I had heard that the rocks in the Sawtooth area were of an unlikely composite origin. So, I asked a friend to send me an abstract of the geology (as if I would understand it).
The following abstract seems to indicate that the geologic complexity of this area is more intricate than even geologists previously thought. It looks as if there are several kinds of rocks introduced through widely varying events from as far back as 1.5 billion years up to as recently as 66 million years ago combining unlikely materials to form the obviously unique Stoddard Ridge.
Now, since I have mostly no idea on what I am talking about I will keep going out there and studying the area to see if I can ever understand it.
ABSTRACT GEOLOGY OF THE STODDARD RIDGE AREA, WEST CENTRAL MOJAVE DESERT, SAN BERNARDINO COUNTY CALIFORNIA — BROWN, Howard J. – Omya -Lucerne Valley, CA – May 2013
Stoddard Ridge is a prominent landmark south of Barstow California in the west central Mojave Desert area. The 35 square mile area was mapped in detail at a scale of 1:12,000. The geology is far more complex than depicted on all older published maps. The new mapping adds significant new data regarding the variety of rocks present, and adds new details on the geologic structure and complex geologic history of the area.Several packages of rocks are exposed. At the east end of the ridge the oldest rocks are exposed and include PreCambrian basement gneiss complex, metamorphosed intrusive rocks, and possible Late Proterozoic metasedimentary rocks (schist units). The central part of the ridge exposes several sequences of steeply dipping Mid Jurassic Lower Sidewinder volcanic (JLSV) rocks, and younger (JLSV) rhyolite dome complex that includes extrusive, flow banded and massive hypabyssal intrusives. The western portion of Stoddard Ridge is largely heterogeneous Mid Jurassic plutonic rocks (post JLSV) which form a steeply dipping sheeted intrusive complex, that includes diorite, granodiorite, quartz monzonite and felsite. Plutonic and to a lesser degree volcanic rocks are cut by numerous younger mafic and felsic dikes correlated with the Independence dike swarm of Late Jurassic age. The eastern part of the ridge has been intruded by homogeneous Mid Jurassic plutonic rocks, and Cretaceous granitic intrusive rocks are exposed along the southwestern base of Stoddard Ridge. Several ages of Late Cenozoic alluvial units were also differentiated in mapping.
Geologic structure is complex, the result of several deformational events including shearing, folding, faulting, intrusion and metamorphism of pre Mid Jurassic age, followed by multiple Mid Jurassic age volcanic, intrusive and deformation (folding and faulting) events, and younger Cenozoic age faulting. Most bedrock units have a northwest trending structural grain which likely formed in Jurassic time. Suspected concealed faults are present under alluvium. Several prominant young northwest trending high angle faults are present on the south side of the ridge and can be seen to cut alluvium.
Does this …
… Blow your mind? — Cajon Junction (el. 2950′) at I-15 and Hwy. 138 is actually at about a 300′ higher elevation than Victorville (el. 2650′). The slope from the summit to Victorville is gradual, not as noticeable, and provides us with the illusion that we are further up than we actually are.
Mining History of Cushenbury Canyon
& its Impact on the Victor Valley
Mitsubishi Cement Corp.
The gold discovery in Holcomb Valley in 1860 brought a rush of fortune seekers to the Victor Valley including some foreign interests. The English family of Del Mar’s had a significant impact on Cushenbury Canyon. Holcomb Valley miners affected California history by participating in their own Civil War actions and may have left treasure in their wake.
World War II ended the golden era and Cushenbury Canyon but initiated another mineral rush. The postwar California population boom brought about the industrial minerals revolution fueled by the construction industry.
Kaiser Cement built a cement plant and Cushenbury Canyon as an indirect result of the decision by an American General during World War II. The facility was modernized in 1982 and Mitsubishi Cement Corp. purchased the plant 1988. Today Mitsubishi Cement Corporation Cushenbury Plant is one of the leading industries in the Victor Valley.
The industrial minerals boom has a direct impact on everyone’s lives here in the US. The industrial minerals mined in the Victor Valley fuel the economy in California. San Bernardino County provides largest source mineral commodities in the US. ” If it can’t be grown, it has to be mined!” the mining industry provides the “stuff” to make the “things” we need to continue our lifestyle.
The Mohahve Muse – Volume 4, Issue 3 – March 2001 – Mohahve Historical Society
Leo Lyman – President
Favorite Places – Trona Pinnacles:
At one time, geologically speaking, not long ago, the Mojave had many large lakes fed by water from glacial melting. The Pinnacles show the most obvious evidence of this with its tufa towers extending to where the surface of the water once was.
I’m not sure about the composition of the Kelso Dunes in the Mojave Preserve. The link I provide in the following states that the dunes are from different sources, stacked together. Now, I have a freind that seems more than knowledgeable about these things, and he told me the dunes were made primarily of rose quartz. That he had taken a microscope to the dunes once and examined a sample of the sand grains. He told me these grains of sand were curiously perfectly spherical, and that may account for the ‘booming’ quality of the dunes.
Maybe they are from several different sources as the link claims. I’m not a geologist or expert in eolian forces. It’s all interesting to me, but for now I’ve chosen to run with saying the dunes are composed generally of rose quartz. Why? Well, because it sounds cool, and, because I can.
Bob Reynolds, the one-time earth sciences curator for the San Bernardino County Museum and lifelong explorer of the geology and paleontology of the Mojave Desert is the only dude I know that has had a mineral named after him–reynoldsite.
In this shot Bob is talking about fossil deer tracks and how they may have come to be at this undisclosed location in the Mojave Desert millions of years after they were made.
Geology icon immortalized with mineral:
Tom Dibblee was born in 1911 in Santa Barbara, California. He first became interested in geology in 1929, when his father hired a geologist to investigate the oil potential on the family property. After Tom graduated from Stanford University, he spent 16 years working for oil companies and then 25 years working for the U.S. Geological Survey. Much of this time was spent alone in the field making geologic maps of California. Tom retired in 1977 and became a Research Associate with the University of California Santa Barbara, and, at the request of the U.S. Forest Service, he began mapping the 1.2 million acres of the Los Padres National Forest. During his career, he mapped over 40,000 square miles of California (about a quarter of the state), a feat that probably will never be equaled. Tom was the first man to map the entire San Andreas Fault. In fact, his early work on the fault indicated that it had moved more than 300 miles, and this became a critical piece to understanding plate tectonics.
Tom received the U.S. Geological Survey Distinguished Service Award in 1967, the American Association of Petroleum Geologists’ Human Needs Award in 1981, and the Presidential Volunteer Action Award from President Reagan in 1983.
Malapai Hill, Geology Tour Road, Joshua Tree National Park The twin peaks of Malapai Hill rise about 400 feet above the valley floor. The black basalt that composes the hill is … click the photo for more information …