Geobulletin alpha

Source info:

Author:	Wayne Ranney
Date:	2015-04-07 22:37:00
Blog:	Earthly Musings
URL:	http://earthly-musings.blogspot.com/2015/04/torres-del-paine-national-park-chile.html

Summary:

This national park is one of the best I've ever visited! I was first here in 1995 and always enjoy coming back.This is Montaña Dorotea (Dorothy Mountain) north of Puerto Natales. It is composes of Upper Cretaceous sandstone and shale. The Argentinian border is just beyond the crest and in the 1978 run-up to war with Chile, the area was filled with land mines. They have now been removed. The trip from Punta Arenas to the Park boundary is five hours by bus. This area is about half-way to the park.We stopped at an exposure of the Upper Cretaceous Cerro Toro Formation for photographs. More on this down in the blog.The opening to Cueva de Milodon (Cave of the Milodon's) within the Cerro Toro Formation. I have photo's from the inside of the cave farther down in the posting.Arrival at Rio Serrano just before sunset. This highly meandering stream drains almost the entire landscape within National Park. The clouds are foreboding of the weather we would experience here.Close-up of the shale lithology of the Cerro Toro Formation. This shale was deposited east of the South American arc about 100 million years ago in the Magallanes basin.After deposition, the formation was subjected to crustal shortening and intense folding can be observed in some outcrops. Our first full day in the Park saw lots of rain and heavy wind - a normal day for this extreme latitude (about 52º south). As such, there were few photographs on this day, visiting the Gray Lake.A beautiful sunset awaited us from the picture windows in our rooms in the Rio Serrano Hotel. View to the north of the Cuernos (Horms) de Paine. The orange glow lasted about 10 minutes - and then it was gone beneath more cloud. Note the interior of the massif is light-colored diorite, which intruded the black shale of the Cerro Toro Formation about 12 Ma. The dome-like mass is classified as a laccolith, since the upper carapace was likely not punctured into a volcano.On our way into the Park on Day 2. Hills in the foreground and middle ground are part of the Cero Toro Formation.Close-up of the Cuernos in a fresh dusting of snow. Winter comes early here. Within the shale are occasional fossils like this Inoceramus.Salto Grande (Big Waterfall) drains Lake Nordenskold over a lip of resistant Cerro Toro Formation.We walked in the rain about a mile to get closer to the Cuernos., draped in cloudsThe end of the hike on the shore of Lake Nordenskold.Out local guide Andrea with the tour leader Nick. They were great companions who showed us a good time in spite of the dismal weather. So glad we did this hike!Our soggy group of Smithsonian travelers are still smiling with the Cuernos de Paine as a backdrop. The rain did let up a bit on the way back.Wildfires have ravaged much of this park in the last 20 years and the ghosts of the beech trees line the shore of Lake Nordenskold.Thinly-bedded shale and sandstone comprise most of the western exposures of the Cerro Toro Formation. However, more eastern exposures have thicker conglomerate. What in the world are conglomerates doing in a deep marine basin? There were likely mobilized during earthquakes in the Upper Cretaceous and ran out along the ocean floor to this deep marine basin. You can read a bit more about this here.Traveling to the east side of the massif, the weather is mostly always much sunnier. The mountains block the eastward movement of the wet rains. And in thrs drier country lives the guanaco, a member of the camel family.Here the guanaco is king of the Patagonian steppe. Note the layered hills in the distance of the Cretaceous seaway in South America.Even with a long lens (300 mm) the Andean Condor looks quite small. But these large scavengers are easy to spot as there are hundreds of them in the park.The Rhea is South America's version of southern flightless birds (the ostrich in Africa and the emu in Australia). They are wary of people and a shot this close is rare.Another sunlit morning from the hotel of the Cuernos de PaineOn the way out of the park, it was a dismal, rainy day again and so we made an unscheduled stop to walk in the Milodon Cave. The cave is much bigger than it seems from a distance.Within the cave were found the mummified remains of milodon's (or milodont's). Here is a life-size recreation within the cave entrance. These were giant Ice Age herbivores related to the North American Giant Shasta ground sloth and modern sloths.Looking deep into the cave some 100 meters. Note the stratigraphic horizon in the left-hand wall of the cave where overlying conglomerate rock rests on the underlying shale. This creates an aquatard in the stratigraphy and the weakening of the sediment cement is what caused the cave to become excavated when the waters of an Ice Age lake lapped onto this horizon.Nearing Punta Arenas on the highway from Puerto Natales. Drumlins can be seen in the distance. I love driving and hiking across the Patagonian landscape!Flying over the Andes Mountains from Punta Arenas to Puerto Montt, we could see many glaciated peaks at sunset.

Content analysis:

Stratigraphic context:

Recognized stratigraphic terms [n]:	Cretaceous [1] Upper Cretaceous [3]
Agenames chronostratigraphy [rating]:	Cretaceous [0.67] Mesozoic [0.67] Phanerozoic [0.67] Upper Cretaceous [0.44]

Geographic context:

Location	Country	Latitude	Longitude
Puerto Montt	CL	-41.4604	-72.9534
Magallanes Province	CL	-53.1515	-70.8987
Puerto Natales	CL	-51.7325	-72.5051
Massachusetts	US	42.1842	-71.7182
National Park	US	39.8678	-75.1858
Australia	AU	-24.9121	133.398
United States	US	37.1679	-95.845
Africa		2.07079	15.8005
South America		-23.0301	-67.9037
Seaway	BR	-5.85971	-35.1939
the Dome	AU	-33.8462	151.067

Keywords:

Argentinian border, black shale, cave entrance, Cero Toro Formation.Close-up, Cerro Toro Formation, Cerro Toro Formation.We, conglomerate rock, Cretaceous Cerro Toro, Cretaceous seaway, crustal shortening, deep marine basin, dismal weather, dome-like mass, eastern exposures, heavy wind, highly meandering stream, Ice Age herbivores, Ice Age lake, Lake Nordenskold.Thinly-bedded shale, Lake.A beautiful sunset, land mines, Magallanes basin.After deposition, Milodon Cave, Montaña Dorotea, national park, Nordenskold.Out local guide, North American Giant, orange glow, Paine National Park, Park boundary, Patagonian landscape, Patagonian steppe, Puerto Natales, Punta Arenas, rare.Another sunlit morning, Rio Serrano, Rio Serrano Hotel, shale lithology, Shasta ground sloth, soggy group, South American arc, southern flightless birds, thicker conglomerate, tour leader Nick, upper carapace, Upper Cretaceous, Upper Cretaceous sandstone, volcano.On our way, western exposures