Dolly Sods

Over the long Labor Day weekend, my fiancée Lily and my friend Seth and I took a three-day backpacking trip in the Dolly Sods Wilderness area of West Virginia:dollysods_04

Dolly Sods is a unique place, a little patch of flora that is more typical of Canada. It sits atop the eastern Continental Divide, and most of the area drains to the Gulf of Mexico via the Ohio River. Parts of Dolly Sods are sparsely treed, and resemble Arctic tundra. It is the easternmost bit of the Appalachian Plateaus province. Many places reminded me of Alaska:dollysods_24

Rolling meadows and bogs occur in patches, interspersed with forest of spruce, hemlock, and aspen (yes, aspen!):dollysods_04

The area was used as a proving ground during World War II, and there are still some dangerous bits and pieces left over from that time:
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Here’s our happy trio, ready to set off on Friday afternoon:
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Very quickly, I clued into the wealth of small blueberries which were omnipresent in the “tundra” landscapes. I snacked on these continuously throughout the weekend:dollysods_05

A glimpse of two forms of power generation off to the north: Mount Storm on the left (a coal-fired electric generation plant) and a field of windmills on the right:dollysods_06

Here and there, outcrops of white rock rose up above the lichens and shrubs:dollysods_11

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This is the Pennsylvanian-aged quartz sandstone of the Conemaugh Group. Occasionally, it outcrops as bedrock, and other times, you just get these clean boulder fields, surrounded by tundra vegetation:dollysods_07

So what do we see when we zoom in on these outcrops and boulder fields? Well, mostly, we see quartz sandstone:
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…Although there is a regular smattering of quartz-pebble conglomerate, too:
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Occasionally, primary structures jump out at the eye, like some graded bedding…
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…or these cross-beds:
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Annotated copy:
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There were even some fossils, like these plant scraps:
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Plant scraps compressed en masse make coal, and there are coal interbeds to be found in places in Dolly Sods, and bituminous coal can also be found as float, as with these chunks:
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There was even some structure to observe!
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Annotated version:
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A bigger outcrop, right around the bend, showed even more pervasive distortion of the sedimentary layers:
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Annotated version:
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What’s going on with these folds? After all, the Allegheny Plateau isn’t known for pervasive structural shenanigans… I’m guessing this might be soft-sediment deformation: slumping and sliding of sedimentary layers before they got lithified… Any other thoughts? (chime in via the comments section below, if so).

Here is sand weathering out of the sandstone, the grains free and loose again for the first time in ~300 million years:
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The plants were a joy:
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Here’s the view at sunset from our third campsite:dollysods_26

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Yesterday (Monday) morning, when we woke, we found that the temperature had dropped below freezing overnight, and a coarse layer of frost covered everything:
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Detail of the frost crystals on my tent’s rain fly:dollysods_31

The sun rose, and starting melting off the frost and dissipating the fog:

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Soon only the fog remained:dollysods_32

In the warmth of the new day, we hiked out, got apple dumplings at the Front Porch Restaurant across from Seneca Rocks, and drove back home along good old (new) Route 55. It was a great weekend away, just the right distance, in wild country, with great weather. I felt rejuvenated by the experience.

DC fossil website is now live

Chris Barr’s informative website of the “Accidental Museum of Paleontology” that can be found in D.C. building stones is now live. You should go and check it out, and if you ever visit the city, you can use it as a guide for your tourism.

A day in the field

I spent last Thursday on a long field trip in the Valley and Ridge province of northernwestern Virginia. Leading the trip was Dan Doctor of the USGS-Reston. Accompanying Dan was a UVA environmental science student named Nathan. And the NOVA crew rounded it out: professor Ken Rasmussen from the Annandale campus, associate professor Victor Zabielski from the Alexandria campus, and me. We met at the Survey at 9am, and headed west towards Strasburg, site of my Massanutten field trip.

We started off by examining three Ordovician carbonate units (all above the Knox Unconformity) on the I-81 exit ramp at Route 11. This is the same sequence seen at the classic Tumbling Run outcrop: the New Market limestone, the Lincolnshire limestone, and the overlying Edinburg Formation. We looked at fossils, stratigraphy, some minor structures, and some interesting lithified gunk on the inside of some solution cavities (small caves). Dan interpreted it as collapse breccia: lithified sediment from inside the cave. The question was: when did it form? We wrestled with the best way to test its age, and didn’t come to any clear conclusions. I love moments like that one: out in the field, one geologist shows another something that’s caught his or her attention, and the other geologist reacts, and the two toy with the idea, batting it around like a cat with an unknown object. Like the cat, geologists will either then get really excited and attack the new idea, or get bored, shrug, and walk away.

Our next stop was Crystal Caverns, a commercial cave that is in ownership limbo. Our spirited guide Babs said that it was likely the last time she would lead a tour down in the cave. She was busy liquidating the artifacts of the adjacent Stonewall Jackson Museum, which had recently been shut down by its board of directors. The cave is accessed via a small building that has been built over its mouth. It was a cool cave with a significant 3D aspect: we descended in a corkscrew like fashion, then came back up via a different route. Very cool. A shame that it is being closed (at least temporarily) to the public.

We followed the cave with lunch at a local Mexican restaurant, and while we were there, a big thunderstorm rolled through. Victor, Dan, and I played dueling iPhones to get imagery of the weather front and plot out our plan for the rest of the afternoon.

The afternoon was spent visiting outcrops on the west side of the Great Valley, working our way up to Route 50, and then west to Gore, VA. I wasn’t especially fastidious about photographing everything we saw, but here’s a sample of where I opened the camera shutter…

Ooids in the Conococheague Formation:

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Same shot, zoomed in to the middle:

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Fossil (blastoid? crinoid?) stem, Needmore Formation:

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There were some lovely Opuntia cactus blooming among the vetch at this Needmore outcrop:

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From there, we checked out the Chaneysville Member of the Mahantango Formation, where we saw some snail fossils…

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…and some spiriferid brachiopod fossils:

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Our last stop of the day was at the Clearville Member of the Mahantango Formation, which had lots of lovely coral fossils in it:

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Dan put together a Google Map of our 17 stops; if you’re interested in checking out some of these places yourself, then this is a great resource.

I’d like to publicly thank Dan for taking a work day to contribute to our understanding. It was a lot of fun!

Straight nautiloid fossil

It seems I forgot to show this fossil when I found it in February of last year with my MSSE advisor John Graves. We were out in the Needmore Formation of the Fort Valley then. The Needmore is a formation I visited again yesterday with some colleagues in other outcrops further to the west.

In shade (penny for scale):

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In sideways-angled sunlight (thumb for scale):

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I’ll debrief yesterday’s field trip when I get some more time… for now, let me just toss this little fellow out there for your enjoyment.

If anyone can I.D. it based on these two images, please leave your assessment in the comments section.

“Geology of Skyline Drive” w/JMU

I mentioned going out in the field last Thursday with Liz Johnson‘s “Geology of Skyline Drive” lab course at James Madison University.

We started the trip south of Elkton, Virginia, at an exposure where Liz had the students collect hand samples and sketch their key features. Here’s one that I picked up:

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Regular readers will recognize those little circular thingies as Skolithos trace fossils, which are soda-straw-like in the third dimension. Rotate the sample by 90°, and you can see the tubes descending through the quartz sandstone:

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This is the Antietam Formation, a distinctive quartz sandstone / quartzite in the Blue Ridge geologic province. But at this location, on the floor of the Page Valley and butted up against the Blue Ridge itself, we see something else in the Antietam:

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Parts of this outcrop are pervasively shattered: a variety of sized clasts of Antietam quartzite are loosely held together in porcupine-like arrays of fault breccia. Turns out that this is the structural signature of a major discontinuity in the Earth’s crust: the Blue Ridge Thrust Fault. This is the fault that divides the Valley & Ridge province on the west from the Blue Ridge province on the east. And here, thanks to a roadcut on Route 340, we can put our hand on the trace of that major fault. Here’s another piece of the fault breccia:

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After grokking on the tectonic significance of this fault surface, we drove up into Shenandoah National Park, to check out some outcrops along Skyline Drive itself, but it was really foggy. Here’s a typical look at the team in the intra-cloud conditions atop the Blue Ridge:

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We checked out primary sedimentary structures in the Weverton Formation at Doyles River Overlook (milepost 81.9), like these graded beds (paleo-up towards the bottom of the photo)…

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…and these cross-beds. You can see that it was raining on us at this point: hence the partly-wet outcrop and glossy reflection at right:

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Cutting through this outcrop was a neat little shear zone where a muddy layer had been sheared out into a wavy/lenticular phyllonite, with a distinctive S-C fabric visible in three dimensions:

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Finally, we went to the Blackrock Trail, which leads up to a big boulder field of quartzite described as Hampton (Harpers) Formation. In some places, exquisite cross-bedding was visible, as here (pen for scale):

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Here’s a neat outcrop, where you can see the tangential cross beds’ relationship to the main bed boundary below them:

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…And then if you spin around to the right, you can see this bedform (with internal cross-bedding) in the third dimension. I’ve laid the pen down parallel to the advancing front of this big ripple:

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That last photo also shows the continuing influence of the fog.

Thanks much to Liz for letting me tag along on this outing! It was a great opportunity for me to observe another instructor leading a field trip, and also to discover some new outcrops in the southernmost third of the park.

Hand lens + iPhone → Macrocamera

Ever since I saw this at Microecos and Myrmecos, the staff here at “Mountainecos” have been wanting to try it out. Behold my first three iPhone photos supplemented by a hand lens (Belomo triplet, at a distance of about 1.5 cm from the subjects):

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That’s a trilobite and a penny, by the way. Try it out; post your results!

Transect Trip 25: sheared microbrachiopods

This one is also from the Millboro Formation: itty bitty brachs (not too much oxygen in those depths for building up big body sizes) that have been sheared during Alleghanian deformation.

Pyrolusite on a pterosaur

All the photos I posted over the weekend here were via iPhone, and hence not particularly high-quality, despite their excellent geological content. Now I’ve downloaded the photos from my real camera, and have a few good ones to show. Here’s a succession of photos of the same specimen of Pterodactylus longirostrus, each progressively more zoomed in than the last. It’s a late Jurassic pterosaur (140 Ma) from the Solnhofen limestone of Germany.

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I mainly took these for the pyrolusite dendrites rather than the fossil itself…

Giant ground sloths

In the American Museum of Natural History:

These mylodontids reminded me of Puerto Natales

Triassic rifting in the Capitol

My girlfriend’s mom was in town in January, and we took her down to visit the Capitol Building. The tour had a good bit of history, but definitely missed the opportunity to talk geology. I was particularly struck by the columns in the Hall of Statuary:
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Close up of one column, with my hand for scale:
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That’s the Leesburg Conglomerate, a Triassic-aged deposit found in the western part of the Culpeper Basin of Virginia. (Technically, it’s “the Leesburg Member of the Balls Bluff Siltstone.”) The photos I showed readers in May 2008 were from the east side of Route 15, just north of Leesburg itself. The Culpeper Basin is a failed rift valley from the time of Pangea’s breakup. I say “failed” in the sense that it failed to become an ocean basin like the Red Sea or the Labrador Sea. While it may have failed to rend the metamorphic rocks underlying Reston, Annandale, and D.C. from the North American continent, it succeeded in accumulating continental sediments for two periods of geologic time, preserving a detailed record written in siltstones, conglomerates, basalt flows, diabase intrusions, dinosaur footprints and fish fossils.

Among the strata that the basin accumulated, the Leesburg Conglomerate stands out as the real rock star. It’s a gorgeous looking rock, a poorly-sorted and well-oxidized mishmash of (mainly) limestone chunks derived from the weathering of the young Appalachian Mountains. Visually striking as it is, it’s not surprising that someone tried to use it as a building stone. However, it’s not well-suited to being sculpted. Rumor has it that after countless episodes of pebbles popping out of otherwise pristine, finished columns, the column-carver swore he would never touch this particular stone again. To my knowledge, the Capitol’s Hall of Statuary is the only place in the world where the Leesburg Conglomerate has been used as a building stone.

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