Albion College

About: Albion College is a education organization based out in Albion, Michigan, United States. It is known for research contribution in the topics: Population & Higher education. The organization has 485 authors who have published 754 publications receiving 20907 citations.

‘A‘ā lava-fed deltas: A new reference tool in paleoenvironmental studies

Abstract: Lava-fed deltas are extraordinarily useful indicators of fossil water (and ice) levels in glacial, marine, and lacustrine environments. Deltas fed by ‘a‘ā lava should be at least as common as those sourced in pāhoehoe, yet they have been rarely described. Although facies models for pāhoehoe lava-fed deltas are well established, the architecture and lithofacies of ‘a‘ā-fed equivalents are substantially different and have thus far largely been unrecognized. This can have profound consequences for paleoenvironmental investigations, particularly those attempting to reconstruct past ice sheets. Essential features of ‘a‘ā lava-fed deltas include (1) a subaerial ‘a‘ā lava capping unit comprising massive internal sheet lava overlain by clinkers; (2) a crudely developed subaerial to subaqueous transition (passage zone); (3) a chaotic subaqueous association of abundant lava lobes and hyaloclastite with admixed vesicular, often reddened (oxidized) lava clinkers; and (4) rare subaqueous stratification with predominantly lower dips (∼10°–20°) than in deltas fed by pāhoehoe lava (∼25°–40°). We develop a generic facies model and investigate the emplacement conditions of ‘a‘ā lava-fed deltas in order to facilitate the recognition and environmental interpretation of these important sequence types in ancient successions.

Borings in early Eocene turtle shell from the Wasatch Formation, South Pass, Wyoming

Abstract: Borings in fossil turtle shells collected from the lowermost beds of the early Eocene Cathedral Bluffs Tongue of the Wasatch Formation in the northwestern part of the Green River Basin near South Pass, Wyoming, are herein described. Individual turtle shells in the study area are characterized by as few as one or two and as many as >100 borings. The borings include both non-penetrative forms (those which do not pass fully though the shell) as well as penetrative forms (those which pass fully from the exterior to the interior surface of the shell). All non-penetrative forms occur on external surfaces of the carapace and plastron (i.e. those that would have been accessible while the host taxon was alive). Two new ichnogenera and four new ichnospecies are established to describe these borings. Karethraichnus (new ichnogenus) includes three ichnospecies: K. lakkos (new ichnospecies), K. kulindros (new ichnospecies), and K. fiale (new ichnospecies). Karethraichnus lakkos are shallow (non-penetrating), hemispherical pits with rounded, to flattened bases. Karethraichnus kulindros are deep, non-penetrative traces with a cylindrical profile, an axis approximately perpendicular to the substrate surface and with rounded to flattened, hemispherical termini. Karethraichnus fiale are penetrative traces with a cylindrical to bi-convex or flask-shaped profile, and an axis approximately perpendicular to the substrate surface. Thatchtelithichnus (new ichnogenus) Thatchtelithichnus holmani (new ichnospecies) consist of non-penetrative borings into a bone substrate. They consist of a ring-shaped trace, with a central pedestal or platform. The position of the borings on the shells, and evidence of syn-emplacement healing of the borings in several of the turtles, indicates that these borings were emplacement by ectoparasites/mesoparasites while the animals were living. Similar traces in modern emydid turtles are attributed to ticks, leeches, or spirorchid liver flukes.

Fourier-PARMA Models and Their Application to River Flows

Abstract: For analysis and design of water resource systems, it is sometimes useful to generate high-resolution (e.g., weekly) synthetic river flows. Periodic autoregressive moving average (PARMA) time series models provide a powerful tool for generating synthetic flows. Periodically stationary models are indicated when the basic statistics (mean, variance, and autocorrelation) of the time series exhibit significant seasonal variations. Parameter estimation for high-resolution PARMA models involves numerous parameters, which can lead to overfitting. Thus, this paper develops a parsimonious method of parameter fitting for high-resolution PARMA models, using discrete Fourier transforms to represent the set of periodic autoregressive and moving average model coefficients. Model parameters are computed via the innovations algorithm, and the asymptotic distributions of the discrete Fourier transform coefficients are obtained. Those asymptotic results are useful to determine the statistically significant Fourier coeffici...

Measurement of spin diffusion length in sputtered Ni films using a special exchange-biased spin valve geometry

Abstract: The authors report the spin diffusion length at 4.2K in sputtered Ni of lsfNi=21±2nm, and spin-dependent scattering parameters in Ni and at Ni∕Cu interfaces. They have employed current perpendicular to plane giant magnetoresistance in both a traditional and an alternative exchange-biased spin valve geometry that inserts a Ni “spoiler” layer into a Py/Cu/Py spin valve. Fits to data of AΔR vs Ni thickness using Valet-Fert theory [Phys. Rev. B 48, 7099 (1993)] show good agreement between fit parameters for both sample geometries.