Mesozoic detrital zircon provenance of Central Africa: implications for Jurassic-Cretaceous tectonics, paleogeography and landscape evolution

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.

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View at Publisher Website: https://doi.org/10.25903/5eb1ed92284d2
 
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Abstract

Jurassic-Cretaceous tectonics, paleogeography and sedimentary provenance of central Africa are poorly constrained and continue to be debated. The lack of constraints on the timing and controls on late Mesozoic sedimentary basin development, drainage evolution and paleoenvironments is problematic because central Africa is well endowed with natural resources, and good understanding of these issues is fundamental to a better assessment of hydrocarbon and alluvial diamond exploration targeting. Moreover, by improving our understanding of Mesozoic strata across this vast region, we can also help to contextualise the ecological and evolutionary relationships of floras and faunas from central Africa with contemporary floras and faunas from different parts of Africa and throughout Gondwana. In particular, refining the depositional age of late Mesozoic units is key to understanding and reconstructing regional paleogeography and drainage patterns during this poorly resolved time period in Africa, which also furthers our understanding of the origins and dispersal pathways for Mesozoic, Cenozoic and modern African floras and faunas, as well as economically significant alluvial mineral resources, such as diamonds, that are important to the economies of this part of the world.

To address these issues a detailed and multifaceted sedimentary provenance analysis of 14 late Mesozoic units from seven sedimentary basins across central Africa (spanning seven different countries) was conducted. This integrated sedimentological approach incorporated sandstone petrography, paleocurrent analysis, U-Pb detrital zircon geochronology, Lu-Hf isotope and trace element geochemistry to investigate Jurassic and Cretaceous continental deposits from central Africa. The main objective was to investigate late Mesozoic sedimentary basin development, drainage evolution and provide constraints on the age of deposition, sediment source and paleofluvial drainage patterns, using core and outcrop samples from across the region; including Democratic Republic of Congo (DRC), Kenya, Angola, Sudan, Tanzania, Zimbabwe and Malawi.

Sandstone petrography and paleocurrent data indicate mixed sediment sources mainly to the south of study areas. Maximum depositional age analyses performed on U-Pb detrital zircon sample results demonstrate that most of the late Mesozoic units in central Africa are younger than previously accepted. Detrital zircon provenance analysis points to primary contributions from Neoproterozoic Pan-African Mobile Belts (e.g., Mozambique and Zambezi belts), which were probably exposed at this time are the dominant (>75%). The Lu-Hf isotope geochemistry results also show a mixed sediment provenance consisting of juvenile mantle and reworked crustal sources, which corroborates the sandstone petrography results. Western areas of central Africa (e.g. DRC and Angola) are dominated by sediments from reworked crustal sources, whereas eastern parts of central Africa (e.g. Sudan, Kenya and Tanzania) are dominated by sediments of juvenile mantle sources. The results further suggest a pattern of large ephemeral lakes in the Middle Jurassic to Early Cretaceous in the Congo and Zambezi basins, followed by the development of a large, dominantly north directed fluvial systems across central Africa in the middle Cretaceous. The results are supportive of a uniform northward continental drainage pattern throughout late Mesozoic, which supports the assertion that the paleo-Congo drainage system was likely north flowing, rather than east flowing out of the Congo Basin and into Indian Ocean as previously suggested. The results of this thesis are also supportive of the hypothesis of a major drainage divide between southern and central Africa during the late Mesozoic and the concept of a major NW trending fluvial drainage pattern into the shear zones within the Central African Rift System, although the ultimate depocentre still remains uncertain. The maximum depositional age of three Cretaceous sedimentary units, including the dinosaur-bearing Wadi Milk Formation of Sudan has been constrained. The new ages shows a generally much younger age of deposition than previous assignations, calling into question the reliability of these overly broad biostratigraphic age for these important sedimentary units.

Item ID: 62916
Item Type: Thesis (PhD)
Keywords: Cretaceous volcanism Cretaceous, detrital zircon geochronology, East African Rift, Kasai-Congo, Lu-Hf, palaeodrainage, Paleocene volcanism provenance, Shendi-Atbara, Turkana Basin and Grits, U-Pb-Lu-Hf, Wadi Milk
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Copyright Information: Copyright © 2018 Prince C. Owusu Agyemang.
Additional Information:

Three publications arising from this thesis are stored in ResearchOnline@JCU, at the time of processing. Please see the Related URLs field. The publications are:

Chapter 2: Owusu Agyemang, Prince C., Roberts, Eric M., and Jelsma, Hielke A. (2016) Late Jurassic-Cretaceous fluvial evolution of central Africa: insights from the Kasai-Congo Basin, Democratic Republic Congo. Cretaceous Research, 67. pp. 25-43.

Chapter 4: Owusu Agyemang, Prince C., Roberts, Eric M., Downie, Bob, and Sertich, Joseph J. W. (2019) Sedimentary provenance and maximum depositional age analysis of the Cretaceous? Lapur and Muruanachok sandstones (Turkana Grits), Turkana Basin, Kenya. Geological Magazine, 156 (8). pp. 1334-1356.

Chapter 5: 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.

Date Deposited: 06 May 2020 00:07
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040303 Geochronology @ 50%
04 EARTH SCIENCES > 0403 Geology > 040310 Sedimentology @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 50%
84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840107 Titanium Minerals, Zircon, and Rare Earth Metal Ore (e.g. Monazite) Exploration @ 50%
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