In this blog, I try to synthesize my trips to the Coyote Mountains near Mexico in the southern California desert east of San Diego and present numerous unreleased photographs.
It has begun pouring rain here on the coast. This time of year always brings back memories of my earliest real field geology experiences. I was very green about field work at New Year, 1995. The nearly 700 mile drive from Chico to Ocotillo was filled with new sights and experiences. I went down there for classes,‘95 and ‘96, then for fun in 2000. These photos come from three subsequent visits since 2007. After I finished undergrad, I used the Coyote Mountains as GIS proving ground of sorts as much as I could.*
In March 2008, I lived in the South. That brutal winter, replete with misery and ice storms snapping powerlines, was broken up by a trip out to the California coast. After attending Steve Gillette’s songwriting seminar in Big Sur, the flight to Nashville went directly over my undergrad field area. It had only been four months since I was last on the ground there.
Above: captured out the window of the big old jetliner, 3:20 pm. 100mm eq.
Perhaps I was too frank in 1995 when I wrote:
An offshoot of the Elsinore fault has complicated the geology of a small area in the southeastern Coyote Mountains. Extensive right-lateral movement and reverse faulting has chewed up a late Tertiary marginal marine sequence, the Imperial formation. In addition, the mid-Tertiary Alverson Andesite and Anza Formation, and the paleozoic metamorphic basement are included in this complex and intriguing region.
Assigned to this area to learn field methods, we discovered no earth-shattering new evidence to change the work done by Dibblee (1954), Bell-Countryman (1984), and Crowell et al.(1979). We mapped the area using basic skills to paste together the best geologic history we could, hopefully to replicate, at worst, the general relationships established by others.
I was honest, but I wasn’t on my way to be a good consultant! Geologists are storytellers as much as scientists. We really believe our stories. What we don’t know is greater than what we do. This is true for everyone.
At right, en route to the Coyote Mountains for the fourth time. I miss that Martin Guitar hat; the Trogdor t-shirt not as much (1/2/07).
In April 2000, I went way down there with my friend Mr. Nicholson. That early page still exists. He writes recently, “It was a little freaky for me that first time having Andrew drive our rental car up a desert wash. Now it's old hat.” Our trip photos are here. Back before blogging was a word, I put up a page about that trip. An excerpt:
We pushed on through to El Centro and camped at my old stomping grounds outside of Ocotillo. There was plenty of daylight, so we hiked up to the top of the nearby peak (about a 1000 feet climb). Went back to El Centro for dinner, returning for a moonlit drunken hike on the upper Imperial Formation. Afterwards, I played DEVO songs on a nylon stringed acoustic (Gut Feeling/Slap Your Mammy if you must know). We ran out of beer (again) and suddenly out came a bottle of Cuervo that Jeff had kept secret. Before long we were fire jumping.
At New Years 2007, I was 33 and just wasn’t sure I wanted to be a geologist anymore. Well, that wasn’t it, but I didn’t see a way through. I was having a great time touring around with Hellbound Glory, but I knew I wanted to get out of Reno. Leroy came up with a catch phrase: ‘everybody hits rock bottom in Reno.’ He later wrote a whole song. I was tired of things there after hitting rock bottom. I was lucky to borrow a perfect condition ‘88 Accord from my brother in law, and made the long trip south to see.
Starting at the Canyon Sin Nombre overlook, east of Sweeney Pass:
Anyway, 1/3/07, I camped right down in the wash. In the morning looked out to the east as the sun was rising. Well, okay, it was almost 11a.m.
At the end of a long day, here is where I camped. You are here. Comforting
About sundown I hiked to the top of the ridge (seen above) and looker further north:
Stepping out a long ways, to a shot from 1/12/09:
After doing all of that fault mapping in the Nevada desert from 2002-2005, I was interested in the range front fault at the Coyotes. Some funny things happened on that trip.
I hiked up to the fault and then southeast along the trace to the familiar Fossil Canyon; about 5 miles. It was grueling. The full moon I counted on for my return did not rise until three hours after sundown. In the end it was about a 15 mile hike. A crazy storm had blown in and once finally back at camp, my tent was gone. After catching my breath there in the dark, I found it about a mile up a wash, partially shredded and pinned in an ocotillo bush.
My old mapping was inadequate and my questions have never relented. The Elsinore Fault rips through the southern tip of the Coyotes beautifully with substantial Quaternary activity. Why, back in ‘96 were we up there taking all of those bedding attitudes on this stately fold in the paleozoic basement?
With Mr. Solecki, Mr. Hern, and Mr. Mikacich, I had a great time nonetheless. Turns out that after my last visit, some new work was completed by Tom Rockwell on that very stretch of the fault, published this April 2011, in JGR
Here is my first ever geologic unit description, March 10, 1995.
The Imperial Formation is Pliocene, strikes north-east, and dips about 20° regionally. Named by Hanna, 1926, the context in this paper is applied to the units following Tarbet and Holman, 1944. It is exposed in a large portion of our study area, with little to no vegetation. The mouth of Fossil Canyon is the south-eastern limit in our field area. Northward, faulting has complicated some stratigraphic relationships, but it typically rests conformably on the Rainey Formation.
The Imperial Formation is consists of three members, simply Lower, Middle, and Upper. Individually distinct, these names relate to stratigraphic position. A typical section of the Lower Member is found just north of the mouth of Chimney Canyon. The Upper Member is typified by the exposures fifty feet east of the mouth of Fossil Canyon.
The Lower Member is a matrix supported conglomerate that lies conformably on the greenish Rainey Formation. This contact is seen well exposed on the western side of pale yellowish brown, largest clast: 12", mean: 2" 75% volcanic, 25% mm & plutonic igneous. Graded and sorted in places
The Middle Member can be broken three main facies; fossiliferous, sandstone, and bioturbated. The fossiliferous facies is well exposed in Chimney Canyon, high on the eastern side, 500 feet from the mouth. A typical sandstone facies is found in Fossil Canyon, at least 1,000 feet from the mouth. At the mouth of Fossil Canyon, a typical bioturbated facies is well exposed. Fine grained, tan to golden. Quartz, micaceous, feldspathic. Extremely bioturbated at top, burrow average size: 2" in diameter. Fossiliferous layer ~ 7 ft. thick in center of unit. Conglomeratic lenses grading into lower member.
The Upper member is yellowish gray with fracture surfaces coated with limonite stain. White flakes of gypsum 1 cm. thick, 5 cm diameter.
From nearby Split Mountain in January 2009, I climbed up on a ridge and photographed the Upper Imperial mudstone with a 200mm equivalent focal length:
This became a fine black and white 8x10 print early this January.
* First off was importing AutoCAD dxf files from a commissioned photogrammetric mission to ArcInfo. I still remember the 5 1/4 floppy, and how big the 11 megabyte uncompressed file seemed to those PCs of that time. Later at the USGS in Menlo Park (1997), I made a digital elevation model (DEM) after learning much about the process from the USGS internal group who were once called ‘national mapping.’ They used digital line graph (DLG) versions of the topographic contours made from the mylar separates known as greenlines on a proprietary Intergraph workstation. Anyway, once I saw Robert Lugo working on it for our Bay Area Landslide Folio (USGS OFR97-745), I learned ArcINFO’s TOPOGRID routine to make a very high resolution DEM of the field area used by Chico State. Soon I became friends with Mr. Saucedo from the California Division of Mines and Geology (now called California Geological Survey). I squandered access to some source mapping for that region. My copy of that mapping-focused PhD from the ‘50’s is buried in a storage unit somewhere.
Thursday, December 29, 2011
- ► 2013 (46)
- ► 2012 (85)
- ▼ December 2011 (13)
- ► 2010 (208)
- ► 2009 (10)
- ► 2008 (41)
- ► 2007 (53)
- ► 2006 (23)