The Romeral fault system () is a megaregional system of major parallel and anastomosing faults in the Central Ranges of the Colombian Andes and the Cauca, Amagá, and Sinú-San Jacinto Basins. The system spans across ten departments of Colombia, from northeast to south Bolívar, Sucre, Córdoba, Antioquia, 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 to the west and the North Andes plate 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 second-most important fluvial artery of Colombia after the Magdalena River.
The major active volcanoes of Colombia, such as Galeras and Romeral are underlain by the Romeral fault system. Segments of the fault zone are active, producing many minor and occasional devastating earthquakes, such as the 1983 earthquake in Popayán, Cauca and the 1999 Armenia earthquake, with a combined total of more than 2000 casualties. The capitals of Sucre (Sincelejo), Antioquia (Medellín), Caldas (Manizales), Quindío (Armenia), Risaralda (Pereira), Valle del Cauca (Cali), 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 Romeral, located in the centre of the fault zone. The system has received various names as Romeral Lineament (), 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 Antioquia. 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 of the Colombian 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 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.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 Sucre, where the lineament runs east of Sincelejo along a north–south strike,Mapa Geológico Sucre 1:250,000, 1999 into Córdoba through Montelíbano.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, Córdoba, and extends southward into Antioquia. Between Bolombolo and Santa Fe de Antioquia, 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 Pereira.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 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 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 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 consists of basic volcanic, andesite and dark sedimentary rocks which probably developed in a marginal basin environment during Early Cretaceous time. On the western block of the fault are a group of low-grade metamorphic rocks which consist of greenschist, amphibolite, 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 deposits and fluvio-glacial deposits.Paris et al., 2000, p.26
Silvia-Pijao Fault