Late Mississippian to Early Pennsylvanian conodont biofacies in central Montana

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Later Mississippian (upper Chesterian) to Early Pennsylvanian (lower Morrowan) conodont faunas were recovered from limestones and calcareous mudstones of the Alaska Bench Formation in central Montana. These faunas define four biofacies, each recognized by the dominance of a particular single element genus for which the biofacies is named. The Adetognathus biofacies represents lagoonal, tidal flat, and barrier sediments. The Declinognathodus/Idiognathoides biofacies represents a deposition in shallow, open marine, offshore conditions. The Rhachistognathus biofacies represents a transitional environment between restricted, intertidal environments and normal marine, offshore environments. The Neognathodus biofacies represents shallow-water bay or lagoonal deposition, where environmental controls have effectively excluded other conodont faunas. The investigation of conodont biofacies provides improved biostratigraphic and paleoenvironmental uses of conodonts.