About 35 miles east-northeast of
The Geographic Center of Nevada, both Highway 50 and Slough Creek go through a gap in the south end of Whistler Mountain, a gap or notch known as
Devils Gate.
Note: Devils Gates are scattered all over Nevada, including a second Eureka County
Devils Gate located north of Eureka, west of the paved road between Eureka and Carlin. Our Devils Gate, the one in this post, is located about ten miles east of
Lone Mountain and seven miles northwest of Eureka (
MSRMaps location).
Coming into Devils Gate from the west just before sundown.
A large breccia can be seen high on the carbonate cliffs north of Highway 50 when you approach the gate from the west. MOH and I first noticed this breccia several months back; we pulled over to check it out with binocs, then mosied on, filing the place away for a future hike. Finally,
coming back from Serbian Christmas, the time was right.
We pulled off the highway onto a little dirt entryway that accesses the old highway south of the main road, parked the truck, and started walking. By the way, we've had the Prius on this old road, so presumably the pullout is suitable for most vehicles. After making it across the highway, we walked down a rabbit-brush infested two-track road, crossed Slough Creek, and then bypassed a fence by walking over to its abutment against the cliff face.
As we skirted around the base of the cliff toward our goal higher in the cliffs, we made a discovery: we found a lower breccia associated with small caves and solution cavities. In the photo above, the upper, larger breccia is in a smallish, bright white patch in the far, upper left part of the cliff; the lower, smaller breccia is clearly visible in the lower right of the photo, closer to Slough Creek.
This labeled Google Earth image shows the location of the upper and lower breccias and our convenient pullout. Re: pullouts, YMMV.
The lower breccia, shown above, is easier to reach than the one high on the cliff, and is recommended if you don't feel like scaling the hillside. The lower breccia contains some large, generally elongated and subrounded carbonate breccia fragments in white calcite cement of varying thickness. The thicker, upper part of the white calcite looks vein-like to almost bedded.
Our goal, the white patch with one conspicuous dark gray fragment, is now obvious in the center of the photo.
Side-hilling up this scrabbly, brushy, talus-covered slope was tricky in places, especially where talus formed only a thin veneer over the bedrock, and where limestone beds jutted out unexpectedly, sometimes forcing a downward retreat.
MOH, on a ledge to the left of the breccia, provides a bit of scale.
This is a large breccia body with large fragments, somewhat remindful of the
Titus Canyon breccia in Death Valley, though not as complex. The large to giant fragments are angular to subrounded, and are set in a matrix of coarsely crystalline white calcite. The breccia body, as exposed, appears to be mostly in one or two layers or beds of the Devonian
Devils Gate Limestone; its shape could be subspherical (possibly cavern-like) or cylindrical (pipe-like).
Nearly the entire cliff face in this alcove is composed of breccia. For scale, the dark olive green ephedra bush near a curved breccia fragment (right of center) is about 3 feet high. Also, see the next photo for a closeup of the curved fragment and the same bush.
The curved fragment behind the ephedra bush shows primary layering or bedding, as does a second curved fragment below it.
Vertical to overhung cliffs of Devils Gate Limestone are towering behind me in the next shot, and I'm having trouble finding solid footing in the talus-ridden alcove. Talus was almost slithering down the slope, about to cascade over cliffy beds of limestone to the tear-a-pants rocks below. No boot-skiing allowed here, unless you know how to ski jump.
The breccia is mostly exposed in this one wall. The alcove may have formed from erosion of breccia; maybe it formed from erosion of solution caverns or caves no longer apparent and partly associated with the breccia. Here, I'm just speculating, as I don't really know the genesis of the breccia or the alcove. The curved fragment from previous photos is now above the 3-foot high ephedra bush and to the right, below and to the right of the large central fragment. From this angle, the curved fragment looks oval. Numerous smaller, angular pieces of dark gray limestone float in white calcite below it.
The ephedra bush suggests an apparent height or thickness of 20+ feet or 6+ meters for our breccia, but viewing angles are deceptive in the alcove.
Fragments are clast supported to matrix supported. One example of matrix support can be seen in the upper part of the cliff exposure, where the mass of calcite appears to be greater than the mass of fragments. It's possible that solution caving caused collapse of pieces and large blocks of limestone, which then concentrated toward the bottom of the collapsed area, leaving the upper area partly open after collapse and before later calcite deposition or infill.
The white breccia matrix consists of large, intergrown calcite crystals. White calcite veinlets in some fragments appear to be mostly, but not entirely, older than than formation of the breccia, and therefore older than the white calcite infilling event. I noted only a few places where late calcite veining appeared to cut across both the breccia fragments and its coarse calcite cement.
The age of all this activity — breccia formation, fragment cementing, and early and late calcite veining — is unknown to me.
An unidentified plant grows on coarse-grained white calcite in a narrows below the alcove.
Update: Identified by
Hollis in comments as
Petrophytum caespitosum.
Here's some more coarse-grained white calcite with a nicely reflective calcite crystal above my boot.
NOTE: More pictures of the calcite matrix can be seen
here, along with one more shot of the petrophytum.
The same
unknown plant is growing on dark gray Devils Gate Limestone in the ledgy area outward from the alcove.
We take one last look at the breccia before starting downhill.
The view from the ledge, looking west: Highway 50 and the partly parallel old highway angle across in the upper left; Slough Creek, surrounded by lots of rabbit brush, meanders through the foreground; Lone Mountain stands alone in the distance.
After making our way downward on some decent, though imperfect, boot-skiing slopes, we looked back at the breccia and wondered if the way we came down would have been easier as a route up than the scrabbly sidehill across loose talus.
We were driving up Monitor Valley towards Potts Ranch Hot Springs (yes, up is north in this case), when we both spotted a strange whiteness on some hills located just north of the playa in the center of the valley. I had noticed this phenomenon at this site once before, but had attributed the light coloring of the hills to white beds of sediment, poorly welded ash-flow tuff, or air-fall tuff in the Tertiary volcanic section, and hence, had just driven on. This time, it looked as though dust or salt had blown northward off the playa.
I'm assuming the bushes are fourwing saltbush, or Atriplex canescens, in its wintry, somewhat non-leafy form.
Yes, they are covered by a thin coating of a white salt, an encrustation that flaked off easily into my hands.
To investigate this phenomenon further, we walked out onto the playa, a soft playa characterized by crusts. The photo (above) shows how the bushes gradually lose their salt crust going away from us along the northeastern playa edge, and shows part of the Monitor Range in the distance.
The wind direction while we were out there was from south to north (right to left in the photo), which explains the salt coating on the bushes, unless the salt coating developed when winds from the south were blowing across a playa covered or partially covered with water.
When the playa surface is examined closely, circular features can be seen in the crusts. These circular patches will come up as blocks if prodded, and are (I hypothesize) most likely some form of biotic or cryptobiotic crust.
Looking back to the north toward my truck: the salt on the bushes is somewhat variable in distribution, apparently thinning away from playa's edge.
Now I turn and look down the five-mile length of the Monitor Valley playa. Monitor Valley continues another 25 miles beyond the south end of the playa, ending in the faint turquoise mountains in the far distance: the southern part of the Monitor Range. There is water on the playa in the far distance on the left (hard to see in this shot), and we have spotted a couple unknowns on the ground in the middle distance.
It's an old, salt-encrusted wooden post, fallen from its previously upright position, along with some other stuff of unknown origin or purpose. Picking the post off the playa floor pulls up the salt crust, revealing white to pinkish crystals on the bottom of the crust. I didn't try a taste test.
