Stratigraphic Evidence for a Major Unconformity Within the Ediacaran System
Earth and planetary science letters(2024)
摘要
The subdivision and correlation of the Ediacaran System within the geologic timescale is desirable, but challenging. The Ediacaran Doushantuo Formation (∼635–550 Ma) in South China is one of the most important sedimentary successions for studying the co-evolution of Earth's environment and life at that time. However, its stratigraphic continuity is confusing and deserves scrutiny. In this study we evaluate stratigraphic continuity of the Doushantuo Formation from a key section deposited in an alleged deep-water “basinal” setting. Using litho-, chemo-, and chrono-stratigraphic data anchored by two new CA-ID-TIMS U-Pb zircon dates of 629.7 Ma and 556.4 Ma from two tuff layers, we reveal that this section contains a cryptic subaerial unconformity with a >44 Myr gap in the sedimentary record. The unconformity occurs immediately prior to the EN3/Shuram δ13C excursion in the mid-Ediacaran, and can be traced regionally and may be correlative to other mid-Ediacaran unconformities globally. We suggest that its development is related to glacio-eustatic sea-level changes during the mid-Ediacaran. This finding provides a critical stratigraphic boundary for future subdivision and correlation of the Ediacaran System in South China, and we advocate for a reconsideration of the completeness of the Ediacaran stratigraphic record in this area.
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关键词
Ediacaran,Unconformity,Shuram delta C-13 excursion,Geochronology
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