Slickenside Ridge #1

Slickenside Ridge is our personal name for a narrow ridge south of Water Canyon, south of an area that MOH and I sometimes call "Dike Hill." Here we are looking across toward Dike Hill, with a face of slickensided, slickenlined quartzite in deep shadow on the right. The contacts between the quartzite and the porphyry dikes, discussed most recently here, seem to be faulted almost everywhere on the lower part of Slickenside Ridge.

Slickensides on quartzite.

Slickenside with slickenlines; hand for scale.

I've reached over to place my hand in the photo, while trying to maintain my camera at verticality.

Slickenside and slickenlines; no hand for scale.

Now I've tried to maintiain verticality without having my hand in the photo. The outcrop was difficult to photograph because of rocks. The first photo not in shadow (second photo above) shows a less oblique, nearly downdip apparent orientation of the slickenlines than the photo above where I was trying hard to get a photo of the true orientation. Not really sure which photo reflects reality better, but I do think the slickenlines were somewhat oblique. (Too bad I don't usually hike with my Brunton!)

Gratuitous shot of spring wildflower: a buttercup, possibly this buttercup, also seen here, though they all look about the same to me.

Slickenside Ridge #3

Coming up Slickenside Ridge past the last little slickenside, we came upon this whopper.

It's hard to tell from this photo, but fractured, brecciated, and slickensided dike rock on the far side of the fault plane is juxtaposed against more dike rock, which is what I'm standing on to take the photo. The fault is dipping more or less to the east, and the slickenlines are almost straight downdip (slightly oblique).

A closter view of the lower part of the slickenside.

An even closer view of the lower part of the slickensided surface.

Using the the direction of some of the steps in the slickensides in these photos, I deduce that the motion is normal, with the east or outcrop side down with respect to the west side. This direction would be expected in a Basin-and-Range setting, but the observed steps don't face uniformly upward, so I can't be sure of my interpretation without further work (offset of beds across the fault would be ideal).

We also noticed a nearby cross-cutting fault of minor displacement running about east-west, offsetting this fault and the faulted dike-dike contact by a few feet. Apparent offset across this cross fault was south side to the east (the fault was poorly exposed and dip direction wasn't obvious).

View of "Dike Hill" across Water Canyon.

We made it up to the notable first juniper tree, and stopped to look across the canyon at the dikes, which were blogged about here, here, and here.

We viewed the hill again a little higher up, from this little shadow created by an outcrop of  quartzite.

We then hiked up to our final outcrop and this view of Winnemucca Mountain (on the left beyond the town of Winnemucca) and the Santa Rosa Range (the bluish mountains on the far right).

Our hike wasn't over, though...

Slickenside Ridge #2

A small set of slickensides, with slickenside float above, on Slickenside Ridge above the last locality, this time in quartzite only.

Looking uphill toward more dike rock, green grass, and blue sky. Quartzite is deep in shadow on the right.

What else will we find?

Things You Find in the Field: Another Rock Wall

Is that a dike leading across the far field to the brownish outcrops?

As I mentioned near the end of my last post about "Slickenside Ridge" , MOH and I had seen a rock wall the first day we hiked up the north side of the canyon to investigate some dikes of rhyolite porphyry. The photo above shows our first view of that rock wall, looking from east to west, before we knew for sure it was a wall and not a dike.

We eventually meandered over to the brown quartzite outcrops and found for sure that we were indeed looking at a rock wall.

We determined to walk back along the wall to discover what we could about who or why it was built.

Aha! Barbed wire.

A former fence post?

Barbed wire and flowers with boulders of dike rock.

More wire, strung along more or less parallel to the length of the wall.

A rusty, old can of unknown age and purpose.

Looking back toward the quartzite knob from a wired exposure of dike rock.

By now we've made it to the middle of the expanse between the location of our first view on the east and what we thought would be the end of the wall at a couple ribs of dike rock in the middle of the area — but the wall, and its associated wire and posts, continues on farther than we expected.

The wall continues on toward a fairly large rib of dike rock.

Fence post with barbed wire attached.

The wall here is composed mostly of yellowish-brown dike rock
and barbed wire.

Post sticking out of a pile of rocks.

Here we've walked to the far eastern side of the large rhyolite porphyry rib, to find a post or two stuck in a cairn made of the same rock.

And the wall continues on toward the dirt road we hiked up.

The truth is, I don't really know who built the rock wall or why, though it was obviously used at some point as a base for a barbed wire fence, presumably a cattle fence. The wall is made mostly of fairly large boulders of both rhyolite porphyry and quartzite, not particularly neatly stacked (or since fallen into disarray), and the wall uses large outcrops and ribs where possible, saving some of the effort that would be required to build wall its entire length were the outcrops not present.

A view of the lower part of the rock wall as seen from across the canyon.

It was after climbing Slickenside Ridge that we discovered that the wall extends at least all the way to the floor of the canyon, where it's built below a rocky section of hill with a lot of outcrops. I suspect that the wall winds up through the rocks as it did near the top of the hill, but we haven't walked that steeper section to check it out.

Fault Breccia on Slickenside Ridge

Up above our last hiking stop on Slickenside Ridge, MOH and I came across this wonderful exposure of a breccia (hiking stick for scale).

Here's a closer view, showing massive and drusy quartz cementing  the breccia and filling vugs left in the rock.

This is a type of fault breccia — though I was so into my admiration of the breccia that didn't think to look for the fault  — and you can see hints of slightly oblique slickenlines on the smooth upper surface in the first photo.

In fact, it just occurred to me to show you what I mean, so here are two photos of that upper surface, one without drawings, one with.

Planar fault surface from the 1st photo, enlarged.

Same photo with some lines drawn in.

The possible slickenlines in the upper left are the ones I noticed first; the second possible slickenline direction shown in the lower right is vaguer, might be my imagination. More field work required!

A zoomed view of the "best" part of the breccia.

Looking northwest toward Winnemucca Mountain (hidden from view by my choice of framing).

Now I've walked back over to the spot where I left you in the last post, looking down Water Canyon toward the northwest. Just above the bright reddish orange dike rock on the right side of the photo, on the hill across the canyon, you can see the lower part of a rock wall first mentioned in this early post about the dikes.

Looking back down the hill and across the canyon.

And so now, as we turn to head back down the hill, we might think about investigating the rock wall on the far hill, the one we sometimes call "Dike Hill."

2013 Top Posts at LFD

...and, like last year, a few more. And to quote myself from last year:

Because of the vagaries of stat reporting (in this case, by Google Analytics), I'm listing both the top ten posts for the year (in large font, with respective Top Ten number), and the top two posts for every month (non-ten-rated posts are in a smaller font).

I've done the same this year, except that in 2013 there were so few posts during the last three months of the year, that I've only listed one each for October, November, and December.

And so, the top 10 posts, plus 14 extra:

January:

• Deskcrop: Dumortierite and Dumortierite Schist #5
• Map Comparisons

February:

• Things You Find in the Field: World's Worst Road?
• Five Year Blogger-versary!!

March:

• Jungle Fever, A Documentary about the Bre-X Gold Scam #3

• Repost: Blackhawk Landslide, California - from Pathological Geomorphology #4

• A Geologist Who Preferred to be Called a Prospector #9

• Things Your Find in the Field: Metal Bars, Mine Dump, and Adit #10

April:

• Accretionary Wedge #56: Landscapes as seen by a Geologist #2
• Things You Find in the Field: Dikes and Drill Holes

May:

• Fault Breccia on Slickenside Ridge
• Things You Find in the Field: Pyramidal Objects #3

June:

• Update from the Lake: Hornets' Nest #1

• Tufa Dome north of I-80–U.S. 95 Junction #6

• Seeing Geology in Patterns #7

July:

• Accretionary Wedge #58: Beware of the Signs! #8

• Things You Find in the Field: Another Rock Wall

August:

• Huge Amounts of Smoke in Nevada from California Fires
• Las Vegas Growth from Google Timelapse

September:

• Across the West and Back Day 2: Pequop Summit to West Wendover
• Across the West and Back Day 2: Across the Salt Lake Desert

October:

• Across the West and Back Day 2: Are We Lost Yet?

November:

• Update from the Lake and a Tribute

December:

• Things You Find in the Field: Speed Traps