SUPPLEMENTARY INFORMATION

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doi:10.1038/nature10566 1 Supplementary Figure 1.

1 doi: /nature Supplementary Figure 1. Map showing the location of airborne geophysical tracks and seismic stations for the Gamburtsev Subglacial Mountains and adjacent regions of East Antarctica used in our study. Red lines show the new AGAP survey grid. The survey provides the first comprehensive view of crustal architecture in interior East Antarctica and images the extent of the East Antarctic Rift System. The main grid over the Gamburtsev Subglacial Mountains (GSM) was flown during the 2008/09 field season with a line spacing of 5 km and tie-line interval of ~33 km. Exploratory lines with a spacing of ~66 km were also flown to link AGAP with: a) a previous survey to the east over Lake Vostok 18 (LV-magenta) 1

2 flown to link AGAP with: a) a previous survey to the east over Lake Vostok 18 (LV-magenta) and to provide reconnaissance data coverage over Lake Sovetskaya (LS) and Lake 90E (L90E) and; b) to connect to Russian aerogeophysical datasets 16,31-32 to the west (orange lines). Exploratory lines were also flown over the Recovery Subglacial Highlands (RSH) and southern Recovery Lakes (RL) region. Dark blue lines show the extent of the PCMEGA survey over the southern Prince Charles Mountains (spcm) and southern Lambert Rift (LR) 17 and pale blue lines show other datasets included in the BEDMAP (Antarctic bedrock topography) compilation 31 and in ADMAP (Antarctic Digital Magnetic Anomaly compilation) 40. The new survey was flown mainly from the AGAP field camps located on the northern and southern side of the Gamburtsevs. Some lines were flown from South Pole station over the Pensacola Pole Basin (PPB) in the hinterland of the Transantarctic Mountains (TAM). Black triangles show passive seismic stations, including the recent GAMSEIS experiment 4 across the Gamburtsevs and adjacent Vostok Subglacial Highlands (VSH), and previous stations 20 over the northern Prince Charles Mountains (npcm), Mawson Escarpment (ME), Grove Mountains (GM) and Lake Vostok 18. Outcrops are indicated in brown. Dashed white line denotes the inferred Gamburtsev Suture. The grey backdrop is the East Antarctic Ice Sheet digital elevation model from the RADARSAT-1 Antarctic Mapping Project (RAMP) ( 2

Supplementary Figure 2. Comparison between satellite magnetic and aeromagnetic data over the Gamburtsev Subglacial Mountains region in East Antarctica.

3 Supplementary Figure 2. Comparison between satellite magnetic and aeromagnetic data over the Gamburtsev Subglacial Mountains region in East Antarctica. a, Hanningfiltered CHAMP satellite magnetic anomaly data from the MF6 model14 (continued to the elevation of the airborne data) downloaded from MF6 resolves the crustal magnetic anomaly field to spherical harmonic degree 3120, corresponding to length scales down to 333 km. The Hanning filter enhances the longwavelength components of the crustal magnetic anomaly field and reduces ringing effects. Note long-wavelength satellite magnetic anomaly signatures over the Ruker, Gamburtsev, Recovery, and South Pole provinces that we interpret as revealing a mosaic of different Precambrian basement provinces in interior East Antarctica. For comparison, note the previously recognised satellite magnetic anomaly high over the Nimrod Province, recently interpreted as imaging a buried Meso to Paleo(?)proterozoic igneous province (~1.4 and 1.7 Ga?) in the hinterland of the Transantarctic Mountains57. b, Compilation of aeromagnetic data revealing a prominent ~1000 km long boundary along the edge of the Gamburtsev Province interpreted from our study as imaging a major W W W. N A T U R that E. C O M / NAT U R E Proterozoic (~1 Ga?) suture zone (dashed white line). The high-frequency NE-SW trends characterise the Gamburtsev Province (10-50 km wavelength) are evident from aeromagnetic 3

4 b, Compilation of aeromagnetic data revealing a prominent ~1000 km long boundary along the edge of the Gamburtsev Province interpreted from our study as imaging a major Proterozoic (~1 Ga?) suture zone (dashed white line). The high-frequency NE-SW trends that characterise the Gamburtsev Province (10-50 km wavelength) are evident from aeromagnetic data and lie ~parallel to aeromagnetic trends of the Prince Charles Mountains and Lambert Rift region that have been linked to exposed ~Grenvillian-age (~1 Ga) basement rocks 16,17. c, Satellite-derived terraced 42 magnetic anomaly map enhancing the boundaries between the different large-scale basement provinces in interior East Antarctica. This map was used in figure 2b to fill-in the aeromagnetic data coverage thereby helping characterise the regional extent of basement provinces. d, Aeromagnetic data displayed with a shaded relief grey scale overlain on terraced satellite magnetic data. Note the high-frequency NE-SW trending basement grain imaged from aeromagnetic data superimposed on the regional satellite magnetic low of the Gamburtsev Province. 4

5 Supplementary Figure 3. Satellite magnetic anomaly maps for East Antarctica. a, View of the Hanning filtered map at continental-scale showing the more weakly magnetic Gamburtsev Province surrounded by other more highly magnetic provinces of the East Antarctic Shield. Note for comparison the satellite magnetic signature over the Archean to Paleoproterozoic Terre Adélie Craton and its distinct eastern margin 57,58. Black rectangle shows location of our study area. b, View of the terraced map at continental-scale confirming the existence of several distinct provinces within a composite East Antarctic Shield. The complex boundaries between these basement provinces in interior East Antarctica likely exert key controls on the East Antarctic Rift System. 5

6 Supplementary Figure 4. Gravity anomalies over East Antarctica and location of our gravity models for the Gamburtsev Subglacial Mountains. a, Bouguer anomaly map for East Antarctica derived from the combination of GRACE (Gravity Recovery and Climate 7 Experiment) and GOCE (Gravity Field and SteadyǦstate Ocean Circulation Explorer) satellite 15 gravity data using the global gravity model GOCO01S downloaded from The satellite gravity field model is resolved up to degree/order 224 of a harmonic series expansion corresponding to a half-wavelength of ~100 km. 6 Prominent satellite-derived Bouguer anomaly lows image thick crust beneath the Vostok Province, the Gamburtsev Province, the hinterland of Dronning Maud Land and the The Lambert Rift, Aurora and Wilkes subglacial basins, and Coats W W W. N A T U RTransantarctic E. C O M / N A T U RMountains. E Land are marked by more positive anomaly values that have been previously modelled as

7 Prominent satellite-derived Bouguer anomaly lows image thick crust beneath the Vostok Province, the Gamburtsev Province, the hinterland of Dronning Maud Land and the Transantarctic Mountains. The Lambert Rift, Aurora and Wilkes subglacial basins, and Coats Land are marked by more positive anomaly values that have been previously modelled as arising from relatively thinner crust 59. The black rectangle denotes the area of panels b and c. b, Location of our 10 2D forward gravity models (thick black lines) that were calculated to estimate crustal thickness beneath the Gamburtsevs region and adjacent East Antarctic Rift System (Figure 2d in main text) superimposed on subglacial topography. Dots with numbers refer to crustal thickness (in km) derived from independent seismic receiver functions 4,20 that were used as tie points for our gravity models. aa and bb denote the location of the two selected gravity models shown in Figure 3 in the main text and Figures S5 and S6. c, Location of the gravity models superimposed on the combined low-pass filtered airborne gravity (50 km wavelength) and satellite gravity anomaly grid for central East Antarctica. Note the NE-SW grain in the Bouguer gravity lows imaged from airborne gravity data over the Gamburtsev Subglacial Mountains (that is ~parallel to the aeromagnetic fabric) and the linear Bouguer anomaly highs over the proposed rift basins of the East Antarctic Rift System. 7

8 Supplementary Figure 5. Two-dimensional gravity model along selected E-W profile across the Gamburtsev Subglacial Mountains. Our preferred gravity models require that the thick crustal root independently imaged from S-wave receiver function analysis under the Gamburtsevs 4 is anomalously high density in its lower part. The upper panel shows that for a normal lower crustal density of ~2900 kg/m 3 a large misfit occurs between calculated and observed gravity anomalies. The best fit in this and other E-W models was obtained for a high density of 3275 kg/m 3 with values of 3200 kg/m 3 and above falling within our data resolution threshold (see also Supplementary Table 1). Note that for the eastern part of the model we used geometries and apparent densities from previous gravity and flexural models across the Vostok Subglacial Highlands and Lake Vostok 18. In this configuration, in addition to significant differences in crustal thickness, a contrast in upper mantle density is also required beneath the Gamburtsev and Vostok provinces. 8

9 Supplementary Figure 6. Two-dimensional gravity model along selected N-S profile across the Gamburtsev Subglacial Mountains. This gravity model was calculated along the GAMSEIS N-S profile 4 and helps, together with other N-S oriented models, to delineate the extent of the high-density lower crustal body under the Gamburtsevs. As in the E-W cases a density of 3275 kg/m 3 yielded the best fit. Relatively lower densities of 3200 kg/m 3 are permissible even without significantly altering upper crustal apparent densities. The residual misfits over the northern part of the Gamburtsevs likely require additional intracrustal bodies that are not modelled here. 9

10 11 Supplementary Figure 7. Location and extent of the high-density lower crustal root beneath the Gamburtsev Subglacial Mountains. Map view of the high density part of the lower crustal root beneath the Gamburtsev Province overlain on the subglacial topography grid. The map was derived by gridding the results of the 10 2D forward gravity models. Note that the thickest part of the high density root (~10 km or more) lies beneath the inferred Gamburtsev Suture, and that the dense root does not appear to extend beneath the southern part of the Gamburtsevs. 10

Supplementary Figure 8. Schematic of 3D inversion used to estimate Te variations for the Gamburtsev Subglacial Mountains and adjacent East Antarctic Rift System.

11 Supplementary Figure 8. Schematic of 3D inversion used to estimate Te variations for the Gamburtsev Subglacial Mountains and adjacent East Antarctic Rift System. The modelling was carried out using Lithoflex software ( with the parameters indicated in the schematic. Surface loads for the modelling included the rebounded topography (i.e. following the removal of the East Antarctic Ice Sheet) and the equivalent topography of the anomalously high density lower crustal root beneath the northern and central Gamburtsev Subglacial Mountains (Fig. S9). The Moho surface was derived from the 10 forward gravity models tied to independent receiver function analyses 4,18, 20 and expanded outside the aerogeophysical study area (to minimise edge effects) using unconstrained 3D inversion of satellite gravity anomalies over East Antarctica (Fig. S4a)

12 Supplementary Figure 9. Schematic showing conversion of high density lower crustal root into an equivalent topography load. For 3D Te modelling in Lithoflex we converted the high density lower crustal root grid shown in figure 7 into a grid of equivalent topography enabling us to incorporate the effect of the root into the calculations. 12

Supplementary Figure 10. Result of 3D inversion of Effective Elastic Thickness (Te) for the Gamburtsev Subglacial Mountains and adjacent East Antarctic Rift System.

13 Supplementary Figure 10. Result of 3D inversion of Effective Elastic Thickness (Te) for the Gamburtsev Subglacial Mountains and adjacent East Antarctic Rift System. The Te grid is overlain on the subglacial topography. It reveals that the thick and dense Precambrian crust that underlies the northern and central Gamburtsevs features high Te values in contrast to the lower values over the rifted regions. Such high Te values are characteristic of most unreworked Precambrian cratonic regions worldwide and the observed heterogeneities and anisotropies along province boundaries are broadly similar to those modelled in other Archean-Protetozoic shields (e.g. in the Canadian Shield) 54. Intermediate values are found over the inferred Proterozoic foreland basin of the Vostok Province 18. Note that the East Antarctic Rift System wraps around the more rigid crustal provinces. 13

Supplementary Figure 11. a, Crustal structure and flexural loads along the selected EW and NS profiles crossing the Gamburtsevs rift flank. The assumed plate breaks are shown in grey.

14 Supplementary Figure 11. a, Crustal structure and flexural loads along the selected EW and NS profiles crossing the Gamburtsevs rift flank. The assumed plate breaks are shown in grey. b, Load from the buoyant root, including the high-density lower crustal root (HLC-orange) and the normal root (grey). Load defined as crust to mantle density contrast. c, Mechanical unload 46, assuming a crustal thickness of ~50 km, and a normal fault dipping at 65 towards the rift. d, Erosional unload, assuming removal of 4 km of rock at the plate breaks 25 and decreasing linearly to zero at the highest topographic peak. e, Unload associated with additional valley incision (fluvial and glacial). f, Te structure used in uplift models

15 West-East (Gamburtsevs-Vostok) model Supplementary Table 1 Density of lower crustal body RMS Difference over GSM low (-240 mgal) South-North (Gambertsevs-Lambert) model Density of lower crustal body RMS Difference over GSM low (-256 mgal) Supplementary References 57. Goodge, J. W., and C. A. Finn. Glimpses of East Antarctica: Aeromagnetic and satellite magnetic view from the central Transantarctic Mountains of East Antarctica, J. Geophys. Res., 115, B09103, doi: /2009jb (2010). 58. Ferraccioli, F., E. Armadillo, T. Jordan, E. Bozzo, and H. Corr. Aeromagnetic exploration over the East Antarctic Ice Sheet: A new view of the Wilkes Subglacial Basin, Tectonophysics, 478, 62 77, doi: /j.tecto (2009). 59. Block, A.E., Bell, R.E., Studinger, M. Antarctic crustal thickness from satellite gravity: Implications for the Transantarctic and Gamburtsev Subglacial Mountains. Earth and Planet. Sci. Lett. 288, , (2009). 15

OZ SEEBASE TM. Datasets. Digital Elevation Model

OZ SEEBASE TM. Datasets. Digital Elevation Model Digital Elevation Model 10 Digital Elevation Models (DEM s) often show the youngest structures, and any active geological structures. They are widely used for neotectonic analysis. The composition of eroding