Abstract

A stratigraphic section of 94.17 meters of thin- to medium-bedded, fine- to coarse-grained peloidal and bioclastic limestones measured in Gardner Canyon at Samaria Mountain, southeastern Idaho, is considered to be a Lodgepole Limestone equivalent. The unit was deposited during the widespread Lower Mississippian (late Kinderhookian to early Osagean) marine transgression of western North America. Four informal members referred to as A, B, C and D, based on topographic expression, are recognized.

Based on conodonts recovered three biozones are recognized. In ascending order, they are: the lower Siphonodella crenulata zone, the Siphonodella isosticha-upper Siphonodella crenulata zone and the Gnathodus typicus zone. Excellent conodont faunas were recovered from the Samaria Mountain section and include the following major platform-type conodonts: Gnathodus cuneiformis, G. typicus, Polygnathus communis communis, P. longipostica, P. spicata, P. symmetrica, Pseudopolygnathus cf. Ps. marginata, Ps. multistriata, Ps. triangula triangula, Siphonodella cooperi, S. crenulata, S. isosticha, S. cf. S. isosticha, S. obsoleta and S. quadruplicata.

Two conodont biofacies are recognized in the lower portion of the measured section. The associated occurrence of Spathognathodus, Polygnathus communis communis and Bispathodus stabilis is indicative of a shallow-water Spathognathodus biofacies. The bathymetrically lower Siphonodella biofacies is indicated by the associated occurrence of Siphonodella, Dinodus, Pseudopolygnathus triangula triangula and Elictognathus. The occurrence of the Siphonodella biofacies indicates that the lowermost Lodgepole equivalent was deposited at depths in excess of 50 meters.