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20 August 2022
Two erratics from coastal Maine
Happy Saturday! Here are two erratics (glacially transported boulders) that I saw last week in coastal Maine. This one shows prominent subparallel striations: And this one, in the town of Penobscot, next to the greasy spoon called Bagaduce Lunch, shows aligned feldspars that suggest magmatic flow: Nothing like a good erratic to get the weekend started off right!
18 August 2022
Quarrying soapstone
Earlier this summer, I was lucky enough to visit a soapstone quarrying operation in Schuyler, Virginia, right on the Albemarle/Nelson County line. These soapstone bodies are metamorphosed ultramafic intrusions into the Neoproterozoic sedimentary deposits of the Lynchburg Group. The protolith peridotite sill crystallized at ~580 Ma, meaning the host sediments are older than that (but younger than the Grenvillian basement complex that underlies both). Then both plutonic rock and sedimentary …
21 February 2017
Q&A, episode 3
A reader asks about the use of zircons in isotopic dating, and the argument for submerged continental crust beneath Mauritius.
11 January 2017
More Messengers from the Mantle
Since I showed off the 3D kimberlite intrusion breccias yesterday, I feel as if I owe you some other photos from that lovely exhibit at the IGC. I apologize for the poor quality of these photos – the gorgeous samples were behind glass and brightly lit, which made photography difficult. But the rocks are sooooooooo pretty, I think you’ll enjoy viewing them just the same. Let’s start with a gargantuan …
23 April 2016
Mineral surfaces under the SEM: 6 new micro-GigaPans
As mentioned yesterday, my student Robin has been having some success lately in making GigaPan-scale imagery using the new desktop scanning electron microscope that our division acquired. They aren’t as super-high resolution as most of the other GigaPan images I post here, but they are very, very small – and thus expand the scope of our imaging initiative. Enjoy exploring: find cleavage planes, microscopic plumose structures, examples showing the constancy …
2 April 2016
Five new GIGAmacro images
Here are a few new images I’ve been working on with my home-based Magnify2 imaging system from GIGAmacro. Strophomenid brachiopods from Mississippian Mauch Chunk Formation, West Virginia: [gigapan id=”185738″] Link Boninite from New Caledonia: [gigapan id=”185707″] Link Lepidodendron scale-tree bark from Poland: [gigapan id=”185689″] Link Potassium feldspar crystal, from a pegmatite: [gigapan id=”185688″] Link Catoctin Formation greenstone from a feeder dike east of Linden, Virginia: [gigapan id=”185681″] Link Enjoy exploring …
17 March 2016
A GIGAmacro view of the front and back of an anorthosite cobble
Here are two views of a single anorthosite cobble, collected in the Adirondack Mountains of upstate New York: Raw, natural surface: [gigapan id=”185220″] Link Slabbed and polished surface: [gigapan id=”185217″] Link As you zoom in and explore these GIGAmacro images, see if you can find the delicate little “necklaces” (reaction rims) of garnet wrapping around the few isolated pyroxenes!
13 November 2014
Gypsum casts? You be the judge — UPDATE: Syneresis cracks!
Silurian aged mud cracks feature small lensoidal features: are they casts of ancient gypsum crystals?
7 May 2013
Brallier Formation 2: tectonic structures
Yesterday we examined primary sedimentary structures (including trace fossils) at an outcrop of Devonian-aged Brallier Formation turbidites between Deerfield and West Augusta, Virginia. Today, we’ll zoom in on the tectonic structures at the site: folds, faults, and joints. Remember, you don’t have to take my word for it. You can explore it for yourself in this M.A.G.I.C. GigaPan: [gigapan id=”128612″] link One thing that’s kind of cool about that GigaPan …
30 April 2013
Strained metaconglomerate in Klingle Valley, DC
Following on yesterday’s post about the kink bands within the strained metagraywacke of the Laurel Formation in DC, let’s take the opportunity today to go to Klingle Valley, site of a different facies within the Laurel Formation: a strained metaconglomerate. Though the exposure isn’t as great as the Purgatory Conglomerate, I think you’ll find plenty to hold your attention in these rocks. Close looks will reveal sericite-after-staurolite pseudomorphs (evidence of …
24 April 2013
Native copper from the Catoctin Formation
Another new insight from last week’s visit to the Outdoor Lab was that they have several fine examples of native copper found in float of the Catoctin Formation on their property. Here are a few examples: Classic examples – a bit of malachite in there too, it looks like. I wasn’t totally shocked when I saw these items, since just a month or two ago, I was shown a similar …
10 November 2012
New GigaPans from the M.A.G.I.C. project
My students Chris Johnson and Robin Rohrback have been busy adding to the Mid-Atlantic Geo-Image Collection. Check out a few of these new GigaPan images: [gigapan id=”117788″] link [gigapan id=”117786″] link [gigapan id=”117390″] link [gigapan id=”117346″] link [gigapan id=”116919″] link
21 January 2012
Turkish blueschist macro-GigaPan
With my new “macrogigapan” rig from Four Chambers Studio, I produced a single image last week as part of my Mid-Atlantic Geo-Image Collection project (M.A.G.I.C.). I’m still learning the ropes of the machine – I shot about 3 times as many photos as I needed to to make this gigapan. Lessons learned, yet again. Anyhow … Dive in! You can make it full screen by clicking on the ‘GigaPan’ logo …
22 December 2011
Virtual sample gigapan #1: pyrolusite dendrites on limestone
With my new “macrogigapan” rig from Four Chambers Studio, I produced this image last week before I left on vacation: [gigapan id=”94714″] That sample measures 18.5 cm long, and is about 4.9 cm wide. Pretty good resolution, eh?
