U-Pb detrital zircon constraints on the depositional age and provenance of the dinosaur-bearing Upper Cretaceous Wadi Milk formation of Sudan

Owusu Agyemang, Prince C., Roberts, Eric M., Bussert, Robert, Evans, David, and Müller, Johannes (2019) U-Pb detrital zircon constraints on the depositional age and provenance of the dinosaur-bearing Upper Cretaceous Wadi Milk formation of Sudan. Cretaceous Research, 97. pp. 52-72.

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Abstract

Cretaceous continental deposits in Sudan have long been recognized as important archives of continental vertebrate fossils in central Africa. A number of different sedimentary units including the Wadi Milk, Shendi and Kababish formations from northern and central Sudan are known to yield dinosaur and other vertebrate fossils. The ages of these deposits are poorly constrained, and traditionally assumed to be of Albian to Santonian age based on biostratigraphic evidence. However, recent palynological analyses suggest a Campanian-Maastrichtian age for the Shendi Formation. Not only are the ages of these units poorly resolved; but stratigraphic correlations within and between them and similar aged units in central Africa, remains tenuous. To address these issues a detailed sedimentary fingerprinting and provenance analysis was conducted on the putatively correlative Shendi and Wadi Milk formations using sandstone petrography and a multifaceted detrital zircon investigation combining U-Pb geochronology, Lu-Hf isotope analysis and trace element geochemistry. The objective was to provide constraints on the age of deposition, sediment sources and paleofluvial drainage patterns. Based on laser ablation ICP-MS U-Pb detrital zircon geochronology of 18 sandstone samples (>1400 detrital zircons), we identified a population of six Late Cretaceous zircons from the Wadi Milk Formation yielding a maximum depositional age of 79.2 +/- 2.4 Ma (MSWD = 0.65, probability 0.62). Specifically, these data restrict the depositional age to Campanian or younger for the Wadi Milk Formation, which significantly refines our understanding of the age of this unit and its fauna. The Lu-Hf-isotope and trace element analyses of the remainder of the dated zircons show a provenance dominated by Neoproterozoic crustal sources and minor Paleoproterozoic and Archean sources for both units, which we interpret as being sourced from the Arabian-Nubian Shield to the south and southeast of the study area. These findings, coupled with the recently updated biostratigraphic age of the Shendi Formation, confirm that both units are correlative to one another and were probably deposited synchronously by north-north westerly flowing fluvial system draining into the Tethys Sea during the Late Cretaceous.

Item ID: 58135
Item Type: Article (Research - C1)
ISSN: 1095-998X
Keywords: Wadi Milk, Shendi-Atbara, Detrital zircon geochronology, U-Pb-Lu-Hf, Provenance, Cretaceous volcanism
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Copyright Information: © 2019 Elsevier Ltd. All rights reserved.
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A version of this publication was included as Chapter 5 of the following PhD thesis: Owusu Agyemang, Prince C. (2018) Mesozoic detrital zircon provenance of Central Africa: implications for Jurassic-Cretaceous tectonics, paleogeography and landscape evolution. PhD thesis, James Cook University, which is available Open Access in ResearchOnline@JCU. Please see the Related URLs for access.

Funders: Australian Government Research Training Program Scholarship, Deutsche Forschungsgemeinschaft (DFG), Royal Ontario Museum
Projects and Grants: DFG Mu 1760/6-1
Date Deposited: 24 Apr 2019 07:34
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040303 Geochronology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040310 Sedimentology @ 50%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840107 Titanium Minerals, Zircon, and Rare Earth Metal Ore (e.g. Monazite) Exploration @ 50%
97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
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