Scientists Still Trying to Explain Evolution's Big Bang Theory. One of the explanations is the "Great Uniformity", a worldwide stratigraphic feature marking a divide between continental crystalline basement rock and younger shallow marine sedimentary deposits. Occasionally — in the Grand Canyon, for example — it is exposed on Earth's surface to dramatic effect. Geologists have been debating the origins and the global impact of the Great Unconformity ever since the term was coined in 1869. Shanan Peters and Robert Gaines presented an analysis of stratigraphic and lithologic data from 830 locations in North America, together with petrologic and geochemical data. They find evidence that the formation of the Great Unconformity caused enhanced continental weathering and increased oceanic alkalinity and ionic strength in expanding shallow seas, which in turn triggered biomineralization and the Cambrian explosion of marine animals.