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Key information on sedimentary or tectonic events is recorded in deformation structures formed in unlithified and lithified sediments. Disputes about the classification and identification of the two types of deformation have become increasingly relevant. The present study systematically summarizes, based on consolidation states, the genetic mechanisms of deformation. Consolidation conditions may affect deformation patterns and morphology; this can be a clue to distinguish soft-sediment deformation from tectonic deformation. Liquefaction is a typical state of unconsolidated sediment and can create clastic dikes, liquefied breccia, convolute laminae, load cast, and water-escape structures. Synsedimentary faults may be formed in weakly consolidated sediments. Most deformation structures of lithified sediments are large-scale folds and faults, but small-scale structures – especially microfolds – are difficult to distinguish from slump folds. Tectonic folds can be formed in different strata and induced by tectonic events; they differ from slump folds in morphology, distribution, and related structures. We demonstrated that consideration of liquefaction, folds in different strata – matched with the regional geological regime, related deformation structures, and micro-deformation structures – can be clues to the identification of deformation origins. [ABSTRACT FROM AUTHOR]

The Cretaceous, with relatively high atmospheric CO2 concentrations, temperatures, and sea levels, is a typical greenhouse period in the geologic history of the Earth. Recently, gradual changes in the understanding of the Early Cretaceous climate have led to the proposal of small-scale polar glaciers or cooling events in polar regions. However, the cooling events in North China at mid-latitudes are still poorly understood. In this study, 48 wedge structures that are 35-240 cm wide and from 120 cm to more than 300 cm in depth down through the bottom of Lower Cretaceous Luohe Formation conglomerate and penetrated vertically downward into Jurassic Anding Formation mudstone in the Ordos Basin, North China. According to findings, these sand wedges are distinguished by large-scale V shapes, vertical to steeply dipping laminations and pebbles, aeolian abrasion of sand grains, ventifacts, upturned host strata, and other features that are most likely the source of thermal contraction cracking in periglacial desert region. The sand wedges formed when thermal contraction cracks were filled with wind-blown deposits and other material in dry, cold, and windy regions. This record may support the hypothesis that the Ordos Basin, western North China, may have been at a high altitude and was cold during the Early Cretaceous. During the Early Cretaceous, the complex topography and climate of North China allowed the Jehol Fauna to coexist with permafrost and glaciers. [ABSTRACT FROM AUTHOR]

While Ediacaran cap dolostones research is a hot topic, detailed sedimentological analysis of barite‐bearing cap dolostones remains scarce. Here, new data are presented from Xiangerwan in northern Three Gorges, South China, to illustrate the sedimentary characteristics, depositional environment and formation mechanism of the barite‐bearing cap dolostone. In ascending order, the succession is divided into: (i) pebbly dolostone; (ii) dolostone with unusual sedimentary structures (for example, sheet cracks and tepee structures); and (iii) barite‐bearing facies. The gravels of the pebbly dolostone record the slow relative sea‐level rise during post‐glacial transgression, with a local terrestrial influence. Sheet cracks and tepee structures represent water escape structures in the supratidal and upper intertidal zone, and gently wavy stromatolites in barite‐bearing facies are deposits typical of the upper intertidal zone. In addition, primary radial length‐slow dolomite cements were originally precipitated at the seafloor. In general, the cap dolostone was formed in a shallow‐water ramp environment. The form and sedimentary characteristics of barites indicate a primary (syngenetic) origin and help to divide the barites into bladed (Type I) and needle‐like (Type II) variants. With the ongoing melting of the Marinoan glacier and water density stratification, the cap dolostone was gradually precipitated, accompanied by exotic gravels input. The stratification persisted, and special sedimentary structures were widely developed. Phosphorus and barium ions were brought up from the deep basin by upwelling, indicated by the flourishing stromatolites and barite fan deposition. Above the sediment–water interface, the Type I barite first grew upward from substrates, then the Type II barite could grow either in the reverse 'V‐shape' cavities between and within the Type I barite clusters, forming rhythm layers with bedded dolomite, or scattered in the laminae of stromatolites or surrounding dolomite. Finally, the formation of barite fans indicates the end of cap dolostone deposition and deeper water sedimentation. [ABSTRACT FROM AUTHOR]

Sedimentary manganese carbonates, especially the black shale type, are generally considered to have been deposited in a deepwater, restricted and reductive sedimentary environment. Deposits of manganese carbonate are well developed in the black shale near the top of the Ediacaran Doushantuo Formation in the Chengkou area of the northern Yangtze Craton. The black shale host rock and cerium anomaly of manganese carbonates is thought to be vital evidence of the sedimentary environment of manganese carbonates, but there is a lack of systematic sedimentologi-cal evidence, with the result that the sedimentary environment of the manganese carbonates in the Chengkou area remains controversial. In this study, the sedimentary textures and structures of the manganese carbonates in this area are described in detail, based on field and core observations and thin section microscopy. This work included a detailed sedimentological study of the Chengkou manganese deposit, and a model of the sedimentary environment was constructed. It was found that the Chengkou manganese carbonate deposit is mainly layered, and contains well-developed stromatolites, oncolites, thrombolites and dendrolites. The frequent bonding growth of the oncolites indicates that the Chengkou manganese deposits are typical microbialites with several kinds of microstructure : clotted, spherical, filamentous, tubular, fibrous and radial. The sedimentary records from drill cores show alternate deposits ofrho-dochrosite and collophanite. In the rhodochrosite, all types of microbialite are deposited cyclically. Normal grain bedding and intraclast layers indicative of stronger hydrodynamic force are rarely recorded. The collophanites are characterized by intraclast depositions in a strong hydrodynamic environment and often overlie the rhodochrosites, evidence of the cyclic sedimentary nature of the series of manganese-bearing rock to phosphorus-bearing rock and indicates gradually shallowing sedimentary water at the end of the Doushantuo Formation in the Chengkou area. When considered together with the sedimentary characteristics of the Doushantuo Formation in adjacent areas, Member I of the formation in the Chengkou area evidently developed a barrier-free coastal sedimentary system without a dolomite cap. Member II was a carbonate ramp sedimentary system with mixed siliciclastic sediments. The manganese carbonate mi-crobialites mainly developed in the barrier and bonding reef sedimentary environment in the lower part of the inner carbonate ramp. It is notable that the development of barriers and bonding reefs at the end of the Doushantuo Formation was an important dynamic factor in the evolution of the sedimentary basin in the study area, promoting the evolving regional sedimentary system from carbonate ramp to carbonate platform. [ABSTRACT FROM AUTHOR]