Gary Dale Mawyer
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The Lore and Legend of a Cambrian Rock

6/30/2014

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I suppose practically everyone has a favorite rock, though it is hard to get people to talk about something so personal. One imagines most people’s favorites would be gems and crystals since they are likely to be prettier than the more utilitarian rocks. However, a list of state rocks, minerals and gems vaulted into public prominence by solemn acts of legislature reveals surprisingly many ordinary stones: coal (three states), granite (four states), marble (three states), limestone (two states) and even various forms of sandstone (four states). One wonders what lobbies might have greased such legislative choices: a secretive Society for the Promotion of Common Objects perhaps? A branch of the Masons?

 
http://en.wikipedia.org/wiki/List_of_U.S._state_minerals,_rocks,_stones_and_gemstones

At the risk of saying too much about myself, I confess that my favorite rock is Erwin Formation/Antietam Formation quartzite, the southern branch of which is named after a site in Tennessee, and the northern branch of
which is named after a site in Maryland.
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These rocks could also be referred to as members of the Chilhowee Group, a collection of sedimentary and metamorphic (or metasedimentary) rocks laid down in the long-gone Iapetus Ocean during the late Precambrian-early Cambrian era. As to when this was exactly, it was quite a ways back on the calendar. These rocks were already fairly old when the Boston Americans beat the Pittsburgh Pirates in the first World Series. For a long time, they were literally prehistoric. Eventually some histories were written, but if you go back far enough this quartzite wasn’t even rock yet. It was sand.
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These beds of fused quartz sand, tending toward white but striated with reddish, purplish or brownish zones of mineralization, contain long straight tubes called Skolithos, presumed to be the fossilized burrows of marine worms. Skolithos is a highly characteristic early Cambrian trace fossil, that is, a trace of an animal rather than the animal itself. Whatever left the Skolithos, it was soft-bodied and did not get preserved.
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The typical position of the major ichnofacies in marine and continental environments: Cr - Cruziana; G - Glossifungites; N - Nereites; Ps - Psilonichnus; Sc - Scoyenia; Sk - Skolithos; Te - Teredolites; Tr - Tripanites; Z - Zoophycos
(after Benton & Harper, 1997)

From:
http://www.es.ucl.ac.uk/tf/ichno.htm

As this chart shows, the Skolithos sand beds (marked Sk) seem to have been offshore shelves of the old beaches that once lined the Iapetus Ocean, wave-sorted into homogeneous layers of shifting sand like the Outer Banks of the Carolinas today. As this ocean system closed up, the shifting would have slowed down and the type of sediment flow would have changed. Eventually subduction, pressure, and heat would have transformed the terminal state of the most stable sediment beds into rock. Later re-exposure, re-burial or re-heating would have
altered the rock type again---in the case of the Erwin, from sand to sandstone to quartzite, preserving the worm tubes throughout. The resulting rocks don’t exactly represent the entire topography of the Iapetus coast in a direct way. The Erwin/Antietam quartzite was formed from the most stable sediment beds that survived the subsequent alterations to that topography.


Cambrian quartzite is well exposed on the west side of the Blue Ridge across Central Virginia, in a lens over a thousand feet thick in some places. Its place in the Chilhowee Group helps tell the story of the Iapetus Ocean, which started as a volcanic rift valley of which the Catoctin basalt flows are the relict. For more, see below.

http://www.nps.gov/shen/naturescience/chilhowee.htm

The group started as river sediments and then as lake and lagoon deposits until the ocean was fully open, at which point white sandbanks along the shores of a deep sea provided a habitat for some of the earlier life on this
planet. Tropical limestone reefs and lagoons followed before the Iapetus was pushed back together and closed. It all sounds very exotic but the most amazing part is that it wasn’t a different world.

But I digress. This rock makes fabulous cliffs and excellent talus slides, and it also makes a great cobble.


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The broken fragments of the Erwin/Antietam Formation slither downhill and then march down creek beds in ceaseless phalanxes like the brooms of the Sorcerer’s Apprentice, wearing themselves into characteristic cobbles
that can be ordered from the garden center and used for walkways.
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To me the greatest mystery in the love of Ignatz Mice for Krazy Kat is the substitution of a manufactured brick for a decent cobble. Thank you, George Herriman, for your rich insights into the emotional lives of animals, plants, and minerals as seen below in a panel from the immortal comic strip.


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But they can coexist… I hope.

As an added bonus, here is the newest inhabitant of our rockwork.
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We have devised a habitat that could hardly be improved on, for an insectivorous lover of sun-baked rocks and porches.
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It's a female, possibly "with eggs," and like many an animal deciding where to live, she has "voted with her feet," as it were.
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Stormy Weather and a Full Moon

6/16/2014

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This past Friday, June 13, was also the night of a full moon, which is a somewhat rare coincidence; we're not slated to have another full moon on Friday the 13th until 2049. We also had the first of this year’s Japanese Iris open on Friday, and this confluence of events seemingly set off a trifecta: not one Iris Torrent, but three of them. The first was just an ordinary midafternoon thunderstorm that growled and spat lightning, dropped an inch of rain, and went away, leaving the air hot, sunny and humid. It seemed a good idea to go out and tie up the tomato bushes, so I did. The second storm trolled by a couple of hours later, shot a few bolts, emitted some hair-raising crashes,  and went chasing after the first one, leaving the air hot, sunny and tropical. 

We could hear other storms afoot that missed us, to the north and to the south, and for a while there was one to the east that looked to be about the size of Mauna Loa, but we weren’t affected. In this part of the world summer thunderstorms can travel in packs, and the storms in these packs can be any size from the width of a county to the size of a football stadium. Due to storm turbulence the wind blows from various directions, and it is not unknown for the same storm to travel ten or fifteen miles, then turn around and come back.

The general chaos inflicted by thunderstorm packs can sometimes be a bit much even for people who really like stormy weather. Friday the 13th’s third Full Moon Iris Torrent blew in just before sunset, which this close to the solstice falls a bit after 9:00 pm. We had no trouble hearing the approaching thunder and seeing the increasingly brilliant electrical displays. At first Storm # 3 appeared to be coming from the northeast. But when the rain actually struck it seemed to be coming from all points of the compass simultaneously. Minute by minute it rained more furiously. Soon we could not see the street. A moment or two later we could not see the driveway. Then the storm reached full whiteout conditions, which normally makes me slightly nervous since I have long had a superstitious belief that the larger tornadoes hide inside these whiteouts.

Faced with a density of water that would batter most fish senseless, were they to be flung up into it somehow, one might be forgiven for thinking it couldn’t really rain any harder. One would be wrong. It proceeded to rain quite a bit harder, although it was still possible to hear the thunder overhead and see the radiance of the lightning, if not the actual bolts. Finally, as the storm reached a crescendo, the rain began to spit out  ice. Hail like volleys of gravel ricocheted across the ground, the windows, the gutters. By turning on the porch light, I could see in a dim subaqueous way that the front iris beds were now half an inch deep in pellets of hail. Then the sky began to lighten, the storm began to lessen, and the Blue Ridge reestablished itself on the horizon as a purple band of mountains under an orange band of sunset. 

We had to wait until morning to learn what had happened in  the deer-proof fortress of chicken wire we call our garden. 

Plants of course have lived with disaster much longer than humans. Lots of early plants, for example, survived the Permian Mass Extinction, 252 million years ago. Though so far as I know nobody has yet found a fossil tomato, tomatoes have been around for a while or two and have developed certain clever tricks, such as waving back and forth, having fibrous stems, etc. Several of the tomato plants in our garden were beheaded, but this doesn’t bother them as it would you and me. The tomatoes are fine.

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 Zucchini, on the other hand, have been hopelessly naïve about pretty much everything since the first day. If you have ever wondered what is inside a zucchini stalk, it turns out the answer is nothing. The zucchini plant is 
basically just a collection of tubes attached to wide, delicate, easily destroyed leaves.

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Below, an infant zucchini squash stands alone amid the desolation of its native plant.
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Bad as this looks, as of the time of this writing (two days later) the infant zucchini in the photo has doubled in size, and crowns of new leaves have started up and are already four inches high, while the plants continue to generate proteins using the shattered old leaves until the new crowns take over.

I managed to find the exact center of the storm. It was over the Armenian cucumbers in the corner of the garden.
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This next photo shows what really caused it all, more than the full moon or the 13th falling on a Friday or any other mere superstition. The Iris Torrent has struck again.
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The pumpkin patch is not as damaged as it looks. Pumpkin tendrils are tough and leathery. The leaves are shot through and through with holes, as if someone had fired grapeshot at them. Such is the effect of hail on pumpkins. It doesn’t seem to bother them much.

I call this variety  the “Vampire Pumpkin” for its practice of wrapping suckers around other plants it meets and jerking them out of the ground. It does not like competition. Just hours before the storm, I had transplanted our surviving eggplants beyond the reach of the Vampire Pumpkins after several of them had been thus ensnared and jerked up by the roots.
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Some plants of course seem built for disasters. This dwarf cryptomeria slept through the whole thing, unruffled.
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Finally, here is a heartrending scene. A baby mantis pauses in prayer over the shattered remains of its watermelon patch. Two days later, I am feeling hopeful that the damage done to this patch will not prove fatal.
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    Gary Dale Mawyer, a Central Virginia native, has over 40 years of publishing and editing experience and lives with his wife Karen and two cats in Albemarle County. 

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