As we motor from Mainprize Park to Estevan we cross an undulating till plain that Quaternary geologists call a kettled ground moraine, a landform consisting of a thin mantle of relatively loose silty supraglacial ablation till resting on relatively dense
subglacially deposited clay-rich basal till. These two juxtaposed surfaces--collapsed ablation till and adjoining eroded basal till--can be seen south of us along the Souris Spillway (Fig. 29), where teardrop-shaped 'islands' of ablation till (A) are surrounded by basal till (B). Airphotos also show a lineated surface on basal till, exposed from a few metres of meltwater erosion fromextreme flows down the Souris River valley following the last glacier occupation of this region (Fig. 30).
