Data repository information accompanying Hoke et al. “Can Quaternary pedogenic car-bonates be used to estimate modern elevations?”

Sample locations and collection

All of the samples collected for this study are from on or near Argentine National Route 7, and Chilean Rte 60. These are the highways that comprise the international pass between the two countries. We exploited natural and man-made exposures of conglomerates and soils (figure DR2 and DR3). Individual conglomerate clasts were removed from the expo-sures and oriented with their up direction to ensure that only carbonate from the bottom of the clast was sampled and analyzed in the laboratory.

Figure DR1. A) Map of the Río Aconcagua and Río Mendoza watersheds. Thin gray lines are simplified 1000 m elevation contours. The watershed outline, ma-jor river branches, sub-bains and simplified 1000 m contours are all derived from STRM 90 m digital topography. The river networks shown in each are color coded according to drainage area. The sub-basins shown represent the areas upstream of each sampled tributary and are color coded according to drainage area (da): light blue basins have da ≤10 km2, red basin have da >10 km2 and ≤ 50 km2, yellow basins >50 km2 and ≤100 km2 and gray basin are >100 km2 . The boundary between the basins is also the international border between Argentina and Chile. River water sample locations are shown by filled circles and authigenic carbonates with filled triangles.

Hoke et al. dr1 p.1GSA DATA REPOSITORY 2009256

Figure DR2. Stage I carbonate carbonate crusts developed on con-glomerate clasts at the mods-08-05 sample site. Argentine one-peso (23 mm diameter) coin for scale.

Figure DR3. Stage I carbonate nodules from sample rt60-1500 (white spots between the three boulders in the center of the photo. Red marks on the tape measure are 10 cm intervals.

Hoke et al. dr1 p.2GSA DATA REPOSITORY 2009256

Data and analytical methods

Water samples

Water samples were collected in 15 ml vials sealed by teflon tape and secured with elec-trical tape to prevent sample leakage or evaporation. All samples were refrigerated until analysis.

We chose to exclude the three lowest elevation samples from the Río Aconcagua with anomalously negative d18Orw values. All the relatively level land area below 1.2 km elevation is cultivated and irrigated with water derived from the high Andes. Based on their d18O values, two samples are of such irrigation water and one was mistakenly collected from a river with >1000 km2 drainage area. Similarly, we exclude two samples from the Río Mendoza watershed; one drainage basin is larger than 100 km2, and another contains sediment laden water with an anomalously positive d18O values collected during a snow squall at 3.2 km.

Analyses are run on a Thermo Electron Corporation Finnegan Delta plus XP mass spec-trometer in continuous-flow mode via the Thermo Electron TC/EA peripheral and a GC-PAL autosampler.

Approximately 200 nL of sample water is directly injected the TC/EA. The reactor is set at a temperature of 1450 degrees Celsius and the GC oven is set at 90 degrees Celsius.

Reporting of Stable Hydrogen and Oxygen Isotope Ratios: Hydrogen and oxygen isotopic results are reported in per mill relative to VSMOW (Vienna Standard Mean Ocean Water) and normalized (Coplen, 1994) on scales such that the hydrogen and oxygen isotopic val-ues of V-SMOW are 0.0 per mill and 0.0 per mill, respectively, and the hydrogen and oxy-gen isotopic values of SLAP are -428 per mill and -55.5 per mill, respectively.

The 2-sigma uncertainties of hydrogen and oxygen isotopic results are 2.4 per mill and 0.20 per mill, respectively, unless otherwise indicated. This means that if the same sample were resubmitted for isotopic analysis, the newly measured value would lay within the un-certainty bounds 95 percent of the time.

Carbonate samples

Analyses are run on a Thermo Electron Corporation Finnegan Delta plus XP mass spec-trometer in continuous-flow mode via the Thermo Electron Gas Bench peripheral and a GC-PAL autosampler.

Samples are loaded into 4mL tubes with piercable, self-healing rubber septa with PTFE liners. Tubes are then flushed with UHP helium (our standard carrier gas) at about 100 mL/minute for 10 minutes. 100% phosphoric acid is injected through the septum, either through the use of the GC-PAL and an acid pump, or manually with at 16-gauge needle and syringe. All samples are vortexed to insure complete mixing of the sample and the acid.

Tubes are loaded into a block heated to 69 degrees Celsius. Carbonate samples react for at least one hour but never more than 12 hours before they are analyzed. Carbon Dioxide

Hoke et al. dr1 p.3GSA DATA REPOSITORY 2009256

gas evolved from the reaction of the acid with the carbonate is then drawn into the instr ment for analysis.

Reporting of Stable Carbon and Oxygen Isotope Ratios Carbon and oxygen isotopic re-sults are reported in per mill relative to VPDB (Vienna Pee-Dee Belemnite) and normalized (Coplen, 1994) on scales such that the carbon and oxygen isotopic values of NBS-19 are 1.95 per mill and -2.2 per mill, respectively, carbon and oxygen isotopic values of NBS-18 are -5.01 per mill and -23 per mill, respectively, and the carbon isotopic value of L-SVEC is -46.6 per mill.

The 2-sigma uncertainties of carbon and oxygen isotopic results are 0.12 per mill and 0.20 per mill, respectively, unless otherwise indicated. This means that if the same sample were resubmitted for isotopic analysis, the newly measured value would lay within the un-certainty bounds 95 percent of the time.

Hoke et al. dr1 p.4GSA DATA REPOSITORY 2009256

Hoke et al. dr1 p.5GSA DATA REPOSITORY 2009256

Temperature corrections for carbonate data

We determined an atmospheric lapse rate of 6.25°C/km for the eastern side of the Andes using station data available on the internet (in Spanish) from the Argentine Meteorological Service (Servicio Meteorológco Naciónal, http://www.smn.gov.ar/). We determined the av-erage annual temperature from monthly averages reported for 4 stations, Mendoza, Uspal-lata, Puente del Inca, and Cristo Redentor.

Figure DR4. Best-fit line between mean annual temperature and elevation for the Eastern half of the Andes at ~33°S.

Hoke et al. dr1 p.6GSA DATA REPOSITORY 2009256

Topographic analysis and drainage network analysis.

We used 3 arc-second resolution Shuttle Radar Topography Mission (SRTM) digital eleva-tion model (DEM) (http://www2.jpl.nasa.gov/srtm/) to analyze the Aconcagua and Mendoza Rivers. The standard hydrologic tools and procedures in the Spatial Analyst® extension of ArcGIS® were used to extract the main basins and sub-basins from the DEM. The result-ing drainage network was classified by increments of drainage area that were later used to accurately guide field sampling of basins with drainage areas of less than 100 km2. Drain-age area were classified according to the following groups: 0-10 km2, 10-50 km2,50-100 km2, 100-500 km2, 500-1000, 1000-10,000, etc.

Upon completion of field sampling we calculated, max, mean, and the average elevation of the contributing area of all samples upstream from the sampling point. These parameters are shown in Table dr2. Relevant files are available from the authors upon request.

Error analysis:

In order to estimate uncertainty in our elevation estimates we used the uncertainties from the statistical analysis or assigned a reasonable range on each parameter used to calcu-late elevations. Using a random number generator we explored 1000 random variations across the entire set of parameters and used the standard deviation all the combinations as a measure of the uncertainty in our elevation estimates.

References:

Coplen, T. B., 1994, Reporting of stable hydrogen, carbon, and oxygen isotopic abun-dances, Pure and Applied Chemistry, 66, 273-276.

IAEA/WMO (2006). Global Network of Isotopes in Precipitation. The GNIP Database. Ac-cessible at http://isohis.iaea.org

Hoke et al. dr1 p.7GSA DATA REPOSITORY 2009256