Raton Basin, Southern Colorado / Northern New Mexico
September 28 - October 1, 2006

Description

This was a field trip run by LPL, my old grad department, to the Raton Basin near the border of Colorado and New Mexico. The primary purpose was to study the K/T (Cretaceous/Tertiary) boundary layers in the area, which record the impact event that killed the dinosaurs as well as many other plant and animal species at the end of the Cretaceous period 65 million years ago. At that time, a large (~10 km diameter) asteroid slammed into the earth, forming the Chicxulub impact crater off the Yucatan peninsula. The environmental effects of that impact led to severe, worldwide mass extinctions. A good description can be found at the USGS site here.

My Photos

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Our first stop was at the Salt River Canyon
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Catherine talked about spheroidal weathering, and we looked at a great example along the road near the canyon
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Neat flaky weathering of the rocks in the outcrop
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Petroglyphs near where we stopped
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View to the other side of the Salt River Canyon, where we can see layers of lava that intruded into the sedimentary rock before the canyon was cut by the river
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Rim gravels of the Colorado Plateau, near our lunch stop on the first day. Despite the fact that the Colorado Plateau is higher than the surroundings, these gravel beds are compositionally similar to the rocks of the surrounding areas and show evidence of having been carried by water from those areas, indicating that the Colorado Plateau was originally much lower and has been uplifted.
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Cinder cones in the Springerville Volcanic Field, the third largest volcanic field in the continental U.S.
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Colin talking about jointing in rocks at La Ventana, a natural sandstone arch
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Good examples of jointing
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The arch
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Random caterpillar on the trail
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El Malpais National Park, a volcanic area active as recently as 3,000 years ago. The dark ares amongst the green are exposed lava flows
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Mt. Taylor in the distance
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Amusing warning sign near the overlook of at El Malpais
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A toreva block landslide at the edge of a mesa. It slid off towards the left, and the intact part of the mesa is on the right, capped by a lava flow that predates the landslide.
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Shatter cones in an outcrop on Rt. 475 close to Santa Fe. Shatter cones are produced in impact events, and the ones here are evidence of an impact that occured very close to this spot, although a crater is not known. They were not produced in the K/T impact.
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A goat in the back of a car at one of our gas stops
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The view as we left our campsite in Trinidad, Colorado on the morning of day 3. It was a bit cold that morning.
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Our first K/T boundary layer outcrop, Madrid East
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The K/T boundary layer. The layers in the continental U.S. have a double-layer structure, with a lower, grey layer of material consisting of material ejected from the Chicxulub crater, and an upper, darker clay layer about 5 mm thick that contains material from the impactor. This upper layer is found worldwide and contains high levels of iridium, impact spherules, and shocked quarts that are evidence for an extraterrestrial impact event. The thick layer above the K/T boundary layer is sandstone and the other layers around it consist of materials like mudstone, shale and coal, indicating a swampy environment.
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Our second K/T outrcop, Longs Canyon
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Set of images of one section of the boundary layer
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Another set of images of a section where the upper boundary layer is very well-defined
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Several sections showing significant variation in the boundary layer thickness
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Our final outcrop, Starkville, where we collected our own samples of the K/T boundary layer. If you visit any of the areas mentioned here, don't collect samples from anywhere other than the Starkville site, as those other sites are still used for ongoing scientific research!
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A volcanic dike that was cut through to build a road.
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A Jerusalem cricket, aka. nino de la tierra (child of the Earth), near our last rest stop. It was about 2 cm long.