Day 95: November 17, 2007 In Salta

  Salta, Argentina
Saturday, November 17, 2007

Day 95: November 17, 2007 In Salta

I got up at 6:00. It was partly cloudy but today would be a go. Hector arrived at 7:00 and I let him in through the front gate. Doing so, triggered the alarm but he was able to shut it off quickly. Chopi arrived 10 minutes later. The first crisis of the day was finding the key to the vehicle. We searched the office and the apartment to no avail. With reluctance, they called Tuity to ask where they were. They were in Tuity's pocket. He told Chopi to walk over and pick them up. When he returned, half an hour later, we loaded the vehicle. Remembering what a long hike this would be from my 1989 and 1991 experiences and considering the weight of the drilling equipment, I decided to not do any drilling. My primary objective for the day would be surviving. The secondary was to find some tuffs with biotites. Tuity's desires had to be tertiary. Since we had already lost an hour, I flushed the idea of bringing the drill.

After filling the tank and picking up some coca, Chopi and I headed out of town. It was clearing off nicely. I took pictures of the Sierra Crestón and Sierra de Metán as we drove toward Metán. We stopped at a gas station minimart, where I bought bottled water, potato chips, and milanesa sandwiches for lunch. The girl behind the counter really liked my Chico Bag. She called all the waitresses over. I never looked at these things as chick magnets but maybe they are!

Sierra Crestón

Front Range of the Cordillera Oriental

Sierra Creston, Cordillera Oriental

We headed to the river, just south of Metán. Toyo had pointed out the route to the entrance to the quebrada, through a maze of farm roads, on Google Earth the day before. We didn't have that image with us but by following our noses, Chopi and I agreed on the most likely route. We got it right the first time.

Incidentally, Metán is the place where I received my first ever speeding ticket, in 1999. It was the only radar trap in the province, at the time and was cleverly placed where a single sign slowed traffic on the new 4-lane highway down to 50 kph (30 mph) for about 500 m. I learned that almost every driver in the province had been caught in the same trap! It was so prolific a trap, that there was a police secretary sitting at a desk, outside, by the side of the highway, with a typewriter to fill in the official documentation. I had noticed her as I went by at 80 kph (50 mph) wondering what the hell she was doing there! I was glad to see it wasn't operating today.

The Río Metán project has been fraught with problems. We initially collected 100 sites in 1989 with a 30 m stratigraphic spacing. Unfortunately, the YPF guys brought brown paint and green flagging to mark the sites so it really didn't stand out against the vegetation and red-brown rocks. I ran the samples at the University of Hawai'i but problems with the thermocouple on the furnace forced me to use AF demagnetization. In spite of assurances that it would work fine from people at the lab, I never considered the results to be top quality.

When we returned to recollect, in 1991, I was surprised to see that a logging road had been put up the stream. Discouragingly, we were not able to relocate any of the 1989 sites. Even though we carefully measured the distances to the sites, few of the 39 new samples helped clear up doubts from the 1989 sampling. Floods, according to the YPF guys, had removed all vestiges of our presence. The road changed things completely; I really didn't recognize anything.

The biggest problem in Río Metán was finding a volcanic ash we could date isotopically. We sampled five tuffs, none of which produced any zircons for fission-track dating. For this reason, I wanted to return to look for tuffs that might have biotites for Ar/Ar dating. A large unconformity in the section requires two isotopic dates, one above and one below. In my old notes I recorded tuffs from both above and below the unconformity. This was confirmed by the original YPF stratigraphic column that Toyo pulled out for me.
Another problem that I had always had was that I had never had a map or air foto of the section so that problem, at least, was now resolved thanks to Google Earth. When I first saw the image, I was surprised to see that there were actually north and south branches to the river. Tuity, Toyo, and I agreed that sampling had taken place on the north branch in 1989.

Chopi drove to the confluence of the two branches. I recognized the cliffs in the Río Piqute Formation just downstream from the confluence. We started driving up the north branch but all signs of the logging road were gone and only a faint track could be seen. We stopped after 100 m where the river cut the track and had deposited large boulders. We got out and started walking. It was 11:00.

Sierra de Metán

Chopi

There are few things I hate more than walking on loose cobbles but all of these quebradas are nothing but loose cobbles. One thing I do hate more is walking on wet, loose cobbles. We had to cross the river 40-50 times. I don't know how I did it back in the days when I refused to use walking sticks. I used both of them on this hike. I only fell down three times: once in the river and twice on the rocks.

Río Guanaco Formation

Río Metán I

Chopi led, hacking away at low-lying branches with his machete. In spite of his 60 years, he seemed to glide over the cobbles that give me such problems. I hate having a bad leg! We followed a horse trail, which I assumed followed the logging road, up the quebrada. Several men on horseback passed us soon after we started out. We hiked at least 8 km like this into the narrow part of the canyon. It is a pretty hike. I was surprised that many of the curves in the canyon looked familiar to me after all of those years.


My body was screaming after 3 1/2 hours of this. We had still not reached the base of the section and I had not examined a single tuff. I knew we were near the base but being concerned that we would not return to the vehicle until after dark, I stopped our ascent of the quebrada. We ate our sandwiches. I was glad we hadn't hauled the drill all the way up there.

Río Metán II

Anta Formation

Walking downstream on wet, loose cobbles is harder than walking upstream. I looked at 8 different tuffs. All were very fine-grained and bentonitized. Not a single biotite was evident. An intense sampling program looking for zircons appears to be our only hope in resurrecting this project.

After about two hours, the men we had seen on horseback in the morning came up from behind. They were led by a creepy-looking, long-haired, young guy, on foot, carrying a machete. He was reluctant to acknowledge me but the three guys on horseback were jovial in their greetings.

About half an hour later, I looked up to see the creepy guy with the machete approaching Chopi 30 m ahead of me. Chopi looked startled and held his machete ready as he started talking with the guy. I went up and started talking with him too. He had some form of speech impediment. He lived alone not far from where we stood. He just wanted to know what we were doing. I'm not sure he understood everything I told him but he was intrigued about the rare white beds in the strata of the canyon being volcanic ashes. We said we would hire him if we came back for more sampling. He told us our truck was about an hour farther down the canyon.

We arrived at the truck a few minutes after the sun set behind the Sierra de Metán. My left buttock was extremely sore from the unaccustomed workout it had received. I left my wet boots on; Chopi had wisely brought a spare pair of shoes. He turned the vehicle around and we started out of the canyon. He pointed up the south branch and said that it had a good road. He had been up there with Claudia and a French geologist a couple of years earlier. I looked up the river and recognized it. Everything dawned on me in a flash. The 1991 resampling was in a completely different stream from the original 1989 sampling! No wonder nothing looked familiar to me then! If only we had had a map in those days, I would have known where we were! Toyo and I were the only ones who had participated on both samplings. He was still very young then and his skills were still not fully appreciated. I made the mistake of assuming that the guy who led the 1991 sampling knew what he was doing. ¡Mierda!

We returned to the highway in the twilight, at 7:30, and drove back to Salta in the dark. We stopped at Chopi's house on the east side of Cerro San Bernardo so he could drop off his field equipment. He drove me back to the apartment arriving at 9:00 and left the vehicle. I gave him bus fare back to his house and went in to take a shower.
I was too sore to go out to dinner so I cooked up our last chorizo and ate a choripan with the rest of the potato chips I bought earlier in the day. I let Elena know I was home. She said she'd be back by 12:00. I knew I would fall asleep so again I left my fone by my head and again it woke me up when she arrived. I let her set the alarm and then I took some aspirin and went to bed.