Joseph F. Mascarenas Karen J. Wenrich 1982 <p>The Hopi Buttes dominate the landscape north of Holbrook, Arizona, commonly rising to heights of 180 m above the surrounding countryside.&nbsp; The buttes are underlain by individual diatremes, or in some cases by a complex of diatremes.&nbsp; Some sediment-filled diatremes also crop out as inconspicuous low hills (some may also be buried beneath the alluvium).&nbsp; The diatremes erupted into the late Miocene-early Pliocene Hopi Lake.&nbsp; No region in the world is known to contain a greater density of diatremes than the Hopi Buttes, where more than 300 diatremes occur within about 2500 km²<span id="_mce_caret" data-mce-bogus="1" data-mce-type="format-caret">.&nbsp; The diatremes of the Hopi Buttes are somewhat unique; they, along with few others, most notably the Miocene diatremes of the Schwabian Alb, formed maars in which lacustrine sediments accumulated.&nbsp; These lacustrine sediments were the hosts for syngenetic uranium mineralization.&nbsp; The funnel-shaped vents are filled with limburgite tuff and tuff breccia, agglomerate, monchiquite dikes, necks, and flows, fine-grained clastic and carbonate rocks, and blocks of sedimentary rocks, especially the Wingate Sanstone, derived from the vent walls.</span></p> application/pdf 10.3133/mf1310 en U.S. Geological Survey Maps showing uranium-bearing diatremes of the Hopi Buttes, Arizona reports