Show CAMPFIRE CAMP FIRE CHATS B by PAUL GLIMPSES INTO THE geological FIELD america in the twilight of its history in former arti articles ales under the above heading the great geological systems were treated successively in connection with their different forms of life appearing on our globe we spoke of the age of invertebrates of fishes reptiles etc until following the scale of evolution through the younger ages man finally made his appearance during the mere yesterday geologically speaking to many of my readers it will be of interest to learn at this time something about the changes our continent has undergone since the twilight of its history during precambrian pre cambrian time there rose from the surrounding ocean the great 1 oi kiei i laud land lt it was a long hook d ridge its longer branches stretched from the north shores of the upper lakes to the arctic ocean whereas the shorter branch extends northeastward as far as the coast of labrador the stump of another mountain range which appears to be of the same age extended east of the appalachians from maine to alabama this ridge has been termed the great seaboard land west of what we now term the great plains stretched another long belt of land which finally consolidated with the eastern lands to form our continent this belt of land extended from the eastern bases of the rocky mountains to western nevada this was the great cordilleran land rising like islands from the universal ocean there were probably other small land areas but as far as knowledge goes the three mentioned continental bodies were the beg beginnings of north america during paleozoic times nearly the whole of the cordilleran land began to subside it kept on sinking until only the highest mountain masses were above sea level eastern california of our times constituted the western mountain body while ahe the continent eastward became an archipelago cambrian sediments were deposited all over its broken surface the great northern land began at the same era to rise and continued so through all paleozoic time As cambrian sediments covered the sea board land it cannot bj be satisfactorily proven whet whether her the land rose or subsided in the progress of the paleozoic ages a continuous sinking of the cordilleran dil leran land took place while the great northern was gradually emerging the latter continued to broaden its base as the remnants of the former grew less during this time the sunken cordilleran area received the sediments of the rapidly eroding continent by the close of paleozoic tim the sediments accumulated over the of the sunken cordilleran region were feet thick in the rocky mountains feet in the wasatch region and feet fe at the extreme western paleozoic limit a few granite islands interrupted the coil coi of the uppermost Carboni carboniferous ferou sheets from nevada to the great plains plain the old precambrian pre cambrian topography of the re r gion was out of sight buried under thou thoi sands of feet of sediments there are some reasons to believe e tha th at the beginning of paleozoic time the appalachian region was annexed to the western wester border of the seaboard land the con GO editions here were then plainly a sinkin land receiving sediments from a bastin land on the west west and east there then fore the fixed and wasting land was ocean oceail ward from the sinking area following this epoch great changes too place the aforementioned afore mentioned nevada a con coi which had supplied the enor enormous nou thickness of paleozoic sediments went dow and in an easterly direction as far as the th region of the wasatch mountains the lan ian 1 l came up the new cordilleran constiner con tinei tiner L was then located in the region of the pres pre ent great basin just as this new con coi was the result of the bulk of sed bed ments derived from the first cordillera continent to the west so the new continent con tinen undergoing erosion in its turn supplied tor t the east and west the conglomerates sand san stones and lime stones which ar now classified as belonging to the jurassin Ju rassi triassic age triassic strata are gene generall raly found reposing on the east conformably confor mabl upon permian uppermost carboniferous 1 beds although in in many cases the geologic geo logies a section is not complete and the latter strat are lacking toward the end of the tria sic sedimentation stopped and the newl laid down beds became subject to arosio for awhile consequently the first strat stratus of jurassic age has been in most puce place found to rest upon the tria ariae sic strata by this time the reader will have unde stood natures method to build demolish damolis and rebuild and as it would lead too fai fa to consider every geological event th tha formed and reformed the american con bonu nent I 1 will restrict this article only to th changes and agencies which were mental in bringing about the structure our intermountain region in which th readers of this publication are natural na mostly interested west of the new basin continent t afi sediments of the triassic and jurassic fa foj lations were laid down 0 oj the eroded surface which had sin suna toward the east they rest conformably 0 pi the carboniferous sheets on the west t tt triassic jurassic sediments attained I 1 thickness of feet whereas on t east they are less than feet thick on tile the east large areas area s of formations belonging to the above names are exposed in southern utah and northern arizona while small exposures are found in colorado wyoming in m the wasatch and uinta mountains and of a still lesser size as far east as south dakota on the west with the exception of a small area east of eureka nevada the system is represented in the nearest mountains east of the humboldt range the lower series consist of and argillaceous beds and the upper of sandstone quartzite and limestone in these western ranges of nevada the system especially the lower part of it is highly metamorphic and more or less affected by irruptive rocks triassic rocks now upturned and partly eroded are exposed near the summit of the sierras in northern california and at various points northward to alaska As rocks belonging to the same system have been recognized in oregon and idaho besides the mentioned occurrences it is surmised that large areas of the west are underlain by these formations although concealed in our day by igneous rocks and by sedimentary beds of lesser age |