Integrative Natural History of Old Ore Road, Part 7: When Is a Jar Not a Jar? | Big Bend National Park, Texas, USA
Looking southwestward at a small canyon of a Tornillo Creek tributary.
In this location we're about 6.9 road mi / 11.1 road km north of the intersection of Old Ore Road and Park Road 12. So we're almost 5 mi (8 km) farther up this rocky track from the site of the previous, wildly popular and deeply appreciated photo in this series.
Whoever Carlota was, she certainly had quite an impact on the local landscape.
I've already shown and described Cuesta Carlota, the prominent ridge that parallels the lower portion of Old Ore Road and whose northern end terminates just east of here. And this scenic spot is known as Carlota Tinaja. That requires a bit of explaining.
It's my understanding the Spanish term tinaja denotes a large jar or other similar ceramic container. This leads me to this post's title, which is a play on the old schoolyard riddle, "When is a door not a door? — When it's ajar." Get it? When . . . it's . . a . . . jar. Of course, it loses its punch when it has to be explained.
But in this case, when is a tinaja/jar not a jar? — When it's a natural depression in the bedrock where standing water collects and wildlife and livestock come to drink. That's a nice poetic adaptation of the word, but I don't know if it has that additional meaning far and wide in Mexico and the adjacent US, or is just another of those funky things specific to the alternative universe that is Big Bend.
In any case, there must have been one of those watering holes down in that streambed.
If you've been to this park and spent some time in Boquillas Canyon and Santa Elena Canyon, you know that one of the area's big geologic stories has to do with the series of distinctly stratified Cretaceous-period formations on dramatic display. These contain a lot of limestone, but include other sedimentary rock types, too. They formed after North and South America parted company during the breakup of Pangaea.
In the big Rio Grande canyons, however, most of what you see are Lower Cretaceous units, including the massive, cliff-forming Santa Elena Limestone. Here, however there's a beatifically lovely exposure of the Upper Cretaceous Boquillas Formation. And according to the USGS map of the park I often cite (Kenzie J. Turner et al., 2011), the rock here belongs specifically to the Boquillas' San Vincente Member.
The booklet that accompanies the map describes the San Vicente as
Medium-gray, finely crystalline, thin-bedded limestone, and brownish-gray and yellowish- to light-gray claystone, calcareous shale, marl, and chalk. Limestone is argillaceous and chalky; claystone is calcareous and contains some clay minerals including kaolinite, montmorillonite, and illite; about 145 m thick.
And thin-bedded it definitely is. Such flaggy strata as these can produce striking patterns and textures.
Apparently the Boquillas Formation owes its origin to sea level rise and the establishment of the Western Interior Seaway. This great swath of seawater not only covered the Big Bend region; it transected this continent from north to south. An ambitious mosasaur or ammonite could have traveled all the way from the Arctic Ocean to the correctly named Gulf of Mexico.
To see the other photos and descriptions in this set, visit my my Integrative Natural History of Old Ore Road album.
Integrative Natural History of Old Ore Road, Part 7: When Is a Jar Not a Jar? | Big Bend National Park, Texas, USA
Looking southwestward at a small canyon of a Tornillo Creek tributary.
In this location we're about 6.9 road mi / 11.1 road km north of the intersection of Old Ore Road and Park Road 12. So we're almost 5 mi (8 km) farther up this rocky track from the site of the previous, wildly popular and deeply appreciated photo in this series.
Whoever Carlota was, she certainly had quite an impact on the local landscape.
I've already shown and described Cuesta Carlota, the prominent ridge that parallels the lower portion of Old Ore Road and whose northern end terminates just east of here. And this scenic spot is known as Carlota Tinaja. That requires a bit of explaining.
It's my understanding the Spanish term tinaja denotes a large jar or other similar ceramic container. This leads me to this post's title, which is a play on the old schoolyard riddle, "When is a door not a door? — When it's ajar." Get it? When . . . it's . . a . . . jar. Of course, it loses its punch when it has to be explained.
But in this case, when is a tinaja/jar not a jar? — When it's a natural depression in the bedrock where standing water collects and wildlife and livestock come to drink. That's a nice poetic adaptation of the word, but I don't know if it has that additional meaning far and wide in Mexico and the adjacent US, or is just another of those funky things specific to the alternative universe that is Big Bend.
In any case, there must have been one of those watering holes down in that streambed.
If you've been to this park and spent some time in Boquillas Canyon and Santa Elena Canyon, you know that one of the area's big geologic stories has to do with the series of distinctly stratified Cretaceous-period formations on dramatic display. These contain a lot of limestone, but include other sedimentary rock types, too. They formed after North and South America parted company during the breakup of Pangaea.
In the big Rio Grande canyons, however, most of what you see are Lower Cretaceous units, including the massive, cliff-forming Santa Elena Limestone. Here, however there's a beatifically lovely exposure of the Upper Cretaceous Boquillas Formation. And according to the USGS map of the park I often cite (Kenzie J. Turner et al., 2011), the rock here belongs specifically to the Boquillas' San Vincente Member.
The booklet that accompanies the map describes the San Vicente as
Medium-gray, finely crystalline, thin-bedded limestone, and brownish-gray and yellowish- to light-gray claystone, calcareous shale, marl, and chalk. Limestone is argillaceous and chalky; claystone is calcareous and contains some clay minerals including kaolinite, montmorillonite, and illite; about 145 m thick.
And thin-bedded it definitely is. Such flaggy strata as these can produce striking patterns and textures.
Apparently the Boquillas Formation owes its origin to sea level rise and the establishment of the Western Interior Seaway. This great swath of seawater not only covered the Big Bend region; it transected this continent from north to south. An ambitious mosasaur or ammonite could have traveled all the way from the Arctic Ocean to the correctly named Gulf of Mexico.
To see the other photos and descriptions in this set, visit my my Integrative Natural History of Old Ore Road album.