NATURE OF BEDROCK 295 



THE BEDROCK COMPLEX 



General composition and character. — The bedrock complex, so far as 

 known, consists of marine sediments of Triassic or Jurassic age, with an 

 occasional area of a granular intrusive. The rocks are, in general, folded, 

 sometimes strongly plicated, faulted, and partially altered by dynamic 

 action. 



Lithological character. — The great bulk of the bedrock complex consists 

 of marine sediments now in the form of shales or slates, limestones, and 

 quartzites. The Triassic group consists chiefly of shale or slate and im- 

 pure shaly gray or drab to black limestones, with here and there a thin 

 layer of quartzite, which may, however, occasionally reach several hun- 

 dred feet in thickness. Not infrequently a yellow or buff limestone 

 occurs, carrying plentiful cubes of pyrite one-sixteenth to one-fourth 

 inch on the edge. Gypsum appears irregularly, sometimes in thick 

 lenses, as, for example, some 4 miles east of Lovelock, on the west flank 

 of the range. Coarse oolitic and brecciated limestones occur to the 

 southeast of Lovelock. Rarely a pure white marble can be found. 



The Jurassic is chiefly gray to greenish gray slate, with subordinate 

 limestone. 



No attempt was made to measure the thickness of these groups of 

 rocks, for in no place could they be seen in even approximately com- 

 plete section. The Triassic is, however, much thicker than the Jurassic, 

 and areally is much more important. 



The rocks of the Humboldt Lake mountains are quite barren of fos- 

 sils. Several fossiliferous horizons have, however, been found in Muttle- 

 berry canyon which allow of definite age determinations. The most 

 abundant Triassic species is Pseudomonotis subcircularis, which is found 

 either alone or associated with other forms. At the richest locality in 

 Muttleberry canyon, Professor J. P. Smith has determined Pseudomonotis 

 subcircularis Gabb, Arcesles sp. nov., Rhabdoceras russelli Wyatt, Placites, 

 sp. nov. and other characteristic forms. He considers them to indicate 

 the Noric horizon of the Upper Trias, At the Muttleberry summit a 

 limestone carries Arietites sp. nov. which Smith considers undoubted 

 Jurassic. The Jurassic strata are apparently unconformable above the 

 Triassic. These formations have been most thoroughly studied, how- 

 ever, in the northern part of the Star Peak group, where fossils are quite 

 abundant. Triassic fossils were reported and described by the California 

 Geological Survey and the Fortieth Parallel Survey, in the sixties and 

 seventies. Recently the localities have been studied by Professor Smith 

 as to their invertebrates, and Professor Merriam has collected and de- 

 scribed good specimens of Ichthyopterygia. No Cretaceous or pre-Triassic 



