GEOL 101 Lecture Notes - Lecture 18: Cambrian Explosion, Supercontinent Cycle, Supercontinent
Document Summary
Banded iron formations: deposited between 3. 5 & 2 billion years ago as oxygen was added to the atmosphere and immediately removed by oxidation of iron in the oceans. Earth"s first continents: first, the crust was mainly oceanic. Then, subduction created island arcs with more continental compositions. These crashed together to form the first contients. Ancient super-continents: the idea that rifting and dispersal of fragments of one super- continent is followed by a long period of separation and then reassembly of another super-continent is called the super-continent cycle. Precambrian fossils: 3. 2 billion years ago; seen in modern-day australia, stromatolites: fossils formed from layers of cyanobacteria and sediment. Precambrian animals: ediacaran biota; existed at end of time period. Prokaryotes & eukaryotes: prokaryotes: no membrane-bound organelles; bacteria & cyanobacteria, eukaryotes: membrane-bound organelles; amoebae & multicellular life. Middle cambrian animals: burgess, shale, canada, arthropods, corals, sponges, 505m years ago. Devonian: age of fishes: dorsal hollow nerve cord: spinal cord appears.
