Abstract
Ooids are coated carbonate grains, which exist in shallow water marine and lacustrine environments. There is an ongoing debate about whether the origin of ooids is inorganic or organic. Qinghai Lake is the largest inland lake in China, and ooids are seen on the lake shore. This paper focuses on whether environmental energy has an impact on the growth and size of ooids. Through hydrochemical analysis, thin section observation, and scanning electron microscope, the carbonate coats of beach sands from Qinghai Lake were studied. The research shows that the carbonate-coated grain content from the different shores of the lake present variations. The hydrodynamics and particularly the waves seem to control the distribution of carbonate coats in the lake shore, not the hydrochemical condition. In addition, the integrity and thickness of carbonate coats from the shores with a strong hydrodynamic force are high and thick, respectively. The carbonate coats are often observed on medium-grained sands, and the maximum carbonate-coated grain occurred under the strongest waves, indicating that ooids can be produced only when hydrodynamic force and particle size are well matched. Bacteria or extracellular polymeric substances are not observed within the ooid cortices by scanning electron microscopy. So, bacteria may not be a major factor in the formation and growth of ooids, but hydrodynamic forces appear to play a great role in carbonate grain coat distribution, integrity, thickness, and ooid grain size.
Highlights
Ooids are poorly to well-developed cortices accreted around a nucleus, which are found in both ancient and modern sedimentary environments (Ball, 1967; Harris et al, 1979; Beukes, 1983; Simonson and Jarvis, 1993; Li et al, 2013; Liu et al, 2021)
It shows that the concentrations of most ions in lakes are generally higher than those in rivers, except calcium ion
Formed micritic carbonate minerals, like high-Mg calcite and aragonite, are about 1–15 μm and are found in the upper 10 m water of Qinghai Lake and at the bottom of the lake, while they are not found in the lake shore (LZIG, 1979; Jin et al, 2013)
Summary
Ooids are poorly to well-developed cortices accreted around a nucleus, which are found in both ancient and modern sedimentary environments (Ball, 1967; Harris et al, 1979; Beukes, 1983; Simonson and Jarvis, 1993; Li et al, 2013; Liu et al, 2021). Ooids have been used as paleoclimatic and paleoceanographic proxies for sea level, redox state, water depth, temperature, salinity, and hydrodynamic environment (Kump and Hine, 1986; Opdyke and Wilkinson, 1990; Lu et al, 2020) It has been debated for over a hundred years whether the formation of ooids is inorganic or organic. The size of ooids is determined by a balance between growth by chemical precipitation and erosion by abrasion (Trower et al, 2017; Sipos et al, 2018) This oratory result lacks validation with field data (Diaz and Eberli, 2019). Whether the environmental energy has an impact on the growth of ooids needs more field data
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