Abstract
The Abiquiu Embayment is to be found in north-central New Mexico. Through the (angular) unconformity way, both sedimentary and volcanic (rocks) superimposes pre-tertiary ones. Chicoma is the oldest form of volcanic formation. latite and andesite (flows) are its main components. It has a thickness that can measure up to several thousand feet. The tertiary sedimentary is subdivided into three types of formations: the Abiquiu tuff consists of more than a thousand feet of laid volcanic conglomerates and tuff. It also has some small interbedded volcanic emission flows. Another type of formation is El Rito which grades sandstone and conglomerates from talus breccia, its thickness can reach a maximum of two hundred feet.
The last type is the Santa Fe formation; this constitutes very thick deposits which has certain basalt flows interbedded on them. As the tertiary period approached, a severe deformation (through the process of normal faulting) occurred. There was some process of downfaulting and down warping of tertiary sediments which occurred against pre-tertiary rocks. This led to many irregular fault blocks.
The Rio Grande rift is composed of many right-stepped en echelon basins; these include the San Luis basin, Albuquerque basin, and the Espanola Basin. The basins are set apart by certain zones which were established as forms of extended directions; these took place through gradual changes. In the case of the Espanola basin, there was the transfer of displacement from Miocene dominated Canones fault to Quaternary Pajarito fault; the motion that falls along the Embuto fault had a shift from mainly dip-slip to mainly strike-slip.
Introduction
Abiquiu is one of the most significant places that are of great geological importance to geologists and students of geology. It has got some of the unique features associated with volcanic activities. It is one of the landforms that are used to study the formation of the earth’s surfaces. Due to frequent visits by geologists and tourists, it has become one of the most unique places to witness the recent activities of volcanicity.
Geologic History
The sedimentologic, structural, and stratigraphic information from the members found within the Oligocene-lower Miocene Abiquiu Formation avails reliable information about the late deformation of the Cenozoic; it also establishes the landscape evolution that took place in north-central New Mexico. The members of the members found within the Abiquiu Formation are unconformably realized to lie on Mesozoic Formation strata and also they locally lie on the Cenozoic El Rito Formation. The Abiquiu Formation is a thick sequence of interbedded cobble conglomerates, boulder, and coarse-grained sandstone; this forms a thickness of 125 meters.
The period running from 27Ma to 18Ma; the period between the late Oligocene and early part of Miocene there was more widespread volcanic activities that happened all through the developing region of the western rift (Dickinson, pp23-106). The widespread tuffs, flows of lava together with other debris of volcanism covered the slopes of the peaks of volcanoes and also the local volcanic fans. All these together with inter-bedded less viscous flows combined to establish widespread sheets which covered topographic unconformity, that is, Los Pinos Formation and Abiquiu tuff formation (Dethier, pp14-27).
Rock unit
The Abiquiu is overlain by rock units of volcanic origin. The rock units are of Paliza Canyon Formation. Abiquiu embayment is a structural superficial bench that lies to the western margin of the rift of the Rio Grande located in northern New Mexico. It contains about 1l00 to 1500 meters of Miocene and Oligocene sedimentary and also volcanic fill. The volcanic fill is found to be adjacent to the tilted east San Luis basin (Karlstrom and Keller, p291).
The margin of most parts of the western embayment are existing as discrete faults that divide the strata within Oligocene and Miocene on one part and leaves on the other part the upper Paleozoic via the lower Tertiary rocks found in the Plateau of Colorado. The sedimentary rocks on Miocene and Oligocene nature are gotten in the west of these two faults in northern Sierra Nacimiento and at Cerro Pedernal. The strata of the basin-filling that is founded within the Abiquiu embayment usually thickens towards the east crossing series of steep east-dipping faults. This takes place in such a manner that the most aged sediments are the only ones exposed to the western fault blocks (Karlstrom and Keller, p304).
The formation of the Abiquiu of northern New Mexico comprises several units of conglomerate units. These units are directly obtained from the terranes source from the basement of proterozoic rocks. It is important to note that the nomenclature of the age of the Oligocene has been revised. In this case, the conglomerate is separated from the basal section of the Abiquiu Formation; it is integrated into volcanic clastic strata.
The original name that was given to Abiquiu is “Abiquiu tuff” it is recorded that succeeding workers later changed the name to Abiquiu Formation; this was due to the reason that it is composed of sandstones together with conglomerates that have thin deposits of tephra. A fine-grained bed of hashes is also found within it. Abiquiu Formation is a term that is now restricted to strata that were referred to as the upper members before. The Abiquiu Formation overlies the Ritito conglomerates; the higher part of Ritito conglomerate found at del Cobre region contains sandstones and little pebbles.
Regional geologic setting
The Rio Grande rift that is located in northern New Mexico institutes four major important asymmetric half-graben basins. These basins include San Luis which is located to the north, southern Albuquerque-Belen, and north basins found on the southern part and the Espanola Basin. Both the northern Albuquerque-Belen and the San Luis are the eastward dipping half grabens, while the southern Albuquerque-Belen and the Espanola form the westward dipping half grabens. These basins are bound to the east sides by the Precambrian cored which includes the Sandia Mountain and the Sangre de Cristo, to the east they are bound by Paleozoic sedimentary rocks (Menzies,pp34-65).
The Plateau of Colorado comprises the upper Paleozoic via Mesozoic sedimentary rocks. The plateau binds the basins on the western side. The northwestern boundary of the Abuquiu is formed by the Precambrian cored. The Abiquiu has been considered as part of the topographic and sedimentary component of the Espanola basin which falls to the North West. However, looking at it tectonically it serves as the pivot to the San Luis basin; this is set apart from the nearing Espanola basin by the existence of the Embudo fault which serves as an intra-continental fault connecting San Luis and the basin of Espanola with a motion that contains the variations that happen between the west-dipping basins and east-dipping basin (Menzies, p273)
The structure of the Abiquiu Embayment
The Abiquiu Embayment is found in north-central New Mexico. It stretches to the western side of Rio Grande Valley; The Rio Grande rift is composed of many right-stepped en echelon basins; these include the San Luis basin, Albuquerque basin, and the Espanola Basin. A strip of it is found in Taos County and the rest of its part is located in the Rio Arriba County.
The region is found in the west of the extreme south of the southern part of the Province of Rocky Mountain. The main drainage of Abiquiu Embayment includes the Rio Grande through the south of the quadrangle. This also includes the River Chama and its tributaries (Wilson, pp45-76).
This embayment (Abiquiu) is believed to be 1:24000 i.e. in the quadrangle scale. There are exposed rocks which include Cenozoic and Mesozoic. Mesozoic rocks characterize the Plateau of Colorado; Todilto and Jurassic Entrada Sandstone. Cenozoic rocks are upper and lower members. Examples of these members are such as Oligocene-Meocene Abiquiu and Eocene El Rito formations. The members of the Tesuque Formation of the group of Santa Fe are constituted of volcanic rocks.
The volcanic rocks include the El Alto Basalt, the intermediate lava of Tschicoma Formation, and the Lobato Basalt. Fan alluvium, pediment alluvium among others makes the Quaternary deposits. Locate between thirty meters and one hundred and fifteen meters are the axial terrace benches. A set of benches which is found at about 115m of height is estimated to be about 640ka; this is based on the availability of the lava creek Bash in the eastern part of the map area. The tributary gravels consist of clasts of the fluvial system which is suspected to be representative of numerous familial courses of Rio Chama (Wilson, pp77-89).
The Abiquiu is an early basin that is bordering Canones fault on the west side that is tilted to the regional tendency of the rift of Rio Grande; this lies within the region where there are changes in the polarity of the rift. To comprehend the subdivisions of the Rio Grande it is crucial to be knowledgeable on the kinematics, slip history, and the geometry of the faults that bind the basin of Abiquiu. The mapping that has been done by various geologists indicates that the system of Canone faults is an east-dipping. It is an oblique fault that stretches for about 20 kilometers in the northeast. The Abiquiu Embayment contrasts with Triassic and the Permian formations in its wall that lies against the upper part of Jurassic rocks; its draping Tertiary basin fixes it by about 300 meters (Wilson, p469).
The Abiquiu Formation jutes out on the Nacimiento uplift in the West of the Espanola basin found in the north-central part of New Mexico, and the north of Jemez Mountain. The Abiquiu formation has been segmented into three units. These include the upper, lower, and pedernal members. The primordial Miocene is believed to be from the upper member. Both pedernal and the lower (members) from the upper Oligocene (to Lower Miocene). Widespread Zia sand outcrops are found to the South of the Nacimiento.
Geomorphology
It has been widely thought that the Abuquiu embayment is mostly physiographic due to the high Jemez volcanic mound and that its structural basin maintained the normal depth under the volcanic mound between the Albuquerque and Espanola basins. The evidence from the structural Jemez bench suggests that the Albiquiu embayment is more tectonic than what it has always been perceived to be (Riecker, P64). In the valley of Chama which is to the west of the Abiquiu the basin beds in most cases overlap with the existing pre-basin beds. There is also a bench that stretches for about 300 to 400 meters of lower Santa Fe beds that exists primarily between two faults, Canone-Cobre, and Gonzale faults, on the west side.
The basal of the Abiquiu tuff of Santa Fe stretch for not less than 15 kilometers towards the west on the Plateau of Colorado. To the northeast side toward El Rito and then up El Rito Canyon moving to Brazos uplift, the basin boundary is nontectonic and the basin fill diminishes to below 200 meters and is somehow less than a thickness of one kilometer in the East of El Rito (Riecker, P64).
Conclusion
Abiquiu embayment is a structural superficial bench that stretches out to the western margin of the rift of the Rio Grande existing in northern New Mexico; this contains about 1l00 to 1500 meters of Meocene and Oligocene sedimentary and also volcanic fill. The margin of most parts of the western embayment are existing as discrete faults that divide the strata within Oligocene and Miocene on one part and leaves on the other part, the upper Paleozoic via the lower Tertiary rocks found in the Plateau of Colorado. The members found within Abiquiu Formation are non-conformably realized to lie on Mesozoic Formation strata and also they locally lie on Cenozoic El Rito Formation.
The Abiquiu Formation is a thick sequence of interbedded cobble conglomerates, boulder, and course-grained sandstone; this forms a thickness of 125 meters. The Abiquiu Embayment is found in north-central New Mexico (Wilson, pp40-76). It stretches to the western side of Rio Grande Valley. A strip of it is found in Taos County and the rest of its part is located in the Rio Arriba County. The region is found in the west of the extreme south of the southern part of the Province of Rocky Mountain. The main drainage of Abiquiu Embayment includes the Rio Grande through the south of the quadrangle. This also includes the River Chama and its tributaries.
It can also be said that the Abiquiu is an early basin that is bordering Canones fault on the west side that is tilted to the regional tendency of the rift of Rio Grande; this lies within the region where there are changes in the polarity of the rift. It is has been found out that the system of Canone faults is an east-dipping; it is an oblique fault that stretches for about 20 kilometers in the northeast. The Embayment contrasts with Triassic and the Permian formations in its wall that lies against the upper part of Jurassic rocks; its draping Tertiary basin fixes it by about 300 meters (Wilson, p469).
The Abiquiu Formation jutes out on the Nacimiento uplift in the West of Espanola basin found in the north-central part of New Mexico, and the north of Jemez Mountain. The tertiary sedimentary is subdivided into three types of formations: the Abiquiu tuff consists of more than a thousand feet of laid volcanic conglomerates and tuff. It also has some small interbedded volcanic emission flows. Another type of formation is El Rito which grades sandstone and conglomerates from talus breccia, its thickness can stretch to a limit of two hundred feet. The last type is the Santa Fe formation; this constitutes very thick deposits which has certain basalt flows interbedded on them.
A severe deformation was witnessed as the tertiary era came to an end. There was some process of down faulting and down warping of tertiary sediments which occurred against pre-tertiary rocks. This led to many irregular fault blocks.
The margin of most parts of the western embayment are existing as discrete faults that divide the strata within Oligocene and Miocene on one part and leaves on the other part the upper Paleozoic via the lower Tertiary rocks found in the Plateau of Colorado. The sedimentary rocks on Miocene and Oligocene nature are gotten in the west of these two faults in northern Sierra Nacimiento and at Cerro Pedernal. The strata of the basin-filling that is founded within the Abiquiu embayment usually thickens towards the east crossing series of steep east-dipping faults. The sedimentary rocks on Miocene and Oligocene nature are gotten in the west of these two faults in northern Sierra Nacimiento and at Cerro Pedernal.
Works cited
Dethier, David. “New Mexico Bureau of Mines and Mineral Resources.” Geoinfo, 1991. Web.
Dickinson, William. “Tectonic setting of faulted tertiary strata associated with the Catalina core complex in southern Arizona.” Volume 264 of Special papers. Geological Society of America. 1991.
Karlstrom, Karl and Keller, George. The Rocky Mountain Region: An Evolving Lithosphere. New York: American Geophysical Union, 2005.
Klemperer, Simon. The George A. Thompson volume; The lithosphere of western North America and its geophysical characterization. New York: Geological Society of America. 2003.
Menzies, Martin. Volcanic rifted margins. New York: Geological Society of America. 2002.
Riecker, Robert. “American Geophysical Union.” Tectonics and Magmatism, Inter-Union Commission on Geodynamics. American Geophysical Union. 1979.
Wilson, John. Stratigraphy and structure of part of the Abiquiu embayment of the Rio Grande rift. New Mexico: University of New Mexico. 1977.