Slides:  Proterozoic Eon

 

1.      Paleoproterozoic Vishnu Schist (2 Ga) overlain by the Lower Cambrian Tapeats Sandstone forming the “Great Unconformity”.

2.      Mesoproterozoic Castner Marble (1.2 – 1.4 Ga) exposed in the Franklin Mountains along Transmountain Drive in El Paso, Texas.

3.      East side of Enchanted Rock, the exposed part of the much larger Mesoproterozoic Enchanted Rock Pluton (1.08 Ga) northwest of Fredericksburg, Texas.

4.      Quarry in Mesoproterozoic Keweenawan basalts associated with the 1 to 1.2 Ga Mid-Continent Rift Zone; near Houghton on the Keweenawan Peninsula in the Upper Peninsula of Michigan. These basalts host native copper deposits that were mined extensively in the late 19th and early 20th century.

5.      Dike cutting dipping beds of the Mesoproterozoic Hakati Shale (1.1 Ga), Unkar Group in the Grand Canyon; the near-horizontal Lower Cambrian Tapeats Sandstone overlies the shale forming an angular unconformity (the “Great Unconformity)

6.      Neoproterozoic glacial tillite (around 700 Ma) overlain and underlain by limestone in Namibia, southwestern Africa. This outcrop, exposures in the Canadian Rockies and others like them are evidence for continental glaciation in the tropics. This has led some geologists to refer to this time as the “Snowball Earth.”

7.      Impression of a Neoproterozoic jellyfish belonging to the Ediacaran fauna, one of the first collections of multicellular animals (metazoans); from the Vendian Rawnsley Quartzite, Ediacara Hills of South Australia