Friday, June 11, 2010

Stromatoporoids

In solidarity with my fellow bloggers at Views of the Mahantango and Swimming the Ordovician Seas, I present a post on local stromatoporoids.

Looking at some large pieces of Silurian Period Louisville Limestone that reside in the flower bed, revealed quite a bit of biodiversity.  A chunk of limestone appears to contain the partially eroded remains of a sponge.


Part of the rock contains Halysites coral which dates it to the Silurian Period.


A Silurian brachiopod with crinoid stem pieces with a Halysites coral in the background in another section of the rock.


This tube coral is somewhat of a mystery. It looks like a Devonian coral but since this rock has the Silurian Period index fossil Halysites this must be Louisville Limestone.


Close up of Silurian Period brachiopod shown earlier, that might be a Sphaerirhynchia.


These next two pictures are of a Silurian Period sponge fossil with a lot of layers.  It is almost 20 cm wide.  Fossil found in Jefferson County, Kentucky.




This next type of stromatoporoid is one of my favorites. It is a mounding sponge and the shapes sometimes remind me a scoop of chocolate ice cream.
Mounding Sponge Fossil
Louisville Limestone
Silurian Period - Jefferson County, Kentucky

The Falls of the Ohio State Park Visitor Interpretation Center has a nice display on these ancient sponge creatures.  Paraphrasing it, the Jeffersonville Limestone found at the park has about 30 identified species of calcium carbonate fossils.  The creatures typically are found in sheet, hemispherical or mound-like shapes.  Colonies could range from 30-250 cm in size.  It is thought these sponges existed in warm, clear, shallow seas.  The fossils might be related to modern sclerosponges.

Hindia sphaeroidalis Stromatoporid
Devonian Period
Jeffersonville Limestone - Louisville, Kentucky


Matting Sponge on Heliophyllum Coral
Devonian Period
Beechwood Limestone - Clark County, Indiana

Learn more about stromatoporoids at the Kentucky Geological Survey web page.

4 comments:

Dave said...

Wow, Great pics and diversity Mike. The link to the KGS page is terrific too. In the closeup of the tubular fossils from the Louisville Limestone, Could they be sponges as well? The KGS page mentions that some stromatoporids had finger or tube shapes. Also looking at the closeup photo I see a star shaped object just to the right of the tubes. Is that a spicule from another sponge?

Fossil Detective said...

Dave,

Good points. The tubes might be part of a stromatoporid.

I saw the star shape and thought it might be part of inside crinoid column. On closer examination, it is a six pointed star and crinoids are usually based on 5 points so maybe that is a spicule.

soliussymbiosus said...

At first, I thought that the "tubes" were worm tubes, but as there is no lamellar growth, it appears that they are sponge.

While looking for cystoids in Cherokee Park(Louisville Lm.) last month, a kind of large mud mound grabbed my attention. While checking it out, I noticed a nice stromatoporoid in the face of the outcrop. I took some photos, and will write it up sometime...

My daughter has a photo shoot in the "Ville" later this month, so I will have a few hours to kill. If you want to hit some outcrops, let me know.

Carbon Freeze said...

The six-pointed star on a shieldlike plate is almost certainly from a rare beast, a cystoid! I don't know the Silurian ones well, but I have found similar forms belonging to (I believe) Cheirocystis in the Upper Ordovician of Illinois. They have 5-ridged, 6-ridged, and 7-ridged plates, depending on local plate topology. Photos of isolated Cheirocystis plates can be found here: http://strata.uga.edu/cincy/fauna/rhombifera/Cheirocystis.html