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41-756: The basin is structurally bounded by the Palestina Fault to the west and the Bucaramanga Fault to the east. The Middle Magdalena Valley hosts the middle course of the Magdalena River , the main river of Colombia, flowing from the Upper Magdalena Valley in the south to the Lower Magdalena Valley to the northwest. The basin is elongated with an approximate width of 80 km (50 mi) and extends to

82-775: A result of erosion in the Central Ranges . The second subsequence is the Miocene Real Group, consisting of fluvial sandstones and conglomerates. Similar to the Real Group, the final subsequence is the Pliocene Mesa Formation, which is composed of sandstones and conglomerates deposited due to the Eastern Ranges uplift. The uppermost sedimentary rocks of the basin are Pleistocene alluvial fan deposits, overlain by Holocene sediments of

123-408: A sedimentary sequence, such as the top and base of a relatively strong sandstone layer bounded by two relatively weak mudstone layers. When a thrust that has propagated along the lower detachment, known as the floor thrust , cuts up to the upper detachment, known as the roof thrust , it forms a ramp within the stronger layer. With continued displacement on the thrust, higher stresses are developed in

164-628: A shallow marine environment with siltstone and shale deposits of the Cumbre Formation . Sea level continued to rise throughout the Middle Cretaceous when the Tablazo and Salto limestones and Simití shales were deposited. The La Luna Formation represents a maximum flooding surface with deep marine deposits of limestone, chert, and shale. Sea level then began to fall, returning the environment to shallow marine with deposition of

205-740: A sinistral strike-slip system, in the east. The major surface structures of the Middle Magdalena Basin are asymmetric synclines and basement cored anticlines , which formed as a result of thrusting from the Eastern and Central Ranges . The thrusting initiated faulting in the Pre-Mesozoic basement. The faults then pushed through the Jurassic layers to the Cretaceous ductile stratigraphy. The faults then form horizontally at

246-447: A so-called ramp-flat geometry. Thrusts mainly propagate along zones of weakness within a sedimentary sequence, such as mudstones or halite layers; these parts of the thrust are called decollements . If the effectiveness of the decollement becomes reduced, the thrust will tend to cut up the section to a higher stratigraphic level until it reaches another effective decollement where it can continue as bedding parallel flat. The part of

287-576: A total length of 369.6 kilometres (229.7 mi) and runs along an average north-northeast to south-southwest strike of 017.8 ± 11 along the Central Ranges of the Colombian Andes . The Palestina Fault extends from the Serranía de San Lucas in the department of Antioquia in the north, to the Nevado del Ruiz volcanic zone in the south. The Otú Norte and Bagre Norte Faults splay off

328-493: Is a break in the Earth's crust, across which older rocks are pushed above younger rocks. A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal ) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an overthrust or overthrust fault . Erosion can remove part of

369-742: Is reported, which probably occurred before Quaternary time. However, the Quaternary movement is believed to be sinistral. Before Miocene time, most of the faults of northern and western Colombia probably had dextral movement. The main volcanoes Nevado del Ruiz , Nevado de Santa Isabel and Nevado El Cisne are located above the fault.       Gómez Tapias, Jorge; Montes Ramírez, Nohora E.; Almanza Meléndez, María F.; Alcárcel Gutiérrez, Fernando A.; Madrid Montoya, César A.; Diederix, Hans (2015). Geological Map of Colombia . Servicio Geológico Colombiano . pp. 1–212 . Retrieved 2019-10-29 . Thrust faults A thrust fault

410-614: Is their producing formation, the lithologies of the formations, and the structure of the fields containing the hydrocarbons . The Tune and Avechucos Formations are equivalent to the Chorro and Chuspas Groups. Both the Casabe and Yariguí-Cantagallo Fields are located on the Magdalena River towards the western margin of the basin with the Yariguí-Cantagallo Field located approximately 40 kilometres (25 mi) north of

451-416: Is typically a lozenge-shaped duplex. Most duplexes have only small displacements on the bounding faults between the horses, which dip away from the foreland. Occasionally, the displacement on the individual horses is more significant, such that each horse lies more or less vertically above the other; this is known as an antiformal stack or imbricate stack . If the individual displacements are still greater,

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492-611: The Alps , and the Appalachians are prominent examples of compressional orogenies with numerous overthrust faults. Thrust faults occur in the foreland basin , marginal to orogenic belts. Here, compression does not result in appreciable mountain building, which is mostly accommodated by folding and stacking of thrusts. Instead, thrust faults generally cause a thickening of the stratigraphic section . When thrusts are developed in orogens formed in previously rifted margins, inversion of

533-640: The Casabe Field . Approximately 30 kilometres (19 mi) east of the Casabe Field is the oldest and largest La Cira-Infantas Field , situated towards the central to eastern margin of the basin. The Velásquez Field is located at the southern end of the basin near the Upper Magdalena Valley. Current exploration is focused in the southern area of the basin, where heavy amounts of faulting could house potential hydrocarbons . Aside from

574-872: The Early Tertiary to present day. Within this sequence, there are three subsequences that are the result of deformation and uplift of the Central and Eastern Ranges. The first subsequence consists of the Chorro Group with the La Paz and Esmeraldas Formations and the Chuspas Group with the Mugrosa and Colorado Formations , all deposited during the Eocene to Oligocene . These groups consist of fluvial sandstones, mudstones, siltstones, and shales, and are

615-573: The Eastern Ranges in the Pliocene . Now the Middle Magdalena basin is an intermontane basin situated between the uplifted Central and Eastern Ranges. Faulting in the Middle Magdalena Basin is primarily reverse and thrust faulting. Reverse faulting is high angle in the west and low angle in the eastern and central areas of the basin with normal faults also developing along the eastern margin. These thrust faults formed from thrusting from

656-731: The Magdalena River . During the Jurassic period, Pangea began to pull apart causing separation of North America from South America. This rifting produced a subduction zone where the Nazca Plate was subducting to the east under the South American Plate . Part of this subducting plate was the Baudo-Island Arc separated from the South American continent by the marginal Colombian Sea. The formation of

697-412: The ocean trench margin of subduction zones, where oceanic sediments are scraped off the subducted plate and accumulate. Here, the accretionary wedge must thicken by up to 200%, and this is achieved by stacking thrust fault upon thrust fault in a melange of disrupted rock, often with chaotic folding. Here, ramp flat geometries are not usually observed because the compressional force is at a steep angle to

738-660: The La Luna limestone, other potential source rocks include Early Cretaceous sediments such as the Paja and Simití Formations , or the Late Cretaceous shales of the Umir Formation . Palestina Fault The Palestina Fault ( Spanish : Falla de Palestina ) is a regional sinistral oblique thrust fault in the departments of Antioquia , Caldas and Bolívar in central Colombia . The fault has

779-575: The Magdalena River. The primary reservoirs in the Middle Magdalena Basin are fluvial sandstones and conglomerates from the Churro and Chuspas Groups, which have 20 to 25% porosity and 0.5 to 1 D permeability . The main source of hydrocarbons is the La Luna limestone, with a Total Organic Carbon (TOC) content of 3 to 4% and Type II marine kerogen , sealed by overlying Eocene shales. There are three types of traps that house hydrocarbons in

820-540: The Middle Magdalena Basin can be divided into three sequences separated by angular unconformities. The basement of these sequences is Pre-Mesozoic metaclastics and sediments which are now exposed on the surface of the Central Cordillera as a result of its deformation and uplift. This geologic basement is at most 15 kilometres (9.3 mi) deep, with faulted sections shifted up to approximately 10 kilometres (6.2 mi) in depth. The unconformity that separates

861-413: The Middle Magdalena Basin. The two structural traps are large anticlines in the center of the basin and smaller anticlines along the western margin. Both of these anticlinal traps produce from Tertiary sandstones within the Churro and Chuspas Groups. The third trap is stratigraphical with the La Luna limestone sealed by overlying shales. The table above shows some of the largest producing fields. Included

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902-496: The Palestina Fault. It mainly extends along the eastern slope of the Central Ranges , displacing Paleozoic crystalline metamorphic rocks and, in lesser amounts, Mesozoic plutonic rocks . The oldest rocks are mainly in the western block, which elevates a probable Miocene erosion surface whose eroded remnants are characterized by aligned flat narrow benches and spurs. The fault forms outstanding slope break between

943-628: The South American continent. This caused accretion of the Western Ranges and uplift of the Central Ranges transforming the back-arc basin into the pre-Andean foreland basin . Around the time of the Oligocene , the Nazca Plate increased its subduction to the east while the South American Plate experienced a westward pull. This caused the Andean orogeny in the Miocene and uplift of

984-637: The Umir Formation of shales and sandstones. Finally, the Paleocene saw the deposition of the Lisama Formation , consisting of deltaic mudstones and sandstones. This entire middle sequence indicates a marine megacycle consisting of five transgressive-regressive cycles. The angular unconformity between the second and third sequences is a result of erosion from the accretion of the Western Ranges . The final sequence represents deposition from

1025-534: The basement from the first sequences indicates the approximate time rifting began. The first sequence was deposited in the Jurassic during the rifting which caused the initial formation of the basin. This Jurassic formation is called the Girón Formation which consists of siltstones and rhyolitic tuffs. During this period, the basin also experienced granitic plutonism along its western margins. The Jurassic - Cretaceous angular unconformity, separating

1066-514: The buried paleo-rifts can induce the nucleation of thrust ramps. Foreland basin thrusts also usually observe the ramp-flat geometry, with thrusts propagating within units at very low angle "flats" (at 1–5 degrees) and then moving up-section in steeper ramps (at 5–20 degrees) where they offset stratigraphic units. Thrusts have also been detected in cratonic settings, where "far-foreland" deformation has advanced into intracontinental areas. Thrusts and duplexes are also found in accretionary wedges in

1107-541: The ductile-brittle transition for 10 to 20 kilometres (6.2 to 12.4 mi) before cutting through the upper brittle stratigraphy. The resulting structure is a syncline against the hanging wall of the fault next to an inclined anticline . Key folds in the basin for hydrocarbon exploration include the Nuevo Mundo and Guaduas Synclines. As suggested by the formation of the folds, both of these synclines are bounded by thrust faulting and anticlines. The stratigraphy of

1148-548: The eastern margin of the Central Ranges in the Eocene and the western margin of the Eastern Ranges in the Miocene . The major thrust faults in the Middle Magdalena Basin include the Infantas Thrust, La Salina Thrust , and Cantagallo Thrust. The basin is structurally bounded by the Palestina Fault , a dextral strike-slip fault system, in the west and the Bucaramanga-Santa Marta Fault ,

1189-478: The extensional back-arc basin associated with this subduction is the origin of the Middle Magdalena Basin in the late Jurassic . Throughout the Cretaceous , the basin experienced thermal subsidence and five transgressive-regressive cycles as part of a marine megacycle. In the Paleocene , the rate of subduction increased causing the marginal Colombian Sea to close and the Baudo-Island Arc to collide with

1230-544: The first and second sequence, is representative of the post-rift boundary. The middle sequence represents the formations deposited throughout the Cretaceous and Early Paleocene . The oldest formations in this sequence are the Tambor and Los Santos Formations . The conglomerates and sandstones indicate a continental to fluvial depositional environment . In the Early Cretaceous , sea level began to rise and formed

1271-429: The footwall of the ramp due to the bend on the fault. This may cause renewed propagation along the floor thrust until it again cuts up to join the roof thrust. Further displacement then takes place via the newly created ramp. This process may repeat many times, forming a series of fault-bounded thrust slices known as imbricates or horses , each with the geometry of a fault-bend fold of small displacement. The final result

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1312-505: The horses have a foreland dip. Duplexing is a very efficient mechanism of accommodating the shortening of the crust by thickening the section rather than by folding and deformation. Large overthrust faults occur in areas that have undergone great compressional forces. These conditions exist in the orogenic belts that result from either two continental tectonic collisions or from subduction zone accretion. The resultant compressional forces produce mountain ranges. The Himalayas ,

1353-588: The lack of surface evidence, blind thrust faults are difficult to detect until rupture. The destructive 1994 earthquake in Northridge, Los Angeles, California , was caused by a previously undiscovered blind thrust fault. Because of their low dip , thrusts are also difficult to appreciate in mapping, where lithological offsets are generally subtle and stratigraphic repetition is difficult to detect, especially in peneplain areas. Thrust faults, particularly those involved in thin-skinned style of deformation, have

1394-699: The north for approximately 450 km (280 mi), where it terminates against the Santander Massif and Cesar Valley. To the south, it terminates against the Upper Magdalena Valley, which consists of the Girardot and Neiva Sub-basins where the Central and Eastern Ranges converge. The basin is an important producer of oil in Colombia, with main fields Yariguí-Cantagallo , Moriche , Casabe , La Cira-Infantas , Velásquez , Santos , Palagua , Teca , Payoa and Lisama . The first three fields were among

1435-412: The overlying block, creating a fenster (or window ) – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called klippen (singular klippe ). If the fault plane terminates before it reaches the Earth's surface, it is called a blind thrust fault. Because of

1476-890: The sedimentary layering. Thrust faults were unrecognised until the work of Arnold Escher von der Linth , Albert Heim and Marcel Alexandre Bertrand in the Alps working on the Glarus Thrust ; Charles Lapworth , Ben Peach and John Horne working on parts of the Moine Thrust in the Scottish Highlands ; Alfred Elis Törnebohm in the Scandinavian Caledonides and R. G. McConnell in the Canadian Rockies. The realisation that older strata could, via faulting, be found above younger strata

1517-562: The thrust behind the fault tip continues. The formation of an asymmetric anticline-syncline fold pair accommodates the continuing displacement. As displacement continues, the thrust tip starts to propagate along the axis of the syncline. Such structures are also known as tip-line folds . Eventually, the propagating thrust tip may reach another effective decollement layer, and a composite fold structure will develop with fault-bending and fault-propagation folds' characteristics. Duplexes occur where two decollement levels are close to each other within

1558-409: The thrust linking the two flats is known as a ramp and typically forms at an angle of about 15°–30° to the bedding. Continued displacement on a thrust over a ramp produces a characteristic fold geometry known as a ramp anticline or, more generally, as a fault-bend fold . Fault-propagation folds form at the tip of a thrust fault where propagation along the decollement has ceased, but displacement on

1599-470: The twenty most producing fields of Colombia in 2016. Until 2008, La Cira-Infantas and Casabe produced more than 730 million barrels (116 × 10 ^  m) and 289 million barrels (45.9 × 10 ^  m) respectively. Main producing reservoirs are the Colorado, Mugrosa, Esmeraldas and La Paz Formations. Secondary reservoirs are Lisama and La Luna. The name of the basin is taken from the middle course of

1640-504: The western uplifted block and the eastern peneplain surface. In the western block, there are flat bench-like remnants of a Tertiary erosion surface. The fault zone is characterized by fault scarps , saddles, linear ridges, displaced streams, shutter ridges, and aligned springs. Some topographic features show evidence of sinistral offset. Locally, two fault traces bound a depressed block ( pull-apart basin ). Based on stratigraphic evidence, dextral movement of about 15 kilometres (9.3 mi)

1681-439: Was arrived at more or less independently by geologists in all these areas during the 1880s. Geikie in 1884 coined the term thrust-plane to describe this special set of faults. He wrote: By a system of reversed faults, a group of strata is made to cover a great breadth of ground and actually to overlie higher members of the same series. The most extraordinary dislocations, however, are those to which for distinction we have given

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