Power Point Lectures on Chemostratigraphy
These lectures were assembled by Charlotte Schreiber, now a professor at U. Washington, Department of Earth and Space Sciences, for her university classes and short courses. They are for everyone's use and education. The lectures can be reached by clicking on the "hot" items below or the sub-menu items in the left sidebar.
The lectures are focused on how stratigraphic interpretations are improved from an understanding of certain chemical properties of sedimentary rocks which can be used to determine their age and depositional and diagenetic settings.
These lectures can be used (unless the material is specifically excluded) under the Creative Commons license: http://creativecommons.org/licenses/by-sa/3.0/
This topics of the lectures are broad, including all isotopic tools geologists use to discern the actual age and associated conditions during which a sediment or sedimentary rock was formed.
In this set of presentations (4th year, undergraduate level) provides reviews of the background and application for five of the most commonly utilized techniques presently employed in age dating. There is relatively little text given in most of the powerpoints and they represent a collection of figures, tables and statements which may be used to teach about each topic. The figures are mostly taken from published papers and redrawn (attributions given, where known). Some figures are from anonymous website collections of diagrams (no attribution). The photosequence attached to the presentation of 'sulphur' is made up of a unique set of photographs taken by B.C. Schreiber, from several sulphur mines (now closed) in Sicily. This set visually documents the diagenetic formation of sulphur by bacteria from the original primary gypsum
/anhydrite together with the organic matter that drives the process (an unusual and unique collection).
Associated reference lists and pdfs of most references used in creating each of these powerpoints is also offered but there is no claim that the lists are complete or even totally appropriate - certainly many useful and appropriate references are missing. None of the figures/photos may be used for publication, and apologies are given where attributions were missed or misassigned. This is a classroom lecture collection and not a publication.
- These are intended for the novitiate trying to understand the use of chemostratigraphy for the first time.
History of stratigraphy
- Atmosphere Evolution
- Ocean Evolution
– The only one of these techniques that actually yields ~absolute age dates- but it has the disadvantage of both requiring the presence of sediments bearing radioactive isotopes (rare), plus the assurance of a sealed system in which the mother and daughter isotopes remain in 100% primary proportions.
- Most effectively used for age dating of organic matter and especially in carbonate
rich sediments. Also useful in determining carbon sources because different plant groups produce identifiable isotopic signatures.
- Useful in determining water sources in sulphate-rich sediments and in determining degrees/and types of diagenesis. Volcanogenic S, not included, except as a reference list.
- Largely employed to determine the
temperature of the water from which the sediments were formed.
87Sr/86Sr Isotope Ratios
- Generally used to reveal
the relationship of continental water influx into oceanic waters. Affected by
rate of sea-floor spreading versus continental weathering plus meteoric influx
into the sea. Particularly useful in dating Cenozoic sediment deposits.