Santiago Peak

by Administrator on October 4, 2009

The other major landmark in the southern Marathon Basin is Santiago Peak (6,521 feet), seen here in a photograph taken 6.4 miles south of Highway 90. The peak is one of the most striking landmarks in the Big Bend, rising 3,250 feet very steeply the Maravillas Creek valley below. The upper part is a nepheline syenite intrusion 1,250 feet thick and about three-quarters of a mile in diameter. Debris covers the intrusion’s lower boundary so it is not possible to say whether the intrusion is a plug or the remnant of a larger sill such as the ones capping Nine Point Mesa and Elephant Mountain. Its shape suggests that it is a plug. The intrusion overlies 900 feet of volcaniclastic sandstones, the most easterly occurrence of tuff-derived material.

The mountain in the left foreground is Simpson Springs Mountain (4,685 feet), showing steeply dipping beds of Devonian? (416-359 million years old) Caballos Novaculite on its crest and flanks. The poorly outcropping strata between the novaculite is mapped as Dagger Flat Sandstone, Cambrian (542-488 million years old) and Ordovician (488-444 million years old) in age. The Marathon Basin provides the most complete sequence of Paleozoic rocks in Texas, the only period missing being the Silurian (444-416 million years old).

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Marathon Basin

by Administrator on October 1, 2009

Continuing my journey around the Marathon Basin, this photograph, taken one mile south of the Highway 90/385 junction, is a good illustration of the basin south of Hwy 90. Many of the hills there are capped by a chert bed known as the Caballos Novaculite, Caballos from Horse Mountain in the basin where the chert is particularly thick and prominent. The term “novaculite” comes from Arkansas where this rock also crops out. There it is used for whetstones. The novalculite is very hard, microcrystalline, chemically inert, and brittle. It doesn’t erode chemically, only mechanically, and so caps hills. Note the scallopped outcrops in mid-picture, called “flatirons” by geologists. Flatirons are are found on the flanks of several hills in the basin.

The mesa on the right horizon is Elephant Mountain, prominent to the west of the basin. The mountain is capped by an enormous nepheline syenite sill, four miles long, two miles wide and 1,200 feet thick, weighing about 3 billion tons. The mountain was named for its shape, which resembles an elephant’s back when viewed from some angles. For more see River Road Vistas.

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Cathedral Mountain in the Glass Mountains

September 29, 2009

I have been taking photographs in the Marathon area in preparation for a small book on the basin. The original Big Bend Vistas had a section on the Marathon basin but I had to drop it in the Second Edition to keep the book down to an affordable size.
Cathedral Mountain in the Glass Mountains (confusingly [...]

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Chisos Basin

September 19, 2009

Chisos Mountains Lodge and Casa Grande (7,325 feet) in the early morning mist. Casa Grande is a square-topped monolith of bare volcanic rock with sheer, towering cliffs overlooking the Lodge some 2,000 feet below. The volcanic rhyolite dome capping the mountain is slow to erode, and forms solid cliffs. Below it, thinly layered surge deposits [...]

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Indian Lodge

September 19, 2009

Indian Lodge from below – the design is pueblo revival, something quite foreign to West Texas except though the work of architects like Henry Trost. The Civilian Conservation Corp, who built the lodge, employed its own architects, in this case Arthur F. Fehr, who also worked on restoring the San Antonio missions.

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Historic Fort Davis

September 18, 2009

This view of the old fort has Sleeping Lion Mountain (5,202 feet) on the left horizon with the buildings in front of Hospital Canyon and the columnar lava cliffs just coming into view on the right. The lavas are porphyritic rhyolite of the Sleeping Lion Formation, about 200 feet thick here. It erupted in a [...]

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West Alpine Basin

September 14, 2009

Ranger Peak (6,246 feet) on the left with Twin Peaks (6,133 and 6,112 feet) on the right, photographed yesterday on a beautiful fall afternoon. All three are igneous intrusions into lavas of the Decie Formation.
In mid-photograph, Lizard Mountain is another intrusion. For more see Davis Mountains Vistas.

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Hotel El Capitan

September 9, 2009

We stayed at the newly opened Hotel El Capitan in Van Horn over the weekend. The hotel was built by Charles Bassett of El Paso and opened in 1930. It was one of five hotels that he built in west Texas and eastern New Mexico for the Gateway Hotel chain. He commissioned notable architect Henry [...]

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Haystacks & Puertacitas Mountains

September 7, 2009

I took this photograph yesterday from the Davis Mountains Scenic Loop about 4 miles from the 166/17 junction just south of Fort Davis.
The Haystacks on the left horizon are twin trachyte intrusions (6,895 and 6,670 feet). Their age is unknown; a nearby intrusion was dated at 34.6 Ma, about 700,000 years after the main phase [...]

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Mule Ear Peaks

September 5, 2009

Another favorite image is this one of Mule Ear Peaks from Big Bend Vistas. As I said there,
“Part of the mystique of Big Bend National Park comes from the bizarre shapes that igneous rocks can assume, shapes that are not found anywhere else in Texas. The Mule Ear Peaks are two rhyolite dikes that have [...]

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