Large Thrombolites
with Eurypterid-bearing Waterlimes Fused to the Upper Surface
Samuel J. Ciurca, Jr., Rochester, New York
Large Thrombolite: The author and a large thrombolite (scanned image of B&W photo used in
New York State Geological Association Fieldtrip Guidebook).
Thrombolites and stromatolites are abundant structures within the Fiddlers Green Formation of the Niagara Peninsula of Ontario,
Canada. Note the light-colored rock (waterlime) fused to the top of this boulder. It is mostly these fine-grained dolostones (waterlimes)
that bear the abundant eurypterid remains collected at this site. The quarry workers place these large boulders along the edges of
active quarrying operations. The Fiddlers Green Formation in this region consists of massive crystalline dolostone of the Victor Member
overlain by the eurypterid-bearing waterlimes of the Ellicott Creek Breccia Member. The Ellicott Creek Breccia bears an upper
stromatolitic bed ('topographic waterlime'), a more finely crystalline and more massive middle section, and a lower waterlime
sequence. A "Black Shale Marker Bed" separates the two members of the Fiddlers Green Formation.
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