"Those aren't pillows!"

In the 1987 comedy Planes, Trains, and Automobiles, John Candy and Steve Martin have a funny experience. It involves a cozy hotel room (one bed only) and the two travelers are huddled up for warmth. As he wakes up, John Candy thinks he is warming his hand “between two pillows.” At hearing this, Steve Martin’s … Read more

Mineral phantasms?

Ice… serpentine… halite… What do they all have in common? I’ve discussed mineral “ghosts” here before — really, those are only pseudomorphs, where one mineral’s chemistry becomes unstable due to a change in conditions, and then a new mineral forms in the same space. I’ve also brought up the issue of clasts of minerals which … Read more

Flames and pillows, Route 55

I took a look at some interesting blobby structures in the Swift Run Formation last week, and walked readers through my logic in tentatively concluding that they were ball & pillow structures (soft sediment deformation), though overprinted by a pervasive (Alleghanian) cleavage. As we move west in the Appalachian mountain belt, the rocks are less … Read more

3,2,1, Contact!

On my structure field trip just over a week ago, we found the contact between the Mesoproterozoic-aged Blue Ridge basement complex and the overlying Neoproterozoic Catoctin flood basalts (now metamorphosed to greenstone). This nonconformity can be found just west of the Appalachian Trail at the Little Stony Man parking area in Shenandoah National Park. Here’s … Read more

Heroes

For the twenty-fourth edition of the Accretionary Wedge, I selected “heroes” as the theme. For those of you new to the geoblogosphere, the Accretionary Wedge is a ~monthly geoblog “carnival,” wherein various and sundry geobloggers write posts on a common theme. Broadly speaking, submissions to this edition fell into three categories: (1) professional heroes, (2) … Read more

Ball & pillow in cleaved Swift Run Formation?

On my structural geology field trip this past weekend, I made one major modification compared to last year’s iteration. I added a fifth detailed “field study area” at an outcrop of the Swift Run Formation, a Neoproterozoic sedimentary unit that is discontinuous in extent between the underlying Blue Ridge basement complex and overlying Catoctin Formation … Read more