Supplementary File B. Plate Reconstructions and Kinematics

Supplementary file B. Plate Reconstructions and Kinematics

In this study, the reconstructed kinematics of the South American plate’s interaction with the Nazca and Farallon plates is derived by ordered combinations of spline-interpolated plate reconstructions acrossfive accretionary (seafloor spreading) boundaries, at 2.5 m.y. intervals, from Present to 80 Ma. The accretionary boundaries include the Nazca (NZ, ~25 Ma and younger) and Farallon (FA~25 to 80 Ma) plates relative to the Pacific (PC) plate, Pacific to the West Antarctic (WA) plate, West Antarctic to the East Antarctic (EA) plate, East Antarctic to African (AF) plate, and African to South American (SA) plate.

Available reconstruction sequences across each spreading ridge may not necessarily consist of identical magnetic anomaly isochrons (“chrons”) from ridge to ridge; therefore interpolation of reconstructions across each spreading ridgesis undertaken so as to calculate the total reconstructions at the constant time interval. Most previous interpolation methods typically include 1) assumptions of constant spreading parameters (rotation pole and angular rate) between sequential reconstructions, or, less commonly, 2) cubic spline interpolation at regular time intervals (e.g., Pilger, 2003, 2007; Wessel and Kroenke, 2008). The former method, while more easily calculated, has the disadvantage of forcing changes in spreading direction and/or rate to coincide with identified chrons; analysis of the spreading process (e.g., Atwater and Menard, 1968) and inspection of interpreted chron and transform fault patternsindicate that the more clearly identified chrons correspond with periods of nearly constant local spreading direction, in other words.Spline interpolation may result in better characterisation of the plate kinematics; as a side effect, the time derivatives of each splined rotation parameter can be used for extraction of continuous instantaneous parameters (Pilger, 2003). Cande and Kent (1992, 1995) used spline interpolation of magnetic anomaly profiles (distance versus age) as part of their reconstruction of the geomagnetic time scale; Gradstein et al. (2004), expanded spline fits to their revised geomagnetic and geologic time scale as well.

For this study the primary splined, interpolated, and combined rotations and the derivative instantaneous kinematics use the 2004 geomagnetic time scale of Gradstein et al. (2005). Table 1 presents source reconstruction parameters and Table 2 the interpolated reconstruction parameters for each spreading ridge within the circuit. In Table 3 the derived parameters for the South America-Nazca reconstructions together with derived instantaneous convergence parameters of the Nazca and Farallon plates relative to South America, calculated at discrete points along the submarine plate boundary (mostly the Peru-Chile trench). Fig. 1 illustrates original and interpolated parameters; Fig. 2 displays digitized selected points (filled squares) of the Nazca-South American plate boundary used for calculations in Figures 3-6 of the convergence calculations versus age: 3.total convergence rate; 4.convergence angle (90° is normal to the plate boundary); 5. Convergence rate normal to the plate boundary; and 6. (shear) convergence component parallel with the plate boundary.

Discussion of Kinematic Calculations

The calculations produce variations in total convergence rate (Fig. 3) between the South American and Nazca plates with two major relative peaks at ~47 Ma and ~20 Ma. A small peak at ~26-27 Ma, followed by a dip at ~24-25 Ma may record the break-up of the central and southern Farallon plate into the Cocos and Nazca plates (approximately the same time as the first impingement of the Pacific plate on North America, forming the Proto-San Andreas fault connecting the nascent Cocos and northern Farallon plates; Pilger and Henyey, 1979).The fine scale variations between 38 and 45 Ma might represent slight errors in the geomagnetic timescale (calculations using the timescale of Cande and Kent, 1995, demonstrate similar fluctuations). Alternatively, incorporation of finer scale reconstructions such as those of Croon et al. (2008; for the Pacific and West Antarctic plates) across the other accretionary plate sets and greater refinement of the geomagnetic time scale might prove the variations are actual spreading rate fluctuations.

The remaining figures showing convergence azimuth (Fig. 4), normal components (Figure 5), and shear components (Fig. 6).The variations in shear motion may also correlate with recognized wrench faults, such as the Atacama.

One important consideration in evaluating the convergence calculations is that the Nazca/Farallon plate may not be the only plate to interact with the South American plate. For example, the Phoenix plate may have been subducted beneath the southern and, perhaps central, Andes in early to mid-Cenozoic time (e.;g., Eagles and Scott, submitted; Eagles et al., 2009).

Tables

Table 1.Source plate reconstruction parameters.

Initial Rotations:
Age (Ma) / Longitude / Latitude / Angle|Rate / Reference
South America-Central Africa
0.000 / -39.000 / 60.900 / 0.295 / DeMets et al. (2010)
9.740 / -40.590 / 62.050 / 3.180 / Müller et al. (1999)
19.048 / -37.320 / 58.770 / 7.050 / Müller et al. (1999)
25.823 / -36.270 / 57.590 / 9.960 / Müller et al. (1999)
33.058 / -33.640 / 56.170 / 13.410 / Müller et al. (1999)
38.426 / -33.000 / 57.100 / 15.910 / Müller et al. (1999)
46.264 / -31.150 / 56.950 / 19.110 / Müller et al. (1999)
52.364 / -31.180 / 58.890 / 21.380 / Müller et al. (1999)
55.904 / -32.210 / 61.350 / 22.270 / Müller et al. (1999)
65.578 / -33.610 / 63.880 / 24.760 / Müller et al. (1999)
71.071 / -33.380 / 63.410 / 26.570 / Müller et al. (1999)
79.075 / -34.360 / 62.920 / 30.990 / Müller et al. (1999)
83.000 / -34.260 / 61.880 / 33.510 / Müller et al. (1999)
East Antarctica-Central Africa
0.000 / -34.300 / -6.200 / 0.158 / DeMets et al. (2010)
9.880 / -49.400 / 8.200 / 1.530 / Royer and Chang (1991)
20.131 / -47.900 / 10.700 / 2.780 / Royer and Chang (1991)
33.058 / -48.400 / 12.000 / 5.460 / Royer and Chang (1991)
39.552 / -41.400 / 13.600 / 7.470 / Bernard et al. (2005)
50.946 / -40.800 / 8.500 / 10.010 / Bernard et al. (2005)
63.067 / -49.600 / 11.300 / 11.100 / Bernard et al. (2005)
75.500 / -40.900 / -4.000 / 14.030 / Bernard et al. (2005)
76.300 / -40.600 / -4.600 / 14.390 / Bernard et al. (2005)
83.000 / -40.010 / -0.450 / 17.770 / Nankivell(1998)
West Antarctica-East Antarctica
0.000 / -17.850 / -18.150 / 0.000 / Granot et al. (2013)
10.000 / -17.850 / -18.150 / 0.000 / Granot et al. (2013)
20.000 / -17.850 / -18.150 / 0.000 / Granot et al. (2013)
25.000 / -17.850 / -18.150 / 0.000 / Granot et al. (2013)
26.189 / -17.850 / -18.150 / 0.000 / Granot et al. (2013)
33.545 / -17.850 / -18.150 / 0.700 / Granot et al. (2013)
43.789 / -17.850 / -18.150 / 1.700 / Granot et al. (2013)
52.663 / -17.850 / -18.150 / 1.700 / Granot et al. (2013)
61.098 / -17.850 / -18.150 / 2.200 / Granot et al. (2013)
65.000 / -17.850 / -18.150 / 2.200 / Granot et al. (2013)
70.000 / -17.850 / -18.150 / 2.200 / Granot et al. (2013)
80.000 / -17.850 / -18.150 / 2.200 / Granot et al. (2013)
Pacific-Nazca
0.000 / -87.800 / 55.900 / 1.311 / DeMets et al. (2010)
0.783 / -90.500 / 48.120 / 1.056 / Wilder (2003)
3.040 / -88.200 / 53.800 / 4.300 / Wilder (2003)
6.567 / -94.660 / 54.380 / 9.680 / Wilder (2003)
8.862 / -93.640 / 58.230 / 13.180 / Wilder (2003)
10.949 / -93.270 / 60.010 / 16.860 / Wilder (2003)
13.065 / -92.790 / 62.000 / 19.630 / Wilder (2003)
15.095 / -96.390 / 64.520 / 23.100 / Wilder (2003)
17.446 / -90.730 / 72.220 / 26.490 / Wilder (2003)
24.058 / -91.020 / 59.680 / 38.450 / Wilder (2003)
24.730 / -91.140 / 61.150 / 38.880 / Wilder (2003)
28.283 / -97.390 / 65.600 / 43.830 / Wilder (2003)
30.709 / -99.890 / 67.100 / 46.900 / Wilder (2003) and Muller et al. (2008)
33.058 / -100.860 / 68.660 / 49.750 / Wilder (2003) and Muller et al. (2008)
39.552 / -101.720 / 75.650 / 55.940 / Wilder (2003) and Muller et al. (2008)
47.906 / -107.950 / 81.430 / 65.840 / Wilder (2003) and Muller et al. (2008)
55.904 / -134.680 / 87.290 / 73.770 / Wilder (2003) and Muller et al. (2008)
67.735 / -194.280 / 88.210 / 82.210 / Wilder (2003) and Muller et al. (2008)
83.000 / -242.250 / 86.550 / 95.130 / Wilder (2003) and Muller et al. (2008)
Pacific-Farallon
0.000 / -142.200 / 0.600 / 0.625 / DeMets et al. (2010)
9.880 / -89.750 / 60.110 / 14.880 / Muller et al. (2008)
23.069 / -92.610 / 73.530 / 31.080 / Muller et al. (2008)
33.058 / -110.700 / 76.100 / 45.270 / Muller et al. (2008)
40.130 / -122.970 / 82.190 / 52.240 / Muller et al. (2008)
47.906 / -160.160 / 85.240 / 62.780 / Muller et al. (2008)
55.904 / -224.560 / 84.280 / 71.470 / Muller et al. (2008)
67.735 / -234.180 / 82.930 / 80.170 / Muller et al. (2008)
83.000 / -240.240 / 81.350 / 93.370 / Muller et al. (2008)
Pacific-West Antarctica
0.000 / -78.500 / 65.900 / 0.887 / DeMets et al. (2010)
0.781 / -81.212 / 64.303 / 0.676 / Croon et al. (2008)
1.860 / -81.138 / 64.901 / 1.606 / Croon et al. (2008)
2.150 / -81.225 / 65.204 / 2.227 / Croon et al. (2008)
3.580 / -81.165 / 65.897 / 3.109 / Croon et al. (2008)
4.180 / -80.533 / 66.624 / 3.702 / Croon et al. (2008)
5.105 / -80.658 / 66.909 / 4.480 / Croon et al. (2008)
5.894 / -81.081 / 67.091 / 5.211 / Croon et al. (2008)
6.567 / -81.202 / 67.331 / 5.808 / Croon et al. (2008)
8.072 / -80.540 / 68.162 / 6.830 / Croon et al. (2008)
8.862 / -79.969 / 68.833 / 7.639 / Croon et al. (2008)
9.740 / -78.566 / 69.707 / 8.417 / Croon et al. (2008)
10.949 / -77.813 / 70.356 / 9.481 / Croon et al. (2008)
12.243 / -76.115 / 71.293 / 10.631 / Croon et al. (2008)
13.065 / -75.122 / 71.746 / 11.283 / Croon et al. (2008)
14.395 / -73.576 / 72.381 / 12.420 / Croon et al. (2008)
15.095 / -73.192 / 72.601 / 13.012 / Croon et al. (2008)
16.370 / -72.498 / 72.974 / 13.948 / Croon et al. (2008)
16.641 / -72.032 / 73.181 / 14.344 / Croon et al. (2008)
17.446 / -71.580 / 73.394 / 14.929 / Croon et al. (2008)
18.781 / -70.909 / 73.617 / 15.418 / Croon et al. (2008)
19.048 / -70.936 / 73.712 / 15.946 / Croon et al. (2008)
20.131 / -70.157 / 74.001 / 16.727 / Croon et al. (2008)
21.158 / -70.089 / 74.133 / 17.381 / Croon et al. (2008)
23.069 / -69.727 / 74.385 / 18.675 / Croon et al. (2008)
22.829 / -69.581 / 74.482 / 19.347 / Croon et al. (2008)
24.835 / -69.664 / 74.509 / 19.923 / Croon et al. (2008)
25.823 / -69.836 / 74.499 / 20.625 / Croon et al. (2008)
26.554 / -69.806 / 74.511 / 21.175 / Croon et al. (2008)
27.027 / -69.900 / 74.455 / 21.531 / Croon et al. (2008)
27.972 / -69.747 / 74.401 / 22.234 / Croon et al. (2008)
28.283 / -69.504 / 74.407 / 22.575 / Croon et al. (2008)
28.512 / -69.543 / 74.330 / 22.953 / Croon et al. (2008)
29.401 / -68.714 / 74.378 / 23.662 / Croon et al. (2008)
30.098 / -68.430 / 74.329 / 24.232 / Croon et al. (2008)
30.479 / -67.750 / 74.366 / 24.708 / Croon et al. (2008)
30.939 / -67.593 / 74.320 / 25.058 / Croon et al. (2008)
33.058 / -64.739 / 74.444 / 26.969 / Croon et al. (2008)
33.545 / -64.015 / 74.479 / 27.395 / Croon et al. (2008)
34.655 / -61.886 / 74.621 / 28.395 / Croon et al. (2008)
34.940 / -61.485 / 74.634 / 28.615 / Croon et al. (2008)
35.685 / -60.180 / 74.702 / 29.234 / Croon et al. (2008)
36.341 / -59.047 / 74.750 / 29.808 / Croon et al. (2008)
36.618 / -58.638 / 74.763 / 30.049 / Croon et al. (2008)
37.848 / -57.440 / 74.816 / 30.678 / Croon et al. (2008)
38.426 / -56.211 / 74.855 / 31.411 / Croon et al. (2008)
40.130 / -54.460 / 74.868 / 32.620 / Croon et al. (2008)
41.389 / -53.254 / 74.859 / 33.532 / Croon et al. (2008)
42.536 / -52.225 / 74.856 / 34.217 / Croon et al. (2008)
42.774 / -51.610 / 74.775 / 35.288 / Croon et al. (2008)
47.906 / -50.190 / 74.520 / 37.640 / Cande et al. (1995)
53.347 / -52.500 / 73.620 / 40.030 / Cande et al. (1995)
61.098 / -55.570 / 71.380 / 44.900 / Cande et al. (1995)
67.735 / -55.520 / 68.940 / 49.600 / Larter et al. (2002)
73.619 / -55.040 / 66.720 / 53.740 / Larter et al. (2002)
83.000 / -52.380 / 65.580 / 63.070 / Larter et al. (2002)

Table 2. Interpolated South American-Nazca rotations and derived instantaneous plate kinematic parameters.

Interpolated Rotations: / Instantaneous Rotations
Age (Ma) / Longitude / Latitude / Angle|Rate / Longitude / Latitude / Rate
0 / -99.273 / 54.949 / 0.673
2.5 / -98.121 / 39.496 / 1.351 / -99.273 / 54.949 / 0.673
5 / -98.554 / 54.212 / 3.936 / 82.435 / -25.197 / 0.719
7.5 / -101.838 / 53.075 / 6.215 / 81.163 / -60.941 / 2.781
10 / -99.229 / 57.926 / 8.884 / 73.273 / -52.322 / 2.339
12.5 / -96.688 / 59.754 / 11.148 / 93.057 / -68.337 / 2.669
15 / -101.677 / 62.621 / 14.013 / 97.77 / -65.472 / 2.221
17.5 / -95.109 / 74.952 / 16.593 / 49.953 / -72.298 / 2.924
20 / -86.88 / 66.079 / 20.683 / -125.186 / -56.952 / 4.165
22.5 / -87.32 / 55.45 / 25.794 / 98.872 / -38.17 / 4.215
25 / -88.152 / 60.141 / 26.742 / 83.54 / -8.304 / 6.044
27.5 / -93.863 / 63.852 / 29.023 / 112.317 / -82.976 / 3.139
30 / -99.453 / 65.683 / 30.658 / -59.403 / -65.882 / 3.638
32.5 / -104.594 / 67.37 / 32.039 / -30.217 / -63.91 / 2.616
35 / -111.748 / 69.613 / 33.504 / -46.611 / -63.385 / 2.096
37.5 / -122.364 / 72.832 / 35.273 / -61.222 / -54.267 / 2.283
40 / -135.564 / 74.907 / 36.93 / -77.842 / -47.709 / 2.849
42.5 / -146.8 / 75.881 / 39.231 / -77.925 / -42.259 / 2.74
45 / -156.077 / 76.368 / 41.665 / -73.372 / -59.903 / 2.993
47.5 / -164.727 / 76.99 / 44.635 / -59.482 / 33.293 / 2.919
50 / -176.601 / 77.424 / 47.32 / -116.327 / -83.56 / 6.459
52.5 / 169.737 / 77.056 / 49.595 / -106.307 / -70.781 / 5.357
55 / 158.104 / 75.672 / 51.545 / -94.849 / -34.866 / 3.577
57.5 / 150.648 / 73.81 / 53.255 / -89.877 / -23.084 / 3.512
60 / 146.79 / 72.028 / 54.782 / -86.733 / -30.144 / 3.15
62.5 / 145.255 / 70.462 / 56.222 / -81.115 / -36.019 / 2.525
65 / 145.224 / 69.097 / 57.787 / -69.49 / -35.396 / 1.94
67.5 / 145.929 / 67.849 / 59.723 / -52.685 / -31.592 / 1.731
70 / 146.633 / 66.697 / 62.154 / -42.724 / -33.67 / 2.012
72.5 / 147.112 / 65.611 / 64.934 / -41.944 / -41.136 / 2.58
75 / 147.249 / 64.527 / 67.65 / -44.12 / -44.901 / 3.027
77.5 / 147.031 / 63.393 / 69.848 / -49.188 / -43.307 / 3.036
80 / 146.797 / 62.223 / 71.232 / -57.355 / -35.629 / 2.648

Table 3.Derived rotation parameters among plates within the South American-Nazca reconstruction circuit.