Guest geology/geophysics drive-by by David Middleton

H/T to Dr. Willie Soon

Cool story, stupid headline…

Scientists Found a Hidden ‘Jurassic World’ Buried Underneath Australia
The subterranean remains of 100 volcanoes formed some 180 million years ago were detected under a major petroleum hotspot.

By Becky Ferreira
Aug 14 2019

A trove of 100 Jurassic-era volcanoes has been discovered deep underneath a petroleum-rich region of central Australia, according to a new study.

The ancient volcanoes formed between 180 and 160 million years ago, just as the prehistoric supercontinent Gondwana—of which Australia was once a part—began to break apart. For millennia, this underground volcanic landscape lay buried underground, eluding detection.

[…]

These deposits have been a hotspot of oil and gas production since the 1960s, and the region is currently Australia’s largest onshore source of hydrocarbons, which made the new find particularly surprising.
According to the study authors, finding such an epic volcanic landscape in an area that has already undergone substantial data collection “raises the prospect of other undiscovered […] volcanic provinces both in Australia and in other continental areas worldwide.”

Some 1,400 oil wells have been drilled in this area over the past half-century, some of which turned up igneous rocks that suggested ancient lava might be preserved in the sediment.

[…]

Vice

There’s a “Jurassic world” buried under just about every Cretaceous and younger “hotspot of oil and gas production” in the world… The Jurassic is almost always below the Cretaceous… unless the beds have been overturned, it’s in an overthrust belt or it’s Jurassic-aged mobile salt. The Gulf of Mexico features a Jurassic desert buried 20,000′ below the seafloor, places where there are 1,000’s of feet of Jurassic salt above Cenozoic “rocks,” and mysterious volcanoes too… Plus… If the Gulf of Mexico ever froze, there would be enough ice to replace the Greenland ice sheet… That’s like eleventy gazillion Olympic-sized swimming pools.

The headline may have been stupid, but, the science is way cool! They were able to make fairly detailed maps of what appear to be volcanic features by integrating seismic, gravity and well data…

A pre-print full version of their paper can be accessed here.

The “Warnie volcanic province” is actually in between two hydrocarbon basins…

The Cooper and Eromanga Basins of South Australia and Queensland are the largest onshore hydrocarbon producing region in Australia. Igneous rocks have been documented infrequently within end of well reports over the past 34 years, with a late Triassic to Jurassic age determined from well data. However, the areal extent and nature of these basaltic rocks were largely unclear. Here, we integrate seismic, well, gravity, and magnetic data to clarify the extent and character of igneous rocks preserved within Eromanga Basin stratigraphy overlying the Nappamerri Trough of the Cooper Basin. We recognise mafic monogenetic volcanoes that extend into tabular basalt lava flows, igneous intrusions and, more locally, hydrothermally altered compound lava flows. The volcanic province covers ~7500 km2 and is proposed to have been active between ~180–160 Ma. We term this Jurassic volcanic province the Warnie Volcanic Province (WVP) after the Warnie East 1 exploration well, drilled in 1985. The distribution of extrusive and intrusive igneous rocks is primarily controlled by basement structure, with extrusive and intrusive igneous rocks elongate in a NW-SE direction. Finally, we detail how the WVP fits into the record of Jurassic volcanism in eastern Australia. The WVP is interpreted as a product of extension and intraplate convective upwelling above the subducting Pacific Slab. The discovery of the WVP raises the possibility of other, yet unidentified, volcanic provinces worldwide.

[…]

Hardman et al., 2019

Just because I expect this to be mentioned in numerous comments: No! These are not the hydrocarbon source rocks of the Cooper Basin. The Cooper Basin is much older and lies unconformably below the Eromanga Basin.

Nor are they the source rocks for the younger Eromanga Basin.

How could a volcanic field get between two sedimentary basins?

The San Francisco Peaks of Arizona might just be a modern analogy for the The Warnie Volcanic Province. 10’s of millions of years in the future, parts of it might just be covered by a future sedimentary basin, sandwiched between two basins like the Warnie Volcanic Province.

References

Hardman, Jonathon P.A., Simon P. Holford, Nick Schofield, Mark Bunch, Daniel Gibbins, “The Warnie volcanic province: Jurassic intraplate volcanism in Central Australia”. Gondwana Research, Volume 76, 2019,
Pages 322-347, ISSN 1342-937X, https://ift.tt/2ZdxQbt.

Hardman, Jonathon, Simon Holford, Nick Schofield, Mark Bunch, and Daniel Gibbins. 2018. “The Warnie Volcanic Province: A Jurassic Volcanic Province in Central Australia.” EarthArXiv. December 12. doi:10.31223/osf.io/9zmty.

Kuske, Tehani J., Lisa Hall, Tony Hill, Alison Troup, Dianne Edwards1, Chris Boreham and Tamara Buckler. “Source Rocks of the Cooper Basin”. Search and Discovery Article #10829 (2016)**