Clay Mineralogy in Relation to Deltaic Sedimentation Patterns of Desmoinesian Cyclothems in Iowa-Missouri

Abstract

AMtraet--Almost four decades of study of Desmoinesian strata of Middle Pennsylvanian age in southcentral Iowa and north-central Missouri have provided the stratigraphic control required to test the variation of clay mineralogy vertically and laterally within various paralic clay and shale facies. Local and regional variations in clay mineralogy within Desmoinesian strata are generally predictable and are in agreement with current knowledge of deltaic deposition. A principal environmental variation within a deltaic system is the change from normal marine salinities in deltaic marine environments to brackish-and fresh-water conditions in the marshy delta plains, in upper interdistributary bays, and within flanking interdeltaic embayments. Changes from marine to nonmarine facies coincide with a decrease in illite, and an increase in kaolin, mixed-layer clays, and in the percentage of expansible layers in the mixed-layer clay. The principal clay detritus entering the area was illite, which underwent various degrees of alteration in different aqueous and subaerial environments within deltaic and interdeltalc areas. Clay-mineral composition alone does not provide unique environmental answers. The distribution of clay-mineral suites within these systems, however, both supports the deltaie-interdeltaic depositional model and can be understood within the context of this framework.

Clay mineral variation in Tertiary sediments from the eastern flank of the Niger Delta

“…In well Uda-1, however, kaolinite decreases in abundance with depth (Table 2). This trend is probably indicative of a transition from nonmarine to marine facies (Brown et al, 1977), which supports the interpretation of a detrital orgin for kaolinite.…”

Clay Sedimentology

“…McMurtry and Fan (1975) demonstrate the elose resemblance between the elay mineralogy of downstream sediments from the Santa Ana river, South California, and of marine sediments deposited on the adjacent shelf in the N ortheastern Pacific Ocean (Fig. An exhaustive study performed by Brown et al (1977) on the Desmoinesian (middle Pennsylvanian) of Iowa-Missouri, USA, shows a elose relationship between elay suites and the chronologie and geographie evolution of a deltaic system. The seaward decrease of smectite could be determined either by a marine ingression in the lower course of the river, or a geochemical evolution into illite in K-rich sea water.…”

Sedimentary Mineralogy of Argillaceous Sediments from Deep Sea Drilling Project Holes 436, 438A, and 439, Japan Trench

“…The spacing of the 10 Å is in the range 10.3 to 10.5 Å. This type has been called "degraded illite" by Brown (1954); in the present sample it is considered to be a mixed-layer mineral of illite and montmorillonite, with a large proportion of illite layers.…”

“…Furthermore, such mixed-layer minerals can occur in shallower to considerably deeper levels, and also in young as well as old sediments, as long as an acidic chemical environment is maintained in sediments after deposition. Brown et al (1977) reported that degraded illite occurs in a mixed-layer state or as dioctahedral vermiculite in deltaic sediments of Middle Pennsylvanian age. Therefore, it is possible that the mixed-layer minerals in the lower section of Hole 439 are detrital.…”