Reconstructing mantle flow and continental-scale landscape evolution since the Jurassic Period

Date & time

11am–12pm 30 November 2016

Location

Building 61, Jaeger 7, Rm 224, Hales Seminar Room

Speakers

Dr Nicolas Flamant (University of Sydney)

Event series

Contacts

 Sebastien Allgeyer

Global tectonic reconstructions developed using GPlates can be used as boundary conditions of mantle convection models, to simulate past mantle flow and long-wavelength dynamic topography. The predictions of such models, here using CitcomS, can be compared to seismic tomography and to geological indicators of past vertical motions.

These models can reproduce the present-day structure of the lower mantle, including a structure that resembles the recently discovered Perm Anomaly. The models show that this anomaly formed in isolation within a closed subduction network ~22,000 km in circumference prior to 150 million years ago before migrating ~2,500 km westward at an average rate of 1.7 cm yr-1, indicating a greater mobility of deep mantle structures than previously recognised.

These models predict the highlands of the continental margin of eastern Australia to have been uplifted from 120-80 Ma due to the motion of Australia away from a sinking relict eastern Gondwana slab, followed by uplift due to the gradual motion of the margin over the edge of the large Pacific mantle upwelling. The uplift is predicted to have occurred in two stages in the southern part of the highlands, but to have been gradual their northern part, which is in agreement with published uplift models derived from river profiles.

We use the long-wavelength dynamic topography predicted by mantle flow models to simulate the evolution of the eastern Australian landscape since the Jurassic Period using Badlands. We adjust rainfall regime, erodibility, sea level variations, dynamic topography magnitude and elastic thickness, to find a model that is compatible with the first-order present-day drainage, with the denudation of the eastern highlands and sedimentation along the southern Australian margin. The model predicts that the Murray river reversed from eastward draining between 150 and 120 Ma to westward draining since 120 Ma.

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