| The Sappington Formation, divided into six units by Sandberg et al (1972), contains the Devonian-Carboniferous boundary but has conflicting biostratigraphic ages. Previous studies place the D-C boundary at the base of unit 2, above the base of unit 5, and between units 4 and 6. The Sappington Formation contains three dark shale units, making it ideal for palynostratigraphy. Five sections were systematically sampled, processed according to standard organic microfossil extraction techniques modified by di Pasquo, and examined, yielding palynomorphs in both the Logan Gulch and Moose Creek localities. Based on palynology and conodont biostratigraphy, the D-C boundary is at the base of unit 6. Age diagnostic taxa found in unit 4 are Retispora lepidophyta, Verrucosisporites nitidus, Vallatisporites hystricosus, and Grandispora saurota, indicating a Strunian LN zone for unit 4. Units 1 and 4 were probably deposited in lagoons or bays, and unit 6 was probably deposited offshore. |
