Thermal structure and exhumation history of the Lesser Himalaya in central Nepal

The Lesser Himalaya (LH) consists of metasedimentary rocks that have been scrapped off from the underthrusting Indian crust and accreted to the mountain range over the last ~20 Myr. It now forms a significant fraction of the Himalayan collisional orogen. We document the kinematics and thermal metamorphism associated with the deformation and exhumation of the LH, combining thermometric and thermochronological methods with structural geology. Peak metamorphic temperatures estimated from Raman spectroscopy of carbonaceous material decrease gradually from 520°–550°C below the Main Central Thrust zone down to less than 330°C. These temperatures describe structurally a 20°–50°C/km inverted apparent gradient. The Ar muscovite ages from LH samples and from the overlying crystalline thrust sheets all indicate the same regular trend; i.e., an increase from about 3–4 Ma near the front of the high range to about 20 Ma near the leading edge of the thrust sheets, about 80 km to the south. This suggests that the LH has been exhumed jointly with the overlying nappes as a result of overthrusting by about 5 mm/yr. For a convergence rate of about 20 mm/yr, this implies underthrusting of the Indian basement below the Himalaya by about 15 mm/yr. The structure, metamorphic grade and exhumation history of the LH supports the view that, since the mid-Miocene, the Himalayan orogen has essentially grown by underplating, rather than by frontal accretion. This process has resulted from duplexing at a depth close to the brittle-ductile transition zone, by southward migration of a midcrustal ramp along the Main Himalayan Thrust fault, and is estimated to have resulted in a net flux of up to 150 m^2/yr of LH rocks into the Himalayan orogenic wedge. The steep inverse thermal gradient across the LH is interpreted to have resulted from a combination of underplating and post metamorphic shearing of the underplated units

Durendal, translated: Islamic object genealogies in the chansons de geste

The transfer of Saracen arms into Frankish ownership is a leitmotif of many chansons de geste, but one whose significance for translatio imperii has yet to be elucidated. In this essay, I focus on the Chanson d’Aspremont, a twelfth-century epic set in Calabria that narrates the pre-history of Durendal, Roland’s sword of Song of Roland fame, as an object inherited by Roland from its former royal Muslim owner. Drawing on cultural history and a number of object-translation models derived from material and spolia studies, I read the sword’s symbolic transfer as evidence of Norman desire for and appropriation of former Fatimid imperium in Sicily

Nepal at Risk: Interdisciplinary Lessons Learned from the April 2015 Nepal (Gorkha) Earthquake and Future Concerns,

In response to the devastation caused by the 25 April 2015 MW 7.9 Nepal (Gorkha) earthquake and its aftershocks, the Geological Society of America convened an interdisciplinary session at its 2015 Annual Meeting in Baltimore. The forum allowed researchers from diverse disciplines to exchange information and develop meaningful paths toward reducing the societal impacts of future large earthquakes in the Himalayan region. Major seismic hazards exist near Kathmandu and along the Himalayan front due to incomplete rupture of the Main Himalayan Thrust (MHT) (Avouac et al., 2015; Bendick et al., 2015; Elliott et al., 2015; Lay, 2015) and thousands of co-seismic landslides (Andermann et al., 2015; Gallen et al., 2015; Ohja and DeCelles, 2015; Poudel, 2015). Surprisingly, the 2015 event ruptured a limited region. Given shortening rates and interseismic geodetic indications that the MHT is almost uniformly locked along strike, larger earthquakes may occur along the collision zone