ROCKS OF THE PRE-CRETACEOUS SERIES. 85 



There is no doubt lliat tbcy all belonged originally to silicions organisms 

 of the radiolarian type, but that in the various nictaniorpbic actions to 

 which the rocks have been subjected the structure has been nearly if not 

 quite obliterated. This character was first noted by Dr Becker,-''^ and on 

 the authority of Professor Leidy was considered of organic origin. The 

 silica which forms the mass of the rock belongs more to a chalcedonic 

 variety than to quartz, for it seldom polarizes brightly. The minute in- 

 tersecting veinlets are also partly of the same character; the larger ones, 

 however, seem to consist of normal quartz. 



The lessons to be drawn from these facts are that the jasper in its 

 essential character is not a metamorphic rock, and that it was formed of 

 silicious sediments resulting in great measure from organic life, as has 

 been demonstrated to be the case with similar rocks in other parts of the 

 world. Iii the Manual of Paleontology,t b}^ Nicholson and T.ydekker, the 

 Radiolaria and the part played by them in the formation of silicious 

 rocks is discussed. The following quotation will illustrate : 



"Many of tlie Jurassic Radiolaria occur in jasper, flint or cliert. Jaspers with 

 Radiolaria are considered by Haeckel as of the nature of true * silicified deep-sea 

 Radiolarian ooze.'" 



The entire freedom of the jaspers from any fragmental material depos- 

 ited in the ordinary way near a shore would indicate their formation in 

 deep or at least quiet waters. The very rare occurrence, however, of 

 limestone in this series and the abundance of sandstone would seem to 

 indicate the absence of deep-sea conditions during the deposition of the 

 greater portion. 



No one has yet worked out the stratigraphic position of the jasper beds 

 in the series, and ascertained if they are distributed through it or confined 

 to a single horizon. The wide occurrence of the jasper beds may not, 

 perhaps, result so much from any great extent vertically as from the 

 extremely crushed and l)rokeii condition of the series as a whole. As a 

 result of this condition, strata of the same or nearly the same horizon 

 might be ex])osed in many places. So far as the writer is aware, jasj)ery 

 l)eds are absent from the recognized Cretaceous, but in the Miocene there 

 again appear flinty beds of probably the same origin, but wholly free 

 from the secondary silicification so characteristic of the earlier ones. 



Sandstone. — Dr Becker has described the sandstones of this series, and 

 nothing much that is new can be added. He emphasizes their arkose 

 cliaracter and the evident derivation from granitic rocks, which he con- 

 ceives underlie the greater part of the Coast ranges. The sandstone is 

 by far tlie most extensive portion of the series. It presents a very uni- 



♦ Quicksilver Deposits of the Pacific Slope, p. 1()8. 

 t Vol, i, pp. 147. 148. 



