Axelrod: The Pliocene Verdi Flora of Western Nevada 



107 



Coal Valley rocks. Judging from the evidence of age, as discussed below, altera- 

 tion probably took place near the transition from Early to Middle Pliocene time. 

 5. The northwesterly trending basin fault appears to have been active in the 

 Lower and Middle Pliocene, and more recently as well. The prominent north- 

 westerly trending set may be as old as Late Pliocene to Early Pleistocene, but the 

 younger northeasterly trending set may be Late Pleistocene. 



COMPOSITION OF THE FLORA 



The Verdi flora is now known to include 19 species, distributed among 12 genera and 

 10 families. Three of the plants are herbaceous aquatics, including a thallophyte 

 (Chara), a monocotyledon (Potamogeton) , and a dicotyledon (Nymphaeites) . The 

 remaining 16 are woody, comprising 4 conifers and 12 dicotyledons. 



Systematic List of Species 



Characeae 



Chara verdiana new species 



Pinaeeae 



Abies coneoloroides Brown 

 Pinus florissanti Lesquereux 

 Pinus prelambertiana new species 

 Pinus pretuberculata Axelrod 



Naiadaceae 



Potamogeton verdiana new species 



Salicaceae 



Populus alexanderi Dorf 

 Populus pliotremuloides Axelrod 

 Populus subwashoensis Axelrod 

 Salix boisiensis Smith 

 Salix truckeana Chaney 



Fagaceae 



Quercus prelobata Condit 



Quercus renoana new species 



Quercus wislizenoides Axelrod 

 Nymphaeaceae 



Nymphaeites nevadensis (Knowlton) Brown 

 Grossulariaeeae 



Bibes galeana new species 

 Bosaeeae 



Prunus moragensis Axelrod 

 Bhamnaceae 



Ceanothus precuneatus Axelrod 

 Ericaceae 



Arctostaphylos verdiana new species 



The fossils are represented chiefly by leaf impressions, though conifer needles, 

 cones, and cone-scales form an important part of the record. Judging from the 

 relative abundance of the Verdi specimens, as shown in table 1, leaves of the 

 common Pliocene Cottonwood Populus alexanderi account for over 90 per cent of 

 the material. If we add to this figure the data for the other common riparian 

 species, aspen (Populus pliotremuloides) and willow (Salix truckeana) , stream- 

 border plants comprise 95 per cent of the collection. It is apparent that species 

 representing forest and woodland vegetation are subordinate in the Verdi flora. 



The table 1 shows that aside from the dominant cottonwood, three of the conifers, 

 Abies coneoloroides, Pinus florissanti, and P. pretuberculata are rather common in 

 the flora. In the absence of other evidence, one might suppose that they were living 

 as close to the site of deposition as the species of cottonwood, aspen, and willow, 

 which have a generally similar quantitative record. If these forest trees had lived 

 in moderate numbers near the Verdi site, their usual forest associates should also 

 have a fair representation in the flora ; however, all of them are quite rare. Fur- 

 thermore, many of the common species in related living forests are not now known 

 to have fossil equivalents in the flora. They might well be expected there if forests 

 had occupied sites near at hand. 



The mode of occurrence of the conifers in the Verdi sediments gives a clue to 



