The Kaskaskia Sequence: Middle Devonian—Upper Mississippian

Abstract

Post-Tippecanoe emergence and concomitant erosion erased much of the older stratigraphic record on the craton, especially in the area of the Transcontinental Arch. Thus, earliest returning Kaskaskian seas spread over a deeply eroded topography and resulted in the deposition of carbonate strata in basinal areas while uplifts were still emergent. By the end of the Onesquethaw, however, much of the eastern half of the craton was submerged; the western half remained a land area until finally being flooded by a major eustatic sea-level rise during the Taghanic Age. During the Late Devonian, the rate of detrital-sediment influx from adjacent orogens increased along the eastern, northern, and western margins of the craton. At the same time, much of the eastern half of the craton experienced the deposition of an extensive sheet of black, pyritic shale. On the western half of the craton, shallow-marine carbonates and mature quartz arenites continued to accumulate. Sea level fell at the end of the Devonian, resulting in an unconformity over much of the craton. Returning seas of the Mississippian Period left widespread carbonate deposits over much of the craton except along the northeastern craton, where detrital sediments from marginal orogens fed a large coastal-plain which repeatedly advanced into and retreated from the epeiric sea, producing repetitive strata. Cratonic stratigraphy of the Kaskaskian Sequence is complicated by a number of basins and uplifts which were active, but not in concert with each other, at the same time that true, eustatic sea-level changes were occurring (Fig. 6–1).