The Ka'ena Highstand of O'ahu, Hawai'i: Further Evidence of Antarctic Ice Collapse during the Middle Pleistocene

Marine isotope stage (MIS) 11 may well represent one of the most significant interglacial highstand events of the past million years. Ocean volume changes charted from coastal exposures imply partial or complete melting of some of the world's major ice caps during a middle Pleistocene interglacial. The coastal geology of both Bermuda and the Bahamas yields evidence of an MIS 11 highstand 20 m higher than present. Further support for this catastrophic episode in sea-level history is revealed in subtidal and intertidal deposits at +28 ± 2 m in O'ahu, Hawai'i. The stratigraphy, petrology, and uplift history of the Hawaiian deposits strongly suggest a correlation with MIS 11, and a compilation of amino acid racemization, uranium/thorium (alpha and mass spectrometry), and electron spin resonance ages shows a scatter between 300 and 550 kyr. When corrected for uplift, the Ka'ena Highstand succession at Wai'anae Health Center (OWH1) reveals a "stepping up" of sea level through the interglaciation, similar to that described in the Bahamas. Previous studies on O'ahu attributed all 28 m elevation of the Ka'ena Highstand to uplift since 0.5 Ma, but now it appears that only 8 m of that was caused by uplift, and the remaining 20 m by eustatic sea-level rise. These findings from O'ahu strengthen evidence for the complete disintegration of the Greenland and West Antarctic ice sheets and partial melting of the East Antarctic ice sheet during the middle Pleistocene. If the instability of polar ice sheets can be linked to prolonged warm interglaciations as the data suggest, then existing conservative predictions for the magnitude of sea-level change by future "greenhouse" warming are seriously underestimated

The biogeography and geomorphology of the Niobrara River Valley near Valentine, Nebraska.

Within the study area located near Valentine, Nebraska, the Niobrara River is deeply entrenched in Tertiary siltstones and sandstones, and covered with Pleistocene and Holocene eolian deposits of sand and loess. The 100 m depth of the valley reflects the entrenchment. Periods of equilibrium of the river are indicated by the numerous benchlands that lie within and adjacent to the valley. Mass wasting in the forms of landslides and creep significantly alter the form of these terracelands when it is combined with the shifting of the river and saturation by groundwater. Many of the terraces have been correlated with climatic events of the Pleistocene and Holocene epochs. There is some evidence of uplift in the area. The stratigraphy of the low terraces reflects the overall downcutting interspersed with periods of aggradation. Some elements of vegetative community are unique to the grasslands, to Nebraska, and to the Great Plains. Representatives of the Rocky Mountain, eastern deciduous, and northern forests interact with variables of topography, stratigraphy, and microclimate. Active landslides and newly exposed terraces are revegetated in a definite sequence from annuals to hardwood forests or to grasslands in some cases. The parallel zones of woody vegetation on the right bank is disrupted by mass wasting events. The paper birch is a Pleistocene relic and thrives in the valley under stringent habitat requirements such as north facing slopes, springs, and shade of other trees. The results of this study are numerous and diverse. However, in a synthesis, they present a concept of the dynamic interaction of the physical and biological factors in the area. From these individual factors, a grander hypothesis was formulated that describes the Niobrara River as the principal contributor of sand in the formation of the Nebraska Sandhills

Critical engagement

This book represents the first interdisciplinary study of how memory has driven and challenged the political transition of Irish republicanism from armed conflict to constitutional politics through endorsing policing and the rule of law in the North of Ireland. Locating itself within memory studies, critical criminology and transitional justice, this book uses original interviews with political activists, community workers and former combatants from across the spectrum of modern Irish republicanism to draw out how the past frames internal tensions within the Irish republican constituency as those traditionally opposed to state policing structures opt to buy into them as part of a wider transitional process in post-conflict Northern Ireland. The book critiques the challenges of making peace with the enemy against a backdrop of communal narratives and memories of historic injustice, counterinsurgency policing and human rights abuse that do not simply disappear when war turns to peace. Through a rich empirical basis the book offers an insight into these challenges from the perspective of those who were, and remain, in the thick of the Irish republican debate on policing. In doing so it provides an acute insight into the role that individual and collective memory plays in reshaping ideological outlooks, understanding processes of political transition, contextualising ‘moving on’ processes with former enemies and conditioning views of post-conflict police reform

Spectroscopy of Candidate Members of the Eta Cha and MBM12 Young Associations

We present an analysis of candidate members of the Eta Cha and MBM 12A young associations. For an area of 0.7 deg^2 toward Eta Cha, we have performed a search for members of the association by combining JHK_s photometry from 2MASS and i photometry from DENIS with followup optical spectroscopy at Magellan Observatory. We report the discovery of three new members with spectral types of M5.25-M5.75, corresponding to masses of 0.13-0.08 M_sun by theoretical evolutionary models. Two and three of these members were found independently by Lyo and coworkers and Song and coworkers, respectively. Meanwhile, no brown dwarfs were detected in Eta Cha down to the completeness limit of 0.015 M_sun. For MBM 12A, we have obtained spectra of three of the remaining candidate members that lacked spectroscopy at the end of the survey by Luhman, all of which are found to be field M dwarfs. Ogura and coworkers have recently presented four "probable" members of MBM 12A. However, two of these objects were previously classified as field dwarfs by the spectroscopy of Luhman. In this work, we find that the other two objects are field dwarfs as well.Comment: to be published in The Astrophysical Journal, 19 pages, 7 figure