Martin G. Miller, Richard M. Friedman; Early Tertiary magmatism and probable Mesozoic fabrics in the Black Mountains, Death Valley, California. Geology ; 27 (1): 19–22. doi: https://doi.org/10.1130/0091-7613(1999)027<0019:ETMAPM>2.3.CO;2
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We report two early Tertiary U-Pb zircon ages for pegmatite from the Black Mountains of Death Valley, California. These ages, 54.7 ± 0.6 Ma and 56 ± 3 Ma, are unique for much of southeastern California. The samples belong to a pegmatite suite that occupies part of the footwall of the Badwater turtleback, a late Tertiary extensional feature; similar but undated pegmatite intrudes the footwalls of the Copper Canyon and Mormon Point turtlebacks farther south. The pegmatite suite demonstrates that fabric development on the turtlebacks was at least a two-stage process. Fabrics cut by these pegmatites likely formed during the Mesozoic, whereas those that involve them formed during late Tertiary extension.