Earth’s youngest banded iron formation implies ferruginous conditions in the Early Cambrian ocean
Li, Z.-Q.; Zhang, L.-C.; Xue, C.-J.; Zheng, M.-T.; Zhu, M.-T.; Robbins, L.J.; Slack, J.F.; Planavsky, N.J.; Konhauser, K.O. (2018). Earth’s youngest banded iron formation implies ferruginous conditions in the Early Cambrian ocean. NPG Scientific Reports 8(1). https://dx.doi.org/10.1038/s41598-018-28187-2
In: Scientific Reports (Nature Publishing Group). Nature Publishing Group: London. ISSN 2045-2322; e-ISSN 2045-2322, more
|   |
| Authors | | Top |
- Li, Z.-Q.
- Zhang, L.-C.
- Xue, C.-J.
|
- Zheng, M.-T.
- Zhu, M.-T.
- Robbins, L.J.
|
- Slack, J.F.
- Planavsky, N.J.
- Konhauser, K.O.
|
| Abstract |
It has been proposed that anoxic and iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks—banded iron formation (BIF)—-deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian iron formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine environments were still characterized by chemical- and redox-stratification, thus supporting the view that—despite a dearth of modern marine analogues—ferruginous conditions continued to locally be a feature of early Phanerozoic seawater. |
|
