Origin and paleoenvironmental reconstruction of phosphorus–bearing sandstones of the Cambrian Xinji Formation, southwestern margin of Ordos Basin, China

Increasing exploration interest in oil and gas hosted by early Cambrian strata has focused research effort on early Cambrian sandstones. The origin of phosphorus and the paleoenvironment of phosphorus-bearing sandstones from the Xinji Formation are discussed in this paper. X-ray diffraction, optical microscopy, grain size analysis, total organic carbon (TOC), and the concentrations of major, trace, and rare earth elements (REEs) are analyzed in this work. The sandstones are mostly sublitharenite, with calcareous cement. The quartz content of the sandstone samples is 39.8–73.9%, with illite (7.9–27.6%) and calcite (4.5–29%). The mineral particles of sandstone samples are mainly well sorted with fine particle size, suggesting strong paleohydrodynamic force. The value of SiO2 is 37.69–78.19%, followed by Al2O3 (6.11–13.67%). Compared with UCC, the boron of sandstone samples is relatively enriched, while Sc, Sr, and Ba are relatively depleted. The ΣREE content is 124.46–323.99 ppm. Phosphorus is biogenic origin and enriched by upwelling current. The source of the Xinji Formation sandstone samples was mainly a mixture of sedimentary rock, granite and alkali basalt, with the provenance of terrestrial clastic materials. The sandstone deposited under oxic condition and warm and humid paleoclimate with saline to brackish feature in the passive continental margin. Phosphorus occurred in sandstones is sensitive to paleoclimate that can be used as an indicator to judged paleoclimate, and is more enriched in warm and humid weather.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author