Law of fossil succession strata dating
The third was a young surveyor and canal engineer named William Smith, who possessed an extensive understanding of England’s rock layers, or After dinner, the men made a chart of the rock strata in the vicinity of Bath, identifying strata by color, hardness, and the fossils they held.
In all, they named 23 layers, employing colorful names like Fuller’s Earth, Lias Blue, and Ditto White. Between strata they called Millstone and Pennant Stone was a dramatic change in the kinds of fossils found in the rocks. In the Pennant Stone layer, marine mollusk shells dominated.
By carefully digging, we have found that each trash pit shows a sequence of layers.
Although the types of trash in each pit is quite variable, each layer has a distinctive kind of trash that distinguishes it from other layers in the pits.
In the long run, it helped succeeding generations of scientists uncover the history of life on Earth.
The boundary between the Permian Yellow Sands Formation (above), and the Carboniferous Pennine Upper Coal Measures (below) is exposed along the banks of the River Wear, roughly 500 kilometers north of Bath. Image interpretation by John H Powell, British Geological Survey.) William Smith was born on March 23, 1769.
The lower layer was rich in plants; the upper layer was rich in seashells.
Geologist in the 1800s worked out 7 basic principles of stratigraphy that allowed them, and now us, to work out the relative ages of rocks.
Today, geologists recognize this fossil turnover as the boundary between the Carboniferous Period (360 to 300 million years ago), when abundant swamps laid the foundation for many of today’s coal beds, and the Permian Period (300 to 250 million years ago), when Earth’s landmasses coalesced into a single continent.
In 1799, however, when Smith and his friends noted the fossil shift, they didn’t grasp the hundreds of millions of years of changing landscapes that geologists recognize today.
The goal of this lecture is come to come to a scientific understanding of geologic time and the age of the Earth.
In order to do so we will have to understand the following: To better understand these concepts, let's look at an archeological example: Imagine we are a group of archeologists studying two different trash pits recently discovered on the Tulane University campus and at the Audubon Zoo (where they all aksed for you).