Breccia sedimentation in periglacial conditions

What is it about?

Two genetic types of breccias occur in a section at study site, namely, debris-flow breccias and fluvial breccias, which represent fluvially controlled depositional processes related to the lithological diversity of frozen and steep river banks. Frozen megaclasts of river-bank material formed obstacle marks in the river channel and underwent thermal erosion, mechanical disintegration and fluvial reworking. The preservation of breccia soft-sediment clasts in fluvial sediments depends on their lithology, water-saturation and ice cementation. Both types of breccia (debris-flow and fluvial) are diagnostic lithofacies of thermo-erosional niching of ground-ice-rich river banks of a periglacial river. Debris-flow breccias and fluvial breccias are lithological indicators of periglacial conditions.

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Why is it important?

The objectives of the present study are (1) to identify the textural and structural characteristics of the breccias at study site; (2) to distinguish different lithological types of breccia in the study site fluvial succession; (3) to determine the origin of the breccias; (4) to reconstruct the role of the periglacial environmental conditions in controlling fluvial transport and deposition; and (5) to evaluate the significance of breccias for reconstructing depositional mechanism and environments.