Tuesday, February 16, 2016

Finding a Thesis: Views and Geography and ... Oh, What's That?

And so, we'll leave the millsite and locked gate on the northeast side of Mineral Ridge to get on with thesis hunting outside Nevada, for a change, and ... what's that up ahead? As we round the bend, The Crater, a basalt cinder cone comes fully into view.
The Crater, beyond the metal posts of the old gate.
In the photo above, the low range of hills beyond the Clayton Valley playa on the right is Paymaster Ridge, which we first saw quite a while ago on our way into Clayton Valley from the east. The rest of that hilly, mountainous mess, I mean mass—from directly behind The Crater and northward, to the left—is the Weepah Hills.  The high point in the photo, part of the Weepah Hills, reaches 7753 feet (2362 m).

The Weepah Hills is a more-or-less circular batch of disorganized lowlands, hills, and mountains, with the apparently chaotic to jumbled geologic formations of the area having been horizontally sliced by low-angle faults of probable detachment origin. Tertiary Esmeralda Formation sediments and Quaternary older alluvium cover much of the western part of the hills; a granitic body, the Weepah pluton, probably the same age as the 70 Ma Lone Mountain pluton to the northeast, crops out in a broad area in the northern hills; and a couple small patches of Precambrian Wyman Formation and Reed Dolomite poke through near the central part of the area. The rest of the area is mostly underlain by Cambrian to Ordovician sedimentary formations. Sunshine Mining Company took out a bit of gold at Weepah in the mid 80s; a few other companies have taken a look since then, but so far no additional mining has resulted.

These topo maps show the topography and main features of the area.
The spliced Goldfield and Tonopah 30 x 60 maps (courtesy USGS).
The same map with a few labels.
The whole area shown on these maps is detached.
Here, I've thrown on a few lineaments, including one going up Paymaster Canyon, which gives the eastern side of the Weepah Hills a linear look.
I probably drove straight on down to the cinder cone on my 1976 journey through the area, but on my more recent 2010 photo-taking expedition, I stopped near the old gate to look around at some of the old junk, and to take in the views.
I'm not sure what this old sign said, but it's totally bitten the dust. And it looks like it got run over by a tracked vehicle of some sort.
An old, though not very old, blasting sign.
Beyond the blasting sign, we can see a topographic formation known as The Monocline (this use of a capitalized "The" seems to be quite popular for geographic names in this very local region of Esmeralda County). The Weepah Hills form the broad expanse of hilly country beyond The Monocline, with rugged Lone Mountain forming the bluish mountain beyond that. (Please note that there are several Lone Mountains in Nevada; in fact, I found ten on Trails.com.)

At The Monocline, a thin, dark basalt layer caps soft, white sedimentary rocks, which, according to the Esmeralda County report, are part of the Tertiary Esmeralda Formation. These units have been tilted, maybe as much as 10 degrees.
A closer view of The Monocline and its closer, sister hill, from Google Earth.
Strangely enough, I've never stopped at The Monocline, although it looks like there is a perfectly good dirt road to it!
The Monocline, part of a mine dump, The Crater, and Clayton Valley playa.
The Crater.
A closer look at The Crater is next ... as fast as we can get down the alluvial fan!

Selected References:
List of minerals at Weepah: Mindat.
Weepah Mine: Western Mining History (info last updated in the 80s or 90s).
Weepah Deep: unpub 1989 info from Sunshine Mining Co and FMC Gold.

Weepah Mine in the County of Esmeralda Nevada: unpub 2008 report—much of this info is good, but ignore the Regional and Local Geology sections.

Weepah Reconnaissance/Submittal Summary: unpub 2014 recon report.

Maldonado, Florian, 1984, Bedrock geologic map of the Lone Mountain pluton area, Esmeralda County, Nevada: U.S. Geological Survey Miscellaneous Investigations Series Map I-1533.

Related Posts:
Thesis: Finding an Area
Finding a Thesis: Battle Mountain to Austin to Gabbs
Finding a Thesis: Pole Line Road
Finding a Thesis: Pole Line to Belmont
Finding a Thesis: Klondyke District
Finding a Thesis: A Joshua Tree Aside
Finding a Thesis: Into the Palmetto Mountains
Finding a Thesis: Farther into the Palmetto Mountains
Finding a Thesis: A Bit O' Geology in the Palmetto Mountains
Finding a Thesis: Future Stories from the Palmetto Mountains
Lida Summit Roadcut
Finding a Thesis: Next Stop, Silver Peak!
Finding a Thesis: Coming into Clayton Valley
Finding a Thesis: On the Southern Route to Mineral Ridge
Finding a Thesis: The Northern Route onto Mineral Ridge and a Little Geology
Finding a Thesis: Up to the Millsite and Back

No comments: