Jurassic arc; reconstructing the lost world of eastern Gondwana

The tectonic setting of the Australian sector of the eastern Gondwanan margin during the Jurassic and Cretaceous is enigmatic. Whether this involved convergent tectonism and a long-lived continental magmatic arc or rift-related extension unrelated to subduction is debated. The paucity of Australian...

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Bibliographic Details
Published in:Geology (Boulder) 2021-11, Vol.49 (11), p.1391-1396
Main Authors: Foley, Elliot K, Henderson, R. A, Roberts, E. M, Kemp, A. I. S, Todd, C. N, Knutsen, E. M, Fisher, C, Wainman, C. C, Spandler, Carl
Format: Article
Language:English
Subjects:
absolute age
Australasia
Australia
continental crust
continental margin
Convergence
cores
Cretaceous
crust
Geochemistry
Geology
Gondwana
Great Australian Superbasin
Growth rate
hafnium
Hf-177/Hf-176
isotope ratios
Isotopes
Jurassic
Juveniles
Lava
lithostratigraphy
Magma
magmatism
Mesozoic
metals
nesosilicates
orthosilicates
Outcrops
paleogeography
Paleozoic
Plate margins
Queensland Australia
silicates
stable isotopes
Stratigraphy
Subduction
Subduction (geology)
Tectonics
U/Pb
Zircon
zircon group
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Summary:The tectonic setting of the Australian sector of the eastern Gondwanan margin during the Jurassic and Cretaceous is enigmatic. Whether this involved convergent tectonism and a long-lived continental magmatic arc or rift-related extension unrelated to subduction is debated. The paucity of Australian Jurassic-Cretaceous igneous outcrops makes resolving these competing models difficult. We used the detrital zircon record of the Jurassic-Cretaceous Great Australian Superbasin (GAS) as a proxy for igneous activity. We attribute the persistent magmatism recorded in GAS sedimentary fill throughout the Mesozoic to ca. 95 Ma to continuation of the established Paleozoic continental arc system. The detrital zircon record signals short (∼10 m.y.) pulses of elevated Jurassic and Cretaceous magmatic activity and strongly positive εHf values, indicating juvenile crust or mantle-derived magmatism. Margin reconstruction indicates sustained continental growth at rates of at least ∼55 km3 km-1 m.y.-1, mainly to the tract now represented by submerged northern Zealandia, due to the retreat of this arc system. We posit that arc retreat was a key factor in rapid crust generation and preservation, and that continental sedimentary systems globally may host cryptic records of juvenile crustal addition that must be considered in estimating crustal growth rates along convergent plate margins.
ISSN:0091-7613
1943-2682
DOI:10.1130/G49328.1