Geochemistry of cherts from the northern Jiangxi region, South China: implication for paleoenvironment
Geochemistry of cherts from the northern Jiangxi region, South China: implication for paleoenvironment
Published 12 July 2024 Science Leave a CommentHighlights
- Mineral composition, trace and REEs of the PYC and HT cherts were investigated.
- The PYC and HT cherts primarily originated from direct seawater precipitation, with the PYC siliceous rocks exhibiting some weak hydrothermal evidence.
- There are significant shifts in redox conditions in the E-C transition.
Abstract
The extensive bedded cherts deposited during the Ediacaran–Cambrian (E–C) transition period play a crucial role in understanding the geological evolution of this period, yet the origin of these cherts remains disputed. Here, we present new geochemical data for cherts of the Piyuancun (PYC) Formation deposited during the Late Ediacaran and the Hetang (HT) Formation deposited during the Early Cambrian in northern Jiangxi region, Lower Yangtze region, South China. The PYC cherts contain a small amount of monaxons sponge spicules and radiolarian fragments, while the HT cherts lack siliceous organism evidence. Major and trace element analysis, coupled with discriminant diagrams, indicate a possible shift in redox conditions of seawater during the E–C transition in the northern Jiangxi region. The shift suggests a change from weakly–moderately restricted euxinic conditions to strongly restricted euxinic conditions. Furthermore, the location of both cherts are distant from the source area of siliceous organisms. Fossil evidence, as well as the values of Fe/Ti and Fe/(Mn+Ti), Eu anomalies, Post-Archean Australian Shale (PAAS) normalized REE+Y patterns, and various discriminant diagrams, support the conclusion that the PYC and HT cherts originated primarily from direct seawater precipitation, with the PYC cherts exhibiting weak hydrothermal evidence. Upwelling contributes to the formation of HT cherts and organic matter (OM) accumulation. Ocean acidification, triggered by OM degradation and biodegradation processes during the E–C transition period, leads to the extensive silica precipitation and preservation. These results enhance our understanding of the geological processes during the E–C transition.
Xie G.-L., Zhou G.-J., Sun Y.-Y., Hu Y.-R. & Hao W.-D., in press. Geochemistry of cherts from the northern Jiangxi region, South China: implication for paleoenvironment. Journal of Paleogeography. Article (subscription required).
Related
EIN Presswire does not exercise editorial control over third-party content provided, uploaded, published, or distributed by users of EIN Presswire. We are a distributor, not a publisher, of 3rd party content. Such content may contain the views, opinions, statements, offers, and other material of the respective users, suppliers, participants, or authors.
