[mkl]

The latter. Anything under the glacier would be pulverised into dust (the glaciers even carve out their own valleys). These artefacts must have started up above the ice (on top or down a crack), so the people would have been hunting on the ice or maybe travelling across it.

[nudq]

I don't think we can simply assume that starting position matters to "pulverization" after 1500 years.

Mobility is more likely; the mobile object moves along with the ice, the stationary one gets pulverized.

[mkl]

I think even moving things that started on the ground would probably be crushed by the weight, since they would be at the bottom.