Preliminary research on striated clasts from a variety of depositional environments suggests that scanning electron microscopy (SEM) of striated clasts of varying lithology in diamictons may prove useful in interpreting a glacial origin. Evaluating whether SEM analysis of clasts from diamictons is an applicable technique to define a glacial origin requires a better understanding of the microfeatures occurring on glacial and nonglacial clasts. We describe microtextures and surface characteristics for samples of quartzite, granite, limestone, basalt, chert, pillow basalt, and quartz pebbles collected from a variety of depositional environments. Our study suggests that it is possible to differentiate between glacial and nonglacial deposits based on frequency and morphology of diagnostic surface microfeatures observed on entrained clasts. These microfeatures are best preserved and identified on competent and monomineralic samples (e.g., quartzite, chert, limestone) and poorly preserved on less resistant and polymineralic samples (e.g., basalt and granite).
The primary goal of this study was to characterize and evaluate the potential origins of manganese‐based paint used to decorate the Chinchorro mummies of northern Chile. We sampled small painted fragments from the trunk of two black mummies and nine samples from the cranium/face of the red mummies. In addition, we sampled manganese‐bearing rocks from the Lauca and Huaylas Formations exposed in the Altiplano, approximately 80–90 km northeast of Arica, Chile. Using scanning electron microscopy, energy‐dispersive spectroscopy, X‐ray diffraction, inductively coupled plasma mass spectrometry, and oxygen isotopic data, we propose these two formations are the likely source of manganese used by the Chinchorro culture to create their distinctive mortuary paint. However, the processes by which they collected and transported the raw material are still unclear. It is possible that Chinchorro traveled to the Altiplano, but a more likely cost‐benefit scenario is that manganese‐rich clasts were transported to lower elevations via rivers fed by seasonal rain and snowmelt.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.