ORVEC Fossil: Stromatoporoid EarthCache
Hidden : 10/13/2012
Difficulty:
2.5 out of 5
Terrain:
5 out of 5

Size: Size: other (other)

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Geocache Description:



Stromatoporoid Sponge

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What is a fossil? A fossil is the prehistoric remains of a plant or animal. Fossils are typically preserved when they are buried under many layers of sand and mud. Under great pressure the sand and mud become sedimentary rock. Minerals seep into the fossil replacing the organic matter and creating a replica in stone.


Stromatoporoid


Stromatoporoidea is a class of aquatic invertebrates common in the fossil record from the Ordovician through the Cretaceous. They were especially abundant in the Silurian and Devonian (FoTO). These invertebrates were important reef-formers throughout the Paleozoic and the Late Mesozoic. The group was previously thought to be related to the corals and placed in the Phylum Cnidaria. They are now classified in the sponges (Phylum Porifera), specifically the sclerosponges. There are numerous fossil forms with spherical, branching or encrusting skeletons of laminated calcite with vertical pillars between the laminae.

Stromatoporoids are useful markers whose form and occurrence can diagnose the depositional environment of sedimentary strata.
The Devonian Period occurred between 395 and 345 million years ago. During that time, Indiana and Kentucky languished beneath a warm, tropical sea, and were located about twenty degrees south of the equator. Tectonic shifting of the earth's continents eventually moved this part of the earth's surface to its current location. During the 45 million year span of the Devonian Period, the oceans deposited layer upon layer of lime silt, sediments, and plant and animal remains.

Of these deposits, five distinct fossil layers lie exposed at the Falls:
  • The uppermost layer - or the youngest rock - is the Paraspirifer Acuminatus Zone, which contains fossils of brachiopods (including paraspirifers, a two-shelled animal similar to a clam); bryozoans (commonly called lace coral); trilobites; and some solitary, branching, and colonial corals.
  • Second is the Fenestrate Bryozoan-Brachiopod Zone. Named for the predominant fossils found there, here one also can find crinoid stems in abundance.
  • A six-inch-thick layer called the Brevispirifer Gregarius Zone follows, and contains fossils of brachiopods and gastropods (sea snails), horn corals, or cup corals, and one of the Falls' most unusual corals, the astromatoporoid.
  • The Amphipora Ramosa Zone, commonly called the Cave Zone. Pocket caves have developed here due to the powerful erosive powers of the Ohio River rushing across the rock. This zone occurs along the vertical cliffs of the river channel, where the cutting force of the river reaches its peak.
  • The oldest and most remarkable layer is the largest to be exposed. It bears the name Coral Zone because of its abundance of fossil corals - so many, in fact, that visitors find it difficult to walk on this layer without stepping on fossils exposed in the bedrock.


  • What Was it Like at the Falls 387 Million Years Ago? The local Devonian geography and climate was much different than today. The abundance of corals and limestone rock indicates this area was a warm, tropical, shallow sea.

    We know it was an ocean and not freshwater because the fossils are similar to animals that live in the ocean today. We are certain it was warm and tropical because limestone only forms under those conditions. And we are sure it was shallow because many corals, including some over 40 inches in diameter can be found upside-down. This indicates that strong currents, like those from a hurricane, tossed heavy corals.


    Fossils at FoTO

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    Optional: To share your experience please take a photo of yourself or your GPSr at the listed coordinate.

    And to demonstrate the educational value of this EC, please send answers to the following four questions:

    1. What is the diameter of the Stromatoporoid here?
    2. Is this a 'Cridaria' or 'Porifera' Phylum?
    3. How many other Stromatoporoid examples can be seen within 15 feet of the waypoint?
    4. Is this a rare or common fossil for this ZONE?

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    Please Do not wait on a reply from me. FOUND IT logs which do not meet requirements will be quietly removed.

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