Trace Element Geochemistry and Sedimentary Environment Implications of the Lower Cambrian Qiongzhusi Formation in Qujing, Yunnan Province

Abstract

This study focuses on the black rock sequence of the Lower Cambrian Qiongzhusi Formation in the Qujing area of Yunnan Province. Using elemental geochemical methods, we investigate the characteristics of water salinity, climate, and redox conditions during the deposition of the Qiongzhusi Formation to reconstruct the paleoenvironmental conditions of the Lower Cambrian Qiongzhusi Formation in the Qujing area. The results indicate that Li concentrations ranged from 1.5 to 56.3 μg/g, and Sr/Ba ratios ranged from 0.09 to 0.56, indicating that the Qiongzhusi Formation in the study area was deposited in a predominantly freshwater environment; V/(V+Ni) values ranged from 0.66 to 0.91 (mean 0.79), U/Th values ranged from 0.75 to 15.45 (mean 4.33), and δU values ranged from 1.38 to 1.96 (mean 1.73), collectively indicating that the Qiongzhusi Formation deposition period was generally characterized by an anoxic-reducing environment; The paleoclimate index C ranges from 1.09 to 4.48, and the Sr/Cu ratio ranges from 1.16 to 9.30, indicating that the Qiongzhusi Formation was deposited under a warm and humid climate; the Babio value ranges from 200 to 1309.98, and the P/Ti ratio ranges from 1.59 to 62.5, indicating that the Qiongzhusi Formation deposits exhibited a high level of productivity overall; The concentrations of Ba, Ni, Co, and other elements, as well as the Mn/Fe ratio (average of 0.005) and Rb/Zr ratio (average of 2.27), indicate that the water depth during the Qiongzhusi Formation deposition period was generally shallow; the Sr concentration indicates that the average paleowater temperature of the Qiongzhusi Formation was 30.38°C, suggesting a relatively high water temperature in the depositional environment.