Cloudcroft, New Mexico sits in the heart of the Sacramento Mountains at nearly 8700 feet above sea level. Community residences often use fossils for home, business, or landscape decorations. There are two learning goals for this EarthCache. First, geocachers will learn the type of fossil that is predominately represented at the GZ. Second, geocachers will determine the geographic time period and how many years ago the limestone was laid down.
The sedimentary layers from which these fossils come are the massive layers of the San Andrea Limestone. Limestone is composed primarily of the mineral calcite, or calcium carbonate, which is secreted by various animals and plants -- such as oysters, corals, and algae -- that live in marine, environments. The San Andrea limesrtone formation was created from deposits in the sea that covered this area during the Pennsylvanian and Permian Periods - 330 to 240 million years ago. The sedimentary rocks around Cloudcroft are often sparsely exposed due to the dense vegetation in the area. However, one can observe excellent exposed rock formations along the roads and hiking trails, all within 20 miles radius of Cloudcroft. Also, many places along the roads and trails have markers describing geology and rock formations at the observation points.
A fossil is defined as a remnant or trace of an organism of a past geologic age, such as a skeleton or plant imprint, embedded and preserved in portions of the earth’s crust. Fossils come in various forms — from bones and shells to carbon imprints to footprints and burrows. Finding fossils is relatively easy, but becoming a fossil is not. Only a tiny fraction of organisms that have lived during the past are preserved as fossils. Instead, most are eaten, attacked by bacteria, fragmented, crushed, dissolved, or worn away by wind or water movement. Several factors favor fossilization, but probably none is more important than the possession of hard parts -- sturdy bones in vertebrates, thick shells in invertebrates, wood and seeds in plants. Hard parts hold up better to decay and destruction than such soft tissue as muscles and organs. Thus, for example, we find many more clams than worms in the fossil record.
Rapid burial is also essential for fossilization; it protects an organism from being eaten by scavengers, attacked by bacteria, or battered by running water or wave action. Generally, plants and animals that live in or fall into water are more likely to be buried quickly. They settle to the seafloor, lake bottom, or riverbed and are buried by the sediment that accumulates over time. This is one reason that aquatic organisms are far more represented in the fossil record than those that lived on land. Even if an organism is fossilized, it may subsequently be destroyed by ongoing geologic processes such as mountain building and erosion. If a fossil escapes obliteration, it then becomes part of the fossil record. Still, the odds are decidedly against preservation as a fossil.
Ammonoids are extinct mollusk creatures that lived inside an external shell. They are related to the chambered Nautilus, which survived until today. Like Nautilus, most ammonoids were probably good swimmers, moving through the water by means of a kind of jet propulsion and eating fish, crabs, and other shellfish. Ammonoids evolved in many parts of the world and died out during the mass extinction at the end of the Cretaceous Period that killed the dinosaurs and many other land and sea animals. Many ammonoid shells were coiled in the same plane, like a cinnamon roll; others had straight or erratically coiled shells. The external surface of some shells was ornamented with different color patterns, ribs, nodes, or spines, but this ornamentation is not always preserved. Most Paleozoic ammonoids were golf-ball sized or smaller. At the height of their diversity during the Cretaceous period larger ammonoids, some with diameters up to 10 feet (3 meters), were common.
To claim credit for this EarthCache, send us the answer to the following questions. DO NOT INCLUDE THE ANSWERS IN YOUR LOGS. Logs posted without providing answers to the questions will be deleted.
1. What are the most prevalent type of fossils that you find at the GZ, and range of sizes.
2. In what type of rock do you believe these fossils are located?
3. How many years ago did these fossils live?
Thank you for visiting this EarthCache. Hope you learned a little and enjoyed the experience.
Ref: GEOLOGY OF THE CLOUDCROFT AREA AND SACRAMENTO MOUNTAINS, NEW MEXICO by Verner C. Johnson, Ph.D., Professor of Geology, Colorado Mesa University, Grand Junction, Colorado