Raton Basin
Encyclopedia
The Raton Basin is a geologic
structural basin in southern Colorado
and northern New Mexico
. It takes its name from Raton Pass
and the town of Raton, New Mexico
. In extent, the basin is approximately 50 miles (80.5 km) east-west, and 90 miles (144.8 km) north-south, in Huerfano
and Las Animas Counties, Colorado
, and Colfax County, New Mexico
.
The basin has long been a source of coal, and more recently of coalbed methane. It is known for its well-preserved exposures of the Cretaceous-Tertiary boundary, which has been intensively studied for evidence of meteor impact.
. The basin forms the foothills of the Rocky Mountains, immediately east of the Sangre de Cristo Range
.
, Mesozoic
and Tertiary
age. In the eastern part of the basin, the sedimentary section is capped by flows of basalt
of Miocene
age. The basin is highly asymmetrical, the beds dipping
more steeply on the west side than the east.
The sedimentary rocks of the basin are extensively intruded by igneous plugs, dikes
and sills
of Eocene
to Oligocene
age. Two large granitic
intrusives near the axis of the basin form East Spanish Peak
and West Spanish Peak
. Dikes of felsic
to intermediate composition radiate outward from East and West Spanish Peaks, and on the north side of the peaks have the appearance of large stone walls. Dikes of mafic
and ultramafic composition trend east-northeast to west-southwest across the basin. Basaltic sills tend to intrude along the coal
beds.
The site of the Raton Basin was a coastal plain at the end of Cretaceous and beginning of Tertiary
time, and has a well-preserved sequence of rocks spanning the Cretaceous-Tertiary boundary. For this reason, the Raton Basin has been studied for evidence of the iridium
anomaly thought to be evidence for a large meteor impact at the end of the Cretaceous
that is in turn thought to have caused the Cretaceous–Tertiary extinction event. The boundary is represented in the basin by a 1-cm thick tonstein
clay layer which has been found to contain anomalously high concentrations of iridium. The boundary clay layer is accessible to the public at Trinidad Lake State Park
, among other places in the basin.
mines
opened in the Raton Basin in 1873. Walsenburg, Colorado
, Trinidad, Colorado
and Raton, New Mexico
became coal-mining towns. The coal deposits are in the Vermejo Formation (Cretaceous
) and overlying Raton Formation (Cretaceous and Paleocene
). Most of the mines were underground room-and-pillar, although in later years some mines in New Mexico used longwall mining. Some strip mining was done in New Mexico.
Much of the mining on the Colorado side of the basin supplied the steel mills at Pueblo, Colorado
. Production through 1975 was 326 million short tons (295 million tonnes). There are currently no active coal mines in the basin, although the New Elk coal mine, inactive since 1989 and now owned by Cline Mining of Canada, is expected to reopen in 4th quarter 2010.
on their leasehold in the Raton Basin.
s were drilled into the coal, as a safety measure to drain off gas ahead of mining.
The first wells seeking to produce coalbed methane
were drilled in the Raton Basin in 1982. Thousands of wells have successfully extracted coalbed methane
from the Vermejo Formation
and Raton Formation
coals. The productive coalbed methane area now covers the central part of the basin, and straddles the Colorado
-New Mexico
state line. The two major producing companies are Pioneer Natural Resources
(on the Colorado side) and El Paso Corporation (on the New Mexico side).
In 2007, the coalbed methane field of the Raton Basin produced 124 billion cubic feet of gas, making it the 17th largest source of natural gas in the United States.
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
structural basin in southern Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
and northern New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. It takes its name from Raton Pass
Raton Pass
Raton Pass is a mountain pass on the Santa Fe Trail along the Colorado-New Mexico border in the United States. Raton Pass is a federally designated National Historic Landmark...
and the town of Raton, New Mexico
Raton, New Mexico
Raton is a city in Colfax County, New Mexico, United States. The population was 7,282 at the 2000 census. It is the county seat of Colfax County. The city is located just south of Raton Pass.-Name:...
. In extent, the basin is approximately 50 miles (80.5 km) east-west, and 90 miles (144.8 km) north-south, in Huerfano
Huerfano County, Colorado
Huerfano County is one of the 64 counties of the State of Colorado of the United States. The county was named for the Huerfano Butte, a local landmark. The county population was 7,862 at U.S. Census 2000...
and Las Animas Counties, Colorado
Las Animas County, Colorado
Las Animas County has the largest area of the 64 counties of the State of Colorado of the United States. Las Animas County takes its name from the Mexican Spanish name of the Purgatoire River, originally called El Río de las Ánimas Perdidas en Purgatorio, which means "River of the Lost Souls in...
, and Colfax County, New Mexico
Colfax County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*83.8% White*0.5% Black*1.5% Native American*0.4% Asian*0.1% Native Hawaiian or Pacific Islander*3.6% Two or more races*10.1% Other races*47.2% Hispanic or Latino -2000:...
.
The basin has long been a source of coal, and more recently of coalbed methane. It is known for its well-preserved exposures of the Cretaceous-Tertiary boundary, which has been intensively studied for evidence of meteor impact.
Topography
Although structurally a basin, the Raton Basin forms a topographic high dissected by eastward-flowing streams such as the Purgatoire RiverPurgatoire River
The Purgatoire River is a river in southeastern Colorado, United States. The river is also known locally as the Purgatory River or the Picketwire River...
. The basin forms the foothills of the Rocky Mountains, immediately east of the Sangre de Cristo Range
Sangre de Cristo Range
The Sangre de Cristo Range, called the East Range locally in the San Luis Valley, is a narrow mountain range of the Rocky Mountains running north and south along the east side of the Rio Grande Rift in southern Colorado in the United States...
.
Geology
The sedimentary beds that form the basin are of PaleozoicPaleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
, Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
and Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
age. In the eastern part of the basin, the sedimentary section is capped by flows of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
of Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
age. The basin is highly asymmetrical, the beds dipping
Strike and dip
Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented...
more steeply on the west side than the east.
The sedimentary rocks of the basin are extensively intruded by igneous plugs, dikes
Dike (geology)
A dike or dyke in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across* planar wall rock structures, such as bedding or foliation...
and sills
Sill (geology)
In geology, a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock, beds of volcanic lava or tuff, or even along the direction of foliation in metamorphic rock. The term sill is synonymous with concordant intrusive sheet...
of Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
to Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
age. Two large granitic
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
intrusives near the axis of the basin form East Spanish Peak
East Spanish Peak
East Spanish Peak is a high mountain peak in the US state of Colorado. It is the lower of the two Spanish Peaks, two large igneous stocks which form an eastern outlier of the Culebra Range, a subrange of the Sangre de Cristo Mountains.- Geology :...
and West Spanish Peak
West Spanish Peak
West Spanish Peak is a high mountain peak in the US state of Colorado. It is the higher of the two Spanish Peaks, two large igneous stocks which form an eastern outlier of the Culebra Range, a subrange of the Sangre de Cristo Mountains...
. Dikes of felsic
Felsic
The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium....
to intermediate composition radiate outward from East and West Spanish Peaks, and on the north side of the peaks have the appearance of large stone walls. Dikes of mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
and ultramafic composition trend east-northeast to west-southwest across the basin. Basaltic sills tend to intrude along the coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
beds.
The site of the Raton Basin was a coastal plain at the end of Cretaceous and beginning of Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
time, and has a well-preserved sequence of rocks spanning the Cretaceous-Tertiary boundary. For this reason, the Raton Basin has been studied for evidence of the iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
anomaly thought to be evidence for a large meteor impact at the end of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
that is in turn thought to have caused the Cretaceous–Tertiary extinction event. The boundary is represented in the basin by a 1-cm thick tonstein
Tonstein
Tonsteins are a distinctive type of rock, composed largely of the mineral kaolin. Tonsteins occur in association with coals in the Carboniferous strata of Europe.The individual beds of tonstein are thin but laterally very extensive...
clay layer which has been found to contain anomalously high concentrations of iridium. The boundary clay layer is accessible to the public at Trinidad Lake State Park
Trinidad Lake State Park
Trinidad Lake State Park is a state park near Trinidad, Colorado, United States. The park protects Trinidad Lake, a dammed reservoir. There are hiking trails, and camping and boating opportunities. The park features historical attractions such as the coal mining ruins at Cokedale...
, among other places in the basin.
Coal
Bituminous coalCoal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
mines
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
opened in the Raton Basin in 1873. Walsenburg, Colorado
Walsenburg, Colorado
The City of Walsenburg or Los Leones is a Statutory City that is the county seat and the most populous city of Huerfano County, Colorado, United States...
, Trinidad, Colorado
Trinidad, Colorado
The historic City of Trinidad is a Home Rule Municipality that is the county seat and the most populous city of Las Animas County, Colorado, United States...
and Raton, New Mexico
Raton, New Mexico
Raton is a city in Colfax County, New Mexico, United States. The population was 7,282 at the 2000 census. It is the county seat of Colfax County. The city is located just south of Raton Pass.-Name:...
became coal-mining towns. The coal deposits are in the Vermejo Formation (Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
) and overlying Raton Formation (Cretaceous and Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
). Most of the mines were underground room-and-pillar, although in later years some mines in New Mexico used longwall mining. Some strip mining was done in New Mexico.
Much of the mining on the Colorado side of the basin supplied the steel mills at Pueblo, Colorado
Pueblo, Colorado
Pueblo is a Home Rule Municipality that is the county seat and the most populous city of Pueblo County, Colorado, United States. The population was 106,595 in 2010 census, making it the 246th most populous city in the United States....
. Production through 1975 was 326 million short tons (295 million tonnes). There are currently no active coal mines in the basin, although the New Elk coal mine, inactive since 1989 and now owned by Cline Mining of Canada, is expected to reopen in 4th quarter 2010.
Oil and gas
A number of wells have been drilled over the years seeking conventional oil and natural gas, but none has been produced in economic quantities in the basin. In April 2008, Pioneer Natural Resources announced that they were developing natural gas reserves in the Cretaceous Pierre ShalePierre Shale
The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from North Dakota to New Mexico....
on their leasehold in the Raton Basin.
Coalbed methane
Coals in the Raton Basin were long known to be "gassy." During development of the Morely mine in the early part of the 20th century, two gas relief wellRelief well
A relief well is a well drilled to intersect an oil or gas well that has experienced a blowout. Specialized liquid, such as heavy drilling mud followed by cement, can then be pumped down the relief well in order to stop the flow from the reservoir in the damaged well.The first use of a relief well...
s were drilled into the coal, as a safety measure to drain off gas ahead of mining.
The first wells seeking to produce coalbed methane
Coalbed methane
Coalbed methane or Coal Bed Methane, coalbed gas or coal mine methane is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, and other countries...
were drilled in the Raton Basin in 1982. Thousands of wells have successfully extracted coalbed methane
Coalbed methane
Coalbed methane or Coal Bed Methane, coalbed gas or coal mine methane is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, and other countries...
from the Vermejo Formation
Vermejo Formation
The Vermejo Formation is a geologic formation of Upper Cretaceous age which outcrops in the Raton Basin of northeastern New Mexico and southeastern Colorado....
and Raton Formation
Raton Formation
The Raton Formation is a geological formation of Upper Cretaceous and Paleocene age which outcrops in the Raton Basin of northeast New Mexico and southeast Colorado....
coals. The productive coalbed methane area now covers the central part of the basin, and straddles the Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
-New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
state line. The two major producing companies are Pioneer Natural Resources
Pioneer Natural Resources
Pioneer Natural Resources Co. is an Irving, Texas-based oil and gas company. The company was created in 1997 by the merger of Parker & Parsley Petroleum Company and MESA Inc. In 2004, Pioneer Natural Resources merged with Evergreen Resources, Inc. The company has approximately 1700 employees...
(on the Colorado side) and El Paso Corporation (on the New Mexico side).
In 2007, the coalbed methane field of the Raton Basin produced 124 billion cubic feet of gas, making it the 17th largest source of natural gas in the United States.