Read pages 200-215 in the Online textbook. Ignore the section on “What did they look like” and Non-Radiometric Absolute Dating Methods (end of pg 215). Answer All of the following questions.
The book and PowerPoint review a variety of Relative and Absolute dating techniques applied to the fossil record.
- What is the difference between Relative and Absolute dating?
- Explain the law of superposition and stratigraphic correlation, and discuss how they relate to relative dating?
- What is Fluorine dating and how can it be used to correlate animal remains?
Biostratigraphy is a primary dating technique used in paleontology. It relies heavily on the law of superposition, stratigraphic correlation, and the use of Index Fossils.
- What are Index Fossils? (use book and powerpoint)
- Considering the three principles listed above, what is biostratigraphy and how does it work?
Understanding Radiometric Dating is of great importance to this course. Please consider the book section and the powerpoint carefully
- Define and explain the term Isotope (include the structure of an atom)
- What makes an isotope Radioactive?
- What is Radioactive Decay?
- What is a half-life?
The three radiometric (absolute) dating techniques that we will need to know for this class include Carbon 14, Potassium-Argon, and Uranium Series. For this question you will need to explain each one. Include how the method works, the age range it can be applied too, the material that the date is obtained from, and what circumstances it is best used in.
Carbon 14 (~200-250 wds)
Potassium-Argon (~200-250 wds)
Uranium Series (~200-250 wds)
Dendrochronology, also known as tree-ring dating, utilizes growth patterns in trees to determine the age of well preserved wood in archaeological settings. As trees grow, they develop concentric rings that correlate with periods of cessation and reactivation.
In winter climates tree growth ceases but is then reactivated in the warmer spring season. The thickness of the rings correlates with the length of seasons and is unique year-to-year. These tree-rings will look the same in all trees of that species from that region, regardless of their age. Thus, trees that are 50 years old will develop the same rings in one year as a younger member of the same population (say 5 years old).
Some trees are remarkably long lived, and so carry a record from hundreds of years ago. If a modern-day tree is cut down, a chronologists can count the ring pattern to establish how long the tree has been alive. Importantly, they can also compare the rings to wood beams found in archaeological site. If a house beam from an ancient civilization has a pattern that matches to part of our modern tree sample, we can determine exactly how long ago that beam was part of a living tree.
By correlating a variety of samples, a large database has been established for tree-ring patterns going back hundreds of years. The method does have limitations, however. The biggest limitation is that it does not tell us how old the archaeological site is, just how old the wooden beam is. In all actuality, there is a good chance that the site is much younger than the tree itself. This is because such materials are often reused through time. Another limitation is that it is highly dependent on excellent preservation of wood, which is a rarity.