First Trip into the Ruby Mountains of Nevada

Would you believe...a geologist living mostly in Nevada since 1975, who had never been into the Ruby Mountains until two weeks ago? One who had been over Secret Pass several times and down Ruby Valley once, but never into the mountains?

One reason to go to Lamoille Canyon, if you've never been there, is the excellent scenery. Another reason would be the excellent geology...including geology related to the metamorphic core complex that makes up the Ruby Mountains — along with several, and more than one type, of low-angle faults — and also geology related to the Pleistocene glaciation of the mountains.

Terminal moraine of Lamoille Canyon,
beyond the field that happens to be part of an outwash plain.

The photo above wasn't our first view of Lamoille Canyon, when MOH and I visited about two weeks ago on our way to the NMEC 2nd Annual GBR. That photo is from the second day's morning field trip to see some of the glacial geology of the Rubys (or would that be Rubies?), led by Dr. Mike McFarlane. Instead, our first view of the canyon was as pictured below:

Looking into Lamoille Canyon from just before the entrance to the Ruby Dome Ranch (Google Maps location).

Unnamed hill 9942 forms the flattish-looking knob just right of center, and although it's hard to tell for sure, even from repeated viewings in Google Earth, the jagged knobs in the distance on the left appear to be Ruby Spire at 10,835 ft on the far left, the Wolf's Ear at 10,788 in the center, and an unnamed peak at 10,835 ft on the right (seemingly lower because it's behind the other two jagged knobs). I've gleaned the names Ruby Spire and Wolf's Ear from Panoramio and Google Earth photos rather than from USGS topo maps of the area, suggesting to me that at least some of the supposedly unnamed peaks and knobs of the Rubys may have names known by the locals and other frequenters of the area.

Another view looking into the first part of Lamoille Canyon,
this time from the 2nd day.

With these first views of the canyon, the valley appears to be dominantly V-shaped: the overall U-shape of the valley has been modified by the post-glacial down-cutting of Lamoille Creek.

At this point, where a falling rock sign appears on the side of the road, the overall U-shaped nature of the glacially carved canyon can be seen.

The main part of Lamoille Canyon forms the foreground right of the road and highway sign, and it continues to the far left where cliffs of brownish gneiss, marble, and granite abound. The Right Fork of Lamoille Creek shoots off to the right, into the U-shaped canyon where its eastern, sunlit slopes are covered by green, yellow, and orange aspen trees.

The GBR was located at Camp Lamoille (AKA Lion's Camp Lamoille or the Boy Scout Camp), nestled in a flat area along Right Fork Lamoille Creek (or South Fork Lamoille Canyon). Photos of the area shown below are from Days 1 and 2 of the three-day outing.

Looking south up the South Fork of Lamoille Canyon. Back in the rocky section of the canyon, Ruby Spire and the Wolf's Ear are on the left;
Mt. Gilbert is on the right.

This photo is centered on a lateral moraine of South Fork Lamoille Canyon, which blocked the main canyon (to the left) and has been breached by Lamoille Creek.

In the photo above, besides the breached lateral moraine, the upper portion of a couloir called "Terminal Cancer" can be seen on the far left. Ruby Spire (Google Maps location) is in the center distance (highest spire of the jagged ridge on the east side of the Right Fork of Lamoille Creek. The Wolf's Ear (Google Maps location) forms the center of that jagged ridge.

We've arrived in camp. The Wolf's Ear is still visible as the highest jagged knob near the center of the photo.

Rapidly changing lighting at Camp Lamoille.

Wolf's Ear is on the left (east side of the South Fork canyon). Mt. Gilbert is the tallest peak on the right.

Our campsite below the cliffs. You can see in this photo the very minimal spots of snow below Mt. Gilbert, fairly unusual in the Rubys for late September.

A closer view of the Wolf's Ear.

Looking up the same canyon from one of the trails near the beaver ponds.

An even closer view of the Wolf's Ear (dark knob on the left), taken on the stormy second day.

Another view of the South Fork of Lamoille Canyon, taken during a downpour featuring multiple hail events and (later) lightning directly overhead.

Camping in the stormy weather of two weeks ago was fascinating. The overall camping experience, which could have been a disaster, was mitigated by the presence of a wood-heated lodge or dining area, and abundant free food and drinks.

Memories: First Trip on Highway 50

Toquima Range and Big Smoky Valley in a dust storm.

There are stories, and then there are stories. There are the stories already written, filed away in computer drives and manilla folders, and there are the stories that come to me out of the blue while I’m driving down some road, often Highway 50 where I seem to do most of my on-pavement travel these days. When I look north and south from Highway 50, down the great basins like Big Smoky Valley or along the great mountain ranges like the Toiyabe Range, I see memories as far as I can see—sometimes farther than I can see—often all the way to the next major east-west highway like I-80 to the north and Route 6 to the south. I'm not sure if all those memories should count as belonging to Highway 50 in particular, but some of them clearly do.

It starts this way, whether driving or riding in the passenger seat: I'll spot some familiar canyon or notice a particular bend in a dirt road, ahead of me or way off in the distance, and suddenly I'm part way up that canyon or around that bend, seeing the place the way I saw it the first time. And as I drive by these places—many of them tens of miles from pavement, some of them nearly a hundred, all of them hazy with the time and distance, many of them not quite visible through mountains or over the curvature of the earth—the times and places begin to overlap, and I can see all the times for a particular place and see all the places for some particular time.

Toquima Range and Big Smoky Valley on a clear day.

I've thought of writing up these memories of Highway 50: it’s the highway with the widest reach across my past and across central Nevada, and I've been thinking about this during at least the last four trips. I could start at one end of the state and work my way to the other end—either end being possibly less rich in memories than the middle—or I could start somewhere in time, like the first time, working my way forward into the present, or at least into the 1980s when travel down that road became less and less frequent, until travel became more frequent again sometime after the 1990s.

Having to start somewhere, I’ll start with my first trip on Highway 50, a geology field trip taken with a required graduate class entitiled Geology of Nevada, a semester-long class with three weekend (or weekend plus) field trips. This was our first trip, and for some of us—for non-Nevadans like me—it was our first real foray into Nevada. What do I remember most about Highway 50 and environs from that trip?

Shadows on mountains in central Nevada.

First off, I remember the breathtaking vastness and the unexpected clarity of the views across central Nevada’s basins and ranges. It was fall, and the light was low on the horizon, the shadows were deep, the clouds came and went, casting shadows of their own, changing and adding to the deep browns and bluish purple hues of late September, or was it early October?

I remember looking for graptolites in the brown-weathering shales of the Ordovician Vinini Formation, finding them on moderately steep slopes under a thin piñon and juniper canopy in the early morning of the second day. Did we have breakfast? Or beer the night before? I don’t remember the food or drink; I remember the graptolites and the cool morning, I remember the sun rising and heating up the hills slowly, rising and finally hitting our fossiliferous field stop.

Petes Summit Road, heading toward the pass, passing Spencer Hot Spring.

Petes Summit it was, a low pass over the Monitor Range just east of Spencer Hot Springs, on a dirt road that I’ve since passed over countless times. We had camped there the first night, after a stop at Bob Scott Summit east of Austin. I know we stopped at Bob Scott, though I don’t remember why, but the summit names Austin, Bob Scott, and Pete’s were forever mapped into the topography of my mind.

At the time, I knew nothing about Nevada's cool fall nights, and had bought a mummy bag to replace the thin, rectangular bag I had brought with me from the east coast, where summer nights were often warmer than wanted, usually muggy and humid, maybe cooling if you stayed up late enough. I had sought out a down sleeping bag at the local Army surplus store on 4th Street, as other grad students had recommended. The guy there sold me a clean, used, fluffy bag that was supposed to be "good to 20 degrees," which seemed unfathomably cold to me, surely good enough to for my field trip needs.

It wasn't. I found out later that I had purchased a sleeping bag filled with feathers, not down. No wonder it was so cold that first night under the stars and trees on Pete’s Summit. Weather Underground puts the lows in nearby Austin, NV at 39 to 40 F in late September, down below freezing in early October, and as low as 17 F in late October. I’m not sure what the date was—it was probably late September, but even with the temps just down to 40 F or so, I shivered all night. I bought a space blanket shortly thereafter, and upgraded to real down within a couple years.

Diamond Mountains on the eastern horizon, as seen from near Lone Mountain.

Other memories from that trip come harder, but are also within the range of my views from Highway 50: the old mills at Cortez (at the time, pronounced COR-tehz by the locals, run that last syllable quickly), my first view of Gold Acres across the valley from Cortez, and the triangular facets in Crescent Valley (the latter being closer to I-80 than to Highway 50, but around a viewable corner, visible from a Highway 50 field trip).

Oh, and then there was the spectacular arm waving from a hill just outside Eureka, with arms waving toward and beyond the Diamond Mountains, then back toward the Roberts Creek Mountains, then back to Diamond Peak: waving at and pointing out the overlap terrane of Mississippian Diamond Peak Formation reportedly sitting on both the eastern and western assemblages of the nearly unimaginably huge Roberts Mountains Thrust. Can you see it? Just over there?

Lone Mountain north of Highway 50, near Eureka, NV.

And Lone Mountain. I took a picture of it from the dirt road heading south into Antelope Valley, one of the better viewing spots for the mountain and for the Eureka Quartzite on its west side. I later drew the formations, Op through Srm through Dd, on one of the printed photos I glued into the field trip report I wrote for class. I think of that first time at Lone Mountain anytime I stop to take a picture, anytime I look deeply into the Eureka Quartzite while driving by.

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Yes, those are my first memories of Highway 50: late September or early October, 1975.

Some Thoughts on Weirdness, and A Picture (or Two) (or Three)

I've been thinking about the idea of weird geology, ever since Dana at En Tequila Es Verdad introduced the topic for Accretionary Wedge #34 — I haven't been thinking about it long and hard, mind you, because I've been busy writing geo things at work, using up both my writing and thinking capabilitites. I wrote a little, thought a bit; then, after thinking some more, I thought I’d finish up this morning at the laundromat, but it tuns out they don’t have wi-fi, which is one thing I find not only entirely weird, but just a little bit irritating.

I have a few thoughts about geological weirdness, the biggest of which is that after all these many years (however long it’s been), I am no longer as surprised by the things rocks can do as when I was first starting to map as part of my job back in the late 1970’s. Back then, I learned an important lesson that has stuck with me over the years, which is: if the rocks are doing something you don’t think is possible or which you have never heard of or read about, look again. Have another geologist come check out your contacts and the nature of whatever weirdness you think you spotted, and brainstorm some ideas. Chances are, you have run across something merely unusual but not impossible. You will have to go with whatever the rocks are telling you that they did on their way to becoming whatever thing they are now.

Volcanic rocks, inside or outside the Huge Caldera settings sometimes known as "Supervolcanoes," can do some particularly unexpected things. When anywhere near them, learn to expect the unexpected and to throw out preconceived notions as soon as it becomes clear that you need to (which isn’t all the time, admittedly). Apply this way of thinking to other, non-volcanic settings. Over the years, expecting the unexpected will serve you well.

Other places to expect particular geologic weirdness are 1) anywhere in the Basin and Range province and 2) any time you are anywhere near a metamorphic core complex or where you suspect that you are in detachment or extreme extension terrane. I’ve found tilted Precambrian rocks above a 50-foot thick, crumbly, weakly mineralized mesobreccia of gneissic rocks, all sitting on top of tilted Tertiary sediments that included soft, punky lake beds. Possibly this unusual tectonic stratigraphy of very-much-older over very-much-younger was not produced by extreme extension, possibly the Precambrian was thrust over the middle to late Tertiary via a thrusting method related to left-lateral strike-slip faulting along the Garlock Fault. Who knows? We never drilled deep enough to find out what lay beneath the tilted Tertiary rocks beneath the tilted Precambrian rocks.

As for weird today, I'll just leave you with these pictures of a giant breccia (breccia in the foreground, breccia in the background). We were driving into the slot-canyon portion of Titus Canyon, a one-way dirt route into Death Valley from just south of Beatty. We drove around a curve in the road, suddenly coming face to face with a megabreccia. I slammed on the brakes (not that I was driving very fast to begin with).
The same angular rock fragments from the first photo can be seen in this second photo, this time without anyone for scale. The breccia extends at least 35 to 40 feet up the wall.
In reading up on this breccia, I found more than one explanation, including more than one kind of sedimentary origin to vaguely cited tectonic causes. Anyone have any ideas?

For a picture with better scale, go here.

Too bad I didn’t get a picture of myself standing in front of this magnificent megabreccia!

Related Posts:
Carnival of the Arid #4 is Up! - and Titus Canyon
Things You Find in the Field: Leadfield

UPDATE: Accretionary Wedge #34: Weird Geology is now up at En Tequila Es Verdad.

UPDATE II:The Encore to the #34 Wedge is now up! (The first Wedge to come in two pieces.)

Where it All Began, Part II

Continued from Where It All Began, which ended:

That, anyway, is one way to make a geologist, although I’m sure there are also other ways. One thing that geologists are sure of is the existence and viability of other ways — this idea is technically referred to as “multiple working hypotheses,” and it’s sometimes stated as, “if ten geologists mapped the same area, you’d end up with at least ten different maps."

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Half Dome

The western U.S. — from the subduction-bounded and transform-faulted Pacific coast to the uplifted and locally hog-backed eastern border of the Rocky Mountains — is a tectonically active region. This activity is revealed in the Mesozoic intrusion, cooling, and crystallization of the great Sierra Nevada batholith (65 to 210 million years ago), in the Holocene to Miocene faulting of the San Andreas fault system (0 to 35 million years ago), and in the Pleistocene to Pliocene uplift of the Sierra Nevada Mountains as a block (1 to 3 million years ago especially, with some uplift still continuing). The west coast has been an active continental margin for a long time — back, way back into the early Paleozoic and perhaps beyond into the Precambrian. I was born and grew up in this active geologic area.

When I was almost eleven, my family and I left the west coast semi-permanently and moved to the mostly inactive, even passive, continental margin of the east coast. The east coast — as geologists learned when the theories of continental drift and plate tectonics came together in the 60s and 70s — has been, for the most part, tectonically inactive since the Paleozoic era, with a smattering of activity in the Mesozoic, and even less activity since then (though not entirely zero). It took geologists years to figure out how plate tectonic theory could apply to such a long dead area (geologic history here and here). It’s now known to be a passive margin.

I never felt truly at home there: the mountains were not mountains, the coastlines were not coastlines — unless we drove all the way to Maine — and no huge masses of granite stuck out anywhere to provide a feeling of solidity or to remind me of home. Eventually, I found pieces of home in the granite quarry of Mt. Airy, North Carolina, and in unakite outcrops hidden somewhere amongst the creeping, overgrown underbrush of the Blue Ridge Mountains (unakite = altered granite). I was also rather partial to the kyanite of Willis Mountain, and enjoyed looking for twinned staurolite crystals. These, and other rocks and minerals, are reminders of the the Appalachians' earlier, more tectonically active heydey, but I was not introduced to them until relatively late in my east coast stage of life. I was a geologic orphan.

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When I returned to the west in 1975, I bypassed all known modes of geologic transportation — continental drift, wind and river transport, landslide, fault creep, thrust faulting, and valley rifting — and, instead, traveled across the continent in my ‘72 Opel, with everything I owned fitting inside except my full length mirror. I deposited myself like a graded bed on the east side of the Sierra Nevada and once again drew renewed strength from its high prominences and great length.

I was now in the province of the intermountain west, an area of complex and still unfolding geology, an area of tension and extension that formed, and still form, the quite obvious elevation extremes of basins and ranges that reach from the Sierra Nevada to the Wasatch Range. (Reno, Nevada, and Salt Lake City, Utah, are moving away from each other at a rate of about ½ inch per year.) The topography is simple and seemingly endless: up and down, up and down, up and down: corrugated or not corrugated, depending on how you like to characterize things. Dutton (1886) described our western ranges as looking like "an army of caterpillars crawling northward" — ranges of the Basin and Range province crawl northwestward across Arizona toward Nevada, and crawl northeastward across Nevada toward the Snake River plain.

I was also in a region shaped by tectonic processes more subtle than those that created the definitive horst-graben topography of the Basin and Range, processes that were active long before the land now known as California even existed — before magma arose from the melting zone deep beneath the west coast’s subducting plate to form a batholith that is intermittently present from at least Mexico to the northern reaches of Canada, and even into Alaska. First, sedimentary layers and volcanic flows had accumulated in former oceans and basins; then, as part of repeated accretionary events beginning in the Paleozoic, western siliceous cherts, siltstones, and pillows had been pushed over eastern carbonates along a thrust fault hundreds of miles long: the Roberts Mountains Thrust.

Carlin Unconformity

I was in a land of slammed-together accreted terranes, of compression and obduction, of province-wide, low-angle reverse faults. I was also in a land of thin and hot crust, a land whose huge-caldera volcanism and volcanic pyrotechnics in the Tertiary could easily make the eruptions of Mt. St. Helens, Mt. Mazama, Mt. Pelé, and Krakatoa look puny. In short, I was in the Great Basin — a region that overlaps with the Basin and Range province but is by no means identical to it — where all rivers, creeks, and dry washes flow inward into inland lakes or dry playas, and not outward to the sea.

I was, at long last, in Nevada.

Nevada, the silver state, has long been known for its bonanza gold and silver, and has more recently been known for its no-seeum, low-grade, disseminated gold (not so low-grade anymore, but that's another story). After moving here, I expanded my horizons: Carlin-type gold deposits in 1976, eastern Nevada in 1980, and the Mojave desert in 1981. Because of my own expansion, I gradually came to know that I was in the land of detachment faulting: a land where extreme extension and tectonic denudation have exposed the tortoise-shell–shaped cores of metamorphic core complexes that cut through the North American Cordillera in a band running from north-central Mexico into British Columbia. Detachment faults — large, low-angle normal faults of regional extent — separate the ductilely deformed cores from the broken and faulted rock formations lying tilted and detached above.

I moved here in 1975 and have been extended, disseminated, and detached ever since.

Some References:
Cathro, R.J., 2010, Nevada-type gold deposits (Part 4): CIM Magazine, v. 5, no. 7, p. 88-90.

Dutton, C.E., 1886, Mount Taylor and the Zuni Plateau, p. 105-198 in Volume III of Report of the Secretary of the Interior; being part of the Message and Documents Communicated to the Two Houses of Congress at the Beginning of the First Session of the Forty Ninth Congress in Five Volumes: Washington, Government Printing Office.

Gilbert, G.K., 1890, Lake Bonneville: U.S. Geological Survey Monograph 1, 438 pp.

McPhee, John, 1981, Basin and Range: Farrar; Straus & Giroux, New York.

Troxel, B.W., and Wright, L.A., 1987, Tertiary extensional features, Death Valley region, eastern California: Geological Society of America Centennial Field Guide-Cordilleran Section, 1987, p. 123-132.

Backroads: A Brief Stop in Ophir, NV

After driving up the lower part of Ophir Canyon, we finally came within sight of the ghost town of Ophir at almost 4:00 pm. MOH immediately jumped out of the truck to take photos of the old buildings, and I found a pullout for the truck
This must be one of the most photographed cabins in Ophir: it's the first one you come to from the downhill side, and it's right along the road. In fact, all the buildings we saw were right on the road, because we didn't take the time to walk around. There are, however, enough buildings, partial buildings, and old ruins that real exploration would take at least an entire day. (MSRMaps location; Google Maps route).
This multi-room sturcture is right on the road, not far past the first one.
We duly photographed the magnificent stonework, from several angles. [Photo © 2010 by MOH.]
At least two sites report this as an old store front. After milling around outside a bit, we went inside.
I was fascinated by the rocks the walls were made of, especially this weakly foliated granitic rock. There are several granitic plutons in the region, including a small stock that crops out near the head of Ophir Canyon. Details about the various granitic rocks were hard to come by online, with suggested ages ranging from Jurassic to early Tertiary. The dark greenish gray slaty phyllite could be from one of several Paleozoic formations (see map below).

From the Geologic map of the Tonopah 1 degree by 2 degrees quadrangle, central Nevada by Whitebread and John (1992).

EXPLANATION (in part):

• TKg = Tertiary or Cretaceous granitic rocks
• Kd = Cretaceous dioritic rocks
• Kg = Cretaceous granitic rocks
• Mzg = Mesozoic granitic rocks
• Pd = Permian Diablo Formation
• PMp = ?? This is probably the Mississippian to Permian Pablo Formation, which was listed in the map explanation as Mp.
• DCsv = Cambrian to Devonian sedimentary and volcanic rocks

The main part of the Ophir mining district, including the Murphy Mine, which was the major silver-gold producer of the district back in its day, is in that structural mess where a couple north-south-trending thrust faults are shown.

The mines in Ophir Canyon are commonly listed as being part of the larger Twin River mining district, and the town of Ophir was once called Toiyabe City. Although almost all online references state that the Murphy Mine (or the entire Ophir Canyon district, or even the entire Twin River district) produced $2 million worth of silver and gold, Kleinhampl and Ziony (1984) report a much lower figure, something closer to $800,000 for the entire Twin River district. Most of the gold and silver production came from Ophir Canyon; most of that came from the Murphy Mine.
Back inside the stone store: While I looked at the rocks, MOH examined the walls and construction, noting the whitewashed plaster still left in a few places. [Photo © 2010 by MOH.]
He also was intrigued by the rock and brick work near this door, with a piece of old stovepipe still remaining in a hole through the brick chimney. [Photo © 2010 by MOH.]
And in this corner, you can see some remaining interior plaster, and also the rafters for the former roof. [Photo © 2010 by MOH.]
Meanwhile, the sun was getting incrementally lower, and I was looking up the canyon, thinking about moving on.
This may be the largest structure in the old town of Ophir, again, right along the road. It's the remains of the old 20 stamp mill, located just below a large mass of mine dumps.
Here's another view of the old mill, this time looking back towards the east.
Part of the Toquima Range through old windows (I presume) in the Ophir Canyon mill.
At last, after less than 15 minutes according to the time-date stamp on my photos, it was time to head up the canyon.

A Few References:
Angel , Myron, 1881, History of Nye County, Chapter L in History of Nevada: Thompson and West, Oakland, California.

Kleinhampl, F.J., and Ziony, J.I., 1984, Mineral resources of northern Nye County, Nevada,: Nevada Bur Mines and Geology, Bulletin 99B. NBMG Bulletin 99B [first pages only].

Whitebread, D.H. and John, D.A., 1992, Geologic map of the Tonopah 1 degree by 2 degrees quadrangle, central Nevada: U.S. Geological Survey, Miscellaneous Field Studies Map MF-1877-A, scale 1:250000.

More About Ophir:
Ghost Towns: Ophir

Ghost Town Explorers: Ophir Canyon AKA Toiyabe City AKA Twin River, NV

Ghost Town Seekers: Ophir Canyon and the Murphy Mill!


Nevada Ghost Towns: Ophir Canyon Photos (historic), Page 2, Page 3

Nevada Landmarks: Ophir: Historical Marker 64

Nevada SHPO: Ophir: Nevada Historical Marker 64

Today's Hike: Trees, Wildflowers, Stratigraphy, and Faults

We went on a hike today, and for the first time in several months, I hiked beyond my usual rocky-flowery point (here, first set of photos) to this bonzai-like piñon tree, and beyond that all the way up the hill.
We saw a fair number of different kinds of wildflowers. This is a broomrape, Orobanche L, possibly this one. It's parasitic on other plants and shrubs, just like Indian paintbrush.
Walking up the hill, I pondered the geology. Here, looking south toward Ward Mountain, you can see some variably dipping limestone and shale formations, which I knew to be cut by the low-angle Chainman Fault, which usually places the Ely Limestone on top of the Chainman Shale (younger on older).
After getting back, I stitched several photos together and did some more pondering (click all to enlarge if desired).
I started drawing lines and stratigraphic map symbols. The section starts with a little bit of Permian Riepe Spring Limestone (Prs), above Pennsylvanian Ely Limestone (doublePe), above Mississippian Chainman Shale (Mc), above Mississippian Joana Limestone (Mj), above Devonian-Mississippian Pilot Shale (MDp), above the Devonian Guilmette Formation (Dg). These are fairly widespread and common units in eastern to east-central Nevada, with the cyclothemic Ely Limestone and the two shale formations sandwiching the Joana Limestone being good place markers for figuring out where one is in the section.
Then I went nuts and added teeth to the two low-angle faults, which have been mapped as thrust faults on the two quadrangle maps of the area. To my surprise, I found that the maps show not only the Chainman Fault, which I already knew about, but they also show a low-angle fault between the Joana Limestone and underlying Pilot Shale. I had concluded on this walk that there had to be a fault there, at least on the east side of my photo-drawing, where the Guilmette is rudely cut off by the Joana.

This section and these faults can be seen on the south side of Highway 50 just west of Ely, although the view will be somewhat obscurred by roadcuts and steep hills.
On the way down, I found this rock specimen of a microfault in Devonian or Silurian limestone or dolomite. All in all, it was a good hike.