GEL 25 Lecture Notes - Lecture 6: Dune, Navajo Sandstone, Kayenta Formation
Document Summary
Numerical (radiometric) age-dating requires a mass spectrometer to count the number of atoms of specific elements. Works on all 3 types of rocks. Faulting occurred last because it cross-cuts the sedimentary & volcanic rocks. Volcanic ash is made up of tiny particles of rocks and glass. We use lava rock to create numerical age-dates. We use fossils to create relative age-dates. Even if an area doesn"t have lava we can create numerical age-dates, by looking at other areas with the same fossils (and lava rock). Civilization has only existed for 0. 000001% of earth history. High plateau is cut by fractures and incised by virgin river. Environments represented include shallow seas, coastal plain rivers, tropical swamps, and vast coastal deserts. We know it is mesozoic because footprints of dinosaurs are found in rocks. Zion np is dominated by resistant cliffs of navajo sandstone overlying slopes of less- resistant kayenta formation. Cross-bedding in navajo - vast coastal desert system.
