Figure 4. Generalized composite sedimentary geology of the Ngandong and Jigar “20 meter terrace" denoting stratigraphic positions of Homo erectus fossil material and dated pumices.

At Ngandong, especially in the area in the vicinity of the GMU and Dutch Ingraving 2 excavations, the original erosional basal channel morphology of the 20 meter terrace cut into the Kalibeng is well exposed showing a gradual rise away from the modern Solo River after ascending abruptly from the present river level. Moreover, each of the components of the fluvial association is placed at discrete altimetric positions relative to the water level of the modern river with facies changes at defined distances lateral to the channel (Fig. 5). In our excavations and geotrenches at Ngandong and Jigar, vertebrate remains occur primarily in the basal lag and bar deposits; that is in the lower meter of a 3 to 5 m veneer of fluvial sediments overlying the erosional bench cut into the marine Kalibeng Formation.