Geology and Oil Prospecting.

3.1) The Geology of this region is very fascinating and the areas seems to be active geothermally since there is a well known Hot Springs in this area, and petrolium prospectors have gone over this area for the last 50 years and found positive indications of oil and gas deposits.. According to one source of information on the area:

"The granddad of all gargantuan fire mountains that vulcanized the Trans-Pecos badlands eons ago, the Chinati Mountains caldera belies its savage past as it sinks today in calm seclusion beneath rolling grasslands. This volcano, perhaps the most violent that ever erupted in the state, poured our a pancake of ash that spread from the caldera source almost to Alpine--about 262 cubic miles of material over a 40-mile radius. The eruption began when a gigantic column of ash, vented under tremendous pressure from a magma chamber deep inside the earth, blasted into the sky. As a fountain of superheated ash, much of it fell back to earth and created horizontal avalanche that roared across the landscape at speeds of at least 100 miles per hour. Even when the avalanche of ash slowed down and stopped, it held enough heat to anneal (weld) the shard of volcanic glass suspended inside. This eruption yielded a volume of igneous debris more than 1,000 times greater than Mt. Saint Helens did on May 8, 1980. Fortunately, the world has not experienced an eruption of the Chinatis magnitude in modern times." (


3.2) According to the Handbook of Texas Online:

"The Chinati Mountains are between Pinto Canyon on the northwest and Cibolo Creek on the south and east in southwestern Presidio County (at 2954' N, 10428' W). Their elevations range from 4,605 to 7,728 feet above sea level. Chinati Peak is the highest point in the range, which is elliptical in shape and runs from northwest to southeast for fourteen miles. The Chinatis are a series of terraced and dissected mesas cut by rugged canyons in all directions, formed from several superimposed flows of igneous rock. Vegetation in the area consists primarily of sparse grasses, cacti, and desert conifer and oak shrubs. In the 1880s mining developed in the range when John Spencer found silver-bearing ore near the site of present Shafter. The Presidio Mine, which resulted from his strike, produced over $20 million worth of silver between 1883 and 1941". (Handbook of Texas Online:


3.3) The The Chihuahuan Desert Research Institute gives a long discussion about the geology :

"Visitors to the Trans-Pecos are often surprised by the presence of rugged mountains that encompass a triangle formed by the towns of Fort Davis, Alpine, and Marfa, Texas. In Jeff Davis County near Fort Davis, many of these mountain peaks exceed 6,000 feet in altitude, and include majestic Mt. Livermore, which at 8,382 feet, ranks as the fourth highest summit in Texas.

Most of this rocky Texas high country was built from volcanism that began approximately 48 million years ago during the Tertiary period on the geologic time scale. But few people realize, for example, that by driving on Highway 90 between Marfa and Alpine they are, in fact, traveling through the center of what remains of the collapsed caldera of the enormous Paisano Volcano that erupted approximately 35 million years ago! Geologists believe that plate tectonic motion caused subduction (a diving under) of the dense Farallon oceanic Plate where it meets the less dense continental North American Plate off the western coast of Mexico. This collision resulted in tremendous pressure deep within the earth's mantle that produced magma, or molten rock. And the titanic forces that were released by this event caused widespread volcanism stretching from Mexico's Sierra Madre, through Chihuahua, into southwest Texas, and to points as far north as Montana! During the initial 10 million years of volcanism across the Trans-Pecos, activity occurred primarily in the form of magma seeping to the surface through fissures vents in the earth's crust. This extruded magma called lava, flowed over a wide area, overlapping to build low and broad dome-shaped mountains called shield volcanoes. The famous Mauna Loa in Hawaii is an example of a shield volcano. However, this quiescent form of volcanism gradually evolved into a more violent expression of eruptions throughout the region. All kinds of volcanic strata make up the Davis Mountains of which vertical lava flows, with their columnar jointed palisade appearance, and ash-flow tuffs are the most common. As the volcanic activity began to release its energy more forcefully, the composition of the extruded magma changed from mostly basalt to a type high in silica content called rhyolite, a very fine-grained version of granite. Rhyolite is fine-grained because it came from molten rock that was extruded to the surface so rapidly that no large mineral crystals had time to form. Ash-flow tuffs (a hot mixture of gas and ash that cools to a solid) began to form from powerful eruptions and were deposited as sheets of welded material. Subsequent weathering and erosion has produced a totem-like columnar appearance. This type of rock forms the Sleeping Lion formation that is the distinctive backdrop to Fort Davis and is visible throughout nearby Limpia Canyon. A third type of light-colored igneous rock, trachyte, is also present. Trachyte is fine-grained lava that contains feldspar and other minerals but little or no quartz. Marfa to Alpine: Leaving Marfa, we cross Alamito Creek ("alamito" is Spanish for cottonwood) where more of the alluvial fan (streambed conglomerate) is exposed.

3.4) The next feature that draws our attention is Cathedral Mountain (6,800) on the horizon to the southeast. Cathedral Mountain is the erosional remnant of a sequence of lava flows and sediments. Cathedral was affected by an earthquake which measured 5.6 on the Richter Scale in the spring of 1995. The quake caused landslides that subtly altered its shape. A second earthquake of magnitude 3.6 struck nearby in 1998, proving that not all of the geological dynamics of this region are ancient history.

3.5) On the south side of the road, approximately 9 miles out of Marfa, is the pull-off shoulder area dedicated for the viewing of the Marfa Lights. From this location, a fine view of Chinati peak (7,700) is possible across the Mitchell Flats to the southwest. Approximately half-way to Alpine, the mountains of the Paisano Plateau appear on the skyline. Most notable are Paisano Peak, Twin Sisters (also known as Twin Peaks), and Ranger Peak. We are now entering Paisano Pass where we can examine a series of roadcuts that document evidence of a massive volcano that erupted some 35 million years ago. Following the removal of magma from beneath a volcano, the caldera itself often collapses, forming a broken jumble of angular rocks called breccia, that jam the volcano's neck. The road we're traveling runs directly across this collapsed zone - the center of the Paisano Volcano. As mentioned previously, dikes are magma bodies that are forced upward through fractures and cracks in overlaying rock. When we approach the Baptist encampment on our right, a 3 mile-long dike cuts through the breccia and is exposed in several roadcuts. Light-colored rhyolite is also present in roadcuts just beyond the encampment area where it is neatly cleaved by darker dikes. Just ahead on the left is a roadside picnic area, and as the road exits the pass, dark, reddish-colored lava flows become visible as craggy cliffs and vertical joint columns that are embedded with shallow caves. This area marks the eastern edge of the Paisano volcano and these lava flows are a very distinctive and recognizable type of igneous rock. U.S. 90 then enters the alluvial plain where Alpine is situated. Alpine is the largest city in the three counties our circuit traverses, and is the seat of Brewster County. There are many sites to explore here, including Sul Ross State University. Sul Ross is located on a hill on the east side of the city, and from this vantage point, it is possible to look back down U.S. 90 to the west and see the profile of the Paisano Volcano outlined against the sky." ( From The Chihuahuan Desert Research Institute (CDRI) is a non-profit scientific and educational organization based near Ft Davis, Texas.

3.6) Earthquake of April 14, 1995 from the USGS ( April 14 , 1995 00:32:56.1 30.285 -103.347 18 G 5.6 5.7 1.0 397 WESTERN TEXAS. Mw 5.7 (GS), 5.7 (HRV). Mo=3.9*10**17 Nm (GS). Mo=3.8*10**17 Nm (HRV). Two people were slightly injured in Brewster County. Slight damage (VI) at Alpine and Fort Davis. Also slight damage in the Marathon and Ozona areas. Felt (V) at Balmorhea, Barstow, Coyanosa, Fort Stockton, Imperial, Kermit, Marfa, Pecos, Presidio, Sanderson, Sheffield, Toyah, Wickett and Wink; (IV) at Big Spring, Cameron, Crane, Midland, Odessa, Pyote and Valentine.

3.7) Here is a long discussion of petrolium prospecting in the Marfa Basin from Reliant Petrolium ( :

Reliance currently has 15,000 +/- acres under lease in Presidio, County Texas near the town of Marfa, Texas. Reliance is seeking a 1/3rd for a 1/4 to the casing point on the first well. Reliance Oil and Gas will be responsible for its 1/4 share of the completion costs through the tanks on the first well. On the subsequent four wells Reliance will participate on a heads up or 50/50 cost basis in the development of the Marfa Project. Each well will be assigned a 180-acre track. The estimated value of this find is 600 million dollars.

The approximately 6000 square mile Marfa Basin, although the westernmost portion of the petroleum-rich Delaware Basin, remains one of the least explored and least understood sedimentary basins in Texas. Of the approximately 50 wildcat wells drilled in the basin to date, only half were drilled in the deeper portions of the basin, and only 12 of these tested pre-Wolfcamp age units. It is worth noting that at least 17 (approximately 34%) of these wildcat wells reported some type of oil or gas show. Key wells and regional cross sections are shown in Figure 12, Regional Index-Key Wells and Cross sections. Sporadic exploratory activity over the past 50 years has generated cycles of conflicting opinions of the petroleum producing potential of the basin. Drilling prior to the 1960's appears to have been sited with limited technical or scientific support. During the 1960's through the 1980's a number of major and independent oil companies invested in widely scattered exploratory wells supported by 2D seismic, geochemical, and remote sensing projects. None of these companies maintained a persistent exploration effort or drilled more than a few wells. Most, if not all, of the wells drilled during this period targeted seismically-defined structural closures, primarily upthrown fault blocks.

Relatively minor episodes of normal faulting during the Ordovician and again in the middle to late Devonian are inferred from evidence in the Delaware Basin, Central Basin Platform, and Midland Basin areas. Although faults of these ages are almost certainly present in the Marfa Basin, this has yet to be conclusively demonstrated. It is worth noting that reservoir porosity in many of the larger Permian Basin Siluro-Devonian fields is closely linked to structurally high blocks originally produced by Devonian faulting, and this is likely to be the case in the Marfa Basin.

Deposition of the early Ordovician Ellenburger Formation shelf carbonates in the Tobosa Basin reached thicknesses of over 3000 feet to the Southeast, with as much as 1100 feet deposited in the Marfa Basin. Renewed transgression during late Devonian-early Mississippian deposited approximately 100 feet of organic-rich Woodford Shale in the Marfa Basin and up to 600 feet in other parts of the Tobosa Basin. Over 50% of the Marfa Basin sedimentary fill consists of Pennsylvanian and Permian clastic detrital deposits. Reaching a thickness of over 11,000 feet in the central deep. In the Marfa Basin early Cretaceous seas advanced in stages from both East and West, completely submerging the area by the end of Fredericksburg time. In the Western Marfa Basin Trinity age shales, clean sands, and minor shallow water limestones are present. In the Eastern Marfa Basin Trinity age sediments are absent. Younger Fredericksburg age shallow water limestones subsequently blanketed the entire Marfa Basin. Following a brief period of emergence, late Cretaceous seas again discontinuously transgressed across the Marfa Basin, depositing a thin sequence of multicolored shales and thin-bedded marine limestones. The Cretaceous section in the Marfa Basin reaches a maximum thickness in excess of 5000 feet. During the Tertiary the entire West Texas area was emergent, with extensive erosion cutting deep canyons into the Cretaceous deposits of the Marfa Basin and locally removing them entirely. As a result of the rugged topography produced by this erosion and concurrent faulting, Tertiary volcanic rocks deposited on this surface can vary by hundreds of feet in thickness over short distances. Lithologically, the Tertiary volcanics include tuffs, lava flows, and ignimbrites, together with local sill, dike, and stock intrusives. Most of the volcanic rocks are of Oligocene and Miocene age. Surface gravels, sands, and clays of Quaternary and Recent age complete the sediment cover of the Marfa Basin.

Data from exploratory efforts to date in the Marfa Basin clearly show that all of the basic elements of a productive basin are present. Oil and gas shows from wells distributed across the Basin are positive proof that hydrocarbons have been sourced, matured, and expelled. This is further supported by the positive results shown by a variety of geochemical surveys in the Basin. Drilling has demonstrated that multiple intervals of both seal and reservoir quality rocks are present. The presence of traps has been demonstrated by the recent Barrett well discovery and can further be reasonably inferred from the depositional and tectonic history of the Basin and by analogy from similar productive basins.

Approximately 50 wildcat wells have been drilled in the Marfa Basin, and 17 or more of these (approximately 34%) reported oil or gas shows. Included in these shows is an Ellenburger core bleeding oil that was reported to have been recovered from the Sun #1 McElroy well, located on the Southern shelf. Several other wells also reported shows of oil or gas from the Ellenburger. Additional oil and gas shows have been reported from the Simpson, Silurian, Montoya, and Devonian intervals, all of which are producing zones in the Permian Basin. Wolfcamp and Leonard zones, analogous to Delaware and Val Verde Basin producing intervals, have produced oil and gas shows reported in several Marfa Basin wells. One well, in the Southwestern portion of the Basin, recorded a minor oil show from Cretaceous carbonates. The Knox #1 Barrett well is currently producing 1 to 5 barrels of oil per day from a Permian Guadalupian age dolomite, with additional testing and reservoir stimulation pending. The abundance of oil and gas shows reported to date, strongly suggests that additional discoveries will eventually be found in the Marfa Basin. Well data indicate that source material, sufficient to generate large volumes of hydrocarbons, exists in several intervals within the Marfa Basin. Of these the most significant are the Devonian Woodford Shale, with total organic carbon of 10% or more, the Mississippian Barnett Shale, and the deep slope and basin marine shales of the Permian detrital section.

Tight carbonates, shales, and siltstones capable of providing seals for a variety of reservoir zones are abundant and well distributed throughout the sedimentary section in the Marfa Basin. In the lower Paleozoic, the Ordovician Simpson shales, Silurian shales and tight carbonates, Devonian Woodford shale, and Mississippian Barnett shale all have excellent sealing potential, widely demonstrated across the Permian Basin. Shales and siltstones within the Permian section should provide numerous vertical and lateral seals, as they do in the Delaware and Val Verde Basins. The complex history of the Marfa Basin has undoubtedly created a large number of traps for hydrocarbons, both structural and stratigraphic, throughout the sedimentary section. Multiple episodes of faulting have produced a variety of uplifted horst blocks, tilted blocks, and flower structures, all of which will trap oil and gas if adequate seals are present. Traps of these types are common and effective across the Permian Basin, particularly in the lower Paleozoic units. Surface anticlinal folding, observed around the margins of the Marfa Basin, may also be present at depths where overburden pressure is greater and trapping potential is higher.

Seismic data quality has been highly variable in the Marfa Basin and earlier programs presented considerable difficulty both in acquisition and in interpretation. Several companies, including Amoco, have conducted a variety of geochemical and remote sensing surveys in the Marfa Basin-Diablo Platform area. Prominent among these is radiometric surveying, considered a direct oil and gas finding method, first used in the 1920's for hydrocarbon exploration in other basins. In recent years it has become generally accepted that all sealing rocks leak to some degree with respect to hydrocarbons, allowing vertical migration through the overlying sediments. Various geochemical, biological, and mineralogical anomalies develop in the surface and subsurface in response to these leakage "plumes" or "chimneys" (Figure 5, Idealized Geochemical Chimney), and are measurable and mappable.


Integration of such geochemical anomaly data with geological and geophysical data yields a powerful exploration tool that markedly increases the probability of exploration success. The results of these surveys in the Marfa Basin are extremely encouraging, as they further confirm the generation and accumulation of petroleum in the area, show a high degree of correlation between different methods, and fit well with conventional geological and geophysical data. Within the Marfa Project area, geochemical anomalies (Figure 6, Geochemical Anomalies) tend to cluster along northwest-southeast alignments. This matches the dominant fault pattern in the region, strongly indicating hydrocarbon seepage along faults from deeper accumulations. In addition to the interpreted major fault trends, multiple other geochemical anomalies are distributed in patterns suggestive of structural closures and channel or pinchout stratigraphic traps. Three types of geochemical surveys were acquired over the Marfa Project area, including ground radiometrics, airborne microwave, and soil gas sampling. (Reliant Petrolium Marfa Project:

Here is a map of their oil wells: Wells in Marfa Basin

3.8) Other evidence for active geology can be found in hot springs in the region:

From an oil investment brokerage? ( $478,000,000 (only $25,000,000 needed to start) --- Marfa, an oil play on 15,000 acres in Presidio County, Texas; firm to drill 277 wells over 5 years; after year six the operating expense is only $7 million per year but the fields will produce income of $20 million; loan in hand for 100% financing but needs initial deposit of $25,000,000 (deposit will be guaranteed for depositor by local bank, depositor will earn interest on deposit and share in ownership, depositor carries no personal or corporate debt obligation or other liens); depositors can request repayment in 90 days if necessary; principal has $6 million invested; some investment used to buy out partners; principal is commercial developer who has developed other ski resorts in Snomass, Aspen, Mesa County.

From the Oil and Gas Journal, September 7, 1998 issue online: West Mariah Energy Corp., Austin opened a field in Presidio County which has one other producing area. The 1 Berthold, 40 miles west-northwest of Marfa, pumped 5 b/d of 35.8[degrees] gravity oil with 97 Mcfd of gas and 60 b/d of water from San Miguel-Olmos perforations at 1,597-2,958 ft, Pi reported. The discovery well is 50 miles west-northwest of Riata oil field, opened in 1997. It produces from Pennsylvanian Canyon at 3,810-26 ft (OGJ, Nov. 10, 1997, p. 87). (

Oil and Gas Journal ( Issue: Dec 6, 1999 West Reliance Oil & Gas Inc., Seguin, staked a remote wildcat in the Marfa basin. The 1 Thomas, in Presidio County 8 miles northwest of Marfa, is projected to 9,000 ft. COPYRIGHT 1999 PennWell Publishing Co.

The Chinati (Ruidosa) Hot Springs: This place survives because some local people formed a nonprofit group and volunteer their time to run it. You should CALL AHEAD to let them know your coming (915-229-4165). To get there you must drive 38 miles up river from Presidio, Texas on Farm Road 170 - every mile of which is filled with many swooping dips that send your car airborn if you drive more than 45 mph. After the tiny town of Ruidosa there's a right turn and seven more miles on gravel and dust to the hot spring - a tiny canyon oasis shaded by a few cottonwoods and palms. Fiercely textured mountains, pale and hazy, are on the horizon. They are monstrously huge with exposed horizontal rock layers buckled and tilted - GREAT desert scenery that's part of the same geological drama you find in Big Bend National Park.

Copyright (C) 2001 Dr. Sten Odenwald