Several types of MDGS were observed (Fig. 3 (b)-(e)). First, the geochemical (Fig. 4) and textural variability [10,11] between the MDGS and the matrix indicate different sources and, at least for the studied cases, confirm a separate origin from their hosting matrix. Second, their widespread TOC, CaCO3, and opal % contents (Figs 4a-d) suggests that they can retain different sedimentary environments.

The possibility that such grains can maintain the geochemical identity after their incorporation into over compacted and soft diamictons is in agreement with former observation of ice rafted material, i.e.: till pellets, incorporated in bottom marine sediment from their sources [18].

Figure 5. SEM microphotographs of bulk silt-sized detritus from Sample GS-Y 95-97 cm.

At this point, a general model is needed; one that takes into account the widespread presence (geographic, environmental, and stratigraphic) and composition of such grains and draws relationship with their potential source areas (PSA).

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