One of the principal clastic units in the Roberts Mountains allochthon of north-central Nevada is the Elder Sandstone, which may have been deposited in or about Early Silurian time. Rock fragments in the Elder Sandstone were derived from Paleozoic carbonate rock, argillite, chert, quartzite, and intermediate to basic volcanic rock. Feldspar, zircon, and quartz probably were derived initially from Pre-cambrian crystalline rocks and were recycled into the Elder Sandstone from pre-Silurian supracrustal deposits. U-Pb isotopic data indicate that detrital zircons were derived initially from a source that may have included rocks ∼2.2 b.y. old. The location of the source of detritus in the Elder Sandstone is problematical, and there is nothing in the data presented here that precludes the possibility that detritus was derived from a foreign continent.

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