GEOL 1003 Lecture : Class Notes 6 21 2012 Proterozoic Eon
Document Summary
Proterozoic eon (2. 5 0. 54 ga: first modern orogeny, rise of atmospheric oxygen evolution of eukaryotes, global glaciations, beginning of animal life, assembly of north america. Cratons: large portions of continents that have undergone minor deformation, primarily proterozoic and archean in age. Precambrian shield: craton exposed at surface, largest canadian shield, northern canada. Modern style of orogeny: wopmay orogen (2 ga) formed on the margin of the slave province in canada due to a collision with an island arc. Represents an ancient metamorphic belt and a fold-and- thrust belt: foreland basin formed, then became deformed with the fold-and-thrust belt, shallow shelf deposits, quartz sandstones, carbonate platform with stromatolites, flysch, molasse. Evidence for oxygen rise: before ~2. 3 ga, sediments were made of minerals that require anoxic (low oxygen) conditions (ex. Pyrite fes2: oxidative weathering, fe-hydroxides will stabilize to form fe-oxides, fe-oxides are insoluble because fe bonds strongly with o.
