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Chronology of Late Holocene Moraines, Cordillera Darwin Journal entries


Chronology of Late Holocene Moraines, Cordillera Darwin:
Implications for the Global Extent and Character of the Little Ice Age

Brenda Hall, University of Maine
and Charles Porter

Patagonia Research Foundation, and UMaine
March 1, 2006 to May 1, 2006

Brenda writes from Puerto Williams

March 3rd to 6th

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NFork

We left Puerto Williams the evening of the 3rd en route to our firstdestination, Pia, a fjord on the south side of the Cordillera Darwin.As we left late in the evening, we put into an anchorage only a couplehours or so from Puerto Williams. The next day, we got as far asVentisquero Holanda and an anchorage called Caleta Olla. HolandaGlacier is spectacular! It calves into a proglacial lake and there areplenty of moraines around. We plan to work here later in the trip. Wetook a look around at the moraines and also at a peat bog that we planto core.

On the following day, we headed west along the Beagle Channel,for Pia, but had to change plans partway there. About an hour afterleaving Caleta Olla, we ran into a pretty nasty squall, with lowvisibility and 60 knot headwinds. The seas started to get exciting. Asthe entrance to Pia is rather shallow, we decided to make for anotheranchorage, Caleta Mañana on the south side of the Beagle. There, thingswere pretty calm and we enjoyed some fish Juan cooked up for us.

Finally, on the morning of the 6th, we entered Pia, which has to be oneof the most beautiful places I've ever been. When entering the fjord,one immediately notices the moraines clinging to the fjord walls. Howthey can stay there is a mystery, because it is very steep. The morainecrosses the mouth of the fjord, and Charlie had to find just the rightspot to take the boat across it. We anchored at a small cove in thewest arm, a place that was to be our home for the next week.

March 7th to 14th

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Epia

Kalv Glacier

Brenda writes from Pia

We spent this week working in the area in and around Pia. There is somuch to do here! The weather by and large has been cooperative. Somedays are downright pleasant! Others are a little wet. The fjord itselfhas two arms, east and west, each with glaciers at the head. When wevisited the head of our arm, we saw a lot of calving, an event roughlyevery ten seconds. At one point, a huge slab calved off and a big,curling wave went shooting across the cove. That was the point at whichCharlie put the motor on full throttle and we raced the wave out of thecove. I suppose it would have flipped the zodiac had it caught us.

We also are working at Oblique Glacier, which is located about an hourzodiac ride up the Beagle Channel. On a nice day, it is a pleasanttrip. On a not so nice day, it can be downright nasty. Lucky for us,we've had mostly nice weather. We did get some fancy waves on our lasttrip home, which apparently were caused by a combination of the windand the currents near the mouths of the fjords. Once we got back intoPia, however, things were pretty much calm. Oblique Glacier is neatbecause there is a whole sequence of moraines on land that we can date.We are using a combination of dendrochronology (for the youngestmoraines) and radiometric (radiocarbon and cosmogenic exposure age)dating to obtain ages for the moraines.

The other place we’re working here is on the spectacular Pia moraine.We have been collecting exposure age samples from a place called TheProw, where the moraine comes out of the forest. To get there, we haveto claw our way 350 m nearly straight up from the water. Apparently,the right route is very important. We got the wrong one and it took us2 ½ hours of hauling ourselves up through the puckerbrush using iceaxes to pull ourselves up. The forest is full of all sorts of dense,prickly, thorny bushes. The only consolation is that most of themproduce edible berries. If we found ourselves stuck, we simply stopped andeat for awhile. Life could be worse! The view from the top was morethan worth the exertion!

March 15 to 17 Brenda writes from Puerto Williams

We have people coming aboard to do some hard-rock geology for tendays, so we needed to get back to Puerto Williams to pick them up. Onthe 15th and 16th we were once more anchored at Caleta Olla which hadno fewer than five boats tied up in it one night!

On the 15th, we walked the Holanda terminal moraine system from one end to another. It is an impressive composite moraine with a steep (and rapidly eroding) ice-proximal slope. We spent all of the next day coring a nearby bog and checking out sections along the river. On the 17th, we went back to Puerto Williams.

March 20-29th, 2006

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Cordillera

Brenda writes from Puerto Williams

We had some other geologists on board during this part of the trip. They were looking at bedrock geology and the formation of Cordillera Darwin. We continued our work at Pia and Holanda and got a look at Seno Garibaldi as well. The weather at Garibaldi was a little wet and it even snowed at sea level. But, when it cleared, it was spectacular! At Pia and Holanda, we continued our work mapping the moraines. It is fall now and the Nothofagus antarctica (beech) has turned a rusty orange. The contrast between it and the N. betuloides is very sharp because the latter is an evergreen and does not turn color. We're back in Puerto Williams right now to drop off the other geologists and to stock up for our longer trip around to the north side of the mountains.

Cheers,
Brenda

 
 

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