Variations in Zircon Provenance Constrain Age and Geometry of an Early Paleozoic Rift in the Pinjarra Orogen, East Gondwana

Abstract

The Tumblagooda Sandstone in Western Australia documents Early Paleozoic rifting in East Gondwana and provides the earliest evidence for terrestrial activity of multicellular animals on Earth. We constrain the provenance of this sequence using 737 concordant U–Pb ages of detrital zircons from two stratigraphic wells in the northern Perth Basin and Southern Carnarvon Basin and outcrops of the type sections near Kalbarri. Detrital zircon age signatures are linked to infrared spectral data and stratigraphic logs. These ages span 3,312–466 Ma, including major Precambrian age peaks at 1,079–1,544 Ma, 1,695–2,403 Ma, and 2,640–2,879 Ma, consistent with igneous sources in the West Australian Craton. Significant Early Paleozoic age peaks at 499–541 Ma suggest a North Indian Orogen source. The maximum depositional age is constrained by the youngest detrital zircon, which yields an age of 466 ± 8 Ma. Our age constraints imply that terrestrial activity of multicellular animals on Earth may not be older than Middle Ordovician (Darriwilian). Rifting resulted in the exposure of the Yilgarn Craton and the segmentation of the Pinjarra Orogen. The Northampton Complex segment of the Pinjarra Orogen constituted a basement high that separated subbasins during the onset of rifting. Discordant Archean zircons provide a consistent record of radiogenic Pb loss at ~470 Ma, which we interpret as being related to the denudation of the Yilgarn Craton. The Pb loss event suggests that intracratonic rifting in the Pinjarra Orogen was initiated in the Middle Ordovician, after the Kuunga Orogeny completed the final amalgamation of Gondwana.

The applicability of modern tidal analogues to pre‐vegetation paralic depositional models

“…Previous studies of ichnotaxa initially suggested a similarity to the Devonian Taylor Group (Trewin & McNamara, 1994). Recent work by Markwitz et al (2017) on detrital zircon ages also supports a middle Ordovician age for deposition of 466 AE 8 Ma placing it firmly in the time prior to the evolution of rooted land plants.…”

“…Recent work by Markwitz et al . () on detrital zircon ages also supports a middle Ordovician age for deposition of 466 ± 8 Ma placing it firmly in the time prior to the evolution of rooted land plants.…”

“…The Tumblagooda Sandstone is up to 2000 m thick and forms the lowest unit in the Kalbarri Group which unconformably overlies gneissic basement and records deposition during the Early Palaeozoic rifting in East Gondwana (Markwitz et al, 2017). The formation is dominated by compositionally mature quartz arenite and subarkose sandstones (Kettanah et al, 2015) with abundant trough and tabular low-angle crossbedding, planar lamination and well-preserved bioturbated intervals (Hocking, 1991).…”

The Tumblagooda Sandstone revisited: exceptionally abundant trace fossils and geological outcrop provide a window onto Palaeozoic littoral habitats before invertebrate terrestrialization

“…Detrital zircon dates from the Tumblagooda Sandstone set a maximum possible age at 466 ± 8 Ma (Markwitz et al 2017). When considered alongside the c. 430 Ma Rb-Sr ages for regional uplift across SW Australia (Libby & De Laeter, 1998;McNamara, 2014), which were dated using biotites from the Yilgarn Craton (a minor provenance source for the Tumblagooda Sandstone; Figure 1 is highlighted by the blue box.…”

U–Th–Pb geochronology and simultaneous analysis of multiple isotope systems in geological samples by LA-MC-ICP-MS

“…However, the calculated alpha dose per gram provides a sensible estimate of the radiation damage only if the zircon structure has experienced no signicant annealing of radiation damage since crystallization, 106,107 and obtaining FWHM values for individual crystals is only feasible for a limited number of grains representative of magmatic populations 99,102 and is not practical for detrital studies, for example, where >120 grains per sample are oen analyzed to derive statistically signicant population distributions (e.g., ref. [105][106][107][108][109].…”