Bucaramanga–Santa Marta Fault

The Bucaramanga–Santa Marta is a major fault system which extends for a total distance of from the Colombian Caribbean coast to the Eastern Ranges of the Colombian Andes to as far as about 6.5° N, south of the capital of Santander, Bucaramanga. The fault system, with an average strike of 341 ± 23 degrees, is a major wrench fault with a sinistral (left-lateral) displacement ranging from and a fault slip rate of per year. The Santa Marta Fault forms the boundary between several distinct geological provinces: it is the western limit of the Santa Marta Massif with the Sinú-San Jacinto Basin, farther to the south the fault separates the Lower Magdalena Valley and northern Middle Magdalena Valley from the Cesar-Ranchería Basin. The Santander Massif is separated from the central part of the Middle Magdalena Valley along the southern Bucaramanga Fault segment of the fault system. The fault divides the northern part of the Eastern Ranges in two structurally distinct regions. The Andean uplifted eastern block mainly comprises crystalline igneous and metamorphic rocks of Paleozoic and pre-Cambrian age, with lesser amounts of Jurassic, Triassic, and Tertiary sedimentary rocks. In the western downthrown block, predominately sedimentary rocks of Quaternary and Tertiary age are found, with lesser amounts of Cretaceous and Jurassic rocks. The northern half of the fault is partially covered by Quaternary deposits in the Cesar and Magdalena valleys. and the main Santa Marta fault segment in the northern part of the fault system. Between the two main outcropping segments, the Algarrobo Fault is present in the subsurface, overlain by Quaternary sediments. The urban centre of the major coal producing municipality El Paso, Cesar is located right above the fault. The fault can be traced until San Andrés, Santander. The Bucaramanga Fault possibly continues as the compressional Boyacá and Soapaga Faults on the Altiplano Cundiboyacense. Municipalities == Tectonic setting ==

, South American and Caribbean Plates The Bucaramanga-Santa Marta Fault system is located in northwestern South America, on the North Andes Plate, where the /yr east to southeastward moving Caribbean, /yr eastward subducting Malpelo, and South American Plates converge. Since Early Mesozoic times, the western portion of Colombia was subjected to different episodes of subduction, accretion and collision, at the boundaries of the South America continental and the oceanic Farallon, Nazca, and Caribbean Plates and various island arcs. The interaction of the plate tectonic movements formed the Northern Andean Block, separated from the Maracaibo Block by the Bucaramanga-Santa Marta Fault. The Northern Andean Block is subdivided into tectonic realms, with the Bucaramanga-Santa Marta Fault separating the Central Continental Sub-plate Realm in the west from the Maracaibo Sub-plate Realm in the east. It has been suggested that these two realms are dominated by respectively Nazca and Caribbean Plate subduction. The compressional stress regime caused the formation of the oblique sinistral Bucaramanga-Santa Marta Fault and dextral Oca and Boconó Faults. The interplay between the Santa Marta and Oca Faults produced offshore Caribbean platforms and valleys north of the Sierra Nevada de Santa Marta near Taganga. Uplift along the western margin of the Santa Marta Fault probably commenced in the Pliocene. The Bucaramanga Fault intersects with the Boconó Fault at the Santander Massif. In this area, the top of the subducting slab has been estimated at an initial depth of approximately , then a horizontal part for about , and a farther descending section to reach a depth of around . The slab section, called Bucaramanga slab, here has a dip that continues to the oceanic crust of the Caribbean seafloor. Towards the north of the Bucaramanga Nest or Swarm, in a north–south area approximately in length, a well-defined Wadati-Benioff Zone extending to depth has been identified. == Activity ==

A study published in 2009 about the Bucaramanga segment of the fault system revealed that the fault had eight episodes of activity during the late Holocene. The most recent activity has been inferred to have been around the year 1020. During this pre-Columbian era, the area around Bucaramanga was inhabited by the indigenous Guane. The authors consider the Bucaramanga Fault therefore as active. == Panorama ==

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