DSC07978

136 L Sudzułka+ska

Value* of the abraiion iodei show sligfat changes m che long profile. Hus i$ ipcciatty true of the maiimum Wo vaiues, whereas the vamhłe minimum Wo vaJuc* suggeni that morphosekciion of grains took płace. The less well abraded gram* were transported a greater disiance.

Drogomyii - Therc occur overbank deposits. Natura! levee deposits dating from the younger Subatlamic period pass into floodbasin deposits which have been recognized in a section across the floodplain (Fig. 11).

The levee deposit overlying the point bar deposits consists of sandy dusts which pasa upward into dusty sands. This deposit indudes bands of very fine iand, especially in its topmost part. The upward increase in grain sizes i$ refiected in the Mz values which vary from 5.9 to 4.1 0 (Fig. 12). Sorting also improves upward from 2.2 to 1.9. The Iow Wo index (540) is typical of angular quartz grains. The łevee deposit shows a less well defined parallel lamination The floodbasin deposits rest immediately on an erosional gravel suiface (Fig. 11). Deposits increase in thickness up to 7 m toward the basin margins. In proflles which are located in the western part of the floodplain the flning upward of the floodbasin deposits is noted. They are very fine (Mz = 6.0-7.0 0) and very poorly sorted (Tab. 5). Particles become finer toward the basin margins as indicated by both minimum and maximum Mz values. The decreasing ranges of the extreme Mz and o_x values show that the deposiu become morę homogeneous. The floodbasin deposits are finer and less well sorted than those of the adjacent natural levees.

Table 5. Minimum and nuuimum values of grain size indices of ovcrbank deposits at Drogomyśl site. A — levee deposits; 1—7 — floodbasin deposits

Proflles	Mz [0]		Skf	Kg
A	4.1-5.9	1.9-2.3	0.3-0.6	1.0-1.9
7	5.6—6.3	16-18	0.2—0.5	1.0-1.9
6	4.5—7.0	14-4.0	0.1-0.6	1.0-13
5	4.8-6.4	10-3.0	0.1-0.6	1.0-1.5
4	4.5-8.4	14-4.3	0.2—0.5	0.9-1.5
2	4.7-7.2	14-3.9	0.3—0.6	0.9-1.7
1	5.8—7.4	13-4.2	0.3-0.6	1.2-13

Another example of overbank deposits are braided river deposits dating from the Younger Pleniglacial. These are forming the top of the alluvial fans built up by the braided Vistula (Chybie site) and by the Biała (Kaniów site). Such deposits are composed of sandy dusty and clayey dusty strata. At the top there occur less well developed sandy and clayey bands. The characteristic brown colour of the deposits is due to the high organie matter content. For the most part, deposits are fine (Mz = 5.0—6.2 0), and they become coarser upward. Sorting is poor at the base and very poor at the top (Fig. 13). Quartz grains are less well abraded.

Channel fili deposits belong to two sub-facies. The first one is represented by abandoned channel fills due to the slow sedimentation from suspension and to the abundant growth of water plants. Organie deposits tend to dominate. They comprise both peaty laminae and strata, as well as thin dusty clayey