The 'Sawdust Sand'; an Eocene sediment of floccule origin

Abstract

The Sawdust Sand of the Eocene-Wilcox in western Tennessee is an unconsolidated sediment composed largely of aggregate grains. The aggregate grains and cross-stratification give the Sawdust Sand the appearance of medium to coarse, well-sorted sands. When disaggregated the sands become poorly sorted, silty and clayey, very fine sands, indicating a break-down of the aggregate particles. Two general types of aggregates are present: those composed chiefly of clay mineral particles in a three dimensional array of face to face (FF), edge to edge (EE) and edge to face (EF) configurations; and those where silt and fine sand-sized quartz and feldspar are included in the clay mineral particle network. The aggregates have clay mineral compositions of kaolinite-montmorillonite or kaolinite and the two mineralogical suites are stratigraphically segregated. The fabrics and textures of the aggregate grains, their mineralogical associations and their primary stratification lead to the conclusion that the aggregate grains in the Sawdust Sand are relict floccules.