Title: General Lithofacies Relationship of St. Peter Sandstone and Simpson Group
Abstract: Stratigraphic relationships and area of distribution of the St. Peter sandstone and the Simpson group indicate that the two constitute an extensive and continuous sheet of clastic rocks interlayered with equally extensive bodies of carbonate strata. Certain bulk physical properties of the clastic sheet, such as sand-shale ratio, number of sands, and thickness, increase systematically into southern Oklahoma, the thickest part of the Simpson basin. Except for local thickening in Illinois, the St. Peter shows no regular changes in percentage of shale, number of sandstone beds, or grain size, but it is strikingly uniform. In southern Indiana and western Kentucky, the sandstone sheet grades abruptly into carbonates without intervening shales; whereas, in the Simpson basin abun ant shales characterize the section. Here intertonguing of shale and sandstone is noteworthy. Particle-size distribution of sandstone of the Simpson parallels that of the St. Peter and suggests genetic relationship of the source material. Distribution and position of the shale and carbonates indicate a northern source of clay and sand debris. Carbonates of the Dutchtown and Joachim which overlie the St. Peter in an area of southern Illinois, Missouri, and Indiana indicate that sand deposition migrated northward as these carbonates accumulated. A generally northward transgression of shorelines is interpreted. The St. Peter is theorized to be a continuous series of coalescent shoreline sands migrating over a stable shelf. Simpson deposition represents transgression and local regression of shorelines spread outward from the major part of the subsiding basin.
Publication Year: 1955
Publication Date: 1955-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 35
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