GEOG 2110 Lecture Notes - Lecture 3: Isotopes Of Nitrogen, Radiocarbon Dating, Foraminifera
Document Summary
So we need proxy records of climate, eg. tree rings, ice cores, pollen, coral reefs, foraminifera, geoduck shells, ect. Tree rings: conducive conditions to growth wide tree ring. Can have thousands of years of tree ring data. Sediments: lake bottoms (nothing decomposed but well preserved), best from sea floor. Best available record over 99% of geological time. On land surface: oxygen decomposed and animal interference. Ice cores see different types of weather systems. Sea pollen and dionomids (insect tolerance to conditions). Oldest sediment: 12 thousand because canada was covered in ice. Two stable isotopes: 16 o and 18 o. they have different numbers of neutrons. 18 o is heavier because of two extra neutrons. So moves slower and takes more energy to evaporate. Warm years have an lots of 18 o. abundance states as depletion or enrichment relative to a standard. For oxygen, its mean ocean water, eg. -2% = 2 parts per thousand less.