Toothpaste tectonics - Rates and timescales, predicting where the rain fell
This project investigates the extrusion rate of Toothpaste Tectonics in the Eyre Peninsula.
Deformation of the crust involves brittle processes at low temperatures and plastic processes at higher temperatures. There is now a widespread recognition that plastic crust can flow over large distances, with the best present-day example being the escape of material from beneath Tibet into central Nepal and SW China.
However, what is less appreciated is that rocks can also flow within rheologically weak, narrow zones sandwiched between much stronger crust. Within these channels, rocks can be effectively extruded upwards (Toothpaste Tectonics!), creating long mountain belts.
The aim of this project is to investigate an example of Toothpaste Tectonics on eastern Eyre Peninsula where crust was extruded from depths of more than 40km. The specific aim is to determine how fast the extrusion process was, and to understand the development of the mountain belt it created.
A secondary aim is to test a hypothesis that Toothpaste-like extrusion of the lower crust occurs as a result of large differences in the rates of erosion (caused by differences in rainfall) on either side of the mountain belt. Different rates of extrusion will be recorded by the patterns of the mineral assemblages that formed on either side of the belt.
The outcrops on eastern Eyre Peninsula are spectacular. They are located right on the beach and will suit a person who likes sun, sand and beautiful geology. The project will involve detailed outcrop mapping, a number of different methods of geochronology, geochemistry and petrological modelling. Oh....and visits to the beach.