The Andean foothills in Southern Peru are the site of a 10-day geological research intensive for College of the Atlantic faculty and students.The Andean foothills in Southern Peru are the site of a 10-day geological research intensive for College of the Atlantic faculty and students.

Alba Mar Rodriguez Padilla ’18, Gemma Venuti ’18, and COA Anne T. and Robert M. Bass Chair in Earth Systems and GeoSciences Dr. Sarah Hall joined three Peruvian geologists from Instituto Geologico, Minero y Metalurgico (INGEMMET) on the trip. This experience was part of Rodriguez and Venuti’s senior project work and Hall’s ongoing research in Peru.

COA earth sciences professor Dr. Sarah Hall, left, and seniors Alba Mar Rodriguez Padilla '18 and Gemma Venuti '18 during a ten-day research trip to the Atacama Desert of Southern Peru.COA earth sciences professor Dr. Sarah Hall, left, and seniors Alba Mar Rodriguez Padilla '18 and Gemma Venuti '18 during a ten-day research trip to the Atacama Desert of Southern Peru.The team targeted several field sites located between Tacna and Moquegua, mainly in the Andean foothills region. Every day provided opportunity for new adventures: hiking across faults, traversing rivers, and sliding down cones of loose sediment.

“Good rock exposures are so abundant in Southern Peru due to the hyperarid climate of the Atacama Desert. It’s a Geologist’s dream playground!” Rodriguez said.

The team mapped landscape features such as stream beds, faults, and debris flow deposits in an effort to reconstruct the climate and tectonic record at a few specific localities. As this extremely dry region is subject to intense rainfall during large El Niño events, finding evidence for past floods will hopefully enable a better understanding of the periodicity of these large events. Further, as this is a tectonic active region, mapping active faults and determining their paleoseismic record will assist in geohazards assessments.

The team collected samples from ash, shells, roots, and sediments in debris flow deposits in hopes of dating the different events. They also collected samples from fault planes—places where the rock is broken due to repeated earthquake ruptures. The students have assisted with sample analysis following the trip, with the aid of collaborators at the University of Maine.

Both students mentioned that the field methods they learned, practiced, and consolidated during the Southern California ESTEM trip last summer were a necessary set of COA Anne T. and Robert M. Bass Chair in Earth Systems and GeoSciences Dr. Sarah Hall uses the Peru trip to continue with an ongoing research project.COA Anne T. and Robert M. Bass Chair in Earth Systems and GeoSciences Dr. Sarah Hall uses the Peru trip to continue with an ongoing research project. Credit: Alba Mar Rodríguez Padilla ’18skills for the field work they conducted in Peru.

One of the most interesting field sites is the Purgatorio Fault site where a 3.5m vertical wall of rock has been offset during a recent rupture that likely occurred around 700 years ago (Benavente et al., 2017). The site encompasses multiple sets of abandoned river terraces and dry, braided stream beds within which the team surveyed and sampled in order to establish a clearer record of the timing of tectonic deformation and El Niño events in Southern Peru.

Venuti and Rodriguez do not hesitate when asked to recall the most exciting point in the trip: “the bulldozer.” One of the major goals for the project was to view the Purgatorio Fault in cross section, which required digging a trench across the fault. The team originally intended to manually dig the trench, and colleague Dr. Carlos Benavente, an INGEMMET geologist, went into the nearby town of Mirave to look for assistance. Approximately an hour later, Venuti, Rodriguez, and Hall were surveying some streams when they saw a cloud of dust and heard a rumbling noise creeping up from down the valley.  

“This bulldozer was driving up the valley towards us! We all stopped what we were doing to watch!” Venuti exclaimed.

For the next two hours, the bulldozer dug a trench that exceeded all expectations the team had.

Dr. Sarah Hall and Gemma Venuti ’18 collect samples in the Atacama desert from ash, shells, roots, and sediments for further analysis back on College of the Atlantic campus.Dr. Sarah Hall and Gemma Venuti ’18 collect samples in the Atacama desert from ash, shells, roots, and sediments for further analysis back on College of the Atlantic campus. Credit: Alba Mar Rodríguez Padilla ’18“Upon seeing the dozer climbing up the valley, I was worried about what we’d gotten ourselves into—but the results were amazing! The trench provided an amazing view of the fault and enabled mapping and sampling beyond anything I imagined possible at this site,” Venuti said.

As a local hiking trail passes very near the site, the Peruvian geologists suggested making this location a “FF site of interest” for hikers along the trail. The data collected inside the trench are part of Rodriguez’s senior project as well as for paleoseismic work by INGEMMET geologist Lorena Rosell. Other exciting discoveries at the site included a thick ash layer in one of the recent river terraces, likely from the 1600 Huaynaputina eruption, and small shells and fragments of plant matter in the marine terrace sediment as well as the sediment in the Purgatorio Fault trench.