This is an Earthcache – as such, there is no physical cache. Instead you will partake in a geology lesson by making observations and answering 6 questions about the limestone monument at the posted coordinates. A magnifying glass or a camera phone will be helpful to zoom in on the fossils. Special thanks to St. Mary’s College of Maryland for granting permission to place this earthcache.

FREEDOM OF CONSCIENCE MONUMENT

To celebrate Maryland’s 300th year, Baltimore Sculptor Hans Schuler was commissioned to create a 15-foot monument from Indiana Limestone to memorialize the practice of religious tolerance by the original colonists of Maryland.

The statue, known today as the “Freedom of Conscience Statue,” was a gift from the original counties of Maryland, and intended to serve as a marker for the entrance to the colonial settlement of St. Mary’s City. While not erected until a year after the tercentennial celebrations, Schuler’s statue became a notable landmark here in the city.

INDIANA LIMESTONE

The stone monument you see before you is made of a sedimentary rock that is formed from living organisms in a shallow inland sea over 300 million years ago. These fossilized creatures had shells made of calcium carbonate that piled up over time when they died.

The bodies of these creatures sunk in warm tropical waters that were shallow enough for waves to move coarse carbonate sand across the seafloor. Battered by constant wave action, the larger shells were battered and broken, while the smallest particles washed away. Over time and under pressure these shells fossilized and were cemented into limestone. The process of loose sediments, such as this, becoming compacted into stone is referred to as lithification.

With its excellent physical properties, good workability, fire resistance, durability, and sustainability, Indiana Limestone is one of the most used and versatile building stones in the United States. It exhibits three colors: gray, buff (a light brownish yellow), and variegated (includes patterns of both gray and buff).

FOSSILS

Indiana Limestone consists mostly of small fossil fragments. Identifiable Crinoid and Bryozoan fossils are commonly found in the stone. They may sometimes resemble flowers, but they are not plants. Instead, they were both invertebrates. Like their relatives starfish, sea cucumbers, and sea urchins, these were animals that neither possessed nor developed a vertebral column (commonly known as a backbone or spine.

Crinoids have lived in the world's oceans since at least the beginning of the Ordovician Period, which was roughly 485 million years ago. They peaked during the Mississippian Period, when the shallow, marine environments they carpeted were widespread on several continents.

Crinoids came close to extinction toward the end of the Permian Period, about 252 million years ago. The end of the Permian was marked by the largest extinction event in the history of life. Fossil records show that nearly all crinoid species died out at this time. The few surviving lineages eventually gave rise to the crinoids that are still populating the oceans today. Some of the massive limestone formations in North America are made up almost entirely formed from crinoid fragments.

Bryozoans are among the common fossils. The oldest ones come from Cambrian rocks over 500 million years old, and their descendants live today. During the Mississippian Period bryozoan were so common that their broken skeletons formed entire limestone beds.

Bryozoans are microscopic aquatic invertebrates’ exoskeletons similar to those of corals. They live in colonies in freshwater, brackish water, and marine environments and are usually attached to structures such as a rock or submerged vegetation.

Here in Southern Maryland you can find Miocene bryozoans along the fossils of Calvert Cliffs. Modern fenestrate bryozoans are still living in the Chesapeake Bay today. Named Conopeum chesapeakensis, these bryozoans are tan-colored, erect, branching, tubular structures, with the branches widening into flat ribbons near their tips.

LOGGING REQUIREMENTS:

To log this Earthcache: Read the geology lesson above. Answer all six questions posted below and post photo. Answers can be sent via e-mail or messenger contacts on my Geocaching profile. Group answers are fine, but do not post the answers to the questions in your logs.

QUESTION 1. The process of sediments turning to stone is referred to as what? (The "L" Word!)

QUESTION 2.From the reading, what is the name of the Modern fenestrate bryozoans that live in the Chesapeake Bay today?

QUESTION 3. On the back of the monument, look about an inch to the right of the "M" in "FROM." Is this a Crinoid Crown fossil or a Bryozoan Net fossil?

QUESTION 4. About how big is it? (Example: The fossil is the size of a dime, housekey, or the side of a driver’s license. Use what you have available, but your scale should be something that is consistent in size.)

QUESTION 5. Search the memorial for another a different fossil and identify it. Did you find a bryozoan, a crinoid, or something else?

QUESTION 6. From the reading we learned that Indiana Limestone comes in three colors. How would you describe the color of this monument?
A. Gray
B. Buff
C. Variegated

OPTIONAL PHOTO: Posting a photo in your log readily indicates that you (and anyone else logging the find) are at the location.

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REFERENCES