Sequence stratigraphic framework and application to the Precambrian

Available online at www.sciencedirect.com

Gondwana Research 14 (2008) 22 – 32 www.elsevier.com/locate/gr Models on Snowball Earth and Cambrian explosion: A synopsis
S. Maruyama a,⁎, M. Santosh b a Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo 152-8551, Japan b Faculty of Science, Kochi University, Akebono-cho 2-5-1, Kochi 780-8520, Japan

Received 13 November 2007; received in revised form 21 December 2007; accepted 8 January 2008
Available online 8 February 2008

Abstract
During the late Proterozoic from 1000 to 542 Ma, the Earth is thought to have been frozen at least during two times: in the Sturtian (715–680 Ma) and in the Marinoan (680–635 Ma) global glaciations. Following the Marinoan Snowball Earth, large multi-cellular animals of the Ediacara fauna flourished as a prelude to the Phanerozoic world. Here we summarize the most popular models on the cause and cessation of Snowball Earth. Episodic decrease of greenhouse gas occurs through the effect of erosion and weathering promoted by either mountain building or by an increase in the coastlines during the break-up of supercontinents. Effects on the globe caused by true polar wander, eruption of voluminous flood basalts, or dramatic reduction in planetary obliquity can also lead to ice ages and mass extinction. A radically revised concept based on Earth's magnetic intensity has also been proposed, which explains the true polar wander through a quasi-polar dynamo model. The ‘switch-on’ and ‘switch-off’ of the Earth's strong dynamo can lead to the onset and disappearance of the Snowball Earth. The galactic model infers that gamma ray burst associated with starburst creates huge amounts of clouds which would cut off sun rays and freeze the Earth.
The Snowball Earth event is considered to have exerted a significant control on the subsequent revolutionary changes in the evolution of life forms. Although according to the biological clock, extensive