Stratigraphic Studies in Southwestern Montona and Adjacent Idaho-Lower Tertiary Anaconda conglomerate and Mesoproterozoic Gunsight Formation

摘要

The Anaconda Conglomerate, a new name applied to discontinuous exposures of lower Tertiary course conglomeratic deposits along the eastern margins of the Anaconda and Flint Creek Ranges, is a syntectonic sedimentary rock unit related to the formation of the Anaconda metamorphic core complex. The conglomerate, which ranges from course sedimentary breccia to poorly sorted boulder-to-pebble, well-rounded conglomerate interlayered with lenses of sandstone and siltstone, attains a maximum exposed thickness of 650 feet. Pebble, cobbles, and boulders in the sedimentary breccia are derived solely from the detached upper, unmetamorphosed plate of the core complex. Fluvial and alluvial conglomeratic rocks were derived mainly from the upper plate rocks but locally contain sparse metamorphosed lower plate clasts.