PESA WA August Luncheon – Evolution of “Tres Hombres”

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PESA WA Branch hosted Chris Hurren from BHB Billiton, with special gratitude to our four technical series sponsors, to talk our members through the evolution of the large mid-crustal “Tres Hombres” structure within the northern Beagle Sub-basin, offshore WA.

Three enigmatic circular structures in the outer part of the Beagle sub-basin, known as the three brothers, or possibly named after the album of the same name by ZZ Top, have attracted passing interest and quite a bit of head scratching in the past based on some rather sparse 2D seismic lines. Now that they are beautifully imaged on the TGS’s Capreolus MC3D seismic, there is a lot more evidence for their nature and origin. The WA PESA branch was treated to a detailed and thorough explanation of the BHP Billiton’s team’s understanding of the origin of the largest of these structures by Chris, reporting on a truly team based effort.

Chris considered three different possible origins for “Tres Hombres” – structural inversion, salt related and igneous. He explained that a structural origin can be discounted based on shape, while the large associated gravity and magnetic anomalies preclude salt and strongly supports an igneous origin. From stratigraphic relationships, a Jurassic age is considered most likely. Chris compared the structure to a large batholith, intruded at deep crustal levels, presumably related to an early stage of the break-up of the margin. Some lively discussion followed, particularly related to the timing, and whether there is any evidence for more recent reactivation.

The talk was an excellent example of a multidisciplinary approach being applied to some high quality data to provide some new insights into the evolution of a previously poorly understood part of the continental margin.

The next technical luncheon on the 20th September will be on the “Salt tectonics in the Petrel Sub-basin, Australia” presented by Prof. Chris Elders – who was Chris Hurren’s supervisor at Royal Holloway several years ago! Registrations are also open for more upcoming events in October and November – login to receive member discounts. For all upcoming WA events click here 

In October, PESA WA branch is hosting a rigourous four-day training course on “Structural geology and seismic in petroleum exploration and productions” by Kevin Hill and a second annual weekend fieldtrip to Perth Basin. Registrations are still available for these events, book early to avoid disappointments!

Again, we would like to thank our four sponsors of the WA Branch Technical Series, Spectrum (Platinum), CGG (Gold), Searcher Seismic (Gold) and DUG (Gold).

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