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7 December 2022

The coastal section at Esterillos Oeste, Costa Rica

Callan documents a geological stroll along the coast of Esterillos Oeste, in central southern Costa Rica, investigating the sequence of sediment in the Punta Judas Formation (Mid-Miocene) exposed there. Fossils, sedimentary structure, diagenetic features, structural deformation, and modern weathering all make prominent appearances.


11 July 2019

A submarine slump complex at Sandy Cove, Newfoundland

Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.


5 June 2017

3D models of sedimentary structures

I’ve been busy making 3D models lately. Here are three ones united by a theme of being sand that was deposited relative to mud. In one case we have scouring to make flutes, in another case we have have localized sagging to make “ball & pillow” structures, and in the third case we have an extraordinary submarine landslide deposit. For two of them, the shale has been preferentially etched away, …


27 February 2017

Bedding / cleavage intersections at Indian Spring, Fort Valley

A new outcrop in Fort Valley shows Devonian fossil-rich mudrocks overprinted by a tectonic cleavage imparted during Pangaea’s birth throes.


25 February 2017

Concretions in the Millboro Formation, Fort Valley

Some enormous concretions are encountered in a shale quarry in the central Fort Valley. Concretions like these are typical of the Devonian-aged Millboro Formation.


28 June 2016

“Dunbar marble” at Barns Ness, Scotland

Thanks to the website, run by Angus Miller, I learned of Barns Ness, a Mississippian-aged limestone fossil site on the shore not far from where we are staying at Dunbar. We ventured out there on Saturday afternoon, in search of fossils. The presence of the Dunbar Cemenet Works nearby is an indication that this is the most extensive limestone outcrop in central Scotland. I set my field assistant loose …


23 June 2016

Mega-trace fossils in the floor of the Old Bushmills Distillery, Northern Ireland

We arrived at Old Bushmills at 4:06pm, and the last tour of the distillery for the day had left at 4:00. But all was not lost – We were delighted to see that the visitor center area was paved in slabs of shale with tremendously large, well-preserved trace fossils – sinuous burrows parallel to the bedding plane, in some cases cross-cutting or looping back over themselves! Great stuff – balm …


15 March 2016


Join Callan for a virtual field trip, as he shares dozens of photos from a recent ‘field review’ of a new geological map in Virginia’s Valley & Ridge province. Highlights: graptolites, trace fossils, geopetal structures, folds and faults.


12 October 2015

Bedding/cleavage GigaPans at Harpers Ferry, WV

I’ve been thinking lately about Harpers Ferry, the spot where West Virginia, Virginia, and Maryland meet, at the confluence of the Potomac River and the Shenandoah River. I’ve noted small outcrops of its overturned beddding here previously, and also described a book I read about the man who made the place infamous: John Brown. I went out there again last week with my NOVA colleague Beth Doyle, and we explored …


28 July 2015

Millboro Formation shale in outcrop and in hand sample

Another site from the GMU sedimentology field trip in April: An outcrop on Route 33 in Brandywine, West Virginia, showing the Millboro Formation. It’s mostly shale, with some intriguing sandstones, too. There are fossils and diagenetic carbonate nodules (concretions). Here’s the outcrop, the largest GigaPan I’ve taken so far (7.9 billion pixels): [gigapan id=”171447″] link The shale itself looks… like shale. It’s fine-grained, and dark (high carbon content, suggesting low …


6 April 2015

Exploring Mahantango Zoophycos traces in GigaPan

Recently, I posted about an excellent road cut in Fort Valley showing well-developed 10 cm+ Zoophycos trace fossils. Presented here are three new GigaPan images (two outcrop; one macro) of Zoophycos from the Devonian-aged Mahantango Formation: [gigapan id=”170978″] link [gigapan id=”170977″] link [gigapan id=”170875″] link These images are part of a new “virtual field trip” that I organized to supplement my historical geology field trip to examine the geologic history …


19 March 2015

Zoophycos trace fossils in Mahantango Formation, Fort Valley

A morning’s field trip yields an outcrop of excellent Zoophycos trace fossils in southern Fort Valley, Virginia.


12 December 2014

Friday fold: Miette slate, Alberta

The Friday fold returns to Canada, looking at Neoproterozoic slate and quartzite at the southern terminus of the Icefields Parkway. Bonus features include ripple marks, graded beds, cross-bedding, cleavage, and boudinage.


8 August 2014

Friday fold: Buckle vs. passive folding in the Chancellor Group slates

The Friday fold is an outcrop in Yoho National Park that showcases differences between buckle folding and passive folding.


1 October 2013

New macro GigaPans of sedimentary rocks from the Massanutten Synclinorium

I have two new GigaPans of hand samples to share with you this morning… The Edinburg Formation graptolites from Mint Spring, Virginia, that I featured here back in May, can now be explored in GIGAmacro hand sample: [gigapan id=”140510″] link Students: are these colonial or solitary organisms? Benthic, nektonic, or planktonic? Does this relate to their usefulness as index fossils? And here’s a graded bed from the Martinsburg Formation (Ordovician …


23 April 2013

Return to the Outdoor Lab

Two years ago, I took a trip to the Phoebe Hall Knipling Outdoor Lab, which is Arlington, Virginia’s outdoor education facility in the Pond Mountains (southern continuation of the Bull Run Mountains), on the eastern edge of the Blue Ridge geologic province. I was invited back last week to look at some new exposures. I brought the GigaPan along. There had been additional erosion on the saprolitic exposure of Harpers …


21 April 2013

Sleeping Inn with the Martinsburg Formation

Three new GigaPans I shot last Friday east of Staunton, Virginia, at a semi-legendary exposure behind the Sleep Inn at the 250 / 81 intersection. [gigapan id=”127959″] link [gigapan id=”127962″] link [gigapan id=”127961″] link Students: Which way is up? Which criteria did you use to make that determination?


2 April 2013

GigaPan suite from the South Page Valley Martinsburg Outcrop

Are you into structure? Sedimentology? Stratigraphy? Well, I’ve got some good news for you – I’ve imaged several key outcrops on the newly-discovered (to me) roadcut on South Page Valley Road, showcasing the middle Martinsburg Formation turbidites (and their Alleghanian structural overprint). [gigapan id=”126510″] link [gigapan id=”126514″] link [gigapan id=”126509″] link [gigapan id=”126483″] link [gigapan id=”126482″] link [gigapan id=”126475″] link See if you can find: an anticline a syncline a …


20 March 2013

Upper Martinsburg “Cub Sandstone” in GigaPan

Today, two GigaPans shot of the uppermost Martinsburg Formation, informally known as the “Cub Sandstone” since it crops out along Cub Run in the southern part of the Massanutten range. 10 or 15 meters upsection (west) of these two outcrops is the base of the Silurian-aged Massanutten Sandstone, the ridge-forming unit. Lower in the section: [gigapan id=”125617″] link Higher in the section: [gigapan id=”125616″] link If you explore these GigaPans, …


15 March 2013

Friday fold: a recumbent anticline in an abandoned quarry

Yesterday, I spent a pleasant day in the field with John Singleton, the new structural geology professor at George Mason University. I was showing John a couple of sites I’ve used as field trip locations for the GMU structural geology class, and John was showing a couple of new sites to me – places he visited on last fall’s Virginia Geological Field Conference. I missed VGFC last fall, as I …