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Stromatoporoids have a "plastic" morphology which makes them sensitive indicators of paleoenvironments but which presents problems for stratigraphic correlation. A zone at adjacent outcrops may have different genera and species. Nevertheless, stromatoporoids can be useful to determine the time framework of strata.
An Amphipora Zone has been recognized for years in the Mid-Continent North American Middle Devonian. Range charts also have been made previously, and at least one work has established several stromatoporoid zone fossils, but authors have noted difficulties of correlation.
A small fauna was collected from two adjacent localities in the Niagara Peninsula of Ontario, near the contact of the Onondaga Limestone with the underlying Bois Blanc Formation. The fauna consists of seven species belonging to three genera (22 specimens), not a statistically significant number. However, the stratigraphic ranges of previously reported occurrences of the species accurately determine the correct age when equated to the continental European standard section. The plotted ranges are based on systematic works in which descriptions and illustrations can give some idea of the validity of species identifications. Stratigraphic works with species lists which cannot be documented were not considered.
The longest ranging species is Stromatoporella granulata from the lower middle Siegenian well into the Frasnian. Other previously described species in the fauna are confined to the Eifelian, especially to the lower Eifelian. Three species (representing 77% of the specimens collected)--S. granulata, S. selwyni, and S. tuberculatum--were all previously reported many years ago from the "Corniferous" Limestone at Port Colborne by H. A. Nicholson. S. selwyni has also been reported from the basal Jeffersonville Limestone of Indiana. Stictostroma excellens and Stromatoporella perannulata are described from the area for the first time. Both have been described previously from the Jeffersonville Limestone; Stictostroma excellens from Indiana and Stromatoporella perannulata from Kentucky. One s ecimen is compared with Stromatoporella composita Yavorsky. Although Yavorsky's species is not conspecific, it is morphologically similar enough to be of stratigraphic significance. Yavorsky's species comes from the lower Eifelian beds on the margin of the Kuznetz basin.
A question has been raised as to whether Nicholson's fauna reported from nearby Port Colborne came from Onondaga or Bois Blanc beds. Despite of the relatively small number of specimens, one can say that due to strong faunal similarities, Nicholson's material came from the same zone as the material herein reported and further, that both faunas are probably lower Eifelian in age, equivalent to the Edgecliff Member of the Onondaga Formation, which is in agreement with previous correlations based especially on corals and brachiopods.
Although stromatoporoid faunas may differ significantly from outcrop to outcrop at the same stratigraphic zone, and although stromatoporoid faunas are frequently represented in collections by small numbers of specimens, they can give a good indication of their position in geologic time when the identified taxons are compared with the world literature.
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