Paleoenvironmental evolution and isotopic stratigraphy of the Lower Cambrian in the Tarim Basin: Implications for global paleoenvironmental reconstruction

Abstract

The Ediacaran-Cambrian transition marks a critical period in Earth’s history, characterized by significant shifts in continental configuration, biological evolution, climate, and ocean geochemistry. This study examines the paleoenvironmental evolution of the Lower Cambrian in the Tarim Basin, NW China, through a detailed analysis of carbon (δ¹³C), oxygen (δ¹⁸O), and strontium (⁸⁷Sr/⁸⁶Sr) isotopic stratigraphy, along with rare earth and trace elements. Using samples from the Luntan-1 and Zhonghan-1 wells, we identified substantial isotopic variations, with δ¹³C values ranging from −1.98‰ to −5.18‰ in Luntan-1 and −6.39‰ to −0.63‰ in Zhonghan-1, and ⁸⁷Sr/⁸⁶Sr ratios from 0.708709 to 0.711123 in Luntan-1 and 0.715349 to 0.725398 in Zhonghan-1. The δ¹⁸O values indicate fluctuations in ocean temperatures and regional conditions, while REE and trace elements suggest influence from submarine hydrothermal activities and variable redox conditions during deposition. The δ¹³C excursions correlate with global events such as the Basal Cambrian Carbon Isotope Excursion (BACE) and the Cambrian Explosion, linking isotopic signatures to global carbon cycle disruptions and major biological shifts. The elevated ⁸⁷Sr/⁸⁶Sr ratios reflect regional influences like continental weathering and hydrothermal activity. This study underscores the importance of redox conditions in early Cambrian ecosystem development and offers insights into the interplay of tectonics, climate, and biology during this transformative period, contributing to future paleoclimatology and geochemistry research.