Welcome to my Earthcache!
Local Geology
The geology around Chelsea, Michigan, features a thick blanket (up to 450 feet) of glacial drift from the Ice Age overlying ancient sedimentary bedrock. This dynamic glacial past created the area's rolling topography and left behind a treasure trove of Ice Age fossils, unique rockhounding sites, and vital groundwater aquifers.
Underneath the surface sand, gravel, and clay, Chelsea sits on the edge of the vast Michigan Basin. The bedrock consists of Mississippian and Devonian sedimentary rocks. The western part of Washtenaw County is primarily underlain by the Marshall Formation, a highly reliable sandstone bedrock aquifer.
While the bedrock is buried deep beneath glacial till, local limestone and shales from these ancient tropical sea environments yield fossils like horn corals and brachiopods.
Type of Rock
Limestone - A chemical or biological rock composed primarily of calcium carbonate (CaCO₃). It often forms in clear, shallow ocean waters from the skeletal fragments of marine organisms, and it breaks into hard, blocky pieces.
Shale - A clastic rock formed from compressed mud, clay, and silt. It is known for its "fissile" texture—meaning it easily splits into thin, flat layers.
Fossil identification
Questions:
To log this cache, attach your photo(s) with your log entry. Also, please message me, the answers to the following questions:
1. Do you believe this rock to be Limestone or Shale? Why?
2. Is this rock type native to this region?
3. Find a fossil and use the chart above to identify it. What fossil did you find?
4. Post a picture of yourself or personal item at ground zero(REQUIRED)
Thanks for visiting my Earthcache.
https://www.thefossilforum.com/topic/138922-hunting-the-silica-shale-in-michigan/
https://umorf.ummp.lsa.umich.edu/wp/mis-backyard-fossils/
https://kgs.uky.edu/kgsmap/helpfiles/litho_help.shtm