This EarthCache will introduce you to the name of this geologic tool and show you how geologists determine the age of the rocks used to build the pavilion.
Learning Goals
There are two learning goals for this EarthCache. First, geocachers will name the type of fossil that is predominantly represented in the limestone at gz. Second, geocachers will determine the geographic time period and how many years ago the limestone was laid down.
Welcome to The Legacy Pavilion
River Legacy Park
The park's hours are 5:00am until 10:00pm. There is no fee to enter the park.
When you arrive at the coordinates for this EarthCache, take a seat on the low wall with a broad top that surrounds the Legacy Pavilion, and check out the beautiful open-aired structure that covers several picnic tables.
Notice that there are two types of stones used to make the pavilion. The majority of the structure is made with a roughly honed stone that is a soft, light brown color with hints of orange, bronze, and yellow. The other type of stone is very smooth, is a light cream color, and is covered with indentations to accent and decorate the pavilion's columns and covers the top of the low wall you are sitting on. As you sit on the low wall, turn to face the south and see the two types of stone in one of the huge columns near you.
The main building material for the pavilion is limestone. Limestone is a sedimentary rock composed primarily of calcium carbonate in the form of the mineral calcite. It most commonly is formed primarily in shallow sea water from marine life, such as clams, scallops, or coral, which use calcium and bicarbonate in the water to form their protective shells. Over time, as the organisms die and the shells are left behind, they fall to the bottom and accumulate in layers, where they combine together to form limestone.
The type of stone used to create decorative features of the pavilion’s huge columns and the top of the low wall is called Fossiliferous limestone because it contains an abundance of fossils or fossil traces. This type of limestone often contains fossils or fossil traces from crinoid stems, brachiopods, gastropods, and other hard-shelled mollusk remains.
Geologists use these fossils to help identify and define the geologic period that the sedimentary layer was formed. This type of fossil is called an index fossil and it is the "tool" you will use to determine the age of and geologic period that this sandstone was laid down.
Geologic Time Scale and Index Fossils
Geologists have divided the Earth's history into a series of time intervals based on significant events. The geologic time scale shows the duration of each period of time and the name for the Eons, Eras, and Periods of geologic time.
Shown below are five images of a few types of index fossils and the period of time they lived in Earth's history. Only one of the index fossils shown here is visible in the Fossiliferous sandstone at gz. As you sit on the low wall at gz, there are several indentations that you can feel and see. These are fossil traces or ichnofossils. Notice that there is ONE fossil trace that is the largest (about 3 inches in diameter) and is the most predominant across the top of the fossiliferous sandstone. This is the index fossil (the "tool") that will tell you the age of the sandstone. Notice the shape, texture, and details of the fossil. Compare this with the images shown below to determine the name of the fossil trace at gz and how many years ago the sandstone was created.
As of November 16, 2019, all log entries are required to include a photo of the cacher at gz. This is per the new EarthCache guidelines posted in June 2019. https://www.geocaching.com/help/index.php? NOTE: Do not include any image that gives away the answers to the questions. ECO reserves the right to delete any log entrees that include images that give away the answer.
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Calico Scallop
The scientific name for this fossil is Pecten Gibbus and is associated with the Quaternary Period, approximately 1.6 million years ago. This is the most recent time in earth's history .
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Viviparous Galacialis
This index fossil is associated with the Tiglian or Early Pleistocene time period, about 1/2 a million years ago. 
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Scaphites Hippocrepis
This index fossil is associated with the Cretaceous time period, about 145 to 66 million years ago.
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Muscrospirfer
This index fossil is associated with the Devonian time period, about 416 to 359 million years ago.
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Paradoxides
This index fossil is associated with the Cambrian time period, about 509 to 500 million years ago.
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Logging Requirements
Please do NOT post your answers to the questions in your log. If you do, I will delete your log and that just makes me sad. Please DO post photos!! Photos of the animals near the pavilion. Photos of your friends at the pavilion. Photos of your self!! Most importantly, please take just a minute to share something special about your visit to River Legacy Park and what you have learned from this EarthCache. If you MUST use the overused and unimaginative standard geocaching abbreviations, do so with such creativity and flair that everyone who reads your log nods with approval and admiration.
Send an email to me with the title "Index Fossil at River Legacy" with the answer the following questions.
1. What is the name of the index fossil on the low wall at gz?
2. How many millions of years ago was this sandstone created?
3. How many decorative squares of fossiliferous sandstone are on ONE of the huge columns near gz?
4. Walk around the low wall that surrounds the Legacy Pavilion. Look for the man-made impressions of animal tracks and the name of the animal, reptile, or bird found in River Legacy Park. How many names of animals are shown in the wall?
References
Index Fossils https://en.wikipedia.org/wiki/Index_fossil
Fossils and the Geologic Time Scale http://pubs.usgs.gov/gip/fossils/numeric.html
Types of Index Fossils http://geolnew.blogspot.com/2009/07/types-of-index-fossils.html
Limestone http://geology.com/rocks/limestone.shtml
Fossiliferous Limestone https://en.wikipedia.org/wiki/Fossiliferous_limestone
Congratulations to TerraViators for FTF!