Doubts about How the Middle Horizon Collapsed (ca. A.D. 1000) and Other Insights from the Looted Cemeteries of the Lower Ica Valley, South Coast of Peru

This paper presents new information from funerary contexts in the lower Ica Valley, south coast of Peru, spanning two millennia from the end of the Early Horizon to the Late Intermediate Period. Although severely looted, these sites can still yield valuable information. We discuss their architecture and material culture in the context of radiocarbon dates. Among other findings, these cast new light on the poorly understood transition from the Middle Horizon to the Late Intermediate Period, for which a paucity of archaeological data from c. A.D. 1000 to 1250 has long been taken as evidence of an environmentally or socially-induced demographic collapse. Yet the data we present here suggests that the basins of the lower Ica Valley were likely occupied continuously over this period, and that the echoes of Wari influence here may have lasted longer than previously thought.We thank the Ministerio de Cultural del Perú for granting permission for the fieldwork (No. 0028-2010-VMPCIC-MC) and analysis of samples for dating (No. 369-2011-VMPCIC-MC); Alberto Benavides Ganoza and the people of Samaca for facilitating fieldwork, all participants of the Proyecto de investigación arqueológica Samaca and Viviana Siveroni and Ruben Garcia for their useful thoughts and suggestions. This work was funded by the Arts and Humanities Research Council

Textural variation in the pyrite-rich ore deposits of the Roros district, Trondheim Region, Norway: implications for pyrite deformation mechanisms

The Røros district is a pyrite-rich polymetallic sulfide orefield in the southeastern part of the Trondheim region, Central Norwegian Caledonides. All of the ore deposits at Røros are hosted within a Cambrian to Silurian succession that was deformed and metamorphosed at lower greenschist to lower amphibolite facies conditions during the Caledonian orogeny. Samples from five individual deposits across the orefield have been analyzed using a combination of reflected light petrographic observation, orientation contrast imaging, and electron backscatter diffraction. Results indicate that, whereas samples from each ore deposit have a variety of different textures, all of them preserve plastic deformation in pyrite grains that occurred at peak metamorphic conditions characterized by the development of internal lattice misorientation within pyrite grains and low-angle (∼2°) dislocation walls. These observations indicate that the principal deformation mechanisms at peak metamorphic conditions were dislocation glide and creep. The preservation of brittle fracturing represents later overprinting events.Craig D. Barrie, Nigel J. Cook and Alan P. Boyl