Petrology and burial diagenesis of Plio-Pleistocene sediments, northern Gulf of Mexico

Plio-Pleistocene sediments and rocks beneath the Louisiana and adjacent Texas shelves are the youngest of several thick packages of terrigenous sediment which prograded into the Gulf of Mexico during the Cenozoic. Comparison of diagenesis in these young sediments (more than 300 samples from 45 wells on the Louisiana-Texas shelf) to diagenesis of older Cenozoic rocks at similar burial depths elsewhere along the Gulf margin confirms that diagenesis is not strictly analogous among the various Cenozoic units. There has been an evolution of diagenesis during filling of the Gulf of Mexico. Differences in diagenesis cannot be attributed to differences in bulk mineralogy of the sands because PIio-Pleistocene sands are lithic arkoses and feldspathic litharenites with essentially the same QFR proportions as observed in subsurface Eocene and Oligocene sandstones along the Texas coast. Unaltered plagioclase is slightly more calcic (average An 24) than unaltered plagioclase in the older rocks. Burial diagenesis in Plio-Pleistocene sediments has involved essentially the same processes as observed in the older rocks, but overall, diagenesis has advanced to a lesser degree at any given depth. Cementation by quartz and carbonate, dissolution of potassium-feldspar and heavy minerals, albitization of plagioclase, and the transformation of smectite to illite have occurred in Plio-Pleistocene sediments, but cements and altered grains are not volumetrically significant shallower than 4 to 4.5 km. The temperature at which reaction of detrital constituents begins (approximately 90° C) is similar to that observed elsewhere in the Gulf, but the zone of reaction is spread over a greater depth range. The similar temperatures observed for the advent of detrital reactions across the Gulf basin suggest that these processes are more highly dependent upon temperature than upon time and that differences observed among the various units may be attributed, at least in part, to variations in the geothermal gradient. The degree of detrital grain alteration observed in these young sediments shows that significant loss of provenance information occurs quite early in the burial history. Alteration in the deep subsurface is very effective in modifying the primary detrital assemblage.Geological Science

Design Considerations for Efficient and Effective Microarray Studies

This paper describes the theoretical and practical issues in experimental design for gene expression microarrays. Specifically, this paper (1) discusses the basic principles of design (randomization, replication, and blocking) as they pertain to microarrays, and (2) provides some general guidelines for statisticians designing microarray studies

Experimental Evidence for Resonant-Tunneling in a Luttinger-Liquid

We have measured the low temperature conductance of a one-dimensional island embedded in a single mode quantum wire. The quantum wire is fabricated using the cleaved edge overgrowth technique and the tunneling is through a single state of the island. Our results show that while the resonance line shape fits the derivative of the Fermi function the intrinsic line width decreases in a power law fashion as the temperature is reduced. This behavior agrees quantitatively with Furusaki's model for resonant tunneling in a Luttinger-liquid.Comment: 3 pages, 5 figures, corrected typo

Anisotropic Transport of Quantum Hall Meron-Pair Excitations

Double-layer quantum Hall systems at total filling factor $\nu_T=1$ can exhibit a commensurate-incommensurate phase transition driven by a magnetic field $B_{\parallel}$ oriented parallel to the layers. Within the commensurate phase, the lowest charge excitations are believed to be linearly-confined Meron pairs, which are energetically favored to align with $B_{\parallel}$. In order to investigate this interesting object, we propose a gated double-layer Hall bar experiment in which $B_{\parallel}$ can be rotated with respect to the direction of a constriction. We demonstrate the strong angle-dependent transport due to the anisotropic nature of linearly-confined Meron pairs and discuss how it would be manifested in experiment.Comment: 4 pages, RevTex, 3 postscript figure

Low-temperature behavior of a Magnetic Impurity in a Heisenberg Chain

Using the bosonization technique, we have studied a spin-1/2 magnetic impurity in Heisenberg chain, and shown that the impurity specific heat and spin susceptibility have an anomalous temperature dependence.Comment: 12 pages, Revtex, no figure, to be published in Phys. Rev. Let

From Tomonaga-Luttinger to Fermi liquid in transport through a tunneling barrier

Finite length of a one channel wire results in crossover from a Tomonaga-Luttinger to Fermi liquid behavior with lowering energy scale. In condition that voltage drop $(V)$ mostly occurs across a tunnel barrier inside the wire we found coefficients of temperature/voltage expansion of low energy conductance as a function of constant of interaction, right and left traversal times. At higher voltage the finite length contribution exhibits oscillations related to both traversal times and becomes a slowly decaying correction to the scale-invariant $V^{1/g-1}$ dependence of the conductance.Comment: 12 pages of RevTex file and 1 PS file figur

Electron-phonon interactions on a single-branch quantum Hall edge

We consider the effect of electron-phonon interactions on edge states in quantum Hall systems with a single edge branch. The presence of electron-phonon interactions modifies the single-particle propagator for general quantum Hall edges, and, in particular, destroys the Fermi liquid even at integer filling. The effect of the electron-phonon interactions may be detected experimentally in the AC conductance or in the tunneling conductance between integer quantum Hall edges.Comment: 9 pages (revtex) + one postscript file with 2 figures. A complete postscript file with all figures + text (5 pages) is available from http://FY.CHALMERS.SE/~eggert/fqh.ps or by request from [email protected]

Using Outcrop Exposures on the Road to Yellowknife Bay to Build a Stratigraphic Column, Gale Crater, Mars

Since landing in Gale Crater on August 5, 2012, the Curiosity rover has driven 450 m east, descending approximately 15 m in elevation from the Bradbury landing site to Yellowknife Bay. Outcrop exposure along this drive has been discontinuous, but isolated outcrops may represent windows into underlying inplace stratigraphy. This study presents an inventory of outcrops targeted by Curiosity (Figs. 1-2), grouped by lithological properties observed in Mastcam and Navcam imagery. Outcrop locations are placed in a stratigraphic context using orbital imagery and first principles of stratigraphy. The stratigraphic models presented here represent an essential first step in understanding the relative age relationships of lithological units encountered at the Curiosity landing site. Such observations will provide crucial context for assessing habitability potential of ancient Gale crater environments and organic matter preservation

Tunneling into the edge of a compressible Quantum Hall state

We present a composite fermion theory of tunneling into the edge of a compressible quantum Hall system. The tunneling conductance is non-ohmic, due to slow relaxation of electromagnetic and Chern-Simons field disturbances caused by the tunneling electron. Universal results are obtained in the limit of a large number of channels involved in the relaxation. The tunneling exponent is found to be a continuous function of the filling factor nu, with a a slope that is discontinuous at nu=1/2 in the limit of vanishing bulk resistivity rho_xx. When nu corresponds to a principal fractional quantized Hall state, our results agree with the chiral Luttinger liquid theories of Wen, and Kane, Fisher and Polchinski.Comment: 5 pages, 1 EPS figure, RevTeX, epsfi