NAP -
North Andes plateSAP -
South American plateMP -
Malpelo plateCMP -
Coiba microplatePMP -
Panama microplate , situated in the valley of the
Cauca River and
Armenia,
Pereira and
Manizales in the adjacent mountainous areas are all affected by the movements of the Romeral fault system with frequent smaller and occasional major earthquakes The megaregional Romeral fault system represents the geological boundary between the
Western and Central Ranges of the Colombian Andes. The fault system was active since the Triassic. During the Cretaceous, this was the western margin of northwestern South America. 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. 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 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.
Segments of the 1999 Armenia earthquake, associated with the
Córdoba-Navarco segment of the Romeral fault system , where the lineament runs east of
Sincelejo along a north–south strike, into
Córdoba through
Montelíbano.
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. The fault delimits the western edge of the Arquía Complex schists. In the department of Risaralda, the system receives the name Cauca-Almaguer Fault again, running east of
Pereira. The name appears again in the department of Valle del Cauca, bordering Cali to the west, and in Cauca east of Popayán.
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.
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.
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 .
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.
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.
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.
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. The fault is noted in the south of the Cauca Department.
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.
Silvia-Pijao Fault The Silvia-Pijao segment continues southward from Popayán, where it runs parallel to the Cauca-Almaguer and Buesaco Faults. 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.
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 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. The fault zone separates the
Barroso Formation from the Quebradagrande Complex. Both units are comparable in
lithology, the Barroso Formation consisting of
basalts,
andesites and
pyroclastic rocks and the Quebradagrande Complex comprising basalts, andesites, pyroclastic rocks and
gabbros. Cooling ages of the volcanics have been estimated at the Early Cretaceous, between 127 and 119 Ma. Regionally, the Romeral fault system separates the Central from the Western Ranges and corresponds to an extensive
shear zone 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 overlain by the
Oligocene-
Miocene coal-bearing
Amagá Formation and the
Mio-
Pliocene volcanics of the
Combia Formation. • 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
Nazca plates 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 allochthonous geologic terranes Western Ranges and
Serranía del Baudó 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
subduction zone 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. Three
Neogene 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 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.
Activity Individual fault segments of the Romeral fault system have slip rates ranging from per year. The fault system is active and produced two major earthquakes in Colombia; an Mw 5.5 earthquake in 1983 destroying the capital of Cauca, Popayán, and in 1999 (Mw 6.2) devastating the capital of
Quindío, Armenia. == See also ==