LOESS STRATIGRAPHY OF THE LOWER MISSISSIPPI VALLEY

Loesses of the Lower Mississippi Valley (LMV) are world-famous. Sir Ch arles Lyell (1847), Hilgard (1860), Stafford (1869), Call (1891) and M abry (1898), thought the LMV loess was a single water deposit although ''double submergence'' was noted by Call (1891) and Salisbury (1891). Shimek (1902) and Emerson (1918) recognized LMV loess as a wind depos it which came from the valley. Although wind-deposited loess gained wi de acceptance, Russell (1944a) published his controversial theory of ' 'loessification'' which entailed weathering of backswamp deposits, dow nslope movement and recharge by carbonates to form loess. Wascher et a l. (1947) identified three LMV loesses, mapped distributions and stron gly supported eolian deposition. Leighton and Willman (1950), identifi ed four loesses and supported eolian deposition as did Krinitzsky and Turnbull (1967) and Snowden and Priddy (1968), but Krinitzsky and Turn bull questioned the deepest loess. Daniels and Young (1968) and Touche t and Daniels (1970) studied the distribution of loesses in south-cent ral Louisiana. West et al. (1980) and Rutledge et al. (1985) studied t he source areas and wind directions which deposited the loesses on and adjoining Crowley's Ridge. B.J. Miller and co-workers (Miller et al., 1985, 1986, Miller and Alford, 1985) proposed that the Loveland Silt was Early Wisconsin rather than Illinoian age and advanced the name Si cily Island loess. They proposed the underlying loess was Illinoian an d advanced the name Crowley's Ridge. We termed the loesses, from the s urface downward, Peoria Loess, Roxana Silt, Loveland/Sicily Island loe ss, Crowley's Ridge Loess and Marianna loess. Researchers agree that t he surfical Peoria Loess is Late Wisconsin and the Roxana Silt is Late to Middle Wisconsin, but little agreement exists on the age of the ol der loesses. Rye and Johnson (1988) proposed Early Wisconsin for the L oveland/Sicily Island. McKay and Follmer (1985) suggested this loess c orrelated with a loess under Illinoian till. Clark et al. (1989) agree d on Crowley's Ridge, but suggested the Loveland/Sicily Island loess o n Sicily Island was older. Mirecki and Miller (1994) and Millard and M aat (1994) suggested an Illinoian age for the Loveland/Sicily Island l oess. Miller and co-workers suggested, as did Rye and Johnson (1988), an Illinoian age for the Crowley's Ridge loess. McKay and Follmer (198 5) suggested it correlated with a loess under ''Kansan'' till. Stratig raphy indicates the Marianna is the older of the five loesses. Researc hers identified loess on both the east and west side of the LMV as wel l as on higher terraces within the valley. Many researchers assumed un altered loesses were commonly yellowish brown, and silts or silt loams (West et al., 1980; Miller et al., 1986). The nonclay fraction of unw eathered LMV loesses was dominated by quartz followed sby carbonates, mainly dolomites, followed by feldspars, and micas. Clays were dominat ed by montmorillonite followed by micaceous minerals, kaolinite and ve rmiculite (Miller et al., 1986). Soils in the Crowley's Ridge loess ar e most developed, followed by the soils in the Loveland/Sicily island which are more developed than the modern soils in the Peoria Loess. So ils in the Roxana and Marianna loesses are least developed and the Far mdale Soil of the Roxana is the weaker of the two (Miller et al., 1986 ). There is certainly overlapping range in the degree of soil developm ent in the various loesses.