tag:blogger.com,1999:blog-4130421352415377273.post8906442340036068825..comments2024-03-29T07:54:19.736-07:00Comments on Books in Northport: “This Changes Everything!”P. J. Grathhttp://www.blogger.com/profile/12693462910472164289noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-4130421352415377273.post-52315951711602503862019-02-27T18:05:48.060-08:002019-02-27T18:05:48.060-08:00BB, Precambrian outcrops in the area of Dos Cabeza...BB, Precambrian outcrops in the area of Dos Cabezas certain show on a map of the state in Geology of Arizona, but the chapter on “The Precambrian Era” makes no mention of anything in Cochise County. A later chapter tells of the volcanism that formed the Chiricahua Mountains 30 to 20 million years ago and mentions metaphoric core complexes (magmas that did not reach earth’s surface, i.e., formed no volcanoes) that built the Pinaleños Mountains, north of Cochise County in Graham County. But what happened in the region of the present Dos Cabezas Mountains between the Precambrian and Tertiary periods? How were those mountains and the Dragoon Mountains formed? Lynn R. Bailey’s book, The Dragoon Mountains, notes that the range is generally rounded “in contrast to the mid-section and northern portion … which are serrated due to an intrusion of granite through the Paleozoic and Cretaceous rocks about seventy-three million years ago. Weathering {geologists call it exfoliation} of the intruded quartz-monzanite created rough and craggy terrain in the mid-section and at the northern end of the mountains.” Bailey tells us that folding and faulting were responsible for what came to be used as “passes” through the range from east to west and back. Texas Canyon, through which the present I-10 passes, is another region of exfoliated granite. — But how and how long ago did all these processes take place? It’s the timeline I want: a specific timeline for Dragoons and another for the Dos Cabezas Mountains. Because the latter look almost like a continuation of the Chiricahuas, and yet the Chiricahua Mountains were formed by volcanoes, not by “folding and faulting.” What meets the uneducated eye upon first acquaintance can easily lead the mind astray. <br /><br />To change the subject, see my post after this one for the reason we could not go higher in the Chiricahuas after the snowstorm. If we'd tried a couple of days later, we wouldn't have been able to get as far as the visitors center!P. J. Grathhttps://www.blogger.com/profile/12693462910472164289noreply@blogger.comtag:blogger.com,1999:blog-4130421352415377273.post-36916927625034026352019-02-26T12:00:00.353-08:002019-02-26T12:00:00.353-08:00I only knew two geologists (MS). The first was a ...I only knew two geologists (MS). The first was a high school friend who spent summers prospecting with his uncle in the four corners. He<br />was so taken with the hands on prospecting that he got a masters. He knew much of formation, but mostly was looking for minerals, petroleum etc. The second was more theoretical, into chemical analysis and oddly accepted plate tectonics, while being a new earth<br />creationist type. (?!) I guess in come cases we end up with little technical information about mountain formation and are left with the<br />Native American stories of their origin? BB-Idahohttps://www.blogger.com/profile/01388509941702241290noreply@blogger.comtag:blogger.com,1999:blog-4130421352415377273.post-49317203909555116662019-02-26T11:34:15.562-08:002019-02-26T11:34:15.562-08:00SIGH!!! McPhee provides the time scale in the fron...SIGH!!! McPhee provides the time scale in the front of his book, but the other thing he does is give a narrative to the changes through time, and that's what I want. Also, some of the rocks may be precambrian, but that doesn't mean the mountains looked then as they look now. It's all those millions of years in between that get left out.<br /><br />One of the sad things I've learned from reading is that, in a way similar to sociology shifting from "qualitative" to "quantitative," geology has split into subspecialties, with "field geology" now being considered the most old-fashioned and bottom of the barrel. Field geologists are the ones who spend their lives outdoors, who recognize rocks and land formations by sight, who ask themselves questions about what they see and then form theories and look for evidence that confirms or disconfirms their best guesses. Modern (postmodern?) geologists mostly work in laboratories and with expensive instruments. Some of them come to geology from physics. They do not bother to obtain intimate acquaintance of specific locales. It breaks my heart.All that fancy information and no recognition of what's really there.<br />P. J. Grathhttps://www.blogger.com/profile/12693462910472164289noreply@blogger.comtag:blogger.com,1999:blog-4130421352415377273.post-59678063681477828392019-02-26T07:27:17.336-08:002019-02-26T07:27:17.336-08:00How did those particular mountains get there? Some...How did those particular mountains get there? Some of the many smaller ranges are less published and studied. There is some information on the Dos Cabazos <a href="http://earth.geology.yale.edu/~ajs/2001/Nov/qn0901000773.PDF" rel="nofollow">here</a><br />based on U235 halflife as it turns into Lead as well as the geologic typography. It isn't very helpful, being written in 'geologicalese', but pp 779-778 (toggle down) offer a historical geology. The numerical terms ma and ga (mega and giga annum) are the more comfortable million and billion years. It would seem the formation took place in the late pre-cambrian in the larger time span of the paleoproterozioc with the volcanoclastic activity moving SW to NE over some 20-40 million years.<br />I suspect that might be out of your wheelhouse, as it is out of mine. Contacting the Geology Dept<br />at one of the AZ universities might provide enough interpretation and additional information to<br />put together an understandable story...maybe even a movie? :) <br />ps. you may need a <a href="https://en.wikipedia.org/wiki/Proterozoic" rel="nofollow">geological time scale</a><br />to translate from the dry technical to the possibly very interesting story....BB-Idahohttps://www.blogger.com/profile/01388509941702241290noreply@blogger.com