Monday, March 25, 2019

Geology of the National Parks Through Pictures - DeSoto National Memorial

My next post about the Geology of the National Parks Through Pictures  from a recent trip to visit my mother in Florida. I managed to convince the family to hit up the nearby national park. 

You can find more Geology of the National Parks Through Pictures as well as my Geological State Symbols Across America series at my website


DeSoto National Memorial

 The obligatory entrance sign with my Gummy Bear.

 The park sits at the mouth of Tampa Bay along the south shore of the Manatee River. This is an estuary environment where the salt water from the Gulf of Mexico mixes with the fresh water from the Manatee River.

The ecological environments within this small park range from beach front dune to mangrove swamp.

 But with many archeological parks, one of the primary geological aspects are the building stones used to make the dwellings. Here we have the remains of the "Tabby House". Tabby is a building stone made from the mixture of oyster shells, lime, sand, and water creating a hardened stone brick over about three days. The bricks were then coated in a plaster of lime, sand, and water.

 A view over DeSoto Point overlooking the Manatee River.

 Here is a shell midden, which is essentially a garbage pile of discarded remains of mollusks, shellfish, and bones. You can see within this midden the rather large gastropod (snail) shells.

 Another geological aspect commen in many parks are the building stones used in monuments. Here is a view of the Holy Eucharist Monument. The base of the monument is limestone cut in Mankato, Minnesota. The limestone in use is the Ordovician age Kasota limestone, which is actually a dolomitic limestone, part of the Oneota dolomitic strata. The color of the stone is known as a "buff color" which is that slightly reddish-brown color due to the 1% iron oxide composition providing a rust staining to the stone. Although the Kasota does not have many fossils, it does have a significant number of traces fossils running through the rock, however I am not certain the type of trace fossils preserved.

The carving stone came from Madrid, unfortunately I cannot find any information about the type of stone used, nor did I take any better pictures or get a closer look at the stone to determine for myself.

 Taking a stroll though the dense beach forest.

 The Desoto Trail marker, using "granite" from an unknown location.

A closer view of the "granite", but based on this picture it may more accurately be described as a diorite, however I don't recall what type of rock it was from my visit.


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