What are Diapirs? Examples from the Flinders Ranges
Thursday October 1st
Mawson Lecture Theatre
University of Adelaide
Dr Nick Lemon
Retired from Santos
Diapirs are "bubbles" of low density rock, such as salt or over pressured shale, that slowly rise to the surface of a sedimentary basin. They are pushed up by the weight of overlying denser sandstone and carbonate sediments. Diapirs are an important mechanism for forming hydrocarbon traps. There are over 120 examples of diapirs in the Flinders Ranges, ranging in age from Late Precambrian to the present day. Historically physical models made using different density liquids have been used to study diapir formation. Stratified sand box models with a flexible membrane acting at the diapir boundary slip plane can also be used. The timing of diapir movement is interpreted from the age of the associated sediments. In the Flinders Ranges these are typically conglomerates of older rocks either from within the diapir or eroded from the top or flanks of the structure.
Nick Lemon graduated from the University of Adelaide in 1973 with a BSc (Honours) in geology. He then worked for BHP Whyalla for 10 years in iron ore and coal exploration. He returned to the University of Adelaide to undertake PhD studies of sedimentation around diapirs in the Flinders Ranges. After completing his PhD he assisted in founding the NCPGG (National Centre for Petroleum Geology and Geophysics) at the University of Adelaide, which eventually became part of the Australian School of Petroleum. His academic work covered several areas including sandstone / carbonate diagenesis and reservoir petrology. Nick moved to work at Santos Ltd. starting as a development geologist working on the Cooper Basin. He retired in 2017 as Principal Sedimentologist in the Subsurface Services group specialising in reservoir quality and depositional environment interpretation from core and cuttings. He enjoyed leading regular tours of the geology and wine of the McLaren Vale for Santos and PESA. In recent years he has maintained an active interest in geology as he continues to recover from a brain injury.
*PLEASE READ CAREFULLY: At time of publication this is planned as a live meeting in the Mawson Lecture Theatre. However: Due to COVID restrictions numbers attending are limited to 44. If you wish to attend it is essential to register by contacting Frances Williams (email@example.com or if you do not have email by calling 0403 153 726). We will make every effort to live “zoom” the meeting as well. The link to attend via zoom will be circulated a few days prior to the meeting. For live attendees we will be strictly adhering to a COVID-SAFE plan formulated by SA Health. This will involve social distancing, hand sanitization and keeping a record, with contact details, of everyone who attends the meeting. You will need to provide these details before entering the lecture theatre. There will also be a few other guidelines so please follow all directions which will be posted at the meeting.
Due to the restrictions it will be a slightly curtailed meeting – there will be no pre-lecture tutorial or ten-minute talk. However, there will be a raffle, and simple refreshments (cold drinks and individually wrapped biscuits) served in the Sprigg Room upstairs following the meeting. As usual, ring the FGC doorbell for admittance but note that it will not be possible to admit latecomers. Cynthia Pyle will be running her popular Geological Workshop in the Sprigg room upstairs prior, to the lecture – details following. Last but not least – as you realise, the situation can change at a moment’s notice and if further restrictions are emplaced we will revert to Zoom only. Notification of any change will be posted on the home page under “Upcoming excursion and Lecture : Lecture”. YOU ARE STRONGLY ADVISED TO CHECK THIS BEFORE ATTENDING THE LECTURE.
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