Big Bend 2010! Dinosaurs and diabase in the desert

Undergraduate majors head for the border

by Shanan Peters

Undergrads set up camp.

Spring break in Weeks Hall means gearing up for the field and the spread of GeoBadgers into the wild, to seek out new rocks in (sometimes strange) new places. This year, under the guidance of Shanan Peters, and fearless, indispensable graduate student co-leaders JoAnn Gage and MaryRuth Kotelnicki, a group of 12 undergraduate students struck out for the Rio Grande and the beautiful desert landscape of Big Bend National Park.

The group left Madison on Friday, March 26 after classes were over, and headed west through Wisconsin. After camping on the drive down, we drove past the Wichitas in Oklahoma early the next day. The sight of Mount Scott, a large Cambrian granitic pluton, was a poignant moment for many of us. Already a year had passed since a group of GeoBadgers stood on top of Mt. Scott, surveying the landscape before them at the start of their spring break ’09 adventure (link). After enduring the long drive through Texas, our group arrived in the Chisos Mountains and our reservations at the beautiful Chisos Basin campground, just in time to take in the evening twilight.

An unusual rock formation in Big Bend National Park.

The next day, we were all eager to stretch our legs, so we packed our daypacks with water and food and headed up into the mountains, taking advantage of the well-marked trails to find our way to the top of the park. From the high vantage point of Emory Peak, we could see the lay of the land. On the far west side of the park, we could see the dramatic walls of Santa Elena Canyon, which were formed by the Rio Grande’s cut through Early Cretaceous carbonates, folded and faulted out of horizontal during the Laramide. To the east we could see the hills over Boquillas Canyon, which is also a canyon in the resistant Cretaceous rocks carved by the Rio Grande. In the more immediate surroundings we could see and hold in our hands the intrusive and extrusive igneous rocks and terrestrial sediments that give Big Bend much of its beauty.  It was a perfect start for our trip.

From Chisos Basin, we explored the rest of the park. We first went east, to Rio Grande Village and took in the geology around Boquillas Canyon. Sadly, our planned mapping exercise in the interior, off-road part of the park was then thwarted. Our university minivans were not of sufficient durability to get permission to enter the backcountry, mainly due to recent washouts. So, it was back to the west, where we bought topo sheets and tried an on-the-fly mapping exercise, in somewhat oppressive low elevation desert heat! From there it was back to the river, but on the west side of the park near Cottonwood Canyon, where we were able to see spectacular fluvial sediments in the Rio Grande valley and spectacular structures where the Early Cretaceous carbonates were thrust up and over younger Cretaceous rocks.

Students with Shanan Peters in the Rio Grande Valley.

After enduring the desert heat, our group of students, Boomer Bain, Erik Bakko, Brian Boston (watch out for subway and skunks!), Angeline Catena, Reba Heiden, Carl Holtan, Michael Hurth, Alex Katsnelson, Rob Malandri, Jim Senn, Marshal Tofte, and Matt Wessale all deserved a little comfort. So it was off to Terlingua and La Kiva for the night! All in all, we saw a large amount of really excellent geology and had a great time. So, once again, it was mission accomplished for our spring break GeoBadgers.

Originally published in The Outcrop for 2010, UW-Madison Department of Geoscience, p. 19.