Glacial sediments and erosional pavements near the Cambrian—Precambrian boundary in western Henan Province, China

Abstract

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.

Chapter 23 Glacial deposits of the Bokson Group, East Sayan Mountains, Buryatian Republic, Russian Federation

“…can be correlated to the negative anomaly of d 13 C at the base of the Nemakit-Daldyn stage (Pokrovskiy & Missarzhevskiy 1993). On an interregional scale, it is possible to correlate the Bokson diamictites to the Baykonur Glacial Horizon in Kazakhstan and Kyrgyzstan (Chumakov 1981(Chumakov , 2011 and to the Hankalchough and Luoguan formations of northern China (Baode et al 1986), based on their similar stratigraphic position.…”

Basal Melt‐out Structure in the Luoquan Formation and Its Significance1

“…In the column there occurs distinct ice pavement between the Luoquan Formation and the underlying quartzose sandstone cPt3s)of the Sanjiaotang Formation. Guan Baode et al (1986)and Wu Ruitang et al (1988) have discussed it in detail. According to various kinds of fracture structure and abrasive structure on the ice pavement it is inferred that the glacier in the area flowed from south to north at that time.…”

“…On the basis of previous work, Wang Yuelun et al (1980), Guan Baode et al (1986) and Wu Ruitang et al (1988 compared their depositional features with those of some recent tills in the Arc-Distributed widely on the southern margin of the North China platform, the Luoquan Formation is composed mainly of massive diamictite and bedded diamictite with small amounts of varved clay and lenticular conglomerate and sandstone, of which massive diamictite usually accounts for more than 2/3 of the total thickness of the section. Therefore, the understanding ol the processes of deposition of massive diamictite is one of the keys to the analysis of the depositional environment of the Luoquan Formation.…”

“…Since the middle and late eighties, mo-re intensive studies have been made on the origin of diamictites of the Late Precambrian Luoquan Formation of China. On the basis of previous work, Wang Yuelun et al (1980), Guan Baode et al (1986) and Wu Ruitang et al (1988Ruitang et al ( , 1991 compared their depositional features with those of some recent tills in the Arctic region (e.g. Alaska and Spitsbergen) and held that both are analogous.…”

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

“…The basic sedimentary types and their environmental interpretations are listed in Table 1. 1. Lodgement till and undermelt till at the bottom The massive diamictites (Dm) deposited directly on glacial pavement are generally considered as lodgement tillites (Guan et al 1986, Gravenor et al 1984, Boulton and Deynoux, 1981. The characteristics of the massive diamictites are given in Table 1.…”