Pliocene diatoms from the Bryce Canyon Area, Utah

Abstract

The diatomite deposits were collected at 6,650 foot elevation near Hillsdale (vicinity of Bryce Canyon National Park), Utah, Preliminary investigation showed that the deposits were of pliocene age and probably equivalent to the Salt Lake group of northern Utah. Twelve genera showed that the lake was at first fresh but later became brackish as indicated by the presence of @iCocconeis lineata@@ Ehrenberg and @iSurirella craticula@@ (= @iStictodesmis craticula@@) which are characteristic of such a habitat. The fragmentary condition of these indicated agitation during sedimentation. The ratio between the planktonic and benthonic diatoms indicated near-shore deposition. The two extinct species (?), @iSurirella craticula@@ (= @iStictodesmis craticula@@) and @iNavicula@@ sp. n. sp., and @iDiatomella balfourinana@@ (= @iGrammatophora marina@@, a rare species, were recognized. Most of the species identified are modern forms living today, while three of them are fossil forms