Correlation of the Retispora lepidophtya assemblage with conodonts near the Devonian-Carboniferous boundary in the Middle Sappington Formation, Montana, USA

RICE, B.J., ; M. DI PASQUO,; P.T. DOUGHTY, ; G.W. GRADER ; P. ISAACSON

Paraná

Simposio; XVII Simposio Argentino de Paleobotánica y Palinología; 2018

ALPP y UADER

Current research on the Sappington FormaVon of Montana is providing new informaVon on theupper and lower range of Re0spora lepidophyta. The Sappington FormaVon consists of 6 units: anupper (unit 6) and lower (unit 1) black shale, and a middle member (units 2?5) composed of a varietyof near-shore marine strata including limestone, silty sandstone, and green shale. The Re0sporalepidophyta-Verrucosisporites ni0dus (LN) palynozone previously confirmed from the Unit 4 greenshale within the Middle Sappington FormaVon at many localiVes in southwestern Montana has nowbeen extended into the overlying Unit 5 lithologies at the Co)onwood-Mill Creek Divide and YankeePete localiVes. At Dry Hollow, palynomorphs of the LN Zone were recorded from Unit 4, and the indexconodont Siphonodella praesulcata was recovered from the base of Unit 5. Siphonodella praesulcatahas been recovered from Unit 5 strata at the Lick Creek and Snake Pit localiVes without associatedpalynomorphs. Uppermost Devonian conodonts have been recovered from other Unit 5 localiVes atBlue Ox, Bombing Range, Horseshoe Canyon West, and Vermont. Therefore, the upper range ofRe0spora lepidophyta is extended through Unit 5 along with the record of S. praesulcata. Thesemicrofossils are absent in the overlying Unit 6 and Lodgepole FormaVon. This confirms thatSappington units 4 and 5 represent the global Uppermost Famennian Hangenberg event insouthwestern Montana.*Project supported by CONICET PIP 0812-2015; NGS (9808-15); PRISEM Geoscience Consulting; University of Idaho.