Textures from a Tufa Dome III

These are the last photos from this short mini-series showing textures of tufa from a tufa mound near Trinity, Nevada (read more about it and get directions to the spot here).

These photos show what appear to be a piece from the outer edge of a formerly spherical part of the tufa mound, like one I described here earlier, and ones seen in Figures 18 and 19 from Larry Benson's 2004 circular, The Tufas of Pyramid Lake.

Enlargement of the same piece.

I like the first photo for showing the bright orange lichen in the background. The second photo, besides being an enlargement, shows some pale to medium yellow lichen on the piece I'm holding.

Tufa Dome north of I-80–U.S. 95 Juntion

A somewhat eroded tufa dome.

Every now and then, when driving east or west on I-80 in northern Nevada, I get off and check out local items of geological or historical interest.

Here I've stopped at a partly eroded tufa mound located north-northeast of the junction of U.S. 95 and I-80 (map and location below). It's fairly easy to reach with an SUV or other 4WD vehicle.

View of the tufa mound looking northward toward the low hills of the Trinity Range.

Another view, this time with more of the basaltic-looking hills in the background.

Closeup of some the tufa structures, looking in toward a small crevice.

I tried focusing on the tufa textures in the foreground and background at the same time, but it was a cloudy day: not quite enough light.

Tufa covered by bright orange lichen on the north-facing side.

Looking south toward the U.S. 95–I-80 junction, and 95 beyond that going south toward Fallon.

The view above shows the eastern part of the White Plains of the Fortymile Desert, with the west end of the Mopung Hills of the West Humboldt Range in the left part of the photo (MSRMaps location).

View Directions to Tufa Dome in Larger Map

Embedding this map directly from Scribble Maps (see original map here); didn't work, so I imported the "scribble" to Google Maps.

To get to this particular tufa dome (there are many in the general area between a few miles east of Nightingale Hot Springs and Toulon), take I-80 exit 83 from either the eastbound or westbound lane. If going west, turn right nearly immediately (at a location known as Trinity, now with former buildings gone), and follow a paved road to the north-northwest. If going east on I-80, turn left from the off-ramp onto highway 95, go under the I-80 underpass, follow the road as it curves to the east, and turn left on the same paved road just before entering the on-ramp loop for Reno and points west.

Drive about 0.3 miles on the paved road until you reach a power line access road, a dirt road that may not be appropriate for cars. Turn right, taking this road for about 0.7 miles, including a deviation from the power line itself, where the original road is at least partly washed out. You will then reach just the right sand wash road, which will take you up to the tufa dome (and beyond to a small prospect). I can't say for sure that the turn I marked into the wash road is exact; look for tracks heading in the right direction.

Careful examination of a Google Maps or Google Earth view of the area will reveal another road that comes in from the west just uphill from the tufa dome. I have no idea whether this road will work as an access route, but it will (or would?) go past a couple other domes.

While there, note the several Lake Lahontan shorelines and the desert pavement.

Things You Find in the Field: Fauna on and near Rocks...OR...on and amongst the Flora

Blue belly lizard near some foliated andesite (this is the Great Basin Fence Lizard, or Sceloporus occidentalis longipes).
(click any photo to enlarge)

The lizard was rather skittish, and I couldn't get very close.
Read more about blue bellies in an earlier post.

A lizard of unknown denomination running over a lichen-covered outcrop.

A very small gray and white bird perched on a gray rock
atop an iron-stained outcrop (upper right).

Two shining leaf chafers or "Little Bears."

AKA Paracotalpa granicollis, a kind of scarab beetle.

Ladybug!

And finally, a meadowlark atop a sagebrush.

I hear meadowlarks often, but am not always quite so lucky as to see them. This time, I was crossing a muddy little stream by a meadow, on my way to take the long way home (I didn't know it was *such* a long way, but oh well) when I heard this one singing.

Things You Find in the Field: Pyramidal Objects #1

Quartzite on top of "Dike Hill."

I came across this small, pyramidal rock on top of the hill seen first in this earlier post about dikes and drill holes. I didn't know what its full shape would be until I walked over to it, having gotten a glimpse of it from below. The first view made it look like a nearly perfect, small Pyramid of Giza.

View showing all sides.

Yes! It's in the shape of a pyramid, in this case a right, rectangular (not perfectly square) pyramid, a little eroded and lichen-covered on its more northerly sides. Pretty well-formed for a rock, eh?

At the Cabin: AK2011 Day 4

After dinner and beer at Buckets, we made our way back to the cabin, which we hadn't stayed in for three years. The canal looked about the same as it did in 2008, possibly with a few more moose-munched cottonwood trees growing here and there along the bank.

We walked around and looked at the sights:

Boats.

Reflections from boats and cabins.

Float planes and more reflections.

Old, licheny docks and fish-cleaning tables.

More float planes, this one roaring by to land upriver.

After the seaplane landed, it taxied up the canal to pull in and tie up. While we were there, several float planes came to stay near the canal by the cabin; I counted as many as four at once, maybe five. These are quite popular for hieing down to the river when the reds come running in large numbers, as they had a couple days prior to our arrival on the Kenai. The sockeye surge was just beginning to come into the upper river, and fish-cleaning operations were going on all around us. People typically have tables right along the river or canalside; some fishermen and fisherwomen bring portable cleaning tables over to the river from their off-river cabins.
We decided to go for a walk, to check out a fishing spot I knew we could use (if we could just figure out how to put wet flies on rods for the reds or could find any non-leaky hip waders).

Sights seen along the way:

Leaves, twigs, and dried spruce needles.

Cotton from cottonwood trees, on what looks like gravel from graywacke.

Miscellaneous cabinish junk and Alaskana, including this scenic (IMO) old pickup.

Fishing related decorations: old floats.

Fishing-related decorations on cabins, garages, and carports.

We did make it down to the fishing hole, decided to wait for further instructions from the fisher-people arriving the next day, a day that would be dedicated to fishing, getting new hip waders, and eating dinner at the St. Elias Brewery.

More Cross Bedding

There we were, at the end of the Canyon Overlook Trail in Zion National Park, looking west toward the southern end of Zion Canyon, where the North Fork of the Virgin River flows through (not that you will see it the Virgin in this post).
Reddish brown to orange cross beds of the Jurassic Navajo Sandstone (Jn) were everywhere, available for angled sun bathing, photography, and a bit of careful climbing. And beyond and above, there is the ever-present white (and still cross-bedded) upper portion of the Navajo.
I zoomed in on a fascinating section of white to yellowish sandstone in the cliff below the upper white sandstone: cross beds amongst cross beds.
A small tree, and a mini-tree below it, grow near the edge of the 400-foot drop into the lower canyon of Pine Creek. Wedge and trough cross strata can be seen in the nearby reddish cliff behind the tree. In the distance, an inset arch may eventually form beneath the uppermost reddish layer, below the upper white sandstone.
I looked over the edge at the actual trail end, which has a convenient metal railing. One of the windows for the mile-long tunnel on the Zion – Mount Carmel Highway (Utah S.R. 9) can barely be seen in the deep shadow to the right of the sunlit cliff.
If we could hang way over the edge, we'd see The Great Arch, an inset arch just beneath us. I took the photo from one of S.R. 9's many switchbacks (six, to be exact) as it makes it's way up to the west tunnel entrance. This kind of inset arch is sometimes called a blind arch.
Finally, we have to turn away from the overlook to head back towards the trailhead and the road east.

Indian paintbrush on sandstone.

A narrow part of the trail, with a small dropoff, heads back toward the cave seen in the last post. The inset arch visible from the cave, across the slot-canyon portion of Pine Creek, can be seen in the shaded background of this photo.
Around the corner, the trail goes into a sandy narrows between pale orange sandstone and a reddish brown layer. The cross beds here (and in much of Zion) are generally dipping to the south, as can be seen in the far cliffs, indicating that the wind blowing the dune sand came from the north. Here, the the pale orange beds we've been walking on are dipping to the south, and the reddish brown layer we're about to walk on dips to the north.

Cross bedding! (With foot and lichen.)

On the way back, the Bighorn Sheep we passed on our way out had moved closer to the trail (right on the trail!) and closer to the trailhead. This one was munching on bushes near this magnificent exposuring of cross bedding. I'll show more pictures of these critters in another post.

Even more cross bedding, with some tafoni-like weathering accentuating some of the layers.

We're now in the home stretch on our way to the parking area, having passed the overhung cave. This is one of the heavily hand-railed sections of the trail: there's a ledge about 5 feet below the trail, then a couple-hudred-foot drop to the slotted canyon of Pine Creek below. Ahead, the trail goes around a corner to turn more easterly, goes past the leaning tree of the first post, and then goes into relatively steep, somewhat slippery, sand-covered sandstone ledges and the doubly railed steep stairs carved in sandstone at the beginning of the trail.

I strongly recommend going out of your way to take this hike.

This mini-series will now go in at least two directions, one being the road from St. George, Utah, to Zion, through the tunnel and over the pass to Mount Carmel Junction, with a couple photos on the loop road toward Cedar Breaks and into Cedar City. There will be no pictures from Cedar Breaks: the highway department hadn't even considered plowing snow from the south entrance, where it was at least two feet deep.

Geology on the Road: Breccia with Flow-Banded Rhyolite

The other day, we looked at some flow-banded rhyolite, beginning at the vertical fractures near the fence on the left side of this photo, and ending on top of the knobby hill overlooking the corral. Warning: we won't see much flow banding, if any, today, but its still there. We will, however, find out why we stopped here while on our way to somewhere else. For scale, the log forming the top of the corral fence is about 5.5 feet above the ground. Location: near Middlegate and The Shoe Tree, just north of Highway 50 (Google Maps, Google Maps Street View, MSRMaps).
This mass of breccia in the center of the exposure immediately caught our attention, but we stopped to examine the caves, and only after stopping noticed the breccia. Note the bird nest, possibly an owl's, on the upper flat surface. And note the several caves, with MOH for scale climbing up to check one of them out. You'll also want to note that about waist high on MOH, and over to the right just before the rightmost vertical fracture, you can see a large dark patch or two. These are breccia fragments.
The inside of the upper cave: a good place to find pack-rat middens and small bones.
The largest, uppermost breccia fragment is about 2.5 feet in length and perhaps a foot or more wide. It appears to be surrounded by small fragments, with another large fragment below it to the left. I didn't try chimneying up the fracture to check them out in more detail, so we'll have to rely on this crude description.
In the main exposure to the right of the caves, large breccia fragments are within reach of even short people like myself. Besides the large, dark brown fragments to the right, you can see several small fragments near my hand. The breccia fragments consist of angular to subrounded pieces of rhyolite, which are set in a matrix of smaller fragments.
This large fragment shows what looks like volcanic flow banding or hydrothermal streaming around the right side of the fragment. I suspect that more than one type of brecciation might be exhibited at this outcrop. Candidates include primary volcanic brecciation, brecciation associated with caldera formation, and tectonic brecciation associated with faulting. Another candidate is hydrothermal brecciation.
Here's another example of what the matrix looks like, closer to that first exposure of flow-banded rhyolite from the other day, and visible as a large bright orange spot near the fence on the left side of today's first photo. At first glance, this pale to dark yellow orange to dark yellow brown mass looks like a clast or breccia fragment, but I think what we're seeing is a weathering phenomena, with a piece of the outer, dark brown weathering rind broken off, exposing relatively fresh rock beneath. We can see some light gray veinlets of silica shooting vertically through the yellow orange mass, and there are hints of large fragments cut by small veinlets. The next picture shows a portion of the rock to the right of the middle silica veinlet.
The rhyolite is fractured, possibly brecciated or at least crackled, and shows moderate iron-oxides, mostly goethite and jarosite.
A closer view shows a lot of very fine-grained to microcrystalline light gray silica that forms a matrix around tiny breccia fragments, or has at least replaced an earlier volcanic matrix. Possibly some of the brecciation seen in this exposure is hydrothermal. I recommend petrographic work to get down to the nitty gritty and to really understand what we're seeing.
From the top of the knob, we see the main road north into the central part of the Clan Alpine Mountains. We'll drive up there later, and make a sharp right turn in about a half mile, not far past the second little bend.
And lo, there's Fairview Peak off to the southwest, visible through two knobs of lichen-covered flow-banded rhyolite and rhyolite breccia. Middlegate Station is behind the knob on the right. Will we make it beyond Middlegate Station to Fairview Peak?