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An 17O record of late Neoproterozoic glaciation in the Kimberley region, Western Australia
Huiming Bao;  Zhong-Qiang Chen;  Chuanming Zhou
Source PublicationPrecambrian Research

We have recently reported non-mass-dependent 17O depletion in sulfate deposited after the Marinoan glacial meltdown at ca. 635 million years ago. Further investigation linking the Δ17O of barite to its sedimentological–geological context in Marinoan South China reveals that the 17O depletion in sulfate is most pronounced at sites near paleo-continents, supporting the hypothesis that atmospheric O2 was the source of the depletion which was transferred to sulfate via oxidative weathering of sulfides. Host minerals or rocks for the Marinoan 17O depletion have been limited to barite (southern China and western Africa) and carbonate-associated sulfate (CAS) in limestone lenses within a diamictite (Svalbard). If the Marinoan 17O depletion event is indeed related to an extraordinary atmospheric condition, the signal should be global in its distribution. The Kimberley region of Western Australia was close to a continent in the late Neoproterozoic and will serve as a test of our hypothesis that the anomalous 17O depletion may be widely recorded in the rock records of this time period.

We report here that the CAS in the Moonlight Valley (MV) cap dolostones, Texas/Mabel Downs (TMD), the eastern Kimberley region, Western Australia is anomalously depleted in 17O (Δ17O value as low as −0.68‰). The magnitude of the anomaly decreases gradually toward the overlying Ranford mud-silt-sandstones. This finding not only expands the geographic distribution of the depleted 17O signal, but also the type of host rocks or minerals that the anomalous sulfate resides. The CAS in the MV cap dolostones in Palm Spring (PS) section, ∼150 km south of TMD, however, does not bear a 17O depletion. Neither does the CAS in the Egan cap dolostones. The presence and absence of pronounced 17O anomalies in the two time-equivalent yet spatially different MV cap dolostones are consistent with the paleogeography that indicates TMD was close to the continent while PS was at an open-ocean environment. While sharing some of the same sedimentological features with that of the MV cap dolostones at TMD, the Egan cap has distinct δ13C and δ18O values for dolostones and distinct Δ17O, δ34S and δ18O values for CAS, supporting an earlier assignment of the Egan glaciation to be younger than Marinoan in the late Neoproterozoic.

Keyword17o Depletion Carbonate-associated Sulfate Kimberley Neoproterozoic Glaciation Cap Dolostones
Indexed BySCI
Document Type期刊论文
Affiliation1.Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, United States
2.State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), Wuhan 430074, China
3.State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
Recommended Citation
GB/T 7714
Huiming Bao;Zhong-Qiang Chen;Chuanming Zhou. An 17O record of late Neoproterozoic glaciation in the Kimberley region, Western Australia[J]. Precambrian Research,2012,216–219:152-161.
APA Huiming Bao;Zhong-Qiang Chen;Chuanming Zhou.(2012).An 17O record of late Neoproterozoic glaciation in the Kimberley region, Western Australia.Precambrian Research,216–219,152-161.
MLA Huiming Bao;Zhong-Qiang Chen;Chuanming Zhou."An 17O record of late Neoproterozoic glaciation in the Kimberley region, Western Australia".Precambrian Research 216–219(2012):152-161.
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