Page:Centennial History of Oregon 1811-1912, Volume 1.djvu/231



ages of the earth. But Liudgi-en tells us that the great amount of surface lava and other voleauic material mingled with the lime stones and shales of its sea bed indicate that in the region of the Blue mountains the Triassic ocean was comparatively shallow with land masses not far distant.

During this Triassic age the seas were full of great lizard-like reptiles or saurians, and as they were world-wide in their distribution they must have lived in Oregon waters. In fact, Dr. Merriam, of Berkeley, reports several species from the Triassic limestones of the eastern part of the Siskiyou region, now part of northern California, and from the location of the fossils, Dr. Merriam has called these marine reptiles shastasaurus.

At the close of tlie Triassic period, or later, there came a time of great up- heaval in the Blue mountain region. The low lying land and adjacent sea bed became what was probably Oi-egon's first high mountain.

The clay and quartz sediment which had been part of the deep Palfeozoic sea bed, became the mountains round about Baker, of which the Elkhorns are the most typical and the most conspicuous ; while a portion of the shallower Tri- assic sea bed with its lime, its shales and its abundance of volcanic rocks, became the Eagle Creek or Powder River mountains.

The elevation of these older portions of the Blue mountains was not a steady, gentle long-continued process that only required time for its completion, but was accompanied bj- great violence.

The Paleozoic rocks of silicious clay and the coarser limestones, shales and tuffs of the Triassic sea wei"e both subject to the same violence. Both were thrust upward into lofty mountains. The once horizontal sedimentary rocks were folded, compressed, crumpled and fused until the rocks themselves were greatly altered. Later deep fissures were opened, through which poured heated vapors laden with their precious burden'of gold, silver and copper, and these old moun- tains became a rich treasure house of Oregon's wealth.

There are mountains in the Siskiyou region made of the same fine granited argillite rocks that tell of the same deep paleozoic sea ; the marbles and limestone of the Eagle Creek or Powder River mountains are repeated in the more south- ern land, while the Blue mountain mines of gold, silver and copper ai-e rivaled by those of the Siskiyou region. In fact, in his Two Islands, Prof. Condon has greatly emphasized the intimate relationship of these two regions of Shoshone and Siskiyou.

Still another period, the Jurassic, is hidden within the area on map marked Pre-Cretaceous, for Jurassic sea shells are found at Burns and Silvies and other localities showing that much of the lower part of the Blue mountain region was still beneath the ocean, 'but after referring to the great erosion that had taken place in the older portions of the range, Lindgren writes: "The Blue mountains in Jurassic and early Cretaceous times must have been a range of imposing height."

The Olalla creek beds of the Siskiyou region give us a glimpse into the beauty of Oregon's Jurassic forests.

Near Olalla creek in Douglas county there was an old lake into whose depths drifted the leaves and fruits of the Jurassic forests. It was then too early in plant evolution to look for oaks or maples and other hardwood trees, and there were as yet no true palms ; but there were conifers, ferns and many a