Wooster’s Fossils of the Week: A stromatoporoid-stromatolite
combination (Upper Silurian of Saaremaa Island, Silurian) Mark
Wilson July 22nd, 2012 There are two common fossil types that
begin with “strom” and look roughly alike to the untrained eye.
One is the stromatoporoid, which is a calcareous sponge, and the
other is the stromatolite, which is a layered structure produced
by photosynthetic bacteria. I hadn’t seen them together until
our expedition to the Silurian of Estonia last summer. Wooster
senior Nick Fedorchuk (’12) collected the specimen above at his
outcrop of limestones and dolomites just above the
Wenlock/Ludlow Boundary along Soeginina Cliff, Saaremaa. (In the
rock sequence Richa Ekka is now studying.) We thought it was
simply a stromatolite until he cut it to show that the base was
a stromatoporoid. “Stroma” is Greek for a bed or layer. Both
stromatolites and stromatoporoids have horizontally laminated
structures. The “lite” in stromatolite means rock, so a
stromatolite is literally a “layere