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.

Lunulichnus Tuberosus Ichnogen. and Ichnosp. Nov. from the Early Eocene Wasatch Formation, Fossil Butte National Monument, Wyoming: An Arthropod-Constructed Trace Fossil Associated with Alluvial Firmgrounds

Abstract: A new trace fossil, Lunulichnus tuberosus, is described from fluvial deposits of the Wasatch Formation (early Eocene) at Fossil Butte National Monument, southwestern Wyoming, USA. L. tuberosus are straight, vertical to obliquely oriented, unlined cylindrical burrows with pronounced crescent-shaped wall sculptings. In situ examples of these trace fossils are most commonly preserved as sand-filled casts emanating from the erosional bases of fluvial channel sandstone bodies into underlying floodplain mudstone/siltstone beds. L. tuberosus is interpreted as the dwelling trace of a stream-dwelling decapod crustacean. Excellent preservation of fine detail, particularly their diagnostic crescent-shaped wall sculptings, support the hypothesis that L. tuberosus were excavated in firm substrata subjacent to fluvial erosional surfaces. As such, they are interpreted as constituents of alluvial Glossifungites trace fossil assemblages.

No Change in the Recent Lunar Impact Flux Required Based on Modeling of Impact Glass Spherule Age Distributions

Abstract: The distributions of 40Ar/39Ar-derived ages of impact glass spherules in lunar regolith samples show an excess at <500 Ma relative to older ages. It has not been well understood whether this excess of young ages reflects an increase in the recent lunar impact flux or is due to a bias in the samples. We developed a model to simulate the production, transport, destruction, and sampling of lunar glass spherules. A modeled bias is seen when either (1) the simulated sampling depth is 10 cm, consistent with the typical depth from which Apollo soil samples were taken, or (2) when glass occurrence in the ejecta is limited to >10 crater radii from the crater, consistent with terrestrial microtektite observations. We suggest that the observed excess of young ages for lunar impact glasses is likely due to limitations of the regolith sampling strategy of the Apollo program, rather than reflecting a change in the lunar impact rate. Plain Language Summary Lunar regolith samples collected by the Apollo astronauts contain impact glass spherules that record the age of formation in the Ar-Ar isotope dating system. There are as many spherules with measured ages within the last 500 million years as there is in the previous 4 billion years of lunar history, and it has remained a mystery as to whether this is because the impact rate was higher in the recent past, or if there was some process that was biasing these samples toward a young age. We have developed a three-dimensional computer model that simulates the production, transport, destruction, and sampling of impact-generated glass spherules on the Moon. Using reasonable assumptions that are backed up from data on Earth craters, we are able to reproduce the observed excess of young spherule ages seen in the Apollo samples assuming that impact rate has not changed over the last three billion years. We find that the young age bias is only seen because the Apollo samples were collected in the upper few centimeters of the lunar surface. Future glasses collected from the upper few meters of the surface should have ages that better reflect the true rate of impacts over time.

Reactivity and Survivability of Glycolaldehyde in Simulated Meteorite Impact Experiments

Abstract: Sugars of extraterrestrial origin have been observed in the interstellar medium (ISM), in at least one comet spectrum, and in several carbonaceous chondritic meteorites that have been recovered from the surface of the Earth. The origins of these sugars within the meteorites have been debated. To explore the possibility that sugars could be generated during shock events, this paper reports on the results of the first laboratory impact experiments wherein glycolaldehyde, found in the ISM, as well as glycolaldehyde mixed with montmorillonite clay, have been subjected to reverberated shocks from ~5 to >25 GPa. New biologically relevant molecules, including threose, erythrose and ethylene glycol, were identified in the resulting samples. These results show that sugar molecules can not only survive but also become more complex during impact delivery to planetary bodies.

Pay, productivity and aging in Major League Baseball

Abstract: Using panels of player pay and performance from Major League Baseball (MLB), we examine trends in player productivity and salaries as players age. Pooling players of all ability levels leads to a systematic bias in regression coefficients. After addressing this problem by dividing players into talent quintiles, we find that the best players peak about 2 years later than marginal players, and development and depreciation of performance appear to be more pronounced for players with the highest ability levels. Within-career variation, however, is less pronounced than between-player variation, and the performance level of players within a given quintile will typically remain lower than the talent level for rookies in the next higher quintile. We also find preliminary evidence that free agents are paid proportionately to their production at all ability levels, whereas young players’ salaries are suppressed by similar amounts.