Ash-flow tuffs in the Nine Hill, Nevada, paleovalley and implications for tectonism and volcanism of the western Great Basin, USA

Cenozoic ash-flow tuffs are key units for analyzing the tectonic and magmatic evolution of the Great Basin. The tuffs are commonly assumed to have spread nearly radially from source calderas and to have formed nearly continuous, flat-lying deposits. Based on detailed mapping and paleomagnetic investigations of the Nine Hill paleovalley in western Nevada and analysis of the regional distribution of the 27–23 Ma tuffs that crop out in the paleovalley, we find numerous features that differ markedly from these presumed characteristics.