Exceptionally well-preserved glaciated pavements and a variety of glacigenic sediments comprising the Luoquan Formation in Henan Province, central China, are believed to have formed close to the Cambrian–Precambrian boundary. They may therefore be younger than the better known Sinian tillites representing the Changan and Nantuo ice ages. They perhaps belong to a distinct glacial epoch that is recorded elsewhere in China and in other continents, but for which there is less evidence than for earlier Late Proterozoic glacial periods.
Lithofacies represented in the Luoquan Formation are massive diamictite (signifying deposition as lodgement or melt-out till), bedded diamictite (waterlain till or glaciomarine/glaciolacustrine sediments with dropstones), rhythmites with dropstones (glaciolacustrine or fjord deposits, possibly varves), tabular conglomerates and sandstones (outwash, deltaic or sub-aqueous mass-flow deposits), lens-shaped breccia deposits (sub-aqueous mass-flow deposits) and gravel-sand wedges (frost contraction crack infillings).
The glaciated pavements reveal well-preserved striations, grooves (often intersecting), 'plastically moulded' forms, crescentic gouges and steps. On a regional scale the linear features are of variable orientation, but they indicate a dominant ice flow direction towards the southeast. All this evidence points to upland glaciation with erosion followed by deposition in a terrestrial glacial and glaciolacustrine environment.
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 dïamictites is as follows, I. 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 de.posits are the redeposited diamictites and should be termed as glacigenic sediment gravity flow deposits. on tillites.
Two Carboniferous trilobites, Ditomopyge convexa sp.nov. and Paladin {Paladin) sp.ind., are described from the Nordenskioldbreen Formation in Spitsbergen. The new material is of considerable interest as it extends the known distribution of Carboniferous trilobites and provides further information on palaeobiogeography.
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