Jurassic Arc: Reconstructing the Lost World of eastern Gondwana

Abstract

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.

Deciphering Late Cretaceous palaeo‐river catchments in eastern Australia: Recognition of distinct northern and southern drainage basins

“…Overall, Normanton Formation sandstones plot in the ‘mixed’ to ‘dissected arc’ fields of Dickinson et al (1983), due to the moderate abundance of both feldspars and lithic grains in relation to quartz. This is consistent with the interpretations of Tucker et al (2016), Wainman et al (2019) and Foley et al (2020), Foley, Henderson, et al (2021) that a continental magmatic arc dominated the eastern margin of the Australian continent from the Jurassic through to the mid‐Cretaceous, and thus acted as a primary source of the volcanoclastic sediment of the Normanton Formation.…”

“…(b) Cretaceous (145–85 Ma) detrital zircon record of the Normanton Formation. Age ranges of basement sources are modified after Fergusson et al (2017), and Foley, Henderson, et al (2021)…”

“…45%), of Albian and particularly Cenomanian age (Figures 6 and 7). The young nature of the Normanton Formation's detrital zircon record, approaching the unit's TDA, is typical of successions prone to abundant syndepositional magmatic activity (Cawood et al, 2012), and likely the product of arc volcanism (Foley, Henderson, et al, 2021; Tucker et al, 2016). The volcanoclastic nature of Normanton Formation sediments, which display abundant volcanic lithics and devitrified volcanic glass, and yield a ‘mixed’ to ‘dissected arc’ petrographic signature (Figures 8 and 9) also corroborate the interpretation of these youngest zircons as approximating the age of deposition.…”

“…A similarly prominent Albian-Cenomanian U-Pb age peak has been documented in the detrital zircon record of the Winton Formation (Tucker et al, 2013(Tucker et al, , 2016 (Figure 11). This peak, and the volcanoclastic nature of the formation, have been attributed to long-lived continental arc magmatism, exemplified by the Early Cretaceous Whitsunday Volcanic Province, which dominated eastern Australia through the late Palaeozoic and much of the Mesozoic (Foley, Henderson, et al, 2021;Tucker et al, 2016). Alternatively, the Whitsunday Volcanic Province has been interpreted as a silicic large igneous province (SLIP), emplaced during rift-related magmatism prior to eastern Gondwana breakup (Bryan et al, 2012).…”

“…The Great Australian Superbasin (Cook et al, 2013; Foley, Henderson, et al, 2021) is a Jurassic to Early Cretaceous epicontinental sedimentary system that dominates eastern Australia, spanning almost one‐fifth of the continent (Figure 1a) (Habermehl, 2020). The superbasin has been the subject of several studies incorporating U‐Pb detrital zircon geochronology for sediment provenance and palaeogeographic reconstructions in recent years (e.g.…”