ESCI 402 Lecture Notes - Lecture 3: Weathering, Breccia, Clastic Rock
Document Summary
Sedimentary rocks: composed of sediment that has been consolidated by compaction, cementation and crystallization. Make up 5% by volume of earth"s crust cover 75% of world"s exposed land surface area primary archives of fossils characteristics of sedimentary rocks provide info about ancient environment. What does grain composition tell us: more resistant minerals survive longer transport, weaker minerals stay in general areas. What does grain roundness tell us? o o rounder grains= longer transport less round= stay in general areas fossil: any physical evidence of past life. What do fossils can teach us about earth history? evolution: fossils represent only direct evidence of past life. All other methods of historical reconstruction rely on inference inferences from genetic info comparative anatomy vestigial organs: structures not used for organism anymore. The geologic time scale biostratigraphy: using occurrence of fossils to correlate strata from one place to another.
