, improvement to the formal [5+2] annulation strategy is described. Negishi cross-coupling of methoxyethynyl zinc chloride using a palladium Xantphos catalyst is optimized for iodo-cyclohexene. Application of this technology to an iodo-pyrone geranyl ester allowed for formation and isolation of the eneyne product. Hydration of the enenye product forms natural metabolite basiliopyrone. Furthermore, the eneyne product can undergo an ICR/DA cascade and form transtaganolides C and D in a single step from an achiral monocyclic precursor.

General-domain compressible Navier-Stokes solvers exhibiting quasi-unconditional stability and high-order accuracy in space and time

This thesis presents a new class of solvers for the subsonic compressible Navier-Stokes equations in general two- and three-dimensional spatial domains. The proposed methodology incorporates: 1) A novel linear-cost implicit solver based on use of higher-order backward differentiation formulae (BDF) and the alternating direction implicit approach (ADI); 2) A fast explicit solver; 3) Dispersionless spectral spatial discretizations; and 4) A domain decomposition strategy that negotiates the interactions between the implicit and explicit domains. In particular, the implicit methodology is quasi-unconditionally stable (it does not suffer from CFL constraints for adequately resolved flows), and it can deliver orders of time accuracy between two and six in the presence of general boundary conditions. In fact this thesis presents, for the first time in the literature, high-order time-convergence curves for Navier-Stokes solvers based on the ADI strategy---previous ADI solvers for the Navier-Stokes equations have not demonstrated orders of temporal accuracy higher than one. An extended discussion is presented in this thesis which places on a solid theoretical basis the observed quasi-unconditional stability of the methods of orders two through six. The performance of the proposed solvers is favorable. For example, a two-dimensional rough-surface configuration including boundary layer effects at Reynolds number equal to one million and Mach number 0.85 (with a well-resolved boundary layer, run up to a sufficiently long time that single vortices travel the entire spatial extent of the domain, and with spatial mesh sizes near the wall of the order of one hundred-thousandth the length of the domain) was successfully tackled in a relatively short (approximately thirty-hour) single-core run; for such discretizations an explicit solver would require truly prohibitive computing times. As demonstrated via a variety of numerical experiments in two- and three-dimensions, further, the proposed multi-domain parallel implicit-explicit implementations exhibit high-order convergence in space and time, useful stability properties, limited dispersion, and high parallel efficiency.

Gauge Invariant Spectral Cauchy Characteristic Extraction of Gravitational Waves in Computational General Relativity

We present a complete system for Spectral Cauchy characteristic extraction (Spectral CCE). Implemented in C++ within the Spectral Einstein Code (SpEC), the method employs numerous innovative algorithms to efficiently calculate the Bondi strain, news, and flux.

Spectral CCE was envisioned to ensure physically accurate gravitational wave-forms computed for the Laser Interferometer Gravitational wave Observatory (LIGO) and similar experiments, while working toward a template bank with more than a thousand waveforms to span the binary black hole (BBH) problem’s seven-dimensional parameter space.

The Bondi strain, news, and flux are physical quantities central to efforts to understand and detect astrophysical gravitational wave sources within the Simulations of eXtreme Spacetime (SXS) collaboration, with the ultimate aim of providing the first strong field probe of the Einstein field equation.

In a series of included papers, we demonstrate stability, convergence, and gauge invariance. We also demonstrate agreement between Spectral CCE and the legacy Pitt null code, while achieving a factor of 200 improvement in computational efficiency.

Spectral CCE represents a significant computational advance. It is the foundation upon which further capability will be built, specifically enabling the complete calculation of junk-free, gauge-free, and physically valid waveform data on the fly within SpEC.