The Giant Lavas of Kalkarindji: rubbly pāhoehoe lava in an ancient continental flood basalt province

Abstract

The Kalkarindji continental flood basalt province of northern Australia erupted in the mid Cambrian . It now consists of scattered basaltic lava fields, the most extensive being the Antrim Plateau Volcanics (APV) -a semi-continuous outcrop (c. 50,000 km 2 ) reaching a maximum thickness of 1.1 km. Cropping out predominately in the SW of the APV, close to the top of the basalt succession, lies the Blackfella Rockhole Member (BRM). Originally described as 'basaltic agglomerate' the BRM has, in recent years, been assumed to be explosive tephra of phreatomagmatic origin, thus providing a potent vehicle for volatile release to the upper atmosphere. Our detailed field investigations reveal that this basaltic agglomerate is, in reality, giant rubble collections (15 -20 m thick) forming the upper crusts of rubbly pāhoehoe lava units 25 -40 m thick; covering 18,000 -72,000 km 2 and an estimated volume of 1,500 -19,200 km 3 . These flows, rheologically but not chemically, distinct from the majority of Kalkarindji lavas, indicate a fundamental change in eruption dynamics. A low volatile content, induced high amounts of pre-eruptive degassing causing super-cooling and an increase in crystal nucleation and viscosity. A more viscous lava and a consistently faster rate of effusion (analogous to that of Laki, Iceland) created the flow dynamics necessary to disturb the lava crust to the extent seen in the BRM. Volatile release is estimated at 1.65 × 10 4 -2.11 × 10 5 Tg total CO2 at a rate of 867 Tg a -1 and 9.07 × 10 3 -1.16 × 10 5 Tg SO2 at 476.50 Tg a -1 . These masses accounted for 0.5% of Cambrian atmospheric conditions whilst limiting factors reduced the effect of volatile delivery to the atmosphere, thus any potential global impact caused by these flows alone was minimal.

The eogenetic karst of the Cambrian Longwangmiao Formation in the Yangtze Platform: Implications for the eustatic and stratigraphic correlations of Toyonian (Cambrian)

“…Besides that, the other plausible mechanism is driven by the Kalkarindji large igneous province (LIP) of northern Australia (511–505 ± 2 Ma; Faggetter et al, ; Glass & Phillips, ; Hough et al, ; Jourdan et al, ; Marshall, Widdowson, & Murphy, ). The oldest Phanerozoic continental flood basalt province (CFB), Kalkarindji (eruptive volume exceeded 5 × 10 5 km 3 ), covers a large tract of northern Australia, which was erupted onto the North Australian Craton forming part of Gondwana (Marshall et al, ). Simultaneously, the eruptive period of Kalkarindji is correlated with the Hawke Bay sea‐level regression episode, which may be related to lithospheric updoming associated with mantle plume ascent and CFB volcanism (Williams & Gostin, ).…”

“…Besides that, the other plausible mechanism is driven by the Kalkarindji large igneous province (LIP) of northern Australia (511-505 ± 2 Faggetter et al, 2017;Glass & Phillips, 2006;Hough et al, 2006;Jourdan et al, 2014;Marshall, Widdowson, & Murphy, 2016).…”

“…The oldest Phanerozoic continental flood basalt province (CFB), Kalkarindji (eruptive volume exceeded 5 × 10 5 km 3 ), covers a large tract of northern Australia, which was erupted onto the North Australian Craton forming part of Gondwana (Marshall et al, 2016).…”

Trilobite extinctions, facies changes and the ROECE carbon isotope excursion at the Cambrian Series 2–3 boundary, Great Basin, western USA

“…The Series 2 -Series 3 boundary interval saw the eruption of the Kalkarindji flood basalt province (Glass and Phillips, 2006;Jourdan et al, 2014;Marshall et al, 2016). In younger intervals of the Phanerozoic, the formation of large igneous provinces frequently coincides with mass extinctions (Wignall, 2015;Bond and Grasby, 2016) and the eruption of large volumes of volcanic volatiles provides a causal mechanism for driving biologic crises.…”

“…Volcanism may also have played a role in ROECE (Glass and Phillips, 2006). The Kalkarindji LIP is a Cambrian flood basalt province of northern and central Australia with an estimated original surface area of ~ 2.1 x 10 6 km 2 (Glass and Phillips, 2006;Jourdan et al, 2014;Marshall et al, 2016).…”