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Supplemental material: A new model for Quaternary lava dams in Grand Canyon based on 40Ar/39Ar dating, basalt geochemistry, and field mapping

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journal contribution
posted on 27.08.2015 by Ryan S. Crow, Karl E. Karlstrom, William McIntosh, Lisa Peters, Laura Crossey, Athena Eyste
Geosphere, October 2015, v. 11, p. 1305-1342, doi:10.1130/GES01128.1, Supplemental File - Supplemental File. Supplemental text, 8 supplemental figures, and 11 supplemental tables. Supplemental Figures: (1) Preliminary geologic map of volcanic features in western Grand Canyon. (2) Graph showing incision rates variations due to fault offset and fault-related flexures from Karlstrom et al. (2007). These incision rates were used to estimate the original thickness of dam. (3) Step-heated spectra for the newly reported 40Ar/39Ar ages. (4) Reverse isochrons for the newly reported 40Ar/39Ar ages. (5) Rare-earth element (REE) signatures from duplicate analyses from this study (A) and Fenton et al. (2004) and Fenton (2002). (C). B, D, E, and F compare results from this study and Fenton et al. (2004). (6) Equal area plots of paleomagnetic data. (A) Data for remnants of the Lower Black Ledge flow between river mile (RM) 194 and 253. Consistent paleomagnetic directions support the theory that all of these remnants were part of the same flow. (B) Data for Vulcans Anvil and a nearby sill. The consistent paleomagnetic directions of these two samples suggest that Vulcan?s Anvil has not rotated significantly. (C) Data from the 183.4-mile remnant. The consistent paleomagnetic directions that are very close to the present-day axial dipole direction (shown in all plots by the black circle) indicate that the 183.4-mile remnant has not rotated significantly. However, it may have slumped down without rotating—see text. (7) (A) Graph showing the reservoir capacity of dams of various heights sited at Lava Falls based on modern topography. (B) Graph showing the time needed to completely fill those reservoirs with sediment assuming the historic sediment accumulation rate measured in Lake Mead from 1935 to 1963 (Ferrari, 2008). (C) Graph showing the time needed to completely fill those reservoirs with water assuming the historic Grand Canyon discharge from 1923 to 1962. (8) Representative demagnetization behavior. On the left, vector component diagrams are plotted, and on the right, the corresponding magnetic intensity (J/J0) is plotted. In the vector component diagrams, the least squares linear fit with decay to the origin is indicated by pale arrows. (A) Graph shows the behavior for core sample A1314- 1A; (B) shows the behavior for core sample A1314-7C; and (C) shows the behavior for core sample A1314-8D. Supplemental Tables: (1) 40Ar/39Ar data tables. (2) X-ray fluorescence (XRF) data. (3) Duplicate XRF analyses from the same sample. (4) Duplicate XRF analyses on the same remnant. (5) Inductively coupled plasma mass spectrometer (ICPMS) data. (6) Duplicate ICPMS analyses from the same sample. (7) Duplicate ICPMS analyses from the same remnant. (8) Duplicate ICPMS analyses from Fenton et al. (2004) and Fenton (2002). (9) Individual paleomagnetism core data. (10) Mean paleomagnetism core data. (11) Summary of analytical setup for 40Ar/39Ar dating including blank values and sensitivities for different analyses. File size is ~24 MB.

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