Basement-cover relationships in a forced orocline - an integrated geophysical-structural study: how does basement geometry affect oroclinal bending in fold-thrust-belts?
Project Investigators
Project details
The Adelaide Fold Belt, comprising the Fleurieu and Nackara Arcs, is a world class, full scale tectonic laboratory right on our doorstep, and is a good example of an orocline ("bent mountain belt"). The outcropping structure of the belt has been intensively studied, and advanced models developed for how the geometry of basement buttresses have influenced fold thrust deformation in the overlying Adelaidean and Kanmantoo Group sequences. In particular, many previous workers have sought to explain why the foldbelt has an overall sigmoidal shape. The only problem with this is that where the basement is inferred to critically influence the cover deformation, it doesn't crop out! However, the Adelaide Fold Belt is also covered with high quality aeromagnetic and gravity data, and in one or two places, seismic data. CERG has recently begun to apply the use of these non-structural tools to "blind" structural problems in this orogen (Brock, Hons 2003; Direen et al., 2005). This can be done because of the strong contrast in properties between the basement and the cover sequences.
This project will constrain the 3D geometry of the oroclinal bend between Cape Jervis & KI, adding to existing work on Cape Jervis, by building a new pair of constrained sections; one section will be based on forward modelling PIRSA seismic data in Backstairs Passage, and the Investigator-1 drillhole; the second section will be based on that published by Flöttmann et al (1995), and will require some fieldwork on KI to gather representative rock property data. Field structural mapping around the Cape Jervis area on southern Fleurieu peninsula will be used to constrain models for the accommodation of deformation.
