TAG - Geological Society of Australia

Book ReviewSalt Tectonics, Sedimentsand ProspectivityGI Alsop, SG Archer, AJ Hartley, NT Grant &R Hodgkinson (Eds)Geological Society of London, SpecialPublication 363, London, 2012, 624 pagesISBN 978-1862393417The work covers many of the world’ssignificant diapiric provinces: the CretaceousLa Popa Basin in Mexico, the Flinders Rangesin South Australia, the Santos Basin offshoreBrazil, the Kwanza Basin offshore Gabon, theGulf of Mexico, the Laurentian Basin GrandBanks in eastern Canada and the offshoreParentis Basin in the Bay of Biscay. The bookalso covers the Polish and Central Europeansalt basins: the Dnieper–Donetz BasinUkraine, the Levant Basin off Tel Aviv in theEastern Mediterranean, offshore Holland, theSouth Oman Salt Basin, the Zagros Mountainsand Great Kavir of Iran, northern Tunisiaand Haute Provence in France. Finally there isa discussion of the Poza de la Sal Diapir inthe Basque Pyrenees and if we are not yetsatisfied, we are treated to salt evacuationstructures/welds near Watchet on the southcoast of the Bristol Channel, UK.It is the first Geological Society SpecialPublication dedicated to salt tectonics andis the result of a London conference inJanuary 2010 of the Petroleum Group ofthe Geological Society and the Society forSedimentary Geology. The main themes of thepapers are halokinetic sequence stratigraphy,salt in passive-margin settings, the centralEuropean salt basins, deformation within andadjacent to salt, salt in contractional settingsand salt glaciers. There are five papers in thefirst category by nine different authors, tenpapers with 28 authors in the second andfour papers with ten authors on the Europeansalt basins. Deformation related to salt hassix papers with the combined expertise of22 authors. Contractional settings and saltglaciers has four papers with 14 contributingauthors. In total, 80 or so authors arerepresented in the volume.This volume is presented with clear figures ofseismic interpretations, modelling studies,field maps and photographs with colour.There is some unfamiliar nomenclature suchas inverted depocentres, mechanisms offlip-flop salt tectonics, expulsion basins andsalt sheet breakouts. There is also extensionalsalt withdrawal, welding and contractionalsalt inflation and extrusion, along withprogradational extrusion and salt nappes withminibasin formation, along with many more.An early stage of salt tectonics appears tobe extensional slip and passive salt diapirismdue to downbuilding in a salt basin. Thismight develop in different ways, giving riseto a whole classification of diapiric bodies,minibasin forms and welds. Rejuvenationby squeezing of the dominant salt diapirs,pillows and allochthonous canopies can thenlead to more complex structures and nappes.Complexity in the sequence stratigraphy ofsalt basins has its own nomenclaturedependent on the interaction of saltmovement, sedimentation and erosion withthe ultimate possibility of canyon formationand submarine ‘salt glaciers’. It is worthcommenting that many such examples are tobe seen in the published geological mappingof the Flinders Ranges.The authors clearly form an integrated groupof global researchers who have access toworldwide study areas and selected seismicand other modern data, which are presentedbeautifully with liberal colour and adequateexplanatory figures. The compilation is adelight to review.It is pleasing to see Australia’s ownWitchelina Diapir presented as a hyperspectralimage for the chosen example ofa naturally outcropping cross-section of adiapir. It is described as having a megaflapand primary minibasin and breakout of ‘salt’into a welded canopy. I must point out, however,that the labelling of ‘autochthonoussalt’ in the core of the structure isunsubstantiated. This is a point ofconsiderable significance as we are yet toidentify the evaporites in the AdelaideGeosyncline.The most detailed paper on depositional andhalokinetic sequence stratigraphy is based onthe Wonoka Formation (Wilpena Group) ofthe Ediacaran in the Central Flinders Ranges.In this paper, Kernen et al discuss thePatawarta Diapir as an allochthonous saltsheet and provide paleogeographic settingsand stratal relationships as determined fromsurface mapping. It is a good example of theinformation available in accessible areas inSouth Australia’s Neoproterozoic andCambrian diapir province, which must rankamong the world’s premier study areas.I really recommend this book to thoseinterested in development and comparison ofsalt structures during basin evolution. It is avaluable compilation of modern data frommost of the world’s premium evaporite basinsand should be a reference for all petroleumstudents and structural geologists. This copywill be passed on to those working in thisfield at Adelaide University.It is unfortunate that history has lost track ofthe similar compiled work Diapirism andDiapirs (Memoir 8 AAPG 1968, J Braunsteinand GD O’Brien, Eds), which covered similarworld provinces and included a jointcontribution by this reviewer on diapiricstructures and sedimentation in the FlindersRanges. This publication was the result of aconference in New Orleans in 1965 and itprovides an overview of diapirism at thattime. In particular it provides an excellentindex and indexed bibliography, whichare useful for reference. Advances inunderstanding since this date areconsiderable although the principles in manyof the examples quoted in current literaturewere clear from early phases of geologicalmapping, mining, oil and gas exploration andlaboratory work. Quality seismic is the realbreakthrough for subsurface examples andpetroleum search and this is well presentedin the present volume.R DALGARNOPO Box 8051Mount Gambier East, SAOmission…In the photograph on p 39 ofTAG 164, Brian Skinner and PeterHoward were featured with ProfessorCatherine Skinner and Michelle Vale.46 |TAG December 2012