Data Repository. GSA Data Repository Item

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1 GSA Data Repository Item Young, H.H., and Hilley, G.E., 2018, Millennial-scale denudation rates of the Santa Lucia Mountains, California: Implications for landscape evolution in steep, high-relief, coastal mountain ranges: GSA Bulletin, Data Repository TABLE DR1. NORMALIZED CHANNEL STEEPNESS TABLE DR2. CHANNEL STEEPNESS OF LITH. GROUPS TABLE DR3. CATCHMENT ESTIMATES OF K Figure DR1. DEM of Santa Lucia Mountains with sample sites plotted and log-transformed channel steepness data from sampled catchments overlaid. Plotted steepness data corresponds to steepness data shown in Table 2.

2 METHODS SUPPLEMENTARY INFORMATION Sample Processing Collected sediment was sieved to isolate the μm size fraction for processing following a procedure modified from Kohl and Nishiizumi (1992). Samples were soaked in 1:1 hydrochloric acid with trace amounts of hydrogen peroxide for at least one week to remove carbonates and iron oxides, then repeatedly rinsed with deionized water to remove residue and fines. Samples were divided into approximately 60 g sub-samples and leached four to seven times in 1 L of a 2.5% hydrofluoric acid and 3% nitric acid solution to remove accessory silicates and meteoric 10 Be. The sub-samples were heated and rotated on commercial grade hot dog rollers for eight hour intervals while leaching. Between each treatment, leachant was discarded and samples were rinsed with deionized water. For a subset of samples lithium metatungstate (LMT) was used for two rounds of heavy liquid separation of minerals prior to leaching. The LMT was mixed to produce densities greater and less than that of quartz (approximately 2.7 g/ml and 2.5 g/ml, respectively). Three leaches were then completed using 2.5%/3% hydrofluoric acid/nitric acid solution, and additional leaches used a 1.25% hydrofluoric acid and 1.5% nitric acid solution. Once sub-samples had been leached to reduce aluminum content below 100 mg per total dissolved sample, the remaining cleaned quartz was re-aggregated, dried, and mixed with approximately 1 mg of Be carrier for each sample. Concentrated hydrofluoric and nitric acids ware used to dissolve the samples in teflon beakers. Samples were evaporated to dryness and treated three times with aqua regia. Complete sample drying was repeated between applications. Dried samples were then dissolved in concentrated hydrochloric acid and a total sample aliquot was prepared for measurement of aluminum ppm in sample. Samples were dried down again,

3 dissolved in concentrated sulfuric acid, then transferred to platinum crucibles and heated to remove fluoro-silica compounds. After samples had again evaporated to dryness and cooled, they were dissolved in concentrated hydrochloric acid. The dissolved solutions were run through 10 ml anion exchange columns to separate the Be and Al and remove Fe, Mn, Mg, and Co. The Be and Al fractions were evaporated to dryness, treated with hydrogen peroxide, and re-dissolved in milliq water with trace amounts of hydrogen peroxide and sulfuric acid. Sample solutions were run through 10 ml cation exchange columns, separating the Ti, Be, and Al fractions. Be fractions were dried, re-dissolved with 6 N hydrochloric acid and beryllium hydroxide precipitated. The beryllium hydroxide was then loaded into quartz crucibles and fired in a tube furnace to produce beryllium oxide. The oxide was mixed with niobium and loaded into accelerator mass spectrometer (AMS) targets. Loaded targets were sent to Lawrence Livermore National Laboratory (LLNL) for AMS measurement. Results from LLNL were used to compute the ratio of 10 Be/gram of dissolved sample.

4 SUPPLEMENTARY TABLES θ = 0.3; (m 0.6 ) TABLE DR1. NORMALIZED CHANNEL STEEPNESS χ θ = 0.4; (m 0.8 ) χ

5 θ = 0.6; (m 1.2 ) TABLE DR1 CONT. NORMALIZED CHANNEL STEEPNESS χ θ = 0.7; (m 1.4 ) χ * Corresponds to Figures 2 & 3. L is number of lithologic categories slope-area data was extracted from for calculation of k sn. All five categories used for these k sn measurements. L is number of lithologic categories slope-area data was extracted from for calculation of k sn. For these measurements of k sn, slope-are data was extracted from granitoid and granitic schist, sandstone, and Franciscan metasediments and serpentinite portions of drainage basins.

6 TABLE DR2. CHANNEL STEEPNESS OF LITH. GROUPS Basin k sn (m 0.8 ) ID * slope-area data from Gr, Ss, & Fr slope-area data from all lithologies slope-area data from Ms & Ls ** * Corresponds to Sample ID numerals in Figures 2 & 3 and Table 1, e.g. Samples 7a, 7b, and 7c are all from Basin 7. m = 0.4 and n = 1 and area-slope data from specified lithologies used to derive k sn. Gr: granitoid and granitic schist; Ss: sandstone; Fr: Franciscan metasediments and serpentinite. ** Ms: mudstone; Ls: limestone. TABLE DR3. CATCHMENT ESTIMATES OF K K from slope-area K from χ k sn K from spatially k sn (m 0.2 /yr) x 10-6 weighted slopearea (m 0.2 /yr) x 10-6 k sn (L = 5) K from spatially weighted slopearea k sn (L = 3) (m 0.2 /yr) x 10-6 (m 0.2 /yr) x ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± a 14.7 ± ± ± ± 1.2 7b 9.4 ± ± ± ± 1.9 7c 16.3 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.68 * Corresponds to Figure 1. L is number of lithologic categories slope-area data was extracted from for calculation of k sn. All five categories used for these k sn measurements. L is number of lithologic categories slope-area data was extracted from for calculation of k sn. For these measurements of k sn, slope-are data was extracted from granitoid and granitic schist, sandstone, and Franciscan metasediments and serpentinite portions of drainage basins.

7 36 o 30 o 122 0'0"W 22 N 36 30'0"N W 0 1 N '0"W 122 0'0"W 122 0'0"W o 2 12 W '0"N 36 0'0"N 36 o 0 N 36 0'0"N 121 0'0"W '0"W Log10(ksn) (m) '0"W o W '0"N o Drainage divide Esri, DeLorme, GEBCO and other contributors N 121 0'0"W '0"W Kilometers 5 0 Sample site 10 Kilometers