EARTH 10 Lecture Notes - Lecture 8: Unconformity, Enderby Land, Orogeny
Document Summary
Relative = 3 principles: original horizontality: sediments usually accumulate as horizontal layers, superposition: layers on bottom older than ones on top, cross-cutting relationships: rock must form before it can be cross-cut. Unconformities: an interruption in deposition in sedimentary rocks, usually of long duration. Fossils: remains and other traces of prehistoric life; succeeded each other through time in a definite and recognizable order rock ages can be recognized based on fossil content. Index fossil: fossil that indicates age of the rocks containing it. Orogeny : period of mountain building; forces and events leading to a large structural deformation of the lithosphere due to tectonic activity. 4,000 million years ago in napier orogeny--first rocks--small corner in upper right. Sweat hypothesis = sw usa and e. aa once connected. E. aa and laurentia (early n. america) Along present pacific margin of n. america. Gondwana (500 mya) = formed after cambrian, before pangea.
