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16 September 2022
Friday fold: isoclinal limestone near Harrisonburg
This weekend, my family and I traveled to a little agrotainment complex north of Harrisonburg, Virginia, a joint called Back Home On The Farm. It featured a corn maze, hayrides, petting zoo, apple cider donuts, and pumpkin picking. All typical fall frolic; good clean fun. But there were also big blocks of limestone everywhere on the property. I did my best to check them all out. I was mainly scanning …
13 November 2020
Friday fold: stairsteps in the Tonoloway
A quick “Friday fold” that is expressed in three dimensions – “stairstep” style folds deforming a bed of Tonoloway Formation dolostone…
7 August 2020
Friday fold: syncline in Helderberg Group limestones
I went on a day of field work last week to Corridor H, West Virginia, to help make drone-based photogrammetric 3D models of the huge outcrops there. One site we stopped at is this beautiful V-shaped syncline in Devonian-aged Helderberg Group limestones. Click to enlarge Here are two layers traced out: Here is a GigaPan that Alan Pitts shot of this outcrop several years ago, when it was a bit …
19 June 2020
Friday fold: Scaglia Rossa chevrons at Lago di Fiastra
My friend Alan Pitts is orchestrating a virtual field camp for George Mason University this summer, utilizing outcrops in central Italy’s Apennine Mountains. Here’s a 3D model he just posted of one of the most impressive outcrops there: the chevron folds in the Scaglia Rossa limestones at Lago di Fiastra. I featured the site as a Friday fold 3 years ago when Alan took me there in person, but this …
13 March 2020
Friday fold: Bizarro folding in Titus Canyon
Hi everyone, and greetings from eastern California’s Death Valley, where I’m leading a field geology course over our spring break. I found an excellent Friday fold for you: That’s the Cambrian-aged Bonanza King Formation, a package of limestones, as exposed in lower Titus Canyon, Death Valley National Park. Here’s the thing: the lower part of that outcrop is Upper Bonanza King Formation, while the upper part of the cliff is …
22 November 2019
Friday fold: Noonday Dolomite in Mosaic Canyon
Because I’m putting together a field course for spring break 2020 to Death Valley California, I was looking through old Death Valley photos this week, from the last time I went to that special place. It was seven years ago! How time flies… This one is in Mosaic Canyon, and was taken by my student Marcelo Arispe, a talented photographer as well as a talented geologist: By the standards of …
6 September 2019
Friday fold: Gonzen, Switzerland
Science writer Gabe Popkin shared two fold photos with me this week – both from near Sargans, Switzerland, adjacent to the Rhine River Valley and the border with Lichtenstein. The photos shows the mountain called Gonzen. There, Jurassic limestones crop out in a very wavy pattern: I don’t know the geology of this area in any kind of detail, but I decided to trace out a distinctive upper surface of …
27 July 2019
Offset limestone layers at Broom Point
Yesterday, I featured some folds from Broom Point, but there are also faults there. With the intriguing local limestone conglomerates providing easily-discernible marker beds, these apparently vertical faults are easy to spot. Here are three examples:
26 July 2019
Friday folds: Broom Point, Gros Morne National Park, Newfoundland
Here’s a look at some of the outcrops at Broom Point, within sight of the famous uplifted fjord called Western Brook Pond: The limestone beds here are Ordovician in age, and they dip to the east: In places through there are folds to be spotted in the beds:
12 July 2019
Friday fold: Wiltondale, Newfoundland
Here is an outcrop of folded limestone along route 430 in Newfoundland, inside Gros Morne National Park, just west of the crossroads called Wiltondale: A detailed look at the left antiformal portion of the outcrop: A zoomed-in examination of the rightmost part, where a goopy looking synform resides: Just down the way, a second outcrop shows another fold with the same sense of asymmetry, on a smaller scale: Happy Friday …
8 March 2019
Friday fold: Dent de Morcles
The Friday fold is a recumbent anticline/syncline pair, deforming the K/Pg boundary in the Swiss Alps, as photographed from the air by Bernhard Edmaier.
23 November 2018
Friday fold: loopy limestone in Utah
The countryside near Provo, Utah yields a terrific Friday fold in an outcrop of Cambrian limestone.
7 September 2018
Friday folds: Continuing contorted Conestoga carbonates
The first Friday of September calls out for a fold. The Burle Business Park in Lancaster, Pennsylvania has an answer – several of them, in fact!
31 August 2018
Friday folds: Rifugio Fontana in the Dolomites
TGIF: “Thank Geology It’s Friday!”
Time for a fold or a dozen – let’s travel to the Italian Dolomites to see some kinky crumpled limestones…
16 August 2018
A suite of deformational features in Lancaster limestones
In the Landisville Quarry, Lancaster, Pennsylvania, there is a quarry that cuts into Cambrian limestones. (The exact identity of these limestones is apparently a matter of some dispute, but that’s not going to stop us!) I visited the quarry in June on a field trip offered through the NAGT’s Eastern Section annual meeting. We witnessed multiple varieties of deformation there. First off, there was straight-up brittle extension, resulting in bedding-perpendicular …
9 June 2018
Friday fold: contorted carbonates of the Conestoga Formation
Today, in Millersville, Pennsylvania, on the campus on Millersville University, I saw these contorted carbonates. They are of the Cambrian Conestoga Formation, and I saw them on a NAGT Eastern Section field trip led by Lynn Marquez of Millersville University. This deformation is purported to be Taconian, but it looks very much like Alleghanian deformation in similar aged and composition rocks in Virginia. Interesting!
18 April 2018
Visiting St. Francis’s lovely limestone
The Cretaceous-Paleogene limestone called Scaglia Rossa was used to construct a basilica in tribute to St. Francis. Let’s head to Assisi and take a look.
10 April 2018
An outcrop showcasing a strand of the Kentucky River Fault System
Roadcuts in Kentucky show Ordovician limestones of two distinct types, replete with fossils and primary sedimentary structures, and juxtaposed by a fault, one strand in the Kentucky River Fault System.
9 April 2018
Orthocone nautiloids of the Lexington Limestone
I took a trip last week to Kentucky. My colleague Kent Ratajeski from the University of Kentucky took me out on a nice all-day field trip to examine some of the local geology. I was particularly impressed with the large straight nautiloid fossils that abounded in the Ordovician-aged Lexington Limestone. Here are a series of photos I took of these orthocones, all on pavement exposures (horizontal bedding planes) with my …
6 April 2018
Friday fold: “wrecumbent in Wrangellia”
Darrel Cowan of the University of Washington has pitched in a Friday fold. Check this lovely scene out: Darrel says this is a recumbent fold in the Upper Triassic Nizina and Chitistone limestones. I took the photo when I worked for Shell in 1973 or 1974. I’m pretty sure it is on the west wall of the canyon occupied by the Root Glacier, several kilometers NW of McCarthy, Alaska. The …
