The thickest and best-developed Upper Triassic reef complex in the entire North American Cordillera is at Lime Peak in the southern Yukon. The Lime Peak reef complex is a Dachstein-type, Tethyan reef that lies within Whitehorse Trough stratigraphy of Stikinia, an inboard island-arc terrane of unknown Mesozoic paleogeography. Initial studies of Lime Peak reef faunas revealed characteristics similar to other North American Triassic reefs. Our investigation attempts to better define these paleontological relationships and establish paleobiogeographical associations.
Paleontological samples from five carbonate localities within the Lewes River Group contain corals, sponges, brachiopods, bivalves, disjectoporids, and spongiomorphs. For this study, corals and giant bivalves are identified and compared with fauna from Triassic reef deposits found in the Chulitna (Alaska), Quesnel (southern BC), Wallowa and Western Great Basin (western US), and Antimonio (Mexico) terranes. Preliminary field observations in the Yukon confirm the presence of Wallowaconchid bivalves known previously only from the Wallowa and Antimonio, and systematic analysis of Lime Peak corals identified seven species common in the Quesnel, Wallowa, or Antimonio terranes. These findings demonstrate that reef fossils found in the Whitehorse Trough of southern Yukon constitute an important paleobiogeographical link between Stikinia and other exotic terranes of the Cordillera.
