The Romeral Fault System ( es, Sistema de Fallas (de) Romeral) is a megaregional system of major parallel and anastomosing faults in the

Central Ranges Central Ranges (code CER) is an Australian bioregion, with an area of 101,640.44 square kilometres (39,244 sq mi) spreading across two states and one territory: South Australia, Western Australia, and the Northern Territory.Andes and the Cauca, Amagá, and Sinú-San Jacinto Basins. The system spans across ten

departments Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military *Department (administrative division), a geographical and administrative division within a country, ...

of Colombia, from northeast to south Bolívar,

Sucre Sucre () is the Capital city, capital of Bolivia, the capital of the Chuquisaca Department and the List of cities in Bolivia, 6th most populated city in Bolivia. Located in the south-central part of the country, Sucre lies at an elevation of . T ...

, Córdoba,

Antioquia Antioquia is the Spanish form of Antioch. Antioquia may also refer to: * Antioquia Department, Colombia * Antioquia State, Colombia (defunct) * Antioquia District, Peru * Antioquia Railway The Antioquia Railway ( es, Ferrocarril de Antioquia) i ...

, Caldas, Risaralda, Quindío, Valle del Cauca, Cauca and Nariño. The fault zone extends into Ecuador where it is known as the Peltetec Fault System. The in detail described part of the Romeral Fault System south of Córdoba has a total length of with a cumulative length of and runs along an average north to south strike of 017.6 ± 16, cross-cutting the central-western portion of Colombia. The fault system, active during more than 200 million years from the Triassic to recent, represents the ancient western continental margin of northwestern South America and forms the boundary between obducted oceanic crust to the west of the fault zone and continental crust to the east. The Romeral Fault System is situated at the intersection of five tectonic plates; the Caribbean Plate in the north, the Panama, Coiba and Malpelo Plates, formerly considered part of the

Nazca Plate The Nazca Plate or Nasca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Na ...

to the west and the

North Andes Plate The North Andes Plate or North Andes Block is a small tectonic plate ( microplate) located in the northern Andes. It is squeezed between the faster moving South American Plate and the Nazca Plate to the southwest. Due to the subduction of the Mal ...

where the fault system is located. The Romeral Fault System forms the structural boundary between the Western and Central Ranges of the Colombian Andes. The tectonic depression produced by the fault zone in the central and southern portion is filled by the valley of the

Cauca River The Cauca River () is a river in Colombia that lies between the Occidental and Central cordilleras. From its headwaters in southwestern Colombia near the city of Popayán, it joins the Magdalena River near Magangue in Bolivar Department, and th ...

, the second-most important fluvial artery of Colombia after the Magdalena River. The major active

volcanoes of Colombia A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

, such as Galeras and

Romeral Romeral is a Chilean town and commune in Curicó Province, Maule Region. The commune spans and area of . Demographics According to the 2002 census of Population and Housing by the National Statistics Institute, the Romeral commune had 12,707 in ...

are underlain by the Romeral Fault System. Segments of the fault zone are active, producing many minor and occasional devastating

earthquakes An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

, such as the 1983 earthquake in Popayán, Cauca and the

1999 Armenia earthquake The 1999 Armenia, Colombia earthquake occurred on 25 January 1999 at with an epicenter west south west of Ibagué, Colombia.

, with a combined total of more than 2000 casualties. The capitals of Sucre ( Sincelejo), Antioquia (

Medellín Medellín ( or ), officially the Municipality of Medellín ( es, Municipio de Medellín), is the second-largest city in Colombia, after Bogotá, and the capital of the department of Antioquia. It is located in the Aburrá Valley, a central re ...

), Caldas ( Manizales), Quindío ( Armenia), Risaralda (

Pereira Pereira (Portuguese and Galician for "pear tree") may refer to: People * Pereira (surname) Places *Brazil **Pereira (Bahia) (est. 1534) in the present-day Barra neighborhood of Salvador in Bahia **Pereira Barreto, municipality in São Paulo **Pe ...

), Valle del Cauca (

Cali Santiago de Cali (), or Cali, is the capital of the Valle del Cauca department, and the most populous city in southwest Colombia, with 2,227,642 residents according to the 2018 census. The city spans with of urban area, making Cali the second ...

), Cauca ( Popayán) and Nariño ( Pasto) are all situated near or on top of the fault zone.

Etymology

The Romeral Fault System is named after the volcano

, located in the centre of the fault zone. The system has received various names as Romeral Lineament ( es, Lineamiento Romeral), Romeral Fault, Romeral Fault Zone,Sierra et al., 2012 Romeral Shear Zone, and many individual segments of the system are known by local names.Paris et al., 2000, p.19

Description

The megaregional Romeral Fault System represents the geological boundary between the Western and Central Ranges of the Colombian Andes.Rodríguez & Zapata, 2013, p.40 The fault system was active since the Triassic.Vinasco & Cordani, 2012, p.121 During the Cretaceous, this was the western margin of northwestern South America.Vinasco & Cordani, 2012, p.112 It is one of the most active and continuous fault systems in Colombia. It extends southward into Ecuador and is known there as the Peltetec Fault System.Marín & Vinasco, 2012, p.61 In the literature, several names have been applied to the fault system as it traverses the length of the country. The oldest name is the Guayaquil-Dolores Megashear, which involves a whole set of parallel fractures in western Colombia. The number of faults that comprise the width of the system ranges between three and five, depending upon location in the country. Near latitude 7° N, the fault system includes the Peque, Heliconia, Sabanalarga, and Cauca Occidental Faults, mainly in the department of

. Farther south, between about latitudes 1° and 5° N, the faults are known from north to south as the Pijao-Silvia, Quebradagrande, Potrerillos, Guabas-Pradera, Cauca-Almaguer, Rosas-Julumito, Popayán, Paispamba, El Rosal, and Buesaco Faults. The fault system with described segments totalling almost in length comprises several parallel regional fractures (faults) that form the transition zone between oceanic rocks to the west and continental rocks to the east. The geology of the western domain consists of an ophiolitic belt with oceanic gabbroic, basaltic and sedimentary rocks of Cretaceous age. The eastern domain consists primarily of continentalised metamorphic schistose, oceanic, and continental rocks, mainly of Paleozoic age. The Romeral Fault System forms a wide deformed belt that is parallel to the western slope of the

Central Ranges Central Ranges (code CER) is an Australian bioregion, with an area of 101,640.44 square kilometres (39,244 sq mi) spreading across two states and one territory: South Australia, Western Australia, and the Northern Territory.Andes; it extends from the Gulf of Guayaquil in Ecuador in the south through Colombia to the Caribbean Sea in the north. At least one ancient

subduction zone Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...

is believed to underlay some parts of the zone. Although this is the most studied fault system in Colombia, little is still known about its paleoseismic characteristics (most recent faulting, slip rates, and recurrence intervals). Parallel to the Romeral Fault System runs the Cauca-Pujilí Fault that also extends into Ecuador in the south. The two fault zones converge in the northern part of the

Cauca Basin Cauca may refer to: * Cauca Department, an administrative division of Colombia * Valle del Cauca Department, an administrative division of Colombia * Cauca Department (Gran Colombia), former administrative division * Cauca, an extinct Choco langua ...

.Sierra et al., 2012, p.145 The fault system is reverse sinistral (left lateral) in the northern part of the country, conspicuous to about latitude 5° N, from there south to Ecuador, it is mainly reverse-dextral (right lateral). The system forms prominent fault lines and well-developed fault scarps as much as high on Pleistocene-aged sedimentary deposits, and eroded scarps on older Cretaceous to Paleozoic rocks. The system forms an outstanding break-in-slope above the easternmost parallel set of faults. The upper part of the easternmost major scarps forms the topographic divide of the Central Ranges of Colombia. Regional neotectonic features include linear valleys, offset drainages, aligned creeks, triangular facets, saddles, and L-shaped spurs and linear ridges. The fault offsets Quaternary volcanic rocks, alluvium and colluvium.Paris et al., 2000, p.20

Segments

Several segments of the Romeral Fault System have been identified under different names in the geological literature. The system starts as the Romeral Lineament in northern Colombia, in the department of Bolívar, where the lineament is covered by young sediments and runs parallel to and southeast from the Guamo Anticlinal,Mapa Geológico Bolívar 1:400,000, 1999 continuing into

, where the lineament runs east of Sincelejo along a north–south strike,Mapa Geológico Sucre 1:250,000, 1999 into Córdoba through

Montelíbano Montelíbano is a town and municipality located in the Córdoba Department of Colombia. It is the seat of the Roman Catholic Diocese of Montelíbano. Montelíbano is host of one of the largest ferronickel mines, the Cerro Matoso mine The Ce ...

.Mapa Geológico Córdoba 1:250,000, 1997

Cauca-Almaguer Fault

The Cauca-Almaguer Fault is a name given to several segments of the Romeral Fault System. In the north, the segment bearing this name starts in

Puerto Libertador Puerto Libertador () is a town and municipality located in the Córdoba Department, northern Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicar ...

, Córdoba, and extends southward into Antioquia. Between Bolombolo and

Santa Fe de Antioquia Santa Fe de Antioquia is a municipality in the Antioquia Department, Colombia. The city is located approximately north of Medellín, the department capital. It has a population of approximately 23,000 inhabitants. History Founded in 1541 by ...

, the fault covers a zone of wide with anastomosing fault segments. The fault connects to the Sabanalarga East Fault.Gónzalez, 2001, p.183 The fault delimits the western edge of the Arquía Complex schists.Gónzalez, 2001, p.182 In the department of Risaralda, the system receives the name Cauca-Almaguer Fault again, running east of

.Mapa Geológico Risaralda 1:200,000, 1990 The name appears again in the department of Valle del Cauca, bordering Cali to the west,Plancha 300, 1985 and in Cauca east of Popayán.Plancha 342, 1999

Sabanalarga East Fault

The Sabanalarga East Fault is the segment of the Romeral Fault System in Antioquia between Sabanalarga in the north and Liborina in the south.Mapa Geológico Antioquia 1:400,000, 1999

Romeral Fault

The system is known as Romeral Fault when cutting north to south through the department of Caldas, where the fault runs west of Manizales.Mapa Geológico Caldas 1:250,000, 1990

Montenegro Fault

The Montenegro Fault runs through the western slope of the Central Ranges. The fault is located to the west of the city of Armenia. The fault crosscuts and deforms the Pleistocene volcanic and volcano-sedimentary deposits of the Quindío Fan (''Abanico del Quindío''), which covers about .

Armenia Fault

The Armenia Fault is part of the Romeral Fault System on the western slope of the Central Ranges. The fault runs west of Pereira and the Cauca-Almaguer Fault in the department of Risaralda. Farther south, the fault crosses the city of Armenia and displaces Pliocene to Pleistocene volcanic and volcano-sedimentary deposits of the Quindío Fan. The geometric and neotectonic features of the Montenegro and Armenia Faults are very similar.Paris et al., 2000, p.21

Córdoba-Navarco Fault

This section of the fault system is formed by the locally named Córdoba and Navarco Faults, which are eastern strands of the Romeral Fault System, south of the city of Armenia. These faults lie within the epicentre area of the Armenia earthquake of January 25, 1999. The faults extend through sheared cataclastic and undeformed basaltic and sedimentary Cretaceous oceanic rocks, cropping out on the eastern slope of the Central Ranges.Paris et al., 2000, p.25

Paraíso Fault

The Paraíso Fault is located at the western slope of the Central Ranges, east of the city of Palmira. The fault displaces alluvial fans and debris flows on the eastern border of the department of Valle del Cauca. North of the Amaime River, the fault seems to be more active in late Quaternary than the portion south of the river. Two trenches were opened in the northern part: the Venecia and Piedechinche trenches, each of which show Holocene tectonic deformation.Paris et al., 2000, p.22

Piendamó Fault

The Piendamó Fault is located at the base of the mountain front of the western slope of the Central Ranges, north of the city of Popayán, Cauca. The fault displaces

pyroclastic Pyroclastic rocks (derived from the el, πῦρ, links=no, meaning fire; and , meaning broken) are clastic rocks composed of rock fragments produced and ejected by explosive volcanic eruptions. The individual rock fragments are known as pyroc ...

deposits and mud flows of the Tertiary to Quaternary Popayán Formation. It forms an outstanding topographic and tectonic block bounded by two intersecting faults.Paris et al., 2000, p.23

Rosas-Julumito Fault

The Rosas-Julimito Fault is a rather short section of about length, of which have active tectonic movement. The fault section parallels the Cauca-Almaguer Fault, which is one of the largest older fracture zones in western Colombia. The Rosas-Julumito Fault runs about west of the city of Popayán. The fault crosses the Pliocene-Pleistocene Popayán Formation, which consists of pyroclastic flow, mud flow and ash-fall deposits. It is believed that either the Rosas Fault or the nearby Julumito Fault (less than to the west) produced the earthquake of March 31, 1983 that partially destroyed the city of Popayán.Paris et al., 2000, p.24 The fault is noted in the south of the Cauca Department.

Popayán Fault

The Popayán Fault segment of the Romeral Fault System is noted near the village of

Timbío Timbio is a town and municipality in the Cauca Department Cauca Department (, es, Departamento del Cauca) is a Department of Southwestern Colombia. Located in the southwestern part of the country, facing the Pacific Ocean to the west, the ...

in the department of Cauca, joining to the south with the Rosas-Julumito Fault. Here, also the Silvia-Pijao Fault segment is present, just west of the Sotará volcano.Plancha 364, 1999

Buesaco-Aranda Fault

The Buesaco-Aranda Faults, which are parallel, extend in a north-northeast to northeast direction from near the

Galeras Volcano Galeras (Urcunina among the 16th-century indigenous people) is an Andean stratovolcano in the Colombian department of Nariño, near the departmental capital Pasto. Its summit rises above sea level. It has erupted frequently since the Spanish ...

in southwestern Colombia. The Buesaco Fault is located to the west of the Aranda Fault. On the eastern block of the Buesaco Fault, the

basement rock In geology, basement and crystalline basement are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment. The baseme ...

consists of basic volcanic, andesite and dark sedimentary rocks which probably developed in a marginal basin environment during

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

time. On the western block of the fault are a group of low-grade metamorphic rocks which consist of greenschist,

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...

, quartzite and black schist, all of Paleozoic age. The area is mostly covered by a Pliocene blanket of pyroclastic rocks and calc-alkaline lavas, Quaternary

lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extreme ...

deposits and fluvio- glacial deposits.Paris et al., 2000, p.26

Silvia-Pijao Fault

The Silvia-Pijao segment continues southward from Popayán, where it runs parallel to the Cauca-Almaguer and Buesaco Faults.Plancha 411, 2002 Farther south, this segment of the fault system runs just north of Pasto, the capital of Nariño and this fault trace continues into Ecuador, crossing the border east of the Chiles and Cerro Negro volcanoes.Plancha 5-18, 2015

Geology

Geometrically, the Romeral shear zone is characterised by an anastomosed arrange of faults yielding a block tectonic configuration, interpreted as an extensive shear zone (kilometric-scale) composed of multiple lithological units of varying ages, diverse origins, poly-deformed, and in faulted contact, which González (1980) named the Romeral Mélange. The system has been traditionally considered as a strike-slip shear zone, however, systematic observation of thrust faults suggests the importance of a compressive component of the system, configuring a dominant transpressive regime at least for the Cenozoic and eventually the Upper Cretaceous. Evidences for post-

Coniacian The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by t ...

thrusting of Quebradagrande volcanics over a feldspar granitoid, and post-Miocene thrusting of ultramafic rocks over Oligo-Miocene clastic rocks of the Amagá Formation are reported.Vinasco & Cordani, 2012, p.113 The fault zone separates the Barroso Formation from the Quebradagrande Complex. Both units are comparable in

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

, the Barroso Formation consisting of basalts, andesites and

rocks and the Quebradagrande Complex comprising basalts, andesites, pyroclastic rocks and gabbros.Rodríguez & Zapata, 2013, p.54 Cooling ages of the volcanics have been estimated at the Early Cretaceous, between 127 and 119 Ma.Vinasco & Cordani, 2012, p.117 Regionally, the Romeral Fault System separates the Central from the Western Ranges and corresponds to an extensive

shear zone In geology, a shear zone is a thin zone within the Earth's crust or upper mantle that has been strongly deformed, due to the walls of rock on either side of the zone slipping past each other. In the upper crust, where rock is brittle, the shear ...

hosting a series of rocks; # Early Cretaceous volcano-sedimentary rocks of the Quebradagrande Complex, characterised by mid-ocean ridge basalts (MORB) and arc-related rocks # Low-grade possibly Paleozoic meta-sedimentary rocks grouped into the Sinifaná-Meta sediments # Mafic and ultramafic Triassic intrusives # Permian and/or Cretaceous low-to-medium-grade meta-volcano-sedimentary N-MORB type sequences of the Arquía Complex These older rock units are

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

- Miocene coal-bearing Amagá Formation and the

Mio Mio or MIO may refer to: shortened form of Mioritic Shepherd dog or Mioritic sheepdog; a Romanian mountain dog. Places * Mio, Michigan, a town in the US Music * ''Mío'', 2011 album by David Bustamante * "Mío", 1992 song by Paulina Rubio Bra ...

- Pliocene volcanics of the Combia Formation.

Tectonic history

The western part of present-day Colombia was affected by a series of large-scale tectonic movements from the Mesozoic to Cenozoic. The tectonic history of the Romeral Fault System is determined by several phases of plate tectonic movements:Ramírez et al., 2012, p.125 # Subduction of the Farallones Plate during the Jurassic to Cretaceous # East- and northeastward movement of the Caribbean Plate relative to South America since the Cretaceous to Miocene # Break-up of the Farallones Plate into the Cocos and

s in the Late Oligocene (around 25 Ma) # Eastward subduction of the Coiba and Malpelo Plates, formerly considered the northern portion of the Nazca Plate since the Miocene # Accretion of allochtonous geologic terranes Western Ranges and

Serranía del Baudó The Serranía del Baudó is a coastal mountain range on the Pacific coast of Colombia. It is separated from the West Andes by the Atrato valley where the Atrato River flows and Quibdó is located. From the south the range extends from the Baud� ...

in the Late Cretaceous and Miocene to Pliocene respectively The fault system reached its "actual" configuration when the trans-American plate boundary (the fundamental pre-Aptian east-dipping

located to the west of the American margin) underwent a major transformation to a southwest dipping subduction zone beneath the future Caribbean Arc, impelling the closure of the Quebradagrande oceanic arc-back arc system. Initiation of this arc is likely constrained by HP-LT metamorphic rocks present in the circum-Caribbean subduction complexes, including examples from Colombia in the Barragán area (Valle del Cauca).Vinasco & Cordani, 2012, p.118 Three

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...

phases of strike-slip faulting along the Romeral Fault System have been deduced from the formation of the Irrá Basin, the deformation of its sediments, and rotation of its remagnetised sediments. The corresponding ages and slip-sense of these phases are

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

right-lateral (syndepositional), approximately Pleistocene left-lateral (syndeformational), Pleistocene to recent right-lateral (rotation of the remagnetised Irrá Formation). An additional phase, of left-lateral present-day slip has been deduced from microseismicity activity.Sierra et al., 2012, p.157

Activity

Individual fault segments of the Romeral Fault System have slip rates ranging from per year.Paris et al., 2000, pp.20–26 The fault system is active and produced two major earthquakes in Colombia; an M_w 5.5 earthquake in 1983 destroying the capital of Cauca, Popayán, and in 1999 (M_w 6.2) devastating the capital of Quindío, Armenia.Marín Arias et al., 2006, p.94

References

Bibliography

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Maps

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