Glacigenic Characteristics of the Luoquan Formation and Sediment Gravity Flow Reworking on It

Abstract

Abstract The origin of the Luoquan Formation which occurs along the southern margin of the North China Block has long been argued. Based on recent work, the Formation is considered as a glacial sedimentary sequence partially reworked by sediment gravity flow. The major evidence for the glacigene of Luoquan Formation diamictites is as follows: 1. a striated and polished pavement with various features resulting from glacial abrasion and plucking, such as crescentic gouge, crescentic fracture, streamlined form and glaciated step; 2. unsorted diamictites with striated clast, faceted clast and iron‐shaped stone formed by glaciation; 3. rhythmite with dropstones; 4. a glacial sedimentary sequence bearing advance‐retreat cycles; and 5. wide distribution of the diamictites. Glacial deposits can be distinguished from sediment gravity flow deposits by the features mentioned above. Some characteristics of sediment gravity flow existing in the Luoquan Formation diamictites indicate that glacial deposits might have been partially reworked by sediment gravity flow. Therefore, this paper suggests that the Luoquan Formation diamictite is a result of a glacial event rather than a mud flow deposit. The primary tillites are the principal contribution of the Luoquan Formation, while sediment gravity flow deposits are the redeposited diamictites and should be termed as glacigenic sediment gravity flow deposits.