ABSTRACT
Glacial debris can be recognized in sediments that had once been submerged under the ocean. “Ice rock,” stones with their scrape marks are among the more obvious clues. Dramatic as it certainly seems, the picture behind snowball Earth is that our planet went through a number of episodes in which it was basically entirely covered in ice to depths of hundreds of feet. Any appreciable subsequent appearance of oxygen in the atmosphere or surface waters such as via flourishing photosynthetic bacteria consuming carbon dioxide, would then efficiently precipitate the iron, giving rise to sedimenting red iron oxide bands. According to climate calculations, the carbon dioxide level dropped to nearly one-quarter of its earlier values and temperatures approached freezing. At the end of glaciation with warming and recovery of photosynthetic microbes, enrichment of the heavier carbon isotope in new carbonate deposits the glacial rocks are the so-called “caps.”.
