oceany: Snowball Earth

Evidence: 100 • authority: 72

The Snowball Earth is a geohistorical hypothesis proposing that during one or more of Earth's icehouse climates, the planet's surface was nearly entirely frozen, with little or no liquid water exposed. This global glaciation hypothesis is most commonly associated with the Cryogenian Period, which included two major glacial episodes: the Sturtian (c. 717–660 Ma) and Marinoan (c. 650–635 Ma). Proponents of the hypothesis argue that it best explains sedimentary deposits that are generally believed to be of glacial origin at tropical palaeolatitudes and other enigmatic features in the geological record. Opponents of the hypothesis contest the geological evidence for global glaciation and the ge…

Evidence: 42 • authority: 88

Varves versus Snowball: Seasonal rhythmite in the glacial deposits of the Nichatka Formation (South Siberia).. <p>The paleomagnetic data obtained from the Neoproterozoic rocks stratigraphically related to glacial deposits suggest the ice sheets' near-equatorial occurrence. Based on these data, the Snowball Earth hypothesis proposing the Cryogenian period's total glaciations has been developed and became almost a paradigm.&amp;#160;Quaternary glacial successions usually contain varves (seasonally laminated deposits) as they were formed in high latitudes. Therefore, we suggest that varves provide an independent sedimentological test of the paleolatitude position of Precambrian glacial deposit…

Evidence: — • authority: 72

The Cambrian explosion (also known as the Cambrian radiation or Cambrian diversification) is an interval of time beginning approximately 538.8 million years ago in the Cambrian period of the early Paleozoic, during which a sudden radiation of complex life occurred. The fossil record of this period contains the first appearances of practically every animal phyla, implying that nearly all animal life has its origin during this radiation. It lasted between 13 and 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversification in other groups of organisms as well. Before early Cambrian diversification, most organisms were relativ…