Comparison of rudite-rich facies in Tertiary intermontane basins, Montana and Wyoming

Conference · Wed Mar 01 00:00:00 EST 1989 · AAPG Bull.; (United States)

OSTI ID:5794916

Weaver, J N; Flores, R M; M'Gonigle, J W

Rudite-rich deposits are characteristic near the margins of Tertiary intermontane coal basins in the Medicine Lodge basin, Montana, and Powder River basin, Wyoming, The rudites are graded, crudely imbricated, framework to matrix-supported, pebble to boulder-size deposits that have basal erosional contacts. In the Medicine Lodge basin, the rudite-rich facies includes basally scoured conglomeratic sandstone, siltstone, fish scale-bearing mudstone, biohermal carbonate, and coaly carbonaceous shale. Matrix-supported rudites occur in the lower part of coarsening-upward sequences. Framework-supported rudites and offset conglomeratic sandstone, which are common in the upper part of these sequences, are interbedded with coal-bearing units along with fish scale-bearing mudstones, gradational to mixed siliciclastics, and biohermal carbonates. In the Powder River basin, the rudite-rich facies consists of fining-upward sequences. Framework-supported rudites are common in the lower part of these sequences, and conglomeratic sandstones are common in the upper part; matrix-supported rudites are absent. Finer grained, freshwater mollusk-bearing, and coaly sediments bound these coarse facies.

• Research Organization: Geological Survey, Denver, CO (USA)
• OSTI ID: 5794916
• Report Number(s): CONF-890404-
• Journal Information: AAPG Bull.; (United States), Vol. 73:3; Conference: AAPG annual convention with DPA/EMD Divisions and SEPM, San Antonio, TX, USA, 23-26 Apr 1989
• Country of Publication: United States
• Language: English

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