GEOL 106 Lecture Notes - Lecture 48: Oceanic Basin, Isotopes Of Nitrogen, Dendrochronology
26 May 2018
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SEDIMENTS
- oceans of world are repository for sediments from land delivered by rivers, wind, volcanic eruptions,
sediment from ocean itself (e.g. shells of dead organisms)
- lakes, bogs, ponds accumulate sediment over time that can be sampled for climate signal
- when sediment deposits are sampled and studied → these provide paleo-proxy data sources for
climate change
- sediments are recovered by drilling in bottom of ocean basin or lake
- from the cores, samples may be taken of small fossils and chemicals that are contained within
sediments that may be interpreted to better understand past climate change
- strongest evidence for past climate changes comes from these proxy records
ICE CORES
- glaciers contain accumulation record of snow that has been transformed into glacial ice over hundreds
of thousands of years
- drill ice and obtain core → study in detail to learn about past condition
- ice cores contain small bubbles of air deposited at time of snow
o composition and ratio of past atmospheric gases preserved in ice may be studied and used to
infer number of paleoclimatic variables
- ice cores also contain:
o variety of chemicals and materials
▪ volcanic ash and dust
o can provide proxy data to assist evaluation of climate change
- ice itself may be studied to determine paleo-isotopic composition of water → info. about volume of
ice on land as well as processes occurring paleo-oceans (oceans of past as determined from sediments)
POLLEN
- pollen along with other sediments accumulates in variety of environments including oceans, bogs,
lakes
- study abundance and types of pollen in order to investigate past climate
o if climate cools → change in types and quantities of pollen found in sediments that reflect
change in climate
- pollen may be dated
- grains preserved in sedimentary layers that also might be dated → chronology can be developed
- based on types of plants found at different times, climatic history can be reconstructed
CORAL
- coral reefs consist of corals that have hard skeletons composed of calcium carbonate extracted by
corals from seawater
- calcium carbonate contains isotopes of O2 as well as variety of trace metals that can be uses to
estimate temperature of water in which coral grew
- corals are a source of paleo-proxy data that can help us interpret climate change
- corals may be dated by several dating techniques and chronology of change over time may be
constructed
CARBON-14
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Document Summary
Oceans of world are repository for sediments from land delivered by rivers, wind, volcanic eruptions, sediment from ocean itself (e. g. shells of dead organisms) lakes, bogs, ponds accumulate sediment over time that can be sampled for climate signal. Ice cores glaciers contain accumulation record of snow that has been transformed into glacial ice over hundreds of thousands of years. Based on types of plants found at different times, climatic history can be reconstructed grains preserved in sedimentary layers that also might be dated chronology can be developed. Production of 14c produced in upper atmosphere is caused by collisions between neutrons and nitogrn-14: nitrogen is part of cosmic rays that come from outer space and are product of energy from. Sun: as sun spot activity increased (solar active areas) energy from sun that reaches earth also increased frequency of sunspots have been measured for decade and observed by people for 1000 years.
