Issues

ON COVER – Foreground: Calcite replacing primary bedded barite layer with a disaggregated median layer of pyrobitumen. Note the undulatory replacement boundary within the layer showing replacement of primary barite from the center outward toward the boundary with the host shale. See related paper by Bryndzia et al. on p. 379 of this issue of the Bulletin. Background: Dolomitic calcareous sandstone lithofacies: field emission-scanning electron microscopy images of argon ion beam milled samples. See related paper by Ramiro-Ramirez et al. on p. 293 of this issue of the Bulletin.