Lake Turkana has a geologic history that favored the preservation of fossils. Scientists suggest that the lake as it appears today has only been around for the past , years. The current environment around Lake Turkana is very dry. Over the course of time, though, the area has seen many changes. Over time the sediment solidified into rock. This volcanic matter eventually settles and over time is compacted to form a special type of sedimentary rock called tuff. During the Pliocene geologic epoch 5. This allowed for erosional forces to expose rock that was buried long ago. These processes also exposed the fossils buried within those layers of rock. The layers of volcanic rock are extremely important to reconstructing the history of the Turkana Basin because they allow scientists to calculate the age of hominin fossils found in the region. Dating of the fossils contributes to a clearer timeline of evolutionary history. However, the fossils in the Turkana region can be dated more accurately because they are found in the sedimentary rock between datable layers of tuff. Although radiometric dating of the tuff is scientifically valid, difficulties still exist.
Cart 0. Crabs, Lobsters, Shrimp, etc. Fish Fossils. Floating Frame Display Cases. Other Fossil Shellfish. Petrified Wood Bookends. Petrified Wood Bowls. Petrified Wood Spheres. Plant Fossils.
Reptile, Amphibians, Synapsids Fossils. Whole, Unopened Geodes. Picasso Picture Stone. Rose Quartz. Cactus Spirit Quartz. About FossilEra. About Xiphactinus. About Fossils. So, how do we know how old a fossil is? There are two main methods determining a fossils age, relative dating and absolute dating. Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.
Relative Dating The majority of the time fossils are dated using relative dating techniques. Using relative dating the when you start dating someone new is compared to something for which an age is already known.
For example if you have a fossil trilobite and it was found in the Wheeler Formation. The Wheeler Formation has been previously dated to approximately million year old, so we know the trilobite is also about million years old.
Scientists can use certain types of fossils referred to as index fossils to assist in relative dating via correlation. Index fossils are fossils that are known to only occur within a very specific age range. Typically commonly occurring fossils that had a widespread geographic distribution such as brachiopods, trilobites, and ammonites work best as index fossils.
If the fossil you are trying to date occurs alongside one of these index fossils, then the fossil you are dating must fall into the age range of the index fossil. Sometimes multiple index fossils can be used. In a hypothetical example, a rock formation contains fossils of a type of brachiopod known to occur between and million years. The same rock formation also contains a type of trilobite that was known to live to million years ago. Since the dating fossils accuracy formation contains both types of fossils the ago of the rock formation must be in the overlapping date range of to million years.
Studying the layers of rock or strata can also be useful. Layers of rock are deposited sequentially. If a layer dating fossils accuracy rock containing the fossil is higher up in the sequence that another layer, you know that layer must be younger in age. This can often be complicated by the fact that geological forces can cause faulting and tilting of rocks. Absolute Dating Absolute dating is used to determine a precise age of a rock or fossil through radiometric dating methods.
This uses radioactive minerals that occur in rocks and fossils almost like a geological clock. So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range dating fossils accuracy the fossil containing rocks. The atoms in some chemical elements have different forms, called isotopes.
These isotopes break down at a constant rate over time through radioactive decay. By measuring the ratio of the amount of the original parent isotope to the amount of the daughter isotopes that it breaks down into an age can be determined. We define the rate of this radioactive decay in half-lives. If a radioactive isotope is said to have a half-life of 5, years that means after 5, years exactly half of it will have decayed from the parent isotope into the daughter isotopes.
Then after another 5, years source of the remaining parent isotope will have decayed. While people are most familiar with carbon dating, carbon dating is rarely applicable to fossils. Carbon, the radioactive isotope of carbon used in carbon dating has a half-life of years, so it decays too fast.
It can only be used to date fossils younger than about 75, years. Potassium on the other hand has a half like of 1. This makes it ideal for dating much older rocks and sorry, family guy brian dating show topic.