Stalagmite growth perturbations from the Kumaun Himalaya as potential earthquake recorders

The central part of the Himalaya (Kumaun and Garhwal Provinces of India) is noted for its prolonged seismic quiescence, and therefore, developing a longer-term time series of past earthquakes to understand their recurrence pattern in this segment assumes importance. In addition to direct observations of offsets in stratigraphic exposures or other proxies like paleoliquefaction, deformation preserved within stalagmites (speleothems) in karst system can be analyzed to obtain continuous millennial scale time series of earthquakes. The Central Indian Himalaya hosts natural caves between major active thrusts forming potential storehouses for paleoseismological records. Here, we present results from the limestone caves in the Kumaun Himalaya and discuss the implications of growth perturbations identified in the stalagmites as possible earthquake recorders. This article focuses on three stalagmites from the Dharamjali Cave located in the eastern Kumaun Himalaya, although two other caves, one of them located in the foothills, were also examined for their suitability. The growth anomalies in stalagmites include abrupt tilting or rotation of growth axes, growth termination, and breakage followed by regrowth. The U-Th age data from three specimens allow us to constrain the intervals of growth anomalies, and these were dated at 4273?±?410 years BP (2673–1853 BC), 2782?±?79 years BP (851–693 BC), 2498?±?117 years BP (605–371 BC), 1503?±?245 years BP (262–752 AD), 1346?±?101 years BP (563–765 AD), and 687?±?147 years BP (1176–1470 AD). The dates may correspond to the timings of major/great earthquakes in the region and the youngest event (1176–1470 AD) shows chronological correspondence with either one of the great medieval earthquakes (1050–1250 and 1259–1433 AD) evident from trench excavations across the Himalayan Frontal Thrust.     

A conceptual model for the longitudinal distribution of wood in mountain streams

Wood load, channel parameters and valley parameters were surveyed in 50 contiguous stream segments each 25 m in length along 12 streams in the Colorado Front Range. Length and diameter of each piece of wood were measured, and the orientation of each piece was tallied as a ramp, buried, bridge or unattached. These data were then used to evaluate longitudinal patterns of wood distribution in forested headwater streams of the Colorado Front Range, and potential channel‐, valley‐ and watershed‐scale controls on these patterns. We hypothesized that (i) wood load decreases downstream, (ii) wood is non‐randomly distributed at channel lengths of tens to hundreds of meters as a result of the presence of wood jams and (iii) the proportion of wood clustered into jams increases with drainage area as a result of downstream increases in relative capacity of a stream to transport wood introduced from the adjacent riparian zone and valley bottom. Results indicate a progressive downstream decrease in wood load within channels, and correlations between wood load and drainage area, elevation, channel width, bed gradient and total stream power. Results support the first and second hypotheses, but are inconclusive with respect to the third hypothesis. Wood is non‐randomly distributed at lengths of tens to hundreds of meters, but the proportion of pieces in jams reaches a maximum at intermediate downstream distances within the study area. We use these results to propose a conceptual model illustrating downstream trends in wood within streams of the Colorado Front Range. Copyright © 2009 John Wiley & Sons, Ltd.     

Inner forearc response to subduction of the Panama Fracture Zone,southern Central America

Subduction of the right-lateral Panama Fracture Zone, along the convergent margin of Central America creates abrupt lateral variations in convergence rate, obliquity, and subducting crustal thickness at its intersection with the Middle America Trench. This intersection, known as the Panama (CO-NZ-CA) Triple Junction, is migrating to the southeast at a rate of 55 mm/yr, and currently coincides with the lateral termination of the Fila Costeña Thrust Belt in the inner forearc of the overriding plate. Mapping in the inner forearc in the area that straddles the subducting Panama Fracture Zone reveals that Cocos–Caribbean convergence west of the triple junction leads to the development of an inner forearc thrust belt inboard of the colliding Cocos Ridge, while little deformation is evident inboard of Nazca–Caribbean convergence, east of the triple junction. This results in the lateral termination of the Fila Costeña Thrust Belt in the region of the forearc that projects over the Panama Fracture Zone, where four out of five mapped thrust faults tip out and are buried by lahars. Three new balanced cross-sections indicate a steep gradient in shortening from the center of the thrust belt to its southeastern termination. The short-term history of the inner forearc recorded in the landscape and topography of the Fila Costeña is consistent with the southeastward migration of the thrust belt and the Panama Triple Junction throughout the past ～ 3 Ma, with evidence for the growth of a new topographic divide and reorganization of stream channel networks.     

Poynting Robertson effects due to a logarithmic correction to the Newtonian potential

Astrophysics and Space Science - We performed a detailed timing study of the Atoll source 4U 1705-44 in order to understand the accretion disk geometry. Cross correlation function (CCF) studies...     

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky  (| b | > 10°)  . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with  ( K , H , J , r _F, b _J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75)  . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with   z ≤ 0.1  , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS .     

The dilemma of decontamination: A Gramscian analysis of the Mexican transgenic maize dispute

An intense environmental dispute surrounds the maize-fields of Mexico. Mexican maize traditional varieties (or ‘landraces’) constitute a global genetic resource that may well be critical to future agricultural development and corn breeding. Many environmentalists, farmers, and consumers in Mexico are therefore concerned that their maize landraces may have been ‘contaminated’ by imported transgenic maize, grown in the USA. The criticisms of this transgenic technology are complex and call into question the nature of the boundary between political and ecological (i.e. scientific) disputes. Our paper surveys these criticisms, and this political-scientific boundary, in a three-part analysis. First, we turn to Gramsci’s notes on science from his eleventh prison notebook to rethink the political ecology of transgenic maize, i.e., the way the ecological analysis of transgenic introgression is treated as politics. Second, we present the multiple criticisms of transgenic maize as scalar phenomena. Third, we review the recent scientific literature on transgene introgression to evaluate recent calls for the ‘decontamination’ of Mexican maize. Our reading illustrates two dilemmas facing the group that occupies the hegemonic subject-position in this dispute, ecological scientists. First, the popular desire to ‘decontaminate’ Mexican maize exceeds their capacities (due to complications involved with sampling). Second, although the political debate surrounding ‘contaminated’ Mexican maize exceeds science, the boundary between the dispute’s scientific and parascientific elements cannot be adjudicated scientifically. In other words, the boundary between science and politics is porous. Thus in two respects the dispute is ecological, yet beyond the capacity of this science to resolve. Yet, following Gramsci, these findings should not lead us to see science as mere ideology, or apolitical, or encourage a retreat into metaphysics. Rather it points to the need for a social transformation that sees science as “humanity forging its methods of research … in other words, culture, the conception of the world.” By exploring the dilemmas of decontamination, the dispute over transgene introgression in Mexican maize-fields provides an opportunity to elaborate upon Gramsci’s neglected insights into the politics of science.     

Sinking ships: conservation options for endemic taxa threatened by sea level rise

Low-elevation islands face threats from sea level rise (SLR) and increased storm intensity. Evidence of endangered species?? population declines and shifts in vegetation communities are already underway in the Florida Keys. SLR predictions indicate large areas of these habitats may be eliminated in the next century. Using the Florida Keys as a model system, we present a process for evaluating conservation options for rare and endemic taxa. Considering species characteristics and habitat, we assess central issues that influence conservation options. We contrast traditional and controversial options for two animal and two plant species giving special emphasis to perceptions of ecological risk and safety from SLR and suggest courses of action. Multiple strategies will be required to spread extinction risk and will be effective for different time periods. Global climate change presents an uncertain, perhaps no-analog future that will challenge land managers and practitioners to re-evaluate equilibrium-state-conceived laws and policies not only for these taxa, but for many facing similar threats. To embrace conservation in a changing world will require a new dialogue that includes controversial ideas, a review of existing laws and policies, and preparation for the oncoming change.