Abstract
Four major deposystems were mapped in the Cypress Sandstone using SP (spontaneous potential) and resistivity log character in a statewide cross-section grid. Illinois was a shallow, gently sloping embayment subject to periodic influx of sediment and changes in sea level during Late Mississippian (Chesterian) time. Cypress log character varies predictably from the eastern margin of Illinois to the western erosional limit. Deposystem interpretations based on log character have identified (1) a deltaic zone characterized by thin sandstones interbedded with shale and siltstone in easternmost central Illinois, (2) an offshore marine zone characterized by sand bodies 50-150 ft thick, displaying blocky SP in a 20-mi wide band in east-central Illinois, (3) an offshore marine zone characterized by sandstone bodies 15-40 ft thick in central Illinois, and (4) an offshore marine zone characterized by predominantly shale log character in west-central Illinois. Presence of the shale coincident with the DuQuoin monocline suggests that Cypress deposition was influenced by structural expression of the monocline.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
