| A new Silurian (lower Ludlow) biota from the Eramosa Dolostone in southern Bruce Peninsula provides an unusual window into the diverse, but normally poorly preserved biota in a very shallow water marine environment. The flora consists of both dasycladalean and non-dasycladalean thallophytic algae, an important but rarely preserved component of any marine paleoecosystem. The fauna contains phyllocarid crustaceans, and several soft-bodied and lightly sclerotized arthropods and worms similar to the older Brandon Bridge (Llandovery) fauna of Wisconsin, including an arthropod of uncertain affinity with a pair of large grasping anterior appendages. Also present within this biota are brachiopods, cephalopods, gastropods, trilobites, chelicerates, sponges, and conularids. In contrast to the Wisconsin fauna, there is also a significant echinoderm fauna, including ophiuroids and lepidocentrid echinoids (perhaps the oldest echinoids yet found in Canada).; The biota occurs within very thinly laminated, light to very dark brown, petroliferous dolostones downslope from a slight paleo-topographic high produced by patch reefs within the underlying Amabel Formation. Calcitic faunal elements are very poorly preserved and normally decalcified, though the echinoderm and trilobite material is articulated. Chitinous organisms are preserved as thin films, sometimes secondarily mineralized. Many of the organisms are represented by carcasses, the articulated phyllocarids having intact jaw elements. The fauna is mostly autochthonous, as the very large number of echinoids are all preserved in life position with oral surfaces oriented downward. Also examined in this study is the regional geology, stratigraphy and sedimentology of the Eramosa as it relates to the biota, using a variety of techniques including the use of Ground Penetrating Radar to image the subsurface. |
