Preservation of Cyanobacterial UVR‐Shielding Pigment Scytonemin in Carbonate Ooids Formed in Pleistocene Salt Lakes in the Qaidam Basin, Tibetan Plateau

Abstract

AbstractThe formation of ooids and their use as a proxy to trace biogeochemical cycles have long been controversial. Here, we examined three beds of evaporite‐cemented ooids in the Qaidam Basin, including a layer of dolomitic ooids formed at 293 ± 4 kyr and cemented by gypsum at 266 ± 3 kyr, a layer of aragonitic ooids formed at 163 ± 1 kyr and cemented by halite at 111 ± 0.8 kyr, and another layer of aragonitic ooids formed at 38 ± 0.5 kyr and cemented by gypsum at 23 ± 0.3 kyr. The Raman spectra of organic extracts from these ooids indicate ubiquitous preservation of scytonemin, a unique cyanobacterial ultraviolet radiation (UVR)‐shielding pigment. This discovery suggests that ooids are capable of preserving biomarker from their depositional environment. Consequently, ooid may be used as a proxy for tracing biogeochemical processes and potentially applied to the search for life on Mars.