README FOR folder --Shephard_2012_ArgentineBasin Author: G Shephard grace.shephard@sydney.edu.au Date created: Feb 29 2012 Abstract: A substantial portion of Earth's topography is known to be caused by the viscous coupling of mantle flow to the lithosphere but the relative contributions of shallow asthenospheric flow versus deeper flow remains controversial. The Argentine Basin, located offshore of the Atlantic margin of southern South America, is one of the most anomalously deep ocean regions as it is significantly deeper than its age would suggest. Previously, the anomalous depth has been attributed to asthenospheric flow and the coupling of the South American plate's westward motion to the shallow mantle. Using a combination of geophysical observations and geodynamic modeling we propose that subducted slab-driven dynamic topography has primarily driven the long-wavelength anomalous residual basin depth since the opening of the South Atlantic. Using an inverse mantle convection model with plate motions since the early Cretaceous, we suggest that the median of present-day dynamic topography of the basin is -400 m. When the residual basement depth is lowpass filtered the depth anomaly is -730 m, suggesting that more than half of the residual basement depth can be attributed to deep-seated mantle dynamics.We conclude that coupled plate tectonic-mantle convection models tied to seismic tomography, bathymetry and sediment thickness data can help to elucidate the driving forces behind Earth's topography, one of the most fundamental characteristics of this planet. This folder contains the raster and grid files associated with Figures 3 and 4 from Shephard et al., (2012). #### Figure 3: "Shephard_scaled_dynamic_topo_50Ma" Grid of absolute dynamic topography at 50 Ma "Shephard_scaled_dynamic_topo_0Ma" Grid of absolute dynamic topography at 0 Ma "Shephard_change_dynamic_topo_50to0Madiff.grd" Grid of change in dynamic topography between 50 and 0 Ma "ArgentineBasin.xy" outline of Argentine Basin used. "scaled_dynamic_topo.sh" Basic GMT script for plotting the above #### Figure 4: "global_mean_Crosby_nonans.nc" Global grid of combined residual basement depth model (Crosby and McKenzie 2009) and continental topography (ETOPO2) corrected for mean continental elevation averaged elevation (563 m; Harrison et al., 1983). This grid is free from NaNs which is a requirement for the grdfft command. There were NaNs because the etopo and residual basement grids are separate datasets did not completely overlap (e.g. around the COB). Note that in some areas adjacent to the continental margin there may be an over/under prediction of the values that replace the NaNs. Regional scales should be checked. "global_Crosby09_fft_500km.grd" The low-pass filtered grid removing wavelengths less than 500 km and passed for wavelengths greater than 750 km i.e. with grdfft command option -F-/-/750000/500000. Be wary of artefact at date line. The process could be repeated with any other model of residual basement (here Crosby and McKenzie model was used).The user might also want to change the filtering value to another type or value e.g. -F-/-/750000/500000.For example -/-/40000/250000 will lowpass filter i.e. remove wavelengths less than 250km, pass wavelengths greater than 400km "resbasetopo_filt.sh" Basic GMT script for plotting the above If you use any of the resources, please cite the following publication: G.E. Shephard, L. Liu, R.D. Müller, M. Gurnis, Dynamic topography and anomalously negative residual depth of the Argentine Basin, Gondwana Research, Volume 22, Issue 2, September 2012, Pages 658-663, ISSN 1342-937X, 10.1016/j.gr.2011.12.005. (http://www.sciencedirect.com/science/article/pii/S1342937X11003522)