Previous workers have delineated deltaic sedimentation from a western source within the South Platte Formation. Outcrop studies in the Morrison-Deer Creek area provide a model for sedimentation within the region of maximum channel development of the South Platte Formation. The total thickness of the South Platte Formation is 170 to 245 ft.

The sequence at the base of the South Platte represents marginal marine deposits and alternate fresh to marine interdistributary bays.

Ten to 20-ft sandstones, approximately 300 ft wide are active or partly active fills of minor distributary channels, or crevasse-splay channels associated with delta-plain sedimentation of a major delta lobe. Major multiple distributary channels formed as the delta

End_Page 914------------------------------

lobes developed and prograded. These lenticular sandstone units, such as the Kassler sandstone are 20-40 ft deep and 1,500-2,800 ft wide. Active channel fill is 50 to 90%. Similar major channels are developed within the upper part and at the top of the South Platte ("J" sandstone interval). One channel at Turkey Creek is oil saturated.

Minor penecontemporaneous faulting within the South Platte Formation produced offsets of 0.5 to 7 ft, with reconstructed strikes of the faults being perpendicular to and parallel with major channel trends. The faults may have been caused by rapid sedimentation and compaction or by minor offsets above basement-fault systems.

End_of_Article - Last_Page 915------------